LC medium

Abstract

The present invention relates to LC media and LC displays comprising these media, in particular to displays addressed by means of an active matrix and in particular to displays in IPS, PS‑IPS, FFS, PS‑FFS, HB‑FFS, U‑IPS, TN, PS‑TN, STN or TN‑TFT mode.

Description

Technical Field

[0001] The present invention relates to liquid crystal (LC) media and LC displays (LCDs) comprising these media, in particular to LCDs addressed by an active matrix, and in particular to LCDs in IPS, PS-IPS, FFS, PS-FFS, HB-FFS, U-IPS, TN, PS-TN, STN or TN-TFT mode. Background Art

[0002] LCD is used for information display in many fields. LCD is used for both direct-view display and projection display. The electro-optical modes used are, for example, twisted nematic (TN), super twisted nematic (STN), optically compensated bending (OCB) and electrically controlled birefringence (ECB) modes and their various variations, as well as other modes. All these modes use an electric field substantially perpendicular to the substrate or liquid crystal layer. In addition to these modes, there are also electro-optical modes that use an electric field substantially parallel to the substrate or liquid crystal layer, such as in-plane switching (IPS) mode (such as those disclosed in DE 40 00 451 and EP 0 588 568) and fringe field switching (FFS) mode, in which there is a strong "fringe field", i.e., a strong electric field close to the edge of the electrode, and an electric field with both a strong vertical component and a strong horizontal component throughout the liquid crystal cell. These latter two electro-optical modes are particularly used for LCDs in modern desktop monitors and displays for televisions and multimedia applications. Liquid crystals according to the present invention are preferably used in displays of this type. Typically, dielectrically positive liquid-crystalline media having rather low dielectric anisotropy values ​​are used in FFS displays, but in some cases liquid-crystalline media having dielectric anisotropy values ​​of only about 3 or even lower are also used in IPS displays.

[0003] Another development is the so-called PS ("polymer stabilized") or PSA ("polymer stabilized alignment") type displays, for which the term "polymer stabilized" is occasionally also used. In these, small amounts (e.g. 0.3% by weight, typically <1% by weight) of one or more polymerizable compounds, preferably polymerizable monomeric compounds, are added to a liquid-crystalline medium and, after the liquid-crystalline medium has been charged into the display, are polymerized or crosslinked in situ (generally by UV photopolymerization), while optionally applying a voltage to the electrodes of the display. The polymerization takes place at a temperature at which the liquid-crystalline medium exhibits a liquid-crystalline phase, generally at room temperature. The addition of polymerizable mesogens or liquid-crystalline compounds (also called reactive mesogens or "RMs") to the liquid-crystalline mixture has proven to be particularly suitable.

[0004] For these displays, new liquid crystal media with improved properties are needed. For many types of applications, in particular the addressing time must be improved. Therefore, liquid crystal media with lower viscosity (η) and especially lower rotational viscosity (γ1) are needed. In addition to these viscosity parameters, the medium must have a nematic phase range of suitable width and position and a suitable birefringence (Δn), and the dielectric anisotropy (Δε) should be high enough to allow reasonably low operating voltages.

[0005] The displays according to the invention are preferably addressed by an active matrix (active matrix LCD, abbreviated AMD), preferably by a matrix of thin film transistors (TFTs). However, the liquid crystals according to the invention can also be advantageously used in displays having other known addressing methods.

[0006] Liquid-crystal media suitable for LCDs and in particular for IPS displays are known, for example, from JP 07-181 439 (A), EP 0 667 555, EP 0 673 986, DE 195 09 410, DE 195 28 106, DE 195 28107, WO 96 / 23 851 and WO 96 / 28 521. However, these liquid-crystal media have certain disadvantages. Among other disadvantages, they mostly lead to disadvantageously long addressing times, have insufficient resistivity values ​​and / or require too high an operating voltage. Improvements are necessary here both in terms of the operating properties and in terms of the shelf life.

[0007] Especially in the case of the use of LC media in the growing public information display (PID) and automotive display markets, high reliability and a wide operating range are extremely important factors. Therefore, for these applications, LC media with a high brightness temperature (Tni), good LTS (low temperature stability) and high reliability are required. Summary of the invention

[0008] The object of the present invention is to provide a medium, in particular for FFS, IPS, TN or STN displays of this type, in particular for active-matrix displays, for example those of the TFT (thin-film transistor) type, which does not exhibit the disadvantages indicated above or has them only to a lesser extent and which preferably exhibits one or more of the following: a wide operating range, a high brightness temperature, a high reliability, a low threshold voltage, a high dielectric anisotropy, a good low-temperature stability (LTS), a low rotational viscosity and a fast response time

[0009] This object is achieved by providing LC media as described and claimed hereinafter.

[0010] The invention relates to an LC medium having positive dielectric anisotropy, characterized in that it comprises one or more compounds of formula I in a concentration >0 and ≤10%

[0011]

[0012] Where R 1 and R 2 Independently of one another represent an alkyl group having 1 to 6 carbon atoms.

[0013] Preferably, the birefringence of the LC medium is < 0.15, more preferably between 0.8 and 0.15.

[0014] The invention also relates to the use of the LC media described above and below for electro-optical purposes, in particular for shutter glasses, for 3D applications, in IPS, PS-IPS, FFS, PS-FFS, HB-FFS, U-IPS, TN, PS-TN, STN or TN-TFT displays.

[0015] The invention further relates to an electro-optical LC display comprising an LC medium as described above and below, in particular an IPS, PS-IPS, FFS, PS-FFS, HB-FFS, U-IPS, TN, PS-TN, STN or TN-TFT display.

[0016] The present invention furthermore relates to a process for the preparation of an LC medium as described above and below, comprising the step of mixing one or more compounds of the formula I with one or more further LC compounds and optionally one or more additives.

[0017] In the present application, all atoms also include their isotopes. In particular, one or more hydrogen atoms (H) can be replaced by deuterium (D), which is particularly preferred in some embodiments; high deuteration enables analytical determination of compounds or simplifies analytical determination of compounds, particularly in the case of low concentrations.

[0018] If R 0 R represents an alkyl and / or alkoxy radical, which can be straight-chain or branched. It is preferably straight-chain and has 2, 3, 4, 5, 6 or 7 carbon atoms and thus preferably represents an ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy or heptyloxy radical, as well as a methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy or tetradecyloxy radical. 0 Preferably it denotes a straight-chain alkyl group having 2 to 6 carbon atoms.

[0019] Oxaalkyl preferably denotes straight-chain 2-oxapropyl (=methoxymethyl), 2-(=ethoxymethyl) or 3-oxabutyl (=2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanononyl, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl.

[0020] If R 0 It denotes an alkyl radical in which one CH2 group has been replaced by -CH=CH-, which can then be straight-chain or branched. It is preferably straight-chain and has 2 to 10 carbon atoms. Thus, it particularly denotes vinyl, prop-1- or -2-enyl, but-1-, -2- or -3-enyl, pent-1-, -2-, -3- or -4-enyl, hex-1-, -2-, -3-, -4- or -5-enyl, hept-1-, -2-, -3-, -4-, -5- or -6-enyl, oct-1-, -2-, -3-, -4-, -5-, -6- or -7-enyl, non-1-, -2-, -3-, -4-, -5-, -6-, -7- or -8-enyl, dec-1-, -2-, -3-, -4-, -5-, -6-, -7-, -8- or -9-enyl.

[0021] If R 0 If alkyl or alkenyl is at least monosubstituted by halogen, the radical is preferably straight-chain and halogen is preferably F or Cl. In the case of polysubstitution, halogen is preferably F. The resulting radicals also include perfluorinated radicals. In the case of monosubstitution, the fluorine or chlorine substituent may be in any desired position, but is preferably in the ω position.

[0022] In the formula of the context, X 0 Preferably, it is F, Cl or a mono- or poly-fluorinated alkyl or alkoxy group having 1, 2 or 3 carbon atoms or a mono- or poly-fluorinated alkenyl group having 2 or 3 carbon atoms. 0 Particularly preferred are F, Cl, CF3, CHF2, OCF3, OCHF2, OCFHCF3, OCFHCHF2, OCFHCHF2, OCF2CH3, OCF2CHF2, OCF2CHF2, OCF2CF2CHF2, OCF2CF2CHF2, OCFHCF2CF3, OCFHCF2CHF2, OCF2CF2CF3, OCF2CF2CClF2, OCC1FCF2CF3, OCH═CF2 or CH═CF2, very particularly preferred are F or OCF3, and CF3, OCF═CF2, OCHF2 or OCH═CF2.

[0023] Particularly preferred are those in which X0 It represents F or OCF3, preferably a compound of F.

[0024] In the compound of formula I, R 1 and R 2 Preferred are selected from ethyl, propyl, butyl and pentyl, all of which are straight-chain.

