JP2002116464A - Perpendicular alignment type ecb mode liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a perpendicular alignment type ECB mode liquid crystal display device having excellent electro-optical characteristics in which the viewing angle characteristics can be easily improved. SOLUTION: A phase difference plate having the following characteristics is disposed in the outside of a liquid crystal cell for a perpendicular alignment type ECB mode liquid crystal display device having 85 to 60 deg. pretilt angle imparted to the liquid crystal molecules. In the phase difference plate, the effective in-plane refractive indices nx, ny are different from each other and both are higher than the effective refractive index nz in the thickness direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric birefringence control (ECB) mode liquid crystal display device and a method for compensating viewing angle characteristics thereof, and more particularly to an ECB in which liquid crystal molecules are vertically aligned.
1. Field of the Invention The present invention relates to a mode liquid crystal display device (hereinafter, this liquid crystal display device is referred to as a “vertical alignment type ECB mode liquid crystal display device”) and a method for compensating viewing angle characteristics thereof.

[0002]

2. Description of the Related Art In an ECB mode liquid crystal display device, display is performed by utilizing a change in birefringence of a liquid crystal cell which occurs when an electric field is applied to the liquid crystal cell to change the arrangement of liquid crystal molecules. Multicolor display can be performed relatively stably with a simple element configuration.

[0003] By making the ECB mode liquid crystal display element of a vertical alignment type, transmitted light can be satisfactorily blocked even in a low applied voltage state. When this liquid crystal display element is combined with a polarizing plate having a crossed Nicols arrangement, the black level of the crossed polarizing plate can be obtained as it is, so that good black display can be realized.

However, in the vertical alignment type ECB mode liquid crystal display device, the transmitted light intensity increases only relatively slowly with an increase in applied voltage. The change of the transmitted light intensity with respect to the change of the applied voltage is slow. It is difficult to increase the number of scanning lines, that is, the duty ratio, to drive the scanning.

[0005]

DISCLOSURE OF THE INVENTION The present inventors have developed a vertical alignment type ECB mode liquid crystal display device having excellent electro-optical characteristics, that is, the intensity of transmitted light changes sharply with a change in applied voltage, resulting in a bright display. We have already developed a vertical alignment type ECB mode liquid crystal display device that has high light transmittance at the time and can perform high-contrast display. A patent application has already been filed for this liquid crystal display element (Japanese Patent Application No. 11-1041).
No. 97).

In this vertical alignment type ECB mode liquid crystal display device, a pretilt angle of 85 to 60 ° is given to liquid crystal molecules. The twist angle (twist angle) may or may not be provided. When imparting a twist angle, it is preferable to select within a range of 180 to 270 °. By providing a twist angle of 220 to 270 °, a bistable vertical alignment type ECB mode liquid crystal display device can be obtained (see Japanese Patent Application No. 11-104198).

The vertical alignment type ECB mode liquid crystal display element has optical anisotropy with the optical axis in the thickness direction of the liquid crystal cell. When light obliquely enters the liquid crystal cell, the light transmittance characteristic changes. That is, it has a viewing angle dependency.

This viewing angle dependency can be improved by the multi-domain method. In the multi-domain method, a plurality of alignment domains having different alignment directions of liquid crystal molecules are formed in one pixel. However, when the multi-domain method is applied, the manufacturing process of the liquid crystal display element becomes complicated.

For a vertical alignment type ECB mode liquid crystal display device in which no pretilt is given to liquid crystal molecules, a negative uniaxial optical compensation film ("NOC (negative optical compensator)" composed of a biaxially stretched film is used. The viewing angle dependency can be improved by using a “film” or “C-plate”) as a retardation plate.

In the vertical alignment type ECB mode liquid crystal display device developed by the inventors of the present invention, the viewing angle dependency can be improved by disposing the NOC film outside the liquid crystal cell. However, 180-
When a twist angle of about 270 ° is given, even if the twist angle is NO
Even when the C film is used, asymmetry of the viewing angle characteristic appears in a direction orthogonal to the director of the liquid crystal molecules at the center in the thickness direction of the liquid crystal layer in a plan view.

An object of the present invention is to provide a vertical alignment type ECB mode liquid crystal display device which is excellent in electro-optical characteristics and can easily improve viewing angle characteristics.

Another object of the present invention is to provide a method for compensating for the viewing angle characteristic of a vertical alignment type ECB mode liquid crystal display device having excellent electro-optical characteristics.

[0013]

According to one aspect of the present invention, there is provided a cell container having two transparent substrates which are opposed to each other at an interval, and a liquid crystal layer contained in the cell container. Liquid crystal molecules are arranged under a twist angle of 180 ° or more, and a liquid crystal layer in which a pretilt angle of 85 ° to 60 ° is given to the liquid crystal molecules, and an outer surface of each of the two transparent substrates. The retardation plates are arranged one by one, and the effective in-plane refractive indices nx and ny are different from each other, and each of these effective in-plane refractive indices nx and ny has an effective thickness. A vertical alignment type ECB mode liquid crystal display device comprising a retardation plate having a refractive index larger than the vertical direction refractive index nz.

According to another aspect of the present invention, there are provided a cell container having two transparent substrates disposed to face each other at an interval, and a liquid crystal layer contained in the cell container, comprising:
Liquid crystal molecules are arranged below a twist angle of 0 ° or more, and a liquid crystal layer in which a pretilt angle of 85 ° to 60 ° is given to the liquid crystal molecules, and one on the outer surface of each of the two transparent substrates. The retardation plates are disposed one by one, wherein the effective optical axis in each is inclined from the in-plane direction, and the optical axis is z
Assuming an xyz rectangular coordinate system as an axis, the refractive index nx in the x-axis direction and the refractive index ny in the y-axis direction are substantially the same,
These refractive indexes nx and ny are the refractive indexes nz in the z-axis direction.
A vertical alignment type ECB mode liquid crystal display device having a larger phase difference plate.

