CA1095755A - Colored soft contact lens and method and apparatus for forming - 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 developed 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.

Description

~-~5'755 Background of the Invention A conventional soft or flexible contact lens is formed of a hydrated gel polymer, commonly polyhydroxyethyl methacrylate (HEMA). ~arious 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.
Summary of the Invention and Ob~jects 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 thereafter 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 ~L~9S'7~5 the diazonium salt and azo coupler may be reversed in this latter procedure.
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 pH in its area of the lens to a level conduc-ive to coupling. Exposure to ammonia gas is preferred as it avoids extensive contact of the lens with a potentially harmful base solution.
Apparatus is provided for precise alignment of the symbols deposit-ed on the lens from the gel relief. It includes one or more 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 embodi-ment, 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 invention to provide a method of the foregoing type in which there is no detrimental 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 invention, therefore, there is provided in a method for forming a colored image in a limited area of a soft hydrated gel contact lens, the steps of: absorbing an aqueous solution of a diazonium salt onto an absorptive relief portion of an imaging sub-strate, contacting said relief portion with said lens for sufficient time for said diazonium salt to permeate and disperse into the lens to form a latent image of said relief portion, developing said latent image by contact-ing the lens with an aqueous solution of an azo coupler for sufficient timefor the azo coupler to permeate the latent ~ e area and couple wi~h the diazonium salt dispersed therein.

, . . .
.~ ~ -3-~(~957S5 According to another broad aspect of the invention, there is provided apparatus for precisely depositing an imaging liquid onto a limited area of a contact lens comprising means for supporting said lens including a lens contoured surface, striking means including a movable striker arm with a striking surface position adjacent said contoured sur-face, and an imaging liquid absorptive relief layer having an imaging sur-face carried by said striking surface, said striker arm being movable between a normal position spaced apart from said contoured surface and a striking position in which said relief layer is pressed against a limited area of a contact lens on said contoured surface.
Further objects and features of the invention -3a-.~ "
,,,, ,~

will be apparent from the following description of the preferred embodiments taken in conjunction with the appended drawings.
Brief Description of the Drawings 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 of an apparatus including multiple striker arm strips on a wheel for sequential application of coded symbols to a contact lens.
Figure 3 is an end view of the apparatus of Figure 2.
Detailed Description of the Preferred Embodiments The pxesent invention relates to the formation of a colored image in a limited area of a soft (i.e., flexible) hydrated gel contact lens. The most widely used type of such flexible lens are sold under the trademark "SOE'LENS"
by Bausch & Lomb. Such lenses are formed of hydrated polyhydroxyethyl methacrylate. The properties of such lenses are well known. In its fully hydrated condition (about 39~ water by weight), the lens is soft and supple.
Typically, the lenses are packaged in a sterile condition in normal saline solution.
Soft lenses are sized to overlap the white area of the eye. Accordingly, 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 the eye during wear.
The following technique for coloring the lens, designated "the photomask method" is particularly adapted ~?gS'~S

for coloring such an image area of relatively large size and in which an absolutely sharp boundary is not essential.
In the first step, the lens is soaked or immersed in a solution of a diazonium salt for sufficient time for the salt to permeate and disperse throughout the gel matrix of the contact lens. ~he precise length of time for immersion depends on the temperature 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 ]cnown 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 hydrochloric 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 photomask is placed between the light source and lens which transmits light only to the area surrounding the desired image area of the lens. Thus, to dye only a central area of the lens, light is transmitted only to the periphery of the central area. A suitable mask includes a black form on a transparent base.
The effect of exposure is to decompose the diazonium salt to a sufficient extent that the exposed area will not form a color when the lens is subsequently 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 exposure is from a lO0 watt mercury vapor lamp at a distance of one foot in an exposure time of 5 - 10 minutes.

