JP2024541860A - Liquid crystal medium - Google Patents

Abstract

A liquid-crystalline medium is provided.
[Solution] The present invention relates to a liquid-crystalline medium as defined in claim 1 which comprises a) one or more compounds of formula I, b) one or more compounds selected from the group of formulae IIA, IIB, IIC and IID and c) one or more compounds of formula III and has negative dielectric anisotropy, and to the use of this LC medium which is beneficial for optical, electro-optical and electronic purposes, in particular for enabling energy-saving LC displays of the VA, IPS or FFS type.

[Selection diagram] None

Description

The present invention relates to liquid crystal (LC) media with negative dielectric anisotropy and their use for optical, electro-optical and electronic purposes, for example in LC displays.

One of the liquid crystal display (LCD) modes currently in use is the TN ("twisted nematic") mode. However, TN LCDs have the disadvantage that their contrast is strongly dependent on the viewing angle.

In addition, so-called VA ("vertically aligned") displays are known which have wider viewing angles. The LC cell of a VA display comprises a layer of an LC medium between two transparent electrodes, where the LC medium usually has negative dielectric anisotropy. In the switched-off state the molecules of the LC layer are aligned perpendicular to the electrode surfaces (homeotropic) or have a tilted homeotropic alignment. When a voltage is applied to the two electrodes a reorientation of the LC molecules occurs parallel to the electrode surfaces.

Also known are so-called IPS ("in-plane switching") displays which have an LC layer between two substrates, in which two electrodes are arranged on only one of the two substrates, preferably with an interdigitated comb structure. When a voltage is applied to the electrodes, this creates an electric field between the electrodes which has a significant component parallel to the LC layer. This leads to a reorientation of the LC molecules in the layer plane.

Furthermore, so-called FFS ("fringe-field switching") displays have been reported (see in particular S.H. Jung et al., Jpn. J. Appl. Phys., Vol. 43, No. 3, 2004, p. 1028 (Non-Patent Document 1)), which have two electrodes on the same substrate, one of which is comb-structured and the other unstructured. This results in a strong so-called "fringe field", i.e. a strong electric field close to the electrode edges, which leads to an electric field across the cell with both a strong vertical component and a strong horizontal component. FFS displays have a low viewing angle dependence of the contrast. FFS displays usually contain an LC medium with positive dielectric anisotropy and an alignment layer, usually a polyimide alignment layer, which provides a planar alignment for the molecules of the LC medium.

FFS displays can be operated as active matrix displays or passive matrix displays. In the case of active matrix displays, the individual pixels are typically addressed by integrated non-linear active elements, such as transistors (e.g. thin-film transistors ("TFTs")), whereas in the case of passive matrix displays, the individual pixels are typically addressed by multiplexing methods known from the prior art.

Further, FFS displays have been disclosed that have electrode designs and layer thicknesses similar to those of FFS displays, but with LC medium layers with negative dielectric anisotropy instead of LC medium layers with positive dielectric anisotropy (see, for example, S.H. Lee et al., Appl. Phys. Lett. vol. 73 (no. 20), 1998, pp. 2882-2883 (Non-Patent Document 2); S.H. Lee et al., Liquid Crystals vol. 39 (no. 9), 2012, pp. 1141-1148 (Non-Patent Document 3)). LC media with negative dielectric anisotropy exhibit more favorable director alignment with smaller tilt and higher twist alignment than LC media with positive dielectric anisotropy, and as a result these displays have higher transmittance. The display further comprises an alignment layer, preferably a polyimide alignment layer on at least one of the substrates, which is in contact with the LC medium and induces planar alignment of the LC molecules of the LC medium. These displays are also known as "Ultra Brightness FFS" (UB-FFS) mode displays. These displays require a highly reliable LC medium.

In more recent types of VA displays, the uniform alignment of the LC molecules is restricted to relatively small domains within the LC cell. Disclinations may exist between these domains, also known as tilt domains. VA displays with tilt domains have larger contrast-independent viewing angles and grey levels compared to conventional VA displays. In addition, this type of display is easier to manufacture and further treatment of the electrode surface, for example by rubbing, to achieve a uniform alignment of the molecules in the switched-on state is no longer necessary. Instead, the preferred direction of the tilt or pretilt angle is controlled by a special design of the electrodes.

In so-called MVA ("multi-domain vertical alignment") displays, this is usually achieved by electrodes with protrusions, which cause a local pretilt. As a result, the LC molecules are aligned parallel to the electrode surface in different directions and in different defined areas of the cell upon application of a voltage. This achieves a "controlled" switch and prevents the formation of interfering disclination lines. This arrangement improves the viewing angle of the display, but results in a reduced transparency to light. A further development of MVA uses protrusions only on one electrode side, while the opposite electrode has slits, which improves the transparency to light. The slitted electrode generates a non-uniform electric field in the LC cell upon application of a voltage, which means that controlled switching is still achieved. The spacing between the slits and the protrusions can be increased to further improve the transparency to light, but this in turn results in a longer response time. In so-called PVA ("patterned VA") displays, the protrusions are completely redundant in that both electrodes are structured with slits on the opposite side, which results in increased contrast and improved transmission to light, but is technically difficult and makes the display more sensitive to mechanical influences (such as "tapping"). However, for many applications, such as monitors and especially television screens, shorter response times and improvements in the contrast and brightness (transmission) of the display are required.

A further development are the so-called PS ("polymer sustained") or PSA ("polymer sustained alignment") type displays, for which the term "polymer stabilized" is also sometimes used. In these displays, small amounts (e.g. 0.3% by weight, typically less than 1% by mass) of one or more polymerizable compound(s), preferably polymerizable monomeric compound(s), are added to the LC medium, which is polymerized or crosslinked in situ after filling the display with the LC medium, usually by UV photopolymerization, optionally with the application of a voltage to the electrodes of the display. The polymerization is carried out at a temperature at which the LC medium exhibits a liquid crystal phase, usually at room temperature. The addition of polymerizable mesogens or liquid crystal compounds, also known as reactive mesogens or "RMs", to the LC mixture has proven to be particularly suitable.

On the other hand, the PS(A) principle is used in various conventional LC display modes. Thus, for example, PS-VA, PS-OCB, PS-IPS, PS-FFS, PS-UB-FFS and PS-TN displays are known. Polymerization of the RM is preferably carried out with applied voltage in the case of PS-VA and PS-OCB displays, and with or without applied voltage, preferably without applied charge, in the case of PS-IPS displays. As can be demonstrated in test cells, the PS(A) method results in a pretilt in the cell. In the case of PS-VA displays, the pretilt has a positive effect on the response time. For PS-VA displays, standard MVA or PVA pixel and electrode layouts can be used. In addition, however, it is also possible to make do without protrusions, for example with only one electrode side structured, which significantly simplifies production and at the same time results in very good contrast and at the same time very good transparency to light.

PS-VA displays are described, for example, in EP 1170626 A1, U.S. Pat. No. 6,861,107 B1, U.S. Pat. No. 7,169,449 B1, U.S. Pat. No. 2004/0191428 B1, U.S. Pat. No. 2006/0066793 B1 and U.S. Pat. No. 2006/0103804 B1. PS-OCB displays are described, for example, in T.-J-Chen et al., Jpn. J. Appl. Phys. Vol. 45, 2006, pp. 2702-2704 (Non-Patent Document 4) and S. H. Kim, L.-C-Chien, Jpn. J. Appl. Phys. 43, 2004, pp. 7643-7647 (Non-Patent Document 5). PS-IPS displays are described, for example, in U.S. Pat. No. 6,177,972 (Patent Document 7) and Appl. Phys. Lett. 1999, vol. 75 (no. 21), p. 3264 (Non-Patent Document 6). PS-TN displays are described, for example, in Optics Express 2004, vol. 12 (no. 7), p. 1221 (Non-Patent Document 7).

PSA displays typically have an alignment layer on one or both of the substrates forming the display cell below the layer formed by the phase-separated and polymerized RM that induces the pretilt angle described above, which provides an initial alignment of the LC molecules before the polymer stabilization step. The alignment layer is usually applied on the electrodes (if such electrodes are present) so as to be in contact with the LC medium and induce an initial alignment of the LC molecules. The alignment layer may for example comprise or consist of polyimide and may be rubbed or prepared by photoalignment methods.

Like the conventional LC displays described above, PSA displays can be operated as active-matrix or passive-matrix displays. In the case of active-matrix displays, the individual pixels are typically addressed by integrated nonlinear active elements, such as transistors (e.g. thin-film transistors ("TFTs")), whereas in the case of passive-matrix displays, the individual pixels are typically addressed by multiplexing methods as known from the prior art.

Especially for monitor and especially television applications, there is a continuing demand for optimisation of the response time but also the contrast and brightness (and therefore also the transmission) of LC displays. Here the PSA method can offer significant advantages: in the case of PS-VA, PS-IPS and PS-FFS displays in particular, a reduction in the response time, which correlates with the pretilt measurable in test cells, can be achieved without any significant adverse effect on the other parameters.

Another problem observed in the prior art was that the use of conventional LC media in LC displays, including but not limited to PSA type displays, often resulted in mura in the display, especially when the LC media was filled into display cells manufactured using the one drop filling (ODF) method. This phenomenon is also known as "ODF mura". It would therefore be desirable to provide an LC medium that leads to reduced ODF mura.

Another problem observed in the prior art is that LC media for use in displays, including but not limited to PSA type displays, often exhibit high viscosity and, as a result, high switching times. To reduce the viscosity and switching time of the LC medium, it has been suggested in the prior art to add LC compounds with alkenyl groups. However, it has been observed that LC media containing alkenyl compounds often exhibit reduced reliability and stability as well as a reduced VHR, especially after exposure to UV radiation. In particular, since the photopolymerization of RMs in PSA displays is usually carried out by exposure to UV radiation, this can cause a reduction in the VHR in the LC medium, which is quite disadvantageous for use in PSA displays.

Especially from the perspective of mobile devices, there is a great demand for displays with high transmittance, which will require less backlighting and therefore longer battery life. In return, of course, this allows for brighter displays with improved contrast, especially under ambient light.

In addition, there is a great demand for displays and LC media for use in such displays that enable a large operating temperature range as well as high resistivity, short response times even at low temperatures, and low threshold voltages, low pretilt angles, a large number of grey levels, high contrast and wide viewing angles, high reliability and high values for VHR after UV exposure, and, in the case of polymerizable compounds, low melting points and high solubility in LC host mixtures. For PSA displays for mobile applications, it is particularly desirable to have available LC media that exhibit low threshold voltages and high birefringence.

European Patent Application Publication No. 1170626 U.S. Pat. No. 6,861,107 U.S. Pat. No. 7,169,449 US Patent Application Publication No. 2004/0191428 US Patent Application Publication No. 2006/0066793 US Patent Application Publication No. 2006/0103804 U.S. Pat. No. 6,177,972

S. H. Jung et al., Jpn. J. Appl. Phys. , Volume 43, Issue 3, 2004, Page 1028 S. H. Lee et al., Appl. Phys. Lett. Volume 73 (No. 20), 1998, pp. 2882-2883 S. H. Lee et al., Liquid Crystals Volume 39 (No. 9), 2012, pp. 1141-1148 T. - J-Chen et al., Jpn. J. Appl. Phys. Volume 45, 2006, pp. 2702-2704 S. H. Kim, L. -C-Chien, Jpn. J. Appl. Phys. Volume 43, 2004, pp. 7643-7647 Appl. Phys. Lett. 1999, Volume 75 (No. 21), Page 3264 Optics Express 2004, Volume 12 (No. 7), Page 1221

The present invention is based on the object of providing new suitable LC media for use in displays, which may contain reactive mesogens (RM) and which do not have, or have to a reduced extent, the disadvantages indicated above.

In particular, the invention is based on the objective of an LC medium which allows displays having high transmittance and at the same time very high resistivity values, high VHR values, high reliability, low threshold voltage, short response times, high birefringence, reducing or preventing the occurrence of "image sticking" and "ODF mura" in the display, and in the case of media containing RMs, allows a fast polymerization which is as rapid and complete as possible and shows high solubility of the RM in the LC medium used as a host mixture in PSA displays.

These objects have been achieved according to the present invention by the materials and methods described in this application. It has been particularly surprising to find that the above-mentioned advantageous effects can be achieved by using a liquid crystal host as described below.

The present invention relates to a liquid crystal medium comprising a) one or more compounds of formula I, b) one or more compounds selected from the group of formulae IIA, IIB, IIC and IID, c) one or more compounds of formula III and d) optionally a reactive mesogen.

In the formula,
^R1 represents n-butyl or n-pentyl.

