MXPA00000291A - Neutral grey absorbing film - Google Patents

Abstract

A color neutral absorbing film applied as a coating on a glass substrate. The film is an antimony/tin oxide alloy coating containing at least about five atomic percent antimony. The coating is suitable for use in antireflective coatings containing other metal oxides or mixed metal oxides to achieve a coated glass article having a visible light transmittance of 30%or greater and a reflectance of less than 5%.

Description

GRAY NEUTRAL ABSORBENT FILM BACKGROUND OF THE INVENTION This invention relates to a neutral absorbent film suitable for use as a coating on a glass substrate. More particularly, this invention relates to a non-conductive and energy absorbing coating of an antimony / tin oxide alloy. Even more particularly, this invention is directed to a coating of antimony / tin oxide applied on a glass substrate to impart energy absorption and antireflective properties before the coated glass article. Glass coatings are commonly used to provide light attenuation and light transmission properties. Additionally, the coatings are designed to reduce the reflections of the interfaces between the individual coating layers and the glass when a plurality of coatings is applied to a glass substrate. Coated articles are often used singularly, or in combination with other coated articles, to form a glaze.

The attributes of the coated glass substrate depend on the specific coatings applied to the glass substrate. The coating compositions and the thicknesses impart energy absorption and light transmission properties within the coated article while also affecting the spectral properties. The desired attributes can be obtained by adjusting the compositions or thicknesses of the coating layer or the coating layers. However, adjustments to improve a specific property can adversely impact other transmission properties or other spectral properties of the coated glass article. It is often difficult to obtain the desired spectral properties when it comes to combining the specific absorption of energy and the properties of light transmission in a coated glass article. Antireflective coatings in glass are used to reduce the reflection of the surface of an optical component and to reduce the reflectance of an interface between optical media with different refractive indexes. - The reduction of visible reflection is achieved through the principle of optical interference. When the light af ela on the air-film, film-film and film-glass interfaces, a portion of the beam is reflected in each of the interfaces. Through a correct choice of thin film materials and thicknesses, the individual rays of reflected light can interfere destructively, thus reducing the observed visual reflectance. The use of a coating that has absorption properties allows an additional reduction of reflection through absorbing light while traveling through the film with a high absorption rate, thus reducing the incident light energy in the interface of the back part of the glass and in the film-glass interface. The absorption of visible light results in the reduction of visible light transmitted through the glass. Generally, the absorbent films are strongly colored and therefore do not result in neutral transmission or reflectance. The use of an energy absorbing film is preferred when the minimization of visible reflection is desired and a reduction in visible light transmission is acceptable. Absorbent films can also adversely impact the transmission of visible light to an unacceptable level for antireflection and solar control applications. For example, the publication of European Patent EP0780346 Al discloses a method for producing tin oxide films composed of antimony oxide. These films are applied pyrolytically and result in a film with a molar ratio of tin to antimony from 1: 0.2 to 1: 0.5. The resulting films, when applied to a neutral glass substrate with a thickness of around 50 nm to 1,500 nm, they result in a visible light transmission of less than 10 percent. The color of the films is usually a gray - dark violet color. Thus, the low transmission of visible light and the spectral properties make these films undesirable for anti-reflective glass applications. It may be advantageous to provide a coated glass article having a non-conductive, neutral-colored absorbent film that is capable of reducing the visible reflection of the glass while allowing the transmission of visible light of at least 30 percent. The film should also provide the desirable neutral color in both transmission and reflectance. It could further be advantageous to provide a neutral color non-conductive absorbent film that could be applied pyrolytically on a glass substrate. A pyrolytic film allows the disposition of the film in line, for example, in a process of production of floating glass. SUMMARY OF THE INVENTION In accordance with the present invention, a neutral color non-conductive absorbent film suitable for use as a glass coating has been provided. The film can be used for solar control or anti-reflective glass items. The film is an antimony / tin oxide alloy produced by combining a source of antimony with conventional tin oxide deposition precursors. The amount of antimony present in the film is at least five percent atomic weight. Due to considerations of cost and ease of manufacture, the amount of antimony present in the film is preferably from about five percent atomic weight to about ten percent atomic weight. The antimony / tin oxide alloy is preferably pyrolytically applied, in line in a strip of floating glass. The energy absorption properties of the film make it suitable for use as solar control or antireflective glassware. In an anti-reflective glass, where the energy absorbing film has a refractive index of about 1.8 to about 2.6, a metal oxide, having a lower refractive index, can be used to form the coated glass article . The film with a high refractive index is applied closer to the glass, where the film with the low refractive index works as an outer layer. High / low batteries reduce visible reflection to a lower level of five percent through the principle of optical interference. Additionally, the absorbent properties of the film allow a further reduction in visible reflection to a level below two percent. The thicknesses and optical characteristics of the coating stack can be adjusted to achieve a wide range of the specified transmission values. However, in a preferred embodiment, the coated glass article has a visible light transmission (111 C) of at least 30%. The reflection and the transmission of visible light are aesthetically neutral in their color. It is an object of the present invention to provide an energy absorbing film with neutral color for use as a coating on a glass substrate. The antimony / tin oxide alloy is an energy absorbing film that can be deposited on a glass substrate. The energy absorbing properties allow the use of the film in antireflective coating batteries and for solar control. In addition, the film exhibits a desired neutral color in both transmission and reflection. It is further an object of the present invention to provide an absorbent film that can be deposited pyrolytically on a glass substrate. The antimony / tin oxide alloy of the present invention is suitable for use in conventional tin oxide deposition precursors. The pirblitica deposition allows the application of the film in a strip of floating glass directly in the glass production process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In accordance with the present invention, it has been found that the antimony / tin oxide alloy film has about five percent atomic weight up to ten percent atomic weight. antimony, is suitable for use in a coated glass article. The film is an energy absorbing film that exhibits a neutral color in the transmission of visible light and reflection. The glazed glass item is especially suitable for use with anti-reflective glassware used for computer displays or monitors. However, the coated glass article of the present invention can also be used in other applications, such as architectural glazing and vehicle windows. Suitable glass substrates for use in the preparation of a coated glass article, in accordance with the present invention, can include any of the conventional clear glass compositions known in the art. The preferred substrate is a strip of clear float glass where the coating of the present invention can be applied together with other optional coatings, in the heated zone of the floating glass process. However, other conventional processes for applying coatings on glass substrates for use with the present inventive coating are also suitable. Additionally, colored glass compositions can be used with the antimony / tin oxide alloy film of the present invention to achieve specific spectral and energy attenuation properties. The antimony / tin oxide coating of the present invention is a non-conductive film of neutral color suitable for deposition on a glass substrate. The film is a mixed tin antimony / oxide alloy that is produced by including an amount of antimony of about five percent atomic weight to about ten percent atomic weight in a tin oxide film. The antimony / tin oxide alloy films of the present invention "allow the attenuation of light energy while passing through the coated glass article.The energy applied to the coated glass article is transmitted, reflected or absorbed. The antimony / tin oxide alloy is an energy absorbing film that reduces the amount of incident light energy to the rear glass-air interface and the film-glass interface, thus, the amount of reflected light is The absorption of light results in the reduction of light transmitted through the glass.The absorption properties make the coating suitable for glass applications for both antireflective coatings and solar control coatings.

