CN110997870A - Liquid crystal medium and liquid crystal device - Google Patents

Abstract

The invention relates to compounds of formula (I), R¹¹‑A¹¹‑(Z¹¹‑A¹²)_p‑X¹¹‑Sp¹¹‑X¹²‑(A¹³‑Z¹³)_q‑A¹⁴‑R¹²I wherein R¹¹、R¹²、A¹¹To A¹⁴、Z¹¹、Z¹³、X¹¹、X¹²、Sp¹¹P and q have one of the meanings given below. Book (I)The invention also relates to a process for preparing the compounds of the formula I, to the use of the compounds in liquid-crystalline media and to liquid-crystalline media comprising one or more compounds of the formula I. Furthermore, the invention relates to a method for producing such a liquid-crystalline medium, to the use of such a medium in a liquid-crystal device, in particular in an flexoelectric liquid-crystal device, and to an flexoelectric liquid-crystal device comprising a liquid-crystalline medium according to the invention.

Description

Liquid crystal medium and liquid crystal device

The present invention relates to compounds of formula (I),

R¹¹-A¹¹-(Z¹¹-A¹²)_p-X¹¹-Sp¹¹-X¹²-(A¹³-Z¹³)_q-A¹⁴-R¹²I

wherein R is¹¹、R¹²、A¹¹To A¹⁴、Z¹¹、Z¹³、X¹¹、X¹²、Sp¹¹P and q have one of the meanings given below. The invention also relates to a process for preparing the compounds of the formula I, to the use of said compounds in liquid-crystalline media and to liquid-crystalline media comprising one or more compounds of the formula I. Furthermore, the invention relates to a method for producing such a liquid-crystalline medium, to the use of such a medium in a liquid-crystal device, in particular in an flexoelectric liquid-crystal device, and to a flexoelectric liquid-crystal device comprising a liquid-crystalline medium according to the invention.

Background and Prior Art

Flexoelectric effects are described, for example, in 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 utilizing the flexoelectric effect and liquid crystal media particularly suitable for flexoelectric devices are known from EP0971016, GB2356629 and Coles, h.j., Musgrave, b., Coles, m.j., and Willmott, j., j.matter.chem., 11, pages 2709 to 2716 (2001).

The uniform horizontal helix (ULH) has a high potential as a fast switching liquid crystal display mode. It is capable of sub-millisecond switching at 35 deg.c and has an inherently high aperture ratio, resulting in an energy efficient display mode.

Materials commonly used in dielectrics that are suitable for ULH mode are typically bimesogenicAnd (4) crystallizing. Due to the size of these materials and the presence of polar groups such as terminal cyano groups, they typically have high rotational viscosities (γ) of the order of several thousand mpa.s at 35 ℃₁). High gamma₁The values are not problematic at elevated temperatures, e.g. 35 ℃, since the switching speed is directly related to γ₁And (4) in proportion. On the other hand, γ₁The value of (d) is also proportional to the square of the chiral pitch. Since the chiral pitch is typically in the range of 300nm, this means that the switching speed is still very fast, in the region of 1 or a few milliseconds.

However, upon reaching lower temperatures, e.g., room temperature, γ, at which ULH devices typically operate₁The value of (a) increases exponentially, and even with short pitch materials, the switching speed increases beyond a favorable level.

In order to maintain a fast switching speed at temperatures below 35 deg.C, it is necessary to reduce the value γ of the liquid-crystal mixture₁And thus there is a need to identify compounds with lower gamma₁The mixture of (1).

Therefore, there is a great need for new bimesogenic compounds that exhibit advantageously low γ₁The values, while preferably showing:

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 liquid-crystalline media should exhibit an advantageously low γ₁The values, while preferably showing:

a low melting point of the acid component,

the brightness of the high-definition bright spot,

a broad range of chiral nematic phases,

a short temperature independent pitch length,

high bending electrical coefficient, and

advantageous low-temperature stability, no crystallization effect in the box and in the bulk (in the bulk).

Other objects of the present invention will be 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", "mesomorphic 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 a liquid crystal 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 a liquid crystalline phase per se. They may also exhibit liquid-crystalline phase behavior only in mixtures with other compounds. For the sake of simplicity, the term "liquid crystal" is used hereinafter for both mesogenic and liquid crystal 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 both saturated rings and heterocyclic groups" 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. containing only one ring (e.g. cyclohexane), or polycyclic, i.e. containing 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 radicals 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 fused radicals, e.g. tetralin, decahydronaphthalene, 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 radicals are 1, 4-phenylene, 4 '-biphenylene, 1, 4-terphenylene, 1, 4-cyclohexylene, 4' -dicyclohexylene and 3, 17-hexadecahydro-cyclopenta [ a ]]Phenanthrene, which is optionally substituted by one or more identical or different groups 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" above and below denotes F, Cl, Br or I.

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 CH₂Where a radical is replaced by-O-, preferably for example straight-chain 2-oxapropyl (═ methoxymethyl), 2- (═ ethoxymethyl) or 3-oxabutyl (═ 2-methoxyethyl), 2-, 3-or 4-oxapentyl, 2-, 3-, 4-or 5-oxahexyl, 2-, 3-, 4-, 5-or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6-or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7-or 8-oxanonyl or 2-, 3-, 4-, 5-, 6-, 7-, 8-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 (orientational 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" in, for example, 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 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 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 the ordinary refractive index, and the average refractive index n_av.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 this application, the term "dielectrically positive" is used for compounds or components having a Δ ε >3.0, "dielectrically neutral" is used for compounds or components having a Δ ε ≦ 1.5 and "dielectrically negative" is used for compounds or components having a Δ ε < -1.5. Δ ε was measured at a frequency of 1kHz and at 20 ℃. The dielectric anisotropy of each compound was determined from the results of a 10% solution of each individual compound in a nematic host mixture. In the case where the solubility of each compound in the host medium is less than 10%, then its concentration is reduced by one-half until the resulting medium is sufficiently stable to at least allow its properties to be determined. Preferably, however, the concentration is kept at least 5% to maintain the significance of the results as high as possible. The capacitance of the test mixture was measured in a cell with both homeotropic and planar alignment. The cell thickness of both types of cells was about 20 μm. The applied voltage is a rectangular wave with a frequency of 1kHz and a root mean square value of typically 0.5V to 1.0V; however, it is always selected to be below the capacitance threshold of the respective test mixture.

Δ ε is defined as_||-ε_⊥) And is of_av.Is (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. Extrapolating the valueTo 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,

and

represents a trans-1, 4-cyclohexylene group,

and

represents a1, 4-phenylene group.

