High temperature liquid crystal substances of four rings and liquid crystal compositions containing the same

Liquid crystal compounds which exhibit a liquid crystal phase within a broad temperature range and have a high clearing point and nevertheless a low viscosity, and liquid crystal compositions containing the same are provided, which liquid crystal compounds have positive dielectric anisotropy values and are expressed by the general formula ##STR1## wherein R represents hydrogen atom or an alkyl group of 1 to 10 carbon atoms; ##STR2## Y represents H or F; and X represent a halogen atom or CN.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to novel low viscosity, liquid crystal substances 
exhibiting a liquid crystal phase within a broad temperature range up to 
higher temperatures and also having a positive dielectric anisotropy, and 
liquid-crystalline compositions containing the same. 
2. Description of the Prior Art 
Display elements using liquid crystals have come to be broadly used for 
watches, desk calculators, etc. Such liquid crystal display elements 
utilize properties of the optical anisotropy and dielectric anisotropy of 
liquid crystal substances, and the liquid crystal phase includes nematic 
liquid crystal phase, smectic liquid crystal phase and cholesteric liquid 
crystal phase. However, display elements utilizing nematic liquid crystals 
among the above-mentioned phases have been practically used most broadly. 
Further the display mode of such display elements includes TN type 
(twisted namatic type), DS type (dynamic scattering type), guest-host 
type, DAP type, etc. and properties required for the liquid crystal 
substances used for the respective types are different. At any rate, 
however, it is preferred that the liquid crystal substances used for these 
display elements exhibit a liquid crystal phase within as broad a 
temperature range as possible in the natural world. At present, however, 
no single compound which satisfies by itself such conditions is present, 
and it is the present status that substances which are endurable to 
practical use for the present have been obtained by blending several kinds 
of liquid crystal compounds on non-liquid crystal compounds. Further, 
these substances should, of course, be stable to moisture, light, heat, 
air, etc. and also it is preferred for them that the threshold voltage and 
saturation voltage required for driving such display elements be as low as 
possible and their viscosities be as low as possible in order to make the 
response speed higher. 
Now, in order to broaden the liquid-crystalline temperature range toward 
higher temperatures, it is necessary to use liquid crystal substances 
having a higher melting point as a component. As compounds for attaining 
such an object, those expressed by the general formula 
##STR3## 
wherein R represents an alkyl group or an alkoxy group of 1 to 12 carbon 
atoms, have been known (see U.S. Pat. No. 4,154,697). However, such liquid 
crystal substances having a higher melting point generally have a higher 
viscosity and hence liquid crystal compositions containing these also have 
a higher viscosity; thus the response speed, particularly that at lower 
temperatures, of liquid crystal display elements which are usable up to 
higher temperatures such as 100.degree. C. have been liable to be notably 
retarded. 
As improved compounds considerably free from such drawbacks, the present 
inventors have previously invented 
4-[trans-4(trans-4-alkylcyclohexyl)cyclohexyl] substituted benzenes 
expressed by the general formula 
##STR4## 
wherein R represents H or an alkyl group of 1 to 10 carbon atoms; Y 
represents H or F; and X represents halogen atom or CN, and applied for 
patent (Japanese patent application laid-open Nos. Sho 57-64626, Sho 
57-114531, Sho 57-154135 and Sho 58-10552. 
However, the recent technical advance in liquid crystal display elements 
has been remarkable and display elements being actuated within a range 
from further lower temperatures up to further higher ones have been 
required. 
The object of the present invention is to provide liquid crystal compounds 
which satisfy the above-mentioned requirements i.e. exhibit a liquid 
crystal phase within a broad temperature range and have a high clearing 
point and nevertheless a low viscosity. 
SUMMARY OF THE INVENTION 
The present invention resides in: 
liquid crystal compounds having positive dielectric anisotropy values, 
expressed by the general formula 
##STR5## 
wherein R represents hydrogen atom or an alkyl group of 1 to 10 carbon 
atoms; 
##STR6## 
Y represents H or F; and X represent a halogen atom or CN, and liquid 
crystal compositions containing at least one kind of the same. 
