CA1147199A - Method for forming a colored image in a soft contact lens using a diazonium salt - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A method for forming a colored image in a limited area of a vision-corrective soft contact lens. In one method, the lens is soaked in a diazonium salt and then exposed to actinic light through a mask which transmits light only to the non-image area of the lens. Then, the unexposed image area is deve-loped by contact with an azo coupler. In a second method, the diazonium salt is soaked in a gel relief of the desired image configuration and contacted with the lens. The image is developed by soaking in the azo coupler. In a third method, the diazonium salt, azo coupler, and a coupling inhibitor (a pH reducing agent) are premixed and applied by the gel relief. The image is then developed by raising the image pH level as by contact with ammonia gas. Also, apparatus for precisely contacting the lens with the gel relief image.

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Description

~7~S~9 This application is a divisional of copending Canadian applica-tion Serial Number 3680G8 filed January 7 1981, Messrs Meshel and Gregory, which is in turn a divisional of application Serial Number 283867, now Canadian Patent Number 1095755 which issued on February 17, 1981 to Meshel and Gregory.
A conventional soft or flexible contact lens is formed of a hydrated gel polymer, commonly polyhydroxyethyl methacrylate (HEMA).
Various attempts have been made to color such lenses as with vegetable coloring, earth pigments, and water insoluble marking pigments. However, these methods have not been successful as the pigments may leach out of the lens and irritate the eye. Furthermore, some pigments are readily removed by soaking solution or boiling.
In accordance with the present invention, a colored image is formed in a limited area of a soft hydrated gel contact lens. In one method, the lens is soaked in a diazonium salt solution and is there-after exposed to actinic light through a mask which transmits light only to the non-image area of the lens. Thereafter, the unexposed image area is developed by soaking the lens in an aqueous solution of azo coupler. This method is particularly adapted to forming large images such as of the patient's iris.
In another technique, an aqueous solution of the diazonium salt in a gel relief of the desired image is contacted with the soft lens to form a latent image of the relief. Then, the image is developed by contacting the lens with an aqueous solution!of azo coupler. The order of application of the diazonium salt and azo coupler may be reversed in this latter procedure.

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In a third technique, an aqueous azo dye solution is preformed including a diazonium salt, an azo coupler, and a coupling inhibitor ~- (a pH reducing agent). This solution is soaked into a gel relief of the foregoing type and contacted with a soft lens to form a latent image.
The image is developed by increasing the p~l in its area of the lens to a level conducive to coupling. Exposure to ammonia gas is preferred as it avoids extensive contact of the lens with a potentially harm~ul base solution. Apparatus is provided for precise alignment of the symbols deposited on the lens from the gel relief. It includes one or mo~e striker arms, preferably resilient, carrying said relief images and which are movable toward and away from a lens retained on a contact surface. ;In one embodiment, the striker arms are carried by a rotating wheel for rapid deposition of multiple coded symbols on different lenses.
Also, enlarged coding means may be provided for ready visibility of the symbol to be deposited.
It is an object of the invention to provide a rapid, effective method for the permanent deposition of a precise colored image on a soft contact lens.
It is a further object of the lnvention to provide a method of the foregoing type in which there is no dstrimental affect upon the lens.
It is a specific object of the invention to apply diazo dye techniques to the permanent coloring of a soft contact lens.
According to a broad aspect of the present invention, there is provided in a method for forming a colored image in a limited area of 2 soft hydrated gel contact lens, the steps of:

t~1~9 (a) soaking the lens in a solution of a diazonium salt for sufficient time for said salt to permeate and disperse throughout the lens gel matrix.
~ b) exposing the soaked lens to actinic light through a photomask . whîch transmits light to only the non-image area of the lens, the intensity and time of exposure in the non-image area being sufficient to decompose the diazonium salt therein to prevent the coupling reaction in step (c), ~ c) developing the unexposed image area of said lens by soaking the lens in an aqueous solution of an azo coupler for sufficient time for the azo coupler to permeate the gel matrix and couple with the un-decomposed diazonium salt dispersed therein.
The present inventionJthat of copending application Serial Number 36~068 and that of Patent Number 1095755 will now be described in greater detail with reference to the accompanying drawings in which:
Figure 1 is a striker arm strip containing a relief image for coloring a soft contact lens in accordance with the present invention;
Figure 2 is a side elevational view o~ an apparatus including multiple striker arm strips on a wheel for sequential application o~
coded symbols to a contact lens; and Figure 3 is an end view of the apparatus of Figure 2.
The present invention relates to the formation of a colored image r7~

