JP2001006417A - Surface light source device, light guide plate and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate increase and equalization of the luminance of emitted light in a surface light source device capable of illuminating a display panel with either light from an inside light source or outside light by forming a light guide plate such that a distance between an emission face and an opposite face to the mission face becomes small as it goes away from an incident face. SOLUTION: In this surface light source device, a second incident face 12 allowing incidence of light from an inside light source 2 is disposed on the first incident face 11 side allowing incidence of outside light to an emission area 13a of an emission face 13. Thereby, with securing areas of the incident faces 11, 12 allowing incidence of the outside light or the light from the inside light source 2, a distance between the emission face 13 and a rear face 14 can be reduced as it goes away from the first incident face 11 in the emission area 13a.

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, a light guide plate used in the surface light source device, and a display device using the surface light source device. The present invention relates to a surface light source device that can be used.

[0002]

2. Description of the Related Art In a non-light-emitting display device represented by a liquid crystal display device, for example, when it is incorporated into a product such as a digital still camera, a video camera, or a portable liquid crystal television, a back surface is provided on the rear surface for illumination. A light unit is provided. As one structure of the backlight unit, a light source, a light guide plate that receives light from the light source from the side and emits the light from the emission surface, and condenses light emitted from the emission surface (emission light) within a viewing angle. There is known a lens sheet for improving luminance and a reflection sheet provided on the rear surface side of the light guide plate for returning light that has escaped from the rear surface back into the light guide plate.

[0003] In order to obtain uniform and high-brightness emitted light, for example, the light guide plate may be shaped such that the distance between the exit surface and the opposite surface of the exit surface decreases as the distance from the entrance surface increases, or In order to diffuse the light (incident light) from the light source over the entire area of the light guide plate, a diffusing means composed of a pattern formed by printing using irregularities or a diffusing agent-containing ink is provided on the back surface.

In portable electronic devices such as liquid crystal televisions and electronic cameras, external light such as sunlight or room light is introduced to reduce the power consumption and extend the life of the internal light source. One that illuminates a display panel has also been developed (see, for example, Japanese Patent Application Laid-Open No. 10-68948).

[0005]

In the case where the display panel can be illuminated by either the light from the internal light source or the external light, the internal light source is located between the light incident surface of the light guide plate and the external light incident surface. Were provided on the opposite surface side. For this reason, in order to secure the amount of incident light, it is not possible to reduce the incident surface of the external light and the incident surface of the light from the internal light source. However, it has not been possible to adopt a shape in which the distance between the exit surface and the opposing surface of the exit surface decreases as the distance from the entrance surface increases, as the shape of the light guide plate.

[0006] Further, even when the diffusion means is provided,
Since the incident directions of the external light and the light from the internal light source in the light guide plate are different, for the light from each direction, that is, either when the light from the internal light source is incident or when the external light is taken in Even in such a case, it is necessary to design the diffusion pattern of the diffusion means so as to exhibit uniform luminance on the emission surface. However, for light from such two different directions, it is not easy to design a diffusion pattern capable of exhibiting uniform luminance in any case of light, and it requires a great deal of manpower and time to design. This could lead to increased costs and reduced market competitiveness.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and in a surface light source device having a configuration in which a display panel can be illuminated by either light from an internal light source or external light, a light guide plate is provided. It is possible to adopt a shape in which the distance between the exit surface and the opposite surface of the exit surface becomes smaller as the distance from the entrance surface increases, and it is possible to achieve higher luminance and uniform luminance of the exit light. It is still another object of the present invention to provide a surface light source device, a light guide plate, and a display device using the same, which do not require a diffusion pattern that provides uniform brightness for each of light from two different directions.

[0008]

According to a first aspect of the present invention, there is provided a surface light source device according to the present invention, wherein a first incident surface on which external light is incident, an exit surface on which the incident light exits, and light on the exit surface are emitted. A light guide plate having a second incident surface provided on the first incident surface side with respect to the emission region, an internal light source provided facing the second incident surface, and a second incident surface in the thickness direction of the light guide plate And a reflection member provided on the light guide plate surface opposite to the position where the light guide plate is provided.

According to a second aspect of the present invention, there is provided the surface light source device according to the first aspect of the present invention, wherein the light guide plate has a surface on which the light exit surface faces the light exit surface as the distance from the light entrance surface increases in a region where the light exit surface is formed. Is formed to have a small distance from

According to a third aspect of the present invention, in the surface light source device according to the first or second aspect, a lens is integrally formed on the second incident surface of the light guide plate.

