Tetralin compound, liquid crystal material, liquid crystal composition and liquid crystal element

The present invention provides a tetralin compound represented by the following formula: EQU R--X--A.sup.1 --Y.sup.1 --A.sup.2 --(Y.sup.2 --A.sup.3).sub.n --Z--R* wherein R is an alkyl group of 3-20 carbon atoms; X is --O-- CO--, --O-- or a single bond; n is 0 or 1; each of A.sup.1, A.sup.2 and A.sup.3 is a divalent aromatic group; each of Y.sup.1 and Y.sup.2 is --COO--, --O--CO--, --CH.sub.2 CH.sub.2 --, --CH.sub.2 O-- or --OCH.sub.2 --; Z is --O--, --O--CO-- or a single bond; and R* is a specific optically active group. The invention also provides a liquid crystal material comprising the above-mentioned tetralin compound, a liquid crystal composition comprising the tetralin compound and a liquid crystal compound other than the tetralin compound, and a liquid crystal element using the tetralin compound. The tetralin compound of the invention is favorably used as a liquid crystal material because it has a large tilt angle and shows excellent liquid crystal properties.

FIELD OF THE INVENTION 
The present invention relates to a novel tetralin compound, a liquid 
crystal material comprising the tetralin compound, a liquid crystal 
composition comprising the tetralin compound and a liquid crystal compound 
other than the tetralin compound, and a liquid crystal element comprising 
the liquid crystal material. 
BACKGROUND OF THE INVENTION 
Display devices using liquid crystal compounds, which are used widely at 
present, are driven in a TN (twisted nematic) mode. 
Such driving display devices, however, have problems that since the 
position of the molecule of the liquid crystal compound present in the 
element must be changed in order to change displayed images, the driving 
time necessary therefor is prolonged, and also a voltage necessary for 
changing the position of the molecule of the liquid crystal compound 
becomes higher and electric power consumption becomes larger. 
Differing from switching elements utilizing the TN mode or a STN mode, 
switching elements comprising ferroelectric liquid crystal compounds are 
able to function as switching elements only by changing the direction of 
molecular orientation of the liquid crystal compounds, and hence the 
switching time required for operating the switching elements is 
prominently shortened. Further, because a Ps.times.E value obtained from a 
spontaneous polarization (Ps) of the ferroelectric liquid crystal compound 
and an intensity of the electric field (E) applied thereto is an effective 
energy output for changing the direction of molecular orientation of the 
liquid crystal compound, the electric power consumption required therefor 
can also be extremely reduced. Such ferroelectric liquid crystal compounds 
are suitable particularly for use in display devices for moving picture, 
because they have two stable states depending upon the direction of the 
applied electric field, namely, bi-stability, and have very favorable 
switching threshold value characteristics. 
When such ferroelectric liquid crystal compounds are used in optical 
switching elements or the like, these compounds are required to have 
various characteristics such that an operating temperature is in the 
vicinity of or below ordinary temperature, an operating temperature range 
is broad, a switching speed is high (fast), and a switching threshold 
value voltage is within an appropriate range. In particular, of these 
characteristics, the operating temperature range is very important when 
the ferroelectric crystal compounds are put into practical use. 
However, in ferroelectric liquid crystal compounds known hitherto, the 
operating temperature range is generally narrow, and even in the case of 
ferroelectric liquid crystal compounds having a wide operating temperature 
range, the operating temperature range is in a high temperature region out 
of room temperature, as described, for example, in a paper by R. B. Meyer 
et al., "J. de Phys.", Vol. 36, p. L-69 (1975) or in a paper by M. Taguchi 
and T. Harada, "Proceedings of Eleventh Conference on Liquid Crystal," p. 
168 (1985). Thus, no ferroelectric liquid crystal compounds satisfactory 
from the standpoint of practical use are obtainable yet. 
OBJECT OF THE INVENTION 
An object of the present invention is to provide a novel tetralin compound, 
a liquid crystal material comprising the tetralin compound and a liquid 
crystal compound other than the tetralin compound, a liquid crystal 
composition comprising the tetralin compound and a liquid crystal element 
in which the tetralin compound is used. In particular, the object of the 
invention is to provide a novel tetralin compound capable of forming a 
liquid crystal element having excellent properties such as wide operating 
temperature range, high switching speed, prominently reduced electric 
power consumption and stable contrast, and uses of the tetralin compound. 
SUMMARY OF THE INVENTION 
The tetralin compound of the invention is represented by the following 
formula [I]: 
EQU R--X--A.sup.1 --Y.sup.1-- A.sup.2 --(Y.sup.2 --A.sup.3).sub.n --Z--R* [I] 
wherein 
R is an alkyl group of 3-20 carbon atoms, 
X is --O--CO--, --0-- or a single bond, 
n is 0 or 1, and 
when n is 0, one of A.sup.1 and A.sup.2 is 
##STR1## 
and the residual A.sup.1 or A.sup.2 is a group selected from the group 
consisting of 
##STR2## 
and when n is 1, one of A.sup.1, A.sup.2 and A.sup.3 is 
##STR3## 
and the residual two of A.sup.1 A.sup.2 and A.sup.3 are 1,4-phenylene 
group, 
Y.sup.1 and Y.sup.2 are each independently a group selected from the group 
consisting of --COO--, --O--CO--, --CH.sub.2 CH.sub.2 --, --CH.sub.2 O-- 
and --OCH.sub.2 --, 
Z is --O--, --O--CO-- or a single bond, and 
R* is a group selected from the group consisting of 
--C*H(CF.sub.3)--C.sub.6 H.sub.13, --C*H (CH.sub.3) --C.sub.6 H.sub.13, 
--C*H (CH.sub.3) --C.sub.5 H.sub.11, --C*H (C.sub.2 H.sub.5)--C.sub.5 
H.sub.11, --C*H (C.sub.2 H.sub.5)--C.sub.6 H.sub.13, --CH.sub.2 13 C*H 
(CH.sub.3) --C.sub.2 H.sub.5, --CH.sub.2).sub.3 --C*H(CH.sub.3)--C.sub.2 
H.sub.5 and --C*H (CF.sub.3)--CH.sub.2 --COO--C.sub.2 H.sub.5. 
The liquid crystal material of the invention comprises the tetralin 
compound represented by the above formula [I]. 
The liquid crystal composition of the invention comprises the tetralin 
compound represented by the above formula [I]and a liquid crystal compound 
other than the tetralin compound. 
The liquid crystal element of the invention is a liquid crystal element 
comprising a cell and a liquid crystal material or composition, said cell 
comprising two substrates facing to each other and a gap formed by the 
substrates, said liquid crystal material or composition being filled in 
the gap of the cell, wherein the liquid crystal material or composition 
comprises the tetralin compound represented by the above formula [I]. 
According to the present invention, a novel tetralin compound is provided. 
The tetralin compound is very useful as a liquid crystal material. 
Therefore, a liquid crystal composition comprising this tetralin compound 
shows excellent liquid crystal characteristics, and further a liquid 
crystal element formed by filling a liquid crystal material or composition 
comprising this tetralin compound in a gap between two substrates also 
shows excellent liquid crystal characteristics. 
By the use of the tetralin compound of the invention as a liquid crystal 
material, there can be obtained various kinds of devices having excellent 
characteristics such as wide operating temperature range, high switching 
speed, very small electric power consumption and stable high contrast.

DETAILED DESCRIPTION ON THE INVENTIQN 
The present invention is described below in detail. 
First, the tetralin compound and the liquid crystal material of the 
invention are described. 
The tetralin compound of the invention is represented by the following 
formula [I]. 
EQU R--X--A.sup.1 Y.sup.1 A.sup.2 (Y.sup.2 --A.sup.3).sub.n --Z--R* [I] 
In the above formula [I], R is an alkyl group of 3-20 carbon atoms. 
The liquid crystal material of the invention comprises the tetralin 
compound represented by the above formula [I]. 
The alkyl group may have any form of straight chain, branched and alicyclic 
forms. In particular, the tetralin compound having a straight chain alkyl 
group as R exhibits excellent liquid crystal properties because the 
molecule has a rigid linear structure. Concrete examples of the straight 
chain alkyl groups include hexyl group, heptyl group, octyl group, nonyl 
group, decyl group, undecyl group, dodecyl group, tetradecyl group, 
hexadecyl group and octadecyl group. 
In the above formula [I], X is --O--CO--, --O-- or a single bond. Of these, 
preferred is --O-- or a single bond in view of characteristics of the 
tetralin compound used as a liquid crystal material. 
In the above formula [I], n is 0 or 1. Accordingly, when n is 0, none of 
Y.sup.2 and A.sup.3 are present in the formula [I]. 
When n is 0, one of A.sup.1 and A.sup.2 is 
##STR4## 
and the residual A.sup.1 or A.sup.2 is a group selected from the group 
consisting of 
##STR5## 
When n is 1, one of A.sup.1, A.sup.2 and A.sup.3 is 
##STR6## 
and the residual two of A.sup.1 A.sup.2 and A.sup.3 are 1,4-phenylene 
group. 
For the use of the tetralin compound of the invention as a liquid crystal 
compound, it is preferred that the molecule is linear as a whole. On that 
account, the 1,2,3,4-tetrahydronaphthyl group is preferably 
1,2,3,4-tetrahydro-2,6-naphthyl group. 
Likewise, the 5,6,7,8-tetrahydronaphthyl group is preferably 
5,6,7,8-tetrahydro-2,6-naphthyl group. 
Examples of structures of the tetralin compound represented by the formula 
[I] wherein A.sup.1 A.sup.2 and A.sup.3 are the above-mentioned groups are 
given below. Examples of 1,2,3,4-tetrahydro-2,6-naphthyl group or 
5,6,7,8-tetrahydro-2,6-naphthyl group are: 
##STR7## 
In the above examples, examples in the groups (1) and (2) are those of the 
tetralin compound represented by the formula [I] wherein n is 0, while 
examples in the groups (3) are those of the tetralin compound represented 
by the formula [I] wherein n is 1. 
When n is 0, one of A.sup.1 and A.sup.2 is 
##STR8## 
and the residual A.sup.1 or A.sup.2 is a group selected from the group 
consisting of 
##STR9## 
When n is 1, one of A.sup.1 A.sup.2 and A.sup.3 is 
##STR10## 
and the residual two of A.sup.1, A.sup.2 and A.sup.3 are 1,4-phenylene 
group. 
In the above formula [I], Y.sup.1 and Y.sup.2 are each independently a 
group selected from the group consisting of --COO--, --O--CO--, --CH.sub.2 
CH.sub.2 --, --CH.sub.2 O--and --OCH.sub.2 --. When the tetralin compound 
of the invention is used as a liquid crystal material, it is preferred 
that Y.sup.1 and Y.sup.2 are each independently --COO--, --O--CO--or a 
single bond. Especially when the linearity of the molecule is taken into 
account, it is desirable that at least one of Y.sup.1 and Y.sup.2, 
preferably both of them, are --O--CO-- or --COO--. 
