Polarizer, optical element, lighting device and liquid crystal display

Abstract

Disclosed are (1) a polarizer having a function of separating incident light into polarized light through reflection and transmission, which has (a) a haze of 10% or less, or (b) a ratio of parallel transmitted light to incident light of 40 to 60%, (c) a ratio of mirror reflected light to the incident light of 25% or more, (d) a ratio of diffusion reflected light to the incident light of 20% or less or (e) a fraction of mirror reflected light to the whole reflected light of 60% or more; (2) an optical element comprising the polarizer, and a ¼ wavelength formed by one or two or more retardation layers disposed on at least one side thereof; (3) a lighting device comprising a surface light source, and the polarizer or the optical element disposed thereon; and (4) a liquid crystal display comprising the lighting device and a liquid crystal cell arranged on the light outgoing side thereof, with a polarizing plate intervening therebetween.

What is claimed is:  
     
       1. A polarizer having a function of separating incident light into polarized light through reflection and transmission, which has (a) a haze of 10% or less, or (b) a ratio of parallel transmitted light to incident light of 40 to 60%, (c) a ratio of mirror reflected light to the incident light of 25% or more, (d) a ratio of diffusion reflected light to the incident light of 20% or less or (e) a fraction of mirror reflected light to the whole reflected light of 60% or more. 
     
     
       2. The polarizer according to  claim 1 , wherein (a) the in-plane dispersion of the haze is 6% or less, or (b) the in-plane dispersion of the ratio of parallel transmitted light is 15% or less, (c) the in-plane dispersion of the ratio of mirror reflected light is 10% or less, (d) the in-plane dispersion of the ratio of diffusion reflected light is 10% or less or (e) the in-plane dispersion of the fraction of mirror reflected light is 15% or less. 
     
     
       3. The polarizer according to  claim 1 , wherein the ratio of transmitted light to incident light is from 40% to 65%. 
     
     
       4. The polarizer according to  claim 3 , wherein the in-plane scatter of the ratio of transmitted light is 15% or less. 
     
     
       5. The polarizer according to  claim 1 , wherein the ratio of diffusion transmitted light to incident light is 10% or less. 
     
     
       6. The polarizer according to  claim 5 , wherein the in-plane dispersion of the ratio of diffusion transmitted light is 6% or less. 
     
     
       7. The polarizer according to  claim 1 , wherein the function of separating incident light into polarized light through reflection and transmission is based on a Grandjean-oriented cholesteric liquid crystal layer. 
     
     
       8. The polarizer according to  claim 7 , wherein helical pitch in Grandjean orientation of the cholesteric liquid crystal layer changes in the direction of thickness. 
     
     
       9. The polarizer according to  claim 7 , wherein the cholesteric liquid crystal layer composed of a laminated product of two or more cholesteric liquid crystal polymer layers different in center wavelengths of reflected light. 
     
     
       10. An optical element comprising the polarizer according to  claim 1 , and a ¼ wavelength formed by one or two or more retardation layers disposed on at least one side thereof. 
     
     
       11. The optical element according to  claim 10 , wherein linearly polarized light having a specified polarization axis is transmitted, and the other light is reflected. 
     
     
       12. The optical element according to  claim 10 , wherein the retardation layer is composed of one or two or more liquid crystal polymer layers. 
     
     
       13. The optical element according to  claim 12 , wherein the liquid crystal polymer layer is formed of a liquid crystal polymer of twisted orientation. 
     
     
       14. The optical element according to  claim 10 , wherein a polarizing plate containing a dichroic substance is disposed on the ¼ wavelength plate. 
     
     
       15. A lighting device comprising a surface light source, and the polarizer according to  claim 1  or the optical element according to  claim 10  disposed thereon. 
     
     
       16. The lighting device according to  claim 15 , wherein said device has at least one prism array layer. 
     
     
       17. The lighting device according to  claim 16 , wherein two or more prism array layers are arranged in a state in which arranging directions of prism arrays in the upper and lower layers intersect each other. 
     
     
       18. A liquid crystal display comprising the lighting device according to  claim 15 , and a liquid crystal cell arranged on a light outgoing side thereof, with a polarizing plate intervening therebetween. 
     
     
       19. The polarizer according to  claim 1 , comprising constituent layers which are all or partly adhered by means of adhesive layers. 
     
