Liquid crystal medium and PNLC light modulation element

Abstract

The present invention relates to a cholesteric liquid crystal (LC) medium for a polymer network liquid crystal (PNLC) light modulation element, a method for manufacturing the same, and the use of the cholesteric medium in a light modulation element. Furthermore, the present invention relates to the light modulation element itself, a method for manufacturing the same, the use of the light modulation element in an optical or electro-optical device, particularly in a display, and an optical or electro-optical device comprising the light modulation element of the present invention.

Description

Technical Field

[0001] The present invention relates to a cholesteric liquid crystal (LC) medium for a polymer network liquid crystal (PNLC) light modulation element, a method for manufacturing the same, and use of the cholesteric LC medium in a PNLC light modulation element. Further, the present invention relates to the PNLC light modulation element itself, a method for manufacturing the same, use of the light modulation element in an optical or electro-optical device, particularly in an LC display, and an optical or electro-optical device including the light modulation element of the present invention. Background of the Invention

[0003] A switchable waveguide is a liquid crystal device that enables a transparent display. When the LC cell is of the edge-lit type, light can undergo total internal reflection within the boundaries of the LC cell.

[0004] In the normal, aligned state, as long as the refractive index of the LC host is higher than that of the glass substrate, the light path is not obstructed. When the chiral liquid crystal cell is switched, a focal conic domain is formed and this large change in the apparent refractive index results in turbidity and subsequently light is coupled out from the LC cell.

[0005] In this case, a helical pitch in the micron range is required so that the reflection band is within the infrared spectrum. This eliminates any color effects in the LC cell and liquid crystal window applications have been reported in WO 2017 / 041872A1. However, the switching-off times (t off ) exhibited by these systems are not suitable for display applications that require fast switching.

[0006] In addition, a polymer network system for dynamic scattering with a medium turbidity value of 44% has been proposed in WO 2018 / 215393 A1. In this regard, there is still a great need in the industry to develop systems for display applications that have a high % turbidity value while maintaining fast switching of these devices.

[0007] In view of the above problems, the present invention is based on the object of providing novel suitable materials, particularly a cholesteric LC medium for a PNLC light modulation element, wherein the helical pitch is in the micron range, and thus the reflection band is in the infrared spectrum, which does not have the disadvantages shown above or has a reduced degree of disadvantages. Other objects of the present invention will be readily apparent to those skilled in the art from the following description.

[0008] Surprisingly, the inventors have found that one or more of the objects defined above and below can be achieved by the present invention according to claim 1.

[0009] Brief Description

[0010] Accordingly, the present invention relates to a cholesteric LC medium for a PNLC light modulation element, which comprises

[0011] A) one or more polymerizable compounds, in an amount of ≥ 2% to ≤ 10% by weight, at least one of which is a compound of formula I,

[0012] P 11 -Sp 11 -Ar-Sp 12 -P 12 I

[0013] wherein Ar is selected from groups of the following formula

[0014]

[0015]

[0016] which is optionally substituted by one or more groups L,

[0017] L is the same or different each time it appears and is F, Cl, CN, P-Sp-, or a straight-chain, branched-chain or cyclic alkyl group having 1 to 25 C atoms, wherein one or more non-adjacent CH2-groups are optionally replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that the O- and / or S-atoms are not directly connected to each other, and wherein one or more H atoms are each optionally replaced by F or Cl,

[0018] P 11 and P 12 each independently of one another represent polymerizable groups,

[0019] Sp 11 and Sp 12 each independently of one another represent a spacer group or a single bond optionally substituted by one or more groups P 11 or P 12 and

[0020] B) one or more non-polymerizable mesogenic or liquid-crystalline compounds, and

[0021] C) one or more chiral compounds.

[0022] The liquid-crystalline component B) of the cholesteric LC medium according to the invention is also referred to below as "LC host mixture" and preferably comprises one or more, preferably at least two, mesogenic or LC compounds selected from non-polymerizable low-molecular-weight compounds.

[0023] The invention further relates to a cholesteric LC medium or a PNLC light modulation element as described in the context, wherein the compound of formula I or the polymerizable compounds of component A) are polymerized.

[0024] The invention further relates to a method for preparing a cholesteric LC medium as described in the context, which comprises the step of mixing the following:

[0025] one or more mesogenic or LC compounds, or an LC host mixture or an LC component B),

[0026] a polymerizable component A) in an amount of ≥2% to ≤10% as described in the context, which comprises one or more polymerizable compounds, preferably consisting of one or more polymerizable compounds, at least one of which is a compound of formula I, a chiral component C), which comprises one or more chiral compounds and optionally other LC compounds and / or additives.

[0027] The invention further relates to the use of a cholesteric LC medium as described in the context in a light modulation element based on the PNLC mode.

[0028] The invention further relates to a PNLC light modulation element, which comprises a pair of opposing substrates, an in-plane electrode structure and a cholesteric LC medium in the intermediate space between the substrates, characterized in that the light modulation element comprises a polymer network, which can be obtained from the cholesteric LC medium of the invention by exposing the cholesteric LC medium to actinic radiation that induces the photopolymerization of the polymerizable compounds in the cholesteric LC medium.

[0029] The invention further relates to a PNLC light modulation element comprising a polymer network, which can be obtained by polymerizing one or more compounds of formula I or the polymerizable component A) as described in the context.

[0030] The invention further relates to the use of a PNLC light modulation element as described in the context in an optical or electro-optical device. Accordingly, the invention also relates to an optical or electro-optical device itself comprising a PNLC light modulation element as described in the context.

[0031] The invention further relates to a method for preparing a PNLC light modulation element as described in the context, wherein a cholesteric LC medium as described in the context is introduced into an LC cell having two substrates and an electrode structure as described in the context, and wherein the polymerizable compounds of the cholesteric LC medium are polymerized.

[0032] In particular, by using the cholesteric LC medium of the invention in a PNLC light modulation element, the requirements mentioned in the context can preferably be met simultaneously, etc.

[0033] Specifically, the PNLC light modulation element of the invention preferably exhibits simultaneously

[0034] - a high turbidity value,

[0035] - a favorable fast response time, especially a favorable fast switching-off time (t off ), and

[0036] - Advantageous low voltage required for addressing.

[0037] Furthermore, the PNLC light modulation element can be produced by compatible, generally known methods for mass production.

[0038] Terms and Definitions

[0039] Unless otherwise explicitly stated, the following meanings apply in the above and below:

[0040] The terms "liquid crystal", "mesomorphic compound", or "mesogenic compound" (also simply referred to as "mesogen") mean a compound that can exist as a mesophase (nematic phase, smectic phase, etc.) or especially as an LC phase under suitable temperature, pressure, and concentration conditions. Non-amphiphilic mesogenic compounds include, for example, one or more rod-shaped, banana-shaped, or disc-shaped mesogenic groups.

[0041] The term "mesogenic group" means a group having the ability to induce liquid crystal phase (or mesophase) behavior. Compounds containing mesogenic groups do not necessarily have to exhibit a liquid crystal mesophase themselves. It may also only show a liquid crystal mesophase in a mixture with other compounds or when the mesogenic compound or material or its mixture is polymerized. This includes low molecular weight non-reactive liquid crystal compounds, reactive or polymerizable liquid crystal compounds, and liquid crystal polymers. For the sake of simplicity, the term "liquid crystal" is used hereinafter for both mesogenic materials and LC materials.

[0042] Rod-shaped mesogenic groups generally include a mesogenic core composed of one or more aromatic or non-aromatic cyclic groups directly connected to each other or via a linking group, optionally including end groups connected to the ends of the mesogenic core, and optionally including one or more side groups connected to the long sides of the mesogenic core, where these end groups and side groups are generally selected from, for example, carbonyl or hydrocarbon groups, polar groups (such as halogen, nitro, hydroxyl, etc.), or polymerizable groups.

[0043] The term "reactive mesogen" or "polymerizable LC compound" means a polymerizable mesogen or liquid crystal compound, preferably a monomeric compound. These compounds can be used as pure compounds or as a mixture of reactive mesogens with other compounds that act as photoinitiators, inhibitors, surfactants, stabilizers, chain transfer agents, non-polymerizable compounds, etc.

[0044] A polymerizable compound having one polymerizable group is also called a "monoreactive" compound, a compound having two polymerizable groups is also called a "di-reactive" compound, and a compound having more than two (i.e., three, four, five, or more) polymerizable groups is also called a "multi-reactive" compound. A compound having no polymerizable group is also called a "non-reactive or non-polymerizable" compound.

[0045] The term "non-mesogenic compound or material" means a compound or material that does not contain a mesogenic group as defined above or below.

[0046] As used herein, the term "non-polymerizable compound or non-polymerizable mesogenic or liquid-crystalline compound" will be understood to mean a liquid-crystalline compound 1 that does not contain functional groups suitable for polymerization under the conditions normally applied for RM polymerization.

[0047] The "polymerizable group" (P) is preferably selected from the group consisting of groups containing a C═C double bond or a C≡C triple bond and groups suitable for polymerization with a ring opening (such as (for example) an oxetane or an epoxy group).

[0048] Preferably, the polymerizable group (P) is selected from the group consisting of: CH2═CW 1 -COO-, CH2═CW 1 -CO-, CH2═CW 2 -(O) k3 -, CW 1 ═CH-CO-(O) k3 -, CW 1 ═CH-CO-NH-, CH2═CW 1 -CO-NH-, CH3-CH═CH-O-, (CH2═CH)2CH-OCO-, (CH2═CH-CH2)2CH-OCO-, (CH2═CH)2CH-O-, (CH2═CH-CH2)2N-, (CH2═CH-CH2)2N-CO-, CH2═CW 1 -CO-NH-, CH2═CH-(COO) k1 -Phe-(O) k2 -, CH2═CH-(CO) k1 -Phe-(O) k2 -, Phe-CH═CH-,

[0049] where

[0050] W 1 represents H, F, Cl, CN, CF3, phenyl or an alkyl group having 1 to 5 C atoms, in particular H, F, Cl or CH3,

[0051] W 2 represents H or an alkyl group having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl,

[0052] W 3 and W 4Each independently represents H, Cl or an alkyl group having 1 to 5 C atoms, Phe represents 1,4-phenylene, which is optionally substituted by one or more groups L as defined above but different from P-Sp, preferably, the preferred substituent L is F, Cl, CN, NO2, CH3, C2H5, OCH3, OC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF3, OCF3, OCHF2, OC2F5, in addition phenyl, and

[0053] k1, k2 and k3 each independently represent 0 or 1, k3 preferably represents 1, and k4 is an integer from 1 to 10.

[0054] Particularly preferred polymerizable groups (P) are CH2=CH-COO-, CH2=C(CH3)-COO-, CH2=CF-COO-, CH2=CH-, CH2=CH-O-, (CH2=CH)2CH-OCO-, (CH2=CH)2CH-O-, and where W 2 represents H or an alkyl group having 1 to 5 C atoms, particularly H, methyl, ethyl or n-propyl and k1 represents 0 or 1.

[0055] More preferred polymerizable groups (P) are vinyl, vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxy group, most preferably acrylate or methacrylate, particularly acrylate.

[0056] Preferably, all polyreactive polymerizable compounds and their sub-formulas contain one or more branched groups containing two or more polymerizable groups P (polyreactive polymerizable groups) rather than one or more groups P-Sp.

[0057] Suitable groups of this type, and polymerizable compounds containing them, are described, for example, in US7,060,200 B1 or US2006 / 0172090 A1.

