Pressure sensitive adhesive sheet for optics

1. An ultraviolet cross-linkable pressure sensitive adhesive sheet comprising:

a (meth)acrylic copolymer of a monomer containing a (meth)acrylic acid ester having an ultraviolet cross-linkable site,

wherein the ultraviolet cross-linkable site has a benzophenone structure,

wherein the storage modulus of the pressure sensitive adhesive sheet before ultraviolet cross-linking is from 5.0×10 4 to 1.0×10 6 Pa at 30° C. and 1 Hz and 5.0×10 4 Pa or less at 80° C. and 1 Hz, and

wherein the storage modulus of the pressure sensitive adhesive sheet after ultraviolet cross-linking is 1.0×10 3 Pa or more at 130° C. and 1 Hz.

2. The ultraviolet crosslinkable pressure sensitive adhesive sheet as claimed in claim 1 , wherein the ultraviolet crosslinkable site has an (meth)acryloyl structure.

3. The ultraviolet cross-linkable pressure sensitive adhesive sheet as claimed in claim 1 , wherein the monomer contains a hydrophilic monomer and the content of the hydrophilic monomer is from 10 to 30 mass % based on the total mass of monomers.

4. The ultraviolet cross-linkable pressure sensitive adhesive sheet as claimed in claim 1 , wherein the ultraviolet cross-linkable pressure sensitive adhesive sheet further contains diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide.

5. A laminate comprising a first substrate having a step or a bump on at least one surface, a second substrate and the ultraviolet cross-linkable pressure sensitive adhesive sheet claimed in claim 1 , which is disposed between said first substrate and the second substrate, wherein the at least one surface of the first substrate is in contact with the ultraviolet cross-linkable pressure sensitive adhesive sheet and the ultraviolet cross-linkable pressure sensitive adhesive sheet conforms to the step or bump.

6. The laminate as claimed in claim 5 , wherein the first substrate is a surface protective layer and the second substrate is an image display module or a touch panel.

7. A method of producing a laminate, wherein the laminate includes a first substrate having a step or a bump on at least one surface, a second substrate and the ultraviolet cross-linkable pressure sensitive adhesive sheet claimed in claim 1 , which is disposed between the first substrate and the second substrate, the method comprising:

disposing the ultraviolet cross-linkable pressure sensitive adhesive sheet to adjoin the first substrate on said at least one surface side;

disposing said second substrate to adjoin the ultraviolet cross-linkable pressure sensitive adhesive sheet;

heating and/or pressurizing the ultraviolet cross-linkable pressure sensitive adhesive sheet to conform to the step or bump; and

irradiating an ultraviolet ray on the ultraviolet cross-linkable pressure sensitive adhesive sheet.