In the above formula [I], Z is --O--, --O--CO-- or a single bond. 
Particularly, a compound having --O-- or --O--CO-- as Z is prominently 
improved in the tilt angle, as compared with, for example, a compound 
having --COO-- as Z. 
The tilt angles of compounds represented by the following formula wherein Z 
is --O--, --O--CO-- or --COO--, respectively, are shown in the following 
table. 
__________________________________________________________________________ 
##STR11## 
Z Tilt angle 
__________________________________________________________________________ 
O 45.degree. 
OCO 23.degree. 
COO 0.degree. (Exhibited SmA phase only) 
__________________________________________________________________________ 
As is apparent from the above table, the tilt angle of the tetralin 
compound is markedly changed by changing Z to --O--, --O--CO-- or --COO--. 
The tetralin compound wherein Z is the group defined by the invention or a 
single bond has a large tilt angle, and particularly the tetralin compound 
wherein Z is --O-- has an extremely large tilt angle. When such compound 
having a large tilt angle is used as a liquid crystal material, an optical 
switching element showing excellent properties can be obtained. 
Accordingly, for the use of the tetralin compound of the invention as a 
liquid crystal material, Z is particularly preferably --O--. 
In the formula [I], R* is preferably a group selected from the group 
consisting of --C*H(CF.sub.3) --C.sub.6 H.sub.13, --C*H(CH.sub.3)--C.sub.6 
H.sub.13, --C*H (CH.sub.3) --C.sub.5 H.sub.11, --C*H (C.sub.2 
H.sub.5)--C.sub.5 H.sub.11, --C*H (C.sub.2 H.sub.5)--C.sub.6 
H.sub.13,--CH.sub.2 --C*H(CH.sub.3)--Ch.sub.2 H.sub.5, --(CH.sub.2).sub.3 
--C*H(CH.sub.3)--C.sub.2 H.sub.5 and --C*H(CF.sub.3) --CH.sub.2 
--COO--C.sub.2 H.sub.5. That is, R* is an optically active group having at 
least one asymmetric carbon. A carbon atom which is bonded to the 
above-mentioned carbon atom for forming the optically active group may 
have a halogen atom such as a fluorine atom. 
Of the above-mentioned groups, preferred is either of the following groups 
in view of characteristics of the tetralin compound used as a liquid 
crystal material. 
--C*H(CF.sub.3)--C.sub.6 H.sub.13 
--C*H(CH.sub.3)--C.sub.6 H.sub.13 
Accordingly, concrete examples of the tetralin compound represented by the 
formula [I]are those set forth in Tables 1-1 to 1-3 and Tables 2-1 to 2-6. 
That is, concrete examples of the tetralin compound represented by the 
formula [I] wherein n is 1, namely, a tetralin compound represented by the 
following formula [I-A], are shown in Table 1-1 to Table 1-3. 
EQU R--X--A.sup.1 --Y.sup.1 --A.sup.2 --Y.sup.2 --A.sup.3 --Z--R* [I--A] 
TABLE 1-1 
__________________________________________________________________________ 
[n = 1] 
Com. Ex. 
No. R X A.sup.1 Y.sup.1 
A.sup.2 No. 
__________________________________________________________________________ 
1 C.sub.7 H.sub.15 
O 
##STR12## 
OCO 
##STR13## 1 
2 C.sub.8 H.sub.17 
" " " " 
3 C.sub.9 H.sub.19 
" " " " 
4 C.sub.10 H.sub.21 
" " " " 
5 C.sub.11 H.sub.23 
" " " " 
6 C.sub.12 H.sub.23 
" " " " 
7 C.sub.14 H.sub.29 
" " " " 
8 C.sub.16 H.sub.33 
" " " " 
9 C.sub.7 H.sub.15 
-- 
##STR14## 
OCO 
##STR15## 
10 C.sub.8 H.sub.17 
" " " " 
11 C.sub.9 H.sub.19 
" " " " 
12 C.sub.10 H.sub.21 
" " " " 
13 C.sub.11 H.sub.23 
" " " " 
14 C.sub.12 H.sub.23 
" " " " 
15 C.sub.14 H.sub.29 
" " " " 
16 C.sub.16 H.sub.33 
" " " " 
17 C.sub.7 H.sub.15 
O 
##STR16## 
OCO 
##STR17## 5 
18 C.sub.8 H.sub.17 
" " " " 
19 C.sub.9 H.sub.19 
" " " " 
20 C.sub.10 H.sub.21 
" " " " 
21 C.sub.11 H.sub.23 
" " " " 
22 C.sub.12 H.sub.23 
" " " " 
23 C.sub.14 H.sub.29 
" " " " 
24 C.sub.16 H.sub.33 
" " " " 
__________________________________________________________________________ 
[n = 1] 
Com. Ex. 
No. Y.sup.2 A.sup.3 Z R* No. 
__________________________________________________________________________ 
1 OCO 
##STR18## 
O C*H(CH.sub.3)C.sub.6 H.sub.13 
1 
2 " " " " 
3 " " " " 
4 " " " " 
5 " " " " 
6 " " " " 
7 " " " " 
8 " " " " 
9 OCO 
##STR19## 
O C*H(CH.sub.3)C.sub.6 H.sub.13 
10 " " " " 
11 " " " " 
12 " " " " 
13 " " " " 
14 " " " " 
15 " " " " 
16 " " " " 
17 OCO 
##STR20## 
OCO C*H(CH.sub.3)C.sub.6 H.sub.13 
5 
18 " " " " 
19 " " " " 
20 " " " " 
21 " " " " 
22 " " " " 
23 " " " " 
24 " " " " 
__________________________________________________________________________ 
TABLE 1-2 
__________________________________________________________________________ 
Com. Ex. 
No. R X A.sup.1 Y.sup.1 
A.sup.2 No. 
__________________________________________________________________________ 
25 C.sub.10 H.sub.21 
O 
##STR21## COO 
##STR22## 
26 " " " CH.sub.2 CH.sub.2 
" 
27 " " " CH.sub.2 O 
" 
28 " " " OCH.sub.2 
" 
29 C.sub.10 H.sub.21 
O 
##STR23## OCO 
##STR24## 
30 " " " " " 
31 " " " " " 
32 " " " " " 
33 " " " " " 
34 " " " " " 
35 C.sub.10 H.sub.21 
O 
##STR25## OCO 
##STR26## 
36 C.sub.10 H.sub.21 
-- " " " 
37 C.sub.10 H.sub.21 
OCO " " " 
38 C.sub.10 H.sub.21 
O 
##STR27## OCO 
##STR28## 
39 C.sub.10 H.sub.21 
-- " " " 
40 C.sub.10 H.sub.21 
OCO " " " 
41 C.sub.10 H.sub.21 
O 
##STR29## OCO 
##STR30## 
42 C.sub.10 H.sub.21 
-- " " " 
43 C.sub.10 H.sub.21 
OCO " " " 
__________________________________________________________________________ 
Com. Ex. 
No. Y.sup.2 A.sup.3 Z R* No. 
__________________________________________________________________________ 
25 OCO 
##STR31## O C*H(CH.sub.3)C.sub.6 H.sub.13 
26 " " " " 
27 " " " " 
28 " " " " 
29 OCO 
##STR32## O C*H(CF.sub.3)C.sub.5 H.sub.11 
30 " " " C*H(C.sub.2 H.sub.5)C.sub.5 H.sub.11 
31 " " " C*H(C.sub.2 H.sub.5)C.sub.6 H.sub.11 
32 " " " CH.sub.2 C*H(CH.sub.3)C.sub.2 H.sub.5 
33 " " " (CH.sub.2).sub.3 C*H(CH.sub.3)C.sub.2 
H.sub.5 
34 " " " C*H(CF.sub.3)CH.sub.2 COOC.sub.2 H.sub.5 
35 OCO 
##STR33## O C*H(CH.sub.3)C.sub.6 H.sub.13 
36 " " " " 
37 " " " " 
38 OCO 
##STR34## O C*H(CH.sub.3)C.sub.6 H.sub.13 
39 " " " " 
40 " " " " 
41 OCO 
##STR35## O C*H(CH.sub.3)C.sub.6 H.sub.13 
42 " " " " 
43 " " " " 
__________________________________________________________________________ 
TABLE 1-3 
__________________________________________________________________________ 
Com. Ex. 
No. R X A.sup.1 Y.sup.1 
A.sup.2 No. 
__________________________________________________________________________ 
44 C.sub.10 H.sub.21 
O 
##STR36## OCO 
##STR37## 
45 C.sub.10 H.sub.21 
-- " " " 
46 C.sub.10 H.sub.21 
OCO " " " 
47 C.sub.10 H.sub.21 
O 
##STR38## OCO 
##STR39## 
48 C.sub.10 H.sub.21 
-- " " " 
49 C.sub.10 H.sub.21 
OCO " " " 
50 C.sub.10 H.sub.21 
O 
##STR40## COO 
##STR41## 
2 
51 C.sub.10 H.sub. 21 
-- " " " 
52 C.sub.10 H.sub.21 
OCO " " " 
__________________________________________________________________________ 
Com. Ex. 
No. Y.sup.2 A.sup.3 Z R* No. 
__________________________________________________________________________ 
44 OCO 
##STR42## O C*H(CH.sub.3)C.sub.6 H.sub.13 
45 " " " " 
46 " " " " 
47 OCO 
##STR43## O C*H(CH.sub.3)C.sub.6 H.sub.13 
48 " " " " 
49 " " " " 
50 COO 
##STR44## O C*H(CH.sub.3)C.sub.6 H.sub.13 
2 
51 " " " " 
52 " " " " 
__________________________________________________________________________ 
Further, concrete examples of the tetralin compound represented by the 
formula [I] wherein n is 0, namely, a tetralin compound represented by the 
following formula [I-B], are shown in Table 2-1 to Table 2-6. 
EQU R--X--A.sup.1 --Y.sup.1 --A.sup.2 --Z--R* [I-B] 
TABLE 2-1 
__________________________________________________________________________ 
[n = 0] 
Com. Ex. 
No. R X A.sup.1 Y.sup.1 
No. 
__________________________________________________________________________ 
53 C.sub.10 H.sub.21 
O 
##STR45## OCO 
54 C.sub.10 H.sub.21 
-- " " 
55 C.sub.9 H.sub.19 
OCO " " 
56 C.sub.10 H.sub.21 
O 
##STR46## OCO 
57 C.sub.10 H.sub.21 
-- " " 
58 C.sub.9 H.sub.19 
OCO " " 
59 C.sub.10 H.sub.21 
O 
##STR47## OCO 
60 C.sub.10 H.sub.21 
-- " " 
61 C.sub.9 H.sub.19 
OCO " " 
62 C.sub.10 H.sub.21 
O 
##STR48## OCO 
63 C.sub.10 H.sub.21 
-- " " 
64 C.sub.9 H.sub.19 
OCO " " 
65 C.sub.10 H.sub.21 
O 
##STR49## OCO 
66 C.sub.10 H.sub.21 
-- " " 
67 C.sub.9 H.sub.19 
OCO " " 
68 C.sub.10 H.sub.21 
O 
##STR50## OCO 
69 C.sub.10 H.sub.21 
-- " " 
70 C.sub.9 H.sub.19 
OCO " " 
__________________________________________________________________________ 
Com. Ex. 
