Plastic and nonmetallic article shaping or treating: processes – With step of cleaning – polishing – or preconditioning...
Reexamination Certificate
2000-03-02
2002-02-26
Dawson, Robert (Department: 1712)
Plastic and nonmetallic article shaping or treating: processes
With step of cleaning, polishing, or preconditioning...
C428S426000, C428S427000, C428S428000, C428S432000, C428S446000, C428S450000, C427S162000, C427S164000, C427S165000
Reexamination Certificate
active
06350397
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an improved optical member such as a transparent, planar, curved or shaped member or glass sheet having at least one layer or coating that provides useful, improved washability or cleanability properties. The coatings of the invention provide a surface composition and a shaped nanostructure that promotes removal of particulate soils when the surface and soil are contacted with water or aqueous cleaning solution. More particularly, the invention relates to an optical member used in a window pane, window light, window glass, wind screen, electronic display, wind shield or other substantially planar transparent member used in any structure, conveyance, instrument, device, etc., using a transparent member to permit viewing through or across a boundary.
BACKGROUND OF THE INVENTION
Optical or transparent members are made of materials that permit transmittal of light in a manner that does not substantially distort an image. Such images include an aspect or environmental scene, an interior setting, an incandescent or florescent image, etc. Transparent members are typically made of non-crystalline materials used above the glass transition temperature. Transparent materials include inorganic glasses such as silicate glass, silicate-soda ash glass, borosilicate glass, etc.; thermoplastics such as polycarbonate, acrylic, etc. and other specialty crystalline and glassy materials.
The most common transparent members comprise silicate, and silicate-soda ash glass. Such glass technology has evolved since antiquity. These glass materials are typically understood to be an inorganic substance in a highly thickened but “liquid” state of the substance. As a result of a reversible change in viscosity, such materials attain such a high degree of viscosity to be, for all practical purposes (in a 40+ year useful life) rigid and non-flowing. Common silicate-soda ash window glass is manufactured from commonly available silicate (SiO
2
) minerals and carbonate (Na
2
CO
3
) minerals. The basic structure of silicate glass is the silicon-oxygen tetrahedron in which a silicon atom is in an sp
3
tetrahedral bonding structure coordinated to four surrounding oxygen atoms. The oxygen shared between tetrahedron are called bridging oxygens. Virtually all such glass compositions comprise silicate glasses containing modifiers and intermediates. The addition of a modifier such as sodium oxide, boron compounds or sodium carbonate to the silica network alters the structure cleaving Si—O—Si bonds to form an Si—O—Na
+
or other modified linkage. Examples of chemicals that have been used to improve the physical nature of the glass layer include alkaline earth metal compounds; boric oxide compounds; alumino-silicate glass generating compounds; lead compounds; borate and phosphate glass compounds; oxides including germanium, arsenic, antimony oxides, etc,; sulfur, selenium and tellurium compounds; and halogens such as zinc chloride, and BeF
2
are also known. The purpose of these chemical modifications to the glass composition improves the mechanical properties such as hardness, the chemical stability, the heat resistance, or other physical or optical properties of the glass relating to end use requirements.
Most silica glass currently manufactured results from a process in which raw materials are converted at very high temperatures to an homogeneous flowable melt. The melt results from heating a combination of one or more typical ingredients such as glass sand (SiO
2
), soda ash (sodium carbonate), limestone (CaCO
3
), feldspar or other inorganic oxides such as potassium oxide, magnesium oxide, zinc oxide, barium oxide, lead oxide, etc. The inorganic materials are blended and melted at high temperatures typically from about 1500° C. to 1800° C. forming a flowable melt. The melt is then drawn from the heater and is drawn, rolled or quenched depending on the desired shape and end use. Bottles, dishes, optical lenses, tubes, sheets, cylinders, etc. are formed by floating, blowing, pressing, casting or spinning the glass to cool the glass to a solid. Large glass sheets are typically manufactured by floating the melt on molten tin in a non-oxidizing or reducing environment to form a planar extremely flat glass sheet with parallel faces. The glass face contacting the tin bath tends to acquire an amount of tin oxide (SnO
2
) on the glass that typically range in trace amounts on the glass sheet. Such tin residues do not comprise any nanostructure regions but are only a random surface scattering of tin oxide. These chemically modified glasses typically enhance the macro thermal, electrical and mechanical properties of the gross material.
The formation of association of one or more functional layers with one or more transparent layers of an optical member or glass sheet is also known. Mirrored layers have been made since antiquity. The association of a macro polymeric layer with one or more glass sheets is also known, for example, Safety glass in automobile manufacture comprises a sandwich comprising two layers of glass with an intermediate polyvinylbutyral layer. Optical members such as glass sheets have been surface modified using various chemical deposition techniques to form organic and inorganic layers on the glass. Such layers have been combined with organic silicone compounds, organic film forming materials, surface derivatizing organic materials, olefinic polymeric forming compositions and other materials that form macro layers on the glass surface. The formation of inorganic coatings on glass sheets is also commonly performed during glass manufacture. At high temperature, glass sheets tend to favorably react with organic and inorganic materials to form active macro coatings on the glass. Kirkbride et al., U.S. Pat. No. 4,019,887; Landau, U.S. Pat. No. 4,188,444; Shibata et al., U.S. Pat. No. 5,304,399; and others show the formation of a silicon or silica complex from continuous chemical treatment of the hot glass substrate with a non-oxidizing reactive silane containing compound. The formation of other simple macro layers using such deposition techniques is well within the skill of the ordinary artisan in this technology area. These relatively simple macro coatings typically improve the mechanical, chemical and thermal resistance of the glass surface to conditions in its use locus.
Coatings on optical members such as glass sheets having an improved geometry are also known. Ohwaki et al., U.S. Pat. No. 4,855,176, disclose macro structures (structures having millimeter size dimensions) with hydrophilic and hydrophobic regions to improve the anti-blurring properties of optical members used in windows, mirrors, etc. Similar to the technology shown in the Ohwaki et al. disclosure other patents relate to forming macro films on optical members that have varying degrees of tendency to associate with aqueous materials such as Komatsu, U.S. Pat. No. 5,594,585, which shows a hydrophilic film made from silicon dioxide. Sugawara et al., Japanese Application No. 07-33599, show a hydrophilic mirror coating comprising a metal oxide having a macro structure. Kai et al., Japanese Application No. 05-315261, show a hydrophilic mirror coating comprising silicon dioxide, zirconium dioxide, titanium dioxide, aluminum oxide and others to form a surface that rapidly drains incident water. Endo et al., Japanese Application No. 62-168702, show a hydrophilic transparent film made from indium oxide, tin oxide and others. Tiller et al., European Application No. 594171, disclose a SiO
x
coating using flame-pyrolytic deposition of an organo silane to form a hydrophilic surface.
The prior art taken as a whole focuses on forming chemical modified surface layers having thick layers or macro structures (dimension greater than 1 mm) for the purpose of improving chemical, thermal and physical resistance and to improve the hydrophilicity of the surface to improve visibility.
Self-cleaning glass technology is also known and are different in mechanism than improved cleaning materials. The improved cleani
Arney Michael S.
Fairman James E.
Heikkila Kurt E.
Pylkki Russell J.
Wilken Douglas E.
Aspen Research Corporation
Dawson Robert
Feely Michael J
Merchant & Gould P.C.
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