Ferroelectric smectic liquid crystal medium

Abstract

The present invention relates to novel media exhibiting a novel spontaneous, self-supporting ferroelectric smectic phase. The present invention relates to ferroelectric compounds generally comprising one or more dielectric neutral aromatic compounds as further described in the specification in highly polar host mixtures typical for ferroelectric nematic mixtures. The mixture can be used in electro-optics, electronics, electromechanical and other applications related to materials with very high dielectric permittivity. The invention further relates to a liquid crystal device, an electrical component and an electronic component comprising the liquid crystal medium according to the invention.

Description

[0001] The new liquid crystal media according to the invention exhibit new spontaneous, self-supporting ferroelectric smectic phases over a relatively wide range of temperatures. They generally comprise one or more dielectrically neutral aromatic compounds, as further described in the specification, in a highly polar host mixture typical for ferroelectric nematic mixtures. The mixtures can be used in electro-optics, electronics, electromechanics and other applications for materials with very high dielectric permittivity. Furthermore, the invention relates to liquid crystal devices, electrical components and electronic components containing the liquid crystal media according to the invention.

[0002] In the last few years, the application areas of liquid crystal (LC) compounds have significantly expanded to various types of display devices, electro-optical devices, electronic components, sensors, etc. For this reason, many different structures have been proposed, especially in the field of nematic liquid crystals. Nematic liquid crystal mixtures have currently found the most widespread use in flat panel display devices.

[0003] Most of these devices employ a nematic liquid crystal phase, including all common LCD televisions, LCD desktop monitors, and mobile LCD devices. Some alternative liquid crystal phases are known, such as the smectic phase or the blue phase. However, ferroelectric smectic phases have only been realized in very thin films, and no liquid crystal material has been found that inherently exhibits such intrinsic properties. Until recently, only a few chemical structures have been reported to exhibit ferroelectric nematic behavior.

[0004] Hiroya Nishikawa, Kazuya Shiroshita, Hiroki Higuchi, Yasushi Okumura, Yasuhiro Haseba, Shin-ichi Yamamoto, Koki Sago and Hirotsugu Kikuchi, Adv. Mater. (2017), 29, 1702354, first described that the compound of formula A has ferroelectric nematic behavior at temperatures between about 45°C and 68°C.

[0005]

[0006] Furthermore, Nerea Sebastián et al., Physical Review Letters (2020), 124, 037801 describe compounds of formula B having similar behavior between about 120°C and 133°C.

[0007]

[0008] Xi Chen et al., PNAS (June 23, 2020), 117(25)14021-14031, the only two f-LC phases were further compared. O.D. Lavrentovich, Proc Nat Acad Sci USA (2020), 117 (26), 14629-14631 emphasizes the new N f The emergence of the -LC phase is of great significance.

[0009] The publication Li et al., Sci. Adv. 2021, 7 reports very high dielectric polarizability values ​​of these materials and some of their structural variants.

[0010] Atsutaka Manabe, Matthias Bremer, Martin Kraska (2021): Ferroelectric phase at and below room temperature, Liquid Crystals, 48, 1079-1086 (DOI 10.1080 / 02678292.2021.1921867) discloses a new ferroelectric nematic material of formula C, which is described as having a ferroelectric nematic liquid crystal phase (N f -LC phase). Ambient temperature, sometimes also referred to as room temperature, here means in a narrow sense a temperature of 20°C.

[0011]

[0012] Y. Song et al. (Phys. Chem. Chem. Phys., 2022, DOI: 10.1039 / d2cp01110g) describe a material having a ferroelectric nematic phase at high temperature, which has the following structure D:

[0013]

[0014] No ferroelectric smectic phase has been reported for any of these compounds.

[0015] The development of ferroelectric LC phases for technological applications would obviously benefit from suitability for ambient temperature. Technological devices and electronic applications are usually designed to have an operating range above and below ambient temperature, or room temperature, for example 15°C to 25°C, preferably 0°C to 50°C, and more preferably even wider.

[0016] Some ferroelectric smectic thin films consisting of bent-core bimesogens have been reported. See, for example, S. Nakasugi et al., Mater. Adv., 2021, 2, 7017-702. The ferroelectric phase only appears in very thin cells. The compounds used all have similar polarity.

[0017] The use of fluorinated liquid crystal substances is known to those skilled in the art. Various compounds containing two 2,6-difluorinated 1,4-phenylene rings have been described as liquid crystal or mesogenic materials, such as in publication WO 2015 / 101405 A1 and various further publications. The compounds proposed therein have three to four aromatic rings and are characterized as conventional smectic materials without ferroelectric smectic properties.

[0018] An object of the present invention is to discover ferroelectric smectic liquid crystal media (S f -LC phase medium) of the mixture concept of normally induced smectic phase.

[0019] It is therefore a further object of the present invention to find compounds which are suitable as components of ferroelectric smectic liquid-crystalline media, which preferably have high bright spots and low melting points, while exhibiting a broad and suitable temperature range for the ferroelectric smectic phase. Furthermore, it is also an object to make the mixture thermally and photochemically stable under the conditions prevailing in the field of application.

[0020] Unexpectedly, it has been found that a medium comprising a selected class of compounds as described below can spontaneously acquire a ferroelectric smectic phase in the bulk at a favorable temperature range. It can be used to obtain LC media with unprecedented properties, including but not limited to liquid crystal media for devices requiring particularly high or even extremely high dielectric anisotropy, for electro-optical displays and for other devices, for electronic applications, capacitors and electromechanical devices that exploit the high dielectric permittivity of the material. The medium and compounds according to the invention are sufficiently stable and colorless. In particular, they are characterized by extremely high dielectric constants and, in particular, very high dielectric anisotropy (Δε), and therefore low threshold voltages are required when used in optical switching components. The present invention enables the formation of the desired S at ambient temperature and well below ambient temperature. f -LC phase.

[0021] High dielectric permeability will enable excellent physical properties. High (relative) dielectric permittivity is also particularly beneficial for dielectrics in capacitors, since the dielectric induces high capacitance at specific electrode areas. In addition, the dielectric has very low conductivity and is superior to conventional high-ε dielectrics due to its fluid properties. r material (e.g., barium titanate).

[0022] Compared to nematic LC, the material according to the invention has a high viscosity. This unique feature can be particularly beneficial if the low viscosity liquid nature of the nematic material causes problems. Due to the high viscosity, gel leakage such as ferroelectric smectic materials is very unlikely. In order to fill the medium into a box or any other container, it can be heated above its transition temperature to make it have a low viscosity.

[0023] In one main aspect, the invention therefore relates to a liquid crystal medium exhibiting a ferroelectric smectic phase, wherein the medium comprises 5% or more of a first component with a low polarity of -5 < Δε < 5, and 60% or more of a second polar component with a Δε of 20 or more (measured at 20° C. and 1 kHz). The ferroelectric smectic phase is obtained already in the bulk medium, without having to use certain boundary layers and layer thicknesses.

[0024] The compounds of the first component are preferably aromatic, more preferably contain biphenyl substructures and have a total of 2 to 4 ring systems.

[0025] In another aspect, the present invention relates to a method for preparing a liquid crystal medium exhibiting a ferroelectric nematic phase, wherein 5 wt. % or more of a first component having a low polarity of -5<Δε<5, 60 wt. % or more of a compound contained in a second polar component, and any other components or additives are combined and mixed with one another, wherein the second polar component initially itself has a ferroelectric nematic phase.

[0026] The invention further relates to ferroelectric smectic liquid-crystalline media comprising one or more compounds of the formula IA,

[0027]

[0028] in

[0029] A 1A express

[0030]

[0031] A 2A express

[0032]

[0033] A 3A express

[0034]

[0035] L 3A are each independently H, alkyl, alkoxy or alkoxyalkyl, each having 1 to 7 C atoms, preferably H,

[0036] Z 1A and Z 2A are independently a single bond, -C≡C- or -CH=CH-,

[0037] R 1A are independently alkyl groups having 1 to 12 C atoms, wherein in addition, one or more CH2 groups in these groups may in each case independently of one another be -C≡C-, -CH=CH-, -O-, -S-, -(CO)-O- or -O-(CO)- in such a way that the O / S atoms are not directly bonded to one another and wherein in addition one or more H atoms may be replaced by halogen; or represents H,

[0038] R 2A are independently alkyl groups having 1 to 12 C atoms, wherein in addition, one or more CH2 groups in these groups may in each case independently of one another be -C≡C-, -CH=CH-, -O-, -S-, -(CO)-O- or -O-(CO)- in such a way that the O / S atoms are not directly bonded to one another and wherein in addition one or more H atoms may be replaced by halogen; or represents H,

[0039] and

[0040] n1 is 0, 1 or 2, preferably 1. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Graph showing the relative dielectric permittivity εr of a sample mixture at various temperatures. The sample mixture corresponds to mixture Example No. 1.1, with 10% of compound PUS-3-2 in a ferroelectric nematic host mixture. The mixture exhibits a ferroelectric smectic phase below a transition temperature of 21°C.

