CN111971618B - LCD Display - Google Patents

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

LCD Display

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

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.

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.

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 ( _td ).

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.

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.

Therefore, it is an object of the present invention to provide a method for manufacturing a TN LCD 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 achieving simultaneously one or more of a low driving voltage, a high contrast ratio and a high transmittance. Another object of the present invention is to provide a TN LCD, in particular a polymer-stabilized (PS) TN LCD, obtained by such a method, which allows achieving a fast response time 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.

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

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

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,

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,

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),

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

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

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

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,

Wherein the polymer layer is formed from one or more polymerisable mesogenic compounds which are contained in the LC medium in a concentration of <3%, preferably 0.05 to <3%, and which are polymerised in situ after the LC medium has been dispensed between the two substrates.

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

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,

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,

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),

Wherein the LC medium comprises, preferably consists of:

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

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

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

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

wherein the concentration of the polymerizable mesogenic compound in the LC medium is <3%, preferably from 0.05 to <3%, 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

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

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°,

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°, more preferably to 80 to 100°, very preferably to 90°,

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

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),

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).

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

The invention also relates to an LC medium as described above and below for use in an LC display.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 exemplarily and schematically illustrates the structure of a PS-UF TN-LC display according to the present invention.

2a - c show schematically suitable and preferred drive schemes for applying a voltage in step c) of the method of the present invention.

FIG. 3 shows the transmittance versus voltage curve for a display test cell containing a mixture according to Example 1 of the present invention.

4a-c show the transmittance versus voltage curves at different temperatures for a display test cell containing a mixture according to Example 1 of the present invention.

FIG. 5 shows the transmittance versus voltage curve for a display test cell containing a mixture according to Example 2 of the present invention.

FIG. 6 shows the transmittance versus voltage curve for a display test cell containing a mixture according to Example 3 of the present invention.

FIG. 7 shows the transmittance versus voltage curve for a display test cell containing a mixture according to Example 4 of the present invention.

FIG. 8 shows the transmittance versus voltage curve for a display test cell containing a mixture according to Example 5 of the present invention.

Terms and Definitions

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.

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.

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.

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.

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".

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

The expression "the polymer obtained by polymerizing the polymerizable component B" or "the polymer obtained by polymerizing one or more polymerizable compounds" as used herein and herein is understood to cover 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 is precipitated 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 or electrode structures deposited thereon.

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."

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.

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.

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.

In context,

represents a trans-1,4-cyclohexylene ring, and

It represents a 1,4-phenylene ring.

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

"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.

"Halogen" means F, Cl, Br or I.

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

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.

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

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).

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.

Further preferred carbon and hydrocarbon groups are C ₁ -C ₂₀ alkyl, C ₂ -C ₂₀ alkenyl, C ₂ -C ₂₀ alkynyl, C ₃ -C ₂₀ allyl, C ₄ -C ₂₀ alkyldienyl, C _{4 -C 20 polyenyl, C 6 -C 20 cycloalkyl ,} C ₄ -C ₁₅ cycloalkenyl, C ₆ -C ₃₀ aryl, C ₆ -C ₃₀ alkylaryl, C ₆ -C ₃₀ aralkyl, C 6 -C ₃₀ alkylaryloxy, C ₆ -C ₃₀ arylalkoxy, C ₂ -C ₃₀ heteroaryl, C _{2 -C 30} heteroaryloxy.

Particularly preferred are C ₁ -C ₁₂ alkyl, C ₂ -C ₁₂ alkenyl, C ₂ -C ₁₂ alkynyl, C ₆ -C ₂₅ aryl and C ₂ -C ₂₅ heteroaryl.

Further preferred carbon 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, independently of one another, be replaced by -C( ^Rx )=C( ^Rx )-, -C≡C-, -N( ^Rx )-, -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.

^Rx preferably 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 represents 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.

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.

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

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

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.

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

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.

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.

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.

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.

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.

(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.

(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 CH ₂ groups may be substituted by-O- and/or-S-.

Preferred alicyclic and heterocyclic groups are, for example, 5-membered groups, such as cyclopentane, tetrahydrofuran, tetrahydrothiophene, pyrrolidine; 6-membered groups, such as cyclohexane, 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.

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.

Preferred substituents, also referred to below as "L", are F, Cl, Br, I, -CN, -NO ₂ , -NCO, -NCS, -OCN, -SCN, -C(=O)N(R ^x ) ₂ , -C(=O)Y ¹ , -C(=O)R ^x , -N(R ^x ) ₂ , straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25 C atoms, wherein one or more H atoms may optionally be 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,

wherein ^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

Y ¹ represents halogen.

“Substituted silyl or aryl” preferably means that it is substituted by halogen, —CN, R ⁰ , —OR ⁰ , —CO—R ⁰ , —CO-OR ⁰ , —O—CO—R ⁰ or —O—CO—OR ⁰ , wherein R ⁰ represents H or alkyl having 1 to 20 C atoms.

Particularly preferred substituents L are, for example, F, Cl, CN, _NO2 , _CH3 , _C2H5 , _OCH3 , _OC2H5 , _{COCH3 , COC2H5 , COOCH3 , COOC2H5 , CF3 , OCF3} , _OCHF2 , _OC2F5 and furthermore _phenyl .

Preferably

wherein L has one of the meanings indicated above.

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.

Preferred groups P are selected from the group consisting of: CH ₂ ═CW ¹ —CO—O—, CH ₂ ═CW ¹ —CO—, CH ₂ ＝CW ² -(O) _k3 -, CW ¹ ＝CH-CO-(O) _k3 -, CW ¹ ＝CH-CO-NH-, CH ₂ ＝CW ¹ -CO-NH-, CH ₃ -CH＝CH-O-, (CH ₂ ＝CH) ₂ CH-OCO-, (CH ₂ ＝CH-CH ₂ ) ₂ CH-OCO-, (CH ₂ ＝CH) ₂ CH-O-, (CH ₂ =CH-CH ₂ ) ₂ N-, (CH ₂ =CH-CH ₂ ) ₂ N-CO-, HO-CW ² W ³ -, HS-CW ² W ³ -, HW ² N-, HO-CW ² W ³ -NH-, CH ₂ =CW ¹ -CO-NH-, CH ₂ =CH-(COO) _k1 -Phe-(O) _k2 -,CH _W2 ＝CH-(CO) _k1 -Phe-(O) _k2- , Phe-CH＝CH-, HOOC-, ^OCN- and ^W4W5W6Si- , wherein ^W1 represents H, F, Cl, CN, _CF3 , phenyl or alkyl having 1 to ⁵ C atoms, in particular H, F, Cl or _CH3 , ^W2 and ^W3 each independently of one another represent H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, ^W4 , ^W5 and ^W6 each independently of one another represent Cl, oxaalkyl having 1 to 5 C atoms or oxacarbonylalkyl, ^W7 and ^W8 each independently of one another represent H, Cl or alkyl having 1 to 5 C atoms, Phe represents 1,4-phenylene which is optionally substituted by one or more radicals L as defined above which are different from P-Sp-, _k1 , _k2 and _k3 each independently of one another represent 0 or 1, k _{K 3} preferably represents 1, and k ₄ represents an integer from 1 to 10.

