LCD Display

Abstract

The present invention relates to a method for manufacturing a liquid crystal display (LCD) in polymer-stabilized ultrafast (PS-UF) twisted nematic (TN) mode, to an LCD obtained by the method and to an LC medium used therein.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a polymer-stabilized (PS) twisted nematic (TN) mode liquid crystal display (LCD), to an LCD obtained by this method and to an LC medium used therein. Background Art

[0002] Currently used LCDs offer many good properties, such as low weight, flatness, and wide viewing angles. However, the response time of prior art LCDs is generally not fast enough, thus posing an obstacle to their implementation in various novel applications such as gaming and virtual reality (VR). In order to make color sequential technology possible, a response time of about 1 millisecond is required. If such a fast response time could be achieved, LCDs could potentially become a low-power technology, thereby extending the battery life of mobile devices. Therefore, LCD manufacturers are investing a lot of effort in reducing the response time of LCDs.

[0003] However, to date, no feasible solution has been developed for LCD modes with ultrafast response times that are also suitable for mass production. For example, currently used LCD modes such as TN, multi-domain vertical alignment (MVA), in-plane switching (IPS), and fringe field switching (FFS) modes cannot fully meet the requirements of fast response time and high transmittance due to their cell configurations. In order to achieve this goal, new LCD modes are therefore needed.

[0004] Recently, a solution to this problem has been proposed by using short pitch TN LCDs to achieve fast response times. TN LCDs are doped with chiral nematic LC materials to achieve a shorter pitch (p) of the twisted nematic LC molecules, thereby achieving a faster decay response time (t d ).

[0005] However, when the ratio of the cell gap (d) to the pitch (p), d / p, is greater than 0.5, the 270° super twisted nematic (STN) LC director configuration is energetically more stable than the 90° TN LC director configuration designed for short pitch length, while the 90° TN configuration becomes unstable and transforms into a 270° STN configuration. Therefore, it is desirable to maintain a short pitch with d / p>0.5, but at the same time maintain the TN LC configuration required to achieve fast switching times.

[0006] In the literature, it is reported that a 270° STN configuration can be changed to a 90° TN configuration by applying a voltage, and the 90° TN configuration can then be stabilized by, for example, photopolymerization, for example, by forming a polymer network in the LC medium, see K. Takatoh et al., "Fast-response twisted nematic liquid crystals with ultrashortpitch liquid crystalline materials", Liq. Cryst. 2012, 39, 715-720. It is also reported that a 90° TN configuration can be stabilized by forming a polymer wall in the LC medium, see IDW 2014, LCT1-2, "Polymer-Wall Stabilization of Ultra-Short-Pitch TN-LCDs". However, the stable TN LCDs described therein have lower transmittance and / or lower contrast ratio than conventional unstable TN LCDs, and require higher driving voltages.

[0007] Therefore, the object of the present invention is to provide a method for producing a device having a fast response time, in particular a fast turn-off or decay time (t d ), while still maintaining a 90° TN LC director configuration, and simultaneously achieving a TN LCD having one or more of low driving voltage, high contrast ratio and high transmittance. Another object of the present invention is to provide a TN LCD obtained by this method, in particular a polymer-stabilized (PS) TN LCD, which allows a fast response time to be achieved and overcomes the disadvantages of the prior art TN LCDs and PS-TN LCDs, such as high driving voltage, low contrast ratio and low transmittance. Other objects of the present invention will be apparent to the skilled person from the following description.

[0008] It has been found that these objects can be achieved by providing a method for manufacturing a TN LCD as disclosed and claimed hereinafter. In particular, it has been found that by polymer stabilization of the TN LCD according to this method (even when only small amounts of polymer are used), fast response times can be achieved while maintaining a 90° TN LC director configuration and still being able to achieve low drive voltages, high contrast ratios and high transmittance. The display obtained by this method according to the invention is also referred to hereinafter as a "polymer-stabilized (ultrafast) twisted nematic LCD" or "PS(-UF)-TN LCD". Summary of the invention

[0009] The present invention relates to a polymer stabilized twisted nematic (PS-TN) mode liquid crystal display (LCD), comprising

[0010] a) a first substrate provided with a first electrode layer and optionally a first alignment layer, and a second substrate provided with a second electrode layer and optionally a second alignment layer,

[0011] b) a layer of a nematic LC medium distributed between the first and second substrates, the nematic LC medium comprising chiral additives and having a positive dielectric anisotropy,

[0012] c) optionally, a first polarizer on the side of the first substrate facing away from the LC layer and a second polarizer on the side of the second substrate facing away from the LC layer, said polarizers preferably being oriented such that their transmission planes are at right angles for plane-polarized light (crossed nicols),

[0013] wherein the longitudinal axes of the LC molecules are oriented parallel or tilted relative to the plane of the substrate, and the chiral additive induces a helical twist with a given pitch p in the LC molecules of the LC medium along an axis perpendicular to the substrate, and

[0014] wherein the layer thickness of the LC medium is d and the ratio d / p is ≥ 0.5, preferably > 0.5, very preferably 0.6-0.8, and

[0015] wherein the twist angle of the helical twist of the LC molecules is from 60 to 120°, preferably from 80 to 100°, very preferably 90°, and

[0016] wherein the display further comprises a polymer layer deposited on one or both of the first and second electrodes or, if present, on one or both of the first and second alignment layers,

[0017] Wherein the polymer layer is formed from one or more polymerisable mesogenic compounds which are contained in the LC medium in a concentration of 1 to <3%, preferably 2 to <3%, and which are polymerised in situ after the LC medium has been dispensed between the two substrates.

[0018] The present invention also relates to a method for manufacturing a PS-TN mode LCD, comprising the following steps:

[0019] a) providing a first substrate provided with a first electrode layer and optionally a first alignment layer, and a second substrate provided with a second electrode layer and optionally a second alignment layer,

[0020] wherein the first and / or the second substrate is preferably provided with fixing means, preferably a sealant material and / or a spacer, which fixing means fix the first and second substrate at a constant distance relative to each other and with their planes parallel to each other,

[0021] b) distributing a layer of a nematic LC medium having positive dielectric anisotropy between the first and second substrates so that the LC medium is in contact with the first and second alignment layers (if these layers are present),

[0022] Wherein the LC medium comprises, preferably consists of:

[0023] A) a liquid-crystalline component A (hereinafter also referred to as "LC host mixture"), which comprises, preferably consists of, mesogenic or liquid-crystalline molecules,

[0024] B) a polymerizable component B comprising, preferably consisting of, one or more polymerizable mesogenic compounds (hereinafter also referred to as "reactive mesogens"),

[0025] C) one or more chiral additives, preferably selected from chiral dopants,

[0026] D) optionally one or more further additives, preferably selected from polymerization initiators, stabilizers and self-aligning additives,

[0027] wherein the concentration of the polymerizable mesogenic compound in the LC medium is from 1 to <3%, preferably from 2 to <3%, and

[0028] wherein the longitudinal axes of the LC molecules are oriented parallel or tilted relative to the plane of the substrate, and the chiral additive induces a helical twist with a given pitch p in the LC molecules of the LC medium along an axis perpendicular to the substrate, and

[0029] wherein the thickness of the LC medium layer is d, and the ratio d / p is ≥ 0.5, preferably > 0.5, very preferably 0.6-0.8, and

[0030] wherein the twist angle of the helical twist of the LC molecules caused by the chiral additive is >210°, preferably from 210 to 330°, more preferably from 240 to 300°, very preferably 270°,

[0031] c) applying a voltage to the first and second electrodes such that the twist angle of the helical twist of the LC molecules decreases to <150°, preferably to the range of 60 to 120°, more preferably to 80 to 100°, most preferably to 90°,

[0032] d) polymerizing the polymerizable mesogenic compound of polymerizable component B of the LC medium between the first and second substrates after or while applying a voltage, preferably by exposure to UV radiation, thereby stabilizing the twisted nematic configuration of the LC medium with reduced twist angle of step c), and

[0033] e) optionally, subjecting the LC medium to a second polymerisation step, preferably by exposure to UV radiation, without applying a voltage to the first and second electrodes, thereby polymerising any polymerisable compounds which have not reacted in step d),

[0034] f) optionally providing a first polarizer on the side of the first substrate facing away from the LC layer and a second polarizer on the side of the second substrate facing away from the LC layer, wherein the polarizers are preferably oriented so that their transmission planes are at right angles to plane polarized light (orthogonal polarizations).

[0035] The invention also relates to an LC display obtainable by the process described above and below.

[0036] The present invention furthermore relates to an LC medium comprised in an LC display as described above and below, wherein the polymerisable mesogenic compound is unpolymerised.

[0037] The present invention furthermore relates to an LC medium comprised in an LC display as described above and below, wherein the polymerisable mesogenic compound is polymerised.

[0038] Terms and Definitions

[0039] As used herein, the terms "active layer" and "switchable layer" mean in an electro-optical display, for example in an LC display, a layer comprising one or more molecules with structural and optical anisotropy (for example LC molecules), which molecules change their orientation when subjected to an external stimulus such as an electric or magnetic field, which results in a change in the transmittance of the layer for polarized or unpolarized light.

[0040] As used herein, the terms "twist" and "twist angle" are understood to refer to a LC medium in which the longitudinal axes of the LC molecules are substantially parallel to the plane of the nearest substrate of the display cell and are twisted along a helical axis perpendicular to the plane of the substrates.

[0041] As used herein, the terms "tilt" and "tilt angle" are understood to refer to an orientation wherein the longitudinal axes of the LC molecules of the LC medium form an angle with the plane of the nearest substrate of the display cell.

[0042] As used herein, the term "director" or "LC director" is understood to mean the average direction of the long molecular axis of the LC molecules.

[0043] As used herein, the terms "reactive mesogen" and "RM" are understood to mean a compound comprising a mesogenic or liquid crystal backbone and attached thereto one or more functional groups suitable for polymerization, also referred to as "polymerizable groups" or "P".

[0044] Unless otherwise indicated, the term "polymerizable compound" as used herein is to be understood as a polymerizable monomeric compound.

[0045] The expression "the polymer obtained by polymerizing the polymerizable component B" or "the polymer obtained by polymerizing one or more polymerizable compounds" as used above and below is to be understood as covering embodiments in which the polymer partially remains in the LC medium or is completely dispersed in the LC medium, as well as embodiments in which the polymer precipitates from the LC medium and forms a polymer layer on one or both of the substrates, or on one or both of the alignment layers deposited on the substrate (or electrode structures), or on one or both of the electrode structures deposited on the substrate.

[0046] As used herein, the term "low molecular weight compound" is understood to mean a compound that is monomeric and / or not prepared by polymerization, as opposed to a "polymeric compound" or "polymer."

[0047] As used herein, the term "non-polymerizable compound" is understood to mean a compound that does not contain functional groups suitable for polymerization under the conditions normally applied to RM polymerization.

[0048] As used herein, the term "mesogenic group" is known to those skilled in the art and is described in the literature and refers to a group that substantially contributes to the generation of a liquid crystal (LC) phase in a low molecular weight or polymeric substance due to its anisotropy of attractive and repulsive interactions. A compound comprising a mesogenic group (mesogenic compound) does not necessarily have an LC phase per se. A mesogenic compound may also exhibit LC phase behavior only after mixing with other compounds and / or after polymerization. Typical mesogenic groups are, for example, rigid rod-shaped or disc-shaped units. Terms and definitions used in connection with mesogenic or LC compounds are given in Pure Appl. Chem. 2001, 73 (5), 888 and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368.

[0049] As used herein, the term "spacer" (hereinafter also referred to as "Sp") is known to those skilled in the art 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 term "spacer" or "spacer" refers to a flexible group, for example an alkylene group, which is connected to the mesogenic group and the polymerizable group (one or more) in the polymerizable mesogenic compound.

[0050] In context,

[0051]

[0052] represents a trans-1,4-cyclohexylene ring, and

[0053]

[0054] It represents a 1,4-phenylene ring.

[0055] "Organic group" in this context means a carbon or hydrocarbon group.

[0056] "Carbon group" means a mono- or polyvalent organic group containing at least one carbon atom, wherein the group contains no other atoms (e.g. -C≡C-) or optionally contains one or more other atoms, such as N, O, S, B, P, Si, Se, As, Te or Ge (e.g. carbonyl, etc.). The term "hydrocarbyl group" means a carbon group which additionally contains one or more H atoms and optionally one or more heteroatoms, such as N, O, S, B, P, Si, Se, As, Te or Ge.

[0057] "Halogen" means F, Cl, Br or I.

[0058] -CO-, -C(=O)- and -C(O)- represent carbonyl groups, i.e.

[0059] The carbon or hydrocarbon group can be a saturated or unsaturated group. Unsaturated groups are, for example, aryl, alkenyl or alkynyl groups. Carbon or hydrocarbon groups with more than 3 C atoms can be straight chain, branched and / or cyclic and can also contain spiro connections or condensed rings.

[0060] The terms "alkyl", "aryl", "heteroaryl" and the like also include polyvalent groups such as alkylene, arylene, heteroarylene and the like.

[0061] The term "aryl" refers to an aromatic carbon group or a group derived therefrom. The term "heteroaryl" refers to an "aryl" as defined above containing one or more heteroatoms (preferably selected from N, O, S, Se, Te, Si and Ge).

[0062] Preferred carbon and hydrocarbon radicals are optionally substituted, linear, branched or cyclic alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy and alkoxycarbonyloxy radicals having 1 to 40, preferably 1 to 20, very preferably 1 to 12 C atoms, optionally substituted aryl or aryloxy radicals having 5 to 30, preferably 6 to 25 C atoms, or optionally substituted alkylaryl, aralkyl, alkylaryloxy, arylalkyloxy, arylcarbonyl, aryloxycarbonyl, arylcarbonyloxy and aryloxycarbonyloxy radicals having 5 to 30, preferably 6 to 25 C atoms, where one or more C atoms may also be replaced by heteroatoms, preferably selected from N, O, S, Se, Te, Si and Ge.

[0063] Further preferred carbon and hydrocarbon groups are C1-C 20 Alkyl, C2-C 20 Alkenyl, C2-C 20 Alkynyl, C3-C 20 Allyl, C4-C 20 Alkyldiene, C4-C 20 Polyene, C6-C 20 Cycloalkyl, C4-C 15 Cycloalkenyl, C6-C 30 Aryl, C6-C 30 Alkyl aryl, C6-C 30 Arylalkyl, C6-C 30 Alkyl aryloxy, C6-C 30 Arylalkoxy, C2-C 30 Heteroaryl, C2-C 30 Heteroaryloxy.

[0064] Particularly preferred is C1-C 12 Alkyl, C2-C 12 Alkenyl, C2-C 12 Alkynyl, C6-C 25 Aryl and C2-C 25 Heteroaryl.