in a limited area of a soft (i.e., flexible) hydrated gel contact lcns. The most widely used ~ype of such flexible lens are sold under the trademark "SO~LENS" by Bausch ~ Lomb. Such lenses are formed of hydrated polyhydroxyethyl methacrylate. The properties of such lenses are weil known. In its -fully hyd-rated condition (about 39% water by weight) the lens is soft and supple.
Typically, the lenses are packaged in a sterile condition in normal saline sol-ution.
Soft lenses are sized to overlap the white area of the eye. Accord-ingly, for cosmetic reasons~ coloring of the contact lens, as for cutting glare, must be done selectively so that the colored portion of the lens covers only the iris of ~he eye during wear.
The following technique for coloring the lens, designated "the photomask method" is particularl~ adapted for coloring such an image area of relatively large size and in which an a~solutely sharp boundary is not essential.
In the first step, the lens is soaked or immersed in a solution of a diazonium salt for sufficient ~ime for the salt to permeate and disperse throughout the gel matrix of the contact lens. The precise length of time for immersion de-peD~3 on the ~.emperature and type of dye. At room temperature, a time of one-half hour to one hour has been found to be a sufficient period.
It is known that diazonium salts are stabilized in a mildly acid solution, say at a pH of 6 to 7. Suitably, a low concentration of an acid such as hydroc}lloric acid may be included for this purpose.
After soaking in diazonium salt, the lens is precisely positioned at a fixed distance from a source of actinic light. Then, a pho~omask is placed bet~een the ligh-t source and lens ~hich transmits ligllt only to the arca surrounding the desircd image area of thc lens. Thus, to dye only a cen-tral area of the lcns, light is transmitted only to the periphery of the cen-tral area. A suitable mask includes a black form on a transparen~ base.

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The effect of exposure is to clecompose the diazonium salt to a suf-ficient extent that the exposec!area will not form a color when the lens is sub-sequently developed with an azo coupler, Thus, the intensity and time of exposure should be sufficient for this purpose. A preferred source of actinic light emits radiation in the ultraviolet range. An effective intensity of ex-posure is from a 100 watt mercury vt*or lamp at a distance of one foot in an exposure time-of 5-10 minutes.
After the exposure step, the unexposed area in the form of the de-sired image is developed by soaking the lens in an aclueous solution of an azo coupler which foTms the desired color when combined with the selected diazonium salt.
It is known that the coupling of diazonium salt such as used in diazo-type photocopying processes is preferably perormed at a slightly alka-line pH levelJ e.g., a pH of 7 to 8. ThusJ the azo coupler preferably is dis-solved in an aqueous solution maintained at that pH level. Ef~ective pH ad-justing agents for this purpose include alkaline salts such as sodium borate, sodium acetateJ sodium carbonateJ or sodium bicarbonate. AltcrnativelyJ a non-salt such as a 1% ammonia solution may also be employed.
Sllfficient tlme should be permitted for the development step so that the azo cuupler pe~meates the gel matrix and couples with essentially all decomposed diazonium salt dispersccl therein. Although such timing is dependent upon the part;cular azo couplerJ it has been found that immersion of the lens in the coupler solution will develop the desired dye in about 5 minutes or more.
After the development stepJ the lens is washed in distilled water to remove reactants in the coloring procedure. Then~ the lens is boiled in normal saline solution to render it more compatible with the fluids of the eye.
It has been found that by following the above procedureJ a soft 7~L9~

