Surface light source device and display apparatus using the same

• US 20060139960A1
• Filed: 12/02/2005
• Published: 06/29/2006
• Est. Priority Date: 12/27/2004
• Status: Abandoned Application

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Sakai, Seiji, Yoneda, Toshiyuki
• Application Number:
  US11/291,979
• Publication Number:
  US 20060139960A1
• Time in Patent Office: Days
• US Class Current: 362/623
• CPC Class Codes: G02B 6/0043 provided on the surface of the light guide
• CPC Class Codes: G02B 6/0061 to provide homogeneous light output intensity
• CPC Class Codes: G02B 6/0076 Stacked arrangements of multiple light guides of the same or different cross-sectional area
• CPC Class Codes: G02B 6/0078 Side-by-side arrangements, e.g. for large area displays
• CPC Class Codes: G02F 1/133609 including means for improving the color mixing, e.g. white

Abstract

A surface light source device includes a housing having an opening portion provided in a top surface thereof, a reflection sheet disposed on a bottom surface of the housing, a light guide plate disposed on the reflection sheet on a side of the opening, and a light source disposed on at least one of side surfaces of the housing. The reflection sheet has a first reflection region on a side opposite to the light source, and a reflectance of the first reflection region at shorter wavelengths in a wavelength region of visible light outputted from the light source is higher than a reflectance at longer wavelengths in the wavelength region of the visible light.

Claims

1. A surface light source device comprising:

a housing having an opening portion provided in a top surface thereof;

a reflection sheet disposed on a bottom surface of the housing;

a light guide plate disposed on the reflection sheet on a side of the opening; and

a light source disposed on at least one of side surfaces of the housing,

wherein the reflection sheet has a first reflection region on a side opposite to the light source, and

a reflectance of the first reflection region at shorter wavelengths in a wavelength region of visible light outputted from the light source is higher than a reflectance at longer wavelengths in the wavelength region of the visible light.

9. The surface light source device according to claim 1,

wherein a difference between the reflectance at the longer wavelengths and the reflectance at the shorter wavelengths of the reflection sheet increases as a distance of the reflection sheet from the light source increases.

11. The surface light source device according to claim 1,

wherein the reflection sheet is colored to obtain a desired value of reflectance.

12. The surface light source device according to claim 11,

wherein the reflection sheet is colored with a complementary color that cancels change in hue of light, which is outputted from the light source, at the opening portion.

13. The surface light source device according to claim 11,

wherein a surface of the reflection sheet on a side of the bottom surface of the housing is colored.

17. The surface light source device according to claim 1,

wherein a selective reflecting sheet disposed on the reflection sheet on a side of the opening.

18. The surface light source device according to claim 1,

wherein the light source is a linear light source.

19. The surface light source device according to claim 1,

wherein the light source is a light emitting diode that emits red, green, or blue monochromatic light.

2. A surface light source device comprising:

a housing having an opening portion provided in a top surface thereof;

a reflection sheet disposed on a bottom surface of the housing;

a light guide plate disposed on the reflection sheet on a side of the opening; and

a light source disposed on at least one of side surfaces of the housing,

wherein the reflection sheet has a second reflection region on a side of the light source, and

a reflectance of the second reflection region at shorter wavelengths in a wavelength region of visible light outputted from the light source is lower than a reflectance at longer wavelengths in the wavelength region of the visible light.

10. The surface light source device according to claim 2,

wherein a difference between the reflectance at the longer wavelengths and the reflectance at the shorter wavelengths of the reflection sheet decreases as a distance of the reflection sheet from the light source increases.

3. A surface light source device comprising:

a housing having an opening portion provided in a top surface thereof;

a light guide plate disposed in the housing corresponding to the opening portion;

a reflection sheet disposed on a bottom surface of the housing;

a color mixing light guide plate disposed between the reflection sheet and the bottom surface of the housing; and

a light source disposed on an incidence face of the color mixing light guide plate,

wherein the reflection sheet has a reflection region, and

a reflectance of the reflection region of at least a part of wavelength in a wavelength region corresponding to a wavelength region of visible light outputted from the light source differs from a reflectance of other wavelength in the wavelength region.

4. A surface light source device comprising:

a housing having an opening portion;

a diffusion plate disposed along the opening portion;

a reflection sheet disposed in the housing to form a hollow region between the diffusion plate and the reflection sheet; and

a light source disposed in the housing,

wherein the reflection sheet has a reflection region, and

a reflectance of the reflection region of at least a part of wavelength in a wavelength region corresponding to a wavelength region of visible light outputted from the light source differs from a reflectance of other wavelength in the wavelength region.

5. A surface light source device comprising:

a housing having an opening portion provided-in a top surface thereof;

at least one reflection sheet disposed on a bottom surface of the housing; and

a light source disposed in the housing,

wherein the surface light source device has a plurality of reflection sheets;

at least one of the reflection sheets is a first reflection sheet having a reflection region adapted to vary a reflectance in a surface thereof, and

the surface of the first reflection sheet, in which the reflection region is provided, faces other reflection sheets.

6. The surface light source device according to claim 5,

wherein the first reflection sheet has a reflection region, and

a reflectance of the reflection region of at least a part of wavelength of a wavelength region respectively corresponding to a color of visible light outputted from the light source differs from a reflectance at a wavelength of the other wavelength region.

7. The surface light source device according to claim 6,

wherein the first reflection sheet has a first reflection region on a side opposite to the light source, and

a reflectance of the first reflection region at shorter wavelengths in a wavelength region of visible light outputted from the light source is higher than a reflectance at longer wavelengths in the wavelength region of the visible light.

8. The surface light source device according to claim 5,

wherein among the plurality of reflection sheets, a reflection sheet disposed on a side of the opening of the housing has reflectance lower than a reflectance of a reflection sheet disposed on a side of the bottom surface of the housing.

14. A surface light source device comprising:

a housing having an opening portion provided in a top surface thereof;

a reflection sheet disposed on a bottom surface of the housing;

a color conversion sheet disposed on the reflection sheet on a side of the opening; and

a light source disposed in the housing,

wherein the color conversion sheet has a transmission region adapted to vary a transmissivity in a surface thereof.

15. The surface light source device according to claim 14,

wherein the color conversion sheet has a transmission region, and

a transmissivity of the transmission region at wavelength of at least one of wavelength regions respectively corresponding to colors of visible light outputted from the light source differs from a transmissivity at wavelength of other wavelength region.

16. The surface light source device according to claim 15, further comprising:

a light guide plate disposed on a part of the reflection sheet on a side of the opening,

wherein the light source is disposed on at least one of side surfaces of the housing,

the color conversion sheet has a first transmission region on a side opposite to the light source, and

a transmissivity of the first transmission region at shorter wavelengths of a wavelength region of visible light outputted from the light source is higher than a transmissivity at longer wavelengths of the wavelength region of the visible light.

20. A display apparatus comprising:

a surface light source device; and

a display portion disposed on an upper part of the surface light source device,

wherein the surface light source device includes;

a housing having an opening portion provided in a top surface thereof;

a reflection sheet disposed on a bottom surface of the housing;

a light guide plate disposed on the reflection sheet on a side of the opening; and

a light source disposed on at least one of side surfaces of the housing,

the reflection sheet has a first reflection region on a side opposite to the light source, and

a reflectance of the first reflection region at shorter wavelengths in a wavelength region of visible light outputted from the light source is higher than a reflectance at longer wavelengths in the wavelength region of the visible light.