[0058] Particularly preferred polyreactive polymerizable groups are selected from the following formulas:

[0059] -X-alkyl-CHP x -CH2-CH2P y I*a

[0060] -X-alkyl-C(CH2P x )(CH2P y )-CH2P z I*b

[0061] -X-alkyl-CHPx CHP y -CH2P z I*c

[0062] -X-alkyl-C(CH2P x )(CH2P y )-C aa H 2aa+1 I*d

[0063] -X-alkyl-CHP x -CH2P y I*e

[0064] -X-alkyl-CHP x P y I*f

[0065] -X-alkyl-CP x P y -C aa H 2aa+1 I*g

[0066] -X-alkyl-C(CH2P v )(CH2P w )-CH2OCH2-C(CH2P x )(CH2Py)CH2P z I*h

[0067] -X-alkyl-CH((CH2) aa P x )((CH2) bb P y ) I*i

[0068] -X-alkyl-CHP x CHP y -C aa H 2aa+1 I*k

[0069] wherein

[0070] alkyl represents a single bond or a straight-chain or branched-chain alkylene group having 1 to 12 C atoms, where one or more non-adjacent CH2 groups may each independently be replaced by -C(R x )=C(R x )-, -C≡C-, -N(R x ), -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- such that the O and / or S atoms are not directly connected to each other, and where (in addition) one or more H atoms may be replaced by F, Cl or CN, where Rx has one of the meanings described above,

[0071] aa and bb each independently represents 0, 1, 2, 3, 4, 5 or 6,

[0072] X has one of the meanings specified for X', and

[0073] P v to P z each independently has one of the meanings specified above for P.

[0074] As used herein, the term "spacer group" (hereinafter also referred to as "Sp") is known to those skilled in the art and is described in the literature, see, for example, Pure Appl. Chem. 2001, 73(5), 888 and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340 - 6368. As used herein, the term "spacer group" or "spacer" means a flexible group that connects the mesogenic group and the polymerizable group in a polymerizable mesogenic compound, for example, an alkylene group.

[0075] If the spacer Sp is not a single bond, it is preferably of the formula Sp'-X', such that each group P-Sp- follows the formula P-Sp'-X', where

[0076] Sp' represents an alkylene group having 1 to 20, preferably 1 to 12 C atoms, which is optionally mono- or polysubstituted by F, Cl, Br, I or CN and in which (in addition) one or more non-adjacent CH2 groups may each independently be replaced by -O-, -S-, -NH-, -NR xx -, -SiR xx R yy -, -CO-, -COO-, -OCO-, -OCO-O-, -S-CO-, -CO-S-, -NR xx -CO-O-, -O-CO-NR xx -, -NR xx -CO-NR yy -, -CH=CH- or -C≡C-, with the proviso that O and / or S atoms are not directly connected to each other,

[0077] X' represents -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR xx -, -NR xx -CO-, -NR xx -CO-NR yy-, -OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -CF2CH2-, -CH2CF2-, -CF2CF2-, -CH=N-, -N=CH-, -N=N-, -CH=CR xx -, -CY xx =CY xx -, -C≡C-, -CH=CH-COO-, -OCO-CH=CH- or a single bond,

[0078] Preferably -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR xx -, -NR xx -CO-, -NR xx -CO-NR yy - or a single bond.

[0079] R xx and R yy each independently represent H or an alkyl group having 1 to 12 C atoms, and

[0080] Y xx and Y yy each independently represent H, F, Cl or CN.

[0081] Typical spacer Sp' is for example -(CH2) p1 -, -(CH2CH2O) q1 -CH2CH2-, -CH2CH2-S-CH2CH2-, -CH2CH2-NH-CH2CH2- or -(SiR xx R yy -O) p1 -, where p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and R xx and R yy independently of one another have one of the meanings given above.

[0082] Particularly preferred groups -X'-Sp' are -(CH2) p1 -, -O-(CH2) p1 -, -OCO-(CH2) p1 -, -OCOO-(CH2) p1 -, where p1 is an integer from 1 to 12.

[0083] Particularly preferred groups Sp’ are, for example, methylene, ethylene or straight-chain alkyl chains, such as, for example, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene or ethyleneoxyethylene, methylenoxybutylene, ethylenethioethylene, ethyl-N-methyliminoethylene, 1-methylalkylene, vinylidene, propenylene and butenylene.

[0084] As used herein, the term "polymer" is understood to refer to a molecule having a backbone that includes one or more different types of repeating units (the smallest building blocks of the molecule), and it includes the well-known terms "oligomer", "copolymer", "homopolymer", etc. In addition, it should be understood that the term polymer includes, in addition to the polymer itself, residues from initiators, catalysts and other elements associated with the synthesis of such polymers, where such residues are understood not to be covalently incorporated therein. In addition, such residues and other elements, although typically removed during the purification process after polymerization, are typically mixed or admixed with the polymer such that they are typically retained in the polymer when the polymer is transferred between containers or between solvents or dispersion media.

[0085] As used in the present invention, the term "(meth)acrylic polymer" includes polymers obtained from (meth)acrylic monomers, polymers obtainable from (meth)acrylic monomers, and corresponding copolymers obtainable from mixtures of methacrylic monomers and acrylic monomers.

[0086] A "polymer network" is a network in which all polymer chains are interconnected through numerous crosslinks to form a single macroscopic entity, and preferably, if used in a PNLC device, it extends throughout the cell. The polymer network can exist in the following types:

[0087] 1. Graft polymer molecules are branched polymer molecules in which one or more side chains are structurally or conformationally different from the main chain.

[0088] 2. Star polymer molecules are branched polymer molecules in which a single branch point gives rise to multiple straight chains or arms. If the arms are identical, the star polymer molecule is considered regular. If adjacent arms consist of different repeating subunits, the star polymer molecule is considered variegated.

[0089] 3. Comb polymer molecules consist of a main chain having two or more trifunctional branch points and linear side chains. If the arms are identical, the comb polymer molecule is considered regular.

[0090] 4. Brush polymer molecules consist of a main chain and linear unbranched side chains, and in which one or more branch points have tetrafunctional or greater functionality.

[0091] The term "polymerization" means a chemical process of forming a polymer by bonding together a plurality of polymerizable groups or polymer precursors (polymerizable compounds) containing the polymerizable groups.

[0092] The definitions given in C. Tschierske, G. Pelzl and S. Diele, Angew. Chem. 2004, 116, 6340 - 6368 shall additionally apply to the definitions given above and in particular to undefined terms related to the liquid crystal materials in the present application.

[0093] In this text, the birefringence Δn is defined by the following formula

[0094] Δn = n e - n o

[0095] where n e is the extraordinary refractive index and n o is the ordinary refractive index and the effective average refractive index n av is given by the following equation

[0096] n av . = [(2n o 2 + n e 2 ) / 3] 1 / 2 .

[0097] The extraordinary refractive index n e and the ordinary refractive index n o can be measured, for example, using a modified Abbe refractometer according to "Merck Liquid Crystals, Physical Properties of Liquid Crystals", Status Nov. 1997, Merck KGaA, Germany.

[0098] Visible (VIS) light is electromagnetic radiation with wavelengths in the range of approximately 400 nm to approximately 800 nm. Unless otherwise specified, ultraviolet (UV) light is electromagnetic radiation with wavelengths in the range of approximately 200 nm to approximately 400 nm. Unless otherwise specified, infrared (IR) light is electromagnetic radiation with wavelengths in the range of approximately 800 nm to approximately 1 mm.

[0099] The term "transparent" in the context of this application means that the VIS light transmitted through the PNLC light modulation element is at least 65%, more preferably at least 80%, even more preferably at least 90% of the incident light.

[0100] Radiation dose (E e) is defined as the electromagnetic radiation power (dθ) per unit area (dA) incident on a surface:

[0101] E e = dθ / dA.

[0102] The radiation intensity (H e ) is defined as the radiation dose (E e ) per time (t):

[0103] H e = E e •t.

[0104] The term "clearing point" means the temperature at which the transition between the mesophase with the highest temperature range and the isotropic phase occurs.

[0105] Generally, the term "chiral" is used to describe an object that is not superimposable on its mirror image.

[0106] An "achiral" (non-chiral) object is identical to its mirror image.

[0107] Unless otherwise explicitly described, the terms "cholesteric" and "chiral nematic" are used synonymously in this application.

[0108] A cholesteric texture or cholesteric liquid crystal (CLC) exhibits selective reflection of circularly polarized light, where the direction of rotation of the light vector corresponds to the direction of rotation of the cholesteric helix.

[0109] According to the following equation, the reflection wavelength λ is given by the pitch P of the cholesteric helix and the average birefringence n of the cholesteric liquid crystal:

[0110] λ = n•p

[0111] A CLC medium can be prepared, for example, by doping a nematic LC medium with a chiral dopant having a high twisting power. Then, the pitch p of the induced cholesteric helix is provided by the concentration c of the chiral dopant and the helical twisting power HTP according to the following equation:

[0112] p = (HTP c) -1

[0113] Two or more dopants can also be used, for example, to compensate for the temperature dependence of the HTP of each dopant and thus achieve a low temperature dependence of the helical pitch and reflection wavelength of the CLC medium. For the total HTP (HTP 总 ), the following equation approximately applies:

[0114] HTP 总 = ∑ i c i HTP i

[0115] where c i is the concentration of each individual dopant and HTP i is the helical twisting power of each individual dopant.

[0116] Throughout this application and unless otherwise clearly stated, all concentrations are expressed as weight percentages and refer to the respective complete mixtures, all temperatures are in degrees Celsius and all temperature differences are in degree differences.

[0117] In this application, the term "dielectric positive" is used for compounds or components with Δε > 3.0, "dielectric neutral" for compounds or components with -1.5 ≤ Δε ≤ 3.0, and "dielectric negative" for compounds or components with Δε < -1.5.

[0118] Δε is measured at a frequency of 1 kHz and at 20 °C. The dielectric anisotropy of each compound is determined from the results of a 10% solution of each individual compound in a nematic host mixture. In cases where the solubility of each compound in the host medium is less than 10%, its concentration is reduced by half until the resulting medium is stable enough to at least allow the determination of its properties. However, in a preferred embodiment, the concentration is maintained at at least 5% to maintain the highest possible result significance. The capacitance of the test mixture is measured in cells with both homeotropic and planar alignments. The cell thickness of both types of cells is approximately 20 μm. The applied voltage is a rectangular wave with a frequency of 1 kHz and a root mean square value typically of 0.5 V to 1.0 V; however, it is always selected to be below the capacitance threshold of each test mixture.

[0119] Δε is defined as (ε || - ε ⊥ ), and ε av . is (ε || + 2ε ⊥ ) / 3. The dielectric permittivity of the compound is determined from the change in each value of the host medium after the addition of the compound of interest. This value is extrapolated to a concentration of 100% of the compound of interest. Typical host media are ZLI-4792 or BL-087, both of which are purchased from Merck, Darmstadt.

[0120] Unless the context otherwise clearly indicates, the plural form of a term as used herein shall be construed to include the singular form and vice versa.

[0121] For the purposes of this invention,

[0122] and represent 1,4-cyclohexylene, preferably and represent trans-1,4-cyclohexylene.

[0123] For the purposes of the present invention

[0124] and

[0125] represents 1,4-phenylene.

[0126] For the purposes of the present invention, the group -COO-, -C(=O)O- or -CO2- represents an ester group of the formula and the group -OCO-, -OC(=O)-, -O2C- or -OOC- represents an ester group of the formula of an ester.

[0127] In the group the single bond shown between two ring atoms may be attached to any free position of the benzene ring.

