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  • C09K19/02—Liquid crystal materials characterised by optical, electrical or physical properties of the components, in general
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  • C09K19/586—Optically active dopants; chiral dopants
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  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
  • G02F1/137—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
  • G02F1/139—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on orientation effects in which the liquid crystal remains transparent
  • G02F1/1396—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on orientation effects in which the liquid crystal remains transparent the liquid crystal being selectively controlled between a twisted state and a non-twisted state, e.g. TN-LC cell
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  • C09K19/00—Liquid crystal materials
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  • C09K2019/0444—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit characterized by a linking chain between rings or ring systems, a bridging chain between extensive mesogenic moieties or an end chain group
  • C09K2019/0448—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit characterized by a linking chain between rings or ring systems, a bridging chain between extensive mesogenic moieties or an end chain group the end chain group being a polymerizable end group, e.g. -Sp-P or acrylate
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  • C09K19/00—Liquid crystal materials
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  • C09K2019/0444—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit characterized by a linking chain between rings or ring systems, a bridging chain between extensive mesogenic moieties or an end chain group
  • C09K2019/0466—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit characterized by a linking chain between rings or ring systems, a bridging chain between extensive mesogenic moieties or an end chain group the linking chain being a -CF2O- chain
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  • C09K19/00—Liquid crystal materials
  • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
  • C09K19/06—Non-steroidal liquid crystal compounds
  • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
  • C09K19/10—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings
  • C09K19/12—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings at least two benzene rings directly linked, e.g. biphenyls
  • C09K2019/121—Compounds containing phenylene-1,4-diyl (-Ph-)
  • C09K2019/122—Ph-Ph
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  • C09K19/06—Non-steroidal liquid crystal compounds
  • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
  • C09K19/10—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings
  • C09K19/12—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings at least two benzene rings directly linked, e.g. biphenyls
  • C09K2019/121—Compounds containing phenylene-1,4-diyl (-Ph-)
  • C09K2019/123—Ph-Ph-Ph
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  • C09K19/06—Non-steroidal liquid crystal compounds
  • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
  • C09K19/10—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings
  • C09K19/12—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings at least two benzene rings directly linked, e.g. biphenyls
  • C09K2019/121—Compounds containing phenylene-1,4-diyl (-Ph-)
  • C09K2019/124—Ph-Ph-Ph-Ph
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  • C09K19/06—Non-steroidal liquid crystal compounds
  • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
  • C09K19/30—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing saturated or unsaturated non-aromatic rings, e.g. cyclohexane rings
  • C09K19/3001—Cyclohexane rings
  • C09K19/3003—Compounds containing at least two rings in which the different rings are directly linked (covalent bond)
  • C09K2019/3004—Cy-Cy
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  • C09K19/06—Non-steroidal liquid crystal compounds
  • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
  • C09K19/30—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing saturated or unsaturated non-aromatic rings, e.g. cyclohexane rings
  • C09K19/3001—Cyclohexane rings
  • C09K19/3003—Compounds containing at least two rings in which the different rings are directly linked (covalent bond)
  • C09K2019/3025—Cy-Ph-Ph-Ph
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
  • G02F1/137—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
  • G02F1/13775—Polymer-stabilized liquid crystal layers

Definitions

• the present invention relates to a method of manufacturing a liquid crystal display (LCD) of the polymer stabilized (PS) twisted nematic (TN) mode, to an LCD obtained by this method and to an LC medium used therein.
• LCD liquid crystal display
• PS polymer stabilized
• TN twisted nematic
• LCDs provide many good properties such as low weight, flatness, and wide viewing angle.
• response time of state-of-the- art LCDs is often not fast enough, and therefore constitutes a barrier for their implementation in various novel applications such as gaming and virtual reality (VR).
• VR virtual reality
• a response time is required which is around 1 ms. If such fast response times could be realized, LCDs could become a low power consumption technology to enlarge the battery life time for mobile devices. LCD manufacturers of LCD are therefore investing high effort to reduce the response time of LCDs.
• LCD mode with ultra fast response time that is also suitable for mass production.
• LCD modes such as TN, multidomain vertically aligned (MVA), in-plane switching (IPS), and fringe-field switching (FFS) mode could not fully meet the requirements of both fast response time and high transmittance due to their cell configuration. In order to reach this target, a new LCD mode is therefore necessary.
• MVA multidomain vertically aligned
• IPS in-plane switching
• FFS fringe-field switching
• the TN LCD is doped with a chiral nematic LC material such that a shorter helical pitch (p) of the twisted nematic LC molecules is achieved, thereby enabling a faster decay response time (t d ).
• the 270° super-twisted nematic (STN) LC director configuration is energetically more stable than the 90° TN LC director configuration of the short pitch length design, while the 90° TN configuration becomes unstable and transforms into the 270° STN configuration. Therefore, it is desired to keep a short pitch with d/p>0.5, but at the same time maintain the TN LC configuration which is needed to realize fast switching times.
• the 270° STN configuration can be changed to the 90° TN configuration by applying an electric voltage, and the 90° TN configuration can then be stabilized by photopolymerization, e.g. by formation of a polymer network in the LC medium, see K. Takatoh et al.,“Fast- response twisted nematic liquid crystals with ultrashort pitch liquid crystalline materials”, Liq. Cryst. 2012, 39, 715-720. It was also reported that the 90° TN configuration can be stabilized by the formation of polymer walls in the LC medium, see IDW 2014, LCT1 -2, "Polymer-Wall Stabilization of Ultra-Short- Pitch TN-LCDs". However, the stabilized TN LCDs as described therein have lower transmittance and/or lower contrast ratio and require higher driving voltage compared to a conventional, unstabilized TN LCD.
• a TN LCD with fast response times, especially fast switch-off or decay time (t d ), while still maintaining a 90° TN LC director configuration, and at the same time achieve one or more of a low driving voltage, a high contrast ratio and a high transmittance.
• Another aim of the invention is to provide a TN LCD, especially a polymer stabilized (PS) TN LCD, obtained by this method which allows to achieve a fast response time and overcome the
• the invention relates to a liquid crystal display (LCD) of the polymer- stabilized twisted-nematic (PS-TN) mode comprising
• the second substrate being equipped with a second electrode layer and optionally a second alignment layer
• polarizers 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 for plane-polarized light are at right angles (crossed nicols),
• layer of the LC medium has a thickness d, and the ratio d/p is 30.5, preferably >0.5, very preferably from 0.6 to 0.8, and
• twist angle of the helical twist of the LC molecules is from 60 to 120°, preferably from 80 to 100°, very preferably 90°, and
• the display further comprises a polymer layer deposited on one or both of said first and second electrode or, if present, on one or both of said first and second alignment layer,
• polymer layers are formed from one or more polymerizable mesogenic compounds, which are contained in the LC medium at a concentration ⁇ 3%, preferably from 0.05 to ⁇ 3%, and which are polymerized in situ after the LC medium has been dispensed between the two substrates.
• the invention further relates to a method of manufacturing an LCD of the PS- TN mode comprising the steps of
• first substrate being equipped with a first electrode layer and optionally with a first alignment layer
• second substrate being equipped with a second electrode layer and optionally with a second alignment layer
• first and/or the second substrate are preferably equipped with fixing means, preferably a sealant material and/or spacers, fixing the first and second substrate at a constant distance relative to each other and with their planes parallel to each other,
• the LC medium comprises, preferably consists of,
• LC host mixture a liquid crystal component A (hereinafter also referred to as "LC host mixture") comprising, preferably consisting of, mesogenic or liquid- crystalline molecules,
• a polymerizable component B comprising, preferably consisting of, one or more polymerizable mesogenic compounds (hereinafter also referred to as "reactive mesogens”),
• the longitudinal axes of the LC molecules are oriented parallel or tilted relative to the planes of the substrates, and the chiral additive induces in the LC molecules of the LC medium a helical twist along an axis perpendicular to the substrates with a given pitch p, and
• layer of the LC medium has a thickness d, and the ratio d/p is 30.5, preferably >0.5, very preferably from 0.6 to 0.8, and wherein the twist angle of the helical twist of the LC molecules induced by the chiral additive is >210°, preferably from 210 to 330°, more preferably from 240 to 300°, very preferably 270°,
• step 15 e) optionally subjecting the LC medium to a second polymerization step, preferably by exposure to UV radiation, without applying a voltage to the first and second electrodes, thereby polymerizing any polymerizable compounds which have not reacted in step d),
• polarizers are preferably oriented such that their transmission planes for plane-polarized light are at right angles (crossed nicols).
• the invention further relates to an LC display obtained by the method as described above and below.
• the invention further relates to an LC medium for use in an LC display as described above and below.
• Fig. 1 exemplarily and schematically illustrates the structure of a PS-UF TN- LC display according to the present invention.
• Fig. 2a-c exemplarily show suitable and preferred driving schemes for applying a voltage in the process step c) of the present invention.
• Fig. 3 shows the transmittance vs. voltage curves of display test cells containing mixtures according to Example 1 of the present invention.
• Fig. 4a-c show the transmittance vs. voltage curves of display test cells containing mixtures according to Example 1 of the present invention at different temperatures.
• Fig. 5 shows the transmittance vs. voltage curves of display test cells containing mixtures according to Example 2 of the present invention.