contact lens is colored with a substantially fixed non-leacha~le dye. The color of this fixed or permancnt dye is determined by the combination of dia-zonium salt and azo coupler which is employed. For e~ample, it has been found that a single dye may be formed into a variety of colors depending upon the selection of azo couplers.
Any of a large variety of diazonium salts such as used in diazo-type photocopying processes may be employed to color the soft contact lenses.
The art is highly developed with respect to aromatic diazo compounds. Ilnder acid condition, these compounds exist as diazonium salts. ~'articularly effective diazonium salts for purpose of the present invention include one or more of the followings compounds:
DIAZO~IU~I SALTS
p-diazo-o-chloro-N-diethylaniline p-diazo-N-diethyl-m-phentidine 4-diazomorpholino-2J5-dibutoxybenzene 4-diazo-N-benzoyl-2,5-dibutoxyaniline

2-diazo-L,-napthol-5-sulfonic acid p-diazo-diphenvlaminesulfate 4-diazo-(4'-toluyl)-mercapto-2,5-diethoxybenzene Azo couplers for diazonium salts are well ~nown and include phenols, napthols, and amincs. Particularly erfective azo couplers for the foregoing diazonium salts include one or more of the following compounds:
AZO COUPLERS

2,7-dihylroxy-~,6-naphthalcnedisodiumsulfonate beta oxynapthoic-monocthanolamidc beta oxynapthoic-aminocthyleneamide-hydrocllloride resorcinol m-hydroxyphenylurea 6,7-dihydroxy-2-naphthalenesodiumsulfonate phloroglucinal As set forth above, the coupler or diazonium saits may be varied by the use of different couplers. For e~ampleJ p-diazo-o-chloro-N-diethylani-line coupled with 2,7-dihydroxy-3,6-naphthalenedisodiumsolfonate ~orms a sepia color while the s~ne diazonium salt coupled with beta oxynapthoic-aminoe-thyleneamide-hydrochloride forms a brown color. Similarly, p-diazo-diphenyl--aminesulfate coupled with $,7-dihydro~v-2-napi~thalenesodiumsulfonate forms a blue color while the same diazonium salt coupled with resorcinol forms a yellow cr.10r. In another example, 4-diazo-~4!-toluyl)-mercapto-2,5-diethyoxy-ben~ene and phloroglucinol forms a black color while 4-diazo(4'-toluyl)-mercapto-2,5-diethoxybenzene and resorcinal forms a red color.
One of the advantages of the ability to form different colors with a single diazonium salt and a variety of azo couplers is in the flexibility o~
the laboratcry technician to dye a variety of lenses with different colors on short notice. A few diazonium salts may be employed on the shelf of the tech-nician together with appropriate a~o couplers to form a large variety of colors.
In the indicated form, the reagents are relatively stable.
Other methods may be employed for forming the desi~ed image.
Two of these methods described herein involve the use of an aqueous gel relief for transferring the desired image and so will be designated as the "first relief method" and "second relief method", respectively. They are particular'y applicable for the formation of a relatively small image with a sharp border.
One use for thcse techniques would be to apply a colored coded symbol 0l1 the lens as for thc dcsignation of the lens power.
In the first relief method~ an aqueous solution of a dia~onium 71~9 salt of ~hc foregoing type is dispersed and absorbed by an aqueous gel relief portion of an ilnaging substrate. Tho relief portion is contacted with the lens to tr~nsfer the dia~onium salt to th~ lens. Flnally, the lens is con-tacted with the a~o coupler for development.
The imagiilg substrate and gel relief portion nn~y be formed by any conventional technique. For example, a solution of a gel precursor prior to setting may be deposited in a mold wllich includes a relief in the form of a negative image of the desired configuration. Then, the gel is permitted to set. Any of a variety of gels, e.g., gelatin or cross-linked starch, may be employed for this purpose.
The colored image may take the form of coded symbols such as let-ters or numbers. To form the gel relief image, a ~old such as formed of plas-er of paris may be constructed by solidification of the plaster in contact with typeface. Then, the gel precursor is flowed into the mold and permitted to set.
Other forms of gel relief may also be employed for special pur-poses. For exa~ple, photo-derived reliefs may be employed such as used in the photo-engraving industry.
