Liquid crystal medium and liquid crystal display

Abstract

The present invention relates to dielectrically positive liquid-crystalline media comprising one or more compounds of the formulae S1 and S2, and one or more compounds selected from the group consisting of compounds of the formulae II and III and / or IV and / or VIII, wherein the parameters have the respective meanings indicated in the description, and optionally one or more further dielectrically positive compounds and optionally one or more further dielectrically neutral compounds, and to liquid-crystalline displays comprising these media, in particular active-matrix displays, in particular TN, IPS and FFS displays.

Description

Technical Field

[0001] The present invention relates to liquid-crystalline media and to liquid-crystalline displays containing these media, in particular to displays addressed by means of an active matrix and in particular to displays of the twisted nematic (TN), in-plane switching (IPS) or fringe field switching (FFS) type. Background Art

[0002] Existing technologies and problems to be solved

[0003] Liquid crystal displays (LCDs) are used for information display in many fields. LCDs are used for both direct-view displays and for 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 various variations, as well as other modes. All these modes use an electric field that is 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 that is substantially parallel to the substrate or liquid crystal layer, such as in-plane switching (IPS) modes (such as those disclosed in DE 40 00 451 and EP 0 588 568) and fringe field switching (FFS) modes, 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 intended 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.

[0004] For these displays, new liquid-crystalline media with improved properties are required. For many types of applications, in particular the addressing time must be improved. Therefore, liquid-crystalline media with lower viscosities (η) and in particular with lower rotational viscosities (γ) are required. 1 ) of a liquid crystal medium. In particular for monitor applications, the rotational viscosity should be 80 mPa·s or less, preferably 60 mPa·s or less, in particular 55 mPa·s or less. In addition to these viscosity parameters, the medium must have a nematic phase range of suitable width and position and a suitable birefringence (Δn). Furthermore, the dielectric anisotropy (Δε) should be high enough to allow a fairly low operating voltage. Δε should preferably be greater than 2, more preferably greater than 3, but preferably not greater than 20, in particular not greater than 17, since this prevents at least a fairly high resistivity.

[0005] For use as a display for notebook computers or other mobile applications, the rotational viscosity should preferably be 120 mPa·s or less, particularly preferably 100 mPa·s or less. The dielectric anisotropy (Δε) should preferably be greater than 8, particularly preferably greater than 12.

[0006] 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.

[0007] There are many different display modes that use composite systems of low molecular weight liquid crystal materials with polymer materials. These are, for example, polymer dispersed liquid crystals (PDLC), nematic curve alignment phases (NCAP) and polymer network (PN) systems, such as disclosed in WO 91 / 05 029, or axisymmetric microdomain (ASM) systems, etc. In contrast to these, a particularly preferred mode according to the invention uses the liquid crystal medium itself, which is oriented on the surface. These surfaces are usually pretreated to achieve a uniform alignment of the liquid crystal material. The display mode according to the invention preferably uses an electric field substantially parallel to the composite layer.

[0008] Liquid crystal compositions 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 compositions have serious disadvantages. Among other drawbacks, they mostly lead to disadvantageously long addressing times, have insufficient resistivity values ​​and / or require too high an operating voltage. In addition, it is desirable to improve the low-temperature behavior of LCDs. The following improvements are necessary in this context: both in terms of operating properties and in terms of shelf life, in particular stability to visible light and UV radiation, and to heat, in particular the stability to a combination of heat and light and / or UV radiation.

[0009] This not only relates to the usual life cycle of the display, but also to the individual steps in the production of the display, wherein, compared with normal operation, these displays are subjected to extreme loads in some cases. Thus, for example, a method is often adopted in the production of the bonding of the frame, which leads to a very high thermal load of the display that already contains the liquid crystal. In order to make the liquid crystal withstand (survive) this strong thermal load as much as possible without damage, it is advantageous to add one or more heat stabilizers to the liquid crystal formulation. In the subsequent daily operation of the display, the light due to the backlight and the load caused by the ambient light (usually daylight) and the temperature load from the environment may then occur as an important load factor. This means that, in particular, the combination of various load amounts may be of particular importance in practice.

[0010] This combination of various loads can occur in sequential time sequence or in parallel in time. Thus, for example, a display used as an electronic billboard can be subjected to strong heating and sunlight both during operation and in the stationary state, depending on the installation location.

[0011] EP 3 246 374 et al. disclose dielectrically positive LC mixtures comprising

[0012]

[0013] EP 3 112 441 also discloses a dielectrically positive LC mixture comprising

[0014]

[0015] It also preferably comprises

[0016]

[0017] or

[0018]

[0019] Many liquid crystal media, especially those with large polarity or high dielectric anisotropy, do not meet the high stability requirements required for practical applications.

[0020] There is therefore a considerable demand for liquid-crystalline media having properties suitable for practical applications, such as a broad nematic phase range, a suitable optical anisotropy Δn corresponding to the type of display used, a high Δε and a particularly low viscosity for particularly short response times. Summary of the invention

[0021] Surprisingly, it has been found that it is possible to achieve liquid-crystalline media having a suitably high Δε, a suitable phase range and a suitable Δn which do not exhibit the disadvantages of the materials of the prior art, or at least exhibit said disadvantages only to a significantly lesser extent.

[0022] Surprisingly, it has been found here that compounds of the formulae S1 and S2, as shown below, lead to considerable and, in most cases, sufficient stabilization of the liquid-crystal mixtures.

[0023] The present invention relates to a liquid crystal medium having a nematic phase and positive dielectric anisotropy, comprising:

[0024] a) one or more compounds of formula S1 and one or more compounds of formula S2, preferably in a concentration range of 1 ppm to 5,000 ppm each, more preferably in a concentration range of 100 ppm to 2,000 ppm each,

[0025]

[0026]

[0027] The individual radicals, independently of one another and identically or differently on each occurrence, have the following meanings:

[0028] express

[0029] R a-d is a straight-chain or branched alkyl radical having 1 to 10 C atoms, preferably having 1 to 6 C atoms, very preferably having 1 to 4 C atoms, most preferably methyl,

[0030] X is H, CH 3 , OH or O ● , preferably H,

[0031] A is a linear, branched or cyclic alkylene group having 1 to 20 C atoms, which is optionally substituted, preferably -(CH 2 ) 8 -,and

[0032] n is an integer of 1 to 6, preferably 3.

