Resin film, graphite sheet, and method for producing same

A resin film having a multilayer structure in which a second non-thermoplastic polyimide layer is laminated on at least one surface of a first non-thermoplastic polyimide layer, the birefringence of the first non-thermoplastic polyimide layer being 0.095 or more, and the second non-thermoplastic polyimide layer being obtainable by a thermocuring method. The birefringence (B) of the second non-thermoplastic polyimide layer is less than 0.095 when the second non-thermoplastic polyimide layer is a single-layer film alone. The present invention addresses the problem of producing a graphite sheet having excellent thermal diffusivity using a polyimide film that can be obtained by thermal curing. The problem of the present invention can be solved by using the resin film. 一种树脂膜，其具有相对第1非热塑性聚酰亚胺层的至少一个面层叠第2非热塑性聚酰亚胺层而成的多层构造，其中，第1非热塑性聚酰亚胺层的双折射率是0.095以上，第2非热塑性聚酰亚胺层能通过热固化法获得，且第2非热塑性聚酰亚胺层独自为单层膜时的双折射率B低于0.095。本发明的课题在于，采用能通过热固化获得的聚酰亚胺膜来制造热扩散率优异的石墨片。通过使用该树脂膜，能解决本发明课题。