Liquid crystal display device with negative retardation of retardation plates being approximately zero.
View Patent ↗A liquid crystal display device includes a liquid crystal cell, polarizers, a first retardation plate arranged between the liquid crystal cell and the first polarizer, and a second retardation plate arranged between the liquid crystal cell and the second polarizer. Each retardation plate has an optical axis in a plane parallel to the substrate surface and a retardation of substantially λ/4. The optical axis of one retardation plate is perpendicular to the optical axis of the other. The polarizing axes of the polarizers are arranged at an angle of 45° with respect to the optical axes of the retardation plates. The liquid crystal cell is arranged such that a state of alignment of liquid crystal molecules changes, accompanying a change in a polar angle and/or change in an azimuth, upon application of a voltage.
1. A liquid crystal display device comprising:
a liquid crystal cell comprising a pair of substrates and a liquid crystal layer arranged between the pair of substrates, the liquid crystal of the liquid crystal cell being of a vertical alignment type;
first and second polarizers arranged on either side of the liquid crystal cell;
a first retardation plate arranged between the liquid crystal cell and the first polarizer;
a second retardation plate arranged between the liquid crystal cell and the second polarizer;
each of the first and second retardation plates having an optical axis in a plane parallel to the surfaces of the substrates and a retardation of substantially λ/4, the optical axis of the first retardation plate being perpendicular to the optical axis of the second retardation plate, the negative retardation ((nx+ny) /2−nz) of each of the retardation plates being approximately zero;
a first optical plate arranged on or near the liquid crystal cell and having refractive indices in the relationship of nx=ny>nz, the first optical plate having a retardation the value of which is identical to that of the liquid crystal layer and the sign of which is reverse to that of the liquid crystal layer;
a second optical plate having refractive indices in the relationship of nx=ny<nz, said second optical plate or a part thereof being arranged on or near the first polarizer; and
a third optical plate arranged on or near the second polarizer and having refractive indices in the relationship of nx>ny=nz.
2. A liquid crystal display device according to claim 1 , wherein the retardation of the second optical plate is not less than 80 nm and not more than 300 nm.
3. A liquid crystal display device according to claim 1 , wherein the retardation of the third optical plate is not less than 25 nm and not more than 160 nm.