Liquid crystal medium

Abstract

The invention relates to a liquid-crystalline medium comprising at least one compound of formula I, # imgabs 0 # and one or more compounds selected from the group of compounds of formulae IIA, IIB and IIC, # imgabs 1 # wherein the groups and parameters occurring have the meanings indicated in claim 1, the invention also relates to the use thereof for active matrix displays, in particular based on VA, PSA, PA-VA, SS-VA, SA-VA, PS-VA, PALC, IPS, PS-IPS, UB-FFS, U-IPS, FFS or PS-FFS effects.

Description

[0001] This application is a divisional application of the Chinese patent application with the application date of December 18, 2018, application number 201880081719.9, and invention name “Liquid Crystal Medium”. Technical Field

[0002] The invention relates to a liquid-crystalline medium comprising one or more compounds of the formula I,

[0003]

[0004] in

[0005] R 11 and R 12 Each independently of one another designates H, an alkyl group or an alkoxy group having 1 to 15 C atoms, wherein in addition, one or more CH2 groups in these groups may each independently of one another be connected via -C≡C-, -CF2O-, -OCF2-, -CH=CH-, -C≡C-, -C≡ ... -O-, -CO-O- or -O-CO-, and in which in addition one or more H atoms may be replaced by halogen,

[0006] A 1 Refers independently of each other at each occurrence

[0007] a) 1,4-cyclohexenyl or 1,4-cyclohexylene, in which one or two non-adjacent CH2 groups may be replaced by -O- or -S-,

[0008] b) 1,4-phenylene, one or two CH groups of which may be replaced by N,

[0009] c) a radical from the group of the radicals piperidine-1,4-diyl, 1,4-bicyclo[2.2.2]octylene, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, phenanthrene-2,7-diyl and fluorene-2,7-diyl,

[0010] wherein the groups a), b) and c) may be singly or polysubstituted by halogen atoms,

[0011] a refers to 1 or 2, preferably 1,

[0012] Z 1In each occurrence, independently of one another, they represent -CO-O-, -O-CO-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -CH2-, -CH2CH2-, -(CH2)4-, -CH=CH-CH2O-, -C2F4-, -CH2CF2-, -CF2CH2-, -CF=CF-, -CH=CF-, -CF=CH-, -CH=CH-, -C≡C-, or a single bond, and

[0013] L 11 and L 12 Each independently of one another refers to F, Cl, CF3 or CHF2, preferably H or F, most preferably F,

[0014] as well as

[0015] One or more compounds selected from the group of compounds of formula IIA, IIB and IIC

[0016]

[0017] in

[0018] R 2A , R 2B and R 2C Each independently of one another designates H, an alkyl or alkenyl radical which is unsubstituted, monosubstituted by CN or CF3 or at least monosubstituted by halogen and has up to 15 C atoms, wherein in addition one or more CH2 groups in these radicals can be linked to one another via -O-, -S-, -S-, -S-, -S- or -S- in such a way that the O atoms are not directly connected to one another. -C≡C-, -CF2O-, -OCF2-, -OC-O- or -O-CO-,

[0019] L 1 To L 4 each independently of the other refers to F, Cl, CF3 or CHF2,

[0020] Z 2 and Z 2’ each independently of the others refers to a single bond, -CH2CH2-, -CH=CH-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -COO-, -OCO-, -C2F4-, -CF=CF-, -CH=CHCH2O-,

[0021] p refers to 0, 1 or 2,

[0022] q refers to 0 or 1, and

[0023] v refers to 1 to 6.

[0024] Media of this type can be used in particular in electro-optical displays with active-matrix addressing based on the ECB effect and in IPS (in-plane switching) displays or FFS (fringe field switching) displays. Background Art

[0025] The principle of electrically controlled birefringence, the ECB effect or DAP (distortion of orientation phase) effect, was first described in 1971 (MF Schieckel and K. Fahrenschon, "Deformation of nematic liquid crystals with vertical orientation in electrical fields", Appl. Phys. Lett. 19 (1971), 3912). This was subsequently described in papers by JF Kahn (Appl. Phys. Lett. 20 (1972), 1193) and G. Labrunie and J. Robert (J. Appl. Phys. 44 (1973), 4869).

[0026] The papers by J. Robert and F. Clerc (SID 80 Digest Techn. Papers (1980), 30), J. Duchene (Displays 7 (1986), 3) and H. Schad (SID 82 Digest Techn. Papers (1982), 244) show that the liquid crystal phase must have a high value of the elastic constant K3 / K1 ratio, a high value of the optical anisotropy Δn and a dielectric anisotropy value of Δε≤-0.5 in order to be suitable for high-information display elements based on the ECB effect. Electro-optical display elements based on the ECB effect have a homeotropic edge alignment (VA technology = vertical alignment ). Dielectrically negative liquid-crystalline media can also be used in displays which use the so-called IPS or FFS effect.

[0027] In addition to IPS ( In-plane switching ) displays (e.g. Yeo, SD, Paper 15.3: "An LC Display for the TV Application", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pp. 758 & 759) and the long-known TN ( Twisted Nematic ) displays, displays using the ECB effect, such as in MVA ( Multi-domain vertical alignment, for example: Yoshide, H. et al., Paper 3.1: "MVA LCD for Notebook or Mobile PCs...", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book I, pp.6 to 9, and Liu, CT et al., Paper 15.1: "A 46-inch TFT-LCD HDTV Technology...", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pp.750 to 753), PVA ( Patterned vertical alignment , for example: Kim, Sang Soo, paper 15.4: "Super PVA Sets New State-of-the-Art for LCD-TV", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pp.760 to 763), ASV ( Advanced Super Vision horn , for example: Shigeta, Mitzuhiro and Fukuoka, Hirofumi, paper 15.2: "Development of HighQuality LCDTV", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pp.754 to 757) mode in the so-called VAN ( Vertically aligned nematicThe display has established itself as one of the three most important newer liquid crystal displays today, especially for television applications. The technology is compared in general form, for example, in Souk, Jun, SID Seminar 2004, seminar M-6: "Recent Advances in LCD Technology", Seminar Lecture Notes, M-6 / 1 to M-6 / 26, and Miller, Ian, SID Seminar 2004, seminar M-7: "LCD-Television", Seminar Lecture Notes, M-7 / 1 to M-7 / 32. Although the response time of modern ECB displays has been significantly improved by addressing methods under overdrive, for example: Kim, Hyeon Kyeong et al., Paper 9.1: "A 57-in. Wide UXGA TFT-LCD for HDTV Application", SID2004 International Symposium, Digest of Technical Papers, XXXV, Book I, pp. 106 to 109, obtaining video-compatible response time, especially grayscale switching, remains a problem that has not been satisfactorily solved.

[0028] Industrial application of this effect in electro-optical display elements requires LC phases which must meet a number of requirements. Of particular importance here is the chemical resistance to moisture, air and physical influences such as heat, infrared, visible and ultraviolet radiation as well as direct and alternating electric fields.

[0029] Furthermore, industrially useful LC phases need to have a liquid-crystalline mesophase in a suitable temperature range and with low viscosity.

[0030] None of the series of compounds disclosed so far having a liquid-crystalline mesophase comprises a single compound that meets all of these requirements. Therefore, mixtures of 2 to 25, preferably 3 to 18 compounds are usually prepared to obtain substances that can be used as LC phases. However, it has not been possible to easily prepare the optimal phase in this way, because there are currently no available liquid-crystalline materials with a significant negative dielectric anisotropy and suitable long-term stability.

[0031] Matrix liquid crystal displays (MLC displays) are known. Non-linear elements that can be used for single switching of individual pixels are, for example, active elements (ie transistors). Hence the term "active matrix" is used, wherein the following two types can be distinguished:

[0032] 1. MOS (metal oxide semiconductor) transistors located on a silicon wafer (as a substrate)

[0033] 2. Thin-film transistors (TFTs) located on a glass plate (as a substrate).

