Bleaching and dyeing; fluid treatment and chemical modification – Nontextile – dyeing process or product – including inorganic... – Contact lens
Patent
1995-11-06
1998-02-03
Einsmann, Margaret
Bleaching and dyeing; fluid treatment and chemical modification
Nontextile, dyeing process or product, including inorganic...
Contact lens
8552, 8602, D06P 500, C08J 704
Patent
active
057139636
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a procedure for staining contact lenses and a colour coating formulation for use in the procedure.
The purpose of stained contact lenses is to change the apparent color of the wearer's iris. In a staining technique used at present, a colour coating configuration is produced on the surface of contact lenses with a view to achieving an impression which is as natural as possible.
The coating may be accomplished by imprinting a colour mix containing bonding agent polymer, colour substance and possibly solvent and other substances modifying the polymer, and of which the viscosity has been adapted to be appropriate for the printing process. The colour coating formed by printing is then affixed to the lens surface. This adhering takes place by chemically curing the bonding agent polymer.
The contact lens staining technique has its deficiencies when one considers the printing technique, permanence and wear resistance of the stain, wearing comfort and interaction between printing and lens.
Towards affixing the colour coating, difunctional agents have been used which cause cross-linking between the bonding agent polymer contained in the colour coating and the polymer of the lens. In the contact lens manufacturing procedure disclosed in the Patent FI-84111, in the colour coating is used a compound containing, among others, two isocyanate groups, for affixing the colour coating. In the procedure of this reference the bonding agent polymer and the lens polymer are bonded together by means of a reaction between said isocyanate groups and hydroxyl, carboxyl and/or amino groups. It has now been found that the arrangement falls to work in practice. The cause responsible is untimely reaction of the highly reactive isocyanate groups with polymers containing functional groups of the types mentioned. For instance, when the diisocyanate compound is added to a printer's ink mixture of the generally known HEMA (hydroxyethylmethacrylate) bonding agent polymer, the compound reacts immediately with the bonding agent polymer, gelifying the mixture, thus rendering printing infeasible. Furthermore, isocyanates are substances highly harmful to human health, and therefore their use in a contact lens staining procedure involves a health risk.
The object of the present invention is to eliminate the drawbacks mentioned.
The object of the invention is specifically, to disclose a procedure enabling convenient coating of contact lenses with a colour coating containing cross-linking agent, and by which firm fixing of the colour coating on the lens surface is attained.
The object of the invention is, further, to disclose a colour coating information for contact lens coating.
Regarding the features characterizing the invention, reference is made to the claims.
In the procedure of the invention, at least part of the surface of a lens consisting of polymer containing hydroxyl and/or carboxyl groups is coated with a colour coating containing colour matter, bonding agent polymer containing hydroxyl and/or carboxyl groups and as polymer-cross-linking agent a compound containing at least two urethane groups, or a mixture of such compounds. The colour coating is affixed on the lens surface by curing the bonding agent and by effecting a controlled urethane exchange reaction.
It has now unexpectedly being found in studies connected with the invention that urethane compounds containing at least two urethane groups can be used to cross-link bonding agent polymers and lens polymers. It was found in the studies that it is possible in a lens arrangement coated as above described, to effect a controlled urethane exchange reaction by reacting the urethane groups in appropriate conditions with the hydroxyl and/or carboxyl groups of the bonding agent polymer and the lens polymer. Thanks to the new urethane bonds thus formed, the polymers can be coupled with each other, that is, cross-linking is accomplished.
In the procedure of the invention, one uses for lens coating, advantageously, a colour coating formulation containing colour su
REFERENCES:
patent: 4373009 (1983-02-01), Winn
patent: 4668240 (1987-05-01), Loshaek
patent: 4857072 (1989-08-01), Narducy et al.
patent: 5219638 (1993-06-01), Imamura et al.
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