JP3316438B2 - Light guide plate, surface light source and liquid crystal display - Google Patents

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, and a liquid crystal display device, and more particularly, to a light guide plate having an external light take-in portion for taking in external light from sunlight or a fluorescent lamp. The present invention relates to a surface light source for a backlight of a liquid crystal display device using the light guide plate and a backlight type liquid crystal display device such as a liquid crystal monitor for projecting a subject with a digital still camera or a video camera.

[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. The emission surface 1e and the light reflection surface 1d are the same surface, and are in the direction of the liquid crystal panel 9 (that is, the upward direction in the drawing).
And does not protrude below the light reflecting surface 1d.
The surface area of the external light intake surface cannot be increased, and as a result, there is a problem that the efficiency of external light intake is very poor, and power consumption cannot be reduced.

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. It is an object of the present invention to provide a light guide plate, a surface light source, and a liquid crystal display device that can be used.

[0006]

According to a first aspect of the present invention, there is provided a light guide plate which is formed integrally with a resin to achieve the above object. Input part, a light exit surface that emits external light taken from the external light intake unit, and a light reflection surface that reflects external light taken from the external light intake unit and is a surface facing the light exit surface. The external light intake section is a cylindrical lens,
It is characterized by projecting from the light emitting surface and the light reflecting surface.

A light guide plate according to a second aspect of the present invention is a light guide plate integrally formed of resin, and includes an external light intake section for receiving external light, and an external light intake section for emitting external light from the external light intake section. A light-exiting surface, and a light-reflecting surface that reflects external light taken in from the external light-introducing portion on one surface facing the light-emitting surface, and the external light-introducing portion is a cylindrical lens, The light-emitting surface protrudes from the light-emitting surface and the light-reflecting surface, and a thickness width of the external light-receiving portion is larger than a thickness width of the light-emitting surface and the light-reflecting surface.

According to a third aspect of the present invention, there is provided a surface light source, comprising: a light source; a light incident surface on which light emitted from the light source is incident;
An external light intake unit that faces the light incident surface and receives external light, a light emission surface that emits light emitted from the light incident surface and external light taken in from the external light intake unit, and the light emission surface A light reflecting surface that reflects external light taken in from the external light intake portion, and the external light intake portion protrudes from the light exit surface and the light reflection surface, and is integrally formed of resin. And a light guide plate, wherein the light source is provided substantially parallel to a light incident surface. The liquid crystal display device of the present invention according to claim 4 is an external light intake section for taking in external light, a light exit surface for emitting external light taken in from the external light intake section, and a surface facing the light exit surface. A light-reflecting surface that reflects external light taken from the external light-introducing portion, wherein the external light-introducing portion protrudes from the light-emitting surface and the light-reflecting surface, and a light guide plate integrally formed of resin. A liquid crystal panel mounted in close proximity to a light exit surface of the light guide plate, wherein an external light intake of the light guide plate does not protrude in a light exit direction from a display surface of the liquid crystal panel. And

[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 the light guide plate 1 is manufactured by resin molding using a mold, and at the same time, an external light intake portion 1a is formed.
Is formed at one upper end of the light guide plate 1. Reference numeral 1a denotes an outside light taking-in section, which takes in outside light such as sunlight or room light as main light. This external light intake portion 1a is provided with a light exit surface 1 described later.
e and the light reflecting surface 1d protrude in the vertical direction in the drawing, and as a result, the surface area of the external light receiving surface is larger than that of the conventional light guide plate. The shape of the external light intake 1a is
This is a cylindrical lens having a substantially fan-shaped cross section and an arc-shaped tip, and the lens effect efficiently takes in external light not only directly above but also immediately beside or obliquely from above and below. However,
The external light intake portion 1a is not limited to a fan-shaped cylindrical lens, and may be, for example, a trapezoidal column having a flat shape in which no lens is formed.

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, which is substantially fan-shaped and has an arc-shaped cross section on the left side of the external light intake portion 1a and an oblique straight line on the right side. In FIG. 5B, the trapezoidal shape is substantially trapezoidal, the left side of the external light intake section 1a is flat, and the right side is oblique straight.

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. 5E, a plurality of fisheye lenses 1f are formed on the left side of the external light intake 1a of the light guide plate in FIG. 5B.

