Illumination device and display device using the same

• US 20060062016A1
• Filed: 08/23/2005
• Published: 03/23/2006
• Est. Priority Date: 08/25/2004
• Status: Active Grant

• Current Assignee: Dawncrest IP LLC (IP Edge LLC)
• Original Assignee: Seiko Instruments Incorporated (Seiko Group)
• Inventors: Kurihara, Makoto, Dejima, Norihiro, Sado, Takayasu, Honma, Katsunori
• Granted Patent: US 7,484,873 B2
• Time in Patent Office: Days
• US Class Current: 362/600
• 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 6/0036 2-D arrangement of prisms, protrusions, indentations or roughened surfaces
• CPC Class Codes: G02B 6/0061 to provide homogeneous light output intensity
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/4206 Optical features G02B6/4207, G02B6/421 take precedence
• CPC Class Codes: G02B 6/4298 coupling with non-coherent light sources and/or radiation detectors, e.g. lamps, incandescent bulbs, scintillation chambers
• CPC Class Codes: H04M 1/22 Illumination; Arrangements for improving the visibility of characters on dials

Abstract

A thin illumination device with a high efficiency of utilizing light and a display element using the same are realized. In an illumination device according to the present invention, a light incident body (3) having a light incident surface (4) is optically coupled to a light guide plate (2), light coming from a light source (1) being incident on the light incident surface (4). At least part of the light incident body between the light incident surface (4) and the light guide plate (2) is oval in cross section.

Claims

1. An illumination device for emitting light coming from a light source from a light emitting surface of a light guide plate, comprising:

a light incident body optically coupled to the light guide plate at one end portion thereof; and

a light incident surface formed at another end portion of the light incident body, light coming from the light source being incident on the light incident surface,

wherein the light incident body has an oval portion in outer shape.

2. An illumination device according to claim 1, wherein:

the light incident surface is formed to be located between an anterior focal point on a side of the light source in the oval portion and a center of the oval portion; and

a coupling portion between the light incident body and the light guide plate is formed to be located near a posterior focal point.

3. An illumination device according to claim 2, wherein a light emitting surface of the light source is located between the anterior focal point and the light incident surface.

4. An illumination device according to claim 1, wherein a surface of the light guide plate on a side of the light emitting surface and a surface of the light guide plate on an opposing side are coupled to the oval portion by a pair of wedge-like planes having a tapered thickness from the light incident body towards the light guide plate.

5. An illumination device according to claim 4, wherein end portions of the pair of wedge-like planes on the side of the light source are formed from locations near points of intersection between lines that pass through the posterior focal point and form a critical angle with the light guide plate and a surface of the oval portion.

6. An illumination device according to claim 4, wherein a pair of light reflecting layers are provided to oppose the pair of wedge-like planes and a part of the light guide plate.

7. An illumination device according to claim 1, wherein a top of the light incident body is flush with the light emitting surface of the light guide plate.

8. An illumination device according to claim 7, wherein an underside of the light guide plate on a side of the light emitting surface and an underside of the light guide plate on an opposing side are coupled to the oval portion by a wedge-like plane having a tapered thickness from the light incident body towards the light guide plate.

9. An illumination device according to claim 1, wherein in the coupling portion, a longitudinal direction of the oval shape of the light incident body and the light emitting surface of the light guide plate are not in parallel to each other and form an angle.

10. An illumination device according to claim 1, wherein:

a light reflector is provided between the light incident body and the light source; and

an opening is provided for the light reflector at a position opposing the light incident surface.

11. An illumination device according to claim 10, wherein a size of the opening provided for the light reflector is equal to or larger than that of the light emitting surface of the light source.

12. An illumination device according to claim 1, wherein a rectangular portion is formed on the side of the light source of the light incident body to continue to the oval portion;

and

the light incident surface is provided at the rectangular portion.

13. An illumination device according to claim 1, wherein a plurality of concave micro-structures for light-scattering having a longitudinal direction are formed on the surface of the light guide plate opposite to the light emitting surface into the light guide plate;

and

the plurality of micro-structures for light-scattering are arranged to have the longitudinal direction arranged substantially in parallel to a line passing through the micro-structures for light-scattering and the light source.

14. An illumination device for emitting light coming from a light source from a light emitting surface of a light guide plate, comprising:

an oval surface formed between the light source and the light guide plate to guide the light emitted from the light source to the light incident surface of the light guide plate; and

a light reflector provided to oppose the surface.

15. An illumination device according to claim 14, further comprising a casing for receiving the light source and the light guide plate,

wherein the oval surface is formed in the casing.

16. An illumination device according to claim 14, wherein a resin fills a space between the oval surface and the light reflector.

17. An illumination device according to claim 16, wherein a phosphor is dispersed in the resin.

18. An illumination device according to claim 16, wherein beads having a different refractive index from that of the resin are dispersed in the resin.

19. A display device, comprising:

a non-self light emitting type display element;

an illumination device provided for illuminating the display element;

a light source;

a light guide plate for emitting light coming from the light source to the display element; and

a light incident body optically coupled to the light guide plate at one end portion thereof, wherein a light incident surface is formed at another end portion of the light incident body, light coming from the light source being incident on the light incident surface; and

the light incident body has an oval portion in outer shape.