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WO2024260930A1 - Lame demi-onde - Google Patents

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Publication number
WO2024260930A1
WO2024260930A1 PCT/EP2024/066836 EP2024066836W WO2024260930A1 WO 2024260930 A1 WO2024260930 A1 WO 2024260930A1 EP 2024066836 W EP2024066836 W EP 2024066836W WO 2024260930 A1 WO2024260930 A1 WO 2024260930A1
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Prior art keywords
chiral
group
atoms
diyl
wave plate
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Inventor
Stephen Mulcahy
Jack Bradford
Owain Llyr Parri
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Merck Patent GmbH
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Merck Patent GmbH
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/52—Liquid crystal materials characterised by components which are not liquid crystals, e.g. additives with special physical aspect: solvents, solid particles
    • C09K19/58—Dopants or charge transfer agents
    • C09K19/586—Optically active dopants; chiral dopants
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K2019/0444—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit characterized by a linking chain between rings or ring systems, a bridging chain between extensive mesogenic moieties or an end chain group
    • C09K2019/0448—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit characterized by a linking chain between rings or ring systems, a bridging chain between extensive mesogenic moieties or an end chain group the end chain group being a polymerizable end group, e.g. -Sp-P or acrylate

Definitions

  • the invention relates to a half-wave plate comprising two layers of a chiral liquid crystal (LC) polymer with a pitch gradient (as a subcategory of liquid crystal material), a method for its preparation, and its use as diffractive optical element in optical or electrooptica I components or devices, especially for digital optics or augmented reality or virtual reality (AR/VR) applications like polarizers, optical compensators, reflective films, diffraction or surface gratings, Bragg polarization gratings (Bragg PG), polarization volume gratings (PVG), polarization volume holograms (PVH), Pancharatnam Berry (PB) gratings, nonmechanical beam steering elements, optical waveguides, optical couplers, optical combiners, polarization beam splitters, partial mirrors or lenses.
  • LC chiral liquid crystal
  • a pitch gradient as a subcategory of liquid crystal material
  • Half-wave plates are extremely important in the field of digital optics. They are used in Pancharatnam-Berry (PB) optical elements also known as cycloidal diffractive waveplates, as described for example in Yun-Han Lee et al., Opt. Data Process. Storage, 3, 79-88 (2017). These are patterned half-wave plates where the director profile continuously changes as a function across the X-Y plane.
  • the PB optical elements include PB lenses (PBL) and PB gratings (PBG). In a PBL the director continuously changes along a radial axis in a parabolic fashion as illustrated in Fig. 1a, whereas in a PBG the director profile changes linearly in a longitudinal direction as illustrated in Fig. 1b, both of which are shown in the aforementioned reference.
  • the PBLs and PBGs gratings can be active devices made from liquid crystals which can be electrically switched. Alternatively they can be static devices made from polymerisable LCs, also known as reactive mesogens (RMs) to provide thin lenses and gratings on plastic susbtrates.
  • RMs reactive mesogens
  • a half-wave plate utilising a single film made from RMs has issues with chromaticity due to the optical dispersion of the RMs. Optimizing the thickness of the RM film to get a half-wave plate at a specific wavelength will mean that for all other wavelengths, the film will not be a half-wave plate and so there will be light leakage.
  • One common method to improve this light leakage due to the dispersion of the material is to use a negative dispersion RM film. This has advantages in that a single film can compensate across the blue and green areas of the visible spectrum. However there is always a trade off in the red wavelengths as the dispersion flatterns in this area.
  • One aim of the present invention is to provide improved polymer films, and methods for their production, which can be used as half-wave plates with reduced chromaticity.
  • Other aims of the present invention are immediately evident to the person skilled in the art from the following detailed description.
  • the invention relates to a half-wave plate comprising, preferably consisting of, two layers, each layer comprising, preferably consisting of, a polymerised chiral RM mixture with helically twisted structure, wherein in each layer the helical pitch increases or decreases in the film thickness direction, and wherein the two layers have opposite twist sense.
