Ferroelectric polymer network liquid crystal with vertical alignment

Abstract

A polymer network stabilised liquid crystal material (PN-LCs) having a ferroelectric liquid crystal phase is presented. Claimed is a process of aligning liquid crystal mixtures exhibiting a ferroelectric nematic or ferroelectric smectic A liquid-crystalline phase in a polar vertical state in relation to a boundary surface. The liquid crystal mixture is stabilized by a polymer network in a vertical alignment relative to the substrate planes enclosing the mixtures. In addition, the present invention relates to electric and electronic elements which contain the poled and aligned ferroelectric liquid crystal material according to the invention.

Description

[0001] Ferroelectric polymer network liquid crystal with vertical alignment

[0002] This disclosure deals with polymer network stabilised liquid crystal materials (PN-LCs) having a ferroelectric liquid crystal phase. Claimed is a process of aligning liquid crystal mixtures exhibiting a ferroelectric nematic or ferroelectric smectic A liquid-crystalline phase in a polar vertical state in relation to a boundary surface. The liquid crystal mixture is stabilized by a polymer network in a vertical alignment relative to the substrate planes enclosing the mixtures. In addition, the present invention relates to electric and electronic elements which contain the poled and aligned ferroelectric liquid crystal material according to the invention.

[0003] Background

[0004] Energy harvesting is becoming more important in various situations, such as wearable devices. See Xu, C., Song, Y., Han, M. et al., Portable and wearable self-powered systems based on emerging energy harvesting

[0005] technology, Microsyst Nanoeng 7, 25 (2021), (https: / / doi.org / 10.1038 / s41378-021-00248-z) for an overview of technologies. Further, see Mishra,

[0006] S., Unnikrishnan, L., Nayak, S. K., Mohanty, S., Macromol. Mater. Eng. 2018, 1800463, (https: / / doi.org / 10.1002 / mame.201800463) for an overview of current technologies using piezoelectric polymer composites in comparison to conventional solid state piezo-ceramics. Utilising the properties of some ferroelectric materials such as piezoelectricity is a recognized method to achieve energy harvesting and these properties can also be used for mechanical sensors and sound generation. Piezoelectricity is exhibited by some non-centrosymmetric crystal structures and poled polymers. However suitable materials are limited. In previous years, the areas of application for liquid crystal compounds have been considerably expanded to various types of display devices, electro-optical devices, electronic components, sensors, etc. For this reason, a number of different structures have been proposed, in particular in the area of nematic liquid crystals. The nematic liquid-crystal mixtures have to date found the broadest use in flat-panel display devices. They have been employed, in particular, in passive TN or STN matrix displays or systems having a TFT active matrix, including the well-known TN, IPS, FFS and VA systems.

[0007] Most of these devices employ the nematic liquid crystal phase, including all common LCD television sets, LCD desktop monitors and mobile LCD devices. Some alternative liquid-crystalline phases are known, like ferroelectric smectic C phases or blue phases. However, a ferroelectric nematic phase (NF-LC phase) had been postulated by theory for decades only, without finding a suitable liquidcrystalline material with such property. Only recently, a few chemical structures have been reported to show ferroelectric nematic behaviour at certain temperatures.

[0008] Firstly, Hiroya Nishikawa, Kazuya Shiroshita, Hiroki Higuchi, Yasushi Okumura, Yasuhiro Haseba, Shin-ichi Yamamoto, Koki Sago, and Hirotsugu Kikuchi, Adv. Mater. (2017), 29, 1702354, describe a compound of formula A to have a ferroelectric nematic behaviour at temperatures between about 45°C to 68°C.

[0009]

[0010] Further, Nerea Sebastian, Luka Cmok, Richard J. Mandle, Maria Rosario de la Fuente, Irena Drevensek Olenik, Martin Copic and Alenka Mertelj, Physical Review Letters (2020), 124, 037801, describe a compound of formula B with similar behaviour between about 120°C to 133°C.

[0011]

[0012] O-CH3

[0013] Further comparison of the two only available substances for NF-LC phases is presented by Xi Chen et al., PNAS (June 23, 2020), 117 (25) 14021-14031. The high significance of the advent of the new NF-LC phase underlines O. D.

[0014] Lavrentovich, ProcNatAcadSciUSA (2020), 117(26), 14629-14631. Very high values of the dielectric susceptibility of these substances and some structural variations thereof is reported in the publication Li et al., Sci. Adv. 2021, 7.

[0015] A further ferroelectric nematic substance of formula C is published by Atsutaka Manabe, Matthias Bremer, Martin Kraska (2021): Ferroelectric phase at and below room temperature, Liquid Crystals, 48, 1079-1086 (DOI 10.1080 / 02678292.2021.1921867), which is described to have a ferroelectric nematic liquid-crystalline phase (NF-LC phase) close to ambient temperature. Ambient temperature, also sometimes called room temperature, means in a narrower sense a temperature of 20°C here.

[0016]

[0017] Ferroelectric nematic mixtures for room temperature application have been disclosed in WO2022117552 A1.

[0018] Ferroelectric smectic liquid crystals are classified by chiral and non-chiral systems. Both types are usually (globally) non-polar due to alternating layered domains with opposite polarity (Atsushi Yoshizawa, Crystals 2024, 14, 350., https: / / doi.org / 10.3390 / cryst14040350). An exception are the polar SmA phases (SmAp), where the layered domains are unidirectional. These polar ferroelectric smectic A phases show ferroelectric behaviour on a macroscopic scale like the ferroelectric nematic phase.

[0019] Short description of the invention

[0020] There is a need for piezoelectric materials that are easy to provide and which are easily formed into any desired shape. They should have a strong response to pressure or shape change. However, a strong performance of the ferroelectric material also depends from the alignment relative to the substrates as this alignment also controls the polarization of the phase and many of its unique properties like piezoelectricity and high dielectricity.

[0021] An object of the present invention is to provide polar liquid crystal materials having a vertical alignment for fulfilling technical needs in applications like harvesting mechanical or thermal energy, sensors, piezoelectric devices, semisolid forms of liquid crystals, actuators and other new applications of liquid crystals.

[0022] In addition, it is an aim for the materials and their alignment to be thermally and photochemically stable under the conditions prevailing in the areas of application, in particular at room temperature and 10 K, 20 K or more above and / or below. Surprisingly, it has been found that a piezoelectric polymer network liquid crystal having the NF-LC phase aligned in a vertical (homeotropic) fashion can be made while preserving the ferroelectric properties. The resulting material is highly suitable for piezoelectric applications and other applications requiring a directed unipolar alignment vertical to the electrode surface.

[0023] In one embodiment the invention relates to a method of aligning, optionally also poling, a ferroelectric nematic or ferroelectric smectic A liquid crystal mixture between substrates in a vertical state of alignment relative to the substrates by bringing the liquid crystal mixture containing 0.2 to 25 % by weight of a polymerizable component into a non-ferroelectric phase with vertical alignment, polymerizing the polymerizable component to yield a polymer network liquid crystal phase while the mixture enters the ferroelectric phase and while the vertical alignment is maintained.

[0024] In another aspect the invention relates to a novel polymer network liquid crystal (PN-LC) that comprises a ferroelectric nematic or ferroelectric smectic A liquid crystal and 0.2 to 25 % by weight of polymerizable or polymerized component as detailed below and in the claims.

[0025] The invention furthermore relates to a ferroelectric nematic or ferroelectric smectic A liquid crystal mixture comprising 0.2 to 25 % by weight of a polymerizable component of formula M:

[0026] Ra-B1-(Zm-B2)m-RbM

[0027] Ra, RbP, P-Sp-, H, F, Cl, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, SF5or straight-chain or branched alkyl having 1 to 25 C atoms, in which, in addition, one or more non-adjacent CH2groups may each be replaced, independently of one another,

[0028] by -C(R°)=C(R00)-, -C=C-, -N(R00)-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O- CO-O- in such a way that O and / or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F, Cl, Br, I, CN, P or P-Sp-, where, if B1and / or B2contain a saturated C atom, Raand / or Rbmay also denote a radical which is spiro-linked to this saturated C atom,

[0029] wherein at least one of the radicals Raand Rbdenotes or contains a group P or P-Sp-,

[0030] P a polymerizable group, Sp a spacer group, which is optionally substituted by L, or a single bond, B1, B2an aromatic, heteroaromatic, alicyclic or heterocyclic group, preferably having 4 to 25 ring atoms, which may also contain fused rings, and which is unsubstituted, or mono- or polysubstituted by L,

[0031] Zm-O-, -S-, -CO-, -CO-O-, -OCO-, -O-CO-O-, -OCH2-, -CH2O-,

[0032] -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -(CH2)n1-, -CF2CH2-, -CH2CF2-, -(CF2)m-, -CH=CH-, -CF=CF-, -CH=CF-, -CF=CH-, - C=C-, -CH=CH-COO-, -OCO-CH=CH-, -CH2CH2-CO-O-, O-CO-CH2-CH2-, -CR°R°°- or a single bond,

[0033] R°, R00H or alkyl having 1 to 12 C atoms,

[0034] m 0, 1, 2, 3 or 4,

[0035] n1 1, 2, 3 or 4,

[0036] L P, P-Sp-, OH, CH2OH, F, Cl, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, -C(=O)N(RX)2, -C(=O)Y1, -C(=O)RX, -N(RX)2, optionally substituted silyl, optionally substituted aryl having 6 to 20 C atoms, or straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having up to 25 C atoms, in which, in addition, one or more H atoms may be replaced by F, Cl, P or P-Sp-,

[0037] Y1halogen,

[0038] RxP, P-Sp-, H, halogen, straight-chain, branched or cyclic alkyl having up to 25 C atoms, in which, in addition, one or more non-adjacent CH2 groups may be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and / or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F, Cl, P or P-Sp-, an optionally substituted aryl or aryloxy group having 6 to 40 C atoms, or an optionally substituted heteroaryl or heteroaryloxy group having 2 to 40 C atoms.

[0039] The PN-LC having vertical alignment according to the invention have stable alignment and are colourless. In particular, they are distinguished by extraordinarily high effective dielectric constants and piezoelectricity versus the substrate surface and optional electrodes thereon.

[0040] In addition, the PN-LC used according to the present invention have suitable working temperatures and high clearing points. The PN-LC exhibits a ferroelectric liquid-crystalline phase over a significant range of temperatures, including ambient temperature.

[0041] The ferroelectric PN-LC according to the invention exhibit outstanding dielectric properties. The ferroelectric PN-LC not only provides improved properties for energy harvesting and electro-mechanic devices but also has potential uses in other electric and electronic devices.

[0042] Due to their outstanding properties the PN-LC can perform in many new areas of technology and may have use for electro-optical purposes, for capacitors including supercapacitors, non-linear optic elements, mechanical sensors, sensors for electrical fields, memory devices and electro-mechanic devices, including electric generators (i. e. energy harvesting devices) and actuators. The materials may for example enable unconventional modes of energy harvesting from vibrational motion.

[0043] Another aspect of the invention involves a liquid crystal device comprising a polymer network liquid crystal between substrates, preferably a piezoelectric element with electrodes on one or two of the substrates, comprising a ferroelectric nematic or ferroelectric smectic A PN-LC between the substrates in a vertical state of alignment relative to the substrates. Specifically, the piezoelectric element includes a mechanical substrate that may impart mechanical deformation to the PN-LC. This substrate is in contact with the ferroelectric PN-LC, where the PN-LC generates a charge in response to mechanical stress or exhibits a mechanical response to an applied electric field. The piezoelectric element can be used in a variety of applications, including in a mechanical sensor or an energy harvesting device. When it makes a response to an electric field it can be used as an actuator, for example as a linear motor or an active element of a (ultra-)sound generator. This invention provides a solution to the difficulties when a ferroelectric phase is to be aligned vertically. More efficient energy harvesting devices and piezoelectric elements can be made by utilizing the vertically aligned state and elastomeric properties of ferroelectric PN-LCs. The invention represents a significant advancement in the field of energy harvesting and mechanical sensor devices and has potential applications in a variety of electric and electronic devices. The high dielectric permeability orthogonal to the substrate and electrodes enables outstanding physical performance. The high (relative) dielectric permittivity is also especially advantageous for dielectrics in capacitors, since it causes high capacitance on a specific electrode area. In addition, the PN-LCs have very low electric conductivity and are unique over conventional high-εrmaterials (e.g. barium titanates) due to their initially liquid nature. The initially liquid nature of the material discerns them from solid materials in an advantageous way. In comparison a conventional solid piezoelectric material is prone to cracking.

[0044] The PN-LC can be formed from the liquid state for coating substrates. The flexible nature allows to adopt its form to any substrate or surface after formation. A very close contact can therefore be formed to electrodes. In a preferred mode of the invention the PN-LC is used to form a capacitor, a piezoelectric element or a mechanical sensor. Preferably the substrates enclosing the liquid crystal medium are planar and the pair of substrates is parallel to each other.

[0045] The ferroelectric PN-LC can in principle be also be used for displays based on the principle of the guest-host effect, the effect of deformation of aligned phases (DAP) or ECB (electrically controlled birefringence), FFS (fringe field switching) or dynamic scattering.

[0046] Ferroelectric PN-LCs show unique spontaneous polarization and piezoelectric behaviour, with values not dissimilar or even better than existing poled polymers (e.g. PVDF) or rigid brittle inorganic materials (e.g. zirconium titanate PZT). As all ferroelectric materials, they also show pyroelectricity.

[0047] The combination of the NFphase with the polymer network allows to transfer the NFphase into an anisotropic, ferroelectric soft solid. In comparison to the pure NFphase, the FLNC PN-LC shows no or reduced flow and is mechanically more stable, which allows for easier processing of the ferroelectric LC material.