[0033] and

[0034] b) one or more compounds selected from the group consisting of compounds of formula II and III

[0035]

[0036] in

[0037] R 2 and R 3, independently of one another represent an alkyl group, an alkoxy group, a fluoroalkyl group or a fluoroalkoxy group having 1 to 7 C atoms, an alkenyl group, an alkenyloxy group, an alkoxyalkyl group or a fluoroalkenyl group having 2 to 7 C atoms, and preferably R 2 and R 3 represents an alkyl or alkenyl group,

[0038] to

[0039] At each occurrence, they are expressed independently of each other

[0040]

[0041] Best

[0042]

[0043] L 21 , L 22 , L 31 and L 32 , independently of each other, represent H or F,

[0044] Best

[0045] L 21 and / or L 31 Indicates F,

[0046] X 2 and X 3 , independently of one another represent halogen, haloalkyl or alkoxy having 1 to 3 C atoms or haloalkenyl or alkenyloxy having 2 or 3 C atoms, preferably F, Cl, -OCF 3 or -O-CH=CF 2 , -CF 3 , especially F,-OCF 3 or -O-CH=CF 2 ,

[0047] Z 3 Indicates -CH 2 CH 2 -, -CF 2 CF 2 -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH 2 O- or single bond, preferably -CH 2 CH 2 -, -COO-, trans-CH=CH- or a single bond and very preferably -COO-, trans-CH=CH- or a single bond, and

[0048] m and n, independently of each other, represent 0, 1, 2 or 3,

[0049] m preferably represents 1, 2 or 3, and

[0050] n preferably represents 0, 1 or 2 and particularly preferably 1 or 2,

[0051] and / or

[0052] c) one or more compounds of formula IV

[0053]

[0054] in

[0055] R 41 and R 42 , independently of each other, have the above formula II for R 2 The meaning shown is preferably R 41 represents an alkyl group and R 42 represents an alkyl group or an alkoxy group or R 41 represents alkenyl and R 42 represents an alkyl group,

[0056]

[0057] independently of each other, and if appears twice, then these also represent independently of each other

[0058]

[0059] Best

[0060] One or more of

[0061] Z 41 and Z 42 , independently of each other and, if Z 41 appears twice, these also represent independently of each other -CH 2 CH 2 -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH 2 O-, -CF 2 O-, -C≡C- or a single bond, preferably one or more of them represent a single bond, and

[0062] p represents 0, 1 or 2, preferably 0 or 1,

[0063] and / or

[0064] d) one or more compounds of formula VIII

[0065]

[0066] in

[0067] R 81 and R 82 , independently of each other, have the above formula II for R 2 The meaning shown, and

[0068] express Best

[0069] express

[0070]

[0071] Z 81 and Z 82 , independently represent -CH 2 CH 2 -, -C≡C-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH 2 O-, -CF 2 O- or a single bond, preferably one or more of them represent a single bond and very preferably both represent a single bond,

[0072] L 81 and L 82 , independently represent CF or N, preferably L 81 and L 82 One or both represent CF and very preferably both represent CF, and

[0073] s represents 0 or 1 and

[0074] L 81 and L 82 , independently represent CF or N, preferably L 81 and L 82 One or both represent CF and very preferably both represent CF, and

[0075] exist

[0076] express In the case of

[0077] L 81 and L 82 One or both may alternatively represent CH.

[0078] The present invention also relates to an LC medium as described above and below, which additionally comprises one or more polymerisable compounds.

[0079] In the present application, elements all include their respective isotopes. In particular, one or more H in the compound can be replaced by D, and this is also particularly preferred in certain embodiments. The corresponding high degree of deuteration of the corresponding compound enables, for example, detection and identification of the compound. This is very useful in some cases, particularly in the case of formula S1 and S2 compounds.

[0080] In this application,

[0081] Alkyl particularly preferably denotes straight-chain alkyl, in particular CH 3 -, C 2 H 5 -, nC 3 H 7 -, nC 4 H 9 - or nC 5 H 11 -,and

[0082] Alkenyl particularly preferably represents CH 2 =CH-, E-CH 3 -CH=CH-, CH 2 =CH-CH 2 -CH 2 -, E-CH 3 -CH=CH-CH 2 -CH 2 - or E-(nC 3 H 7 )-CH=CH-.

[0083] The liquid-crystalline medium according to the present application preferably comprises a total of 1 ppm to 25,000 ppm, preferably 50 ppm to 20,000 ppm, even more preferably 100 to 15,000 ppm, preferably up to 10,000 ppm, very particularly preferably 200 ppm to 10,000 ppm of compounds of the formulae S1 and S2. In another preferred embodiment, the liquid-crystalline medium according to the present application comprises a total of 1 ppm to 2,000 ppm, preferably 10 ppm to 1,000 ppm, even more preferably 20 to 600 ppm, preferably up to 500 ppm, and very particularly preferably 50 ppm to 400 ppm of compounds of the formulae S1 and S2.

[0084] The compounds of formulae S1 and S2 are very suitable as stabilizers in liquid crystal mixtures. In particular, they provide very effective thermal stability for such mixtures. In contrast to these compounds, the compounds known to date that provide good thermal stability lead to a more or less significant reduction in the "voltage holding ratio" (VHR or just HR for short) upon UV exposure. In contrast, the compounds of formulae S1 and S2 show a significant improvement. Although the HR of the mixture often still decreases after UV exposure, this reduction in the HR of the UV exposure is significantly reduced compared to what occurs in the case of the materials known to date.

[0085] Preferred compounds of formula S1 are selected from the following sub-formulas

[0086]

[0087]

[0088] Most preferred are compounds of formula S1a.

[0089] Preferred compounds of formula S2 are selected from the following sub-formulas

[0090]

[0091] Most preferred are compounds of formula S2a.

[0092] In a preferred embodiment of the invention, the medium according to the invention comprises one or more compounds of the formulae S1 and S2, preferably selected from the respective preferred subformulae thereof,

[0093] and

[0094] One or more compounds of formula II, preferably selected from preferred subformulae thereof,

[0095] and / or

[0096] One or more compounds of formula III, preferably selected from preferred subformulae thereof,

[0097] and / or

[0098] One or more compounds of formula IV, preferably selected from preferred subformulae thereof,

[0099] and / or

[0100] The one or more compounds of formula VIII are preferably selected from preferred subformulae thereof.

[0101] In addition to compounds of formulae S1 and S2 or preferred subformulae thereof, the medium according to the invention preferably contains one or more dielectrically neutral compounds of formula Iv in a total concentration of 5% or more to 90% or less, preferably 10% or more to 80% or less, particularly preferably 20% or more to 70% or less.

[0102] The compounds of formulae II and III are preferably dielectrically positive compounds, preferably having a dielectric anisotropy greater than 3.

[0103] The compound of formula IV is preferably a dielectrically neutral compound, preferably having a dielectric anisotropy of -1.5 to 3.

[0104] The compounds of formulae S1 and S2 are very suitable as stabilizers in liquid crystal mixtures. In particular, they provide very effective thermal stabilization of the mixture. Materials that have provided good thermal stability to date lead to a more or less significant reduction in HR upon UV exposure. In contrast, the compounds of formulae S1 and S2 show an improvement, i.e. a reduction in the reduction in HR upon UV exposure.

[0105] The individual compounds of formula II and / or III are used in a concentration of 1-20%, preferably 1-15%. In particular, these restrictions apply if two or more homologous compounds, i.e. compounds of the same formula, are used in each case. If only a single substance of a compound of formula is used, i.e. only one homolog, its concentration may be 2 to 20%, preferably 3 to 14%.

[0106] Besides the compounds of the formulae S1 and S2 or preferred subformulae thereof, the medium according to the invention preferably comprises one or more dielectrically positive compounds having a dielectric anisotropy greater than 3, selected from the compounds of the formulae II and III.