[0025] Preferred compounds of formula I are selected from the following sub-formulae.

[0026]

[0027]

[0028] Compounds of formula 12 are very preferred.

[0029] The concentration of the compounds of the formula I and its subformulae in the LC medium is preferably from 0.2 to 10%, more preferably from 1.0 to 10%, very preferably from 1.0 to 8%.

[0030] Preferably, the LC medium comprises 1, 2 or 3 compounds of the formula I or a subformulae thereof.

[0031] Further preferred embodiments of the LC media according to the invention, including any combinations thereof, are shown below:

[0032] - the medium further comprises one or more compounds selected from the following formulae

[0033]

[0034] where the individual radicals are independent of one another and have the following meanings when they occur identically or differently:

[0035] for

[0036] for

[0037] R 0 is an unsubstituted or halogenated alkyl or alkoxy radical having 1 to 15 C atoms, wherein in addition, in these radicals one or more CH2 groups may each independently of one another be replaced by -C≡C-, -CF2O-, -CH=CH-, -O-, -CO-O- or -O-CO- is substituted in such a way that the O atoms are not directly connected to each other, or represents

[0038] X 0 is F, Cl, CN, SF5, SCN, NCS, a haloalkyl group, a haloalkenyl group, a haloalkoxy group or a haloalkenyloxy group having up to 6 C atoms, and

[0039] Y 0 is H or CH3,

[0040] Y 1-6 It is H or F.

[0041] In the compounds of formula II and III and subformulae thereof, R 0 Preferably it denotes straight-chain alkyl having 1 to 6 carbon atoms, in particular methyl, ethyl or propyl, and alkenyl having 2 to 6 carbon atoms, in particular vinyl, 1E-propenyl, 1E-butenyl, 3-butenyl, 1E-pentenyl, 3E-pentenyl or 4-pentenyl.

[0042] -LC medium comprises one or more wherein Y 0 The compound of formula II wherein H is preferably selected from the following sub-formula

[0043]

[0044]

[0045] Where R 0 and X 0 has the meaning given above.

[0046] Preferred compounds are those of the formulae III, II2 and II3, very preferred are those of the formulae III and II2.

[0047] In the compounds of formulae II1 to II7, R 0 preferably represents an alkyl radical having 1 to 6 C atoms, very preferably an ethyl radical or a propyl radical, and X 0 Preferably it represents F or OCF3, very preferably F.

[0048] - the medium contains one or more of which Y 0 The compound of formula II wherein CH3 is preferably selected from the following sub-formula

[0049]

[0050]

[0051] Where R 0 and X 0 has the meaning given above.

[0052] Preferred compounds are those of the formulae IIA1, IIA2 and IIA3, very preferred are those of the formulae IIA1 and IIA2.

[0053] In the compounds of Formulae IIA1 to IIA7, R 0preferably represents an alkyl radical having 1 to 6 C atoms, very preferably an ethyl radical or a propyl radical, and X 0 Preferably it represents F or OCF3, very preferably F.

[0054] - the medium contains one or more of which Y 0 The compound of formula III wherein H is preferably selected from the following sub-formula

[0055]

[0056]

[0057]

[0058]

[0059] Where R 0 and X 0 has the meaning given above.

[0060] Preferred compounds are those of formula III1, III4, III6, III16, III19 and III20.

[0061] In the compounds of formula III1 to III21, R 0 Preferably denotes alkyl having 1 to 6 C atoms, very preferably ethyl or propyl, X 0 Preferably represents F or OCF3, very preferably F, and Y 2 Preferably it represents F.

[0062] - the medium contains one or more of which Y 0 The compound of formula III wherein CH3 is preferably selected from the following sub-formula

[0063]

[0064]

[0065]

[0066]

[0067]

[0068] Where R 0 and X 0 has the meaning given above.

[0069] Preferred compounds are those of formula IIIA1, IIIA4, IIIA6, IIIA16, IIIA19 and IIIA20.

[0070] In the compounds of formulae IIIA1 to IIIA21, R 0 Preferably denotes alkyl having 1 to 6 C atoms, very preferably ethyl or propyl, X 0 Preferably represents F or OCF3, very preferably F, and Y 2 Preferably it represents F.

[0071] - The medium additionally comprises one or more compounds selected from the following formulae:

[0072]

[0073] in

[0074] R 0 , X 0 and Y 1-4 has the meaning given above, and

[0075] Z 0 represents -C2H4-, -(CH2)4-, -CH=CH-, -CF=CF-, -C2F4-, -CH2CF2-, -CF2CH2-, -CH2O-, -OCH2-, -COO- or -OCF2-, and may also be a single bond in formulas V and VI, and may also be -CF2O- in formulas V and VIII.

[0076] r represents 0 or 1, and

[0077] s represents 0 or 1;

[0078] - the medium comprises one or more compounds of formula IV selected from the following subformulae:

[0079]

[0080] Where R 0 and X 0 Has the meanings stated above.

[0081] R 0 Preferably, X represents an alkyl radical having 1 to 6 C atoms. 0 Preferably represents F or OCF3, furthermore represents OCF=CF2 or Cl;

[0082] - the medium comprises one or more compounds of formula IVa selected from the following subformulae:

[0083]

[0084] Where R 0 has the above meanings and is preferably propyl or pentyl.

[0085] - the medium comprises one or more compounds of formula IVc selected from the following subformulae:

[0086]

[0087] Where R 0 has the above meanings and is preferably propyl or pentyl.

[0088] - the medium comprises one or more compounds of formula V selected from the following subformulae:

[0089]

[0090]

[0091] Where R 0 and X 0 Has the meanings stated above.

[0092] R 0 Preferably, X represents an alkyl radical having 1 to 6 C atoms. 0 Preferably represents F and OCF3, furthermore represents OCHF2, CF3, OCF=CF2 and OCH=CF2;

[0093] - the medium comprises one or more compounds of formula VI selected from the following subformulae:

[0094]

[0095]

[0096] Where R 0 and X 0 Has the meanings stated above.

[0097] R 0 Preferably, X represents an alkyl radical having 1 to 6 C atoms. 0 Preferably it represents F, furthermore it represents OCF3, CF3, CF=CF2, OCHF2 and OCH=CF2;

[0098] - the medium comprises one or more compounds of formula VII selected from the following subformulae:

[0099]

[0100] Where R 0 and X 0 Has the meanings stated above.

[0101] R 0 Preferably, X represents an alkyl radical having 1 to 6 C atoms. 0 Preferably it represents F, furthermore it represents OCF3, OCHF2 and OCH═CF2.

[0102] - The medium additionally comprises one or more compounds selected from the following formulae:

[0103]

[0104] Where X 0 has the meanings given above, and

[0105] "alkyl" means C 1-6 -alkyl,

[0106] "alkenyl" means C 2-6 -Alkenyl,

[0107] L means H or F,

[0108] R" means C 1-6 -alkyl, C 1-6 -alkoxy or C 2-6 -alkenyl,

[0109] R a1 , R b1 independently represent CH3 or C2H5,

[0110] i, k are independently 0, 1, 2 or 3,

[0111] - the medium comprises one or more compounds of formulae IX-XII selected from the following subformulae:

[0112]

[0113]

[0114] wherein "alkyl" has the meaning given in formula IX.

[0115] In formulae IX, IXa and IXb, "alkyl" preferably represents C2H5, n-C3H7, n-C4H9 or n-C5H 11 , especially n-C3H7.

[0116] In formulae IXa and IXb, "alkyl" preferably denotes CH3 or C2H5, in particular CH3.

[0117] - the medium comprises one or more compounds of formulae IX to XII selected from the following subformulae;

[0118]

[0119]

[0120] Very particular preference is given to compounds of the formulae IXa2, IXb1, XIa1 and XIa2.

[0121] - The medium does not contain any compound of the following formula:

[0122]

[0123] Where L 1 and L 2 independently of one another represent H or F, R', identically or differently on each occurrence, represents alkyl or alkoxy having 1 to 12 C atoms, R", identically or differently on each occurrence, represents alkenyl having 2 to 7 C atoms containing a terminal vinyl group, and R"' represents R' or R".

[0124] - The medium additionally comprises one or more compounds selected from the following formulae:

[0125]

[0126] Where R 3 and R 4 Each independently of one another represents n-alkyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyl each having up to 6 C atoms and preferably each independently of one another represents alkyl having 1 to 6 C atoms or alkenyl having 2 to 6 C atoms.

[0127] - the medium comprises one or more compounds of formula XV selected from the following subformulae:

[0128]

[0129] wherein "alkyl" has the meaning given above, and preferably represents methyl, ethyl or propyl.

[0130] - the medium comprises one or more compounds of formula XV selected from the following subformulae:

[0131]

[0132]

[0133] Compounds of formula XVd1 and XVe1 are very preferred.

