Source: http://www.google.com/patents/US4596745?dq=5,960,411
Timestamp: 2017-10-17 04:31:13
Document Index: 26850393

Matched Legal Cases: ['art 1', 'art 2', 'arts 1', 'arts 1', 'art 1', 'art 2', 'arts 1', 'arts 1', 'arts 1', 'art 1', 'art 2']

Patent US4596745 - Non-glare coating - Google Patents
A coating for reducing specular reflection on optical glass screens comprises a partially hydrolized metal alkoxide polymer. These alkoxides have the general formula M(OR)4 where M is selected from the group consisting of silicon, titanium and zirconium where R is alkyl with 1 to 6 carbon. The equivalent...http://www.google.com/patents/US4596745?utm_source=gb-gplus-sharePatent US4596745 - Non-glare coating
Publication number US4596745 A
Application number US 06/607,270
Publication number 06607270, 607270, US 4596745 A, US 4596745A, US-A-4596745, US4596745 A, US4596745A
Inventors Paul Chao
Original Assignee Cotek Company
US 4596745 A
Another glare reducing coating is disclosed in U.S. Pat. No. 3,635,751, and is prepared by a method comprising the steps of: warming the surface of the glass screen to about 30° C. to about 100° C.; coating the warmed surface with an aqueous solution containing about 1 to 10 weight percent of a lithium-stabilized silica sol; drying the coating; and, heating the dry coating at about 150° C. to 450° C.
An improvement to the lithium silicate coating method is described in U.S. Pat. No. 3,940,511. It was observed that glare-reducing lithium silicate coatings on cathode ray tube face plates developed objectionable haze or "bloom" upon standing or storage at normal ambient humidities and temperatures. The haze is objectionable esthetically and reduces the brightness and color fidelity of the transmitted image. A similar haze was observed for sodium and potassium silicate coatings that have been baked at temperatures of about 400° C. to about 500° C. It was further observed that some glare-reducing lithium-silicate coatings which contained light attenuating particles transmitted an image which appeared to have a brownish or other tint. In the method according to the improvement, the dry baked coating is washed or rinsed with hot water subsequent to the baking step. Washing the coating with hot water reduces or eliminates the tendency of the coating to form a haze or bloom. The washing was believed to remove soluble lithium compounds which were present in the coating. In order to correct for any tint in the transmitted image which might be imparted by the glare-reducing coating, the coating might also include a small amount of a color-correcting dye.
Glare-reducing coatings are also of interest in applications other than glass screens, for example, on the surfaces of semiconductor solar cells. The object of anti-reflective coatings in this application is to promote transmission of, and to prevent reflection back into the atmosphere of solar radiation. Proper coatings can reduce the amount of light reflected when applied in thicknesses of one quarter of a wave length. Such coatings, as described in U.S. Pat. No. 4,361,598, can be made from clear solutions which contain oxide constituents in a soluble polymerized form and from which uniform and continuous glass-like oxide films can be deposited on substrates at relatively low temperatures. Such a solution is prepared by reacting metal alkoxide with a mixture of critical amounts of water and/or acid in an alcohol diluted medium. Alkoxides may be Ti(OR)4 or Ta(OR)5, or another metal alkoxide such as Si(OR)4 in admixture with these alkoxides. Acids may be HCl or HNO3. Quarter wave inorganic optical coatings are deposited by applying the alkoxide solutions to a substrate and then heating the coating at a temperature above 350° C. Of course, glare reducing coatings for such solar cells must be bounded to a surface of silicon doped with germanium, for example, which can be expected to react differently than glass in bonding with surface coatings.
The glass screen or panel to be coated is first cleaned, if necessary, and then preheated to a temperature in the range of approximately 20° C. to 75° C., higher temperatures producing a more defined surface topology, and therefore a greater diffusion effect. After the solution is sprayed onto the screen or panel, the screen or panel is baked at a temperature in the range of approximately 500° C. to 550° C., for a time period in the range of five to twenty minutes.
With reference to the schematic illustration of FIG. 3, the panel and coating must be baked for a sufficient period of time, and at a sufficient temperature, to drive off the alcohol and water molecules from the coating. As a result, the coating becomes densified and transformed into a glossy material. At the same time, this material bonds to the glass surface through M-O-Si bonding. Temperatures below 500° C. are insufficient to stabilize the coating by driving off the solvent and water molecules. Temperatures in excess of 550° C. may damage or distort the glass panel. It has been found that baking the panel at a temperature of approximately 520° C. for approximately five minutes, or 500° C. for approximately twenty minutes, is sufficient to completely stabilize and bond the coating to the glass screen or panel.
The clean glass screens or panels are preheated to a temperature in the range of approximately 20° C. to 75° C. Such higher temperatures produce a more defined topology of the surface 16 of the film or coating 14, thereby providing a greater diffusion effect.
After the solution has been applied, the coating must be bonded and stabilized to the glass surface as shown in FIG. 3. This is accomplished by baking the panel and the solution applied thereto at a temperature in the range of approximately 500° C. to 550° C. for a sufficient amount of time to drive off the solvent and water in the solution, leavin a silica-titania-zirconia glass. The partially hydrolized metal alkoxides in the solution have the general formula [M(OR)2-x (OH)x ]n as shown on the film side of the film/glass interface before baking. At the elevated baking temperature, the OR and OH group of the polymer bonds with the SiOH group of the glass surface, forming an alcohol and water. This alcohol and water is then evaporated from the coating. As a result, the coating becomes dense and chemically bonded to the glass surface. When the baking is complete, the solution has completely evaporated, leaving a silica titania-zirconia glass as the anti-glare coating. As set forth in FIG. 2, it has been found that baking at a temperature of approximately 520° C. for approximately five minutes is sufficient.