According to a fourth aspect of the present invention, there is provided a surface light source device according to the present invention, wherein a first incident surface on which external light is incident, an exit surface on which the incident light exits, and an exit region on the exit surface on which the light exits. A light guide plate having a second incident surface provided on the first incident surface side, wherein the distance between the exit surface and the opposing surface of the exit surface decreases as the distance from the entrance surface increases in a region where the exit surface is formed; , And an internal light source provided to face the second incident surface.

According to a fifth aspect of the present invention, in the surface light source device of the fourth aspect, a lens is integrally formed on the second incident surface of the light guide plate.

According to a sixth aspect of the present invention, there is provided a light guide plate according to the present invention, wherein a first incident surface on which external light is incident, an exit surface on which the incident light exits, and an exit region on the exit surface on which the light exits. And a second incident surface provided on the first incident surface side.

According to a seventh aspect of the present invention, in the light guide plate according to the sixth aspect, a lens is integrally formed on the second incident surface.

According to an eighth aspect of the present invention, there is provided a display device according to any one of the first to fifth aspects, a non-light-emitting display means provided on an exit surface side, and a first incident surface. And a lid member having a reflection surface on a surface facing the first incidence surface.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an embodiment according to the present invention.

Reference numeral 1 denotes a light guide plate made of a light-transmitting material, which has a first incident surface 11 on which external light is incident, a second incident surface 12 on which light from an internal light source to be described later is incident, and a light guide plate on which incident light is guided. The light-emitting device includes an emission surface 13 from which light is emitted while passing through the light plate, and a back surface 14 facing the emission surface 13. Second incident surface 12
Is provided on the side opposite to the emission surface 13, that is, on the back surface 14 side, closer to the first incidence surface 11 with respect to the emission region 13 a of the emission surface 13 (in the present embodiment, provided in contact with the first incidence surface 11). Further, in the portion where the light exit surface 13 is formed, the distance (that is, the thickness) between the light exit surface 13 and the rear surface 14 gradually decreases as the distance from the light entrance surface (particularly, the first light entrance surface 11) increases. Is formed. At this time, the emission surface 13 has a surface parallel to a diffusion plate or a liquid crystal display panel described later. The second incident surface 12 is formed with a lens 12a having a convex surface, and the lens 12a refracts and condenses the light incident from the second incident surface 12 so as to be reflected by the first incident surface 11 as much as possible. Is done. Although not shown, a diffusion pattern may be formed on the back surface 14 as diffusion means that is designed so that incident light is emitted from the emission surface 13 with uniform luminance.

Since such a light guide plate is usually formed by injection molding using a thermoplastic resin, even if the light guide plate has a first incident surface, a second incident surface having a lens, and a diffusion pattern. Such a light guide plate is integrally and easily formed by a general molding process using a mold.

2 is provided to face the second incident surface 12,
An internal light source 3 such as a cold cathode fluorescent lamp for supplying light into the light guide plate 1 is provided behind the internal light source 2, and an internal surface for efficiently guiding light from the internal light source 2 to the second incident surface 12 is provided. The reflector 4 serving as a reflection surface is a reflection plate which is disposed to face the back surface 14 and returns light leaked from the back surface 14 into the light guide plate 1 again.

Reference numeral 5 denotes a total reflection surface facing the light exit surface 13, and a surface opposite to the side on which the second light incident surface 12 is provided in the thickness direction of the light guide plate 1, that is, on the light exit surface 13 side. A reflecting member provided near the first incident surface 11 at a position substantially facing the second incident surface 12. The reflecting member 5 is provided on a portion of the light guide plate 1 that is slightly inclined toward the second incident surface 12,
For example, a white seal is attached to a corresponding portion, or provided by printing and applying using a white ink or the like.
Note that the emission area 13a is formed by the reflection member 5 on the emission surface 13.
Is a portion excluding the region where the is provided.

Reference numeral 6 denotes a diffusion plate provided to face the emission surface 13 for uniformly distributing the emitted light. Reference numeral 7 denotes a transmission type non-light-emitting display means provided on the emission surface 13 via the diffusion plate 6. Liquid crystal display panel. Although not shown, the lens sheet may be replaced with the liquid crystal display panel 7 and the diffusion plate 6 as necessary.
Or between the diffusion plate 6 and the light guide plate 1.

Reference numeral 8 denotes a lid member, whose surface facing the first incident surface 11 is a reflection surface, and is provided so as to be able to face the first incident surface 11. The lid member 8 is provided rotatably about a shaft 8 a and can face the first incident surface 11. By rotating the lid member 8, the first incident surface 11 is covered or exposed. It is configured to be able to.