Very preferred groups P are selected from the group consisting of: CH ₂ ═CW ¹ —CO—O—, CH ₂ ═CW ¹ —CO—, CH ₂ =CW ² -O-, CH ₂ =CW ² -, CW ¹ =CH-CO-(O) _k3 -, CW ¹ =CH-CO-NH-, CH ₂ =CW ¹ -CO-NH-, (CH ₂ =CH) ₂ CH-OCO-, (CH ₂ =CH-CH ₂ ) ₂ CH-OCO-, (CH ₂ =CH) ₂ CH-O-, (CH ₂ =CH-CH ₂ ) ₂ N-, (CH ₂ =CH-CH ₂ ) ₂ N-CO-, CH ₂ =CW ¹ -CO-NH-, CH ₂ =CH-(COO) _k1 -Phe-(O) _k2 -, CH ₂ =CH-(CO) _k1 -Phe-(O) _k2 -, Phe-CH=CH- and W ⁴ W ⁵ W ⁶ Si-, where W ^W1 represents H, F, Cl, CN, _CF3 , phenyl or an alkyl group having 1 to 5 C atoms, in particular H, F, Cl or _CH3 , ^W2 and ^W3 each independently represent H or an alkyl group having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, ^W4 , ^W5 and ^W6 each independently represent Cl, an oxaalkyl group or an oxacarbonylalkyl group having 1 to 5 C atoms, ^W7 and ^W8 each independently represent 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.

Very preferred radicals P are selected from the group consisting of _CH2 = ^CW1 -CO-O-, in particular _CH2 =CH-CO-O-, _CH2 =C( _CH3 )-CO-O- and _CH2 =CF-CO-O-, and also _CH2 =CH-O-, ( _CH2 =CH) _2CH -O-CO-, ( _CH2 =CH) _2CH -O-,

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.

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

Sp" denotes alkylene having 1 to 20, preferably 1 to 12 C atoms, which is optionally mono- or polysubstituted by F, Cl, Br, I or CN, and wherein in addition, one or more non-adjacent _CH2 groups are each independently of one another replaced by -O-, -S-, -NH-, -N( ^R0 )-, -Si( ^R0R00 )-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -S-CO-, -CO-S-, -N( ^R00 )-CO-O-, -O-CO-N( ^R0 )-, ^{-N(R0)-CO-N(R00 ) -} , -CH=CH- or -C≡C- in such a way that the O and/or S atoms are not directly connected to one another,

X" represents -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 )-, -OCH ₂ -, -CH ₂ O-, -SCH ₂ -, -CH ₂ S-, -CF ₂ O-, - OCF ₂ -, -CF ₂ S-, -SCF ₂ -, -CF ₂ CH ₂ -, -CH ₂ CF ₂ -, -CF ₂ CF ₂ -, -CH＝N-, -N＝CH-, -N＝N -, -CH＝CR ⁰ -, -CY ² =CY ³ -, -C≡C-, -CH＝CH-CO-O-, -O-CO-CH＝CH- or single bond,

^R0 and ^R00 each independently represent H or an alkyl group having 1 to 20 C atoms, and

^Y2 and ^Y3 each independently represent H, F, Cl or CN.

X" is preferably -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR ⁰ -, -NR ⁰ -CO-, -NR ⁰ -CO-NR ⁰⁰ - or a single bond.

Typical spacer groups Sp _and -Sp"-X"- are, for example, -( _CH2 ) _p1- , -( _CH2CH2O ) _{q1 - CH2CH2- ,} -CH2CH2 _{-S-CH2CH2-, -CH2CH2-NH-CH2CH2- or -(SiR0R00-O)p1- , wherein p1 is} ^{an integer} _from 1 to ₁₂ , q1 is an integer _from 1 to 3, and ^R0 and ^R00 have the meanings indicated above.

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.

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

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°.

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

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)

HTP＝(p·c) ^-1 (1)

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

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.

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°.

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).

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.

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.

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.

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.

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.

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.

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

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, preferably selected from chiral dopants,

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

The concentration of the polymerizable mesogenic compound of component B in the LC medium is 0.1 to <3% by weight.

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.

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

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 identical or different

R ²¹ , R ³¹ are each independently an alkyl, alkoxy, oxaalkyl or alkoxyalkyl radical having 1 to 9 C atoms or an alkenyl or alkenyloxy radical having 2 to 9 C atoms, all of which are optionally fluorinated,

^X0 is F, Cl, a haloalkyl or alkoxy group having 1 to 6 carbon atoms or a haloalkenyl or alkenyloxy group having 2 to 6 carbon atoms,

Z ³¹ is -CH ₂ CH ₂ -, -CF ₂ CF ₂ -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH ₂ O-, or a single bond, preferably -CH ₂ CH ₂ -, -COO-, trans-CH=CH-, or a single bond, particularly preferably -COO-, trans-CH=CH-, or a single bond.

L ²¹ , L ²² , L ³¹ , and L ³² are each independently H or F,

^LS is H or CH ₃ , wherein preferably at least one of the two groups ^LS attached to the same benzene ring is H,

g is 0, 1, 2 or 3.

_In the compounds of formulae A and B, ^X0 is preferably F, Cl, _{CF3 , CHF2} , _OCF3 , _{OCHF2 ,} OCFHCF3, _OCFHCHF2 , _{OCFHCHF2 , OCF2CH3 ,} OCF2CHF2, OCF2CHF2 _, OCF2CF2CHF2, OCF2CF2CHF2, _{OCFHCF2CF3 , OCFHCF2CHF2} , _{OCF2CF2CF3 , OCFHCF2CHF2 , OCF2CF2CF3 , OCF2CF2CClF2 , OCCIFCF2CF3 or} CH= _{CF2 , very} preferably _F or _OCF3 , _most preferably _F.

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

Preferred representation

In addition, it stated

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

In the compounds of the formulae A and B, R ²¹ and R ³¹ are preferably selected from straight-chain alkyl or alkoxy having 1, 2, 3, 4, 5 or 6 C atoms, and straight-chain alkenyl having 2, 3, 4, 5, 6 or 7 C atoms.

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

In the compounds of formula B, Z ³¹ is preferably COO, trans-CH=CH or a single bond, very preferably COO or a single bond.

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

wherein A ²¹ , R ²¹ , X ⁰ , L ²¹ , L ²² and ^LS have the meanings given in formula A, L ²³ and L ²⁴ are each independently H or F, and X ⁰ is preferably F. Particular preference is given to compounds of the formulae A1 and A2.

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

wherein R ²¹ , X ⁰ , L ²¹ and L ²² have the meanings given in formula A1, L ²³ , L ²⁴ , L ²⁵ and L ²⁶ are each independently H or F, and X ⁰ is preferably F.

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.

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

wherein R ²¹ is as defined in formula A1.

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.

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

wherein R ²¹ , X ⁰ , L ²¹ and L ²² have the meanings given in formula A2, L ²³ , L ²⁴ , L ²⁵ and L ²⁶ are each independently H or F, and X ⁰ is preferably F.

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.

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

wherein R ²¹ and X ⁰ are as defined in Formula A2.

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.

