JP3521515B2 - Color filter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color filter used for a liquid crystal display device suitable for color display.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been widely used in various monitors, OA equipment display devices, and thin TVs as thin and lightweight displays capable of full-color display.

A conventional liquid crystal display device has, as its basic structure, a liquid crystal cell in which a transparent electrode and an alignment film are sequentially formed on the inner surfaces of two transparent substrates facing each other, and a liquid crystal is sealed in a gap between them. Polarizing plates are arranged on both sides of the liquid crystal cell, and a white light source (backlight) is arranged outside one of the polarizing plates. When full-color display is required, an R filter that selectively transmits light in the red (R) wavelength region and a light in the green (G) wavelength region are selectively selected according to the three primary colors of light. A color filter including a G filter that transmits and a B filter that selectively transmits light in the blue (B) wavelength region is provided on the inner surface of the substrate on the light source side.

By the way, in each color filter, light in the visible light region other than the color is absorbed without being transmitted. Therefore, in the color filters of each color, only 1/3 or less of the white light emitted from the light source is transmitted. This indicates that the light use efficiency of the color filters for each color is 1/3.

Therefore, it is required to improve the light utilization efficiency of each color filter. However, as long as the same color filter and white light source as the conventional one are used in the same manner, there is a problem that the light utilization rate cannot exceed 1/3 due to the characteristics of the color filter.

As one effective method for solving this problem, light containing a large amount of light in the wavelength range of each color is made incident on each of the R, G, and B color filters to be absorbed by the color filters of each color. Reduce the proportion of light
It is conceivable to improve the light utilization rate of each color filter.

FIG. 3 shows a method using this idea.
A liquid crystal display element having a structure as shown in (1) has been proposed (Japanese Patent Laid-Open No. 61-138233). This liquid crystal display device includes a polarizing plate 35 and a transparent support substrate 36 below the R, G and B color filters 32, 33 and 34 provided inside the liquid crystal cell 31, corresponding to the respective filters.
A red phosphor thin film 37, a green phosphor thin film 38, and a blue phosphor thin film 39 are provided via the, and a light source 40 that emits light in the ultraviolet region to the near ultraviolet region for exciting those phosphors is further provided. It has a structure. In this liquid crystal display element, the red phosphor thin film 37 is provided by the light from the light source 40.
Emits red fluorescence, the green phosphor thin film 38 emits green fluorescence, and the blue phosphor thin film 39 emits blue fluorescence. Here, it can be considered that the light source 40 functions as a primary light source for causing each phosphor thin film to emit light, and each phosphor thin film functions as a secondary light source of the corresponding color filter. The fluorescence emitted from each phosphor thin film functioning as such a secondary light source passes through the polarizing plate 35 and then enters each corresponding color filter. As a result, the R, G, and B color filters are made to enter light containing a large amount of light in the wavelength range of the respective colors to reduce the proportion of the light absorbed by the respective color filters, and the light in the color filters of the respective colors is reduced. Is improving the usage efficiency.

[0008]

However, in the liquid crystal display device shown in FIG. 3, since the polarizing plate 35 and the transparent support substrate 36 are present between each color filter and each phosphor thin film, they are not provided. Cannot be formed in a self-aligning manner, it is difficult to form with high relative positional accuracy, and there is a problem that a clear image is difficult to obtain. Further, since the thickness of the polarizing plate 35 and the transparent supporting substrate 36 is not negligible, when the liquid crystal display element is viewed from an oblique direction, each phosphor thin film and each color filter corresponding thereto are visually deviated. Another problem is that the viewing angle of the liquid crystal display element is narrowed.

Further, since it is necessary to use a lamp which emits light in the ultraviolet region to the near ultraviolet region as the light source 40,
There is a problem that the conventional general white light source cannot be used.

The present invention is intended to solve the above-mentioned problems of the prior art, in which the utilization efficiency of light is improved and a clear image can be obtained while using a conventional general white light source. It is an object of the present invention to provide a color filter that does not narrow the viewing angle.

[0011]

The inventor of the present invention can improve the light utilization efficiency if at least a part of the light absorbed as unnecessary light in the white light source can be converted into necessary light. , And for that purpose, under the colored layer corresponding to the conventional color filter, has a transmission wavelength range overlapping the transmission wavelength range of light of the colored layer, and at least a part of the absorption wavelength range of light of the colored layer. It is only necessary to form a fluorescent light emitting layer capable of absorbing light and emitting fluorescence within the light transmission wavelength range of the colored layer, and if the colored layer and the fluorescent light emitting layer are arranged adjacent to each other, the viewing angle is increased. They have found that a clear image can be obtained without narrowing it, and have completed the present invention.