[0048] Additionally, the gained elasticity enables reversible deformation and thus makes for a long-lasting mechanical energy harvester. The low elastic modulus of the NF-LC PN-LC in comparison to typical ceramic (PZT) or polymeric (PVDF) ferroelectric materials leads to a higher mechanical deformation for similar forces and thus to a greater change in effective spontaneous polarization. Due to the inverse piezoelectric effect an applied electric field leads to deformation of the NF-PN-LC and can as a result act as an electro-mechanical actuator (electrostriction). In comparison to existing pyro- and piezoelectric materials, one main advantage of NF-PN-LCS is their simple, adaptive and sustainable low-temperature processing via polymerization.

[0049] This invention also includes the use of the PN-LCs for electric and electronic elements. Although polymer stabilization for liquid crystals has been previously described in other patents and publications, the combination of PN-LC with ferroelectric nematic liquid crystals has not yet been achieved. In summary, the present invention discloses a novel and useful ferroelectric PN-LC and its potential uses in various electric and electronic devices. Application of force / movement of the electrodes compresses the PN-LC leading to movement of charge and hence energy harvesting.

[0050] Detailed description of the invention

[0051] The method of aligning a ferroelectric phase according to the invention follows a specific temperature scheme starting above the NF-N transition. This method is supported by the circumstance that during polymerization the temperature range of the ferroelectric nematic phase is reached naturally by the decrease of polymerizable monomers in the mixture. The decrease of monomers increases the transition temperature until it reaches the actual temperature of the mixture. The process temperature should be chosen accordingly. Preferably the process temperature T is chosen a few degrees above the NF-N transition of the unpolymerized mixture.

[0052] It is advantageous to conduct the method where polymerization is initiated at a temperature 1 to 10 degrees above the transition temperature of the NF-N transition.

[0053] The invention thus in one main aspect preferably relates to a liquid crystal (PN-LC) comprising 75 % by weight or more of a ferroelectric nematic or ferroelectric smectic A liquid crystal mixture and 0.2 to 25 % by weight of a polymerizable or polymerized component. Preferably the PN-LC according to the invention comprises 1 or more, more preferably 3 % by weight or more of a polymerizable component. The PN-LC contains preferably 25 % by weight of the polymerizable or polymerized component or less, more preferably 15% or less. Most preferably the polymerizable component is used in an amount of 3 to 15 % by weight. It is combined with the NFmaterial and polymerized in the state of the desired vertical or tilted vertical alignment relative to the substrates while in the non-ferroelectric nematic phase. The resulting PN-LC is preferably piezoelectric.

[0054] Tilted vertical alignment here means having a deviation angle from the vertical alignment of >0 to 45 degree.

[0055] Suitable polymerizable compounds used in the present invention generally have one, two or more, preferably one or two polymerizable groups capable of forming intermolecular bonds in the polymer network. Preferably the method according to the current invention involves using a polymerizable component which comprises one or more compounds with two or more polymerizable groups P.

[0056] The polymerizable group P is a group which is suitable for a polymerization reaction, such as, for example, free-radical or ionic chain polymerization, polyaddition or polycondensation, or for a polymer-analogous reaction, for example addition or condensation onto a main polymer chain. Particular preference is given to groups for chain polymerization, in particular those containing a C=C double bond or -C=C- triple bond, and groups which are suitable for polymerization with ring opening, such as, for example, oxetane or epoxide groups.

[0057] Preferred groups P are selected from the group consisting of

[0058] 0 „ / \ CH2=CW1-CO-O-, CH2=CW1-CO-, VV HC — CH-.,2 (CH2)k1-O-, Q

[0059] (CH2)—

[0060] , CH2=CW2-(O)k3-, CW1=CH-CO-(O)k3-,

[0061]

[0062] o CW1=CH-CO-NH-, CH2=CW1-CO-NH-, CH3-CH=CH-O-,

[0063] (CH2=CH)2CH-OCO-, (CH2=CH-CH2)2CH-OCO-, (CH2=CH)2CH-O-, (CH2=CH-CH2)2N-, (CH2=CH-CH2)2N-CO-, H0-CWW-, HS-CW2W3-, HW2N-, HO-CW2W3-NH-, CH2=CW1-CO-NH-, CH2=CH-(COO)ki-Phe-(O)k2-, CH2=CH-(CO)ki-Phe-(O)k2-, Phe-CH=CH-, HOOC-, OCN- and W4W5W6Si-, in which W1denotes H, F, Cl, CN, CF3, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, Cl or CH3, W2and W3each, independently of one another, denote H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, W4, W5and W6each, independently of one another, denote Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms, W7and W8each, independently of one another, denote H, Cl or alkyl having 1 to 5 C atoms, Phe denotes 1,4-phenylene, which is optionally substituted by one or more radicals L as defined above which are other than P-Sp-, k1, k2and k3each, independently of one another, denote 0 or 1, k3preferably denotes 1, and k4denotes an integer from 1 to 10.

[0064] Very preferred groups P are selected from the group consisting of

[0065] CH2=CW1-CO-O-, CH2=CW1-CO-, W2HC—CH(CH2)k1-O-

[0066] , CH2=CW2-O-, CH2=CW2-, CW1=CH-CO-(O)k3-, CW1=CH-CO-NH-, CH2=CW1-CO-NH-, (CH2=CH)2CH-OCO-, (CH2=CH-CH2)2CH-OCO-, (CH2=CH)2CH-O-, (CH2=CH-CH2)2N-, (CH2=CH-CH2)2N-CO-, CH2=CW1-CO-NH-, C

[0067]

[0068] H2=CH-(COO)ki-Phe-(O)k2-, CH2=CH-(CO)ki-Phe-(O)k2-, Phe-CH=CH- and W4W5W6Si-, in which W1denotes H, F, Cl, CN, CF3, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, Cl or CH3, W2and W3each, independently of one another, denote H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, W4, W5and W6each, independently of one another, denote Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms, W7and W8each, independently of one another, denote H, Cl or alkyl having 1 to 5 C atoms, Phe denotes 1,4-phenylene, ki, k2and k3each, independently of one another, denote 0 or 1, k3preferably denotes 1, and k4denotes an integer from 1 to 10.

[0069] Very particularly preferred groups P are selected from the group consisting of CH2=CW1-CO-O-, in particular CH2=CH-CO-O-, CH2=C(CH3)-CO-O- and CH2=CF-CO-O-, furthermore CH2=CH-O-, (CH2=CH)2CH-O-CO-, (CH2=CH)2CH- O

[0070] O / \

[0071] 2 'x\z

[0072] O

[0073]

[0074] -, W HC - CH- andw2^~(CH2)k1-O-.

[0075] Further preferred polymerizable groups P are selected from the group consisting of vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxide, most preferably from acrylate and methacrylate.

[0076] Very preferably all polymerizable groups in the polymerizable compound have the same structure. If the spacer group Sp is different from a single bond, it is preferably of the formula Sp"-X", so that the respective radical P-Sp- conforms to the formula P-Sp"-X"-, wherein

[0077] Sp" denotes linear or branched alkylene having 1 to 20, preferably 1 to 12, C atoms, which is optionally mono- or polysubstituted by F, Cl, Br, I or CN and in which, in addition, one or more non-adjacent CH2 groups may each be replaced, independently of one another, by -O-, -S-, -NH-, -N(R0)-, - Si(R°R00)-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -S-CO-, -CO-S-, -N(R°°)-CO- O-, -O-CO-N(R°)-, -N(R°)-CO-N(R00)-, -CH=CH- or -C=C- in such a way that O and / or S atoms are not linked directly to one another,

[0078] X" denotes -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -CO-N(R0)-, -N(R°)-CO-, -N(R°)-CO-N(R00)-, -OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, - CF2S-, -SCF2-, -CF2CH2-, -CH2CF2-, -CF2CF2-, -CH=N-, -N=CH-, -N=N-, - CH=CR°-, -CY2=CY3-, -C=C-, -CH=CH-CO-O-, -O-CO-CH=CH- or a single bond,

[0079] R° and R00each, independently of one another, denote H or alkyl having 1 to 20 C atoms, and

[0080] Y2and Y3each, independently of one another, denote H, F, Cl or CN.

[0081] X" is preferably -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR0-, -NR°-CO-, -NR°-CO-NR°°- or a single bond.

[0082] Typical spacer groups Sp and -Sp"-X"- are, for example, -(CH2)p1-, -(CH2)p1-O-, -(CH2)p1-O-CO-, -(CH2)p1-CO-O-, -(CH2)p1-O-CO-O-, -(CH2CH2O)q1-CH2CH2-, -CH2CH2-S-CH2CH2-, -CH2CH2-NH-CH2CH2- or -(SiR°R00-O)p1-, in which p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and R° and R00have the meanings indicated above.

[0083] Particularly preferred groups Sp and -Sp"-X"- are -(CH2)p1-, -(CH2)p1-O-, -(CH2)p1-O-CO-, -(CH2)p1-CO-O-, -(CH2)p1-O-CO-O-, in which p1 and q1 have the meanings indicated above.

[0084] Particularly preferred groups Sp" are, in each case straight-chain, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethylenethioethylene, ethylene-N-methyliminoethylene, 1 -methylalkylene, ethenylene, propenylene and butenylene. In one embodiment of the invention the polymerizable compounds contain a spacer group Sp that is substituted by one or more polymerizable groups P, so that the group Sp-P corresponds to Sp(P)s, with s being >2 (branched polymerizable groups).

[0085] Preferred polymerizable compounds according to this embodiment are those wherein s is 2, i.e. compounds which contain a group Sp(P)2. Very preferred polymerizable compounds according to this preferred embodiment contain a group selected from the following formulae:

[0086] -X-alkyl-CHPP S1

[0087] -X-alkyl-CH((CH2)aaP)((CH2)bbP) S2

[0088] -X-N((CH2)aaP)((CH2)bbP) S3

[0089] -X-alkyl-CHP-CH2-CH2P S4

[0090] -X-alkyl-C(CH2P)(CH2P)-CaaH2aa+1S5

[0091] -X-alkyl-CHP-CH2P S6

[0092] -X-alkyl-CPP-CaaH2aa+1S7

[0093] -X-alkyl-CHPCHP-CaaH2aa+1S8

[0094] in which P is as defined for formula M,

[0095] alkyl denotes a single bond or straight-chain or branched alkylene having 1 to 12 C atoms which is unsubstituted or mono- or polysubstituted by F, Cl or CN and in which one or more non-adjacent CH2groups may each, independently of one another, be replaced by -C(R°)=C(R0)-, -C=C-, -N(R0)-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and / or S atoms are not linked directly to one another, where R° has the meaning indicated above,

[0096] aa and bb each, independently of one another, denote 0, 1, 2, 3, 4, 5 or 6, X has one of the meanings indicated for X", and is preferably O, CO, SO2,

[0097] O-CO-, CO-O or a single bond.

[0098] Preferred spacer groups Sp(P)2are selected from formulae S1, S2 and S3.

[0099] Very preferred spacer groups Sp(P)2are selected from the following subformulae: -CHPP S1a

[0100] -O-CHPP S1b

[0101] -CH2-CHPP S1c

[0102] -OCH2-CHPP S1d -CH(CH2-P)(CH2-P) S2a

[0103] -OCH(CH2-P)(CH2-P) S2b

[0104] -CH2-CH(CH2-P)(CH2-P) S2C

[0105] -OCH2-CH(CH2-P)(CH2-P) S2d

[0106] -CO-NH((CH2)2P)((CH2)2P) S3a

[0107] P is preferably selected from the group consisting of vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxide, very preferably from acrylate and methacrylate, most preferably from methacrylate.

[0108] Further preferably all polymerizable groups P that are present in the same compound have the same meaning, and very preferably denote acrylate or methacrylate, most preferably methacrylate.

[0109] Sp preferably denotes a single bond or -(CH2)p1-, -(CH2)p2-CH=CH-(CH2)P3-, -O-(CH2)PI-, -O-CO-(CH2)p1, or -CO-O-(CH2)p1, wherein p1 is 2, 3, 4, 5 or 6, preferably 2 or 3, p2 and p3 are independently of each other 0, 1, 2 or 3 and, if Sp is -O-(CH2)p1-, -O-CO-(CH2)p1or -CO-O-(CH2)p1the O-atom or CO-group, respectively, is linked to the benzene ring.

[0110] Further preferably at least one group Sp is a single bond.

[0111] Further preferably at least one group Sp is different from a single bond, and is preferably selected from -(CH2)Pi-, -(CH2)p2-CH=CH-(CH2)p3-, -O-(CH2)PI-, -O-CO-(CH2)p1, or -CO-O-(CH2)p1, wherein p1 is 2, 3, 4, 5 or 6, preferably 2 or 3, p2 and p3 are independently of each other 0, 1, 2 or 3 and, if Sp is -O-(CH2)p1-, -O-CO-(CH2)p1or -CO-O-(CH2)p1the O-atom or CO-group, respectively, is linked to the benzene ring.

[0112] Very preferably Sp is different from a single bond, and is selected from -(CH2)2-, -(CH2)3-, -(CH2)4-, -O-(CH2)2-, -O-(CH2)3-, -O-CO-(CH2)2and -CO-O-(CH2)2-, wherein the O atom or the CO group is attached to the benzene ring.

[0113] Particularly preferred compounds of the formula M are those in which B1and B2each, independently of one another, denote 1,4-phenylene, 1,3-phenylene, naphthalene-1,4-diyl, naphthalene-2,6-diyl, phenanthrene-2,7-diyl, 9,10-dihydro-phenanthrene-2,7-diyl, anthracene-2,7-diyl, fluorene-2,7-diyl, coumarine, flavone, where, in addition, one or more CH groups in these groups may be replaced by N, cyclohexane-1,4-diyl, in which, in addition, one or more non-adjacent CH2groups may be replaced by O and / or S, 1,4-cyclohexenylene, bicycle[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl, piperidine- 1,4-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, indane-2,5-diyl or octahydro-4, 7-methanoindane-2,5-diyl, where all these groups may be unsubstituted or mono- or polysubstituted by L as defined above.

