Front-illuminating device and a reflection-type liquid crystal display using such a device

• US 6,879,354 B1
• Filed: 09/13/1999
• Issued: 04/12/2005
• Est. Priority Date: 03/28/1997
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Masuda, Takeshi, Sumida, Yukihiro, Sawayama, Yutaka, Ebi, Tsuyoshi
• Primary Examiner(s): Parker, Kenneth
• Application Number:
  US09/394,327
• Time in Patent Office: 2,038 Days
• Field of Search: 362/31, 362/26, 349/62, 349/63
• US Class Current: 349/63
• 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 6/0025 Diffusing sheet or layer; Prismatic sheet or layer
• 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 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0056 for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements
• CPC Class Codes: G02B 6/0065 Manufacturing aspects; Material aspects
• CPC Class Codes: G02B 6/0076 Stacked arrangements of multiple light guides of the same or different cross-sectional area
• CPC Class Codes: G02F 1/133504 Diffusing, scattering, diffracting elements associated to illuminating devices G02F1/133606
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• CPC Class Codes: G02F 1/133616 Front illuminating devices
• CPC Class Codes: G02F 1/133626 providing two modes of illumination, e.g. day-night

Abstract

Featured are a front-illuminating device including a light source and first and second light-directing bodies. The first light-directing body is disposed in front of an object to be illuminated and has a first light-releasing surface from which light is released to the object to be illuminated and a second light-releasing surface, placed face to face with the first light-releasing surface, for releasing light reflected from the object to be illuminated. The second light-releasing surface also is formed into a step shape and includes slanting portions that reflect light mainly from the light source toward the first light-releasing surface. The second light-directing body is disposed between the first light-directing body and the object to be illuminated and is configured and arranged so a distance from each of the slanting portions to the surface of the second light-directing body second surface is essentially uniform.

Claims

1. A front-illuminating device comprising:

a light source; and

a first light-directing body that is placed disposed in front;

of an object to be illuminated, the firs light-directing body having an incident surface on which light from the light source is made incident, a first light-releasing surface from which light is released to the object to be illuminated and a second light-releasing surface, placed face to face with the first light-releasing surface, for releasing light reflected from the object to be illuminated,

a second light-directing body having a first surface and a second surface that faces the first surface, the second light directing body being disposed between the first light-directing body and the object to be illuminated such that the first surface of the second light-directing body faces the first light-releasing surface of the first light-directing body and the second surface of the second light-directing body releases light that has been made incident thereon from the first light-directing body through the first surface to the object to be illuminated;

wherein the second light-releasing surface of the first light directing body is formed into a step shape in which slanting portions for reflecting light mainly from the light source toward the first light-releasing surface and flat portions for transmitting light reflected mainly from the object to be illuminated are alternately placed; and

the second light directing body is configured and arranged so a distance from each of the slanting portions on the second light-releasing surface of the fist light-directing body to the surface of the second surface of the second light-directing body is essentially uniform.

2. The front-illuminating device as defined in claim 1, wherein the second light-directing body is further configured and arranged so as to average the luminance distribution of light released from the first light-releasing surface of the first light-directing body.

3. The front-illuminating device as defined in claim 1, wherein the first light-directing body and the second light-directing body are formed into an integral part.

4. The front-illuminating device as defined in claim 1, wherein an optical means, which suppresses light from the second light-releasing surface of the first light-directing body from being reflected by the second surface, is placed on the second surface of the second light-directing body as a third light-directing body.

5. The front-illuminating device as defined in claim 4, wherein the optical means is an anti-reflection film.

6. The front-illuminating device as defined in claim 4, wherein the optical means is bonded to a second light-directing body by a bonding agent having a refractive index that is virtually equal to a refractive index of the second light-directing body.

7. The front-illuminating device as defined in claim 2, wherein the second light-directing body is a light-diffusing body that diffuses light from the first light-releasing surface of the first light-directing body.

8. The front-illuminating device as defined in claim 7, wherein:

the light-diffusing body is an anisotropic diffusing body for diffusing only light that is incident thereon from within a predetermined angle range, and at least one portion of an angle range in which the light released from the first light-directing body is made incident on the second light-directing body is included within said predetermined angle range.

