Liquid crystal composition and liquid crystal display device

A liquid crystal composition comprising a fluorine liquid crystal material and at least one azo dichroic dye selected from each of the groups (A), (B), (C) and (D) represented by the following general formulae (I)-(IV): ##STR1##

FIELD OF THE INVENTION 
The present invention relates to a liquid crystal composition for a liquid 
crystal display device which is used as a display device or the like, and 
a liquid crystal display device utilizing such liquid crystal composition. 
BACKGROUND OF THE INVENTION 
Recently liquid crystal displays have been desired which have 
high-performance display quality closely approaching the performance of 
usual displays or Braun tubes. With the problems involving response time, 
contrast, visual angle characteristics and the like, it has been difficult 
to provide such liquid crystal displays according to the simple 
matrix-driven system using the super twist nematic liquid crystals (STN) 
or the like of the prior art. Therefore the active matrix-driven system 
has been proposed which employs an active element such as thin-film 
transistor or the like. 
For active matrix-driven displays, charge is supplied to each pixel only 
during the line access time. Therefore, it is important for each pixel to 
hold this charge over the frame time in order to realize maximum 
brightness and contrast ratio. 
In other words, the voltage holding ratio has a very important significance 
for active matrix-driven displays. At low voltage holding ratios, the 
voltage supplied across the pixel electrode and the opposite electrode 
drops during the field cycle. 
That is, the effective voltage applied to the liquid crystal lowers, 
thereby causing a drastic decrease in contrast, and thus the provision of 
high-performance displays has been difficult. 
Thus it has become necessary to use a liquid crystal material with a high 
capacity of holding charge over the frame time, i.e., a material having a 
high voltage holding ratio. 
For these liquid crystal elements there have usually been used, instead of 
the cyano group-containing liquid crystal materials of the prior art, 
fluorine liquid crystal materials with a substituent comprising a fluorine 
atom, e.g., fluorine atom itself, fluoromethyl group such as 
trifluoromethyl group or fluoromethoxy group such as trifluoromethoxy 
group, which are hard to include ionic impurities. With addition of a 
dichroic dye thereto, these fluorine liquid crystal materials, however, 
often raise a problem of greatly spoiled voltage holding properties, for 
which the utilization of active matrix-driven liquid crystal display 
devices by making use of guest-host liquid crystal compositions has been 
difficult. 
In addition, relating to these dichroic dyes and guest-host liquid crystal 
compositions with them added thereto, it is difficult to determine whether 
the spoiling of the voltage holding properties is due to the influence of 
the ionic impurities which are included in the dye or is caused by the 
molecular structure of the dye, for which and some other reasons the 
cause-effect relationship between the voltage holding ratio and the other 
parameters has not been elucidated. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide a color liquid crystal 
composition with a high voltage holding ratio and liquid crystal display 
device, which can be a solution to the problem of the prior art mentioned 
above. 
Aiming to solve the above-described problem of the spoiled voltage holding 
ratio for guest-host liquid crystal compositions, we the inventors have 
made intensive investigations and, as a result, we have found that the 
combined use of plural dichroic dyes of certain molecular structures and a 
fluorine liquid crystal material makes it possible to keep the voltage 
holding ratio of guest-host liquid crystal compositions at 80% or more, 
preferably 90% or more, of that of host liquid crystal materials, thus 
having achieved the present invention. 
In brief, the present invention resides in a liquid crystal composition 
characterized by containing a fluorine liquid crystal material and at 
least one dichroic dye selected from each of the groups (A), (B), (C) and 
(D) described hereinafter and a liquid crystal display device 
characterized by comprising such liquid crystal composition sandwiched 
between electrode plates at least one of which is transparent. 
Hereunder a more detailed explanation will be made of the present invention 
.

DETAILED DESCRIPTION OF THE INVENTION 
The liquid crystal composition according to the present invention has hues 
of black, dark blue, brown and so on, and the dyes used according to the 
present invention produce expected effects when they are combinations of 
dichroic dyes belonging to the respective groups referred to hereunder, 
all of which are publicly known. The dyes represented by the general 
formula (I) given below are described in, for example, U.S. Pat. No. 
4,737,310, those represented by the general formula (II) given below, in, 
for example, U.S. Pat. No. 4,600,527 and those represented by the general 
formula (IV) given below, in, for example, U.S. Pat. No. 4,507,221, 
respectively. 
