CN111263800A

CN111263800A - Liquid crystal medium and liquid crystal device

Info

Publication number: CN111263800A
Application number: CN201880069315.8A
Authority: CN
Inventors: S·希米安诺斯基; H·诺鲁齐·阿拉西; K·阿德莱姆; M·赫尼尔; K·凯塞尔
Original assignee: Merck Patent GmbH
Current assignee: Merck Patent GmbH
Priority date: 2017-10-25
Filing date: 2018-10-22
Publication date: 2020-06-09
Also published as: DE112018005004T5; TW201925434A; WO2019081389A1

Abstract

The invention relates to compounds R of formulae (I ') to (I')¹¹(‑A¹¹‑Z¹¹)_o‑A¹²(‑Z¹²‑A¹³)_p‑X¹¹‑Sp‑X¹²‑(A¹⁴‑Z¹³‑)_qA¹⁵‑(Z¹⁴‑A¹⁶‑)_rR¹²(I’)；A¹²(‑Z¹²‑A¹³)_p‑X¹¹‑Sp‑X¹²‑(A¹⁴‑Z¹³‑)_qA¹⁵‑(Z¹⁴‑A¹⁶‑)_rR¹²(I”)；A¹²(‑Z¹²‑A¹³)_p‑X¹¹‑Sp‑X¹²‑(A¹⁴‑Z¹³‑)_qA¹⁵(I'). Wherein R is¹¹、R¹²、A¹¹To A¹⁶、Z¹¹To Z¹⁴、X¹¹、X¹²Sp, o, p, q and r have one of the meanings given below. The invention further relates to a process for preparing compounds of the formula I, the use of said compounds in LC media and LC media comprising one or more compounds of the formulae (I ') to (I'). In addition, the present invention relates to a method for producing such LC media, the use of such media in LC devices, in particular in flexoelectric LC devices, and flexoelectric LC devices comprising LC media according to the present invention.

Description

Liquid crystal medium and liquid crystal device

The invention relates to compounds of formulae I 'to I',

R¹¹(-A¹¹-Z¹¹)_o-A¹²(-Z¹²-A¹³)_p-X¹¹-Sp-X¹²-(A¹⁴-Z¹³-)_qA¹⁵-(Z¹⁴-A¹⁶-)_rR¹²I’

A¹²(-Z¹²-A¹³)_p-X¹¹-Sp-X¹²-(A¹⁴-Z¹³-)_qA¹⁵-(Z¹⁴-A¹⁶-)_rR¹²I”

A¹²(-Z¹²-A¹³)_p-X¹¹-Sp-X¹²-(A¹⁴-Z¹³-)_qA¹⁵I”’

wherein R is¹¹、R¹²、A¹¹To A¹⁶、Z¹¹To Z¹⁴、X¹¹、X¹²Sp, o, p, q and r have one of the meanings given below. The invention further relates to a method for producing compounds of the formulae I to I ', the use of said compounds in LC media and LC media containing one or more compounds of the formulae I to I'. In addition, the present invention relates to a method for the preparation of such LC media, the use of such media in LC devices, especially in flexoelectric LC devices, and flexoelectric LC devices comprising LC media according to the present invention.

Background and Prior Art

The flexoelectric effect is described, for example, by Chandrasekhar, "Liquid Crystals", 2 nd edition, Cambridge university Press (1992) and P.G. DeGennes et al, "The Physics of Liquid Crystals", 2 nd edition, Oxford Science Publications (1995).

Flexoelectric devices such as ULH devices and liquid crystal media particularly suitable for use in flexoelectric devices, which utilize the flexoelectric effect, are known from EP 0971016, GB 2356629 and Coles, h.j., Musgrave, b., Coles, m.j., and Willmott, j., j.j.j.mate.chem., 11, page 2709-.

Uniform Lying Helix (ULH) has a great potential as a fast switching liquid crystal display mode. Which is capable of sub-millisecond switching at 35 c and has an inherently high aperture ratio, resulting in a highly efficient display mode.

Materials commonly used in media suitable for ULH mode are typically bimesogenic. Due to the size and the presence of polar groups, such as terminal cyano groups, these materials typically have high rotational viscosities (γ) of about several thousand mpa.s at 35 ℃₁). At elevated temperatures, e.g. 35 ℃, high gamma₁The value does not cause problems because of the switching speed and gamma₁Is in direct proportion. On the other hand, the value of γ 1 is also proportional to the square of the chiral pitch. Since the chiral pitch is typically about 300nm, this means that the switching speed is still very fast, about 1 or a few milliseconds.

However, γ upon reaching the lower temperatures, such as room temperature, at which ULH devices typically operate₁Increases exponentially and the switching speed increases beyond a favourable level even in the case of short pitch materials.

Gamma of LC mixture for maintaining fast switching speed at temperature lower than 35 deg.C₁The value needs to be reduced and thus the identification of compounds with lower gamma needs to be made₁The mixture of (1).

Accordingly, there is a great need for novel bimesogenic compounds that exhibit advantageously low γ₁The values simultaneously preferably exhibit:

advantageous e/K (V)^-1) The value of the one or more of,

an advantageously broad nematic phase range and

high bright spots.

In addition to these requirements, the corresponding LC media should exhibit a favorably low γ₁The values simultaneously preferably exhibit:

a low melting point of the acid component,

the brightness of the high-definition bright spot,

a broad range of chiral nematic phases,

short temperature independent pitch length,

high flexoelectric coefficient and

advantageous low temperature stability without box and crystallization effects in the bulk.

Other objects of the present invention will become immediately apparent to those skilled in the art from the following detailed description.

Surprisingly, the inventors have found that one or more of the above objects can be achieved by providing a compound according to claim 1.

Terms and definitions

The terms "liquid crystal", "liquid crystalline compound" or "mesogenic compound" (also simply referred to as "mesogen") mean a compound which can be present as an intermediate phase (nematic, smectic, etc.) or especially as an LC phase under the conditions of suitable temperature, pressure and concentration. The non-amphiphilic mesogenic compound comprises for example one or more rod-like, banana-like or disc-like mesogenic groups.

In this context, the term "mesogenic group" means a group having the ability to induce Liquid Crystal (LC) phase behavior. The compound comprising mesogenic groups does not necessarily have to exhibit an LC phase per se. They may also exhibit LC phase behavior only in mixtures with other compounds. For the sake of simplicity, the term "liquid crystal" is used hereinafter for both mesogenic and LC materials.

Throughout this application, unless specifically stated otherwise, the terms "aryl and heteroaryl" encompass groups which may be monocyclic or polycyclic, i.e., they may have one ring (e.g., phenyl) or two or more rings, which may also be fused (e.g., naphthyl) or covalently linked (e.g., biphenyl), or contain a combination of fused rings and connecting rings.

Heteroaryl contains one or more heteroatoms preferably selected from O, N, S and Se. Particularly preferred are monocyclic, bicyclic or tricyclic aryl groups having 6 to 25C atoms, and monocyclic, bicyclic or tricyclic heteroaryl groups having 2 to 25C atoms, which optionally contain fused rings and are optionally substituted. Further preferred are 5-, 6-or 7-membered aryl and heteroaryl, wherein, in addition, one or more CH groups may be replaced by N, S or O in such a way that the O atoms and/or S atoms are not directly connected to one another.

Preferred aryl radicals are, for example, phenyl, biphenyl, terphenyl, [1,1':3',1 "]-terphenyl-2' -yl, naphthyl, anthracenyl, binaphthyl, phenanthrenyl, pyrene, dihydropyrene,

Perylene, tetracene, pentacene, benzopyrene, fluorene, indene, indenofluorene, spirobifluorene (spirobifluorene), and the like, and more preferably 1, 4-phenylene, 4' -biphenylene, and 1, 4-terphenylene.

Preferred heteroaryl groups are, for example, 5-membered rings, such as pyrrole, pyrazole, imidazole, 1,2, 3-triazole, 1,2, 4-triazole, tetrazole, furan, thiophene, selenophene, oxazole, isoxazole, 1, 2-thiazole, 1, 3-thiazole, 1,2, 3-oxadiazole, 1,2, 4-oxadiazole, 1,2, 5-oxadiazole, 1,3, 4-oxadiazole, 1,2, 3-thiadiazole, 1,2, 4-thiadiazole, 1,2, 5-thiadiazole, 1,3, 4-thiadiazole, 6-membered rings, such as pyridine, pyridazine, pyrimidine, pyrazine, 1,3, 5-triazine, 1,2, 4-triazine, 1,2, 3-triazine, 1,2,4, 5-tetrazine, 1,2,3, 4-tetrazine, 1,2,3, 5-tetrazine or fused radicals, such as indole, isoindole, indolizine, indazole, benzimidazole, benzotriazole, purine, naphthoimidazole, phenanthroimidazole, pyridoimidazole, pyrazinoimidazole, quinoxaloimidazole, benzoxazole, naphthooxazole, anthraoxazole, phenanthroioxazole, isoxazole, benzothiazole, benzofuran, isobenzofuran, dibenzofuran, quinoline, isoquinoline, pteridine, benzo-5, 6-quinoline, benzo-6, 7-quinoline, benzo-7, 8-quinoline, benzisoquinoline, acridine, phenothiazine, phenoxazine, benzopyridazine, benzopyrimidine, quinoxaline, phenazine, naphthyridine, azacarbazole, benzocarbazine, phenanthridine, phenanthroline, thieno [2,3b ] thiophene, thieno [3,2b ] thiophene, Dithienothiophene, isobenzothiophene, dibenzothiophene, benzothiadiazole thiophene, or combinations of these groups. Heteroaryl groups may also be substituted with alkyl, alkoxy, thioalkyl, fluoro, fluoroalkyl or other aryl or heteroaryl groups.

In the context of the present application, the term "(non-aromatic) alicyclic group" encompasses saturated rings and "heterocyclyl" encompasses both saturated rings, i.e. those containing only single bonds, and partially unsaturated rings, i.e. those which may also contain multiple bonds. The heterocycle contains one or more heteroatoms, preferably selected from Si, O, N, S and Se. The (non-aromatic) alicyclic and heterocyclic groups may be monocyclic, i.e. contain only one ring (e.g. cyclohexane), or polycyclic, i.e. contain multiple rings (e.g. decahydronaphthalene or bicyclooctane). Preference is furthermore given to mono-, bi-or tricyclic radicals having 3 to 25C atoms, which optionally contain fused rings and are optionally substituted. Further preferred are 5-, 6-, 7-or 8-membered carbocyclic groups in which, in addition, one or more C atoms may be replaced by Si and/or one or more CH groups may be replaced by N and/or one or more non-adjacent CH groups₂The groups may be replaced by-O-and/or-S-. Preferred alicyclic and heterocyclic groups are, for example, 5-membered groups, such as cyclopentane, tetrahydrofuran, tetrahydrothiophene, pyrrolidine; 6-membered groups such as cyclohexane, silacyclohexane (silane), tetrahydropyran, tetrahydrothiopyran, 1, 3-dioxane, 1, 3-dithiane, piperidine; 7-membered groups, such as cycloheptane; and a fused group,for example tetralin, decalin, indane, bicyclo [1.1.1]Pentane-1, 3-diyl, bicyclo [2.2.2]Octane-1, 4-diyl, spiro [3.3]Heptane-2, 6-diyl, octahydro-4, 7-methanoindan-2, 5-diyl, more preferably 1, 4-cyclohexylene, 4' -dicyclohexylene, 3, 17-hexadecahydro-cyclopenta [ a ]]Phenanthrene, which is optionally substituted by one or more identical or different groups L.

