Adhesive film, flexible metal-clad laminate including the same with improved dimensional stability, and production method therefor
View Patent ↗It is an object of the present invention to provide an adhesive film which is used for producing, by a laminating method, a flexible metal-clad laminate in which the change in dimensions is suppressed, a flexible metal-clad laminate including the adhesive film, and a production method therefor. The present invention relates to an adhesive film including a polyimide film and an adhesive layer containing a thermoplastic polyimide, the adhesive layer being disposed on at least one surface of the polyimide film, a flexible metal-clad laminate produced by laminating a metal foil to the adhesive film with a thermal roll laminator, and a production method therefor, wherein the polyimide film is formed by a process including step (A) of mixing a polyamic acid solution, a dehydrating agent, and an imidization catalyst, and casting and applying the mixture onto a support to form a gel film; step (B) of stripping off the gel film and fixing both ends of the gel film; and step (C) of heating and transporting the film with both ends being fixed in a state loosened in the TD direction.
1. A method for producing a flexible metal-clad laminate, the method comprising laminating a metal foil to an adhesive film with a thermal roll laminator including at least one pair of metal rollers, the adhesive film including a polyimide film and an adhesive layer containing a thermoplastic polyimide, the adhesive layer being disposed on at least one surface of the polyimide film, the method comprising forming the polyimide film by a process comprising:
step (A) of casting and applying a solution containing a polyamic acid onto a support to form a gel film;
step (B) of stripping off the gel film and fixing both ends of the gel film; and
step (C) of heating and transporting the film with both ends being fixed,
wherein in at least a portion of step (C), the film is transported in a state loosened in the TD direction such that a distance between from one fixed end to a second fixed end of said both ends of gel film is smaller than a width of the film.
2. The method according to claim 1 , wherein the loosened state is achieved before the film is heated and transported.
3. The method according to claim 1 , wherein the polyimide film satisfies relationship −15≦θ≦15 at any position in the width direction (TD direction) of the film, wherein θ(°) is the angle of molecular orientation axis to the MD direction of the polyimide film.
4. The method according to claim 1 , wherein the polyimide film satisfies relationships 2≦α 1 ≦10, 13≦α 2 ≦25, and 20≦(α 1 +α 2 )≦40, wherein α 1 (ppm/° C.) is the coefficient of linear expansion (200° C. to 300° C.) of the polyimide film in the MD direction, and α 2 (ppm/° C.) is the coefficient of linear expansion (200° C. to 300° C.) of the polyimide film in the TD direction.
5. The method according to claim 1 , said method being a method for producing such a flexible metal-clad laminate that a total of a rate of change in dimensions before and after removal of the metal foil and a ratio of change in dimensions before and after heating the flexible metal-clad laminate from which the metal foil has been removed at 250° C. for 30 minutes is in a range of −0.06% to +0.06% both in the MD direction and in the TD direction.