No. A.sup.2 Z R* No. 
__________________________________________________________________________ 
53 
##STR51## O C*H(CH.sub.3)C.sub.6 H.sub.13 
54 " " " 
55 " " " 
56 
##STR52## O C*H(CH.sub.3)C.sub.6 H.sub.13 
57 " " " 
58 " " " 
59 
##STR53## O C*H(CH.sub.3)C.sub.6 H.sub.13 
60 " " " 
61 " " " 
62 
##STR54## O C*H(CH.sub.3)C.sub.6 H.sub.13 
63 " " " 
64 " " " 
65 
##STR55## O C*H(CH.sub.3)C.sub.6 H.sub.13 
66 " " " 
67 " " " 
68 
##STR56## O C*H(CH.sub.3)C.sub.6 H.sub.13 
69 " " " 
70 " " " 
__________________________________________________________________________ 
TABLE 2-2 
__________________________________________________________________________ 
Com. No. 
R X A.sup.1 Y.sup.1 
Ex. No. 
__________________________________________________________________________ 
71 C.sub.10 H.sub.21 
O 
##STR57## OCO 
72 C.sub.10 H.sub.21 
-- " " 
73 C.sub.9 H.sub.19 
OCO " " 
74 C.sub.10 H.sub.21 
O 
##STR58## OCO 
75 C.sub.10 H.sub.21 
-- " " 
76 C.sub.9 H.sub.19 
OCO " " 
77 C.sub.10 H.sub.21 
O 
##STR59## OCO 
78 C.sub.10 H.sub.21 
-- " " 
79 C.sub.9 H.sub.19 
OCO " " 
80 C.sub.10 H.sub.21 
O 
##STR60## OCO 
81 C.sub.10 H.sub.21 
-- " " 
82 C.sub.9 H.sub.19 
OCO " " 
83 C.sub.10 H.sub.21 
O 
##STR61## OCO 
84 C.sub.10 H.sub.21 
-- " " 
85 C.sub.9 H.sub.19 
OCO " " 
86 C.sub.10 H.sub.21 
O 
##STR62## OCO 
87 C.sub.10 H.sub.21 
-- " " 
88 C.sub.9 H.sub.19 
OCO " " 
__________________________________________________________________________ 
Com. No. A.sup.2 Z R* Ex. No. 
__________________________________________________________________________ 
71 
##STR63## O C*H(CH.sub.3)C.sub.6 H.sub.13 
72 " " " 
73 " " " 
74 
##STR64## O C*H(CH.sub.3)C.sub.6 H.sub.13 
75 " " " 
76 " " " 
77 
##STR65## O C*H(CH.sub.3)C.sub.6 H.sub.13 
78 " " " 
79 " " " 
80 
##STR66## O C*H(CH.sub.3)C.sub.6 H.sub.13 
81 " " " 
82 " " " 
83 
##STR67## O C*H(CH.sub.3)C.sub.6 H.sub.13 
84 " " " 
85 " " " 
86 
##STR68## O C*H(CH.sub.3)C.sub.6 H.sub.13 
87 " " " 
88 " " " 
__________________________________________________________________________ 
TABLE 2-3 
__________________________________________________________________________ 
Com. No. 
R X A.sup.1 Y.sup.1 
Ex. No. 
__________________________________________________________________________ 
89 C.sub.10 H.sub.21 
O 
##STR69## OCO 
90 C.sub.10 H.sub.21 
-- " " 
91 C.sub.9 H.sub.19 
OCO " " 
92 C.sub.10 H.sub.21 
O 
##STR70## OCO 
93 C.sub.10 H.sub.21 
-- " " 
94 C.sub.9 H.sub.19 
OCO " " 
95 C.sub.10 H.sub.21 
O 
##STR71## OCO 
96 C.sub.10 H.sub.21 
-- " " 
97 C.sub.9 H.sub.19 
OCO " " 
98 C.sub.10 H.sub.21 
O 
##STR72## OCO 
99 C.sub.10 H.sub.21 
-- " " 
100 C.sub.9 H.sub.19 
OCO " " 
101 C.sub.10 H.sub.21 
O 
##STR73## OCO 
102 C.sub.10 H.sub.21 
-- " " 
103 C.sub.9 H.sub.19 
OCO " " 
104 C.sub.10 H.sub.21 
O 
##STR74## OCO 
105 C.sub.10 H.sub.21 
-- " " 
106 C.sub.9 H.sub.19 
OCO " " 
__________________________________________________________________________ 
Com. No. A.sup.2 Z R* Ex. No. 
__________________________________________________________________________ 
89 
##STR75## O C*H(CH.sub.3)C.sub.6 H.sub.13 
90 " " " 
91 " " " 
92 
##STR76## O C*H(CH.sub.3)C.sub.6 H.sub.13 
93 " " " 
94 " " " 
95 
##STR77## O C*H(CH.sub.3)C.sub.6 H.sub.13 
96 " " " 
97 " " " 
98 
##STR78## O C*H(CH.sub.3)C.sub.6 H.sub.13 
99 " " " 
100 " " " 
101 
##STR79## O C*H(CH.sub.3)C.sub.6 H.sub.13 
102 " " " 
103 " " " 
104 
##STR80## O C*H(CH.sub.3)C.sub.6 H.sub.13 
105 " " " 
106 " " " 
__________________________________________________________________________ 
TABLE 2-4 
__________________________________________________________________________ 
Com. No. 
R X A.sup.1 Y.sup.1 
Ex. No. 
__________________________________________________________________________ 
107 C.sub.10 H.sub.21 
O 
##STR81## OCO 
108 C.sub.10 H.sub.21 
-- " " 
109 C.sub.9 H.sub.19 
OCO " " 
110 C.sub.10 H.sub.21 
O 
##STR82## OCO 
111 C.sub.10 H.sub.21 
-- " " 
112 C.sub.9 H.sub.19 
OCO " " 
113 C.sub.10 H.sub.21 
O 
##STR83## OCO 
114 C.sub.10 H.sub.21 
-- " " 
115 C.sub.9 H.sub.19 
OCO " " 
116 C.sub.10 H.sub.21 
O 
##STR84## OCO 
117 C.sub.10 H.sub.21 
-- " " 
118 C.sub.9 H.sub.19 
OCO " " 
119 C.sub.10 H.sub.21 
O 
##STR85## OCO 
120 C.sub.10 H.sub.21 
-- " " 
121 C.sub.9 H.sub.19 
OCO " " 
122 C.sub.10 H.sub.21 
O 
##STR86## OCO 
123 C.sub.10 H.sub.21 
-- " " 
124 C.sub.9 H.sub.19 
OCO " " 
__________________________________________________________________________ 
Com. No. A.sup.2 Z R* Ex. No. 
__________________________________________________________________________ 
107 
##STR87## O C*H(CH.sub.3)C.sub.6 H.sub.13 
108 " " " 
109 " " " 
110 
##STR88## O C*H(CH.sub.3)C.sub.6 H.sub.13 
111 " " " 
112 " " " 
113 
##STR89## O C*H(CH.sub.3)C.sub.6 H.sub.13 
114 " " " 
115 " " " 
116 
##STR90## O C*H(CH.sub.3)C.sub.6 H.sub.13 
117 " " " 
118 " " " 
119 
##STR91## O C*H(CH.sub.3)C.sub.6 H.sub.13 
120 " " " 
121 " " " 
122 
##STR92## O C*H(CH.sub.3)C.sub.6 H.sub.13 
123 " " " 
124 " " " 
__________________________________________________________________________ 
TABLE 2-5 
__________________________________________________________________________ 
Com. No. 
R X A.sup.1 Y.sup.1 
Ex. No. 
__________________________________________________________________________ 
125 C.sub.10 H.sub.21 
O 
##STR93## OCO 
126 C.sub.10 H.sub.21 
-- " " 
127 C.sub.9 H.sub.19 
OCO " " 
128 C.sub.10 H.sub.21 
O 
##STR94## OCO 
129 C.sub.10 H.sub.21 
-- " " 
130 C.sub.9 H.sub.19 
OCO " " 
131 C.sub.10 H.sub.21 
O 
##STR95## OCO 
132 C.sub.10 H.sub.21 
-- " " 
133 C.sub.9 H.sub.19 
OCO " " 
134 C.sub.10 H.sub.21 
O 
##STR96## OCO 
135 C.sub.10 H.sub.21 
-- " " 
136 C.sub.9 H.sub.19 
OCO " " 
137 C.sub.10 H.sub.21 
O 
##STR97## OCO 
138 C.sub.10 H.sub.21 
-- " " 
139 C.sub.9 H.sub.19 
OCO " " 
140 C.sub.10 H.sub.21 
O 
##STR98## OCO 
141 C.sub.10 H.sub.21 
-- " " 
142 C.sub.9 H.sub.19 
OCO " " 
__________________________________________________________________________ 
Com. No. A.sup.2 Z R* Ex. No. 
__________________________________________________________________________ 
125 
##STR99## O C*H(CH.sub.3)C.sub.6 H.sub.13 
126 " " " 
127 " " " 
128 
##STR100## O C*H(CH.sub.3)C.sub.6 H.sub.13 
129 " " " 
130 " " " 
131 
##STR101## O C*H(CH.sub.3)C.sub.6 H.sub.13 
132 " " " 
133 " " " 
134 
##STR102## O C*H(CH.sub.3)C.sub.6 H.sub.13 
135 " " " 
136 " " " 
137 
##STR103## O C*H(CH.sub.3)C.sub.6 H.sub.13 
138 " " " 
139 " " " 
140 
##STR104## O C*H(CH.sub.3)C.sub.6 H.sub.13 
141 " " " 
142 " " " 
__________________________________________________________________________ 
TABLE 2-6 
__________________________________________________________________________ 
Com. No. 
R X A.sup.1 Y.sup.1 
Ex. No. 
__________________________________________________________________________ 
143 C.sub.10 H.sub.21 
O 
##STR105## OCO 
144 C.sub.10 H.sub.21 
-- " " 
145 C.sub.9 H.sub.19 
OCO " " 
146 C.sub.10 H.sub.21 
O 
##STR106## OCO 
147 C.sub.10 H.sub.21 
-- " " 
148 C.sub.9 H.sub.19 
OCO " " 
149 C.sub.10 H.sub.21 
O 
##STR107## COO 3 
150 C.sub.10 H.sub.21 
-- " " 
151 C.sub.9 H.sub.19 
OCO " " 
__________________________________________________________________________ 
Com. No. A.sup.2 Z R* Ex. No. 