Particularly preferred aryl-, heteroaryl-, alicyclic-and heterocyclic groups are 1, 4-phenylene, 4 '-biphenylene, 1, 4-terphenylene, 1, 4-cyclohexylene, 4' -dicyclohexylene and 3, 17-hexadecahydro-cyclopenta [ a ] phenanthrene, which are optionally substituted by one or more identical or different radicals L.

Preferred substituents (L) of the above-mentioned aryl-, heteroaryl-, alicyclic-and heterocyclic groups are, for example, solubility-promoting groups (e.g. alkyl or alkoxy) and electron-withdrawing groups (e.g. fluorine, nitro or nitrile).

Particularly preferred substituents are, for example, halogen, CN, NO₂、CH₃、C₂H₅、OCH₃、OC₂H₅、COCH₃、COC₂H₅、COOCH₃、COOC₂H₅、CF₃、OCF₃、OCHF₂Or OC₂F₅。

"halogen" hereinbefore and hereinafter denotes F, Cl, Br or I, preferably F or Cl.

The terms "alkyl", "aryl", "heteroaryl", and the like above and below also encompass multivalent groups such as alkylene, arylene, heteroarylene, and the like.

The term "aryl" denotes an aromatic carbon group or a group derived therefrom.

The term "heteroaryl" denotes an "aryl" group according to the above definition, containing one or more heteroatoms.

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

Preferred alkoxy radicals are, for example, methoxy, ethoxy, 2-methoxyethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, 2-methylbutoxy, n-pentoxy, n-hexoxy, n-heptoxy, n-octoxy, n-nonoxy, n-decoxy, n-undecoxy, n-dodecoxy.

Preferred alkenyl groups are, for example, ethenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl and octenyl.

Preferred alkynyl groups are, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl, octynyl.

Oxaalkyl, i.e. one of CH₂The radicals are substituted by-O-, preferably for example straight-chain 2-oxapropyl (═ methoxymethyl); 2-oxabutyl (═ ethoxymethyl) or 3-oxabutyl (═ 2-methoxyethyl); 2-oxapentyl, 3-oxapentyl or 4-oxapentyl; 2-oxahexyl, 3-oxahexyl, 4-oxahexyl or 5-oxahexyl; 2-oxaheptyl, 3-oxaheptyl, 4-oxaheptyl, 5-oxaheptyl, or 6-oxaheptyl; 2-oxaoctyl, 3-oxaoctyl, 4-oxaoctyl, 5-oxaoctyl, 6-oxaoctyl or 7-oxaoctyl; 2-oxanonyl, 3-oxanonyl, 4-oxanonyl, 5-oxanonyl, 6-oxanonyl, 7-oxanonyl or 8-oxanonyl or 2-oxadecyl, 3-oxadecyl, 4-oxadecyl, 5-oxadecyl, 6-oxadecyl, 7-oxadecyl, 8-oxadecyl or 9-oxadecyl.

Preferred amino groups are, for example, dimethylamino, methylamino, methylphenylamino, phenylamino.

In general, the term "chiral" is used to describe objects that are non-superimposable on their mirror images.

An "achiral" (achiral) object is the same object as its mirror image.

Unless explicitly described otherwise, the terms "chiral nematic" and "cholesteric" are used synonymously in this application.

The term "bimesogenic compound" relates to a compound comprising two mesogenic groups in the molecule. As with conventional mesogens, they can form a number of mesophases, depending on their structure. In particular, bimesogenic compounds can induce a second nematic phase when added to a nematic liquid crystal medium. Bimesogenic compounds are also known as "dimeric liquid crystals".

The term "director" is known in the art and means the preferred direction of orientation of the long molecular axis (in the case of rod-like compounds) or the short molecular axis (in the case of discotic compounds) of the liquid crystal molecules. In the case of such uniaxial ordering of anisotropic molecules, the director is the axis of anisotropy.

"alignment" or "orientation" relates to the alignment (orientation ordering) of anisotropic units of a material (such as small molecules or fragments of large molecules) in a common direction called the "alignment direction". In an alignment layer of a liquid crystal material, the liquid crystal director coincides with the alignment direction such that the alignment direction corresponds to the direction of the anisotropy axis of the material.

The term "planar orientation/alignment", for example in a layer of liquid crystal material, means that a proportion of the long molecular axes (in the case of calamitic compounds) or the short molecular axes (in the case of discotic compounds) of the liquid crystal molecules are oriented substantially parallel (about 180 °) to the plane of the layer.

The term "homeotropic orientation/alignment" in, for example, a layer of liquid crystal material means that the long molecular axes (in the case of calamitic compounds) or the short molecular axes (in the case of discotic compounds) of a proportion of the liquid crystal molecules are oriented at an angle θ ("tilt angle") of about 80 ° to 90 ° relative to the plane of the layer.

The term "uniform orientation" or "uniform alignment" of the liquid crystal material, for example in a material layer, means that the long molecular axes (in the case of calamitic compounds) or the short molecular axes (in the case of discotic compounds) of the liquid crystal molecules are oriented substantially in the same direction. In other words, the lines of the liquid crystal directors are parallel.

Unless explicitly specified otherwise, the wavelength of light generally referred to in this application is 550 nm.

The birefringence Δ n herein is defined by the following equation:

Δn＝n_e-n_o

wherein n is_eIs an extraordinary refractive index and n_oIs an ordinary refractive index and an effective average refractive index n_avIs given by the following equation.

n_av.＝[(2n_o ²+n_e ²)/3]^1/2

Extraordinary refractive index n_eAnd ordinary refractive index n_oCan be measured using an Abbe refractometer.

In the present application, the term "dielectrically positive" is used for compounds or components having a Δ ∈ >3.0, "dielectrically neutral" for compounds or components having a frequency of-1.5 ≦ △ ≦ 3.0 and "dielectrically negative" for compounds or components having a value of △ ∈ < -1.5. △ ∈ is measured at a frequency of 1kHz and at 20 ℃.

△ ε is defined as (ε)_||-ε_⊥) And is of_avIs (epsilon)_||+2ε_⊥)/3. The dielectric permittivity of the compound is determined from the change in the respective values of the host medium after addition of the compound of interest. This value is extrapolated to a concentration of 100% of the compound of interest. Typical host media are ZLI-4792 or BL-087, both available from Merck, Darmstadt.

With respect to the present invention, it is,

represents a trans-1, 4-cyclohexylene group,

represents a1, 4-phenylene group.

For the purposes of the present invention, the radicals- -COO- -, - -CO- -O- -C (═ O) O- -or- -CO₂Is represented by the formula

And the radicals-OCO-, -O-CO-, -OC (═ O) -, -O₂C-or-OOC-represents a compound of formula

Ester group of (a).

Furthermore, definitions as given in c.tscierske, g.pelzl and s.diele, angelw.chem.2004, 116,6340-6368 will apply to undefined terms in the present application with respect to liquid crystal materials.

Detailed Description

The invention relates to compounds of formulae I 'to I',

A¹²(-Z¹²-A¹³)_p-X¹¹-Sp-X¹²-(A¹⁴-Z¹³-)_qA¹⁵I”’

wherein

R¹¹And R¹²Each independently represents halogen, F, Cl, CN, NO₂NCO, NCS or a linear or branched alkyl group which may be unsubstituted, mono-or polysubstituted with halogens or CN and in which one or more are not adjacent and are not terminal CH₂The groups may be replaced independently of each other at each occurrence by: -O-, -S-, -NH-, -N (CH)₃) -, -CO-, -COO-, -OCO-, -O-CO-O-, -S-CO-, -CO-S-, -CH ═ CH-, -CH ═ CF-, -CF ═ CF-or-C.ident.C-, in such a way that the oxygen atoms are not directly linked to one another,

preferably F, Cl, CN, NO₂NCO, NCS, straight-chain or branched alkyl, alkenyl or alkoxy which may be unsubstituted, mono-or polysubstituted with halogen or CN,

A¹¹to A¹⁶Each independently at each occurrence represents 1, 4-phenylene, in which additionally one or more CH groups may be replaced by N; trans-1, 4-cyclohexylene radical, in addition to one or two non-adjacent CH radicals₂The radicals may be replaced by O and/or S; 1, 4-cyclohexylene; naphthalene-2, 6-diyl; decahydronaphthalene-2, 6-diyl; 1,2,3, 4-tetrahydro-naphthalene-2, 6-diyl, all of which may be unsubstituted, mono-, di-, tri-or tetrasubstituted by F, Cl, CN or alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl, wherein one or more H atoms may be substituted by F or Cl, with the proviso that A¹²Or A¹⁵At least one of which represents a1, 4-phenylene group in which one or more CH groups are replaced by N,

preferably in each occurrence independently 1, 4-phenylene, in which additionally one or more CH groups may be replaced by N; or trans-1, 4-cyclohexylene, in addition to one or two non-adjacent CH₂The radicals may be substituted by O and/or S, both cyclic groups may be unsubstituted, mono-, di-, tri-or tetrasubstituted by F, Cl, CN or alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl, wherein one or more H atoms may be substituted by F or Cl, with the proviso that A¹²Or A¹⁵At least one of which represents a1, 4-phenylene group in which one or more CH groups are replaced by N,

