JP2002107714A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device superior in display quality. SOLUTION: The liquid crystal display device is provided with a first substrate 20, a second substrate 10 provided on the observer side of the first substrate 20, a liquid crystal layer 30 installed between the first substrate 20 and the second substrate 10, a polarizing plate 16 installed on the observer side of the liquid crystal layer 30, a diffusing reflection layer 23 installed on the liquid crystal layer 30 side of the first substrate 20, and a diffusion layer 15 installed on the observer side of the liquid crystal layer 30 and plural pixels arranged like a matrix. The diffusion layer 15 suppresses diffraction of light caused by plural pixels.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device capable of displaying in a reflection mode.

[0002]

2. Description of the Related Art In recent years, a liquid crystal display device has been provided with OA equipment such as a word processor and a personal computer, portable information equipment such as an electronic organizer and a game machine, or a liquid crystal monitor by utilizing the characteristics of being thin and having low power consumption. Widely used in camera-integrated VTRs.

A liquid crystal display device is not a self-luminous display device that emits light by itself, unlike a CRT (cathode ray tube) or EL (electroluminescence).
In the case of a transmissive liquid crystal display device using a pixel electrode (transparent electrode) formed of a transparent conductive material such as (Indium Tin Oxide), a lighting device (a so-called backlight) such as a fluorescent tube is disposed behind the liquid crystal panel. do it,
The display is performed by the light incident from there.

Since the transmission type liquid crystal display device performs display using the backlight as described above, there is an advantage that display with a high contrast ratio is less affected by ambient brightness and can be performed. However, there is a problem that power consumption is increased due to the backlight. About 50 times the power consumption of a normal transmissive liquid crystal display
% Or more is consumed by the backlight. Further, in a very bright use environment (for example, outdoors in fine weather), the visibility is reduced, or power consumption is further increased when the brightness of the backlight is increased to maintain the visibility. There is.

Therefore, in order to solve the above-mentioned problem of the transmissive liquid crystal display device, a reflective plate or a reflective layer is provided instead of the backlight, and a reflective liquid crystal display which performs a reflective mode display using ambient light. Equipment is being developed.

In addition, a transflective liquid crystal display having a reflection area for displaying a reflection mode using ambient light and a transmission area for displaying a transmission mode using light from a backlight for each display pixel. Equipment has also been developed.

As described above, in a liquid crystal display device capable of displaying in a reflection mode, a reflection layer for reflecting ambient light is provided on a liquid crystal layer of a substrate (a TFT substrate or a substrate provided on a side opposite to a viewer). Side, and furthermore, a configuration in which the reflection layer itself is used as an electrode for applying a voltage to the liquid crystal layer is widely used (for example, Japanese Patent Laid-Open No. 6-117).
No. 11).

In order to realize a good paper white display in the reflection mode, various studies have been made on the production of a reflective layer having an appropriate diffuse reflection characteristic (light distribution), and such a diffuse reflection characteristic is realized. For this purpose, a reflective layer having a surface formed in an uneven shape has been developed. In addition,
In order to realize paper white display, a reflective liquid crystal display device having a light scattering film on a substrate on the observer side has also been proposed.

[0009]

However, a liquid crystal display device capable of displaying in a reflection mode has a reflection region in which a reflection layer is formed for each pixel arranged in a matrix. The inventors of the present application have found that since are periodically arranged, light is diffracted by the reflective layer, and a rainbow-colored phenomenon is observed, thereby lowering visibility. Since the display defect becomes more remarkable as the ambient light becomes stronger, the display quality is degraded when used outdoors or the like under fine weather. Further, in a high-definition liquid crystal display device, the above-described display defect becomes more remarkable.

When the surface of the reflective layer is a mirror surface, the coloring phenomenon due to diffraction is observed only in the specular reflection direction of the incident light, so that the deterioration of the display quality is relatively slight. When also functions as a diffuse reflection layer, for example, when the surface of the reflection layer is formed in an uneven shape,
Since the coloring phenomenon is observed in almost all angle ranges in the viewing direction, the display quality is significantly reduced.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a liquid crystal display device having excellent display quality.

[0012]

A liquid crystal display device according to the present invention comprises a first substrate, a second substrate provided on the viewer side of the first substrate, and a first substrate and a second substrate. A liquid crystal layer provided therebetween, a polarizing plate provided on the viewer side of the liquid crystal layer, a reflective layer provided on the liquid crystal layer side of the first substrate, and a reflector provided on the viewer side of the liquid crystal layer. Diffusion layer,
And a liquid crystal display device having a plurality of pixels arranged in a matrix, wherein the diffusion layer suppresses diffraction of light caused by the plurality of pixels, thereby achieving the above object.

[0013] The reflection layer may also function as an electrode for applying a voltage to the liquid crystal layer.

[0014] The reflection layer may be a diffuse reflection layer.

[0015] The diffuse reflection layer may have an uneven shape on the surface.

The combination of the specular reflection layer and the further diffusion layer can function as a diffusion reflection layer for displaying a reflection mode excellent in paper whiteness.

It is preferable that the diffusion layer is disposed on the viewer side of the second substrate.

It is preferable that the diffusion layer is disposed between the liquid crystal layer and the polarizing plate.

[0019] The diffusion layer may be arranged on the viewer side of the polarizing plate.

The polarizing plate may further have an anti-glare layer on the viewer side.

The haze value of the diffusion layer is 30% to 80%.
The following is preferred.

The total haze value of the diffusion layer and the antiglare layer is preferably 35% or more and 80% or less.

Preferably, the diffusion layer has a flat surface.

The distance between the diffusion layer and the liquid crystal layer is as follows:
It is preferable that it is 4 mm or less.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a liquid crystal display device according to an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following embodiments.

(Embodiment 1) Embodiment 1 according to the present invention
The liquid crystal display device 100 will be described with reference to FIGS. FIG. 1 is a sectional view schematically showing a liquid crystal display device 100 according to the present invention, and FIG.
FIG. 2 is a top view of the TFT substrate 20 included in the TFT substrate 0. FIG.
Corresponds to a cross-sectional view taken along line AA ′ of FIG.

