Photo-curable liquid optically clear adhesive composition and the use thereof

1. A photo-curable liquid optically clear adhesive composition, comprising:

(a) at least one (meth)acrylic copolymer having a weight average molecular weight of from about 10000 to about 600000 g/mol and a glass transition temperature of from about −40° C. to about 40° C., wherein the (meth)acrylic copolymer is a reaction product of monomers selected from the group consisting of a (meth)acrylamide monomer, a hydroxyl group containing (meth)acrylic monomer, an C 1 -C 20 alkyl (meth)acrylate monomer and combinations thereof,

(b) at least one non-functional (meth)acrylic monomer,

(c) at least one photo initiator, and

(d) at least one functional (meth)acrylic monomer,

wherein the adhesive has a Brookfield viscosity at 25° C. of about 1000 to about 100000 mPa·s, and, when photo-cured to a cure ratio of at least 95%, is tacky and capable of being laminated to a surface.

2. The adhesive composition according to claim 1 , wherein the non-functional (meth)acrylic monomer (b) is selected from the group consisting of mono-, di-, tri- and tetra-(meth)acrylic monomers and combinations thereof.

3. The adhesive composition according to claim 2 , wherein the mono-, di-, tri- and tetra-(meth)acrylic monomers are selected from the group consisting of n-butyl (meth) acrylate, iso-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, iso-decyl (meth) acrylate, iso-octyl (meth)acrylate, iso-stearyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, caprolactone (meth)acrylate, N-(meth)acryloyl morpholine, dicyclopentenyloxyethyl (meth) acrylate, dicyclopentadienyl (meth) acrylate, 2-(2-ethoxyethoxy) ethyl (meth)acrylate, methoxy polyethylene glycol (meth)acrylate, cyclohexyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, benzyl (meth) acrylate, tetramethylene dimethacrylate, ethylene dimethacrylate, cyclohexanedimethylol di(meth)acrylate, dicyclopentadienedimethylol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, nonanediol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, 1,4-butanediol diacrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and combinations thereof.

4. The adhesive composition according to claim 1 , wherein the (meth)acrylamide monomer of component (a) is selected from the group consisting of caprolactone (meth) acrylate, N,N-dimethyl (meth) acrylamide, N-methyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, N-t-butyl (meth)acrylamide, N-phenyl (meth)acrylamide and N-methylol (meth)acrylamide, N-(meth)acryloylmorpholine, N-(meth)acryloylpyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine and N-(meth) acryloyl-4-piperidone and combinations thereof.

5. The adhesive composition according to claim 1 , wherein the C 1 -C 20 alkyl (meth)acrylate monomer of component (a) is selected from the group consisting of methyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, iso-decyl (meth)acrylate, iso-octyl (meth)acrylate, iso-stearyl (meth)acrylate, lauryl (meth)acrylate, n-stearyl (meth)acrylate, isobornyl (meth) acrylate, dicyclopentenyloxyethyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, cyclohexyl (meth)acrylate and combinations thereof.

6. The adhesive composition according to claim 1 , wherein the hydroxyl group containing(meth)acrylic monomers of component (a) are selected from the group consisting of hydroxylalkyl (meth)acrylates, the ethoxylated and propoxylated derivatives thereof, the adducts thereof with lactones and polyalkoxy monohydroxyl mono(meth)acrylates, and combinations thereof.

7. The adhesive composition according to claim 1 , wherein the (meth)acrylic copolymer is a reaction product of the monomers selected from at least two of the group consisting of 2-ethylhexyl (meth)acrylate, N-(meth)acryloyl morpholine, isobutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate.

8. The adhesive composition according to claim 1 , wherein the (meth)acrylic copolymer has a weight average molecular weight of from about 30000 to about 300000 g/mol.

9. The adhesive composition according to claim 1 , wherein the (meth)acrylic copolymer has a glass transition temperature of from about −35° C. to about 30° C.

10. The adhesive composition according to claim 1 , wherein the amount of component (a) is from about 30 to about 95% by weight, based on the total weight of the adhesive composition.

11. The adhesive composition according to claim 1 , wherein the non-functional (meth)acrylic monomer (b) is selected from the group consisting of 2-(2-ethoxyethoxy) ethyl (meth) acrylate, pentaerythritol tetra(meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, and combinations thereof.

