Reflection type liquid crystal panel

Abstract

The present invention relates to liquid crystal (LC) panels using liquid crystal (LC) media having negative dielectric anisotropy and LC media included therein. The disclosed liquid crystal medium (LC medium) is a negative dielectric anisotropy liquid crystal material having high optical anisotropy. It is particularly useful in electro-optic displays including projection systems based on vertical alignment (VA) nematic panels.

Description

Technical Field

[0001] The present invention relates to a liquid crystal on silicon panel (LCoS panel) using a liquid crystal (LC) medium having negative dielectric anisotropy and to the liquid crystal medium contained therein.

[0002] The liquid crystal medium (LC medium) of the present invention has negative dielectric anisotropy and high optical anisotropy and is particularly suitable for electro-optical displays including projection systems based on vertically aligned (VA) nematic panels. Background Art

[0003] LCoS panels are used as reflective matrix arrays for devices such as, for example, projection systems, near-eye displays or beam control applications. In the most common mode, the display modulates the polarization orientation (amplitude modulation) like most conventional LC displays. Some applications of LCoS utilize the controlled phase modulation of coherent light to control the spatial distribution of light beams, including image projection. Given new applications and light sources, there is room for improvement in the development of LCoS panels in many fields.

[0004] An alignment layer is usually applied on the electrodes (if such electrodes exist) to bring it into contact with the liquid crystal medium and induce an initial alignment of the liquid crystal molecules. The alignment layer in LCoS panels often consists of an inorganic alignment material, which is more heat-resistant than the polyimide layer mainly used in other liquid crystal panels for desktop or television applications. The various alignment characteristics of these inorganic materials need to be carefully tested. For LCoS panels, a liquid crystal medium with high alignment characteristics on the inorganic alignment material is required. In addition, these devices usually require high light stability and a longer service life at high light intensities.

[0005] Another problem observed in the prior art is that the use of conventional liquid crystal media in LCoS panels often results in the appearance of bubbles and ultimately dark defects in the display, due to the harsh temperatures and radiation during use. Therefore, there is a need to provide a liquid crystal medium that reduces display defects after continuous use. This means that they must be stable themselves and bond well with adjacent materials (such as the alignment layer).

[0006] Another problem observed in the prior art is that LC media for displays (including but not limited to LCoS-type displays) often exhibit high viscosity and thus long switching times.

[0007] In addition, there is also a great demand for displays and LC media for such displays that can achieve high resistivity, while having a large operating temperature range, short response time, low threshold voltage, multiple gray levels, high contrast, high reliability after UV exposure, and high VHR value. Summary of the Invention

[0008] The object of the present invention is to provide a novel and suitable LC medium for devices which does not have the above-mentioned disadvantages or has them to a reduced extent.

[0009] Another object of the present invention is to provide an LCoS panel which does not have the above-mentioned disadvantages or has them only to a reduced extent, and which at the same time has a low viscosity, a high birefringence, a negative dielectric anisotropy, a high transmittance or reflectance, and a high definition.

[0010] In particular, an object of the present invention is to provide an LC medium which reduces or prevents the occurrence of bubbles and dark defects in a display.

[0011] According to the present invention, these objects have been achieved by the materials and methods described in the present application. In particular, it has surprisingly been found that the above-mentioned advantageous effects can be achieved by using the liquid crystal host described below.

[0012] In one aspect, the present invention relates to an LCoS panel comprising an LC medium which comprises

[0013] one or more compounds of formula IV

[0014]

[0015] wherein

[0016] R 41 represents an unsubstituted alkyl group having 1-7 C atoms or an unsubstituted alkenyl group having 2-7 C atoms, preferably an n-alkyl group, particularly preferably having 2, 3, 4 or 5 C atoms, and

[0017] R 42 represents an unsubstituted alkyl group having 1-7 C atoms, an unsubstituted alkoxy group having 1-6 C atoms (both preferably having 2-5 C atoms) or an unsubstituted alkenyl group having 2-7 C atoms, preferably having 2, 3 or 4 C atoms, more preferably vinyl or 1-propenyl and especially vinyl,

[0018] where one or more compounds of formula IV are selected from formula IV-2,

[0019]

[0020] wherein

[0021] alkyl represents an alkyl group having 1-7 C atoms, and

[0022] alkoxy represents an alkoxy group having 1 to 5 carbon atoms.

[0023] The present invention also relates to a liquid crystal medium which comprises

[0024] a) one or more compounds of formula IV

[0025]

[0026] wherein

[0027] R 41 represents an unsubstituted alkyl having 1 - 7 C atoms or an unsubstituted alkenyl having 2 - 7 C atoms, preferably n-alkyl, particularly preferably having 2, 3, 4 or 5 C atoms, and

[0028] R 42 represents an unsubstituted alkyl having 1 - 7 C atoms or an unsubstituted alkoxy having 1 - 6 C atoms, both preferably having 2 - 5 C atoms, an unsubstituted alkenyl having 2 - 7 C atoms, preferably having 2, 3 or 4 C atoms, more preferably vinyl or 1-propenyl and especially vinyl,

[0029] wherein one or more compounds of formula IV are selected from formula IV-2,

[0030]

[0031] wherein

[0032] alkyl represents an alkyl having 1 - 7 C atoms, and

[0033] alkoxy represents an alkoxy having 1 to 5 carbon atoms,

[0034] and

[0035] b) one or more compounds of formula I

[0036]

[0037] wherein

[0038] R 11 represents an alkyl having 1 - 7 C atoms, an alkoxy having 1 - 7 C atoms or an alkoxyalkyl, alkenyl or alkenoxy having 2 - 7 C atoms, wherein in addition, one or more CH 2 groups can each be independently replaced by alternatively,

[0039] R 12 represents an alkyl having 1 - 7 C atoms, an alkoxy having 1 - 7 C atoms or an alkoxyalkyl, alkenyl or alkenoxy having 2 - 7 C atoms,

[0040] and

[0041] c) 0.1% to 0.9% of one or more compounds of formula ST-1

[0042]

[0043] wherein

[0044] R ST represents H, an alkyl or alkoxy group having 1 - 15 C atoms, wherein furthermore, one or more CH 2 groups may each independently of one another be replaced by -C≡C-, -CF 2 O-, -OCF 2 -, -CH=CH-, -O-, -CO-O- or -O-CO- in such a way that the O atoms are not directly linked to one another, and wherein furthermore, one or more H atoms may be replaced by halogen,

[0045] in each occurrence, represents, identically or differently, or

[0046] Z ST each independently represents -CO-O-, -O-CO-, -CF 2 O-, -OCF 2 -, -CH 2 O-, -OCH 2 -, -CH 2 -, -CH 2 CH 2 -, -(CH 2 ) 4 -, -CH=CH-, -CH 2 O-, -C 2 F 4 -, -CH 2 CF 2 -, -CF 2 CH 2 -, -CF=CF-, -CH=CF-, -CF=CH-, -CH=CH-, -C≡C- or a single bond, and

[0047] p represents 0, 1 or 2.

[0048] The medium may preferably also contain one or more compounds of the formulae selected from d) and e):

[0049] d) formulae IIA, IIB, IIC, IID and IIE,

[0050]

[0051] wherein

[0052] R 2A , R 2B , R 2C , R 2D , R 2E1 and R 2E2 each independently represents H, alkyl having 1 to 7 C atoms or alkenyl having 2 to 7 C atoms, each of which is unsubstituted or at least monosubstituted by halogen, wherein one or more CH 2 The group can be -O-, -S-, -C≡C-, -CF 2 O-、-OCF 2 -, -OC-O- or -O-CO- are substituted in such a way that the O atoms are not directly connected to each other,

[0053] L 1 and L 2 Each independently represents F, Cl, CF 3 or CHF 2 ,

[0054] Y represents H, F, Cl, CF 3 , CHF 2 or CH 3 ,

[0055] Z 2 , Z 2B and Z 2D Each independently represents a single bond, -CH 2 CH 2 -、-CH=CH-、-CF 2 CF 2 -、-CF=CF-、-CF 2 O-、-OCF 2 -、-CH 2 O-、-OCH 2 -, -COO-, -OCO-,

[0056] p represents 0, 1 or 2,

[0057] q represents 0 or 1, and

[0058] v means 1, 2, 3, 4, 5 or 6;

[0059] and

[0060] e) Formula III

[0061]

[0062] in

[0063] R 31 and R32 each independently represents H, an alkyl or alkoxy group having 1 to 7 C atoms, wherein one or more CH 2 groups may each independently of one another be -C≡C-, -CF 2 O-, -OCF 2 -, -CH=CH-, -O-, -CO-O- or -O-CO- in such a way that O atoms are not directly linked to one another, and wherein one or more H atoms may be replaced by halogen,

[0064] A 3 each independently represents 1,4-phenylene in each occurrence, wherein one or two CH groups may be replaced by N, or 1,4-cyclohexylene or 1,4-cyclohexenylene, wherein one or two non-adjacent CH 2 groups may be replaced by -O- or -S-,

[0065] wherein the groups may be mono- or polysubstituted by halogen atoms,

[0066] n represents 0, 1 or 2,

[0067] Z 3 each independently represents -CF 2 O-, -OCF 2 -, -CH 2 O-, -OCH 2 -, -CH 2 -, -CH 2 CH 2 -, -CH=CH-, -C≡C- or a single bond,

[0068] L 31 and L 32 each independently represents F, Cl, CF 3 or CHF 2 and

[0069] W represents O or S.

[0070] The invention further relates to a method for preparing an LC medium as described in the context, comprising the step of mixing one or more compounds of formula I, IV-2 and ST-1, optionally in admixture with other LC compounds and / or additives.

[0071] The invention further relates to a projection device comprising an LCoS panel according to the invention and an optical guiding element. The optical guiding element may be selected from lenses, mirrors, semi-reflecting mirrors, prisms or the like.

[0072] The invention also relates to the use of the liquid crystal medium according to the invention in a display. The invention also relates to an LC display of the IPS, FFS, UB-FFS, UBplus, VA or PS-VA type comprising the LC medium according to the invention. The invention also relates to the use of the LC medium according to the invention in a polymer-stabilized VA or self-aligned VA display, and to a polymer-stabilized VA display comprising the LC medium according to the invention.

[0073] The invention also relates to an LC display of the VA or PSA type, comprising two substrates, at least one of which is transparent to light, on each of which one electrode is provided or two electrodes provided only on one of the substrates, and an LC medium layer between the substrates, the LC medium comprising one or more polymerizable compounds and an LC component as described in the context, wherein the polymerizable compounds polymerize between the substrates of the display.

[0074] The invention also relates to a VA type LC display, comprising two opposite substrates, one substrate being transparent and one substrate being a silicon semiconductor backplane.

[0075] The invention also relates to a method of manufacturing an LCoS panel as described in the context, comprising the steps of filling or otherwise providing the LC medium as described in the context between the substrates of the panel and sealing it.

[0076] Preferred embodiments are also disclosed in the dependent claims and their combinations.

[0077] The display according to the invention has two electrodes, preferably applied in the form of a transparent layer on one or both substrates. In a typical reflective display, a continuous transparent electrode is applied to the transparent substrate. The opposite electrode is formed as individually addressable pixels.

[0078] Surprisingly, it has been found that the use of the liquid crystal medium according to the invention enables a display having a fast response time, a low threshold voltage and a high birefringence, as well as high reliability when exposed to radiation and thermal stress.

[0079] In particular, the medium according to the invention is characterized by good alignment properties on various alignment materials.

[0080] The LC medium according to the invention exhibits the following advantageous properties when used in a VA or FFS display:

[0081] - Improved display transmittance,

[0082] - High clear bright temperature,

[0083] - Sufficient stability to heat and / or UV,

[0084] - High voltage holding ratio,

[0085] - Relatively fast switching,

[0086] and

[0087] - Good LTS.

[0088] The LC medium of the present invention exhibits the following advantageous properties when used in reflective displays (including projection systems):

[0089] - High clear bright temperature,

[0090] - Relatively fast switching,

[0091] - Sufficient stability against heat, light and / or UV, and

[0092] - Excellent alignment on inorganic alignment materials.