[0128] In the above and below, "carbon-based group" means a monovalent or polyvalent organic group containing at least one carbon atom, which contains no other atoms (e.g., -C≡C-) or optionally contains one or more other atoms (e.g., N, O, S, P, Si, Se, As, Te or Ge) (e.g., carbonyl group, etc.). "Hydrocarbyl group" means a carbon-based group that additionally contains one or more H atoms and optionally contains one or more heteroatoms (e.g., N, O, S, P, Si, Se, As, Te or Ge).

[0129] The carbon-based group or hydrocarbyl group may be a saturated or unsaturated group. Unsaturated groups are, for example, aryl, alkenyl or alkynyl. The carbon-based group or hydrocarbyl group having more than 3 C atoms may be straight-chain, branched and / or cyclic and may contain spiro links or fused rings.

[0130] Throughout this application, unless otherwise expressly stated, the term "aryl and heteroaryl" encompasses groups that may be monocyclic or polycyclic, i.e., they may have one ring (e.g., phenyl), or two or more rings, which may also be fused (e.g., naphthyl) or covalently linked (e.g., biphenyl), or contain a combination of fused and linked rings.

[0131] Heteroaryl contains one or more heteroatoms preferably selected from O, N, S and Se. Particularly preferred are monocyclic, bicyclic or tricyclic aryl groups having 6 to 25 C atoms, and monocyclic, bicyclic or tricyclic heteroaryl groups having 2 to 25 C atoms, which optionally contain fused rings and are optionally substituted. Further preferred are 5-, 6- or 7-membered aryl and heteroaryl groups, wherein in addition, one or more CH groups may be replaced by N, S or O in such a way that O atoms and / or S atoms are not directly connected to each other. Preferred aryl groups are, for example, phenyl, biphenyl, terphenyl, [1,1':3',1"]-terphenyl-2'-yl, naphthyl, anthracenyl, binaphthyl, phenanthryl, pyrene, dihydropyrene, Perylene, tetracene, pentacene, benzopyrene, fluorene, indene, indenofluorene, spirobifluorene, etc., more preferably 1,4-phenylene, 4,4'-biphenylene, 1,4-terphenylene.

[0132] Preferred heteroaryl groups are for example 5-membered rings such as pyrrole, pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, tetrazole, furan, thiophene, selenophene, oxazole, isoxazole, 1,2-thiazole, 1,3-thiazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole, 1,3,4-thiadiazole, 6-membered rings such as pyridine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, 1,2,4-triazine, 1,2,3-triazine, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine, 1,2,3,5-tetrazine or fused groups such as indole, isoindole, indolizine, indazole, benzimidazole, benzotriazole, purine, naphthimidazole, phenanthrimidazole, pyridinimidazole, 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, benzoisoquinoline, acridine, phenothiazine, phenoxazine, benzopyridazine, benzopyrimidine, quinoxaline, phenazine, naphthyridine, azacarbazole, benzocarbazole, phenanthridine, phenanthroline, thiophene[2,3b]thiophene, thiophene[3,2b]thiophene, dithienothiophene, isobenzothiophene, dibenzothiophene, benzothiadiazolethiophene, or combinations of these groups. The heteroaryl groups may also be substituted by alkyl, alkoxy, thioalkyl, fluorine, fluoroalkyl or other aryl or heteroaryl groups.

[0133] In the context of the present application, the term “(non-aromatic) alicyclic group and heterocyclic group” encompasses both saturated rings, i.e., those containing only single bonds, and partially unsaturated rings, i.e., those that may also contain multiple bonds. The heterocyclic ring contains one or more heteroatoms, preferably selected from Si, O, N, S, and Se. The (non-aromatic) alicyclic group and heterocyclic group may be monocyclic, i.e., containing only one ring (e.g., cyclohexane), or polycyclic, i.e., containing multiple rings (e.g., decalin or bicyclooctane). Saturated groups are particularly preferred. Also preferred are mono-, bi- or tricyclic groups having 3 - 25 C atoms, which optionally contain fused rings and are optionally substituted. Further preferred are 5-, 6-, 7- or 8-membered carbocyclic groups, wherein, additionally, one or more C atoms may be replaced by Si and / or one or more CH groups may be replaced by N and / or one or more non-adjacent CH2 groups may be replaced by -O- and / or -S-. Preferred alicyclic groups and heterocyclic groups are, for example, 5-membered groups such as cyclopentane, tetrahydrofuran, tetrahydrothiophene, pyrrolidine; 6-membered groups such as cyclohexane, silinane, cyclohexene, tetrahydropyran, tetrahydrothiopyran, 1,3-dioxane, 1,3-dithiane, piperidine; 7-membered groups such as cycloheptane; and fused groups such as tetralin, decalin, indane, bicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl, octahydro-4,7-methanoindane-2,5-diyl, more preferably 1,4-cyclohexylene, 4,4'-biscyclohexylene, 3,17-hexahydro-cyclopenta[a]phenanthrene, which are optionally substituted by one or more identical or different groups L. Particularly preferred aryl-, heteroaryl-, alicyclic- and heterocyclic groups are 1,4-phenylene, 4,4'-biphenylene, 1,4-terphenylene, 1,4-cyclohexylene, 4,4'-biscyclohexylene and 3,17-hexahydro-cyclopenta[a]phenanthrene, which are optionally substituted by one or more identical or different groups L.

[0134] Preferred substituents (L) of the above-mentioned aryl-, heteroaryl-, alicyclic- and heterocyclic groups are, for example, solubility-promoting groups (such as alkyl or alkoxy) and electron-withdrawing groups (such as fluorine, nitro or nitrile).

[0135] Preferred substituents, also referred to hereinafter as “L”, are, for example, F, Cl, Br, I, -OH, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, -C(=O)N(R x )2, -C(=O)Y x , -C(=O)R x , -C(=O)OR x , -N(R x )2, where R xhas the meaning mentioned above, and the above Y x represents halogen, optionally substituted silyl, optionally substituted aryl or heteroaryl having 4 to 40, preferably 4 to 20 ring atoms, and straight-chain or branched alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25 C atoms, where one or more H atoms may optionally be replaced by F or Cl.

[0136] "Substituted silyl or aryl" preferably means silyl or aryl substituted by halogen, -CN, R y 、-OR y 、-CO-R y 、-CO-O-R y 、-O-CO-R y or -O-CO-O-R y where R y represents H; a straight-chain, branched or cyclic alkyl chain having 1 to 12 C atoms.

[0137] In the formulas shown above and below, the substituted phenylene ring

[0138] is preferably

[0139] where L is the same or different in each occurrence and has one of the meanings given above and below, and is preferably F, Cl, CN, NO2, CH3, C2H5, C(CH3)3, CH(CH3)2, CH2CH(CH3)C2H5, OCH3, OC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF3, OCF3, OCHF2, OC2F5 or P-Sp-, very preferably F, Cl, CN, CH3, C2H5, OCH3, COCH3, OCF3 or P-Sp-, most preferably F, Cl, CH3, OCH3, COCH3 or OCF3.

[0140] "Halogen" represents F, Cl, Br or I, preferably F or Cl, more preferably F.

[0141] The terms "alkyl", "aryl", "heteroaryl", etc. above and below also cover polyvalent groups, such as alkylene, arylene, heteroarylene, etc.

[0142] The term "aryl" represents an aromatic carbon group or a group derived therefrom.

[0143] The term "heteroaryl" represents "aryl" as defined above containing one or more heteroatoms.

[0144] Preferred alkyl groups are, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 2-methylbutyl, n-pentyl, sec-pentyl, cyclopentyl, n-hexyl, cyclohexyl, 2-ethylhexyl, n-heptyl, cycloheptyl, n-octyl, cyclooctyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, dodecyl, trifluoromethyl, perfluoro-n-butyl, 2,2,2-trifluoroethyl, perfluorooctyl, perfluorohexyl, etc.

[0145] Preferred alkoxy groups are, for example, methoxy, ethoxy, 2-methoxyethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, 2-methylbutoxy, n-pentyloxy, n-hexyloxy, n-heptyloxy, n-octyloxy, n-nonyloxy, n-decyloxy, n-undecyloxy, n-dodecyloxy.

[0146] Preferred alkenyl groups are, for example, vinyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl, cyclooctenyl.

[0147] Preferred alkynyl groups are, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl, octynyl.

[0148] Preferred amino groups are, for example, dimethylamino, methylamino, methylphenylamino, phenylamino.

[0149] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of these words (such as "comprising" and "comprises") mean "including but not limited to", and are not intended (and do not) exclude other components. On the other hand, the word "comprise" also encompasses the term "consisting of", but is not limited thereto.

[0150] Throughout the description and claims of this specification, the words "obtainable" and "obtain" and variations of these words mean "including but not limited to", and are not intended (and do not) exclude other components. On the other hand, the word "obtainable" also encompasses the term "obtain" but is not limited thereto.

[0151] The term "alignment" or "orientation" refers to the alignment (orientational ordering) of anisotropic units of a material (such as small molecules or macromolecular fragments) in a common direction called the "alignment direction". In the alignment layer of a liquid crystal material, the liquid crystal director is aligned with the alignment direction so that the alignment direction corresponds to the direction of the anisotropic axis of the material.

[0152] The term "planar alignment" (e.g., in a liquid crystal material layer) means that the long molecular axes (for rod-shaped compounds) or short molecular axes (for disc-shaped compounds) of a proportion of liquid crystal molecules are oriented substantially parallel (about 180°) to the layer plane.

[0153] The term "vertical alignment" (e.g., in a liquid crystal material layer) means that the long molecular axes (for rod-shaped compounds) or short molecular axes (for disc-shaped compounds) of a proportion of liquid crystal molecules are oriented at an angle θ ("tilt angle") between about 80° and 90° relative to the layer plane.

[0154] Detailed description

[0155] Preferably, in the compounds of formula I and its sub-formulas as described above and below, all polymerizable groups P present in the compound have the same meaning, and more preferably represent acrylate or methacrylate, most preferably methacrylate.

[0156] More preferably, the compounds of formula I and its sub-formulas, wherein the group Ar is selected from formulae Ar5, Ar6 and Ar7, and the groups P present in the compound are the same or different.

[0157] In the compounds of formula I and its sub-formulas as described above and below, Ar is preferably selected from formulae Ar1, Ar2 and Ar5.

[0158] Preferred compounds of formula I are selected from the following sub-formulas

[0159]

[0160]

[0161] wherein P, Sp and L have one of the meanings given in formula I,

[0162] r1, r3, r7 are each independently 0, 1, 2 or 3,

[0163] r2 is 0, 1, 2, 3 or 4,

[0164] r4, r5, r6 are each independently 0, 1 or 2.

[0165] Very preferably, the compounds of formulae I1, I2 and I5.

[0166] More preferred compounds of formula I are selected from the following sub-formulas

[0167]

[0168]

[0169]

[0170] wherein P, Sp, L, r1 - r7 have the meanings given by formula I or one of the preferred meanings given above and below.

[0171] Very preferably, the compounds of formula I are selected from the following sub - formulas:

[0172]

[0173]

[0174]

[0175]

[0176] wherein P, Sp have the meanings given above or below, and La and L b each independently of one another have the meanings given above or below for L.

[0177] Very preferably, the compounds of sub - formulas I1 - 1 - 1 to I2 - 1 - 18 are those in which all groups P are the same and represent acrylate or methacrylate groups, and further, those in which Sp is -(CH2) p1 -, -(CH2) p1 -O -, -(CH2) p1 -O - CO - or -(CH2) p1 -CO - O -, where p1 is an integer from 1 to 12 (preferably 1 to 6), and the O - or CO - group is attached to the benzene ring, and further, those in which L a and L b represent F, CH3, CH2CH3, OCH3, OC2H5, O(CH2)2CH3, OC(CH3)3 or OCF3.