  • the half-wave plate is comprising two quarter-wave plates, wherein each of said quarter-wave plates comprises, preferably consists of, a layer of a polymerised chiral RM mixture with helically twisted structure wherein the helical pitch increases or decreases in the film thickness direction, and wherein the two quarter-wave plates have opposite twist sense.
  • the chiral RM mixture comprises at least one, preferably exactly one, chiral compound with one or more isomerisable groups, preferably one or more photoisomerisable groups, which is preferably polymerisable.
  • the chiral RM mixture comprises at least two, more preferably exactly two, chiral compounds with opposite handedness, one of which contains an isomerisable group, and the other of which does not contain an isomerisable group, and wherein one or both chiral compounds are polymerisable.
  • the invention further relates to a process of preparing a half-wave plate as described above and below.
  • the invention further relates to an optical, electronic or electro optical component or device as such, comprising a half-wave plate as described above and below.
  • the invention further relates to an optical, electrooptical or electronic device or a component comprising a half-wave plate as described above and below.
  • Said components include, without limitation, optical retardation films, polarizers, optical compensators, diffraction or surface gratings such as Bragg polarization gratings (Bragg PG), polarization volume gratings (PVG), Pancharatnam Berry gratings (PBG) or Pancharatnam Berry lenses (PBL), furthermore nonmechanical beam steering elements, optical waveguides, optical couplers or combiners, polarization beam splitters, partial mirrors, reflective films, alignment layers, colour filters, antistatic protection sheets, electromagnetic interference protection sheets, lenses for light guides, focusing and optical effects, polarization controlled lenses, and IR reflection films; for example for use in LC displays (LCDs), organic light emitting diodes (OLEDs), autostereoscopic 3D displays, see-through near-eye displays, augmented reality( AR) or virtual reality (VR) systems, switchable windows, spatial light modulators, optical data storage, remote optical sensing, holography, spectroscopy, optical telecommunications, polarimetry or front/
  • Said devices include, without limitation, electro optical displays, especially LCDs, OLEDs, non-linear optic (NLO) devices, autostereoscopic 3D displays, see-through near-eye displays, AR/VR systems, goggles for AR/VR applications, switchable windows, spatial light modulators, optical data storage devices, optical sensors, holographic devices, spectrometers, optical telecommunication systems, polarimeters or front-/backlights.
  • electro optical displays especially LCDs, OLEDs, non-linear optic (NLO) devices, autostereoscopic 3D displays, see-through near-eye displays, AR/VR systems, goggles for AR/VR applications, switchable windows, spatial light modulators, optical data storage devices, optical sensors, holographic devices, spectrometers, optical telecommunication systems, polarimeters or front-/backlights.
  • Fig. 1a and b exemplarily and schematically illustrate the LC director orientation in a PB lens (a) and a PB grating (b).
  • Fig. 2 shows the twist profile in a half-wave plate according to Example 1 of the present invention.
  • Fig. 3 shows the transmission vs. wavelength plot for a film stack of Example 1 (a) with a half-wave plate according to the present invention, consisting of two quarter- wave plates with a pitch gradient, between crossed polarizers, and for a film stack of Comparison Example 1 (b) with a standard half-wave between crossed polarizers.
  • Fig. 4 shows the transmission vs. wavelength plot for a film stack of Example 1 (a) with a half-wave plate according to the present invention, consisting of two quarter- wave plates with a pitch gradient, between crossed polarizers, and for a film stack of Comparison Example 2 (b) with a standard half-wave plate consisting of two standard quarter-wave plates between crossed polarizers.
  • the expression “the two layers (or quarter-wave plates) have opposite twist sense” means that the twist sense of the helically twisted structure in the first of the said two layers (or quarter-wave plates) is opposite to the twist sense of the helically twisted structure in the second of the said two layers (or quarter-wave plates).
