CN118207002A - Liquid-crystalline medium - Google Patents

Abstract

The present invention relates to Liquid Crystal (LC) media and to Liquid Crystal Displays (LCDs) containing these media, in particular to energy saving displays addressed by active matrix and in particular to LC displays of the TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, XB-FFS, PS-FFS, SA-HB-FFS, SA-XB-FFS, polymer stabilized SA-HB-FFS, polymer stabilized SA-XB-FFS, positive VA or positive PS-VA type. The media has improved long term stability at lower temperatures and is well suited for automotive and outdoor applications.

Description

Liquid-crystalline medium

The present invention relates to Liquid Crystal (LC) media and to Liquid Crystal Displays (LCDs) containing these media, in particular to energy saving displays addressed by active matrix and in particular to LC displays of the TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, XB-FFS, PS-FFS, SA-HB-FFS, SA-XB-FFS, polymer stabilized SA-HB-FFS, polymer stabilized SA-XB-FFS, positive VA or positive PS-VA type. The medium has improved Low Temperature Stability (LTS) and high long term stability against UV radiation and high temperatures.

Liquid Crystal Displays (LCDs) are used in many fields for information display. LCDs are used for both direct view and projection displays. The electro-optical modes used are, for example, twisted Nematic (TN), super Twisted Nematic (STN), optically Compensated Bend (OCB) and Electrically Controlled Birefringence (ECB) modes and their variants, among others. All of these modes utilize an electric field generated substantially perpendicular to the substrates and the liquid crystal layer.

In addition to these modes, there are electro-optic modes that utilize an electric field that is substantially parallel to the substrate or liquid crystal layer. For example, WO 91/10936 discloses a liquid crystal display in which the electrical signal is generated in such a way that the electric field has a significant component parallel to the liquid crystal layer, and since then it is known as an in-plane switching (IPS) display. The principle of operation of such a display is described, for example, by R.A. Soref in Journal of APPLIED PHYSICS, journal of applied physics, volume 45, 12, pages 5466-5468 (1974).

The IPS display contains an LC layer between two substrates with an in-plane orientation, wherein the two electrodes are arranged on only one of the two substrates and preferably have an interdigitated comb structure. When a voltage is applied to the electrodes, an electric field is generated between them with a significant component parallel to the LC layer. This results in a realignment of LC molecules in the layer plane.

For example, EP 0 588 568 discloses various possibilities for designing electrodes and for addressing IPS displays. DE 198 24 137 likewise describes various embodiments of such IPS displays.

Liquid crystal materials for IPS displays of this type are described, for example, in DE 195 28 104.

Furthermore, so-called "fringe field switching" (FFS) displays have been reported (see inter alia s.h.jung et al, jpn.j.appl.Phys. [ journal of applied physics ], volume 43, stage 3, 2004,1028) which contain two electrodes on the same substrate, one of which is structured in a comb-like fashion and the other of which is unstructured. Thereby creating a strong so-called "fringe field", i.e. a strong electric field near the edges of the electrodes, and an electric field having both a strong vertical component and also a strong horizontal component throughout the cartridge. FFS displays have low contrast viewing angle dependence. FFS displays typically contain an LC medium with positive dielectric anisotropy, and an alignment layer, typically polyimide, that provides planar alignment for the molecules of the LC medium.

IPS and FFS electro-optic mode liquid crystal displays are particularly suitable for modern desktop monitors, televisions and multimedia applications. In displays of this type, the liquid-crystalline medium according to the invention (LC medium) is preferably used. Typically, dielectrically positive liquid-crystalline media with a rather low value of dielectric anisotropy are used in FFS displays, but in some cases LC media with a dielectric anisotropy of only about 3 or even lower are also used in IPS displays.

Further improvements have been achieved by the HB-FFS mode. One of the unique features of the HB-FFS mode is that it enables higher transmittance compared to conventional FFS techniques, which allows the panel to be operated with less energy consumption.

Another recently developed mode is the XB-FFS mode, in which the LC medium additionally contains polar liquid crystal compounds with low dielectric anisotropy.

Liquid crystal compositions suitable for LCDs and in particular for FFS and IPS displays are known in the art, for example from JP 07-181 439 (A), EP0 667 555, EP0 673 986, DE 195 09 410, DE 195 28 106, DE 195 28 107, WO 96/23851 and WO 96/28 521. However, these compositions have certain drawbacks. Among other drawbacks, most of them result in disadvantageously long addressing times, have insufficient resistivity values, and/or require excessive operating voltages. Improvements in both handling characteristics and also in shelf life are necessary here.

FFS and IPS displays may operate as Active Matrix Displays (AMD) or Passive Matrix Displays (PMD). In the case of active matrix displays, the individual pixels are usually addressed by integrated, non-linear active elements, such as, for example, thin Film Transistors (TFTs), whereas in the case of passive matrix displays the individual pixels are usually addressed by multiplexing methods as known from the prior art.

The display according to the invention is preferably a matrix through an active matrix, preferably through TFTs. However, the liquid crystal according to the invention can also be advantageously used in displays with other known addressing schemes.

Typical applications of in-plane switching (IPS) and Fringe Field Switching (FFS) technologies are monitors, notebook computers, televisions, mobile phones, tablet PCs, etc.

Both IPS and FFS techniques have certain advantages over other LCD techniques, such as, for example, vertical Alignment (VA) techniques, e.g., wide viewing angle dependence of contrast.

Providing additional LC media and their use in displays with high transmittance, good black state and high contrast is a central challenge for modern FFS and IPS applications. In addition, modern applications require good low temperature stability and fast addressing times.

Matrix liquid crystal display (MFK) displays with full array LED backlights, which have become more common in recent years, include a large number of Light Emitting Diodes (LEDs) arranged directly behind a layer with FK medium. Modern high performance InGaN LEDs sometimes reach operating temperatures in excess of 70 ℃ and, depending on the design, can emit UV radiation in addition to visible light. Therefore, direct contact between the LED and the LC medium puts special demands on UV stability and temperature resistance of the LC medium. Thus, state-of-the-art MFK displays are not capable of meeting today's requirements.

Recently, MFK displays are also increasingly used for outdoor applications such as PIDs (public information displays) for displaying various types of information at railway stations, roads, airports, hotels, and shopping malls. PID requires much higher long-term resistance to solar UV radiation and high temperatures, and a wider operating temperature range, than conventional MFK displays (such as those used in TV applications). In addition, such displays are also typically exposed to temperatures as low as-20 ℃ and thus need to have adequate Low Temperature Stability (LTS) and a broad nematic phase range. Display types with relatively high energy consumption have been used for such purposes, since no suitable LC medium has been obtained until now.

The object of the present invention is to provide LC media, in particular for FFS and IPS displays, but also for TN, positive VA or STN displays, and in particular for active matrix displays like those addressed by TFTs, which do not exhibit the disadvantages indicated above or exhibit only to a small extent and preferably have a high specific resistance, a low threshold voltage, a high dielectric anisotropy, good Low Temperature Stability (LTS) and a broad nematic phase range, fast response times and low rotational viscosity, excellent long-term stability against UV radiation and an increased operating temperature and enable high brightness. In other words, such LC media should be suitable for energy efficient LC displays for outdoor use.

These objects have been achieved by providing an LC medium as described and claimed below.

In the case of FFS displays, there is a need to further optimize response time, contrast, brightness and reliability. However, it has been found that the prior art liquid crystal materials generally do not meet all of these requirements at the same time.

It has now surprisingly been found that LC media according to the invention containing a combination of one or more compounds of formula I and at least one compound of formula T1 and/or T2 show several improvements, especially when used in FFS mode displays like good solubility, excellent LTS values, a broad nematic phase range and a low γ1/K ₁ ratio and fast response times.

The liquid-crystalline media according to the invention are particularly suitable for use in FFS, HB-FFS, XB-FFS and IPS mode liquid-crystal displays based on dielectrically positive liquid crystals and polymer-stabilised variants thereof.

The prior art, for example WO 2010/099853 A1 and DE 10 2010 027 099 A1, discloses thiophene-containing LC media. WO 2010/099853 A1 teaches compounds containing thiophene-2, 5-diyl units which are directly linked to 2-and/or 6-substituted 1, 4-phenylene units. WO 2010/099853 A1 describes the development of new materials for LC displays. This object is achieved by providing a compound having the formula

Wherein A ⁰ represents a2, 6-difluoro-1, 4-phenylene unit, A ¹ and A ² represent, among other things, a1, 4-phenylene or 1, 4-cyclohexylene unit, and Z ¹ and Z ² represent bridging elements or single bonds.

Specific examples described are, for example, the following compounds (see WO 2010/099853 A1):

for many practical applications in LC displays, known LC media comprising thiophene compounds have only moderate LTS. Exposure to temperatures below-20 ℃ generally results in the formation of undesirable smectic phases. In particular, LC media comprising thiophene compounds and a large amount of diluents such as CC-3-V or CC-3-V1 often show insufficient LTS and are therefore unsuitable for use at low temperatures.

JP H01-240592A describes liquid-crystalline compositions for TN and STN applications which have a broad nematic phase range and comprise, in particular, a diphenylacetylene compound having the following structure:

The document does not mention diluents such as CC-3-V or CC-3-V1 and mesogenic thiophene compounds.

The subject of the present invention is an LC medium, characterized in that it comprises one or more compounds of formula I

Wherein each substituent has the following meaning:

R ¹ and R ² are each, independently of one another, H atom, alkyl or alkoxy having 1 to 12C atoms or alkenyl or alkenyloxy having 2 or 12C atoms, wherein one or more non-adjacent CH ₂ groups are optionally substituted by-C.ident.C-, -CF ₂O-、-OCF₂ -, -ch=ch-, -O-, -CO-O-or-O-CO-substitution in such a way that the O atoms are not directly connected to each other and wherein one or more H atoms may be replaced by halogen atoms or cycloalkyl or cycloalkoxy groups having 3 to 12C atoms, wherein one or more H atoms may be replaced by halogen atoms,

A ⁰、A¹、A² each independently of the other represents phenylene-1, 4-diyl, wherein, in addition, one or two CH groups may be replaced by N and one or more H atoms may be replaced by halogen, CN, CH ₃、CHF₂、CH₂F、CF₃、OCH₃、OCHF₂ or OCF ₃, cyclohexane-1, 4-diyl, wherein, in addition, one or two non-adjacent CH ₂ groups may be replaced by O and/or S and one or more H atoms may be replaced by F, cyclohexene-1, 4-diyl, bicyclo [1.1.1] pentane-1, 3-diyl, bicyclo [2.2.2] octane-1, 4-diyl, spiro [3.3] heptane-2, 6-diyl, tetrahydropyran-2, 5-diyl or 1, 3-dioxane-2, 5-diyl,

Z ¹ and Z ² each independently of one another represent -CF₂O-、-OCF₂-、-CH₂O-、-OCH₂-、-CO-O-、-O-CO-、-C₂H₄-、-C₂F₄-、-CF₂CH₂-、-CH₂CF₂-、-CFHCFH-、-CFHCH₂-、-CH₂CFH-、-CF₂CFH-、-CFHCF₂-、-CH＝CH-、-CF＝CH-、-CH＝CF-、-CF＝CF-、-C≡C- or a single bond,

K and l each independently of one another represent 0,1, 2 or 3.

In addition to one or more compounds of formula I as defined above, the LC medium also contains one or more compounds selected from the group consisting of formulas T1 and T2

Wherein the method comprises the steps of

R ³ and R ⁴ each independently of one another represent alkyl or alkoxy having 1 to 12C atoms or alkenyl having 2 to 12C atoms, wherein one or more CH ₂ groups are optionally replaced by-C.ident.C-, -CF ₂O-、-OCF₂ -, -ch=ch-, -O-, -CO-O-or-O-CO-substitution in such a way that O atoms are not directly connected to each other and wherein one or more H atoms may be replaced by halogen atoms,

L ^1-6 each independently of the other represents H or F,

X ⁰ represents F, cl, CN, SF ₅, SCN, NCS, haloalkyl or haloalkoxy having 1 to 6C atoms, or haloalkenyl or haloalkenoxy having 2 to 6C atoms

Y ^1-3 each independently of the other represents H or a linear or branched alkyl or alkoxy group having 1 to 6C atoms, or a cycloalkyl or cycloalkoxy group having 3 to 6C atoms; and

M and n each independently of the other represent 0 or 1.

The invention further relates to the use of LC media as described above and below for electro-optical purposes, in particular in liquid crystal displays, shutter glasses, LC windows, 3D applications, preferably in TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, XB-FFS, PS-HB-FFS, PS-XB-FFS, SA-HB-FFS, SA-XB-FFS, polymer-stabilized SA-HB-FFS, polymer-stabilized SA-XB-FFS, positive VA and positive PS-VA displays, very preferably in FFS, HB-FFS, IPS, PS-HB-FFS and PS-IPS displays.

The invention further relates to electro-optic liquid crystal displays, in particular TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, XB-FFS, PS-HB-FFS, PS-XB-FFS, SA-HB-FFS, SA-XB-FFS, polymer stabilized SA-HB-FFS, polymer stabilized SA-XB-FFS, positive VA or positive PS-VA displays, preferably FFS, HB-FFS, IPS, PS-HB-FFS or PS-IPS displays, containing an LC medium as described above and below.

In the present application, all atoms also include their isotopes. In some embodiments, one or more hydrogen atoms (H) may be replaced with deuterium (D); the high degree of deuteration enables or simplifies analytical determination of the compounds, especially at low concentrations.

In the formulae above and below, if R ¹、R²、R³、R⁴ or R ⁰ preferably represents alkyl and/or alkoxy, it may be linear or branched. It is preferably straight-chain, has 2, 3,4, 5, 6 or 7C atoms and thus preferably represents ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, furthermore methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octoxy, nonoxy, decyloxy, undecoxy, dodecoxy, tridecyloxy or tetradecyloxy. R ⁰ preferably represents a straight-chain alkyl group having 2 to 6C atoms.

The oxaalkyl preferably represents a linear 2-oxapropyl (=methoxymethyl), 2-oxabutyl (=ethoxymethyl) or 3-oxabutyl (=2-methoxyethyl), 2-oxapentyl, 3-oxapentyl or 4-oxapentyl, 2-oxahexyl, 3-oxahexyl, 4-oxahexyl or 5-oxahexyl, 2-oxaheptyl, 3-oxaheptyl, 4-oxaheptyl, 5-oxaheptyl or 6-oxaheptyl, 2-oxaoctyl, 3-oxaoctyl, 4-oxaoctyl, 5-oxaoctyl, 6-oxaoctyl or 7-oxaoctyl, 2-oxanonyl, 3-oxanonyl, 4-oxanonyl, 5-oxanonyl, 6-oxanonyl, 7-oxanonyl or 8-oxanonyl, 2-oxadecyl, 3-oxadecyl, 4-oxadecyl, 5-oxadecyl, 6-oxadecyl, 7-oxadecyl, 8-oxadecyl or 9-oxadecyl.

If R ¹、R²、R³、R⁴ or R ⁰ represents an alkoxy or oxaalkyl group, it may also contain one or more further oxygen atoms, provided that the oxygen atoms are not directly connected to one another.

In another preferred embodiment, one or more of R ¹、R²、R³、R⁴ or R ⁰ is selected from -S ¹-F、-O-S¹-F、-O-S¹-O-S², wherein S ¹ is C _1-12 -alkylene or C _2-12 -alkenylene and S ² is H, C _1-12 -alkyl or C _2-12 -alkenyl, and very preferably one or more of R ¹、R²、R³、R⁴ or R ⁰ is selected from

-OCH₂OCH₃、-O(CH₂)₂OCH₃、-O(CH₂)₃OCH₃、-O(CH₂)₄OCH₃、-O(CH₂)₂F、-O(CH₂)₃F、-O(CH₂)₄F A group of groups.

If R ¹、R²、R³、R⁴ or R ⁰ represents an alkyl group in which one of the CH ₂ groups has been replaced by-ch=ch-, it may be straight or branched. It is preferably linear and has 2 to 10C atoms. Thus, it denotes in particular vinyl, prop-1-enyl or prop-2-enyl, but-1-enyl, but-2-enyl or but-3-enyl, pent-1-enyl, pent-2-enyl, pent-3-enyl or pent-4-enyl, hex-1-enyl, hex-2-enyl, hex-3-enyl, hex-4-enyl or hex-5-enyl, hept-1-enyl, hept-2-enyl, hept-3-enyl, hept-4-enyl, hept-5-enyl or hept-6-enyl, oct-1-enyl, oct-2-enyl, oct-3-enyl, oct-4-enyl, oct-5-enyl, oct-6-enyl or oct-7-enyl, non-1-enyl, non-2-enyl, non-3-enyl, non-4-enyl, non-6-enyl, non-7-enyl or non-8-enyl, dec-1-enyl, dec-2-enyl, dec-3-enyl, dec-6-enyl, dec-8-enyl.

