JPH10148832A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the visual angle characteristics of a liquid crystal display device of an active matrix type much better than those of conventional liquid crystal display devices, to black display the parts to be displayed black and to improve a contrast. SOLUTION: This liquid crystal display device has liquid crystal panel 100 of an orientation division structure comprising a pair of transparent substrates 11, 12, liquid crystals 18 encapsulated between these substrates, pixel electrodes 14, counter electrodes 25 and oriented films 16, 17 an optically isomeric film 21 which has an optical characteristic of nx>ny=nz is disposed on the outer side of this liquid crystal panel 100 is such a manner that its delay phase axis overlaps on the same direction as the rubbing direction of the oriented film 16 nearer the liquid crystal panel 100 and polarizing plates 19, 20 which are so arranged that the directions of the each other's absorption axes intersect with each other so as to hold the liquid crystal panel 100 provided with this film 21. The retardation (Δnd value) of the film 21 is specified to 20 to 200nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to an active matrix type TN type liquid crystal display device in which the potential of each pixel is controlled by an active element.

[0002]

2. Description of the Related Art Liquid crystal display devices are widely used in various electronic devices because they are thin and lightweight, can be driven at a low voltage, and consume little power. In particular, in recent years, TFT (Th
In an active matrix type liquid crystal display device in which an active element such as an in-film transistor is provided for each pixel, an excellent display quality can be obtained comparable to a CRT (cathode-ray tube). For example, it is used for displays of portable televisions, personal computers, and the like.

In general, a liquid crystal display device has a structure in which liquid crystal is sandwiched between two transparent substrates. Of the two opposing surfaces (opposing surfaces) of the transparent substrate, an opposing electrode and an alignment film are formed on one surface side, and an active matrix circuit, a pixel electrode and an alignment film are formed on the other surface side. A film or the like is formed. Further, a polarizing plate is attached to a surface of each transparent substrate opposite to the opposite surface. These two polarizing plates are arranged such that, for example, the absorption axes (directions perpendicular to the polarization direction) of the polarizing plates are orthogonal to each other. According to this, light is transmitted when no electric field is applied, In the state where is applied, the mode becomes a light-shielding mode, that is, a normally white mode. On the contrary, 2
When the absorption axes of the polarizing plates are parallel, a normally black mode is set.

The active matrix type liquid crystal display device generally has a poor viewing angle characteristic as compared with a CRT, that is, has a drawback that the contrast changes depending on the viewing angle of the screen. To improve this,
A liquid crystal display device having an alignment division structure in which one pixel is divided into two regions and the alignment directions of liquid crystal molecules in each region are different from each other has been proposed.

FIG. 29 is a plan view showing a conventional liquid crystal display device of this type, and FIG. 30 is a cross-sectional view taken along line YY of FIG. The glass substrates 1 and 2 are arranged to face each other, and a liquid crystal 8 is sealed between the substrates 1 and 2. A plurality of pixel electrodes 4 are arranged in a matrix on the lower glass substrate 1. Between each pixel electrode 4, a data bus line 3A and a gate bus line 3B are formed so as to intersect at right angles. The TFT 3 is located near the intersection between the data bus line 3A and the gate bus line 3B.
Are arranged. An alignment film 6 is formed on the substrate 1 so as to cover the gate bus line 3B, the TFT 3, the pixel electrode 4, and the like.

A color filter 2A is formed below the upper glass substrate 2. The color filter 2A has one of the colors red (R), blue (B), or green (G) for each pixel. A counter electrode 5 is provided below the color filter 2A, and an alignment film 7 is provided below the counter electrode 5. The alignment films 6 and 7 are made of, for example, polyimide, and are subjected to a so-called rubbing treatment in which the surfaces are rubbed with a roll to which a cloth such as rayon is adhered. In the liquid crystal display device of the alignment division structure, one pixel is divided into two regions I and II.
The directions A and B in which the liquid crystal molecules rise in the two regions I and II of one pixel are opposite to each other. TN (Twis
In a ted Nematic) type liquid crystal display device, two alignment films 6 and 7 are arranged so that their rubbing directions are orthogonal to each other when viewed from above.

[0007] The glass substrates 1 and 2 are arranged with a spherical spacer (not shown) interposed therebetween for keeping the interval between them constant. Further, polarizing plates 9 and 10 are provided on the lower surface side of the substrate 1 and the upper surface side of the substrate 2, respectively. FIG.
1 (A) and (B) are diagrams schematically showing liquid crystal molecules 8A between substrates 1 and 2 of a liquid crystal display device having an alignment division structure, and FIG. 31 (A) shows that a voltage is applied between electrodes. FIG. 31B shows a state where a voltage is applied. However,
Actually, the liquid crystal molecules 8 are formed between the pixel electrode 4 side and the counter electrode 5 side.
Although the arrangement direction of A is twisted by 90 °, FIG. 31 shows the liquid crystal molecules 8A in an untwisted state for easy understanding.