Z¹¹to Z¹⁴Independently of one another in each occurrence, is a single bond, -COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O-、-OCF₂-、-CF₂O-、-CH₂CH₂-、-(CH₂)₄-、-CF₂CF₂-, -CH-, -CF-, -CH-COO-, -OCO-CH-or-C.ident.C-, which are optionally substituted by one or more F, S and/or Si,

preferably-COO-, -OCO-, -OCF₂-、-CF₂O-or a single bond,

more preferably a single bond, and more preferably a single bond,

o, p, q and r are each and independently 0, 1 or 2, provided however that o + p + q + r.gtoreq.1, preferably o + p + q + r.gtoreq.1. ltoreq.4, more preferably o + p + q + r.gtoreq.2. ltoreq.4, even more preferably o + p + q + r. ltoreq.4,

sp is a spacer group comprising 3 or 5 to 20C atoms, one or more of which are not adjacent and are not terminal CH₂The groups may also be replaced by: -O-, -S-, -NH-, -N (CH)₃)-、-CO-、-O-CO-、-S-CO-、-O-COO-、-CO-S-、-CO-O-、-CF₂-、-CF₂O-、-OCF₂-、-C(CF₃) -, -C (CN) -C (OH) -, -CH (alkyl) -, -CH (alkenyl) -, -CH (alkoxy) -, -CH (oxaalkyl) -, -CH ═ CH-or-C.ident.C-, but alternatively such that no two O atoms are adjacent to one another and no two radicals selected from the group consisting of-O-CO-, -S-CO-, -O-COO-, -CO-S-, -CO-O-and-CH ≡ CH-are adjacent to one another, preferably- (CH-CO-, -C (O-CO-, -S-CO-, -O-CO-and-CH ≡ CH-)₂)_n-, where n represents 3 or an integer from 5 to 15, more preferably an odd integer from 3 to 15, most preferably 3,5, 7, 9 or 11,

X¹¹and X¹²Independently of one another, from the group consisting of a single bond, -CO-O-, -O-CO-, -O-COO-, -O-, -CH-, -C.ident.C-, -CF ═ C-₂-O-、-O-CF₂-、-CF₂-CF₂-、-CH₂-O-、-O-CH₂-, -CO-S-, -S-CO-, -CS-S-, -S-CS-, -S-CSS-and-S-, wherein in-X¹¹-Sp¹-X¹²In which two O atoms, two-CH-groups and two groups selected from-O-CO-, -S-CO-, -O-COO-, -CO-S-and-CO-O-are each not linked directly to one another, preferably-CO-O-,-O-CO-、-O-、-C≡C-、-CF₂-O-、-O-CF₂-or a single bond,

more preferably X¹¹Or X¹²One of them represents a single bond and X¹¹Or X¹²The other represents-COO-, -OCO-or a single bond,

even more preferably X¹¹And X¹²All represent single bonds.

In the case of compounds of the formulae I 'to I' having nonpolar wing groups, R¹¹And/or R¹²Preferably represents alkyl, alkoxy, alkenyl or alkynyl, more preferably alkyl, alkoxy, these groups having up to 15C atoms, preferably up to 10C atoms, more preferably 2 to 5C atoms.

In addition, containing branched radicals R¹¹And/or R¹²The compounds of formulae I' to I "may occasionally be of importance, for example due to a reduced tendency towards crystallization. Branched groups of this type generally do not contain more than one chain branch. Preferred achiral branched groups are isopropyl, isobutyl (═ methylpropyl), isopentyl (═ 3-methylbutyl), isopropoxy, 2-methyl-propoxy and 3-methylbutoxy.

In the case of compounds of the formulae I 'to I' having terminal polar groups, R¹²And/or R¹¹Selected from CN, NO₂、NCS、NCO、OCH₃、OCN、SCN、COR^x、COOR^xOr a mono-, oligo-or polyfluorinated alkyl or alkoxy group having 1 to 4C atoms. R^xIs an optionally fluorinated alkyl group having 1 to 4, preferably 1 to 3, C atoms.

In a preferred embodiment, the radical R in the compounds of the formula I¹¹(-A¹¹-Z¹¹)_o-A¹²(-Z¹²-A¹³)_p-X¹¹-and the group-X¹²-(A¹⁴-Z¹³-)_qA¹⁵-(Z¹⁴-A¹⁶-)_rR¹²With the radical A in the compound of the formula I'¹²(-Z¹²-A¹³)_p-and- (A)¹⁴-Z¹³-)_qA¹⁵Identical or mirror images.

In another preferred embodiment, the radical R in the compounds of the formula I¹¹(-A¹¹-Z¹¹)_o-A¹²(-Z¹²-A¹³)_p-X¹¹-and-X¹²-(A¹⁴-Z¹³-)_qA¹⁵-(Z¹⁴-A¹⁶-)_rR¹²With the radical A in the compound of the formula I'¹²(-Z¹²-A¹³)_p-and- (A)¹⁴-Z¹³-)_qA¹⁵Different.

Preferably the compound of formula I' is selected from the group of compounds of the following list:

wherein

r represents 0, 1 or 2,

l each independently of the others represents F, Cl, CH₃、OCH₃Or COCH₃Preferably, the amount of the compound represented by F,

each is andrepresent, independently of one another:

if r represents 0, then

If r represents 1, then

If r represents 2, then

And wherein R¹¹、R¹²、Z¹¹To Z¹⁴、X¹¹、X¹²And Sp has one of the meanings given above under formula I'.

More preferred compounds of the formulae I '-1 to I' -44 are those in which the radical-X¹¹-Sp-X¹²-represents-Sp-, -Sp-CO-O-, -Sp-O-CO-, -CO-O-Sp-, -O-CO-Sp-O-CO-, -O-CO-Sp-CO-O-or-CO-O-Sp-CO-O-, more preferably-Sp-, -Sp-CO-O-, -O-CO-Sp-or-O-CO-Sp-CO-O-, wherein Sp has one of the meanings given above under formula I'.

More preferred compounds of the formulae I '-1 to I' -44 and the subformulae thereof are those in which Z is¹¹To Z¹⁴Each independently represents-COO-, -OCO-, -OCF₂-、-CF₂O-or a single bond, more preferably Z¹¹And Z¹⁴All represent a single bond and Z¹²And Z¹³Each independently represents-COO-, -OCO-, -OCF₂-、-CF₂O-or a single bond, even more preferably Z¹¹To Z¹⁴All represent single bonds.

More preferred compounds of the formulae I 'to I' formulae I '-1 to I' -44 and subformulae thereof are those in which R is¹²And/or R¹¹Selected from halogen, CN, NO₂、NCS、NCO、OCH₃、OCN、SCN、COR^x、COOR^xOr a mono-, oligo-or polyfluorinated alkyl or alkoxy group having 1 to 4C atoms. R^xIs an optionally fluorinated alkyl group having 1 to 4, preferably 1 to 3, C atoms.

More preferably, the compound of formula I' is selected from the group of compounds of the following list:

more preferred compounds of the formulae I '-10-1 to I' -11-3 are those in which the radical-X¹¹-Sp-X¹²-represents-Sp-, -Sp-CO-O-, -O-CO-Sp-or-O-CO-Sp-CO-O-, wherein Sp has one of the meanings as given above under formula I'.

More preferred compounds of the formulae I '-10-1 to I' -11-3 and the subformulae thereof are those in which Z is¹¹And Z¹⁴All represent a single bond and Z¹²And Z¹³Each independently represents-COO-, -OCO-, -OCF₂-、-CF₂O-or a single bond, even more preferably Z¹¹To Z¹⁴All represent single bonds.

More preferred compounds of the formulae I '-1-1 to I' -11-3 are those in which R is¹¹And/or R¹²Selected from F or CN.

wherein

n represents 3 or an integer from 5 to 15, more preferably an odd integer from 3 to 15, most preferably 3,5, 7, 9 or 11, and

R¹¹and R¹²Each and independently represents F or CN, preferably both represent CN.

Preferably the compound of formula I "is selected from the group of compounds of the following list:

wherein

r represents 0, 1 or 2,

each and independently of the other represent:

if r represents 0, then

If r represents 1, then

If r represents 2, then

And wherein R¹²、Z¹¹To Z¹⁴、X¹¹、X¹²And Sp have one of the meanings given above under formula I'.

More preferred compounds of formula I' are those wherein Z is¹¹To Z¹⁴Each independently represents-COO-, -OCO-, -OCF₂-、-CF₂O-or a single bond, morePreferably Z¹¹And Z¹⁴All represent a single bond and Z¹²And Z¹³Each independently represents-COO-, -OCO-, -OCF₂-、-CF₂O-or a single bond, even more preferably Z¹¹To Z¹⁴All represent single bonds.

More preferred compounds of the formulae I '-1 to I' -14 and the subformulae thereof are those in which R is¹²Selected from halogen, CN, NO₂、NCS、NCO、OCH₃、OCN、SCN、COR^x、COOR^xOr a mono-, oligo-or polyfluorinated alkyl or alkoxy group having 1 to 4C atoms. R^xIs an optionally fluorinated alkyl group having 1 to 4, preferably 1 to 3, C atoms.

More preferably, the compound of formula I "is selected from the group of compounds of the following list:

more preferred compounds of the formulae I '-7-1 to I' -8-11 are those in which the radical-X¹¹-Sp-X¹²-represents-Sp-, -Sp-CO-O-, -Sp-O-CO-, -CO-O-Sp-, -O-CO-Sp-O-CO-, -O-CO-Sp-CO-O-, or-CO-O-Sp-CO-O-, more preferably-Sp-, -Sp-CO-O-, or-O-CO-Sp-CO-O-, wherein Sp has one of the meanings given above under formula I ".

More preferred compounds of the formulae I '-7-1 to I' -8-11 are those in which Z is¹²And Z¹³Each independently represents-COO-, -OCO-, -OCF₂-、-CF₂O-or a single bond, even more preferably Z¹¹To Z¹⁴All represent single bonds.

More preferred compounds of the formulae I '-7-1 to I' -8-11 are those in which R is¹²Selected from F or CN.

wherein

R¹²represents F or CN.

Preferably the compound of formula I' "is selected from the group of compounds of the following list:

wherein

r represents 0, 1 or 2

each independently of the other

If r represents 0, then

If r represents 1, then

If r represents 2, then

And wherein Z¹¹To Z¹⁴、X¹¹、X¹²And Sp have one of the meanings as given above under formula I' ".

More preferred compounds of formula I' "are those wherein Z is¹¹To Z¹⁴Each independently represents-COO-, -OCO-, -OCF₂-、-CF₂O-or a single bond, more preferably Z¹¹And Z¹⁴All represent a single bond and Z¹²And Z¹³Each independently represents-COO-, -OCO-, -OCF₂-、-CF₂O-or a single bond, even more preferably all Z¹¹To Z¹⁴All represent single bonds.

More preferred compounds of formula I '-1 to formula I' -4 are those wherein the group-X is¹¹-Sp-X¹²-represents-Sp-, -Sp-CO-O-, -Sp-O-CO-, -CO-O-Sp-, -O-CO-Sp-O-CO-, -O-CO-Sp-CO-O-, or-CO-O-Sp-CO-O-, more preferably-Sp-or-O-CO-Sp-CO-O-, wherein Sp has one of the meanings given above under formula I'.

The compounds of the formulae I 'to I' and their sub-formulae can be synthesized according to or analogously to methods known per se and described in standard works of organic chemistry, for example Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag, Stuttgart.