The absorption properties - of a coating or film are indicated by the extinction of the coefficient (k). Nonabsorbent films have extinction coefficients of zero. The extinction coefficients for absorbent films are greater than 0.1, where higher values indicate higher energy absorption properties. The extinction coefficient for the antimony alloy / tin oxide coating is preferably from about 0.1 to about 0.3. Additionally, the antimony / tin oxide coating of the present invention is a non-conductive film. Non-conductive films generally have a resistance sheet greater than about 500 ohms per square. Coatings with sheet strength values less than 500 ohms per square meter are considered conductive coatings. Typically, the absorbent materials are strongly colored. Therefore, when applied to the films they allow a neutral color in the transmission or in the reflectance, but generally they can not be adjusted to achieve both.

The present inventive coating exhibits an aesthetically neutral color in both transmission and reflectance. The color is preferably indicated by the CIELAB color value scale being a * of about 6 to -9 and b * of about 6 to about -9. For the pyrolytic deposition, the antimony / tin oxide alloy is deposited on the glass substrate by incorporating a source of antimony with conventional tin oxide precursors. An example may include the use of antimony trichloride in an organic solvent, which is vaporized and injected into a stream of precursor gas containing dimethyltin dichloride, oxygen and water in a helium conducting gas. The absorbent coating of the present invention can be used as an antireflective coating in conjunction with other coatings to reduce visible reflection through the principle of optical interference. In this way, the present inventive coating has a refractive index of about 1.8 to about 2.6, which can be used with a film having a low refractive index to achieve additional reductions in visible reflection beyond those achieved through absorption. An antireflective coating produced in accordance with the present invention can reduce visible reflections below 5%, and preferably below 2%. The reduction in visible reflection is achieved while maintaining a visible light transmission (Illuminant observer grade C two) of at least 30% or more, preferably at least 40% or more, and more preferably by at least 50% or higher For example, the present inventive coating can be used with a film having a refractive index of about 1.45 to about 1.6, such as silicon oxide (SiO2). A stack of film on a clear substrate that includes a layer of antimony / tin oxide followed by a layer of silicon oxide is capable of achieving a visible reflectance below 2% and a transmission of neutral visible light (111 C) of more than 30%. Additionally, a barrier layer can be applied to the glass prior to the application of the antimony / tin oxide film.