[0093] In particular, the liquid crystal medium according to the present invention exhibits a favorable ratio γ 1 / K 1 . This helps to improve the switching behavior, especially at low driving voltages, which is useful for achieving energy-saving displays.

[0094] The necessary and optional components of the LC medium are disclosed in more detail below, which relate to the preferred embodiments of the medium and LC displays containing them.

[0095] The preferred compounds of formulas IIA, IIB, IIC, IID and IIE are shown below:

[0096]

[0097]

[0098]

[0099]

[0100]

[0101]

[0102]

[0103]

[0104]

[0105]

[0106]

[0107]

[0108]

[0109] where the parameter a represents 1 or 2, alkyl and alkenyl each independently represent a straight-chain alkyl group having 1 to 6 C atoms, and alkenyl represents a straight-chain alkenyl group having 2 to 6 C atoms, and (O) represents an oxygen atom or a single bond, preferably an oxygen atom. Alkenyl preferably represents any one of the following groups: CH * =CH-, CH 2 =CHCH 2 CH 2 CH 2 -, CH 3 -CH=CH-, CH 3 -CH 2 -CH=CH-, CH 3 -(CH 2 ) 2 -CH=CH-, CH 3 -(CH 2 ) 3 -CH=CH- or CH 3 -CH=CH-(CH 2 ) 2 -.

[0110] Highly preferred compounds of formula IID are selected from the following sub-formulas:

[0111]

[0112]

[0113]

[0114]

[0115]

[0116] where v represents 1, 2, 3, 4, 5 or 6.

[0117] In a preferred embodiment, the medium comprises one or more compounds of formula IID-12a

[0118]

[0119] where each group is defined as shown in formula IID above,

[0120] Preferably, R2 representation where r is 0, 1, 2, 3, 4, 5 or 6, and s is 1, 2 or 3.

[0121] In a preferred embodiment, the medium comprises one or more compounds of the following formula I IE:

[0122]

[0123] where the groups and parameters occurring therein have the meanings given above in formula I IE.

[0124] More preferably, the medium according to the invention comprises one or more compounds of formulae I IA-2, I IA-8, I IA-10, I IA-16, I IA-18, I IA-40, I IA-41, I IA-42, I IA-43, I IB-2, I IB-10, I IB-16, IIC-1, I ID-4 and I ID-10.

[0125] Very preferably, the medium according to the invention comprises one or more compounds of formula I IB-2

[0126]

[0127] where alkyl and alkyl * each independently of one another represent a straight-chain alkyl having 1 - 6 C atoms, and (O) represents an oxygen atom or a single bond, in particular compounds I IB-2-1 and I IB-2-2:

[0128]

[0129] Preferably, the medium according to the invention comprises at least one compound of formula IIC-1,

[0130]

[0131] where alkyl and alkyl * have the above meanings, with a preferred content of 0.5% to 5% by weight, in particular 1% to 3% by weight.

[0132] In particular, the medium comprises one or more compounds of formula I IA-2 selected from the following sub-formulae:

[0133]

[0134]

[0135] Alternatively, preferably, in addition to the compounds of formulas IIA-2-1 to IIA-2-5, the medium further comprises one or more compounds of formulas IIA-2a-1 to IIA-2a-5:

[0136]

[0137] In particular, the medium comprises one or more compounds of formula IIA-10 or IIA-52 selected from the following sub-formulas:

[0138]

[0139] Alternatively, preferably, in addition to the compounds of formulas IIA-10-1 to IIA-10-5, the medium further comprises one or more compounds of formulas IIA-10a-1 to IIA-10a-5:

[0140]

[0141]

[0142] In particular, the medium comprises one or more compounds of formula IIB-10 selected from the following sub-formulas:

[0143]

[0144] Alternatively, preferably, in addition to the compounds of formulas IIB-10-1 to IIB-10-5, the medium further comprises one or more compounds of formulas IIB-10a-1 to IIB-10a-5:

[0145]

[0146] Very preferably, the medium according to the invention comprises one or more compounds of formula IIE, in particular compounds of formulas IIE-1-1 to IIE-1-8, and most preferably one or more compounds of formulas IIE-1-1-1 to IIE-1-1-4:

[0147]

[0148] The compound of formula III is preferably selected from the compounds of formulas III-1, III-2 and / or III-4

[0149]

[0150] wherein the groups occurring have the same meanings as given in formula III above, and preferably

[0151] R 31 and R 32Each independently represents an alkyl or alkoxy group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms. More preferably, one or two of them represent an alkoxy group having 1 to 7 carbon atoms, and

[0152] L 31 and L 32 preferably represents F.

[0153] The liquid crystal medium according to the invention preferably contains one, two or more compounds of formula III-2. In a preferred embodiment, the liquid crystal medium contains at least one compound of formula III-1 and at least one compound of formula III-2. In a further preferred embodiment, the liquid crystal medium contains at least one compound of formula III-2 and at least one compound of formula III-3.

[0154] Preferably, the compounds of formula III-1 are selected from the compounds of formula III-1-1 to III-1-10, preferably the compound of formula III-1-6,

[0155]

[0156]

[0157] wherein

[0158] alkyl and alkyl * each independently represents a straight-chain alkyl group having 1 to 6 carbon atoms, alkenyl and alkenyl * each independently represents a straight-chain alkenyl group having 2 to 6 carbon atoms, alkoxy and alkoxy * each independently represents a straight-chain alkoxy group having 1 to 6 carbon atoms, and L 31 and L 32 each independently represents F or Cl, preferably both are F.

[0159] Preferably, the compounds of formula III-2 are selected from the compounds of formula III-2-1 to III-2-10, preferably the compound of formula III-2-6,

[0160]

[0161]

[0162] wherein

[0163] alkyl and alkyl * each independently represents a straight-chain alkyl group having 1 to 6 carbon atoms, alkenyl and alkenyl *Each independently represents a straight-chain alkenyl group having 2 to 6 carbon atoms, alkoxy, and alkoxy * Each independently represents a straight-chain alkoxy group having 1 to 6 carbon atoms, and L 31 and L 32 Each independently represents F or Cl, preferably both are F.

[0164] Optionally, the medium contains one or more compounds of formula IIIA-1 and / or IIIA-2

[0165]

[0166] wherein L 31 and L 32 have the same meanings as given under formula III, (O) represents O or a single bond,

[0167] R IIIA represents an alkyl or alkenyl group having at most 7 carbon atoms, or the group Cy-C m H 2m+1 ,

[0168] m and n are the same or different and are 0, 1, 2, 3, 4, 5 or 6, preferably 1, 2 or 3, very preferably 1,

[0169] Cy represents an alicyclic group having 3, 4 or 5 ring atoms, which is optionally substituted with an alkyl or alkenyl group each having at most 3 carbon atoms, or with a halogen or CN, and preferably represents cyclopropyl, cyclobutyl, cyclopentyl or cyclopentenyl.

[0170] The compounds of formula IIIA-1 and / or IIIA-2 can be contained in the LC medium instead of or additionally to the compounds of formula III, preferably additionally.

[0171] Very preferred compounds of formula IIIA-1 and IIIA-2 are as follows:

[0172]

[0173] where alkoxy represents a straight-chain alkoxy group having 1 to 6 carbon atoms, or alternatively represents –(CH 2 ) n F, where n is 2, 3, 4 or 5, preferably C 2 H 4 F.

[0174] In a preferred embodiment of the present invention, the medium contains one or more compounds of formula III-3

[0175]

[0176] wherein

[0177] R 31 、R 32 independently represent, identically or differently, H, an alkyl or alkoxy group having 1 to 15 C atoms, where one or more CH 2 groups are optionally, independently of one another, replaced by -C≡C-, -CF 2 O-, -OCF 2 -, -CH=CH-, -O-, -CO-O- or -O-CO- in such a way that the O atoms are not directly linked to one another, and where, furthermore, one or more H atoms may be replaced by halogen.

[0178] The compounds of formula III-3 are preferably selected from the compounds of formulae III-3-1 to III-3-10:

[0179]

[0180]

[0181] where R 32 represents an alkyl group having 1 to 7 C atoms, preferably ethyl, n-propyl or n-butyl, or alternatively represents cyclopropylmethyl, cyclobutylmethyl or cyclopentylmethyl, or alternatively represents –(CH 2 ) n F, where n is 2, 3, 4 or 5, preferably C 2 H 4 F.

[0182] In a preferred embodiment of the invention, the medium comprises one or more compounds of formulae III-4 to III-6, preferably formula III-5,

[0183]

[0184] where the parameters have the meanings given above, R 31 preferably represents a straight-chain alkyl group having 1 to 7 C atoms and R 32 preferably represents an alkoxy group having 1 to 7 C atoms.

[0185] In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula III selected from formulae III-7 to III-9, preferably formula III-8,

[0186]

[0187] where the parameters have the meanings given above, R 31 preferably represents a straight-chain alkyl group having 1 to 7 C atoms and R 32Preferably represents an alkoxy having 1 - 7 C atoms.

[0188] In a preferred embodiment, the medium comprises one or more compounds of formula IV,

[0189]

[0190] wherein

[0191] R 41 represents an unsubstituted alkyl having 1 - 7 C atoms or an unsubstituted alkenyl having 2 - 7 C atoms, preferably n-alkyl, particularly preferably having 2, 3, 4 or 5 C atoms, and

[0192] R 42 represents an unsubstituted alkyl having 1 - 7 C atoms or an unsubstituted alkoxy having 1 - 6 C atoms (both preferably having 2 - 5 C atoms), an unsubstituted alkenyl having 2 - 7 C atoms, preferably having 2, 3 or 4 C atoms, more preferably vinyl or 1-propenyl and particularly vinyl.

[0193] wherein the compounds of formula I are excluded from formula IV and its sub-formulas.

[0194] The compounds of formula IV are preferably selected from the compounds of formula IV-1 to IV-4,

[0195]

[0196]

[0197] wherein

[0198] alkyl and alkyl’ independently of one another represent an alkyl having 1 - 7 C atoms, preferably having 2 - 5 C atoms,

[0199] alkenyl represents an alkenyl having 2 - 5 C atoms, preferably having 2 - 4 C atoms, particularly preferably 2 C atoms,

[0200] alkenyl’ represents an alkenyl having 2 - 5 C atoms, preferably having 2 - 4 C atoms, particularly preferably having 2 - 3 C atoms, and

[0201] alkoxy represents an alkoxy having 1 - 5 C atoms, preferably having 2 - 4 C atoms.

[0202] Preferably, in addition to the compounds of formula IV-2, the medium further contains one or more compounds selected from the compounds of formula IV-1 and IV-3.

[0203] Preferably, the medium comprises one or more compounds selected from the compounds of formula IV-1-1 to IV-1-4

[0204]

[0205] Very preferably, the medium according to the invention comprises a compound of formula IV-1-1.

[0206] Very preferably, the medium according to the invention comprises one or more compounds of formula IV-2-1 and / or IV-2-2

[0207]

[0208] In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula IV-3,

[0209]

[0210] wherein very preferably, alkyl represents an alkyl group having 1-7 C atoms, in particular n-ethyl or n-propyl, very particularly n-propyl, and alkenyl represents wherein m is 0, 1 or 2, preferably 0, and n is 0, 1 or 2, preferably 0 or 1,

[0211] in particular compounds selected from formulae IV-3-1 to IV-3-6, very particularly preferably the compound of formula IV-3-2:

[0212]

[0213]

[0214] In a preferred embodiment, in particular in addition to the compounds of formulae IV-3-1 to IV-3-6, the medium further comprises one or more compounds of formulae IV-3-7 to IV-3-9

[0215]

[0216] Preferably, the concentration of the compounds of formulae IV-3-7 to IV-3-9 in the medium according to the invention is less than 5% or less than 4% or less than 3%, very preferably 0% to 1%, in particular 0%.

[0217] Very preferably, the medium according to the invention comprises one or more compounds of formula IV-3 and one or more compounds of formula IV-1, wherein the total concentration of the compounds of formula IV-1 is in the range of 1% to 30%.

