(Meth)acrylic copolymer, adhesive composition containing same, and adhesive sheet
A (meth)acrylic copolymer (A) having a mass average molecular weight of 50,000 to 1,000,000, in which the (meth)acrylic copolymer (A) is obtained by polymerizing a monomer mixture including a macromonomer (a) that has a number average molecular weight of 500 or more and less than 6000 and a vinyl monomer (b), and preferably includes 7 to 40% by mass of a repeat unit derived from the macromonomer (a), has sufficient coating workability, adhesive holding power and adhesive property as an adhesive composition.
1. An adhesive composition comprising a (meth)acrylic copolymer (A) having a mass average molecular weight of 50,000 to 1,000,000,
wherein the (meth)acrylic copolymer (A) is obtained by polymerizing a monomer mixture comprising a macromonomer (a) having a number average molecular weight of 1,900 or more and 4,500 or less and a vinyl monomer (b),
wherein the monomer (a) is represented by Formula (1):
where in Formula (1),
n is 4 to 5,999;
each of R and R 1 to R n is independently a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group, in which the alkyl group, the cycloalkyl group, the aryl group or the heterocyclic group optionally have a substituent;
each of X 1 to X n is independently a hydrogen atom or a methyl group; and
Z is a terminal group of the macromonomer (a),
wherein the (meth)acrylic copolymer (A) comprises 7 to 30% by mass of a repeat unit derived from the macromonomer (a),
wherein the adhesive composition is in a solution state in the presence of at least one of a solvent and a liquid vinyl monomer, or is a hot melt-based adhesive composition without solvent.
2. The adhesive composition according to claim 1 , wherein the (meth)acrylic copolymer (A) comprises 9 to 20% by mass of a repeat unit derived from the macromonomer (a).
3. The adhesive composition according to claim 1 , wherein the glass transition temperature (Tga) of the macromonomer (a) is 30 to 120° C.
4. The adhesive composition according to claim 1 , wherein the melt viscosity at 130° C. of the (meth)acrylic copolymer (A) is 20 to 800 Pa·s.
5. An adhesive sheet using the adhesive composition according to claim 1 .
6. The adhesive composition according to claim 2 , wherein the glass transition temperature (Tga) of the macromonomer (a) is 30 to 120° C.
7. The adhesive composition according to claim 2 , wherein the (meth)acrylic copolymer (A) has a melt viscosity at 130° C. of 20 to 800 Pa·s.
8. The adhesive composition according to claim 3 , wherein the (meth)acrylic copolymer (A) has a melt viscosity at 130° C. of 20 to 800 Pa·s.
9. An adhesive sheet using the adhesive composition according to claim 2 .
10. An adhesive sheet using the adhesive composition according to claim 3 .
11. An adhesive sheet using the adhesive composition according to claim 4 .
12. An adhesive sheet using the adhesive composition according to claim 8 .
13. The adhesive composition according to claim 1 , wherein the macromonomer (a) has a number average molecular weight of 3,500 or less.
14. The adhesive composition according to claim 1 , wherein the macromonomer (a) has a number average molecular weight of 2,600 or less.
15. The adhesive composition according to claim 1 , wherein the terminal group of the macromonomer (a) is selected from the group consisting of a methacryloyl group, an acryloyl group, a vinyl group and a terminal polymerizable functional group represented by the following Formula (2):
wherein R z represents R, R 1 to R n in Formula (1).
16. The adhesive composition according to claim 1 , wherein
the macromonomer (a) is obtained from methyl (meth)acrylate and isobornyl (meth)acrylate.
17. The adhesive composition according to claim 16 , wherein
a ratio of methyl (meth)acrylate to isobornyl (meth)acrylate is approximately 50/50.