JPH09146089A - Surface light source for color display device and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light source constituted so that a mixed color is not recognized by the sense of eye by arranging the pixels of three primary colors but the mixed color is color-displayed by one pixel by transmitting the mixed color or preventing it from being transmitted by providing plural light emission sources emitting the different-color light and a reflection plate reflecting the light of the light emission source in the direction of a light diffusion plate in a housing. SOLUTION: The red LED 3, the green LED 4, the blue LED 5 being the light emission sources and the reflection plate 6 reflecting the light are provided in the housing 2. Then, the light emitted from the LED 3 is radiated forward extending over a wide angle, reflected on the plate 6 and advanced in the direction of the light diffusion plate 1. The light emitted from the LED 4 and the LED 5 are also similarly reflected on the plate 6 and they arrive at the plate 1. As the result, three colors of red, green and blue are mixed on the plate 1. By controlling the intensity and the turning-on/off of the respective lights, the desired color is obtained and uniformly radiated from the surface of the plate 1 in a direction shown by arrows OPTO.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar light source for a color display device, which is suitable for a backlight for irradiating light from the back side of a display device such as a color liquid crystal display panel or an illuminated signboard. More specifically, the present invention relates to a planar light source for a color display device that can obtain a uniform color display even when a display device is viewed nearby.

[0002]

2. Description of the Related Art Conventionally, when color display is performed on a liquid crystal display panel or the like, as shown in FIG. 3 (a) or FIG. 3 (b), red (R), green (G), and blue (B) are displayed. Each dot of the three primary colors is set as one set to form one dot 11, and red,
3 by changing the intensity of green and blue
Color display for each dot 11 is performed by the mixed color of one pixel. That is, in the case of a liquid crystal display panel, each color filter is provided on the transparent substrate corresponding to the red, green, and blue pixels, and the color of the mixed light is changed by controlling the light that passes through the pixels. I am letting you.

[0003]

In a conventional color display device in which a backlight is provided on the back surface side of a display panel for color display, as described above, three adjacent pixels are red-lighted by color filters. A method of displaying three primary colors of green, green, and blue and recognizing one dot as a mixed color when viewed from a distance is used. Therefore, a white light source having a constant brightness is used as a light source provided on the back side of the display panel as a backlight, and a switching element must be provided for each color pixel in order to transmit or block light of mixed colors. .

Further, according to this method, since adjacent colors are viewed as if they were mixed by the sense of the eye, it is possible to recognize them as a mixed color if each pixel is made very small. However, there is a problem that in the vicinity of the display screen, the colors are recognized not as mixed colors but as separate colors, and not as a beautiful color display screen.

The present invention solves such a problem and provides a color flat type display device which displays an image by arranging a light source on the back surface side of a display panel and transmitting or not transmitting the light.
Provided is a planar light source for a color display device capable of displaying a color mixed by one pixel by transmitting or not transmitting the color mixed by one pixel instead of arranging pixels of three primary colors side by side to recognize the color mixed by the eyes. The purpose is to do.

[0006]

A planar light source for a color display device according to the present invention comprises a box body provided with a light diffusion plate on one surface, and a plurality of boxes provided in the box body for emitting light of different colors. The light emitting source includes a light emitting source and a reflecting plate that faces the light emitting source and reflects the light from the light emitting source toward the light diffusing plate.

Each of the plurality of light emitting sources is composed of an LED and has a control means capable of changing its brightness for each color, which consumes less power and has a long life.
This is preferable because it is easy to obtain a display screen capable of obtaining an arbitrary mixed color and displaying a full color.

A plurality of planar light sources according to claim 1 are arranged in a matrix, and the light diffusing plate is provided continuously over at least two boxes, corresponding to each pixel. This is preferable because the assembly of the planar light sources is easy.