[0134] - the medium comprises one or more compounds of formula XVI,

[0135]

[0136] Where L, R 3 and R 4 The abovementioned meanings and preferably each independently of one another represent alkyl radicals having 1 to 6 C atoms.

[0137] Particularly preferred compounds of formula XVI are those of the following sub-formula

[0138]

[0139]

[0140] in

[0141] Alkyl and alkyl* each independently represent a straight-chain alkyl group having 1 to 6 carbon atoms, in particular ethyl, propyl or pentyl,

[0142] Alkenyl and alkenyl* each independently of one another represent a straight-chain alkenyl radical having 2 to 6 C atoms, in particular CH2═CHC2H4, CH3CH═CHC2H4, CH2═CH and CH3CH═CH.

[0143] Particular preference is given to compounds of the formulae XVIb, XVIc and XVIg. Very particular preference is given to compounds of the formula:

[0144]

[0145]

[0146] Very preferred are compounds of formula XVIc2, XVIg1 and XVIg2;

[0147] - the medium contains one or more compounds of the following formula;

[0148]

[0149] Where R 3 and R 4 have the abovementioned meanings and preferably each independently of one another denote an alkyl radical having 1 to 6 C atoms. L denotes H or F;

[0150] - The medium additionally comprises one or more compounds selected from the following formulae:

[0151]

[0152] Where R 0 and X 0 Each independently has one of the above meanings, and Y 1-4 Each independently represents H or F. 0 Preferably F, Cl, CF3, OCF3 or OCHF2. 0 Preferably it denotes alkyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyl, each having up to 6 C atoms.

[0153] Very preferably, the mixtures according to the invention comprise one or more compounds of the formula XXIa,

[0154]

[0155] Where R 0 has the meaning given above. 0 Preferably it denotes straight-chain alkyl, in particular ethyl, n-propyl, n-butyl and n-pentyl, very particularly preferably n-propyl. The compounds of the formula XXI, in particular the formula XXIa, are preferably used in the mixtures according to the invention in an amount of 1 to 15% by weight, particularly preferably 2 to 10% by weight.

[0156] Further preferably, the mixtures according to the invention comprise one or more compounds of the formula XXIIIa,

[0157]

[0158] Where R 0 has the meaning given above. 0 Preferably denotes straight-chain alkyl, in particular ethyl, n-propyl, n-butyl and n-pentyl, very particularly preferably n-propyl. The compound of the formula XXIII, in particular the compound of the formula XXIIIa, is preferably used in the mixture according to the invention in an amount of 0.5 to 10% by weight, particularly preferably 0.5 to 5% by weight.

[0159] - the medium additionally comprises one or more compounds of formula XXIV,

[0160]

[0161] Where R 0 , X 0 and Y 1-6 has the meanings shown in formula I, s represents 0 or 1, and

[0162] express

[0163] In Formula XXIV, X 0 It may also represent an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms. The alkyl group or alkoxy group is preferably straight-chain.

[0164] R 0 Preferably, X represents an alkyl radical having 1 to 6 C atoms. 0 Preferably F;

[0165] - The compound of formula XXIV is preferably selected from the following formulae:

[0166]

[0167]

[0168] Where R 0 , X 0 and Y1 has the meaning given above. 0 Preferably, X represents an alkyl radical having 1 to 6 C atoms. 0 Preferably represents F, and Y 1 F is preferred;

[0169]

[0170]

[0171] -R 0 is a straight chain alkyl or alkenyl group having 2 to 6 carbon atoms;

[0172] - the medium contains one or more compounds of the following formula;

[0173]

[0174] Where R 3 and X 0 has the meaning given above. 3 Preferably, X represents an alkyl radical having 1 to 6 C atoms. 0 Preferably, X represents F or Cl. 0 Very particularly preferably it represents Cl.

[0175] - The medium contains one or more compounds of the following formula:

[0176]

[0177]

[0178] Where R 3 and X 0 has the meaning given above. 3 Preferably, X represents an alkyl radical having 1 to 6 C atoms. 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 it denotes F. The compounds of the formulae XXVI to XXIX are preferably used in the mixtures according to the invention in an amount of 1 to 20% by weight, particularly preferably 1 to 15% by weight. Particularly preferred mixtures comprise at least one compound of the formula XXIX.

[0179] Very preferably, the mixtures according to the invention comprise one or more compounds of the formula XXIXa,

[0180]

[0181] Where R 3has the above meanings and preferably denotes straight-chain alkyl, in particular ethyl, n-propyl, n-butyl and n-pentyl, very particularly preferably n-propyl. The compound of the formula XXIXa is preferably used in the mixture according to the invention in an amount of 1 to 15% by weight, particularly preferably 2 to 10% by weight.

[0182] - the medium contains one or more compounds of the formula

[0183]

[0184] Where R 3 and R 4 has the abovementioned meanings and preferably independently of one another denotes alkyl having 1 to 6 C atoms, very preferably methyl, ethyl or n-propyl.

[0185] Preferred compounds of formula XXX are those of formula XXXa

[0186]

[0187] Further preferred LC media are selected from the following preferred embodiments, including any combination thereof;

[0188] - The medium contains one or more compounds of formula II, preferably selected from formula III, II2 and II3, very preferably selected from formula III and II2. The individual concentration of each of these compounds is preferably 1 to 15% by weight. The total concentration of these compounds is preferably 5 to 25% by weight.

[0189] - The medium contains one or more compounds of formula III, which are preferably selected from formula III1, III4, III6, III16, III19 and III20, very preferably from formula III16 and III20. The individual concentration of each of these compounds is preferably 1 to 15% by weight. The total concentration of these compounds is preferably 2 to 25% by weight.

[0190] The medium contains one or more compounds of formula IV, which are preferably selected from formula IVa or IVc, very preferably from formula IVa1 or IVc1. The individual concentration of each of these compounds is preferably 1 to 15% by weight. The total concentration of these compounds is preferably 5 to 25% by weight.

[0191] - The medium contains one or more compounds of the formula IX, preferably selected from the formulae IXa and IXb, very preferably selected from the formulae IXa2 and Xb1. The individual concentration of each of these compounds is preferably 1 to 15% by weight. The total concentration of these compounds is preferably 5 to 25% by weight.

[0192] - The medium contains one or more compounds of formula XI, preferably selected from formula XIa and XIb. The individual concentration of each of these compounds is preferably 1 to 20% by weight. The total concentration of these compounds is preferably 5 to 25% by weight.

[0193] The medium contains one or more compounds of the formula XII, preferably the formula XIIa. The total concentration of these compounds is preferably between 3 and 20% by weight.

[0194] The medium contains one or more compounds of the formula XV, preferably selected from the formulae XVd and XVe, very preferably selected from the formulae XVd1 and XVe1. The individual concentration of each of these compounds is preferably 1 to 10% by weight. The total concentration of these compounds is preferably 2 to 15% by weight.

[0195] The medium comprises one or more compounds of the formula XVIc, preferably of the formula XVIc2. The concentration of these compounds is preferably from 1 to 15% by weight.

[0196] The medium comprises one or more compounds of the formula XVIg, preferably of the formula XVIg1 and / or XVIg2. The concentration of these compounds is preferably from 5 to 25% by weight.

[0197] - The medium contains one or more compounds of the formula XVIIa or XVIIb. The concentration of these compounds is preferably 0.5-5% by weight.

[0198] The medium comprises one or more compounds of the formula XXI, preferably of the formula XXIa. The concentration of these compounds is preferably from 0.5 to 8% by weight.

[0199] The medium contains one or more compounds of the formula XXIII, preferably of the formula XXIIIa. The concentration of these compounds is preferably 0.5-5% by weight.

[0200] The medium contains one or more compounds of the formula XXIX, preferably of the formula XXIXa. The concentration of these compounds is preferably from 2 to 10% by weight.

[0201] The medium contains one or more compounds of the formula XXX, preferably of the formula XXXa. The concentration of these compounds is preferably from 2 to 10% by weight.

[0202] - the medium comprises one or more compounds of formula I and one or more compounds selected from the group consisting of formulae II, III, IV, IX, XI, XII, XV, XVI, XXI, XXIX and XXX.

[0203] - the medium comprises one or more compounds of formula I and one or more compounds selected from the group consisting of formula III, II2, II3, III1, III4, III6, III16, III19, III20, IVa, IVc, IXa, IXb, XIa, XIb, XIIa, XVd, XVe, XVIc, XXIa, XXIXa and XXXa.

[0204] - the proportion of compounds of the formulae II, III, IV, IX, XI, XII, XV, XVI, XXI, XXIX and XXX in the mixture as a whole is 90-99% by weight.