• Fig. 6 shows the transmittance vs. voltage curves of display test cells containing mixtures according to Example 3 of the present invention.
• Fig. 7 shows the transmittance vs. voltage curves of display test cells containing mixtures according to Example 4 of the present invention.
• Fig. 8 shows the transmittance vs. voltage curves of display test cells containing mixtures according to Example 5 of the present invention.
• active layer and "switchable layer” mean a layer in an electrooptical display, for example an LC display, that comprises one or more molecules having structural and optical anisotropy, like for example LC molecules, which change their orientation upon an external stimulus like an electric or magnetic field, resulting in a change of the transmission of the layer for polarized or unpolarized light.
• the terms “twist” and “twist angle” are understood to refer to an orientation where the longitudinal axis of the LC molecules of the LC medium are substantially parallel to the plane of the nearest substrate of the display cell, and are twisted along a helical axis that is perpendicular to the plane of the substrate.
• the terms “tilt” and “tilt angle” are understood to refer to an orientation where the longitudinal axis of the LC molecules of the LC medium form an angle with the plane of the nearest substrate of the display cell.
• director or "LC director” is understood to mean the average direction of the long molecular axes of the LC molecules.
• reactive mesogen and "RM” will be understood to mean a compound containing a mesogenic or liquid crystalline skeleton, and one or more functional groups attached thereto which are suitable for polymerization and are also referred to as “polymerizable group” or "P".
• polymerizable compound as used herein will be understood to mean a polymerizable monomeric compound.
• the LC medium comprises "a polymer obtained by polymerizing a polymerizable component B" or "a polymer obtained by polymerizing one or more polymerizable compounds” is to be understood to cover both the embodiment where the polymer remains partially or completely dispersed in the LC medium, and the embodiment where the polymer precipitates from the LC medium and forms a polymer layer on one or both of the substrates, or on one or both of the alignment layers or electrode structures deposited thereon.
• unpolymerizable compound will be understood to mean a compound that does not contain a functional group that is suitable for polymerization under the conditions usually applied for the polymerization of the RMs.
• mesogenic group as used herein is known to the person skilled in the art and described in the literature, and means a group which, due to the anisotropy of its attracting and repelling interactions, essentially contributes to causing a liquid-crystal (LC) phase in low-molecular-weight or polymeric substances.
• Compounds containing mesogenic groups do not necessarily have to have an LC phase themselves. It is also possible for mesogenic compounds to exhibit LC phase behaviour only after mixing with other compounds and/or after polymerization. Typical mesogenic groups are, for example, rigid rod- or disc-shaped units.
• spacer group hereinafter also referred to as "Sp”, as used herein is known to the person skilled in the art and is described in the literature, see, for example, Pure Appi Chem. 2001 , 73(5), 888 and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368.
• spacer group or “spacer” mean a flexible group, for example an alkylene group, which connects the mesogenic group and the polymerizable group(s) in a polymerizable mesogenic compound.
• organic group denotes a carbon or hydrocarbon group.
• Carbon group denotes a mono- or polyvalent organic group containing at least one carbon atom, where this either contains no further atoms (such as, for example, -CoC-) or optionally contains one or more further atoms, such as, for example, N, O, S, B, P, Si, Se, As, Te or Ge (for example carbonyl, etc.).
• hydrocarbon group denotes a carbon group which
• H atoms additionally contains one or more H atoms and optionally one or more heteroatoms, such as, for example, N, O, S, B, P, Si, Se, As, Te or Ge.
• heteroatoms such as, for example, N, O, S, B, P, Si, Se, As, Te or Ge.
• Healogen denotes F, Cl, Br or I.
• a carbon or hydrocarbon group can be a saturated or unsaturated group.
• Unsaturated groups are, for example, aryl, alkenyl or alkynyl groups.
• a carbon or hydrocarbon radical having more than 3 C atoms can be straight-chain, branched and/or cyclic and may also contain spiro links or condensed rings.
• alkyl also encompass polyvalent groups, for example alkylene, arylene, heteroarylene, etc.
• aryl denotes an aromatic carbon group or a group derived therefrom.
• heteroaryl denotes “aryl” as defined above, containing one or more heteroatoms, preferably selected from N, O, S, Se, Te, Si and Ge.
• Preferred carbon and hydrocarbon groups are optionally substituted, straight- chain, branched or cyclic, alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy and alkoxycarbonyloxy having 1 to 40, preferably 1 to 20, very preferably 1 to 12, C atoms, optionally substituted aryl or aryloxy having 5 to 30, preferably 6 to 25, C atoms, or optionally substituted alkylaryl, arylalkyl, alkylaryloxy, arylalkyloxy, arylcarbonyl, aryloxycarbonyl, arylcarbonyloxy and aryloxycarbonyloxy having 5 to 30, preferably 6 to 25, C atoms, wherein one or more C atoms may also be replaced by hetero atoms, preferably selected from N, O, S, Se, Te, Si and Ge.
• hetero atoms preferably selected from N, O, S, Se, Te, Si
• carbon and hydrocarbon groups are C 1 -C 20 alkyl, C 2 -C 20 alkenyl, C2-C20 alkynyl, C3-C20 allyl, C 4 -C2o alkyldienyl, C 4 -C2o polyenyl, Ce- C 20 cycloalkyl, C 4 -Cis cycloalkenyl, C6-C30 aryl, C6-C3o alkylaryl, C6-C30 arylalkyl, C6-C30 alkylaryloxy, C6-C3o arylalkyloxy, C6-C3o arylalkyloxy, C 2 -C30 heteroaryl, C 2 -C30 heteroaryloxy.
• C 1 -C 12 alkyl C 2 -C 12 alkenyl, C 2 -C 12 alkynyl, C6-C25 aryl and C2-C25 heteroaryl.
• R x preferably denotes H, F, Cl, CN, a straight-chain, branched or cyclic alkyl chain having 1 to 25 C atoms, in which, in addition, one or more non-adjacent C atoms may be replaced by -O-, -S-, -CO-, -C0-0-, -O-CO-, -O-CO-O- and in which one or more FI atoms may be replaced by F or Cl, or denotes an optionally substituted aryl or aryloxy group with 6 to 30 C atoms, or an optionally substituted heteroaryl or heteroaryloxy group with 2 to 30 C atoms.
• Preferred alkyl groups are, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, 2-methylbutyl, n-pentyl, s-pentyl, cyclopentyl, n-hexyl, cyclohexyl, 2-ethyl hexyl, n-heptyl, cycloheptyl, n-octyl, cyclooctyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, dodecanyl, trifluoromethyl, perfluoro- n-butyl, 2,2,2-trifluoroethyl, peril uorooctyl, perfluorohexyl, etc.
• Preferred alkenyl groups are, for example, ethenyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl, cyclooctenyl, etc.
• Preferred alkynyl groups are, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl, octynyl, etc.
• Preferred alkoxy groups are, for example, methoxy, ethoxy, 2-methoxy- ethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy, 2- methylbutoxy, n-pentoxy, n-hexoxy, n-heptoxy, n-octoxy, n-nonoxy, n- decoxy, n-undecoxy, n-dodecoxy, etc.
• Preferred amino groups are, for example, dimethylamino, methylamino, methylphenylamino, phenylamino, etc.
• Aryl and heteroaryl groups can be monocyclic or polycyclic, i.e. they can contain one ring (such as, for example, phenyl) or two or more rings, which may also be fused (such as, for example, naphthyl) or covalently bonded (such as, for example, biphenyl), or contain a combination of fused and linked rings.
• Heteroaryl groups contain one or more heteroatoms, preferably selected from O, N, S and Se.
• Preferred aryl groups are, for example, phenyl, biphenyl, terphenyl,
• 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
• benzimidazole benzotriazole, purine, naphthimidazole, phenanthrimidazole, pyridimidazole, pyrazinimidazole, quinoxalinimidazole, benzoxazole, naphthoxazole, anthroxazole, phenanthroxazole, isoxazole, benzothiazole, benzofuran, isobenzofuran, dibenzofuran, quinoline, isoquinoline, pteridine, benzo-5, 6-quinoline, benzo-6, 7-quinoline, benzo-7, 8-quinoline, benzoisoquin- oline, acridine, phenothiazine, phenoxazine, benzopyridazine, benzopyrimi- dine, quinoxaline, phenazine, naphthyridine, azacarbazole, benzocarboline, phenanthridine, phenanthroline, thieno
• aryl and heteroaryl groups mentioned above and below may also be substituted by alkyl, alkoxy, thioalkyl, fluorine, fluoroalkyl or further aryl or heteroaryl groups.
• the (non-aromatic) alicyclic and heterocyclic groups encompass both saturated rings, i.e. those containing exclusively single bonds, and also partially unsaturated rings, i.e. those which may also contain multiple bonds.
• Heterocyclic rings contain one or more heteroatoms, preferably selected from Si, 0, N, S and Se.
• the (non-aromatic) alicyclic and heterocyclic groups can be monocyclic, i.e. contain only one ring (such as, for example, cyclohexane), or polycyclic, i.e. contain a plurality of rings (such as, for example, decahydronaphthalene or bicyclooctane). Particular preference is given to saturated groups. Preference is furthermore given to mono-, bi- or tricyclic groups having 5 to 25 ring atoms, which optionally contain fused rings and are optionally substituted.
