Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-07-17
2004-08-17
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C252S518100, C252S519320, C252S519330, C252S519340, C252S520100, C524S399000, C524S434000, C524S555000, C524S557000, C524S910000
Reexamination Certificate
active
06777477
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a coating solution for forming, on a substrate such as a glass or ceramic substrate or on an object, transparent conductive tin oxide film predominantly containing tin oxide, as well as to a method for producing the solution. The present invention is useful for producing components of electromagnetic shields, infrared-ray-reflectors, solar cells, liquid crystal displays (LCDs), plasma display panels (PDPs), electrodes of electroluminescent devices, and freezer showcases, or for producing anti-fogging electric heater glass panels employed in aircraft carriers. Particularly, the present invention is suited for a variety of applications such as transparent electrodes used in display devices; e.g., LCDs and PDPs; prevention of charging phosphor activated by a low-speed electron beam; conversion of fluorescent tubes to those of a rapid-start type (inner surface coating); surface electrodes of imaging tubes; surface electrodes of fluorescent tubes; homogenization of electric charge on the surface of phosphors used in a PDP; and prevention of charging synthetic fiber. In addition, the invention is useful for hard film material and applications suitable for high-refractive and high-reflective properties.
BACKGROUND ART
Conventionally, electrode materials having high transparency to visible light have been used in electrodes of display devices such as liquid crystal display devices, plasma display panels, and electroluminescent devices and have served as resistance heaters for preventing fogging and freezing of window panes of, for example, automobiles, aircraft, and buildings. Among such transparent conductive materials, compounds such as antimony-containing tin oxide (ATO) and tin-containing indium oxide (ITO) are known to serve as transparent conductive material, and, inter alia, ITO is widely used, in view of properties such as low specific resistance. However, since tin oxide exhibits superior stability under high-temperature and high-voltage conditions as compared with ITO, extensive studies have been performed on the formation of transparent conductive tin oxide film exhibiting properties which are comparable to those of ITO.
Several methods for forming tin oxide film; i.e., (1) sputtering, (2) spraying, and (3) CVD, have been known. When any of the methods (1) to (3) is employed, formation of tin oxide thin film on a large-area substrate is difficult. When a uniform, thin film is to be formed on such a substrate, a coating method is suitably employed. The coating method is advantageous in that thin film can be formed by use of a comparatively simple apparatus as compared with a complex and expensive apparatus for carrying out sputtering or a similar coating method. Thus, extensive studies have been carried out on the above application method.
One known coating method is a method involving application of an organic tin compound serving as raw material, to thereby form thin film. However, disadvantageously, carbon remains in the formed thin film, since the coating solution predominantly comprises organic compounds.
Among coating methods, another known coating method is a sol-gel method involving hydrolysis and polycondensation of a metal alkoxide. This method attains comparatively easy control of the composition of the film to be formed, and therefore, has been extensively investigated in connection with formation of thin film having excellent uniformity in film properties. However, the metal alkoxide is generally expensive, and carbon disadvantageously remains in the produced thin film.
Although coating methods are suitable for forming uniform thin film also-on a large-area substrate, as mentioned above, when the film is formed through a conventional coating method, there arise problems in the generation of pinholes and of microcracks due to carbon remaining in the produced thin film.
From another point of view, stannic acid is known to dissolve in an ammonia solution (Ullmann's Encyclopedia of Industrial Chemistry, Encyclopaedia Chimica, etc.). In this connection, Japanese Patent Publication (kokoku) No. 5-43647 discloses a method of producing conductive film by applying an ammonium stannate solution to a substrate.
However, the conductive film as disclosed in the aforementioned patent publication exhibits a surface resistivity of 5×10
5
(&OHgr;/□), which is 100 times or more that of tin oxide film formed through a previously known coating method. Thus, such conductive film cannot be put into practice.
In view of the foregoing, an object of the present invention is to provide a coating solution for forming transparent conductive tin oxide film, which solution is prepared from an inexpensive tin compound such as tin chloride serving as a raw material and can provide tough tin oxide film endowed with excellent conductivity and transparency. Another object is to provide a method for producing transparent conductive tin oxide film. Still another object is to provide a transparent conductive tin oxide film.
DISCLOSURE OF THE INVENTION
In order to solve the aforementioned problems, in a first mode of the present invention, there is provided a coating solution for forming transparent conductive tin oxide film, which solution is intended to be used for forming, through a coating method, transparent conductive film predominantly containing tin oxide, characterized by comprising an aqueous solution containing stannic acid as its major component, and a water-soluble polymer having a polar group, which polymer is dissolved in the aqueous solution in the presence of at least one compound selected from the group consisting of ammonia and a water-soluble amine.
In a second mode of the present invention, there is provided a coating solution for forming transparent conductive tin oxide film according to the first mode, wherein the stannic acid is obtained by dissolving, in water, a hydroxide (stannic acid) obtained through hydrolysis of a tin compound selected from the group consisting of tin halides, organotin halides, stannate salts, and esters containing tin.
In a third mode of the present invention, there is provided a coating solution for forming transparent conductive tin oxide film according to the second mode, wherein the tin compound is a tin chloride.
In a fourth mode of the present invention, there is provided a coating solution for forming transparent conductive tin oxide film according to any one of the first to third modes, wherein the water-soluble polymer having a polar group is at least one species selected from the group consisting of poly(vinyl alcohol) (PVA), polyvinylacetamide (PNVA), polyvinylformamide (PNVF), polydimethylacrylamide (PDMAA), polyacrylamide (PAAM), polyacrylmorpholine (PAM), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), and carboxymethyl cellulose (CMC).
In a fifth mode of the present invention, there is provided a coating solution for forming transparent conductive tin oxide film according to any one of the first to fourth modes, wherein the water-soluble polymer having a polar group is contained in an amount of 0.1-5 wt. %.
In a sixth mode of the present invention, there is provided a coating solution for forming transparent conductive tin oxide film according to any one of the first to fifth modes, wherein the pH of the solution is 10 or more.
In a seventh mode of the present invention, there is provided a coating solution for forming transparent conductive tin oxide film according to any one of the first to sixth modes, wherein the water-soluble amine is at least one species selected from the group consisting of tetramethylammonium hydroxide, triethylamine, diethylamine, trimethylamine, and dimethylamine.
In an eighth mode of the present invention, there is provided a coating solution for forming transparent conductive tin oxide film according to any one of the first to seventh modes, wherein the solution contains, as a dopant, a water-soluble compound containing at least one of antimony, bismuth, and niobium.
In a ninth mode of the present invention, there is provided a
Kimura Masateru
Niume Kazuma
Uchida Takashi
Huntley & Associates LLC
Niland Patrick D.
Toyo Gosei Kogyo Co. Ltd.
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