Compositions – Liquid crystal compositions – Containing nonsteryl liquid crystalline compound of...
Reexamination Certificate
1999-12-03
2001-03-20
Lambkin, Deborah C. (Department: 1613)
Compositions
Liquid crystal compositions
Containing nonsteryl liquid crystalline compound of...
C252S299630, C349S182000, C349S193000, C556S009000, C585S534000
Reexamination Certificate
active
06203724
ABSTRACT:
SUMMARY OF THE INVENTION
The invention relates to novel cyclohexane derivatives of the formula I
in which
B and B
1
, independently of one another, are
where the rings B and B
1
are each bonded to the group (X)
p
via the axial bond, and, in addition, one or two non-adjacent CH
2
groups in these rings may be replaced by O,
Y, independently of one another if it occurs more than once, is C or Si,
Q and Q
1
, independently of one another, are CH or SiH,
X, independently of one another if it occurs more than once, is —C≡C—, —CH═CH—, —CF═CF—, —CF═CH—, —CH
2
—, —COO— or 1,4-phenylene, in which, in addition, one or more CH groups may, independently of one another, be replaced by N or CF,
p is 1, 2, 3 or 4,
R, R
1
, R
2
, R
3
and R
4
, independently of one another, are H, an alkyl radical having 1-12 carbon atoms which is unsubstituted or at least monosubstituted by halogen and in which, in addition, one or more CH
2
groups may each, independently of one another, be replaced by —O—, —S—, —CO—,
—CO—O—, —O—CO—, —O—CO—O— or —CH═CH— in such a way that heteroatoms are not connected directly, or are —CN, —F, —CF
3
, —OCHF
2
, —OCF
3
, —OCHFCF
3
, —OCH
2
CF
3
, —OCF
2
—CF
3
or —CH═CF
2
,
A, A
1
, A
2
and A
3
, independently of one another, are
or 1,4-phenylene in which one or more CH groups are replaced by N, where the rings A, A
1
, A
2
and A
3
, independently of one another, may be substituted by one or more F atoms or —NCS, —CN, —CF
3
or —OCF
3
,
Z, Z
1
, Z
2
, and Z
3
are each, independently of one another, —CO—O—, —O—CO—, —CH
2
O—, —CH═CH—, —O—, —O—CH
2
—, —CH
2
CH
2
—, —(CH
2
)
3
—, —(CH
2
)
4
—, —CF
2
—CF
2
—, —OCF
2
— or a single bond, and
n, m, r and s, independently of one another, are 0, 1 or 2.
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 frequently have a small positive or negative value of the dielectric anisotropy and 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.
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 invention this provides novel, stable, liquid-crystalline or mesogenic compounds of particularly low optical anisotropy &Dgr;n and negative or positive dielectric anisotropy which are suitable as components of liquid-crystalline media, in particular for TFT and STN displays.
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. The compounds of the formula I preferably have an optical anisotropy value &Dgr;n of <0.05, particularly preferably <0.03, which is attributable to a particularly high value of n
195
, at a reduced temperature of 0.9 and a wavelength of 589 nm. The reduced temperature here is defined as follows:
measurement
temperature
in
K
clearing
point
temperature
in
K
=
reduced
temperature
Small values of An are achieved in accordance with the invention by the group (X)
p
being perpendicular to the longitudinal axis of the molecule through its axial position. The resultant increased polarizability transverse to this axis results in an increased n
⊥
. With &Dgr;n=n
∥
−n
⊥
(for example L. Pohl, U. Finkenzeller, in Liquid Crystals, Vol. 1, 152, Ed. B. Bahadur, World Scientific, 1990), small values of the optical anisotropy thus arise.
Liquid-crystalline media having very small optical anisotropy values are of particular importance for reflective and transflective applications, i.e. applications in which the particular LCD experiences no or only supportive background illumination.
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 compounds of the formula I to liquid-crystalline base materials from other classes of compound 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.
Addition of compounds of the formula I to liquid-crystalline dielectrics allows the &Dgr;n values of such media to be considerably reduced.
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 form, the compounds of the formula I are also suitable as chiral dopants and in general for producing chiral mesophases.
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.
At a decreasing wavelength of light, the values of n
∥
of conventional calamitic liquid crystals increase more strongly than the values of n
⊥
and, since &Dgr;n=n
∥
−n
⊥
, an increase of &Dgr;n results.
In contrast to these conventional lc-materials, the n
∥
and n
⊥
values of compounds of the present invention exhibit an unusual frequency dependence:
At decreasing wavelength, the values of n
⊥
of the compounds of formula I increase more strongly than the values of n
∥
. Thus, a decrease of &Dgr;n results.
Preferred compounds of the formula I display very low values of &Dgr;n measured under usual conditions (20° C., 598 nm). At certain wavelengths n
∥
and n
⊥
of these compounds adopt the same value (&Dgr;n=0, see example 266). At even shorter wavelengths n
⊥
is larger than n
∥
and &Dgr;n is negative. Thus, dependent on the wavelength of the light used, the inventive compounds exhibit an inversion of &Dgr;n.
The inventive compounds are therefore preferably suitable for the compensation of the frequency dependence of &Dgr;n in conventional liquid crystalline mixtures.
Furthermore, these compounds can be used for the production of optical switches or filters, which remove only certain wavelengths of light reaching them.
The compounds of the formula I can be converted into liquid-crystalline polymers through elevated temperature or use of UV 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 comprising at least one compound of the formula I, and to liquid-crystal display elements, optical switches or filters, in particular electro-optical display elements, which contain media of this type.
Above and below, B, B
1
, R, R
1
, R
2
, R
3
, R
4
, A, A
1
, A
2
, A
3
, X, p, Z, Z
1
, Z
2
, Z
3
, Q, Q
1
, Y, n, m, r and s are as defined above, unless expressly stated otherwise. If the radical X occurs more than once, it can have the same or different meanings. The same applies to all othe
Bremer Matthias
Heckmeier Michael
Reiffenrath Volker
Lambkin Deborah C.
Merck Patent Gesellschaft mit beschrankter Haftung
Millen White Zelano & Branigan P.C.
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