For example, the film positive may be made of a desired coded symbol such as a number of letter. Then, such film positive is contacted with a photomechanical film including a gelatin surface ~ith silver salt dis-persed therein on a plastic film backing ~e.g., Mylar). Thereafter, such photomechanical film is developed to form a negative image area in which the silver is in free form surrounding the positive image of the symbol in clear gelatin form. Thereafter, the gelatin in the area of the negative image is ren~ovcd by contact with a solution which attacks only the free silver-con-taining black portion. A suitable solution for this purpose includes nascent Trademark g ox~gen produced by an aqueous solution of copper sulfate, nltric acid, potas-sium bromide, and hydrogen peroxide. Then~ the dissolved negative image is removed leavin~ a relief of the clear gelatin positive of the desired symbol on a plastic film base. Typically, such a relief is a very thin film (e.g., 0.01 - 0.05 mm thick) with precisely defined borders.
The gel relief portion may be molded onto a non-gel backing, if desired. If the images are of a substantial size, it is preferable to form *he gel relief of a material which is sufficiently flexible to conform to the contour of the lens.
After the gel relief is soaked with diazonium salt, it is contacted with the lens for a sufficient time, e.g., one minute or more, for the diazo-nium salt to permeate and disperse into the lens to form an image of the relief portion.
Then, the latent image on the lens is developed by contact with an aqueous solution of an azo coupler of the foregoing type. This step is per-formed by soaking with the azo coupler for a sufficient time for it to permeate ; the latent image area and coupl0 with the diazonium salt dispersed therein.
This coupling step is quite rapid and may possibly be accomplished by wiping thesu~face with a cloth soaked with azo coupler. After development, the foregoing steps of washing and boilin~ in saline solution are performed.
It is believed that azo couplers are more compatible with the sal--ine solution than are the diazonium salts. Thus, it may be advantageous to reverse the order of addition of the diazonium salt and azo coupler in the firstrelief method. For e~ample, the azo cou~ler would be dispersed in an aqueous solution into the gel relief portion of the imaging substrate and contacted Wit]the len~s to impart a latent image. Thcn, the latent image would be developcd by contact with a diazonium salt. This may be accomplisiled rapidly as by wiping _ 9 _ ~7~L~39 the surface of the lens and latent image arca with a cloth soaked with diazon-ium salt.
Prior to contacting the soft lens with the diazonium salt solution for eithcr the photomask or relief methods, it is preferable to hydrate the lens in distilled water in contrast to concentrated saline solution. ~his is because the salt of a conventional saline solution may interfere with the per-meation of the diazonium salt solution. The diazonium salt may permeate the lens if sufficient salt is leached first from the lens.
In the second relief method, an aqueous azo dye solution is pre-formed which includes a diazonium salt, an azo couplerJ and a coupling inhibi-tor (a pH reducing agent~. This solution is soaked into a gel relief of the foregoing type and contacted with the soft lens to form the latent image. A
suitable pH reducing agent comprising a food grade acid such as citric acid.
Citric acid is advantageous in that it can be stored in a solid crystal form for indefinite periods. Also, the diazonium salt and azo couplers may be stored in solid form. Thus, all ingredients of the latent dye solution may be stored for an indefinite period of time in a solid form tmtil just prior to use. Thenl the solids may be mixed into water to form the latent dye ~- solution.
The pH reducing agent serves as a coupling inhibitor because of the well known phenomenon that coupling does not occur at low pH levels. In the absence of this inhibitor, coupling would occur in a matter of minutes. This would necessitate constant mixing of individual solutionsJ a time consuming procedure. It has been found that in the presence of sufficient acid to lower the pH level of the otherwise neutral mixture to say about 5.5 - 6.5, the latent dye solution is stable for storage times on the order of as long as one to two weeks.

