Liquid crystalline medium and liquid crystal display

Details Liquid crystalline medium and liquid crystal display Liquid crystalline medium and liquid crystal display

2002-01-16

2004-02-17

Wu, Shean C. (Department: 1756)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

C252S299660, C252S299630

Reexamination Certificate

active

06692796

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to liquid crystalline media and to liquid crystal displays comprising these media, preferably to displays operating in the TN mode and in particular to TN displays addressed by an active matrix.
PROBLEM TO BE SOLVED AND STATE OF THE ART
L
iquid
C
rystal
D
isplays (LCDs) are widely used to display information. Still the most widely used electro-optical mode is the
t
wisted
n
ematic (TN)-mode. Besides this mode also displays using the
s
uper
t
wisted
n
matic (STN)- and the
e
lectrically
c
ontrolled
b
irefringence (ECB)-mode with their various modifications, as well as others. Besides these modes, which all do use an electrical field, which is substantially perpendicular to the substrates, respectively to the liquid crystal layer, there are also electro-optical modes employing an electrical field substantially parallel to the substrates, respectively the liquid crystal layer, like e.g. the
i
n-
p
lane switching (IPS)-mode (as disclosed e.g. in DE 40 00 451 and EP 0 588 568).
A further promising electrooptical mode for LCDs is the
o
ptically
c
ompensated
b
end (OCB) mode. This mode has a favorable small viewing angle dependence of the contrast. Further the response times in this mode are small.
Especially for micro displays operating in the TN-mode, fast switching cells have to be realized. For this task the cell gap preferably is reduced, which in turn requires liquid crystalline media with higher values of the birefringence.
Preferably TN-cells are operated with an optical retardation corresponding the first transmission minimum according to Gooch and Tarry.
Liquid crystal mixtures consisting predominantly or even entirely of terminally cyano substituted biphenyls and terphenyls are as a rule characterized by suitable high &Dgr;&egr; values, but have limited values of &Dgr;n and already are likely to show insufficient stability at low temperatures, i.e. in most cases either formation of a smectic phase and or crystallization. Liquid crystal mixtures using large quantities of halogenated tolane compounds with three phenyl rings, which are almost dielectrically neutral, are disclosed, e.g. in the European Patent Application No. EP 99111782.1 are characterized by comparatively low &Dgr;&egr; values which are not suitable for most applications and often even show severe problems with respect to the stability of the nematic phase at low temperatures.
Thus, there is a significant need for liquid crystal media with suitable properties for practical applications such as a wide nematic phase range, low viscosities, appropriate optical anisotropy &Dgr;&egr; according to the display mode used especially a suitably high &Dgr;n for OCB displays and for composite systems like PDLCs and in particular with suitably large good compatibility with polymer precursors for composite systems.
PRESENT INVENTION
Surprisingly, it now has been found that liquid crystal media with high &Dgr;n especially useful for fast switching TN AMD displays can be realized, which do not exhibit these drawbacks of the materials of the prior art or at least do exhibit them to a significantly lesser degree.
These improved liquid crystal media according to the instant application are realized by comprising at least two components:
a first liquid crystal component (called component A),
comprising compounds of formula I, which are compounds with very high values of &Dgr;n, preferably of 0.15 or more, more preferably 0.15 to 0.80, more preferably 0.20 to 0.60, more preferably of 0.22 or more and most preferably of 0.25 to 0.55.
wherein
R
11
and R
12
are, independently of one another, n-alkyl, n-alkoxy with 1 to 7 C atoms, preferably 2 to 5 C atoms, alkenyl, alkenyloxy or alkoxyalkyl with 2 to 7 C atoms, preferably with 2 to 5 C atoms, preferably alkyl, alkenyl or alkoxy, especially preferred n-alkyl or n-alkoxy,
at least one of
 and the others of
 each, independently of each other, are
 and alternatively
