In the early 1980s, Japanese UBE Company successfully developed a new type of linear polyimide films, namely biphenyl films, including Upilex R, Upilex S and Upilex C series films, breaking the 20-year monopoly in the market represented by "Kapton", which used PMDA and DDE as raw materials to manufacture polyimide films. The anhydride component is diphenyltetracarboxylic anhydride, and the diamine component is diamino-diphenyl ether or p-phenylenediamine. According to the different structure of the diamine, the positioning of the combination with diamino-phenyl ether type R, and the positioning of the combination with p-phenylenediamine. [more]