Patent ID: 6433853
Filing Date: 2002-08-13
Classification: G02B,G02F

Abstract:
A cholesteric liquid crystal layer having Grandjean orientation in which a helical pitch changes in the thickness direction, wherein circular dichroism by which natural light is separated into reflected light comprising circularly polarized light and transmitted light is exhibited over a wavelength region having a width of at least 50 nm and including a wavelength of 520 nm, said cholesteric liquid crystal layer showing either (a) polarization characterizations such that when the reflected light or the transmitted light is converted to linearly polarized light through a quarter-wavelength plate, then the linearly polarized light in the visible light region has a maximum value of degree of polarization at a wavelength of 520 nm or shorter, or (b) polarization characteristics such that when the degree of polarization of the linearly polarized light in the visible light region is integrated in the wavelength region where the circular dichroism is exhibited, then the integrated degree of polarization for the region on the shorter-wavelength side of 520 nm is greater than that for the region on the longer-wavelength side of 520 nm.