Tolan derivatives, and liquid-crystalline medium

Details Tolan derivatives, and liquid-crystalline medium Tolan derivatives, and liquid-crystalline medium

1999-06-17

2001-01-09

Wu, Shean C. (Department: 1721)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

C252S299610, C252S299630, C549S369000, C568S610000, C568S647000, C570S127000, C570S129000, C570S131000

Reexamination Certificate

active

06171664

ABSTRACT:

The invention relates to novel tolan derivatives of the formula I
in which
R
1
is H or an alkyl radical having 1-12 carbon atoms which is unsubstituted, monosubstituted by CN or CF
3
or monosubstituted to perhalosubstituted by halogen, where one or more non-adjacent CH
2
groups in these radicals may also, independently of one another, each be replaced by —CH═CH—, —O—, —S—, —CO—,
—CO—O—, —O—CO— or —O—CO—O—,
R
2
is alkyl or alkoxy having 1 to 10 carbon atoms which is unsubstituted or monosubstituted to perhalosubstituted by halogen; alkenyl or alkenyloxy having 2 to 10 carbon atoms which is unsubstituted or at least monosubstituted by —CN, —CF
3
or —F; or —F, —Cl, —CF
3
, —OCHF
2
, —OCF
3
, —OCHFCF
3
or —OCF
2
CF
3
,
L
1
, L
2
, L
3
, L
4
, L
5
, L
6
are each, independently of one another, H or F,
Q is —O— or a single bond
A is a trans-1,4-cyclohexylene radical, in which, in addition, one or more non-adjacent CH
2
groups may be replaced by —O— and/or —S—, or 1,4-cyclohexenylene, where the rings may be substituted by CN, Cl or F,
Z is —CO—O—, —O—CO—, —CH
2
O—, —O—, —O—CH
2
—, —CH
2
CH
2
—, —CH═CH—, —C≡C— or a single bond,
when there are more than one A or Z groups, they may have the above meanings independently from one another,
n is 0, 1, 2, 3 or 4 and
m is 0, 1 or 2,
with the provisos that compounds of the formula I in which either
a) m is 0 and simultaneously R
2
is alkyl or alkoxy, or
b) m is 0 and simultaneously L
1
, L
2
, L
3
, L
4
, L
5
and L
6
are H, or
c) L
6
is F and simultaneously L
3
is H, or
d) L
2
and L
5
are F and simultaneously L
3
and L
4
are H
are excluded.
The invention also relates to the use of the compounds of the formula I as components of liquid-crystalline media, and to liquid-crystal and electro-optical display elements which contain the liquid-crystalline media according to the invention.
The compounds of the formula I can be used as components of liquid-crystalline media, in particular for displays based on the principle of the twisted cell, the guest-host effect, the effect of deformation of aligned phases (DAP) or electrically controlled birefringence (ECB) or the effect of dynamic scattering.
BACKGROUND OF THE INVENTION
The substances employed hitherto for this purpose all have certain disadvantages, for example inadequate stability to the action of heat, light or electric fields, or unfavorable elastic and/or dielectric properties.
The compounds excepted by the proviso are compounds of the formula I without lateral fluorination in which m is 0. These bicyclic tolans which are disclosed, for example, in JP 040 216 40, have relatively low solubility and are therefore less suitable for practical applications.
Compounds of the formula I in which m is 0 are disclosed, for example, in JP 063 296 31, but this specification only mentions tolans which have alkyl or alkoxy terminal groups. Compounds of this type exhibit a relatively low optical anisotropy value and a relatively low clearing point and are likewise excepted by the proviso.
Although fluorinated compounds of the formula I containing terminal alkenyl radicals or polar radicals in which m is 0 are amongst the compounds covered by the very broad generic claims in EP 0 648 723 and JP 093 019 01, these documents make absolutely no mention of the advantageous specific lateral fluorination of the compounds of the formula I. EP 543 244, JP 080 601 58, JP 072 343 9 and JP 080 536 74 describe tricyclic fluorinated tolan derivatives, but these likewise differ from the compounds of the formula I according to the invention through the position of the lateral fluorination.
SUMMARY OF THE INVENTION
The invention had an object of finding novel, stable, liquid-crystalline or mesogenic compounds of high optical anisotropy at the same time as low negative to highly positive dielectric anisotropy which are suitable as components of liquid-crystalline media, in particular for TFT and STN displays.
