Optically active liquid crystal compound having methyleneoxy group and composition containing same

A novel, superior, optically active liquid crystal compound exhibiting a smectic C* phase, and a liquid crystal composition containing the same are provided, which compound is expressed by the formula ##STR1## wherein X represents --CH.sub.2 O-- or --OCH.sub.2 --; Y represents --COO-- or --OCO--; and either one of R.sup.1 or R.sup.2 represents an optically active alkyl group, alkoxy group or alkoxycarbonyl group and the other represents a non-optically-active alkyl group or alkoxy group each of 4 to 18 carbon atoms.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a novel liquid crystal substance and a liquid 
crystal composition containing the same. More particularly it relates to a 
chiral liquid crystal substance having an optically active group and a 
chiral liquid crystal composition containing the same. 
2. Description of the Prior Art 
At present, as to liquid crystal display elements, TN (Twisted Nematic) 
type display mode has been most broadly employed, but as far as the 
response speed is concerned, such TN type display elements are inferior to 
emissive type display elements (such as those of electroluminescence, 
plasma display, etc.). Although various improvements in this respect have 
been attempted, it appears that the possibility of improvement to a large 
extent has not been realized. Thus, various liquid crystal display devices 
based on a different principle from that of TN type display elements have 
been attempted. As one of such devices, there is a display mode utilizing 
a ferroelectric liquid crystal (N. A. Clark et al: Applied Phys. lett., 
36, 899 (1980)). This mode utilizes the chiral smectic C phase 
(hereinafter abbreviated to SC* phase) or the chiral smectic H phase 
(hereinafter abbreviated to SH* phase) of the ferroelectric liquid 
crystal, and those having these phases in the vicinity of room temperature 
are preferred. 
SUMMARY OF THE INVENTION 
Mainly in order to develop a liquid crystal substance which is more 
suitable to be used in this display mode and has superior specific 
features, the present inventors have extensively searched for a liquid 
crystal substance having an optically active group, and have attained the 
present invention. 
The present invention resides in an optically active liquid crystal 
compound expressed by the formula 
##STR2## 
wherein X represents --CH.sub.2 O-- or --OCH.sub.2 --; Y represents 
--COO-- or --OCO--; and either one of R.sup.1 or R.sup.2 represents an 
optically active alkyl group, alkoxy group or alkoxycarbonyl group and the 
other represents a non-optically-active alkyl group or alkoxy group each 
of 4 to 18 carbon atoms, and a chiral liquid crystal composition 
containing the same. 
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Concrete examples of the compounds of the formula (I) of the present 
invention are as follows: 
##STR3## 
In the above formulas, R* indicates the case where R.sup.1 or R.sup.2 in 
the formula (I) is an optically active group and R indicates the case 
where R.sup.1 or R.sup.2 is a non-optically-active group. 
The phase transition temperatures, spontaneous polarization values and tilt 
angles of representatives of these compounds are shown in Table 1 and 
Table 2. 
TABLE 1 
__________________________________________________________________________ 
Sam- 
ple 
In formula (I) For- 
Phase transition point 
(.degree.C.)*.sup.1 
No. 
X Y R.sup.1 R.sup.2 mula 
C SI* SB SC* SA Ch I 
Note 
__________________________________________________________________________ 
1 CH.sub.2 O 
COO C.sub.7 H.sub.15 O 
##STR4## 
Ia .cndot. 118.4 
-- -- .cndot. 125.9 
.cndot. 140.0 
--.cndot. 
Ex- am- ple 
1 
2 " " C.sub.8 H.sub.15 O 
" Ia .cndot. 120.7 
-- -- .cndot. 129.0 
.cndot. 140.8 
--.cndot. 
3 " " C.sub.10 H.sub.21 O 
" Ia .cndot. 107.8 
-- -- .cndot. 132.1 
.cndot. 138.6 
--.cndot. 
4 " " C.sub.12 H.sub.25 O 
" Ia .cndot. 95.0 
- - .cndot. 118.0 
.cndot. 127.0 
-.cndot. 
5 " " C.sub.10 H.sub.21 O 
##STR5## 
Ia .cndot. 85.9 
-- -- .cndot. 105.3 
-- --.cndot. 
6 " " C.sub.12 H.sub.25 O 
" Ia .cndot. 77.2 
-- -- .cndot. 102.5 
-- --.cndot. 