If R ¹、R²、R³、R⁴ or R ⁰ represents an alkyl or alkenyl group which is at least monosubstituted by halogen, the group is preferably straight-chain and the halogen is preferably F. In the case of polysubstitution, halogen is preferably F. The resulting groups also include perfluorinated groups. In the case of monosubstituted, the fluorine or chlorine substituent may be in any desired position, but is preferably in the ω -position.

In the formulae above and below, X ⁰ is preferably CN, SCN, NCS, a mono-or polyfluorinated alkyl or alkoxy group having 1,2 or 3C atoms or a mono-or polyfluorinated alkenyl group having 2 or 3C atoms. X ⁰ is particularly preferably CN、CF₃、CHF₂、OCF₃、OCHF₂、OCFHCF₃、OCFHCHF₂、OCFHCHF₂、OCF₂CH₃、OCF₂CHF₂、OCF₂CHF₂、OCF₂CF₂CHF₂、OCF₂CF₂CHF₂、OCFHCF₂CF₃、OCFHCF₂CHF₂、OCF₂CF₂CF3、OCH＝CF₂ or ch=cf ₂, very particularly preferably F or OCF ₃, furthermore CF ₃、OCF＝CF₂、OCHF₂ or och=cf ₂.

In the LC medium according to the invention, the use of a compound of formula I in combination with one or more compounds selected from the group consisting of formulae T1 and T2 and preferably with a compound of formulae Z1 to Z8 or subformulae thereof enables high LTS values, increased epsilon _⊥ values and simultaneously reduced rotational viscosity and ratios of γ1/K ₂ and γ1/K ₁ and thus fast response times. LC media are therefore well suited for automotive applications such as navigation systems or various instruments.

Compounds of formula I

Preference is given to LC media comprising compounds of the formula I in which a ⁰ represents phenylene-1, 4-diyl, wherein, in addition, one or two CH groups may be replaced by N and one or more H atoms may be replaced by halogen, CN, CH ₃、CHF₂、CH₂F、OCH₃、OCHF₂、CF₃ or OCF ₃. Particularly preferred are the following compounds wherein A ⁰ represents

More preferably

And very particularly preferably therein

A ₀ represents

Preferred compounds of formula I produce LC media with particularly high clear light, low rotational viscosity, broad nematic phase range, high birefringence and excellent thermal and UV stability.

Furthermore, preference is given to compounds of the formula I in which k and l represent 0, 1 or 2, particularly preferably 0 or 1. Particular preference is given to compounds of the formula I in which l denotes 0, i.e. the thiophene ring is a terminal ring. Furthermore, preference is given to compounds of the formula I in which k represents 0, 1 or 2, preferably 1 or 2 and very particularly preferably 1.

A ⁰、A¹ and A ² in the formula I particularly preferably represent phenylene-1, 4-diyl, which may also be monosubstituted or polysubstituted by F, in addition to cyclohexane-1, 4-diyl, cyclohexene-1, 4-diyl, tetrahydropyran-2, 5-diyl or 1, 3-dioxane-2, 5-diyl.

Z ¹ and Z ² in the formula I particularly preferably represent-CF ₂O-、-OCF₂ -or a single bond, with single bonds being particularly preferred.

A ¹ and A ² in the formula I particularly preferably represent

Unsubstituted 1, 4-phenylene is preferred, wherein L represents halogen, CF ₃ or CN, preferably F.

Furthermore, preference is given to compounds of the formula I in which R ¹ and R ² each independently of one another represent H, F, cl, br, -CN, -SCN, -NCS, SF ₅, halogen or alkyl, alkenyl or alkynyl having up to 8, preferably up to 5, C atoms, each of which is optionally substituted by halogen, in particular F.

Particularly preferred radicals R ¹ and R ² in formula I represent H, halogen, or alkyl, alkenyl, alkynyl or alkoxy having up to 12 (preferably up to 8) C atoms, each of which is optionally substituted by halogen, in particular F, particularly preferred is H, F, alkyl, alkenyl or alkynyl having up to 8 carbon atoms. Preferably, at least one group is not H, particularly preferably neither of the two groups R ¹ and R ² is H. R ¹ is very particularly preferably equal to alkyl. R ² is furthermore preferably H, alkyl or fluorine. Very particular preference is given to R ¹ being alkyl and R ² being H or alkyl. R ¹、R² very particularly preferably each independently of the other represents an unbranched alkyl radical having 1 to 5C atoms. If R ¹ and R ² represent substituted alkyl, alkoxy, alkenyl or alkynyl groups, the total number of C atoms in the two radicals R ¹ and R ² is preferably less than 10.

Preferred alkyl groups are, for example, methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl and n-octyl.

Preferred alkenyl groups are, for example, ethenyl, propenyl, butenyl and pentenyl.

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

Preferred alkoxy groups are, for example, methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, n-hexoxy, n-heptoxy and n-octoxy.

Halogen preferably represents F or Cl, F being most preferred.

Particularly preferred compounds of formula I are those selected from the following subformulae:

Wherein R ¹ and R ² have the meanings indicated in formula I, and L ¹ to L ⁶ independently represent H or F. Wherein R ¹ and R ² preferably represent optionally fluorinated alkyl or alkoxy groups having 1 to 12C atoms, optionally fluorinated alkenyl or alkynyl groups having 2 to 12C atoms, optionally fluorinated cycloalkyl groups having 3 to 12C atoms.

Particularly preferred are optionally fluorinated alkyl, alkenyl or alkynyl groups having up to 5C atoms. L ² in the formulae I-1-1 to I-1-6 preferably represents F. In the formulae I-1-4 to I-1-6, L ³ and L ⁴ preferably represent H. In the formulae I-1-4 to I-1-6, L ³ and L ⁴ preferably represent F.

In a particularly preferred embodiment, the compound having formula I is selected from the following structures:

wherein R ¹ has the same meaning and is as in formula I

R ² represents a straight-chain or branched alkyl or alkoxy group having 1 to 7C atoms, or an alkenyl, alkenyloxy, alkoxyalkyl group having 2 to 7C atoms, or cycloalkyl or cycloalkoxy having 3 to 12C atoms, wherein one or more non-adjacent CH ₂ groups are optionally substituted by-C.ident.C-, -CF ₂O-、-OCF₂ -, -ch=ch-, -O-, -CO-O-or-O-CO-substitution in such a way that the O atoms are not directly connected to each other, and wherein one or more H atoms may be replaced by halogen atoms, wherein one or more H atoms may be replaced by halogen atoms.

LC media according to the invention with a particularly high LTS, a broad nematic phase range and a high long-term stability to UV radiation and high temperatures and low rotational viscosity are obtainable by the following compounds with the general formula I:

Wherein R ¹ and R ² are as defined above.

Furthermore, LC media comprising the following compounds having formula I are particularly preferred:

most preferred compounds of formula I include in particular one or more of the following:

as a further possibility, the following compounds having formula I may be used:

as a further possibility, the following compounds having formula I may be used:

The compounds of formula I can be prepared analogously to methods known to the person skilled in the art and described in standard works of organic chemistry, such as, for example, houben-Weyl, methoden der organischen Chemie [ Methods of Organic Chemistry [ organic chemical method ] ], thieme-Verlag, stuttgart.

Compounds having the formula T1 and T2

Preferably, the one or more compounds having the formulae T1 and T2 are selected from the group consisting of compounds having the following formulae:

Wherein the method comprises the steps of

R ³ and R ⁴ each independently of one another represent alkyl or alkoxy having 1 to 6C atoms or alkenyl having 2 to 6C atoms, wherein one or more CH ₂ groups are optionally replaced by-C.ident.C-, -CF ₂O-、-OCF₂ -, -ch=ch-, -O-, -CO-O-or-O-CO-substitution in such a way that O atoms are not directly connected to each other and wherein one or more H atoms may be replaced by halogen atoms,

L ¹ and L ² each independently of one another represent H or F,

X ⁰ represents CN, SCN, NCS, or a haloalkyl group having 1 to 6C atoms; and

Y ¹ and Y ² each independently of one another represent H or a straight-chain or branched alkyl or alkoxy group having 1 to 6C atoms, or a cycloalkyl or cycloalkoxy group having 3 to 6C atoms, preferably H or CH ₃.

Although the substituents R ³ and R ⁴ in formula I are not particularly limited in their choice, it is particularly advantageous to choose R ³ and R ⁴ as alkyl or cycloalkyl having up to 6C atoms, of which R ³ and R ⁴ selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, cyclopentyl are particularly preferred. Y ⁰ can also be represented by a CH ₃ group.

In a particularly preferred embodiment, the compounds having the general formulae T1 and T2 may be represented by one of the following:

Wherein the method comprises the steps of

R ³ is alkyl having 1 to 6C atoms, where one or more CH ₂ groups are optionally replaced by-C.ident.C-, -CF ₂O-、-OCF₂ -, -O-, -CO-O-or-O-CO-substitution in such a way that the O atoms are not directly connected to each other and wherein one or more H atoms may be replaced by halogen atoms, preferably alkyl groups having 1 to 4C atoms, alkenyl or alkenyloxy groups having 2 to 6C atoms or cycloalkyl or cycloalkoxy groups having 3 to 6C atoms, with vinyl, allyl or cyclopentyl groups being particularly preferred;

Y ¹ represents H or CH ₃, preferably H; and

M represents 1, 2, 3 or 4.

In the context of the present invention, the use of compounds having the formula T1-1a offers advantages over the use of T1-1b in terms of low temperature stability of the resulting LC medium.

Very preferred compounds of formula T1 are those selected from the group consisting of the following subformulae:

wherein Y ¹ is H or CH ₃, preferably H.

Very preferred compounds of formula T2 are those selected from the group consisting of the following subformulae:

wherein Y ¹ is H or CH ₃, preferably H.

The LC medium of the invention preferably comprises from 1% to 20% by weight, more preferably from 2% to 15% by weight, particularly preferably from 3% to 10% by weight, of compounds of the general formulae T1 and/or T2.

Additional mesogenic component

Preferably, the LC medium contains, in addition to one or more compounds of formula I and T1 and/or T2, one or more compounds selected from the following formulae:

Wherein the method comprises the steps of

"Alkyl" and "alkyl ^*" are independently of each other C _1-6 -alkyl and preferably denote ethyl, propyl, butyl or pentyl, very preferably ethyl, propyl or butyl "alkenyl" and "alkenyl ^*" preferably denote C _2-6 -alkenyl. Very preferred are compounds having the formulae Z1 and Z2.

Preferred compounds of the formulae Z1 to Z11 are those selected from the following subformulae:

In another preferred embodiment, the medium contains one or more compounds of the formula Z1 or its preferred subformulae and/or one or more compounds selected from the formulae Z2, Z3, Z4 and Z5 or its preferred subformulae.

Preferably, the total proportion of compounds of the formulae Z1, Z2, Z3, Z4, Z5 and Z6 or sub-formulae thereof, such as CC-3-V, in the medium is from 10% to 65%, very preferably from 20% to 60%, most preferably from 25% to 55% by weight. In yet a more preferred embodiment, the compound having formula Z1-1 is used in a concentration ranging from 10 to 60wt. -%, more preferably 25 to 50wt. -%, based on the total weight of the LC medium. In a further preferred embodiment, the LC medium comprises a total of 50 to 70wt. -% of the compounds represented by the formulae Z1-1 and Z4-2.

Preferably, the LC medium contains 1, 2 or 3 compounds selected from the formulae Z1, Z2, Z3 and Z4 or sub-formulae thereof.

The LC medium may additionally comprise one or more compounds having the general formula:

Wherein the method comprises the steps of

R ¹ and R ² each independently of one another represent C _1-6 -alkyl, C _1-6 -alkoxy or C _2-6 -alkenyl

The compounds of formula XII are preferably described by the following subformulae:

wherein "alkyl" and "alkyl ^*" each independently represent methyl, butyl, pentyl or hexyl.

Particular preference is given to compounds of the formulae XIIa and XIIC. In formula XIIb, "alkyl" preferably denotes, independently of one another, n-C ₃H₇, n-C ₄H₉ or n-C ₅H₁₁, in particular n-C ₃H₇. In formula XIIC, "alkyl" preferably means n-C ₃H₇ and "alkyl ^*" is preferably CH ₃ or n-C ₃H₇.

Particularly preferred compounds of formula XII are described by the following structure:

the LC medium may additionally comprise one or more compounds selected from the following formulae:

Wherein L ¹ and L ² have the meaning indicated in formula T1, and R ¹ and R ² each independently of one another represent n-alkyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyl, each having up to 6C atoms, and preferably each independently of one another represent alkyl having 1 to 6C atoms; in the compounds of formula XIV, at least one of the radicals R ¹ and R ² preferably represents an alkenyl group having 2 to 6C atoms.

The LC medium may further comprise one or more compounds of formula XIV, wherein at least one of the groups R ¹ and R ² represents an alkenyl group having 2 to 6C atoms, preferably selected from those of the following subformulae:

Wherein "alkyl" and "alkyl ^*" have the meanings indicated above and each, independently of the other, preferably represents methyl, ethyl or propyl.

The compound having formula XIV is preferably selected from the following subformulae:

Very preferred are compounds having the formulae XIVd1, XIVe-1, XIVe-2 and XIVe-3.

In yet further embodiments, the LC medium may comprise one or more compounds having formula XVI:

Wherein R ¹ and R ² have the meaning indicated in formula I and preferably each independently of the other represent an alkyl group having 1 to 6C atoms. L represents H or F.

Particularly preferred compounds of the formula XVI are those having the following subformulae

Wherein the method comprises the steps of

Alkyl and alkyl ^* each independently of one another denote straight-chain alkyl having 1 to 6C atoms, in particular ethyl, propyl or pentyl, and

Alkenyl and alkenyl ^* each independently of one another represent a straight-chain alkenyl radical having 2 to 6C atoms, in particular CH ₂＝CHC₂H₄、CH₃CH＝CHC₂H₄、CH₂ =ch and CH ₃ ch=ch.

Particularly preferred for administration are compounds having formulas XVIb and XVIc. Very particular preference is given to compounds having the following subformulae:

Very particular preference is given to compounds of the formula XVIc-2.

In a further preferred embodiment, the LC medium may comprise one or more compounds having the formula:

Wherein the method comprises the steps of

R ¹ and R ² each have the meaning indicated in formula I and preferably each independently of the other represent an alkyl group having 1 to 6C atoms. L represents H or F.

Very preferred are compounds of formula XVIIa wherein L is H and compounds of formula XVIIb wherein L is F.

The LC medium may additionally comprise one or more compounds having the formula:

Wherein L, R ¹ and R ² have the meanings indicated in formula Y for L ¹、R¹ and R ², respectively. R ¹ and R ² preferably represent alkyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyl groups, each having up to 6C atoms.

In a further preferred embodiment, the LC medium may comprise one or more compounds selected from formulas XXXIVa and XXXIVb:

wherein the individual radicals have the following meanings identically or differently on each occurrence and independently of one another:

R ⁰ is an alkyl group having 1 to 12C atoms or an alkenyl group having 2 to 12C atoms, wherein one or more CH ₂ groups are optionally replaced by-C.ident.C-, -CF ₂O-、-OCF₂ -, -ch=ch-, -O-, -CO-O-or-O-CO-substitution in such a way that O atoms are not directly connected to each other and wherein one or more H atoms may be replaced by halogen atoms,

R ² is an alkyl group having 1 to 6C atoms, or an alkenyl group having 2 to 6C atoms, wherein one or more CH ₂ groups are optionally replaced by-C.ident.C-, -CF ₂O-、-OCF₂ -, -ch=ch-,-O-, -CO-O-or-O-CO-substitution in such a way that the O atoms are not directly connected to each other, and wherein one or more H atoms may be replaced by halogen atoms;

L ¹ and L ² H, F or Cl,

Y ⁰ H or CH ₃;

wherein the individual substituents are identical or different on each occurrence and each independently of the other have the following meanings:

R ⁰ is an alkyl group having 1 to 12C atoms or an alkenyl group having 2 to 12C atoms, wherein one or more CH ₂ groups are optionally replaced by-C.ident.C-, -CF ₂O-、-OCF₂ -, -ch=ch-, -O-, -CO-O-or-O-CO-substitution in such a way that O atoms are not directly connected to each other and wherein one or more H atoms may be replaced by halogen atoms,

X ² F atom or alkyl or alkoxy having 1 to 6C atoms or alkenyl or alkenyloxy having 2 to 6C atoms, wherein one or more H atoms are replaced by F atoms, preferably F, CF ₃ or OCF ₃, and

L ¹ and L ² H, F or Cl,

Y ⁰ H or CH ₃.

