JP2000235119A - Light transmission plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the luminance at the corner parts of a light transmission plate near a non-light emitting part of a light source when the light source has the non-light emitting part and the effective light emission length is smaller than the length at the light incident end face of the light transmission plate. SOLUTION: The light transmission plate 10 has the length L0 approximately equal to the length of a liquid crystal display section 30. A cold cathode tube 20 has electrode parts 22 and 23 at both ends and the length AL1 of the effective light emitting part 21 is smaller than L0. The parts 12 and 13 facing the non-light emitting part opposite to the electrode part within the end faces of the light transmission plate facing the cold cathode tube project from the portion facing the effective light emitting part opposite to the effective light emitting part. The light emitted from near the end the effective light emitting part of the cold cathode tube is made incident on the inside of the light transmission plate from an arcuate portion connecting the portion facing the effective light emitting part and the portion facing the non-light emitting par. These light rays are emitted from the corner parts A and B and improved the luminance of the corner parts A and B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a light guide plate used for a backlight or a front light of a liquid crystal display device.

[0002]

2. Description of the Related Art An illumination device called a backlight or a front light is used to make it easier to see the display surface of a liquid crystal display device. In these, light from a light source arranged on the side is guided by a light guide plate to each part on the front side or the back side of the liquid crystal display surface and emitted toward the liquid crystal display surface.

In developing a liquid crystal display device, it is required that the liquid crystal display surface be made as large as possible for easy viewing. Therefore, the size of the liquid crystal display surface is determined first, a light guide plate of the same size is prepared, and a light source having a length that can be arranged at the size (length or width) is adopted. It is.

Here, a linear light source called a cold-cathode tube is often used as a light source, and this cold-cathode tube must be provided with an electrode portion connected to a power source at both ends. Therefore, the actual length of the light emitting portion of the cold cathode tube is smaller than the length or width of the light guide plate. As a result, there is a problem in that the brightness of the corners of the light guide plate near the non-light emitting portion due to the electrode portions is reduced.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides a light source having a non-light-emitting portion and an effective light-emitting length smaller than the length of the light-entering portion end face of the light guide plate. An object of the present invention is to improve the brightness at the corner of the light guide plate near the light emitting unit.

[0006]

According to the first aspect of the present invention, there is provided a light guide plate for receiving light from a linear light source disposed opposite to a side end face from a side end face, wherein the light source is an end part. The light emitting plate has a non-light emitting portion, the length of the side end surface of the light guide plate is longer than the length of the light emitting portion of the light source, and the light emitting portion facing the side end surface of the light guide plate facing the light emitting portion of the light source. There is provided a light guide plate in which a non-light-emitting portion-facing portion of a side end surface of a light guide plate facing a non-light-emitting portion of a light source projects toward the light source side.

According to the light guide plate configured as described above, a portion of the side end face of the light guide plate between the light-emitting portion-facing portion and the protruding non-light-emitting portion-facing portion is provided near the non-light-emitting portion of the light source. The light emitted from the light emitting part of the light source is incident, and the light improves the brightness at the corner of the light guide plate near the non-light emitting part of the light source.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a top view showing the structure of a first embodiment in which the present invention is applied to a backlight type lighting device of a liquid crystal display device, and FIG. 2 is a side view, which is exaggerated for explanation. ing. The light guide plate 10 is substantially rectangular, and a cold cathode tube 20 as a light source is arranged along one side surface thereof. The area indicated by the broken line is the area where the liquid crystal display unit 30 is arranged.

The light guide plate 10 has a length L0 substantially equal to that of the liquid crystal display unit 30. The total length of the cold cathode tube 20 is also this length L.
0, but the cold-cathode tube 20 has electrode portions 22, 2 at both ends.
3, the length L1 of the effective light emitting portion 21 indicated by hatching is shorter than L0. And
Of the end faces of the light guide plate 10 facing the cold cathode tubes 20, the ends facing the electrode portions 22 and 23, ie, the non-light emitting portion facing portions 12 and 13 are the effective light emitting portion facing portions facing the effective light emitting portion 21. It protrudes more than 11. In the first embodiment, the non-light emitting portion facing portions 12 and 13 project in an arc shape from the effective light emitting portion facing portion 11.

As a result, the effective light emitting portion 21 of the cold cathode fluorescent lamp 20
Are emitted from the vicinity of the end of the light guide plate 10 from the arc portion connecting the effective light emitting portion facing portion 11 and the non-light emitting portion facing portions 12 and 13 to the light guide plate 10. Can be emitted from the corners A and B indicated by horizontal hatching. The brightness of the corners A and B is improved.