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The foregoing latent azo dye solution is soaked into a Eel relief as described above for a sufficient time for absorbtion into the gel. A
suitab]e time for this purpose is from one to five minutes.
The soaked gel relief is then contacted with a soft contact lens to form a latent image. This is a very rapid process and may be accomplished in about one to five seconds. Thereafter~ the latent image is developed by increasing the pH level in its area of the contact lens to a sufficient extent to promote coupling. A pH level on the order of 7.S - 8.5 is generally suit-able for this purpose.
A unique technique for increasing the pH level of the lens for development while avoiding extensive contact of the lens with a potentially harmful basic solution is to expose the lens to a basic gas. For example, exposure to ammonia ~as produced by a weak ammonia aqueous solution leads to a very rapid development of the image. Soaking the lens in a basic solution could be practiced as a less desirable alternative.
One advantage of the second relief method is that only a minute portion of the lens in the form of the coded symbol is contacted with dye solution. This is desirable from a health standpoint. In addition, potential harmful expansion or attack of the lens by a basic solution is avoided by the useOf the gas for~ of the base.
Ater development, the foregoing steps of washing and boiling in saline solution are performed.
It is apparent that the foregoing relief metho~s are of particular advantage where the image is relatively small and a precise boundary is desired for the colorcd image. Thus, such methods may be employed for coding with numbcrs or letters. This may be accomplished with a series of spaced rclief images soaked with appropriate dia~onium salt for the rapid coding of such lenses. For example, a wheel with a strip of flexible non-slip gel relief images may be used.
Referring to the drawingsJ an apparatus is prov:ided for precisely depositing an imaging liquid on~o a limited area of a contact lens. Such imaging liquid could include either the diazonium salts or azo couplers of the first relief method or the latent dye solut~n of the second relief method.
In any event, the apparatus provides means for precisely contacting a limited area of the contact lens with the desired symbol provided in a relief layer to form a crisp image.
Referring specifically to the embodiment of Figures 2 and 3, a device 11 is illustrated for rapidly imprinting one or more contact lenses with the same or different symbols. Device 11 includes a platform 12 to ~hich is mounted means 13 for supporting the sof~ contac~ lens. Such means includes vertical suppor-t base 14 which threadedly receives an adjustment scre~ 16.
Body 17 is mounted for adjustable pivotal movement to screw 16 and includes a projecting convex surface 18 contained to firmly support the soft contact lens illustrated by dotted lines 19. By adjustable mounting in this manner) the portion of the lens to be contacted and the level of the lens wi~h respect to the striker arm described hereinafter may be adjusted to the desired extent.
A vertical support member 20 is mounted to platform 13 and carries a plurality of striker arms each including a relief layer as described herein-after. A rotatable striker arm mounting means 21 includes a central shaft 22 carriedby an openinginsupport member 20 with removable gripping knob 23 a~ one side of membcr 20 and a striker arm support body 24 carried at the other side of membcr 20. ~ody 2~ is of square cross-section and includes four flat mounting surfaces 24a - 24d for providing multiple support areas for striker arms carried by the support body at 90~ angles to each othcr. hlore surfaces may be provided for more striker arms as desired.
Striking means is provided including a movable striker arm 26 illustratcd in expanded view in ~igure 1. Arm 26 includes mounting openings 27 for riveting to each of respective surfaces 24a - 24d. In the embodiments of ~igures 2 and 3, the striker arms mounted ~o surfaces 24a - 24d will be designatcd 26a - 26d, respectively. The individual striker arms include a minute imaging liquid absorptive relief layer 28 at the free end of the arm.
Such relief layer may be formed in the manner set forth above.
Stiker arm 26 is preferably formed as a resilient strip of a trans-parent plastic material such as the polyester ilm sold under the trademark "Mylar". Other resilient materials also may be employed.
Support body 24 is rotatable by knob 23 ~o move the free ends ofany of striker arms 2~a-2~d into a position adjacent to convex surface 18 to permit striking of the same with the symbol of relief layer 28, mounted to face exterior support body 24. In the embodiment of Figures 2 and 3, arm 26c is in a horizontal position ready for striking. In this position, the striker arm is movable between the i`llustrated normal position spaced apart from surface 18 and a striking position in which the relief layer is pressed against a limited area of contact lens 19 on surface 18. The actual striking motion ~0 actuation may be accomplished by manually pressing arm 26a against the lens for a short period of time. Alternatively, remote means may be provided for actu-ation. In any event, the overall apparatus serves to accomplish this objective in a precise manner.
It is apparent that different symbols may be employed for each of the relief layers on the different striker arms to employ different codes for a succession of lenses placed on convex surface 18. In this manner~ for ex ample, a code for the prescription of different lenses ma~ be printed on a ~1~7~

