Surface protection sheet

A surface protection sheet comprising a substrate and a pressure-sensitive adhesive layer placed on one face of the substrate, wherein

• the surface protection sheet has 500% or greater elongation at break in its machine direction as well as 500% or greater elongation at break in its transverse direction,
• the pressure-sensitive adhesive layer is directly formed from an emulsion pressure-sensitive adhesive composition,
• the substrate is a linear low density polyethylene film or a low density polyethylene film and has a thickness of 40 μm or larger and 100 μm or smaller,
• the emulsion pressure-sensitive adhesive composition comprises 100 parts by weight of an acrylic polymer as a base polymer having a glass transition temperature of −40° C. or higher and −10° C. or lower, and 0.01 part by weight or greater and 10 parts by weight or less of a crosslinking agent,
• the acrylic polymer is a polymer formed from a monomer mixture, wherein, in the monomer mixture, (a) a content of an acrylic monomer is 50% by weight or more based on the total monomer content, (b) a content of a methyl methacrylate is 35% by weight or more based on the total monomer content, and (c) a content of a carboxyl group-containing monomer is 0.5% by weight or higher and 20% by weight or lower based on the total monomer content,
• the pressure-sensitive adhesive layer has toluene-insoluble fractions having a gel fraction GC of 75% or higher and toluene-soluble fractions having a weight average molecular weight SMw of 20×104 or higher and 100×104 or lower, and
• the pressure-sensitive adhesive layer shows, in nanoindentation, an unloading curve having a minimum load Lmin of less than −2.0 μN.

A surface protection sheet comprising a substrate and a pressure-sensitive adhesive layer placed on one face of the substrate, wherein:

• the surface protection sheet has 200% or greater elongation at break in its machine direction as well as 200% or greater elongation at break in its transverse direction,
• the pressure-sensitive adhesive layer is directly formed from an emulsion pressure-sensitive adhesive composition,
• the emulsion pressure-sensitive adhesive composition comprises 100 parts by weight of an acrylic polymer as a base polymer having a glass transition temperature of −50° C. or higher, and 0.01 parts by weight or greater and 10 parts by weight or less of a crosslinking agent, and
• the acrylic polymer is formed from a monomer mixture, wherein, in the monomer mixture, (a) a content of an acrylic monomer is 50% by weight or more based on the total monomer content, (b) a content of a monomer whose homopolymer has a glass transition temperature of 60° C. or higher is 35% by weight or more based on the total monomer content, (c) a content of a carboxyl group-containing monomer is 0.5% by weight or higher and 20% by weight or lower based on the total monomer content, and the monomer whose homopolymer has a glass transition temperature of 60° C. or higher includes 70% by weight cycloalkyl (meth)acrylate,
• the pressure-sensitive adhesive layer has toluene-insoluble fractions having a gel fraction GC of 75% or higher,
• the pressure-sensitive adhesive layer has toluene-soluble fractions having a weight average molecular weight SMw of 20×104 or higher and 100×104 or lower, and
• the pressure-sensitive adhesive layer shows, in nanoindentation, an unloading curve having a minimum load Lmin of less than −2.0 μN.