Patent ID: 8212433

Claim:
An electret comprising a laminate wherein a layer (A) containing a polymer compound (a) having a relative dielectric constant of from 1.8 to 3.0 and a layer (B) containing a polymer compound (b) having a relative dielectric constant higher than the polymer compound (a) are directly laminated, wherein the difference between the relative dielectric constant of the polymer compound (b) and the relative dielectric constant of the polymer compound (a) is at least 0.3; the layer (A) is disposed on the outermost surface on a side opposite to the side where electric charge is injected at the time of injecting electric charge into the laminate to form the electret; and the layer (B) has a thickness of at least 1 μm; wherein the polymer compound (a) is a fluorinated polymer having an alicyclic structure, wherein the fluorinated polymer is at least one member selected from the list consisting of: (i) a polymer having a unit based on a cyclic fluorinated monomer, and (ii) a polymer having a unit formed by cyclopolymerization of a diene type fluorinated monomer; wherein the layer (A) consists essentially of the polymer compound (a) and a silane coupling agent; and wherein the polymer compound (b) is at least one member selected from the group consisting of: a polyimide, a polyparaxylylene resin, a polycarbonate, a polyarylene, a polyarylene ether, a polyether sulfone, and a polysulfone.