JP2000056125A - Liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the decline of a resolution due to blotting or the like, to reduce the loss of light and to perform bright display with less visual dependency by providing a color filter layer with a filter base material and the particle of a light refractive index different from it. SOLUTION: The red, green and blue color filter layers 3-5 of an opposite substrate 200 are composed of the respective filter base materials 31-33 and fine balls 51-53 dispersed in them and the fine balls 51-53 are provided with the refractive index different from the filter base materials 31-33. The filter base materials 31-33 are provided with the action of filtering and the fine balls 51-53 are provided with a lens action. When light made to pass through a liquid crystal layer 300 passes through the fine balls 51-53, an optical path is changed by the lens effect and the light is diffused as a result. Since the lens effect of refracting the light by the fine balls 51-53 is utilized a scattering effect by diffusion is not generated, the deflection state of the light is not disturbed at the time of passing through the color filter layer and the problem of disturbing the deflection state of the light and lowering image quality is not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a liquid crystal display device. More specifically, the present invention relates to a liquid crystal display device having a high display resolution and a very low viewing angle dependency by including an optical element for diffusing light.

[0002]

2. Description of the Related Art In recent years, a liquid crystal display device having a great advantage of being thin and light and having low power consumption has been actively used as a display device of a personal OA device such as a Japanese word processor and a desktop personal computer. Most of these liquid crystal display devices (hereinafter abbreviated as LCDs) use twisted nematic liquid crystals, and their display methods can be roughly classified into two modes, an optical rotation mode and a birefringence mode.

[0003] In an optical rotation mode LCD, for example, a twisted nematic (T) having a molecular arrangement twisted by 90 ° is used.
There is an N) -type liquid crystal (TN-LCD). This TN type liquid crystal shows a high contrast ratio and good gradation display in black and white display in principle.
Active-matrix drive with a switching element for each pixel, and a full-color display liquid crystal television combined with a color filter (TFT-LCD
And MIM-LCD).

On the other hand, a typical example of a birefringence mode display type LCD is a super twisted nematic (STN; Super T) having a molecular arrangement twisted by 90 ° or more.
twisted Nematic liquid crystal (STN-LC)
D). Since it has steep electro-optical characteristics, it is easy to use time-division driving without using a switching element such as a thin film transistor or diode for each pixel, using a simple matrix electrode structure with a simple structure and low manufacturing cost. A large capacity (large screen) display can be realized.

[0005] As an important problem relating to the image quality of these liquid crystal display elements, there is an improvement in viewing angle characteristics, and various methods have been proposed. As a typical method of improving the viewing angle of a TN-LCD, a pixel capacity division method (for example, KR Sarm
a, et. al. , SID'89 Digest, pp
148-150 (1989)), a pixel alignment division method (for example, KH Yang, Conf. Record of of).
IDRC '91, pp. 68-72), a method using a compensator (for example, Hisatake, et al .: IEICE Transactions,
C-11, vol. J76-C-11, No. 1; 5, pp
322-328 (1993)).

The use of a display mode other than TN is also being studied, and an OCB mode (optical) in which a bend-aligned liquid crystal cell and a biaxial optical compensator are combined.
lyCompensated Birefringen
ce mode) and an IPS (In-Plane Switching) mode in which liquid crystal molecules are driven by a lateral electric field have been proposed. Documents that disclose the OCB mode include, for example, Y. Yamaguchi, e
t. al. , SID'93 Digest, pp277
-280 (1993); Miyashit
a, et. al. , Eurodisplay Dige
st, pp277-280 (1993), or C-
L. Kuo, et. al. , SID'94 Diges
t, pp 927-930 (1984);
Miyashita, et al. , SID'95 D
egest, pp797-800 (1995). References disclosing the IPS mode include, for example, R.S. Kiefer, et. a
l. , Japan Display '92 Dige
st, pp547-550 (1992) or M.E. O
he, et. al. , Asia Display '95
Digest, pp-577-580 (1995).