[0043] Detailed description

[0044] The compound of formula IA has low polarity, preferably -5<Δε<5, more preferably -3<Δε<3, and is summarized under the first component.

[0045] The liquid-crystalline medium preferably further comprises one or more compounds selected from the compounds of the formulae IB and IC, which are preferably part of the second polar component,

[0046]

[0047] R 1C -A 3C -Z 2C -A 2C -Z 1C -A 1C -X 1C IC

[0048] in

[0049] X 1B represents -CN, F or -NCS, preferably represents -CN,

[0050] X 1Crepresents -CN, F, CF3, -OCF3, -NCS, SF5 or O-CF=CF2, preferably represents -CN or -NCS, most preferably represents -CN,

[0051] Z 1B and Z 2B independently of one another represent a single bond, -(CO)-O- or -CF2-O-, preferably represent a single bond,

[0052] Z 1C and Z 2C One of the two groups represents -(CO)-O- or -CF2-O- and the other represents a single bond. Preferably, Z 1C is -(CO)-O- or -CF2-O- and Z 2C is a single key,

[0053] L 1B are independently H or CH3, preferably H,

[0054] A 1B express

[0055]

[0056] Best

[0057]

[0058] Where L 8B denotes alkyl, alkoxy or alkoxyalkyl, each having 1 to 7 C atoms, preferably CH3, OCH3, OCH2CH3, CH2OCH3, CH2OCH2CH3, CH2CH2OCH3, CH2CH2OCH3, CH2CH2OCH2CH3 or CH2CH2CH2OCH3,

[0059] A 1C Independently express

[0060]

[0061] Best

[0062]

[0063] Best choice

[0064]

[0065] A 2C express

[0066]

[0067] Best

[0068]

[0069] A 3C express

[0070]

[0071] n2 is 1 or 2, preferably 1,

[0072] R 1B and R 1C independently of one another represent an alkyl radical having 1 to 12 C atoms, preferably 1 to 8, more preferably 1 to 6 and most preferably 1 to 5 C atoms, wherein in addition one or more CH2 groups in these radicals may in each case independently of one another be replaced by -C≡C-, -CF2-O-, -OCF2-, -CH=CH-, -O-, -S-, -(CO)-O- or -O-(CO)- in such a way that the O / S atoms are not directly bonded to one another and wherein in addition one or more H atoms may be replaced by halogen; or represents H,

[0073] Preferably, R 1A , R 1B and R 1C are independently halogenated or unsubstituted alkyl radicals having 1 to 10 C atoms, wherein in addition one or more CH2 groups in these radicals may be replaced by -O- or -CH=CH- in such a way that the O atom is not directly bonded.

[0074] The media contains:

[0075] - preferably 15% by weight or more of a compound of formula IB, and / or

[0076] - Preferably 15 wt. %, preferably 20 wt. %, more preferably 30 wt. % and most preferably 40 wt. % or more of one or more compounds of formula IC, which are preferably selected from formulae IC-1 to IC-3 as described below.

[0077] The percentages are provided with the entire media constituting 100% by weight of the media.

[0078] The radical R in the corresponding formulae IA, IB and IC and in the corresponding subformulae thereof 1A , R 1B and R 1C Preferably, it represents an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms or an alkenyl group having 2 to 8 carbon atoms. These alkyl chains are preferably straight-chain or preferably have a 1C In the case of R, the alkyl chain is branched by a single methyl or ethyl substituent, preferably in the 2- or 3-position. 1A , R 1Band R 1C Particularly preferred is straight-chain alkyl having 1 to 7 C atoms or unbranched alkenyl having 2 to 8 C atoms, in particular unbranched alkyl having 1 to 5 C atoms.

[0079] The preferred groups R 1A , R 1B and R 1C is selected from cyclopentyl, 2-fluoroethyl, cyclopropylmethyl, cyclopentylmethyl, cyclopentylmethoxy, cyclobutylmethyl, 2-methylcyclopropyl, 2-methylcyclobutyl, 2-methylbutyl, 2-ethylpentyl and 2-alkoxyethoxy.

[0080] Containing branched or substituted terminal groups R 1A , R 1B and R 1C Compounds of the formulae IA, IB and IC1 to IC-3 may sometimes be important due to their better solubility in liquid crystal base materials. 1A , R 1B and R 1C Each is preferably a straight chain.

[0081] Group R 1A , R 1B and R 1C Particularly preferably, they are selected from the following:

[0082] CH3

[0083] C2H5

[0084] n-C3H7

[0085] n-C4H9

[0086] n-C5H 11

[0087] C2H5CH(CH3)CH2

[0088] n-C6H 13

[0089] n-C7H 15

[0090] n-C3H7CH(C2H5)CH2

[0091] n-C8H 17

[0092] c-C3H5

[0093] c-C3H5CH2

[0094] c-C4H7

[0095] c-C5H7

[0096] c-C5H9

[0097] c-C5H9CH2

[0098] CH2=CH

[0099] CH3CH=CH

[0100] CH2=CH(CH2)2

[0101] CH3O

[0102] C2H5O

[0103] n-C3H7O

[0104] n-C4H9O

[0105] n-C5H 11 O

[0106] CH3OCH2

[0107] C2H5OCH2

[0108] CH3OCH2CH2

[0109] C2H5OCH2CH2

[0110] H

[0111] The following end group abbreviations are used:

[0112]

[0113] A further embodiment of the invention relates to a ferroelectric smectic liquid-crystalline medium comprising one or more compounds selected from the group consisting of formula IA, formula IB and formula IC as defined above.

[0114] In a preferred embodiment, the medium according to the invention preferably comprises one, two, three or more compounds of the formula IA-A:

[0115]

[0116] in

[0117] A 3A express

[0118]

[0119] Z 1A and Z 2A are independently -(CO)-O- or -C≡C-,

[0120] L1A is F or H,

[0121] L 2A is F or H,

[0122] L 3A As defined for formula IA, preferably H or CH3,

[0123] L 4A is F or H, preferably H,

[0124] R 1A are independently alkyl groups having 1 to 12 C atoms, wherein in addition, one or more CH2 groups in these groups may in each case independently of one another be substituted by -C≡C-, -CF2-O-, -OCF2-, -CH=CH-, -O-, -S-, -(CO)-O- or -O-(CO)-, in such a way that the O / S atoms are not directly bonded to one another and in which in addition one or more H atoms may be replaced by a halogen; or represents H, and

[0125] n1 is 1 or 2, preferably 1.

[0126] In the above formula IA and its subformula IA-A, preferably R 1A and R 1B independently represents an alkyl group having 1 to 7 C atoms or an alkenyl group having 2 to 7 C atoms.

[0127] The compounds of formula IA and formula IA-A are preferably selected from one, two, three or more compounds of formula IA-1 to IA-3:

[0128]

[0129] in

[0130] R 1A and R 2A As defined with respect to Formula IA,

[0131] L 1A To L 6A are independently H, CH3 or F,

[0132] Preferably selected from the group consisting of the following formulae IA-1-1 to IA-3-2:

[0133]

[0134]

[0135] in

[0136] The parameters have the corresponding meanings given above and preferably independently represent an alkyl radical having 1 to 7 C atoms or an alkenyl radical having 2 to 7 C atoms. More preferably, the low Δε compound of the medium according to the invention is selected from the formulae IA-1-1, IA-1-2, IA-2-1, IA-2-3 and IA-3-1, most preferably from IA-1-1 or IA-2-1.

[0137] In a preferred embodiment, the present invention relates to a ferroelectric smectic liquid crystal medium comprising one or more compounds selected from the group consisting of formulae IC-1 to IC-3 as defined below, preferably in the percentages and preferred formulas as provided throughout the present invention:

[0138]

[0139]

[0140] wherein the variables are as defined for Formula IC and

[0141] m, n are 0 or 1, where m+n = 1. More preferably, the medium according to the invention has at least one compound of the formula IC-1.