(c) 3.18 ml H2 O+0.5 ml HNO3
(d) 5.5 gm TPT (titanium isopropoxide; Ti(OC3 H7)4)
Initially, the TEOS (b) was mixed into the 2-propanol (a), the mixture being then heated to a temperature of approximately 55° C. After heating, the water and nitric acid (c) were added and mixed during a period of approximately thirty minutes. Thereafter, the TPT (d) was added and mixed during a period of approximately fifteen minutes. Finally, the additional water and additional 2-propanol (e) were added and mixed during a period of approximately one and one half hours. At this point, the solution was ready for application to the glass screen or panel, preferably by spraying.
(c) 3.55 ml H2 O+0.7 ml HNO3
(d) 3.36 gm TBT (titanium butoxide; Ti(OC4 H9)4)+3.63 gm zirconium n-propoxide (Zr(OC3 H7)4)
(c) 3.2 ml H2 O+0.5 ml HNO3
(d) 6.72 gm TBT
(c) 3.91 ml H2 O+0.7 ml HNO3
(d) 5.76 gm TBT+0.93 gm Zr(OC3 H7)4
(e) 1.78 ml H2 O+6.0 ml 2-propanol
(d) 3.36 gm TBT+3.625 gm Zr(OC3 H7)4
Example 3 utilized formulation II, and was intended to demonstrate the effect of the number of passes of the spray gun used to form the coating. In this test, the air pressure was 47 psig, the fluid pressure was 18.5 inches and the distance from the spray gun to the CRT screen panel was 113/4 inches. In the absence of any coating, the gloss reading was 88.5±3.6. When the coating was formed from three passes of the spray gun the gloss reading was 66.2±4. When the coating was formed from four passes of the spray gun the gloss reading was 61±3.7.
Example 4 utilized formulation II, and was intended to demonstrate the effect of preheating the optical glass screen or panel. In part 1 of this test the air pressure was 47 psig, the fluid pressure was 18 inches, the distance from the spray gun to the panel was 113/4 inches and the coating was applied by five passes of the spray gun. In the absence of any coating the gloss reading was 89.4±1.9. When the coating was applied after preheating the panel between 45° C. and 50° C. the gloss reading was 62.2±2.7. When the coating was applied after preheating the panel to 60° C. the gloss reading was 53±3.
In part 2 of this test the air pressure was 47 psig, the fluid pressure was 18.5 inches, the distance from the spray gun to the panel was 113/4 inches and the coating was applied by four passes of the spray gun. In the absence of a coating the gloss reading was 88.5±3.6. When the coating was applied after preheating the panel to a temperature between 58° C. and 60° C. the gloss reading was 61±3.7. When the solution was applied after preheating the panel to 67° C. the gloss reading was 60.8±4.1. When the coating was applied after preheating the panel to 77° C. the gloss reading was 58.5±3.3.
Parts 1 and 2 of this test utilized formulations III and IV respectively, and were intended to demonstrate the effect of a reduction in the amount of metal alkoxide. The parameters of this test were held constant for both parts 1 and 2, except as noted. In part 1 of this test the molar ratio of SiO2 :TiO2 was 9.65:1. The coating was applied by five passes of the spray gun. The gloss reading was 72.7±2.5.
In part 2 of this test, the molar ratio of SiO2 :TiO2 was increased to 11:1, while the thickness of the coating was reduced by applying the coating with only four passes of the spray gun. In this part the gloss reading was 65.4±2.2.
This test utilized formulation II, and was intended to demonstrate that additional coatings could be applied after an initial baking of prior coatings. During this test the air pressure was 47 psig, the fluid pressure was 18 inches and the distance from the spray gun to the panel was 113/4 inches. A first coating was applied by three passes of the spray gun and baked at a temperature of 520° C. for approximately seven minutes. The gloss reading was 70.5±3.1. Thereafter, more solution was applied by three additional passes of the spray gun, and once again the panel was heated to a temperature of approximately 520° C. for approximately seven minutes. The gloss reading after the second application was 64.8±3.
Parts 1 and 2 of this test were made with formulations V and VI respectively, and were intended to demonstrate that changing the ratio of TiO2 to ZrO2 did not significantly alter the gloss reading, although zirconium imparts better alkali resistance to the stabilized film than does titanium. In each of parts 1 and 2 the parameters were held constant. In each of parts 1 and 2 the solution included 0.2 moles of SiO2. In part 1 the molar ratio of TiO2 :ZrO2 was 5.67:1. The gloss reading was 74.5±2.5.
In part 2, the molar ratio of TiO2 :ZrO2 was 1:1. The gloss reading was 75.5±1.3.
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U.S. Classification 428/428, 427/165, 428/432
International Classification G02B1/11, H01J29/89, C03C17/25
Cooperative Classification C03C2217/212, H01J29/896, C03C2217/22, C03C2217/23, C03C2217/213, C03C2218/113, C03C17/25, G02B1/111
European Classification H01J29/89F, G02B1/11B, C03C17/25
Owner name: COTEK COMPANY A PARTNERSHIP COMPRISING PAUL CHAU O
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:CHAO, PAUL;REEL/FRAME:004310/0547