The barrier layers are used to prevent the migration of alkali metal ions from the glass substrate into the film. The migration of alkali metal ions reduces the quality of the coated glass article and results in an undesirable appearance of fog in the article. The barrier layers may include coatings of silicon oxide, silicon oxycarbide or aluminum oxide. Generally, a barrier layer with a thickness of around 100-200 angstroms is applied. Alternatively, a conductive coating can also be applied in an antireflective coating stack in conjunction with the coating of the present invention. A conductive coating can improve the use of an anti-reflective film by allowing the coated article to dissipate the static charges that may form on the computer's monitor screens.The conductive coating is generally applied to the antimony / tin oxide alloy before of applying the metal oxide coating Conventional conductive coatings generally recognized in the art may be suitable for use in the present invention The conductive metal oxide suitable for use with the invention includes compounds selected from the group consisting of indium compound with tin, indium oxide compound with fluorine, tin oxide composed with fluorine, tin oxide composed with antimony (less than 5, and typically 1 to 2 percent atomic weight of antimony), zinc oxide composed with aluminum , zinc oxide compound with fluorine, zinc oxide compound with boron and tungsten oxide composed with fluorine. The conductive metal oxide is applied with a thickness of about 200"angstroms to about 5000 angstroms". Preferred conductive coatings include the tin oxide compound with fluorine and the indium oxide compound with tin. In an anti-reflective coating, the thickness of each of the layers is in the function of the stack of the desired component and of the preferred reflectivity. Thus, the thickness of each of the layers is selected based on the refractive indices of each of the films used in the stack and the preferred level of reflectivity. An example of an antireflective coating includes the deposition of a barrier layer of about 1QQ angstroms of silicon oxide on a strip of floating glass 0.317 mm (0.125 inches) thick. About 1200 angstroms of antimony / tin oxide are applied on the barrier layer. - A layer of silicon oxide about 700 angstroms thick is applied over the antimony / tin oxide coating. The resulting article has a visible light transmission (111 C) of 52% and a visible reflection of about 1.7%. Compared with the prior conventional antireflective coatings, the present invention significantly reduces visible reflection while also reducing the transmission of visible light. Antireflective coatings before two conventional layers use a stack where each of the layers is 1/4? with a design wavelength of 550 nm. The layers have high and low alternating refractive indices. An example may include a layer of tin oxide without composing about 705 angstroms in thickness on a 0.317 mm (0.125 inch) glass substrate with a silicon oxide layer of about 948 angstroms in thickness applied over a layer of tin oxide. The resulting coated articles exhibit a visible light transmission (111 C) of 92.5% and a visible reflection of 5.5%. The present inventive coating has achieved a visible light transmission (111 C) of 52% and a reflection of 1.7%. A clear glass substrate without coating will typically reflect more than 8% of visible light. The antimony / tin oxide alloy of the present invention can also be used with antireflective batteries before conventional multiple layers having more than two antireflection films before. The antimony / tin oxide alloy is suitable for use as a coating with a medium or high refractive index, depending on the refractive index of other coatings used within the multilayer stack. For example, the antimony / tin oxide alloy of the present invention can be applied to a glass substrate with a coating of titanium oxide applied over the antimony / tin oxide coating and a coating of silicon oxide applied over the coating of titanium oxide. The titanium oxide coating may have a higher refractive index where the antimony / antimony alloy has an intermediate refractive index. - The coated article will have a visible light transmission (111 C) of at least 30% and a visible reflectance, from the side of the film, of at least 1%. The antireflective coated glass article is ideally suited for use on computer screens where high contrast and a neutral transmission with low light reflection visible from the screen are desired. Additionally, the antimony / tin oxide alloy film is suitable for use in various