Antireflection laminate

Abstract

There is provided an antireflective laminate having a low refractive index and excellent mechanical strength, which comprises a coating layer of an ionizing radiation curing-type resin composition comprising ionizing radiation curing group-containing hollow silica fine particles. The antireflective laminate comprises a light transparent base material and at least a low refractive index layer having a refractive index of not more than 1.45 provided on the light transparent base material, wherein the low refractive index layer comprises an ionizing radiation curing-type resin composition and silica fine particles having an outer shell layer with the interior of the silica fine particles being porous or void, and, for a part or all of the silica fine particles, at least a part of the surface of the silica fine particle has been treated with an ionizing radiation curing group-containing silane coupling agent.

Description

TECHNICAL FIELD [0001] The present invention relates to an antireflective or antireflection laminate having a low refractive index and excellent mechanical strength, which comprises a coating layer of an ionizing radiation curing-type resin composition comprising ionizing radiation curing group-containing hollow silica fine particles. BACKGROUND ART [0002] Display surfaces in image display devices such as liquid crystal displays (LCDs) or cathode ray tube display devices (CRTs) are required to cause no significant reflection of light applied from external light sources such as fluorescent lamps from the viewpoint of enhancing the visibility of the image. [0003] The phenomenon that the reflectance is reduced by coating a low refractive index transparent film onto the surface of a transparent object has hitherto been known. The visibility can be improved by providing an antireflection film utilizing this phenomenon onto the display surface of an image display device. Antireflection fi...

AI Technical Summary

Benefits of technology

[0018] In view of the above problems of the prior art, the present invention has been made, and an object of the present invention is to provide an antireflective laminate having a low refractive index and excellent mechanical strength, comprising a coating layer of an ionizing radiation curing resin composition containing ionizing radiation curable group-containing hollow silica fine particles.

[0022] According to the present invention, the silica fine particles have fine voids in the exterior and interior parts thereof, and the voids are filled with gas, for example, air having a refractive index of 1. Therefore, the refractive index of the silica fine particles per se is low and, even when the silica fine particles are homogenously dispersed without the formation of any aggregate in the coating film, the refractive index of the coating film can be lowered. Specifically, the refractive index of the void-containing silica fine particles has a lower refractive index of 1.20 to 1.45 which is lower than conventional silica fine particles free from gas in the interior thereof (refractive index n=about 1.46), and, thus, the refractive index of the coating film can be brought to not more than 1.45, preferably not more than 1.40. Further, since voids are protected by an outer shell of fine particles, the formed coating film is compacted by the aggregative force and hardness of the fine particles dispersed in the cured resin composition, contributing to improved mechanical strength of the coating film.

[0023] These fine particles are slightly aggregated in the coating film, and, consequently, concaves and convexes having a fineness approximately below the wavelength of the visible light are formed particularly on the outermost surface of the coating film. As a result, a nanoporous structure is formed within or on the surface of the coating film, and, thus, a structure into which air is introduced more easily than the case of a conventional flat film consisting of a resin only can be realized. By virtue of this, the attained effect is expected to be more than that attained by the refractive index possessed by the fine particles. Further, even when the content of silica fine particles based on the resin composition is significantly increased, a significant lowering in hardness and strength of the coating film can be avoided.

[0024] Further, since an ionizing radiation curing group-containing silane coupling agent is introduced into at least a part of the surface of the silica fine particles, the affinity for the binder component is improved and homogeneous dispersion of the silica fine particles in the coating liquid or coating film can be realized.

[0025] Furthermore, since the ionizing radiation curing group in the silane coupling agent introduced into this surface chemically forms a covalent bond with the ionizing radiation curing group in the binder component directly and / or through an ionizing radiation curing group in a free silane coupling agent, the silica fine particles functions as a crosslinking agent for the binder component. Therefore, even when the content of the silica fine particles based on the resin composition is very high, a significant lowering in hardness and strength of the coating film can be avoided and a low refractive index layer having a low refractive index and possessing excellent mechanical strength can be realized.

Problems solved by technology

Further, the gas phase method involves a problem that, since a special heating device or ion generating accelerator is used, the production apparatus is complicated, and, thus, the size of the production apparatus is so large that the production cost is necessarily increased.

In addition, in the gas phase method, it is difficult to form a large-area transparent thin film or to evenly form a transparent thin film on the surface of a film or the like having a complicated shape.

On the other hand, the formation of the low refractive index layer by spraying, i.e., one of the coating methods, is disadvantageous, for example, in that the utilization efficiency of the coating liquid is low and the regulation of film formation conditions is difficult.

The formation of the low refractive index layer by roll coating, gravure coating, slide coating, dip coating, screen printing or the like can realize good utilization efficiency of the film forming material and thus is excellent in mass production and equipment cost, but on the other hand, in general, it involves a problem that the transparent thin film formed by the coating method is inferior to that formed by the gas phase method in function and quality.

However, increasing the fluorine atom content of the coating film disadvantageously lowers the hardness and strength of the coating film.

This technique, however, involves a problem that, when the amount of microvoids for lowering the refractive index is excessively large, the hardness and strength of the coating film are lowered.

As with the above technique, however, the technique disclosed in this publication involves a problem that, when the amount of these voids is excessively large, the hardness and strength of the coating film are lowered.

This low refractive index layer is a highly hard coating film by virtue of the use of an inorganic component-containing binder, but on the other hand, the low refractive index layer suffers from a problem that, due to its poor in resistance to external impact, the mechanical strength, particularly scratch resistance, of the coating film is poor.

Further, by virtue of the aggregating effect of the hollow silica particles, the hardness of the coating film is higher than that of the hollow silica particle-free coating film, but on the other hand, since brittleness is also increased, it is difficult to realize a low-refractive index and highly mechanically strong coating film.

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