Sheet for solar cell encapsulant and solar cell module
A sheet for solar cell encapsulant including (A) an ethylene copolymer selected from 1a to 5a; and (B) an ethylene copolymer selected from 1b to 3b, the copolymer (A) having a melting point of 90° C. or higher and containing constituent unit derived from ethylene [1a: ethylene-vinyl acetate (VA) copolymer, 2a: ethylene-acrylate copolymer, 3a: high-pressure method low-density polyethylene, 4a: ethylene-α-olefin copolymer, 5a: ethylene-G(M)A copolymer other than the below-described 1b, 1b: ethylene-G(M)A copolymer, 2b: ethylene-VA-G(M)A copolymer, 3b: ethylene-acrylate-G(M)A copolymer]. In the ethylene copolymer (B), the total ratio of the constituent unit derived from glycidyl(meth)acrylate (G(M)A) is preferably from 2% to 30% by mass. As a result of this, crosslinking treatment is substantially unnecessary, and practical adhesion and adhesion stability are achieved without heat treatment for crosslinking.
1. A sheet for a solar cell encapsulant consisting of:
at least one ethylene copolymer (A) selected from the group consisting of the following (1a) to (4a), the ethylene copolymer (A) having a melting point of 90° C. or higher and containing a constituent unit derived from ethylene:
(1a) an ethylene-vinyl acetate copolymer wherein a content ratio of a constituent unit derived from vinyl acetate is 15% by mass or less;
(2a) an ethylene-acrylate copolymer wherein a content ratio of a constituent unit derived from acrylate is 15% by mass or less;
(3a) a high-pressure method low-density polyethylene; and
(4a) an ethylene-α-olefin copolymer having a density of 0.895 g/cm 3 or more;
at least one ethylene copolymer (B) selected from the group consisting of the following (1 b) to (3b):
(1b) an ethylene-glycidyl (meth)acrylate copolymer;
(2b) an ethylene-vinyl acetate-glycidyl (meth)acrylate copolymer wherein a content ratio of a constituent unit derived from vinyl acetate is 30% by mass or less; and
(3b) an ethylene-acrylate-glycidyl (meth)acrylate copolymer wherein a content ratio of a constituent unit derived from acrylate is 30% by mass or less;
optionally a copolymer (C) obtained by copolymerization of at least α-olefin and an ethylenically unsaturated silane compound;
optionally a silane coupling agent (D); and
optionally an ultraviolet absorber, a light stabilizer, an antioxidant, or combinations thereof.
2. The sheet for a solar cell encapsulant according to claim 1 , wherein the ethylene copolymer (A) and the ethylene copolymer (B) have a melt flow rate (JIS K7210-1999, 190° C., load of 2160 g) of from 0.1 g/10 minutes to 50 g/10 minutes.
3. The sheet for a solar cell encapsulant according to claim 1 consisting of:
the ethylene copolymer (A);
the ethylene copolymer (B);
the copolymer (C); and
optionally the ultraviolet absorber, the light stabilizer, the antioxidant, or combinations thereof.
4. The sheet for a solar cell encapsulant according to claim 1 consisting of:
the ethylene copolymer (A);
the ethylene copolymer (B);
the silane coupling agent (D); and
optionally the ultraviolet absorber, the light stabilizer, the antioxidant, or combinations thereof.
5. The sheet for a solar cell encapsulant according to claim 1 consisting of:
the ethylene copolymer (A);
the ethylene copolymer (B);
the copolymer (C); and
the silane coupling agent (D); and
optionally the ultraviolet absorber, the light stabilizer, the antioxidant, or combinations thereof.
6. The sheet for a solar cell encapsulant according to claim 3 , wherein the copolymer (C) further comprises a constituent unit derived from at least one of vinyl acetate or acrylate.
7. The sheet for a solar cell encapsulant according to claim 1 , wherein the ethylene-α-olefin copolymer (4a) of the ethylene copolymer (A) is an ethylene-propylene copolymer, an ethylene-1-butene copolymer, an ethylene-4-methyl-1-pentene copolymer, or an ethylene-1-hexene copolymer.
