JP2005099499A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display having satisfactory display quality. <P>SOLUTION: The liquid crystal display is provided with a liquid crystal display panel 10 having an array substrate 100 having a black matrix BM partitioning pixels provided with color filters CF(R, G, B), a counter substrate 200 disposed opposite to the array substrate 100, and a liquid crystal layer 300 held between the array substrate 100 and the counter substrate 200, a backlight unit 400 with which the liquid crystal panel 10 is illuminated from the rear side of the array substrate, polarizing plates PL1 and PL2 disposed on the outer surfaces of the array substrate 100 and the counter substrate 200, respectively, and at least one diffusion layer DF disposed between the liquid crystal layer side surface of the counter substrate 200 and the outer surface of the polarizing plate PL2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device, and more particularly to a transmissive liquid crystal display device having a diffusion layer introduced to improve display quality.

  The liquid crystal display device includes a liquid crystal display panel configured by sandwiching a liquid crystal layer between an array substrate and a counter substrate. Recently, for the purpose of increasing the aperture ratio, a structure including a color filter layer on an array substrate, that is, a so-called color filter on array (COA) structure has been put into practical use.

  In this COA structure, a color filter layer colored in a color corresponding to each pixel on the array substrate is disposed, and each pixel is partitioned by a black matrix. The black matrix is arranged at substantially equal intervals along the row direction and the column direction of the pixels.

On the other hand, in a simple matrix driving type liquid crystal display device, a technique for forming a diffusion layer having a haze value of 40 to 70% on the display surface side of the liquid crystal display panel has been proposed in order to effectively reduce crosstalk. (For example, refer to Patent Document 1).
JP 2003-66452 A

  In recent years, liquid crystal display devices have been reduced in size and weight, and the opportunity to use them outdoors has increased. In the case of a liquid crystal display device having a COA structure, external light such as sunlight penetrates into the liquid crystal display panel, is reflected by a black matrix arranged at almost equal intervals on the array substrate, and interferes on the screen. A phenomenon occurs in which reflected light is reflected in the extending direction of the black matrix around the light source.

  For example, when an array substrate in which black matrices are arranged at equal intervals along the pixel row direction and column direction is employed, when the liquid crystal display device is observed outdoors, the cross direction is centered on sunlight as shown in FIG. In some cases, interference light may be reflected on the display, which may deteriorate the display quality.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a liquid crystal display device with good display quality.

A liquid crystal display device according to an aspect of the present invention
An array substrate having a black matrix for partitioning a pixel having a color filter layer; a counter substrate disposed opposite to the array substrate; and a liquid crystal layer sandwiched between the array substrate and the counter substrate; A liquid crystal display panel having
A backlight unit that illuminates the liquid crystal display panel from the back side of the array substrate;
Polarizing plates respectively disposed on the outer surfaces of the array substrate and the counter substrate;
At least one diffusion layer disposed between the liquid crystal layer side surface of the counter substrate and the outer surface of the polarizing plate;
It is provided with.

  According to the present invention, a liquid crystal display device with good display quality can be provided.

  A liquid crystal display device according to an embodiment of the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, a liquid crystal display device, for example, an active matrix liquid crystal display device includes a transmissive liquid crystal display panel 10. The liquid crystal display panel 10 is configured by sandwiching a liquid crystal composition between a pair of substrates. That is, the liquid crystal display panel 10 includes an array substrate 100, a counter substrate 200 disposed opposite to the array substrate 100, and a liquid crystal layer 300 including liquid crystal molecules disposed between the array substrate 100 and the counter substrate 200. And.

  The array substrate 100 and the counter substrate 200 are bonded together by the seal member 11 while forming a predetermined cell gap for sandwiching the liquid crystal layer 300. The liquid crystal layer 300 is composed of a liquid crystal composition sealed between the array substrate 100 and the counter substrate 200.

  Such a liquid crystal display panel 10 includes an effective display section 12 that displays an image inside the area surrounded by the seal member 11. The effective display unit 12 includes a plurality of pixels PX (R, G, B) arranged in a matrix. These pixels include a red pixel PXR, a green pixel PXG, and a blue pixel PXB.