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

Detailed description of the invention

The present invention relates to compounds of formula (I),

R¹¹-A¹¹(-Z¹¹-A¹²-)_p-X¹¹-Sp¹¹-X¹²-(A¹³-Z¹²-)_qA¹⁴-R¹²I

wherein the content of the first and second substances,

R¹¹denotes straight-chain or branched alkyl, in which one or more non-adjacent and non-terminal CH groups₂The radicals may, independently of one another in each occurrence, be substituted 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-are replaced by oxygen atoms which are not linked directly to one another,

R¹²denotes F, Cl, CN and NCS, or a linear or branched alkyl radical, which may be unsubstituted, mono-or polysubstituted by halogen or CN, wherein one or more are non-adjacent and non-terminalCH₂The radicals may, independently of one another in each occurrence, be substituted 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-are replaced by oxygen atoms which are not linked directly to one another,

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

more preferably F, CN or OCF₃，

A¹¹To represent

A¹²To A¹⁴Independently at each occurrence, is 1, 4-phenylene in which, in addition, one or more CH groups may be replaced by N; trans-1, 4-cyclohexylene, in which, in addition, one or two non-adjacent CH' s₂The groups may be replaced by O and/or S; 1, 4-cyclohexylene; naphthalene-2, 6-diyl; decahydro-naphthalene-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, in which one or more H atoms may be replaced by F or Cl,

preferably, in each occurrence, independently of one another, is 1, 4-phenylene in which, in addition, one or more CH groups may be replaced by N, or trans-1, 4-cyclohexylene in which, in addition, one or two non-adjacent CH groups₂The radicals may be replaced by O and/or S, and both cyclic groups 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 replaced by F or Cl,

Z²¹and Z²²Independently 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 of F, S and/or Si,

preferably a single bond,

p and q are each independently 0, 1,2,3 or 4, preferably 0, 1,2 or 3, and most preferably 1 or 2.

Sp¹¹Is a spacer group comprising 1,3 or 5 to 40C atoms, wherein one or more CH groups are not adjacent and are not terminal₂The radicals may also be substituted by-O-, -S-, -NH-, -N (CH)₃)-、-CO-、-O-CO-、-S-CO-、-O-COO-、-CO-S-、-CO-O-、-CF₂-、-CF₂O-、-OCF₂- - -C (OH) - -, - -CH (alkyl) - -, - -CH (alkenyl) - -, - -CH (alkoxy) - -, - -CH (oxaalkyl) - -, - -CH ═ CH- -or- -C.ident.C- -are replaced in such a way that no two O- -atoms are adjacent to one another and in such a way that 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- -, - -S- -CO- -, - -O- -and- -CH ≡ CH- -₂)_n-, where n is an integer of 1,3 or 5 to 15, more preferably 3 to 11, most preferably an odd integer (i.e., 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 at-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 not directly connected to each other, respectively.

If R is¹¹Or R¹²Is an alkyl or alkoxy group, it may be straight or branched. It is preferably straight-chain, having 2,3,4, 5,6, 7 or 8 carbon atoms, and is therefore preferably, for example, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy or octoxy, and furthermore methyl, nonyl, decyl, undecyl, dodecyl, and also,Dodecyl, tridecyl, tetradecyl, pentadecyl, nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy or tetradecyloxy.

If R is¹¹Or R¹²Is an alkenyl group, it may be straight-chain or branched. It is preferably straight-chain, having up to 15C atoms, and more preferably vinyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl and the corresponding isomers.

In the case of compounds having two nonpolar groups, R¹¹Or R¹²One of which is preferably an alkenyl or alkynyl group having up to 15 carbon atoms, preferably an alkenyl group, the other of which is preferably an alkyl, alkenyl or alkynyl group, most preferably an alkyl or alkenyl group having 2 to 15 carbon atoms, or an alkoxy group having 1 to 15, preferably 2 to 15 carbon atoms.

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

In the case of compounds having terminal polar groups, R¹²Selected from CN, NO₂Halogen, OCH₃、OCN、SCN、COR^x、COOR^xOr mono-, oligo-or polyfluorinated alkyl or alkoxy groups having 1 to 4C atoms. R^xIs an optionally fluorinated alkyl group having 1 to 4, preferably 1 to 3, C atoms. Halogen is preferably F or Cl.

Particularly preferably, R in the formula I¹²Selected from H, alkenyl, F, Cl, CN, NO₂、OCH₃、COCH₃、COC₂H₅、COOCH₃、COOC₂H₅、CF₃、C₂F₅、OCF₃、OCHF₂And OC₂F₅In particular vinyl, propenyl, butenyl, F, Cl, CN, CF₃、OCH₃And OCF₃Especially propenyl, butenyl, F, CN and OCF₃。

Preferred radicals-A comprising only 6-membered rings are listed below¹¹(-Z¹¹-A¹²-)_pOr the smaller group in MG-11. For the sake of simplicity, Phe in these radicals is 1, 4-phenylene and 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 7 carbon atoms, very preferably F, Cl, CN, OH, NO₂、CH₃、C₂H₅、OCH₃、OC₂H₅、COCH₃、COC₂H₅、COOCH₃、COOC₂H₅、CF₃、OCF₃、OCHF₂、OC₂F₅Especially F, Cl, CN, CH₃、C₂H₅、OCH₃、COCH₃And OCF₃Most preferred are F, Cl and CH₃、OCH₃And COCH₃And Cyc represents

This list includes the sub-formulas shown below,

wherein the content of the first and second substances,

cyc is

Preferably, it is

Phe is a1, 4-phenylene radical,

PheL is 1, 4-phenylene which is substituted by one, two or three fluorine atoms, by one or two Cl atoms or by one Cl atom and one F atom, and

z has the formula I¹¹And if present twice, at least one is preferably selected from the group consisting of-C.ident.C-, -C ═ C-, -COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O-、-OCF₂-or-CF₂O-。

Particular preference is given to the sub-formulae in which Z independently in each case has the Z given in formula I¹¹And if present twice, preferably one of Z is-COO-, -OCO-, -CH₂-O-、-O-CH₂-、-CF₂-O-or-O-CF₂-。

Preferably MG-11 is selected from subformulae which do not contain two groups Z, more preferably MG-11-2 to MG-11-13, more preferably MG-11-2 or MG-11-3.