On the other hand, as a method different from the method of improving the viewing angle of the LCD, a method of disposing a diffusion plate (screen) on the surface side of a liquid crystal cell has been proposed (M. Mc).
Farland, et. al. , Asia Displ
ay'95 Digest, pp 739-742 (19
95)). In this case, if the backlight is a parallel light, the light use efficiency is increased, the “bleeding” of the display is reduced, and the contrast is increased, which is practically desirable.
The above-described pixel division method, the method using a compensating plate, or each method such as OCB and IPS have a problem that the color of the display changes when the viewing angle is changed. Since the viewing angle improving method used diffuses the light after passing through the liquid crystal cell, there is an advantage that the color of the display does not change even if the viewing angle is changed in principle.

As the screen used here, there are a diffuser plate by multiple scattering using a liquid crystal dispersed polymer film or the like, a mirror array using multiple reflection, or a lenticular lens array.

[0009]

However, the method for improving the viewing angle characteristics of the LCD using these diffusers has the following problems. In other words, there is a problem that the resolution is reduced due to "bleeding" or "blurring" of the display. This is because the light of the backlight used for LCD is not completely parallel light but has a certain spread.
This is because the light passing through each pixel of D overlaps with the light passing through the surrounding pixels, enters the screen, and is diffused. Such a decrease in resolution becomes more severe as the distance between the liquid crystal layer and the diffusion layer increases. Also, there is a problem that the "smearing" of the display becomes more severe as the thickness of the screen itself increases.

The present invention has been made based on the recognition of such a problem. In other words, the purpose is to “blurr” or “blurr” the display on the liquid crystal display device of the diffuser type.
Another object of the present invention is to provide a liquid crystal display device which can reduce a decrease in resolution due to the above and can realize a bright display with little loss of light and a display with extremely small viewing angle dependency.

[0011]

That is, a liquid crystal display device of the present invention is provided on at least one of a pair of substrates, a liquid crystal layer sandwiched between the pair of substrates, and the pair of substrates. A color filter layer, wherein the color filter layer comprises a filter base material, and substantially spherical particles dispersed in the filter base material and having a different light refractive index from the filter base material. And, characterized by having, the light is diffused by the substantially spherical particles without disturbing its polarization state, while suppressing a decrease in resolution, light loss is less bright display and viewing angle dependence An extremely small display can be realized.

Here, the substantially spherical particles have substantially the same color as the base material of the filter, so that a filtering action and a light diffusing action can be realized at the same time.

The light diffusion layer and the polarizing plate are arranged in this order on the surface of the substrate on which the color filter layer is not formed on the surface on which the color filter layer is not formed. It is possible to realize image display with extremely small viewing angle dependency while eliminating image disturbance due to light, and to further diffuse the light at a wider angle to further reduce viewing angle dependency.

Further, the color filter layer is disposed between a first polarizing plate provided on the counter substrate and a second polarizing plate provided on the array substrate. Accordingly, it is possible to realize image display with extremely small viewing angle dependency while eliminating image disturbance due to ambient light.

Further, a light diffusion layer for diffusing light is provided on a side opposite to the second polarizing plate as viewed from the first polarizing plate, so that light can be further wide-angled. And the viewing angle dependency can be further reduced.

Further, a light diffusion layer for diffusing light is provided between the first polarizing plate and the second polarizing plate, so that the light is diffused at a wider angle. Thus, the viewing angle dependency can be further reduced.

[0017]

According to the present invention, an optical element for diffusing light, such as a fine sphere, is mixed into a color filter layer of a liquid crystal display device, so that the viewing angle dependence is extremely small while suppressing the reduction in resolution. Image display can be realized.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view illustrating the cross-sectional structure of the liquid crystal display device according to the first embodiment of the present invention. The liquid crystal display device shown in FIG. 1 includes an array substrate 100, a counter substrate 200, a liquid crystal layer 300, and a backlight 400. The array substrate 100 and the opposing substrate 200 are opposed to each other at a predetermined interval, and a liquid crystal 300 is sandwiched between them. A backlight 400 is provided on the back side of the array substrate 100.

The array substrate 100 has a light-transmitting substrate 8 and switching elements 10 provided thereon in a matrix. The switching element 10 has a role of supplying a predetermined video signal to each pixel region 9. As the switching element 10, for example, a thin film transistor (TFT) using amorphous (amorphous) silicon (a-Si), poly (polycrystalline) silicon (p-Si), or the like
Can be used.

