Coating processes – Applying superposed diverse coating or coating a coated base – Metallic compound-containing coating
Reexamination Certificate
1998-12-18
2002-03-12
Barr, Michael (Department: 1762)
Coating processes
Applying superposed diverse coating or coating a coated base
Metallic compound-containing coating
C427S126300, C427S164000, C427S419300, C427S430100, C502S350000, C502S351000
Reexamination Certificate
active
06355308
ABSTRACT:
This application claims priority under 35 U.S.C. §§119 and/or 365 to 349077/1997 filed in Japan on Dec. 18, 1997; 349094/1997 filed in Japan on Dec. 18, 1997; 59742/1998 filed in Japan on Mar. 11, 1998: 59745/1997 filed in Japan on Mar. 11, 1998; the entire content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods for producing a composite comprising plural metal oxides, a composite comprising a metal oxide and microparticles of a material other than the metal oxide, and a composite of metal oxide doped with metal ions. In particular, the production methods of the present invention can be applied even to materials of which substrates are not heat-resistant since heating at a high temperature is not required. The composites and oxides doped with metal ions obtained by the methods of the present invention are useful as, depending the nature of the oxides, materials for photocatalysts, memory devices, batteries, sensors, photonics and the like.
The present invention further relates to a method for forming a titanium oxide coating layer on plastic articles. In particular, because the method of the present invention does not require heating at a high temperature, it enables formation of a titanium oxide coating layer on heatlabile plastic substrates, which had been difficult by conventional methods. The photocatalytic function of titanium oxide can be imparted to plastic articles by the methods of the present invention.
The present invention also relates to a method for producing titanium oxide doped with metal ions, which is useful as a photocatalyst having visible light absorbing properties, and a photocatalyst having visible light absorbing properties.
The present invention further relates to a titanium oxide based anti-fogging material, a coating film comprising the anti-fogging material, and a substrate having the coating film such as spectacle lenses. The anti-fogging material of the present invention has excellent anti-fogging properties, and is a anti-fogging material of a low surface reflectance. The present invention further relates to a production method of the aforementioned anti-fogging material.
2. Background Art
It has been known that titanium oxide has photocatalytic function, and its applications are being developed in various fields because antibacterial, antifouling, and anti-fogging properties can be imparted by forming titanium oxide layers on surfaces.
However, titanium oxide can utilize light with limited wavelength in ultraviolet range. In order to utilize light contained in sun light effectively, it is desirable to utilize not only light in ultraviolet range but also light in visible light range. In this respect, it has been known that titanium oxide originally exhibiting catalytic reactions only with UV absorption is converted to one utilizable light in visible light range by doping with chromium ions (see, for example, Kubokawa, Honda, and Saito, “Photocatalyst”, (1998)). In particular, Anpo et al. have successfully formed a titanium oxide film of visible light absorbing type by doping titanium oxide with chromium ions without aggregation of the ions through injection of the chromium ions by ion-implantation technique. Anpo et al. have succeeded in decomposition of NO
x
with light at 450 nm, which is within the visible light range, by using titanium oxide injected with chromium ions through the ion-implantation technique (1996, Proc. In DOE Workshop on Solar Hydrogen Production (1996)). In general, doping of semiconductor materials with a certain metal causes an impurity level in the semiconductor materials, thereby a new absorption band is added to absorption bands of the materials. However, it has been considered that because electrons and positive holes formed by light excitation of band gap are recombined on the chromium ions and inactivated, the photocatalytic reaction would not proceed. To the contrary, Anpo et al. have made it possible to control physical properties of solid titanium oxide by injecting chromium ions thereinto through irradiation of metal ion beam accelerated to high energy.
As a typical example of the technique for ceramic thin film formation under a low temperature condition which is utilizable in the field of photocatalysts, the fog-resistant coating compositions can be mentioned (Japanese Patent Unexamined Publication No. Hei 9-59041/1997). These compositions comprises a mixture consisting of a blend of a silicon precursor, amorphous silica precursor and photocatalyst particles (specifically, a mixture of silica sol, trimethoxymethylsilane, and titania sol), and thin films are made by applying the mixture on a substrate, and sintering it at a low temperature, i.e., 150° C.
By the Kanagawa Industrial Technology Research Institute, goldtitania composite ultramicroparticles having a core/shell structure have been produced by surrounding gold particles as nuclei with titanium oxide by the vapor-in-gas technique. Applications of these composite ultramicroparticles as materials of catalysts, wet type solar batteries, and capacitors are studied because they exhibit sun light absorbing properties and thermal stability.
As described above, it has been attempted to add a third component to a metal oxide or make a composite of metal oxides in order to improve function of the metal oxide or to prolong the duration where the function is retained. However, the aforementioned ion-implantation method requires enormous facility and hence is impractical, and the vapor method requires vaporization of the starting metal oxide material at a high temperature and has problems as described hereinafter.
It has also been known to use platinum and ruthenium oxide as a promoter along with titanium oxide when titanium oxide is used as a photocatalyst. It is preferred that these promoters should be incorporated into the surface of titanium oxide as dense as possible from the viewpoint of improvement of the catalytic function.
However, such a process requiring sintering at a high temperature for making a composite with a third component to a catalyst may not yield a desired composite, because it may form an intermediate according to chemical thermodynamics depending on the nature of the material to be combined.
Therefore, the first object of the present invention is to provide a method for making a composite of a metal oxide with another oxide or metal as a third component, or doping a metal oxide with metal ions as a third component without treatment at a high temperature.
As described above, there has been developed a technique capable of forming a titanium oxide coating film with sintering at a lower temperature (100-150° C.) (Japanese Patent Unexamined Publication No. Hei 9-59041/1997). However, when the articles desired to be imparted with the photocatalytic function are poorly heat-resistant plastic materials or the like, the aforementioned method for forming coating films using a sintering step is not applicable.
Therefore, a titanium oxide coating material of low temperature drying type has been developed. This material is for adhering titanium oxide particles to substrates with an organic or inorganic binder. With this coating material, films are formed by spray coating, dip coating, photogravure printing and the like as ordinary paints. While the obtained films will have practical transparency, peeling property and weather resistance, they disadvantageously have a low hardness of 3-5H. It is obviously inferior than that of the films obtained by sintering at high temperature, which is 5-7H. From the viewpoint of practical use, such hardness as mentioned above may be a significant drawback in a certain field requiring scratch resistance.
Therefore, the second object of the present invention is to provide a method capable of forming titanium oxide coating layers having transparency, low peeling property and weather resistance, which are comparable to or even more excellent than those of conventional ones, and surface hardness comparable to that obtained by the
Ohmi Shigeaki
Sato Koji
Barr Michael
Burnes, Doane, Swecker & Mathis LLP
Hoya Corporation
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