Photo-curable adhesive composition, its preparation and use thereof
The present invention relates to a photo-curable adhesive composition comprising a (meth)acrylate capped aliphatic polyurethane having an average number of ethylenically unsaturated groups less than 1, a mono-functional (meth)acrylate monomer or oligomer and a photoinitiator. The adhesive composition can be used in a method of bonding a substrate to a liquid crystal display. The adhesive composition according to the present invention has improved side curing depth.
1. A photo-curable adhesive composition comprising
a) a (meth)acrylate capped aliphatic polyurethane having an average functionality from 0.01 to 0.99 and comprising structure I and structure III, and optionally structure II,
wherein X denotes C1-C20 alkyl, cycloalkyl, alkenyl, acryl or aralkyl terminated with (meth)acrylate;
Y denotes C1-C20 alkyl, cycloalkyl, alkenyl, acyl or aralkyl group;
A denotes polyether, polyester, polycarbonate or polyhydrocarbon; and
B denotes C1-C10 alkyl, cycloalkyl, alkenyl, acyl or alkyl groups; and n is integer from 1 to 500;
b) a (meth)acrylate monomer selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-(2-ethoxyethoxy) ethyl acrylate, tetrahydrofurfuryl (meth)acrylate, lauryl acrylate, isooctyl acrylate, n-octyl acrylate, isodecyl acrylate, n-decyl acrylate, isobornyl acrylate, 2-phenoxythyl acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2(or 4)-hydroxybutyl (meth)acrylate, caprolactone acrylate, morpholine (meth)acrylate, behenyl acrylate, n-hexyl acrylate, 2-propylheptyl acrylate, and mixtures thereof; and
c) an initiator selected from the group consisting of a photoinitiator.
2. A photo-curable adhesive composition according to claim 1 , wherein said (meth)acrylate capped aliphatic polyurethane has the number average molecular weight from 1000 to 100,000.
3. A photo-curable adhesive composition according to claim 1 , wherein said (meth)acrylate capped aliphatic polyurethane has average functionality from 0.01 to 0.3.
4. A photo-curable adhesive composition according to claim 1 , wherein the composition comprises a (meth)acrylate capped aliphatic polyurethane from 5% to 95% by weight of the total weight of the composition.
5. A photo-curable adhesive composition according to claim 1 , wherein the composition comprises a (meth)acrylate monomer from 5% to 95% by weight of the total weight of the composition.
6. A photo-curable adhesive composition according to claim 1 , wherein the composition comprises a photoinitiator from 0.05% to 5% by weight of the total weight of the composition.
7. A photo-curable adhesive according to claim 1 , wherein, said composition has a thixotropic Index greater than 3, wherein the thixotropic index is measured according to the standard ASTM D2196-10.
8. A photo-cured adhesive composition according to claim 1 , wherein said cured composition has a modulus greater than 10000 and less than 150000.
9. The photo-cured adhesive composition according to claim 1 , wherein said cured composition has a side curing depth greater than 2.0 cm.
10. A method of bonding a substrate to a liquid crystal display comprising steps of:
i) applying the adhesive composition according to claim 1 onto the surface of substrate or liquid crystal display or both;
ii) contacting the surfaces of substrate and liquid crystal display; and
iii) UV curing the adhesive composition.
11. A display device or touch panel comprising the photo-cured adhesive composition according to claim 10 , wherein said cured adhesive composition is in a form of optically clear laminates.