| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical device which can reflect or transmit light of a specified color with optimum purity and luminance, and to provide a method for its production. SOLUTION: The optical device 20 is formed by using at least one cholesteric liquid crystal film 23 so as to reflect light in at least one specified wavelength band from the incident light. The device has such features that the gradient of non-zero birefringence is present in a part or whole thickness of the film. The gradient is obtained by especially laminating layers 24a to 24j each having a birefringent coefficient increasing or decreasing with layers. Since the gradient of birefringence eliminates the side band in the reflection spectrum, it has an effect to saturate the color of the reflected light to the high luminance. This effect is intensively sensed by human eyes for the side band in a yellow color region, the device is especially advantageous for a red color. |