The compounds of the formula (I) can be further classified into those of 
preferred types of the formulas (II) to (V) as follows: 
##STR7## 
wherein R and X are as defined above; 
##STR8## 
wherein R is as defined above and X represents F, Cl or Br; 
##STR9## 
wherein R is as defined above; and 
##STR10## 
wherein R is as defined above. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The compounds of the present invention have a broad liquid crystal 
temperature range; they also exhibit a liquid crystal phase up to higher 
temperatures and have low viscosities for such a characteristic; they have 
a N-I point of about 270.degree. C. to 300.degree. C. or higher; and yet 
when they are added in a small amount to other liquid crystal compounds 
such as ester liquid crystal compounds, biphenyl liquid crystal compounds, 
phenylcyclohexane liquid crystal compounds, Schiff liquid crystal 
compounds, azoxy liquid crystal compounds, hetero-ring-containing liquid 
crystal compounds, etc., they are very useful as a component of liquid 
crystal compositions used for liquid crystal display cells which are 
actuated within a broad temperature range of low temperatures to high 
temperatures. Further, in spite of the fact that they have dielectric 
anisotropy values .DELTA. .epsilon. of about +2 to 4, the threshold 
voltage and saturation voltage of liquid crystal compositions obtained by 
adding the compounds of the present invention do not rise so much as 
compared with those of liquid crystal compositions having no compounds of 
the present invention added, but the formers are almost the same as the 
latters. Furthermore the compounds of the present invention are stable to 
light, heat, air, moisture, etc.; hence their application ranges are 
extremely broad. 
Next, preparation of the compounds of the present invention will be 
described. 
First, among the compounds of the formula (I), those of the formulas (II), 
(III) and (IV) (wherein X represents F, Cl or Br) will be mentioned. 
A 4-methoxy-[trans-4-(trans-4-alkylcyclohexyl) cyclohexyl]benzene prepared 
according to a known method (Japanese patent application laid-open No. Sho 
57-165,328/1972) is subjected to demethylation reaction with hydrobromic 
acid in acetic acid to obtain a 
4-hydroxy-[trans-4-(trans-4-alkylcyclohexyl)cyclohexyl]benzene, which is 
then dissolved in ethanol and catalytically reduced in the presence of 
ruthenium catalyst at 180.degree. C. and 50 Kg/cm.sup.2 to obtain a 
trans-4-alkyl-4"-hydroxy-trans-octadecahydro-p-terphenyl, which is then 
dissolved in acetone and oxidized with anhydrous chromic acid to obtain a 
trans-4-alkyl-4"-one-trans-octadecahydro-p-terphenyl, which is then 
dissolved in tetrahydrofuran. The resulting solution is added to a 
tetrahydrofuran solution of a 4- or 3,4-di-halogenobenzenemagnesium 
bromide as a Grignard's reagent obtained with metal magnesium, to obtain a 
trans-4-alkyl-4"-ol-4"-(4- or 
3,4-di-halogenophenyl)-trans-octadecahydro-p-terphenyl, which is then 
dehydrated with anhydrous potassium hydrogen sulfate to obtain a 
trans-4-alkyl-4"-(4- or 
3,4-di-halogenophenyl)-trans-octadecahydro-p-terphenyl-3"-yl, which is 
then dissolved in toluene and catalytically reduced with a Raney nickel 
catalyst to obtain an objective trans-4-alkyl-trans-4"-(4- or 
3,4-di-halogenophenyl)-trans-octadecahydro-p-terphenyl. The foregoing is 
illustrated by the following chemical formulas: 
##STR11## 
wherein X represents F, Cl or Br and Y represents H or F. 
Next, preparation of the compounds of the formula (II) wherein X represents 
I and those of the formula (V) will be described. 