The liquid crystal display device 100 includes a color filter substrate 10, a TFT substrate 20, and a color filter substrate 10.
And a liquid crystal layer 30 provided between the TFT substrate 20 and a reflective liquid crystal display device that performs display using ambient light.

The TFT substrate 20 includes a TFT 4 provided on a liquid crystal layer 30 side of a transparent substrate (eg, a glass substrate) 21.
A reflective electrode (pixel electrode) 23 made of a high-reflectance metal layer (for example, an Al layer) electrically connected to the drain electrode 44 of the TFT 4. The reflective electrode 23 has an uneven shape on the surface, and also functions as a diffuse reflection layer. By using light diffusely reflected on the uneven surface of the reflective electrode 23, a paper white display is realized.

The structure of the TFT substrate 20 will be described in more detail below. First, on the liquid crystal layer 30 side of the transparent substrate 21, the gate wiring 2 and the gate electrode 6, and the common electrode wiring (auxiliary capacitance wiring) 5 for forming an auxiliary capacitance are formed. Further, a gate insulating layer 7 is formed so as to cover them. A semiconductor layer, an n-type semiconductor layer, a source electrode 43, and a drain electrode 44 are formed on a gate insulating layer 7 located on the gate electrode 6, and these are formed of TF.
T4. The source electrode 43 of the TFT 4 is electrically connected to the source wiring 3. The auxiliary capacitance electrode 46 formed on the gate insulating layer 7 constitutes an auxiliary capacitance by the gate insulating layer 7 formed thereunder and the common electrode wiring (auxiliary capacitance wiring) 5, and the liquid crystal layer 30 It serves to hold the voltage applied to the.

An interlayer insulating film 8 is formed so as to cover almost the entire surface of the transparent substrate 21 on which the TFT 4 is formed, and a reflective electrode 23 is formed on the interlayer insulating film 8. Since the surface of the interlayer insulating film 8 has an uneven shape,
Reflective electrode 2 formed on the uneven surface of interlayer insulating film 8
The surface of No. 3 has an uneven shape. The above uneven shape is
For example, it can be formed using a photolithography process as disclosed in JP-A-6-27481. In the present embodiment, the pitch of the unevenness (the interval between the peak and the valley) on the surface of the reflective electrode 23 is about 5 μm to about 20 μm, and the height difference of the unevenness is about 0.1 μm to about 1.
2 μm. The reflection electrode 23 is connected to the drain electrode 44 in the contact hole 9 provided in the interlayer insulating film 8.
Is electrically connected to

The color filter substrate 10 facing the TFT substrate 20 includes a color filter 12 provided on a liquid crystal layer 30 side of a transparent substrate (eg, a glass substrate) 11 and a transparent conductive material (eg, ITO) on the color filter 12. It has a counter electrode 13 formed using the above, a diffusion layer 15 provided on the viewer side of the transparent substrate 11, and a polarizing plate 16 provided on the diffusion layer 15.

As the liquid crystal layer 30, a liquid crystal layer capable of displaying a polarization mode is used. For example, a TN (twisted nematic) mode liquid crystal layer is used. Depending on the liquid crystal layer used, alignment layers 14 and 27 are provided on the surface of the color filter substrate 10 and the TFT substrate 20 on the liquid crystal layer 30 side.

The region where the opposing electrode 12 provided on the color filter substrate 10 and the pixel electrode (reflective electrode) 23 provided on the TFT substrate 20 oppose a pixel is defined. It has a plurality of pixels arranged in a shape. In the present embodiment, the pixel arrangement is a stripe arrangement as shown in FIG. 2, and the pixel pitch H in the horizontal direction (short direction of the pixel) is about 90 μm and the pixel pitch H in the vertical direction (longitudinal direction of the pixel) Is about 270 μm.

The inventor of the present application has proposed that in a liquid crystal display device having a conventional configuration, particularly in a high definition liquid crystal display device having a pixel pitch of about 120 μm or less, a reflective electrode formed for each pixel arranged in a matrix is used. It has been found that there is a problem that light is diffracted by the (reflection layer), and a rainbow-colored phenomenon caused by the diffraction is observed and visibility is reduced.

A liquid crystal display device capable of displaying in the reflection mode is suitable for outdoor use because of its low power consumption and the like. However, in the outdoors, since parallel sunlight is used for display, Light diffraction due to the plurality of pixels as described above is likely to occur, and the visibility is significantly reduced.

Further, in the liquid crystal display device having a small pixel pitch, the deterioration of the display quality becomes more remarkable because the diffraction angle of diffraction by the periodically arranged reflective electrodes (reflective layers) increases as the pitch decreases. It is considered that the coloring phenomenon is easily observed.

Further, when the reflection layer has a diffuse reflection characteristic, this coloring phenomenon is observed in almost all angles in the viewing direction, so that the visibility is significantly reduced.
In particular, in the case of a diffuse reflection layer having an uneven shape on the surface,
In particular, as described above, in the case of a diffuse reflection layer having irregularities formed by using a photolithography process, it is difficult to completely randomly control the distribution of the irregularities.
It is considered that the unevenness tends to have a certain degree of periodicity, and that light diffraction due to the unevenness also contributes to the deterioration of display quality.

The diffusion layer 15 included in the liquid crystal display device 100 according to the present invention has a function of suppressing the diffraction of light caused by a plurality of pixels arranged in a matrix. A display with good visibility, in which no is observed, is realized.

That is, the liquid crystal display device 100 according to the present invention
, The substrate (color filter substrate) 1 on the observer side
0 is provided with the diffusion layer 15, so that the light enters from the observer side and is reflected by the reflection electrode (diffuse reflection layer) 23.
Light transmitted through the liquid crystal layer 30 passes through the diffusion layer 15 before being emitted to the viewer side, and is scattered by the diffusion layer 15. Therefore, diffraction of light caused by the plurality of pixels is suppressed, and as a result, a display with good visibility in which a rainbow coloring phenomenon is not observed is realized.

