Patent ID: 8883894

Claim:
An insulating film comprising: a (A) binder polymer; (B) spherical organic beads; and (C) fine particles containing at least one element selected from the group consisting of phosphorus, aluminum, and magnesium, both the (B) spherical organic beads and the (C) fine particles being dispersed in the insulating film, the (B) spherical organic beads occupying a 20% to 50% area of any 125 μm×15 μm region of a cross section of the insulating film which cross section is cut along a thickness direction of the insulating film, the (B) spherical organic beads being cross-linked spherical organic beads having a urethane bond in its molecule, the (C) fine particles containing at least element selected from the group consisting of phosphorus, aluminum, and magnesium having an average particle diameter of 1 μm to 10 μm.