Optical: systems and elements – Having significant infrared or ultraviolet property
Reexamination Certificate
2000-11-13
2003-02-18
Spyrou, Cassandra (Department: 2872)
Optical: systems and elements
Having significant infrared or ultraviolet property
C359S359000, C359S360000, C252S587000
Reexamination Certificate
active
06522463
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an optical filter, and more particularly to an optical filter which has a high transmittance in the visible light region and which is capable of intercepting infrared radiation. The filter of the present invention is especially useful for display purposes.
BACKGROUND ART
The following filters have been conventionally used as a heat ray-absorbing filter or as a filter for adjusting the visibility of 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.).
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 purposes, importance is laid on a color balance. In such case, it is difficult 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 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 processability compared with the filter (1). However, the filter (3) exhibits sharp absorption and absorbs the red color of light beams as is the case with the filter (1), raising the same problem as the filter (1) that the filter (3) looks blue.
In the filter (4), various infrared-absorbing materials can be used. Examples of useful materials are phthalocyanine, nickel complex, azo compound polymethine, 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. Further, when the filter is left to stand at a high temperature or a high humidity for a long time, the infrared-absorbing materials involve problems of decomposing or oxidizing, bringing about absorption in the visible light region or ceasing absorption in the infrared region.
An object of the present invention is to provide an infrared absorption filter which can achieve absorption in the near-infrared region, the filter showing a high transmittance in the visible light region, being free from marked absorption of a light of specific wavelength in the visible light region, and being excellent in environmental stability and in processability and productivity.
DISCLOSURE OF THE INVENTION
The present invention was completed in view of the foregoing situation. The infrared absorption filters of the present invention which have overcome the above-mentioned problems are as described below.
The first invention provides an infrared-absorbing filter which has a transmittance of not higher than 30% in the near-infrared region in the wavelength range of 800 to 1100 nm; a difference of 10% or less between a maximum value and a minimum value,of transmittance in the visible light region in the wavelength range of 450 to 650 nm; and a transmittance of not lower than 50% at a wavelength of 550 nm,
said filter, after being left to stand in the air atmosphere of a temperature of 60° C. and a humidity of 95% for 1000 hours, having a transmittance of not higher than 30% in the near-infrared region in the wavelength range of 800 to 1100 nm, and a difference of 10% or less between a maximum value and a minimum value of transmittance in the visible light region in the wavelength range of 450 to 650 nm.
The second invention provides an infrared absorption filter as defined in the first invention, wherein after being left to stand in the air atmosphere of a temperature of 80° C. for 1000 hours, the filter has a transmittance of not higher than 30% in the near-infrared region in the wavelength range of 800 to 1100 nm and has a difference of 10% or less between a maximum value and a minimum value of transmittance in the visible light region in the wavelength range of 450 to 650 nm.
The third invention provides an infrared absorption filter as defined in the first invention, wherein the filter has an infrared-absorbing layer on a transparent substrate, the layer being composed of a coloring matter, dye or pigment for absorbing infrared radiation and a polymer serving as a dispersing medium.
The 4th invention provides an infrared absorption filter as defined in the third invention, wherein the amount of the solvent remaining in the infrared-absorbing layer is 5.0 wt. % or less.
The 5th invention provides an infrared absorption filter as defined in the third invention, wherein the transparent substrate has a total light transmittance of not lower than 89%, a haze of not higher than 1.6%, a coefficient of static friction of not higher than 0.6 and a coefficient of dynamic friction of not higher than 0.6.
The 6th invention provides an infrared absorption filter as defined in the third invention, wherein the transparent substrate is a polyester film.
The 7th invention provides an infrared absorption filter as defined in the third invention, wherein the polymer constituting the infrared-absorbing layer has a glass transition temperature of not lower than 80° C.
The 8th invention provides an infrared absorption filter as defined in the 7th invention, wherein the polymer constituting the infrared-absorbing layer is a polyester resin.
The 9th invention provides an infrared absorption filter as defined in the third invention, wherein the filter has an electroconductive layer of metal mesh having an aperture ratio of not less than 50% on the same side as the infrared-absorbing layer of the filter or on the opposed side thereof.
The 10th invention provides an infrared absorption filter as defined in the third invention, wherein the filter has a transparent electroconductive layer on the same side as the infrared-absorbing layer of the filter or on the opposed side thereof.
The 11th invention provides an infrared absorption filter as defined in the 10th invention, wherein the transparent electroconductive layer is formed of a metal oxide.
The 12th invention provides an infrared absorption filter as defined in the 10th invention, wherein the transparent electroconductive layer has a repeatedly laminated structure in which at least three layers are laminated in the order of metal oxide/metal/metal oxide.
The 13th invention provides an infrared absorption filter as defined in the 12th invention, wherein the constituent metal layer of the transparent electroconductive layer is formed of silver, gold or a compound containing any of them.
The 14th invention provides an infrared absorption filter as defined in the first invention, wherein a hard coat-treated layer is formed as an outermost layer of the filter.
The 15th invention
Kobayashi Masanori
Onomichi Shinya
Shimomura Tetsuo
Yamada Yozo
Yokoyama Seiichiro
Assaf Fayez
Toyo Boseki Kabushiki Kaisha
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