JPH06301033A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a liquid crystal display device which is bright in display surface and has good visibility without having interference fringes by arranging a flat plane lens in such a manner that the pitch direction of this lens attains an angle of a specific range with the pitch direction of the matrix of the pixels of a liquid crystal display element. CONSTITUTION:Electrodes are arranged in a matrix form, by which the many pixels are disposed on the substrate of the liquid crystal display element 1 and the opaque black matrix is formed in the non-display parts between the pixels. An illumination device 2 of a direct underneath type is arranged on the rear surface side in the lower part of the liquid crystal display element 1 and a cathode ray tube is used for the light source of this illumination device 2. Further, a light diffusion plate 3 is arranged between the liquid crystal display element 1 and the illumination device 2 and the light from the cathode ray tube is distributed uniformly over the entire surface of the liquid crystal display element 1. The flat plate lens 4 having a pitch in one direction is arranged between the liquid crystal display element 1 and the illumination device 2. This lens is so arranged that the pitch direction of the flat plate lens attains 43 to 47 deg. angle with the pitch direction of the matrix of the pixels of the liquid crystal display element.

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 high brightness and excellent visibility.

[0002]

2. Description of the Related Art A matrix type liquid crystal display element is used for displaying characters, symbolic figures and images. That is, electrodes are arrayed at a predetermined pitch in one direction on the surfaces of a pair of transparent substrates that are opposed to each other, and the electrode arrays are arrayed substantially orthogonally between the pair of transparent substrates. The liquid crystal composition is sandwiched between such a pair of transparent substrates, and the smallest section surrounded by the array electrodes serves as a pixel.

An illuminating device called a backlight is arranged outside one substrate of such a liquid crystal display element. The light from the illuminating device is naturally required to be uniform over the entire surface of the liquid crystal display element. However, since the light source used is not generally a surface light source, a light diffusing plate is arranged between the lighting device and the liquid crystal display element so that the light transmitted through the liquid crystal display element is as uniform as possible.

Further, in order to increase the brightness of the liquid crystal display device and improve the visibility, it has been considered to further dispose a flat lens between the liquid crystal display element and the light diffusing plate. As the flat lens, a prism diffusion plate or a lenticular lens in which a surface of a transparent polymer film or glass is provided with periodic streaky irregularities of a predetermined pitch can be used depending on the form of the liquid crystal display element. . That is, by refracting and condensing the light from the light source with such a flat lens, it is possible to increase the brightness of the liquid crystal display element and improve the visibility.

[0005]

However, in the liquid crystal display element, the electrodes are arranged in a matrix to form pixels, and the electrodes are arranged at a predetermined pitch in both the horizontal axis and the vertical axis. Has been done. When the above-mentioned flat lens is arranged in such a liquid crystal display element, the pitch of the matrix-shaped electrode array and the array pitch of the flat lens optically interfere with each other to generate an interference fringe called a moire pattern, which causes Remarkably reduces visibility. Further, in a liquid crystal display device in which a non-display portion between pixels is made opaque in order to improve contrast, that is, in a liquid crystal display device in which a so-called black matrix is formed, a difference in optical transmittance between the pixel portion and the non-display portion is further increased. Since it is emphasized, the above-mentioned moiré reduction will occur more significantly.

In order to prevent the occurrence of such interference fringes,
The cycle (pitch length) of the flat lens and the cycle (pitch length) of the electrode array of the liquid crystal display element may be matched, and the array direction thereof may be matched. However, even in a liquid crystal display device with a screen size of about 10 inches diagonally used most, since the array electrodes thereof are several hundreds or more in both horizontal and vertical directions, the pitches of both electrodes are made to completely match on the entire screen. That is extremely difficult. Further, even if the pitches of the both are made to coincide with each other on the entire surface of the screen, an apparent cycle shift occurs depending on the viewing angle direction, and thus interference fringes are also generated. This is a phenomenon peculiar to the liquid crystal display device due to the viewing angle dependency of the liquid crystal display device.

[0007]

According to the present invention, a liquid crystal composition is sandwiched between a pair of transparent substrates having electrodes formed on the surface and opposed to each other, and pixels are arranged in a matrix between the electrodes on the pair of substrates. In a liquid crystal display device comprising at least a liquid crystal display element formed with, and a lighting device arranged outside one substrate of the liquid crystal display device, in one direction between the liquid crystal display element and the lighting device. A flat lens having a pitch is arranged, and a pitch direction of the flat lens is 4 with respect to a pitch direction of a matrix of pixels of the liquid crystal display element.
The liquid crystal display device is arranged at an angle of 3 to 47 degrees.