[0034] In the case of type 1, the electro-optical effect used is usually dynamic scattering or the guest-host effect. The use of single-crystal silicon as substrate material limits the display size, since even modular assembly of the various partial displays creates problems at the joints.

[0035] In the case of the more promising type 2, which is preferred, the electro-optical effect used is generally the TN effect.

[0036] A distinction is made between two technologies: TFTs comprising compound semiconductors (eg CdSe), or TFTs based on polycrystalline or amorphous silicon. The latter technology is being intensively developed worldwide.

[0037] The TFT matrix is ​​applied to the inside of one glass plate of the display, while the other glass plate carries a transparent counter electrode on its inside. The TFTs are very small compared to the size of the pixel electrodes and have almost no adverse effect on the image. The technology can also be extended to full-color functional displays, where a mosaic of red, green and blue filters is arranged in such a way that a filter element is opposite each switchable pixel.

[0038] The term MLC display here covers any matrix displays with integrated non-linear elements, ie in addition to active matrices, also displays with a passive matrix (MIM=metal-insulator-metal).

[0039] MLC displays of this type are particularly suitable for TV applications (e.g. pocket TVs) or for high-information displays in automobile or aircraft construction. In addition to the problems with the angular dependence of the contrast and the response time, problems also arise in MLC displays due to the insufficiently high specific resistance of the liquid crystal mixture [TOGASHI, S., SEKIGUCHI, K., TANABE, H., YAMAMOTO, E., SORIMACHI, K., TAJIMA, E., WATANABE, H., SHIMIZU, H., Proc. Eurodisplay 84, Sept. 1984: A 210-288 Matrix LCD Controlled by Double Stage Diode Rings, pp. 141 ff., Paris; STROMER, M., Proc. Eurodisplay 84, Sept. 1984: Design of Thin Film Transistors for Matrix Addressing of Television Liquid Crystal Displays, pp. 145 ff., Paris]. As the resistance decreases, the contrast of the MLC display deteriorates. The specific resistance of the liquid crystal mixture generally decreases over the lifetime of an MLC display due to interactions with the inner surfaces of the display, so a high (initial) resistance is very important for displays that must have acceptable resistance values ​​after long-term operation.

[0040] Therefore, there is still a great need for MLC displays which have a very high specific resistance and at the same time a large operating temperature range, short response times and a low threshold voltage, by means of which different gray scales can be produced.

[0041] Disadvantages of the frequently used MLC-TN displays are due to their relatively low contrast, the relatively high viewing angle dependence and the difficulty in producing grey scales in these displays.

[0042] The market for VA, PS-VA, IPS, FFS and UB-FFS applications is looking for LC mixtures with fast response times and very high reliability. One approach for achieving fast response times is to identify highly polar LC materials with low rotational viscosity, which promote the desired effect in the LC mixture. However, the use of this type of highly polar LC materials has an adverse effect on reliability parameters, especially after exposure. Summary of the invention

[0043] The object of the present invention is to provide liquid-crystal mixtures, in particular for monitor and TV applications, based on the ECB, UB-FFS, IPS or FFS effect, which do not have the abovementioned disadvantages or have them only to a reduced extent. In particular, for monitors and televisions it must be ensured that they operate at very high and very low temperatures and at the same time have very short response times and at the same time have an improved reliability behavior, in particular exhibit no or significantly reduced image sticking after long operating times.

[0044] The following compounds

[0045]

[0046] In European patent application No. EP 17161352.4 it is mentioned as a constituent of liquid-crystalline media.

[0047] The following formula is also disclosed

[0048]

[0049] as well as

[0050]

[0051] However, only a single compound

[0052]

[0053] In the medium used in this document, n is 2 and m is 5.

[0054] The present invention thus relates to a liquid-crystalline medium comprising at least one compound of the formula I and one or more compounds selected from the group of compounds of the formulae IIA, IIB and IIC. These media are particularly suitable for realizing liquid-crystalline displays which exhibit fast response times and good voltage holding ratios and also very good stability (during storage) at deep temperatures which is sufficient for many applications.

[0055] The mixtures according to the invention preferably exhibit a very broad nematic phase range (with a clearing point ≥70° C., preferably ≥75° C., in particular ≥80° C.), very favorable capacitance thresholds, relatively high retention values ​​and at the same time very good low temperature stability at −20° C. and −30° C., as well as very low rotational viscosity values ​​and short response times. In addition to the improvement in the rotational viscosity γ1, the mixtures according to the invention are characterized in that a relatively high elastic constant K for improved response time can be observed. 33 The use of the compound of formula I in LC mixtures, preferably LC mixtures with negative dielectric anisotropy, reduces the rotational viscosity γ1 and the elastic constant K i ratio.

[0056] Some preferred embodiments of the mixtures according to the invention are indicated below.

[0057] In the compound of formula I, R 11 and R 12 Preferably each independently of one another refers to: linear alkyl, in particular CH3, n-C2H5, n-C3H7, n-C4H9, n-C5H 11 、n-C6H 13 - or n-C7H 15 ; straight chain alkoxy, in particular CH3-O, n-C2H5-O, n-C3H7-O, n-C4H9-O, n-C5H 11 -O or n-C6H 13 -O; in addition, alkenyl, in particular CH3=CH, CH3CH=CH, CH3CH=CHCH2 or CH3CH2CH=CH; branched alkoxy, in particular (CH3)2CH(CH2)3O; and alkenyloxy, in particular CH2=CHO, CH2=CH2CHO, CH3CH2=CHCHO or O CH2CH2CH=CHCH2O.

[0058] R 11 Particularly preferably, it refers to a straight-chain alkyl radical having 1 to 7 C atoms, and R 12 Particular preference is given to straight-chain alkoxy having 1 to 6 C atoms, in particular methoxy, ethoxy, propoxy, butoxy, pentyloxy or hexyloxy.

[0059] L in Formula I 11 and L 12 Preferably, both refer to F.

[0060] The parameter "a" in formula I preferably refers to 1.

[0061] Preferred compounds of formula I present in the medium are compounds of formulae I-1 to I-3, preferably formula I-2,

[0062]

[0063] in

[0064] The parameters have the meanings given above, R 11 refers to a straight chain alkyl group, and R 12 Preferably refers to an alkoxy group, and L 11 and L 12 Preferably, both refer to F.

[0065] In a preferred embodiment, the medium comprises one or more compounds of formula I selected from the group of compounds of formulae IO-1 to IO-3, preferably compounds of formula IO-2

[0066]

[0067] where the parameters have the meanings given above.

[0068] In another preferred embodiment, the medium comprises one or more compounds of formula I selected from the group of compounds of formulae IS-1 to IS-3, preferably compounds of formula IS-2,

[0069]

[0070] where the parameters have the meanings given above.

[0071] In a preferred embodiment of the invention, the medium comprises one or more compounds selected from the group of compounds of formulae IO-1 to IO-3 and one or more compounds selected from the group of compounds of formulae IS-1 to IS-3.

[0072] For example, compounds of formula I can be prepared as described in US 2005 / 0258399 or WO 02 / 055463 A1.

[0073] The medium according to the invention preferably comprises one, two, three, four or more, preferably one, two or three, compounds of the formula I.

[0074] The compounds of the formula I are preferably used in the liquid-crystalline medium in an amount of ≥1% by weight, preferably ≥3% by weight, based on the mixture as a whole. Particularly preferred are liquid-crystalline media comprising 1 to 40% by weight, very particularly preferably 2 to 30% by weight, of one or more compounds of the formula I.

[0075] In a preferred embodiment, the medium comprises one or more compounds of formula I I Compound

[0076]

[0077] wherein the parameters have the same meanings as given above for formula I, and preferably

[0078] R 11 and R 12 each independently of one another refers to an alkyl group or an alkoxy group having 1 to 15 C atoms, more preferably one or both of them refer to an alkoxy group, and

[0079] L 11 and L 12 Each preferably refers to F.

