Ferroelectric smectic liquid crystal medium

Abstract

A ferroelectric smectic liquid crystal medium is provided. 【Solution means】The novel LC medium exhibits a new spontaneous, self-supporting ferroelectric smectic phase. These typically contain one or more dielectrically neutral aromatic compounds as further described herein in a highly polar host mixture typical of ferroelectric nematic mixtures. The mixtures are useful for electro-optical, electronics, electromechanical and other applications for materials having a very high dielectric constant. Further, the present invention relates to a liquid crystal device, an electrical and electronic element containing the liquid crystal medium according to the present invention.

Description

Technical Field

[0001] The novel liquid crystal media according to the present invention exhibit a novel spontaneous, self-supporting ferroelectric smectic phase over a wide range of temperatures. These typically contain one or more dielectrically neutral aromatic compounds, further described herein, in a highly polar host mixture typical of ferroelectric nematic mixtures. This mixture is useful for electro-optics, electronics, electromechanics, and other applications of materials having a very high dielectric constant. Further, the present invention relates to liquid crystal devices, electrical and electronic elements containing the liquid crystal media according to the present invention.

Background Art

[0002] In recent years, the fields of application of liquid crystal (LC) compounds have expanded significantly to various types of display devices, electro-optical devices, electronic components, sensors, etc. For this reason, particularly in the field of nematic liquid crystals, a large number of various structures have been proposed. Nematic liquid crystal mixtures have found the widest use to date in flat panel display devices.

[0003] Most of these devices, including all common LCD television sets, LCD desktop monitors, and mobile LCD devices, employ a nematic liquid crystal phase. Some alternative liquid crystal phases such as the smectic phase or the blue phase are known. However, while no liquid crystal materials have been found that essentially exhibit such unique properties, the ferroelectric smectic phase has only been realized in very thin films. More recently, several chemical structures have been reported to exhibit ferroelectric nematic behavior.

[0004] First, Hiroya Nishikawa, Kazuya Shiroshita, Hiroki Higuchi, Yasushi Okumura, Yasuhiro Haseba, Shin-ichi Yamamoto, Koki Sago, and Hirotsugu Kikuchi, Adv. Mater. (2017), Vol. 29, p. 1702354 (Non-Patent Document 1) describes compounds of Formula A having ferroelectric nematic behavior at temperatures between about 45°C and 68°C.

[0005]

Chem.

[0006] Furthermore, Nerea Sebastian et al., Physical Review Letters (2020), Vol. 124, p. 037801 (Non-Patent Document 2) describes compounds of Formula B having similar behavior at temperatures between about 120°C and 133°C.

[0007]

Chem.

[0008] Furthermore, N f -LC phase, a comparison of the only two substances available for the N-LC phase, is presented by Xi Chen et al., PNAS (June 23, 2020), Vol. 117 (No. 25), pp. 14021 - 14031 (Non-Patent Document 3). O.D. Lavrentovich, Proc Nat Acad Sci USA (2020), Vol. 117 (No. 26), pp. 14629 - 14631 (Non-Patent Document 4) emphasizes the high significance of the new N f -LC phase.

[0009] Very high values of the dielectric constant of these substances and some of their structural variants are reported in the paper by Li et al., Sci. Adv. 2021, Vol. 7 (Non-Patent Document 5).

[0010] A new ferroelectric nematic substance of formula C was published by Atsutaka Manabe, Matthias Bremer, Martin Kraska (2021): Ferroelectric phase at and below room temperature, Liquid Crystals, Volume 48, Pages 1079 - 1086 (DOI 10.1080 / 02678292.2021.1921867) (Non - Patent Document 6), and is described as having a ferroelectric nematic liquid crystal phase (N f -LC phase) close to ambient temperature. The ambient temperature, sometimes also called room temperature, narrowly means a temperature of 20 °C in this specification.

[0011]

Chemical formula

[0012] Y. Song et al. (Phys.Chem.Chem.Phys., 2022, DOI: 10.1039 / d2cp01110g) (Non - Patent Document 7) describes substances that exhibit a ferroelectric nematic phase at high temperatures, which have the following structure D.

[0013]

Chemical formula

[0014] For none of these compounds has a ferroelectric smectic phase been reported.

[0015] Developing ferroelectric LC phases for technical applications has obvious advantages due to their applicability at ambient temperature. Technical devices and electronic applications are usually designed to have an operating range above and below ambient temperature, room temperature, for example 15 °C - 25 °C, preferably 0 °C - 50 °C, and more preferably an even wider range.

[0016] Ferroelectric nematic displays have been proposed in German Patent Application Publication No. 19629551 (Patent Document 1), but no specific materials that can satisfy the required ferroelectric nematic properties are disclosed at all.

[0017] The use of fluorinated liquid crystal materials is known to those skilled in the art. Various compounds containing two 2,6-difluorinated 1,4-phenylene rings have already been described as liquid crystal materials or mesogenic materials, for example, in International Publication No. 2015 / 101405 (Patent Document 2) and in various other documents. The compounds proposed therein have three to four aromatic rings and are characterized as conventional smectic materials without ferroelectric smectic properties.

Prior Art Documents

Patent Documents

[0018]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Non-Patent Documents

[0019]

Non-Patent Document 1

Non-Patent Document 2

[0020] The object of the present invention was to find a mixture concept for the normal induced smectic phase of a ferroelectric smectic liquid crystal phase medium (S f -LC phase medium).

[0021] Therefore, a further object of the present invention was to find a compound suitable as a component of a ferroelectric smectic liquid crystal medium, preferably having a high clearing point and a low melting point, showing a wide and appropriate temperature range of the ferroelectric smectic phase, and further, the mixture was intended to be thermally and photochemically stable under general conditions in the field of use.

Means for Solving the Problem

[0022] Surprisingly, it has been found that a medium containing several types of compounds selected as follows can spontaneously realize a ferroelectric smectic phase in the bulk within an advantageous temperature range. By using these, an LC medium having unprecedented characteristics can be obtained. This includes not only devices that require particularly high or extremely high dielectric anisotropy, liquid crystal media for electro-optical displays, but also liquid crystal media for other devices such as electronic applications that utilize the high dielectric constant of materials, capacitors, and electromechanical devices, but is not limited thereto. The media and compounds used according to the present invention are sufficiently stable and colorless. In particular, they are characterized by a very high dielectric constant, especially a very high dielectric anisotropy (Δε), and therefore, when used in an optical switching element, a low threshold voltage is required. According to the present invention, at room temperature and much lower temperatures, the desired S f -LC phase can be formed.

