Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
1999-12-08
2001-10-16
Bareford, Katherine A. (Department: 1762)
Stock material or miscellaneous articles
Composite
Of silicon containing
C427S503000, C427S515000, C427S387000
Reexamination Certificate
active
06303229
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a process for forming a hydrophilic inorganic coated film having high fogging resistance, staining resistance, weather resistance, and durability on a surface of the exterior of a building, a display panel, a vehicle and a glass material, and to an inorganic coating composition for use in this process.
BACKGROUND OF THE INVENTION
In recent years, an attempt to impart high hydrophilicity to a surface of a product has been made, in order to preventing the surface of glass or mirror from fogging, or to automatically remove the stains, adsorbed to the surface of an outdoor building, by the aid of rain water.
Methods for imparting high hydrophilicity to a surface of a product are disclosed, for instance, in Japanese Patent Application Laid-Open (JP-A) No. S61-83106 and WO96/29375. These methods described there are all characterized in that an inorganic coated film containing a photo-semiconductor material, e.g., titanium oxide is formed on a surface of a product, and the photocatalytic action of the photo-semiconductor material is utilized.
The photocatalytic action of a photo-semiconductor material means the action of decomposing organic substances, etc. present there as the result of redox reaction which is produced on the surface of the photo-semiconductor material when the light (ultraviolet rays) with excitation wavelength (for example, 400 nm) is applied to the photo-semiconductor material. Organic substances are generally hydrophobic. Hence, when these organic substances are decomposed and removed, the surface of the photo-semiconductor material becomes hydrophilic. As a result, the contact angle of water to the surface of the coated film becomes low, and the surface of the coated film tends to get wet (familiar with water).
However, it takes a certain period of time to develop the photocatalytic action of the photo-semiconductor material after it is irradiated with ultraviolet rays. Therefore there are the problems of, for instance, that the coated surface does not become hydrophilic, and tends to fog and stain for a certain fixed time after the film is formed. Also, there is, for instance, the problem of that it takes a longer period of time to develop the photocatalytic action at the place that is scarcely irradiated with ultraviolet rays, and the use of the photo-semiconductor materials is limited to the applications at which ultraviolet rays is easily applied.
SUMMARY OF THE INVENTION
The present invention solves such conventional problems and has the object of providing a process for forming a hydrophilic inorganic coated film, and an inorganic coating composition for use in the process. The surface of the coated film exhibits high hydrophilicity even just after the film is formed and even when ultraviolet rays is scarcely applied.
The present invention provides a process for forming a hydrophilic inorganic coated film on a surface of a base material, the process comprising the steps of:
(1) preparing an inorganic coating composition which contains, as a major component, a silicone resin obtained by hydrolyzing and condensation-polymerizing only the tetra-functional alkoxysilane represented by formula (I):
Si(OR)
4
(I)
[wherein R represents an alkyl group having carbon atoms up to and including 7 or an aryl group], and has a total solid content of not more than 5% by weight;
(2) applying the inorganic coating composition to a surface of the base material to form a coated layer; and
(3) drying and curing the coated layer to form a cured coated film having a thickness of 0.01 to 0.5 &mgr;m.
The present invention also provides an inorganic coating composition which contains, as a major component, a silicone resin and is used to form a hydrophilic inorganic coated film by applying itself to a surface of a base material, followed by drying and curing, wherein the silicone resin is obtained by hydrolyzing and condensation-polymerizing only the tetra-functional alkoxysilane represented by formula (I);
the total solid content of the inorganic coating composition is not more than 5% by weight; and
the film thickness of the hydrophilic inorganic coated film is 0.01 to 0.5 &mgr;m.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a process for forming a hydrophilic inorganic coated film on a surface of a base material by applying an inorganic coating composition containing a silicone resin as its major component to the surface of a subject product, followed by drying and curing. Hydrophilicity of the surface of the hydrophilic inorganic coated film formed according to the process of the present invention is exhibited just after the film is formed, and no irradiation with ultraviolet rays is needed to develop the hydrophilicity.
The silicone resin is a binder component for the inorganic coating composition and is also a component which primarily imparts durability and strength to the coated film to be formed and hydrophilicity (water-wettability) to the surface of the coated film to provide fogging resistance and staining resistance by the aid of the rain water cleaning.
The silicone resin is a polysiloxane formed by hydrolyzing and condensation-polymerizing only tetra-functional alkoxysilane as a polymerizable component. Using only the tetra-functional alkoxysilane as a polymerizable component implies that any tri- or less-functional alkoxysilane is not contained. If the tri- or less-functional alkoxysilane is added as a polymerizable component, performances of the coated film, such as hydrophilicity, fogging resistance, staining resistance by the aid of the rain water cleaning, weather resistance, durability and strength, of the coated film to be formed are impaired. The form of the silicone resin in the inorganic coating composition is not limited to, but for example, may be the form of a solution or dispersion solution.
The silicone resin is contained as a major component in the inorganic coating composition. The meaning of the major component is that the silicone resin is present in an amount of 50 to 100% by weight in a solid of the inorganic coating composition. The amount of the silicone resin present in a solid of the inorganic coating composition is preferably 50 to 80% by weight and more preferably 50 to 70% by weight.
The tetra-functional alkoxysilane preferable as a raw material of the silicone resin is those having the structure represented by formula (I). In formula (I), R is preferably at least one type selected from the group consisting of a methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group and phenyl group.
Specific examples of the tetra-functional alkoxysilane include tetraalkoxysilane such as tetramethoxysilane, tetraethoxysilane, tetra n-propoxysilane, tetraisopropoxysilane and tetra-t-butoxysilane. These tetra-functional alkoxysilane are used either singly or in combinations of two or more.
The inorganic coating composition may include various functional components other than the silicone resin for the convenience of film-forming operation and for imparting various functions to the film to be formed. Such functional components include curing catalysts, fillers, photo-semiconductor materials, colorants, film-forming adjuvants, application adjuvants, antioxidants and ultraviolet absorbers.
The inorganic coating composition may further include a curing catalyst for promoting the curing of the applied layer by promoting condensation reaction of the silicone resin. Examples of the curing catalyst include, but is not limited to, alkyl titanates; metal carboxylates such as tin octylate, dibutyltin dilaurate and dioctyltin dimaleate; amine salts such as dibutylamine-2-hexoate, dimethylamine acetate and ethanolamine acetate; quaternary ammonium carboxylates such as tetramethylammonium acetate; amines such as tetraethylpentamine, amine type silane coupling agents such as N-&bgr;-aminoethyl-&ggr;-aminopropyltrimethoxysilane and N-&bgr;-aminoethyl-&ggr;-aminopropylmethyldimethoxysilane; acids such as p-toluenesu
Ikenaga Junko
Inoue Minoru
Nakamoto Shoichi
Takahama Koichi
Bareford Katherine A.
Matsushita Electric & Works Ltd.
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