Light source device, display device, and terminal device

• US 20070076434A1
• Filed: 09/19/2006
• Published: 04/05/2007
• Est. Priority Date: 09/30/2005
• Status: Active Grant

• Current Assignee: Vista Peak Ventures LLC (Dominion Harbor Enterprises, LLC)
• Original Assignee: NEC Corporation, NEC LCD Technologies Limited (NEC Corporation)
• Inventors: Uehara, Shin-ichi, Imai, Masao
• Granted Patent: US 7,534,026 B2
• Time in Patent Office: Days
• US Class Current: 362/616
• 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 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0076 Stacked arrangements of multiple light guides of the same or different cross-sectional area
• CPC Class Codes: G02F 1/1323 Arrangements for providing a switchable viewing angle
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side

Abstract

In a display device equipped with a light source device, a second light-guide member is provided to the back surface of a first light-guide member that has an emitted light control sheet provided to the front surface thereof. The emitted light control sheet is composed of a flat plate portion and protrusions. A first light source mounted to a side surface of the first light-guide member, and a second light source mounted to a side surface of a second light-guide member are switched and turned on. The emitted light control sheet has light-condensing effects when the first light source is on, and has diffusing effects when the second light source is turned on. The angle range of illuminating light can thereby be switched.

Claims

1. A light source device comprising:

first and second light sources;

a first light-guide member on which light from said first light source is incident;

a second light-guide member on which light from said second light source is incident; and

an emitted light control sheet on which light emitted from said first and second light-guide members is incident and which controls an emission direction of emitted light;

wherein

said emitted light control sheet is composed of a transparent material and has a flat plate portion and protrusions formed on a surface of the flat plate portion on the side facing said first light-guide member;

apexes of said protrusions are closely contacted to said first light-guide member; and

said second light-guide member is disposed on the opposite side of said first light-guide member in relation to the side on which said emitted light control sheet is mounted.

2. The light source device according to claim 1, wherein said first light-guide member is a parallel flat plate.

3. The light source device according to claim 1, wherein a tilted surface irradiated by light that is incident from said second light source is formed in said second light-guide member.

4. The light source device according to claim 1, wherein

said first light source is disposed on a first side surface of said first light-guide member;

and

a reflecting panel is mounted to a second side surface of said first light-guide member on an opposite side from the first side surface.

5. The light source device according to claim 4, wherein

said first light source is a point light source mounted to a side surface of said first light-guide member;

and

a reflecting panel is mounted outside a region in which the point light source is mounted on the side surface.

6. The light source device according to claim 1, wherein a reflecting panel is mounted on a side of said second light-guide member that is opposite a surface to which said first light-guide member is mounted.

7. The light source device according to claim 1, wherein said first light source and said second light source are mounted to side surfaces on the same sides as said first light-guide member and said second light-guide member, respectively.

8. The light source device according to claim 1, wherein a position of said first light source in relation to said first light-guide member differs from a position of said second light source in relation to said second light-guide member.

9. The light source device according to claim 8, wherein said first light source is mounted to a corner of said first light-guide member.

10. The light source device according to claim 1, wherein an imaginary straight line that connects apexes of said protrusions extends in three different directions that are parallel to a surface of said flat plate portion.

11. The light source device according to claim 10, wherein an imaginary straight line that connects apexes of said protrusions forms an equilateral triangle.

12. The light source device according to claim 10, wherein a diffusion pattern for diffusing transmitted light is formed on a surface opposite from the side on which said protrusions are formed in said flat plate portion of said emitted light control sheet.

13. The light source device according to claim 1, wherein an intensity of said first light source is smaller than an intensity of said second light source.

14. The light source device according to claim 1, wherein

said first light source is composed of one or a plurality of point light sources;

said second light source is composed of a plurality of point light sources; and

a number of point light sources that constitute said first light source is smaller than a number of point light sources that constitute said second light source.

15. The light source device according to claim 1, wherein said first light source is also on when said second light source is on.

16. The light source device according to claim 1, wherein a size of said first light-guide member is greater than a size of said second light-guide member.

17. The light source device according to claim 1, wherein an opaque sheet is mounted between said first light-guide member and said second light-guide member.

18. The light source device according to claim 17, wherein said opaque sheet has adhesive properties.

19. The light source device according to claim 1, wherein said light source device is housed in a holder, and the holder has light-absorbing properties.

20. The light source device according to claim 19, wherein said holder is black.

21. A display device comprising;

the light source device according to claim 1;

and

a transmissive display panel for transmitting light emitted from the light source device, whereby

an image is associated with the light.

22. The display device according to claim 21, wherein said transmissive display panel is a transmissive liquid crystal panel.

23. The display device according to claim 22, wherein said transmissive liquid crystal panel is a horizontal field mode, multi-domain vertical alignment mode, or film-compensated TN mode liquid crystal panel.

24. The display device according to claim 21, wherein said transmissive display panel and the emitted light control sheet of said light source device are closely contacted together.

25. The display device according to claim 23, wherein

said transmissive liquid crystal panel has a polarizing plate on at least a surface facing said light source device;

and

the polarizing plate is a low-reflectance polarizing plate whose surface is treated to reduce reflectance.

26. The display device according to claim 23, wherein

said transmissive liquid crystal panel has a polarizing plate on at least a surface facing said light source device;

and

the polarizing plate is a circular polarizing plate.

27. The display device according to claim 26, wherein said transmissive liquid crystal panel is an active matrix-type transmissive liquid crystal panel.

28. The display device according to claim 27, wherein said transmissive liquid crystal panel is a transflective liquid crystal panel having a reflective region in a pixel electrode.

29. A terminal device comprising the display device according to claim 21.

30. The terminal device according to claim 29, wherein the device is a mobile phone, a personal information terminal, a gaming device, a digital camera, a video camera, a video player, a notebook-type personal computer, a cash dispenser, or a vending machine.

31. The terminal device according to claim 30, comprising a mobile telephone wherein said first and second light sources are disposed on the top side and/or bottom side of a display screen.

32. The terminal device according to claim 29, comprising an intensity adjustment unit for adjusting intensities of said first and second light sources independently from each other.

33. The terminal device according to claim 29, comprising:

a power storage unit for supplying electrical power to at least said first and second light sources;

a residual power detection unit for detecting electrical power remaining in the power storage unit; and

a control unit for controlling a light intensity of said first and second light sources based on results of detection by the residual power detection unit;

wherein

said control unit turns on only said first light source when the remaining electrical power detected by said residual power detection unit is less than a prescribed value.

34. The terminal device according to claim 29, comprising:

an input detection unit for detecting an input operation;

a timer for measuring a specific time; and

a control unit for controlling a light intensity of said first and second light sources;

wherein

said control unit turns on only said first light source when said input detection unit has not detected an input operation during said specific time measured by said timer.