Vinylene and ethyl compounds

Details Vinylene and ethyl compounds Vinylene and ethyl compounds

2000-09-25

2002-10-22

Wu, Shean C. (Department: 1756)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

C252S299630, C252S299660, C570S129000

Reexamination Certificate

active

06468608

ABSTRACT:

The invention relates to novel vinylidene compounds and ethyl compounds of the formula I
in which
R
1
and R
2
are each, independently of one another, an alkyl or alkenyl radical having 1 to 15 carbon atoms which is unsubstituted monosubstituted by CN or CF.
3
or at least monosubstituted by halogen, where one or more CH
2
groups in these radicals may also, in each case independently of one another, be replaced by —O—, —S—, —⋄— —CO—, —CO—O—, —O—CO— or —O—CO—O— in such a way that O atoms are not linked directly to one another,
A
1
(a) is a tarns-1,4-cyclohexyl 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 1,4-cyclohexenylene radical,
(d) a radical from the group consisting of 1,4-bicyclo[2.2.2]octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl and 1,2,3,4-tetrahydronaphthalene-2,6-diyl,
where the radicals (a), (b) and (c) may be monosubstituted or polysubstituted by CN or fluorine,
Z
1
, Z
2
or Z
3
is each, independently of one another, —CO—O—, —O—CO—, —CH
2
O—, —OCH
2
—, —CH
2
CH
2
—, —CH═CH—, —C≡C—, —CF
2
O—, —OCF
2
—, —(CH
2
)
4
— or a single bond,
L
1
to L
6
are each, independently of one another, H or F, where at least one of the radicals L
1
and L
2
is F or L
3
to L
6
are F and the other radical L
1
or L
2
is H or F and the other radicals L
3
to L
6
are H or F,
m is 0 or 1, and
n is 1 or 2,
with the proviso that at least one bridge Z
1
, Z
2
or Z
3
is
The invention furthermore relates to the use of these compounds as components of liquid-crystalline media, and to liquid-crystal and electro-optical display elements which contain the novel liquid crystalline media.
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 compounds of the formula I are distinguished by clearly negative anisotropy of the dielectric constant and are aligned in an electric field with their longitudinal molecular axes perpendicular to the field direction. This effect is known and is utilized to control the optical transparency in various liquid-crystal displays, for example in liquid-crystal cells of the light-scattering type (dynamic scattering), of the DAP (deformation of aligned phases) type, of the ECB (electrically controlled birefringence) type or of the guest-host interaction type.
Compounds of the formula I are furthermore suitable as components of chiral tilted smectic phases. Chiral tilted smectic liquid-crystalline phases having ferroelectric properties can be prepared by adding a suitable chiral dopant to base mixtures having one or more tilted smectic phases (L. A. Veresnev et al., Mol. Cryst. Liq. Cryst. 89, 327 (1982); H. R. Brand et al., J. Physique 44 (lett.), L-771 (1983). Such phases can be used as dielectrics for fast-switching displays based on the principle of SSFLC technology described by Clark and Lagerwall (N. A. Clark and S. T. Lagerwall, Appl. Phys. Lett. 36, 899 (1980); U.S. Pat. No. 4,367,924) on the basis of the ferroelectric properties of the chiral tilted phase.
A number of liquid-crystalline compounds having slightly negative dielectric anisotropy have already been synthesized. By contrast, relatively few liquid-crystal components having highly negative anisotropy of the dielectric constant are known. Moreover, the latter generally have disadvantages, such as, for example, poor solubility in mixtures, high viscosity, high melting points and chemical instability. There is thus a demand for further compounds having negative dielectric anisotropy which allow the properties of mixtures to be further improved for a wide variety of electro-optical applications.
Liquid-crystal compounds having negative dielectric anisotropy which contain two or three rings linked via carboxyl groups or covalent bonds and one or more side groups, such as halogen, cyano or nitro groups, are disclosed in DE 22 40 864, DE 26 13 293, DE 28 35 662, DE 28 36 086, EP 023 728, EP 0 084 194 and EP 0 364 538.
JP 05 070 382 covers, in a broad generic formula, the transmonofluoroethylene compounds claimed here. The prior art thus neither reveals to the person skilled in the art possible syntheses of the claimed compounds having negative dielectric anisotropy in a simple manner nor suggests that the compounds according to the invention have favourably located mesophase ranges and are distinguished by large negative dielectric anisotropy at the same time as low viscosity and have increased low-temperature stability.
The invention had the object of indicating stable, liquid-crystalline or mesogenic compounds having a large negative dielectric anisotropy and at the same time low viscosity and high low-temperature stability, with an unrestricted nematic phase range.
It has been found that the compounds of the formula I are eminently suitable as components of liquid-crystalline phases. In particular, they can be used to prepare stable liquid-crystalline phases having a broad mesophase range and comparatively low viscosity and high low-temperature stability.
The compounds of the formula I are furthermore suitable as components of chiral tilted smectic liquid-crystalline phases.
In addition, the provision of the compounds of the formula I 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 be used as base materials of which liquid-crystalline phases 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 vary the dielectric and/or optical anisotropy and/or the viscosity and/or the spontaneous polarization and/or the phase ranges and/or the tilt angle and/or the pitch of a dielectric of this type.
The compounds of the formula I are furthermore suitable as intermediates in the preparation of other substances which can be used as constituents of liquid-crystalline dielectrics.
In the pure state, the compounds of the formula I are colourless and form liquid-crystalline mesophases in a temperature range which is favourably located for electro-optical use. They are very stable chemically, thermally and to light.
The invention thus relates to the compounds of the formula I. The invention furthermore relates to the use of the compounds of the formula I as components of liquid-crystalline mixtures. The invention furthermore relates to liquid-crystalline phases containing at least one compound of the formula I, and to liquid-crystal display elements containing such phases. The compounds are distinguished, in liquid-crystal mixtures, by the fact that low viscosity and an increase in the low-temperature stability are achieved, with an unrestricted nematic phase range.
In the compounds of the formulae above and below, each R
1
, independently of the others, is preferably straight-chain alkyl, 1E-alkenyl or 3E-alkenyl, and R
2
is preferably straight-chain alkoxy having 1-5 carbon atoms, in particular OCH
3
or OC
2
H
5
, furthermore alkyl having 1-5 carbon atoms, in particular CH
3
or C
2
H
5
.
Preference is furthermore given to compounds of the formulae above and below in which R
1
is alkoxy or oxaalkyl (for example alkoxymethyl).
Z
1
, Z
2
and Z
3
are each, independently of one another, preferably a single bond or a —C
2
H
4
bridge.
The radicals R
1
and R
2
in the formulae above and below preferably have 2-12 carbon atoms, in particular 3-10 carbon atoms. One or two CH
2
groups in R
1
and R
2
may also be replaced. Preferably, only one CH
2
group is replaced, by —O— or —CH═CH—.
In the f

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