12. The adhesive composition according to claim 1 , wherein the amount of non-functional (meth)acrylic monomer (b) is from about 2 to about 60% by weight based on the total weight of the adhesive composition.

13. The adhesive composition according to claim 1 , wherein the photo initiator (c) is selected from the group consisting of acetophenones, acylphosphine oxides, benzoin ethers, and combinations thereof.

14. The adhesive composition according to claim 1 , wherein the amount of photo initiator (c) is from about 0.02 to about 5% by weight based on the total weight of the adhesive composition.

15. The adhesive composition according to claim 1 , wherein the functional (meth)acrylic monomer (d) is selected from (meth)acrylic monomers having at least one functional group selected from a hydroxyl, an amide, a carboxyl, a tetrahydrofurfuryl, a morpholine, an amino, and an isocyanate group.

16. The adhesive composition according to claim 1 , wherein the functional (meth)acrylic monomer (d) is selected from (meth)acryloyl morphiline, caprolactone acrylate, tetrahydrofurfuryl acrylate, and combinations thereof.

17. The adhesive composition according to claim 1 , wherein the amount of functional (meth)acrylic monomer (d) is about 0.5 to about 30% by weight based on the total weight of the adhesive composition.

18. The adhesive composition according to claim 1 , wherein the Brookfield viscosity of the adhesive composition at 25° C. is from about 1500 to about 50000 mPa·s according to ASTM D1084.

19. The adhesive composition according to claim 1 , wherein the hydroxyl group containing (meth)acrylic monomers of component (a) are selected from the group consisting of hydroxylalkyl (meth)acrylates and ethoxylated and propoxylated derivatives thereof, adducts thereof with lactones and polyalkoxy monohydroxyl mono(meth)acrylates and ethoxylated and/or propoxylated derivatives thereof, and adducts thereof with lactones and polyalkoxy monohydroxyl mono(meth)acrylates, and combinations thereof.

20. The adhesive composition according to claim 1 , wherein the hydroxyl group containing (meth)acrylic monomers of component (a) are selected from the group consisting of hydroxylalkyl (meth)acrylates having from about 1 to about 20 carbon atoms in the alkyl group and ethoxylated and/or propoxylated derivatives thereof, β-carboxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, (meth)acrylates of glycidyl versatate, and combinations thereof.

21. The adhesive composition according to claim 1 , wherein the (meth)acrylic copolymer has a weight average molecular weight of from about 50000 to about 200000 g/mol.

22. The adhesive composition according to claim 1 , wherein the amount of component (a) is from about 50 to about 90% by weight, based on the total weight of the adhesive composition.

23. The adhesive composition according to claim 1 , wherein the amount of non-functional (meth)acrylic monomer (b) is from about 10 to about 50% by weight, based on the total weight of the adhesive composition.

24. The adhesive composition according to claim 1 , wherein the photo initiator (c) is selected from the group consisting of 2-hydroxyl-2-methylpropiophenone, 1-hydroxycyclohexyl phenyl ketone, bis(2,4,6-trimethylbenzoy)phenylphosphine oxide, benzoin methyl ether, benzoin ethyl ether, and combinations thereof.

25. The adhesive composition according to claim 1 , wherein the amount of photo initiator (c) is from about 0.5 to about 4.0% by weight, based on the total weight of the adhesive composition.

26. The adhesive composition according to claim 1 , wherein the amount of functional (meth)acrylic monomer (d) is about 1 to about 10% by weight, based on the total weight of the adhesive composition.

27. An article comprising the adhesive composition according to claim 1 .

28. A cured adhesive produced from the adhesive composition according to claim 1 .

29. An article comprising the adhesive composition of the cured adhesive according to claim 28 .

30. A curing method, comprising curing the photo-curable liquid optically clear adhesive composition according to claim 1 by exposure to electromagnetic radiation having a wavelength ranging from 200 nm to 500 nm to a curing ratio of at least about 95%.

31. A laminating process for binding a top substrate to a base substrate, comprising:

(a) applying the photo-curable liquid optically clear adhesive composition according to claim 1 onto the top side of the base substrate,

(b) curing the photo-curable liquid optically clear adhesive composition by exposure to electromagnetic radiation having a wavelength ranging from 200 nm to 500 nm to a curing ratio of at least about 95%, and

(c) attaching the top substrate on the cured adhesive layer of step (b).