Polarization converting system, method of manufacturing the same and liquid crystal display using the same

Abstract

A polarization converting system and a method of manufacturing the same are provided. The polarization converting system includes a polarization splitting unit splitting incident unpolarized light into two orthogonal polarizations and a polarization converting unit converting incident light into specific polarized light. The polarization converting unit has first and second regions that correspond to the polarization splitting unit and are different in a polarization converting extent from each other.

1 . A polarization converting system comprising: 
 a polarization splitting unit which splits incident unpolarized light into a first polarized light and a second polarized light which have orthogonal polarizations; and    a polarization converting unit on which the first polarized light and the second polarized light are incident, the polarization converting unit comprising first and second regions that correspond to the polarization splitting unit and are different in a polarization converting extent from each other.    
   
   
       2 . The polarization converting system of  claim 1 , wherein one of the first and second regions is a polarization maintaining region which maintains a polarization state of the first polarized light and the other of the first and second regions is a polarization converting region which converts a polarization state of the second polarized light to the polarization state of the first polarized light.  
   
   
       3 . The polarization converting system of  claim 1 , wherein the first region comprises a first liquid crystal layer region and the second region comprises a second liquid crystal layer region, and the first and second liquid crystal layer regions are different in a polarization converting extent from each other, and the first and second liquid crystal layer regions are formed of one of liquid crystals and liquid crystal polymers.  
   
   
       4 . The polarization converting system of  claim 3 , wherein one of the first and second liquid crystal layer regions is a polarization maintaining region which maintains a polarization state of the first polarized light and the other of the first and second liquid crystal layer regions is a polarization converting region which converts a polarization state of the second polarized light into the polarization state of the first polarized light.  
   
   
       5 . The polarization converting system of  claim 4 , wherein the polarization converting unit further comprises first and second liquid crystal alignment layers between which the first and second liquid crystal layer regions are disposed; and 
 the polarization converting region is formed in a twisted nematic (TN) mode and the polarization maintaining region is formed in a hybrid aligned nematic (HAN) mode.    
   
   
       6 . The polarization converting system of  claim 5 , wherein the first liquid crystal alignment layer includes homeotropic and homogeneous alignment regions, the second liquid crystal alignment layer includes homogeneous alignment regions, the polarization converting region, which corresponds to the homogeneous alignment region of the first liquid crystal alignment layer, is the TN mode, and the polarization maintaining region, which correspond to the homeotropic alignment region of the first liquid crystal alignment layer, is the HAN mode.  
   
   
       7 . The polarization converting system of  claim 5 , wherein the first and second liquid crystal alignment layers are formed of photopolymer.  
   
   
       8 . The polarization converting system of  claim 7 , wherein the homogeneous and homeotropic alignment regions of the first liquid crystal alignment layer are formed by selectively irradiating first polarized ultraviolet light and the homogeneous alignment regions of the second liquid crystal alignment layer is formed by irradiating second polarized ultraviolet light orthogonal to the first polarized ultraviolet light.  
   
   
       9 . The polarization converting system of  claim 8 , wherein the first and second polarized ultraviolet lights are linearly polarized ultraviolet light, orthogonal to each other.  
   
   
       10 . The polarization converting system of  claim 1 , wherein the first and second regions are alternately formed on the polarization converting unit.  
   
   
       11 . The polarization converting system of  claim 10 , wherein the polarization splitting unit comprises: 
 a polarization splitting portion which splits the unpolarized light into the first polarized light which is incident on a location corresponding to one of the first and second regions and the second polarized light; and    a light path changing portion which changes a transmission direction of the second polarized light so that the second polarized light is incident on the other of the first and second regions.    
   
   
       12 . The polarization converting system of  claim 11 , wherein the polarization splitting portion comprises a first polarization splitter which splits the incident unpolarized light into the first polarized light and the second polarized light by transmitting the first polarized and reflecting the second polarized light; and 
 the light path changing portion comprises a first reflector which reflects the second polarized light in a direction identical to the first polarized light,    wherein the first polarization splitter and the first reflector are alternately arranged to correspond to an arrangement of the first and second regions, respectively.    
   