[0114] Particularly preferred compounds of the formula M are those in which B1and B2each, independently of one another, denote 1,4-phenylene, 1,3-phenylene, naphthalene-1,4-diyl or naphthalene-2,6-diyl.

[0115] Further preferred compounds of the formula M are those in which the group -B1-(Zm-B2)m- in formula M is selected from the following formulae

[0116]

[0117]

[0118] wherein the benzene rings are optionally further substituted by one or more groups L or P-Sp-.

[0119] Preferred compounds of formula M and its sub-formulae are selected from the following preferred embodiments, including any combination thereof:

[0120] - All groups P in the compound have the same meaning,

[0121] - -B1-(Zm-B2)m- is selected from formulae A1, A2, A3, A4 and A5,

[0122] - the compounds contain exactly one or two polymerizable groups (represented by the groups P),

[0123] - at least one compound contains exactly two polymerizable groups (represented by the groups P),

[0124] - P is selected from the group consisting of acrylate, methacrylate and oxetane, very preferably acrylate or methacrylate,

[0125] - P is methacrylate,

[0126] - all groups Sp are a single bond,

[0127] - at least one of the groups Sp is a single bond and at least one of the groups Sp is different from a single bond,

[0128] - Sp, when being different from a single bond, is -(CH2)p2-, -(CH2)p2-O-, -(CH2)p2-CO-O-, -(CH2)p2-O-CO-, wherein p2 is 2, 3, 4, 5 or 6, and the O-atom or the CO-group, respectively, is connected to the benzene ring,

[0129] - Sp is a single bond or denotes -(CH2)p2-, -(CH2)p2-O-, -(CH2)p2-CO-O-, -(CH2)p2- O-CO-, wherein p2 is 2, 3, 4, 5 or 6, and the O-atom or the CO-group, respectively, is connected to the benzene ring,

[0130] - Rbdenotes -CN,

[0131] - L is F.

[0132] Very preferred compounds of formula M having two or more polymerizable groups are selected from the following formulae:

[0133]

[0134] M12

[0135] (L)s

[0136] M13

[0137] (L)r(L)r (L)r

[0138] M14 P2 M17

[0139] M18

[0140] M19

[0141] M20

[0142] M21 P1-Sp1

[0143] M22

[0144] M23

[0145] M24

[0146] M25 M26 M27

[0147]

[0148]

[0149] in which the individual radicals, on each occurrence identically or differently, and each, independently of one another, have the following meaning: P1, P2, P3a polymerizable group, preferably selected from vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxy, very preferably acrylate or methacrylate,

[0150] Sp1, Sp2, Sp3a single bond or a spacer group where, in addition, one or more of the radicals P1-Sp1-, P2-Sp2- and P3-Sp3- may denote RM, with the proviso that at least one of the radicals P1-Sp1-, P2-Sp2and P3-Sp3- present is different from RM, preferably having one of the preferred meanings of Sp as given above, very preferably - (CH2)PI-, -(CH2)PI-O-, -(CH2)p1-CO-O- or -(CH2)p1-O-CO-O-, wherein p1 is an integer from 1 to 12,

[0151] RMH, F, Cl, CN or straight-chain or branched alkyl having 1 to 25 C atoms, in which, in addition, one or more non-adjacent CH2groups may each be replaced, independently of one another, by -C(R°)=C(R00)-, -C=C-, -N(R°)-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and / or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F, Cl, CN or P1-Sp1-, particularly preferably straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms (where the alkenyl and alkynyl radicals have at least two C atoms and the branched radicals have at least three C atoms), and wherein Raadoes not denote or contain a group P1, P2or P3,

[0152] R0, R00H or alkyl having 1 to 12 C atoms,

[0153] Ryand RzH, F, CH3or CF3,

[0154] X1, X2, X3-CO-O-, -O-CO- or a single bond,

[0155] ZM1-O-, -CO-, -C(RyRz)-, -CF2CF2-, -CF2O- or -OCF2-,

[0156] ZM2, ZM3-CO-O-, -O-CO-, -CH2O-, -OCH2-, -CF2O-, -OCF2- or -(CH2)n-, where n is 2, 3 or 4,

[0157] L F, Cl, CN or straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, thioalkyl, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms,

[0158] L', L" H, F or Cl,

[0159] k 0 or 1,

[0160] r 0, 1, 2, 3 or 4,

[0161] s 0, 1, 2 or 3,

[0162] t 0, 1 or 2,

[0163] x 0 or 1.

[0164] Very preferred are compounds of formulae M2, M8, M11, M12 and M14, especially direactive compounds containing exactly two polymerizable groups P1and P2. In the compounds of formulae M1 to M32 the group

[0165]

[0166] wherein L on each occurrence, identically or differently, has one of the meanings given above or below, and is preferably F, Cl, CN, NO2, CH3, C2H5, C(CH3)3, CH(CH3)2, CH2CH(CH3)C2H5, -CH=CH2, C(CH3)=CH2, SCH3, OCH3, OC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF3, OCF3, OCHF2, OC2F5 or P-Sp-, more preferably F, Cl, CH3, CF3, C2H5, -CH=CH2, C(CH3)=CH2, SCH3, OCH3, COCH3 or OCF3, most preferably F, CF3, CH3 or C2H5.

[0167] Preferred compounds of formulae M1 to M32 are those wherein P1, P2and P3denote an acrylate, methacrylate, oxetane or epoxy group, very preferably an acrylate or methacrylate group, most preferably a methacrylate group.

[0168] Further preferred compounds of formulae M1 to M32 are those wherein Sp1, Sp2and Sp3are a single bond. Further preferred compounds of formulae M1 to M32 are those wherein one of Sp1, Sp2and Sp3is a single bond and another one of Sp1, Sp2and Sp3is different from a single bond.

[0169] Further preferred compounds of formulae M1 to M32 are those wherein those groups Sp1, Sp2and Sp3that are different from a single bond denote -(CH2)s1-X"-, wherein s1 is an integer from 1 to 6, preferably 2, 3, 4 or 5, and X" is X" is the linkage to the benzene ring and is -O-, -O-CO-, -CO-O, -O-CO-O- or a single bond.

[0170] Further preferred polymerizable compounds are selected from Table E below, especially selected from the group consisting of formulae RM-64, RM-65, RM-66, RM-67, RM-68, RM-69, RM-185 or RM-186.

[0171] In a preferred embodiment the polymerisable component comprises one or more compounds of formula M-A

[0172]

[0173] where Ra, L and Zmare defined as for formula M,

[0174] L1, L2denote H or F, preferably F,

[0175] Badenotes an aromatic, heteroaromatic, alicyclic or heterocyclic group, preferably having 4 to 25 ring atoms, which may also contain fused rings, and which is unsubstituted, or mono- or polysubstituted by L, preferably 1,4-phenylene, 1,3-phenylene, naphthalene-1,4-diyl, naphthalene-2,6-diyl, phenanthrene-2,7-diyl, 9,10-dihydro-phenanthrene- 2,7-diyl, anthracene-2,7-diyl, fluorene-2,7-diyl, coumarine, flavone, where, in addition, one or more CH groups in these groups may be replaced by N, cyclohexane-1,4-diyl, in which, in addition, one or more non-adjacent CH2groups may be replaced by O and / or S, 1,4-cyclohexenylene, bicycle[1.1.1 ]- pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl, piperidine-1,4-diyl, decahydronaphthalene-2,6-diyl, 1, 2,3,4- tetrahydronaphthalene-2,6-diyl, indane-2,5-diyl or octahydro-4, 7- methanoindane-2,5-diyl, where all these groups may be unsubstituted or mono- or polysubstituted by L, L1, L2independently denote H or F,

[0176] Zndenotes -CO-O- or -CF2O-, and

[0177] Rbdenotes -CN, -NO2, F, Cl, CF3, -OCF3or -NCS, preferably CN or F, n is 0, 1, 2 or 3, and

[0178] r independently is 0 or 1.

[0179] Very preferred compounds of formula M-A having one polymerizable group are selected from the following formulae:

[0180] MA1

[0181] MA2

[0182]

[0183] in which the individual radicals, on each occurrence identically or differently, and each, independently of one another, have the following meaning:

[0184] P1a polymerizable group, preferably selected from vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxy, very preferably acrylate or methacrylate,

[0185] Sp1a single bond or a spacer group where, in addition, preferably having one of the preferred meanings of Sp as given above, very preferably -(CH2)PI-, -(CH2)PI-O-, -(CH2)p1-CO-O- or- (CH2)PI-O-CO-O-, wherein p1 is an integer from 1 to 12, L F, Cl, CN or straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, thioalkyl, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having up to 12 C atoms, ZN-CO-O- or -CF2O-,

[0186] X -CN, -NO2, F, Cl, CF3, -OCF3or -NCS, preferably F or CN, independently 0, 1 or 2.

[0187] Particularly preferred are LC media comprising one, two or three polymerizable compounds of formula M.

[0188] Further preferred are LC media comprising two or more polymerizable compounds of formula M.

[0189] The term "spacer group", hereinafter also referred to as " Sp", as used herein is known to the person skilled in the art and is described in the literature, see, for example, Pure Appl. Chem. 2001, 73(5), 888 and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368. As used herein, the terms "spacer group" or "spacer" mean a flexible group, for example an alkylene group, which connects the mesogenic group and the polymerizable group(s) in a polymerizable mesogenic compound.

[0190] Unless stated otherwise, the term "polymerizable compound" as used herein will be understood to mean a polymerizable monomeric compound.

[0191] As used herein, the term "low-molecular-weight compound" will be understood to mean to a compound that is monomeric and / or is not prepared by a polymerization reaction, as opposed to a "polymeric compound" or a "polymer". In the following the ferroelectric LC mixture used as basis for the PN-LCs is described in more detail.

[0192] Said ferroelectric nematic or ferroelectric smectic LC material preferably comprises at least two compounds with a molecular structure of formula I,

[0193]

[0194] A2denotes independently denotes

[0195]

[0196] n is 0, 1, 2 or 3, preferably 0, 1 or 2,

[0197] R1is an alkyl radical having 1 to 12 C atoms, preferably 1 to 8, more preferably 1 to 6 and most preferably 1 to 5 C atoms, where, in addition, one or more CH2groups in these radicals may in each case be replaced, independently of one another, by -C≡C-, -CF2-O-,

[0198] -OCF2-, -CH=CH-,

[0199]

[0200] 's"’ -(CO)-O- or -O-(CO)- in such a way that O / S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen,

[0201] or denotes H,

[0202] X is CN, F, CF3, -OCF3, -NCS, Cl, preferably CN or F,

[0203] L1is H or CH3,

[0204] Z1is CF2O or -(CO)-O- or a single bond, preferably CF2O or -(CO)-O-, most preferably -(CO)-O-,

[0205] and Z2, Z3independently, are CF2O or -(CO)-O- or a single bond, preferably -(CO)-O- or a single bond.

[0206] Preferably one of the groups Z1and Z2is CF2O or -(CO)-O- and the other cis a single bond.

[0207] The ferroelectric medium for use in PN-LCs preferably comprises at least 30 % of compounds of formula I, more preferably 40 %, more preferably 50 % and most preferably 80%, 90% or 95 % or more by weight of compounds of formula I. More preferably the invention uses as the ferroelectric nematic / smectic liquid crystal mixture a mixture comprising two or more compounds selected from the compounds of formulae IA, IB, IC-1, IC-2 and IC-3,

[0208]

[0209] IC-3

[0210]

[0211] in which

[0212] X1Bdenotes -CN or -NCS, preferably -CN,

[0213] X1Cdenotes -CN, F, CF3, -OCF3, -NCS, SF5or O-CF=CF2, preferably - CN or F, most preferably CN,

[0214] Z1Aand Z1Bindependently of one another denote -(CO)-O- or -CF2-O- or a single bond,

[0215] preferably -(CO)-O- or -CF2-O-,

[0216] Z2Aand Z2Bindependently of one another denote a single bond, -(CO)-O- or - CF2-O-,

[0217] preferably a single bond,

[0218] Z1Cand Z2Cone of the both groups denotes -(CO)-O- or -CF2-O- and the other a single bond,

[0219] preferably Z1Cis -(CO)-O- or -CF2-O-and Z2Cis a single bond, L1A, L1Band L1Cindependently of each other denote H or CH3, preferably H, L2Ais F or H, preferably F,

[0220] L3Ais F or H, preferably F,

[0221] L2Bis F or H, preferably F,

[0222] L3Bis F or H, preferably F,

[0223] L2Cis F or H, preferably F,

[0224] A1Adenotes

[0225]

[0226] preferably wherein L8Bdenotes alkyl, alkoxy or alkoxyalkyl, each with 1 to 7 C atoms, preferably CH3, OCH3, OCH2CH3, CH2OCH3, CH2OCH2CH3, CH2CH2OCH3, CH2CH2OCH2CH3or CH2CH2CH2OCH3, A1Cindependently denotes

[0227]

[0228] preferably

[0229]

[0230] A2Cdenotes

[0231]

[0232] m, n 0, 1 or 2, where (m + n) is 1 or 2,

[0233] R1A, R1Band R1Cindependently of each another denote an alkyl radical having 1 to 12 C atoms, preferably 1 to 8, more preferably 1 to 6 and most preferably 1 to 5 C atoms, where, in addition, one or more CH2groups in these radicals may in each case be replaced, independently of one another, by -C≡C-, -CF2-O-, -OCF2-, -

[0234]

[0235] CH=CH-,

[0236]

[0237] \__y~, -O-, -S-, -(CO)-O- or -O-(CO)- in such a way that O / S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen, or denotes H, preferably R1A, R1Band R1Cindependently are a halogenated or unsubstituted alkyl radical having 1 to 10 C atoms, where, in addition, one or more CH2groups in these radicals may be replaced by -O- or - CH=CH- in such a way that O atoms are not linked directly. In a preferred embodiment the used ferroelectric LC mixture comprises 90 % by weight or more of two or more of compounds selected from compounds of formula IA, IB and IC-1.