[0065] Further preferred carbyl and hydrocarbon radicals are straight-chain, branched or cyclic alkyl radicals having 1 to 20, preferably 1 to 12 C atoms, which are unsubstituted or mono- or polysubstituted by F, Cl, Br, I or CN, and in which one or more non-adjacent CH2 groups can each be replaced independently of one another by -C(R x )=C(R x )-、-C≡C-、-N(R x )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that the O and / or S atoms are not directly connected to each other.

[0066] Rx Preferably it represents H, F, Cl, CN, a straight-chain, branched or cyclic alkyl chain having 1 to 25 C atoms, wherein, in addition, one or more non-adjacent C atoms may be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, and wherein one or more H atoms may be replaced by F or Cl, or an optionally substituted aryl or aryloxy group having 6 to 30 C atoms, or an optionally substituted heteroaryl or heteroaryloxy group having 2 to 30 C atoms.

[0067] Preferred alkyl groups are, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 2-methylbutyl, n-pentyl, sec-pentyl, cyclopentyl, n-hexyl, cyclohexyl, 2-ethylhexyl, n-heptyl, cycloheptyl, n-octyl, cyclooctyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, dodecyl, trifluoromethyl, perfluoro-n-butyl, 2,2,2-trifluoroethyl, perfluorooctyl, perfluorohexyl, and the like.

[0068] Preferred alkenyl groups are, for example, ethenyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl, cyclooctenyl and the like.

[0069] Preferred alkynyl groups are, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl, octynyl and the like.

[0070] Preferred alkoxy groups are, for example, methoxy, ethoxy, 2-methoxyethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, 2-methylbutoxy, n-pentoxy, n-hexyloxy, n-heptyloxy, n-octyloxy, n-nonyloxy, n-decyloxy, n-undecyloxy, n-dodecyloxy, and the like.

[0071] Preferred amino groups are, for example, dimethylamino, methylamino, methylphenylamino, phenylamino and the like.

[0072] Aryl and heteroaryl groups may be monocyclic or polycyclic, i.e. they may contain one ring (e.g. phenyl) or two or more rings, which may also be fused (e.g. naphthyl) or covalently bonded (e.g. biphenyl), or a combination of fused and linked rings. Heteroaryl contains one or more heteroatoms, preferably selected from O, N, S and Se.

[0073] Particularly preferred are mono-, bi- or tricyclic aryl radicals having 6 to 25 C atoms and mono-, bi- or tricyclic heteroaryl radicals having 5 to 25 ring atoms, which optionally contain fused rings and are optionally substituted. Further preferred are 5-, 6- or 7-membered aryl and heteroaryl radicals, in which, in addition, one or more CH groups may be replaced by N, S or O in such a way that the O atoms and / or S atoms are not directly connected to one another.

[0074] Preferred aryl groups are, for example, phenyl, biphenyl, terphenyl, [1,1':3',1"]-terphenyl-2'-yl, naphthyl, anthracenyl, binaphthyl, phenanthrenyl, 9,10-dihydro-phenanthrenyl, pyrene, dihydropyrene, Perylene, tetracene, pentacene, benzopyrene, fluorene, indene, indenofluorene, spirobifluorene, and the like.

[0075] Preferred heteroaryl groups are, for example, 5-membered rings, such as pyrrole, pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, tetrazole, furan, thiophene, selenophene, oxazole, isoxazole, 1,2-thiazole, 1,3-thiazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole, 1,3,4-thiadiazole, 6-membered rings, such as pyridine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, 1,2,4-triazine, 1,2,3-triazine, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine, 1,2,3,5-tetrazine or fused groups, such as indole, isoindole , indolizine, indazole, benzimidazole, benzotriazole, purine, naphthimidazole, phenanthimidazole, pyridimidazole, pyrazimidazole, quinoxalineimidazole, benzoxazole, naphthimidazole, anthraxazole, phenanthimidazole, isoxazole, benzothiazole, benzofuran, isobenzofuran, dibenzofuran, quinoline, isoquinoline, pteridine, benzo-5,6-quinoline, benzo-6,7-quinoline, Benzo-7,8-quinoline, benzisoquinoline, acridine, phenothiazine, phenoxazine, benzopyridazine, benzopyrimidine, quinoxaline, phenazine, naphthyridine, azacarbazole, benzocarboline, phenanthridine, phenanthroline, thieno[2,3b]thiophene, thieno[3,2b]thiophene, dithienothiophene, isobenzothiophene, dibenzothiophene, benzothiadiazolethiophene, or a combination of these groups.

[0076] The aryl and heteroaryl groups mentioned above and below may also be substituted by alkyl, alkoxy, thioalkyl, fluorine, fluoroalkyl or other aryl or heteroaryl groups.

[0077] (Non-aromatic) alicyclic and heterocyclic groups include both saturated rings, i.e. rings containing only single bonds, and partially unsaturated rings, i.e. those which may also contain multiple bonds. The heterocyclic ring contains one or more heteroatoms, preferably selected from Si, O, N, S and Se.

[0078] (Non-aromatic) alicyclic groups and heterocyclic groups can be monocyclic, i.e. contain only one ring (e.g. cyclohexane), or polycyclic, i.e. contain multiple rings (e.g. decalin or bicyclooctane). Saturated groups are particularly preferred. In addition, mono-, bi- or tricyclic groups with 5-25 ring atoms are preferred, which optionally contain fused rings and are optionally substituted. Further preferred are 5-, 6-, 7- or 8-membered carbocyclic groups, wherein in addition, one or more C atoms may be substituted by Si and / or one or more CH groups may be substituted by N and / or one or more non-adjacent CH2 groups may be substituted by-O- and / or-S-.

[0079] Preferred alicyclic and heterocyclic groups are, for example, 5-membered groups, such as cyclopentane, tetrahydrofuran, tetrahydrothiophene, pyrrolidine; 6-membered groups, such as cyclohexane, silinane, cyclohexene, tetrahydropyran, tetrahydrothiopyran, 1,3-dioxane, 1,3-dithiane, piperidine; 7-membered groups, such as cycloheptane; and condensed groups, such as tetralin, decalin, indane, bicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl, octahydro-4,7-methanoindan-2,5-diyl.

[0080] Preferred substituents are, for example, solubility promoting groups, such as alkyl or alkoxy groups; electron withdrawing groups, such as fluorine, nitro or nitrile; or substituents used to increase the glass transition temperature (Tg) of the polymer, especially bulky groups, such as tert-butyl or optionally substituted aryl groups.

[0081] Preferred substituents, hereinafter also referred to as "L", are F, Cl, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, -C(=O)N(R x )2, -C(=O)Y 1 、-C(=O)R x 、-N(R x )2, linear or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25 C atoms, in which one or more H atoms may be optionally replaced by F or Cl, optionally substituted silyl having 1 to 20 Si atoms, or optionally substituted aryl having 6 to 25, preferably 6 to 15 C atoms,

[0082] Where Rx represents H, F, Cl, CN, or a straight-chain, branched or cyclic alkyl group having 1 to 25 C atoms, wherein one or more non-adjacent CH2-groups are optionally replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that the O- and / or S-atoms are not directly connected to one another, and wherein one or more H atoms are each optionally replaced by F, Cl, P- or P-Sp-, and

[0083] Y 1 Represents halogen.

[0084] "Substituted silyl or aryl" preferably means that it is replaced by halogen, -CN, R 0 、-OR 0 、-CO-R 0 、-CO-OR 0 、-O-CO-R 0 OR-O-CO-OR 0 Substitution, where R 0 represents H or an alkyl group having 1 to 20 C atoms.

[0085] Particularly preferred substituents L are, for example, F, Cl, CN, NO2, CH3, C2H5, OCH3, OC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF3, OCF3, OCHF2, OC2F5 and also phenyl.

[0086] Preferably

[0087] wherein L has one of the meanings indicated above.

[0088] The polymerizable group P is a group suitable for polymerization reactions (e.g. free radical or ionic chain polymerization, addition polymerization or condensation polymerization), or a group suitable for polymer-analogous reactions (e.g. addition or condensation on the polymer backbone). Particularly preferred are groups for chain polymerization, in particular those containing a C=C double bond or a -C≡C- triple bond, and groups suitable for ring-opening polymerization, such as oxetane or epoxy groups.

[0089] Preferred groups P are selected from the group consisting of: CH2=CW 1 -CO-O-, CH2=CW 1 -CO-, CH2=CW 2 -(O) k3 -、CW 1 =CH-CO-(O) k3 -、CW1 =CH-CO-NH-, CH2=CW 1 -CO-NH-, CH3-CH=CH-O-, (CH2=CH)2CH-OCO-, (CH2=CH-CH2)2CH-OCO-, (CH2=CH)2CH-O-, (CH2=CH-CH2)2N-, (CH2=CH-CH2)2N-CO-, HO-CW 2 W 3 -、HS-CW 2 W 3 -、HW 2 N-、HO-CW 2 W 3 -NH-, CH2=CW 1 -CO-NH-, CH2=CH-(COO) k1 -Phe-(O) k2 -、CH2=CH-(CO) k1 -Phe-(O) k2 -, Phe-CH=CH-, HOOC-, OCN- and W 4 W 5 W 6 Si-, where W 1 represents H, F, Cl, CN, CF3, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, Cl or CH3, W 2 and W 3 each independently of one another represents H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, W 4 , W 5 and W 6 each independently represents Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms, W 7 and W 8 Each independently represents H, Cl or an alkyl group having 1 to 5 C atoms, Phe represents 1,4-phenylene which is optionally substituted by one or more groups L different from P-SP- as defined above, k1, k2 and k3 each independently represent 0 or 1, k3 preferably represents 1, and k4 represents an integer from 1 to 10.

[0090] Very preferred groups P are selected from the group consisting of: CH2=CW 1 -CO-O-, CH2=CW 1 -CO-, CH2=CW 2 -O-, CH2=CW 2 -、CW 1=CH-CO-(O) k3 -、CW 1 =CH-CO-NH-, CH2=CW 1 -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=CW 1 -CO-NH-, CH2=CH-(COO) k1 -Phe-(O) k2 -、CH2=CH-(CO) k1 -Phe-(O) k2 -, Phe-CH=CH- and W 4 W 5 W 6 Si-, where W 1 represents H, F, Cl, CN, CF3, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, Cl or CH3, W 2 and W 3 each independently of one another represents H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, W 4 , W 5 and W 6 each independently represents Cl, an oxaalkyl or oxacarbonylalkyl radical having 1 to 5 C atoms, W 7 and W 8 Each independently represents H, Cl or an alkyl group having 1 to 5 C atoms, Phe represents 1,4-phenylene, k1, k2 and k3 each independently represent 0 or 1, k3 preferably represents 1, and k4 represents an integer of 1 to 10.

[0091] Very preferably the group P is selected from the group consisting of: CH2=CW 1 -CO-O-, in particular CH2=CH-CO-O-, CH2=C(CH3)-CO-O- and CH2=CF-CO-O-, also CH2=CH-O-, (CH2=CH)2CH-O-CO-, (CH2=CH)2CH-O-,

[0092] Other particularly preferred polymerizable groups P are selected from vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxy groups, most preferably from acrylate and methacrylate groups.

[0093] If Sp is different from a single bond, it is preferably of the formula Sp"-X", so that each group P-Sp- corresponds to the formula P-Sp"-X"-, in which

[0094] Sp" denotes an alkylene radical 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 are each independently substituted by -O-, -S-, -NH-, -N(R 0 )-、-Si(R 0 R 00 )-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -S-CO-, -CO-S-, -N(R 00 )-CO-O-、-O-CO-N(R 0 )-、-N(R 0 )-CO-N(R 00 )-, -CH=CH- or -C≡C- in such a way that the O and / or S atoms are not directly connected to each other,

[0095] X" means -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -CO-N(R 0 )-、-N(R 0 )-CO-、-N(R 0 )-CO-N(R 00 )-, -OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -CF2CH2-, -CH2CF2-, -CF2CF2-, -CH=N-, -N=CH-, -N=N-, -CH=CR 0 -、-CY 2 =CY 3 -, -C≡C-, -CH=CH-CO-O-, -O-CO-CH=CH- or a single bond,

[0096] R 0 and R 00 each independently of one another represents H or an alkyl group having 1 to 20 C atoms, and

[0097] Y 2 and Y 3 Each independently of one another represents H, F, Cl or CN.

[0098] X" is preferably -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR 0 -、-NR 0 -CO-、-NR0 -CO-NR 00 - or single key.

[0099] Typical spacer groups Sp and -Sp"-X"- are, for example, -(CH2) p1 -、-(CH2CH2O) q1 -CH2CH2-, -CH2CH2-S-CH2CH2-, -CH2CH2-NH-CH2CH2- or -(SiR 0 R 00 -O) p1 -, wherein p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and R 0 and R 00 has the meaning indicated above.

[0100] 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-, wherein p1 and q1 have the meanings indicated above.

[0101] Particularly preferred radicals Sp" are in each case linear ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethylenethioethylene, ethylene-N-methylimino-ethylene, 1-methylalkylene, vinylene, propenylene and butenylene. DETAILED DESCRIPTION

[0102] In the method according to the invention, the twisted nematic LC configuration has an initial short pitch corresponding to a STN configuration, with d / p>0.5 and a twist angle in the range of 210 to 330°, preferably 270°.

[0103] This is achieved by adding chiral dopants with certain twisting powers to the LC medium.

[0104] The helical twisting power or HTP of a chiral dopant is a measure of its ability to induce a helical twist in a particular nematic LC medium. The HTP of a chiral dopant is an intrinsic property and can be defined by equation (1)

[0105] HTP=(p·c) -1 (1)

[0106] where p is the pitch of the induced helical twist and c is the concentration c of the chiral dopant in the LC medium.

[0107] Two or more chiral dopants may also be used, for example, in order to compensate for the temperature dependence of the HTP of the individual dopants, thus reducing the temperature dependence of the pitch.

[0108] During the manufacturing process, a defined voltage is then applied to the electrodes of the display. As a result, the twist angle is reduced to a value corresponding to a TN configuration, for example 90°.

[0109] According to Takatoh et al., Liq. Cryst. 2012, 39, 715-720, the change in twist angle from 270° to 90° can be explained by the LC molecules changing from a twist-splay state (as in the STN configuration) to a twist-bend state (as in the TN configuration).

[0110] The TN configuration induced by this voltage is metastable and usually relaxes to the initial STN configuration after a certain time when the voltage is turned off.

[0111] In the method according to the invention, relaxation of the twist angle from the TN-LC to the STN-LC configuration is prevented by polymerizing the polymerizable compound of component B, preferably by UV light polymerization. As a result, a metastable TN configuration with an "unnaturally" low twist angle is maintained despite the short pitch caused by the chiral dopant. As a result, the LC molecules in the LC medium are forced into a state in which the degree of twist is lower than the natural pitch of the LC medium given by the above equation (1). In other words, the actual twist angle of the LC molecules does no longer correspond to the "natural" pitch of the helical twist caused by the chiral dopant and the d / p value of the display cell.