－Ｃ≡Ｃ－、－ＣＦ_２Ｏ－、－ＯＣＦ_２－、－ＯＣ－Ｏ－または－Ｏ－ＣＯ－で置き換えられてよく、
Ｌ^１およびＬ^２は、それぞれ互いに独立に、Ｆ、Ｃｌ、ＣＦ_３またはＣＨＦ_２を表し、
Ｙは、Ｈ、Ｆ、Ｃｌ、ＣＦ_３、ＣＨＦ_２またはＣＨ_３を表し、
Ｚ^２、Ｚ^２ＢおよびＺ^２Ｄは、それぞれ互いに独立に、単結合、－ＣＨ_２ＣＨ_２－、－ＣＨ＝ＣＨ－、－ＣＦ_２－ＣＦ_２－、－ＣＦ＝ＣＦ－、－ＣＦ_２Ｏ－、－ＯＣＦ_２－、－ＣＨ_２Ｏ－、－ＯＣＨ_２－、－ＣＯＯ－、－ＯＣＯ－を表し、
ｐは、０、１または２を表し、
ｑは、０または１を表し、および
ｖは、１、２、３、４、５または６を表す。 In the formula,
R ^2A , R ^2B , R ^2C and R ^2D each independently represent H, an alkyl group having 1 to 7 C atoms or an alkenyl group having 2 to 7 C atoms, each of which is unsubstituted or at least monosubstituted with a halogen, provided that one or more CH ₂ groups in these groups are -O-, -S-, ...

may be replaced by —C≡C—, —CF ₂ O—, —OCF ₂ —, —OC—O— or —O—CO—;
^L1 and ^L2 each independently represent F, Cl, _CF3 or _CHF2 ,
Y represents H, F, Cl, _CF3 , _CHF2 or _CH3 ;
Z ² , Z ^2B and Z ^2D each independently represent a single bond, -CH ₂ CH ₂ -, -CH═CH-, -CF ₂ -CF ₂ -, -CF═CF- _, -CF 2 O-, -OCF ₂ -, -CH ₂ O-, -OCH ₂ -, -COO- or -OCO-;
p represents 0, 1 or 2;
q represents 0 or 1; and v represents 1, 2, 3, 4, 5 or 6.

－Ｃ≡Ｃ－、－ＣＦ_２Ｏ－、－ＯＣＦ_２－、－ＣＨ＝ＣＨ－、－Ｏ－、－ＣＯ－Ｏ－または－Ｏ－ＣＯ－で、それぞれ互いに独立に置き換えられてよく、該基において１個以上のＨ原子はハロゲンで置き換えられてよく、
Ａ^３は、それぞれの出現で互いに独立に、１，４－フェニレン基（該基において、１個または２個のＣＨ基はＮで置き換えられてよい。）または１，４－シクロヘキセニレンもしくは１，４－シクロヘキシレン基（該基において、１個または２個の隣接しないＣＨ_２基は－Ｏ－または－Ｓ－で置き換えられてよい。）を表し、ただし基はハロゲン原子で一置換または多置換されてよく、
ｎは、０、１または２を表し、
Ｚ^３は、それぞれの出現で互いに独立に、－ＣＦ_２Ｏ－、－ＯＣＦ_２－、－ＣＨ_２Ｏ－、－ＯＣＨ_２－、－ＣＨ_２－、－ＣＨ_２ＣＨ_２－、－ＣＨ＝ＣＨ－、－Ｃ≡Ｃ－または単結合を表し、
Ｌ^３１およびＬ^３２は、それぞれ互いに独立に、Ｆ、Ｃｌ、ＣＦ_３またはＣＨＦ_２を表し、および
Ｗは、ＯまたはＳを表す。 In the formula,
R ³¹ and R ³² each independently represent H, an alkyl or alkoxy group having 1 to 7 C atoms, with the proviso that one or more CH ₂ groups in these groups are not directly linked to the O atoms with each other,

each independently may be replaced by —C≡C—, —CF ₂ O—, —OCF ₂ —, —CH═CH—, —O—, —CO—O— or —O—CO—, in which one or more H atoms may be replaced by halogen;
A ³ independently at each occurrence represent a 1,4-phenylene group in which one or two CH groups may be replaced by N or a 1,4-cyclohexenylene or 1,4-cyclohexylene group in which one or two non-adjacent CH ₂ groups may be replaced by -O- or -S-, with the proviso that the group may be mono- or polysubstituted by halogen atoms,
n represents 0, 1 or 2;
^Z3 's in each occurrence independently represent _-CF2O- , -OCF2-, _-CH2O- , _-OCH2- , _-CH2- , _-CH2CH2- , -CH=CH-, _-C≡C- or a _single bond;
L ³¹ and L ³² each independently represent F, Cl, CF ₃ or CHF ₂ ; and W represents O or S.

The present invention further relates to an LC display comprising an LC medium as described above and below.

The present invention further relates to a method for preparing an LC medium as described above and below, comprising the step of mixing one or more compounds of formulae I and III and one or more compounds selected from formulae IIA, IIB, IIC and IID, optionally with a reactive mesogen, further LC compounds and/or additives.

The present invention further relates to the use of the LC medium according to the invention in PSA displays, preferably in particular in PSA displays comprising an LC medium for the generation of a tilt angle in the LC medium by in situ polymerization of a polymerizable compound in the PSA display in an electric or magnetic field. Preferred polymerizable compounds, also called reactive mesogens (RM), are described for example in EP 3 839 008 A1, paragraphs 0094 and 0155 and pages 111 to 129, which are hereby incorporated by reference.

The present invention further relates to an LC display of the IPS, FFS, UB-FFS, UBplus, VA or PS-VA type comprising an LC medium according to the invention.

The present invention further relates to the use of an LC medium according to the invention in a polymer-stabilized SA-VA display and to a polymer-stabilized SA-VA display comprising an LC medium according to the invention.

The invention further relates to an LC display of the VA or PSA type comprising two substrates, at least one of which is transparent to light, an electrode provided on each substrate or two electrodes provided on only one of the substrates, and a layer of an LC medium as described above and below, comprising one or more polymerizable compounds and an LC component, and disposed between the substrates, with the proviso that the polymerizable compound is polymerized between the substrates of the display.

The present invention further relates to a method for producing an LC display as described above and below, comprising the steps of filling or otherwise providing an LC medium as described above and below between the substrates of the display, which may comprise one or more polymerizable compounds, and optionally polymerizing the polymerizable compounds.

Preferred embodiments are the subject of dependent claims and may also be taken from this specification.

PSA displays according to the invention have two electrodes, preferably in the form of transparent layers, coated on one or both of the substrates. In some displays, for example PS-VA displays, one electrode is coated on each of the two substrates.

In a preferred embodiment, the polymerizable component is polymerized in the LC display while a voltage is applied to the electrodes of the display.

The polymerizable compound of the polymerizable component is preferably polymerized by photopolymerization, very preferably by UV photopolymerization.

Surprisingly, it has been found that the use of the liquid crystal medium according to the invention allows displays with improved transmittance, high VHR values, generally fast response times, low threshold voltages, high birefringence, and improved reliability even when exposed to outdoor environments, while maintaining excellent performance with regard to process-relevant parameters, i.e. without the addition of photoinitiators in the case of PSA displays, in particular at long UV wavelengths in the range of 300-380 nm, in particular above 320 nm, and allows for rapid generation of large and stable pretilt angles, reduced image sticking and ODF mura in displays.

In particular, the media according to the present invention are distinguished by excellent low-temperature stability (LTS).

The LC media according to the invention, when used in VA or FFS displays, exhibit the following advantageous properties:
- improved transparency of the display,
-High clearing temperature,
-High voltage holding rate,
- Fast switch,
- sufficient stability against heat and/or UV, especially when used outdoors;
-Excellent LTS.

The LC media according to the invention exhibit the following advantageous properties when used in PSA displays:
- improved transparency of the display,
-High clearing temperature,
- Proper tilt generation within a specific process window,
Fast polymerization with minimal RM residue after UV processing;
-High voltage retention rate after UV processing,
- Good tilt stability,
- sufficient stability against heat and/or UV, especially when used outdoors;
・High-speed switch.

In particular, the liquid-crystalline media according to the invention exhibit advantageously low ratios of the rotational viscosity to the splay elastic constant γ ₁ /K _1. This contributes to improved switching behavior especially at low driving voltages and helps to realise energy-saving displays.

Preferred compounds of formula IIA, IIB, IIC and IID are shown below.

In the formula, the parameter a stands for 1 or 2, alkyl and alkyl ^* each independently stand for a linear alkyl group having 1 to 6 C atoms, alkenyl stands for a linear alkenyl group having 2 to 6 C atoms, (O) stands for an oxygen atom or a single bond, preferably an oxygen atom. Alkenyl preferably stands for CH ₂ ═CH-, CH ₂ ═CHCH ₂ CH ₂ -, CH ₃ -CH═CH-, CH ₃ -CH ₂ -CH═CH-, CH ₃ -(CH ₂ ) ₂ -CH═CH-, CH ₃ -(CH ₂ ) ₃ -CH═CH- or CH ₃ -CH═CH-(CH ₂ ) ₂ -.

Highly preferred compounds of formula IID are selected from the following subformulae:

In the formula, v represents 1, 2, 3, 4, 5, or 6.

In a preferred embodiment, the medium comprises one or more compounds of formula IID-10a.

を表し、式中、ｒは０、１、２、３、４、５または６であり、ｓは１、２または３である。 wherein the occurring groups and parameters have the meanings given above under formula IID, and ^R2 is

wherein r is 0, 1, 2, 3, 4, 5 or 6; and s is 1, 2 or 3.

Preferred compounds of formula IID-10a are compounds IID-10a-1 to IID-10a-14.

More preferred media according to the invention include one or more compounds of formula IIA-2, IIA-8, IIA-10, IIA-16, IIA-18, IIA-40, IIA-41, IIA-42, IIA-43, IIB-2, IIB-10, IIB-16, IIC-1, IID-4 and IID-10.

Highly preferred media according to the present invention comprise one or more compounds of formula IIB-2:

In the formula, alkyl and alkyl ^* each independently represent a linear alkyl group having 1 to 6 C atoms and (O) represents an oxygen atom or a single bond, in particular the compounds of the formulae IIB-2-1 and IIB-2-2.

Preferred media according to the invention contain at least one compound of formula IIC-1, preferably in an amount of 0.5% to 5% by weight, in particular 1% to 3% by weight.

In the formula, alkyl and alkyl ^* have the meanings given above.

In particular, the medium comprises one or more compounds of formula IIA-2 selected from the following subformulas:

Alternatively and preferably, in addition to the compounds of formulae IIA-2-1 to IIA-2-5, the medium comprises one or more compounds of formulae IIA-2a-1 to IIA-2a-5.

In particular, the medium comprises one or more compounds of formula IIA-10 or IIA-52 selected from the following subformulas:

Alternatively, and preferably in addition to the compounds of formulae IIA-10-1 to IIA-10-5, the medium comprises one or more compounds of formulae IIA-10a-1 to IIA-10a-5.

In particular, the medium comprises one or more compounds of formula IIB-10 selected from the following subformulas:

Alternatively, and preferably in addition to the compounds of formulae IIB-10-1 to IIB-10-5, the medium comprises one or more compounds of formulae IIB-10a-1 to IIB-10a-5.

The compound of formula III is preferably selected from compounds of formula III-1, III-2 and/or III-4.

in which the occurring radicals have the same meanings as given in formula III above, preferably R ³¹ and R ³² are each independently of one another an alkyl or alkoxy group having 1 to 15 C atoms or an alkenyl group having 2 to 15 C atoms, more preferably one or both of them represent an alkoxy group having 1 to 7 C atoms,
L ¹¹ and L ¹² preferably represent F.

The liquid-crystalline medium according to the invention preferably comprises one or more compounds of the formula III-2. In a preferred embodiment the liquid-crystalline medium comprises at least one compound of the formula III-1 and at least one compound of the formula III-2. In a further preferred embodiment the liquid-crystalline medium comprises at least one compound of the formula III-2 and at least one compound of the formula III-3.

Preferably, the compound of formula III-1 is selected from the group of compounds of formulae III-1-1 to III-1-10, preferably of formula III-1-6.

In the formula,
alkyl and alkyl ^* each independently represent a linear alkyl group having 1 to 6 C atoms, alkenyl and alkenyl ^* each independently represent a linear alkenyl group having 2 to 6 C atoms, alkoxy and alkoxy ^* each independently represent a linear alkoxy group having 1 to 6 C atoms, and L ³¹ and L ³² each independently represent F or Cl, preferably both represent F.

Preferably, the compound of formula III-2 is selected from the group of compounds of formulas III-2-1 to III-2-10, preferably of formula III-2-6.

In the formula,
alkyl and alkyl ^* each independently represent a linear alkyl group having 1 to 6 C atoms, alkenyl and alkenyl ^* each independently represent a linear alkenyl group having 2 to 6 C atoms, alkoxy and alkoxy ^* each independently represent a linear alkoxy group having 1 to 6 C atoms, and L ³¹ and L ³² each independently represent F or Cl, preferably both represent F.

