JPS63110422A - Transmissive liquid crystal display device - Google Patents

Abstract

PURPOSE:To eliminate a reflection loss so as to utilize the luminous flux of a light source more effectively, by providing a lenticular lens in such a way that stripes of the lens are made almost parallel to the longitudinal direction of a tubular or linear light source. CONSTITUTION:A tubular light source 1 is put in a box body 5, whose inner surfaces are formed of light reflecting surfaces, and a lenticular lens 2 is provided above the light source 1. A milky white plate 3 is provided above the lens 2 and a transmissive liquid crystal panel 4 is provided above the plate 3. The milky white plate 3 is a light diffusing plate which is formed by uniformly impregnating a transparent plate with a light diffusing agent. When such constitution is used, rays of light 6 projected upward from the top of the tubular light source 1 are diffused as rays of light 6-1, 6-2, and 6-3 after they are made incident to the lenticular lens 2. The diffused rays of light are made incident on the milky white plate 3 and form a high-luminance planar light source which is less in luminance unevenness. When the liquid crystal panel 4 is provided above the high-luminance planar light source, a high-luminance liquid crystal displaying picture can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention mainly relates to a thin transmissive liquid crystal display device suitable for increasing the brightness of transmissive liquid crystal displays, transmissive liquid crystal televisions, and the like.

[Conventional technology]

In order to make the transmissive liquid crystal display device thinner and to increase the brightness of the displayed image, it is necessary to make the lighting device thinner and brighter.
．． 9, NIL 47 (February 1986), pp. 5-8. In this method, a light screen made of a transparent plastic plate with metallic At films scattered in dots is placed between a fluorescent tube as a light source and an opalescent plate as a light diffusion plate (see the figure in the above-mentioned document). 2) With this method, even if the lighting device is made thin, the occurrence of uneven brightness can be kept within a practical range.

The principle of preventing brightness unevenness using the optical screen method is to reflect a part of the luminous flux directly above the fluorescent tube on the metal aluminum arranged in a dot shape, and to transmit the remaining luminous flux, which can be applied to the area around the surface light source and the central area. In this case, some of the light reflected by the metal aluminum film reaches the opalescent plate after being reflected again by other parts, but by repeating the reflection, Since light loss also occurs, the average brightness of the surface light source is thought to be slightly lower than in the case without a light screen.

[Problem that the invention seeks to solve]

In the above-mentioned conventional technology, the light reflected by the optical screen cannot be used effectively because of reflection loss.Therefore, in order to increase the brightness of a surface light source with a high sheath layer, it is necessary to prevent the reflection loss from occurring.

SUMMARY OF THE INVENTION An object of the present invention is to provide a transmissive liquid crystal display device for use with a thin surface light source device that eliminates the above-mentioned reflection loss and effectively utilizes the luminous flux emitted from the light source to increase brightness.

[Means for solving problems]

The above object is achieved by arranging a lenticular lens in place of the light screen so that the stripes of the lens are substantially parallel to the longitudinal direction of the tubular or linear light source.

[Effect]

Of the light emitted from the tubular or linear light source, light from near the top of the light source enters the lenticular lens and is diffused in a direction perpendicular to the longitudinal direction of the light source. after that,
The diffused light enters a light diffusing plate uniformly containing a light diffusing agent, is diffused in all directions, and is emitted. In this case, the light emitted from the light source and incident on the lenticular lens is about 98% if the lens does not contain light-absorbing substances such as impurities and the surface of the lens is treated with anti-reflection coating. Since a certain degree of light transmittance can be obtained, light can be diffused in a direction perpendicular to the longitudinal direction of the light source with almost no light loss due to the lens. Due to the above action, the light source 1, 3 is directly above the light source.

By directing the high brightness portions that occur in the longitudinal direction toward the peripheral portions with almost no optical loss, it is possible to equalize the brightness of the surface light source. By combining the surface light source configured as described above with a liquid crystal panel, a display image with high brightness and uniform brightness can be obtained.