[0008] As shown in FIG.
Are oriented according to the rubbing directions of the alignment films 6 and 7, and are inclined at a certain angle α. The angle α is called a pretilt angle, and differs depending on a constituent material of the alignment film. In a TN-type liquid crystal display device in which polarizing plates 9 and 10 are orthogonally arranged, two alignment films 6 and 6 are provided.
The liquid crystal molecules 8 </ b> A between 7 change the alignment direction spirally from one glass substrate 1 to the other glass substrate 2. When the voltage between the pixel electrode 4 and the counter electrode 5 is gradually increased, the liquid crystal molecules 8A start rising in the direction of the electric field at a certain voltage (threshold), and when a sufficient voltage is applied, As shown in FIG. 31B, the liquid crystal molecules 8A are almost perpendicular to the substrates 1 and 2. That is, the liquid crystal molecules 8A change from a state almost parallel to the substrates 1 and 2 to a state almost perpendicular to the substrates 1 and 2 according to the applied voltage, and the transmittance of light transmitted through the liquid crystal display device changes accordingly. Accordingly, the light transmittance can be controlled for each pixel, and a desired image can be displayed on the liquid crystal display device.

FIG. 3 shows a TV (transmittance-voltage) characteristic in a normally white mode of such a liquid crystal display device.
It is shown in FIG. In FIG. 32, a solid line a represents a TV characteristic when the liquid crystal display device having the alignment division structure is viewed from the front. The dashed line b shows the TV characteristics when the line of sight is tilted 40 ° downward in a normal liquid crystal display device having no alignment division structure. The dashed line c is the TV characteristic when the line of sight of the ordinary liquid crystal display device is inclined by 40 ° in the upward direction. A two-dot chain line d is a TV characteristic when the liquid crystal display device having the alignment division structure is viewed from above or below 40 °. The TV characteristic of d is obtained by averaging the downward TV characteristic and the upward TV characteristic of a normal liquid crystal display device. That is, in the characteristic of d, the transmittance on the high voltage side is lower than that of the characteristic of c, and the hump-like characteristic seen in the characteristic of b is not observed. Therefore, in the liquid crystal display device of the alignment division structure, since the amount of change in the optical characteristics when the viewing angle is changed is smaller than that of a normal liquid crystal display device, the viewing angle characteristics when the liquid crystal panel is viewed from above and below are remarkable. Be improved.

[0010]

However, in the conventional liquid crystal display device of the normally white mode and the alignment division structure, even if the viewing angle characteristics when the liquid crystal panel is viewed from above and below can be improved, the right and left directions can be improved. It is difficult to improve the viewing angle characteristics when viewing the liquid crystal panel from the direction. Note that Japanese Patent Application Laid-Open
JP-A-118406 proposes to superpose an optically anisotropic film exhibiting positive uniaxiality on a liquid crystal panel in order to improve the viewing angle characteristics of a liquid crystal display device having a normally black mode and an alignment division structure. I have. Then, when the retardation value is Δnd, 100 ≦ Δnd ≦ 40
It is shown that a 0 nm optically anisotropic film is used. However, since the wavelength characteristic of the liquid crystal material is greatly affected at the time of black display, there is a problem that a portion that should be black is colored or a contrast when the liquid crystal panel is viewed from the front is reduced. .

The present invention has been made in view of the above-mentioned problems of the prior art, and has more excellent viewing angle characteristics than a conventional liquid crystal display device, and can display a portion to be displayed black in black. It is an object of the present invention to provide a liquid crystal display device having good contrast.

[0012]

SUMMARY OF THE INVENTION The above-mentioned objects are attained by providing a pair of transparent substrates disposed to face each other, a liquid crystal sealed between the pair of transparent substrates, and each of the opposing surfaces of the pair of transparent substrates. And a first and a second alignment film that are processed so that liquid crystal molecules rise in opposite directions in first and second regions that divide one pixel into two, and An optically anisotropic film disposed on one of the outer surfaces of the liquid crystal panel and having a slow axis overlapping in the same direction as the rubbing direction of the closer one of the first and second alignment films. A pair of polarizing plates sandwiching the optically anisotropic film and the liquid crystal panel and arranged so that the directions of absorption axes are orthogonal to each other, and the optically anisotropic film has x, x in orthogonal coordinates. The refractive index in the y and z axis directions is nx, y, when the nz, nx> ny =
a first liquid crystal having an optical characteristic represented by nz and a retardation (Δnd value) represented by (nx−ny) · d of 20 to 200 nm, where d is a thickness of the first liquid crystal. Solved by the display device.

[0013] The above object is achieved by disposing a pair of transparent substrates arranged opposite to each other, a liquid crystal sealed between the pair of transparent substrates, and an opposing surface of the pair of transparent substrates.
In the first and second regions that divide one pixel into two, the first and second regions are processed so that liquid crystal molecules rise in directions opposite to each other.
And a second alignment film, and a liquid crystal panel arranged on both sides of the liquid crystal panel, and is delayed in the same direction as the rubbing direction of the closer alignment film of the first and second alignment films. A pair of optically anisotropic films where the phase axes overlap,
A pair of polarizing plates sandwiching the optically anisotropic film and the liquid crystal panel and arranged so that the directions of the absorption axes are orthogonal to each other, wherein the optically anisotropic film has x, y in orthogonal coordinates. , Ny, nz
Has the optical property represented by nx> ny = nz, and when its thickness is d, the retardation (Δnd value) represented by (nx−ny) · d is 20 to 100.
The problem is solved by the second liquid crystal display device characterized in that it is nm.