[0218] Very preferably, the medium according to the invention comprises a compound of formula IV-4, in particular a compound selected from formulae IV-4-1 to IV-4-3, in particular the compound of formula IV-4-3

[0219]

[0220]

[0221] In a preferred embodiment, the medium according to the invention comprises a combination of one or more compounds of formula I selected from compounds of formulae I-1 to I-4 with one or more compounds selected from compounds of formulae IA-1 to IA-18:

[0222]

[0223]

[0224]

[0225] wherein alkyl represents methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or n-pentyl.

[0226] The LC medium according to the invention preferably comprises one or more compounds of formula IVa,

[0227]

[0228] wherein

[0229] R 41 and R 42 each independently of one another represent a straight-chain alkyl, alkoxy, alkenyl, alkoxyalkyl or alkenyloxy group having up to 12 C atoms, and

[0230] represents

[0231] Z 4 represents a single bond, -CH 2 CH 2 -, -CH=CH-, -CF 2 O-, -OCF 2 -, -CH 2 O-, -OCH 2 -, -COO-, -OCO-, -C 2 F 4 -, -C 4 H 8 - or -CF=CF-.

[0232] Preferred compounds of formula IVa are shown below:

[0233]

[0234] wherein alkyl and alkyl *Each independently represents a straight-chain alkyl group having 1 to 6 carbon atoms.

[0235] The medium according to the invention preferably comprises at least one compound of formula IVa-1 and / or formula IVa-2, very preferably a compound of formula IVa-2, in particular a compound of formula IVa-2 in which alkyl represents n-propyl and alkyl * represents methyl.

[0236] The proportion of the compound of formula IVa in the entire mixture is preferably less than 5% by weight, very preferably less than 2% by weight.

[0237] Preferably, the medium comprises one or more compounds of formula IVb-1 to IVb-3

[0238]

[0239] wherein

[0240] alkyl and alkyl * each independently represents a straight-chain alkyl group having 1 to 6 carbon atoms, and

[0241] alkenyl and alkenyl * each independently represents a straight-chain alkenyl group having 2 to 6 carbon atoms.

[0242] The proportion of the compounds of formula IV-1 to IV-3 in the entire mixture is preferably less than 3% by weight, in particular less than 2% by weight.

[0243] Among the compounds of formula IVb-1 to IVb-3, the compound of formula IVb-2 is particularly preferred.

[0244] Very particularly preferred biphenyls are

[0245]

[0246] where alkyl * represents an alkyl group having 1 to 6 carbon atoms, and preferably represents n-propyl or n-butyl. The medium according to the invention particularly preferably comprises one or more compounds of formula IVb-1-1 and / or IVb-2-3.

[0247] In the compound of formula IVb-1-1, alkyl preferably represents propyl, butyl and pentyl, most preferably propyl.

[0248] In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula V

[0249]

[0250] wherein

[0251] R 51 and R 52 represent an alkyl group having 1 - 7 C atoms, an alkoxy group having 1 - 7 C atoms, or an alkoxyalkyl group, alkenyl group or alkenyloxy group having 2 - 7 C atoms,

[0252] represents

[0253] represents

[0254] Z 51 and Z 52 each independently of one another represent -CH 2 -CH 2 -, -CH 2 -O-, -CH=CH-, -C≡C-, -COO- or a single bond, and

[0255] n is 1 or 2.

[0256] The compound of formula V is preferably selected from the compounds of formulae V-1 to V-14:

[0257]

[0258]

[0259] wherein R 51 and R 52 have the meanings as defined above for formula V.

[0260] R 51 and R 52 are preferably each independently of one another a straight-chain alkyl group having 1 - 7 C atoms or an alkenyl group having 2 - 7 C atoms.

[0261] The preferred medium comprises one or more compounds of formulae V-1, V-3, V-4, V-6, V-7, V-10, V-11, V-12 and / or V-14.

[0262] In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula Vb

[0263]

[0264] wherein

[0265] R 51 and R 52represents an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, or an alkoxyalkyl, alkenyl or alkenyloxy group having 2 to 7 carbon atoms,

[0266] represents

[0267] represents

[0268] Z 51 and Z 52 each independently of the other represent -CH 2 -CH 2 -, -CH 2 -O-, -CH═CH-, -C≡C-, -COO- or a single bond, and

[0269] n is 2.

[0270] The compounds of formula Vb are preferably selected from the compounds of formulae Vb-1 to Vb-2:

[0271]

[0272] In a preferred embodiment of the invention, the medium further comprises one or more compounds of formula VI

[0273]

[0274] wherein R 6 and R 62 have the meaning of R 2A as defined in claim 1, and R 62 alternatively represents F, Cl, CF 3 or OCF 3 , preferably F, and L 61 and L 62 and L 63 and L 64 and L 65 and L 66 independently represent H or F, where at least one of L 61 and L 62 and L 63 and L 64 and L 65 and L 66 represents F, and wherein compounds of formulae IIC and IIE are excluded.

[0275] The compounds of formula VI are preferably selected from formulae VI-1 to VI-20, especially from formulae VI-1, VI-2, IV-4, VI-14, VI-19 and VI-20:

[0276]

[0277]

[0278]

[0279] wherein R 6 represents a straight-chain alkyl or alkoxy group having 1 to 6 C atoms, (O) represents -O- or a single bond, m is 0, 1, 2, 3, 4, 5 or 6, and n is 0, 1, 2, 3 or 4.

[0280] R 6 preferably represents methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy or pentyloxy.

[0281] Compounds of formulae VI-1, VI-2, VI-4, VI-19 and VI-20 are particularly preferred.

[0282] In a preferred embodiment of the present invention, the medium further comprises one or more compounds of formula VIA

[0283]

[0284] wherein R 6 and R 62 have the meaning of R as defined in claim 1, and R 2A alternatively represents F, Cl, CF 62 or OCF 3 or OCF 3 , preferably F, and L 61 , L 62 , L 63 , L 64 , L 65 and L 66 independently represent H or F, wherein at least one of L 61 , L 62 , L 63 , L 64 , L 65 and L 66 represents F and

[0285] Z 61 and Z 62 independently represent a single bond, -CH 2 -CH 2 -, -CH 2 -O-, -CH=CH-, -C≡C-, -COO- or -CF 2 -O- provided that Z 61 ≠Z 62 .

[0286] Very preferably, the medium according to the invention comprises a compound of formula VIA-1 and / or formula X

[0287]

[0288] wherein R 6 and m have the meanings defined above, and preferably R 6 represents methyl, ethyl, n-propyl, n-butyl or n-pentyl, and m is 2, 3 or 4. In a particularly preferred embodiment, R 6 represents n-propyl and m represents 2.

[0289] In a preferred embodiment of the invention, the medium further comprises one or more compounds of formula VII-1 to VII-9

[0290]

[0291] wherein R 7 represents a straight-chain alkyl or alkoxy group having 1-6 C atoms, or a straight-chain alkenyl group having 2-6 C atoms, and

[0292] w is an integer from 1 to 6.

[0293] Particularly preferably, a mixture comprising at least one compound of formula VII-9 is included.

[0294] Further preferred embodiments are as follows:

[0295] a) The liquid crystal medium comprises at least one compound of formula Z-1 to Z-8,

[0296]

[0297]

[0298] wherein R has the meaning of R in formula IIA 2A and alkyl represents a straight-chain alkyl group having 1-6 C atoms.

[0299] In a preferred embodiment, the liquid crystal mixture according to the invention contains at least one compound of formula Z-8.

[0300] b) The preferred liquid crystal medium according to the invention comprises one or more substances containing a tetrahydronaphthyl or naphthyl unit, such as compounds of formula N-1 to N-5,

[0301]

[0302] wherein R 1N and R 2NEach independently has the above meaning for R 2A as defined above, preferably represents a linear alkyl, linear alkoxy or linear alkenyl, and

[0303] Z 1 and Z 2 each independently represents -C 2 H 4 -, -CH=CH-, -(CH 2 ) 4 -, -(CH 2 ) 3 O-, -O(CH 2 ) 3 -, -CH=CHCH 2 CH 2 -, -CH 2 CH 2 CH=CH-, -CH 2 O-, -OCH 2 -, -COO-, -OCO-, -C 2 F 4 -, -CF=CF-, -CF=CH-, -CH=CF-, -CF 2 O-, -OCF 2 -, -CH 2 -, or a single bond.

[0304] c) A preferred mixture comprises one or more compounds selected from difluorodibenzochroman compounds of formula BC, chromans of formula CR, and fluorophenanthrene compounds of formula PH-1 and PH-2,

[0305]

[0306] wherein R B1 , R B2 , R CR1 , R CR2 , R 1 , R 2 each independently has the meaning of R 2A . c is 0, 1 or 2. R 1 and R 2 preferably independently of each other represent an alkyl or alkoxy having 1-6 C atoms.

[0307] Particularly preferred compounds of formulae BC and CR are compounds BC-1 to BC-7 and CR-1 to CR-5,

[0308]

[0309]

[0310] wherein

[0311] alkyl and alkyl * each independently represents a straight-chain alkyl group having 1 to 6 C atoms, and

[0312] alkenyl and alkenyl * each independently represents a straight-chain alkenyl group having 2 to 6 C atoms.

[0313] Very particularly preferably, the mixture comprises one, two or three compounds of formula BC-2, BF-1 and / or BF-2.

[0314] d) The preferred mixture comprises one or more indane compounds of formula In,

[0315]

[0316] wherein

[0317] R 11 、R 12 and R 13 each independently represents a straight-chain alkyl group, alkoxy group, alkoxyalkyl group or alkenyl group having 1 to 6 C atoms.

[0318] R 12 and R 13 alternatively represent halogen, preferably F,

[0319] represents

[0320]

[0321] i represents 0, 1 or 2.

[0322] The preferred compounds of formula In are the compounds of formulae In-1 to In-16 described below:

[0323]

[0324]

[0325]

[0326] Particularly preferred are the compounds of formulae In-1, In-2, In-3 and In-4.

[0327] e) The preferred mixture additionally comprises one or more compounds of formulae L-1 to L-11,

[0328]

[0329]

[0330] in

[0331] R, R 1 and R 2 Each independently has the above R 2A The parameter s represents 1 or 2.

[0332] The compounds of the formulae L-1 to L-11 are preferably used in a concentration of 5 to 15% by weight, in particular 5 to 12% by weight and very particularly preferably 8 to 10% by weight.

[0333] f) Preferred mixtures additionally contain one or more compounds of the formula IIA-Y

[0334]

[0335] Where R 11 and R 12 With the above formula IIA R 2A One of the meanings given, and L 1 and L 2 Identically or differently represent F or Cl and L 3 Indicates H or CH 3 .

[0336] Preferred compounds of formula IIA-Y are selected from the following sub-formulas

[0337]

[0338]

[0339]

[0340] Among them, alkyl and alkyl * Each independently represents a straight-chain alkyl radical having 1 to 6 C atoms, alkoxy represents a straight-chain alkoxy radical having 1 to 6 C atoms, alkenyl and a lkenyl * each independently of one another represents a straight-chain alkenyl group having 2 to 6 C atoms, and O represents an oxygen atom or a single bond. * Preferably CH 2 =CH-, CH 2 =CHCH 2 CH 2 -、CH 3 -CH=CH-, CH 3 -CH 2 -CH=CH-, CH 3 -(CH 2) 2 -CH=CH-, CH 3 -(CH 2 ) 3 -CH=CH- or CH 3 -CH=CH-(CH 2 ) 2 -.

[0341] Particularly preferred compounds of formula I IA-Y are selected from the following sub-formulas:

[0342]

[0343] where alkoxy and alkoxy * have the meanings defined above and preferably represent methoxy, ethoxy, n-propoxy, n-butoxy or n-pentyloxy.