[0080] In a preferred embodiment, the medium comprises a I -O-1 to I I -O-10, preferably the group of compounds of formula II -O-6 compounds of one or more formula I I Compounds,

[0081]

[0082]

[0083] in

[0084] Alkyl and alkyl* each independently refer to a straight-chain alkyl group having 1 to 6 C atoms, akenyl and akenyl* each independently refer to a straight-chain alkenyl group having 2 to 6 C atoms, alkoxy and alkoxy* each independently refer to a straight-chain alkoxy group having 1 to 6 C atoms, and L 1 and L 2 Each independently of the other refers to F or Cl.

[0085] In another preferred embodiment, alternatively or additionally, the medium comprises a I -O-1 to I I -O-10, one or more compounds of the group of compounds, one or more compounds of formula I I The compound, wherein X1 is S, is preferably selected from the group consisting of formula I I -S-1 to I I -S-10, preferably the group of compounds of formula I I -S-6 compounds having the same number of formula I I -O-1 to I I -O-10 has the same structure as the corresponding compound, with the only exception being the bridging atom (i.e., X 1 ) is a S atom instead of an O atom.

[0086] Preferred embodiments of the liquid-crystalline media according to the invention are indicated below:

[0087] a) a liquid-crystalline medium which additionally comprises one or more compounds selected from the group of compounds of the formulae IIA, IIB and IIC,

[0088] In the compounds of formula IIA and IIB, Z 2 can have the same or different meanings. In the compounds of formula IIB, Z 2 and Z 2’ Can have the same or different meanings.

[0089] In the compounds of formula IIA, IIB and IIC, R 2A , R 2B and R 2Ceach preferably refers to an alkyl radical having 1 to 6 C atoms, in particular CH3, C2H5, n-C3H7, n-C4H9, n-C5H 11 .

[0090] In the compounds of Formula IIA and IIB, L 1 , L 2 , L 3 and L 4 Preferably refers to L 1 =L 2 = F, and L 3 =L 4 =F, in addition L 1 = F, and L 2 =Cl,L 1 =Cl, and L 2 =F,L 3 = F, and L 4 =Cl,L 3 =Cl, and L 4 =F. Z in Formula IIA and IIB 2 and Z 2 ' preferably each independently of one another designates a single bond and furthermore a -C2H4- bridge.

[0091] In Formula IIB, if Z 2 =-C2H4- or -CH2O-, then Z 2’ Preferably a single bond, or if Z 2’ =-C2H4- or -CH2O-, then Z 2 In the compounds of formula IIA and IIB, (O)C v H 2v+1 Preferably refers to OC v H 2v+1 In addition, C v H 2v+1 In the compound of formula IIC, (O)C v H 2v+1 Preferably refers to C v H 2v+1 In the compound of formula IIC, L 3 and L 4 Preferably each refers to F.

[0092] Preferred compounds of formula IIA, IIB and IIC are indicated below:

[0093]

[0094]

[0095]

[0096]

[0097]

[0098]

[0099]

[0100]

[0101]

[0102]

[0103] in

[0104] Alkyl and alkyl* each independently of one another denote a straight-chain alkyl radical having 1 to 6 C atoms, and

[0105] Akenyl and akenyl* each independently of one another denote a straight-chain alkenyl radical having 2 to 6 C atoms.

[0106] Particularly preferred mixtures according to the invention comprise one or more compounds of the formulae IIA-2, IIA-8, IIA-14, IIA-26, II-28, IIA-33, IIA-39, IIA-45, IIA-46, IIA-47, IIA-50, IIB-2, IIB-11, IIB-16 and IIC-1.

[0107] The proportion of compounds of the formula IIA and / or IIB in the mixture as a whole is preferably at least 20% by weight.

[0108] Particularly preferred media according to the invention comprise at least one compound of the formula IIC-1,

[0109]

[0110] wherein alkyl and alkyl* have the meanings indicated above, preferably in an amount of >3% by weight, in particular >5% by weight and particularly preferably from 5 to 25% by weight.

[0111] b) a liquid-crystalline medium which additionally comprises one or more compounds of the formula III,

[0112]

[0113] in

[0114] R 31 and R 32each independently of one another designates a straight-chain alkyl, alkoxy, alkenyl, alkoxyalkyl or alkoxy radical having up to 12 C atoms, and d means en means ot

[0115] Z 3 It refers to a single bond, -CH2CH2-, -CH=CH-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -COO-, -OCO-, -C2F4-, -C4H8-, -CF=CF-.

[0116] Preferred compounds of formula III are indicated below:

[0117]

[0118] in

[0119] Alkyl and alkyl* each independently of one another denote a straight-chain alkyl radical having 1 to 6 C atoms.

[0120] The medium according to the invention preferably comprises at least one compound of the formula IIIa and / or formula IIIb.

[0121] The proportion of the compound of the formula III in the mixture as a whole is preferably at least 5% by weight.

[0122] c) a liquid-crystalline medium which additionally comprises a compound of the formula:

[0123] and / or

[0124] and / or

[0125]

[0126] Preference is given to total amounts of ≥5% by weight, in particular ≥10% by weight.

[0127] Furthermore, preference is given to mixtures according to the invention which comprise the following compound (acronym: CC-3-V1): An amount of 2 to 15% by weight is preferred.

[0128] Preferably the mixture comprises 5 to 60% by weight, preferably 10 to 55% by weight, in particular 20 to 50% by weight of a compound of the formula (acronym: CC-3-V)

[0129]

[0130] Furthermore, preference is given to mixtures comprising compounds of the formula (acronym: CC-3-V)

[0131] And the following compound (acronym: CC-3-V1)

[0132]

[0133] An amount of 10 to 60% by weight is preferred.

[0134] d) a liquid-crystalline medium which additionally comprises one or more tetracyclic compounds of the formula

[0135]

[0136] in

[0137] R 7-10 Each independently has the following characteristics as claimed in claim 5 for R 2A one of the meanings indicated, and

[0138] w and x each independently refer to 1 to 6.

[0139] Especially preferred are mixtures comprising at least one compound of the formula V-9.

[0140] e) a liquid-crystalline medium which additionally comprises one or more compounds of the formulae Y-1 to Y-6,

[0141]

[0142] Where R 14 To R 19 each independently of one another denotes an alkyl or alkoxy group having 1 to 6 C atoms; z and m each independently of one another denote 1 to 6; and x denotes 0, 1, 2 or 3.

[0143] The medium according to the invention particularly preferably comprises one or more compounds of the formulae Y-1 to Y-6, preferably in an amount of ≥5% by weight.

[0144] f) a liquid-crystalline medium which additionally comprises one or more fluorinated terphenyls of the formulae T-1 to T-21,

[0145]

[0146]

[0147] in

[0148] R denotes straight-chain alkyl or alkoxy having 1 to 6 C atoms, and m=0, 1, 2, 3, 4, 5 or 6 and n denotes 0, 1, 2, 3 or 4.

[0149] R preferably denotes methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy, pentyloxy.

[0150] The medium according to the invention preferably comprises the terphenyls of the formulae T-1 to T-21 in an amount of 2 to 30% by weight, in particular 5 to 20% by weight.

[0151] Particularly preferred are compounds of formula T-1, T-2, T-4, T-20 and T-21. In these compounds, R preferably refers to an alkyl group (also an alkoxy group) each having 1 to 5 C atoms. In the compound of formula T-20, R preferably refers to an alkyl group or an alkenyl group, especially an alkyl group. In the compound of formula T-21, R preferably refers to an alkyl group.

[0152] Terphenyl is preferably used in the mixture according to the invention if the Δn value of the mixture is ≥ 0.1. Preferred mixtures comprise 2 to 20% by weight of one or more terphenyl compounds selected from the group of compounds T-1 to T-21.

