JP2008233728A - Liquid crystal display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display panel for reducing light leakage current of TFT having an a-Si layer caused by reflection light from a black matrix of a color filter substrate and having excellent display image quality in the liquid crystal display panel using a back light. <P>SOLUTION: The liquid crystal display panel 10A includes an array substrate for forming a-SiTFT in each pixel region surrounded by a scanning line and a signal line arranged in the form of a matrix, and a color filter substrate having a black matrix 14 formed at positions corresponding to the scanning line 20, the signal line 21 and TFT and respective stripe color filter layers 15R, 15G, 15B of at least red, green and blue. The surface of the black matrix of the position corresponding to TFT and the positions corresponding to the scanning line 20 and the signal line 21 adjacent to TFT out of the green color filter layer 15G is replaced by the other color color-filter layer 15B'. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention provides a liquid crystal display panel using a backlight, which can be manufactured without significant changes in the conventional manufacturing process, and an amorphous silicon (a-Si) layer caused by reflected light from a black matrix of a color filter substrate. Thin film transistor TFT (Thin Film
The present invention relates to a liquid crystal display panel with reduced display light leakage current and good display image quality.

A TFT using a-Si is widely used as a switching element of a liquid crystal display panel because the manufacturing process can be performed at a low temperature. Since this a-Si generates a photocurrent when it is exposed to light, it is usually formed as an inverted stagger type TFT in which the gate electrode is on the lower side and the a-Si layer is on the upper side of the gate electrode. Is shielded by the gate electrode so that the light from the backlight does not directly hit the a-Si layer.

However, in recent years, since a bright display has been demanded also in a liquid crystal display panel, a light source with higher luminance (for example, 10000 cd or more) has been used as a backlight. However, when such a high-brightness backlight is used, light leakage current generated in the TFT due to stray light, reflected light, or the like increases in proportion to the brightness of the backlight.

In particular, the light in the green region, which has the highest human visibility, is a color that can be perceived by the human eye even with slight color development. Therefore, if the TFT leaks light, the light in the green region with high visibility is felt strongly.
For example, in the case of black display, the light leakage current of such a TFT is greenish black in a normally white liquid crystal display panel, and is purple black in a normally black liquid crystal display panel. End up. In the case of white display, in a liquid crystal display panel using color filters of the three primary colors R, G, and B, the green color is relatively reduced when white display is performed. And red become prominent and appear as a purple-white display defect.

In order to reduce the light leakage current of such a TFT, the following Patent Documents 1 to 3 disclose liquid crystal display panels in which a light shielding film larger than the TFT is formed on the transparent substrate side. Patent Document 4 listed below does not describe TFT light leakage current, but discloses a liquid crystal display panel in which TFT channel formation region is covered with a red color filter layer to prevent TFT deterioration due to light. ing.
JP-A-9-90409 JP 2000-47254 A JP 2000-298290 A JP 2006-126855 A

If a light-shielding film larger than the TFT is formed on the transparent substrate side as in the liquid crystal display panels disclosed in Patent Documents 1 to 3, light directly incident on the TFT from the backlight is effectively shielded by the light-shielding film. Therefore, the light leakage current of the TFT can be reduced. However, in recent portable devices typified by mobile phones, the size of individual pixels has become very small with the progress of high definition.

When a light shielding film is formed on the transparent substrate side in such a small pixel, this light shielding film is a TFT.
Therefore, the light from the backlight in the area used for display is also blocked, resulting in a decrease in luminance. In addition, if the formation position of the light-shielding film is slightly shifted due to mask displacement or the like, the luminance of one pixel is lowered by that amount.

Further, it has been found that when a high-brightness backlight is used, a light leakage current flows through the TFT also by reflected light from the black matrix on the color filter substrate side.
This phenomenon will be described with reference to FIGS.