According to still another aspect of the present invention, there is provided a cell container having two transparent substrates disposed to face each other at an interval, and a liquid crystal layer contained in the cell container,
Compensation of viewing angle characteristics of a vertical alignment type ECB mode liquid crystal display device comprising a liquid crystal layer in which liquid crystal molecules are arranged under a twist angle of 180 ° or more and a pretilt angle of 85 ° to 60 ° is given to the liquid crystal molecules. A method wherein one of the two transparent substrates has an effective in-plane refractive index nx and ny.
Providing a retardation plate in which both of these effective in-plane refractive indices nx and ny are larger than the effective thickness direction refractive index nz, and the other of the two transparent substrates Also, the effective in-plane refractive indexes nx and ny are different from each other, and these effective in-plane refractive indexes nx and ny
And a step of providing a retardation plate having a refractive index greater than the effective refractive index nz in the thickness direction.

According to still another aspect of the present invention, there is provided a cell container having two transparent substrates disposed to face each other at an interval, and a liquid crystal layer contained in the cell container,
Compensation of viewing angle characteristics of a vertical alignment type ECB mode liquid crystal display device comprising a liquid crystal layer in which liquid crystal molecules are arranged under a twist angle of 180 ° or more and a pretilt angle of 85 ° to 60 ° is given to the liquid crystal molecules. A method wherein an effective optical axis is inclined from an in-plane direction on one of the two transparent substrates, and assuming an xyz orthogonal coordinate system having the optical axis as a z-axis, x Refractive index nx in the axial direction and refractive index n in the y-axis direction
y is approximately the same, and their refractive indices nx and ny are z
Arranging a phase difference plate having a refractive index greater than the axial refractive index nz; and the other of the two transparent substrates has an effective optical axis inclined from the in-plane direction, Xyz
Assuming a rectangular coordinate system, the refractive index nx in the x-axis direction is substantially the same as the refractive index ny in the y-axis direction, and these refractive indexes nx and ny are larger than the refractive index nz in the z-axis direction. Providing a viewing angle characteristic of a vertical alignment type ECB mode liquid crystal display device, which includes a step of disposing a plate.

As described above, the liquid crystal molecules have an angle of 85 to 60 °.
By giving the pretilt angle of?, It is possible to obtain a vertical alignment type ECB mode liquid crystal display device having excellent electro-optical characteristics.

In this vertical alignment type ECB mode liquid crystal display device, the tilt angle (tilt angle) of the liquid crystal molecules changes as follows when no electric field is applied. That is, the pretilt angle is at the interface on the transparent substrate side constituting the cell container, but the tilt angle gradually increases from the transparent substrate side to the center in the thickness direction of the liquid crystal layer, and the center of the liquid crystal layer in the thickness direction is gradually increased. It is almost 90 ° at the part.

The viewing angle dependence in such a vertical alignment type ECB mode liquid crystal display device is presumed to be caused by the existence of a region where the tilt angle of liquid crystal molecules is gradually changed when no electric field is applied.

By disposing a retardation plate of the following (A) or (B) outside the liquid crystal cell, the above vertical alignment type E
The viewing angle characteristics of the CB mode liquid crystal display device can be improved. (A) An effective in-plane refractive index nx and ny are different from each other, and each of these effective in-plane refractive indexes nx and ny is larger than an effective thickness direction refractive index nz (hereinafter, referred to as a retardation plate). This retardation plate is referred to as a “biaxial NOC film”.) (B) Assuming that an effective optical axis is inclined from the in-plane direction and an xyz orthogonal coordinate system having the optical axis as the z axis, x
The refractive index nx in the axial direction and the refractive index ny in the y-axis direction are substantially the same, and these refractive indexes nx and ny are larger than the refractive index nz in the z-axis direction (hereinafter, this retardation plate is referred to as “phase difference plate”). It is written as "inclined NOC film".)

The in-plane retardation of the biaxial NOC film (A) is preferably in the range of about 0 to 137.5 nm, more preferably in the range of 5 to 60 nm. The in-plane retardation can be determined by multiplying the difference between the two in-plane refractive indices nx and ny (usually a positive value) by the thickness d, where d is the thickness of the retardation plate. .

The effective tilt of the optical axis in the tilted NOC film (B) is preferably about 25 ° or less on average from the in-plane direction, more preferably about 10 ° to 20 °. .

[0023]

FIG. 1 schematically shows the structure of a vertical alignment type ECB mode liquid crystal display device according to a first embodiment. The vertical alignment type ECB mode liquid crystal display element 30 (hereinafter, abbreviated as “liquid crystal display element 30”) shown in FIG.
A cell container 10, a liquid crystal layer 15 contained in the cell container 10, phase plates 20a and 20b provided on the outer surface of the cell container 10, and polarized light provided on the phase plate 20a. It comprises a plate (analyzer) 25a and a polarizing plate (polarizer) 25b provided on the retardation plate 20b. Hereinafter, each component will be specifically described.

The cell container 10 includes an upper transparent substrate 1a and a lower transparent substrate 1b formed of, for example, transparent glass or a transparent resin, and a resin made of, for example, resin which holds the transparent substrates 1a, 1b at a predetermined interval. And a spacer 5.

