Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Physical dimension specified
Reexamination Certificate
2003-07-07
2004-10-12
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Physical dimension specified
C204S192140, C204S192150, C428S421000, C428S422000, C428S451000
Reexamination Certificate
active
06803098
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a synthetic resin molded material and a method for its production.
BACKGROUND ART
Heretofore, a synthetic resin substrate having hydrophobicity has sometimes had a trouble attributable to the hydrophobicity. For example, a fluorine-containing resin film as a typical example of a synthetic resin substrate having hydrophobicity, is excellent in transparency, durability, weather resistance, antisoiling property, etc., and by virtue of such characteristics, it has been used as a film for an agricultural or horticultural house instead of a vinyl chloride resin. However, when a fluorine-containing resin film is used for an agricultural or horticultural house, moisture condensation is likely to form on the inside surface of the film as the film has no hydrophilicity, whereby problems are likely to result such that sunlights required for the growth of plants tend to be blocked, or deposited water drops are likely to drop directly on crop plants instead of flowing in the form of a water film on the film surface, to present adverse effects.
To solve such problems, as a method for imparting hydrophilicity to the surface of a synthetic resin substrate, a coating method has heretofore reported in which a mixture of a silica-type sol and a surfactant, is coated on the resin surface, followed by drying to impart hydrophilicity (e.g. JP-A-62-179938, JP-A-5-59202 and JP-A-5-59203).
However, with the hydrophilic film obtained by this method, the hydrophilicity does not last for a long period of time, and in a case where it is used for a synthetic resin which has a long useful life like a fluorine resin film, there has been a problem that costs and time will be required, as it is necessary to carry out recoating periodically.
The present invention is intended to solve the above-mentioned problems of the prior art and to provide a synthetic resin molded material having adequate hydrophilicity, whereby the hydrophilicity will last for a long period of time.
DISCLOSURE OF THE INVENTION
The present invention provides a synthetic resin molded material characterized in that a thin film made of an oxide of at least one metal selected from the group consisting of Si, Zr, Ti, Ta, Hf, Mo, W, Nb, Sn, In, Al, Cr and Zn is formed by a dry method on a synthetic resin substrate having hydrophobicity.
In the present invention, it is important to form the thin film made of an oxide of at least one metal selected from the group consisting of Si, Zr, Ti, Ta, Hf, Mo, W, Nb, Sn, In, Al, Cr and Zn by a dry method, whereby a desired synthetic resin substrate having hydrophobicity can effectively be made hydrophilic.
The above treatment to impart hydrophilicity is to modify the hydrophobic synthetic resin surface to be hydrophilic. As a result, a drop flowing property (a property to let water drops deposited on the surface flow), an antifogging property (a property to prevent fogging by moisture condensation), an anti-mist property (a property to prevent a mist attributable to water drops deposited on the film surface), an antistatic property (a property to prevent electrification of static electricity), a wettability (a nature to be readily wetted) or the like will be improved.
The thin film of an oxide to be used in the present invention, is not particularly limited so long as it is an oxide of at least one metal selected from the group consisting of Si, Zr, Ti, Ta, Hf, Mo, W, Nb, Sn, In, Al, Cr and Zn.
It is preferably a thin film made of an oxide of a metal containing at least Si, since it is thereby possible to obtain high hydrophilicity. This is believed to be attributable to the fact that Si present on the outermost surface of the thin film layer and moisture present in the atmosphere will bond to form a highly hydrophilic SiOH state.
Specific examples of the oxide of a metal containing at least Si, include oxides comprising SiO
2
, oxides of Si and Zr, oxides of Si and Ti, oxides of Si and Ta, oxides of Si and Nb, oxides of Si and Sn, oxides of Si and Zn, or oxides of Si, Sn and Ti, as the main components.
From the viewpoint of the initial hydrophilicity, the durability of hydrophilicity for a long period of time and the material cost, an oxide comprising SiO
2
as the main component is preferred.
From the viewpoint of the initial hydrophilicity, the durability of hydrophilicity for a long period of time, the adhesion to the substrate and the productivity, oxides comprising oxides of Si and Sn, oxides of Si and Zr, or oxides of Si and Ti, as the main components, are preferred. Particularly preferred are oxides comprising oxides of Si and Sn as the main component.
Further, with a view to providing a photocatalytic function so as to provide an effect for decomposing or preventing deposition of a stain, by irradiation of sunlight, against deposition of a stain which is considered to be one of factors to prevent the long lasting effect of hydrophilicity, oxides comprising oxides of Si and Sn, oxides of Si and Ti, or oxides of Si, Sn and Ti, as the main components, are preferred.
From the viewpoint of providing various properties including the above-mentioned drop flowing property, the thickness of the thin film of an oxide in the present invention is preferably at least 3 nm. Further, from the viewpoint of maintenance of visible light transmittance, maintenance of flexibility of the synthetic resin substrate and adhesion to the substrate, the thickness is preferably at most 100 nm, more preferably at most 30 nm.
In a case where the thin film of an oxide in the present invention contains at least Si, the proportion of Si is preferably such that Si is from 20 to 80 atomic %, more preferably from 30 to 70 atomic %, to the total metals.
By adjusting the proportion of Si within the above range, it is possible to obtain effects such that 1) by the effect of contained Si, the refractive index of the oxide film can be properly made small, and it is possible to obtain a synthetic resin molded material having a desired color, 2) by the effect of metal components other than Si, the above-mentioned various properties including the drop flowing property can be obtained even when the oxide film is made thin, and 3) when a direct current sputtering method is employed as a film forming method, arching can be prevented by using an alloy target having a compositional range similar to that of the oxide film.
The contact angle to water of the oxide film tends to increase as the time passes from immediately after the film formation. However, the larger the proportion of Si (for example when Si is at least 50 atomic %), the smaller the change with time of the contact angle to water.
On the other hand, in a case where an alloy target is employed, if the proportion of Si increases, the film-forming speed tends to decrease. Accordingly, from the viewpoint of the productivity, Si is preferably at most 70 atomic %.
In the present invention, the method for obtaining the thin film of an oxide is not particularly limited so long as it is a dry method. With the dry method, the film can be made uniform, and the adhesion of the formed film to the substrate is high, as compared with a wet system. Accordingly, the dry method is one of important requirements for accomplishing the object of the present invention.
The dry method may, for example, be a vacuum vapor deposition method, a sputtering method, a CVD method or an ion plating method. Particularly preferred is a sputtering method, since it is excellent in the productivity and is widely used on an industrial scale, and it is possible to obtain by the method a film which is very dense and has high adhesion to the substrate, in a uniform film thickness.
The sputtering method may be a direct current sputtering method or a radio frequency sputtering method. A direct current sputtering method is preferred, since it is thereby possible to form a film efficiently at a high film forming speed on a substrate having a large surface.
As an example of a film of the oxide comprising SiO
2
as the main component, a thin film made of SiO
2
may be mentioned. The
Harada Kazuo
Hayashi Atsushi
Kaya Seitoku
Momii Tatsuo
Takakura Teruo
Asahi Glass Company Ltd.
Nakarani D. S.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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