Namely, the present invention provides a color filter colored layer is formed on a transparent substrate, between the transparent substrate and the colored layer, and the fluorescent emission layer is formed so as to be adjacent to the colored layer , the fluorescent emission layer has a transmission wavelength range overlapping with the transmission wavelength region of the light on the colored layer, and absorbs at least a part of the light absorption wavelength region of the light on the colored layer, said <br/> Provided is a color filter for a white light source, which emits fluorescence within a light transmission wavelength range of a colored layer.

Hereinafter, preferred examples of the color filter of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic sectional view of a color filter of the present invention. In this color filter, glass,
Red fluorescent light emitting layer 2 on transparent substrate 1 such as plastic
a, a green fluorescent light emitting layer 3a and a blue fluorescent light emitting layer 4a are formed, and a red colored layer 2b, a green colored layer 3b and a blue colored layer 4b are respectively laminated on these layers, and a black matrix is provided between the colored layers. Five are arranged.

Here, the red fluorescent light emitting layer 2a transmits, of the white light from the back surface side of the transparent substrate 1 (in the direction of the arrow in the figure), light in the red wavelength range, but light in other wavelength ranges. Is a layer that absorbs at least a part of and emits red fluorescence. Similarly, the green fluorescent light emitting layer 3a is a layer that transmits light in the green wavelength region but absorbs at least a part of light in the other wavelength regions to emit green fluorescence, and the blue fluorescent light emitting layer 4a. Is a layer that transmits light in the blue wavelength range but emits blue fluorescence by absorbing at least part of the light in the other wavelength ranges. When a color filter is constructed by providing such a fluorescent light emitting layer between the transparent substrate and the colored layer, for example, in the case of red, light in the red wavelength region is colored red with the red fluorescent light emitting layer 2a as usual. The layer 2b can be transmitted, and further, the red fluorescence emitted by the red fluorescent light emitting layer 2a by absorbing at least a part of light in a wavelength range other than red can also be transmitted through the red colored layer 2b. Therefore, when white light from a conventional general white light source is made incident on the color filter of the present invention, the light intensity in the red wavelength region on the emission side is higher than the light intensity in the red wavelength region on the incident side. You can Since the same applies to green and blue light, as a result, the color filter of the present invention has a higher light utilization efficiency than the conventional color filter, and can also improve brightness.

Further, in the color filter of the present invention, since the fluorescent light emitting layer and the colored layer are arranged adjacent to each other, the fluorescence emitted from the fluorescent light emitting layer is made to enter the colored layer without being largely diffused. be able to. Therefore, a clearer image can be formed and the viewing angle is not narrowed.

Red fluorescent light emitting layer 2a and green fluorescent light emitting layer 3a
As the method for forming the blue fluorescent light emitting layer 4a, a composition in which a fluorescent material such as a fluorescent organic dye or an inorganic fluorescent material that emits red, green or blue fluorescence is dispersed or dissolved in a transparent photosensitive resin. And can be formed by a photolithography method. Alternatively, it can be also formed by forming a pattern with a dyeable photosensitive resin such as gelatin or casein sensitized by adding dichromate and dyeing this pattern with a dyeable phosphor. It can also be formed by a printing method using a composition obtained by adding a phosphor to an acrylic resin, an epoxy resin, an epoxy melamine resin, or the like.

As the phosphor used in the present invention,
For example, in the case of an inorganic phosphor, Y ₂ O ₂ S: Eu or Y ₂ O ₂ : Eu which emits red fluorescence, and ZnSiO ₃ : Mn or ZnS: CuAl which emits green light.
Such as ZnS: Ag and ZnS.
Alternatively, ZnO: Ag and the like can be preferably exemplified. Also,
In the case of fluorescent organic dyes, SULFORODAMINE 101, TETRAMETHYLRODAMINE PRECHLO
RATE, or RHODAMINE 3B PERCHLORATE, etc. that emit green fluorescence, RHODAMINE 101, RHODAMINE
6G PERCHLORATE, COUMARIN 6, COUMARIN 30 or FL
CARBOS, which emits blue fluorescence, such as UORESCEIN
TYRIL 124, CARBOSTRIL 165, COUMARIN 1, COUMARIN
2, COUMARIN4, COUMARIN 10, COUMARIN 102 or CO
UMARIN 120 and the like can be preferably exemplified. In addition to this, Mitsui Toatsu Dyestuff's luminescent dye EB-501 (blue), EG
-302, EG-307 (green), ER-120, ER-122 (red) and the like can also be preferably used.