[0014] The above object is achieved by disposing a pair of transparent substrates disposed opposite to each other, a liquid crystal sealed between the pair of transparent substrates, and a pair of transparent substrates disposed on respective opposing surfaces of the pair of transparent substrates.
In the first and second regions that divide one pixel into two, the first and second regions are processed so that liquid crystal molecules rise in directions opposite to each other.
And a second alignment film, and a liquid crystal panel arranged on both sides of the liquid crystal panel, in a direction orthogonal to the rubbing direction of the closer one of the first and second alignment films. A pair of optically anisotropic films having a slow axis overlapping each other, and a pair of polarizing plates sandwiching the optically anisotropic film and the liquid crystal panel, and arranged with the directions of the absorption axes orthogonal to each other; The optically anisotropic film has a refractive index of nx, n in the x, y, and z axis directions in orthogonal coordinates.
When y and nz are used, the optical characteristics are represented by nx>ny> nz, and when the thickness is d, [(nx + n
y) / 2-nz] · d (Δ
n'd value) is 70 to 150 nm.

In the third liquid crystal display device, preferably, the optically anisotropic film is (nx-nz) / (n
An Nz value represented by (x-ny) is 1.2 to 1.85. Hereinafter, the operation of the present invention will be described. The present inventors have conducted various experiments on the characteristics and arrangement conditions of an optically anisotropic film in a liquid crystal display device of a normally white mode having an alignment division structure, and have obtained the following knowledge.

In the first liquid crystal display device of the present invention, an optically anisotropic film having optical characteristics of nx> ny = nz is disposed between the light incident side polarizing plate and the liquid crystal panel. When the thickness of this optically anisotropic film is d, (nx−n
y) When the range of the retardation (Δnd value) indicated by d is 20 to 200 nm, the isocontrast curve is shifted rightward and leftward as compared with a conventional liquid crystal display device without an optically anisotropic film. Expanding.

Thus, the viewing angle characteristics of the liquid crystal display device of the present invention can be improved as compared with the conventional liquid crystal display device. Further, in the second liquid crystal display device of the present invention, nx> ny = nz is provided between the light incident side polarizing plate and the liquid crystal panel.
The first optically anisotropic film having the above optical characteristics is disposed, and the second optically anisotropic film having the above optical characteristics is disposed between the polarizing plate on the light emission side and the liquid crystal panel. When the thickness of these optically anisotropic films is d, when the range of the retardation (Δnd value) indicated by (nx−ny) · d is 20 to 100 nm,
Compared to a conventional liquid crystal display device without an optically anisotropic film, the isocontrast curve is about 10 ° in polar angle.
It can be expanded to the left and right. Thereby, the viewing angle characteristics can be improved as in the first liquid crystal display device.

Further, in the third liquid crystal display device of the present invention,
Nx>ny> between the light incident side polarizing plate and the liquid crystal panel
A first optically anisotropic film having optical characteristics of nz is disposed, and a second optically anisotropic film having the above-mentioned optical characteristics is disposed between the polarizing plate on the light emission side and the liquid crystal panel. . When the thickness of these optically anisotropic films is d, the retardation (Δn′d value) represented by [(nx + ny) / 2−nz] · d is 70 to 150 nm, Compared to a conventional liquid crystal display device without an anisotropic film, the isocontrast curve can be expanded to the left and right by about 10 to 15 ° in polar angle.

The Nz value is preferably set to 1.2 to 1.85.

[0020]

Embodiments of the present invention will be described below with reference to the accompanying drawings. (1) First Embodiment FIG. 1 is a plan view showing a normally white mode liquid crystal display device with an orientation division structure according to a first embodiment of the present invention. FIG. 2 is a sectional view taken along line XX of FIG.

The liquid crystal panel 100 includes glass substrates (transparent substrates) 11 and 12 which are arranged to face each other, and
The liquid crystal 18 is enclosed between the first and the second liquid crystal 12.
Pixel electrodes 14 are arranged in a matrix on the glass substrate 11, and a data bus line 13A and a gate bus line are provided between the pixel electrodes 14 on the glass substrate 11.
13B are formed to intersect at right angles. A TFT 13 is formed near the intersection of the data bus line 13A and the gate bus line 13B.
The drain of the TFT 13 is connected to the data bus line 13A, the gate is connected to the gate bus line 13B, and the source is connected to the pixel electrode 14. The TFT 13 and the data bus line are provided on the glass substrate 11.
An alignment film 16 is formed so as to cover 13A, the gate bus line 13B, and the pixel electrode 14. The area surrounded by the data bus lines 13A and the gate bus lines 13B is each pixel area.

On the other hand, a color filter 12A having any one of red (R), green (G) and blue (B) is provided for each pixel below the glass substrate 12. A counter electrode 15 is provided below 12A.
An alignment film 17 is provided below the counter electrode 15. Each pixel region is divided into two regions I and II, and the alignment direction of liquid crystal molecules in region I (indicated by arrow A)
Is opposite to the orientation direction of liquid crystal molecules in the region II (indicated by arrow B). In order to reverse the alignment direction of the liquid crystal molecules in the regions I and II in this manner, for example, the alignment film 1
6 and 17 can be realized by performing a rubbing process in which the rubbing direction of the liquid crystal molecules in the region I and the rubbing direction of the liquid crystal molecules in the region II are opposite to each other. The alignment films 16 and 17 are arranged such that the rubbing directions are orthogonal to each other when the liquid crystal panel 100 is viewed from above.