Also the dyes represented by the general formula (III) are described in 
Japanese Patent Laid-Open No. 301850/88 et al., some of which are 
commercially available from Nihon Kanko Sikiso Inc. 
Hereunder the details of the dyes available for use according to the 
present invention will be explained. 
Group (A): Azo dichroic dyes represented by the following general formula 
(I): 
##STR2## 
wherein R.sup.1 usually represents a hydrogen atom, alkyl group, 
alkoxyalkyl group, alkoxy group, halogen atom, or cyclohexyl or phenyl 
group which may be substituted with an alkyl group, alkoxy group, halogen 
atom or alkoxyalkyl group, preferably a hydrogen atom, alkyl group, 
alkoxyalkyl group or alkoxy group, and more preferably a C.sub.1-12 alkoxy 
group; 
R.sup.2 usually represents an alkyl group, alkoxyalkyl group, or 
cyclohexylmethyl or benzyl group which may be substituted with an alkyl 
group, alkoxyalkyl group, alkoxy group or halogen atom, preferably 
##STR3## 
wherein 
##STR4## 
epresents a cyclohexyl or phenyl group, and R.sup.16 represents a hydrogen 
atom, an alkyl group, alkoxyalkyl group, alkoxy group or halogen atom, and 
more preferably 
##STR5## 
wherein R.sup.17 represents a C.sub.1-12 alkoxy group; and usually R.sup.3 
-R.sup.5 each represents a hydrogen atom, methyl group, methoxy group or 
halogen atom, or R.sup.4 and R.sup.5 may be connected to each other to 
form an aromatic ring when they are located on neighboring carbon atoms, 
preferably R.sup.3 represents a hydrogen atom or methyl group, and more 
preferably a hydrogen atom, and preferably R.sup.4 and R.sup.5 each 
represent a hydrogen atom or are located on neighboring carbon atoms to be 
connected to each other thereby forming an aromatic ring, and more 
preferably R.sup.4 and R.sup.5 are located on neighboring carbon atoms to 
be connected to each other thereby forming a naphthylene group as a whole 
together with the phenylene group to which they combine. 
Group (B): Azo dichroic dyes represented by the following general formula 
(II): 
##STR6## 
wherein R.sup.6 and R.sup.7 each usually represents a hydrogen atom, alkyl 
group, alkoxyalkyl group, alkoxy group, halogen atom, or cyclohexyl or 
phenyl group which may be substituted with an alkyl group, alkoxy group, 
alkoxyalkyl group or halogen atom, preferably a hydrogen atom, alkyl 
group, alkoxyalkyl group, alkoxy group, 
##STR7## 
wherein 
##STR8## 
represents a phenyl or cyclohexyl group, and R.sup.18 represents a 
hydrogen atom, alkyl group or alkoxy group, or halogen atom, and more 
preferably R.sup.6 represents a C.sub.1-12 alkyl group, and R.sup.7 
represents an C.sub.1-12 alkoxy group. 
Group (C): Azo dichroic dyes represented by the following general formula 
(III): 
##STR9## 
wherein R.sup.8 -R.sup.10 each usually represents a hydrogen atom, alkyl 
group, alkoxyalkyl group, alkoxy group, halogen atom, or cyclohexyl or 
phenyl group which may be substituted with an alkyl group, alkoxy group, 
halogen atom or alkoxyalkyl group, preferably an alkyl group, alkoxyalkyl 
group or alkoxy group, and more preferably a C.sub.1-12 alkyl group; and 
R.sup.11 -R.sup.13 each usually represents a hydrogen atom, methyl group, 
methoxy group or halogen atom, or R.sup.12 and R.sup.13 may be connected 
to each other to form an aromatic ring when they are located on 
neighboring carbon atoms, preferably R.sup.11 represents a hydrogen atom, 
and R.sup.12 and R.sup.13 are connected to each other to form an aromatic 
ring when they are located on neighboring carbon atoms, and more 
preferably R.sup.11 represents a hydrogen atom, and R.sup.12 and R.sup.13 
are located on neighboring carbon atoms to be connected to each other 
thereby forming a naphthylene group as a whole together with the phenylene 
group to which they combine. 