On the inner surface of the upper transparent substrate 1a, ITO
A large number of transparent electrodes 2a formed of a transparent electrode material such as (indium oxide / tin) are formed in a stripe shape. For example, a vertical alignment film 3a formed of polyimide, polyamic acid, a SiO oblique deposition film, or the like covers these. Similarly, a large number of transparent electrodes 2b are formed in stripes on the inner surface of the lower transparent substrate 1b, and the vertical alignment film 3b
Covers these. The transparent electrode 2a and the transparent electrode 2b intersect in plan view.

The easy axis (orientation direction) of the vertical alignment film 3a and the easy axis (orientation direction) of the vertical alignment film 3b intersect in plan view.

Liquid crystal layer 15 formed in cell container 10
Constitutes a liquid crystal cell together with the cell container 10. Liquid crystal layer 1
5 is, for example, a liquid crystal material having a negative dielectric anisotropy;
Chiral agents.

As shown in FIG. 2, in the liquid crystal layer 15, the liquid crystal molecules 15a are arranged under a twist angle (twist angle) selected within a range of approximately 180 to 270 °. The twist angle is more preferably selected within a range of approximately 220 to 270 °, and further preferably selected within a range of approximately 240 to 270 °.

The liquid crystal molecules 15a are provided with a pretilt selected within a range of approximately 85 to 60 °. The magnitude of the pretilt angle θp is more preferably selected within a range of approximately 85 to 70 °, and even more preferably selected within a range of approximately 85 to 75 °. Note that the arrow n in FIG. 2 indicates the director of the liquid crystal molecules 15a.

A phase difference plate 20a is provided on the outer surface of the upper transparent substrate 1a shown in FIG. 1, and a phase difference plate 20b is provided on the outer surface of the lower transparent substrate 1b.

Each of the retardation plates 20a and 20b includes a positive uniaxial optical compensation film 21 disposed on a transparent substrate,
A biaxial NOC film including a negative uniaxial optical compensation film 22 disposed thereon.

In the positive uniaxial optical compensation film 21, 2
One of the in-plane refractive indices nx and ny (for example, nx) is larger than the other, and the refractive index nz in the thickness direction is equal to the smaller in-plane refractive index. Positive uniaxial optical compensation film 21
Is also called "A-plate" and is constituted by, for example, a uniaxially stretched film.

In the negative uniaxial optical compensation film 22, 2
The two in-plane refractive indices nx and ny are substantially equal, and the refractive index nz in the thickness direction is smaller than any of the in-plane refractive indices nx and ny. The negative uniaxial optical compensation film 22 is the same as the NOC described above.
It is a film and is constituted by, for example, a biaxially stretched film.

There are two modes according to the specification of laminating the two phase difference plates 20a and 20b. One is a mode in which the retardation plates 20a and 20b are bonded together such that the slow axis of each of the retardation plates 20a and 20b is parallel to the transmission axis of the outer polarizing plate 25a or 25b.
Called mode. The other is that the slow axis of each of the retarders 20a and 20b is different from the polarizer 25a or 25
b, these phase difference plates 20a,
This is a mode in which 20b is pasted, and is called an E mode.

The phase difference plate 20a may be provided on a predetermined surface of the upper transparent substrate 1a before assembling the cell container 10, or provided on a predetermined surface of the upper transparent substrate 1a after assembling the cell container 10. You may. The same applies to the phase difference plate 20a.

The polarizing plate (analyzer) 25a provided on the phase difference plate 20a and the polarizing plate (polarizer) 25b provided on the phase difference plate 20b are arranged in orthogonal Nicols. One set of polarizing elements is configured.

In the liquid crystal display element 30 having the above configuration, the intersection of the transparent electrode 2a and the transparent electrode 2b in plan view corresponds to a pixel. When a voltage is applied to the transparent electrode 2a and the transparent electrode 2b, each of the liquid crystal molecules 15a in the pixel sequentially falls from the one near the center in the thickness direction of the cell container 10, and the retardation of the liquid crystal layer 15 changes with it. . The light transmittance at the pixel gradually increases.

By controlling the voltage value applied to each transparent electrode 2a and each transparent electrode 2b, the light transmittance of a desired pixel can be controlled. Desired character display can be performed.

The liquid crystal display device 30 was compared with a liquid crystal simulator “LCD M” manufactured by Shintech Co., Ltd.
ASTER ". The simulation conditions are shown below. (1) Liquid crystal material: Merck Japan MJ94357,
(2) Pretilt angle: 83 °, (3) Twist angle (twist angle): Right 250 °, (4) Ratio d / p between cell thickness d and chiral pitch p: 0.65, (5) Cell thickness d : 6 μm, (6) In-plane retardation of the positive uniaxial optical compensation film 21: 16 nm, (7) Negative uniaxial optical compensation film 2
2: VAC-C160 manufactured by Sumitomo Chemical Co., Ltd., (8) Operating conditions:
15.49 bias drive, CR _max setting (non-selection voltage V
(ns = 3V, selection voltage Vs = 3.2V), (9) Axial angle (azimuth) in vertical alignment film, positive uniaxial optical compensation film, negative uniaxial optical compensation film and polarizing plate, and thickness of liquid crystal cell Azimuth angle of director n of liquid crystal molecules at the center in the vertical direction: as shown in Table 1.

In the VAC-C160 used as the negative uniaxial optical compensation film 22, an optical compensation film main body is formed on a base film. Therefore, V
AC-C160 is not a perfect uniaxial optical compensation film, but has an in-plane retardation of about 6 nm. Therefore, the in-plane retardation of each of the retarders 20a and 20b under the above conditions is about 22 nm.

