Light pipe and polarized-light source

Abstract

A light pipe is obtained by laminating on one or both surfaces of a light-transmitting resin plate a polarized-light scattering plate having fine birefringent domains dispersed therein and hence showing anisotropy in scattering. The polarized-light scattering plate comprises a transparent film having fine domains dispersed therein comprising a liquid crystal polymer which exhibits nematic at temperatures lower than the glass transition temperature of the polymer constituting matrix of the transparent film and has a glass transition temperature of 50° C. or higher. The light pipe as a laminate may further comprise a specular reflection layer, a polarization-retaining lens and a light diffusion layer laminated thereon. The light pipe may further comprise a light source mounted at least on one side face thereof to provide a planar polarized-light source.

1 . A light pipe comprising: 
 a light-transmitting resin plate; and    a polarized-light scattering plate laminated on at least one surface of said light-transmitting resin plate, said polarized-light scattering plate having fine birefringent domains dispersed therein to exhibit anisotropy in scattering depending on a polarization direction.    
     
     
         2 . A light pipe according to  claim 1 , wherein said polarized-light scattering plate comprises a transparent film having fine domains, difference in refractive index between the fine domains and other portion of said transparent film is 0.03 or more in an optical axial direction Δn 1  which exhibits maximum value among the difference in refractive index in various light axes of fine domains, the difference in refractive indices of each of two other axial directions Δn 2  and Δn 3  perpendicular to Δn 1  direction Δn 2  is 50% or less of Δn 1 , and Δn 2  and Δn 3  are equal to each other.  
     
     
         3 . A light pipe according to  claim 2 , wherein Δn 1  direction in the polarized-light scattering plate is parallel to a surface of said transparent film.  
     
     
         4 . (canceled).  
     
     
         5 . A polarized-light source comprising: a light pipe according to any one of  claims 2  to  3 ; a light source disposed at least on one side face of said light pipe; and a specular reflection layer provided on one of both surfaces of said light pipe.  
     
     
         6 . A light pipe comprising: 
 a light-transmitting resin plate; and    a polarized-light scattering plate laminated on at least one surface of said light-transmitting resin plate, said polarized-light scattering plate having fine birefringent domains dispersed therein to exhibit anisotropy in scattering depending on a polarization direction,    wherein said polarized-light scattering plate comprises a transparent film having the fine domains comprising a liquid crystal polymer which exhibits nematic at temperatures lower than a glass transition temperature of the polymer constituting other portion of the transparent film and has a glass transition temperature of 50° C. or higher.    
     
     
         7 . A light pipe according to  claim 6 , wherein the polymer constituting the transparent film has a deflection temperature of 80° C. or higher under load and the glass transition temperature of 110° C. or higher.  
     
     
         8 . A light pipe according to  claim 1 , wherein difference in refractive index between the fine domains and other portion of said transparent film is 0.03 or more in an optical axial direction Δn 1  which exhibits maximum value among the difference in refractive index in various light axes of fine domains, the difference in refractive indices of each of two other axial directions Δn 2  and Δn 3  perpendicular to Δn 1  direction Δn 2  is 50% or less of Δn 1 , and Δn 2  and Δn 3  are equal to each other.  
     
     
         9 . A light pipe according to  claim 8 , wherein Δn 1  direction in the transparent film is parallel to a surface of said transparent film.  
     
     
         10 . (canceled).  
     
     
         11 . A polarized-light source comprising: a light pipe according to any one of  claims 6  to  9  a light source disposed at least on one side face of said light pipe; and a specular reflection layer provided on one of both surfaces of said light pipe.  
     
     
         12 . A light pipe comprising: 
 a laminate having a birefringent light-transmitting resin plate, and a polarized-light scattering plate laminated on at least one surface of said light-transmitting resin plate, said polarized-light scattering plate having fine birefringent domains dispersed therein to exhibit anisotropy in scattering depending on a polarization direction; and    a specular reflection layer provided on one surface of said laminate.    
     
     
         13 . A light pipe according to  claim 12 , wherein a phase difference due to birefringence of the light-transmitting resin plate is 50 nm or more based on an average phase difference in a plane of said light-transmitting resin plate.  
     
     
         14 . A light pipe according to  claim 13 , wherein a retardation axis of the light-transmitting resin plate and a light axis of the polarized-light scattering plate in the laminate cross each other at an angle of 5 degrees or more.  
     
