초록 ▼

A front-illuminating device of the present invention, which is placed over the entire surface of an object to be illuminated such as a reflection-type liquid crystal display device when it is used, is provided with a light source and a light-directing body. The light-directing body has an incident s

A front-illuminating device of the present invention, which is placed over the entire surface of an object to be illuminated such as a reflection-type liquid crystal display device when it is used, is provided with a light source and a light-directing body. The light-directing body has an incident surface on which light from the light source (light-source light) is made incident, a first light-releasing surface for releasing the light toward the object to be illuminated, and a second light-releasing surface which faces the first light-releasing surface and releases reflected light from the object to be illuminated. The second light-releasing surface is formed into a step shape in which slanting portions and flat portions are alternately placed. The light source light, released from the first light-releasing surface to the object to be illuminated, is reflected by the object to be illuminated and the reflected light is allowed to reach the observer from the first light-releasing surface through the flat portions. In this case, among the light-source light rays, the light components progressing in parallel with the flat portions are reflected by the slanting portions and directed to the object to be illuminated. Consequently, the present invention makes it possible to provide a brighter front-illuminating device in which the efficiency of use of the light-source light is improved.

대표청구항 ▼

What is claimed is: 1. A front-illuminating device comprising: a light source; and a light-directing body that is placed in front of 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 surfac