In the liquid crystal display device of the present invention, a liquid crystal panel in which a plurality of pixels whose transmission and non-transmission of light are independently controlled are formed in a matrix, and each of the pixels on the back surface side of the liquid crystal panel are provided. The planar light source according to claim 1 is provided.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a planar light source for a color display device of the present invention and a liquid crystal display device using the same will be described.

FIG. 1 is a perspective view for explaining a planar light source of the present invention and a diagram for explaining its operating principle, and FIG. 2 is an explanatory view of a liquid crystal display device using the planar light source.

In FIG. 1, reference numeral 1 is a light diffusion plate made of polyethylene terephthalate (PET), polycarbonate or the like, which allows even light coming from an oblique direction to be uniformly radiated in all directions on the surface, and 2 is a box, A plurality of light emitting sources, for example, red LEDs 3, are provided on the inner surface of one side surface.
A green LED 4 and a blue LED 5 are provided, and a reflection plate 6 that reflects light from a light emitting source toward the light diffusion plate 1 is provided in the box body 2. The reflection plate 6 may not be provided as a separate component, but a part of the wall surface of the box body may be used as the reflection plate. Further, it is preferable that the box body 2 be completely surrounded because the waste of light is eliminated, but the box body 2 may not be completely surrounded.

The box body 2 is preferably formed of a metal plate made of aluminum or the like that easily reflects light. However, the box body 2 is not limited to the metal plate and may be made of plastic or the like so that the inner surface is easily reflected. . The reason why the inner surface is easily reflected is to effectively use the light from the light emitting source. That is, the light emitted from the light emitting source is reflected and emitted to the outside through the light diffusing plate 1 as shown in FIG. It is preferable to apply a white paint or the like to the inner surface of the box body 2 because the internal reflection is further improved and the light loss is reduced.

As shown in FIG. 1A, a red LED 3, a green LED 4 and a blue LED are provided on one side surface of the box body 2.
Two pieces of each 5 are arranged horizontally and are arranged vertically. This is based on the assumption that the pixel is, for example, about 2 cm × 2 cm, and the LED has a diameter of about 5 mm. However, if the LED chip is used, the size is further reduced, and the number of LEDs to be arranged and the type of LEDs are not limited, depending on the size of the pixel. In addition, the LEDs are arranged in the same color without arranging them in a line, as shown in FIG.
The red LED 3, the green LED 4 and the blue LED 5 may be alternately arranged as shown in FIG. The present invention is characterized in that the light sources of a plurality of emission colors are provided in the box body in this way. That is, the light of a desired color obtained by mixing the light from the light emitting sources of a plurality of colors is used as the backlight.

FIG. 1 (c) is a view for explaining the principle that the lights from the respective light emitting sources are mixed in the box to obtain the desired light. As shown in FIG. 1C, for example, red LE
The light emitted from D3 is emitted over a wide front angle. Then, the light is reflected by the reflection plate 6 in front of it, and proceeds toward the light diffusion plate 1. On the other hand, the light emitted from the green LED 4 and the blue LED 5 is also reflected by the reflection plate 6 and reaches the light diffusion plate 1. As a result, the light diffusion plate 1
The above three colors of red, green and blue are mixed, and the desired color is obtained by controlling the intensity and on / off of each light, and the light is uniformly irradiated from the surface of the light diffusion plate 1 in the direction of the arrow OPTO. To be done. As described above, since the light emitted from each light emitting source is emitted at a wide angle and reaches the entire surface of the light diffusion plate 1 uniformly, the order of arranging the LEDs 3, 4, 5 which are each light emitting source does not matter so much. .

Although an LED is used as a light emitting source in the above-mentioned example, an LED is preferable because it is small and easy to provide even in a narrow space, and can be driven with a low voltage and has a long life. Further, since LEDs can be stacked as semiconductor chips as they are, they are convenient when used as a planar light source for a small display screen (pixel). However, the light source is not limited to the LED, and a white light source such as a normal miniature bulb covered with a color filter may be used. Also, a number of point light sources can be arranged to form a linear light source.