〔Example〕

The present invention will be explained below using examples. FIG. 1 is a schematic cross-sectional view of a transmission type liquid crystal display device as an embodiment of the present invention. A tubular light source 1 is arranged inside a box 5 whose inner surface is formed of a light reflecting surface, a lenticular lens 2 is placed above the light source 1, a milky white plate 3 is placed above the lenticular lens 2, and furthermore, the milky white plate 3 is placed above the lenticular lens 2. A transmissive liquid crystal panel 4 is placed above the screen. The opalescent plate 3 is a light diffusing plate in which a light diffusing agent is uniformly contained in a transparent plate. With the above configuration, the light ray 6 emitted directly upward from the top of the tubular light source 1 enters the lenticular lens 2 and is diffused as shown in the rays 6-1, 6-2, and 6-3, and hits the opalescent plate 3. incident. The light ray 6-1 incident on the opalescent plate 3 is further diffused by the opalescent plate 3 to obtain an output beam 9. In addition, after the light ray 7 emitted from the upper part of the light source 1 in an oblique direction enters the lenticular lens 2, the light ray 7-1.7-2.7-3
It is diffused as follows and enters the opalescent plate 3. A light ray 8 emitted from the side of the tubular light source 1 is reflected by the inner surface of the box 5 and directly enters the opalescent plate 3. Note that the width of the lenticular lens 2 is made narrower than the width of the opalescent plate 3 so that the light ray 8 follows the above-mentioned optical path. When setting this width, the optimum value is determined by considering the shape of the box 5, the light diffusion angle of the lenticular lens 2, and other values. The light beam incident on the opalescent plate 3 is further diffused in all directions, and an output beam 9 is obtained which is almost uniformly diffused across the upper surface of the opalescent plate 3. This allows a high-brightness flat light source with less uneven brightness. By arranging the liquid crystal panel 4 on the high-brightness flat light source, it is possible to view a high-brightness liquid crystal display image. As an example of the flat light source of the liquid crystal display device of the present invention, for example, the diagonal dimension of the flat light source part is about 5 inches, and the milky white plate 3
The distance between the lenticular lens 2 and the lenticular lens 2 is 1 mm, the thickness of the lenticular lens 2 is approximately 1 mm, the light diffusion angle is 17°, the distance between the lenticular lens 2 and the tubular light source 1 is 1 cm, the diameter of the tubular light source 1 is 15.5-φ, and the tubular shape is The distance between light source 1 and the box is 5 m,
A case is set in which a 4W fluorescent tube is used as the tubular light source 1.

FIG. 2 shows a comparison of the brightness of this and a conventional liquid crystal display device using an optical screen. In this case, the size (particularly the thickness) of the two liquid crystal display devices is kept constant. The brightness of a liquid crystal display using the surface light source device according to the present invention is about 1.2 times that of a liquid crystal display using a conventional surface light source device using an optical screen, and the brightness unevenness is almost the same.

Here, the brightness unevenness was evaluated by the ratio of the brightness of the maximum brightness point (center part of the surface light source) to the brightness of the minimum brightness point (part of the corner of the surface light source) of the surface light source. The brightness unevenness of 1.8 is approximately 1.8 for both devices, and the actual measured value of the brightness unevenness is approximately 2 based on the above definition of a color television using a cathode ray tube, so the brightness unevenness 1 and 8 are sufficiently acceptable values.

Furthermore, in the device of the present invention, when the lenticular lens 2 is removed, the value of the luminance unevenness becomes about 2.3, so the effect of installing the lenticular lens 2 is sufficiently recognized. In addition, in FIG. 1, the end 2-1 of the lenticular lens 2 is used as a light diffusing surface. This is because Note that this shadow can be reduced by reducing the thickness of the lenticular lens 2 (approximately 0.5
(below) can be made to a level that cannot be visually seen in mass sales.

FIG. 3 shows another embodiment of the invention. When the area of the surface light source to be irradiated is large, it is necessary to diffuse the light from the tubular light source 1 over a wider area.In such a case, as shown in FIG.
In some cases, it may be necessary to use two lenticular lenses 2', 2''.

FIG. 4 also shows another embodiment of the present invention, in which the opalescent plate 3 in FIG. 1 is used as a converging lens.

In reality, a Fresnel lens shape is used to reduce the lens thickness. Generally, the liquid crystal panel 4 has narrow viewing angle characteristics, and it is impossible to view images from all angles. Therefore, the light emitted from the surface light source that illuminates the liquid crystal panel 4 does not need to be emitted in all directions. From the above point of view, in the embodiment shown in FIG. 4, the luminous flux is directed mainly upward, but by applying this embodiment to a liquid crystal display device, the luminous flux diverging over a wide angle can be made into an effective viewing angle. The light can be concentrated in a suitable narrow range, and the brightness of the surface light source can be improved.

FIG. 5 also shows another embodiment of the present invention, in which the converging lens 10 in FIG. 4 is decentered.

In an actual liquid crystal panel, the direction in which the image contrast is best is not perpendicular to the liquid crystal panel, but is often slightly inclined. In such a case, if the angle of inclination and the direction in which the light rays are emitted from the surface light source match, the best contrast direction and the maximum brightness direction will match, which will be convenient for viewing the image. The embodiment shown in FIG. 5 is an example of a structure that can match the best contrast direction and the maximum brightness direction, and the maximum brightness direction of the surface light source is not in the vertical direction of the screen but in a slightly tilted direction.

In the embodiments shown in FIGS. 4 and 5, when the degree of diffusion of the light rays 9' and 9'' emitted from the surface light source is small, the converging lens 1
0.11 may be mixed with some light diffusing substance to make it opalescent.