Returning to FIG. 2, the description will be continued. 1c is
A light incident surface, as described below.
Light emitted from a light source (not shown) disposed substantially parallel to the light enters. However, it is also possible to arrange a light source on one or both of the two side surfaces 1b to be a light incident surface. 1d
Is a light reflecting surface, and after a resin molding, in order to prevent light from leaking and to enhance the reflection efficiency, a reflecting plate such as aluminum 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 1b of the light guide plate 1, and almost all of the incident light finally has a 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. Since the sunlight enters the outside light intake portion 1a of the light guide plate 1 outdoors and the outside light from a fluorescent lamp or the like efficiently enters the room, a liquid crystal display device including the light guide plate according to the present invention is provided. When used in a digital still camera or a video camera to display an image on an LCD monitor, etc., sufficient lighting can be provided so that the light source does not need to be turned on. As a result, the power consumption of various camera devices themselves is reduced. Can be achieved.

When the light source is turned on, the light from the light source incident on the light incident surface 1c and the external light introduced from the external light receiving portion 1a receive light from the light reflecting surface 1d and the two side surfaces of the light guide plate 1. The light is reflected by 1b, and is emitted from the light emission surface 1e as combined light having uniform directivity. FIG. 3 is a schematic diagram showing a surface light source according to the present invention.

Reference numeral 2 denotes a surface light source, which is 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).
And so on. 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 is incident on the light incident surface 1c of the light guide plate 1, and external light such as natural light is transmitted from the external light receiving portion 1a of the light guide plate 1.
, Is reflected by the reflection plate 5 and the side end surface 1b attached to the lower part of the light reflection surface 1d, repeatedly focused, and emitted from the light exit surface 1e of the light guide plate 1 to the diffusion plate 6. Further, the light incident on the diffusion plate 6 is uniformly and isotropically diffused within a desired angle range by the diffusion plate 6 and the lens sheet 7 and is emitted from the lens sheet 7. However, depending on the application, it is also possible to remove the fluorescent tube and the control circuit (not shown) from the main surface light source 2 to obtain a surface light source of a type that receives only external light.

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 an external light intake portion protruding 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.

[0020]

As described above, according to the light guide plate of the present invention, the external light intake portion protrudes from the light exit surface and the light reflection surface. The surface area of the surface can be increased, 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 use of the light guide plate improves the external light intake efficiency, so that 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 changed depending on the application. It becomes possible to make it unnecessary.

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 the user of the device to be injured 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 the 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]

 DESCRIPTION OF SYMBOLS 1 Light guide plate 1a External light intake part 1b Side surface 1c Light incidence surface 1d Light reflection surface 1e Light emission surface 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 (56) References JP-A-8-87010 (JP, A) JP-A-5-11249 (JP, A) JP-A-11-133236 (JP, A) 47297 (JP, U) Actually open 57-195175 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F21V 8/00 601 G02F 1/13357 G02B 6/00 331

Claims (4)

(57) [Claims] 1. A light guide plate integrally formed of resin, comprising: an external light intake section for receiving external light; a light emission surface for emitting external light introduced from the external light intake section; And a light reflecting surface that reflects external light taken in from the external light intake unit, and the external light intake unit is a cylindrical lens, and is a surface facing the light exit surface and the light reflection surface. A light guide plate that protrudes. 2. A light guide plate integrally formed of a resin, comprising: an external light intake section for receiving external light; a light exit surface for emitting external light introduced from the external light intake section; And a light reflecting surface that reflects external light taken in from the external light intake unit, and the external light intake unit is a cylindrical lens, and is a surface facing the light exit surface and the light reflection surface. The light guide plate, wherein the light guide plate protrudes, and a thickness width of the external light intake portion is larger than a thickness width of the light exit surface and the light reflection surface. 3. A light source, a light incident surface on which light emitted from the light source is incident, and
An external light intake section facing the light incident surface and receiving external light;
From the light irradiated from the light incident surface and the external light intake section
A light emitting surface for emitting the external light taken in, and the light emitting surface;
Opposing surface, outside taken in from the outside light intake section
A light reflecting surface for reflecting light, wherein the external light intake section is
It protrudes from the light emitting surface and the light reflecting surface and is integrally formed of resin.
A light guide plate that is shaped, and wherein the light source is provided substantially parallel to a light incident surface . 4. An external light intake section for receiving external light, and said external light
A light emitting surface for emitting external light taken from the intake unit,
One surface facing the light exit surface and taken from the outside light intake section
A light reflecting surface for reflecting the external light that has entered.
The input portion protrudes from the light exit surface and the light reflection surface, and a resin
And integrally molded light guide plate in, comprising a liquid crystal panel mounted in proximity to the light emitting surface of the light guide plate, outside light intake portion of said light guide plate, the display surface of the liquid crystal panel
The liquid crystal display device does not protrude in the light emitting direction .