[0107] In a preferred embodiment of the invention, the medium according to the invention comprises one or more compounds selected from the group consisting of compounds of the formulae II-1 to II-4, preferably formulae II-1 and / or II-2,

[0108]

[0109]

[0110] wherein the parameters have the respective meanings indicated above under formula II, and L 23 and L 24 , independently of each other, represent H or F, preferably L 23 represents F, and

[0111] With

[0112] One of the meanings given above and, in the case of formulae II-1 and II-4, X 2 Preferably F or OCF 3 , particularly preferably F, and, in the case of formula II-3,

[0113] Independently of each other, preferably

[0114]

[0115] and / or a compound selected from formula III-1 and III-2:

[0116]

[0117] Therein the parameters have the meanings given under formula III.

[0118] In a preferred embodiment, the media according to the invention comprise, instead of or in addition to the compounds of the formula III-1 and / or III-2, one or more compounds of the formula III-3

[0119]

[0120] where the parameters have the respective meanings as indicated above, and the parameter L 31 and L 32 , independently of each other and of the other parameters, represent H or F.

[0121] The medium according to the invention preferably comprises one or more compounds selected from the group consisting of compounds of the formulae II-1 to II-4, in which L 21 and L 22 and / or L 23 and L 24 Both mean F.

[0122] In a preferred embodiment, the medium comprises one or more compounds selected from the group consisting of compounds of formula II-2 and II-4, wherein L 21 , L 22 , L 23 and L 24 All mean F.

[0123] The medium preferably comprises one or more compounds of formula II-1. The compound of formula II-1 is preferably selected from the compounds of formula II-1a to II-1f:

[0124]

[0125] wherein the parameters have the respective meanings as indicated above, and L 23 To L 25 , independently of each other and of the other parameters, represent H or F, and

[0126] Best

[0127] In formula II-1a and II-1b

[0128] L 21 and L22 Both represent F,

[0129] In formula II-1c and II-1d

[0130] L 21 and L 22 Both mean F and / or L 23 and L 24 Both represent F, and

[0131] In formula II-1e

[0132] L 21 , L 22 and L 25 Denotes F, and the other parameters have in each case the respective meanings given above.

[0133] Particularly preferred compounds of formula II-1 are

[0134]

[0135]

[0136] Where R 2 have the above-mentioned meanings, in particular compounds of the formula II-1a-2.

[0137] The medium preferably comprises one or more compounds of formula II-2, which are preferably selected from compounds of formulae II-2a to II-2k

[0138]

[0139]

[0140]

[0141] wherein the parameters have the respective meanings as indicated above, and L 25 To L 28 , independently of each other, represent H or F, preferably L 27 and L 28 Both represent H, and L is particularly preferred 26 represents H, and other parameters have the respective meanings described above.

[0142] The medium according to the invention preferably comprises one or more compounds selected from the group consisting of compounds of the formulae II-2a to II-2k, in which L 21 and L 22 Both mean F and / or L 23 and L 24 Both represent F, and other parameters have the respective meanings described above.

[0143] In a preferred embodiment, the medium according to the invention comprises one or more compounds selected from the group consisting of compounds of the formulae II-2a to II-2k, in which L 21 , L 22 , L 23 and L 24 All represent F, and other parameters have the respective meanings described above.

[0144] Particularly preferred compounds of formula II-2 are compounds of the formula:

[0145]

[0146]

[0147]

[0148] Where R 2 and X 2 has the above meaning, and X 2 Preference is given to compounds of F, particularly preferably compounds of the formula II-2a-1 and / or II-2h-1 and / or II-2j-1 and / or II-2k-1.

[0149] The medium according to the invention preferably comprises one or more compounds of the formula II-3, which are preferably selected from the compounds of the formulae II-3a to II-3c

[0150]

[0151] wherein the parameters have the respective meanings as indicated above, and L 21 and L 22 Preferably, both represent F.

[0152] In a preferred embodiment, the medium according to the invention comprises one or more compounds of the formula II-4, preferably compounds of the formula II-4a,

[0153] where the parameters have the meanings given above, and X 2 Preferably F or OCF 3 , F is particularly preferred.

[0154] The medium according to the invention preferably comprises one or more compounds of the formula III-1, which are preferably selected from the compounds of the formulae III-1a and III-1b

[0155]

[0156] where the parameters have the respective meanings as indicated above, and the parameter L 33 and L 34, independently of each other and of the other parameters, represent H or F.

[0157] The medium according to the invention preferably comprises one or more compounds of the formula III-1a, which are preferably selected from the compounds of the formulae III-1a-1 to III-1a-6:

[0158]

[0159]

[0160] Where R 3 has the meanings as indicated above.

[0161] The medium according to the invention preferably comprises one or more compounds of the formula III-1b, which are preferably selected from the formulae III-1b-1 to III-1b-4, preferably the compound of the formula III-1b-4:

[0162]

[0163]

[0164] Where R 3 has the meanings as indicated above.

[0165] The medium according to the invention preferably comprises one or more compounds of the formula III-2, which are preferably selected from the compounds of the formulae III-2a to III-2k:

[0166]

[0167]

[0168]

[0169] wherein the parameters have the meanings given above and preferably wherein the parameters have the respective meanings indicated above, and the parameter L 33 , L 34 , L 35 and L 36 , independently of each other and of the other parameters, represent H or F.

[0170] The medium according to the invention preferably comprises one or more compounds of the formula III-2a, which are preferably selected from the compounds of the formulae III-2a-1 to III-2a-5

[0171]

[0172] Where R 3 Has the meanings stated above.

[0173] The medium according to the invention preferably comprises one or more compounds of the formula III-2b, which are preferably selected from the formulae III-2b-1 to III-2b-2, preferably compounds of the formula III-2b-2

[0174]

[0175] Where R 3 Has the meanings stated above.

[0176] The medium according to the invention preferably comprises one or more compounds of the formula III-2c, which are preferably selected from the compounds of the formulae III-2c-1 to III-2c-6:

[0177]

[0178]

[0179] Where R 3 Having the above meanings, particular preference is given to compounds of the formulae III-2c-1 and / or III-2c-2 and / or III-2c-4.

[0180] The medium according to the invention preferably comprises one or more compounds selected from the compounds of the formulae III-2d and III-2e, preferably selected from the compounds of the formulae III-2d-1 and III-2e-1

[0181]

[0182] Where R 3 Has the meanings stated above.

[0183] The medium according to the invention preferably comprises one or more compounds of the formula III-2f, which are preferably selected from the compounds of the formulae III-2f-1 to III-2f-5

[0184]

[0185]

[0186] Where R 3 Has the meanings stated above.

[0187] The medium according to the invention preferably comprises one or more compounds of the formula III-2g, which are preferably selected from the compounds of the formulae III-2g-1 to III-2g-5

[0188]

[0189]

[0190] Where R 3Has the meanings stated above.

[0191] The medium according to the invention preferably comprises one or more compounds of the formula III-2h, which are preferably selected from the formulae III-2h-1 to III-2h-3, preferably the compound of the formula III-2h-3

[0192]

[0193] where the parameters have the meanings given above, and X 3 Preferably it represents F.