Preferred- (A) s containing only 6-membered rings are listed below¹³-Z¹²-)_qA¹⁴-or the smaller of the MG-12 groups. For the sake of simplicity, Phe in these radicals is 1, 4-phenylene and 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 7 carbon atoms, very preferably F, Cl, CN, OH, NO₂、CH₃、C₂H₅、OCH₃、OC₂H₅、COCH₃、COC₂H₅、COOCH₃、COOC₂H₅、CF₃、OCF₃、OCHF₂、OC₂F₅Especially F, Cl, CN, CH₃、C₂H₅、OCH₃、COCH₃And OCF₃Most preferred are F, Cl and CH₃、OCH₃And COCH₃And CHex is 1, 4-cyclohexylene. This list includes the sub-formulas shown below,

wherein

CHex is 1, 4-cyclohexylene, preferably trans-1, 4-cyclohexylene,

phe is a1, 4-phenylene radical,

PheL is 1, 4-phenylene which is substituted by one, two or three fluorine atoms, by one or two Cl atoms or by one Cl atom and one F atom, and

z has the formula Z given in part formula II¹¹One of the meanings and if present twice, at least one is preferably selected from-C.ident.C-, -C ═ C-, -COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O-、-OCF₂-or-CF₂O-。

Particular preference is given to the sub-formulae in which Z independently in each case has the Z given in formula I¹¹And if present twice, preferably one of Z is-COO-, -OCO-, -CH₂-O-、-O-CH₂-、-CF₂-O-or-O-CF₂-。

In the preferred sub-formulae of MG-11 and MG-12 given above,

PheL preferably represents a radical

Radical (I)

Very preferably represents

And

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

Preferably MG-12 is selected from a subformula which does not contain two groups Z, more preferably from MG-12-1 to MG-12-38, even more preferably from MG-12-4 or MG-12-38, especially MG-12-9 to MG-12-12 or MG-12-32 to MG-12-38.

Particularly preferred are compounds of formula I wherein the corresponding mesogenic group pair MG-11 and MG-12 each comprise two or three six-atom rings, more preferably MG-11 and MG-12 each comprise two six-atom rings, or MG-11 comprises two six-atom rings and MG-12 comprises three six-atom rings, or MG-11 comprises three six-atom rings and MG-12 comprises two six-atom rings.

Further preferred are compounds of formula I, wherein

Sp¹¹Is represented by- (CH)₂)_n-, and

n is an integer of 1 to 15, wherein one or more-CH₂The group can be replaced by-CO-, preferably an odd number, more preferably 3,5, 7, 9, 11 or 13,

further preferred compounds of the formula I are those in which,

-X¹¹-Sp¹¹-X¹²is-Sp¹¹-、-Sp¹¹-O-、-Sp¹¹-CO-O-、-Sp¹¹-O-CO-、-CO-O-Sp¹¹、-O-CO-Sp¹¹、-O-Sp¹¹-、-O-Sp¹¹-CO-O-、-O-Sp¹¹-O-CO-、-O-CO-Sp¹¹-O-、-O-CO-Sp¹¹-O-CO-、-CO-O-Sp¹¹-O-or-CO-O-Sp¹¹-CO-O-, with the proviso that in-X³¹-Sp³-X³²No two O atoms of-are adjacent to each other, no two-CH ═ CH-groups are adjacent to each other and no two groups selected from-O-CO-, -S-CO-, -O-COO-, -CO-S-, -CO-O-, and-CH ═ CH-are adjacent to each other.

Further preferred compounds of formula I are selected from the following substructures,

wherein the content of the first and second substances,

l in each case independently of one another denotes F, Cl, CH₃、OCH₃And COCH₃Preferably, the amount of the compound represented by F,

r represents an integer from 0 to 4, preferably 0, 1 or 2,

R¹¹represents an alkyl or alkoxy group which may be linear or branched having 2,3,4, 5,6, 7 or 8 carbon atoms,

R¹²denotes CN, NO₂、F、OCH₃、OCN、SCN、COR^x、COOR^xOr mono-, oligo-or polyfluorinated alkyl or alkoxy having 1 to 4 carbon atoms,

R^xis an optionally fluorinated alkyl group having 1 to 4, preferably 1 to 3 carbon atoms, and

n represents 3,5, 7, 9, 11 or 13.

Further preferred compounds of formula I are selected from the following substructures,

R¹¹denotes alkyl, which may be straight-chain or branched having 2,3,4, 5,6, 7 or 8 carbon atoms, preferably straight-chain alkyl having 3,4 or 5 carbon atoms,

R¹²denotes CN, F, CF₃Or OCF₃Preferably CN or F, and

n represents 3,5, 7, 9, 11 or 13, preferably 7, 9 or 11.

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

In a preferred embodiment, the compounds of formula I and subformulae thereof may be synthesized according to or analogously to the following synthesis schemes 1 or 2:

synthesis scheme 1:

wherein L, R, R¹¹And R¹²Has one of the meanings given above, and n represents an integer from 0 to 12.

Synthesis scheme 2:

wherein L, R, R¹¹And R¹²Having one of the meanings given above, n represents an integer from 1 to 11.

For example, one of the main advantages of using compounds of formula I in liquid crystalline media for flexoelectric applications is the improvement of the switching speed in ULH (uniformly aligned helix) geometry, especially at temperatures below 35 ℃. Benefits are also observed in terms of phase range, in terms of increased isotropic to nematic clearing points, and in terms of reduced nematic to nematic twist bend transition temperatures below room temperature.

The invention therefore also relates to the use of the compounds of the formula I in liquid-crystalline media and to liquid-crystalline media comprising one or more compounds of the formula I themselves.

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

R²¹-A²¹-A²²-(CH₂)_a-A²³-A²⁴-R²²II

wherein the content of the first and second substances,

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 radicals may also be substituted independently of one another by-O-, -S-, -NH-, -N (CH) in each occurrence₃) -, -CO-, -COO-, -OCO-, -O-CO-O-, -S-CO-, -CO-S-, -CH ═ CH-, -CH ═ CF-, -CF ═ CF-or-C.ident.C-are replaced in such a way that oxygen atoms are not linked directly to one another, preferably F, Cl, CN, straight-chain or branched alkyl or alkoxy which may be unsubstituted, mono-or polysubstituted by halogen or CN,

more preferably F, CN or OCF₃，

A²¹To A²⁴Independently at each occurrence, represents aryl-, heteroaryl-, alicyclic-and heterocyclic radicals, preferably 1, 4-phenylene, in which, in addition, one or more CH groups may be replaced by N, 1, 4-bicyclo- (2,2,2) -octylene, naphthalene-2, 6-diyl, decahydro-naphthalene-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 in each occurrence independently of one another 1, 4-phenylene in which, in addition, one or more CH groups may be replaced by N, or trans-1, 4-cyclohexylene in which, in addition, one or two non-adjacent CH groups₂Where the radicals may be substituted by O and/or S, and both cyclic radicals may be unsubstituted or mono-, di-, tri-or tetrasubstituted by F, Cl, CN or alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl, where one or more H atoms may be replaced by F or Cl,

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

Preferred compounds of formula II are selected from the group (-A) thereof²¹-A²²-) and (-A)²³-A²⁴-) are each independently selected from the group consisting of,

wherein the content of the first and second substances,

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 7 carbon atoms, very preferably F, Cl, CN, OH, NO₂、CH₃、C₂H₅、OCH₃、OC₂H₅、COCH₃、COC₂H₅、COOCH₃、COOC₂H₅、CF₃、OCF₃、OCHF₂、OC₂F₅Especially F, Cl, CN, CH₃、C₂H₅、OCH₃、COCH₃And OCF₃Most preferred are F, Cl and CH₃、OCH₃And COCH₃And are and

cyc is 1, 4-cyclohexylene.

