Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2002-04-29
2004-08-10
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S220000, C428S332000, C428S334000, C428S335000, C428S336000, C428S688000, C428S689000, C428S702000, C428S913000, C359S585000, C359S586000
Reexamination Certificate
active
06773835
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a film for optical applications and, more particularly, to a film for optical applications which effectively prevents reflection of light at the surface of image display devices such as plasma displays (PDP), cathode ray tubes (CRT) and liquid crystal displays (LCD), exhibits excellent scratch resistance and can be produced at a low cost.
2. Description of Related Art
When a display device such as PDP, CRT and LCD is used, light from the outside is occasionally reflected at the surface of the display and difficulty arises in watching images on the display. In particular, as the size of flat panel displays increases recently, solving the above problem is becoming more important.
To solve the above problem, various treatments for preventing reflection of light and anti-glare treatments have been made on various display devices. As one of such treatments, a film for preventing reflection of light is used for various display devices.
The film for preventing reflection of light has heretofore been prepared in accordance with a dry process such as vapor deposition and sputtering. A thin film of a substance having a low refractive index such as MgF
2
is formed on a substrate film or layers of a substance having a high refractive index such as ITO (indium oxide doped with tin) and TiO
2
and layers of a substance having a low refractive index such as MgF
2
and SiO
2
are alternately laminated. However, the film for preventing reflection of light prepared in accordance with the dry process has a drawback in that the cost of production is high.
Recently, preparation of a film for preventing reflection of light in accordance with a wet process, i.e., a coating process, has been attempted. However, the film for preventing reflection of light prepared in accordance with the wet process has a drawback in that scratch resistance of the surface of the prepared film is inferior to that of the film prepared in accordance with the dry process.
SUMMARY OF THE INVENTION
The present invention has an object of providing a film for optical applications which effectively prevents reflection of light at the surface of image display devices such as PDP, CRT and LCD, exhibits excellent scratch resistance and can be produced at a low cost.
As the result of extensive studies by the present inventors on the film for preventing reflection of light which exhibits excellent property of preventing reflection of light and excellent scratch resistance and can be produced at a low cost, it was found that a film for preventing reflection of light which was formed by successively laminating a hard coat layer, a high refractivity layer, a low refractivity layer and, optionally, an antifouling layer each having a specific property and a specific thickness on a substrate film in accordance with a wet process could be used advantageously as the film for optical application achieving the above object. The present invention has been completed based on the knowledge.
The present invention provides:
(1) A film for optical applications comprising (A) a hard coat layer which comprises a resin cured by an ionizing radiation and has a thickness in a range of 2 to 20 &mgr;m, (B) a high refractivity layer which comprises a resin cured by an ionizing radiation and at least two metal oxides comprising tin oxide doped with antimony and has a refractive index in a range of 1.65 to 1.80 and a thickness in a range of 60 to 160 nm and (C) a low refractivity layer which comprises a siloxane-based polymer and has a refractive index in a range of 1.37 to 1.47 and a thickness in a range of 80 to 180 nm, layers (A) to (C) being successively laminated at least on one face of a substrate film;
(2) A film described in (1), wherein the hard coat layer of layer (A) is a hard coat layer having an anti-glare property;
(3) A film described in any one of (1) and (2), wherein, in the high refractivity layer of layer (B), a content of the tin oxide doped with antimony in an entire amount of the metal oxides is 25 to 90% by weight;
(4) A film described in any one of (1) to (3), wherein at least two metal oxides comprised in the high refractivity layer of layer (B) are mixed metal oxides comprising tin oxide doped with antimony and at least one metal oxide selected from titanium oxide and indium oxide doped with tin;
(5) A film described in any one of (1) to (4), wherein the low refractivity layer of layer (C) has an antistatic property; and
(6) A film described in any one of (1) to (5), which further comprises (D) an antifouling coating layer disposed on layer (C).
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The film for optical applications of the present invention is a film for preventing reflection of light which is prepared in accordance with a wet process and has a structure comprising (A) a hard coat layer, (B) a high refractivity layer, (C) a low refractivity layer and, optionally, (D) an antifouling layer disposed on layer (C), which are successively laminated at least on one face of a substrate film.
The substrate film used for the film for optical applications of the present invention is not particularly limited and can be suitably selected from conventional plastic films heretofore used as the substrate for films for preventing reflection of light in optical applications. Examples of the plastic film include films of polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, polyethylene films, polypropylene films, cellophane, diacetylcellulose films, triacetylcellulose films, acetylcellulose butyrate films, polyvinyl chloride films, polyvinylidene chloride films, polyvinyl alcohol films, ethylene-vinyl acetate copolymer films, polystyrene films, polycarbonate films, polymethylpentene films, polysulfone films, polyether ether ketone films, polyether sulfone films, polyether imide films, polyimide films, fluororesin films, polyamide films and acrylic resin films.
The substrate film may be transparent or translucent and may be colored or colorless. These properties of the substrate film can be suitably selected in accordance with the application. For example, when the film is used as a protective film of a liquid crystal display, a colorless transparent film is preferable as the substrate film.
The thickness of the substrate film is not particularly limited and suitably selected in accordance with the situation. The thickness is, in general, in the range of 15 to 250 &mgr;m and preferably in the range of 30 to 200 &mgr;m. One or both surfaces of the substrate film may be treated, for example, by oxidation or by a treatment of forming rough surfaces, where desired, so that adhesion with layers disposed on the surfaces is enhanced. Examples of the treatment of the surface by oxidation include the treatment by corona discharge, the treatment by chromic acid (a wet process), the treatment by flame, the treatment by heated air and the irradiation with ultraviolet light in the presence of ozone. Examples of the treatment of forming rough surfaces include the treatment by sand blasting and the treatment with a solvent. The surface treatment is suitably selected in accordance with the type of the substrate film. In general, the treatment by corona discharge is preferable from the standpoint of the effect and the operability. The substrate film may be treated by forming a primer on one or both faces thereof.
In the film for optical applications of the present invention, the hard coat layer of layer (A) comprising a resin cured by an ionizing radiation is disposed as the first layer at least on one surface of the substrate film. It is preferable that the hard coat layer has the anti-glare property. Therefore, the hard coat layer may further comprise various types of fillers providing the anti-glare property in combination with the resin cured by an ionizing radiation.
The hard coat layer can be formed, for example, by coating the substrate film with a coating fluid for forming the hard coat layer which comprises a compound c
Maruoka Shigenobu
Onozawa Yutaka
Shoshi Satoru
Boss Wendy
Frishauf Holtz Goodman & Chick P.C.
Jones Deborah
Lintec Corporation
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