[0112] As a result of this approach, significantly shorter response times can be achieved compared to displays made from similar materials but with a reduced amount of chiral dopant, resulting in a longer pitch and lower d / p value, all matched to a reduced twist angle.

[0113] It has been found that the addition of only small amounts of polymerizable mesogenic compounds < 3% to the LC medium enables low-twist polymer stabilization and the advantageous effects of PS-TN LCDs according to the invention, such as fast rise and decay times, high transmittance and good contrast, to be achieved.

[0114] It has also been found that in a PS-TN LCD according to the present invention, most of the polymer formed from the polymerizable mesogen compound will phase separate or precipitate from the LC medium and form a polymer layer on the substrate or electrode, or on an alignment layer provided thereon. This can be confirmed by microscopic measurements (such as SEM or AFM), which show that the formed polymer is mainly aggregated at the interface of the LC layer / substrate. Therefore, the transmittance loss of the LCD can be reduced, and a high transmittance can be achieved, in particular, compared to an unstabilized TN LCD.

[0115] These are significant advantages that could not be expected from the prior art (such as the publications cited above), in which it is reported that a certain minimum amount of monomers is required when forming polymer networks or polymer walls in LC media, and that polymer networks or polymer walls in such LC media lead to lower transmittance.

[0116] Preferably, the LC medium used in the display according to the invention comprises

[0117] A) a liquid crystal component A comprising mesogens or liquid crystal molecules,

[0118] B) a polymerizable component B comprising one or more polymerizable mesogenic compounds,

[0119] C) one or more chiral additives, preferably selected from chiral dopants,

[0120] D) optionally one or more further additives, preferably selected from stabilizers and polymerization initiators,

[0121] The concentration of the polymerizable mesogenic compound of component B in the LC medium is 1 to <3% by weight, preferably 2 to <3% by weight.

[0122] The liquid-crystalline component A) of the LC media used in the displays according to the invention is also referred to hereinafter as "LC host mixture" and preferably comprises exclusively LC compounds from the group of non-polymerizable, low molecular weight compounds.

[0123] Preferably, component A of the LC medium or the LC host mixture comprises one or more compounds selected from the group consisting of formulae A and B

[0124]

[0125] where the individual radicals, independently of one another and identically or differently on each occurrence, have the following meanings:

[0126] Each independently of the others and identically or differently on each occurrence is

[0127]

[0128] R 21 ,R 31 each independently of one another is alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C atoms or alkenyl or alkenyloxy having 2 to 9 C atoms, all of which are optionally fluorinated,

[0129] X 0 is F, Cl, a haloalkyl or alkoxy group having 1 to 6 C atoms or a haloalkenyl or alkenyloxy group having 2 to 6 C atoms,

[0130] Z 31 is -CH2CH2-, -CF2CF2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O- or a single bond, preferably -CH2CH2-, -COO-, trans-CH=CH- or a single bond, particularly preferably -COO-, trans-CH=CH- or a single bond,

[0131] L 21 , L 22 , L 31 , L 32 Each independently is H or F,

[0132] L S is H or CH3, wherein the two groups L are preferably attached to the same benzene ring S At least one of them is H,

[0133] g is 0, 1, 2 or 3.

[0134] In the compounds of formula A and B, X 0 Preferred are F, Cl, CF3, CHF2, OCF3, OCHF2, OCFHCF3, OCFHCHF2, OCFHCHF2, OCF2CH3, OCF2CHF2, OCF2CHF2, OCF2CF2CHF2, OCF2CF2CHF2, OCFHCF2CF3, OCFHCF2CHF2, OCF2CF2CF3, OCF2CF2CClF2, OCC1FCF2CF3 or CH═CF2, very preferably F or OCF3, most preferably F.

[0135] In the compounds of formula A and B and subformulae thereof, the ring

[0136]

[0137] Preferred representation

[0138]

[0139] In addition, it stated

[0140]

[0141] In a preferred embodiment, at least one of the compounds of formula A and B or subformulae thereof contains at least one cyclic

[0142]

[0143] In the compounds of formula A and B, R 21 and R 31 It is preferably selected from straight-chain alkyl or alkoxy radicals having 1, 2, 3, 4, 5 or 6 C atoms, and straight-chain alkenyl radicals having 2, 3, 4, 5, 6 or 7 C atoms.

[0144] In the compounds of formula A and B, g is preferably 1 or 2.

[0145] In the compound of formula B, Z 31 Preferred are COO, trans-CH=CH or a single bond, very preferred are COO or a single bond.

[0146] Preferably, component A) of the LC medium comprises one or more compounds of the formula A selected from the group consisting of:

[0147]

[0148]

[0149] Among them A 21 , R 21 , X 0 , L 21 , L 22 and L S has the meaning given in formula A, L 23 and L 24 are each independently H or F, and X 0 Preferred is F. Particularly preferred are compounds of the formulae A1 and A2.

[0150] Particularly preferred compounds of formula A1 are selected from the following sub-formulae:

[0151]

[0152]

[0153] Where R 21 , X 0 , L 21 and L 22 has the meaning given in formula A1, L 23 , L 24 , L 25 and L 26 are each independently H or F, and X 0 Preferred is F.

[0154] Further preferred are compounds of the formulae A1a to A1g in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0155] Very particularly preferred compounds of the formula A1 are selected from the group consisting of the following subformulae:

[0156]

[0157]

[0158]

[0159] Where R 21 As defined in Formula A1.

[0160] Further preferred are compounds of the formulae A1a1 to A1g1 in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0161] Particularly preferred compounds of formula A2 are selected from the group consisting of the following subformulae:

[0162]

[0163]

[0164]

[0165] Where R 21 , X 0 , L 21 and L 22 has the meaning given in formula A2, L 23 , L 24 , L 25 and L 26 are each independently H or F, and X 0 Preferred is F.

[0166] Further preferred are compounds of the formulae A2a to A21 in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0167] Very particularly preferred compounds of the formula A2 are selected from the group consisting of the following subformulae:

[0168]

[0169]

[0170]

[0171] Where R21 and X 0 As defined in Formula A2.

[0172] Further preference is given to compounds of the formulae A2a1 to A2l2 in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0173] Particularly preferred compounds of formula A3 are selected from the group consisting of the following subformulae:

[0174]

[0175]

[0176] Where R 21 , X 0 , L 21 and L 22 has the meaning given in formula A3, and X 0 Preferred is F.

[0177] Further preferred are compounds of the formulae A3a to A3c, in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0178] Particularly preferred compounds of formula A4 are selected from the following sub-formulae:

[0179]

[0180] Where R 21 As defined in formula A4.

[0181] Further preference is given to compounds of the formula A4a in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0182] Preferably, component A) of the LC medium comprises one or more compounds of the formula B selected from the group consisting of:

[0183]

[0184]

[0185] Where g, A 31 , A 32 , R 31 , X 0 , L 31 , L 32 and L S has the meaning given in formula B, and X 0 Preferred is F. Particularly preferred are compounds of the formulae B1 and B2.

[0186] Particularly preferred compounds of formula B1 are selected from the group consisting of the following subformulae:

[0187]

[0188] Where R 31 , X 0 , L 31 and L 32 has the meaning given in formula B1, and X 0 F is preferred.

[0189] Further preferred are compounds of the formulae B1a-B1b in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0190] Very particularly preferred compounds of the formula B1a are selected from the group consisting of the following subformulae:

[0191]

[0192]

[0193] Where R 31 As defined in Formula B1.

[0194] Further preferred are compounds of the formulae B1a1 to B1a6, in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0195] Very particularly preferred compounds of the formula B1b are selected from the group consisting of the following subformulae:

[0196]

[0197]

[0198] Where R 31 As defined in Formula B1.

[0199] Further preferred are compounds of the formulae B1b1 to B1b4 in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0200] Particularly preferred compounds of formula B2 are selected from the group consisting of the following subformulae:

[0201]

[0202]

[0203]

[0204] Where R 31 , X 0, L 31 and L 32 has the meaning given in formula B2, L 33 , L 34 , L 35 and L 36 are each independently H or F, and X 0 Preferred is F.

[0205] Further preferred are compounds of the formulae B2a to B21, in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0206] Very particularly preferred compounds of the formula B2 are selected from the group consisting of the following subformulae:

[0207]

[0208]

[0209] Where R 31 As defined in Formula B2.

[0210] Further preference is given to compounds of the formulae B2a1 to B2a5, in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0211] Very particularly preferred compounds of the formula B2b are selected from the group consisting of the following subformulae:

[0212]

[0213] Where R 31 As defined in Formula B2.

[0214] Further preferred are compounds of the formulae B2b1 to B2b4 in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0215] Very particularly preferred compounds of the formula B2c are selected from the group consisting of the following subformulae:

[0216]

[0217]

[0218] Where R 31 As defined in Formula B2.

[0219] Further preferred are compounds of the formulae B2c1 to B2c5, in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0220] Very particularly preferred compounds of the formulae B2d and B2e are selected from the group consisting of the following subformulae:

[0221]

[0222] Where R 31 As defined in Formula B2.

[0223] Further preferred are compounds of the formulae B2d1 and B2e1 in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0224] Very particularly preferred compounds of the formula B2f are selected from the group consisting of the following subformulae:

[0225]

[0226] Where R 31 As defined in Formula B2.

[0227] Further preferred are compounds of the formulae B2f1 to B2f5, in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0228] Very particularly preferred compounds of the formula B2g are selected from the group consisting of the following subformulae:

[0229]

[0230] Where R 31 As defined in Formula B2.

[0231] Further preferred are compounds of the formulae B2g1 to B2g5, in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0232] Very particularly preferred compounds of the formula B2h are selected from the following sub-formulae:

[0233]

[0234]

[0235] Where R 31 As defined in Formula B2.

[0236] Further preferred are compounds of the formulae B2h1 to B2h3 in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0237] Very particularly preferred compounds of the formula B2i are selected from the group consisting of the following subformulae:

[0238]

[0239] Where R 31 As defined in Formula B2.

[0240] Further preferred are compounds of the formulae B2i1 and B2i2 in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0241] Very particularly preferred compounds of the formula B2k are selected from the group consisting of the following sub-formulae

[0242]

[0243] Where R 31 As defined in Formula B2.

[0244] Further preferred are compounds of the formulae B2k1 and B2k2 in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0245] Very particularly preferred compounds of the formula B21 are selected from the group consisting of the following sub-formulae

[0246]

[0247] Where R 31 As defined in Formula B2.

[0248] Further preference is given to compounds of the formulae B211 and B212 in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0249] Alternatively, or in addition to the compounds of the formula B1 and / or B2, component A) of the LC medium may also comprise one or more compounds of the formula B3 as defined above.

[0250] Particularly preferred compounds of formula B3 are selected from the following sub-formulae:

[0251]

[0252] Where R 31 As defined in Formula B3.

[0253] Further preferred are compounds of the formulae B3a and B3b in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0254] Preferably, component A) of the LC medium comprises, in addition to compounds of the formula A and / or B, one or more compounds of the formula C

[0255]

[0256] The various groups have the following meanings:

[0257] independently of each other, and

[0258] Each time it appears, it is the same or different

[0259]

[0260] R 41 , R 42 each independently of one another is alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C atoms, or alkenyl or alkenyloxy having 2 to 9 C atoms, all of which are optionally fluorinated,

[0261] Z 41 , Z 42 Each independently of one another is -CH2CH2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O-, -CF2O-, -C≡C- or a single bond, preferably a single bond,

[0262] h is 0, 1, 2 or 3.

[0263] In the compound of formula C, R 41 and R 42 It is preferably selected from straight-chain alkyl or alkoxy radicals having 1, 2, 3, 4, 5 or 6 C atoms, and straight-chain alkenyl radicals having 2, 3, 4, 5, 6 or 7 C atoms.

[0264] In the compounds of formula C, h is preferably 0, 1 or 2.

[0265] In the compound of formula C, Z 41 and Z 42 It is preferably selected from the group consisting of COO, trans-CH═CH and a single bond, very preferably selected from the group consisting of COO and a single bond.

[0266] Preferred compounds of formula C are selected from the group consisting of the following subformulae:

[0267]

[0268]

[0269]

[0270] where f is 0 or 1, and R 41 and R 42 has the meanings given in formula C and preferably each independently of one another represents alkyl, alkoxy, fluoroalkyl or fluoroalkoxy having 1 to 7 C atoms or alkenyl, alkenyloxy, alkoxyalkyl or fluoroalkenyl having 2 to 7 C atoms.

[0271] Compounds of formulae C1, C4, C5 and C9 are very preferred.

[0272] Preferred compounds of formula C are selected from the following sub-formulae:

[0273]

[0274]

[0275] Here, alkyl and alkyl* each independently represent a straight-chain alkyl radical having 1 to 6 C atoms.

[0276] Particularly preferred are compounds of the formula C1a, very preferably those selected from the following subformulae:

[0277]

[0278]

[0279] Among them, propyl, butyl and pentyl are straight chain groups.

[0280] Most preferred are compounds of formula C1a1.

[0281] In another preferred embodiment of the present invention, component A) of the LC medium comprises, in addition to the compounds of the formula A and / or B and / or C, one or more compounds of the formula D

[0282]

[0283] Among them A 41 , A 42 , Z 41 , Z 42 , R 41 , R 42 and h have the meanings given in formula C or one of the preferred meanings given above.

[0284] Preferred compounds of formula D are selected from the following sub-formulae:

[0285]

[0286] Where R 41 and R 42 has the meanings given in formula D and preferably denotes alkyl.

[0287] Very preferred compounds of formula D are selected from the following sub-formulae:

[0288]

[0289]

[0290] wherein alkyl and alkyl* each independently represent a straight-chain alkyl group having 1 to 6 C atoms, and alkenyl represents a straight-chain alkenyl group having 2 to 7 carbon atoms, preferably CH2=CH-, CH2=CHCH2CH2-, CH3-CH=CH-, CH3-CH2-CH=CH-, CH3-(CH2)2-CH=CH-, CH3-(CH2)3-CH=CH- or CH3-CH=CH-(CH2)2-.

[0291] The most preferred compounds of formula D are selected from the following sub-formulae:

[0292]

[0293] In a further preferred embodiment of the invention, component A) of the LC medium comprises, in addition to compounds of the formula A and / or B, one or more compounds of the formula E which contain an alkenyl group.

[0294]

[0295] The individual radicals have the following meanings, identically or differently on each occurrence and independently of one another:

[0296] express

[0297] express

[0298] R A1 is alkenyl having 2 to 9 C atoms, or, if at least one of the rings X, Y and Z represents cyclohexenyl, then R A1 Also has R A2 One of the meanings,

[0299] R A2 is an alkyl radical having 1 to 12 C atoms, wherein furthermore one or two non-adjacent CH2 groups may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that the O atoms are not directly connected to one another,

[0300] x is 1 or 2.

[0301] R A2 Preference is given to straight-chain alkyl or alkoxy radicals having 1 to 8 C atoms or straight-chain alkenyl radicals having 2 to 7 C atoms.

