Stock material or miscellaneous articles – Liquid crystal optical display having layer of specified...
Reexamination Certificate
2001-04-18
2004-07-13
Wu, Shean C. (Department: 1756)
Stock material or miscellaneous articles
Liquid crystal optical display having layer of specified...
C252S299630, C252S299660, C252S299670, C252S299610
Reexamination Certificate
active
06761938
ABSTRACT:
The invention relates to an electro-optical liquid-crystal display having a realignment layer, for realigning the liquid crystals, whose field has a component parallel to the liquid-crystal layer which is crucial for the realignment, containing a liquid-crystalline medium of positive dielectric anisotropy, where the medium comprises at least one mesogenic compound of the formula I
wherein
R
1
is H, alkyl or alkoxy having 1 to 7 carbon atoms or alkenyl, alkenyloxy or alkoxyalkyl having 2 to 7 carbon atoms, and
Y
11
, Y
12
and Y
13
are each, independently of one another, H or F.
In conventional liquid-crystal displays (TN, STN, OMI AMD-TN), the electric fields for the realignment are generated essentially perpendicular to the liquid-crystal layer.
International Patent Application WO 91/10936 discloses a liquid-crystal display in which the electric signals are generated in such a way that the electric fields have a significant component parallel to the liquid-crystal layer (IPS, in-plane switching). The principles of operation of a display of this type are described, for example, by R. A. Soref in Journal of Applied Physics, Vol. 45, No. 12, pp. 5466-5468 (1974).
For example, EP 0 588 568 discloses various possibilities for designing the electrodes and for addressing a display of this type. DE 198 24 137 likewise describes various embodiments of IPS displays of this type.
Liquid-crystalline materials for use in IPS displays of this type are described, for example, in DE 198 48 181.
IPS displays containing the known liquid-crystalline media are characterized by inadequately long response times and often by excessively high operating voltages. There is thus a need for IPS displays which do not have these disadvantages, or only do so to a reduced extent. Liquid-crystalline materials required for this purpose are in particular those which, in addition to an adequate phase range, a low crystallization tendency at low temperatures, a low birefringence and an adequate electrical resistance, in particular have low threshold voltages (V
10
) and low rotational viiscosities (&ggr;
1
) which are crucial for the response times.
Surprisingly, this object has been achieved by using liquid-crystalline materials which comprise at least one compound of the formula I.
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.
The IPS mixtures according to the invention are notable for their relatively high clearing points, their low rotational viscosities and their low thresholds.
The invention thus relates to an electro-optical liquid-crystal display having a realignment layer, for realigning the liquid crystals, whose field has a significant component parallel to the liquid-crystal layer, containing a liquid-crystalline medium of positive dielectric anisotropy, where the medium comprises at least one compound of the formula I
in which
R
1
is alkyl or alkoxy having 1 to 7 carbon atoms, preferably n-alkyl or n-alkoxy, particularly preferably having 1 to 5 carbon atoms, or alkenyl, alkenyloxy or alkoxyalkyl having 2 to 7 carbon atoms, preferably 1E-alkenyl, 1E-alkenyloxy or straight-chain alkoxylalkyl, particularly preferably having 2 to 5 carbon atoms and
Y
11
, Y
12
and Y
13
are each, independently of one another, H or F.
Particular preference is given to liquid-crystal displays containing a liquid-crystal medium which comprises at least one compound of the formula I in which at least one of the radicals Y
11
to Y
13
is F. Very particular preference is given to such liquid-crystal displays containing a liquid-crystal medium which comprises at least one compound of the formula I in which at least one of the radicals Y
11
and Y
12
is F.
The liquid-crystal displays preferably contain liquid-crystal media which comprise at least one compound selected from the group consisting of the compounds of the formulae Ia to If
Particular preference is given to compounds selected from the group consisting of the compounds of the subformulae Ic, Ie and If, very particularly preferably of the subformulae Ic and If.
