1,4-disubstituted 2,6-difluorobenzene compounds, and a...

Details 1,4-disubstituted 2,6-difluorobenzene compounds, and a... 1,4-disubstituted 2,6-difluorobenzene compounds, and a...

2000-02-28

2001-12-04

Wu, Shean C. (Department: 1756)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

C252S299640, C252S299650, C252S299670, C570S127000, C570S128000, C570S129000, C560S065000

Reexamination Certificate

active

06326066

ABSTRACT:

The invention relates to novel 1,4-disubstituted 2,6-difluorobenzene compounds of the formula I
where
R is an alkyl or alkenyl radical having 1 to 15 carbon atoms which is unsubstituted or at least monosubstituted by halogen, it also being possible for one or more CH
2
groups in these radicals to be replaced, in each case in-dependently of one another, by
in such a manner that oxygen atoms are not linked directly to one another,
A
1
and A
2
, in each case independently of one another, are
(a) 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—,
(b) a 1,4-phenylene radical in which, in addition, one or two CH groups may be replaced by N,
(c) a radical from the group comprising 1,4-cyclohexenylene, 1,4-bicyclo(2,2,2)octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl and 1,2,3,4-tetrahydro-naphthalene-2,6-diyl,
it being possible for the radicals (a) and (b) to be substituted by CN or monosubstituted or disubstituted by fluorine,
Z
1
and Z
2
in each case independently of one another, are —CO—O—, —O—CO—, —CH
2
O—, —OCH
2
—, —CH
2
CH
2
—, —CH═CH—, —C≡C—or a single bond,
m and n in each case independently of one another, are 0, 1, 2 or 3, where
(m+n) is 1, 2 or 3, and
X has one of the meanings of R or is F, Cl, —CF
3
, —OCF
3
—, —OCF
2
H, —OC
2
F
5
, —CN or —NCS, with the proviso that at least one of the radicals Z
1
and z
2
present in the molecule is —CO—O—, —O—CO—, —CH
2
—O—, —OCH
2
—, —CH
2
CH
2
—, —CH═CH—or —C≡C and/or at least one of the radicals A
1
and A
2
present in the molecule is
and/or n is 1 or 2, where, in the case where
X is F, Cl, —CF
3
, —OCF
3
, —OCF
2
H, —OC
2
F
5
, —CN or —NCS.
The invention furthermore relates to the use of these compounds as components of liquid-crystalline media, and to liquid-crystal and electrooptical displays 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 or the effect of dynamic scattering.
The invention had the object of finding novel stable liquid-crystalline or mesogenic compounds which are suitable as components of liquid-crystalline media and in particular have at the same time comparatively low viscosity and a relatively high dielectric anisotropy.
It has now been found that compounds of the formula I are eminently suitable as components of liquid-crystalline media. In particular, they have comparatively low viscosities. Using them, stable liquid-crystalline media which have a broad mesophase range, advantageous values for the optical and dielectric anisotropy and outstanding ultraviolet and temperature stability are obtained.
Liquid crystals of the formula
have already been disclosed in DE 3209178. JP 62-103057 discloses compounds of the formulae
Finally, JP 63-216858 describes compounds of the formula
In view of the very wide range of areas of application of such compounds having very high &Dgr;&egr;, it was, however, desirable to have further compounds available which have properties precisely customized to the particular applications.
Liquid crystals of the formula
have already been disclosed in WO 89/02425 and are distinguished by high birefringence and relatively high viscosity.
In view of the very wide variety of areas of application of such compounds having positive &Dgr;&egr;, it was desirable to have further compounds available which have properties precisely customized to the particular applications.
