Coating processes – Electrical product produced – Hollow article
Reexamination Certificate
2000-03-03
2003-08-05
Meeks, Timothy (Department: 1762)
Coating processes
Electrical product produced
Hollow article
C427S109000, C427S255190, C427S255240, C427S255320, C427S255350, C427S255500, C065S060500, C065S060510
Reexamination Certificate
active
06602541
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a neutral absorbing 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 an antimony/tin oxide alloy coating applied onto a glass substrate to impart energy absorption and anti-reflective properties to the coated glass article.
Coatings on glass are commonly utilized to provide specific energy attenuation and light transmittance properties. Additionally, coatings are designed to reduce reflections from interfaces between individual coating layers and the glass when a plurality of coatings are applied onto a glass substrate. The coated articles are often utilized singularly, or in combination with other coated articles, to form a glazing.
The attributes of a coated glass substrate are dependent upon the specific coatings applied to the glass substrate. The coating compositions and thicknesses impart energy absorption and light transmittance properties within the coated article while also affecting the spectral properties. Desired attributes may be obtainable by adjusting the compositions or thicknesses of the coating layer or layers. However, adjustments to enhance a specific property can adversely impact other transmittance or spectral properties of the coated glass article. Obtaining desired spectral properties is often difficult when trying to combine specific energy absorption and light transmittance properties in a coated glass article.
Anti-reflective coatings on glass are utilized to reduce the surface reflection of optical components and to reduce the reflectance of an interface between optical media with different refractive indices. The reduction of visible reflection is achieved by the principle of optical interference. When light impinges on the air-film, film-film, and film-glass interfaces, a portion of the beam is reflected at each interface. By proper choice of thin film materials and thicknesses, the individual reflected light beams can destructively interfere thereby reducing the observed visual reflectance.
The utilization of a coating having absorption properties enables further reduction in reflection by absorbing the light as it travels through the high index absorbing film thereby reducing the light energy incident on the back glass interface and glass-film interface. The absorption of visible light results in the reduction of visible light transmitted through the glass. Generally, absorbing films are strongly colored and therefore do not result in a neutral transmittance or reflectance. The utilization of an energy absorbing film is preferred when the minimization of visible reflection is desired and a reduction of visible light transmittance is acceptable.
Absorbing films may also adversely impact the visible light transmittance to a level unacceptable for anti-reflective and solar control applications. For example, European Patent publication EP0780346 A1 discloses a method for producing tin oxide films doped with antimony oxide. The films are applied pyrolytically and result in a film having a molar ratio of tin to antimony of 1:0.2 to 1:0.5. The resulting films, when applied onto a neutral glass substrate at a thickness of about 50 nm to about 1,500 nm, result in a visible light transmittance of less than 10 percent. The color of the films are generally a dark, gray-violet color. Thus, the low visible light transmittance and spectral properties renders such films undesirable for anti-reflective glass applications.
It would be advantageous to provide a coated glass article having a non-conductive, color neutral absorbing film that is capable of reducing the visible reflection from the glass while permitting a visible light transmittance of at least 30 percent. The film should also provide the desirable neutral color in both transmittance and reflectance.
It would be a further advantage to provide a non-conductive, color neutral absorbing film that may be applied pyrolytically onto a glass substrate. A pyrolytic film enables the deposition of the film on-line, for example, in a float glass production process.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a non-conductive, color neutral absorbing film suitable for use as a coating on glass. The film may be utilized for either solar control or anti-reflective glass articles. The film is an antimony/tin oxide alloy produced by combining an antimony source with conventional tin oxide deposition precursors. The amount of antimony present in the film is at least about five atomic percent. Due to considerations of cost and ease of manufacture, the amount of antimony present in the film is preferably from about five atomic percent to about ten atomic percent.
The antimony/tin oxide alloy is preferably applied pyrolytically, on-line onto a float glass ribbon. The energy absorption properties of the film make it suitable for use with either solar control or anti-reflective glass articles.
In an anti-reflective glass, the energy absorbing film, having a refractive index of about 1.8 to about 2.6, may be utilized with a metal oxide, having a lower refractive index, to form a coated glass article. The high refractive index film is applied closest to the glass with the low refractive index film functioning as an outer layer. The high/low stack reduces visible reflection to a level below five percent by the principle of optical interference. Additionally, the absorbing properties of the film enable a further reduction in visible reflection to a level below two percent. The thicknesses and optical characteristics of the coating stack may be adjusted to achieve a broad range of specified transmittance values. However, in a preferred embodiment, the coated glass article has a visible light transmittance (Ill C) of at least 30%. The reflection and transmittance of visible light are both aesthetically neutral in color.
It is an object of the present invention to provide an energy absorbing, neutral colored film for use as a coating on a glass substrate. The antimony/tin oxide alloy is an energy absorbing film that may be deposited onto a glass substrate. The energy absorbing properties enable the use of the film in both anti-reflective and solar control coating stacks. Furthermore, the film exhibits a desirable neutral color in both transmittance and reflection.
It is a further object of the present invention to provide an absorbing film that can be pyrolytically deposited onto a glass substrate. The antimony/tin oxide alloy of the present invention is suitable for use in conventional tin oxide deposition precursors. The pyrolytic deposition enables the application of the film onto a float glass ribbon directly in the glass production process.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In accordance with the present invention, it has been discovered that an antimony/tin oxide alloy film, having about five atomic percent to about ten atomic percent antimony, is suitable for use in a coated glass article. The film is an energy absorbing film that exhibits a neutral color in visible light transmission and reflection. The coated glass article is especially suitable for use with anti-reflective glass articles utilized for computer displays or monitors. However, the coated glass article of the present invention may also be utilized for other applications, such as architectural glazings and vehicle windows.
The glass substrates suitable for use in preparing the coated glass article according to the present invention may include any of the conventional clear glass compositions known in the art. The preferred substrate is a clear float glass ribbon wherein the coating of the present invention, along with other optional coatings, is applied in the heated zone of the float glass process. However, other conventional processes for applying coatings on glass substrates are suitable for use with the present inventive coating. Additionally, colored glass composi
McCurdy Richard J.
Soubeyrand Michel J.
Strickler David A.
Libbey-Owens-Ford Co.
Marshall & Melhorn LLC
Meeks Timothy
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