Acetylene derivatives, and liquid-crystalline medium

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

1999-12-01

2001-10-16

Wu, Shean C. (Department: 1756)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

C252S299610, C252S299630, C549S373000, C549S374000, C549S369000, C570S188000

Reexamination Certificate

active

06303194

ABSTRACT:

The invention relates to novel acetylene derivatives of the formula I
in which
R
1
and R
2
, independently of one another, are H, —CN, —F, —OCHF
2
, —OCF
3
, —OCHFCF
3
, —OCH
2
CF
3
or —OCF
2
—CF
3
, an alkyl radical having 1-12 carbon atoms which is unsubstituted or at least monosubstituted by halogen or CN 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,
X
1
, X
2
,
X
3
and X
4
are each, independently of one another, H or —C≡C—R
3
in the axial position, where at least one of the groups X
1
, X
2
, X
3
and X
4
is not H,
R
3
is H, alkyl having 1 to 8 carbon atoms, Cl, CN, SF
5
or CF
3
,
Q is —CH
2
— or —O—,
Y
1
and Y
2
, independently of one another, are C or Si,
A
1
and A
2
, independently of one another, are an unsubstituted or F- or CN-substituted 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
Z
1
and Z
2
are each, independently of one another, —CO—O—, —O—CO—, —CH
2
O—, —O—, —O—CH
2
—, —CH
2
CH
2
—, —CH═CH—, or a single bond, and
n and m, independently of one another, are 0, 1, 2 or 3, where
m+n is 1, 2, 3 or 4.
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 unfavourable elastic and/or dielectric properties.
The invention had the object of finding 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 amd 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 have an optical anisotropy value &Dgr;n of <0.03, preferably <0.02, which is attributable to a particularly high value of n⊥, 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
Liquid-crystalline media having very small optical anisotropy values are of particular importance for reflective and transmissive applications, i.e. applications in which the particular LCD experiences no or only supportive background illumination. Low values of &Dgr;n are achieved by using substituents X
1
, X
2
, X
3
and/or X
4
having the highest possible polarizability. Owing to the small volume of the substituents X
1
, X
2
, X
3
and/or X
4
groups, the other LC properties, such as clearing point and viscosity, of liquid-crystal mixtures to which the compounds according to the invention are added are only impaired slightly.
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 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.
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, in particular electro-optical display elements, which contain media of this type.
Above and below, n, m, R
1
, R
2
, R
3
, X
1
, X
2
, X
3
, X
4
, Z
1
, Z
2
, A
1
, A
2
, Q, Y
1
and Y
2
are as defined above, unless expressly stated otherwise. If the radical X
1
occurs more than once, it can have the same or different meanings. The same applies to all other groups which occur more than once.
For reasons of simplicity, Cyc below denotes a cyclohexane-1,4-diyl radical or a 1- or 4-silacyclohexane-1,4-diyl radical, Dio denotes a 1,3-dioxane-2,5-diyl radical, Dit denotes a 1,3-dithiane-2,5-diyl radical, and Bi denotes a bicyclo[2.2.2]octylene radical, where Cyc may be unsubstituted or mono- or polysubstituted by F or CN.
W denotes the following structural unit:
in which X
1
, X
2
, X
3
, X
4
, Q, Y
1
, Y
2
and Z
2
are as defined above, and p is 0, 1, 2 or 3.
Preferred meanings of the group W are given by the sub-formulae W1 to W7:
in which Z
2
and R
3
are as defined above.
The formula I covers the preferred compounds of the sub-formulae Ia1 to Ia12, which, besides the group W, contain a six-membered ring:
R
1
—W-Cyc-R
2
Ia1
R
1
—W—CH
2
CH
2
-Cyc-R
2
Ia2
R
1
—W—COO-Cyc-R
2
Ia3
R
1
—W-Dio-R
2
Ia4
R
1
—W—CH
2
CH
2
-Dio-R
2
Ia5
R
1
—W—COO-Dio-R
2
Ia6
R
1
-Cyc-W—R
2
Ia7
R
1
-Dio-W—R
2
Ia8
R
1
-Cyc-CH
2
CH
2
—W—R
2
Ia9
R
1
-Dio-CH
2
CH
2
—W—R
2
Ia10
R
1
-Cyc-COO—W—R
2
Ia11
R
1
-Dio-COO—W—R
2
Ia12
furthermore the likewise preferred compounds of the sub-formulae Ib1 to Ib72, which, in addition to the group W, contain two six-membered rings:
R
1
-Cyc-Cyc-W-R
2
Ib1 
R
1
-Dio-Cyc-W-R
2
Ib2 
R
1
-Cyc-CH
2
CH
2
-Cyc-W-R
2
Ib3 
R
1
-Dio-CH
2
CH
2
-Cyc-W-R
2
Ib4 
R
1
-Cyc-COO-Cyc-W-R
2
Ib5 
R
1
-Dio-COO-Cyc-W-R
2
Ib6 
R
1
-Cyc-Dio-W-R
2
Ib7 
R
1
-Dio-Dio-W-R
2
Ib8 
R
1
-Cyc-CH
2
CH
2
-Dio-W-R
2
Ib9 
R
1
-Dio-CH
2
CH
2
-Dio-W-R
2
Ib10
R
1
-Cyc-COO-Dio-W-R
2
Ib11
R
1
-Dio-COO-Dio-W-R
2
Ib12
R
1
-Cyc-Cyc-CH
2
CH
2
-W-R
2
Ib13
R
1
-Dio-Cyc-CH
2
CH
2
-W-R
2
Ib14
R
1
-Cyc-Dio-CH
2
CH
2
-W-R
2
Ib15
R
1
-Dio-Dio-CH
2
CH
2
-W-R
2
Ib16
R
1
-Cyc-Cyc-COO-W-R
2
Ib17
R
1
-Dio-Cyc-COO-W-R
2
Ib18
R
1
-Cyc-Dio-COO-W-R
2
Ib19
R
1
-Dio-Dio-COO-W-R
2
Ib20
R
1
-Cyc-W-Cyc-R
2
Ib21
R
1
-Dio-W-Cyc-R
2
Ib22
R
1
-Cyc-CH
2
CH
2
-W-Cyc-R
2
Ib23
R
1
-Dio-CH
2
CH
2
-W-Cyc-R
2
Ib24
R
1
-Cyc-COO-W-Cyc-R
2
Ib25
R
1
-Dio-COO-W-Cyc-R
2
Ib26
R
1
-Cyc-W-CH
2
CH
2
-Cyc-R
2
Ib

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