[0302] Preferred compounds of formula E are selected from the following sub-formulae:

[0303]

[0304]

[0305] Among them, alkyl and alkyl * each independently of one another represents a straight-chain alkyl radical having 1 to 6 C atoms, and alkenyl and alkenyl * each independently of one another represents a straight-chain alkenyl radical having 2 to 7 C atoms. * Preferably it represents CH2=CH-, CH2=CHCH2CH2-, CH3-CH=CH-, CH3-CH2-CH=CH-, CH3-(CH2)2-CH=CH-, CH3-(CH2)3-CH=CH- or CH3-CH=CH-(CH2)2-.

[0306] Very preferred compounds of formula E are selected from the following sub-formulae:

[0307]

[0308] Where m represents 1, 2, 3, 4, 5 or 6, i represents 0, 1, 2 or 3, and R b1 Represents H, CH3 or C2H5.

[0309] Very particularly preferred compounds of the formula E are selected from the following sub-formulae:

[0310]

[0311]

[0312] Most preferred are compounds of formula E1a2, E1a5, E6a1 and E6a2.

[0313] In a further preferred embodiment of the invention, component A) of the LC medium comprises, in addition to the compounds of the formula A and / or B, one or more compounds of the formula F.

[0314]

[0315] where the individual radicals are independent of one another and have the following meanings, identically or differently on each occurrence:

[0316] express

[0317]

[0318] R 21 , R 31 each independently of one another is alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C atoms or alkenyl or alkenyloxy having 2 to 9 C atoms, all of which are optionally fluorinated,

[0319] X 0 is F, Cl, a haloalkyl or alkoxy group having 1 to 6 C atoms or a haloalkenyl or alkenyloxy group having 2 to 6 C atoms,

[0320] Z 21 is -CH2CH2-, -CF2CF2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O-, -CF2O-, -C≡C- or a single bond, preferably -CF2O-,

[0321] L 21 , L 22 , L 23 , L 24 Each independently is H or F,

[0322] L S is H or CH3, wherein the two groups L are preferably attached to the same benzene ring S At least one of them is H,

[0323] g is 0, 1, 2 or 3.

[0324] In the compounds of formula F and its subformulae, the ring

[0325]

[0326] Preferred representation

[0327]

[0328] In addition, it stated

[0329]

[0330] In a preferred embodiment, at least one compound of formula F or its subformulae contains at least one cyclic

[0331]

[0332] Particularly preferred compounds of formula F are selected from the following:

[0333]

[0334]

[0335] Where R 21 , X 0 , L 21 and L 22 has the meaning given in formula F, L 25 and L 26 are each independently H or F, and X0 Preferred is F.

[0336] Very particularly preferred compounds of the formulae F1 to F3 are selected from the following sub-formulae:

[0337]

[0338]

[0339] Where R 21 As defined in formula F1.

[0340] Further preferred are compounds of the formulae F1-F3 and F1a-F3b, in which at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in the para-position to the fluorine atom.

[0341] The proportion of compounds of the formulae A and B in the LC host mixture is preferably from 2 to 60%, very preferably from 3 to 45%, most preferably from 4 to 35%.

[0342] The proportion of compounds of the formulae C and D in the LC host mixture is preferably from 2 to 70%, very preferably from 5 to 65%, most preferably from 10 to 60%.

[0343] The proportion of compounds of the formula E in the LC host mixture is preferably from 5 to 50%, very preferably from 5 to 35%.

[0344] The proportion of compounds of the formula F in the LC host mixture is preferably from 2 to 30%, very preferably from 5 to 20%.

[0345] Other preferred embodiments of the present invention are listed below, including any combinations thereof.

[0346] a) Component A or the LC host mixture comprises one or more compounds of the formula A and / or B having a high positive dielectric anisotropy, preferably Δε>15.

[0347] b) Component A or the LC host mixture comprises one or more compounds selected from the group consisting of the formulae A1a2 (CCQU), A1b1 (ACQU), A1d1 (PUQU), A1f1 (GUQU), A2a1 (APUQU), A2h1 (CDUQU), A2l1 (DUUQU), A2l2 (DGUQU), A2k1 (PGUQU), B2d1 (CDU), B2g2 (PGU), B2i1 (CPGU), B2h3 (CCGU), B2k1 (PPGU), B2l1 (DPGU), F1a (GUQGU). The total proportion of these compounds in the LC host mixture is preferably 4 to 40%, very preferably 5 to 35%. The proportion of individual ones of these compounds in the LC host mixture is preferably 0.5 to 10%.

[0348] c) Component A or the LC host mixture comprises one or more compounds selected from the group consisting of the formula B2c1 (CCP-nOCF3), B2c4 (CCP-nF.FF), B2f2 (BCH-nF.F) and B2f4 (BCH-nF.FF). The total proportion of these compounds in the LC host mixture is preferably 2 to 40%, very preferably 5 to 35%. The proportion of a single one of these compounds in the LC host mixture is preferably 0.5 to 10%.

[0349] d) Component A or the LC host mixture comprises one or more compounds selected from the group consisting of the formulae C1 (CCH), C4 (PCH), C5 (CCP), C7 (BCH), C9 (CBC) and D2 (PGP), preferably C1a (CCH-nm), C4b (PCH-nOm), C5b (CCP-nOm), C7b (BCH-nOm), C9b (CBC-nmF), D2a (PGP-nm) and D2b (PGP-n-mV). The total proportion of these compounds in the LC host mixture is preferably 5 to 60%, very preferably 8 to 50%. The proportion of a single one of these compounds in the LC host mixture is preferably 0.5 to 10%.

[0350] e) The LC host mixture comprises one or more compounds selected from the group consisting of the formulae E1 (CC-alkenyl), E3 (PP-alkenyl) and E6 (CCP-alkenyl), preferably E1a (CC-n-Vm), E3a (PP-n-kVm) and E6a (CCP-Vn-m), very preferably E1a2 (CC-3-V), E1a5 (CC-3-V1), E3a1 (PP-3-V), E3a3 (PP-1-2V1) and E6a1 (CCP-V-1). The total proportion of these compounds in the LC host mixture is preferably 5 to 75%, very preferably 10 to 65%. The proportion of a single one of these compounds in the LC host mixture is preferably 0.5 to 10%.

[0351] Preferably, the proportion of LC component A) in the LC medium is from 95 to <100%, preferably from 95 to 97%, very preferably from 96 to 99%.

[0352] The LC component A) or the LC host mixture is preferably a nematic LC mixture.

[0353] The polymerizable mesogenic compound of the polymerizable component B of the LC medium is preferably selected from the group consisting of

[0354] R a -B 1 -(Z b -B 2 ) m -Rb I

[0355] where the individual radicals have the following meanings, identically or differently on each occurrence and independently of one another:

[0356] R a and R b is P, P-Sp-, H, F, Cl, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, SF5 or a straight-chain or branched alkyl radical having 1 to 25 C atoms, wherein in addition, one or more non-adjacent CH2 groups may each be replaced independently of one another by -C(R 0 )=C(R 00 )-、-C≡C-、-N(R 00 )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, in such a way that O and / or S atoms are not directly connected to one another, and wherein in addition, one or more H atoms may be replaced by F, Cl, Br, I, CN, P or P-Sp-, wherein if B 1 and / or B 2 Contains saturated C atoms, then R a and / or R b It can also represent a group that is spiro-attached to the saturated C atom,

[0357] The group R a and R b At least one of them represents or contains a group P or P-Sp-,

[0358] P is a polymerizable group,

[0359] Sp is a spacer group or a single bond,

[0360] B 1 and B 2 is 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,

[0361] Z b is -O-, -S-, -CO-, -CO-O-, -OCO-, -O-CO-O-, -OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -(CH2) n1 -, -CF2CH2-, -CH2CF2-, -(CF2) n1 -, -CH=CH-, -CF=CF-, -C≡C-, -CH=CH-COO-, -OCO-CH=CH-, CR 0 R00 or single key,

[0362] R 0 and R 00 each independently of one another represents H or an alkyl radical having 1 to 12 C atoms,

[0363] m represents 0, 1, 2, 3 or 4,

[0364] n1 means 1, 2, 3 or 4,

[0365] L is P, P-Sp-, OH, CH2OH, F, Cl, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, -C(=O)N(R x )2, -C(=O)Y 1 、-C(=O)R x 、-N(R x )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 1 to 25 C atoms, wherein in addition one or more H atoms may be replaced by F, Cl, P or P-Sp-,

[0366] P and Sp have the meanings indicated above,

[0367] Y 1 Represents halogen,

[0368] R x represents P, P-Sp-, H, halogen, straight-chain, branched or cyclic alkyl having 1 to 25 C atoms, wherein, 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 the O and / or S atoms are not directly connected to one another, and wherein, in addition, one or more H atoms may be replaced by F, Cl, P or P-Sp-, optionally substituted aryl or aryloxy having 6 to 40 C atoms, or optionally substituted heteroaryl or heteroaryloxy having 2 to 40 C atoms.

[0369] Particularly preferred compounds of formula I are those wherein B 1 and B 2each independently of one another represents 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, coumarin, flavonoids, wherein in addition one or more CH groups in these radicals may be replaced by N, cyclohexane-1,4-diyl, wherein in addition one or more non-adjacent CH2 groups may be replaced by O and / or S, 1 ,4-cyclohexenylene, bicyclo[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, all of which may be unsubstituted or mono- or polysubstituted by L as described above.

[0370] Particularly preferred compounds of formula I are those wherein B 1 and B 2 those which each independently represent 1,4-phenylene, 1,3-phenylene, naphthalene-1,4-diyl or naphthalene-2,6-diyl,

[0371] Very preferred compounds of formula I are selected from the following formula:

[0372]

[0373]

[0374]

[0375]

[0376]

[0377] where the individual radicals have the following meanings, identically or differently on each occurrence and independently of one another:

[0378] P 1 , P 2 , P 3 is a vinyloxy group, an acrylate group, a methacrylate group, a fluoroacrylate group, a chloroacrylate group, an oxetane group or an epoxy group,

[0379] Sp 1 , Sp 2 , Sp 3 is a single bond or a spacer group, wherein in addition, the group P 1 -Sp 1 -、P 1 -Sp2 - and P 3 -Sp 3 -One or more of them can represent R aa , provided that the group P 1 -Sp 1 -、P 2 -Sp 2 and P 3 -Sp 3 - at least one of them is different from R aa ,

[0380] R aa is H, F, Cl, CN or a straight-chain or branched alkyl radical having 1 to 25 C atoms, wherein in addition, one or more non-adjacent CH2 groups may each be replaced independently of one another by -(R 0 )=C(R 00 )-,-C≡C-,-N(R 0 )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that the O and / or S atoms are not directly connected to one another, and wherein in addition one or more H atoms may be replaced by F, Cl, CN or P 1 -Sp 1 -substituted, particularly preferably, by straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy radicals having 1 to 12 C atoms (wherein the alkenyl and alkynyl radicals have at least two C atoms and the branched radicals have at least three C atoms),

[0381] R 0 , R 00 is H or an alkyl radical having 1 to 12 C atoms,

[0382] R y and R z is H, F, CH3 or CF3,

[0383] X 1 , X 2 , X 3 is -CO-O-, -O-CO- or a single bond,

[0384] Z 1 -O-, -CO-, -C(R y R z )-or-CF2CF2-,

[0385] Z 2 , Z 3 -CO-O-, -O-CO-, -CH2O-, -OCH2-, -CF2O-, -OCF2- or -(CH2)n -, where n is 2, 3 or 4,

[0386] L is F, Cl, CN or a straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy radical having 1 to 12 C atoms,

[0387] L', L" are H, F or Cl,

[0388] r is 0, 1, 2, 3 or 4,

[0389] s is 0, 1, 2, or 3,

[0390] t is 0, 1 or 2,

[0391] x is 0 or 1.

[0392] Very preferred are compounds of the formulae M2, M10 and M13, in particular compounds containing exactly two polymerizable groups P 1 and P 2 of bi-reactive compounds.

[0393] Further preferred are compounds selected from the formulae M15 to M31, in particular compounds selected from the formulae M17, M18, M19, M22, M23, M24, M25, M26, M30 and M31, especially compounds containing exactly three polymerizable groups P 1 , P 2 and / or P 3 of tri-reactive compounds.

[0394] In the compounds of formulae M1 to M31, the group

[0395] Preferably

[0396] in which L, at each occurrence, identically or differently, has one of the meanings given above and below, and is preferably F, Cl, CN, NO2, CH3, C2H5, C(CH3)3, CH(CH3)2, CH2CH(CH3)C2H5, OCH3, OC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF3, OCF3, OCHF2, OC2F5 or P-Sp-, very preferably F, Cl, CN, CH3, C2H5, OCH3, COCH3, OCF3 or P-Sp-, more preferably F, Cl, CH3, OCH3, COCH3 or OCF3, in particular F or CH3.

[0397] Preferred compounds of formula M1 to M30 are those wherein P 1 , P2 and P 3 Those representing acrylate, methacrylate, oxetane or epoxy groups (acrylate or methacrylate groups being very preferred).

[0398] Further preferred compounds of formula M1 to M31 are those wherein Sp 1 , Sp 2 and Sp 3 Those that are single bonds.

[0399] Further preferred compounds of formula M1 to M31 are those wherein Sp 1 , Sp 2 and Sp 3 One of them is a single bond and Sp 1 , Sp 2 and Sp 3 The other one in is different from those of single bonds.

[0400] Further preferred compounds of the formulae M1 to M31 are those in which the radical Sp which is different from a single bond is 1 , Sp 2 and Sp 3 Represents -(CH2) s1 -X"-, wherein s1 is an integer from 1 to 6, preferably 2, 3, 4 or 5, and X" is a linker to the benzene ring and is -O-, -O-CO-, -CO-O-, -O-CO-O- or a single bond.

[0401] Further preferred compounds of formula I are those selected from the group consisting of formulae RM-1 to RM-131 in Table D below, in particular those selected from the group consisting of formulae RM-1, RM-4, RM-8, RM-17, RM-19, RM-35, RM-37, RM-39, RM-40, RM-41, RM-48, RM-51, RM-52, RM-54, RM-57, RM-64, RM-74, RM-76, RM-88, RM-91, RM-102, RM-103, RM-109, RM-117, RM-120, RM-121 and RM-122.

[0402] LC media which comprise one, two or three polymerisable compounds of the formula I are particularly preferred.

[0403] Further preferred are polymerizable compounds, preferably selected from formula I, very preferably from formulae M1 to M31, most preferably from the above formulae of Table D, which have an absorption maximum in the wavelength range from 320 to 360 nm.

[0404] Preference is also given to LC media in which the polymerisable component B) consists exclusively of polymerisable compounds of the formula I.

