Light guide plate, light source device equipped therewith and display device

• US 20030137821A1
• Filed: 10/04/2002
• Published: 07/24/2003
• Est. Priority Date: 01/23/2002
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Fujitsu Display Technologies Corporation (Fujitsu Limited)
• Inventors: Hayashi, Keiji, Suzuki, Toshihiro, Hamada, Tetsuya, Kobayashi, Tetsuya, Sugawara, Mari, Gotoh, Takeshi
• Granted Patent: US 7,073,933 B2
• Time in Patent Office: Days
• US Class Current: 362/31
• CPC Class Codes: G02B 6/0016 Grooves, prisms, gratings, scattering particles or rough surfaces
• CPC Class Codes: G02B 6/0048 with stepwise taper
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources

Abstract

A display device used for a display unit of portable electronic equipment, a light source device therefor and a light guide plate, suppressing dispersion in the brightness and featuring a high contrast and a good display quality. The constitution includes a light incidence surface on where light emitted from an LED falls, a light reflection surface formed facing the light incidence surface and reflects light from the light incidence surface, a light outgoing surface arranged between the light incidence surface and the light reflection surface, and has a circularly polarizing plate intimately adhered onto the surface thereof, and an opposing surface formed facing the light outgoing surface and in which there are alternately arranged first opposing surfaces for guiding the incident light to the light outgoing surface as well as to the light reflection surface, and second opposing surfaces for emitting the light reflected by the light reflection surface through the light outgoing surface.

Claims

1. A light guide plate comprising:

a light incidence portion having a light incidence surface on where light emitted from a point source of light falls;

a light reflection surface formed facing the light incidence surface to reflect light from the light incidence surface;

a light outgoing surface arranged between the light incidence surface and the light reflection surface, and having a circularly polarizing plate intimately adhered onto the surface thereof;

an opposing surface formed facing the light outgoing surface and in which there are alternately arranged first opposing surfaces for guiding the incident light to the light reflection surface with the light outgoing surface, and second opposing surfaces for emitting the light reflected by the light reflection surface through the light outgoing surface; and

side end surfaces arranged between the light incidence surface and the light reflection surface, and are formed at both ends of the light outgoing surface and of the opposing surface.

4. A light guide plate according to claim 1, wherein the first opposing surfaces are formed being so inclined as to become lower toward the side of the light incidence portion, the angle α

of inclination with respect to the light outgoing surface being 0°

≦

α

≦

1.0°

.

5. A light guide plate according to claim 1, wherein the second opposing surfaces are formed being so inclined as to become lower toward the side of the light incidence portion, the angle β

of inclination with respect to the light outgoing surface being 30°

≦

β

≦

40°

.

6. A light guide plate according to claim 1, wherein the light incidence portion has a directivity-improving portion for improving the directivity of incident light.

7. A light guide plate according to claim 6, wherein the directivity-improving portion has a tapered surface which so works as to increase the angles of incidence of light incident upon the light outgoing surface and upon the first opposing surfaces.

8. A light guide plate according to claim 6, wherein the directivity-improving portion has a surface that is tapered as viewed from the side of the display screen, and when the distance between the light incidence surface and the light reflection surface is denoted by L3, and the distance between the side ends by W3, then, the angle θ

4 between the tapered surface and the side ends is θ

4≦

tan<sup>−

1</sup> (W3/(2×

L3)).

9. A light guide plate according to claim 1, wherein the side end surfaces have light-absorbing portions for absorbing incident light.

10. A light guide plate according to claim 1, wherein the light incidence portion has a light reflection portion for reflecting the reflected light in the regions other than the region where the light falls.

11. A light guide plate according to claim 1, wherein the direction of extension of corner portions formed by the first opposing surfaces and by the second opposing surfaces, is inclined with respect to the light incidence surface.

12. A light guide plate according to claim 11, wherein the angle θ

3 between the direction of extension and the light incidence surface is 10°

≦

|θ

3|≦

30°

.

2. A light guide plate comprising:

a light incidence portion having a light incidence surface on which light emitted from a point source of light falls;

a light reflection surface formed in a parabolic shape facing the light incidence surface with the position where the point source of light is arranged as a focal point, and reflects light from the light incidence surface;

a light outgoing surface arranged between the light incidence surface and the light reflection surface;

an opposing surface formed facing the light outgoing surface and in which there are alternately arranged first opposing surfaces for guiding the incident light to the light reflection surface with the light outgoing surface, and second opposing surfaces for emitting the light reflected by the light reflection surface through the light outgoing surface; and

side end surfaces arranged between the light incidence surface and the light reflection surface, and are formed at both ends of the light outgoing surface and of the opposing surface.

3. A light guide plate according to claim 2, wherein the light outgoing surface has a circularly polarizing plate that is intimately adhered to the surface thereof.