An optically anisotropic film 21 is provided below the glass substrate 11 (on the light incident surface side), and a polarizing plate 19 is joined under the optically anisotropic film 21. . A polarizing plate 20 is bonded on the glass substrate 12. When the thickness of the optically anisotropic film 21 is d, the retardation (Δnd value) represented by (nx−ny) · d is 20 to 200 nm, and the thickness d is, for example, 5 nm.
Those having a size of 0 to 100 μm are used.

FIG. 3 is a perspective view showing the refractive index of the optically anisotropic film of the present embodiment in the triaxial directions in orthogonal coordinates. In this figure, when the normal direction of the optically anisotropic film 21 is the z direction, nx is the refractive index in the x direction, ny is the refractive index in the y direction, and nz is the refractive index in the z direction. . The film 21 has optical characteristics of nx> ny = nz, and shows a positive uniaxial orientation.

FIG. 4 is a schematic diagram showing a configuration of the liquid crystal display device of the present embodiment. In this figure, the alignment films 16,
Each solid arrow 17 indicates a rubbing direction. Also,
The solid line of the optically anisotropic film 21 indicates the direction of the slow axis, and the solid lines of the polarizing plates 19 and 20 indicate the direction of the absorption axis. In the present embodiment, as shown in FIG.
1 is disposed so that the direction of its slow axis and the rubbing direction of the alignment film 16 are parallel (within 0 ± 10 °). The polarizing plate 19 is disposed such that the direction of the absorption axis and the rubbing direction of the alignment film 16 are perpendicular to each other. Polarizing plate 2
0 is disposed such that the direction of the absorption axis is perpendicular to the rubbing direction of the alignment film 17. When the directions of the absorption axes of the polarizing plates 19 and 20 are overlapped at right angles to each other in this manner, a normally white mode liquid crystal display device is formed.

In the liquid crystal display device of the present embodiment configured as described above, light is transmitted when no voltage is applied between the electrodes 14 and 15, and when a voltage is applied between the electrodes 14 and 15, the light is transmitted between the electrodes 14 and 15. The existing liquid crystal molecules 18A are aligned with the alignment film 16,
It rises along the rubbing direction of No. 17 and blocks light. The liquid crystal display device of the present embodiment has two regions I and II for each pixel, and the liquid crystal molecules 18A in each region I and II.
Since the liquid crystal panel has an orientation division structure in which the orientation directions are different from each other, the viewing angle characteristics when the liquid crystal panel is viewed from above or below are excellent. In addition, in the present embodiment, the Δnd value of the optically anisotropic film 21 exhibiting positive uniaxial orientation is set to 20 to 20.
Since the thickness is set to 0 nm, a viewing angle characteristic more excellent than that of the conventional liquid crystal display device can be obtained, and a portion to be displayed black can be displayed in black, so that good contrast can be obtained.

Hereinafter, the result of actually manufacturing the liquid crystal display device of the present embodiment and examining the visibility thereof will be described in comparison with a comparative example. A normally white mode liquid crystal display device (hereinafter, referred to as an example liquid crystal display device) having the alignment division structure shown in FIGS. 1 to 4 was manufactured. The size of the liquid crystal panel 100 is 1
0.4 inches (diagonal length), 640 x 48 pixels
0 dots, and the size of each pixel is 100 × 290 μm. The Δnd value of the optically anisotropic film 21 is 150
nm.

The direction of the slow axis of the optically anisotropic film 21 was set to be parallel to the rubbing direction of the alignment film 16 of the liquid crystal panel 100. On the other hand, as a comparative example, a liquid crystal display having the configuration shown in FIG. 5 was manufactured. The liquid crystal display device of this comparative example has the same configuration as that of the example except that the optical anisotropic film 21 is not provided. With respect to the liquid crystal display devices of these Examples and Comparative Examples, the contrast in each viewing direction was examined by changing the viewing direction.

FIG. 6 is a diagram showing an isocontrast curve (Viewing Cone) of the liquid crystal display device of the comparative example, and FIG. 7 is a diagram showing an isocontrast curve of the liquid crystal display device of the embodiment. However, in FIGS. 6 and 7, the center point in the figure indicates the front of the liquid crystal panel 100, and the concentric scale lines (0, 20,.
(40, 60, 80) indicate the angle (polar angle or viewing angle θ °) between the normal line of the liquid crystal panel 100 and the line of sight. In FIGS. 6 and 7, the azimuth angle φ is set such that the right direction of the liquid crystal panel 100 is 0 °, the upper direction is 90 °, the left direction is 180 °, and the lower direction is 270 °. ing.

Further, the bold line in the figure indicates that the contrast value is 100.
, The thin line is an isocontrast curve with a contrast value of 20, the dashed line is an isocontrast curve with a contrast value of 10, and the two-dot chain line is an isocontrast curve with a contrast value of 5. The curves are shown. In the liquid crystal display device of this embodiment, the equal contrast curve spreads in the left-right direction as compared with the liquid crystal display device of the comparative example. In particular, in the viewing angle characteristics when the liquid crystal panel 100 is viewed from the left and right directions, the equal contrast value is smaller. The obtained region could be enlarged by 3 to 8 degrees with the polar angle θ.