The medium may contain one or more compounds of formula IIIA-1 and/or IIIA-2.

wherein L ³¹ and L ³² have the same meaning as given above in formula III, and (O) represents O or a single bond;
R ^IIIA represents alkyl or alkenyl having up to 7 C atoms or the group Cy-C _m H _2m+1 -,
m and n are the same or different and are 0, 1, 2, 3, 4, 5 or 6, preferably 1, 2 or 3, very preferably 1,
Cy represents alkyl or alkenyl, each having up to 3 C atoms, or an alicyclic group having 3, 4 or 5 ring atoms, which may be substituted by halogen or CN, and preferably represents cyclopropyl, cyclobutyl, cyclopentyl or cyclopentenyl.

The compounds of formula IIIA-1 and/or IIIA-2 are included in the medium either alternatively or additionally, preferably additionally, to the compound of formula III.

Highly preferred compounds of formula IIIA-1 and IIIA-2 are:

In the formula, alkoxy denotes a straight-chain alkoxy group having 1 to 6 C atoms or alternatively -( _CH2 ) _nF , where n is 2, 3, 4 or ₅ , preferably _C2H4F .

In a preferred embodiment of the invention, the medium comprises one or more compounds of formula III-3.

－Ｏ－、－ＣＯ－Ｏ－または－Ｏ－ＣＯ－で置き換えられてよく、該基において加えて１個以上のＨ原子はハロゲンで置き換えられてよい。 In the formula, R ³¹ and R ³² are the same or different and each represents H, an alkyl or alkoxy group having 1 to 15 C atoms, provided that one or more CH ₂ groups in these groups are -C≡C-, -CF ₂ O-, -OCF ₂ -, -CH═CH-, so that O atoms are not directly linked to each other.

It may be replaced by -O-, -CO-O- or -O-CO-, in which additionally one or more H atoms may be replaced by halogen.

The compound of formula III-3 is preferably selected from the group of compounds of formulae III-3-1 to III-3-10.

in which R ³² represents alkyl having 1 to 7 C atoms, preferably ethyl, n-propyl or n-butyl, or alternatively cyclopropylmethyl, cyclobutylmethyl or cyclopentylmethyl or alternatively -(CH ₂ ) _n F, where n is 2, 3, 4 or 5, preferably C ₂ H ₄ F.

In a preferred embodiment of the invention, the medium comprises one or more compounds of formulae III-4 to III-6, preferably of formula III-5.

in which the parameters have the meanings given above, R ³¹ preferably represents a straight-chain alkyl having 1 to 7 C atoms and R ³² preferably represents an alkoxy having 1 to 7 C atoms.

In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula III selected from the group of compounds of formulae III-7 to III-9, preferably of formula III-8.

in which the parameters have the meanings given above, R ³¹ preferably represents a straight-chain alkyl having 1 to 7 C atoms and R ³² preferably represents an alkoxy having 1 to 7 C atoms.

In a preferred embodiment, the medium comprises one or more compounds of formula IV.

In the formula,
R ⁴¹ represents an unsubstituted alkyl group having 1 to 7 C atoms or an unsubstituted alkenyl group having 2 to 7 C atoms, preferably an n-alkyl group, particularly preferably having 2, 3, 4 or 5 C atoms;
R ⁴² represents an unsubstituted alkyl group having 1 to 7 C atoms or an unsubstituted alkoxy group having 1 to 6 C atoms (both of which preferably have 2 to 5 C atoms), an unsubstituted alkenyl group having 2 to 7 C atoms, preferably having 2, 3 or 4 C atoms, more preferably a vinyl group or a 1-propenyl group, in particular a vinyl group;
However, compounds of formula I are excluded from formula IV and its subformulas.

The compound of formula IV is preferably selected from the group of compounds of formulas IV-1 to IV-4.

In the formula,
alkyl and alkyl' independently denote alkyl having 1 to 7 C atoms, preferably having 2 to 5 C atoms,
alkenyl represents an alkenyl group having 2 to 5 C atoms, preferably having 2 to 4 C atoms, particularly preferably having 2 C atoms,
alkenyl' denotes an alkenyl group having 2 to 5 C atoms, preferably having 2 to 4 C atoms and particularly preferably having 2 to 3 C atoms,
Alkoxy denotes alkoxy having 1 to 5 C atoms, preferably having 2 to 4 C atoms.

Preferably, the medium contains one or more compounds selected from the compounds of formulae IV-1-1 to IV-1-4.

Very preferably, the medium according to the invention comprises a compound of formula IV-1-1.

Very preferably, the medium according to the invention comprises one or more compounds of formula IV-2-1 and/or IV-2-2.

In a preferred embodiment, the medium according to the present invention comprises one or more compounds of formula IV-3.

を表し、式中、ｍは０、１または２、好ましくは０であり、ｎは０、１または２、好ましくは０または１である。 in which alkyl very preferably denotes an alkyl group having 1 to 7 C atoms, in particular n-ethyl or n-propyl, very particularly n-propyl, and alkenyl is

wherein m is 0, 1 or 2, preferably 0; and n is 0, 1 or 2, preferably 0 or 1.

In particular, it is selected from the compounds of the formulae IV-3-1 to IV-3-6, very particularly preferably from the compounds of the formula IV-3-2.

In a preferred embodiment, the medium comprises, in addition to the compounds of formulae IV-3-1 to IV-3-6, one or more compounds of formulae IV-3-7 to IV-3-9.

Preferably, the concentration of the compounds of formulae IV-3-7 to IV-3-9 in the medium according to the invention is less than 5% or less than 4% or less than 3%, very preferably between 0% and 1%, in particular 0%.

Highly preferably, the medium according to the invention comprises one or more compounds of formula IV-3 and one or more compounds of formula IV-1, with the total concentration of the compounds of formula IV-1 being in the range of 1% to 30%.

Very preferably, the medium according to the invention comprises a compound of formula IV-4, in particular selected from the compounds of formulae IV-4-1 to IV-4-3, in particular the compound of formula IV-4-3.

In a preferred embodiment, the medium according to the present invention comprises one or more compounds of formula I selected from the group of compounds of formulae I-1 to I-4 in combination with one or more compounds selected from the group of compounds of formulae IA-1 to IA-18.

In the formula, alkyl represents methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or n-pentyl.

The liquid crystal medium according to the invention preferably comprises one or more compounds of formula IVa.

Ｚ^４は、単結合、－ＣＨ_２ＣＨ_２－、－ＣＨ＝ＣＨ－、－ＣＦ_２Ｏ－、－ＯＣＦ_２－、－ＣＨ_２Ｏ－、－ＯＣＨ_２－、－ＣＯＯ－、－ＯＣＯ－、－Ｃ_２Ｆ_４－、－Ｃ_４Ｈ_８－、－ＣＦ＝ＣＦ－を表す。 In the formula,
R ⁴¹ and R ⁴² each independently represent a straight-chain alkyl, alkoxy, alkenyl, alkoxyalkyl or alkenyloxy group having up to 12 C atoms, and

^Z4 represents a _single bond, _-CH2CH2- , -CH=CH-, _-CF2O- , _-OCF2- , -CH2O-, _-OCH2- , -COO-, _-OCO- , _-C2F4- , _-C4H8- or -CF _{= CF-} .

Preferred compounds of formula IVa are shown below.

In the formula,
Alkyl and alkyl ^* each independently represent a straight-chain alkyl group having 1 to 6 C atoms.

The medium according to the invention preferably comprises at least one compound of the formula IVa-1 and/or of the formula IVa-2, very preferably of the formula IVa-2, in particular the compound IVa-2 in which alkyl represents n-propyl and alkyl ^* represents methyl.

The proportion of compounds of formula IVa in the overall mixture is preferably less than 5% by weight, very preferably less than 2% by weight.

Preferably, the medium comprises one or more compounds of formulae IVb-1 to IVb-3.

In the formula,
Alkyl and alkyl ^* each independently represent a straight-chain alkyl group having 1 to 6 C atoms, and alkenyl and alkenyl ^* each independently represent a straight-chain alkenyl group having 2 to 6 C atoms.

The proportion of compounds of formulae IV-1 to IV-3 in the entire mixture is preferably less than 3% by weight, in particular less than 2% by weight.

Among the compounds of formulae IVb-1 to IVb-3, the compound of formula IVb-2 is particularly preferred.

Very particularly preferred are biphenyls.

in which alkyl ^* stands for an alkyl group having 1 to 6 C atoms, preferably for n-propyl or n-butyl. The medium according to the invention particularly preferably comprises one or more compounds of the formulae IVb-1-1 and/or IVb-2-3.

In the compound of formula IVb-1-1, alkyl preferably represents propyl, butyl and pentyl, most preferably propyl.

In a particularly preferred embodiment, the medium according to the invention comprises one or more compounds of formula V:

を表し、
Ｚ^５１、Ｚ^５２は、それぞれ互いに独立に－ＣＨ_２－ＣＨ_２－、－ＣＨ_２－Ｏ－、－ＣＨ＝ＣＨ－、－Ｃ≡Ｃ－、－ＣＯＯ－または単結合を表し、および
ｎは、１または２である。 In the formula,
R ⁵¹ and R ⁵² each represent an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, or an alkoxyalkyl group, an alkenyl group, or an alkenyloxy group having 2 to 7 carbon atoms;

represents
Z ⁵¹ and Z ⁵² each independently represent -CH ₂ -CH ₂ -, -CH ₂ -O-, -CH=CH-, -C≡C-, -COO- or a single bond, and n is 1 or 2.

The compound of formula V is preferably selected from the compounds of formulas V-1 to V-17.

in which R ⁵¹ and R ⁵² have the meanings given above in formula V. R ⁵¹ and R ⁵² preferably each independently of one another represent a straight-chain alkyl having 1 to 7 C atoms or an alkenyl having 2 to 7 C atoms.

Preferred media comprise one or more compounds of formula V-1, V-3, V-4, V-6, V-7, V-10, V-11, V-12, V-14, V-15, V-16 and/or V-17, very preferably V-16, in particular the compound of formula V-16 in which R ⁵¹ represents n-propyl and R ⁵² represents ethyl.

In a preferred embodiment of the invention, the medium additionally comprises one or more compounds of formula VI.

wherein R ⁶ and R ⁶² have the meaning of R ^2A as defined in claim 1, or R ⁶² represents F, Cl, CF ₃ or OCF ₃ , preferably F, and L ⁶¹ , L ⁶² , L ⁶³ , L ⁶⁴ , L ⁶⁵ and L ⁶⁶ independently represent H or F, with the proviso that at least one of L ⁶¹ , L ⁶² , L ⁶³ , L ⁶⁴ , L ⁶⁵ and L ⁶⁶ represents F.

The compound of formula VI is preferably selected from formulae VI-1 to VI-21, in particular formula VI-4.

in which R ⁶ represents a linear alkyl or alkoxy group having 1 to 6 C atoms, (O) represents -O- or a single bond, m is 0, 1, 2, 3, 4, 5 or 6 and n is 0, 1, 2, 3 or 4. R ⁶ preferably represents methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy or pentoxy.

Compounds of formulae VI-1, VI-2, VI-4, VI-20 and VI-21 are particularly preferred.

Very preferably, the medium according to the invention comprises a compound of formula IV-4, in particular a compound of formula IV-4-1.

In this formula, R ⁶ and m have the meanings defined above, preferably R ⁶ represents methyl, ethyl, n-propyl, n-butyl or n-pentyl and m is 2, 3 or 4.

In a preferred embodiment of the invention, the medium additionally comprises one or more compounds of formula VIA.

in which R ⁶ and R ⁶² have the meaning of R ^2A as defined in claim 1, or R ⁶² represents F, Cl, CF ₃ or OCF ₃ , preferably F, and L ⁶¹ , L ⁶² , L ⁶³ , L ⁶⁴ , L ⁶⁵ and L ⁶⁶ independently represent H or F, with the proviso that at least one of L ⁶¹ , L ⁶² , L ⁶³ , L ⁶⁴ , L ⁶⁵ and L ⁶⁶ represents F,
Z ⁶¹ and Z ⁶² independently represent a single bond, --CH ₂ --CH ₂ --, --CH ₂ --O--, --CH═CH--, --C≡C--, --COO-- or --CF ₂ --O--, provided that Z ⁶¹ and Z ⁶² are not the same.

Very preferably, the medium according to the invention comprises a compound of formula VIA-1 and/or formula X.

wherein R ⁶ and m have the meanings defined above, preferably R ⁶ represents methyl, ethyl, n-propyl, n-butyl or n-pentyl and m represents 2, 3 or 4. In a particularly preferred embodiment R ⁶ represents n-propyl and m represents 2.

In a preferred embodiment of the invention, the medium additionally comprises one or more compounds of formulae VII-1 to VII-9.

In the formula,
R ⁷ represents a linear alkyl or alkoxy group having 1 to 6 C atoms or a linear alkenyl group having 2 to 6 C atoms, and w is an integer from 1 to 6.

Mixtures containing at least one compound of formula VII-9 are particularly preferred.

