Method of making a liquid crystal device

Details Method of making a liquid crystal device Method of making a liquid crystal device

1998-07-14

2001-12-18

Sikes, William L. (Department: 2871)

Liquid crystal cells, elements and systems

Particular structure

Having significant detail of cell structure only

C349S154000

Reexamination Certificate

active

06331884

ABSTRACT:

This application is based on Japanese application No. 9-193488, the contents of which is hereby incorporated by reference.
FIELD OF THE INVENTION
The present invention relates to a method of making a liquid crystal device which uses liquid crystal material for displaying or recording images and others.
BACKGROUND OF THE INVENTION
Various kinds of liquid crystal devices having a memory effect have been proposed.
U.S. Pat. No. 3,578,844 has disclosed a liquid crystal device in which a cholesteric liquid crystal material capsulated by a polymer compound such as gelatin or gum arabi is held between a pair of bases. According to the disclosure, this liquid crystal device has a memory effect, and attains a predetermined display state when a voltage is applied thereto, and this display state will be stably maintained even after stopping the application of a voltage. This is liquid crystal device performs the display based on a difference in quantity of reflected light, which is caused by applying the voltage to change the orientation state of cholesteric liquid crystal material having a selective reflection wavelength in a visible range.
The above liquid crystal device having the composite layer or film, which includes the polymer material and the cholesteric liquid crystal material, does not require a polarizer because it utilizes selective reflection of incident light by the liquid crystal material. Therefore, it is capable of bright display of the reflection type. Further, high-resolution display can be performed by simple matrix driving without using a memory element such as a TFT or an MIM.
The liquid crystal device of the reflection type utilizing the selective reflection of the cholesteric liquid crystal material changes the display state by selectively attaining the planar orientation and the focal conic orientation. In the planar orientation, helical axes of the liquid crystal molecules forming each domain are perpendicular to the base. In the focal conic orientation, the helical axes of the liquid crystal molecules forming each domain are irregularly directed or substantially parallel to the base.
FIGS.
7
(A) and
7
(B) schematically show an example of a conventional liquid crystal device having a composite layer, which includes a polymer material and a liquid crystal material exhibiting a cholesteric-characteristic.
In this liquid crystal device, a composite layer
3
is retained between a pair of transparent bases or plates
1
a
and
1
b
opposed to each other. Transparent conductive films
2
a
and
2
b
are formed on inner surfaces of the bases
1
a
and
1
b
, respectively. The composite layer
3
is made of, e.g., a mesh structure
3
b
of resin and a liquid crystal material
3
a
filling a space in the resin structure
3
b
. A black light absorbing layer
4
is arranged on the outer side of the transparent base
1
b
. The liquid crystal material
3
a
exhibits a cholesteric characteristic, and displays a predetermined color by reflecting the light of the selective reflection wavelength corresponding to the helical pitch length when it is in a planar orientation shown in FIG.
7
(A), if the selective reflection wavelength is in the visible range. In the focal conic orientation shown in FIG.
7
(B), it displays the background color, i.e., black. If the helical pitch length is relatively long, e.g., in such a case that the selective reflection wavelength is in an infrared range, the liquid crystal material
3
a
reflects the light in the infrared range to exhibit a transparent appearance when it is in the planar orientation shown in FIG.
7
(A), and exhibits an opaque appearance when it is in the focal conic orientation shown in FIG.
7
(B). Accordingly, this liquid crystal device can perform the mono-color display between the selective reflection color (planar orientation) and the background color (focal conic orientation) or between the background color (planar orientation) and white (focal conic orientation). For driving this liquid crystal device, a predetermined pulse voltage is applied across the conductive films
2
a
and
2
b
from a power source (not shown) for switching the state of the liquid crystal material
3
a
between the planar orientation and the focal conic orientation.
For attaining a multi-color display by the liquid crystal device having the composite layer which includes the resin and the liquid crystal material exhibiting the cholesteric characteristic, the liquid crystal device may have a layered structure including multiple composite layers which are layered together and can attain the planar orientations exhibiting different colors, respectively. An example of the liquid crystal device of the multi-layer type is shown in FIG.
8
. The structure of the liquid crystal device shown in
FIG. 8
was devised by the inventors and others during development of the invention.
This liquid crystal device includes three composite layers
3
A,
3
B and
3
C, each of which is held between a pair of transparent bases or plates. These layers
3
A,
3
B and
3
C reflect visible rays of different wavelengths and thereby exhibit different colors, respectively, when they are in the planar orientation. The composite layer
3
A is held between the transparent bases
1
A and
1
B which are provided with transparent conductive films
2
A and
2
B opposed to the layer
3
A, respectively. The composite layer
3
B is held between the transparent bases
1
B and
1
C which are provided with transparent conductive films
2
C and
2
D opposed to the layer
3
B, respectively. The transparent base
1
B is commonly used for holding the composite layers
3
A and
3
B, and the transparent conductive films
2
B and
2
C are arranged on the opposite surfaces thereof, respectively. The composite layer
3
C is held between the transparent bases IC and
1
D, which are provided with transparent conductive films
2
E and
2
F opposed to the layer
3
C, respectively. The transparent base
1
C is commonly used for holding the composite layers
3
B and
3
C, and carries the transparent conductive films
2
D and
2
E on its opposite surfaces, respectively. A black absorbing layer
4
′ is arranged on the outer side of the transparent base
1
D.
The composite layers
3
A,
3
B and
3
C are formed of resin structures
3
b
A,
3
b
B and
3
b
C of, e.g., mesh forms, and liquid crystal materials
3
a
A,
3
a
B and
3
a
C filling the spaces in the resin matrixes
3
b
A,
3
b
B and
3
b
C, respectively. Liquid crystal materials
3
a
A,
3
a
B and
3
a
C exhibit red, green and blue appearances when they are in the planar orientation, respectively, and exhibit transparent appearances when they are in the focal conic orientation.
FIG. 8
shows the liquid crystal materials
3
a
A,
3
a
B and
3
a
C in the planar orientation.
The transparent conductive films
2
A-
2
F form electrodes, each of which takes the form of a matrix, and forms pixels with respect to the corresponding composite layer.
When driving this liquid crystal device, the display states of the composite layers
3
A,
3
B and
3
C are individually controlled by controlling application of voltages from the power source (not shown) across the transparent conductive films
2
A and
2
B, across transparent conductive films
2
C and
2
D, and across the transparent conductive films
2
E and
2
E, respectively. Thereby, the display in multiple colors and, more specifically, eight colors including black can be performed on a predetermined pixel.
However, the following disadvantages arise when performing the multi-color display by the liquid crystal device of the above layered type.
First, all the composite layers are set to the focal conic orientation to attain transparent states so as to perform black display. In this case, a large quantity of incident light is reflected by the base surfaces and thus the degree of transparency lowers because the bases arranged between the viewer side and the black light absorbing layer are large in number. Consequently, the contrast is liable to be low.
Secondly, relative positioning between the respec

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