~57S5 After the exposure step, the unexposed area in the form of the desired image is developed by soaking the lens in an aqueous solution of an azo coupler which forms 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 performed at a slightly alkaline pH level, e.g., a pH of 7 to 8. I'hus, the azo coupler preferably is dissolved in an aqueous solution maintained at that pH
level. Effective pH adjusting agents for this purpose include alkaline salts such as sodium borate, sodium acetate, sodium carbonate, or sodium bicarbonate.
Alternatively, a non-salt such as a 1% ammonia solution may also be employed.
Sufficient time should be permitted for the development step so that the azo coupler permeates the gel matrix and couples with essentially all decomposed diazonium salt dispersed therein. Although such timing is dependent upon the particular azo coupler, 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 step, 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 procedure, a soft contact lens is colored with a substantially fixed non-leachable dye. The color of this fixed or permanent dye is determined by the combination of diazonium salt and azo coupler which is employed. For 1~5755 example, it has been found that a sinle 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. Under acid condition, these compounds exist as diazonium salts.
Particularly effective diazonium salts for purpose of the present invention include one or more of the following compounds:
DIAZONIUM SALTS
p-diazo-o-chloro-N-diethylaniline p-diazo-N-diethyl-m-phentidine 4-diazomorpholino-2,5-dibutoxybenzene 4-diazo-N-benzoyl-2,5-dibutoxyaniline

2-diazo--L-napthol-5-sulfonic acid p-diazo-diphenylaminesulfate 4-diazo-(4'-toluyl)-mercapto-2,5-diethoxybenzene Azo couplers for diazonium salts are well known and include phenols, napthols, and amines. Partlcularly effective azo couplers for the foregoing diazonium salts include one or more of the following compounds:

S'7SS

AZO COUPLERS
2,7-dihydroxy-3,6-naphthalenedisodiumsulfonate beta oxynapthoic monoethanolamide beta oxynapthoic-aminoethyleneamide-hydrochloride resorcinol m-hydroxyphenylurea 6,7-dihydroxy-2-naphthalenesodiumsulfonate phloroglucinol As set forth above, the coupler or diazonium salts may be varied by the use of different couplers. For example, p-diazo-o-chloro-N-diethylaniline coupled with 2,7-dihydroxy-3,6-naphthalenedisodiumsulfonate forms a sepia color while the same diazonium salt coupled with beta oxynapthoic-aminoethyleneamide-hydrochloride forms a brown color. Similarly, p-diazo-diphenylaminesulfate coupled with 6,7-dihydroxy-2-naphthalenesodiumsulfonate forms a blue color while the same diazonium salt coupled with resorcinol forms a yellow color. In another example, 4-diazo-(4'-toluyl)-mercapto-2,5-diethyoxybenzene and phloroglucinol forms a black color while 4-diazo-(4'-toluyl)-mercapto-2,5-diethoxybenzene and resorcinol 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 of the laboratory 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 technician together with appropriate azo couplers to form a large variety of colors. In the indicated form, the reagents are relatively stable.

~95755 Other methods may be employed for forming the desired 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 particularly applicable for the formation of a relatively small image with a sharp border. One use for these techniques would be to apply a colored coded symbol on the lens as for the designation of the lens power.
In the first relief method, an aqueous solution of a diazonium salt of the foregoing type is dispersed and absorbed by an aqueous gel relief portion of an imaging substrate. The relief portion is contacted with the lens to transfer the diazonium salt to the lens. Finally, the lens is contacted with the azo coupler for development.
The imaging substrate and gel relief portion may be formed by any conventional technique. For example, a solution of a gel precursor prior to setting may be deposited in a mold which 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 letters or numbers. To form the gel relief image, a mold such as formed of plaster 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.

_9 1(~95'755 Other forms of gel relief may also be employed for special purposes. For example, 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 with silver salt dispersed 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 removed by contact with a solution which attacks only the free silver-containing black por~ion. A suitable solution for this purpose includes nascent oxygen produced by an aqueous solution of copper sulfate, nitric acid, potassium bromide, and hydrogen peroxide. Then, the dissolved negative image is removed leaving 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 the 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 diazonium salt to permeate and disperse into the lens to form an image of the 1~9575S