13. A light source device comprising:

a point source of light for emitting light; and

a light guide plate for guiding light;

wherein the light guide plate comprises a light incidence portion having a light incidence surface on where light emitted from the point source of light falls;

a light reflection surface formed facing the light incidence surface to reflect light from the light incidence surface;

a light outgoing surface arranged between the light incidence surface and the light reflection surface, and having a circularly polarizing plate intimately adhered onto the surface thereof;

an opposing surface formed facing the light outgoing surface and in which there are alternately arranged first opposing surfaces for guiding the incident light to the light reflection surface with the light outgoing surface, and second opposing surfaces for emitting the light reflected by the light reflection surface through the light outgoing surface; and

side end surfaces arranged between the light incidence surface and the light reflection surface, and are formed at both ends of the light outgoing surface and of the opposing surface.

14. A light source device comprising:

a plurality of point sources of light arranged maintaining a predetermined distance L to emit light;

a light-mixing region having a predetermined width D in a direction in which light travels to mix the rays of light emitted from the plurality of point sources of light; and

a planar light source region having a light outgoing surface for emitting the rays of light mixed in the light-mixing region.

15. A light source device according to claim 14, wherein the distance L and the width D satisfy a relation,

D>

(L/2)×

cot A

where A is a half-brightness angle of light falling on the light-mixing region.

16. A light source device according to claim 14, wherein the light-mixing region includes n regions Sn having a refractive index Nn relative to the planar light source region and a width Dn in a direction in which light travels, and wherein the distance L, refractive index Nn and width Dn satisfy a relation,

(D1×

sin B/((N1²−

(sin B)²)^1/2)+(D2×

sin B/((N2²−

(sin B)²)^1/2)+ . . . +(Dn×

sin B/((Nn²−

(sin B)²)^1/2)>

L/2

where B is a half-brightness angle of light falling on the planar light source region.

17. A light source device according to claim 14, wherein the plurality of point sources of light emit rays of light of a plurality of colors, the point sources of light emitting rays of light of nearly the same color are arranged maintaining a predetermined distance L′

, and the distance L′ and

the width D satisfy a relation,

D>

(L′

/2)×

cot A

where A is a half-brightness angle of light falling on the light-mixing region.

18. A light source device according to claim 14, wherein the plurality of point sources of light emit rays of light of a plurality of colors, the point sources of light emitting rays of light of nearly the same color are arranged maintaining a predetermined distance L′

, the light-mixing region includes n regions Sn having a refractive index Nn relative to the planar light source region and a width Dn in a direction in which light travels, and wherein the distance L′

, refractive index Nn and width Dn satisfy a relation,

(D1×

sin B/((N1²−

(sin B)²)^1/2)+(D2×

sin B/((N2²−

(sin B)²)^1/2)+ . . . +(Dn×

sin B/((Nn²−

(sin B)²)^1/2)>

L′

/2

where B is a half-brightness angle of light falling on the planar light source region.

19. A light source device comprising:

a plurality of point sources of light arranged maintaining a predetermined distance to emit light;

a light incidence portion arranged neighboring the plurality of point sources of light and having a light incidence surface on where the light falls;

a light reflection surface formed facing the light incidence surface and reflects the light;

a light outgoing surface for emitting the light reflected by the light reflection surface; and

an opposing surface formed facing the light outgoing surface and in which there are alternately arranged first opposing surfaces to guide light incident on the light incidence surface to the light reflection surface, and second opposing surfaces for reflecting the light reflected by the light reflection surface so as to be emitted through the light outgoing surface.

20. A light source device comprising:

a plurality of linear sources of light for emitting light;

a light incidence portion arranged neighboring the plurality of linear sources of light and having a plurality of light incidence surfaces on where the light falls;

a light outgoing surface for emitting the light; and

an opposing surface formed facing the light outgoing surface and in which there are arranged first opposing surfaces for guiding light and second opposing surfaces for reflecting the light so as to be emitted through the light outgoing surface.

21. A display device comprising:

a display panel having pixels arranged like a matrix; and

a light source device for illuminating the display panel;

wherein the light source device comprises a point source of light for emitting light; and

a light guide plate for guiding light;

wherein the light guide plate comprises a light incidence portion having a light incidence surface on where light emitted from the point source of light falls;

a light reflection surface formed facing the light incidence surface to reflect light from the light incidence surface;

a light outgoing surface arranged between the light incidence surface and the light reflection surface, and having a circularly polarizing plate intimately adhered onto the surface thereof;

an opposing surface formed facing the light outgoing surface and in which there are alternately arranged first opposing surfaces for guiding the incident light to the light reflection surface with the light outgoing surface, and second opposing surfaces for emitting the light reflected by the light reflection surface through the light outgoing surface; and

side end surfaces arranged between the light incidence surface and the light reflection surface, and are formed at both ends of the light outgoing surface and of the opposing surface.

22. A display device according to claim 21, wherein the light source device is arranged on the side of the display screen of the display panel.

23. A display device according to claim 21, wherein the display panel is a liquid crystal display panel having a pair of substrates and liquid crystals sealed between the pair of substrates.