JPH0943597A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify production processes, to lower a manufacturing cost and to improve the dependency on an angle of visibility by disposing a light diffusive optical film which has projections paired with the pixels of a liquid crystal panel and has the diameter of the projections smaller than a pixel pitch on a polarizer on a display screen side. SOLUTION: Phase difference films 16, 18 and the polarizers 17, 19 are respectively successively arranged on both main surfaces of the liquid crystal panel and further, the light diffusive optical film 2 which is provided with the projecting parts paired with the pixels of the liquid crystal panel and is made smaller in the diameter of the projecting parts than the pixel pitch is disposed on the polarizer 17. The light is scattered by the projecting parts at the time is cast to the human eyes through the light diffusive optical film 2. Further, the light is transmitted through the film by the entire part of its flat parts, by which its luminance is enhanced. The lowering of the front surface luminance of the respective pixels by the flat parts is thereby averted and the angle of visibility is widened by the projecting parts. The dependency on the angle of visibility is thus improved.

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 any of these devices are on the market. For example, according to the STN type simple matrix type liquid crystal display device, many transparent electrodes are arranged in parallel on each inner surface of two glass substrates arranged so as to face each other, and the parallel transparent electrode group is further arranged. A structure in which both glass substrates are arranged so as to be orthogonal to each other, an alignment film is formed on each parallel transparent electrode group, and nematic liquid crystal molecules are twist-arranged between 180 ° and 270 ° between both glass substrates. Is. Then, a polarizing plate and a retardation plate are arranged outside the both glass substrates (see, for example, Japanese Patent Publication No. 3-50249).

[0003]

However, according to the above STN type simple matrix type liquid crystal display device, nematic type liquid crystal molecules are 180 ° between both glass substrates.
Since the structure has a twisted arrangement of ˜270 °, Δn
And the thickness d changes depending on the viewing direction of the display screen, and the optical path difference Δnd changes accordingly, and as a result, the viewing angle dependence that the brightness of the display screen changes depending on the viewing direction,
That is, there are problems that (1) the entire screen is recognized as a whitish image, and (2) the entire screen becomes dark, and the light and dark are inverted in the black portion of the image (image inversion).

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

In order to solve such a viewing angle dependency, S
In the TN type simple matrix type, the refractive index of the retardation plate in the three-dimensional direction (thickness direction) is adjusted, and in the other TN type active matrix type, different voltage-transmittance characteristics are obtained for the divided pixels. It has also been proposed to provide the above (pixel division method), to give different orientations to the divided pixels (orientation division method), and to improve the retardation plate.

However, although the viewing angle dependence of each of the methods is somewhat improved, it is not yet satisfactory, and further improvement of the viewing angle dependence is desired.

In the pixel division method and the orientation division method,
There is also a problem in that the steps required for the division and the difficulty of the division are added to increase the manufacturing cost.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above problems and to provide a liquid crystal display device which simplifies the manufacturing process to reduce the manufacturing cost and improves the viewing angle dependency.

[0009]

In the liquid crystal display device of the present invention, a retardation film and a polarizer are sequentially arranged on both main surfaces of a liquid crystal panel, and a liquid crystal is formed on the polarizer on the display screen side. It is characterized in that a light diffusing optical film is provided, which has a projection that forms a pair with a pixel of the panel, and the diameter of the projection is smaller than the pixel pitch.

Another liquid crystal display device of the present invention is the same as the above liquid crystal display device of the present invention, wherein the light diffusing optical film is provided on a polarizer, and a liquid crystal panel and a retardation film are provided between the liquid crystal panel and the retardation film. It is characterized by being arranged in.

In still another liquid crystal display device of the present invention, in the liquid crystal display device of the present invention, instead of disposing the light diffusing optical film on a polarizer, a retardation film and a polarizer are provided. It is characterized by being placed in between.

Thus, in each of the above-described liquid crystal display devices of the present invention, the projections forming a pair with the pixels of the liquid crystal panel are provided, and the light diffusing optical film having the diameter of the projections smaller than the pixel pitch is provided on the display screen side. As a result, each pixel has a protrusion with a protrusion at the corresponding portion and a flat portion without a protrusion. Light is scattered by the protrusion and light is transmitted by the entire flat portion. The luminance is prevented from being lowered, and thus the front luminance of each pixel is prevented from being lowered by the flat portion, and the viewing angle can be widened by the protruding portion, and the viewing angle dependency can be improved.