[0194] The medium according to the invention preferably comprises one or more compounds of the formula III-2i, which are preferably selected from the group consisting of the formula III-2i-1 and III-2i-2, particularly preferably the compound of the formula III-2i-2

[0195]

[0196] where the parameters have the meanings given above, and X 3 Preferably F or OCF 3 .

[0197] The medium according to the invention preferably comprises one or more compounds of the formula III-2j, which are preferably selected from the formulae III-2j-1 to III-2j-2, particularly preferably compounds of the formula III-2j-1

[0198]

[0199] wherein the parameters have the meanings given above.

[0200] The medium according to the invention preferably comprises one or more compounds of the formula III-2k, preferably compounds of the formula III-2k-1:

[0201]

[0202] where the parameters have the meanings given above and X 3 Preferably it represents F.

[0203] Instead of or in addition to the compounds of formula III-1 and / or III-2, the medium according to the invention may comprise one or more compounds of formula III-3

[0204]

[0205] wherein the parameters have the respective meanings indicated above under formula III.

[0206] These compounds are preferably selected from the group consisting of formula III-3a and III-3b

[0207]

[0208] Where R 3 Has the meanings stated above.

[0209] The liquid-crystalline medium according to the invention preferably comprises a dielectrically neutral component, component C. This component has a dielectric anisotropy in the range of -1.5 to 3. It preferably comprises, more preferably consists essentially of, even more preferably consists essentially of and very preferably consists entirely of dielectrically neutral compounds having a dielectric anisotropy in the range of -1.5 to 3. This component preferably comprises one or more dielectrically neutral compounds, more preferably consists essentially of, even more preferably consists essentially of and very preferably consists entirely of dielectrically neutral compounds of the formula IV having a dielectric anisotropy in the range of -1.5 to 3.

[0210] The dielectrically neutral component, component C, preferably comprises one or more compounds selected from the group consisting of compounds of formulae IV-1 to IV-8:

[0211]

[0212] Where R 41 and R 42 have the respective meanings as indicated above under formula IV, and in formulae IV-1, IV-6 and IV-7, R 41 Preferably represents an alkyl group or an alkenyl group, preferably an alkenyl group, and R 42 Preferably represents an alkyl group or an alkenyl group, preferably an alkyl group, and in formula IV-2, R 41 and R 42 Preferably represents an alkyl group, and in formula IV-5, R 41 Preferably represents an alkyl group or an alkenyl group, more preferably an alkyl group, and R 42 Preferably represents an alkyl group, an alkenyl group or an alkoxy group, more preferably an alkenyl group or an alkoxy group, and in formulas IV-4 and IV-8, R 41 Preferably represents an alkyl group and R 42 Preferably it represents an alkyl group or an alkoxy group, more preferably an alkoxy group.

[0213] The dielectric neutral component, component C, preferably comprises one or more compounds selected from compounds of formula IV-1, IV-5, IV-6 and IV-7, preferably one or more compounds of formula IV-1 and one or more compounds selected from formula IV-5 and IV-6, more preferably one or more compounds of each of formula IV-1, IV-5 and IV-6, and very preferably one or more compounds of each of formula IV-1, IV-5, IV-6 and IV-7.

[0214] In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula IV-4, more preferably selected from the individual subformulae of formula CP-Vn and / or CP-nV-m and / or CP-Vn-m, more preferably from formula CP-Vn and / or CP-V2-n, very preferably from formula CP-V-1 and CP-V2-1. The definitions of these abbreviations (acronyms) are shown in Table D below or are obvious from Tables A to C.

[0215] In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula IV-5, more preferably one or more compounds selected from the respective subformulas of formula CCP-Vn and / or CCP-nV-m and / or CCP-Vn-m, said subformulas being more preferably formula CCP-Vn and / or CCP-V2-n and very preferably selected from CCP-V-1 and CCP-V2-1. The definitions of these abbreviations (acronyms) are indicated below in Table D or are apparent from Tables A to C.

[0216] In a likewise preferred embodiment, the medium according to the invention comprises one or more compounds of formula IV-1, more preferably selected from its subformulae, which are formula CC-nm, CC-nV, CC-n-Vm, CC-VV, CC-V-Vn and / or CC-nV-Vm, more preferably formula CC-nV and / or CC-n-Vm, and very preferably selected from formula CC-3-V, CC-4-V, CC-5-V, CC-3-V1, CC-4-V1, CC-5-V1, CC-3-V2 and CC-V-V1. The definitions of these abbreviations (acronyms) are likewise indicated below in Table D or are apparent from Tables A to C.

[0217] In another preferred embodiment of the present invention, which may be the same as the previous one or a different one, the liquid crystal mixture according to the present invention comprises component C, which comprises, preferably consists essentially of and very preferably consists entirely of a compound of formula IV, which is selected from the compounds of formulae IV-1 to IV-8 and optionally compounds of formulae IV-9 to IV-15 as shown above:

[0218]

[0219]

[0220] in

[0221] R 41 and R 42 , independently of one another represent alkyl, alkoxy, fluoroalkyl or fluoroalkoxy having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluoroalkenyl having 2 to 7 C atoms, and

[0222] L 4 Indicates H or F.

[0223] In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula IV-10, more preferably one or more compounds selected from its subformulae, said subformulae being formula CPP-3-2, CPP-5-2 and CGP-3-2, more preferably formula CPP-3-2 and / or CGP-3-2 and very particularly preferably formula CPP-3-2. The definitions of these abbreviations (acronyms) are indicated below in Table D or are apparent from Tables A to C.

[0224] The liquid-crystalline media according to the invention preferably comprise one or more compounds of the formula V

[0225]

[0226] in

[0227] R 51 and R 52 , independently of each other, have the above formula II for R 2 The meaning indicated, preferably R 51 represents an alkyl group and R 52 represents an alkyl or alkenyl group,

[0228] If it occurs twice, in each case independently of each other, on each occurrence, it means

[0229]

[0230] Best

[0231] One or more of

[0232] Z 51 and Z 52 , independently of each other, and if Z 51 appears twice, these also represent independently of each other -CH 2 CH 2 -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH 2 O-, -CF 2 O- or a single bond, preferably one or more of them represent a single bond, and

[0233] r represents 0, 1 or 2, preferably 0 or 1, and particularly preferably 1.

[0234] The compound of formula V is preferably a dielectrically neutral compound having a dielectric anisotropy in the range of -1.5 to 3.

[0235] The medium according to the invention preferably comprises one or more compounds selected from the group consisting of compounds of the formulae V-1 and V-2

[0236]

[0237] Where R 51 and R 52 have the respective meanings as indicated above under formula V, and R 51 Preferably represents an alkyl group, and in formula V-1, R 52 Preferably represents alkenyl, preferably -(CH 2 ) 2 -CH=CH-CH 3 , and in Formula V-2, R 52 Preferably represents an alkyl or alkenyl group, preferably -CH=CH 2 ,-(CH 2 ) 2 -CH=CH 2 or -(CH 2 ) 2 -CH=CH-CH 3 .

[0238] The medium according to the invention preferably comprises one or more compounds selected from the group consisting of compounds of the formulae V-1 and V-2, in which R 51 Preferably represents an n-alkyl group, and in formula V-1, R 52 Preferably represents alkenyl, and in formula V-2, R 52 Preferably it represents n-alkyl.

