Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
1999-10-04
2001-04-03
Hamilton, Cynthia (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S271100, C428S317900, C428S328000, C428S331000, C348S834000
Reexamination Certificate
active
06210858
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an anti-reflection film comprising a high refractive index layer and a low refractive index layer, an anti-reflection film comprising a low refractive index layer, and a display device using the anti-reflection film.
PRIOR ART
Anti-reflection films are used in various display devices such as a liquid crystal display device (LCD), a plasma display panel (PDP), an electroluminescence display (ELD), and a cathode-ray tube (CRT). Further, they are generally provided on lenses of glasses or cameras.
As the anti-reflection film, a multi-layered film comprising plural transparent metal oxide layers superposed one on another has been widely employed. The plural transparent metal oxide layers reduce reflections of light in a wide wavelength region, and are formed by chemical vapor deposition (CVD) process or physical vapor deposition (PVD) process (especially, vacuum deposition process). Although the transparent metal oxide layers give an anti-reflection film having excellent optical characteristics, the deposition process has insufficient productivity for mass-production.
In place of the deposition process, it is proposed to employ a coating liquid containing inorganic fine particles to prepare an anti-reflection film.
Japanese Patent Publication No. 60-59250 describes an anti-reflection film comprising fine holes and inorganic fine particles. The film is formed by using a coating liquid, and the formed film is subjected to active gas treatment. By the treatment, the gas escapes from the film to form the fine holes.
Japanese Patent Provisional Publication No. 59-50401 describes an anti-reflection film comprising a support, a high refractive index layer and a low refractive index layer superposed in order. This publication also discloses an anti-reflection film further comprising a middle refractive index layer provided between the support and the high refractive index layer. In each film, the low refractive index layer is formed by using a coating liquid containing a polymer or inorganic fine particles.
Japanese Patent Provisional Publication No. H2-245702 discloses an anti-reflection film comprising two or more kinds of micro particles (for example, SiO
2
and MgF
2
). The mixing ratio of the particles varies in the thickness direction so that the refractive index would gradually vary in the thickness direction. The film having that structure has optical characteristics similar to those of the film in No. 59-50401, which comprises both high and low refractive index layers. In the film of Publication No. H2-245702, the micro particles are combined via SiO
2
formed by thermal decomposition of ethyl silicate. In the thermal decomposition, the ethyl part of ethyl silicate is burnt to evolve carbon dioxide and water vapor. The produced carbon dioxide and water vapor escape from the film to form voids by the adjacent micro particles (as shown in
FIG. 1
of the publication).
Japanese Patent Provisional Publication No. H5-13021 discloses an anti-reflection film in which the voids described in Publication No. 2(1990)-245702 are filled with a binder.
Japanese Patent Provisional Publication No. H7-48527 discloses an anti-reflection film comprising a binder and inorganic fine particles of porous silica.
Japanese Patent Provisional Publications No. H8-110401 and No. H8-179123 disclose an anti-reflection film which comprises a high refractive index film (having a refractive index of 1.80 or more) containing inorganic fine particles of high refractive index dispersed in a plastic material.
SUMMARY OF THE INVENTION
The present inventors made studies on incorporation of inorganic fine particles into a high refractive index layer and a low refractive index layer of anti-reflection film. For forming the layers, it is advantageous to employ a coating liquid containing inorganic fine particles, because the process has enough productivity for mass-production. However, the inventors noted the problems in forming the layers of high and low refractive indexes.
In forming a high refractive index layer, it is difficult to finely disperse the inorganic particles and further to form the layer having a well dispersed phase.
For preparing a high refractive index layer as a transparent film, the inorganic particles need to be dispersed finely and uniformly. It is generally known that surface active agents and (cationic or anionic) polymers are used for dispersing the particles. Those agents can be used only when the layer is formed. After forming the layer, they show no function, and further often impair physical strength (abrasion resistance) and chemical strength (chemical resistance) of the high refractive index layer.
It is also difficult to prepare a low refractive index layer having both a proper refractive index and enough physical strength.
The study of the inventors revealed that the refractive index can be decreased by micro voids in the layer. By piling up two or more inorganic fine particles in the layer, the micro voids can be formed between the particles. However, a low refractive index layer containing the voids generally has insufficient strength. Since the low refractive index layer is often placed on the screen of image display device or the outer surface of lens, the layer needs to have enough strength. If the voids are filled with a binder the layer has sufficient strength. However, according to the study of the inventors, such voids can not satisfyingly lower the refractive index of the layer.
An object of the invention is to provide an anti-reflection film suitable for mass-production.
Another object of the invention is to provide an anti-reflection film comprising a transparent high refractive index layer having an increased high refractive index.
Further, it is also an object of the invention to provide an anti-reflection film comprising a low refractive index layer having an decreased low refractive index.
Furthermore, it is an object of the invention to provide an anti-reflection film comprising a high or low refractive index layer having excellent strength.
In addition, an object of the invention is to provide a display device in which the reflection of light is lowered by proper means.
The objects of the invention are achieved by the following improvements (1) to (4) of high refractive index layer, the following improvements (10) to (13) of low refractive index layer, the following improvements (5) to (8) of both layers, and the following display devices (9) and (14) equipped with improved anti-reflection films.
(1) An anti-reflection film comprising a high refractive index layer having a refractive index of 1.65 to 2.40 and a low refractive index layer having a refractive index of 1.20 to 1.55, wherein the high refractive index layer contains inorganic fine particles having a mean particle size of 1 to 200 nm in an amount of 5 to 65 vol. % and a crosslinked polymer comprising phosphoric acid group or sulfonic acid group as an anionic group in an amount of 35 to 95 vol. %.
(2) The anti-reflection film of (1), wherein the polymer having the anionic group in the high refractive index layer further contains amino group or ammonium group.
(3) The anti-reflection film of (1), wherein the inorganic fine particles in the high refractive index layer have an average refractive index of 1.80 to 2.80.
(4) The anti-reflection film of (1), wherein the high refractive index layer is formed by applying a coating liquid, and the polymer having the anionic group is formed by polymerization reaction during or after the application.
(5) The anti-reflection film of (1), wherein the low refractive index layer contains inorganic fine particles having a mean particle size of 0.5 to 200 nm in an amount of 50 to 95 wt. % and a polymer in an amount of 5 to 50 wt. %, and two or more of said particles are piled up to form micro voids between the adjacent particles.
(6) The anti-reflection film of (5), wherein the low refractive index layer has a void volume in the range of 3 to 50 vol. %.
(7) The anti-reflection film of (5), wherein the inorganic fine parti
Nakamura Kazuhiro
Nakamura Ken'ichi
Nakamura Taku
Yasuda Tomokazu
Ashton Rosemary
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
Hamilton Cynthia
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