  • film as used herein includes rigid or flexible, self-supporting or free- standing films with mechanical stability, as well as coatings or layers on a supporting substrate or between two substrates.
  • monolithic film means a one-layer (or single-layer) film which is consisting of a single layer of a specific material, like for example a polymerised chiral RM mixture as described above and below.
  • reactive mesogen and "RM” will be understood to mean a compound containing a mesogenic or liquid crystalline skeleton, and one or more functional groups attached thereto, optionally via spacer groups, which are suitable for polymerisation and are also referred to as “polymerisable group” or "P".
  • polymerisable compound as used herein will be understood to mean a polymerisable monomeric compound.
  • Polymerisable compounds or RMs with one polymerisable group are also referred to as “monoreactive” compounds, polymerisable compounds or RMs with two polymerisable groups as “direactive” compounds, and polymerisable compounds or RMs with more than two polymerisable groups as “multireactive” compounds.
  • Compounds without a polymerisable group are also referred to as “non-reactive” compounds.
  • liquid crystal means a compound that under suitable conditions of temperature, pressure and concentration can exist as a mesophase or in particular as a LC phase.
  • clearing point means the temperature at which the transition between the mesophase with the highest temperature range and the isotropic phase occurs.
  • mesogenic group as used herein is known to the person skilled in the art and described in the literature, and means a group which, due to the anisotropy of its attracting and repelling interactions, essentially contributes to causing a liquid-crystal (LC) phase in low-molecular-weight or polymeric substances.
  • Compounds containing mesogenic groups do not necessarily have to have an LC phase themselves. It is also possible for mesogenic compounds to exhibit LC phase behaviour only after mixing with other compounds and/or after polymerisation. Typical mesogenic groups are, for example, rigid rod- or disc-shaped units.
  • RM formulation means at least one RM or RM mixture, and one or more other materials added to the at least one RM or RM mixture to provide, or to modify, specific properties of the RM formulation and/or of the at least one RM therein. It will be understood that an RM formulation is also a vehicle for carrying the RM to a substrate to enable the forming of layers or structures thereon. Exemplary materials include, but are not limited to, solvents, polymerisation initiators, surfactants and adhesion promoters, etc. as described in more detail below.
  • the percentage of a compound in an RM mixture as given above and below means % by weight of the total RM mixture, excluding solvents or additives as described above and below that are used in the RM formulation.
  • PFAS per- and/or polyfluoroalkyl substance
  • polyfluorinated alkyl or aryl group as used herein means an alkyl or aryl group which is substituted by two or more F atoms (wherein the F atoms may be attached either to the same or different C atoms), thus including perfluorocarbon groups.
  • polymer will be understood to mean a molecule that encompasses a backbone of one or more distinct types of repeating units (the smallest constitutional unit of the molecule) and is inclusive of the commonly known terms “oligomer”, “copolymer”, “homopolymer” and the like. Further, it will be understood that the term polymer is inclusive of, in addition to the polymer itself, residues from initiators, catalysts, and other elements attendant to the synthesis of such a polymer, where such residues are understood as not being covalently incorporated thereto. Further, such residues and other elements, while normally removed during post polymerisation purification processes, are typically mixed or co-mingled with the polymer such that they generally remain with the polymer when it is transferred between vessels or between solvents or dispersion media.
  • polymerisation means the chemical process to form a polymer by bonding together multiple polymerisable groups or polymer precursors (polymerisable compounds) containing such polymerisable groups.
  • a “polymer network” is a network in which all polymer chains are interconnected to form a single macroscopic entity by many crosslinks.
  • a graft polymer molecule is a branched polymer molecule in which one or more the side chains are different, structurally or configurationally, from the main chain.
  • a star polymer molecule is a branched polymer molecule in which a single branch point gives rise to multiple linear chains or arms. If the arms are identical, the star polymer molecule is said to be regular. If adjacent arms are composed of different repeating subunits, the star polymer molecule is said to be variegated.