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 performed by soaking with the azo coupler for a sufficient time for it to permeate the latent image area and couple with the diazonium salt dispersed therein. This coupling step is quite rapid and may possibly be accomplished by wiping the surface with a cloth soaked with azo coupler. After development, the foregoing steps of washing and boiling in saline solution are performed.
It is believed that azo couplers are more compatible with the saline 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 first relief method. For example, the azo coupler would be dispersed in an aqueous solution into the gel relief portion of the imaging substrate and contacted with the lens to impart a latent image. Then, the latent image would be developed by contact with a diazonium salt. This may be accomplished rapidly as by wiping the surface of the lens and latent image area with a cloth soaked with diazonium salt.
Prior to contacting the soft lens with the diazonium salt solution for either the photomask or relief methods, it is preferable to hydrate the lens in distilled water in contrast to concentrated saline solution. This is because the salt of a conventional saline solution may interfere with the permeation of the diazonium salt solution. The diazonium salt may permeate the lens if sufficient salt is leached first from the lens.

~gS75~

In the second relief method, an aqueous azo dye solution is preformed which includes 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 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 until just prior to use. Then, 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 solutions, 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 ordex of as long as one to two weeks.
The foregoing latent azo dye solution .is soaked into a gel relief as described above for a sufficient time for absorption into the yel. A suitable 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.

~L~957S5 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 7.5 -8.5 is generally suitable for this purpose.
A unique technique for increasing the pH level of the lens for development whlle 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 gas 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 use of the gas form of the base.
After development, the foregoing steps of washing and boiling in saline solution are performed.
It is apparent that the foregoing relief methods are of particular advantage where the image is relatively small and a precise boundary is desired for the colored image. Thus, such methods may be employed for coding with number~ or letters. This may be accomplished with a series of spaced relief images soaked with appropriate diazonium 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.
R~ferring to the drawings, an apparatus is provided for precisely depositing an imaging liquid onto a limited ~sst7ss 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 solution 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 which is mounted means 13 for supporting the soft contact lens. Such means includes vertical support base 14 which threadedly receives an adjustment screw 16. Body 17 is mounted for adjustab]e 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 with 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 hereinafter. A rotatable striker - 25 arm mounting means Zl includes a central shaft 22 carried by ~ an opening in support member 20 with removable gripping knob ; 23 at one side of member 20 and a striker arm support body 24 carried at the other side of member 20. Body 24 is of square cross-section and includes four flat mounting surfaces 24a - -24d for providing multiple support areas for s-triker arms ';

l~9S755 carried by the support body at 90 angles to each otl1er. More surfaces may be provided for more striker arms as desired.
Striking means is provided including a movable striker arm 26 illustrated in expanded view in Figure 1.
Arm 26 includes mounting openings 27 for riveting to each of respective surfaces 24a - 24d. In the embodiments of Figures 2 and 3, the striker arms mounted to surfaces 24a -24d will be designated 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.
Striker arm 26 is preferably formed as a resilient strip of a transparent plastic material such as the polyester film sold under the trademark "Mylar". Other resilient materials also may be employed.
Support body 24 is rotatable by knob 23 to move the free ends of any of striker arms 26a - 26d 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 illustrated 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 Oll surface 18. The actual striking motion 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 actuation. In any event, the overall apparatus serves to accomplish this objective in a precise manner.