[0178] More preferably, the compounds of formula I and its sub - formulas are selected from the following preferred embodiments, including any combination thereof:

[0179] - All groups P in the compound have the same meaning,

[0180] - Ar is selected from formulae Ar1, Ar2, Ar3 and Ar4, and all groups P present in the compound have the same meaning,

[0181] - Ar is selected from formulae Ar1, Ar2, Ar3, Ar4 and Ar5, and all groups P present in the compound have the same meaning,

[0182] - Ar is selected from formulae Ar1, Ar2, Ar3, Ar4 and Ar6, and all groups P present in the compound have the same meaning,

[0183] - Ar is selected from the formulas Ar1, Ar2, Ar3, Ar4 and Ar7, and all groups P present in the compound have the same meaning.

[0184] - Ar is selected from the formulas Ar1, Ar2, Ar3, Ar4, A5 and Ar7, and all groups P present in the compound have the same meaning.

[0185] - Ar is selected from the formulas Ar1, Ar2, Ar3, Ar4, A6 and Ar7, and all groups P present in the compound have the same meaning.

[0186] - Ar is selected from the formula Ar5, and the groups P present in the compound may have the same or different meanings.

[0187] - Ar is selected from the formula Ar6, and the groups P present in the compound may have the same or different meanings.

[0188] - Ar is selected from the formula Ar7, and the groups P present in the compound may have the same or different meanings.

[0189] - The compound contains exactly two polymerizable groups (denoted as group P).

[0190] - P is selected from the group consisting of acrylate, methacrylate and oxetane.

[0191] - When not a single bond, Sp is -(CH2) p2 -、-(CH2) p2 -O-、-(CH2) p2 -CO-O-、-(CH2) p2 -O-CO-, where p 2 is 2, 3, 4, 5 or 6, and the O-atom or the CO-group is respectively connected to the benzene ring.

[0192] - When not L a , L b represents F, Cl or CN.

[0193] - L a is F, CH3, CH2CH3, OCH3, OC2H5, O(CH2)2CH3, OC(CH3)3 or OCF3.

[0194] - r1, r2 and r3 represent 0 or 1.

[0195] - r1, r2, r3, r4, r5 and r6 represent 0 or 1.

[0196] - One of r1 and r7 is 0 and the other is 1.

[0197] - r1 is 1, and r2 and r3 are 0,

[0198] - r3 is 1 and r1 and r2 are 0,

[0199] - One of r4 and r5 is 0 and the other is 1,

[0200] - r4 and r6 are 0 and r5 is 1,

[0201] - r1 and r4 are 0 and r3 is 1,

[0202] - r1 and r3 are 0 and r4 is 1,

[0203] - r3 and r4 are 0 and r1 is 1.

[0204] More preferred compounds of formula I and its sub-formulas are selected from the compounds of formula I1-1-1, I1-1-3, I1-2-2 and I2-1-1 to I2-1-6, wherein P is selected from the group consisting of acrylate, methacrylate and oxetane, L a and L b each and independently of one another is F, CH3, CH2CH3, OCH3, OC2H5, O(CH2)2CH3, OC(CH3)3 or OCF3.

[0205] The compounds of formula I and its sub-formulas and intermediates can be prepared analogously to methods known to those skilled in the art and described in standard works of organic chemistry (such as, for example, Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], Thieme-Verlag, Stuttgart).

[0206] For example, acrylate or methacrylate can be prepared by esterifying the corresponding alcohol with an acid derivative (such as, for example, (meth)acryloyl chloride or (meth)acrylic anhydride) in the presence of a base (such as pyridine or triethylamine) and 4-(N,N-dimethylamino)pyridine (DMAP). Alternatively, the ester can be prepared by esterifying the alcohol with (meth)acrylic acid in the presence of a dehydrating reagent, for example according to Steglich with dicyclohexylcarbodiimide (DCC), N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide (EDC) or N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and DMAP.

[0207] Particularly preferred are cholesteric LC media in which the polymerizable component A) comprises one, two or three polymerizable compounds of formula I.

[0208] Furthermore preferred are cholesteric LC media in which the polymerizable component A) exclusively comprises polymerizable compounds of the formula I.

[0209] Optionally, one or more polymerization initiators may be added to the cholesteric LC medium. Suitable conditions for polymerization and suitable types and amounts of initiators are known to the person skilled in the art and are described in the literature.

[0210] Suitable for free-radical polymerization are, for example, commercially available photoinitiators or (Ciba AG). If a polymerization initiator is used, its proportion is preferably from 0.001% by weight to 5% by weight, particularly preferably from 0.001% by weight to 1% by weight.

[0211] The polymerizable compounds according to the invention are also suitable for polymerization without an initiator, which has considerable advantages such as, for example, lower material costs and, in particular, less contamination of the cholesteric LC medium by possible residual amounts of the initiator or its degradation products. Polymerization can therefore also be carried out without the addition of an initiator. In a preferred embodiment, the cholesteric LC medium does not contain a polymerization initiator.

[0212] The cholesteric LC medium may also contain one or more stabilizers to prevent unwanted spontaneous polymerization of the RM, for example during storage or transport. Suitable types and amounts of stabilizers are known to the person skilled in the art and are described in the literature.

[0213] Particularly suitable are, for example, commercially available stabilizers from the series (Ciba AG) (such as, for example, 1076). If stabilizers are used, their proportion (based on the total amount of RM or polymerizable component (component A)) is preferably from 10 - 500,000 ppm, particularly preferably from 50 - 50,000 ppm.

[0214] Preferably, the cholesteric LC media according to the invention consist essentially of: polymerizable component A) or one or more polymerizable compounds of the formula I, LC component B) or LC host mixture, and chiral component C) comprising one or more chiral compounds as described in context.

[0215] However, the cholesteric LC medium may additionally contain one or more other components or additives, preferably selected from the list consisting of, but not limited to: inhibitors, other stabilizers, wetting agents, lubricants, dispersants, water repellents, binders, flow improvers, defoamers, degassing agents, diluents, reactive diluents, auxiliaries, colorants, dyes, pigments and nanoparticles.

[0216] In another preferred embodiment, the polymerizable component A) contains, in addition to the compound of formula I, one or more other polymerizable compounds ( "comonomers") preferably selected from RM.

[0217] Suitable and preferred mesogenic comonomers are selected from the following formulae:

[0218]

[0219]

[0220]

[0221]

[0222] wherein each group has the following meanings:

[0223] P 1 、P 2 and P 3 each independently of one another represent an acrylate group or a methacrylate group,

[0224] Sp 1 、Sp 2 and Sp 3 each independently of one another represent a single bond or a spacer group having one of the meanings indicated above and below for Sp, and particularly preferably represent -(CH2) p1 -、-(CH2) p1 -O、-(CH2) p1 -CO-O-、-(CH2) p1 -O-CO- or -(CH2) p1 -O-CO-O-, where p1 is an integer from 1 to 12, and wherein, furthermore, the group P 1 -Sp 1 -、P 1 -Sp 2 - and P 3 -Sp 3 - of one or more may represent R aa , with the proviso that at least one of the groups P 1 -Sp 1 -、P 2 -Sp 2 and P 3 -Sp 3 - is not R aa ,

[0225] R aa represents H, F, Cl, CN or a straight-chain or branched alkyl group having 1 to 25 C atoms, where (in addition) one or more non-adjacent CH2 groups may each independently be replaced by C(R0 ) = C(R 00 )-, -C≡C-, -N(R 0 )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- substitution, with the substitution method being that O and / or S atoms are not directly connected to each other, and one or more H atoms can be replaced by F, Cl, CN or P 1 -Sp 1 - substitution, especially preferably a straight-chain or branched-chain, optionally mono- or poly-substituted alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms (wherein the alkenyl and alkynyl have at least two C atoms and the branched-chain group has at least three C atoms),

[0226] R 0 、R 00 each independently of one another and, each time they occur, the same or different, represent H or an alkyl having 1 to 12 C atoms,

[0227] R y and R z each independently represent H, F, CH3 or CF3,

[0228] X 1 、X 2 and X 3 each independently represent -CO-O-, -O-CO- or a single bond,

[0229] Z 1 represents –O-, -CO-, -C(R y R z )- or -CF2CF2-,

[0230] Z 2 and Z 3 each independently represent -CO-O-, -O-CO-, -CH2O-, -OCH2-, -CF2O-, -OCF2- or -(CH2) n -, where n is 2, 3 or 4,

[0231] L, each time it occurs, the same or different, represents F, Cl, CN or a straight-chain or branched-chain, optionally mono- or poly-fluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms, preferably F,

[0232] L’ and L" each independently represent H, F or Cl,

[0233] r represents 0, 1, 2, 3 or 4,

[0234] s represents 0, 1, 2 or 3,

[0235] t represents 0, 1 or 2,

[0236] x represents 0 or 1.

[0237] Particularly preferred are the compounds of formulae M2, M13, M17, M22, M23, M24 and M30.

[0238] More preferred are the tri-reactive compounds M15 to M30, in particular M17, M18, M19, M22, M23, M24, M25, M26, M30 and M31.

[0239] In the compounds of formulae M1 to M31, the group

[0240] is preferably

[0241] wherein L, each time it occurs, is the same or different and has one of the meanings given above or below, and is preferably F, Cl, CN, NO2, CH3, C2H5, C(CH3)3, CH(CH3)2, CH2CH(CH3)C2H5, OCH3, OC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF3, OCF3, OCHF2, OC2F5 or P-Sp-, very preferably F, Cl, CN, CH3, C2H5, OCH3, COCH3, OCF3 or P-Sp-, more preferably F, Cl, CH3, OCH3, COCH3 or OCF3, especially F or CH3.

[0242] In addition to the above-mentioned polymerizable compounds, the LC medium for an LC display according to the invention comprises a liquid-crystalline component B) or an LC host mixture exhibiting positive dielectric anisotropy, which preferably comprises one or more, more preferably two or more LC compounds (which are selected from non-polymerizable low-molecular-weight compounds). These LC compounds are selected such that they are stable and / or non-reactive towards the polymerization reaction under the conditions of the polymerization of the polymerizable compounds.

[0243] Preferred LC compounds which can be used for the liquid-crystalline component B) according to the invention are as shown below:

[0244]

[0245] wherein each group, independently of one another and each time it occurs, the same or different, has the following meanings:

[0246]

[0247] Each independently of one another and, each time they occur, the same or different, is

[0248]

[0249] R 21 、R 31 Each independently of one another is an alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C atoms or an alkenyl or alkenyloxy having 2 to 9 C atoms, each of which is optionally fluorinated,

[0250] X 0 is F, Cl, CN, a halogenated alkyl or alkoxy having 1 to 6 C atoms or a halogenated alkenyl or alkenyloxy having 2 to 6 C atoms,

[0251] Z 31 is -CH2CH2-, -CF2CF2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O- or a single bond, preferably -CH2CH2-, -COO-, trans-CH=CH- or a single bond, particularly preferably -COO-, trans-CH=CH- or a single bond,

[0252] L 21 、L 22 、L 31 、L 32 Each independently of one another is H or F,

[0253] g is 0, 1, 2 or 3.

[0254] In the compounds of formulae A and B, X 0 is preferably F, Cl, CF3, CHF2, OCF3, OCHF2, OCFHCF3, OCFHCHF2, OCFHCHF2, OCF2CH3, OCF2CHF2, OCF2CHF2, OCF2CF2CHF2, OCF2CF2CHF2, OCFHCF2CF3, OCFHCF2CHF2, OCF2CF2CF3, OCF2CF2CClF2, OCClFCF2CF3 or CH=CF2, very preferably F or OCF3, and most preferably F.

