Pigment colored contact lenses and method for making same

Colored contact lenses are produced by providing a contact lens constructed of polymer and coating at least a portion of the lens with coloring substance and binding polymer. The lens and binding polymers are bonded to each other by the reaction of functional groups selected from at least one of --COOH, --OH, and --NH--R, wherein R is hydrogen or alkyl, with functional groups selected from at least one of --NCO and epoxy.

The present invention relates to contact lenses capable of imparting an 
apparent color modification to the wearer's iris. The inventive lenses may 
be prepared with or without an optical prescription for correcting visual 
defects. The inventive lenses may contain an opaque color coat which can 
bring about a fundamental color change in the apparent color of the 
wearer's iris, for example from dark brown to light blue. Alternatively, 
the color coat may be transparent, in which case the apparent eye tint may 
be enhanced or the apparent color of light-colored eyes may be changed, 
for example, from light blue to green. Hence, as used throughout the 
present specification and claims, the term "colored contact lens" is 
intended to mean a lens having either a transparent or an opaque color 
coat. 
The invention provides a high degree of flexibility in coloring the lenses. 
Not only is it possible to choose from opaque or transparent color coats, 
but it is also possible to color selected portions of the lens. Moreover 
with the invention, it is possible to color the lens in a pattern that 
simulates the fine structure of the iris, using more than one color if 
that is desirable. Alternatively, it is possible to deposit an opaque 
pattern over the iris portion of the lens in a manner that can change the 
apparent color of the iris, but allows visualization of the structure of 
the iris, as described in U.S. patent application Ser. No. 600,860, filed 
Apr. 16, 1984 and having an assignee in common with the present 
application now U.S. Pat. No. 4,582,402. Both hard, i.e., non-hydrophilic 
lenses, and soft, i.e., hydrophilic lenses, may be colored provided the 
lens polymer contains the required functional groups as discussed later. 
The inventive lenses are quite durable and retain their color upon 
prolonged use, even though subjected to the usual disinfecting and 
cleaning procedures. 
Prior colored contact lenses do not possess all of the advantages of the 
present invention. U.S. Pat. No. 4,468,229 (Su) discloses colored lenses 
having reactive dyes bonded to the lens polymer throughout the depth of 
the lens. However, it is not possible to deposit the reactive dyes in the 
highly desirable patterns as discussed above. 
U.S. Pat. Nos. 3,679,504 (Wichterle) and 3,535,386 (Spivack) disclose 
lenses wherein the pigment is sandwiched between two layers of polymer or 
wherein liquid polymer is coated over the pigment and solidified. However, 
the sandwich lenses would be thicker than those of the present invention. 
Both the sandwich and the overcoated lenses would be more likely to 
delaminate than those of the present invention. 
U.S. Pat. Nos. 3,786,034 (Blair et al.), 3,821,136 (Hudgin et al.,), and 
4,359,558 (Gould et al.) disclose contact lenses made of polyurethane. 
However, these patents do not disclose the use of isocyanate compounds as 
a color binding material. 
This invention is predicated on the surprising discovery that a reaction 
mechanism previously used to coat and color leather (i.e. totally 
non-analogus art), as disclosed in U.S. Pat. Nos. 2,884,340 (Loshaek) and 
2,884,336 (Loshaek et al.) can be used to bind color substances to the 
surface of contact lenses, producing colored contact lenses that are very 
durable, can be hydrophilic or non-hydrophilic, can obtain transparent or 
opaque coloring substances, and have substantially the same thickness as 
ordinary, non-colored, contact lenses. 
SUMMARY OF THE INVENTION 
The present invention comprises a method of making a colored contact lens 
comprising the steps of: 
(a) providing a contact lens constructed of polymer, 
(b) coating at least a portion of a surface of the lens with a color coat 
comprising coloring substance and binding polymer, and 
(c) binding the lens polymer to the binding polymer by the reaction of 
functional groups selected from at least one of --COOH, --OH, and --NH--R, 
wherein R is hydrogen or alkyl with functional groups selected from at 
least one of --NCO and epoxy, wherein either 
(A) the lens polymer and binding polymer have functional groups selected 
from at least one of --COOH, --OH, and --NH--R, and the color coat also 
comprises an additional compound having at least two groups per molecule 
selected from at least one of --NCO and epoxy; or 
(B) the lens polymer has functional groups selected from at least one of 
--COOH, --OH, and --NH--R, and the binding polymer has functional groups 
selected from at least one of --NCO and epoxy; or 
(C) the lens polymer has functional groups selected from at least one of 
--NCO and epoxy, and the binding polymer has functional groups selected 
from at least one of --COOH, --OH, and --NH--R; or 
(D) the lens polymer and binding polymer have functional groups selected 
from at least one of --NCO and epoxy and the color coat also comprises an 
additional compound having at least two groups per molecule selected from 
at least one of --COOH, --OH, and --NH--R. 
