Light-guiding plate, lighting device and display device

• US 20040130882A1
• Filed: 12/01/2003
• Published: 07/08/2004
• Est. Priority Date: 11/29/2002
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Tanaka, Akira, Yamada, Hiroshi, Abe, Makoto, Hara, Yasushi, Takahashi, Toshikazu, Nishio, Chikara, Hirabayashi, Masashi
• Granted Patent: US 6,974,241 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 6/002 by shaping at least a portion of the light guide, e.g. with collimating, focussing or diverging surfaces
• CPC Class Codes: G02B 6/0031 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0036 2-D arrangement of prisms, protrusions, indentations or roughened surfaces
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/0043 provided on the surface of the light guide
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: Y10S 385/901 Illuminating or display apparatus

Abstract

A reflector has a curved part covering the light source and a pair of end parts extending at the two sides of the curved part. The inside surface of each end part has a plurality of substantially parallel projections or depressions. The light-guiding plate has an incident surface and an emission surface substantially perpendicular to the incident surface, the incident surface having a plurality of projections or depressions extending substantially parallel to the emission surface. Also, the reflection surface of the light-guiding plate has projections.

Claims

1. A light-guiding plate comprising an incident surface and an emission surface substantially perpendicular to said incident surface, said incident surface having a plurality of projections or depressions extending substantially parallel to said emission surface.

2. A light-guiding plate as set forth in claim 1 wherein a pitch of said plurality of projections or depressions changes at an end of the incident surface on the emission surface side and at other positions.

4. A light-guiding plate as set forth in claim 1 or 3, wherein said light-guiding plate has projections at the emission surface.

3. A light-guiding plate comprising an incident surface, an emission surface substantially perpendicular to said incident surface, and a reflection surface substantially perpendicular to said incident surface, said reflection surface having projections.

5. A light source device comprising a side light source, a light-guiding plate, and a prism sheet,

wherein said side light source is arranged at one side surface among two side surfaces opposite to each other of said light-guiding plate and said light-guiding plate, said prism sheet are superposed on each other, and

wherein said prism sheet includes a plurality of prism parts on said light-guiding plate side and is configured so that the ratio of area of inclined surfaces per unit area decreases in a region of a range up to a predetermined distance from said side light source.

6. A light source device as set forth in claim 5, wherein said prism sheet includes a plurality of inclined surfaces and at least one flat part at said light-guiding plate side, and is configured so that the ratio of area of said flat part to area of inclined surfaces per unit area becomes larger in a region of a range up to a predetermined distance from said side light source.

7. A light source device as set forth in claim 6, wherein the prism parts of said prism sheet are configured so that the ratio of area of the inclined surfaces per unit area gradually decreases the closer to said side light source at a region of a range up to a predetermined distance from said side light source.

8. A light source device as set forth in claim 7, wherein each of said plurality of prism parts includes two inclined surfaces and in that a pitch of said prisms is larger at a region of a range up to a predetermined distance from said side light source.

9. A light source device as set forth in claim 8, wherein a pitch of said prisms gradually becomes larger the closer to said side light source in a region of a range up to a predetermined distance from said side light source.

10. A light source device as set forth in claim 9, wherein the region of a range up to a predetermined distance from said side light source of said prism sheet is a region of a range up to a distance of at least three times the maximum thickness of said side light source side of said light-guiding plate.

11. A light source device as set forth in claim 10, wherein each of the prism parts of a region of a range up to a predetermined distance from said side light source of said plurality of prism parts is of a substantially quadrangular prism shape including two inclined surfaces and one flat surface, and each of the prism parts of a region outside the region of a range up to a predetermined distance from said side light source of said plurality of prism parts is of a substantially triangular prism shape including two inclined surfaces.

12. A light source device as set forth in claim 11, wherein each of said plurality of prism parts is of a substantially triangular prism shape including two inclined surfaces, and each flat surface is arranged between two prism parts.

13. A light source device as set forth in claim 5, wherein the surface of said prism sheet at said light-guiding plate side and/or the surface at the opposite side from said light-guiding plate at a region of a range up to a predetermined distance from said side light source of said prism sheet is treated for diffusion.

14. A light source device as set forth in claim 13, wherein the degree of diffusion given to said prism sheet becomes larger at a region of a range up to a predetermined distance from said side light source compared with a center region.

15. A light source device as set forth in claim 13 or 14 characterized in that the degree of diffusion given to said prism sheet substantially becomes gradually larger the closer to said side light source at a region of a range up to a predetermined distance from said side light source.

16. A light source device as set forth in claim 5, wherein the entire surface of said prism sheet on the side opposite to said light-guiding plate is treated for diffusion.

17. A light source device as set forth in claim 16, wherein the degree of diffusion given to the entire surface of said prism sheet at the side opposite to said light-guiding plate is substantially constant at a region outside of a region of a range up to a predetermined distance from said side light source.

18. A light source device as set forth in claim 13 or 16, wherein the degree of diffusion given to said prism sheet is different between a direction parallel to and a direction perpendicular to at least a longitudinal direction of said light source.

19. A light source device as set forth in claim 13 or 16, wherein the degree of diffusion given to said prism sheet becomes stronger in a direction perpendicular to at least a longitudinal direction of said light source compared with a direction parallel to said longitudinal direction.

20. A light source device as set forth in claim 13 or 16, wherein a diffusion sheet is further arranged superposed over said prism sheet at a side of said prism sheet opposite to said light-guiding plate.

21. A light source device as set forth in claim 5, wherein a diffusion part is provided near an end of said prism sheet side of a side surface of said light-guiding plate on said side light source side.

22. A prism sheet comprising a plurality of prisms at one of the major surfaces of a sheet, and being configured so that a degree of area of inclined surfaces per unit area decreases the closer to said one side at a region of a range up to a predetermined distance from one side of said major surface compared with a center region.

23. A liquid crystal display comprising a side light source, a light-guiding plate, a prism sheet, and a liquid crystal panel,

wherein said side light source is arranged at one of the side surfaces among two side surfaces opposite to each other at said light-guiding plate, and

said prism sheet includes a plurality of prism parts at said light-guiding plate side and is configured so that a ratio of area of inclined surfaces per unit area decreases in a region of a range up to a predetermined distance from said side light source.

24. An electronic device comprising a side light source, a light-guiding plate, a prism sheet, and a liquid crystal panel,

wherein said side light source is arranged at one of the side surfaces among two side surfaces facing each other at said light-guiding plate, and

said prism sheet includes a plurality of prism parts at said light-guiding plate side and is configured so that a ratio of area of inclined surfaces per unit area decreases in a region of a range up to a predetermined distance from said side light source.