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AssigneeUbe Industries, Ltd.
InventorsTakao Miyamoto, Hideki Iwai, Toshiyuki Nishino, Yasuhiro Nagoshi
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A polyimide film having one smooth surface favorably employable for a substrate of a display or an electronic paper is prepared by the steps of forming a laminated film by coating a polyimide precursor solution containing no filler, in which the polyimide is prepared from an acidic component comprising 3,3′,4,4′-biphenyltetracarboxylic dianhydride and a diamine component comprising p-phenylene diamine, on one surface of a self-supporting film of a polyimide precursor solution containing a filler, in which the polyimide is prepared from an acidic component comprising 3,3′,4,4′-biphenyltetracarboxylic dianhydride and a diamine component comprising p-phenylene diamine; and heating the laminated film to perform imidization.
A polyimide film having a thickness in the range of 20 to 150 μm which comprises a lower filler-containing polyimide resin layer comprising a polyimide resin prepared from an acidic component comprising 3,3′,4,4′-biphenyltetracarboxylic dianhydride and a diamine component comprising p-phenylene diamine and a filler dispersed in the polyimide resin and an upper polyimide resin layer comprising a polyimide resin prepared from an acidic component comprising 3,3′,4,4′-biphenyltetracarboxylic dianhydride and a diamine component comprising p-phenylene diamine formed continuously on the lower filler-containing polyimide resin layer, in which the polyimide film has a surface showing Ra of more than 1.0 nm but not more than 2.5 nm on the side of the filler-containing polyimide resin layer and a surface showing Ra of 1.0 nm or less on a reverse side.
Dependencies are inferred from the claim text.