7 " " 
##STR6## 
OC.sub.5 H.sub.11 
Ib .cndot. 105.2 
-- -- (.cndot. 91.0 
-- .cndot.92.9).cndot 
. 
8 " " " OC.sub.8 H.sub.17 
Ib .cndot. 106.0 
-- -- (.cndot. 97.1) 
-- --.cndot. 
9 " " " OC.sub.12 H.sub.25 
Ib .cndot. 50.8 
-- -- -- -- --.cndot. 
10 " " 
##STR7## 
OC.sub.5 H.sub.11 
Ib .cndot. 99.3 
(.cndot. 96.1) 
-- .cndot. 108.0 
.cndot. 112.5 
--.cndot. 
11 " " " OC.sub.8 H.sub.17 
Ib .cndot. 110.9 
-- -- (.cndot. 109.3) 
-- --.cndot. 
Ex- 
12 " " " OC.sub.12 H.sub.25 
Ib .cndot. 102.4 
-- -- (.cndot. 101.9) 
-- --.cndot. 
am- 
13 " OCO C.sub.8 H.sub.17 O 
##STR8## 
Ic .cndot. 90.0 
-- -- (.cndot. 83.6 
-- .cndot.88.5).cndot 
. ple 2 
14 " " 
##STR9## 
OC.sub.3 H.sub.17 
Id .cndot. 68.8 
-- -- (.cndot. 61.4 
-- .cndot.63.5) .cndo 
t. 
15 " " " C.sub.9 H.sub.19 
Id .cndot. 72.6 
-- -- (.cndot. 66.2 
-- .cndot.67.3).cndot 
. 
16 " " 
##STR10## 
OC.sub.8 H.sub.17 
Id .cndot. 46.9 
-- (.cndot. 36.8) 
.cndot. 67.0 
.cndot.74.4-.cndot 
. 
17 " C.sub.9 H.sub.19 
Id .cndot. 45.8 
-- .cndot. 49.5 
.cndot. 68.0 
.cndot.78.1-.cndot 
. 
__________________________________________________________________________ 
*.sup.1 The symbol .cndot.below the column indicating the respective 
phases indicates that the compound exhibits the phase, and the numeral on 
the right side thereof indicates a transition point from the phase to the 
phase on the right side of the numeral 
TABLE 2 
______________________________________ 
Test No.*.sup.1 
Ps (nC/cm.sup.2) 
Tilt angle (degree)*.sup.4 
______________________________________ 
1 ca. 1 -- 
2 ca. 1 -- 
3 ca. 1 -- 
4 ca. 1 -- 
5 63.7 28.0 
6 57.5 28.3 
7 70.8*.sup.2 
.sup. 32.8*.sup.2 
8 79.3*.sup.2 
.sup. 37.3*.sup.2 
9 52.3 -- 
Extrapolation 
value*.sup.3 
10 87.3 23.2 
11 106.2*.sup.2 
.sup. 31.1*.sup.2 
12 .gtoreq.59*.sup.2 
.sup. 32.0*.sup.2 
13 43.0*.sup.2 
.sup. 43.0*.sup.2 
14 77.9 42.1 
15 73.2 41.5 
16 104.8 27.4 
17 77.9 24.8 
______________________________________ 
*.sup.1 Sample No. is the same as that in Table 1. 
*.sup.2 Value measured at a temperature 5.degree. C. lower than the upper 
limit temperature of SC* phase. Other values were measured at a 
temperature 10.degree. C. lower than that. 
*.sup.3 The extrapolation value refers to a value sought from Ps value 
measured in the form of a mixture thereof with other SC liquid crystal by 
extrapolation method. 
*.sup.4 The tilt angle refers to an angle of the normal to the layer of 
SC* phase made against the major axis of the molecule. 
The compounds expressed by the formula (I) exhibit smectic C* phase in the 
form of a single substance, and among the compounds, those having an R* of 
1-methylalkyl type exhibit much larger spontaneous polarization values 
(Ps) than those of so far known SC* phase compounds; hence the compounds 
of the formula (I) of the present invention can be said to be superior 
ferroelectric liquid crystal compounds. Some of the compounds of the 
formula (I) of the present invention have PS values amounting to 100 
nC/cm.sup.2 or more, whereas a known compound, e.g. 