 may also be
one of Z
11
and Z
12
is —C≡C— and the other one, if present, is —C≡C—,—CH
2
O—, —CF
2
O—, —OCF
2
— trans- —CH═CH—, trans- —CF═CF—, —COO— —CH
2
—CH
2
—, —CF
2
—CF
2
— or a single bond, preferably a single bond and
n is 0 or 1,
preferably
 when present, is
 or their mirror images,
and/or preferably
 or their mirror images,
and/or preferably
 or their mirror images,
and simultaneously a second component (component B) comprising one or more dielectrically positive compounds of formula II
wherein
R
2
has the meaning given for R
11
under formula I above,
 each independently have the meaning given for
above under formula I
Z
21
Z
22
are independently of each other —CH
2
CH
2
—, —COO—, trans- CH═CH—, trans- —CF═CF—, —CH
2
O—, —CF
2
O— or a single bond, preferably at least one of them is a single bond, most preferably both are a single bond,
X
2
is, F, Cl, CF
3
, OCF
2
H or OCF
3
, preferably F or OCF
3
, most preferably F and
m is 0, 1 or 2
and optionally a third component (component C) which comprises dielectrically neutral compounds of formula Ill
wherein
R
31
and R
32
each, independently of each other, have the meaning given for R
11
under formula I above,
Z
31
and Z
32
are, independently of each other, —CH
2
CH
2
—, —COO—, —C≡C—, trans- CH≡CH—, trans- —CF═CF—, —CH
2
O—, —CF
2
O— or a single bond, preferably a single bond,
 each independently have the meaning given for
above under formula I
k is 0 or 1
and optionally a fourth component (component D) which comprises dielectrically neutral compounds of formula IV
wherein
R
41
and R
42
independently of each other, have the meaning given above under formula I for R
11
,
Z
4
are, independently of each other, —CH
2
CH
2
—, —COO—, —C≡C— or a single bond, preferably a single bond and
o is 0 or 1.
Preferably the liquid crystalline media according to the instant invention contain a component A comprising, preferably predominantly consisting of and most preferably entirely consisting of compounds of formula I.
Comprising in this application means in the context of compositions that the entity referred to, e.g. the medium or the component, contains the compound or compounds in question, preferably in a total concentration of 10% or more and most preferably of 20% or more.
Predominantly consisting, in this context, means that the entity referred to contains 80% or more, preferably 90% or more and most preferably 95% or more of the compound or compounds in question.
Entirely consisting, in this context, means that the entity referred to contains 98% or more, preferably 99% or more and most preferably 100.0% of the compound or compounds in question.
The compounds of formula I are preferably selected from the group of sub-formulae I-1 to I-7
wherein
R
11
and R
12
have the meaning given under formula I above
Y
11
and Y
2
are, independently of each other, H or F.
In a preferred embodiment the liquid crystalline media according to the instant invention contains a component B comprising, preferably predominantly consisting of and most preferably entirely consisting of compounds of formula II.
The compounds of formula II are preferably selected from the group of sub-formulae II-1 to II-7
wherein
R
2
, X
2
and
 have the respective meanings given under formula II above and preferably
R
2
is n-alkyl or 1-E-alkenyl,
X
2
is F or OCF
3
and
Y
21
, Y
22
and Y
23
are, independently of each other, H or F.
In a further preferred embodiment the liquid crystal medium contains a liquid crystal component C which is preferably predominantly consisting of and most preferably entirely consisting of compounds of formula III
The compounds of formula III are preferably selected from the group of sub-formulae III-1 to III-6
wherein
R
31
, R
32
, Z
31
,
 each have the meaning given for
under formula I above, and preferably
R
31
and R
32
are, independently of each other, n-alkyl, n-alkoxy or 1-E-alkenyl,
Z
31
is —COO—, —CH
2
—CH
2
—, trans- —CH═CH—, trans- —CF═CF—, —CF
2

Affiliated with

Also associated with

Rating

Liquid crystalline medium and liquid crystal display does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Liquid crystalline medium and liquid crystal display, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid crystalline medium and liquid crystal display will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3313675