Further preferred embodiments are listed below.

a) A liquid crystal medium containing at least one compound of formulas Z-1 to Z-8.

In the formula IIA, R has the meaning of R ^2A and alkyl stands for a straight-chain alkyl group having 1 to 6 C atoms. In a preferred embodiment the liquid-crystalline media according to the invention comprise at least one compound of the formula Z-8.

b) Preferred liquid crystal media according to the invention comprise one or more substances containing a tetrahydronaphthyl or naphthyl unit, such as, for example, the compounds of the formulae N-1 to N-5.

In the formula, R ^1N and R ^2N each independently have the meaning shown in R ^2A , preferably linear alkyl, linear alkoxy or linear alkenyl,
^Z1 and ^Z2 each independently _{represent -C2H4-} , -CH=CH-, -( _CH2 ) _4- , _- ( _CH2 )3O-, _-O ( _{CH2 ) 3-} , -CH= _CHCH2CH2- , -CH2CH2CH=CH-, -CH2O- _{, -OCH2- ,} -COO-, -OCO-, -C2F4-, _-CF =CF-, -CF ₌ CH-, -CH=CF- _{, -CF2O-} , _-OCF2- , _-CH2- or a single bond.

c) Preferred mixtures include one or more compounds selected from the group of difluorodibenzochroman compounds of formula BC, chromans of formula CR and fluorinated phenanthrenes of formula PH-1 and PH-2.

In the formula,
R ^B1 , R ^B2 , R ^CR1 , R ^CR2 , R ¹ , R ² each independently have the meaning of R ^2A , where c is 0, 1 or 2. ^{R 1} and R ² preferably independently of each other denote alkyl or alkoxy having 1 to 6 C atoms.

Particularly preferred compounds of formula BC and CR are compounds BC-1 to BC-7 and CR-1 to CR-5.

In the formula,
alkyl and alkyl ^* each independently represent a linear alkyl group having 1 to 6 C atoms,
Alkenyl and alkenyl ^* each independently denote a straight-chain alkenyl group having 2 to 6 C atoms.

Mixtures containing one, two or three compounds of the formulae BC-2, BF-1 and/or BF-2 are very particularly preferred.

d) Preferred mixtures include one or more indane compounds of formula In.

を表し、
ｉは０、１または２を表す。 In the formula,
R ¹¹ , R ¹² and R ¹³ each independently represent a linear alkyl, alkoxy, alkoxyalkyl or alkenyl group having 1 to 6 C atoms;
R ¹² and R ¹³ are alternatively halogen, preferably F;

represents
i represents 0, 1 or 2.

Preferred compounds of formula In are compounds of formulas In-1 to In-16 shown below.

Compounds of formula In-1, In-2, In-3 and In-4 are particularly preferred.

e) Preferred mixtures additionally contain one or more compounds of formulae L-1 to L-5.

In the formula,
R, ^R1 and ^R2 each independently have the meaning given under ^R2A in formula IIA above, alkyl represents an alkyl group having 1 to 6 C atoms. The parameter s represents 1 or 2.

The compounds of the formulae L1 to L9 are preferably used in concentrations of 5 to 15% by weight, in particular 5 to 12% by weight, very particularly preferably 8 to 10% by weight.

f) Preferred mixtures additionally contain one or more compounds of formula IIA-Y.

in which R ¹¹ and R ¹² have one of the meanings given for R ^2A in formula IIA above, L ¹ and L ² are the same or different and represent F or Cl, and L ³ represents H or CH ₃ .

Preferred compounds of formula IIA-Y are selected from the group consisting of the following subformulae:

In the formula, alkyl and alkyl ^* each independently represent a linear alkyl group having 1 to 6 C atoms, alkoxy represents a linear alkoxy group having 1 to 6 C atoms, alkenyl and alkenyl ^* each independently represent a linear alkenyl group having 2 to 6 C atoms, and O represents an oxygen atom or a single bond. Alkenyl and alkenyl ^* preferably represent CH ₂ ═CH-, CH ₂ ═CHCH ₂ CH ₂ -, CH ₃ -CH═CH-, CH ₃ -CH ₂ -CH═CH-, CH ₃ -(CH ₂ ) ₂ -CH═CH-, CH ₃ -(CH ₂ ) ₃ -CH═CH- or CH ₃ -CH═CH-(CH ₂ ) ₂ -.

Particularly preferred compounds of formula IIA-Y are selected from the group consisting of the following subformulae:

In the formulae, alkoxy and alkoxy ^* have the meanings defined above and preferably represent methoxy, ethoxy, n-propyloxy, n-butyloxy or n-pentyloxy.

g) The medium additionally contains one or more compounds selected from the compounds of formulae P-1 to P-4.

In the formula,
R ^P represents a straight-chain alkyl or alkoxy group having 1 to 6 C atoms or an alkenyl group having 2 to 6 C atoms,
^XP represents linear alkyl having 1 to 6 C atoms, F, Cl, CF3, _OCF2H , _OCF3 , _OCHFCF3 , _OCF2CHFCF3 , _OCH = _CF2 , preferably F, _OCF3 or _CF3 , _{CH3 ,}
L ^P1 , L ^P2 and L ^P3 each independently represent H or F.

Preferred compounds of formulas P1 to P4 are listed below.

in which R ^P has the meaning given above. Preferably R ^P represents alkyl or alkenyl, in particular ethyl, propyl, butyl, pentyl, CH ₂ ═CH—, CH ₂ ═CHCH ₂ CH ₂ —, CH ₃ —CH═CH—, CH ₃ —CH ₂ —CH═CH—, CH ₃ —(CH ₂ ) ₂ —CH═CH—, CH ₃ —(CH ₂ ) ₃ —CH═CH— or CH ₃ —CH═CH—(CH ₂ ) ₂ —, where alkyl represents a straight-chain alkyl group having 1 to 6 carbon atoms.

h) In a preferred embodiment, the mixture according to claim 1 comprises at least one compound selected from the group of compounds of formulae IIA-18, IIA-42, IIA-49, IIA-51, IIA-52, IID-4, IID-10, III-3, III-4, IIIA-1-3, IVb-1, IV-b-2, VIA-1, X, V-11, V-17, Z-8 and IIA-Y.

Preferably, the medium according to the invention comprises one compound of formula H.

を表し；
Ｒ^Ｈは、Ｈ、Ｏ^・、ＣＨ_３、ＯＨまたはＯＲ^Ｓ、好ましくはＨまたはＯ^・を表し；
Ｒ^Ｓ１、Ｒ^Ｓ２、Ｒ^Ｓ３およびＲ^Ｓ４は同一または異なって、１～６個のＣ原子、好ましくは１～３個のＣ原子を有するアルキル、非常に好ましくはＣＨ_３を表し；
Ｇは、ＨもしくはＲ^Ｓまたは基Ｚ^Ｓ－ＨＡを表し；
ｚは、１～６の整数であり；および
ｑは、３または４である。 In the formula,
Ar represents an aromatic or heteroaromatic hydrocarbon group having 4 to 40 C atoms, preferably having 6 to 30 C atoms;
Sp represents a spacer group;
R 1 ^S represents H, alkyl having 1 to 12 C atoms or alkenyl having 2 to 12 C atoms;
^ZS represents -O-, -C(O)O-, -(CH ₂ ) _z - or -(CH ₂ ) _z O-, or a single bond;
H.A.

represents;
R ^H represents H, ^O. , CH ₃ , OH or OR ^S , preferably H or O ^.;
R ^S1 , R ^S2 , R ^S3 and R ^S4 are identical or different and represent alkyl having 1 to 6 C atoms, preferably having 1 to 3 C atoms, very preferably CH ₃ ;
G represents H or R 2 ^S or a group Z ² -HA;
z is an integer from 1 to 6; and q is 3 or 4.

In formula H, aryl preferably represents an aromatic or heteroaromatic hydrocarbon group having 4 to 40 C atoms and contains 1, 2, 3 or 4 aromatic rings and fused rings which may be linked directly or via an alkylene linking group having 1 to 12 C atoms, with the proviso that one or more H atoms may be replaced by alkyl or alkoxy having 1 to 6 C atoms or alkenyl having 2 to 6 C atoms, or by CN, _CF3 or halogen, with the proviso that one or more _CH2 groups may be replaced by -O-, -S-, -NH-, -N( _C1 - _C4 -alkyl)-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -CH=CH- or -C≡C-, in each case independently of one another, such that the O or S atoms are not directly linked to one another.

Preferred aryl groups are benzene, naphthalene, anthracene, biphenyl, m-terphenyl, p-terphenyl and (phenylalkyl)benzene, where alkyl is a straight-chain alkyl having 1 to 12 C atoms.

Compounds of formula H are described in EP 3 354 710 and EP 3 354 709.

The compound of formula H is preferably selected from compounds of formula H-1, H-2 and H-3.

in which R ^H has the meaning given above and preferably represents H or ^O.
n is an integer from 0 to 12, preferably 5, 6, 7, 8 or 9, very preferably 7;
Sp represents a spacer group, preferably an alkylene having 1 to 12 C atoms in which one or more non-adjacent --CH ₂ -- groups may be replaced by --O--.

Preferred compounds of formula H-1 are selected from compounds of formula H-1-1.

in which R 1 ^H has the meaning given above and preferably represents H or ^O. , and n is an integer from 0 to 12, preferably 5, 6, 7, 8 or 9, very preferably 7.

Preferred compounds of formula H-2 are selected from compounds of formula H-2-1.

in which R ^H has the meaning given above and preferably represents H or ^O.
n2 is the same or different at each occurrence and is preferably the same and is an integer from 1 to 12, preferably 2, 3, 4, 5 or 6, very preferably 3; R ^S is the same or different at each occurrence and is preferably the same and represents alkyl having 1 to 6 C atoms, preferably n-butyl.

Preferred compounds of formula H-3 are selected from compounds of formula H-3-1.

in which R ^H has the meaning given above and preferably represents H or ^O.
n is an integer from 0 to 12, preferably 5, 6, 7, 8 or 9, and most preferably 7.

Preferably, the medium according to the present invention comprises a compound selected from the group of compounds of formulas ST-1 to ST-18.

－Ｏ－、－ＣＯ－Ｏ－、－Ｏ－ＣＯ－で、それぞれ互いに独立に置き換えられてよく、該基において加えて１個以上のＨ原子はハロゲンで置き換えられてよく、

は、それぞれの出現で同一または異なって、

を表し、
Ｚ^ＳＴは、それぞれ互いに独立に－ＣＯ－Ｏ－、－Ｏ－ＣＯ－、－ＣＦ_２Ｏ－、－ＯＣＦ_２－、－ＣＨ_２Ｏ－、－ＯＣＨ_２－、－ＣＨ_２－、－ＣＨ_２ＣＨ_２－、－（ＣＨ_２）_４－、－ＣＨ＝ＣＨ－、－ＣＨ_２Ｏ－、－Ｃ_２Ｆ_４－、－ＣＨ_２ＣＦ_２－、－ＣＦ_２ＣＨ_２－、－ＣＦ＝ＣＦ－、－ＣＨ＝ＣＦ－、－ＣＦ＝ＣＨ－、－ＣＨ＝ＣＨ－、－Ｃ≡Ｃ－または単結合を表し、
Ｌ^１およびＬ^２は、それぞれ互いに独立にＦ、Ｃｌ、ＣＨ_３、ＣＦ_３またはＣＨＦ_２を表し、
ｐは、０、１または２を表し、
ｑは、１、２、３、４、５、６、７、８、９または１０を表す。 In the formula, R ^ST represents H, an alkyl or alkoxy group having 1 to 15 C atoms, provided that in addition, one or more CH ₂ groups in these groups are not directly linked to O atoms, and are represented by -C≡C-, -CF ₂ O-, -OCF ₂ -, -CH═CH-,

-O-, -CO-O-, -O-CO-, each of which may be replaced independently, in which one or more H atoms may additionally be replaced by halogen;

may be the same or different in each occurrence,

represents
Z ^ST each independently represent -CO-O-, -O-CO-, -CF ₂ O-, -OCF ₂ -, -CH ₂ O-, -OCH ₂ -, -CH ₂ -, -CH ₂ CH ₂ -, -(CH ₂ ) ₄ -, -CH=CH-, -CH ₂ O-, -C ₂ F ₄ -, -CH ₂ CF ₂ -, -CF ₂ CH ₂ -, -CF=CF-, -CH=CF-, -CF=CH-, -CH=CH-, -C≡C- or a single bond;
^L1 and ^L2 each independently represent F, Cl, _CH3 , _CF3 or _CHF2 ;
p represents 0, 1 or 2;
q represents 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

Of the compounds of formula ST, the compounds of formula ST-1 and ST-3 and especially the following are particularly preferred:

In the compounds of formula ST-3a and ST-3b, n is preferably 3. In the compounds of formula ST-2a, n is preferably 7.