[0255] In the compounds of formulae A and B, R 21 and R 31 are preferably selected from straight-chain alkyl or alkoxy having 1, 2, 3, 4, 5 or 6 C atoms and straight-chain alkenyl having 2, 3, 4, 5, 6 or 7 C atoms.

[0256] In the compounds of formulae A and B, g is preferably 1 or 2.

[0257] In the compounds of formula B, Z31 Preferably COO, trans-CH=CH or a single bond, very preferably COO or a single bond.

[0258] Preferably, component B) of the cholesteric LC medium comprises one or more compounds of formula A selected from the group consisting of the following formulas:

[0259]

[0260] wherein A 21 , R 21 , X 0 , L 21 and L 22 have the meanings given in formula A, L 23 and L 24 are each independently of the other H or F, and X 0 is preferably F. Particularly preferred are the compounds of formulas A1 and A2.

[0261] Particularly preferred compounds of formula A1 are selected from the group consisting of the following sub-formulas:

[0262]

[0263]

[0264] wherein R 21 , X 0 , L 21 and L 22 have the meanings given in formula A1, L 23 , L 24 , L 25 and L 26 are each independently of the other H or F, and X 0 is preferably F.

[0265] Very particularly preferred compounds of formula A1 are selected from the group consisting of the following sub-formulas:

[0266]

[0267]

[0268] wherein R 21 is as defined in formula A1.

[0269] Particularly preferred compounds of formula A2 are selected from the group consisting of the following sub-formulas:

[0270]

[0271]

[0272]

[0273] wherein R 21 , X 0 , L 21 and L 22 have the meanings given in formula A2, and L 23 , L 24 , L 25 and L 26 are each independently H or F, and X 0 is preferably F.

[0274] Very particularly preferred compounds of formula A2 are selected from the group consisting of the following sub-formulas:

[0275]

[0276]

[0277]

[0278] wherein R 21 and X 0 are as defined in formula A2.

[0279] Particularly preferred compounds of formula A3 are selected from the group consisting of the following sub-formulas:

[0280]

[0281]

[0282] wherein R 21 , X 0 , L 21 and L 22 have the meanings given in formula A3, and X 0 is preferably F.

[0283] Particularly preferred compounds of formula A4 are selected from the group consisting of the following sub-formulas:

[0284]

[0285] wherein R 21 is as defined in formula A4.

[0286] Preferably, component B) of the cholesteric LC medium comprises one or more compounds of formula B selected from the group consisting of the following sub-formulas:

[0287]

[0288] wherein g, A 31 , A 32 , R 31 , X0 , L 31 and L 32 have the meanings given in formula B, and X 0 is preferably F or CN. Highly particularly preferred are the compounds of formulae B1 and B2.

[0289] Highly particularly preferred compounds of formula B1 are selected from the group consisting of the following sub-formulae:

[0290]

[0291] wherein R 31 , X 0 , L 31 and L 32 have the meanings given in formula B1, and X 0 is preferably F.

[0292] Highly particularly preferred compounds of formula B1a are selected from the group consisting of the following sub-formulae:

[0293]

[0294]

[0295] wherein R 31 is as defined in formula B1.

[0296] Highly particularly preferred compounds of formula B1b are selected from the group consisting of the following sub-formulae:

[0297]

[0298] wherein R 31 is as defined in formula B1.

[0299] Particularly preferred compounds of formula B2 are selected from the group consisting of the following sub-formulae:

[0300]

[0301]

[0302]

[0303] wherein R 31 , X 0 , L 31 and L 32 have the meanings given in formula B2, L 33 , L 34 , L 35 and L 36 are each independently H or F, and X 0 is preferably F or CN.

[0304] Very particularly preferred compounds of formula B2 are selected from the group consisting of the following sub-formulas:

[0305]

[0306]

[0307] wherein R 31 is as defined in formula B2.

[0308] Very particularly preferred compounds of formula B2b are selected from the group consisting of the following sub-formulas

[0309]

[0310] wherein R 31 is as defined in formula B2.

[0311] Very particularly preferred compounds of formula B2c are selected from the group consisting of the following sub-formulas:

[0312]

[0313]

[0314] wherein R 31 is as defined in formula B2.

[0315] Very particularly preferred compounds of formula B2d and B2e are selected from the group consisting of the following sub-formulas:

[0316]

[0317] wherein R 31 is as defined in formula B2.

[0318] Very particularly preferred compounds of formula B2f are selected from the group consisting of the following sub-formulas:

[0319]

[0320]

[0321] wherein R 31 is as defined in formula B2.

[0322] Very particularly preferred compounds of formula B2g are selected from the group consisting of the following sub-formulas:

[0323]

[0324]

[0325] wherein R 31 is as defined in formula B2.

[0326] Very particularly preferred compounds of formula B2h are selected from the group consisting of the following sub-formulas:

[0327]

[0328] wherein R 31 is as defined in formula B2.

[0329] Very particularly preferred compounds of formula B2i are selected from the group consisting of the following sub-formulas:

[0330]

[0331] wherein R 31 is as defined in formula B2.

[0332] Very particularly preferred compounds of formula B2k are selected from the group consisting of the following sub-formulas:

[0333]

[0334] wherein R 31 is as defined in formula B2.

[0335] Very particularly preferred compounds of formula B2l are selected from the group consisting of the following sub-formulas:

[0336]

[0337] wherein R 31 is as defined in formula B2.

[0338] Alternatively or additionally, the compounds of component B) of the cholesteric LC medium of formula B1 and / or B2 may also comprise one or more compounds of formula B3 as defined above.

[0339] Very particularly preferred compounds of formula B3 are selected from the group consisting of the following sub-formulas:

[0340]

[0341] wherein R 31 is as defined in formula B3.

[0342] Preferably, component B) of the cholesteric LC medium comprises one or more compounds of formula C in addition to the compounds of formula A and / or B

[0343]

[0344] where each group has the following meanings:

[0345] Each, independently of one another and, each time it appears, the same or different, is

[0346]

[0347] R 41 、R 42 Each, independently of one another, is an alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C atoms, or an alkenyl or alkenyloxy having 2 to 9 C atoms (each of which is optionally fluorinated),

[0348] Z 41 、Z 42 Each, independently of one another, is -CH2CH2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O-, -CF2O-, -C≡C- or a single bond, preferably a single bond,

[0349] h is 0, 1, 2 or 3.

[0350] In the compound of formula C, R 41 and R 42 are preferably selected from straight-chain alkyl or alkoxy having 1, 2, 3, 4, 5 or 6 C atoms and straight-chain alkenyl having 2, 3, 4, 5, 6 or 7 C atoms.

[0351] In the compound of formula C, h is preferably 0, 1 or 2.

[0352] In the compound of formula C, Z 41 and Z 42 are preferably selected from COO, trans-CH=CH and a single bond, very particularly preferably selected from COO and a single bond.

[0353] Preferred compounds of formula C are selected from the group consisting of the following sub-formulas:

[0354]

[0355]

[0356] wherein R 41 and R 42 have the meanings given in formula C and preferably each, independently of one another, represents an alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, or an alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms.

[0357] Preferably, component B) of the cholesteric LC medium comprises, in addition to the compounds of formula A and / or B, one or more compounds of formula D

[0358]

[0359] wherein A 41 and A 42 and Z 41 and Z 42 and R 41 and R 42 and h have one of the meanings given in formula C or one of the preferred meanings given above.

[0360] Preferred compounds of formula D are selected from the group consisting of the following sub-formulas:

[0361]

[0362] wherein R 41 and R 42 have the meanings given in formula D and R 41 preferably represents alkyl, and in formula D1, R 42 preferably represents alkenyl, particularly preferably -(CH2)2-CH=CH-CH3, and in formula D2, R 42 preferably represents alkyl, -(CH2)2-CH=CH2 or -(CH2)2-CH=CH-CH3.

[0363] Preferably, component B) of the cholesteric LC medium further comprises one or more alkenyl-containing compounds of formula E in addition to the compounds of formula A and / or B

[0364]

[0365] wherein each group, each time it appears the same or different, independently of one another has the following meanings:

[0366]

[0367] R A1 is alkenyl having 2 to 9 C atoms, or, if at least one of the rings X, Y and Z represents cyclohexenyl, also has one of the meanings of R A2

[0368] R A2 is alkyl having 1 to 12 C atoms, wherein (in addition) one or two non-adjacent CH2 groups may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO-, with the proviso that the O atoms are not directly linked to each other

[0369] x is 1 or 2.

[0370] 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.

[0371] Preferred compounds of formula E are selected from the following sub-formulas: ​

[0372]

[0373]

[0374] wherein alkyl and alkyl* each independently of one another represent straight-chain alkyl groups having 1 to 6 C atoms, and alkenyl and alkenyl* each independently of one another represent straight-chain alkenyl groups having 2 to 7 C atoms. Alkenyl and alkenyl* preferably represent CH2═CH—, CH2═CHCH2CH2—, CH3—CH═CH—, CH3—CH2—CH═CH—, CH3—(CH2)2—CH═CH—, CH3—(CH2)3—CH═CH— or CH3—CH═CH—(CH2)2—.

[0375] Very preferably, the compounds of formula E are selected from the following sub-formulas:

[0376]

[0377]

[0378] where m represents 1, 2, 3, 4, 5 or 6, i represents 0, 1, 2 or 3, and R b1 represents H, CH3 or C2H5.

[0379] Very particularly preferably, the compounds of formula E are selected from the following sub-formulas:

[0380]

[0381] Most preferably, the compounds of formula E1a2, E1a5, E3a1 and E6a1.

[0382] Preferably, component B) of the cholesteric LC medium comprises, in addition to the compounds of formula A and / or B, one or more compounds of formula F

[0383]

[0384] where each group independently of one another and each time it occurs, whether identically or differently, has the following meanings:

[0385] represents

[0386]

[0387] R 21 、R 31 are each independently of one another an alkyl, alkoxy, oxaalkyl or alkoxyalkyl group having 1 to 9 C atoms or an alkenyl or alkenyloxy group having 2 to 9 C atoms, all of which are optionally fluorinated,

[0388] X 0 is F, Cl, a haloalkyl or alkoxy group having 1 to 6 C atoms, or a haloalkenyl or alkenyloxy group having 2 to 6 C atoms,

[0389] Z 21 is -CH2CH2-, -CF2CF2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O- or a single bond, preferably -CH2CH2-, -COO-, trans-CH=CH- or a single bond, particularly preferably -COO-, trans-CH=CH- or a single bond,

[0390] L 21 L 22 L 23 L 24 each independently of one another is H or F,

[0391] g is 0, 1, 2 or 3.

[0392] Particularly preferred compounds of formula F are selected from the group consisting of the following formulas:

[0393]

[0394] wherein R 21 X 0 L 21 and L 22 have the meanings given in formula F, L 25 and L 26 each independently of one another is H or F, and X 0 is preferably F.

[0395] Very particularly preferred compounds of formulas F1 - F3 are selected from the group consisting of the following sub-formulas:

[0396]

[0397]

[0398] wherein R 21 is as defined in formula F1.