In a particularly preferred embodiment, the compounds having the general formulae XXXIVa and XXXIVb may be represented by one of the following:

Wherein the method comprises the steps of

R ⁰ is alkyl having 1 to 12C atoms, where one or more CH ₂ groups are optionally replaced by-C.ident.C-, -CF ₂O-、-OCF₂ -, -O-, -CO-O-or-O-CO-substitution in such a way that the O atoms are not directly connected to one another and wherein one or more H atoms may be replaced by halogen atoms, preferably alkyl having 1 to 4C atoms, alkenyl or alkenyloxy having 2 to 6C atoms or cycloalkyl or cycloalkoxy having 3 to 6C atoms, with vinyl, allyl or cyclopentyl being particularly preferred,

N represents 1,2,3, 4 or 5, and

M represents 1, 2, 3 or 4.

One or more compounds of the formula XXXIV, in particular of the formula XXXIVa, are preferably used in the LC medium according to the invention in an amount of from 0.5% to 10% by weight, particularly preferably from 1% to 5% by weight.

In further embodiments, the LC medium may comprise one or more compounds having the formula:

Wherein R ¹ and R ² have the meanings indicated for the compounds of formula I. Preferably, R ¹ represents an alkyl or alkenyl group having 1 to 6 or 2 to 6C atoms respectively and R ² represents an alkenyl group having 2 to 6C atoms.

Preferred compounds of formula XXXV include in particular,

Wherein "alkyl" represents an alkyl group having 1 to 6C atoms.

In some further embodiments, the LC medium may comprise one or more compounds having the formula:

Wherein R ¹ and R ² have the meaning indicated in formula I and preferably each independently of the other represent an alkyl group having 1 to 6C atoms.

The LC medium may additionally comprise one or more compounds selected from the following formulae:

Wherein the individual radicals independently of one another and identically or differently at each occurrence have the following meanings:

R ⁰ in formula I is one of the meanings given for R ¹,

X ⁰ F, cl, haloalkyl, haloalkenyl, haloalkoxy or haloalkenoxy having up to 6C atoms,

L ^1-6 H or F, and

Y ⁰ H or CH ₃.

Preferred compounds of formulae II and III are those in which Y ⁰ is H.

Further preferred compounds of formulae II and III are those wherein R ⁰ represents an alkyl group having 1 to 6C atoms, very preferably ethyl or propyl, and X ⁰ represents F or OCF ₃, very preferably F.

In a preferred embodiment, the LC medium comprises one or more compounds of formula II having a formula selected from the following subformulae:

wherein R ⁰ and X ⁰ have the meanings given in formula II.

Preferred compounds are those of the formulae II-1, II-2 and II-3, very particularly preferred are those of the formulae II-1 and II-2.

In the compounds of formulae II-1 to II-7, R ⁰ preferably represents alkyl having 1 to 6C atoms, very preferably ethyl or propyl, and X ⁰ preferably represents F or OCF ₃, very preferably F.

In a further preferred embodiment, the LC medium contains one or more compounds of formula II or sub-formulae thereof as described above and below, wherein Y ⁰ is CH ₃, very preferably the medium according to this preferred embodiment contains one or more compounds of formula II selected from the following sub-formulae:

wherein R ⁰ and X ⁰ have the meanings given in formula II.

Preferred compounds are those of the formulae IIA-1, IIA-2 and IIA-3, very particularly preferred are those of the formulae IIA-1 and IIA-2.

In the compounds of formulae IIA-1 to IIA-7, R ⁰ preferably represents alkyl having 1 to 6C atoms, very preferably ethyl or propyl, and X ⁰ preferably represents F or OCF ₃, very preferably F.

The LC medium comprises one or more compounds having formula III selected from the following subformulae:

wherein R ⁰ and X ⁰ have the meanings given in formula II.

Preferred compounds are those having the formulas III-1, III-4, III-6, III-16, III-19 and III-20.

In the compounds of the formulae III-1 to III-21, R ⁰ preferably represents alkyl having 1 to 6C atoms, very preferably ethyl or propyl, X ⁰ preferably represents F or OCF ₃, very preferably F, and Y ² preferably represents F.

In yet further embodiments, the LC medium contains one or more compounds having formula III or subformulae thereof as described above and below, wherein Y ⁰ is CH ₃. Very preferably, the LC medium according to this preferred embodiment comprises one or more compounds having formula III selected from the following subformulae:

Wherein R ⁰ and X ⁰ have the meanings given in formula III.

Preferred compounds are those having the formulas IIIA-1, IIIA-4, IIIA-6, IIIA-16, IIIA-19 and IIIA-20.

In the compounds of the formulae IIIA-1 to IIIA-21, R ⁰ preferably denotes alkyl having 1 to 6C atoms, very preferably ethyl or propyl, X ⁰ preferably denotes F or OCF ₃, very preferably F, and Y ² preferably denotes F.

In further embodiments, the LC medium further comprises one or more compounds selected from the following formulae:

Wherein the method comprises the steps of

R ⁰、X⁰、Y⁰ and L ^1-5 have the meanings indicated in formulae II and III,

Z ⁰ represents -C₂H₄-、-(CH₂)₄-、-CH＝CH-、-CF＝CF-、-C₂F₄-、-CH₂CF₂-、-CF₂CH₂-、-CH₂O-、-OCH₂-、-COO- or-OCF ₂ -, in the case of formulae V and VI a single bond or-CF ₂ O-, in the case of formulae V and VIII,

R represents 0 or 1, and

S represents 0 or 1.

The compound having formula IV is preferably selected from the following formulae:

Wherein R ⁰ and X ⁰ have the meanings indicated in formulae II and III.

R ⁰ preferably represents an alkyl group having 1 to 6C atoms. X ⁰ preferably represents F or OCF ₃, furthermore ocf=cf ₂ or Cl.

The compound having formula IVa is preferably represented by the following subformula:

The compound having formula IVb is preferably represented by the following subformula:

the compound having formula IVc is preferably represented by the following subformula:

Wherein R ⁰ has the meaning indicated in formula II and is preferably propyl or pentyl.

One or more compounds of the formula IVc, in particular of the formula IVc-1, are preferably used in the LC medium according to the invention in an amount of from 1% to 20% by weight, particularly preferably from 2% to 15% by weight.

The compound having formula V is preferably selected from the following subformulae:

Wherein R ⁰ and X ⁰ have the meanings indicated in formula II.

R ⁰ preferably represents an alkyl group having 1 to 6C atoms. X ⁰ preferably represents F and OCF ₃, in addition OCHF ₂、CF₃、OCF＝CF₂ and och=cf ₂;

The compound having formula VI is preferably selected from the following subformulae:

Wherein R ⁰ and X ⁰ have the meanings indicated in formula II.

R ⁰ preferably represents an alkyl group having 1 to 6C atoms. X ⁰ preferably represents F, in addition to OCF ₃、CF₃、CF＝CF₂、OCHF₂ and och=cf ₂.

The compound having formula VII is preferably selected from the following subformulae:

Wherein R ⁰ and X ⁰ have the meanings indicated in formula II.

R ⁰ preferably represents an alkyl group having 1 to 6C atoms. X ⁰ preferably represents F, in addition to OCF ₃、OCHF₂ and och=cf ₂.

In some embodiments, the LC medium further comprises one or more compounds selected from the following formulas:

Wherein the method comprises the steps of

R ⁰ and X ⁰ each independently of one another have one of the meanings indicated in the formula II,

L ^1-4 each independently of the other represents H or F,

Y ⁰ represents H or CH ₃, preferably H,

X ⁰ is preferably F, cl, CF ₃、OCF₃ or OCHF ₂,

R ⁰ preferably represents alkyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyl, each having up to 6C atoms.

Very preferably, the LC medium according to the invention comprises one or more compounds of formula XXa,

Wherein R ⁰ has the meaning of R ¹ in formula I. R ⁰ preferably represents a linear alkyl radical, in particular ethyl, n-propyl, n-butyl or n-pentyl and very particularly preferably n-propyl.

One or more compounds of the formula XX, in particular of the formula XXa, are preferably used in the LC medium according to the invention in amounts of from 0% to 15% by weight, particularly preferably from 1% to 10% by weight.

Very preferably, the LC medium according to the invention comprises one or more compounds of formula XXIa,

Wherein R ⁰ has the meaning of R ¹ in formula I. R ⁰ preferably represents a linear alkyl radical, in particular ethyl, n-propyl, n-butyl or n-pentyl and very particularly preferably n-propyl.

One or more compounds of the formula XXI, in particular of the formula XXIa, are preferably used in the LC medium according to the invention in an amount of from 1% to 15% by weight, particularly preferably from 2% to 10% by weight.

It is further preferred that the LC medium according to the invention comprises one or more compounds of formula XXIIIa,

Wherein R ⁰ has the meaning of R ¹ in formula I. R ⁰ preferably represents a linear alkyl radical, in particular ethyl, n-propyl, n-butyl or n-pentyl and very particularly preferably n-propyl.

One or more compounds of the formula XXIII, in particular of the formula XXIIIa, are preferably used in the LC medium according to the invention in an amount of from 0.5% to 5% by weight, particularly preferably from 0.5% to 2% by weight.

The LC medium may additionally comprise one or more compounds of formula XXIV:

Wherein the method comprises the steps of

R ⁰、X⁰ and L ^1-6 have the meanings indicated in formula III,

S represents 0 or 1, and

Representation

In formula XXIV, X ⁰ may also represent an alkyl group having 1 to 6C atoms or an alkoxy group having 1 to 6C atoms. The alkyl or alkoxy group is preferably linear.

R ⁰ preferably represents an alkyl group having 1 to 6C atoms. X ⁰ preferably represents F;

the compound having formula XXIV is preferably selected from the following subformulae:

Wherein R ⁰、X⁰ and L ¹ have the meanings indicated in formula III. R ⁰ preferably represents an alkyl group having 1 to 6C atoms. X ⁰ preferably represents F, and L ¹ preferably is F;

Preferably/>

R ⁰ is a straight chain alkyl or alkenyl group having 2 to 6C atoms;

the LC medium may further comprise one or more compounds having the formula:

Wherein R ¹ and X ⁰ have the meaning of R ⁰ and X ⁰, respectively, indicated in formula II. R ¹ preferably represents an alkyl group having 1 to 6C atoms. X ⁰ preferably represents F or Cl. In formula XXIV, X ⁰ very particularly preferably represents Cl.

The LC medium may further comprise one or more compounds having the formula:

Wherein R ¹ and X ⁰ have the meaning of R ⁰ and X ⁰, respectively, indicated in formula II. R ¹ preferably represents an alkyl group having 1 to 6C atoms. X ⁰ preferably represents F. The medium according to the invention particularly preferably comprises one or more compounds of the formula XXIX, in which X ⁰ preferably denotes F.

One or more compounds of the formulae XXVI to XXIX are preferably used in LC media according to the invention in amounts of 1% to 20% by weight, particularly preferably 1% to 15% by weight. Particularly preferred LC media comprise at least one compound of formula XXIX.

Very preferably, the LC medium according to the invention comprises one or more compounds of formula XXIXa:

wherein R ¹ has the meaning indicated in formula I and preferably represents a linear alkyl radical, in particular ethyl, n-propyl, n-butyl or n-pentyl and very particularly preferably n-propyl.

One or more compounds of the formula XXIXa are preferably used in the LC medium according to the invention in amounts of 1% to 15% by weight, particularly preferably 2% to 10% by weight.

The LC medium may further comprise one or more of the following pyrimidine or pyridine compounds having the formula:

Wherein R ¹ and X ⁰ have the meanings indicated for R ⁰ and X ⁰, respectively, in formula II. R ¹ preferably represents an alkyl group having 1 to 6C atoms. X ⁰ preferably represents F. The medium according to the invention particularly preferably comprises one or more compounds of the formula XXX-1, wherein X ⁰ preferably represents F. One or more compounds of the formulae XXX-1 to XXX-3 are preferably used in the LC medium according to the invention in an amount of 1% to 20% by weight, particularly preferably 1% to 15% by weight.

In a preferred embodiment according to the invention, the LC medium contains, in addition to the compounds of the formulae I and T1 and/or T2, one or more compounds selected from the formulae Y and B

Wherein the individual radicals have the following meanings identically or differently on each occurrence and independently of one another:

R ¹、R² in formula I for one of the meanings given for R ¹ and R ²,

R ³ is one of the meanings given for R ¹,

Z^x、Z^y-CH₂CH₂-、-CH＝CH-、-CF₂O-、-OCF₂-、-CH₂O-、-OCH₂-、-CO-O-、-O-CO-、-C₂F₄-、-CF＝CF-、-CH＝CH-CH₂O-、 Or a single bond, preferably a single bond,

Z ^z CH₂O、-O-、-C₂H₄-、-OCH₂ -, or a single bond,

Y ¹ -CH₂ -, -O-or-S-,

L ^1-4 H, F or Cl, preferably H or F, very preferably F,

X, y 0,1 or 2, wherein x+y.ltoreq.3,

Z 0 or 1,

Wherein in formula B the dibenzofuran or dibenzothiophene group may also be further substituted by methyl or methoxy, and

Wherein the compound of formula Y contains at least one substituent L ^1-4 which is F or Cl, preferably F.

Preferably, the LC medium according to this first preferred embodiment contains one or more compounds having the formula I and T1 and/or T2, one or more compounds selected from the group consisting of formulae Z1, Z2 and Z3 and one or more compounds selected from the group consisting of formulae Y and B.

The LC medium according to this first preferred embodiment is particularly suitable for use in HB-FFS or PS-HB-FFS mode LC displays.

In a second preferred embodiment according to the invention, the LC medium does not contain compounds having the formula Y or B.

In the compounds of the formula Y and its subformulae, R ¹ and R ² preferably represent straight-chain alkyl or alkoxy having 1 to 6C atoms, in addition to alkenyl having 2 to 6C atoms, in particular vinyl, 1E-propenyl, 1E-butenyl, 3-butenyl, 1E-pentenyl, 3E-pentenyl or 4-pentenyl.

In the compounds of the formula Y and its subformulae, preferably both groups L ¹ and L ² represent F. In another preferred embodiment of the invention, in the compounds of formula Y and its subformulae, one of the radicals L ¹ and L ² represents F and the other represents Cl.

In a preferred embodiment of the invention, the LC medium contains one or more compounds of formula Y selected from the following subformulae

Wherein L ¹、L²、R¹、R²、Z^x、Z^y, x and Y have the meanings given in formula Y or one of the preferred meanings given above in formula I,

A represents a group consisting of 1 and 2,

B represents 0 or 1, and the number of the groups is,

Representation

Representation

L ³、L⁴ represents F or Cl, preferably F, and

L ⁵ represents an H atom or CH ₃.

Preferably, in the compounds having the formulas Y1 and Y2, L ¹ and L ² both represent F or one of L ¹ and L ² represents F and the other represents Cl, or L ³ and L ⁴ both represent F or one of L ³ and L ⁴ represents F and the other represents Cl.

Preferably, the LC medium comprises one or more compounds of formula Y1 selected from the group consisting of the following subformulae

Wherein the method comprises the steps of

A represents a group consisting of 1 and 2,

"Alkyl" and "alkyl ^*" each independently of the other denote a straight-chain alkyl radical having 1 to 6C atoms,

"Alkenyl" means a straight chain alkenyl group having 2 to 6C atoms, an

L ⁵ represents an H atom or CH ₃.

"Alkenyl" preferably means CH₂＝CH-、CH₂＝CHCH₂CH₂-、CH₃-CH＝CH-、CH₃-CH₂-CH＝CH-、CH₃-(CH₂)₂-CH＝CH-、CH₃-(CH₂)₃-CH＝CH- or CH ₃-CH＝CH-(CH₂)₂ -.

Very preferably, the LC medium contains one or more compounds having the formula Y1 selected from the group consisting of the formulae Y1-1, Y1-2, Y1-7, Y1-12, Y1-17, Y1-22, Y1-40, Y1-41, Y1-42, Y1-44, Y1-50 and Y1-68. L ⁵ preferably represents an H atom.

Further preferred, the LC medium comprises one or more compounds of formula Y2 selected from the group consisting of the following subformulae

Wherein the method comprises the steps of

"Alkyl" and "alkyl ^*" each independently of the other denote a straight-chain alkyl radical having 1 to 6C atoms, and

"Alkenyl" means a straight chain alkenyl group having 2 to 6C atoms, and (O) means an oxygen atom or a single bond, and

L ⁵ represents an H atom or CH ₃, preferably an H atom.

"Alkenyl" preferably means CH₂＝CH-、CH₂＝CHCH₂CH₂-、CH₃-CH＝CH-、CH₃-CH₂-CH＝CH-、CH₃-(CH₂)₂-CH＝CH-、CH₃-(CH₂)₃-CH＝CH- or CH ₃-CH＝CH-(CH₂)₂ -.

Very preferably, the LC medium contains one or more compounds having the formula Y2 selected from the group consisting of the formulae Y2-2 and Y2-10.

The proportion of compounds of the formula Y1 or its subformulae in the LC medium is preferably from 0 to 10% by weight.

The proportion of compounds of the formula Y2 or its subformulae in the LC medium is preferably from 0 to 10% by weight.