Group (D): Anthraquinone dichroic dyes represented by the following general 
formula (IV): 
##STR10## 
wherein R.sup.14 and R.sup.15 each usually represents a hydrogen atom; 
alkyl group; alkoxyalkyl group; alkoxy group; halogen atom; or cyclohexyl 
or phenyl group which may be substituted with an alkyl group, alkoxyalkyl 
group, halogen atom or alkoxy group, preferably R.sup.14 represents an 
alkyl group, alkoxy group or alkoxyalkyl group, and R.sup.15 represents a 
hydrogen atom, alkyl group, alkoxy group or alkoxyalkyl group, and more 
preferably R.sup.14 and R.sup.15 each represents a C.sub.1-12 alkyl group. 
Examples of the alkyl group used for the definition of R.sup.1 , R.sup.2, 
R.sup.6 -R.sup.10, R.sup.14 and R.sup.15 in the general formulae (I), 
(II), (III) and (IV) given above include C.sub.1-12 linear and branched 
alkyl groups such as methyl group, ethyl group, propyl group, butyl group, 
pentyl group, hexyl group, octyl group, nonyl group, dodecyl group, etc.; 
examples of the alkoxy group include C.sub.1-12 linear and branched alkyl 
groups which correspond to the above-enumerated alkyl groups; examples of 
the alkoxyalkyl group include C.sub.2-8 linear and branched alkyl groups, 
e.g., methoxymethyl group, buthoxymethyl group, ethoxyethyl group, 
buthoxyethyl group and so on; and examples of the halogen atom include 
fluorine atom, chlorine atom, bromine atom, etc. The above-listed examples 
are also illustrations of the substituents of the substituted cyclohexyl 
group, substituted cyclohexylmethyl group, substituted phenyl group and 
substituted benzyl group in R.sup.1, R.sup.2, R.sup.6 -R.sup.10, R.sup.14 
and R.sup.15. 
At least one is selected from each of those groups for use according to the 
present invention, and for the combined use of the dyes, and selection is 
made preferably of desired ones of the respective groups, and most 
preferably of the most desired ones chosen from each of the groups. Here, 
the dye selected from each of the groups is not necessary to be one, and 
two or more may be selected therefrom for use. 
Examples of these dyes of the respective groups used according to the 
present invention are enumerated in Table-1 given below. 
TABLE 1 
__________________________________________________________________________ 
General Formula 
I: 
##STR11## 
Dyes 
R.sup.1 
R.sup.2 R.sup.3 
R.sup.4 R.sup.5 
__________________________________________________________________________ 
I-1 
C.sub.8 H.sub.17 (n) 
##STR12## H Connected to each other to form a part of a 
naphthalene ring. 
I-2 
C.sub.8 H.sub.17 (n) 
##STR13## H Connected to each other to form a part of a 
naphthalene ring. 
I-3 
C.sub.4 H.sub.9 (n) 
##STR14## H Connected to each other to form a part of a 
naphthalene ring. 
I-4 
C.sub.4 H.sub.9 (n) 
##STR15## CH.sub.3 
H H 
I-5 
C.sub.4 H.sub.9 (n) 
##STR16## H Connected to each other to form a part of a 
naphthalene ring. 
I-6 
OC.sub.4 H.sub.9 (n) 
##STR17## H Connected to each other to form a part of a 
naphthalene ring. 
I-7 
H 
##STR18## H Connected to each other to form a part of a 
naphthalene ring. 
I-8 
C.sub.4 H.sub.9 (n) 
##STR19## H H H 
__________________________________________________________________________ 
General Formula 
II: 
##STR20## 
Dyes 
R.sup.6 R.sup.7 
__________________________________________________________________________ 
I-1 C.sub.4 H.sub.9 (n) OC.sub.4 H.sub.9 (n) 
I-2 C.sub.4 H.sub.9 (n) OC.sub.5 H.sub.11 (n) 
I-3 C.sub.4 H.sub.9 (n) H 
I-4 OC.sub.3 H.sub.7 (n) OC.sub.4 H.sub.9 (n) 
I-5 Br OC.sub.4 H.sub.9 (n) 
I-6 Br C.sub.4 H.sub.9 (n) 
I-7 C.sub.4 H.sub.9 (n) C.sub.7 H.sub.15 (n) 
I-8 
##STR21## Cl 
__________________________________________________________________________ 
General Formula 
III: 
##STR22## 
Dyes 
R.sup.8 
R.sup.9 
R.sup.10 
R.sup.11 
R.sup.12 R.sup.13 
__________________________________________________________________________ 
III-1 
C.sub.4 H.sub.9 (n) 
C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
H Connected to each other to form a 
part of a naphthalene ring. 
