Note: Descriptions are shown in the official language in which they were submitted.
~L2~9~j28
This invention relates to novel nematic compounds
which have a negative anisotropy of the dielectric
constant (DC) and are suitable as components for liquid
crystal (LC) mixtures. This invention also relates to
nematic LC mixtures which contain the novel compounds as
components and have an overall negative DC anisotropy.
Nematic liquid crystal mixtures with negative
dielectric constant anisotropy (DCA) are required for
operating certain displays, for example for the so-
called guest/host displays (GHD) and homotropic-nematic
d-isplays (HND) with a positive image display or posi-
tive contrast. Similar compounds are known~ for example
from J. C. Dubois et al., Mol. Cryst. Liq. Cryst. 42
(1977) 139; German Offenlegungschriften No. 2,240,864,
2,613,293, 2,835,682, and 2,937,700, and European
Patent Application No. 80200464.8.
However, no satisfactory nematic LC mixtures,
which have a sufficiently strong negative DCA (for
~259~i~8
--2--
example 2 or better) in combination with the further
properties, necessary for perfect operation of display
cells, of LC mixtures, such as chemical stability in
general, photochemical, electrochemical and thermal
stability, and a sufficiently wide range of anisotropy
as well as sufficiently short response times even at
low temperatures, for example at most about one second
at the lower end of the anisotropy range, are yet
obtainable by means of the compounds hitherto known.
Thus, it is an object of the invention to provide
novel nematic compounds which enable LC mixtures with a
markedly negative DCA and the further properties
mentioned to be prepared.
These objects have been obtained by providing
compounds of the formula I
~:a2ci~2~ z {~
in which m = 1 or 2, r is zero or 1 and m + r = 1 or 2,
and R1 and R2 are identical or different and are selected
from alkyl and alkoxy groups each having 1 - 12 carbon
atoms in a straight or branched chain, which may be
chiral, Z is a bridge member selected from a single bond
~L~5~628
--3--
and the groups of the formulae -CH2CH2-, -OCH2-, -O-CO-
or -CO-O-, one of the groups X and Y is selected from
fluorine, chlorine, bromine and cyano and the other of
the groups X and Y is selected from hydrogen, fluorine,
chlorine, bromine and cyano, with the proviso that m =
r = 1 if X and Y are both cyano.
It has been found that the compounds of the formula
I are outstandingly suitable as components of liquid-
crystalline phases. In particular, stable liquid--
crystalline phases with an overall negative dielectric
anisotropy and comparat;vely low viscosity can be pre-
pared by means of these compounds.
The compounds of the formula I can be used, in
the same way as similar compounds,as components of
liquid-crystalline phases, such as are required especially
for electro-optical displays of the type of guest/hcst
displays or homotropic-nematic displays.
Moreover, by the provision of the compounds of
the formula (I), the range of liquid-crystalline sub-
stances, which are suitable under different application
aspects for the preparation of nematic mixtures, is
quite generally widened considerably.
The subject of the invention thus concerns the
compounds of the formula (I) and the use of the com-
pounds of the formula (I) as components of liquid-
crystalline mixtures. A further subject of the inven-
tion concerns liquid-crystalline mixtures containing at
-
~S9~i2~3
4--
least one compound of the formula (I) and electro-
optical display elements which contain such mixtures.
In these novel compounds, the cyclohexyl rings
are each in the trans-configuration, as indicated by
dots in formula I.
At least one of the groups X and Y is a substi-
tuent having a polarizing action, from the group com-
prising fluorine,~chlorine, bromine and cyano.
Particularly preferred are those compounds of the
formula (~) in which one of the groups X and Y ;s
fluorine, chlorine or cyano, in particular those in
which X is fluorine and Y is hydrogen.
If r = 1, the bridge member Z then present can be
a single bond or a grouping selected from the groups of
the formulae -CHzCH2-, -OCHz-, -O-CO- or -CO-O-.
Preferably, Z is -CH2CH2-, -OCH2- or -O-CO-.