Very particularly preferred mixtures according to the invention comprise one or more stabilizers from the group of compounds of the formulae ST-2a-1, ST-3a-1, ST-3b-1, ST-8-1, ST-9-1, ST-12.

The compounds of formulae S and ST-1 to ST-19 are preferably present in the liquid crystal mixture according to the invention in an amount of 0.005 to 0.5%, respectively, based on the mixture.

If the mixture according to the invention contains two or more compounds from the group of compounds of formulae ST-1 to ST-18, the concentrations increase correspondingly to 0.01 to 1% for two compounds, based on the mixture.

However, it is preferred that the total proportion of compounds of formulae ST-1 to ST-18 based on the mixture according to the invention does not exceed 2%.

The medium according to the invention preferably has a negative dielectric anisotropy. In a preferred embodiment, the medium further comprises one or more compounds.

As used herein, the term "reliability" refers to the quality of a display's performance over time under different stress loads such as light load, temperature, humidity, voltage, and display effects such as image sticking (area and line image sticking), mura, smearing, etc., known to those skilled in the art in the field of liquid crystal displays. As a standard parameter for classifying reliability, the voltage holding ration (VHR) value is usually used, which is a measure of maintaining a constant electrical voltage in a test display. A high VHR is a prerequisite for a reliable LC medium.

Unless otherwise specified, in the following, the term "PSA" will be used to refer to polymer-maintained alignment displays in general, and the term "PS" will be used to refer to specific display modes such as PS-VA and PS-TN.

Unless otherwise indicated, the term "RM" is also used hereinafter to refer to polymerizable mesogenic compounds or polymerizable liquid crystal compounds.

As used herein, the terms "active layer" and "switchable layer" refer to a layer in an electro-optical display, e.g., an LC display, that contains one or more types of molecules with structural and optical anisotropy, e.g., LC molecules, that undergo a change in molecular orientation upon application of an external stimulus, such as an electric or magnetic field, resulting in a change in the transparency of the layer to polarized or unpolarized light.

As used herein, the terms "tilt" and "tilt angle" are understood to mean the tilted orientation of the LC molecules of the LC medium in an LC display (herein, preferably, a PSA display) relative to the cell surface. In this specification, tilt angle means the average angle (less than 90°) between the molecular long axis (LC director) of the LC molecules and the surface of the flat, parallel outer plates forming the LC cell. In this specification, low values of tilt angle (i.e., large deviations from the 90° angle) correspond to large tilt. A suitable method for measuring the tilt angle is given in the examples. Unless otherwise indicated, the tilt angle values disclosed above and below refer to this measurement method.

As used herein, the terms "reactive mesogen" and "RM" are understood to mean a compound that contains a mesogenic or liquid crystal backbone and one or more functional groups attached to the backbone that are suitable for polymerization, which functional groups are also referred to as "polymerizable groups" or "P."

Unless otherwise stated, as used herein, the term "polymerizable compound" is understood to mean a polymerizable monomer compound.

As used herein, the term "low molecular weight compound" is understood as opposed to "polymeric compound" or "polymer" to mean a compound that is monomeric and/or not prepared by a polymerization reaction.

As used herein, the term "non-polymerizable compound" is understood to mean a compound that does not contain functional groups suitable for polymerization under conditions normally applied for the polymerization of RMs.

As used herein, the term "mesogenic group" refers to a group known to the skilled artisan and described in the literature, which essentially contributes to the generation of a liquid-crystalline (LC) phase in low molecular weight or polymeric substances by the anisotropy of its attractive and repulsive interactions. A compound containing a mesogenic group (mesogenic compound) does not necessarily have an LC phase by itself. It is also possible that a mesogenic compound shows LC phase behavior only after mixing with other compounds and/or after polymerization. Typical mesogenic groups are, for example, rigid rod- or disk-shaped units. A review of the terms and definitions used in relation to mesogenic or LC compounds can be found in Pure Appl. Chem. 2001, 73(5), 888 and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, Vol. 116, pp. 6340-6368.

As used herein, the terms "optically active" and "chiral" are synonymous for a material that can induce a helical pitch in a nematic host material, also referred to as a "chiral dopant."

As used herein, the term "spacer group", hereinafter also referred to as "Sp", is known to those skilled in the art and described in the literature, see for example Pure Appl. Chem. 2001, 73(5), 888 and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368. As used herein, the term "spacer group" or "spacer" refers to a flexible group, e.g., an alkylene group, that links the mesogenic group and the polymerizable group(s) in a polymerizable mesogenic compound.

Throughout this patent application, 1,4-cyclohexylene and 1,4-phenylene rings are represented as follows:

The cyclohexylene ring is a trans-1,4-cyclohexylene ring.

は、トランス－１，４－シクロヘキシレン環を表す。 Above and below,

represents a trans-1,4-cyclohexylene ring.

において２個の環原子の間に示される単結合は、ベンゼン環の結合していない任意の位置に連結できる。 Base

The single bond shown between two ring atoms in can be attached to any non-bonded position on the benzene ring.

In the above and below, "organic group" refers to a carbon or hydrocarbon group.

The term "carbon group" refers to a monovalent or polyvalent organic group containing at least one carbon atom, which may either contain no additional atoms (e.g., -C≡C-) or may contain one or more additional atoms, such as, for example, N, O, S, B, P, Si, Se, As, Te, or Ge (e.g., carbonyl). The term "hydrocarbon group" refers to a carbon group which additionally contains one or more H atoms and may contain one or more heteroatoms, such as, for example, N, O, S, B, P, Si, Se, As, Te, or Ge.

"Halogen" refers to F, Cl, Br or I, preferably F or Cl.

を表す。 -CO-, -C(=O)- and -C(O)- are carbonyl groups, i.e.

Represents.

The carbon or hydrocarbon group may be saturated or unsaturated. Unsaturated groups are, for example, aryl, alkenyl or alkynyl groups. Carbon or hydrocarbon groups with more than three C atoms may be linear, branched and/or cyclic and may contain spiro-linked or fused rings.

The terms "alkyl", "aryl", "heteroaryl", etc. also include polyvalent groups such as alkylene, arylene, heteroarylene, etc. The term "aryl" refers to an aromatic carbon group or a group derived therefrom. The term "heteroaryl" refers to an "aryl" as defined above containing one or more heteroatoms (preferably selected from N, O, S, Se, Te, Si and Ge).

In this specification, alkyl is linear or branched and has 1 to 15 C atoms, preferably linear and, unless otherwise indicated, has 1, 2, 3, 4, 5, 6 or 7 C atoms and is therefore preferably methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl or n-heptyl.

In this specification, branched alkyl is an alkyl having secondary and/or tertiary, preferably secondary, carbon atoms, preferably isopropyl, sec-butyl, isobutyl, isopentyl, 2-methylhexyl or 2-ethylhexyl, 2-methylpropyl, 2-pentyl, 3-pentyl, 2-methylbutyl, 3-methylbutyl.

In this specification, a cyclic alkyl group is intended to mean a cyclic aliphatic or alkyl group in which a methylene group is replaced by a cyclic aliphatic group (i.e., cycloalkylalkyl or alkylcycloalkylalkyl), which may be saturated or partially unsaturated, and preferably represents cyclopropyl, methylcyclopropyl, cyclobutyl, methylcyclobutyl, cyclopentyl, methylcyclopentyl, cyclopent-1-enyl, cyclopropylmethyl, cyclopropylethyl, cyclobutylmethyl, cyclobutylethyl, cyclopentylmethyl, cyclopentylethyl, cyclopent-1-enylmethyl.

In this specification, alkoxy groups are linear or branched and contain 1 to 15 C atoms. They are preferably linear and, unless otherwise indicated, have 1, 2, 3, 4, 5, 6 or 7 C atoms and are therefore preferably methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, n-hexoxy or n-heptoxy.

In the present specification, an alkenyl group is preferably an alkenyl group having 2 to 15 C atoms, being linear or branched and containing at least one C-C double bond. It is preferably linear and has 2 to 7 C atoms. It is therefore preferably vinyl, prop-1- or -2-enyl, but-1-, -2- or -3-enyl, pent-1-, -2-, -3- or -4-enyl, hex-1-, -2-, -3-, -4- or -5-enyl, hept-1-, -2-, -3-, -4-, -5- or -6-enyl. If two C atoms of the C-C double bond are substituted, the alkenyl group may be in the form of the E and/or Z isomers (trans/cis). In general, the respective E isomers are preferred. Of the alkenyl groups, prop-2-enyl, but-2- and -3-enyl, and pent-3- and -4-enyl are particularly preferred.

In the present specification, alkynyl is taken to mean an alkynyl group having 2 to 15 C atoms, being linear or branched and containing at least one C-C triple bond. 1- and 2-propynyl and 1-, 2- and 3-butynyl are preferred.

Preferred carbon and hydrocarbon groups are optionally substituted linear, branched or cyclic alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy and alkoxycarbonyloxy having 1 to 40, preferably 1 to 20, particularly preferably 1 to 12 C atoms, aryl or aryloxy having 5 to 30, preferably 6 to 25 C atoms, or optionally substituted alkylaryl, arylalkyl, alkylaryloxy, arylalkyloxy, arylcarbonyl, aryloxycarbonyl, arylcarbonyloxy and aryloxycarbonyloxy having 5 to 30, preferably 6 to 25 C atoms, whereby one or more C atoms may be replaced by heteroatoms, preferably selected from N, O, S, Se, Te, Si and Ge.

More preferred carbon and hydrocarbon groups are _C1 - _C20 alkyl, _C2 - _C20 alkenyl, C2- _C20 alkynyl, _C3 - _C20 allyl, _C4 - _C20 alkyldienyl, _C4 - _C20 polyenyl, _C6 - _C20 cycloalkyl, _C4 - _C15 cycloalkenyl, _C6 - _C30 aryl, _C6 - _C30 alkylaryl, _C6 - _C30 arylalkyl, _C6 - _C30 alkylaryloxy, _{C6 - C30} arylalkyloxy, _C2 - _C30 heteroaryl, _C2 - _C30 heteroaryloxy.

Particularly preferred are C ₁ -C ₁₂ alkyl, C ₂ -C ₁₂ alkenyl, C ₂ -C ₁₂ alkynyl, C ₆ -C ₂₅ aryl and C ₂ -C ₂₅ heteroaryl.

Further preferred carbon and hydrocarbon groups are alkyl, linear, branched or cyclic, having 1 to 20, preferably 1 to 12, C atoms, which are unsubstituted or mono- or polysubstituted by F, Cl, Br, I or CN, with the proviso that one or more non-adjacent _CH2 groups may each be replaced independently by -C(R ^x )=C(R ^x )-, -C≡C-, -N(R ^x )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, such that the O and/or S atoms are not directly linked to one another.

R ^x preferably represents H, F, Cl, CN, a linear, branched or cyclic alkyl chain having 1 to 25 C atoms (with the proviso that in addition, one or more non-adjacent C atoms may be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, with the proviso that one or more H atoms may be replaced by F or Cl), or an optionally substituted aryl or aryloxy group having 6 to 30 C atoms, or an optionally substituted heteroaryl or heteroaryloxy group having 2 to 30 C atoms.

Preferred alkyl groups include, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, 2-methylbutyl, n-pentyl, s-pentyl, cyclopentyl, n-hexyl, cyclohexyl, 2-ethylhexyl, n-heptyl, cycloheptyl, n-octyl, cyclooctyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, dodecanyl, trifluoromethyl, perfluoro-n-butyl, 2,2,2-trifluoroethyl, perfluorooctyl, and perfluorohexyl.

Preferred alkenyl groups are, for example, ethenyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl, cyclooctenyl, etc.

Preferred alkynyl groups are, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl, octynyl, etc.

Preferred alkoxy groups include, for example, methoxy, ethoxy, 2-methoxyethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy, 2-methylbutoxy, n-pentoxy, n-hexoxy, n-heptoxy, n-octoxy, n-nonoxy, n-decoxy, n-undecoxy, and n-dodecoxy.

Preferred amino groups are, for example, dimethylamino, methylamino, methylphenylamino, phenylamino, etc.

Aryl and heteroaryl groups may be monocyclic or polycyclic, i.e., they may contain one ring (e.g., phenyl) or two or more rings, and the groups may be fused (e.g., naphthyl) or covalently linked (e.g., biphenyl) or may contain a combination of fused and linked rings. Heteroaryl groups preferably contain one or more heteroatoms selected from O, N, S and Se.

Particularly preferred are monocyclic, bicyclic or tricyclic aryl groups having 6 to 25 C atoms and monocyclic, bicyclic or tricyclic heteroaryl groups having 5 to 25 ring atoms, which may contain fused rings and may be substituted. Furthermore, 5-, 6- or 7-membered aryl and heteroaryl groups are preferred, provided that in addition, one or more CH groups may be replaced by N, S or O, such that the O and/or S atoms are not directly linked to each other.

