Surface light emitting device

1. A surface light emitting device, comprising:

an organic EL element having a first face and a second face opposite to said first face, said organic EL element configured to emit light from said first face;

a protection substrate having transparency for light emitted from said organic EL element, said protection substrate facing said first face, and said protection substrate having a primary surface facing said first face of said organic EL element;

a protector facing said second face of said organic EL element, said protector configured to constitute a housing in combination with said protection substrate, and said housing configured to accommodate said organic EL element to protect said organic EL element from water; and

a light extractor interposed between said first face of said organic EL element and said protection substrate, said light extractor configured to suppress reflection of light emitted from said organic EL element on at least one of said first face of said organic EL element and said primary surface of said protection substrate.

2. A surface light emitting device as set forth in claim 1 , wherein

said organic EL element comprises a light-emitting layer configured to emit light and a formation substrate having transparency for light emitted from said light-emitting layer, and

said light-emitting layer is provided over a first surface of said formation substrate, and

said first face of said organic EL element is defined by a second surface of said formation substrate opposite to said first surface, and

said formation substrate has a refractive index higher than a refractive index of said protection substrate.

3. A surface light emitting device as set forth in claim 2 , wherein said protection substrate has a weatherproof property and a waterproof property higher than a weatherproof property and a waterproof property of said formation substrate.

4. A surface light emitting device as set forth in claim 3 , wherein

said formation substrate is a plastic substrate, and

said protection substrate is a glass substrate.

5. A surface light emitting device as set forth in claim 2 , wherein

said light extractor is a recessed and protruded structure provided to said first face of said organic EL element, and

said protection substrate forms a space between said recessed and protruded structure and said protection substrate, said protection substrate having a refractive index higher than a refractive index of a medium filling the space.

6. A surface light emitting device as set forth in claim 5 , wherein said recessed and protruded structure has a refractive index equal to or higher than a refractive index of said formation substrate.

7. A surface light emitting device as set forth in claim 5 , wherein

said recessed and protruded structure includes a periodic recessed and protruded structure, and

said recessed and protruded structure has a period in a range of one fourth to ten times a wavelength of light emitted from said organic EL element.

8. A surface light emitting device as set forth in claim 5 , wherein

said recessed and protruded structure is in surface contact with said primary surface of said protection substrate.

9. A surface light emitting device as set forth in claim 5 , wherein

said primary surface of said protection substrate has a recess configured to accommodate said recessed and protruded structure, and

said space is a gap between an inner surface of said recess and a surface of said recessed and protruded structure.

10. A surface light emitting device as set forth in claim 1 , wherein

said surface light emitting device further comprises a light transmitter having transparency for light emitted from said organic EL element and a refractive index not greater than a refractive index of said protection substrate, and

said light extractor is a recessed and protruded structure provided to said first face of said organic EL element, and

said light transmitter is interposed between said recessed and protruded structure and said protection substrate.

11. A surface light emitting device as set forth in claim 1 , wherein

said light extractor includes a matrix placed in contact with said first face of said organic EL element, and light-diffusing members dispersed in said matrix, and

said matrix has a refractive index not less than a refractive index of part of said organic EL element in contact with said matrix, and

said light-diffusing members have a refractive index different from a refractive index of said matrix.

12. A surface light emitting device as set forth in claim 11 , wherein said light-diffusing members are fine particles.

13. A surface light emitting device as set forth in claim 1 , wherein

said light extractor includes a matrix in contact with said first face of said organic EL element, and holes provided inside said matrix, and

said matrix has a refractive index which is not less than a refractive index of part of said organic EL element in contact with said matrix and is different from that of a medium filling said holes.

14. A surface light emitting device as set forth in claim 2 , wherein

said surface light emitting device further comprises a transparent portion having transparency for light emitted from said organic EL element and a refractive index not less than a refractive index of said formation substrate, and

said light extractor is a recessed and protruded structure provided to said primary surface of said protection substrate, and

said transparent portion is interposed between said recessed and protruded structure and said formation substrate.

15. A surface light emitting device as set forth in claim 14 , wherein said recessed and protruded structure has a refractive index not greater than a refractive index of said protection substrate.

16. A surface light emitting device as set forth in claim 14 , wherein

said recessed and protruded structure includes a periodic recessed and protruded structure, and

said recessed and protruded structure has a period in a range of one fourth to ten times a wavelength of light emitted from said organic EL element.

17. A surface light emitting device as set forth in claim 1 , wherein

said surface light emitting device further comprises a heat dissipater interposed between said second face of said organic EL element and said protector and configured to transmit heat generated at said organic EL element to said protector, and

said organic EL element is fixed to said protector and not in contact with said protection substrate.

18. A surface light emitting device as set forth in claim 1 , wherein

said protection substrate has a secondary surface opposite to said primary surface of said protection substrate, and

an antireflection coating is provided to at least one of said primary surface and said secondary surface of said protection substrate.

19. A surface light emitting device as set forth in claim 1 , wherein

said protection substrate has a secondary surface opposite to said primary surface of said protection substrate, and

a moth-eye structure is provided to at least one of said primary surface and said secondary surface of said protection substrate.

20. A surface light emitting device as set forth in claim 1 , wherein

said surface light emitting device comprises a plurality of said organic EL elements, and

the plurality of said organic EL elements is arranged in a plane parallel to said primary surface of said protection substrate.

21. A surface light emitting device as set forth in claim 1 , wherein

said protector has an inner face facing said second face of said organic EL element, and

a light reflector is provided to said inner face of said protector part and is configured to reflect light emitted from said organic EL element.

22. A surface light emitting device as set forth in claim 1 , wherein

said protector has transparency for light emitted from said organic EL element, and

said protector has an inner face facing said second face of said organic EL element and an outer face opposite to said inner face, and

said protector is provided at said outer face with a light reflector configured to reflect light emitted from said organic EL element.

23. A surface light emitting device as set forth in claim 1 , wherein

said surface light emitting device further comprises a heat transferor having thermal conductivity greater than a thermal conductivity of said protector, and

said protector has an inner face facing said second face of said organic EL element and an outer face opposite to said inner face, and

said heat transferor is provided to said outer face of said protector.