JPH063527A - Side light system backlight - Google Patents

Abstract

PURPOSE:To provide a side light system backlight whose brightness is made as uniform as possible. CONSTITUTION:This backlight is provided with a light source 10 constituted by arraying LEDs 12 on a substrate for a light source 11, and a light transmission plate 20 arranged by the side of the light source 10; and the surface 21 of the plate 20 is a light emitting surface, and the back surface 22 and the side surface thereof are light shielding surfaces; then a blasted area is formed on the inner side of the back surface 22 by performing blasting processing so as to get sparse near the light source 10 and dense as it goes from the light source 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sidelight type backlight for an electronic device such as a liquid crystal display which requires a surface emitting light source.

[0002]

2. Description of the Related Art A sidelight type backlight generally includes a light source 80 and a light guide plate 90 arranged beside the light source 80, as shown in FIG. Light source 80
Includes a plurality of light emitting diodes (LEs) on the light source substrate 81.
D) 82 are arranged at regular intervals. Light guide plate 90
The front surface (upper surface) 91 is a light emitting surface, and the back surface (lower surface) 92 and the side surfaces 93, 94, 95 are light shielding surfaces. In such a backlight, the light from the LED 82 is emitted from the light guide plate 9
It is guided to the entire surface of the light emitting surface 91 while being reflected by the inner surface of 0. In order to guide the light to the light emitting surface 91 more efficiently, the inside of the light emitting surface 91 may be subjected to a blast treatment (texturing treatment), or a translucent diffusion sheet may be attached to the outside of the light emitting surface 91. Further, the light shielding surfaces 92 to 95 are painted white or a white sheet is attached to the light shielding surfaces 92 to 95 so that indirect light does not leak to the outside of the light guide plate 90.

[0003]

However, in the above-described backlight, the light unevenness on the light emitting surface 91 is likely to be conspicuous, and as shown in FIG. 7, the brightness tends to decrease and become darker as the distance from the light source 80 increases. There is. Therefore, an object of the present invention is to provide a sidelight type backlight in which brightness is made as uniform as possible.

[0004]

In order to achieve the above-mentioned object, the sidelight type backlight of the present invention is the above-mentioned conventional backlight, which is rough inside the back surface of the light guide plate, near the light source, and from the light source. It is characterized in that it is subjected to a blast treatment that becomes denser as it goes away.

[0005]

[Function] The inner surface of the back surface of the light guide plate is blasted so that it becomes coarser and denser as it gets farther from the light source, so the light from the light source is diffused more efficiently, is uniformly guided to the light emitting surface, and is bright. Is almost uniform regardless of the distance from the light source, and light unevenness on the light emitting surface is almost eliminated.

[0006]

EXAMPLES The sidelight type backlight of the present invention will be described below based on examples. FIG. 1 is an external perspective view of a backlight according to the embodiment, and FIG. 2 is a cross-sectional view of a main part. This backlight has the same constituent elements as the conventional one, and includes a light source 10 and a light guide plate 20 arranged beside the light source 10. Further, in this embodiment, a translucent diffusion sheet 30 is attached to the outside of the light emitting surface (front surface) of the light guide plate 20, and a reflection sheet 40 is attached to the outside of the back surface, and a portion of the diffusion sheet 30 near the light source 10 is attached. A light-shielding sheet 50 is attached to the.

The light source 10 is the light source substrate 1 as described above.
One is a plurality of light emitting diodes (LEDs) 12 mounted in a row at regular intervals. Surface 21 of light guide plate 20
Is a light emitting surface, the back surface 22 and the side surfaces 23, 24, 25 are light shielding surfaces, and a light shielding sheet (not shown) is attached to the outside of the light shielding surfaces 23, 24, 25 to prevent leakage of indirect light. There is.

The blast treatment, which is a feature of the present invention, is applied to the inside of the back surface 22 of the light guide plate 20, and an inside plan view of the back surface 22 is shown in FIG. The blast region 60 formed by the blast process has a pattern as shown in the drawing, and each has a slender taper shape in which the width becomes wider as the distance from each LED 12 increases. Further, the blast region 60 is in a rough state near the LED 12 and is denser as the distance from the LED 12. It is in a state.

When the light guide plate 20 having the back surface 22 having the blast region 60 is used, the degree of irregular reflection of the light from the LEDs 12 increases toward the dense state of the blast region 60. In addition, the brightness of the light emitting surface 21 is made uniform. That is, as shown by the arrows in FIG. 4 in which the relationship between light rays and brightness (brightness) is shown, the lightness per light ray is high near the LED 12, but the amount of light rays traveling to the light emitting surface 21 side is small. On the other hand, as the distance from the LED 12 increases, the lightness per ray decreases, but the amount of rays increases. As a result, the brightness of the light emitting surface 21 becomes uniform irrespective of the distance from the LED 12, and the uneven light emission on the light emitting surface 21 is almost eliminated.

Further, FIG. 5 is a graph showing the relationship between the distance from the light source 10 and the brightness of the light emitting surface 21 of the light guide plate 20. It can be seen that the brightness becomes almost constant by the blasting process performed on the back surface 22 of the light guide plate 20, but it becomes brighter in the vicinity of the light source 10 than in the other parts.
However, since it is desired to make the brightness as uniform as possible for the backlight, it is preferable to block the light in the shaded area in the figure, and for that reason, the light source 10 of the diffusion sheet 30 is used.
A light-shielding sheet 50 is attached to the nearer portion. This makes it possible to obtain a backlight having a uniform brightness regardless of the distance from the light source 10.

[0011]

As described above, in the sidelight type backlight of the present invention, the inside of the back surface of the light guide plate is subjected to the blasting process in which the light source is rough near the light source and becomes denser as the distance from the light source increases. Therefore, it has the following effects. (1) The brightness of the light emitting surface of the light guide plate is uniform, and the quality is higher than the conventional one. (2) Since the light guide plate is a molded product, the unit price of the light guide plate is the same as before even if blasting is applied to the inside of the back surface of the light guide plate, and other components are the same as before, resulting in high cost. I won't. (3) It is particularly suitable for a backlight of a thin (about 1 mm) surface emitting device.

[Brief description of drawings]

FIG. 1 is an external perspective view of a backlight according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of main parts of the backlight shown in FIG.

FIG. 3 is a plan view of the inside of the back surface of the light guide plate in the backlight shown in FIG.

FIG. 4 is an explanatory diagram showing the relationship between the light amount and the brightness of the backlight of the present invention.

FIG. 5 is a graph showing the relationship between the brightness on the light emitting surface of the light guide plate and the distance from the light source in the backlight of the present invention.

FIG. 6 is a configuration perspective view of a backlight according to a conventional example.

FIG. 7 is a graph showing the relationship between the brightness on the light emitting surface of the light guide plate and the distance from the light source in the conventional backlight.

[Explanation of symbols]

 10 Light Source 11 Light Source Substrate 12 Light Emitting Diode 20 Light Guide Plate 21 Light Emitting Surface (Front) 22 Light Shielding Surface (Back) 23, 24, 25 Light Shielding Side (Side) 60 Blast Processing Area

Claims (1)

[Claims] 1. A light source, and a light guide plate which is arranged beside the light source, has a front surface serving as a light emitting surface and surfaces other than the front surface (rear surface and side surface) serving as light shielding surfaces and guiding light from the light source to the light emitting surface. The sidelight-type backlight is characterized in that the inside of the back surface of the light guide plate is subjected to a blast treatment that is rough near the light source and becomes denser as the distance from the light source increases.