Photochromic laminates for improvement of the daylight contrast of cathode ray tubes and plasma displays

摘要

The contrast and color saturation of cathode ray tube (CRT) and plasma display images is negatively affected by the reflection of ambient light at the white phosphor dots. A variable photochromic transmission filter reversibly darkens upon exposure to sunlight, and could offer the optimal compromise between contrast and brightness of the image under a range of illumination conditions. The photochromic transmission filter that we present here consists of a soft polymer layer doped with a photochromic dye that has been sandwiched between the CRT screen and a front glass panel. The fabrication process of such a photochromic laminate involves the in-situ polymerization of a resin in the presence of the dye. For this purpose we have studied the radical polymerization of several (meth)acrylates in the presence of a photochromic dye, and evaluated the optical properties of the dye in the resulting polymer films. In this way a photochromic laminate has been developed that upon irradiation turns from a transparent state to an almost neutrally colored state and exhibits sufficiently fast coloration and decoloration kinetics. The photochromic laminate significantly improves the daylight contrast of the CRT under high illumination conditions (e.g. direct sunlight), while at the same time the brightness of the CRT is retained under low illumination conditions.