##STR11## 
described in Japanese patent application laid-open No. Sho 53-22883/1978 
(corresponding patents: U.S. Pat. No. 4,257,911; G.B. Pat. No. 1,592,161; 
DE Pat. No. 2,736,424) has a Ps value as small as about 1 nC/cm.sup.2 
according to the measurement of the present inventors; thus the Ps values 
of the present invention can be said to be surprisingly large. 
Further, a superior specific feature of these substances is that the tilt 
angle of SC* phase is large. In the guest-host type light-switching 
element using a SC* liquid crystal composition shown in an Example 
described later, the tilt angle of SC* phase is ideally preferred to be 
45.degree.. Thus, such specific features indicate that the compounds of 
the present invention have much superior properties as a constituting 
component of SC* liquid crystal compositions for guest-host type 
light-switching elements. 
Display elements exhibiting the light-switching effect of SC* phase have 
the following three superior specific features as compared with those of 
TN display mode: 
The first specific feature is that the display elements reply at a very 
high rate so that the response time is 1/100 or less of those of 
conventional TN mode display elements. The second specific feature is that 
there is a memory effect so that the multiplex drive is easy in 
combination thereof with the above high rate response properties. The 
third specific feature is that when the gray scale is given in the case of 
TN display mode, this is effected by adjusting the impressed voltage, but 
there are raised difficult problems such as temperature dependency of 
threshold voltage, voltage dependency of response rate, etc.; whereas when 
the light-switching effect of SC* phase is applied, it is possible to 
readily obtain the gray scale by adjusting the reverse time of polarity 
and hence the display elements are very suitable to graphic display. 
As to the display method, the following two may be considered: 
One method is of birefringence type using two plates of polarizers and 
another is of guest-host type using a dichroic dyestuff. Since SC* phase 
has a spontaneous polarization, the molecule is reversed around the 
helical axis as a rotating axis by reversing the polarity of impressed 
voltage. When a liquid crystal composition having SC* phase is filled in a 
liquid crystal display cell subjected to aligning treatment so that the 
liquid crystal molecules can be aligned in parallel to the electrode 
surface, followed by placing the liquid crystal cell between two plates of 
polarizers arranged so that the direct of the liquid crystal molecules can 
be in parallel to the polarization plane on one side, impressing a voltage 
and reversing the polarity, then a bright field of view and a dark field 
of view are obtained depending on the opposition angle of the polarizers. 
On the other hand, in the case of operation by way of the guest-host type, 
it is possible to obtain a bright field of view and a colored field of 
view (depending on the arrangement of the polarization plate), by 
reversing the polarity of impressed voltage. 
In general, it is difficult to align liquid crystal molecules in parallel 
to the wall surface of a glass plate in the smectic state thereof; hence 
liquid crystal molecules have been aligned by very slowly cooling the 
molecules starting from the isotropic liquid thereof (1.degree. 
C..about.2.degree. C./hr) in a magnetic field of several tens gausses or 
more. But, in the case of a liquid crystal substance exhibiting the 
cholesteric phase thereof in a temperature range higher than the 
temperature at which the smectic phase is exhibited, it is possible to 
easily obtain a uniformly aligned monodomain state, by cooling the 
molecules from the temperature at which the cholesteric phase thereof is 
exhibited, down to the temperature at which the smectic phase is 
exhibited, at a cooling rate of 1.degree. C./min., while impressing a 
direct current voltage of 50 to 100 V in place of the magnetic field. 
In addition, racemic form compounds corresponding to the compound of the 
formula (I) may be similarly prepared by replacing the optically active 
alcohol used as a raw material in the preparation of the optically active 
substance (I), as shown below, by racemic form alcohols corresponding 
thereto, and the resulting racemic form compounds exhibit almost the same 
phase transition points as those in the case of (I), although they exhibit 
non-chiral liquid crystal phase. 
Further, since the compound of the formula (I) contains an optically active 
carbon atom, it has a capability of inducing a twisted structure when 
added to a nematic liquid crystal. A nematic liquid crystal having a 
twisted structure, i.e. a chiral nematic liquid crystal, does not form the 
so-called reverse domain of TN type display elements; hence it is possible 
to use the compound of the formula (I) as an agent for preventing the 
reverse domain from forming. 