The total proportion of compounds of the formulae Y1 and Y2 or sub-formulae thereof in the LC medium is preferably from 1 to 20% by weight, very preferably from 2 to 15% by weight.

Preferably, the LC medium contains 1,2 or 3 compounds of the formulae Y1 and Y2 or sub-formulae thereof, very preferably selected from the formulae Y1-2, Y1-22, Y1-66, Y1-70, Y2-6 and Y2-22.

In another preferred embodiment of the invention, the LC medium contains one or more compounds of formula Y selected from the following subformulae

Wherein L ¹、L²、R¹ and R ² have one of the meanings given in formula Y or one of the preferred meanings as given in formula I and its subformulae.

Preferred compounds having the formula Y3 are selected from the group consisting of the following subformulae:

Wherein,

"Alkyl" and "alkyl ^*" each independently of the other denote a straight-chain alkyl radical having 1 to 6C atoms,

"Alkenyl" and "alkenyl ^*" each independently of the other denote straight-chain alkenyl groups having 2 to 6C atoms, and

O represents an oxygen atom or a single bond.

"Alkenyl" and "alkenyl ^*" preferably represent CH₂＝CH-、CH₂＝CHCH₂CH₂-、CH₃-CH＝CH-、CH₃-CH₂-CH＝CH-、CH₃-(CH₂)₂-CH＝CH-、CH₃-(CH₂)₃-CH＝CH- or CH ₃-CH＝CH-(CH₂)₂ -.

Particularly preferred compounds of formula Y3 are selected from the group consisting of the following subformulae:

Wherein "alkoxy" and "alkoxy ^*" each independently of the other preferably represent a straight-chain alkoxy group having 3, 4 or 5C atoms.

Preferably, in the compounds having the formula Y3 and its subformulae, both L ¹ and L ² represent F. Further preferably, in the compound having formula Y3, one of the groups L ¹ and L ² represents F and the other represents Cl.

The proportion of compounds of the formula Y3 or its subformulae in the LC medium is preferably from 1 to 10% by weight, very preferably from 1 to 6%.

Preferably, the LC medium contains 1,2 or 3 compounds of formula Y3 or a subformula thereof, preferably compounds of formula Y3-6, very preferably compounds of formula Y3-6A.

In another preferred embodiment of the invention, the LC medium contains one or more compounds of formula Y selected from the group consisting of the subformulae Y4:

wherein R ¹ and R ² each independently of one another have one of the meanings indicated above in the formula Y, and

Each independently of the other represent

Wherein L ⁵ represents F or Cl, preferably F, and L ⁶ represents F, cl, OCF ₃、CF₃、CH₃、CH₂ F or CHF ₂, preferably F, and preferably at least one of rings G, I and K is different from unsubstituted benzene.

Preferred compounds having the formula Y4 are selected from the group consisting of the following subformulae:

Wherein the method comprises the steps of

R represents a linear alkyl or alkoxy group having 1 to 7C atoms,

R ^* represents a straight-chain alkenyl group having 2 to 7C atoms,

(O) represents an oxygen atom or a single bond, and

M represents an integer from 1 to 6.

R ^* preferably represents CH ₂＝CH-、CH₂＝CHCH₂CH₂-、CH₃ -CH=CH-

CH₃-CH₂-CH＝CH-、CH₃-(CH₂)₂-CH＝CH-、CH₃-(CH₂)₃-CH＝CH- Or (b)

CH₃-CH＝CH-(CH₂)₂-。

R preferably represents methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy or pentoxy.

The proportion of compounds of the formula Y4 or its subformulae in the LC medium is preferably from 1 to 10% by weight, very preferably from 1 to 6%.

Particularly preferred compounds are those having the following subformulae

Wherein the method comprises the steps of

Alkyl and alkyl ^* each independently of one another represent a straight-chain alkyl radical having 1 to 6C atoms, in particular ethyl, propyl or pentyl.

The use of the following compounds is particularly advantageous:

in another preferred embodiment of the invention, the LC medium contains one or more compounds of formula Y selected from the group consisting of the following subformulae:

Wherein the method comprises the steps of

R ⁵ has one of the meanings indicated above for R ¹ in formula Y,

"Alkyl" means a straight chain alkyl group having 1 to 6C atoms,

L ^x represents a group consisting of H and F,

X represents F, cl, OCF ₃、OCHF₂ or och=cf ₂,

D represents 0 or 1, and

Z and m each independently represent an integer from 1 to 6.

R ⁵ in these compounds is particularly preferably C _2-6 -alkyl or-alkoxy or C _2-6 -alkenyl, d being preferably 1. X in these compounds is particularly preferably F. The LC medium according to the invention preferably comprises one or more compounds of the formula mentioned above in an amount of ≡5% by weight.

In the compounds of the formula B and its subformulae, R ¹ and R ³ preferably represent straight-chain alkyl or alkoxy having 1 to 6C atoms, in particular methoxy, ethoxy, propoxy or butoxy, and furthermore alkenyl having 2 to 6C atoms, in particular vinyl, 1E-propenyl, 1E-butenyl, 3-butenyl, 1E-pentenyl, 3E-pentenyl or 4-pentenyl.

Further preferred embodiments are indicated below:

the LC medium comprises one or more compounds of formula Y selected from the following subformulae

Wherein R ¹、R²、L¹、L², X, X and Z ^x have the meanings given in formula Y, and wherein at least one of the rings X is cyclohexenylene.

Preferably, both groups L ¹ and L ² represent F. Further preferably, one of the groups L ¹ and L ² represents F and the other represents Cl.

The compound having formula LY is preferably selected from the group consisting of the following subformulae:

wherein R ¹ has the meaning indicated above in formula Y, (O) represents an oxygen atom or a single bond, and v represents an integer from 1 to 6. R ¹ preferably represents a linear alkyl radical having 1 to 6C atoms or a linear alkenyl radical having 2 to 6C atoms, in particular CH ₃、C₂H₅, n-C ₃H₇, n-C ₄H₉, n -C₅H₁₁、CH₂＝CH-、CH₂＝CHCH₂CH₂-、CH₃-CH＝CH-、CH₃-CH₂-CH＝CH-、CH₃-(CH₂)₂-CH＝CH-、CH₃-(CH₂)₃-CH＝CH- or CH ₃-CH＝CH-(CH₂)₂ -.

Very preferred are compounds having the formula LY 4.

Preferably, the LC medium contains 1, 2 or 3 compounds of formula LY, very preferably compounds of formula LY 4.

The proportion of compounds of the formula LY or its subformulae in the LC medium is preferably from 1 to 10% by weight.

The LC medium comprises one or more compounds of formula Y selected from the following subformulae

Wherein R ¹、R²、L¹、L², Y, Y and Z ^y have the meanings given in formula Y, and wherein at least one of the rings Y is tetrahydropyran.

The compound having the formula AY is preferably selected from the group consisting of the following subformulae:

Wherein the method comprises the steps of

R ¹ has the meaning indicated above,

"Alkyl" means a straight chain alkyl group having 1 to 6C atoms,

(O) represents an oxygen atom or a single bond, and

V represents an integer from 1 to 6.

R ¹ preferably represents a linear alkyl radical having 1 to 6C atoms or a linear alkenyl radical having 2 to 6C atoms, in particular CH ₃、C₂H₅, n-C ₃H₇, n-C ₄H₉, n -C₅H₁₁、CH₂＝CH-、CH₂＝CHCH₂CH₂-、CH₃-CH＝CH-、CH₃-CH₂-CH＝CH-、CH₃-(CH₂)₂-CH＝CH-、CH₃-(CH₂)₃-CH＝CH- or CH ₃-CH＝CH-(CH₂)₂ -.

In a preferred embodiment of the invention, the LC medium contains one or more compounds of formula B selected from the following formulas

Wherein L ¹、L²、R¹ and R ³ have the meanings given in formula B.

Preferred compounds of formula B1 are selected from the following subformulae:

Wherein R ¹ and R ³ independently represent a linear alkyl group having 1 to 6C atoms, wherein one or more CH ₂ groups are optionally replaced by-C.ident.C-, -CF ₂O-、-OCF₂ -, -ch=ch-, -O-, -CO-O-or-O-CO-substitution in such a way that the O atoms are not directly connected to each other, and wherein one or more H atoms may be replaced by halogen atoms. Very preferred are compounds of the formulae B1-1 and B1-2 in which both radicals (O) represent oxygen atoms and R ¹ and R ³ independently represent alkyl radicals of methyl, ethyl, propyl, butyl, pentyl or hexyl, which are preferably straight-chain. Very preferably, one "alkyl" is ethyl and the other "alkyl" is n-pentyl.

Very particular preference is given to compounds of the formula B1-2.

Preferably, the compound of formula B1-1 is selected from the group of compounds of formulae B1-1-1 to B1-1-11, preferably the compound of formula B1-1-6,

Wherein the method comprises the steps of

"Alkyl" and "alkyl ^*" each independently of the other denote a straight-chain alkyl radical having 1 to 6C atoms,

"Alkenyl" and "alkenyl ^*" each independently of one another denote a straight-chain alkenyl radical having 2 to 6C atoms,

"Alkoxy" and "alkoxy ^*" each independently represent a straight-chain alkoxy group having 1 to 6C atoms.

Preferably, the compound of formula B1-2 is selected from the group of compounds of formulae B1-2-1 to B1-2-10, preferably compounds of formula B1-2-6,

Wherein the method comprises the steps of

"Alkyl" and "alkyl ^*" each independently of the other denote a straight-chain alkyl radical having 1 to 6C atoms,

"Alkenyl" and "alkenyl ^*" each independently of one another denote a straight-chain alkenyl radical having 2 to 6C atoms,

"Alkoxy" and "alkoxy ^*" each independently represent a straight-chain alkoxy group having 1 to 6C atoms.

Optionally, the LC medium comprises one or more compounds having the formula B1-1A and/or B1-2A

Wherein the method comprises the steps of

(O) represents O or a single bond,

R ^IIIA represents an alkyl or alkenyl group having up to 7C atoms or a group Cy-C _mH_2m+1 -, m and n are identical or different and are 0,1, 2,3, 4, 5 or 6, preferably 1,2 or 3, very preferably 1,

Cy represents a cycloaliphatic radical having 3, 4 or 5 ring atoms, optionally substituted by alkyl or alkenyl groups each having up to 3C atoms, or by halogen or CN, and preferably represents cyclopropyl, cyclobutyl or cyclopentyl.

The compounds of the formulae B1-1A and/or B1-2A may alternatively or additionally be contained in the LC medium, preferably in addition to the compounds of the formulae B1-1 and B1-2.

Highly preferred compounds of formula B1-1A and/or B1-2A are as follows:

Wherein "alkoxy" represents a straight chain alkoxy group having 1 to 6C atoms or alternatively- (CH ₂)_n F, wherein n is 2,3, 4 or 5, preferably C ₂H₄ F).

The proportion of compounds of the formula B1 or its subformulae in the LC medium is preferably from 1 to 20% by weight, very preferably from 1 to 15% by weight.

Preferably, the LC medium contains 1,2 or 3 compounds of formula B1 or its subformulae.

In a preferred embodiment of the invention, the LC medium may comprise one or more compounds of formula B2-2

Wherein the method comprises the steps of

R ¹、R³ identical or different represent H, alkyl or alkoxy having 1 to 6C atoms, wherein one or more CH ₂ groups of these radicals are optionally substituted independently of one another by-C.ident.C-, -CF ₂O-、-OCF₂ -, -ch=ch-, -O-, -CO-O-or-O-CO-substitution in such a way that the O atoms are not directly connected to each other, and wherein, in addition, one or more H atoms may be replaced by halogen.

The compound having the formula B2-2 is preferably selected from the group of compounds having the formulae B2-2-1 to B2-2-10:

Wherein R ³ represents an alkyl group having 1 to 6C atoms, preferably ethyl, n-propyl or n-butyl, or alternatively cyclopropylmethyl, cyclobutylmethyl or cyclopentylmethyl or alternatively- (CH ₂)_n F), wherein n is 2, 3, 4 or 5, preferably C ₂H₄ F.

Particularly preferred compounds of formula B2 are selected from the following subformulae:

The proportion of compounds of the formula B2 or its subformulae in the LC medium is preferably from 1 to 20% by weight, very preferably from 1 to 15% by weight.

Preferably, the LC medium contains 1,2 or 3 compounds of formula B2 or a subformula thereof.

Preferred compounds of formula B3 are selected from the following subformulae:

Wherein R ¹ has one of the meanings given in formula B3 and preferably represents a straight-chain alkyl group having 1 to 6C atoms, very preferably methyl, ethyl, propyl, butyl, pentyl or hexyl, more preferably ethyl or propyl, most preferably propyl, and X ¹ has one of the meanings given in formula B3 and preferably represents CF ₃ or OCF ₃.

Preferred compounds of formula B3 are selected from the following subformulae:

Wherein R ¹ has one of the meanings given in formula B3 and preferably represents a straight-chain alkyl group having 1 to 6C atoms, very preferably methyl, ethyl, propyl, butyl, pentyl or hexyl, more preferably ethyl or propyl, most preferably propyl.

Most preferred are compounds having the formulae B3-1-1 and B3-2-2.

In a further preferred embodiment, the LC medium contains one or more compounds of the formula B or its subformulae B1, B2, B3, B1-1, B1-2, B2-1, B2-2, B2-3, B3-1, B3-2, B3-1-1, B3-1-2, B3-2-1 and B3-2-2, wherein the dibenzofuran or dibenzothiophene group is substituted with methyl or methoxy, preferably with methyl, more preferably in the para position of substituent F, very preferably in the para position of substituent F (i.e. in the meta position of terminal group R ² or X ¹).

The proportion of compounds of the formula B3 or its subformulae in the LC medium is preferably from 1 to 20% by weight, very preferably from 1 to 10% by weight.

Preferably, the LC medium contains 1,2 or 3 compounds of formula B3 or its subformulae.

Preferably, the total proportion of compounds of the formulae Y and B or sub-formulae thereof in the LC medium is from 2 to 25% by weight, very preferably from 3 to 20%.

Further preferred embodiments are indicated below:

the LC medium does not contain compounds of formula Y, B, LY or AY.

The LC medium contains no compounds having 1, 4-phenylene groups which are substituted in the 2-and 3-positions by F or Cl.

Compounds of formula ST

In some preferred embodiments of the invention, the LC medium may further comprise one or more compounds having the general formula ST:

wherein each substituent has the following meaning:

Representation/>

X ²¹、X²² are each independently of one another ground representation-O-, -CH ₂-、-CHR²³ -or-N-R ²³ -,

R ²¹ and R ²² each independently of one another represent H atoms or alkyl or alkoxy groups having 1 to 12C atoms, alkenyl, alkynyl, alkenyloxy or alkoxyalkyl groups having 2 to 12C atoms or cycloalkyl groups having 3 to 12C atoms, wherein one or more non-adjacent CH ₂ groups are optionally substituted by-C.ident.C-, -CF ₂O-、-OCF₂ -, -ch=ch-, -O-, -CO-O-or-O-CO-substitution in such a way that the O atoms are not directly connected to each other and wherein one or more H atoms may be replaced by halogen atoms or cycloalkyl or cycloalkoxy groups having 3 to 12C atoms, wherein one or more H atoms may be replaced by halogen atoms,

R ²³ represents an H atom, an alkyl group having 1 to 10C atoms or an alkoxy group, and R represents 0 or 1.

LC media comprising compounds having the following subformulae ST-1, ST-2 and ST-3 exhibit particularly high long-term thermal and UV stability:

Wherein each substituent has the following meaning:

Representation/>

R ²¹ and R ²² each independently of one another represent H atoms or alkyl or alkoxy groups having 1 to 7C atoms, and

R represents 0 or 1.

In a particularly preferred embodiment, the compound having the general formula ST may be selected from the following specific structures:

in a further preferred embodiment, the LC medium according to the invention may comprise at least one further sterically hindered phenol, which is mentioned in table B below.