R1 and R2 are ;dentical or different ring groups
selected from C1-C12-alkyl and C1-C12-alkoxy groups
having a straight or branched chain, ~hich may be
chiral, of the alkyl moiety, for example methyl, ethyl,
propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl,
decyl, undecyl or dodecyl as the alkyl moiety,
including the corresponding chiral isomeric alkyl
moieties, for example 1-methylpropyl, 1-methylbutyl,
2-methylbutyl, 1-methylpentyl, 2-methylpentyl, 3-
methylpentyl, 1- or 2- or 3- or 4- methylhexyl, 1- or
2- or 3- or 4- or 5-methylheptyl and further alkyl-
alkyl groups formed in accordance with this principle
and having an asymmetrical carbon atom. Alkyl moieties
having 2 - 8 carbon atoms, in particular 3 - 8 carbon
atoms, are frequently preferred.
R1 is preferably straight-chain alkyl having
2 - 8 carbon atoms. In the case of r = û, RZ is prefer-
ably straight-chain alkoxy having Z - 8 carbon atoms and,
;n the case of r = 1, ;t ;s preferably stra;ght-chain alkyl
hav;ng Z - 8 carbon atoms.
Preferred groups of compounds of the formula I
according to the invention are of the follo~ing formulae
Ia, Ib, Ic, Id, Ie, and If, in uhich R1, R2, X and Y
have the mean;ngs g;ven above for formula I.:
X Y
Rl~_ CX2CEi2- ;<~ C~2{3~2 Ia
9628
6--
X Y
R1{~} CE2CE2~CE2C:12--~ R2 Ib
X Y
R1--~ ~} C~2C~I2 ~}R2 Ic
X Y
R 1 ~--CE2 CH2~a-CO--Q--R2 Id
X Y
Rl {~}CEzCE2~ CO-O--~3 R2 Ie
Rl_O--C 12CE2~-- R2 If
i28
,7-
Those compounds of the formula If are preferred
in which R2 is ~lkoxy and R1 is alkyl.
The novel compounds (I) can be prepared by va-
rious processes. A f;rst general process is based on the
S condensation of a corresponding carboxylic acid deriva-
tive of the formula A-CH2COOH, preferably in the form
~ of the corresponding acid halide, in which A represents
the left-hand part of the molecule of the compound (I),
that is to say
with a corresponding anisole derivative of the formula
B
X Y
~ OC~3 3
in order to form the corresponding ketone of the formula
15 C
X
2 C ~ O-CH3 C
which is then reduced for replacing the ketocarbonyl
oxygen by two hydrogen atoms, a compound of the formula
--8--
X Y
A C~2-CR2 ~ 0-C~3 D
be;ng formed.
For modifying R2 or/and (if r = 1) for introdu-
S cing the structure E
~ Z ~ E
the compound D can be converted to a compound F
X Y
. A 2 2 ~ L1 F
in which L1 is a first reactive group, such as hydroxyl,
COOH or halogen, and the compound F can then be reac-
ted ~ith a compound of the formula G
~2 ~ z ~ ~2
in which L2 is a second reactive group, in order to form
1S the target compound I or a pre-compound which can be
converted ;nto the latter.
Alternatiyely~ the compounds I can also be
A :~L ;;2 5 9 ~ ~ 8
_9_
prepared from appropriate pre-compounds of analogous
structure, but u;thout transversely polari~;ng suhstitu-
ents, by halogenation or transhalogenation and, if approp-
riate, nitrilation treplacement of halogen by cyano).
S A specific example of the synthesis of preferred
compounds I is illustrated by the equation uhich fol-
- lous:
R~ ) Rl--O-- (2) oC~2Br
X Y
R1 ~ 2 ~ OCa3 ~~~ R ~ H2C02H
~ (S)
X Y- X Y
Rl ~ C2H4 ~ (6) ~ 2~4 ~ o~
~7
x Y
R ~ C2H4 ~ ~1)--C~2 ~ R2
9~
- 1 0 -
t1) reduction, for examp~e with LiAlH4
(2) bromination, for example with elementary bromine
in acetonitrile
(3) C2 Grignard
(4) conversion into acid halide and reaction with
2-Y-3-X-anisole
(S) reduction
(6) demethylation, for example with boron tribromide
(7) condensation with (trans-4-R2-cyclohexyl)-methyl
bromide.