[0399] The medium preferably comprises one or more neutral compounds of general formula N,

[0400]

[0401] wherein

[0402] R N1 and R N2Each independently represents an alkyl or alkoxy group having 1 to 15 carbon atoms, wherein (in addition) one or more CH2 groups in these groups may each independently be replaced by -C≡C-, -CF2O-, -O-, -CO-O-, -O-CO-, provided that the O atoms are not directly connected to each other, and wherein, in addition, one or more H atoms may be replaced by halogen,

[0403] Ring A N1 、A N2 and A N3 Each independently represents 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 2,6-difluoro-1,4-phenylene, 3,5-difluoro-1,4-phenylene, trans-1,4-cyclohexylene, wherein (in addition) one or two CH2 groups may be replaced by -O- or 1,4-cyclohexylene,

[0404] Z N1 and Z N2 Each independently represents a single bond or -C≡C-, wherein at least one of Z N1 and Z N2 represents -C≡C-,

[0405] n represents 0, 1 or 2.

[0406] The following shows preferred compounds of formula N:

[0407]

[0408] wherein

[0409] alkyl and alkyl* each independently represent a straight-chain alkyl group having 1 to 9 carbon atoms, preferably 2 to 6 carbon atoms, and alkenyl and alkenyl* each independently represent a straight-chain alkenyl group having 2 - 6 carbon atoms.

[0410] The concentration of the compounds of formula A and B in the LC host mixture is preferably 2 to 60%, very preferably 3 to 55%, and most preferably 4 to 50%.

[0411] The concentration of the compounds of formula C and D in the LC host mixture is preferably 5 to 75%, very preferably 10 to 70%, and most preferably 15 to 60%.

[0412] The concentration of the compound of formula E in the LC host mixture is preferably 5 to 30%, very preferably 10 to 25%.

[0413] The concentration of the compound of formula F in the LC host mixture is preferably 2 to 30%, very preferably 5 to 20%.

[0414] The following lists more preferred embodiments of the present invention, including their combinations.

[0415] 2a) The LC host mixture comprises one or more compounds of formula A and / or B having a high positive dielectric anisotropy, preferably having Δε > 15.

[0416] 2b) The LC host mixture comprises one or more compounds selected from the group consisting of formula A1a2, A1b1, A1d1, A1f1, A2a1, A2h1, A2l2, A2k1, B2g3 and / or B2F. The proportion of these compounds in the LC host mixture is preferably from 5 to 50.

[0417] 2c) The LC host mixture comprises one or more compounds selected from the group consisting of formula C3, C4, C5, C9 and D2. The proportion of these compounds in the LC host mixture is preferably from 8 to 75%, very preferably from 10 to 70%.

[0418] 2d) The LC host mixture comprises one or more compounds selected from the group consisting of formula E1, E3 and E6, preferably E1a, E3a and E6a, very preferably E1a2, E1a5, E3a1 and E6a1. The proportion of these compounds in the LC host mixture is preferably from 5 to 40%, very preferably from 10 to 25%.

[0419] The optimal mixing ratio of the compounds of the above formulae in the liquid crystal component B) basically depends on the desired properties, the selection of the components of the above formulae and the selection of any other components that may be present. The following gives the preferred physical properties.

[0420] In a preferred embodiment, the liquid crystal component B) according to the present invention is characterized by an optical anisotropy value as high as possible. Preferably, the liquid crystal component B) exhibits an optical anisotropy (Δn) in the range from 0.05 or greater to 0.500 or less, more preferably in the range from 0.100 or greater to 0.300 or less, and particularly preferably in the range from 0.150 or greater to 0.250 or less.

[0421] Preferably, the liquid crystal component B) according to the present invention is characterized by a relatively high positive dielectric anisotropy value (Δε) as high as possible. In a preferred embodiment, the liquid crystal component B) exhibits a dielectric positive anisotropy in the range from 3 to 50, preferably from 4 or greater to 25 or less, and particularly preferably from 5 or greater to 20 or less.

[0422] The nematic phase of the liquid crystal component B) according to the present invention preferably extends from at least 0 °C or lower to 70 °C or higher, more preferably from at least -20 °C or lower to 75 °C or higher, very preferably from at least -30 °C or lower to 75 °C or higher and particularly from at least -40 °C or lower to 80 °C or higher.

[0423] The clearing point of the liquid crystal component B) according to the invention is preferably in the range from 10 °C to 120 °C, particularly preferably in the range from 40 °C to 110 °C and very particularly preferably in the range from 60 °C to 100 °C.

[0424] The rotational viscosity of the liquid crystal component B) is preferably as low as possible. Preferably, the liquid crystal component B) exhibits a rotational viscosity of about 500 mPas or less, preferably in the range from 1 mPas or more to 500 mPas or less, more preferably in the range from 10 mPas or more to 300 mPas or less, and particularly preferably in the range from 50 mPas to 200 mPas.

[0425] The cholesteric liquid crystal according to the invention comprises one or more chiral dopants or chiral components C).

[0426] Preferably, the cholesteric LC medium according to the invention comprises one or more chiral compounds which, individually or in combination with one another, have a helical twisting power (|HTP|) of 5 µm -1 or more, preferably 10 µm -1 or more, more preferably 15 µm -1 or more and an absolute value of the helical twisting power (|HTP 总 |).

[0427] Preferred are chiral dopants having a high helical twisting power (HTP), in particular those disclosed in WO 98 / 00428.

[0428] Generally, the chiral dopants used are, for example, commercially available R / S-5011, CD-1, R / S-811 and CB-15 (from Merck KGaA, Darmstadt, Germany).

[0429] In another preferred embodiment, the chiral dopant is preferably selected from formula Ch I,

[0430]

[0431] and / or formula Ch II,

[0432]

[0433] including the corresponding (S,S) enantiomers,

[0434] wherein E and F are each independently 1,4-phenylene or trans-1,4-cyclohexylene, v is 0 or 1, Z 0 is -COO-, -OCO-, -CH2CH2- or a single bond, and R is an alkyl, alkoxy or alkanoyl group having 1 to 12 C atoms.

[0435] The compounds of formula Ch I and their synthesis are described in WO 98 / 00428. The compounds of formula Ch II and their synthesis are described in GB2,328,207.

[0436] The chiral dopants R / S-5011 and the compounds of formulae Ch I and Ch II mentioned above exhibit a very high helical twisting power (HTP) and are thus particularly suitable for the purposes of the present invention.

[0437] The liquid crystal medium preferably contains preferably 1 to 5, in particular 1 to 3, very preferably 1 or 2 chiral dopants preferably selected from the above-mentioned formulae Ch I and / or Ch II and / or R-5011 or S-5011. Very preferably, the chiral compounds are R-5011, S-5011.

[0438] Generally, the absolute value of the helical twisting power (|HTP|) of the chiral compounds in the cholesteric liquid crystal medium as a whole is 5 μm -1 or greater, and the amount of the chiral compound is preferably ≥0.1% to ≥0.9% of the total weight of the mixture. 总 |) is preferably ≥0.1% to ≥0.9% of the total weight of the mixture.

[0439] The cholesteric LC medium should additionally have the property such that different reflection wavelengths, especially in the infrared region, can be achieved by simple and targeted variation. Preferably, the cholesteric pitch of the cholesteric LC medium is selected such that its reflection wavelength is in the infrared range of the electromagnetic spectrum, i.e., in the range of 800 nm to 5000 nm, more preferably 1000 nm to 4000 nm. Specifically, the reflection wavelength of the liquid crystal medium is in the range of 2000 nm to 3500 nm.

[0440] The cholesteric LC medium of the present invention is prepared in a conventional manner per se, for example, by mixing one or more of the above-mentioned polymerizable compounds with one or more non-polymerizable compounds and one or more chiral compounds (both as defined above) and optionally other liquid crystal compounds and / or additives.

[0441] Generally, the components required in a smaller amount are advantageously dissolved in the components constituting the main component at an elevated temperature. Solutions of the components in an organic solvent (e.g., acetone, chloroform or methanol) can also be mixed, and after thorough mixing, the solvent is removed, for example, by distillation. Therefore, the present invention also relates to a method for preparing the cholesteric LC medium of the present invention.

[0442] The cholesteric LC medium of the present invention is very suitable for use in different types of PNLC light modulation elements. Therefore, the present invention also relates to the use of the cholesteric LC medium as described above in PNLC light modulation elements.

[0443] Accordingly, the present invention also relates to a PNLC light modulation element, which comprises a pair of opposing substrates; an electrode structure, preferably an in-plane electrode structure; a cholesteric LC medium located in the intermediate space between the substrates, characterized in that the PNLC light modulation element comprises a polymer network, which can be obtained by exposing the cholesteric LC medium as described above to actinic radiation that induces photopolymerization of polymerizable compounds in the cholesteric LC medium.

[0444] The present invention further relates to a method for preparing a PNLC light modulation element, which comprises at least the following steps

[0445] - Cutting and cleaning the substrates,

[0446] - Providing an electrode structure on one or both substrates,

[0447] - Optionally providing an alignment layer on the electrode structure,

[0448] - Assembling the cell,

[0449] - Filling the cell with the cholesteric LC medium of the present invention, and

[0450] - Exposing the cholesteric LC medium to actinic radiation to induce photopolymerization of polymerizable compounds in the LC medium.

[0451] In one embodiment of the present invention, the cholesteric LC medium is injected between the first and second substrates or filled into the assembled cell by capillary force or vacuum filling after combining the first and second substrates.

[0452] However, it is also preferred that the liquid crystal composition can be inserted between the first and second substrates by combining the second substrate with the first substrate after loading the liquid crystal composition onto the first substrate. In a preferred embodiment, the liquid crystal is dispersed dropwise onto the first substrate by a method called "one drop filling" (ODF) method or using an inkjet printing (IJP) method as disclosed in, for example, JPS63-179323 and JPH10-239694.

[0453] In the irradiation step, the cell is exposed to actinic radiation, which causes photopolymerization of the polymerizable functional groups of the polymerizable compounds contained in the cholesteric liquid crystal medium.

[0454] Polymerization is achieved, for example, by exposing the polymerizable material to heat or preferably actinic radiation. Actinic radiation means irradiation with light (such as UV light, IR light or visible light), irradiation with X-rays or γ-rays or irradiation with high-energy particles (such as ions or electrons).

[0455] Preferably, the polymerization is carried out by UV irradiation. Regarding the light source for actinic radiation, for example, a single UV lamp or a set of UV lamps can be used. Another possible source of actinic radiation is a laser, such as, for example, a UV, IR or visible light laser.

[0456] Due to the irradiation, the polymerizable compound substantially crosslinks in situ between the substrates forming the PNLC light modulation element in the liquid crystal medium, thereby forming a polymer network preferably extending through the entire switching layer.

[0457] Thus, the formed polymer network reduces the effective cell gap to a much smaller extent than the typical cell gap usually considered for LC cells. This allows for faster switching and the relaxation of the focal conic texture back to the aligned helical twist. The switching time can be reduced to about (sub-) milliseconds, rather than about 10 seconds or longer switching times.

[0458] The wavelength used for actinic radiation should not be too low to avoid damaging the LC molecules of the medium, and should preferably be different from the maximum UV absorption of the LC host mixture, and very preferably greater than the maximum UV absorption of the LC host mixture.

[0459] On the other hand, the wavelength of the light radiation should not be too high to allow for rapid and complete UV photopolymerization of the polymerizable compound, and should not be higher than, preferably equal to or lower than the maximum UV absorption of the polymerizable component.

[0460] Suitable wavelengths are preferably selected from wavelengths in the range of 250 to 450 nm, such as 400 nm or less, preferably 350 nm or less, and preferably 300 nm or less.