Compounds of formula H

In some preferred embodiments of the invention, the LC medium may further comprise at least one compound having formula H:

Wherein the method comprises the steps of

R ¹¹ each independently of the other represents a H atom, F, alkyl having 1 to 20C atoms, one of the-CH ₂ -groups or if present, multiple-CH ₂ -groups can be replaced by-O-or-C (=o) -, but two adjacent-CH ₂ -groups cannot be replaced by-O-, and one or if present, more-CH ₂ -groups can be replaced by-ch=ch-or-c≡c-, and one H atom or H atoms can be replaced by F, OR ¹³、N(R¹³)(R¹⁴) or R ¹⁵,

R ¹² each independently of the other represents an H atom, an alkyl group having 1 to 20C atoms, one of the-CH ₂ -groups OR a plurality of the-CH ₂ -groups may be replaced by-O-OR-C (=O) -, but two adjacent-CH ₂ -groups cannot be replaced by-O-hydrocarbon groups containing cycloalkyl OR alkylcycloalkyl units, and wherein one-CH ₂ -group OR a plurality of-CH ₂ -groups can be replaced by-O-OR-C (=O) -but two adjacent-CH ₂ -groups cannot be replaced by-O-, and wherein one H atom OR H atoms may be replaced by F, OR ¹³、N(R¹³)(R¹⁴) OR R ¹⁵, OR an aromatic OR heteroaromatic hydrocarbon radical, wherein one H atom OR H atoms may be replaced by OR ¹³、N(R¹³)(R¹⁴) OR R ¹⁵,

R ¹³ and R ¹⁴ each independently of one another represent an alkyl or acyl group having 1 to 10C atoms or an aromatic hydrocarbon or carboxylic acid group having 6 to 12C atoms;

R ¹⁵ each independently of the other represents an alkyl radical having 1 to 10C atoms, one-CH ₂ -group or a plurality of-CH ₂ -groups can be replaced by-O-or-C (=o) -but two adjacent-CH ₂ -groups cannot be replaced by-O-,

R ¹⁶ is each, independently of one another, H atom, alkyl or alkoxy having 1 to 10C atoms, O-cycloalkyl having 3 to 12C atoms, O ^· or OH,

S ¹¹ and S ¹² each independently of one another represent alkylene having 1 to 20C atoms, one of the-CH ₂ -groups or if present a plurality of-CH ₂ -groups can be replaced by-O-or-C (=o) -but two adjacent-CH ₂ -groups cannot be replaced by-O-, and one of the H atoms or H atoms can be replaced by F, OR ¹³、N(R¹³)(R¹⁴) or R ¹⁵, or represent a single bond,

Y ¹¹ to Y ¹⁴ each independently of one another represent methyl or ethyl,

X ¹¹ is a group represented by the formula C,

Z ¹¹ to Z ¹⁴ each independently of the other represent-O-; - (c=o) -, -O- (c=o) -; - (C=O) -O-, -O- (C=O) -O-, - (N-R13) -, -N-R13- (C=O) -or a single bond, if S ¹¹ is a single bond, then both Z ¹¹ and Z ¹² do not simultaneously represent-O-; if S ¹² is a single bond, then both Z ¹³ and Z ¹⁴ do not simultaneously represent-O-; and, if q represents 0, then both Z ¹² and Z ¹³ do not simultaneously represent-O-,

P represents either 1 or 2 and is preferably chosen,

Q represents either 0 or 1 and,

O represents (3-p),

N represents an integer from 1 to 10,

M represents an integer from 0 to 8, wherein

N is an integer from 1 to 10, preferably from 3 to 8, and

Represents an organic moiety having an (m+n) bonding site.

In some preferred embodiments of the invention, in the compounds having formula H,

Wherein the method comprises the steps of

-Z ¹²-S¹¹-Z¹¹ -represents, independently of one another at each occurrence, -O-、S¹¹-O-、-O-S¹¹-O-、-(C＝O)-O-S¹¹-O-、-O-(C＝O)-S¹¹-O-、-O-(C＝O)-S¹¹-(C＝O)-O-、-O-S¹¹-(C＝O)-O-、-(C＝O)-O-S¹¹-C、-(C＝O)-O-S¹¹-O-(C＝O)- or- (N-R ¹³)-S¹¹-O-、-(N-R13-C(＝O)-S¹¹ - (c=o) -O or a single bond, preferably-O-, -S ¹¹-O-、-O-S¹¹-O-、-(C＝O)-O-S¹¹-O-、-O-(C＝O)-S¹¹ -O-or-O-S ¹¹ - (c=o) -O-, and/or

S ¹¹ preferably represents alkylene having 1 to 20C atoms, and/or

R ¹¹, if present, represents alkyl, alkoxy or H, preferably H or alkyl, and/or

R ¹² represents H, methyl, ethyl, propyl, isopropyl or 3-heptyl, or cyclohexyl. In a preferred embodiment of the application, in the compounds of formula H,

Represents a group selected from the group of the following formulas

In a further preferred embodiment of the invention, in the compounds of formula H,

Represents a group selected from the group of the following formulas

In a still further preferred embodiment of the present invention, in the compounds of formula H, wherein p preferably represents 1,

Representation ofPreferably-O-S ¹¹-O-、-S¹¹ -O-or-O-S ¹¹ -, particularly preferred is-O-S ¹¹ -O-or-S ¹¹ -O-.

In a further preferred embodiment of the invention, in the compounds of formula H, the radicals

Represents a group selected from the group of the following formulas

In a further preferred embodiment of the present invention, wherein p is 2, which may be the same or different from those described above, in the compounds of formula H,

Represents a group selected from the group of the following formulas

And

In a still further preferred embodiment of the invention, which may be the same as or different from those described above, in the compounds of formula H, the radicals

At each occurrence, independently of each other, represent

Preferably

Compounds having the general formulae H-1-1, H-1-2 and H-1-3 show to be particularly effective UV stabilizers in LC media, in particular in terms of VHR stability:

Wherein ZG, R ¹⁶ and n are as defined above and n represents an integer from 1 to 8. These compounds are well suited as stabilizers in LC media and stabilize the VHR of LC media upon UV exposure.

In particularly preferred embodiments, the one or more compounds having formula H may be selected from the group consisting of compounds having the following formulas H-2-1 through H-2-6:

Wherein the method comprises the steps of

R ¹¹ each independently of the other represents an H atom, an alkyl group having 1 to 20C atoms, one of the-CH ₂ -groups or if present, multiple-CH ₂ -groups can be replaced by-O-or-C (=o) -, but two adjacent-CH ₂ -groups cannot be replaced by-O-, and one or if present, more-CH ₂ -groups can be replaced by-ch=ch-or-c≡c-, and one H atom or H atoms can be replaced by F, OR ¹³、N(R¹³)(R¹⁴) or R ¹⁵,

R ¹⁶ represents a H atom or O,

N represents an integer from 0 to 12, and

S ¹¹ and S ¹² each independently of one another represent alkylene having 1 to 20C atoms, one of the-CH ₂ -groups or if present a plurality of-CH ₂ -groups can be replaced by-O-or-C (=o) -but two adjacent-CH ₂ -groups cannot be replaced by-O-, and one of the H atoms or H atoms can be replaced by F, OR ¹³、N(R¹³)(R¹⁴) or R ¹⁵, or represent a single bond.

In a preferred embodiment of the invention, the LC medium according to the invention comprises in each case one or more compounds of the formula H selected from the group of compounds of the formula

And

Further preferred LC media are selected from the following preferred embodiments, including any combination thereof:

The total content of compounds of formula I in the LC medium is preferably from 1% to 35% by weight, preferably from 5% to 30% by weight, and particularly preferably from 10% to 28% by weight, based on the weight of the LC medium.

It has proven to be surprisingly advantageous to select the compounds of the formula I in such a way that they can be described in the LC medium according to the invention by a single formula selected from the group consisting of I-1-1 to I-1-17 and I-2-1 to I-2-53. It is particularly preferred that all compounds of formula I can be described by one of the following formulae:

I-3-1、I-3-2、I-3-3、I-3-4、I-3-5、I-3-6、I-3-7、I-3-8、I-3-9、I-3-10、I-3-11、I-3-12、I-3-15、I-3-16、I-3-17、I-3-18、I-3-19、I-3-20、I-3-21、I-3-22.

in some embodiments, LC media according to the present invention may further comprise at least one, preferably at least two compounds having one of the following formulas:

I-3-9-2、I-3-9-3、I-3-9-4、I-3-9-5、I-3-9-6、I-3-9-7、I-3-9-8、I-3-9-9、I-3-22-4、I-3-6-3、I-3-7-3。

It has been shown that the combination of at least two different compounds of formula I in the LC medium of the present invention not only has a better solubility than the single compound of formula I, but also shows a significantly improved stability to UV radiation and high temperatures. The stabilizing effect of the compounds of the general formula H is thus enhanced in a synergistic manner.

If two compounds of the formula I are present in the LC medium according to the invention, their weight ratio is preferably between 10:90 and 90:10, particularly preferably between 20:80 and 80:20, even more preferably between 30:70 and 70:30, based on the total weight of the two compounds of the formula I.

Further preferred embodiments are as follows:

The LC medium comprises one or more compounds of formula I or a subformula thereof, compounds of formula T1 and/or T2 and one or more compounds selected from the group consisting of formulae Z1、Z2、Z3、Z4、Z5、Y、B、LY、AY、II、III、IV、V、VI、VII、VIII、IX、X、XI、XII、XIII、XIV、XV、XVI、XVIIa、XVIIb、XVIIc、XVIII、XIX、XX、XXI、XII、XXIII、XXIV、XXV、XXVI、XXVII、XXVIII、XXIX、XXX、XXX1、XXX2、XXX3、XXXI、XXXII、XXXIII and XXXIV and subformulae thereof.

The LC medium comprises one or more compounds of formula I or subformulae thereof, compounds of formula T1 and/or T2 and one or more compounds selected from the group consisting of formulae Z1, Z2, Z3, Z4, Z5, Y, B, II, III, IV, VI, IX, X, XIV, XVI, XVIIa, XVIIb, XVIIc, XX, XII, XXIII, XXIX, XXXI and XXXIV and subformulae thereof.

The LC medium does not contain compounds having the formula Y, B, AY or LY.

The LC medium comprises one or more compounds of formula II, preferably selected from the group consisting of formulae II-1, II-2 and II-3, very preferably from formulae II-1 and II-2. The individual concentration of each of these compounds is preferably from 2% to 15% by weight. The total concentration of these compounds is preferably from 5 to 25% by weight.

The LC medium comprises one or more compounds of formula III, preferably selected from the group consisting of formulae III-1, III-4, III-6, III-16, III-19 and III-20, very preferably from the group consisting of formulae III-1, III-6, III-16 and III-20. The individual concentration of each of these compounds is preferably from 2% to 15% by weight. The total concentration of these compounds is preferably from 5 to 30% by weight.

The LC medium comprises one or more compounds of formula IV, preferably selected from formula IVa or IVc, very preferably selected from formula IVa1 or IVc1, most preferably formula IVc1. The individual concentration of each of these compounds is preferably from 2% to 15% by weight. The total concentration of these compounds is preferably from 5% to 20% by weight.

The LC medium comprises one or more compounds of formula VI, preferably selected from formula VIb. The individual concentration of each of these compounds is preferably from 1% to 20% by weight. The total concentration of these compounds is preferably from 5% to 20% by weight.

The LC medium comprises one or more compounds of formula Z1, preferably selected from the formulae Z1-1. The total concentration of these compounds is preferably from 1 to 25% by weight.

The LC medium comprises one or more compounds of formula Z2, preferably selected from the formulae Z2-1 and Z2-2. The total concentration of these compounds is preferably from 2 to 35% by weight, very preferably from 3 to 25%.

The LC medium comprises from 5 to 20% by weight of a compound of formula Z3, preferably of formula Z3-1.

The LC medium comprises from 5 to 20% by weight of a compound of formula Z4, preferably of formula Z4-1.

The LC medium comprises from 10 to 65%, very preferably from 20 to 60% by weight of a compound of formula Z5.

The LC medium comprises one or more compounds of formula XII, preferably of formula XIIa or XIIb, very preferably of formula XIIa, most preferably of formula XIIa 1. The concentration of these compounds is preferably from 2% to 15% by weight.

The LC medium comprises from 1 to 15% by weight of a compound of formula XIIb.

The LC medium comprises one or more compounds of formula XIV, preferably of formula XIVd, very preferably of formula XIVd 1. The concentration of these compounds is preferably from 2% to 10% by weight.

The LC medium comprises one or more compounds of the formula XVIb, preferably of the formula XVIb1, XVIb2 and/or XVI 3. The concentration of these compounds is preferably from 2% to 15% by weight.

The LC medium comprises one or more compounds of the formula XVIc, preferably of the formula XVIc-1, XVIc-2 and/or XVIc-3. The concentration of these compounds is preferably from 2% to 20% by weight.

The LC medium comprises one or more compounds of the formula XVIg, preferably of the formula XVIg-1 and/or XVIg-2. The total concentration of these compounds is preferably from 5 to 25% by weight.

The LC medium comprises one or more compounds selected from the group consisting of formulae XVIIa, XVIIb and XVIIc, very preferably a compound of formula XVIIa wherein L is H and a compound of formula XVIIb wherein L is F. The total concentration of these compounds is preferably from 0.5% to 5% by weight.

The LC medium comprises one or more compounds of formula XX, preferably of formula XXa. The concentration of these compounds is preferably from 2% to 10% by weight.

The LC medium comprises one or more compounds of formula XXI, preferably of formula XXIa. The concentration of these compounds is preferably from 2% to 10% by weight.

The LC medium comprises one or more compounds of the formula XXIII, preferably of the formula XXIIIa. The concentration of these compounds is preferably from 0.5% to 5% by weight.

The LC medium comprises one or more compounds of formula XXIX, preferably of formula XXIXa. The concentration of these compounds is preferably from 2% to 10% by weight.

The LC medium comprises one or more compounds of formula XXX, preferably of formula XXXa. The concentration of these compounds is preferably from 2% to 10% by weight.

The LC medium comprises one or more compounds of formula XXXI. The concentration of these compounds is preferably from 2% to 10% by weight.

The LC medium comprises one or more compounds of formula XXXI. The concentration of these compounds is preferably from 2% to 10% by weight.

The LC medium comprises one or more compounds of formula XXXIV, preferably of formula XXXIVa. The concentration of these compounds is preferably from 1% to 5% by weight.

The LC medium comprises one or more compounds of the formula I, preferably of the formula I-2-6, compounds of the formula T1 and/or T2, one or more compounds selected from the group consisting of the formulae Z1, Z2 and Z3, Z4, Z5 or sub-formulae thereof, one or more compounds selected from the group consisting of the formulae XIV or sub-formulae thereof, one or more compounds selected from the group consisting of the formulae II, III, IV, VI, XX, XXIII and XXIX or sub-formulae thereof, and one or more compounds selected from the group consisting of the formulae XII, XVI, XVIIa, XVIIb, XVIIc, XXXI and XXXIV or sub-formulae thereof.

The LC medium comprises one or more compounds of formula I, preferably of formula I-2-6, compounds of formula T1 and/or T2, one or more compounds selected from the group consisting of formulae Z1, Z2 and Z3, Z4, Z5 or sub-formulae thereof, one or more compounds selected from the group consisting of formulae Z1-1, Z2-2, Z5 and XIVd or sub-formulae thereof, one or more compounds selected from the group consisting of formulae II, III, IVc, VIb, XXa, XXIIIa and XXIXa or sub-formulae thereof, and one or more compounds selected from the group consisting of formulae XIIb, XVIb, XVIc, XVIIa, XVIIb, XVIIc, XXXI and XXXIVa or sub-formulae thereof.

The LC medium comprises one or more, preferably two or more compounds of formula I, preferably of formula I-2-6, compounds of formula T1 and/or T2, one or more compounds selected from the group consisting of formulae Z1, Z2, Z3, Z4 and Z4 or sub-formulae thereof, one or more compounds of formula Y, preferably selected from the group consisting of formulae Y1 and Y2, one or more compounds selected from the group consisting of formulae XIV or sub-formulae thereof, one or more compounds selected from the group consisting of formulae II, III, IV, VI, XX, XXIII and XXIX or sub-formulae thereof, and one or more compounds selected from the group consisting of formulae XII, XVI, XVIIa, XVIIb, XVIIc, XXXI and XXXIV or sub-formulae thereof.

The LC medium comprises one or more, preferably two or more compounds of formula I, preferably of formula I-2-6, compounds of formula T1 and/or T2, one or more compounds selected from the group consisting of formulae Z1, Z2, Z3, Z4 and Z5 or sub-formulae thereof, one or more compounds of formula B, preferably selected from the group consisting of formulae B1, B2 and B3, one or more compounds selected from the group consisting of formulae Z1-1, Z2-2, Z5 and XIVd or sub-formulae thereof, one or more compounds selected from the group consisting of formulae II, III, IVc, VIb, XXa, XXIIIa and XXIXa or sub-formulae thereof, and one or more compounds selected from the group consisting of formulae XIIb, XVIb, XVIc, XVIIa, XVIIb, XVIIc, XXXI and XXXIVa or sub-formulae thereof.

In addition to the compounds of the formulae I and T1 and/or T2, the LC medium contains further compounds selected from the group of compounds of the formulae Z1, Z2, Z3, Z4, Z5, Y, B, IV, XII, XIV, XVI, XVIIa, XVIIb, XVIIc, XXI, XXIII, XXIX, XXX, XXXI and XXIV or sub-formulae thereof.

In addition to the compounds of the formulae I and T1 and/or T2, the LC medium contains further compounds selected from the group of compounds of the formulae Z1, Z2, Z3, IV, XII, XIV, XVI, XVIIa, XVIIb, XVIIc, XXI, XXIII, XXIX, XXX, XXXI and XXIV or their subformulae.

