Liquid crystal display with phase difference plate having particular .DELTA . .DELTA.nxd at 45.degree. angle to surface
First Claim
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1. A liquid crystal display device, comprising:
- a twisted nematic liquid crystal display cell defining a display screen having a rear edge as viewed from the user and including a pair of spaced apart opposed substrates with electrodes selectively disposed thereon and a nematic liquid crystal material disposed in the space between the substrates;
a pair of polarizing plates disposed on opposite sides of the liquid crystal cell;
at least one layer of an optically anisotropic substance disposed between said liquid crystal cell and one of said polarizing plates and serving as a phase difference plate; and
a reflector disposed beneath the lower of the polarizing plates, wherein the value of the ratio K of the product Δ
n1·
d1, where Δ
n1 is the optical anisotropy and d1 is the thickness in the vertical direction of said phase difference plate, to the product Δ
n2·
d2, wherein Δ
n2 is the optical anisotropy and d2 is the thickness of said phase difference plane when inclined at 45°
from the vertical direction of said phase difference plate in the direction of the optical axis, is set at a predetermined level, and the optical axis of said phase difference plane is disposed at a predetermined angle with respect to the observation direction, said observation direction being both in the plane of the display screen and substantially perpendicular to the rear edge thereof, the observation direction being the direction of the projection in the plane of the display screen of the direction from which a user of said display device most frequently views said display screen, said predetermined angle being chosen in relation to said predetermined level of K such that the reflectance of said display is substantially maximized;
wherein the value of K is greater than or equal to 1.20 and the predetermined angle at which the optical axis of said phase difference plane is disposed with respect to the observation direction is in the range from about +30°
to about +60°
or in the range from about -30°
to about -60°
, wherein the values of these angles are positive when measured clockwise from the observation direction.
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Abstract
A liquid crystal display device having a phase difference plate and a reflector, which is capable of providing a bright display. When the value of the ratio K of the product Δn1·d1, where Δn1 is the optical anisotropy and d1 is the thickness in the vertical direction of the phase difference plate to the product Δn2·d2, where Δn2 is the optical anisotropy and d2 is the thickness of the phase difference plate when inclined at 45° from the vertical direction of the phase difference plate in the direction of the optical axis, is in the range of K≧1.20, the optical axis of the phase difference plate is disposed at an angle in the range of from about +30° to about +60° or in the range of from about -30° to about -60° with respect to the direction of observation, where the values of angles are positive when measured clockwise from the observation direction, whereas, when K<1.20, the optical axis of the phase difference plate is disposed at an angle in the range of from about +30° to +120° with respect to the observation direction.
132 Citations
6 Claims
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1. A liquid crystal display device, comprising:
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a twisted nematic liquid crystal display cell defining a display screen having a rear edge as viewed from the user and including a pair of spaced apart opposed substrates with electrodes selectively disposed thereon and a nematic liquid crystal material disposed in the space between the substrates; a pair of polarizing plates disposed on opposite sides of the liquid crystal cell; at least one layer of an optically anisotropic substance disposed between said liquid crystal cell and one of said polarizing plates and serving as a phase difference plate; and a reflector disposed beneath the lower of the polarizing plates, wherein the value of the ratio K of the product Δ
n1·
d1, where Δ
n1 is the optical anisotropy and d1 is the thickness in the vertical direction of said phase difference plate, to the product Δ
n2·
d2, wherein Δ
n2 is the optical anisotropy and d2 is the thickness of said phase difference plane when inclined at 45°
from the vertical direction of said phase difference plate in the direction of the optical axis, is set at a predetermined level, and the optical axis of said phase difference plane is disposed at a predetermined angle with respect to the observation direction, said observation direction being both in the plane of the display screen and substantially perpendicular to the rear edge thereof, the observation direction being the direction of the projection in the plane of the display screen of the direction from which a user of said display device most frequently views said display screen, said predetermined angle being chosen in relation to said predetermined level of K such that the reflectance of said display is substantially maximized;wherein the value of K is greater than or equal to 1.20 and the predetermined angle at which the optical axis of said phase difference plane is disposed with respect to the observation direction is in the range from about +30°
to about +60°
or in the range from about -30°
to about -60°
, wherein the values of these angles are positive when measured clockwise from the observation direction. - View Dependent Claims (2)
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3. A liquid crystal display device, comprising:
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a twisted nematic liquid crystal display cell defining a display screen having a rear edge as viewed from the user and including a pair of spaced apart opposed substrates with electrodes selectively disposed thereon and a nematic liquid crystal material disposed in the space between the substrates; a pair of polarizing plates disposed on opposite sides of the liquid crystal cell; at least one layer of an optically anisotropic substance disposed between said liquid crystal cell and one of said polarizing plates and serving as a phase difference plate; and a reflector disposed beneath the lower of the polarizing plates, wherein the value of the ratio K of the product Δ
