Illumination device

• US 6,874,922 B2
• Filed: 12/12/2002
• Issued: 04/05/2005
• Est. Priority Date: 12/13/2001
• Status: Expired due to Fees

• Current Assignee: Toyoda Gosei Company Limited (Toyota Motor Corporation)
• Original Assignee: Toyoda Gosei Company Limited (Toyota Motor Corporation)
• Inventors: Matsuura, Yoshihiro, Misawa, Akihiro, Tatewaki, Yasumasa, Iwasa, Tadanobu
• Primary Examiner(s): Sember, Thomas M.
• Application Number:
  US10/317,125
• Publication Number:
  US 20030128549A1
• Time in Patent Office: 845 Days
• Field of Search: 362/497, 362/511, 362/555, 362/559, 362/800, 362/235, 362/249, 362/812, 362/31, 362/558, 402/05, 405/74
• US Class Current: 362/497
• CPC Class Codes: B60Q 1/56 for illuminating registrations or the like , e.g. for licence plates
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0081 Mechanical or electrical aspects of the light guide and light source in the lighting device peculiar to the adaptation to planar light guides, e.g. concerning packaging

Abstract

The illumination device comprises at least one light source, and a light pipe positioned at the front side of a license plate, and a light diffusing means. A light of the light sources is led, the light pipe emitting a leading light from the surface of the license plate face. The light emitted from the observed face is diffused by the light diffusing means. The light diffusing means is provided with, rugged portions of an observed face opposite to a light emitting face, or, a light diffusing layer composed of two or more kinds of light transmitting materials, refractive indexes of which are different each other, on the observing face, and a light led from a light leading face is reflected and diffused on the light diffusing layer.

Claims

1. An illumination device adapted for a license plate, comprising:

at least one light source;

a light pipe positioned at a front side of the license plate and including a light inlet face for introducing light into the light pipe from the light source, a license plate face for emitting light to the license plate, and an observing face provided at a side opposite to the license plate face; and

light diffusing means provided on a side of the observing face with respect to the license plate,

wherein light from said at least one light source is diffused at the light diffusing means and led to the license plate so as to emit through the license plate face, and

wherein said at least one light source comprises an LED.

2. An illumination device as set forth in claim 1, wherein rugged portions are formed on at least one of the license plate face and the observing face.

3. An illumination device as set forth in claim 2, wherein the rugged portions are formed with a plurality of grooves and a density of the grooves in a region becomes higher as the region is located farther from the light inlet face.

4. An illumination device as set forth in claim 1, wherein the light source is positioned in opposition to the end face of the light pipe.

5. An illumination device as set forth in claim 1, wherein the at least one light source comprises a plurality of LEDs, and the plurality of LEDs are linearly arranged under a condition of opposing to a common end face defining the light inlet face the light pipe.

6. An illumination device as set forth in claim 1, wherein the light diffusing means comprises a light diffusing layer formed on the observing face and comprising at least two kinds of light transmitting materials, and

wherein refractive indexes of at least two of said light transmitting materials are different from each other.

7. An illumination device as set forth in claim 6, wherein the light diffusing layer comprises particles that are contained in a basic material of the light transmission materials, the particles comprising material having a refractive index different from that of the basic material.

8. An illumination device asset forth in claim 7, wherein the particles comprise an acrylic resin.

9. An illumination device as set forth in claim 7, wherein the light diffusing layer is formed by printing.

10. An illumination device as set forth in claim 6, wherein the light diffusing layer is formed in dot matrix on the observing face.

11. An illumination device as set forth in claim 6, wherein a rate of an area of the light diffusing layer occupying an area of the observing face is 30 to 90%.

12. An illumination device as set forth in claim 6, wherein light transmittance in a direction of the light emitting face from the light diffusing layer is 70 to 95%.

13. An illumination device as set forth in claim 6, wherein the light diffusing layer comprises silica.

14. A light guide member comprising:

a light pipe operable to be positioned at a front side of an illuminating object and comprising a light inlet face for introducing light into the light pipe, a light emitting face for emitting light to the illuminating object, and an observing face provided at a side opposite to the light emitting face; and

a light diffusing means provided on a side of the observing face with respect to the illuminating object,

wherein light introduced from the light inlet face is diffused at the light diffusing means and led to the illumination object so as to emit through the illumination object face.