The starting materials required for the various
syntheses of the compounds I are either known or car, be
prepared by methods known per se from known starting
materials.
The chemistry involved in the reactions described
above is fully conventional per se and as applied to
this invention. See, e.g., Houben-Weyl, Methoden der
Organischer, Chemie (M~thods of Organic Chemistry),
Georg-Thieme Verlag, Stuttgart; Organic Reactions, John
Wiley ~ Sons, Inc., New York.
In the pure state, the compounds of the formula
(I) are colorless and form liquid-crystalline mesophases
in a temperature range favorable for electro-optical
use. They are very stable chemically, thermally and
towards light.
The compounds of the formula (I) have a wide
range of application. Depending on the selection of
the substituents, these compounds can be used as base
~%~3628
materials, of which liquid-crystalline dielectrics are
predominantly composed; however, liquid-crystalline
base materials from other classes of compounds can also
be added to compounds of the formula (I), for exam~le
in order to lower the dielectric and/or optical aniso-
tropy of such a dielectric. The compounds of the
formula (I) are also suitable as intermediates for the
preparation of other substances, which can be used as
constituents of liquid-crystalline dielectrics
To prepare LC mixtures according to the invention,
in each case at least one specific compound I is used
as a component and is mixed, if appropriate, with other
specific compounds I and/or with compounds known for
the preparation of LC mixtures having a clearly nega-
tive DCA for use in GHD or HND systems. The compound I,
of which there is at least one, here amounts as a rule to
at least 5% by weight and, as a maximum, to 30% by weight
of the LC mixture. If several compounds I are used, these
can represent a predominant proportion, for example 50-90%
by weight, of the mixture, with appropriate conventional
selection. Preferably the LC mixtures contain 10-40% by
weight of the compounds of formula I.
LC mixtures which virtually consist only of compound
I are also included in the invention, up to 95-100% by weight.
One skilled in the art can, using the preceding de-
scription, utilize the present invention to its fullest
extent. rhe following preferred specific
1;Z5~
-12-
embodiments are, therefore, to be construed as merely
illustrative.
. In the following
examples and in the preceding text, all temperatures
are set forth uncorrected in degrees Celsius and all
parts and percentages are by weight, unless otherwise
indicated.
In the examples, M is the melting point and C is
the clear point of a liquid crystal substance.
"Usual working-up" means: water is added, the
mixture is extracted with methylene chloride, the
phases are separated, the organic phase is dried and
evaporated, and the product is purified by crystalli-
zation and/or chromatography. The phase transition
temperatures quoted relate to degrees centigrade and
are in each case given between the corresponding symbols
of the phases "C" (crystalline), "N" (nematic)~ "I"
(isotropic), IISA" (A-smectic).
628
-13-
Example 1
(a) Preparation ~of trans-4-pentylcyclohexylacetyl
chloride
For conversion into the acid chloride, trans-4-
pentylcyclohexylacetic ac;d ~12.0 9, 0.0566 mol) was
reacted for about 1 hour on an oil bath at 80C w;th
thionyl chlor;de (50 ml). The solution obtained was
evaporated under reduced pressure, treated with absolute
toluene (S0 ml) and once more evaporated under reduced
pressure.
(b) Preparat;on of 2-fluoro-4-m~thoxy-~-(trans-4-
pentylcyclohexyl)-acetophenone
The acid chloride obtained according to section
(a) was taken up in absolute dichloromethane (50 ml),
1S without further purification, and added dropwise under
virtually anhydrous conditions to a solution of 3-fluoro-
an;sole t7.1 9, 0.05S6 mol), aluminum chloride (8.3 9,
- 0.0623 mol) and absolute dichloromethane (150 ml). The
mixture thus formed uas stirred for 12 hours and then
Z0 poured onto ice water wh;ch contained S0 ml of concentra-
ted hydrochloric acid. The organic phase was separated
off, and the aqueous phase ~as again extracted with di-
chloromethane (2 x 10Q ml). The combined organic phases
were then washed with ~ater, sodium bicarbonate and
water, and dried over magnesium sulfate. The crude pro-
duct obtained after evaporation of the dichloromethane
under reduced pressure was purified by recrystalli~ation
from hexane at 0C. rhis gave 11.5 9 (64~ yield) of
pure 2-fluoro-4-metho~y ~ -(trans-4-PentYlcYclohe~Yl)~
- ~259~;~8
~-14-
.
acetophenone, M. 71 to 72C.