III-2 
C.sub.8 H.sub.17 (n) 
C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
H Connected to each other to form a 
part of a naphthalene ring. 
III-3 
C.sub.4 H.sub.9 (n) 
C.sub.3 H.sub.7(n) 
C.sub.3 H.sub.7(n) 
H Connected to each other to form a 
part of a naphthalene ring. 
__________________________________________________________________________ 
General Formula 
IV: 
##STR23## 
Dyes 
R.sup.6 R.sup.7 
__________________________________________________________________________ 
IV-1 C.sub.4 H.sub.9 (n) 
C.sub.4 H.sub.9 (n) 
IV-2 C.sub.4 H.sub.9 (n) 
C.sub.8 H.sub.17 (n) 
IV-3 C.sub.3 H.sub.7 (n) 
Cl 
I-4 C.sub.4 H.sub.9 (n) 
OCH.sub.3 
IV-5 C.sub.8 H.sub.17 (n) 
H 
IV-6 C.sub.4 H.sub.9 (n) 
##STR24## 
__________________________________________________________________________ 
The liquid crystal material as used according to the present invention 
includes a fluorine liquid crystal material composition consisting mainly 
of liquid crystal materials with a substituent comprising a fluorine atom, 
e.g., fluorine atom itself, fluoromethyl group such as trifluoromethyl 
group or fluoromethoxy group such as trifluoromethoxy group, which are 
mixtures of various liquid crystal materials represented by the structural 
formulae given below, and having a voltage holding ratio of 95% or more 
even at a high temperature of 100.degree. C. 
##STR25## 
wherein R' and X' each represents independently alkyl group, alkoxyalkyl 
group, alkoxy group, alkylphenyl group, alkoxyalkylphenyl group, 
alkoxyphenyl group, alkylcyclohexyl group, alkoxyalkylcyclohexyl group, 
alkylcyclohexylphenyl group, halogen atom, fluoromethyl group such as 
trifluoromethyl group, fluoromethoxy group such as trifluoromethoxy group, 
alkylphenylalkyl group, alkoxyalkylphenylalkyl group, alkylcyclohexylalkyl 
group, alkoxyalkoxycyclohexylalkyl group, alkoxyphenylalkyl group, 
alkylcyclohexylphenylalkyl group, and the alkyl and alkoxy chains in the 
above-described respective groups may have optically active centers. In 
addition, the phenyl or phenoxy group in R' and X' may be further 
substituted with a halogen atom such as fluorine atom, chlorine atom or 
the like. The phenyl group in each of the formulae may be additionally 
substituted with one or two halogen atoms such as fluorine atoms or 
chlorine atoms. 
Most of the liquid crystal materials mentioned above have positive 
dielectric anisotropy, but even publicly known liquid crystals having 
negative dielectric anisotropy may be employed if they are mixed with 
liquid crystals of positive dielectric anisotropy to produce liquid 
crystal materials whose dielectric anisotropy is positive on the whole. 
Moreover, even liquid crystal materials of negative dielectric anisotropy 
may be used alone by selection of an appropriate device structure and 
driving system. 
Furthermore, the above-mentioned liquid crystal materials may contain 
additional additives, e.g., an optically active substance such as 
cholesteryl nonanoate, ultraviolet absorber, antioxidant, etc. 
The liquid crystal composition according to the present invention may be 
easily prepared by dissolving at least one dye selected from each of the 
groups (A), (B), (C) and (D) in the liquid crystal material referred to 
above in a publicly known manner. 
The quantity of the dyes to be used is 0.1-15% by weight, and preferably 
0.5-5% by weight of the liquid crystal material. 
The resulting guest-host liquid crystal composition usually has a voltage 
holding ratio of the guest-host liquid crystal composition/voltage holding 
ratio of the host liquid crystal material of 0.8 or more, and preferably 
0.9 or more. 