[0205] - the proportion of compounds of the formulae III, II, II, III, III, III, III, III, IV, IVc, IXa, IXb, XIa, XIb, XIIa, XVd, XVe, XVIc, XXIa, XXIXa and XXXa in the mixture as a whole is 90 to 99% by weight.

[0206] The term "alkyl" or "alkyl*" in the present application encompasses straight-chain and branched alkyl groups having 1 to 6 carbon atoms, in particular the straight-chain groups methyl, ethyl, propyl, butyl, pentyl and hexyl. Groups having 2-5 carbon atoms are generally preferred.

[0207] The term "alkenyl" or "alkenyl*" encompasses straight-chain and branched alkenyl groups having 2 to 6 carbon atoms, in particular straight-chain groups. Preferred alkenyl groups are C2-C7-1E-alkenyl, C4-C6-3E-alkenyl, in particular C2-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 CH2=CH, CH3CH=CH.

[0208] The term "fluoroalkyl" preferably encompasses straight-chain groups with 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.

[0209] The term "oxaalkyl" or "alkoxy" preferably encompasses groups of the formula C n H 2n+1 -O-(CH2) m A linear group of wherein n and m each independently represent 1 to 6. m may also represent 0. Preferably, n=1 and m=1-6 or m=0 and n=1-3.

[0210] By properly choosing R 0 and X 0 The meaning of, addressing time, threshold voltage, steepness of the transfer characteristic line, etc. can be modified in a desired manner. For example, compared with alkyl and alkoxy groups, 1E-alkenyl, 3E-alkenyl, 2E-alkenyloxy, etc. generally lead to shorter addressing times, improved nematic phase tendency and elastic constant k 33 (bend) and k 11 Compared with alkyl and alkoxy groups, 4-alkenyl, 3-alkenyl, etc. generally have lower threshold voltage and lower k 33 / k 11 The mixtures according to the invention are characterized in particular by high Δε values ​​and therefore have significantly faster response times than the mixtures of the prior art.

[0211] The optimum mixing ratio of the compounds of the above formulae depends essentially on the desired properties, the choice of the components of the above formulae and the choice of any additional components that may be present.

[0212] An appropriate mixing ratio within the above range can be easily determined according to circumstances.

[0213] The total amount of the compound of the above formula in the liquid crystal medium according to the invention is not important. Therefore, for the purpose of optimizing various properties, the mixture may contain one or more other components. However, the observed effect on the desired improvement of the medium properties is generally greater, the higher the total concentration of the compound of the above formula.

[0214] In a particularly preferred embodiment, the liquid-crystalline media according to the invention comprise compounds of the formulae IV to VIII (preferably IV and V), in which X 0 Denotes F, OCF3, OCHF2, OCH=CF2, OCF=CF2 or OCF2-CF2H. The favorable synergy with the compounds of formula IA, IIA, IB and IIB leads to particularly favorable properties. In particular, mixtures of compounds of formula IA or IIA and IB or IIB are characterized by their low threshold voltage.

[0215] The individual compounds of the abovementioned formulae and subformulae which can be used in the liquid-crystalline media according to the invention are known or can be prepared analogously to the known compounds.

[0216] In another preferred embodiment of the present invention, the liquid crystal medium further comprises one or more polymerizable compounds. The polymerizable compounds are preferably selected from the group consisting of: a -B 1 -(Z b -B 2 ) m -R b M

[0217] where the individual radicals, identically or differently on each occurrence and independently of one another, have the following meanings:

[0218] R a and R b is P, P-Sp-, H, F, Cl, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, SF5 or a straight-chain or branched alkyl radical having 1 to 25 C atoms, wherein in addition, one or more non-adjacent CH2 groups may each be replaced independently of one another by -C(R 0 )=C(R 00 )-、-C≡C-、-N(R 00 )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, in such a way that 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 Contains saturated C atoms, then R a and / or R b It can also represent a group that is spiro-attached to the saturated C atom,

[0219] The group R a and R b At least one of them represents or contains a group P or P-Sp-,

[0220] P is a polymerizable group,

[0221] Sp is a spacer group or a single bond,

[0222] B 1 and B 2 is an aromatic, heteroaromatic, alicyclic or heterocyclic group, preferably having 4 to 25 ring atoms, which may also contain fused rings, and which is unsubstituted or mono- or polysubstituted by L,

[0223] Z b is -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-, CR 0 R 00 or single key,

[0224] R 0 and R 00 each independently of one another represents H or an alkyl radical having 1 to 12 C atoms,

[0225] m represents 0, 1, 2, 3 or 4,

[0226] n1 means 1, 2, 3 or 4,

[0227] L is P, P-Sp-, OH, CH2OH, F, Cl, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, -C(=O)N(R x )2, -C(=O)Y 1 、-C(=O)R x 、-N(R x )2, optionally substituted silyl, optionally substituted aryl having 6 to 20 C atoms, or straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25 C atoms, wherein in addition one or more H atoms may be replaced by F, Cl, P or P-Sp-,

[0228] P and Sp have the meanings indicated above,

[0229] Y 1 Represents halogen,

[0230] R x represents P, P-Sp-, H, halogen, straight-chain, branched or cyclic alkyl having 1 to 25 C atoms, wherein, in addition, one or more non-adjacent CH2 groups may be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- 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 40 C atoms, or optionally substituted heteroaryl or heteroaryloxy having 2 to 40 C atoms.

[0231] Particularly preferred compounds of formula I are those wherein B 1 and B 2each independently of one another represents 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, flavonoids, wherein in addition one or more CH groups in these radicals may be replaced by N, cyclohexane-1,4-diyl, wherein in addition one or more non-adjacent CH2 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, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, indane-2,5-diyl or octahydro-4,7-methanoindane-2,5-diyl, all of which may be unsubstituted or mono- or polysubstituted by L as described above.

[0232] Particularly preferred compounds of formula M are those wherein B 1 and B 2 those which each independently represent 1,4-phenylene, 1,3-phenylene, naphthalene-1,4-diyl or naphthalene-2,6-diyl,

[0233] Very preferred compounds of formula M are selected from the following formula:

[0234]

[0235]

[0236]

[0237]

[0238]

[0239] where the individual radicals, identically or differently on each occurrence and independently of one another, have the following meanings:

[0240] P 1 , P 2 , P 3 is a polymerizable group, preferably selected from vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxy groups,

[0241] Sp 1 、Sp 2 、Sp 3 is a single bond or a spacer group, wherein in addition, the group P 1 -Sp 1 -、P 1-Sp 2 - and P 3 -Sp 3 -One or more of them can represent R aa , provided that the group P 1 -Sp 1 -、P 2 -Sp 2 and P 3 -Sp 3 - at least one of them is different from R aa , preferably -(CH2) p1 -、-(CH2) p1 -O-, -(CH2) p1 -CO-O- or -(CH2) p1 -O-CO-O-, wherein p1 is an integer from 1 to 12,

[0242] R aa is H, F, Cl, CN or a straight-chain or branched alkyl radical having 1 to 25 C atoms, wherein in addition, one or more non-adjacent CH2 groups may each be replaced independently of one another by -C(R 0 )=C(R 00 )-、-C≡C-、-N(R 0 )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -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 -Sp 1 -substituted, particularly preferably, by straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy radicals having 1 to 12 C atoms (wherein the alkenyl and alkynyl radicals have at least two C atoms and the branched radicals have at least three C atoms),

[0243] R 0 , R 00 is H or an alkyl radical having 1 to 12 C atoms,

[0244] R y and R z is H, F, CH3 or CF3,

[0245] X 1 , X 2 , X 3 is -CO-O-, -O-CO- or a single bond,

[0246] Z M1 -O-, -CO-, -C(R y R z)-or-CF2CF2-,

[0247] Z M2 , Z M3 -CO-O-, -O-CO-, -CH2O-, -OCH2-, -CF2O-, -OCF2- or -(CH2) n -, where n is 2, 3 or 4,

[0248] L is F, Cl, CN or a straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy radical having 1 to 12 C atoms,

[0249] L', L" are H, F or Cl,

[0250] k is 0 or 1

[0251] r is 0, 1, 2, 3, or 4,

[0252] s is 0, 1, 2, or 3,

[0253] t is 0, 1, or 2,

[0254] x is either 0 or 1.

[0255] Especially preferred are compounds of formulae M2 and M13.

[0256] Further preference is given to the trireactive compounds M15 to M31, in particular M17, M18, M19, M22, M23, M24, M25, M30, M31 and M32.

[0257] In the compounds of formulae M1 to M32, the group

[0258] Best

[0259]

[0260] in which L, at each occurrence, identically or differently, has one of the meanings given above and 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, CH3, C2H5, OCH3, COCH3, OCF3 or P-Sp-, more preferably F, Cl, CH3, OCH3, COCH3 or OCF3, in particular F or CH3.