The proportion of the compounds of formula I or its subformulae in the LC medium is from 1% to 30%, very preferably from 2% to 25%, most preferably from 2% to 20% by weight.

The proportion of compounds of the formulae Z1, Z2 and Z3 or their subformulae in the LC medium is generally from 10% to 65%, very preferably from 20% to 60%.

The proportion of compounds of the formula Y or its subformulae in the LC medium is generally from 1% to 20%, very preferably from 2% to 15%.

The proportion of compounds of the formula B or its subformulae in the LC medium is generally from 1% to 20%, very preferably from 2% to 18%.

The proportion of the compounds of the formulae II, III, IV to VIII, XVIII to XXIII and XXVII to XXX in the LC medium is generally from 30 to 60% by weight.

The proportion of the compounds of the formula IX-XV in the LC medium is generally 40% to 70% by weight.

The proportion of the compounds of the formulae XIV, XVIIa-c and XXXI-XXXIV in the LC medium is generally from 0.5 to 15% by weight.

The term "alkyl" or "alkyl ^*" in the present application includes straight and branched chain alkyl groups having 1 to 6 carbon atoms, in particular the straight chain groups methyl, ethyl, propyl, butyl, pentyl and hexyl. Groups having 2 to 5 carbon atoms are generally preferred.

The term "alkenyl" or "alkenyl ^*" includes straight and branched chain alkenyl groups having 2 to 6 carbon atoms, especially straight chain groups. Preferred alkenyl groups are C ₂-C₇ -1E-alkenyl, C ₄-C₆ -3E-alkenyl, in particular C ₂-C₆ -1E-alkenyl. Examples of particularly preferred alkenyl groups are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl and 5-hexenyl. Groups having up to 5 carbon atoms are generally preferred, in particular CH ₂＝CH、CH₃ ch=ch.

The term "fluoroalkyl" preferably includes straight-chain groups having a terminal fluorine, i.e., fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorohexyl and 7-fluoroheptyl. However, other positions of fluorine are not excluded.

The term "oxaalkyl" or "alkoxy" preferably includes a linear group having the formula C _nH_2n+1-O-(CH₂)_m, wherein n and m each independently of the other represent 1 to 6.m may also represent 0. Preferably, n=1 and m=1-6 or m=0 and n=1-3. Further preferably, the alkoxy or oxaalkyl groups may also contain one or more further O atoms, such that the oxygen atoms are not directly connected to each other.

By appropriately selecting the meanings of R ⁰ and X ⁰, the addressing time, threshold voltage, steepness of the transfer characteristic line, and the like can be changed in a desired manner. For example, 1E-alkenyl, 3E-alkenyl, 2E-alkenyloxy, and the like generally result in shorter addressing times, improved nematic tendencies, and higher ratios between the elastic constants K ₃ (bending) and K ₁ (splay) as compared to alkyl and alkoxy groups. 4-alkenyl, 3-alkenyl, etc. typically result in lower threshold voltages and lower K ₃/K₁ values compared to alkyl and alkoxy groups. The LC medium according to the invention is characterized in particular by a high delta epsilon value and thus has a significantly faster response time than prior art LC media.

The optimum mixing ratio of the compounds having the above-mentioned formula is essentially dependent on the desired properties, the choice of the components of the above-mentioned formula and the choice of any further components which may be present.

Suitable mixing ratios within the ranges indicated above can be readily determined from case to case.

The total amount of compounds having the above mentioned formula in the LC medium according to the invention is not critical. Thus, the LC medium may contain one or more additional components for the purpose of optimizing various characteristics. However, the greater the effect observed on the desired improvement of the characteristics of the medium, the higher the total concentration of the compounds having the formula mentioned above.

In a particularly preferred embodiment, the LC medium according to the invention comprises compounds having the formulae IV to VIII (preferably IV and V), wherein X ⁰ represents F, OCF ₃、OCHF₂、OCH＝CF₂、OCF＝CF₂ or OCF ₂-CF₂ H. Advantageous synergism with compounds having the formula I, T and/or T2 results in particularly advantageous properties. In particular, LC media comprising compounds having formulae I, T1 and/or T2, II and III are characterized by their low threshold voltages.

The individual compounds of the formulae and their subformulae mentioned above which can be used in the LC medium according to the invention are known or can be prepared analogously to known compounds.

The invention also relates to a method for producing LC media as described above and below by mixing one or more compounds of formula I with one or more compounds of formula Y1, Y2 or Y3, one or more compounds of formula B, and one or more compounds selected from the group consisting of formulas II, III, IV, VI, XIV, XII, XVI, XVIIa, XVIIb, XVIIc, XX, XXIII, XXIX, XXXI and XXXIV.

In another preferred embodiment of the invention, the LC medium additionally comprises one or more polymerisable compounds. The polymerisable compounds are preferably selected from the group consisting of formula M

R^a-B¹-(Z^b-B²)m-R^b M

Wherein the individual radicals have the following meanings identically or differently on each occurrence and independently of one another:

R ^a and R ^b P、P-Sp-、H、F、Cl、Br、I、-CN、-NO₂、-NCO、-NCS、-OCN、-SCN、SF₅ or a linear or branched alkyl radical having 1 to 25C atoms, wherein, in addition, one or more non-adjacent CH ₂ groups can each be, independently of one another, represented by-C (R ⁰)＝C(R⁰⁰)-、-C≡C-、-N(R⁰⁰) -, -O-, -S-, -CO-O-, -O-CO-O-substitution, in such a way that the O and/or S atoms are not directly connected to one another, and wherein, in addition, one or more H atoms may be replaced by F, cl, br, I, CN, P or P-Sp-, wherein, if B ¹ and/or B ² contain saturated C atoms, R ^a and/or R ^b may also represent groups which are spiro-connected to the saturated C atoms,

Wherein at least one of the radicals R ^a and R ^b represents or contains a group P or P-Sp-, wherein

A group which is polymerizable and is a group which is polymerizable,

Sp is a spacer or a single bond,

B ¹ and B ² are aromatic, heteroaromatic, cycloaliphatic or heterocyclic radicals, preferably having from 4 to 25 ring atoms, which may also contain condensed rings, and which are unsubstituted or monosubstituted or polysubstituted by L,

Z^b-O-、-S-、-CO-、-CO-O-、-OCO-、-O-CO-O-、-OCH₂-、-CH₂O-、-SCH₂-、-CH₂S-、-CF₂O-、-OCF₂-、-CF₂S-、-SCF₂-、-(CH₂)_n1-、-CF₂CH₂-、-CH₂CF₂-、-(CF₂)_n1-、-CH＝CH-、-CF＝CF-、-C≡C-、-CH＝CH-COO-、-OCO-CH＝CH-、CR⁰R⁰⁰ Or a single bond,

R ⁰ and R ⁰⁰ each independently of one another represent H or alkyl having 1 to 12C atoms,

M represents 0, 1, 2, 3 or 4,

N1 represents 1,2, 3 or 4,

L P、P-Sp-、OH、CH₂OH、F、Cl、Br、I、-CN、-NO₂、-NCO、-NCS、-OCN、-SCN、-C(＝O)N(R^x)₂、-C(＝O)Y¹、-C(＝O)R^x、-N(R^x)₂、 Optionally substituted silyl, optionally substituted aryl having 6 to 20C atoms, or straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25C atoms, where, in addition, one or more H atoms may be replaced by F, cl, P or P-Sp-,

P and Sp have the meanings indicated above,

Y ¹ is a halogen atom, and is a halogen atom,

R ^x represents P, P-Sp-, H, halogen, straight-chain, branched or cyclic alkyl having 1 to 25C atoms, wherein, in addition, one or more non-adjacent CH ₂ groups may be replaced by-O-, -S-, -CO-, -CO-O-, -O-CO-O-substitution, in such a way that the O and/or S atoms are not directly connected to one another, and wherein, in addition, one or more H atoms may be replaced by F, cl, P or P-Sp-, optionally substituted aryl or aryloxy having 6 to 40C atoms, or optionally substituted heteroaryl or heteroaryloxy having 2 to 40C atoms.

Particularly preferred compounds of the formula M are those in which B ¹ and B ² each independently of one another represent 1, 4-phenylene, 1, 3-phenylene, naphthalene-1, 4-diyl, naphthalene-2, 6-diyl, phenanthrene-2, 7-diyl, 9, 10-dihydro-phenanthrene-2, 7-diyl, anthracene-2, 7-diyl, fluorene-2, 7-diyl, coumarin, flavone, wherein, in addition, one or more CH groups of these groups may be replaced by N, cyclohexane-1, 4-diyl, wherein, in addition, one or more non-adjacent CH ₂ groups may be replaced by O and/or S, 1, 4-cyclohexenylene, bicyclo [1.1.1] pentane-1, 3-diyl, bicyclo [2.2.2] octane-1, 4-diyl, spiro [3.3] heptane-2, 6-diyl, piperidine-1, 4-diyl, decahydro-2, 6-diyl, 4-naphthyridine, or octanedione, wherein, in addition, one or more CH ₂ groups may be replaced by O and/or S, respectively, are as defined as examples, or as examples, 2, 5-dihydro-2, 6-diyl.

Particularly preferred compounds of the formula M are those in which B ¹ and B ² each independently of one another represent 1, 4-phenylene, 1, 3-phenylene, naphthalene-1, 4-diyl or naphthalene-2, 6-diyl.

Very preferred compounds of formula M are selected from the following formulae:

wherein the individual radicals have the following meanings identically or differently on each occurrence and independently of one another:

p ¹、P²、P³ is a polymerizable group, preferably selected from the group consisting of ethyleneoxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetanyl and epoxy,

Sp ¹、Sp² and Sp ³ are single bonds or spacers, where, in addition, one or more of the groups P ¹-Sp¹-、P¹-Sp² -and P ³-Sp³ -may represent R ^aa, provided that at least one of the radicals P ¹-Sp¹-、P²-Sp² -and P ³-Sp³ -is present and is different from R ^aa, preferably- (CH ₂)_p1-、-(CH₂)_p1-O-、-(CH₂)_p1 -CO-O-or- (CH ₂)_p1 -O-CO-O-, wherein P1 is an integer from 1 to 12,

R ^aa H, F, cl, CN or a linear or branched alkyl radical having 1 to 25C atoms, where, in addition, one or more non-adjacent CH ₂ groups may each be replaced independently of one another by-C (R ⁰)＝C(R⁰⁰)-、-C≡C-、-N(R⁰) -, -O-, -S-, -CO-O-, -O-CO-O-, in such a way that the O and/or S atoms are not directly connected to each other, and wherein, in addition, one or more H atoms may be replaced by F, cl, CN or P ¹-Sp¹ -, particularly preferably straight-chain or branched, optionally mono-or polyfluorinated, alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy groups having 1 to 12C atoms, where alkenyl and alkynyl have at least two C atoms and the branched radical has at least three C atoms,

R ⁰、R⁰⁰ H or alkyl having 1 to 12C atoms,

R ^y and R ^z H、F、CH₃ or CF ₃,

X ¹、X²、X³ -CO-O-, -O-CO-or a single bond,

Z ^M1 -O-、-CO-、-C(R^yR^z) or-CF ₂CF₂ -,

Z ^M2、Z^M3 -CO-O-、-O-CO-、-CH₂O-、-OCH₂-、-CF₂O-、-OCF₂ -or- (CH ₂)_n) -where n is 2, 3 or 4,

L F, cl, CN or straight-chain or branched, optionally mono-or polyfluorinated, alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12C atoms,

L ', L' H, F or Cl,

R0, 1, 2, 3 or 4,

S0, 1,2 or 3,

T 0,1 or 2,

X 0 or 1.

Particularly preferred are compounds having the formulae M2 and M13.

Further preferred are the three reactive compounds M15 to M31, in particular M17, M18, M19, M22, M23, M24, M25, M30 and M31.

In the compounds of the formulae M1 to M31, the radicals

Preferably

Wherein L has, identically or differently on each occurrence, one of the meanings given above or below, and is preferably F、Cl、CN、NO₂、CH₃、C₂H₅、C(CH₃)₃、CH(CH₃)₂、CH₂CH(CH₃)C₂H₅、OCH₃、OC₂H₅、COCH₃、COC₂H₅、COOCH₃、COOC₂H5、CF₃、OCF₃、OCHF₂、OC₂F₅ or P-Sp-, very preferably F, cl, CN, CH ₃、C₂H₅、OCH₃、COCH₃、OCF₃ or P-Sp-, more preferably F, cl, CH ₃、OCH₃、COCH₃ or OCF ₃, in particular F or CH ₃.

Preferred compounds of the formulae M1 to M31 are those in which P ¹、P² and P ³ represent acrylate, methacrylate, oxetane or epoxy groups, very preferably acrylate or methacrylate groups.

Further preferred compounds of formulae M1 to M31 are those wherein Sp ¹、Sp² and Sp ³ are single bonds.

Further preferred compounds of formulae M1 to M31 are those wherein one of Sp ¹、Sp² and Sp ³ is a single bond and the other of Sp ¹、Sp² and Sp ³ is different from a single bond.

Further preferred compounds of the formulae M1 to M31 are those in which the groups Sp ¹、Sp² and Sp ³, which are different from the single bond, represent- (CH ₂)_s1 -X "-, wherein s1 is an integer from 1 to 6, preferably 2, 3, 4 or 5, and X' is a linking group with a benzene ring and is-O-; -O-CO-, -CO-O-, -O-CO-O-, or a single bond.

Particular preference is given to LC media comprising one, two or three polymerizable compounds of the formula M, preferably selected from the formulae M1 to M31.

Further preferably, the LC medium according to the present invention comprises one or more polymerizable compounds selected from the following table E.

Preferably, the proportion of polymerizable compound (preferably selected from formula M and table E) in the LC medium is from 0.01% to 5%, very preferably from 0.05% to 1%, most preferably from 0.1% to 0.5%.

It was observed that the addition of one or more polymerizable compounds to the LC medium, like those selected from formula M and table E, resulted in favorable properties like fast response times. Such LC media are particularly suitable for PSA displays, where they exhibit low image retention, fast and complete polymerization, fast generation of low pretilt angles that are stable after UV exposure, high reliability, high VHR values after UV exposure, and high birefringence. By a suitable choice of polymerizable compounds, the absorption of the LC medium at longer UV wavelengths can be increased, so that such longer UV wavelengths can be used for polymerization, which is advantageous for the display manufacturing process.

The polymerizable groups P are those which are suitable for polymerization reactions, such as, for example, free-radical or ionic chain polymerization, polyaddition or polycondensation, or for polymer-like reactions, such as, for example, addition or condensation on the main polymer chain. Particularly preferred are groups for chain polymerization, in particular those containing a c=c double bond or-c≡c-triple bond, and groups suitable for ring-opening polymerization, such as for example oxetane or epoxy groups.

Preferred groups P are selected from the group consisting of: CH ₂＝CW¹-CO-O-、CH₂＝CW¹ -CO-, CH₂＝CW²-(O)_k3-、CW¹＝CH-CO-(O)_k3-、CW¹＝CH-CO-NH-、CH₂＝CW¹-CO-NH-、CH₃-CH＝CH-O-、(CH₂＝CH)₂CH-OCO-、(CH₂＝CH-CH₂)₂CH-OCO-、(CH₂＝CH)₂CH-O-、(CH₂＝CH-CH₂)₂N-、(CH₂＝CH-CH₂)₂N-CO-、HO-CW²W³-、HS-CW²W³-、HW²N-、HO-CW²W³-NH-、CH₂＝CW¹-CO-NH-、CH₂＝CH-(COO)_k1-Phe-(O)_k2-、CH₂＝CH-(CO)_k1-Phe-(O)_k2-、Phe-CH＝CH-、HOOC-、OCN- And W ⁴W⁵W⁶ Si-, wherein W ¹ represents H, F, cl, CN, CF ₃, phenyl or alkyl having 1 to 5C atoms, in particular H, F, cl or CH ₃,W² and W ³ each independently of the other represent H or alkyl having 1 to 5C atoms, in particular H, methyl, ethyl or n-propyl, W ⁴、W⁵ and W ⁶ each independently of the other represent Cl, oxaalkyl having 1 to 5C atoms or oxacarbonylalkyl, W ⁷ and W ⁸ each independently of the other represent H, cl or alkyl having 1 to 5C atoms, phe represents 1, 4-phenylene, which is optionally substituted by one or more groups L (other than P-Sp-) as defined above for formula M, k ₁、k₂ and k ₃ each independently of the other represent 0 or 1, k ₃ preferably represent 1, and k ₄ represents an integer from 1 to 10.

