Transparent double-sided self-adhesive sheet

Abstract

A transparent double-sided self-adhesive sheet is provided which, when bonding to an adherend, not only excels in the ability to conform to steps or surface irregularities caused by a printing site, but also excels in workability such as cutting processability. A transparent double-sided self-adhesive sheet is proposed, having an intermediate resin layer (A) and pressure-sensitive adhesive layers (B) as front and reverse side layers, each of the layers being a layer having one or more species of (meth)acrylic acid ester series (co)polymer as the base resin, in which transparent double-sided self-adhesive sheet, the shear storage elastic modulus (G′(A)) at a frequency of 1 Hz of the intermediate resin layer (A) is higher than the pressure-sensitive adhesive layers (B) in a temperature range of 0° C. to 100° C., and, the indentation hardness (ASKER C2 hardness) of the entire sheet is 10 to 80.

1 - 13 . (canceled) 
     
     
         14 . An image display device structural member, comprising:
 a transparent double-sided self-adhesive sheet adhered into a single body between two members,   wherein at least one of the two members is a protective panel having a step on a surface contacted with the transparent double-sided self-adhesive sheet,   wherein the transparent double-sided self-adhesive sheet consists of three layers,   wherein the three layers consist of an intermediate layer (A) and two pressure-sensitive adhesive surface layers (B) as front and reverse side layers, wherein each of the three layers is formed from a composition comprising a (meth)acrylic acid ester copolymer as a base resin, and   wherein the transparent double-sided self-adhesive sheet has:   an indentation hardness, ASKER C2 hardness, of from 10 to 80, and   a creep value measured by the following method comprising (a) to (d) is from 1 mm to 15 mm:   a) adhering one side of the sheet to a vertically standing SUS plate wherein an adhesion surface area is 15 mm×20 mm,   b) curing the sheet under an atmosphere of 60° C. for 15 minutes,   c) applying a weight of 4.9 N to the sheet in the vertical direction, and then   d) measuring the creep value of an adhesion position at the end of 60 minutes.   
     
     
         15 . The image display device structural member of  claim 14 , wherein the intermediate layer (A) of the transparent double-sided self-adhesive sheet is a layer comprising a crosslinked structure of the (meth)acrylic acid ester copolymer. 
     
     
         16 . The image display device structural member of  claim 15 , wherein a shear storage elastic modulus at a frequency of 1 Hz of the intermediate layer (A) is greater than a shear storage elastic modulus of the two pressure-sensitive adhesive surface layers (B) at a temperature of from 0° C. to 100° C. 
     
     
         17 . The image display device structural member of  claim 15 , wherein the indentation hardness, ASKER C2 hardness, of the transparent double-sided self-adhesive sheet is from 10 to 60. 
     
     
         18 . The image display device structural member of  claim 15 , wherein the indentation hardness, ASKER C2 hardness, of the transparent double-sided self-adhesive sheet is from 25 to 80. 
     
     
         19 . The image display device structural member of  claim 15 ,
 wherein the transparent double-sided self-adhesive sheet satisfies the following thickness ratio between the intermediate layer (A) and the two pressure-sensitive adhesive layers (B):
   0.5<( A )/( B )<10, and 
   wherein a thickness of the two pressure-sensitive adhesive layers (B) is from 10 μm to 200 μm.   
     
     
         20 . The image display device structural member of  claim 17 , wherein the transparent double-sided self-adhesive sheet satisfies the following thickness ratio between the intermediate layer (A) and the two pressure-sensitive adhesive layers (B):
   0.5<( A )/( B )<10, and   wherein a thickness of the two pressure-sensitive adhesive layers (B) is from 10 μm to 200 μm.   
     
     
         21 . The image display device structural member of  claim 15 , wherein the transparent double-sided self-adhesive sheet has a value of Tan δ (B) for the two pressure-sensitive adhesive layers (B) of from 0.4 to 1.4 at a temperature of from 0° C. to 100° C. 
     
     
         22 . The image display device structural member of  claim 17 , wherein the transparent double-sided self-adhesive sheet has a value of Tan δ (B) for the two pressure-sensitive adhesive layers (B) of from 0.4 to 1.4 at a temperature of from 0° C. to 100° C. 
     
     
         23 . The image display device structural member of  claim 14 , wherein the transparent double-sided self-adhesive sheet has a shear storage elastic modulus, G′(A), of the intermediate layer (A) of from 5×10 3  to 5×10 8  Pa at a temperature of from 0° C. to 100° C., and
 wherein a shear storage elastic modulus, G′(A), of the intermediate layer (A) and a shear storage elastic modulus, G′(B), of any of the two pressure-sensitive adhesive layers (B) satisfy the following relationship at a temperature of from 0° C. to 100° C.:
   1.1< G ′( A )/ G ′( B )<80.
 
 
 
     
     
         24 . The image display device structural member of  claim 14 , wherein each layer of the intermediate layer (A) and the two pressure-sensitive adhesive layers (B) is formed from a composition further comprising a photopolymerization initiator. 
     
     
         25 . The image display device structural member of  claim 15 , wherein each layer of the intermediate layer (A) and the two pressure-sensitive adhesive layers (B) is formed from a composition further comprising a photopolymerization initiator. 
     
     
         26 . The image display device structural member of  claim 24 , wherein only the intermediate layer (A) is a layer comprising the crosslinked structure of the (meth)acrylic acid ester copolymer. 
     
     
         27 . The image display device structural member of  claim 25 , wherein only the intermediate layer (A) is a layer comprising the crosslinked structure of the (meth)acrylic acid ester copolymer. 
     
     
         28 . The image display device structural member of  claim 14 , wherein the (meth)acrylic acid ester copolymer comprises monomer components comprising a first monomer A and a second monomer B,
 wherein the first monomer A has a glass transition temperature when it has become homopolymer of from −100° C. to 0° C., and comprises at least one selected from a group consisting of ethyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, hydroxyethyl acrylate, hydroxybutyl acrylate, and glycidyl (meth)acrylate; and   wherein the second monomer B has a glass transition temperature when it has become homopolymer of from 0° C. to 250° C., and comprises at least one selected from a group consisting of methyl (meth)acrylate, vinyl acetate, acrylic acid, glycidyl (meth)acrylate, acrylamide, acrylonitrile, and methacrylonitril.   
     
     
         29 . The image display device structural member of  claim 28 , wherein a difference in the glass transition temperatures between the second monomer B and the first monomer A, the second monomer B−the first monomer A, is from 25° C. to 300° C. 
     
     
         30 . The image display device structural member of  claim 15 , wherein the crosslinked structure consists of crosslinked (meth)acrylic acid ester copolymer that is formed with at least one crosslinker selected from the group consisting of a multifunctional (meth)acrylate having two or more (meth)acryloyl groups; a multi-functional organofunctional group resin having two or more organic functional groups selected from a group consisting of an isocyanate group, epoxy group, melamine group, glycol group, siloxane group and amino group; and an organic compound comprising a metal complex of zinc, aluminum, sodium, zirconium, or calcium. 
     
     
         31 . The image display device structural member of  claim 14 , wherein a thickness of the transparent double-sided self-adhesive sheet is from 50 μm to 350 μm.