[0344] g) The medium additionally contains one or more compounds selected from formulas P-1 to P-4:

[0345]

[0346]

[0347] where

[0348] R P represents a straight-chain alkyl or alkoxy group having 1-6 C atoms or an alkenyl group having 2-6 C atoms, preferably an alkyl group, each of which is unsubstituted or at least monosubstituted by halogen, where one or more CH 2 groups in these groups may be replaced by -O-, -S-, -C≡C-, -CF 2 O-, -OCF 2 -, -OC-O- or -O-CO- in such a way that the O atoms are not directly connected to each other;

[0349] X P represents a straight-chain alkyl group having 1-6 C atoms, F, Cl, CF 3 , OCF 2 H, OCF 3 , OCHFCF 3 , OCF 2 CHFCF 3 , OCH=CF 2 , preferably F, OCF 3 or CF 3 , CH 3 ,

[0350] L P1 , LP2 and L P3 each independently represents H or F, and

[0351] L P4 represents H or CH 3 , preferably H.

[0352] Preferred compounds of formulas P1 to P4 are listed below:

[0353]

[0354]

[0355] wherein

[0356] L P4 represents H or CH 3 ;

[0357] R P has the meaning given above. Preferably, R P represents alkyl, cycloalkyl, cycloalkylalkyl or alkenyl, especially ethyl, propyl, butyl, pentyl, cyclopropyl, cyclopentyl, CH 2 =CH-, CH 2 =CHCH 2 CH 2 -, CH 3 -CH=CH-, CH 3 -CH 2 -CH=CH-, CH 3 -(CH 2 ) 2 -CH=CH-, CH 3 -(CH 2 ) 3 -CH=CH- or CH 3 -CH=CH-(CH 2 ) 2 -, alkyl represents a straight-chain alkyl having 1-6 carbon atoms.

[0358] The compound of formula P-1 has a stabilizing property for the liquid crystal medium. In a preferred embodiment, the medium according to the invention comprises at least one compound of formula P-1, more preferably the compound of formula P-1a, preferably in a content of 0.1-5% by weight, more preferably 0.4-2.5% by weight.

[0359] h) The medium additionally comprises one or more compounds selected from the compounds of formulas PII and PIII:

[0360]

[0361] wherein

[0362] R 2 and R 3 represent an unsubstituted or halogenated straight-chain or branched alkyl or alkoxy group having 1 to 15 C atoms, where one or more CH 2 groups in these groups can each independently of one another be replaced by -C≡C-, -CF 2 O-, -CH=CH-, -O-, -CO-O- or -O-CO- in such a way that the O atoms are not directly connected to one another,

[0363] to and to independently of one another represent

[0364]

[0365] Preferably

[0366] L 21 、L 22 、L 31 and L 32 independently of one another represent H or F, preferably F,

[0367] Y 2 and Y 3 independently of one another represent H or CH 3 ,

[0368] X 2 and X 3 independently of one another represent halogen, CN, a halogenated alkyl or alkoxy group having 1 to 3 C atoms or a halogenated alkenyl or alkenyloxy group having 2 or 3 C atoms, preferably F, Cl, OCF 3 or CF 3 , most preferably F, CF 3 or OCF 3 ,

[0369] Z 3 represents -CH 2 CH 2 -, -CF 2 CF 2 -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH 2 O- or a single bond, preferably -CH 2 CH 2 -, -COO-, trans-CH=CH-, most preferably -COO-, and

[0370] l, m, n and o are each independently 0 or 1,

[0371] Preferably, l + m is 2.

[0372] The preferred compound of formula PIII is formula PIII-1

[0373]

[0374] where

[0375] R 3 represents an unsubstituted or halogenated straight-chain or branched alkyl group having 1 to 15 C atoms, where one or more CH 2 groups of these groups may each independently be replaced by -C≡C-, -CF 2 O-, -CH=CH-, -O-, -CO-O- or -O-CO- in such a way that the O atoms are not directly connected to each other,

[0376] L 31 and L 32 are the same or different and represent H or F, preferably F,

[0377] Y 3 are the same or different and represent H or CH 3 ,

[0378] X 3 are the same or different and represent halogen, CN, a halogenated alkyl or alkoxy group having 1 to 3 C atoms or a halogenated alkenyl or alkenyloxy group having 2 or 3 C atoms, preferably F, CN, OCF 3 or CF 3 , most preferably F or CN, and

[0379] n is independently 0 or 1, preferably n is 0.

[0380] Preferably, in PIII and PIII-1, the groups independently represent one or more of the following:

[0381] X 3 represents CN,

[0382] L 31 represents F,

[0383] L 32 represents H,

[0384] n represents 0,

[0385] L 33 , L 34 represent H, and

[0386] Y 3 represents H.

[0387] Preferably, the liquid crystal medium according to the invention comprises one or more compounds of formula H

[0388]

[0389] wherein

[0390] A represents a q-valent aliphatic, aromatic or heteroaromatic hydrocarbon radical having 1 to 40 C atoms, preferably 6 to 30 C atoms; or a single bond when q = 2;

[0391] Sp represents a spacer group or a single bond;

[0392] R S represents H, an alkyl group having 1 to 12 C atoms or an alkenyl group having 2 to 12 C atoms;

[0393] Z S represents -O-, -C(O)O-, -(CH 2 ) z -, or -(CH 2 ) z O- or a single bond; preferably -C(O)O-, HA represents

[0394] R H represents H, O·, CH 3 , OH or OR S , preferably H or O·,

[0395] R S1 、R S2 、R S3 and R S4 are the same or different and represent an alkyl group having 1 to 6 C atoms, preferably having 1 to 3 C atoms, very preferably CH 3 ,

[0396] G represents H or R S or the group Z S -HA,

[0397] z is an integer from 1 to 6, and

[0398] q is 1, 2, 3 or 4, preferably 2.

[0399] In formula H, the aryl group preferably represents an aromatic or heteroaromatic hydrocarbon radical having 4 to 40 C atoms, which comprises one, two, three or four aromatic rings (including fused rings which may be directly linked or linked via an alkylene linking group having 1 to 12 C atoms), wherein one or more H atoms are optionally replaced by an alkyl or alkoxy group having 1 to 6 C atoms or an alkenyl group having 2 to 6 C atoms, or by CN, CF3 or halogen substitution, and one or more CH 2 groups may each independently of one another be replaced by -O-, -S-, -NH-, -N(C 1 -C 4 -alkyl)-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -CH═CH- or -C≡C- in such a way that O or S atoms are not directly connected to each other.

[0400] Preferred aliphatic groups are alkylene, cycloalkylene, more preferably -(CHR S5 ) s -, where R S5 is H or alkyl having 1 - 5 C atoms, and s is an integer from 1 to 20.

[0401] Preferred aryl groups are phenyl, naphthyl, anthracenyl, biphenyl, m-terphenyl, p-terphenyl and (phenylalkyl)phenyl, where the alkyl is a straight-chain alkyl having 1 - 12 C atoms.

[0402] Compounds of formula H are described in EP 3354710 A1 and EP 3354709 A1.

[0403] Compounds of formula H are preferably used in the range of 0.1 to 0.3% (by weight).

[0404] In a preferred embodiment, the medium comprises one or more compounds of formula H selected from compounds of formula H-A

[0405]

[0406] wherein

[0407] A a represents alkylene having 2 - 12 carbon atoms, where one or two CH 2 groups may each be replaced by 1,4-cyclohexylene, and

[0408] R H represents H or O · .

[0409] Group A a preferably represents

[0410]

[0411] (biphenyl-1,1',3,3'-tetrayl),

[0412] (benzene-1,2,4,5-tetrayl)

[0413] (benzene-1,3,5-triyl),

[0414] (benzene-1,2,4-triyl),

[0415] -(CH 2 -) 2 、-(CH 2 -) 3 、-(CH 2 -) 4 、-(CH 2 -) 5 、-(CH 2 -) 6 、-(CH 2 -) 7 、-(CH 2 -) 8 ,

[0416] i.e., ethane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl,

[0417] (1,4-phenylene),

[0418] (1,3-phenylene),

[0419] (1,2-phenylene) or

[0420] (trans-1,4-cyclohexylene) and / or wherein

[0421] S 11 represents an alkylene group having 1-20 C atoms, and the compound of formula H is preferably selected from the compounds of formula H-1 to H-12:

[0422]

[0423]

[0424]

[0425]

[0426] wherein R H has the meaning given above and preferably represents H or O · , and

[0427] n is an integer from 0 to 12, preferably 5, 6, 7, 8 or 9, very preferably 7, and

[0428] Sp represents a spacer group, preferably an alkylene group having 1 to 12 C atoms, wherein one or more non-adjacent -CH 2 - groups can be replaced by -O-.

[0429] Preferred compounds of formula H-10 are selected from compounds of formula H-10-1:

[0430]

[0431] wherein R H has the meanings given above and preferably represents H or O · , and n is an integer from 0 to 12, preferably 5, 6, 7, 8 or 9, very preferably 7.

[0432] Preferred compounds of formula H-11 are selected from compounds of formula H-11-1:

[0433]

[0434] wherein R H has the meanings given above and preferably represents H or O · , and

[0435] n2 is the same or different, preferably the same, each time it appears and is an integer from 1 to 12, preferably 2, 3, 4, 5 or 6, very preferably 3, and R S is the same or different, preferably the same, each time it appears and represents an alkyl group having 1 to 6 C atoms, preferably n-butyl.

[0436] Preferred compounds of formula H-12 are selected from compounds of formula H-12-1:

[0437]

[0438] wherein R H has the meanings given above and preferably represents H or O · , and n is an integer from 0 to 12, preferably 5, 6, 7, 8 or 9, very preferably 7.

[0439] Preferred stabilizer H is as follows:

[0440]

[0441]

[0442] Preferably, the medium according to the invention comprises a compound selected from formulas ST-1 to ST-12:

[0443]

[0444]

[0445]

[0446] wherein

[0447] R ST represents H, an alkyl or alkoxy group having 1 to 15 C atoms, wherein, in addition, one or more CH 2 groups may each independently of one another be replaced by -C≡C-, -CF 2 O-, -OCF 2 -, -CH=CH-, -O-, -CO-O-, -O-CO- in such a way that O atoms are not directly linked to one another, and wherein, furthermore, one or more H atoms may be replaced by halogen, preferably an alkyl or cyclopentyl group having 1 to 7 C atoms,

[0448] in each occurrence, represents, identically or differently,

[0449] Z ST each independently of one another represents -CO-O-, -O-CO-, -CF 2 O-, -OCF 2 -, -CH 2 O-, -OCH 2 -, -CH 2 -, -CH 2 CH 2 -, -(CH 2 ) 4 -, -CH=CH-, -CH 2 O-, -C 2 F 4 -, -CH 2 CF 2 -, -CF 2 CH 2 -, -CF=CF-, -CH=CF-, -CF=CH-, -CH=CH-, -C≡C- or a single bond,

[0450] L 1 and L 2 each independently of one another represents F, Cl, CH 3 CF 3 or CHF 2 ,

[0451] p represents 0, 1 or 2,

[0452] q represents 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0453] Among the compounds of formula ST, compounds of formula ST-1 and ST-3 are particularly preferred, especially any one of the following:

[0454]

[0455] where n = 1, 2, 3, 4, 5, 6 or 7, preferably n = 3

[0456]

[0457] where n = 1, 2, 3, 4, 5, 6 or 7, preferably n = 1 or 7

[0458]

[0459] where n = 1, 2, 3, 4, 5, 6 or 7, preferably n = 3

[0460]

[0461]

[0462] A very particularly preferred mixture according to the invention comprises one or more compounds selected from compounds of formula ST-1a, ST-1b-1 and ST-1c-1:

[0463]

[0464] In the liquid crystal mixture according to the invention, the compounds of formula ST-1 to ST-12 are preferably each present in an amount of 0.1 - 0.5% based on the mixture.

[0465] However, based on the mixture according to the invention, the total proportion of the compounds of formula ST-1 to ST-12 should not exceed 2%.

[0466] The medium according to the invention preferably has negative dielectric anisotropy.

[0467] Definition

[0468] As used herein, the term "reliability" means the quality of the performance of a display over a period of time and under different stress loads, such as light load, temperature, humidity, voltage, and includes display effects such as image sticking (surface and line image sticking), color mura, non-uniformity (yogore), etc., which are known to those skilled in the art of LC displays. As a standard parameter for classifying reliability, the voltage holding ratio (VHR) value is typically used, which is a measure of the amount of voltage maintained constant in the test display. Among other factors, a high VHR is a prerequisite for high reliability of the LC medium.

