Light-emitting device
View Patent ↗Provided is a light-emitting device provided with a light reflection layer which has a high light reflectivity and which is less susceptible to deterioration of the reflectivity due to corrosion, and having an improved light extraction efficiency. A light-emitting device comprising a substrate having a conductor layer formed on its surface and a light-emitting element disposed on the conductor layer, characterized in that an overcoat layer is formed between the conductor layer and the light-emitting element, and the overcoat layer is a borosilicate glass which comprises, as represented by mol % based on oxides, from 62 to 84% of SiO 2 , from 10 to 25% of B 2 O 3 , from 0 to 5% of Al 2 O 3 and from 0 to 5% in total of at least one of Na 2 O and K 2 O, provided that the total content of SiO 2 and Al 2 O 3 is from 62 to 84%, and may contain from 0 to 10% of MgO and at least one of CaO, SrO and BaO in a total content of at most 5%.
1. A light-emitting device, comprising:
a substrate having a conductor layer formed on a surface thereof;
a light-emitting element disposed on the conductor layer; and
an overcoat layer formed between the conductor layer and the light-emitting element;
wherein the overcoat layer is made a borosilicate glass, the borosilicate glass comprising, by mol % based on oxides:
62 to 84% of SiO 2 ;
10 to 25% of B 2 O 3 ;
0 to 5% of Al 2 O 3 ;
0 to 5% in total of at least one of Na 2 O and K 2 O;
62 to 84% in total of SiO 2 and Al 2 O 3 ;
0 to 10% of MgO; and
0 to 5% of at least one of CaO, SrO, and BaO.
2. The light-emitting device according to claim 1 , further comprising a phosphor layer, wherein the phosphor layer emits visible light when excited by light radiated from the light-emitting element.
3. The light-emitting device according to claim 1 , wherein:
the surface of the substrate comprises a terminal area to which the light-emitting element is electrically connected; and
the overcoat layer is provided in a region other than the terminal area.
4. The light-emitting device according to claim 1 , wherein:
the substrate comprises a concave region; and
the light-emitting element is disposed on a bottom surface of the concave region.
5. The light-emitting device according to claim 1 , wherein the borosilicate glass comprises, by mol % based on oxides:
78 to 82% of SiO 2 ;
16 to 18% of B 2 O 3 ; and
0.9 to 4% in total of at least one of Na 2 O and K 2 O.
6. The light-emitting device according to claim 1 , wherein the borosilicate glass comprises, by mol % based on oxides:
72 to 78% of SiO 2 ;
13 to 18% of B 2 O 3 ;
0.9 to 4% in total of at least one of Na 2 O and K 2 O; and
2 to 10% of MgO.
7. The light-emitting device according to claim 1 , wherein the overcoat layer has an elution amount of at most 30 μg/cm 2 when immersed in an oxalic acid solution with pH 1.68 at 85° C. for 1 hour.
8. The light-emitting device according to Claim 1 , wherein the overcoat layer covers the conductor layer.
9. The light-emitting device according to claim 1 , wherein the substrate is made of an inorganic material.
10. The light-emitting device according to claim 1 , wherein the overcoat layer is formed by firing.
11. The light-emitting device according to claim 1 , wherein the substrate is made of a low temperature co-fired ceramic.
12. The light-emitting device according to claim 1 , wherein the conductor layer is a silver conductor layer.
13. The light-emitting device according to claim 1 , wherein the conductor layer is formed by firing a paste.
14. The light-emitting device according to claim 1 , wherein:
the substrate is made of an inorganic material; and
the conductor layer is in contact with the substrate.
15. A light-emitting device, comprising:
a substrate having a conductor layer formed on a surface thereof;
a light-emitting element disposed on the conductor layer; and
an overcoat layer formed between the conductor layer and the light-emitting element;
wherein:
the overcoat layer comprises, by mass %, at least 60% of a borosilicate glass and at most 40% of a ceramics filler; and
the borosilicate glass comprises, by mol % based on oxides:
62 to 84% of SiO 2 ;
10 to 25% of B 2 O 3 ;
0 to 5% of Al 2 O 3 ;
0 to 5% in total of at least one of Na 2 O and K 2 O;
62 to 84%, in total of SiO 2 and Al 2 O 3 ;
0 to 10% of MgO; and
0 5% in total of at least one of CaO, SrO and BaO.
16. The light-emitting device according to claim 15 , wherein the ceramics filler is alumina.
17. The light-emitting device according to claim 15 , wherein the overcoat layer covers the conductor layer.
18. The light-emitting device according to claim 15 , wherein the substrate is made of an inorganic material.
19. The light-emitting device according to claim 15 , wherein the overcoat layer is formed by firing.
20. The light-emitting device according to claim 15 , wherein the substrate is made of a low temperature co-fired ceramic.
21. The light-emitting device according to claim 15 , wherein the conductor layer is a silver conductor layer.
22. The light-emitting device according to claim 15 , wherein the conductor layer is formed by firing a paste.
23. The light-emitting device according to claim 15 , further comprising a phosphor layer, wherein the phosphor layer emits visible light when excited by light radiated from the light-emitting element.
24. The light-emitting device according to claim 15 , wherein:
the surface of the substrate comprises a terminal area to which the light-emitting element is electrically connected; and
the overcoat layer is provided in a region other than the terminal area.
25. The light-emitting device according to claim 15 , wherein:
the substrate comprises a concave region; and
the light-emitting element is disposed on a bottom surface of the concave region.
26. The light-emitting device according to claim 15 , wherein the borosilicate glass comprises, by mol % based on oxides:
78 to 82% of SiO 2 ;
16 to 18% of B 2 O 3 ; and
0.9 to 4% in total of at least one of Na 2 O and K 2 O.
27. The light-emitting device according to claim 15 , wherein the borosilicate glass comprises, by mol % based on oxides:
72 to 78% of SiO 2 ;
13 to 18% of B 2 O 3 ;
0.9 to 4% in total of at least one of Na 2 O and K 2 O; and
2 to 10% of MgO.
28. The light-emitting device according to claim 15 , wherein the overcoat layer has an elution amount of at most 30 μg/cm 2 when immersed in an oxalic acid solution with pH 1.68 at 85° C. for 1 hour.