[0041]

[Table 1] FIG. 3A shows the easy axis AX1 of each of the vertical alignment films 3a and 3b and the slow axis A of the positive uniaxial optical compensation film 21 in the O mode of the simulation under the above conditions.
X2, V used as the negative uniaxial optical compensation film 22
Slow axis AX3 of AC-C160 and polarizing plate 25
a, 25b The axis angle (azimuth angle) of each transmission axis AX4
Is illustrated.

FIG. 3B shows the easy axis (orientation direction) AX1 of each of the vertical alignment films 3a and 3b and the slow axis AX2 of the positive uniaxial optical compensation film 21 in the E mode of the simulation under the above conditions. Slow axis AX of VAC-C160 used as negative uniaxial optical compensation film 22
3, and the transmission axis A of each of the polarizing plates 25a and 25b
The axis angle (azimuth angle) of X4 is illustrated.

However, in these figures, for convenience,
An upper transparent substrate 1a or a lower transparent substrate 1b is shown instead of the vertical alignment films 3a and 3b, and these transparent substrates 1a,
1b shows an axis of easy orientation (orientation direction) AX1. The thicknesses of the positive uniaxial optical compensation film 21, the negative uniaxial optical compensation film 22, and the polarizing plates 25a and 25b are neglected.

FIG. 4 shows a simulation result in the O mode. As shown in the figure, in the O-mode liquid crystal display element 30, left and right (corresponding to the x-axis direction in FIG. 3).
Are almost symmetric. When the polar angle is in the range of 0 to 60 °, the azimuth is approximately 65 to 120 °, and the polar angle is approximately 43 °.
Only an inversion region (a region where the contrast ratio is less than 1) is found in the above range, and good characteristics are exhibited. A viewing angle characteristic with almost no inversion area in the left-right direction is obtained.

The inversion area is mainly caused by light leakage at the black level. In the O-mode liquid crystal display element 30, a good black level can be obtained particularly in the left and right lower directions.

FIG. 5 shows a simulation result in the E mode. As shown in the figure, also in the E-mode liquid crystal display element 30, the left and right viewing angle characteristics are almost symmetric. It shows good characteristics with no inversion region when the polar angle is in the range of approximately 0 to 55 °. A region where a good black level is obtained extends in a rectangular shape that is long in the left and right directions near the center.

Next, the O-mode liquid crystal display element 30 was simulated by variously changing only the in-plane retardation of the positive uniaxial optical compensation film 21, and the change in viewing angle characteristics was examined.

FIG. 6 shows a positive uniaxial optical compensation film 21.
Shows the simulation results when the in-plane retardation of the sample was 52 nm. The iso-contrast characteristics shown in the figure are the best obtained by simulation under the above conditions.

FIG. 7 shows a positive uniaxial optical compensation film 21.
Shows the simulation results when the in-plane retardation of is set to 126 nm. As is clear from the comparison with FIG. 4, the inversion region expands in the left-right direction, and the inversion region in the azimuth direction of 90 ° penetrates into a region with a polar angle of about 40 °. The viewing angle range (viewing angle) is considerably narrow.

As the in-plane retardation of the positive uniaxial optical compensation film 21 was increased, the region having high contrast tended to expand. However, when the in-plane retardation of the positive uniaxial optical compensation film 21 is further increased, the viewing angle range (viewing angle) is reduced.

Next, the vertical alignment type EC according to the second embodiment
FIGS. 8A and 8B show a B-mode liquid crystal display element.
This will be described with reference to FIG.

FIG. 8A is a sectional view schematically showing a vertical alignment type ECB mode liquid crystal display element 130 according to the second embodiment.

FIG. 8B shows an effective optical axis (optical axis) OA of the phase difference plate 120a in the vertical alignment type ECB mode liquid crystal display element 130.

As shown in FIG. 8A, the vertical alignment type EC
B-mode liquid crystal display element 130 (hereinafter referred to as “liquid crystal display element 1
30 ". ) Are the phase difference plates 120a, 120b
Is different from the liquid crystal display element 30 according to the first embodiment in that it is constituted by one optical compensation film. Except for this point, the liquid crystal display element 130 has the same configuration as the liquid crystal display element 30. 8A that are the same as the components shown in FIG. 1 are assigned the same reference numerals as those used in FIG. 1 and the description thereof is omitted.

As shown in FIG. 8B, the phase difference plate 120
The effective optical axis OA of “a” is inclined at an angle θ from the in-plane direction Ds. In other words, the effective optical axis OA of the phase difference plate 120a is inclined at an angle θ with respect to the main surfaces S1 and S2. The main surfaces S1, S2 are parallel to the in-plane direction Ds.

Assuming an xyz orthogonal coordinate system having the effective optical axis OA as the z-axis, the refractive index nx in the x-axis direction and the refractive index ny in the y-axis direction of the phase difference plate 120a are substantially the same. Are larger than the refractive index nz in the z-axis direction. The same applies to the phase difference plate 120b. That is, each of the phase difference plates 120a and 120b is formed of a tilted NOC film. Less than,
The tilt angle θ of the optical axis OA from the in-plane direction is defined as “the tilt angle of the optical axis”.
That.

The equicontrast characteristics of the liquid crystal display element 130 were measured using a liquid crystal simulator “LCD MA” manufactured by Shintec.
Simulation was performed using "STER". The simulation conditions are the same as the simulation conditions of the liquid crystal display element 30 according to the first embodiment, except for the following points (1) and (2). (1) Each of the phase difference plates 120a and 120 is constituted by a VAC-C160 manufactured by Sumitomo Chemical Co., Ltd.
A point where the effective optical axis OA in each case was tilted below a tilt angle of 15 °, 10 ° or 20 ° to obtain a tilted NOC film. Note that the optical axis of the actual VAC-C160 is perpendicular to the in-plane direction. (2) The axis angles (azimuth angles) in the vertical alignment film, the retardation plate and the polarizing plate and the azimuth angles of the director n of the liquid crystal molecules in the center in the thickness direction of the liquid crystal cell were set to the values shown in Table 2.

