JPH11133236A - Light transmission plate, and surface light source and liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a light transmission plate capable of improving external light take-in efficiency and reducing power consumption in a main light source by providing structure that an external light take-in part projects from a light emission surface. SOLUTION: The external light take-in part 1a of the light transmission plate 1 is constituted to project from the light emission surface 1e. Sunlight is made incident on the take-in part 1a outdoors and external light such as a fluorescent lamp is made incident thereon indoors. Since the take-in part 1a largely projects from the surface 1e in a light projecting direction, the surface area of an external light take-in surface is much larger than the conventional one, and the external light is efficiently taken in the take-in part 1a. As a result, in the case of using a liquid crystal display device equipped with the plate 1 for a view finder, illumination which is so sufficient that a light source need not be turned on is realized, whereby the power consumption is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate, a surface light source using the light guide plate, and a liquid crystal display device. More specifically, the present invention relates to a backlight for a liquid crystal display device, a surface used for lighting advertisement, a traffic sign, and the like. The present invention relates to a light source, a light guide plate included in the surface light source, and a backlight type liquid crystal display device such as a view finder.

[0002]

2. Description of the Related Art As a surface light source for a backlight of a liquid crystal display device, a side light type using a light-transmitting flat plate as a light guide plate is known. In such a surface light source, light from a light source such as a fluorescent lamp is incident from one of the side end surfaces of a light guide plate made of a transparent parallel flat plate or a wedge-shaped flat cross section, and the total internal reflection inside the translucent flat plate is used. Light is propagated throughout the light guide plate, and a part of the propagated light is made into a diffuse reflection light of less than a critical angle by a light scattering reflector on the back surface of the light guide plate, and diffuse light is emitted from the surface of the light guide plate (actually open). 55-162201).

[0003] Further, a surface light source for a backlight in which an external light intake portion is provided on a side end surface of a light guide plate in order to use external light such as sunlight or indoor light as an auxiliary light source is also known. The shape of the entrance portion is arc-shaped in cross section to constitute one cylindrical lens (JP-A-5-11249).

[0004]

However, in the conventional light guide plate of the liquid crystal display device, as shown in FIG. 1, the light of the light guide plate 1 on which the liquid crystal panel 9 is mounted and the external light receiving surface of the external light receiving section 1a. Since the light exit surface 1e is the same surface and does not protrude in the direction of the liquid crystal panel 9 (that is, the upward direction in the drawing), the surface area of the external light intake surface cannot be increased. There is a problem that the efficiency of taking in is very poor and it is not possible to reduce the power consumption.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the power consumption of the main light source can be reduced by improving the efficiency of taking in external light. An object of the present invention is to provide a light guide plate, a surface light source using the light guide plate, and a liquid crystal display device.

[0006]

According to a first aspect of the present invention, there is provided a light guide plate according to the first aspect of the present invention, wherein the light guide plate integrally molded with resin is provided with an external light take-in portion for taking in external light. A light exit surface for emitting external light taken in from the external light intake portion, wherein the external light intake portion protrudes from the light exit surface in a light emission direction.

According to a second aspect of the present invention, there is provided a surface light source comprising: the light guide plate according to the first aspect; and a light source attached to a surface of the light guide plate other than the external light receiving portion and the light emitting surface. It is characterized by. The liquid crystal display of the present invention according to claim 3 is
A light guide plate according to claim 1, and a liquid crystal panel mounted near the light exit surface of the light guide plate.

According to a fourth aspect of the present invention, there is provided a liquid crystal display device comprising:
4. The liquid crystal display device according to claim 3, wherein the external light receiving portion of the light guide plate does not protrude from the display surface of the liquid crystal panel in a light emitting direction.

[0009]

Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 is a schematic view of a light guide plate according to the present invention. Reference numeral 1 denotes a light guide plate, and at the same time as the light guide plate 1 is manufactured by resin molding using a mold, an external light intake portion 1a described later is formed. 1a is an external light intake unit,
External light such as sunlight or indoor light is taken in as auxiliary light. The external light intake portion 1a protrudes from the light exit surface 1e described later in the emission direction of the combined light (that is, the upward direction in the drawing).
As a result, the surface area of the external light intake surface is larger than that of the conventional light guide plate.