  Each pixel PX (R, G, B) has basically the same structure, but includes a colored layer, that is, a color filter layer colored in a corresponding color. That is, the pixel PXR includes a color filter layer made of a red resin material. The pixel PXG includes a color filter layer made of a green resin material. The pixel PXB includes a color filter layer made of a blue resin material.

  Further, the liquid crystal display panel 10 includes a frame-shaped light shielding portion 13 along the outer periphery of the effective display portion 12. The light shielding portion 13 includes a light shielding layer formed of a resin material having a light shielding property.

  Further, the liquid crystal display panel 10 includes a circuit unit 14 around the effective display unit 12. The circuit unit 14 includes at least a part of a driving circuit. Here, the scanning line driving circuit 18 supplies driving signals (scanning signals) to the m scanning lines Y1 to Ym, and the n signal lines X1. The signal line drive circuit 19 for supplying drive signals (video signals) to .about.Xn.

  In the effective display unit 12, the array substrate 100 includes m scanning lines Y1 to Ym, n signal lines X1 to Xn, m × n switching elements 121, m × n pixel electrodes 151, and the like. Yes. Further, in the effective display unit 12, the counter substrate 200 includes a counter electrode 204 common to all the pixels PX.

  Each scanning line Y (1 to m) extends along the row direction of the pixel PX. Each signal line X (1 to n) extends along the column direction of the pixels PX. Each switching element 121 is disposed in the vicinity of the intersection between the scanning line Y and the signal line X in each pixel PX.

  The gate electrode 121G of the switching element 121 is connected to the scanning line Y (or formed integrally with the scanning line Y). The drain electrode 121D of the switching element 121 is in contact with the drain region of the semiconductor layer and connected to the signal line X (or formed integrally with the signal line X). The source electrode 121S of the switching element 121 is in contact with the source region of the semiconductor layer and is connected to the pixel electrode 151.

  The pixel electrodes 151 are independent for each pixel and are arranged in a matrix in the effective display unit 12. Each pixel electrode 151 is connected to the switching element 121 in each pixel PX. The pixel electrode 151 is formed of a light-transmitting conductive member such as ITO (indium tin oxide).

  The counter electrode 204 is disposed in common for all the pixels PX, and faces all the m × n pixel electrodes 151 through the liquid crystal layer 300. The counter electrode 204 is formed of a light-transmitting conductive member such as ITO.

  That is, as shown in FIG. 2, the liquid crystal display device includes a transmissive liquid crystal display panel 10 and a backlight unit 400 that illuminates the liquid crystal display panel 10 from the back side of the array substrate 100.

  In the transmissive liquid crystal display panel 10 having the structure shown in FIG. 2, the array substrate 100 is configured using a light-transmissive insulating substrate 101 such as a glass substrate. In the effective display unit 12, scanning lines, signal lines, etc. Various wirings, switching elements, pixel electrodes, and the like. Furthermore, the array substrate 100 includes a red color filter layer CFR, a green color filter layer CFG, and a blue color filter layer CFB, which are arranged in the red pixel PXR, the green pixel PXG, and the blue pixel PXB, respectively, and a black matrix BM that partitions the respective pixels. , An alignment film 103 disposed so as to cover the entire effective display portion 12 is provided. The black matrix BM is arranged at substantially equal intervals along the row direction and the column direction of the pixels PX.

  On the other hand, the counter substrate 200 is configured using a light-transmitting insulating substrate 201 such as a glass substrate. The effective display unit 12 includes a counter electrode and the like, and further covers the entire effective display unit 12. An alignment film 205 and the like are provided.

  In the liquid crystal display panel 10, a polarizing plate PL1 is provided on the outer surface of the array substrate 100. A polarizing plate PL <b> 2 is provided on the outer surface of the counter substrate 200. Further, at least one diffusion layer DF is disposed between the surface of the counter substrate 200 on the liquid crystal layer 300 side (the surface of the alignment film 205 in the example shown in FIG. 2) and the outer surface of the polarizing plate PL2. Yes. The diffusion layer DF has a function of diffusing transmitted light transmitted through the liquid crystal layer 300 in a random direction.

  In the liquid crystal display device including such a transmissive liquid crystal display panel 10, the light emitted from the backlight unit 400 illuminates the liquid crystal display panel 10 from the back side of the array substrate 100. Light that has entered the liquid crystal display panel 10 through the polarizing plate PL1 on the array substrate 100 side in the liquid crystal display panel 10 is modulated via the liquid crystal composition 300 and is selectively selected by the polarizing plate PL2 on the counter substrate 200 side. Is transmitted through. As a result, an image is displayed in the display area 102 of the liquid crystal display panel 10.