[0469] As used herein, the terms "active layer" and "switchable layer" denote a layer in an electro-optical display, such as in an LC display, containing one or more molecules (e.g., LC molecules) having structural and optical anisotropy, which change their orientation when subjected to an external stimulus such as an electric or magnetic field, which results in a change in the transmittance of the layer for polarized or non-polarized light.

[0470] Unless otherwise specified, as used herein, the term "liquid crystal display" refers to an information display based on switchable liquid crystals. It includes backlit and reflective displays, for direct or indirect viewing, for virtual reality or augmented reality systems or projection systems. The size ranges from microdisplays to large screens. Addressing can be achieved by: an LC display includes simple electrodes on a substrate, a thin film transistor array having electrodes for each pixel, or a structured silicon semiconductor as a backplane, with the latter being preferred.

[0471] As used herein, the terms "optically active" and "chiral" are synonyms for materials capable of inducing a helical pitch in a nematic host material, also known as "chiral dopants".

[0472] Throughout the patent application, the 1,4-cyclohexylene ring and the 1,4-phenylene ring are described as follows:

[0473]

[0474] The cyclohexylene ring is a trans-1,4-cyclohexylene ring.

[0475] In context, represents a trans-1,4-cyclohexylene ring.

[0476] In the group the single bond shown between two ring atoms can be connected to any free position of the benzene ring.

[0477] The "organic group" in context means a carbon group or a hydrocarbon group.

[0478] "Carbon group" means a monovalent or polyvalent organic group containing at least one carbon atom, where the group contains no other atoms (e.g., -C≡C-) or optionally contains one or more other atoms such as N, O, S, B, P, Si, Se, As, Te, or Ge (e.g., carbonyl, etc.). The term "hydrocarbyl group" means a carbon group that additionally contains one or more H atoms and optionally one or more heteroatoms such as N, O, S, B, P, Si, Se, As, Te, or Ge.

[0479] "Halogen" means F, Cl, Br, or I, preferably F or Cl.

[0480] -CO-, -C(=O)-, and -C(O)- represent a carbonyl group, i.e.,

[0481] The carbon-based or hydrocarbyl group can be a saturated or unsaturated group. Unsaturated groups are, for example, aryl, alkenyl, or alkynyl groups. The carbon-based or hydrocarbyl group having more than 3 C atoms can be straight-chain, branched, and / or cyclic and can also contain spiro linkages or fused rings.

[0482] The terms "alkyl", "aryl", "heteroaryl", etc. also include polyvalent groups such as alkylene, arylene, heteroarylene, etc.

[0483] The term "aryl" means an aromatic carbon group or a group derived therefrom. The term "heteroaryl" means an "aryl" as defined above that contains one or more heteroatoms (preferably selected from N, O, S, Se, Te, Si, and Ge).

[0484] In this text, the alkyl group is straight-chain or branched and has 1 to 15 C atoms, preferably straight-chain and, unless otherwise specified, has 1, 2, 3, 4, 5, 6, or 7 C atoms, and is therefore preferably methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, or n-heptyl.

[0485] In this text, the branched alkyl group is an alkyl group having secondary and / or tertiary carbon atoms, preferably secondary carbon atoms, and is preferably isopropyl, s-butyl, isobutyl, isopentyl, 2-methylhexyl, or 2-ethylhexyl, 2-methylpropyl, 2-pentyl, 3-pentyl, 2-methylbutyl, 3-methylbutyl.

[0486] In this text, cycloalkyl refers to an alicyclic group or an alkyl group in which a methylene group is replaced by an alicyclic group (i.e., cycloalkylalkyl or alkylcycloalkylalkyl), which can be saturated or partially unsaturated, and preferably represents cyclopropyl, methylcyclopropyl, cyclobutyl, methylcyclobutyl, cyclopentyl, methylcyclopentyl, cyclopent-1-enyl, cyclopropylmethyl, cyclopropylethyl, cyclobutylmethyl, cyclobutylethyl, cyclopentylmethyl, cyclopentylethyl, cyclopent-1-enylmethyl.

[0487] In the present text, the alkoxy group is straight-chain or branched and contains 1 to 15 C atoms. It is preferably straight-chain and, unless otherwise stated, has 1, 2, 3, 4, 5, 6 or 7 C atoms, and is thus preferably methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, n-hexyloxy or n-heptyloxy.

[0488] In the present text, the alkenyl group is preferably an alkenyl group having 2 to 15 C atoms, which is straight-chain or branched and contains at least one C═C double bond. It is preferably straight-chain and has 2 to 7 C atoms. It is thus preferably vinyl, prop-1- or -2-enyl, but-1-, -2- or -3-enyl, pent-1-, -2-, -3- or -4-enyl, hex-1-, -2-, -3-, -4- or -5-enyl, hept-1-, -2-, -3-, -4-, -5- or -6-enyl. If the two C atoms of the C═C double bond are substituted, the alkenyl group can be in the form of E and / or Z isomers (trans / cis). Generally, the corresponding E isomer is preferred. Among the alkenyl groups, prop-2-enyl, but-2- and but-3-enyl, pent-3- and pent-4-enyl are particularly preferred.

[0489] In the present text, the alkynyl group refers to an alkynyl group having 2 to 15 C atoms, which is straight-chain or branched and contains at least one C≡C triple bond. 1- and 2-propynyl and 1-, 2- and 3-butynyl are preferred.

[0490] The preferred carbon-based and hydrocarbon-based groups are optionally substituted, straight-chain, branched or cyclic alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy and alkoxycarbonyloxy groups having 1 to 40, preferably 1 to 20, very preferably 1 to 12 C atoms, optionally substituted aryl or aryloxy groups having 5 to 30, preferably 6 to 25 C atoms, or optionally substituted alkylaryl, aralkyl, alkylaryloxy, arylalkyloxy, arylcarbonyl, aryloxycarbonyl, arylcarbonyloxy and aryloxycarbonyloxy groups having 5 to 30, preferably 6 to 25 C atoms, where one or more C atoms can also be replaced by heteroatoms (preferably selected from N, O, S, Se, Te, Si and Ge).

[0491] Further preferred carbon-based and hydrocarbon-based groups are C 1 -C 20 alkyl, C 2 -C 20 alkenyl, C 2 -C 20 alkynyl, C 3 -C 20 allyl, C 4 -C 20 alkyl-dienyl, C 4 -C 20 poly-alkenyl, C6 -C 20 cycloalkyl, C 4 -C 15 cycloalkenyl, C 6 -C 30 aryl, C 6 -C 30 alkylaryl, C 6 -C 30 aralkyl, C 6 -C 30 alkylaryloxy, C 6 -C 30 arylalkyloxy, C 2 -C 30 heteroaryl, C 2 -C 30 heteroaryloxy.

[0492] Particularly preferred are C 1 -C 12 alkyl, C 2 -C 12 alkenyl, C 2 -C 12 alkynyl, C 6 -C 25 aryl and C 2 -C 25 heteroaryl.

[0493] Further preferred carbon-based and hydrocarbon-based groups are straight-chain, branched-chain or cyclic alkyl groups having 1 - 20, preferably 1 - 12 C atoms, which are unsubstituted or mono- or polysubstituted by F, Cl, Br, I or CN, and in which one or more non-adjacent CH 2 groups can each independently of one another be replaced by -C(R x )=C(R x )-, -C≡C-, -N(R x )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and / or S atoms are not directly linked to one another.

[0494] R x preferably represents H, F, Cl, CN, a straight-chain, branched-chain or cyclic alkyl chain having 1 to 25 C atoms, in which furthermore one or more non-adjacent C atoms can be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, and in which one or more H atoms can be replaced by F or Cl, or represents an optionally substituted aryl or aryloxy group having 6 to 30 C atoms, or an optionally substituted heteroaryl or heteroaryloxy group having 2 to 30 C atoms.

[0495] Preferred alkyl groups are, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 2-methylbutyl, n-pentyl, sec-pentyl, cyclopentyl, n-hexyl, cyclohexyl, 2-ethylhexyl, n-heptyl, cycloheptyl, n-octyl, cyclooctyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, dodecyl, trifluoromethyl, perfluorobutyl, 2,2,2-trifluoroethyl, perfluorooctyl, perfluorohexyl, etc.

[0496] Preferred alkenyl groups are, for example, vinyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl, cyclooctenyl, etc.

[0497] Preferred alkynyl groups are, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl, octynyl, etc.

[0498] Preferred alkoxy groups are, for example, methoxy, ethoxy, 2-methoxyethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, 2-methylbutoxy, n-pentyloxy, n-hexyloxy, n-heptyloxy, n-octyloxy, n-nonyloxy, n-decyloxy, n-undecyloxy, n-dodecyloxy, etc.

[0499] Preferred amino groups are, for example, dimethylamino, methylamino, methylphenylamino, phenylamino, etc.

[0500] Aryl groups and heteroaryl groups can be monocyclic or polycyclic, i.e., they can contain one ring (e.g., phenyl) or two or more rings, which can also be fused (e.g., naphthyl) or covalently bonded (e.g., biphenyl), or contain a combination of fused and linked rings. Heteroaryl contains one or more heteroatoms, preferably selected from O, N, S, and Se.

[0501] Particularly preferred are mono-, bi- or tricyclic aryls having 6 - 25 C atoms and mono-, bi- or tricyclic heteroaryls having 5 - 25 ring atoms, which optionally contain fused rings and are optionally substituted. Further preferred are 5-, 6- or 7-membered aryls and heteroaryls, wherein additionally, one or more CH groups can be replaced by N, S or O in such a way that O atoms and / or S atoms are not directly connected to each other.

[0502] Preferred aryl groups are, for example, phenyl, biphenyl, terphenyl, [1,1':3',1”]-terphenyl-2'-yl, naphthyl, anthracenyl, binaphthyl, phenanthryl, 9,10-dihydro-phenanthryl, pyrene, dihydropyrene, picene, tetracene, pentacene, benzopyrene, fluorene, indene, indenofluorene, spirobifluorene, etc.

[0503] Preferred heteroaryl groups are, for example, 5-membered rings such as pyrrole, pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, tetrazole, furan, thiophene, selenophene, oxazole, isoxazole, 1,2-thiazole, 1,3-thiazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole, 1,3,4-thiadiazole, 6-membered rings such as pyridine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, 1,2,4-triazine, 1,2,3-triazine, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine, 1,2,3,5-tetrazine or fused groups such as indole, isoindole, indolizine, indazole, benzimidazole, benzotriazole, purine, naphthimidazole, phenanthrimidazole, pyridinimidazole, pyrazinimidazole, quinoxalinimidazole, benzoxazole, naphthoxazole, anthroxazole, phenanthroxazole, isoxazole, benzothiazole, benzofuran, isobenzofuran, dibenzofuran, quinoline, isoquinoline, pteridine, benzo-5,6-quinoline, benzo-6,7-quinoline, benzo-7,8-quinoline, benzoisoquinoline, acridine, phenothiazine, phenoxazine, benzopyridazine, benzopyrimidine, quinoxaline, phenazine, naphthyridine, azacarbazole, benzocarbazole, phenanthridine, phenanthroline, thiophene[2,3b]thiophene, thiophene[3,2b]thiophene, dithienothiophene, isobenzothiophene, dibenzothiophene, benzothiophene, benzothiadiazolethiophene, or combinations of these groups.

[0504] Aryl and heteroaryl groups mentioned in the context may also be substituted by alkyl, alkoxy, thioalkyl, fluorine, fluoroalkyl or other aryl or heteroaryl groups.

[0505] (Non-aromatic) alicyclic groups and heterocyclic groups include both saturated rings, i.e., rings containing only single bonds, and partially unsaturated rings, i.e., those that may also contain multiple bonds. The heterocycle contains one or more heteroatoms, preferably selected from Si, O, N, S and Se.