[0238] In a more preferred embodiment the used ferroelectric LC mixture comprises 15 % by weight or more of one or more of compounds of formula IA,

[0239] 15 % by weight or more of one or more of compounds of formula IB,

[0240] and 15%, preferably 20 % by weight or more of one or more compounds selected from formula IC-1 to IC-3.

[0241] The percentages are provided under the circumstance that the whole medium makes up 100% by weight of the medium.

[0242] The radicals R1A, R1Band R1Cin the respective formulae IA, IB and IC-1 to IC-3 and their respective sub-formulae preferably denote alkyl having 1 to 8 carbon atoms, alkoxy having 1 to 8 carbon atoms or alkenyl having 2 to 8 carbon atoms. These alkyl chains are preferably linear or they, preferably in case of R1C, are branched by a single methyl or ethyl substituent, preferably in 2- or 3-position. R1A, R1Band R1Cparticularly preferably denote a straight-chain alkyl radical having 1 to 7 C atoms or an unbranched alkenyl radical having 2 to 8 C atoms, in particular unbranched alkyl having 1 to 5 C atoms.

[0243] Alternative preferred radicals R1A, R1Band R1Care selected from cyclopentyl, 2-fluoroethyl, cyclopropylmethyl, cyclopentylmethyl, cyclopentylmethoxy, cyclobutylmethyl, 2-methylcyclopropyl, 2-methylcyclobutyl, 2-methylbutyl, 2-ethylpentyl and 2-alkyloxyethoxy.

[0244] Compounds of the formula IA, IB and IC1 to IC-3 containing branched or substituted end groups R1A, R1Band R1C, respectively, may occasionally be of importance owing to better solubility in the liquid-crystalline base materials. The groups R1A, R1Band R1C, respectively, are preferably straight chain. The radicals R1A, R1Band R1C, respectively, particularly preferably selected from the moieties:

[0245] CH3

[0246] C2H5

[0247] n-C3H7

[0248] n-C4H9

[0249] n-C5H11

[0250] C2H5CH(CH3)CH2

[0251] n-C6H13

[0252] n-C7H15

[0253] n-C3H7CH(C2H5)CH2

[0254] n-C8H17

[0255] c-C3H5

[0256] c-C3H5CH2

[0257] c-C4H7

[0258] c-C5H7

[0259] c-C5H9

[0260] c-C5H9CH2

[0261] CH2=CH

[0262] CH3CH=CH

[0263] CH2=CH(CH2)2

[0264] CH3O

[0265] C2H5O

[0266] n-C3H7O

[0267] n-C4H9O

[0268] n-C5H11O

[0269] CH3OCH2

[0270] C2H5OCH2

[0271] CH3OCH2CH2

[0272] C2H5OCH2CH2

[0273] CH3C(O)O

[0274] C2H5C(O)O

[0275] n-C3H7C(O)O

[0276] n-C4H9C(O)O

[0277] n-C5H11C(O)O

[0278] wherein the following abbreviations for the end groups are used: C-C3H5

[0279] C-C3H5CH2

[0280] C-C4H7

[0281] C-C5H7

[0282] c-C5H9

[0283]

[0284] and

[0285] c-C5H9CH2

[0286]

[0287] A preferred embodiment of the invention makes use of a ferroelectric nematic or smectic liquid-crystalline medium comprising one or more compounds selected from formulae IA, IB, IC-1, IC-2 and IC-3 as defined above.

[0288] In a preferred embodiment, the media according to the present invention preferably comprise one, two, three or more compounds of formula IA-1

[0289] R1A-A IA-1

[0290]

[0291] preferably selected from the group of formulae IA-1 to IA-3, preferably of formula IA-1:

[0292] IA-1-1

[0293]

[0294] IA-1-3

[0295]

[0296] in which the parameters have the respective meanings given above and preferably Z1Adenotes -CF2-O-.

[0297] In a preferred embodiment, the media according to the present invention preferably comprise one, two, three or more compounds of formula IB-1 and / or IB-2, preferably of formula IB-1,

[0298] IB-1

[0299] IB-2

[0300]

[0301] R1Bdenotes an alkyl radical having 1 to 12 C atoms, preferably 1 to 7, more preferably 1 to 6 and most preferably 1 to 5 C atoms, where, in addition, one or more CH2groups in these radicals may in each case be replaced, independently of one another, by -C≡C-, -CF2-O-, - OCF2-, -CH=CH-, >

[0302]

[0303] , -O-, -S-, -CO-O- or -O-CO- in such a way that O / S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen, or denotes H, preferably R1Bis a halogenated or unsubstituted alkyl radical having 1 to 12 C atoms, where, in addition, one or more CH2groups in these radicals may in each case be replaced, independently of one another, by -C≡C- or -CH=CH-,

[0304] denotes

[0305]

[0306] and

[0307] Z1B, Z2Bindependently denote -(CO)-O- or -CF2-O-,

[0308] preferably selected from the group of the following formulae, formulae IB-1-1 to IB-2-3,:

[0309] IB-1-1

[0310] IB- 1-2

[0311]

[0312] IB-1-3

[0313] IB-2-1

[0314] IB-2-2

[0315] IB-2-3

[0316]

[0317] in which the parameters have the respective meanings given above

[0318] and, in particular, in formula IB-1-1 to IB-1-3,

[0319] Z1Bpreferably denotes -CF2-O- and, in particular, in formula IB-2-1 and IB-2-2,

[0320] Z2Bdenotes preferably -CF2-O-;

[0321] and, in particular, in formula IB-2-3,

[0322] Z2Bdenotes preferably -C(O)O-.

[0323] In a preferred embodiment, the media according to the present invention preferably comprise one, two, three or more compounds selected of formulae IC-1-1 to IC-3-5: IC-1-1

[0324] IC-1-2

[0325] IC-1-3

[0326] IC-1-4

[0327] IC-2-1

[0328] IC-3-1

[0329] IC-3-2

[0330] IC-3-3

[0331] IC-3-4 wherein A1Cis defined as above,

[0332] preferably selected from the group of formulae IC-1-1-1 to IC-3-5-2, more preferably selected from the group of formulae IC-1-1-1, IC-1-1-2, IC-1-1-3, IC-1-1-4, IC-3-1-1 and IC-3-2-1:

[0333] F F F

[0334]

[0335] IC-1-1-7

[0336] IC-1-1-8

[0337] IC- 1-2-2

[0338] IC-1-2-1

[0339] IC-1-4-1

[0340] IC-3-1-1

[0341] IC-3-2-1

[0342] IC-3-3-1

[0343]

[0344] IC-3-3-2

[0345] IC-3-4-1

[0346] IC-3-4-2

[0347] IC-3-5-1

[0348] IC-3-5-2

[0349]

[0350] in which the parameters have the respective meanings given above and preferably

[0351] L1Cdenotes H,

[0352] Z1Cdenotes -CF2-O- or -(CO)-O-, and

[0353] X1Cdenotes -CN or F, preferably -CN.

[0354] Particularly preferred compounds of the formula IC-1-1 to IC-1-4 used in the media are the compounds of the formulae below:

[0355] IC-1-1-1-1

[0356]

[0357] IC-1-1-2-1

[0358] IC-1-1-3-1

[0359] IC-1-1-4-1

[0360]

[0361] wherein the parameters are defined as above, preferably L1Cis H.

[0362] In one embodiment the medium is a ferroelectric smectic A medium (also known as polar longitudinal smectic A phase, SmAP). Preferred ferroelectric smectic liquid crystalline media comprise, in addition to compounds of group 1, one or more compounds of formula IS,

[0363] R1 A_^1 A _ z1A_^2A_ _^2A _ / \3A_ _R2A

[0364] IS

[0365]

[0366] n1

[0367] wherein

[0368] A1A

[0369]

[0370] A2A

[0371]

[0372] A3A

[0373]

[0374] L3Aeach independently H, alkyl, alkoxy or alkoxyalkyl, each with 1 to 7 C atoms, preferably H,

[0375] Z1Aand Z2Aindependently of one another are a single bond, -C≡C- or -CH=CH-

[0376] R1Aindependently is an alkyl radical having 1 to 12 C atoms, where, in addition, one or more CH2groups in these radicals may in each case be replaced, independently of one another, by -C≡C-,

[0377] -

[0378]

[0379] CH=CH-, -O-, -S-, -(CO)-O- or -O-(CO)- in such a way that O / S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen, or denotes H,

[0380] R2Aindependently is an alkyl radical having 1 to 12 C atoms, where, in addition, one or more CH2 groups in these radicals may in each case be replaced, independently of one another, by -C≡C-,

[0381]

[0382] -O-, -S-, -(CO)-O- or -O-(CO)- in such a way that O / S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen, or denotes H, F, -CN, -OCF3or - CF3.

[0383] and

[0384] n1 0, 1 or 2, preferably 1.

[0385] Compounds of formulae I, IA, IB and IC-1 are preferably excluded from formula IS.

[0386] The preferred content of compounds of formula IS in a SmAp phase is 5 % or more, more preferably 10 %, more preferably 15 % or more and most preferably 20 % by weight or more of compounds of formula IS, and preferably 25 % or less of compounds of formula IS.

[0387] In a preferred embodiment of the present invention the media comprise up to 100 % of one or more compounds, preferably of three, four, five, six or more, compounds selected from group 1 of compounds, the group of compounds of formulae IA, IB and IC-1 / -2 / -3 and optionally IS. In this embodiment the media preferably predominantly consist of, more preferably they essentially consist of, and most preferably, they virtually completely consist of these compounds.

[0388] For the present invention, the following definitions apply in connection with the specification of the constituents of the compositions, unless indicated otherwise in individual cases:

[0389] - "comprise": the concentration of the constituents in question in the composition is preferably 5 % or more, particularly preferably 10 % or more, very particularly preferably 20 % or more,

[0390] - "predominantly consist of': the concentration of the constituents in question in the composition is preferably 50 % or more, particularly preferably 55 % or more and very particularly preferably 60 % or more,

[0391] - "essentially consist of': the concentration of the constituents in question in the composition is preferably 80 % or more, particularly preferably 90 % or more and very particularly preferably 95 % or more, and - "virtually completely consist of": the concentration of the constituents in question in the composition is preferably 98 % or more, particularly preferably 99 % or more and very particularly preferably 100.0 %.

[0392] Preferably the media according to the present application fulfil one or more of the following conditions. They preferably comprise:

[0393] - 20 % or more of compounds of formula IA, more preferably 25 %, more preferably 27 % or more and most preferably 32 % by weight or more of compounds of formula IA,

[0394] 17 % or more of compounds of formula IB, more preferably 20 % or more, more preferably 22 % or more and most preferably 25 % by weight or more of compounds of formula IB,

[0395] - 40 % or more of compounds selected from formula IA and IB, more preferably 45 %, more preferably 50 % or more and most preferably 55 % by weight or more of compounds selected from formula IA and IB, i. e. the sum of compounds of formula IA and IB preferably is at least of the above values, - 20 % or more, preferably 25 % or more of compounds selected of formula IC- 1, IC-2 and IC-3, more preferably 28 %, more preferably 32 % or more and most preferably 34 % by weight or more,

[0396] - optionally 2 % or more of compounds of formula ID (ID-1, ID-2, ID-3, ID-4), more preferably 5 %, more preferably 10 % or more and most preferably 15 % by weight or more of compounds of formula ID,

[0397] - one, two, three or more, preferably three or more, compounds of the formula IA- 1-1, preferably of formula DUUQU-n-F, most preferably selected from the group of the compounds DUUQU-2-F, DUUQU-3-F, DUUQU-4-F and DUUQU-5-F and DUUQU-6-F,

[0398] - one, two, three or more, preferably three or more, compounds of the formula IB-1, preferably of formulae GUUQU-n-N and / or DUUQU-n-N, most preferably selected from the group of the compounds GUUQU-2-N, GUUQU-3-N, GUUQU-4-N, GUUQU-5-N, GUUQU-6-N, GUUQU-7-N, DUUQU-2-N, DUUQU-3-N, DUUQU-4-N, DUUQU-5-N and DUUQU-6-N,

[0399] - one, two, three or more compounds of the formula IA-1-3, preferably of formula GUUQU-n-F, more preferred selected from the group of the compounds GUUQU-3-F, GUUQU-4-F and GUUQU-5-F, - one, two, three or more compounds of the formula IB-1-3, preferably of formula DUUQU-n-N, more preferred selected from the group of the compounds DUUQU-3-N, DUUQU-4-N and DUUQU-5-N,

[0400] - one, two, three or more compounds of the formula IC-1-1, preferably of formula MUZU-n-N or MUQU-n-N, more preferred selected from the group of the compounds MUZU-2-N, MUZU-3-N, MUZU-4-N and MUZU-5-N,

[0401] - one, two, three or more compounds of the formula IC-3, preferably selected from the formulae MUU-n-N or UMU-n-N, more preferably selected from the group of the compounds MUU-3-N, MUU-4-N, MUU-5-F, UMU-3-N, UMU-4-N and UMU-5-N,

[0402] - one, two, three or more compounds of the formula IC-1-1, preferably selected from the formulae GUZU-n-N or GUQU-n-N, more preferably selected from the group of the compounds GUZU-3-N, GUZU-4-N, GUZU-5-F, GUQU-3-N, GUQU-4-N and GUQU-5-N,

[0403] - one, two, three or more compounds of the group of formulae IC-1-1-3 and IC- 1-1 -4, preferably of formulae UUZU-n-N and / or UUQU-n-N, most preferably selected from the group of the compounds UUZU-2-N, UUZU-3-N, UUZU-4-N, UUZU-5-N, UUQU-2-N, UUQU-3-N and UUQU-4-N,

[0404] - and / or

[0405] one or more compounds selected from the group of compounds DUZGU-1-F, DUZGU-2-F, DUZGU-3-F, DUZGU-4-F, or DUZGU-5-F,

[0406] wherein n is 1, 2, 3, 4, 5, 6 or 7.