• Preferred alicyclic and heterocyclic groups are, for example, 5-membered groups, such as cyclopentane, tetrahydrofuran, tetrahydrothiofuran, pyrroli- dine, 6-membered groups, such as cyclohexane, silinane, cyclohexene, tetrahydropyran, tetrahydrothiopyran, 1 ,3-dioxane, 1 ,3-dithiane, piperidine, 7-membered groups, such as cycloheptane, and fused groups, such as tetrahydronaphthalene, decahydronaphthalene, indane, bicyclo[1.1.1 ]- pentane-1 ,3-diyl, bicyclo[2.2.2]octane-1 ,4-diyl, spiro[3.3]heptane-2,6-diyl, octahydro
• Preferred substituents are, for example, solubility-promoting groups, such as alkyl or alkoxy, electron-withdrawing groups, such as fluorine, nitro or nitrile, or substituents for increasing the glass transition temperature (Tg) in the polymer, in particular bulky groups, such as, for example, t-butyl or optionally substituted aryl groups.
• Preferred substituents are F, Cl, Br,
• Y 1 denotes halogen
• Substituted silyl or aryl preferably means substituted by halogen, -CN, R°, -OR 0 , -CO-R 0 , -CO-O-R 0 , -O-CO-R 0 or -O-CO-O-R 0 , wherein R° denotes
• substituents L are, for example, F, Cl, CN, NO 2 , CFI3, C2H5, OCHs, OC2H5, COCHs, COC2H5, COOCHs, COOC2H5, CFs, OCFs, OCFIF 2 , OC 2 F 5 , furthermore phenyl.
• the polymerizable group P is a group which is suitable for a polymerization reaction, such as, for example, free-radical or ionic chain polymerization, polyaddition or polycondensation, or for a polymer-analogous reaction, for example addition or condensation onto a main polymer chain.
• a polymerization reaction such as, for example, free-radical or ionic chain polymerization, polyaddition or polycondensation, or for a polymer-analogous reaction, for example addition or condensation onto a main polymer chain.
• groups which are suitable for polymerization with ring opening such as, for example, oxetane or epoxide groups.
• W 1 denotes H, F, Cl, CN, CF 3 , phenyl or alkyl having 1 to 5 C atoms, in particular H, F, Cl or CFI 3 , W 2 and W 3 each, independently of one another, denote FI or alkyl having 1 to 5 C atoms, in particular FI, methyl, ethyl or n-propyl, W 4 , W 5 and W 6 each, independently of one another, denote Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms, W 7 and W 8 each, independently of one another, denote FI, Cl or alkyl having 1 to 5 C atoms, P
• W 1 denotes H, F, Cl, CN, CF3, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, Cl or CFI3, W 2 and W 3 each, independently of one another, denote FI or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, W 4 , W 5 and W 6 each, independently of one another, denote Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms, W 7 and W 8 each, independently of one another, denote H, Cl or alkyl having 1 to 5 C atoms, Phe denotes 1 ,4-phenylene, ki,
• polymerizable groups P are selected from the group consisting of vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxide, most preferably from acrylate and methacrylate.
• Sp is different from a single bond, it is preferably of the formula Sp"-X", so that the respective radical P-Sp- conforms to the formula P-Sp"-X"-, wherein
• R° and R°° each, independently of one another, denote FI or alkyl having 1 to 20 C atoms, and
• Y 2 and Y 3 each, independently of one another, denote FI, F, Cl or CN.
• X" is preferably -0-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR 0 -, -NR°- CO-, -NR°-CO-NR°°- or a single bond.
• Typical spacer groups Sp and -Sp"-X"- are, for example, -(CFh)pi-,
• Sp and -Sp”-X are -(CFh)pi-, -(CFh)pi-O-, -(CFl 2 )pi-0-C0-, -(CFl 2 )pi-C0-0-, -(CFl 2 )pi-0-C0-0-, in which p1 and q1 have the meanings indicated above.
• Particularly preferred groups Sp" are, in each case straight-chain, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethylenethioethylene, ethylene-N-methylimino- ethylene, 1-methylalkylene, ethenylene, propenylene and butenylene.
• a twisted nematic LC configuration is provided with an initially short pitch corresponding to an STN configuration, where d/p is >0.5 and the twist angle is in the range from 210 to 330°, preferably 270°.
• the helical twisting power or HTP of a chiral dopant is a measure of its ability to induce a helical twist in a specific 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 ) wherein p is the pitch of the induced helical twist, and c is the concentration c of the chiral dopant in the LC medium.
• a defined voltage is then applied to the electrodes of the display.
• the twist angle is reduced to a value corresponding to a TN configuration, like 90°.
• This voltage-induced TN configuration is metastable and would normally relax to the initial STN configuration after a certain time when the voltage is switched off.
• relaxation of the twist angle from the TN-LC to the STN-LC configuration is prevented by polymerizing the polymerizable compounds of component B, preferably by UV-photo- polymerization.
• the metastable TN configuration with the "unnaturally" low twist angle is preserved, despite the short pitch induced by the chiral dopant.
• the LC molecules in the LC medium are thus forced into a state where the twist is lower than the natural pitch of the LC medium as given by equation (1 ) above.
• the actual twist angle of the LC molecules does no longer correspond to the "natural" pitch of the helical twist induced by the chiral dopant and the d/p value of the display cell.
• mesogenic compounds will phase-separate or precipitate from the LC medium and form a polymer layer on the substrates or electrodes, or the alignment layer provided thereon. This could be confirmed by microscopic measurements (like SEM or AFM) which show that the formed polymer mainly accumulates at the LC layer/substrate interface. Thereby especially the loss of transmittance LCDs compared to unstabilized TN LCDs could be reduced and high transmittance could be realized.
• the LC medium used in the display according to the present invention comprises
• liquid crystal component A comprising mesogenic or liquid-crystalline molecules
• a polymerizable component B comprising one or more polymerizable mesogenic compounds
• concentration of the polymerizable mesogenic compounds of component B in the LC medium is from 0.1 to ⁇ 3% by weight.
• the liquid-crystalline component A) of an LC medium as used in the display according to the present invention is hereinafter also referred to as "LC host mixture", and preferably contains only LC compounds that are selected from low-molecular-weight compounds which are unpolymerizable.
• component A or LC host mixture of the LC medium comprises one or more compounds selected from formula A and B
• R 21 , R 31 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,
• L 21 , L 22 , L 31 , L 32 each, independently of one another, FI or F,
• R 21 and R 31 are preferably selected from straight-chain alkyl or alkoxy with 1 , 2, 3, 4, 5 or 6 C atoms, and straight-chain alkenyl with 2, 3, 4, 5, 6 or 7 C atoms.
• g is preferably 1 or 2.
• component A) of the LC medium comprises one or more compounds of formula A selected from the group consisting of the following formulae:
• a 21 , R 21 , X°, L 21 , L 22 and L s have the meanings given in formula A, L 23 and L 24 each, independently of one another, are H or F, and X° is preferably F.
• Particularly preferred are compounds of formulae A1 and A2.
• Particularly preferred compounds of formula A1 are selected from the group consisting of the following subformulae:
• R 21 , X°, L 21 and L 22 have the meaning given in formula A1 , L 23 , L 24 , L 25 and L 26 are each, independently of one another, FI or F, and X° is preferably F.
• Very particularly preferred compounds of formula A1 are selected from the group consisting of the following subformulae:
• R 21 is as defined in formula A1.
• R 21 , X°, L 21 and L 22 have the meaning given in formula A2, L 23 , L 24 , L 25 and L 26 each, independently of one another, are FI or F, and X° is preferably F.
• compounds of formula A2a-A2l wherein at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in para-position to a fluorine atom.
• Very particularly preferred compounds of formula A2 are selected from the group consisting of the following subformulae:
• R 21 and X° are as defined in formula A2.
• Particularly preferred compounds of formula A3 are selected from the group consisting of the following subformulae:
• R 21 , X°, L 21 and L 22 have the meaning given in formula A3, and X° is preferably F.
• compounds of formula A3a-A3c wherein at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in para-position to a fluorine atom.
• Particularly preferred compounds of formula A4 are selected from the group consisting of the following subformulae:
• R 21 is as defined in formula A4.
• component A) of the LC medium comprises one or more compounds of formula B selected from the group consisting of the following formulae:
• Particularly preferred compounds of formula B1 are selected from the group consisting of the following subformulae:
• R 31 , X°, L 31 and L 32 have the meaning given in formula B1 , and X° is preferably F.
• Very particularly preferred compounds of formula B1 a are selected from the group consisting of the following subformulae: in which R 31 is as defined in formula B1 .
• Very particularly preferred compounds of formula B1 b are selected from the group consisting of the following subformulae: in which R 31 is as defined in formula B1 .
• Particularly preferred compounds of formula B2 are selected from the group consisting of the following subformulae:
• R 31 , X°, L 31 and L 32 have the meaning given in formula B2
• L 33 , L 34 , L 35 and L 36 are each, independently of one another, H or F
• X° is preferably F.
• Very particularly preferred compounds of formula B2 are selected from the group consisting of the following subformulae: in which R 31 is as defined in formula B2.
• Very particularly preferred compounds of formula B2b are selected from the group consisting of the following subformulae in which R 31 is as defined in formula B2.
• R 31 is as defined in formula B2.
• R 31 is as defined in formula B2.