__________________________________________________________________________ 
143 
##STR108## O C*H(CH.sub.3)C.sub.6 H.sub.13 
144 " " " 
145 " " " 
146 
##STR109## O C*H(CH.sub.3)C.sub.6 H.sub.13 
147 " " " 
148 " " " 
149 
##STR110## O C*H(CH.sub.3)C.sub.6 H.sub.13 
3 
150 " " " 
151 " " " 
__________________________________________________________________________ 
Such tetralin compound as described above can be prepared by means of a 
combination of known synthetic techniques. 
For example, the tetralin compound can be synthesized in accordance with 
the following synthesis route. 
##STR111## 
That is, for example, a mixture of 6-alkoxynaphthalene-2-carboxylic acid 
and 1,2-diethoxyethane is refluxed while dropwise adding isoamyl alcohol 
to the mixture in the presence of metallic sodium, to obtain 
1,2,3,4-tetrahydro-6-alkoxynaphthalene-2-carboxylic acid. 
The 1,2,3,4-tetrahydro-6-alkoxynaphthalene-2-carboxylic acid thus obtained 
is reacted with acetic acid and hydrobromic acid, to obtain 
1,2,3,4-tetrahydro-6-hydroxynaphthalene-2-carboxylic acid. 
The 1,2,3,4-tetrahydro-6-hydroxynaphthalene-2-carboxylic acid thus obtained 
is reacted with benzyl bromide in the presence of potassium hydroxide, to 
obtain 1,2,3,4-tetrahydro-6-benzyloxynaphthalene-2-carboxylic acid. 
Subsequently, hydroquinone monoalcohol ether separately synthesized by a 
conventional process is reacted with the 
1,2,3,4-tetrahydro-6-benzyloxynaphthalene-2-carboxylic acid obtained in 
the above step in the presence of 4-N,N-dimethylaminopyridine and 
methylene chloride (as a solvent) while dropwise adding a solution of 
N,N'-dicyclohexylcarbodiimide, to obtain 
1,2,3,4-tetrahydro-6-benzyloxynaphthalene-2-carboxylic 
acid-4'-alkoxyphenyl ester. 
The 1,2,3, 4-tetrahydro-6-benzyloxynaphthalene-2-carboxylic 
acid-4'-alkoxyphenyl ester thus obtained is introduced into a solvent such 
as tetrahydrofuran, and the resulting solution is reduced with hydrogen in 
the presence of a reducing catalyst such as palladium/carbon, to obtain 
1,2,3,4-tetrahydro-6-hydroxynaphthalene-2-carboxylic acid-4'-alkoxyphenyl 
ester. 
Then, 4-alkoxybenzoic acid containing an asymmetric carbon is reacted with 
the 1,2,3,4-tetrahydro-6-hydroxynaphthalene-2-carboxylic 
acid-4'-alkoxyphenyl ester obtained in the above step in the presence of 
4-N,N-dimethylaminopyridine and methylene chloride (as a solvent) while 
dropwise adding a solution of N,N'-dicyclohexylcarbodiimide, to obtain the 
tetralin compound of the invention. 
The above-described process is one example of a process for preparing the 
tetralin compound of the invention, and the tetralin compound of the 
invention is in no way limited to the compound prepared by the process. 
A .sup.1 H-NMR spectrum of 
6-[4'-(R-2"-octyloxy)benzoyioxy]-1,2,3,4-tetrahydronaphthalene-2-carboxyli 
c acid-4"'-decyloxyphenyl ester [Exemplified Compound (4)]represented by 
the following formula, which is one example of the tetralin compound of 
the invention, is shown in FIG. 1. 
In the following formula, symbols "eq" and "ax" mean equatorial 
conformation and axial conformation, respectively. 
##STR112## 
In the above formula, each of numbers 1 to 12 indicates hydrogen atom, and 
each of the numbers corresponds to the same number attached to either one 
of peaks shown in FIG. 1. A .sup.1 H-NMR spectrum of 4-(6'-decyloxy-5', 
6', 7', 8'-tetrahydro-2"-naphthoyloxy) benzoic acid-4"- 
(R-2"'-octyloxy)phenyl ester [Exemplified Compound (50) ] represented by 
the following formula, which is also one example of the tetralin compound 
of the invention, is shown in FIG. 2. 
##STR113## 
In the above formula, each of numbers 1 to 19 indicates hydrogen atom, and 
each of the numbers corresponds to the same number attached to either one 
of peaks shown in FIG. 2. 
A .sup.1 H-NMR spectrum of 
6-decyloxy-1,2,3,4-tetrahydronaphthalene-2-carboxylic acid-4'- 
(R-2"-octyloxy)phenyl ester [Exemplified Compound (149)] represented by 
the following formula, which is also one example of the tetralin compound 
of the invention, is shown in FIG. 3. 
##STR114## 
In the above formula, each of numbers 1 to 14 indicates hydrogen atom, and 
each of the numbers corresponds to the same number attached to either one 
of peaks shown in FIG. 3. 
The tetralin compound of the formula [I] obtained as above may be used, for 
example, as a liquid crystal material. 
In particular, the tetralin compound having optical activity may be used as 
a ferroelectric liquid crystal compound or an antiferroelectric liquid 
crystal compound. 
Of such tetralin compounds as described above, compounds represented by the 
following formulas [4], [20], 50] and [149] exhibit particularly excellent 
liquid crystal characteristics. 
##STR115## 
Phase transition temperatures of the compounds represented by the formulas 
[4], [50]and [149] which are particularly excellent as liquid crystal 
compounds are shown in Table 3, wherein Cry, SmC.sub.A * SmC* SmA, Ch and 
Iso denote a crystal phase, an antiferroelectric phase, a ferroelectric 
phase, a smectic A phase, a cholesteric phase and an isotropic liquid, 
respectively. 
TABLE 3 
______________________________________ 
Cry--SmC.sub.A * 
SmC.sub.A *--SmA 
SmA--Iso 
or SmC*--CmA or Ch or Ch 
______________________________________ 
[4] 40.degree. C. SmC.sub.A * 
82.degree. C. Ch 
103.degree. C. 
[50] 40.degree. C. SmC* 
59.degree. C. SmA 
108.degree. C. 
[149] 21.degree. C. SmA 
-- 34.degree. C. 
______________________________________ 
In the liquid crystal compounds of the invention, there are many compounds 
exhibiting a smectic phase over a broad temperature range, as shown in 
Table 3. 
There have been known few liquid crystal compounds which, if used alone as 
a liquid crystal material, exhibit a smectic phase over such a broad 
temperature range as in the above-mentioned compounds. In addition to the 
fact that the liquid crystal material of the invention exhibits a smectic 
phase in a broad temperature range, a liquid crystal element filled with 
such liquid crystal material, for example, an optical switching element, 
is excellent in high response speed. 
The liquid crystal material of the invention may be used either singly or 
in a mixture with other liquid crystal material in the form of a liquid 
crystal composition. For example, the liquid crystal material of the 
invention may be used as a major component of a ferroelectric or 
antiferroelectric liquid crystal composition or as a minor component of a 
liquid crystal composition which exhibits a smectic phase. That is, of the 
tetralin compounds of the invention, a tetratin compound exhibiting a 
smectic phase can be used as a major component of a liquid crystal 
composition or a minor component of a liquid crystal composition which 
contains other liquid crystal material as a major component, while a 
tetralin compound which does not exhibit a smectic phase can be used as an 
assistant of a liquid crystal composition which contains other liquid 
crystal material as a major component. 
The liquid crystal composition of the present invention comprises the 
tetralin compound of the formula [I] and a liquid crystal compound other 
than the tetralin compound. 
Examples of liquid crystal compounds which may be used in the invention in 
combination with the compound represented by the formula [I] include those 
listed below. 
(+)-4'-(2"-methylbutyloxy)phenyl-6-octyloxynaphthalene-2-carboxylate, 
4'-decyloxyphenyl-6-((+)-2"-methylbutyloxy)naphthalene-2-carboxylate, 
##STR116## 
In addition to the above, there may be mentioned the following compounds 
having a cyclic structure and an optical activity. 
##STR117## 
Further, there also may be mentioned Schiff base type liquid crystal 
compounds such as 
##STR118## 
azoxy type liquid crystal compounds such as 
##STR119## 
benzoate type liquid crytal compounds such as 
##STR120## 
cyclohexylcarboxylate type liquid crystal compounds such as 
##STR121## 
phenyl type liquid crystal compounds such as 
##STR122## 
terphenol type liquid crystal compounds such as 
##STR123## 
cyclohexyl type liquid crystal compounds such as 
##STR124## 
and pyrimidine type liquid crystal compounds such as 
##STR125## 
An amount of the tetralin compound of the formula [I] contained in the 
liquid crystal composition can be optionally determined in consideration 
of characteristics of the resulting composition. The composition of the 
invention contains the tetralin compound of the formula [I] in an amount 
of usually 1-99 parts by weight, preferably 5-75 parts by weight, based on 
100 parts by weight of the total amount of liquid crystal materials 
contained in the composition. 
In addition to the liquid crystal materials mentioned as above, the liquid 
crystal composition may further contain additives which are conventionally 
used in liquid crystal compositions, for example, conductivity-imparting 
agents and life-improving agents. 
The liquid crystal composition of the invention can be prepared by mixing 
the above-mentioned tetralin compound with other liquid crystal material, 
and if desired, additives. 
When a voltage is applied to the liquid crystal composition comprising the 
above-mentioned liquid crystal material, an optical switching phenomenon 
takes place. Utilizing this phenomenon, a display device exhibiting a good 
response can be produced. In the invention, with regard to elements 
utilizing such phenomenon or methods of driving the elements, reference to 
for example Japanese Patent L-O-P Publns. Nos. 107216/1981 and 118744/1984 
may be made. 
The liquid crystal material that may be used in the display device referred 
to above may include such compounds as exhibiting any of smectic C phase, 
smectic F phase, smectic G phase, smectic H phase, smectic I phase, 
smectic J phase and smectic K phase. Display devices using liquid crystal 
materials exhibiting other phases than the smectic C phase generally have 
a low response speed, and hence it has heretofore been considered that it 
is effective to drive a display device by means of a liquid crystal 
material exhibiting the smectic C phase having a high response speed. 
However, it has been found that it is possible in the invention to 
advantageously use the liquid crystal material even when it exhibits a 
smectic A phase other than the smectic C phase by utilizing a method in 
which the display device is driven by means of a liquid crystal material 
exhibiting a smectic A phase as proposed by the present inventors in 
Japanese Patent L-O-P Publn. No. 3632/1989. That is, by virtue of 
utilization of this driving method, the liquid crystal element of the 
invention can be driven in a wide phase range, and at the same time, it is 
possible to speed up an electro-optical response. 