9. The front-illuminating device as defined in claim 7, wherein the light-diffusing body is a front-diffusing body.

10. The front-illuminating device as defined in claim 2, further comprising optical means which suppresses light from the second light-releasing surface of the first light-directing body from being reflected by the first light-releasing surface of the first light-directing body the optical means being disposed between the first light-releasing surface of the fist light-directing body and the first surface of the second light-directing body.

11. The front-illuminating device as defined in claim 10, wherein the optical means is an anti-reflection film.

12. The front-illuminating device as defined in claim 10, wherein the optical means is bonded to the second light-directing body by a bonding agent having a refractive index that is virtually equal to a refractive index of the second light-directing body.

13. The front-illuminating device as defined in claim 1, further comprising a filler that is introduced into a gap between the first light-directing body and the second light-directing body the filter being constituted so as to alleviate the difference of refractive indexes on an optical interface located between the first and second light-directing bodies.

14. The front-illuminating device as defined in claim 13, further comprising:

a light-controlling means for restricting spread of light from the light source to a range in which light components directly made incident on the first light-releasing surface of the first light-directing body from the incident surface are virtually eliminated, the light-controlling means being placed between the light source and the incident surface.

15. The front-illuminating device as defined in claim 1, wherein the incident surface is located on a side face of the light-directing body.

16. The front-illuminating device as defined in claim 15, wherein a sum of projections of the slanting portions onto a flat surface perpendicular to the first light-releasing surface is virtually equal to a projection of the incident surface onto the flat surface.

17. The front-illuminating device as defined in claim 15, wherein the incident surface and the first light-releasing surface are set so as to make an obtuse angle.

18. The front-illuminating device as defined in claim 1, further comprising:

a light-converging means for allowing light from the light source to be made incident only on the incident surface.

19. The front-illuminating device as defined in claim 1, wherein a sum of projections of the slanting portions onto the first light-releasing surface is smaller in area than a sum of projections of the flat portions onto the first light-releasing surface.

20. The front-illuminating device as defined in claim 1, wherein the flat portions are set in parallel with the first light-releasing surface, or set to have an angle of inclination of not more than 10°

with respect to the first light-releasing surface.

21. The front-illuminating device as defined in claim 1, wherein supposing that the refractive index of the light-directing body is n₂ and that the refractive index of an external medium contacting the slanting portions is n₁, the incident angle θ

of light that is to be made incident on the slanting portions from the light source satisfies the following inequality;

θ

≧

arc sin(n₁/n₂).

22. The front-illuminating device as defined in claim 1, wherein a reflective member for reflecting light is placed on the surface of the slanting portions.

23. The front-illuminating device as defined in claim 22, wherein supposing that the refractive index of the light-directing body is n₂ and that the refractive index of an external medium contacting the slanting portions is n₁, the incident angle θ

of light that is to be made incident on the slanting portions from the light source satisfies the following inequality;

θ

<

arc sin(n₁/n₂).

24. The front-illuminating device as defined in claim 22, wherein a light-shielding member is installed on the surface of the reflective member.

25. The front-illuminating device as defined in claim 1, further comprising:

a compensating means for aligning light-releasing directions of a light ray released from each flat portion and a light ray released from each slanting portion on the second light-releasing surface.

26. The front-illuminating device as defined in claim 25, wherein:

the compensating means has a first surface facing the second, light-releasing surface of the light-directing body and a second surface facing the first surface, and the first surface of the compensating means is formed into a step shape in which slanting faces virtually parallel to the slanting portions of the second light-releasing surface of the light-directing body and flat faces virtually parallel to the flat portions of the second light-releasing surface are alternately placed in a manner so as to conform to the second light-releasing surface, and the second surface of the compensating means is placed virtually in parallel with the first light-releasing surface of the light-directing body.

27. The front-illuminating device as defined in claim 25, wherein:

the compensating means comprises;

areas on which light rays mainly released from the slanting portions of the second light-releasing surface are made incident, and

areas on which light rays mainly released from the flat portions of the second light-releasing surface are made incident, the respective areas being set to have refractive indexes different from each other.

28. The front-illuminating device as defined in claim 25, wherein the compensating means comprises:

diffraction elements that are placed on the areas on which light rays mainly released from the slanting portions of the second light-releasing surface are made incident.

29. The front-illuminating device as defined in claim 25, wherein the compensating means comprises:

a light-shielding member that is placed on the areas on which light rays mainly released from the slanting portions of the second light-releasing surface are made incident.

