Pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet

A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer, wherein

• the pressure-sensitive adhesive layer comprises a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound, and a tackifier resin,
• wherein the tackifier resin comprises:
• a natural product-based tackifier resin (A) having a softening point of 100° C. or higher and 200° C. or lower, and containing no aromatic ring;
• and
• a petroleum-based tackifier resin (B) having a softening point of 125° C. or higher and 200° C. or lower, and containing an aromatic ring,
• the tackifier resin (A) comprises:
• a tackifier resin (A1) wherein the tackifier resin (A1) is a terpene resin having a softening point of 100° C. or higher and 200° C. or lower;
• and
• a tackifier resin (A2) wherein the tackifier resin (A2) is a rosin-based resin having a softening point of 120° C. or higher and 200° C. or lower,
• the tackifier resin (A1) and the tackifier resin (A2) are contained to satisfy a ratio (A1/A2) of ⅓ or greater and 3 or less on weight basis, wherein A1 is the amount of the tackifier resin (A1) and A2 is the amount of the tackifier resin (A2),
• the amount of a phenol-based tackifier resin in the pressure-sensitive adhesive layer is less than 1 part by weight with respect to 100 parts by weight of the block copolymer, and
• the pressure-sensitive adhesive sheet satisfies the following characteristics:
• having an adhesive strength to a soft urethane foam of 3 N/10 mm or greater, wherein the adhesive strength is measured in an environment of 23° C. and 50% RH under the conditions of a tensile speed of 300 mm/min and a peel angle of 180 degrees;
• and
• not falling off in a cohesive strength test for a stainless steel plate measured under the conditions of a temperature of 70° C., an adhered area of 10 mm×30 mm, a load of 500 g, and a holding time of 1 hour.