[0239] In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula V-1, more preferably compounds of sub-formula PP-n-2Vm thereof, even more preferably compounds of formula PP-1-2V1. The definitions of these abbreviations (acronyms) are indicated below in Table D or are obvious from Tables A to C.

[0240] In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula V-2, more preferably compounds of the subformulae PGP-nm, PGP-nV, PGP-n-2Vm, PGP-n-2V and PGP-n-2Vm thereof, even more preferably compounds of the subformulae PGP-3-m, PGP-n-2V and PGP-n-V1 thereof, very preferably selected from the group consisting of compounds of formulae PGP-3-2, PGP-3-3, PGP-3-4, PGP-3-5, PGP-1-2V, PGP-2-2V and PGP-3-2V. The definitions of these abbreviations (acronyms) are likewise indicated below in Table D or are apparent from Tables A to C.

[0241] Instead of or in addition to the compounds of formula II and / or III, the media according to the invention may also comprise one or more dielectrically positive compounds of formula VI

[0242]

[0243] in

[0244] R 6 represents an alkyl, alkoxy, fluoroalkyl or fluoroalkoxy radical having 1 to 7 C atoms, an alkenyl, alkenyloxy, alkoxyalkyl or fluoroalkenyl radical having 2 to 7 C atoms, and preferably an alkyl or alkenyl radical

[0245] to Independently express

[0246]

[0247] L 61 and L 62 , independently represent H or F, preferably L 61 Indicates F,

[0248] X 6 represents halogen, haloalkyl or alkoxy having 1 to 3 C atoms or haloalkenyl or alkenyloxy having 2 or 3 C atoms, preferably F, Cl, -OCF 3 or -CF 3 , very preferably F, Cl or -OCF 3 ,

[0249] Z 6 Indicates -CH 2 CH 2 -, -CF 2 CF 2 -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH 2 O- or -CF 2 O-, preferably -CH 2 CH 2 -, -COO- or trans-CH=CH- and very preferably -COO- or trans-CH=CH-, and

[0250] q represents 0 or 1.

[0251] The medium according to the invention preferably comprises one or more compounds of the formula VI, which are preferably selected from the compounds of the formulae VI-1 and VI-2

[0252]

[0253] where the parameters have the respective meanings as indicated above, and the parameter L 63 and L 64 , independently of each other and of the other parameters, represents H or F, and Z 6 Preferred representation -CH 2 -CH 2 -.

[0254] The compound of formula VI-1 is preferably selected from the compounds of formula VI-1a and VI-1b

[0255]

[0256] Where R 6 Has the meanings stated above.

[0257] The compound of formula VI-2 is preferably selected from the compounds of formula VI-2a to VI-2d

[0258]

[0259] Where R 6 Has the meanings stated above.

[0260] In addition, the liquid-crystalline media according to the invention may comprise one or more compounds of the formula VII

[0261]

[0262] in

[0263] R 7 With the above formula II under R 2 The meaning indicated,

[0264] The ring of existence

[0265] to One of them said

[0266]

[0267] Best

[0268]

[0269] Best

[0270] express and other groups have the same meaning or represent independently of each other

[0271] Best

[0272]

[0273] Z 71 and Z 72 , independently represent -CH 2 CH 2 -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH 2 O-, -CF 2 O- or a single bond, preferably one or more of them represent a single bond and very preferably both represent a single bond,

[0274] t represents 0, 1 or 2, preferably 0 or 1, more preferably 1, and

[0275] X 7 With the above formula II for X 2 The meaning indicated, or alternatively, is independent of R 7 , can have for R 7 One of the meanings indicated.

[0276] The compound of formula VII is preferably a dielectrically positive compound.

[0277] In addition, the liquid-crystalline media according to the invention may comprise one or more compounds of the formula VIII

[0278]

[0279] in

[0280] R 81 and R 82 , independently of each other, have the above formula II for R 2 The meaning shown, and

[0281] express Best

[0282] express

[0283] Z 81 and Z 82 , independently represent -CH 2 CH 2 -, -C≡C-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH 2 O-, -CF 2 O- or a single bond, preferably one or more of them represent a single bond and very preferably both represent a single bond,

[0284] s represents 0 or 1 and

[0285] L 81 and L 82 , independently represent CF or N, preferably L 81 and L 82 One or both represent CF and very preferably both represent CF, and

[0286] exist

[0287] express In the case of

[0288] L 81 and L 82 One or both may alternatively represent CH.

[0289] The compound of formula VIII is preferably a dielectrically negative compound. Preferably, the compound of formula VIII is selected from the following compounds of the sub-formula of formula VIII

[0290]

[0291]

[0292] The individual radicals, independently of one another and identically or differently on each occurrence, have the following meanings:

[0293] express

[0294] express

[0295] wherein at least one ring F is cyclohexenylene,

[0296] R 1 and R 2 is an alkyl radical having 1 to 12 C atoms, wherein in addition, one or two non-adjacent CH 2 The radicals may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that the O atoms are not directly attached to one another, preferably alkyl or alkoxy radicals having 1 to 6 C atoms,

[0297] Z x and Z y -CH 2 CH 2 -, -CH=CH-, -CF 2 O-, -OCF 2 -,-CH 2 O-, -OCH 2 -, -CO-O-, -O-CO-, -C2 F 4 -, -CF=CF-, -CH=CH-CH 2 O- or a single bond, preferably a single bond,

[0298] L 1-4 F, Cl, OCF 3 , C.F. 3 , CH 3 , CH 2 F, CHF 2 ,

[0299] a is 1 or 2,

[0300] b is 0 or 1, and

[0301] f is 1 or 2.

[0302] The liquid-crystalline media according to the invention preferably comprise one or more compounds selected from the group consisting of compounds of the formulae I to VIII, preferably compounds of the formulae I to VII and more preferably compounds of the formulae I and II and / or III and / or IV and / or VI. They particularly preferably consist predominantly of these compounds, even more preferably consist essentially of these compounds and very preferably consist entirely of these compounds.

[0303] In the present application, "comprising" in relation to a composition means that the entity in question, ie the medium or the component, contains the indicated component(s) or compound(s), preferably in a total concentration of 10% or more, and very preferably 20% or more.

[0304] In this context, "consisting essentially of" means that the entity in question contains 55% or more, preferably 60% or more and very preferably 70% or more of the indicated component or components or compound or compounds.

[0305] In this context, "consisting essentially of" means that the entity in question comprises 80% or more, preferably 90% or more and very preferably 95% or more of the indicated component or components or compound or compounds.

[0306] In this context, "consisting almost entirely of" or "consisting entirely of" means that the entity in question contains 98% or more, preferably 99% or more and very preferably 100% of the indicated component or components or compound or compounds.

[0307] Other mesogenic compounds not explicitly mentioned above may also be used optionally and advantageously in the media according to the invention. Such compounds are known to those skilled in the art.

[0308] The liquid-crystalline media according to the invention preferably have a clearing point of 70° C. or more, more preferably 75° C. or more, particularly preferably 80° C. or more and very particularly preferably 85° C. or more.

