| 摘要 |
PROBLEM TO BE SOLVED: To enhance display contrast at low cost, and improve the visibility of display by installing a circularly polarizing filter layer on the outer surface or the inner surface of a front side board that is installed facing to a back side board interposing discharge space. SOLUTION: When randomly polarized external light is made incident on a circularly polarizing filter layer, only linearly polarized light having a predetermined polarization plane P is transmitted through a polarized light separation surface 21 of the circularly polarizing filter surface while the lights having other polarization planes are reflected there. Then, the linearly polarized light having the polarization plane P transmitted from the polarized light separation surface 21 is converted into, for instance, right circularly polarized light by a 1/4 phase difference surface 22, and the circularly polarized light impinges on a reflecting surface 23 and is regularly reflected on its surface and converted left into circularly polarized light. The left circularly polarized light is converted into linearly polarized light having a polarization plane S perpendicular to the predetermined polarization plane P by the 1/4 phase difference surface 22, and is not emitted to the outside because it is reflected by the polarized light separation surface 21. |
