JPH0943564A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower the dependency on a visual field angle by shifting the position where the twist arrangement of an optical anisotropic film starts by a specific angle when viewed from the display surface of a liquid crystal panel. SOLUTION: This liquid crystal display device 1 is constituted by disposing the optical anisotropic film 2 on the display screen side of the liquid crystal panel formed by enclosing a liquid crystal layer 13 of a twist arrangement angle of >=180 deg. between both glass substrates 3, 4 formed with oriented films 7, 12 on their respective inner surfaces. The difference in the twist arrangement angles between the optical anisotropic film 2 and the liquid crystal layer 13 is <=10 deg. and the position where the twist arrangement of the optical anisotropic film 2 starts is shifted by 170 to 190 deg. from the position where the twist arrangement of the liquid crystal layer 13 starts when viewed from the display surface of the liquid crystal panel.

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 having improved viewing angle dependency.

[0002]

2. Description of the Related Art A TN type or STN type simple matrix type liquid crystal display device and a TN type active matrix type liquid crystal display device have been proposed, and both devices have already been commercialized. For example, in a STN type simple matrix type liquid crystal display device, many transparent electrodes are arranged in parallel on the inner surfaces of two glass substrates that are arranged to face each other, and both parallel transparent electrode groups are arranged so as to be orthogonal to each other. A glass substrate is arranged, and an alignment film is formed on the parallel transparent electrode group so that liquid crystal molecules are 180 ° to 2 ° between both glass substrates.
It is a structure in which a 70 ° twist arrangement is used. And a polarizing plate and a phase difference plate are arranged outside both glass substrates.

[0003]

However, the above S
The TN simple matrix type liquid crystal display device has a structure in which liquid crystal molecules are twisted by 180 ° to 270 ° between both glass substrates. Therefore, Δn and thickness d of the liquid crystal molecules change depending on the viewing direction of the display screen. The optical path difference Δnd also fluctuates with this, and as a result, the viewing angle dependency that the brightness of the display screen changes depending on the viewing direction, that is, (1) the entire screen is recognized as a whitish image, or (2) the screen There is a problem that the entire image becomes dark and the light and dark are reversed in the black part of the image (image inversion).

This viewing angle dependency is not limited to the STN type simple matrix type liquid crystal display device using a twisted nematic type liquid crystal display device such as a TN type simple matrix type liquid crystal display device or a TN type active matrix type liquid crystal display device. This is a problem that cannot be solved.

The present inventor has made earnest studies in view of the above circumstances, and as a result, in providing an optically anisotropic film on a liquid crystal panel, the relationship between the optically anisotropic film and the twist alignment angle between the liquid crystal layer and It has been found that the viewing angle dependence is improved by setting each of the relationship between the optically anisotropic film and the twist alignment start position of the liquid crystal layer within a predetermined range.

Therefore, the present invention has been completed based on the above findings, and an object of the present invention is to provide a high-performance liquid crystal display device in which the viewing angle dependency is reduced and the viewing angle is further widened.

[0007]

According to the present invention, a liquid crystal layer of 180 ° is formed between both transparent substrates each having an alignment film formed on the inner surface thereof.
In the liquid crystal display device in which the optically anisotropic film is arranged on the surface of the liquid crystal panel which is twisted and arranged as described above, the twisted arrangement angle difference between the optically anisotropic film and the liquid crystal layer is 10 ° or less. In addition, the twist alignment start position of the optically anisotropic film is 170 ° to 190 ° compared to the twist alignment start position of the liquid crystal layer when viewed from the display surface of the liquid crystal panel.
Characterized by shifting.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.
This will be described below. FIG. 1 is a schematic sectional view of an STN type simple matrix type color liquid crystal display device 1.

