Color binding mechanism for contact lenses

Details Color binding mechanism for contact lenses Color binding mechanism for contact lenses

1991-10-01

1993-12-21

Lusignan, Michael

Stock material or miscellaneous articles

Composite

8507, 8509, 351162, 427164, 428500, B32B 904

Patent

active

052720101

DESCRIPTION:

BRIEF SUMMARY
U.S. Pat. No. 4,668,240 (Loshaek) discloses colored contact lenses produced, in its preferred embodiment, from lens polymers and binding polymers containing the functional groups --OH and --COOH and an additional compound containing at least two groups per molecule of the group --NCO (isocyanate). U.S. Pat. application Ser. No. 124,724, filed Nov. 24, 1987, now U.S. Pat. No. 4,857,072 discloses a color binding mechanism that is different from that of Loshaek, but which also, in its preferred embodiment, requires an isocyanate compound.
Although lenses produced in accordance with the Loshaek patent's preferred embodiment are an enormous commercial success, their manufacture requires use of an isocyanate compound for binding the color to the lens. The isocyanate compound has several disadvantages. Its vapors are noxious and toxic if inhaled excessively. Thus it must be used with great caution. The isocyanate compound is very reactive chemically with active hydrogen groups such as --OH in the water molecule. Thus its concentrations can be wastefully reduced, if such molecules are present in the production environment. Its great reactivity also gives rise to pot-life problems, after it is added to the color coating compound. Thus, after the isocyanate compound is added to the color coating ink, the viscosity increases rapidly to a point where the ink must be discarded. The changing viscosity makes control of the coating process difficult and affects the quality of the coating.
The present invention, which does not require use of an isocyanate compound, has several advantages over Loshaek's preferred embodiment:
1. Handling noxious and toxic isocyanate compounds is not necessary.
2. It is possible to print hydrophilic lenses that are fully hydrated, which is not believed practical using ink containing isocyanate compounds.
3. The inks, containing no isocyanate compounds, have better pot life.
4. Ink viscosity is more stable and easier to control.


SUMMARY OF THE INVENTION

A first aspect of the invention may be summarized as a method for making a colored contact lens comprising the steps of:
a) providing a contact lens constructed of non-hydrophilic polymers having functional groups selected from at least one of --COOH, --OH, and --NH--R, wherein R is hydrogen or C.sub.1 to C.sub.8 alkyl or hydrophilic polymers;
b) coating at least a portion of a surface of the lens with a color coat comprising at least one pigment, binding polymer having functional groups selected from at least one of --COOH, --OH, and --NH--R, wherein R is hydrogen or C.sub.1 to C.sub.8 alkyl, and an adhesion promotor having at least two functional groups per molecule of the formula --CH.sub.2 --O--R.sup.1 wherein R.sup.1 is hydrogen or C.sub.1 to C.sub.16 alkyl, and said --CH.sub.2 --O--R.sup.1 groups are attached to a carbon atom that is part of an aromatic ring, or attached to a nitrogen or oxygen atom;
c) subjecting the coated lens to conditions which cause the color coat to adhere to the lens.
Preferably, the lens polymer is hydrophilic and has functional groups selected from at least one of --COOH, --OH, and --NH--R, wherein R is hydrogen or C.sub.1 to C.sub.8 alkyl.
Also preferred is that the lens polymer and binding polymer are hydrophilic and are formed from monomers comprising at least one of acrylic acid, methacrylic acid, hydroxy C.sub.1 to C.sub.6 alkyl ester of acrylic acid and methacrylic acid, amino C.sub.1 to C.sub.8 alkyl ester of acrylic and methacrylic acid, glycerol esters of acrylic and methacrylic acid, and mixtures thereof.
More preferably, the lens polymer and binding polymers are formed from a mixture of monomers comprising hydroxyethyl methacrylate, ethoxyethyl methacrylate, and methacrylic acid.
Also preferred is that the lens polymer is hydrophilic and is formed from monomer comprising vinyl pyrrolidone and hydrophobic monomer.
Also preferred is that the adhesion promotor is ##STR1## wherein R is a carbon-to-carbon single bond or C.sub.1 to C.sub.6 alkylene and R.sup.5 is independently C.sub.1 to C.sub.6 alkyl, #

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