(c) Preparation;of 2.(trans-4-pentylcyclohexyl)-
1-(2-fluoro-4-methoxYphenyl)-ethane
A mixture of the 2-fluoro-4-methoxy-~-(trans-4-
S pentylcyclohexyl)-acetophenone (10.0 g, 0~0313 mol)
obtained according to sect;on (b), aluminum l;thium hy-
dride (Z.1 9, 0.0560 mol)~ aluminùm chloride (15.0 g,
0.1125 mol), absolute ether (70 ml) and absolute chloro-
form (70 ml) uas heated to gentle reflux for 5.5 hours
under virtually anhydrous conditions.
The reaction solution was then cooled and subse-
quently treated with water-containing ether, water and
concentrated hydrochloric acid. The aqueous phase ~as
separated off and extracted twice more ~ith ether (2 x
100 ml). The combined organic phases uere then washed
uith ~ater, sodium bicarbonate and water, dried over mag-
nes;um sulfa~e and then concentrated~ The crude product
was distilled in a bulb tube at 150C/about 4 x 10 Z
mm ~9. This product (9.û 9, 94% yield) can be used for
the following reaction without further purification.
(d) Preparation of 3-fluoro-4-~Z-(trans-4-pentyl-
cyclohexyl)-l-ethyl]-phenol
A solution of the 2-~trans-4-pentylcyclohexyl)-1-
(2-fluoro-4-methoxyphenyl)-ethane (9.0 g, 0.0294 mol)
obtained accord;ng to section (c) in absolute dichlorome-
thane (100 ml) uas added dropwise to a solution of boron
tribromide (11.0 9, 0.0441 ~ol) and absolute dichlorome-
thane (100 ml) under virtually anhydrous conditions at
0C. The mixture thus formed uas stirred for 1 hour
~25~62~3
-15-
.
and then poured onto ice water. The organic phase was
separated off, and the aqueous phase was extracted again
with dichloromethane (Z x 50 ml). The combined organic
phases were washed with water and dried over magnesium
sulfate. The crude product obtained after evaporation
was recrystalli~zed from hexane at 0C. 8~5 9 ~9O~
yield) of pure target product were obtained.
~e) Preparation of 1-C2-ttrans-4-pentylcyclo-
hexyl)-1-ethyl]~4-(trans-4-propylcyclohexyl)-methoxy-2-
1 0 f luorobenzene
A mixture of the 3-fluoro-4-CZ-(trans-4-pentyl-
cyclohexyl)-1~ethyl]-phenol (2.0 g, 0.00068 mol) ob-
tained according to section (d), (trans-4-propylcyclo-
hexyl)-methyl bromide (2.0 g, 0.00089 mol), anhydrous
potassium carbonate (3.8 g, 0.0274 mol) and absolute di-
methylformamide (100 ml) was heated for 24 hours under
reflux.
The reaction mixture was worked up as in section
(d)~ The crude product was purified by column chromato-
graphy on silica gel with toluene as the eluant. Afterevaporation of the toluene, the product was recrystal-
li~ed several times from ethanol, until the phase transi-
t;on temperatures were constant; the corresponding values
are as follows: C 61.5 N 110 I.
Examples 2 to 7
According to the process indicated in Example 1,
and using the corresponding (trans-4-alkylcyclohexyl)
methyl bromides, the following compounds (I) according to
the invention were prepared:
` ~2596~:8
-16-
(Example)
(2) 1-C2-(trans-4-pentylcyclohexyl)-1-ethyl]-4-(trans-4-
pentylcyclohexyl)-methoxy-2-fluorobenzene;
C 72 - SA 7~ N 113 ~ I;
(3) 1-C2-(trans-4-pentylcyclohexyl)-1-ethyl]-4-(trans~4-
heptylcyclohexyl)-methoxy-2-fluorobenzene; C 88 ~ SA
- 94 N 110 ~ I;
(4) 1-C2-(trans-4-propylcyclohexyl)-1-ethyl]-4-(trans-4-
propylcyclohexyl)-methoxy-2-fluorobenzene; C 64 ~ N
10B I;
(S) 1-C2-(trans-4-propylcyclohexyl)-1-ethyl~-4-(trans-4-
pentylcyclohexyl)-methoxy-2-fluorobenzene; C 54.5 N
110.5 I;
(6) 1-C2-(trans-4-propylcyclohexyl)-1-ethyl] 4-(trans-4-
1S heptylcyclohexyl)-methoxy-2-fluorobenzene; C 72.5 ~ SA
7~5 ~ N 107.5 ~ I;
~7) 1-C2-(trans-4-heptylcyclohexyl)-1-ethyl~-4-(trans-4-
propyLcyclohexyl)-methoxy-2-fluorobenzene; C 45 N
108 ~ I.
