Transparent antistatic layer-coated substrate and optical...

Details Transparent antistatic layer-coated substrate and optical... Transparent antistatic layer-coated substrate and optical...

1999-10-13

2002-04-23

Nakarani, D. S. (Department: 1773)

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Physical dimension specified

C428S216000, C428S520000, C428S521000, C428S522000, C428S922000

Reexamination Certificate

active

06376066

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a transparent antistatic layer-coated substrate which has excellent transparency, antistatic property, hardness and solvent resistance and shows no deterioration in the transparency or the antistatic property in the condition of a high temperature and a high humidity and an optical article comprising the laminate and a layer of suppressed reflection which is a thin layer comprising a fluorine compound having hydroxyl group and disposed on the laminate. The transparent antistatic layer-coated substrate and optical article of the present invention are advantageously used for a display material and a cover material at the front face of display apparatuses, a front panel of projection televisions, a cover material of instruments, a wall material of clean rooms and a packaging material for semiconductors.
2. Description of the Related Arts
Transparent substrates are widely used as light-transmitting materials for electric appliances and buildings and as covers for instruments. However, the transparent substrates have drawbacks in that surface properties such as hardness and chemical resistance are poor and that static electricity tends to be formed and accumulated although the substrates show excellent electric insulation. These drawbacks cause a problem in that, due to dusts and other contaminating substances attracted by the electrostatic force of the formed electrostatic charge, transparency and gloss decrease and appearance becomes poor to deteriorate the commercial value. In particular, front panels of CRT displays, LCD displays and projection televisions have a problem in that electrostatic charge tends to be formed on these panels and visibility of images is deteriorated by dusts and other contaminating substances attracted by the formed electrostatic force. The panels have another problem in that visibility of images is deteriorated by reflection of outside lights such as the sun light and fluorescent lights and also by reflection of outside images.
As the method for improving the antistatic property, a surfactant may be added to a panel material and mixed with it or the surface of a panel may be coated with a surfactant. However, these methods have drawbacks in that the effect of the improvement cannot be sustained for a long time and the effect is lost when the panel is wiped or washed with water. A sustained effect for improving the antistatic property can be obtained by coating a panel with a coating material containing an alkylene glycol having a double bond, a derivative thereof or a halogen compound such as alkylamine halides. However, this method has drawbacks in that the antistatic property markedly changes depending on the humidity and a sufficient antistatic property cannot be obtained in the condition of a low humidity and that detachment of the coating layer and formation of haze take place in the condition of a high temperature and a high humidity. To overcome the above problems, transparent coating materials containing conductive fine powder which contains tin oxide as the main component are disclosed in the specifications of Japanese Patent Application Laid-Open Nos. Showa 58(1983)-91777 and Showa 60(1985)-60166. In accordance with these methods, conductivity is not affected by the temperature and the humidity and remains stable due to the electronic conductive property of the formed coating layer. Detachment of the coating layer or formation of haze does not take place even in the condition of a high temperature and a high humidity and excellent hardness and solvent resistance can be maintained. However, in accordance with this method, the conductive fine powder must be incorporated into the coating layer in a great amount and this causes drawbacks in that transparency becomes poor and that cost of the coating material itself increases. As the method for preventing reflection of outside images to improve visibility of the images, a layer for preventing reflection which contains metal oxides may be formed in accordance with the vapor deposition process or the sputtering process, or a thin layer having a small refractive index which contains compounds having fluorine may be formed in accordance with the coating process. The method using the vapor deposition process or the sputtering process has drawbacks in that the mechanism of the apparatus allows application of the process only to relatively small articles and that cost of the application is great because of the batch process. The method using the coating process has drawbacks in that heat deformation of plastic substrates is inevitable due to the high temperature generally required for drying or curing the coating layer and that adhesion to a substrate or wear resistance is insufficient although relatively large articles can be coated and cost of the application can be reduced by adopting a continuous operation.
SUMMARY OF THE INVENTION
An object of the present innovation is to provide a transparent antistatic layer-coated substrate which has excellent transparency, antistatic property, hardness and solvent resistance and does not show deterioration in the transparency or the antistatic property in the condition of a high temperature and a high humidity, and an optical article showing suppressed reflection and excellent wear resistance.
As the result of extensive studies by the present inventors, it was found that the above object could be achieved by the present invention which is summarized in the following.
The present invention provides:
(1) A transparent antistatic layer-coated substrate comprising a transparent substrate and an antistatic layer which comprises 20 to 70% by weight of conductive zinc antimonate and is disposed on at least one face of the transparent substrate, wherein the antistatic layer is formed by photocuring a composition comprising (A) a photocurable material comprising a (meth)acrylate having at least one hydroxyl group and two or more (meth)acryloyl groups in a molecule, (B) conductive zinc antimonate and (C) a photopolymerization initiator;
(2) A transparent antistatic layer-coated substrate described in (1), wherein the (meth)acrylate having at least one hydroxyl group and two or more (meth)acryloyl groups in a molecule is an epoxy-based (meth)acrylate;
(3) A transparent antistatic layer-coated substrate described in (1), wherein the (meth)acrylate having at least one hydroxyl group and two or more (meth)acryloyl groups in a molecule is an epoxy-based (meth)acrylate having a refractive index of 1.54 or more
(4) A transparent antistatic layer-coated substrate described in (1), wherein the transparent substrate comprises a copolymer of methyl methacrylate and styrene;
(5) A transparent antistatic layer-coated substrate described in (1), wherein the photopolymerization initiator is a compound derived from &agr;-aminoacetophenone;
(6) A transparent antistatic layer-coated substrate described in (1), wherein the antistatic layer has a refractive index of 1.56 or more;
(7) A transparent antistatic layer-coated substrate described in (6), wherein a thickness d of the antistatic layer satisfies following equation (1):
d=1/(4n
a
)×&lgr;×(2n+1)  (1)
wherein n
a
represents a refractive index of the antistatic layer, &lgr; represents a wave length used for designing the antistatic layer and is in a range of 530 to 570 nm and n represents 1 or 2; and
(8) An optical article comprising a transparent antistatic laminate described in (7) and a thin layer which comprises a fluorine compound having hydroxyl group and is disposed on the laminate.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The transparent substrate used in the present invention may be any substrate made of a transparent resin or a transparent glass. Examples of the transparent resin include acrylic resins, copolymer resins of methyl methacrylate and styrene, polycarbonate resins, styrene resins, polyester resins and vinyl chloride resins. Among these resins, copolymer resins of methyl methacrylate and styrene

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