Contact lens and method of manufacturing the same Patent Application (2025)

U.S. patent application number 12/230306 was filed with the patent office on 2009-03-05 for contact lens and method of manufacturing the same. This patent application is currently assigned to MENICON CO., LTD.. Invention is credited to Yukihisa Sakai, Hiroaki Suzuki, Hiroyuki Yamaguchi.

Contact lens and method of manufacturing the same

Abstract

A contact lens having a mark on at least one of an anterior faceand a posterior face thereof, wherein the improvement including:the mark being defined by a concave annular section having insideand outside peripheral borders of circular shape, and a centerprojection situated in a center of the concave annular section; anoutside diameter dimension of the concave annular section is heldwithin a range of 0.1-0.5 mm; a widthwise center section of theconcave annular section in radial cross section is a flat sectionhaving smaller depth change and greater radius of curvature thanwidthwise side sections; and at least the flat section of the markhas a rough surface The method of manufacturing the contact lens isalso disclosed.

 OLIFF & BERRIDGE, PLC P.O. BOX 320850 ALEXANDRIA VA 22320-4850 US

Foreign Application Data

Claims

1. A contact lens having a mark on at least one of an anterior faceand a posterior face thereof, wherein the improvement comprises:the mark being defined by a concave annular section having insideand outside peripheral borders of circular shape, and a centerprojection situated in a center of the concave annular section; anoutside diameter dimension of the concave annular section beingheld within a range of 0.1-0.5 mm; a widthwise center section ofthe concave annular section in radial cross section being a flatsection having smaller depth change and greater radius of curvaturethan widthwise side sections; and at least the flat section of themark having a rough surface.

2. The contact lens according to claim 1, wherein on a groovedcontour of the radial cross section of the concave annular section,the flat section is formed on a bottom portion thereof with a widthdimension equal to one-third or more of a width dimension of anopening of the groove, and with a flatness of the flat sectionbeing 5 .mu.m or less.

3. The contact lens according to claim 1, wherein a distal end faceof the center projection has an outside diameter dimension of asize equal to 0.02 mm .phi. or greater.

4. The contact lens according to claim 3, wherein the distal endface of the center projection has a rough surface of a degree ofsurface roughness smaller than the rough surface of the flatsection of the concave annular section.

5. The contact lens according to claim 1, wherein a connectingsection of an inside peripheral border of the concave annularsection with the center projection, and a connecting section of anoutside peripheral border of the concave annular section with anoutside peripheral section of the concave annular section, havesmoothly curving shape in radial cross section, respectively.

6. The contact lens according to claim 1, wherein an outsideperipheral section of the concave annular section is imparted aboutan entire circumference with a rough surface having smaller degreeof surface roughness than the rough surface of the flat section ofthe concave annular section.

7. The contact lens according to claim 1, wherein a groove depth inthe radial cross section of the concave annular section is heldwithin a range of 12-36 .mu.m at an average face of the flatsection.

8. The contact lens according to claim 1, wherein the rough surfaceof the flat section in the concave annular section has an Ra valuethat is held within a range of 0.2 .mu.m-5 .mu.m.

9. The contact lens according to claim 1, wherein a ring-shapedsmall projecting portion of 1.8 .mu.m or less in height is formedin an outside peripheral section of the concave annularsection.

10. The contact lens according to claim 1, wherein the mark isformed simultaneously with molding of the lens using a lens-moldingresin mold that has been produced with a mold die, by means oftransferring a mark pattern that has been formed in the mold die tothe lens-molding resin mold, and subsequent re-transfer thereof tothe lens; and the mark pattern in the mold die is formed throughscanning of a laser beam in a circumferential direction over awidth equivalent to two or more scan lines in a radialdirection.

11. The contact lens according to claim 10, wherein the laser beamused to form the mark pattern on the mold die has a spot diameterof 0.05 mm or less.

12. The contact lens according to claim 10, wherein the markpattern is formed through scanning of the laser beam along two ormore scan lines in the radial direction of the mark pattern, with acenter axis of the laser beam positioned at intervals of 0.03 mm orless.

13. The contact lens according to claim 10, wherein the markpattern is formed by scanning the laser beam along four or morescan lines in the radial direction of the mark pattern.

14. The contact lens according to claim 10, wherein the markpattern on the mold die has been formed through irradiation withthe laser beam while submerged in a liquid.

15. The contact lens according to claim 1, wherein the mark issituated in a peripheral zone formed surrounding an optical zone ofthe lens, and is formed in zone between 2.7 mm and 6.0 mm radiallyoutward from a lens center.

16. The contact lens according to claim 1, wherein a plurality ofmarks are formed in a grouped arrangement.

17. The contact lens according to claim 16, wherein the groupingarea in the mark has a size of 2.2 mm or smaller in a radialdirection of the lens.

18. The contact lens according to claim 16, wherein a distanceseparating the plurality of the marks from one another isequivalent to between one-third and twice an outside diameterdimension of the mark.

19. A method of manufacturing a contact lens having a mark formedon at least one of an anterior face and a posterior face of thecontact lens, the mark being produced simultaneously with moldforming of the contact lens in a lens molding cavity defined by alens-molding resin mold which has been produced by a mold die,through transfer of a mark pattern that has been formed in the molddie to the lens-molding resin mold and subsequent re-transferthereof to the contact lens, the method comprising the step of:producing the mark pattern that includes a concave annular sectionhaving circular inner and outer peripheral borders and a centerprojection situated to a center of the concave annular section byengraving the concave annular section into the mold die using alaser beam, while submerged in a liquid.

20. The method of manufacturing a contact lens according to claim19, wherein the mark pattern in the mold die is formed with a shapesuch that an outside diameter dimension of the concave annularsection is held within a range of 0.1-0.5 mm, and a widthwisecenter section of the concave annular section in radial crosssection constitutes a flat section having smaller depth change andgreater radius of curvature than widthwise side sections.

21. The method of manufacturing a contact lens according to claim19, wherein the mark pattern is formed through scanning of thelaser beam in a circumferential direction by an equivalent of twoor more scan lines in a radial direction.

22. The method of manufacturing a contact lens according to claim21, wherein, during scanning of the laser beam, a spacing of scansof the laser beam at a center axis thereof in the radial directionof the mark pattern is smaller than a spot of the laser beam.

23. The method of manufacturing a contact lens according to claim19, wherein the laser beam comprises a laser beam with spotdiameter of 0.05 mm or smaller.

Description

INCORPORATED BY REFERENCE

[0001] The disclosure of Japanese Patent Application No.2007-227041 filed on Aug. 31, 2007 including the specification,drawings and abstract is incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a contact lens, and inparticular relates to a marked contact lens and to a method ofmanufacturing the same.

[0004] 2. Description of the Related Art

[0005] Contact lenses of soft type or hard type, or that combineelements of both, are sometimes provided on the lens surface withan indicia (a mark) for the purpose of identifying the lens asbeing for use in either the left or right eye; or in the case of alens that needs to be positioned correctly in the circumferentialdirection (for example a toric lens or bifocal lens), to identifythe circumferential position of the lens; or to indicate the lensserial number, lot number, or other control information.

[0006] Techniques for inscribing a contact lens with such markingshave been disclosed, for example in Japanese Unexamined PatentPublication No. JP-A-62-31821 and Japanese Unexamined PatentPublication No. JP-A-4-270312. These techniques involve methodssuch as impregnating the interior of the molded lens with a dye,then developing or fixing the impregnated dye through a chemicalreaction. However, since such methods require a process forimpregnating each molded lens with dye, it is difficult to achievegood production efficiency. Moreover, there is an anxiety that themark will disappear with repeated cleaning of the lens throughrubbing, disinfection through boiling, and so on.

[0007] Accordingly, laser processing techniques as proposed, forexample in Japanese Unexamined Patent Publication No. JP-A-8-194193have come to be widely used, whereby an engraved marking, producedby directing a laser beam of high-density focused light energy ontothe die which is used to mold the resin mold for shaping thecontact lens, is transferred to the lens surface via the resinmold; or a laser beam is aimed directly onto the lens surface tomodify the shape of the lens surface and create a mark. With suchprocesses, since the mark is actually engraved onto the lenssurface, the anxiety of the mark disappearing is reduced. come tobe widely used. With such processes, since the mark is actuallyengraved onto the lens surface, the anxiety of the markdisappearing is reduced.

[0008] However, since a mark integrally formed on the lens surfacein this way will have transparency comparable to the lens surface,it may be a problem to ensure adequate visibility. In view of thisproblem, various mark morphologies have been examined with a viewto improving visibility.

[0009] For example, U.S. Pat. No. 6,203,156 proposes a markmorphology having a bottom face of smooth concave shape. With sucha mark, visibility will be improved through focused reflection ofan incident light beam from the smooth concave bottom face.However, with a smooth face, since most of the incident light istransmitted rather than reflected, it may be difficult to producesufficient reflected light. Accordingly, in order to ensureeffective visibility it was necessary for the mark to have largersize (enlargement) and greater depth (deepening) in order toeffectively capture most of the incident light and effectivelyfocus the incident light.

[0010] U.S. Pat. No. 6,568,807 on the other hand proposes a markmorphology having a bottom face of smooth convex shape. However,with the mark taught in this publication as well, since the bottomface is a smooth face most of the incident light will betransmitted through the bottom face, making it difficult to obtainsufficient reflected light. Thus for the same reason as in U.S.Pat. No. 6,203,156, it was necessary for the mark to enlarged inorder to obtain much reflected light. Furthermore, with the marktaught in U.S. Pat. No. 6,568,807 as well, formation of an annularconcave portion surrounding the convex portion at the center couldcause the mark to deepen.

[0011] Thus, with the contact lenses of both U.S. Pat. No.6,203,156 and U.S. Pat. No. 6,568,807; enlarging and deepening ofthe mark were the only ways to enhance visibility of the mark.However, enlarging and deepening of the mark is undesirable due toproblems such as: (1) diminished lens strength and durabilitycaused by thinning of the lens due to the mark; (2) possible injuryto the anterior part of the eye due to increased irritation of theeye by the mark; (3) rotation or shifting of the lens when beingplaced in the eye due to the mark catching on the eyelid etc.; or(4) adverse effects on vision caused by refracted light, reflectedlight, or lens distortion in the area of the mark.

SUMMARY OF THE INVENTION

[0012] It is accordingly one object of the present invention toprovide a contact lens of novel construction furnished with a markthat affords better visibility, while avoiding the need to enlargeor deepen the mark.

[0013] It is another object of the present invention to provide anovel method of manufacture of a contact lens, whereby a contactlens furnished with such a mark can be manufacturedadvantageously.

[0014] The above and/or optional objects of this invention may beattained according to at least one of the following modes of theinvention. The following modes and/or elements employed in eachmode of the invention may be adopted at any possible optionalcombinations.

[0015] A first aspect of the present invention relates to a contactlens, and a first mode thereof provides a contact lens having amark on at least one of an anterior face and a posterior facethereof, wherein the improvement comprises: the mark being definedby a concave annular section having inside and outside peripheralborders of circular shape, and a center projection situated in acenter of the concave annular section; an outside diameterdimension of the concave annular section being held within a rangeof 0.1-0.5 mm; a widthwise center section of the concave annularsection in radial cross section being a flat section having smallerdepth change and greater radius of curvature than the widthwiseside sections; and at least the flat section of the mark having arough surface.

[0016] In the contact lens of construction according to this modeof the invention, when light impinges on the mark, transmission ofincident light will be reduced and scattering of the incident lightwill be produced at the rough surface of the flat section. The flatsection will therefore appear brighter so that the visibility ofthe mark is enhanced. At the same time, when light impinges on themark, the center projection will cast a shadow on the concaveannular section. Thus, according to this mode, since the flatsection appear bright due to scattering of light by the roughsurface, the center projection will cast a shadow with moredefinite contrast onto the concave annular section, so that thevisibility of the mark can be further enhanced as a result.

