JPH06242731A - Back light device for display surface - Google Patents

Abstract

PURPOSE:To obtain a wide light emission surface and also to prevent the light emission surface from becoming irregular in luminance by arranging a light guide plate which transmits light and has a reflecting surface on its back surface side and a light straightening plate which has an uneven surface on its back surface side on the top surface side of the light guide plate. CONSTITUTION:A U-shape-sectioned light source holder 1 is provided with a groove part 2 in its length direction and plural light emitting elements 3 are arranged in the groove part 2. Further, the light guide plate 7 is fitted and fixed in the groove part 2 and the reflecting surface 8 where a reflective sheet is adhered is formed on the reverse surface. The light straightening plate 9 is mounted on the top surface of the light guide plate 7 and the peripheral edge is heated and sealed. The light straightening plate is constituted by forming saw-toothed projected/recessed stripes 11, having tops and bottoms in 90 deg. isosceles triangle shape, on its back surface in parallel to the length-directional end edges. Light emitted by the light emitting elements 3 into the light guide plate 7 are refracted and reflected by the uneven stripes on the reverse surface of the light straightening plate 9 and reflected by the reflecting surface 8 repeatedly, so that the light straightening plate 9 transmits reflected light from the reflecting surface 8 to the side of a diffusion plate 13 at a right angle uniformly over the entire surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight device for irradiating light on the back surface of a liquid crystal display surface, a photographic film, a see-through plate for drawings or the like.

[0002]

2. Description of the Related Art As a conventional backlight device for a liquid crystal display surface or a display surface such as a see-through plate, a light source holder 1 having a plurality of light sources 3 such as light emitting elements (LEDs) as shown in FIGS. It has been known that a light guide plate 7 made of an acrylic plate or the like is attached, and a diffusion plate (not shown) is combined on the surface side of the light guide plate 7 with a constant space.

[0003]

However, in the above-mentioned conventional example, the light guide plate 7 gradually decreases in brightness from the base end side close to the light source 3 toward the front end side, and uneven brightness occurs, and the base of the light guide plate 7 is also generated. Irradiation part 5 of each light source 3 at the end side and the intermediate part.
a, a non-irradiated portion 5b to which no light is emitted, and a duplicated illuminated portion 5c in which the projected ranges of the adjacent light sources 3 overlap each other, a luminance unevenness occurs as a whole, and the luminance of the display surface is not uniform. I couldn't keep it. Therefore, in order to keep the brightness of the display surface uniform, it is necessary to separate the liquid crystal plate from the light guide plate 7 of the backlight device, which increases the thickness of the backlight device and is costly to maintain the brightness of the light source. There was a drawback of inviting.

[0004]

In order to solve the above-mentioned problems, the present invention mounts a light source 3 in a groove 2 formed on the peripheral surface of a light source holder 1 and provides a translucency in the groove 2. An apparatus in which an end of a plate-shaped light guide 7 having a reflection surface 8 is fixed on the back side and a light-regulating plate 9 made of a film or a plate-like material serving as a light emitting surface is arranged on the front side of the light guide 7. In the above, the first feature is that the light control plate 9 has an uneven surface on the back side. A second feature is that the uneven surface is composed of the uneven strip 11 having a sawtooth cross section. A third feature is that the inner surface of the groove 2 is a reflective surface.

[0005]

The light projected from the light source 3 is applied to the light guide 7 directly or to the reflecting surface 8 or the uneven surface, and is repeatedly refracted and reflected in the light guide 7, and finally is adjusted by the uneven strip 11. The light is transmitted to the front side with a uniform luminance in a direction perpendicular to the light plate 9, and the front side of the dimming plate 9 is illuminated. As a result, the light control plate 9
Even when a display plate such as a liquid crystal panel is installed on the front side of the display panel, the brightness of the display surface is kept uniform regardless of the proximity distance of the display plate.

[0006]

EXAMPLE A light source holder 1 (having a total length of 60 mm) having a U-shaped cross section formed of white polycarbonate or the like has a longitudinal direction extending from one end to the other end of its inner side surface. The groove 2 is provided in
A plurality of light emitting elements (light sources) 3 such as LEDs are arranged in the groove portion 2, and each light emitting element 3 is inserted into a hollow guide member 4 attached to the outer side surface of the light source holder 1 to form a wiring 6.
It is connected to the.

The light source holder 1 has a rectangular shape (60 m) in plan view.
A light guide plate 7 (thickness: 1.5 mm) made of a transparent acrylic plate (m × 20 mm) is fitted and fixed in the groove portion 2. The back surface of the light guide plate 7 is coated with a reflective paint or coated with a reflective sheet. The reflective surface 8 is formed by applying the garment.