[0008]

When the liquid crystal display element and the flat lens are combined, the interference fringes are caused by the deviation of the period between the pixel pitch and the flat lens pitch along a certain direction. Therefore, the interference fringes cannot be seen only when the pitch periods of both pitches along all directions are completely the same or when one of them is an integral multiple of the other, when the periods are slightly deviated, that is, When the pitch directions of the two are deviated, interference fringes occur.

The width of the interference fringes becomes smaller and less conspicuous as the deviation angle increases, but since the pixels are arranged in a matrix, the width of the interference fringes is reduced due to the interference due to the period of the pixel pitch in the vertical direction. It will spread. Therefore, by setting the pitch direction of the flat lens to an angle of 43 to 47 degrees centered on 45 degrees which is the direction having the largest angle with respect to the horizontal and vertical pixel pitch directions of the liquid crystal display element, It is possible to effectively prevent the generation of interference fringes.

[0010]

EXAMPLES Examples of the present invention will be described below.
Since the liquid crystal display element itself applied to the liquid crystal display device of the present invention is the same as the conventional one, the description of the configuration of the liquid crystal display element will be omitted. FIG. 1 is an exploded configuration diagram showing components of the liquid crystal display device of the present invention.

In FIG. 1, electrodes are arranged in a matrix on a substrate of a liquid crystal display element 1 to arrange a large number of pixels, and an opaque black matrix is formed in a non-display portion between the pixels ( (Not shown). Pixel pitch length is 300μ in the direction of C and the direction orthogonal to C
m.

A direct type illuminating device 2 is arranged on the back side of the lower part of the liquid crystal display element 1. This lighting device 2
A cold cathode tube is used as the light source. Further, a light diffusing plate 3 is arranged between the liquid crystal display element 1 and the lighting device 2,
The light from the cold cathode tubes is evenly distributed over the entire surface of the liquid crystal display element 1.

Between the liquid crystal display element 1 and the light diffusing plate 3, a flat lens 4 made of a prism diffusing plate is arranged. FIG. 2 is a schematic configuration diagram showing a part of the flat lens 4 made of this prism diffusion plate.

The prism diffusion plate has a pitch length P of 350 μm,
A depth D of 150 μm is used. The pitch direction L of the prism diffuser plate is arranged at an angle of 45 degrees with respect to the pitch direction C of the pixels of the liquid crystal display element 1. That is, the pitch direction L of the prism diffuser plate is arranged so as to form an angle of 45 degrees with respect to any of the matrix-shaped electrode arrays of the liquid crystal display element 1.

As a result of displaying on such a liquid crystal display device, substantially no interference fringes that would give a visually uncomfortable feeling were observed. In the above embodiments, the example in which the pitch direction L of the prism diffuser plate is arranged at an angle of 45 degrees with respect to the pitch direction C of the pixels of the liquid crystal display element 1 has been described, but it is substantially 43 degrees. The occurrence of interference fringes can be prevented in the range of up to 47 degrees.

[0016]

As described above, according to the present invention, the pitch direction of the flat plate lens arranged between the liquid crystal display element and the illuminating device and having a pitch in one direction is the pitch direction of the matrix of the pixels of the liquid crystal display element. By arranging the liquid crystal display device at an angle of 43 degrees to 47 degrees, a liquid crystal display device having a bright display surface and no interference fringes and good visibility can be obtained.

[Brief description of drawings]

FIG. 1 is an exploded configuration diagram showing components of an embodiment of a liquid crystal display device of the present invention.

FIG. 2 is a schematic configuration diagram showing a part of the flat lens 4 of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display element 2 ... Illumination device 3 ... Light diffusing plate 4 ... Flat lens

Claims (1)

[Claims] 1. A liquid crystal display device in which a liquid crystal composition is sandwiched between a pair of transparent substrates which have electrodes formed on the surface and are arranged to face each other, and pixels are formed in a matrix between the electrodes on the pair of substrates. A liquid crystal display device including at least a lighting device arranged outside one substrate of the liquid crystal display device, wherein a flat lens having a pitch in one direction is arranged between the liquid crystal display device and the lighting device. The liquid crystal display device, wherein the pitch direction of the flat lens is arranged at an angle of 43 to 47 degrees with respect to the pitch direction of the matrix of pixels of the liquid crystal display element.