FIG. 8 is a diagram in which the horizontal axis represents the viewing angle θ ° and the vertical axis represents the light transmittance (black transmittance expressed as a percentage) Tb% when displaying black. However, 50, 150, 2
50, 350, and 450 nm correspond to the optically anisotropic film 21.
Is the value of Δnd. The relationship between the viewing angle θ ° and the black transmittance Tb% was examined when the film 21 having these Δnd values was used and when the optically anisotropic film 21 was not used. The optically anisotropic film 21 is made of polycarbonate (P
C) was used. Its thickness d is 60 μm.

As is apparent from this figure, when the Δnd value is 2
By using an optically anisotropic film having a thickness of not more than 00 nm, the black transmittance Tb% is reduced and the contrast is improved as compared with the case where no optically anisotropic film is provided. Where Δ
Films with an nd value less than 20 nm are difficult to manufacture.
Therefore, as the optically anisotropic film 21, Δnd = 2
Those having a thickness of 0 to 200 nm can be used.

(2) Second Embodiment FIG. 9 is a sectional view showing a configuration of a liquid crystal display device of a normally white mode with an orientation division structure according to a second embodiment of the present invention. In the second embodiment, the liquid crystal panel 100
Are provided with optically anisotropic films on the front and back sides, respectively. Note that components having the same symbols and the same names as those in the first embodiment have the same functions, and thus description thereof will be omitted.

In the liquid crystal display device of the second embodiment, the first optically anisotropic film 22 is provided on the light incident surface side of the liquid crystal panel 100, and on the light incident surface side of the film 22. A polarizing plate 19 is provided. LCD panel 100
A second optically anisotropic film 23 is disposed on the light exit surface side of the light emitting device, and a polarizing plate 20 is disposed on the light exit surface side of the film 23.

The optically anisotropic films 22 and 23 have nx>
It has optical characteristics of ny = nz. When the thickness of these films is d, a film having a retardation (Δnd value) represented by (nx−ny) · d of 20 to 100 nm is used. FIG. 10 is a schematic diagram illustrating a configuration of the liquid crystal display panel of the present embodiment. In this figure, the optically anisotropic film 22 has a direction of its slow axis and an orientation film 16.
Is arranged so as to be parallel (within 0 ± 10 °), and the polarizing plate 19 is arranged such that the direction of its absorption axis and the direction of the slow axis of the optically anisotropic film 22 are parallel. Placed in

The optically anisotropic film 23 is disposed such that the direction of the slow axis of the film 23 is parallel to the rubbing direction of the alignment film 17 (within 0 ± 10 °). The direction of the absorption axis and the direction of the slow axis of the optically anisotropic film 23 are arranged so as to be substantially parallel. As described above, the optically anisotropic films 22 and 23 each having a Δnd value of 20 to 100 nm are provided on the front and back sides of the liquid crystal panel 100.
The viewing angle characteristics of the liquid crystal display device can be improved as compared with the conventional liquid crystal display device having no optically anisotropic film as in the first embodiment.

Hereinafter, the result of actually manufacturing the liquid crystal display device of the present embodiment and examining the visibility thereof will be described in comparison with a comparative example. A liquid crystal display device of a normally white mode (hereinafter, referred to as a liquid crystal display device of the embodiment) having the alignment division structure shown in FIGS. 9 and 10 was manufactured. The size of the liquid crystal panel 100, the number of pixels, and the size of each pixel are the same as in the first embodiment. Also, Δnd of the optically anisotropic films 22 and 23
The value is 50 nm.

The optically anisotropic film 22 is disposed so that the direction of the slow axis is parallel to the rubbing direction of the alignment film 16 of the liquid crystal panel 100.
Were arranged such that the direction of the slow axis was parallel to the rubbing direction of the alignment film 17. The determination of the quality of the viewing angle characteristics was based on the viewing angle characteristics of the liquid crystal display device of the comparative example shown in FIG.

Then, with respect to the liquid crystal display device of the embodiment,
The contrast in each gaze direction was examined by changing the gaze direction. FIG. 11 is a diagram showing an equal contrast curve of the liquid crystal display device of the example. In the liquid crystal display device of this embodiment, compared to the liquid crystal display device of the comparative example, the viewing angle characteristics of the liquid crystal panel 100 as viewed from the diagonal left and diagonal directions are different.
The region where an equal contrast value is obtained is defined as a polar angle θ of 6 to
It could be enlarged by 11 °.

FIG. 12 is a diagram in which the horizontal axis represents the viewing angle θ °, and the vertical axis represents the light transmittance (black transmittance expressed as a percentage) Tb% when black display is to be performed. However, 25, 50, 1
50, 250, 350 and 450 nm are Δnd values of the optically anisotropic films 22 and 23. When the films 22 and 23 having these Δnd values are used and when the optically anisotropic films 22 and 23 are not used, the viewing angle θ ° −
The relationship between the black transmittance Tb% was examined. Optically anisotropic film 2
Polycarbonate (PC) was used for 2 and 23. Its thickness d is 60 μm.