On the other hand, a rectangle (6 having the same shape as the light guide plate 7 in plan view)
A light regulating plate 9 (thickness: 0 mm × 20 mm) made of a transparent resin plate or a lens film (0.6 mm in thickness) is superposed on the surface of the light guide plate 7, and the periphery is fixed to the light guide plate 7 by heat fusion. There is. The light control plate 9 has a depth of 0.05 mm to 0.1 mm and a pitch of 0.1 mm on its back surface.
An uneven strip 11 having a sawtooth cross section having an isosceles triangle of 0.2 mm and peaks and valleys of 90 ° is formed parallel to the longitudinal edge. A diffusing plate 13 made of a liquid crystal plate or the like is attached in parallel to the light adjusting plate 9 above the light adjusting plate 9 of the backlight device body 12.

According to the above structure, the light radiated into the light guide plate 7 by the light emitting element 3 is provided with the uneven strips 11 on the back surface of the dimming plate 9.
By repeating the refraction and reflection at 8 and the reflection at the reflecting surface 8 of the light guide plate bottom surface 7b, the dimming plate 9 transmits the reflected light from the reflecting surface 8 to the diffuser plate 13 side at a right angle and uniformly. As a result, the display surface of the diffusion plate 13 is uniformly illuminated from the back side, and a uniform light emitting display surface with no brightness unevenness is formed. Therefore, the diffuser plate 1
3 can be attached to the front side of the light control plate 9 so as to be in close contact therewith.

In the above structure, it is desirable that the peripheral surface of the light guide plate is coated with a reflective paint or a reflective sheet is attached to form the reflective surface 8 so that light does not pass through the outer peripheral surface of the light guide plate. Further, it is desirable to similarly form the reflecting surfaces 8 on both sides of the groove 2 around the mounting of the light emitting element 3 so that the light emitted from the light source 3 is concentrated and emitted to the front side. When a white material is used for the light source holder 1 as in the embodiment, the inner surface of the groove 2 of the light source holder 1 can be a reflecting surface. Normally, the light source holder 1 only needs to be attached on one side of the light guide plate 7, but when the diffusion plate 13 is large, the light source holder 1 is attached to both sides of the light guide plate 7 as shown by the imaginary line in FIG. It is enough to irradiate from.

Incidentally, as a mounting structure of the light source holder 1, the light guide plate 7 and the light adjusting plate 9 of the present invention, FIG.
The backlight effect was confirmed by the structures as shown in (B) and (C). The performance of the embodiment shown in FIG. 2 was superior to those structures in terms of brightness and uniformity. It was The reason is that the light is projected from the narrow groove portion 2 at the end portion of the light guide plate 7 so that the light can be projected further in the light guide plate 7 and the reflection effect of the inner surface of the groove portion 2 is obtained. Guessed.

[0012]

According to the device of the present invention configured as described above, the light reaches the light guide plate even at a position distant from the light source as compared with the conventional device, so that a wide light emitting surface can be obtained. There is an advantage that uneven brightness on the light emitting surface can be prevented and uniform brightness can be obtained. Therefore, when applied to a liquid crystal display surface, the liquid crystal plate can be attached in close contact with the light control plate, and the backlight portion or the entire device using the backlight can be thinned.

[Brief description of drawings]

FIG. 1A is a side view of a backlight device,
(B) is a plan view of the same.

FIG. 2 is an enlarged cross-sectional view of a backlight device showing an embodiment of the present invention.

FIG. 3 is an enlarged perspective view showing the structure of a light source holder.

FIG. 4 is a plan view showing a luminance distribution of a backlight device in a conventional example.

5A to 5C are cross-sectional views showing a failure example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source holder 2 Groove part 3 Light source 7 Light guide 8 Reflective surface 9 Light-regulating plate 11 Concavo-convex 13 Diffuser plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Gonda 5-17-9 Minamioi, Shinagawa-ku, Tokyo Kuroda Electric Co., Ltd. Tokyo branch office (72) Inventor Shigetoshi Sekiyama 2-32-27 Okubo, Konan-ku, Yokohama

Claims (3)

[Claims] 1. A light source (3) is mounted in a groove (2) formed on a peripheral surface of a light source holder (1), and a light-transmitting property is provided in the groove (2) and a reflective surface (8) is provided on the back side. The plate-shaped light guide (7) having the end is fixed, and a light-regulating plate (9) made of a film or a plate-like material serving as a light emitting surface on the surface side of the light guide (7)
A backlight device for a display surface, in which the light-regulating plate (9) has an uneven surface on the back side. 2. The backlight device for a display surface according to claim 1, wherein the uneven surface comprises an uneven line (11) having a serrated cross section. 3. The backlight device for a display surface according to claim 1, wherein the inner surface of the groove (2) is a reflective surface.