[0461] The irradiation or exposure time should be selected such that the polymerization is as complete as possible, but should still not be too high to allow for a smooth production process. In addition, the radiation intensity should be high enough to allow for rapid and complete polymerization as much as possible but should not be too high to avoid damaging the cholesteric liquid crystal medium.

[0462] The curing time depends particularly on the reactivity of the polymerizable material, the thickness of the coated layer, the type of polymerization initiator, and the power of the UV lamp. The curing time is preferably ≤ 10 minutes, very preferably ≤ 5 minutes, and most preferably ≤ 1 minute. Generally speaking, for large-scale production, a shorter curing time is preferred, such as, about 60 seconds to 1 second.

[0463] The suitable UV radiation power is preferably in the range of 5 to 150 mW / cm -2 more preferably in the range of 10 to 75 mW / cm -2 especially in the range of 25 to 60 mW / cm -2 and particularly in the range of 45 to 55 mW / cm -2 .

[0464] The polymerization is preferably carried out in an inert gas atmosphere (preferably in a nitrogen atmosphere), but it can also be carried out in air.

[0465] The polymerization is preferably carried out at a temperature in the range of -10 °C to +70 °C, more preferably 0 °C to +50 °C, and even more preferably +15 °C to +40 °C.

[0466] In a preferred embodiment, the PNLC light modulation element can additionally be annealed after polymerization, preferably at a temperature higher than 20 °C and lower than 140 °C, more preferably higher than 40 °C and lower than 130 °C, and most preferably higher than 70 °C and lower than 120 °C, to achieve complete conversion of the monomers and to achieve the most preferred stability.

[0467] Generally, the structure of the PNLC light modulation element according to the present invention corresponds to the conventional structure of a display, which is known to those skilled in the art.

[0468] Regarding the substrate, for example, a glass or quartz sheet or a plastic film can be used. When using two substrates in the case of curing by actinic radiation, at least one substrate must transmit the actinic radiation for polymerization.

[0469] Suitable and preferred plastic substrates are, for example, polyester films such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), polyvinyl alcohol (PVA), polycarbonate (PC), or triacetyl cellulose (TAC), very preferably PET or TAC films. For example, a uniaxially stretched plastic film can be used as the birefringent substrate. PET films can be commercially obtained, for example, from DuPont TeijinFilms under the trade name Commercially available.

[0470] In a preferred embodiment, the substrates are arranged at a distance from each other in the range of about 1 μm to about 20 μm, preferably at a distance from each other in the range of about 3 μm to about 10 μm, and more preferably at a distance from each other in the range of about 3 μm to about 6 μm. The layer of the cholesteric LC medium is thus located in the gap.

[0471] The substrate layers can be held at a defined distance from each other, for example, by spacers or raised structures in the layer. Typical spacer materials are well known to experts, such as spacers made of, for example, plastic, silica, epoxy resin, etc.

[0472] In another preferred embodiment of the present invention, the cholesteric LC dielectric layer is located between two flexible layers (such as flexible polymer films). The corresponding PNLC light modulation element according to the present invention is thus flexible and bendable and can be, for example, rolled up. The flexible layers can represent a substrate layer, an alignment layer, and / or a polarizer. Other preferably flexible layers may also be present. For a more detailed disclosure regarding the preferred embodiment in which the liquid crystal dielectric layer is located between flexible layers, reference is made to application US 2010 / 0045924 A1.

[0473] Furthermore, in the PNLC light modulation element according to the present invention, there is an electrode configuration and optionally other electrical components and connections to facilitate the electrical switching of the PNLC light modulation element, comparable to the switching of an LC display.

[0474] Preferably, the PNLC light modulation element comprises an electrode configuration that is capable of allowing an electric field to be applied substantially parallel to the main plane of the substrate or the cholesteric cholesteric liquid crystal dielectric layer. Suitable electrode configurations or in-plane electrode structures that meet this requirement are generally known to experts.

[0475] For example, the first substrate includes pixel electrodes and a common electrode for generating an electric field substantially parallel to the surface of the first substrate in the pixel region. Various displays having at least two electrodes on one substrate are known to those skilled in the art, where the most significant difference is that both the pixel electrodes and the common electrode are structured, which is typical for IPS displays, or only the pixel electrodes are structured while the common electrode is unstructured, which is the case for FFS displays.

[0476] It should be understood that the present invention relates to any kind of electrode configuration suitable for generating an electric field substantially parallel to the surface of the first substrate in the pixel region; as mentioned above, that is, IPS as well as FFS displays.

[0477] Suitable electrode materials are well known to experts, such as electrode structures made of metals or metal oxides (such as indium tin oxide (ITO), which is preferred according to the present invention).

[0478] The ITO film is preferably deposited on the substrate, for example, by physical vapor deposition, electron beam evaporation, or sputtering deposition techniques.

[0479] Preferably, the electrodes of the PNLC light modulation element are associated with switching elements (such as thin film transistors (TFTs) or thin film diodes (TFDs)).

[0480] In a preferred embodiment, the PNLC light modulation element may comprise at least one dielectric layer. Typical dielectric layer materials are generally known to experts, such as SiOx, SiNx, Cytop, Teflon, and PMMA.

[0481] The dielectric layer material can be applied to a substrate or an electrode layer by conventional coating techniques such as spin coating, roll coating, blade coating, or vacuum deposition (such as PVD or CVD). It can also be applied to a substrate or an electrode layer by conventional printing techniques known to relevant experts, such as, for example, screen printing, lithography, reel-to-reel printing, letterpress printing, gravure printing, rotogravure printing, flexographic printing, intaglio printing, pad printing, heat seal printing, inkjet printing, or printing by means of a stamp or a printing plate.

[0482] In other preferred embodiments, the PNLC light modulation element comprises at least one alignment layer, which is preferably provided adjacent to the cholesteric LC medium. The PNLC light modulation element may have other alignment layers in direct contact with the liquid crystal medium.

[0483] The alignment layer can also serve as a substrate layer, so a substrate layer is not necessarily required in the PNLC light modulation element. If a substrate layer is additionally present, in each case the alignment layer is disposed between the substrate layer and the liquid crystal medium layer.

[0484] Preferably, the alignment layer induces planar alignment (preferably throughout the liquid crystal medium).

[0485] Suitable planar alignment layer materials are known to experts, such as, for example, AL-3046 or AL-1254, both of which are commercially available from JSR.

[0486] The alignment layer material can be applied to a substrate array or an electrode structure by conventional coating techniques such as spin coating, roll coating, dip coating, or blade coating. It can also be applied to a substrate by vapor deposition or conventional printing techniques, such as, for example, screen printing, lithography, reel-to-reel printing, letterpress printing, gravure printing, rotogravure printing, flexographic printing, intaglio printing, pad printing, heat seal printing, inkjet printing, or printing by means of a stamp or a printing plate.

[0487] In a preferred embodiment, the planar alignment layer is treated by rubbing or photoalignment techniques known to those skilled in the art, preferably by rubbing techniques. Thus, a uniform and preferably oriented director can be achieved without any physical treatment of the cell (such as shearing of the cell (mechanical treatment in one direction), etc.). The rubbing direction is immaterial and mainly only affects the orientation in which a polarizer must be applied. However, a planar alignment layer with reverse parallel rubbing is preferred. Generally, the rubbing direction is in the range of + / -45°, more preferably in the range of + / -20°, even more preferably in the range of + / -10°, and particularly in the range of + / -5° relative to the maximum extension direction of the substrate.

[0488] In another preferred embodiment of the present invention, the PNLC light modulation element optionally comprises two or more polarizers, with at least one disposed on one side of the liquid crystal medium layer and at least one disposed on the opposite side of the liquid crystal medium layer. The liquid crystal medium layer and the polarizers herein are preferably arranged parallel to each other.

[0489] The polarizer can be a linear polarizer. Preferably, there are exactly two polarizers in the PNLC light modulation element. In this case, in addition, both polarizers are preferably linear polarizers. If there are two linear polarizers in the PNLC light modulation element, then according to the present invention, the polarization directions of the two polarizers preferably cross.

[0490] In addition, it is preferred that there are two circular polarizers in the PNLC light modulation element such that these have the same polarization direction, i.e., both are right-handed circular polarizations or both are left-handed circular polarizations.

[0491] The polarizer can be a reflective or absorptive polarizer. A reflective polarizer reflects light having one polarization direction or a type of circularly polarized light in the sense of this application, however, is transparent to light having another polarization direction or another type of circularly polarized light. Correspondingly, an absorptive polarizer absorbs light having one polarization direction or a type of circularly polarized light, however, is transparent to light having another polarization direction or another type of circularly polarized light. Reflection or absorption is generally non-quantitative; it means that the light passing through the polarizer is not completely polarized.

[0492] For the purposes of the present invention, both absorptive and reflective polarizers can be used. Polarizers in the form of thin optical films are preferably used. Examples of reflective polarizers that can be used in the PNLC light modulation element according to the present invention are DRPF (Diffuse Reflective Polarizer Film, 3M), DBEF (Dual Brightening Film, 3M), DBR (multilayer polymer distributed Bragg reflector as described in US 7,038,745 and US 6,099,758), and APF (Advanced Polarizer Film, 3M).

[0493] Examples of absorptive polarizers that can be used in the PNLC light modulation element according to the present invention are Itos XP38 polarizer film and Nitto Denko GU-1220DUN polarizer film. An example of a circular polarizer that can be used according to the present invention is the APNCP37-035-STD polarizer (American Polarizers). Another example is the CP42 polarizer (ITOS). The PNLC light modulation element can additionally comprise a filter (e.g., a UV filter) that blocks light of a specific wavelength. According to the present invention, other functional layers can also be present, such as, for example, a protective film, a thermal insulation film, or a metal oxide layer.

[0494] The functional principle of the PNLC light modulation element according to the invention will be explained in detail below. It should be noted that the scope of the claimed invention is not restrictive, which is not presented in the claims and can be derived from the evaluation of the assumed functional mode.

[0495] In a first preferred embodiment, the retardation change or phase change of the PNLC light modulation element according to the invention depends on the applied electric field. Preferably, the retardation gradually increases while applying the electric field with a gradually increasing voltage.

[0496] In this preferred embodiment, components A and B are selected in a manner that depends on each other such that the birefringence of the polymerizable component A matches the birefringence of component B. Preferably, the difference in birefringence values is less than 10%, more preferably less than 5% and even more preferably less than 3%.

[0497] The required applied electric field strength mainly depends on the electrode spacing and the Δε modulus of the LC mixture. The applied electric field strength is usually lower than about 50 V / μm -1 , preferably lower than about 30 V / μm -1 and even more preferably lower than about 25 V / μm -1 . In particular, the applied electric field strength is in the range of 1 V / μm -1 to 20 V / μm -1 .

[0498] Preferably, the driving voltage applied to switch the PNLC light modulation element should be as low as possible. Usually, the applied driving voltage is in the range of 2 V to about 20 V, more preferably in the range of about 5 V to about 10 V.

[0499] In this first preferred embodiment, the retardation change or phase change (Γ) is given by the following formula

[0500]

[0501] where d is the layer thickness of the applied liquid crystal medium, λ is the wavelength of the incident light and n eff is the effective birefringence caused by the reorientation of the LC in the applied electric field.

[0502] In a second preferred embodiment, the PNLC light modulation element according to the invention has a boundary state A and a boundary state B.

[0503] The PNLC light modulation element preferably has a boundary state A with a transmittance T A when no electric field is applied, i.e., the so-called "off state" or transparent state.