Some coloring substances have functional groups which may also react with 
the above described functional groups, and this reaction is also within 
the scope of the invention. However, as explained later, the choice of 
coloring substances is not limited to those having reactive functional 
groups. 
A second aspect of the invention comprises colored contact lenses made by 
the inventive method. 
DETAILED DESCRIPTION OF THE INVENTION 
The lenses colored by the inventive process are constructed of a polymer 
having functional groups selected from Group A or B: 
Group A: at least one of --COOH, --OH, and --NH--R, wherein R is hydrogen 
or alkyl, preferably lower alkyl. 
Group B: --NCO and epoxy. 
The term polymer means a material formed by polymerizing one or more 
monomers or a blend of such polymers. The functional groups project from 
the polymer backbone or from another group that projects from the polymer 
backbone. For example, polymerized hydroxyethyl methacrylate may be 
represented by: 
##STR1## 
The hydroxyl functional group is at the bottom of the above 
representation. 
As used herein the term "alkyl" means a straight-chain, branched-chain and 
cyclic saturated hydrocarbon groups having 1 to 8 carbon atoms; C.sub.1 to 
C.sub.2 alkyl groups are preferred. 
Examples of suitable monomers that may be used for providing the functinal 
groups of Group A include acrylic acid; methacrylic acid; hydroxy C.sub.1 
to C.sub.6 alkyl esters of acrylic and methacrylic acid, such as 
hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl 
methacrylate and hydroxyethyl acrylate; amino C.sub.1 to C.sub.6 
alkylesters of acrylic and methyacrylic acid, such as aminoethyl 
methacrylate, aminooctyl methacrylate, N-methyl aminoethyl methacrylate, 
N-Octylaminoethyl methacrylate, and aminopentyl acrylate; glyceryl esters 
of acrylic and methacrylic acid, such as glyceryl mono methacrylate, 
glyceryl mono acrylate, and combinations thereof. Examples of suitable 
monomers that may be used for providing the functional groups of Group B 
include isocyanato ethyl methacrylate, glycidyl methacrylate, and 
combinations thereof. 
In addition to the above, the contact lenses may also contain copolymerized 
monomers not having the functional groups, for example, N-vinyl 
heterocyclic monomers, such as N-vinyl-2-pyrrolidone; C.sub.1 to C.sub.6 
alkyl vinyl ethers, such as vinyl ethyl ether; C.sub.1 to C.sub.6 alkyl 
ester of acrylic or methacrylic acid, such as methyl methacrylate and 
propyl acrylate; C.sub.1 to C.sub.6 alkyl styrene, such as t-butyl 
styrene; vinyl monomers, such as vinyl chloride and vinyl acetate; diene 
monomers, such as isoprene; and C.sub.1 to C.sub.6 alkoxy C.sub.1 to 
C.sub.6 alkyl esters of acrylic or methacrylic acid, such as ethoxyethyl 
methacrylate or methoxypropyl acrylate. 
A preferred monomer for making the lenses is hydroxyethyl methacrylate. 
Examples of preferred lens polymers are described in U.S. Pat. No. 
4,405,773 (Loshaek et al.) and contain 75 to 95 weight percent hydroxy 
straight-or-branched-chain C.sub.2 to C.sub.4 alkyl monoester of acrylic 
or methacrylic acid (preferably hydroxyethyl methacrylate), 5 to 20 
percent C.sub.2 -C.sub.4 alkoxy C.sub.2 -C.sub.4 alkyl ester of acryilc or 
methacrylic acid (preferably ethoxyethyl methacrylate) and 0.3 to 4 
percent acrylic or methacrylic acid (preferably methacrylic acid). 
If the lens is to be hydrophilic, large amounts of hydrophilic monomers 
which provide --OH, or --COOH functional groups, such as hydroxyethyl 
methacrylate and methacrylic acid, are used. For hard lenses, large 
amounts of monomers not containing hydrophilic functional groups, such as 
methyl methacrylate or t-butyl styrene, are used in combination with small 
amounts, i.e. amounts sufficient to provide the required adhesion, of 
monomers having the functional groups. 