[0405] In another preferred embodiment, in addition to or as an alternative to the polymerizable compounds of formula I according to the preferred sub-formulas and sub-groups above, component B) comprises one or more polymerizable mesogenic compounds containing one or more polymerizable groups and one or more polar anchoring groups, the polar anchoring groups being selected from, for example, hydroxyl, carboxyl, amino or thiol groups. These compounds can be used as self-aligning (SA) additives and can be used in SA mode displays according to the present invention. Suitable and preferred polymerizable mesogenic SA additives of this type are selected from compounds of formula I or M1-M31, wherein at least one group B 1 , B 2 , R a , R b , R x , L, Sp, Sp 1 , Sp 2 , Sp 3 or R aa Substituted with hydroxyl, carboxyl, amino or thiol groups, preferably hydroxyl groups. Further preferred polymerizable mesogenic SA additives of this type are selected from the group consisting of formulae SA-9 to SA-34 in Table E.

[0406] The proportion of polymerizable compounds of component B) in the LC medium is preferably 1 to <3%, more preferably 2 to <3%, very preferably 2 to 2.5%, most preferably 2 to 2.2%.

[0407] In addition to components A and B, the LC medium preferably comprises a component C which comprises one or more optically active compounds, preferably selected from chiral dopants.

[0408] The helical twisting force and the amount of dopant in the LC medium are preferably chosen such that the d / p ratio in the display according to the invention is ≥ 0.5, very preferably 0.5 to 1.2, more preferably 0.55 to 1.0, most preferably 0.6 to 0.8.

[0409] The proportion of chiral dopant in the LC medium is preferably from 0.01 to 6%, very preferably from 0.05 to 3%, more preferably from 0.1 to 0.5%.

[0410] Suitable and preferred chiral dopants are mentioned in the following Table B. Preferred chiral dopants are for example selected from R- or S-1011, R- or S-2011, R- or S-3011, R- or S-4011 or R- or S-5011.

[0411] Preferably, the twist angle of the helical twist induced by the chiral dopant in the LC medium (before application of a voltage) is from 210° to 330°, more preferably from 240 to 300°, most preferably 270°.

[0412] Preferably, the pitch of the helical twist induced by the chiral dopant in the LC medium is from 2 to 10 μm, very preferably from 3 to 6 μm.

[0413] Preferably, the d / p ratio in the display according to the invention is ≥ 0.5, very preferably from 0.5 to 1.2, more preferably from 0.55 to 1.0, most preferably from 0.6 to 0.8.

[0414] Preferably, the LC medium comprises one or more polymerisation initiators.

[0415] Suitable conditions for the polymerization and suitable types and amounts of initiators are known to the person skilled in the art and are described in the literature. Suitable for free-radical polymerization are, for example, commercially available photoinitiators or (Ciba AG).

[0416] If a polymerization initiator is added to the LC medium, its proportion is preferably from 0.001 to 1% by weight, particularly preferably from 0.001 to 0.5% by weight.

[0417] In another preferred embodiment, the LC medium comprises one or more stabilizers. The use of stabilizers can prevent the RMs from undesired spontaneous polymerization, for example during storage or transport.

[0418] Suitable types and amounts of stabilizers are known to those skilled in the art and are described in the literature.

[0419] The LC media according to the invention may, for example, also comprise one or more UV stabilizers, for example TUNA from CibaChemicals. Series, e.g. 770, or from Series, e.g. 1076 (all from BASF). Other suitable and preferred stabilizers are those selected from Table C below.

[0420] In another preferred embodiment of the present invention, the LC medium comprises one or more further stabilizers, which are preferably selected from the following formulae:

[0421]

[0422] where the individual radicals, independently of one another and identically or differently on each occurrence, have the following meanings

[0423] R a-d is a straight-chain or branched alkyl radical having 1 to 10, preferably 1 to 6, very preferably 1-4 C atoms, most preferably methyl,

[0424] X S H, CH3, OH or O· ,

[0425] A S is an optionally substituted straight-chain, branched or cyclic alkylene group having 1 to 20 C atoms,

[0426] n is an integer of 1 to 6, preferably 3.

[0427] Preferred stabilizers of formula S3 are selected from formula S3A

[0428]

[0429] wherein n2 is an integer from 1 to 12, and wherein the group (CH2) n2 One or more H atoms in are optionally replaced by methyl, ethyl, propyl, butyl, pentyl or hexyl.

[0430] Very preferred stabilizers are selected from the following formula

[0431]

[0432]

[0433]

[0434] In a preferred embodiment, the liquid-crystalline medium comprises one or more stabilizers selected from the group consisting of formulae S1-1, S2-1, S3-1, S3-1 and S3-3.

[0435] In a preferred embodiment, the liquid-crystalline medium comprises one or more stabilizers selected from Table C.

[0436] Preferably, the proportion of stabilizers (such as those of the formulae S1 to S3) in the liquid-crystalline medium is from 10 to 500 ppm, very preferably from 20 to 100 ppm.

[0437] In another preferred embodiment, the LC media according to the invention comprise a self-aligning (SA) additive, preferably in a concentration of 0.1 to 2.5%.

[0438] Preferred SA additives used in this preferred embodiment are selected from compounds comprising a mesogenic group and a linear or branched alkyl side chain terminated by one or more polar anchoring groups selected from hydroxyl, carboxyl, amino or thiol groups.

[0439] Further preferred SA additives contain one or more polymerizable groups, optionally linked to the mesogenic group via a spacer group.These polymerizable SA additives can be polymerized in the LC medium under similar conditions as applied for RMs in the PSA process.

[0440] Suitable SA additives are disclosed, for example, in US 2013 / 0182202 A1, US 2014 / 0838581 A1, US 2015 / 0166890 A1 and US 2015 / 0252265 A1.

[0441] In another preferred embodiment, the LC medium or polymer-stabilized display according to the invention comprises one or more self-aligning additives selected from Table E below.

[0442] In a preferred embodiment, the display according to the invention comprises no alignment layer.

[0443] The LC media according to the present invention may also contain other additives, for example selected from the following list including, but not limited to, antioxidants, free radical scavengers, defoamers, wetting agents, lubricants, dispersants, hydrophobic agents, binders, flow improvers, degassing agents, diluents, reactive diluents, auxiliaries, colorants, dyes, pigments and nanoparticles.

[0444] In addition, the following substances can be added to the liquid crystal medium, for example 0-15% by weight of pleochroic dyes, conductive salts for improving the conductivity, preferably 4-hexyloxybenzoic acid ethyldimethyl dodecyl ammonium, tetraphenyl borate tetrabutyl ammonium or crown ether complex salts (for example, see Haller et al., Mol. Cryst. Liq. Cryst. 24 , 249-258 (1973)), or substances for changing dielectric anisotropy, viscosity and / or nematic alignment. Such substances are described, for example, in DE-A 22 09 127, 22 40 864, 23 21 632, 23 38 281, 24 50 088, 26 37 430 and 28 53 728.

[0445] In a preferred embodiment, the LC medium comprises, preferably consists of:

[0446] A) a liquid crystal component A comprising one or more compounds selected from the group consisting of formulae A and B as defined above or subformulae thereof, one or more compounds selected from the group consisting of formulae C and D as defined above or subformulae thereof, and optionally one or more compounds of formula E as defined above or subformulae thereof,

[0447] B) a polymerizable component B comprising one or more polymerizable mesogenic compounds of formula I as defined above, preferably selected from formulae M1 to M31, very preferably selected from table D,

[0448] C) one or more chiral additives, preferably selected from the group consisting of chiral dopants, very preferably selected from Table B,

[0449] D) optionally one or more further additives, which are preferably selected from polymerization initiators, stabilizers (which are very preferably selected from table C) and self-aligning additives (which are very preferably selected from table E),

[0450] wherein the concentration of the polymerizable mesogenic compound in the LC medium is from 0.05 to <3%, and

[0451] The concentration of the chiral additives is selected such that they induce a twist angle of >210°, preferably from 210 to 330°, more preferably from 240 to 300°, very preferably 270° in the LC medium.

[0452] In another preferred embodiment, the LC medium comprises, preferably consists of:

[0453] A) a liquid crystal component A comprising one or more compounds selected from the group consisting of formulae A and B as defined above or subformulae thereof, one or more compounds selected from the group consisting of formulae C and D as defined above or subformulae thereof, and optionally one or more compounds of formula E as defined above or subformulae thereof,

[0454] B) a polymerizable component B comprising one or more polymerizable mesogenic compounds of formula I as defined above, preferably selected from formulae M1 to M31, very preferably selected from table D,

[0455] C) one or more chiral additives, preferably selected from the group consisting of chiral dopants, very preferably selected from Table B,

[0456] D) optionally one or more further additives, which are preferably selected from polymerization initiators, stabilizers (which are very preferably selected from table C) and self-aligning additives (which are very preferably selected from table E),

[0457] wherein the concentration of the polymerizable mesogenic compound in the LC medium is from 0.05 to <3%, and

[0458] The concentration of the chiral additives is selected in such a way that they induce a helical pitch of 2 to 10 μm, very preferably of 3 to 6 μm, in the LC medium.

[0459] In another preferred embodiment, the polymerisable mesogenic compound in the LC medium is unpolymerised.

[0460] In another preferred embodiment, the polymerisable mesogenic compound in the LC medium is polymerised.

[0461] In another preferred embodiment, the LC medium comprises one or more compounds selected from the following groups or any combination thereof:

[0462] In another preferred embodiment, the LC medium comprises one or more compounds selected from the following groups or any combination thereof:

[0463] 1) One or more compounds selected from the group consisting of formula A2a1, A2k1, and B2k1. These compounds can increase dielectric anisotropy, optical anisotropy, and operating temperature.

[0464] 2) One or more compounds selected from the group consisting of formula A1d1. These compounds can increase dielectric anisotropy and optical anisotropy, but reduce the operating temperature.

[0465] 3) One or more compounds selected from formula A1a2. These compounds can increase the dielectric anisotropy but reduce the operating temperature.

[0466] 4) One or more compounds selected from the group consisting of formula C1a, C1b, E1a. These compounds can reduce viscosity and adjust optical anisotropy, but will reduce the working temperature.

[0467] 5) Optionally, one or more compounds selected from formula C4b. These compounds can reduce viscosity but will reduce the working temperature.

[0468] 6) One or more compounds selected from the group consisting of formula C7a, D2, and E6. These compounds can reduce dielectric anisotropy and operating temperature.

[0469] 7) One or more chiral dopants, preferably selected from Table B, very preferably selected from the formulas R / S-1011, R / S-2011, R / S-3011, R / S-4011 and R / S-5011. These compounds induce helically twisted structures and twist angles in the layer with LC molecules.

[0470] 8) One or more reactive mesogens, preferably selected from formula I, very preferably from formulas M1 to M31, more preferably from formulas RM-1 to RM-131 of Table D, most preferably from formulas RM-1, RM-4, RM-8, RM-17, RM-19, RM-35, RM-37, RM-39, RM-40, RM-41, RM-48, RM-51, RM-52, RM-54, RM-57, RM-64, RM-74, RM-76, RM-88, RM-91, RM-102, RM-103, RM-109, RM-117, RM-120, RM-121 and RM-122. These compounds provide polymer stability that reduces the twist angle.

[0471] 9) one or more stabilizers, preferably selected from Table C, very preferably selected from the following formula

[0472]

[0473]

[0474] wherein n is 1, 2, 3, 4, 5, 6 or 7, preferably 3,

[0475] 10) One or more photoinitiators. These compounds initiate the polymerization of component B and the polymerizable compounds of group 8 above.

[0476] 11) One or more self-aligning additives. These compounds make it possible to omit an alignment layer.

[0477] 12) One or more additives selected from antioxidants, UV absorbers, colorants, defoamers.

[0478] The individual components of preferred embodiments of the LC media according to the invention are known or processes for preparing them are available from the prior art by a person skilled in the relevant art, since they are based on standard processes described in the literature.

[0479] It goes without saying to the person skilled in the art that the LC media according to the invention can also comprise compounds in which H, N, O, Cl, F are replaced by corresponding isotopes, for example deuterium.

[0480] The LC media used according to the invention are prepared in a manner conventional per se, for example by mixing one or more LC compounds selected from the formulae A to F or one or more compounds of the preferred embodiments described above with one another and / or other LC compounds and / or additives (e.g. polymerizable compounds or RMs). Typically, the desired amount of the component used in smaller amounts is dissolved in the component constituting the main constituent, which is advantageously done at elevated temperature. It is also possible to mix the solutions of the components in an organic solvent, for example acetone, chloroform or methanol, and to remove the solvent again after thorough mixing, for example by distillation.

[0481] It goes without saying that, by suitable selection of the components of the liquid-crystal medium according to the invention, higher clearing points (for example above 100° C.) can also be achieved at higher threshold voltages or lower clearing points at lower threshold voltages while retaining other advantageous properties. At a correspondingly only slightly increased viscosity, liquid-crystal media with higher Δε and thus lower thresholds can also be obtained. The MLC displays according to the invention are preferably operated in the first Gooch and Tarry transmission minimum [CH Gooch and HATarry, Electron. Lett. 10, 2-4, 1974; CH Gooch and HATarry, Appl. Phys., Vol. 8, 1575-1584, 1975], where, in addition to particularly advantageous electro-optical properties, such as high steepness of characteristic lines and low angular dependence of contrast (German Patent 30 22 818), a lower dielectric anisotropy is sufficient at the same threshold voltage as in similar displays at the second minimum. This makes it possible to obtain significantly higher specific resistance values ​​in the first minimum using the mixtures according to the invention than in the case of liquid-crystal media comprising cyano compounds. By suitable selection of the individual components and their weight proportions, the person skilled in the art can set the birefringence required for a predetermined layer thickness for MLC displays using simple conventional methods.

[0482] The LC media and LC host mixtures according to the invention preferably have a nematic phase range of ≥80 K, very preferably ≥100 K at 20° C. and preferably a rotational viscosity of ≤250 mPa·s, very preferably ≤200 mPa·s.

[0483] The birefringence Δn of the LC media and LC host mixtures according to the invention is preferably from 0.07 to 0.15 at 20° C., particularly preferably from 0.08 to 0.15.

[0484] The LC medium and the LC host mixture have a positive dielectric anisotropy Δε. Preferably, the LC medium and the LC host mixture have a positive dielectric anisotropy Δε of +2 to +30, more preferably +3 to +20, very preferably +4 to +15, most preferably +4 to +8 at 20°C and 1 kHz.

[0485] The structure of the PS-UF TN-LC display according to the invention corresponds to the customary geometry of TN displays described in the prior art cited at the outset.

[0486] The construction of the PS-UF TN-LC display according to the invention consisting of polarizer, electrode substrate and surface-treated electrodes corresponds to the conventional design of such displays. The term "conventional design" is understood here in a broad sense and also includes all derivatives and variants of LC displays, in particular including matrix display elements based on polysilicon TFTs or MIMs.