FIG. 6 shows an example in which two fluorescent tubes are used as the tubular light source, and a lenticular lens 2-1.2-2 is placed above each fluorescent tube 1-1.1-2. This ensures that the light beam is evenly diffused.

A special case of two fluorescent tubes 1-1, 1-2 is a U-shaped light tube 1' shown in FIG. An example of a lenticular lens installed on the U-shaped light tube is shown in FIG.

FIG. 8(a) is a front view, and FIG. 8(b) is a sectional view along c and c'.

The lenticular lens 2 has lenticular lens stripes formed in a U-shape. By arranging the lenticular lens 2 shown in FIG. 8 on the U-shaped light tube 1', the light beam can be diffused in a direction perpendicular to the axis of the fiU-shaped light tube 1'.

FIG. 9 shows an embodiment in which a U-shaped light tube 1' is used, and a normal-shaped lenticular lens 2-3 is used as a lenticular lens installed thereon. FIG. 10 is a front view of the lenticular lens 2-3. Even in the structure shown in FIG. 9, the density of the opalescent plate 3,
By adjusting the distance between the opalescent plate 3 and the lenticular lens 2-3, the light 9 emitted from the opalescent plate 3 can be made into a sufficiently uniform, high-intensity light beam.

In the above example, a lenticular lens is used! - Although the case where one or two sheets are used has been described, if three or more sheets are required to make the emitted light uniform, a configuration using three or more sheets may be used. Furthermore, if it is necessary to diffuse the light rays also in the longitudinal direction of the light source 1, the lenticular lenses 2, 2
．． 2.2.2.

Other lenticular lenses may be arranged such that the light diffusion direction is perpendicular to the light diffusion direction of 2-3. Further, in the above description, a tubular light source is assumed as the light source 1.1, but it may be a linear light source. In addition, if necessary, lenticular lenses 2.2', 2", 2III,
21111, 2-3 The light diffusion angle may be made different between the central part and the peripheral part. For example, it is effective to provide a surface light source with uniform brightness by setting the center part to have a light diffusion effect and the peripheral part to have a light diffusion rate.

〔Effect of the invention〕

As described above, according to the transmission type liquid crystal display device of the present invention,
If the device thickness and brightness unevenness are kept constant, it is possible to reduce the illumination surface light source brightness of the liquid crystal panel by approximately 20 times compared to the conventional surface light source brightness. A transmissive liquid crystal display device with a thickness of approximately 20% can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a transmissive liquid crystal display device as an embodiment of the present invention, and FIG. 2 is a comparison diagram of the central part luminance distribution of the transmissive liquid crystal display device according to the present invention and a conventional transmissive liquid crystal display device. Figures 3, 4, and 5. FIG. 6 is a schematic sectional view of another embodiment of the transmission type liquid crystal display device according to the present invention, and FIG. 7 is an explanatory diagram showing an example of a U-shaped light tube as an example of a tubular light source applied to the device of the present invention. , FIG. 8 is an explanatory diagram showing an example of a lenticular lens applied when the U-shaped light tube shown in FIG. 7 is used, and FIG.
The figure is a schematic sectional view of still another embodiment of the present invention, and FIG. FIG. 6 is a clear view showing another example of the applied lenticular lens. 1.1'...Tubular light source 2.2-1.2-2.2-4.2.2.2. 2...
Lenticular lens 3...Opalescent plate 4...Liquid crystal panel 5...Box body 6.6-1. +5-2.6-3.7.7-1.7-2.
7-3゜8.9.9', 9", III, 9'11
1...Light ray 10...Converging lens 11...Eccentric converging lens A...Brightness distribution of the liquid crystal display device of the present invention B...Brightness distribution of the conventional liquid crystal display device.

Claims (1)

[Scope of Claims] 1. In a transmissive liquid crystal display device configured by disposing a light diffusing plate between a transmissive liquid crystal panel and a tubular or linear light source, as the light diffusing plate, the lens stripe is A transmissive liquid crystal display device characterized by using a light diffusing means including at least a lenticular lens light transmitting plate arranged substantially parallel to the longitudinal direction of a light source. 2. In the transmission type liquid crystal display device according to claim 1, the light diffusing means includes a light transmitting plate formed by uniformly containing and diffusing a light diffusing substance, and a lens stripe extending approximately in the longitudinal direction of the light source. A transmission type liquid crystal display device comprising a combination of lenticular lenses and light transmitting plates arranged in parallel. 3. In the transmission type liquid crystal display device according to claim 1, the light diffusing means comprises a Fresnel converging lens plate;
A transmissive liquid crystal display device comprising: a lenticular lens light transmitting plate arranged so that lens stripes are substantially parallel to the longitudinal direction of the light source;