The diffusion layer 15 is made of a material obtained by dispersing and mixing fine particles (for example, SiO ₂ ) having a refractive index different from that of the base material in a colorless and transparent base material (for example, an acrylic resin). Preferably, it is formed. The average particle diameter of the fine particles is preferably in the range of about 0.5 μm to about 10 μm. If the average particle diameter is smaller than about 0.5 μm, a sufficient diffusion effect cannot be obtained. Since the entire layer 15 is thick, it is difficult to control the film thickness uniformly and control the distribution of fine particles. Addition amount of fine particles (weight)
May be appropriately set so as to obtain a desired diffusivity (haze value) in consideration of a difference in refractive index from a substrate, an average particle diameter, specific gravity, and the like.

The diffusion layer 15 may be formed as a thin film on the surface of another member (for example, a polarizing plate) or may be formed as a self-supporting film. In addition, a diffusion layer and an adhesive layer may be formed using a material having a diffusive property and an adhesive property. When the diffusion layer 15 is formed as the diffusion layer and the adhesive layer, the thickness of the diffusion layer 15 is
It is preferable that the thickness be in the range of about 5 μm to about 50 μm from the viewpoint of ease of handling (handling properties) of the diffusion layer 15 and reworkability when a defect occurs. Further, the diffusion layer 15 preferably has a flat surface from the viewpoint of improving adhesion to layers or substrates disposed on both sides of the diffusion layer 15 and reducing backscattering. Further, the diffusion layer 15 may have photosensitivity, and may be appropriately patterned by a photolithography process or the like. However, from the viewpoint of workability and the like, it is preferable to provide it on almost the entire display surface, and it is also preferable to double as the adhesive layer.

The diffusion layer 15 has a function of scattering light as described above (hereinafter referred to as “diffusion function”), and the diffusion function depends on the optical characteristics of the diffusion layer 15. One of the physical properties indicating the optical characteristics of the diffusion layer 15 is a haze value calculated by the following equation. The larger the haze value of the diffusion layer 15, the stronger the diffusion function. Haze value: H (%) = (diffuse transmittance / total light transmittance) · 100 In order to suppress diffraction of light caused by a plurality of pixels, the diffusion function of the diffusion layer 15 needs to be sufficiently strong. However, if the diffusion function is too strong, blurring of the displayed image occurs. By using the diffusion layer 15 having an appropriate diffusion function, that is, by using the diffusion layer 15 having an appropriate haze value, a high-quality display in which a coloring phenomenon due to diffraction and a blur of a display image are suppressed is realized.

Table 1 shows the results of visual evaluation of the coloring phenomenon due to diffraction and image blurring when the haze value of the diffusion layer 15 is changed in the liquid crystal display device 100. [Table 1] Haze value of diffusion layer (%) Coloring phenomenon due to diffraction Image blur 10 × ◎ 20 × ◎ 30 ○ ◎ 40 ◎ ◎ 50 ◎ ◎ 60 ◎ ◎ 70 ◎ ○ 80 ◎ ○ 90 ◎ × The evaluation was performed under the following conditions. First,
As the diffusion layer 15, a diffuser manufactured by Nitto Denko Co., Ltd., which is an adhesive having a light diffusing property, was used, and the haze value was changed by changing the amount of fine particles mixed with the base material. The haze value of the diffusion layer 15 is measured using an integrating sphere type light transmittance measuring device (haze meter) according to JIS K710.
5 was measured. In addition, 2.
A 3-type color TFT-LCD module was used. The thickness of the transparent substrates 11 and 21 of this module is about 0.7 m
m, and the diffusion layer 15 is composed of the transparent substrate 11 and the polarizing plate 16.
Since the liquid crystal layer 30 is provided immediately above the transparent substrate 11 also as an adhesive layer, the distance between the liquid crystal layer 30 and the diffusion layer 15 is about 0.1 mm.
7 mm. The surface treatment of the polarizing plate is hard coat clear. Further, in order to simulate the parallel light of sunlight and to keep the light source constant, a light source box capable of obtaining an illuminance of 50,000 lux was prepared and used as a light source for external light (ambient light). Then, small pictures and characters are displayed on the display screen, and the subjects are 30 men and women in their 20s to 50s who are randomly selected.

Further, coloring phenomenon by diffraction in Table 1
The criteria for the visual evaluation of the image blur are as follows.

<Coloring Phenomenon Due to Diffraction> ：: 70% or more of the subjects “has little knowledge of the coloring phenomenon due to diffraction” ○: 40% or more of the subjects “not noticeable though some coloring phenomenon due to diffraction is observed” × : 40% or more of the subjects "clearly observed the coloring phenomenon due to diffraction and could not withstand the display quality"<Imageblur> ◎: 70% or more of the subjects "Don't mind image blur at all" ○: Subject Of 40% or more of the subjects was "not very concerned about blurring of the image" ×: At least 40% of the subjects "observed the blurring of the image clearly and could not withstand the display quality" As can be seen from Table 1, the haze value was about 30% or more about 80
% Or less, a high-quality display in which the coloring phenomenon due to diffraction and the occurrence of image blur are suppressed is realized. In particular, when the diffusion layer 15 having a haze value of about 40% or more and about 60% or less is used, a higher quality display in which a coloring phenomenon due to diffraction and image blurring are further suppressed is realized. When the diffusion layer 15 having a haze value of less than about 30% is used, blurring of an image does not occur, but diffraction of light caused by a plurality of pixels cannot be sufficiently suppressed, and a coloring phenomenon is observed to lower visibility. . When the haze value exceeds about 80%, although a coloring phenomenon due to diffraction is not observed, an image is blurred because the diffusion function is too strong.

As described above, by using the diffusion layer 15 having an appropriate haze value, high-quality display is realized.

The distance between the diffusion layer 15 and the liquid crystal layer 30 (more precisely, the distance between the diffusion layer 15 and the reflection electrode (diffuse reflection layer) 2)
3) greatly affects the suppression of light diffraction caused by the plurality of pixels.

