LCD device including an illumination device having a polarized light separating sheet between a light guide and the display

Abstract

An illumination device for a direct viewing type display element comprising a flat light guide; a light source set such that light is incident on a side portion of said flat light guide; a polarized light separating flat set on a first side of a light emitting side of the flat light guide for transmitting a p polarized light component and reflecting at least a portion of an s polarized light component with respect to a light ray substantially having a predetermined direction of incidence; and a light reflecting sheet disposed on a second side opposite to said light emitting side of the flat light guide in parallel with the light emitting site.

We claim:  
     
       1. An illumination device for a direct viewing type display element, comprising: 
       a flat light guide;  
       a light source set such that light is incident on a side portion of said flat light guide;  
       a polarized light separating sheet, comprising a planar multilayer film having at least two planar layers with different refractive indices, set on a light emitting side of the flat light guide for transmitting a p polarized light component and reflecting at least a portion of an s polarized light component with respect to a light ray substantially having a predetermined direction of incidence ; and  
       a light reflecting sheet disposed on another side opposite to and facing said light emitting side of the flat light guide in parallel with the emitting side, said light reflecting sheet converting said portion of s polarized light component reflected by said polarized light separating sheet into p polarized light and reflecting the converted p polarized light to said polarized light separating sheet for transmission of the converted p polarized light through said polarized light separating sheet in overlapping relationship with the p polarized light component.  
     
     
       2. The illumination device for a direct viewing type display element according to claim  1 , wherein the polarized light separating sheet is comprising a multi-layered structure wherein light transmitting media having a relatively large refractive index and light transmitting media having a relatively small refractive index are laminated. 
     
     
       3. The illumination device for a direct viewing type display element according to claim  1 , wherein the polarized light separating sheet comprises a transparent supporter and at least one dielectric thin film laminated on said transparent supporter having a thickness which is equal to or smaller than a wavelength of visible light. 
     
     
       4. The illumination device for a direct viewing type display element according to claim  1 , wherein the polarized light separating sheet comprises a plurality of laminated transparent polymer layers having different refractive indices. 
     
     
       5. A liquid crystal display device, wherein the illumination device according to claim  1  is disposed on a rear side of a direct viewing type liquid crystal display element such that a principle polarization direction of emitted light from the illumination device substantially agrees with a direction of an optical axis of polarization of a polarizing sheet on a light-incident side of a liquid crystal display element. 
     
     
       6. The liquid crystal display device according to claim  5  further comprising: 
       a light deflecting means disposed between the polarized light separating sheet and the liquid crystal display element for deflecting a direction of a light ray maximizing a light intensity among light distributing directions to a direction substantially perpendicular to a display face of the liquid crystal display element.  
     
     
       7. The liquid crystal display device according to claim  5 , further comprising: 
       a means for rotating polarization direction disposed between the illumination device and the liquid crystal display element for rotating the principle direction of emitted light.  
     
     
       8. An illumination device for a direct viewing type display element, comprising: 
       a flat light emitting means for emitting a diffused light including a first polarized light component having a first direction of polarization and a second polarized light component having a second direction of polarization perpendicular to the first direction of polarization; and  
       a polarized light converting and emitting means disposed in an optical path of a light emitted from said flat light emitting means for emitting said first polarized light component and for emitting, in overlapping relationship with the emitted first polarized light component, at least a portion of said second polarized light component after selectively converting said portion of said second polarized light component into the first polarized light component, comprising,  
       
         a polarized light separating sheet comprising a planar multilayer film having at least two planar layers with different refractive indices for transmitting said first polarized light component and reflecting at least a portion of said second polarized light component, and  
       
       
         a light reflecting sheet disposed to receive the second polarized light component reflected by said polarized light separating sheet and convert at least a portion of the reflected second polarized light component into light having the polarization of the first polarized light component and reflecting the converted light for transmission through said polarized light separating sheet in overlapping relationship with the first polarized light component.  
       
     
     
       9. An illumination device for a direct viewing type display element, comprising: 
       a flat light guide;  
       a light source set such that light is incident on a side portion of said flat light guide;  
       a polarized light separating sheet, comprising a planar multilayer film having at least two planar layers with different refractive indices, set on a light emitting side of the flat light guide for transmitting a p polarized light component and reflecting at least a portion of an s polarized light component with respect to light rays substantially having a predetermined direction of incidence ; and  
       a light reflecting sheet disposed on another side opposite to and facing said light emitting side of the flat light guide in parallel with the emitting side, said light reflecting sheet converting said portion of s polarized light component reflected by said polarized light separating sheet into p polarized light and reflecting the converted p polarized light to said polarized light separating sheet for transmission of the converted p polarized light through said polarized light separating sheet in overlapping relationship with the p polarized light component.  
     