  • chiral in general is used to describe an object that is non-superimposable on its mirror image.
  • isomerisable I photoisomerisable compound means a compound comprising one or more isomerisable or photoisomerisable groups, respectively.
  • isomerisation means a functional group of a molecule that causes a change of the geometry of the molecule, i.e. isomerisation, either by bond rotation, skeletal rearrangement or atom- or group- transfer, or by dimerization, which can be induced, e.g., thermally or photochemically or by adding a catalyst.
  • photoisomerisable group means a functional group of a molecule that causes a change of the geometry of the molecule, i.e. isomerisation, either by bond rotation, skeletal rearrangement or atom- or group- transfer, or by dimerization, upon irradiation with light of a suitable wavelength that can be absorbed by the molecule (photoisomerisation).
  • a chiral RM mixture in accordance with the present invention can be prepared, for example, by doping a host mixture comprising one or more RMs with a chiral compound having a high twisting power.
  • a low value of the pitch is hereinafter also referred to as “short pitch”, and a high value of the pitch is hereinafter also referred to as “long pitch”.
  • a short pitch corresponds to a highly twisted structure, i.e. , a higher twist angle
  • a long pitch corresponds to a slowly twisted structure, i.e., a lower twist angle, around the helix axis within a given distance.
  • the twist angle, 0, through a thickness, d is defined by the following equation: where p is the pitch as defined above.
  • HTPtotal ⁇ i ci HTPi wherein q is the concentration of each individual chiral compound and HTPi is the helical twisting power of each individual chiral compound.
  • IHTP ⁇ I ( ⁇ s Cs HTPs) - (( ⁇ rCr HTP r ) wherein c s is the concentration of each individual chiral compound with S configuration, HTP S is the helical twisting power of each individual chiral compound having S configuration and wherein c r is the concentration of each individual chiral compound with R configuration and HTPR is the helical twisting power of each individual chiral compound having R configuration.
  • the birefringence An is defined as follows
  • n av . ((2n 0 2 + n e 2 )/3) 1/2
  • the average refractive index n av . and the ordinary refractive index n 0 can be measured using an Abbe refractometer. An can then be calculated from the above equations.
  • ⁇ ⁇ n , .
  • UV light means electromagnetic radiation with a wavelength in a range from about 400 nm to about 740 nm.
  • UV light means electromagnetic radiation with a wavelength in a range from about 200 nm to about 450 nm.
  • linearly polarised light means light, which is at least partially linearly polarized.
  • the aligning light is linearly polarized with a degree of polarization of more than 5:1.
  • Wavelengths, intensity and energy of the linearly polarised light are chosen depending on the photosensitivity of the photoalignable material.
  • the wavelengths are in the UV-A, UV-B and/or UV-C range or in the visible range.
  • the linearly polarised light comprises light of wavelengths less than 450 nm, more preferably less than 420 nm at the same time the linearly polarised light preferably comprises light of wavelengths longer than 280nm, preferably more than 320nm, more preferably over 350nm.
  • the Irradiance (E e ) or radiation power is defined as the power of electromagnetic radiation (d0) per unit area (dA) incident on a surface:
  • the radiant exposure or radiation dose (H e ), is as the irradiance or radiation power (E e ) per time (t):
  • “Polarisability” means the ease with which the electron distribution in the atom or molecule can be distorted.
  • the polarizability increases with greater number of electrons and a more diffuse electron cloud.
  • the polarizability can be calculated using a method described in e.g. Jap. J. Appl. Phys. 42, (2003) p. 3463.
  • optical retardation at a given wavelength R( ) (in nm) of a layer of liquid crystalline or birefringent material is defined as the product of birefringence at that wavelength ⁇ n( ⁇ ) and layer thickness d (in nm) according to the following equation:
  • optical retardation R represents the difference in the optical path lengths in nanometres travelled by S-polarised and P-polarised light whilst passing through the birefringent material.