[0504] When an electric field is applied, the PNLC light modulation element preferably has another boundary state B, namely the so-called "on state" or light-blocking state, wherein

[0505] T A >T B 。

[0506] In this second preferred embodiment, components A and B are interdependent and are selected such that the birefringence of the polymerizable component A is different from the birefringence of component B. Preferably, the difference in birefringence values is greater than 3%, more preferably greater than 5% and even more preferably greater than 10%.

[0507] The required applied electric field strength mainly depends on the electrode gap and the Δε modulus of the LC mixture. The applied electric field strength is generally lower than about 50 V / μm -1 , preferably lower than about 30 V / μm -1 and even more preferably lower than about 25 V / μm -1 。In particular, the applied electric field strength is in the range of 1 V / μm -1 to 20 V / μm -1 。

[0508] Preferably, for switching the PNLC light modulation element, the applied driving voltage should be as low as possible. Generally, the applied driving voltage is in the range of 2 V to about 200 V, more preferably in the range of about 3 V to about 100 V, and even more preferably in the range of about 5 V to about 50 V.

[0509] The transmittance change is determined by the strength of the applied electric field. When more electric field is applied to the system, the degree of scattering increases, which causes a decrease in the intensity of the light propagating forward and an increase in the light emitted in other directions. Therefore, for a side-illuminated device, the amount of visible light orthogonal to the illumination direction increases with the increase in the applied electric field strength.

[0510] As described above, the PNLC light modulation element of the present invention can be used in various types of optical and electro-optical devices. Therefore, the present invention also relates to the use of a PNLC light modulation element as described above in an optical or electro-optical device and to an optical or electro-optical device including the PNLC light modulation element according to the present invention.

[0511] The optical and electro-optical devices include but are not limited to electro-optical displays, liquid crystal displays (LCDs), non-linear optical (NLO) devices, optical information storage devices, light shutters, smart windows, privacy windows, lenses, virtual reality devices and augmented reality devices.

[0512] It will be appreciated that many of the features described above of the particular preferred embodiments are inventive in themselves and not just as part of the embodiments of the invention. Independent protection may be sought for these features in addition to or in lieu of any invention currently claimed.

[0513] It should be understood that changes may be made to the foregoing embodiments of the present invention while still falling within the scope of the present invention. Unless otherwise specified, alternative features that provide the same, equivalent or similar purpose may replace each feature disclosed in this specification. Therefore, unless otherwise specified, each feature disclosed is only an example of a series of equivalent or similar features.

[0514] All features disclosed in this specification can be combined in any combination, but do not include at least some of the features and / or steps that are mutually exclusive. In particular, the preferred features of the present invention are applicable to all aspects of the present invention and can be used in any combination. Similarly, the features that are not necessarily combined can be used separately (not in combination).

[0515] Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent.The following examples are therefore to be construed as merely illustrative and not limitative of the remainder of the disclosure in any way whatsoever.

[0516] The parameter ranges indicated in this application all include the limit values, including the maximum permissible errors known to the expert. Different upper and lower limit values specified for the various property ranges result in other preferred ranges when combined with one another.

[0517] In the present application and in particular in the following examples, the structures of the liquid crystal compounds are indicated as abbreviations, also referred to as "acronyms". The abbreviations are directly converted to the corresponding structures according to the following three Tables A to C. Table A lists the symbols used for ring elements, Table B lists those used for linking groups, and Table C lists the symbols used for the left-hand and right-hand terminal groups of the molecule.

[0518] All groups C n H 2n+1 , C m H 2m+1 and C I H2 I+1 Preference is given to straight-chain alkyl radicals having n, m and 1 C atoms, respectively, all radicals C n H 2n , C m H 2m and C I H 2I Preferably, they are (CH2) n 、(CH2) m and (CH2) IAnd -CH=CH- is preferably a trans -E vinylidene group respectively.

[0519] Table A: Ring element

[0520]

[0521]

[0522]

[0523] Table B: Linking group

[0524]

[0525] Table C: End group

[0526]

[0527]

[0528] Wherein n and m are each integers, and the three dots "..." indicate the positions for other symbols in the table. Examples

[0529] Compound

[0530] The polymerizable liquid crystal compound used - Component A)

[0531]

[0532] The host mixture used - Component B)

[0533] Mixture N -!:

[0534]

[0535]

[0536] The chiral compound used - Component C)

[0537]

[0538] Test cell

[0539] Test cell 1: VHR AL16301 type

[0540] · Cell gap = 6 μm, without spacer

[0541] · Cell type = reverse parallel planar alignment type PI

[0542] · Electrode structure = ITO = 200 Å, 1 cm × 1 cm square pattern.

[0543] Test cell 2: Type VHR AL16301

[0544] · Cell gap = 6 μm, no spacer

[0545] · Cell type = reverse parallel planar alignment type PI

[0546] · Electrode structure = ITO = 200 Å, 1 cm × 1 cm square pattern.

[0547] Method

[0548] Switching speed measurement:

[0549] Record the switching time using a microscope or by using a HeNe laser operating at 632.8 nm. In both cases, the sample is placed between crossed polarizers. The transmitted light is received by a photodiode (which is connected to an oscilloscope in the microscope case or to a data acquisition board in the laser case). Obtain the switching time from the oscilloscope or by analyzing the data acquired from the data acquisition board.

[0550] Turbidity

[0551] The turbidity level is determined according to the definition of ASTM D1003 standard turbidity.

[0552] Four different transmittance measurements (T1 to T4) are made, which are well known to those skilled in the art:

[0553] T1: Transmittance without sample and with a white light reflection standard

[0554] T2: Transmittance with sample and with a white light reflection standard

[0555] T3: Transmittance without sample and with a light trap

[0556] T4: Transmittance with sample and with a light trap

[0557] As is well known to those skilled in the art, therefore, the total transmittance (T2) is defined as the sum of the parallel transmittance and the diffuse transmittance (T4).

[0558] Therefore, turbidity is defined as follows: Turbidity = [(T4 / T2) – (T3 / T1)] x 100%

[0559] Obtain turbidity data only from the active area of the cell. Shield the glue from the measurement system to avoid non-uniformity.

[0560] Working Examples

[0561] Experiment 1

[0562] Cholesteric LC mixtures were prepared as given in the following table. The corresponding mixtures were capillary filled in test cell 1 using capillary action at room temperature, annealed at 100°C for 1 hour, and then exposed to linearly polarized UV light (35 mW / cm 2 ) for a predetermined time. Then the box is cooled to room temperature.

[0563] V op ,t on and t off Measured using a Speedy electro-optical microscope setup.

[0564] Turbidity % was measured in transmission mode on a Shimadzu 3600 UV-Vis using a single wavelength of 550 nm. op It is measured when the maximum turbidity % is achieved. on and T off is the time when switching between 10% and 90%. The results are summarized in the following table:

[0565]

[0566] As shown above, using chiral systems leads to good turbidity values compared to not using chiral systems (see Exp. 1.1). Crucially, in polymer network chiral systems, t off The time is significantly smaller than that for the system without polymer network (see Exp. 1.2), indicating good relaxation to the ordered state.

[0567] Experiment 2

[0568] Cholesteric LC mixtures were prepared as given in the table below. The corresponding mixtures were capillary filled in test cell 2 using capillary action at room temperature, annealed at 100°C for 1 hour, and then illuminated with linearly polarized UV light (35 mW / cm 2 ) for a predetermined time. Then the box is cooled to room temperature.

[0569] V op ,t on and t off Measured using a Speedy electro-optical microscope setup.

[0570] Turbidity % was measured in transmission mode on a Shimadzu 3600 UV-Vis using a single wavelength of 550 nm. op It is measured when the maximum turbidity % is achieved. on and T off is the time when switching between 10% and 90%. The results are summarized in the following table:

[0571]

[0572]

[0573] As shown above, compared to the thicker cartridges given in Experiment 1, the reduced cartridge thickness has the effect of reducing V op This also slightly reduces the maximum turbidity % achieved.

Claims

1. A cholesteric LC medium for a PNLC light modulation element, comprising A) one or more polymerizable compounds in an amount of ≥ 2% to ≤ 10% by weight, at least one of which is a compound of formula I, P 11 -Sp 11 -Ar-Sp 12 -P 12 I wherein Ar is selected from groups of the following formula: which is optionally substituted by one or more groups L, L is, each time it occurs, the same or different, F, Cl, CN, P-Sp-, or a straight-chain, branched-chain or cyclic alkyl group having 1 to 25 C atoms, wherein one or more non-adjacent CH₂-groups are optionally replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that the O- and / or S-atoms are not directly connected to each other, and wherein one or more H atoms are each optionally replaced by F or Cl, P 11 and P 12 each independently and from one another represent polymerizable groups, Sp 11 and Sp 12 each independently of one another represent an optionally one or more groups P 11 or P 12 substituted spacer group, or a single bond, and B) one or more non-polymerizable mesogenic or liquid-crystalline compounds, and C) one or more chiral compounds in an amount of 0.5% to 0.9% by weight, One or more of the chiral compounds each individually or in combination with each other have a helical twisting power absolute value (|HTP -1 |) of 5 μm 总 or greater. wherein the one or more non-polymerizable mesogenic or liquid-crystalline compounds are selected from compounds of formula A and / or B, wherein each group, independently of one another and each time it occurs, has the following meaning: Each is independently of the others and, each time it occurs, is the same as or different from R 21 、R 31 each independently of one another is an alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C atoms or an alkenyl or alkenyloxy having 2 to 9 C atoms, all of which are optionally fluorinated, X 0 is F, Cl, a haloalkyl or alkoxy group having 1 to 6 C atoms, or a haloalkenyl or alkenoxy group having 2 to 6 C atoms, Z 31 is -CH2CH2-, -CF2CF2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH2O- or a single bond, L 21 , L 22 , L 31 and L 32 are each independently H or F, g is 0, 1, 2 or 3.

2. A method for preparing a cholesteric LC medium according to claim 1, which comprises at least the step of mixing the non-polymerizable compound and the chiral compound with a polymerizable LC compound in an amount of ≥ 2% to ≤ 10%.

3. Use of the cholesteric LC medium according to claim 1 in a PNLC light modulation element.

4. A PNLC optical modulation element, comprising a pair of opposing substrates, an in-plane electrode structure, and a cholesteric LC medium located in the intermediate space between the substrates, characterized in that The light modulation element comprises a polymer network which can be obtained from the cholesteric LC medium according to claim 1 by exposing the cholesteric LC medium to actinic radiation which induces photopolymerization of the polymerizable compounds in the cholesteric LC medium.

5. A PNLC light modulation element according to claim 4, which comprises an electrode structure corresponding to an IPS or FFS electrode structure.

6. A PNLC light modulation element according to claim 4 or 5, wherein the intermediate space between the two opposing substrates is in the range of 1 μm to 20 μm.

7. A method for preparing a PNLC light modulation element according to any one of claims 4 to 6, which comprises at least the following steps: - cutting and cleaning the substrates, - providing an in-plane electrode structure on one of the substrates, - optionally providing an alignment layer on the electrode structure, - assembling the cell, - filling the cell with the cholesteric LC medium according to claim 1, and - exposing the cholesteric LC medium to actinic radiation which induces photopolymerization of the polymerizable compounds in the cholesteric LC medium.

8. The method according to claim 7, wherein the photopolymerization step is carried out using light having a wavelength in the range of 250 nm to 450 nm.

9. The method according to claim 7 or 8, wherein the photopolymerization step is carried out using an irradiation intensity in the range of 5 mW / cm 2 to 150 mW / cm 2 2.

10. Use of a PNLC light modulation element according to any one of claims 4 to 6 in an optical or electro-optical device.

11. An optical or electro-optical device, which comprises a PNLC light modulation element according to any one of claims 4 to 6.

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