Table 2 shows the results of visual evaluation of coloring phenomenon due to diffraction and image blurring when the distance between the diffusion layer 15 and the liquid crystal layer 30 was changed. In this visual evaluation, the diffusion layer 15 having a haze value of about 50% was used.
Was used. Further, the distance between the diffusion layer 15 and the liquid crystal layer 30 (in the present embodiment, the distance between the black matrix (not shown) of the color filter 12 and the diffusion layer 15) is determined by adjusting the thickness of the transparent substrate 11. Changed. The diffusion layer 15 is formed on the transparent substrate 11 similarly to the visual evaluation in Table 1.
And the polarizing plate 16. However, the distance is about 0mm
In the case of (1), it was arranged between the transparent substrate 11 and the color filter 12. Other experimental conditions and criteria are the same as the experimental conditions and criteria in Table 1. [Table 2] Distance between diffusion layer and liquid crystal layer (mm) Coloring phenomenon due to diffraction Image blur 0 ○ ◎ 0.2 ◎ ◎ 0.4 ◎ ◎ 0.5 ◎ ◎ 0.7 ◎ ◎ 1.1 ◎ ◎ 1.4 ◎ 1.6 ◎ × As can be seen from Table 2, when the distance between the diffusion layer 15 and the liquid crystal layer 30 is about 1.4 mm or less, the occurrence of coloring phenomenon and image blur due to diffraction is suppressed. High-quality display is realized. In particular, when the distance between the diffusion layer 15 and the liquid crystal layer 30 is about 1.1 mm or less, a higher quality display in which the coloring phenomenon due to diffraction and the occurrence of image blur are further suppressed is realized. The distance between the diffusion layer 15 and the liquid crystal layer 30 is about 1.
If it exceeds 4 mm, although the coloring phenomenon due to diffraction does not occur, the image is blurred because the diffusion function is too strong (or the parallax becomes large).

As described above, by arranging the diffusion layer 15 and the liquid crystal layer 30 such that the distance between the diffusion layer 15 and the liquid crystal layer 30 is an appropriate distance, a high-quality display is realized.

In the liquid crystal display device 100 according to the present invention, since the diffusion layer 15 is arranged on the viewer side of the color filter substrate 10, by changing the thickness of the transparent substrate 11, The distance from the layer 30 can be easily controlled. Therefore, it is possible to more easily suppress the coloring phenomenon due to diffraction and the occurrence of image blur.

In the liquid crystal display device 100 according to the present invention, since the diffusion layer 15 is disposed between the liquid crystal layer 30 and the polarizing plate 16, the distance between the liquid crystal layer 30 and the diffusion layer 15 is relatively short. The configuration is easy. Therefore,
The occurrence of image blur can be more easily suppressed.

Further, since the diffusion layer 15 is disposed between the liquid crystal layer 30 and the polarizing plate 16 as described above, part of the incident light is absorbed by the polarizing plate when ambient light reaches the diffusion layer. Have been. The backscattered light generated in the diffusion layer 15 also passes through the polarizing plate when emitted, so that the backscatter is considerably reduced. Therefore, display with a high contrast ratio is realized by suppressing backscattering.

In this embodiment, as shown in FIG. 2, the case where the pixel arrangement is a stripe arrangement has been described. However, it is needless to say that the pixel arrangement may be a delta arrangement, and the pixel pitch is the same as that of this embodiment. It is not limited to.

Further, a retardation plate may be provided between the transparent substrate 11 and the polarizing plate 16 in order to increase the viewing angle and improve the contrast ratio. If a retardation plate is provided, the diffusion layer 15
May be arranged between the transparent substrate 11 and the phase difference plate, or may be arranged between the phase difference plate and the polarizing plate 16.
When using the diffusion layer 15 which also functions as an adhesive layer,
Transparent substrate 11, adhesive layer, retardation plate, adhesive layer, polarizing plate 16
In this order, and at least one of the two adhesive layers may be the diffusion layer 15 functioning as an adhesive layer.

Further, in the present embodiment, the case where the diffusion layer 15 is disposed between the liquid crystal layer 30 and the polarizing plate 16 as shown in FIG. 1 has been described, but as shown in FIG. The diffusion layer (for example, IDS film IDS16K manufactured by Dai Nippon Printing Co., Ltd.) 15 may be arranged on the viewer side of the polarizing plate 16.

When such a configuration is adopted, the diffusion layer 15
Is provided closer to the viewer than the polarizing plate 16, the light incident from the backlight and transmitted through the liquid crystal layer 30 is disturbed by the diffusion layer 15 before entering the polarizing plate 16. There is no. Therefore, light leakage in the black display state is suppressed, and as a result, display with a high contrast ratio is realized.

In the present embodiment, the diffusion layer 15
Has been described on the observer side of the color filter substrate 10, but the diffusion layer 15 may be disposed on the liquid crystal layer side of the color filter substrate 10. It may be disposed between the transparent substrate 11 and the color filter 12, or may be disposed on the viewer side of the color filter 12, for example, between the color filter 12 and the counter electrode 13 as shown in FIG. And may be arranged between the counter electrode 13 and the alignment layer 14. The color filter 12
Alternatively, a color filter having a light diffusion function and also functioning as a diffusion layer may be used. A color filter having a light diffusion function can be formed using a material in which fine particles having a refractive index different from that of a material forming an ordinary color filter are dispersed.

In this embodiment, the diffusion layer 15 is provided separately from the transparent substrate 11 of the color filter substrate 10.
Has been described, but a transparent substrate 11 having a function as the diffusion layer 15 may be used. (Embodiment 2) FIG. 5 schematically shows a liquid crystal display device 200 according to Embodiment 2 of the present invention. The liquid crystal display device 200
The liquid crystal display device 100 has the same configuration as that of the liquid crystal display device 100 except that an antiglare layer (anti-glare film) 17 is provided on the observer side of the polarizing plate 16 (the surface of the liquid crystal display device 200 on the observer side). In the following description, for simplicity,
Differences from the liquid crystal display device 100 will be mainly described, and similar points will be simplified. In the following drawings, components having substantially the same function are denoted by the same reference numerals.

The anti-glare layer 17 provided on the viewer side surface of the liquid crystal display device 200 is formed of a transparent material.
Since the surface has an uneven shape, external light (ambient light) incident mainly from the observer side is diffusely reflected (scattered). Therefore, the specular reflection (specular reflection) of the ambient light on the surface of the liquid crystal display device 200 is suppressed, and as a result, a display with good visibility without surrounding image reflection is realized. As the anti-glare layer 17, for example, AG30 manufactured by Nitto Denko Corporation (haz
%), AGT1 (Haze value: 15%) manufactured by Nitto Denko Corporation and AGS1 (Haze value: 25%) manufactured by Nitto Denko Corporation can be used.