[0153] g) a liquid-crystalline medium which additionally comprises one or more biphenyls of the formulae B-1 to B-3,

[0154]

[0155]

[0156] in

[0157] Alkyl and alkyl* each independently of one another denote a straight-chain alkyl radical having 1 to 6 C atoms, and

[0158] Akenyl and akenyl* each independently of one another denote a straight-chain alkenyl radical having 2 to 6 C atoms.

[0159] The proportion of the biphenyls of the formulae B-1 to B-3 in the mixture as a whole is preferably at least 3% by weight, in particular ≥5% by weight.

[0160] Among the compounds of formulae B-1 to B-3, the compound of formula B-2 is particularly preferred.

[0161] Particularly preferred biphenyls are

[0162]

[0163] Among them, alkyl * refers to an alkyl radical having 1 to 6 C atoms. The medium according to the invention particularly preferably comprises one or more compounds of the formula B-1a and / or B-2c.

[0164] h) a liquid-crystalline medium comprising at least one compound of the formulae Z-1 to Z-7,

[0165]

[0166]

[0167] wherein R and alkyl have the meanings indicated above.

[0168] i) a liquid-crystalline medium which additionally comprises at least one compound of the formulae O-1 to O-18,

[0169]

[0170]

[0171] Where R 1 and R 2 With R 2A The meaning indicated. 1 and R 2 Preferably each independently of one another designates a straight-chain alkyl or alkenyl group.

[0172] Preferred media comprise one or more compounds of formula O-1, O-3, O-4, O-6, O-7, O-10, O-11, O-12, O-14, O-15, O-16 and / or O-17.

[0173] Particularly preferred media comprise one or more compounds selected from the group of compounds of formula O-17.

[0174] The mixtures according to the invention very particularly preferably comprise compounds of the formulae O-10, O-12, O-16 and / or O-17, in particular in an amount of 5% to 30%.

[0175] Preferred compounds of formula O-10 and O-17 are indicated below:

[0176]

[0177] The medium according to the invention particularly preferably comprises a tricyclic compound of the formula O-10a and / or O-10b and one or more bicyclic compounds of the formulae O-17a to O-17d. The total proportion of the compound of the formula O-10a and / or O-10b combined with one or more compounds selected from the bicyclic compounds of the formulae O-17a to O-17d is 5% to 40%, very particularly preferably 15% to 35%.

[0178] Very particularly preferred mixtures comprise the compounds O-10a and O-17a:

[0179]

[0180] The compounds O-10a and O-17a are preferably present in the mixture in a concentration of 15% to 35%, particularly preferably 15% to 25% and particularly preferably 18% to 22%, based on the mixture as a whole.

[0181] Very particularly preferred mixtures comprise the compounds O-10b and O-17a:

[0182]

[0183] The compounds O-10b and O-17a are preferably present in the mixture in a concentration of 15% to 35%, particularly preferably 15% to 25% and particularly preferably 18% to 22%, based on the mixture as a whole.

[0184] Very particularly preferred mixtures comprise the following three compounds:

[0185]

[0186]

[0187] The compounds O-10a, O-10b and O-17a are preferably present in the mixture in a concentration of 15% to 35%, particularly preferably 15% to 25% and particularly preferably 18% to 22%, based on the mixture as a whole.

[0188] Preferred mixtures contain at least one compound selected from the group consisting of

[0189]

[0190] Where R 1 and R 2 Preferably, in compounds O-6, O-7 and O-17, R 1 refers to an alkyl or alkenyl group having 1 to 6 or 2 to 6 C atoms, respectively, and R 2 refers to alkenyl groups having 2 to 6 C atoms.

[0191] Preferred mixtures contain at least one compound of formula O-6a, O-6b, O-7a, O-7b, O-17e, O-17f, O-17g and O-17h:

[0192]

[0193]

[0194] Here, alkyl refers to an alkyl group having 1 to 6 C atoms.

[0195] The compounds of the formulae O-6, O-7 and O-17e-h are preferably present in the mixture according to the invention in an amount of 1 to 40% by weight, preferably 2 to 35% by weight and very particularly preferably 2 to 30% by weight.

[0196] j) Preferred liquid-crystalline media according to the invention comprise one or more substances containing tetrahydronaphthyl or naphthyl units, such as, for example, compounds of the formulae N-1 to N-5,

[0197]

[0198]

[0199] Where R 1N and R 2N Each independently has a 2A The indicated meanings preferably refer to straight-chain alkyl, straight-chain alkoxy or straight-chain alkenyl, and

[0200] Z 1 and Z 2 Each independently refers to -C2H4-, -CH=CH-, -(CH2)4-, -(CH2)3O-, -O(CH2)3-, -CH=CHCH2CH2-, -CH2CH2CH=CH-, -CH2O-, -OCH2-, -COO-, -OCO-, -C2F4-, -CF=CF-, -CF=CH-, -CH=CF-, -CF2O-, -OCF2-, -CH2- or a single bond.

[0201] k) Preferred mixtures comprise one or more compounds selected from the group of difluorodibenzochroman compounds of formula BC, chromans of formula CR, fluorinated phenanthrenes of formula PH-1 and PH-2, fluorinated dibenzofurans of formula BF-1 and BF-2,

[0202]

[0203]

[0204] in

[0205] R B1 , R B2 , R CR1 , R CR2 , R 1 , R 2 Each independently has R 2A c is 0, 1 or 2, and d is 1 or 2. 1 and R 2Preferably, independently of one another, it refers to an alkyl or alkoxy radical having 1 to 6 C atoms. The compounds of the formulae BF-1 and BF-2 are not to be identified with one or more compounds of the formula I.

[0206] The mixture according to the invention preferably comprises the compounds of the formula BC, CR, PH-1, PH-2 and / or BF in an amount of 3 to 20% by weight, in particular in an amount of 3 to 15% by weight.

[0207] Particularly preferred compounds of formula BC and CR are compounds BC-1 to BC-7 and CR-1 to CR-5,

[0208]

[0209]

[0210]

[0211] in

[0212] Alkyl and alkyl* each independently of one another denote a straight-chain alkyl radical having 1 to 6 C atoms, and

[0213] Akenyl and akenyl* each independently of one another denote a straight-chain alkenyl radical having 2 to 6 C atoms.

[0214] Very particular preference is given to mixtures comprising one, two or three compounds of the formulae BC-2, BF-1 and / or BF-2.

[0215] 1) Preferred mixtures contain one or more indane compounds of the formula In,

[0216]

[0217] in

[0218] R 11 , R 12 , R 13 each independently of one another denotes a straight-chain alkyl, alkoxy, alkoxyalkyl or alkenyl radical having 1 to 6 C atoms,

[0219] R 12 and R 13 Also refers to halogen, preferably F,

[0220] Reference

[0221]

[0222] i refers to 0, 1, or 2.

[0223] Preferred compounds of formula In are compounds of formula In-1 to In-16 indicated below:

[0224]

[0225]

[0226] Particularly preferred are compounds of formulae In-1, In-2, In-3 and In-4.

[0227] The compounds of the formula In and the subformulae In-1 to In-16 are preferably used in the mixtures according to the invention in a concentration of ≥5% by weight, in particular 5 to 30% by weight and very particularly preferably 5 to 25% by weight.

[0228] m) Preferred mixtures additionally comprise one or more compounds of the formulae L-1 to L-11,

[0229]

[0230] in

[0231] R, R 1 and R 2 Each independently has the following characteristics as claimed in claim 5 for R 2A The meanings indicated are as follows, and alkyl refers to an alkyl group having 1 to 6 C atoms. s refers to 1 or 2.

[0232] Particularly preferred are compounds of formula L-1 and L-4, especially L-4.

[0233] The compounds of the formulae L-1 to L-11 are preferably employed in a concentration of 5 to 50% by weight, in particular 5 to 40% by weight and very particularly preferably 10 to 40% by weight.