A control means for arranging the above-mentioned planar light source in accordance with each pixel of the flat panel display device and changing the light intensity (luminance) of each light emitting source in accordance with the information signal of each pixel is provided. If provided, each pixel can have an arbitrary emission color, and full-color image display can be obtained. In this case, if the light diffuser plates of the planar light source that are arranged vertically and horizontally are combined into a large one, only the box part without the upper surface of the planar light source is prepared, and it is used as a large light diffuser plate. By sticking, a large color planar light source for a flat panel display device in which a planar light source corresponding to each pixel is formed vertically and horizontally can be obtained.

FIG. 2 shows a cross-sectional explanatory view of a liquid crystal display device using such a planar light source. In FIG. 2, 21, 22
Is a transparent substrate made of glass or the like, 23 and 24 are transparent electrodes provided on the transparent substrate, respectively, one is formed vertically and horizontally and the other is formed left and right, and the intersections thereof are pixels,
Pixels are formed in a matrix. Reference numerals 25 and 26 are alignment films, 27 is a sealant for attaching two transparent substrates, 28
Is a liquid crystal material injected between two transparent substrates, 29, 30
Is a polarizing plate, and these structures have the same structure as a normal liquid crystal panel. In the liquid crystal display device of the present invention, the backlight is not a single light source common to the entire liquid crystal panel, but a separate planar light source for each pixel (common light diffusion plate 1 in FIG. 2).
Is characterized in that separate boxes 2) are continuously arranged. That is, in the liquid crystal display device of the present invention, the planar light source as shown in FIG. 1 is provided so as to be located below each pixel. As a result, light of a color suitable for each pixel can be combined for each pixel, and the combined light can be transmitted for observation. Therefore, instead of visually mixing colors, there is no color unevenness when viewing close up or even in a liquid crystal display device having a large display screen and a large pixel per pixel, and natural color display is required. You can In this example, the light diffusion plates of the adjacent surface light sources are commonly provided, but they may be separately configured.

[0019]

As described above, according to the present invention, the three primary colors of light are not arranged and three pixels are observed as one dot, but the mixed color is transmitted through each pixel. Therefore, it is possible to obtain a beautiful natural color display screen without being observed in different colors that are not mixed depending on the viewing position.

Further, since one color can be formed by a plurality of light sources, even if one light source becomes defective, the whole pixel does not turn off and becomes black, and stable display can be obtained.

Furthermore, since each color can be represented by one pixel, the number of pixels, switching elements, etc. can be reduced, and the light source can be totally reduced, so that excellent display characteristics can be obtained. It is possible to obtain the color display device having the same at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a planar light source of the present invention and its operating principle.

FIG. 2 is a diagram illustrating a structure of a liquid crystal display device of the present invention.

FIG. 3 is an explanatory diagram of a conventional color display.

[Explanation of Codes] 1 Light Diffusing Plate 2 Box Body 3 Red LED 4 Green LED 5 Blue LED 6 Reflector

Claims (4)

[Claims] 1. A box body provided with a light diffusion plate on one surface, a plurality of light emitting sources provided in the box body for emitting light of different colors, and a light emitting source provided opposite to the light emitting source. A planar light source for a color display device, comprising a reflecting plate that reflects light in the direction of the light diffusing plate. 2. The planar light source according to claim 1, wherein each of the plurality of light emitting sources is composed of an LED, and has a control unit capable of changing the brightness for each color. 3. A color display device comprising a plurality of the planar light sources according to claim 1 arranged in a matrix and the light diffusing plate provided continuously over at least two boxes. Area light source. 4. A liquid crystal panel in which a plurality of pixels whose transmission and non-transmission of light can be independently controlled are formed in a matrix, and the pixels are provided for each of the pixels on the back surface side of the liquid crystal panel. A liquid crystal display device comprising the planar light source described.