Liquid crystal display device comprising compensation films having negative photo-elastic constant
View Patent ↗Described herein is an LCD device in which retardation may be removed from a glass substrate when stress is applied to a display screen, thereby minimizing light leakage from the display screen. In the LCD device, a film having a negative photo-elastic constant (NPEC) is arranged to adjoin glass substrates so as to remove photo-elasticity. Specifically, in the LCD device, the NPEC films having negative photo-elasticity are respectively arranged at upper and lower sides of a liquid crystal cell, wherein the liquid crystal cell includes opposing glass substrates with a liquid crystal layer disposed therebetween.
1. A liquid crystal display device, comprising:
first and second substrates each having a positive photo-elastic constant property and being an optical isotropic body when stress is not applied to the first and second substrates, the first and second substrates being the thickest among members constituting the liquid crystal display device and having the most retardation when an external force is applied to the liquid crystal display device such that the retardation in the substrates becomes retardation in the liquid crystal display device;
a liquid crystal layer disposed between the first and second substrates and in direct contact with the first and second substrates; and
first and second compensation films in direct contact with the first and second substrates, respectively, each compensation film having a negative photo-elastic constant (NPEC),
wherein the first and second compensation films remove a photo-elastic effect of the first and second substrates that occurs when stress is applied to one of the first and second substrates to minimize retardation of light, and
wherein the first and second NPEC compensation films are formed of a high polymer that includes styrene maleic anhydride.
2. The liquid crystal display device according to claim 1 , further comprising:
at least one polarizer disposed outside at least one of the first and second NPEC compensation films.
3. The liquid crystal display device according to claim 1 , wherein the first and second NPEC compensation films are first and second polarizers for polarizing a light.
4. The liquid crystal display device according to claim 3 , wherein the first NPEC compensation film functioning as the first polarizer defines a first single piece, and the second NPEC compensation film functioning as the second polarizer defines a second single piece.
5. The liquid crystal display device according to claim 1 , wherein the first and second NPEC compensation films include first and second polarizers each having a negative photo-elastic constant.
6. The liquid crystal display device according to claim 1 , wherein the first and second compensation films include first and second phase difference films each having a negative photo-elastic constant.
7. The liquid crystal display device according to claim 1 , further comprising:
first and second phase difference films disposed outside the first and second compensation films to compensate for optical distortion of the liquid crystal layer.
8. The liquid crystal display device according to claim 7 , further comprising:
first and second polarizers disposed outside the first and second phase difference films.
9. The liquid crystal display device according to claim 1 , further comprising:
a polarizer disposed outside the first compensation film; and
a phase difference film disposed outside the second compensation film to compensate for optical distortion of the liquid crystal layer.
10. The liquid crystal display device according to claim 1 , further comprising a first polarizer and a second polarizer each including one of the first and second compensation films in the form of a polymer substrate, and a polarizing layer coated on the polymer substrate.
11. The liquid crystal display device according to claim 10 , wherein the polymer substrate of each of the first and second polarizers is formed of polystyrene.