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

wherein R ²¹ , X ⁰ , L ²¹ and L ²² have the meanings given in formula A3, and X ⁰ is preferably F.

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.

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

wherein R ²¹ is as defined in formula A4.

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.

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

wherein g, A ³¹ , A ³² , R ³¹ , X ⁰ , L ³¹ , L ³² and ^LS have the meanings given in formula B, and X ⁰ is preferably F. Particular preference is given to compounds of the formulae B1 and B2.

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

wherein R ³¹ , X ⁰ , L ³¹ and L ³² have the meanings given in formula B1, and X ⁰ is preferably F.

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.

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

wherein R ³¹ is as defined in formula B1.

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.

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

wherein R ³¹ is as defined in formula B1.

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.

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

wherein R ³¹ , X ⁰ , L ³¹ and L ³² have the meanings given in formula B2, L ³³ , L ³⁴ , L ³⁵ and L ³⁶ are each independently H or F, and X ⁰ is preferably F.

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.

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

wherein R ³¹ is as defined in formula B2.

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.

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

wherein R ³¹ is as defined in formula B2.

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.

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

wherein R ³¹ is as defined in formula B2.

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.

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

wherein R ³¹ is as defined in formula B2.

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.

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

wherein R ³¹ is as defined in formula B2.

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.

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

wherein R ³¹ is as defined in formula B2.

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.

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

wherein R ³¹ is as defined in formula B2.

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.

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

wherein R ³¹ is as defined in formula B2.

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.

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

wherein R ³¹ is as defined in formula B2.

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.

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

wherein R ³¹ is as defined in formula B2.

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.

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.

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

wherein R ³¹ is as defined in formula B3.

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.

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

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 are each independently of one another 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,

Z ⁴¹ and Z ⁴² are each independently -CH ₂ CH ₂ -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH ₂ O-, -CF ₂ O-, -C≡C- or a single bond, preferably a single bond.

h is 0, 1, 2 or 3.

In the compounds of the formula C, R ⁴¹ and R ⁴² are preferably selected from straight-chain alkyl or alkoxy having 1, 2, 3, 4, 5 or 6 C atoms, and straight-chain alkenyl having 2, 3, 4, 5, 6 or 7 C atoms.

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

In the compounds of the formula C, Z ⁴¹ and Z ⁴² are preferably selected from COO, trans-CH═CH and a single bond, very preferably from COO and a single bond.

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

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

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

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

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

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

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

Most preferred are compounds of formula C1a1.

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

wherein 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.

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

wherein R ⁴¹ and R ⁴² have the meanings given in formula D and preferably represent alkyl.

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

wherein alkyl and alkyl* each independently of one another denote a straight-chain alkyl group having 1 to 6 C atoms, and alkenyl denotes 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- .

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

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.

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

express

express

^RA1 is alkenyl having 2 to 9 C atoms or, if at least one of the rings X, Y and Z represents cyclohexenyl, ^RA1 also has one of the meanings of ^RA2 ,

^RA2 is alkyl 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.

^RA2 is preferably a straight-chain alkyl or alkoxy group having 1 to 8 C atoms, or a straight-chain alkenyl group having 2 to 7 C atoms.

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

wherein alkyl and alkyl ^* each independently of one another denote a straight-chain alkyl group having 1 to 6 C atoms, and alkenyl and alkenyl ^* each independently of one another denote a straight-chain alkenyl group having 2 to 7 C atoms. Alkenyl and alkenyl ^* preferably denote _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- .

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

wherein m represents 1, 2, 3, 4, 5 or 6, i represents 0, 1, 2 or 3, and R ^b1 represents H, CH ₃ or C ₂ H ₅ .

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

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

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.

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

express

R ²¹ , R ³¹ are each independently an alkyl, alkoxy, oxaalkyl or alkoxyalkyl radical having 1 to 9 C atoms or an alkenyl or alkenyloxy radical having 2 to 9 C atoms, all of which are optionally fluorinated,

^X0 is F, Cl, a haloalkyl or alkoxy group having 1 to 6 carbon atoms or a haloalkenyl or alkenyloxy group having 2 to 6 carbon atoms,

Z ²¹ is -CH ₂ CH ₂ -, -CF ₂ CF ₂ -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH ₂ O-, -CF ₂ O-, -C≡C- or a single bond, preferably -CF ₂ O-,

L ²¹ , L ²² , L ²³ , and L ²⁴ are each independently H or F,

^LS is H or CH ₃ , wherein preferably at least one of the two groups ^LS attached to the same benzene ring is H,

g is 0, 1, 2 or 3.

In the compounds of formula F and its subformulae, the ring

Preferred representation

In addition, it stated

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

Particularly preferred compounds of formula F are selected from the following formulae:

wherein R ²¹ , X ⁰ , L ²¹ and L ²² have the meanings given in formula F, L ²⁵ and L ²⁶ are each independently H or F, and X ⁰ is preferably F.

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

wherein R ²¹ is as defined in Formula F1.

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.

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%.

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%.

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%.

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%.

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

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.

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) B2g2 (PGU), B2i1 (CPGU), B2h3 (CCGU), B2k1 (PPGU), B2l1 (DPGU), F1a (GUQGU). The proportion of these compounds in the LC host mixture is preferably 4 to 40%, very preferably 5 to 35%.

c) Component A or the LC host mixture comprises one or more compounds selected from the group consisting of: formula 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-n-m) and D2b (PGP-n-mV). The proportion of these compounds in the LC host mixture is preferably 5 to 60%, very preferably 8 to 50%.

d) 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 proportion of these compounds in the LC host mixture is preferably 5 to 750%, very preferably 10 to 65%.

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%.

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

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

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:

^Ra and ^Rb are P, P-Sp-, H, F, Cl, Br, I, -CN, _-NO2 , -NCO, -NCS, -OCN, -SCN, _SF5 or straight-chain or branched alkyl having 1 to 25 C atoms, wherein in addition, one or more non-adjacent _CH2 groups may each independently of one another be replaced by -C( ^R0 )=C( ^R00 )-, -C≡C-, -N( ^R00 )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and/or S atoms are not 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 ^B1 and/or ^B2 contain a saturated C atom, ^Ra and/or ^Rb may also represent a group which is spiro-bonded to this saturated C atom,

wherein at least one of the groups ^Ra and ^Rb 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 are aromatic, heteroaromatic, alicyclic or heterocyclic radicals, preferably having 4 to 25 ring atoms, which may also contain fused rings, and which are unsubstituted or mono- or polysubstituted by L,

Z ^b is -O-, -S-, -CO-, -CO-O-, -OCO-, -O-CO-O-, -OCH ₂ -, -CH ₂ O-, -SCH ₂ -, - CH ₂ S-, -CF ₂ O-, -OCF ₂ -, -CF ₂ S-, -SCF ₂ -, -(CH ₂ ) _n1 -, -CF ₂ CH ₂ -, -CH ₂ CF ₂ -, - (CF ₂ ) _n1 -, -CH＝CH-, -CF＝CF-, -C≡C-, -CH＝CH-COO-, -OCO-CH＝CH-, CR ⁰ R ⁰⁰ or single bond,

^R0 and ^R00 each independently represent H or an alkyl group having 1 to 12 C atoms,

m represents 0, 1, 2, 3 or 4,

n1 means 1, 2, 3 or 4,

L is P, P-Sp-, OH, CH ₂ OH, F, Cl, Br, I, -CN, -NO ₂ , -NCO, -NCS, -OCN, -SCN, -C(=O)N(R ^x ) ₂ , -C(=O)Y ¹ , -C(=O)R ^x , -N(R ^x ) ₂ , optionally substituted silanyl, optionally substituted aryl having 6 to 20 C atoms, or straight-chain or branched alkyl having 1 to 25 C atoms, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy, wherein, in addition, one or more H atoms may be replaced by F, Cl, P or P-Sp-,

P and Sp have the meanings indicated above,

Y ¹ represents halogen,

^Rx 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.

