LCD with a pair of retardation films on one side of normally white liquid crystal layer
AssigneeOIS Optical Imaging Systems, Inc.
InventorsAdiel Abileah, John VanDerploeg, Gang Xu
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Abstract
A normally white twisted nematic liquid crystal display is disclosed having a pair of retardation films disposed between the liquid crystal layer and an adjacent polarizer, both retardation films being on one side of the liquid crystal layer. Both retardation films, if uniaxial, have retardation values of from about 100-200 nm. Optionally, biaxial retarders (n.sub.X >n.sub.Y >n.sub.Z) may be used, such biaxial retarders having retardation values from about .DELTA..sub.ZX =-100 to -200 nm, and .DELTA..sub.ZY =-10 to -100 nm. Accordingly, inversion is reduced and contrast rations are improved at large viewing angles.
Claims23
A normally white liquid crystal display comprising:
- a rear, light-entrance polarizer having a transmission axis oriented in a first direction;
- a front, light-exit polarizer having a transmission axis oriented in a second direction with respect to said first direction so as to define a normally white display;
- first and second positively birefringent uniaxial retardation films both disposed between a twisted nematic liquid crystal layer and one of:
- (i) said rear, light-entrance polarizer;
- and (ii) said front, light-exit polarizer;
- wherein said liquid crystal layer in the off state twists at least one normally incident visible wavelength of light less than about 110.degree. as it passes therethrough, and said first and second uniaxial retardation films each have retardation values of from about 80-200 nm;
- and
- wherein the transmission axes of said polarizers and optical axes of said retardation films are so arranged each with respect to the others so as to achieve high contrast ratios over a large range of predetermined viewing angles.
A normally white liquid crystal display comprising:
- a rear, light-entrance polarizer having a transmission axis oriented in a first direction;
- a front, light-exit polarizer having a transmission axis oriented in a second direction wherein said first and second directions are oriented so as to define a normally white display;
- first and second biaxial retardation films both disposed between a twisted nematic liquid crystal layer and one of said rear and front polarizers, wherein said liquid crystal layer in the off state twists at least one wavelength of normally incident visible light at least about 85.degree. as it passes therethrough;
- and
- wherein said first and second biaxial retardation films each have the following retardation values:
- d.multidot..DELTA.n.sub.ZX =from about -100 to -200 nm
- d.multidot..DELTA.n.sub.ZY =from about -10 to -100 nm
- wherein n.sub.X >n.sub.Y >n.sub.Z and "d" is the thickness of the film such that the viewing zone of said display has high contrast ratios and reduced inversion throughout an enlarged range of viewing angles.
A normally white twisted nematic liquid crystal display comprising:
- a plurality of pixels, each said pixel including electrode means and a twisted nematic liquid crystal layer for twisting at least one normally incident visible wavelength of light passing therethrough from about 80.degree. to 100.degree. when the liquid crystal layer is in the off state;
- a rear light-entrance polarizer having a transmission axis oriented in a first direction;
- a front, light-exit polarizer or analyzer having a transmission axis oriented in a second direction with respect to said first direction thereby defining a twisted nematic normally white display;
- a first retardation film;
- a second retardation film;
- and
- wherein the transmission axes of said rear and front polarizers and the optical axes of said first and second retardation films are so arranged with respect to the others so as to achieve a white light contrast ratio of at least about 10:1 over a horizontal angular span, at a predetermined vertical angle, of at least about 120.degree. and over a vertical angular span of greater than about 50.degree. at a predetermined horizontal angle.
A normally white twisted nematic liquid crystal display comprising:
- a twisted nematic liquid crystal layer which twists at least one normally incident visible wavelength of light from about 80.degree.-100.degree. as it passes therethrough when the liquid crystal is in the off state;
- electrode means for applying voltage to said liquid crystal layer so as to selectively display image data to a viewer;
- a first negative retardation film having a retardation value of from about -80 to -200 nm;
- a second negative retardation film having a retardation value of from about -80 to -200 nm;
- and
- wherein the optical axes of said first and second negative retardation films are oriented relative to one another so as to achieve a high contrast ratio over a predetermined range of viewing angles.
Dependencies are inferred from the claim text.