[0058]

[Table 2] FIG. 9A shows the easy alignment axis AX1 of each of the vertical alignment films 3a and 3b, the slow axis AX5 of each of the phase difference plates 120a and 120b, and the polarizing plates 25a and 25b in the O mode of the simulation under the above conditions. The axial angle (azimuth) of each transmission axis AX4 is illustrated.

FIG. 9B shows the easy axis AX1 of each of the vertical alignment films 3a and 3b, the slow axis AX5 of each of the phase difference plates 120a and 120b, and the polarizing plate in the E mode of the simulation under the above conditions. 25a, 25b
The axial angle (azimuth) of each transmission axis AX4 is illustrated.

However, in these figures, for convenience,
An upper transparent substrate 1a or a lower transparent substrate 1b is shown instead of the vertical alignment films 3a and 3b, and these transparent substrates 1a,
1b shows an axis of easy orientation (orientation direction) AX1. Further, the phase difference plates 120a, 120b and the polarizing plates 25a, 25b
About, each thickness is ignored.

FIG. 10 shows a simulation result when the effective tilt angle θ of the optical axis OA of each of the phase difference plates 120a and 120b is set to 15 ° and these phase difference plates 120a and 120b are arranged under the O mode. Is shown. Note that the inclination directions of the optical axes of the phase difference plates 120a and 120b are the same as the azimuthal direction of the slow axis AX5 shown in FIG. This is the same in other simulations for the liquid crystal display element 130.

As shown in FIG. 10, in the O-mode liquid crystal display element 130, similarly to the above-described liquid crystal display element 30, the viewing angle characteristics in the left and right directions (corresponding to the x-axis direction in FIG. 9A). Becomes almost symmetric. A viewing angle characteristic with few reversal regions in the left-right direction is obtained. As is clear from comparison with FIG. 4, the region showing high contrast is wider than the O-mode liquid crystal display element 30. It is very effective when the liquid crystal display element 130 is used for an application where the left and right viewing angles (viewing angles) are regarded as important.

FIG. 11 is a simulation result when the effective tilt angle θ of the optical axis OA of each of the phase difference plates 120a and 120b is 15 ° and the phase difference plates 120a and 120b are arranged under the E mode. Is shown.

As shown in the figure, the viewing angle characteristics of the left and right (corresponding to the x-axis direction in FIG. 9B) in the E-mode liquid crystal display element 130 as well as the liquid crystal display element 30 described above. Becomes almost symmetric. It is possible to configure a liquid crystal display device having a small number of inversion regions in the left-right direction.

FIG. 12 shows a simulation result when the effective tilt angle θ of the optical axis OA of each of the phase difference plates 120a and 120b is 10 ° and these phase difference plates 120a and 120b are arranged under the O mode. Is shown.

FIG. 13 shows a simulation result when the effective tilt angle θ of the optical axis OA of each of the phase difference plates 120a and 120b is set to 20 ° and the phase difference plates 120a and 120b are arranged under the O mode. Is shown.

As can be seen from comparison between FIGS. 10, 12 and 13, as the effective inclination angle θ of the optical axis OA in each of the phase difference plates 120a and 120b increases,
The area showing high contrast is on the upper side (90 ° azimuth side)
, While the inversion region tends to expand on the lower side (on the azimuth angle of 270 °).

Conversely, as the effective inclination angle θ of the optical axis OA decreases, the viewing angle range (viewing angle) also appears to expand, but the right and left viewing angle characteristics tend to be asymmetric. It seems.

From these results, when the retardation plate is constituted by a tilted NOC film, the effective tilt angle of the optical axis of the tilted NOC film is preferably set to about 25 ° or less on average, and generally from 10 to 20 °. It is considered that it is more preferable to be within the range of °.

Next, a vertical alignment type ECB mode liquid crystal display device was actually produced based on the above simulation results, and its isocontrast characteristics were measured. This liquid crystal display element is hereinafter referred to as “the liquid crystal display element 2 according to the third embodiment.
30 "or" Liquid crystal display element 230 ".

FIG. 14 is a sectional view schematically showing a liquid crystal display element 230 according to the third embodiment. As shown in the figure, the liquid crystal display element 230 has three optical compensation films 2.
22 are provided.

As the individual optical compensation films 222,
VAC-C50 manufactured by Sumitomo Chemical Co., Ltd. was used. VAC-C5
0 is a negative uniaxial optical compensation film. However, in the VAC-C50, the optical compensation film main body is provided on the base film. Therefore, VAC-C50 is not a complete uniaxial optical compensation film. VAC-C5
By laminating a plurality of 0s, a negative biaxial optical compensation film (biaxial NOC film) can be obtained. The in-plane retardation of each of the retarders 220a and 220b is about 18 nm.

The structure of the liquid crystal display element 230 is the same as that of the liquid crystal display element 30 according to the first embodiment except for the configuration of each of the retardation plates 220a and 220b and the arrangement of liquid crystal molecules in the liquid crystal layer 15 described below. Is the same as 8, those components that are functionally common to the components shown in FIG. 1 are denoted by the same reference numerals as those used in FIG. Omitted.

The liquid crystal layer 15 of the liquid crystal display element 230 was constructed using SLM89145 manufactured by Merck Japan.
The twist angle (twist angle) of the liquid crystal molecules in the liquid crystal layer 15 is 250 ° to the left, and the pretilt angle is 86 °. The cell thickness d is 5 μm, and the ratio d / p between the cell thickness d and the chiral pitch p is 0.7.