The transparent substrate 1, the colored layers 2b, 3b and 4b, and the black matrix 5 used in the color filter of the present invention may have the same structure as that used in a conventional color filter. .

In FIG. 1, the black matrix 5 is formed at the same level as the colored layer in order to block the spread of fluorescence from the fluorescent light emitting layer and suppress color mixture to improve the contrast. However, it may be provided at the same level as the fluorescent light emitting layer or both layers.

When the color filter shown in FIG. 1 is directly applied to the TN type liquid crystal cell, the following problems occur. That is, it is necessary to allow polarized light to enter the liquid crystal cell from a light source through a color filter. However, even if polarized light is incident on the color filter, the fluorescence emitted by the fluorescent light emitting layer becomes non-polarized light, and the non-polarized light is superimposed on the polarized light from the light source, so that the polarization degree of the light passing through the colored layer decreases. Therefore, the contrast is also lowered.

Therefore, when the color filter of the present invention is used for such an application, it is preferable to form the polarizing layer 6 on each of the colored layers 2b, 3b and 4b as shown in FIG. In this case, non-polarized white light may be incident on the color filter instead of polarized light.

Such a polarizing layer 6 can be formed by a known method. For example, a polymer film of polyvinyl alcohol, polyimide, polyether imide, polyamide imide or the like is applied to a thickness of 100 nm to 10 μm, and after rubbing treatment, potassium iodide or an aqueous solution of iodine and potassium iodide mixed, Alternatively, it can be formed by coating an aqueous solution in which a suitable dichroic dye such as disazo, trisazo or dianisidine is dispersed. For protection of the polarizing layer 6, a transparent overcoat layer of acrylic resin, urethane resin, epoxy resin or the like may be provided on the polarizing layer 6, if necessary.

The color filter of the present invention can be manufactured by using known materials and techniques.

[0025]

In the color filter of the present invention, between the substrate and the coloring layer, there is a transmission wavelength range overlapping with the transmission wavelength range of light of the coloring layer, and at least one of the absorption wavelength range of light of the coloring layer. A fluorescent light-emitting layer capable of absorbing light of a certain portion and emitting fluorescence within the light transmission wavelength range of the colored layer is formed.
Therefore, when white light from a conventional general white light source is incident on the color filter of the present invention, the light intensity in the wavelength range transmitted by the colored layer is increased on the emission side rather than the incidence side, and the light utilization efficiency is improved. It becomes possible to improve.

Further, in the color filter of the present invention, since the fluorescent light emitting layer and the coloring layer are arranged so as to be adjacent to each other, the fluorescence emitted from the fluorescent light emitting layer is allowed to enter the coloring layer without being largely diffused. Therefore, a clearer image can be formed, and the viewing angle can be prevented from being narrowed.

[0027]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 and Comparative Example 1 As a red fluorescent dye, 100 parts by weight of solid content of polyvinyl alcohol (PVA-SbQ) resin (SPP-L, manufactured by Toyo Gosei Co., Ltd.) having a stilbazolium residue as a photosensitizer was used as a red fluorescent dye. A red fluorescent photosensitive resin coating liquid was prepared by uniformly mixing 80 parts by weight of RHODDAMIN B.

Next, this red fluorescent photosensitive resin coating liquid is
A glass substrate (7059 glass, manufactured by Corning Incorporated) on which a black matrix is formed by a Cr film according to a conventional method
Was coated using a spin coater to a dry thickness of 2 μm. Then, it was irradiated with ultraviolet rays through a red pattern photomask and washed with water to form a red fluorescent light emitting layer.

The same operation as described above was repeated to form a green fluorescent light emitting layer and a blue fluorescent light emitting layer on a glass substrate.
COUMARIN 6 was used as the green fluorescent dye, COUMARIN 10 was used as the blue fluorescent dye, and 80 parts by weight were used for each 100 parts by weight of the solid content of the photosensitive resin.

To this substrate, a color mosaic CK-7000 manufactured by Fuji Hunt Co., Ltd. was applied, exposed and developed to form a black matrix pattern, and then ammonium dichromate was added to the gelatin which was sensitized to form a red pattern. The film was irradiated with ultraviolet rays through a photomask of No. 1 and developed to form a relief pattern for red colored pixels having a film thickness of 1 μm. Next, 1 of red dye red 14P manufactured by Nippon Kayaku Co., Ltd.
% To a red dyeing solution to form a red colored layer.

The same operation was repeated to form a green colored layer and a blue colored layer, whereby the color filter of Example 1 was manufactured. As the green dye, Green 1P manufactured by Nippon Kayaku Co., Ltd. was used, and as the blue dye, Blue 5P manufactured by Nippon Kayaku Co., Ltd. was used.