Very preferred groups P are selected from the group consisting of: CH ₂＝CW¹-CO-O-、CH₂＝CW¹ -CO-, CH₂＝CW²-O-、CH₂＝CW²-、CW¹＝CH-CO-(O)_k3-、CW¹＝CH-CO-NH-、CH₂＝CW¹-CO-NH-、(CH₂＝CH)₂CH-OCO-、(CH₂＝CH-CH₂)₂CH-OCO-、(CH₂＝CH)₂CH-O-、(CH₂＝CH-CH₂)₂N-、(CH₂＝CH-CH₂)₂N-CO-、CH₂＝CW¹-CO-NH-、CH₂＝CH-(COO)_k1-Phe-(O)_k2-、CH₂＝CH-(CO)_k1-Phe-(O)_k2-、Phe-CH＝CH- And W ⁴W⁵W⁶ Si-, wherein W ¹ represents H, F, cl, CN, CF ₃, phenyl or alkyl having 1 to 5C atoms, in particular H, F, cl or CH ₃,W² and W ³ each independently of the other represent H or alkyl having 1 to 5C atoms, in particular H, methyl, ethyl or n-propyl, W ⁴、W⁵ and W ⁶ each independently of the other represent Cl, oxaalkyl having 1 to 5C atoms or oxacarbonylalkyl, W ⁷ and W ⁸ each independently of the other represent H, cl or alkyl having 1 to 5C atoms, phe represents 1, 4-phenylene, k ₁、k₂ and k ₃ each independently of the other represent 0 or 1, k ₃ preferably represent 1, and k ₄ represents an integer from 1 to 10.

Very particularly preferred groups P are selected from the group consisting of: CH ₂＝CW¹ -CO-O-, in particular CH ₂＝CH-CO-O-、CH₂＝C(CH₃) -CO-O-and CH ₂ =cf-CO-O-, in addition, CH ₂＝CH-O-、(CH₂＝CH)₂CH-O-CO-、(CH₂＝CH)₂ CH-O-,

Further preferred polymerizable groups P are selected from the group consisting of: vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxy, most preferably selected from the group consisting of acrylate and methacrylate.

If Sp is different from a single bond, it is preferably of the formula Sp "-X" such that the corresponding group P-Sp-corresponds to the formula P-Sp "-X" -, where

Sp "represents an alkylene radical having 1 to 20, preferably 1 to 12, C atoms, which is optionally monosubstituted or polysubstituted by F, cl, br, I or CN, and wherein, furthermore, one or more non-adjacent CH ₂ groups may each, independently of one another, be replaced by -O-、-S-、-NH-、-N(R⁰)-、-Si(R⁰R⁰⁰)-、-CO-、-CO-O-、-O-CO-、-O-CO-O-、-S-CO-、-CO-S-、-N(R⁰⁰)-CO-O-、-O-CO-N(R⁰)-、-N(R⁰)-CO-N(R⁰⁰)-、-CH＝CH- or-C.ident.C-in such a way that the O and/or S atoms are not directly connected to one another,

X' represents -O-、-S-、-CO-、-CO-O-、-O-CO-、-O-CO-O-、-CO-N(R⁰)-、-N(R⁰)-CO-、-N(R⁰)-CO-N(R⁰⁰)-、-OCH₂-、-CH₂O-、-SCH₂-、-CH₂S-、-CF₂O-、-OCF₂-、-CF₂S-、-SCF₂-、-CF₂CH₂-、-CH₂CF₂-、-CF₂CF₂-、-CH＝N-、-N＝CH-、-N＝N-、-CH＝CR⁰-、-CY²＝CY³-、-C≡C-、-CH＝CH-CO-O-、-O-CO-CH＝CH- or a single bond,

R ⁰ and R ⁰⁰ each independently of one another represent H or alkyl having 1 to 20C atoms, and

Y ² and Y ³ each independently represent H, F, cl or CN.

X' is preferably-O-, -S-; -CO-, -COO-, -OCO-, -O-COO-, -CO-NR ⁰-、-NR⁰-CO-、-NR⁰-CO-NR⁰⁰ -, or a single bond.

Typical spacers Sp and-Sp "-X" -are, for example, ,-(CH₂)_p1-、-(CH₂CH₂O)_q1-CH₂CH₂-、-CH₂CH₂-S-CH₂CH₂-、-CH₂CH₂-NH-CH₂CH₂- or- (SiR ⁰R⁰⁰-O)_p1 -, where p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and R ⁰ and R ⁰⁰ have the meanings indicated above in formula M.

Particularly preferred groups Sp and-Sp "-X" -are -(CH₂)_p1-、-(CH₂)_p1-O-、-(CH₂)_p1-O-CO-、-(CH₂)_p1-CO-O-、-(CH₂)_p1-O-CO-O-, wherein p1 and q1 have the meanings indicated above.

Particularly preferred groups Sp' are in each case straight-chain ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxy ethylene, methyleneoxy butylene, ethylenethio ethylene, ethylene-N-methyliminoethylene, 1-methylalkylene, ethylene, propylene and butylene groups.

In order to produce PSA displays, the polymerisable compounds contained in the LC medium are polymerised or crosslinked (if one compound contains two or more polymerisable groups) by in situ polymerisation 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 geometry of PSA displays, as described in the prior art cited at the outset. The geometry without protrusions is preferred, in particular, among others, those in which, furthermore, the electrode on the color filter side is unstructured and only the electrode on the TFT side has grooves. Particularly suitable and preferred electrode structures for PS-VA displays are described, for example, in US 2006/0066793 A1.

The combination of the above-mentioned compounds of the preferred embodiments with the above-mentioned polymeric compounds gives a low threshold voltage, a low rotational viscosity and a very good low temperature stability in the LC medium according to the invention, while at the same time giving a constant high definition bright spot and a high VHR value.

The use of LC media containing polymerizable compounds allows for a fast build up of particularly low pretilt angles in PSA displays. In particular, LC media exhibit significantly reduced response times, particularly also gray scale response times, in PSA displays compared to prior art media.

LC media with a nematic liquid crystal phase are generally preferred, and LC media without a chiral liquid crystal phase are preferred.

The invention also relates to the use of an LC medium according to the invention as described above and below for electro-optical purposes, in particular in shutter glasses, for 3D applications, in TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, XB-FFS, PS-FFS, positive VA and positive PS-VA displays, and to electro-optical displays, in particular displays of the above-mentioned type, which contain an LC medium according to the invention as described above and below, in particular TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, XB-FFS, PS-FFS, positive VA (vertical alignment) or positive PS-VA displays.

The invention also relates to an electro-optical display, such as for example an STN or MLC display, having two plane-parallel outer plates which together with a frame form a cell, an integrated nonlinear element for switching individual pixels on the outer plates, and a nematic liquid crystal medium with positive dielectric anisotropy and high specific resistance located in the cell, wherein the nematic liquid crystal medium is an LC medium according to the invention as described above and below.

The LC medium according to the invention enables a significantly broader range of usable parameters. The achievable combination of clearing point, viscosity at low temperature, excellent low temperature stability, high thermal and UV stability and high optical anisotropy is far superior to prior art materials.

In particular, the combination of a compound of formula I with a compound of formula Y and/or B, and additionally with a compound selected from formulas II-XXXIV or subformulae thereof, results in LC media exhibiting a moderately positive dielectric anisotropy and at the same time an increased dielectric constant ε _⊥ perpendicular to the longitudinal axis of the liquid crystal molecule, while maintaining a low rotational viscosity and a low value of the ratio γ1/K ₁. This allows liquid crystal displays, particularly FFS, HB-FFS, XB-FFS and IPS mode liquid crystal displays, to have high brightness and transmittance and low response time.

The LC medium according to the invention is suitable for mobile applications and TFT applications, such as for example mobile phones and PDAs. Furthermore, the LC medium according to the invention is particularly suitable for use in FFS, HB-FFS, XB-FFS and IPS displays based on dielectrically positive liquid crystals.

According to the LC medium of the present invention, while maintaining a nematic phase as low as-20 ℃ and preferably as low as-30 ℃, particularly preferably as low as-40 ℃, and a clearing point of ≡75 ℃, preferably ≡80 ℃, simultaneously allowing a rotational viscosity γ1 of +.110 mPas, particularly preferably +.100 mPas to be achieved, enabling excellent MLC displays with fast response times to be obtained. The rotational viscosity was measured at 20 ℃.

The dielectric anisotropy Δεof the LC medium according to the invention is preferably ∈1.5, very preferably from +2 to +6, at 20℃and 1 kHz.

The birefringence Δn of the LC medium according to the invention at 20 ℃ is preferably from 0.08 to 0.15, very preferably from 0.1 to 0.14.

The rotational viscosity γ1 of the LC medium according to the invention is preferably ∈80 mPas, more preferably ∈70 mPas, very preferably ∈60 mPas.

The ratio γ1/K ₁ of the LC medium according to the invention (where γ1 is the rotational viscosity γ1 and K ₁ is the elastic constant of the splay deformation) is preferably ∈4.6 mPas/pN, very preferably ∈4.2 mPas/pN, most preferably ∈4.0 mPas/pN.

The nematic phase range of the LC medium according to the invention preferably has a width of at least 90 ℃, more preferably at least 100 ℃, in particular at least 110 ℃. This range preferably extends at least from-25 ℃ to +80℃.

It goes without saying that by a suitable choice of the components of the LC medium according to the invention, it is also possible to achieve a higher clearing point at a higher threshold voltage (for example above 100 ℃) or a lower clearing point at a lower threshold voltage, while maintaining other advantageous properties. When the viscosity is correspondingly only slightly increased, LC media with a higher Δε and thus a low threshold value can likewise be obtained. The MLC displays according to the invention are preferably operated at a first Gooch and Tarry transmittance minimum [ c.h. Gooch and H.A.Tarry, electron.Lett ] [ electronic flash ]10,2-4,1974; gooch and H.A.Tarry, appl.Phys [ applied physics ], volume 8, 1575-1584,1975], wherein, in addition to particularly advantageous electro-optical properties, such as, for example, a high steepness of the characteristic line and a low angular dependence of the contrast (german patent 30 22 818), a lower dielectric anisotropy is sufficient at the same threshold voltage as in a similar display at the second minimum. This enables a significantly higher specific resistance value to be achieved at the first minimum value using the LC medium according to the present invention than in the case of LC media comprising cyano compounds. By appropriate selection of the individual components and their proportions by weight, the person skilled in the art is able to set the desired birefringence of the pre-specified layer thickness of the MLC display using simple conventional methods.

Measurement of Voltage Holding Rate (HR) [ S.Matsumoto et al, liquid Crystals [ Liquid Crystals ]5,1320 (1989); niwa et al, proc.SID Conference, san Francisco, month 6, 1984, page 304 (1984); weber et al, liquid Crystals [ Liquid Crystals ]5,1381 (1989) ] have shown and include compounds of the formulaCyanophenylcyclohexane or of the formulaThe LC medium according to the invention comprising compounds of formula ST-1, ST-2, RV, IA and IB shows significantly less HR decrease on UV exposure than similar LC media comprising compounds of formula ST-1, ST-2, RV, IA and IB.

The light stability and UV stability of the LC media according to the invention are significantly better, i.e. they show significantly less HR decrease when exposed to light, heat or UV.

The construction of the MLC display according to the invention, which consists of polarizers, electrode substrates and surface-treated electrodes, corresponds to the usual design of displays of this type. The term general design is broadly depicted herein and also includes all derivatives and variants of MLC displays, including in particular matrix display elements based on poly-Si TFTs or MIMs.

However, a significant difference between the display according to the invention and the conventional displays hitherto based on twisted nematic cells is the choice of the liquid crystal parameters of the liquid crystal layer.

LC media which can be used according to the invention are prepared in a manner customary per se, for example by mixing one or more compounds as claimed in claim 1 with one or more compounds of the formulae II to XXXV or with further liquid-crystalline compounds and/or additives. In general, the desired amount of the component used in a smaller amount is dissolved in the component constituting the main component, advantageously at a high temperature. It is also possible to mix solutions of the components in organic solvents such as acetone, chloroform or methanol and to remove the solvent again after thorough mixing, for example by distillation.

The LC medium may also contain further additives known to the person skilled in the art and described in the literature, such as, for example, polymerization initiators, inhibitors, surface-active substances, light stabilizers, antioxidants (e.g. BHT, TEMPOL), microparticles, radical scavengers, nanoparticles, etc. For example, 0% to 15% of polychromatic dye or chiral dopant or initiator like651 Or907. Suitable stabilizers and dopants are mentioned in tables C and D below.

In a preferred embodiment of the invention, the LC medium contains one or more further stabilizers, preferably selected from the group consisting of

Wherein the method comprises the steps of

N is an integer from 1 to 6, preferably 3.

Very preferred stabilizers are selected from the group consisting of:

in a preferred embodiment, the LC medium comprises one or more stabilizers selected from the group consisting of formulas S1-1, S2-1.

In a preferred embodiment, the LC medium comprises one or more stabilizers selected from table D.

Preferably, the proportion of stabilizers (like those of the formula S1-S3) in the LC medium is from 10 to 2000ppm, very preferably from 30 to 1000ppm.

In another preferred embodiment, the LC medium according to the invention contains a self-alignment (SA) additive, preferably in a concentration of 0.1% to 2.5%. The LC medium according to this preferred embodiment is particularly suitable for use in a polymer stabilized SA-FFS, SA-HB-FFS or SA-XB-FFS display.

In a preferred embodiment, the SA-FFS, SA-HB-FFS or SA-XB-FFS display according to the present invention does not contain a polyimide alignment layer. In another preferred embodiment, the SA-FFS, SA-HB-FFS or SA-XB-FFS display according to the preferred embodiment contains a polyimide alignment layer.

The SA additive used in this preferred embodiment is selected from compounds comprising mesogenic groups and linear or branched alkyl side chains that are terminated with one or more polar anchoring groups selected from hydroxyl, carboxyl, amino or thiol groups.

Further preferred SA additives contain one or more polymerizable groups, optionally attached to the mesogenic groups by spacers. These polymerizable SA additives can be polymerized in LC medium under similar conditions as applied for RM in PSA processes.

Suitable SA additives for inducing homeotropic alignment, in particular for use in SA-VA mode displays are disclosed, for example, in US 2013/0182202 A1, US 2014/0838581 A1, US2015/0166890A1 and US 2015/0252265 A1.

In another preferred embodiment, an LC medium or polymer stabilized SA-FFS, SA-HB-FFS or SA-XB-FFS display according to the invention contains one or more self-aligning additives selected from Table F below.

Furthermore, polychromatic dyes, for example 0 to 15% by weight, may be added to the LC medium, in addition to nanoparticles, conductive salts, preferably complex salts of ethyldimethyldodecylammonium 4-hexyloxybenzoate, tetrabutylammonium tetraphenylborate or crown ethers (see, for example, haller et al mol. Cryst. Liq. Cryst. [ molecular crystals and liquid crystals ]24,249-258 (1973)), substances for improving the conductivity, or for changing the dielectric anisotropy, viscosity and/or alignment of the nematic phase. Substances of this type are described, for example, in DE-A22 09 127, 22 40 864, 23 21632, 23 38 281, 24 50 088, 26 37 430 and 28 53 728.

For the present invention and in the examples below, the structure of LC compounds is indicated by acronyms, the conversion to chemical formula is performed according to tables a to C below. All radicals C _mH_2m+1、C_nH_2n+1 and C _lH_2l+1 or C _mH_2m-1、C_nH_2n-1 and C _lH_2l-1 are straight-chain alkyl or alkylene radicals having in each case n, m and l C atoms, respectively. 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 cores of the compounds, table B lists the bridging units, and table C lists the meanings of the symbols of the left-hand and right-hand end groups of the molecules. The acronym consists of: the code of the ring element with optional linking groups is followed by the code of the first hyphen and the left-hand end group, and the code of the second hyphen and the right-hand end group. Table D shows the illustrative structures of the compounds and their respective abbreviations.

Table a: ring element

Table B: bridging unit

Table C: end group

Where n and m are each integers and the three points "…" are placeholders from other abbreviations of the table.

The following abbreviations are used:

n, m, k and l are each independently of the other integers, preferably from 1 to 9, preferably from 1 to 7,k and l possibly also from 0 and preferably from 0 to 4, more preferably 0 or 2 and most preferably 2, n is preferably 1, 2, 3, 4 or 5, in the combination "-nO-" it is preferably 1, 2, 3 or 4, 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".

Preferred LC medium components are shown in tables D and E.

Table D

Table E

In the following formulae, n and m each independently of one another represent 0, 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, in particular 2, 3, 5, furthermore 0, 4, 6.

Particularly preferred for administration are LC media comprising at least one, two, three, four or more compounds of table E.

Table F

Table F indicates possible dopants that are typically added to LC media according to the present invention. The LC medium preferably contains 0% to 10% by weight, in particular 0.01% to 5% by weight and particularly preferably 0.01% to 3% by weight of dopants.

Table G

Below, stabilizers are mentioned, which may be additionally added to the LC medium according to the invention, for example in an amount of 0% -10% by weight.

Table H

Table H shows illustrative reactive mesogenic compounds (RM) that may be used in LC media according to the invention.

