Compositions: coating or plastic – Coating or plastic compositions – Silicon containing other than solely as silicon dioxide or...
Reexamination Certificate
2001-05-30
2003-08-19
Moore, Margaret G. (Department: 1712)
Compositions: coating or plastic
Coating or plastic compositions
Silicon containing other than solely as silicon dioxide or...
C106S287150, C106S287160, C528S032000, C528S039000
Reexamination Certificate
active
06607590
ABSTRACT:
BACKGROUND OF THE INVENTION
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.
Plastic materials commonly are used for ophthalmic lenses because they are lighter, easier to process and provide better impact resistance than glass. 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. This problem may be alleviated by coating the lens surfaces with an abrasion and stain resistant thin film that commonly is known as a hardcoat.
The most desirable materials for hardcoating lenses are inorganic oxides such as quartz, fused silica, glass, aluminum dioxide, titanium dioxide and other ceramics. Because thin films of these inorganic oxides are best applied in traditional processes that reach 1000° 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.
Polymer coating materials have been developed that provide better abrasion and stain resistance than the surfaces of the plastic materials that are used for ophthalmic lenses, and many of these coating materials include an inorganic component for enhancing the abrasion resistance of the coating. The abrasion resistant properties of these polymer coating materials increase with increasing crosslinking of the polymer molecules because the density and hardness of the protective film that is formed from the coating material increases. Most abrasion resistant polymer coatings are formed by either thermal or radiation curing. The thermal process involves a condensation reaction of reactive monomers or oligomers, while the radiation process involves free radical polymerization.
One measure of the degree of crosslinking, hardness, abrasion resistance and porosity of a coating is whether or not a protective film applied to a lens is tintable. Protective films formed from known polymer coating materials are tintable because the pores of the film are larger than the dye pigment molecules. In a known wet molecular adsorption tinting process, a coated lens is submerged in a dye bath or organic dye molecules and water maintained at 95-100° C., and this elevated temperature expands the size of the pores in the protective film by different amounts depending on the degree of crosslinking in the coating polymer. In known protective films, the pores are large enough to be penetrated by the dye molecules which range in size between about 5-30 angstroms.
Highly crosslinked polymer coatings that are more abrasion resistant than the polymers used for ophthalmic lenses are disclosed in many U.S. patents, several of which are mentioned hereafter by way of example. U.S. Pat. No. 4,407,855 discloses a pentaerythritol-based polyacrylate or polymethacrylate composition. U.S. Pat. No. 4,954,591 discloses a tintable coating composition of polyfunctional acrylate, n-vinyl derivatives and ethylenically unsaturated copolymer. U.S. Pat. No. 5,246,728 discloses a composition of tri- and tetra-acrylates in butanol. U.S. Pat. No. 5,401,541 discloses a highly crosslinked acrylic copolymer that is derived from a multifunctional aliphatic acrylate monomer. U.S. Pat. No. 5,459,176 discloses a tintable composition of polyacryloylated alkane polyols.
Although polymer coating compositions of the type described in the above patents form protective films that are much harder than the surfaces of the polymeric ophthalmic lenses, the nature of the carbon-carbon and carbon-hydrogen bonds in the films is not changed. In addition, the improvement in abrasion resistance does not approach the abrasion resistance provided by protective films of inorganic oxides.
The hardness and abrasion resistance of organic polymer coatings is improved by mixing an inorganic oxide, such as silica, with the composition that is used to form the coating. These compositions may be thermally cured or may be cured by ultraviolet radiation depending on the polymer that is used. Film coatings produced with such compositions are clear provided the individual silica particles are well dispersed and smaller than the visible wavelengths of light.
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. Polymer compositions that include colloidal silica are disclosed in many U.S. patents, several of which are mentioned hereafter by way of example. U.S. Pat. No. 4,499,217 discloses a dispersion of colloidal silica in a thermosetting polymer. U.S. Pat. Nos. 4,973,612, 5,075,348 and 5,188,900 disclose blends of multifunctional acrylates, unsaturated organic compounds and colloidal silica. U.S. Pat. No. 5,104,929 discloses a blend of colloidal silica in ethylenically unsaturated aliphatic and/or cycloaliphatic monomers. 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.
Attempts to alleviate the problems inherent in the lack of a chemical bond between the colloidal silica and the polymer have included the addition of reactive silane compounds to the composition for modifying the surfaces of the colloidal silica particles or for reacting with same. Disclosures of such compositions may be found in many U.S. patents, several of which are mentioned hereafter by way of example. U.S. Pat. No. 4,348,462 discloses a radiation curable composition that includes colloidal silica, acryloxy or glycidoxy functional silanes, non-silyl acrylates, and catalytic amounts of ultraviolet light sensitive cationic and radical type photoinitiators. This composition is said to cure to a transparent hard coating with improved abrasion resistance. U.S. Pat. No. 3,986,997 discloses a composition that includes colloidal silica, hydroxylated organosiloxanes and a silanol condensation catalyst. U.S. Pat. No. 4,478,876 discloses a composition that includes a blend of acrylate monomer, colloidal silica and acryloxy functional silane. U.S. Pat. No. 5,426,131 discloses a composition that includes acrylic monomers, functionalized colloidal silica and acrylated urethane. U.S. Pat. No. 4,177,315 discloses the generation of silica within the composition by hydrolyzing tetraethyl orthosilicate and aging the composition followed by the addition of organic silanol compounds to modify the preformed silica. U.S. Pat. No. 4,211,823 discloses a composition that has one or more compounds selected from a group that includes an epoxy group, a silanol gro
Jin Dan L.
Singh Brij P.
Jones Day
nanoFILM Ltd.
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