FIG. 5 is a front view of an external light intake section of the light guide plate according to the present invention, and particularly exemplifies a shape that can be adopted for the external light intake section. FIG. 5 (A) shows the light guide plate of FIG. 2, in which the left side of the external light intake part 1a has an arc-shaped cross section and the right side has an oblique straight line shape. In FIG. 5B, the left and right sides of the external light intake unit 1a are obliquely linear.

In FIG. 5C, the left and right sides of the external light intake portion 1a are arc-shaped in cross section. FIG. 5D shows the external light intake unit 1.
The left side of “a” has an arc-shaped cross section and the right side has a vertical straight line. In FIG. 5 (E), the left side of the external light intake section 1a has a semicircular shape, and the right side has a vertical linear shape.

In FIG. 5 (F), the left side of the external light intake section 1a has a semicircular arc shape, and the right side has an oblique straight line shape. FIG. 5 (G)
Has a plurality of fisheye lenses 1f formed on the left side of the external light receiving portion 1a of the light guide plate in FIG. 5B. Here, returning to FIG. 2, the description will be continued.

Reference numeral 1c denotes a light incident surface. As will be described below, light irradiated from a light source (not shown) disposed substantially parallel to the light incident surface 1c enters. In addition, two sides 1
It is also possible to arrange a light source on one side of b and use it as a light incident surface. Reference numeral 1d denotes a light reflection surface. After resin molding, in order to prevent light from leaking and to increase reflection efficiency, a reflection plate made of aluminum or the like is attached after performing dot printing (not shown).

Reference numeral 1e denotes a light exit surface, which is an external light intake section 1a.
In addition, light incident from the light incident surface 1c is reflected by the light reflecting surface 1d and the two side surfaces of the light guide plate 1, and almost all of the incident light is finally combined light having uniform directivity from the light emitting surface 1e. Is emitted. In addition, a leakage prevention member such as a white tape is attached to the side surface 1b in order to prevent light leakage.

The material of the light guide plate 1 is selected from light-transmissive materials, and usually acrylic or polycarbonate resin is used. The shape of the light guide plate is a parallel flat plate or a flat wedge-shaped flat plate, and the thickness thereof is generally about 1 to 10 mm. Other translucent materials include acrylate or methacrylate homo- or copolymers such as polymethyl methacrylate and polymethyl acrylate, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polycarbonates, and the like. Thermoplastic resins such as polystyrene and polymethylpentene, or acrylates such as polyfunctional urethane acrylates and polyester acrylates cross-linked by ultraviolet rays or electron beams, transparent resins such as unsaturated polyesters, transparent glass, transparent ceramics, etc. are used. Can be

Next, the operation of the light guide plate according to the present invention will be described with reference to FIG. Sunlight enters the outside light intake portion 1a of the light guide plate 1 outside the room, and outside light such as a fluorescent lamp enters the room inside. The external light intake portion 1a protrudes more in the light emission direction than the light emission surface 1e, so that the surface area of the external light intake surface is much larger than that of the conventional light guide plate (see FIG. 1). The external light is efficiently taken into the external light take-in portion 1a. as a result,
When a liquid crystal display device including the light guide plate according to the present invention is used for a viewfinder or the like, sufficient illumination can be performed so that the light source does not need to be turned on, so that power consumption can be reduced.

When the light source is turned on, light from the light source and external light incident from the light incident surface 1c are reflected by the light reflecting surface 1c.
d and the two side surfaces 1b of the light guide plate 1
e, the light is emitted as synthesized light having uniform directivity.
FIG. 3 is a schematic diagram showing a surface light source according to the present invention. 2
Is a surface light source, which comprises a light guide plate 1 according to the present invention, a light source 3 such as a fluorescent tube, and various control circuits (not shown). The control circuit also includes, for example, a circuit that detects the total amount of light emitted from the light emission surface of the light guide plate 1 and adjusts and supplies power to the light source 3 so that the amount of emitted light is optimized.