What is claimed is: 1. A front-illuminating device comprising: a light source; and a light-directing body that is placed in front of 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 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, wherein the object to be illuminated is a reflection-type liquid crystal element, wherein the second light-releasing surface is formed into a stepped shape having 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 an optical means, which suppresses light from the slanting portions on the second light-releasing surface of the light-directing body from being reflected by the first light-releasing surface, is placed on the first light-releasing surface, wherein the second light-releasing surface is formed so as to include N steps (N>1), each step including one flat portion and one slanting portion and having a width (Wi) and wherein the width of each step is such as to satisfy the following relationship: W1<W2<W3 . . . <Wn. 2. The front-illuminating device as defined in claim 1, wherein said light-directing body includes a first light-directing body portion, and a second light-directing body portion optically coupled to the first light-directing body portion and being configured so as to average the luminance distribution of light released from the first light-releasing surface. 3. The front illuminating device as defined in claim 2, wherein refractive indexes of the first light-directing body portion and the second light-directing body portion are virtually equal to each other. 4. The front-illuminating device as defined in claim 2, wherein the first light-directing body portion and the second light-directing body portion are formed into an integral part. 5. The front-illuminating device as defined in claim 1, wherein the optical means is an anti-reflection film. 6. The front-illuminating device as defined in claim 1, wherein the incident surface is located on a side face of the light-directing body. 7. The front-illuminating device as defined in claim 6, 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. 8. 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. 9. 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. 10. 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≧arcsin(n1/n2). 11. A front-illuminating device comprising: a light source; a light-directing body that is placed in front of 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 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; wherein the object to be illuminated is a reflection-type liquid crystal element, wherein the second light-releasing surface is formed into a stepped shape having 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; an optical means, which suppresses light from the slanting portions on the second light-releasing surface of the light-directing body from being reflected by the first light-releasing surface, is placed on the first light-releasing surface; and wherein a reflective member for reflecting light is placed on the surface of the slanting portions, wherein the second light-releasing surface is formed so as to include N steps (N>1), each step including one flat portion and one slanting portion and having a width (Wi) and wherein the width of each step is such as to satisfy the following relationship: W1<W2<W3 . . . <Wn. 12. The front-illuminating device as defined in claim 11, 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<arcsin(n1/n2). 13. A reflection-type liquid crystal display comprising: a reflection-type liquid crystal element having a reflective plate, and wherein the front-illuminating device as disclosed in claim 1 is placed in front of the reflection type liquid crystal element. 14. The reflection-type liquid crystal display as defined in claim 13, wherein the reflection-type liquid crystal element is provided with a reflective plate having a surface on which protrusions and recesses are formed. 15. The reflection-type liquid crystal display as defined in claim 14, 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. 16. 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; wherein the reflection-type liquid crystal element is provided with a reflective plate having a surface on which protrusions and recesses are formed; 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; and wherein the front illuminating device is attached to the reflection-type liquid crystal element so as to be freely opened and closed. 17. The front-illuminating device as defined in claim 1, wherein the second light-releasing surface is formed so as to include a plurality of steps, each step including one flat portion and one slanting portion and a having a width (Wi) and wherein the width of each step varies from the incident surface. 18. The front-illuminating device as defined in claim 17, wherein a width of one flat portion is Wf and the width of the slanting portion is Ws and wherein the ratio of the width of the flat and slanting portion is such as to satisfy the following relationship: 0.01≦Ws/Wf≦0.20. 19. The front-illuminating device as defined in claim 17, wherein the width of each step satisfies the following relationship: 0.05 mm≦Wi≦1.0 mm. 20. The front-illuminating device as defined in claim 1, wherein the second light-releasing surface is formed so as to include a plurality of steps, each step including one flat portion having a width Wf and one slanting portion having a width Ws and wherein the ratio of the width of the flat and slanting portion Ws/Wf increases for each step from the incident surface. 21. The front-illuminating device as defined in claim 1, wherein: the second light-releasing surface is formed so as to include a plurality of blocks of steps; each block includes at least one step and each of the at least one step includes one flat portion and a slanting portion; and each block is characterized as having an interval (Ibi) in a direction generally orthogonal to the light incident surface, the intervals for the plurality of blocks is decreased block by block in the direction from the incident surface. 22. The reflection-type liquid crystal display as defined in claim 13, wherein the second light-releasing surface of the front illuminating device is formed so as to include a plurality of steps, each step including one flat portion and one slanting portion and a having a width (Wi) and wherein the width of each step varies from the incident surface. 23. The reflection-type liquid crystal display device as defined in claim 13, wherein the second light-releasing surface of the front-illuminating device is formed so as to include a plurality of steps, each step including one flat portion having a width Wf and one slanting portion having a width Ws and wherein the ratio of the width of the flat and slanting portion Ws/Wf increases for each step from the incident surface. 24. The reflection-type liquid crystal display device as defined in claim 13, wherein: the second light-releasing surface of the front-illuminating device is formed so as to include a plurality of blocks of steps; each block includes at least one step and each of the at least one step includes one flat portion and a slanting portion; and each block is characterized as having an interval (Ibi) in a direction generally orthogonal to the light incident surface, the intervals for the plurality of blocks is decreased block by block in the direction from the incident surface. 25. The front-illuminating device as defined in claim 1, wherein the light-directing body is placed in front of the object to be illuminated, the object to be illuminated being for observation from an observer through the light directing body. 26. The front-illuminating device as defined in claim 25, wherein the object to be illuminated is for observation from an observer through the second light-releasing surface of the light directing body. 27. The front-illuminating device as defined in claim 26, wherein the object to be illuminated is for observation from an observer through the flat portions of the second light-releasing surface of the light directing body. 28. The front-illuminating device as defined in claim 1, wherein the front-illuminating device is for being placed in contact with the object to be illuminated. 29. The front-illuminating device as defined in claim 28, wherein the light-directing body is placed in placed in contact with the object to be illuminated through the optical means. 30. The front-illuminating device as defined in claim 29, wherein the optical means is joined to an interface between the object to be illuminated and the first light-releasing surface of the light directing body. 31. The front-illuminating device as defined in claim 11, wherein the light-directing body is placed in front of the object to be illuminated, the object to be illuminated being for observation from an observer through the light directing body. 32. The front-illuminating device as defined in claim 31, wherein the object to be illuminated is for observation from an observer through the second light-releasing surface of the light directing body. 33. The front-illuminating device as defined in claim 26, wherein the object to be illuminated is for observation from an observer through the flat portions of the second light-releasing surface of the light directing body. 34. The front-illuminating device as defined in claim 11, wherein the front-illuminating device is for being placed in contact with the object to be illuminated. 35. The front-illuminating device as defined in claim 34, wherein the light-directing body is placed in placed in contact with the object to be illuminated through the optical means. 36. The front-illuminating device as defined in claim 35, wherein the optical means is joined to an interface between the object to be illuminated and the first light-releasing surface of the light directing body.