JPH04322204A - Plane lighting device - Google Patents

Abstract

PURPOSE:To obtain the thin, lightweight plane lighting device which guides light from a light source into a light guide plate with efficiency and has a bright light projection surface by providing a light converging member in specific structure between the light source and light guide plate. CONSTITUTION:The light converging member 3 having a reflecting function for guiding the light photodetected from the light source 1 into the light guide plate 2 is arranged on the light incidence end surface of the light guide plate 2. At least one surface of the light converging member 3 is a light reflecting surface. Further, a reflector 4 reflects and gathers the light of the light source 1 and the light reflected by the light converging member 3 to the light converging member 3. In this case, a reflection process is performed for the reflecting surface of the light converging member 3 and its shape is not limited specially, but a linear curved surface shape is used. The surface which photodetects the light from the light source 1 is transparent and its shape is preferably plane. Then the light converging member 3 and light guide plate 2 are connected optically homogeneously so that light is neither reflected nor scattered on the connection border surface. Transparent material is used as the materials of the light converging member 3 and light guide plate 2.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination device that is disposed on the back side of a transmissive image display device and illuminates the image display device from the back side.

0002

2. Description of the Related Art Display devices for advertisements and promotions or display devices such as transmission type liquid crystal display devices are often illuminated by a light source provided on the back side. Conventionally, such a lighting device generally used a fluorescent lamp, which is a linear light source, and a light diffusing plate placed on the back side for illumination. However, in order to make the illumination surface uniform in brightness in such lighting devices, it is necessary to increase the distance between the light diffusion plate and the fluorescent lamps, to place a large number of fluorescent lamps close together back to back, or to make the illumination surface uniform in brightness. In addition, a reflecting mirror and a light guiding section are further provided on the back surface of the illumination device, which has the disadvantage that the illumination device becomes extremely large.

[0003] For example, liquid crystal display devices are required to have large displays of 10 inches or more, and if a fluorescent lamp and a light diffusing plate are arranged on the back side, the thickness of the planar illumination device is about 30 mm, which is extremely thick. .

[0004] Japanese Patent Application Laid-Open No. 62-235905 discloses a device having a light source enclosed in a light guiding portion.
Therefore, the thickness of the device becomes large.

[0005] In order to correct these drawbacks, a single light guide plate is used to guide light from its end face, thereby illuminating the surface. This light guide plate type has been required to have a surface as uniform in brightness as possible, but recently there has been a demand for one with a bright screen, one that is large, thin, and lightweight.

[0006]

[Problems to be Solved by the Invention] An object of the present invention is to efficiently guide light from a light source into a light guide plate without increasing the thickness of the light guide plate, and to provide a large, thin, and bright light emitting surface. An object of the present invention is to provide a lightweight flat lighting device.

[0007]

[Means for Solving the Problems] In view of the above-mentioned problems, the inventors of the present invention have made extensive studies and have devised a method to reduce light from the light source by providing a light condensing member with a specific structure between the light source and the light guide plate. The present inventors have discovered that light can be efficiently guided into a light guide plate, and have completed the present invention.

That is, the present invention provides a light-concentrating member (3) having a light reflecting function for guiding the light received from the light source (1) into the light guide plate (2) on the light incident end surface of the light guide plate (2). This is a flat illumination device characterized in that at least one surface of the light condensing member (3) is a light reflecting surface.

The light condensing member (3) of the present invention is characterized in that at least one surface thereof is a light reflecting surface. Further, it is necessary that the light condensing member (3) is optically homogeneously connected to the light guide plate (2) by integral molding or adhesion. If the optical connection is not sufficient, the reflection and scattering of light at the interface of the connection surface will increase, and the efficiency of incidence on the light guide plate will deteriorate. In the light condensing member (3), the surface that receives light from the light source (1) is transparent, and its shape is not particularly limited, but a planar shape is preferred because it is easy to process.

In the condensing member (3), the surface that reflects the light received from the light source (1) toward the light guide (2) is subjected to a reflective treatment, and its shape is not particularly limited. However, in order to efficiently reflect light, a one-dimensional curved or flat surface is preferably used. Examples of the reflection treatment method include a method using total reflection based on the refractive index of the material, a method of applying a reflective paint, and a method of forming a thin metal film or a thin metal oxide film on the surface. In addition, the light guide plate (2) made of transparent resin has a thickness of 0.
．． Those with a diameter of 5 to 20 mm are used.

The light collecting member (3) may be directly connected to the light guide plate (2), or may be connected to a light guide joint (2) to facilitate attachment of the liquid crystal display or the parts of the display.
5) may be connected to the light guide plate (2). The material of the light guide joint (5) is the light collecting member (3) or the light guide plate (2) in order to reduce loss due to reflection at the interface.
It is preferable that at least one of the following is the same.

Light guide plate (2) and light condensing member (3) of the present invention
Alternatively, the light guide joint (5) uses transparent resin as its material. Examples of the transparent resin include polystyrene, polycarbonate, polymethyl methacrylate, acrylonitrile-styrene copolymer, diethylene glycol bisaryl carbonate resin, and polymethyl methacrylate is particularly preferred in terms of transparency and ease of molding.