   
       13 . The polarization converting system of  claim 12 , further comprising one of a reflective mirror and a light shielding member, which is provided on a surface of the polarization splitting unit at a location corresponding to the first reflector to allow the unpolarized light to be incident only on the first polarization splitter.  
   
   
       14 . The polarization converting system of  claim 12 , further comprising an array of micro lenses that are provided on a side of the polarization unit on which the unpolarized light is incident and correspond to a pair of the first polarization splitter and the first reflector that are adjacent to each other, the micro lens array increasing an intensity of light incident on the first polarization splitter by collecting the incident unpolarized light.  
   
   
       15 . The polarization converting system of  claim 12 , wherein the polarization splitting unit further comprises a plate having a first surface provided with a plurality of first and second inclined portions that are alternately arranged and the first polarization splitter and the first reflector are respectively disposed on the first and second inclined portions.  
   
   
       16 . The polarization converting system of  claim 11 , wherein the polarization splitting unit comprises: 
 a plurality of first splitting members which form the polarization splitting portion are arranged to correspond to one of the first and second regions; and    a second splitting member which functions as the light path changing portion, the second splitting member having a first surface provided with a plurality of coupling grooves in which the first splitting members are disposed and a second surface provided with a plurality of refracting portions which correspond to the other of the first and second regions,    wherein one of each first splitting member and the second splitting member is formed of an anisotropic medium and the other is formed of an isotropic medium,    the coupling grooves are formed such that a boundary surface between each first splitting member and the second splitting member defines an inclined surface,    the boundary surface functions as the polarization splitting portion, and    the unpolarized light incident on the first splitting members is transmitted through the boundary surface as the first polarized light and is refracted at the boundary surface as the second polarized light, and    the refracting portions refract the second polarized light refracted on the boundary surface to travel in a direction in parallel to the first polarized light transmitted through the boundary surface.    
   
   
       17 . The polarization converting system of  claim 16 , wherein each of the refracting portions includes at least one refracting groove which is formed on the second surface of the second splitting member to correspond to the other of the first and second regions, and the at least one refracting groove defines inclined surface refracting the second polarized light.  
   
   
       18 . The polarization converting system of  claim 17 , wherein the refracting groove has a triangular shape.  
   
   
       19 . The polarization converting system of  claim 16 , further comprising one of a reflective mirror and a light shielding member, which is provided on a surface of the polarization splitting unit at a location corresponding to a region between the first splitting members to allow the unpolarized light to be incident only on the first splitting members.  
   
   
       20 . A method of manufacturing a polarization converting system, the method comprising: 
 providing a polarization splitting unit having a polarization splitting portion which splits unpolarized light into first and second polarized lights which have orthogonal polarizations and a light path changing portion which changes a transmission direction of one of the first and second polarized lights so that the first and second polarized lights travel in a same direction;    disposing a first member having a first liquid crystal alignment layer formed by depositing photoreactive photopolymer on the polarization splitting unit;    forming two types of liquid crystal alignment regions by irradiating ultraviolet light only to one of a region corresponding to the polarization splitting portion and a region corresponding to the light path changing portion by directing first polarized ultraviolet light to the polarization splitting portion of the polarization splitting unit to make alignment states of the two types of the liquid crystal alignment regions, different from each other;    forming a single liquid crystal alignment region by irradiating ultraviolet rays of second polarized ultraviolet light orthogonal to the first polarized ultraviolet light to a front surface of a second member having a second liquid crystal alignment layer formed by depositing photoreactive photopolymer; and    forming a liquid crystal layer by injecting one of liquid crystals and polymerizable liquid crystals with an initiator capable of forming the polymerizable liquid crystal into liquid crystal polymer, the liquid crystal layer having first and second regions that are different in a polarization converting extent from each other and automatically aligned with the polarization splitting portion and the light path changing portion of the polarization splitting unit.    
   
