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ECB type liquid crystal display device having birefringent layer with equal refractive indexes in the thickness and plane directions
| Details |
Inventors: Kanemoto, Akihiko; Takiguchi, Yasuyuki; Iimura, Haruo;
Assignee: Ricoh Company, Ltd. (Tokyo, JP)
Primary Examiner: James; Andrew J.
Assistant Examiner: Duong; Tai V.
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt
A liquid crystal display device including (1) a liquid crystal cell in which a liquid crystal layer with a liquid crystal composition having a positive dielectric anisotropy is sandwiched between a pair of substrates each having at least one electrode, and the liquid crystal molecules in the liquid crystal layer are homogeneously aligned between the substrates, (2) a pair of polarizers disposed so as to sandwich the liquid crystal cell therebetween and (3) at least one birefringent layer sandwiched between the liquid crystal layer and the polarizer, in which the maximum refractive index direction within the plane of the birefringent layer is substantially perpendicular to the aligning direction of the liquid crystal molecules. The device is excellent particularly in highly multiplexing driving characteristic as a black and white light shutter or a color display device. |
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DETAILED DESCRIPTION OF THE INVENTION The present invention concerns a liquid crystal display device comprising: (1) a liquid crystal cell in which a liquid crystal layer comprising a liquid crystal composition having a positive dielectric anisotropy is sandwiched between a pair of substrates each having at least one electrode, and liquid crystal molecules in the liquid crystal layer are homogeneously aligned between both the substrates, (2) a pair of polarizers disposed so as to sandwich the liquid crystal cell therebetween, and (3) at least one birefringent layer sandwiched between the liquid crystal layer and at least one of both the polarizers, wherein (i) the transmission axes of both the polarizers are substantially perpendicular to each other, (ii) the maximum refractive index direction within the plane of the birefringent layer is substantially perpendicular to the aligning direction of the liquid crystal molecules in the liquid crystal layer and makes an angle of from 6.
degree.
to 84.
degree.
relative to the transmission axis or the absorption axis of the polarizer adjacent to the birefringent layer and, further, (iii) the product .
DELTA.
n.
sub.
L .
multidot.
d.
sub.
L of the refractive index anisotropy .
DELTA.
n.
sub.
L of the liquid crystal layer and the thickness d.
sub.
L of the liquid, crystal layer, and the product .
DELTA.
n.
sub.
C .
multidot.
d.
sub.
C of the refractive index anisotropy .
DELTA.
n.
sub.
C within the plane of the birefringent layer and the thickness d.
sub.
C of the birefringent layer have the following relationship: -0.
1 .
mu.
m<(.
DELTA.
n.
sub.
L .
multidot.
d.
sub.
L -.
DELTA.
n.
sub.
C .
multidot.
d.
sub.
C).
ltoreq.
0.
27 .
mu.
m In the liquid crystal display device according to the present invention, if the difference between the retardation .
DELTA.
n.
sub.
L .
multidot.
d.
sub.
L of the liquid crystal layer and the retardation .
DELTA.
n.
sub.
C .
multidot.
d.
sub.
C of the birefringent layer is greater than 0.
27 .
mu.
m, the device is colored in the bright state owing to the birefringence.
In the liquid crystal display device according to the present invention, when the difference between the retardation
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LCD 
