Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Reexamination Certificate
1999-07-14
2001-11-13
Hen, Bruce (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
C428S216000, C428S457000, C428S458000, C428S461000, C428S469000, C428S473500, C428S689000
Reexamination Certificate
active
06316084
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to coatings that protect a solid substrate from wear and abrasion and/or which provide properties such as magnetism electrical conductivity and UV absorption. More particularly, the invention relates to the formation of a transparent, abrasion-resistant optical coating on solid plastic substrates to prevent degradation and wear due to scratches and abrasion, and a method for making same, as well as for providing coating on substrates having UV resistance, responsiveness to magnetic fields, and electrical conductivity.
2. Background Description
Polymer (i.e. plastic) materials have many special properties that make them unique and ideal for use in many applications. In particular, optically transparent plastics such as polycarbonate, CR-39® (allyl diglycol carbonate), and acrylics (for example, polymethyl methacrylate) have found various commercial advantages in that they are not only light in weight and substantially shockproof (shatter-resistant), but they are also easier to fabricate and lower in cost than inorganic glass materials. Plastics have various practical applications for the direct replacement of inorganic glass components in products such as sunglass lenses, ophthalmic lenses, automobile, boat, truck, bus, train and airplane windows and headlight covers, camera lenses, microscope lenses, binocular lenses, telescope lenses, ski glasses, diving masks, display panels, signboards, name plates, commercial advertising displays, optical filters and windows, architectural building glazing, bar code scanner windows, reflectors, and mirrors.
However, most polymer materials suffer a serious drawback, i.e. they mar and scratch easily by physical contact with harder materials. Continuous marring and scratching result in impaired visibility and poor aesthetics, and often requires replacement of the plastic components.
Thus, highly transparent and abrasion-resistant coating for plastic substrate are of great interest and in great demand.
Several prior techniques disclose various methods to improve the abrasion wear resistance of plastic substrates (see, for example U.S. Pat. Nos. 5,679,413, 5,618,619, 5,190,807, 5,633,049, 4,544,572, 5,741,831, and 5,385,955). These patents teach that coating solutions may be spread onto the desired plastic substrates by dip, spray, spin, or flow techniques. The resulting coatings generally offer significant improvement of abrasion-resistance, but generally exhibit flow marks on the surface and an uneven coating thickness distribution that may cause undesirable optical aberrations. U.S. Pat. Nos. 4,073,967 and 4,084,021 teach that abrasion-resistant coatings form by spin dip, spray or flow methods and can be formed on smooth surfaces such as optical elements in spectacle lenses. However, the build-up of the coating material at the outer edge of the lens can cause optical aberration. These techniques are less satisfactory when they are used to coat irregular surfaces. Moreover, the application of many of the prior abrasion resistance coatings require thermally activated initiators so the plastic substrates must be exposed to elevated temperature in order to fully develop the physical properties of the coating and to remove the solvents. Such high temperature processing may significantly degrade the quality of the plastic, through the incorporation of residual stresses.
Vapor deposition techniques for coating application have also been employed. For example, U.S. Pat. No. 4,190,681 teaches a method for the vapor deposition of a top layer of silicon dioxide onto an intermediate layer of an acrylate-type polymer that has, in turn, been coated onto a polycarbonate substrate. However, this evaporative technique of applying a layer of silicon dioxide is often undesirable for several reasons, including (i) insufficient bond strength between the silicon dioxide layer and the underlying polymer layer, (ii) the resulting non-uniform surface is often characterized by pinholes, pits, and other imperfections, (iii) the difficulty to obtain uniformly thick coatings on curved or irregular or large-size substrates, (iv) the significant degradation of the plastic due to its exposure to high temperature, and (v) the spalling and cracking that occurs when the film thickness is increased beyond approximately 0.5 micrometer.
Even though some improvements in abrasion resistant coatings have been made over the abrasion resistance of uncoated plastic substrates, obtaining high quality abrasion-resistant coatings remains a major problem in industry, particularly for Ophthalmic lenses, automobile windows, and the many other areas as mentioned above. Moreover, a low-temperature process to fabricate optically transparent coating with the same abrasion resistance as inorganic glass on substrates (including plastics) of arbitrary sizes and geometries has heretofore not been developed.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide novel abrasion and scratch protective, magnetic, electrically conductive, thermally conductive, UV blocking coatings on solid substrates of arbitrary sizes and geometries using room temperature and pressure processing.
It is another object of the present invention to provide a novel protective coating which imparts abrasion and scratch resistance to plastic substrates of arbitrary sizes and geometries including, but not limited to ophthalmic lenses, sunglass lenses, automobile, boats, truck, bus, train and airplane windows and headlight covers, camera lenses, microscope lenses, binocular lenses, telescope lenses, ski glasses, diving masks, display panels, signboards, name plates, commercial advertising displays optical filters, lenses, and windows, architectural building glazing, bar code scanner windows, reflectors, mirrors, and other devices.
A still further object of the present invention is to provide a novel protective coating which imparts abrasion and scratch resistance to solid substrates and other relatively smooth solid surfaces including metals, alloys, semiconductors, dielectrics, ceramics, and carbon surfaces.
Another object of the present invention is to provide a novel protective coating that imparts not only abrasion and scratch resistance, but also UV light irradiation-resistance and control of the refractive index of the outermost coating layer, to solid substrates and other relatively smooth solid surfaces.
The inventive coating comprises multiply oppositely charged layers having at least two materials held together and held to a substrate by electrostatic charges. Each layer has a thickness between 0.1 nm to 100 nm and the aggregate thickness of the multiple oppositely charged layers being 1 nm to 1000 &mgr;m thick.
Accordingly, several advantages of the present invention are:
a) the manufacture of the coatings does not require the use of any compounding facility, high temperature or vacuum processing;
b) avoidance of volatile organic compounds, specialized process gases and clean room environmental conditions;
c) room temperature processing eliminates the formation of residual stresses that may be created by processing at high temperature, such residual stresses may degrade the mechanical performance of polymer substrate materials;
d) the combination of tough nanosized inorganic clusters (particle size less than 30 nm is preferred) and flexible organic (or polymer) molecules makes it possible to fabricate composite films tens to hundreds of micrometers in thickness with large pores, excellent stress relaxation and controlled or graded refractive index;
e) the solution-based coating process removes virtually all constrains on substrate size, shape and species;
f) the molecular-level uniformity of the thickness of the coatings formed by solution processing eliminates the effects of optical aberrations introduced by the nonuniform thickness of coatings produced by other methods;
g) the use of clusters having particle sizes less than 30 nm eliminates significant light scattering, and results in coatings that a
Claus Richard O.
Liu Yanjing
Hen Bruce
McGuireWoods LLP
Nanosonic, Inc.
Xu Ling
LandOfFree
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