Planar light source device and display apparatus incorporating same

Abstract

A planar light source device with highly uniform intensity and high light utilization efficiency, and a display apparatus incorporating the same, are provided. A light guide plate, configured by a material such as plate-shaped and transparent acryl resin, polycarbonate resin, or glass, causes incident light to propagate within the light guide plate and then to exit the light through an exit surface as a surface emitting light. A first recess is formed substantially in the center of the exit surface. The first recess is cylinder-shaped, and on a bottom thereof is provided a lens that refracts incident light from a light source, in a direction away from the center of a circle on the bottom.

1 . A planar light source device, comprising;
 a light source; and   a light guide plate that receives light from the light source and that emits from its exit surface the received light as a surface emitting light, the light guide plate including
 a first recess formed on the exit surface, a bottom of the first recess being disposed opposite the light source, and 
 a refraction part, disposed on the bottom of the first recess, that refracts light passing through the bottom toward a side of the first recess so that light having passed through the bottom enters the side of the first recess. 
   
     
     
         2 . The planar light of  claim 1 , wherein the refraction part is a prism array where a plurality of circles is formed whose centers are located at a central portion of the first recess, each circle having a triangle in cross section. 
     
     
         3 . The planar light source device of  claim 2 , wherein among interior angles, formed on the bottom of the first recess, of the triangle forming the prism array, a basic angle b is greater than a basic angle c where a first angle formed away from the center of the first recess is designated as the basic angle b that is 45 degrees or more and smaller than 90 degrees (45°≦b<90° and a second angle formed toward the center of the first recess is designated as the basic angle c that is greater than 45 degrees (c>45°). 
     
     
         4 . The planar light source device of  claim 1 , wherein the first recess of the light guide plate has an oblique face at the side, and is formed so that an opening of the first recess at the exit surface is greater in size than the bottom thereof. 
     
     
         5 . The planar light source device of  claim 1 , wherein the light guide plate further includes, on its other surface opposing the exit surface, a second recess that is located opposite the first recess, the light source being accommodated in the second recess. 
     
     
         6 . The planar light source device of  claim 5 , wherein the second recess includes a convexed portion on a bottom thereof, the convexed portion extending toward an opening of the second recess. 
     
     
         7 . A planar light source device, comprising:
 a light source; and   a light guide plate that propagates therewithin light from the light source and then emits from its exit surface the light as a surface emitting light, the light guide plate including
 a first recess on the exit surface, the first recess being cone-shaped, 
 a second recess that is located opposite the first recess, the light source being accommodated in the second recess 
 a convexed portion on a bottom of the second recess, the convexed portion having a transmission capability and extending toward an opening of the second recess. 
   
     
     
         8 . The planar light source device of  claim 7 , wherein the first recess is formed by a plurality of cone shapes each having an apex thereof in a normal direction from the exit surface toward the opposite surface, the plurality of cone shapes being combined to form a cone-like shape. 
     
     
         9 . The planar light source device of  claim 6 , wherein the convexed portion formed in the second recess is a convex lens having its focal point at a light emission center of the light source. 
     
     
         10 . The planar light source device of  claim 6 , wherein the convexed portion formed in the second recess is a convex lens having its focal point at a location farther away from the convexed portion than a light emission center of the light source. 
     
     
         11 . The planar light source device of  claim 9 , wherein the convex lens has a spherical shape whose conic constant K is greater than −1 and zero or less. 
     
     
         12 . The planar light source device of  claim 11 , wherein conic constant K that defines the shape of a spherical surface forming the convex lens is zero 
     
     
         13 . The planar light source device of  claim 6 , wherein the convexed portion formed in the second recess is a prism array in which a plurality of circles each having a triangular cross section is formed on the bottom of the second recess, a center of each circle being located at a center of the recess. 
     
     
         14 . The planar light source device of  claim 1 , wherein the light source device includes at an opening of the first recess a light intensity adjusting member for adjusting an amount of light to exit from the first recess. 
     
     
         15 . The planar light source device of  claim 14 , wherein the light intensity adjusting member includes a reflective sheet having a reflection capability to reflect light emitted from the light source, and a diffusion sheet having a diffusion capability. 
     
     
         16 . The planar light source device of  claim 15 , wherein the reflective sheet has transmission capability of total light transmission factor of 2% or more. 
     
     
         17 . The planar light source device of  claim 15 , wherein the reflective sheet has diffusion capability to diffuse light passing therethrough. 
     
     
         18 . The planar light source device of  claim 15 , wherein black color printing is made on the reflective sheet. 
     
     
         19 . The planar light source device of  claim 15 , wherein color printing is made on the reflective sheet. 
     
     
         20 . The planar light source device of  claim 19 , wherein the color printing is made in blue color. 
     
     
         21 . The planar light source device of  claim 1 , wherein the light source is a light emitting diode (LED). 
     
     
         22 . A display apparatus comprising:
 a display element at a location facing the exit surface of the planar light source device of  claim 1 .   
     
     
         23 . A planar light source device, comprising:
 a light source; and   a light guide plate that propagates therewithin light from the light source and then emits from its exit surface the light as a surface emitting light, the light guide plate including
 a first recess on the exit surface, the first recess being elliptical cone-shaped, 
 a second recess that is located opposite the first recess, the light source being accommodated in the second recess being elliptic cylindrical, and 
 a convexed portion on a bottom of the second recess, the convexed portion having a transmission capability and extending toward an opening of the second recess. 
   
     
     
         24 . A planar light source device, comprising:
 a light source; and   a light guide plate that propagates therewithin light from the light source and then emits from its exit surface the light as a surface emitting light, the light guide plate including
 a first recess on the exit surface, the first recess being cone-shaped and having an opening of an oval figure, 
 a second recess that is located opposite the first recess, the light source being accommodated in the second recess having an opening of an elongate hole, and 
 a convexed portion on a bottom of the second recess, the convexed portion having a transmission capability and extending toward an opening of the second recess. 
   
     
     
         25 . The planar light source device of  claim 6 , wherein the convexed portion formed in the second recess is a Fresnel lens in which a saw-toothed shape in cross section is formed on the bottom of the second recess, and configured by a straight line portion substantially perpendicular to the exit surface and a curve line portion connecting with the straight line portion.