• compounds of formula B2f1 -B2f5 wherein at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in para-position to a fluorine atom.
• Very particularly preferred compounds of formula B2g are selected from the group consisting of the following subformulae: in which R 31 is as defined in formula B2.
• Very particularly preferred compounds of formula B2h are selected from the group consisting of the following subformulae: in which R 31 is as defined in formula B2.
• R 31 is as defined in formula B2.
• R 31 is as defined in formula B2.
• compounds of formula B2k1 and B2k2 wherein at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in para-position to a fluorine atom.
• R 31 is as defined in formula B2.
• compounds of formula B2I1 and B2I2 wherein at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in para-position to a fluorine atom.
• the compounds of formula B1 and/or B2 component A) of the LC medium may also comprise one or more compounds of formula B3 as defined above.
• Particularly preferred compounds of formula B3 are selected from the group consisting of the following subformulae:
• R 31 is as defined in formula B3.
• component A) of the LC medium comprises, in addition to the compounds of formula A and/or B, one or more compounds of formula C
• R 41 , R 42 each, independently of one another, alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C atoms or alkenyl or
• Z 41 , Z 42 each, independently of one another, -CH2CH2-, -COO-, trans-
• R 41 and R 42 are preferably selected from straight-chain alkyl or alkoxy with 1 , 2, 3, 4, 5 or 6 C atoms, and straight- chain alkenyl with 2, 3, 4, 5, 6 or 7 C atoms.
• h is preferably 0, 1 or 2.
• Preferred compounds of formula C are selected from the group consisting of the following subformulae:
• R 41 and R 42 have the meanings given in formula C, and preferably denote each, independently of one another, alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy with 1 to 7 C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2 to 7 C atoms.
• alkyl and alkyl * each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms.
• propyl, butyl and pentyl groups are straight-chain groups.
• component A) of the LC medium comprises, in addition to the compounds of formula A and/or B and/or C, one or more compounds of formula D in which 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 group consisting of the following subformulae:
• R 41 and R 42 have the meanings given in formula D and preferably denote alkyl.
• alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms
• alkenyl denotes a straight-chain alkenyl radical having 2-7 C atoms
• CH2 CH-
• CH 2 CHCH 2 CH 2 -
• CH 3 -CH CH-
• CH 3 -CH 2 -CH CH-
• CH 3 -(CH 2 ) 2 -CH CH-
• component A) of the LC medium comprises, in addition to the compounds of formula A and/or B, one or more compounds of formula E containing an alkenyl group in which the individual radicals, on each occurrence identically or differently, each, independently of one another, have the following meaning:
• R A2 is preferably straight-chain alkyl or alkoxy having 1 to 8 C atoms or straight-chain alkenyl having 2 to 7 C atoms.
• Preferred compounds of formula E are selected from the following sub- formulae:
• alkyl and alkyl * each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms
• alkenyl and alkenyl * each, independently of one another, denote a straight-chain alkenyl radical having 2-7 C atoms.
• component A) of the LC medium comprises, in addition to the compounds of formula A and/or B, one or more compounds of formula F
• R 21 , R 31 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, x° F, Cl, halogenated alkyl or alkoxy having 1 to 6 C atoms or halogenated alkenyl or alkenyloxy having 2 to 6 C atoms,
• L 21 , L 22 , L 23 , L 24 each, independently of one another, FI or F L s Fl or CFI3, wherein preferably at least one of two groups L s attached to the same benzene ring is FI,
• Particularly preferred compounds of formula F are selected from the group consisting of the following formulae:
• R 21 , X°, L 21 and L 22 have the meaning given in formula F
• L 25 and L 26 are each, independently of one another, FI or F
• X° is preferably F.
• Very particularly preferred compounds of formula F1 -F3 are selected from the group consisting of the following subformulae:
• R 21 is as defined in formula F1 .
• compounds of formula F1 -F3 and F1 a-F3b wherein at least one of the fluorine-substituted benzene rings is additionally substituted by a methyl group in para-position to a fluorine atom.
• the proportion of the compounds of formula 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 the compounds of formula 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 the compounds of formula E in the LC host mixture is preferably from 5 to 50%, very preferably from 5 to 35%.
• the proportion of the compounds of formula F in the LC host mixture is preferably from 2 to 30%, very preferably from 5 to 20%.
• the component A or LC host mixture comprises one or more
• the component A or LC host mixture comprises one or more
• A1 a2 (CCQU), A1 b1 (ACQU), A1d1 (PUQU), A1fl (GUQU), A2a1 (APUQU), A2h1 (CDUQU), A2I1 (DUUQU), A2I2 (DGUQU), A2k1 (PGUQU), B2g2 (PGU), B2i1 (CPGU), B2h3 (CCGU), B2k1 (PPGU), B2I1 (DPGU), F1 a2 (CCQU), A1 b1 (ACQU), A1d1 (PUQU), A1fl (GUQU), A2a1 (APUQU), A2h1 (CDUQU), A2I1 (DUUQU), A2I2 (DGUQU), A2k1 (PGUQU), B2g2 (PGU), B2i1 (CPGU), B2h3 (CCGU), B2k1 (PPGU), B2I1 (DPGU), F1 a
• the proportion of these compounds in the LC host mixture is preferably from 4 to 40%, very preferably from 5 to 35%.
• the component A or LC host mixture comprises one or more
• C1 C1 (CCH), C4 (PCH), C5 (CCP), C 7 (BCH), C9 (CBC) and D2 (PGP), preferably C1 a (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 from 5 to 60%, very preferably from 8 to 50%.
• the LC host mixture comprises one or more compounds selected from the group consisting of formulae E1 (CC-alkenyl), E3 (PP-alkenyl) and E6 (CCP-alkenyl), preferably E1 a (CC-n-Vm), E3a (PP-n-kVm) and E6a (CCP-Vn-m), very preferably E1 a2 (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 from 5 to 750%, very preferably from 10 to 65%.
• the proportion of the 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 LC host mixture is preferably a nematic LC mixture.
• the polymerizable mesogenic compounds of the polymerizable component B of the LC medium are preferably selected from formula I
• R a -B 1 -(Z b -B 2 ) m -R b I in which the individual radicals, on each occurrence identically or differently, and each, independently of one another, have the following meaning:
• R a and R b P, R-Sp-, H, F, Cl, Br, I, -CN, -N0 2 , -NCO, -NCS, -OCN, -SCN,
• B 1 and B 2 an aromatic, heteroaromatic, alicyclic or heterocyclic group, preferably having 4 to 25 ring atoms, which may also contain fused rings, and which is unsubstituted, or mono- or polysubstituted by L,
• R° and R 00 each, independently of one another, denote FI or alkyl having 1 to
• n1 denotes 1 , 2, 3 or 4
• R x denotes P, R-Sp-, H, halogen, straight-chain, branched or cyclic alkyl having 1 to 25 C atoms, in which, in addition, one or more non-adjacent CFte groups may be replaced by -0-, -S-, -CO-, -CO-0-, -O-CO-, -O-CO-O- in such a way that O and/or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F, Cl, P or R-Sp-, an optionally substituted aryl or aryloxy group having 6 to 40 C atoms, or an optionally substituted heteroaryl or hetero- aryloxy group 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, denote 1 ,4-phenylene, 1 ,3- phenylene, naphthalene-1 ,4-diyl, naphthalene-2, 6-diyl, phenanthrene-2,7- diyl, 9,10-dihydro-phenanthrene-2,7-diyl, anthracene-2, 7-diyl, fluorene-2,7- diyl, coumarine, flavone, where, in addition, one or more CH groups in these groups may be replaced by N, cyclohexane-1 , 4-diyl, in which, in addition, one or more non-adjacent CFte groups may be replaced by O and/or S, 1 ,4- cyclohexenylene, bicycle[1 .1 .1 ]pentane-1 ,3-diyl, bicyclo[2.2.2]o
• Particularly preferred compounds of the formula I are those in which B 1 and B 2 each, independently of one another, denote 1 ,4-phenylene, 1 ,3- phenylene, naphthalene-1 ,4-diyl or naphthalene-2, 6-diyl.
• P 1 -Sp 1 -, P 2 -Sp 2 and P 3 -Sp 3 - present is different from R aa ,
• R aa H, F, Cl, CN or straight-chain or branched alkyl having 1 to
• R y and R z H, F, CFb or CF3,
• compounds of formulae M2, M10 and M13 especially direactive compounds containing exactly two polymerizable groups P 1 and P 2 .
• compounds selected from formulae M15 to M31 in particular from formulae M17, M18, M19, M22, M23, M24, M25, M26, M30 and M31 , especially trireactive compounds containing exactly three
• L on each occurrence identically or differently, has one of the meanings given above or below, and is preferably F, Cl, CN, NO 2 , CH3, C 2 H 5 , C(CH 3 ) 3 , CH(CH 3 ) 2 , CH 2 CH(CH 3 )C 2 H5, OCHS, OC2H5, COCHs, COC2H5, COOCH 3 , COOC 2 H 5 , CF 3 , OCF 3J OCFIF 2 , OC 2 F 5 or R-Sp-, very preferably F, Cl, CN, CFI 3 , C 2 FI 5 , OCFI 3 , COCFI 3 , OCF 3 or R-Sp-, more preferably F, Cl, CFI 3 , OCFI 3 , COCFI 3 Oder OCF 3 , especially F or CFI 3 .