n1·
d1, where Δ
n1 is the optical anisotropy and d1 is the thickness in the vertical direction of said phase difference plate, to the product Δ
n2·
d2, wherein Δ
n2 is the optical anisotropy and d2 is the thickness of said phase difference plane when inclined at 45°
from the vertical direction of said phase difference plate in the direction of the optical axis, is set at a predetermined level, and the optical axis of said phase difference plane is disposed at a predetermined angle with respect to the observation direction, said observation direction being both in the plane of the display screen and substantially perpendicular to the rear edge thereof, the observation direction being the direction of the projection in the plane of the display screen of the direction from which a user of said display device most frequently views said display screen, said predetermined angle being chosen in relation to said predetermined level of K such that the reflectance of said display is substantially maximized;wherein the value of K is less than 1.20 and the predetermined angle at which the optical axis of said phase difference plane is disposed with respect to the observation direction is from about +30°
to about +120°
, where the values of these angles are positive when measured clockwise from the observation direction. - View Dependent Claims (4)
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5. A liquid crystal display device, comprising:
-
a twisted nematic liquid crystal display cell defining a display screen having a rear edge as viewed from the user and including a pair of spaced apart opposed substrates with electrodes selectively disposed thereon and a nematic liquid crystal material having positive dielectric anisotropy disposed in the space between the substrates such that the liquid crystal molecules are essentially homogeneously aligned so as to provide a helical structure having a twist angle of about 180°
to about 270°
;a pair of polarizing plates disposed on opposite sides of the liquid crystal cell; at least one layer of an optically anisotropic substance disposed between said liquid crystal cell and one of said polarizing plates and serving as a phase difference plate for color compensation; and a reflector disposed beneath the lower of the polarizing plates, wherein the value of the ratio K of the product Δ
n1·
d1, where Δ
n1 is the optical anisotropy and d1 is the thickness in the vertical direction of said phase difference plate, to the product Δ
n2·
d2, where Δ
n2 is the optical anisotropy and d2 is the thickness of said phase difference plate when inclined at 45°
from the vertical direction of said phase difference plate in the direction of the optical axis, is in the range of K equal to or greater than 1.20, and the optical axis of said phase difference plate is disposed at an angle in the range from about +30°
to about +60°
, or in the range of from about -30°
to about -60°
with respect to the observation direction, where the values of angles are positive when measured clockwise from the observation direction, said observation direction being both in the plane of the display screen and substantially perpendicular to the rear edge thereof, the observation direction being the direction of the projection in the plane of the display screen of the direction from which a user of said display device most frequently views said display screen.
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6. A liquid crystal display device, comprising:
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a twisted nematic liquid crystal display cell defining a display screen having a rear edge as viewed from the user and including a pair of spaced apart opposed substrates with electrodes selectively disposed thereon and a nematic liquid crystal material having positive dielectric anisotropy disposed in the space between the substrates such that the liquid crystal molecules are essentially homogeneously aligned so as to provide a helical structure having a twist angle of about 180°
to about 270°
;a pair of polarizing plates disposed on opposite sides of the liquid crystal cell; at least one layer of an optically anisotropic substance disposed between said liquid crystal cell and one of said polarizing plates and serving as a phase difference plate for color compensation; and a reflector disposed beneath the lower of the polarizing plates, wherein the value of the ratio K of the product Δ
n1·
d1, where Δ
n1 is the optical anisotropy and d1 is the thickness in the vertical direction of said phase difference plate, to the product Δ
n2·
d2, where Δ
n2 is the optical anisotropy and d2 is the thickness of said phase difference plate when inclined at 45°
from the vertical direction of said phase difference plate in the direction of the optical axis, is set in the range of K less than 1.20, and the optical axis of said phase difference plane is disposed at an angle in the range of from about +30°
to about +120°
with respect to the observation direction, where the values of the angles are positive when measured clockwise from the observation direction, said observation direction being both in the plane of the display screen and substantially perpendicular to the rear edge thereof, the observation direction being the direction of the projection in the plane of the display screen of the direction from which a user of said display device most frequently views said display screen.
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Specification
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Current AssigneeSeiko Epson Corporation (Seiko Group)
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Original AssigneeSeiko Epson Corporation (Seiko Group)
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InventorsWada, Hiroshi, Nishizawa, Hitoshi
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Primary Examiner(s)Gross, Anita P.
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Application NumberUS08/009,848Time in Patent Office440 DaysField of Search359/73, 359/63, 359/102US Class Current349/119CPC Class CodesG02F 1/133531 characterised by the arrang...G02F 1/13363 Birefringent elements, e.g....G02F 1/1396 the liquid crystal being se...G02F 2202/40 Materials having a particul...G02F 2413/02 Number of plates being 2G02F 2413/08 with a particular optical a...