     
       10. The illumination device for a direct viewing type display element according to claim  9 , wherein the polarized light separating sheet comprises a transparent supporter and at least one dielectric thin film laminated on said transparent supporter having a thickness which is equal to or smaller than a wavelength of visible light. 
     
     
       11. The illumination device for a direct viewing type display element according to claim  9 , wherein the polarized light separating sheet is composed of a multi-layer structure including  comprises alternately laminated light transmitting media, having a refractive index, n 0 , and other transmitting media, having a refractive index, n 1 , smaller than the refractive index n 0 . 
     
     
       12. The illumination device for a direct viewing type display element according to claim  9 , wherein a λ/4 phase interference plate is provided on the back face of the light guide and a side face of the light guide opposing the light source. 
     
     
       13. The illumination device for a direct viewing type display element according to claim  10 , wherein a λ/4 phase interference plate is provided on the back face of the light guide and a side face of the light guide opposing the light source. 
     
     
       14. The illumination device for a direct viewing type display element according to claim  9 , wherein a prism shape is formed on a surface of the light guide. 
     
     
       15. The illumination device for a direct viewing type display element according to claim  14 , wherein the prism shape is a lenticular lens array. 
     
     
       16. The illumination device for a direct viewing type display element according to claim  9 , further comprising a light deflector. 
     
     
       17. The illumination device for a direct viewing type display element according to claim  16 , wherein a micro lens array or prism array having a lenticular shape or Fresnel shape is employed as the light deflector. 
     
     
       18. An illumination device for a direct viewing type display element, comprising: 
       a flat light guide;  
       a light source set such that light is incident on a side portion of said flat light guide;  
       a polarized light separating sheet set on a light emitting side of the flat light guide for transmitting a p polarized light component and reflecting at least a portion of an s polarized light component with respect to a light ray substantially having a predetermined direction of incidence ; and  
       a light reflecting sheet disposed on another side opposite to and facing said light emitting side of the flat light guide in parallel with the emitting side, wherein said polarized light separating sheet is planar and parallel to the light emitting side of the flat light guide, comprises plural planar layers, and is set in proximity to the flat light guide in the light emitting direction.  
     
     
       19. The illumination device of claim  18 , wherein said polarized light separating sheet comprises plastic. 
     
     
       20. The illumination device of claim  19 , wherein said polarized light separating sheet comprising plastic is obtained by multi- layer extrusion.   
     
     
       21. The illumination device of claim  20 , wherein the difference in the refractive indices between at two layers is not less than  0 . 03 . 
     
     
       22. The illumination device according to claim  1 , wherein the direction of light distribution of light for said display element is substantially perpendicular to said display element. 
     
     
       23. The illumination device according to claim  8 , wherein the direction of light distribution of light for said display element is substantially perpendicular to said display element. 
     
     
       24. The illumination device according to claim  9 , wherein the direction of light distribution of light for said display element is substantially perpendicular to said display element. 
     
     
       25. The illumination device according to claim  18 , wherein the direction of light distribution of light for said display element is substantially perpendicular to said display element. 
     
     
       26. The illumination device according to claim  1 , comprising: 
       
         a phase interference material provided between said light reflecting sheet and said polarized light separating sheet. 
       
     
     
       27. The illumination device according to claim  8 , comprising: 
       
         a phase interference material provided between said light reflecting sheet and said polarized light separating sheet. 
       
     
     
       28. The illumination device according to claim  9 , comprising: 
       
         a phase interference material provided between said light reflecting sheet and said polarized light separating sheet. 
       
     
     
       29. The illumination device according to claim  18 , comprising: 
       
         a phase interference material provided between said light reflecting sheet and said polarized light separating sheet. 
       
     
     
       30. The illumination device according to claim  1 , wherein said polarized light separating sheet comprises plastic. 
     
     
       31. The illumination device according to claim  8 , wherein said polarized light separating sheet comprises plastic. 
     
     
       32. The illumination device according to claim  9 , wherein said polarized light separating sheet comprises plastic. 
     
     
       33. The illumination device of claim  30 , wherein the difference in the refractive indices between at two layers is not less than  0 . 03 . 
     