Polymerization and lens shaping are well known in the art and are not part 
of this invention. Any of the well known techniques may be used, provided 
the lens polymer has the functional groups. 
To produce lenses in accordance with the invention, at least a portion of 
the surface of the lens is coated with a color coat comprising coloring 
substance and binding polymer which, like the lens polymer also has 
functional groups selected from Group A or Group B. If the lens polymer 
contains functional groups from Group A and the binding polymer has 
functional groups from Group B, or vice versa, the lens and binding 
polymers may be bonded directly to each other. However, if both the lens 
and binding polymers have functional groups from the same Group, for 
example Group A, then a compound having at least two functional groups per 
molecule of the other Group is used, e.g. if both lens and binding polymer 
have functional groups per molecule from Group B is used. Furthermore, if 
both lens and binding polymer have functional groups from the same Group, 
the functional groups need not be the same or in the same amount in the 
lens and binding polymer. It is within the scope of this invention to use 
more than one color coat on the same lens, with each color coat comprising 
the same or different binding systems described herein. 
Suitable compounds having at least two functional groups of Group B include 
hexamethylene diisocyanate (OCN--(CH.sub.2).sub.6 --NCO), and bisphenol A 
diepoxide, 
##STR2## 
Suitable compounds having at least two functional groups of Group A include 
ethylene glycol, ethylene diamine, and adipic acid. 
Either the front or rear surface or both may be coated, but the front 
convex surface is easier to coat than the rear concave surface. The coated 
lens is then subjected to conditions which cause the functional groups of 
Group A to react with the functional groups of Group B. If the coloring 
substance is transparent and the lens is a hard lens having a diameter no 
larger than that of the iris, then the entire lens surface may be coated. 
If the coloring substance is opaque, than only the portion of the lens 
corresponding to the iris should be coated, leaving the pupil section 
clear. For hydrophilic lenses, which are larger than the iris, the portion 
of the lens extending beyond the iris may be left uncoated. 
The presently preferred embodiment of the invention is to use lens and 
binding polymer having functional groups from Group A, and to use a 
compound having at least two isocyanate groups per molecule to supply the 
functional groups from Group B. The remainder of this description is 
directed to that embodiment. However, other embodiments may be carried out 
using similar principles. 
There are three preferred ways to carry out the coating step of the 
inventive method: 
(1) A mixture comprising coloring substance, binding polymer, isocyanate 
compound, and a solvent is coated onto the lens surface or portion 
thereof. 
(2) The lens is first coated with a mixture of isocyanate compound and a 
solvent and this coating is, in turn, coated with a mixture of binding 
polymer, coloring substance, and solvent. 
(3) The separate coating steps of method (2) are reversed. The lens is 
first coated with a mixture of binding polymer, coloring substance, and 
solvent and this coating is coated with a mixture of the isocyanate 
compound and solvent. 
The description of monomers used in preparing the binding polymer is the 
same as that for monomers used in making the lens. The functional groups 
(at least one of --OH, --COOH, and --NH--R) are present. For hydrophilic 
lenses the binding polymer may be made from the same monomers present in 
the same concentration as was used to make the lens. However, this is not 
absolutely necessary, as long as both polymers are such that upon 
hydration warpage does not occur. The binding polymer is preferably 
prepared in a solution that initially contains the selected monomers, 
solvent for the monomers, a molecular weight modifier and a polymerization 
initiator in a reaction vessel that is heated for a period sufficient to 
achieve a satisfactory polymerization level. This produces an 
uncrosslinked polymer dissolved in solvent which preferably contains some 
residual unreacted monomer. It is desirable to limit the molecular weight 
and amount of crosslinking of the polymers to maintain the viscosity of 
the reaction solution in a usable range. 
The molecular weight of the binding polymer may be conveniently controlled 
by using a molecular weight modifier such as a chain transfer agent, as is 
well known in the art. Suitable chain transfer agents include 2-mercapto 
ethanol, 1-dodecyl mercaptan and other alkyl mercaptans. Use of extra 
solvent is also a way to control molecular weight. 
Suitable polymerization initiators include free radial initiators such as 
2,2-azobis(isobutyronitrile), benzoyl peroxide, t-butyl peroxybenzoate, 
and t-butyl peroxide. However, the exact method of polymerizing the 
binding polymer is not critical. 