In the counter substrate 200, a red color filter layer 3, a green color filter layer 4, and a blue color filter layer 5 are formed on the lower surface side of the translucent substrate 1, respectively. It is laminated. Each color filter layer is arranged so as to correspond to the pixel region 9 of the array substrate 100, and the boundary portion is shielded from light by the black matrix 2.

As the liquid crystal layer 300 sandwiched between these two substrates, for example, a nematic liquid crystal can be used, for example, having a 90 ° twisted TN liquid crystal alignment. Polarizing plates 11 and 12 are provided outside these substrates. The backlight 400 includes a parallel light lens sheet 14, a light guide plate 13, and a fluorescent lamp 15. That is, the light emitted from the fluorescent lamp 15 is guided to the light guide plate 13 via the lens sheet 14, enters the array substrate 100 as planar light, and passes through the liquid crystal layer 300 and the counter substrate 200, and the light is emitted from each pixel. And a predetermined image is displayed. That is,
The display image is viewed from above the polarizing plate 12 in FIG.

In FIG. 1, the backlight 40
Although the case where 0 is provided is illustrated, the present invention is not limited to this. That is, instead of the backlight, a reflection structure or the like that appropriately reflects external light may be provided.

In the present invention, the red, green, and blue color filter layers 3, 4, and 5 of the counter substrate 200 are respectively composed of filter base materials 31, 32, and 33, and fine spheres 51, 52 dispersed therein. , 53. That is, the filter base material of the red color filter layer 3 includes the red filter base material 31 and the red fine spheres 51. Further, the green filter layer 4 and the blue filter layer 5 also have a green filter base material 32 and a green fine sphere 52, respectively.
It is composed of a blue filter base material 33 and blue fine spheres 53. Here, the fine spheres 51, 52, 53 are made of a material having a different refractive index from the filter base materials 31, 32, 33.

Each of the filter base materials 31, 32, and 33 has an original filtering function. On the other hand, the fine spheres 51, 52, 53 in the color filter layer have a lens function. That is, when the light that has passed through the liquid crystal layer 300 passes through the microsphere, the light path is changed by the lens effect, and as a result, the light is diffused. The present invention utilizes the lens effect of the microspheres to refract light, and does not cause a so-called scattering effect by diffusion, so that the polarization state of light is not disturbed when passing through the color filter layer. That is, there is no problem that the polarization state of light is disturbed and the image quality is reduced.

In the case of the structure illustrated in FIG. 1, the color filter layers 3, 4, and 5 for diffusing light are replaced with the liquid crystal layer 30.
0 can be provided very near. As a result, "bleeding" of display can be significantly reduced as compared with the case where the light diffusion layer is arranged outside the counter substrate, and an extremely clear image display can be obtained.

An example of the method for manufacturing the liquid crystal display device of the present invention will be described as follows. First, as an array substrate, an a-Si thin film transistor (TFT) array having 480 pixels vertically, 640 pixels horizontally, and a pixel pitch of 0.33 mm by 0.11 mm is placed on a transparent substrate 8 such as glass or quartz. Formed.

On the other hand, as a filter base material of the color filter layer, R, which is obtained by dispersing an ordinary pigment in a polyimide resin,
G, B color resins 31, 32, and 33 are prepared, and fine spheres 51, 52, and 53 having a diameter of about 1.2 μm formed by mixing R, G, and B dyes with a styrenic resin are dispersed therein. Let it. Here, the refractive indices of the polyimide resin and the styrene resin are 1.65 and 1.57, respectively.

This fine sphere-dispersed color resin is applied on the glass substrate 1 of the opposite substrate to a thickness of about 1.5 μm, and this is applied to each display of the TFT array by a usual photoengraving technique. The color filter layers 3, 4, and 5 are formed by patterning according to the pixels.
Further, ITO (indium tin oxide) is deposited thereon as a transparent electrode.

On the array substrate and counter substrate thus formed, AL-105 manufactured by Nippon Synthetic Rubber Co., Ltd. was used as an alignment film.
1 is applied, the surface is rubbed, and assembled facing each other. Further, a nematic liquid crystal material MLC-2001 manufactured by Merck Japan was injected between these substrates,
The polarizing plates 11 and 12 are attached, and a predetermined drive circuit is connected. The drive circuit may be formed, for example, partially or entirely on the array substrate 100.

