Organic-inorganic hybrid polymer and method of making same

Abstract

An optically clear protective thin film having covalent chemical bonds on a molecular level between organic polymer and in situ generated silica molecules is formed from a hydrolyzed coating solution of tetraalkyl orthosilicate, epoxyalkylalkoxy silanes, (math)acryloxyalkylalkoxy silanes and solvent.

Description

RELATED APPLICATIONS[0001] This application is a division of copending U.S. Serial No. 09 / 870,221 filed May 30, 2001 which is a division of copending U.S. Ser. No. 09 / 528,276 filed Mar. 17, 2000.BACKGROUND OF THE INVENTION[0002] This application relates to the art of compositions and, more particularly, to an organic-inorganic hybrid polymer composition and a method of making same. The invention is particularly applicable to compositions for applying optically clear protective thin films to the surfaces of plastic eyeglass lenses and will be described with specific reference thereto. However, it will be appreciated that the invention has broader aspects and that the composition can be used for other purposes as well as for coating other plastic substrate surfaces, such as transparent display cases, windows and crystals for covering faces of clocks, watches and other instruments.[0003] Plastic materials commonly are used for ophthalmic lenses because they are lighter, easier to proce...

AI Technical Summary

Benefits of technology

[0026] A protective film in accordance with the present application has a very high density and a very high hardness to provide excellent abrasion and stain resistance. The high density and hardness are achieved by a high degree of cross linking between organic molecules and inorganic silica.

[0044] It is a further object of the invention to provide a composition that cures faster on plastic surfaces.

Problems solved by technology

However, the surfaces of the plastic materials used in ophthalmic lenses are relatively soft and porous compared to glass, and this frequently results in reduced optical clarity due to abrasion and staining of the lens surface.

Because thin films of these inorganic oxides are best applied in traditional processes that reach 1000.degree. C. or more, they cannot be used with lenses that are made of organic polymers which will decompose at such temperatures.

Inorganic oxides can be applied to organic polymers by such processes as chemical vapor deposition and the sol-gel process but it is difficult to achieve a good bond because of the inherent incompatibility between the inorganic coating and the organic substrate.

The different coefficients of thermal expansion for the inorganic coating and the organic substrate tend to cause delamination.

Inorganic films with sufficient thickness to adequately protect relatively soft plastic substrate surfaces may become brittle and are prone to crazing.

Equipment for chemical vapor deposition also requires a large capital investment and, because the necessary high vacuum chamber is relatively small, the numbers and sizes of articles that can be processed is limited.

In addition, the improvement in abrasion resistance does not approach the abrasion resistance provided by protective films of inorganic oxides.

The amount of silica that can be added to a coating material for ophthalmic lenses is limited by the requirements of avoiding agglomeration of silica particles and insuring good dispersion so that the silica particles will not be visible in the protective film.

These compositions do not have chemical bonding between the silica and the polymer, and protective thin film coatings formed with such compositions tend to fail in a relatively short time.

As previously mentioned, the silica particles sometimes become visible in the protective thin film coatings formed from the compositions or otherwise interfere with the optical clarity of the lenses on which the coatings are applied.

The relatively porous preformed silica particles also are relatively fragile and do not significantly alter the relatively soft nature of the plastic matrix.

However, methyl is an inert organic group that dramatically reduces the possible degree of crosslinking bonds.

Decreased crosslinking reduces the density of a film formed by the composition so that it remains relatively porous and does not have optimum hardness.

The absence of any curing compound also reduces the possible crosslinking reactions by silanol condensation and by ring opening polymerization of epoxy groups.

Thin film coatings formed by this composition also do not provide optimum abrasion resistance to the surface.

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