architectural and automotive applications where high reflectivity is not desired. The following examples constitute the best modality currently contemplated by the inventors for the practice of the present invention, these are presented only for the purpose of further illustrating and disclosing the present invention, and should not be construed as limiting the invention: EXAMPLE 1 A floating glass process was used to produce a strip of floating glass having a thickness of 0.317 mm (125 inches). The glass strip traveled at a line speed of about 1.09 m (433 inches) per minute. A conventional apparatus for coating in a flotation bath was used to apply a coating of 203 angstroms of silicon oxide on the surface of the strip of the float glass. The coating was applied by directing 12 standard liters per minute (standard liters per minute (slm)) of ethylene, 5 standard liters per minute (slm) of oxygen and 2 standard liters per minute (slm) of silane SiH in standard 535 liters per minute (slm) of nitrogen-conducting gas. A coating of 1156 angstroms of the antimony / tin oxide alloy was applied on a silicon oxide coating. Approximately 7.718 Kg. (17 pounds) per hour of dimethyltin dichloride, 270 standard liters per minute (slm) of oxygen, 150 cc per minute of water in 200 standard liters per minute (slm) of a helium conductive gas. cc per minute of antimony trichloride in solution at a precursor flow rate The antimony trichloride solution contained about 30 percent molecular weight trimoxuxus of antimony in ethyl acetate, a coating of 692 angstroms of silicon oxide was applied over the antimony / tin oxide film The outer layer was applied by directing a precursor gas mixture containing 42 standard liters per minute (slm) of ethylene, 21 standard liters per minute (slm) of oxygen and 7 liters standard per minute (slm) of silane in standard 535 liters per minute (slm) of a nitrogen-conducting gas over the coated glass strip.The resulting glass article exhibited 52.3% light transmission visible (111 C) with a neutral color, in accordance with CIELAB's Illuminant grade C 2 observation standard, exhibited by a value a * of 2.1 and a value b * of -1.5. The article had a visible light reflection of 1.7 and a neutral color as designated by the value a * of 3.8 and the value b * of -4.1. The sheet resistance of the film was greater than 100,000 ohms per square. The antimony content of the antimony / tin oxide alloy was 11 percent atomic weight. EXAMPLE 2 A floating glass process was used to produce a strip of clear floating glass with a thickness of 0.317 mm (0.125 inches). The glass strip traveled at a line speed of about 1.09 m (433 inches) per minute. A conventional apaxate was used for the coating in a flotation bath to apply a coating of 220 angstroms of silicon oxide on the surface of the strip of the floating glass. The coating was applied through direct standard 12 liters per minute (slm) of ethylene, standard 8 liters per minute (slm) of oxygen and 2 standard liters per minute (slm) of silane SiH in standard 535 liters per minute (slm) of nitrogen-conducting gas. A coating of 15-84 angstroms of antimony / tin oxide alloy was applied on the silicon oxide coating. Approximately 8.626 Kg were provided. (19 pounds) per hour of dimethyltin dichloride, 270 standard liters per minute (slm) of oxygen and 130 cc per minute of water in 150 standard liters per minute (slm) of a helium conductive gas. About 35 cc per minute of antimony trichloride in solution was added to a precursor flow rate. The antimony trichloride solution contained about 30 percent molecular weight of antimony trichloride in ethyl acetate. A coating of 692 angstroms of silicon oxide was applied on a fluorine coating composed of tin oxide. The outer layer was applied by directing a precursor gas mixture containing 45 standard liters per minute (slm) of ethylene, 30 standard liters per minute (slm) of oxygen and 7.5 standard liters per minute (slm) of silane in standard 535 liters per minute (slm) of a nitrogen conducting gas over the coated glass strip. The resulting coated glass article exhibited 37.2% visible light transmission (111 C) with a neutral color according to CIELAB's Illuminant grade C 2 observation standard, of a * of 4.8 and b * of -6.5. The article had a visible light reflection of 1.4% and a neutral color as designated by a value a * of 0.0 and a value b * of -7.3". The sheet of resistance of the film was around 40 ohms per square after removing the silicon oxide layer with hydrofluoric acid The antimony content of the antimony / tin oxide alloy was 6.2 weight percent.