[0023] The high dielectric constant enables outstanding physical performance. Also, a high (specific) dielectric constant is particularly advantageous as a dielectric in a capacitor because it produces a high capacitance on a specific electrode area. In addition, the media have very low electrical conductivity and are unique compared to conventional high ε r materials (such as barium titanate) due to their fluidity.

[0024] Compared to nematic LC, the materials of the present invention have a high viscosity. This unique feature can be particularly beneficial when the properties of the low-viscosity liquid of nematic materials cause problems. The possibility of leakage of the gel-like ferroelectric smectic material is very low due to its high viscosity. It can be heated above the transition temperature to lower the viscosity for filling cells or other containers.

[0025] Thus, in one main aspect, the present invention relates to a liquid crystal medium exhibiting a ferroelectric smectic phase, the medium comprising, at 5 wt% or more, a first component having a low polarity of -5 < Δε < 5 (measured at 20 °C and 1 kHz) and, at 60 wt% or more, a second polar component having a Δε of 20 or more. The ferroelectric smectic phase can be obtained in the bulk medium without the need to use specific boundary layers or layer thicknesses.

[0026] The compound of the first component is preferably aromatic, more preferably contains a biphenyl substructure, and has a total of 2 to 4 ring systems.

[0027] Thus, in another aspect, the present invention relates to a method for preparing a liquid crystal medium exhibiting a ferroelectric smectic phase, which comprises combining, mixing with each other, a first component having a low polarity of -5 < Δε < 5 at 5 wt% or more, a compound contained in a second ferroelectric component at 60 wt% or more, and other components or additives, and the second polar component has a ferroelectric nematic phase by itself from the beginning.

[0028] The present invention further relates to a ferroelectric smectic liquid crystal medium containing one or more compounds of formula IA.

Chemical formula

[0029] In the formula,

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Brief Description of the Drawings

[0030]

Figure 1

Mode for Carrying Out the Invention

[0031] (Detailed Description) The compounds of formula IA are of low polarity, preferably -5 < Δε < 5, more preferably -3 < Δε < 3, and are grouped as the first component.

[0032] The liquid crystal medium preferably further comprises one or more compounds selected from the compounds of formula IB and IC, and is preferably part of the second polar component.

[0033]

Chemical formula

[0034]

Chemical formula

[0035] In the formula, X 1B represents -CN, F or -NCS, preferably -CN, X 1C represents -CN, F, CF3, -OCF3, -NCS, SF5 or O-CF=CF2, preferably -CN or -NCS, most preferably -CN, Z 1B and Z 2B each independently represent a single bond, -(CO)-O- or -CF2-O-, Z 1C and Z 2C one of both groups represents -(CO)-O- or -CF2-O-, and the other represents a single bond, preferably Z 1C represents -(CO)-O- or -CF2-O-, and Z 2C represents a single bond, L 1B independently represents H or CH3, preferably H,

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Chemical formula

[0036] The medium is, · Preferably, 15% by weight or more of the compound of formula IB, and / or · Preferably, one or more compounds of formula IC selected from the following formulas IC-1 to IC-3, preferably 15% by weight, preferably 20% by weight, more preferably 30% by weight, most preferably 40% by weight or more are included.

[0037] The percentages are provided under the situation where the whole medium constitutes 100% by weight of the medium.

[0038] Each of the groups R in formulas IA, IB and IC and their respective sub-formulas 1A , R 1B and R 1C preferably represents alkyl having 1 to 8 carbon atoms, alkoxy having 1 to 8 carbon atoms or alkenyl having 2 to 8 carbon atoms. These alkyl chains are preferably linear or, in the case of R 1C , preferably branched by a single methyl or ethyl substituent at the 2- or 3-position. R 1A , R 1B and R 1C particularly preferably represent a linear alkyl group having 1 to 7 C atoms or an unbranched alkenyl group having 2 to 8 C atoms, particularly an unbranched alkyl having 1 to 5 C atoms.

[0039] Alternatively, preferred groups R 1A , R 1B and R 1C are selected from cyclopentyl, 2-fluoroethyl, cyclopropylmethyl, cyclopentylmethyl, cyclopentylmethoxy, cyclobutylmethyl, 2-methylcyclopropyl, 2-methylcyclobutyl, 2-methylbutyl, 2-ethylpentyl and 2-alkyloxyethoxy.

[0040] Compounds of formulas IA, IB and IC1 to IC-3 containing branched or substituted terminal groups R 1A , R 1B and R 1C are important for better solubility in the liquid crystal base material. Group R1A , R 1B and R 1C are each preferably linear.

[0041] The group R 1A , R 1B and R 1C are each particularly preferably selected from the following substructures.

[0042]

Chemical formula

[0043] However, for the terminal groups, the following abbreviations are used.

[0044]

Chemical formula

[0045] A further embodiment of the present invention is directed to a ferroelectric smectic liquid crystal medium containing one or more compounds selected from formulas IA, IB, and IC as defined above.

[0046] In a preferred embodiment, the medium according to the present invention preferably contains one, two, or three or more compounds of formula IA-A.

[0047]

Chemical formula

[0048] wherein

Chemical formula

Chemical formula

[0049] In the above formula IA and its sub-formula IA-A, R 1A and R 1B preferably independently represent alkyl having 1 to 7 C atoms or alkenyl having 2 to 7 C atoms.

[0050] The compounds of formula IA and IA-A are preferably selected from one, two or more than two compounds of formula IA-1 to IA-3.

[0051]

Chemical formula

[0052] wherein, R 1A and R 2A are defined by formula IA, L 1A ~L 6A are independently H, CH3 or F, and are preferably selected from the group of the following formulas IA-1-1 to IA-3-2.

[0053] [Chemical formula]

[0054] In the formula, the parameters have the respective meanings given above, and preferably represent an alkyl having 1 to 7 carbon atoms or an alkenyl having 2 to 7 carbon atoms.

[0055] More preferably, the low Δε compounds of the medium of the present invention are selected from the formulas IA-1-1, IA-1-2, IA-2-1, IA-2-3 and IA-3-1, and most preferably IA-1-1 or IA-2-1.

