| 主权项 |
1. A base film of a dicing sheet, the base film comprising a cutting-fragment suppression layer (A) and an expandable layer (B) laminated on one main surface of the cutting-fragment suppression layer (A),
the expandable layer (B) having a laminate structure of a plurality of resin-based sublayers, the plurality of resin-based sublayers comprising a resin-based sublayer (B1) that is disposed nearest to the cutting-fragment suppression layer (A) and a resin-based sublayer (B2) that is at least one of other resin-based sublayers than the resin-based sublayer (B1), the resin-based sublayer (B1) having a stress-relaxation rate R1 (unit: %) after 5 minutes of 10%-stretching, the resin-based sublayer (B2) having a stress-relaxation rate R2 (unit: %) after 5 minutes of 10%-stretching, the stress-relaxation rate R1 and the stress-relaxation rate R2 satisfying conditions represented by Expressions (i) to (iii) below, the cutting-fragment suppression layer (A) comprising a ring-containing resin (a1) that is a thermoplastic resin having at least one type of an aromatic series-based ring and an aliphatic series-based ring and an acyclic olefin-based resin (a2) that is an olefin-based thermoplastic resin other than the ring-containing resin (a1), wherein
R1≦30% (i)R2≧20% (ii)R1<R2 (iii). |
