Photocurable adhesive composition

1. A photocurable adhesive composition comprising:

a) a (meth)acrylate oligomer having one or more functional groups,

b) a mono-functional monomer, a multi-functional monomer, or a mixture thereof,

c) a photoinitiator, and

d) a plasticizer having a refractive index of no less than 1.48, wherein the plasticizer is selected from the group consisting of phosphates, alkyl sulfonic esters, polyol esters, epoxies and a mixture thereof.

2. The adhesive composition according to claim 1 , wherein the (meth)acrylate oligomer is selected from the group consisting of a urethane (meth)acrylate, an epoxy (meth)acrylate, a polyester (meth)acrylate, a (meth)acrylate and a mixture thereof.

3. The adhesive composition according to claim 2 , wherein the (meth)acrylate oligomer is a urethane (meth)acrylate.

4. The adhesive composition according to claim 1 , wherein the amount of the (meth)acrylate oligomer based on the total weight of the composition is from about 20% to about 90%.

5. The adhesive composition according to claim 4 , wherein the amount of the (meth)acrylate oligomer based on the total weight of the composition is from about 40% to about 85%.

6. The adhesive composition according to claim 1 , wherein the mono-functional (meth)acrylate monomer is selected from the group consisting of methyl methacrylate, butyl methacrylate, 2-phenoxy ethyl acrylate, ethoxylated 2-phenoxy ethyl acrylate, 2-(2-ethoxyethoxy)ethyl acrylate, cyclic trimethylolpropane formal acrylate, β-carboxyethyl acrylate, lauryl methacrylate, isooctyl acrylate, stearyl methacrylate, isodecyl acrylate, isobornyl methacrylate, benzyl acrylate, 2-hydroxyethyl metharcrylate phosphate, hydroxyethyl acrylate, 2-hydroxyethyl methacrylate and a mixture thereof; and the multi-functional (meth)acrylate is selected from the group consisting of hydroxypivalyl hydroxypivalate diacrylate, ethoxylated 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, tricyclodecane dimethanol diacrylate, ethoxylated dipropylene glycol diacrylate, neopentyl glycol diacrylate, propoxylated neopentyl glycol diacrylate, ethoxylated bisphenol-A dimethacrylate, 2-methyl-1,3-propanediol diacrylate, ethoxylated 2-methyl-1,3-propanediol diacrylate, 2-butyl-2-ethyl-1,3-propanediol diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, tris(2-hydroxy ethyl) isocyanurate triacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, propoxylated pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, tripropylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, allylated cyclohexyl dimethacrylate, isocyanurate dimethacrylate, ethoxylated trimethylolpropane trimethacrylate, propoxylated glycerol trimethacrylate, tris(acryloxyethyl) isocyanurate, trimethylolpropane triacrylate and a mixture thereof.

7. The adhesive composition according to claim 1 , wherein the amount of component b) based on the total weight of the composition is from about 5% to about 80%.

8. The adhesive composition according to claim 7 , wherein the amount of component b) based on the total weight of the composition is from about 5% to about 40%.

9. The adhesive composition according to claim 1 , wherein the photoinitiator is selected from the group consisting of benzophenone, benzoin, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxy cyclohexyl phenyl ketone, 2,4,6-trimethylbenzoyl diphenyl phosphine oxide and a mixture thereof.

10. The adhesive composition according to claim 9 , wherein the photoinitiator is benzophenone, 1-hydroxy cyclohexyl phenyl ketone or 2,4,6-trimethylbenzoyl diphenyl phosphine oxide.

11. The adhesive composition according to claim 1 , wherein the amount of the photoinitiator based on the total weight of the composition is from about 0.1% to about 5%.

12. The adhesive composition according to claim 11 , wherein the amount of the photoinitiator based on the total weight of the composition is from about 0.5% to about 3%.

13. The adhesive composition according to claim 1 , wherein the plasticizer has a refractive index of no less than 1.49.

14. The adhesive composition according to claim 1 , wherein the plasticizer is a phosphate of the following formula (2) or (3):

where R 3 , R 4 and R 5 can be the same or different, and each independently represent a straight or branched C 1 -C 12 alkyl or phenyl, wherein said phenyl can be optionally substituted with one to three straight or branched C 1 -C 4 alkyl; R 6 represents a straight or branched C 1 -C 12 alkylene or phenylene, wherein said phenylene can be optionally substituted with one to three straight or branched C 1 -C 4 alkyl; and m is an integer from 1 to 30.

15. The adhesive composition according to claim 14 , wherein the plasticizer is a phosphate of the following formula (4):

where the occurrences of n can be the same or different, and each independently represent 0, 1, 2 or 3; and the occurrences of R can be the same or different, and each independently represent a straight or branched C 1 -C 4 alkyl.

16. The adhesive composition according to claim 14 , wherein the plasticizer is a phosphate of the following formula (5):

where the occurrences of n can be the same or different, and each independently represent 0, 1, 2 or 3; m is an integer from 1 to 15; and the occurrences of R can be the same or different, and each independently represent a straight or branched C 1 -C 4 alkyl.

17. The adhesive composition according to claim 14 , wherein the plasticizer is selected from the group consisting of triphenyl phosphate, tricresyl phosphate, tri(isopropylphenyl) phosphate, cresyl diphenyl phosphate, tetraphenyl resorcinol diphosphate, poly(triphenyl phosphate), poly(cresyl diphenyl phosphate) and a mixture thereof.

18. The adhesive composition according to claim 1 , wherein the amount of the plasticizer based on the total weight of the composition is from about 1% to about 60%.

19. The adhesive composition according to claim 18 , wherein the amount of the plasticizer based on the total weight of the composition is from about 5% to about 50%.

20. The adhesive composition according to claim 1 for use in a display or touch panel.