First, a trans-4-alkyl-trans-4"-phenyl-trans-octadecahydro-p-terphenyl (a 
compound of the formula (I) wherein X and Y each represent hydrogen atom) 
is prepared in the same manner as above except that the above-mentioned 
halogenobenzenemagnesium bromide is replaced by benzenemagnesium bromide, 
followed by subjecting the terphenyl to iodination reaction with iodine 
and iodic acid to obtain a 
trans-4-alkyl-trans-4"-(4-iodophenyl)-trans-octadecahydro-p-terphenyl (a 
compound of the formula (II) wherein X represents I), which is then 
subjected to cyanogenation reaction with cuprous cyanide in 
dimethylformamide to obtain an objective 
trans-4-alkyl-trans-4"-(4-cyanophenyl)-trans-octadecahydro-p-terphenyl. 
The foregoing is illustrated by the following chemical formulas:

The present invention will be further described in more detail by way of 
Examples. 
EXAMPLE 1 
Preparation of 
trans-4-propyl-4"-(4-fluorophenyl)-trans-octadecahydro-p-terphenyl-3"-yl 
(a compound of the formula (III) wherein R=C.sub.3 H.sub.7 and X=F) 
4-Methoxy-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]benzene (40 g) was 
dissolved in acetic acid (400 ml) and hydrobromic acid (47%, 450 ml) was 
added, followed by reflux for 30 hours. After cooling, a large amount of 
water was added and the resulting precipitate was filtered off, followed 
by recrystallizing the residue from ethanol, dissolving the crystals (8.0 
g) in ethanol (400 ml), adding ruthenium/C (1.0 g), subjecting it to 
catalytic reduction at 180.degree. C. and 50 Kg/cm.sup.2 for 5 hours, 
filtering off the catalyst, and distilling off the solvent under reduced 
pressure, to obtain trans-4-propyl-4"-ol-trans-octadecahydro-p-terphenyl, 
which was then dissolved in acetone (4 l), followed by dropwise adding a 
mixed solution of anhydrous chromic acid and conc. sulfuric acid (20 ml) 
at a reaction temperature of 0.degree. to 3.degree. C., completing the 
reaction when the orange color of the reaction liquid did no longer 
disappear, neutralizing the reaction liquid with sodium hydrogen 
carbonate, filtering the solution under reduced pressure, distilling off 
the solvent, subjecting the residue to extraction with toluene, washing it 
with water, distilling off toluene under reduced pressure and 
recrystallizing from toluene to obtain 
trans-4-propyl-4"-one-trans-octadecahydro-p-terphenyl. On the other hand, 
to magnesium piece (0.24 g) was dropwise added a solution of 
4-fluorobromobenzene (1.75 g) in tetrahydrofuran. Magnesium reacted to 
give 4-fluorobenzenemagnesium bromide. To this solution was added a 
solution obtained by dissolving 
trans-4-propyl-4"-one-trans-octadecahydro-p-terphenyl prepared above in 
tetrahydrofuran (50 ml). At that time, the temperature was kept so as not 
to exceed 30.degree. C. and after the addition, the mixture was refluxed 
for one hour. After cooling, 3N hydrochloric acid (50 ml) was added, 
followed by extracting it with toluene (200 ml), washing with water, 
distilling off the solvent, adding potassium hydrogen sulfate (1 g), 
dehydrating in nitrogen current at 160.degree. C. for 2 hours, cooling, 
filtering off potassium hydrogen sulfate, dissolving in toluene (200 ml), 
washing the solution with water till the washing liquid became neutral, 
distilling off toluene under reduced pressure and recrystallizing the 
residue from toluene to obtain 
trans-4-propyl-4"-(4-fluorophenyl)-trans-octadecahydro-p-terphenyl-3"-yl. 
Yield: 2.1 g (14%). C-S point: 82.7.degree. C. S-N point: 220.degree. C. 
N-I point: 279.degree. C. 
In the same manner as above was prepared 
trans-4-heptyl-4"-(4-chlorophenyl)-trans-octadecahydro-p-terphenyl-3'-yl. 
C-S point: 81.3.degree. C. S-N point: 189.degree. C. N-I point: 300.degree. 