[0017] Additionally, according to this mode, the flat section isformed in the concave annular section, making it possible to limitthe depth dimension of the mark, as well as to limit enlargement ofthe mark while at the same time ensuring a larger effective surfacearea. It will be possible thereby to ensure effective visibility onthe part of the mark, while keeping its outside diameter dimensionsmall. By thusly limiting enlargement and deepening of the mark, itwill be possible to completely prevent problems such as (1)diminished lens strength and durability caused by thinning of thelens due to the mark, (2) possible injury to the anterior part ofthe eye due to increased irritation of the eye by the mark, (3)rotation or shifting of the lens when being placed in the eye dueto the mark catching on the eyelid etc., and (4) adverse effects onvision caused by refracted light, reflected light, or lensdistortion in the area of the mark.

[0018] Furthermore, since the mark of construction according tothis mode of the invention has annular shape, its outer peripheralborder lacks any straight section. Thus, contact pressure by theeyelid etc. can be deftly relieved to either side of the mark inthe circumferential direction. For this reason, the anxiety ofcatching can be advantageously avoided, and it will be possible toachieve effective reduction in friction against the eyelid, and toachieve effective reductions in slippage, interference, orirritation in association with blinking during wear.

[0019] In preferred practice, in the mark of construction accordingto this mode, the flat section at the widthwise center of thegrooved contour of the radial cross section of the concave annularsection will have a greater radius of curvature than do theconnecting sections thereof that connect with side wall sections toeither side. In this case the presence in the widthwise centersection of the groove of a zone having a greater radius ofcurvature than the widthwise side sections of the groove enablesthe presence of the flat section at the bottom of the groove to berecognizable. More preferably, the radius of curvature of the flatsection will be greater by a factor of 10 or more than the minimumvalue of radius of curvature of the connecting sections with theside wall sections at either side; a substantially flat face havingan infinitely large radius of curvature (i.e. a straight line inhorizontal cross section) would be acceptable as well.

[0020] Typically, in the flat section, the center of curvature,inclusive of the connecting sections with the side wall sections ateither side, will be situated towards the opening side of thegroove. Furthermore, in preferred practice, the inside face of thegroove in transverse cross section, over the entirely thereofinclusive of the side wall sections at either widthwise side, theflat section, and the connecting sections thereof, will be definedby a smooth curve of gradually varying radius of curvature devoidof inflection points; or by a curve and straight line.

[0021] Furthermore, in this mode of the invention, while it issufficient for at least the flat section to be imparted with arough surface, it would be acceptable to impart a rough surface tothe entire surface of the mark inclusive of the centerprojection.

[0022] A second mode of the first aspect of the present inventionprovides the contact lens according to the first mode, wherein on agrooved contour of the radial cross section of the concave annularsection, the flat section is formed on a bottom portion thereofwith a width dimension equal to one-third or more of a widthdimension of an opening of the groove, and with a flatness of theflat section being 5 .mu.m or less.

[0023] In the contact lens of construction according to this modeof the invention, deepening of the mark can be limited moreeffectively while still effectively ensuring effective visiblesurface area of the mark. Specifically, on the grooved contour ofthe radial cross section of the concave annular section, if theflat section is smaller than one-third of the width dimension ofthe groove opening, the flat section will be too small toeffectively afford the effect of increased visible surface areaetc. At the same time, if the flat section is too small, thedifference in groove depth of the concave annular section betweenwhen a flat section is present and when one is not will becomenegligible, making it difficult to effectively limit deepening ofthe mark. Moreover, if the flatness of the flat section is greaterthan 5 .mu.m, the mark will tend to deepen, posing an anxiety ofdiminished lens strength.

[0024] In this mode, flatness refers to a value for a surfacederived from an average surface of the rough surface. That is, itindicates variation in groove depth dimension on the averagesurface, and is expressed as the difference in depth dimensionbetween the deepest point and the shallowest point. In other words,the condition of this mode shall be deemed to be met where, in theradial cross section of a groove whose rough surface has beenrepresented by an average surface, if two points respectivelyhaving groove depth of -5 .mu.m are designated to either side inthe width direction from the point of maximum depth, the widthwisedistance between these two points will be equal to one-third orgreater of the width of the groove opening. In order to furtherimprove visibility of the mark, in preferred practice the flatnessof the flat section will be no more than 2 .mu.m.

[0025] A third mode of the first aspect of the present inventionprovides the contact lens according to the first or second mode,wherein a distal end face of the center projection has an outsidediameter dimension of a size equal to 0.02 mm .phi. or greater.

[0026] In the contact lens of construction according to this modeof the invention, the distal end face of the center projection hasa specific outside diameter dimension, thereby giving the centerprojection a generally truncated cone shape. With this arrangement,the direction of light reflection can be varied between the distalend face of the center projection and the inside peripheral wall ofthe concave annular section which surrounds the center projection,so that visibility of the mark can be further improved. At the sametime, the anxiety of the distal end of the center projectionbecoming caught on the eyelid can be reduced as well, thus reducingthe anxiety of rotation of the lens or a sensation of a foreignbody, caused by catching on the eyelid.

[0027] It will be appreciated from the description of this modethat, for example in the preceding first mode of the invention, thedistal end face of the center projection may be formed as a pointsubstantially devoid of any planar dimensions. In this case, sincethe inside peripheral wall of the concave annular sectionsurrounding the center projection has generally conical shape inits entirety, the direction of light reflection on the mark surfacewill differ, which will have the effect of improving visibility dueto the presence of the center projection.

[0028] Imparting a prescribed size to the distal end face of thecenter projection in accordance with this mode of the inventionwill result in a more marked difference in the direction of lightreflection between the distal end face of the center projection andthe inside peripheral wall of the concave annular sectionsurrounding the center projection, thus affording furtherimprovement in visibility of the mark overall.

[0029] While in preferred practice, the distal end face of thecenter projection will be constituted as a flat surface in order toproduce a more marked difference in slope angle (and hence in thedirection of light reflection) relative to the inside peripheralwall of the concave annular section surrounding it and to therebyimprove the visibility of the mark, the distal end face could alsohave a curving surface such as a convex spherical face.

[0030] A fourth mode of the first aspect of the present inventionprovides the contact lens according to the third mode, wherein thedistal end face of the center projection has a rough surface of adegree of surface roughness smaller than the rough surface of theflat section of the concave annular section.

[0031] In the contact lens of construction according to this modeof the invention, a rough surface is provided to the distal endface of the center projection in addition being provided to theflat section, whereby the effect of scattering light impinging onthe mark can be afforded more effectively, and visibility of themark can be improved further. Additionally, by imparting differingdegrees of surface roughness to the flat section and to the distalend face of the center projection, it will be possible to produceconditions of light scattering that differ between the flat sectionand the distal end face of the center projection and to createzones having different visibility, whereby visibility can beimproved further. At the same time, by employing smaller surfaceroughness at the distal end face of the center projection whichduring wear will be positioned in proximity to the eyelid or thecornea, the anxiety of catching or of a sensation of a foreign bodycan be reduced. In this mode, surface roughness refers to a peakand valley pattern, exclusive of any curve of the surface.

[0032] A fifth mode of the first aspect of the present inventionprovides the contact lens according to any one of the first tofourth modes, wherein a connecting section of the inside peripheralborder with the center projection, and a connecting section of theoutside peripheral border with the lens surface, have smoothlycurving shape in radial cross section, respectively.

[0033] In the contact lens of construction according to this modeof the invention, the radial cross section of the mark is definedover its entirety by a smooth curve or by a curve and a straightline. With this arrangement, irritation of the eyelid etc. can bereduced further, and the anxiety of catching can be lowered. Inthis mode, a radial cross section with a smoothly curving shaperefers to a cross sectional shape having gradually varying radiusof curvature overall and devoid of inflection points, i.e. ofturning points lacking a common tangent. In the present invention,the entire surface of the mark may be constituted as a roughsurface, in which case the radius of curvature of the average lineof the rough surface will vary gradually, with no turningpoints.

[0034] A sixth mode of the first aspect of the present inventionprovides the contact lens according to any one of the first tofifth modes, wherein the outside peripheral section of the concaveannular section is imparted about an entire circumference with arough surface having smaller degree of surface roughness than therough surface of the flat section of the concave annularsection.

[0035] In the contact lens of construction according to this modeof the invention, by imparting a rough surface to the outsideperipheral section of the concave annular section, transmission ofa beam of light impinging on the concave annular section can bereduced, so that more effective scattering of incident tight can beachieved. Thus, an effect comparable to enlarging the concaveannular section can be achieved, and the concave annular sectioncan be substantially enlarged so that visibility of mark can beimproved further. Moreover, by imparting the flat section and theoutside peripheral section of the concave annular section withdiffering degrees of surface roughness, it will be possible toendow the flat section and the outside peripheral section of theconcave annular section with differing conditions of lightscattering and to create zones having different visibility, wherebyvisibility can be improved further.

[0036] Moreover, since actual enlargement of the concave annularsection may be avoided, the anxiety of problems such as diminishedlens strength or catching on the eyelid etc. associated with anenlarged mark can be avoided more effectively as well.Additionally, by employing smaller surface roughness at the outsideperipheral section of the concave annular section which during wearwill be positioned in proximity to the eyelid or the cornea, theanxiety of catching or of a sensation of a foreign body can bereduced.

[0037] A seventh mode of the first aspect of the present inventionprovides the contact lens according to any one of the first tosixth modes, wherein a groove depth in the radial cross section ofthe concave annular section is held within a range of 12-36 .mu.mat an average face of the flat section.

[0038] In the contact lens of construction according to this modeof the invention, good visibility can be ensured withoutsacrificing lens strength. Specifically, if the groove depth of theconcave annular section is smaller than 12 .mu.m, the surface areaof the concave annular section (and consequently of the flatsection) will be too small to afford sufficient scattering actionby the rough surface of the flat section; at the same time, theheight dimension of the center projection will be too short to casta distinct shadow, posing an anxiety of diminished visibility. Onthe other hand, if the groove depth is greater than 36 .mu.m, thereis an anxiety of diminished lens strength due to excessive depth ofthe concave annular section.

[0039] An eighth mode of the first aspect of the present inventionprovides the contact lens according to any one of the first toseventh modes, wherein the rough surface of the flat section in theconcave annular section has an Ra value that is held within a rangeof 0.2 .mu.m-5 .mu.m.

[0040] In the contact lens of construction according to this modeof the invention, good visibility can be ensured while maintaininglens strength. Specifically, if the rough surface of the flatsection has an Ra value of less than 0.2 .mu.m, it will essentiallybe no different from a sleek, smooth surface and will tend totransmit most incident light, making it difficult to attain goodvisibility. On the other hand, if the rough surface of the flatsection has an Ra value of greater than 5 .mu.m, the projections onthe flat section will be too large, posing the anxiety of inabilityof the center projection to cast a distinct shadow onto the flatsection, with the attendant anxiety of reduced visibility; while atthe same time producing sections of considerable groove depth inthe concave annular section, posing the anxiety of diminished lensstrength.

[0041] A ninth mode of the first aspect of the present inventionprovides a contact lens according to any one of the first to eighthmodes, wherein a ring-shaped small projecting portion of 1.8 .mu.mor less in height is formed in the outside peripheral section ofthe concave annular section.