rapid succession of lenses. It is apparent that each striker arm is horizon-tally positioned to strike a succession of contact lenses ~ convex surface 18 at mutually exclusive times during rotation of the mounting means.
Coding means is operatively associated with each striker arm in the form of enlarged symbols corresponding to the respecti~e images on ~he relif layer imaging surfaces. Such images are illustrated by the figure 8 in Figure 1. It is desirable because the relief layers 28 are so small as to not be readily visible to the naked eye. Thus, this provides a safety measure to assure that the proper image is imprinted on the lens.
A table 29 is provided with a visible line on its generally hori-zontal top surface for registry with the corresponding line 30 of the striker arm as an indication that relief layer 28 is precisely aligned for proper im-printing onto the lens. Alternatively, this system could be performed by ap-propriate stops in the rotation of support body 24. However, alignment as illustrated herein is a very economlcal manner o accomplishing this objective.
Support body 24 is removable from member 20 by disengaging knob 23 and sliding the body ~n the opposite direction. Thus, the relief layer con-taining portions of all striker arms may be soaked simultaneously in a dye solution. Also, if desired, another body with previously soaked striker arms may be used in the apparatus during tllis time.
Soft contact lenses colored by the foregoing techni.ques may be employed for a number of different purposes. For example, a transparent con-t-act lens with a central opaque portion may be employed to occlude the retina of the eye to treat a patient with amblyopia. Also, ~he colored portion of the contact lenc co~ld be used as a ~ilter to replace sun glasses, e.g., as a ski lens. Furthermore, the lells may bc e~ployed for various cosmctic reasonss-lcl as changing the color of the wearer's iris or even to provide colored images ~7~9 such as stars or lines radiating from the iris, in the white portion of the we~rerls eyes.
A further disclosure of the nature of the present inventionis pro-vid~d by the following specific examples of the practice of the same. It should be understood that the data disclosed serve only 2S examples and are not in-tende~ to limit the scope of the inv~ntion.
Exam~le 1 The following is a description o~ ~he photomask method. The lens ;~ is first immersed in a solution of p-diazo-o-chloro-N-diethylan~line at a con-centration of 0.1 gram of salt in 4 ounces or dislilled waler Coa~L~
0.025% hydrochloric acid. The lens is immersed at 75~F for 45 minutes.
After the immersion step, the lens is disposed one foot from a 100 ~Yatt mercury vapor lamp. A photomask is positioned intermediate the lens and lamp upon which an image in black of the desired configuration is posi-tioned on a transparent base. This image is in the form of the iris of the eye. Then, the lamp is activated for an exposure time of g minutes to de-compose the diazonium salt in the exposed areas so that it will not form a color when developed.
After exposure, the lens is soaked in a solution of an azo coupler color developer comprising 2,7-dihydroxy-3,6-naphthalenedisodiumsulfonate at a concentration of 0.1 gram in 4 ounces of t~ater. 3 cc of this solution is comblncd with 1 cc of a dilute sodium carbonate solution formed from 1 gram of sodium carbonate dissolved in 1 liter of water. The time of immersion is about 5 minutes during which a sepia color is developed. After development, the lens is washed in distillcd water and boiled in normal saline solution.
The color formed in the image area is insoluble in water and is distributed throughout thc thickness of the lens.

