Anti-reflective material

Details Anti-reflective material Anti-reflective material

2000-07-28

2003-01-28

Thibodeau, Paul (Department: 1773)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

With viewing layer of specified composition

C428S001320, C428S336000, C428S422000, C428S448000

Reexamination Certificate

active

06511721

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an anti-reflective material having particularly excellent display stainproofing properties, durability anci anti-reflective properties, which is suited for use in displays such as CRTS, LCDs, and PDPs.
2. Description of Related Art
With the recent development of displays such as CRTs, LCDs, and PDPs, various types of equipment incorporating these displays are used in various fields. When using such equipment in places exposed to comparatively bright light such as outdoors, problems such as reflections from external light such as sunlight and light from fluorescent lamps in the display have increased. Therefore, it is strongly required to prevent the reflection of external light on display surfaces, that is, to prevent reflection.
Therefore, display surface are frequently provided with anti-reflective films to improve their visibility. Such anti-reflective films are generally formed by providing the surface with a material having a refractive index lower than that of a lower layer in an optical film thickness which is n/4 times (wherein n is an odd number) as large as the wavelength of the light of interest. As the method of forming this outermost layer, for example, there can be used a method of forming the layer by deposition or sputtering of materials such as magnesium fluoride and silica, a method of coating a coating solution prepared by dispersing these materials, and a method of forming a fluorine-based polymer film by deposition and coating.
However, the anti-reflective film according to the above prior art has the problems that adhesion of dust or oily substances in the atmosphere to the surface of the substrate or adhesion of fingerprints is liable to quickly show as soiling. For example, stains on the surface of transparent glass or plastic impairs the appearance of display window glass, impairs the field of view in case of eyeglasses, and prevents safe driving in case of vehicle windows. Furthermore, for optical instruments such as cameras, stains impair their performance. Therefore, there has been demand for an anti-reflective film to which stains do not readily adhere, and from which stains can be easily removed once they adhere.
To prevent stains, various methods have hitherto been suggested. For example, Japanese Unexamined Patent Application, First Publication No. Sho 58-142958, Japanese Unexamined Patent Application, First Publication No. Sho 58-147483, and Japanese Unexamined Patent Application, First Publication No. Sho 58-147484 disclose that a water- and oil-repellent agent for glass surfaces, comprising a polyfluoroalkyl group-containing silane compound or a partially hydrolyzed condensate thereof, water-glass or a silane coupling agent and colloidal silica, is effective. Japanese Unexamined Patent Application, First Publication No. Sho 60-49079 discloses a fingerprint adhesion inhibitor comprising a compound having a C
4-21
polyfluoroalkyl group or a polyfluoroether group. Japanese Unexamined Patent Application, First Publication No. Hei 4-89877 discloses a protective water-repellent composition for coating of vehicles, comprising an organic solvent-soluble organopolysiloxane resin partially having a perfluoroalkyl group and a lubricant oil which is insoluble in water. Japanese Unexamined Patent Application, First Publication No. Hei 5-125083 discloses a method of preparing a surface treating agent by reacting a tetraalkoxide of Ti or Zr with a fluorine-containing alkyl silane compound. Furthermore, Japanese Unexamined Patent Application, First Publication No. Hei 9-157582 discloses a stainproofing base material comprising a base material, and a layer of a silicon-containing organic fluoropolymer with a specific structure having a perfluoropolyether group which is formed on the surface of the base material.
In Japanese Unexamined Patent Application, First Publication No. Hei 9-127307, an anti-reflective filter coated with perfluoroether having a polar group at a terminal and a display device are suggested for stainproofing properties of a single-layer or multi-layer anti-reflective film comprising as a principal component silicone dioxide formed on a transparent substrate by a vacuum deposition or sputtering method, as an example wherein special attention is paid to use for displays. Furthermore, a stainproofing film containing alkoxysilane compound with a specific structure having a perfluoropolyether group is disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 9-255919 and a surface modified film and a filter for display device, which are obtained by using the alkoxysilane compound having a perfluoropolyether group in combination with various materials are disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 9-326240, Japanese Unexamined Patent Application, First Publication No. Hei 10-26701, Japanese Unexamined Patent Application, First Publication No. Hei 10-120442, and Japanese Unexamined Patent Application, First Publication No. Hei 10-148701.
However, the above-mentioned prior arts with respect to the stainproofing properties have the following problems. That is, when various fluorine-containing compounds having stainproofing properties for an outermost layer of the anti-reflective material are applied to a low-refraction index layer made of silicon dioxide formed by a deposition or sputtering method, the anti-reflective properties are impaired and the stainproofing properties, particularly the durability in stainproofing properties, are poor. The reason is that the stainproofing effect is reduced over time, though excellent stainproofing properties are retained shortly after coating of the fluorine compound. It has also been found that conventional stainproofing measure have the problem that, when stains adhering to a base material coated with a stainproofing component are wiped off repeatedly, the stainproofing component is also wiped off, and the stainproofing properties are reduced, namely, contact adhesion between the low-refractive index layer and the stainproofing coated film is poor.
BRIEF SUMMARY OF THE INVENTION
Thus, an object of the present invention is to provide an anti-reflective material which is provided with a stainproofing layer having excellent durability of the stainproofing effect without exerting an adverse effect on the stainproofing capability.
The present inventors have carried out intensive studies to improve the stainproofing properties of the display surface, thus attaining the above object by the following method. That is, the present invention provides an anti-reflective material comprising a transparent substrate and at least a low-refractive index layer and a stainproofing layer laminated in order on said transparent substrate, wherein said low-refractive index layer is a silica film formed by the sol-gel method, and said stainproofing layer contains at least a perfluoroalkyl ether compound. The present invention also provides an anti-reflective material film using, as the perfluoroalkyl ether compound, a compound having one or more functional groups having high affinity with silica and/or chemically bonding functional groups at the molecular terminal.
The anti-reflective material of the present invention can easily exhibit excellent stainproofing properties, durability, and anti-reflective properties when used as a display.
DETAILED DESCRIPTION OF THE INVENTION
The stainproofing layer in the present invention contains at least a perfluoroalkyl ether compound, and the compound serves as a stainproofing component which substantially exhibits stainproofing properties and a compound having a perfluoroalkyl ether group is appropriately used. Among these compounds, a compound having one or more functional groups having high affinity with a silica film described hereinafter and/or chemically bonding functional groups at the molecular terminal is preferable. Examples of the perfluoroalkyl compounds are compounds represented by the following formulae 1 and 2.
Rf-R
1
-X
1
formula 1
X

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