Particularly preferred compounds of the formula I are those in which B ¹ and B ² each independently of one another represent 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, in which in addition one or more CH groups in these radicals may be replaced by N, cyclohexane-1,4-diyl, in which in addition one or more non-adjacent CH The ₂ radical 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.

Particularly preferred compounds of the formula I are those in which B ¹ and B ² each independently of one another represent 1,4-phenylene, 1,3-phenylene, naphthalene-1,4-diyl or naphthalene-2,6-diyl,

Very preferred compounds of formula I are 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 , and P ³ are vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane, or epoxy,

Sp ¹ , Sp ² , Sp ³ are single bonds or spacer groups, wherein in addition, one or more of the groups P ¹ -Sp ¹ -, P ¹ -Sp ² - and P ³ -Sp ³ - may represent ^Raa , provided that at least one of the groups P ¹ -Sp ¹ -, P ² -Sp ^{2 -} and P ³ -Sp ³ - present is different from ^Raa ,

^Raa is H, F, Cl, CN or straight-chain or branched alkyl having 1 to 25 C atoms, wherein in addition, one or more non-adjacent _CH2 groups may each independently of one another be replaced by -( ^R0 )=C( ^R00 )-, -C≡C-, -N( ^R0 )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and/or S atoms are not directly connected to one another, and wherein in addition, one or more H atoms may be replaced by F, Cl, CN or ^P1 - ^Sp1- , particular preference being given to straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms (wherein alkenyl and alkynyl groups have at least two C atoms and branched groups have at least three C atoms),

R ⁰ , R ⁰⁰ are H or an alkyl group having 1 to 12 C atoms,

R ^y and R ^z are H, F, CH ₃ or CF ₃ ,

^X1 , ^X2 , ^X3 are -CO-O-, -O-CO- or a single bond,

Z ¹ is -O-, -CO-, -C(R ^y R ^z )- or -CF ₂ CF ₂ -,

Z ² , Z ³ are -CO-O-, -O-CO-, -CH ₂ O-, -OCH ₂ -, -CF ₂ O-, -OCF ₂ - or -(CH ₂ ) _n -, wherein 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 either 0 or 1.

Very particular preference is given to compounds of the formulae M2, M10 and M13, in particular direactive compounds containing exactly two polymerizable groups ^P1 and ^P2 .

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 trireactive compounds containing exactly three polymerizable groups ^P1 , ^P2 and/or ^P3 .

In the compounds of formulae M1 to M31, the group

Preferably

in which L has, identically or differently, on each occurrence, one of the meanings given above and below, and is preferably F, Cl, CN, NO ₂ , CH ₃ , C ₂ H ₅ , C(CH ₃ ) ₃ , CH(CH ₃ ) ₂ , CH ₂ CH(CH ₃ )C ₂ H ₅ , OCH ₃ , OC ₂ H ₅ , COCH ₃ , COC ₂ H ₅ , COOCH ₃ , COOC ₂ H ₅ , CF ₃ , OCF ₃ , OCHF ₂ , OC ₂ F ₅ or P—Sp—, very preferably F, Cl, CN, CH ₃ , C ₂ H ₅ , OCH ₃ , COCH ₃ , OCF ₃ or P—Sp—, more preferably F, Cl, CH ₃ , OCH ₃ , COCH ₃ or OCF ₃ and in particular F or CH ₃ .

Preferred compounds of the formulae M1 to M30 are those in which P ¹ , P ² and P ³ represent an acrylate, methacrylate, oxetane or epoxy group (very preferably an acrylate or methacrylate group).

Further preferred compounds of the formulae M1 to M31 are those in which Sp ¹ , Sp ² and Sp ³ are single bonds.

Further preferred compounds of the formulae M1 to M31 are those wherein one of Sp ¹ , Sp ² and Sp ³ is a single bond and the other of Sp ¹ , Sp ² and Sp ³ is different from a single bond.

Further preferred compounds of the formulae M1 to M31 are those in which the groups Sp ¹ , Sp ² and Sp ³ other than single bonds represent -(CH ₂ ) _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.

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.

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

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

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 , ^Ra , R ^b , R ^x , L, Sp, Sp ¹ , Sp ² , Sp ³ or ^Raa is substituted by a hydroxyl, carboxyl, amino or thiol group, preferably a hydroxyl group. Further preferred polymerizable mesogenic SA additives of this type are selected from formulas SA-9 to SA-34 in Table E.

Preferably, the proportion of polymerizable compounds of component B) in the LC medium is from 0.05% to <3%, more preferably from 0.1% to 2.8%, very preferably from 0.1% to 2.5%, most preferably from 0.2% to 2.2%. In a further preferred embodiment, the proportion of polymerizable compounds of component B) in the LC medium is <1.7%, more preferably from 0.1 to 1.0%, very preferably from 0.1 to 0.8%, most preferably from 0.1 to 0.5%.

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.

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.

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%.

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.

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°.

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.

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.

In a further preferred embodiment, the LC medium contains one or more polymerisation initiators.

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).

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.

In another preferred embodiment, the LC medium contains no polymerisation initiator.

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.

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

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.

If stabilizers are used, their proportion, based on the total amount of RM or polymerizable component (component A), is preferably 10 to 500,000 ppm, particularly preferably 50 to 50,000 ppm.

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.

Furthermore, the following substances can be added to the liquid-crystalline medium, for example 0 to 15% by weight of pleochroic dyes, conductive salts for improving the conductivity, preferably ethyldimethyldodecyl ammonium 4-hexyloxybenzoate, tetrabutylammonium tetraphenylborate or complex salts of crown ethers (see, for example, Haller et al., Mol. Cryst. Liq. Cryst. 24 , 249-258 (1973)), or substances for changing the 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.

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

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,

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,

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

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),

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

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.

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

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,

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,

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

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),

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

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.

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

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.

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.

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

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.

5) One or more compounds selected from formula C4b. These compounds can reduce viscosity but will reduce the working temperature.

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.

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.

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.

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

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

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

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

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

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.

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.

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.

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 the 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 [C.H. Gooch and H.A. Tarry, Electron. Lett. 10, 2-4, 1974; C.H. Gooch and H.A. Tarry, 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.

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.

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.

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, particularly preferably +3 to +20 at 20° C. and 1 kHz.

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.

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.

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

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,

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,

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,

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,

- 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).