The liquid crystal element of the invention comprises a cell filled with a 
liquid crystal material or composition, and polarizing plates. In detail, 
the liquid crystal element of the invention, for example, as shown in FIG. 
6, is formed from a cell 13 comprising two transparent substrates 11a and 
11b arranged so as to form a gap 14 to be filled with a liquid crystal 
material 12, and transparent electrodes 15a and 15b formed on the surfaces 
of the transparent substrates 11a and 11b, said surfaces individually 
facing the liquid crystal material 12, the liquid crystal material 12 
charged in the gap 14 of the cell 13, and two polarizing plates (not shown 
in FIG. 6) each arranged on an outer side of the cell 13. 
In the invention, employable as the transparent substrate are, for example, 
glass and transparent polymer plates. When glass substrates are used, the 
substrate surfaces may be provided with an undercoat layer (i.e., a layer 
for inhibiting permeation of unnecessary component) comprising silicon 
oxide as a major component to prevent deterioration of the liquid crystal 
material caused by elution of alkali component of the glass. The 
transparent substrate, for example, glass substrate, usually has a 
thickness of 0.01-1.0 mm. 
In the invention, flexible transparent substrates may be used as the 
transparent substrates. In this case, one of the substrates may be a 
flexible transparent substrate, or both substrates may be flexible 
transparent substrates. Useful as such flexible transparent substrates are 
polymer films. When the flexible transparent substrates are used as the 
transparent substrates of the invention, it is preferred that a thickness 
t (mm) of each flexible transparent substrate, a modulus of elasticity E 
(kgf/m.sup.2) and a width a (mm) of the gap formed in the cell have the 
following relationship. 
##EQU1## 
On the surface of each transparent substrates, a transparent electrode is 
provided. The transparent electrode is formed, for example, by coating the 
transparent substrate surface with iridium oxide, tin oxide, etc. The 
transparent electrode can be formed by a known method. The thickness of 
the transparent electrode is usually in the range of 100 to 2,000 .ANG.. 
The transparent substrate having the transparent electrode may be further 
provided with an orientation layer or a ferroelectric material layer on 
the surface of the transparent electrode. The orientation layer includes, 
for example, an organic thin film formed by chemical adsorption thereon of 
an organic silane coupling agent or a carboxylic acid polynuclear complex, 
and an inorganic thin film. Examples of the organic thin film include thin 
films of polymers such as polyethylene, polypropylene, polyester, 
polyamide, polyvinyl alcohol and polyimide. The organic thin film may be 
formed by such techniques as coating, adhesion, deposition or 
polymerization (e.g., plasma polymerization) on the substrate. 
Examples of the inorganic thin film include thin films of oxides such as 
silicon oxide, germanium oxide and alumina, thin films of nitrides such as 
silicon nitride, and thin films of other semi-conductors. The inorganic 
thin film may be formed by such techniques as deposition (e.g. rhombic 
deposition) and sputtering. 
The thin film as mentioned above is imparted with orientation by imparting 
anisotropy or stereospecificity to the thin film itself in the film 
forming procedure, or externally imparting orientation to the thin film 
after the film forming procedure. In concrete, there may be mentioned a 
method in which the thin film is formed by coating a polymer material such 
as polyimide resin on the transparent electrode, followed by rubbing the 
film in a definite direction; a method in which a polymer film is 
subjected to stretching to impart orientation to the stretched film; and a 
method in which an oxide is subjected to rhombic deposition to form the 
oriented oxide film. 
Such thin film (e.g, orientation layer) may be so formed that it also 
serves as a spacer described later. 
Two of the transparent substrates as mentioned above are arranged in such a 
manner that the transparent electrodes formed on the substrates face each 
other and a gap to be filled with a liquid crystal material (or 
composition) is formed by these two transparent substrates. The gap thus 
formed has a width of usually 1-10 .mu.m, preferably 1-5 .mu.n. The gap 
may be formed, for example, by arranging the two substrates so as to hold 
a spacer therebetween. Usable as the spacer is a polyimide type polymer 
material which is obtained, for example, by patterning a photosensitive 
polyimide precursor. By the use of the spacer, a monodomain is formed by 
the interfacial effect between the spacer and the liquid crystal material. 
As shown in FIG. 7 (a) and FIG. 7 (b) that is a sectional view taken on 
line A--A of FIG. 7 (a), integration of the orientation film with the 
spacer may be made, for example, by using a concentric spacer 26 which 
acts as an orientation film. In FIG. 7 (a) and FIG. 7 (b) , the 
transparent substrates are indicated by numeral 27, the transparent 
electrodes are indicated by numeral 25, and the liquid crystal material is 
indicated by numeral 23. 
As shown in FIG. 8 (a) and FIG. 8 (b) that is a sectional view taken on 
line A--A of FIG. 8 (a), integration of the orientation film with the 
spacer may be made, for example, by using a comb-like spacer 36 which acts 
as an orientation film. In FIG. 8 (a) and FIG. 8 (b) , the transparent 
substrates are indicated by numeral 37, the transparent electrodes are 
indicated by numeral 35, and the liquid crystal material is indicated by 
numeral 33. 
As shown in FIG. 9, fibers 46 may be incorporated into a liquid crystal 
material 43 instead of using the above-mentioned spacer. In this case, a 
definite gap is held between transparent substrates 47 each provided with 
a transparent electrode 45 owing to the fibers. 
The fibers used herein preferably have the following relationship between 
an average diameter and an average length of the fibers. 
##EQU2## 
wherein d is an average diameter of the fibers, and q is an average length 
of the fibers. 
Various kinds of fibers are employable as the fibers, but preferred are 
those obtained by spinning alkali glass. 
It is also possible to incorporate particulate materials into the liquid 
crystal material in place of or in combination with the above-mentioned 
fibers. 
The particulate materials include those of melamine resin, urea resin or 
benzoguanamine resin having a particle diameter of 1-10 .mu.m. 
The two transparent substrates arranged so as to form the gap in the manner 
described above are combined together by sealing their peripheries with a 
sealer. Useful as the sealer are, for example, epoxy resin and silicone 
resin. The epoxy resin or the like used as the sealer may be modified with 
acrylic materials or silicone rubbers. 
The gap of the liquid crystal cell having such a structure as mentioned 
above is filled with a liquid crystal material (or composition) comprising 
the tetralin compound represented by the formula [I]. 
The liquid crystal material filled in the gap of the liquid crystal cell 
can be oriented, for example, by utilizing a monoaxial orientation control 
method such as a temperature gradient method using a spacer edge or a 
surface treatment method using an orientation film. In the invention, it 
is also possible to carry out initial orientation of the liquid crystal 
material, for example, by applying a direct bias voltage to the liquid 
crystal material while heating the material. 
The liquid crystal cell filled with the liquid crystal material and 
subjected to initial orientation as described above is disposed between 
two polarizing plates. As shown in FIG. 10, two or more of cells 58 each 
of which comprises two transparent substrates 57 and two transparent 
electrodes 55 and is filled with a liquid crystal material 53 may also be 
disposed between two polarizing plates 56. 
In the liquid crystal element of the invention, two polarizing plates can 
be disposed so that planes of polarization of the polarizing plates meet 
at an angle of 70.degree.-110.degree.. Preferably, the polarizing plates 
are disposed so that the directions of polarized lights of the two 
polarizing plates meet at right angles, namely, at an angle of 90.degree.. 
Usable as the polarizing plates are polarizing films which are imparted 
with polarizing properties by stretching a resin film such as a polyvinyl 
alcohol resin film or a polyvinyl butyral resin film in the presence of 
iodine or the like so as to allow the film to absorb the iodine. The 
polarizing film may have a multi-layer construction by coating its surface 
with other resin. 
In the present invention, the above-mentioned liquid crystal cell may be 
disposed between two polarizing plates having been arranged as described 
above so that a rotation angle of the cell is within the range of 
.+-.10.degree. based on the state wherein an amount of the transmitted 
light is the least (i.e., the darkest state), preferably the darkest state 
is attained. The liquid crystal cell may also be disposed between the 
polarizing plates having been arranged as described above so that a 
rotation angle of the cell is within the range of .+-.10.degree. from the 
state wherein an amount of the transmitted light is the most (i.e., the 
brightest state), preferably the brightest state is attained. 
The liquid crystal element of the invention can be prepared, as shown in 
FIG. 6, by filling the gap 14 of the cell 13 with the liquid crystal 
material 15 mentioned as above and subjecting the crystal material 15 to 
initial orientation. 
The liquid crystal material 15 is usually heated until it reaches a molten 
state, and the molten material is injected into the vacuumized gap 14 of 
the cell 13 through an inlet provided in the cell. After the injection 
operation, the inlet is sealed. 
After sealing the inlet, the cell 13 is heated to a temperature higher than 
the temperature at which the liquid crystal material 15 filled in the cell 
13 exhibits an isotropic phase, and then the cell is cooled to a 
temperature at which the liquid crystal material 15 exhibits a liquid 
crystal phase. 
The cooling is carried out at a rate of, preferably not more than 2.degree. 
C./min, more preferably 0.1.degree.-2.0.degree. C./min, particularly 
preferably 0.1.degree.-0.5.degree. C./min. By cooling the cell 13 at such 
a cooling rate as mentioned above, the state of initial orientation of the 
liquid crystal material 15 is improved, and thereby a liquid crystal 
element having a liquid crystal phase consisting of a monodomain of less 
orientation defect can be easily prepared. The initial orientation 
referred to herein implies the state of arrangement of the liquid crystal 
material prior to changing orientation vector of the liquid crystal 
material by applying a voltage to the material. 
The liquid crystal element of the invention prepared as above is markedly 
excellent in characteristics such as contrast as compared with 
conventional liquid crystal elements, and hence the element of the 
invention can be favorably used as, for example, a surface stabilized 
ferroelectric liquid crystal element, a helical modulation element, an 
excess scattering element, a guest-host type element and a vertical 
orientation liquid crystal element. 
In the case where the liquid crystal element of the invention is driven by 
applying thereto an electric field, the electric field is controlled to 
have a frequency of usually 1 Hz to 100 KHz, preferably 10 Hz to 10 KHz, 
and to have a voltage of usually 0.01 to 60 Vp-p/.mu.m.sup.t (voltage per 
thickness of 1 .mu.m), preferably 0.05 to 30 Vp-p/.mu.m.sup.t. 
When the liquid crystal element of the invention using an optically active 
liquid crystal material which comprises the tetralin compound represented 
by the aforementioned formula [I] is driven by application of an electric 
field, two kinds of hysteresis curves of the transmitted light through the 
liquid crystal element are drawn, by changing a width of the wave (driving 
wave) of the electric field to be applied. One of the hysteresis curves is 
drawn by a driving method in which a so-called bi-stability of the liquid 
crystal material is utilized, and the other is a curve drawn by a driving 
method in which a so-called tri-stability of the liquid crystal material 
is utilized. 