[0487] The preferred PS-UF TN-LC display of the present invention comprises:

[0488] a first substrate comprising pixel electrodes defining pixel areas, the pixel electrodes being connected to a switching element arranged in each pixel area, and optionally a first alignment layer arranged on the pixel electrodes,

[0489] a second substrate comprising a common electrode layer and optionally a second alignment layer, the common electrode layer being arranged on the entire portion of the second substrate facing the first substrate,

[0490] a nematic LC medium layer having positive dielectric anisotropy, which is distributed between the first substrate and the second substrate and comprises a liquid crystal component A, which comprises, preferably consists of, one or more mesogens or liquid crystal molecules, and further comprises a component C, which comprises one or more chiral additives, and optionally a component D, which comprises one or more other additives,

[0491] a polymer layer deposited on each of said first and second electrodes or, if present, on each of said first and second alignment layers, wherein said polymer layer is formed of one or more polymerisable mesogenic compounds which are present in the LC medium in a concentration of 0.1% to <3% and which polymerises in situ after dispensing the LC medium between the two substrates,

[0492] - Optionally, a first polarizer on the side of the first substrate facing away from the LC layer and a second polarizer on the side of the second substrate facing away from the LC layer, said polarizers preferably being oriented such that their transmission planes are at right angles for plane-polarized light (orthogonal polarizations).

[0493] The present invention also relates to a method for manufacturing a polymer stabilized twisted nematic (PS-TN) mode liquid crystal display (LCD), comprising the following steps:

[0494] a) providing a first substrate provided with a first electrode layer and optionally a first alignment layer, and a second substrate provided with a second electrode layer and optionally a second alignment layer,

[0495] wherein the first and / or the second substrate is preferably provided with fixing means, preferably a sealant material and / or a spacer, which fixing means fix the first and second substrate at a constant distance relative to each other and with their planes parallel to each other,

[0496] b) distributing a layer of a nematic LC medium having positive dielectric anisotropy between the first and second substrates so that the LC medium is in contact with the first and second alignment layers (if these layers are present),

[0497] Wherein the LC medium comprises, preferably consists of:

[0498] A) a liquid crystal component (hereinafter also referred to as "LC host mixture"), which comprises, preferably consists of, mesogenic or liquid crystal molecules,

[0499] B) a polymerizable component B comprising, preferably consisting of, one or more polymerizable mesogenic compounds (hereinafter also referred to as "reactive mesogens"),

[0500] C) one or more chiral additives, preferably selected from chiral dopants,

[0501] D) optionally one or more further additives, preferably selected from polymerization initiators, stabilizers and self-aligning additives,

[0502] wherein the proportion of polymerizable mesogenic compounds in the LC medium is <3%, preferably from 0.05 to <3%, and

[0503] wherein the longitudinal axes of the LC molecules are oriented parallel or tilted relative to the plane of the substrate, and the chiral additive induces a helical twist with a given pitch p in the LC molecules of the LC medium along an axis perpendicular to the substrate, and

[0504] wherein the thickness of the LC medium layer is d, and the ratio d / p is ≥ 0.5, preferably > 0.5, very preferably 0.6-0.8, and

[0505] wherein the twist angle of the helical twist of the LC molecules caused by the chiral additive is >210°, preferably in the range of 210 to 330°, more preferably in the range of 240 to 300°, very preferably 270°,

[0506] c) applying a voltage to the first and second electrodes such that the twist angle of the helical twist of the LC molecules decreases to <150°, preferably to a range of 60 to 120°, preferably 80 to 100°, most preferably to 90°,

[0507] d) polymerizing the polymerizable mesogenic compound of polymerizable component B of the LC medium between the first and second substrates after or while applying a voltage, preferably by exposure to UV radiation, thereby stabilizing the twisted nematic configuration of the LC medium with reduced twist angle of step c), and

[0508] e) optionally, subjecting the LC medium to a second polymerisation step, preferably by exposure to UV radiation, without applying a voltage to the first and second electrodes, thereby polymerising any polymerisable compounds which have not reacted in step d),

[0509] f) optionally providing a first polarizer on the side of the first substrate facing away from the LC layer and a second polarizer on the side of the second substrate facing away from the LC layer, wherein the polarizers are preferably oriented so that their transmission planes are at right angles to plane polarized light (orthogonal polarizations).

[0510] The substrate used in step a) of the display and the process for its production according to the invention is preferably a glass substrate. For flexible LC displays, plastic substrates are preferably used. These plastic substrates preferably have a low birefringence. Examples of suitable and preferred plastic substrates are polycarbonate (PC), polyethersulfone (PES), polycyclic olefin (PCO), polyarylate (PAR), polyetheretherketone (PEEK) or colorless polyimide (CPI) substrates.

[0511] At least one substrate should be transmissive to the light radiation used for polymerizing the polymerizable compounds used in the method according to the invention.

[0512] If the substrates are provided with alignment layers produced by photopolymerization and / or photoalignment, at least one of the substrates should be transmissive for the light radiation used for the photopolymerization or photoalignment of the alignment layer material or its precursors.

[0513] The electrode layers can be designed by a skilled person according to the respective display type.In the LC display according to the invention, the first substrate and the second substrate are each provided with an electrode layer.

[0514] Further preferably, one of the first electrode layer and the second electrode layer is a pixel electrode defining a pixel area, the pixel electrode being connected to a switching element arranged in each pixel area and optionally including a micro-slit pattern, and the other electrode layer of the first electrode layer and the second electrode layer is a common electrode layer, which can be arranged on an entire portion of the substrate facing the other substrate.

[0515] The first and / or second substrate may carry additional layers or components including, but not limited to, color filters, TFT arrays, black matrices, polyimide coatings, or other components typically found on display substrates.

[0516] Preferably, at least one of the first and second substrates, more preferably each substrate, is provided with an alignment layer, which is typically applied over the electrodes such that it contacts the LC medium.

[0517] The first and / or second alignment layer controls the alignment direction of the LC molecules of the LC layer.In the display according to the invention the alignment layers are chosen such that they impart a parallel or slightly tilted orientation direction to the LC molecules with respect to the substrate.

[0518] Suitable and preferred alignment layers include, for example, or consist of polyimides, which can also be prepared by photoalignment methods or by rubbing. Solution-processable alignment layer materials are preferred. These are preferably processed from solutions in solvents, preferably organic solvents, such as N-methylpyrrolidone, 2-butoxyethanol or gamma-butyrolactone.

[0519] In a preferred embodiment, the alignment layer is formed by depositing an alignment layer material such as a polyimide or a precursor thereof such as a solution of a polyimide precursor on the substrate and optionally curing the alignment layer material or precursor thereof by exposure to heat and / or actinic radiation such as UV radiation.

[0520] The alignment layer material or its precursor may be deposited on the substrate, for example, by coating or printing methods.

[0521] In case a solvent is used to deposit the alignment layer material, it is preferably dried or evaporated off after deposition.The evaporation of the solvent may be supported, for example, by applying heat and / or reduced pressure.

[0522] Preferred methods for curing the alignment layer are thermal curing and photocuring, with photocuring being very preferred. Photocuring is performed, for example, by exposure to UV radiation. The skilled person can select suitable curing conditions based on his common general knowledge and as described in the literature, depending on the precursor material used. In the case of commercially available materials, suitable processing and / or curing conditions are usually provided together with the sale or sampling of the material.

[0523] In displays according to the invention the alignment layers are preferably chosen such that they impart a planar (or parallel) alignment to the LC molecules, i.e. wherein the longitudinal axes of the LC molecules are parallel to the surface of the nearest substrate and wherein the longitudinal axes of the LC molecules may also be slightly tilted relative to the surface of the substrate.

[0524] Preferably, the tilt angle of the longitudinal axes of the LC molecules located near the substrate surface relative to the substrate is >0° to 20°, preferably 0.1° to 20°, very preferably 0.2° to 3.5°.

[0525] In order to impart a preferred two-dimensional alignment direction to the LC molecules in the plane of the substrate, the alignment layer, for example, comprises an alignment layer material, such as polyimide, which is unidirectionally rubbed or prepared by a photoalignment method.

[0526] Preferably, the alignment direction or average orientation direction (also called "director") of the longitudinal axes of the LC molecules near the first and second substrates are at right angles, i.e. at 90° relative to each other. Further preferably, the alignment direction or LC director near the first and second substrates is at 45° relative to the edge of the substrate.

[0527] For example, this can be achieved by using a first alignment layer and a second alignment layer, for example comprising polyimide, both of which are unidirectionally rubbed and arranged so that their rubbing directions are at right angles, and wherein the rubbing direction of the alignment layer corresponds to the alignment direction of the LC molecules. Alternatively, this can be achieved by preparing the alignment layer by photoalignment using linearly polarized light, wherein the polarization direction of the polarized light corresponds to the alignment direction of the LC molecules.

[0528] The display according to the invention preferably comprises a first alignment layer and a second alignment layer, preferably comprising polyimide, which are both rubbed unidirectionally and wherein the rubbing directions are at right angles to each other.

[0529] The display according to the invention may comprise further elements, such as colour filters, a black matrix, a passivation layer, an optical retardation layer, transistor elements for addressing the individual pixels etc., all of which are well known to those skilled in the art and may be used without inventive skill.

[0530] In step b), a nematic LC medium layer having positive dielectric anisotropy and containing components A, B, C and optionally D as described above and below is distributed between the first and second substrates such that the LC medium is in contact with the first and second alignment layers (where such alignment layers are present).

[0531] The LC medium can be dispensed or filled onto the substrate or into the display, respectively, by methods conventionally used by display manufacturers.

[0532] Preferably, the LC medium is deposited onto the substrate by using one of the following deposition methods: one drop filling (ODF), inkjet printing, spin coating, slot coating, flexographic printing or a comparable method.

[0533] The preferred method is inkjet printing.

[0534] Another preferred method is the ODF method, which preferably comprises the following steps:

[0535] b1) dispensing a droplet or an array of droplets of LC medium on a first substrate, and

[0536] b2) providing a second substrate with dispensed droplets of LC medium on top of the first substrate, preferably under vacuum conditions, so that the droplets of LC medium spread and form a continuous layer between the two substrates.

[0537] The applied LC medium forms a thin, uniform film having a thickness of the target final cell gap of the display.

[0538] Preferably, the display according to the invention comprises fixing means which fix the first and second substrates at a constant distance relative to each other and with their planes parallel to each other. Preferably, the fixing means comprises sealant material and spacer material to maintain a constant cell gap and LC layer thickness.

[0539] Preferably, the first and second substrates are fixed or glued together by fixing means such as a sealant material provided on the substrates, preferably in areas close to the edges of the substrates.

[0540] Preferably, a sealant material is deposited onto the first substrate, or between the first substrate and the second substrate, before dispensing the LC medium between the first substrate and the second substrate.

[0541] The sealant material is arranged on the first substrate, or between the first and second substrates, preferably in the region between the LC medium and the edge of the respective substrate. The sealant material is for example a cross-linked polymer formed from a curable polymer precursor. The sealant material is then cured, preferably after assembling the first and second substrates to form the LC cell, but before photopolymerization of the polymerizable compound contained in the LC medium. Preferably, the sealant material is cured by exposure to heat and / or light radiation.

[0542] The spacer material consists for example of transparent glass or plastic beads.In a preferred embodiment, the spacers are dispensed between the substrates together with the LC medium.

[0543] In another preferred embodiment, in order to maintain a constant cell gap and LC layer thickness, the display comprises spacer material, such as photospacers, outside the LC layer, eg above the black matrix, and the LC layer comprises no spacer material.

[0544] Suitable sealants and spacers are known to the skilled person and are commercially available.

[0545] In step c), a voltage is applied to the first electrode and the second electrode such that the twist angle of the helical twist of the LC molecules in the LC layer is reduced from the range 210-330°, preferably 240-300°, very preferably 270° to 60-120°, preferably 80 to 100°, very preferably to 90° (given by the LC layer thickness and the natural helical twist caused by the chiral dopant).

[0546] Suitable ways, conditions, parameters and driving schemes for applying voltage to achieve the desired twist angle (and then stabilize the polymer) are well known to those skilled in the art or are described in the literature, for example in K. Takatoh et al., Liq. Cryst. 2012, 39(6), 715-720, and can be used without inventive skill.

[0547] The choice of suitable voltages and the driving scheme for applying the voltages also depends on the physical properties of the LC medium and the collocation between the LC medium and the alignment layer.

[0548] In a preferred embodiment, the applied voltage and the driving scheme are selected so that the TN orientation with reduced twist angle as described above is stable for a given period of time, for example, a few (>1) seconds, a few (>1) minutes or a few (>1) hours. This allows the polymerization step d) to be performed after step c), i.e. without any overlap in time.

[0549] In step d), the polymerizable compounds of polymerizable component B comprised in the LC medium are then polymerized or crosslinked (if the compounds comprise two or more polymerizable groups) by in situ polymerization in the LC medium between the substrates of the LC display, optionally applying a voltage to the electrodes for at least a portion of the polymerization process. In optional step e), the polymerizable compounds not completely reacted in step d) are polymerized or crosslinked by in situ polymerization without applying a voltage.

[0550] In steps d) and e), the polymerizable compounds of polymerizable component B are preferably polymerized by photopolymerization, very preferably by UV photopolymerization.

[0551] Upon polymerization, the polymerizable compound forms polymers or cross-linked polymers, which stabilize the reduced twist angles of the LC molecules in the LC medium. Without wishing to be bound by a particular theory, it is believed that most of the polymer obtained from the polymerizable compound will phase separate or precipitate from the LC medium and form a polymer layer on the substrate or electrode or alignment layer provided thereon. Microscopic measurement data (such as SEM and AFM) have confirmed that the polymer is mainly aggregated at the LC layer / substrate interface.

[0552] Suitable and preferred polymerisation methods are, for example, thermal polymerisation or photopolymerisation, preferably photopolymerisation, in particular UV-induced photopolymerisation, which can be achieved by exposing the polymerisable compound to UV radiation.

[0553] The polymerization can be carried out in one step (step d) or in two or more steps (steps d and e or a repetition thereof) as described above and below. Step d) is hereinafter also referred to as the "UV1" step, while step e) is hereinafter also referred to as the "UV2" step.

[0554] In a preferred embodiment of the present invention, the method for preparing a display comprises one or more of the following features:

[0555] - exposing the polymerisable LC medium to UV light in a two-step process comprising a first UV exposure step (step d or UV1) which is carried out simultaneously with or after applying a voltage to the electrodes, preferably after applying a voltage to the electrodes, and a second UV exposure step (step e or UV2) to complete the polymerisation without applying a voltage to the electrodes,

[0556] Preferably in the UV2 step, and optionally also in the UV1 step, the polymerisable LC medium is exposed to a UV lamp with a wavelength of 300 to 380 nm, preferably with an intensity of 0.5 mW / cm 2 Up to 30mW / cm 2 , more preferably 1 to 20 mW / cm 2 UV light,

[0557] - exposing the polymerisable LC medium to UV light having a wavelength of 340 nm or more, preferably 400 nm or less.