In such a device, when the liquid crystal display panel 7 is illuminated by turning on the internal light source 2, the lid member 8
Is a position facing the first incident surface 11, that is, the first incident surface 11
Is turned to a position covering the. When the internal light source 2 is turned on in this state, the light emitted from the internal light source 2 is directly or partially reflected by the reflector 3 and is incident on the light guide plate 1 from the second incident surface 12. The light incident from the second incident surface 12 is refracted and condensed by the lens 12a and is reflected by the first incident surface 11 or passes through the first incident surface 11 and is reflected by the reflection surface of the lid member 8. Then, the light enters the light guide plate 1 again, or is reflected by the reflection member 5 and travels inside the light guide plate 1 in the direction of the solid arrow. The light repeats reflection and diffusion on the back surface 14 and the like while traveling in the light guide plate 1, and is emitted from the emission surface 13. The emitted light is further diffused by the diffusion plate 6 to illuminate the liquid crystal display panel 7 from the back.

Next, when external light is taken in and the liquid crystal display panel 7 is illuminated by the external light, the lid member 8 is rotated to a position where the first incident surface 11 is exposed. When the first incident surface 11 is exposed to the outside, external light is incident from the first incident surface 11 and the incident light travels in the light guide plate 1 in the direction of the solid arrow. In the same manner as described above, the light repeatedly reflects and diffuses on the back surface 14 and the like while traveling in the light guide plate 1, and the light exit surface
Is emitted. The emitted light is further diffused by the diffusion plate 6 and illuminates the liquid crystal display panel 7 from the back. First
Part of the light incident from the incident surface 11 once goes out of the second incident surface 12, but part of the light is reflected by the reflector 3 and enters the light guide plate 1 again. The light re-incident from the second incident surface 12 behaves in the same manner as when the internal light source 2 is turned on.
Used as illumination light.

In the case where the liquid crystal display panel 7 is illuminated by taking in external light, the internal light source 2 may be used as an auxiliary light source. In conjunction with the rotation, control may be performed such that the internal light source 2 is turned off whenever the internal light source 2 is at a position where the first incident surface 11 is exposed.

As described above, the second incident surface 12 on which the light from the internal light source 2 is incident is provided on the first incident surface 11 side on which the external light is incident with respect to the exit region 13a of the exit surface 13. Thus, while securing the area of the incident surface on which external light or light from the internal light source 2 is incident, the first incident surface 11
Can be formed so that the distance between the emission surface 13 and the back surface 14 decreases as the distance from the surface increases. Thus, even in the case where the display panel can be illuminated by either the light from the internal light source or the external light, it is possible to achieve higher luminance and uniform luminance of the emitted light due to the shape of the light guide plate. .

The second light from the internal light source 2 is incident.
Even when the incident surface is provided on the first incident surface 11 side on which the external light is incident with respect to the exit region 13a of the exit surface 13, the second
By providing the reflecting member 5 provided near the first incident surface 11 at a position substantially facing the incident surface, it is possible to more efficiently guide the light from the internal light source 2 into the light guide plate 1 and increase the illumination intensity. Become.

FIG. 2 is a schematic diagram showing another embodiment according to the present invention. The other embodiment shown in FIG. 2 is significantly different from the embodiment shown in FIG. 1 in that the second incident surface is formed on the exit surface side.

Reference numeral 20 denotes a light guide plate, a first incident surface 21 on which external light is incident, and a second incident surface 2 on which light from an internal light source is incident.
2. It has an emission surface 23 from which the incident light is emitted while passing through the light guide plate, and a back surface 24 facing the emission surface 23. The second incident surface 22 is on the side where the exit surface 23 is provided,
It is provided near the first incident surface 21 with respect to the emission region 23a (in other embodiments, it is provided in contact with the first incident surface 21). The distance (that is, the thickness) between the emission surface 23 and the back surface 24 is gradually reduced as the distance from the surface (particularly, the first incidence surface 21) increases. The second incident surface 22 is formed with a lens 22a having a convex surface. The lens 22a refracts and condenses the light incident from the second incident surface 22 as much as possible on the first incident surface 21. Is done. Also, on the back surface 24, the incident light is
3, a diffusion pattern 24a is formed as diffusion means, which is designed to emit light with uniform luminance.

30 is an internal light source, 31 is a reflector, 32
Is a reflection plate provided opposite to the back surface 24 in a region other than the reflection member described later. Reference numeral 33 denotes a total reflection surface facing the back surface 24, and the second incidence surface 22 on the side opposite to the side on which the second incidence surface 22 is provided in the thickness direction of the light guide plate 20, that is, on the back surface 24 side. At the position substantially opposed to the first incident surface 2
It is a reflection member provided at one side.