For comparison, a color filter of Comparative Example 1 was produced by repeating the above operation except that the fluorescent light emitting layer was not formed.

As a result of installing these color filters on a white light backlight and measuring the brightness, the color filter of Example 1 is improved in brightness by about 30% as compared with the color filter of the conventional structure of Comparative Example 1. I was seen.

Example 2 Polyvinyl alcohol (manufactured by Fuji Yakuhin Kogyo Co., Ltd.) was coated on the colored layer of the color filter obtained by repeating the same operation as in Example 1 so that the dry thickness was 1 μm, and The surface was rubbed with a rubbing device (manufactured by Kyoei Semiconductor Co., Ltd.) using a rubbing cloth made of nylon with a tip of 1 mm. Further, this glass substrate was treated with an aqueous solution containing iodine and potassium iodide (iodine 0.
5% by weight and 8% by weight of potassium iodide) to form a polarizing layer. Further, an acrylic resin (Optoma-SS-2211, manufactured by Japan Synthetic Rubber Co., Ltd.) was applied thereon to form an overcoat layer by a dry thickness of 1 μm, and the overcoat layer was formed. A color filter was produced.

Next, an ITO film for a transparent electrode is formed on this color filter with a sputtering device to a thickness of 150 nm.
It was formed into a thick film. The sheet resistance of this transparent electrode is 30Ω /
It was □. Further, a polyimide film (LQT-120, manufactured by Japan Synthetic Rubber Co., Ltd.) was applied as an alignment film on the transparent electrode so as to have a dry film thickness of about 90 nm, followed by rubbing treatment.

The obtained transparent substrate and an active matrix element substrate on which a TFT element was formed as a substrate facing the transparent substrate were assembled so that the cell gap was 5 μm, and the nematic liquid crystal (Z
A TN type liquid crystal cell was produced by injecting LI-4792, manufactured by Merck Japan Ltd.

The display test of the obtained liquid crystal cell was conducted by using an ordinary white lamp as a light source. As a result, the brightness ratio (contrast) of the lit pixel and the non-lit pixel is 10
It was 0: 1.

For comparison, a liquid crystal cell was separately prepared by repeating the above operation except that the polarizing layer was not formed. Then, both sides of the liquid crystal cell were sandwiched by polarizing plates, and a display test was conducted in the same manner as in Example 2. As a result, the contrast was 50: 1.

[0040]

According to the color filter of the present invention, the light utilization efficiency can be improved even when a white light source is used. Therefore, the color filter of the present invention can display brighter than a conventionally known color filter, and can realize high brightness and low power consumption of a liquid crystal display.

Further, according to the color filter of the present invention having the polarizing layer on the coloring layer, the incident light passes through the fluorescent light emitting layer and the coloring layer and then passes through the polarizing layer to become polarized light. Even if the filter is applied to a TN type liquid crystal cell or the like, there is no reduction in contrast, and it is possible to achieve both bright display and high contrast.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a color filter of the present invention.

FIG. 2 is a schematic sectional view of a color filter of the present invention.

FIG. 3 is a schematic sectional view of a liquid crystal display element using a conventional color filter.

[Explanation of symbols]

1 transparent substrate 2a Red fluorescent light emitting layer 2b Red colored layer 3a Green fluorescent light emitting layer 3b Green colored layer 4a Blue fluorescent light emitting layer 4b Blue colored layer 5 Black Matrix 6 Polarizing layer

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-6-295683 (JP, A) JP-A-5-72415 (JP, A) JP-A-5-142530 (JP, A) JP-A-63- 15221 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02B 5/20 101 G02F 1/1335 505

Claims (3)

(57) [Claims] 1. A color filter colored layer is formed on a transparent substrate, between the transparent substrate and the colored layer, before
Serial and the fluorescent-emitting layer is formed so as to be adjacent to the colored layer, the fluorescent-emitting layer has a transmission wavelength range overlapping with the transmission wavelength region of the light on the colored layer, and the light absorption wavelength of the colored layer white light source, characterized in that to absorb at least a portion of the light band, fluoresce transmission wavelength region of light of the colored layer
Use a color filter. 2. The colored layer comprises a red colored layer, a green colored layer and a blue colored layer, and the fluorescent light emitting layer has a red fluorescent light emitting layer, a green fluorescent light emitting layer and a blue fluorescent light emission corresponding to the colors of the respective colored layers. The color filter according to claim 1, comprising a layer. 3. The color filter according to claim 1, further comprising a polarizing layer formed on the colored layer.