[0261] Preferred compounds of formula M1 to M32 are those wherein P 1 , P 2 and P 3 Those representing acrylate, methacrylate, oxetane or epoxy groups (acrylate or methacrylate groups being very preferred).

[0262] Further preferred compounds of formula M1 to M32 are those wherein Sp 1 , Sp 2 and Sp 3 Those that are single bonds.

[0263] Further preferred compounds of formula M1 to M32 are those wherein Sp 1 , Sp 2 and Sp 3 One of them is a single bond and Sp 1 , Sp 2 and Sp 3 The other one in is different from those of single bonds.

[0264] Further preferred compounds of the formulae M1 to M32 are those in which the radical Sp which is different from a single bond is 1 , Sp 2 and Sp 3 Represents -(CH2) s1 -X"-, wherein s1 is an integer from 1 to 6, preferably 2, 3, 4 or 5, and X" is a linker to the benzene ring and is -O-, -O-CO-, -CO-O-, -O-CO-O- or a single bond.

[0265] Further preferred polymerizable compounds of formulae M1 to M32 are those selected from Table D below.

[0266] Particular preference is given to liquid-crystalline media which comprise one, two or three polymerizable compounds of the formula M, preferably selected from the formulae M1 to M32.

[0267] Preferably, the proportion of polymerizable compounds (including those of the formula M and subformulae thereof) in the liquid-crystalline medium is from 0.01 to 5%, very preferably from 0.05 to 1%, most preferably from 0.1 to 0.5%.

[0268] It is observed that the addition of one or more polymerizable compounds of formula M to the liquid crystal medium results in advantageous properties such as fast response time. Such liquid crystal media are particularly suitable for PSA displays, where they exhibit low image viscosity, fast and complete polymerization, rapid generation of low pretilt angles (which are stable after UV exposure), high reliability, high VHR values ​​after UV exposure and high birefringence. By appropriate selection of the polymerizable compound, the absorption of the liquid crystal 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.

[0269] The polymerizable group P is a group suitable for polymerization reactions (e.g. free radical or ionic chain polymerization, addition polymerization or condensation polymerization), or a group suitable for polymer-analogous reactions (e.g. addition or condensation on the polymer backbone). Particularly preferred are groups for chain polymerization, in particular those containing a C=C double bond or a -C≡C- triple bond, and groups suitable for ring-opening polymerization, such as oxetane or epoxy groups.

[0270] Preferred groups P are selected from CH2=CW 1 -CO-O-, CH2=CW 1 -CO-, CH2=CW 2 -(O) k3 -, CW 1 =CH-CO-(O) k3 -, CW 1 =CH-CO-NH-, CH2=CW 1 -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-CW 2 W 3 -, HS-CW 2 W 3 -, H.W. 2 N-, HO-CW 2 W 3 -NH-, CH2=CW 1 -CO-NH-, CH2=CH-(COO) k1 -Phe-(O) k2 -, CH2=CH-(CO) k1 -Phe-(O) k2 -, Phe-CH=CH-, HOOC-, OCN- and W 4 W5 W 6 Si-, where W 1 represents H, F, Cl, CN, CF3, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, Cl or CH3, W 2 and W 3 each independently of one another represents H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, W 4 , W 5 and W 6 each independently represents Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms, W 7 and W 8 Each independently represents H, Cl or an alkyl group having 1 to 5 C atoms, Phe represents 1,4-phenylene, which is optionally substituted by one or more groups L different from P-SP- as defined above, k1, k2 and k3 each independently represent 0 or 1, k3 preferably represents 1, and k4 represents an integer from 1 to 10.

[0271] Very preferably the group P is selected from CH2=CW 1 -CO-O-, CH2=CW 1 -CO-, CH2=CW 2 -O-, CH2=CW 2 -, CW 1 =CH-CO-(O) k3 -, CW 1 =CH-CO-NH-, CH2=CW 1 -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=CW 1 -CO-NH-, CH2=CH-(COO) k1 -Phe-(O) k2 -, CH2=CH-(CO) k1 -Phe-(O) k2 -, Phe-CH=CH- and W 4 W 5 W 6 Si-, where W 1 represents H, F, Cl, CN, CF3, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, Cl or CH3, W 2 and W 3each independently of one another represents H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, W 4 , W 5 and W 6 each independently represents Cl, an oxaalkyl or oxacarbonylalkyl radical having 1 to 5 C atoms, W 7 and W 8 Each independently represents H, Cl or an alkyl group having 1 to 5 C atoms, Phe represents 1,4-phenylene, k1, k2 and k3 each independently represent 0 or 1, k3 preferably represents 1, and k4 represents an integer of 1 to 10.

[0272] Very particularly preferred groups P are selected from the group consisting of CH2=CW 1 -CO-O-, in particular CH2=CH-CO-O-, CH2=C(CH3)-CO-O- and CH2=CF-CO-O-, furthermore CH2=CH-O-, (CH2=CH)2CH-O-CO-, (CH2=CH)2CH-O-,

[0273] Further preferred polymerizable groups P are selected from vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxy groups, most preferably from acrylate and methacrylate groups.

[0274] If Sp is different from a single bond, it preferably has the formula Sp"-X", so that the corresponding group P-Sp- corresponds to the formula P-Sp"-X"-, where

[0275] Sp" denotes an alkylene radical having 1 to 20, preferably 1 to 12 C atoms, which is optionally mono- or polysubstituted by F, Cl, Br, I or CN and wherein, in addition, one or more non-adjacent CH2 groups may each independently of one another be substituted by -O-, -S-, -NH-, -N(R 0 )-、-Si(R 0 R 00 )-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -S-CO-, -CO-S-, -N(R 00 )-CO-O-、-O-CO-N(R 0 )-、-N(R 0 )-CO-N(R 00 )-, -CH=CH- or -C≡C- are replaced in such a way that O and / or S atoms are not directly connected to each other,

[0276] X" means -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -CO-N(R 0 )-、-N(R 0 )-CO-、-N(R 0 )-CO-N(R 00 )-, -OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -CF2CH2-, -CH2CF2-, -CF2CF2-, -CH=N-, -N=CH-, -N=N-, -CH=CR 0 -、-CY 2 =CY 3 -, -C≡C-, -CH=CH-CO-O-, -O-CO-CH=CH- or a single bond,

[0277] R 0 and R 00 each independently of one another represents H or an alkyl group having 1 to 20 C atoms, and

[0278] Y 2 and Y 3 Each independently of one another represents H, F, Cl or CN.

[0279] X" is preferably -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR 0 -、-NR 0 -CO-、-NR 0 -CO-NR 00 - or single key.

[0280] Typical spacer groups Sp and -Sp"-X"- are, for example, -(CH2) p1 -、-(CH2CH2O) q1 -CH2CH2-, -CH2CH2-S-CH2CH2-, -CH2CH2-NH-CH2CH2- or -(SiR 0 R 00 -O) p1 -, wherein p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and R 0 and R 00 has the meaning indicated above.

[0281] 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.

[0282] Particularly preferred radicals Sp" are in each case linear ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethylenethioethylene, ethylene-N-methylimino-ethylene, 1-methylalkylene, vinylene, propenylene and butenylene.

[0283] To produce PSA displays, the polymerizable compounds contained in the LC medium are polymerized or crosslinked (if one compound contains two or more polymerizable groups) by polymerization in situ in the LC medium between the substrates of the LC display, optionally with application of a voltage to the electrodes.

[0284] 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. Geometries without protrusions are preferred, in particular those in which, among other things, the electrode on the color filter side is unstructured and only the electrode on the TFT side has slots. A particularly suitable and preferred electrode structure for PS-VA displays is described, for example, in US 2006 / 0066793 A1.

[0285] The combination of the compounds of the abovementioned preferred embodiments with the abovementioned polymerized compounds leads in the liquid-crystalline media according to the invention to low threshold voltages, low rotational viscosities and very good low-temperature stability with simultaneously constantly high clearing points and high VHR values.

[0286] The use of liquid-crystalline media containing polymerizable compounds allows particularly low pretilt angles to be established rapidly in PSA displays. In particular, the liquid-crystalline media exhibit significantly shortened response times, in particular also gray-to-gray response times, in PSA displays relative to the media of the prior art.

[0287] Preference is generally given to liquid-crystalline media which have a nematic liquid-crystalline phase, and preferably no chiral liquid-crystalline phase.

[0288] The present invention also relates to the use of a liquid-crystalline medium according to the invention as described above and below for electro-optical purposes, in particular for shutter glasses, for 3D applications, in IPS, PS-IPS, FFS, PS-FFS, HB-FFS, U-IPS, TN, PS-TN, STN or TN-TFT displays, and to an electro-optical display, in particular an electro-optical display of the aforementioned type, containing a liquid-crystalline medium according to the invention as described above and below, in particular an IPS, PS-IPS, FFS, PS-FFS, HB-FFS, U-IPS, TN, PS-TN, STN or TN-TFT display.

