UV-curable pressure-sensitive adhesive composition and its pressure-sensitive adhesive sheet

Abstract

Provided are a UV-curable pressure-sensitive adhesive composition comprising a photoinitiator which has a molar absorptivity at 365 nm of at least 1,000 mol −1 ·cm −1 and the maximum absorption wavelength of at least 420 nm on a long wavelength side; and an adhesive sheet having a layer of the composition disposed over a photo-transmitting base film. The pressure-sensitive adhesive sheet according to the invention can be cured even by exposure to ultraviolet rays at a low intensity or for short time so that it can contribute to energy saving and productivity improvement as a sheet for processing, fixation or surface protection of a semiconductor wafer.

What is claimed is:  
     
         1 . A UV-curable pressure-sensitive adhesive composition comprising a photoinitiator which has a molar absorptivity at 365 nm of at least 1,000 mol −1 ·cm −1  and a maximum absorption wavelength of at least 420 nm on a long wavelength side.  
     
     
         2 . The UV-curable pressure-sensitive adhesive composition according to    claim 1   , which contains the photoinitiator in an amount of 0.4 to 20 wt. % based on the whole pressure-sensitive adhesive composition in terms of solid content.  
     
     
         3 . The UV-curable pressure-sensitive adhesive composition according to    claim 1   , wherein the photoinitiator is 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl)-butanone-1.  
     
     
         4 . The UV-curable pressure-sensitive adhesive composition according to    claim 1   , wherein the photoinitiator is bis (2,4,6-trimethylbenzoyl)-phenylphosphine oxide.  
     
     
         5 . A UV-curable pressure-sensitive adhesive composition, which comprises: 
 a pressure-sensitive adhesive polymer;    a polymerization component; and    a photoinitiator,    wherein the photoinitiator has a molar absorptivity at 365 nm of at least 1,000 mol −1 ·cm −1  and a maximum absorption wavelength of at least 420 nm on a long wavelength side, and the UV-curable pressure-sensitive adhesive composition contains the photoinitiator in an amount of 0.4 to 20 wt. % based on the whole pressure-sensitive adhesive composition in terms of solid content.    
     
     
         6 . A pressure-sensitive adhesive sheet comprising: 
 a photo-transmitting base film; and    a layer comprising a UV-curable pressure-sensitive adhesive composition as claimed in    claim 1   .    
     
     
         7 . The pressure-sensitive adhesive sheet according to    claim 6   , which is for use in processing, fixation or surface protection of a semiconductor wafer.