[0142] In a preferred embodiment, the medium according to the invention preferably comprises one, two, three or more compounds of the formula IB-1 and / or IB-2 and / or IB-3, preferably of the formula IB-1,

[0143]

[0144] R 1B denotes an alkyl radical having 1 to 12 C atoms, preferably 1 to 7, more preferably 1 to 6 and most preferably 1 to 5 C atoms, wherein in addition, one or more CH2 groups in these radicals may in each case independently of one another be substituted by -C≡C-, -CF2-O-, -OCF2-, -CH=CH-, -O-, -S-, -CO-O- or -O-CO- in such a way that the O / S atoms are not directly bonded to one another and wherein in addition one or more H atoms may be replaced by a halogen; or represents H,

[0145] Preferably, R 1B is a halogenated or unsubstituted alkyl radical having 1 to 12 C atoms, wherein in addition one or more CH2 groups in these radicals may in each case independently of one another be replaced by -C≡C- or -CH=CH-,

[0146] A 1B express

[0147]

[0148] Best

[0149]

[0150] and Z 1B , Z 2B independently represents -(CO)-O- or -CF2-O-,

[0151] Preferably, it is selected from the following formulae, ie, the group of formulae IB-1-1 to IB-2-3:

[0152]

[0153]

[0154] wherein the parameters have the corresponding meanings given above and in particular, in formulae IB-1-1 to IB-1-3,

[0155] Z 1B Preferably represents -CF2-O-

[0156] And in particular, in Formula IB-2-1 and Formula IB-2-2,

[0157] Z 2B Preferably represents -CF2-O-; and in particular, in formula IB-2-3,

[0158] Z 2B Preferably it represents -(CO)-O-.

[0159] In a preferred embodiment, the medium according to the invention preferably comprises one, two, three or more compounds selected from the group consisting of the formulae IC-1-1 to IC-3-6:

[0160]

[0161]

[0162] Among them A 1C As defined above,

[0163] It is preferably selected from the group of the following formulae IC-1-1-1 to IC-3-5-2, preferably selected from the group of formulae IC-1-1-1, IC-1-1-2, IC-1-1-3, IC-1-1-4, IC-3-1-1 and IC-3-2-1:

[0164]

[0165]

[0166]

[0167] wherein the parameters have the corresponding meanings given above, and preferably L 1C Indicates H,

[0168] Z 1C represents -CF2-O- or -(CO)-O-, and

[0169] X 1C It represents -CN or -SCN, preferably it represents -CN.

[0170] Particularly preferred compounds of the formulae IC-1-1 to IC-1-4 for use in the medium are compounds having the following formula:

[0171]

[0172] Wherein the parameters are as defined above, preferably L 1C For H.

[0173] In a preferred embodiment of the invention, the medium comprises up to 100% of a compound selected from the group consisting of compounds of formulae IA, IB and IC, preferably one or more compounds of formula IA and three, four, five, six or more compounds of formulae IB and IC. In this embodiment, the medium preferably consists predominantly of these compounds, more preferably it consists essentially of these compounds, and most preferably it consists almost entirely of these compounds.

[0174] In addition to the compounds of the formulae IA, IB and IC-1 / IC-2 / IC-3, the medium according to the invention optionally preferably necessarily comprises one, two, three or more compounds selected from the group consisting of the compounds of the formulae ID-1 to ID-4

[0175]

[0176] X D represents CN, F, CF3, -OCF3, NCS, SF5 or O-CF=CF2, preferably represents -CN, F, -CF3, -OCF3, -Cl or -NCS, most preferably represents F or CN,

[0177] L 1D , L 2D , L 3D , L 4D , L 5D , L 6D and L 7D independently denotes F, H, alkyl, alkoxy or alkoxyalkyl each having 1 to 7 C atoms, preferably denotes H, F, CH3, OCH3, OCH2CH3, CH2OCH3, CH2OCH2CH3, CH2CH2OCH3, CH2CH2OCH2CH3 or CH2CH2CH2OCH3,

[0178] Z 1D and Z 2D independently represent -(CO)-O-, -CF2-O-, a single bond, and preferably both represent -(CO)-O-,

[0179] R 1D denotes an alkyl radical having 1 to 12 C atoms, preferably 1 to 7, more preferably 1 to 6 and most preferably 1 to 5 C atoms, wherein in addition, one or more CH2 groups in these radicals may in each case independently of one another be substituted by -C≡C-, -CF2-O-, -OCF2-, -CH=CH-, -O-, -S-, -(CO)-O- or -O-(CO)- in such a way that the O / S atoms are not directly bonded to one another and wherein in addition one or more H atoms may be replaced by halogen; or represents H,

[0180] Preferably, R 1D is a halogenated or unsubstituted alkyl radical having 1 to 12 C atoms, wherein in addition one or more CH2 groups in these radicals may in each case independently of one another be replaced by -C≡C- or -CH=CH-,

[0181] R 2D denotes alkyl, alkoxy or alkoxyalkyl, each having 1 to 7 C atoms, preferably CH3, OCH3, OCH2CH3, CH2OCH3, CH2OCH2CH3, CH2CH2OCH3, CH2CH2OCH3, CH2CH2OCH2CH3 or CH2CH2CH2OCH3,

[0182] A 1D represents a single bond,

[0183]

[0184] Preferred single bonds,

[0185]

[0186] Where L 8D denotes alkyl, alkoxy or alkoxyalkyl, each having 1 to 7 C atoms, preferably CH3, OCH3, OCH2CH3, CH2OCH3, CH2OCH2CH3, CH2CH2OCH3, CH2CH2OCH3, CH2CH2OCH2CH3 or CH2CH2CH2OCH3,

[0187] Preferably, it comprises one or more of formulas ID-1-1 to ID-3-1:

[0188]

[0189]

[0190] The variable group R 1D and L 8D As defined above.

[0191] The compounds of formulae IA, IB, IC and ID represent "Group 1" compounds. In a preferred embodiment of the invention, the medium comprises up to 100% of one or more compounds, preferably three, four, five, six or more compounds, selected from Group 1 compounds. In this embodiment, the medium preferably consists mainly of these compounds, more preferably it consists essentially of these compounds, and most preferably it consists almost completely of these compounds.

[0192] For the present invention, unless otherwise indicated in individual cases, the following definitions apply to the description of the ingredients of the compositions:

[0193] - "comprising": the concentration of the ingredient in question in the composition is preferably 5% or more, particularly preferably 10% or more, very particularly preferably 20% or more,

[0194] - "consists essentially of": the concentration of the ingredient in question in the composition is preferably 50% or more, particularly preferably 55% or more and very particularly preferably 60% or more,

[0195] - "essentially consists of": the concentration of the ingredient in question in the composition is preferably 80% or more, particularly preferably 90% or more and very particularly preferably 95% or more, and

[0196] - "consists almost entirely of": the concentration of the ingredient in question in the composition is preferably 98% or more, particularly preferably 99% or more and very particularly preferably 100.0%.

[0197] The medium according to the present invention preferably comprises 10%, 15% or even 20% or more of a first component with low polarity of -5 < Δε < 5 (measured at 20°C and 1kHz). The medium preferably comprises 75%, more preferably 80% or more of a polar component with Δε of 20 or more, preferably Δε of 50 or 100 or more (measured at 20°C and 1kHz). Preferably, the medium exhibits a rotational viscosity of 2 Pa·s or more, more preferably 5 Pa·s at 10°C, measured in a 100 μm thick cell. The medium preferably further exhibits a relative dielectric permittivity ε of 100 or more at 10°C and 1kHz. r , or exhibits ε of 1000 or greater at 10 Hz r .