For example, one of the main advantages of using one or more compounds of formula I 'to formula I' "in LC media for flexoelectric applications is the improvement of the flexoelectric ratio. Benefits are also observed in terms of switching speed in ULH (uniform horizontal helix) geometry (especially at temperatures below 35 ℃), phase range, increased isotropic to nematic transition, high clearing point, and reduced nematic to nematic twist-bend transition temperature below room temperature.

The invention therefore also relates to the use of one or more compounds of the formulae I 'to I' "in LC media and to LC media comprising one or more compounds of the formulae I 'to I'" as such.

In a preferred embodiment, the LC medium according to the invention comprises one or more compounds of the formula II,

R²¹-A²¹-A²²-(CH₂)_a-A²³-A²⁴-R²²II

wherein

R²¹And R²²Independently represents H, F, Cl, CN, NCS or a linear or branched alkyl group which may be unsubstituted, mono-or polysubstituted by halogen or CN, one or more non-adjacent CH₂The groups may also be replaced independently of one another at each occurrence by: -O-, -S-, -NH-, -N (CH)₃) -, -CO-, -COO-, -OCO-, -O-CO-O-, -S-CO-, -CO-S-, -CH ═ CH-, -CH ═ CF-, -CF ═ CF-or-C.ident.C-, in such a way that the oxygen atoms are not directly linked to one another,

preferably F, Cl, CN, straight-chain or branched alkyl or alkoxy which may be unsubstituted, mono-or polysubstituted with halogen or CN,

more preferably F, CN or OCF₃，

A²¹To A²⁴Independently at each occurrence, represents an aryl group, an alicyclic group, and a heterocyclic group, preferably a1, 4-phenylene group; 1, 4-bicyclo- (2,2,2) -octylene; naphthalene-2, 6-diyl; decahydronaphthalene-2, 6-diyl; 1,2,3, 4-tetrahydro-naphthalene-2, 6-diyl; cyclobutane-1, 3-diyl; spiro [3.3]Heptane-2, 6-diyl or dispiro [3.1.3.1]Decane-2, 8-diyl, all of which may be unsubstituted, mono-, di-, tri-or tetrasubstituted by F, Cl, CN or alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl, in which one or more H atoms may be substituted by F or Cl,

more preferably, independently at each occurrence, is, 1, 4-phenylene; or trans-1, 4-cyclohexylene, in addition to one or two non-adjacent CH₂The radicals being substituted by O and/or S, both cyclic groups being unsubstituted or substitutedF. Cl, CN or alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl, wherein one or more H atoms may be substituted by F or Cl,

a represents an integer of 1 to 15, preferably an odd (i.e. non-even) integer, and more preferably 3,5, 7, 9 or 11.

Preferred compounds of formula II are selected from the group consisting of wherein²¹-A²²-) and (-A)²³-A²⁴-) are each and independently selected from the group consisting of

-Phe-Phe-MG1

-PheL-PheL-MG2

-Phe-PheL-MG3

-PheL-Phe-MG4

Wherein,

phe in these radicals is 1, 4-phenylene,

PheL is 1, 4-phenylene which is substituted by 1 to 4 radicals L, where L is preferably F, Cl, CN, OH, NO₂Or optionally fluorinated alkyl, alkoxy or alkanoyl having 1 to 7C atoms, very preferably F, Cl, CN, OH, NO₂、CH₃、C₂H₅、OCH₃、OC₂H₅、COCH₃、COC₂H₅、COOCH₃、COOC₂H₅、CF₃、OCF₃、OCHF₂、OC₂F₅In particular F, Cl, CN, CH₃、C₂H₅、OCH₃、COCH₃And OCF₃Most preferred are F, Cl and CH₃、OCH₃And COCH₃And is

Cyc is 1, 4-cyclohexylene.

Preferred is PheL representation

Wherein

r represents a number of 1 or 2,

l each independently of the others represents F, Cl, CH₃、OCH₃Or COCH₃Preferably F, and

preferably each and independently of one another:

if r represents 1, then

If r represents 2, then

Preferred are compounds of the formula II, where the radical (R) in formula II²¹-A²¹-A²²-) and (-A)²³-A²⁴-R²²) Identical or mirror images.

Preference is likewise given to compounds of the formula II in which (R) is²¹-A²¹-A²²-) and (-A)²³-A²⁴-R²²) Different.

Preferred compounds of formula II are shown below:

wherein

n represents an integer from 1 to 15, preferably an odd (i.e. non-even) integer, and more preferably 3,5, 7, 9 or 11.

The compounds of the formula II can be synthesized according to or analogously to methods known per se and described in standard works of organic chemistry, such as Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag, Stuttgart. A preferred preparation method is available from WO 2013/004333 a 1.

To further increase the switching speed while maintaining a good phase range and favorable e/K values, it is particularly useful to employ compounds of the formula II in addition to the compounds of the formula I in the mixtures according to the invention.

In a preferred embodiment, the LC medium according to the invention comprises one or more compounds of the formula III,

R³¹-A³¹-A³²-(A³³)_b-Z³¹-(CH₂)_c-Z³²-A³⁴-A³⁵-A³⁶-R³²III

wherein

R³¹And R³²Each and independently of one another, as in formula II for R²¹And R²²One of the meanings given is as follows,

A³¹to A³⁶Each and independently of one another as in formula II for A²¹To A²⁴One of the meanings given is as follows,

Z³¹and Z³²Each occurrence independently being-COO-, -OCO-, -O-CO-O-, -CF₂-O-、-O-CF₂-、-OCH₂-、-CH₂O-、-CH₂CH₂-、-(CH₂)₄-、-CF₂CF₂-, -CH-, -CF-, -CH-COO-, -OCO-CH-or-C.ident.C-, which are optionally substituted by one or more F, preferably-COO-, -OCO-or-O-CO-O-, more preferably-COO-or-OCO-,

b represents 0 or 1, preferably 0, and

c represents an integer from 1 to 15, preferably an odd (i.e. non-even) integer, and more preferably 3,5, 7 or 9.

Preferred compounds of formula III are selected from the group consisting of wherein c represents 0 and the group (-A)³¹-A³²-) a compound selected from the groups MG1 to MG4 as given above.

More preferred compounds of formula III are selected from those wherein c represents 1 and the group (-A)²⁴-A²⁵-A²⁶-) and (-A)²¹-A²²-A²³-) are each and independently selected from the group consisting of

-Phe-Phe-Phe-MG5

-Phe-Phe-PheL-MG6

-Phe-PheL-Phe-MG7

-PheL-Phe-Phe-MG8

-PheL-Phe-PheL-MG9

-PheL-PheL-Phe-MG10

-PheL-PheL-PheL-MG11

Wherein

Phe, PheL and L have one of the meanings given above for the radicals MG-1 to MG-4.

More preferred compounds of formula III are selected from the group consisting of wherein c represents 0 and the group (-A)²¹-A²²-) is selected from the groups MG1 to MG4 as given above and wherein the group (-A)²⁴-A²⁵-A²⁶-) a compound selected from the groups MG5 to MG 11.

Particularly preferred compounds of formula III are selected from the group of compounds of the formula:

the compounds of the formula III can be synthesized according to or analogously to methods known per se and described in standard works of organic chemistry, such as Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag, Stuttgart.

To achieve high stability, an advantageously high clearing point and a broad phase range and a lower appearance of nematic twisted-bent phases, it is particularly useful to employ the compounds of the formula III in addition to the compounds of the formulae I 'to I' "in the mixtures according to the invention.

In a more preferred embodiment, the LC medium according to the invention comprises one or more compounds of the formula IV,

R⁴¹-A⁴¹-A⁴²-Z⁴¹-(CH₂)_d-Z⁴²-A⁴³-A⁴⁴-R⁴²IV

wherein

R⁴¹And R⁴²Each and independently having the same general formula as above for R under formula II²¹One of the meanings given is as follows,

A⁴¹to A⁴⁴Each and independently of one another as above for A under formula II²¹One of the meanings given is as follows,

Z⁴¹and Z⁴²Each occurrence independently is-COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O-、-CH₂CH₂-、-(CH₂)₄-、-CF₂-O-、-O-CF₂-、-CF₂CF₂-, -CH ═ CH-, -CF ═ CF-, -CH ═ CH-COO-, -OCO-CH ═ CH-or-C ≡ C-, which is optionally substituted with one or more F, preferably-COO-, -OCO-or-O-CO-O-, more preferably-COO-or-OCO-.

d represents an integer from 1 to 15, preferably an odd (i.e. non-even) integer, and more preferably 3,5, 7 or 9.

Preferred compounds of formula IV are selected from the group (-A) thereof⁴¹-A⁴²-) and (-A)⁴³-A⁴⁴-) are each and independently selected from the group of MG1 to MG4 as given above.

Particularly preferred compounds of formula IV are selected from the group of compounds of the following formula:

-symmetrical compounds (IVa and IVb):

-asymmetric compound (IVc):

the compounds of the formula IV are known or can be synthesized in accordance with or analogously to methods known per se and described in standard works of organic chemistry (e.g.Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag, Stuttgart).

In order to reduce the nematic twist-bend phase while maintaining favorable e/K values, it is particularly useful to employ the compounds of the formula IV in addition to the compounds of the formulae I 'to I' "in the mixtures according to the invention.

In a more preferred embodiment, the LC medium according to the invention additionally comprises one or more compounds of the formula V,

R⁵¹-A⁵¹-Z⁵¹-(CH₂)_e-Z⁵²-A⁵²-(A⁵³)_f-R⁵²V

wherein

R⁵¹And R⁵²Each and independently having the same general formula as above for R under formula II²¹One of the meanings given is as follows,

A⁵¹to A⁵³Each and independently of one another as above for A under formula II²¹One of the meanings given is as follows,

Z⁵¹and Z⁵²Each occurrence independently is-COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O-、-CH₂CH₂-、-(CH₂)₄-、-CF₂-O-、-O-CF₂-、-CF₂CF₂-, -CH-, -CF-, -CH-COO-, -OCO-CH-or-C.ident.C-, which are optionally substituted by one or more F, preferably-COO-, -OCO-or-O-CO-O-, more preferably-COO-or-OCO-,

e represents an integer from 1 to 15, preferably an odd (i.e. non-even) integer, and more preferably 3,5, 7 or 9, and

f represents 0 or 1.

Particularly preferably wherein A⁵¹Selected from the following formulae Va' to VaVf ' and mirror image of formula Vd ' and Ve ' compounds of formula V

Preferably R in formula V⁵¹And R⁵²Selected from H, F, Cl, CN, NO₂、OCH₃、COCH₃、COC₂H₅、COOCH₃、COOC₂H₅、CF₃、C₂F₅、OCF₃、OCHF₂And OC₂F₅In particular H, F, Cl, CN, OCH₃And OCF₃Especially H, F, CN and OCF₃。

Preferred compounds of formula V are selected from the group of compounds of formulae VA to VD, preferably of formulae VA and/or VC, most preferably of formula VC,

wherein

LG⁵¹Is Z⁵¹-(CH₂)_z-Z⁵²，

(F)₀Represents H, and

(F)₁represents F.