Regarding the constitution of the liquid crystal panel, 3 is a glass substrate on the segment side as the transparent substrate,
4 is also a common-side glass substrate as the transparent substrate, and a plurality of transparent electrodes 5 made of ITO (indium tin oxide) arranged in parallel on the glass substrate 3,
An overcoat layer 6 made of SiO ₂ and an alignment film 7 made of a polyimide resin rubbed in a certain direction are sequentially formed.

On the other glass substrate 4, a color filter 8 arranged for each pixel and a black matrix 9 of chromium metal arranged between the color filters 8 are formed. The color filter 8 is formed by a pigment dispersion method, that is, a photosensitive resist prepared in advance with a pigment is applied on a substrate and photolithography is performed.
The R, G, and B indications in the figure indicate that the color filters 8 are colored red, green, and blue, respectively. Then, an overcoat layer 10 made of an acrylic resin is formed thereon,
A large number of transparent electrodes 11 made of ITO arranged in parallel are formed. The transparent electrode 11 is orthogonal to the transparent electrode 5. Further, an alignment film 12 made of a polyimide resin rubbed in a certain direction is formed on the transparent electrode 11.

Both glass substrates 3, 4 formed as described above
Are bonded by a sealant 14 through the liquid crystal layer 13, and the liquid crystal layer 13 is made of chiral nematic liquid crystal and twisted between the glass substrates at an angle of 180 ° or more. A large number of spacers 15 are arranged between the glass substrates 3 and 4 in order to keep the thickness of the liquid crystal layer 13 constant.

For the above liquid crystal panel, an optically anisotropic film 2 made of polyester, polyamide, polycarbonate, etc. and an iodine-based polarizer 17 are sequentially arranged on the outer surface of the glass substrate 3, and the other one is arranged. A retardation film 17 made of polycarbonate and an iodine-based polarizer 18 are sequentially arranged on the outer surface of the glass substrate 4.

Moreover, the twist alignment angle difference in the molecular alignment between the optically anisotropic film 2 and the liquid crystal layer 13 is 10 °.
In the following description, the twist alignment start position of the optically anisotropic film 2 is compared with the twist alignment start position of the liquid crystal layer 13,
It is displaced from 170 ° to 190 ° when viewed from the display surface of the liquid crystal panel.

In the color liquid crystal display device 1 described above, light emitted from a light source device such as a backlight disposed outside the polarizer 18 enters the device through the polarizer 18, and further passes through the retardation film 17. Then, each is colored through the various color filters 8, and the overcoat layer 10, the transparent electrode 11 and the alignment film 1 are formed.
2, the liquid crystal layer 13, the alignment film 7, the overcoat layer 6, and the transparent electrode 5 in that order, and then the optically anisotropic film 2
And the polarizer 16 are sequentially passed, and the passing light is projected onto the human eye.

Thus, the color liquid crystal display device 1 having the above structure
According to this, there is almost no difference in the twist alignment angle between the optically anisotropic film 2 and the liquid crystal layer 13, and the twist alignment start position of the optically anisotropic film 2 is compared with the twist alignment start position of the liquid crystal layer 13, Almost 1 when viewed from the display surface of the liquid crystal panel
A shift of 80 ° is preferred for maximum effect. However, the optically anisotropic film 2 having a twist alignment angle difference of 10 ° or less is provided, and the twist alignment start position of the optically anisotropic film 2 and the twist alignment start position of the liquid crystal layer 13 are set as described above. Also by setting it within such a predetermined range, it is possible to reduce the dependence of the brightness of each pixel on the viewing angle and further widen the viewing angle, and to sufficiently achieve the object of the present invention.

[0016]

EXAMPLE As an example of the present invention, a twist alignment angle (250) is set for a liquid crystal panel of the liquid crystal layer 13 having a twist angle (twist alignment angle) of 250 °.
Fig. 2 shows the case where the optically anisotropic film 2 having
This will be described with reference to FIG.