[0506] (Non-aromatic) alicyclic groups and heterocyclic groups may be monocyclic, i.e., containing only one ring (e.g., cyclohexane), or polycyclic, i.e., containing multiple rings (e.g., decalin or bicyclooctane). Saturated groups are particularly preferred. Also preferred are mono-, bi- or tricyclic groups having 5-25 ring atoms, which optionally contain fused rings and are optionally substituted. Further preferred are 5-, 6-, 7- or 8-membered carbocyclic groups, wherein, additionally, one or more C atoms may be replaced by Si and / or one or more CH groups may be replaced by N and / or one or more non-adjacent CH 2 groups may be replaced by -O- and / or -S-.

[0507] Preferred alicyclic and heterocyclic groups are, for example, 5-membered groups such as cyclopentane, tetrahydrofuran, tetrahydrothiophene, pyrrolidine; 6-membered groups such as cyclohexane, silinane, cyclohexene, tetrahydropyran, tetrahydrothiopyran, 1,3-dioxane, 1,3-dithiane, piperidine; 7-membered groups such as cycloheptane; and fused groups such as tetralin, decalin, indane, bicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl, octahydro-4,7-methanoindane-2,5-diyl.

[0508] Preferred substituents are, for example, solubility enhancing groups such as alkyl or alkoxy; electron withdrawing groups such as fluorine, nitro or nitrile; or substituents for increasing the glass transition temperature (Tg) of the polymer, especially bulky groups such as tert-butyl or optionally substituted aryl.

[0509] Preferred substituents, also referred to hereinafter as "L", are, for example, F, Cl, Br, I, -CN, -NO 2 , NCO, -NCS, -OCN, -SCN, -C(=O)N(R x ) 2 , -C(=O)Y 1 , -C(=O)R x , -N(R x ) 2 , straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 - 25 C atoms, where one or more H atoms may optionally be replaced by F or Cl, optionally substituted silyl having 1 to 20 Si atoms, or optionally substituted aryl having 6 to 25, preferably 6 to 15 C atoms.

[0510] where R x represents H, F, Cl, CN, or straight-chain, branched or cyclic alkyl having 1 to 25 C atoms, where one or more non-adjacent CH 2 -groups are optionally replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O- and / or S-atoms are not directly linked to each other, and where one or more H atoms are each optionally replaced by F, Cl, P- or P-Sp-, and

[0511] Y 1 represents halogen.

[0512] "Substituted silyl or aryl" preferably means that it is substituted by halogen, -CN, R 0 , -OR 0 , -CO-R0 、 -CO-O-R 0 、 -O-CO-R 0 or -O-CO-O-R 0 substituted, where R 0 represents H or an alkyl group having 1 to 20 C atoms.

[0513] Particularly preferred substituents L are, for example, F, Cl, CN, NO 2 、CH 3 、C 2 H 5 、OCH 3 、OC 2 H 5 、COCH 3 、COC 2 H 5 、COOCH 3 、COOC 2 H 5 、CF 3 、OCF 3 、OCHF 2 、OC 2 F 5 and in addition phenyl.

[0514] The LC medium according to the invention can additionally contain one or more other components or additives, preferably selected from the list including but not limited to the following: comonomers, polymerization initiators, inhibitors, stabilizers, surfactants, wetting agents, lubricants, dispersants, water repellents, binders, flow improvers, defoamers, degassing agents, diluents, reactive diluents, auxiliaries, colorants, dyes, pigments and nanoparticles.

[0515] The LC medium according to the invention can contain one, two or three chiral dopants, preferably one chiral dopant.

[0516] The following lists the preferred embodiments, either alone or in combination. The medium according to the invention preferably contains

[0517] - a compound of formula I, the concentration of which is in the range of 2% - 20%, preferably 3% - 16%, very preferably 3% - 14%;

[0518] - a compound of formula IV-2, the concentration of which is in the range of 4% - 20%, preferably 5% - 15%, very preferably 6% - 12%;

[0519] - a compound of formula ST-1, the concentration of which is in the range of 0.11% - 0.85%, preferably 0.15% - 0.40%, very preferably 0.16% - 0.30%, or other combinations of these boundaries;

[0520] - A compound of formula H, preferably a compound of formula H-A, more preferably a compound of formula H-1, with a concentration in the range of 0.008% - 0.08%, preferably 0.012% - 0.06%, very preferably 0.015% - 0.04%;

[0521] - One or more compounds of formulae IIA, IIB, IIC, IID, IIE and III, with a total concentration in the range of 68% - 88%, more preferably 70% - 85%, very preferably 71% - 83%;

[0522] - One, two, three or more compounds of formula III, preferably a compound of formula III-1 and / or III-2, more preferably a compound of formula III-2, with a total concentration in the range of 0% - 15%, more preferably 1% - 12%, very preferably 2% - 10%, especially 3% - 8%;

[0523] - One or more compounds of formula IIA, with a total concentration in the range of 15% - 50%, more preferably 15% - 45%, very preferably 35% - 43% or 20% - 25%;

[0524] - One or more compounds of formula IIA-2, with a total concentration in the range of 3% - 18%, more preferably 5% - 16%, very preferably 5% - 16%;

[0525] - One or more compounds of formula IIA-10, with a total concentration in the range of 10% - 32%, more preferably 12% - 30%, very preferably 13% - 29%;

[0526] - One or more compounds selected from formula IIC, more preferably compounds of formula IIC-1 and IIC-2, preferably a compound of formula IIC-1, with a total concentration in the range of 1% - 25%, more preferably 4% - 25%, very preferably 8% - 22%;

[0527] - One or more compounds of formula IIE, preferably a compound of formula IIE-1, with a total concentration in the range of 1% - 18%, more preferably 2% - 15%, very preferably 3% - 12%;

[0528] - One or more compounds of formula IIB, preferably compounds of formula IIB-2 and / or IIB-10, with a total concentration in the range of 7% - 30%, more preferably 8% - 27%, very preferably 9% - 26%;

[0529] - One or more compounds of formula IIB-2, with a total concentration in the range of 7% - 30%, more preferably 8% - 27%, very preferably 9% - 26%;

[0530] -One or more compounds of formula I IA and one or more compounds of formula I IB, preferably selected from formula I IA-2, I IA-10, I IB-2 and I IB-10, preferably with a total concentration in the range of 44% - 70%, more preferably 45% - 68%, very preferably 40% - 67%;

[0531] -One or more compounds of formula IV-1, preferably compound IV-1-3, with a total concentration in the range of 1% - 15%, more preferably 2% - 12%, very preferably 5% - 12%;

[0532] -One or more compounds of formula IV-3, preferably compounds of formula IV-3-2 and / or IV-3-5, with a total concentration in the range of 1% - 25%, more preferably 2% - 20%, very preferably 3% - 16%;

[0533] -Two or more compounds of formula I and formula IV, with a total concentration in the range of 18% - 30%, more preferably 19% - 25%, very preferably 20% - 24%;

[0534] -Two or more compounds of formula I and compounds of formula IV and compounds of formula V, with a total concentration in the range of 20% - 30%, more preferably 20% - 28%, very preferably 20% - 27%, especially 21% - 27%;

[0535] Particularly preferred mixture concepts are as follows: (The acronyms used are explained in Tables A - D. Here, n and m each independently represent 1 - 6).

[0536] The mixture according to the invention preferably comprises

[0537] -PYP-n-m, especially PYP-2-3 and / or PYP-2-4,

[0538] preferably with a concentration > 5%, especially 8 - 30%, based on the entire mixture,

[0539] and / or

[0540] -CPY-n-Om, especially CPY-2-O2, CPY-3-O2 and / or CPY-5-O2, preferably with a concentration > 5%, especially 10 - 30%, based on the entire mixture,

[0541] and / or

[0542] -B-nO-Om and / or B(S)-nO-Om, preferably with a concentration of 1 - 15%,

[0543] and / or

[0544] -CY-n-Om, preferably CY-3-O2, CY-3-O4, CY-5-O2 and / or CY-5-O4, preferably at a concentration > 5%, in particular 15 - 50%, based on the entire mixture,

[0545] and / or

[0546] -CCY-n-Om, preferably CCY-4-O2, CCY-3-O2, CCY-3-O3, CCY-3-O1 and / or CCY-5-O2, preferably at a concentration > 5%, in particular 10 - 30%, based on the entire mixture,

[0547] and / or

[0548] -CLY-n-Om, preferably CLY-2-O4, CLY-3-O2 and / or CLY-3-O3, preferably at a concentration > 5%, in particular 10 - 30%, based on the entire mixture,

[0549] and / or

[0550] -LY-n-Om, preferably LY-3-O2, preferably at a concentration > 5%, in particular 10 - 30%, based on the entire mixture,

[0551] and / or

[0552] -CCOY-n-Om, preferably CCOY-3-O2, preferably at a concentration > 5%, in particular 10 - 30%, based on the entire mixture,

[0553] and / or

[0554] -CLOY-n-Om, preferably CLOY-3-O2, preferably at a concentration > 5%, in particular 10 - 30%, based on the entire mixture.

[0555] For the liquid crystal medium according to the invention it is advantageous to preferably have a nematic phase with ≤ -20 °C to ≥ 90 °C, particularly preferably ≤ -30 °C to ≥ 100 °C, very particularly preferably ≤ -40 °C to ≥ 105 °C.

[0556] In a preferred embodiment, the medium according to the invention has a clearing temperature (clear point) of 90 °C or higher, preferably 100 °C or higher, and in particular 105 °C or higher.

[0557] In this text, the statement "having a nematic phase at a given temperature" means that no smectic phase and no crystallization are observed at low temperatures and, on the other hand, that no clearing (phase transition to the isotropic phase) occurs when the nematic phase is heated at the given temperature. The low-temperature studies are carried out in a flow viscometer at the corresponding temperature and are checked by storing in a test cell having a layer thickness corresponding to electro-optical use for at least 100 hours. If the storage stability in the 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 the temperatures of -30 °C and -40 °C, the corresponding times are 500 hours and 250 hours, respectively. At high temperatures, the clearing point is measured in a capillary by conventional methods.

[0558] The liquid-crystal mixture preferably has a nematic range of at least 60 K and a flow viscosity ν of at most 30 mm 2 ×s -1 at 20 °C. 20 .

[0559] The mixture is nematic at -20 °C or lower, preferably at -30 °C or lower, very preferably at -40 °C or lower.

[0560] The birefringence of the medium according to the invention is in the range from 0.085 to 0.170, preferably from 0.13 to 0.16, in particular from 0.14 to 0.16.

[0561] In a preferred embodiment, the birefringence of the medium is from 0.1480 to 0.155, preferably from 0.147 to 0.153, in particular from 0.158 to 0.152.

[0562] In a preferred embodiment, the dielectric anisotropy Δε of the medium according to the invention is from -2.5 to -6.0, preferably from -2.8 to -4.7, in particular from -3.5 to -4.5,

[0563] In a very preferred embodiment, the dielectric anisotropy Δε of the liquid-crystal mixture according to the invention is from -3.8 to -4.2.

[0564] The rotational viscosity γ at 20 °C 1 is preferably in the range from 90 to 300 mPa·s, more preferably from 100 to 290 mPa·s.

[0565] The elastic constant K of the medium according to the invention 1 is in the range from 16 to 20 pN.

[0566] In a preferred embodiment, the ratio γ 1 / K 1 of the rotational viscosity to the splay elastic constant of the medium according to the invention -1 is 15 mPa·s pN or less.

[0567] According to the present invention, the liquid crystal medium has a relatively low threshold voltage (V 0 ) value. They are preferably in the range from 1.7 V to 3.0 V, particularly preferably ≤2.6 V and very particularly preferably ≤2.4 V.

[0568] For the present invention, unless otherwise explicitly stated, the term "threshold voltage" relates to the capacitive threshold (V 0 ), also known as the Freedericks threshold.

[0569] Furthermore, the liquid crystal medium of the present invention has a high voltage holding ratio value in the liquid crystal cell.

[0570] Generally, liquid crystal media with low addressing voltage or threshold voltage show lower voltage holding ratios than those LC media with higher addressing voltage or threshold voltage, and vice versa.