     
       34. The illumination device according to claim  30 , wherein said polarized light separating sheet comprising plastic further comprises polymer multi- layers having a thickness not less than  0 . 05  μm and not more than  0 . 45  μm.   
     
     
       35. The illumination device according to claim  31 , wherein said polarized light separating sheet comprising plastic further comprises polymer multi- layers having a thickness not less than  0 . 05  μm and not more than  0 . 45  μm.   
     
     
       36. The illumination device according to claim  32 , wherein said polarized light separating sheet comprising plastic further comprises polymer multi- layers having a thickness not less than  0 . 05  μm and not more than  0 . 45  μm.   
     
     
       37. The illumination device according to claim  33 , wherein said polarized light separating sheet comprising plastic further comprises polymer multi- layers having a thickness not less than  0 . 05  μm and not more than  0 . 45  μm.   
     
     
       38. The illumination device according to claim  30 , wherein said polarized light separating sheet comprising plastic is obtained by extrusion. 
     
     
       39. The illumination device according to claim  31 , wherein said polarized light separating sheet comprising plastic is obtained by extrusion. 
     
     
       40. The illumination device according to claim  32 , wherein said polarized light separating sheet comprising plastic is obtained by extrusion. 
     
     
       41. The illumination device according to claim  33 , wherein said polarized light separating sheet comprising plastic is obtained by extrusion. 
     
     
       42. The illumination device according to claim  1 , comprising a deflector element used with said polarized light separating sheet. 
     
     
       43. The illumination device according to claim  8 , comprising a deflector element used with said polarized light converting and emitting means. 
     
     
       44. The illumination device according to claim  9 , comprising a deflector element used with said polarized light separating sheet. 
     
     
       45. The illumination device according to claim  18 , comprising a deflector element used with said polarized light separating sheet. 
     
     
       46. An illumination device comprising: 
       
         a flat light guide having a light emitting side and a light reflecting side;  
       
       
         a light source arranged such that light is incident on an edge portion of said flat light guide, said flat light guide arranged for emitting light from said light source through said light emitting side;  
       
       
         a light reflecting element disposed on said light reflecting side; and  
       
       
         a planar polarized light separating structure comprising at least two planar layers of light transmitting media with different refractive indices disposed on said light emitting side, said structure transmitting a first polarized light component and reflecting at least a portion of a second polarized light component of light emitted from said light emitting side. 
       
     
     
       47. The illumination device according to claim  46 , wherein said multi- layered structure comprises layers of a transparent plastic material.   
     
     
       48. The illumination device according to claim  46 , further comprising: 
       
         a Fresnel shape element which converts a direction of light distribution of the light emitted from said light emitting side. 
       
     
     
       49. The illumination device according to claim  48 , wherein said Fresnel shape element comprises a microlens array or a prism array. 
     
     
       50. The illumination device according to claim  48 , wherein the direction of light distribution of light from said Fresnel shape element is substantially perpendicular to a display element. 
     
     
       51. The illumination device according to claim  46 , wherein said first polarized component is a P polarized light component and said second polarized component is an S polarized light component. 
     
     
       52. The illumination device according to claim  46 , wherein said multi- layered structure comprises plural layers formed of a transparent dielectric medium.   
     
     
       53. The illumination device according to claim  46 , comprising: 
         a planar transparent supporter on which said multi - layered structure is formed.   
     
     
       54. The illumination device according to claim  46 , comprising: 
       
         a λ/ 4  phase interference plate provided between said light reflecting element and said planar polarized light separating structure. 
       
     
     
       55. The illumination device according to claim  46 , wherein said at least two layers of said planar polarized light separating structure comprise a plurality of polymer layers. 
     
     
       56. The illumination device according to claim  55 , wherein one of said polymer layers has a thickness not less than  0 . 05  μm and not more than  0 . 45  μm. 
     
     
       57. The illumination device according to claim  55 , wherein said multi- layered structure comprising polymer layers is obtained by extrusion.   
     
     
       58. The illumination device according to claim  55 , wherein said multi- layered structure comprising polymer layers is obtained by lamination.   
     
     
       59. An illumination device comprising: 
       
         a flat light guide having opposed sides;  
       
       
         a light source arranged such that light is incident on an edge portion of said flat light guide, said flat light guide having one side thereof arranged for emitting light;  
       
       
         a light reflecting sheet disposed on a side of the flat light guide opposite the light emitting side of said flat light guide; and  
       
         a polarized light separating sheet comprising a multi - layered structure including plural planar layers of light transparent materials having different refractive indices, said structure transmitting a first polarized light component and reflecting at least a portion of a second polarized light component of light emitted from said light emitting side of said flat light guide.   
     