5 is a plan view of several pixels as viewed from the color filter substrate side of the conventional liquid crystal display panel, FIG. 6 is a plan view of the black matrix of FIG. 5, and FIG. FIG.
FIG. 7B is a schematic cross-sectional view taken along the line C′-C ′ of FIG. 5, and FIG. 7C is a diagram showing the incident light reflected on the TFT. FIG. 2 is an enlarged schematic cross-sectional view for one pixel in order to explain the principle to perform.

The liquid crystal display panel 10C includes an a-Si layer 1 in each pixel region on a transparent substrate 11 such as glass.
2 (see FIG. 7C) is provided with an array substrate AR on which a thin film transistor TFT is formed. The configuration of the thin film transistor TFT having the a-Si layer 12 is an inverted stagger type a
Since it is known as -Si TFT, its detailed description is omitted. Another transparent substrate 1
3, a black matrix 14 made of, for example, chrome metal is formed at positions corresponding to the scanning lines 20, the signal lines 21, and the TFTs of the array substrate AR, and the black matrix 14 and a region surrounded by the black matrix 14 are formed. For example, three color filter layers 15R, 15G, and 15B of R, G, and B are formed in stripes.

As apparent from the description of FIGS. 5, 7 </ b> A, and 7 </ b> B, the black matrix 14 corresponds to the scanning lines 20, the signal lines 21, and the TFTs of the array substrate AR on the surface of the transparent substrate 11. It is formed to shield the position. Further, as shown in FIG. 6, the color filter layers 15R, 15G, and 15B are formed in stripes so that each of R, G, and B partially overlaps the black matrix 14.

In this liquid crystal display panel 10C, as shown in FIG. 7C, when incident light from a backlight (not shown) hits the black matrix 14, a part of the incident light is reflected and a- of the TFT. The light enters the Si layer 12. Therefore, as the luminance of the backlight increases, the light leakage current of the TFT increases in proportion thereto.

The light-shielding film of the liquid crystal display panel disclosed in the above Patent Documents 1 to 3 is not limited to the backlight.
Since it is intended to block light that goes directly to the FT side, none of them can cope with the reflected light from the black matrix on the color filter substrate side as described above.

On the other hand, in the liquid crystal display panel disclosed in Patent Document 4, the surface of the TFT is covered with a red color filter layer. Therefore, since this red color filter layer can absorb the reflected light from the black matrix on the color filter substrate side to some extent, the light leakage current of the TFT due to the reflected light can be temporarily suppressed. However, an extra process is required to form a red color filter layer on the surface of the TFT, which leads to an increase in manufacturing steps and cost.

In addition, it is possible to reduce the reflected light by applying a surface treatment to the black matrix made of chromium metal. In this case, however, it is necessary to change the manufacturing process, and in some cases, it is necessary to modify the device. So it is difficult to adopt it immediately. It is also conceivable to use a resin black matrix having a lower reflectance than the chromium metal black matrix, but in this case as well, a significant change in the manufacturing process is required.

The present invention has been made in order to solve the above-described problems of the prior art, and can be manufactured in a liquid crystal display panel using a backlight, particularly without significant change in the conventional manufacturing process. An object of the present invention is to provide a liquid crystal display panel having a good display image quality, in which a light leakage current of a TFT caused by reflected light from a black matrix or a color filter of a substrate is reduced.

In order to achieve the above object, a liquid crystal display panel according to the present invention includes an array substrate on which thin film transistors each having an amorphous silicon layer are formed in each pixel region surrounded by scanning lines and signal lines arranged in a matrix, and the scanning lines. A color having a black matrix formed at a position corresponding to the signal line and the thin film transistor, and at least red, green, and blue color filter layers formed on the black matrix and in a region surrounded by the black matrix In the liquid crystal display panel including the filter substrate, the surface of the black matrix at the position corresponding to the thin film transistor and the position corresponding to the signal line and the scanning line adjacent to the thin film transistor in the green color filter layer That the color filter layer of the color is replaced And butterflies.