[0571] For the present invention, the term "dielectrically positive compound" denotes a compound having Δε > 1.5, the term "dielectrically neutral compound" denotes those having -1.5 ≤ Δε ≤ 1.5 and the term "dielectrically negative compound" denotes those having Δε < -1.5. Here, the dielectric anisotropy of the compound is determined by dissolving 10% of the compound in a liquid crystal host in at least one test cell and measuring the capacitance of the resulting mixture, the test cell having a layer thickness of 20 μm and homeotropic and planar surface alignments at 1 kHz in each case. The measuring voltage is generally 0.5 V - 1.0 V, but always below the capacitance threshold of the respective liquid crystal mixture under investigation.

[0572] All temperature values according to the present invention are in °C.

[0573] The mixtures according to the present invention are suitable for all VA - TFT applications, such as VAN, MVA, (S)-PVA, ASV, PSA (polymer stabilized VA) and PS - VA (polymer stabilized VA). Furthermore, they are also suitable for IPS (in - plane switching) and FFS (fringe field switching) applications with negative Δε.

[0574] The mixtures are also particularly suitable for VA - TFT applications of the LCoS type, more preferably LCoS microdisplays. An LCoS microdisplay is a reflective display which typically comprises a liquid crystal layer with a nematic structure between a silicon backplane and a cover glass. The silicon backplane is a pixel array, each pixel having a mirror which also serves as an electrical conductor. Each pixel comprises a fixed mirror covered by an active liquid crystal layer having a twisted nematic alignment which can be switched between homeotropic and planar alignment by applying a voltage. LCoS microdisplays are very small, typically having a diagonal of less than 1.0 inch, but still having a high resolution.

[0575] Due to the small pixel size, the cell thickness of LCoS displays is also very small, typically around 1 micrometer. Therefore, the liquid crystal phases used in these displays must have high optical anisotropy Δn values, compared to conventional reflective LC displays which usually require liquid crystal phases with low Δn.

[0576] In a preferred embodiment, the LCoS panel according to the present invention comprises an inorganic alignment layer, more preferably a vertical alignment layer for vertical alignment of the liquid crystal medium. Most preferably, SiO x Alignment layer. This inorganic alignment layer is particularly suitable for LCoS panels.

[0577] It goes without saying to the person skilled in the art that the VA, IPS or FFS mixtures according to the invention can also contain compounds in which H, N, O, Cl, F are replaced by corresponding isotopes, such as deuterium.

[0578] The compounds according to the invention can be synthesized by or in a manner analogous to known methods described in the literature (e.g. in standard works such as Houben-Weyl, Methoden der Organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart) under reaction conditions known and suitable for the reaction. Variants known per se but not mentioned here can also be used here. In particular, they can be prepared as described in the following reaction schemes or in an analogous manner. Other methods for preparing the compounds of the invention can be obtained from the examples.

[0579] In the media according to the invention, it is also possible and advantageous to use further mesogenic compounds which have not been explicitly mentioned above. These compounds are known to those skilled in the art.

[0580] For the present invention and in the following examples, the structures of the liquid-crystal compounds are indicated with the aid of abbreviations, which are converted into chemical formulae according to the following Tables A to C. m H 2m+1 , C n H 2n+1 and C l H 2l+1 or C m H 2m-1 , C n H 2n-1 and C l H 2l-1is a straight-chain alkyl group or an alkylene group, each having n, m, and l carbon atoms in each case. Preferably, n, m, and l are each independently 1, 2, 3, 4, 5, 6, or 7. Table A shows the codes for the ring elements of the compound nucleus, Table B lists the bridging units, and Table C lists the symbolic meanings of the left- and right-hand end groups of the molecule. The abbreviations consist of the code for the ring element with an optional linking group, followed by a first hyphen and the left-hand end group code, and a second hyphen and the right-hand end group code. Table D shows the exemplary structures of the compounds and their respective abbreviations.

[0581] Table A: Ring elements

[0582]

[0583]

[0584]

[0585]

[0586] Table B: Bridging units

[0587]

[0588] Table C: End groups

[0589]

[0590]

[0591] where n and m are each integers, and the three dots "..." are placeholders for other abbreviations from the table.

[0592] In addition to the compounds of formulae IV-2, I, and ST-1, the mixtures according to the invention optionally contain one or more compounds from Table D.

[0593] The following abbreviations are used, where:

[0594] (n, m, k, and l are each independently integers, preferably 1-9, preferably 1-7, k and l may also be 0 and are preferably 0-4, more preferably 0 or 2, and most preferably 2, n is preferably 1, 2, 3, 4, or 5, and in the combination "-nO-", it is preferably 1, 2, 3, or 4, preferably 2 or 4, m is preferably 1, 2, 3, 4, or 5, and in the combination "-Om", it is preferably 1, 2, 3, or 4, more preferably 2 or 4. The combination "-lVm" is preferably "2V1").

[0595] Table D

[0596] The following illustrative structures are examples and compounds which are preferably additionally used in a medium:

[0597]

[0598]

[0599]

[0600]

[0601]

[0602]

[0603]

[0604]

[0605]

[0606]

[0607]

[0608]

[0609]

[0610]

[0611]

[0612]

[0613]

[0614]

[0615]

[0616] Table E shows the chiral dopants preferably used in the mixtures according to the present invention.

[0617] Table E

[0618]

[0619]

[0620]

[0621] In a preferred embodiment of the present invention, the medium according to the present invention comprises one or more compounds selected from Table E. Detailed Description of the Invention

[0622] Examples

[0623] The present invention is described in detail by the following non-limiting working examples.

[0624] The following abbreviations and symbols are used:

[0625] V 0 Represents the threshold voltage at 20 °C, capacitive [V],

[0626] n e Represents the extraordinary refractive index at 20 °C and 589 nm,

[0627] n o Represents the ordinary refractive index at 20 °C and 589 nm,

[0628] Δn represents the optical anisotropy at 20 °C and 589 nm,

[0629] ε ⊥ Represents the dielectric constant perpendicular to the director at 20 °C and 1 kHz,

[0630] ε ‖ Represents the dielectric constant parallel to the director at 20 °C and 1 kHz,

[0631] Δε represents the dielectric anisotropy at 20 °C and 1 kHz,

[0632] cl.p., T(N,I) represents the clearing point [°C],

[0633] γ 1 Represents the rotational viscosity at 20 °C [mPa×s],

[0634] K 1 Represents the elastic constant at 20 °C, "splay" deformation [pN],

[0635] K 2 Represents the elastic constant at 20 °C, "twist" deformation [pN],

[0636] K 3 Represents the elastic constant at 20 °C, "bend" deformation [pN].

[0637] Unless otherwise explicitly stated, all concentrations in this application are given as weight percentages and refer to the corresponding entire mixture, which includes all solid or liquid crystal components (without solvent).

[0638] Unless otherwise stated, all temperature values indicated in this application, such as the melting point T(C,N), the transition from the smectic phase (S) to the nematic phase (N) T(S,N), and the clearing point T(N,I), are expressed in degrees Celsius (°C). M.p. represents the melting point and cl.p. = the clearing point. In addition, C = liquid crystal phase, N = nematic phase, S = smectic phase, and I = isotropic phase. The data between these symbols represent transition temperatures.

[0639] All physical properties are and have been determined according to "Merck Liquid Crystals, Physical Properties of Liquid Crystals" Status November 1997, Merck KGaA, Germany, and apply to a temperature of 20 °C, and Δn is measured at 589 nm and Δε is measured at 1 kHz, unless otherwise explicitly stated in each case.

[0640] The term "threshold voltage" used in the present invention relates to the capacitive threshold (V 0 ), which is also referred to as the Freedericks threshold, unless otherwise stated. In the examples, the optical threshold is also given as usual for a relative contrast of 10% (V 10 ).

[0641] Unless otherwise stated, the test cells are prepared and their electro-optical and other properties are measured by the methods described below or similar methods.

[0642] The display for measuring the capacitive threshold voltage consists of two plane-parallel glass outer plates with a distance of 25 μm between them. Each outer plate has an electrode layer on the inner side and an unrubbed polyimide alignment layer on the top, which results in a homeotropic alignment of the liquid crystal molecules.

[0643] Unless otherwise stated, VHR is measured at 20 °C (VHR 20 ) and after being placed in an oven at 100 °C for 5 minutes (VHR 100 ) in a commercially available instrument Model LCM-1 (O0004) from TOYO Corporation, Japan. Unless otherwise more precisely stated, the frequency range of the applied voltage is from 1 Hz to 60 Hz.

[0644] The stability to ultraviolet irradiation is studied in a commercially available instrument "Suntest CPS+" from Heraeus, Germany using a xenon lamp NXE1500B. Unless otherwise explicitly stated, the sealed test cells are irradiated for 2.0 hours without additional heating. The radiation power in the wavelength range of 300 nm to 800 nm is 765 W / m 2V. A UV “cut-off” filter with an edge wavelength of 310 nm was used to simulate the so-called window glass mode. In each series of experiments, at least four test cells were studied for each condition, and the corresponding results were expressed as the average of the corresponding individual measurements.

[0645] To study the low temperature stability (also known as “LTS”), i.e., the stability of the liquid crystal mixture in the bulk against spontaneous crystallization of individual components or the appearance of the smectic phase (as the case may be) at low temperatures, several sealed vials (each containing approximately 1 g of material) were stored at one or more given temperatures, typically -10 °C, -20 °C, -30 °C, and / or -40 °C, and visually inspected regularly for the occurrence of phase transitions. Once a change was observed in the first sample at a given temperature, the time was recorded. The time until no change was observed at the last inspection was recorded as the corresponding LTS.

[0646] The ion density required for calculating the resistivity was measured using a commercially available LC Material Characteristics Measurement System Model 6254 from Toyo Corporation, Japan, with a cell gap of 3.2 μm and a VHR test cell with AL16301 Polyimide (JSR Corp., Japan). The measurement was carried out after storing in an oven at 60 °C or 100 °C for 5 minutes.

[0647] The clearing point was measured using a Mettler Thermosystem FP900. The optical anisotropy (Δn) was measured using an Abbe Refractometer H005 (Natrium-spectral lamp Na10, 589 nm, 20 °C). The dielectric anisotropy (Δε) was measured using an LCR-Meter E4980A / Agilent (G005) at 20 °C (ε-parallel cell with JALS2096-R1). The threshold voltage (V 0 ) was measured using an LCR-Meter E4980A / Agilent (G005) at 20 °C (ε-parallel cell with JALS2096-R1). The rotational viscosity (γ 1 ) was measured using a TOYO LCM-2 (0002) at 20 °C (γ1 negative cell with JALS2096-R1). The elastic constant (K 1 , splay) was measured using an LCR-Meter E4980A / Agilent (G005) at 20 °C (ε-parallel cell with JALS2096-R1). K 3 : The elastic constant (K 3, Bending was measured at 20 °C using an LCR-Meter E4980A / Agilent (G005) (ε-parallel cell with JALS2096-R1).

[0648] The following mixture examples with negative dielectric anisotropy are particularly suitable for vertically aligned liquid crystal displays.