The liquid crystal element of the invention in which a liquid crystal cell 
filled with the optically active liquid crystal material is disposed 
between two polarizing plates which are arranged so that the polarizing 
planes meet at right angles and the darkest state is attained when no 
electric field is applied, may be driven, for example, by application of 
an electric field of any wave form having a frequency of 50 Hz to 100 KHz, 
preferably 70 Hz to 10 KHz, such as rectangular wave (or pulse wave), 
triangular wave, sine wave and a combination thereof. For example, when an 
electric field of rectangular wave or pulse wave or combination thereof is 
applied, the driving speed of the liquid crystal element can be increased 
by setting a width of the electric field to not more than 10 millisec., 
preferably within a range of 0.01 to 10 millisec. In this range, the 
liquid crystal element of the invention can be used as a liquid crystal 
element having a bi-stability. On the other hand, by setting the width of 
the electric field to more than 10 millisec., preferably within a range of 
33 to 1,000 millisec., the liquid crystal element of the invention can be 
used as a liquid crystal element having a tri-stability in the region 
where not so high driving speed is required. The term "width of the 
electric field" used herein means that, in the electric field of 
rectangular wave, for example, the time span for which a designated 
voltage is maintained. 
By using the liquid crystal element of the invention, various liquid 
crystal display devices and electro-optical display devices can be 
manufactured. The liquid crystal element of the invention which is filled 
with a liquid crystal material exhibiting a smectic phase may be used for 
manufacturing a memory-type liquid crystal display device or an 
electro-optical display device incorporated with, for example, a 
thermal-write or laser-write type liquid crystal display element. Further, 
in addition to the above-mentioned uses, by the use of a liquid crystal 
material comprising the tetralin compound having ferroelectricity, there 
can be manufactured a liquid crystal display device or an electro-optical 
display device incorporated with, for example, an optical switching 
element for an optical shutter or a liquid crystal printer, a 
piezoelectric element and a pyroelectric element. 
That is, the liquid crystal material of the invention exhibits the 
tri-stability or bi-stability, and hence the liquid crystal element of the 
invention can be allowed to have optical switching function or display 
function by inverting the electric field so as to attain the tri-stable 
state and bi-stable state. 
The liquid crystal material exhibiting the bi-stability has a spontaneous 
polarization, and hence when a voltage is applied once to the liquid 
crystal element comprising this liquid crystal material, the liquid 
crystal element keeps a memory effect even after elimination of the 
electric field. That is, it is not necessary to apply continuously the 
electric field to the liquid crystal element in order to keep this memory 
effect. Accordingly, in the display device using the liquid crystal 
element of the invention, the consumption of electric power can be 
reduced. Also in the case of the liquid crystal element comprising the 
liquid crystal material exhibiting the tristability, the memory effect can 
be maintained. Moreover, a display device using such liquid crystal 
element is very clear because of stable contrast. 
Further, in the switching element of the invention comprising the liquid 
crystal material represented by the aforementioned formula [I], it is 
possible to perform switching operation only by changing the direction of 
orientation of the molecule. In this case, the first order of the electric 
field strength acts on the driving of the switching element, and hence the 
switching element of the invention can be driven at a low voltage. 
By using this switching element, a high speed response of not longer than 
several 10 .mu. seconds can be attained, and hence the operating time of 
the element can be shortened sharply. Accordingly, a display (liquid 
crystal display device) having large numbers of scanning lines and a large 
screen can be easily manufactured by using the liquid crystal element of 
the invention. Moreover, this display can be driven without using an 
auxiliary means for controlling a driving temperature, because it can be 
driven at room temperature or lower. 
Further, when an electric field is applied to the liquid crystal material 
of the invention, inclination of the molecule of the material is induced 
even in a smectic A phase which has been generally considered not to 
exhibit a bi-stability, and hence optical switching can be performed in 
this phase by utilizing such properties of the liquid crystal material. 
That is, it has been considered that when ferroelectric liquid crystal 
compounds are used, a practical response speed cannot be attained, and the 
smectic A phase thereof is not used generally. However, it is possible to 
drive a display device using the liquid crystal element of the invention 
by utilizing a driving method and an apparatus proposed by the present 
inventors in Japanese Patent L-O-P Publn. Nos. 3632/1989 and 918/1990. 
Further, the liquid crystal material used in the invention exhibits two or 
more stable states even in the smectic F phase which is in better order 
than the smectic C phase, and hence optical switching can be performed in 
the same manner as described above by utilizing plural stable states in 
this phase. 
The display device using the liquid crystal element of the invention may be 
driven by various methods, and concrete examples of those methods are 
described below. 
The first method comprises interposing the liquid crystal element of the 
invention between two polarizing plates, applying an external voltage to 
the liquid crystal element to change an orientation vector of the liquid 
crystal material filled in the element, and thereby performing display 
utilizing birefringence caused by the two polarizing plates and the liquid 
crystal material. 
The second method is to utilize dichroism of a dichromic dye incorporated 
in a liquid crystal material. This method is to perform display by 
changing the orientation direction of the liquid crystal compound to cause 
a change of wavelength of light absorbed by the dye. The dye which may be 
used in this case generally is a dichromic dye, and examples thereof 
include azo dyes, naphthoquinone dyes, cyanine dyes and anthraquinone 
dyes. 
The display device prepared by using the liquid crystal element of the 
invention may be driven by an electric address display system, an optical 
address display system, a heat address display system and a light beam 
display system, wherein any of driving means such as static drive, simple 
matrix drive and composite matrix drive may be employed. 
Further, when the display device in the invention is driven by application 
of an electric field, a nonlinear element or an active element can be used 
as an element for driving each picture element. More particularly, as a 
nonlinear element of two-terminal element, there may be mentioned, for 
example, an element utilizing nonlinearities of a varistor, MIM (Metal 
Insulator Metal) and diode arranged on one transparent substrate, as shown 
in FIG. 11 (a). Further, as an active element of three-terminal element, 
there may be mentioned, for example, an element in which TFT (thin film 
transistor), Si-MOS (Si-metal oxide semiconductor field-effect transistor) 
or SOS (Silicon on Sapphire) is arranged on a picture element, as shown in 
FIG. 11 (b). 
EFFECT OF THE INVENTION 
As described above, a novel tetralin compound is provided by the present 
invention. 
The novel tetralin compound is optically active. Further, in the compound, 
1,2,3,4-tetrahydronaphthalene ring and benzene ring are linked by means of 
an ester linkage, and when two benzene rings exist, these benzene rings 
are also linked by means of an ester linkage. For these reasons, the 
tetralin compound exhibits a smectic phase over a wide temperature range 
including room temperature, and can be used as a ferroelectric liquid 
crystal material or an antiferroelectric liquid crystal material. 
By combining the liquid crystal material of the invention with the same or 
different kind of liquid crystal material, the temperature range where the 
liquid crystal exhibits effective properties can be widened without 
marring ferroelectricity or antiferroelectricity of the liquid crystal 
material of the invention. 
Accordingly, by the use of such liquid crystal material, a liquid crystal 
element having a high speed response in a wide temperature range can be 
obtained. 
Further, in a liquid crystal display prepared by using such element, the 
operating time can be shortened sharply. In addition, the consumption of 
electric power can be reduced, and a high contrast and a stable contrast 
can be obtained. Moreover, the liquid crystal display can be driven at a 
low voltage. 
When the tetralin compound of the invention is used as an antiferroelectric 
liquid crystal compound, the memory characteristics may be obtained 
without difficulty, and the orientation characteristics may also be 
improved. 
By the use of the liquid crystal material of the invention, there can be 
obtained various devices having excellent characteristics such as wide 
operating temperature range, high switching speed, very small consumption 
of electric power and stable contrast. 
The present invention is further described below with reference to 
examples, but it should be construed that the invention is in no way 
limited to those examples. In the examples, R and S mean R body and S body 
of an optically active compound, respectively. 
EXAMPLE 1 
Synthesis of 
6-[4'-(R-2"-Octyloxy)Benzoyloxy]-1,2,3,4-Tetrahydronaphthalene-2-Carboxyli 
c Acid-4"'-Decyloxyphenyl Ester [Exemplified Compound (4)] 
##STR126## 
First Stage 
To a mixture of 3.86 g (11.8 mmol) of 6-decyloxynaphthalene-2-carboxylic 
acid and 130 ml of 1,2-diethoxyethane was added 3.0 g (130 mg atom) of 
metallic sodium with stirring at 120.degree. C. in a nitrogen atmosphere, 
and the resulting mixture was heated to a reflux temperature. 
To the mixture was dropwise added 10 g (114 mmol) of isoamyl alcohol over 1 
hour, and they were reacted with each other for 11 hours under reflux. 
After cooling of the reaction system to room temperature, to the reaction 
mixture was added ethanol to change the remaining metallic sodium to 
sodium alcoholate. Then, the reaction mixture was made acidic using 20% 
hydrochloric acid. 
To the reaction mixture was added 100 ml of water, then the resulting 
organic phase was separated from the mixture, and the organic phase was 
washed with water. 
The organic phase was concentrated under a reduced pressure to obtain 4.25 
g of a solid. This solid was recrystallized with toluene to obtain 2.95 g 
(8.89 mmol) of 1,2,3,4-tetrahydro-6-decyloxynaphthalene-2-carboxylic acid. 
Second Stage 
A mixture of 16.6 g (50 mmol) of the 
1,2,3,4-tetrahydro-6-decyloxynaphthalene-2-carboxylic acid obtained in the 
first stage, 250 ml of acetic acid and 86.5 g (0.5 mol) of 47% hydrobromic 
acid was heated under reflux at 130.degree. C. for 7 hours. After addition 
of distilled water, the mixture was concentrated under a reduced pressure 
to obtain 10.60 g (50 mmol) of 
1,2,3,4-tetrahydro-6-hydroxynaphthalene-2-carboxylic acid. 
Third Stage 
A mixture of 10.60 g (50 mmol) of the 
1,2,3,4-tetrahydro-6-hydroxynaphthalene-2-carboxylic acid obtained in the 
second stage, 12.85 g (75 mmol) of benzyl bromide, 6.6 g (100 mmol) of 85% 
potassium hydroxide, 0.525 g (3.5 mmol) of sodium iodide, 200 ml of 
ethanol and 25 ml of distilled water was heated under reflux at 
100.degree. C. for 12 hours. To the mixture was further added 50 ml of 10% 
potassium hydroxide, and they were heated under reflux for 2 hours. After 
cooling of the reaction system to room temperature, the reaction mixture 
was added to cold water, and the reaction mixture was made acidic using 
36% hydrochloric acid. 
The mixture was filtered to obtain a precipitate, and the precipitate was 
recrystallized with toluene to obtain 13.08 g (46.4 mmol) of 
1,2,3,4-tetrahydro-6-benzyloxynaphthalene-2-carboxylic acid. 