And the other parameters have the respective meanings given above, including the preferred meanings.

Preferably Z⁵¹-(CH₂)_z-Z⁵²represents-O-CO- (CH)₂)_n-CO-O-、-O-(CH₂)_n-O-or- (CH)₂)_n-more preferably-O-CO- (CH)₂)_n-CO-O-, wherein n represents 3,5, 7 or 9.

Particularly preferred compounds of formula VA are selected from the group of compounds of formulae VA-1 to VA-3:

wherein the parameters have the respective meanings given above, including the preferred meanings.

Particularly preferred compounds of formula VB are selected from the group of compounds of formulae VB-1 to VB-3:

The compounds of formula VC are very preferred. And wherein especially preferred compounds are selected from the group of compounds of formulae VC-1 to VC-3:

The compounds of the formula V can be synthesized on the basis of or analogously to methods known per se and described in standard works of organic chemistry, such as Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag, Stuttgart. Preferred preparation methods are disclosed in, for example, WO 2015/036079A 1.

In a more preferred embodiment, the LC medium according to the invention additionally comprises one or more compounds of the formula VI,

R⁶¹-A⁶¹-A⁶²-(CH₂)_g-Z⁶¹-A⁶³-A⁶⁴-(A⁶⁵)_h-R⁶²VI

wherein

R⁶¹And R⁶²Each and independently having the same general formula as above for R under formula II²¹One of the meanings given is as follows,

A⁶¹to A⁶⁴Each and independently having the same meanings as above for A under formula II²¹One of the meanings given is as follows,

Z⁶¹represents-O-, -COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O、-CH₂CH₂-、-(CH₂)₄-、-CF₂-O-、-O-CF₂-、-CF₂CF₂-, -CH-, -CF-, -CH-COO-, -OCO-CH-or-C.ident.C-, which are optionally substituted by one or more F,

preferably-O-, -COO-, -OCO-or-O-CO-O-,

more preferably-O-, -COO-or-OCO-, most preferably-COO-or-OCO-,

h represents 0 or 1, and

g represents an integer from 1 to 15, preferably an odd (i.e. non-even) integer, and more preferably 3,5, 7 or 9.

Preferred compounds of formula VI are selected from the group consisting of⁶¹-A⁶²-) and (-A)⁶³-A⁶⁴-) are each and independently selected from the group of MG1 to MG4 given above.

More preferred are those in which h represents 0 and the group (-A) in formula VI⁶¹-A⁶²-) and (-A)⁶³-A⁶⁴-(A⁶⁵)_h) A compound of formula VI which is not identical or is not a mirror image or wherein h represents 1.

Especially preferred compounds of formula VI are selected from the group of compounds of the formula:

the compounds of the formula VI can be synthesized according to or analogously to methods known per se and described in standard works of organic chemistry, such as Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag, Stuttgart. Preferably, the compound of formula VI is synthesized according to or in analogy to the method disclosed in WO 2014/005672 a 1.

To achieve higher clearing points and favorable e/K values, it is particularly useful to employ compounds of the formula VI in addition to the compounds of the formulae I 'to I' "in the mixtures according to the invention.

In a more preferred embodiment, the LC medium according to the invention additionally comprises one, two, three or more compounds of the formula VII,

R⁷¹-A⁷¹-Z⁷¹-A⁷²-(Z⁷²-A⁷³)_i-(CH₂)_j-(A⁷⁴-Z⁷³-)_k-A⁷⁵-Z⁷⁴-A⁷⁶-R⁷²VII

wherein

R⁷¹And R⁷²Each and independently having the same general formula as above for R under formula II²¹One of the meanings given is as follows,

A⁷¹to A⁷⁶Each and independently having the same meanings as above for A under formula II²¹One of the meanings given is as follows,

Z⁷¹to Z⁷⁴Each independently represents-COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O-、-OCF₂-、-CF₂O-、-CH₂CH₂-、-(CH₂)₄-、-CF₂CF₂-, -CH-, -CF-, -CH-COO-, -OCO-CH-or-C.ident.C-, which are optionally substituted by one or more F,

preferably-COO-, -OCO-, -O-CO-O-, -OCF₂-、-CF₂O-or single bond

More preferably-COO-, -OCO-, -OCF₂-、-CF₂O-or a single bond,

with the proviso that Z⁷¹To Z⁷⁴At least one of which is not a single bond,

j represents an integer of 1 to 15, preferably an odd (i.e. non-even) integer, and more preferably 3,5, 7 or 9, and

i and k each independently represent 0 or 1.

Preferred compounds of the formula VII are selected from the group-A⁷¹-Z⁷¹-A⁷²-(Z⁷²-A⁷³)_i-、-(A⁷⁴-Z⁷³-)_k-A⁷⁵-Z⁷⁴-A⁷⁶-compounds of which at least one is selected from the group consisting of MGa to MGn and mirror image thereof

Wherein

Wherein preferably L is, independently of one another at each occurrence, F, Cl, CN or an optionally fluorinated alkyl, alkoxy or alkanoyl radical having 1 to 7C atoms, very preferably F, Cl, CN, CH₃、C₂H₅、OCH₃、OC₂H₅、COCH₃、COC₂H₅、COOCH₃、COOC₂H₅、CF₃、OCF₃、OCHF₂、OC₂F₅In particular F, Cl, CN, CH₃、C₂H₅、OCH₃、COCH₃And OCF₃Most preferred are F, Cl and CH₃、OCH₃And COCH₃And r is, independently of one another at each occurrence, 0, 1,2,3 or 4, preferably 0, 1 or 2.

Ball

Wherein L is preferably F, Cl, CH₃、OCH₃And COCH₃。

More preferred are those wherein the group-A in formula VII⁷¹-Z⁷¹-A⁷²-(Z⁷²-A⁷³)_i-and- (A)⁷⁴-Z⁷³-)_k-A⁷⁵-Z⁷⁴-A⁷⁶-compounds of formula VII, identical or mirror images, with the proviso that Z⁷¹To Z⁷⁴At least one of which is not a single bond.

More preferred are compounds of formula VII, wherein i and k both represent 1, more preferably one of i and k represents 0 and the other represents 1, most preferably both i and k represent 0.

Particularly preferred compounds of formula VII are selected from the group of compounds of the formula:

wherein R is⁷¹And R⁷²Each and independently represents F or CN.

The compounds of the formula VII can be synthesized on the basis of or analogously to methods known per se and described in standard works of organic chemistry, for example Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag, Stuttgart. Preferably, the compound of formula VII is synthesized according to or in analogy to the methods disclosed in, for example, WO 2013/174478a 1.

In a more preferred embodiment, the medium according to the invention optionally comprises one or more chiral dopants, especially when used in a flexoelectric device.

The chiral compound being induced to have a helical pitch (P)₀) The pitch is inversely proportional to the concentration (c) of the chiral material used, to a first approximation. The constant of proportionality of this relationship is called the helical twisting force (HTP) of the chiral species and is defined by the following equation

HTP≡1/(c·P₀) (1)

Wherein

c is the concentration of the chiral compound.

For example, the uniform lying helix structure is realized using a chiral nematic liquid crystal having a short pitch generally in the range of 0.2 μm to 1 μm, preferably 1.0 μm or less, especially 0.5 μm or less, which is unidirectionally aligned in such a way that its helical axis is parallel to the substrates (e.g., glass plates) of the liquid crystal cell. In this configuration, the helical axis of the chiral nematic liquid crystal is equivalent to the optical axis of the birefringent plate.

Preferred are chiral dopants having a high Helical Twisting Power (HTP), in particular the chiral dopants disclosed in WO 98/00428.

Chiral dopants commonly used are, for example, commercially available R/S-5011, CD-1, R/S-811 and CB-15 (from Merck KGaA, Darmstadt, Germany).

In another preferred embodiment, the chiral dopant is preferably selected from the group consisting of formula VIII,

and/or of the formula IX,

including the individual (S, S) enantiomers,

wherein E and F are each independently 1, 4-phenylene or trans-1, 4-cyclohexylene, v is 0 or 1, Z⁰is-COO-, -OCO-, -CH₂CH₂-or a single bond, and R is an alkyl, alkoxy or alkanoyl group having 1 to 12C atoms.

Compounds of formula VIII and their synthesis are described in WO 98/00428. Compounds of formula IX and their synthesis are described in GB 2,328,207.

The chiral dopants R/S-5011 and the compounds of the formulae VIII and IX described above exhibit very high Helical Twisting Power (HTP) and are therefore particularly suitable for the purposes of the present invention.

The liquid-crystalline medium preferably comprises preferably 1 to 5, in particular 1 to 3, very preferably 1 or 2 chiral dopants, which are preferably selected from the above formulae VIII and/or IX and/or R-5011 or S-5011, very preferably the chiral compound is R-5011 or S-5011.

The amount of chiral compound in the liquid-crystalline medium is preferably from 0.1 to 15% by weight, in particular from 0.5 to 10% by weight, very preferably from 1 to 5% by weight, based on the total mixture.

Preferably, the LC medium comprises one or more nematic LC compounds selected from the group consisting of the compounds shown below:

wherein

R^2ARepresents H, alkyl or alkoxy having 1 to 15C atoms, further wherein one or more CH of these radicals₂The radicals may each, independently of one another, be replaced by: -C ≡ C-, -CF₂O-、-CH＝CH-、

-O-, -CO-O-or-O-CO-in such a way that the O atoms are not directly linked to one another and in addition one or more H atoms can be replaced by halogen,

L¹and L²Each independently of the others represents F, Cl, CF₃Or CHF₂Preferably, each of them represents F,

Z²and Z^2’Each independently of the other represents a single bond, -CH₂CH₂-、-CH＝CH-、-C≡C-、-CF₂O-、-OCF₂-、-CH₂O-、-OCH₂-、-COO-、-OCO-、-C₂F₄-, -CF ═ CF-or-CH ═ CHCH₂O-，

p represents 0, 1 or 2,

q represents a number of 0 or 1,

(O)C_vH_2v+1represents OC_vH_2v+1Or C_vH_2v+1And is and

v represents 1 to 6.

The liquid-crystalline medium may contain further additives such as, for example, stabilizers, inhibitors, surface-active compounds, lubricants, wetting agents, dispersants, hydrophobing agents, binders, flow improvers, defoamers, deaerators, diluents, reactive diluents, auxiliaries, colorants, dyes, pigments or nanoparticles in customary concentrations. The total concentration of these other components, based on the total mixture, is in the range of 0.1% to 10%, preferably 0.1% to 6%. The concentration of each compound used is preferably in the range of 0.1% to 3% each.