8. The sheet for a solar cell encapsulant according to claim 3 , wherein the α-olefin of the copolymer (C) is at least one of ethylene, propylene, 1-butene, isobutylene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 1-heptene, 1-octene, 1-nonene, or 1-decene.
9. The sheet for a solar cell encapsulant according to claim 3 , wherein the ethylenically unsaturated silane compound is selected from vinylsilane and (meth)acryloxysilane.
10. The sheet for a solar cell encapsulant according to claim 3 , wherein the ethylenically unsaturated silane compound is vinyltrimethoxysilane or γ-methacryloxypropyltrimethoxysilane.
11. A solar cell module comprising at least a substrate at which sunlight is incident, a solar cell element, and the sheet for a solar cell encapsulant according to claim 1 .
12. The sheet for a solar cell encapsulant according to claim 1 , wherein the ethylene-α-olefin copolymer (4a) of the ethylene copolymer (A) is an ethylene-1-butene copolymer, an ethylene-4-methyl-1-pentene copolymer, or an ethylene-1-hexene copolymer.
13. The sheet for a solar cell encapsulant according to claim 1 , wherein the ethylene-α-olefin copolymer (4a) of the ethylene copolymer (A) is an ethylene-1-butene copolymer.
14. The sheet for a solar cell encapsulant according to claim 1 , wherein the ethylene-α-olefin copolymer (4a) of the ethylene copolymer (A) is an ethylene-4-methyl-1-pentene copolymer.
15. The sheet for a solar cell encapsulant according to claim 1 , wherein the ethylene-α-olefin copolymer (4a) of the ethylene copolymer (A) is an ethylene-1-hexene copolymer.
16. The sheet for a solar cell encapsulant according to claim 1 , wherein the ethylene copolymer (A) is the ethylene-vinyl acetate copolymer (1a) and the ethylene copolymer (A) optionally further comprises one or more selected from the group consisting of the following (2a) to (4a):
(2a) the ethylene-acrylate copolymer;
(3a) the high-pressure method low-density polyethylene; and
(4a) the ethylene-α-olefin copolymer.
17. The sheet for a solar cell encapsulant according to claim 1 , wherein the ethylene copolymer (A) is the ethylene-acrylate copolymer (2a) and the ethylene copolymer (A) optionally further comprises one or more selected from the group consisting of the following (1a), (3a), and (4a):
(1a) the ethylene-vinyl acetate copolymer;
(3a) the high-pressure method low-density polyethylene; and
(4a) the ethylene-α-olefin copolymer.
18. The sheet for a solar cell encapsulant according to claim 1 , wherein the ethylene copolymer (B) is the ethylene-vinyl acetate-glycidyl (meth)acrylate copolymer (2b) and the ethylene copolymer (B) optionally further comprises one or more selected from the group consisting of the following (1 b) and (3b):
(1 b) the ethylene-glycidyl (meth)acrylate copolymer; and
(3b) the ethylene-acrylate-glycidyl (meth)acrylate copolymer.
19. The sheet for a solar cell encapsulant according to claim 1 , wherein the ethylene copolymer (B) is the ethylene-acrylate-glycidyl (meth)acrylate copolymer (3b) and the ethylene copolymer (B) optionally further comprises one or more selected from the group consisting of the following (1 b) and (2b):
(1 b) the ethylene-glycidyl (meth)acrylate copolymer; and
(2b) the ethylene-vinyl acetate-glycidyl (meth)acrylate copolymer.
20. The sheet for a solar cell encapsulant according to claim 1 , wherein the ethylene copolymer (B) is selected from the group consisting of the following (2b) and (3b):
(2b) the ethylene-vinyl acetate-glycidyl (meth)acrylate copolymer; and
(3b) the ethylene-acrylate-glycidyl (meth)acrylate copolymer.