Example 8
From 1-(4-trans-heptylcyclohexyL)-2-(3-fluoro-4-
hydroxyphenyl)-ethane CM. 70 - 71; obtainable analo-
gously to Example 1] and (trans-4-pro~ylcyclohexyl)-
methyl bromide 1-C2-~trans-4-heptylcyclohexyl)-1-e~hyl~~
4-(trans-4-propylcyclohexyL)-methoxy-3-fluorobenzene is
obtained analogously to Example 1;
C 50.5 ~ SA 90 ~ N 110 ~ I.
~5~ 8
-17-
Example
From 1-(4-trans-heptylcyclohexyl)-2-(3-bromo-4-
hydroxyphenyl)-ethane CM. 50 - 51; obtainable by brom;-
nati~n of 1-(4-trans-heptylcyclohexyl)-2-(4-hydroxy-
phenyl)-ethane in dichloromethane], 1-C2-trans-4-heptyl-
cyclohexyl)-1-ethyl]-4-~trans-4-propylcyclohexyl)-
methoxy-3-bromobenzene is obtained analogously to Example
8; C 44 N 85.S I.
Example 10
From 1-(4-trans-4-heptylcyclohexyl)-2-(3-chloro-
4-hydroxyphenyl)-ethane CM. 56 - 57, obtainable analo-
gously to Example 1] and (trans-4-propylcyclohexyl)-
methyl bromide, 1-C2-(trans-4-heptylcyclohexyl)-1-ethyl]-
4-(trans-4-propylcyclohexyl)-methoxy-3-chLorobenzene is
obtained analogously to Example 1; C 46 N 96 I.
Example 11
From 1-(4-trans-4-heptylcyclohexyl)-~-~3-cyano-4-
hydroxyphenyl)-ethane and (trans-4-propylcyclohexyl)-
methyl bromide, 1-C2-(trans-4-heptylcyclohexyl)-1-ethyl]-
4-(trans-4-propylcyclohexyl)-methoxy-3-cyanobenzene is
obtained analogously to Example 1; C 57 SA 90 I.
Example 12
A mixture of 1.0 9 of 1-(4-trans-pentyLcyclo-
hexyl)-2-(2-fluoro-4-hydroxyphenyl)-ethane (Example 1),
0.8 9 of 1-bromobutane, 1.9 9 of potassium carbonate and
30 ml of butanone is boiled overnight. The reaction
mixture is added to 250 ml of water, and this is extrac-
ted with three times 50 ml of chloroform. rhe combined
organic phases are washed with twice 500 ml of water and
~L2~962~3
-18-
dried over MgS04. Conventional working-up gives 1-(4-
trans-pentylcyc~ohex.yl)-2-t2-fluoro-4-butoxyphenyl~-
ethane; C 24 - N 26 I.