C. or higher. 
EXAMPLE 2 
Preparation of 
trans-4-propyl-trans-4"-(4-fluorophenyl)-trans-octadecahydro-p-terphenyl 
(a compound of the formula (II) wherein R=C.sub.3 H.sub.7 and X=F) 
Trans-4-propyl-4"-(4-fluorophenyl)-trans-octadecahydro-p-terphenyl-3"-yl 
prepared in Example 1 (1.1 g) was dissolved in toluene (50 ml) and Raney 
nickel catalyst (0.5 g) was added, followed by catalytically reducing it 
at ordinary temperature and ordinary pressure, tracing the reaction by 
means of gas chromatography, completing the reaction when the raw material 
disappeared, filtering off the catalyst, and repeating recrystallization 
to obtain the objective 
trans-4-propyl-trans-4"-(4-fluorophenyl)-trans-octadecahydro-p-terphenyl. 
Yield: 0.8 g (27%). C-S point: 105.9.degree. C. S-N point: 238.degree. C. 
N-I point: 279.degree. C. 
In the same manner as above was prepared 
trans-4-heptyl-trans-4"-(4-chlorophenyl)-trans-octadecahydro-p-terphenyl. 
C-S point: 56.6.degree. C. S-N point: 248.degree. C. N-I point: 274.degree. 
C. 
EXAMPLE 3 
Preparation of 
trans-4-butyl-trans-4"-(4-iodophenyl)-trans-octadecahydro-p-terphenyl (a 
compound of the formula (II) wherein R=C.sub.4 H.sub.9 and X=I) 
In the same manner as in Example 1, 
trans-4-butyl-4"-one-trans-octadecahydro-p-terphenyl (4 g) was reacted 
with a Grignard's reagent obtained by reacting Mg (0.73 g) with 
bromobenzene (4.7 g), followed by dehydration and reduction steps in the 
same manner as in Example 1 to obtain 
trans-4-butyl-trans-4"-phenyl-trans-octadecahydro-p-terphenyl. This 
product (0.5 g) was dissolved in acetic acid (200 ml) and sulfuric acid (1 
ml), iodic acid (0.09 g) and iodine (0.17 g) were added, followed by 
refluxing for 15 hours, cooling, filtering off crystals, and 
recrystallizing from toluene to obtain the objective 
trans-4-butyl-trans-4"-(4-iodophenyl)-trans-octadecahydro-p-terphenyl. 
C-S point: 110.degree. C. S-N point: 238.degree. C. N-I point: 298.degree. 
C. 
EXAMPLE 4 
Preparation of 
trans-4-butyl-trans-4'-(3,4-difluorophenyl)-trans-octadecahydro-p-terpheny 
l (a compound of the formula (IV) wherein R=C.sub.4 H.sub.9) 
In the same manner as in Example 1, 
trans-4-butyl-4"-one-trans-octadecahydro-p-terphenyl (2.4 g) was reacted 
with a Grignard's reagent obtained by reacting 3,4-difluorobromobenzene 
(5.8 g) with Mg (0.73 g), followed by dehydration with potassium hydrogen 
sulfate to obtain 
trans-4-butyl-4"-(3,4-difluorophenyl)-trans-octadecahydro-p-terphenyl-3"-y 
l. 
C-S point: 87.1.degree. C. S-N point: 174.0.degree. C. N-I point: 
245.0.degree. C. 
This product (2.0 g) was dissolved in toluene (100 ml) and Raney Ni (1 g) 
was added, followed by catalytically reducing it at ordinary temperature 
and ordinary pressure, filtering off the catalyst, removing the solvent 
and repeating recrystallization to obtain the objective 
trans-4-butyl-trans-4'-(3,4-difluorophenyl)-trans-octadecahydro-p-terpheny 
l. 
Yield: 1.2 g. C-S point: 72.2.degree. C. S-N point: 217.degree. C. N-I 
point: 299.degree. C. 
EXAMPE 5 
Preparation of 
trans-4-butyl-trans-4"-(4-cyanophenyl)-trans-octadecahydro-p-terphenyl (a 
compound of the formula (V) wherein R=C.sub.4 H.sub.9) 
Trans-4-butyl-trans-4"-(4-iodophenyl)-trans-octadecahydro-p-terphenyl (0.2 
g) was dissolved in dimethylformamide (200 ml) and cuprous cyanide (0.02 
g) was added, followed by refluxing for 10 hours, cooling, adding aqueous 
ammonia (100 ml), extracting with toluene (200 ml), washing with an acid, 
washing with water, distilling off the solvent under reduced pressure and 
recrystallizing from toluene to obtain the objective 
trans-4-butyl-trans-4"-(4-cyanophenyl)-trans-octadecahydro-p-terphenyl. 