[0309] The nematic phase of the medium according to the present invention preferably extends at least from 0°C or less to 70°C or more, more preferably at least from -20°C or less to 75°C or more, very preferably at least from -30°C or less to 75°C or more and in particular at least from -40°C or less to 80°C or more.

[0310] At 1 kHz and 20° C., the Δε of the liquid-crystal media according to the invention is preferably 2 or more, more preferably 3 or more, even more preferably 4 or more and very preferably 6 or more. Δε is preferably 30 or less, Δε is particularly preferably 20 or less.

[0311] At 589nm (Na D ) and 20° C., the Δn of the liquid crystal medium according to the present invention is preferably in the range of 0.060 or more to 0.300 or less, preferably in the range of 0.070 or more to 0.150 or less, more preferably in the range of 0.080 or more to 0.140 or less, even more preferably in the range of 0.090 or more to 0.135 or less and very particularly preferably in the range of 0.100 or more to 0.130 or less.

[0312] In a first preferred embodiment of the present application, the Δn of the liquid crystal medium according to the present invention is preferably in the range of 0.080 or greater to 0.120 or less, more preferably in the range of 0.090 or greater to 0.110 or less and very particularly preferably in the range of 0.095 or greater to 0.105 or less, while Δε is preferably in the range of 6 or greater to 11 or less, preferably in the range of 7 or greater to 10 or less and particularly preferably in the range of 8 or greater to 9 or less.

[0313] In this embodiment, the nematic phase of the medium according to the present invention preferably extends at least from -20°C or less to 70°C or more, more preferably at least from -20°C or less to 70°C or more, very preferably at least from -30°C or less to 70°C or more and in particular at least from -40°C or less to 70°C or more.

[0314] In a second preferred embodiment of the present application, the Δn of the liquid crystal medium according to the present invention is preferably 0.060 or greater to 0.300 or less, preferably in the range of 0.100 or greater to 0.140 or less, more preferably in the range of 0.110 or greater to 0.130 or less and very particularly preferably in the range of 0.115 or greater to 0.125 or less, while Δε is preferably in the range of 7 or greater to 13 or less, preferably in the range of 9 or greater to 20 or less and particularly preferably in the range of 10 or greater to 17 or less.

[0315] In this embodiment, the nematic phase of the medium according to the present invention preferably extends at least from -20°C or less to 80°C or more, more preferably at least from -20°C or less to 85°C or more, very preferably at least from -30°C or less to 80°C or more and in particular at least from -40°C or less to 85°C or more.

[0316] According to the invention, the compounds of formulae S1 and S2 are preferably used together in a total concentration of 1 ppm to 5,000 ppm, more preferably 10 ppm to 3,000 ppm, more preferably 100 ppm to 2,000 ppm, more preferably 200 ppm to 1,500 ppm and very preferably 250 ppm to 1,000 ppm of the overall mixture in the medium.

[0317] The compounds selected from the formulae II and III are preferably used in a total concentration of 2% to 60%, more preferably 3% to 35%, even more preferably 4% to 20%, very preferably 5% to 15% of the overall mixture.

[0318] The compound of formula IV is preferably used in a total concentration of 5% to 70%, more preferably 20% to 65%, even more preferably 30% to 60%, very preferably 40% to 55% of the overall mixture.

[0319] The compounds of the formula V are preferably used in a total concentration of 0% to 30%, more preferably 0% to 15%, very preferably 1% to 10%, of the overall mixture.

[0320] The compounds of formula VI are preferably used in a total concentration of 0% to 50%, more preferably 1% to 40%, even more preferably 5% to 30%, very preferably 10% to 20%, of the overall mixture.

[0321] The medium according to the invention may optionally contain other liquid crystal compounds in order to adjust the physical properties. Such compounds are known to those skilled in the art. Their concentration in the medium according to the invention is preferably from 0% to 30%, more preferably from 0.1% to 20%, very preferably from 1% to 15%.

[0322] In a preferred embodiment, the concentration of the compound of the formula CC-3-V in the medium according to the invention can be 50% to 65%, particularly preferably 55% to 60%.

[0323] The liquid-crystalline media preferably contain a total of 50% to 100%, more preferably 70% to 100%, very preferably 80% to 100%, in particular 90% to 100% of compounds of the formulae I to VII, preferably selected from the compounds of the formulae I-1, I-2 and II to VI, particularly preferably compounds of the formulae I to V, in particular compounds of the formulae I-1, I-2, II, III, IV, V and VII and very particularly preferably compounds of the formulae I-1, I-2, II, III, IV and V. They preferably consist predominantly of these compounds and very preferably consist almost entirely of these compounds. In a preferred embodiment, the liquid-crystalline media contain in each case one or more compounds of each of these formulae.

[0324] In the present application, the expression "dielectrically positive" describes compounds or components in which Δε>3.0, "dielectrically neutral" describes those in which -1.5≤Δε≤3.0, and "dielectrically negative" describes those in which Δε<-1.5. Δε is determined at a frequency of 1 kHz and at 20°C. The dielectric anisotropy of the individual compounds is determined from the results of a 10% solution of the individual compounds in a nematic host mixture. If the solubility of the individual compound in the host mixture is less than 10%, the concentration is reduced to 5%. The capacitance of the test mixture is measured both in a liquid crystal cell with homeotropic alignment and in a liquid crystal cell with planar alignment. The cell thickness of both types of liquid crystal cells is about 20 μm. The applied voltage is a rectangular wave with a frequency of 1 kHz and an effective value of typically 0.5 V to 1.0 V, but it is always selected to be below the capacitance threshold of the individual test mixture.

[0325] ∆ε is defined as (ε||-ε ⊥ ), and ε 平均 is (ε||+2ε ⊥ ) / 3.

[0326] The host mixture for dielectrically positive compounds was mixture ZLI-4792, and the host mixture for dielectrically neutral and dielectrically negative compounds was mixture ZLI-3086, both from Merck KGaA, Germany. The absolute values ​​of the dielectric constants of the compounds were determined from the changes in the corresponding values ​​of the host mixtures when the compound of interest was added. The values ​​were extrapolated to a concentration of 100% of the compound of interest.

[0327] Components having a nematic phase at a measurement temperature of 20° C. were measured as such, and all other substances were treated as compounds.

[0328] In the present application, in both cases, unless explicitly stated otherwise, the expression "threshold voltage" relates to the optical threshold and is quoted as 10% relative contrast (V 10 ), and the expression "saturation voltage" relates to optical saturation and is quoted as 90% relative contrast (V 90 ). Capacitor threshold voltage (V 0 ), also known as the Freedericks threshold (V Fr ) are only used if explicitly mentioned.

[0329] The parameter ranges indicated in this application all include the limit values, unless explicitly stated otherwise.

[0330] The different upper and lower value limits indicated for the various ranges of properties in combination with one another give rise to additional preferred ranges.

