Surface light source device, backlight unit and liquid crystal display having the same

Abstract

The present invention is directed to a surface light source device utilizing a light pipe. The present invention is also directed to a backlight unit and a liquid crystal display which are provided with such surface light source device. A surface light source device comprises at least one light source generating light; and at least one hollow light pipe, the light pipe includes a first light waveguide unit with structured surface on at least one side; and, a second light waveguide unit with structured surface on at least one side and disposed substantially parallel to the first light waveguide unit, wherein a longitudinal direction of the structured surface of the first light waveguide unit and a longitudinal direction of the structured surface of the second light waveguide unit form a certain angle.

1 . A liquid crystal display comprising:
 a liquid crystal panel displaying images according to electrical signals provided from the outside device; and   a backlight unit for illuminating the liquid crystal panel from the back of the liquid crystal panel, the backlight unit comprising:
 a surface light source device for providing surface light, the surface light source device including:
 at least one light source generating light; and 
 at least one hollow light pipe including:
 a first light waveguide unit with structured surface on at least one side; and 
 a second light waveguide unit with structured surface on at least one side and disposed substantially parallel to the first light waveguide unit, 
 
 
   wherein a longitudinal direction of the structured surface of the first light waveguide unit and a longitudinal direction of structured surface of the second light waveguide unit form a certain angle.   
   
   
       2 . The liquid crystal display of  claim 1 , wherein the structured surface includes an array of prisms, wherein the certain angle formed by a longitudinal direction of the prisms of the first light waveguide unit and a longitudinal direction of the prisms of the second light waveguide unit is a substantially right angle. 
   
   
       3 . A backlight unit for illuminating a liquid crystal panel from the back of the liquid crystal panel, the backlight unit comprising a surface light source device for providing surface light, the surface light source device including:
 at least one light source generating light; and   at least one hollow light pipe including:
 a first light waveguide unit with structured surface on at least one side; and 
 a second light waveguide unit with structured surface on at least one side and disposed substantially parallel to the first light waveguide unit, 
 wherein a longitudinal direction of the structured surface of the first light waveguide unit and a longitudinal direction of the structured surface of the second light waveguide unit form a certain angle. 
   
   
   
       4 . The backlight unit of  claim 3 , further comprising at least one optical sheet disposed in one side of the surface light source device, wherein the optical sheet receives the light emitted from the surface light source device and provides the light to the liquid crystal panel. 
   
   
       5 . The backlight unit of  claim 3 ,wherein the structured surface includes an array of prisms 
   
   
       6 . The backlight unit of  claim 3 , wherein the at least one light source is LEDs, and wherein the surface light source further comprises:
 a printed circuit board electrically connecting a electric power source to the LEDs, wherein the LEDs are mounted on the printed circuit board; and   a housing receiving and supporting the printed circuit board.   
   
   
       7 . The backlight unit of  claim 3 , further comprising a reflective sheet disposed under the light pipe to reflect the light emitted through a bottom surface of the light pipe and re-input the light into the inside of the light pipe. 
   
   
       8 . The backlight unit of  claim 3 , wherein the light source is CCFLs or EEFLs disposed inside or along at least one side of the light pipe. 
   
   
       9 . The backlight unit of  claim 3 , further comprising a diffusive layer disposed on the outer surface of the light pipe to receive at least the light emitted from the light emitting surface, the diffusive layer including:
 a base material consisting of a light-transmissive resin; and   a plurality of diffusion particles distributed in the base material.   
   
   
       10 . The backlight unit of  claim 9 , wherein the diffusion particles are beads. 
   
   
       11 . The backlight unit of  claim 9 , further comprising a reflector having a surface capable of reflecting light, wherein the reflector is disposed inside the light pipe. 
   
   
       12 . The backlight unit of  claim 9 , further comprising a reflector having a surface capable of reflecting light, wherein the reflector is disposed outside the light pipe. 
   
   
       13 . The backlight unit of  claim 5 , wherein the certain angle formed by a longitudinal direction of the prisms of the first light waveguide unit and a longitudinal direction of the prisms of the second light waveguide unit is a substantially right angle. 
   
   
       14 . The backlight unit of  claim 5 , wherein the prisms of the first waveguide unit are enlarged as the distance from the light source is farther. 
   
   
       15 . A surface light source device for providing surface light, comprising:
 at least one light source generating light; and   at least one hollow light pipe including:
 a first light waveguide unit with structured surface on at least one side; and 
 a second light waveguide unit with structured surface on at least one side and disposed substantially parallel to the first light waveguide unit, 
 wherein a longitudinal direction of the structured surface of the first light waveguide unit and a longitudinal direction of the structured surface of the second light waveguide unit form a certain angle. 
   
   
   
       16 . The surface light source device of  claim 15  wherein the structured surface includes an array of prisms. 
   
   
       17 . The surface light source device of  claim 15 , wherein the at least one light source is LEDs, and wherein the surface light source further comprises:
 a printed circuit board electrically connecting a electric power source to the LEDs, wherein the LEDs are mounted on the printed circuit board; and   a housing receiving and supporting the printed circuit board.   
   
   
       18 . The surface light source device of  claim 15 , wherein the light source is CCFLs or EEFLs disposed inside or along at least one side of the light pipe. 
   
   
       19 . The surface light source device of  claim 15 , further comprising a diffusive layer disposed on the outer surface of the light pipe to receive at least the light emitted from the light emitting surface, the diffusive layer including:
 a base material consisting of a light-transmissive resin; and   a plurality of diffusion particles distributed in the base material.   
   
   
       20 . The surface light source device of  claim 16 , wherein the certain angle formed by a longitudinal direction of the prisms of the first light waveguide unit and a longitudinal direction of the prisms of the second light waveguide unit is a substantially right angle. 
   
   
       21 . The surface light source device of  claim 16 , wherein the prisms of the first waveguide unit are enlarged as the distance from the light source is farther.