~71~9 Example 2 The procedure o~ Examplc i is followed with the exception that the coupler is formed of beta oxynapthoic aminoethyleneamide-hydrochloride.
A brown color is formed in the image area.
Example 3 The procedure of Example l is followed with the exception that p-diazo-diphenylaminesulfate is subst.ituted for p-dia~o-o-chloro-N-diethy-laniline and 6,7-dihydroxy-2-naphthalenesodiumsulfonate is substituted for 2,7-dihydroxy-3,6-naphthalenedisodiumsulfonate. A blue color is formed.
Example 4 The procedure of Example 3 is followed with the exception that resorcinol is substituted for 6,7-dihydroxy-2-naphthalenesodiumsulfonate. A
yellow color is formed.
Example 5 The procedure of Example I is followed with the exception that 4-diazo-(4'-toluyl~-mercapto-2,5-diethoxybenzene is substituted for p-diazo-o-chloro-N-diethylaniline and phloroglucinol is substituted for 2,7-dihydroxy-

3,6-naphthalenedisodiumsulfonate. A black color is formed Example 6 The procedure of Example 5 is followed with the exception that resorcinol is substituted for phloroglucinol. A red color is formed.
Example 7 - The following procedure is an example forming a ~isible image on the soft contact lens by the second relief method. The aqueous latent azo dye solution is formed by mixing the following ingredients in dry powder form into 8 ounccs of distilled water:

0.6 grams of p-diazo-N-diethyl-M-phenetidinc zinc chloride 0.6 grams of p-diphenylamine sulfate 0.2 grams of citric acid crystals 0.5 grams of 6,7-dihydroxy-2-naph-thalene sodium sulfonate A film including a relief of the coded symbol is dipped into the solution for a sufficient time to permit absorption of the solution into the gel relief. Then, the symbol is rapidly contacted with the soft lens to im-part a latent image to the same. Finally, the lens is exposed to weak ammonia vapors for several seconds to develop the image into a permanent blue color.
Thereafter, the lens is washea in distilled water and boiled in normal saline solution.

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Claims (6)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a method for forming a colored image in a limited area of a soft hydrated gel contact lens, the steps of:
(a) soaking the lens in a solution of a diazonium salt for sufficient time for said salt to permeate and disperse throughout the lens gel matrix, (b) exposing the soaked lens to actinic light through a photomask which transmits light to only to non-image area of the lens, the intensity and time of exposure in the non-image area being sufficient to decompose the diazonium salt therein to prevent the coupling reaction in step (c), (c) developing the unexposed image area of said lens by soaking the lens in an aqueous solution of an azo coupler for sufficient time for the azo coupler to permeate the gel matrix and couple with the undecomposed diazonium salt dis-persed therein.

2. The method of Claim 1 in which said developing step is performed at a slightly alkaline pH level.

3. The method of Claim 1 in which said diazonium salt is selected from the group consisting of p-diazo-o-chloro-N-diethylaniline, p-diazo-N-diethyl-m-phenetidine, 4-diazomorpholino-2,5-dibutoxybenzene, 4-diazo-N-benzoyl-2,5-di-butoxyaniline, 2-diazo-L-napthol-5-sulfonic acid, p-diazo-diphenylaminesulfate and 4-diazo-[4'-toluyl)-mercapto-2,5-diethoxybenzene.

4. The method of Claim 1 in which said azo coupler is selected from the group consisting of 2,7-dihydroxy-3,6-naphthalenedisodiumsulfonate, beta oxynapthoic-monoethanolamide, beta oxynapthoic-aminoethyleneamide-hydrochloride, resorcinol, m-hydroxy-phenylurea, 6,7-hydroxy-2-napthalenesodiumsulfonate, and phloroglucinol.

5. The method of Claim 4 in which said diazonium salt is selected from the group consisting of p-diazo-o-chloro-N-diethylaniline, p-diazo-N-diethyl-m-phenetidine, 4-diazomorpholino-2,5-dibutoxybenzene, 4-diazo-N-benzoyl-2,5-di-butoxyaniline, 2-diazo-L-napthol-5-sulfonic acid, p-diazo-diphenylaminesulfate, and 4-diazo-(4'toluyl)-mercapto-2,5-diethoxybenzene.

6. The method of Claim 1 in which said hydrated gel contact lens is formed of hydrated polyhydroxyethyl methacrylate.