[0289] The invention also relates to an electro-optical display, such as an STN or MLC display, having two plane-parallel outer plates, which together with the frame form a box, an integrated non-linear element for switching the individual pixels on the outer plates, and a nematic liquid-crystal mixture with positive dielectric anisotropy and high specific resistance located in the box, wherein the nematic liquid-crystal mixture is a liquid-crystal medium according to the invention as described above and below.

[0290] The liquid-crystalline media according to the invention enable a significant expansion of the achievable parameter range. The combination of achievable clearing points, viscosity at low temperatures, thermal and UV stability and high optical anisotropy is far superior to the materials known to date from the prior art.

[0291] The liquid-crystalline media according to the invention are suitable for mobile applications and TFT applications, for example mobile phones and PDAs. Furthermore, the liquid-crystalline media according to the invention are particularly suitable for use in FFS and IPS displays.

[0292] The liquid-crystalline media according to the invention preferably remain in the nematic phase down to -20° C., very preferably down to -30° C., most preferably down to -40° C. The liquid-crystalline media according to the invention preferably have a clearing point of ≥85° C., very preferably ≥95° C., most preferably ≥105° C.

[0293] The liquid-crystal media according to the invention preferably have a rotational viscosity γ1 of ≤130 mPa·s, very preferably ≤115 mPa·s, whereby excellent MLC displays with fast response times can be obtained. The rotational viscosity is determined at 20° C.

[0294] In a preferred embodiment, the dielectric anisotropy Δε of the liquid-crystal media according to the invention at 20° C. is preferably ≥+4, very preferably ≥+6 and most preferably ≥+8.

[0295] The birefringence Δn of the liquid-crystalline medium according to the invention at 20° C. is preferably in the range from 0.080 to 0.150, more preferably from 0.090 to 0.140, particularly preferably from 0.100 to 0.130.

[0296] The nematic phase range of the liquid-crystal media according to the invention preferably has a width of at least 100°, more preferably at least 110°, in particular at least 130°. This range preferably extends at least from -25°C to +105°C.

[0297] It goes without saying that, by suitable selection of the components of the liquid-crystal medium according to the invention, higher clearing points (for example above 100° C.) can also be achieved at higher threshold voltages or lower clearing points at lower threshold voltages while retaining other advantageous properties. At a correspondingly only slightly increased viscosity, liquid-crystal media with higher Δε and thus lower thresholds can also be obtained. The MLC displays according to the invention are preferably operated in the first Gooch and Tarry transmission minimum [CH Gooch and HA Tarry, Electron. Lett. 10, 2-4, 1974; CH Gooch and HA Tarry, Appl. Phys., Vol. 8, 1575-1584, 1975], where, in addition to particularly advantageous electro-optical properties, such as high steepness of characteristic lines and low angular dependence of contrast (German Patent 30 22 818), a lower dielectric anisotropy is sufficient at the same threshold voltage as in similar displays at the second minimum. This makes it possible to achieve significantly higher resistivity values ​​in the first minimum using the mixtures according to the invention than in the case of liquid-crystal media comprising cyano compounds. By suitable selection of the individual components and their weight proportions, the person skilled in the art can set the birefringence required for a predetermined layer thickness for MLC displays using simple conventional methods.

[0298] Measurement of voltage holding ratio (HR) [S. Matsumoto et al., Liquid Crystals 5 , 1320 (1989); K. Niwa et al., Proc.SID Conference, San Francisco, June 1984, p.304 (1984); G. Weber et al., Liquid Crystals 5 , 1381 (1989)] have shown that the liquid-crystalline media according to the invention comprising compounds of the formulae ST-1, ST-2, RV, IA and IB show, on UV exposure, a higher degree of activity than the liquid-crystalline media according to the invention comprising compounds of the formulae Cyanophenylcyclohexane or A significantly smaller decrease in HR is observed for a similar mixture of esters of Formula I ST-1, ST-2, RV, IA and IB rather than compounds of Formula I ST-1, ST-2, RV, IA and IB.

[0299] The light stability and UV stability of the liquid-crystalline media according to the invention are significantly better, ie they show a significantly smaller drop in the HR on exposure to light, heat or UV.

[0300] The construction of the MLC display according to the invention consisting of polarizer, electrode substrate and surface-treated electrodes corresponds to the conventional design of such displays. The term "conventional design" is understood here in a broad sense and also includes all derivatives and variants of MLC displays, in particular including matrix display elements based on polysilicon TFTs or MIMs.

[0301] However, a significant difference between the displays according to the invention and hitherto conventional displays based on twisted nematic cells lies in the choice of the liquid-crystal parameters of the liquid-crystal layer.

[0302] The liquid-crystalline media which can be used according to the invention are prepared in a conventional manner per se, for example by mixing one or more compounds according to claim 1 with one or more compounds of the formula IV-XXX or with other liquid-crystalline compounds and / or additives. Usually, the desired amount of the components used in smaller amounts is advantageously dissolved at elevated temperature in the components constituting the main constituents. It is also possible to mix solutions of the components in organic solvents, for example solutions in acetone, chloroform or methanol, and to remove the solvent again, for example by distillation, after thorough mixing.

[0303] The liquid crystal medium may also contain further additives known to the person skilled in the art and described in the literature, such as polymerization initiators, inhibitors, surface-active substances, light stabilizers, antioxidants, such as BHT, TEMPOL, microparticles, free radical scavengers, nanoparticles, etc. For example, 0 to 15% of polychromatic dyes or chiral dopants or initiators such as or Suitable stabilizers and dopants are mentioned in Tables C and D below.

[0304] In a preferred embodiment, the liquid crystal medium comprises one or more chiral dopants, preferably in a concentration of 0.01 to 1% by weight, very preferably 0.05 to 0.5% by weight. The chiral dopant is preferably selected from the compounds of Table B below, very preferably selected from R- or S-1011, R- or S-2011, R- or S-3011, R- or S-4011, and R- or S-5011.

[0305] In a further preferred embodiment, the liquid-crystalline medium comprises the racemate of one or more chiral dopants, which are preferably selected from the chiral dopants mentioned in the previous paragraph.

[0306] In another preferred embodiment of the present invention, the liquid-crystalline medium comprises one or more further stabilizers, which are preferably selected from the group consisting of

[0307]

[0308] where the individual radicals, independently of one another and identically or differently on each occurrence, have the following meanings

[0309] R a-d is a straight-chain or branched alkyl radical having 1 to 10, preferably 1 to 6, very preferably 1-4 C atoms, most preferably methyl,

[0310] X S H, CH3, OH or O ● ,

[0311] A S is an optionally substituted straight-chain, branched or cyclic alkylene group having 1 to 20 C atoms,

[0312] n is an integer of 1 to 6, preferably 3.

[0313] Preferred stabilizers of formula S3 are selected from formula S3A

[0314]

[0315] wherein n2 is an integer from 1 to 12, and wherein the group (CH2) n2 One or more H atoms in are optionally replaced by methyl, ethyl, propyl, butyl, pentyl or hexyl.

[0316] Very preferred stabilizers are selected from the following formula

[0317]

[0318]

[0319]

[0320] In a preferred embodiment, the liquid-crystalline medium comprises one or more stabilizers selected from the group consisting of formulae S1-1, S2-1, S3-1, S3-1 and S3-3.

[0321] In a preferred embodiment, the liquid-crystalline medium comprises one or more stabilizers selected from Table D.

[0322] Preferably, the proportion of stabilizers (such as those of the formulae S1 to S3) in the liquid-crystalline medium is from 10 to 500 ppm, very preferably from 20 to 100 ppm.

[0323] In another preferred embodiment, the LC media according to the invention comprise a self-aligning (SA) additive, preferably in a concentration of 0.1 to 2.5%.

[0324] Preferred SA additives used in this preferred embodiment are selected from compounds comprising a mesogenic group and a linear or branched alkyl side chain terminated by one or more polar anchoring groups selected from hydroxyl, carboxyl, amino or thiol groups.

[0325] Further preferred SA additives contain one or more polymerizable groups, which may optionally be linked to the mesogenic group via a spacer group.These polymerizable SA additives can be polymerized in the LC medium under similar conditions as applied for RMs in the PSA process.

[0326] Suitable SA additives are disclosed, for example, in US 2013 / 0182202 A1, US 2014 / 0838581 A1, US 2015 / 0166890 A1 and US 2015 / 0252265 A1.

[0327] In another preferred embodiment, the LC medium or polymer-stabilized display according to the invention comprises one or more self-aligning additives selected from Table E below.

[0328] In a preferred embodiment, the display according to the invention comprises no alignment layer.

