Dispersion-type acrylic copolymer

1. A dispersion-type acrylic copolymer comprising a matrix (I) formed of an acrylic copolymer with a glass transition temperature of 50° C. or higher and a polymer unit (II) formed of an acrylic copolymer with a glass transition temperature of less than 50° C., in which the polymer unit (II) forms a localized region having an average diameter of 5 to 300 nm in the matrix (I), the matrix (I) and polymer unit (II) contain units of a crosslinking component, and the content of the units of a crosslinking component is more than 2% by mass relative to the total weight of the acrylic copolymer.

2. The dispersion-type acrylic copolymer according to claim 1 , wherein the localized region has an average diameter of 10 to 250 nm.

3. The dispersion-type acrylic copolymer according to claim 1 , wherein the localized region has an average area of 20 to 50000 nm 2 .

4. The dispersion-type acrylic copolymer according to claim 1 , wherein the localized region has an average area of 80 to 35000 nm 2 .

5. The dispersion-type acrylic copolymer according to claim 1 , wherein the acrylic copolymer for forming the matrix (I) has a glass transition temperature of 80° C. or higher.

6. The dispersion-type acrylic copolymer according to claim 1 , wherein the crosslinking component is represented by the following general formula (1):

CH 2 ═CR—COO—(X) n —COCR═CH 2   (1)

wherein (X) is at least one repeating unit selected from a group consisting of C 2 H 4 O, C 3 H 6 O, and C 4 H 8 O, molecular weight of (X) n , is 500 or more, and R is H or CH 3 .

7. The dispersion-type acrylic copolymer according to claim 1 , wherein the crosslinking component is represented by the following general formula (2):

CH 2 ═CR—COO—(C 4 H 8 O) n —COCR═CH 2   (2)

wherein molecular weight of (C 4 H 8 O) n is 500 or more and R is H or CH 3 .

8. A dispersion-type acrylic copolymer obtained by polymerizing a monomer mixture containing a (meth)acrylic acid ester monomer (A), a di(meth)acrylic acid ester monomer (B) represented by the following general formula (1) in which molecular weight of (X) n , is 2500 or more, and a di(meth)acrylic acid ester monomer (C) represented by the following general formula (1) in which molecular weight of (X) n , is 500 to 1800, in which mass composition of the monomer mixture is within a region surrounded by the point [60,6,34], the point [91,6,3], and the point [60,37,3] of a ternary phase diagram of [(A),(B),(C)]:

CH 2 ═CR—COO—(X) n —COCR═CH 2   (1)

wherein (X) is at least one repeating unit selected from a group consisting of C 2 H 4 O, C 3 H 6 O, and C 4 H 8 O and R is H or CH 3 .

9. A dispersion-type acrylic copolymer obtained by polymerizing, at temperature condition of 30 to 90° C., a monomer mixture containing 60 to 97.5% by mass of a (meth)acrylic acid ester monomer (A), and 2.5 to 40% by mass of a di(meth)acrylic acid ester monomer (B) represented by the following general formula (1) in which molecular weight of (X) n , is 2500 or more:

CH 2 ═CR—COO—(X) n —COCR═CH 2   (1)

wherein (X) is at least one repeating unit selected from a group consisting of C 2 H 4 O, C 3 H 6 O, and C 4 H 8 O and R is H or CH 3 .

10. The dispersion-type acrylic copolymer according to claim 8 , wherein (X) is C 4 H 8 O.

11. An acrylic sheet formed of the dispersion-type acrylic copolymer according to claim 1 .

12. The acrylic sheet according to claim 11 , wherein the sheet has a thickness of 0.01 to 30 mm.

13. The acrylic sheet according to claim 12 , wherein the elongation at break is 10% or more at elongation rate of 5 mm/minute when the thickness is 3 mm.

14. The acrylic sheet according to claim 12 , wherein the haze is 25% or less when the thickness is 3 mm.

15. The acrylic sheet according to claim 12 , wherein the total light transmittance is 80% or more when the thickness is 3 mm.

16. A dispersion-type acrylic copolymer obtained by polymerizing a monomer mixture containing a (meth)acrylic acid ester monomer (A), a di(meth)acrylic acid ester monomer (B) represented by the following general formula (2) with n ≧35, and a di(meth)acrylic acid ester monomer (C) represented by the following general formula (2) with 7≦n≦25, in which mass composition of the monomer mixture is within a region surrounded by the point [60,6,34], the point [91,6,3], and the point [60,37,3] of a ternary phase diagram of [(A),(B),(C)]:

CH 2 ═CR—COO—(C 4 H 8 O) n —COCR═CH 2   (2)

with the proviso that R is H or CH 3 .

17. The dispersion-type acrylic copolymer according to claim 9 , wherein (X) is C 4 H 8 O.