The thus prepared liquid crystal composition may be sandwiched between a 
pair of electrode plates at least one of which is transparent to construct 
a variety of display devices utilizing the guest-host effect, including, 
for example, the Heilmeier mode guest-host, phase transition mode 
guest-host and twist nematic (TN) mode guest-host described in "Handbook 
on Liquid Crystal Devices" edited by the 142nd committee of the Japan 
Society for the Promotion of Science, pp. 315-329, Nikkan Kogyo 
Shinbunsha, and elsewhere, the macromolecular dispersion mode guest-host 
described on pages 367-370 of the "Handbook on Liquid Crystal Devices", 
supra, and elsewhere. 
As mentioned above, a variety of modes of liquid crystal display devices 
may be used according to the present invention, and particularly preferred 
is the phase transition mode producing a bright display, which is obtained 
by adding an optically active substance to a nematic liquid crystal 
composition and does not require the use of a polarizing plate which is 
usually a requisite. 
As an embodiment of the liquid crystal display device of the present 
invention, schematic sectional views of an active-driven phase transition 
mode guest-host type of a liquid crystal display device are shown in FIGS. 
1 and 2. FIG. 1 represents a state of a crystal display device where no 
voltage is applied, while FIG. 2 represents a state of a crystal display 
device where voltage is applied. In the figures, 1 is an incident light, 2 
is a transparent glass plate, 3 is a transparent electrode, 4 is an active 
element, 5 is an alignment layer, 6 is a liquid crystal material, and 7 is 
a dichroic dye. 
The liquid crystal material (6) shows a cholesteric phase when no voltage 
is applied (FIG. 1). As both the dichroic dye (7) and the liquid crystal 
material (6) have a cholesteric structure, the dye (7) is absorbed without 
using a polarizing plate even if the incident light (1) is natural light. 
When voltage is applied (FIG. 2), the liquid crystal material (6) and the 
dichroic dye (7) align in the direction of the electric field thereby 
transmitting the light. 
Transmission and absorption of light in liquid crystal display devices can 
be controlled in this way depending on the presence or absence of electric 
field. 
EXAMPLES 
Hereunder the present invention will be concretely explained with reference 
to the Examples, which however never limit the present invention thereto. 
EXAMPLE 1 
Liquid crystal composition-I was prepared by dissolving the following 
dichroic dyes in 100 g of a liquid crystal mixture commercially available 
under the trade name of ZLI-4792 (manufactured by E. Merck Inc. ) which 
consisted mainly of a fluorine compound. 
______________________________________ 
Dyes: 
______________________________________ 
(I-2) 0.75 g 
(II-1) 
0.20 g 
(III-1) 
0.50 g 
(IV-1) 
2.00 g 
______________________________________ 
This liquid crystal composition-I was sealed in a cell with a gap of 9 
.mu.m which comprised transparent electrodes-fitted glass substrates which 
had been subjected to application of a polyimide resin thereon followed by 
curing, and rubbing treatment for homogeneous alignment and was 
constructed in such a manner that the alignment-treated surfaces faced 
each other, thus preparing a liquid crystal device. This cell was baked at 
a constant temperature of 110.degree. C. for 1 hour, after which at 
25.degree. C. pulse signals were applied thereto at a frame frequency of 
30 Hz and a voltage of 5 V for an ON time of 60 .mu.seconds for the 
determination of the voltage-holding ratio. The voltage-holding ratio of 
the guest-host liquid crystal composition/the voltage holding ratio of the 
host liquid crystal material was calculated to be a satisfactory value of 
0.93. 
EXAMPLE 2 
Liquid crystal composition-II was prepared by dissolving the following 
dichroic dyes in 100 g of a liquid crystal mixture commercially available 
under the trade name of ZLI-5080 (manufactured by E. Merck Inc.) which 
consisted mainly of a fluorine compound. 
______________________________________ 
Dyes: 
______________________________________ 
(I-2) 0.72 g 
(II-1) 
0.23 g 
(III-1) 
0.43 g 
(IV-1) 
2.02 g 
______________________________________ 
This liquid crystal composition-II was sealed in a cell with a gap of 6 
.mu.m which comprised transparent electrodes-fitted glass substrates which 
had been subjected to application of a polyimide resin thereon followed by 
curing, and rubbing treatment for homogeneous alignment and was 
constructed in such a manner that the alignment-treated surfaces faced 
each other, thus preparing a liquid crystal device. This cell was baked at 
a constant temperature of 110.degree. C. for 1 hour, after which at 
70.degree. C. pulse signals were applied thereto at a frame frequency of 
30 Hz and a voltage of 5 V for an ON time of 60 .mu.seconds for the 
determination of the voltage-holding ratio. The voltage-holding ratio of 
the guest-host liquid crystal composition/the voltage holding ratio of the 
host liquid crystal material was calculated to be a satisfactory value of 
0.98. 
