To provide a backlight for liquid crystal display using a photoreactive polymer liquid crystal having high heat resistance, high optical anisotropy and controlling properties with high accuracy and having polarization properties in order to solve the problem that an optical wave emitted from a currently used backlight for liquid crystal display has low light utilizing efficiency because of its random polarization state and to heighten utilizing efficiency of light of a liquid crystal display element.

The backlight for liquid crystal display having the polarization properties contains a polymer layer having a fixed molecular alignment structure which is periodically changed. The backlight for liquid crystal display having the polarization properties is formed by applying a film which is formed by irradiating a photoreactive polymer liquid crystal thin film with polarized interference light or polarized light and then subjecting the resultant film to heat treatment to induce and fix optically designed periodical molecular alignment to the film.