The inventor of the present application has found that when an anti-glare layer is provided in a conventional liquid crystal display device capable of displaying in a reflection mode to realize the above-described display, reflection of surrounding images is suppressed. However, it has been found that a coloring phenomenon due to light diffraction is more remarkably observed, and there is a problem that visibility is further reduced.

The diffusion layer 15 included in the liquid crystal display device 200 according to the present invention has a function of suppressing the diffraction of light caused by a plurality of pixels arranged in a matrix. A display with good visibility in which no phenomenon is observed is realized.

That is, the liquid crystal display device 100 according to the present invention
, The substrate (color filter substrate) 1 on the observer side
0 is provided with the diffusion layer 15, so that the light enters from the observer side and is reflected by the reflection electrode (diffuse reflection layer) 23.
Light transmitted through the liquid crystal layer 30 passes through the diffusion layer 15 before being emitted to the viewer side, and is scattered by the diffusion layer 15. Therefore, since the diffraction of light caused by the plurality of pixels is suppressed, the coloring phenomenon does not become more apparent due to the anti-glare layer 17, and as a result, a display with good visibility in which the rainbow coloring phenomenon is not observed is obtained. Is achieved.

Also in the liquid crystal display device 200 according to the present invention, high quality display is realized by using the diffusion layer 15 having an appropriate haze value. Table 3 shows the results of visual evaluation of the coloring phenomenon due to diffraction and the blur of an image when the haze value of the diffusion layer 15 is changed in the liquid crystal display device 200. In this visual evaluation, AGT1 manufactured by Nitto Denko (having a haze value of 15) was used as the antiglare layer 17.
%) And other experimental conditions and criteria are shown in Table 1.
Are the same as the experimental conditions and criteria. [Table 3] Haze value of diffusion layer (%) Coloring phenomenon due to diffraction Image blur 10 × ◎ 20 ○ ◎ 30 ◎ ◎ 40 ◎ ◎ 50 ◎ ◎ 60 ◎ ◎ 70 ◎ ○ 80 ◎ × 90 ◎ × Table 3 Thus, the haze value is about 20% or more and about 70%.
% Or less, a high-quality display in which the coloring phenomenon due to diffraction and the occurrence of image blur are suppressed is realized. In particular, when the diffusion layer 15 having a haze value of about 30% or more and about 60% or less is used, a higher quality display in which the coloring phenomenon due to diffraction and the occurrence of image blur are further suppressed is realized. When the diffusion layer 15 having a haze value of less than about 20% is used, blurring of an image does not occur, but diffraction by the reflective electrode cannot be sufficiently suppressed, and a coloring phenomenon is observed, thereby lowering visibility. If the haze value exceeds about 70%, no coloring phenomenon is observed, but the image is blurred because the diffusion function is too strong.

As described above, by using the diffusion layer 15 having an appropriate haze value, high-quality display is realized.

As described above, when the anti-glare layer is provided in the conventional liquid crystal display device, the coloring phenomenon is more remarkably observed. However, as in the liquid crystal display device 200 of the present invention, the liquid crystal layer 30 and the anti-glare When the diffusion layer 15 is further provided between the anti-glare layer 17 and the diffusion layer 15, the anti-glare layer 17 and the diffusion layer 15 cooperate to suppress diffraction.

Although the optical characteristics of the diffusion layer 15 can be indicated by using the haze value as described above, the optical characteristics of the antiglare layer 17 can also be indicated by using the haze value. In No. 17, the larger the haze value, the stronger the function of diffusing and reflecting (or scattering) ambient light.

Table 4 shows the results of visual evaluation of the coloring phenomenon due to diffraction and image blurring when the total haze value of the diffusion layer 15 and the antiglare layer 17 was changed. In this visual evaluation, NITTO DENKO AGT1 (haze value: about 15%) was used as the antiglare layer 17,
Other experimental conditions and criteria are the same as the experimental conditions and criteria in Table 3. [Table 4] Total (%) of haze values of antiglare layer and diffusion layer Coloring phenomenon due to diffraction Image blur 20 × ◎ 30 ○ ◎ 40 ◎ ◎ 50 ◎ ◎ 60 ◎ ◎ 70 ◎ ◎ 80 ◎ ○ 90 ◎ × Table 4, when the total haze value of the diffusion layer 15 and the antiglare layer 17 is about 30% or more and about 80% or less,
A high-quality display in which the coloring phenomenon due to diffraction and the occurrence of image blur are suppressed is realized. In particular, when the total haze value is about 40% or more and about 70% or less, a higher quality display is realized in which the coloring phenomenon due to diffraction and the occurrence of image blur are further suppressed. If the total haze value is less than about 30%, the image is not blurred, but the diffraction of light due to the plurality of pixels cannot be sufficiently suppressed, and a coloring phenomenon is observed to lower the visibility. The total haze value is about 8
If it exceeds 0%, although the coloring phenomenon due to diffraction does not occur, the image is blurred because the diffusing function is too strong.

As described above, by using the diffusion layer 15 having an appropriate haze value according to the antiglare layer 17 to be used, a high quality display is realized. However, the haze value of the antiglare layer 17 provided on the outermost surface of the liquid crystal display device and having irregularities on the surface is preferably in the range of about 5% to about 30%, and more preferably in the range of about 7% to about 25%. It is more preferred that there be. If the haze value of the antiglare layer is less than about 5%, the reflection of surrounding images cannot be sufficiently suppressed, and if it exceeds about 30%, the displayed image is blurred. On the other hand, when the haze value exceeds about 30%, the reflection on the surface of the antiglare layer 17 becomes large, and the screen becomes white and the contrast ratio is lowered.

The sum of the haze values of the diffusion layer 15 and the anti-glare layer 17 is a haze value measured in an arrangement where light continuously passes through the diffusion layer 15 and the anti-glare layer 17. This value is slightly smaller than the sum of the haze values measured individually for each of the diffusion layer 15 and the antiglare layer 17. (Embodiment 3) FIG. 6 schematically shows a liquid crystal display device 300 according to Embodiment 3 of the present invention.