Vertical alignment film 3 in liquid crystal display element 230
a, 3b, retardation plates 220a, 220b and polarizing plate 2
Table 3 shows the axial angles (azimuth angles) at 5a and 25b and the azimuth angles of the director n of the liquid crystal molecules at the center in the thickness direction of the liquid crystal cell.

[0076]

[Table 3] FIG. 15 shows vertical alignment films 3a, 3a in the liquid crystal display 230.
b Each easy axis AX1, phase difference plate 220a, 2
20b each slow axis AX6 and the polarizing plate 25
a, 25b The axis angle (azimuth angle) of each transmission axis AX4
Is illustrated.

However, in the figure, for convenience, the upper transparent substrate 1a or the lower transparent substrate 1b is shown instead of the vertical alignment films 3a, 3b, and these transparent substrates 1a, 1b are provided with an easy axis (orientation direction). AX1 is shown. The thicknesses of the retarders 220a and 220b and the polarizers 25a and 25b are ignored.

It is apparent from the fact that the slow axis AX6 of the phase plate 220a is parallel to the transmission axis AX4 of the polarizing plate 25a, and the slow axis AX6 of the phase plate 220b is parallel to the transmission axis AX4 of the polarizing plate 25b. The liquid crystal display element 230 is an O-mode liquid crystal display element.

The liquid crystal display element 230 having the above configuration
Under driving conditions under which the maximum contrast is obtained.
Equal contrast characteristics were measured by driving 49 bias or 11.94 bias.

FIG. 16 shows isocontrast characteristics obtained at the time of the above 15.49 bias drive. As shown in the figure, the viewing angle characteristics of the left and right (corresponding to the x-axis direction in FIG. 15) are substantially symmetric. It is visually perceived that the left and right viewing angles (viewing angles) are widened. It is easy to configure a liquid crystal display device having few inversion regions in the left-right direction.

FIG. 17 shows isocontrast characteristics obtained at the time of the above-mentioned 11.94 bias driving. As shown in the figure, the left and right viewing angle characteristics are substantially symmetric, and no reversal region is observed in all directions unless the polar angle is in the range of 0 to 60 °. A viewing angle (a liquid crystal display device having an extremely wide viewing angle can be formed.

Also, the appearance of the liquid crystal display element 230 changes symmetrically in the left-right direction. The viewing angle (viewing angle) in the left-right direction is felt wide.

If the steepness of the liquid crystal display element 230 is higher, that is, if the change of the transmitted light intensity with respect to the change of the applied voltage is steeper, even in the case of the 11.94 bias driving, the liquid crystal display element 230 covers all directions. It is presumed that no reversal region is observed and that a viewing angle characteristic with high left-right symmetry is obtained.

For comparison, VAC-C4 manufactured by Sumitomo Chemical Co., Ltd.
A liquid crystal display element having the same configuration as the liquid crystal display element 230 in other configurations was manufactured by using only one of the liquid crystal display elements 30 to form the upper phase difference plate and omitting the lower phase difference plate. VAC-C
430 is a negative uniaxial optical compensation film constituted by a biaxially stretched film, that is, a NOC film. However, VAC-C430 is not a complete uniaxial optical compensation film, but has an optical compensation film main body provided on a base film. It has an in-plane retardation of about 6 nm.

FIG. 18 shows an easy axis AX of each of the vertical alignment films 3a and 3b in the liquid crystal display device for comparison.
1. The axis angle (azimuth) of the slow axis AX7 of the upper retardation plate 320 and the transmission axis AX4 of each of the polarizing plates 25a and 25b is illustrated.

However, in the figure, for convenience, the upper transparent substrate 1a or the lower transparent substrate 1b is shown instead of the vertical alignment films 3a, 3b, and these transparent substrates 1a, 1b are provided with an easy axis (orientation direction). AX1 is shown. The thicknesses of the retardation plate 320 and the polarizing plates 25a and 25b are ignored.

The liquid crystal display device was driven under a driving condition of obtaining a maximum contrast under a driving condition of 15.49 bias or 11.94 bias to measure isocontrast characteristics.

FIG. 19 shows isocontrast characteristics obtained at the time of the above 15.49 bias drive. As shown in the figure, the symmetry of the left and right viewing angle characteristics is extremely low. The visible region is biased toward the upper region (region with an azimuth angle of 0 to 180 °) and the lower region (region with an azimuth angle of 180 to 360 °).
Is almost invisible. The right and left viewing angle range (viewing angle) is also narrow.

FIG. 20 shows isocontrast characteristics obtained at the time of the above-mentioned 11.94 bias driving. As shown in the figure, the symmetry of the left and right viewing angle characteristics is improved as compared with the case where the 15.49 bias drive is performed. However, the visible range in the lower region (region with an azimuth angle of 180 to 360 °) is extremely narrow.

Also, in the appearance, the liquid crystal display device for comparison causes a different color change in the left-right direction. The viewing angle (viewing angle) in the left-right direction is felt to be narrow.

Although the vertical alignment type ECB mode liquid crystal display device according to the embodiments has been described above, the present invention is not limited to the vertical alignment type ECB mode liquid crystal display device.

For example, in addition to the XY matrix type, the structure of the cell container may be a segment type, a dot matrix type, or the like according to the intended use of the vertical alignment type ECB mode liquid crystal display device.

The retardation plate may be constituted by one biaxial NOC film. Even in that case, the in-plane retardation is preferably 137.5 nm,
More preferably, it is within a range of about 5 to 60 nm.
It is desirable that the two retardation plates constituting one liquid crystal cell have the same optical characteristics.

