JPH11149073A - Surface light source device and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a surface light source device thinner, lighter in weight and to reduce a cost with respect to the large screen display of high luminance by providing one pair of light transmission plates, the light diffusing means suspended on the surface of the same flat surface side in between the light transmission plates and a light reflecting means at a surface side opposite to the same flat surface side of the light transmission plates. SOLUTION: This light source unit is composed of a piece of a long light source 3, one pair of light transmission plates 4, 5 diffusing radiant lights of the left and right directions from the light source 3 on all surfaces of the display area of a display panel 1, a diffusion member 6 transmittingly diffusing the radiant lights from the light source 3 and a reflection plate reflection lights of a direction opposite to the panel 1. Incident lights on the light transmission plates 4, 5 are diffracted by V grooves being at a side opposite to a light-emitting surface while being totally reflected to be emitted from the light-emitting surface. However, lights transmitting the diffusion member 6 are emitted in a panel 1 direction, reflected lights pass the gap between the light source 3 and the plates 4, 5 to be guided to the reflection plate 7. Optical paths of lights radiated to the lower direction from the lights source 3 are changed with slopes of chevron projecting part being on the reflection plate 7 and the lights are reflected by the inclinations of both end parts of the plate 7 to be emitted in the panel 1 direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light source device used for a backlight of an illuminated display or a liquid crystal display.

[0002]

2. Description of the Related Art Conventionally, as a surface light source device used for a backlight of a liquid crystal display, a direct light type in which a light source is arranged in a display area on the back side of a liquid crystal panel and illuminated by direct light from the light source, An edge type in which a light source is arranged outside the display area on the back surface side of the liquid crystal panel and light is guided to the display area by a light guide plate made of a transparent acrylic resin or the like and illuminated.

In such a surface light source device, since there is a limit to the area that can be illuminated by a single light source, a technique using a plurality of light sources has been proposed to increase the size and brightness of a recent display screen. Have been.

As an example of a direct type, see, for example, Japanese Patent Laid-Open No. 7-14
As disclosed in Japanese Patent Application Laid-Open No. 1908, a plurality of light sources are arranged in parallel with an interval, but the upper portion of the light source has high brightness, and uneven brightness tends to occur in stripes. However, it is necessary to increase the distance, and there is a problem that the device becomes thick.

As an example of the edge type, see, for example,
As shown in JP-A-36178 and JP-A-9-90135, a light source is arranged around a light guide plate,
There is a light guide plate with multiple light sources arranged on the end face,
There is a problem that the non-display area around the display screen becomes large and the thickness of the light guide plate becomes large, so that the whole device becomes heavy.

The light emitted from the light source is reflected by a lamp reflector leading to the incident end face of the light guide plate. However, most of the light is blocked by the light source, and the efficiency of using the light emitted from the light source is low.

Japanese Patent Application Laid-Open No. 9-61821 discloses a technique in which a direct type and an edge type are combined, and a light source is arranged immediately below a panel and diffused by a light guide plate.

In this technique, as shown in FIG. 7, a concave portion is provided on the lower surface of a central portion of a light guide plate, and a light source is disposed in the concave portion. A dot pattern for light diffusion is provided on the lower surface of the light guide plate and the concave portion. It was printed.

[0009]

However, in the above-described technique, there are various problems in illuminating a large screen with high luminance.

A light source having an extremely thin and long shape is liable to fluctuate in position due to vibration or bending. If the light guide plate facing the light source has a curved or polygonal incident surface, the position of the light source changes. The luminance distribution from the light guide plate changes, causing uneven luminance.

In order to provide a plurality of light sources in order to cope with an increase in brightness and display of a large screen, for example, a plurality of light sources are arranged in a concave portion, or a plurality of concave portions are formed below a light guide plate, and It has been proposed to arrange light sources, but the arrangement of multiple light sources increases the thickness of the light guide plate and makes it heavier, and the provision of multiple recesses tends to cause distortion, bending, and cracking during processing such as molding, and assembling. There were problems such as poor handling at the time.