• Preferred compounds of formulae M1 to M30 are those wherein P 1 , P 2 and P 3 denote an acrylate, methacrylate, oxetane or epoxy group, very preferably an acrylate or methacrylate group.
• Further preferred compounds of formulae M1 to M31 are those wherein one of Sp 1 , Sp 2 and Sp 3 is a single bond and another one of Sp 1 , Sp 2 and Sp 3 is different from a single bond.
• Further preferred compounds of formulae M1 to M31 are those wherein those groups Sp 1 , Sp 2 and Sp 3 that are different from a single bond denote - (CFl 2 )si-X"-, wherein s1 is an integer from 1 to 6, preferably 2, 3, 4 or 5, and X" is X" is the linkage to the benzene ring and is -0-, -O-CO-, -CO-O, -O-CO- O- or a single bond.
• Further preferred compounds of formula I are those selected from formulae RM-1 to RM-131 in Table D below, especially those selected from the group consisting of of formula 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,
• LC media comprising one, two or three polymerizable compounds of formula I.
• component B) consists exclusively of polymerizable compounds of formula I.
• component B) comprises, in addition or alternatively to the polymerizable compounds of formula I according to the preferred subformulae and subgroups as described above, one or more polymerizable mesogenic compounds which contain one or more
• polymerizable groups and one or more polar anchor groups selected for example from hydroxy, carboxy, amino or thiol groups can serve as self-aligning (SA) additives and are useful for SA mode displays according to the present invention.
• SA self-aligning
• Suitable and preferred polymerizable mesogenic SA additives of this type are selected from compounds of formulae I or M1 to M31 wherein at least one group B 1 , B 2 , R a , R b , R x , L, Sp, Sp 1 , Sp 2 , Sp 3 or R aa is substituted by a hydroxy, carboxy, amino or thiol group, preferably a hydroxy group.
• Further preferred polymerizable mesogenic SA additives of this type are selected from formula SA-9 to SA-34 in Table E.
• the proportion of the 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%.
• the proportion of the 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%.
• the LC medium preferably contains a component C comprising one or more optically active compounds, preferably selected from chiral dopants.
• the helical twisting power and amount of the dopant in the LC medium are preferably selected such that the ratio d/p in the display according to the present invention is 30.5, very preferably from 0.5 to 1.2, more preferably from 0.55 to 1.0, most preferably from 0.6 to 0.8.
• the proportion of the chiral dopants 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%.
• 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.
• the twist angle of the helical twist induced in the LC medium by the chiral dopants is from 210° to 330°, more preferably from 240 to 300°, most preferably 270°.
• the pitch of the helical twist induced in the LC medium by the chiral dopants is from 2 to 10 m ⁇ ti, very preferably from 3 to 6 m ⁇ ti.
• the ratio d/p in a display according to the present invention is 30.5, very preferably from 0.5 to 1.2, more preferably from 0.55 to 1.0, most preferably from 0.6 to 0.8.
• the LC medium contains one or more polymerization 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, the commercially available photoinitiators Irgacure651®, Irgacure184®,
• LC medium does not contain a polymerization initiator
• the LC medium contains one or more stabilizers.
• stabilizers can prevent undesired spontaneous polymerization of the RMs, for example during storage or transport.
• the LC media according to the present invention may, for example, also comprise one or more UV stabilizers, for example from the Tinuvin ® series from Ciba Chemicals, such as Tinuvin ® 770, or from the Irganox® series, such as Irganox® 1076 (all from BASF). Further suitable and preferred stabilizers are those selected from Table C below.
• the LC medium according to the invention may also comprise further additives for example selected from the list including but not limited to antioxidants, free- radical scavengers, defoaming agents, wetting agents, lubricating agents, dispersing agents, hydrophobing agents, adhesive agents, flow improvers, deaerators, diluents, reactive diluents, auxiliaries, colourants, dyes, pigments and nanoparticles.
• LC media for example, 0 to 15% by weight of pleochroic dyes, conductive salts, preferably ethyldimethyldodecyl- ammonium 4-hexoxybenzoate, tetrabutylammonium tetraphenylborate or complex salts of crown ethers (cf., for example, Haller et al ., Mol. Cryst. Liq. Cryst. 24, 249-258 (1973)), for improving the conductivity, or substances for modifying the dielectric anisotropy, the viscosity and/or the alignment of the nematic phases. Substances of this type 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.
• conductive salts preferably ethyldimethyldodecyl- ammonium 4-hexoxybenzoate, tetrabutylam
• the LC medium comprises, preferably consists of,
• liquid crystal component A comprising one or more compounds
• a polymerizable component B comprising one or more polymerizable mesogenic compounds of formula I as defined above, preferably selected from formulae M1 -M31 , very preferably selected from Table D,
• polymerization initiators stabilizers, which are very preferably selected from Table C
• self-aligning additives which are very preferably selected from Table E
• LC medium is from 0.05 to ⁇ 3%
• concentration of the chiral additives is selected such that twist angle they induce in the LC medium is >210°, preferably from 210 to 330°, more preferably from 240 to 300°, very preferably 270°.
• the LC medium comprises, preferably consists of
• liquid crystal component A comprising one or more compounds
• a polymerizable component B comprising one or more polymerizable mesogenic compounds of formula I as defined above, preferably selected from formulae M1 -M31 , very preferably selected from Table D,
• polymerization initiators stabilizers, which are very preferably selected from Table C
• self-aligning additives which are very preferably selected from Table E
• LC medium is from 0.05 to ⁇ 3%
• concentration of the chiral additives is selected such that the helical pitch they induce in the LC medium is from 2 to 10 m ⁇ ti, very preferably from 3 to 6 m ⁇ ti.
• One or more chiral dopants preferably selected from Table B, very preferably from formulae R/S-1011 , R/S-2011 , R/S-3011 , R/S-4011 and R/S- 5011. These compounds induce a helically twisted structure and a twist angle in the layer with the LC molecules.
• One or more reactive mesogens preferably selected of formula I, very preferably from formulae M1 to M31 , more preferably from formulae RM-1 to RM-131 of Table D, most preferably 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.
• These compounds provide polymer stabilization that reduces the twist angle.
• n 1 , 2, 3, 4, 5, 6 or 7, preferably 3,
• One or more self-aligning additives enable to omit the alignment layer.
• One or more additives selected from antioxidants, UV absorbers, coloring materials, antifoaming agents.
• the LC media according to the invention may also comprise compounds in which, for example, H, N, O, Cl, F have been replaced by the corresponding isotopes like deuterium etc.
• the LC media which can be used in accordance with the invention are prepared in a manner conventional per se, for example by mixing one or more LC compounds selected from formulae A to F or one or more corn- pounds of the above-mentioned preferred embodiments with each other and/or with further LC compounds and/or additives, like polymerizable compounds or RMs.
• the desired amount of the components used in the smaller amount is dissolved in the components making up the principal constituent, advantageously at elevated temperature.
• the MLC displays ac- cording to the invention preferably operate at the first Gooch and Tarry trans- mission minimum [C.H. Gooch and H.A. Tarry, Electron. Lett. 10, 2-4, 1974; C.H. Gooch and H.A. Tarry, Appl. Phys., Vol.
• the LC media and LC host mixtures of the present invention preferably have a nematic phase range > 80 K, very preferably > 100 K, and preferably a rotational viscosity ⁇ 250 mPa s, very preferably ⁇ 200 mPa s, at 20°C.
• the birefringence Dh of LC media and LC host mixtures according to the invention is preferably preferably from 0.07 to 0.15, particularly preferably from 0.08 to 0.15 at 20°C.
• the LC medium and LC host mixture have a positive dielectric anisotropy De.
• Preferably the LC medium and and the LC host mixture have a positive dielectric anisotropy De from +2 to +30, particularly preferably from +3 to +20, at 20°C and 1 kHz.
• the structure of the PS-UF TN-LC displays according to the present invention corresponds to the usual geometry for TN displays as described in the prior art cited at the outset.
• PS-UF TN-LC display according to the invention from polarisers, electrode base plates and surface-treated electrodes corresponds to the usual design for displays of this type.
• the term usual design is broadly drawn here and also encompasses all derivatives and modifications of the LC display, in particular including matrix display elements based on poly-Si TFTs or MIM.
• a preferred PS-UF TN-LC display of the present invention comprises:
• a first substrate including a pixel electrode defining pixel areas, the pixel electrode being connected to a switching element disposed in each pixel area, and optionally a first alignment layer disposed on the pixel electrode,
• a second substrate including a common electrode layer, which may be disposed on the entire portion of the second substrate facing the first substrate, and optionally a second alignment layer,
• a layer of a nematic LC medium having positive dielectric anisotropy which is dispensed between the first and second substrates and comprises a liquid crystal component A comprising, preferably consisting of, one or more mesogenic or liquid-crystalline molecules, and further comprises a component C comprising one or more chiral additives, and optionally comprises a component D comprising one or more further additives,
• polymer layer deposited on each of said first and second electrode or, if present, on each of said first and second alignment layer, wherein the polymer layers are formed from one or more polymerizable mesogenic compounds which are present in the LC medium at a concentration from 0.1 to ⁇ 3%, and which are polymerized in situ after the LC medium has been dispensed between the two substrates,
• first polarizer on the side of the first substrate facing away from the LC layer
• 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 for plane-polarized light are at right angles (crossed nicols).