The liquid crystal display device 300 includes a color filter substrate 10, a TFT substrate 20, and a color filter substrate 10.
And a liquid crystal layer 30 provided between the TFT substrate 20 and a transflective liquid crystal for performing display using light from a backlight 90 and / or ambient light provided on the TFT substrate 20 side. A display device.

The color filter substrate 10 includes a color filter 12 provided on the liquid crystal layer 30 side of a transparent substrate (eg, a glass substrate) 11 and a color filter 12 formed on the color filter 12 using a transparent conductive material (eg, ITO). Electrode 13
And a diffusion layer 15 provided on the viewer side of the transparent substrate 11.
And a polarizing plate 16 provided on the diffusion layer 15 and the polarizing plate 1
Antireflection (AR) layer 18 provided on 5
And The anti-reflection layer 18 is formed, for example, by laminating a plurality of materials having different refractive indexes from each other.
By providing 8, the reflection of external light (ambient light) incident from the observer side on the observer-side surface of the liquid crystal display device 200 is suppressed, thereby realizing a display with good visibility.

The TFT substrate 20 includes a polarizing plate 22 provided on the backlight side of a transparent substrate (eg, a glass substrate) 21.
A source line, a gate line, and a TFT (not shown) provided on the liquid crystal layer 30 side of the transparent substrate 21;
Pixel electrode 25 electrically connected to the drain electrode of FT
And

As shown in FIGS. 6 and 7, the pixel electrode 25 is formed using a transparent electrode 24 formed using a transparent conductive material (eg, ITO) and a high-reflectivity metal (eg, Al). The reflective electrode 23 'has a concave-convex shape on its surface and also functions as a diffuse reflective layer. By using the light diffusely reflected on the uneven surface of the reflection electrode 23 ', a paper white reflection mode display is realized. Further, the reflection electrode 2
The interlayer insulating film 26 below the reflective electrode 23 ′ is made of a transparent electrode such that the thickness of the liquid crystal layer 30 above 3 ′ is about の of the thickness of the liquid crystal layer 30 above the transparent electrode 24. It is formed to be thicker than an interlayer insulating film (not shown) below 24.

As the liquid crystal layer 30, a liquid crystal layer capable of displaying a polarization mode is used, for example, a TN (twisted nematic) mode liquid crystal layer. An alignment film (not shown) is provided on the surface of the color filter substrate 10 and the TFT substrate 20 on the liquid crystal layer side according to the liquid crystal layer used.

The area where the opposing electrode 12 provided on the color filter substrate 10 and the pixel electrode 25 provided on the TFT substrate 20 oppose each other defines a pixel.
00 has a plurality of pixels arranged in a matrix. In this embodiment, the pixel arrangement is a stripe arrangement, and the pixel pitch in the horizontal direction (short direction of the pixel) is about 72.5 μm, and the pixel pitch in the vertical direction (longitudinal direction of the pixel) is about 138.5 μm. is there. The length of the transparent electrode 24 in the horizontal direction is about 38 μm, and the length in the vertical direction is about 82 μm. The transparent electrode 24 has a transparent portion where the transparent electrode 24 is formed and a reflective portion where the reflective electrode 23 ′ is formed. The area ratio is about 6: 4. Further, the transparent electrode 24 is provided at the center of the pixel as shown in FIG.

The diffusion layer 15 included in the liquid crystal display device 300 according to the present invention has a function of suppressing light diffraction by the reflection electrode (diffuse reflection layer) 23 ′. A display with good visibility that is not observed is realized.

That is, the liquid crystal display device 300 according to the present invention
, The substrate (color filter substrate) 1 on the observer side
0 is provided with the diffusion layer 15, the backlight 9
0, which is incident from the observer side and transmits through the liquid crystal layer 30, and which is incident from the observer side, is reflected by the reflective electrode 23 ', and
Light transmitted through the diffusion layer 1 before exiting to the observer side.
5 and is scattered by the diffusion layer 15. Therefore,
Diffraction of light by the reflective electrode (diffuse reflective layer) 23 'is suppressed, and as a result, a display with good visibility in which a rainbow coloring phenomenon is not observed is realized.

Table 5 shows the results of visual evaluation of coloring phenomenon due to diffraction and image blurring when the haze value of the diffusion layer 15 is changed in the liquid crystal display device 300. In addition,
In this visual evaluation, as the diffusion layer 15, a diffuser manufactured by Nitto Denko Co., Ltd., which is an adhesive having a light diffusing property, was used to change the haze value of the diffusion layer 15 by changing the amount of fine particles added to the base material. Was. In addition, a type 2 color TFT-LCD module was used as a liquid crystal module. Other experimental conditions and criteria are the same as the experimental conditions and criteria for visual evaluation in Table 1. [Table 5] Haze value of diffusion layer (%) Coloring phenomenon due to diffraction Image blur 10 × ◎ 20 × ◎ 30 ○ ◎ 40 ◎ ◎ 50 ◎ ◎ 60 ◎ ◎ 70 ◎ ◎ 80 ◎ ○ 90 ◎ × Table 5 Thus, the haze value is about 30% or more and about 80
The use of a diffusion layer of not more than% realizes high-quality display in which display roughness and image blurring are suppressed.
In particular, the diffusion layer 1 having a haze value of about 40% or more and about 70% or less
The use of No. 5 realizes a higher quality display in which the coloring phenomenon due to diffraction and the occurrence of image blur are further suppressed.

In the above-described visual evaluation, the distance between the diffusion layer 15 and the liquid crystal layer 30 was set to about 0.7 mm.
When making the distance between 5 and liquid crystal layer 30 shorter than about 0.7 mm, it is preferable to use diffusion layer 15 having a relatively strong diffusion function (having a relatively large haze value).

In this embodiment, the case where the area ratio between the reflection part and the transmission part is about 6: 4 has been described.
The present invention is not limited to this, and may have an arbitrary area ratio.