[0056] In a preferred embodiment, the present invention relates to a ferroelectric smectic liquid crystal medium containing one or more compounds selected from IC-1 to IC-3, which are preferably the ratios and preferred formulas defined below and provided throughout this disclosure.

[0057] [Chemical formula]

[0058] In the formula, the variables are defined in formula IC, m and n are 0 or 1, and m + n = 1. More preferably, the medium according to the present invention contains at least one compound of formula IC-1.

[0059] In a preferred embodiment, the medium of the present invention preferably contains one, two or more than two compounds of formula IB-1 and / or IB-2 and / or IB-3.

[0060] [Chemical formula] R 1Bis an alkyl group having 1 to 12 carbon atoms, preferably 1 to 7, more preferably 1 to 6, and most preferably 1 to 5 carbon atoms (provided that in addition, one or more CH2 groups in these groups are each independently such that O / S atoms are not directly connected to each other to form -C≡C-, -CF2-O-, -OCF2-, -CH=CH-,

Chemical formula

Chemical formula

[0061]

Chemical formula

[0062]

Chemical formula

[0063] In the formula, the parameters have the respective meanings given above, and in particular in formulas IB-1-1 to IB-1-3, Z 1B preferably represents -CF2-O-, and in particular in formulas IB-2-1 and IB-2-2, Z 2B preferably represents -CF2-O-, and in particular in formula IB-2-3, Z 2B preferably represents -C(O)O-.

[0064] In a preferred embodiment, the medium according to the invention preferably comprises one, two or more than two compounds selected from the group of formulas IC-1-1 to IC-3-6.

[0065]

Chemical formula

[0066] wherein A 1C is defined as above and is preferably selected from the group of formulas IC-1-1-1 to IC-3-5-2, preferably from the group of formulas 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.

[0067]

Chemical formula

[0068]

Chemical formula

[0069]

Chemical formula

[0070] wherein the parameters have the respective meanings given above and preferably L 1C represents H, Z 1C represents -CF2-O- or -(CO)-O-, and X 1C represents -CN or F, preferably -CN.

[0071] Particularly preferred compounds among the compounds of Formulas IC-1-1 to IC-1-4 for use in the medium are compounds of the following formula.

[0072]

Chemical formula

[0073] In the formula, the parameters are defined as above, preferably L 1C is H.

[0074] In a preferred embodiment of the present invention, the medium comprises compounds selected from compounds of Formulas IA, IB and IC, preferably one or more of Formula IA and three, four, five, six or more compounds of Formulas IB and IC up to 100%. In this embodiment, the medium preferably consists mainly of these compounds, more preferably they consist essentially of them, and most preferably they consist substantially entirely of them.

[0075] In addition to the compounds of Formulas IA, IB and IC-1 / -2 / -3, the medium of the present invention optionally, preferably essentially, contains one, two, three or more compounds selected from Formulas ID-1 to ID-4.

[0076]

Chemical formula

Chemical formula

Chemical formula

[0077] In the formula, the variable groups R 1D and L 8D are defined as above.

[0078] Compounds of formulas IA, IB, IC and ID represent "Group 1" of the compounds. In a preferred embodiment of the present invention, the medium contains up to 100% of one or more compounds selected from Group 1 of the compounds, preferably 3, 4, 5 or 6 or more compounds. In this embodiment, the medium preferably consists mainly of these compounds, more preferably they consist essentially of them, and most preferably they consist substantially entirely of them.

[0079] In the present invention, unless otherwise indicated in individual cases, the following definitions apply in relation to the identification of the components of the composition.

[0080] · "Containing": The concentration of the component in question in the composition is preferably 5% or more, particularly preferably 10% or more, and very particularly preferably 20% or more.

[0081] · "Consisting mainly of": The concentration of the component in question in the composition is preferably 50% or more, particularly preferably 55% or more, and very particularly preferably 60% or more.

[0082] · "Consisting essentially of": The concentration of the component in question in the composition is preferably 80% or more, particularly preferably 90% or more, and very particularly preferably 95% or more. And

[0083] · "Substantially completely composed": The concentration of the target component in the composition is preferably 98% or more, particularly preferably 99% or more, and very particularly preferably 100.0%.

[0084] The medium according to the present invention preferably contains 10%, 15%, or 20% or more of a first component having a low polarity of -5 < Δε < 5 (measured at 20 °C and 1 kHz). The medium preferably contains 75% or more, more preferably 80% or more, of a polar component having Δε of 20 or more, preferably Δε of 50 or 100 or more (measured at 20 °C and 1 kHz). Preferably, the medium exhibits a rotational viscosity of 2 Pa·s or more, more preferably 5 Pa·s, when measured in a 100-μm-thick cell at 10 °C. Further, the relative permittivity ε r is 100 or more at 10 °C, 1 kHz, or the relative permittivity ε r is preferably 1000 or more at 10 Hz.

[0085] Preferably, the medium according to the present application satisfies one or more of the following conditions. They are preferably

[0086] · 5% by weight or more of the compound of formula IA, more preferably 10% by weight or more, more preferably 15% by weight or more, and most preferably 20% by weight or more of the compound of formula IA, and preferably 25% by weight or less of the compound of formula IA,

[0087] · 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,

[0088] · 40% by weight or more of the compound selected from formula IA and IB, more preferably 60% by weight or more, more preferably 75% by weight or more, and most preferably 90% by weight or more of the compound selected from formula IA and IB, that is, the total of the compounds of formula IA and IB is preferably at least the upper limit,

[0089] · Compounds selected from formulae IC-1, IC-2 and IC-3, in an amount of 5% by weight or more, preferably 10% by weight or more, more preferably 15% by weight or more, even more preferably 20% by weight or more, and most preferably 25% by weight or more,

[0090] · Optionally, compounds of formula ID (ID-1, ID-2, ID-3, ID-4) in an amount of 2% by weight or more, more preferably 5% by weight or more, even more preferably 10% by weight or more, and most preferably 15% by weight or more of the compound of formula ID,

[0091] · One, two or more than two compounds selected from formula IA-1-1 or formula IA-1-2, preferably formula AUUQGU-n-N, AUUQGG-n-N, PGGUQU-n-F, and most preferably compounds selected from the group consisting of AUUQGU-2-N, AUUQGU-3-N, AUUQGU-4-N, AUUQGU-5-N and AUUQGU-6-N,

[0092] · One, two or more than two, preferably three or more compounds of formula IB-1, preferably formula GUUQU-n-N and / or DUUQU-n-N, and most preferably compounds selected from the group consisting of 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,