In addition, among the raw material optically active 2-alkanols used in the 
preparation of the compound of the present invention, as described below, 
S(+)-2-octanol, R(-)-2-octanol and S(-)-2-methylbutanol are readily 
commercially available, but other optically active 2-alkanols are at 
present unsuitable for use in a large quantity. The present inventors used 
as raw material, products obtained by subjecting racemic substances to 
optical resolution according to the description of the literature (R. H. 
Pickard et al, J. Chem. Soc., 99, 45 (1911)), and by using the thus 
obtained optically active 2-alkanols, it is possible to obtain various 
compounds of the formula (I) having different kinds of R.sup.1 and 
R.sup.2. However, change in the liquid crystal phase transition points 
depending on the chain lengths of R.sup.1 and R.sup.2 is slight; hence it 
is preferred to use as raw material, optically active 2-octanol and 
2-methylbutanol, but it is also possible in principle to use other 
optically active alkanols. 
(Preparation of the compound) 
Compounds of the formula (I) wherein X=--CH.sub.2 O-- and Y=--COO--, i.e. 
those of formulas (Ia) and (Ib), may be prepared through the following 
route: 
##STR12## 
Further, the above compounds may also be prepared through the following 
route; the number of steps of this process is more than that of the above 
process, but this process is easier: 
##STR13## 
Compounds of the formula (I) wherein X=--CH.sub.2 O-- and Y=--OCO, i.e. 
those of formulas (Ic) and (Id), may be prepared through the following 
route: 
##STR14## 
Compounds of the formula (I) wherein X=--OCH.sub.2 -- and Y=--COO--, i.e. 
those of formulas (Ie) and (If), may be prepared through the following 
route: 
##STR15## 
Compounds of the formula (I) wherein X=--OCH.sub.2 -- and Y=--OCO--, i.e. 
those of formulas (Ig) and (Ih), may be prepared through the following 
route:

The optically active ester liquid crystal compounds of the present 
invention will be described in more detail by way of Examples. 
As the optically active alcohols used as raw material in the following 
Examples, only those of S type are used, but even when those of R type are 
used as raw material, the resulting compounds have the same phase 
transition points as those in the case of S type. This is theoretically 
natural, but the angle of rotation, the helical twist sense and the sense 
of spontaneous polarization of the compounds of R type are contrary to 
those of S type. 
EXAMPLE 1 
Preparation of optically active p-(p'-decyloxybenzyloxy)benzoic 
acid-p-(1-methyl-heptyloxy)phenyl ester (a compound of the formula (I) 
wherein X=--CH.sub.2 O--, Y=--COO--, R.sup.1 =C.sub.10 H.sub.21 O-- and 
##STR17## 
sample No. 5) 
(i) Preparation of optically active p-toluenesulfonic acid 1-methylheptyl 
ester 
S(+)-2-octanol (200 g, 1.536 mol) was dissolved in dry pyridine (600 ml), 
followed by dropwise adding to the solution, a solution of 
p-toluenesulfonic acid chloride (292.8 g, 1.536 mol) dissolved in dry 
toluene (440 ml), while keeping the temperature inside the system so that 
it might not exceed 10.degree. C., thereafter agitating the mixture at 
room temperature for one hour, increasing the temperature inside the 
system to 50.degree. C., keeping the temperature for 2 hours, thereafter 
cooling, further adding water (1 l) and toluene (500 ml), agitating the 
mixture, wahsing the separated toluene layer with 6N-HCl, further with 
2N-NaOH aqueous solution and further with water until the wash water 
became neutral, and distilling off toluene to obtain as residue, optically 
active p-toluenesulfonic acid 1-methyl-heptyl ester (321.0 g). 
(ii) Preparation of p-benzyloxybenzoic acid chloride 
Thionyl chloride (63.1 g, 0.53 mol) was added to p-benzyloxybenzoic acid 
(100.0 g, 0.44 mol), followed by refluxing the mixture for about 2 hours, 
and completely removing excess thionyl chloride by distillation under 
reduced pressure to obtain p-benzyloxybenzoic acid chloride (63.4 g). 
