Liquid crystalline medium and liquid crystal display

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

2002-01-18

2004-02-24

Wu, Shean (Department: 1756)

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

C252S299610, C252S299660

Reexamination Certificate

active

06695979

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to liquid crystalline media comprising a first dielectrically positive component (component A) comprising one or more compounds of formula I, which have high values of &Dgr;n
wherein
R
1
is n-alkyl, n-alkoxy with 1 to 7 C-atoms, alkenyl, alkenyloxy or alkoxyalkyl with 2 to 7 C-atoms,
X
1
is F, Cl, CF
3
, OCF
3
or OCF
2
H and
one of Y
11
, Y
12
, Y
13
, Y
14
, Y
15
and Y
16
is F and the others are independently of each other H or F, and
simultaneously
a second dielectrically positive component (component B) comprising one or more compounds of formula II
wherein
R
2
is n-alkyl, n-alkoxy with 1 to 7 C-atoms, alkenyl, alkenyloxy or alkoxyalkyl with 2 to 7 C-atoms,
X
2
is F, Cl, CF
3
, OCF
3
or OCF
2
H and
Y
2
H or F,
to the use of these media especially in liquid crystal displays and to LCDs comprising these media, preferably to displays of the TN mode and in particular to displays addressed by an active matrix.
PROBLEM TO BE SOLVED AND STATE OF THE ART
Liquid Crystal Displays (LCDs) are widely used to display information. They are used for direct view displays, as well as for projection type displays. Probably the most widely employed electro-optical mode still is the twisted nematic (TN)-mode. Besides this mode also other modes are already used or being investigated. Amongst the effects widely used are e.g. the super twisted nematic (STN)-effect, which is used for directly driven displays and the electrically controlled birefringence (ECB)-mode, also called vertically aligned nematic (VAN)-mode, which is used in active matrix addressed displays (AMDs), as well as their modifications. The TN-mode is beneficially used both in directly addressed displays and in AMDs.
A promising electrooptical mode for LCDs is the optically compensated bend (OCB) mode. This mode has a favorable small viewing angle dependence of the contrast. Further the response times in this mode are small.
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 in-plane switching (IPS)-mode (as disclosed e.g. in DE 40 00 451 and EP 0 588 568).
For TN-AMDs liquid crystalline media with an excellent resistivity are required. For direct view TN-AMDs with small cell gaps, as well as for reflective TN-AMDs with very small cell gaps, liquid crystalline media with higher birefringence (&Dgr;n) are required compared to commonly used direct view TN-AMDs with cell gaps of about 4 to 5 &mgr;m, operating in the first transmission minimum according to Gooch and Tarry. Especially for modern TFT driven displays with polycrystalline silicon as the active medium such media with elevated &Dgr;n are required.
Liquid crystalline media containing compounds of formula I are known from DE 195 29 106. These media, however, are characterized by a low birefringence and have a rather high threshold voltage. Liquid crystalline media containing compounds of formula II with a terminal Cl atom are known from U.S. Pat. No. 5,328,644. These media, however, are characterized by a high birefringence.
Similar media are disclosed in JP 06-264 059 (A).
Thus, there is a significant need for liquid crystalline media with suitable properties for practical applications such as a wide nematic phase range, low viscosities, especially low rotational viscosities, appropriate optical anisotropy &Dgr;n according to the display mode used especially a suitably high &Dgr;n for TN-AMDs with small cell gaps.
PRESENT INVENTION
Surprisingly, it now has been found that liquid crystal media with suitable &Dgr;n especially useful for TN-AMDs can be realized which do not exhibit the 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 invention are realized by using at least two components:
a first dielectrically positive liquid crystal component (called component A), comprising compounds of formula I, which are strongly dielectrically positive compounds with high values of &Dgr;n
wherein
R
1
is 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,
X
1
is F, Cl, CF
3
, OCF
3
or OCF
2
H, preferably F or Cl, most preferably F and
one of Y
11
, Y
12
, Y
13
, Y
14
, Y
15
and Y
16
is F and the others are, independently of each other, H or F, preferably at least one of the others is F
and simultaneously a second dielectrically positive component (component B) comprising one or more compounds of formula II
wherein
R
2
is 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,
X
2
is F, Cl, CF
3
, OCF
3
or OCF
2
H, preferably F or Cl, most preferably F and
Y
2
H or F, preferably F.
In a preferred embodiment, the liquid crystalline media according to the present invention comprise a further dielectrically positive component (called component C) which is comprising dielectrically positive compounds of formula III
wherein
R
31
and R
32
independently of each other, have the meaning given for R
1
under formula I above,
Z
31
and Z
32
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, if both are present, preferably at least one of them is a single bond,
 or their mirror images,
X
3
is F, Cl, halogenated alkyl, halogenated alkenyl or halogenated alkoxy, each having 1 to 6 C atoms, preferably F, Cl, OCF
3
or OCF
2
H and
n is 0 or 1,
preferably
Z
31
and Z
32
Z are, independently of each other, —CH
2
CH
2
—, —COO—, trans- CH═CH—, —CF
2
O— or a single bond, if both are present, preferably at least one of them is a single bond,
and/or preferably
and/or preferably
In yet a further preferred embodiment, the liquid crystalline media according to the present invention additionally comprise a dielectrically neutral component (called component D) which is comprising dielectrically neutral compounds of formula IV
wherein
R
41
and R
42
independently of each other, have the meaning given for R
1
under formula I above,
Z
41
and Z
42
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, if both are present, preferably at least one of them is a single bond,
 each have the meaning given for
 above under formula I and
m is 0, 1 or 2.
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, one or more 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-3
wherein
R
1
and X
1
have the respective meanings given under formula I above.
Especially preferred are media comprising compounds selected from the group of sub-formulae I-1a, I-1b, I-2a and I-2b
wherein
R
1
has the meaning given under formula I above.
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 cons

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-3329832