When a concave portion is formed in the lower surface of the central portion of the light guide plate to accommodate the light source, the light emitting surface of the light guide plate is distorted due to heat from the light source, which adversely affects a displayed image.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thin, lightweight, and inexpensive surface light source device for displaying a large screen with high brightness.

[0014]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a straight tube light source and a light source which is opposed to the light source with a gap therebetween and has one surface orthogonal to the surface facing the light source. A pair of light guide plates in a plane, light diffusion means interposed between the pair of light guide plates and suspended on the same plane side, and light reflection means on the opposite side of the light guide plate on the same plane side are provided. And

Further, the present invention provides a straight tube light source, a pair of light guide plates opposed to each other with a gap therebetween, and one surface orthogonal to the surface facing the light source is coplanar, and a pair of light guide plates. The light diffusing means is provided at a position facing the light source on the same plane side of the light guide plate in the gap portion of the light guide plate, and the light reflecting means is provided at a position facing the light source on the same plane side and the opposite side, and the light source of the light diffusing means is provided. The opposing surfaces are two elliptical curved surfaces having a focal point at the center point of the light source and a point at the shortest distance from the light source center point on the surface of the light guide plate facing the light source, and the surface of the light reflecting means facing the light source is the light source. And protruding toward the light source at the shortest position.

Further, the present invention for achieving the above object provides a straight tube light source and a pair of light guide plates which face each other with a gap therebetween and have one surface orthogonal to the surface facing the light source on the same plane. A plurality of light source modules, each of which is comprised of a light diffusing means suspended between a pair of light guide plates and suspended on the same plane side, are arranged in parallel to the axial direction of the light source and have the same plane of the light guide plate on the same plane of the light source modules. The light guide plate is arranged so as to be planar, and the light guide plate is provided with light reflecting means over the entire area on the same plane side and on the opposite side.

Further, the present invention provides a straight tube light source, a pair of light guide plates facing each other with a gap therebetween, and one surface orthogonal to the surface facing the light source is coplanar, and a pair of light guide plates. And a plurality of illumination modules comprising light diffusion means suspended on the same plane surface between the light guide plates are arranged and supported so that the light guide plates are parallel to the axial direction and the light guide plates have the same plane surface on the same plane surface. In addition, a liquid crystal panel is provided on the same plane side of the illumination module, and reflection means is provided on the opposite side of the illumination module on the same plane side, and the arrangement pitch of the illumination module is set to an integral multiple of the pixel pitch of the liquid crystal panel. I do.

Further, the connection position of the adjacent optical unit is matched with the non-pixel position of the liquid crystal panel.

According to the present invention, a light source and a pair of light guide plates are modularized by the above-described configuration, and a plurality of the light sources are arranged to realize illumination of a large screen. be able to.

Further, a part of the light emitted from the light source in the direction immediately above is guided to the reflector without being blocked by the light source by the light diffusing means, and passes through the gap between the light guide plates to the light guide plate again. Since the light is incident, the utilization efficiency is significantly increased, and high-luminance illumination is possible.

Further, by arranging a plurality of light source modules in parallel and connecting the light source modules to non-pixel positions of the liquid crystal panel, it is possible to provide a large-screen liquid crystal display device which does not impair visibility.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show the structure of the present invention, and FIG. 3 shows the detailed structure of the light source unit.

Reference numeral 1 denotes a display panel on which a transmission image is printed on a transparent film resin or the like, and 2 denotes a support frame for supporting the display panel 1, and a light source unit is accommodated therein.

The light source unit includes one long light source 3,
A pair of light guide plates 4 and 5 for diffusing left and right radiated light from the light source 3 over the entire display area of the display panel 1; a diffusing member 6 for transmitting and diffusing upward radiated light from the light source 3; And a reflecting plate 7 for reflecting light in the opposite direction.

The light source 3 is a straight tube such as a cold-cathode fluorescent lamp, and both ends are detachably supported by the support frame 2 and are turned on by a drive circuit (not shown).

The pair of light guide plates 4 and 5 are rectangular plate members made of a transparent material such as acrylic resin, and light incident surfaces 4a and 5a are arranged on both sides of the light source 3 so as to face each other with a gap therebetween. The light-exiting surfaces 4b and 5b orthogonal to 5a are supported by the support frame 2 so as to be on the same plane.

