Collimating light guide plate, diffusing unit, and display apparatus employing the same

Abstract

A diffusing unit includes: a polarizing plate; and a diffusing layer integrally provided on a surface of the polarizing plate without an air layer therebetween. By using a display apparatus employing a collimating light guide plate and the diffusing unit, the optical performances such as resolution and viewing angle can be improved. Also, because gray scale inversion and color shifts can be reduced or eliminated using collimated light, image quality of the display apparatus can be improved.

1 . A diffusing unit comprising:
 a polarizing plate; and   a diffusing layer integrally provided on a surface of the polarizing plate without an air layer therebetween.   
   
   
       2 . The diffusing unit of  claim 1 , wherein the diffusing layer comprises beads mixed with a binder so that the beads are partially exposed beyond the binder and the mixture is coated on the polarizing plate. 
   
   
       3 . The diffusing unit of  claim 1 , wherein the diffusing layer comprises beads mixed with a binder so that the beads are embedded in the binder and the mixture is coated on the polarizing plate. 
   
   
       4 . The diffusing unit of  claim 1 , wherein the polarizing plate comprises first and second tri-acetyl-cellulose (TAC) layers and a polyvinyl alcohol (PVA) layer disposed between the first and second TAC layers,
 wherein the diffusing layer is an adhesive layer disposed between the second TAC layer and the PVA layer.   
   
   
       5 . A diffusing unit comprising:
 a first tri-acetyl-cellulose (TAC) layer;   a second TAC layer disposed over the first TAC layer;   a polyvinyl alcohol (PVA) layer disposed between the first and second TAC layers; and   beads mixed in the second TAC layer.   
   
   
       6 . The diffusing unit of  claim 5 , wherein the diameter of each of the beads is less than a pitch between sub-pixels. 
   
   
       7 . A display apparatus comprising:
 a backlight unit;   a first polarizing plate which transmits light having a predetermined polarization among light emitted by the backlight unit;   a liquid crystal layer forming an image using light transmitted through the first polarizing plate;   a color filter which transmits light having a predetermined wavelength among light transmitted through the liquid crystal layer; and   a diffusing unit disposed on the color filter, and comprising a second polarizing plate and a diffusing layer integrally provided on a top surface of the second polarizing plate without an air layer between the second polarizing plate and the diffusing layer.   
   
   
       8 . The display apparatus of  claim 7 , wherein the diffusing layer comprises beads mixed with a binder so that the beads are partially exposed beyond the binder and the mixture is coated on the second polarizing plate. 
   
   
       9 . The display apparatus of  claim 7 , wherein the diffusing layer comprises beads mixed with a binder so that the beads are embedded in the binder and the mixture is coated on the second polarizing plate. 
   
   
       10 . The display apparatus of  claim 7 , wherein the second polarizing plate comprises first and second tri-acetyl-cellulose (TAC) layers and a polyvinyl alcohol (PVA) layer disposed between the first and second TAC layers,
 wherein the diffusing layer is an adhesive layer disposed between the second TAC layer and the PVA layer.   
   
   
       11 . The display apparatus of  claim 10 , wherein the diameter of each of the beads is less than a pitch between sub-pixels. 
   
   
       12 . The display apparatus of  claim 7 , further comprising a transparent substrate disposed between the color filter and the second polarizing plate,
 wherein, when the thickness from the transparent substrate to the diffusing layer is d, a pitch between sub-pixels is Ps, and the angle of luminance half width at half maximum (HWHM) of light transmitting through the transparent substrate is O′, the thickness d satisfies
     d<{ 1.5 Ps}/{ tan θ′}. 
   
   
   
       13 . The display apparatus of  claim 7 , wherein the backlight unit comprises a light source and a light guide plate, and the angle of luminance half width at half maximum (HWHM) of light emitted by the light guide plate is within the range of 15 degrees. 
   
   
       14 . The display apparatus of  claim 13 , wherein the light guide plate comprises a first prismatic structure array arranged on a bottom surface thereof in a direction parallel to the optical axis of light emitted by the light source and a second prismatic structure array arranged on a top surface thereof in a direction perpendicular to the direction of the first prismatic structure array. 
   
   
       15 . The display apparatus of  claim 13 , wherein the light guide plate comprises a first prismatic structure array arranged on a bottom surface thereof in a direction perpendicular to the optical axis of light emitted by the light source, and a second prismatic structure array arranged on a top surface thereof in a direction perpendicular to the direction of the first prismatic structure array. 
   
   
       16 . A light guide plate comprising:
 a first prismatic structure array arranged on a bottom surface of the light guide plate in a direction perpendicular to the optical axis of light emitted by a light source; and   a second prismatic structure array arranged on a top surface of the light guide plate in a direction perpendicular to the direction of the first prismatic structure array to collimate incident light.   
   
   
       17 . The light guide plate of  claim 16 , wherein the first prismatic structure array has first prism surfaces closer to the light source and second prism surfaces facing the first prism surfaces,
 wherein the first prism surfaces are inclined at an angle of less than 5 degrees and the second prism surfaces are inclined at an angle of greater than 40 degrees.   
   
   
       18 . The light guide plate of  claim 16 , wherein the angle of luminance half width at half maximum (HWHM) of light outcoupled by the light guide plate is within the range of 15 degrees. 
   
   
       19 . A light guide plate comprising:
 a first prismatic structure array arranged on a bottom surface of the light guide plate in a direction parallel to the optical axis of light emitted by a light source; and   a second prismatic structure array arranged on a top surface of the light guide plate in a direction perpendicular to the direction of the first prismatic structure array to collimate incident light.   
   
   
       20 . The light guide plate of  claim 19 , wherein the second prismatic structure array has first prism surfaces closer to the light source and second prism surfaces facing the first prism surfaces,
 wherein the first prism surfaces are inclined at an angle of less than 5 degrees and the second prism surfaces are inclined at an angle of greater than 40 degrees.   
   
   
       21 . The light guide plate of  claim 19 , wherein the angle of luminance half width at half maximum (HWHM) of light outcoupled by the light guide plate is within the range of 15 degrees.