The a-Si layer easily absorbs light in the green region. The light in the green region is the region with the highest human visual sensitivity, and is a color that can be perceived by the human eye even with slight color development. On the other hand, R, G, B 3
In a liquid crystal display panel using a primary color filter layer, the R filter layer transmits light in the red region, but absorbs light in the green region and blue region. The G filter layer transmits light in the green region, but absorbs light in the red region and blue region. Similarly, the B filter layer transmits light in the blue region, but absorbs light in the red region and green region.

As described above, the color filter layer of the other color formed on the green color filter layer absorbs light in the green region, and therefore, the light in the green region of the reflected light reaching the surface of the TFT is reduced.
Light emission of each pixel region due to the light leakage current of FT is reduced. The present invention can be applied not only to a liquid crystal display panel using three primary color filters as described above, but also to a liquid crystal display panel using four or more color filters.

In addition, since the liquid crystal display panel of the present invention uses a color filter substrate in which a part of the G color filter layer is replaced with a color filter layer of another color, the manufacturing process of the conventional color filter substrate is almost changed. You don't have to.

The liquid crystal display panel of the present invention is equally applicable as long as it uses a backlight such as a transflective liquid crystal display panel as well as a transmissive liquid crystal display panel. Furthermore, not only the TN (Twisted Nematic) type liquid crystal display panel, which has been widely used, but also the VA (Vertical Alignment) type liquid crystal display panel and MVA (Multi-domain Vertica).
l Alignment type liquid crystal display panels are equally applicable.

In the liquid crystal display panel of the present invention, it is preferable that the surface of the black matrix at the position corresponding to the scanning line in the green color filter layer is replaced with a color filter layer of another color. In the liquid crystal display panel of the present invention, the green color filter layer can be replaced with another color filter layer only at positions corresponding to the signal lines and scanning lines adjacent to the TFT. However, when all the positions corresponding to the scanning lines are replaced with color filter layers of other colors, the best effect is obtained.

In the liquid crystal display panel of the present invention, the size of the color filter layer of the other color is preferably smaller than the black matrix at the corresponding position. This is because if the color filter layer of the other color protrudes slightly beyond the black matrix, the light that passes through the color filter layer of the other color increases, which affects the green color.

In the liquid crystal display panel of the present invention, the color filter layer of the other color is preferably a blue color filter layer. The a-Si layer easily absorbs light in the green region, but light in the blue region is less likely to absorb than light in the green region. Further, since the blue color filter layer has a low light transmittance, the intensity of the reflected light can be further reduced. Therefore, when a blue color filter layer is used as the color filter layer of another color, the effect of the present invention is remarkably exhibited.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings, taking as an example the case of a transmissive liquid crystal display panel using color filters of three primary colors of RGB. The embodiments described below are not intended to limit the present invention to those described herein, and the present invention can be modified in various ways without departing from the technical idea described in the claims. It can be equally applied to the food.

In the liquid crystal display panels of the following embodiments, the arrangement of the black matrix of the color filter substrate, the arrangement of the scanning lines, signal lines and TFTs of the array substrate are shown in FIGS.
5 is the same as that of the conventional example shown in FIG. 5, and the schematic cross-sectional view of the position corresponding to the line CC in FIG. 5 is the same as that of the conventional example shown in FIG. The detailed configuration of FIG.
), The same components as those of the liquid crystal display panel 10C of the conventional example are denoted by the same reference numerals, and detailed description thereof is omitted.

1 is a plan view of several pixels seen through the black matrix viewed from the color filter substrate side in the liquid crystal display panel 10A of the first embodiment, and FIG. 2A is along the line AA in FIG. FIG. 2B is a schematic cross-sectional view taken along the line A′-A ′ of FIG. 1. FIG. 3 is a plan view of several pixels seen through the black matrix viewed from the color filter substrate side in the liquid crystal display panel 10B of Example 2, and FIG. 4A is along the line BB in FIG. FIG. 4B is a schematic cross-sectional view taken along line B′-B ′ of FIG. 3.