11~9S'755 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 example, a code for the prescription of different lenses may be printed on a rapid succession of lenses. It is apparent that each striker arm is horizontally positioned to strike a succession of contact lens on 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 respective images on the relief layer imaging surfaces.
Such images are illustrated by the figure 8 in Figure l.
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 horizontal top surface for registry with the ; 20 corresponding line 30 of the striker arm as an indication that relief layer 28 is precisely aligned for proper imprinting onto the lens. Alternatively, this system could be performed by appropriate stops in the rotation of support - body 24. However, alignment as illustrated herein is a very economical manner of accomplishing this objective.
Support body 24 is xemovable from member 20 by aisengaging knob 23 and sliding the body in the opposite direction. Thus, the relief layer containing portions of all striker arms may be soaked simultaneously in a dye solution.
Also, if desired, another body with previously soaked striker ~L~957S5 arms may be used in the apparatus during this time.
Soft contact lenses colored by the foregoing techniques may be employed for a number of different purposes.
For example, a transparent contact lens with a central opaque portion may be employed to occlude the retina of the eye to treat a patient with amblyopia. Also, the colored portion of the contact lens could be used as a filter to replace sun glasses, e.g., as a ski lens. Furthermore, the lens may be employed for various cosmetic reasons such as changing the color of the wearer's iris or even to provide colored images such as stars or lines radiating from the iris, in the white portion of the wearer's eyes.
A further disclosure of the nature of the present invention is provided by the following specific examples of the practice of the same. It should be understood that the data disclosed serve only as examples and are not intended to limit the scope of the invention.
Example 1 The fol]owing is a description of the photomask method. The lens is first immersed in a solution of p-diazo-o-chloro-N-diethylaniline at a concentration of 0.1 gram of salt in 4 ounces of distilled water containing 0.025% hydrochloric acid. The lens is immersed at 75F
for 45 minutes.
After the immersion step, the lens is disposed one foot from a 100 watt mercury vapor lamp. A photomask is positioned intermediate the lens and lamp upon which an image in black of the desired configuration is positioned on a transparent base. This image is in the form of the iris of the eye. Then, the lamp is activated for an ~957S5 exposure time of 8 minutes to decompose 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 water. 3 cc of this solution is combined 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 distilled water and boiled in normal saline solution.
The color formed in the image area is insoluble in water and is distributed throughout the thickness of the lens.
Example 2 The procedure of Example 1 is followed with the exception that the coupler is formed of beta oxynapthoic-aminoethyleneamide-hydrochlorlde. A brown color is formed in the image area.
Example 3 The procedure of Example 1 is followed with the exception that p-diazo-diphenylarninesulfate is substituted for p-diazo-o-chloro-N-diethylaniline 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 ye~low color is formed.

iO95755 Example 5 The procedure of Example 1 is followed with the exception that 4-diazo-(4'-toluyl)-mercapto-2,5-diethoxy-benzene 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 visible 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 ounces of distilled water:
0.6 grams of p-diazo-N-diethyl-M-phenetidine zinc chloride 0.6 grams of p-diphenylamine sulfate 0.2 grams of citric acid crystals 0.5 grams of 6,7-dihydroxy-2-naphthalene 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 impart 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 washed 15'~55 in distilled water and boiled in normal saline solution.

Claims (10)

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) absorbing an aqueous solution of a diazonium salt onto an absorptive relief portion of an imaging substrate, (b) contacting said relief portion with said lens for sufficient time for said diazonium salt to permeate and disperse into the lens to form a latent image of said relief portion, (c) developing said latent image by contacting the lens with an aqueous solution of an azo coupler for sufficient time for the azo coupler to permeate the latent image area and couple with the 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-diazomorphorlino-2,5-dibutoxybenzene, 4-diazo-N-benzoyl-2,5-dibutoxyaniline, 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 oxynapthoicmonoethanolamide, beta oxynapthoic-aminoethyleneamide-hydro-chloride, resorcinol, m-hydroxy-phenylurea, 6,7-dihydroxy-2-naphthalene-sodiumsulfonate, 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-dibutoxyaniline, 2-diazo-I-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.

7. Apparatus for precisely depositing an imaging liquid onto a limited area of a contact lens comprising means for supporting said lens including a lens contoured surface, striking means including a movable striker arm with a striking surface position adjacent said contoured surface, and an imaging liquid absorptive relief layer having an imaging surface carried by said striking surface, said striker arm being movable between a normal posi-tion spaced apart from said contoured surface and a striking position in which said relief layer is pressed against a limited area of a contact lens on said contoured surface.

8. The apparatus of Claim 7 in which said striker arm is a resilient strip mounted at an opposed side of said striker arm from said relief sur-face.

9. The apparatus of Claim 7 together with rotatable mounting means and a plurality of striker arms carried by said mounting means to extend in spaced apart relationship in the same direction, each striker arm being positioned to s-trike a contact lens on said contoured surface at mutually exclusive times during rotation of said mounting means.

10. The apparatus of Claim 9 together with coding means operatively associated with said striker arm, said coding means having enlarged symbols corresponding to the respective images on said relief layer imaging surfaces.