The surface 4 of the light guide plate opposite to the exit surfaces 4b and 5b
c · 5c is inclined so as to become thinner as the distance from the light source 3 is increased.
A minute V-groove for emitting light is formed at a.5a.

The V-groove to be formed is parallel to the axial direction of the light source 3, and the smaller the arrangement pitch is, the more the exit surfaces 4b and 5 of the light guide plate are.
b, the striped luminance unevenness is reduced and the visibility is improved. However, from the viewpoint of workability, the groove width is 1/2 to 1/5 of the arrangement pitch, and the emission luminance distribution of the light guide plate is within the range of 200 to 500 μm. It is preferable that the groove width is set to be larger as the distance from the light source 3 is increased in order to uniformize the width.

The diffusing member 6 is made of, for example, a light diffusing material in which materials having different refractive indices are dispersed in a transparent acrylic resin, and is disposed above the light source 3 in a gap between the pair of light guide plates 4 and 5. Both ends are placed on the ends of the emission surfaces 4b and 5b of the pair of light guide plates.

The surface of the diffusion member 6 facing the light source 3 is
It is a W-shape composed of two concave curved surfaces, each concave curved surface is an elliptical shape, one focus of the ellipse is at the center O of the light source, and the other focal points P1 and P2 are incident surfaces 4a and 4a of the light guide plates 4.5. 5a is on the horizontal axis which is the shortest distance from the light source.

On the concave surface, a material having reflection and diffusion properties is formed in a dot pattern by, for example, printing. This dot pattern is to prevent an increase in brightness immediately above the light source 3 and reflects a part of the light from the light source 3.

The closer the light source 3 is to the dot pattern, the more the reflected light is increased by making the dot pattern denser, so that the light emitted to the panel 1 can be made uniform.

The light source side ends of the light guide plate emission surfaces 4b and 5b on which the diffusion member 6 is mounted tend to have uneven brightness due to birefringence, and a dot pattern is formed on the contact surface of the diffusion member 6. Brightness can be made uniform.

The reflecting plate 7 is a thin metal plate made of aluminum or the like, and is provided on the back side of the pair of light guide plates 4 and 5. A metal film such as aluminum or silver is deposited on the surface facing the light guide plates 4 and 5. Have been.

Both ends of the reflection plate 7 are attached to surfaces 4d and 5d on the opposite side to the incident surfaces of the pair of light guide plates. Has formed.

On the bottom surface of the reflection plate 7, a mountain-shaped projection 7a is provided directly below the light source 3 and is parallel to the axial direction of the light source. I have.

Next, the operation of the surface light source device having the above configuration will be described. The light source 3 such as a cold-cathode fluorescent tube emits light in all directions from the inner wall surface of the tube, which will be described with reference to a conceptual diagram based on the center of the light source. In FIG. 4, of the light emitted from the light source, light having an angle φ1 facing the incident surfaces 4 a and 5 a of the light guide plate is the light guide plate 4.
The light having an angle φ2 in the upward direction, which is incident on the light guide plate 5 and does not face the light guide plate, advances to the diffusion member 6, and the light having the angle φ3 in the downward direction advances to the reflection plate 7.

The light incident on the light guide plates 4 and 5 travels while repeating total reflection in the light guide plates, and the light exit surfaces 4c and 5c opposite to each other.
Is refracted by the V-groove and is emitted from the emission surfaces 4b and 5b.

The light to the diffusion member 6 is divided into light reflected by the reflective dots and light transmitted therethrough.
Light emitted from the light source 3 and the reflected light
5) It is guided to the lower reflector 7 through the gap with 5.

The light radiated downward from the light source 3 is changed in optical path along with the light reflected by the diffusion member 6 on the slope of the mountain-shaped projection 7a of the reflection plate 7, and is guided through the space layer. The light proceeds toward both ends of the bodies 4 and 5 and is reflected by the slopes 7b at both ends of the reflection plate 7, and the surfaces 4c and 5 opposite to the emission surface of the light guide plate.
c and exits in the direction of panel 1.