[0198] Preferably, the medium according to the present application satisfies one or more of the following conditions. It preferably includes:

[0199] - 5 wt% or more of the compound of formula IA, more preferably 10 wt%, more preferably 15 wt% or more and most preferably 20 wt% or more of the compound of formula IA, and preferably 25 wt% or less of the compound of formula IA,

[0200] - 5% by weight or more of the compound of formula IB, more preferably 10% by weight or more, more preferably 20% by weight or more and most preferably 50% by weight or more of the compound of formula IB,

[0201] -40% by weight or more of the compounds selected from the group consisting of formulae IA and IB, more preferably 60% by weight, more preferably 75% by weight or more and most preferably 90% by weight or more of the compounds selected from the group consisting of formulae IA and IB, i.e. the sum of the compounds of formulae IA and IB is preferably at least the above value

[0202] -5% by weight or more, preferably 10% by weight or more, more preferably 15% by weight or more, more preferably 20% by weight or more and most preferably 25% by weight or more of a compound selected from the group consisting of formula IC-1, IC-2 and IC-3,

[0203] -optionally 2 wt% or more of a compound of formula ID (ID-1, ID-2, ID-3, ID-4), more preferably 5 wt%, more preferably 10 wt% or more and most preferably 15 wt% or more of a compound of formula ID,

[0204] - One, two, three or more compounds of formula IA-1-1 or IA-1-2, preferably compounds of formula AUUQGU-nN, AUUQGG-nN, PGGUQU-nF, most preferably selected from the group of compounds AUUQGU-2-N, AUUQGU-3-N, AUUQGU-4-N, AUUQGU-5-N and AUUQGU-6-N.

[0205] - one, two, three or more, preferably three or more compounds of formula IB-1, preferably compounds of formula GUUQU-nN and / or DUUQU-nN, most preferably selected from the group of compounds GUUQU-2-N, GUUQU-3-N, GUUQU-4-N, GUUQU-5-N, GUUQU-6-N, GUUQU-7-N, DUUQU-2-N, DUUQU-3-N, DUUQU-4-N, DUUQU-5-N and DUUQU-6-N,

[0206] - one, two, three or more compounds of formula IB-1-3, preferably a compound of formula GUUQU-nN, more preferably selected from the group of compounds GUUQU-3-N, GUUQU-4-N and GUUQU-5-N,

[0207] - one, two, three or more compounds of formula IB-3-1, preferably a compound of formula DUUQU-nF, more preferably selected from the group of compounds DUUQU-3-F, DUUQU-4-F and DUUQU-5-F,

[0208] - one, two, three or more compounds of formula IC-1-1, preferably compounds of formula MUZU-nN or MUQU-nN, more preferably selected from the group of compounds MUZU-2-N, MUZU-3-N, MUZU-4-N and MUZU-5-N,

[0209] - one, two, three or more compounds of formula IC-3, preferably selected from compounds of formula IC-3-2 and IC-3-3, more preferably selected from compounds of formula MUU-nN or UMU-nN, more preferably selected from the group of compounds MUU-3-N, MUU-4-N, MUU-5-F, UMU-3-N, UMU-4-N and UMU-5-N,

[0210] - one, two, three or more compounds of formula IC-1-1, preferably selected from the group consisting of compounds of formula GUZU-nN or GUQU-nN, more preferably selected from the group consisting of compounds GUZU-3-N, GUZU-4-N, GUZU-5-F, GUQU-3-N, GUQU-4-N and GUQU-5-N, and / or

[0211] - one, two, three or more compounds of the group of formula IC-1-1-3 and IC-1-1-4, preferably compounds of formula UUZU-nN and / or UUQU-nN, most preferably selected from the group of compounds UUZU-2-N, UUZU-3-N, UUZU-4-N, UUZU-5-N, UUQU-2-N, UUQU-3-N and UUQU-4-N,

[0212] wherein n is 1, 2, 3, 4, 5, 6 or 7.

[0213] In another preferred embodiment of the present invention, the compounds of formula IA, IB and IC-1 / IC-2 / IC-3 are the first group of compounds, i.e., Group 1 compounds. In this embodiment, the concentration of the compounds of this Group 1 compound is preferably in the range of 70% or more, preferably 80% or more, more preferably 90% or more to 100% or less.

[0214] The medium according to the present disclosure optionally contains one or more compounds selected from the group of compounds of formulae II and III (Group 2), the concentration of which is preferably greater than 0% to 40% or less,

[0215]

[0216]

[0217] in

[0218] R 2 represents an alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy radical having 1 to 7 C atoms, an alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl radical having 2 to 7 C atoms, and preferably represents an alkyl or alkenyl radical,

[0219] and

[0220] In each occurrence, they are expressed independently of each other

[0221]

[0222] Best

[0223]

[0224]

[0225] L 21 and L 22 represents H or F, preferably L 21 Indicates F,

[0226] L 32 and L 33 represents H, F or CH3, preferably represents H,

[0227] X 2 represents halogen, halogenated alkyl or alkoxy having 1 to 3 C atoms or halogenated alkenyl or alkenyloxy having 2 or 3 C atoms, preferably represents F, Cl, -OCF3, -O-CH2CF3, -O-CH=CH2, -O-CH=CF2 or -CF3, very preferably represents F, Cl, -O-CH=CF2 or -OCF3,

[0228] m represents 0, 1, 2 or 3, preferably represents 1 or 2, and particularly preferably represents 2,

[0229] R 3denotes alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms, and preferably denotes n-alkyl, cyclopropyl, cyclopentyl or alkenyl,

[0230] and

[0231] At each occurrence, independently of each other

[0232]

[0233] Best

[0234]

[0235] L 31 and L 32 independently represent H or F, preferably L 31 Indicates F,

[0236] X 3 represents halogen, halogenated alkyl or alkoxy having 1 to 3 C atoms or halogenated alkenyl or alkenyloxy having 2 or 3 C atoms, F, Cl, -OCF3, -OCHF2, -O-CH2CF3, -O-CH═CF2, -O-CH═CH2 or -CF3, very preferably represents F, Cl, -O-CH═CF2, -OCHF2 or -OCF3,

[0237] Z 3 represents -CH2CH2-, -CF2CF2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O- or a single bond, preferably represents -CH2CH2-, -COO-, trans-CH=CH- or a single bond and very preferably represents -(CO)-O-, trans-CH=CH- or a single bond, and

[0238] n represents 0, 1, 2 or 3, preferably represents 1, 2 or 3, and particularly preferably represents 1,

[0239] wherein the individual rings, preferably the phenylene ring, may optionally each be substituted by one or two alkyl groups, preferably by methyl and / or ethyl groups, preferably by one methyl group, and

[0240] Wherein the compounds of formula IA, formula IB, formula IC and formula ID are not included in the compound of formula II,

[0241] Optionally, alternatively or additionally, one or more compounds selected from the group of compounds of formula IV and V (Group 3) are contained, preferably in a concentration of greater than 0% to 15%,

[0242]

[0243]

[0244] in

[0245] R 41 and R 42 Independently of each other, the above formula II with respect to R 2 The indicated meaning, preferably R 41 represents an alkyl group and R 42 represents an alkyl group or an alkoxy group, or R 41 represents an alkenyl group and R 42 represents an alkyl group,

[0246] and

[0247] Independent of each other and if

[0248] Appears twice,

[0249] These also represent independently of each other

[0250]

[0251]

[0252] Best

[0253] and One or more of

[0254] express

[0255]

[0256] Z 41 and Z 42 are independent of each other, and if Z 41 appears twice, these also independently represent -CH2CH2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O-, -CF2O-, -C≡C- or a single bond, preferably one or more of which represent a single bond, and

[0257] p represents 0, 1 or 2, preferably represents 0 or 1, and

[0258] R 51 and R 52 Independently of each other, they have 41 and R 42one of the meanings given, and preferably denotes alkyl having 1 to 7 C atoms, preferably n-alkyl, particularly preferably n-alkyl having 1 to 5 C atoms; alkoxy having 1 to 7 C atoms, preferably n-alkoxy, particularly preferably n-alkoxy having 2 to 5 C atoms; alkoxyalkyl, alkenyl or alkenyloxy, preferably alkenyloxy, having 2 to 7 C atoms, preferably 2 to 4 C atoms,

[0259] to

[0260] If there are independent representations of each other

[0261]

[0262]

[0263] Best

[0264]

[0265] Best

[0266] express

[0267] and, existence

[0268] Preferred representation

[0269] Z 51 To Z 53 each independently of one another represents -CH2-CH2-, -CH2-O-, -CH=CH-, -C≡C-, -COO- or a single bond, preferably represents -CH2-CH2-, -CH2-O- or a single bond, and particularly preferably represents a single bond,

[0270] i and j each independently represent 0 or 1,

[0271] (i+j) preferably represents 0, 1 or 2, more preferably represents 0 or 1, and most preferably represents 1,