[0093] · One, two or more than two compounds of formula IB-1-3, preferably formula GUUQU-n-N, more preferably compounds selected from the group consisting of GUUQU-3-N, GUUQU-4-N and GUUQU-5-N,

[0094] · One, two or more than two compounds of formula IB-3-1, preferably formula DUUQU-n-F, more preferably compounds selected from the group consisting of DUUQU-3-F, DUUQU-4-F and DUUQU-5-F,

[0095] ·One, two, or three or more compounds selected from the group of formulas IC-1-1, preferably formula MUZU-n-N or MUQU-n-N, more preferably compounds selected from the group consisting of compounds MUZU-2-N, MUZU-3-N, MUZU-4-N, and MUZU-5-N,

[0096] ·One, two, or three or more compounds selected from the group of formulas IC-3, preferably formulas IC-3-2 and IC-3-3, more preferably selected from formula MUU-n-N or UMU-n-N, and even more preferably compounds selected from the group consisting of compounds MUU-3-N, MUU-4-N, MUU-5-F, UMU-3-N, UMU-4-N, and UMU-5-N,

[0097] ·One, two, or three or more compounds selected from the group of formulas IC-1-1, preferably selected from formula GUZU-n-N or GUQU-n-N, and more preferably compounds 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,

[0098] and / or ·One, two, or three or more compounds selected from the group of formulas IC-1-1-3 and IC-1-1-4, preferably formula UUZU-n-N and / or UUQU-n-N, and most preferably compounds selected from the group consisting of compounds UUZU-2-N, UUZU-3-N, UUZU-4-N, UUZU-5-N, UUQU-2-N, UUQU-3-N, and UUQU-4-N,

[0099] wherein n is 1, 2, 3, 4, 5, 6, or 7.

[0100] In another preferred embodiment of the present invention, the above-mentioned compounds of formulas IA, IB, and IC-1 / -2 / -3 are the first group of compounds, compound group 1. In this embodiment, the concentration of the compounds in this compound group 1 is preferably in the range of 70% or more, preferably 80% or more, more preferably 90% or more to 100% or less.

[0101] The medium according to the present specification contains one or more compounds selected from the group of compounds of formula II and III (Group 2), preferably at a concentration of more than 0% to 40% or less.

[0102]

Chemical formula

[0103]

Chemical formula

[0104] In the formula, R 2 represents alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 carbon atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 carbon atoms, preferably alkyl or alkenyl,

Chemical formula

Chemical formula

[0105] Again, optionally either in substitution or addition, contains one or more compounds selected from the group of compounds of formula IV and V (Group 3), preferably at a concentration of more than 0% to 15%.

[0106]

Chem.

[0107] In the formula, R 41 and R 42 each independently has the meaning shown above for R 2 in Formula II, and preferably R 41 represents alkyl, R 42 represents alkyl or alkoxy, or R 41 represents alkenyl, R 42 represents alkyl,

Chem.

Chem.

[0108] Optionally again, either alternatively or additionally, one or more compounds selected from the group of compounds of formulas I and VI - IX, preferably two or more compounds, are preferably included at a concentration of more than 0% to 20%.

[0109]

Chemical formula

[0110] In the formula, represents TIFF2025520133000052.tif247166,

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Chemical formula

[0111] Again, optionally preferably necessarily, either alternatively or additionally, preferably contains one or more compounds selected from the group of compounds of formula B, group 5, preferably 2 or 3 or more compounds, preferably at a concentration of more than 0% to 20%.

[0112] [Chemical formula]

[0113] wherein [Chemical formula] [Chemical formula] represents n represents 0, 1 or 2, preferably 1, R 1 is an alkyl group having 1 to 7 C atoms (however, in this group, one or more CH2 groups, preferably one CH2 group, may each independently be -C≡C-, -CF2-O-, -OCF2-, -O-, -(CO)-O-, -O-(C=O)-, cyclopropylene, 1,3-cyclobutylene, 1,3-cyclopentylene, 1,3-cyclopentenylene, preferably cyclopropylene or 1,3-cyclopentylene, and preferably one CH2 group may be replaced by a 1,2-cyclopropylene group, a 1,3-cyclopentylene group or a 1,3-cyclopentenylene group), an alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms, preferably alkyl or alkenyl (however, one -CH2- group is arranged so that O atoms are not directly connected to each other and may be replaced by cyclopropylene, 1,3-cyclobutylene, 1,3-cyclopentylene, 1,3-cyclopentenylene, preferably cyclopropylene or 1,3-cyclopentenylene, and one or more H atoms in the group may be replaced by halogen), and X 1 is F, Cl, a fluorinated alkyl, a fluorinated alkenyl, a fluorinated alkoxy or a fluorinated alkenyloxy (the latter four groups preferably have 1 to 4 C atoms), more preferably F, Cl, CF3 or OCF3, However, each ring, preferably a phenylene ring, may optionally be substituted by one or two alkyl groups, preferably a methyl group and / or an ethyl group, preferably one methyl group each.

[0114] A medium containing one or more compounds of Groups 1 and 2 is preferred.

[0115] The corresponding starting materials can generally be readily prepared by synthetic methods known from the literature by those skilled in the art or are commercially available. The reaction methods and reagents used are in principle known from the literature.

[0116] In the present disclosure, the 2,5-disubstituted dioxane ring of the following formula is

Chemical formula

Chemical formula

[0117] The liquid crystal medium according to the invention has a wide temperature range of the ferroelectric smectic phase. It exhibits the range of the ferroelectric smectic phase at 20° and above and below (ambient temperature). It extends over a technically most interesting range of at least 10 to 50 °C and significantly beyond to lower and / or higher temperatures. Therefore, it is suitable for all kinds of household or industrial use and to some extent even outdoors. The medium exhibits the ferroelectric smectic phase in a temperature range of at least 20 Kelvin or more, more preferably 30 K or more, and most preferably 40 K or more. Preferably, the medium exhibits the temperature range of the enantiotropic ferroelectric smectic phase, i.e., the ferroelectric smectic phase that occurs not only during cooling from a high temperature but also during heating from a low temperature. The achievable combinations of the temperature range, clearing point, low-temperature stability (LTS), (specific) dielectric constant, dielectric anisotropy, and optical anisotropy of the ferroelectric smectic phase containing the compounds of formulae IA, IB, and IC-1 / -2 / -3 are far superior to equivalent types of previous materials from the prior art. So far, materials with a ferroelectric smectic phase range could only be utilized when appropriate boundary conditions existed and when using rare materials such as bimesogens.