  • On-axis retardation means the retardation at normal incidence to the sample surface.
  • the retardation ( R( ⁇ )) of a material can be measured using a spectroscopic ellipsometer, for example the M2000 spectroscopic ellipsometer manufactured by J. A. Woollam Co. This instrument can measure the optical retardance in nanometres of a birefringent sample e.g., Quartz over a range of wavelengths typically, 370nm to 2000nm. From this data it is possible to calculate the dispersion (R(450)/R(550) or An(450)/An(550)) of a material.
  • director is known in prior art and means the preferred orientation direction of the long molecular axes (in case of calamitic compounds) or short molecular axes (in case of discotic compounds) of the liquid-crystalline or RM molecules. In case of uniaxial ordering of such anisotropic molecules, the director is the axis of anisotropy.
  • alignment or “orientation” relates to alignment (orientational ordering) of anisotropic units of material such as small molecules or fragments of big molecules in a common direction named “alignment direction”.
  • alignment direction In an aligned layer of liquid- crystalline or RM material the liquid-crystalline director coincides with the alignment direction so that the alignment direction corresponds to the direction of the anisotropy axis of the material.
  • uniform orientation or “uniform alignment” of an liquid-crystalline or RM material, for example in a layer of the material, mean that the long molecular axes (in case of calamitic compounds) or the short molecular axes (in case of discotic compounds) of the liquid-crystalline or RM molecules are oriented substantially in the same direction. In other words, the lines of liquid-crystalline director are parallel.
  • homeotropic structure I alignment I orientation refer to a film wherein the optical axis is substantially perpendicular to the film plane.
  • planar structure /alignment I orientation refer to a film wherein the optical axis is substantially parallel to the film plane.
  • It is preferably straight-chain, has 2, 3, 4, 5, 6 or 7 C atoms and accordingly preferably denotes ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexyloxy or heptyloxy, furthermore methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetra- decyl, pentadecyl, methoxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy or tetradecyloxy.
  • R including any variations thereof such as R 1 , R°, R°°, R*°, R 11 , R 22 , R c , R 3 , R 4 etc., or L denotes an alkyl radical and/or an alkoxy radical, this may be straight-chain or branched.
  • R including any variations thereof such as R 1 , R°, R°°, R°*, R 11 , R 22 , R c , R 3 , R 4 etc., or L denotes an alkyl radical wherein one or more CH2 groups are replaced by S, this may be straight-chain or branched. It is preferably straight-chain, has 1 , 2, 3, 4, 5, 6 or 7 C atoms and accordingly preferably denotes thiomethyl, thioethyl, thiopropyl, thiobutyl, thiopentyl, thiohexyl or thioheptyl.
  • R including any variations thereof such as R 1 , R°, R°°, R*°, R 11 , R 22 , R c , R 3 , R 4 etc., or L denotes an alkoxy or oxaalkyl group it may also contain one or more additional oxygen atoms, provided that oxygen atoms are not linked directly to one another.
  • one or more of R including any variations thereof such as R 1 , R°, R°°, R*°, R 11 , R 22 , R c , R 3 , R 4 etc., or L are selected from the group consisting of
  • Ci-12-alkyl or C2-i2-alkenyl and very preferably are selected from the group consisting of
  • R including any variations thereof such as R 1 , R0, R00, R*0, R 11 , R 22 , R c , R 3 , R 4 etc., or L denotes an alkyl or alkenyl radical which is at least monosubstituted by halogen, this radical is preferably straight- chain, and halogen is preferably F or Cl. In the case of polysubstitution, halogen is preferably F.
  • the resultant radicals also include perfluorinated radicals. In the case of monosubstitution, the fluorine or chlorine substituent may be in any desired position, but is preferably in the ⁇ -position.
  • Halogen is preferably F or Cl, very preferably F.