The liquid crystal display device thus obtained has almost no viewing angle dependency and a good display without display "bleeding".

FIG. 2 is a graph illustrating transmittance dispersion characteristics of a filter base material and fine spheres of a color filter layer used in the present invention. Here, the filter base material is an R, G, B color resin in which a normal pigment is dispersed in a polyimide resin. In addition, the fine spheres are represented by R,
G and B dyes are mixed and polymerized.

As shown in the figure, the transmittance dispersion characteristics R ', G', B 'of the red, green, and blue fine spheres 51, 52, 53 are shown.
Are the filter base materials 31, 32 of each color filter layer,
33 can be made very similar to the optical characteristics R, G, B. For this reason, the above-described light diffusion effect can be generated without impairing color characteristics such as color purity and transmittance.

Further, the fine spheres in the color filter layer of the present invention can be made, for example, with a diameter of about several μm, and each of such fine spheres acts as a lens. Therefore, even if the number of the microsphere layers is, for example, five, the thickness of the entire color filter layer is several tens μm.
The following can be easily suppressed. That is, since the thickness of the layer is very thin as compared with the diffusion plate using the conventional lens array, it is very advantageous for "bleeding" of the displayed image.

Further, in the conventional diffusion plate based on multiple scattering or the diffusion plate based on a mirror array, there is a problem that if the light is sufficiently diffused, the number of interfaces in the optical path increases and the light loss increases. . On the other hand, the color filter layer containing fine spheres of the present invention utilizes the refraction effect and has a small number of interfaces on the optical path, so that light loss is small.

Further, the microspheres of the present invention have little effect on the polarization state of light. This not only has an effect on the problem of “bleeding” of the display image, but also can prevent the adverse effect of ambient light, that is, light incident on the liquid crystal display device from the outside. Conventionally, when a light diffusing plate is provided on the front surface of a liquid crystal display device, there has been a problem that ambient light is scattered and the quality of a displayed image deteriorates. On the other hand, according to the present invention, since light is diffused in the filter layer provided between the two polarizing plates, the polarized light must be polarized before the ambient light enters the filter layer and is scattered. Attenuated through the plate. As a result, it is possible to reduce the scatter component of the ambient light and eliminate the deterioration of the quality of the displayed image.

In the color filter layer containing fine spheres of the present invention, it is better that the arrangement of the spheres is somewhat random in order to avoid a diffraction image. It is better that the degree of overlap is random. In addition, from the viewpoint of the problem of “bleeding”, it is better that the distance between the fine sphere layers is small, but care should be taken because too close proximity causes multiple scattering.

In order to arrange the microspheres in one layer without overlapping, it is desirable that the diameters of the microspheres are relatively uniform.

Further, the refractive index n1 of the filter base material enclosing the fine sphere and the refractive index n2 of the fine sphere may be larger, but as the ratio between the two deviates from 1, the light diffusion of one layer becomes larger. The degree can be higher.

On the other hand, the shape of the fine spheres to be mixed with the color filter layer may be a spheroidal shape, an oval shape or the like in addition to the spherical shape. However, if there are corners or plane portions on the surface of the microsphere, the light is reflected and diffused and the polarization state is disturbed, so that the effect of the present invention may not be sufficiently obtained. Therefore, it is desirable that the fine sphere has a shape with a curved surface, and more preferably a spherical shape.

It is desirable that the diameter of the fine sphere is at least twice the wavelength of light. If the wavelength is smaller than twice the wavelength of the light, the light cannot be sufficiently refracted. In addition, as a result of the experiment of the present inventors, the diameter of the fine sphere was 30 to 50.
When it was larger than μm, the gap between the spheres became large, and light tended to leak and pass. In such a case, when the displayed image is observed with the naked eye, the image quality tends to be rough as “glitter”. Therefore, it is desirable that the diameter of the fine sphere be smaller than about 100 μm.

On the other hand, examples of the material for the fine spheres include silica, acrylic, polystyrene, divinylbenzene, and barium titanate glass.