   
       21 . The method of  claim 20 , wherein one of the first and second regions is a polarization maintaining region which maintains a polarized state of the first polarized light and the other of the first and second regions is a polarization converting region which converts a polarized state of the second polarized light to the polarization state of the first polarized light.  
   
   
       22 . The method of  claim 21 , a portion of the liquid crystal layer, which corresponds to the polarization converting region, is formed in a twisted nematic mode and a portion of the liquid crystal layer, which corresponds to the polarization maintaining region, is formed in a hybrid aligned nematic mode.  
   
   
       23 . The method of  claim 22 , wherein the two types of the alignment regions formed on the fist liquid crystal alignment layer are homogeneous and homeotropic alignment regions, respectively, and the single liquid crystal alignment layer of the second liquid crystal alignment layer is a homogeneous alignment region.  
   
   
       24 . The method of  claim 20 , wherein the first and second polarized ultraviolet lights are linearly polarized ultraviolet light having orthogonal polarization each other.  
   
   
       25 . The method of  claim 20 , wherein the polarization splitting and light path changing portions of the polarization splitting unit are alternately arranged, and 
 the first and second regions are alternately arranged to correspond to an arrangement of the polarization splitting and light path changing portions of the polarization splitting unit.    
   
   
       26 . The method of  claim 25 , wherein the polarization splitting unit allows the light to be incident only on the polarization splitting portion.  
   
   
       27 . A liquid crystal display comprising: 
 a liquid crystal panel;    a backlight system which irradiates light; and    a polarization converting system which converts the light irradiated from the backlight system to polarized light and directs the polarized light to the liquid crystal panel,    wherein the polarization converting system comprises:    a polarization splitting unit which splits incident unpolarized light into a first polarized light and a second polarized light which have orthogonal polarizations; and    a polarization converting unit on which the first polarized light and the second polarized light are incident, the polarization converting unit comprising first and second regions that correspond to the polarization splitting unit and are different in a polarization converting extent from each other.    
   
   
       28 . The liquid crystal display of  claim 27 , wherein one of the first and second regions wherein one of the first and second regions is a polarization maintaining region which maintains a polarization state of the first polarized light and the other of the first and second regions is a polarization converting region which converts a polarization state of the second polarized light to the polarization state of the first polarized light.  
   
   
       29 . The liquid crystal display of  claim 27 , wherein the first region comprises a first liquid crystal layer region and the second region comprises a second liquid crystal layer region, the first and second liquid crystal layer regions are different in a polarization converting extent from each other, and the first and second liquid crystal layer regions are formed of one of liquid crystals and liquid crystal polymers.  
   
   
       30 . The liquid crystal display of  claim 29 , wherein one of the first and second liquid crystal layer regions is a polarization maintaining region which maintains a polarization state of the first polarized light and the other of the first and second liquid crystal layer regions is a polarization converting region which converts a polarization state of the second polarized light into the polarization state of the first polarized light.  
   
   
       31 . The liquid crystal display of  claim 30 , wherein the polarization converting unit further comprises first and second liquid crystal alignment layers between which the first and second liquid crystal layer regions are disposed; and 
 the polarization converting region is formed in a twisted nematic (TN) mode and the polarization maintaining region is formed in a hybrid aligned nematic (HAN) mode.    
   
   
       32 . The liquid crystal display of  claim 31 , wherein the first liquid crystal alignment layer includes homeotropic and homogeneous alignment regions, the second liquid crystal alignment layer includes homogeneous alignment regions, the polarization converting region, which corresponds to the homogeneous alignment region of the first liquid crystal alignment layer, is the TN mode, and the polarization maintaining region, which correspond to the homeotropic alignment region of the first liquid crystal alignment layer, is the HAN mode.  
   
   
       33 . The liquid crystal display of  claim 31 , wherein the first and second liquid crystal alignment layers are formed of photopolymer.  
   