Preferred are those wherein the radical (R) in formula II²¹-A²¹-A²²-) and (-A)²³-A²⁴-R²²) The same or a mirror image of a compound of formula II.

Also preferred is a compound wherein (R) in formula II²¹-A²¹-A²²-) and (-A)²³-A²⁴-R²²) A different compound of formula II.

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, more preferably 3,5, 7, 9 or 11.

The compounds of the formula II can be synthesized according to or in analogy to methods known per se and described in standard works for organic chemistry, for example the methods described in Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag, Stuttgart. A preferred preparation process is obtainable from WO2013/004333A 1.

The use of compounds of the formula II in addition to compounds of the formula I in the mixtures according to the invention is particularly useful for further improving the switching speed while maintaining a good phase range and favorable e/K values.

In a preferred embodiment, the liquid-crystalline 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 independently of the other having the formula II for R²¹And R²²One of the meanings given is as follows,

A³¹to A³⁶Each independently of the other having the formula II for A²¹To A²⁴One of the meanings given is as follows,

Z³¹and Z³²Each occurrence independently is-COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O-、-CH₂CH₂-、-(CH₂)₄-、-CF₂CF₂-, -CH-, -CF-, -CH-COO-, -OCO-CH-or-C.ident.C-, which is optionally substituted by F, S and/or one or more of Si, preferably-COO-, -OCO-or-O-CO-O-, more preferably-COO-or-OCO-,

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

c represents 0 or 1, preferably 0.

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

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

wherein

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

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

Particularly preferred compounds of formula III are selected from compounds of the formula,

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

In the mixtures according to the invention, the further use of compounds of the formula III in addition to compounds of the formula I is particularly useful for achieving high stability, advantageously high clearing points and a broad phase range and low occurrence of nematic twist-bend phases.

In a further preferred embodiment, the liquid-crystalline 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 independently of the other having the formula II above for R²¹One of the meanings given is as follows,

A⁴¹to A⁴⁴Each independently of the others having the formula II above for A²¹One of the meanings given is as follows,

Z⁴¹and Z⁴²Each occurrence independently is-COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O-、-CH₂CH₂-、-(CH₂)₄-、-CF₂CF₂-, -CH ═ CH-, -CF ═ CF-, -CH ═ CH-COO-, -OCO-CH ═ CH-or-C ≡ C-, which is optionally substituted by one or more of F, S and/or Si, 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 independently selected from the group of MG1 to MG4 as given above.

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

symmetrical formulae (IVa and IVb):

asymmetric formula (IVc):

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

In the mixtures according to the invention, the further use of compounds of the formula IV in addition to compounds of the formula I is particularly useful for reducing the nematic twist-bend phase while maintaining favorable e/K values.

In a further preferred embodiment, the liquid-crystalline medium according to the invention also comprises one or more compounds of the formula V,

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

wherein

R⁵¹And R⁵²Each independently of the other having the formula II above for R²¹One of the meanings given is as follows,

A⁵¹to A⁵³Each independently of the other having the formula II above for A²¹One of the meanings given is as follows,

Z⁵¹and Z⁵²Each occurrence independently is-COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O-、-CH₂CH₂-、-(CH₂)₄-、-CF₂CF₂-, -CH ═ CH-, -CF ═ CF-, -CH ═ CH-COO-, -OCO-CH ═ CH-or-C ≡ C-, which is optionally substituted by one or more of F, S and/or Si, 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 preferred is a compound wherein A⁵¹A compound of formula V selected from the mirror images of formulae Va 'to Vf' and formulae Vd 'and Ve' below:

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 OCF₃Particularly H, F, CN and OCF₃。

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

wherein the content of the first and second substances,

LG⁵¹is Z⁵¹-(CH₂)_Z-Z⁵²，

(F)₀Represents H, and

(F)₁represents F.

And 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-O-CO- (CH) is more preferable₂)_n-CO-O-, wherein n represents 3,5, 7 or 9,

particularly preferred compounds of formula VA are selected from the group consisting 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 compounds of formulae VB-1 to VB-3,

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

Very particular preference is given to compounds of the formula VC. And these particularly preferred compounds are selected from the group consisting of compounds of the formulae VC-1 to VC-3,

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

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

In a further preferred embodiment, the liquid-crystalline 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 the content of the first and second substances,

R⁶¹and R⁶²Each independently of the other having the formula II above for R²¹One of the meanings given is as follows,

A⁶¹to A⁶⁴Each independently of the other having the formula II above for A²¹One of the meanings given is as follows,

Z⁶¹represents-O-, -COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O、-CH₂CH₂-、-(CH₂)₄-、-CF₂CF₂-, -CH-, -CF-, -CH-COO-, -OCO-CH- ═ CH-or-C.ident.C-, which is optionally substituted by F, S and/or one or more of Si, 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, more preferably 3,5, 7 or 9.

Preferred compounds of formula VI are selected from the group (-A) thereof⁶¹-A⁶²-) and (-A)⁶³-A⁶⁴-) are each independently selected from the group of MG1 to MG4 as given above.

Further preferred are those of formula VI wherein h represents 0 and a group (-A)⁶¹-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.

Particularly preferred compounds of formula VI are selected from the group consisting of compounds of the formula,

the compounds of the formula VI can be synthesized according to or in analogy to methods known per se and described in standard works for organic chemistry, for example the methods described in Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag, Stuttgart. Preferably, the compound of formula VI is synthesized according to or in a manner analogous to the method disclosed in, for example, WO2014/005672a 1.

The use of compounds of the formula VI in addition to compounds of the formula I in the mixtures according to the invention is particularly useful for obtaining high clearing points and favorable e/K values.

In a further preferred embodiment, the liquid-crystalline medium according to the invention also 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 independently of the other having the formula II above for R²¹One of the meanings given is as follows,

A⁷¹to A⁷⁶Each independently of the other having the formula II above for A²¹One 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 is optionally substituted by one or more of F, S and/or Si, or a single bond, preferably-COO-, -OCO-, -O-CO-O-, -OCF₂-、-CF₂O-or a single bond, more preferably-COO-, -OCO-, -OCF₂-、-CF₂O-or a single bond,

provided that Z is⁷¹To Z⁷⁴At least one of which is not a single bond,

j represents an integer from 1 to 15, preferably an odd (i.e., non-even) integer, 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 consisting of⁷¹-Z⁷¹-A⁷²-(Z⁷²-A⁷³)_i-、-(A⁷⁴-Z⁷³-)_k-A⁷⁵-Z⁷⁴-A⁷⁶-at least one compound selected from the group consisting of MGa to MGn groups and their mirror images,

wherein the content of the first and second substances,

wherein L is, independently of one another, preferably F, Cl, CN or an optionally fluorinated alkyl, alkoxy or alkanoyl radical having 1 to 7 carbon atoms, very preferably F, Cl, CN, CH₃、C₂H₅、OCH₃、OC₂H₅、COCH₃、COC₂H₅、COOCH₃、COOC₂H₅、CF₃、OCF₃、OCHF₂、OC₂F₅Especially 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.