[0042] In the contact lens of construction according to this modeof the invention, the direction of reflection of incident lightwill be different due to the presence of the ring-shaped projectionat the outside peripheral border of the mark, so that the contoursof the mark can be made to stand out, affording even bettervisibility. By limiting the height of the ring-shaped projection tono more than 1.8 .mu.m, contact pressure against the eyelid orcornea can be minimized so as to ensure good wear comfort.

[0043] A tenth mode of the first aspect of the present inventionprovides the contact lens according to any one of the first toninth modes, wherein the mark is formed simultaneously with moldingof the lens using a lens-molding resin mold that has been producedwith a mold die, by means of transferring a mark pattern that hasbeen formed in the mold die to the lens-molding resin mold, andsubsequent re-transfer thereof to the lens; and the mark pattern inthe mold die is formed through scanning of a laser beam in acircumferential direction over a width equivalent to two or morescan lines in a radial direction.

[0044] In the contact lens of construction according to this modeof the invention, through scanning of a laser beam in thecircumferential direction, a region corresponding to the concaveannular section of the mark can be formed in the section scanned bythe laser beam, while a region corresponding to the centerprojection of the mark can be formed in the center section which isnot irradiated with the laser beam.

[0045] During subsequent transfer of the mark pattern produced inthis way to the lens surface, it will be possible for transfer totake place through a process comparable to mold processes widelyemployed in manufacture of contact lenses in the past, so thatthere is substantially no increase in the number of process stepson the lens production line, and so that excellent productionefficiency can be achieved Moreover, since the mark pattern formedon the die is transferred to the lens surface, variability in markshape can be reduced even in situations where large numbers oflenses are manufactured, so that superior product consistency isachieved.

[0046] An eleventh mode of the first aspect of the presentinvention provides the contact lens according to the tenth mode,wherein the laser beam used to form the mark pattern on the molddie has a spot diameter of 0.05 mm or less.

[0047] In the contact lens of construction according to this modeof the invention, a mark having peak and valley dimensions suchthat lens strength does not suffer can be formed advantageously,while maintaining good visibility. Specifically, if the spotdiameter of the laser beam exceeds 0.05 mm, melting of theprocessing surface will be produced over a wider range, resultingin larger peaks and valleys of the rough surface that is formed onthe flat section, which in turn poses the anxiety of reducedscattering of incident light and reduced visibility. Additionally,larger spot diameter is associated with greater depth dimension onthe processing surface, with an anxiety of diminished lensstrength.

[0048] A twelfth mode of the first aspect of the present inventionprovides the contact lens according to the tenth or eleventh mode,wherein the mark pattern is formed through scanning of the laserbeam along two or more scan lines in the radial direction of themark pattern, with a center axis of the laser beam positioned atintervals of 0.03 mm or less.

[0049] In the contact lens of construction according to this modeof the invention, the spot of the laser beam can be scanned inoverlapping fashion, thereby reducing the anxiety that anyunprocessed portions or ridges will remain at the scan lineboundaries. The flat section may be formed advantageously on thebottom face of the concave annular section thereby.

[0050] A thirteenth mode of the first aspect of the presentinvention provides the contact lens according to any one of thetenth to twelfth modes, wherein the mark pattern is formed byscanning the laser beam along four or more scan lines in the radialdirection of the mark pattern.

[0051] In the contact lens of construction according to this modeof the invention, the flat section of the mark can be formedadvantageously. Specifically, since a processed section formed in asingle pass of the laser beam will have a curved cross sectionalshape, in order to produce a flat shape it is preferable to scanthe spot repeatedly in overlapping fashion; but if the number ofscan passes is less than four lines, the bottom face of the concaveannular section will tend to have a curved shape due to the smallnumber of times of overlap by the spot.

[0052] A fourteenth mode of the first aspect of the presentinvention provides the contact lens according to any of the tenthto thirteenth modes, wherein the mark pattern on the mold die hasbeen formed through irradiation with the laser beam while submergedin a liquid.

[0053] In the contact lens of construction according to this modeof the invention, the rough surface of sections corresponding tothe flat section etc. of the mark pattern can be formed with finerdetail and clearer definition, as compared to where laserirradiation is carried out in the air. Accordingly, the roughsurface of the flat section etc. of the mark produced throughtransfer of the mark pattern to the lens face can be formed withfiner detail and clearer definition. Moreover, bulging of the outerperipheral border of the mark pattern can be limited, so that theheight dimension of the ring-shaped projection taught in thepreceding ninth mode can be advantageously kept to no more than 1.8.mu.m.

[0054] While the scientific basis for why a better rough surfacecan be formed with laser irradiation carried out while submerged inliquid, as compared to laser irradiation carried out in the air, isnot sure, it is thought that where laser irradiation is carried outin the air, heat tends be transferred to the area around the focalpoint location as well, inducing melting over a relatively widerange in a vicinity that includes the focal point location, so thata smooth surface tends to form. In contrast, it is thought thatwhere laser irradiation carried out in a liquid, evolution of heatin the vicinity of the focal point location will be limited so thatmelting will take place intensively at the focal point location;and that redeposition of swarf produced by laser machining isavoided, thereby reducing the drop in energy density of the laserbeam caused by swarf. Moreover, while the scientific basis for whybulging of the outer peripheral border of the mark pattern ispoorly understood, it is thought that where laser irradiationcarried out in liquid, there will be less bulging of the outerperipheral border of the mark pattern caused by thermaldeformation, owing to reduced evolution of heat in the vicinity ofthe focal point location.

[0055] Additionally, by carrying out laser irradiation in liquid,redeposition of swarf produced by laser processing can be reduced.It is accordingly possible to limit soiling or molding defectscaused by deposited swarf, and to obviate the need for a cleaningstep, thereby affording better production efficiency.

[0056] A fifteenth mode of the first aspect of the presentinvention provides the contact lens according to any one of thefirst to fourteenth modes, wherein the mark is situated in aperipheral zone formed surrounding an optical zone of the lens, andis formed in zone between 2.7 mm and 6.0 mm radially outward from alens center.

[0057] In the contact lens of construction according to this modeof the invention, since the mark will be situated at location awayfrom the pupil of the eye during wear, the anxiety of adverseeffects of refraction or reflection by the mark on the opticalproperties of the lens can be avoided. Also, since it will bepossible to avoid forming the mark in the outside peripheral edgepart of the lens, diminished wear comfort or rotation of the lensdue to catching on the eyelid etc. can be advantageously avoided.It is moreover possible to avoid making the edge of the lensthinner due to formation of the mark at the edge of the lens, withthe anxiety of reduced strength.

[0058] A sixteenth mode of the first aspect of the first aspect ofthe present invention provides the contact lens according to anyone of the first to fifteenth modes, wherein a plurality of marksare formed in a grouped arrangement.

[0059] In the contact lens of construction according to this modeof the invention, by forming a plurality of appropriately arrayedmarks it will be possible to represent any of various shapes,alphanumeric characters, graphic symbols, and the like. Accordingto the mark herein in particular, since excellent visibility can beachieved without enlarged size, even if an alphanumeric characteror the like is depicted using multiple marks, it will be possibleto form the alphanumeric character with smaller size while stillmaintaining good visibility. This makes it possible to reduce theanxiety that the alphanumeric character will stand out to theextent that the appearance of the lens suffers, as well as todepict more alphanumeric characters or graphic symbols on the lenssurface of a contact lens having a limited area for depiction, sothat more information can be represented.

[0060] Furthermore, since alphanumeric characters formed bymultiple marks can be smaller in size, catching on the eyelid canbe suppressed, thus reducing the anxiety of rotation of the lens orsensation of a foreign body, caused by catching. In particular,since the mark herein is annular in shape and devoid of anystraight sections at its outer border, the anxiety of catching canbe reduced more advantageously.

[0061] A seventeenth mode of the first aspect of the presentinvention provides the contact lens according to the sixteenthmode, wherein the grouping area in the mark has a size of 2.2 mm orsmaller in a radial direction of the lens.

[0062] In the contact lens of construction according to this modeof the invention, the anxiety of diminished appearance or ofsensation of a foreign body can be reduced. Specifically, if themark grouping area has a size greater than 2.2 mm, there is ananxiety that the mark grouping will stand out to the point thatappearance is diminished, and of overlap with the eyelid producinga sensation of a foreign body. Since the marks herein afford goodvisibility despite their small outside diameter dimension, goodvisibility will be afforded even where the grouping area is no morethan 2.2 mm in size.

[0063] An eighteenth mode of the first aspect of the presentinvention provides the contact lens according to the sixteenth orseventeenth mode, wherein the distance separating the plurality ofthe marks from one another is equivalent to between one-third andtwice the outside diameter dimension of the mark.

[0064] In the contact lens of construction according to this modeof the invention, the anxiety of catching on the eyelid etc. can bereduced while still maintaining good visibility. Specifically, ifmarks are situated too close together, there is an anxiety ofconsiderable sensation of a foreign body, or of rotation orposition shift of the lens caused by catching on the eyelid etc.,as well as of reduced lens strength owing to the marks beinggrouped densely together. On the other hand, if the marks are toofar apart, there is an anxiety that graphic symbols or alphanumericcharacters represented by a grouping of marks will not be readilyrecognizable as such.

[0065] A second aspect of the present invention relates to a methodof marking a contact lens, and a first mode of the second aspectprovides a method of manufacturing a contact lens having a markformed on at least one of an anterior face and a posterior face ofthe contact lens, the mark being produced simultaneously with moldforming of the contact lens in a lens molding cavity defined by alens-molding resin mold which has been produced by a mold die,through transfer of a mark pattern that has been formed in the molddie to the lens-molding resin mold and subsequent re-transferthereof to the contact lens, the method comprising the step of:producing the mark pattern that includes a concave annular sectionhaving circular inner and outer peripheral borders and a centerprojection situated to a center of the concave annular section byengraving the concave annular section into the mold die using alaser beam, while submerged in a liquid.

[0066] According to the method of this mode of the invention, sincethe mark can be produced through a process comparable to moldprocesses widely employed in manufacture of contact lenses in thepast, there will be substantially no increase in the number ofprocess steps on the lens production line, and excellent productionefficiency can be achieved. Moreover, since the mark pattern formedon the die is transferred to the lens surface, variability in markshape can be reduced even in situations where large numbers oflenses are manufactured, so that superior product consistency isachieved.

[0067] In the method according this mode, the mold die isirradiated with a laser beam while submerged in a liquid. By sodoing, the peak and valley contours of the rough surface ofsections corresponding to the flat section etc. of the mark patterncan be formed with finer detail and clearer definition, as comparedto where laser irradiation is carried out in the air; andaccordingly the rough surface of the flat section etc. of the markproduced through transfer of this mark pattern to the lens face canbe formed with finer detail and clearer definition. Moreover,bulging of the outer peripheral border of the mark pattern can belimited, so that the height dimension of the ring-shaped projectiontaught in the preceding ninth mode can be advantageously kept to nomore than 1.8 .mu.m.

[0068] Additionally, by carrying out laser processing in liquid,deposition of swarf produced by laser processing can be reduced. Itis accordingly possible to limit soiling or molding defects causedby deposited swarf, and to obviate the need for a cleaning step,thereby affording better production efficiency.

[0069] The mark formed through transfer of the mark pattern to thelens face in this way includes a concave annular section havingcircular inner and outer peripheral borders, and a centerprojection formed to the center of the concave annular section.When a beam of light impinges on the mark, since the concaveannular section has a rough surface, transmission of light incidenton the concave annular section will be limited and of the lightwill be effectively scattered. At the same time, the centerprojection will cast a shadow on the concave annular section,producing distinct contrast through reflection from the concaveannular section and the shadow of the center projection, whereby amark having excellent visibility can be obtained at excellentproduction efficiency.