Suitable solvents include ethyl cellosolve, cyclopentanone, ethanol, 
t-butanol, acetone and other aliphatic and alicyclic ketones. A 
combination of solvents may be used. Ethyl lactate is a good co-solvent 
and under some circumstances water may be used as a co-solvent. The 
preferred solvent is a combination of cyclopentanone and ethyl lactate. 
The binding polymer solution and coloring substance are milled to form a 
colorant paste. 
If the binding polymer, coloring substance and isocyanate compound are to 
be applied in one step, the colorant paste, isocyanate compound and 
optional additional monomers are blended to form an ink, paint, or other 
applyable material which is coated onto the lens. If the applyable 
material is to be stored for long periods of time, it should be prepared 
without the isocyanate compound, which can be blended with the applyable 
material just prior to its being coated on to the lens. The pot life of 
the applyable material depends upon the reactivity of the isocyanate 
compound with the functional groups of the binding polymer. 
The choice of coloring substances is quite flexible, since they need not 
necessarily contain functional groups. Preferred coloring substances 
include for a blue color, phthalocyanine blue (Pigment Blue 15, C.I. 
74160); for a green color, phthalocyanine green (Pigment Green 7, C.I. 
74260) and chromium sesquioxide; for yellow, red, brown and black colors, 
various iron oxides. Of course, blends of such coloring substances are 
used to achieve the desired shade. For an opaque coating, titanium dioxide 
is a preferred opaquing agent. Opaquing agents, which are considered to be 
coloring substances within the present specification and claims, are 
blended with the other coloring substances into the colorant paste. 
Hexamethylene diisocyanate (OCN--(CH.sub.2).sub.6 --NCO) is the preferred 
isocyanate compound. However, use of any isocyanate having the formula 
R.sup.1 (NCO).sub.n wherein n is greater than or equal to two, (preferably 
two) is within the scope of this invention. R.sup.1 may be a di- or 
greater valent organic radical such as aliphatic, alicyclic, 
aliphatic-alicyclic, aromatic, or aliphatic-aromatic hydrocarbon. Thus, 
other suitable isocyanate compounds are 2,4-toluene diisocyanate and 
bis(isocyanato phenyl)methane. 
It has been found that the addition of a crosslinking agent for the lens 
and binding polymer, such as ethylene glycol dimethacrylate reduces the 
amount of isocyanate compound needed to achieve good adhesion. 
The coated lens is then subjected to conditions which cause the isocyanate 
groups to react with the functional groups of the binding and lens 
polymers, thereby firmly binding the lens and binding polymer to each 
other and entrapping the coloring substance within the binding polymer in 
a manner which forms a very stable, durable colored contact lens. Of 
course, some coloring substances may have functional groups that also 
react directly with the isocyanate groups, and such additional reaction is 
also within the scope of this invention. Typically the lens is dried under 
vacuum at at least about 20.degree. C. (preferably 50.degree. C.) for at 
least about 15 (preferably 30 minutes) to evaporate the solvent, then 
cured at at least about 70.degree. C. (preferably 90.degree. C.) for at 
least about 30 miinutes (preferably 90 minutes). Catalyst to speed the 
reaction of the isocyanate compound with the lens and binder polymers may 
be added to the ink immediately prior to its being coated onto the lens. 
Such catalysts include tertiary amines, such as triethylamine, benzyl 
dimethylamine, dimethylcyclohexyl amine; and metallic catalysts such as 
stannous octoate and dibutyltin dilaurate. The above conditions are 
illustrative and not intended to limit the scope of the invention. Time 
and temperature can be optimized for any combination of materials. 
For colored hydrophilic contact lenses, the cured lenses are hydrated by 
methods commonly used for uncolored hydrophilic lenses. 
The following table shows the desirable amounts of ingredients used to form 
inks in accordance with the invention. 