The concentration of these and similar additives is not taken into account for the values and ranges of the concentrations of the liquid-crystalline components and compounds of the liquid-crystalline medium in the present application. This also applies to the concentration of the dichroic dye used in the mixture, which is not accounted for when specifying the concentrations of the compounds and components of the host medium, respectively. The concentration of the individual additives is always given relative to the final doping mixture.

In general, the total concentration of all compounds in the medium according to the present application is 100%.

The liquid-crystalline medium according to the invention consists of several compounds, preferably 2 to 40, more preferably 3 to 30 and most preferably 4 to 25 compounds.

The media according to the invention exhibit a higher elastic constant k₁₁And higher flexoelectric coefficient e. The liquid-crystalline medium preferably exhibits k₁₁100pN or less, preferably 20pN or less.

The liquid-crystalline medium preferably exhibits k₃₃100pN or less, preferably 15pN or less.

The liquid-crystalline medium preferably exhibits a flexural electrical coefficient |, e₁₁L is not less than 0.2pC/m, preferably not less than 1 pC/m.

The liquid-crystalline medium preferably exhibits a flexural electrical coefficient |, e₃₃L is not less than 0.2pC/m, preferably not less than 2 pC/m.

The liquid-crystalline medium preferably exhibits a flexibility-elasticity ratio (flip-elastic ratio) (yao/K) of from 1 to 10V^-1In the range of 1 to 7V, preferably^-1In the range of 1 to 5V, more preferably^-1Within the range.

The media according to the present invention exhibit a high clearing point of at most 55 ℃ and higher, preferably at most 60 ℃ and higher and more preferably at most 65 ℃ and higher.

The media according to the invention exhibit a broad nematic phase of 30 ℃ and more, preferably 35 ℃ and more or even 40 ℃ or more.

The media according to the invention exhibit an N of less than 20 ℃ or less, preferably less than 15 ℃ or less and more preferably less than 0 ℃ or less_TBAnd (4) phase(s).

The media according to the invention exhibit a high stability against crystallization at room temperature of more than 100 hours, preferably more than 250 hours or more than 1000 hours.

The media according to the invention exhibit a higher stability against crystallization (LTS) even at low temperatures. Accordingly, the medium does not crystallize even at temperatures as low as 0 ℃, preferably as low as-10 ℃, more preferably as low as-20 ℃.

In a preferred embodiment, the LC medium comprises:

1 to 10, preferably 1 to 5, more preferably 1 or 3, most preferably 1 or 2 compounds of the formulae I 'to I' ". The amount of the compound or compounds of the formulae I 'to I' "in the overall liquid-crystalline medium is preferably in the range from 5 to 50% by weight, in particular in the range from 6 to 30% by weight, in particular in the range from 7 to 20% by weight, based on the total mixture,

and

optionally 1 to 10, preferably 1 to 5, more preferably 1 or 3, most preferably 1 or 2 compounds of formula II, preferably selected from among (-A) in formula II²¹-A²²-) and (-A)²³-A²⁴-) are identical or mirror images of compounds of formula II, more preferably of formula II 'a-5 and/or II' a-6. If present, the amount of compound of formula II in the liquid-crystalline medium is preferably in the range from 0 to 30% by weight, more preferably in the range from 1 to 20% by weight, even more preferably in the range from 2 to 10% by weight of the total mixture,

and/or

Optionally 1 to 10, preferably 1 to 5, more preferably 1 or 3, most preferably 1 or 2 compounds of formula III, which are preferably selected from the symmetrical compounds of the above formula IIIc-2 and/or IIIc-3. If present, the amount of compound of formula III in the liquid-crystalline medium is preferably in the range from 1 to 50% by weight, more preferably in the range from 5 to 30% by weight, even more preferably in the range from 10 to 20% by weight of the total mixture,

and/or

Optionally 1 to 10, preferably 1 to 5, more preferably 1 or 3, most preferably 1 or 2 compounds of formula IV, preferably selected from symmetrical compounds IVb and/or asymmetrical compounds IVc, more preferably selected from formulae IVb-5, IVc-2, IVc-3, IVc-12 and/or IVc-15. If present, the amount of compound of formula IV in the liquid-crystalline medium is preferably in the range from 1 to 98% by weight, more preferably in the range from 20 to 80% by weight, even more preferably in the range from 30 to 60% by weight of the total mixture,

and/or

Optionally 1 to 6, in particular 2 to 5, very preferably 3 or 4 compounds of the formula V, which are preferably selected from the above formulae VA-1, VC-2 and/or VC-3. If present, the amount of compound of formula V in the liquid-crystalline medium is preferably in the range from 1 to 70% by weight, more preferably in the range from 10 to 60% by weight, even more preferably in the range from 20 to 50% by weight of the total mixture,

and/or

Optionally 1 to 10, preferably 1 to 5, more preferably 1 or 3, most preferably 1 or 2 compounds from formula VI above, preferably in the form of compounds of formula VI-4, VI-5, VI-7 and/or VI-8. If present, the amount of compound of the formula VI in the liquid-crystalline medium is preferably from 1 to 40% by weight, in particular from 5 to 25% by weight, very preferably from 10 to 15% by weight, of the total mixture,

and/or

Optionally 1 to 10, preferably 1 to 5, more preferably 1 or 3, most preferably 1 or 2 compounds from formula VII above, preferably compounds of formula VII-4, VII-5 and/or VII-8. If present, the amount of compound of the formula VII in the liquid-crystalline medium is preferably from 1 to 35% by weight, in particular from 5 to 25% by weight, very preferably from 10 to 15% by weight, of the total mixture,

and/or

Optionally 1 to 5, in particular 1 to 3, very preferably 1 or 2 chiral dopants, which are preferably selected from the above formulae VIII and/or IX and/or R-5011 or S-5011, very preferably the chiral compound is R-5011 or S-5011. If present, the amount of chiral compound in the liquid-crystalline medium is preferably from 1 to 15% by weight, in particular from 0.5 to 10% by weight, very preferably from 0.1 to 5% by weight, and/or of the total mixture

Optionally up to 25, especially up to 20, very preferably up to 15, different compounds selected from the compounds of the formula X. The amount of compounds of the formula X in the liquid-crystalline medium, if present, is preferably from 1 to 50% by weight, in particular from 5 to 30% by weight, very preferably from 10 to 25% by weight, of the total mixture,

and/or

Other additives, such as stabilizers, antioxidants, etc., optionally in the usual concentrations. If present, the total concentration of these other components ranges from 0.1% to 10%, preferably from 0.1% to 6%, based on the total mixture. The concentration of each compound used is preferably in the range of 0.1% to 3% each.

In another preferred embodiment, the LC medium of the present invention consists only of a compound selected from the group consisting of formula I 'to formula I' "and formula II to formula X, very preferably the LC medium consists only of a compound selected from the group consisting of formula I 'to formula I'" and formula II to formula IX.

The compounds forming the LC medium of the present invention are mixed in a conventional manner. Generally, the desired amount of a compound used in a smaller amount is dissolved in a compound used in a larger amount. The completion of the dissolution process is particularly easy to observe in the case of temperatures above the clearing point of the compounds used in higher concentrations. However, the medium can also be prepared by other conventional methods, for example using so-called premixes which can be, for example, homologous (homologous) or eutectic media of the compounds, or using so-called multi-vial systems, the ingredients themselves being the ready-to-use media. The invention therefore also relates to a method for producing an LC medium as set forth above and below.

In particular, the present invention relates to a process for the preparation of an LC medium comprising the step of mixing one or more compounds of formulae I 'to I' ", wherein at least one compound is selected from compounds of formulae II to X.

The liquid-crystalline media according to the invention can be used in electro-optical devices, for example in liquid-crystalline devices, such as STN, TN, AMD-TN, temperature-compensated, guest-host, phase-change or surface-stabilized or polymer-stabilized cholesteric texture (SSCT, PSCT) displays, in particular in active and passive optical components, such as polarizers, compensators, reflectors, alignment layers, color filters or holographic components, in adhesives, synthetic resins with anisotropic mechanical properties, cosmetics, diagnostic devices, liquid-crystal pigments, in decorative and security applications, in nonlinear optics, optical information storage or as chiral dopants. Accordingly, a further aspect of the present invention is the use of an LC medium comprising at least one compound of formulae I 'to I' "in an electro-optical device.

Since the medium according to the invention is particularly advantageous for devices for flexoelectric liquid crystal display applications, such as ULH or USH modes.

Therefore another object of the present invention is a liquid crystal device, preferably a flexoelectric device, comprising a medium comprising one or more compounds of formulae I 'to I' ".

A flexoelectric display according to a preferred embodiment of the present invention comprises two planar parallel substrates, preferably glass plates with transparent conductive layers, such as Indium Tin Oxide (ITO), on their inner surfaces; an optional alignment layer; and media comprising one or more compounds of formulae I 'to I' "and a chiral dopant as described above and below.

If an electric field is applied to the construction perpendicular to the helix axis, the optical axis rotates in the plane of the cell, similar to the director of a ferroelectric liquid crystal rotating in a surface-stabilized ferroelectric liquid crystal display.

This field induces a splay-bend structure in the director, which is modulated by the tilt angle in the optical axis. The rotation angle of the shaft is first approximately proportional and linearly proportional to the electric field strength. The best optical effect is seen when the liquid crystal cell is placed between crossed polarizers with the optical axis in the unpowered state (22.5 ° to the absorption axis of one of the polarizers). This angle of 22.5 is also the ideal rotation angle of the electric field, so that by reversal of the electric field the optical axis is rotated by 45, and by appropriate selection of the relative orientation of the axis of the helix, the preferred direction of the absorption axis of the polarisers and the direction of the electric field, the optical axis can be switched from being parallel to one polariser to being at the central angle between the two polarisers. When the total angle of the optical axis switching is 45 deg., the best contrast is achieved. In this case, the arrangement can be used as a switchable quarter wave plate, provided that the optical retardation (i.e. the product of the effective birefringence of the liquid crystal and the cell thickness) is chosen to be a quarter of the wavelength. Unless explicitly stated otherwise, in this context the wavelength mentioned is 550nm, for which the sensitivity of the human eye is highest.

A good approximation of the rotation angle (Φ) of the optical axis is given by:

tanΦ＝eP₀E/(2πK)

wherein P is₀Is the undisturbed pitch of the cholesteric liquid crystal,

the quotient is the splay flexoelectric coefficient (e)₁₁) And flexural modulus of elasticity (e)₃₃) Mean value of [ sic ═ 1/2 (e)₁₁+e₃₃)]，

E is the electric field strength and

k is the splay elastic constant (K)₁₁) And bending elastic constant (k)₃₃) Average value of (K) 1/2 (K)₁₁+k₃₃)]And wherein

The e/K is called the flexibility-elasticity ratio.