[0272] wherein the individual rings, preferably the phenylene ring, may optionally each be substituted by one or two alkyl groups, preferably by methyl and / or ethyl groups, preferably by one methyl group, and

[0273] Optionally, alternatively or additionally, one or more compounds selected from Group 4, i.e. the group of compounds of formulae I and VI to IX, preferably two, three or more compounds, preferably in a concentration of greater than 0% to 20%, wherein

[0274]

[0275] in

[0276] express

[0277]

[0278] express

[0279]

[0280] Best

[0281]

[0282] n represents 0 or 1,

[0283] R 11 and R 12 independently of one another denotes alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy, preferably having 1 to 7 C atoms, in which one CH2 group may be replaced by 1,2-cyclopropyl, 1,3-cyclopentyl or 1,3-cyclopentenylene, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl, preferably alkyl, alkoxy, alkenyl or alkenoxy, most preferably alkyl, alkoxy or alkenoxy,

[0284] R 61 represents an unsubstituted alkyl group having 1 to 7 C atoms, preferably a straight-chain alkyl group, more preferably a n-alkyl group, most preferably a propyl group or a pentyl group; an unsubstituted alkenyl group having 2 to 7 C atoms, preferably a straight-chain alkenyl group, particularly preferably a group having 2 to 5 C atoms; an unsubstituted alkoxy group having 1 to 6 C atoms; or an unsubstituted alkenyloxy group having 2 to 6 C atoms,

[0285] R 62 represents an unsubstituted alkyl group having 1 to 7 C atoms, an unsubstituted alkoxy group having 1 to 6 C atoms or an unsubstituted alkenyloxy group having 2 to 6 C atoms, and

[0286] l means 0 or 1,

[0287] R 71 represents an unsubstituted alkyl group having 1 to 7 C atoms, preferably a straight-chain alkyl group, more preferably a n-alkyl group, most preferably a propyl group or a pentyl group; or an unsubstituted alkenyl group having 2 to 7 C atoms, preferably a straight-chain alkenyl group, particularly preferably a group having 2 to 5 C atoms,

[0288] R 72represents an unsubstituted alkyl group having 1 to 7 C atoms, preferably having 2 to 5 C atoms; an unsubstituted alkoxy group having 1 to 6 C atoms, preferably having 1, 2, 3 or 4 C atoms; or an unsubstituted alkenyloxy group having 2 to 6 C atoms, preferably having 2, 3 or 4 C atoms, and

[0289] express

[0290]

[0291] R 81 represents an unsubstituted alkyl group having 1 to 7 C atoms, preferably a straight-chain alkyl group, more preferably a n-alkyl group, most preferably a propyl group or a pentyl group; or an unsubstituted alkenyl group having 2 to 7 C atoms, preferably a straight-chain alkenyl group, particularly preferably a group having 2 to 5 C atoms,

[0292] R 82 represents an unsubstituted alkyl radical having 1 to 7 C atoms, preferably having 2 to 5 C atoms; an unsubstituted alkoxy radical having 1 to 6 C atoms, preferably having 1, 2, 3 or 4 C atoms; or an unsubstituted alkenyloxy radical having 2 to 6 C atoms, preferably having 2, 3 or 4 C atoms,

[0293] express

[0294]

[0295] Best

[0296]

[0297] More preferred

[0298]

[0299] Z 8 represents -(CO)-O-, -CH2-O-, -CF2-O- or -CH2-CH2-, preferably represents -(CO)-O- or -CH2-O-,

[0300] o means 0 or 1,

[0301] R 91 and R 92 Independently of each other, they have the above 72 The meaning given,

[0302] R 91 preferably denotes an alkyl radical having 2 to 5 C atoms, preferably having 3 to 5 C atoms,

[0303] R 92preferably represents an alkyl or alkoxy group having 2 to 5 C atoms, more preferably an alkoxy group having 2 to 4 C atoms, or an alkenyloxy group having 2 to 4 C atoms,

[0304] express

[0305] p and q independently represent 0 or 1, and

[0306] (p+q) preferably represents 0 or 1, provided that

[0307] express

[0308] Alternatively, preferably p=q=1,

[0309] wherein the individual rings, and preferably the phenylene ring, may optionally each be substituted by one or two alkyl groups, preferably by methyl and / or ethyl groups, preferably by one methyl group,

[0310] Especially the ring

[0311] alternatively Alternative,

[0312] and wherein the compound of formula VII is not included in the compound of formula IX, and the compound of formula I is not included in the compounds of formulae VI to IX or the compound of formula IX,

[0313] Optionally, preferably necessarily alternatively or additionally, one or more compounds selected from Group 5, i.e. the group of compounds of formula B, preferably two, three or more compounds, preferably in a concentration of greater than 0% to 20%, wherein

[0314]

[0315] in

[0316] express

[0317]

[0318] In each occurrence, they are expressed independently of each other

[0319]

[0320] Best

[0321] Best choice

[0322] n represents 0, 1 or 2, preferably represents 1,

[0323] R 1 represents an alkyl group having 1 to 7 C atoms, wherein one or more CH2 groups in this group, preferably one CH2 group, can each independently be replaced by -C≡C-, -CF2-O-, -OCF2-, -O-, -(CO)-O-, -O-(C=O)-, cyclopropylene, 1,3-cyclobutylene, 1,3-cyclopentylene, 1,3-cyclopentenylene, preferably by cyclopropylene or 1,3-cyclopentylene, preferably one CH2 group can be replaced by 1,2-cyclopropylene , 1,3-cyclopentylidene or 1,3-cyclopentenylidene; alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms, and preferably alkyl or alkenyl, in which one -CH2- group may be replaced by cyclopropylene, 1,3-cyclobutylene, 1,3-cyclopentylidene, 1,3-cyclopentenylidene, preferably by cyclopropylene or 1,3-cyclopentenylidene, in such a way that the O atoms are not directly bonded to one another, and in which one or more H atoms may be replaced by halogen, and

[0324] X 1 represents F, Cl, fluorinated alkyl, fluorinated alkenyl, fluorinated alkoxy or fluorinated, the latter four groups preferably having 1 to 4 C atoms; more preferably represents F, Cl, CF3 or OCF3, and

[0325] Therein, the individual rings, preferably the phenylene ring, may optionally each be substituted by one or two alkyl groups, preferably by methyl and / or ethyl groups, preferably by one methyl group.

[0326] Preferred are media comprising one or more compounds of group 1 and group 2.

[0327] The corresponding starting materials can generally be prepared easily by the person skilled in the art by synthetic methods known from the literature or are commercially available. The reaction methods and reagents used are known in principle from the literature.

[0328] In the present invention, the 2,5-disubstituted dioxane ring of the formula

[0329]

[0330] Preferably represents a dioxane ring in 2,5-trans configuration, ie the substituents R are preferably all in the equatorial position in a preferred chair conformation. A 2,5-disubstituted tetrahydropyran of the formula

[0331]

[0332] Likewise preferably is intended a tetrahydropyran ring in the 2,5-trans configuration, ie the substituents are preferably all in the equatorial position in a preferably chair conformation.

[0333] The liquid crystal medium according to the present invention has a wide ferroelectric smectic phase temperature range. It exhibits a ferroelectric smectic phase range at 20°C and above and below 20°C (ambient temperature). It covers the range of most technical interest from at least 10°C to 50°C and significantly beyond to lower and / or higher temperatures. Therefore, it is very suitable for all kinds of domestic or industrial uses and even has some restrictions outdoors. The medium exhibits a ferroelectric smectic phase at least in a temperature range of 20 Kelvin or higher, more preferably in a temperature range of 30K or higher and most preferably in a range of 40K or higher. Preferably, the medium exhibits an enantiotropic ferroelectric smectic phase, i.e. a temperature range in which a ferroelectric smectic phase appears when cooling from a higher temperature and when heating from a lower temperature. The temperature range of the ferroelectric smectic phase, clearing point, low temperature stability (LTS), (relative) dielectric permittivity, dielectric anisotropy and optical anisotropy achievable combinations of compounds containing formula IA, IB and IC-1 / IC-2 / IC-3 are far superior to previous materials of similar class from the prior art. Previously, materials with a ferroelectric smectic phase range were available only in the presence of suitable boundary conditions and with the use of unusual materials like bimesocrystals.