Reference numeral 34 denotes a diffusion plate, 35 denotes a liquid crystal display panel,
Reference numeral 6 denotes a cover member provided rotatably about a shaft 36a. Although not shown, a lens sheet may be provided between the liquid crystal display panel 35 and the diffusion plate 34 or the diffusion plate 3 if necessary.
4 and the light guide plate 20.

In the other embodiment shown in FIG. 2, similarly to the embodiment shown in FIG. 1, a light guide plate is used in which the display panel can be illuminated by either the light from the internal light source or the external light. The brightness of the emitted light can be increased and the brightness can be made uniform by the shape of the light emitting device.

Further, since the external light and the light from the internal light source 30 travel in the same solid arrow direction in the light guide plate 20,
When designing the diffusion pattern 24a, a pattern design that can provide uniform luminance with respect to light traveling from one direction, even if the display panel can be illuminated by either light from the internal light source or external light. Just do it. Thus, the design of the diffusion pattern is facilitated, so that the cost of the entire apparatus can be reduced and the speed of introduction into the market can be increased.

[0035]

According to the present invention, as is apparent from the above description, the second incident surface on which the light from the internal light source is incident is located on the first incident surface side on which the external light is incident with respect to the exit surface. The distance between the exit surface and the back surface decreases as the distance from the first entrance surface increases in the region where the exit surface is formed, while securing the area of the entrance surface on which external light or light from the internal light source is incident. Shape. This allows
Even in the case where the display panel can be illuminated by either the light from the internal light source or the external light, it is possible to increase the luminance of the emitted light and make the luminance uniform by the shape of the light guide plate.

At this time, by providing a reflecting member provided near the first incident surface at a position substantially opposed to the second incident surface, the light from the internal light source is more efficiently guided into the light guide plate, and the illumination intensity is improved. Can be raised.

Thus, in the case where the display panel can be illuminated by either the light from the internal light source or the external light, the liquid crystal display panel can be uniformly illuminated by any of the lights, and the illumination performance is improved. It is possible to provide an excellent surface light source device and a display device having good display characteristics.

Further, in the case where the light guide plate is provided with a diffusion pattern, it is sufficient to design a pattern capable of exhibiting uniform luminance with respect to light traveling in one direction, so that the design of the diffusion pattern becomes easy, and It can contribute to cost reduction and speed to market.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of one embodiment according to the present invention.

FIG. 2 is a schematic configuration diagram of another embodiment according to the present invention.

[Explanation of symbols]

 1, 20 Light guide plate 11, 21 First incident surface 12, 22 Second incident surface 12a, 22a Lens 13, 23 Outgoing surface 14, 24 Back surface (surface facing the outgoing surface) 24a Diffusion pattern 2, 30 Internal light source 4, 32 Reflecting plate 5, 33 Reflecting member 7, 35 Liquid crystal display panel (non-light emitting display means) 8, 36 Lid member

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroshi Mabuchi 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. F-term (reference) 2H091 FA14Z FA23Z FA26Z FA32Z FA42Z FB02 FD22 FD23 LA18

Claims (8)

[Claims] 1. A first incident surface on which external light is incident, an exit surface on which the incident light exits, and a first incident surface provided on the first incident surface side with respect to an exit region on the exit surface from which light exits. A light guide plate having a second light incident surface, an internal light source provided to face the second light incident surface, and a light guide plate surface opposite to a position where the second light incident surface is provided in the thickness direction of the light guide plate. A surface light source device comprising a reflection member. 2. The surface according to claim 1, wherein the light guide plate is formed such that the distance between the exit surface and the opposing surface of the exit surface decreases with increasing distance from the entrance surface in the region where the exit surface is formed. Light source device. 3. The surface light source device according to claim 1, wherein a lens is integrally formed on the second incident surface of the light guide plate. 4. A first incident surface on which external light is incident, an exit surface on which the incident light exits, and a first incident surface provided on the first incident surface side with respect to an exit region of the exit surface on which light exits. A light guide plate having a second incident surface, wherein the distance between the exit surface and the opposing surface of the exit surface decreases as the distance from the entrance surface increases in a region where the exit surface is formed; A surface light source device comprising: an internal light source provided. 5. The surface light source device according to claim 4, wherein a lens is integrally formed on the second incident surface of the light guide plate. 6. A first incident surface on which external light is incident, an exit surface on which the incident light exits, and a first incident surface provided on the first incident surface side with respect to an exit region of the exit surface on which light exits. A light guide plate having two incident surfaces. 7. The light guide plate according to claim 6, wherein a lens is integrally formed on the second incident surface. 8. The surface light source device according to claim 1, a non-light-emitting display means provided on an emission surface side, and provided so as to be able to face the first incidence surface and opposed to the first incidence surface. A display device comprising: a lid member having a reflective surface.