     
         15 . A polarized-light source comprising: a light pipe according to any one of  claims 12  to  14 ; and a light source disposed at least on one side face of said light pipe.  
     
     
         16 . A light pipe comprising: 
 a laminate having a light-transmitting resin plate, and a polarized-light scattering plate laminated on at least one surface of said light-transmitting resin plate, said polarized-light scattering plate having fine birefringent domains dispersed therein to exhibit anisotropy in scattering depending on a polarization direction;    a specular reflection layer provided on a first surface of said laminate; and    a polarization-retaining light diffusion layer provided on second surface of said laminate.    
     
     
         17 . A light pipe according to  claim 16 , wherein said light diffusion layer comprises one of (i) an optically isotropic light-transmitting resin layer having transparent particles of a refractive index ratio of from 0.9 to 1.1 dispersed therein and (ii) an optically isotropic light-transmitting resin layer having a finely roughened surface structure.  
     
     
         18 . A light pipe according to  claim 17 , wherein said optically isotropic light-transmitting resin is at least one of cellulose triacetate-based resin, methyl polymethacrylate, polycarbonate and norbornene-based resin.  
     
     
         19 . A polarized-light source comprising: a light pipe according to any one of  claims 16  to  18 ; and a light source disposed at least on one side face of said light pipe.  
     
     
         20 . A light pipe comprising: 
 a laminate having a light-transmitting resin plate, and a polarized-light scattering plate laminated on at least one surface of said light-transmitting resin plate, said polarized-light scattering plate having fine birefringent domains dispersed therein to exhibit anisotropy in scattering depending on a polarization direction;    a specular reflection layer provided on a first surface of said laminate; and    a polarization-retaining lens sheet provided on a second surface of said laminate.    
     
     
         21 . A light pipe according to  claim 20 , wherein said lens sheet comprises one or more resins having a low birefringence.  
     
     
         22 . A light pipe according to  claim 20 , wherein said lens sheet comprises at least one of a cellulose triacetate-based resin, methyl polymethacrylate, polycarbonate and norbornene-based resin.  
     
     
         23 . A light pipe according to  claim 20 , wherein said lens sheet has a linear or dotted roughened structure provided on one surface thereof.  
     
     
         24 . A light pipe according to  claim 23 , wherein said lens sheet has a linear roughened structure and a linear direction is parallel to or perpendicular to a light axis of the polarized-light scattering plate.  
     
     
         25 . A light pipe according to  claim 20 , further comprising a polarization-retaining light diffusion layer is provided between said lens sheet and said laminate or on an emission side of said lens sheet.  
     
     
         26 . A polarized-light source comprising: a light pipe according to any one of  claims 20  to  25 ; and a light source disposed on one side face of said light pipe.  
     
     
         27 . A light pipe comprising: 
 a light-transmitting resin plate;    a polarized-light scattering plate laminated on at least one surface of said light-transmitting resin plate, said polarized-light scattering plate having fine birefringent domains dispersed therein to exhibit anisotropy in scattering depending on a polarization direction; and    a light path interposed between said light-transmitting resin plate and said polarized-light scattering plate to thereby partially bond said said light-transmitting resin plate and said polarized-light scattering plate in close contact.    
     
     
         28 . A light pipe according to  claim 27 , wherein said light path comprises a convex portion in a roughened structure provided on one of the light-transmitting resin plate and the polarized-light scattering plate, and said roughened structure has a rectangular section comprising a flat surface on concave and convex portions thereof.  
     
     
         29 . A light pipe according to  claim 27 , wherein there is a variation of distribution density of light path.  
     
     
         30 . A light pipe according to  claim 27 , wherein length of said light path is from 0.5 to 1,000 μm.  
     
     
         31 . A light pipe according to  claim 27 , wherein the light-transmitting resin plate side of the light path has a section having a continuous primary differential curve free of acute corner.  
     
     
         32 . A light pipe according to  claim 27 , wherein said light path is made of an adhesive material.  
     
     
         33 . A light pipe according to  claim 27 , further comprising a polarization-retaining reflection layer on one of both surfaces of said light pipe.  
     
     
         34 . A light pipe according to  claim 27 , further comprising a polarization-retaining light diffusion layer on one of both surfaces of said light pipe.  
     
     
         35 . A light pipe according to  claim 27 , further comprising a polarization-retaining lens sheet on one of both surfaces of said light pipe.  
     
     
         36 . A polarized-light source comprising: light pipe according to any one of  claims 27  to  35 ; and a light source provided at least on one side face of said light pipe.