The configuration of the liquid crystal display panel 10A of the first embodiment is different from that of the conventional liquid crystal display panel 10C described above in that the position corresponding to the TFT of the array substrate AR and the scanning line 20 in the G color filter layer 15G. The point is that the G color filter layer provided on the signal line 21 at the position adjacent to the TFT is replaced with the B color filter layer 15B ′.

Since the a-Si layer easily absorbs light in the green region, when the light in the green region hits the a-Si layer of the TFT, the light leakage current is more likely to increase than in the case of light in other color regions. The R filter layer transmits light in the red region, but absorbs light in the green region and blue region. The G filter layer transmits light in the green region, but absorbs light in the red region and blue region. B
The filter layer transmits light in the blue region, but absorbs light in the red region and green region.

Therefore, when the G color filter layer is formed on the black matrix 14, the light from the backlight incident on the G color filter layer 15G is transmitted through the G color filter layer 15G. Since it is absorbed, the green light in the reflected light increases.

Therefore, in the liquid crystal display panel 10A of the first embodiment, in the G color filter layer 15G, the signal line 21 is provided at a position corresponding to the TFT of the array substrate AR, a position corresponding to the scanning line 20, and a position adjacent to the TFT. The G color filter layer is replaced with the B color filter layer 15B ′. With this configuration, the black matrix 1
Since the B color filter layer 15B ′ on 4 absorbs light in the green region, the reflected region has very little light in the green region.

Therefore, in the liquid crystal display panel 10A of Example 1 due to the characteristics of the a-Si layer described above,
Since the light leakage current of the TFT is reduced, a liquid crystal display panel with good display image quality can be obtained. The color filter substrate CF having the pattern as shown in FIG.
Since it can be produced simply by changing the 5G production mask pattern, it can be produced with little change in the production process of the conventional color filter substrate.

In the liquid crystal display panel 10A of Example 1, the size of the replaced color filter layer 15B ′ needs to be smaller than that of the black matrix 14. Theoretically, the size of the replaced color filter layer 15B ′ may be the same as that of the black matrix 14, but when the replaced color filter layer 15B ′ protrudes from the black matrix 14 due to mask displacement or the like, light in the blue region is emitted. It will be transparent. In such a state, since the light in the blue region is mixed with the light in the green region, the green color is adversely affected.

Further, in the liquid crystal display panel 10A according to the first embodiment, the G color filter layer 15G at a position corresponding to the signal line 21 of the array substrate AR is also formed on the black matrix. All the G color filter layers 15G at positions corresponding to the signal lines 21 may be replaced with B color filter layers.

However, since the G color filter layer 15G at the position corresponding to the signal line 21 is formed adjacent to the same black matrix 14 in the other color filter layers,
The width is narrow. It is technically difficult to form such a narrow B color filter layer so as not to protrude from the black matrix. In addition, since the reflected light from a position away from the TFT is difficult to enter the TFT, the influence on the light leakage current of the TFT is small. Therefore, in the liquid crystal display panel 10A of the first embodiment, the G color filter layer at the position corresponding to the signal line 21 adjacent to the TFT is replaced with the B color filter layer 15B ′, but it corresponds to the other signal lines 21. The G color filter layer at the position was not replaced with the B color filter layer.

Further, in the liquid crystal display panel 10A according to the first embodiment, the G provided on the signal line 21 at the position corresponding to the TFT of the array substrate AR, the position corresponding to the scanning line 20, and the position adjacent to the TFT.
In this example, the B color filter layer 15B ′ is replaced with the B color filter layer. However, since the R color filter layer also absorbs light in the green region, even if the R color filter layer is used, the same effects and advantages are obtained. However, since the B color filter layer has a low light transmittance, the intensity of the reflected light can be further reduced. Therefore, the effect is more prominent than when the R color filter layer is used.