[0118] In addition, the mixture according to the invention exhibits a very wide smectic-nematic phase range with a clearing point of generally 85 °C or higher.

[0119] The liquid crystal medium according to the invention preferably exhibits a temperature range of the ferroelectric smectic phase of 20 degrees width or more, which preferably extends over a range of 40 degrees or more, more preferably 60 degrees or more.

[0120] Preferably, the liquid crystal medium according to the invention exhibits a ferroelectric smectic phase of preferably 0 °C to 10 °C, more preferably 0 °C to 20 °C, more preferably -10 °C to 25 °C, more preferably -20 °C to 30 °C, and most preferably -20 °C to 40 °C.

[0121] In another preferred embodiment, the liquid crystal medium according to the invention preferably exhibits a ferroelectric smectic phase at 10 °C to 40 °C, more preferably at 10 °C to 50 °C, more preferably at 10 °C to 60 °C, and most preferably at 10 °C to 70 °C.

[0122] The liquid crystal medium according to the invention exhibits outstanding dielectric properties.

[0123] Due to its outstanding properties, the medium can function in many new technical fields and can be used for electro-optical purposes, for supercapacitors, non-linear optical elements, electric field sensors, memory devices and electrical machines including generators (i.e., ambient power generation devices) and actuators. The material may enable, for example, unconventional modes of ambient power generation from vibrational motion.

[0124] The medium according to the invention preferably has a value of ε r of 700 or more, more preferably 800 or more, more preferably 15000, still more preferably 30000 or more, and even more preferably 35000 or more (at 20 °C and 10 Hz).

[0125] These dielectric properties are achieved at the temperature at which the medium is in the ferroelectric smectic phase. The dielectric properties may in particular exhibit hysteresis behavior with respect to temperature changes, in which case the value obtained at a certain temperature may depend on the history of the material, i.e., whether the material has been heated or cooled.

[0126] This effect can be beneficially used, inter alia, in electro-optical devices, for example to enable the operation of a device in a bistable mode, as is known, for example, from ferroelectric smectic devices.

[0127] The liquid crystal medium according to the present invention contains, as further constituent components in addition to one or more compounds according to the present invention, preferably 2 to 40 kinds, particularly preferably 4 to 20 kinds of compounds. In particular, these media may contain, in addition to one or more compounds according to the present invention, 1 to 25 kinds of components. These further constituent components are preferably selected from ferroelectric smectic or nematogenic (monotropic or isotropic) substances.

[0128] Prior art ferroelectric substances and similar compounds having a high dielectric constant for combination with the substances of the present application are selected, for example, from the following structures.

[0129]

Chemical formula

[0130] The medium according to the present invention preferably contains 1% to 100%, more preferably 10% to 100%, particularly preferably 50% to 100% of the compounds of formula IA and / or IB and / or IC-1 / IC-2 / IC-3 preferably used according to the present invention.

[0131] The present invention also relates to a method for preparing a liquid crystal medium described herein, which comprises combining at least one or more compounds of formula IA, preferably one or more compounds of formula IB, IC, ID at 5% by weight, 10% by weight, 15% by weight or 20% by weight or more and other components or additives and mixing them with each other. The resulting mixture amounts to 100% by weight.

[0132] The liquid crystal mixture according to the present invention is prepared by conventional methods per se. Generally, the desired amounts of components used in smaller amounts are preferably dissolved at high temperature in the components constituting the main component. It is also possible to mix solutions of the components in an organic solvent, such as acetone, chloroform or methanol, and after thorough mixing, remove the solvent again, for example by distillation. Furthermore, it is possible to prepare the mixture using other conventional methods, such as premixes, such as homolog mixtures, or using a so-called "multi-bottle" system.

[0133] The liquid crystal mixture is also known to those skilled in the art and may contain further additives described in the literature. For example, 0 to 15%, preferably 0 to 10% of a dichroic dye, chiral dopant, stabilizer or nanoparticles can be added. The individual compounds added are used at a concentration of 0.01 to 6%, preferably 0.1 to 3%. However, in this specification, the concentration data of the other components of the liquid crystal mixture, i.e., the liquid crystal or mesogenic compounds, are given without considering the concentrations of these additives.

[0134] The liquid crystal mixture according to the present invention makes it possible to significantly broaden the range of available parameters.

[0135] The present invention also relates to an electro-optical display comprising a medium of this type (in particular, a TFT display having two planar parallel outer plates forming a cell together with a frame, an integrated non-linear element for switching the individual pixels on the outer plates, and a smectic liquid crystal mixture having positive dielectric anisotropy and high specific resistance arranged in the cell), and to the use of these media for electro-optical purposes.

[0136] The expression "alkyl" includes unbranched and branched alkyl groups having from 1 to 12 carbon atoms, preferably from 1 to 10 carbon atoms, particularly preferably unbranched groups methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl and n-heptyl, and alternatively n-butyl, n-pentyl, n-hexyl and n-heptyl groups substituted with one methyl, ethyl or propyl. Groups having from 1 to 5 carbon atoms are generally preferred.

[0137] The expression "alkenyl" includes unbranched and branched alkenyl groups having up to 12 carbon atoms, particularly unbranched groups. Particularly preferred alkenyl groups are C2-C7-1E-alkenyl, C4-C7-3E-alkenyl, C5-C7-4-alkenyl, C6-C7-5-alkenyl and C7-6-alkenyl, particularly C2-C7-1E-alkenyl, C4-C7-3E-alkenyl and C5-C7-4-alkenyl. Examples of preferred alkenyl groups 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 the like. Groups having from 2 to 5 carbon atoms are generally preferred.

[0138] The expression "halogenated alkyl group" preferably includes mono- or polyfluorinated and / or chlorinated groups. Perhalogenated groups are included. Fluorinated alkyl groups, particularly CF3, CH2CF3, CH2CHF2, CHF2, CH2F, CHFCF3 and CF2CHFCF3 are particularly preferred. The expression "halogenated alkenyl group" and related expressions are correspondingly explained.