Further, the fine spheres may be colored,
It may be colorless and transparent. In the case of color, even if the color of the filter base material is light, it is possible to supplement with the color of the fine sphere even if the color of the filter base material is light. Preparation can also be performed. Further, when the fine spheres are colorless, the color of the color filter can be determined only by the color of the filter base material, and the light transmittance is higher than that of the case of color, and a bright image can be displayed. There is also an advantage.

Next, a second embodiment of the present invention will be described. FIG. 3 is a schematic view illustrating a cross-sectional structure of a liquid crystal display device according to a second embodiment of the present invention. The liquid crystal display device of the present embodiment has a configuration in which a light diffusion layer 16 is further provided on the front surface of the liquid crystal display device illustrated in FIG.

That is, also in the liquid crystal display device shown in FIG. 3, the array substrate 100 and the counter substrate 200 'are arranged at a predetermined interval, and the liquid crystal 300 is sandwiched between them. A backlight 400 is provided on the back side of the array substrate 100. Here, since each component can be substantially the same as the liquid crystal display device illustrated in FIG. 1, the same portions are denoted by the same reference numerals and detailed description will be omitted.

According to the present embodiment, the light can be diffused more widely by providing the light diffusion layer 16 on the front surface side of the counter substrate 200 '. In other words, depending on the application, the tolerance of the viewing angle characteristic required for the liquid crystal display device may become more severe, but by further providing the light diffusion layer 16 as in the present embodiment, the light diffusivity can be reduced. Can be even higher.

In the present embodiment, since the light diffusion layer 16 is provided outside the polarizing plate 12, there is no need to restrict the light diffusion layer 16 so as not to disturb the polarization characteristics. For this purpose, as a specific example of the light diffusing plate 16, various configurations can be used. For example, by forming irregularities on the surface of the polarizing plate in addition to the method of applying fine spheres. Can be formed.

Next, a third embodiment of the present invention will be described. FIG. 4 is a schematic view illustrating a cross-sectional structure of a liquid crystal display device according to a third embodiment of the present invention. The liquid crystal display device of the present embodiment has a light diffusion layer 16 'provided between the polarizing plate 12 and the substrate 1 on the front surface of the liquid crystal display device illustrated in FIG.

That is, also in the liquid crystal display device shown in FIG. 4, the array substrate 100 and the opposing substrate 200 "are arranged at a predetermined interval, and the liquid crystal 300 is sandwiched between them. Is provided with a backlight 400. Here, since each element can be substantially the same as the liquid crystal display device illustrated in Fig. 1, the same portions are denoted by the same reference numerals. The detailed description is omitted.

Also in this embodiment, the light can be diffused more widely by providing the light diffusion layer 16 '. That is, depending on the application, the tolerance of the viewing angle characteristic and the blurring characteristic required for the liquid crystal display device may become more severe, but by further providing the light diffusion layer 16 ′ as in this embodiment, the light Can be further enhanced.

Since the diffusion layer 16 'in this embodiment is provided between the polarizing plates 11 and 12, it is desirable that the diffusion characteristics are not disturbed. Therefore, as a specific example of the light diffusion layer 16 ', for example, it is desirable to arrange microspheres in a single layer or a plurality of layers, or to form a diffusion layer by a hologram method using a photoreactive resin material.

The embodiment of the invention has been described with reference to examples. However, the present invention is not limited to these specific examples. For example, the switching elements arranged on the array substrate are not limited to TFTs,
It may be an IM (metal insulator metal) type element. In addition, the type and number of colors of the color filter layer or their arrangement pattern can be appropriately selected.

Further, both the light diffusion layer described with reference to FIG. 3 and the light diffusion layer described with reference to FIG. 4 may be provided.

The effect of the present invention is that the structure of the liquid crystal cell is changed to O.
CB mode, 180 ° twist mode, STN mode,
It goes without saying that the present invention is similarly exerted when applied to various liquid crystal modes such as a hybrid mode and a ferroelectric mode.

Further, the effects of the present invention are not limited to the materials and conditions described in the embodiments of the present invention, and similar effects can be obtained with other materials and other conditions.

[0056]

The present invention is embodied in the form described above, and has the following effects.