[0334] Furthermore, the mixtures according to the invention generally exhibit a very broad smectic-nematic phase range with a clearing point of 85° C. or higher.

[0335] The liquid-crystalline media according to the invention preferably exhibit a temperature range of the ferroelectric smectic phase which is 20 degrees wide or more, which preferably extends over a range of 40 degrees or more, more preferably over a range of 60 degrees or more.

[0336] Preferably, the liquid-crystalline medium according to the present invention exhibits a ferroelectric smectic phase, preferably from 0°C to 10°C, more preferably from 0°C to 20°C, more preferably from -10°C to 25°C, more preferably from -20°C to 30°C and most preferably from -20°C to 40°C.

[0337] In another preferred embodiment, the liquid-crystalline media according to the invention exhibit a ferroelectric smectic phase preferably from 10 to 40°C, more preferably from 10 to 50°C, more preferably from 10 to 60°C and most preferably from 10 to 70°C.

[0338] The liquid-crystalline media according to the invention exhibit outstanding dielectric properties.

[0339] Due to the outstanding properties, the medium can play a role in many new technological fields and can be used for electro-optical purposes, for supercapacitors, nonlinear optical components, electric field sensors, storage devices and electromechanical devices including generators (i.e., energy harvesting devices) and actuators. The material can, for example, enable unconventional modes of harvesting energy from vibrational motion.

[0340] Preferably, the ε of the medium according to the invention is r The value (at 20° C. and 10 Hz) is 700 or more, more preferably 800 or more, more preferably 15,000 or more, even more preferably 30,000 or more and more preferably 35,000 or more.

[0341] These dielectric properties are achieved at temperatures that place the medium in the ferroelectric smectic phase. Dielectric characteristics can exhibit hysteretic behavior, especially at varying temperatures, and in this case the value obtained at a certain temperature can depend on the history of the material, i.e., whether the material has been subjected to heating or cooling.

[0342] This effect enables, among other things, the device to be operated, for example, in a bistable mode and can thus be advantageously used in electro-optical devices, as are known, for example, from ferroelectric smectic devices.

[0343] The liquid-crystalline media according to the invention preferably contain from 2 to 40, particularly preferably from 4 to 20 compounds as further constituents in addition to one or more compounds according to the invention. In particular, these media may contain from 1 to 25 components in addition to one or more compounds according to the invention. These further constituents are preferably selected from ferroelectric smectic or nematic (monotropic or isotropic) substances.

[0344] Prior art ferroelectric materials and similar compounds with high dielectric permittivity for combination with the materials of the present invention are selected from, for example, the following structures:

[0345]

[0346] The medium according to the invention preferably comprises 1% to 100%, more preferably 10% to 100% and especially preferably 50% to 100% of the compounds of the formulae IA and / or IB and / or IC-1 / IC-2 / IC-3 preferably used according to the invention.

[0347] The present invention also relates to a process for preparing the liquid-crystalline media described herein, wherein preferably 5% by weight, 10% by weight, 15% by weight or 20% by weight or more of at least one or more compounds selected from the group consisting of formula IA, one or more compounds of formula IB, IC, ID and any other components or additives are combined and mixed with one another. The resulting mixture is equal to 100% by weight.

[0348] The liquid crystal mixture according to the invention is prepared in a conventional manner per se. In general, the required amount of the component used in a smaller amount is dissolved in the component constituting the main constituent, preferably at elevated temperature. It is also possible to mix the components in an organic solvent, for example a solution in acetone, chloroform or methanol, and after thorough mixing, remove the solvent, for example by distillation. Furthermore, the mixture can be prepared in other conventional ways, for example by using premixes, for example homologous mixtures, or using a so-called "multi-bottle" system.

[0349] The liquid crystal mixture may also contain other additives known to the person skilled in the art and described in the literature. For example, 0 to 15%, preferably 0 to 10%, of pleochroic dyes, chiral dopants, stabilizers or nanoparticles may be added. The individual compounds added are used in a concentration of 0.01 to 6%, preferably 0.1 to 3%. However, the concentration data for the other constituents of the liquid crystal mixture (i.e. the liquid crystal or mesogenic compound) are given here without taking into account the concentrations of these additives.

[0350] The liquid-crystal mixtures according to the invention make it possible to significantly broaden the available parameter latitude.

[0351] The invention also relates to electro-optical displays containing such media, in particular TFT displays having two plane-parallel external plates which together with a frame form a box, integrated non-linear components on the external plates for switching individual pixels, and a ferroelectric smectic liquid crystal material with positive dielectric anisotropy and high resistivity located in the box, as well as the use of these media for electro-optical purposes.

[0352] The expression "alkyl" encompasses unbranched and branched alkyl radicals having 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, in particular and preferably the unbranched radicals methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl and n-heptyl, and further, alternatively, the radicals n-butyl, n-pentyl, n-hexyl and n-heptyl substituted by one methyl, ethyl or propyl radical. Radicals having 1 to 5 carbon atoms are generally preferred.

[0353] The expression "alkenyl" encompasses unbranched and branched alkenyls with up to 12 carbon atoms, especially unbranched groups. Particularly preferred alkenyls are C2-C7-1E-alkenyls, C4-C7-3E-alkenyls, C5-C7-4-alkenyls, C6-C7-5-alkenyls and C7-6-alkenyls, especially C2-C7-1E-alkenyls, C4-C7-3E-alkenyls and C5-C7-4-alkenyls. Preferred examples of alkenyls are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl and similar groups. Groups having 2 to 5 carbon atoms are generally preferred.

[0354] The expression "halogenated alkyl" preferably encompasses mono- or polyfluorinated and / or chlorinated groups. Perhalogenated groups are included. Particularly preferred are fluorinated alkyl groups, in particular CF3, CH2CF3, CH2CHF2, CHF2, CH2F, CHFCF3 and CF2CHFCF3. The expression "halogenated alkenyl" and related expressions are to be interpreted accordingly.

[0355] The matrix display according to the present invention, which is constructed by polarizers, electrode substrate plates and surface-treated electrodes, corresponds to the common design of such displays. The term common design is described broadly here and also covers all derivatives and variants of matrix displays, especially matrix display components based on polysilicon TFTs.

[0356] However, a fundamental difference between the display according to the invention and the hitherto conventional displays based on twisted smectic cells lies in the choice of the liquid crystal parameters of the liquid crystal layer.

[0357] The following examples illustrate the invention without intending to limit it. A person skilled in the art will be able to discover from the examples working details which are not given in detail in the general description, generalize them according to general expert knowledge and apply them to specific problems.

[0358] Above and below, percentage data refer to percentages by weight. Unless explicitly indicated otherwise, all temperature values ​​indicated in the present application, such as melting point T(C,N), phase transition T(S,N) from smectic phase (Sm) to nematic phase (N) or T(S f ,N f ) and clearing point T(N,I) or T(N f, I), are indicated in degrees Celsius (°C), and all temperature differences are indicated in different degrees (° or degrees) accordingly. In addition, C = crystalline state, N = nematic phase, Sf = ferroelectric smectic phase, Nf = ferroelectric nematic phase, Sm = smectic phase (more particularly SmA, SmB, etc.), Tg = glass transition temperature and I = isotropic phase. The data between these symbols represent the transition temperature. Δn represents optical anisotropy (589nm, 20°C), Δε represents dielectric anisotropy (1kHz, 20°C).

[0359] The physical, physicochemical and electro-optical parameters are determined by generally known methods, in particular as described in the handbook "Merck Liquid Crystals - -Physical Properties of Liquid Crystals-Description of the Measurement Methods”, 1998, Merck KGaA, Darmstad. Ferroelectric phase measurements were performed according to A. Manabe, M. Bremer, M. Kraska (2021), Liquid Crystals, 48, 1079-1086 (DOI10.1080 / 02678292.2021.1921867) and the literature cited therein.

[0360] The presence of the ferroelectric smectic phase of the material is identified using differential scanning calorimetry (DSC) by observing the texture under a polarizing microscope equipped with a hot stage for controlled cooling or heating, and is additionally confirmed by determining the temperature dependence of the dielectric properties. The transition temperature is primarily determined by probing the optical behavior under a polarizing microscope. The permittivity is measured at a frequency of 1 kHz or 10 Hz by a dielectric spectrometer from Novocontrol, which consists of an Alpha-N high-resolution dielectric analyzer and a Novocool temperature control unit. The sample holder is a standard sample holder BDS1200 with a custom sample box designed for liquid samples. The sample box is made of polished stainless steel with a box gap of 110 μm. Measurements are performed when heating and when cooling the sample.