The present inventor has proposed that the above-described liquid crystal display device 200
, The transmissive portion (transparent electrode 24) is smaller, for example, the pixel pitch in the horizontal direction is about 95 μm, the pixel pitch in the vertical direction is about 280 μm, and the horizontal length of the transparent electrode 24 is about 51 μm. About 135μm
It has been experimentally confirmed that when the area ratio between the reflection part and the transmission part is set to be about 8: 2, the display defect becomes more remarkable. Therefore, when the size of the transmission part is set as described above, it is preferable to use the diffusion layer 15 having a relatively strong diffusion function (having a relatively large haze value).

Table 6 shows the results of visual evaluation of the coloring phenomenon due to diffraction and the blurring of the image when the haze value of the diffusion layer 15 is changed in the liquid crystal display device 300 in which the transmitting portion is set as described above. . The experimental conditions and criteria for visual evaluation in Table 6 are the same as the experimental conditions and criteria for visual evaluation in Table 5. [Table 6] Haze value of diffusion layer (%) Coloring phenomenon due to diffraction Image blur 10 × ◎ 20 × ◎ 30 × ◎ 40 ○ ◎ 50 ◎ ◎ 60 ◎ ◎ 70 ◎ ◎ 80 ◎ ○ 90 ◎ × Table 6 As described above, when the transmissive portion is set as described above, when a haze value of about 40% or more and about 80% or less is used, high-quality display in which the coloring phenomenon due to diffraction and the occurrence of image blur are suppressed. Is realized. In particular, when the diffusion layer 15 having a haze value of about 50% or more and about 70% or less is used, a higher-quality display in which a coloring phenomenon due to diffraction and a blur of an image are further suppressed is realized.

In this embodiment, the case where the arrangement of the pixels is a stripe arrangement has been described. Of course, the arrangement may be a delta arrangement, and the value of the pixel pitch is not limited to the value of this embodiment. In addition, the transmitting portion may be provided at a position other than the central portion of the pixel, and a plurality of transmitting portions may be provided.

(Embodiment 4) FIG. 8 schematically shows a liquid crystal display device 400 according to Embodiment 4 of the present invention.

The liquid crystal display device 400 includes a color filter substrate 10, a TFT substrate 20, and a color filter substrate 10.
And a liquid crystal layer 30 provided between the TFT substrate 20 and a reflective liquid crystal display device that performs display using ambient light.

The TFT substrate 20 includes a source wiring provided on the liquid crystal layer 30 side of a transparent substrate (eg, a glass substrate) 21,
Gate wiring and TFT (both not shown), TFT
Pixel electrode (reflective electrode) 28 made of a high-reflectance metal layer (for example, Al layer) electrically connected to the drain electrode of
And The surface of the reflective electrode 28 is a mirror surface formed substantially flat.

The color filter substrate 10 has a color filter 12 provided on the liquid crystal layer 30 side of a transparent substrate (eg, a glass substrate) 11 and a color filter 12 formed on the color filter 12 using a transparent conductive material (eg, ITO). Electrode 13
And a diffusion layer 15 provided on the viewer side of the transparent substrate 11.
And a polarizing plate 16 provided on the diffusion layer 15 and the polarizing plate 1
And a light diffusion layer 19 provided on the light diffusion layer 6. The light diffusion layer 19 functions as a diffusion reflection layer for performing paper white display in the reflection mode in combination with the reflection electrode 28 having a mirror surface.

As the liquid crystal layer 30, a liquid crystal layer capable of displaying a polarization mode is used. For example, a TN (twisted nematic) mode liquid crystal layer is used. An alignment layer (not shown) is provided on the surface of the color filter substrate 10 and the TFT substrate 20 on the liquid crystal layer side according to the liquid crystal layer used.

The area where the opposing electrode 12 provided on the color filter substrate 10 and the pixel electrode (reflective electrode) 28 provided on the TFT substrate 20 oppose each other defines a pixel. It has a plurality of pixels arranged in a shape. In the present embodiment, the pixel arrangement is a stripe arrangement, and the pixel pitch in the horizontal direction (short direction of the pixel) is about 90 μm, and the pixel pitch in the vertical direction (longitudinal direction of the pixel) is about 270 μm.

The diffusion layer 15 included in the liquid crystal display device 400 according to the present invention has a function of suppressing light diffraction caused by a plurality of pixels arranged in a matrix. A display with good visibility in which no phenomenon is observed is realized.

That is, the liquid crystal display device 400 according to the present invention
, The substrate (color filter substrate) 1 on the observer side
Since the diffusion layer 15 is provided on the light-emitting layer 0, the light that enters from the observer side, is reflected by the reflective electrode (reflection layer) 28, and transmits through the liquid crystal layer 30 before being emitted to the observer side. And is scattered by the diffusion layer 15. Therefore, diffraction of light caused by the plurality of pixels is suppressed, and as a result, a display with good visibility in which a rainbow coloring phenomenon is not observed is realized.

The reflection electrode (reflection layer) 28 of the liquid crystal display device 400 has a mirror-finished surface.
In the case of 00, the coloring phenomenon due to diffraction is observed only in the regular reflection direction of the incident light. Therefore, the visibility is slightly reduced and the haze value is relatively small (diffusion function is relatively weak) as compared with the case where the reflective electrode has an uneven surface.
Even with the use of the diffusion layer 15, a display with good visibility is realized.

Table 7 shows the results of visual evaluation of coloring phenomena due to diffraction and image blurring when the haze value of the diffusion layer 15 is changed in the liquid crystal display device 400. In addition,
The experimental conditions and criteria in Table 7 are the same as the experimental conditions and criteria for visual evaluation in Table 1. [Table 7] Haze value of diffusion layer (%) Coloring phenomenon due to diffraction Image blur 10 × ◎ 20 ○ ◎ 30 ○ ◎ 40 ◎ ◎ 50 ◎ ◎ 60 ◎ ◎ 70 ◎ ◎ 80 ◎ ○ 90 ◎ × Table 7 Thus, the haze value is about 20% or more and about 80%.
The use of a diffusion layer of not more than% realizes high-quality display in which display roughness and image blurring are suppressed.
In particular, the diffusion layer 1 having a haze value of about 40% to about 70%.
The use of No. 5 realizes a higher quality display in which the coloring phenomenon due to diffraction and the occurrence of image blur are further suppressed.

