| 摘要 |
PROBLEM TO BE SOLVED: To obtain the subject solution comprising a specific polyamic acid and a specified solvent, low in viscosity, capable of exhibiting an excellent film formability and coatability, capable of forming films low in linear expansion coefficients and excellent in mechanical characteristics and dimensional stability, and useful for electric wiring boards, etc. SOLUTION: This polyamic acid solution comprises (A) a polyamic acid of the formula (X, Y are each a number satisfying the equation: X/Y=1 to 4), wherein the component A is contained in an amount of >=5wt.% based on the solution, and (B) a solvent comprising (B1 ) two or more solvents selected from water-soluble etheric compounds, water-soluble ketonic compounds, water- soluble alcoholic compounds and water or (B2 ) a compound having an ether group and an alcoholic OH group in the same molecule, and has a viscosity of <=200 poises. The solution can be formed into a film, which can be converted into the polyimide film having a linear expansion coefficient of <2.5×10<-5> / deg.C at 30-250 deg.C.
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