Examp~.les 13 to 25:
S Follo~ing the procedure indicated in Example 12
the follo~ing compounds I according to the invention
~ere prepared, us;ng the corresponding 1-(4-trans-alkyl-
cyclohexyl)-2-t2 fluoro-4-hydroxyphenyl)-ethanes or the
corresponding 1-(4-trans-alkylcyclohexyl)-2-t3~fluoro-4-
hydroxyphenyl)-e~hanes and the corresponding 1-bromo-
alkanes:
tExample)
(13)
1-(4-trans-propylcyclohexyl)-2-t2-fluoro-4-ethoxyphenyl)-
ethane; M. 22; C. 14 tmonotropic);
(14)
1-t4-trans-propylcyclohexyl)-2-(2-fluoro-4-butoxyphenyl)-
ethane; M. 21; C. 12 tmonotropic);
( 1 5 )
1-(4-trans-propylcyclohexyl)-2-(2-fluoro-4-hexyloxy-
phenyl)-ethane; M. 28; C. 22 (monotropic);
t16)
- 1-t4-trans-pentylcyclohexyL)-2-(2-fluoro-4-ethoxyphenyL)-
ethane; M. 32; C. 28 tmonotropic);
(17)
1-(4-trans-pentylcyclohexyl)-2-(2-fluoro-4-propoxy-
phenyl)-ethane; M. 22.5; C. 10 (monotropic);
.(18)
1-(4-trans-pentylcyclohexyl)-2-(2-fluoro-4-pentyloxy-
5~628
. .
phenyl)-ethane; M. 26; C. 12 (monotropic);
~19)
1-(4-trans-pentylcyclohexyl)-2-~Z-fluoro-4-hexyloxy-
phenyl^)-ethane; M. 23.5; C. 29.5;
(2~)
1-(4-trans-heptylcyclohexyl)-2-(2-fluoro-4-ethoxyphenyl)-
ethane; M. 46; C 35 (monotropic);
(21)
1-(4-trans-heptylcyclohexyl)-2-(2-fluoro-4-butoxyphenyl)-
ethane; M. 31; C. 34;(22~
1-~4-trans-heptylcyclohexyl)-2-(2-fluoro-4-hexyloxyphe-
nyl)-ethane; M. 29.5; C. 35;
(23)
tS 1-(4-trans-heptylcyclohexyl)~2-(3-fluoro-4-methoxyphe-
nyl)-ethane; M. 32; C. 29 ~monotropic);
t24)
1-(4-trans-heptylcyclohexyl)-3-~3-fluoro-4-ethoxyphenyl)-
ethane; M. 53; C. 34 (monotropic);
(25)
1-~4-trans-heptylcyclohexyl)-3-~3-fluoro-4-hexyloxy-
phenyl)-ethane; Ma 45; C~ 35 (monotropic).
Example 26
A mixture of 0.65 9 of trans-4-pentylcyclohexane-car-
boxylic acid chloride and 10 ml toluene is added to a mix-
ture of 0., g of 1-(trans-4-pentylcyclohexyl) 2-(2-fluoro-
4-hydroxyphenyl)-ethane (Example 1), 2 ml of pyrid;ne and
10 ml of toluene, and the whole is stirred overnight. rhe
reaction mixture is poured into cold, dilute hydrochloric
~;~59~28
--20--
acid and ~orked up as usual. This gives 3-fluoro-4-CZ-
(trans-4-pentylcyclohexyl)-ethyl]phenyltrans-4-pentyl-
cyclohexane-carboxylate; M. 7Z.5, C. 147.
Examples 27 to 31
Following the procedure indicated in Example Z6,
the follow;ng compounds I according to the in~ention
- are prepared:
(Z7)
3-fluoro-4-C2-(trans-4~propylcyclohexyl)-ethyl~-phenyl
trans-4-propylcyclohexane-carboxylate; M. 72; C. 140;
~28)
3-fluoro-4-C2-(trans-4-propylcyclohexyl)-ethyl]-phenyl
trans-4-pentylcyclohexane-carboxylate; M. 68; C. 146.5;
(29)
3-fluoro-4-~2-~trans-4-propylcyclohexyl)-ethyl~-phenyl
trans-4-heptylcyclohexane-carboxylate; C. 84
SA 91 N 140 ~ I;
(30)
3-fluoro-4-C2-(trans-4-pentylcyclohexyl)-ethyl]-phenyl
trans-4-propylcyclohexane-carboxylate; M. 65; C~ 141;
(31)
3-fluoro-4-C2-(trans-4-pentylcyclohexyl~-ethyl]-phenyl
trans-4-heptylcyclohexane-carboxylate;
C. 100 SA 111 ~ N 142 ~ I.
Z5 ~he following are further examples of compounds
of the formula I: ~hey are prepared analogously to the foregoing.