Preference is furthermore given to liquid-crystal displays containing a liquid-crystalline medium which comprises one or more compound(s) of the formula II
in which
R
2
is alkyl or alkoxy having 1 to 7 carbon atoms or alkenyl, alkenyloxy or alkoxyalkyl having 2 to 7 carbon atoms,
are each, independently of one another,
X
2
is F, Cl, CN or NCS, and
Z
2
is CH
2
CH
2
, COO, CF
2
O or a single bond,
with the proviso that compounds of the formula I are excluded.
Particular preference is given to compounds of the formula II in which
Preference is furthermore given to compounds of the formula II in which
Preference is furthermore given to compounds of the formula II in which X
2
is CN.
Preference is furthermore given to liquid-crystal displays in which the liquid-crystalline medium comprises one or more compound(s) of the formula III
in which
R
31
and R
32
are each, independently of one another, alkyl or alkoxy having 1 to 7 carbon atoms or alkenyl, alkenyloxy or alkoxyalkyl having 2 to 7 carbon atoms,
are each, independently of one another,
Z
31
is CH═CH, COO, CH
2
CH
2
or a single bond.
Particular preference is given to compounds of the formula III in which at least one of the radicals R
31
and R
32
is alkenyl having 2 to 7 carbon atoms, preferably 2 or 3 carbon atoms.
Preference is furthermore given to compounds of the formula III in which Z
31
is CH═CH or a single bond.
Preference is furthermore given to compounds of the formula III in which
at least one of
particularly preferably both are
Preference is furthermore given to liquid-crystal displays in which the liquid-crystalline medium comprises one or more compounds of the formula IV
in which
R
4
is alkyl or alkoxy having 1 to 7 carbon atoms or alkenyl, alkenyloxy or alkoxyalkyl having 2 to 7 carbon atoms,
and are each, independently of one another,
Z
41
and Z
42
are each, independently of one another, CF
2
O, COO, CH
2
CH
2
, CF═CF, CH═CH, CF═CH, CH═CF or a single bond,
n is 0 or 1,
X is OCF
3
, OCF
2
H or F,
and
Y
41
and Y
42
are each, independently of one another, H or F.
Particular preference is given to compounds of the formula IV in which at least one of
Preference is furthermore given to compounds of the formula IV in which Z
41
and Z
42
are each, independently of one another, CH
2
CH
2
or a single bond.
Preference is furthermore given to compounds of the formula IV in which X is OCF
3
and Y
41
and Y
42
are H, and to compounds of the formula IV in which X is F and Y
41
and Y
42
are F.
Particular preference is given to media which comprise at least one compound of the formula I and at least one compound of the formula II.
Particular preference is given to liquid-crystal displays in which the liquid-crystalline medium comprises one or more compound(s) of the formula II selected from the group consisting of the subformulae IIa to IIe.
in which R
2
is as defined above under formula II.
The liquid-crystal display particularly preferably contains a liquid-crystalline medium comprising one or more compound(s) selected from the group consisting of compounds of the subformulae IIa, IIc, IId, IIe and IIf, in particular IIe and IIf.
Preference is furthermore given to liquid-crystal displays in which the liquid-crystalline medium comprises one or more compound(s) of the formula III selected from the group consisting of the subformulae IIIa to IIIc.
where
k is 1, 2, 3, 4 or 5,
m and n are each, independently of one another, 0, 1, 2 or 3, and m+n≦5, and
o is 0 or 1.
Preference is furthermore given to liquid-crystal displays in which the liquid-crystalline medium comprises one or more compound(s) of the formula IV selected from the group consisting of the subformulae IVa to IVo.
in which R
4
is as defined above under formula IV.
Preference is furthermore given to liquid-crystal displays in which the liquid-crystalline medium comprises one or more compounds) of the
Heckmeier Michael
Reiffenrath Volker
Reuter Marcus
Merck Patent GmbH
Millen, White, Zelano, Branogan, P.C.
Wu Shean C.
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