[0407] In another preferred embodiment of the present invention said compounds of formulae IA, IB and IC-1 / -2 / -3 are a first group of compounds, group 1, of compounds. In one embodiment the medium has a ferroelectric nematic phase and the concentration of the compounds of this group 1 of compounds preferably is in the range from 70 % or more, preferably 80 % or more, more preferably 90 % or more to 100 % or less. In another embodiment the medium has a ferroelectric smectic A phase and the concentration of the compounds of this group 1 of compounds preferably is in the range from 70 % or more, preferably 75 % or more, more preferably 80 % or more to 100 % or less. In addition to the compounds of formulae IA, IB and IC-1 / -2 / -3 the media according to the invention optionally, preferably obligatory, comprise one, two, three or more compounds selected from formula ID-1 to ID-4

[0408] ID-1

[0409] ID-2

[0410] ID-3

[0411] ID-4

[0412]

[0413] XDdenotes CN, F, CF3, -OCF3, NCS, SF5or O-CF=CF2, preferably -CN,

[0414] F, -CF3, -OCF3, -Cl or -NCS, most preferably F or CN,

[0415] L1D, L2D, L3D, L4D, L5D, L6Dand L7D, independently denote F, H, alkyl, alkoxy or alkoxyalkyl, each with 1 to 7 C atoms, preferably H, F, CH3, OCH3, OCH2CH3, CH2OCH3, CH2OCH2CH3, CH2CH2OCH3, CH2CH2OCH2CH3or CH2CH2CH2OCH3,

[0416] Z1Dand Z2Dindependently of one another denote -(CO)-O-, -CF2-O-, a single bond, and preferably both -(CO)-O-,

[0417] R1Ddenotes an alkyl radical having 1 to 12 C atoms, preferably 1 to 7, more preferably 1 to 6 and most preferably 1 to 5 C atoms, where, in addition, one or more CH2groups in these radicals may in each case be replaced, independently of one another, by -C≡C-, -CF2-O-, - OCF2-, -CH=CH-, Z\, ~ ’

[0418]

[0419] . -0-, -S-, -(CO)-O- or -O-(CO)- in such a way that O / S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen, or denotes H, preferably R1Dis a halogenated or unsubstituted alkyl radical having 1 to 12 C atoms, where, in addition, one or more CH2groups in these radicals may in each case be replaced, independently of one another, by -C≡C- or -CH=CH-,

[0420] denotes alkyl, alkoxy or alkoxyalkyl, each with 1 to 7 C atoms, preferably CH3, OCH3, OCH2CH3, CH2OCH3, CH2OCH2CH3, CH2CH2OCH3, CH2CH2OCH2CH3or CH2CH2CH2OCH3,

[0421] denotes a single bond,

[0422] or

[0423]

[0424] preferably a single bond,

[0425] [_8D

[0426] or

[0427]

[0428] wherein

[0429] |_8D denotes alkyl, alkoxy or alkoxyalkyl, each with 1 to 7 C atoms,

[0430] preferably CH3, OCH3, OCH2CH3, CH2OCH3, CH2OCH2CH3, CH2CH2OCH3, CH2CH2OCH2CH3or CH2CH2CH2OCH3, preferably it comprises one or more of formulae ID-1-1 to ID-2-1:

[0431]

[0432] wherein the variable groups R1Dand L8Dare defined as above.

[0433] The media optionally comprise additionally one or more compounds selected from the following groups of compounds:

[0434] Additional ferroelectric substances and similar compounds with high dielectric permittivity for combination with the current substances are selected from e.g. the following structures:

[0435]

[0436]

[0437] Corresponding starting materials can generally readily be prepared by the person skilled in the art by synthetic methods known from the literature or are commercially available. The reaction methods and reagents used are in principle known from the literature. Further reaction conditions are exemplified by the working examples. Further preferred process variants, not mentioned above, are revealed by the examples or the claims.

[0438] In the present disclosure, the 2,5-disubstituted dioxane ring of the formula

[0439]

[0440] preferably denotes a 2,5-trans-configured dioxane ring, i.e., the substituents are preferably both in the equatorial position in the preferred chair conformation. The 2,5-disubstituted tetra hydro pyran of the formula

[0441]

[0442] likewise preferably denotes a 2,5-trans-configured tetrahydropyran ring, i.e., the substituents are preferably both in the equatorial position in the preferred chair conformation.

[0443] Preferably the liquid crystal media according to the invention exhibit the ferroelectric nematic or ferroelectric smectic phase from 10°C to 30°C, more preferably from 10°C to 40°C, more preferably from 10°C to 50°C, more preferably from 0°C to 50°C and, most preferably, from -10°C to 50°C.

[0444] In another preferred embodiment the liquid crystal media according to the invention preferably exhibit the ferroelectric nematic or ferroelectric smectic phase from 10°C to 40°C, more preferably from 10°C to 50°C, more preferably from 10°C to 60°C and, most preferably, from 10°C to 70°C.

[0445] Preferably the media according to the invention have values of εrof 700 or more, more preferably of 800 or more (at 20 °C and 10 Hz). These dielectric properties are achieved at temperatures at which the media are in the ferroelectric phase. The dielectric characteristics may show a hysteresis behaviour, particularly over varying temperature, and in that case the values obtained at a certain temperature may depend on the history of the material, i.e. whether the material is being heated up or cooled down.

[0446] This effect enables, amongst others, the operation of devices e.g. in bistable modes, which may be used beneficially in electro-optical devices, as e.g. known from ferroelectric smectic devices.

[0447] The liquid crystal media according to the invention preferably comprise 2 to 40, particularly preferably 4 to 20, compounds as further constituents besides one or more compounds according to the invention. In particular, these media may comprise 1 to 25 components besides one or more compounds according to the invention. These further constituents are preferably selected from ferroelectric nematic or nematogenic (monotropic or isotropic) substances,

[0448] The media according to the invention preferably comprise 1 % to 95 %, more preferably 10 % to 90 % and, particularly preferably, 50 % to 90 %, of the compounds of formulae IA and / or IB and / or IC-1 / IC-2 / IC-3 preferably used according to the invention. The resulting mixture generally amount to 100 % by weight.

[0449] The liquid-crystal mixtures and PN-LCs according to the invention are prepared in a manner which is conventional per se. In general, the desired amount of the components used in lesser amount is dissolved in the components making up the principal constituent, preferably at elevated temperature. It is also possible to mix solutions of the components in an organic solvent, for example in acetone, chloroform or methanol, and to remove the solvent again, for example by distillation, after thorough mixing. It is furthermore possible to prepare the mixtures in other conventional manners, for example by using premixes, for example homologue mixtures, or using so-called “multi-bottle” systems.

[0450] The liquid-crystal mixtures and PN-LCs may also comprise further additives known to the person skilled in the art and described in the literature. For example, 0 to 15%, preferably 0 to 10%, of pleochroic dyes, chiral dopants, stabilisers or nanoparticles can be added. The individual compounds added are employed in concentrations of 0.01 to 6%, preferably 0.1 to 3%. However, the concentration data of the other constituents of the liquid-crystal mixtures, i.e. the liquid- crystalline or mesogenic compounds, are given here without taking into account the concentration of these additives.

[0451] The invention also relates to electro-optical displays (in particular TFT displays having two plane-parallel outer plates, which, together with a frame, form a cell, integrated non-linear elements for switching individual pixels on the outer plates, and a ferroelectric liquid-crystal PN-LC having positive dielectric anisotropy and high specific resistance located in the cell).

[0452] The expression "alkyl" encompasses unbranched and branched alkyl groups having 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, in particular and preferably the unbranched groups methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl and n-heptyl and further, alternatively, the groups n-butyl, n-pentyl, n-hexyl and n-heptyl substituted by one methyl, ethyl or propyl. Groups having 1-5 carbon atoms are generally preferred.

[0453] The expression "alkenyl" encompasses unbranched and branched alkenyl groups having up to 12 carbon atoms, in particular the unbranched groups. Particularly preferred alkenyl groups are C2-C7-1E-alkenyl, C4-C7-3E-alkenyl, C5-C7-4-alkenyl, C6-C7-5-alkenyl and C7-6-alkenyl, in particular C2-C7-1E-alkenyl, C4-C7-3E-alkenyl and C5-C7-4-alkenyl. Examples of preferred alkenyl groups are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl and the like. Groups having 2 to 5 carbon atoms are generally preferred.

[0454] The expression "halogenated alkyl radical" preferably encompasses mono- or polyfluorinated and / or -chlorinated radicals. Perhalogenated radicals are included. Particular preference is given to fluorinated alkyl radicals, in particular CF3, CH2CF3, CH2CHF2, CHF2, CH2F, CHFCF3and CF2CHFCF3. The expression "halogenated alkenyl radical" and related expressions are explained correspondingly.

[0455] The following examples explain the invention without intending to restrict it. The person skilled in the art will be able to glean from the examples working details that are not given in detail in the general description, generalise them in accordance with general expert knowledge and apply them to a specific problem. Above and below, percentage data denote per cent by weight. All temperature values indicated in the present application, such as, for example, the melting point T(C, N), the smectic (Sm) to nematic (N) phase transition T(S, N) and the clearing point T(N, I) are indicated in degrees Celsius (°C) and all temperature differences are correspondingly indicated in differential degrees (° or degrees), unless explicitly indicated otherwise. Furthermore, C = crystalline state, N = nematic phase, NF = ferroelectric nematic phase, Sm = smectic phase (more especially SmA, SmB, etc.), SmAP= polar ferroelectric smectic A phase, Tg = glasstransition temperature and I = isotropic phase. The data between these symbols represent the transition temperatures. Δn denotes optical anisotropy (589 nm, 20°C), Δε the dielectric anisotropy (1 kHz, 20°C).

[0456] The physical, physicochemical and electro-optical parameters are determined by generally known methods, as described, inter alia, in the brochure " Merck Liquid Crystals - Licristal® - Physical Properties of Liquid Crystals - Description of the Measurement Methods", 1998, Merck KGaA, Darmstadt.

[0457] The occurrence of the ferroelectric nematic or smectic phase of the materials is identified using differential scanning calorimetry (DSC), via observation of the textures under a polarising microscope equipped with a hot-stage for controlled cooling resp. heating and additionally confirmed by temperature dependent determination of the dielectric properties. Transition temperatures are predominantly determined by detection of the optical behaviour under a polarising microscope.

[0458] The dielectric anisotropy As of the individual substances is determined at 20°C and 1 kHz. To this end, 5 to 10 % by weight of the substance to be investigated are measured dissolved in the dielectrically positive mixture ZLI-4792 (Merck KGaA), and the measurement value is extrapolated to a concentration of 100%. The optical anisotropy An is determined at 20°C and a wavelength of 589.3 nm by linear extrapolation.

[0459] The relative dielectric permittivity (εr) of the materials, especially in the ferroelectric nematic phase is directly determined by measuring the capacitance of at least one test cell containing the compound and having cell thickness of 250 μm with homeotropic and with homogeneous alignment, respectively.

[0460] Temperature is controlled by a Novocontrol Novocool system set to temperature gradients of + / -1 K / min; + / -2 K / min; + / -5 K / min; + / - 10 K / min applied to the sample cell. Capacitance is measured by a Novocontrol alpha-N analyzer at a frequency of 1 kHz or 10 Hz with a typical voltage < 50 mV down to 0.1 mV in order make sure to be below the threshold of the investigated compound. Measurements are performed both upon heating and upon cooling of the sample(s).

[0461] In the present application, unless explicitly indicated otherwise, the plural form of a term denotes both the singular form and the plural form, and vice versa. Further combinations of the embodiments and variants of the invention in accordance with the description also arise from the appended claims or from combinations of a plurality of these claims.

[0462] Examples

[0463] The present invention is described in detail by the following non-restrictive examples. Further combinations of the embodiments of the current invention and variants of the invention are also disclosed by the claims.

[0464] 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. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever. The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and / or operating conditions of this invention forthose used in the preceding examples.

[0465] From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.

[0466] This applies both to the media as compositions with their constituents, which can be groups of compounds as well as individual compounds, and also to the groups of compounds with their respective constituents, the compounds. Only in relation to the concentration of an individual compound relative to the medium as a whole does the term “comprise” mean: the concentration of the compound or compounds in question is preferably 1% or more, particularly preferably 2% or more, very particularly preferably 4% or more.

[0467] For the present invention, "<" means less than or equal to, preferably less than, and ">" means greater than or equal to, preferably greater than.

[0468] For the present invention

[0469]

[0470] denote trans- 1,4-cyclohexylene,

[0471]

[0472] denotes a mixture of both cis- and trans-1,4-cyclohexylene and

[0473]

[0474] denote 1,4-phenylene.