(iii) Preparation of optically active p-(1-methylheptyloxy)phenol 
To hydroquinone monobenzyl ether (200.0 g, 1.00 mol) were added ethanol 
(1,000 ml), p-toluenesulfonic acid 1-methyl-heptyl ester (212.0 g, 1.10 
mol) prepared above in (i) and a solution of NaOH (48.0 g, 1.20 mol) 
dissolved in water (50.0 g), followed by refluxing the mixture for about 
10 hours, distilling off ethanol, adding to the residue, 6N-HCl (400 ml) 
and toluene (500 ml), agitating the mixture, washing the toluene layer 
with 6N-HCl, then with 2N-NaOH aqueous solution and further with water 
until the wash water became neutral, drying the toluene layer, distilling 
off toluene, subjecting the residue to column chromatography with 
activated alumina (200 g), dissolving the residue in ethanol (200 ml), 
reducing it in the presence of 5% Pd/C (10.0 g) to obtain raw optically 
active p-(1-methyl-heptyloxy)phenol, and distilling the raw product under 
reduced pressure to obtain optically active p-(1-methyl-heptyloxy)phenol 
(142.4 g, 1.5 mm Hg 132.degree. C.). 
(iv) Preparation of optically active p-benzyloxybenzoic acid 
p-(1-methyl-heptyloxy)phenyl ester 
Optically active p-(1-methyl-heptyloxy)phenol (50.0 g, 0.22 mol) was 
dissolved in pyridine (300 ml), followed by dropwise adding to the 
solution, a solution of p-benzyloxybenzoic acid chloride (50.0 g, 0.20 
mol) prepared above in (ii), dissolved in toluene (300 ml), under ice 
cooling, agitating the mixture for 2 hours while keeping it at about 
50.degree..about.60.degree. C., allowing it to stand overnight, thereafter 
adding toluene (1,500 ml) and water (1,000 ml), agitating the mixture, 
washing the toluene layer with 6N-HCl, then with 2N-NaOH aqueous solution 
and further with water until the wash water became neutral, distilling off 
toluene, and recrystallizing the residue from ethanol to obtain optically 
active p-benzyloxybenzoic acid p-(1-methyl-heptyloxy)phenyl ester (69.0 
g). 
(v) Preparation of optically active p-hydroxybenzoic acid 
p-(1-methyl-heptyloxy)phenyl ester 
Optically active p-benzyloxybenzoic acid p-(1-methylheptyloxy)phenyl ester 
(69.0 g, 0.16 mol) prepared above in (iv) was dissolved in a mixed solvent 
(2:1) (1,000 ml) of ethyl acetate-ethanol, followed by reducing it in the 
presence of 5% PdC (5.0 g) to obtain optically active p-hydroxybenzoic 
acid p-(1-methyl-heptyloxy)phenyl ester (49.8 g). 
(vi) Preparation of captioned compound 
50% Hydrogenated sodium (1.6 g, 0.07 mol) was decanted a few times with 
n-heptane (50 ml) followed by dropwise adding thereto optically active 
p-hydroxybenzoic acid p-(1-methyl-heptyloxy)phenyl ester (10 g, 0.03 mol) 
prepared above in (v), adding DMSO (50 ml) after completion of hydrogen 
evolution, dropwise adding to the mixture a solution of p-decyloxybenzyl 
chloride (8.3 g, 0.03 mol) dissolved in THF (50 ml), further adding DMSO 
(50 ml), agitating the mixture at room temperature for 1.about.2 hours, 
subjecting it to extraction with toluene, washing with 6N-HCl, then with 
2N-NaOH aqueous solution and further with water until the wash water 
became neutral, distilling off toluene and recrystallizing the residue 
from ethanol or ethyl acetate to obtain optically active 
p-(p'-decyloxybenzyloxy)benzoic acid p-(1-methyl-heptyloxy)phenyl ester 
(7.2 g). The phase transition points of this product were as follows: 
C-SC* point 85.9.degree. C., SC*-I point 105.3.degree. C. 
By replacing p-decyloxybenzyl chloride used above by optically active 
p-alkylbenzyl chlorides, optically active p-alkyloxybenzyl chlorides or 
optically active p-alkyloxycarbonylbenzyl chloride, and by replacing 
optically active p-(1-methyl-heptyloxy)phenol by non-optically-active 
p-alkylphenols or p-alkyloxyphenols, compounds of formula (Ib) are 
obtained. 