FIG1 exemplarily and schematically illustrates the structure of a preferred PS-UF TN-LC display according to the present invention in an off state or non-addressed state (i.e., no voltage is applied to the electrodes). The display (100) comprises a first substrate (110) and a second substrate (150), each provided with an ITO electrode (115, 155) and an optional alignment layer (120, 160), preferably unidirectionally rubbed and arranged so that their rubbing directions are at right angles; an LC medium (140) located between the two substrates, wherein the LC molecules are aligned parallel or tilted relative to the substrates and twisted helically along an axis perpendicular to the substrates; and a polymer layer (130, 170) formed on the alignment layer (120, 160) by polymerization of a polymerizable mesogenic compound contained in the LC medium. The display further comprises two polarizers (180, 190) sandwiching the display, which are arranged so that their transmission planes are at 90° relative to each other (orthogonal polarization) with respect to plane polarized light.

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:

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,

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,

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),

Wherein the LC medium comprises, preferably consists of:

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

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

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

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

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

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

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°,

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°, very preferably to 90°,

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

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),

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).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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°.

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.

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.

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.

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.

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.

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).

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

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.

The preferred method is inkjet printing.

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

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

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.

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

Preferably, the display according to the invention comprises fixing means which fixes 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.

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.

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.

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.

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.

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.

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

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).

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.

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.

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.

Suitable and preferred driving schemes for applying the voltage in step c) are exemplarily depicted in Figures 2a, 2b and 2c.

For example, suitable and preferred driving schemes for applying voltage in step c) include, but are not limited to:

Apply a square wave of +20V to -20V and a frequency of 50 to 100Hz.

or

Apply a square wave, wherein the pulse height is 0V to +20V, the pulse width is 50 to 150ms, preferably 100ms, and the cycle length of one pulse is 2 to 8s, preferably 5s (see FIG. 2a ),

or

Apply a square wave with a pulse height of +20V to -20V, wherein each pulse contains one positive sub-pulse and one negative sub-pulse, wherein the pulse width is 50 to 150ms, preferably 100ms, the cycle length of one pulse is 5 to 15s, preferably 10s, and the sub-cycle length of one sub-pulse is 2 to 8s, preferably 5s (see FIG. 2b )

or

A square wave is applied with a pulse height of 0V to +30V, a pulse width of the first pulse of 1 to 10s, preferably 5s, and a pulse width of the second and further pulses of 50 to 150ms, preferably 100ms, and a pause of 10 to 40s, preferably 30s between pulses (see FIG. 2c ).

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.

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

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.

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.

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.

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

- 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,

- preferably in the UV2 step, and optionally also in the UV1 step, exposing the polymerisable LC medium to UV light generated by a UV lamp having a wavelength of 300-380 nm, preferably with an intensity of 0.5 to 30 mW/ ^cm2 , more preferably 1 to ²⁰ mW/ ^cm2 ,

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

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.

"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.

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.

The polymer obtained by polymerisation of the polymerisable compound 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 or electrode structures deposited thereon.

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

Table A

In Table A, m and n are each 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 means C _m H _2m+1 or OC _m H _2m+1 .

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

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.

Table B

Table C

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

Table D

Table D shows illustrative reactive mesogenic compounds which can be used in the LC media according to the invention.

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.

Table E

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:

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.

Example

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.

In addition, the following abbreviations and symbols are used:

t _off , t _d , τ _off represents the turn-off or decay time at 20°C [ms]

t _on , t _r , τ _on represents the turn-on or rise time at 20°C [ms]

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

V ₀ , V _th represents the threshold voltage at 20°C, capacitive [V],

V _op represents the operating voltage [V]

_ne represents the extraordinary refractive index at 20°C and 589 nm,

n _o is the ordinary refractive index at 20 °C and 589 nm,

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

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

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

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

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

γ ₁ represents the rotational viscosity at 20°C [mPa·s],

K ₁ represents the elastic constant at 20°C, “slope” deformation [pN],

_K2 represents the elastic constant at 20°C, "twist" deformation [pN],

_K3 represents the elastic constant at 20°C, "bending" deformation [pN].

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

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).

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). M.p. 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.

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.

The term "threshold voltage ( _Vth , _V0 )" used in the present invention relates to the capacitive threshold ( _V0 ), which is also called Freedericks threshold unless otherwise stated. In the embodiments, the optical threshold is also given as usual for a relative contrast ratio of 10% ( _V10 ).

The term "operating voltage (V _op )" of the present invention refers to a voltage given by 2xV ₁₀ and then selecting the next larger multiple of 0.5 V. For example, when V ₁₀ =4.8 V, then V _op =10 V, when V ₁₀ =5.2 V, then V _op =10.5 V, when V ₁₀ =5.6 V, then V _op =11.5 V.

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").

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.

Example 1

The nematic LC host mixture N1 was prepared as follows:

Mixture A1 was prepared by adding 2.75% chiral dopant S-4011 to LC host mixture N1. The pitch of the mixture induced by the chiral dopant was 5 micrometers.

Mixture B1 was prepared by adding 0.39% chiral dopant S-4011 to LC host mixture N1. The pitch of the mixture induced by the chiral dopant was 35 micrometers.

By adding 1.5% RM-51, 0.5% RM-1 and 1% The mixture PS-A1 was prepared with 651 (relative to the total concentration of RM). The pitch of the mixture caused by the chiral dopant was 5 microns.

TN test box manufacturing

A TN test cell was prepared, which included two polished SL glass substrates (Corning, thickness 1.1 mm) equipped with an ITO electrode layer (thickness 200A, 10 Ohm/sq, 1 cm×1 cm); a rubbed polyimide alignment layer (JSR AL3046) with rubbing directions of 0° and 90°, respectively; a spacer to achieve a cell gap of 3.14 μm; and a sealant (XN-1500, obtained from Mitsubishi Chemicals).

Each of the mixtures N1, B1 and PS-A1 was filled into a test box.

PS-TN test box manufacturing

The test cells using mixture PS-A1 were 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.

UV Step 1 (UV1):

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

UV Step 2 (UV2):

Toshiba C-type fluorescent lamp, green UV, no 365 nm filter, UV intensity 0.5 mW/cm ² , with UV power detector Ushio UIT-250, UVD-S365, irradiation time 60 minutes.

Twist Angle

Twist angle measurement using AxoStep-Mueller matrix imaging polarimeter (brand: Axometrics)

In the test cell using the chiral doping mixture B1 , the twist angle was measured to be -90.5°, which corresponds to a TN configuration, as expected from the low d/p value of 0.09.

In the test cell using the chiral doped polymer stabilized mixture PS-A1, the twist angle was measured to be -90.8°, which also corresponds to a TN configuration, but is significantly lower than expected based on the high d/p value of 0.62. This can be explained by the polymerization of the RM under applied voltage stabilizing the unusually low twist angle.

This demonstrates that it is possible to produce polymer-stabilized TN mode displays having high d/p values but low twist angles using the method according to the invention.

E/O performance, response time

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

In addition, the response time of each mixture was calculated using the following equation

K＝K ₁₁ +0.25(K ₃₃ -2K ₂₂ )+2K ₂₂ /(p/d)

where _τoff is the decay time, _γ1 is the rotational viscosity, d is the cell gap, p is the pitch, and _K11 , _K22 and _K33 are the elastic constants for splay, twist and bending deformations, respectively.