  When such a liquid crystal display device is used outdoors, even if external light such as sunlight enters the liquid crystal display device and is reflected by the black matrix BM on the array substrate 100, it passes through the diffusion layer DF. The traveling direction of the light is dispersed, and the reflected light after passing through the diffusion layer DF is diffused. Therefore, even if this diffused light reaches the screen, the diffusion direction is random and random, and interference by the diffused light is suppressed. For this reason, it is possible to realize excellent display quality with little reflection due to light interference even outdoors.

  The diffusion layer DF described above is desirably disposed on the polarizing plate PL2 side on the counter substrate 200 in order to sufficiently suppress the reflection of the external light source. In the embodiment shown in FIG. 2, the diffusion layer DF is arranged between the counter substrate 200 and the polarizing plate PL2. The diffusion layer DF may be formed integrally with the polarizing plate PL2, or may be provided as a film or thin film separate from the polarizing plate PL2.

  For example, the polarizing plate PL2 shown in FIG. 3 includes two protective layers 501 and 502, and further includes an analyzer 503 disposed between the protective layers 501 and 502 and the outside of the protective layer 501. An adhesive layer 504 disposed on the surface is provided. The adhesive layer 504 contains a diffusion material having a light diffusion function in addition to the adhesive, and also has a function as the diffusion layer DF. By bonding the polarizing plate PL2 to the outer surface of the counter substrate 200 via the adhesive layer 504, the diffusion layer DF is disposed between the counter substrate 200 and the analyzer 503 of the polarizing plate PL2.

  As a result, compared to the case where the diffusion layer is provided separately, the thickness of the entire liquid crystal display device can be reduced, the number of manufacturing steps can be reduced, and the cost can be reduced. .

  Note that the diffusion layer DF is not limited to the polarizing plate PL2 side on the counter substrate 200, and may be disposed between the insulating substrate 201 and the counter electrode 204, or the counter electrode 204 has a light diffusion function. And may have a function as a diffusion layer DF.

  Further, the diffusion layer DF applied here may be configured to have directivity. In particular, it is desirable that the diffusion layer DF has a preference that has a high degree of diffusion in a direction orthogonal to the direction in which the black matrix BM extends.

  That is, the diffusion layer DF has a characteristic that the diffusion degree of the light incident on the diffusion layer DF at a predetermined incident angle after passing through the liquid crystal layer 300 is higher than the light incident on the other incident angles. Such a diffusion layer DF is incident on the diffusion layer DF from a tilt angle that falls in a predetermined axial direction with respect to the normal of the diffusion layer DF when the diffusivity of transmitted light transmitted in one direction is defined by a haze value. Based on the relationship between the incident angle of the incident light and the diffusivity of the emitted light emitted from the diffusion layer DF, that is, the haze value, the maximum value of the haze value is set at a predetermined incident angle.

  The haze value is measured using a haze measuring device 3 as shown in FIG. That is, the light source 4 is disposed on the opposite side to the haze measuring device 3 with the diffusion layer DF interposed therebetween. Further, the haze measuring device 3 is fixed in the normal direction Z of the diffusion layer DF. When the light source 4 is tilted at a tilt angle θ in the predetermined axial direction P with respect to the normal Z of the diffusion layer DF, the haze value of the transmitted light that has passed through the diffusion layer DF is measured by the haze measuring device 3.

  The predetermined incident angle at which the haze value has a maximum value is preferably set in the vicinity of the reflection angle at which the reflected light from the black matrix BM interferes. Where the predetermined incident angle is set, and what is the haze value at that time? Whether to set is appropriately determined according to the specification of the liquid crystal display panel.

  The greater the haze value, the greater the effect of suppressing optical interference. However, when the haze value is set to a large diffusivity exceeding 90%, the characters appear blurred when the character is displayed, or the front brightness decreases. Problems occur. Further, when the maximum value of the haze value is less than 5%, the light interference suppression effect is reduced, and an external light source or interference light is reflected. Therefore, the haze value is desirably 5% or more and 90% or less, and more desirably 20% or more and 60% or less.