Further, according to the present invention, the sharpness of the image is different depending on where the light diffusing optical film is arranged in relation to the retardation film and the polarizer. That is,
Compared to disposing the light diffusing optical film on the polarizer, it is better to dispose the light diffusing optical film in advance between the liquid crystal panel and the retardation film or between the retardation film and the polarizer. The light with improved viewing angle dependence will pass through the polarizer, and this has the advantage that the sharpness of the image is improved because the light passes through the polarizer in a state in which the directions of the light are aligned. is there.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

(Example 1) FIG. 1 is a schematic sectional view of an STN type simple matrix type color liquid crystal display device 1, and FIGS. 2 and 3 are an enlarged plan view and enlarged view of an essential part of a light diffusing optical film 2 made of polycarbonate. FIG.

In the color liquid crystal display device 1 of FIG. 1, first, regarding the liquid crystal panel, 3 is a glass substrate on the segment side, 4 is a glass substrate on the common side, and a large number of glass substrates are arranged in parallel on the glass substrate 3. An arrayed transparent electrode 5 made of ITO, 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. Then, an alignment film 12 made of a polyimide resin rubbed in a certain direction is formed on the transparent electrode 11. Further, the glass substrates 3 and 4 formed as described above are bonded together by the sealant 14 via the liquid crystal layer 13 made of chiral nematic liquid crystal twisted at an angle of 250 °, for example. A spacer 15 is provided between the glass substrates 3 and 4 in order to keep the thickness of the liquid crystal layer 13 constant.
Are arranged in large numbers.

A retardation film made of polycarbonate, an iodine-based polarizer, and a light diffusing optical film are provided on the liquid crystal panel having the above structure as follows. That is, the retardation film 16, the polarizer 17, and the light diffusing optical film 2 are sequentially arranged on the outer surface of the glass substrate 3, and the retardation film 18 and the polarizer 19 are sequentially arranged on the outer surface of the other glass substrate 4. Deploy.

In the color liquid crystal display device 1, the light emitted from a light source device such as a backlight arranged outside the polarizer 19 enters the device through the polarizer 19 and further passes through the retardation film 18. 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 this order, and further sequentially passes through the retardation film 16, the polarizer 17, and the light diffusing optical film 2, and the passing light is It is projected in the eyes of people.

FIG. 2 showing the light diffusing optical film 2
According to the above, the pyramid-shaped projections P are arranged at the positions forming a pair with the pixels of the liquid crystal panel. Further, FIG. 3 is a cross-sectional view taken along the section line AA of one pixel shown in FIG.

Each pixel size is composed of a protrusion and a flat portion, and the pixel size is a × b, while the protrusion size is e × b and the flat portion size is f × b.
Further, c and d each represent a pixel pitch. These dimensions are, for example, a of 0.30 to 0.32 mm and b of 0.0
8 to 0.10 mm, c is 0.10 to 0.12 mm, d is 0.32 to 0.34 mm, and e is 0.15 to 0.16 m.
m and f are 0.15 to 0.16 mm.

Thus, the color liquid crystal display device 1 having the above structure
In the case of passing through the light diffusing optical film 2 and being projected onto the human eye, a protrusion and a flat portion are provided corresponding to each pixel, and the light is scattered by the protrusion, and further the flat portion. Through the whole, the light is transmitted to increase the brightness, so that the flat part of each pixel does not lower the front brightness, and the projection part can widen the viewing angle, improving the viewing angle dependence. .

(Example 2) Color liquid crystal display device 1a of this example
Differs from the color liquid crystal display device 1 in the location of the light diffusing optical film 2, and instead of disposing the light diffusing optical film 2 on the polarizer 17, a liquid crystal panel is provided. It is arranged between the retardation film 16. The other structure is the same as that of the color liquid crystal display device 1. The same parts as those of the color liquid crystal display device 1 of FIG. 1 are designated by the same reference numerals.

