Optical filter comprising transparent support and filter...

Details Optical filter comprising transparent support and filter... Optical filter comprising transparent support and filter...

1999-10-20

2001-10-30

Harris, Cynthia (Department: 1774)

Compositions

Light transmission modifying compositions

Infrared

C252S582000, C428S212000, C359S885000, C359S590000, C313S478000

Reexamination Certificate

active

06309564

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an optical filter comprising a transparent support and a filter layer, which has an absorption within a specific wavelength region. In more detail, the invention relates to an optical filter covering a display surface of a display device such as a liquid crystal display device (LCD), a plasma display panel (PDP), an electroluminescence display (ELD), a cathode-ray tube (CRT), a fluorescent indicator tube or a field emission display to improve the color reproducibility of the display.
BACKGROUND OF THE INVENTION
A display device such as a liquid crystal display device (LCD), a plasma display panel (PDP), an electroluminescence display (ELD), a cathode-ray tube (CRT), a fluorescent indicator tube or a field emission display displays a color image with a combination of the three primary colors (i.e., red, blue, green). However, it is very difficult (substantially impossible) to use the ideal three primary colors. For example, the plasma display panel uses phosphors of the three primary colors, which emit light containing an unnecessary component (in the wavelength region of 560 to 620 nm). Therefore, it has been proposed to correct the color balance of the displayed image by an optical filter absorbing the unnecessary component. The optical filter for the color correction is described in Japanese Patent Provisional Publication Nos. 58(1983)-153904, 60(1985)-118748, 60(1985)-18749, 61(1986)-188501, 3(1991)-231988, 5(1993)-203804, 5(1993)-205643, 7(1995)-307133, 9(1997)-145918, 9(1997)-306366 and 10(1998)-26704.
The display device needs prevention of reflection as well as the color collection. On the screen of the display device, the surrounding scene is often reflected to impair the contrast of the displayed image. Various anti-reflection films have been proposed to solve the problem of reflection. The known anti-reflection layers are categorized into two types, namely evaporating (and depositing) layers and coating layers. The evaporating layers are superior to the coating layers in view of optical characteristics, but the coating layers are easily formed compared with the evaporating layers.
The evaporating layers have been used as anti-reflection films for lenses of glasses or cameras. The layers are generally formed by a vacuum deposition process, a spattering method, an ion plating method, a CVD method or a PVD method.
The coating layers can be formed by coating a dispersion of fine particles and a binder. The coating layers are described in Japanese Patent Provisional Publication Nos. 59(1984)-49501, 59(1984)-50401, 60(1985)-59250 and 7(1995)-48527.
The anti-reflection layers can be introduced into the optical filters. The optical filters having the anti-reflection layers are disclosed in Japanese Patent Provisional Publication Nos. 61(1986)-188501, 5(1993)-205643, 9(1996)-145918, 9(1996)-306366 and 10(1997)-26704. The optical filter described in 61(1986)-188501, 5(1993)-205643, 9(1996)-145918 or 9(1996)-306366 has a transparent support containing a dye or a pigment so that the support functions as an optical filter. Further, the optical filter described in 10(1997)-26704 comprises a colored hard coating (surface hardening) layer provided between a support and an anti-reflection layer, so that the hard coating layer functions as an optical filter.
SUMMARY OF THE INVENTION
A colored transparent support or a colored hard coating layer can function as an optical filter. However, it is difficult to incorporate a dye or pigment into the support or the hard coating layer.
The transparent support is made of glass or plastics (usually, plastics). Therefore, the dye or pigment contained in the support must have enough heat resistance to a high temperature in the production process of the support.
The hard coating layer generally comprises a cross-linked polymer. In forming the layer, the polymer is cross-linked after coating a polymer solution. The dye or pigment added in the solution often fades at the cross-linking reaction.
Many cyanine dyes have been researched in the field of silver halide photography. The cyanine dyes have various absorption spectra. The cyanine dyes have been developed to be contained in a photographic material (usually in a gelatin layer). The cyanine dyes contained in the support or the hard coating layer usually have problems such as fading.
On the other hand, various absorption spectra are required for color correction of various display devices. The restricted kinds of dyes or pigments, which can be contained in the support or the hard coating layer, do not satisfy the requirement for color correction.
The applicants have tried to add the cyanine dyes not in the support or the hard coating layer (which restricts the dyes or pigments), but in a polymer layer. The polymer layer can be formed under moderate conditions. Many photographic cyanine dyes can be contained in the polymer layer, which functions as an optical filter. However, the polymer layer does not protect the dyes, compared with the support and the hard coating layer. Therefore, the cyanine dyes to be contained in the polymer layer should be improved in durability (particularly, light resistance).
An object of the present invention is to provide an optical filter improved in not only light resistance as well as color correction performance.
The present invention provides an optical filter which comprises a transparent and a filter layer containing a dye and a binder polymer, wherein the dye is a cyanine dye represented by the formula (I), and the filter layer further contains a metal complex represented by the formula (IIa):
in which each of Z
1
and Z
2
independently is an non-metallic atomic group forming a five-membered or six-membered nitrogen-containing heterocyclic ring; each of R
1
and R
2
independently is an alkyl group, an alkenyl group, an aralkyl group or an aryl group; L
1
is a methine chain consisting of an odd number of methines; X is an anion; and each of a, b and c independently is 0 or 1;
L
n1
M
m1
  (IIa)
in which L is a ligand, M is a metal atom, n1 is an integer of 1 to 10, and m1 is an integer of 1 or 2.
The invention also provides a plasma display panel having a display surface covered with an optical filter which comprises a transparent and a filter layer containing a dye and a binder polymer, wherein the dye is a cyanine dye represented by the formula (I), and the filter layer further contains a metal complex represented by the formula (IIa).
According to the study of the applicants, the metal complex of the formula (IIa) gives light resistance (durability against light) to the cyanine dye of the formula (I) contained in an optical filter, which is continually exposed to strong light. According to the present invention, various known cyanine dyes for photographic materials can be used in the optical filter. The absorption spectra of many cyanine dyes have been well studied in the field of photographic materials. Therefore, the color of the displayed image can be easily corrected by selecting a cyanine dye having an appropriate absorption spectrum.


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patent: 03161394 A2 (1991-07-01), None
patent: 409277693 (1997-10-01), None
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