[0558] The method of the preferred embodiment can be carried out, for example, by using a desired UV lamp, or by using a bandpass filter and / or a cutoff filter, which is substantially transmissive for UV light having a corresponding desired wavelength and substantially blocks light having a corresponding undesirable wavelength. For example, when radiation with a UV light having a wavelength λ of 300-400nm is desired, UV exposure can be carried out using a wide bandpass filter that is substantially transmissive for a wavelength of 300nm<λ<400nm. When radiation with a UV light having a wavelength λ greater than 365nm is desired, UV exposure can be carried out using a cutoff filter that is substantially transmissive for a wavelength of λ>365nm.

[0559] "Substantially transmit" means that the filter transmits a majority, preferably at least 50%, of the intensity of incident light of a desired wavelength. "Substantially block" means that the filter does not transmit a majority, preferably at least 50%, of the intensity of incident light of an undesired wavelength. "Desired (undesired) wavelengths" means, for example, wavelengths within (outside) a given λ range in the case of a bandpass filter and wavelengths above (below) a given λ value in the case of a cutoff filter.

[0560] The method of this preferred embodiment enables the manufacture of displays by using longer UV wavelengths, thereby reducing or even avoiding the dangerous and damaging effects of the short UV light component.

[0561] The polymer obtained by polymerisation of the polymerisable compounds of component B of the LC medium preferably forms a layer on one or both of the substrates or on one or both of the alignment layers deposited on the substrate (or electrode structures) or on one or both of the electrode structures deposited on the substrate.

[0562] Preferably, at least during a portion of the polymerization process, preferably during step UV1 as described above, the polymerizable compounds of polymerizable component B are polymerized while applying a voltage in order to stabilize the reduced distortion. However, the desired orientation with reduced distortion can also be achieved by polymerizing after applying a voltage in step c), preferably the UV1 process step.

[0563] Therefore, in a preferred embodiment of the present invention, step d) (UV1) of polymerizing the polymerizable compounds of polymerizable component B is performed simultaneously with step c) of applying a voltage, or step d) is performed so as to at least partially overlap with step c).

[0564] In another preferred embodiment of the present invention, step d) of polymerizing the polymerizable compounds of the polymerizable component B (UV1) is carried out after step c) of applying a voltage.

[0565] In a preferred embodiment, the display according to the invention does not comprise a polyimide alignment layer. In another preferred embodiment, the display according to the invention comprises a polyimide alignment layer on one or both of the substrates.

[0566] In another preferred embodiment, the LC media according to the invention comprise a self-aligning (SA) additive, preferably in a concentration of 0.1 to 2.5%.The LC media according to this preferred embodiment are particularly suitable for polymer-stabilized SA (PS-SA) displays.

[0567] Preferred SA additives used in this preferred embodiment are selected from compounds comprising a mesogenic group and a linear or branched alkyl side chain terminated by one or more polar anchoring groups selected from hydroxyl, carboxyl, amino or thiol groups.

[0568] Further preferred SA additives contain one or more polymerizable groups, which are optionally linked to the mesogenic group via a spacer group.These polymerizable SA additives can be polymerized in the LC medium under similar conditions as applied to the polymerizable compounds of polymerizable component B.

[0569] In another preferred embodiment, the LC medium or the polymer-stabilized SA-VA or SA-FFS display according to the invention comprises one or more self-aligning additives selected from Table E below.

[0570] In this context, any SA additives having a mesogenic group and one or more polymerizable groups (such as those of formulae SA-9 to SA-34 in Table E) contained in the LC medium are understood to be part of the polymerizable component B. Therefore, the preferred compositions and concentration ranges given above and below for the polymerizable component B and its ingredients are understood to include both RMs that are not SA additives and RMs that are SA additives and contain one or more polar anchoring groups selected from, for example, hydroxyl, carboxyl, amino or thiol groups.

[0571] The following examples are intended to illustrate the invention but not to limit it. Above and below, percentage data represent weight percentages; all temperatures are expressed in degrees Celsius.

[0572] Table A

[0573] In Table A, m and n are independently an integer from 1 to 12, preferably 1, 2, 3, 4, 5 or 6, k is 0, 1, 2, 3, 4, 5 or 6, and (O) C m H 2m+1 Meaning C m H 2m+1 or OC m H 2m+1 .

[0574]

[0575]

[0576]

[0577]

[0578]

[0579]

[0580]

[0581]

[0582]

[0583]

[0584]

[0585] Particular preference is given to liquid-crystal mixtures which comprise at least one, two, three, four or more compounds from Table A.

[0586] Table B indicates possible dopants which are usually added to the mixtures according to the invention. The mixtures preferably comprise 0 to 10% by weight, in particular 0.001 to 5% by weight, particularly preferably 0.001 to 3% by weight of dopant.

[0587] Table B

[0588]

[0589]

[0590] Table C

[0591] Mentioned below are stabilizers which can be added to the mixture according to the invention, for example in an amount of 0 to 10% by weight.

[0592]

[0593] n = 1, 2, 3, 4, 5, 6 or 7

[0594]

[0595] n = 1, 2, 3, 4, 5, 6 or 7

[0596]

[0597] n = 1, 2, 3, 4, 5, 6 or 7

[0598]

[0599]

[0600]

[0601]

[0602]

[0603] Table D

[0604] Table D shows exemplary reactive mesogenic compounds which can be used in the LC media according to the present invention.

[0605]

[0606]

[0607]

[0608]

[0609]

[0610]

[0611]

[0612]

[0613]

[0614]

[0615]

[0616]

[0617]

[0618]

[0619]

[0620]

[0621]

[0622]

[0623]

[0624] In a preferred embodiment, the mixture according to the invention comprises one or more polymerizable compounds, which are preferably selected from polymerizable compounds of formula RM-1 to RM-140. Among these compounds, compounds RM-1, RM-4, RM-8, RM-17, RM-19, RM-35, RM-37, RM-39, RM-40, RM-41, RM-48, RM-51, RM-52, RM-54, RM-57, RM-64, RM-74, RM-76, RM-88, RM-91 RM-102, RM-103, RM-109, RM-117, RM-120, RM-121 and RM-122 are particularly preferred.

[0625] Table E

[0626] Table E shows self-aligning additives for homeotropic alignment which can be used together with the polymerisable compounds of the formula I in the LC media of SA-VA and SA-FFS displays according to the invention:

[0627]

[0628]

[0629]

[0630]

[0631]

[0632]

[0633]

[0634]

[0635] In a preferred embodiment, the LC media, SA-VA and SA-FFS displays according to the invention comprise one or more SA additives selected from the group consisting of formulae SA-1 to SA-34.

[0636] Example

[0637] The following examples explain the present invention without limiting it. However, they show preferred mixture concepts and preferably used compounds and their corresponding concentrations and their combinations with each other to those skilled in the art. In addition, the examples illustrate obtainable properties and property combinations.

[0638] In addition, the following abbreviations and symbols are used:

[0639] t off , t d, τ off Indicates the turn-off or decay time at 20°C [ms]

[0640] t on , t r , τ on Indicates the opening or rise time at 20°C [ms]

[0641] d represents the cell gap or LC thickness of the switchable LC layer [μm]

[0642] V0, V th represents the threshold voltage at 20°C, capacitive [V],

[0643] V op Indicates the operating voltage [V]

[0644] n e represents the extraordinary refractive index at 20°C and 589nm,

[0645] n o represents the ordinary refractive index at 20°C and 589nm,

[0646] △n represents the optical anisotropy at 20°C and 589nm,

[0647] ε ⊥ represents the dielectric constant perpendicular to the director at 20°C and 1kHz,

[0648] ε || represents the dielectric constant parallel to the director at 20°C and 1kHz,

[0649] Δε represents the dielectric anisotropy at 20°C and 1kHz,

[0650] cl.p., T(N,I) represents the clearing point [℃],

[0651] γ1 represents the rotational viscosity at 20°C [mPa·s],

[0652] K1 is the elastic constant at 20°C, “slope” deformation [pN],

[0653] K2 represents the elastic constant at 20°C, "torsion" deformation [pN],

[0654] K3 represents the elastic constant at 20°C, “bending” deformation [pN].

[0655] Unless expressly stated otherwise, all parameters and values ​​given above and below refer to a temperature of 20°C.

[0656] Unless expressly stated otherwise, all concentrations and ratios in the present application are given as percentages by weight and relate to the respective entire mixture, which comprises all solid or liquid-crystalline components (without solvent).

[0657] Unless otherwise stated, all temperature values ​​indicated in this application, such as melting point T(C,N), transition from smectic phase (S) to nematic phase (N) T(S,N) and clearing point T(N,I) are expressed in degrees Celsius (°C). Mp stands for melting point, cl.p. = clearing point. In addition, C = liquid crystal phase, N = nematic phase, S = smectic phase and I = isotropic phase. The data between these symbols represent transition temperatures.

[0658] All physical properties are and have been determined according to "Merck Liquid Crystals, Physical Properties of Liquid Crystals" Status November 1997, Merck KGaA, Germany, and are valid for a temperature of 20°C, with Δn measured at 589 nm and Δε measured at 1 kHz, unless expressly stated otherwise in each case.

[0659] The term "threshold voltage (V th , V0)" relates to the capacitive threshold (V0), which is also referred to as the Freedericks threshold unless otherwise stated. In the embodiments, the optical threshold is also as usual for a relative contrast of 10% (V 10 ) is given.

[0660] The term "operating voltage (V op )" refers to 2xV 10 Then select the voltage given by the next larger multiple of 0.5V. For example, when V 10 =4.8V, then V op =10V, when V 10 =5.2V, then V op =10.5V, when V 10 =5.6V, then V op =11.5V.

[0661] Unless otherwise stated, the process of polymerising polymerisable compounds in polymer-stabilised displays as described above and below is carried out at a temperature where the LC medium exhibits a liquid crystal phase, preferably a nematic phase, and most preferably at room temperature (also abbreviated "RT").

[0662] Unless otherwise stated, the methods for preparing the test cells and measuring their electro-optical and other properties were performed by the methods described below or methods analogous thereto.

[0663] Example 1

[0664] Nematic LC host mixture N1 was prepared as follows:

[0665]

[0666] To mixture N1 was added 0.04% of stabilizer S2-1 to form mixture S1.

[0667]

[0668] 2.61% of chiral dopant S-4011 was added to mixture S1 to form mixture D1A. The pitch of the mixture caused by the chiral dopant was 5 microns.

[0669] 0.21% of chiral dopant S-4011 was added to mixture S1 to form mixture D1B. The pitch of the mixture caused by the chiral dopant was 60 micrometers.

[0670] Add 2% RM-64 and 0.02% photoinitiator to mixture D1A 651 to form mixture P1A.

[0671] Add 2% RM-64 and 0.02% photoinitiator to mixture D1B 651 to form mixture P1B.

[0672]

[0673] TN test box manufacturing

[0674] A TN test cell was prepared, comprising two polished SL glass substrates (Corning, thickness 1.1 mm) equipped with an ITO electrode layer (thickness 200A, 10 Ohms / sq, 1 cm x 1 cm), a rubbed polyimide alignment layer (JSR AL3046) (with rubbing directions of 0° and 90°, respectively), a spacer and a sealant (XN-1500 from Mitsubishi Chemicals) to achieve a cell gap of 3 or 2.7 microns, respectively.

[0675] Fill the mixture into individual test boxes.

[0676] PS-TN test box manufacturing

[0677] The test cell with the mixture containing the polymerizable compound was subjected to a two-step UV curing process, where a voltage was applied to the electrodes in the first step and no voltage was applied in the second UV step.

[0678] UV Step 1 (UV1):

[0679] Fe / I lamp with 365nm filter, UV intensity 4.0mW / cm 2 , with UV power detector Ushio UIT-250, UVD-S365; electric field: pulse 5s / cycle, pulse height 18V, pulse width 100ms. Irradiation time 300s.

[0680] UV Step 2 (UV2):

[0681] Toshiba C fluorescent lamp, green UV, without 365nm filter, UV intensity 0.5mW / cm 2 , with UV power detector Ushio UIT-250, UVD-S365, irradiation time 60 minutes.

[0682] E / O performance, response time

[0683] The electro-optical performance (transmittance vs. voltage) and response time of the test box were measured using an LCD evaluation system (LCD-5200, Otsuka electronics Co., Ltd).

[0684] The results are shown in Table 1.

[0685]

[0686] It can be seen that the response time is significantly reduced in the chirally doped and polymer-stabilized mixtures P1A and P1B compared to the undoped mixture N1.

[0687] The above results show that the method of the present invention is able to manufacture PS-UF TN-LCD with high d / p value while maintaining a 90° TN configuration and achieve fast response time, especially faster decay time, while maintaining high transmittance.

[0688] Example 2

[0689] To the mixture D1B of Example 1, 2% of RM-51 and 0.02% of photoinitiator were added. 651 (relative to the total concentration of RM) to form mixture P1C.

[0690]

[0691] Example 3

[0692] To the mixture D1B of Example 1, 2% of RM-52 and 0.02% of photoinitiator were added. 651 to form mixture P1D.

[0693]

[0694] Example 4

[0695] The nematic LC host mixture N2 was prepared as follows:

[0696]

[0697] To mixture N2, 0.04% of stabilizer S2-1 was added to form mixture S2.

[0698] 0.35% of chiral dopant S-4011 was added to mixture S2 to form mixture D2. The pitch of the mixture caused by the chiral dopant was 30 micrometers.

[0699] Add 2% RM-64 and 0.02% photoinitiator to mixture D2 651, to form mixture P2.

[0700] Example 5

[0701] Nematic LC host mixture N3 was prepared as follows:

[0702]

[0703] To mixture N3 was added 0.04% of stabilizer S2-1 to form mixture S3.

[0704] 0.24% of chiral dopant S-4011 was added to mixture S3 to form mixture D3. The pitch of the mixture caused by the chiral dopant was 40 micrometers.

[0705] Add 2% RM-64 and 0.02% photoinitiator to mixture D3 651, to form mixture P3.

Claims

1. LC display, including a) a first substrate and a second substrate, the first substrate being provided with a first electrode layer and the second substrate being provided with a second electrode layer, b) a layer of a nematic LC medium distributed between the first and second substrates, the nematic LC medium comprising chiral additives and having a positive dielectric anisotropy, wherein the longitudinal axes of the LC molecules are oriented parallel or tilted relative to the plane of the substrate, and the chiral additive induces a helical twist with a given pitch p in the LC molecules of the LC medium along an axis perpendicular to the substrate, and where the thickness of the layer of the LC medium is d and the ratio d / p is ≥ 0.5, wherein the twist angle of the helical twist of the LC molecule is 60 to 120°, and wherein the display further comprises a polymer layer deposited on one or both of the first and second electrodes, wherein the polymer layer is formed from one or more polymerizable mesogenic compounds which are contained in the LC medium in a concentration of 2-2.8% and which are polymerized in situ after the LC medium has been dispensed between the two substrates, wherein the LC medium has a dielectric anisotropy of +4 to +15 at 20° C. and 1 kHz, It is characterized in that The LC medium comprises one or more compounds selected from the following formulae: where the individual radicals, independently of one another and identically or differently on each occurrence, have the following meanings: Independently of each other and in each occurrence is identically or differently R 21 , R 31 each independently of one another is alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C atoms or alkenyl or alkenyloxy having 2 to 9 C atoms, all of which are unfluorinated or fluorinated, X 0 is F, Cl, a haloalkyl or alkoxy group having 1 to 6 C atoms or a haloalkenyl or alkenyloxy group having 2 to 6 C atoms, Z 31 is -CH2CH2-, -CF2CF2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O- or a single bond, L 21 , L 22 , L 31 , L 32 Each independently is H or F, L S is H or CH3, g is 0, 1, 2 or 3.