According to the color liquid crystal display device 1a having the above-described structure, the light diffusing optical film 2 is arranged between the liquid crystal panel and the retardation film 16 as compared with the case where the light diffusing optical film 2 is arranged on the polarizer 17. The light whose viewing angle dependence has been improved by the light diffusing optical film 2 passes through the polarizer 17 in advance, so that the light passes through the polarizer 17 in a state in which the directions of the light are aligned. The sharpness of the image is improved.

(Example 3) Also in the color liquid crystal display device 1b of this example, the location of the light diffusing optical film 2 is changed in the same manner, and the light diffusing optical film 2 is arranged on the polarizer 17. Instead, it is arranged between the retardation film 16 and the polarizer 17. The other structure is the same as that of the color liquid crystal display device 1. The same parts as those of the color liquid crystal display device 1 of FIG. 1 are designated by the same reference numerals.

Also in the color liquid crystal display device 1b having the above-mentioned structure, compared to the case where the light diffusing optical film 2 is arranged on the polarizer 17, the light whose viewing angle dependency is improved passes through the polarizer 17. As a result, since the light passes through the polarizer 17 in the same direction, the sharpness of the image is improved.

The present invention is not limited to the above embodiments, and various modifications and improvements can be made without departing from the scope of the present invention. For example, although the protrusion P of the protrusion is pyramidal in the above embodiment, it may be conical or hemispherical instead.

In the present embodiment, the STN type simple matrix type color liquid crystal display device is used as an example, but a monochrome STN type simple matrix type liquid crystal display device is also used. Alternatively, the same effect can be obtained with a TN type simple matrix type liquid crystal display device or a TN type active matrix type twisted nematic type liquid crystal display device.

[0028]

As described above, according to the liquid crystal display device of the present invention, there is provided a light diffusing optical film in which the projections forming a pair with the pixels of the liquid crystal panel are provided and the diameter of the projections is made smaller than the pixel pitch. By providing each pixel, the flat part does not lower the front brightness, the projection part can widen the viewing angle, and the light diffusing optical film can be easily formed by a molding technique such as injection molding. Therefore, no process is required for that, and as a result, the manufacturing process is simplified and the manufacturing cost is reduced.
It is possible to provide a liquid crystal display device with further improved viewing angle dependency.

Further, according to the liquid crystal display device of the present invention, as compared with the liquid crystal display device in which the light diffusing optical film is arranged on the polarizer, it is arranged between the liquid crystal panel and the retardation film, or If it is placed between the retardation film and the polarizer, the light with the viewing angle dependence previously improved by the light diffusing optical film will pass through the polarizer, which will polarize the light in the same direction. Since the image passes through the child, the sharpness of the image is improved. As a result, it is possible to provide a liquid crystal display device in which the manufacturing cost is reduced and the image sharpness and the viewing angle dependency are further improved.

[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 enlarged plan view of an essential part of a light diffusing optical film.

FIG. 3 is an enlarged cross-sectional view of a main part of a light diffusing optical film.

FIG. 4 is a schematic cross-sectional view of a color liquid crystal display device of another embodiment.

FIG. 5 is a schematic cross-sectional view of a color liquid crystal display device of another embodiment.

[Explanation of symbols]

 1, 1a, 1b Color liquid crystal display device 2 Light diffusing optical film 3, 4 Glass substrate 5, 11 Transparent electrode 7, 12 Alignment film 8 Color filter 13 Liquid crystal layer 16, 18 Phase difference film 17, 19 Polarizer P protrusion

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuo Miyazaki 999-3 Hayato-cho, Aira-gun, Kagoshima Prefecture Kyocera Corporation Hayato factory

Claims (3)

[Claims] 1. A retardation film and a polarizer are sequentially arranged on both main surfaces of a liquid crystal panel, and projections paired with pixels of the liquid crystal panel are provided on the polarizer on the display screen side. Moreover, a liquid crystal display device is provided with a light diffusing optical film in which the diameter of the protrusion is smaller than the pixel pitch. 2. The liquid crystal display device crystal according to claim 1, wherein the light diffusing optical film is arranged between a liquid crystal panel and a retardation film instead of being arranged on a polarizer. Liquid crystal display device. 3. The liquid crystal display device crystal according to claim 1, wherein the light diffusing optical film is provided between the retardation film and the polarizer, instead of being provided on the polarizer. Liquid crystal display device.