In these preferred formulae, the radical

Is very preferably represented by

And

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

Further 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 mirrored, with the proviso that Z⁷¹To Z⁷⁴Is not a single bond.

Further 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 compounds of the formula,

wherein R is⁷¹And R⁷²Each independently represents F or CN.

The compounds of the formula VII can be synthesized according to or in analogy to methods known per se and described in standard works of organic chemistry, for example the methods described in Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag, Stuttgart. Preferably, the compound of formula VII is synthesized according to or similar to the methods disclosed in, for example, WO2013/174478a 1.

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

Chiral compound induction with pitch (P)₀) The pitch is inversely proportional to the concentration (c) of the chiral material used in the first approximation. The proportionality constant of this correlation is called the Helical Twisting Power (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, a uniform horizontal helical texture is achieved using chiral nematic liquid crystals having a short pitch, typically in the range of 0.2 μm to 1 μm, preferably 1.0 μm or less, in particular 0.5 μm or less, which are unidirectionally aligned with their helical axes in the liquid crystal cell parallel to the substrates (e.g. glass plates). 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 those disclosed in WO 98/00428.

Chiral dopants which are customarily used are, for example, the 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 XI,

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 GB2,328,207.

The chiral dopants R/S-5011 and the compounds of formulae VIII and IX described above exhibit very high Helical Twisting Power (HTP) and are therefore particularly useful 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 abovementioned formulae VIII and/or formula IX and/or R-5011 or S-5011, very preferably the chiral compounds are R-5011, 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, of the total mixture.

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

wherein the content of the first and second substances,

R^2Arepresents H, alkyl or alkoxy having 1 to 15 carbon atoms, where, in addition, one or more CH groups in these radicals₂The radicals may each, independently of one another, be-C.ident.C-, -CF₂O-、-CH＝CH-、

-O-, -CO-O-or-O-CO-being replaced in such a way that the O atoms are not directly linked to one another, and wherein, 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_vH₂₊₁And are and

v represents 1 to 6.

The liquid-crystalline medium may contain further additives, such as stabilizers, inhibitors, surface-active compounds, lubricants, wetting agents, dispersants, hydrophobicizing agents, binders, flow improvers, defoamers, deaerators, diluents, reactive diluents, adjuvants, colorants, dyes, pigments or nanoparticles, in customary concentrations. The total concentration of these other ingredients 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.

The concentrations of these and similar additives are not taken into account in respect of the concentration values and ranges of the liquid-crystalline components and compounds of the liquid-crystalline medium in the present application. This also applies to the concentration of dichroic dye used in the mixture, which is not counted when specifying the concentration of the components or compounds of the host medium. The concentration of each additive is always given relative to the final doped mixture.

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

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

The media according to the invention exhibit a high elastic constant k₁₁Value and high flexoelectric coefficient e. The liquid-crystalline medium preferably exhibits k₁₁100pN or less, preferably 20pN or less.

The liquid-crystalline medium preferably exhibits k₃₃Less than or equal to 100pN, preferably less than or equal to 15 pN.

Excellent liquid crystal mediumSelecting the bending electric coefficient | e₁₁L is 0.2pC/m or more, preferably 1pC/m or more.

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 voltage of from 1 to 10V^-1In the range of preferably 1 to 7V^-1In the range of 1 to 5V is more preferable^-1A flexibility-elasticity ratio (z/K) in the range.

The media according to the invention exhibit high clearing points of up to 60 ℃ and higher, preferably up to 65 ℃ and higher and more preferably up to 70 ℃ and higher.

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

The media according to the invention exhibit an N of 20 ℃ or less, preferably 15 ℃ or less and preferably 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 100h, preferably more than 250h or more than 1000 h.

The media according to the invention exhibit a high stability against crystallization even at Low Temperatures (LTS). Thus, 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 liquid-crystalline medium comprises:

1 to 10, preferably 1 to 5, more preferably 1 or 3, most preferably 1 or 2 compounds of formula I. The amount of the compounds of the formula I in the entire liquid-crystalline medium is preferably from 5 to 50% by weight, in particular from 6 to 30% by weight, in particular from 7 to 20% by weight,

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 formula II (-A)²¹-A²²-) and (-A)²³-A²⁴-) are the same or mirror images of compounds of formula II, more preferably compounds of formula II 'a-5 and/or II' a-6. The amount of compound of formula II (if present) in the liquid-crystalline medium is preferably from 0 to 30% by weight, more preferably from 1% by weight to 20% by weight, based on the total mixtureWt%, even more preferably from 2 wt% to 10 wt%,

and/or

Optionally 1 to 10, preferably 1 to 5, more preferably 1 or 3, most preferably 1 or 2 compounds of formula III, preferably selected from the above symmetrical compounds of formula IIIc-2 and/or IIIc-3. The amount of compound of formula III (if present) in the liquid-crystalline medium is preferably from 1 to 50% by weight, more preferably from 5% to 30% by weight, even more preferably 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 of formula IVb and/or asymmetrical IVc, more preferably selected from IVb-5, IVc-2, IVc-3, IVc-12 and or IVc-15. The amount of compound of formula IV (if present) in the liquid-crystalline medium is preferably from 1 to 98% by weight, more preferably from 20% to 98% by weight, even more preferably 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, preferably selected from the above formulae VA-1, VC-2 and/or VC-3. The amount of compound of formula V (if present) in the liquid-crystalline medium is preferably from 1 to 70% by weight, more preferably from 10% to 60% by weight, even more preferably 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 selected from compounds of formula VI-4, VI-5, VI-7 and/or VI-8. The amount of compound of formula VI (if present) in the liquid-crystalline medium is preferably from 1 to 40% by weight, more preferably from 5% to 25% by weight, even more preferably from 10% to 15% by weight,

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 selected from compounds of formula VII-4, VII-5 and/or VII-8. The amount of the compound of the formula VII, if present, in the liquid-crystalline medium is preferably from 1 to 35% by weight, in particular from 5% to 25% by weight and very preferably from 10% to 15% by weight, based on the total mixture,

and/or

Optionally, 1 to 5, in particular 1 to 3, very preferably 1 or 2 chiral dopants, 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 (if present) 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, of the total mixture,

and/or

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

and/or

Optionally, other additives present in usual concentrations, such as stabilizers, antioxidants, etc. These other ingredients, if present, are present in a total concentration of 0.1 to 10%, preferably 0.1 to 6%, based on the total mixture. The concentrations of the individual compounds used are each preferably from 0.1 to 3%.