[0139] The structure of the matrix display according to the present invention from a polarizing plate, an electrode substrate, and a surface-treated electrode corresponds to a normal design for this type of display. The term normal design as used herein is broadly described and encompasses all derivatives and modifications of matrix displays, and in particular matrix display elements based on poly-Si-TFTs.

[0140] However, the essential difference between the display according to the present invention and a conventional display based on a twisted smectic cell lies in the selection of the liquid crystal parameters of the liquid crystal layer.

[0141] The following examples are not intended to limit the present invention, but to illustrate it. Those skilled in the art will be able to obtain from the examples details not given in the general description, and will be able to generalize them according to general expertise and apply them to specific problems.

[0142] Above and below, the percentage data represents weight %. Unless otherwise specified, for example, melting point T(C,N), phase transition from smectic (Sm) to nematic (N) T(S,N), T(S t ,N f ) and clearing point T(N,I), T(N f ,I) and all temperature values shown in this application are indicated in degrees Celsius (°C), and all temperature differences are correspondingly indicated in degrees (° or degrees). Further, C is the liquid crystal state, N is the nematic phase, Sf is the ferroelectric smectic phase, Nf is the ferroelectric nematic phase, Sm is the smectic phase (more specifically SmA, SmB, etc.), Tg is the glass transition temperature and I is the isotropic phase. The data between these symbols represents the transition temperature. Δn represents the optical anisotropy (589 nm, 20 °C), and Δε represents the dielectric anisotropy (1 kHz, 20 °C).

[0143] Physical, physicochemical, and electro-optical parameters are determined by generally known methods, in particular as described in the document "Merck Liquid Crystals - Licristal® - Physical Properties of Liquid Crystals - Explanation of Measurement Methods", 1998, Merck, Darmstadt. The ferroelectric phase measurements were carried out according to A. Manabe, M. Bremer, M. Kraska (2021), Liquid Crystals, Vol. 48, pp. 1079 - 1086 (DOI 10.1080 / 02678292.2021.1921867) and the references cited therein.

[0144] The appearance of the ferroelectric smectic phase of the material is identified using differential scanning calorimetry (DSC), observing the texture under a polarized microscope with a hot stage for controlling cooling or heating respectively, and additionally confirmed by the temperature dependence of the dielectric properties. The transition temperatures are mainly determined by detecting the optical behavior under a polarized microscope. The dielectric permittivity is measured at a frequency of 1 kHz or 10 Hz using a dielectric spectrometer from Novocontrol consisting 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-made sample cell designed for liquid samples. The sample cell is made of polished stainless steel with a cell gap of 110 pm. The measurements are performed both during heating and cooling of the sample.

[0145] The dielectric anisotropy Δε of the individual substances is determined at 20 °C and 1 kHz. For this purpose, 5 - 10 wt% of the substance to be investigated and measured is dissolved in the dielectrically positive mixture ZLI-4792 (Merck), and the measured values are extrapolated to a concentration of 100%. The optical anisotropy Δn is determined at 20 °C and a wavelength of 589.3 nm.

[0146] In this application, unless otherwise explicitly stated, the plural form of a term represents both the singular and plural forms, and vice versa. Further combinations of embodiments and variations of the present invention according to the detailed description also arise from the appended claims or from multiple combinations of these claims.

[0147] Further combinations of embodiments of the present invention and modifications of the present invention are also disclosed by the claims.

[0148] It is confident that those skilled in the art can make the most of the present invention using the foregoing description without further consideration. Therefore, the foregoing preferred specific embodiments should be considered merely illustrative and not limiting in any way the remainder of the present disclosure. The foregoing examples can be repeated successfully in the same manner by substituting the reactants and / or operating conditions of the present invention described generally or specifically in the foregoing examples with those used in the foregoing examples.

[0149] From the foregoing description, those skilled in the art can easily identify the essential features of this invention and make various modifications and changes to adapt the present invention to various uses and conditions without departing from its spirit and scope.

[0150] This applies to both the medium as a composition having a group of compounds of the composition and the components that can be the individual compounds of the composition, and the group of compounds having their respective components and compounds. As far as the concentration of the individual compounds with respect to the whole medium is concerned, the term "comprising" means that the concentration of the compound(s) of interest is preferably 1% or more, particularly preferably 2% or more, and very particularly preferably 4% or more.

[0151] In the present invention, "≦" means less than or equal to, preferably less than, and "≧" means greater than or equal to, preferably greater than.

[0152] In the present invention,

Chemical formula

[0153] In the present invention, the expression "dielectrically positive compound" means a compound having Δε > 1.5, the expression "dielectrically neutral compound" means a compound having -1.5 ≤ Δε ≤ 1.5, and the expression "dielectrically negative compound" means a compound having Δε < -1.5. The dielectric anisotropy of a compound is determined herein by dissolving 10% of the compound in a liquid crystal host and determining the capacitance of the mixture obtained at 1 kHz in at least one test cell having a cell thickness of 20 μm, a homeotropic surface alignment, and a homogeneous surface alignment in each case. The measurement voltage is typically 0.5 V to 1.0 V, but is always lower than the capacitance threshold of each liquid crystal mixture (material) under consideration.

[0154] The host mixture used for dielectrically positive and dielectrically neutral compounds is ZLI-4792, and the host mixture used for dielectrically negative compounds is ZLI-2857, both of which are manufactured by Merck KGaA, Germany. The value of each compound under consideration is obtained from the change in the dielectric constant of the host mixture after adding the compound under consideration, and the compound used is extrapolated to 100%. The compound under consideration is dissolved in the host mixture in an amount of 10%. If the solubility of the substance is too low for this purpose, the concentration is halved stepwise until the examination can be carried out at the desired temperature.

[0155] The liquid crystal medium according to the invention may also contain further additives, such as stabilizers, etc., in a conventional amount, if necessary. The amount of these additives used is preferably a total amount, based on the amount of the entire mixture, of 0% or more to 10% or less, particularly preferably 0.1% or more to 6% or less. The concentration of the individual compounds used is preferably 0.1% or more to 3% or less. The concentrations of these and similar additives are generally not considered when specifying the concentration and concentration range of the liquid crystal compounds in the liquid crystal medium.

[0156] For the purposes of the present invention, all concentrations are given in weight percent (%) unless otherwise explicitly stated, and relate to the entire corresponding mixture or the entire mixture components unless otherwise explicitly indicated. In this context, the term "mixture" describes the liquid crystal medium.

[0157] Unless otherwise specified, the following symbols are used: T(N,I) or T(N f ,I) (or clp.) Clearing point (°C).