The light source (1) used in the present invention has a light guide (
2) It is arranged at one or more places around the object and consists of one or more light emitters. As the light emitting body, incandescent lamps, fluorescent lamps, etc. are used, and fluorescent lamps are preferable from the viewpoint of luminous efficiency and lifespan. The light source (1) is equipped with a reflector (4) to efficiently collect light on a condensing member (3) and return the light reflected from the condensing member (3) back to the condensing member (3). It is preferable to have the following.

The present invention will be further explained below using the drawings. In FIG. 1(A), the light-concentrating member (3) is attached to the end of the light guide plate (2).
) is a plan view showing a flat illumination device in which light from a light source (1) can be incident on a light guide plate (2). Figure 1(B) is a vertical cross-sectional view of this at X and Y.
(C) is also an enlarged vertical cross-sectional view of the condensing member (3) portion. One surface of the light condensing member (3) is concave and has been subjected to a reflection treatment, so that light from the light source can be efficiently introduced into the light guide plate. By this method, it is possible to obtain an illumination device with a bright and uniform illumination surface without any protrusion above the illumination surface.

FIGS. 2 and 7 are a plan view and a vertical sectional view of a flat illumination device in which one surface of the condensing member (3) is flat and has been subjected to reflection treatment.

FIGS. 3 and 4 show an illumination device in which two fluorescent lamps are arranged as light sources (1), and an extremely bright and uniform illumination device can be obtained with the same thickness as in the case of one fluorescent lamp. The condensing member (3) shown in FIG. 3 has a concave reflective surface, and the condensing member (3) shown in FIG. 4 has a planar reflective surface.

FIGS. 5 and 6 show a flat illumination device that guides light from a light source (1) to a light guide plate (2) through a light condensing member (3) and a light guide joint (5). As a result, the liquid crystal display (
6) A lighting device with a bright and uniform illumination surface can be obtained without any protrusions appearing above the upper surface and by minimizing the number of protrusions on the back surface of the lighting device.

FIG. 8 shows a flat illumination device in which a member for holding a light source (1), a light condensing member (3) and a light guide plate (2) are integrally molded. One side of the light condensing member (3) is reflectively treated, and there is no loss at the connection surface between the light condensing member (3) and the light guide plate (2), so the light from the light source is efficiently transferred to the light guide plate. It can be introduced as follows.

[0019]

[Effects of the Invention] The flat lighting device of the present invention not only can efficiently send light from a light source to a light guide plate, but also provides a thin flat lighting device with a bright light output surface.
The arrangement of the light source and the light guide can be set according to the arrangement of the liquid crystal display or other parts.

[Brief explanation of drawings]

FIG. 1 (A) is a plan view showing a flat illumination device of the present invention;
(B) is a vertical cross-sectional view along the X-Y section of the flat illumination device, and (C) is a partially enlarged cross-sectional view of the light condensing member.

FIG. 2 (A) is a plan view showing a flat illumination device of the present invention;
(B) is a vertical cross-sectional view in the X-Y section of the flat illumination device.

FIG. 3 (A) is a plan view showing a flat illumination device of the present invention;
(B) is a vertical cross-sectional view in the X-Y section of the flat illumination device.

FIG. 4(A) is a plan view showing a flat illumination device of the present invention;
(B) is a vertical cross-sectional view in the X-Y section of the flat illumination device.

FIG. 5 (A) is a plan view showing a flat illumination device of the present invention;
(B) is a vertical cross-sectional view in the X-Y section of the flat illumination device.

FIG. 6(A) is a plan view showing a flat illumination device of the present invention;
(B) is a vertical cross-sectional view in the X-Y section of the flat illumination device.

FIG. 7(A) is a plan view showing a flat illumination device of the present invention;
(B) is a vertical cross-sectional view in the X-Y section of the flat illumination device.

FIG. 8(A) is a plan view showing a flat illumination device of the present invention;
(B) is a vertical cross-sectional view in the X-Y section of the flat illumination device.

[Explanation of symbols]

1. light source
2. Light guide plate 3. Light condensing material
4. Reflector 5. Light guiding joint 6. Liquid crystal display 7. Light diffusing plate 3-a. reflective surface
3-b. Light receiving surface 3-c. light guiding surface

Claims (3)

[Claims] Claim 1: The light received from the light source (1) is transferred to the light guide plate (2).
A light condensing member (3) having a light reflecting function for guiding light into the light is arranged on the light incident end surface of the light guide plate (2), and at least one surface of the light condensing member (3) is a light reflecting surface. A flat illumination device characterized by: 2. The planar illumination device according to claim 1, further comprising a reflector (4) for sending light from the light source (1) to the condensing member (3). Claim 3: The light condensing member (3) and the light guide plate (2) are connected by a light guide joint (5) made of the same material as the light condensing member (3) or the light guide plate (2). Item 1. Flat illumination device according to item 1.