   
       34 . The liquid crystal display of  claim 33 , wherein the homogeneous and homeotropic alignment regions of the first liquid crystal alignment layer are formed by selectively irradiating first polarized ultraviolet light and the homogeneous alignment regions of the second liquid crystal alignment layer is formed by irradiating second polarized ultraviolet light orthogonal to the first polarized ultraviolet light.  
   
   
       35 . The liquid crystal display of  claim 34 , wherein the first and second polarized ultraviolet lights are linearly polarized ultraviolet light, orthogonal each other.  
   
   
       36 . The liquid crystal display of  claim 27 , wherein the polarization converting unit of the polarization converting system comprises first and second regions that are alternately arranged.  
   
   
       37 . The liquid crystal display of  claim 36 , wherein the polarization splitting unit of the polarization converting system comprises: 
 a polarization splitting portion which splits the unpolarized light into the first polarized light which is incident on a location corresponding to one of the first and second regions and the second polarized light; and    a light path changing portion which changes a transmission direction of the second polarized light so that the second polarized light is incident on the other of the first and second regions.    
   
   
       38 . The liquid crystal display of  claim 37 , wherein the polarization splitting portion comprises a first polarization splitter which splits the incident unpolarized light into the first polarized light and the second polarized light by transmitting the first polarized and reflecting the second polarized light; and 
 the light path changing portion comprises a first reflector which reflects the second polarized light in a direction identical to the first polarized light,    wherein the first polarization splitter and the first reflector are alternately arranged to correspond to an arrangement of the first and second regions, respectively.    
   
   
       39 . The liquid crystal display of  claim 38 , further comprising one of a reflective mirror and a light shielding member, which is provided on a surface of the polarization splitting unit at a location corresponding to the first reflector to allow the unpolarized light to be incident only on the first polarization splitter.  
   
   
       40 . The liquid crystal display of  claim 38 , further comprising an array of micro lenses that are provided on a side of the polarization unit on which the unpolarized light is incident and correspond to a pair of the first polarization splitter and the first reflector that are adjacent to each other, the micro lens array increasing an intensity of light incident on the first polarization splitter by collecting the incident unpolarized light.  
   
   
       41 . The liquid crystal display of  claim 38 , wherein the polarization splitting unit further comprises a plate having a first surface provided with a plurality of first and second inclined portions that are alternately arranged and the first polarization splitter and the first reflector are respectively disposed on the first and second inclined portions.  
   
   
       42 . The liquid crystal display of  claim 37 , wherein the polarization splitting unit comprises: 
 a plurality of first splitting members which form the polarization splitting portion are arranged to correspond to one of the first and second regions; and    a second splitting member which functions as the light path changing portion, the second splitting member having a first surface provided with a plurality of coupling grooves in which the first splitting members are disposed and a second surface provided with a plurality of refracting portions which correspond to the other of the first and second regions,    wherein one of each first splitting member and the second splitting member is formed of an anisotropic medium and the other is formed of an isotropic medium,    the coupling grooves are formed such that a boundary surface between each first splitting member and the second splitting member defines an inclined surface,    the boundary surface functions as the polarization splitting portion, and    the unpolarized light incident on the first splitting members is transmitted through the boundary surface as the first polarized light and is refracted at the boundary surface as the second polarized light, and    the refracting portions refract the second polarized light refracted on the boundary surface to travel in a direction in parallel to the first polarized light transmitted through the boundary surface.    
   
   
       43 . The liquid crystal display of  claim 42 , wherein each of the refracting portions includes at least one refracting groove which is formed on the second surface of the second splitting member to correspond to the other of the first and second regions, and the at least one refracting groove defines inclined surface refracting the second polarized light.  
   
   
       44 . The liquid crystal display of  claim 43 , wherein the refracting groove has a triangular shape.  
   
   
       45 . The liquid crystal display of  claim 42 , further comprising one of a reflective mirror and a light shielding member, which is provided on a surface of the polarization splitting unit at a location corresponding to a region between the first splitting members to allow the unpolarized light to be incident only on the first splitting members.