• Fig. 1 exemplarily and schematically illustrates the structure of a preferred PS-UF TN-LC display according to the present invention in the off-state or non-addressed state, i.e. without a voltage applied to the electrodes.
• the display (100) comprises a first substrate (110) and a second substrate (150), each being equipped with ITO electrodes (115, 155) and optional alignment layers (120, 160), preferably being both unidirectionally rubbed and arranged such 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 helically twisted along an axis
• the display further contains two polarizers (180, 190) sandwiching the display and being arranged so that their transmission planes for plane-polarized light are at 90° relative to each other (crossed nicols).
• the invention also relates to a method of manufacturing a liquid crystal display (LCD) of the polymer-stabilized twisted-nematic (PS-TN) mode comprising the steps of
• first substrate being equipped with a first electrode layer and optionally with a first alignment layer
• second substrate being equipped with a second electrode layer and optionally with a second alignment layer
• first and/or the second substrate are preferably equipped with fixing means, preferably a sealant material and/or spacers, fixing the first and second substrate at a constant distance relative to each other and with their planes parallel to each other,
• the LC medium comprises, preferably consists of,
• LC host mix- ture a liquid crystal component comprising, preferably consisting of, mesogenic or liquid- crystalline molecules
• a polymerizable component B comprising, preferably consisting of, one or more polymerizable mesogenic compounds (hereinafter also referred to as "reactive mesogens”),
• the longitudinal axes of the LC molecules are oriented parallel or tilted relative to the planes of the substrates, and the chiral additive induces in the LC molecules of the LC medium a helical twist along an axis perpendicular to the substrates with a given pitch p, and, wherein layer of the LC medium has a thickness d, and the ratio d/p is 30.5, preferably >0.5, very preferably from 0.6 to 0.8, and
• twist angle of the helical twist of the LC molecules induced by the chiral additive is >210°, preferably in the range from 210 to 330°, more preferably from 240 to 300°, very preferably 270°,
• step c) after applying the voltage or while applying the voltage, polymerizing the polymerizable mesogenic compounds of the polymerizable component B of the LC medium between the first and second substrate, preferably by exposure to UV radiation, thereby stabilizing the twisted nematic configuration of the LC medium with the reduced twist angle of step c), and
• step d) optionally subjecting the LC medium to a second polymerization step, preferably by exposure to UV radiation, without applying a voltage to the first and second electrodes, thereby polymerizing any polymerizable compounds which have not reacted in step d),
• polarizers 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 said polarizers are preferably oriented such that their transmission planes for plane-polarized light are at right angles (crossed nicols).
• the substrates used in the display according to the present invention and in step a) of its manufacturing process are preferably glass substrates.
• plastic substrates are used. These plastic substrates preferably have a low birefringence.
• suitable and preferred plastic substrates are polycarbonate (PC), polyethersulfone (PES), polycyclic olefine (PCO), polyarylate (PAR), polyetheretherketone (PEEK), or colourless polyimide (CPI) substrates.
• At least one substrate should be transmissive for the photoradiation used for polymerizing the polymerizable compounds used in the process according to the present invention. In case the substrates are equipped with alignment layers that are prepared by photopolymerization and/or photoalignment, at least one substrate should be transmissive for the photoradiation used for photopolymerization or
• the electrode layers can be designed by the skilled person depending on the individual display type.
• the first and second substrate are each equipped with an electrode layer.
• one of the first and second electrode layers is a pixel electrode defining pixel areas, the pixel electrode being connected to a switching element disposed in each pixel area and optionally including a micro-slit pattern, and the other of the first and second electrode layers is a common electrode layer, which may be disposed on the entire portion of the substrate facing the other substrate.
• the first and/or second substrate may carry further layers or components including but not limited to a colour filter, TFT arrays, a black matrix, a polyimide coating, or other components typically found on a display
• the first and second substrates is equipped with an alignment layer which is usually applied on 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.
• the alignment layers are selected such that they impart to the LC molecules an orientation direction parallel or slightly tilted relative to the substrate.
• a suitable and preferred alignment layer comprises or consist of, for example, a polyimide, which may also be rubbed or prepared by a
• Solution processable alignment layer materials are preferred. These are preferably processed from solution in a solvent, preferably an organic solvent, like for example N-methylpyrrolidone, 2- butoxyethanol or y-butyrolactone.
• the alignment layer is formed by depositing a solution of an alignment layer material like for example polyimide, or a precursor thereof like for example a polyimide precursor, on the substrate, and optionally curing the alignment layer material or its precursor by exposure to heat and/or actinic radiation, for example UV radiation.
• an alignment layer material like for example polyimide, or a precursor thereof like for example a polyimide precursor
• the alignment layer material can be deposited on the substrate for example by coating or printing methods.
• solvent for deposition of the alignment layer material, it is preferably dried off or evaporated off after deposition. Solvent evaporation can be supported for example by applying heat and/or reduced pressure.
• Preferred methods for curing the alignment layer are thermal curing and photocuring, very preferably photocuring. Photocuring is for example carried out by exposure to UV radiation.
• Suitable curing conditions can be selected by the skilled person depending on the precusor material used, based on his common knowledge and as described in the literature. In case of commercially available materials suitable processing and/or curing conditions are often provided together with the sales or sampling of the material.
• the alignment layers are preferably selected such that they impart to the LC molecules planar (or parallel) alignment, i.e. wherein the longitudinal axis of the LC molecules is parallel to the surface of the nearest substrate, and wherein the longitudinal axis of the LC molecules may also be slightly tilted relative to the surface of the substrate.
• the tilt angle of the longitudinal axis of the LC molecules located in proximity to the surface of a substrate relative to said substrate is from >0° to 20°, preferably from 0.1 ° to 20°, very preferably from 0.2° to 3.5°.
• the alignment layers for example comprise an alignment layer material, for example a polyimide, which is unidirectionally rubbed or is prepared by a photoalignment method.
• the alignment direction, or the average orientation direction of the longitudinal axes of the LC molecules (also referred to as "director") in vicinity to the first and second substrates are at right angles, i.e. at an angle of 90° relative to each other.
• the alignment direction or LC director in vicinity to the first and second substrates is at an angle of 45° relative to the edges of the substrates.
• first and second alignment layer for example comprising polyimide, which are both unidirectionally rubbed and which are arranged such 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.
• this can be achieved by preparing the alignment layers 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 present invention preferably comprises a first and second alignment layer, preferably comprising polyimide, which are both unidirectionally rubbed and wherein the rubbing directions are at right angles to each other.
• the display according to the present invention may comprise further elements, like a colour filter, a black matrix, a passivation layer, optical retardation layers, transistor elements for addressing the individual pixels, etc., all of which are well known to the person skilled in the art and can be employed without inventive skill.
• step b) a layer of a nematic LC medium having positive dielectric anisotropy, and containing components A, B, C and optionally D as described above and below, is dispensed between the first and the second substrate, such that the LC medium is in contact with the first and second alignment layer in case such an alignment layer is present.
• the LC medium can be dispensed or filled onto the substrates or into the display, respectively, by methods that are conventionally used by display manufacturers.
• the LC medium is deposited onto the substrate by using one of the following deposition methods: one drop filling (ODF), ink jet printing, spin coating, slit coating, flexo printing, or a comparable method.
• ODF one drop filling
• a preferred method is ink jet printing.
• ODF method preferably comprising the following steps b1 ) dispensing a droplet or an array of droplets of the LC medium on the first substrate, and b2) providing the second substrate on top of the first substrate with the dispensed droplets of the LC medium, preferably under vacuum conditions, causing the droplets of the LC medium to spread and form a continuous layer between the two substrates.
• the applied LC medium forms a thin, uniform film with the thickness of the targeted final cell gap of the display.
• the display according to the present invention comprises a fixing means, fixing the first and second substrate at a constant distance relative to each other and with their planes parallel to each other.
• the fixing means comprises a sealant material and a spacer material, in order to maintain a constant cell gap and LC layer thickness.
• the first and second substrate are fixed or glued together by the fixing means, for example a sealant material, that is provided on the substrates, preferably in the region close to the edges of the substrates.
• the sealant material is deposited onto the first substrate, or between the first and the second substrate, before the LC medium is dispensed between the first and the second substrate.
• the sealant material is provided on the first substrate, or between the first and the second substrate, preferably in the region between the LC medium and the edges of the respective substrate.
• the sealant material is for example a crosslinked polymer which is formed from a curable polymer precursor.
• the sealant material is then cured, preferably after the first and second substrates are assembled to form an LC cell, but before
• sealant material is cured by exposure to heat and/or photoradiation.
• the spacer material for example consists of transparent glass or plastic beads.
• the spacer is dispensed between the substrates together with the LC medium.
• the display in order to maintain a constant cell gap and LC layer thickness, contains a spacer material, for example a photospacer, outside the LC layer, for example above the black matrix, and the LC layer does not contain a spacer material.
• a spacer material for example a photospacer
• Suitable sealants and spacers are known to the skilled person and are commercially available.