From this figure, by using an optically anisotropic film having a Δnd value of 100 nm or less, the black transmittance Tb% is reduced and the contrast is improved as compared with the case where no optically anisotropic film is provided. However, it is difficult to produce a film having a Δnd value of less than 20 nm. Therefore, as the optically anisotropic film, a film having a Δnd value of 20 to 100 nm can be used.

(3) Third Embodiment FIG. 13 is a schematic diagram showing a configuration of a normally white mode liquid crystal display panel having an orientation division structure according to a third embodiment of the present invention. Note that components having the same symbols and the same names as those in the first embodiment have the same functions, and thus description thereof will be omitted. In the third embodiment, the first optically anisotropic film 32 is disposed on the light incident surface side of the liquid crystal panel 100, and the polarizing plate 19 is disposed on the light incident surface side of the film 32. ing. A second optically anisotropic film 33 is disposed on the light exit surface side of the liquid crystal panel 100, and the polarizing plate 20 is disposed on the light exit surface side of the film 33.

In FIG. 13, the optically anisotropic film 32
Are arranged such that the direction of the slow axis is orthogonal (within 90 ± 10 °) to the rubbing direction of the alignment film 16. In the polarizing plate 19, the direction of the absorption axis of the polarizing plate 19 and the direction of the slow axis of the optically anisotropic film 32 are arranged substantially at right angles.
The optically anisotropic film 33 is disposed such that the direction of the slow axis is perpendicular to the rubbing direction of the alignment film 17 (within 90 ± 10 °). In the polarizing plate 20, the direction of the absorption axis of the polarizing plate 20 and the direction of the slow axis of the optically anisotropic film 33 are arranged substantially at right angles.

The optically anisotropic films 32 and 33 have nx> n
It has optical characteristics of y> nz, and exhibits positive biaxial orientation. When the thickness of the films 32 and 33 is d, the retardation (Δn′d value) represented by [(nx + ny) / 2−nz] · d is 70 to 150 n.
m, having a thickness of, for example, 50 to 100 μm, and (nx−
nz) / (nx−ny) is Nz value of 1.2 to
Use what is 1.85. Thereby, the viewing angle characteristics are further improved.

As described above, on the front and back sides of the liquid crystal panel 100,
Since the optically anisotropic films 32 and 33 each having a Δn′d value of 70 to 150 nm and exhibiting a positive biaxial orientation are arranged, similar to the first and second embodiments, the conventional liquid crystal display device can be used. In comparison, the viewing angle characteristics of the liquid crystal panel 100 can be improved. Hereinafter, the result of actually manufacturing the liquid crystal display device of the present embodiment and examining the visibility thereof will be described in comparison with a comparative example.

Table 1 shows films having positive biaxial orientation (trade names N) used as the optically anisotropic films 32 and 33.
EW-VAC film: manufactured by Sumitomo Chemical Co., Ltd.) in the triaxial direction, retardation Δn′d value and Nz
Indicates the value.

[0047]

[Table 1]

FIG. 14 is a diagram showing an equal contrast curve of the liquid crystal display device of the first embodiment. In this figure, looking at the viewing angle characteristics of the left and right diagonal directions of the liquid crystal display device of Example 1, the range where the contrast value 100 can be obtained is as shown in FIG.
As compared with the isocontrast curve of the comparative example shown in FIG.
The range where 20 was obtained extended to around 53 °, the range where 10 was obtained extended to around 65 °, and the range where 5 was obtained extended to 80 ° or more.

FIG. 15 is a diagram showing an equal contrast curve of the liquid crystal display device of the second embodiment. In this figure, the isocontrast curve of Example 2 was almost the same as the isocontrast curve of Example 1. FIG. 16 is a diagram showing an equal contrast curve of the liquid crystal display device of the third embodiment. In this figure, the isocontrast curves of Example 3 correspond to those of Examples 1 and 2.
, But expanded in comparison with the isocontrast curve of the comparative example shown in FIG.

FIG. 17 is a view showing an equal contrast curve of the liquid crystal display device of the fourth embodiment. In this figure, the isocontrast curve of Example 4 is further expanded as compared with the isocontrast curve of Example 1. FIG. 18 is a diagram showing an equal contrast curve of the liquid crystal display device of Example 5. In this figure, the isocontrast curve of Example 5 was almost the same as the isocontrast curve of the comparative example shown in FIG.

FIG. 19 is a diagram showing an equal contrast curve of the liquid crystal display device of the sixth embodiment. In this figure, the isocontrast curve of Example 6 is almost the same as that of Example 3. FIG. 20 is a diagram showing an equal contrast curve of the liquid crystal display device of Comparative Example 1. In this figure, the range in which the contrast value 100 can be obtained is reduced to about 20 ° in polar angle as compared with the isocontrast curve of the comparative example shown in FIG.
The range where 20 was obtained was also reduced to around 30 °, the range where 10 was obtained was also reduced to around 36 °, and the range where 5 was obtained was also reduced to around 44 °.