[0475] For the present invention, the expression "dielectrically positive compounds" means compounds having a As of > 1.5, the expression "dielectrically neutral compounds" means compounds having -1.5 < As < 1.5 and the expression "dielectrically negative compounds” means compounds having As < -1.5. The dielectric anisotropy of the compounds is determined here by dissolving 10% of the compounds in a liquid-crystalline host and determining the capacitance of the resultant mixture in each case in at least one test cell having a cell thickness of 20 pm with homeotropic and with homogeneous surface alignment at 1 kHz. The measurement voltage is typically 0.5 V to 1.0 V, but is always lower than the capacitive threshold of the respective liquid-crystal mixture (material) investigated. The host mixture used for dielectrically positive and dielectrically neutral compounds is ZLI-4792 and that used for dielectrically negative compounds is ZLI-2857, both from Merck KGaA, Germany. The values for the respective compounds to be investigated are obtained from the change in the dielectric constant of the host mixture after addition of the compound to be investigated and extrapolation to 100% of the compound employed. The compound to be investigated is dissolved in the host mixture in an amount of 10%. If the solubility of the substance is too low for this purpose, the concentration is halved in steps until the investigation can be carried out at the desired temperature.

[0476] The liquid-crystal media according to the invention may, if necessary, also comprise further additives, such as, for example, stabilisers in the usual amounts. The amount of these additives employed is preferably in total 0 % or more to 10 % or less, based on the amount of the entire mixture, particularly preferably 0.1 % or more to 6 % or less. The concentration of the individual compounds employed is preferably 0.1 % or more to 3 % or less. The concentration of these and similar additives is generally not taken into account when specifying the concentrations and concentration ranges of the liquid-crystal compounds in the liquid-crystal media.

[0477] For the purposes of the present invention, all concentrations are, unless explicitly noted otherwise, indicated in per cent by weight and relate to the corresponding mixture as a whole or mixture constituents, again a whole, unless explicitly indicated otherwise. In this context the term “the mixture” describes the liquidcrystalline medium.

[0478] The following symbols are used, unless explicitly indicated otherwise:

[0479] T(N, I) or clp.

[0480] clearing point [°C],

[0481] Dielectric properties at 1 kHz and preferably at 20°C or at the respective temperature specified:

[0482] ε⊥ dielectric susceptibility perpendicular to the director,

[0483] ε∥ dielectric susceptibility parallel to the director,

[0484] Δε dielectric anisotropy and especially for the screening data of single compounds.

[0485] And, in particular for the data from the screening of the respective compounds in the nematic host mixture ZLI-4792,:

[0486] neextraordinary refractive index measured at 20°C and 589 nm, n0ordinary refractive index measured at 20°C and 589 nm and An optical anisotropy measured at 20°C and 589 nm.

[0487] The following examples explain the present invention without limiting it. However, they show the person skilled in the art preferred mixture concepts with compounds preferably to be employed and the respective concentrations thereof and combinations thereof with one another. In addition, the examples illustrate the properties and property combinations that are accessible.

[0488] Definitions of structural elements by abbreviations for use in acronyms for chemical compounds: Table A: Ring elements

[0489] C

[0490] D

[0491] A

[0492] P

[0493] G

[0494] U

[0495] Y

[0496] P(F, CI)Y

[0497] np

[0498] n3f

[0499]

[0500]

[0501] Table B: Bridging units E -CH2-CH2- V -CH=CH- T -C≡C- W -CF2-CF2- B -CF=CF- Z -CO-O- Zl -O-CO- X -CF=CH- XI -CH=CF- 0 -CH2-O- Ol -O-CH2-

[0502]

[0503] Q -CF2-O- Ql -O-CF2-

[0504] Table C: End

[0505]

[0506] On the left individually or in combiOn the right individually or in comnation bination

[0507] -n- CnH2n+1- -n -CnH2n+1

[0508] -nO- CnH2n+1-O- -On -O- CnH2n+1

[0509] -V- CH2=CH- -V -CH=CH2

[0510] -nV- CnH2n+1-CH=CH- -nV -CnH2n-CH=CH2-Vn- CH2=CH- CnH2n- -Vn -CH=CH-CnH2n+1-nVm- CnH2n+1-CH=CH-CmH2m- -nVm - CnH2n-CH=CH-CmH2m+i-N- NEC- -N -CEN

[0511] -S- S=C=N- -S -N=C=S

[0512] -F- F- -F -F

[0513] -CL- Cl- -CL -Cl

[0514] -M- CFH2- -M -CFH2

[0515] -D- CF2H- -D -CF2H

[0516] -T- CF3- -T -CF3

[0517] -MO- CFH2O - -OM -OCFH2

[0518] -DO- CF2HO - -OD -OCF2H

[0519] -TO- CF3O - -OT -OCF3

[0520] -A- H-C=C- -A -C≡C-H

[0521] -nA- CnH2n+i-C≡C- -An -C≡C-CnH2n+i

[0522] -NA- NEC-C≡C- -AN -C≡C-CEN

[0523]

[0524] On the left only in combination On the right only in combination

[0525]

[0526] -...n... -CnH2n- -... M...- -CFH- -... M... -CFH- -... D...- -CF2- -... D... -CF2- -... V...- -CH=CH- -... V... -CH=CH- -... Z...- -CO-O- -... Z... -CO-O- -... Zl...- -o-co- -... Zl... -o-co- -... K...- -CO- -... K... -CO- -... W...- -CF=CF- -... W... -CF=CF-in which n and m are each integers, and the three dots are placeholders for other abbreviations from this table.

[0527] Besides the compounds of formulae IA, IB and IC-1 / -2 / -3 the mixtures according to the invention preferably comprise one or more compounds of the compounds mentioned below.

[0528] The following abbreviations are used:

[0529] (n, m, k and I are, independently of one another, each an integer, preferably 1 to 9 preferably 1 to 7, k and I possibly may be also 0 and preferably are 0 to 4, more preferably 0 or 2 and most preferably 2, n preferably is 1, 2, 3, 4 or 5, in the combination “-nO-” it preferably is 1, 2, 3 or 4, preferably 2 or 4, m preferably is 1, 2, 3, 4 or 5, in the combination “-Om” it preferably is 1, 2, 3 or 4, more preferably 2 or 4. The combination “-IVm” preferably is “2V1”.)

[0530] For the present invention and in the following examples, the structures of the liquid-crystal compounds are indicated by means of acronyms, with the transformation into chemical formulae taking place in accordance with Tables A to C above. All radicals CnH2n+i, CmH2m+1and C1H21+1 or CnH2n, CmH2mand CiH2iare straight-chain alkyl radicals or alkylene radicals, in each case having n, m and I C atoms respectively. Preferably n, m and I are independently of each other 1, 2, 3, 4, 5, 6, or 7. Table A shows the codes for the ring elements of the nuclei of the compound, Table B lists the bridging units, and Table C lists the meanings of the symbols for the left- and right-hand end groups of the molecules. The acronyms are composed of the codes for the ring elements with optional linking groups, followed by a first hyphen and the codes for the left-hand end group, and a second hyphen and the codes for the right-hand end group. Table D shows illustrative structures of compounds together with their respective abbreviations.

[0531] Table D

[0532] Exemplary, preferred compounds of formula IA

[0533]

[0534] Exemplary, preferred compounds of formula IB

[0535]

[0536] GUQGU-n-N Exemplary, preferred compounds of formula IC-1

[0537] GUQU-n-N GUZU-n-N

[0538]

[0539] Exemplary, preferred compounds of formula IC-3

[0540]

[0541] Exemplary, other compounds of formula I

[0542]

[0543] UZPUQU-n-N

[0544] Table E

[0545] Table E shows illustrative reactive mesogenic compounds (polymerisable compounds) with two or more polymerisable groups, which can be used in the LC media in accordance with the present invention.

[0546]

[0547] RM-1 RM-2

[0548]

[0549] RM-15

[0550] RM-17 RM-18

[0551] RM-19 RM-20

[0552] RM-21 RM-22

[0553] RM-23 RM-24

[0554]

[0555] RM-25 RM-26 RM-27 RM-28 RM-29 RM-30 RM-31 RM-33 RM-35 RM-36

[0556]

[0557] RM-38 RM-48

[0558]

[0559] RM-49 RM-50

[0560]

[0561] RM-58 RM-59 RM-60 RM-61 RM-62

[0562] RM-66 RM-67

[0563] RM-68

[0564]

[0565] RM-70 RM-71 RM-77

[0566] RM-81

[0567] RM-83

[0568]

[0569] RM-84 RM-85

[0570] RM-91

[0571]

[0572] RM-92 RM-93 RM-94 RM-95 RM-96 RM-97 RM-98 RM-99

[0573] RM-100

[0574]

[0575] RM-101 RM-102 RM-103 RM-104

[0576]

[0577] RM-105 RM-106 RM-107 RM-108 RM-109 RM-110 RM-111 RM-112 RM-113 RM-114

[0578]

[0579] RM-115 RM-116 RM-117 RM-118 RM-119 RM-120 RM-121 RM-122

[0580]

[0581] RM-123 RM-124 RM-125 RM-126

[0582]

[0583] RM-127 RM-128 RM-129 RM-130 RM-131 RM-132 RM-133 RM-134 RM-135 RM-136

[0584]

[0585] RM-138

[0586] RM-137 RM-139 RM-140 RM-141 RM-142 RM-143 RM-144 RM-145

[0587]

[0588] RM-146 RM-147 RM-148 RM-149 RM-150

[0589] RM-151 RM-152

[0590] RM-153

[0591] RM-154 RM-155 RM-156

[0592]

[0593] RM-157 RM-158

[0594]

[0595] RM-159 RM-160 RM-161 RM-162 RM-163 RM-164 RM-165 RM-166 RM-167 RM-168 RM-169 RM-170 RM-171 RM-172 RM-173 RM-174 RM-175 RM-176

[0596]

[0597] RM-177 RM-178 RM-181 RM-182

[0598] RM-183 RM-184

[0599]

[0600] Table F

[0601] Table F shows illustrative reactive mesogenic compounds (polymerisable compounds) with one polymerisable groups, which can be used in the LC media in accordance with the present invention.

[0602]

[0603] Mixture Examples

[0604] Mixtures representing ferroelectric nematic PN-LCs are prepared by combining a ferroelectric nematic liquid crystal host mixture and a polymerizable component and optionally further components and additives as indicated. Mixtures representing ferroelectric smectic A PN-LCs are prepared by combining a ferroelectric smectic liquid crystal host mixture analogously.

[0605] The following liquid crystal host mixtures (Base Mixtures) are used for the preparation of exemplary mixtures. The mixtures are ferroelectric nematic at ambient temperature unless described differently.

[0606] Base mixture 1

[0607] The following mixture (M-1) is prepared.

[0608] Mixture M-1

[0609] Composition Physical properties

[0610] Compound Concentration

[0611] T(N, I) = 81 °C No. Abbreviation / % by weight

[0612] T(FerroN)c = 32 °C 1 DUUQU-3-F 10.0

[0613] 2 DUUQU-4-F 10.0

[0614] 3 DUUQU-5-F 5.0

[0615] 4 GUUQU-3-N 6.0

[0616] 5 GUUQU-4-N 10.0

[0617] 6 GUUQU-5-N 3.0

[0618] 7 GUZU-4-N 15.0

[0619] 8 GUZU-5-N 10.0

[0620] 9 GUQU-4-N 7

[0621] 10 GUQU-3-N 12

[0622] 11 GUQU-2-N 12

[0623]

[0624] Σ 100.0

[0625] c) value upon cooling,

[0626] Base mixture 2 The following mixture (M-2) is prepared.

[0627] Mixture M-1

[0628] Composition Physical properties

[0629] Compound Concentration

[0630] T(N, I) = 97 °C No. Abbreviation / % by weight

[0631] T(FerroN)c = 52 °C 1 DUUQU-3-F 18.0

[0632] 2 DUUQU-4-F 18.0

[0633] 3 DUUQU-5-F 7.0

[0634] 4 GUUQU-3-N 10.0

[0635] 5 GUUQU-4-N 13.0

[0636] 6 GUUQU-5-N 4.0

[0637] 7 GUZU-4-N 15.0

[0638] 8 GUQU-4-N 15.0

[0639]

[0640] Σ 100.0

[0641] c) value upon cooling,

[0642] Base Mixture 3

[0643] The following mixture (M-3) is prepared.

[0644] Mixture M-3

[0645] Composition Physical properties

[0646] Compound Concentration

[0647] T(N, I) = 97 °C No. Abbreviation / % by weight

[0648] T(FerroN)c = 49 °C 1 DUUQU-3-F 16.0

[0649] 2 DUUQU-4-F 16.0

[0650] 3 DUUQU-5-F 7.0

[0651]

[0652] 4 GUUQU-3-N 10.0 5 GUUQU-4-N 13.0

[0653] 6 GUUQU-5-N 4.0

[0654] 7 GUZU-4-N 13.0

[0655] 8 GUZU-5-N 8.0

[0656] 9 GUQU-4-N 13.0

[0657]

[0658] Σ 100.0

[0659] c) value upon cooling,

[0660] Base Mixture 4

[0661] The following mixture (M-4) is prepared.

[0662] Mixture M-4

[0663] Composition Physical properties

[0664] Compound Concentration

[0665] T(N, I) = 96 °C No. Abbreviation / % by weight

[0666] T(FerroN)c = 41 °C 1 DUUQU-3-F 15.0

[0667] 2 DUUQU-4-F 14.0

[0668] 3 DUUQU-5-F 6.0

[0669] 4 GUUQU-3-N 9.0

[0670] 5 GUUQU-4-N 12.0

[0671] 6 GUUQU-5-N 4.0

[0672] 7 GUZU-4-N 15.0

[0673] 8 GUZU-5-N 10.0

[0674] 9 GUQU-4-N 15.0

[0675]

[0676] Σ 100.0

[0677] c) value upon cooling,

[0678] These is the highest value of the relative dielectric permittivity εrfor any physical matter known to the authors so far. Base Mixture 5

[0679] The following mixture (M-5) is prepared.