2-(trans-4-pentyl-4'-bicyclohexyl~-1-(3-fluoro-4 pentyl-
phenyl)-ethane;
2-(trans-4-pentyl-4'-bicyclohexyl)-1-(2-fluoro 4-pentyl-
6~3
-21-
phenyl)-ethane;
2-ttrans-4-pentyl-4'-bicyclohexyl)-1-(3-fluoro-4-butoxy-
phenyl)-ethane;
2-(trans-4-pentyl-4'-bicyclohexyl)-1-(2-fluoro-4-butoxy-
phenyl)-ethane;
Z-(trans-4-pentyl-4'-bicyclohexyl)-1-(3-cyano-4-pentyl-
phenyl)-ethane;
Z-(trans-4-pentyl-4'-bicyclohexyl)-1-(Z-cyano-4-pentyl-
phenyl)-ethane;
Z-(trans-4-pentyl-4'-bicyclohexyl)-1-(3-cyano-4-ethoxy-
phenyl)-ethane;
Z-(trans-4-pentyl-4'-bicyclohexyl)-1-(3-cyano-4-butoxy-
phenyl)-ethane;
2-(trans-4-pentyl-4'-bicyclohexyl)-1-(3-cyano-4-hexyloxy-
phenyl)-ethane;
2-(trans 4-pentyl-4'-bicyclohexyl)-1-(2-cyano-4-ethoxy-
phenyl)-ethane;
2-~trans-4-pentyl-4'-bicyclohexyl)-1-(2-cyano-4-butoxy-
phenyl)-ethane;
2-(trans-4-pentyl-4'-b;cyclohexyl)-1-(2-cyano-4-he%yloxy~
phenyl)-ethane;
2-fluoro-1-~2-(trans-4-propylcyclohexyl)-1-ethyl]-4~C2-
<trans-4-pentylcyclohexyl)-1-ethyl]-benzene;
3-fluoro-1-CZ-(trans-4-propylcyclohexyl)-1-ethyl~-4-C2-
ZS (trans-4-pentylcyclohexyl)-1-ethyl~-benzene;
Z-fluoro-1,4-d;-C2-(trans-4-pentylcyclohexyl)-1-ethyl~-
; ben2ene;
2,3-difluoro-1,4-di-CZ-(trans-4-propylcyclohexyl)-1-ethyl]-
benzene;
g~:8
.
-22-
2,3-difluoro-1,4-di-CZ-(trans-4-pentyLcyclohexyl)-1-ethyl]-
benzene;
2,3-difluoro~1,4-di-~2-(trans-4-heptylcyclohexyl)-1-ethyl~-
benzene;
2-cyano-1-C2-~trans-4-propylcyclohexyl)-1-ethyl]-4-C2-
(trans-4-pentylcyclohexyl)-1-ethyl]-benzene;
3-cyano-1-C2-(trans-4-propylcyclohexyl)-1-ethyl~-4-C2-
(trans-4-pentylcyclohexyl)-1-ethyl]-benzene;
Z-cyano-1,4-d;-C2-(trans-4-pentylcyclohexyl)-1-ethyl]-ben-
zene;
2,3-dicyano-1,4-d;-C2-(trans-4-propylcyclohexyl)-1-ethyl]-
benzene;
2,3-dicyano-1,4-di-C2-(trans-4-pentylcyclohexyl)-1-ethyl~-
benzene;
2,3-dicyano~1,4-di-C2-(trans-4-heptylcyclohexyl)-1-ethyl~-
benzene~
The following examples relate to mixtures of com-
pounds of formula I with other liquid-crystall1ne substances
whcih can be used as dielectrics according to the invention.
Example A
A liquid crystalline dielectric is prepared by
mixing 0.25 g of 1-[2-trans-4-pentylcyclohexyl)-1~ethyl~-
4-(trans-4-propylcyclohexyl)-methoxy-2-fluorobenzene (com-
pound according to example 1) with 0.75 g of a known liquid
crystalline phase consisting of 24.0% by weight of trans-
5~?628
-22a-
1-(4-etlloxyphenyl)-b-propylcyclohexane~ 21.2% by weight
of trans-1-(4-butoxyphenyl)-4-propylcyclohexane, 19.3%
by weight of trans,trans-4-butylcyclohexanecarboxylic
acid-4'-(4-propylcyclohexyl)phenylester and 35.5% by
weight, of 4'-(trans-4-propyl-cyclohexyl)-benzoicacid-
2'-cyano-4'-butyl phenylester.