2. The display according to claim 1, wherein a) the first substrate is provided with a first electrode layer and a first alignment layer, and the second substrate is provided with a second electrode layer and a second alignment layer.

3. A display according to claim 2, wherein the polymer layer is deposited on one or both of the first and second alignment layers.

4. A display according to claim 1, comprising c) a first polariser on the side of the first substrate facing away from the LC layer and a second polariser on the side of the second substrate facing away from the LC layer.

5. The display according to claim 4, wherein: The polarizers are oriented so that their transmission planes are at right angles to plane-polarized light (orthogonal polarization). The display according to claim 1 , wherein the ratio d / p>0.

5.

7. The display according to claim 1, wherein the ratio d / p is 0.6-0.

8.

8. The display device according to claim 1, wherein the twist angle of the helical twist of the LC molecules is 80 to 100°.

9. The display device of claim 1, wherein the twist angle of the helical twist of the LC molecules is 90°.

10. The display according to claim 1, characterized in that The LC medium comprises a photoinitiator.

11. The display according to any one of claims 1 to 10, characterized in that: A twist angle of helical twist of the LC molecules between the first substrate and the second substrate is 80° to 100°.

12. The display according to any one of claims 1 to 10, characterized in that: The ratio d / p of the layer thickness d of the LC medium to the pitch p of the helical twist induced by the chiral additive is from 0.6 to 0.

8.

13. The display according to any one of claims 1 to 10, characterized in that The longitudinal axes of the LC molecules of the LC medium located on the surface of each substrate exhibit a tilt angle of >0° to 20° relative to said substrate.

14. The display according to any one of claims 1 to 10, characterized in that The first substrate and the second substrate are provided with fixing means which fixes the first and second substrates at a constant distance relative to each other and in such a manner that their planes are parallel to each other.

15. The display according to any one of claims 1 to 10, characterized in that The LC medium comprises one or more compounds selected from the following formulae: The various groups have the following meanings: independently of each other, and Each time it appears, it is the same or different R 41 , R 42 each independently of one another is alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C atoms or alkenyl or alkenyloxy having 2 to 9 C atoms, all of which are unfluorinated or fluorinated, Z 41 , Z 42 each independently of the other is -CH2CH2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O-, -CF2O-, -C≡C- or a single bond, h is 0, 1, 2 or 3.

16. The display according to any one of claims 1 to 10, characterized in that: The LC medium comprises one or more compounds selected from the following formulae: The individual radicals have the following meanings, identically or differently on each occurrence and independently of one another: express express R A1 is alkenyl having 2 to 9 C atoms or, if at least one of the rings X and Y represents cyclohexenyl, then R A1 Also has R A2 One of the meanings, R A2 is an alkyl radical having 1 to 12 C atoms, wherein furthermore one or two non-adjacent CH2 groups may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that the O atoms are not directly connected to one another, x is 1 or 2.

17. The display according to any one of claims 1 to 10, characterized in that: The polymerizable mesogenic compound is selected from the group consisting of Formula I R a -B 1 -(Z b -B 2 ) m -R b I where the individual radicals have the following meanings, identically or differently on each occurrence and independently of one another: R a and R b is P, P-Sp-, H, F, Cl, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, SF5 or a straight-chain or branched alkyl radical having 1 to 25 C atoms, wherein in addition, one or more non-adjacent CH2 groups may each be replaced independently of one another by -C(R 0 )=C(R 00 )-,-C≡C-,-N(R 00 )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and / or S atoms are not directly connected to one another, and wherein in addition, one or more H atoms may be replaced by F, Cl, Br, I, CN, P or P-Sp-, wherein if B 1 and / or B 2 Contains saturated C atoms, then R a and / or R b It can also represent a group that is spiro-attached to the saturated C atom, The group R a and R b At least one of them represents or contains a group P or P-Sp-, P is a polymerizable group, Sp is a spacer group or a single bond, B 1 and B 2 is an aromatic, heteroaromatic, alicyclic or heterocyclic radical having 4 to 25 ring atoms, which may also contain fused rings, and which is unsubstituted or mono- or polysubstituted by L, Z b is -O-, -S-, -CO-, -CO-O-, -OCO-, -O-CO-O-, -OCH2-, -CH2O-, -SCH 2- , -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -(CH2) n1 -, -CF2CH2-, -CH2CF2-, -(CF2) n1 -, -CH=CH-, -CF=CF-, -C≡C-, -CH=CH-COO-, -OCO-CH=CH-, CR 0 R 00 or single key, R 0 and R 00 is H or an alkyl radical having 1 to 12 C atoms, m is 0, 1, 2, 3 or 4, n1 is 1, 2, 3 or 4, L is P, P-Sp-, OH, CH2OH, F, Cl, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, -C(=O)N(R x )2, -C(=O)Y 1 , -C(=O)R x , -N(R x )2, substituted or unsubstituted silyl, substituted or unsubstituted aryl having 6 to 20 C atoms, or straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25 C atoms, wherein in addition one or more H atoms may be replaced by F, Cl, P or P-Sp-, Y 1 For halogen, R x is P, P-Sp-, H, halogen, straight-chain, branched or cyclic alkyl with 1 to 25 C atoms, wherein 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 the O and / or S atoms are not directly connected to one another, and wherein in addition, one or more H atoms may be replaced by F, Cl, P or P-Sp-, substituted or unsubstituted aryl or aryloxy with 6 to 40 C atoms, or substituted or unsubstituted heteroaryl or heteroaryloxy with 2 to 40 C atoms.

18. The display according to any one of claims 1 to 10, characterized in that The polymerizable mesogenic compound is selected from the following formula: where the individual radicals have the following meanings, identically or differently on each occurrence and independently of one another: P 1 , P 2 , P 3 is a vinyloxy group, an acrylate group, a methacrylate group, a fluoroacrylate group, a chloroacrylate group, an oxetane group or an epoxy group, Sp 1 , Sp 2 , Sp 3 is a single bond or a spacer group, wherein in addition, the group P 1 -Sp 1 -、P 2 -Sp 2 - and P 3 -Sp 3 -One or more of them can also represent R aa , provided that the group P 1 -Sp 1 -、P 2 -Sp 2 and P 3 -Sp 3 - at least one of them is different from R aa , R aa is H, F, Cl, CN or a straight-chain or branched alkyl radical having 1 to 25 C atoms, wherein in addition, one or more non-adjacent CH2 groups may each be replaced independently of one another by -C(R 0 )=C(R 00 )-、-C≡C-、-N(R 0 )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, in such a way that the O and / or S atoms are not directly connected to each other, and wherein in addition, one or more H atoms may be replaced by F, Cl, CN or P 1 -Sp 1 - Alternative, R 0 , R 00 is H or an alkyl radical having 1 to 12 C atoms, X 1 , X 2 , X 3 is -CO-O-, -O-CO- or a single bond, Z 1 -O-, -CO-, -C(R y R z )-or-CF2CF2-, R y and R z is H, F, CH3 or CF3, Z 2 , Z 3 -CO-O-, -O-CO-, -CH2O-, -OCH2-, -CF2O-, -OCF2- or -(CH2) n -, where n is 2, 3 or 4, L is F, Cl, CN or a straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy radical having 1 to 12 C atoms, L', L" are H, F or Cl, r is 0, 1, 2, 3 or 4, s is 0, 1, 2, or 3, t is 0, 1 or 2, x is 0 or 1.

19. The display according to any one of claims 1 to 10, characterized in that The LC medium comprises one or more chiral dopants.

20. The display according to any one of claims 1 to 10, characterized in that The LC medium comprises one or more stabilizers and / or self-aligning additives.

21. A method for manufacturing a display according to any one of claims 1 to 20, comprising the following steps: a) providing a first substrate and a second substrate, the first substrate being provided with a first electrode layer, the second substrate being provided with a second electrode layer, b) distributing a layer of a nematic LC medium having positive dielectric anisotropy between the first and second substrates, wherein the LC medium comprises the following: A) a liquid crystal component A comprising mesogens or liquid crystal molecules, B) a polymerizable component B comprising one or more polymerizable mesogenic compounds, C) one or more chiral additives, wherein the proportion of polymerizable mesogenic compounds in the LC medium is 2-2.8%, and wherein the longitudinal axes of the LC molecules are oriented parallel or tilted relative to the plane of the substrate, and the chiral additive induces a helical twist with a given pitch p in the LC molecules of the LC medium along an axis perpendicular to the substrate, and The thickness of the LC dielectric layer is d, and the ratio d / p is ≥ 0.5, and The twist angle of the helical twist of the LC molecule caused by the chiral additive is >210°. c) applying a voltage to the first and second electrodes so that the twist angle of the helical twist of the LC molecules is reduced to a range of 60 to 120°, d) polymerizing the polymerizable mesogenic compound of polymerizable component B of the LC medium between the first and second substrates after or while applying a voltage, thereby stabilizing the twisted nematic configuration of the LC medium with a reduced twist angle of step c), and wherein the LC medium has a dielectric anisotropy of +4 to +15 at 20° C. and 1 kHz, It is characterized in that The LC medium comprises one or more compounds selected from the following formulae: where the individual radicals, independently of one another and identically or differently on each occurrence, have the following meanings: Independently of each other and in each occurrence is identically or differently R 21 , R 31 each independently of one another is alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C atoms or alkenyl or alkenyloxy having 2 to 9 C atoms, all of which are unfluorinated or fluorinated, X 0 is F, Cl, a haloalkyl or alkoxy group having 1 to 6 C atoms or a haloalkenyl or alkenyloxy group having 2 to 6 C atoms, Z 31 is -CH2CH2-, -CF2CF2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O- or a single bond, L 21 , L 22 , L 31 , L 32 Each independently is H or F, L S is H or CH3, g is 0, 1, 2 or 3.

22. The method according to claim 21, wherein a) the first substrate is provided with a first electrode layer and with a first alignment layer, and the second substrate is provided with a second electrode layer and with a second alignment layer.

23. A method according to claim 21, wherein b) a layer of a nematic LC medium having positive dielectric anisotropy is dispensed between the first and second substrates such that the LC medium is in contact with the first and second alignment layers.

24. The method of claim 21, wherein the ratio d / p is > 0.

5.

25. The method of claim 21, wherein the ratio d / p is 0.6-0.

8.

26. The method of claim 21, wherein the twist angle of the helical twist of the LC molecules caused by the chiral additive is 210 to 330°.

27. The method of claim 21, wherein a twist angle of the helical twist of the LC molecules caused by the chiral additive is 240 to 300°.

28. The method of claim 21, wherein the twist angle of the helical twist of the LC molecules caused by the chiral additive is 270°.

29. The method of claim 21, wherein c) applying a voltage to the first and second electrodes reduces a twist angle of the helical twist of the LC molecules to a range of 80 to 100°.

30. The method of claim 21, wherein c) applying a voltage to the first and second electrodes reduces a twist angle of the helical twist of the LC molecules to 90°.

31. A method according to claim 21, wherein it comprises d) polymerizing the polymerizable mesogenic compound of the polymerizable component B of the LC medium between the first and second substrates by exposure to UV radiation after or while applying a voltage, thereby stabilizing the twisted nematic configuration of the LC medium with a reduced twist angle of step c).

32. A method according to claim 21, comprising e) subjecting the LC medium to a second polymerisation step without applying a voltage to the first and second electrodes, thereby polymerising any polymerisable compound which has not reacted in step d).

33. A method according to claim 21, comprising e) subjecting the LC medium to a second polymerisation step by exposure to UV radiation without applying a voltage to the first and second electrodes, thereby polymerising any polymerisable compound that has not reacted in step d).

34. The method according to claim 21, wherein the first and / or second substrate is provided with fixing means which fix the first and second substrate at a constant distance relative to each other and with their planes parallel to each other.

35. The method of claim 34, wherein the fixing means is a sealant material and / or a spacer.

36. The method according to claim 21, wherein the LC medium comprises D) one or more further additives selected from polymerization initiators, stabilizers and self-aligning additives.

37. The method according to any one of claims 21 to 36, characterized in that The twist angle of the helical twist of the LC molecules between the first substrate and the second substrate is 240° to 300° before applying the voltage in step c), and is 80° to 100° after applying the voltage in step c).

38. LC medium comprising A) a liquid crystal component A comprising one or more compounds selected from the group consisting of formula A and B as defined in claim 1, one or more compounds selected from the group consisting of formula C and D as defined in claim 15, and optionally one or more compounds of formula E as defined in claim 16, B) a polymerizable component B comprising one or more polymerizable mesogenic compounds of formula I as defined in claim 17, C) one or more chiral additives, D) one or more polymerization initiators and optionally one or more stabilizers and / or self-aligning additives, wherein the concentration of the polymerizable mesogenic compound of component B in the LC medium is 2-2.8%, and wherein the concentrations of the chiral additives are chosen such that the twist angle they induce in the LC medium is >210°, wherein the LC medium has a dielectric anisotropy of +4 to +15 at 20° C. and 1 kHz, It is characterized in that The LC medium comprises one or more compounds selected from the following formulae: where the individual radicals, independently of one another and identically or differently on each occurrence, have the following meanings: Independently of each other and in each occurrence is identically or differently R 21 , R 31 each independently of one another is alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C atoms or alkenyl or alkenyloxy having 2 to 9 C atoms, all of which are unfluorinated or fluorinated, X 0 is F, Cl, a haloalkyl or alkoxy group having 1 to 6 C atoms or a haloalkenyl or alkenyloxy group having 2 to 6 C atoms, Z 31 is -CH2CH2-, -CF2CF2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O- or a single bond, L 21 , L 22 , L 31 , L 32 Each independently is H or F, L S is H or CH3, g is 0, 1, 2 or 3.

39. LC medium according to claim 38, wherein the concentrations of the chiral additives are chosen such that they induce a twist angle in the LC medium of from 210 to 330°.

40. LC medium according to claim 38, wherein the concentrations of the chiral additives are chosen such that the twist angles they induce in the LC medium are between 240 and 300°.

41. LC medium according to claim 38, wherein the concentrations of the chiral additives are chosen such that the twist angle they induce in the LC medium is 270°.

42. LC medium according to any one of claims 39 to 41, characterized in that The polymerizable mesogenic compound is polymerized.

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