FIGS. 21 to 28 are graphs showing isocontrast curves of the liquid crystal display devices of Comparative Examples 2 to 9. In these figures, the isocontrast curves of Comparative Examples 2 to 9 are smaller than those of Examples 1 to 6 as in Comparative Example 1. These FIG.
28, the retardation (Δn) of the optically anisotropic films 32 and 33 exhibiting positive biaxial orientation.
When 'd value) is 70 to 150 nm, N
When the z value is 1.2 to 1.85, the optically anisotropic film 3
Compared with the conventional liquid crystal display devices not including the liquid crystal display devices 2 and 33 and the liquid crystal display devices of Comparative Examples 1 to 9, the viewing angle characteristics in the left and right diagonal directions of the liquid crystal panel widen a region with high contrast, resulting in black. When the display should be performed, the tendency of the display viewed from an oblique direction to appear whitish was improved, and the contrast could be increased by changing black to black. Optically anisotropic film 3
By arranging Nos. 2 and 33, not only the viewing angle characteristics of the contrast but also the gradation inversion were suppressed, and good display characteristics were obtained.

[0053]

As described above, the liquid crystal display device of the present invention exhibits a positive uniaxial orientation and a Δnd value of 20 to 2
Since the optically anisotropic film of 00 nm is provided between the polarizing plate on the light incident side and the liquid crystal panel, the viewing angle characteristics of the liquid crystal display device can be improved as compared with the conventional liquid crystal display device.

In another liquid crystal display device of the present invention, an optically anisotropic film exhibiting a positive uniaxial orientation is provided between the light incident side polarizing plate and the liquid crystal panel, and the light emitting side polarizing plate is provided. An optically anisotropic film exhibiting a positive uniaxial orientation is also provided between the liquid crystal panel and when the retardation value of these films is 20 to 100 nm, the viewing angle characteristics of the liquid crystal display device are higher than those of the conventional liquid crystal display device. Could be improved.

Further, in another liquid crystal display device of the present invention, an optically anisotropic film having a positive biaxial orientation is provided between the light incident side polarizing plate and the liquid crystal panel, and the light emitting side polarizing plate is provided. An optically anisotropic film exhibiting positive biaxial orientation is also provided between the liquid crystal panel and the liquid crystal panel. When the retardation value of these films is 70 to 150 nm, the Nz value is 1.2 to 1.
At 85, the viewing angle characteristics of the liquid crystal display device could be improved as compared with the conventional liquid crystal display device.

This greatly contributes to the provision of a liquid crystal display device capable of excellent display over a wide viewing angle.

[Brief description of the drawings]

FIG. 1 is a plan view illustrating a configuration of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of the liquid crystal display device according to the first embodiment of the present invention.

FIG. 3 is a perspective view showing a triaxial refractive index of the optically anisotropic film of the first embodiment.

FIG. 4 is a schematic diagram illustrating a configuration of the liquid crystal display device according to the first embodiment.

FIG. 5 is a schematic diagram illustrating a configuration of a liquid crystal display device of a comparative example.

FIG. 6 is a diagram showing an equal contrast curve of a liquid crystal display device of a comparative example.

FIG. 7 is a diagram showing an equal contrast curve of the liquid crystal display device of the example.

FIG. 8 is a view showing the viewing angle dependence of an optically anisotropic film of a liquid crystal display device of an example.

FIG. 9 is a cross-sectional view illustrating a configuration of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 10 is a schematic diagram illustrating a configuration of a liquid crystal display device according to a second embodiment.

FIG. 11 is a diagram showing an equal contrast curve of the liquid crystal display device of the example.

FIG. 12 is a view showing the viewing angle dependence of an optically anisotropic film of a liquid crystal display device of an example.

FIG. 13 is a schematic diagram illustrating a configuration of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 14 is a view showing an equal contrast curve of the liquid crystal display device (optically anisotropic film; Δnd = 70 nm) of Example 1.

FIG. 15 is a view showing an isocontrast curve of the liquid crystal display device of Example 2 (optically anisotropic film; Δnd = 95 nm).

FIG. 16 is a view showing an isocontrast curve of the liquid crystal display device (optically anisotropic film; Δnd = 105 nm) of Example 3.

FIG. 17 is a view showing an isocontrast curve of the liquid crystal display device (optically anisotropic film; Δnd = 136 nm) of Example 4.

FIG. 18 is a view showing an isocontrast curve of the liquid crystal display device of Example 5 (optically anisotropic film; Δnd = 140 nm).

FIG. 19 is a view showing an isocontrast curve of the liquid crystal display device (optically anisotropic film; Δnd = 142 nm) of Example 6.

FIG. 20 is a view showing an isocontrast curve of the liquid crystal display device (optically anisotropic film; Δnd = 174 nm) of Comparative Example 1.

FIG. 21 is a diagram showing an isocontrast curve of the liquid crystal display device of Comparative Example 2 (optically anisotropic film; Δnd = 189 nm).

FIG. 22 is a diagram showing an isocontrast curve of the liquid crystal display device of Comparative Example 3 (optically anisotropic film; Δnd = 203 nm).

FIG. 23 is a view showing an isocontrast curve of the liquid crystal display device (optically anisotropic film; Δnd = 210 nm) of Comparative Example 4.

FIG. 24 is a view showing an isocontrast curve of the liquid crystal display device of Comparative Example 5 (optically anisotropic film; Δnd = 236 nm).

