Abstract: A flexible substrate has heat resistance to endure the high temperature such as sintering of a photovoltaic conversion layer of a compound-type thin film solar cell, can prevent permeation and/or diffusion of metal into the photovoltaic conversion layer, and can be used for many applications. The polyimide layer-containing flexible substrate has a metal substrate of metal foil made of ordinary steel or stainless steel having a coefficient of thermal expansion in a plane direction of not more than 15 ppm/K, or a metal substrate of metal foil made of that ordinary steel or stainless steel on the surface of which a metal layer comprising one of copper, nickel, zinc, or aluminum or an alloy layer of the same is provided, over which a polyimide layer having a layer thickness of 1.5 to 100 ?m and a glass transition point temperature of 300 to 450° C. is formed.

Abstract: This invention relates to a laminate which is excellent in heat resistance after moisture absorption required in a lead-free solder joint, and is suitable for use in flexible printed wiring boards or HDD suspensions. The laminate for electronic materials of this invention is constituted of a conductor layer and an insulating resin layer having a polyimide-based resin layer (A) and a polyimide-based resin layer (B). The polyimide-based resin layer (A) constituting the insulating layer includes a polyimide-based resin obtained by reacting a diamine containing 40 mol % or more of 4,4?-diamino-2,2?-dimethylbiphenyl with an aromatic tetracarboxylic acid, and the polyimide-based resin layer (B) includes a polyimide-based resin containing 80 mol % or more of a structural unit generated from bis(4-aminophenoxy)benzene or 2,2-bis[4-(4-aminophenoxy)phenyl]propane, and pyromellitic acid, benzophenonetetracarboxylic acid, diphenylsulfonetetracarboxylic acid or biphenyltetracarboxylic acid.

Abstract: This invention relates to a laminate which changes in dimension to such a small extent as not to cause curling and warpage when the ambient humidity changes and is useful for flexible printed wiring boards. The laminate possesses a polyimide layer or layers of polyimides formed on a conductor by coating and at least one of the polyimide layers is composed of polyimide of low hygroscopic expansion obtained by the reaction of diamines containing 20 mol % or more of 4,4?-diamino-2,2?-dimethylbiphenyl with a tetracarboxylic acid compound and exhibiting a coefficient of linear hygroscopic expansion of 15×10?6/% RH or less.

Abstract: This invention relates to a laminate which is excellent in heat resistance after moisture absorption required in a lead-free solder joint, and is suitable for use in flexible printed wiring boards or HDD suspensions. The laminate for electronic materials of this invention is constituted of a conductor layer and an insulating resin layer having a polyimide-based resin layer (A) and a polyimide-based resin layer (B). The polyimide-based resin layer (A) constituting the insulating layer includes a polyimide-based resin obtained by reacting a diamine containing 40 mol % or more of 4,4′-diamino-2,2′-dimethylbiphenyl with an aromatic tetracarboxylic acid, and the polyimide-based resin layer (B) includes a polyimide-based resin containing 80 mol % or more of a structural unit generated from bis(4-aminophenoxy)benzene or 2,2-bis[4-(4-aminophenoxy)phenyl]propane, and pyromellitic acid, benzophenonetetracarboxylic acid, diphenylsulfonetetracarboxylic acid or biphenyltetracarboxylic acid.