First, according to the present invention, by dispersing fine spheres in the color filter layer, light can be refracted and the viewing angle dependency can be improved extremely effectively.

Further, according to the present invention, since the scattering effect by so-called diffusion does not occur, the polarization state of light is not disturbed when passing through the color filter layer. That is, there is no problem that the polarization state of light is disturbed and the image quality is reduced.

Further, according to the present invention, a color filter layer for diffusing light can be provided very close to the liquid crystal layer. As a result, "bleeding" of display can be significantly reduced as compared with the case where the light diffusion layer is arranged outside the counter substrate, and an extremely clear image display can be obtained.

Further, according to the present invention, the transmittance dispersion characteristics of the fine spheres can be made very similar to the filter base material. For this reason, a light diffusion effect can be produced without impairing color characteristics such as color purity and transmittance.

Further, according to the present invention, the fine spheres can be formed, for example, with a diameter of about several μm, and each such fine sphere acts as a lens. Therefore, even if the number of the microsphere layers is, for example, five, the thickness of the entire color filter layer can be easily suppressed to several tens μm or less. That is, since the thickness of the layer is very thin as compared with the diffusion plate using the conventional lens array, it is very advantageous for "bleeding" of the displayed image.

Further, in the conventional diffusion plate based on multiple scattering or the diffusion plate based on a mirror array, there is a problem that if the light is sufficiently diffused, the number of interfaces in the optical path increases and the loss of light increases. . On the other hand, the color filter layer containing fine spheres of the present invention utilizes the refraction effect and has a small number of interfaces on the optical path, so that light loss is small.

Further, according to the present invention, the light is diffused in the filter layer provided between the two polarizing plates. Therefore, before the ambient light enters the filter layer and is scattered, the polarized light must be polarized. Attenuated through the plate. As a result, it is possible to reduce the scatter component of the ambient light and eliminate the deterioration of the quality of the displayed image.

Further, according to the present invention, the light can be diffused more widely by providing the light diffusion layer on the front side of the counter substrate. Further, in this case, since the light diffusion layer is provided outside the polarizing plate, there is no need to restrict the light diffusion layer so as not to disturb the polarization characteristics.

Alternatively, according to the present invention, light can be diffused more widely by providing a light diffusion layer between two polarizing plates.

That is, according to the present invention, there is no reduction in resolution due to display bleeding or blurring, and it is possible to realize a display that is bright, has little loss of light, and has extremely small viewing angle dependency, and has a great industrial advantage. is there

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating a cross-sectional structure of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a graph illustrating the transmittance dispersion characteristics of a filter base material and fine spheres used in the present invention.

FIG. 3 is a schematic view illustrating a cross-sectional structure of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 4 is a schematic view illustrating a cross-sectional structure of a liquid crystal display device according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Black matrix 3 Red color filter layer 4 Green color filter layer 5 Blue color filter layer 6 Transparent electrode 7 Alignment film 8 Substrate 9 Pixel electrode 10 Thin film transistor 11 Polarizer 12 Polarizer 13 Light guide plate 14 Parallel light lens sheet 15 Fluorescent lamp 16, 16 'Diffusion layer 31, 32, 33 Filter base material 51, 52, 53 Microsphere 100 Array substrate 200, 200', 200 "Counter substrate 300 Liquid crystal 400 Backlight

Continued on the front page F term (reference) 2H048 BA45 BA48 BB02 BB10 BB14 BB44 2H091 FA02Y FA08X FA08Z FA14Z FA31X FA31Z FA35Y FA41Z FB02 FB12 GA13 HA07 KA01 LA19

Claims (3)

[Claims] 1. A liquid crystal display device comprising: a pair of substrates; a liquid crystal layer sandwiched between the pair of substrates; and a color filter layer provided on at least one of the pair of substrates. The liquid crystal display device according to claim 1, wherein the color filter layer includes a filter base material and substantially spherical particles dispersed in the filter base material and having a different light refractive index from the filter base material. 2. The liquid crystal display device according to claim 1, wherein said substantially spherical particles have substantially the same color as said filter base material. 3. A light diffusion layer and a polarizing plate are arranged in this order on a surface of the substrate on which the color filter layer is formed, on a surface on which the color filter layer is not formed. The liquid crystal display device according to the above.