Preferred aryl groups include, for example, phenyl, biphenyl, terphenyl, [1,1':3',1"]terphenyl-2'-yl, naphthyl, anthracene, binaphthyl, phenanthrene, 9,10-dihydrophenanthrene, pyrene, dihydropyrene, chrysene, perylene, tetracene, pentacene, benzopyrene, fluorene, indene, indenofluorene, and spirobifluorene.

Preferred heteroaryl groups are, for example, pyrrole, pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, tetrazole, furan, thiophene, selenophene, oxazole, isoxazole, 1,2-thiazole, 1,3-thiazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4- Five-membered rings such as thiadiazole, 1,2,5-thiadiazole, and 1,3,4-thiadiazole; six-membered rings such as pyridine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, 1,2,4-triazine, 1,2,3-triazine, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine, and 1,2,3,5-tetrazine; or indole, isoindole, indolizine, indazole, benzimidazole, benzotriazole, pristine, etc. , naphthaimidazole, phenanthroimidazole, pyridaimidazole, pyrazineimidazole, quinoxalineimidazole, benzoxazole, naphthoxazole, anthroxazole, phenanthroxazole, isoxazole, benzothiazole, benzofuran, isobenzofuran, dibenzofuran, quinoline, isoquinoline, pteridine, benzo-5,6-quinoline, benzo-6,7-quinoline, benzo-7,8-quinoline, benzoi Condensed groups such as isoquinoline, acridine, phenothiazine, phenoxazine, benzopyridazine, benzopyrimidine, quinoxaline, phenazine, naphthyridine, azacarbazole, benzocarboline, phenanthridine, phenanthroline, thieno[2,3b]thiophene, thieno[3,2b]thiophene, dithienothiophene, isobenzothiophene, dibenzothiophene, and benzothiadiazothiophene; or combinations of these groups.

Additionally, the aryl and heteroaryl groups described above and below may be substituted with alkyl, alkoxy, thioalkyl, fluorine, fluoroalkyl or further aryl or heteroaryl groups.

(Non-aromatic) alicyclic and heterocyclic groups include both saturated rings, i.e. those containing exclusively single bonds, and also partially unsaturated rings, i.e. those which may also contain multiple bonds. Heterocyclic rings preferably contain one or more heteroatoms selected from Si, O, N, S and Se.

(Non-aromatic) alicyclic and heterocyclic groups may be monocyclic, i.e. containing only one ring (such as, for example, cyclohexane) or polycyclic, i.e. containing several rings (such as, for example, decahydronaphthalene or bicyclooctane). Saturated groups are particularly preferred. Furthermore, monocyclic, bicyclic or tricyclic groups having 5 to 25 ring atoms are preferred, which may contain fused rings and may be substituted. Furthermore, 5-, 6-, 7- or 8-membered carbocyclic groups are preferred, provided that in addition, one or more C atoms may be replaced by Si and/or one or more CH groups may be replaced by N and/or one or more non-adjacent _CH2 groups may be replaced by -O- and/or -S-.

Preferred alicyclic and heterocyclic groups are, for example, 5-membered groups such as cyclopentane, tetrahydrofuran, tetrahydrothiofuran, pyrrolidine, 6-membered groups such as cyclohexane, silanane, cyclohexene, tetrahydropyran, tetrahydrothiopyran, 1,3-dioxane, 1,3-dithiane, piperidine, 7-membered groups such as cycloheptane, and fused groups such as tetrahydronaphthalene, decahydronaphthalene, indane, bicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl, octahydro-4,7-methanoindan-2,5-diyl.

Preferred substituents are, for example, solubility-promoting groups such as alkyl or alkoxy, electron-withdrawing groups such as fluorine, nitro or nitrile, or substituents for increasing the glass transition temperature (Tg) in the polymer, especially bulky groups such as, for example, t-butyl or optionally substituted aryl groups.

Preferred substituents are also referred to hereinafter as "L" and are, for example, F, Cl, Br, I, -CN, -NO ₂ , -NCO, -NCS, -OCN, -SCN, -C(=O)N(R ^x ) ₂ , -C(=O)Y ¹ , -C(=O)R ^x , -N(R ^x ) ₂ , linear or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy, each having 1 to 25 C atoms (provided that one or more H atoms may be replaced by F or Cl), optionally substituted silyl having 1 to 20 Si atoms, or optionally substituted aryl having 6 to 25, preferably 6 to 15, C atoms.

in which R ^x represents H, F, Cl, CN, a linear, branched or cyclic alkyl chain having 1 to 25 C atoms, with the proviso that one or more non-adjacent CH ₂ groups may be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, such that the O- and/or S- atoms are not directly linked to one another, with the proviso that one or more H atoms may be replaced by F, Cl, P- or P-Sp-, respectively,

and ^Y1 represents a halogen.

"Substituted silyl or aryl" preferably denotes substitution by halogen, --CN, R ⁰ , --OR ⁰ , --CO-R ⁰ , --CO-O-R ⁰ , --O-CO-R ⁰ or --O-CO-O-R ⁰ , where R ⁰ represents H or alkyl having 1 to 20 C atoms.

Particularly preferred substituents L are, for example, F, Cl, CN, _NO2 , CH3, _C2H5 , _{OCH3 , OC2H5} , _{COCH3 , COC2H5 , COOCH3 , COOC2H5} , _{CF3 , OCF3} , _OCHF2 , _{OC2F5 ,} furthermore phenyl.

To produce a PSA display, the polymerizable compounds contained in the LC medium are polymerized or crosslinked (if a compound contains more than one polymerizable group) by in situ polymerization in the LC medium between the substrates of the LC display, optionally with the application of a voltage to the electrodes.

The structure of the PSA display according to the invention corresponds to the usual configuration of a PSA display as described in the prior art cited at the beginning. Configurations without protrusions are preferred, in particular in which the electrode on the color filter side is not structured and only the electrode on the TFT side has slits. Particularly suitable and preferred electrode structures for PS-VA displays are described, for example, in US Patent Application Publication No. 2006/0066793.

The LC media according to the invention may additionally comprise one or more further components or additives selected without limitation from the following list: comonomers, chiral dopants, polymerization initiators, inhibitors, stabilizers, surfactants, wetting agents, lubricants, dispersants, hydrophobizing agents, adhesives, flow improvers, antifoaming agents, degassing agents, diluents, reactive diluents, auxiliaries, colorants, dyes, pigments and nanoparticles.

The LC medium according to the invention preferably comprises one, two or three chiral dopants, very preferably one chiral dopant.

LC media containing one, two or three polymerizable compounds, also called reactive mesogens (RM), are particularly preferred.

LC media having a chiral nematic LC phase are further preferred.

Preferably the proportion of polymerizable compound (RM) in the LC medium is between >0% and <5%, very preferably between >0% and <1%, most preferably between 0.01% and 0.5%.

Preferred embodiments are listed below, either alone or in combination with one another. The medium according to the present invention is preferably

- A compound of formula I at a concentration ranging from 0.5% to 15%, preferably from 1% to 10%, very preferably from 2% to 7%;

- one, two or more compounds of formula III, preferably of formula III-1 and/or III-2, more preferably of formula III-2, in a total concentration in the range of 2% to 15%, more preferably 3% to 12%, very preferably 4% to 10%, in particular 5% to 8%;

- one or more compounds of formula IIA in a total concentration ranging from 10% to 40%, more preferably from 15% to 35%, very preferably from 18% to 28% or from 20% to 25%;

- one or more compounds of formula IIA-2 in a total concentration ranging from 1% to 12%, more preferably from 2% to 8%, and most preferably from 3% to 6%;

- one or more compounds of formula IIA-10 in a total concentration ranging from 10% to 30%, more preferably from 12% to 25%, and very preferably from 15% to 20%;

- one or more compounds of formula IIB, preferably of formula IIB-2 and/or IIB-10, in a total concentration in the range of 10% to 30%, more preferably 12% to 25%, very preferably 14% to 19%;

- one or more compounds of formula IIB-2 in a total concentration ranging from 1% to 12%, more preferably from 2% to 8%, and most preferably from 3% to 6%;

- one or more compounds of formula IIB-10 in a total concentration ranging from 5% to 25%, more preferably from 8% to 18%, and most preferably from 10% to 15%;

- one or more compounds of formula IIA and one or more compounds of formula IIB, preferably selected from formula IIA-2, IIA-10, IIB-2 and IIB-10, in a total concentration preferably in the range of 25% to 55%, more preferably 32% to 50%, very preferably 35% to 42%;

- one or more compounds of formula IIA-2 and one or more compounds of formula IIB-2 in a combined concentration ranging from 3% to 20%, more preferably from 4% to 15%, and most preferably from 6% to 11%;

- one or more compounds of formula III and one or more compounds selected from formulae IIA, IIB, IIC and IID in a total concentration ranging from 25% to 65%, more preferably from 35% to 55%, and very preferably from 40% to 50%;

- one or more compounds of formula IV-1, preferably compound IV-1-1, in a total concentration ranging from 5% to 40%, more preferably from 10% to 30%, and very preferably from 15% to 23%;

- one or more compounds of formula IV-3, preferably of formula IV-3-2 and/or IV-3-5, in a total concentration ranging from 5% to 25%, more preferably from 10% to 20%, very preferably from 12% to 16%;

- one or more compounds of formula I and a compound of formula IV-3-2 in a combined concentration ranging from 3% to 20%, more preferably from 6% to 15%, and very preferably from 8% to 12%;

- one or more compounds of formula I and compounds of formula IV-3-2 and compounds of formula IV-1-1 in a combined concentration in the range of 15% to 45%, more preferably 22% to 40%, very preferably 26% to 34%, in particular 28% to 32%;

- Compound of formula IV-3-6 in a total concentration ranging from 0% to 5%, preferably 0%;

- one or more compounds of formula I and one or more compounds selected from formulae IV and IVa in a total concentration ranging from 20% to 50%, more preferably from 28% to 45%, very preferably from 33% to 40%;

- one or more compounds of formula I and one or more compounds selected from formula IV and IVa and one or more compounds of formula V in a total concentration in the range of 35% to 60%, more preferably 38% to 52%, very preferably 40% to 48%;

- one or more compounds of formula IVa and/or IVb in a total concentration in the range of 5% to 18%, more preferably 7% to 15%, very preferably 8% to 13%;

- Containing one or more compounds of formula V, preferably of formula V-16, in a total concentration in the range of 1% to 12%, more preferably 2% to 10%, even more preferably 3% to 10%, very preferably 4% to 8%.

Particularly preferred mixture concepts are given below (the acronyms used are explained in Tables A-D, where n and m each independently represent 1-6):

The mixture according to the present invention is preferably

- PYP-n-m, especially PYP-2-3 and/or PYP-2-4, preferably at a concentration of more than 5%, especially 8-30% of the total mixture,

and/or CPY-n-Om, in particular CPY-2-O2, CPY-3-O2 and/or CPY-5-O2, preferably in a concentration of more than 5%, in particular from 10 to 30%, relative to the total mixture,

and/or B-nO-Om and/or B(S)-nO-Om, preferably in a concentration of from 1 to 15,

and/or CY-n-Om, preferably CY-3-O2, CY-3-O4, CY-5-O2 and/or CY-5-O4, preferably in a concentration of more than 5%, in particular from 15 to 50%, relative to the total mixture,

and/or CCY-n-Om, preferably CCY-4-O2, CCY-3-O2, CCY-3-O3, CCY-3-O1 and/or CCY-5-O2, preferably in a concentration of more than 5%, in particular from 10 to 30%, relative to the total mixture,

and/or CLY-n-Om, preferably CLY-2-O4, CLY-3-O2 and/or CLY-3-O3, preferably in a concentration of more than 5%, in particular from 10 to 30%, relative to the total mixture,

and/or LY-n-Om, preferably LY-3-O2, preferably in a concentration of more than 5%, in particular from 10 to 30%, relative to the total mixture,

and/or CCOY-n-Om, preferably CCOY-3-O2, in a concentration of preferably more than 5%, in particular from 10 to 30%, relative to the total mixture,

and/or CLOY-n-Om, preferably CLOY-3-O2, in a concentration preferably greater than 5%, in particular between 10 and 30%, relative to the total mixture,

CK-n-F, preferably CK-3-F, CK-4-F and/or CK-5-F, preferably at a concentration of more than 5%, in particular 5-25% relative to the total mixture,

and/or at least two compounds of the formula PY-n-Om, preferably PY-1-O2 and PY-3-O2
Includes.

Further preferred are mixtures according to the invention which include the following mixture concepts:
(n and m each independently represent 1 to 6.)

- CPY-n-Om and CY-n-Om, preferably at a concentration of 10-80% of the total mixture,

and/or CPY-n-Om and CK-n-F, preferably in concentrations between 10 and 70% relative to the total mixture,

and/or CPY-n-Om and PY-n-Om, preferably CPY-2-O2 and/or CPY-3-O2 and PY-3-O2, preferably in a concentration of 10 to 40% relative to the total mixture,

and/or CPY-n-Om and CLY-n-Om, preferably in a concentration of 10 to 80% relative to the total mixture,

and/or CC-3-V1, preferably in an amount of 3 to 15%,

and/or PGIY-n-Om, preferably in an amount of 3 to 15%,

and/or CC-n-2V1, preferably in an amount of 3-20%.

