Adhesive composition

1. An adhesive composition comprising:

(a) at least one acidic group-containing polymerizable monomer selected from the group consisting of a phosphate group-containing polymerizable monomer, a pyrophosphate group-containing polymerizable monomer, a thiophosphate group-containing polymerizable monomer and a sulfonate group-containing polymerizable monomer;

(b) a polymerizable monomer represented by the general formula (I):

wherein R 1 is hydrogen atom or methyl group; R 2 is a halogen atom, hydroxyl group, mercapto group or —O—R 3 —OH group, wherein R 3 is an alkylene group having 6 to 25 carbon atoms; and Y is oxygen atom or sulfur atom; and

(c) at least one hydrophilic polymerizable monomer selected from the group consisting of hydroxyalkyl (meth)acrylates having an alkylene group of 2 or 3 carbon atoms; di-, tri- or tetra-hydroxy (meth)acrylates having an alkylene group of 3 to 5 carbon atoms; mono-, di- or tri-hydroxy di(meth)acrylates having an alkylene group of 3 to 5 carbon atoms; (meth)acryloyloxyalkyl trialkylammonium halides having an alkylene group of 2 to 20 carbon atoms; (meth)acrylamides; mono- or di(hydroxyalkyl) (meth)acrylates having 2 or 3 carbon atoms; and

polyethylene glycol di(meth)acrylates having at least 9 oxyethylene groups, wherein the weight ratio of the polymerizable monomer (b)/acidic group-containing polymerizable monomer (a) is 0.001 to 0.5.

2. The adhesive composition according to claim 1 , wherein the acidic group-containing polymerizable monomer (a) is a phosphate group-containing polymerizable monomer.

3. The adhesive composition according to claim 2 , wherein the phosphate group-containing polymerizable monomer is represented by the general formula (II):

wherein R 4 is hydrogen atom or methyl group; R 5 is an alkylene group having 6 to 25 carbon atoms; and R 6 is hydrogen atom, an alkyl group or phenyl group.

4. The adhesive composition according to claim 1 , wherein the polymerizable monomer (b) is a hydroxyl group-containing polymerizable monomer represented by the general formula (III):

wherein R 1 is hydrogen atom or methyl group; and R 7 is an alkylene group having 6 to 25 carbon atoms.

5. The adhesive composition according to claim 1 , wherein the acidic group containing polymerizable monomer (a) is a phosphate group-containing polymerizable monomer represented by the general formula (II):

wherein R 4 is hydrogen atom or methyl group; R 5 is an alkylene group having 6 to 25 carbon atoms; and R 6 is hydrogen atom, an alkyl group or phenyl group, and the polymerizable monomer (b) is a hydroxyl group-containing polymerizable monomer represented by the general formula (III):

wherein R 1 is hydrogen atom or methyl group; and R 7 is an alkylene group having 6 to 25 carbon atoms, and R 5 is identical to R 7 .

6. The adhesive composition according to claim 1 , wherein the polymerizable monomer (b) comprises a hydroxyl group-containing polymerizable monomer represented by the general formula (III):

wherein R 1 is hydrogen atom or methyl group; and R 7 is an alkylene group having 6 to 25 carbon atoms, and a polymerizable monomer represented by the general formula (IV):

wherein R 1 is hydrogen atom or methyl group; R 8 is a halogen atom, hydroxyl group or mercapto group; and Y is oxygen atom or sulfur atom.

7. The adhesive composition according to claim 1 , further comprising (d) 10 water.

8. The adhesive composition according to claim 1 , further comprising (e) a polymerization initiator.

9. The adhesive composition according to claim 1 , wherein the acidic group-containing polymerizable monomer (a) is a pyrophosphate group-containing polymerizable monomer.

10. The adhesive composition according to claim 1 , wherein the acidic group-containing polymerizable monomer (a) is a thiophosphate group-containing polymerizable monomer.

11. The adhesive composition according to claim 1 , wherein the acidic group-containing polymerizable monomer (a) is a sulfonate group-containing polymerizable monomer.

12. The adhesive composition according to claim 6 , wherein a weight ratio of the monomer of formula (III) to the monomer of formula (IV) is 0.005 to 200.

13. The adhesive composition according to claim 6 , wherein a weight ratio of the monomer of formula (III) to the monomer of formula (IV) is 0.05 to 20.

14. The adhesive composition according to claim 1 , wherein the weight ratio of the polymerizable monomer (b)/acidic group-containing polymerizable monomer (a) is 0.005 to 0.3.

15. The adhesive composition according to claim 1 , wherein the weight ratio of the polymerizable monomer (b)/acidic group-containing polymerizable monomer (a) is 0.01 to 0.1.

16. The adhesive composition according to claim 1 , wherein the hydrophilic polymerizable monomer (c) has a solubility of at least 10%.

17. The adhesive composition according to claim 1 , wherein the amount of water is 0.1 to 80% by weight.

18. A coating, comprising:

the adhesive composition according to claim 1 .

19. The coating according to claim 18 , having a thickness of at least 10 μm.

20. The adhesive composition according to claim 1 , which is cured.