  Furthermore, it is desirable that the haze value of the diffusion layer DF applied here is set to be larger than the haze value of the polarizing plate PL <b> 2 itself disposed on the outer surface of the counter substrate 200. That is, a light diffusing layer is provided on the outer surface of the polarizing plate PL2 in order to prevent reflection of an external light source or interference light on the screen of the liquid crystal display panel. From this point of view, it is desired to eliminate this light diffusion layer. Accordingly, the light diffusion performance of the polarizing plate PL2 itself is low, and naturally the haze value is also small.

  Therefore, by disposing a diffusion layer DF having a haze value larger than that of the polarizing plate PL2 itself between the polarizing plate PL2 and the counter substrate 200, reflection of an external light source and interference light is sufficiently suppressed. It becomes possible to do.

  As described above, the liquid crystal display device according to this embodiment includes a COA-structure transmissive liquid crystal display panel having a color filter layer and a black matrix on an array substrate, and the liquid crystal layer side of the counter substrate. At least one diffusion layer is provided between the surface and the outer surface of the polarizing plate.

  For this reason, even if a polarizing plate that does not have a diffusion layer on the surface is applied to the outer surface on the counter substrate side from the viewpoint of improving image contrast or a clear appearance, external light enters the liquid crystal display panel. When reflected by the black matrix on the array substrate, the reflected light is diffused by passing through the diffusion layer, and does not interfere on the screen, realizing excellent display performance with little reflection due to light interference even outdoors. it can.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the spirit of the invention in the stage of implementation. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

FIG. 1 schematically shows a configuration of a liquid crystal display device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing the structure of the effective display portion of the liquid crystal display device shown in FIG. FIG. 3 is a cross-sectional view schematically showing the structure of a polarizing plate applicable to the liquid crystal display device shown in FIG. FIG. 4 is a diagram for explaining the principle for measuring the haze value of the diffusion layer. FIG. 5 is a diagram schematically illustrating an example of reflection of an external light source or interference light on the screen.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Liquid crystal display device, 12 ... Effective display part, 100 ... Array substrate, 103 ... Orientation film, 200 ... Opposite substrate, 205 ... Orientation film, 300 ... Liquid crystal layer, PL1 ... Polarizing plate, PL2 ... Polarizing plate, DF ... Diffusion Layer, BM ... Black matrix

Claims (10)

An array substrate having a black matrix for partitioning a pixel having a color filter layer; a counter substrate disposed opposite to the array substrate; and a liquid crystal layer sandwiched between the array substrate and the counter substrate; A liquid crystal display panel having
A backlight unit that illuminates the liquid crystal display panel from the back side of the array substrate;
Polarizing plates respectively disposed on the outer surfaces of the array substrate and the counter substrate;
At least one diffusion layer disposed between the liquid crystal layer side surface of the counter substrate and the outer surface of the polarizing plate;
A liquid crystal display device comprising:   The liquid crystal display device according to claim 1, wherein the diffusion layer is disposed on the polarizing plate side on the counter substrate.   The liquid crystal display device according to claim 2, wherein the diffusion layer is disposed between the counter substrate and the polarizing plate.   The liquid crystal display device according to claim 3, wherein the diffusion layer is an adhesive layer for adhering the polarizing plate to an outer surface of the counter substrate.   The liquid crystal display device according to claim 1, wherein the diffusion layer diffuses transmitted light transmitted through the liquid crystal layer in a random direction.   2. The liquid crystal display according to claim 1, wherein the diffusion layer has a higher diffusivity of light incident on the diffusion layer at a predetermined incident angle after passing through the liquid crystal layer than light incident on another incident angle. apparatus.   The liquid crystal display device according to claim 1, wherein the diffusion layer has a haze value of 5% or more and 90% or less.   The liquid crystal display device according to claim 1, wherein a haze value of the diffusion layer is larger than a haze value of the polarizing plate disposed on an outer surface of the counter substrate.   2. The liquid crystal display device according to claim 1, wherein the diffusion layer is disposed between an insulating substrate constituting the counter substrate and a counter electrode disposed on the liquid crystal layer side of the insulating substrate.   The liquid crystal display device according to claim 1, wherein the diffusion layer is included in a counter electrode disposed on the liquid crystal layer side of the counter substrate.

Images