Coating processes – Optical element produced – Transparent base
Reexamination Certificate
2003-02-13
2003-12-02
Jones, Deborah (Department: 1775)
Coating processes
Optical element produced
Transparent base
C427S163100, C427S165000, C427S168000, C428S437000, C428S697000, C428S699000, C428S701000, C428S702000, C428S704000
Reexamination Certificate
active
06656523
ABSTRACT:
BACKGROUND OF INVENTION
This invention relates to coated glass used in residential, architectural and vehicle windows and miscellaneous applications where both solar control and low emissivity properties are desired. The coatings for solar control and low emissivity contain tin oxide having various dopants. The invention avoids the need for an anti-iridescence underlayer. The glass articles may be of any shape but are typically flat or curved. The glass composition can very widely but is typically soda lime glass produced by the float process. It may be annealed, heat strengthened or tempered.
DESCRIPTION OF PRIOR ART
Solar-control is a term describing the property of regulating the amount of solar heat energy which is allowed to pass through a glass article into an enclosed space such as a building or an automobile interior. Low emissivity is a term describing the property of an article's surface wherein the absorption and emission of mid-range infrared radiation is suppressed, making the surface a mid-range infrared reflector and thereby reducing heat flux through the article by attenuating the radiative component of heat transfer to and from the low emissivity surface (sometimes referred to as Low E). By suppressing solar heat gain, building and automobile interiors are kept cooler, allowing a reduction in air conditioning requirements and costs. Efficient low emissivity coatings improve comfort during both summer and winter by increasing the thermal insulating performance of a window.
Important to commercially acceptable coated glass articles which possess both solar-control and low emissivity properties are, of course, economic processes for producing the articles and durability and maintenance of associated properties such as light transmission, visibility, color, clarity and reflection.
As explained below, various technologies have been employed to meet the requirement for solar-control and low emissivity glass, however, no one system has successfully met all of the performance requirements in an economic manner.
Many coatings and coating systems cause iridescent colors to develop in the coated article. This may be caused by the chemical composition of the coating, the thickness of an individual layer or layers, or an interaction of the substrate and coatings to incident light. Such iridescence can, in some cases, be minimized or eliminated by placing an anti-iridescence layer between the glass substrate and the first coating. The use of an interference layer between the glass and a subsequent functional layer or layers to suppress iridescence or color reflection was first demonstrated by Roy G. Gordon, and was the subject of U.S. Pat. No. 4,187,336, issued Feb. 5, 1980. The Gordon technology has been the state of the art for coated solar control glass as evidenced by recently issued U.S. Pat. No. 5,780,149 (McCurdy et al, Jul. 14, 1998) which applied two layers to obtain solar control on top of a Gordon type interference layer. The interference layer frequently contains silicon dioxide. Surprisingly, the present invention represents a dramatic breakthrough and eliminates the need for a Gordon type underlayer to control reflected color.
U.S. Pat. No. 3,149,989 discloses compositions of coatings useful in producing radiation reflecting (solar-control) glass. At least two coatings are used with the first coating, adhered to the glass substrate, being comprised of tin oxide doped with a relatively high level of antimony. The second coating is also comprised of tin oxide and is doped with a relatively low level of antimony. The two films may be superimposed, one on another, or may be applied to opposite sides of the glass substrate. In either case, these solar-control coatings do not contribute significant low emissivity properties to the glass article.
U.S. Pat. No. 4,287,009 teaches a heat absorbing glass designed to convert incident sun rays into heat energy that is transferred to a working fluid for heat transfer. Accordingly, the coated glass absorbs at least 85% of the solar wavelength range rays and has a relatively low emissivity characteristic of less than 0.2. The coatings are positioned on the outside of the glass (i.e. the side facing the sun) and the fluid for heat transfer contacts the inside surface of the glass. The coatings comprise a first coating of metal oxides deposited on the smooth glass layer which oxides are selected from tin, antimony, indium, and iron and a second coating of metal oxides deposited on the first coating selected from the same group of metals. The films as designed will have very low visible transmissions and no teaching on the control of reflected color is given.
U.S. Pat. No. 4,601,917 teaches liquid coating compositions for producing high-quality, high-performance, fluorine-doped tin oxide coatings by chemical vapor deposition. One of the uses of such coatings is in the production of energy-efficient windows, also known in the trade as low-E or low-E windows. Methods of producing the coated glass are also described. This patent does not teach how to produce coated glass articles which possess both solar-control and low emissivity properties.
U.S. Pat. No. 4,504,109, assigned to Kabushiki Kaisha Toyota Chou, describes glass coated with infrared shielding multilayers comprising a visible light transparent substrate and an overlying component lamination consisting of “at least one infrared shield layer and at least one interferential reflection layer alternatively lying on each other . . . ” Indium oxide doped with Sn is used in the examples as the infrared shield layer and TiO
2
was used as the interferential shield layer. In order to reduce iridescence the infrared shield layer and the interferential reflection layer thickness must have a value of one quarter lambda (lambda/4) with a permissible deviation of from 75% to 130% of lambda/4. Although other formulations are disclosed for the infrared shield layer and the interferential reflection layer such as SnO
2
with or without dopants, (see column 6 lines 12 to 27), however, the specific combination of doped SnO
2
layers of the present invention that accomplishes solar control, low emissivity and anti-iridescence without requiring a lambda/4 thickness limitation is neither disclosed nor exemplified to suppress iridescence or color reflection.
U.S. Pat. No. 4,583,815, also assigned to Kabushiki Kaisha Toyota Chou describes a heat wave shield laminate consisting of two indium tin oxide overlayers containing different amounts of tin. Antireflection layers, above or below the indium tin oxide layers are also described. Other formulations are disclosed for the infrared shield layer and the interferential reflection layer such as SnO
2
with a dopant that becomes a positive ion with a valence of +5 such as Sb, P, As, Nb, Ta, W, or Mo or an element such as F which readily becomes a negative ion with a valence of −1, (see column 22 lines 17 to 23). However, the specific combination of doped SnO
2
layers of the present invention that accomplishes solar shielding, low emissivity and anti-iridescence is neither disclosed nor exemplified. There is no claim to tin oxide layers nor any teaching in the specification to describe the composition of such layers, e.g. the ratio of dopant to tin oxide. It should also be noted that the teaching leads to the use of the same dopant in both layers (indium tin oxide) whereas in the instant patent application, one layer must contain a different dopant than the other layer.
U.S. Pat. No. 4,828,880, assigned to Pilkington PLC, describes barrier layers which act to inhibit migration of alkali metal ions from a glass surface and/or act as color suppressing underlayers for overlying infrared reflecting or electrically conducting layers. Some of these color suppressing layers are used in solar-control or low emissivity glass construction.
U.S. Pat. No. 4,900,634 assigned to Glaverbel discloses a pyrolytic coating of tin oxide containing a mixture of fluorine and antimony dopants coated on glass and imparting low emissivity and a specific haze
McKown Clem S.
Roger Christophe
Russo David A.
Stricker Jeffrey L.
Atofina Chemicals, Inc.
Debenedictis Nicholas J.
Jones Deborah
Piziali Andrew
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