JPH0511577Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a lighting device for a liquid crystal display provided in an electronic device.

(B) Prior Art Conventionally, in devices that display digital clocks and counters using liquid crystal displays, backlighting is provided for displaying in dark places.

As this back lighting, there are those using light emitting diodes and those using lamps.

Conventionally, as a backlighting means using a lamp, a device as disclosed in, for example, Japanese Utility Model Application Laid-open No. 49-65172 (101E5) is known.

(c) Problems to be solved by the invention In devices that use light-emitting diodes for backlighting, if the size of the liquid crystal display is large, for example, if it is rectangular, multiple light-emitting diodes are required. Therefore, there were problems in that the cost was very high and uneven illumination appeared in various places. In addition, in devices that use lamps, the lamp becomes a point light source, so unless the reflection shape of the reflector is modified, it is not possible to irradiate uniform light over the entire liquid crystal display. There was a problem that the image became dark.

(d) Means for solving the problems In view of the above-mentioned problems, the present invention provides a lighting device that irradiates lamp light from the back of a rectangular liquid crystal display with a reflective case in which a lamp is held in the center of the back. a first light diffusing plate made of semi-transparent plastic attached to the front opening of the reflective case and arranged in parallel with the back surface of the liquid crystal display; and a first light diffusing plate made of semi-transparent plastic disposed close to the lamp in the reflective case. and a third light diffusing plate made of translucent plastic that is arranged parallel to the second light diffusing plate at a constant interval and irradiating uniform light to the first light diffusing plate. The present invention provides an illumination device for a liquid crystal display panel comprising:

(e) Effect The lamp light from the center of the back of the reflection case is directly diffused by the second light diffusion plate, and the weak light that has been diffused and transmitted by the second light diffusion plate is diffused by the third light diffusion plate. Ru. This evens out the strong light in the center,
By irradiating uniform light onto the first light diffusing plate attached to the front opening of the reflective case, the back surface of the liquid crystal display can be evenly illuminated.

(F) Embodiments Below, embodiments of the device of the present invention shown in the drawings will be described.

Fig. 1 is a perspective view of the device of the present invention, Fig. 2 is a cross-sectional view thereof, and Fig. 3 is a longitudinal sectional view thereof. The reflective case 1 is made of opaque plastic and has a front opening 1b. Reference numeral 4 denotes a first light diffusing plate made of semi-transparent plastic with a color film sheet 5 pasted on its inner surface, and is attached to the front opening 1b of the reflective case 1.

Reference numeral 6 denotes a rectangular liquid crystal display, which is fixed on a printed circuit board 7 as shown in FIG. 3, and the first light diffusing plate 4 is arranged in parallel on the back side.

Reference numerals 8 and 9 denote second and third light diffusing plates arranged in parallel with and close to the lamp 3 within the reflective case 1, and each of which is made of semi-transparent plastic. The second light diffusing plate 8 is inserted into the square hole 1c of the reflection case 1 facing the lamp 3, and the third light diffusing plate 9 is placed at a certain distance from the second light diffusing plate 8 (according to the inventor's experiment). They are inserted into the square holes 1d of the reflective case 1 so that they are parallel to each other with a diameter of approximately 3 mm.

Therefore, according to the device of the present invention configured as described above, the light from the lamp 3, especially the direct light that has the shortest distance to the liquid crystal display panel 6, is diffused by the second light diffusing plate 8. It will be spread. At this time, most of the direct light from the lamp 3 is diffused by the second light diffusing plate 8, but a bright portion remains in the center as shown by diagonal lines in FIG. Therefore, the light diffused and transmitted by the second light diffusing plate 8 passes through the third light diffusing plate 9, which is about 3 mm away, as described above.
Since the light is further diffused by the light, the strong light in the center can be made uniform in illuminance, and the light emitted from the single lamp 3 is irradiated onto the first light diffusing plate 4 within the reflective case 1. However, the back surface of the liquid crystal display panel 6 can be uniformly illuminated.

According to experiments conducted by the present inventor, the optimum distance between the second light diffusing plate 8 and the third light diffusing plate 9 was approximately 3 mm, and uneven illumination was completely eliminated. Both light diffusers 8,
If the distance between 9 and 9 approaches 2 mm or less, the unevenness will be reproduced, and 3.5
When the distance was more than mm, a shadow of the diffuser plate appeared.

(g) Effects of the invention Since the invention is constructed as described above, it is possible to uniformly diffuse and irradiate the back surface of the liquid crystal display with a single lamp light, and to create a rectangular liquid crystal display. This allows for efficient backlighting of the entire body.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the device of the present invention, FIG. 2 is a cross-sectional view, FIG. 3 is a vertical cross-sectional view, and FIG. 4 is a diagram illustrating the state of the second light diffusing plate. 1...Reflection case, 3...Lamp, 4...First
Light diffusion plate, 6...Liquid crystal display, 8...Second light diffusion plate, 9...Third light diffusion plate.

Claims (1)

[Scope of utility model registration request] A lighting device that emits lamp light from the back of a rectangular liquid crystal display, which includes a reflective case that holds a lamp in the center of the back, and a reflective case that is attached to the front opening of the reflective case and that is arranged in parallel on the back of the liquid crystal display. a first light diffusing plate made of semi-transparent plastic, which is disposed close to the lamp in the reflective case, and a second light diffusing plate made of semi-transparent plastic arranged in parallel with the second light diffusing plate at a constant interval. and a third light diffusing plate made of semi-transparent plastic, which is disposed on the substrate and irradiates uniform light onto the first light diffusing plate.