Photocurable adhesive composition

Abstract

Provided is a photocurable adhesive composition which causes no damage to adherends during bonding and which, when used in bonding rugged adherends, can bond the adherends without forming a gap therebetween. The photocurable adhesive composition of the present invention comprises (A) 100 parts by mass of a urethane (meth)acrylate oligomer having a weight-average molecular weight of 20,000 to 100,000, (B) 5 parts to 70 parts by mass of a phenoxy resin, and (C) 0.1 parts to 10 parts by mass of a photopolymerization initiator. The uncured composition has a loss tangent (loss modulus/storage modulus) of less than 1 at 25° C. and the temperature at which the loss tangent of the uncured composition reaches 1 or more is 80° C. or less.

1 . A photocurable adhesive composition comprising
 (A) 100 parts by mass of a urethane (meth)acrylate oligomer having a weight-average molecular weight in a range of 20,000 to 100,000,   (B) 5 parts to 70 parts by mass of a phenoxy resin, and   (C) 0.1 parts to 10 parts by mass of a photopolymerization initiator,   wherein an uncured composition of the photocurable adhesive composition has a loss tangent (loss modulus/storage modulus) of less than 1 at 25° C., and   the temperature at which the loss tangent of the uncured composition reaches 1 or more is 80° C. or less.   
     
     
         2 . The photocurable adhesive composition according to  claim 1 , wherein the uncured composition has a loss tangent of 0.1 to 0.6 at 25° C. 
     
     
         3 . The photocurable adhesive composition according to claim  1  or  2 , wherein the temperature at which the loss tangent of the uncured composition reaches 1 or more is in a range of 40° C. to 80° C. 
     
     
         4 . The photocurable adhesive composition according to  claim 1  or  2 , wherein the uncured composition is solid at 25° C. and melts at a temperature in a range of 40° C. to 80° C. 
     
     
         5 . The photocurable adhesive composition according to  claim 1  or  2 , wherein the uncured composition is in a form of sheet or film. 
     
     
         6 . The photocurable adhesive composition according to  claim 1  or  2 , wherein a cured composition of the photocurable adhesive composition has an elastic modulus of 1.0×10 5  Pa to 1.0×10 7  Pa. 
     
     
         7 . The photocurable adhesive composition according to  claim 1  or  2 , wherein the cured composition has a total light transmittance of 85% or more. 
     
     
         8 . The photocurable adhesive composition according to  claim 1  or  2  for bonding a liquid crystal panel. 
     
     
         9 . A laminate structure bonded with the photocurable adhesive composition according to  claim 1  or  2 . 
     
     
         10 . A laminate structure comprising a liquid crystal panel and a cover panel thereof bonded with the adhesive composition according to  claim 1  or  2 .