     
       60. The illumination device according to claim  59 , wherein said multi- layered structure comprises layers of a transparent plastic material.   
     
     
       61. The illumination device according to claim  59 , further comprising: 
       
         a microlens array or a prism array which converts a direction of light distribution of the light for a display element. 
       
     
     
       62. The illumination device according to clam  61 , wherein the direction of light distribution of light from said microlens array or said prism array is substantially perpendicular to the display element. 
     
     
       63. The illumination device according to claim  59 , comprising: 
       
         a λ/ 4  phase interference plate provided between said light reflecting sheet and said polarized light separating sheet. 
       
     
     
       64. The illumination device according to claim  59 , wherein said multi- layered structure comprises a plurality of polymer layers.   
     
     
       65. The illumination device according to claim  64 , wherein one of said polymer layers has a thickness not less than  0 . 05  μm and not more than  0 . 45  μm. 
     
     
       66. The illumination device according to claim  64 , wherein said multi- layered structure comprising polymer layers is obtained by extrusion.   
     
     
       67. The illumination device according to claim  64 , wherein said multi- layered structure comprising polymer layers is obtained by lamination.   
     
     
       68. A display device comprising: 
       
         an illumination device comprising,  
       
       
         a flat light guide having a light emitting side and a light reflecting side,  
       
       
         a light source arranged such that light is incident on an edge portion of said flat light guide, said flat light guide arranged for emitting light from said light source through said light emitting side,  
       
       
         a light reflecting element disposed on said light reflecting side, and  
       
       
         a planar polarized light separating structure comprising at least two planar layers of light transmitting media with different refractive indices disposed on said light emitting side, said structure transmitting a first polarized light component and reflecting at least a portion of a second polarized light component of light emitted from said light emitting side; and  
       
       
         a liquid crystal display element disposed opposite said polarized light separating sheet of said illumination device. 
       
     
     
       69. A display device comprising: 
       
         an illumination device comprising,  
       
       
         a flat light guide having opposed sides,  
       
       
         a light source arranged such that light is incident on an edge portion of said flat light guide, said flat light guide having one side thereof arranged for emitting light,  
       
       
         a light reflecting sheet disposed on a side of the flat light guide opposite the light emitting side of said flat light guide, and  
       
         a polarized light separating sheet comprising a multi - layered structure including plural planar layers of light transparent materials having different refractive indices, said structure transmitting a first polarized light component and reflecting at least a portion of a second polarized light component of light emitted from said light emitting side of said flat light guide; and    
       
         a liquid crystal display element disposed opposite said polarized light separating sheet of said illumination device. 
       
     
     
       70. The display device according to claim  68 , wherein said liquid crystal display element comprises an RGB color TFT driving liquid crystal display cell. 
     
     
       71. The display device according to claim  69 , wherein said liquid crystal display element comprises an RGB color TFT driving liquid crystal display cell. 
     
     
       72. An illumination device for a direct viewing type display element, comprising: 
       
         a planar polarized light separating sheet comprising plural planar layers, including at least one layer made of plastic, which separates incident light into a first polarized light component and a second polarized light component, said light separating sheet transmitting said first polarized light component and reflecting said second polarized light component; and  
       
         a reflecting element disposed opposite said planar polarized light separating sheet to reflect and produce phase - interference of the second polarized light component.   
     
     
       73. The illumination device of claim  72 , comprising: 
       
         a light guide disposed between said planar polarized light separating sheet and said reflecting element; and  
       
       
         a light source disposed adjacent an edge of said light guide. 
       
     
     
       74. The illumination device according to claim  72 , wherein said planar polarized light separating sheet comprises a plurality of layers having a thickness not less than  0 . 05  μm and not more than  0 . 45  μm. 
     
     
       75. The illumination device according to claim  72 , comprising: 
       
         a deflector element disposed adjacent a light emitting side of said planar polarized light separating sheet and deflecting said first polarized light component transmitted through said light separating sheet. 
       
     
     
       76. The illumination device of claim  18  wherein said polarized light separating sheet comprises at least one planar layer of a dielectric film. 
     
     
       77. The illumination device according to claim  20 , wherein said polarized light separating sheet comprising plastic further comprises polymer multi- layers having a thickness not less than  0 . 05  μm and not more than  0 . 45  μm.   
     
     
       78. The illumination device of claim  41 , wherein the difference in the refractive indices between at two layers is not less than  0 . 03 .