__________________________________________________________________________ 
WEIGHT PERCENT OF COMPONENTS 
IN INK 
MORE PREFERRED 
INGREDIENT BROAD RANGE 
PREFERRED RANGE 
RANGE 
__________________________________________________________________________ 
Binding Polymer 
10-40 13-25 16-23 
(including residual 
unreacted monomer) 
Isocyanate Functional (1) 
0.5-10 1.5-5 
Compound Amount 
Opaque Coloring Sub- 
Functional (1) 
Functional (1) 
6.5-30 
stance (if opaque 
Amount Amount 
color is desired) 
Transparent Coloring 
Functional (1) 
Functional (1) 
1-20 
Substance (if trans- 
Amount Amount 
parent color is 
desired) 
Polymerization 
0-1.0 0.05-0.5 0.1-0.3 
Initiator 
Additional Functional (1) 
0-50 15-30 
Monomers Amount 
Solvent q.s. ad 100% 
q.s. ad 100% 
q.s. ad 100% 
__________________________________________________________________________ 
(1) "Functional Amount" means the amount which an experimenter, skilled i 
the art, would use to achieve the desired result.

The following examples illustrate invention. In the examples the following 
abbreviations are used. 
HEMA is 2-hydroxyethyl methacrylate 
EOEMA is 2-ethoxyethyl methacrylate 
MAA is methacrylic acid 
AIBN is azobis(isobutyronitrile) 
HMD is hexamethylene diisocyanate 
ME is 2-mercapto ethanol 
EXAMPLES 
Example 1 
Preparation of a Binding Polymer-Solvent Mixture 
Prepare a mixture containing 91.5 parts HEMA, 8 parts EOEMA, 0.5 parts MAA, 
0.5 parts ME and 0.5 parts AIBN. Dissolve 43 parts of this mixture in 57 
parts of ethylcellosolve (57 parts cyclopentanone is currently preferred). 
Polymerize by heat (typically 38.degree. C. for 48 hours for this mixture) 
until only about 10 percent of the monomer remains. This amount of 
polymerization for this formulation has been found to provide the proper 
application viscosity and adhesion characteristics. The amount of residual 
monomer remaining at any time can be determined by gas chromatrography. 
The viscosity of the mixture after polymerization was about 25,000 cps. To 
100 parts of the resulting mixture, add 38 parts of ethyl lactate and 
dissolve. The resulting Binding Polymer-Solvent mixture is used as a 
starting material in further examples. 
Example 2 
Preparation of a Colorant Paste 
The binding polymer-solvent mixture prepared in example 1 is blended with 
coloring substance in the ratios shown in the table below to form a 
slurry. The slurry is milled on a roll mill for about 15 minutes until a 
homogeneous paste results. Alternatively, the paste may be prepared by 
ball milling the coloring substance with the binding polymer and solvents. 
______________________________________ 
Parts 
Parts Binding- 
Ex- Coloring polymer 
am- Coloring Sub- Solvent 
Resulting 
ple Substance stance Mixture 
Color 
______________________________________ 
2A Phthalocyanine 1 66 Trans- 
blue parent 
blue 
2B Chromium sesquioxide 
4 9 Green 
and phthalocyanine blue 
(300:1) 
2C Same as for example 2B 
1 3 Green 
2D Iron oxides and chromium 
4 13 Brown 
sesquioxide (3:2) 
2E Phthalocyanine blue 
1 12.5 Opaque 
and TiO.sub.2 (1:21) blue 
______________________________________ 
Example 3 
Preparation of Ink 
Because the color coat is to be applied to the lens by printing, the 
materials prepared by these examples are inks. However, other application 
methods, such as painting or spraying are possible. Hence, use of inks, 
paints, and other color coating substances are in accordance with the 
invention. 
Transparent and opaque inks suitable for coating on to contact lenses are 
prepared by blending the ingredients listed in the following table. 
______________________________________ 
Example No. Ingredients 
______________________________________ 
3A 3 parts paste of example 2E 
1 part monomer mixture containing 
HEMA 91.5 parts 
EOEMA 8 parts 
MAA 0.5 parts 
AIBN 0.5 parts 
______________________________________ 
Example 3A uses no isocyanate compound and is for comparison purposes only. 