15. An illumination device as set forth in claim 14, wherein rugged portions are formed on at least one of the light emitting face and the observing face.

16. An illumination device as set forth in claim 14, wherein the light diffusing means comprises a light diffusing layer formed on the observing face and comprises at least two kinds of light transmitting materials, and

wherein refractive indexes of at least two of said light transmitting materials are different from each other.

17. A planar lighting unit, comprising a light guide member as set forth in claim 14 and at least one light source.

18. A planar lighting unit as set forth in claim 17, wherein the light source comprises a white LED.

19. A license plate apparatus comprising:

a planar lighting unit as set forth in claim 14, and

a license plate disposed so that an indication face of the license plate is opposed to a side of the light emitting face of the planar lighting unit.

20. An illumination device adapted for a license plate, comprising:

at least one light source;

a light pipe disposed at a front side of the license plate and comprising;

a light inlet face for introducing light into the light pipe from the light source,

a light emitting face adjacent to the license plate, for emitting light to the license plate, and

an observing face provided at a side opposite to the light emitting face; and

a light diffusing layer provided on the observing face,

wherein light from the at least one light source is diffused at the light diffusing layer and directed through the light emitting face to the license plate.

21. An illumination device as set forth in claim 20, wherein the light diffusing layer comprises at least two kinds of light transmitting material, and

wherein refractive indexes of at least two of the light transmitting materials are different from each other.

22. An illumination device as set forth in claim 21, wherein the light diffusing layer comprises:

a light transmitting material; and

particles in the light transmitting material,

wherein a refractive index of the light transmitting material is not equal to a refractive index of the particles.

23. An illumination device as set forth in claim 22, wherein the particles comprise an acrylic resin.

24. An illumination device set forth in claim 22, wherein the light diffusing layer comprises a printed light diffusing layer.

25. An illumination device as set forth in claim 21, wherein the light diffusing layer comprises a dot matrix light diffusing layer on the observing face.

26. An illumination device as set forth in claim 21, wherein an area of the light diffusing layer is equal to 30% to 90% of an area of the observing face.

27. An illumination device as set forth in claim 21, wherein light transmittance in a direction of the light emitting face from the light diffusing layer is 70% to 95%.

28. An illumination device as set forth in claim 21, wherein the light diffusing layer comprises silica.

29. An illumination device as set forth in claim 22, wherein a diameter of the particles is smaller than a thickness of the light diffusing layer.

30. An illumination device as set forth in claim 22, wherein an average diameter of the particles is between 3 μ

m and 20 μ

m.

31. An illumination device as set forth in claim 22, wherein an average diameter of the particles is between 6 μ

m and 12 μ

m.

32. An illumination device as set forth in claim 22, wherein a thickness of the light diffusing layer satisfies the expression:

r<

t<

2r

wherein r is an average particle diameter, and t is the thickness of the light diffusing layer.

33. A light guide member comprising:

a light pipe operable to be disposed at a front side of an illuminating object and comprising;

a light inlet face for introducing light into the light pipe,

a light emitting face for emitting light to the illuminating object, and

an observing face provided at a side opposite to the light emitting face;

a light diffusing layer provided on the observing face,

wherein light introduced from the light inlet face is diffused at the light diffusing layer and directed through the light emitting face to the illuminating object.

34. An illumination device as set forth in claim 33, wherein the light diffusing layer is disposed on the observing face and comprises at least to kinds of light transmitting materials, and

wherein refractive indexes of at least two of the light transmitting materials are different from each other.

35. A license plate apparatus comprising:

a planar lighting unit comprising;

a light pipe disposed at a front side of an illuminating object and including a light inlet face that introduces light into the light pipe, a light emitting face that emits light to the illuminating object, and an observing face provided at a side opposite to the light emitting face; and

light diffusing means for diffusing light, provided on a side of the observing face with respect to the illuminating object,

wherein light introduced from the light inlet face is diffused at the light diffusing means and led to the illumination object to emit through the illumination object face; and

a license plate disposed such that an indication face of the license plate is opposed to a side of the light emitting face of the planar lighting unit.