Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
2000-05-24
2003-06-10
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C428S325000, C428S336000, C428S428000, C428S432000, C428S446000, C428S702000, C501S134000, C501S154000
Reexamination Certificate
active
06576344
ABSTRACT:
FIELD OF THE ART
The present invention concerns anti-fogging, anti-soiling articles, wherein an anti-fogging film or anti-soiling film is formed on the surface of a substrate, such as glass, ceramic, plastic, or metal, etc., methods of producing such articles, and compositions for forming such articles. In particular, the present invention concerns anti-fogging, anti-soiling articles, which are suitable as window glass, mirrors, lenses, air conditioner heat exchanger fins, biological materials, film sheets, showcases, etc., that are used for construction, vehicles, optical parts, industrial use, agricultural use, goods for daily use, and residential and medical purposes, provide good anti-fogging or anti-soiling performance over long periods, and in particular exhibit their performance under weak ultraviolet light or visible light, the methods of producing such articles, and compositions for forming such articles.
BACKGROUND ART
Since priorly, there have been strong needs for anti-fogging, anti-soiling glass plates, mainly in the fields of automobiles and construction. Especially with automobiles, the addition of anti-fogging properties to window glass is becoming an important issue from the standpoint of safe driving.
Since priorly, various anti-fogging coatings for glass articles have been examined. These include, for example, a coating of an organic and/or inorganic thin film containing a surfactant (Laid-open Japanese Patent Publication (Koukai) No. Hei 7-117202; first method), a coating of hydrophilic polymer (Japanese Patent Publication (Koukoku) No. Shou 61-9264; second method), and a coating of an organic-inorganic complex film containing an organic hydrophilic functional group (Laid-open Japanese Patent Publication (Koukai) No. Hei 6-220428; third method), etc.
Also recently, anti-fogging, anti-soiling articles have been proposed in which titanium oxide, which is an oxide semiconductor that acts as a photocatalyst, is coated onto the surface of a substrate (Japanese Patent No. 2756474; fourth method 4). This method makes use of the phenomenon wherein the titanium oxide on the glass surface absorbs ultraviolet light and the organic substance adsorbed on the glass surface is oxidized and decomposed efficiently by the energy of the absorbed ultraviolet light to provide a clean surface with significant hydrophilic properties. Also, since the entire anti-fogging, anti-soiling articles is made of inorganic substances in terms of material, it is excellent in mechanical strength, and even when dirt becomes attached, the surface can be made clean again and the hydrophilic surface can be revived once it is exposed to ultraviolet light. As long as the surface retains hydrophilic properties, it will be difficult for black, lipophilic dirt, which is the type of dirt encountered in urban settings, to become attached, and any attached dirt will be removed readily by rain (see for example, Toshiki Komatsuzawa and Toshikazu Nakaiye, “New Anti-soiling Coatings,” Coating Technology, Jan., 1995, 94-99 (1995); Shoichi Tanaka, “Degradation by Soiling and Anti-soiling Coating Technologies (Industrial Coatings),” Coating Technology, Oct., 1996 extra issue, 95-102 (1995)). So-called self-cleaning properties are thus provided, enabling use as anti-soiling material.
In such methods using titanium oxide, the photocatalytic activity of the titanium oxide may be pointed out as an important factor that determines anti-fogging and anti-soiling performance. Methods for improving the photocatalytic activity of titanium oxide include a method in which titanium oxide is made to carry a precious metal (see for example, Catalyst Vol. 19 No. 5, 334-350 (1977)), a method in which titanium oxide is made to carry a vanadium compound (see for example, Laid-open Japanese Patent Publication No. Hei 7-275704), a method in which niobium is dissolved in titanium oxide (see for example, Laid-open Japanese Patent Publication No. Hei 9-267037), a method in which titanium oxide is doped with fluorine (see for example, International Patent Publication WO 98/05413).
Also, methods for obtaining titanium oxide that exhibit photocatalytic activity under illumination by visible light include a method for doping a minute amount of dopant selected from the group comprised of vanadium, chromium, manganese, iron, cobalt, nickel, and copper (Laid-open Japanese Patent Publication No. Hei 9-192496) and a method in which a minute amount of metal ion, selected from the group comprised of chromium, vanadium, copper, iron, magnesium, silver, palladium, nickel, manganese, and platinum, is injected into a titanium oxide crystal. (Laid-open Japanese Patent Publication No. Hei 9-262482).
With the abovementioned first method, although the initial performance is excellent, since the surfactant is consumed gradually, it has the disadvantage of being short in life.
Although the second method is an effective means depending on the application, it cannot be applied to glass for automobiles, buildings, etc., with which a relatively large mechanical strength is required.
Although the third method was proposed so that both anti-fogging performance and mechanical strength will be provided at the same time, both types of performance are limited with this method. Also with this method, the anti-fogging performance drops significantly once dirt, etc., become attached.
Though the fourth method in principle has features that cannot be realized by the other methods, since the intensity of ultraviolet light in the interior of a vehicle or building is extremely weak, anti-fogging article that can be put to practical use have not yet been obtained by this method. Also with anti-soiling articles, there are problems wherein use is difficult at locations where the intensity of ultraviolet light is weak.
On the other hand, compositions and article obtained by the abovementioned prior arts that purport to improve the photocatalytic activity of titanium oxide upon ultraviolet light illumination or the expression of photocatalytic activity under visible light illumination do not exhibit adequate anti-fogging performance under illumination of weak ultraviolet light or visible light, and since the improvement of hydrophilicity is also inadequate, it cannot be said that such compositions and article are improved significantly in anti-fogging and anti-soiling performance over ordinary titanium oxide.
The present invention has been made in view of the prior arts and an article thereof is to provide compositions, which express excellent anti-fogging and anti-soiling properties even under environments of weak ultraviolet light or visible light and can maintain good anti-fogging and anti-soiling performance over long periods, and anti-fogging, anti-soiling articles with excellent anti-fogging and anti-soiling performance that can be used, for example, in window glass for automobiles and buildings, mirrors, optical parts, as well as glasses, etc.
DISCLOSURE OF THE INVENTION
As a result of diligent examination towards achieving the above article, the present inventors have found that (1) by adding a significantly large amount of a specific metal compound to titanium oxide or other oxide semiconductor, the hydrophilicity is improved by illumination of weak ultraviolet light or visible light, (2) by adding silicon oxide to this composition, the anti-fogging and anti-soiling performance is improved further, and (3) the performance is improved further if the titanium oxide takes the form of microparticles.
The present inventors also found that (4) when an overcoat layer comprised of metal oxide is formed after forming such a composition as a thin film on a substrate, the anti-fogging and anti-soiling properties are improved and/or (5) by forming an organic substance adhesion prevention layer comprised of a silicon oxide layer or an organosilane layer, the anti-fogging and anti-soiling performance is improved, and have thus come to complete the present invention.
That is, the present invention provides in a photocatalyst article including oxide semiconductors, a photocatalyst ar
Doushita Kazuhiro
Inomata Hiroyuki
Butler, Esq. Gregory B.
Conlin, Esq. David G.
Edwards & Angell LLP
Jones Deborah
Nippon Sheet Glass Co. Ltd.
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