FIG. 2 shows the relationship between the orientations of the optically anisotropic film 2 and the liquid crystal panel as viewed from the display screen side. In each case, the orientation on the display screen side is shown by a solid line,
The orientation is twisted by 250 ° as it goes toward a light source device such as a backlight, and the final twisted orientation is shown by a broken line.

Further, the relationship between the orientation of each molecule of the optically anisotropic film 2 and the liquid crystal layer 13 and the position of the observer with respect to this is shown in FIG. The T characteristic and the VT characteristic of the liquid crystal layer 13 differ depending on the difference in molecular orientation, and are shown as an average value of both VT characteristics at the observer's viewpoint position. The twist alignment angle difference in each molecular alignment between the optically anisotropic film 2 and the liquid crystal layer 13 is made as small as possible, and the twist alignment start position of the optically anisotropic film 2 and the twist alignment start position of the liquid crystal layer 13 are set. , 180 °, the average VT characteristic value between the two becomes the VT characteristic as viewed from the front even if the viewing angle is changed, so that the viewing angle dependency is eliminated.

Next, the viewing angle characteristics of the color liquid crystal display device 1 obtained in this example were measured and compared with those of the conventional one, and the results shown in FIG. 4 were obtained. In this conventional example, the optically anisotropic film 2 of the color liquid crystal display device 1 of this example is replaced with a retardation film.

In the figure, the solid line is the embodiment and the broken line is the conventional example. According to the color liquid crystal display device 1 of this example, the viewing angle dependence of the brightness of each pixel is reduced to reduce the viewing angle. It can be seen that was made even wider.

The present invention is not limited to the above embodiments, and various modifications and improvements may be made without departing from the scope of the present invention. For example, although the STN type simple matrix type color liquid crystal display device has been described in the above embodiment, a monochrome STN type simple matrix type liquid crystal display device or a TN type simple matrix type liquid crystal display device may be used. Similar effects can be obtained even in a liquid crystal display device or a twisted nematic liquid crystal display device such as a TN active matrix type.

[0022]

As described above, according to the present invention, the twist alignment angle difference between the optically anisotropic film and the liquid crystal layer is 10 °.
It is as follows, and the viewing angle dependence is reduced by shifting the twist alignment start position of the optically anisotropic film from the twist alignment start position of the liquid crystal by 170 ° to 190 ° when viewed from the display surface of the liquid crystal panel. As a result, a high-performance liquid crystal display device having a wider viewing angle can be provided.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a color liquid crystal display device of an example.

FIG. 2 is an explanatory diagram showing a twist alignment relationship between a liquid crystal panel and an optically anisotropic film.

FIG. 3 is an explanatory diagram showing the molecular orientation of a liquid crystal panel and an optically anisotropic film.

FIG. 4 is a view angle characteristic diagram of an example and a conventional example.

[Explanation of symbols]

 1 Color Liquid Crystal Display Device 2 Optically Anisotropic Film 3, 4 Glass Substrate 5, 11 Transparent Electrode 7, 12 Alignment Film 8 Color Filter 13 Liquid Crystal Layer 17 Retardation Film 16, 18 Polarizer

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[Procedure amendment]

[Submission date] October 3, 1995

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

In the figure, the solid line is the conventional example, while
The broken line is an example, and it is understood that according to the color liquid crystal display device 1 of the present example, the viewing angle dependence of the brightness of each pixel can be reduced and the viewing angle can be further widened.

Claims (1)

[Claims] 1. A liquid crystal display in which an optically anisotropic film is arranged on the display screen side surface of a liquid crystal panel in which a liquid crystal layer is twisted and arranged by 180 ° or more between both transparent substrates each having an alignment film formed on each inner surface. In the device, the twist alignment angle difference between the optically anisotropic film and the liquid crystal layer is 10 ° or less, and the twist alignment start position of the optically anisotropic film is different from the twist alignment start position of the liquid crystal layer, A liquid crystal display device, wherein the liquid crystal display device is shifted from the display surface of the panel by 170 ° to 190 °.