[0361] The dielectric anisotropy Δε of the individual substances was determined at 20° C. and 1 kHz. For this purpose, 5 to 10% by weight of the substance under investigation dissolved in the dielectrically positive mixture ZLI-4792 (Merck KGaA) were measured and the measured values ​​were extrapolated to a concentration of 100%. The optical anisotropy Δn was determined at 20° C. and a wavelength of 589.3 nm by linear extrapolation.

[0362] In this application, unless explicitly indicated otherwise, plural forms of terms refer to both the singular and the plural, and vice versa. According to this description, other combinations of embodiments and variants of the invention also result from the appended claims or from a combination of a plurality of these claims.

[0363] Further combinations of embodiments of the invention and variants of the invention are also disclosed by the claims.

[0364] Without further elaboration, it is believed that one skilled in the art can utilize the foregoing description to the greatest extent possible the present invention. Therefore, the foregoing preferred embodiments should be construed as merely illustrative and not limiting in any way whatsoever the remainder of the invention. The foregoing examples may be similarly and successfully repeated by substituting the generically or specifically described reactants and / or operating conditions of the present invention for the reactants and / or operating conditions used in the foregoing examples.

[0365] From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope of the invention, can make various changes and modifications of the invention to adapt it to various usages and conditions.

[0366] This applies to the medium as a composition with its components, which may be groups of compounds as well as individual compounds, and it applies to the group of compounds with its individual components (i.e. compounds). With regard only to the concentration of the individual compounds relative to the medium as a whole, the term comprises means that the concentration of the compound or compounds in question is preferably 1% or more, particularly preferably 2% or more, very particularly preferably 4% or more.

[0367] For the present invention, "≤" means less than or equal to, preferably less than, and "≥" means greater than or equal to, preferably greater than.

[0368] For the present invention,

[0369] and

[0370] represents trans-1,4-cyclohexylene,

[0371]

[0372] represents a mixture of cis-1,4-cyclohexylene and trans-1,4-cyclohexylene, and

[0373] as well as

[0374] It represents 1,4-phenylene.

[0375] For the purposes of the present invention, the expression "dielectrically positive compound" means a compound with Δε>1.5, the expression "dielectrically neutral compound" means a compound with -1.5≤Δε≤1.5, and the expression "dielectrically negative compound" means a compound with Δε<-1.5. The dielectric anisotropy of the compound is determined here by dissolving 10% of the compound in a liquid-crystalline host and determining the capacitance of the resulting mixture in each case in at least one test cell with a cell thickness of 20 μm and a homeotropic and homogeneous surface alignment at 1 kHz. The measuring voltage is generally between 0.5 V and 1.0 V, but always below the capacitance threshold of the respective liquid-crystalline mixture (material) under investigation.

[0376] The host mixture for dielectrically positive and dielectrically neutral compounds was ZLI-4792 and the host mixture for dielectrically negative compounds was ZLI-2857, both from Merck KGaA, Germany. The values ​​for the individual compounds to be investigated were obtained from the change in the dielectric constant of the host mixture after addition of the compound to be investigated and extrapolated to 100% of the compound used. The compound to be investigated was dissolved in the host mixture in an amount of 10%. If the solubility of the substance was too low to be used for this purpose, the concentration was halved in the steps until the investigation could be carried out at the desired temperature.

[0377] If necessary, the liquid crystal medium according to the present invention may also contain other additives, such as stabilizers in conventional amounts. The amount of these additives used is preferably 0% or more to 10% or less in total, particularly preferably 0.1% or more to 6% or less, based on the amount of the entire mixture. The concentration of each compound used is preferably 0.1% or more to 3% or less. When specifying the concentration and concentration range of the liquid crystal compound in the liquid crystal medium, the concentration of these and similar additives is generally not considered.

[0378] For the purposes of the present invention, all concentrations are indicated as weight percent (%) unless expressly stated otherwise and relate to the respective mixture as a whole or mixture components unless expressly stated otherwise.In this context, the term "mixture" describes a liquid-crystalline medium.

[0379] Unless explicitly stated otherwise, the following symbols are used:

[0380] T(N,I) or T(N f ,I)(or clp.)

[0381] Clearing point [℃],

[0382] S f Ferroelectric Smectic Phase

[0383] N f Ferroelectric Nematic Phase

[0384] Dielectric properties at 1kHz and preferably at 20°C or at the respective specified temperatures:

[0385] ε ┴ The dielectric polarizability perpendicular to the director,

[0386] ε || The dielectric polarizability parallel to the director,

[0387] Δε dielectric anisotropy and in particular screening data for a single compound.

[0388] Again, particularly with respect to the data obtained from screening individual compounds in the smectic host mixture ZLI-4792:

[0389] n e The extraordinary refractive index measured at 20°C and 589nm,

[0390] n o Ordinary refractive index measured at 20°C and 589nm and

[0391] Δn is the optical anisotropy measured at 20°C and 589 nm.

[0392] The following examples explain the present invention, but do not limit the present invention. However, they show the preferred mixture concept of the compounds and their respective concentrations and their combinations with each other that are preferably adopted to those skilled in the art. In addition, the examples illustrate obtainable properties and property combinations.

[0393] The structural elements are defined by the abbreviations used for each compound:

[0394] Table A: Ring elements

[0395]

[0396]

[0397]

[0398] Table B: Bridge Unit

[0399]

[0400]

[0401] Table C: End Groups

[0402]

[0403]

[0404] Where n and m are each integers, and the three dots “…” are placeholders for other abbreviations in this table.

[0405] Besides the compounds of the formulae IA, IB and IC-1 / IC-2 / IC-3, the mixtures according to the invention preferably comprise one or more of the compounds mentioned below.

[0406] The following abbreviations are used: (n, m, k and l are each independently an integer, preferably 1 to 9, preferably 1 to 7; k and l may also be 0 and are preferably 0 to 4, more preferably 0 or 2 and most preferably 2; n is preferably 1, 2, 3, 4 or 5, in the combination "-nO-", it is preferably 1, 2, 3 or 4, preferably 2 or 4; m is preferably 1, 2, 3, 4 or 5, in the combination "-Om", it is preferably 1, 2, 3 or 4, more preferably 2 or 4. The combination "-lVm" is preferably "2V1".)

[0407] For the present invention and in the following examples, the structures of the liquid crystal compounds are indicated with the aid of acronyms and the conversion of the chemical formulae is carried out according to Tables A to C above. All groups C n H 2n+1 , C m H 2m+1 and C l H 2l+1 or C n H 2n , C m H 2m and C l H 2l are straight-chain alkyl or alkylene groups, in each case with n, m and 1 C atoms, respectively. Preferably, n, m and 1 are independently 1, 2, 3, 4, 5, 6 or 7. Table A shows the codes of the ring elements of the compound core, Table B lists the bridging units, and Table C lists the symbols of the left and right end groups of the molecule. The acronyms consist of the code of the ring element with the optional linking group, followed by the first hyphen and the code of the left end group, and the second hyphen and the code of the right end group. Table D shows the illustrative structures of the compounds and their respective abbreviations.

[0408] Table D

[0409] Exemplary preferred compounds of formula IA

[0410]

[0411]

[0412] Exemplary preferred compounds of formula IB:

[0413]

[0414]

[0415] Exemplary preferred compounds of formula IC-1:

[0416]

[0417]

[0418]

[0419] Exemplary preferred compounds of formula IC-3:

[0420]

[0421]

[0422] Other compounds used optionally:

[0423]

[0424]

[0425]

[0426] Mixture Examples

[0427] Exemplary mixtures are disclosed below.

[0428] The following base mixture (H-1) was prepared and used as the host mixture for preparing the exemplary mixtures.

[0429]

[0430]

[0431] c ) value when cooling,

[0432] Mixture Example 1

[0433] Compound PUS-3-2 was added to the host mixture H-1 at percentages of 10 wt %, 15 wt % and 20 wt %.

[0434]

[0435] The mixture was examined at different temperatures with the aid of microscopy, dielectric properties and calorimetry.

