Emission device, surface light source device, display and light flux control member

Abstract

A display has a member irradiated by a surface light source device comprising a light diffusion member and emission device. The emission device is provided with a light flux control member having a recess and light control emission face which is configurated so as to satisfy Conditions 1 and 2 in a range at least covering a half-intensity-angular-range. Light emitting element(s) may be sealed. Condition 1 is that relation θ5/θ1>1 is satisfied except for light emitted from a light emitting element toward within an angular-neighbourhood of a standard optical axis of the emission device, and Condition 2 is that value of θ5/θ1 decreases gradually according to increasing of θ1, where θ1 is an emission angle of any light at being emitted from the light emitting element, and θ5 is an emission angle of that light of θ1 at then being emitted from the light control emission face of the light flux control member.

What is claimed is: 
     
       1. An emission device comprising a light flux control member provided with a recess and an light control emission face, and a light emitting element accommodated in said recess, said light emitting element emits light which is emitted from said light control emission face after travelling within said light flux control member,
 wherein said light control emission face is configured so as to satisfy the following Conditions 1 and 2 for at least light which is emitted toward within a half-intensity-angular-range around a maximum-intensity-emission-direction from said light emitting element;
 Condition 1: Relation θ 5 /θ 1 >1 is satisfied except for light emitted toward within an angular-neighborhood of a standard optical axis of said emission device; 
 Condition 2: Value of θ 5 /θ 1  decreases gradually according to increasing of θ 1 ; 
   
       where θ 1  is an emission angle of any light at being emitted from said light emitting element, and θ 5  is an emission angle of that light of θ 1  at then being emitted from said light control emission face of said light flux control member. 
     
     
       2. The emission device in accordance with  claim 1 , wherein said recess provides a concave surface which is in contact with an light emitting surface of said light emitting element. 
     
     
       3. The emission device in accordance with  claim 1 , wherein said recess provides a concave surface and a gap is formed between said concave surface and an light emitting surface of said light emitting element. 
     
     
       4. The emission device in accordance with  claim 1 ,  2  or  3 , wherein said light control emission face includes a first emission face region crossing with said standard optical axis and a second emission face region extending around said first emission face region, said first and second emission face regions having a connecting portion in which a point of inflection exists. 
     
     
       5. A surface light source device comprising an emission device and a light diffusion member which diffuses and transmits light from said emission device,
 wherein said emission device is an emission device in accordance with  claim 1 ,  2  or  3 .   
     
     
       6. A surface light source device comprising an emission device and a light diffusion member which diffuses and transmits light from said emission device,
 wherein said emission device is an emission device in accordance with  claim 4 .   
     
     
       7. The surface light source device comprising an emission device and a light diffusion member which diffuses and transmits light from said emission device,
 wherein said emission device is an emission device in accordance with  claim 5 .   
     
     
       8. The surface light source device comprising an emission device and a light diffusion member which diffuses and transmits light from said emission device,
 wherein said emission device is an emission device in accordance with  claim 6 .   
     
     
       9. The emission device in accordance with  claim 1 , wherein said light emitting element is sealed by a sealing material so that light emitted from said light emitting element impinges on said light flux control member after transmitting through said sealing material. 
     
     
       10. The emission device in accordance with  claim 9 , wherein said recess provides a concave surface which is in contact with an outer surface of said sealing material. 
     
     
       11. The emission device in accordance with  claim 9 , wherein said recess provides a concave surface and a gap is formed between said concave surface and an outer surface of said sealing material. 
     
     
       12. The emission device in accordance with  claim 9 ,  10  or  11 , wherein said light control emission face includes a first emission face region crossing with said standard optical axis and a second emission face region extending around said first emission face region, said first and second emission face regions having a connecting portion in which a point of inflection exists. 
     
     
       13. The surface light source device comprising an emission device and a light diffusion member which diffuses and transmits light from said emission device,
 wherein said emission device is an emission device in accordance with  claim 9 ,  10  or  11 .   
     
     
       14. The surface light source device comprising an emission device and a light diffusion member which diffuses and transmits light from said emission device,
 wherein said emission device is an emission device in accordance with  claim 12 .   
     
     
       15. The surface light source device comprising an emission device and a light diffusion member which diffuses and transmits light from said emission device,
 wherein said emission device is an emission device in accordance with  claim 13 .   
     
