| 摘要 |
PROBLEM TO BE SOLVED: To obtain an optical film which has excellent heat resistance and moisture resistance, substantially prevents the occurrence of foaming and peeling and is hardly degraded in visibility by forming the superposed layers of tacky adhesive layers on one or both surfaces of an optical film blank in such a manner that the tacky adhesive layer having the longest stress relief time exists outermost and has a specific thickness. SOLUTION: The optical film blank 2 has the superposed layers 3 of the tacky adhesive layers 32, 32 on one or both surfaces thereof. The superposed layers 3 consist of the combination of the tacky adhesive layers 32, 32 varying in the stress relief time and the tacky adhesive layer 32 having the longest stress relief time is formed of the layer which is positioned outermost and of which the thickness is <=80% the overall thickness of the tacky adhesive layers. This stress relief time of the tacky adhesive layer 32 of the outermost layer of the superposed layers 3 is >=100sec, above all 150 to 1000sec and more particularly 200 to 500sec at 23 deg.C in accordance with the stress relief time of the tacky adhesive layers 31, 32. The stress relief time of the tacky adhesive layer 31 of the lower layer thereof is <=300sec and the time difference in the stress relief time between the tacky adhesive layer 32 and the tacky adhesive layer 31 is >=50sec and above all, >=60sec. |
