OPTICAL ELEMENT, CONDENSING BACKLIGHT SYSTEM AND LIQUID CRYSTAL DISPLAY UNIT

摘要

An optical element comprising, disposed in the order mentioned, a polarizing element (A) that polarizes and separates an incident light before outputting it and is formed of cholesteric liquid crystal -- wherein an output light for a normal-direction incident light has a distortion rate of at least 0.5, an output light for an incident light entered inclined at least 60° from the normal direction has a distortion rate of up to 0.2, and the larger an incident angle the larger the linearly polarized light component of an output light is --, a 1/2 wavelength plate (B), a layer (C) having a front phase difference (normal direction) of almost zero and producing a phase difference for an incident light inclined with respect to the normal direction, and 1/4 wavelength plate (D), the 1/4 wavelength plate (D) being provided with a linearly polarized reflection type polarizer (E) that transmits one of orthogonally crossing linearly polarized lights and selectively reflects the other so that its transmission axis and the axis of a transmitted light passing through the polarizing element (A) through the 1/4 wavelength plate (D) in this order are disposed in the same direction. This optical element can condense and parallelize an incident light from a light source to prevent the transmission of an arbitrary-direction light.