Reflective liquid crystal display device comprising a liquid crystal layer having a twist angle
The present invention provides a liquid crystal display device comprising a liquid crystal layer sandwiched between an upper substrate and a lower substrate having a twist angle in the range of about 40 to 65 degrees and a light diffusive reflective electrode having recesses and projections provided on the lower substrate wherein a product of the height of the recesses and projections and a birefringence of the liquid crystal layer is in the range of about 10 to 53 nm at the twist angle of about 40 degrees and about 10 to 64 nm at the twist angle of about 65 degrees, respectively.
1. A liquid crystal display device, configured in a normally closed display mode, comprising:
an upper substrate and a lower substrate disposed in a mutually facing relation;
a liquid crystal layer sandwiched between said upper substrate and said lower substrate, the liquid crystal layer having a twist angle in the range of about 40 to 65 degrees;
a light diffusive reflective electrode having recesses and projections provided on said lower substrate;
a recess and projection forming layer disposed between said lower substrate and said light diffusive reflective electrode;
a single phase plate provided on an outer surface of said upper substrate;
a polarizing plate provided on an outer surface of said single phase plate;
an electrode disposed between said upper substrate and said liquid crystal layer;
a plurality of signal lines;
a plurality of scanning lines disposed orthogonally to said plurality of signal lines; and
a thin film transistor connected to said signal line and said scanning line;
wherein a product of a height of said recesses and projections of the light diffusive reflective electrode and a birefringence of said liquid crystal layer is in the range of about 10 to 53 nm,
wherein the twist angle and the retardation of said liquid crystal layer are within a region bounded by a straight line sequentially connecting a first set of points on a graph defined by the abscissa being the twist angle of a liquid crystal layer expressed in degrees and the ordinate being the retardation of the liquid crystal layer expressed in nm, the first set of points being: (50 degrees, 200 nm), (50 degrees, 275 nm), (40 degrees, 305 nm), (40 degrees, 350 nm), (65 degrees, 275 nm) and (65 degrees, 200 nm);
wherein the twist angle of said liquid crystal layer and the retardation of said single phase plate are within a region bounded by a straight line sequentially connecting a second set of points on a graph defined by the abscissa being the twist angle of a liquid crystal layer expressed in degrees and the ordinate being the retardation of the single phase plate expressed in nm, the second set of points being: (50 degrees, 340 nm), (40 degrees, 420 nm), (40 degrees, 480 nm), (65 degrees, 440 nm) and (65 degrees, 290 nm); and
wherein the single phase plate slow axis azimuth and the polarizing of plate absorption axis azimuth are defined counterclockwise by observing the liquid crystal display device from the normal direction of the upper substrate and setting the orientation direction of the lower substrate to be 0 degrees, and being within the region bounded by a straight line sequentially connecting a third set of points on a graph defined by the abscissa being the single phase plate slow axis azimuth expressed in degrees and the ordinate being the polarizing of plate absorption axis azimuth expressed in degrees, the third set of points being: (30 degrees, 32 degrees), (40 degrees, 50 degrees), (70 degrees, 88 degrees) and (75 degrees, 88 degrees),
the azimuth is defined counterclockwise by observing said liquid crystal display device from the normal direction of said upper substrate and setting the orientation direction of said lower substrate to be 0 degrees.
2. A liquid crystal display device of claim 1 , wherein the phase plate has a Nz coefficient of 0.0.