In another preferred embodiment, the liquid-crystalline medium of the invention consists exclusively of compounds selected from the formulae I to X, very preferably the liquid-crystalline medium consists exclusively of compounds selected from the formulae I to IX.

In another preferred embodiment, the liquid-crystalline medium of the invention consists exclusively of compounds selected from the formulae I to X, wherein none of the compounds contains a CN group. It is well known that cyanide-containing materials have problems when considering active driving. This is due to the reduced VHR (voltage holding ratio) and other reliability related parameters like image sticking. Another advantage of materials without cyano groups is that they are generally less toxic and more environmentally friendly. This makes the synthesis and subsequent transport of materials without cyano groups more attractive than materials containing cyano groups.

The compounds forming the liquid-crystalline medium according to the 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 process for the preparation of a liquid-crystalline medium as set forth above and below.

In particular, the present invention relates to a process for the preparation of a liquid-crystalline medium comprising the step of mixing one or more compounds of formula I with at least one compound selected from the group consisting of the compounds of formulae II to X.

The liquid-crystalline media according to the invention can be used in electro-optical devices, for example 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, for active and passive optical components such as polarizers, compensators, reflectors, alignment layers, color filters or holographic components, for adhesives, synthetic resins with anisotropic mechanical properties, cosmetics, diagnostic devices, liquid-crystal pigments, for decorative and security applications, for nonlinear optics, optical information storage or as chiral dopants. Thus, a further aspect of the present invention is the use of a liquid-crystalline medium comprising at least one compound of the formula I in an electro-optical device.

Since the medium according to the invention is particularly useful for flexo liquid crystal display applications, such as devices in ULH or USH mode.

Accordingly, a further object of the present invention is a liquid crystal device, preferably a flexoelectric device, comprising a medium comprising one or more compounds of formula I.

A flexoelectric display according to a preferred embodiment of the invention comprises two planar parallel substrates, preferably glass plates, covered on their inner surfaces with a transparent conducting layer, for example Indium Tin Oxide (ITO), an optional alignment layer and a medium comprising one or more compounds of formula 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 by reversal of the electric field, the optical axis is rotated by 45 °, and by appropriate selection of the relative orientations of the axis of the helix, the preferred direction of the absorption axis of the polarizer, and the direction of the electric field, the optical axis can be switched from parallel to one polarizer to the central angle between the two polarizers. 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＝e P₀E/(2πK)

wherein

P₀Is the undisturbed pitch of the cholesteric liquid crystal,

the yam is the splay-bend electrical coefficient (e)₁₁) And bending modulus (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 the 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 ℃ C.) typically in the range of 1ms to 10ms_on+T_off) Preference is given to<5ms, and even more preferably<3 ms. It is further characterized by excellent 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/(ε_0·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 according to the invention can be aligned with their cholesteric phase into different orientation 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 "in-plane 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. In-plane 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 alignment quality thereof 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. The flexoelectric switching of the material of the invention is described in further detail in the above introduction and in the examples.

Starting also from a focal conic texture, ULH texture can be 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 curved electrical 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 in degrees Celsius without modification, and all parts and percentages are by weight, unless otherwise indicated.

It is obvious to the person skilled in the art that the liquid-crystalline 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_TBSecond alignment type; s or Sm is smectic; ch ═ cholesteric; i is isotropic; tg ═ glass transition. The numbers between the symbols represent the phase transition temperature in c.

In the present application and in particular in the following examples, the structure of the liquid-crystalline compounds is indicated by abbreviations also referred to as "acronyms". 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_IH_2I+1Preferably a linear alkyl radical having n, m and I C atoms, respectively, all radicals C_nH_2n、C_mH_2mAnd C_IH_2IPreferably (CH) respectively₂)_n、(CH₂)_mAnd (CH)₂)_Iand-CH ═ CH-is preferably trans-or E-ethenylene. Preferably, n, m and I represent an integer 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-hand and right-hand terminal groups of the molecules.

Table a: ring element

Table B: linking group

Table C: terminal group

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

Examples

Test cartridge and method

Typically, 3 μm thick cells with antiparallel rubbed PI alignment layers on their mutually opposite substrates are filled on a hot plate at a temperature at which the flexoelectric mixture is in the isotropic phase.

After the cartridge has been filled, the phase transitions (including clearing points and crystallization behavior) are determined using Differential Scanning Calorimetry (DSC) and verified by optical inspection. For optical phase transition measurements, a mettler FP90 hot stage controller connected to an 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 recorded.

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.

Unless otherwise specifically noted, to measure the flexoelectric response of a material, the change in the tilt dimension of the optical axis was measured as a function of the voltage rising at a temperature of 35 ℃. This is achieved by using the following equation:

wherein

Is the tilt angle 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 K₃Average value of) and e is the flexoelectric coefficient (where e is 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 to achieve a typical cholesteric pitch of 350 to 275 nm.

Examples of mixtures

Host mixture H-1

The following mixture H1 was prepared

Compound (I)	% amount-w/w
		N-PP-ZI-9-Z-GP-F	9.52
F-PGI-ZI-7-Z-PP-N	9.52
		F-PGI-ZI-9-Z-PU-N	6.60
F-PGI-ZI-7-Z-PUU-N	10.25
		N-UIUI-9-UU-N	5.86
N-GIGI-9-GG-N	2.92
		N-PGI-ZI-9-Z-GU-F	8.78
N-GI-ZI-9-Z-G-N	7.33
		F-PGI-ZI-9-Z-G-N	3.32
N-PP-ZI-9-Z-G-N	3.32
		F-PGI-ZI-9-Z-P-N	3.32
F-PGI-ZI-9-PUU-N	12.46
		CY-3-O2	2.33
CCY-3-O1	1.17
		CCY-3-O2	1.17
CPY-2-O2	1.46
		CPY-3-O2	1.46
CLY-3-O2	1.17
		Y-4O-O4	1.75
CPTP-3-OD	1.17
		CZY-3-O2	1.46
CZY-5-O2	1.46
		R-5011	2.20

Experiment 1

C.1.1 mixture example M-1

15% w/w of compound 3-LPP-7-GG-F was added to 85% w/w of the host mixture H-1.

The resulting mixture was homogenized and filled into test cartridges as described above. Carrying out a handover performance, T_NI(clearing Point), e/K (flexural elastic constant) and N_TB(transition temperature to second nematic phase or nematic twisted-bend phase)The results are summarized in the table below.