[0331] Throughout this application, the following conditions and definitions apply, unless expressly stated otherwise. All concentrations are indicated as weight percent and relate to the respective mixture as a whole, all temperatures are quoted in degrees Celsius, and all temperature differences are quoted in differential degrees. All physical properties are measured according to "Merck Liquid Crystals, Physical Properties of Liquid Crystals", November 1997 Status, Merck KGaA, Germany, and are quoted for a temperature of 20°C, unless expressly stated otherwise. The optical anisotropy (△n) is measured at a wavelength of 589.3 nm. The dielectric anisotropy (△ε) is measured at a frequency of 1 kHz. The threshold voltage, as well as all other electro-optical properties, are measured using a test box produced at Merck KGaA, Germany. The test box used to measure △ε has a box thickness of about 20 μm. The electrode is a 1.13 cm 2 The alignment layer, for the homeotropic orientation (ε||), was SE-1211 from Nissan Chemicals, Japan, and for the axial orientation (ε||), was SE-1211 from Nissan Chemicals, Japan. ⊥ ), is polyimide AL-1054 obtained from Japan Synthetic Rubber, Japan. The capacitance was measured using a Solatron 1260 frequency response analyzer using a 0.3V rms The light used in the electro-optical measurements was white light. The apparatus of the DMS instrument commercially available from Autronic-Melchers, Germany was used in this paper. The characteristic voltage was determined under perpendicular observation. The threshold (V 10 )、Medium Gray(V50 ) and saturation (V 90 ) The voltages were measured for 10%, 50% and 90% relative contrast.

[0332] The liquid crystal media according to the invention may contain further additives and chiral dopants in the usual concentrations. The total concentration of these further ingredients is in the range of 0% to 10%, preferably 0.1% to 6%, based on the mixture as a whole. The concentrations of the individual compounds used are each preferably in the range of 0.1% to 3%. When quoting values ​​and concentration ranges for the liquid crystal components and compounds of the liquid crystal media in this application, the concentrations of these and similar additives are not taken into account.

[0333] The liquid crystal medium according to the invention consists of a plurality of compounds, preferably 3 to 30, more preferably 4 to 20, and very preferably 4 to 16 compounds. These compounds are mixed in a conventional manner. Usually, the desired amount of compound used in a smaller amount is dissolved in the compound used in a larger amount. If the temperature is above the clearing point of the compound used in a higher concentration, the completion of the dissolution process is particularly easy to observe. However, the medium can also be prepared in other conventional ways, for example using a so-called premix, which can be, for example, a homologous or eutectic mixture of compounds, or using a so-called "multi-bottle" system, the components of which are themselves ready-to-use mixtures.

[0334] By adding suitable additives, the liquid-crystal media according to the invention can be modified in such a way that they can be used in all known types of liquid-crystal displays which either use the liquid-crystal media as such, for example TN, TN-AMD, ECB-AMD, VAN-AMD, IPS-AMD, FFS-AMD LCDs, or in composite systems, for example PDLC, NCAP, PN LCDs and in particular ASM-PA LCDs.

[0335] All temperatures, such as the melting point T(C,N) or T(C,S) of the liquid crystal, the transition point T(S,N) from the smectic (S) phase to the nematic (N) phase and the clearing point T(N,I), are quoted in degrees Celsius. All temperature differences are quoted in differential degrees.

[0336] In the present invention and in particular in the following examples, the structures of the mesogenic compounds are indicated with the aid of abbreviations, also known as acronyms. In these acronyms, the chemical formulae are abbreviated as described below using the following Tables A to C. All radicals C n H 2n+1 , C m H 2m+1 and C l H 2l+1 or C n H2n-1 , C m H 2m-1 and C l H 2l-1 Refers to straight chain alkyl or alkenyl, preferably 1E-alkenyl, each having n, m and 1 C atoms respectively. Table A lists the coding of the ring elements for the core structure of the compound, while Table B shows the linking group. Table C gives the meaning of the coding for the left-hand or right-hand end group. The acronym consists of the coding of the ring elements with an optional linking group, followed by the first hyphen and the coding for the left-hand end group, and the second hyphen and the coding for the right-hand end group. Table D shows the exemplary structure of the compound and their respective abbreviations.

[0337] Table A: Ring elements

[0338]

[0339]

[0340]

[0341] Table B: Linking Groups

[0342]

[0343] Table C: End Groups

[0344]

[0345]

[0346] wherein n and m each represent an integer, and the three dots "..." are placeholders for other abbreviations taken from the table.

[0347] The following table shows exemplary structures and their respective abbreviations. These are shown to illustrate the meaning of the conventions of the abbreviations. They further represent compounds that are preferably used.

[0348] Table D: Example Structure

[0349]

[0350]

[0351]

[0352]

[0353]

[0354]

[0355]

[0356]

[0357]

[0358]

[0359]

[0360]

[0361]

[0362]

[0363]

[0364]

[0365]

[0366]

[0367]

[0368]

[0369]

[0370]

[0371]

[0372]

[0373]

[0374]

[0375]

[0376] wherein n, m and l preferably represent 1 to 7 independently of one another.

[0377] The following table (Table E) shows exemplary compounds that can be used as additional stabilizers in the mesogenic medium according to the present invention.

[0378] Table E

[0379]

[0380]

[0381]

[0382] In a preferred embodiment of the present invention, the mesogenic medium comprises one or more compounds selected from the compounds obtained from Table E.

[0383] Table F below shows exemplary compounds that can be preferably used as chiral dopants in the mesogenic medium according to the present invention.

[0384] Table F

[0385]

[0386]

[0387]

[0388] In a preferred embodiment of the present invention, the mesogenic medium comprises one or more compounds selected from the compounds obtained from Table F.

[0389] The mesogenic medium according to the present application preferably comprises two or more, preferably four or more compounds selected from the compounds from the above table.

[0390] The liquid-crystalline media according to the invention preferably comprise

[0391] - seven or more, preferably eight or more, individual compounds (preferably three or more, particularly preferably four or more different formulae), selected from the compounds from Table D. DETAILED DESCRIPTION

[0392] Example

[0393] The following examples illustrate the present invention without limiting the present invention in any way.

[0394] However, the physical properties show the person skilled in the art what properties can be achieved and within what range they can be improved. In particular, the combinations of various properties which can preferably be achieved are therefore well defined for the person skilled in the art.

[0395] Liquid crystal mixtures having the compositions and properties shown in the table below were prepared and studied.

[0396] Example 1

[0397] An LC mixture with positive dielectric anisotropy (M-1.0) was prepared as follows.

[0398]

[0399]

[0400] The above mixture (M1-0) was divided into four parts. The first part was studied as is. To each of the other three parts, 300 ppm, 500 ppm or 1,000 ppm of stabilizer S1a and 500 ppm of stabilizer S2a1 were added (mixtures M-11 to M-1-3).

[0401]

[0402] Use Example

[0403] LC media M1-1 to M-1-3 prepared as in Example 1 were filled into VHR test cells as described above.

[0404] The test box was subjected to thermal stress (100°C). 热 ) after which the VHR was measured as described above. For comparison purposes, the measurement was repeated with reference LC medium M1-0 (which was formulated as in Example 1). The VHR values ​​are shown in Table 1 below.

[0405] Table 1: VHR after thermal load

[0406]

[0407]

[0408] Another set of filled test boxes are exposed through the backlight unit of the LCD. 光 ) and then measured VHR as described above. The VHR values ​​are shown in Table 2 below.