EXAMPLE 3 
Liquid crystal composition-III was prepared by dissolving the following 
dichroic dyes in 100 g of a liquid crystal mixture commercially available 
under the trade name of ZLI-5091 (manufactured by E. Merck Inc.) which 
consisted mainly of a fluorine compound. 
______________________________________ 
Dyes: 
______________________________________ 
(I-2) 0.79 g 
(II-1) 
0.25 g 
(III-1) 
0.46 g 
(IV-1) 
1.98 g 
______________________________________ 
This liquid crystal composition-III was employed in the same manner as in 
Example 2 for the preparation of a liquid crystal device. The result of 
the calculation of the voltage holding ratio of the guest-host liquid 
crystal composition/the voltage holding ratio of the host liquid crystal 
material which was made in the same manner as in Example 2 was a 
satisfactory value of 0.96. 
EXAMPLE 4 
Liquid crystal composition-IV was prepared by dissolving the following 
dichroic dyes in 100 g of a liquid crystal mixture commercially available 
under the trade name of ZLI-5092 (manufactured by E. Merck Inc.) which 
consisted mainly of a fluorine compound. 
______________________________________ 
Dyes: 
______________________________________ 
(I-2) 0.75 g 
(II-1) 
0.24 g 
(III-1) 
0.54 g 
(IV-1) 
2.07 g 
______________________________________ 
This liquid crystal composition-IV was employed in the same manner as in 
Example 2 for the preparation of a liquid crystal device. The result of 
the calculation of the voltage holding ratio of the guest-host liquid 
crystal composition/the voltage holding ratio of the host liquid crystal 
material which was made in the same manner as in Example 2 was a 
satisfactory value of 0.98. 
EXAMPLE 5 
Liquid crystal composition-V was prepared by dissolving the following 
dichroic dyes in 100 g of a liquid crystal mixture commercially available 
under the trade name of ZLI-4792 (manufactured by E. Merck Inc.) which 
consisted mainly of a fluorine compound. 
______________________________________ 
Dyes: 
______________________________________ 
(I-2) 0.41 g 
(II-1) 
0.11 g 
(III-1) 
0.31 g 
(IV-1) 
1.72 g 
(IV-2) 
1.07 g 
______________________________________ 
This liquid crystal composition-V was employed in the same manner as in 
Example 2 for the preparation of a liquid crystal device. The result of 
the calculation of the voltage holding ratio of the guest-host liquid 
crystal composition/the voltage holding ratio of the host liquid crystal 
material which was made in the same manner as in Example 2 was a 
satisfactory value of 0.98. 
EXAMPLE 6 
Liquid crystal composition-VI was prepared by dissolving the following 
dichroic dyes in 100 g of a liquid crystal mixture commercially available 
under the trade name of ZLI-4792 (manufactured by E. Merck Inc.) which 
consisted mainly of a fluorine compound. 
______________________________________ 
Dyes: 
______________________________________ 
(I-1) 0.89 g 
(II-2) 
0.28 g 
(III-1) 
0.22 g 
(IV-2) 
2.09 g 
______________________________________ 
This liquid crystal composition-VI was employed in the same manner as in 
Example 2 for the preparation of a liquid crystal device. The result of 
the calculation of the voltage holding ratio of the guest-host liquid 
crystal composition/the voltage holding ratio of the host liquid crystal 
material which was made in the same manner as in Example 2 was a 
satisfactory value of 0.98. 
EXAMPLE 7 
Liquid crystal composition-VII was prepared by dissolving the following 
dichroic dyes in 100 g of a liquid crystal mixture commercially available 
under the trade name of ZLI-4792 (manufactured by E. Merck Inc.) which 
consisted mainly of a fluorine compound. 
