Curable pressure-sensitive adhesive sheet, multi-layer sheet and liquid crystal display device

Abstract

The curable pressure-sensitive adhesive sheet A of this invention comprises an optically transparent substrate on which the curable pressure-sensitive adhesive layer 2 is layered on and integrated therewith. The curable pressure-sensitive adhesive layer 2 comprises a curable pressure-sensitive adhesive composite comprising a cationically-polymerizable compound, a polymer and a photocationic polymerization initiator. Surface roughness R t of a surface of the curable pressure-sensitive adhesive layer is 2 μm or less.

What is claimed is:  
     
         1 . A curable pressure-sensitive adhesive sheet in which a curable pressure-sensitive adhesive layer is layered on and integrated with a surface of an optically transparent substrate, said curable pressure-sensitive adhesive layer comprising; 
 a curable pressure-sensitive adhesive composite having a cationically polymerizable compound, a polymer, and a photocationic polymerization initiator,    wherein a surface roughness R t  of a surface of the curable pressure-sensitive adhesive layer is 2 μm or less.    
     
     
         2 . The curable pressure-sensitive adhesive sheet as claimed in  claim 1 , wherein a surface of the substrate on which the curable pressure-sensitive adhesive layer is layered, has a surface roughness R t  of 2 μm or less.  
     
     
         3 . The curable pressure-sensitive adhesive sheet as claimed in  claim 1 , wherein the pressure-sensitive adhesive layer has a storage modulus of 9.0×10 5  Pa or less, by dynamic viscoelasticity spectrum at 23° C. before hardening, and has a storage modulus of 4.0×10 6  Pa or more, by dynamic viscoelasticity spectrum at 23° C. after hardening.  
     
     
         4 . The curable pressure-sensitive adhesive sheet as claimed in  claim 2 , wherein the pressure-sensitive adhesive layer has a storage modulus of 9.0×10 5  Pa or less, by dynamic viscoelasticity spectrum at 23° C. before hardening, and has a storage modulus of 4.0×10 6  Pa or more, by dynamic viscoelasticity spectrum at 23° C. after hardening.  
     
     
         5 . The curable pressure-sensitive adhesive sheet as claimed in  claim 3 , wherein the curable pressure-sensitive adhesive layer has a storage modulus of 1.0×10 4 ˜9.0×10 5  Pa, by dynamic viscoelasticity spectrum at 23° C. before hardening, and has a storage modulus of 4.0×10 6 ˜1.0×10 10  Pa, by dynamic viscoelasticity spectrum at 23° C. after hardening.  
     
     
         6 . The curable pressure-sensitive adhesive sheet as claimed in  claim 4 , wherein the curable pressure-sensitive adhesive layer has a storage modulus of 1.0×10 4 ˜9.0×10 5  Pa, by dynamic viscoelasticity spectrum at 23° C. before hardening, and has a storage modulus of 4.0×10 6 ˜1.0×10 10  Pa, by dynamic viscoelasticity spectrum at 23° C. after hardening.  
     
     
         7 . A multi-layer sheet comprising; 
 an optically transparent substrate,    a cured pressure-sensitive adhesive layer formed by hardening a curable pressure-sensitive layer of a curable pressure-sensitive adhesive sheet in which the curable pressure-sensitive adhesive layer is layered on and integrated with a surface of the optically transparent substrate, and    a light-diffusing sheet having a lens surface; a part of a lens element of the lens surface being embedded in a surface of the cured pressure-sensitive adhesive layer,    wherein the curable pressure-sensitive adhesive layer comprises a curable pressure-sensitive adhesive composite having a cationically-polymerizable compound, a polymer, and a photocationic polymerization initiator and the said curable pressure-sensitive adhesive layer has a surface roughness R t  of 2 μm or less.    
     
     
         8 . The multi-layer sheet as claimed in  claim 7 , further comprising a polarizer layered on and integrated with another surface of the substrate in the multi-layer sheet via a pressure-sensitive adhesive layer or an adhesive layer.  
     
     
         9 . A liquid crystal display device comprising; 
 a multi-layer sheet including an optically transparent substrate, a cured pressure-sensitive adhesive layer formed by hardening a curable pressure-sensitive layer of a curable pressure-sensitive adhesive sheet in which the curable pressure-sensitive adhesive layer is layered on and integrated with a surface of the optically transparent substrate,    a light-diffusing sheet having a lens surface; a part of a lens element of the lens surface being embedded in a surface of the cured pressure-sensitive adhesive layer,    a polarizer layered on and integrated with another surface of the substrate in the multi-layer sheet via a pressure-sensitive adhesive layer or an adhesive layer, and    a liquid crystal display element; said display element being layered on and integrated with the multi-layer sheet via the polarizer,    wherein the curable pressure-sensitive adhesive layer comprises a curable pressure-sensitive adhesive composite having a cationically-polymerizable compound, a polymer, and a photocationic polymerization initiator and the said curable pressure-sensitive adhesive layer has a surface roughness R t  of 2 μm or less.