  • substituents L are, for example, F, Cl, CN, NO2, CH3, C2H5, OCH 3 , SCH 3 , OC2H5, SC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF 3 , OCF 3 , OCHF2, OC2F5, furthermore phenyl. in which L has one of the meanings indicated above.
  • aryl and heteroaryl groups encompass groups, which can be monocyclic or polycyclic, i.e. they can have one ring (such as, for example, phenyl) or two or more rings, which may also be fused (such as, for example, naphthyl) or covalently linked (such as, for example, biphenyl), or contain a combination of fused and linked rings.
  • Heteroaryl groups contain one or more heteroatoms, preferably selected from O, N, S and Se.
  • Preferred aryl groups are, for example, phenyl, biphenyl, terphenyl, [1 ,1':3',1"]- , -'terphenyl-2'-yl, naphthyl, anthracene, binaphthyl, phenanthrene, pyrene, dihydropyrene, chrysene, perylene, tetracene, pentacene, benzopyrene, fluorene, indene, indenofluorene, spirobifluorene, more preferably 1,4- phenylene, 4,4’-biphenylene, 1 , 4-tephenylene.
  • 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-t
  • the polymerisable group P is a group which is suitable for a polymerisation reaction, such as, for example, free- radical or ionic chain polymerisation, polyaddition or polycondensation, or for a polymer-analogous reaction, for example addition or condensation onto a main polymer chain.
  • a polymerisation reaction such as, for example, free- radical or ionic chain polymerisation, polyaddition or polycondensation, or for a polymer-analogous reaction, for example addition or condensation onto a main polymer chain.
  • groups which are suitable for polymerisation with ring opening such as, for example, oxetane or epoxide groups.
  • CW 1 CH-CO-(O) k3 -
  • CW 1 CH-CO-NH-
  • CH 2 CW-CO-NH-
  • W 1 denotes H, F, Cl, CN, CF3, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, Cl or CH3, W 2 and W 3 each, independently of one another, denote H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, W 4 , V ⁇ and W 5 each, independently of one another, denote Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms, W 7 and W 8 each, independently of one another, denote
  • Very particularly preferred groups P including any variations thereof such as P°, P 1 ,
  • CH 2 CH-CO-O-
  • CH 2 C(CH 3 )-CO-O-
  • P°, P 1 , P 2 , P*° are selected from the group consisting of vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxide, most preferably from acrylate and methacrylate.
  • all polymerisable groups have the same meaning, and preferably denote acrylate or methacrylate, very preferably acrylate.
  • the spacer group including any variations thereof such as Sp0, Sp 1 , Sp 2 , Sp*°, when being different from a single bond, is preferably of the formula Sp"-X", so that the respective radical P-Sp- etc. conforms to the formula P-Sp"-X"-, wherein
  • R° and R°° each, independently of one another, denote H or alkyl having 1 to 20 C atoms, and
  • Y 2 and Y 3 each, independently of one another, denote H, F, Cl or CN.
  • X" is preferably -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR 0 -, -NR°-CO-, -NR°- CO-NR 00 - or a single bond.
  • Typical spacer groups Sp including any variations thereof such as Sp°, Sp 1 , Sp 2 , Sp*°, and -Sp"-X"- are, for example, -(CH 2 ) P1 -, -(CH 2 ) P1 -O-, -(CH 2 ) P1 -O-CO-, -(CH 2 ) P1 -CO-O-, - (CH 2 ) P1 -O-CO-O-, -(CH2CH 2 O) q i-CH 2 CH2-, -CH2CH2-S-CH2CH2-, -CH2CH2-NH-CH2CH2- or -(SiR0R 00 -O) p1 -, in which p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and R° and R°° have the meanings indicated above.
  • Particularly preferred groups Sp including any variations thereof such as Sp°, Sp 1 , Sp 2 , Sp*°, and -Sp"-X"- are -(CH 2 ) P1 -, -(CH 2 ) P1 -O-, -(CH 2 ) P1 -O-CO-, -(CH 2 ) P1 -CO-O-, -(CH 2 ) P1 -O- CO-O-, in which p1 and q1 have the meanings indicated above.
