| 摘要 |
PROBLEM TO BE SOLVED: To provide a reasonable and economical back light unit having the capability of effectively utilizing light emitted from a light source, and facilitating the increase of the brightness of display, the service life of a device and the saving of power by leaps and bounds. SOLUTION: Regarding a back light unit 1 formed to include a light source unit 13 and a light introduction board 11 with a reflective layer for introducing light to the display of the board 11 after receipt from the light source unit 13, a film F formed out of a cholestric liquid crystal body F1 and a 1/4-wavelength board 2, and integrated for circular polarized light separation and recombination having a function of circularly polarizing and separating light into clockwise and counterclockwise polarized types of light, is formed on the display side of the board 11. Alternatively, a film made of a multilayer film formed between polymeric transparent films and integrated for linear polarized light separation and recombination having a function of linearly polarizing and separating the light into P-polarized light and S-polarized light is provided on the display side of the board 11. In this case, a diffusion sheet is preferably provided between the board 11 and either of the films. |