As described above, the light emitted from the light source 3 is guided toward the panel 1 without being absorbed by the light source 3 although it is attenuated by several reflections.

The smaller the distance between the pair of light guide plates 4 and 5, the larger the angles φ 1 and φ 2 and the greater the amount of light incident on the light guide plate, but the light path in the direction of the angle φ 3 reflected by the diffusing member 6. 1.5 d to 2 d with respect to the diameter d of the light source 3
It is preferable to set

The incident light quantity increases as the thickness of the incident surface of the light guide plate increases, but when the light guide plate is made of acrylic resin, the refractive index is 1.49, and the light guide plate is totally reflected and propagated. It is preferable that the light incident angle is about 42 ° and the angle φ1 with the center of the light source is set to about 90 °.

The above specific example is an embodiment of the present invention.
Changes can be made without departing from the gist. For example, the V-grooves formed in the light guide plates 4 and 5 are arranged at equal intervals and the groove width is increased in proportion to the distance from the light source 3. By reducing the size, the distribution of the amount of light emitted from the light guide plate can be made uniform, and V
It is also possible to print a white paint in a dot pattern instead of the groove.

Further, in order to increase the brightness by controlling the viewing angle of light emitted from the light guide plates 4 and 5 and the diffusion member 6 in the panel direction, and to eliminate the bright line due to the V groove formed in the light guide plate. A prism sheet or a diffusion film sheet may be interposed between the light guide plate and the panel.

The reflecting plate 7 and the surface 4 on the side opposite to the exit surface of the light guide plate
The space layer between the light guides c and 5c is a passage for guiding light toward both ends of the light guides 4 and 5, and is inclined at both ends of the reflector 7 by inclining the reflector 7 so as to become narrower in a direction away from the light source. The part 7b can be omitted.

Next, an embodiment in which a large number of the light source units are arranged and used as a backlight of a liquid crystal panel will be described with reference to FIGS. Note that the light source unit has an approximate configuration to that described above, and a description of the overlapping portion will be omitted.

Reference numeral 1 denotes a transmissive display panel in which liquid crystal display elements are arranged in a grid within a display area illuminance A. Reference numeral 2 denotes a box-shaped support frame for supporting the display panel. A plurality (two in the figure) of light source units are arranged.

The pair of light guide plates 4 and 5 of the light source unit are arranged at intervals in the light source 3, and the direction in which the interval is expanded by urging members 8 attached to gaps at both ends outside the display area A. To be in close contact with the light guide plate of the adjacent light source unit.

The biasing member 8 is made of an elastic material such as metal or resin, and is fixed to the support frame 2. The lower surface of each of the light guide plates 4 and 5 is placed on the slope of the support frame 2 via an elastic support such as rubber (not shown) and is in close contact with the back surface of the display panel 1.

The arrangement direction of the light source units is
The arrangement in the short side direction is advantageous in terms of work because the number is small, but it is preferable from the viewpoint of visibility that the arrangement is made in the horizontal direction when the liquid crystal display device is used.

The width (P) of the light source units in the arrangement direction is set to an integral multiple of the liquid crystal pixel pitch of the display panel 8, and the connection portion between adjacent light source units is set at a non-pixel position between pixels. This makes it possible to hide a bright line or a dark line at the connection portion.

The reflecting plate 7 integrally covers the back surface of all the light guide plates, and is fixed to the support frame 2 separately from the light guide plates. On the surface of the reflecting plate 7 facing the light guide plate, mountain-shaped projections 7a and 7c are formed immediately below each light source 3 and directly below the connection position of the light source unit, respectively, in parallel with the axial direction of the light source 3.

Regarding the operation of light in the above embodiment,
Omitted because of duplication. In addition, since a plurality of light sources 3 are used, a voltage or current control adjusting means is provided for each light source to prevent the luminance unevenness on the liquid crystal panel surface 1 due to the aging of the light sources 3 and the variation in the light amount, thereby increasing the luminance. Can be made uniform.

