JPH08171013A - Liquid crystal display element - Google Patents

Abstract

PURPOSE: To improve light utilization efficiency and to make it possible to form bright images having high luminance with the electric power consumption similar the electric consumption of the conventional elements by forming fluorescent light emittable pixel patterns on the surface on the liquid crystal side of one substrate. CONSTITUTION: The red fluorescent light emittable patterns 2 which emit red fluorescence by irradiation with UV rays, the green fluorescent light emittable patterns 3 which emit green fluorescence and the blue fluorescent light emittable patterns 4 which emit blue fluorescence are formed on the lower transparent substrate 1 consisting of glass, plastic, etc. Black matrices 5 are formed at the respective boundaries. The respective flurescent light emittable patterns 2 to 4 absorb the light (UV rays) from a light source 16 and emit the fluorescence of the colors respectively corresponding thereto. In such a case, the light source 16 functions as a primary light source for allowing the respective fluorescent light emittable patterns 2 to 4 to emit light. The respective fluorescent light emittable patterns 2 to 4 function as secondary light sources to emit light in liquid crystal cells A and these pattern themselves function as pixels.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to 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 color filter and the white light source are used as in the conventional case, the light utilization rate is 1 due to the characteristics of the color filter.
There is a problem that it is impossible to exceed / 3.

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 use efficiency of light in the color filters of each color.

FIG. 2 shows a method utilizing this idea.
A liquid crystal display element having a structure as shown in (1) has been proposed (Japanese Patent Laid-Open No. 61-138233). In this liquid crystal display element, a polarizing plate 25 and a transparent support substrate 26 are provided below the R, G, and B color filters 22, 23, and 24 provided inside the liquid crystal cell 21, corresponding to the respective filters. A red phosphor thin film 27, a green phosphor thin film 28, and a blue phosphor thin film 29 are provided via the above, and a light source 30 for exciting those phosphors is further provided. In this liquid crystal display element, the red phosphor thin film 27 emits red fluorescence by the light from the light source 30, and the green phosphor thin film 2
8 emits green fluorescence, and the blue phosphor thin film 29 emits blue fluorescence. Here, it can be considered that the light source 30 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 25 and then enters each corresponding color filter. As a result, the R, G and B color filters are
The ratio of the light absorbed by each color filter is reduced by making light containing a large amount of light in the wavelength range of each color incident, and the light utilization efficiency in the color filter of each color is improved.

[0008]

However, in the liquid crystal display element shown in FIG. 2, since the polarizing plate 25 and the transparent support substrate 26 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 25 and the transparent supporting substrate 26 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 the R, G and B color filters similar to the conventional ones, which absorb unnecessary light and transmit necessary light, are used, the light absorbed by the color filter is completely removed. There is also a problem that it is very difficult to solve.

Further, liquid crystal display elements are constantly required to reduce power consumption and improve brightness.

The present invention is intended to solve the above-mentioned problems of the prior art, and can remarkably improve the utilization efficiency of light to form a clear and high-luminance image with the same power consumption as the conventional one. An object is to provide a liquid crystal display device.

[0012]

SUMMARY OF THE INVENTION The inventor of the present invention does not allow a color filter to absorb unnecessary light in a white light source and transmit necessary light to display a desired color. The present invention has been completed by finding that the above-described object can be achieved by incorporating light sources themselves for R, G, and B colors as pixels into a liquid crystal cell instead of filters.

That is, according to the present invention, in a liquid crystal display device which performs display by applying an electric field to liquid crystal sandwiched between opposed substrates, thereby changing the electro-optical characteristics of the liquid crystal, the liquid crystal side of one substrate is provided. Provided is a liquid crystal display device having a fluorescent pixel pattern formed on the surface of the liquid crystal display device.

Hereinafter, the liquid crystal display device of the present invention will be described in detail with reference to FIG. 1 in which the liquid crystal display device of the present invention is applied to a thin film transistor (TFT) active matrix type color liquid crystal display device using TN liquid crystal.

FIG. 1 is a schematic sectional view of a liquid crystal display device of the present invention. In this liquid crystal display device, on a lower transparent substrate 1 such as glass or plastic, a red fluorescent light emitting pattern 2 that emits red fluorescent light, a green fluorescent light emitting pattern 3 that emits green fluorescent light, and a blue fluorescent light that emits blue fluorescent light when irradiated with ultraviolet rays. Fluorescent patterns 4 are formed, and a black matrix 5 is formed at their boundaries. Also,
A polarizing film 6, an overcoat layer 7, and ITO (Indium-Ti) are formed on each of the fluorescent patterns 2, 3, and 4.
A transparent electrode 8 made of n-Oxide) and an alignment film 9 are sequentially formed. On the other hand, the pixel electrode 11, the TFT 12 and the alignment film 13 are sequentially formed on the surface of the upper transparent substrate 10 on the lower transparent substrate 1 side. Both of these substrates 1 and 1
0 is a gap of about 5 μm and is opposed so that the alignment films 9 and 13 face each other, and a TN liquid crystal 14 is sealed in the gap to form a liquid crystal cell A. Further, on the outer side of the liquid crystal cell A on the side of the lower transparent substrate 1, a light source 16 which emits light having a wavelength necessary to excite the fluorescent light emitting patterns 2, 3 and 4, for example, ultraviolet rays is provided. A polarizing plate 15 is provided on the outer side of the upper transparent substrate 10 side of A.