30. The front-illuminating device as defined in claim 1, further comprising:

a light-controlling means for restricting spread of light from the light source, placed between the light source and the incident surface.

31. The front-illuminating device as defined in claim 30, wherein said light-controlling means limits spread of light from the light source to a range in which the incident angles of the light rays directly made incident on the slanting portions of the second light-releasing surface from the incident surface arc made greater than the critical angle.

38. A reflection-type liquid crystal display comprising:

a reflection-type liquid crystal element having a reflective plate,

wherein the front-illuminating device as disclosed in claim 1 is placed in front of the reflection-type liquid crystal element.

43. The reflection-type liquid crystal display as defined in claim 38, wherein the reflective plate is a reflective electrode that also functions as a liquid crystal driving electrode for driving a liquid crystal layer of the reflection-type liquid crystal element, the reflective plate being adjacent to the liquid crystal layer.

45. The reflection-type liquid crystal display comprising:

a front-illuminating device as disclosed in claim 25, that is placed in front of a reflection-type liquid crystal element having a reflective plate,

wherein;

the compensating means has flexibility responding to a predetermined pressure, and a pair of position-detecting means, which detect a position to which a pressure is given by contacting each other, are respectively installed on the compensating means and the second light-releasing surface.

48. The front-illuminating device as defined in claim 43, wherein the transmitting section has a width smaller than that of the reflection section in the periodic structure.

49. The front-illuminating device as defined in claim 43, wherein the periodic structure including the transmitting section and the reflection section has a width in a range of not less than 0.05 mm to not more than 1.0 mm.

50. The front-illuminating device as defined in claim 43, wherein, supposing that the transmitting section has a width of P1 and that the reflection section has a width of P2, P2/P1, which is a ratio of the width of the reflection section to the width of the transmitting section, is set in a range of not less than 0.01 to not more than 0.02.

51. The front-illuminating device as defined in claim 43, wherein, supposing that the transmitting section has a width of P1 and that the reflection section has a width of P2, P2/P1, which is a ratio of the width of the reflection section to the width of the transmitting section, is made greater as it departs from the incident surface.

52. The front-illuminating device as defined in claim 45, wherein a light-shielding means, which prevents light transmitted through the light-directing body from being released from the second light-releasing surface, is placed on a portion of the light-directing body that corresponds to the reflection section on the second light-releasing surface.

53. The front-illuminating device as defined in claim 48, wherein the light-shielding means has a surface that is subject to a low reflection treatment for suppressing reflection of light.

54. A reflection-type liquid crystal display comprising:

a reflection-type liquid crystal element having a reflective plate,

wherein the front-illuminating device as defined in claim 43, is installed in front of the reflection-type liquid crystal element.

56. The front illuminating device if claim 1, wherein the sum of a pitch of the flat portions and a pitch of the slanting portions that are formed on the light-directing body is set to become smaller as the distance from the incident surface increases.

57. The front-illuminating device as defined in claim 1, wherein the width of the slanting portions on the second light-releasing surface is made smaller than the width of the flat portions thereof.

58. The front-illuminating device as defined in claim 1, wherein the addition of the width of the flat portions and the width of the slanting portions in the light-directing body is set in the range from not less than 0.05 mm to not more than 1.0 mm.

59. The front-illuminating device as defined in claim 1, wherein, supposing that the width of the flat portions is w₁ and the width of the slanting portions is w₂, the ratio w₂/w₁ of the width of the slanting portions to the width of the flat portions is set in a range from not less than 0.01 to not more than 0.2.

60. The front-illuminating device as defined in claim 1, wherein, supposing that the width of the flat portions is w₁ and the width of the slanting portions is w₂, the ratio w₂/w₁ of the width of the slanting portions to the width of the flat portions increases as it departs from the light incident surface.

61. The front illuminating device as defined in claim 1, wherein each of the flat portions of the second-light releasing surface are formed so as to be at angle (θ

) with respect to the first light-releasing surface, the angle satisfying the relation 0>

θ

≧

±

10 deg.

62. The front illuminating device as defined in claim 1, wherein the second light-releasing surface of the first light directing body is formed into a step shape that lowers as a distance from the light source increases.