Claims (27)

1. CLAIMS 1. A coated glass article, comprising: (a) a glass substrate, (b) a coating of an antimony / tin oxide alloy applied to the glass substrate, and (c) an oxide coating of metal applied on the coating of the antimony / tin oxide.
2. 2. A glass article as claimed in Claim 1, wherein the antimony is present in the antimony / tin oxide alloy at levels of about 5 weight percent-atomic or more.
3. 3. A glass article as claimed in claim 1, wherein the antimony is present in the antimony / tin oxide alloy at levels of about 5 percent atomic weight to about 10 percent atomic weight.
4. 4. A glass article as recited in Claim 1, wherein the coated article exhibits a reflectance of less than 5%.
5. 5. A glass article as mentioned in Claim 1, wherein the article has a visible light transmission (111 C) of about 30% or greater. 6. A glass article as claimed in claim 1, wherein the metal oxide coating has a refractive index of about 1.45 to about 1.
6. 6.
7. 7. A glass article as claimed in Claim 6, wherein the metal oxide is Si02
8. 8. A glass article as recited in Claim 1, wherein the article exhibits a neutral color in transmission and in reflectance as defined by the CIELAB system having a value of a * from about 6 to about -9 and a value b * of around 6 to about -9.
9. 9. A glass article as claimed in claim 1, further comprising a barrier layer applied between the glass substrate and the coating of the antimony / tin oxide alloy.
10. 10. A glass article as claimed in claim 1, wherein the substrate is a strip of floating glass and the coatings are pyrolytically deposited on floating glass strips.
11. 11. A glass article as claimed in claim 1, wherein the antimony / tin oxide alloy is applied with a thickness of about 500 angstroms to about 2500 angstroms, and the metal oxide is applied with a thickness of around 650 angstroms up to around J.100 angstroms.
12. 12. A glass article as claimed in claim 1, further comprising a conductive metal oxide applied between the antimony / tin oxide alloy and the metal oxide coating.
13. 13. A glass article as claimed in Claim 11, wherein the conductive metal oxide is selected from the group consisting of indium oxide compound with tin, indium oxide compound with fluorine, tin oxide compound with fluorine, tin oxide compound with antimony, zinc oxide composed with aluminum, zinc oxide composed with fluorine, zinc oxide composed with boron, and tungsten oxide composed with fluorine.
14. 14 A glass article as claimed in Claim 11, wherein the conductive metal oxide is applied with a thickness of about 200 angstroms of up to about 5000 angstroms.
15. 15. A glass article as claimed in Claim 1, wherein the antimony / tin oxide alloy has an extinction coefficient of around 0.1 to about 0.3.
16. 16. A glass article as claimed in Claim 1, wherein the antimony / tin oxide film has a top sheet strength of 500 ohms per square.
17. 17. An antireflective glass article, comprising: (a) a glass substrate, (b) a coating of an antimony / tin oxide alloy having a refractive index of about 1.8 to about 2.6 applied at the glass substrate, and (c) a coating of a metal oxide having a refractive index of about 1.45 up to 1.6 applied over the antimony / tin oxide coating, the coated article has a reflectance of less from
18. 18. A glass article as claimed in Claim 17, wherein the glass article has a visible light transmission (111 C) of at least 30% or greater.
19. 19. A glass article as claimed in claim 17, wherein the glass article includes a metal oxide coating having a refractive index higher than that of the antimony oxide / tin oxide alloy applied between the alloy of antimony / tin oxide and metal oxide coating.
20. 20. A coated glass article, comprising: (a) a glass substrate, and (b) a coating that includes one of the other layers of metal oxides or blended metal oxides applied to the glass substrate, At least one of the antimony / tin oxide alloy layers containing at least 5 percent atomic weight of antimony, the coated glass article has a visible light transmission (111 C) of 30% or greater.
21. 21. A coated glass article as claimed in Claim 20, wherein one or more layers of mixed metal oxides or metal oxides includes a conductive metal oxide.
22. 22. A process for depositing an antimony-containing coating on a surface of a heated glass substrate, comprising: a) dissolving an antimony halide in an organic solvent to form a solution containing antimony; b) vaporizing the solution to form a gaseous antimony precursor; c) directing the gaseous antimony precursor to and along the surface to be coated and reacting the antimony precursor at or near the surface to form a coating containing antimony; and d) cooling the coated glass substrate to room temperature.
23. 23. A process as defined in Claim 22, wherein the organic solvent is ethyl acetate. ~~
24. 24. A process as defined in Claim 22, wherein the antimony halide is antimony trichloride.
25. 25. A process as defined in Claim 22, wherein said antimony gaseous precursor is mixed with a metal precursor, an oxygen-containing compound, and a conductive inert gas to form a gaseous precursor mixture, and wherein the mixture of the gaseous precursor is directed towards and along the surface to be coated and reacted on or near the surface to form a metal oxide coating containing antimony.
26. 26. A process as defined in Claim 25, wherein the metal is tin.
27. 27. A process as defined in Claim 25, wherein the metal precursor is dimethyltin dichloride.