  • Particularly preferred groups Sp" are, in each case straight-chain, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethylenethioethylene, ethylene-N-methyliminoethylene, 1 -methylalkylene, ethenylene, propenylene and butenylene.
  • the polymerisable compounds as disclosed above and below contain a spacer group Sp, including any variations thereof such as Sp°, Sp 1 , Sp 2 , Sp*°, that is substituted by one or more polymerisable groups P, so that the group Sp- P etc. corresponds to Sp(P) s , with s being >2 (branched polymerisable groups).
  • a spacer group Sp including any variations thereof such as Sp°, Sp 1 , Sp 2 , Sp*°, that is substituted by one or more polymerisable groups P, so that the group Sp- P etc. corresponds to Sp(P) s , with s being >2 (branched polymerisable groups).
  • Preferred polymerisable compounds according to this preferred embodiment are those wherein s is 2, i.e. , compounds which contain a group Sp(P)2.
  • Very preferred polymerisable compounds according to this preferred embodiment contain a group selected from the following formulae:
  • X has one of the meanings indicated for X", and is preferably O, CO, SO2, O-CO-, CO-O or a single bond.
  • Very preferred spacer groups Sp(P)2 are selected from the following subformulae:
  • each quarter-wave plate consisting of a polymer film which is formed from a polymerised chiral RM mixture with helically twisted structure and exhibits a pitch gradient, i.e. , wherein the helical pitch increases or decreases, in the film thickness direction, and wherein the helices in the two quarter-wave plates have opposite twist sense.
  • Each quarter-wave plate according to the present invention consists of a monolithic film of a polymerised chiral RM mixture.
  • the chiral RM mixture is hereinafter also referred to as “RM mixture (according to the present invention)”.
  • the film of the polymerised chiral RM mixture forming the quarter-wave plate is hereinafter also simply referred to as “polymer film (according to the present invention)”.
  • a half-wave plate according to the present invention thus comprises, preferably consists, of two polymer films according to the present invention as described above and below.
  • the RM mixture used for preparing the polymer film preferably contains at least one RM and at least one chiral compound with one or more isomerisable groups, preferably one or more photoisomerisable groups, like for example cinnamate groups.
  • the chiral compound with one or more isomerisable groups is preferably polymerisable.
  • the isomerisable group(s) in this chiral compound can undergo a photo driven E/Z isomerisation reaction, and in doing so exhibits a reduction in helical twisting power (HTP).
  • HTP helical twisting power
  • this allows to replicate a two-layer chiral RM film as described in prior art into a one-layer, or monolithic, film.
  • problems related to multilayer film preparation where multiple RM layers with different pitch values have to be coated onto each other, like insufficient alignment transfer between the RM layers, the appearance of alignment defects, damage in the lower RM layer caused by the subsequent layer, or the control of the different pitch values and slant angles in the individual RM layers.
  • the polymer film according to the present invention exhibits a non-linear twist profile with an accelerating twist through the film thickness, which can be achieved by use of the photoisomerisable chiral compound that undergoes isomerisation while partial polymerisation occurs.
  • the non-linear twist profile can be achieved by a process of preparing a polymer film according to the present invention as described above and below. This process contains two steps of irradiating the chiral RM layer with actinic radiation, for example UV light, which causes both photoisomerisation of the chiral compound and photopolymerisation of the RMs.
  • the first irradiation step involves UV irradiation of the RM layer in air rather than in an inert atmosphere such as nitrogen gas.
  • an inert atmosphere such as nitrogen gas.
  • the polymerised LC medium exhibits an accelerated chiral rotation in a direction perpendicular to the main plane of the polymer film, i.e. , in the film thickness direction, thereby creating a non- linear twist through the film thickness.