This mixture shows a DCA of -2.3.
Example B
A liquid crystalline dielectric consisting of 15%
by weight of trans-1-p-ethoxyphenyl-4-propylcyclohexane,
10% by weight of trans-1-p-butoxyphenyl-4-propylcyclohexane
25% by weight of 4-ethyl-4'-(trans-4-pentylcyclohexyl)-
biphenyl, 20% by weight of p-methoxybenzoic acid p-pentyl-
phenylester and 30% by weight of 1-(4-trans-pentylcyclo-
hexyl)-2-(2-fluoro-4-hexyloxyphenyl)-ethane shows a
negative DCA.
Example C
A liquid crystalline dielectric consisting of 7%
by weight of trans-1-p-ethoxyphenyl-4-propylcyclohexane~
30% by weight of 4-ethyl-4'-(trans-4-pentylcyclohexyl)-
2'-fluorbiphenyl, 9% by weight of 4-ethyl-4'-(trans-4-
propylcyclohexyl)-biphenyl, 6% by weight of 4-ethyl-4'-
(trans-4-pentylcyclohexyl)-biphenyl, 15% by weight of
4-(trans-4-pentylcyclohexyl)-4'-(trans-4-propylcyclo-
hexyl)-biphenyl, 23% by weight of p-m-methoxybenzoic
acid p-pentylphenylester, o% by weight of 3-fluoro~4-
C2-(trans-4-pentylcyclohexyl)-ethyl]-phenyl-trans-4-
pentylcyclohexane-carboxylate and 4% by weight of 2-
~9~i~8
- 22b -
(trans-4-pentyl-4'-bicyclohexyl)-1-(3-fluoro-4-pentyl-
phenyl)-ethane shows a negative DCA.
Example D
A liquid crystalline dielectric consisting of 13% by
weight of r-1-cyano-c;s-4-(trans-4-proPylcyclohexyl)-
1-pentylcyclohexane, 6% by weight of Z-p-cyanophenyl-S-
propyl-1,3-dioxane, 9% by weight of 2-p-octyloxyphenyl-5-
pentyl-pyrimidine, 7% by weight of 2-p-nonyloxyphenyl-
5-hexyl-pyrimidine, 10% by weight of trans-4-propyl-
cyclohexane carboxylic acid-p-ethoxyphenylester, f5% by
weight of 4-ttrans-4-pentylcyclohexyl)-4'-(trans-4-
propylcyclohexyl)-biphenyl, 17% by weight of 1-(4-trans-
pentylcyclohexyl)-2-(2-fluoro-4-hexyloxyphenyl)-ethane,
12% by weight of 1-(4-trans-pentylcyclohexyl)-2-(2-fluoro-
4-ethoxyphenyl)-ethene and 11% by weight of 3-fluoro-
4-C2-(trans-4-pentylcyclohexyl)-ethyl]-phenyl-trans-
4-pentylcyclohexane-carboxylate shows a negative DCA~
Example E
A liquid crystalline dielectric consisting of 27%
by weight of 1-(4-trans-pentylcyclohexyl)-2-(2-fluoro-
4-hexyloxyphenyl)-ethane, 11% by weight of 1-C2-(trans-
4-propylcyclohexyl)-1-ethyl]-4-(trans-4-propylcyclohexyl)-
methoxy-2-fluorobenzene, 39% by weight of 1-[2-ttrans-4-
heptylcyclohexyl)-1-ethyl~-4-(trans-4-propylcyclohexyl)-
methoxy-2-fluorobenzene and 23% by weight of 1-~4-trans-
pentylcyclohexyl)-2-(2-fluoro-4-butoxyphenyl)-ethane
shows a negative DCA.
~ 2~96~
, . ,
-23-
The preceding examples can be repeated with
similar success by substituting the generically or
sper,ifically described reactants and/or operating
conditions of this invention for those used in the
preceding examples.
