Patent ID: 10434733

Abstract:
A method for producing a retardation film comprising the steps of: (a) uniaxially stretching an original film for producing retardation film in one direction at either a temperature T1 or T2; and then (b) uniaxially stretching the film stretched in the step (a) in a direction perpendicular to the above-mentioned direction of stretching at a temperature T2 or T1 different from the above-mentioned temperature, in which the original film for producing retardation film has a characteristic that a phase of linearly polarized light entering vertically into the film plane and having an oscillating surface of an electric vector in an X-Z plane against linearly polarized light entering vertically into the film plane and having an oscillating surface of an electric vector in a Y-Z plane lags by uniaxially stretching in the direction of the X axis at a temperature T1, and leads by uniaxially stretching in the direction of the X axis at a temperature T2 different from the above-mentioned temperature T1, in which the X axis is an uniaxially stretching direction, the Y axis is a direction perpendicular to the uniaxially stretching direction in the film plane, and the Z axis is a direction of a thickness of the film.