[0234] Particularly preferred mixture concepts are indicated below: (the acronyms used are explained in Table A. Here n and m each independently of one another denote 1 to 15, preferably 1 to 6).

[0235] The mixture according to the invention preferably comprises

[0236] - one or more compounds of formula I, wherein L 11 =L 12 =F, R 1 = alkyl and R 1* = alkoxy;

[0237] and / or

[0238] CPY-n-Om, in particular CPY-2-O2, CPY-3-O2 and / or CPY-5-O2, in a concentration of preferably >5%, in particular 10 to 30%, based on the mixture as a whole,

[0239] and / or

[0240] - CY-n-Om, preferably CY-3-O2, CY-3-O4, CY-5-O2 and / or CY-5-O4, in a concentration of preferably >5%, in particular 15% to 50%, based on the mixture as a whole,

[0241] and / or

[0242] - CCY-n-Om, preferably CCY-4-O2, CCY-3-O2, CCY-3-O3, CCY-3-O1 and / or CCY-5-O2, in a concentration of preferably >5%, in particular 10 to 30%, based on the mixture as a whole,

[0243] and / or

[0244] - CLY-n-Om, preferably CLY-2-O4, CLY-3-O2 and / or CLY-3-O3, in a concentration of preferably >5%, in particular 10% to 30%, based on the mixture as a whole.

[0245] Furthermore, preference is given to mixtures according to the invention which comprise: (n and m each independently of one another denote 1 to 6.)

[0246] - compounds of formula I, preferably compounds of formulae I-1 to I-3, i.e. compounds of formulae IO-1 to IO-3 and / or IS-1 to IS-3, in particular LB-3-O4 and / or LB(S)-4-O3, in a concentration range of 1 to 20% by weight, more preferably 2 to 15% by weight, particularly preferably 3 to 12% by weight and very particularly preferably 4 to 11% by weight

[0247] - CPY-n-Om and CY-n-Om, preferably in a concentration of 10% to 80% based on the mixture as a whole,

[0248] and / or

[0249] - CPY-n-Om and CK-nF, preferably in a concentration of 10% to 70% based on the mixture as a whole,

[0250] and / or

[0251] CPY-n-Om and PY-n-Om, preferably CPY-2-O2 and / or CPY-3-O2 and PY-3-O2, preferably in a concentration of 10% to 45% based on the mixture as a whole,

[0252] and / or

[0253] - CPY-n-Om and CLY-n-Om, preferably in a concentration of 10% to 80% based on the mixture as a whole,

[0254] and / or

[0255] - CCVC-nV, preferably CCVC-3-V, in a concentration preferably ranging from 2% to 10%, based on the mixture as a whole,

[0256] and / or

[0257] - CCC-nV, preferably CCC-2-V and / or CCC-3-V, preferably in a concentration of 2% to 10% based on the mixture as a whole,

[0258] and / or

[0259] -CC-VV, preferably in a concentration of 5% to 50%, based on the mixture as a whole.

[0260] In a particularly preferred embodiment of the present invention, the medium contains one or more compounds of the formula B-nO-Om and / or (B(S)-nO-Om, in particular compound B-2O-O5, preferably in a concentration ranging from 2% to 8%, compound CC-3-V in a concentration ranging from 25% to 35%, and compound CC-3-V1 in a concentration ranging from 8% to 12%.

[0261] The invention furthermore relates to an electro-optical display with active-matrix addressing based on the ECB, VA, PS-VA, PA-VA, IPS, PS-IPS, FFS or PS-FFS effect, characterised in that it contains a liquid-crystalline medium according to one or more of claims 1 to 11 as dielectric.

[0262] The liquid-crystalline media according to the invention preferably have a nematic phase at ≤-20°C to ≥70°C, particularly preferably ≤-30°C to ≥80°C, very particularly preferably ≤-40°C to ≥90°C.

[0263] The expression "having a nematic phase" here means on the one hand that at low temperatures no smectic phase and no crystallization is observed at the corresponding temperature and on the other hand that the nematic phase does not become clear when heated. The low-temperature investigation is carried out in a flow viscometer at the corresponding temperature and is checked by storage for at least 100 hours in a test cell with a layer thickness corresponding to the electro-optical use. If the storage stability in a corresponding test cell at a temperature of -20°C is 1000 hours or more, the medium is said to be stable at this temperature. At temperatures of -30°C and -40°C, the response times are 500 hours and 250 hours, respectively. At high temperatures, the clearing point is measured in a capillary by conventional methods.

[0264] The liquid crystal mixture preferably has a nematic phase range of at least 60 K and a nematic phase range of at most 30 mm at 20° C. 2 ·s -1 The flow viscosity ν 20 .

[0265] The birefringence Δn in the liquid crystal mixture is usually 0.07-0.16, preferably 0.08-0.13.

[0266] The liquid crystal mixture according to the invention has a Δε, where Δε denotes the dielectric anisotropy, of -0.5 to -8.0, in particular -2.5 to -6.0. The rotational viscosity γ1 at 20° C. is preferably ≤150 mPa·s, in particular ≤120 mPa·s.

[0267] The liquid-crystal media according to the invention have relatively low threshold voltage values ​​(V0). They are preferably in the range from 1.7 V to 3.0 V, particularly preferably ≤2.5 V and very particularly preferably ≤2.3 V.

[0268] For the purposes of the present invention, the term "threshold voltage" relates to the capacitance threshold (V0), also known as the Freedericks threshold, unless explicitly stated otherwise.

[0269] Furthermore, the liquid-crystalline media according to the invention have high voltage holding ratio values ​​in liquid-crystal cells.

[0270] Typically, liquid-crystal media having a low addressing voltage or threshold voltage exhibit lower voltage holding ratios than those having a higher addressing voltage or threshold voltage, and vice versa.

[0271] For the purposes of the present invention, the term "dielectrically positive compounds" refers to compounds with Δε>1.5, the term "dielectrically neutral compounds" refers to those with -1.5≤Δε≤1.5 and the term "dielectrically negative compounds" refers to those with Δε<-1.5. The dielectric anisotropy of the compounds is determined here by dissolving 10% of the compound in a liquid crystal host in at least one test cell, the test cell having in each case a layer thickness of 20 μm and having a homeotropic and planar surface alignment at 1 kHz. The measuring voltage is generally between 0.5 V and 1.0 V, but is always below the capacitance threshold of the respective liquid crystal mixture under investigation.

[0272] All temperature values ​​described in the present invention are expressed in °C.

[0273] The mixtures according to the invention are suitable for all VA-TFT applications, such as, for example, VAN, MVA, (S)-PVA, ASV, PSA (polymer-maintained VA) and PS-VA (polymer-stabilized VA). They are also suitable for IPS (in-plane switching) and FFS (fringe field switching) applications with negative Δε.

[0274] The nematic liquid-crystal mixtures in the displays according to the invention generally comprise two components: A and B, which themselves consist of one or more of the respective compounds.

[0275] Component A has a significantly negative dielectric anisotropy and imparts to the nematic phase a dielectric anisotropy of ≤-0.5. In addition to one or more compounds of the formula I, it preferably comprises compounds of the formulae IIA, IIB and / or IIC and furthermore one or more compounds of the formula O-17.

[0276] The proportion of component A is preferably 45-100%, in particular 60-100%.

[0277] For component A, preference is given to selecting one (or more) individual compounds which have a Δε value ≤ −0.8. The smaller the proportion of A in the overall mixture, the more negative this value must be.

[0278] Component B has significant nematicity and is not greater than 30 mm at 20°C. 2 ·s -1 , preferably no more than 25mm 2 ·s -1 The flow viscosity.

[0279] A wide variety of suitable materials are known to the skilled person from the literature. Particularly preferred are compounds of formula O-17.