The relative relationship between the direction of the transmission axis of the polarizing plate (analyzer) and the direction of the transmission axis of the polarizing plate (polarizer) is shown in FIG.
(A), FIG. 3 (B), FIG. 9 (A), FIG. 9 (B) or the relationship shown in FIG. 15 can be reversed.

FIGS. 3 (A), 3 (B), 9 (A) and 9 (B) show the relative relationship between the easy-orientation axis direction and the transmission axis direction.
(A), the slow axis direction of the phase difference plate on the upper transparent substrate and the slow axis direction of the phase difference plate on the lower transparent substrate while maintaining the same relationship as shown in FIG. 9 (B) or FIG. Can be reversed from the illustrated relationship.

It will be obvious to those skilled in the art that various changes, improvements, combinations, and the like can be made.

[0097]

As described above, according to the present invention,
It becomes easy to obtain a vertical alignment type ECB mode liquid crystal display device having excellent electro-optical characteristics and improved viewing angle characteristics. A multi-color display can be performed with a simple element configuration, and a liquid crystal display element having good viewing angle characteristics can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a configuration of a vertical alignment type ECB mode liquid crystal display device according to a first embodiment.

FIG. 2 is a schematic diagram showing an alignment state of liquid crystal molecules in the liquid crystal display device shown in FIG.

3A is a vertical alignment film, a positive uniaxial optical compensation film, a negative uniaxial optical compensation film, and a polarizing plate in one simulation performed on the liquid crystal display element shown in FIG. 1; FIG. 3B is an exploded perspective view illustrating the axis angle (azimuth angle) of FIG. 3, and FIG. 3B is a vertical alignment film and positive uniaxial optics in another simulation performed on the liquid crystal display element shown in FIG. FIG. 3 is an exploded perspective view illustrating the axis angle (azimuth angle) of each of a compensation film, a negative uniaxial optical compensation film, and a polarizing plate.

FIG. 4 is an iso-contrast curve diagram showing one of simulation results on the iso-contrast characteristics of the liquid crystal display element shown in FIG.

5 is an isocontrast curve diagram showing another simulation result of the isocontrast characteristics of the liquid crystal display device shown in FIG.

6 is an iso-contrast curve diagram showing yet another simulation result of the iso-contrast characteristics of the liquid crystal display element shown in FIG.

FIG. 7 is an iso-contrast curve diagram showing yet another simulation result of the iso-contrast characteristics of the liquid crystal display element shown in FIG.

FIG. 8A shows a vertical alignment type E according to a second embodiment.
FIG. 2 is a cross-sectional view schematically showing a CB mode liquid crystal display element,
FIG. 8B is a schematic diagram showing an effective optical axis of the phase difference plate in the vertical alignment type ECB mode liquid crystal display device according to the second embodiment.

9A is an exploded perspective view illustrating an axis angle (azimuth angle) of each of a vertical alignment film, a retardation plate, and a polarizing plate in one simulation performed on the liquid crystal display element illustrated in FIG. 8; FIG. 9B illustrates the axis angle (azimuth angle) of each of the vertical alignment film, the retardation plate, and the polarizing plate in another simulation performed on the liquid crystal display element illustrated in FIG. 8. It is an exploded perspective view.

FIG. 10 is an iso-contrast curve diagram showing one of the simulation results of the iso-contrast characteristics of the liquid crystal display element shown in FIG.

11 is an isocontrast curve diagram showing another simulation result of the isocontrast characteristics of the liquid crystal display element shown in FIG.

12 is an iso-contrast curve diagram showing still another simulation result of the iso-contrast characteristics of the liquid crystal display element shown in FIG.

FIG. 13 is an iso-contrast curve diagram showing yet another simulation result of the iso-contrast characteristics of the liquid crystal display element shown in FIG.

FIG. 14 is a sectional view schematically showing a vertical alignment type ECB mode liquid crystal display device according to a third embodiment.

15 is an exploded perspective view illustrating an axis angle (azimuth angle) of each of a vertical alignment film, a retardation plate, and a polarizing plate in the liquid crystal display element shown in FIG.

FIG. 16 is an isocontrast curve diagram showing one of the measurement results of the isocontrast characteristics of the liquid crystal display element shown in FIG.

17 is an isocontrast curve diagram showing another measurement result of the isocontrast characteristics of the liquid crystal display element shown in FIG.

FIG. 18 is an exploded perspective view illustrating an axis angle (azimuth angle) of each of a vertical alignment film, a phase difference plate, and a polarizing plate in a vertical alignment type ECB mode liquid crystal display device manufactured for comparison.

FIG. 19 is an isocontrast curve diagram showing one of the measurement results of the isocontrast characteristics of the vertical alignment type ECB mode liquid crystal display element manufactured for comparison.

FIG. 20 is an isocontrast curve diagram showing another measurement result of isocontrast characteristics of a vertical alignment type ECB mode liquid crystal display device manufactured for comparison.