In addition, the provision of the compounds of the formula I very generally considerably extends 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 field of application. Depending on the choice of substituents, these compounds can be used as base materials from which liquid-crystalline media are predominantly composed; however, compounds of the formula I can also be added to liquid-crystalline base materials from other classes of compound, in order, for example, to influence the dielectric and/or optical anisotropy of a dielectric of this type and/or to optimize its threshold voltage and/or its viscosity.
In the pure state, the compounds of the formula I are colorless and form liquid-crystalline mesophases in a very favorable temperature range for electrooptical use. They are stable chemically, thermally and to light.
The invention thus relates to the compounds of the formula I and to 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.
For reasons of simplicity below, A
3
is a radical of the formula
Cyc is a 1,4-cyclohexylene radical, A
4
is a radical of the formula
Che is a 1,4-cyclohexenylene radical, Dio is a 1,3-dioxane-2,5-diyl radical, Dit is a 1,3-dithiane-2,5-diyl radical, Phe is a 1,4-phenylene radical, Pyd is a pyri-dine-2,5-diyl radical, Pyr is a pyrimidine-2,5-diyl radical and Bi is a bicyclo(2,2,2)octylene radical.
The compounds of the formula I accordingly include the preferred dinuclear compounds of the sub-formulae Ia and Ib:
R—A
3
—A
2
—X  Ia
R—A
3
—Z
2
—A
2
—X  Ib
Trinuclear compounds of the sub-formulae Ic to If:
R—A
3
—Z
2
—A
2
—A
2
—X  Ic
R—A
1
—Z
1
—A
3
—Z
2
—A
2
—X  Id
R—A
1
—Z
1
—A
4
—Z
1
—A
3
—X  Ie
R—A
4
—Z
1
—A
1
—Z
1
—A
3
—X  If
and tetranuclear compounds of the sub-formulae Ig to Ij:
R—A
1
—Z
1
—A
3
—Z
2
—A
2
—Z
2
—A
2
—X  Ig
R—A
1
—Z
1
—A
1
—Z
1
—A
3
—Z
2
—A
2
—X  Ih
R—A
1
—Z
1
—A
1
—Z
1
—A
4
—Z
1
—A
3
—X  Ii
R—A
4
—Z
1
—A
4
—Z
1
—A
1
—Z
1
—A
3
—X  Ij
Of these, those of the sub-formulae Id, le, Ih and Ii are particularly preferred.
In the compounds of the formulae above and below, X is preferably —OCF
3
, —OCHF
2
, —CF
3
, F or Cl. Likewise preferred are compounds of the formulae above and below in which X has one of the meanings of R.
In the case where X is F, Cl, —CF
3
, —OCF
3
, —OCHF
2
, —OC
2
F
5
, —CN or —NCS, at least one of the radicals A
1
and A
2
present in the molecule of the formula I is preferably
and/or n is 1 or 2.
R is preferably alkyl, furthermore alkoxy. A
1
and/or A
2
are preferably Phe, Cyc, Che, Pyr or Dio. The compounds of the formula I preferably contain not more than one of the radicals Bi, Pyd, Pyr, Dio or Dit.
Preferred compounds of the formula I and of all the sub-formulae are those in which A
1
and/or A
2
are 1,4-phenylene which is monosubstituted or disubstituted by F or monosubstituted by CN. These are, in particular, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene and 2,3-difluoro-1,4-phenylene, and 2-cyano-1,4-phenylene and 3-cyano-1,4-phenylene.
Z
1
and Z
2
are preferably a single bond, —CO—O—, —O—CO—and —CH
2
CH
2
—, and secondarily preferably —CH
2
O—and —OCH
2
—. Preferably, only one of the groups Z
1
and Z
2
present in the molecule is other than a single bond.
If R is an alkyl radical and/or an alkoxy radical, it may be straight-chain or branched. It is preferably straight-chain, has 2, 3, 4, 5, 6 or 7 C atoms and is accordingly preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, furthermore methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy.
Oxaalkyl is preferably straight-chain 2-oxapropyl (=methoxymethyl), 2- (=ethoxymethyl) or 3-oxabutyl (=2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-,

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