______________________________________ 
Dyes: 
______________________________________ 
(I-2) 1.24 g 
(II-1) 
0.36 g 
(III-1) 
0.23 g 
(IV-1) 
1.88 g 
______________________________________ 
This liquid crystal composition-VII was employed in the same manner as in 
Example 1 for the preparation of a liquid crystal device. This cell was 
baked at a constant temperature of 110.degree. C. for 1 hour, after which 
at 100.degree. C. pulse signals were applied thereto at a frame frequency 
of 30 Hz and a voltage of 5 V for an ON time of 60 .mu.seconds for the 
determination of the voltage holding ratio. The value of this voltage 
holding ratio was calculated in terms of the voltage holding ratio of the 
guest-host liquid crystal composition/the voltage holding ratio of the 
host liquid crystal material, a ratio determined with the voltage holding 
ratio of the host liquid crystal ZLI-4792 as 1. 
The result was a satisfactory value of 0.83. 
Next, as comparisons, some of the publicly known combinations of dyes, 
dichroic dyes for liquid crystals, were dissolved in a fluorine liquid 
crystal and investigated. 
COMISON 1 
Liquid crystal composition-VIII was prepared by dissolving the following 
dichroic dyes as disclosed in Japanese Patent Laid-Opem No. 165483/88, in 
100 g of a liquid crystal mixture commercially available under the trade 
name of ZLI-4792 (manufactured by E. Merck Inc.) which consisted mainly of 
a fluorine compound. 
______________________________________ 
Dyes: 
______________________________________ 
(I-2) 1.16 g 
(II-1) 
0.74 g 
(IV-1) 
2.48 g 
______________________________________ 
Dye of the general structural formula (V) given below 1.51 g 
##STR26## 
This liquid crystal composition-VIII was employed in the same manner as in 
Example 7 for the preparation of a liquid crystal device. The result of 
the calculation of the voltage holding ratio of the guest-host liquid 
crystal composition/the voltage holding ratio of the host liquid crystal 
material which was made in the same manner as in Example 7 was a low value 
of 0.64. 
COMISON 2 
Liquid crystal composition-IX was prepared by dissolving the following 
dichroic dyes as disclosed in Japanese Patent Laid-Open No. 43596/89, in 
100 g of a liquid crystal mixture commercially available under the trade 
name of ZLI-4792 (manufactured by E. Merck Inc.) which consisted mainly of 
a fluorine compound. 
______________________________________ 
Dyes: 
______________________________________ 
(I-2) 1.72 g 
(IV-1) 
1.88 g 
(V) 1.73 g 
______________________________________ 
Dye of the general structural formula (VI) given below 1.87 g 
##STR27## 
Dye of the general structural formula (VII) given below 1.41 g 
##STR28## 
This liquid crystal composition-IX was employed in the same manner as in 
Example 7 for the preparation of a liquid crystal device. The result of 
the calculation of the voltage holding ratio of the guest-host liquid 
crystal composition/the voltage holding ratio of the host liquid crystal 
material which was made in the same manner as in Example 7 was a low value 
of 0.65. 
COMISON 3 
Liquid crystal composition-X was prepared by dissolving the following 
dichroic dyes as disclosed in Japanese Patent Laid-Open No. 154920/91, in 
100 g of a liquid crystal mixture commercially available under the trade 
name of ZLI-4792 (manufactured by E. Merck Inc. ) which consisted mainly 
of a fluorine compound. 
______________________________________ 
Dyes: 
______________________________________ 
(I-2) 1.24 g 
(II-1) 
0.36 g 
(III-1) 
0.23 g 
(IV-1) 
1.88 g 
(V) 1.04 g 
______________________________________ 
This liquid crystal composition-X was employed in the same manner as in 
Example 7 for the preparation of a liquid crystal device. The result of 
the calculation of the voltage holding ratio of the guest-host liquid 
crystal composition/the voltage holding ratio of the host liquid crystal 
material which was made in the same manner as in Example 7 was a low value 
of 0.65. 
Thus it is still difficult to use the dyes which are known for their 
combined use as dichoric dyes for liquid crystals, for active 
matrix-driven liquid crystal devices if they cause a significant drop in 
the voltage holding ratio of the guest-host liquid crystal composition/the 
voltage holding ratio of the host liquid crystal material upon their 
dissolution in a fluorine liquid crystal. 
As mentioned above, the present invention has an effect that the 
preparation of an active matrix liquid display device has become possible 
with a guest-host composition, and there may be obtained a display with an 
improved viewing angle and reproducibility of hues. 
While the invention has been described in detail and with reference to the 
specific embodiments thereof, it will be apparent to one skilled in the 
art that various changes and modifications can be made without departing 
from the spirit and scope thereof.