Optical: systems and elements – Glare or unwanted light reduction – With mirror
Reexamination Certificate
2001-07-11
2003-01-07
Sikder, Mohammad (Department: 2872)
Optical: systems and elements
Glare or unwanted light reduction
With mirror
C359S604000, C359S608000, C359S613000, C359S614000
Reexamination Certificate
active
06502943
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an antireflection film having antiglare property, and a polarizer, a liquid crystal display device and an image display device using the same. The present invention also relates to a coating solution for forming the low refractive index layer of an antiglare and antireflection film.
BACKGROUND OF THE INVENTION
An antiglare film, an antireflection film or an antiglare and antireflection film is generally disposed, in an image display device such as cathode ray tube display device (CRT), plasma display panel (PDP) and liquid crystal display device (LCD), on the outermost surface of a display where the reflectance is reduced by using the principle of optical interference so as to prevent reflection of external light which causes reduction in the contrast or reflection of an image.
An antiglare and antireflection film having an antireflection function is more excellent in such a performance than an antiglare film, and use thereof in a display is recently started.
However, if the antireflection function is imparted, the dust protection on the surface generally changes for the worse and dusts readily attach thereto. Dusts may be gathered on the display for removing the attached dusts but the gathered dusts cannot be removed from the display. This is a serious problem on considering using the antiglare and antireflection film for television in the future.
Heretofore, antireflection function and prevention of dusts from sticking cannot be attained at the same time.
On the other hand, in the antireflection film having only a hard coat layer and a low refractive index layer on a transparent support, the refractive index of the low refractive index layer must be satisfactorily lowered so as to reduce the reflectance. For example, in the case of an antireflection film having a triacetyl cellulose support and using UV cured film of dipentaerythritol hexaacrylate as the hard coat layer, the refractive index must be lowered to 1.40 or less so as to reduce the average reflectance to 1.6% or less in the range from 450 to 650 nm.
With respect to the material having a refractive index of 1.40 or less, the inorganic material include fluorine-containing compounds such as magnesium fluoride and calcium fluoride, and the organic material include fluorine compounds having a large fluorine content. However, these fluorine-containing compounds have no cohesion and therefore, are deficient in the scratch resistance as a film disposed on the outermost surface of a display. In order to have sufficiently high scratch resistance, a compound having a refractive index of 1.43 or more is necessary. As such, it is difficult to attain low refractive index and scratch resistance at the same time.
JP-A-7-287102 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) describes a technique of increasing the refractive index of hard coat layer and thereby reducing the reflectance. However, due to large difference in the refractive index between this high refractive index hard coat layer and the support, color irregularity is generated on the film and the dependency of the reflectance on the wavelength greatly fluctuates.
JP-A-7-333404 describes an antiglare and anti-reflection film excellent in the gas barrier property, antiglare property and antireflection property, where, however, a silicon oxide film by CVD method is indispensable and therefore, the productivity is low as compared with the wet-coating method of forming a film by coating a coating solution. Furthermore, the antiglare and antireflection film obtained as such is not satisfied in the antireflection property.
SUMMARY OF THE INVENTION
According to the knowledge newly found by the present inventors, for obtaining an antiglare and antireflection film excellent in the antireflection property, antifouling property, scratch resistance and clearness of transmitted image by all-wet coating, it is preferred to use resin particles having a narrow particle size distribution with a number average particle size by the Coulter method of about 2 to 3 &mgr;m, in the antiglare hard coat layer. However, in view of the design of surface asperities, such an antiglare hard coat layer suffers from narrow latitude in the average particle size and the particle size distribution of the resin particles used and furthermore, grain-like planar failures are readily caused throughout the film due to a very small amount of coarse grains, environment and mixing of foreign matters mingled into the support or the like.
The present inventors have found that use of a transparent support having excellent smoothness is preferred for obtaining, by all-wet coating, an antiglare and antireflection film excellent in the antireflection property, antifouling property, scratch resistance and clearness of transmitted image and favored with high planar uniformity while reducing the planar unevenness at the wet coating and that in particular, a transparent support for use in the antiglare layer having excellent clearness of transmitted image is required to have high smoothness. The present invention has been accomplished based on these findings.
An object of the present invention is to provide an antiglare and antireflection film which can be formed by a wet-coating method and which is excellent in the antireflection property, antifouling property, scratch resistance, clearness of transmitted image and planar uniformity.
Another object of the present invention is to provide an antiglare and antireflection film which is favored with planar uniformity at the same time with various performances such as antireflection property, antifouling property, scratch resistance and clearness of transmitted image and which can be obtained by an all-wet coating method.
Still another object of the present invention is to provide an antiglare and antireflection film which can be simply and inexpensively produced only by forming an antiglare hard coat layer and a low refractive index layer on a support and which is favored with a sufficiently high antireflection performance, scratch resistance and antifouling property.
Still another object of the present invention is to provide a polarizer and a liquid crystal display device using such an excellent antiglare and antireflection film.
Still another object of the present invention is to provide a polarizer and a liquid crystal display device, which are satisfactorily prevented from the reflection of exterior light and at the same time, favored with excellent antifouling property and high scratch resistance.
Still another object of the present invention is to provide a liquid crystal display device excellent in the contrast, visibility and clearness of image, and favored with good planar uniformity.
Still another object of the present invention is to provide an antiglare and antireflection film excellent in the dust protection (prevention of dusts from sticking) and having a small reflectance.
Still another object of the present invention is to provide a polarizer and an image display device using an antiglare and antireflection film excellent in the above-described properties.
Still another object of the present invention is to provide a coating solution capable of forming a low refractive index layer, which is a layer constituting the antiglare and antireflection film, to have good coated surface state and a uniform coating thickness.
According to the present invention, an antiglare and antireflection film, a polarizer, a liquid crystal display device and a coating solution for a low refractive index layer having the following constructions are provided and the above-described object can be attained.
(1) An antiglare and antireflection film comprising a transparent support having thereon an antiglare hard coat layer and a low refractive index layer having a refractive index of 1.38 to 1.49, wherein the low refractive index layer is formed by a coating method, the solvent of the coating solution for forming the low refractive index layer comprises one or more solvent, and from 5
Arai Tsutomu
Hokazono Hirohisa
Matsunaga Naohiro
Nakamura Kazuhiro
Otani Shinichi
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
Sikder Mohammad
LandOfFree
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