[0158] S f Ferroelectric smectic phase N f Ferroelectric nematic phase Dielectric properties at 1 kHz and preferably at 20 °C or at each temperature specified: ε ⊥ Dielectric permittivity perpendicular to the director, ε ∥ Dielectric permittivity parallel to the director, Δε Dielectric anisotropy and in particular for the screening data of single compounds.

[0159] And in particular for the data from the screening of each compound in the smectic host mixture ZLI-4792: n e Anomalous refractive index measured at 20 °C and 589 nm, n0 Normal refractive index measured at 20 °C and 589 nm, and Δn Optical anisotropy measured at 20 °C and 589 nm.

[0160] The following examples are illustrative without limiting the present invention. However, the following examples show those skilled in the art the concept of preferred mixtures together with the compounds preferably used, their respective concentrations, and their combinations with each other. In addition, the following examples illustrate the achievable properties and combinations of properties.

[0161] Definition of structural elements by abbreviations for use in the initials for chemical compounds.

[0162] <Table A: Ring elements>

[0163] [Table 1]

[0164] [Table 2]

[0165] [Table 3]

[0166] <Table B: Crosslinking units>

[0167] [Table 4]

[0168] <Table C: End groups>

[0169] [Table 5]

[0170] Wherein n and m each represent an integer, and the three dots "..." are spaces for other abbreviations from this table.

[0171] In addition to the compounds of formulae IA, IB and IC-1 / -2 / -3, the mixtures according to the invention preferably contain one or more of the compounds described below.

[0172] The following abbreviations are used: (n, m, k and l are each independently of one another an integer, preferably from 1 to 9, preferably from 1 to 7, and k and l may also be 0, preferably from 0 to 4, more preferably 0 or 2, most preferably 2, n is preferably 1, 2, 3, 4 or 5, preferably 1, 2, 3 or 4, more preferably 2 or 4, in the combination "-nO-", m is preferably 1, 2, 3, 4 or 5, preferably 1, 2, 3 or 4, more preferably 2 or 4, in the combination "-Om". The combination "-lVm" is preferably "2V1".)

[0173] In the present invention and in the following examples, the structures of the liquid crystal compounds are indicated by initial letters, and the conversion into chemical formulae is carried out according to Tables A to C above. All groups C n H 2n+1 、C m H 2m+1 およびC l H 2l+1 またはC n H 2n 、C m H 2m およびC l H 2l are straight-chain alkyl or alkenyl groups having n, m and l C atoms, respectively. Preferably, n, m and l are each independently of one another 1, 2, 3, 4, 5, 6 or 7. Table A shows the codes for the ring elements of the nuclear structure of the compounds, Table B lists the bridging groups, and Table C lists the meanings of the codes for the terminal groups on the left or right side of the molecule. The initial letter consists of the code for the ring element together with any linking group present, followed by the first hyphen and the code for the left terminal group, and the second hyphen and the code for the right terminal group. Table D shows exemplary structures of the compounds together with their respective abbreviations.

[0174] Examples of Preferred Compounds of Formula IA

[0175] [Table 6]

[0176] [Table 7]

[0177] Examples of Preferred Compounds of Formula IB

[0178] [Table 8]

[0179] Examples of Preferred Compounds of Formula IC-1

[0180] [Table 9]

[0181] [Table 10]

[0182] Examples of Preferred Compounds of Formula IC-3

[0183] [Table 11]

[0184] Optionally Used Additional Compounds

[0185] [Table 12]

[0186] [Table 13]

[0187]

Table 14

[0188]

Table 15

[0189] <Mixture Example> The following exemplary mixtures are disclosed.

[0190] Prepare the following base mixture (H-1) and use it as the host mixture for the preparation of the example mixtures.

[0191]

Table 16

[0192] <Mixture Example 1> Add compound PUS-3-2 to the host mixture H-1 at a ratio of 10, 15, 20 wt%.

[0193]

Chemical formula

[0194] The mixtures are examined at different temperatures by microscopy, dielectric properties, and calorimetry.

[0195]

Table 17

[0196] The spontaneous ferroelectric smectic phase is below the ferroelectric nematic phase, N f -S fIt spreads from the transition point to low temperatures. A high ε value indicates that the ferroelectric smectic phase spreads to temperatures about 20 - 30 K lower than the transition temperature. In the case of the present compound (PUS - 3 - 2), it is usually in the range from room temperature to below 0 °C.

[0197] Figure 1 shows the dielectric scan of mixture example 1.1 at 1 kHz. The scan direction here is from high temperature to low temperature. The graph shows a relatively small hysteresis in the Sf region for both the low - temperature and high - temperature cycles. The Sf phase spreads from below - 20 °C to +20 °C, and the ε value is about 10 2 (-12 °C) ~ 10 3 (20 °C). The value of ε becomes significantly higher, 1000 times at 10 Hz.

[0198] <Mixture example 2> Compound PPTUI - 3 - 2 is added to the host mixture H - 1 at ratios of 5, 10, and 15 wt%.

[0199]

Chemical formula

[0200]

Table 18

[0201] The spontaneous ferroelectric smectic phase spreads from the transition point to low temperatures under the ferroelectric nematic phase. A high ε value indicates that the ferroelectric smectic phase spreads to temperatures about 20 - 30 K lower than the transition temperature. In the case of the present compound (PUS - 3 - 2), it is usually in the range from room temperature to below 0 °C.

[0202] Rheology test: Approximately 2 ml samples of each of mixtures 2.1, 2.2, and 2.3 are placed in small glass vials and stored at room temperature. The turbid probe shows a large change in viscosity by the test (Table).

[0203]

Table 19

Claims

1. A liquid crystal medium exhibiting a ferroelectric smectic phase, the medium comprising: at least 5% by weight of a first component having a low polarity with -5 < Δε < 5, a liquid crystal medium comprising at least 60% by weight of a second polar component having Δε of 20 or more at 20 °C and 1 kHz.

2. The liquid crystal medium according to claim 1, which exhibits a rotational viscosity of 2 Pa·s or more at 10 °C when measured in a cell with a thickness of 100 μm.

