Hard coat film and display device having same

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Reexamination Certificate

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Reexamination Certificate

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06686031

ABSTRACT:

The present application claims priority under 35 USC 119 on Japanese patent applications No. 2000-046551, filed on Feb. 23, 2000, No. 2000-057973, filed on Feb. 29, 2000, No. 2000-072443, filed on Mar. 10, 2000, and No. 2000-077097, filed on Mar. 17, 2000, which are herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a hard coat film and a display device having same.
2. Description of the Related Art
Antireflection films are provided on various types of display device such as liquid crystal displays (LCDs), plasma display panels (PDPs), electroluminescent displays (ELDs) and cathode ray tube displays (CRTs).
With regard to the antireflection films, films having a structure in which a transparent film of a metal oxide is applied on a transparent support are used in the art. Antireflection films formed by applying a plurality of transparent films are used for preventing the reflection of light having various wavelengths. A transparent film of a metal oxide can be formed by a chemical vapor deposition (CVD) or physical vapor deposition (PVD) method. It is usually formed by a vacuum vapor deposition method which is one of the physical vapor deposition methods. A multi-layer vapor deposition film made from metal oxide has excellent optical properties as an antireflection film. Methods of forming antireflection films by vapor deposition are described in Japanese Patent Application Laid-open Nos. 60-144702, 61-245449, 62-178901 and 9-197103.
A method of forming an antireflection film by coating instead of vapor deposition has also been proposed. Although the coating method is slightly inferior to the vapor deposition methods in terms of the optical performance, it is characterized by a simple production procedure and high productivity. The coating method involves coating optically functional layers (low refractive index layer, high refractive index layer, medium refractive index layer) on a transparent support so as to form an anti-reflection film. Methods of forming such an anti-reflection film by coating are described in Japanese Patent Publication No. 60-59250 and Japanese Patent Application Laid-open Nos. 59-50401, 2-245702, 5-13021, 8-110401 and 8-179123.
In both the method of forming optically functional layers by vapor deposition and the method of forming optically functional layers by coating, a hard coat layer is usually formed on the transparent support prior to the formation of the optically functional layers. The hard coat layer functions to improve the abrasion resistance of the transparent support. The hard coat layer is therefore usually formed from a hard material such as a crosslinked binder polymer, and the binder polymer is often crosslinked after being applied as a layer.
However, this method often degrades the flatness when forming a hard coat layer so causing a problem in the formation of an antireflection film. Moreover, as the applications of antireflection films have diversified, the abrasion resistance of the current hard coat layers has become inadequate in some cases, and there is a desire for improvement of the abrasion resistance.
The hard coat film of the art is usually produced by forming a thin coating of about 3 to 15 &mgr;m directly or over a primer layer of about 1 &mgr;m on a transparent support film using a heat-curing type resin or a radiation polymerizable resin such as a UV-curing type resin.
On the other hand, TV Braun tubes, cathode ray tubes which are used as computer displays, plasma displays and field emission displays, to which a low reflection and conductive hard coat film has been applied, have the problems that the visibility is degraded by dust adhering to the face panel due to static electricity generated thereon, that electromagnetic radiation is emitted so affecting the surroundings badly, etc. Furthermore, accompanying the flattening of cathode ray tubes, etc. it has become necessary to introduce antireflection properties. Moreover, the face panel has the problem that it is easily abraded when touched by hand or cleaned.
Although a method of directly forming an electrically conductive layer on a face panel by vapor deposition, sputtering, etc. of a metal such as silver or an electrically conductive metal oxide such as ITO has been proposed from the viewpoint of preventing the generation of static electricity, shielding electromagnetic radiation and preventing reflection, since it requires a vacuum treatment or high temperature treatment to form the film, there are problems such as high production cost and poor productivity.
A method of forming an electrically conductive film by coating using the sol-gel method has also been proposed (Hanyu, et. al., National Technical Report 40, No. 1, (1994) 90), but this method has the problems that the required high temperature treatment might degrade the materials used as the transparent plastic film support or hard coat layer and the materials that can be used are therefore limited.
The use of a transparent electrically conductive coating in which fine particles or a colloid of an electrically conductive oxide are dispersed has also been proposed (Japanese Patent Application Laid-open Nos. 6-344489 and 7-268251), but there is the problem that the transparent electrically conductive layer so obtained has low conductivity.
In order to further enhance the conductivity, transparent electrically conductive films comprising metal particles have been proposed (Japanese Patent Application Laid-open Nos. 63-160140 and 9-55175). A method of forming a low reflection transparent electrically conductive film by applying an antireflection coating such as tetraethoxysilane on a transparent electrically conductive film has also been proposed (Japanese Patent Application Laid-open No. 10-142401). However, the following problems occur. That is to say, the mechanical strength is inadequate if metal particles alone are coated on a transparent support, an antireflection coating such as tetraethoxysilane requires a prolonged heat treatment at high temperature, the transparent supports that can be used are limited when applying an antireflection layer by the sol-gel method, and the above-mentioned method of forming a low reflection transparent electrically conductive film can only be used for direct application to a glass face panel.
Furthermore, an improvement in conductivity by coating fine silver particles directly onto a glass face panel by a spin coating method and calcining so as to cause a sintering reaction at around 150° C. and a decomposition reaction of Ag
2
O on the surface has been proposed (Japanese Patent Application Laid-open No. 10-66861), but this method also can also only be applied to a heat-resistant support such as glass.
Therefore, a method in which a preformed film is bonded to a support has been proposed (Taki, et. al., National Technical Report, 42, No. 3 (1996) 264-268), taking a different view from that of the method where a coating is formed directly on the front side of a face panel which requires high equipment cost and a high temperature treatment.
In the above-mentioned method of forming a film, an electrically conductive film is formed by vapor deposition, sputtering, etc. of an electrically conductive metal oxide such as ITO, and the film formation requires a vacuum treatment so increasing the production cost and degrading the productivity.
BRIEF SUMMARY OF THE INVENTION
It is a first object of the present invention to provide a hard coat film and an antireflection film in which shrinkage of the hard coat layer due to crosslinking of the binder polymer is suppressed and deformation is reduced, and also to provide a hard coat film and an antireflection film having excellent abrasion resistance by improving the mechanical properties of the hard coat layer.
It is a second object of the present invention to provide a hard coat film having a hardness of at least 4H in a pencil hardness test by suppressing degradation of the hardness of a radiation cured film due to deformation of the transparent support film.
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