[0280] Particularly preferred individual compounds in component B are very low-viscosity nematic liquid crystals having a viscosity of not more than 18 mm at 20°C. 2 ·s -1 , preferably no more than 12mm 2 ·s -1 The flow viscosity.

[0281] Component B is a monotropic or tautotropic nematic phase, does not have a smectic phase and is able to prevent the appearance of a smectic phase when dropped to very low temperatures in a liquid crystal mixture. For example, if a variety of highly nematic materials are added to a smectic liquid crystal mixture, the nematicity of these materials can be compared by the degree of suppression of the smectic phase achieved.

[0282] The mixture may also optionally comprise a component C comprising compounds having a dielectric anisotropy of Δε≥1.5. These so-called positive compounds are generally present in mixtures of negative dielectric anisotropy in an amount of ≤20% by weight, based on the mixture as a whole.

[0283] Besides one or more compounds of the formula I, the phase preferably comprises 4 to 15, in particular 5 to 12 and particularly preferably <10 compounds of the formulae IIA, IIB and / or IIC and optionally one or more compounds of the formula O-17.

[0284] Besides the compound of formula I and the compound of formula IIA, IIB and / or IIC and optionally O-17, further ingredients may be present, for example, in an amount of up to 45%, but preferably up to 35%, in particular up to 10% of the mixture as a whole.

[0285] The further components are preferably selected from nematic or nematogenic substances, in particular from the known substances of the class of azobenzene, benzylidene aniline, biphenyl, terphenyl, phenyl or cyclohexyl benzoate, phenyl or cyclohexyl cyclohexanecarboxylate, phenylcyclohexane, cyclohexylbiphenyl, cyclohexylcyclohexane, cyclohexylnaphthalene, 1,4-dicyclohexylbiphenyl or cyclohexylpyrimidine, phenyldioxane or cyclohexyldioxane, optionally halogenated stilbenes, benzylphenyl ethers, tolans and substituted cinnamic esters.

[0286] The most important compounds suitable as constituents of this type of liquid-crystalline phase can be characterized by the following formula IV

[0287] R 20 -LGER 21 IV

[0288] wherein L and E each designate a carbocyclic or heterocyclic ring system from the group formed by 1,4-disubstituted benzene and cyclohexane rings, 4,4'-disubstituted biphenyl, phenylcyclohexane and cyclohexylcyclohexane systems, 2,5-disubstituted pyrimidine and 1,3-dioxane rings, 2,6-disubstituted naphthalene, dihydronaphthalene and tetrahydronaphthalene, quinazoline and tetrahydroquinazoline,

[0289] G represents -CH=CH--N(O)=N-

[0290] -CH=CQ--CH=N(O)-

[0291] -C≡C--CH2-CH2-

[0292] -CO-O--CH2-O-

[0293] -CO-S--CH2-S-

[0294] -CH=N--COO-Phe-COO-

[0295] -CF2O--CF=CF-

[0296] -OCF2--OCH2-

[0297] -(CH2)4--(CH2)3O-

[0298] or a CC single bond, Q represents halogen, preferably chlorine or -CN, and R 20 and R 21 Each designates an alkyl, alkenyl, alkoxy, alkoxyalkyl or alkoxycarbonyloxy group having up to 18, preferably up to 8, carbon atoms, or one of these groups designates CN, NC, NO2, NCS, CF3, SF5, OCF3, F, Cl or Br.

[0299] In most of these compounds, R 20 and R 21 Different from each other, one of these groups is usually an alkyl or alkoxy group. Other variations of the proposed substituents are also common. Many such substances or mixtures thereof are also commercially available. All these substances can be prepared by methods known from the literature.

[0300] It goes without saying for the person skilled in the art that the VA, IPS or FFS mixtures according to the invention may also comprise compounds in which, for example, H, N, O, Cl and F are replaced by corresponding isotopes.

[0301] Furthermore, polymerizable compounds (so-called reactive mesogens (RMs), as disclosed, for example, in US Pat. No. 6,861,107, can be added to the mixtures according to the invention in a concentration of preferably 0.01 to 5% by weight, particularly preferably 0.2 to 2% by weight, based on the mixture. These mixtures may also optionally comprise initiators, as described, for example, in US Pat. No. 6,781,665. Initiators, such as, for example, Irganox-1076 from BASF, are preferably added in an amount of 0% to 1% to the mixture comprising the polymerizable compounds. Mixtures of this type can be used in the so-called polymer-stabilized VA mode (PS-VA) or PSA (polymer-sustaining VA), in which polymerization of the reactive mesogens is intended to be carried out in the liquid-crystalline mixture. A prerequisite for this is that the liquid-crystalline compounds of the LC host do not react under the polymerization conditions of the reactive mesogens, i.e., usually upon exposure to UV in the wavelength range of 320 to 360 nm. Liquid-crystalline compounds containing alkenyl side chains, such as, for example, CC-3-V, do not exhibit a reaction under the polymerization conditions for the RMs (UV polymerization).

[0302] The mixtures according to the invention may furthermore comprise customary additives such as, for example, stabilizers, antioxidants, UV absorbers, nanoparticles, microparticles and the like.

[0303] The structure of the liquid-crystal display according to the invention corresponds to the conventional geometry as described in EP-A 0 240 379, for example. DETAILED DESCRIPTION

[0304] The following examples are intended to illustrate the invention without limiting it. Above and below, percentage data refer to percentages by weight; all temperatures are indicated in degrees Celsius.

[0305] Throughout the patent application, 1,4-cyclohexylene rings and 1,4-phenylene rings are depicted as follows:

[0306]

[0307] Unless specifically mentioned otherwise, a cyclohexylene ring is a trans-1,4-cyclohexylene ring.

[0308] Throughout the patent application and the working examples, the structures of the liquid crystal compounds are indicated with the aid of acronyms. Unless otherwise indicated, the conversion into chemical formulae is carried out according to Tables 1 to 3. All groups C n H 2n+1 , C m H 2m+1 and C m’ H 2m’+1 or C n H 2n and C m H 2m is a straight-chain alkyl or alkylene radical having in each case n, m, m' or z C atoms, respectively. n, m, m', z each independently of one another denote 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, preferably 1, 2, 3, 4, 5 or 6. In Table 1, the ring elements of the individual compounds are coded, in Table 2, the bridge members are listed, and in Table 3, the meaning of the symbols indicating the left or right side chains of the compounds is indicated.

[0309] Table 1: Ring elements

[0310]

[0311]

[0312]

[0313] Table 2: Bridge members

[0314]

[0315] Table 3: Side chains

[0316]

[0317]

[0318] In addition to one or more compounds of the formula I, the mixtures according to the invention preferably comprise one or more compounds from the group of compounds mentioned below from Table A.

[0319] Table A

[0320] The following abbreviations are used:

[0321] (n, m, m', z: each independently 1, 2, 3, 4, 5 or 6; (O) C m H 2m+1 Meaning OC m H 2m+1 or C m H 2m+1 )

[0322]

[0323]

[0324]

[0325]

[0326]

[0327]

[0328]

[0329]

[0330]

[0331]

[0332]

[0333]

[0334]

[0335]

[0336]

[0337]

[0338]

[0339]

[0340]

[0341]

[0342]

[0343]

[0344]

[0345]

[0346]

[0347]

[0348] The liquid-crystal mixtures which can be used according to the invention are prepared in a manner conventional per se. Usually, the required amount of the components used is dissolved in smaller amounts in the components which constitute the main constituents, advantageously at elevated temperature. It is also possible to mix the component solutions in an organic solvent, for example acetone, chloroform or methanol, and to remove the solvent again after thorough mixing, for example by distillation.

[0349] By means of suitable additives, the liquid-crystalline phases according to the invention can be modified in such a way that they can be used in any type of ECB, VAN, IPS, GH or ASM-VA LCD displays which have been known to date.

