Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
1999-06-16
2004-12-21
McNeil, Jennifer (Department: 1775)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C428S434000, C428S457000, C428S472000, C428S697000, C428S699000, C428S701000, C428S702000
Reexamination Certificate
active
06833194
ABSTRACT:
FIELD OF THE INVENTION
This invention relates, in general, to protective layers for sputter coated articles such as coated or uncoated glass or transparent. Such articles with the protective layers are shippable, heat treatable, can have low emissivity coating or coatings. The invention also relates to the coated articles and to methods of making the coated articles.
DISCUSSION OF THE PRESENTLY AVAILABLE TECHNOLOGY
U.S. Pat. No. 4,610,771 (“U.S. Pat. No. '771”) discloses an antireflective sputtered metal oxide film deposited using a zinc/tin alloy target. U.S. Pat. No. '771 in column 3, line 26, to column 4, line 12, discusses the use of the alloy target to deposit a zinc stannate film having, in general, oxides of zinc and tin preferably in proportions of 10 to 90 percent zinc and 90 to 10 percent tin.
Although the zinc/tin alloy target disclosed in U.S. Pat. No. '771 to deposit the zinc stannate film is acceptable, there are limitations. More particularly, in a low E coating such as the type described in U.S. Pat. No. '771, an infrared reflecting metal film or layer, e.g., silver is deposited on the zinc stannate film. A silver film deposited on a sputtered zinc stannate film has a higher electrical resistivity and higher emissivity than a silver film deposited on a sputtered zinc oxide film or layer. More particularly, U.S. Pat. No. 5,821,001 (“U.S. Pat. No. '001”) discloses a silver film deposited on a zinc oxide film; the atoms of the silver film deposit in a form characterized by a low electrical resistivity which provides the silver film with a low emissivity. In depositing the zinc oxide film the process parameters are selected to deposit a zinc oxide layer with a suitable crystallinity or preferential crystal growth for favorably affecting deposition of the silver atoms of the silver film.
Sputtering zinc in a reactive atmosphere, e.g., oxygen, to provide a zinc oxide film over which a silver film having a low electrical resistivity is deposited has drawbacks. For example, it is difficult to reactively sputter a pure zinc target, i.e., a target of about 100% zinc metal, in a reactive atmosphere such as oxygen for reasons discussed in more detail below.
U.S. Pat. No. '001 also discloses a heat treatable low emissivity film. The thickness of the primer layers, e.g., titanium films, may be increased to provide enhanced mechanical durability, i.e., improve shear resistance. The shear resistance test consists of applying 20 successive strokes of a cloth wetted with deionized water against the coated surface of glass, followed by visual examination of the tested area. Depending on the appearance of the tested area, letter grades of D−, D, D+ . . . A, A+ are assigned to the coating; then, for numerical analysis, assignments of 5 to D−, 10 to D, 55 to A, and 60 to A+ are made. If a coating shows no signs of shear, not even barely visible scratches, then it receives a maximum rating of 60. Coatings that display uniform shear and delamination at any interface of the multi-layer coating within the test area receive a failing rating of zero. Other levels of performance receive intermediate scores. This method of coating durability characterization has been found to correlate well with field performance of the coating. The drawback with using thick primer layers is that the coating stack after heating, e.g., glass tempering or glass bending operations, is likely to have a hazy appearance when viewed using a dark room, flood-light haze test. In the dark room, floodlight haze test, the coated specimen is viewed in reflection in a dark room at various viewing angles relative to a spotlight, in order to find the geometry yielding maximum scattering of light, or, in other words, haze, possible from the coating. If there is no geometry that can make haze observable, an A+ rating is assigned to the sample. Very poor samples receive D−. For purposes of numerical analysis, the letter grades are given values of 5 to 60, as described above for the shear test. Lower haze corresponds to higher numerical values.
As can be appreciated by those skilled in the art of making sputtered coatings, it would be advantageous to provide a zinc target that may be sputtered in a reactive atmosphere without the drawbacks of the presently available zinc targets and to provide low emissivity coated articles that have mechanical durability so that the coated article may be shipped and subsequently heated without the heated coating having haze.
The disclosures of U.S. Pat. Nos. '771 and '001 are hereby incorporated in toto by reference.
SUMMARY OF THE INVENTION
This invention relates to a sputter cathode target having tin preferably in an amount greater than zero and less than 10 weight percent of the total weight of the target material, and zinc in an amount preferably less than 100 weight percent and more than 90 weight percent of the total weight of the target material. Hereafter, unless indicated otherwise, the term “weight percent” means the weight percent of the total weight of the target material.
As used herein, “a zinc stannate film,” e.g., of the type discussed in U.S. Pat. No. '771 is an oxide of an alloy of zinc and tin. The cathode used is made of an alloy of zinc and tin. A “zinc oxide, tin oxide film,” is a film having oxides of tin and zinc. The cathode used to sputter the zinc oxide, tin oxide film is made of zinc having additions of tin as is discussed in detail below.
In one embodiment of the invention a coating stack has a zinc stannate film deposited on a glass substrate, a zinc oxide, tin oxide film deposited on the zinc stannate film; an infrared reflecting film, e.g., silver, deposited on the zinc oxide, tin oxide film; a primer layer, e.g., a titanium metal film, deposited on the infrared reflecting film; a zinc oxide, tin oxide film deposited on the primer film, a zinc stannate film deposited on the zinc oxide, tin oxide film; an infrared reflecting film deposited on the zinc stannate film; a primer layer deposited on the infrared reflecting layer; a zinc oxide, tin oxide film deposited on the primer layer, a zinc stannate film deposited on the zinc oxide, tin oxide film; and a protective layer, e.g., a titanium metal film and/or a titanium oxide film in either order, deposited over the zinc stannate film. In another embodiment of the invention, a zinc oxide film is used in place of the zinc oxide, tin oxide film. In a further embodiment of the invention, a zinc stannate film is used in place of the zinc oxide, tin oxide film. When a zinc stannate film is used in place of the zinc oxide, tin oxide film, the zinc stannate films differ in composition by at least 5 weight percent. For example, when one of the zinc stannate films is about 50 weight percent zinc and 50 weight percent tin, the other zinc stannate film is about 10-45 or 55-90 weight percent zinc and 55-90 or 45-10 weight percent tin. In a still further embodiment of the invention, a first deposited zinc stannate film is 50±10 weight percent zinc and 50±10 weight percent tin. The second deposited or overlying zinc stannate film has tin equal to or greater than 10 weight percent and less than 40 weight percent and preferably 20 weight percent, and has zinc equal to or less than 90 weight percent and greater than 60 weight percent and preferably 80 weight percent. Overlying zinc stannate films having 90 weight percent zinc and 10 weight percent tin have been used.
Another aspect of the present invention is the composition or films of the protective layer. Of course, the protective layer can be for any multi-layered stack with one or more antireflective layers on a substrate. This multi-layered stack has at least one layer of at least one infrared reflecting film which can be preceded on the near side towards the substrate by one or more dielectric and/or zinc- and/or tin-containing films and can be followed on the side away from the substrate by one or more layers of one or more dielectric and/or zinc- and/or tin-containing films and
McNeil Jennifer
PPG Industries Ohio Inc.
Siminerio Andrew C.
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