[0070] A second mode of the second aspect of the present inventionprovides the method of manufacturing the contact lens according tothe first mode, wherein the mark pattern in the mold die is formedwith a shape such that an outside diameter dimension of the concaveannular section is held within a range of 0.1-0.5 mm, and awidthwise center section of the concave annular section in radialcross section constitutes a flat section having smaller depthchange and greater radius of curvature than the widthwise sidesections.

[0071] In the method according this mode, a contact lens furnishedwith a mark having better visibility can be formed advantageously,while limiting enlargement and deepening of the mark. Specifically,by limiting the outside diameter dimension of the mark pattern tobetween 0.1 and 0.5 mm, the mark formed on the lens face throughtransfer of the mark pattern thereon can be kept to a small outsidediameter dimension. By forming a flat section in the concaveannular section of the mark pattern, it will be possible to limitdeepening of groove depth in an area corresponding to the concaveannular section of the mark so formed. At the same time, sinceformation of the flat section ensures a larger surface area in thearea corresponding to the concave annular section in the mark,greater levels of incident light and reflected light can beensured, and visibility can be improved.

[0072] A third mode of the second aspect of the present inventionprovides the method of manufacturing the contact lens according tothe first or second mode, wherein the mark pattern is formedthrough scanning of the laser beam in a circumferential directionby an equivalent of two or more scan lines in a radialdirection.

[0073] In the method according this mode, by scanning the laserbeam over multiple lines in the radial direction it is possible toadvantageously ensure sufficient radial width dimension for theconcave annular section, while at the same time allowing the markpattern to be formed with highly accurate adjustment of the radialwidth dimension of the concave annular section.

[0074] A fourth mode of the second aspect of the present inventionprovides the method of making a contact lens according to the thirdmode wherein, during scanning of the laser beam, a spacing of scansof the laser beam at a center axis thereof in the radial directionof the mark pattern is smaller than a spot of the laser beam.

[0075] In the method according this mode, the spot of the laserbeam can be scanned in overlapping fashion. It will be possiblethereby to reduce the anxiety of unprocessed portions or ridgesremaining at the scan line boundaries, and to advantageously form aflat section on the bottom face of the concave annular section.

[0076] A fifth mode of the second aspect of the present inventionprovides the method of making a contact lens according to any oneof the first to fourth modes, wherein the laser beam is a laserbeam with spot diameter of 0.05 mm or smaller.

[0077] In the method according this mode, a mark having peak andvalley dimensions such that lens strength will not suffer can beformed advantageously, while maintaining good visibility.Specifically, if the spot diameter of the laser beam exceeds 0.05mm, melting of the processing surface will occur over a widerrange, resulting in larger peaks and valleys of the rough surfacethat is formed on the flat section, which poses the anxiety ofreduced scattering of incident light and reduced visibility.Additionally, larger spot diameter is associated with greater depthdimension on the processing surface, with an anxiety of diminishedlens strength.

BRIEF DESCRIPTION OF THE DRAWINGS

[0078] The foregoing and/or other objects features and advantagesof the invention will become more apparent from the followingdescription of a preferred embodiment with reference to theaccompanying drawings in which like reference numerals designatelike elements and wherein;

[0079] FIG. 1 is a partially cutaway perspective view of a contactlens according to one embodiment of the present invention;

[0080] FIG. 2 is a top plane view of a grouped arrangement of marksformed on the contact lens of FIG. 1;

[0081] FIG. 3 is a front elevational view showing the marks of FIG.2;

[0082] FIG. 4 is a schematic view in a radial cross section of themarks of FIG. 2;

[0083] FIG. 5 is a vertical cross sectional view of a die formolding a female mold used in a manufacturing method according toone example of the present invention;

[0084] FIG. 6 is a vertical cross sectional view illustrating onestep of the manufacturing method of the present invention;

[0085] FIG. 7 is an enlarged view illustrating a principle part ofFIG. 6;

[0086] FIG. 8 is a front elevational view of mark patterns formedby the method of the present invention;

[0087] FIG. 9 is a vertical cross sectional view illustratinganother step of the manufacturing method of the presentinvention;

[0088] FIG. 10 is a vertical cross sectional view illustrating yetanother step of the manufacturing method of the presentinvention;

[0089] FIG. 11 is a front elevational view of mark patterns formedby a manufacturing method according to another example of thepresent invention;

[0090] FIGS. 12A, 12B and 12C are views showing the results ofsurface examination by differential interference microscope ofmarks; and

[0091] FIGS. 13A and 13B are views showing the results of surfaceexamination by scanning electron microscope.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0092] First, FIG. 1 depicts a marked contact lens (hereinafter"contact lens") 10 as one embodiment of the contact lens ofconstruction in accordance with the present invention. The contactlens 10 has a thin, generally spherical shell shape overall, and isadapted to be worn superimposed on the anterior face of the corneaof the eye. The term "wear" herein refers to use placed in thehuman eye.

[0093] To describe in greater detail, it is possible for thecontact lens 10 according to the embodiment to be embodied incontact lenses of various different kinds such as soft contactlenses, hard contact lenses, or disposable type contact lenses. Thecontact lens 10 employs a resin material composed of any of variouspolymerizable monomers endowed with optical properties such aslight transmissivity, specific examples being hydroxyethylmethacrylate (HEMA), polymethyl methacrylate (PMMA), celluloseacetate butyrate (CAB), silicone copolymers, fluorosiliconeacrylate, fluorocarbon polymers, or silicone rubber.

[0094] The contact lens 10 has a lens center axis 12 as its opticalaxis, and is of rotationally symmetric shape about the lens centeraxis 12. As a general rule, the radial direction of the contactlens 10 herein refers to the direction of a straight lineorthogonal to the lens center axis 12.

[0095] The contact lens 10 also has a lens anterior face 14 definedby a generally convex spherical face, and a lens posterior face 16defined by a generally concave spherical face. An anterior faceoptical zone 18 and a posterior face optical zone 20 are formed inthe center sections of the lens anterior and posterior facesrespectively; the anterior face optical zone 18 and a posteriorface optical zone 20 together constitute an optical zone 22. Here,any of a number of shapes, including high order polynomial, may beemployed as the radial cross sectional shape for the anterior faceoptical zone 18. In this embodiment in particular, the anteriorface optical zone 18 has a convex arcuate cross section ofgenerally constant radius of curvature.

[0096] Meanwhile, the posterior face optical zone 20 has a concaveshape generally corresponding to the shape of the anterior surfaceof the cornea, and employs a spherical or aspherical face with anappropriate of radius of curvature, so as produce the requiredoptical properties (such as vision correction ability) incooperation with the anterior face optical zone 18. In thisembodiment in particular, in order to impart vision-correctingoptical properties to the lens, a toric face is formed on theposterior face optical zone 20 so as to produce appropriatecylindrical power through an appropriate cylindrical axis.

[0097] Furthermore, in the optical zone 22 of this embodiment inparticular, the anterior face optical zone 18 and a posterior faceoptical zone 20 are each formed with the lens center axis 12 astheir geometric center axis, and the geometric center axis of theoptical zone 22 is the same as the lens center axis 12. Moreover,while in this embodiment in particular, the anterior face opticalzone 18 has a generally constant curvature radius thereby impartingthe optical zone 22 with a single spherical power, it would bepossible through appropriate design adjustment of the curvatureradius of the anterior face optical zone 18 to impart bifocalspherical power or multifocal spherical power, for example.

[0098] The optical zone 22 is the region intended to provideoptical effect to the eye of the wearer, and its outer peripheralborder, in other words its boundary with a peripheral zone 24(discussed later), typically takes the form of a change point ofcurvature on the longitudinal cross section of the lens anteriorface 14 and the lens posterior face 16 respectively; however, wherefor example the lens face of the optical zone 22 is designed with agradually changing longitudinal cross section in the radialdirection, or where the boundary is defined with prescribed widthin the radial direction by a connecting region that smoothlyconnects the optical zone 22 and the peripheral zone 24 between thelens anterior and posterior faces 14, 16, the boundary of theoptical zone 22 and the peripheral zone 24 on the lens anterior andposterior faces 14, 16 need not necessarily be a distinct line.

[0099] The peripheral zone 24 and an edge zone 26 are formed in theoutside peripheral section surrounding the optical zone 22. Theedge zone 26 has an annular shape at the outermost edge of thecontact lens 10, and in the lens longitudinal cross section isfurnished with lens anterior and posterior faces of chamfered shapeextending inward from the outer peripheral edge face of generallysemicircular shape. The lens anterior and posterior faces of theedge zone 26 connect with anterior and posterior face peripheralzones 28, 30.

[0100] The anterior face peripheral zone 28 and the posterior faceperipheral zone 30 respectively have generally annular shapesurrounding the anterior face optical zone 18 and the posteriorface optical zone 20 about their entire circumference, and aredisposed straddling the anterior and posterior face optical zones18, 20 and the edge zone 26 of the lens. The inner peripheralboundary sections of the anterior and posterior face peripheralzones 28, 30 respectively connect with the anterior and posteriorface optical zones 18, 20, while the outer peripheral boundarysections of the anterior and posterior face peripheral zones 28, 30connect with the edge zone 26. The anterior face peripheral zone 28and the posterior face peripheral zone 30 thereby cooperativelydefine the peripheral zone 24 situated peripherally outward fromthe optical zone 22 of the contact lens 10.

[0101] An indicia symbol 32 is made at a prescribed location on theanterior face peripheral zone 28. The indicia symbol 32 is providedfor the purpose of identifying the anterior or posterior face or acircumferential location on the contact lens 10, whether thecontact lens 10 is intended for wear in the left or right eye, orother such information, and no particular limitation is imposed asto the shape, size, or design thereof, it being possible to employany of various shapes, alphanumeric characters, graphic symbols, orthe like.

[0102] The indicia symbol 32 is composed of a plurality of marks 34of generally dot shape in a grouped arrangement. In thisembodiment, the marks 34 are arranged in six rows in the lensradial direction (the vertical direction in FIG. 2) and two rows inthe lens circumferential direction (the left-right direction inFIG. 2), for a total of 12 marks 34 creating the appearance of arectangle. With the indicia symbol 32 formed in a region located atthe 6 o'clock position during wear of the contact lens 10, with itslengthwise direction (the vertical direction in FIG. 2) extendingin the lens radial direction. Thus, when the contact lens 10 isworn at the correct circumferential position, the indicia symbol 32will indicate the 6 o'clock position in the eye.

[0103] The marks 34 that make up the indicia symbol 32 are similarin constitution to one another. A top view of a mark 34 is depictedin FIG. 3; and a model depiction of the diagonal cross section of amark 34 is depicted in FIG. 4. As will be discussed later, themarks 34 in this embodiment have been provided with a rough surfaceover their entire surface; to aid understanding, in FIG. 4, half ofthe radial cross section (the left half in FIG. 4) is depicted withpeaks and valleys (not to scale) to convey the impression of arough surface. In FIG. 4, for the other half of the radial crosssection (the right half in FIG. 4), an average surface of thesurface of the mark 34 is depicted in ideal form. The mark 34 isintegrally formed with the lens anterior face 14, with a generallyannular shape in plan view in the direction of the lens center axis12. Its shape includes a center projection 36 that projects outwardfrom the lens (in this embodiment, towards the lens anterior face)from the center section. A circumferential recess 38 constituted asa concave annular section that extends about the entirecircumference to the outside of the center projection 36 and thatis convex towards the lens exterior.

