Phase difference plate, liquid crystal projector, and contrast adjustment method

A phase difference plate comprising:

• a substrate;
• and
• a phase difference film formed on at least one surface of the substrate,
• wherein the phase difference film is an oblique film which has a columnar structure body inclined with respect to a normal line of a film formation surface in the substrate, on which the phase difference film is formed, and exhibits a refractivity anisotropy as an optical characteristic,
• in a case where three principal refractive indices in a biaxial refractive index ellipsoid exhibiting the refractivity anisotropy are defined as nx, ny, and nz, and in these principal refractive indices, in a case where nx is a principal refractive index in an X-axis direction which is a longitudinal direction of the columnar structure body, ny is a principal refractive index in a Y-axis direction which is a major-axis direction of an ellipse perpendicular to the X-axis, and nz is a principal refractive index in a Z-axis direction which is a minor-axis direction of the ellipse, Conditional Expression (1) is satisfied, and
• in a case where an incidence angle in a direction inclined to the X-axis side with respect to the normal line is regarded as positive, a phase difference of an incidence light with an incidence angle of +30° is defined as Re(+30), a phase difference of an incidence light with an incidence angle of −30° is defined as Re(−30), and a phase difference ratio of Re(+30) to Re(−30) is defined as a Re(30) ratio, Conditional Expression (2) is satisfied,
• ny>nx>nz (1)
• Re(30) ratio=Re(30)/Re(−30)=1.1 to 4.0 (2).