[0649] Mixture examples

[0650] The stabilizing compounds used are as follows, with their abbreviations as follows:

[0651]

[0652]

[0653] The nematic LC mixtures M1 to M41 have the compositions and physical properties given in the following table: Matrix mixture M1

[0654]

[0655]

[0656] Example mixture M2

[0657]

[0658] Example mixture M3

[0659]

[0660] Matrix mixture M4

[0661]

[0662] Example mixture M5

[0663]

[0664] Matrix mixture M6

[0665]

[0666] Example mixture M7

[0667]

[0668]

[0669] Matrix mixture M8

[0670]

[0671] Example mixture M9

[0672]

[0673]

[0674] Matrix mixture M10

[0675]

[0676] Example mixture M11

[0677]

[0678]

[0679] Matrix mixture M12

[0680]

[0681] Example mixture M13

[0682]

[0683]

[0684] Example mixture M14

[0685]

[0686] Matrix mixture M15

[0687]

[0688]

[0689] Example mixture M16

[0690]

[0691] Matrix mixture M17

[0692]

[0693]

[0694] Example mixture M18

[0695]

[0696] Matrix mixture M19

[0697]

[0698]

[0699] Example mixture M20

[0700]

[0701] Matrix mixture M21

[0702]

[0703]

[0704] Example mixture M22

[0705]

[0706] Example mixture M23

[0707]

[0708]

[0709] Matrix mixture M24

[0710]

[0711] Example mixture M25

[0712]

[0713]

[0714] Matrix mixture M26

[0715]

[0716] Example mixture M27

[0717]

[0718]

[0719] Matrix mixture M28

[0720]

[0721] Example mixture M29

[0722]

[0723]

[0724] Example mixture M30

[0725]

[0726] Matrix mixture M31

[0727]

[0728]

[0729] Example mixture M32

[0730]

[0731] Example mixture M33

[0732]

[0733]

[0734] Matrix mixture M34

[0735]

[0736] Example mixture M35

[0737]

[0738]

[0739] Matrix mixture M36

[0740]

[0741] Example mixture M37

[0742]

[0743]

[0744] Matrix mixture M38

[0745]

[0746] Example mixture M39

[0747]

[0748]

[0749] Example mixture M40

[0750]

[0751] Example mixture M41

[0752]

[0753]

[0754] Example mixture M42

[0755]

[0756]

[0757] Stability test

[0758] Place the mixture of the above embodiments in a test cell or a similar LCoS panel having an inorganic alignment (SiO x ) layer. Test the device under forced temperature and light (stress test blue light, >45 W / cm 2 , 70 °C). Avoid the appearance of air bubbles and dark spots over a long period of time. It is found that the alignment of the mixture is stable for a long time under these conditions. The practical use stability of the mixture in LCoS is improved compared to traditional mixtures.

Claims

1. A liquid crystal on silicon (LCoS) panel comprising: a semiconductor substrate having a plurality of reflective electrodes, a transparent substrate including a transparent electrode assembled with the semiconductor substrate, and a liquid crystal layer arranged between the semiconductor substrate and the transparent substrate, The liquid crystal layer comprises a liquid crystal medium, and the liquid crystal medium comprises a) one or more compounds of formula IV in R 41 represents an unsubstituted alkyl group having 1 to 7 C atoms or an unsubstituted alkenyl group having 2 to 7 C atoms, and R 42 represents an unsubstituted alkyl group having 1 to 7 C atoms, an unsubstituted alkoxy group having 1 to 6 C atoms, or an unsubstituted alkenyl group having 2 to 7 C atoms, Wherein one or more compounds of formula IV are selected from formula IV-2, in Alkyl represents an alkyl group having 1 to 7 C atoms, and Alkoxy represents an alkoxy group having 1 to 5 carbon atoms.

2. The LCoS panel according to claim 1, comprising one or more inorganic alignment layers.

3. The LCoS panel according to claim 1 or 2, wherein the clearing point of the liquid crystal medium is 90°C or higher.

4. LCoS panel according to one or more of claims 1 to 3, wherein the liquid crystal medium is aligned homeotropically with respect to the substrate.

5. A liquid crystal medium comprising a) one or more compounds of formula IV in R 41 represents an unsubstituted alkyl group having 1 to 7 C atoms or an unsubstituted alkenyl group having 2 to 7 C atoms, and R 42 represents an unsubstituted alkyl group having 1 to 7 C atoms, an unsubstituted alkoxy group having 1 to 6 C atoms or an unsubstituted alkenyl group having 2 to 7 C atoms, Wherein one or more compounds of formula IV are selected from formula IV-2, in Alkyl represents an alkyl group having 1 to 7 C atoms, Alkoxy represents an alkoxy group having 1 to 5 carbon atoms, b) one or more compounds of formula I in R 11 represents an alkyl radical having 1 to 7 C atoms, an alkoxy radical having 1 to 7 C atoms or an alkoxyalkyl radical, an alkenyl radical or an alkenyloxy radical having 2 to 7 C atoms, wherein in addition, one or more CH2 radicals in these radicals may each independently of one another be Instead, R 12 represents an alkyl group having 1 to 7 C atoms, an alkoxy group having 1 to 7 C atoms or an alkoxyalkyl group, an alkenyl group or an alkenyloxy group having 2 to 7 C atoms, and c) 0.1% to 0.9% of one or more compounds of formula ST-1 in R ST represents H, alkyl or alkoxy having 1 to 15 C atoms, wherein in addition, one or more CH2 groups in these groups can each independently of one another be replaced by -C≡C-, -CF2O-, -OCF2-, -CH=CH-, -O-, -CO-O- or -O-CO- are substituted in such a way that the O atoms are not directly connected to one another, and wherein in addition one or more H atoms may be replaced by halogen, In each occurrence, the same or different or Z ST each independently represents -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 p represents 0, 1 or 2.

6. Liquid-crystalline medium according to claim 5, wherein the medium comprises one or more compounds of the formula selected from d) and e): d) Formulas IIA, IIB, IIC, IID and IIE, in R 2A , R 2B , R 2C , R 2D , R 2E1 and R 2E2 Each independently of one another represents H, alkyl having 1 to 7 C atoms or alkenyl having 2 to 7 C atoms, each of which is unsubstituted or at least monosubstituted by halogen, wherein one or more CH2 groups in these groups may be replaced by -O-, -S-, -C≡C-, -CF2O-, -OCF2-, -OC-O- or -O-CO- are substituted in such a way that the O atoms are not directly connected to each other; L 1 and L 2 Each independently represents F, Cl, CF3 or CHF2; Y represents H, F, Cl, CF3, CHF2 or CH3; Z 2 , Z 2B and Z 2D Each independently represents a single bond, -CH2CH2-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -COO-, -OCO-; p means 0, 1 or 2 q represents 0 or 1, and v means 1, 2, 3, 4, 5 or 6; e) Formula III in R 31 and R 32 each independently of one another represents H, alkyl or alkoxy having 1 to 7 C atoms, wherein one or more CH2 groups in these groups can each independently of one another be -C≡C-, -CF2O-, -OCF2-, -CH=CH-, replaced by -O-, -CO-O- or -O-CO- in such a way that the O atoms are not directly connected to each other, and wherein one or more H atoms may be replaced by halogen, A 3 independently at each occurrence denotes 1,4-phenylene, in which one or two CH groups may be replaced by N, or 1,4-cyclohexylene or 1,4-cyclohexenylene, in which one or two non-adjacent CH2 groups may be replaced by -O- or -S-, The groups may be substituted singly or polysubstituted by halogen atoms. Z 3 represents, independently of one another, at each occurrence -CF2O-, -OCF2-, -CH2O-, -OCH2-, -CH2-, -CH2CH2-, -CH=CH-, -C≡C- or a single bond, L 31 and L 32 each independently represents F, Cl, CF3 or CHF2, W means O or S, and n represents 0, 1, or 2.

7. A liquid crystal medium according to claim 5 or 6, wherein the medium comprises one or more compounds of formula IIE in R 2E1 independently represents H, alkyl having 1 to 7 C atoms or alkenyl having 2 to 7 C atoms, each of which is unsubstituted or at least monosubstituted by halogen, wherein one or more CH2 groups in these groups may be replaced by -O-, -S-, -C≡C-, -CF2O-, -OCF2-, -OC-O- or -O-CO- are substituted in such a way that the O atoms are not directly connected to each other; R 2E2 independently represents an alkoxy or alkyl radical having 1 to 7 C atoms, or an alkenyl radical having 2 to 7 C atoms, each of which is unsubstituted or at least monosubstituted by halogen, wherein one or more CH2 radicals in these radicals may be Replacement; Y represents H, F, Cl, CF3, CHF2 or CH3; L 1 and L 2 Each independently of one another represents F, Cl, CF3 or CHF2.

8. A liquid-crystalline medium according to any one of claims 5 to 7, wherein the medium comprises one or more compounds of the formula H in A represents a q-valent aliphatic, aromatic or heteroaromatic hydrocarbon group having 1 to 40 C atoms, preferably 6 to 30 C atoms; or a bond when q=2; Sp represents a spacer group or a bond; HA means R S represents H, alkyl having 1 to 12 C atoms or alkenyl having 2 to 12 C atoms; Z S Indicates -O-, -C(O)O-, -(CH2) z -or-(CH2) z O- or a single bond; preferably -C(O)O-, R H Indicates H, O · , CH3, OH or OR S , preferably H or O · ; R S1 , R S2 , R S3 and R S4 represent, identically or differently, an alkyl radical having 1 to 6 C atoms, preferably having 1 to 3 C atoms, very preferably CH3, G stands for H or R S or group Z S -HA, z is an integer from 1 to 6, and q is 1, 2, 3 or 4, preferably 2.

9. Liquid-crystalline medium according to one or more of claims 5 to 8, wherein the medium comprises one or more compounds of the formula HA in A a represents an alkylene group having 1 to 12 carbon atoms, in which one or two CH2 groups may be replaced by 1,4-cyclohexylene, and R H Indicates H or O · .

10. Liquid-crystalline medium according to one or more of claims 5 to 9, wherein the medium comprises one or more compounds of the formulae IV-1 and IV-3, in Alkyl and alkyl' independently of one another denote an alkyl group having 1 to 7 C atoms, preferably 2 to 5 C atoms, Alkenyl is an alkenyl radical having 2 to 5 C atoms, preferably having 2 to 4 C atoms.

11. Liquid-crystalline medium according to one or more of claims 5 to 10, wherein the medium comprises one or more compounds of the formula P-1 in R P represents a straight-chain alkyl or alkoxy radical having 1 to 6 C atoms or an alkenyl radical having 2 to 6 C atoms, each of which is unsubstituted or at least monosubstituted by halogen, wherein one or more CH2 radicals in these radicals may be replaced by -O-, -S-, -C≡C-, -CF2O-, -OCF2-, -OC-O-, or -O-CO- are substituted in such a way that the O atoms are not directly connected to each other; X P represents a straight-chain alkyl group having 1 to 6 C atoms, F, Cl, CF3, OCF2H, OCF3, OCHFCF3, OCF2CHFCF3, OCH=CF2, preferably F, OCF3 or CF3, CH3, L P1 , L P2 and L P3 each independently represents H or F, and L P4 represents H or CH3, preferably H.

12. Liquid-crystalline medium according to one or more of claims 5 to 11, wherein the medium comprises one or more compounds of the formula PIII-1, in R 3 represents unsubstituted or halogenated straight-chain or branched alkyl radicals having 1 to 15 C atoms, wherein one or more CH2 radicals in these radicals may each independently be -C≡C-, -CF2O-, -CH=CH-, -O-, -CO-O- or -O-CO- are replaced in such a way that the O atoms are not directly connected to each other, L 31 and L 32 Identically or differently represent H or F, Y 3 Identically or differently represent H or CH3, X 3 represents, identically or differently, halogen, CN, haloalkyl or alkoxy having 1 to 3 C atoms or haloalkenyl or alkenyloxy having 2 or 3 C atoms, preferably F, CN, OCF3 or CF3, most preferably F or CN, and n is independently 0 or 1, preferably n is 0.

13. Liquid-crystalline medium according to one or more of claims 5 to 12, wherein the medium comprises one or more compounds of the formula VI Where R 6 and R 62 Having R as defined in claim 1 2A The meaning of R 62 Alternatively represents F, Cl, CF3 or OCF3, and L 61 , L 62 , L 63 , L 64 , L 65 and L 66 independently represents H or F, where L 61 , L 62 , L 63 , L 64 , L 65 and L 66 At least one of them represents F, and compounds of formula IIC and IIE are excluded.

14. Liquid-crystalline medium according to one or more of claims 5 to 13 for use in LCoS panels.

15. The LCoS panel according to any one of claims 1 to 4, wherein the liquid crystal medium is a liquid crystal medium according to any one of claims 5 to 14.

16. A projection system comprising an LCoS panel according to any one of claims 1 to 4, a light source and a light guiding element.

17. Use of a liquid-crystalline medium according to one or more of claims 5 to 15 in an LCoS panel, a projection system, a near-eye display or a beam steering application.

Images