In the liquid crystal display panel 10A according to the first embodiment, the color filter layer 15G has the structure shown in FIGS.
As shown in FIGS. 2A and 2B, the position corresponding to the TFT of the array substrate AR, the scanning line 2
In the example, the G color filter layer 15G provided at the position corresponding to 0 and the position corresponding to the signal line 21 adjacent to the TFT is replaced with the B color filter layer 15B ′.
However, since the reflected light from the black matrix portion away from the TFT is difficult to enter the TFT, the place to be replaced by the B color filter layer 15B ′ at the position corresponding to the scanning line 20 is only at the position adjacent to the TFT. There is a good effect.

Therefore, in the liquid crystal display panel 10B of Example 2, among the G color filter layers, FIG.
As shown in FIGS. 4A and 4B, at the position corresponding to the scanning line 20, only the position adjacent to the TFT of the array substrate AR is replaced with the B color filter layer 15B ′. Thus, even if the area replaced by the B color filter layer 15 ′ is smaller than that of the liquid crystal display panel 10A of the first embodiment, the reflected light in the green region from the surface of the black matrix 14 near the G TFT is Since it becomes very weak, the same effect as in the case of the liquid crystal display panel 10A of the first embodiment is obtained.

In Examples 1 and 2, an example of a transmissive liquid crystal display panel is shown. However, the present invention is equally applicable as long as it uses a backlight, such as a transflective liquid crystal display panel.
Furthermore, the present invention is equally applicable not only to TN liquid crystal display panels that have been widely employed, but also to VA liquid crystal display panels and MVA liquid crystal display panels.

In Examples 1 and 2, R is used as the color filter provided on the color filter substrate CF.
However, the present invention is not limited to this, but it is possible to use 4 to 6 colors including at least one of cyan C and magenta M, and more colors. It can also consist of.

In Examples 1 and 2, the example of the color filter formed in a stripe shape is shown. However, the color filter provided on the color filter substrate CF of the present invention includes a color filter in which dots are arranged and a color in which delta arrangement is performed. The filter can also be used for general purposes.

4 is a plan view of several pixels seen through a black matrix viewed from the color filter substrate side in the liquid crystal display panel of Embodiment 1. FIG. It is a schematic cross section along the AA line and A'-A 'line of FIG. 6 is a plan view of several pixels seen through a black matrix viewed from a color filter substrate side in a liquid crystal display panel of Example 2. FIG. It is a schematic cross section along the BB line and B'-B 'line of FIG. It is a top view for several pixels seen from the color filter substrate side of the conventional liquid crystal display panel. FIG. 6 is a plan view seen through the black matrix of FIG. 5. It is a schematic cross section of each part of FIG.

Explanation of symbols

10A to 10C: liquid crystal display panel, 11: transparent substrate: 12: a-Si layer, 13: transparent substrate, 14: black matrix, 15R, 15G, 15B: color filter layer, 20: scanning line, 21: signal line, AR: Array substrate, CF: Color filter substrate

Claims (4)

An array substrate in which a thin film transistor having an amorphous silicon layer is formed in each pixel region surrounded by scanning lines and signal lines arranged in a matrix;
A black matrix formed at positions corresponding to the scanning lines, signal lines and thin film transistors, and at least red, green and blue color filter layers formed on the black matrix and in a region surrounded by the black matrix A color filter substrate having:
In a liquid crystal display panel with
Of the green color filter layer, the surface of the black matrix at a position corresponding to the thin film transistor and a position corresponding to a scanning line and a signal line adjacent to the thin film transistor is replaced with a color filter layer of another color. A characteristic LCD panel. 2. The liquid crystal display panel according to claim 1, wherein a surface of the black matrix at a position corresponding to the scanning line in the green color filter layer is all replaced with a color filter layer of another color. 2. The liquid crystal display panel according to claim 1, wherein the size of the color filter layer of the other color is smaller than a black matrix at a corresponding position. 4. The liquid crystal display panel according to claim 1, wherein the other color filter layer is a blue color filter layer.

Images