     
       16. The surface light source device comprising an emission device and a light diffusion member which diffuses and transmits light from said emission device,
 wherein said emission device is an emission device in accordance with  claim 14 .   
     
     
       17. A light flux control member provided with a recess for accommodating a light emitting element, comprising:
 a light control emission face for causing light coming from said light emitting element after travelling within said light flux control member to be emitted,   wherein said light control emission face is configured so as to satisfy the following Conditions 1 and 2 for at least light which is emitted toward within a half-intensity-angular-range around a maximum-intensity-emission-direction from said light emitting element;   Condition 1: Relation θ 5 /θ 1  >1 is satisfied except for light emitted toward within an angular-neighborhood of a standard optical axis of said light flux control member;
 Condition 2: Value of θ 5 /θ 1  decreases gradually according to increasing of θ 1 ; 
   
       where θ 1  is an emission angle of any light at being emitted from said light emitting element, and θ 5  is an emission angle of that light of θ 1  at then being emitted from said light control emission face of said light flux control member. 
     
     
       18. The light flux control member in accordance with  claim 17 , wherein said recess is a recess for accommodating a light emitting element together with a sealing material that seals said light emitting element. 
     
     
       19. A surface light source device comprising:
 an emission device unit comprising a substrate and emission devices disposed on said substrate, each of said emission devices including a light emitting element and a light flux control member for controlling a light distribution of light emitted from said light emitting element; and   a diffuser disposed over said emission device unit,   wherein said light flux control member includes a light incidence surface on which light emitted from said light emitting element is incident, and an light control emission face which emits light incident on said incidence surface,   said light control emission face is configured so as to satisfy the following Conditions 1 and 2 for at least light which is emitted toward within a half-intensity-angular-range around a maximum-intensity-emission-direction from said light emitting element, and thereby the at least light which is emitted toward within said half-intensity-angular-range around said maximum-intensity-emission-direction from said light emitting element is expanded smoothly;   Condition 1: Relation θ5/θ1>1 is satisfied except for light emitted toward within an angular-neighborhood of a standard optical axis of said emission device;   Condition 2: Value of θ5/θ1 decreases gradually according to increasing of θ1;   where θ1 is an emission angle of any light at being emitted from said light emitting element, and θ5 is an emission angle of that light of θ1 at then being emitted from said light control emission face of said light flux control member,   said emission devices are disposed on said substrate at predetermined intervals so that light from said emission devices adjacent to each other are mixed,   said diffuser is disposed over said emission device unit such that light from said emission devices adjacent to each other are mixed between said emission devices and said diffuser, and   said light emitted from said emission device is directly applied to the diffuser and does not travel through another element disposed between said emission device and said diffuser.   
     
     
       20. The surface light source device in accordance with claim 19, wherein said light control emission face has a substantially circular shape when viewed along said standard optical axis. 
     
     
       21. The surface light source device in accordance with claim 19, wherein said light control emission face includes a first emission face region existing within a predetermined range from said standard optical axis and a second emission face region extending around said first emission face region, said first emission face region having a concave shape being shaped like a partially removed sphere, said first emission face region and second emission face region having a connecting portion in which a point of inflection exists. 
     
     
       22. The surface light source device in accordance with claim 21, wherein θ3 decreases gradually according to increasing of θ1 in said first emission face region, and θ3 increases gradually according to increasing of θ1 in said second emission face region, where θ3 is an angle between a line perpendicular to said standard optical axis and a line being a tangent of said light control emission face at a pass position at which that light of θ1 is emitted from said light control emission face. 
     
     
       23. The surface light source device in accordance with claim 19, wherein a gap is formed between said light incidence surface and a light emitting surface of said light emitting element. 
     
     
       24. The surface light source device in accordance with claim 19, wherein said light emitting element is sealed by a sealing material. 
     
     
       25. The surface light source device in accordance with claim 24, wherein a gap is formed between said light incidence surface and an outer surface of said sealing material. 
     
     
       26. The surface light source device in accordance with claim 19, wherein said emission devices are disposed on said substrate at predetermined intervals such that light from said emission devices adjacent to each other across said emission device are mixed between said emission devices and said diffuser. 
     
     
       27. The emission device to be used in said surface light source device in accordance with claim 19. 
     
     
       28. A display comprising:
 said surface light source device in accordance with claim 19; and   a display member to be irradiated with light emitted from said surface light source device.