______________________________________ 
Example No. Ingredients 
______________________________________ 
3B 3 parts paste of example 2E 
1 part monomer mixture containing 
HEMA 91.5 parts 
EOEMA 8 parts 
MAA 0.5 parts 
AIBN 0.5 parts 
HMD 0.61 percent of the above 4 parts 
3C 3 parts paste of example 2E 
1 part monomer mixture containing 
HEMA 91.5 parts 
EOEMA 8 parts 
MAA 0.5 parts 
AIBN 0.5 parts 
HMD 0.99 percent of the above 4 parts 
3D 3 parts paste of example 2E 
1 part monomer mixture containing 
HEMA 91.5 parts 
EOEMA 8 parts 
MAA 0.5 parts 
AIBN 0.5 parts 
HMD 1.5 percent of the above 4 parts 
3E 3 parts paste of example 2E 
1 part monomer mixture containing 
HEMA 91.5 parts 
EOEMA 8 parts 
MAA 0.5 parts 
AIBN 0.5 parts 
HMD 1.98 percent of the above 4 parts 
3F 3 parts paste of example 2E 
1 part monomer mixture containing 
HEMA 91.5 parts 
EOEMA 8 parts 
MAA 0.5 parts 
AIBN 0.5 parts 
HMD 2.44 percent of the above 4 parts 
3G 3 parts paste of example 2E 
1 part monomer mixture containing 
HEMA 91.5 parts 
EOEMA 8 parts 
MAA 0.5 parts 
AIBN 0.5 parts 
HMD 4.79 percent of the above 4 parts 
3H 3 parts paste of example 2E 
1 part monomer mixture containing 
HEMA 91.5 parts 
EOEMA 8 parts 
MAA 0.5 parts 
AIBN 0.5 parts 
HMD 9.7 percent of the above 4 parts 
3I 3 parts paste of example 2A 
1 part monomer mixture of example 3F 
HMD, 2.44 percent of the above 4 parts 
3J 3 parts paste of example 2B 
1 part monomer mixture of example 3F 
HMD, 2.44 percent of the above 4 parts 
3K 3 parts paste of example 2D 
1 part monomer mixture of example 3F 
HMD, 2.44 percent of the above 4 parts 
______________________________________ 
Example 4 
Alternative Ink Compositions 
Prepare a mixture containing 88.1 parts HEMA, 9.8 parts EOEMA, 2.1 parts 
MAA, 0.5 TS AIBN, and 0.5 parts ME. Dissolve 43 parts of this mixture 
in 57 parts of cyclopentanone. Polymerize by heat until about 10 percent 
of the monomers remain. To 100 parts of the resulting mixture add 38 parts 
of ethyl lactate and dissolve to form a binding polymer-solvent mixture. 
Repeat examples 2A through 2E using this binding polymer-solvent mixture to 
form colorant pastes similar to colorant pastes 2A through 2E. 
Repeat example 3 making inks having the following formulas: 
______________________________________ 
Example No. Ingredients 
______________________________________ 
4A 3 parts paste similar to 2E 
1 part monomer mixture containing 
HEMA 88.1 parts 
EOEMA 9.8 parts 
MAA 2.1 parts 
AIBN 0.1 parts 
HMD 2.44 percent of the above 4 parts 
4B 3 parts paste similar to 2A 
1 part monomer mixture of example 4A 
HMD, 2.44 percent of the above 4 parts 
4C 3 parts paste similar to 2B 
1 part monomer mixture of example 4A 
HMD, 2.44 percent of the above 4 parts 
4D 3 parts paste similar to 2D 
1 part monomer mixture of example 4A 
HMD, 2.44 percent of the above 4 parts 
______________________________________ 
Example 5 
Repeat example 4A, except omit the AIBN, and use 2.75 percent HMD. 
Example 6 
Repeat example 3D, except replace the HMD with an equal amount of 
2,4-toluene diisocyanate. 
Example 7 
Printing and Testing of Colored Lenses 
Unhydrated hydrophilic contact lenses manufactured as described in U.S. 
Pat. No. 4,405,773, are printed in an annular pattern as described in U.S. 
patent application Ser. No. 600,860, filed Apr. 16, 1984, now U.S. Pat. 
No. 4,582,402 with the inks of examples 3 to 6. The printed lenses are 
dried under vacuum at 50.degree. C. for 30 minutes, then cured at 
90.degree. C. for 90 minutes. 
The printed contact lenses are hydrated by submersion in a stirred normal 
saline solution (0.9 percent by weight of salt in water) at pH 8 and 
temperature of 90.degree.-100.degree. C. for 2 hours. The hydrated lenses 
are stored in normal saline buffered at a pH of 7.4. 
Two test methods (the rub test and the methanol test) may be used to 
determine the strength of the adhesive bond. The hydrated lenses are 
folded back upon themselves in the rub test, printed side in, and rubbed 
between the thumb and forefinger. In the methanol test the hydrated lenses 
are sprayed with methanol at room temperature for 30 seconds. In both 
tests adhesion or lack thereof is observed visually. The methanol test is 
more severe than the rub test. Batches of 5 lenses are tested. Results of 
the tests are reported in the table below. 