The liquid crystal medium according to the invention advantageously has a nematic phase preferably below -20°C and above 70°C, particularly preferably below -30°C and above 71°C, very particularly preferably below -40°C and above 72°C.

In a preferred embodiment, the medium according to the invention has a clearing temperature of 70°C or more, more preferably 72°C or more, in particular 73°C or more.

In this specification, the expression "having a nematic phase" at a given temperature means that at low temperatures no smectic phases and no crystallization are observed, while on the other hand at a given temperature no clearing (transition to an isotropic phase) occurs on heating of the nematic phase. The investigation at low temperatures is carried out with a flow viscometer at the corresponding temperature and is confirmed by storage for at least 100 hours in test cells with layer thicknesses corresponding to the electro-optical application. If the storage stability in test cells at a temperature of -20°C is 1000 hours or more, the medium is called stable at this temperature. For temperatures of -30°C and -40°C, the corresponding times are 500 hours and 250 hours, respectively. At high temperatures, the clearing point is measured in a capillary tube in the conventional manner.

The liquid crystal mixture preferably has a nematic phase range of at least 60K and a flow viscosity _v20 of at most 30 ^{mm2.sec -1} at 20°C.

The mixture is nematic at temperatures below -20°C, preferably below -30°C, and very preferably below -40°C.

The medium according to the invention has a birefringence in the range of 0.085 to 0.120, preferably 0.095 to 0.115, in particular 0.100 to 0.110.

In a preferred embodiment, the medium has a birefringence in the range of 0.1005 to 0.1080, preferably 0.1020 to 0.1075, especially 0.1035 to 0.1060.

In a preferred embodiment, the medium has a dielectric anisotropy Δε of -2.4 to -5.0, preferably -2.6 to -4.5, in particular -2.7 to -4.0.

In a highly preferred embodiment, the liquid crystal mixture according to the invention has a dielectric anisotropy Δε of -2.9 to -3.3.

The rotational viscosity _γ1 at 20° C. is in the range of 70 to 200 mPa·s, more preferably 90 to 150 mPa·s.

The rotational viscosity _γ1 at 20° C. is preferably 100 mPa·s or less.

The medium according to the invention has an elastic constant _K1 in the range of 12 to 16 pN.

In a preferred embodiment, the medium according to the invention has a ratio of rotational viscosity to spray elastic constant γ ₁ /K ₁ of less than or equal to 7.2 mPa·s·pN ⁻¹ .

In a preferred embodiment the medium according to the invention has a ratio of rotational viscosity to spray elastic constant γ ¹ /K 1 in the range of 6.6 mPa·s·pN ⁻¹ to 7.4 mPa _· s·pN ⁻¹ , more preferably 6.9 mPa·s·pN ₋₁ to 7.2 mPa·s·pN ⁻¹ .

The liquid-crystalline media according to the invention have relatively low values of the threshold voltages (V ₀ ). They are preferably in the range from 1.7 V to 3.0 V, particularly preferably ≦2.6 V, very particularly preferably ≦2.4 V.

In the present invention, the term "threshold voltage" refers to the capacitive threshold (V ₀ ), also called the Friedericks threshold, unless otherwise specified.

In addition, the liquid crystal medium according to the present invention has a high voltage retention ratio in a liquid crystal cell.

In general, liquid crystal media with lower address voltages or threshold voltages exhibit lower voltage retention than those with higher address voltages or threshold voltages, and vice versa.

In the present invention, the term "dielectrically positive compound" refers to a compound having a Δε greater than 1.5, the term "dielectrically neutral compound" refers to a compound having a Δε greater than -1.5 and less than 1.5, and the term "dielectrically negative compound" refers to a compound having a Δε smaller than -1.5. The dielectric anisotropy of the compound is determined by dissolving 10% of the compound in a liquid crystal host and measuring the capacitance of the resulting mixture at 1 kHz in at least one test cell with homeotropic and homogeneous surface alignment, respectively, with a layer thickness of 20 μm. The measuring voltage is typically between 0.5 V and 1.0 V, but always lower than the capacitance threshold of the respective liquid crystal mixture considered.

All temperature values given in this invention are in °C.

The mixtures according to the invention are suitable for all VA-TFT applications, e.g. VAN, MVA, (S)-PVA, ASV, PSA (polymer sustained VA) and PS-VA (polymer stabilized VA). They are furthermore suitable for IPS (in-plane-switching) and FFS (fringe field switching) applications with negative Δε.

It will be appreciated by those skilled in the art that the VA, IPS or FFS mixtures of the present invention may also include compounds in which, for example, H, N, O, Cl and F are replaced by the corresponding isotopes.

The compounds according to the invention can be synthesized by known methods described in the literature (e.g. standard works such as Houben-Weyl, Methoden der Organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart, etc.) or in a similar manner under known reaction conditions suitable for said reactions. Also variations known per se can be used here, although not mentioned here. In particular, they can be prepared as described in the following reaction schemes or in a similar manner. Further methods for preparing the compounds of the invention can be taken from the examples.

Other mesogenic compounds not explicitly mentioned above can also be advantageously used in the medium according to the invention. Such compounds are known to those skilled in the art.

In the present invention and in the following examples, the structures of the liquid crystal compounds are indicated by acronyms, the conversion into chemical formulas being carried out according to the following tables A to C. All radicals C _m H _2m+1 , C _n H _2n+1 and C _l H _2l+1 or C _m H _2m-1 , C _n H _2n-1 and and C _l H _2l-1 are linear alkyl or alkylene radicals having in each case n, m and l C atoms. Preferably, n, m and l are each independently 1, 2, 3, 4, 5, 6 or 7. Table A shows the codes of the ring elements of the core of the compounds, Table B lists the bridging units and Table C lists the meaning of the symbols of the left and rightmost radicals of the molecules. The acronyms consist of the code of the ring element with any linking group followed by the first hyphen and the code of the leftmost radical, and the second hyphen and the code of the rightmost radical. Table D shows example compound structures along with their respective abbreviations.

<Table A: Ring elements>

<Table B: Cross-linking units>

<Table C: Terminal groups>

In the table, n and m are each integers, and the three dots "..." are places for other abbreviations from this table.

Apart from the compounds of formula I, IIA, IIB, IIC and/or IID, IVa, IVb and V, the mixtures according to the invention preferably contain one or more compounds of the compounds mentioned below.

The following abbreviations are used:
(n, m, k and l are each independently an integer, preferably 1 to 9, preferably 1 to 7; k and l may be 0, preferably 0 to 4, more preferably 0 or 2, most preferably 2; n is preferably 1, 2, 3, 4 or 5; in the combination "-nO-", it is preferably 1, 2, 3 or 4, more preferably 2 or 4; m is preferably 1, 2, 3, 4 or 5; in the combination "-Om", it is preferably 1, 2, 3 or 4, more preferably 2 or 4. The combination "-lVm" is preferably "2V1".)

<Table D>

Table E shows chiral dopants that are preferably employed in the mixtures according to the invention.

<Table E>

In a preferred embodiment of the invention, the medium according to the invention comprises one or more compounds selected from the group of compounds from Table E.

<Table F>
Table F shows exemplary compounds which may preferably be used as reactive mesogenic compounds in the LC media according to the invention. If the mixture according to the invention comprises one or more reactive compounds, they are preferably employed in an amount of 0.01 to 5% by weight. It may also be necessary to add an initiator or a mixture of two or more initiators for the polymerization. The initiator or initiator mixture is preferably added in an amount of 0.001 to 2% by weight, based on the mixture. Suitable initiators are for example Irgacure (BASF) or Irganox (BASF).

In a preferred embodiment, the mixture according to the invention comprises one or more polymerizable compounds, preferably selected from the polymerizable compounds of the formulae RM-1 to RM-102. Media of this type are particularly suitable for PS-FFS and PS-IPS applications. Of the reactive mesogens shown in Table D, the compounds RM-1, RM-2, RM-3, RM-4, RM-5, RM-9, RM-17, RM-42, RM-48, RM-68, RM-87, RM-91, RM-98, RM-99 and RM-101 are particularly preferred.

The reactive mesogens or polymerizable compounds of the formula M and formulae RM-1 to RM-102 are furthermore suitable as stabilizers. In this case, the polymerizable compounds are not polymerized but are instead added to the liquid-crystalline medium in a concentration of more than 1%.

The present invention will now be described in detail with reference to the following non-limiting examples.

The following abbreviations and symbols are used:
V ₀ is the capacitance threshold voltage [V] at 20° C.
n _e is the extraordinary refractive index at 20° C. and 589 nm;
n ₀ is the ordinary refractive index at 20° C. and 589 nm;
Δn is the optical anisotropy at 20° C. and 589 nm;
ε _⊥ is the dielectric constant perpendicular to the director at 20°C and 1 kHz.
ε _∥ is the dielectric constant parallel to the director at 20 °C and 1 kHz,
Δε is the dielectric anisotropy at 20° C. and 1 kHz;
cl.p., T(N,I) is the clearing point [°C],
γ ₁ is the rotational viscosity at 20° C. [mPa·s],
_K1 is the elastic constant for "splay" deformation at 20°C [pN];
_K2 is the elastic constant for "twist" deformation at 20°C [pN],
_K3 is the elastic constant for "bend" deformation at 20°C [pN].

Unless expressly stated otherwise, all concentrations in this application are quoted in weight percent and refer to the corresponding mixture as a whole, consisting of all solid or liquid crystal components, without solvent.

Unless expressly stated otherwise, all temperature values given in this application, such as melting point T(C,N), smectic (S) to nematic (N) phase transition T(S,N) and clearing point T(N,I), are quoted in degrees Celsius (°C). M.p. is melting point, cl.p. is clearing point. Furthermore, C is crystalline state, N is nematic phase, S is smectic phase and I isotropic phase. Data between these symbols represent transition temperatures.

All physical properties are or have been determined according to "Merck Liquid Crystals, Physical Properties of Liquid Crystals", November 1997, Merck, Germany, and apply for a temperature of 20° C., with Δn being determined at 589 nm and Δε at 1 kHz, unless expressly indicated otherwise in each case.

The term "threshold voltage" for the present invention, unless otherwise specified, relates to the capacitive threshold ( _V0 ), also known as the Freederickss threshold. In the examples, and as is generally usual, the optical threshold for 10% relative contrast ( _V10 ) may also be indicated.

Unless otherwise specified, the method for preparing the test cells and the method for measuring the electro-optical properties, etc. will be as described below or similar.

The display used to measure the capacitive threshold voltage consists of two plane-parallel glass outer plates spaced 25 μm apart, each with an electrode layer on the inside and an unrubbed polyimide alignment layer on the top that provides homeotropic alignment of the liquid crystal molecules.

Unless otherwise indicated, VHR is determined at 20° C. (VHR ₂₀ ) and after 5 minutes in an oven at 100° C. (VHR ₁₀₀ ) in an instrument model LCM-1 (O0004) commercially available from Toyo Corporation, Japan. Unless more precisely stated, the voltage used has a frequency in the range of 1 Hz to 60 Hz.

The stability against UV irradiation is studied with a "Suntest CPS+" from Heraeus GmbH, Germany, using a xenon lamp NXE1500B. The sealed test cells are irradiated for 2.0 hours without additional heating, unless expressly indicated. The irradiation power in the wavelength range from 300 nm to 800 nm is 765 W/ ^m2V . To simulate the so-called window glass mode, a UV "cut-off" filter with an edge wavelength of 310 nm is used. In each experimental series, at least four test cells are studied for each condition, and the respective results are presented as the average value of the corresponding individual measurements.

To study low-temperature stability, also known as "LTS" (low-temperature stability), i.e. the stability of LC mixtures in bulk against spontaneous crystallization of the individual components or the development of smectic phases at low temperatures, several sealed bottles, each containing about 1 g of material, are stored at one or more predefined temperatures, typically -10°C, -20°C, -30°C and/or -40°C, and visually inspected at regular intervals to see if a phase transition is observed. The time is recorded when the first sample at a predefined temperature shows a change. The time until the last inspection, at which no change is observed, is recorded as the respective LTS.

Ion density for calculating resistivity is measured using a VHR test cell with AL16301 polyimide (JSR Corporation, Japan) and a cell gap of 3.2 μm using a commercially available LC Material Property Measurement System Model 6254 from Toyo Corporation, Japan. Measurements are taken after storage in an oven at 60°C or 100°C for 5 minutes.