Fourth Stage 
To a mixture of 0.40 g (1.4 mmol) of the 
1,2,3,4-tetrahydro-6-benzyloxynaphthalene-2-carboxylic acid obtained in 
the third stage, 0.35 g (1.4 mmol) of hydroquinone monodecyl ether 
separately synthesized by a conventional process, 0.22 g (0.16 mmol) of 
4-N,N-dimethylaminopyridine and 20 ml of methylene chloride was dropwise 
added 3 ml of a methylene chloride solution containing 0.37 g (1.8 mmol) 
of N,N'-dicyclohexylcarbodiimide over 1.5 hours with stirring at room 
temperature. 
Further, the reaction was carried out at room temperature for 3.5 hours. 
The reaction mixture was filtered, and the filtrate obtained was 
concentrated. The resulting concentrate was separated by means of column 
chromatography to obtain 0.61 g (1.19 mmol) of 
1,2,3,4-tetrahydro-6-benzyloxynaphthalene-2-carboxylic 
acid-4'-decyloxyphenyl ester as a white solid. 
Fifth Stage 
Into a mixture of 0.61 g (1.19 mmol) of the 
1,2,3,4-tetrahydro-6-benzyloxynaphthalene-2-carboxylic 
acid-4"-decyloxyphenyl ester obtained in the fourth stage, 0.30 g of 5% 
palladium/carbon and 10 ml of tetrahydrofuran was blown hydrogen gas for 
16 hours with stirring at room temperature under normal pressure. 
The reaction mixture was filtered using Celite as a filter aid, and the 
filtrate obtained was concentrated to obtain 0.44 g (1.0 mmol) of 
1,2,3,4-tetrahydro-6-hydroxynaphthalene-2-carboxylic 
acid-4'-decyloxyphenyl ester as a white solid. 
Sixth Stage 
To a mixture of 0.44 g (1.0 mmol) of the 
1,2,3,4-tetrahydro-6-hydroxynaphthalene-2-carboxylic 
acid-4'-decyloxyphenyl ester obtained in the fifth stage, 0.25 g (1.0 
mmol) of 4-(R-2 '-octyloxy) benzoic acid, 0.02 g (0.16 mmol) of 
4-N,N-dimethylaminopyridine and 15 ml of methylene chloride was dropwise 
added 3 ml of a methylene chloride solution containing 0.25 g (1.2 mmol) 
of N,N'-dicyclohexylcarbodiimide over 1 hour with stirring at room 
temperature. 
Further, the reaction was carried out at room temperature for 3.5 hours. 
The reaction mixture was filtered, and the filtrate obtained was 
concentrated. The resulting concentrate was separated by means of column 
chromatography to obtain 0.51 g of a colorless semisolid. 
This semisolid had a M/e value in FD-mass spectrum of 656. 
A .sup.1 H-NMR spectrum of this compound is shown in FIG. 1. 
From the analysis of these spectra, this compound was identified as 
6-[4'-(R-2"-octyloxy)benzoyloxy]-1,2,3,4-tetrahydronaphthalene- 
2-carboxylic acid-4"'-decyloxyphenyl ester [Exemplified Compound (4)]. 
This compound had a tilt angle of 45.degree.. 
EXAMPLE 2 
Synthesis of 4- (6'-Decyloxy-5',6',7',8'-Tetrahydro-2"-Naphthoyloxy)Benzoic 
Acid-4"-(R-2"'-Octyloxy)Phenyl ester [Exemplified Compound (50)] 
##STR127## 
First Stage 
328 mg (1.0 mmol) of 6-decyloxynaphthalene-2-carboxylic acid and 0.1 g of 
5% palladium/carbon were mixed with 10 ml of tetrahydrofuran, and the 
resulting mixture was stirred at 120.degree. C. and 25 atmospheric 
pressure in a hydrogen atmosphere. 
After the temperature and the pressure of the reaction system were returned 
to ordinary temperature and normal pressure, the reaction mixture was 
filtered using Celite as a filter aid, and the filtrate obtained was 
concentrated. The resultant solid was recrystallized with hexane to obtain 
90 mg (0.27 mmol) of 
5,6,7,8-tetrahhydro-6-decyloxynaphthalene-2-carboxylic acid as a white 
solid. 
Second Stage 
To a mixture of 16.6 g (50 mmol) of the 
5,6,7,8-tetrahhydro-6-decyloxynaphthalene-2-carboxylic acid obtained in 
the first stage, 11.4 g (50 mmol) of 4-hydroxybenzoic acid benzyl ester 
separately synthesized by a conventional process, 0.61 g (5.0 mmol) of 
4-N,N-dimethylaminopyridine and 150 ml of methylene chloride was dropwise 
added 50 ml of a methylene chloride solution containing 11.39 g (55 mmol) 
of N,N'-dicyclohexylcarbodiimide over 2 hours with stirring at room 
temperature. 
Further, the reaction was carried out at room temperature for 3 hours. 
The reaction mixture was filtered, and the filtrate obtained was 
concentrated. The resulting concentrate was separated by means of column 
chromatography to obtain 21.95 g (40.5 mmol) of 
4-(5',6',7',8'-tetrahydro-6'-decyloxy-2'-naphthoyloxy)benzoic acid benzyl 
ester as a white solid. 
Third Stage 
Into a mixture of 15.37 g (28.4 mmol) of the 
4-(5',6',7',8'-tetrahydro-6'-decyloxy-2'-naphthoyloxy)benzoic acid benzyl 
ester obtained in the second stage, 1.54 g of 5% palladium/carbon and 100 
ml of tetrahydrofuran was blown hydrogen gas for 23 hours with stirring at 
room temperature under normal pressure. 
The reaction mixture was filtered using Celite as a filter aid, and the 
filtrate obtained was concentrated to obtain 12.35 g (27.3 mmol) of 
4-(5',6',7',8'-tetrahydro-6'-decyloxy-2'-naphthoyloxy)benzoic acid as a 
white solid. 
Fourth Stage 
To a mixture of 0.54 g (1.0 mmol) of the 4-(5', 
6',7',8'-tetrahydro-6'-decyloxy-2'-naphthoyloxy) benzoic acid obtained in 
the third stage, 0.22 g (1.0 mmol) of hydroquinone mono-R-2-octyloxy 
ether, 0.012 g (0.1 mmol) of 4-N,N-dimethylaminopyridine and 10 ml of 
methylene chloride was dropwise added 3 ml of a methylene chloride 
solution containing 0.25 g (1.2 mmol) of N,N'-dicyclohexylcarbodiimide 
over 1.5 hours with stirring at room temperature. 
Further, the reaction was carried out at room temperature for 4 hours. 
The reaction mixture was filtered, and the filtrate obtained was 
concentrated. The resulting concentrate was separated by means of column 
chromatography to obtain 0.62 g of a colorless semisolid. 
This semisolid had a M/e value in FD-mass spectrum of 656. 
A .sup.1 H-NMR spectrum of this compound is shown in FIG. 2. 
From the analysis of these spectra, this compound was identified as 
4-(6'-decyloxy-5',6',7',8'-tetrahydro-2"naphthoyloxy) benzoic acid-4"- 
(R-2"'-octyloxy) phenyl ester [Exemplified Compound (50)]. 
EXAMPLE 3 
Synthesis of 6-Decyloxy-1,2,3,4-Tetrahydronaphthalene-2-carboxylic 
acid-4'-(R-2"-Octyloxy)phenyl Ester [Exemplified Compound (149)] 
##STR128## 
First Stage 
To a mixture of 0.33 g (1.0 mmol) of 
1,2,3,4-tetrahydro-6-benzyloxynaphthalene-2-carboxylic acid obtained in 
the same manner as described in the third stage of Example 1, 0.22 g (1.0 
mmol) of hydroquinone mono-R-2-octyloxy ether, 0.02 g (0.16 mmol) of 
4-N,N-dimethylaminopyridine and 15 ml of methylene chloride was dropwise 
added 3 ml of a methylene chloride solution containing 0.25 g (1.2 mmol) 
of N,N'-dicyclohexylcarbodiimide over 1 hour with stirring at room 
temperature. 
Further, the reaction was carried out at room temperature for 5 hours. 
The reaction mixture was filtered, and the filtrate obtained was 
concentrated. The resulting concentrate was separated by means of column 
chromatography to obtain 0.28 g of a colorless semisolid. 
This semisolid had a M/e value in FD-mass spectrum of 536. 
A .sup.1 H-NMR spectrum of this compound is shown in FIG. 3. 
From the analysis of these spectra, this compound was identified as 
6-decyloxy-1,2,3,4-tetrahydronaphthalene-2-carboxylic 
acid-4'-(R-2"-octyloxy)phenyl ester [Exemplified Compound (149)]. 
EXAMPLE 4 
Preparation of Liquid Crystal Composition and Liquid Crystal Element 
The compound [Exemplified Compound (4)] of the following formula which was 
synthesized in Example 1 and a compound [A] represented by the following 
formula were mixed in a mixing ratio (by weight) of 10:90, to prepare a 
liquid crystal composition. 
##STR129## 
A phase transition temperature of the liquid crystal composition obtained 
as above was measured. The result is set forth in Table 4, in which phase 
transition temperatures of the exemplified compound (4) and the compound 
[A] are also set forth. 
TABLE 4 
______________________________________ 
[4] Cry 40.degree. C. 
SmC.sub.A * 82.degree. C. 
Ch 103.degree. C. 
Iso 
[A] Cry 25.degree. C. 
SmC.sub.A * 99.degree. C. 
SMa 130.degree. C. 
Iso 
[4] (10%) + 
Cry 30.degree. C. 
SmC.sub.A * 93.degree. C. 
SmA 129.degree. C. 
Iso 
[A] (90%) 
______________________________________ 
The composition obtained as above was filled in a cell shown in FIG. 6 to 
prepare a liquid crystal element. 
That is, the liquid crystal element was prepared in the following manner. 
The above-mentioned liquid crystal composition (Exemplified Compound 
(4)+Compound [A]) was melted, and the molten composition was injected into 
the vacuumized gap of the cell wherein two orientation control films (each 
thickness: 150 .ANG.) made of polyimide (Optomer AL1251 available from 
Japan Synthetic Rubber Co., Ltd.) and having been subjected to rubbing 
were formed on inner surfaces of ITO (ITO: indium tin oxide) transparent 
electrode substrates so that orientation control directions of the films 
were approximately parallel and the same directions as each other as shown 
in FIG. 6. 
The cell filled with the liquid crystal material as described above was 
heated to 130.degree. C. kept at 130.degree. C. for 5 minutes and then 
cooled to 30.degree. C. at a cooling rate of 1.degree. C./min, to obtain a 
liquid crystal element. 
As a result of measuring a contrast of the liquid crystal element thus 
obtained, the contrast was 54. 