Figure 3 shows the e/o curves of the test cells using host mixture N1 (a), chiral doping mixture B1 (b) and chiral doped polymer stabilized mixture PS-A1 (c). It can be seen that in the test cells using mixture PS-A1, the V/T curve shifts to higher voltages as expected due to the short pitch and polymer stabilization, because the voltage required to overcome the directional forces of the surface polymer is higher than that of the test cells using undoped host mixture N1 and the test cells using mixture B1 with a lower d/p value. It can also be seen that the polymer stabilized mixture PS-A1 maintains high transmittance and contrast ratio, which is an advantage compared to PS-TN displays as reported in the prior art.

Figures 4a-c show the e/o curves measured at 0°C, 10°C, 25°C, 35°C and 50°C (from right to left) for test cells using undoped host mixture N1 (Figure 4a), chiral doping mixture B1 (Figure 4b) and polymer-stabilized chiral doping mixture PS-A1 (Figure 4c), respectively. It can be seen that as the temperature increases, the e/o curve shifts to a lower voltage. It can also be seen that the e/o curve shift shown by the test cell using polymer-stabilized mixture PS-A1 is significantly smaller than that of the test cells using mixtures N1 and B1 that are not polymer-stabilized.

Table 1 shows the calculated response times.

Table 1 - Calculated response times

mixture p(μm) d/p _Vth (V) t _r (ms) t _d (ms) t _r +t _d (ms) N1 0 0.00 0.87 0.39 3.94 4.33 B1 35 0.09 0.96 0.34 3.60 3.95 PS-A1 5 0.63 1.44 0.13 2.39 2.52

_td reduction (from N1 to PS-A1): 39%

It can be seen that according to calculations, when the d/p ratio changes from 0 to 0.63, _td is expected to decrease by 39%.

Table 2 shows the measured response times.

Table 2 - Measured response times

mixture p(μm) d/p V _op (V) t _r (ms) t _d (ms) t _r +t _d (ms) N1 0 0.00 7.5 0.55 2.88 3.43 B1 35 0.09 8.0 0.53 2.54 3.07 PS-A1 5 0.63 13.0 0.31 1.80 2.11

_td reduction (from N1 to PS-A1): 38%

It can be seen that the response times t _r , t _d and t _r + t _d decrease significantly from mixture N1 to mixture PS-A1.

It can also be seen that the measured reduction in decay time _td (38%) is almost identical to the calculated value (39%). The small difference can be explained by the fact that polymer stabilization will affect the operating voltage, and the operating voltage of the polymer-stabilized mixture can still be optimized to further reduce the difference between the calculated and measured response times.

Example 2

Mixture A2 was prepared by adding 2.75% chiral dopant S-4011 to LC host mixture N1. The pitch of the mixture induced by the chiral dopant was 5 micrometers.

By adding 2.0% RM-51 and 1% The mixture PS-A2 was prepared with 651 (relative to the concentration of RM). The pitch of the mixture caused by the chiral dopant was 5 microns.

Mixture B2 was prepared by adding 1.0% chiral dopant S-4011 to LC host mixture N1. The pitch of the mixture induced by the chiral dopant was 13.7 micrometers.

Mixture C2 was prepared by adding 0.39% chiral dopant S-4011 to LC host mixture N1. The pitch of the mixture induced by the chiral dopant was 35 micrometers.

TN, PS-TN test box manufacturing

TN test cells using mixtures N1, B2 and C2 and PS-TN test cells using mixture PS-A2 were prepared as described in Example 1.

E/O performance, response time

The electro-optical performance (transmittance vs. voltage) and response time of the test cells were measured as described in Example 1.

Figure 5 shows (from left to right) the e/o curves of test cells using undoped host mixture N1, chiral doping mixture B2, chiral doping mixture C2, and chiral doped polymer stabilized mixture PS-A2. It can be seen that in the test cells using mixture PS-A2, the V/T curve is shifted to higher voltages compared to the test cells using host mixture N1 and the test cells using mixtures B2 and C2 with lower d/p values for the reasons discussed in Example 1. It can also be seen that the polymer stabilized mixture PS-A2 maintains high transmittance and contrast ratio, which is an advantage compared to PS-TN displays as reported in the prior art.

Table 3 shows the measured response times.

Table 3 - Response time

mixture p(μm) d/p V _op (V) t _r (ms) t _d (ms) t _r +t _d (ms) N1 0 0.00 7.5 0.55 2.88 3.43 B2 35 0.09 8.0 0.53 2.54 3.07 C2 13.7 0.23 9.0 0.42 2.24 2.66 PS-A2 5 0.63 13.0 0.58 1.41 1.99

_td reduction (from N1 to PS-A2): 51%

It can be seen that the response time t _d and t _r +t _d decrease significantly from mixture N1 to mixture PS-A2.

Example 3

Mixture A3 was prepared by adding 0.25% chiral dopant R-5011 to LC host mixture N1. The pitch of the mixture induced by the chiral dopant was 5 micrometers.

By adding 1.5% RM-91, 0.5% RM-1 and 1% The mixture PS-A3 was prepared with 651 (relative to the total concentration of RM). The pitch of the mixture caused by the chiral dopant was 5 microns.

Mixture B3 was prepared by adding 0.035% chiral dopant R-5011 to LC host mixture N1. The pitch of the mixture caused by the chiral dopant was 35 micrometers.

Mixture C3 was prepared by adding 0.09% chiral dopant R-5011 to LC host mixture N1. The pitch of the mixture induced by the chiral dopant was 13.6 micrometers.

TN test box manufacturing

TN test cells using mixtures N1, B3 and C3 were prepared as described in Example 1, but with a cell gap of 2.95 microns.

PS-TN test box manufacturing

The test cells using mixture PS-A3 were 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.

UV step 1 (UV1): Toshiba C fluorescent lamp, green UV, using 365 filter, UV intensity 0.5mW/ ^cm2 , using UV power detector Ushio UIT-250, UVD-S365; electric field (see Figure 2b): each pulse contains one positive pulse and one negative pulse, 10s/cycle, pulse height +/-18V, pulse width 100ms. Irradiation time 600s.

UV step 2 (UV2): The lamp and UV intensity were the same as those used in step UV1, but without filter, and the irradiation time was 60 min.

E/O performance, response time

The electro-optical performance (transmittance vs. voltage) and response time of the test cells were measured as described in Example 1.

6 shows (from left to right) the e/o curves measured at 25° C. for test cells using undoped host mixture N1, chiral doping mixture B3, chiral doping mixture C3, and chiral doped polymer stabilized mixture PS-A3. It can be seen that in the test cell using mixture PS-A3, the V/T curve is shifted to higher voltages due to the short pitch and polymer stabilization, for reasons discussed in Examples 1 and 2. It can also be seen that mixture PS-A3 maintains high transmittance and contrast ratio, which is an advantage over PS-TN displays as reported in the prior art.

Table 4 shows the measured response times.