[0436]

[0437] c ) value when cooling

[0438] The spontaneous ferroelectric smectic phase is formed below the ferroelectric nematic phase from N f -S f The transition point extends to lower temperatures. The high ε value indicates that the ferroelectric smectic phase extends about 20 to 30 K below the transition temperature. For the current compound (PUS-3-2), it is typically in the range of ambient temperature to below 0°C.

[0439] Figure 1 The dielectric scanning diagram of the mixture Example No. 1.1 at 1 kHz is shown. The scanning direction here is from higher temperature to lower temperature. The figure shows that S f The relatively small hysteresis of the region. f The phase extends from below -20°C to +20°C, with an ε value of about 10 2 (-12℃) to 10 3 (20℃).

[0440] At 10 Hz, the ε value is significantly higher, 1000 times.

[0441] Mixture Example 2

[0442] Compound PPTUI-3-2 was added to the host mixture H-1 at percentages of 5 wt %, 10 wt % and 15 wt %.

[0443]

[0444] Table: Transition temperature of liquid crystal phase of mixture examples

[0445] Mixture Example No. Weight % of PPTUI-3-2 Clear Point <![CDATA[N f -S f change c) ]]> <![CDATA[N f -N shift c) ]]> 2.1 5 95℃ 9℃ 30℃ 2.2 10 98℃ 18℃ 28℃ 2.3 15 102℃ 25℃ 30℃

[0446] c ) value when cooling

[0447] The spontaneous ferroelectric smectic phase extends from the transition point to lower temperatures below the ferroelectric nematic phase. The high ε value indicates that the ferroelectric smectic phase extends about 20 to 30 K below the transition temperature. For the current compound (PUS-3-2), it is typically in the range of ambient temperature to below 0°C.

[0448] Rheological test:

[0449] About 2 ml samples of each of the mixtures 2.1, 2.2 and 2.3 were filled into small glass vials and kept at room temperature. The turbidity probe showed a strong change in viscosity by inspection (table).

[0450] Table: Viscosity of Mixture Examples

[0451]

[0452]

Claims

1. A liquid crystal medium exhibiting a ferroelectric smectic phase, wherein the medium comprises 5 wt% or more of a first component having a low polarity of -5<Δε<5, and 60 wt% or more of a second polar component having a Δε of 20 or more at 20°C and 1 kHz. 2 . A liquid-crystalline medium according to claim 1 , which exhibits a rotational viscosity at 10° C. of 2 Pa·s or more, measured in a cell 100 μm thick.

3. A liquid crystal medium according to claim 1 or 2, which exhibits a relative dielectric permittivity ε of 700 or more at 10° C. and 1 kHz. r .

4. A ferroelectric smectic liquid crystal medium comprising one or more compounds of formula IA, in A 1A express A 2A express A 3A express L 3A are each independently H, alkyl, alkoxy or alkoxyalkyl, each having 1 to 7 C atoms, preferably H, Z 1A and Z 2A are independently a single bond, -C≡C- or -CH=CH-, R 1A are independently alkyl groups having 1 to 12 C atoms, wherein in addition, one or more CH2 groups in these groups may in each case independently of one another be -C≡C-, -CH=CH-, -O-, -S-, -(CO)-O- or -O-(CO)- in such a way that the O / S atoms are not directly bonded to one another and wherein in addition one or more H atoms may be replaced by halogen; or represents H, R 2A are independently alkyl groups having 1 to 12 C atoms, wherein in addition, one or more CH2 groups in these groups may in each case independently of one another be -C≡C-, -CH=CH-, -O-, -S-, -(CO)-O- or -O-(CO)- in such a way that the O / S atoms are not directly bonded to one another and wherein in addition one or more H atoms may be replaced by halogen; or represents H, and n1 is 0, 1 or 2.

5. A liquid-crystalline medium according to any one of claims 1 to 4, comprising one or more compounds selected from the group consisting of: in A 3A express Z 1A and Z 2A are independently -(CO)-O- or -C≡C-, L 1A is F or H, L 2A is F or H, L 3A As defined for formula IA, preferably H or CH3, L 4A is F or H, preferably H, R 1A are independently alkyl groups having 1 to 12 C atoms, wherein in addition, one or more CH2 groups in these groups may in each case independently of one another be substituted by -C≡C-, -CF2-O-, -OCF2-, -CH=CH-, -O-, -S-, -(CO)-O- or -O-(CO)-, in such a way that the O / S atoms are not directly bonded to one another and in which in addition one or more H atoms may be replaced by a halogen; or represents H, and n1 is 1 or 2, preferably 1.

6. A liquid-crystalline medium according to any one of claims 1 to 5, comprising One or more compounds selected from formula IB or IC R 1C -A 3C -Z 2C -A 2C -Z 1C -A 1C -X 1C IC in X 1B is -CN, F or -NCS, X 1C represents -CN, F, CF3, -OCF3, -NCS, SF5 or O-CF=CF2, preferably -CN, Z 1B and Z 2B independently of one another represent a single bond, -(CO)-O- or -CF2-O-, Z 1C and Z 2C One of the two groups represents -(CO)-O- or -CF2-O- and the other represents a single bond, L 1B are independently H or CH3, L 2B is F or H, A 1B express Where L 8B denotes alkyl, alkoxy or alkoxyalkyl, each having 1 to 7 C atoms, A 1C express A 2C express A 3C express n2 is 1 or 2, preferably 1, R 1B and R 1C independently of one another represent an alkyl radical having 1 to 12 C atoms, wherein in addition one or more CH2 groups in these radicals can in each case independently of one another be substituted by -C≡C-, -CH=CH-, -O-, -S-, -(CO)-O- or -O-(CO)- in such a way that the O / S atoms are not directly bonded to one another and wherein in addition one or more H atoms may be replaced by halogen; or represents H.

7. Liquid-crystalline medium according to claim 6, which comprises a total of at least 80% of compounds of the formulae IA, IB and IC.

8. A liquid-crystalline medium according to any one of claims 1 to 7, comprising one, two, three or more compounds selected from formula ID-1 to ID-4, in X D Indicates CN, F, CF3, -OCF3, NCS, SF5 or O-CF=CF2, L 1D , L 2D , L 3D , L 4D , L 5D , L 6D and L 7D independently represent F, H, alkyl, alkoxy or alkoxyalkyl, each having 1 to 7 C atoms, Z 1D and Z 2D independently represent -(CO)-O-, -CF2-O-, a single bond, and preferably both represent -(CO)-O-, R 1D denotes an alkyl radical having 1 to 12 C atoms, wherein in addition one or more CH2 groups in these radicals may in each case independently of one another be substituted by -C≡C-, -CH=CH-, -O-, -S-, -(CO)-O- or -O-(CO)- in such a way that the O / S atoms are not directly bonded to one another and wherein in addition one or more H atoms may be replaced by halogen; or represents H, R 2D denotes alkyl, alkoxy or alkoxyalkyl, each having 1 to 7 C atoms, preferably CH3, OCH3, OCH2CH3, CH2OCH3, CH2OCH2CH3, CH2CH2OCH3, CH2CH2OCH3, CH2CH2OCH2CH3 or CH2CH2CH2OCH3, A 1D represents a single bond, in L 8D denotes alkyl, alkoxy or alkoxyalkyl, each having 1 to 7 C atoms, preferably CH3, OCH3, OCH2CH3, CH2OCH3, CH2OCH2CH3, CH2CH2OCH3, CH2CH2OCH3, CH2CH2OCH2CH3 or CH2CH2CH2OCH3.

9. Medium according to one or more of claims 1 to 8, which, upon cooling from a higher temperature, exhibits a ferroelectric smectic phase at least at a temperature between 10°C and 0°C.

10. Medium according to one or more of claims 1 to 9, which exhibits a hysteresis in its dielectric properties at varying temperatures.

11. Medium according to one or more of claims 1 to 10, which exhibits an interconvertible ferroelectric smectic phase.

12. A method for preparing a liquid crystal medium exhibiting a ferroelectric smectic phase, wherein 5 wt% or more of a first component having a low polarity of -5<Δε<5, 60 wt% or more of a compound contained in a second ferroelectric component having a ferroelectric nematic phase, and any other components or additives are combined and mixed with each other.

13. Use of a liquid-crystalline medium according to at least one of claims 1 to 11 for electro-optical purposes, for supercapacitors and for electromechanical devices, including generators and actuators.

14. Use of a liquid-crystalline medium according to at least one of claims 1 to 11 in nonlinear optical components, sensors or memory devices.

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