This rotation angle is half the switching angle in a flexoelectric switching element.

A good approximation of the response time (τ) of this photoelectric effect is given by

τ＝[P₀/(2π)]²·γ/K

Wherein

γ is the effective viscosity coefficient associated with the twist of the helix.

The flexoelectric effect is characterized by a fast response time (T at 35 ℃)_on+T_off) Typically in the range of 1ms to 10ms, preferably < 5ms and even more preferably < 3 ms. It is further characterized by a very preferred gray scale capability.

There is a critical field (E) to unwind the helix_c) Which can be obtained from the following equation

E_c＝(π²/P₀)·[k₂₂/(ε₀·Δε)]^1/2

Wherein

k₂₂Is the constant of the elasticity in torsion,

ε₀is permittivity of vacuum and

Δ ∈ is the dielectric anisotropy of the liquid crystal.

The inventive media of the invention can be aligned with their cholesteric phase into different alignment states by methods known to the expert, for example surface treatment or electric fields. For example, they may be aligned in a planar (gurney) state, a focal conic state, or a homeotropic state.

The term "planar alignment" or orientation of the liquid crystal or mesogenic material in the display cell or on the substrate means that the mesogenic groups in the liquid crystal or mesogenic material are oriented substantially parallel to the plane of the cell or substrate, respectively.

The term "homeotropic alignment" or orientation of the liquid crystal or mesogenic material in the display cell or on the substrate means that the mesogenic groups in the liquid crystal or mesogenic material are oriented substantially perpendicular to the plane of the cell or substrate, respectively.

The switching between different orientation states according to a preferred embodiment of the invention is exemplarily set forth in detail below.

According to this preferred embodiment, the sample is placed in a cell comprising two plane-parallel glass plates coated with an electrode layer (e.g. an ITO layer) and aligned in its cholesteric phase to a planar state, wherein the axis of the cholesteric helix is oriented perpendicular to the cell walls. This state is also referred to as the glancing state and the texture of the sample that can be observed, for example, in a polarizing microscope is referred to as the glancing texture. Planar alignment may be achieved, for example, by surface treating the cartridge walls, for example, by rubbing and/or coating with an alignment layer such as polyimide.

The granny state with high alignment quality and only few defects can be further achieved by heating the sample to the isotropic phase, followed by cooling to the chiral nematic phase at a temperature close to the chiral nematic-isotropic phase transition, and by slightly pressing the flow alignment of the cell.

In the planar state, the sample shows selective reflection of incident light, with the center wavelength of reflection depending on the helical pitch and average refractive index of the material.

When an electric field is applied to the electrodes, e.g. with a frequency of 10Hz to 1kHz and an amplitude of at most 12V_rmsAt an electric field of/. mu.m, the sample switches to a perpendicular state, in which the helix is unwound and the molecules are oriented parallel to the field, i.e. perpendicular to the plane of the electrodes. In the homeotropic state, the sample is transmissive when viewed in normal daylight (normal daylight) and appears black when disposed between crossed polarizers.

After reducing or removing the electric field in the homeotropic state, the sample adopts a focal conic texture in which the molecules exhibit a helical twisted structure and the helical axis is oriented perpendicular to the field, i.e., parallel to the plane of the electrodes. The focal conic state can also be achieved by applying only a weak electric field to the sample in its planar state. In the focal conic state, the sample is scattering when viewed in normal daylight and appears bright between crossed polarizers.

Samples of the medium according to the invention in different orientation states exhibit different light transmission. Therefore, each alignment state and its alignment quality can be controlled by measuring the light transmittance of the sample depending on the intensity of the applied electric field. Thereby, the electric field strength required for achieving a specific orientation state and a transition between these different states can also be determined.

In a sample of the medium according to the invention, the above-mentioned focal conic state consists of a number of disordered birefringent domains. Uniform alignment texture is achieved by applying an electric field higher than the field used to nucleate the focal conic texture, preferably accompanied by additional shearing of the cell, with the helical axis parallel to the plane of the electrodes in large well-aligned areas. This texture is also referred to as Uniform Lying Helix (ULH) texture according to the literature on the current advanced technology of chiral nematic materials, such as p.rudquist et al, liq.cryst.23(4),503 (1997). This texture is required to characterize the flexoelectric properties of the compounds of the present invention.

Starting from ULH texture, the media of the present invention can be subjected to flexoelectric switching by applying an electric field. This causes the optical axis of the material to rotate in the plane of the cell substrate, which rotation causes the transmission to change when the material is placed between crossed polarisers. Flexoelectric switching of the materials of the present invention is described in further detail in the above introduction and in the examples.

It is also possible to start with a focal conic texture, ULH texture being obtained by applying an electric field with a high frequency of e.g. 10kHz to the sample while slowly cooling from the isotropic phase to the cholesteric phase and shearing the cell. The field frequency may be different for different compounds.

In addition to their use in flexoelectric devices, the media according to the invention are also suitable for other types of displays and other optical and electro-optical applications, such as optical compensation or polarizing films, color filters, reflective cholesteric phases, optical rotatory power (optometric power) and optical information storage.

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. Accordingly, the following examples are to be construed as merely illustrative and not limitative of the remainder of the disclosure in any way whatsoever.

As used herein, plural forms of terms herein should be understood to include singular forms, and vice versa, unless the context clearly indicates otherwise.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words (e.g., "comprising" and "includes") mean "including but not limited to" and are not intended to (and do not) exclude other components.

Throughout the present application, it is to be understood that the bond angle at the C atom bonded to three adjacent atoms (e.g. in a C ≡ C or C ≡ O double bond or e.g. in a benzene ring) is 120 °, and the bond angle at the C atom bonded to two adjacent atoms (e.g. in C ≡ C or in a C ≡ N triple bond or in an allylic position C ≡ C) is 180 °, unless these angles are otherwise limited, e.g. as part of a small ring like a 3-, 4-or 5-atom ring, but in some cases in some formulae these angles are not accurately represented.

It will be appreciated that variations may be made to the foregoing embodiments of the invention while still falling within the scope of the invention. Each feature disclosed in this specification may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

All of the features disclosed in this specification may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. In particular, the preferred features of the invention are applicable to all aspects of the invention and may be used in any combination. Also, features described in non-essential combinations may be used separately (not in combination).

The parameter ranges indicated in the present application each include limits that include the maximum allowable error as known to those skilled in the art. The different upper and lower values for each property range are combined with each other to produce other preferred ranges.

The total concentration of all compounds in the medium according to the present application is 100%. All concentrations are given in% w/w unless explicitly stated otherwise.

In the foregoing and in the following examples, all temperatures are set forth uncorrected in degrees celsius and all parts and percentages are by weight unless otherwise indicated.

It is obvious to the person skilled in the art that the LC medium may also comprise compounds in which, for example, H, N, O, Cl, F are replaced by the corresponding isotopes.

The following abbreviations are used to illustrate the liquid crystal phase behavior of the compounds: t is_N,IClearing points; k ═ crystal; n is nematic; n is a radical of_TBA second nematic phase or a twisted-bent nematic phase; s or Sm is smectic; ch ═ cholesterol type; i is isotropic; tg ═ glass transition. The numbers between the symbols indicate the phase transition temperature in c.

In the present application and in particular in the following examples, the structure of the liquid crystal compounds is represented by the abbreviation (which is also referred to as "prefix"). The abbreviations may be directly converted to corresponding structures according to the following three tables a to C.

All radicals C_nH_2n+1、C_mH_2m+1And C_lH_2l+lPreference is given to straight-chain alkyl radicals having n, m and l C atoms, respectively, all radicals C_nH_2n、C_mH_2mAnd C_lH_2lAre preferably each (CH)₂)_n、(CH₂)_mAnd (CH)₂)_land-CH ═ CH-is preferably trans or E ethenylene. Preferably, n, m and l represent integers between 1 and 12.

Table a lists the symbols for the ring elements, table B lists the symbols for the linking groups, and table C lists the symbols for the left and right terminal groups of the molecule.

Table a: ring element

Table B: linking group

Table C: terminal group

Where n and m are each integers and three points indicate the space for other symbols of this table.

Examples

Test cartridge and method

A 3 μm thick cell with antiparallel rubbed PI alignment layers on its substrates facing each other is typically filled on a hot plate at a temperature at which the flexoelectric mixture is in the isotropic phase.

Phase transitions, including clearing points and crystallization behavior, are typically determined using Differential Scanning Calorimetry (DSC) prior to filling the cartridge. In addition, for optical phase transition measurements, a Mettler FP90 hot stage controller connected to the FP82 hot stage was used to control the temperature of the cell. The temperature was increased from ambient temperature at a rate of 5 degrees celsius/minute until the onset of the isotropic phase was observed. Texture changes were observed using an Olympus BX51 microscope via crossed polarizers and the respective temperatures were noted.

Wires (wires) were then attached to the ITO electrodes of the box using indium metal. The cassette was mounted in a Linkam THMS600 hot plate connected to a Linkam TMS93 hot plate controller. The hot stage was mounted in the rotating stage of an Olympus BX51 microscope.

The cell is heated until the liquid crystal is fully isotropic. The cell was then cooled under the applied electric field until the sample was completely nematic. The drive waveform was supplied by a Tektronix AFG3021B arbitrary function generator, sent via a Newtons4th LPA400 power amplifier, and then applied to the cartridge. The cell response was monitored with a Thorlabs PDA55 photodiode. Both the input waveform and the optical response were measured using a Tektronix TDS 2024B digital oscilloscope.

To measure the flexoelectric response of a material, unless explicitly stated otherwise, the change in the magnitude of the tilt of the optical axis is measured as a function of the increased voltage at a temperature of 35 ℃. This is achieved by using the following equation:

tanφ＝(P₀/2π)(e/K)E

wherein

Is the angle of inclination of the optical axis from the initial position (i.e. when E is 0)E is the applied field and K is the elastic constant (K)₁And K₃And e is the flexoelectric coefficient (where e-e)₁+e₃). The applied field was monitored using an HP 34401A multimeter. The tilt angle was measured using the aforementioned microscope and oscilloscope. Undisturbed cholesteric pitch P was measured using an Ocean Optics USB4000 spectrometer attached to a computer₀. A selective reflection band is obtained and the pitch is determined from the spectral data.

The media shown in the examples below are well suited for ULH displays. For this purpose, the chiral dopant(s) used must be applied in a suitable concentration in order to achieve a typical cholesteric pitch of 350 to 275 nm.

Examples of mixtures

Host mixture H-1

The following mixture H1 was prepared.