FIGS. 2A, 2B, and 2C are cross-sectional views taken along lines IIA-IIA, IIB-IIB, and IIC-IIC of FIG. 1, respectively. In FIGS. 2A, 2B, and 2C, reference numeral 40 denotes a reflector which is omitted in FIG. 1 and which emits light emitted from the cold cathode tube 20 on the side opposite to the light guide plate 10. It is directed to the light guide plate 10. Also,
In FIGS. 2A, 2B, and 2C, reference numeral 50 denotes a reflection sheet that is omitted in FIG. 1 and reflects light transmitted through the light guide plate 10 to form the light guide plate 10. This is a sheet for guiding the light guide plate 10 to a mirror surface.

FIG. 3 is a view showing a second embodiment of the present invention. In the end face of the light guide plate 10 facing the cold cathode tube 20, the non-light emitting portion facing portions 12, 13 are effective. The difference from the first embodiment is that a slope is formed and protrudes from the light emitting unit facing portion 11. FIG. 4 is a view showing a second embodiment of the present invention, in which non-light-emitting portion facing portions 12 and 13 of an end face of light guide plate 10 facing cold cathode tube 20 are:
It differs from the first embodiment in that it protrudes in a step-like manner from the effective light emitting unit facing portion 11. Also in the above-described second and third embodiments, the brightness of the corners A and B can be improved as in the first embodiment. In each of the embodiments, if a process for improving the reflection ability, for example, a satin-like embossing is performed on the corners A and B of the reflection sheet 50, the brightness of the corners can be further improved.

FIG. 5 is a diagram showing the structure of the prior art.
The non-light emitting portion facing portions 12 and 13 of the end face of the light guide plate 10 facing the cold cathode tubes 20 are the effective light emitting portion facing portions 11.
And on the same side. As a result, the amount of light reaching the corners A and B is smaller than in each embodiment of the present invention, and the brightness of the corners A and B is smaller.

FIG. 6 is a diagram showing a luminance distribution of the light guide plate corresponding to the area of the liquid crystal display device 30 according to the first embodiment of the present invention, and is divided into five (X1, X2, X
3, X4, X5) and 5 in the direction (width direction) perpendicular to it.
5 for each division (Y1, Y2, Y3, Y4, Y5)
In each of the divided regions of the 25 matrices, the brightest portion is set to 100, and the% value thereof is shown. Areas X1 and Y1 closest to the electrode section 22 of the cold-cathode tube 20 (shown by hatching falling to the left) are 43 with respect to 100 of X3 and Y3 areas (shown by cross hatching), and 43 The number of the regions X5 and Y1 closest to 23 (shown by hatching to the right) is 48.

On the other hand, FIG. 7 shows the distribution in the case of the prior art shown in FIG. 5, in which the electrode portion 2 of the cold-cathode tube 20 is compared with 100 in the region of X3 and Y1 (shown by cross hatching).
Areas X1 and Y1 closest to 2 (shown by hatching leftward) are 35, and areas X5 and Y1 closest to the electrode portion 23 (shown by hatching rightward) are 4.
0. 6 and 7, it is understood that in the present invention, the brightness of the area near the electrode section 22 of the cold cathode tube 20 is improved.

[0016]

According to the invention described in the claims of the present invention,
Light emitted from the light emitting portion near the non-light emitting portion of the light source is incident on a portion between the light emitting portion facing portion of the side end surface of the light guide plate and the non-light emitting portion facing portion that is protruded, and by this light,
The brightness at the corner of the light guide plate near the non-light-emitting portion of the light source is improved.

[Brief description of the drawings]

FIG. 1 is a top view illustrating a structure according to a first embodiment.

FIG. 2 is a side view of the first embodiment.

FIG. 3 is a top view illustrating a structure according to a second embodiment.

FIG. 4 is a top view illustrating a structure according to a third embodiment.

FIG. 5 is a top view showing the structure of the prior art.

FIG. 6 is a diagram illustrating a distribution of brightness of a liquid crystal display unit according to the first embodiment.

FIG. 7 is a diagram illustrating a distribution of brightness of a liquid crystal display unit according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Light guide plate 11 ... Effective light emitting part facing part (of the end surface of the light guide plate) 12, 13 ... Non-light emitting part facing part (of the end surface of the light guide plate) 20 ... Cold cathode tube 21 ... Light emitting part 22, 23 ... Electrode part 30 … Liquid crystal display

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor, Isao Shiozawa, 654 Kawawa-cho, Tsuzuki-ku, Yokohama-shi, Kanagawa Prefecture Inside Fujitsu Kasei Co., Ltd. Inside Fujitsu Kasei Co., Ltd.

Claims (1)

[Claims] 1. A light guide plate for receiving light from a linear light source disposed opposite a side end face from a side end face and emitting light incident from the side end face from a surface portion, wherein the light source is an end face. The portion has a non-light emitting portion, the length of the side end surface of the light guide plate is longer than the length of the light emitting portion of the light source, and the side end surface of the light guide plate faces the light emitting portion of the light source. A light guide plate wherein a non-light-emitting portion-facing portion, which faces a non-light-emitting portion of a light source on a side end surface of the light guide plate, protrudes toward the light source side than a light-emitting portion-facing portion.