[0680] Mixture M-5

[0681] Composition Physical properties

[0682] Compound Concentration

[0683] T(N, I) = 91 °C No. Abbreviation / % by weight

[0684] T(FerroN)c = 33 °C 1 DUUQU-3-F 14.0

[0685] 2 DUUQU-4-F 13.0

[0686] 3 DUUQU-5-F 5.0

[0687] 4 GUUQU-3-N 8.0

[0688] 5 GUUQU-4-N 11.0

[0689] 6 GUUQU-5-N 3.0

[0690] 7 GUZU-4-N 17.0

[0691] 8 GUZU-5-N 12.0

[0692] 9 GUQU-4-N 17.0

[0693]

[0694] Σ 100.0

[0695] c) value upon cooling,

[0696] Base Mixture 6

[0697] The following mixture (M-6) is prepared.

[0698] Mixture M-6

[0699] Composition Physical properties

[0700] Compound Concentration

[0701] T(N, I) = 88 °C No. Abbreviation / % by weight

[0702] T(FerroN)c = 25 °C 1 DUUQU-3-F 13.0

[0703] 2 DUUQU-4-F 11.0

[0704] 3 DUUQU-5-F 4.0

[0705]

[0706] 4 GUUQU-3-N 7.0 GUUQU-4-N 10.0 GUUQU-5-N 3.0 GUZU-4-N 19.0 GUZU-5-N 14.0 GUQU-4-N 19.0

[0707]

[0708] Σ 100.0c) value upon cooling, Base Mixture 7

[0709] The following mixture (M-7) is prepared.

[0710] Mixture M-7

[0711] Composition Physical properties

[0712] Compound Concentration

[0713] T(N, I) = 87 °C No. Abbreviation / % by weight

[0714] T(FerroN)c = 21 °C 1 DUUQU-3-F 12.0

[0715] 2 DUUQU-4-F 10.0

[0716] 3 DUUQU-5-F 4.0

[0717] 4 GUUQU-3-N 6.0

[0718] 5 GUUQU-4-N 10.0

[0719] 6 GUUQU-5-N 3.0

[0720] 7 GUZU-4-N 20.0

[0721] 8 GUZU-5-N 15.0

[0722] 9 GUQU-4-N 20.0

[0723]

[0724] Σ 100.0

[0725] c) value upon cooling, Base Mixture 8

[0726] The following mixture (M-8) is prepared.

[0727] Mixture M-8

[0728] Composition Physical properties

[0729] Compound Concentration

[0730] T(N, I) = 88 °C No. Abbreviation / % by weight

[0731] T(FerroN)c = 35 °C 1 DUUQU-3-F 12.0

[0732] 2 DUUQU-4-F 12.0

[0733] 3 DUUQU-5-F 4.0

[0734] 4 GUUQU-3-N 7.0

[0735] 5 GUUQU-4-N 11.0

[0736] 6 GUUQU-5-N 3.0

[0737] 7 GUZU-4-N 15.0

[0738] 8 GUZU-5-N 10.0

[0739] 9 GUQU-4-N 15.0

[0740] 10 UUZU-4-N 3.0

[0741] 11 UUZU-5-N 3.0

[0742] 12 UUQU-5-N 5.0

[0743]

[0744] Σ 100.0

[0745] c) value upon cooling, Base Mixture 9

[0746] The following mixture (M-9) is prepared.

[0747] Mixture M-9

[0748] Composition Physical properties

[0749] Compound Concentration

[0750] T(N, I) = 88 °C No. Abbreviation / % by weight

[0751] T(FerroN)c = 39 °C 1 DUUQU-3-F 12.0

[0752] 2 DUUQU-4-F 12.0

[0753] 3 DUUQU-5-F 4.0

[0754] 4 GUUQU-3-N 7.0

[0755] 5 GUUQU-4-N 11.0

[0756] 6 GUUQU-5-N 3.0

[0757] 7 GUZU-4-N 13.0

[0758] 8 GUZU-5-N 8.0

[0759] 9 GUQU-4-N 13.0

[0760] 10 UUZU-4-N 5.0

[0761] 11 UUZU-5-N 5.0

[0762] 12 UUQU-5-N 7.0

[0763]

[0764] Σ 100.0

[0765] c) value upon cooling, Base Mixture

[0766] The following mixture (M-10) is prepared.

[0767] Mixture M-10

[0768] Composition Physical properties

[0769] Compound Concentration

[0770] T(N, I) = 89 °C No. Abbreviation / % by weight

[0771] T(FerroN)c = 44 °C 1 DUUQU-3-F 12.0

[0772] 2 DUUQU-4-F 12.0

[0773] 3 DUUQU-5-F 4.0

[0774] 4 GUUQU-3-N 7.0

[0775] 5 GUUQU-4-N 11.0

[0776] 6 GUUQU-5-N 3.0

[0777] 7 GUZU-4-N 11.0

[0778] 8 GUZU-5-N 6.0

[0779] 9 GUQU-4-N 11.0

[0780] 10 UUZU-4-N 7.0

[0781] 11 UUZU-5-N 7.0

[0782] 12 UUQU-5-N 9.0

[0783]

[0784] Σ 100.0

[0785] c) value upon cooling, Base Mixture 11

[0786] The following mixture (M-11) is prepared.

[0787] Mixture M-11

[0788] Composition Physical properties

[0789] Compound Concentration

[0790] T(N, I) = 82 °C No. Abbreviation / % by weight

[0791] T(FerroN)c = 44 °C 1 DUUQU-3-F 10.0

[0792] 2 DUUQU-4-F 12.0

[0793] 3 DUUQU-5-F 4.0

[0794] 4 GUUQU-3-N 4.0

[0795] 5 GUUQU-4-N 11.0

[0796] 6 GUUQU-5-N 3.0

[0797] 7 GUZU-4-N 11.0

[0798] 8 GUZU-5-N 6.0

[0799] 9 GUQU-4-N 10.0

[0800] 10 UUZU-4-N 7.0

[0801] 11 UUZU-5-N 7.0

[0802] 12 UUQU-3-N 5.0

[0803] 12 UUQU-4-N 7.0

[0804] 13 UUQU-5-N 3.0

[0805]

[0806] Σ 100.0

[0807] c) value upon cooling, Base Mixture 12

[0808] The following mixture (M-12) is prepared.

[0809] Mixture M-12

[0810] Composition Physical properties

[0811] Compound Concentration

[0812] T(N, I) = 107 °C No. Abbreviation / % by weight

[0813] T(FerroN)c = 30 °C 1 MUU-4-N 10.0

[0814] 2 MUU-5-N 5.0

[0815] 3 UMU-4-N 10.0

[0816] 4 UMU-5-N 5.0

[0817] 5 UMU-6-N 5.0

[0818] 6 GUUQU-3-N 15.0

[0819] 7 GUUQU-4-N 10.0

[0820] 8 GUUQU-5-N 10.0

[0821] 9 DUUQU-3-F 10.0

[0822] 10 DUUQU-4-F 10.0

[0823] 11 DUUQU-5-F 10.0

[0824]

[0825] Σ 100.0

[0826] c) value upon cooling, Base Mixture 13

[0827] The following mixture (M-13) is prepared.

[0828] Mixture M-13

[0829] Composition Physical properties

[0830] Compound Concentration

[0831] T(N, I) = 108 °C No. Abbreviation / % by weight

[0832] T(FerroN)c = 28 °C 1 MUU-4-N 7.0

[0833] 2 MUU-5-N 4.0

[0834] 3 UMU-4-N 7.0

[0835] 4 UMU-5-N 4.0

[0836] 5 UMU-6-N 3.0

[0837] 6 GUUQU-3-N 15.0

[0838] 7 GUUQU-4-N 13.0

[0839] 8 GUUQU-5-N 12.0

[0840] 9 DUUQU-3-F 7.0

[0841] 10 DUUQU-4-F 9.0

[0842] 11 DUUQU-5-F 4.0

[0843] 12 GUZU-4-N 5.0

[0844] 13 GUZU-5-N 5.0

[0845] 14 GUQU-4-N 5.0

[0846]

[0847] Σ 100.0

[0848] c) value upon cooling, Base Mixture 14

[0849] The following mixture (M-14) is prepared.

[0850] Mixture M-14

[0851] Composition Physical properties

[0852] Compound Concentration

[0853] T(N, I) = 104 °C No. Abbreviation / % by weight

[0854] T(FerroN)c = 30 °C 1 MUU-5-N 4.0

[0855] 2 UMU-4-N 7.0

[0856] 3 UMU-5-N 4.0

[0857] 4 GUUQU-3-N 13.0

[0858] 5 GUUQU-4-N 13.0

[0859] 6 GUUQU-5-N 12.0

[0860] 7 DUUQU-3-F 9.0

[0861] 8 DUUQU-4-F 9.0

[0862] 9 DUUQU-5-F 4.0

[0863] 10 GUZU-4-N 10.0

[0864] 11 GUZU-5-N 5.0

[0865] 12 GUQU-4-N 10.0

[0866]

[0867] Σ 100.0

[0868] c) value upon cooling, Base Mixture 15

[0869] The following mixture (M-15) is prepared.

[0870] Mixture M-15

[0871] Composition Physical properties

[0872] Compound Concentration

[0873] T(N, I) = 103 °C No. Abbreviation / % by weight

[0874] T(FerroN)c = 20 °C 1 MUU-5-N 6.0

[0875] 2 UMU-4-N 8.0

[0876] 3 UMU-5-N 6.0

[0877] 4 GUUQU-3-N 13.0

[0878] 5 GUUQU-4-N 13.0

[0879] 6 GUUQU-5-N 12.0

[0880] 7 DUUQU-3-F 7.0

[0881] 8 DUUQU-4-F 7.0

[0882] 9 DUUQU-5-F 3.0

[0883] 10 GUZU-4-N 10.0

[0884] 11 GUZU-5-N 5.0

[0885] 12 GUQU-4-N 10.0

[0886]

[0887] Σ 100.0

[0888] c) value upon cooling, Base Mixture 16

[0889] The following mixture (M-16) is prepared.

[0890] Mixture M-16

[0891] Composition Physical properties

[0892] Compound Concentration

[0893] T(N, I) = 42 °C No. Abbreviation / % by weight

[0894] T(FerroN)c = °C 1 UUQU-2-N 10

[0895] 2 UUQU-3-N 15

[0896] 3 UUQU-4-N 35

[0897] 4 UUQU-5-N 15

[0898] 5 UUQU-6-N 5

[0899] 6 UUZU-4-N 10

[0900] 7 UUQU-2-N 10

[0901] 8 UUZU-5-N 10.0

[0902]

[0903] S 100.0

[0904] c) value upon cooling,

[0905] Base Mixture 17

[0906] The following smectic mixture (M-17) is prepared.

[0907] Mixture M-17

[0908] Composition Physical properties

[0909] Compound Concentration

[0910] T(S, I) = °C No. Abbreviation / % by weight

[0911] 1 DUUQU-3-F 10.08

[0912] 2 DUUQU-4-F 9.36

[0913] 3 DUUQU-5-F 3.60

[0914] 4 GUUQU-3-N 5.76

[0915]

[0916] 5 GUUQU-4-N 7.92 6 GUUQU-5-N 2.16

[0917] 7 GUZU-4-N 12.24

[0918] 8 GUZU-5-N 8.64

[0919] 9 GUQU-4-N 12.24

[0920] 10 PPTUI-3-2 8.00

[0921] 11 AUUQU-2-N 10.0

[0922] 12 DUZGU-3-F 10.0

[0923]

[0924] S 100.0

[0925] c) value upon cooling,

[0926] Base Mixture 18

[0927] The following smectic mixture (M-18) is prepared.

[0928] Mixture M-18

[0929] Composition Physical properties

[0930] Compound Concentration

[0931] T(S, I) = 98 °C No. Abbreviation / % by weight

[0932] 1 DUUQU-3-F 12.6

[0933] 2 DUUQU-4-F 11.7

[0934] 3 DUUQU-5-F 4.5

[0935] 4 GUUQU-3-N 7.2

[0936] 5 GUUQU-4-N 9.9

[0937] 6 GUUQU-5-N 2.7

[0938] 7 GUZU-4-N 15.3

[0939] 8 GUZU-5-N 10.8

[0940] 9 GUQU-4-N 15.3

[0941] 10 PPTUI-3-2 10.0

[0942]

[0943] Σ 100.0

[0944] c) value upon cooling, Mixture Examples

[0945] Liquid crystal PN-LCs are prepared consisting of the foregoing Base Mixtures and 5 to 20 % by weight of a polymerizable component selected from one or more compounds from foregoing Table E and the following Table 1.

[0946] Table 1. Polymerizable compounds for ferroelectric nematic / smectic PN-LCs:

[0947]

[0948]

[0949]

[0950] IRG-651 (initiator) is added at a ratio of 2 % by weight of the polymerizable compounds (about 0.3 to 0.4 % by weight in total).

[0951] Mixture Examples for PN-LC are detailed in Table 2 below.

[0952] To test if the alignment process is successful, test cells (PI less, 6 pm) are filled with the test mixture by using an oven at 80°C. Before filling the mixtures themselves are placed in the oven as well to avoid filling while the mixture is in a ferroelectric (NF, SmAP) phase. After complete filling the cells are taken out of the oven, cables are soldered, and phases and alignment of each test cell are determined under the microscope.