• step c) a voltage is applied to the first and second electrodes such that the twist angle of the helical twist of the LC molecules in the LC layer is reduced from the range of 210 to 330°, preferably from 240 to 300°, very preferably 270°, as given by the LC layer thickness and the natural helical twist induced by the chiral dopant, to a range from 60 to 120°, preferably from 80 to 100°, very preferably to 90°.
• Suitable ways, conditions, parameters and driving schemes for applying a voltage to achieve the desired twist angle, which is then polymer stabilized, are well known to the person skilled in the art or described in the literature, for example in K. Takatoh et al., Liq. Cryst. 2012, 39(6), 715-720, and can be employed without inventive skill.
• the applied voltage and driving scheme are selected such that the TN orientation with reduced twist angle as described above is stable for a given period of time, for example several (>1 ) seconds, several (>1 ) minutes or several (>1 ) hours. This allows to carry out polymerization step d) after step c), i.e. without any overlap in time.
• Suitable and preferred driving schemes for applying a voltage in step c) are exemplarily depicted in Fig. 2a, 2b and 2c.
• suitable and preferred driving schemes for applying a voltage in step c) include, without limitation:
• each pulse contains one positive and one negative sub-pulse, with a pulse width from 50 to 150 ms, preferably 100ms, a cycle length of 5 to 15s, preferably 10s for one pulse, and a subcycle length from 2 to 8s, preferably 5s, for one sub-pulse (see Fig. 2b)
• a square wave with a pulse height from OV to +30V with a pulse width of the first pulse from 1 to 10s, preferably 5s, and a pulse width of second and further pulses from 50 to 150 ms, preferably 100ms, and a pause between the pulses of 10 to 40s, preferably 30s (see Fig. 2c).
• step d) the polymerizable compounds of the polymerizable component B contained in the LC medium are then polymerized, or crosslinked (if a compound contains two or more polymerizable groups) by in-situ
• step e) the polymerizable compounds which have not completely reacted in step d) are polymerized or crosslinked by in-situ polymerization without applying a voltage.
• step d) and e) the polymerizable compounds of the polymerizable component B are preferably polymerized by photopolymerization, very preferably by UV photopolymerization.
• the polymerizable compounds Upon polymerization the polymerizable compounds form a polymer or crosslinked polymer, which stabilizes the reduced twist angle of the LC molecules in the LC medium. Without wishing to be bound to a specific theory, it is believed that a significant part of the polymer which is obtained from the polymerizable compounds will phase-separate or precipitate from the LC medium and form a polymer layer on the substrates or electrodes, or the alignment layer provided thereon. Microscopic measurement data (like SEM and AFM) have confirmed that the polymer mainly accumulates at the LC layer/substrate interface.
• Suitable and preferred polymerization methods are, for example, thermal or photopolymerization, preferably photopolymerization, in particular UV induced photopolymerization, which can be achieved by exposure of the polymerizable compounds to UV radiation.
• step d The polymerization can be carried out in one step (step d) or in two or more steps (steps d and e or repetitions thereof) as described above and below.
• step d) is hereinafter also referred to as "UV1 " step and step e) is hereinafter also referred to as "UV2" step.
• the polymerizable LC medium is exposed to UV light in a two-step process, including a first UV exposure step (step d or UV1 ) while or after, preferably after, applying a voltage to the electrodes, and further including a second UV exposure step (step e or UV2) to finish polymerization without applying a voltage to the electrodes,
• the polymerizable LC medium is exposed, preferably in the UV2 step, and optionally also in the UV1 step, to UV light generated by a UV lamp in the wavelength range from 300-380nm, preferably with an intensity of from 0.5 mW/cm 2 to 30 mW/cm 2 , more preferably from 1 to 20 mW/cm 2 ,
• the polymerizable LC medium is exposed to UV light having a wavelength of 340 nm or more, and preferably 400 nm or less.
• the process of this preferred embodiment can be carried out for example by using the desired UV lamps or by using a band pass filter and/or a cut-off filter, which are substantially transmissive for UV light with the respective desired wavelength(s) and are substantially blocking light with the respective undesired wavelengths.
• a band pass filter and/or a cut-off filter which are substantially transmissive for UV light with the respective desired wavelength(s) and are substantially blocking light with the respective undesired wavelengths.
• UV exposure can be carried out using a wide band pass filter being substantially transmissive for wavelengths 300nm ⁇ l ⁇ 400nm.
• UV exposure can be carried out using a cut-off filter being substantially transmissive for wavelengths l > 365 nm.
• “Substantially transmissive” means that the filter transmits a substantial part, preferably at least 50% of the intensity, of incident light of the desired wavelength(s). “Substantially blocking” means that the filter does not transmit a substantial part, preferably at least 50% of the intensity, of incident light of the undesired wavelengths.
• “Desired (undesired) wavelength” e.g. in case of a band pass filter means the wavelengths inside (outside) the given range of l, and in case of a cut-off filter means the wavelengths above (below) the given value of l.
• the process of this preferred embodiment enables the manufacture of displays by using longer UV wavelengths, thereby reducing or even avoiding the hazardous and damaging effects of short UV light components.
• the polymer obtained by polymerization of the polymerizable compounds of component B of the LC medium preferably forms a layer on one or both of the substrates, or on one or both of the alignment layers or electrode structures deposited thereon.
• the polymerizable compounds of the polymerizable component B are polymerized while the voltage is applied at least during a part of the polymerization process, preferably during step UV1 as described above, in order to stabilize the reduced twist.
• step d) (UV1 ) of polymerizing the polymerizable compounds of the polymerizable component B is carried out either simultaneously with step c) of applying a voltage, or step d) is carried out such that it overlaps at least partially with step c).
• step d) (UV1 ) of polymerizing the polymerizable compounds of the polymerizable component B is carried after step c) of applying a voltage.
• the display according to the present invention does not contain a polyimide alignment layer. In another preferred embodiment the display according to the present invention contains a polyimide alignment layer on one or both of the substrates.
• the LC medium according to the present invention contains a self-aligning (SA) additive, preferably in a concentration of 0.1 to 2.5 %.
• SA self-aligning
• An LC medium according to this preferred embodiment is especially suitable for use in polymer stabilized SA (PS-SA) displays.
• Preferred SA additives for use in this preferred embodiment are selected from compounds comprising a mesogenic group and a straight-chain or branched alkyl side chain that is terminated with one or more polar anchor groups selected from hydroxy, carboxy, amino or thiol groups.
• SA additives contain one or more polymerizable groups which are attached, optionally via spacer groups, to the mesogenic group. These polymerizable SA additives can be polymerized in the LC medium under similar conditions as applied for the polymerizable compounds of polymerizable component B.
• an LC medium or a polymer stabilized SA- VA or SA-FFS display according to the present invention contains one or more self-aligning additives selected from Table E below.
• any SA additives comprised in the LC medium which contain a mesogenic group and one or more polymerizable groups are understood to be part of the polymerizable component B.
• the preferred compositions and concentration ranges given above and below for polymerizable component B and its ingredients are thus understood to include both RMs which are not SA additives, and RMs which are SA additives and contain one or more polar anchor groups selected for example from hydroxy, carboxy, amino or thiol groups.
• m and n are independently of each other 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 (0)C m H 2 m+i means Cm H2m+1 or OC mH2m +1
• liquid-crystalline mixtures which comprise at least one, two, three, four or more compounds from Table A.
• Table B indicates possible dopants which are generally added to the mixtures according to the invention.
• the mixtures preferably comprise 0-10% by weight, in particular 0.001-5% by weight and particularly preferably 0.001 -3% by weight, of dopants.
• Stabilizers which can be added, for example, to the mixtures according to the invention in amounts of 0-10% by weight are mentioned below.
• Table D shows illustrative reactive mesogenic compounds which can be used in the LC media in accordance with the present invention.
• the mixtures according to the invention comprise one or more polymerizable compounds, preferably selected from the polymerizable compounds of the formulae RM-1 to RM-140.
• 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-1 17, RM-120, RM-121 and RM-122 are particularly preferred.
• Table E shows self-alignment additives for vertical alignment which can be used in LC media for SA-VA and SA-FFS displays according to the present invention together with the polymerizable compounds of formula I:
• the LC media, SA-VA and SA-FFS displays
• threshold voltage for the present invention relates to the capacitive threshold (Vo), also known as the Freedericks threshold, unless explicitly indicated otherwise.
• the optical threshold may also, as generally usual, be quoted for 10% relative contrast (V 10 ).
• operating voltage (V op ) for the present invention relates to the voltage given by 2xVio and then choosing the next larger multiple of 0.5 V.
• the process of polymerizing the polymerizable compounds in the polymer stabilized 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 is carried out at room temperature (also abbreviated as "RT").
• the nematic LC host mixture N1 is formulated as follows:
• Mixture A1 is prepared by adding to the LC host mixture N1 2.75% of the chiral dopant S-4011. The pitch of the mixture induced by the chiral dopant is 5 microns.
• Mixture B1 is prepared by adding to the LC host mixture N1 0.39% of the chiral dopant S-4011. The pitch of the mixture induced by the chiral dopant is 35 microns.
• Mixture PS-A1 is prepared by adding to the Mixture A1 1.5 % of RM-51 , 0.5% of RM-1 , and 1 %, relative to the total concentration of RMs, of lrgacure®651.
• the pitch of the mixture induced by the chiral dopant is 5 microns.