Composition comprising a metal oxide and a metal oxide	M-1
		Ton+Toff(at 35 ℃ C.)	4.07ms
e/K (at 35 ℃ C.)	3.02V-1
		TNI	76℃
NTB	10℃

Experiment 2

C.2.1 mixture example M-2

15% w/w of compound 5-LP-9-Z-GP-N was added to 85% w/w of the host mixture H-1.

The resulting mixture was homogenized and filled into test cartridges as described above. With respect to switching performance, clearing point, flexural modulus and N_TBThe results of the transition temperature measurements are summarized in the following table.

Composition comprising a metal oxide and a metal oxide	M-2
		Ton+Toff(at 35 ℃ C.)	3.76ms
e/K (at 35 ℃ C.)	3.12V-1
		TNI	75.2℃
NTB	9.5℃

Experiment 3

C.3.1 mixture example M-3

15% w/w of compound 5-LP-9-Z-PGG-F was added to 85% w/w of the host mixture H-1.

The resulting mixture was homogenized and filled into test cartridges as described above. With respect to switching performance, clearing point, flexural modulus and N_TBThe results of the transition temperature measurements are summarized in the following table under c.3.3.

C.3.2 comparative mixture example CM-3

15% w/w of compound F-GIGI-9-Z-PGG-F was added to 85% w/w of the host mixture H-1.

The resulting mixture was homogenized and filled into test cartridges as described above. With respect to switching performance, clearing point, flexural modulus and N_TBThe results of the transition temperature measurements are summarized in the table under c.3.3.

C.3.3 summary

Composition comprising a metal oxide and a metal oxide	M-3	CM-3
			Ton+Toff(at 35 ℃ C.)	3.87ms	4.12ms
e/K (at 35 ℃ C.)	3.12V-1	3.05V-1
			TNI	79.9℃	74.6℃
NTB	8.5℃	-1.0℃

From the measurement results given above, it is clear that the material M-3 shows an advantage in switching speed compared to the material CM-3. At the same time, the phase range is kept at an acceptable level. Furthermore, it is particularly surprising that T of the mixture M-3_NIT significantly higher than that of the mixture CM-3_NI。

Experiment 4

C.4.1 mixture example M-4

15% w/w of compound 5-LP-7-Z-PGU-F was added to 85% w/w of the host mixture H-1.

The resulting mixture was homogenized and filled into test cartridges as described above. With respect to switching performance, clearing point, flexural modulus and N_TBThe results of the transition temperature measurements are summarized in the following table under c.4.3.

C.4.2 comparative mixture example CM-4

15% w/w of compound F-GIGI-7-Z-PGU-F was added to 85% w/w of the host mixture H-1.

The resulting mixture was homogenized and filled into test cartridges as described above. With respect to switching performance, clearing point, flexural modulus and N_TBThe results of the transition temperature measurements are summarized in the table under c.4.3.

C.4.3 summary

Composition comprising a metal oxide and a metal oxide	M-4	CM-4
			Ton+Toff(at 35 ℃ C.)	3.35ms	3.87ms
e/K (at 35 ℃ C.)	3.11V-1	3.25V-1
			TNI	76.3℃	70.4℃
NTB	7.0℃	-10.0℃

From the measurements given above, it is clear that material M-4 is in comparison with material CM-4An advantage is shown in terms of switching speed. At the same time, the flexural elastic constant and the phase range are kept at acceptable levels. Furthermore, it is particularly surprising that T of the mixture M-4_NIT significantly higher than that of the mixture CM-4_NI。

Claims (19)

1. A compound of formula I

R¹¹-A¹¹(-Z¹¹-A¹²-)_p-X¹¹-Sp¹¹-X¹²-(A¹³-Z¹²-)_qA¹⁴-R¹²I

Wherein the content of the first and second substances,

R¹¹denotes straight-chain or branched alkyl, in which one or more non-adjacent and non-terminal CH groups₂The radicals may, independently of one another in each occurrence, be substituted 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-are replaced by oxygen atoms which are not linked directly to one another,

R¹²denotes F, Cl, CN, NCS, or a linear or branched alkyl radical, which may be unsubstituted, mono-or polysubstituted by halogen or CN, and CH in which one or more are non-adjacent and non-terminal₂The radicals may, independently of one another in each occurrence, be substituted 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-are replaced by oxygen atoms which are not linked directly to one another,

A¹¹to represent

A¹²To A¹⁴Independently at each occurrence, is 1, 4-phenylene in which, in addition, one or more CH groups may be replaced by N; trans-1, 4-cyclohexylene, in which, in addition, one or two non-adjacent CH' s₂The groups may be replaced by O and/or S; 1, 4-cyclohexylene, naphthalene-2, 6-diyl, decahydro-naphthalene-2, 6-diyl, 1,2,3, 4-tetrahydro-naphthalene-2, 6-A diradical, all of which may be unsubstituted, mono-, di-, tri-or tetra-substituted by F, Cl, CN or alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl, in which one or more H atoms may be replaced by F or Cl,

Z¹¹and Z¹²Independently 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 of F, S and/or Si,

p and q are each independently 0, 1,2,3 or 4,

Sp¹¹is a spacer group comprising 1,3 or 5 to 40C atoms, wherein one or more CH groups are not adjacent and are not terminal₂The radicals may also be substituted by-O-, -S-, -NH-, -N (CH)₃)-、-CO-、-O-CO-、-S-CO-、-O-COO-、-CO-S-、-CO-O-、-CF₂-、-CF₂O-、-OCF₂- - -C (OH) - -, - -CH (alkyl) - -, - -CH (alkenyl) - -, - -CH (alkoxy) - -, - -CH (oxaalkyl) - -, - -CH ═ CH- -or- -C.ident.C- -instead in such a way that no two O- -atoms are adjacent to one another and in such a way that 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, and

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 at-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 not directly connected to each other, respectively.

2. The compound according to claim 1, characterized in that the group-A¹¹(-Z¹¹-A¹²-)_p-a formula selected from the group consisting of,

wherein the content of the first and second substances,

cyc is

Phe is a1, 4-phenylene radical,

PheL is 1, 4-phenylene which is substituted by one, two or three fluorine atoms, by one or two Cl atoms or by one Cl atom and one F atom, and

z has the formula I¹¹And if present twice, at least one is selected from-C ≡ C-, -C ═ C-, -COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O-、-OCF₂-or-CF₂O-。

3. A compound according to claim 1 or 2, characterized in that the group- (a)¹³-Z¹²-)_qA¹⁴-a formula selected from the group consisting of,

wherein the content of the first and second substances,

CHex is 1, 4-cyclohexylene, Phe is 1, 4-phenylene,

PheL is 1, 4-phenylene which is substituted by one, two or three fluorine atoms, by one or two Cl atoms or by one Cl atom and one F atom, and

z has the formula Z given in part formula II¹¹One of the meanings and, if present twice, at least one is selected from the group consisting of-C.ident.C-, -C ═ C-, -COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O-、-OCF₂-or-CF₂O-。

4. A compound according to one or more of claims 1-3, characterized in that Sp¹¹Is represented by- (CH)₂)_n-, and n is an integer of 1 to 15, where one or more-CH₂The-group may be replaced by-CO-.