In a preferred embodiment, the LC medium according to the invention comprises one or more polymerisable compounds, preferably selected from the polymerisable compounds having the formulae RM-1 to RM-182. Of these, compounds RM-1、RM-4、RM-8、RM-17、RM-19、RM-35、RM-37、RM-39、RM-40、RM-41、RM-48、RM-52、RM-54、RM-57、RM-58、RM-64、RM-74、RM-76、RM-88、RM-91、RM-102、RM-103、RM-109、RM-116、RM-117、RM-120、RM-121、RM-122、RM-139、RM-140、RM-142、RM-143、RM-145、RM-146、RM-147、RM-149、RM-156 to RM-163, RM-169, RM-170, and RM-171 to RM-183 are particularly preferable.

TABLE I

Table I shows self-aligning additives for homeotropic alignment which can be used in LC media of SA-FFS, SA-HB-FFS and SA-XB-FFS displays according to the invention, optionally together with polymerizable compounds having formula I:

In a preferred embodiment, the LC medium, SA-VA and SA-FFS display according to the invention comprises one or more SA additives selected from formulae SA-1 to SA-48, preferably from formulae SA-14 to SA-48, very preferably from formulae SA-20 to SA-34 and SA-44 in combination with one or more RMs.

The following examples are intended to illustrate the invention without limiting it.

In the above and below, the percentage data represent weight percentages. All temperatures are expressed in degrees celsius. m.p. represents melting point, cl.p. =clearing point. Furthermore, c=crystalline, n=nematic, s=smectic and i=isotropic. The data between these symbols represents the transition temperature. In addition, the following notations are used

V ₀ the Freedericks threshold voltage at 25 c, capacitive V,

V ₁₀ for a 10% transmittance voltage V,

N _e is the extraordinary refractive index measured at 25℃and 589nm,

N _o the ordinary refractive index measured at 25℃and 589nm,

Optical anisotropy measured at 25℃and 589nm,

Epsilon _⊥ dielectric polarizability (or "dielectric constant") perpendicular to the longitudinal axis of the molecule at 25 c and 1kHz,

Epsilon _|| dielectric polarizability (or "dielectric constant") parallel to the longitudinal axis of the molecule at 25 c and 1kHz,

Dielectric anisotropy of delta epsilon at 25 ℃ and 1kHz,

Cl.p. or

T (N, I) is the clearing point [ DEGC ],

The flow viscosity [ mm ²·s^-1 ] measured at 25℃v,

Gamma 1 rotational viscosity [ mPas ] measured at 25 ℃,

K ₁ spring constant, "splay" deformation [ pN ] at 25 ℃,

K ₂ spring constant, "twist" deformation at 25℃pN,

K ₃ spring constant, "bending" deformation at 25 [ pN ], and

Low temperature stability of the phase of LTS in bulk [ h ]

VHR voltage holding ratio.

All physical properties were determined according to "Merck Liquid Crystals, physical Properties of Liquid Crystals [ merck liquid crystal, physical properties of liquid crystal ]", state 1997, 11 month, merck group (MERCK KGAA), germany, and applicable to temperatures of 25 ℃ unless explicitly indicated otherwise.

Comparative base mixture M1

Nematic LC media were formulated as follows:

LC media exhibit nematic phases at-14 ℃, but the formation of smectic phases occurs at lower temperatures.

Comparative mixture example S1

The nematic LC medium according to the invention is formulated as follows:

Comparative mixture M1	99.99wt.-％
		Compounds of formula ST-1-3	100ppm

The addition of ST-1-3 significantly improved VHR ₁₀₀ after UV exposure compared to unstabilized mixture M1, without affecting the remaining physical properties of mixture M1.

Comparative base mixture M2

Nematic LC media were formulated as follows:

LC media exhibit nematic phase at-15 ℃, but the formation of smectic phase occurs at lower temperatures.

Comparative mixture example S2

The nematic LC medium according to the invention is formulated as follows:

Comparative mixture M2	99.98wt.-％
		Compounds of formula ST-2-3	200ppm

The addition of ST-2-3 significantly improved VHR ₁₀₀ after UV exposure compared to unstabilized mixture M2, without affecting the remaining physical properties of mixture M2.

Base mixture M3 according to the invention

Nematic LC media were formulated as follows:

although the LC medium has a high total content of CC-3-V and CC-3-V1, it maintains a nematic phase even at-23℃and exhibits excellent Low Temperature Stability (LTS) at-20℃due to the presence of CPTP-3-2.

Example of the mixture S3 according to the invention

The nematic LC medium according to the invention is formulated as follows:

Mixture M3 according to the invention	99.9wt.-％
		Compounds of formula H-3-1	1 000ppm

The addition of H-3-1 significantly improved VHR ₁₀₀ after UV exposure compared to unstabilized mixture M3, without affecting the remaining physical properties of mixture M3.

Base mixture M4 of the invention

Nematic LC media were formulated as follows:

Although the LC medium has a high total content of CC-3-V and CC-3-V1, it maintains a nematic phase even at-26℃and exhibits excellent Low Temperature Stability (LTS) at-20℃due to the presence of CPTP-3-O1.

Thus, the presence of a compound having the formula T1, such as CPTP-3-2 or CPTP-3-O1, allows for a significant reduction in the phase transition temperature (nematic to smectic). Furthermore CPTP-3-2 has even better compatibility with LC medium than CPTP-3-O1 at lower temperatures.

Example of the mixture S4 according to the invention

The nematic LC medium according to the invention is formulated as follows:

Mixture M4 according to the invention	99.9wt.-％
		Compounds having the formula H-3-3	1 000ppm

The addition of H-3-3 significantly improved VHR ₁₀₀ after UV exposure compared to unstabilized mixture M4, without affecting the remaining physical properties of mixture M4.

Base mixture M5 of the invention

Nematic LC media were formulated as follows:

Example of the mixture of the invention S5

The nematic LC medium according to the invention is formulated as follows:

Mixture M5 according to the invention	99.995wt.-％
		Compounds of formula H-3-5	50ppm

The addition of H-3-5 significantly improved VHR ₁₀₀ after UV exposure compared to unstabilized mixture M5, without affecting the remaining physical properties of mixture M5.

Base mixture M6 of the invention

Nematic LC media were formulated as follows:

example of the mixture of the invention S6

The nematic LC medium according to the invention is formulated as follows:

Mixture M6 according to the invention	99.99wt.-％
		Compounds of formula ST-1-3	100ppm

The addition of ST-1-3 significantly improved VHR ₁₀₀ after UV exposure compared to unstabilized mixture M6, without affecting the remaining physical properties of mixture M6.

Base mixture M7 of the invention

Nematic LC media were formulated as follows:

example of the mixture of the invention S7

The nematic LC medium according to the invention is formulated as follows:

Mixture M7 according to the invention	99.99wt.-％
		Compounds having the formula BHT-1	100ppm

The addition of BHT-1 improved VHR ₁₀₀ after UV exposure compared to unstabilized mixture M7, without affecting the remaining physical properties of mixture M7.

Base mixture M8 of the invention

Nematic LC media were formulated as follows:

Example of the mixture of the invention S8

The nematic LC medium according to the invention is formulated as follows:

Mixture M8 according to the invention	99.99wt.-％
		Compounds having the formula BHT-6	100ppm

The addition of BHT-6 improved VHR ₁₀₀ after UV exposure compared to unstabilized mixture M8, without affecting the remaining physical properties of mixture M8.

Base mixture M9 of the invention

Nematic LC media were formulated as follows:

example of the mixture of the invention S9

The nematic LC medium according to the invention is formulated as follows:

mixture M9 according to the invention	99.99wt.-％
		Compounds having the formula BHT-7	100ppm

The addition of BHT-6 improved VHR ₁₀₀ after UV exposure compared to unstabilized mixture M9, without affecting the remaining physical properties of mixture M8.

Base mixture M10 of the invention

Nematic LC media were formulated as follows:

Example of the mixture of the invention S10

The nematic LC medium according to the invention is formulated as follows:

Mixture M10 according to the invention	99.99wt.-％
		Compounds of formula ST-1-3	100ppm

The addition of ST-1-3 significantly improved VHR ₁₀₀ after UV exposure compared to unstabilized mixture M10, without affecting the remaining physical properties of mixture M10.

Claims (18)

1. A liquid-crystalline medium, characterized in that it comprises one or more compounds of the formula I

Wherein each substituent has the following meaning:

R ¹ and R ² are each, independently of one another, H atom, alkyl or alkoxy having 1 to 12C atoms or alkenyl or alkenyloxy having 2 or 12C atoms, wherein one or more non-adjacent CH ₂ groups are optionally substituted by-C.ident.C-, -CF ₂O-、-OCF₂ -, -ch=ch-, -O-, -CO-O-or-O-CO-substitution in such a way that the O atoms are not directly connected to each other and wherein one or more H atoms may be replaced by halogen atoms or cycloalkyl or cycloalkoxy groups having 3 to 12C atoms, wherein one or more H atoms may be replaced by halogen atoms,

A ⁰、A¹、A² each independently of the other represents phenylene-1, 4-diyl, wherein, in addition, one or two CH groups may be replaced by N and one or more H atoms may be replaced by halogen, CN, CH ₃、CHF₂、CH₂F、CF₃、OCH₃、OCHF₂ or OCF ₃, cyclohexane-1, 4-diyl, wherein, in addition, one or two non-adjacent CH ₂ groups may be replaced by O and/or S and one or more H atoms may be replaced by F, cyclohexene-1, 4-diyl, bicyclo [1.1.1] pentane-1, 3-diyl, bicyclo [2.2.2] octane-1, 4-diyl, spiro [3.3] heptane-2, 6-diyl, tetrahydropyran-2, 5-diyl or 1, 3-dioxane-2, 5-diyl,

Z ¹ and Z ² each independently of one another represent -CF₂O-、-OCF₂-、-CH₂O-、-OCH₂-、-CO-O-、-O-CO-、-C₂H₄-、-C₂F₄-、-CF₂CH₂-、-CH₂CF₂-、-CFHCFH-、-CFHCH₂-、-CH₂CFH-、-CF₂CFH-、-CFHCF₂-、-CH＝CH-、-CF＝CH-、-CH＝CF-、-CF＝CF-、-C≡C- or a single bond,

K and l each independently of the others represent 0,1, 2 or 3; and

And one or more compounds selected from the group consisting of the formulae T1 and T2

Wherein the method comprises the steps of

R ³ and R ⁴ each independently of one another represent alkyl or alkoxy having 1 to 12C atoms or alkenyl having 2 to 12C atoms, wherein one or more CH ₂ groups are optionally replaced by-C.ident.C-, -CF ₂O-、-OCF₂ -, -ch=ch-, -O-, -CO-O-or-O-CO-substitution in such a way that O atoms are not directly connected to each other and wherein one or more H atoms may be replaced by halogen atoms,

L ^1-6 each independently of the other represents H or F,

X ⁰ represents F, cl, CN, SF ₅, SCN, NCS, haloalkyl or haloalkoxy having 1 to 6C atoms, or haloalkenyl or haloalkenoxy having 2 to 6C atoms, and

Y ^1-3 each independently of the other represents H or a linear or branched alkyl or alkoxy group having 1 to 6C atoms, or a cycloalkyl or cycloalkoxy group having 3 to 6C atoms; and

M and n each independently of the other represent 0 or 1.

2. The medium of claim 1, wherein the compound having formula I is selected from the group consisting of:

Wherein the method comprises the steps of

R ¹ and R ² are as defined in claim 1, and

L ¹ to L ⁶ each independently of one another represent an H atom, F, cl, or an alkyl group having 1 to 4C atoms.

3. The medium according to claim 1 or 2, wherein the one or more compounds having the formulae T1 and T2 are selected from the group consisting of compounds having the following formulae:

Wherein the method comprises the steps of

R ³ and R ⁴ each independently of one another represent alkyl or alkoxy having 1 to 6C atoms or alkenyl having 2 to 6C atoms, wherein one or more CH ₂ groups are optionally replaced by-C.ident.C-, -CF ₂O-、-OCF₂ -, -ch=ch-, -O-, -CO-O-or-O-CO-substitution in such a way that O atoms are not directly connected to each other and wherein one or more H atoms may be replaced by halogen atoms,

L ¹ and L ² each independently of one another represent H or F,

X ⁰ represents CN, SCN, NCS, or a haloalkyl group having 1 to 6C atoms; and

Y ¹ and Y ² each independently of one another represent H or a straight-chain or branched alkyl or alkoxy group having 1 to 6C atoms, or a cycloalkyl or cycloalkoxy group having 3 to 6C atoms, preferably H or CH ₃.

4. A liquid-crystalline medium according to one or more of claims 1 to 3, characterized in that it comprises one or more compounds selected from the following formulae:

Wherein the method comprises the steps of

"Alkyl" and "alkyl ^*" refer to C _1-6 -alkyl,

"Alkenyl" and "alkenyl ^*" each independently represent C _2-6 -alkenyl;

Wherein the medium preferably comprises more than 45% by weight in total of compounds of the formulae Z-1 and Z-4.

5. Liquid-crystalline medium according to one or more of claims 1 to 4, characterized in that it comprises one or more compounds selected from the group consisting of

Wherein the individual radicals independently of one another and identically or differently at each occurrence have the following meanings:

R ⁰ in claim 1 for one of the meanings given for R ¹,

X ⁰ F, cl, haloalkyl, haloalkenyl, haloalkoxy or haloalkenoxy having up to 6C atoms, and

L ^1-6 H or F, which is a single-unit,

Y ⁰ H or CH ₃.

6. The liquid-crystalline medium according to claim 5, wherein the one or more compounds of formula II are selected from the following subformulae:

wherein R ⁰ and X ⁰ have the meanings given in formula II.

7. The liquid-crystalline medium according to claim 5, wherein the one or more compounds of formula III are selected from the following subformulae:

wherein R ⁰ and X ⁰ have the meanings given in formula II.

8. Liquid-crystalline medium according to one or more of claims 1 to 7, characterized in that it additionally comprises one or more compounds selected from the group consisting of

Wherein the method comprises the steps of

R ⁰、X⁰、L¹、L² and Y ⁰ have the meanings given in claim 5,

L ³ and L ⁴ independently of one another have one of the meanings given for L ¹, and

Z ⁰ represents-C ₂H₄-、-(CH₂)₄-、-CH＝CH-、-CF＝CF-、-C₂F₄ -

-CH ₂CF₂-、-CF₂CH₂-、-CH₂O-、-OCH₂ -, -COO-or-OCF ₂ -, in the case of formulae V and VI also a single bond, in the case of formulae V and VIII also-CF ₂ O-,

R represents 0 or 1, and

S represents 0 or 1.

9. Liquid-crystalline medium according to one or more of claims 1 to 8, characterized in that it comprises one or more compounds selected from the group consisting of

Wherein R ¹ and X ⁰ have the meanings indicated for R ⁰ and X ⁰, respectively, in claim 6.

10. Liquid-crystalline medium according to one or more of claims 1 to 9, characterized in that it comprises one or more compounds of formula XIV

Wherein R ¹ and R ² each independently of one another represent n-alkyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyl, each having up to 6C atoms.

11. Liquid-crystalline medium according to one or more of claims 1 to 10, characterized in that it comprises one or more compounds of formula XVI

Wherein L ¹、R¹ and R ² have the meanings indicated in claim 1.

12. Liquid-crystalline medium according to one or more of claims 1 to 11, characterized in that it comprises one or more compounds selected from the group consisting of the following formulae:

Wherein L ¹、R¹ and R ² have the meanings indicated in claim 1.

13. Liquid-crystalline medium according to one or more of claims 1 to 12, characterized in that it comprises a compound of formula I, T and/or T2 and one or more compounds selected from the group consisting of formulae Z1, Z2, Z3, Z4, Z5, II, III, IV, V, VI, VII, VIII, XXVII, XXVIII, XXIX, XXX, XIV, XVI, XXXI, XXXII and XXXIII.

14. Process for preparing a liquid-crystalline medium according to one or more of claims 1 to 13, characterized in that one or more compounds of the formula I and one or more compounds of the formula T1 and/or T2 are mixed with one or more mesogenic compounds and optionally one or more polymerizable compounds and/or one or more additives.

15. Use of a liquid-crystalline medium according to one or more of claims 1 to 13 for electro-optical purposes.

16. An electro-optic liquid-crystal display comprising a liquid-crystalline medium according to one or more of claims 1 to 13.

17. The electro-optic liquid crystal display of claim 16 which is a TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, XB-FFS, PS-HB-FFS, PS-XB-FFS, SA-HB-FFS, SA-XB-FS, polymer stabilized SA-HB-FFS, polymer stabilized SA-XB-FFS, positive VA or positive PS-VA display.

18. An electro-optic liquid crystal display according to claim 16 which is an FFS, HB-FFS, XB-FFS, PS-HB-FFS, PS-XB-FFS, IPS or PS-IPS display.