Conditions of the Cell 
(A) external dimension 
2.5 cm (longitudinal length).times.2.2 cm (crosswise length).times.1.5 mm 
(thickness) 
(B) substrate 
thickness: 0.7 mm, material: glass 
(C) distance between substrates: 2 .mu.m 
(D) side wall dimension 1.8 mm (longitudinal length).times.0.1 cm 
(crosswise length).times.2 .mu.m (thickness) 
The cell used for evaluating the liquid crystal is prepared in the 
following manner. 
Polyimide (Optomer AL1251 available from Japan Synthetic Rubber Co., Ltd.) 
was subjected to spin coating at a rate of 4,000 rpm on a surface of an 
ITO transparent electrode which had been beforehand provided on one 
surface of a glass substrate. Then, the substrate was heated at 
180.degree. C. for 1 hour to harden the polyimide. The thickness of the 
polyimide film thus formed was in the range of 300 to 400 .ANG.. The 
polyimide film was rubbed with nylon cloth in one direction to impart the 
polyimide film with liquid crystal orientation properties, so as to form 
an orientation control film. 
Independently, an epoxy type adhesive (LCB-310B available from EHC Co., 
Ltd.), a hardening agent (LCB-310B available from EHC Co., Ltd.) and beads 
(GP-20 available from EHC Co., Ltd.) for ensuring a cell gap were mixed in 
a mixing ratio (by weight) of 130:30:3, to prepare an adhesive. 
The adhesive was coated on one substrate having the orientation control 
film thereon by means of silk screen printing. On the substrate coated 
with the adhesive was placed other substrate so that the orientation 
control films of the two substrates faced each other, and they were heated 
under the following heating conditions to harden the adhesive, so as to 
combine the two substrates with each other. 
Heating Conditions 
50.degree. C. (15 minutes)-60.degree. C. (15 minutes)-70.degree. C. (15 
minutes)-80.degree. C. (15 minutes)-125.degree. C. (30 minutes)-70.degree. 
C. (60 minutes) 
The cell prepared as above was filled with the liquid crystal, then the 
cell was interposed between two polarizing plates which were arranged so 
that planes of polarization of the polarizing plates meet at right angles, 
and the cell was rotated to measure intensities of the transmitted light 
in the bright state and in the dark state. From the intensities of the 
transmitted light thus measured, a ratio of the intensity in the bright 
state to the intensity in the dark state (I in the bright state/I in the 
dark state) was calculated to determine a contrast of the element in the 
invention. 
COMATIVE EXAMPLE 1 
The procedure of Example 4 was repeated except for not using the 
exemplified compound (4) and using the compound [A] in an amount of 100% 
by weight, to prepare a liquid crystal element. 
This liquid crystal element had a contrast of 16. 
COMATIVE EXAMPLE 2 
Synthesis of 6- 
[4'-R-1"-Methylheptyloxy)carbonylbenzoyloxy]-1,2,3,4-Tetrahydronaphthalene 
-2-Carboxylic Acid-4"'-Decyloxyphenyl Ester 
##STR130## 
First Stage 
To a mixture of 0.28 g (1.5 mmol) of R-1-methylheptanol, 0.51 g (2 mmol) of 
carboxybenzoic acid benzyl ester separately synthesized by a conventional 
process, 0.018 g (0.15 mmol) of 4-N,N-dimethylaminopyridine and 15 ml of 
methylene chloride was dropwise added 7.5 ml of a methylene chloride 
solution containing 0.372 g (1.8 mmol) of N,N'-dicyclohexylcarbodiimide 
over 2 hours with stirring at room temperature. 
Further, the reaction was carried out at room temperature for 48 hours. 
The reaction mixture was filtered, and the filtrate obtained was 
concentrated. The resulting concentrate was separated by means of column 
chromatography to obtain 0.66 g of 4-benzyloxycarbonylbenzoic acid 
R-1'-methylheptyl ester. 
Second Stage 
Into a mixture of 0.66 g (1.5 mmol) of the 4-benzyloxycarbonylbenzoic acid 
R-1'-methylheptyl ester obtained in the first stage, 0.07 g of 5% 
palladium/carbon and 10 ml of tetrahydrofuran was blown hydrogen gas for 
16 hours with stirring at room temperature under normal pressure. 
The reaction mixture was filtered using Celite as a filter aid, and the 
filtrate obtained was concentrated to obtain 0.49 g of 
4-hydroxycarbonylbenzoic acid R-1'-methylheptyl ester as a white solid. 
Third Stage 
To a mixture of 0.34 g (1.2 mmol) of the 
1,2,3,4-tetrahydro-6-benzyloxynaphthalene-2-carboxylic acid obtained in 
the same manner as described in the third stage of Example 1, 0.30 g (1.2 
mmol) of 4-decyloxyphenol synthesized in a conventional process, 
4-N,N-dimethylaminopyridine and 12 ml of methylene chloride was dropwise 
added 6 ml of a methylene chloride solution containing 0.30 g (1.5 mmol) 
of N,N'-dicyclohexylcarbodiimide over 2 hours with stirring at room 
temperature. 
Further, the reaction was carried out at room temperature for 48 hours. 
The reaction mixture was filtered, and the filtrate obtained was 
concentrated. The resulting concentrate was separated by means of column 
chromatography to obtain 0.36 g of 
1,2,3,4-tetrahydro-6-benzyloxynaphthalene-2-carboxylic acid 
(4'-decyloxyphenyl) ster. 
Fourth Stage 
Into a mixture of 0.36 g (0.07 mmol) of the 
1,2,3,4-tetrahydro-6-benzyloxynaphthalene-2-carboxylic acid 
(4'-decyloxyphenyl)ester obtained in the third stage, 0.03 g of 5% 
palladium/carbon and 10 ml of tetrahydrofuran was blown hydrogen gas for 
16 hours with stirring at room temperature under normal pressure. 
The reaction mixture was filtered using Celite as a filter aid, and the 
filtrate obtained was concentrated to obtain 0.29 g (0.07 mmol) of 
1,2,3,4'-tetrahydro-6-hydroxynaphthalene-2-carboxylic acid 
(4'-decyloxyphenyl)ester as a white solid. 
Fifth Stage 
To a mixture of 0.13 g (0.4 mmol) of the 4-hydroxycarbonylbenzoic acid 
R-1'-methylheptyl ester obtained in the second stage, 0.17 g (0.4 mmol) of 
the 1,2,3,4-tetrahydro-6-hydroxynaphthalene-2-carboxylic acid 
(4'-decyloxyphenyl)ester obtained in the fourth stage, 0.005 g (0.04 mmol) 
of 4-N,N-dimethylaminopyridine and 10 ml of methylene chloride was 
dropwise added 5 ml of a methylene chloride solution containing 0.103 g 
(0.5 mmol) of N,N'-dicyclohexylcarbodiimide over 2 hours with stirring at 
room temperature. 
Further, the reaction was carried out for 48 hours. 
The reaction mixture was filtered, and the filtrate obtained was 
concentrated. The resulting concentrate was separated by means of column 
chromatography to obtain 0.05 g of a white solid. 
This white solid had a M/e value in FD-mass spectrum of 738. 
A .sup.1 H-NMR spectrum of this compound is shown in FIG. 4. 
From the analysis of these spectra, this compound was identified as 
6-[4'-(R-1"-methylheptyloxy) 
carbonylbenzoyloxy]-1,2,3,4-tetrahydronaphthalene-2-carboxylic 
acid-4"'-decyloxyphenyl ester represented by the following formula. 
##STR131## 
This compound had a tilt angle of 0.degree., and exhibited a SmA phase 
only. 
EXAMPLE 5 
Synthesis of 
6-[4'-S-2"-Methyloctanoyloxy)Benzoyloxy]-1,2,3,4-Terahydronaphthalene-2-Ca 
rboxylic Acid-4"'-decyloxyphenyl ester [Exemplified Compound 20)] 
##STR132## 
First Stage 
To a mixture of 0.47 g (3 mmol) of S-2-methyloctanoic acid, 0.69 g (3 mmol) 
of 4-hydroxybenzoic acid benzyl ester synthesized by a conventional 
process, 0.037 g (0.3 mmol) of 4-N,N-dimethylaminopyridine and 30 ml of 
methylene chloride was dropwise added 15 ml of a methylene chloride 
solution containing 0.74 g (3.6 mmol) of N,N'-dicyclohexylcarbodiimide 
over 2 hours with stirring at room temperature. 
Further, the reaction was carried out at room temperature for 48 hours. 
The reaction mixture was filtered, and the filtrate obtained was 
concentrated. The resulting concentrate was separated by means of column 
chromatography to obtain 1.01 g of 4-(S-2'-methyloctanoyloxy)benzoic acid 
benzyl ester. 
Second Stage 
Into a mixture of 1.01 g (2.74 mmol) of the 
4-(S-2'-methyloctanoyloxy)benzoic acid benzyl ester obtained in the first 
stage, 0.1 g of 5% palladium/carbon and 20 ml of tetrahydrofuran was blown 
hydrogen gas for 15 hours with stirring at room temperature under normal 
pressure. 
The reaction mixture was filtered using Celite as a filter aid, and the 
filtrate obtained was concentrated to obtain 0.73 g of 
4-(S-2'-methyloctanoyloxy)benzoic acid as a white solid. 
Third Stage 
A mixture of 0.28 g (1.0 mmol) of the 4-(S-2'-methyloctanoyloxy)benzoic 
acid obtained in the second stage, 0.13 g (1.1 mmol) of thionyl chloride, 
0.2 ml of N,N-dimethylformamide and 5 ml of methylene chloride was heated 
with stirring under reflux for 2 hours, to obtain an yellow solution of 
the corresponding acid chloride (methylene chloride solution). 
Fourth Stage 
To a mixture of 0.424 g (1.0 mmol) of the 
1,2,3,4-tetrahydro-6-hydroxynaphthalene-2-carboxylic acid (4'- 
decyloxyphenyl)ester obtained in the same manner as described in the 
fourth stage of Comparative Example 2, 0.40 ml of pyridine, 0.012 g (0.1 
mmol) of 4-N,N-dimethylaminopyridine and 15 ml of methylene chloride was 
dropwise added the whole amount of the methylene chloride solution of acid 
chloride obtained in the third stage over 1 hour at room temperature. 
Further, the reaction was carried out at room temperature for 24 hours. 
The reaction mixture was introduced into water, and then extracted with 
ether. The ether solution obtained was concentrated. The resulting 
concentrate was separated by means of column chromatography to obtain 
0.455 g of a white solid. 
This white solid had a M/e value in FD-mass spectrum of 684. 
A .sup.1 H-NMR spectrum of this compound is shown in FIG. 5. 
From the analysis Of these spectra, this compound was identified as 
6-[4'-(S-2"-methyloctanoyloxy)benzoyloxy]1,2,3,4-tetrahydronaphthalene-2-c 
arbonxylic acid-4"'-decyloxyphenyl ester (Exemplified Compound [20]) 
represented by the following formula. 
##STR133## 
This compound had a tilt angle of 23.degree..