3. A liquid crystal medium according to claim 1 or 2, having a relative dielectric constant 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. 【Chemical 1】 (In the formula, 【Chemical 2】 represents, 【Chemical Formula 3】 represents, 【Chemical Formula 4】 represents, L ３Ａ each independently represents H, alkyl, alkoxy or alkoxyalkyl having 1 to 7 C atoms each, preferably represents H, Z １Ａ and Z ２Ａ each independently represents a single bond, —C≡C— or —CH═CH—, R １Ａ is an alkyl group having 1 to 12 carbon atoms independently (however, in addition, one or more CH ２ groups in these groups are each independently such that O / S atoms are not directly connected to each other, and are -C≡C-, -CH=CH- [Chemical Formula 5] may be replaced by -O-, -S-, -(CO)-O- or -O-(CO)-, provided that in addition one or more H atoms may be replaced by halogen. ) represents, or represents H, R ２Ａ is an alkyl group having 1 to 12 carbon atoms independently (provided that in addition, one or more CH ２ groups in these groups are each independently of the others such that O / S atoms are not directly linked to each other by -C≡C-, -CH=CH- 【Chemical Formula 6】 may be replaced by -O-, -S-, -(CO)-O- or -O-(CO)-, provided that in addition one or more H atoms may be replaced by halogen. ) represents, or represents H, n1 is 0, 1 or 2. )

5. The liquid crystal medium according to any one of claims 1 to 4, comprising one or more compounds selected from formula IA-A. 【Chemical Formula 7】 (In the formula, 【Chemical Formula 8】 represents, Z １Ａ and Z ２Ａ each independently represents -(CO)-O- or -C≡C- L １Ａ is F or H, L ２Ａ is F or H, L ３Ａ is defined by formula IA and is preferably H or CH ３ and L ４Ａ is F or H, preferably H, R １Ａ is an alkyl group having 1 to 12 carbon atoms independently (provided that in addition, one or more CH ２ groups, in each case independently of one another, are such that O / S atoms are not directly linked to each other, and are -C≡C-, -CF ２ -O-, -OCF ２ -, -CH=CH- 【Chemical Formula 9】 may be replaced by -O-, -S-, -(CO)-O- or -O-(CO)-, provided that in addition one or more H atoms may be replaced by halogen. ) represents, or represents H, n1 is 1 or 2, preferably 1. )

6. The liquid crystal medium according to any one of claims 1 to 5, comprising one or more compounds selected from formula IB or IC. 【Chemical Formula 10】 【Chemical 11】 (In the formula, X １Ｂ is -CN, F or -NCS, X １Ｃ is -CN, F, CF ３ , -OCF ３ , NCS, SF ５ or O-CF=CF ２ , preferably represents -CN, Z １Ｂ and Z ２Ｂ each independently represents a single bond, -(CO)-O- or -CF ２ -O- and Z １Ｃ and Z ２Ｃ in which one of both groups represents -(CO)-O- or -CF ２ -O-, and the other represents a single bond L １Ｂ is independently H or CH ３ and L ２Ｂ is F or H, and 【Chemical 12】 represents, In the formula, L ８Ｂ represents alkyl, alkoxy or alkoxyalkyl having 1 to 7 C atoms respectively, 【Chemical 13】 represents, 【Chemical Formula 14】 represents, 【Chemical Formula 15】 represents, n2 is 1 or 2, preferably 1, R １Ｂ and R １Ｃ each independently has an alkyl group having 1 to 12 carbon atoms (provided that, in addition, one or more CH ２ groups in these groups, in each case independently of one another, are such that O / S atoms are not directly linked to each other, and are -C≡C-, -CH=CH-, 【Chemical 16】 may be replaced by -O-, -S-, -(CO)-O- or -O-(CO)-, provided that in addition one or more H atoms may be replaced by halogen. ) represents, or represents H. )

7. The liquid crystal medium according to claim 6, comprising a total of at least 80% of the compounds of formula IA, IB, and IC.

8. The liquid crystal medium according to any one of claims 1 to 7, comprising one, two or more compounds selected from formulae ID-1 to ID-4. 【Chemical 17】 (In the formula, X Ｄ represents CN, F, CF ３ , -OCF ３ , NCS, SF ５ or O - CF = CF ２ and L １Ｄ 、 L ２Ｄ 、 L ３Ｄ 、 L ４Ｄ 、 L ５Ｄ 、 L ６Ｄ and L ７Ｄ each independently represents F, H, alkyl, alkoxy or alkoxyalkyl having 1 to 7 C atoms, Z １Ｄ and Z ２Ｄ are, independently of each other, —(CO)—O—, —CF ２ —O—, a single bond, and preferably both represent —(CO)—O—, R １Ｄ is an alkyl group having 1 to 12 carbon atoms (provided that in addition, one or more CH ２ groups in these groups are each independently of the others such that O / S atoms are not directly linked to each other to form -C≡C-, -CH=CH- 【Chemical Formula 18】 may be replaced by -O-, -S-, -(CO)-O- or -O-(CO)-, provided that in addition one or more H atoms may be replaced by halogen. ) represents, or represents H, R ２Ｄ is alkyl, alkoxy or alkoxyalkyl having 1 to 7 C atoms each, preferably CH ３ , OCH ３ , OCH ２ CH ３ , CH ２ OCH ３ , CH ２ OCH ２ CH ３ , CH ２ CH ２ OCH ３ , CH ２ CH ２ OCH ２ CH ３ or CH ２ CH ２ CH ２ OCH ３ and represents 【Chemical 19】 represents, L ８Ｄ is alkyl, alkoxy or alkoxyalkyl having 1 to 7 C atoms each, preferably CH ３ , OCH ３ , OCH ２ CH ３ , CH ２ OCH ３ , CH ２ OCH ２ CH ３ , CH ２ CH ２ OCH ３ , CH ２ CH ２ OCH ２ CH ３ or CH ２ CH ２ CH ２ OCH ３ .)

9. The medium according to any one of claims 1 to 8, which exhibits a ferroelectric smectic phase at a temperature of at least 10°C to 0°C when cooled from a high temperature.

10. The medium according to any one of claims 1 to 9, which exhibits hysteresis of dielectric properties due to temperature change.

11. The medium according to any one of claims 1 to 10, which exhibits an enantiotropic ferroelectric smectic phase.

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

13. Use of the liquid crystal medium according to any one of claims 1 to 11 for electro-optical purposes, for supercapacitors and for electromechanical devices including generators and actuators.

14. Use of the liquid crystal medium according to any one of claims 1 to 11 for non-linear optical elements, sensors or memory devices.

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