Patent ID: 7400705

Claim:
A method of evaluating the performance of an ion-exchange film, comprising the steps of: setting humidity ambient to ion-exchange film at any desired value separately from temperature of the ion-exchange film; obtaining small-angle scattering curves in each of two angle ranges for the ion-exchange film at different humidities, by means of an X-ray measuring apparatus which is configured to detect X-rays scattered at small angles with respect to the axis of an X-ray applied to the ion-exchange film, said small angles include a first angle in a first angle range of 0.1°≦0.88° in terms of an angle 2θ and a second angle in a second angle range of 0.88°≦5° in terms of the angle 2θ; obtaining each small-angle scattering curve while the film remains in a different condition of humidity; analyzing small-angle scattering curves having peaks, one of which is in the first 2Θ angle range of 0.1° to 0.88° and another of which is in the second 2Θ angle range of 0.88° to 5°, thereby to evaluate the performance of the ion-exchange film, wherein the step of obtaining small-angle scattering curves has a step of obtaining a two-dimensional scattering profile pertaining to the ion-exchange film, by using a two-dimensional X-ray detector; and the X-ray measuring apparatus has a con-focal mirror which is arranged on a propagation path of the X-ray applied to the ion-exchange film and a point-focus X-ray source.