[0104] The center projection 36 gradually decreases in diameterdimension towards its projecting distal end, and at its projectingdistal end section has a generally truncated conical shape on whicha generally flat, projecting flat face 40 has been formed. In thisembodiment, as will be discussed later, since the entire surface ofthe mark is a rough surface, the projecting flat face 40 may beviewed as a plane in which an average line in the lens radial crosssection extends in a direction approximately orthogonal to thecenter axis 41 of the mark 34. Here, the projecting flat face 40will be formed with an outside diameter dimension of 0.02 mm.phi.or larger, preferably 0.05 mm.phi. or larger. If the outsidediameter dimension of the projecting flat face 40 is smaller than0.02 mm.phi., the center projection 36 will take on a pointedshape, posing the anxiety of catching on the eyelid etc. Inpreferred practice, the diameter dimension of the projecting flatface 40 will be made no larger than one-fifth the outside diameterdimension of the circumferential recess 38. If the diameterdimension of the projecting flat face 40 is larger than one-fifththe outside diameter dimension of the circumferential recess 38,the radial width dimension of the circumferential recess 38 will berelatively small, with the anxiety that the light scattering actionproduced by fine peaks and valleys (discussed later) thereon willnot be adequately achieved. In this embodiment, the outsidediameter dimension of the projecting flat face 40 is 0.02 mm.phi.with the contact lens 10 in the swelled condition. In the followingdescription, unless indicated otherwise, the dimensions of themarks 34 and the indicia symbol 32 formed by a grouping thereofrefer to dimensions with the contact lens 10 in the swelledcondition.

[0105] In order to avoid catching on the eyelid etc., theprojecting height dimension of the center projection 36 willpreferably not exceed the maximum depth dimension of thecircumferential recess 38 so that it does not protrude above thelens surface. In this embodiment, the projecting height dimensionof the center projection 36 is 0.024 mm, which is equal to thegroove depth dimension of the average face of a flat bottom face 42of the circumferential recess 38, discussed later.

[0106] Meanwhile, the circumferential recess 38 is of generallyannular shape having generally circular inner and outer peripheralborders. The recess is formed with generally unchanging radialwidth dimension about the entire circumference to the outside ofthe center projection 36, and with a cross section of recessedshape opening toward the lens exterior. Here, the outside diameterdimension of the circumferential recess 38 will be set to within arange between 0.1 mm and 0.5 mm, preferably between 0.2 mm and 0.3mm. Specifically, if the outside diameter dimension of thecircumferential recess 38 is smaller than 0.1 mm, the surface areaof the circumferential recess 38 will be too small, with theanxiety that the effect of scattering incident light will not beeffectively achieved, whereas if the outside diameter dimension ofthe circumferential recess 38 is larger than 0.5 mm, there is ananxiety of catching on the eyelid etc. In this embodiment, theoutside diameter dimension of the mark 34 is 0.23 mm. As noted,this dimension refers to that with the contact lens 10 in swelledcondition, and differs from the dimension on the die, discussedlater. In this embodiment, the outside diameter dimension of themark 34 on the die is 0.19 mm, for example.

[0107] In this embodiment in particular, the flat bottom face 42defining the flat section is formed on the bottom face of theradially medial section of the circumferential recess 38, and aboutthe entire circumference. Since the surface of the flat bottom face42 is a rough surface, the flat bottom face 42 herein refers to azone in which the depth variation of an average line in the lensradial cross section of the circumferential recess 38 is smallerthan the depth variation at either side in the width direction, andin which the radius of curvature is greater. Preferably, the radiusof curvature of the flat bottom face 42 will be greater by a factorof at least 10 than the minimum value of radius of curvature of theconnecting sections with the side wall sections of thecircumferential recess 38 at either side; and a substantially flatface having infinitely large radius of curvature would beacceptable as well. In this embodiment in particular, the flatbottom face 42 is defined by a zone through which an average linein the lens radial cross section of the circumferential recess 38extends in a generally straight line in the radial direction of themark 34; and the average face of the flat bottom face 42 is a flatsurface. Here, the width dimension: PL of the flat bottom face 42in the lens radial direction will preferably equal one-third orgreater of the width dimension: L of the circumferential recess 38in the lens radial direction, i.e., the width dimension L at theopening of the grooved contour of the circumferential recess 38 inthe radial direction. If the width dimension of the flat bottomface 42 is smaller than one-third the width dimension of thecircumferential recess 38, it will be difficult to ensure adequatesurface area of the flat bottom face 42, with the anxiety that theeffect of scattering incident light (discussed later) will not beeffectively achieved. Furthermore, the flatness of the flat bottomface 42 will be 5 .mu.m or less, preferably 2 .mu.m or less. By sodoing, deepening of the mark can be limited further. Herein,flatness refers to a value for a surface derived from an averagesurface of the rough surface. That is, it indicates variation ingroove depth dimension on the average surface, and is expressed asthe difference in depth dimension between the deepest point and theshallowest point. For example, where the flatness of the flatbottom face 42 is 5 .mu.m, in the transverse cross section of thegroove in which the rough surface is represented by an averagesurface, two points respectively having groove depth of -5 .mu.mwill be designated to either side in the width direction from thepoint of maximum depth, and the widthwise distance between thesetwo points will be equal to one-third or greater of the openingwidth dimension of the groove. In this embodiment in particular,the radial width dimension: PL of the mark 34 of the flat bottomface 42 is 0.036 mm.

[0108] The groove depth dimension of the circumferential recess 38in the average surface of the flat bottom face 42 will preferablybe set to within a range between 12 .mu.m and 36 .mu.m; in thisembodiment, it is 24 .mu.m. If the groove depth dimension is lessthan 12 .mu.m, the circumferential recess 38 will be too shallow,and as a result the surface area of the circumferential recess 38will be too small, posing an anxiety that the effect of scatteringincident light (discussed later) will not be effectively achieved;on the other hand, if greater than 36 .mu.m, there is anxiety thatthe circumferential recess 38 will be deep to the point that lensstrength is diminished.

[0109] As a ring shape small projecting portion that projectstowards the lens exterior about the entire circumference, an outerperipheral projection 44 is formed in the outside peripheralsection of the circumferential recess 38. The outer peripheralprojection 44 is of generally annular shape extending about theentire circumference with generally unchanging radial widthdimension. Here, the maximum height dimension: t of the outerperipheral projection 44 from the lens surface will preferably beset to no more than 1.8 .mu.m in order to minimize contact pressureagainst the eye for good wear comfort; in this embodiment, it setto 1 .mu.m.

[0110] The connecting section of the inner peripheral border of thecircumferential recess 38 with the center projection 36, and theconnecting section of the outer peripheral border of thecircumferential recess 38 with the outer peripheral projection 44,each have a radial cross section of smoothly curving shape, withthe center projection 36, the circumferential recess 38, and theouter peripheral projection 44 connecting smoothly to one another.Here, a radial cross section of smoothly curving shape refers to across sectional shape having gradually varying radius of curvatureoverall and devoid of inflection points, i.e. of turning pointslacking a common tangent. In this embodiment, since the entiresurface of the mark 34 is constituted as a rough surface, theradius of curvature of the average line of the rough surface in theradial cross section of the mark 34 will vary gradually, with noturning points.

[0111] Furthermore, in this embodiment the entire surface of themark 34 is a rough surface having fine peak and valley contoursformed thereon. The surface roughness of the rough surface may begenerally constant over the entire face of the mark 34; in thisembodiment however, the projecting flat face 40 of the centerprojection 36, the flat bottom face 42 of the circumferentialrecess 38, and the outer peripheral projection 44 that has beenformed in the outer peripheral section of the circumferentialrecess 38 have been given different surface roughness.Specifically, the surface roughness of the flat bottom face 42,expressed as the Ra value, is at least 0.2 .mu.m but not more than5 .mu.m. If the surface roughness Ra is less than 0.2 .mu.m, thesurface will not be substantially different from a slick, smoothsurface and will transmit most of the light impinging on the flatbottom face 42 so that effective scattering of incident light isnot achieved. The projecting flat face 40 of the center projection36 and the outer peripheral projection 44 have lower surfaceroughness in comparison with the flat bottom face 42.

[0112] A plurality of marks 34 having the above construction areformed in a grouped condition spaced apart at prescribed intervalsin the lens radial direction and in the lens circumferentialdirection to form the indicia symbol 32. Here, the distanceseparating mutually adjacent marks 34 will preferably be betweenone-third and twice the outside diameter dimension of the mark 34.If the gap between marks 34 is smaller than one-third the outsidediameter dimension, the plurality of marks 34 will be grouped tooclosely together, posing the anxiety of catching on the eyelid etc.during blinking so that the lens will tend to rotate, as well asthe anxiety of reduced lens strength due to the marks 34 being tooclose together; on the other hand, if the gap is greater than twicethe outside diameter dimension, the marks 34 will be too far apart,posing the anxiety of being less recognizable as the indicia symbol32. In this embodiment in particular, an indicia symbol 32 havingrectangular shape is formed by a total of twelve marks 34 arrangedin a 6.times.2 rows containing six marks 34 situated at equalintervals of approximately 0.08 mm in the lens radial direction(the vertical direction in FIG. 2) and two marks 34 situated atequal intervals of approximately 0.23 mm in the lenscircumferential direction (the left-right direction in FIG. 2). Itis not necessary for each of the marks 34 to be situated at equalintervals, and it would of course be possible for the marks 34 tobe situated at irregular intervals.

[0113] The indicia symbol 32 is formed at a location that will notoverlap the eyelid or the pupil during wear. Specifically, themarks 34 that make up the indicia symbol 32 will be formed in aregion located in the anterior face peripheral zone 28, between 2.7mm and 6.0 mm outwardly in the radial direction from the lenscenter axis 12 which is the lens center, so as to substantiallyavoid any effect on the optical characteristics of the lens.

[0114] Furthermore, the length dimension of the mark 34 groupingarea in the lens radial direction, in other words, the lengthdimension of the indicia symbol 32 in the lens radial direction,will be 2.2 mm or less, preferably 1.8 mm or less. If the lengthdimension of the indicia symbol 32 in the lens radial direction isgreater than 2.2 mm, there is an anxiety of it overlapping thepupil; of catching on the eyelid and producing a sensation of aforeign body; or that the indicia symbol 32 will stand out to thepoint that appearance during wear suffers. The indicia symbol 32 inthis embodiment has length dimension of 1.78 mm in the lens radialdirection, and length dimension of 0.69 mm in the lenscircumferential direction.

[0115] In the marked contact lens 10 of the above construction,when light impinges on the mark 34, since the entire face of themark 34 is a rough surface, scattering of the incident light willbe produced by the fine peak and valley contours on the roughsurface. Thus, the surface of the mark 34 will take on a brightappearance overall, improving visibility. Moreover, since thesurface is roughened, transmission of incident light will bereduced so that the scattering effect is produced more effectively.Additionally, due to the flat bottom face 42 being formed in thecircumferential recess 38, a larger surface area for thecircumferential recess 38 can be ensured, and thus a greater amountincident light can be captured so that the scattering effect isproduced more effectively; moreover, the groove depth of thecircumferential recess 38 can made shallower in comparison to thecase where the flat bottom face 42 is not provided, therebylimiting deepening of the mark 34 and advantageously ensuring lensstrength. Moreover, since the projecting flat face 40 of the centerprojection 36, the flat bottom face 42 of the circumferentialrecess 38, and the outer peripheral projection 44 have differingsurface roughness, the light scattering effect will differ amongthem as well, thus giving rise to areas with different levels ofvisibility, so that visibility may be improved. Furthermore, due tothe truncated conical shape of the center projection 36, thedifference in the direction of light reflection by the projectingflat face 40 and by the inside peripheral wall of thecircumferential recess 38 can be increased, thereby furtherimproving visibility. In the same way, by forming the outerperipheral projection 44 on the outer peripheral section of thecircumferential recess 38, the difference in the direction of lightreflection by the circumferential recess 38 and by the outerperipheral projection 44 can be increased, thereby improvingvisibility.

