JPH0531625Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a liquid crystal display device using an incandescent light bulb as a backlighting light source.

[Conventional technology]

A conventional example is shown in FIG. In Figure 2, 1 is a liquid crystal cell (LCD), 2 is a printed wiring board, 3 is a light guide (transparent body) placed on this printed wiring board 2, and 4 is a diffuser plate placed on this light guide 3. The liquid crystal cell 1 is arranged on this diffusion plate 4. Reference numeral 5 denotes an incandescent light bulb as a backlighting light source, which is attached to the printed wiring board 2 so as to be close to the side end surface of the light guide 3. 6
is a case attached to the printed wiring board 2 so as to cover the liquid crystal cell 1, light guide 3, diffuser plate 4, light bulb 5, etc. The contact surface of the light guide 3 with the printed wiring board 2 is coated with white paint or the like so as to cause diffused reflection.

In the liquid crystal display device having such a structure, part of the light emitted from the light bulb 5 enters the light guide 3 and hits the bottom surface thereof. Light is diffusely reflected from this bottom surface and travels in various directions, and a portion of the light illuminates the diffuser plate 4. As a result, the entire diffuser plate 4 appears uniformly illuminated, and the display device becomes like a self-luminous display element. Such lighting is called edge lighting.

[Problem that the invention attempts to solve]

In such a structure, the outer dimension lo of the case 6 is larger than the dimension l of the display window by at least the amount of the light bulb 5. Furthermore, in the case of edge lighting, the dimension l of the display window cannot be made too large in order to obtain uniformity of brightness. Furthermore, there is a drawback that the light emitted from the light source (bulb 5) that does not enter the light guide 3 is wasted.

[Means for solving problems]

This invention has a light guide on the printed wiring board.
In a liquid crystal display device in which a diffuser plate and a liquid crystal cell are sequentially laminated, an incandescent light bulb is arranged as a back illumination light source so that the light emitted from the light guide is incident on the light guide, and these are covered with a case and integrated.
A plurality of light bulb mounting portions extending from the bottom of the printed wiring board to the effective display surface in the light guide are formed to mount the incandescent light bulbs, while an air layer is formed between the light guide and the diffuser plate to mount the light bulbs. The light guide is characterized in that a reflective plate is provided on the light guide surface directly above the light guide.

〔Example〕

FIG. 1 shows an embodiment of the present invention.
1 is a liquid crystal cell, 12 is a printed wiring board, and 13 is a light guide disposed on this printed wiring board 12. The printed wiring board 12 and the light guide 13
A light bulb mounting portion (recess) 14 is formed in the middle portion thereof, and an incandescent light bulb 15 as a back illumination light source is mounted in this portion. Reference numeral 16 is a reflecting plate disposed on the upper surface of the light bulb mounting portion 14 of the light guide 13, and 17 is a diffuser plate disposed above the reflecting plate 17 at a required interval (approximately 2 to 5 mm). , an air layer 18 is formed between the light guide 13 and the diffusion plate 17. The liquid crystal cell 11 is placed on the upper surface of the diffusion plate 17, and a case 19 is attached to cover it.

The reflecting plate 16 can be made by () printing a reflective material on the light guide 13, () cutting white paper or the like into an appropriate shape and pasting it on the light guide 13;
() A reflective surface is formed in advance on a transparent sheet by printing or the like and then placed on the light guide 13.

Note that the reflection plate 16 may be formed of a material through which a portion of the incident light is transmitted.

In the liquid crystal display device having the above structure, the light emitted from the light bulb 15 enters the light guide 13, and a part of it is diffusely reflected at the bottom surface (the surface in contact with the printed wiring board 12), causing the light to pass through the diffuser plate 17 and the liquid crystal display as shown by arrow a. Proceed in the direction of cell 11. In addition, a part of the light is reflected by the reflector 16, then diffusely reflected by the bottom surface, and travels as indicated by arrow b.
Then, a part of the diffusely reflected light diagonally crosses the air layer 18 on the reflection plate 16 as shown by arrow c and passes through the diffusion plate 17.
incident on . As a result, the area directly above the light bulb 15 will not be extremely bright or dark due to light shielding by the reflector 16, resulting in a uniform surface light source.

Note that when the reflection plate 16 is formed of a material through which a portion of light passes, a portion of the light incident on the reflection plate 16 is transmitted and directly travels in the direction of the diffuser plate 17 as shown by arrow d. Therefore, the shadow of the reflection plate 16 becomes thinner, and the thickness of the air layer 18 can be reduced.
As a result, the entire structure can be made thinner.

[Effect of idea]

As described above, according to the present invention, when a light guide, a diffusion plate, and a liquid crystal cell are sequentially stacked on a printed wiring board and are integrated by covering them with a case, the middle part of the light guide (within the effective display surface) Since an incandescent light bulb is installed as a backlighting light source by providing a light bulb attachment part on the backlight, the external dimensions relative to the display area can be made smaller than in the case of edge lighting, and it is also possible to illuminate a large area. What's more, the light from the bulb can be used all around, making it more efficient. In addition, an air layer is formed between the light guide and the diffuser plate, and a reflector is provided directly above the bulb, so the area directly above the bulb will not be too bright or dark, making it possible to create a uniform surface light source. It is possible. Moreover, the presence of the air layer can suppress the temperature rise of the liquid crystal cell, and furthermore, the device can be made thinner.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a liquid crystal display device according to the present invention, and FIG. 2 is a sectional view showing a conventional example. 11...Liquid crystal cell, 12...Printed wiring board,
13...Light guide, 14...Light bulb mounting part, 1
5...Incandescent light bulb, 16...Reflector, 17...Diffusion plate, 18...Air layer, 19...Case.

Claims (1)

[Scope of utility model registration request] A light guide, a diffuser plate, and a liquid crystal cell are sequentially laminated on a printed wiring board, and an incandescent light bulb is placed as a back illumination light source so that the light emitted from the light guide enters the light guide, and these are covered with a case and integrated. In the liquid crystal display device, a plurality of light bulb mounting portions extending from the bottom of the printed wiring board to an effective display surface within the light guide are formed to mount the incandescent light bulb, while an air layer is formed between the light guide and the diffuser plate. What is claimed is: 1. A liquid crystal display device, characterized in that a reflective plate is provided on the surface of the light guide directly above the light bulb mounting portion.