| abstract |
A polyimide film that can provide a flexible metal-clad laminate plate which causes no significant dimensional change upon etching of the metal layer. The polyamide film is characterized in that, in the whole width of a continuously produced polyimide film, the ratio of the coefficient of humidity expansion (b) in a direction perpendicular to a molecular orientation axis and the coefficient of humidity expansion. (a) in the direction parallel to the molecular orientation axis, i.e., b/a, is not less than 1.01 to not more than 2.00 and the difference between the maximum value of the coefficient of humidity expansion ratio and the minimum value of the coefficient of humidity expansion ratio is not more than 0.30. The polyimide film in another aspect is characterized in that the coefficient of humidity expansion in a direction parallel to the molecular orientation axis is not less than 3.0 ppm/° C. and not more than 15.0 ppm/% RH, the difference between the maximum value and the minimum value for the molecular orientation angle of the film is not more than 40°, and the molecular orientation angle is regulated within 0±20° when MD direction is 0°. |