[0116] Additionally, when light impinges on the mark 34, the shadowof the center projection 36 will be cast onto the circumferentialrecess 38. This will produce distinct contrast owing to thescattering of incident light on the circumferential recess 38 andthe shadow of the center projection 36, improving the visibility ofthe mark 34 as a result.

[0117] In the marked contact lens 10 constructed according to thisembodiment, effective visibility can be achieved withoutenlargement or deepening of the marks 34. Moreover, since effectivevisibility can be achieved without enlargement of the marks 34, theindicia symbol 32 that is formed by grouping a plurality of marks34 can be formed with effective visibility, while at the same timelimiting enlargement. The indicia symbol 32 can thereby be mademore compact, so that on the surface of a contact lens 10 having alimited area for depiction, the indicia symbol 32 can be smaller,or more indicia symbols 32 can be formed within a prescribedsurface area, so that more information can be represented.

[0118] Furthermore, in the present embodiment, the connectingsection of the inside peripheral border of the circumferentialrecess 38 with the center projection 36 formed in the mark 34, andthe connecting section of the outside peripheral border of thecircumferential recess 38 with the lens anterior face 14, each haveradial cross section of smoothly curving shape in radial crosssection. Catching on the eyelid, the cornea, etc. can be avoidedthereby, thus advantageously reducing the anxiety of a sensation ofa foreign object or of injury to the anterior of the eye due toincreased irritation, as well as advantageously preventing rotationof the lens due to catching.

[0119] Next, a specific example of a method advantageously usedduring manufacture of such a marked contact lens 10 will bedescribed.

[0120] First, as depicted in FIG. 5, a female mold die 60 and amale mold die (not shown) are prepared as the mold dies. The maleand female mold dies are used to manufacture independently alens-molding resin female form 62 and a lens-molding resin maleform 64, which cooperate to form a lens-molding resin mold (seeFIG. 10), by means of known resin molding techniques. These resinmale and female forms 62, 64 are prepared in order to produce themarked contact lens 10 through mold-forming (polymerization). Thesemold dies favorably employ stainless steel, aluminum, high speedsteel, prehardened steel or the like suitable for laser machining,discussed later. However, other metal materials may be used. Inthis embodiment in particular, STAVAX (TM) is used.

[0121] FIG. 5 depicts the female mold die 60. The female mold die60 is composed of a female molding upper die 60a and a femalemolding lower die 60b, mounted onto the fixed platen of a lockingdevice, not shown. The female molding upper die 60a is composed ofan upper die base 66 and an upper die core 68 that are respectivelymounted fixedly on mounting plates (not shown) that are affixed tothe fixed platen. The upper die base 66 has an oblong block shape,and is provided in its center section with an installation opening70 passing through it in the mold mating direction. The upper diecore 68 is installed fitting into the installation opening 70. Aresin molding face 72 of convex spherical shape constituting amolding face is formed in the center section of the lower end faceof the upper die core 68. This convex resin molding face 72 has ashape corresponding to the generally spherical convex shape of thelens anterior face 14 of the contact lens 10.

[0122] Meanwhile, the female molding lower die 60b is composed of alower die base 74 and a lower die core 76 that are respectivelymounted fixedly on mounting plates (not shown) affixed to the fixedplaten. The lower die base 74 has an oblong block shape, and isprovided in its center section with an installation opening 78passing through it in the mold mating direction. The lower die core76 is installed fitting into the installation opening 78. A resinmolding face 80 of concave spherical shape is formed in the centersection of the upper end face of the lower die core 76.

[0123] The female molding upper die 60a and the female moldinglower die 60b are then closed in the axial direction (the verticaldirection in FIG. 5) by the locking device (not shown), therebyforming a mold cavity 82 between the mating faces of the dies 60a,60b. This mold cavity 82 is then filled with a thermoplastic resinmaterial injected by an injection molding device (not shown) forexample, and the resin is cooled and solidified. Examples ofthermoplastic resin materials are polypropylene, polyethylene,polyethylene terephthalate, polystyrene, polycarbonate, vinylchloride, nylon, polyacetal, fluororesin, and so on; while any ofthese may be used, polypropylene is used in this embodiment. Themolded article of resin material is then removed by parting thedies 60a, 60b. The lens-molding resin female form 62 (see FIG. 10)is obtained thereby. Here, a concave spherical-shaped, lens-moldingface 84 of the lens-molding resin female form 62 has been formed bythe resin molding face 72 of the upper die core 68, thereby givingit a shape that corresponds to the lens anterior face 14 of thecontact lens 10.

[0124] Meanwhile, like the female mold die 60, the male mold die iscomposed of a male molding upper die and a male molding lower die,with a mold cavity corresponding in shape to the lens-molding resinmale form 64 (see FIG. 10) defined between the mating surfaces ofthe two dies; using the male mold die, the lens-molding resin maleform 64 is molded by an operation similar to that for the femalemold die 60. Since the construction of the male mold die issubstantially identical to that of the female mold die 60, the malemold die has been omitted from the illustration here. Then, using athermoplastic resin material and the male mold die, thelens-molding resin male form 64 will be obtained by a resin moldingmethod similar to that for the lens-molding resin female form 62.Here, a convex spherical-shaped, lens-molding face 86 of thelens-molding resin male form 64 has been formed by the convex resinmolding face of the upper die core, thereby giving it a shape thatcorresponds to the lens posterior face 16 of the contact lens10.

[0125] In this embodiment in particular, engraved marks 88 servingas mark patterns are formed on the resin molding face 72 of theupper die core 68 of the female mold die 60 by means of lasermachining at locations corresponding to the marks 34 of the contactlens 10, while the die is immersed in liquid.

[0126] As depicted in model form in FIG. 6, in this embodiment, atank 90 open at the top is filled with a liquid 92. While any ofvarious liquids can be employed as the liquid 92, in thisembodiment, distilled water is used so as to limit the reduction inenergy of the laser beam caused by admixed impurities. Here, whileno particular limitation is imposed as to the temperature of theliquid 92, in this embodiment it is set to normal temperature ofbetween 20.degree. C. and 25.degree. C.

[0127] A jig 94 for supporting the upper die core 68 is disposedwithin the tank 90. An insertion opening 96 that opens upward onthe diagonal with respect to plumb vertical is formed in the jig94, and the upper die core 68 is supported inserted into theinsertion opening 96 By so doing, the upper die core 68 issupported on the jig 94, held with its axial direction inclineddiagonally with respect to plumb vertical and with the resinmolding face 72 facing up. In this embodiment in particular, theangle of incline: .alpha. of the axial direction of the upper diecore 68 with respect to plumb vertical is .alpha.=26.degree..

[0128] Furthermore, the entire upper die core 68 inclusive of theresin molding face 72 is submerged in the liquid 92; and as shownin FIG. 7, on the resin molding face 72, an irradiation site 98constituting a location that corresponds to the desired marks 34 ofthe contact lens 10 is submerged in the liquid 92. In thisembodiment in particular, as depicted in FIG. 7, the shape of thejig 94 and the depth of the liquid 92 have been adjusted such thatthe depth: D1 down to the irradiation site 98 from the surface ofthe liquid 92 is 5 mm.

[0129] A laser machining unit 100 is installed in the air above theupper die core 68 which has been supported on the jig 94. The laserused in this manufacturing method herein may be any of the variouskinds of lasers suitable for machining of molds, for example, a YAGlaser, a carbon dioxide laser, an excimer laser, a semiconductorlaser or the like; it would also be favorable to employ afemtosecond laser that produces pulses of extremely short duration(10.sup.-15 s) so as to have less thermal effect on the workpiecethan do other lasers. Any of the commercially available lasermachining devices may be employed as the laser machining unit 100,for example, YVO.sub.4 LASER MARKER MD-V9600 made by Keyence Co.Ltd. In this embodiment, a Class 4 YVO.sub.4 laser is used as thelaser; the laser has a wavelength of 1064 nm, Q switching frequencyof 10 kHz, and output equal to 50% (3 W) of the YVO.sub.4 LASERMARKER MD-V9600 made by Keyence Co. Ltd.

[0130] In preferred practice, the laser employed in themanufacturing method herein will be one producing a spot diameterof 0.05 mm or smaller; in this embodiment, a laser having a spotdiameter of 0.04 mm is used. In the manufacturing method herein,since laser machining is carried out in liquid, the spot diameterof the laser is identified by the diameter at the irradiation site98 on the submerged upper die core 68.

[0131] A glass plate 102 functioning as wave suppression plate isdisposed on the surface of the liquid 92. The glass plate 102 is alight-transmissive component having a flat input face 104 and anoutput face 106; in this embodiment, BK7 with a diameter dimensionof 32 mm and thickness of 6 mm is used. The glass plate 102 isimmersed in the liquid 92 by one-third to one-half its thicknessdimension. By so doing, the input face 104 will be positioned abovethe surface of the liquid and exposed to the air, while the outputface 106 is submerged in liquid.

[0132] A filter pump 108 functioning as a water circulating unit isdisposed on the inside face of the wall of the tank 90, on the sidethereof opposite from the jig 94. The filter pump 108 may be any ofthose known in the prior art. Here, the height location of thespout 110 of the filter pump 108 is positioned at a heightapproximately equal to the height location of the irradiation site98 of the upper die core 68 supported on the jig 94.

[0133] By driving the filter pump 108, a current of water iscreated in the liquid 92 between the resin molding face 72 and theglass plate 102, and flows from the spout 110 towards the upper diecore 68 (from right to left in FIG. 6). Under these conditions, thelaser light from the laser machining unit 100 will be directed withthe optical axis: I aligned with the plumb vertical direction.After entering the input face 104 of the glass plate 102, the laserwill pass through the glass plate 102 and exit from the output face106, passing through the liquid 92 to irradiate the irradiationsite 98 on the upper die core 68.

[0134] Here, as depicted in FIG. 7, since the laser light output bythe laser machining unit 100 undergoes deflection as it enters theglass plate 102 and the liquid 92, the focal point location: Pwwithin the liquid 92 will be shifted upward as compared to thefocal point location: Pa in air. Accordingly, in this embodiment,the focal point location: Pw within the liquid 92 will be set toone below the irradiation site 98, at a distance: D2=1.00 mm in theplumb vertical direction.

[0135] The laser output by the laser machining unit 100 istransmitted through the liquid 92 and scanned a prescribed numberof times at prescribed pitch over the irradiation site 98, therebyinducing melting at the irradiation site 98 and producing at theirradiation site 98 an engraved mark 88 of annular shapecorresponding to the shape of the mark 34.

[0136] In this instance, the laser will preferably be scanned inthe circumferential direction for two or more lines, and preferablyfor four or more lines, in the radial direction of the targetengraved marks 88. By so doing, concave contours of annular shapecorresponding to the circumferential recesses 38 of the marks 34will be produced in the machined portions 114 (see FIG. 8) thathave been scanned with the laser beam; and lands corresponding tothe center projections 36 will be produced in the centernon-machined areas 116 that were not scanned by the laser. Bysetting the number of scan lines to four or greater, melted zonescreated through laser machining and connecting between adjacentscan lines can be produced in succession, and flat contourscorresponding to the flat bottom face 42 of the circumferentialrecess 38 can be produced advantageously, while endowing the flatbottom face 42 with radial width dimension adequate to effectivelyafford increased surface area of the circumferential recess 38 andprevent deepening of the marks 34. In this manufacturing method inparticular, the number of laser scan passes is equivalent to fivelines. In preferred practice, in the engraved marks 88, the outsidediameter dimension of the machined portion 114 corresponding to thecircumferential recess 38 will be set to within a range of between0.1 and 0.5 mm. In this embodiment, the dimension is 0.13 mm. Thescanning direction of the laser beam in the radial direction of theengraved marks 88 can be a single direction only, e.g. radiallyoutward from the center of the engraved marks 88; or reciprocatingscans can be carried out an appropriate number of times in theradial direction of the engraved marks 88.