• TN test cells are prepared comprising two substrates of polished SL glass (Corning, thickness 1 .1 mm), which are equipped with ITO electrode layers (thickness 200 A, 10 Ohms/sq, 1 cm x 1 cm), rubbed polyimide alignment layers (JSR AL3046) with rubbing directions at 0° and 90° respectively, spacers to achieve a cell gap of 3.14 microns, and a sealant (XN-1500 from Mitsubishi Chemicals).
• Each of mixtures N1 , B1 and PS-A1 is filled into a test cell.
• test cell with mixture PS-A1 is subjected to a two-step UV curing process, wherein in the first step a voltage is applied to the electrodes and in the second UV step no voltage is applied.
• UV step 1 UV step 1 (UV1 ):
• UV step 2 Toshiba C type fluorescent lamp, green UV without 365 nm filter, UV intensity 0.5 mW/cm 2 with UV power detector Ushio UIT-250, UVD-S365, irradiation time 60 min. Twist Angle
• the twist angle is measured with and AxoStep-Mueller Matrix Imaging Polarimeter (Brand: Axometrics) In the test cell with chirally doped mixture B1 the twist angle is measured to be -90.5°, which corresponds to an TN configuration, as expected from the low d/p value of 0.09.
• the electrooptical performance (transmission vs. voltage) and response times of the test cells are measured with an LCD evaluation system (LCD- 5200, Otsuka electronics Co., Ltd).
• the response times are calculated for the individual mixtures by using the following equations wherein x 0ff is the decay time, gi is the rotational viscosity, d is the cell gap, p is the helical pitch, and K , K22 and K33 are the elastic constants for splay, twist and bend deformation, respectively.
• Fig. 3 shows the e/o curves of the test cells with host mixture N1 (a), chirally doped mixture B1 (b) and chirally doped, polymer stabilized mixture PS-A1 (c). It can be seen that in the test cell with mixture PS-A1 the V/T curve is shifted to higher voltages due to the short pitch and polymer stabilization as expected, because a higher voltage is needed to overcome the orientation force of the surface polymer, compared to the test cell with undoped host mixture N1 and the test cell with mixture B1 having a lower d/p value. It can also be seen that the polymer stabilized mixture PS-A1 maintains a high transmittance and contrast ratio, which is an advantage compared to PS-TN displays as reported in prior art.
• Fig. 4a-c show the e/o curves measured at 0°C, 10°C, 25°C, 35°C and 50°C (from right to left), respectively, for the test cells with undoped host mixture N1 (Fig. 4a), chirally doped mixture B1 (Fig. 4b) and polymer stabilized, chirally doped mixture PS-A1 (Fig. 4c), respectively. It can be seen that the e/o curves are shifted to lower voltages with increasing temperature. It can also be seen that the test cell with polymer stabilized mixture PS-A1 shows a significantly smaller shift of the e/o curve compared to the test cells with mixture N1 and B1 which are not polymer stabilized.
• Table 1 shows the calculated response times.
• Table 2 shows the measured response times.
• the operating voltage for the polymer stabilized mixture may still be optimized to further reduce the difference between calculated and measured response times.
• Mixture A2 is prepared by adding to the LC host mixture N1 2.75% of the chiral dopant S-401 1 .
• the pitch of the mixture induced by the chiral dopant is 5 microns.
• Mixture PS-A2 is prepared by adding to the Mixture A2 2.0 % of RM-51 and 1 %, relative to the concentration of the RM, of lrgacure®651.
• the pitch of the mixture induced by the chiral dopant is 5 microns.
• Mixture B2 is prepared by adding to the LC host mixture N1 1.0% of the chiral dopant S-4011.
• the pitch of the mixture induced by the chiral dopant is 13.7 microns.
• Mixture C2 is prepared by adding to the LC host mixture N1 0.39% of the chiral dopant S-4011.
• the pitch of the mixture induced by the chiral dopant is 35 microns.
• TN, PS-TN test cell manufacture TN test cells with mixtures N1 , B2 and C2 and a PS-TN test cell with mixture PS-A2 are prepared as described in Example 1.
• Fig. 5 shows (from left to right) the e/o curves of the test cells with undoped host mixture N1 , chirally doped mixture B2, chirally doped mixture C2, and chirally doped, polymer stabilized mixture PS-A2. It can be seen that in the test cell with mixture PS-A2 the V/T curve is shifted to higher voltages, compared to the test cell with host mixture N1 and the test cells with mixtures B2 and C2 having lower d/p value, for the reasons as discussed in Example 1. It can also be seen that the polymer stabilized mixture PS-A2 maintains a high transmittance and contrast ratio, which is an advantage compared to PS-TN displays as reported in prior art.
• Table 3 shows the measured response times. Table 3 - Response Times
• Mixture A3 is prepared by adding to the LC host mixture N1 0.25% of the chiral dopant R-501 1 .
• the pitch of the mixture induced by the chiral dopant is 5 microns.
• Mixture PS-A3 is prepared by adding to the Mixture A3 1 .5 % of RM-91 , 0.5% of RM-1 and 1 %, relative to the total concentration of RMs, of lrgacure®651 .
• the pitch of the mixture induced by the chiral dopant is 5 microns.
• Mixture B3 is prepared by adding to the LC host mixture N1 0.035% of the chiral dopant R-501 1 .
• the pitch of the mixture induced by the chiral dopant is 35 microns.
• Mixture C3 is prepared by adding to the LC host mixture N1 0.09% of the chiral dopant R-501 1 .
• the pitch of the mixture induced by the chiral dopant is 13.6 microns.
• TN test cells with mixtures N1 , B3 and C3 are prepared as described in Example 1 , but wherein the cell gap is 2.95 microns.
• test cell with mixture PS-A3 is subjected to a two-step UV curing process, wherein in the first step a voltage is applied to the electrodes and in the second UV step no voltage is applied.
• UV step 1 UV step 1 (UV1 ):
• UV step 2 UV step 2 (UV2):
• step UV1 Same lamp and UV intensity as used in step UV1 but without filter, irradiation time 60 min.
• the electrooptical performance (transmission vs. voltage) and response times of the test cells are measured as described in Example 1.
• Fig. 6 shows (from left to right) the e/o curves of the test cells with undoped host mixture N1 , chirally doped mixture B3, chirally doped mixture C3, and chirally doped, polymer stabilized mixture PS-A3, measured at 25°C. It can be seen that in the test cell with mixture PS-A3 the V/T curve is shifted to higher voltages due to the short pitch and polymer stabilization for the reasons as discussed in Example 1 and 2. It can also be seen that mixture PS-A3 maintains high transmittance and contrast ratio, which is an advantage compared to PS-TN displays as reported in prior art. Table 4 shows the measured response times. Table 4 - Response Times
• Mixture A4 is prepared by adding to the LC host mixture N1 0.25% of the chiral dopant R-5011.
• the pitch of the mixture induced by the chiral dopant is 5 microns.
• Mixture PS-A4 is prepared by adding to the Mixture A4 1.5 % of RM-51 , 0.5% of RM-1 and 1 %, relative to the total concentration of RMs, of lrgacure®651.
• the pitch of the mixture induced by the chiral dopant is 5 microns.
• Mixture B4 is prepared by adding to the LC host mixture N1 0.035% of the chiral dopant R-5011.
• the pitch of the mixture induced by the chiral dopant is 35 microns.
• TN test cells with mixtures N1 and B4 and a PS-TN test cell with mixture PS- A4 are prepared as described in Example 3.
• Fig. 7 shows (from left to right) the e/o curves of the test cells with undoped host mixture N1 , chirally doped mixture B4 and chirally doped, polymer stabilized mixture PS-A4. It can be seen that in the test cell with mixture PS-A4 the V/T curve is shifted to higher voltages due to the short pitch and polymer stabilization for the reasons as discussed in Example 1 and 2. It can also be seen that mixture PS-A4 maintains high transmittance and contrast ratio, which is an advantage compared to PS-TN displays as reported in prior art. Table 5 shows the measured response times.
• Mixture A5 is prepared by adding to the LC host mixture N1 0.25% of the chiral dopant R-501 1 .
• the pitch of the mixture induced by the chiral dopant is 5 microns.
• Mixture PS-A5 is prepared by adding to the Mixture A5 1 .5 % of RM-51 , 0.5% of RM-1 and 1 %, relative to the total concentration of RMs, of lrgacure®651 .
• the pitch of the mixture induced by the chiral dopant is 5 microns.
• Mixture B5 is prepared by adding to the LC host mixture N1 0.035% of the chiral dopant R-501 1 .
• the pitch of the mixture induced by the chiral dopant is 35 microns.
• TN test cells with mixtures N1 and B5 and a PS-TN test cell with mixture PS- A5 are prepared as described in Example 3.
• the electrooptical performance (transmission vs. voltage) and response times of the test cells are measured as described in Example 1 .
• Fig. 8 shows (from left to right) the e/o curves of the test cells with undoped host mixture N1 , chirally doped mixture B5 and chirally doped, polymer stabilized mixture PS-A5. It can be seen that in the test cell with mixture PS-A4 the V/T curve is shifted to higher voltages due to the short pitch and polymer stabilization for the reasons as discussed in Example 1 and 2. It can also be seen that mixture PS-A5 maintains high transmittance and contrast ratio, which is an advantage compared to PS-TN displays as reported in prior art.
• Table 6 shows the measured response times.

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