[0953] The cells were cured with a MH UV lamp, placed in a UVA Cube 2000 from Hönle, were the temperature, time, UV dose and voltage are controlled. For the polymerization the intensity of the UV lamp is 2 mW / cm2and duration is 30 min. Therefore, a neutral density filter (ND100) and a 320 nm cut-off filter was used. The temperature was controlled at 20°C to 50 °C, so curing the mixture initiates in the nematic (N) or N2phase a few degrees above the upper transition temperature of the NFphase. The voltage is 2, 3 or 4 V, as indicated, DC or AC (square wave) at 0.0083 Hz (~1 min-1). In case of AC 0.0083Hz the UV light was turned on only in the positive frame (1 min) and in the negative frame (1 min) UV light was turned off.

[0954] The resulting mixtures form vertically aligned PN-LCs. Selected results are presented according to the following mixture table (Table 2).

[0955] Table 2. Mixture Examples for PN-LCs:

[0956] No. Base Mixture RM other Result state1)

[0957] (weight %) (weight %)

[0958] 1 M-1 RM-64 (20 %) - X, nematic 2 M-1 RM-64 (10 %) RA-2 (10 %) X, nematic 3 M-1 RM-64 (10 %) RA-2 (5 %) X, nematic 4 M-1 - RA-2 (10 %) O, nematic 5 M-1 RM-64 (10 %) RA-3 (10 %) X, nematic 6 M-1 RM-64 (15 %) RA-3 (5 %) X, nematic 7 M-1 RM-64 (10 %) RA-3 (5 %) X, nematic 8 M-1 RM-184 (10 %) RA-4 (5 %) X, nematic 9 M-1 RM-64 (5 %) RA-3 (5 %) O, nematic 10 M-1 RM-184 (10 %) RA-2 (10 %) X, nematic 11 M-1 RM-184 (15 %) RA-2 (5 %) X, nematic 12 M-1 RM-184 (10 %) RA-2 (5 %) X, nematic 13 M-1 RM-184 (10 %) RA-2 (5 %) ~, nematic 14 M-1 RM- 184 (5 %) RA-2 (5 %) O, nematic 15 M-16 RM- 184 (10 %) RM-64 (10 %) X, nematic 16 M-16 RM- 184 (10 %) RM-64 (5 %) ~, nematic 17 M-17 RM-64 (5 %) RA-3 (10 %) X, smectic

[0959]

[0960] 18 M-17 RM-64 (6.5 %) RA-3 (13.5 %) X, smectic1)After UV, 3 V AC for no. 1 to 16, 4 V DC for no. 17 and 18. Evaluation between crossed polarisers. X: Pure black state, black-grey, O: grey state.

[0961] The examples resulting in pure black state (“X”) have strong alignment with the director aligned vertically combined with low scattering.

[0962] Evaluation of PN-LCs (methods a) to h)): a) Microscopic studies

[0963] To study the optical properties of the NF-LCs, the materials were filled in 4-6 pm thick LC cells (made at Merck facilities) coated with polyimide, where the director n was aligned with a small to non-existent pre-tilt to the rubbing direction. In addition, both sides of the cell are coated with a conductive ITO layer. The studies were performed with a Leica DM 2700 P polarized light microscope, equipped with an Instec heating stage HCS302 controlled by a mk1000 temperature unit. Pictures were taken by a pixeLink PL-D752CU video camera.

[0964] b) X-Ray diffraction

[0965] Small angle X-ray measurements (SAXS) were performed with the SAXSess MC2 system (Anton Paar) and a Mythen 2 K detector (Dectris). The X-ray radiation (Cu-Ka, 2 = 0.15418 nm) was generated by an ISO-DEBYEFLEX 3003 X-ray generator (Seifert).

[0966] Wide angle X-ray measurements were performed with the Bruker AXS NanoSTAR system (Cu-Ka radiation, Goebel mirror monochromator, 100 pm point beam collimator, VANTEC-500 detector), equipped with a heating stage controlled by 2216e (Eurotherm) and a cooling unit Unichiller from Huber. The samples were placed in 0.7 mm outer diameter capillaries out of Gias #14 (Hilgenberg).

[0967] c) Electro-Optic Measurements

[0968] To measure the response of the NF-PN-LC to electric stimuli, the polymerized PN-LC is made in a cell with ITO electrodes on the substrates. The temperature was controlled by a TMS 94 (LINKAM) connected to a LTS 350 hot stage (LINKAM). The spontaneous electric polarization was obtained from recording the current response while applying a triangular AC voltage with a frequency of 20 Hz [K. Miyasato, S. Abe, H. Takezoe, A. Fukuda, E. Kuze, Jpn. J. Appl. Phys. 1983, 22, L661-L663.].

[0969] Result of evaluations:

[0970] The coexistence of ferroelectric nematic or smectic phase and PN-LC (successful polymer stabilization) was proven via POM (characteristic textures), SAXS (characteristic scattering profiles, typical scattering maxima from the NFphase can be observed), dielectric spectroscopy (high dielectric constant in the NFphase) and Ps measurements (proof of ferroelectricity of NF-PN-LCs). In comparison to the non-polymerized NF-LC it was shown that the spontaneous polarization decreases with increasing polymer content, but is still present up to very high polymer contents up to about 20 wt.%. The broad range of polymer concentration that leads to a ferroelectric PN-LC is advantageous since also the mechanical and thermal properties are altered with changing polymer amount (higher mechanical stability and elastic modulus). Thus a material with tailored properties for a given application is possible.

[0971] Device Example: Piezoelectric element and its electric response

[0972] A mixture of 10% RA-1 containing 2 wt% of IRG-651 and 90% Mixture M1 is introduced into a 6 micron gap cell with Sharp PI-4 homeotropic alignment layers to obtain homeotropic alignment. The cell is cooled to 50°C, then cured for 5, 7.5 or 15 minutes at 15, 10 or 5 mW / cm2respectively. The cell is cooled slowly to room temperature by which temperature it has undergone a phase transition to the ferroelectric phase. The homeotropic alignment is maintained successfully after the phase transition.

[0973] M1: Cr<8 NF32 N2 44 N1 80 I

[0974] RA-1: Cr 149 N 182 I (polymerises)

[0975] Mixture, approximate phase behaviour (prior to polymerization):

[0976] NF 25 N242 N1 78 I

[0977] After polymerization the N-l and NF-N2 transition temperatures are about 1-2 degrees lower.

[0978] Piezoelectric response test:

[0979] Applying light to moderate pressure to the cell with 1 cm2active area gives a good piezo type response of over 200 mV on an oscilloscope confirming the possible use for energy harvesting.

[0980] The Piezo response is observed by dropping a weight (mass 3.8 g, diameter 7 mm) from a height of 1.5 cm onto the liquid crystal cell (1.1 mm glass, 6 micron cell gap) and observing the effect directly using a HP oscilloscope. A reference cell containing a conventional nematic liquid crystal E7 (PP-7-N; liquid crystal available from Merck KGaA and other suppliers) gives no response.

Claims

1. Patent Claims1. A method of aligning a ferroelectric nematic or a ferroelectric smectic A liquid crystal mixture between substrates in a vertical state of alignment relative to the substrates by bringing the liquid crystal mixture containing 0.2 to 25 % of a polymerizable component into a non-ferroelectric phase with vertical alignment at a temperature above the ferroelectric phase, polymerizing the polymerizable component to yield a polymer network liquid crystal phase while the mixture enters the ferroelectric phase and while the vertical alignment is maintained.

2. A method of aligning a ferroelectric liquid crystal mixture according to claim 1, where the non-ferroelectric phase is aligned vertically by alignment layers or by an electric field.

3. A method of aligning a ferroelectric liquid crystal mixture according to claim 2, where the vertical alignment is introduced by a DC or alternating DC electric voltage applied to electrodes on the substrate surfaces.

4. A method of aligning a ferroelectric liquid crystal mixture according to claim 3, where a poled vertical alignment is introduced, which remains after polymerization and removal of the electric voltage.

5. A method according to any of claims 1 to 4, where the polymerizable component comprises a compound of formula M7.Ra-B1-(Zm-B2)m-RbM8.wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings9.Ra, Rbindependently denote P, P-Sp-, H, F, Cl, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, SF5 or straight-chain or branched alkyl having 1 to 25 C atoms, in which, in addition, one or more non- adjacent CH2groups may each be replaced, independently of one another, by -C(R°)=C(R00)-, -C=C-,10.-N(R00)-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and / or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F, Cl, Br, I, CN, P or P-Sp-, where, if B1and / or B2contain a saturated C atom,11.Raand / or Rbmay also denote a radical which is spiro-linked to this saturated C atom,12.wherein at least one of the radicals Raand Rbdenotes or contains a group P or P-Sp-,13.P a polymerizable group,14.Sp a spacer group, which is optionally substituted by L, or a single bond,15.B1, B2an aromatic, heteroaromatic, alicyclic or heterocyclic group, preferably having 4 to 25 ring atoms, which may also contain fused rings, and which is unsubstituted, or mono- or polysubstituted by L,16.Zm-O-, -S-, -CO-, -CO-O-, -OCO-, -O-CO-O-, -OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -(CH2)m-, -CF2CH2-, -CH2CF2-, -(CF2)ni-, -CH=CH-, -CF=CF-, -CH=CF-, - CF=CH-, -C=C-, -CH=CH-COO-, -OCO-CH=CH-, -CH2CH2-CO-O-, O-CO-CH2-CH2-, -CR°R00- or a single bond,17.R°, R00H or alkyl having 1 to 12 C atoms,18.m 0, 1, 2, 3 or 4,19.n1 1, 2, 3 or4,20.L P, P-Sp-, OH, CH2OH, F, Cl, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, -C(=O)N(RX)2, -C(=O)Y1, -C(=O)RX, -N(RX)2, optionally substituted silyl, optionally substituted aryl having 6 to 20 C atoms, or straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkyl carbonyl oxy or alkoxycarbonyloxy having up to 25 C atoms, in which, in addition, one or more H atoms may be replaced by F, Cl, P or P-Sp-, Y1halogen,21.RxP, P-Sp-, H, halogen, straight-chain, branched or cyclic alkyl having up to 25 C atoms, in which, in addition, one or more non-adjacent CH2groups may be replaced by -O-, -S-, -CO-, -CO-O-, -O- CO-, -O-CO-O- in such a way that O and / or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F, Cl, P or P-Sp-, an optionally substituted aryl or aryloxy group having 6 to 40 C atoms, or an optionally substituted heteroaryl or heteroaryloxy group having 2 to 40 C atoms.

6. A method according to any of claims 1 to 5, where the polymerizable component comprises a compound of formula23.Ra-(Ba-Zm) R25. 27.wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings28.Rais P or-Sp-P,29.Zm, and L are defined as for structure M in claim 5,30.Baan aromatic, heteroaromatic, alicyclic or heterocyclic group, preferably having 4 to 25 ring atoms, which may also contain fused rings, and which is unsubstituted, or mono- or polysubstituted by L, L1, L2independently denote H or F,31.Znis -CO-O- or-CF20-,32.Rbis -CN, -NO2, F, Cl, CF3, -OCF3or-NCS,33.n is 0, 1, 2 or 3, and34.r independently is 0 or 1.

7. A method according to any of claims 1 to 6, where polymerization is initiated at a temperature 1 to 10 degrees above the transition temperature of the NF- N transition.

8. A method according to any of claims 1 to 7, where the polymerizable component comprises one or more compounds with two or more polymerizable groups P.

9. A liquid crystal device comprising a polymer network liquid crystal (PN-LC) between two substrates exhibiting a ferroelectric nematic or a polar ferroelectric smectic A phase, wherein the phase of the PN-LC is aligned vertically relative to the substrate plane between the substrates.

10. A piezoelectric element comprising a liquid crystal device as in claim 9, which comprises electrodes on one or two of the substrates.

11. A polymer network liquid crystal which exhibits a ferroelectric nematic phase or a ferroelectric smectic A phase.

12. Polymer network liquid crystal according to claim 11 exhibiting a ferroelectric nematic or a ferroelectric smectic A phase at least at a temperature from 10°C to 30°C.

13. Liquid crystal polymer network according to claim 11 exhibiting a ferroelectric nematic or a ferroelectric smectic A phase at least over a temperature range of 20 Kelvin.

14. A ferroelectric nematic or ferroelectric smectic A liquid crystal mixture comprising a polymerizable component comprising 0.2 to 25 % by weight of one or more polymerizable compounds of formula M as defined in claim 5 or a polymerized component from said polymerizable component.

15. A liquid crystal mixture according to claim 14 comprising a polymerizable compound of formula M having two or more polymerizable groups P.

16. A liquid crystal mixture according to claim 14 or 15 comprising1-15% of a polymerizable compound of formula M-A according to claim 6.

17. Liquid crystal mixture according to one or more of claims 14 to 16 comprising one or more compounds of formula I,46. 48.n is 0, 1, 2 or 3, R1is an alkyl radical having 1 to 12 C atoms, preferably 1 to 8, more preferably 1 to 6 and most preferably 1 to 5 C atoms, where, in addition, one or more CH2 groups in these radicals may in each case be replaced, independently of one another, by -C≡C-, -CF2-O-, -OCF2-, -CH=CH-,, “OO-,50.

51. d?, ~^j / ~, -O-, -S-, -(CO)-O- or -O-(CO)- in such a way that O / S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen, or denotes H,52.X is CN, F, CF3, -OCF3, -NCS, Cl,53.L1is H orCH3,54.Z1is CF2O or -(CO)-O- or a single bond,55.and56.Z2, Z3independently are CF2O, -(CO)-O- or a single bond.

18. Use of the polymer network liquid crystal according to claim 11 for energyharvesting applications, electro-mechanic devices including electric generators, mechanical sensors and actuators, for electro-optical purposes, for non-linear optic elements or for capacitors.

19. Piezoelectric element comprising a ferroelectric nematic or ferroelectric smectic A polymer network liquid crystal between electrodes.

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