In this embodiment, the light diffusion layer 1
Paper white display is realized by a combination of the reflective electrode 9 and a reflective electrode (reflective layer) 28 having a mirror surface, but by providing the diffusion layer 15 which also functions as a light diffusion layer,
Paper white display may be realized. When the diffusion layer 15 also functions as a light diffusion layer, the diffusion layer has a relatively strong diffusion function, that is, the diffusion layer 15 having a relatively large haze value.
(For example, a diffusion layer 15 having a haze value of 50% or more) is preferably used. Diffusion layer 1 that also functions as light diffusion layer
5 is preferably provided between the transparent substrate 11 and the polarizing plate 16 from the viewpoint of realizing a display with a high contrast ratio by suppressing backscattering, and suppresses light leakage due to disturbance of the polarization plane. From the viewpoint of realizing a display with a high contrast ratio, it is preferable to provide the polarizing plate 16 on the observer side.

In the first, second, third and fourth embodiments, the case where the reflection layer for reflecting ambient light also functions as an electrode for applying a voltage to the liquid crystal layer 30 is described. Although the description has been made, it is needless to say that the reflective layer does not have to function as an electrode, and a voltage may be applied by an electrode formed separately.

[0096]

According to the present invention, there is provided a liquid crystal display device in which diffraction of light caused by a plurality of pixels is suppressed and display quality is excellent. In particular, a remarkable effect is exhibited in a high-definition liquid crystal display device having a pixel pitch of about 120 μm or less. Also, a remarkable effect can be obtained in a liquid crystal display device having an antiglare layer.

The present invention can be suitably used for a liquid crystal display device capable of displaying in a reflection mode, and is particularly suitably used for a liquid crystal display device used in an environment where ambient light is strong.

[Brief description of the drawings]

FIG. 1 is a liquid crystal display device 100 according to a first embodiment of the present invention.
It is sectional drawing which shows typically.

FIG. 2 is a liquid crystal display device 100 according to a first embodiment of the present invention.
FIG. 2 is a top view schematically showing a TFT substrate 20 of the present invention.

FIG. 3 is a liquid crystal display device 100 according to a first embodiment of the present invention.
It is sectional drawing which shows the other structure of typically.

FIG. 4 is a liquid crystal display device 100 according to a first embodiment of the present invention.
It is sectional drawing which shows the other structure of typically.

FIG. 5 is a liquid crystal display device 200 according to a second embodiment of the present invention.
It is sectional drawing which shows typically.

FIG. 6 shows a liquid crystal display device 300 according to a third embodiment of the present invention.
It is sectional drawing which shows typically.

FIG. 7 is a liquid crystal display device 300 according to a third embodiment of the present invention.
FIG. 2 is a diagram schematically illustrating a pixel electrode 25 included in the pixel electrode.

FIG. 8 is a liquid crystal display device 400 according to a fourth embodiment of the present invention.
It is sectional drawing which shows typically.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 2 Gate wiring 3 Source wiring 4 TFT 5 Common electrode wiring 6 Gate electrode 7 Gate insulating layer 8 Interlayer insulating film 9 Contact hole 10 Color filter substrate 11 Transparent substrate 12 Color filter 13 Counter electrode 14 Alignment layer 15 Diffusion layer 16 Polarizer 17 Prevention Glare layer 18 anti-reflection (AR) layer 19 light diffusion layer 20 TFT substrate 21 transparent substrate 22 polarizing plate 23, 23 ′ reflective electrode (diffuse reflective layer) 24 transparent electrode 27 alignment layer 28 reflective electrode 30 liquid crystal layer 43 source electrode 44 drain Electrode 46 Auxiliary capacitance electrode 100, 200, 300, 400 Liquid crystal display

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02F 1/1343 G02F 1/1343 5G435 G09F 9/00 313 G09F 9/00 313 9/30 338 9/30 338 349 349D F term (reference) 2H042 BA02 BA04 BA15 BA20 2H049 BA02 BA06 BB03 BB51 BB63 BB65 BC14 2H091 FA08X FA14Y FA16Y FA31X FA37X LA16 2H092 JA24 JB03 JB07 NA03 NA26 PA12 5C094 AA02 EA03 EA03 EA03 EA03 5G435 AA01 BB12 BB16 FF03 FF05 FF06 KK05

Claims (12)

[Claims] A first substrate; a second substrate provided on an observer side of the first substrate; a liquid crystal layer provided between the first substrate and the second substrate; A polarizing plate provided on the observer side of, a reflective layer provided on the liquid crystal layer side of the first substrate, and a diffusion layer provided on the observer side of the liquid crystal layer,
A liquid crystal display device having a plurality of pixels arranged in a matrix, wherein the diffusion layer suppresses diffraction of light caused by the plurality of pixels. 2. The liquid crystal display device according to claim 1, wherein the reflection layer also functions as an electrode for applying a voltage to the liquid crystal layer. 3. The reflection layer according to claim 1, wherein the reflection layer is a diffuse reflection layer.
Or the liquid crystal display device according to 2. 4. The liquid crystal display device according to claim 3, wherein the diffuse reflection layer has an uneven shape on a surface. 5. The liquid crystal display device according to claim 1, wherein the diffusion layer is arranged on a viewer side of the second substrate. 6. The liquid crystal display device according to claim 1, wherein the diffusion layer is disposed between the liquid crystal layer and the polarizing plate. 7. The liquid crystal display device according to claim 1, wherein the diffusion layer is disposed on a viewer side of the polarizing plate. 8. The liquid crystal display device according to claim 1, further comprising an antiglare layer on the viewer side of the polarizing plate. 9. The haze value of the diffusion layer is 30% or more and 80% or more.
The liquid crystal display device according to any one of claims 1 to 8, wherein the content is not more than 10%. 10. The liquid crystal display device according to claim 8, wherein a total haze value of the diffusion layer and the antiglare layer is 35% or more and 80% or less. 11. The liquid crystal display device according to claim 1, wherein said diffusion layer has a flat surface. 12. A distance between the diffusion layer and the liquid crystal layer,
The liquid crystal display device according to claim 1, wherein the thickness is 1.4 mm or less.