[0350] The dielectric may also further comprise additives known to the person skilled in the art and described in the literature, for example, UV absorbers, antioxidants, nanoparticles and free radical scavengers. For example, 0-15% of pleochroic dyes, stabilizers (e.g. phenols, HALS (hindered amine light stabilizers)) or chiral dopants may be added. Suitable stabilizers for the mixtures according to the invention are in particular those listed in Table C.

[0351] For example, 0-15% of pleochroic dyes can be added, and furthermore conductive salts, preferably ethyldimethyldodecyl 4-hexyloxyammonium benzoate, tetrabutylammonium tetraphenylboranate or complex salts of crown ethers (see, for example, Haller et al., Mol. Cryst. Liq. Cryst., Vol. 24, pp. 249-258 (1973)), can be added to improve the conductivity or substances can be added to modify the dielectric anisotropy, viscosity and / or alignment of the nematic phase. Substances of this type 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 2853 728.

[0352] Table B

[0353] Table B indicates possible dopants which can be added to the mixture according to the invention. If the mixture comprises a dopant, it is added in an amount of 0.01 to 4% by weight, preferably 0.01 to 3% by weight.

[0354]

[0355]

[0356] The mixture according to the invention comprises at least one stabilizer from Table C given below.

[0357] Table C

[0358] Stabilizers which can be added, for example, to the mixture according to the invention in an amount of 0 to 10% by weight, preferably 0.001 to 5% by weight, in particular 0.001 to 1% by weight, are indicated below.

[0359]

[0360]

[0361]

[0362]

[0363]

[0364]

[0365] Working Example:

[0366] The following examples are intended to illustrate the present invention but are not intended to limit the present invention. In the examples, mp represents the melting point and C represents the clearing point of the liquid crystal substance in degrees Celsius; the boiling point is mp. Further: C represents the crystalline solid state, S represents the smectic phase (the subscript (index) represents the phase type), N represents the nematic phase, Ch represents the cholesteric phase, I represents the isotropic phase, T represents the crystalline solid state, and C represents the crystalline solid state. g Indicates the glass transition temperature. The value between the two symbols indicates the transition temperature in degrees Celsius.

[0367] The host mixture used for determining the optical anisotropy Δn of the compounds of formula I was the commercial mixture ZLI-4792 (Merck KGaA). The dielectric anisotropy Δε was determined using the commercial mixture ZLI-2857. The physical data for the compounds to be investigated were obtained from the change in the dielectric constant of the host mixture after the addition of the compounds to be investigated and extrapolated to 100% of the compound used. Typically, depending on the solubility, 10% of the compounds to be investigated were dissolved in the host mixture.

[0368] Unless otherwise indicated, parts or percentages indicate parts or percentages by weight. In this context:

[0369] V o represents the threshold voltage at 20°C, capacitive [V],

[0370] n e represents the extraordinary refractive index at 20°C and 589nm,

[0371] n o represents the ordinary refractive index at 20°C and 589nm,

[0372] △n represents the optical anisotropy at 20℃ and 589nm,

[0373] ε ⊥ represents the dielectric constant perpendicular to the director at 20°C and 1kHz,

[0374] ε || represents the dielectric constant parallel to the director at 20°C and 1kHz,

[0375] △ε represents the dielectric anisotropy at 20℃ and 1kHz,

[0376] cl.p., T(N,I) represents the clearing point [℃],

[0377] γ1 represents the rotational viscosity [mPa·s] measured at 20°C by the rotation method in a magnetic field,

[0378] K1 is the elastic constant, the "bending" deformation at 20°C [pN],

[0379] K2 represents the elastic constant, the "twist" deformation at 20°C [pN],

[0380] K3 represents the elastic constant, the "bending" deformation at 20°C [pN], and

[0381] LTS means low temperature stability (nematic phase) measured in a test cell or in bulk as specified,

[0382] Unless otherwise stated, all temperature values ​​indicated in this application, such as melting point T(C,N), transition from smectic phase (S) to nematic phase (N) T(S,N) and clearing point T(N,I) or cl.p. are expressed in degrees Celsius (°C). Mp denotes melting point. In addition, Tg = glassy state, C = liquid crystal phase, N = nematic phase, S = smectic phase and I = isotropic phase. The numbers between these symbols indicate the transition temperatures.

[0383] The term "threshold voltage" used in the present invention relates to the capacitive threshold (V0), which is also referred to as the Freedericksz threshold unless otherwise stated. In an embodiment, as usual, the optical threshold may also be the relative contrast ratio (V 10 ) indicated.

[0384] The display used to measure the capacitive threshold voltage consisted of two plane-parallel glass outer plates separated by 20 μm, each with an electrode layer on the inside and an unrubbed polyimide alignment layer on top, which resulted in homeotropic edge alignment of the liquid crystal molecules.

[0385] The display or test cell used to measure the tilt angle consists of two plane-parallel glass outer plates separated by 4 μm, each with an electrode layer on the inside and a polyimide alignment layer on top, where the two polyimide layers are rubbed antiparallel to each other and result in homeotropic edge alignment of the liquid crystal molecules.

[0386] Unless otherwise indicated, VHR was measured in a commercial instrument model 6254 from TOYO Corporation, Japan at 20°C (VHR 20 ) and at 100°C (VHR 100 ) after 5 minutes in an oven. Unless otherwise indicated, the voltages used have a frequency ranging from 1 Hz to 60 Hz.

[0387] The accuracy of the VHR measurement depends on the corresponding VHR value. The accuracy decreases with decreasing values. The deviations that are usually observed in the case of values ​​in various amplitude ranges are summarized in the table below in terms of their order of magnitude.

[0388]

[0389] The stability to UV irradiation was investigated in the commercially available instrument "Suntest CPS" from Heraeus, Germany. Unless otherwise indicated, the sealed test box was irradiated for 30 minutes to 2.0 hours without additional heating. The irradiation power in the wavelength range from 300 nm to 800 nm was 765 W / m 2V. A UV "cut-off" filter with an edge wavelength of 310 nm was used in order to simulate the so-called window glass mode. In each series of experiments, at least four test boxes were investigated for each condition, and each result is indicated as the average of the corresponding individual measurements.

[0390] The reduction in voltage holding ratio (ΔVHR) caused by light exposure (e.g., by UV irradiation or by LCD backlight) is usually determined according to the following equation (1):

[0391] △VHR(t)=VHR(t)-VHR(t=0) (1).

[0392] To study low temperature stability, also called "LTS", i.e. the stability of LC mixtures in bulk against spontaneous crystallization of individual components or the appearance of smectic phases at low temperatures, several sealed bottles, each containing about 1 g of material, were stored at one or more given temperatures, typically -10°C, -20°C, -30°C and / or -40°C, as the case may be, and visually inspected at regular intervals whether a phase change was observed. As soon as the first of the samples showed a change at a given temperature, the time was noted. The time at which no change was observed until the last inspection was noted as the corresponding LTS.

[0393] The resistivity was calculated from the ion density measured using a commercially available LC material characterization measurement system model 6254 from Toyo Corporation, Japan, using a VHR test cell (JSR Corp., Japan) of AL16301 polyimide with a cell gap of 3.2 μm. The measurements were performed after storage in an oven at 60°C or 100°C for 5 min.

[0394] The so-called "HTP" refers to the helical twisting power (in μm) of an optically active or chiral substance in a LC medium. Unless otherwise indicated, the HTP is measured in the commercially available nematic LC host mixture MLD-6260 (Merck KGaA) at a temperature of 20°C.

[0395] Unless explicitly mentioned otherwise, all concentrations in the present application are indicated as weight percent and relate to the corresponding mixture as a whole (without solvent) comprising all solid or liquid crystal components. Unless explicitly indicated otherwise, all physical properties are 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.

[0396] The following mixture embodiments with negative dielectric anisotropy are particularly suitable for liquid crystal displays having at least one planar alignment layer, such as, for example, IPS and FFS displays, in particular UB-FFS (=Ultra Bright FFS), and for VA displays.