[0137] The scan spacing of the laser beam is preferably such thatthe spacing of the center axis of the laser beam in the radialdirection of the engraved marks 88 is smaller than the spotdiameter of the laser beam, specifically, 0.03 mm or less andpreferably 0.01 mm or less. In this method in particular, thecenter axis of the laser beam is scanned at intervals of 0.01 mm.By so doing, scanning can take place with the laser spotoverlapping between adjacent scan lines, thereby reducing theanxiety that any unprocessed portions or ridges will remain at thescan line boundaries, so that flat contours corresponding to theflat bottom faces 42 can be formed advantageously.

[0138] In this way, engraved marks 88 serving as mark patternshaving shape that corresponds to the marks 34 are produced on theresin molding face 72 of the upper die core 68 as depicted in FIG.8. A plurality of these engraved marks 88 are produced by formingthe contours of the engraved mark 88 at a prescribed plurality ofsites on the resin molding face 72 of the upper die core 68, and anindicia symbol engraved mark 112 that corresponds to the indiciasymbol 32 will be formed by the plurality of engraved marks 88.

[0139] In this method in particular, a total of twelve engravedmarks 88 are created by producing the engraved marks 88 in groupsof six in the radial direction of the resin molding face 72 (thevertical direction in FIG. 8) and in groups of two in thecircumferential direction of the resin molding face 72 (theleft-right direction in FIG. 8) at prescribed spacing. Theseengraved marks 88 form the indicia symbol engraved mark 112. Here,the outside diameter dimension of the engraved marks 88 is 0.13 mm,and the outside diameter dimension of the center non-machined area116 that corresponds to the center projection 36 in the engravedmarks 88 is 0.08 mm. The distance dimension between outerperipheral borders of the engraved marks 88 in the radial directionof the resin molding face 72 is 0.13 mm, while the distancedimension between center axes of the engraved marks 88 in thecircumferential direction of the resin molding face 72 is 0.39 mm.Thus, the indicia symbol engraved mark 112 will have a dimension of1.44 mm in the radial direction of the resin molding face 72, and adimension of 0.52 mm in the circumferential direction of the resinmolding face 72. The specific dimensions of the engraved marks 88and of the indicia symbol engraved mark 112 formed by the pluralityof engraved marks 88 do not correspond to the dimensions of themarks 34 formed on the contact lens 10 that was described in thepreceding embodiment, and are shown here by way of specificexemplary die dimensions according to a different mode from themarks 34 described previously. Accordingly, the specific dimensionsof the marks formed in accordance with this manufacturing methodwill differ from the specific dimensions of the marks 34 taught inthe preceding embodiment.

[0140] In the course of resin molding of the lens-molding resinfemale form 62 using the female mold die 60 with the engraved marks88 formed thereon, the engraved marks 88 that have been formed onthe resin molding face 72 of the female mold die 60 will betransferred to the lens-molding face 84 of the lens-molding resinfemale form 62. As a result, mark projections 118 that correspondto the marks 34 will be formed on the lens-molding face 84 of thelens-molding resin female form 62, in sections thereofcorresponding to the locations for forming the target marks 34 onthe contact lens 10.

[0141] Next, the lens-molding resin female form 62 having the markprojections 118 formed thereon, and the lens-molding resin maleform 64 that has been obtained through resin molding using the malemold die, are used to mold the target marked contact lens 10.

[0142] For this process, first, as depicted in FIG. 9, thelens-molding resin female form 62 is supported with its openingfacing vertically upward; and through an injection tube 120, apolymerizable monomer 122 serving as the material for the contactlens 10 is injected into the tray-shaped zone formed by the concavelens-molding face 84. This polymerizable monomer 122 can be any ofvarious appropriate liquid monomer compositions commonly used asmaterials for soft contact lenses or hard contact lenses. Forexample, compositions incorporating one or more types of radicalpolymerizable compounds, or composed of macromers or prepolymerscould be used. The compounds may be optionally combined withappropriate crosslinking agents, sensitizers, thermalpolymerization initiators, photopolymerization initiators, and soon. In this embodiment, a silicone-containing soft contact lensmaterial is used.

[0143] Next, as depicted in FIG. 10, the lens-molding resin maleform 64 is juxtaposed against and fitted into the lens-moldingresin female form 62 in the axial direction (the vertical in FIG.10) from vertically above the lens-molding resin female form 62,thereby defining a sealed mold cavity 124 that is filled with thepolymerizable monomer 122. While maintaining the forms 62, 64 inthe mated state, the polymerizable monomer 122 is subjected to apolymerization process. The polymerization process may be aphotopolymerization process, thermal polymerization process, etc.selected appropriately according to the polymerizable monomer 122being used.

[0144] After polymerizing the polymerizable monomer 122, thelens-molding resin female form 62 and the lens-molding resin maleform 64 are parted and the polymerized molded article, namely thecontact lens 10, is released from the mold to obtain the desiredmarked contact lens 10. Mold release of the contact lens 10 can beaccomplished, for example, by inducing bending deformation of thelens-molding face 86 through squashing of the cylindrical portionof the lens-molding resin male form 64 in the axis-perpendiculardirection so that the contact lens 10 adhering to the lens-moldingface 86 of the parted lens-molding resin male form 64 is releasedfrom the lens-molding face 86; or by release using an appropriatechemical product.

[0145] In the contact lens 10 that has been polymerization-moldedand released from the mold in the above manner, the lens anteriorface 14 has been shaped by the contours of the lens-molding face 84of the lens-molding resin female form 62, while the lens posteriorface 16 has been shaped by the contours of the lens-molding face 86of the lens-molding resin male form 64. The engraved marks 88 thatwere formed on the resin molding face 72 of the upper die core 68that makes up the female mold die 60 were transferred as markprojections 118 to the lens-molding face 84 of the lens-moldingresin female form 62, and in turn the mark projections 118 havebeen transferred to the lens anterior face 14 of the contact lens10, thereby forming concave marks 34 of contours corresponding tothe engraved marks 88, at the desired locations in the peripheralzone of the contact lens 10, with the plurality of marks 34 makingup the indicia symbol 32.

[0146] According to this manufacturing method, through lasermachining carried out in a liquid, rough surfaces having fine peakand valley contours can be formed on the surfaces of the engravedmarks 88, and hence on the surfaces of the marks 34, so that therough surfaces can be formed with a high degree of surfaceroughness. Thus, it will be possible for scattering of light to beeffectively produced at the surface of the marks 34, improvingvisibility. At the same time, uplift of the outer peripheral edgesof the engraved marks 88, and accordingly uplift of the outerperipheral projections 44 situated at the outer peripheral bordersof the marks 34, can be kept to a minimum. Contact pressure againstthe eyelid can be minimized thereby, and good wear comfort can beachieved.

[0147] While the scientific basis for the fact that the engravedmarks 88 can be formed with a high degree of surface roughnesswhile limiting uplift of their outer peripheral edges where lasermachining is carried out with the irradiation site 98 submerged inthe liquid 92 is not entirely clear, it is not an object of thisinvention to elucidate the scientific basis; however, in relationto the ability to produce a high degree of surface roughness, it isthought that the fact that the process takes place in liquid meansthat evolution of heat in the vicinity of the focal point locationwill be limited so that melting takes place intensively at thefocal point location, and that redeposition of swarf produced bylaser processing onto the irradiation site 98 will be limited,thereby avoiding any reduction in energy density of the laser beamcaused by swarf. With regard to why uplift of their outerperipheral edges is limited, it is thought that the fact that theprocess takes place in liquid means that there will be less bulgingat the outer peripheral border of the engraved marks 88 due tothermal deformation, owing to reduced evolution of heat in thevicinity of the irradiation site 98.

[0148] In this embodiment in particular, the filter pump 108creates a current of water flowing approximately orthogonal to thelaser beam irradiation axis: I between the irradiation site 98 andthe glass plate 102. Thus, during laser machining, air bubbles andswarf produced at the irradiation site 98 during laser machiningwill be carried away from on the laser beam irradiation axis: I bythe current of water. It will therefore be possible to reduce theanxiety of the laser beam hitting a location different from theintended location due to deflection caused by interference of thelaser beam with air bubbles, and of reduced energy of the laserbeam due to swarf, so that better machining accuracy may beachieved. Furthermore, since swarf is carried away by the current,better washing action can be achieved as well.

[0149] Additionally, in this mode, the glass plate 102 ispositioned on the surface of the liquid 92 so that the laser beamwill enter the flat input face 104 of the glass plate 102. Thus,deflection of the laser beam in a direction other than the intendedone due to waves forming on the surface of the liquid 92 can belimited, and better machining accuracy may be achieved. In thismode in particular, while waves are more likely to form on thesurface of the liquid 92 due to the use of the filter pump 108, byproviding the glass plate 102 it is possible to advantageouslyavoid the effects of waves.

[0150] In this manufacturing method, the engraved marks 88 areproduced on the female mold die 60 through laser machining, and theengraved marks 88 are then transferred to the lens anterior face 14through the agency of the lens-molding resin female form 62. Forthis reason, even where contact lenses 10 furnished with marks 34are manufactured in large quantities, the labor entailed by lasermachining of each individual contact lens 10 can be avoided, andproductivity can be improved. Moreover, in this manufacturingmethod, by carrying out laser machining in liquid, swarf producedduring laser machining can be prevented from becoming deposited onthe die, obviating the need for a washing process to remove theswarf, so that better production efficiency is afforded.

[0151] The specific shape, size, etc. of the indicia symbol 32 andthe marks 34 constituting it described in the embodiment herein, aswell of as the indicia symbol engraved mark 112 and the engravedmarks 88 constituting it described by way of one specific exampleof the manufacturing method herein, are merely exemplary, and thespecific modes of the present invention are not limited to themodes hereinabove. For example, according to a second specificexample of a manufacturing method according to the presentinvention, it would be possible to form an indicia symbol engravedmark 130 and engraved marks 132 constituting it, like thosedepicted in FIG. 11. In the following description, elementssubstantially like those of the embodiment and method hereinaboveare assigned like symbols and will not be described in anydetail.

[0152] In this embodiment, two engraved marks 132 are formed linedup and spaced apart by a prescribed distance in the radialdirection of the resin molding face 72 on the resin molding face 72of the upper die core 68; the indicia symbol engraved mark 130 iscomposed of these two engraved marks 132.

[0153] To describe in detail, these two engraved marks 132 havemutually similar shape, with each engraved mark 132 differing insize from the engraved marks 88 described in the precedingmanufacturing method, but similar in shape to the engraved marks88. Specifically, the engraved marks 132 have a machined portion114 of annular concave shape of contours similar to the engravedmarks 88 described earlier, formed by scanning of the laser in thecircumferential direction; and in the center section of themachined portion 114, a center non-machined area 116 not scanned bythe laser.

[0154] In this manufacturing method in particular, the outsidediameter dimension of the engraved marks 132 is 0.36 mm and theoutside diameter dimension of the center non-machined areas 116 is0.1 mm. Two of these engraved marks 132 are formed with theiroutermost peripheral edge portions space apart from one another bya distance of 0.72 mm in the radial direction of the resin moldingface 72 (the vertical direction in FIG. 11). Thus, in thismanufacturing method, the dimension of the indicia symbol engravedmark 130 in the radial direction of the resin molding face 72 willbe 1.44 mm.

