Twisted nematic liquid crystal display devices with optical axis of birefringent layer inclined with respect to birefringent layer normal
DC CAFCFirst Claim
1. An electrically controlled display device implementing a layer of twisted nematic liquid crystal placed between two polarizers, uniaxial compensating means with negative birefringence being associated with said layer within the optical cavity formed by said polarizers, wherein the optical axis of said uniaxial compensating means with negative birefringence have an inclination with respect to the normal (Z) to the main faces of said layer.
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Abstract
The disclosure relates to electrically controlled display devices that use the polarization rotation properties of twisted nematic liquid crystal layers. A display device comprises an optical cavity formed by two polarizers enclosing a layer of twisted nematic liquid crystal with which uniaxial birefringent means are associated in order to compensate for the residual birefringence of the liquid crystal layer which tends to reduce the contrast ratio of the display device. Thus, the homogeneity of the angular distribution of the contrast ratio is improved in relation to a device having no compensating means. The disclosed device can be applied in particular to data display devices for computers and to the display of television pictures directly or by projection.
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Citations
14 Claims
- 1. An electrically controlled display device implementing a layer of twisted nematic liquid crystal placed between two polarizers, uniaxial compensating means with negative birefringence being associated with said layer within the optical cavity formed by said polarizers, wherein the optical axis of said uniaxial compensating means with negative birefringence have an inclination with respect to the normal (Z) to the main faces of said layer.
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14. A display device, comprising:
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a first polarizer transmitting therethrough light having a first polarization direction; a second polarizer parallel with and opposing the first polarizer, the second polarizer transmitting therethrough light having a second polarization direction, the second polarization direction being perpendicular to the first polarization direction; a layer of twisted nematic liquid crystal parallel to and between the polarizers; a first birefringent layer extending in a plane that is parallel to and between the first and second polarizers; means for providing a voltage across the liquid crystal layer, comprising a pair of transparent electrodes opposing one another across the liquid crystal layer and a power source connected to the pair of transparent electrodes; and wherein the first birefringent layer has the property that it provides uniaxial negative birefringence along an axis that is inclined with respect to a normal to the plane in which the first birefringent layer extends.
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Specification