Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2004-02-09
2004-11-09
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S130000, C349S129000
Reexamination Certificate
active
06816223
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vertically oriented liquid crystal display element.
2. Brief Description of the Related Art
FIGS. 11A and 11B
are drawings illustrating an arrangement of a typical vertically oriented liquid crystal display element (hereinafter referred as “LCD element”).
FIG. 11A
is a side view and
FIG. 11B
is a plan view.
Reference characters “
101
a
” and “
101
b
” in
FIG. 11A
are an upper glass substrate and a lower glass substrate and liquid crystal molecules
102
are sandwiched in between. On inner surfaces of both glass substrates, transparent electrodes (not shown in
FIG. 11A
) for driving liquid crystal molecules are formed. Reference characters “
103
a
” and “
103
b
” are polarizing plates and a reference character “
104
” is a visual angle compensation film. In
FIG. 11B
, a reference character “X” is a light transmission axis of the upper polarizing plate
103
a
, a reference character “Y” is a light transmission axis of the lower polarizing plate
103
b
and reference character “Z” is a tilting direction of the liquid crystal molecules
102
.
In the LCD element, a liquid crystal cell consisting of the vertically oriented liquid crystal molecules, is arranged between the polarizing plates
103
a
and
103
b
arranged in a cross Nicol relation each other such that the tilting direction Z and the light transmission axis X of the polarizing plate
103
a
form an angle of 45 degree, and the tilting direction Z and the light transmission axis Y of the polarizing plate
103
b
also form an angle of 45 degree. The tilting direction Z of the liquid crystal molecules is controlled by a pre-tilted angle, which is attained when vertically orienting membranes (not shown in
FIG. 11A
) applied and baked on the glass substrates are treated, for example, are rubbed in a predetermined direction. In addition, a visual angle compensation film
104
is inserted between the upper glass substrate
101
a
and the upper polarizing plate
103
a
In order to improve obliquely viewed visibility of the LCD element.
A uniaxial optical film having-an optical axis normal to a film plane and having a negative double refractive index [=(a refractive index in the film plane)−(a refractive index in the optical axis)] is employed as the visual angle compensation film
104
. The visual angle compensation film
104
can be arranged at one side or both sides of the liquid crystal cell. A suitable retardation value of the visual angle compensation film
104
is approximately in a range from one third to the same retardation value of the liquid crystal cell. “Retardation value” is an index defined as follows: (a difference between a refractive index on the film plane and a refractive index in a normal direction to the film plane)×(a thickness of the film). If the visual angle compensation films
104
are arranged on both sides of the liquid crystal cell, a combined retardation value “with retardation values of both films should be adjusted in the above-mentioned range.
The above-mentioned LCD element is proposed by the same inventors as inventors of the present invention.
Another LCD element, for example, Japanese patent registered No. 3108768 proposes an electrode arrangement where transparent electrodes on the upper and lower glass substrates are partially removed, so as to form slits in the electrodes. And the slits on the upper and lower electrodes are alternately arranged when the electrodes are vertically viewed. Other LCD element, for example, Japanese patent registered No. 3324926 proposes another electrode arrangement where elongated slits are respectively formed in pairs on an upper substrate and a lower substrate.
Since liquid crystal molecules in the above-mentioned LCD elements are tilted in one direction, obliquely viewed visibility of these LCD elements is not improved as shown in
FIG. 12
even when visual angle compensation films are combined.
In
FIG. 12
, digits around a most outer circle are viewing directions projected on a horizontal plane. Namely, “0” means, a viewing direction from the right side and “180” means a viewing direction from the left side. Concentric circles (0 to 60) are angles formed between the viewing directions and a normal line to the LCD element, namely, “0” means a viewing direction normal to the LCD element and “60” means a viewing direction having an angle of 60 degree against the normal line. A reference character “CR” in the drawing means a ratio of a bright transmission rate/a dark transmission rate (a contrast value) in respective viewing directions. Which means the larger a CR value is, the clearer a displayed image in the LCD element is.
FIG. 12
indicates the obliquely viewed visibility of the above-mentioned LCD element In a tilting direction of the liquid crystal molecules (in this case in a 6 o'clock direction) is deteriorated such that contrast values In some area are less than 1, in other words, inverted contrast areas are formed (hatched areas in FIG.
12
).
SUMMARY OF THE INVENTION
The present invention is carried out in view of the above-mentioned problems in order to provide a vertically oriented LCD element of higher quality by improving obliquely viewed visibility so as to obtain almost uniform visibility viewed from any direction.
The following arrangements by the present invention can provide the LCD element mentioned above.
(1) A liquid crystal display element comprising: a pair of substrates; transparent electrodes having predetermined patterns formed on the respective substrates; vertical orienting membranes respectively formed on the transparent electrodes; and a liquid crystal layer consisting of the liquid crystal molecules sandwiched by the substrates, wherein: pair of the substrates are arranged such that: respective transparent electrodes face each other; series of the nearly rectangular slits are formed on respective transparent electrodes by removing portions of the electrodes in a display area formed by the electrodes; and series of the slits on one and other transparent electrodes are alternately arranged in a normal direction to a longitudinal direction of series of the slits, when the substrates are viewed vertically.
(2) The liquid crystal display element according to (1), wherein: a width of the slits in the normal direction to the longitudinal direction of the slits is set more than 10 &mgr;m, but less than 30 &mgr;m.
(3) The liquid crystal display element according to (1), wherein: a width of the slits in the normal direction to the longitudinal direction of the slits is set 2.5 times more than a thickness of the liquid crystal layer.
(4) The liquid crystal display element according to (1), wherein: a horizontal distance between two neighboring alternately arranged slits in the normal direction to the longitudinal direction of the slits is set more than 10 &mgr;m, but less than 60 &mgr;m.
(5) The liquid crystal display element according to (1), wherein: a horizontal distance between two neighboring alternately arranged slits in the normal direction to the longitudinal direction of the slits is set more than the width of the slits, but less than 60 &mgr;m.
(6) The liquid crystal display element according to one of (1) to (5), wherein: the display area is a segment display type area.
(7) The liquid crystal display element according to one of (1) to (5), wherein: the display area is a dot-matrix display type area driven by a simple matrix driving method.
(8) The liquid crystal display element according to one of (1) to (5), wherein: the display area is a area combined a segment display type area and a dot-matrix display type area driven by a simple matrix driving method.
(9) The liquid crystal display element according to one of (1) to (5), wherein: the display area is a dot-matrix display type area driven by an active matrix.
(10) The liquid crystal display element according to (7) or (8), wherein: slits both ends of one dot in a normal direction to the longitudinal direction of the slits are formed on the el
Iwamoto Yoshihisa
Sugiyama Takashi
Carella Byrne Bain Gilfillan et al.
Olstein Elliot M.
Squire William
Stanley Electric Co. Ltd.
Ton Toan
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