The clearing point is measured using a Mettler Thermosystem FP900. The optical anisotropy (n) is measured using an Abbe refractometer H005 (sodium spectrum lamp Na10, 589 nm, at 20° C.). The dielectric anisotropy (Δε) is measured using an LCR meter E4980A/Agilent (G005) at 20° C. (ε-parallel cell with JALS2096-R1). The starting voltage (V ₀ ) is measured using an LCR meter E4980A/Agilent (G005) at 20° C. (ε-parallel cell with JALS2096-R1). The rotational viscosity (γ ₁ ) is measured using a Toyo Corporation LCM-2 (0002) at 20° C. (gamma 1 negative cell with JALS-2096-R1). Elastic constant (K ₁ , Spray) is measured using an LCR meter E4980A/Agilent (G005) at 20° C. (ε-parallel cell with JALS2096-R1). K ₃ : Elastic constant (K ₃ , Bend) is measured using an LCR meter E4980A/Agilent (G005) at 20° C. (ε-parallel cell with JALS2096-R1).

The following example mixtures with negative dielectric anisotropy are particularly suitable for liquid crystal displays with at least one planar alignment layer, such as, for example, IPS and FFS displays, in particular UB-FFS (: Ultra Bright FFS), as well as VA displays.

<Mixture Examples>
The nematic LC host mixtures M1-M9 have the compositions and physical properties given in the table below.

<Mixture M1>

<Mixture M2>

<Mixture M3>

Mixture M4 contains compound B(S)-2O-O1(c5).

<Mixture M4>

Mixture M5 contains the following compound CPY-(c3)2-O2:

<Mixture M5>

<Mixture M6>
Mixture M6 consists of 98.87% of mixture M1, 0.03% of compound ST-3a-1 and 0.10% of compound H-1-1.

<Mixture M7>
Mixture M7 consists of 98.965% of mixture M1, 0.03% of compound ST-3a-1 and 0.005% of compound H-1-1.

<Mixture M8>

<Mixture M9>

<Mixture M10>

<Mixture Example P3>
The example mixture P3 consists of 99.595% of mixture M3, 0.40% of compound RM-1 and 0.005% of compound ST-3a-1.

<Mixture M11>

<Mixture M12>

<Mixture M13>

<Mixture M14>

<Mixture M15>

<Mixture M16>

<Mixture M17>

<Mixture M18>

<Mixture M19>

<Mixture M20>

<Mixture M21>

<Mixture M22>

<Mixture M23>

<Mixture M24>

<Mixture M25>

<Mixture M26>

<Mixture M27>

<Mixture M28>

<Mixture M29>

<Mixture M30>

<Mixture M31>

<Mixture M32>

<Mixture M33>

<Mixture M34>

<Mixture M35>

<Mixture M36>

To improve reliability, the mixtures according to examples M11 to M36 may be additionally stabilized with one, two or three stabilizers selected from the group of compounds a) to h) described below, in each case being added in an amount of 0.01 to 0.04% based on the total mixture.

<Example of polymerizable mixture>

<Mixture Example P1>
The example mixture P1 consists of 99.595% of the mixture M1, 0.40% of the compound RM-1 and 0.005% of the compound ST-3a-1.

<Mixture Example P2>
The example mixture P2 consists of 99.595% of the mixture M2, 0.40% of the compound RM-1 and 0.005% of the compound ST-3a-1.

<Mixture Example P3>
The example mixture P3 consists of 99.595% of mixture M3, 0.40% of compound RM-1 and 0.005% of compound ST-3a-1.

<Mixture Example P4>
The example mixture P4 consists of 99.595% of mixture M4, 0.40% of compound RM-1 and 0.005% of compound ST-3a-1.

<Mixture Example P5>
The example blend P5 consists of 99.595% blend M5, 0.40% compound RM-1 and 0.005% compound ST-3a-1.

<Mixture Example P6>
The example mixture P6 consists of 99.595% of the mixture M1, 0.40% of the compound RM-19 and 0.005% of the compound ST-3a-1.

<Mixture Example P7>
The example blend P7 consists of 99.595% of blend M2, 0.40% of compound RM-19 and 0.005% of compound ST-3b-1.

<Mixture Example P8>
The example blend P8 consists of 99.595% blend M3, 0.40% compound RM-35 and 0.005% compound ST-3a-1.

<Mixture Example P9>
The example blend P9 consists of 99.595% of blend M4, 0.40% of compound RM-156 and 0.005% of compound ST-3a-1.

<Mixture Example P10>
The example blend P10 consists of 99.595% of blend M5, 0.40% of compound RM-157 and 0.005% of compound ST-3b-1.

Claims (18)

Liquid-crystalline medium comprising a) one or more compounds of the formula I, b) one or more compounds selected from the group of the formulae IIA, IIB, IIC and IID and c) one or more compounds of the formula III.

(Wherein,
R ¹ represents n-butyl or n-pentyl.

(Wherein,
R ^2A , R ^2B , R ^2C and R ^2D each independently represent H, an alkyl group having 1 to 7 C atoms or an alkenyl group having 2 to 7 C atoms, each of which is unsubstituted or at least monosubstituted with a halogen, provided that one or more CH ₂ groups in these groups are -O-, -S-, ...

may be replaced by —C≡C—, —CF ₂ O—, —OCF ₂ —, —OC—O— or —O—CO—;
^L1 and ^L2 each independently represent F, Cl, _CF3 or _CHF2 ,
Y represents H, F, Cl, _CF3 , _CHF2 or _CH3 ;
Z ² , Z ^2B and Z ^2D each independently represent a single bond, —CH ₂ CH ₂ —, —CF ₂ O—, —OCF ₂ —, —CH ₂ O—, —OCH ₂ —, —COO— or —OCO—;
p represents 0, 1 or 2;
q represents 0 or 1, and v represents 1, 2, 3, 4, 5, or 6.

(Wherein,
R ³¹ and R ³² each independently represent H, an alkyl or alkoxy group having 1 to 7 C atoms, with the proviso that one or more CH ₂ groups in these groups are not directly linked to the O atoms with each other,

each independently may be replaced by —C≡C—, —CF ₂ O—, —OCF ₂ —, —CH═CH—, —O—, —CO—O— or —O—CO—, in which one or more H atoms may be replaced by halogen;
A ³ independently at each occurrence represent a 1,4-phenylene group in which one or two CH groups may be replaced by N or a 1,4-cyclohexenylene or 1,4-cyclohexylene group in which one or two non-adjacent CH ₂ groups may be replaced by -O- or -S-, with the proviso that the group may be mono- or polysubstituted by halogen atoms,
^Z3 's in each occurrence independently represent _-CF2O- , -OCF2-, _-CH2O- , _-OCH2- , _-CH2- , _-CH2CH2- , -CH=CH-, _-C≡C- or a _single bond;
L ³¹ and L ³² each independently represent F, Cl, CF ₃ or CHF ₂ ;
W represents O or S, and n represents 0, 1 or 2. 2. Liquid-crystalline medium according to claim 1, wherein the medium comprises one or more compounds of the formula IIB-2.

(In the formula, alkyl and alkyl ^* each independently represent a linear alkyl group having 1 to 6 C atoms, and (O) represents an oxygen atom or a single bond.) 3. Liquid-crystalline medium according to claim 2, wherein the medium comprises one or more compounds of the formula IIB-2, in which alkyl denotes methyl or propyl and alkyl ^* denotes ethyl. Liquid-crystalline medium according to any one of claims 1 to 3, wherein the medium comprises one or more compounds of the formula IV-3

(wherein alkyl represents an alkyl group having 1 to 7 carbon atoms; alkenyl is

In the formula, m is 0, 1 or 2, and n is 0, 1 or 2. Liquid-crystalline medium according to any one of the preceding claims, wherein the medium comprises one or more compounds of the formula IV-1 in a total amount in the range from 1% to 30%.

(Wherein,
alkyl and alkyl' are the same or different and each represents an alkyl having 1 to 7 C atoms;
However, compounds of formula I are excluded. The liquid crystal medium according to claim 5, wherein alkyl in formula IV-1 represents methyl and alkyl' represents n-propyl. Liquid crystal medium according to any one of claims 1 to 6, wherein the medium comprises one or more compounds of the formula IVa

(Wherein,
R ⁴¹ and R ⁴² each independently represent a straight-chain alkyl, alkoxy, alkenyl, alkoxyalkyl or alkoxy group having up to 12 C atoms, and

^Z4 represents a _single bond, _-CH2CH2- , -CH=CH-, _-CF2O- , _-OCF2- , -CH2O-, _-OCH2- , -COO-, _-OCO- , _-C2F4- , _-C4H8- or -CF _{= CF-} . Liquid crystal medium according to any one of claims 1 to 7, wherein the medium comprises one or more compounds of the formula V

(Wherein,
R ⁵¹ and R ⁵² each represent an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, or an alkoxyalkyl group, an alkenyl group, or an alkenyloxy group having 2 to 7 carbon atoms;

represents
Z ⁵¹ and Z ⁵² each independently represent -CH ₂ -CH ₂ -, -CH ₂ -O-, -CH=CH-, -C≡C-, -COO- or a single bond, and n is 1 or 2. Liquid crystal medium according to any one of claims 1 to 8, wherein the medium comprises one or more compounds of the formula VI

in which R ⁶ and R ⁶² have the meaning of R ^2A as defined in claim 1, or R ⁶² represents F, Cl, CF ₃ or OCF ₃ ,
L ⁶¹ , L ⁶² , L ⁶³ , L ⁶⁴ , L ⁶⁵ and L ⁶⁶ independently represent H or F, provided that at least one of L ⁶¹ , L ⁶² , L ⁶³ , L ⁶⁴ , L ⁶⁵ and L ⁶⁶ represents F. Liquid crystal medium according to any one of the preceding claims, wherein the medium comprises one or more compounds of the formulae P1 to P4.

(R ^P represents a linear alkyl or alkoxy group having 1 to 6 C atoms or an alkenyl group having 2 to 6 C atoms,
^XP represents a linear alkyl having 1 to 6 C atoms, F, Cl, _CF3 , _OCF2H , _OCF3 , OCHFCF3, _OCF2CHFCF3 or _OCH = _{CF2 ,}
L ^P1 , L ^P2 and L ^P3 each independently represent H or F. Liquid-crystalline medium according to any one of claims 1 to 10, wherein the medium comprises one or more compounds selected from the group of compounds of the following formulae:

in which the parameters are as defined in claims 1, 8 and 9, and alkyl and alkyl ^* each independently represent a linear alkyl group having 1 to 6 C atoms,
alkenyl and alkenyl ^* each independently represent a straight-chain alkenyl group having 2 to 6 C atoms,
(O)alkyl ^* or (O)-alkyl represents alkyl ^* or O-alkyl ^* ;
m represents 0, 1, 2, 3, 4, 5 or 6;
R has the meaning of R ^2A in formula IIA,
R ¹¹ and R ¹² each independently have one of the meanings of R ^2A in formula IIA,
^L1 and ^L2 each independently represent F or Cl;
^L3 represents H or _CH3 ;
(O) represents O or a single bond;
R ^IIIA represents an alkyl or alkenyl group having up to 7 C atoms or a group Cy-C _m H _2m+1 ,
m and n are the same or different and each is 0, 1, 2, 3, 4, 5, or 6;
Cy represents an alicyclic group having 3, 4 or 5 ring atoms, which may be substituted with alkyl or alkenyl, each having up to 3 C atoms, or halogen or CN. Liquid crystal medium according to any one of claims 1 to 11, wherein the medium comprises one or more compounds of the formula H

(Wherein,
Ar represents an aromatic or heteroaromatic hydrocarbon group having 4 to 40 C atoms;
Sp represents a spacer group;
R 1 ^S represents H, alkyl having 1 to 12 C atoms or alkenyl having 2 to 12 C atoms;
^ZS represents -O-, -C(O)O-, -(CH ₂ ) _z - or -(CH ₂ ) _z O-, or a single bond;
H.A.

represents;
^RH represents H, ^O. , _CH3 , OH or ^ORS ;
R ^S1 , R ^S2 , R ^S3 and R ^S4 are the same or different and represent alkyl having 1 to 6 C atoms;
G represents H or R 2 ^S or a group Z ² -HA;
z is an integer from 1 to 6; and q is 3 or 4. The liquid crystal medium according to any one of claims 1 to 12, wherein the medium contains one or more additives selected from the group consisting of dyes, dopants and reactive mesogens. A liquid crystal display comprising a liquid crystal medium according to any one of claims 1 to 13. The display of claim 14, wherein the display is a VA, IPS, FFS, PS-VA, PS-IPS or PS-FFS display. Use of a liquid crystal medium according to any one of claims 1 to 13 in a VA, IPS, FFS, PS-VA, PS-IPS or PS-FFS display. Use of a liquid crystal medium according to any one of claims 1 to 13 for energy-saving liquid crystal displays. A method for preparing a liquid crystal medium according to any one of claims 1 to 13, comprising mixing one or more compounds of formulae I and III with one or more compounds selected from formulae IIA, IIB, IIC and IID, optionally with one or more polymerizable mesogens, and optionally with further LC compounds and/or additives.