     
       20. The optical element according to  claim 10 , comprising constituent which layers are all or partly adhered by means of adhesive Layers. 
     
     
       21. The lighting device according to  claim 15 , comprising constituent which layers are all or partly adhered by means of adhesive layers. 
     
     
       22. The liquid crystal display according to  claim 18 , comprising the constituent layers which are all or partly adhered by means of adhesive layers. 
     
     
       23. A polarizer having a function of separating incident light into polarized light through reflection and transmission, which has ( a )  a haze of  10   %  or less,  ( b )  a ratio of parallel transmitted light to incident light of  40  to  60   % ,  ( c )  a ratio of mirror reflected light to the incident light of  25   %  or more   ,  ( d )  a ratio of diffusion reflected light to the incident light of  20   %  or less, and  ( e )  a fraction of mirror reflected light to the whole reflected light of  60   %  or more.    
     
     
       24. The polarizer according to  claim 23 , wherein ( a )  the in - plane dispersion of the haze is  6   %  or less,  ( b )  the in - plane dispersion of the ratio of parallel transmitted light is  15   %  or less,  ( c )  the in - plane dispersion of the ratio of mirror reflected light is  10   %  or less,  ( d )  the in - plane dispersion of the ratio of diffusion reflected light is  10   %  or less, and  ( e )  the in - plane dispersion of the fraction of mirror reflected light is  15   %  or less.    
     
     
       25. The polarizer according to  claim 23 , wherein the ratio of transmitted light to incident light is from  40 %  to  65   %.  
     
     
       26. The polarizer according to  claim 25 , wherein the in- plane scatter of the ratio of transmitted light is  15   %  or less.    
     
     
       27. The polarizer according to  claim 23 , wherein the ratio of diffusion transmitted light to incident light is  10 %  or less.    
     
     
       28. The polarizer according to  claim 27 , wherein the in- plane dispersion of the ratio of diffusion transmitted light is  6   %  or less.    
     
     
       29. The polarizer according to  claim 23 , wherein the function of separating incident light into polarized light through reflection and transmission is based on a Grandjean- oriented cholesteric liquid crystal layer.    
     
     
       30. The polarizer according to  claim 29 , wherein helical pitch in Grandjean orientation of the cholesteric liquid crystal layer changes in the direction of thickness.  
     
     
       31. The polarizer according to  claim 29 , wherein the cholesteric liquid crystal layer composed on a laminated product of two or more cholesteric liquid crystal polymer layers different in center wavelengths of reflected light.  
     
     
       32. An optical element comprising the polarizer according to  claim 23 , and a {fraction ( 1 / 4 )} wavelength formed by one or two or more retardation layers disposed on at least one side thereof.  
     
     
       33. The optical element according to  claim 32 , wherein linearly polarized light having a specified polarization axis is transmitted, and the other light is reflected.  
     
     
       34. The optical element according to  claim 32 , wherein the retardation layer is composed of one or two or more liquid crystal polymer layers.  
     
     
       35. The optical element according to  claim 34 , wherein the liquid crystal polymer layer is formed of a liquid crystal polymer of twisted orientation.  
     
     
       36. The optical element according to  claim 32 , wherein a polarizing plate containing a dichroic substance is disposed on the {fraction ( 1 / 4 )} wavelength plate.  
     
     
       37. A lighting device comprising a surface light source, and the polarizer according to  claim 23  or the optical element according to  claim 32  disposed thereon.  
     
     
       38. The lighting device according to  claim 37 , wherein said device has at least one prism array layer.  
     
     
       39. The lighting device according to  claim 38 , wherein two or more prism array layers are arranged in a state in which arranging directions of prism arrays in the upper and lower layers intersect each other.  
     
     
       40. A liquid crystal display comprising the lighting device according to  claim 37 , and a liquid crystal cell arranged on a light outgoing side thereof, with a polarizing plate intervening therebetween.  
     
     
       41. The liquid crystal display according to  claim 40 , comprising the constituent layers which are all or partly adhered by means of adhesive layers.  
     
     
       42. The lighting device according to  claim 37 , comprising constituent which layers are all or partly adhered by means of adhesive layers.  
     
     
       43. The optical element according to  claim 32 , comprising constituent which layers are all or partly adhered by means of adhesive layers.  
     
     
       44. The polarizer according to  claim 23 , comprising constituent layers which are all or partly adhered by means of adhesive layers.