[0397] Mixture Examples and Comparative Examples

[0398] Comparative mixture C1 was prepared as follows:

[0399]

[0400]

[0401] This mixture has a rather poor response time, but a good VHR value. The VHR measured at 1 V, 1 Hz at 60°C is 95.7%.

[0402] Comparative mixture C2 was prepared as follows:

[0403]

[0404] This mixture shows an improved response time compared to Comparative Example 1, mainly due to its reduced γ1, but shows a lower VHR. The VHR measured at 1 Hz, 1 V at 60°C is 94.2%.

[0405] Mixture M1 was prepared as follows:

[0406]

[0407]

[0408] Mixture M2 was prepared as follows:

[0409]

[0410] Storage tests at deep temperature were performed with the above mixture in 1 ml glass bottles.

[0411] This mixture has a good VHR and at the same time an improved response time, mainly due to its good preferred (γ1 / K1) value relative to CM1 as summarized in the table below.

[0412] Table 1: VHR values

[0413]

[0414] (Note: *All VHR values ​​are measured at 1V, 1Hz and 60℃.)

[0415] Mixture M3 was prepared as follows:

[0416]

[0417] The VHR measured at 1 Hz, 1 V at 60° C. was 94.2%.

[0418] Mixture M4 was prepared as follows:

[0419]

[0420]

[0421] The VHR measured at 60° C., 1 Hz, 1 V was 94.3%.

[0422] Mixture M5 was prepared as follows:

[0423]

[0424] The VHR measured at 60° C., 1 Hz, 1 V was 94.3%.

[0425] Mixture M6 was prepared as follows:

[0426]

[0427]

[0428] The VHR measured at 60° C., 1 Hz, 1 V was 93.0%.

[0429] Mixture M7 was prepared as follows:

[0430]

[0431] The VHR measured at 60° C., 1 Hz, 1 V was 92.9%.

[0432] Mixture M8 was prepared as follows:

[0433]

[0434] The VHR measured at 60° C., 1 Hz, 1 V was 95.4%.

[0435] Mixture M9 was prepared as follows:

[0436]

[0437] The VHR measured at 60° C., 1 Hz, 1 V was 93.0%.

[0438] These results clearly indicate that using B(S)-nO-Om instead of B-nO-Om produces a medium with improved rotational viscosity while the VHR is not reduced so much.

[0439] Especially using B(S)-nO-m in combination with LB-n-Om and / or LB(S)-n-Om, the rotational viscosity of the medium can be reduced even without further sacrificing the VHR, which can remain constant.

Claims

1. A liquid crystal medium, characterized in that It comprises one or more compounds of formula I, in R 11 and R 12 Each independently of one another designates H, an alkyl radical having 1 to 15 C atoms or an alkoxy radical, wherein in addition, one or more CH2 groups in these radicals can each independently of one another be connected to one another via -C≡C-, -CF2O-, -OCF2-, -CH=CH-, -O-, -CO-O-, -O-CO-, and in which in addition one or more H atoms may be replaced by halogen, A 1 Refers independently of each other at each occurrence a) 1,4-cyclohexenyl or 1,4-cyclohexylene, in which one or two non-adjacent CH2 groups may be replaced by -O- or -S-, b) 1,4-phenylene, one or two CH groups of which may be replaced by N, c) a radical from the group of the radicals piperidine-1,4-diyl, 1,4-bicyclo[2.2.2]octylene, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, phenanthrene-2,7-diyl and fluorene-2,7-diyl, wherein the groups a), b) and c) may be singly or polysubstituted by halogen atoms, Z 11 In each case, the following independently represent: -CO-O-, -O-CO-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -CH2CH2-, -(CH2)4-, -CH=CH-CH2O-, -C2F4-, -CH2CF2-, -CF2CH2-, -CF=CF-, -CH=CF-, -CF=CH-, -CH=CH-, -C≡C- or a single bond, and L 11 and L 12 each independently of the other refers to F, Cl, CF3 or CHF2, X 1 refers to O or S, and a refers to 1 or 2, and one or more compounds selected from the group of compounds of formula IIA, IIB and IIC, in R 2A , R 2B and R 2C Each independently of one another designates H, an alkyl or alkenyl radical which is unsubstituted, monosubstituted by CN or CF3 or at least monosubstituted by halogen and has up to 15 C atoms, wherein in addition one or more CH2 groups in these radicals can be linked to one another via -O-, -S-, -S-, -S-, -S- or -S- in such a way that the O atoms are not directly connected to one another. -C≡C-, -CF2O-, -OCF2-, -OC-O- or -O-CO-, L 1 To L 4 Each independently refers to F or Cl, Z 2 and Z 2’ each independently of the others refers to a single bond, -CH2CH2-, -CH=CH-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -COO-, -OCO-, -C2F4-, -CF=CF-, -CH=CHCH2O-, p refers to 0, 1 or 2, q refers to 0 or 1, and v refers to 1 to 6.

2. Liquid-crystalline medium according to claim 1, characterized in that The medium comprises one or more compounds selected from the group of compounds of formulae I-1 to I-3, The parameters have the meanings given in claim 1 .

3. Liquid-crystalline medium according to claim 1 or 2, characterized in that It comprises one or more compounds selected from the group of compounds of formulae IO-1 to IO-3: The parameters have the meanings given in claim 1 .

4. Liquid-crystalline medium according to one or more of claims 1 to 3, characterized in that It comprises one or more compounds selected from the group of compounds of formulae IS-1 to I-SO-3: The parameters have the meanings given in claim 1 .

5. Liquid-crystalline medium according to one or more of claims 1 to 4, characterized in that It comprises one or more compounds of formula IIA: The parameters have the meanings given in claim 1 .

6. Liquid-crystalline medium according to one or more of claims 1 to 5, characterized in that It further comprises one or more compounds of the formula IIB, The parameters have the meanings given in claim 1 .

7. Liquid-crystalline medium according to one or more of claims 1 to 6, characterized in that The medium comprises one or more compounds of formula IIC, The parameters have the meanings given in claim 1 .

8. Liquid-crystalline medium according to one or more of claims 1 to 7, characterized in that The medium additionally comprises one or more compounds selected from the group of compounds of formulae O-1 to O-18, in R 1 and R 2 Each independently has the following characteristics according to claim 6 for R 2A The meaning indicated.

9. Liquid-crystalline medium according to one or more of claims 1 to 8, characterized in that The medium additionally comprises one or more compounds selected from the group of compounds of formulae T-1 to T-21, in R denotes straight-chain alkyl or alkoxy having 1 to 6 C atoms, and m=0, 1, 2, 3, 4, 5 or 6 and n denotes 0, 1, 2, 3 or 4.

10. Liquid-crystalline medium according to one or more of claims 1 to 9, characterized in that The proportion of the compound of the formula I in the mixture as a whole is from 1 to 40% by weight.

11. Liquid-crystalline medium according to one or more of claims 1 to 10, characterized in that The proportion of the compounds of the formulae IIA to IIC in the medium as a whole is in the range from 10% to 70%.

12. Process for producing a liquid-crystalline medium according to one or more of claims 1 to 11, characterized in that One or more compounds of the formula I are mixed with one or more compounds selected from the group of compounds of the formulae IIA to IIC and one or more compounds of this formula.

13. Use of a liquid-crystalline medium according to one or more of claims 1 to 11 in electro-optical displays.

14. An electro-optical display having active matrix addressing, characterized in that The electro-optical display contains a liquid-crystalline medium according to one or more of claims 1 to 11 as dielectric.

15. An electro-optic display according to claim 15, wherein the electro-optic display is a VA, PSA, PA-VA, SS-VA, SA-VA, PS-VA, PALC, IPS, PS-IPS, FFS, UB-FFS, U-IPS or PS-FFS display.

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