Mixture example M-1

15% w/w of compound BM-1:

added to 85% w/w of the host mixture H-1.

The resulting mixture M-1 was homogenized and filled into a test cartridge as described above.

Carrying out a handover performance, T_NI(clearing Point), e/K (Flexible elastic constant) and N_TB(transition temperature to second nematic phase or nematic twist-bend phase) and the results are summarized in the table below.

Mixture example M-2

15% w/w of the compound BM-2

Added to 85% w/w of the host mixture H-1.

The resulting mixture M-2 was homogenized and filled into a test cartridge as described above.

With respect to switching performance, clearing point, compliance spring constant and N_TBThe transition temperatures were measured and the results are summarized in the following table.

Mixture example M-3

15% w/w of the compound BM-3

Added to 85% w/w of the host mixture H-1.

The resulting mixture M-3 was homogenized and filled into a test cartridge as described above.

Claims

1. A compound of formula I ', I ' or I ',

A¹²(-Z¹²-A¹³)_p-X¹¹-Sp-X¹²-(A¹⁴-Z¹³-)_qA¹⁵I”’

wherein

R¹¹And R¹²Each independently represents halogen, CN, NO₂NCO, NCS or a linear or branched alkyl group which may be unsubstituted, mono-or polysubstituted with halogens or CN and in which one or more non-adjacent and non-terminal CH groups are present₂The groups may be replaced independently of each other at each occurrence by: -O-, -S-, -NH-, -N (CH)₃) -, -CO-, -COO-, -OCO-, -O-CO-O-, -S-CO-, -CO-S-, -CH ═ CH-, -CH ═ CF-, -CF ═ CF-or-C.ident.C-, in such a way that the oxygen atoms are not directly linked to one another,

Z¹¹to Z¹⁴Independently of one another in each occurrence, is a single bond, -COO-, -OCO-, -O-CO-O-、-OCH₂-、-CH₂O-、-OCF₂-、-CF₂O-、-CH₂CH₂-、-(CH₂)₄-、-CF₂CF₂-, -CH-, -CF-, -CH-COO-, -OCO-CH-or-C.ident.C-, which radicals are optionally substituted by one or more F,

o, p, q and r are each and independently 0, 1 or 2, provided however that o + p + q + r.gtoreq.1,

sp is a spacer group comprising 3 or 5 to 20C atoms, one or more non-adjacent and non-terminal CH₂The groups may also be replaced by: -O-, -S-, -NH-, -N (CH)₃)-、-CO-、-O-CO-、-S-CO-、-O-COO-、-CO-S-、-CO-O-、-CF₂-、-CF₂O-、-OCF₂-、-C(CF₃) -, -C (CN) -C (OH) -, -CH (alkyl) -, -CH (alkenyl) -, -CH (alkoxy) -, -CH (oxaalkyl) -, -CH ═ CH-or-C.ident.C-but alternatively such that no two O atoms are adjacent to one another and no two radicals selected from the group consisting of-O-CO-, -S-CO-, -O-COO-, -CO-S-, -CO-O-and-CH ≡ CH-are adjacent to one another,

X¹¹and X¹²Independently of one another, from the group consisting of a single bond, -CO-O-, -O-CO-, -O-COO-, -O-, -CH-, -C.ident.C-, -CF ═ C-₂-O-、-O-CF₂-、-CF₂-CF₂-、-CH₂-O-、-O-CH₂-, -CO-S-, -S-CO-, -CS-S-, -S-CS-, -S-CSS-and-S-, wherein in-X¹¹-Sp¹-X¹²In the formula (I), two O atoms, two-CH-groups and two groups selected from-O-CO-, -S-CO-, -O-COO-, -CO-S-and-CO-O-are not directly bonded to each other, respectively.

2. Compound according to claim 1, characterized in that the compound of formula I' is selected from the group of compounds of the following list:

wherein

r represents 0, 1 or 2

each and independently of the other represent:

if r represents 0, then

If r represents 1, then

3. Compound according to claim 1, characterized in that the compound of formula I "is selected from the group of compounds of the following list:

r represents 0, 1 or 2

each and independently of the other represent:

if r represents 0, then

If r represents 1, then

And wherein R¹¹、R¹²、Z¹¹To Z¹⁴、X¹¹、X¹²And Sp have one of the meanings given above under formula I'.

4. Compound according to claim 1, characterized in that the compound of formula I' "is selected from the group of compounds of the following list:

wherein

r represents 0, 1 or 2

each and independently of the other represent:

if r represents 0, then

If r represents 1, then

5. Use of one or more compounds of formula I 'to formula I' "in a liquid crystal medium.

An LC medium comprising one or more compounds of formula I 'to formula I' ".

7. An LC medium according to claim 6, comprising one or more compounds of formula II,

R²¹-A²¹-A²²-(CH₂)_a-A²³-A²⁴-R²²II

wherein

R²¹And R²²Each independently of the others, H, F, Cl, CN or a linear or branched alkyl group which may be unsubstituted, mono-or polysubstituted by halogen or CN, one or more non-adjacent CH₂The groups may also be replaced independently of one another at each occurrence by: -O-, -S-, -NH-, -N (CH)₃) -, -CO-, -COO-, -OCO-, -O-CO-O-, -S-CO-, -CO-S-, -CH ═ CH-, -CH ═ CF-, -CF ═ CF-or-C.ident.C-, in such a way that the oxygen atoms are not directly linked to one another,

A²¹to A²⁴Each occurrence independently and independently represents aryl, heteroaryl, cycloaliphatic and heterocyclic, and

a represents an integer of 1 to 15.

8. The LC medium according to claim 6 or 7, comprising one or more compounds of the formula III,

R³¹-A³¹-A³²-(A³³)_b-Z³¹-(CH₂)_c-Z³²-A³⁴-A³⁵-A³⁶-R³²III

wherein

R³¹And R³²Each and independently of one another, as in formula II for R²¹One of the meanings given is as follows,

A³¹to A³⁶Each and independently of one another as in formula II for A²¹One of the meanings given is as follows,

Z³¹and Z³²Each occurrence independently and independently represents-COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O-、-CH₂CH₂-、-(CH₂)₄-、-CF₂-O-、-O-CF₂-、-CF₂CF₂-, -CH-, -CF-, -CH-COO-, -OCO-CH-or-C ≡ C-, optionally substituted with one or more F,

c represents an integer of 1 to 15, and

b represents 0 or 1.

9. LC medium according to one or more of claims 6 to 8, comprising one or more compounds of the formula IV,

R⁴¹-A⁴¹-A⁴²-Z⁴¹-(CH₂)_d-Z⁴²-A⁴³-A⁴⁴-R⁴²IV

wherein

R⁴¹And R⁴²Each and independently of one another, as in formula II for R²¹One of the meanings given is as follows,

A⁴¹to A⁴⁴Each and independently of one another as in formula II for A²¹One of the meanings given is as follows,

Z⁴¹and Z⁴²Each occurrence independently is-COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O-、-CH₂CH₂-、-(CH₂)₄-、-CF₂-O-、-O-CF₂-、-CF₂CF₂-, -CH-, -CF-, -CH-COO-, -OCO-CH-or-C.ident.C-, which are optionally substituted by one or more F,

d represents an integer of 1 to 15.

10. LC medium according to one or more of claims 6 to 9, comprising one or more compounds of the formula V,

R⁵¹-A⁵¹-Z⁵¹-(CH₂)_e-Z⁵²-A⁵²-(A⁵³)_f-R⁵²V

wherein

R⁵¹And R⁵²Each and independently of one another, as in formula II for R²¹One of the meanings given is as follows,

A⁵¹to A⁵³Each and independently of one another as in formula II for A²¹Give aIn one of the meaning of (a),

Z⁵¹and Z⁵²Each occurrence independently is-COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O-、-CH₂CH₂-、-(CH₂)₄-、-CF₂-O-、-O-CF₂-、-CF₂CF₂-, -CH-, -CF-, -CH-COO-, -OCO-CH-or-C.ident.C-, which are optionally substituted by one or more F,

f represents a number of 0 or 1,

e represents an integer of 1 to 15.

11. LC medium according to one or more of claims 6 to 10, comprising one or more compounds of the formula VI,

R⁶¹-A⁶¹-A⁶²-(CH₂)_g-Z⁶¹-A⁶³-A⁶⁴-(A⁶⁵)_h-R⁶²VI

wherein

R⁶¹And R⁶²Each and independently of one another, as in formula II for R²¹And R²²One of the meanings given is as follows,

Z⁶¹represents-O-, -COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O、-CH₂CH₂-、-(CH₂)₄-、-CF₂-O-、-O-CF₂-、-CF₂CF₂-, -CH-, -CF-, -CH-COO-, -OCO-CH-or-C.ident.C-, which are optionally substituted by one or more F, S and/or Si,

h represents 0 or 1, and

g represents an integer of 1 to 15.

12. LC medium according to one or more of claims 6 to 11, comprising one or more compounds of the formula VII,

wherein

Z⁷¹to Z⁷⁴Each independently represents-COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O-、-OCF₂-、-CF₂O-、-CH₂CH₂-、-(CH₂)₄-、-CF₂CF₂-, -CH ═ CH-, -CF ═ CF-, -CH ═ CH-COO-, -OCO-CH ═ CH-or-C ≡ C-, which is optionally substituted with one or more F, S and/or Si, or represents a single bond, with the proviso that Z is⁷¹To Z⁷⁴At least one of which is not a single bond,

j represents an integer of 1 to 15, and

i and k represent 0 or 1.

13. LC medium according to one or more of claims 6 to 12, comprising one or more chiral dopants.

14. The LC medium according to one or more of claims 6 to 13, comprising one or more nematic LC compounds selected from the group consisting of compounds of the formulae X-1 to X-4,

wherein

R^2AMeans for indicating H, toolsAlkyl, alkenyl or alkoxy having 1 to 15C atoms, further wherein one or more CH's of these radicals₂The radicals may each, independently of one another, be replaced by: -C ≡ C-, -CF₂O-、-CH＝CH-、

L¹and L²Each independently of the others represents F, Cl, CF₃Or CHF₂，

p represents 0, 1 or 2,

q represents a number of 0 or 1,

(O)C_vH_2v+1represents OC_vH_2v+1Or C_vH_2v+1And is and

v represents 1 to 6.

15. Process for the preparation of an LC medium according to one or more of claims 6 to 14, comprising the step of mixing one or more compounds of formulae I 'to I' "with at least one compound selected from compounds of formulae II to X.

16. Use of an LC medium according to one or more of claims 6 to 14 in electro-optical devices.

17. Electro-optical device comprising a medium according to one or more of claims 6 to 14.

18. An electro-optical device as claimed in claim 17, characterized in that the electro-optical device is a flexoelectric device.