Light emitted from the light source 3 is reflected by the reflector 4 and enters the inside of the light guide plate 1 from the light incident surface 1c of the light guide plate 1 and external light such as natural light enters from the external light intake 1a of the light guide plate 1. , Reflector 5 attached below light reflecting surface 1d
The light is repeatedly reflected and reflected by the side end surface 1b, and is emitted from the light exit surface 1e of the light guide plate 1 to the diffusion plate 6. The diffusion plate 6
Is diffused uniformly and isotropically within a desired angle range by the diffusion plate 6 and the lens sheet 7 and is emitted from the lens sheet 7.

FIG. 4 is a schematic view showing a liquid crystal display device provided with the surface light source according to the present invention. FIG. 4A shows that the external light intake portion projects from the display surface of the liquid crystal panel 9 in the light emission direction. On the other hand, FIG. 4B shows that the external light intake portion does not protrude beyond the display surface of the liquid crystal panel 9 in the light emission direction. These two types of liquid crystal display devices are both excellent in the effect of taking in external light. However, in FIG. 4B, since the external light taking-in portion does not protrude from the display surface of the liquid crystal panel 9,
Not only can the external light intake itself be prevented from being damaged or the user being injured, but also the degree of freedom in design is not impaired.

Reference numeral 8 denotes a liquid crystal display, and a liquid crystal panel 9
And the surface light source 2 according to the present invention. Light that is uniformly and isotropically diffused and emitted from the surface light source 2 described above is guided to the liquid crystal panel 9. However, a liquid crystal display device that removes the light source 3 from the surface light source 2 and uses only external light from the light guide plate 1 may be used.

[0021]

As described above, according to the light guide plate of the present invention, since the external light intake portion protrudes from the light exit surface, the surface area of the external light intake surface is smaller than that of the conventional light guide plate. It can be made large, and external light such as sunlight or indoor light can be efficiently taken in as main light. According to the surface light source and the liquid crystal display device according to the present invention, the external light intake efficiency is improved by using the light guide plate,
When obtaining a constant amount of emitted light, not only can the power supplied to the light source be reduced, but also the light source can be made unnecessary depending on the application.

Further, according to the liquid crystal display device of the present invention, since the external light receiving portion of the light guide plate does not protrude beyond the display surface of the liquid crystal panel, there are few factors that cause injuries to the user of the device and the safety is reduced. In addition, it is possible to prevent damage to the external light intake unit itself and to maintain a degree of freedom in design.

[Brief description of the drawings]

FIG. 1 is a schematic view of a conventional liquid crystal display device.

FIG. 2 is a schematic view of a light guide plate according to the present invention.

FIG. 3 is a schematic view showing a surface light source according to the present invention.

FIG. 4 is a schematic view showing a liquid crystal display device including a surface light source according to the present invention.

FIG. 5 is a front view of an external light intake section of the light guide plate according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light guide plate 1 a external light intake portion 1 b side surface 1 c light incident surface 1 d light reflection surface 1 e light emission surface 1 f fisheye lens 2 surface light source 3 light source 5 reflection plate 6 diffusion plate 7 lens sheet 8 liquid crystal display device 9 liquid crystal panel

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takaya Kusabuka 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (4)

[Claims] 1. A light guide plate integrally formed of resin, comprising: an external light intake section for receiving external light; and a light exit surface for emitting external light introduced from the external light intake section. The light guide plate, wherein the intake portion protrudes from the light emission surface in the light emission direction. 2. A surface light source, comprising: the light guide plate according to claim 1; and a light source attached to a surface of the light guide plate other than an external light intake portion and a light emission surface. 3. A liquid crystal display device comprising: the light guide plate according to claim 1; and a liquid crystal panel mounted near a light exit surface of the light guide plate. 4. The liquid crystal display device according to claim 3, wherein the external light receiving portion of the light guide plate does not protrude from the display surface of the liquid crystal panel in a light emitting direction. .