5. Compound according to one or more of claims 1 to 4, characterized in that,

-X¹¹-Sp¹¹-X¹²-represents-Sp¹¹-、-Sp¹¹-O-、-Sp¹¹-CO-O-、-Sp¹¹-O-CO-、-CO-O-Sp¹¹、-O-CO-Sp¹¹、-O-Sp¹¹-、-O-Sp¹¹-CO-O-、-O-Sp¹¹-O-CO-、-O-CO-Sp¹¹-O-、-O-CO-Sp¹¹-O-CO-、-CO-O-Sp¹¹-O-or-CO-O-Sp¹¹-CO-O-, with the proviso that in-X¹¹-Sp¹¹-X¹²No two O atoms of-are adjacent to each other, no two-CH ═ CH-groups are adjacent to each other and no two groups selected from-O-CO-, -S-CO-, -O-COO-, -CO-S-, -CO-O-, and-CH ═ CH-are adjacent to each other.

6. Use of a compound of formula I for liquid-crystalline media.

7. Liquid-crystalline medium comprising one or more compounds of the formula I.

8. A liquid-crystalline medium according to claim 7, comprising one or more compounds of the formula II,

R²¹-A²¹-A²²-(CH₂)_a-A²³-A²⁴-R²²II

wherein the content of the first and second substances,

R²¹and R²²Independently of one another, H, F, Cl, CN, NCS or a linear or branched alkyl radical, which may be unsubstituted, mono-or polysubstituted by halogen or CN, one or more non-adjacent CH₂The radicals may also be substituted independently of one another by-O-, -S-, -NH-, -N (CH) in each occurrence₃) -, -CO-, -COO-, -OCO-, -O-CO-O-, -S-CO-, -CO-S-, -CH ═ CH-, -CH ═ CF-, -CF ═ CF-or-C.ident.C-are replaced in such a way that the oxygen atoms are not directly linked to one another,

A²¹to A²⁴Independently at each occurrence, represent aryl-, heteroaryl-, alicyclic-and heterocyclic groups, and

a represents an integer of 1 to 15.

9. A liquid-crystalline medium according to claim 7 or 8, comprising one or more compounds of the formula III,

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

wherein the content of the first and second substances,

R³¹and R³²Independently of one another, have the formula II for R²¹The meaning given is that of the compounds,

A³¹to A³⁶Independently of one another have the formula II for A²¹The meaning given is that of the compounds,

Z³¹and Z³²Independently of one another in each occurrence-COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O-、-CH₂CH₂-、-(CH₂)₄-、-CF₂CF₂-、-CH＝CH-、-CF＝CF-、-CH-COO-, -OCO-CH-or-C ≡ C-, optionally substituted with one or more of F, S and/or Si,

c represents an integer of 1 to 15, and

a represents 0 or 1.

10. Liquid-crystalline medium according to one or more of claims 7 to 9, comprising one or more compounds of the formula IV,

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

wherein the content of the first and second substances,

R⁴¹and R⁴²Independently of one another, have the formula II above for R²¹One of the meanings given is as follows,

A⁴¹to A⁴⁴Independently of one another have the meanings given above for A in formula II²¹One of the meanings given is as follows,

Z⁴¹and Z⁴²Independently of one another in each occurrence-COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O-、-CH₂CH₂-、-(CH₂)₄-、-CF₂CF₂-, -CH-, -CF-, -CH-COO-, -OCO-CH-or-C.ident.C-, which is optionally substituted by one or more of F, S and/or Si,

d represents an integer of 1 to 15.

11. Liquid-crystalline medium according to one or more of claims 7 to 10, comprising one or more compounds of the formula V,

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

wherein the content of the first and second substances,

R⁵¹and R⁵²Independently of one another, have the abovementioned formula II for R²¹One of the meanings given is as follows,

A⁵¹to A⁵³Independently of one another, have the abovementioned formulae II for A²¹One of the meanings given is as follows,

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

f represents a number of 0 or 1,

e represents an integer of 1 to 15.

12. The liquid-crystalline medium according to one or more of claims 7 to 11, comprising one or more compounds of the formula VI,

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

wherein the content of the first and second substances,

R⁶¹and R⁶²Independently of one another, have the abovementioned formula II for R²¹And R²²One of the meanings given is as follows,

A⁶¹to A⁶⁴Independently of one another, have the abovementioned formulae II for A²¹One of the meanings given is as follows,

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

h represents 0 or 1, and

g represents an integer of 1 to 15.

13. The liquid-crystalline medium according to one or more of claims 7 to 12, comprising one or more compounds of the formula VII,

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

wherein the content of the first and second substances,

R⁷¹and R⁷²Independently of one another, have the abovementioned formula II for R²¹One of the meanings given is as follows,

A⁷¹to A⁷⁶Independently of one another, have the abovementioned formulae II for A²¹One of the meanings given is as follows,

Z⁷¹to Z⁷⁴Independently of one another represent-COO-, -OCO-, -O-CO-O-, -OCH₂-、-CH₂O-、-OCF₂-、-CF₂O-、-CH₂CH₂-、-(CH₂)₄-、-CF₂CF₂-, -CH-, -CF-, -CH-COO-, -OCO-CH-or-C.ident.C-, which is optionally substituted by one or more of F, S and/or Si, or 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.

14. Liquid-crystalline medium according to one or more of claims 7 to 13, comprising one or more chiral dopants.

15. The liquid-crystalline medium according to one or more of claims 7 to 14, comprising one or more nematic liquid-crystalline compounds selected from the group consisting of the compounds of the formulae X-1 to X-4,

wherein the content of the first and second substances,

R^2Arepresents H, alkyl, alkenyl or alkoxy having 1 to 15 carbon atoms, wherein, in addition, one or more CH's in these radicals₂The radicals may each, independently of one another, be-C.ident.C-, -CF₂O-、-CH＝CH-、

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

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

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_vH₂₊₁And are and

v represents 1 to 6.

16. Process for the preparation of a liquid-crystalline medium according to one or more of claims 7 to 15, comprising the step of mixing one or more compounds of the formula I with at least one compound selected from the group consisting of the compounds of the formulae II to X.

17. Use of a liquid-crystalline medium according to one or more of claims 7 to 15 for electro-optical devices.

18. Electro-optical device comprising a medium according to one or more of claims 7-15.

19. An electro-optic device as claimed in claim 18 characterised in that it is an electro-optic bender.