Table 4 - Response time

mixture p(μm) d/p V _op (V) t _r (ms) t _d (ms) t _r +t _d (ms) N1 0 0.00 7.0 0.62 2.82 3.44 B3 35 0.08 7.5 0.48 2.33 2.81 C3 13.6 0.22 8.5 0.42 2.24 2.66 PS-A3 5 0.59 10.0 0.46 2.12 2.58

It can be seen that the response time t _d and t _r +t _d decrease significantly from mixture N1 to mixture PS-A3.

Example 4

Mixture A4 was prepared by adding 0.25% chiral dopant R-5011 to LC host mixture N1. The pitch of the mixture induced by the chiral dopant was 5 micrometers.

By adding 1.5% RM-51, 0.5% RM-1 and 1% The mixture PS-A4 was prepared with 651 (relative to the total concentration of RM). The pitch of the mixture caused by the chiral dopant was 5 microns.

Mixture B4 was prepared by adding 0.035% chiral dopant R-5011 to LC host mixture N1. The pitch of the mixture induced by the chiral dopant was 35 micrometers.

TN, PS-TN test box manufacturing

TN test cells using mixtures N1 and B4 and PS-TN test cells using mixture PS-A4 were prepared as described in Example 3.

E/O performance, response time

The electro-optical performance (transmittance vs. voltage) and response time of the test cells were measured as described in Example 1.

Figure 7 shows (from left to right) the e/o curves of the test cells using the undoped host mixture N1, the chiral doping mixture B4, and the chiral doped polymer stabilized mixture PS-A4. It can be seen that in the test cells using the mixture PS-A4, the V/T curve is shifted to higher voltages due to the short pitch and polymer stabilization, for reasons discussed in Examples 1 and 2. It can also be seen that the mixture PS-A4 maintains high transmittance and contrast ratio, which is an advantage over PS-TN displays as reported in the prior art.

Table 5 shows the measured response times.

Table 5 - Response time

mixture p(μm) d/p V _op (V) t _r (ms) _td (ms) t _r +t _d (ms) N1 0 0.00 7.0 0.62 2.82 3.44 B4 35 0.08 7.5 0.48 2.33 2.81 PS-A4 5 0.59 11.5 0.37 1.80 2.17

_td reduction (from N1 to PS-A4): 37%

It can be seen that the response time t _d and t _r +t _d decrease significantly from mixture N1 to mixture PS-A4.

Example 5

Mixture A5 was prepared by adding 0.25% chiral dopant R-5011 to LC host mixture N1. The pitch of the mixture induced by the chiral dopant was 5 micrometers.

By adding 1.5% RM-51, 0.5% RM-1 and 1% The mixture PS-A5 was prepared with 651 (relative to the total concentration of RM). The pitch of the mixture caused by the chiral dopant was 5 microns.

Mixture B5 was prepared by adding 0.035% chiral dopant R-5011 to LC host mixture N1. The pitch of the mixture induced by the chiral dopant was 35 micrometers.

TN, PS-TN test box manufacturing

TN test cells using mixtures N1 and B5 and PS-TN test cells using mixture PS-A5 were prepared as described in Example 3.

E/O performance, response time

The electro-optical performance (transmittance vs. voltage) and response time of the test cells were measured as described in Example 1.

Figure 8 shows (from left to right) the e/o curves of the test cells using the undoped host mixture N1, the chiral doped mixture B5, and the chiral doped polymer stabilized mixture PS-A5. It can be seen that in the test cell using the mixture PS-A4, the V/T curve is shifted to higher voltages due to the short pitch and polymer stabilization, for reasons discussed in Examples 1 and 2. It can also be seen that the mixture PS-A5 maintains high transmittance and contrast ratio, which is an advantage over PS-TN displays as reported in the prior art.

Table 6 shows the measured response times.

Table 6 - Response time

mixture p(μm) d/p V _op (V) t _r (ms) t _d (ms) t _r +t _d (ms) N1 0 0.00 7.0 0.62 2.82 3.44 B5 35 0.08 7.5 0.48 2.33 2.81 PS-A5 5 0.59 11.5 0.33 1.81 2.14

_td reduction (from N1 to PS-A5): 38%

It can be seen that the response time t _d and t _r +t _d decrease significantly from mixture N1 to mixture PS-A5.

The above results indicate that the method of the present invention is capable of manufacturing PS-UF TN-LCDs having high d/p values while maintaining a 90° TN configuration, and is capable of achieving fast response times, especially faster decay times, and lower temperature dependence of the e/o curves while maintaining reasonably low driving voltages, high contrast ratios, and high transmittances.

Claims (28)