Upon further study of the specification and appended claims, further objects and advantages of this invention will become apparent to those skilled in the art.
It has now been found that the compounds of the formula I are eminently suitable as components of liquid-crystalline media. They can be used to obtain stable liquid-crystalline media, in particular suitable for TFT or STN displays. The novel compounds are distinguished in particular by high thermal stability, which is advantageous for a high holding ratio, and exhibit favorable clearing point values. Preferred compounds of the formula I have a broad nematic phase and a dielectric anisotropy of between −3 and +3.
The provision of compounds of the formula I very generally considerably broadens the range of liquid-crystalline substances which are suitable, from various applicational points of view, for the preparation of liquid-crystalline mixtures.
The compounds of the formula I have a broad range of applications. Depending on the choice of substituents, these compounds can serve as base materials of which liquid-crystalline media are predominantly composed; however, it is also possible to add liquid-crystalline base materials from other classes of compounds to compounds of the formula I in order, for example, to modify the dielectric and/or optical anisotropy of a dielectric of this type and/or to optimize its threshold voltage and/or its viscosity. The meaning of the formula I covers all isotopes of the chemical elements bound in the compounds of the formula I. In enantiomerically pure or enriched forms, the compounds of the formula I are also suitable as chiral dopants and in general for producing chiral mesophases.
In particular, the compounds according to the invention are distinguished by very high optical anisotropy in combination with high clearing point values and excellent solubility in a wide variety of host mixtures.
In the pure state, the compounds of the formula I are colorless and form liquid-crystalline mesophases in a temperature range which is favorably located for electro-optical use. They are stable chemically, thermally and to light.
Aspects of the invention thus include the compounds of the formula I and the use of these compounds as components of liquid-crystalline media. The invention furthermore relates to liquid-crystalline media containing at least one compound of the formula I, and to liquid-crystal display elements, in particular electro-optical display elements, which contain media of this type.
Above and below, R
1
, R
2
, A, Z, L
1
, L
2
, L
3
, L
4
, L
5
, L
6
, Q, m and n are as defined above, unless expressly stated otherwise.
If the radical A occurs more than once, it can have the same or different meanings. The same applies to the group Z.
The following group of compounds of the formulae IA to IL are preferred embodiments of the invention.
in which R
1
, R
2
, A, Z, Q, m and n are as defined above.
R
2
is preferably F, OCF
3
, straight-chain alkyl or alkoxy having 1 to 10 carbon atoms, alkenyl or alkenyloxy having 2 to 10 carbon atoms, in particular, F, alkyl, alkoxy or alkenyl. Very particular preference is given to alkyl or alkoxy.
In the compounds of the formulae above and below, R
1
is preferably H, straight-chain alkyl having 1 to 10 carbon atoms or alkenyl having 2 to 10 carbon atoms, furthermore preferably alkoxy having 1 to 10 carbon atoms.
Q is preferably a single bond.
A is preferably
A is particularly preferably
n is preferably 0, 1 or 2, particularly preferably 0 or 2. m is 0 or 1, particularly preferably 1. Z is preferably —CH
2
CH
2
—, —CH═CH— or a single bond, particularly preferably a single bond, —CH
2
—CH
2
— or —COO—. Z is very particularly preferably a single bond or —COO—.
Particular preference is given to compounds of the formula I which are characterized in that R
1
is H, straight-chain alkyl or alkoxy having 1 to 7 carbon atoms or alkenyl having 2 to 7 carbon atoms and R
2
is alkyl or alkoxy having 1 to 7 carbon atoms, alkenyl or alkenyloxy having 2 to 10 carbon atoms, —F, —OCHF
2
or —OCF
3
.
Preference is furthermore given to compounds of the form

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