[0329] In addition, the following substances can be added to the liquid crystal medium, for example 0-15% by weight of pleochroic dyes, and nanoparticles, conductive salts for improving the conductivity, preferably 4-hexyloxybenzoic acid ethyldimethyl dodecyl ammonium, tetraphenyl borate tetrabutyl ammonium or crown ether complex salts (for example, see Haller et al., Mol. Cryst. Liq. Cryst. 24 , 249-258 (1973)), or substances for changing the dielectric anisotropy, viscosity and / or nematic alignment. Such substances are described, for example, in DE-A 22 09 127, 22 40 864, 23 21 632, 23 38 281, 24 50 088, 26 37 430 and 28 53 728. DETAILED DESCRIPTION

[0330] In the present application and the following examples, the structures of the liquid crystal compounds are indicated by acronyms and converted into chemical formulas according to the following Table A. All groups C n H 2n+1 and C m H 2m+1 is a straight-chain alkyl radical having n and m C atoms, respectively; n, m and k are integers and preferably represent 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12. The coding in Table B is self-explanatory. In Table A, only the acronyms of the parent structures are indicated. In each case, the acronyms of the parent structures are followed by the substituent R separated by a dash.1* , R 2* , L 1* and L 2* The encoding:

[0331]

[0332]

[0333] Preferred mixture compositions are shown in Tables A and B.

[0334] Table A

[0335]

[0336]

[0337]

[0338] Table B

[0339] 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 and furthermore 0, 4, 6.

[0340]

[0341]

[0342]

[0343]

[0344]

[0345]

[0346]

[0347]

[0348]

[0349] Particular preference is given to liquid-crystalline media which, in addition to the compounds of the formula I, comprise at least one, two, three, four or more compounds from Table B.

[0350] Table C

[0351] Table C indicates possible dopants that are typically added to the liquid-crystalline media according to the invention. The liquid-crystalline media preferably comprise 0 to 10% by weight, in particular 0.01 to 5% by weight and particularly preferably 0.01 to 3% by weight of dopant.

[0352]

[0353]

[0354] Table D

[0355] Stabilizers which can additionally be added to the liquid-crystalline media according to the invention in amounts of 0 to 10% by weight are mentioned below.

[0356]

[0357]

[0358]

[0359]

[0360]

[0361] q = 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10

[0362] Table E

[0363] Table E shows exemplary reactive mesogenic compounds (RM) that can be used in the liquid crystal media according to the invention

[0364]

[0365]

[0366]

[0367]

[0368]

[0369]

[0370]

[0371]

[0372]

[0373]

[0374]

[0375]

[0376]

[0377]

[0378]

[0379]

[0380]

[0381]

[0382]

[0383] In a preferred embodiment, the liquid-crystalline media according to the invention comprise one or more polymerizable compounds, preferably selected from the group consisting of polymerizable compounds of the formulae RM-1 to RM-143. 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-64, RM-74, RM-76, RM-88, RM-102, RM-103, RM-109, RM-117, RM-120, RM-121 and RM-122 are particularly preferred.

[0384] Table E

[0385] Table E shows self-aligning additives for homeotropic alignment which can be used together with polymerisable compounds of formula I in LC media according to the invention;

[0386]

[0387]

[0388]

[0389]

[0390]

[0391]

[0392]

[0393]

[0394]

[0395]

[0396]

[0397] In a preferred embodiment, the LC media and displays according to the invention comprise one or more SA additives selected from the group consisting of formulae SA-1 to SA-48, preferably formulae SA-14 to SA-48, very preferably formulae SA-20 to SA-34 and SA-48, preferably in combination with one or more RMs of formula M.

[0398] The following examples are intended to illustrate the present invention rather than to limit it.

[0399] Above and below, unless expressly stated otherwise, all percentage data denote percentages by weight and relate to the entire corresponding mixture, including all solid or liquid-crystalline components, without solvent. Furthermore, unless expressly stated otherwise, all temperatures are expressed in degrees Celsius (° C.). mp = melting point, cl.p. = clearing point. Furthermore, C = crystalline state, N = nematic phase, S = smectic phase and I = isotropic phase. The data between these symbols denote transition temperatures.

[0400] In addition, the following abbreviations and symbols are used:

[0401] V0 threshold voltage at 20°C, capacitive [V],

[0402] n e Extraordinary refractive index at 20°C and 589nm,

[0403] n o Ordinary refractive index at 20°C and 589nm,

[0404] △n optical anisotropy at 20℃ and 589nm,

[0405] ε ⊥ The dielectric constant perpendicular to the director at 20°C and 1kHz,

[0406] ε||Dielectric constant parallel to the director at 20°C and 1kHz,

[0407] Dielectric anisotropy of △ε at 20℃ and 1kHz,

[0408] cl.p., T ni Clearing point [℃],

[0409] γ1 rotational viscosity at 20°C [mPa·s],

[0410] K1 elastic constant, "bending" deformation at 20°C [pN],

[0411] K2 elastic constant, "twist" deformation at 20°C [pN],

[0412] K3 elastic constant, "bending" deformation at 20°C [pN].

[0413] Unless expressly stated otherwise in each case, all physical properties are and have been determined according to "Merck Liquid Crystals, Physical Properties of Liquid Crystals", Status, November 1997, Merck KGaA, Germany and apply to a temperature of 20°C.

[0414] Unless explicitly stated otherwise, the term "threshold voltage" used in the present invention relates to the capacitive threshold (V0), which is also called the Freedericks threshold. In an embodiment, as usual, the optical threshold may also be the relative contrast ratio (V 10 ) indicated.

[0415] Comparative Example 1

[0416] LC mixture C1 was prepared as follows:

[0417]

[0418]

[0419] Add 0.05% of stabilizer S2-1 to 99.95% of mixture C1:

[0420]

[0421] To 99.85% of the resulting LC mixture, 0.05% of stabilizer S2-1 and 0.1% of stabilizer S3-1 were added to obtain a mixture C11.

[0422]

[0423] Example 1

[0424] LC mixture N1 was prepared as follows:

[0425]

[0426]

[0427] The mixture contained 1.0% of the compound of formula I, CPGP-5-2.

[0428] To 99.9% of mixture N1 was added 0.1% of stabilizer S3-1 to obtain mixture N11.

[0429] Example 2

[0430] LC mixture N2 was prepared as follows:

[0431]

[0432]

[0433] The mixture contained 1.0% of the compound of formula I, CPGP-5-2.

[0434] To 99.9% of mixture N2, 0.1% of stabilizer S3-1 was added to obtain mixture N22.

[0435] VHR value

[0436] The VHR values ​​of mixtures C11, N11 and N22 were measured in a VHR test box at 100C, 3Hz and 1V before and after exposure with LED light.

[0437] The results are shown in Table 1.

[0438] Table 1 – VHR values ​​before and after BL load, 3Hz / 100 ℃

[0439]

[0440] As can be seen from Table 1, both before and after backlight stress, the mixtures N11 and N22 according to the invention containing the compound of formula I show significantly higher VHR values ​​than the mixture C11.

[0441] Comparative Example 2

[0442] LC mixture C2 was prepared as follows:

[0443]

[0444]

[0445] This mixture did not show satisfactory LTS.

[0446] Example 3

[0447] LC mixture N3 was prepared as follows:

[0448]

[0449] The mixture contained 0.5% of the compound of formula I, CPGP-5-2.

[0450] Example 4

[0451] LC mixture N4 was prepared as follows:

[0452]

[0453] The mixture contained 1.0% of the compound of formula I, CPGP-5-2, and showed good LTS at -20°C.

[0454] Example 5

[0455] LC mixture N5 was prepared as follows:

[0456]

[0457]

[0458] The mixture contained 2.0% of the compound of formula I, CPGP-5-2, and showed good LTS at -20°C.

[0459] Example 6

[0460] LC mixture N6 was prepared as follows:

[0461]

[0462]

[0463] The mixture contained 4.0% of the compound of formula I, CPGP-5-2, and showed good LTS at -20° and -30°C.

[0464] Example 7

[0465] LC mixture N7 was prepared as follows:

[0466]

[0467] The mixture contained 6.0% of the compound of formula I, CPGP-5-2, and showed good LTS at -20°C, -30°C and -40°C.

[0468] VHR value

[0469] The changes in the VHR values ​​of the mixtures C2, N4, N5, N6 and N7 were measured before and after varying exposure with LED light in a VHR test box at 60°C, 60 Hz / 3 Hz and 1 V.

[0470] The results are shown in Tables 2 and 3.

[0471] Table 2 – VHR values ​​before and after BL load, 60Hz / 60 ℃

[0472]

[0473] Table 3 - VHR values ​​before and after BL load, 3Hz / 60 ℃

[0474]

[0475] As can be seen from Tables 2 and 3, mixtures N4 to N7 according to the invention comprising compounds of formula I show higher VHR values ​​after backlight stress than mixture C2.