FIG. 25 is a view showing an isocontrast curve of the liquid crystal display device (optically anisotropic film; Δnd = 271 nm) of Comparative Example 6.

FIG. 26 is a view showing an equal contrast curve of the liquid crystal display device of Comparative Example 7 (optically anisotropic film; Δnd = 284 nm).

FIG. 27 is a view showing an isocontrast curve of the liquid crystal display device of Comparative Example 8 (optically anisotropic film; Δnd = 339 nm).

FIG. 28 is a view showing an isocontrast curve of the liquid crystal display device (optically anisotropic film; Δnd = 406 nm) of Comparative Example 9.

FIG. 29 is a plan view showing a configuration of a conventional liquid crystal display device.

FIG. 30 is a cross-sectional view illustrating a configuration of a conventional liquid crystal display device.

FIG. 31 is a diagram showing a conventional orientation division method for a liquid crystal display device.

FIG. 32 is a diagram showing TV characteristics of a conventional liquid crystal display device.

[Explanation of symbols]

 1, 2, 11, 12: glass substrate (transparent substrate), 3, 13: TFT, 3A, 13A: data bus line, 3B, 13B: gate bus line, 4, 14: pixel electrode, 5, 15: counter electrode , 6,7,16,17: Alignment film, 8,18: Liquid crystal, 21: Optically anisotropic film, 22, 32: First optically anisotropic film, 23, 33: Second optical anisotropy Film, 8A, 18A: liquid crystal molecules, 9, 10, 19, 20: polarizing plate, 2A, 12A: color filter, 100: liquid crystal panel.

Continued on the front page (72) Takashi Sasabayashi 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Yohei Nakanishi 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Fujitsu Limited

Claims (6)

[Claims] 1. A pair of transparent substrates disposed to face each other, a liquid crystal sealed between the pair of transparent substrates, and a pair of transparent substrates disposed on each of the opposing surfaces of the pair of transparent substrates and dividing one pixel into two. A liquid crystal panel including first and second alignment films that have been subjected to a surface treatment so that liquid crystal molecules rise in directions opposite to each other in the first and second regions, and one of the liquid crystal panels. An optically anisotropic film disposed on an outer surface and having a slow axis overlapping in the same direction as the rubbing direction of the closer alignment film of the first and second alignment films; and A pair of polarizing plates sandwiching the liquid crystal panel and arranged so that the directions of absorption axes are orthogonal to each other; and the optically anisotropic film has x, y,
When the refractive index in the z-axis direction is nx, ny, nz, nx
> Ny = nz, and the thickness is d
Wherein the retardation (Δnd value) represented by (nx−ny) · d is 20 to 200 nm. 2. A pair of transparent substrates disposed opposite to each other, a liquid crystal sealed between the pair of transparent substrates, and a pair of transparent substrates disposed on each of the opposing surfaces of the pair of transparent substrates and dividing one pixel into two. A liquid crystal panel comprising first and second alignment films that have been subjected to a surface treatment so that liquid crystal molecules rise in directions opposite to each other in the first and second regions, and disposed on both sides of the liquid crystal panel. A pair of optically anisotropic films whose slow axes overlap in the same direction as the rubbing direction of the closer one of the first and second alignment films; the optically anisotropic film and the liquid crystal panel And a pair of polarizing plates arranged so that the directions of the absorption axes are orthogonal to each other. The optically anisotropic film has x, y,
When the refractive index in the z-axis direction is nx, ny, nz, nx
> Ny = nz, and the thickness is d
Wherein the retardation (Δnd value) represented by (nx−ny) · d is 20 to 100 nm. 3. An angle between a rubbing direction of an alignment film of the liquid crystal panel and a slow axis of the optically anisotropic film is 0 ± 3.
2. The method according to claim 1, wherein the angle is set within 10 degrees.
Alternatively, the liquid crystal display device according to claim 2. 4. A pair of transparent substrates disposed to face each other, a liquid crystal sealed between the pair of transparent substrates, and one pixel disposed on each opposing surface of the pair of transparent substrates and dividing one pixel into two. A liquid crystal panel including first and second alignment films that have been subjected to surface treatment so that liquid crystal molecules rise in directions opposite to each other in the first and second regions, and are disposed on both sides of the liquid crystal panel. A pair of optically anisotropic films whose slow axes overlap in a direction orthogonal to the rubbing direction of the closer one of the first and second alignment films, the optically anisotropic film and the liquid crystal A pair of polarizing plates sandwiching the panel and arranged so that the directions of the absorption axes are orthogonal to each other; and the optically anisotropic film has x, y,
When the refractive index in the z-axis direction is nx, ny, nz, nx
>Ny> nz, and the thickness is d
, The retardation (Δn′d value) represented by [(nx + ny) / 2−nz] · d is 70 to 150.
a liquid crystal display device characterized in that 5. The optically anisotropic film according to claim 5, wherein (nx-n
z) / (nx-ny) has an Nz value of 1.2 to 1.
The liquid crystal display device according to claim 4, wherein the number is 85. 6. An angle between a rubbing direction of an alignment film of the liquid crystal panel and a slow axis of the optically anisotropic film is 90.
The liquid crystal display device according to claim 4, wherein the angle is set within ± 10 °.