In the liquid crystal display device having the structure shown in FIG. 1, each of the fluorescent emission patterns 2, 3 and 4 absorbs light (ultraviolet rays) from the light source 16 and emits fluorescence of a corresponding color. Here, the light source 16 functions as a primary light source for causing each of the fluorescent light emitting patterns 2, 3 and 4 to emit light, and each of the fluorescent light emitting patterns 2, 3 and 4 serves as a secondary light source that emits light in the liquid crystal cell A. Functioning, and itself functioning as a pixel. Therefore, if each of the fluorescent light emitting patterns 2, 3 and 4 is formed using a fluorescent substance having a good light emitting efficiency, the light utilization efficiency of the light source 16 can be dramatically improved. Therefore, the power consumption of the light source 16 can be reduced and the brightness of the liquid crystal display element can be improved. Further, each of the fluorescent light emitting patterns 2, 3 and 4 can be formed by a printing method or a photolithography method like the conventional color filter, and, unlike the case of FIG. 2, it is not necessary to separately provide a color filter. Therefore, a clear image can be formed without the problem of positional deviation from them. Further, since the fluorescent emission patterns 2, 3 and 4 are formed in the liquid crystal cell A, the viewing angle of the liquid crystal display element is not narrowed.

In the liquid crystal display device of the present invention, the red fluorescent light emitting pattern 2, the green fluorescent light emitting pattern 3 and the blue fluorescent light emitting pattern 4 absorb the ultraviolet light from the light source 16 and are respectively red, green or blue. A fluorescent substance such as a fluorescent organic dye or an inorganic fluorescent substance that emits fluorescence is dispersed or dissolved in a translucent binder.

Such a fluorescent pattern can be formed by a photolithography method from a composition in which a phosphor is dispersed or dissolved in a transparent photosensitive resin. Alternatively, a pattern formed of a dyeable photosensitive resin such as gelatin or casein sensitized by adding dichromate may be formed by dyeing 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,
A material having a sharp emission spectrum of red, green or blue by ultraviolet rays in the wavelength region of 300 to 400 nm which is transmitted through the transparent substrates 1 and 10 such as glass and plastic which sandwich liquid crystal is used. For example, in the case of an inorganic phosphor, Y ₂ O ₂ S: Eu is assumed to emit red fluorescence.
Or Y ₂ O ₂ : Eu or the like, which emits green light, ZnS
ZnO: Ag, ZnS, or ZnO: Ag that emits blue light, such as iO ₃ : Mn or ZnS: CuAl.
And the like can be preferably exemplified. In the case of a fluorescent organic dye, SULFORODAMINE 10
1, TETRAMETHYLRODAMINE PRECHLORATE, or RHODA
MINE 3B PERCHLORATE, etc. that emit green fluorescence, such as RHODAMINE 101, RHODAMINE 6G PERCHLORATE, COUM
CARBOSTYRIL 124, CARBOSTR, which emits blue fluorescence, such as ARIN 6, COUMARIN 30 or FLUORESCEIN
IL 165, COUMARIN 1, COUMARIN 2, COUMARIN 4, COUMAR
IN 10, COUMARIN 102, COUMARIN 120 and the like can be preferably exemplified. In addition to these, luminescent dyes EB-501 (blue), EG-302, EG-307 (green), ER-120, ER-122 (red) manufactured by Mitsui Toatsu Dyes can also be preferably used. .

In the liquid crystal display element of FIG. 1, since the TN liquid crystal is used as the liquid crystal, the polarizing film 6 is used. The polarizing film 6 is also required when using STN liquid crystal. In this case, the polarizing film 6 needs to be formed on the fluorescent emission patterns 2, 3 and 4. This is because when the polarizing film 6 is arranged between the light source 16 and the fluorescent light emitting patterns 2, 3 and 4, even if polarized light is incident on the fluorescent light emitting patterns 2, 3 and 4, light is emitted from it. This is because the light becomes unpolarized.

As such a polarizing film 6, those which can be formed by a known method can be used. For example, after applying a polymer film of polyvinyl alcohol, polyimide, polyether imide, polyamide imide or the like in a thickness of 100 nm to 10 μm and performing a rubbing treatment,
It is possible to use a solution formed by applying an aqueous solution of potassium iodide or a mixture of iodine and potassium iodide, or an aqueous solution in which a suitable dichroic dye such as disazo, trisazo or dianisidine is dispersed.

The polarizing film 6 can be omitted when the liquid crystal mode used is, for example, a phase transition guest-host mode.

