Curable composition

1. A curable composition, which comprises

100 parts by weight of a vinyl polymer (I) a main chain of which is a product of living radical polymerization, and which contains at least one crosslinkable silyl group, and

1 to 50 parts by weight of a graft copolymer (III) obtained by graft polymerization of a crosslinkable rubber-like acrylic ester polymer and a vinyl monomer,

wherein the curable composition is transparent and wherein the curable composition has a viscosity proportion of 1.1 or higher.

2. The curable composition according to claim 1 wherein the vinyl polymer (I) has a molecular weight distribution of less than 1.8.

3. The curable composition according to claim 1 wherein a vinyl monomer constituting the main chain of the vinyl polymer (I) is mainly selected from the group consisting of (meth)acrylic monomers, acrylonitrile monomers, aromatic vinyl monomers, fluorine-containing vinyl monomers and silicon-containing vinyl monomers.

4. The curable composition according to claim 1 wherein the main chain of the vinyl polymer (I) is a (meth)acrylic polymer.

5. The curable composition according to claim 1 wherein the main chain of the vinyl polymer (I) is an acrylic polymer.

6. The curable composition according to claim 5 wherein the main chain of the vinyl polymer (I) is an acrylic ester polymer.

7. The curable composition according to claim 1 wherein the living radical polymerization for producing the main chain of the vinyl polymer (I) is the atom transfer radical polymerization.

8. The curable composition according to claim 7 wherein a metal complex used as the catalyst in the atom transfer radical polymerization is a transition metal complex composed of a VII, VIII, IX, X, or XI group element in the periodic table as a central metal.

9. The curable composition according to claim 8 wherein the metal complex used as the catalyst is a complex composed of copper, nickel, ruthenium or iron as a central metal.

10. The curable composition according to claim 9 wherein the metal complex used as the catalyst is a complex of copper.

11. The curable composition according to claim 1 wherein the crosslinkable silyl group of the vinyl polymer (I) is represented by the general formula 1:

—[Si(R 1 ) 2-b (Y) b O] 1 —Si(R 2 ) 3-a (Y) a   (1)

{wherein, R 1 and R 2 are the same or different and each is an alkyl group containing 1 to 20 carbon atoms, an aryl group containing 6 to 20 carbon atoms, an aralkyl group containing 7 to 20 carbon atoms or a triorganosiloxy group represented by (R′) 3 SiO— (in which R′ represents a univalent hydrocarbon group containing 1 to 20 carbon atoms and the three R′ groups may be the same or different) and, when there are two or more R 1 or R 2 groups, they may be the same or different; Y represents a hydroxyl group or a hydrolyzable group and, when there are two or more Y groups, they may be the same or different; a represents 0, 1, 2 or 3, b represents 0, 1 or 2, and 1 represents an integer of 0 to 19, provided that the relation a +1b≧1 should be satisfied}.

12. The curable composition according to claim 1 wherein the crosslinkable silyl group of the vinyl polymer (I) is at the terminus of the main chain.

13. The curable composition according to claim 1 which further comprises a polyoxyalkylene polymer (IV) containing at least one crosslinkable silyl group in an amount within the range of 0.1 to 1,000 parts by weight per 100 parts by weight of the vinyl polymer (I).

14. The curable composition according to claim 1 which comprises no polyoxyalkylene polymer (IV) containing a crosslinkable silyl group(s).

15. The curable composition according to claim 1 which further comprises 0.1 to 20 parts by weight of a tin curing catalyst (V) per 100 parts by weight of the vinyl polymer (I).

16. An adhesive which comprises the curable composition according to claim 1 .