______________________________________ 
Ink Lens Test Results (Pass/Fail) 
Examle No. Material.sup.a 
RUB Methanol 
______________________________________ 
3A 1 0/5 0/5 
3B 1 1/4 not tested 
3C 1 4/1 not tested 
3D 1 5/0 not tested 
3E 1 5/0 not tested 
3F 1 5/0 5/0 
3G 1 5/0 not tested 
3H 1 5/0 not tested 
3I 1 5/0 5/0 
3J 1 5/0 5/0 
3K 1 5/0 5/0 
4A 2 5/0 5/0 
4B 2 5/0 5/0 
4C 2 5/0 5/0 
4D 2 5/0 5/0 
5 2 5/0 not tested 
6 1 5/0 not tested 
______________________________________ 
.sup.a Lenses made of material 1 contain 
91.5 parts HEMA 
8 parts EOEMA 
0.5 parts MAA 
and had a water content after hydration of 38%. 
Lenses made of material 2 contain 
88.1 parts HEMA 
9.8 parts EOEMA 
2.1 parts MAA 
and had a water content of 55% after hydration. 
In the test results Sample 3A, which contains no diisocyanate in the color 
coat, shows adhesion failure. Adhesion improves as more diisocyanate is 
added. 
Example 8 
A contact lens comprising 88.1 percent HEMA, 9.8 percent EOEMA, and 2.1 
percent MAA is coated with a solution of 1 percent HMD in 2,2-diethoxy 
propane. The lens is air dried and printed with an ink having the same 
composition as the ink of example 3A but containing no diisocyanate. Upon 
hydration, all five lenses pass the rub test. 
This example illustrates an alternative technique for attaching the 
colorant to the lens, i.e., by precoating the lens with the isocyanate 
compound prior to application of the ink. 
Example 9 
A lens containing 91.5 percent HEMA, 8 percent EOEMA, and 0.5 percent MAA 
is printed with the ink of example 3F. The printed pattern is overcoated 
with a clear material containing binding polymer, solvent and HMD, but no 
coloring substance. 
The binder-polymer solvent mixture contains substantially uncrosslinked 
polymers and monomers (approx. 70-80 percent polymerized) of 91.5 percent 
HEMA, 8 percent EOEMA and 0.5 percent MAA as a 25 percent solids solution 
in cyclopentanone. 
The clear coating material consists of 66.50 parts of the binding polymer 
solvent mixture, 33.25 parts cyclopentanone and 0.25 parts HMD. 
Approximately 5 microliters of this solution is spread onto the printed, 
dried surface of the lens. 
After curing the coating, all five lenses pass the rub test. This example 
shows yet another method of causing the ink to adhere to the lens. 
Example 10 
An ink was prepared with Gantrez S-95(1) as the polymeric binder. Gantrez 
S-95(1) is a hydrolyzed methyl vinyl ether-maleic anhydride copolymer from 
GAF Corporation. 
FNT (1) Trademark or Tradename 
8.0 grams of Gantrez S-95 is stirred into 29.0 grams of ethyl cellosolve 
and 11.3 grams of distilled water. 34.4 grams of this mixture is blended 
with 13.2 grams of a slurry of 1.79 weight percent phthalocyanine blue and 
37.08 percent TiO.sub.2 in ethyl lactate. 
2.45 grams of HMD is added to the blended mixture with stirring. Lenses of 
the composition 88.1 percent HEMA, 9.8 percent EOEMA and 2.1 percent MAA 
are printed with this colorant. The printed lenses are heated at 
80.degree. C. for 72 hours at atmospheric pressure. Another set of lenses 
are printed and heated the same way except that the colorant has no HMD. 
The lenses with no HMD in the colorant do not pass the rub test. The 
lenses with HMD in the colorant pass both the rub test and the methanol 
test. This example illustrates the case in which the binding polymer and 
lens polymers are different. 
It can be seen that the present invention provides a degree of versatility 
and durability not achievable with prior coloring technique. The color 
coat may be opaque or transparent. Hard or Soft lenses may be colored. The 
color coating applied to hydrophilic lenses is more durable than coating 
applied by prior art methods. Selected portions of the lens may be coated. 
Indeed the coating may be deposited over the iris section of the lens in a 
highly desirable pattern.