EXAMPLE 2 
Preparation of optically active p-(1-methyl-heptyloxyl)benzoic acid 
p-(p'-octyloxybenzyloxy)phenyl ester (a compound of the formula (I) 
wherein X=--CH.sub.2 O-- Y=--OCO--, R.sup.1 =C.sub.8 H.sub.17 O-- and 
##STR18## 
Sample No. 13) 
(i) Preparation of optically active p-(1-methylheptyloxy)benzoic acid 
Methyl p-hydroxybenzoate ester (177.0 g, 1.16 mol) was dissolved in 
methanol (800 ml), followed by adding KOH (65.0 g, 1.16 mol), adding after 
completion of heat generation, optically active p-toluenesulfonic acid 
1-methyl-heptyl ester (300.0 g, 1.06 mol) prepared in advance, refluxing 
the mixture for about 4 hours, allowing it to stand at room temperature, 
thereafter adding water (1 l) and toluene (500 ml), agitating the mixture, 
washing the separated toluene layer sufficiently with 2N-NaOH aqueous 
solution and further with water until the wash water became neutral, 
distilling off toluene, dissolving the residue in ethanol (50 ml), adding 
a solution of NaOH (30.0 g) dissolved in water (150 ml), refluxing the 
mixture for about one hour, thereafter acidifying the reaction product 
with hydrochloric acid, filtering deposited crystals and recrystallizing 
from heptane to obtain optically active p-(1-methyl-heptyloxy)benzoic acid 
(96.2 g). 
(ii) Preparation of optically active p-(1-methylheptyloxy)benzoic acid 
chloride 
Thionyl chloride (51.2 g, 0.43 mol) was added to optically active 
p-(1-methyl-heptyloxy)benzoic acid (90.0 g, 0.36 mol), followed by 
refluxing the mixture for about 2 hours, thereafter completely removing 
excess thionyl chloride by distillation under reduced pressure to obtain 
optically active p-(1-methyl-heptyloxy)benzoic acid chloride (90.0 g). 
(iii) Preparation of p-(1-methyl-heptyloxy)benzoic acid p-benzyloxyphenyl 
ester 
Hydroquinone monobenzyl ether (100.0 g, 0.50 mol) was dissolved in pyridine 
(600 ml), followed by dropwise adding to the solution, a solution of 
p-(1-methyl-heptyloxy)benzoic acid chloride (122.2 g, 0.45 mol) dissolved 
in toluene (600 ml), under ice cooling, agitating the mixture for 2 hours 
while keeping the temperature at about 50.degree.-60.degree. C., allowing 
it to stand overnight, thereafter adding toluene (3,000 ml) and water 
(2,000 ml), agitating the mixture, washing the toluene layer with 6N-HCl, 
then with 2N-NaOH aqueous solution and further with water until the wash 
water became neutral, distilling off toluene and recrystallizing the 
residue from ethanol to obtain p-(1-methyl-heptyloxy)-benzoic acid 
p-benzyloxyphenyl ester (121.0 g). 
(iv) Preparation of p-[p'-(1-methyl-heptyloxy)benzoyloxy]phenol 
Optically active p-(1-methyl-heptyloxy)benzoic acid p-benzyloxyphenyl ester 
(69.0 g, 0.16 mol) was dissolved in a mixed solvent (1,000 ml) of ethyl 
acetate-ethanol (2:1), followed by reducing it in the presence of 5% Pd/C 
(5.0 g) to obtain optically active 
p-[p'-(1-methyl-heptyloxy)benzoyloxy]phenol (47.6 g). 
(v) Preparation of captioned compound 
50% Hydrogenated sodium (1.6 g, 0.07 mol) was decanted a few times with 
n-heptane (50 ml), followed by dropwise adding thereto optically active 
p-[p'-(1-methyl-heptyloxy)benzoyloxy]phenol (10 g, 0.03 mol), adding DMSO 
(50 ml) after completion of hydrogen evolution, dropwise adding a solution 
of p-octyloxybenzyl chloride (7.6 g, 0.03 mol) dissolved in THF (50 ml), 
further adding DMSO (50 ml), agitating the mixture at room temperature for 
1-2 hours, subjecting it to extraction with toluene, washing with 6N-HCl, 
then with 2N-NaOH aqueous solution and further with water until the wash 
water became neutral, distilling off toluene, and recrystallizing the 
residue from ethanol or ethyl acetate to obtain optically active 
p-(1-methyl-heptyloxy)benzoic acid p-(p'-octyloxybenzyloxy)phenyl ester 
(7.6 g). 
The phase transition points were as follows: 
C-I point 90.0.degree. C., I-Ch point 88.5.degree. C., Ch-SC* point 
83.6.degree. C. 