[0155] While one embodiment and a number of manufacturing methodsaccording to the present invention have been described in detailhereinabove, these are merely exemplary, and the embodiments andmanufacturing method of the present invention should in no way beconstrued as limited to the specific disclosure herein.

[0156] For example, the projecting flat face 40 that is formed onthe projecting distal end of the center projection 36 of the mark34 is not always necessary, and the projecting distal end of thecenter projection 36 could instead be constituted as a convexspherical curving face, or as a point substantially devoid of anyflat surface. In these cases as well, since the inside peripheralwall of the circumferential recess 38 is generally conical, thedirection of light reflection at the surface of the mark 34 willdiffer, producing the effect of improved visibility owing to thepresence of the center projection 36.

[0157] In the marks 34 described above, the surface roughness ofthe flat bottom face 42 of the circumferential recess 38 and thesurface roughness of the distal end face of the center projection36 differ from one another, as does the surface roughness of theflat bottom face 42 and the surface roughness of the outerperipheral projection 44. However, it is possible for surfaceroughness of these to be made the same. Provided that the roughsurface of the mark 34 has been formed on at least the flat bottomface 42, it is not necessary for the mark 34 to have a roughsurface over its entire surface.

[0158] Additionally, whereas in the preceding embodiment, contactagainst the cornea was avoided by forming the marks 34 on the lensanterior face 14, no limitation is imposed that the marks of thepresent invention must be formed on the lens anterior face, and itwould be possible to form them on the lens posterior faceinstead.

[0159] The present invention is not necessarily limited to toriclenses, and may be utilized for the purpose of indicatingcircumferential position in a bifocal lens or other lens that, likea toric lens, requires positioning in the circumferentialdirection; or where the marks of the present invention are employedfor the purpose of identifying whether a lens is for use in theright or left eye, they may be utilized in a single focus lens aswell.

[0160] Furthermore, in the manufacturing methods described above,while a mode employing a combination of a glass plate 102 and afilter pump 108 was shown by way of example, it would of course bepossible to employ either the glass plate 102 or a filter pump 108without the other. Also, no particular limitation is imposedregarding the specific construction of the water circulating unit.For example, instead of using pressure means such as the abovefilter pump 108 as the water circulating unit, a motor ofwaterproof construction could be installed in the tank 90, a screwattached to the output shaft of the motor, and the water circulatedby turning of the screw.

[0161] The manufacturing methods described above are merelyexemplary; the method for producing the mark pattern on the formingdie is not limited to laser machining as described above, it beingpossible instead, for example, to employ a so-called chemicaletching process whereby the forming die is fabricated from steel,electroless nickel, etc., and with the forming die immersed insodium chloride solution or the like, one electrode is hooked up tothe forming die, while another electrode is disposed in proximityto the surface of the forming die on which the mark pattern is tobe formed, and electrical current is then applied thereby givingrise to chemical etching of the mark pattern into the surface ofthe forming die.

EXAMPLE 1

[0162] Example 1 below describes an experiment conducted for thepurpose of demonstrating the technological advantages of contactlenses according to the present invention.

[0163] First, two STAVAX (TM) female forming dies were prepared,and in accordance with the manufacturing method described above, amark pattern (see FIG. 8) was produced on one of the female formingdies by way of a first manufacturing method, and a mark pattern(see FIG. 11) was produced on the other female forming die by wayof a second manufacturing method. Both of the female forming dieswere forming dies for soft contact lenses having a base curveradius of curvature (B. C.) of 8.6 mm on the lens posterior face,lens strength (diopter) of -3.00 in the optical zone, and lensoutside diameter (DIA) of 14.0 mm.

[0164] Designating the mark pattern produced according to the firstmanufacturing method and the marks formed by transfer of this markpattern as Example 1a, and designating the mark pattern producedaccording to the second manufacturing method and the marks formedby transfer of this mark pattern as Example 1b, the marks formed onthe contact lens surfaces were subjected to surface examinationusing a differential interference microscope and to depthmeasurement using a scanning probe microscope (AFM), while thecross section of the mark patterns formed in the female formingdies was subjected to surface examination using a scanning electronmicroscope (SEM). The differential interference microscope was anECLIPS600 by Nikon; the scanning probe microscope was anSPI3800N/SPA300 by Seiko Instruments; and the scanning electronmicroscope was a JSM-5410LV by JEOL.

[0165] FIG. 12(a) shows the results of surface examination bydifferential interference microscope of marks 34a in Example 1a;FIG. 12(b) shows the results of surface examination by differentialinterference microscope of marks 34b in Example 1b. By way of acomparative example, FIG. 12(c) shows the results of surfaceexamination by differential interference microscope of marksproduced using a collimating laser such as YAG in accordance with aconventional manufacturing technique. As will be apparent from FIG.12(a) and (b), the manufacturing methods according to the presentinvention and the marks produced in accordance therewith have acircumferential recess 38 (convex annular section) and a centerprojection 36. The surfaces of the marks, and particularly thesurface of the circumferential recess 38, are rough surfaces havingfine peak and valley contours resembling a grainy texture. Incontrast, it can be seen from FIG. 12(c) that the marks produced bythe conventional manufacturing technique have slick surfaces whosesurfaces are smooth.

[0166] FIG. 13(a) depicts a cross section in the radial directionof an engraved mark 88 as a mark pattern on the die of Example 1a,taken through surface examination by scanning electron microscope(SEM); and FIG. 13(b) depicts a cross section in the radialdirection of an engraved mark 88 as a mark pattern on the die ofExample 1b, taken through surface examination by scanning electronmicroscope (SEM). As will be apparent from FIGS. 13(a) and (b), themark patterns according to the present invention have acircumferential recess 38 of concave shape and a center projection36 of convex shape. It can be seen that a flat bottom face 42 isformed on the bottom face of the circumferential recess 38, therebylimiting deepening of the mark. The gouge-like groove 134 formed onthe bottom face of the circumferential recess 38 in FIG. 13(a) is aburr that formed during cutting.

[0167] Scanning probe microscope (AFM) measurements of depthdimension of marks produced on the contact lenses gave a result of18.8 .mu.m for the mark of Example 1a, and 22.4 .mu.m for the markof Example 1b.

EXAMPLE 2

TABLE-US-00001 [0168] TABLE 1 Evaluation item Class DescriptionLens rotation, position .largecircle. Lens rotation, position shiftnot shift observed in any examined eye .DELTA. Lens rotation,position shift observed in <20% of examined eyes X Lensrotation, position shift observed in .gtoreq.20% of examined eyesVisibility to examiner .largecircle. No lack of visibility observedin any examined eye .DELTA. Lack of visibility observed in <20%of examined eyes X Lack of visibility observed in .gtoreq.20% ofexamined eyes Visibility to wearer .largecircle. No lack ofvisibility observed in any examined eye .DELTA. Lack of visibilityobserved in <20% of examined eyes X Lack of visibility observedin .gtoreq.20% of examined eyes

TABLE-US-00002 TABLE 2 Mark outside dia. (mm) .times. number ofmarks Evaluationitem ##STR00001## ##STR00002## ##STR00003####STR00004## ##STR00005## Lens rotation, X .DELTA. .largecircle..largecircle. .largecircle. position shift Visibility to.largecircle. .largecircle. .largecircle. .largecircle..largecircle. examiner Visibility to .DELTA. .DELTA. .DELTA..largecircle. .largecircle. wearer

[0169] Next, with the length dimension in the lens radial directionof indicia symbols formed by groupings of marks set to a fixedvalue of 1.8 mm, and the distance from the lens center to the lowerend of the indicia symbol (the radially outer edge of the lens) setto a fixed value of 5.0 mm, the items indicated in Table 1 wereevaluated while varying the radial dimension of the marks. For eachitem, results of evaluation carried out on 100 examined eyes of 50subjects are shown in FIG. 2. While the marks are depicted ascircular in Table 2, this is done for simplicity in illustration;the actual marks used in the evaluations have a centerprojection.

[0170] As will be apparent from Table 2, the marks according to thepresent invention were observed to give good results with outsidediameter dimensions within the range of between 0.2 mm and 0.5 mm.In particular, good results for all evaluated items were obtainedat outside diameter dimensions within the range of between 0.2 mmand 0.3 mm, thus demonstrating that outside diameter dimensions ofbetween 0.2 mm and 0.3 mm are particularly favorable for the marksaccording to the present invention.

EXAMPLE 3

TABLE-US-00003 [0171] TABLE 3 Evaluation item Class DescriptionAnterior eye .largecircle. No cases of aggravation problems .DELTA.Cases of aggravation observed, but none to (hyperemia of the anextent making wear impossible palpebral X Cases of aggravation toan extent making conjuctiva, wear impossible observed lacrimalpapilla hypertrophy) Lens rotation, .largecircle. Lens rotation,position shift not observed in position shift any examined eye.DELTA. Lens rotation, position shift observed in <20% ofexamined eyes X Lens rotation, position shift observed in.gtoreq.20% of examined eyes Visibility to .largecircle. No lack ofvisibility observed in any examiner examined eye .DELTA. Lack ofvisibility observed in <20% of examined eyes X Lack ofvisibility observed in .gtoreq.20% of examined eyes Visual field.largecircle. No effect on sight observed in any impairment (effectexamined eye on sight) .DELTA. Effect on sight observed in <20%of examined eyes X Effect on sight observed in .gtoreq.20% ofexamined eyes Visibility to .largecircle. No lack of visibilityobserved in any wearer examined eye .DELTA. Lack of visibilityobserved in <20% of examined eyes X Lack of visibility observedin .gtoreq.20% of examined eyes

TABLE-US-00004 TABLE 4 Distance from lens center to mark lower edge(mm) Mark shape Evaluation item 7 6.5 6 5.5 5 4.5 4 3.5 With centerAnterior eye X .DELTA. .largecircle. .largecircle. .largecircle..largecircle. .largecircle. .largecircle. projection problems Lensrotation, .largecircle. .largecircle. .largecircle. .largecircle..largecircle. .largecircle. .DELTA. X position shift Visibility toX .DELTA. .largecircle. .largecircle. .largecircle. .largecircle..largecircle. .largecircle. examiner Visual field .largecircle..largecircle. .largecircle. .largecircle. .largecircle..largecircle. .DELTA. X impairment Visibility to wearer.largecircle. .largecircle. .largecircle. .largecircle..largecircle. .largecircle. .DELTA. X Without Anterior eye X.DELTA. .largecircle. .largecircle. .largecircle. .largecircle..largecircle. .largecircle. center problems projection Lensrotation, .largecircle. .largecircle. .largecircle. .DELTA. .DELTA.X X X position shift Visibility to X X .DELTA. .largecircle..largecircle. .largecircle. .largecircle. .largecircle. examinerVisual field .largecircle. .largecircle. .largecircle..largecircle. .largecircle. .largecircle. .DELTA. X impairmentVisibility to wearer .largecircle. .largecircle. .largecircle..largecircle. .DELTA. X X X

[0172] Next, for marks of shape according to the present inventionand, by way of a comparative example, for marks lacking a centerprojection, the items indicated in Table 3 were evaluated atdifferent mark formation locations in the lens radial direction.For each item, results of evaluation carried out on 100 examinedeyes of 50 subjects are shown in FIG. 4.

[0173] As will be apparent from Table 4, at all formationlocations, marks of shape according to the present invention,provided with a center projection, afforded evaluation resultsequal to or better than the marks of the comparative examplelacking a center projection. Particularly good results wereobtained where the formation location of the lower end of the markwas within a range of between 4.5 mm and 6.0 mm from the lenscenter. From the above it will be appreciated that marks ofconstruction according to the present invention provided with acenter projection afford good results for each evaluated item, aswell as improved freedom in selecting the mark formationlocation.

* * * * *