[Explanation of symbols]

1a: upper transparent substrate, 1b: lower transparent substrate, 2a,
2b: transparent electrode, 3a, 3b: vertical alignment film, 10 ...
Cell container, 15: liquid crystal layer, 15a: liquid crystal molecule, 2
0a, 20b, 120a, 120b, 220a, 220
b, 320: retardation plate, 21: positive uniaxial optical compensation film, 22, 222: negative uniaxial optical compensation film, 25a, 25b: polarizing plate, 30, 130, 23
0: Vertical alignment type ECB mode liquid crystal display device.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H049 BA06 BA25 BB03 BB62 BC14 BC22 2H088 HA03 HA16 HA18 JA09 KA05 KA06 KA07 KA11 KA14 MA07 2H090 HB03Y HB08Y LA06 LA09 MA01 MA11 MB06 2H091 FA08X FA08 KA11 KA11 KA11 KA11

Claims (16)

[Claims] 1. A cell container having two transparent substrates disposed to face each other at an interval from each other, and a liquid crystal layer contained in the cell container, wherein
A liquid crystal layer in which liquid crystal molecules are arranged under the above twist angle, and a pretilt angle of 85 ° to 60 ° is given to the liquid crystal molecules, and one liquid crystal layer is disposed on each of the outer surfaces of the two transparent substrates. And the effective in-plane indices of refraction nx and ny are different from each other, and both of these effective in-plane indices nx and ny are effective in the thickness direction. a vertical alignment type ECB mode liquid crystal display device comprising a retardation plate larger than nz. 2. The vertical alignment type ECB mode liquid crystal display device according to claim 1, wherein each of the retardation plates includes a plurality of negative uniaxial optical compensation films provided on a base film. 3. The vertical alignment type ECB mode liquid crystal display device according to claim 1, wherein each of the retardation plates includes a positive uniaxial optical compensation film and a negative uniaxial optical compensation film. 4. The vertical alignment type ECB according to claim 1, wherein each of the retardation plates includes a negative biaxial optical compensation film.
Mode liquid crystal display element. 5. The vertical alignment type EC according to claim 1, wherein an in-plane retardation of each of the retardation plates is in a range of 0 to 137.5 nm.
B-mode liquid crystal display element. 6. The liquid crystal display according to claim 1, further comprising a polarizing plate disposed outside each of said retardation plates.
The vertical alignment type ECB mode liquid crystal display device according to any one of the above items. 7. A cell container having two transparent substrates which are opposed to each other with an interval therebetween, and a liquid crystal layer accommodated in the cell container, wherein:
A liquid crystal layer in which liquid crystal molecules are arranged under the above twist angle, and a pretilt angle of 85 ° to 60 ° is given to the liquid crystal molecules, and one liquid crystal layer is disposed on each of the outer surfaces of the two transparent substrates. A retardation plate provided, wherein an effective optical axis of each of the retardation plates is inclined from an in-plane direction, and xy having the optical axis as a z-axis.
Assuming a z orthogonal coordinate system, the refractive index nx in the x-axis direction
And a retardation plate having substantially the same refractive index ny in the y-axis direction and having a refractive index nx and ny larger than the refractive index nz in the z-axis direction. 8. The optical axis has an average of 25 from the in-plane direction.
The vertical alignment type ECB mode liquid crystal display device according to claim 7, wherein the liquid crystal display device is inclined at an angle of not more than 0 °. 9. The vertical alignment type ECB mode liquid crystal display device according to claim 7, further comprising one polarizing plate disposed outside each of the retardation plates. 10. Two oppositely arranged two spaced apart from each other.
A cell container having a plurality of transparent substrates, and a liquid crystal layer accommodated in the cell container, wherein liquid crystal molecules are arranged under a twist angle of 180 ° or more, and a pretilt of 85 ° to 60 ° is applied to the liquid crystal molecules. A method for compensating viewing angle characteristics of a vertical alignment type ECB mode liquid crystal display device comprising a liquid crystal layer provided with an angle, wherein an effective in-plane refractive index nx and ny is different from each other, and both of these effective in-plane refractive indices nx and ny are greater than the effective thickness direction refractive index nz. On the other hand, the effective in-plane refractive index n
x and ny are different from each other, and both of these effective in-plane refractive indices nx and ny are larger than the effective thickness direction refractive index nz. Mode Compensation method for viewing angle characteristics of liquid crystal display element. 11. The viewing angle of the vertical alignment type ECB mode liquid crystal display device according to claim 10, wherein each of the retardation plates is constituted by using a plurality of negative uniaxial optical compensation films provided on a base film. Characteristic compensation method. 12. The vertical alignment type ECB mode liquid crystal display device according to claim 10, wherein each of the retardation plates is constituted by using a positive uniaxial optical compensation film and a negative uniaxial optical compensation film. Viewing angle characteristic compensation method. 13. The method according to claim 10, wherein each of the phase difference plates is formed using a negative biaxial optical compensation film. 14. The vertical alignment type ECB mode liquid crystal display device according to claim 10, wherein an in-plane retardation of each of the retardation plates is in a range of 0 to 137.5 nm. Viewing angle characteristic compensation method. 15. The two opposing arrangements spaced apart from each other.
A cell container having a plurality of transparent substrates, and a liquid crystal layer accommodated in the cell container, wherein liquid crystal molecules are arranged under a twist angle of 180 ° or more, and a pretilt of 85 ° to 60 ° is applied to the liquid crystal molecules. A method for compensating viewing angle characteristics of a vertical alignment type ECB mode liquid crystal display device comprising: And the refractive index nx and y in the x-axis direction when an xyz rectangular coordinate system having the optical axis as the z-axis is assumed.
The refractive indices ny in the axial direction are almost the same, and these refractive indices n
arranging a phase difference plate wherein x and ny are larger than the refractive index nz in the z-axis direction; Assuming an xyz orthogonal coordinate system with the optical axis as the z-axis, the refractive index nx in the x-axis direction and the refractive index ny in the y-axis direction are almost the same, and these refractive indexes nx and ny are Providing a retardation plate having a refractive index greater than nz, and compensating a viewing angle characteristic of the vertical alignment type ECB mode liquid crystal display device. 16. The optical axis has an average of 2 from the in-plane direction.
The vertical alignment type EC according to claim 15, which is inclined at 5 ° or less.
A viewing angle characteristic compensation method for a B-mode liquid crystal display element.