1.LC display, including 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, 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, 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, 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, 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 or, if present, on one or both of the first and second alignment layers, Wherein the polymer layer is formed from one or more polymerisable mesogenic compounds which are contained in the LC medium in a concentration of <3% and which are polymerised in situ after the LC medium has been dispensed between the two substrates. 2. A display according to claim 1, characterised in that the polarisers are oriented so that their transmission planes are at right angles to plane-polarised light. 3. A display according to claim 1, characterised in that the polymer layer is formed from one or more polymerisable mesogenic compounds which are contained in the LC medium in a concentration of 0.05 to <3%. 4 . The display device according to claim 1 , wherein a twist angle of the helical twist of the LC molecules between the first substrate and the second substrate is 80° to 100°. 5 . The display device according to claim 1 , wherein the ratio d/p of the layer thickness d of the LC medium to the pitch p of the helical twist caused by the chiral additive is 0.6 to 0.8. 6. A display according to any one of claims 1 to 4, characterised 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 the substrate. 7. The display according to any one of claims 1 to 4, characterized in that the first substrate and the second substrate are provided with 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. 8. A display according to any one of claims 1 to 4, characterised 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 are each independently an alkyl, alkoxy, oxaalkyl or alkoxyalkyl radical having 1 to 9 C atoms or an alkenyl or alkenyloxy radical having 2 to 9 C atoms, all of which are optionally fluorinated, ^X0 is F, Cl, a haloalkyl or alkoxy group having 1 to 6 carbon atoms or a haloalkenyl or alkenyloxy group having 2 to 6 carbon atoms, Z ³¹ is -CH ₂ CH ₂ -, -CF ₂ CF ₂ -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH ₂ O- or a single bond, L ²¹ , L ²² , L ³¹ , and L ³² are each independently H or F, ^LS is H or CH ₃ , g is 0, 1, 2 or 3. 9. A display according to any one of claims 1 to 4, characterised 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 are each independently of one another 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, Z ⁴¹ and Z ⁴² are each independently -CH ₂ CH ₂ -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH ₂ O-, -CF ₂ O-, -C≡C- or a single bond, h is 0, 1, 2 or 3. 10. A display according to any one of claims 1 to 4, characterised 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 ^RA1 is alkenyl having 2 to 9 C atoms or, if at least one of the rings X, Y and Z represents cyclohexenyl, ^RA1 also has one of the meanings of ^RA2 , ^RA2 is alkyl 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. 11. The display according to any one of claims 1 to 4, characterized in that the polymerizable mesogen 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: ^Ra and ^Rb are P, P-Sp-, H, F, Cl, Br, I, -CN, _-NO2 , -NCO, -NCS, -OCN, -SCN, _SF5 or straight-chain or branched alkyl having 1 to 25 C atoms, wherein in addition, one or more non-adjacent _CH2 groups may each independently of one another be replaced by -C( ^R0 )=C( ^R00 )-, -C≡C-, -N( ^R00 )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and/or S atoms are not 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 ^B1 and/or ^B2 contain a saturated C atom, ^Ra and/or ^Rb may also represent a group which is spiro-bonded to this saturated C atom, wherein at least one of the groups ^Ra and ^Rb represents or contains a group P or P-Sp-, P is a polymerizable group, Sp is a spacer group or a single bond, ^B1 and ^B2 are aromatic, heteroaromatic, alicyclic or heterocyclic radicals having 4 to 25 ring atoms, which may also contain fused rings, and which are unsubstituted or mono- or polysubstituted by L, Z ^b is -O-, -S-, -CO-, -CO-O-, -OCO-, -O-CO-O-, -OCH ₂ -, -CH ₂ O-, -SCH _2- , - CH ₂ S-, -CF ₂ O-, -OCF ₂ -, -CF ₂ S-, -SCF ₂ -, -(CH ₂ ) _n1 -, -CF ₂ CH ₂ -, -CH ₂ CF ₂ -, - (CF ₂ ) _n1 -, -CH＝CH-, -CF＝CF-, -C≡C-, -CH＝CH-COO-, -OCO-CH＝CH-, CR ⁰ R ⁰⁰ or single bond, ^R0 and ^R00 are H or an alkyl group 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, CH ₂ OH, F, Cl, Br, I, -CN, -NO ₂ , -NCO, -NCS, -OCN, -SCN, -C(=O)N(R ^x ) ₂ , -C(=O)Y ¹ , -C(=O)R ^x , -N(R ^x ) ₂ , optionally substituted silanyl, optionally substituted aryl having 6 to 20 C atoms, or straight-chain or branched alkyl having 1 to 25 C atoms, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy, wherein in addition one or more H atoms may be replaced by F, Cl, P or P-Sp-, ^Y1 is halogen, ^Rx is 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. 12. The display according to any one of claims 1 to 4, characterized in that the polymerizable mesogen 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 , and P ³ are vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane, or epoxy groups, Sp ¹ , Sp ² , Sp ³ are single bonds or spacer groups, wherein in addition, one or more of the groups P ¹ -Sp ¹ -, P ¹ -Sp ² - and P ³ -Sp ³ - may also represent ^Raa , provided that at least one of the groups P ¹ -Sp ¹ -, P ² -Sp ^{2 -} and P ³ -Sp ³ - present is different from ^Raa , ^Raa is H, F, Cl, CN or straight-chain or branched alkyl having 1 to 25 C atoms, wherein in addition, one or more non-adjacent _CH2 groups may each independently of one another be replaced by -C( ^R0 )=C( ^R00 )-, -C≡C-, -N( ^R0 )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and/or S atoms are not directly connected to one another, and wherein in addition, one or more H atoms may be replaced by F, Cl, CN or ^P1 - ^Sp1- , R ⁰ , R ⁰⁰ are H or an alkyl group having 1 to 12 C atoms, ^X1 , ^X2 , ^X3 are -CO-O-, -O-CO- or a single bond, Z ¹ is -O-, -CO-, -C(R ^y R ^z )- or -CF ₂ CF ₂ -, R ^y and R ^z are H, F, CH ₃ or CF ₃ , Z ² , Z ³ are -CO-O-, -O-CO-, -CH ₂ O-, -OCH ₂ -, -CF ₂ O-, -OCF ₂ - or -(CH ₂ ) _n -, wherein 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 either 0 or 1. 13. Display according to any one of claims 1 to 4, characterised in that the polymerisable mesogenic compound is polymerised by UV photopolymerisation. 14. A display according to any one of claims 1 to 4, characterised in that the LC medium comprises one or more chiral dopants. 15. A display according to any one of claims 1 to 4, characterised in that the LC medium comprises one or more additives selected from photoinitiators, stabilisers and self-aligning additives. 16. The method for manufacturing a display according to any one of claims 1 to 15, comprising the following steps: 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, 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, 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 selected from chiral dopants, D) optionally one or more other additives selected from polymerization initiators, stabilizers and self-aligning additives, wherein the proportion of polymerizable mesogenic compounds in the LC medium is < 3%, 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 molecules caused by the chiral additive is 210 to 330°. c) applying a voltage to the first and second electrodes such that the twist angle of the helical twist of the LC molecules is reduced to <150°, 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 e) Optionally, subjecting the LC medium to a second polymerisation step without applying a voltage to the first and second electrodes, thereby polymerising any polymerisable compound that was not reacted in step d). 17. The method according to claim 16, wherein the first and/or the 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. 18. The method of claim 17, wherein the fixing means comprises a sealant material and/or a spacer. 19. The method according to any one of claims 16 to 18, wherein d) after or while applying the voltage, the polymerizable mesogenic compound of the polymerizable component B of the LC medium is polymerized between the first and second substrates by exposure to UV radiation, thereby stabilizing the twisted nematic configuration of the LC medium with reduced twist angle of step c). 20. A method according to any one of claims 16 to 18, wherein e) optionally, the LC medium is subjected 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). 21. The method according to any one of claims 16 to 18, wherein the ratio d/p is 0.6-0.8. 22. The method according to any one of claims 16 to 18, 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). 23. A process according to any one of claims 16 to 18, characterised in that component A of the LC medium comprises one or more compounds as defined in any one of claims 8, 9 and 10. 24. Process according to any one of claims 16 to 18, characterised in that the polymerisable mesogenic compound of component B of the LC medium is as defined in claim 11 or 12. 25. 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 8, one or more compounds selected from the group consisting of formula C and D as defined in claim 9, and optionally one or more compounds of formula E as defined in claim 10, B) a polymerizable component B comprising one or more polymerizable mesogenic compounds of formula I as defined in claim 11, C) one or more chiral additives selected from chiral dopants, D) optionally one or more other additives selected from polymerization initiators, stabilizers and self-aligning additives, wherein the concentration of the polymerizable mesogenic compound of component B in the LC medium is from 0.05 to <3%, and The concentrations of the chiral additives are selected in such a way that they induce a twist angle of 210 to 330° in the LC medium. 26. LC medium according to claim 25, 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°. 27. An LC medium comprising A) a liquid crystal component A comprising one or more compounds selected from the group consisting of formulae A and B as defined in claim 8, one or more compounds selected from the group consisting of formulae C and D as defined in claim 9, and optionally one or more compounds of formula E as defined in claim 10, B) a polymerizable component B comprising one or more polymerizable mesogenic compounds of formula I as defined in claim 11, C) one or more chiral additives selected from chiral dopants, D) optionally one or more other additives selected from polymerization initiators, stabilizers and self-aligning additives, wherein the concentration of the polymerizable mesogenic compound in the LC medium is from 0.05 to <3%, and The concentration of the chiral additive is selected such that it induces a helical pitch of 2 to 10 μm in the LC medium. 28. LC medium according to claim 27, wherein the concentration of the chiral additive is chosen such that it induces a helical pitch of 3 to 6 μm in the LC medium.