[0409] Table 2: VHR after backlight load

[0410]

[0411] It can be seen that the LC media M1-1 to M-1-3 containing both stabilizers S1a and S2a1 show a significantly lower decrease in VHR after prolonged heat exposure compared to the LC medium M-1 which does not contain any compounds of formulae S1 and S2.

[0412] The absence of additives resulted in a significant decrease in the HR of the mixture after heating and after backlight testing.

[0413] Example 2

[0414] An LC mixture with positive dielectric anisotropy (M-2.0) was prepared as follows.

[0415]

[0416]

[0417] To the above mixture was added 1,000 ppm of stabilizer S1a and 500 ppm of stabilizer S2a1. The resulting mixture exhibited excellent stability to both heat load and backlight load.

[0418] Example 3

[0419] An LC mixture with positive dielectric anisotropy (M-3.0) was prepared as follows.

[0420]

[0421]

[0422] To the above mixture was added 500 ppm of stabilizer S1a and 500 ppm of stabilizer S2a1. The resulting mixture showed excellent stability to both thermal and backlight loads.

[0423] Example 4

[0424] An LC mixture with positive dielectric anisotropy (M-4.0) was prepared as follows.

[0425]

[0426] To each of the portions of the above mixture was added 500 ppm of stabilizer S2a1 and 100 ppm, 500 ppm, 1,000 ppm or 1,500 ppm of stabilizer S1a. The resulting mixture exhibited excellent stability to both heat load and backlight load.

[0427] Example 5

[0428] An LC mixture with positive dielectric anisotropy (M-5.0) was prepared as follows.

[0429]

[0430] To the above mixture was added 300 ppm of stabilizer S1a and 500 ppm of stabilizer S2a1. The resulting mixture showed excellent stability to both thermal and backlight loads.

[0431] Example 6

[0432] An LC mixture with positive dielectric anisotropy (M-6.0) was prepared as follows.

[0433]

[0434]

[0435] To the above mixture was added 300 ppm of stabilizer S1a and 500 ppm of stabilizer S2a1. The resulting mixture showed excellent stability to both thermal and backlight loads.

[0436] Example 7

[0437] An LC mixture with positive dielectric anisotropy (M-7.0) was prepared as follows.

[0438]

[0439]

[0440] To each of the parts of the above mixture was added 300 ppm of stabilizer S1a and respectively 200 ppm, 500 ppm or 800 ppm of stabilizer S2a1. The resulting mixture showed excellent stability to both thermal and backlight loads.

[0441] Example 8

[0442] An LC mixture with positive dielectric anisotropy (M-8.0) was prepared as follows.

[0443]

[0444] To each of the parts of the above mixture were added 600 ppm of stabilizer S2a1 and 300 ppm or 500 ppm of stabilizer S1a, respectively. The resulting mixture showed excellent stability to both thermal and backlight loads.

[0445] Example 9

[0446] An LC mixture with positive dielectric anisotropy (M-9.0) was prepared as follows.

[0447]

[0448] To the above mixture was added 500 ppm of stabilizer S1a and 500 ppm of stabilizer S2a1. The resulting mixture showed excellent stability to both thermal and backlight loads.

Claims

1. A liquid crystal medium having positive dielectric anisotropy, characterized in that It contains a) one or more compounds of formula S1 and one or more compounds of formula S2, wherein the total content of the compounds of formula S1 and S2 is from 600 ppm to 10,000 ppm, The individual radicals, independently of one another and identically or differently on each occurrence, have the following meanings: express R a To R d is a straight-chain or branched alkyl radical having 1 to 10 C atoms, X represents H, A is a linear, branched or cyclic alkylene group having 1 to 20 C atoms, which is optionally substituted, and n is an integer from 1 to 6, and b) 3 to 35% by weight of one or more compounds selected from the group consisting of compounds of formula II and III in R 2 and R 3 , independently of one another represent an alkyl, alkoxy, fluoroalkyl or fluoroalkoxy radical having 1 to 7 C atoms, an alkenyl, alkenyloxy, alkoxyalkyl or fluoroalkenyl radical having 2 to 7 C atoms, to In each occurrence, they are expressed independently of each other L 21 , L 22 , L 31 and L 32 , independently of each other, represent H or F, X 2 and X 3 , independently of one another represent halogen, a haloalkyl or alkoxy radical having 1 to 3 C atoms or a haloalkenyl or alkenyloxy radical having 2 or 3 C atoms, Z 3 represents -CH2CH2-, -CF2CF2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O- or a single bond, and m and n, independently of each other, represent 0, 1, 2 or 3, and c) 20% to 65% of one or more compounds of formula IV in R 41 and R 42 , independently of each other, have the above formula II for R 2 The meaning shown, independently of each other, and if appears twice, then these also represent independently of each other Z 41 and Z 42 , independently of each other and if Z 41 appears twice, these also independently represent -CH2CH2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O-, -CF2O-, -C≡C- or a single bond, and p represents 0, 1 or 2, and d) one or more compounds of the formula The individual radicals, independently of one another and identically or differently on each occurrence, have the following meanings: express express wherein at least one ring F is cyclohexenylene, R 1 and R 2 is an alkyl radical having 1 to 12 C atoms, wherein, in addition, one or two non-adjacent CH2 groups may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that the O atoms are not directly connected to one another, Z x and Z y -CH2CH2-, -CH=CH-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -CO- O-, -O-CO-, -C2F4-, -CF=CF-, -CH=CH-CH2O- or a single bond, L 1-4 F, Cl, OCF3, CF3, CH3, CH2F, CHF2, a is 1 or 2, b is 0 or 1, and f is 1 or 2; and 1 to 15% by weight of one or more compounds of formula V, in R 51 and R 52 , independently of one another represent an alkyl radical having 1 to 7 C atoms, an alkoxy radical, an alkenyl radical having 2 to 7 C atoms, an alkenyloxy radical or an alkoxyalkyl radical, In each occurrence, they are expressed independently of each other Z 51 and Z 52 , independently of each other, and if Z 51 appears twice, these also independently represent -CH2CH2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O-, -CF2O- or a single bond, and r represents 0, 1 or 2.

2. The medium according to claim 1, characterized in that The total concentration of the compounds of formulae S1 and S2 in the medium is 600 ppm to 2,000 ppm.

3. The medium according to claim 1 or 2, characterized in that The compounds of formula S1 and S2 are compounds selected from the compounds of subformulae S1a and S1b and S2a and S2b thereof, respectively, in n represents an integer of 1 to 6.

4. The medium according to claim 1 or 2, characterized in that It comprises one or more compounds of formula II.

5. The medium according to claim 1 or 2, characterized in that It comprises one or more compounds of formula III.

6. A liquid crystal display, characterized in that It contains the medium according to any one of claims 1 to 5.

7. The display according to claim 6, characterized in that It is addressed by an active matrix.

8. Use of the medium according to any one of claims 1 to 5 in liquid crystal displays.

9. A method for preparing a medium according to any one of claims 1 to 5, characterized in that One or more compounds of formula S1 and one or more compounds of formula S2 as given in claim 1 are mixed with one or more compounds mentioned in claim 1 other than compounds of formulae S1 and S2, and / or one or more other mesogenic compounds and / or one or more additives.

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