| 摘要 |
PROBLEM TO BE SOLVED: To significantly improve the use efficiency of light by disposing a polarizing reflection layer which mostly transmits light in plural small wavelength regions including specified plural wavelengths in a first circularly polarized light component and which mostly reflects light in the regions between the plural small wavelength regions. SOLUTION: In the cholesteric liquid crystal layer 18, the helical pitch of a cholesteric liquid crystal layer 18 changes in the layer thickness direction in such a manner that the product np of the helical pitch p of the layer 18 and the average refractive index n of the cholesteric liquid crystal polymer 19 covers most of the wavelength region in the visible ray region, and that the left-handed circularly polarized light is selectively reflected. However, the device has a structure that transmits left- handed circularly polarized light for the light near the main three wavelengths in the spectrum of the emitted light from a back light Lb. By displaying an image in the display device using the cholesteric liquid crystal layer 18, the reflection to transmission ratio near the region of the main three wavelengths of the back light Lb is 5:95, while in other regions, the ratio is 95:5. In the whole left-handed circularly polarized light emitted from the back light Lb, 95% of the light is transmitted, while 90% of the left-handed circularly polarized light of external light Lf is reflected. |