[0476] Example 8

[0477] To 99.95% of the LC mixture of Example 7, 0.05% of stabilizer S1-1 was added.

[0478]

[0479] Example 9

[0480] To 99.65% of the LC mixture of Example 7, 0.05% of stabilizer S1-1 and 0.3% of monomer RM-1 were added.

[0481]

[0482] Example 10

[0483] To 99.7% of the LC mixture of Example 7 was added 0.3% of the monomer RM-35.

[0484]

[0485] Embodiment 11

[0486] To 99.65% of the LC mixture of Example 7, 0.05% of the stabilizer S2-1 and 0.3% of the monomer RM-64 were added.

[0487]

[0488] Example 12

[0489] To 99.7% of the LC mixture of Example 6 was added 0.3% of the monomer RM-120.

[0490]

[0491] Example 13

[0492] To 99.699% of the LC mixture of Example 5, 0.3% of the monomer RM-19 and 0.001% of Irgacure

[0493]

[0494] Embodiment 14

[0495] To 99.7% of the LC mixture of Example 4 was added 0.3% of monomer RM-121.

[0496]

[0497] Embodiment 15

[0498] To 99.7% of the LC mixture of Example 6 was added 0.3% of monomer RM-122.

[0499]

[0500] Example 16

[0501] To 99.7% of the LC mixture of Example 7 was added 0.3% of the monomer RM-91.

[0502]

[0503] Embodiment 17

[0504] To 99.98% of the LC mixture of Example 7, 0.02% of stabilizer S1-1 was added.

[0505] Embodiment 18

[0506] To 99.99% of the LC mixture of Example 7, 0.01% of stabilizer S2-1 was added.

[0507]

[0508] Embodiment 19

[0509] To 99.98% of the LC mixture of Example 3, 0.02% of stabilizer S3-1 was added.

[0510]

[0511] Embodiment 20

[0512] To 99.95% of the LC mixture of Example 6 was added 0.05% of the stabilizer S3-2.

[0513]

[0514] Embodiment 21

[0515] To 99.98% of the LC mixture of Example 7, 0.02% of stabilizer S3-3 was added.

[0516]

[0517] Embodiment 22

[0518] To 99.7% of the LC mixture of Example 4 was added 0.3% of the monomer RM-39.

[0519]

Claims

1. LC medium with positive dielectric anisotropy, characterized in that it contains one or more compounds of formula I in a concentration >0 and ≤10% Where R 1 and R 2 independently of one another represent an alkyl group having 1 to 6 C atoms, One or more compounds of formula XII Where X 0 is F, Cl, CN, SF5, SCN, NCS, a haloalkyl group, a haloalkenyl group, a haloalkoxy group or a haloalkenyloxy group having up to 6 C atoms, and "alkenyl" means C 2-6 -Alkenyl, L means H or F, Characterized in that it does not contain any compound of the formula: Where L 1 and L 2 independently of one another represent H or F, R', identically or differently on each occurrence, represents alkyl or alkoxy having 1 to 12 C atoms, R", identically or differently on each occurrence, represents alkenyl having 2 to 7 C atoms containing a terminal vinyl group, and R"' represents R' or R". 2 . The liquid-crystalline medium according to claim 1 , characterized in that it has a birefringence of <0.

15.

3. LC medium according to claim 1 or 2, characterised in that it comprises one or more compounds of formula I selected from the following sub-formulae 4. LC medium according to claim 1 or 2, characterized in that The concentration of the compound of formula I or a subformulae thereof in the LC medium is from 1.0 to 10%.

5. LC medium according to claim 1 or 2, characterised in that it further comprises one or more compounds selected from the following formulae: where the individual radicals are independent of one another and have the following meanings when they occur identically or differently: for for R 0 is an unsubstituted or halogenated alkyl or alkoxy group having 1 to 15 C atoms, wherein in addition, one or more CH2 groups in these groups can each be independently replaced by -C≡C-, -CF2O-, -CH=CH-, -O-, -CO-O- or -O-CO- is substituted in such a way that the O atoms are not directly connected to each other, or represents X 0 is F, Cl, CN, SF5, SCN, NCS, a haloalkyl group, a haloalkenyl group, a haloalkoxy group or a haloalkenyloxy group having up to 6 C atoms, and Y 0 H or CH 3, Y 1-6 It is H or F.

6. LC medium according to claim 1 or 2, characterised in that it comprises one or more compounds selected from the following sub-formulae Where R 0 and X 0 has the meaning given in claim 5.

7. LC medium according to claim 1 or 2, characterised in that it comprises one or more compounds selected from the following sub-formulae Where R 0 and X 0 has the meaning given in claim 5.

8. LC medium according to claim 1 or 2, characterised in that it further comprises one or more compounds selected from the following formulae Where R 0 , X 0 and Y 1-4 has the meaning given to it in claim 5, Z 0 represents -C2H4-, -(CH2)4-, -CH=CH-, -CF=CF-, -C2F4-, -CH2CF2-, -CF2CH2-, -CH2O-, -OCH2-, -COO- or -OCF2-, and may also be a single bond in formulas V and VI, and may also be -CF2O- in formulas V and VIII. r represents 0 or 1, and s represents 0 or 1.

9. LC medium according to claim 1 or 2, characterised in that it comprises one or more compounds selected from the group consisting of Where R 0 has the meaning given in claim 5.

10. LC medium according to claim 1 or 2, characterised in that it further comprises one or more compounds selected from the following formulae: "alkyl" means C 1-6 -alkyl, "alkenyl" means C 2-6 -Alkenyl, R" means C 1-6 -alkyl, C 1-6 -alkoxy or C 2-6 -alkenyl, R a1 , R b1 independently represent CH3 or C2H5, i, k are independently 0, 1, 2 or 3.

11. LC medium according to claim 1 or 2, characterised in that it comprises one or more compounds selected from the following subformulae: wherein "alkyl" has the meaning given in claim 10.

12. The LC medium according to claim 1 or 2, wherein the LC medium has a clearing point ≥ 105°C and a birefringence at 20°C of from 0.100 to 0.

130.

13. LC medium according to claim 1 or 2, characterised in that it further comprises one or more compounds selected from the following formulae: Where R 3 and R 4 each independently of one another represents n-alkyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyl, each having up to 6 C atoms.

14. LC medium according to claim 13, characterised in that R 3 and R 4 Each independently of one another represents an alkyl radical having 1 to 6 C atoms or an alkenyl radical having 2 to 6 C atoms.

15. LC medium according to claim 1 or 2, characterised in that it further comprises one or more compounds selected from the following subformulae: wherein "alkyl" has the meaning given in claim 10.

16. LC medium according to claim 1 or 2, characterised in that it comprises one or more compounds of the formula XVI Where R 3 and R 4 has the meaning given in claim 10, and L represents H or F.

17. LC medium according to claim 1 or 2, characterised in that it comprises a compound of formula XVIc2 18. LC medium according to claim 1 or 2, characterised in that it comprises one or more compounds of the formula IA1 Where R 0 is ethyl or propyl and X 0 For F.

19. LC medium according to claim 1 or 2, characterised in that it comprises one or more compounds selected from the group consisting of compounds of the formula Where R 0 , X 0 and Y 1-4 Each has, independently of one another, one of the meanings given in claim 5 .

20. LC medium according to claim 1 or 2, characterised in that it comprises one or more compounds of the formula XXIa Where R 0 represents ethyl, n-propyl, n-butyl or n-pentyl.

21. LC medium according to claim 1 or 2, characterised in that it comprises one or more compounds selected from the group consisting of compounds of the formula Where R 3 has the meaning given in claim 10, and X 0 Has the meaning indicated in claim 5.

22. LC medium according to claim 1 or 2, characterised in that it comprises one or more compounds of the formula XXIXa Where R 3 represents ethyl, n-propyl, n-butyl or n-pentyl.

23. Process for preparing an LC medium according to any one of claims 1 to 22, characterised in that one or more compounds of the formula I or subformulae thereof as defined in claim 1 or 3 are mixed with one or more compounds according to any one of claims 4 to 22 or with other LC compounds.

24. Use of an LC medium according to any one of claims 1 to 22 for electro-optical purposes.

25. Use according to claim 24, wherein the use is use in shutter glasses, use for 3D applications or use in IPS, PS-IPS, FFS, PS-FFS, HB-FFS, U-IPS, TN, PS-TN, STN or TN-TFT displays.

26. LC display comprising an LC medium according to any one of claims 1 to 22.

27. LC display according to claim 26, characterised in that it is an IPS, PS-IPS, FFS, PS-FFS, HB-FFS, U-IPS, TN, PS-TN, STN or TN-TFT display.

Images