Further, in the liquid crystal display element of FIG. 1, in order to protect the polarizing film 6, an acrylic resin, a urethane resin,
Although the transparent overcoat layer 7 made of epoxy resin or the like is provided, it may be omitted if necessary.

Other constituent elements of the liquid crystal display element of the present invention, for example, constituent elements such as a transparent electrode, an alignment film, a TFT, and a light source can have the same constitution as the conventional liquid crystal display element.

The liquid crystal display device of the present invention can be manufactured by using known materials and techniques.

The liquid crystal display device of the present invention is particularly suitable for full-color display, but the present invention can also be applied to a liquid crystal display device for monochrome display. In that case, as the fluorescence emission pattern, R,
It is not necessary to provide the fluorescent emission patterns of the respective colors G and B, and at least one of them, or a fluorescent emission pattern emitting fluorescence of white or another color may be used.

[0027]

In the liquid crystal display device of the present invention, unnecessary light in the white light source is not absorbed by the color filter, and necessary light is not transmitted to display a desired color. Instead of the conventional color filter, the light source itself for each color of R, G and B is built in the liquid crystal cell as a pixel. Therefore, the utilization efficiency of the light emitted from the light source can be remarkably improved, and a clear and high-luminance image can be formed with the same power consumption as the conventional one.

[0028]

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

Example 1 A red fluorescent dye (ER-120, ER-120) was added to 100 parts by weight of a solid content of polyvinyl alcohol (PVA-SbQ) resin (SPP-L, manufactured by Toyo Gosei Co., Ltd.) in which a stilbazolium residue was introduced as a photosensitizer. A red fluorescent photosensitive resin coating liquid was prepared by uniformly mixing 50 parts by weight of Mitsui Toatsu Dye Co., Ltd.).

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 fluorescence emitting pattern.

The same operation as described above was repeated to form a green fluorescent light emitting pattern and a blue fluorescent light emitting pattern on the glass substrate. As the green fluorescent dye, the luminescent dye EG-307 manufactured by Mitsui Toatsu Dye Co., Ltd. is used, and as the blue fluorescent dye, the luminescent dye EB-501 manufactured by Mitsui Toatsu Dye KK is used, and the solid content of the photosensitive resin is 100%. 50 parts by weight was used with respect to parts by weight.

Next, polyvinyl alcohol was applied to a glass substrate on which three-color fluorescence emitting patterns were formed so that the dry thickness was 1 μm, and the surface thereof was rubbed by a rubbing device (manufactured by Kyoei Semiconductor). The rubbing treatment was performed using a nylon rubbing cloth having a tip of 1 mm. Further, this glass substrate was treated with an aqueous solution containing iodine and potassium iodide (0.5 wt% iodine, 8 g potassium iodide).
A polarizing film was formed by immersing the polarizing film in the film.

Next, an acrylic resin (Optoma-SS-2211, manufactured by Japan Synthetic Rubber Co., Ltd.) was applied on the polarizing film so that the dry thickness was 1 μm, thereby forming an overcoat layer.

Then, an ITO film for a transparent electrode was formed in a thickness of 150 nm on this glass substrate by using a sputtering device. The sheet resistance value of this transparent electrode was 30 Ω / □. 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 obtained liquid crystal cell was placed on a backlight equipped with an ultraviolet lamp so that the substrate on which the fluorescent emission pattern was formed was arranged on the backlight side, and TF was used.
A liquid crystal display element was produced by disposing a polarizing plate on the T element substrate.

The obtained liquid crystal display device was able to realize a brightness twice or more that of the commercially available color liquid crystal display device with the same power consumption.

[0038]

According to the liquid crystal display device of the present invention, the utilization efficiency of the light emitted from the light source is remarkably improved, and a clear and high-luminance image can be formed with the same power consumption as the conventional one.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an embodiment of a liquid crystal display device of the present invention.

FIG. 2 is a schematic sectional view of a conventional liquid crystal display device.

[Explanation of symbols]

 1 Lower Transparent Substrate 2 Red Fluorescent Emitting Pattern 3 Green Fluorescent Emitting Pattern 4 Blue Fluorescent Emitting Pattern 5 Black Matrix 6 Polarizing Film 7 Overcoat Layer 8 Transparent Electrodes 9 and 13 Alignment Film 10 Upper Transparent Substrate 11 Pixel Electrode 12 TFT Element 14 liquid crystal 15 polarizing plate 16 light source

Claims (3)

[Claims] 1. A liquid crystal display device which performs display by applying an electric field to liquid crystal sandwiched between opposed substrates, thereby changing the electro-optical characteristics of the liquid crystal, on a surface of one substrate facing the liquid crystal. A liquid crystal display device having a fluorescent light emitting pixel pattern. 2. The liquid crystal display device according to claim 1, wherein the fluorescent light emitting pixel pattern comprises a red fluorescent light emitting pattern, a green fluorescent light emitting pattern and a blue fluorescent light emitting pattern. 3. The liquid crystal display device according to claim 1, wherein a polarizing film is formed on the fluorescent light emitting pixel pattern.