Yield: 0.1 g. C-S point: 60.4.degree. C. S-N point: 207.6.degree. C. N-I 
point: 300.degree. C. or higher. 
EXAMPLE 6 
(Use example 1) 
A liquid crystal composition A consisting of 
trans-4-propyl-(4'-cyanophenyl)cyclohexane (28% by weight), 
trans-4-pentyl-(4'-cyanophenyl)cyclohexane (42% by weight), and 
trans-4-heptyl-(4'-cyanophenyl)cyclohexane (30% by weight), 
has a N-I point of 52.degree. C. When this liquid crystal composition was 
sealed in a TN cell (twisted, nematic cell) of 10 .mu.m thick, the 
resulting cell had an actuation threshold voltage of 1.5 V and a 
saturation voltage of 2.0 V. Its viscosity was 24 cp at 20.degree. C. 
When 
trans-4-propyl-4"-(4-fluorophenyl)-trans-octadecahydro-p-terphenyl-3"-yl 
(3 parts by weight) prepared in Example 1 was added to the above liquid 
crystal composition (97 parts), the resulting liquid crystal composition 
had a N-I point raised up to 58.3.degree. C. The threshold voltage and 
saturation voltage were 1.5 V and 2.1 V, respectively, that is, they did 
not change so much. Its viscosity was 24 cp at 20.degree. C., that is, 
unchanged. As described above, when a small amount of a compound of the 
present invention was added, it was possible to broaden the nematic liquid 
crystal temperature range, without raising the viscosity and the voltage 
values. 
EXAMPLE 7 
(Use example 2) 
To the above liquid crystal composition A (98 parts) was added 
trans-4-propyl-4"-(4-fluorophenyl)-trans-octadecahydro-p-terphenyl 
obtained in Example 2 (2 parts) to obtain a liquid crystal composition. 
N-I point was broadened up to 55.5.degree. C. When it was sealed in the 
above cell, the threshold voltage and saturation voltage were 1.5 V and 
2.0 V, respectively, that is, unchanged. Its viscosity was 24 cp at 
20.degree. C., that is, unchanged. As described above, when the compound 
of the present invention was added, it was possible to broaden the nematic 
temperature range of the liquid crystal composition, without varying the 
viscosity and voltage values. 
EXAMPLE 8 
(Use example 3) 
To the above liquid crystal composition A (97 parts) was added 
trans-4-butyl-trans-4'-(3,4-difluorophenyl)-trans-octadecahydro-p-terpheny 
l (3 parts) shown in Example 4 to obtain a liquid crystal composition. N-I 
point rised up to 60.1.degree. C. When it was sealed in the above cell, 
the threshold voltage and saturation voltage were 1.5 V and 2.1 V, 
respectively, that is, they did not change so much. Its viscosity was 26 
cp at 20.degree. C., that is, no great increase was observed. As described 
above, when the compound of the present invention was added, it was 
possible to prepare a liquid crystal composition having a broad nematic 
range and a low viscosity. 
EXAMPLE 9 
(Use example 4) 
To the liquid crystal composition A (97 parts) was added 
trans-4-butyl-trans-4"-(4-cyanophenyl)-trans-octadecahydro-p-terphenyl 
shown in Example 5 (3 parts) to obtain a liquid crystal composition. N-I 
point rised up to 58.9.degree. C. When it was sealed in the above cell, 
the threshold voltage and saturation voltage were 1.5 V and 2.1 V, 
respectively, that is, they did not change so much. Its viscosity was 26 
cp at 20.degree. C., that is, viscosity did not rise so much. As described 
above, when the compound of the present invention was added, it was 
possible to prepare a liquid crystal composition having a broad nematic 
range, without making the viscosity and the voltage values inferior.