| abstract |
PROBLEM TO BE SOLVED: To improve the adhesion between a polyimide film suitable for a flexible substrate and a metal thin film formed thereon by a dry process, and at the same time, to generate curl regardless of the content of a heat history. Suppress. SOLUTION: A polyimide film for forming an insulating layer of a flexible substrate having an insulating layer disposed on a conductor layer is formed by a first polyimide layer 1 and a second polyimide layer 2. And a third polyimide layer 3 having a three-layer structure, a second polyimide layer 2 having substantially the same coefficient of linear thermal expansion as the conductor, and a first polyimide layer 1 disposed on the side in contact with the conductor layer being a sulfone group. It is composed of contained polyimide. |