By replacing p-octyloxybenzyl chloride used herein by optically active 
p-alkylbenzyl chlorides, optically active p-alkyloxybenzyl chlorides or 
optically active p-alkyloxycarbonylbenzyl chlorides, and by replacing 
optically active p-(1-methyl-heptyloxy)phenol by non-optically-active 
p-alkylphenols or p-alkyloxyphenols, compounds of formula (Id) are 
obtained. 
EXAMPLE 3 (COMPOSITION EXAMPLE 1) 
A nematic liquid crystal composition consisting of 
______________________________________ 
##STR19## 20 wt. % 
##STR20## 40 wt. % 
##STR21## 25 wt. % 
##STR22## 15 wt. % 
______________________________________ 
was sealed in a cell provided with transparent electrodes, subjected to a 
parallel aligning treatment by applying polyvinyl alcohol (PVA) as an 
aligning agent onto the surface, and rubbing the resulting surface and 
having a distance between the electrodes of 10 .mu.m, to prepare a TN type 
display cell, which was then observed with a polarizing microscope. As a 
result, a reverse twist domain was observed to be formed. 
Then the compound of sample No. 1 of the present invention, i.e. 
##STR23## 
was added in a quantity of 1% by weight to the above nematic liquid 
crystal composition and the resulting composition was observed in the same 
TN cell. As a result, the reverse twist domain disappeared and a uniform 
nematic phase was observed. 
EXAMPLE 4 (COMPOSITION EXAMPLE 2) 
The following liquid crystal composition containing as one component 
thereof, the optically active liquid crystal compound of sample No. 17 in 
the above Table 1 was prepared: 
______________________________________ 
##STR24## 30 wt. % 
##STR25## 30 wt. % 
##STR26## 20 wt. % 
##STR27## 20 wt. % 
(No. 17) 
______________________________________ 
Preparation of the composition was carried out by weighing the above four 
liquid crystal compounds in definite quantities, respectively, and 
blending them in a sample bottle while dissolving them on heating. 
The resulting composition was filled in a cell provided with transparent 
electrodes, subjected to a parallel aligning treatment by applying PVA as 
an aligning agent onto the surface, and rubbing the resulting surface and 
having a distance between the electrodes of 2 .mu.m. The resulting liquid 
crystal element was set between two crossed polarizers and an electric 
field was impressed. As a result, change in the intensity of transmitted 
light was observed by impression of 20 V. 
In addition, response time was sought from the change in the intensity of 
transmitted light at that time, to exhibit a value of about 1 msec at 
25.degree. C. 
Further, with the above liquid crystal composition, change in the texture 
with temperature was examined by means of a polarizing microscope. As a 
result, it was seen that a ferroelectric liquid crystal was formed in a 
temperature range of 18.degree. to 55.degree. C. The value of its 
spontaneous polarization was 10 nC/cm.sup.2 at 25.degree. C. and the tilt 
angle was 24.degree.. 
EXAMPLE 5 (COMPOSITION EXAMPLE 3) 
The following liquid crystal composition containing as components thereof, 
optically active compounds of sample Nos. 13, 14 and 15 in the above Table 
1 was prepared in the same manner as in Example 4: 
______________________________________ 
##STR28## 20 wt. % 
##STR29## 20 wt. % 
##STR30## 20 wt. % 
(No. 13) 
##STR31## 20 wt. % 
(No. 14) 
##STR32## 20 wt. % 
(No. 15) 
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An anthraquinone dyestuff (D-16, tradename of product made by BDH Company) 
as a dichroic dyestuff was added to the above composition to prepare a 
composition of the socalled guest-host type, which was then filled in the 
same cell as in Example 4 (but cell thickness: 10 .mu.m), and a polarizer 
was provided so that the polarization plane might be parallel to the 
molecular axis. An electric field was impressed onto the cell. As a 
result, by impression of 40 V, change in the intensity of transmitted 
light was observed. 
Response time was sought from the change in the transmitted light at that 
time to exhibit a value of about 2 msec at 25.degree. C. 
In addition, with the above liquid crystal composition, temperature change 
in the texture thereof was observed by means of a polarizing microscope. 
As a result, it was seen that a ferroelectric liquid crystal was formed in 
the temperature range of 15.degree. C. to 65.degree. C. The value of its 
spontaneous polarization was 20 nC/cm.sup.2 and the tilt angle was 
37.degree..