32. A front-illuminating device comprising:

a light source; and

a first light-directing body that is placed in front of an object to be illuminated, the first light-directing body having a flat bottom surface, a surface facing the bottom surface and an incident surface on which light from the light source is made incident,

wherein the surface is formed into a step shape in which flat portions that are virtually parallel to the bottom surface and slanting portions that are inclined in the same direction to the flat sections are alternately placed;

a second light-directing body having a first surface and a second surface that faces the first surface, the second light directing body being disposed between the first light-directing body and the object to be illuminated such that the first surface of the second light-directing body faces the surface of the first light-directing body and the second surface of the second light-directing body releases light that has been made incident thereon from the first light-directing body through the first surface of the second light-directing body to the object to be illuminated; and

wherein the second light directing body is configured and so a distance from each of the slanting portions of the fist light-directing body to the surface of the second surface of the second light-directing body is essentially uniform.

33. The front illuminating device if claim 32, wherein the sum of a pitch of the flat portions and a pitch of the slanting portions that are formed on the light-directing body is set to become smaller as the distance from the incident surface increases.

34. The front-illuminating device as defined in claim 32, wherein the width of the slanting portions on the second light-releasing surface is made smaller than the width of the flat portions thereof.

35. The front-illuminating device as defined in claim 32, wherein the addition of the width of the flat portions and the width of the slanting portions in the light-directing body is set in the range from not less than 0.05 mm to not more than 1.0 mm.

36. The front-illuminating device as defined in claim 32, wherein, supposing that the width of the flat portions is w₁ and the width of the slanting portions is w₂, the ratio w₂/w₁ of the width of the slanting portions to the width of the flat portions is set in a range from not less than 0.01 to not more than 0.2.

37. The front-illuminating device as defined in claim 32, wherein, supposing that the width of the flat portions is w₁ and the width of the slanting portions is w₂, the ratio w₂/w₁ of the width of the slanting portions to the width of the flat portions increases as it departs from the light incident surface.

39. The reflection-type liquid crystal display as defined in claim 34, wherein the reflection-type liquid crystal element is provided with scanning lines, the scanning lines having a pitch that is virtually equal to the pitch of the flat portions on the second light-releasing surface of the front-illuminating device, the flat portions being placed above the scanning lines.

40. The reflection-type liquid crystal display as defined in claim 34, wherein a sum of pitches of the flat portions and the slanting portions on the second light-releasing surface of the front-illuminating device is smaller than a pitch of the scanning lines.

41. The reflection-type liquid crystal display as defined in claim 34, wherein a sum of pitches of the flat portions and the slanting portions on the second light-releasing surface of the front-illuminating device is greater than a pitch of the scanning lines.

42. The reflection-type liquid crystal display as defined in claim 34, wherein the reflection-type liquid crystal element is provided with a reflective plate having a surface on which protrusions and recesses are formed.

44. The reflection-type liquid crystal display as defined in claim 34, wherein the front-illuminating device is attached to the reflection-type liquid crystal element so as to be freely opened and closed.

46. The reflection-type liquid crystal display as defined in claim 41, wherein:

the reflection-type liquid crystal element is provided with scanning lines, and the position-detecting means has transparent electrodes formed on the flat portions of the second light-releasing surface, pitches of the scanning lines and the transparent electrodes being virtually equal to each other, the transparent electrodes being placed above the scanning lines.

55. A reflection-type liquid crystal display comprising:

a reflection-type liquid crystal element having a reflection place,

wherein the front-illuminating device as defined in claim 44 installed in front of the reflection-type liquid crystal element.

47. A front-illuminating device comprising:

a light source;

a light-directing body that is placed in front of an liquid crystal element that is an object to be illuminated, the light-directing body having an incident surface on which light from the light source is made incident, a first light-releasing surface from which light is released to the liquid crystal element to be illuminated and a second light-releasing surface, placed face to face with the first light-releasing surface, for releasing light reflected from the liquid crystal element to be illuminated;

a periodic structure that is formed on the second light-releasing surface and that includes a transmitting section for transmitting light from the light source and a reflection section for reflecting the light from the light source toward the first light-releasing surface that are alternately placed,

wherein the periodic structure is formed on the second light-releasing surface in such a manner that the periodic structure has an angle in a range of not less than 10°

to not more than 75°

with respect to a repeating direction of a pixel arrangement formed on the liquid crystal element periodically, when placed in front of the liquid crystal element.