STN displays having high contrast, with purple polarizer and residual birefringence causing greenish-gold or purplish-blue coloring
First Claim
1. A display device, comprising:
- first and second polarizing filters having respective first and second transmission axes angularly displaced by about 110°
to about 130°
relative to each other, the first transmission axis transmissive of a neutral polarized color, the first polarizing filter also having another transmission axis orthogonal to the first transmission axis and transmissive of a purple polarized color; and
a supertwisted nematic (STN) liquid crystal cell positioned between the first and second polarizing filters, characterized by a layer twist angle of between about 230° and
about 250°
, and including two spaced-apart electrode structures confining a liquid crystal composition, each electrode structure having an inner surface with an alignment layer conditioned so that the alignment directions of surface-contacting directors of the liquid crystal composition at the inner surfaces are angularly displaced by between about 110° and
about 130°
relative to each other, one of the alignment directions angularly displaced by between about 35°
to about 45°
relative to the second transmission axis, the STN liquid crystal cell producing in combination with the first and second polarizing filters a display in which the residual birefringence causes display cells that are in the nonselected state to appear greenish-gold and display cells that are in the selected state to appear dark purplish-blue when the display system is illuminated by white light and viewed by a human eye substantially along the viewing axis.
1 Assignment
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Accused Products
Abstract
A display system (10) or display (12) has a supertwisted nematic liquid crystal cell (30) located between first and second polarizing filters (24, 54) that have respective first (26) and second (56) transmission axes that form respective polar angles (A, D) with a reference plane (28). The first polarizing filter passes a neutral polarized color along the first transmission axis and has another transmission axis (27) orthogonal to the first transmission axis and transmissive of a purple polarized color; the second polarizing filter is of a neutral density type. The cell has first and second electrode structures (32, 34) confining a liquid crystal composition, each having an inner surface with respective liquid crystal alignment directions (38, 40) of inner-surface-contacting directors of the liquid crystal composition forming respective polar angles (B, C) with the reference plane. The second polarizing filter may be associated with a translucent film (64) to reflect light toward the second polarizing filter. Preferred polar angles include: A=110°; B=150°; C=30°; and D=-10°. With those angles, the display has excellent contrast, viewability, and color hue contrast between display elements (52) in the nonselected state (which appear greenish-gold) and display elements in the selected state (which appear dark purplish-blue); display elements in the relaxed state appear gold at room temperature.
27 Citations
28 Claims
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1. A display device, comprising:
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first and second polarizing filters having respective first and second transmission axes angularly displaced by about 110°
to about 130°
relative to each other, the first transmission axis transmissive of a neutral polarized color, the first polarizing filter also having another transmission axis orthogonal to the first transmission axis and transmissive of a purple polarized color; anda supertwisted nematic (STN) liquid crystal cell positioned between the first and second polarizing filters, characterized by a layer twist angle of between about 230° and
about 250°
, and including two spaced-apart electrode structures confining a liquid crystal composition, each electrode structure having an inner surface with an alignment layer conditioned so that the alignment directions of surface-contacting directors of the liquid crystal composition at the inner surfaces are angularly displaced by between about 110° and
about 130°
relative to each other, one of the alignment directions angularly displaced by between about 35°
to about 45°
relative to the second transmission axis, the STN liquid crystal cell producing in combination with the first and second polarizing filters a display in which the residual birefringence causes display cells that are in the nonselected state to appear greenish-gold and display cells that are in the selected state to appear dark purplish-blue when the display system is illuminated by white light and viewed by a human eye substantially along the viewing axis. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A display system having a viewing axis, comprising:
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first and second polarizing filters positioned on the viewing axis and having respective first and second transmission axes angularly displaced by about 110°
to about 130°
relative to each other, the first transmission axis transmissive of a neutral polarized color, the first polarizing filter also having another transmission axis orthogonal to the first transmission axis and transmissive of a purple polarized color;a supertwisted nematic (STN) liquid crystal cell positioned on the viewing axis between the first and second polarizing filters, characterized by a layer twist angle of between about 230° and
about 250°
, and including two spaced-apart electrode structures confining a liquid crystal composition, each electrode structure having an inner surface with an alignment layer conditioned so that the alignment directions of surface-contacting directors of the liquid crystal composition at the inner surfaces are angularly displaced by between about 110° and
about 130°
relative to each other, one of the alignment directions angularly displaced by between about 35°
to about 45°
relative to the second transmission axis, the electrode structures having respective first and second electrodes, overlapping portions of the first and second electrodes defining display cells, the STN liquid crystal cell producing in combination with the first and second polarizing filters a display in which the residual birefrigence causes display cells that are in the nonselected state to appear greenish-gold and display cells that are in the selected state to appear dark purplish-blue when the display system is illuminated by white light and viewed by a human eye substantially along the viewing axis; andan electrical driving circuit of a character that places chosen overlapping respective first and second electrodes at relaxed, nonselected, and selected electrical potentials effective to place liquid crystal material in a display cell between the chosen overlapping electrodes in respective relaxed, nonselected, and selected states. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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Specification