Optical: systems and elements – Having significant infrared or ultraviolet property
Reexamination Certificate
2000-12-19
2003-04-01
Chang, Audrey (Department: 2872)
Optical: systems and elements
Having significant infrared or ultraviolet property
C359S885000, C252S587000, C252S582000
Reexamination Certificate
active
06542292
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an infrared absorption filter. More particularly, the present invention relates to an infrared absorption filter which contains few foreign materials causing optical defects, has high transmittance in the visible light region, and manifests wide absorption in the near infrared radiation region and intercepts infrared radiation.
DESCRIPTION OF THE RELATED ART
The following filters have been conventionally used as an infrared absorption filter such as a heat ray-absorbing filter or a filter for adjusting the visibility of a video camera:
(1) a filter composed of phosphate glass containing metallic ions such as copper or iron ions (Japanese Unexamined Patent Publication No. 235740/1985, Japanese Unexamined Patent Publication No. 153144/1987, etc.);
(2) an interference filter having plural layers differing from each other in refractive index on a substrate to allow light of specific wavelength to pass by interference of transmitted light (Japanese Unexamined Patent Publication No. 21091/1980, Japanese Unexamined Patent Publication No. 184745/1984, etc.);
(3) an acrylic resin filter composed of a copolymer containing copper ions (Japanese Unexamined Patent Publication No. 324213/1994); and
(4) a filter composed of a binder resin and a coloring matter dispersed in the binder resin (Japanese Unexamined Patent Publication No. 21458/1982, Japanese Unexamined Patent Publication No. 198413/1982, Japanese Unexamined Patent Publication No. 43605/1985, etc.).
Also, various materials have been conventionally investigated as a transparent magnetic wave absorption material, and examples thereof include the following materials. Further, a lot of materials combining them have been suggested.
(5) a magnetic wave shielding material composed of textile of conductive fiber;
(6) a magnetic wave shielding material having a mesh structure produced by etching a thin metal plate; and
(7) a magnetic wave shielding material composed of a thin film produced from high conductive metals such as silver and the like, and transparent conductive materials such as ITO, SnO
2
and the like, using sputtering, vacuum deposition method and the like.
However, the above-mentioned conventional infrared absorption filters have problems as described below.
The filter (1) exhibits sharp absorption in the near-infrared region and can intercept infrared radiation at a very high ratio. However, the filter (1) pronouncedly absorbs part of red color in the visible light region so that the transmitted color looks blue. For display purpose, importance is laid on a color balance. In such purpose, it is unsuitable to use the filter (1). Another problem is raised about the processability of the filter (1) because it is made of glass.
The optical properties of the filter (2) can be freely designed. Further a a filter having properties almost equal to the designed properties can be produced. However, the filter (2) necessitates a plurality of layers differing in refractive index from each other for this purpose, consequently entailing a drawback of incurring high production costs. Moreover, when a large area is required, the filter (2) should have a uniform thickness of high precision over the entire area, resulting in a difficulty in producing the filter.
The filter (3) has improved processablity, a draw back of the filter (1). However, the filter (3) has low degree of freedom in designing optical properties as in the filter (1). Also there remains the problem of the filter (1) that it absorbs part of red color in the visible light region so that the transmitted color looks blue. Further, the absorption of copper ions is low and the amount of copper ions which can be contained an acrylic resin is restricted, causing a problem that the thickness of the acrylic resin has to be increased.
In the filter (4), various infrared-absorbing materials can be used. Examples of useful materials are phthalocyanine, nickel complex, diimmonium salts, azo compounds, polymethines, diphenylmethane, triphenylmethane, quinone and the like. However, when singly used, these materials pose problems of showing insufficient absorption or absorbing a visible light of specific wavelength in the visible light region. Therefore, a plurality of coloring matters are used together. However, when a filter containing a plurality of coloring matters in an infrared absorption layer is left to stand at a high temperature or a high humidity for a long time, the filter causes problems of denaturing a coloring matter due to decomposition and oxidation there of, bringing about absorption in the visible light region, or ceasing absorption in the infrared region, and the like. Further, when these filters comprises a substrate film coated with an infrared absorption layer, there occurs also a problem of deteriorating beam transmission property due to transmittance and haze value of the substrate film.
The above-mentioned problems are not improved even if the above-mentioned infrared absorption filters (1) to (4) are combined with the above-described magnetic wave absorption material (5) to (7).
PDP developed recently as a thin display having a large screen may invite error movement of a remote controller and the like due to near-infrared radiation discharged from the front surface thereof, consequently necessitating setting of an infrared absorption filter which cuts this near-infrared radiation, in front of the screen. However, this infrared radiation shielding filter also does not attain sufficient requirement in the above-mentioned infrared absorption filters, under current condition.
In the filter (4), when a diimmonium salt-based compound is used as an infrared absorption coloring matter, a filter can be obtained which surmounts the above-mentioned problems, provides high absorption in the near-infrared region, and manifests low absorption in the visible region. Further, it can provide an ability also suitable as an infrared absorption filter for PDP.
However, when an foreign material is present in a raw material resin of a substrate film of an infrared absorption filter, molecular orientation of the film is disturbed around this foreign material, in a stretching process in film formation. Resultantly, optical strain occurs, and the foreign material is recognized as a defect larger than the real size, causing remarkable deterioration in grade. For example, even an foreign material having a size of 20 &mgr;m is usually recognized optically as a size of 50 &mgr;m or more, and further, in some cases, it is recognized as an optical defect having a size of 100 &mgr;m or more. For obtaining a film having high transparency, no inclusion of a particle which is used for imparting slipperiness in a substrate film, or an amount of inclusion of a particle as low as possible is preferable. However, when the content of a particle is smaller, transparency of a film tends to increase, and an optical defect due to a fine foreign material tends to more clear. Further, the thickness of a substrate film of this infrared absorption filer is usually 50 &mgr;m or more, and the content of foreign material along the thickness direction per unit area of a film tends to larger in such a thick film as compared with a thin film, consequently, further raising this problem.
Moreover, when no particle is contained in a substrate film or the content of a particle is so lowered that transparency is not disturbed for imparting slipperiness in a substrate film, it is usually necessary that particles intending impartment of slipperiness are contained in an easy adhesion layer, and these particles have to be extremely small so as not to cause disturbance of transparency. However, fine particles having lower particle size tends to coagulate extremely, revealing possibility of formation of a coarse coagulated material. If an easy adhesion layer containing this coarse coagulated material is laminated on a substrate film, this coarse coagulated material becomes an optical defect.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide a
Onomichi Shinya
Shimomura Tetsuo
Yokoyama Seiichiro
Chang Audrey
Kenyon & Kenyon
Toyo Boseki Kabushiki Kaisha
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