Of course, a diffusion film sheet or a lens sheet may be inserted between the light guide plate and the panel for controlling the viewing angle and improving the brightness of the liquid crystal display panel.

[0057]

As described above, according to the present invention,
By arranging a plurality of light source modules composed of a pair of light guide plates of a light source in parallel, a large-screen display can be made thin and lightweight, so that it can be applied to a thin liquid crystal display device such as a large-screen television or a wall-mounted television. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a main part of a surface light source device according to the present invention.

FIG. 2 is a three-dimensional exploded view of an image display device using the surface light source device of the present invention.

FIG. 3 is a conceptual diagram of a light source unit of the present invention.

FIG. 4 is a detailed view of the vicinity of a light source according to the present invention.

FIG. 5 is a cross-sectional view showing a main part of the liquid crystal display device of the present invention.

FIG. 6 is a three-dimensional exploded view of the liquid crystal display device of the present invention.

FIG. 7 is a diagram showing a conventional surface light source device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Display panel 2 Support frame 3 Light source 4 Light guide plate 5 Light guide plate 6 Diffusion member 7 Reflection plate 8 Energizing member

Claims (10)

[Claims] 1. A light source comprising: a pair of light guide plates, a straight tube light source and a light guide plate facing each other with a gap therebetween, and one surface orthogonal to the surface facing the light source is coplanar; A surface light source device comprising a light diffusing unit and a light reflecting unit that face each other with a gap from a light source. 2. A surface light source device according to claim 1, wherein said light diffusing means is made of a light transmitting material mixed with materials having different refractive indexes, and a reflection dot pattern is formed on a surface facing the light source. 3. A surface of the light diffusion means facing the light source comprises two elliptical curved surfaces, one focus of the ellipse being a center point of the light source, and the other focus being a light source on a surface of the light guide plate facing the light source. The surface light source device according to claim 1, wherein the surface light source device is a point located at a shortest distance from the center point. 4. The surface light source according to claim 1, wherein the light reflection means has a reflection surface on a surface facing the light source, and a shortest distance point from the light source is parallel to an axial direction of the light source and protrudes in a mountain shape toward the light source. apparatus. 5. A light source comprising: a pair of light guide plates facing each other with a straight tube light source and a light source facing each other with a gap therebetween and one surface orthogonal to a surface facing the light source being coplanar; A plurality of light source modules each including a light diffusing unit suspended on the same plane side of a pair of light guide plates are parallel to the axial direction of the light source, and the light guide plates on the same plane of each light source module become the same plane. A surface light source device which is arranged in such a manner as to have light reflecting means on the entire surface of the light guide plate on the same plane side and the opposite surface side of the light guide plate. 6. A light reflecting means, wherein the surface facing the light source is a reflecting surface and is separated from the light guide plate, and the shortest distance point between each light source is parallel to the axial direction of the light source and protrudes in a chevron shape toward the light source. Claim 5
The surface light source device as described in the above. 7. The light guide plate of the light source module, wherein a surface of the light guide plate opposite to the surface facing the light source is in contact with a surface of the light guide plate of an adjacent light source module, the surface of the light guide plate opposite to the light source. Item 5. Surface light source device according to item 5. 8. A light source comprising: a pair of light guide plates facing each other with a gap between the straight tube light source and a surface facing the light source, wherein one surface orthogonal to the surface facing the light source is on the same plane; A plurality of light source modules comprising light diffusion means suspended on the same plane side are arranged and supported so that the light guide plates are parallel to the axial direction of the light source and the light guide plates have the same plane side on the same plane. A liquid crystal panel in which transmissive liquid crystal display elements are arranged in a matrix on the same plane side of the module, and light reflecting means on the same plane side and the opposite side of the light source module,
A liquid crystal display device in which the arrangement pitch of the light source modules is an integral multiple of the pixel pitch of the liquid crystal panel. 9. The liquid crystal display device according to claim 8, wherein a connection position of said light source modules adjacent to each other is matched with a non-pixel position of said liquid crystal panel. 10. The liquid crystal display device according to claim 8, further comprising: urging means for urging in a direction in which the gap between the pair of light guide plates of the light source module is expanded.