  • the second irradiation step is carried out in an inert gas atmosphere, for example nitrogen, which completes the polymerisation process also in the upper regions of the RM layer, so that the RM layer is fully polymerised into a polymer film with the non- linear twist locked in.
  • an inert gas atmosphere for example nitrogen
  • the polymer film according to the present invention has planar alignment, and by adding a small amount of a chiral dopant with high twisting power a helical twist is induced in a direction throughout the film thickness. As a result a perpendicular director orientation can be provided in a single film using only one RM mixture. This enables low material cost and increases market competitiveness.
  • the biased helical pitch (or helical pitch gradient), i.e. , wherein the chiral twist angle increases incrementally through the film thickness (i.e., in a direction perpendicular to the film plane), in the polymer film according to the present invention can be already be achieved by application of low intensity UV light.
  • the polymer film and its preparation process according to the present invention can provide the following advantages:
  • the chiral RM mixture can easily be aligned into the desired orientation, for example on a planar alignment layer or on a PB grating,
  • a perpendicular director orientation can be provided in a single film and using only one RM mixture, which enables low material cost and increases market competitiveness,
  • the helical pitch gradient in the polymer film can already be achieved by application of low intensity UV light
  • the process of preparing the polymer film requires only one additional process step compared to the process of preparing a conventional single, planar aligned RM film
  • the said additional process step is a low intensity UV exposure in air to cause photoisomerisation of the chiral compound, and does not require an inert gas atmosphere or additional heating or cooling of the film.
  • each quarter-wave plate according to the present invention contains only one polymer film with a pitch gradient formed from the polymerised chiral RM mixture.
  • the half-wave plate according to the present invention comprises, preferably consists of, two such polymer films with a pitch gradient formed from the polymerised chiral RM mixture.
  • the chiral RM mixture used for preparing a polymer film or quarter-wave plate according to the present invention comprises one or more chiral isomerisable compounds, preferably selected from chiral photoisomerisable compounds.
  • the chiral isomerisable compounds can be polymerisable or not polymerisable. They can be non-mesogenic compounds or mesogenic compounds. If the chiral isomerisable compounds are polymerisable they can be monoreactive or multi reactive.
  • the chiral RM mixture comprises one or more chiral isomerisable compounds which are polymerisable.
  • the chiral RM mixture contains exactly one chiral isomerisable compound.
  • the chiral RM mixture contains only chiral isomerisable compounds which are selected from polymerisable, preferably selected from mono- or direactive, chiral isomerisable compounds.
  • the chiral RM mixture comprises at least two, more preferably exactly two, chiral compounds with opposite handedness, one of which contains an isomerisable group, and the other of which does not contain an isomerisable group, and wherein one or both, preferably both, chiral compounds are polymerisable.
  • the chiral RM mixture does not contain a chiral compound which does not contain an isomerisable group, in particular does not contain a photoisomerisable group.
  • the chiral RM mixture does not contain any other chiral compounds in addition to the chiral isomerisable compound(s).
  • Suitable and preferred polymerisable chiral isomerisable compounds comprise one or more ring elements, linked together by a direct bond or via a linking group and, where two of these ring elements optionally may be linked to each other, either directly or via a linking group, which may be identical to or different from the linking group mentioned.
  • the ring elements are preferably selected from the group of four-, five-, six- or seven-, preferably of five- or six-, membered rings.
  • Preferred chiral isomerisable compounds are selected of formula I*:
  • R 3 , R 4 H, F, Cl, CN, P-Sp- or an alkyl radical with up to 25 C atoms which may be unsubstituted, mono- or polysubstituted by halogen or CN, it being also possible for one or more non-adjacent CH2 groups to be replaced, in each case independently from one another, by -O-, -S-, -NH-, -N(CH3)-, -CO-, - COO- -OCO-, -OCO-O-, -S-CO-, -CO-S- or -C C- in such a manner that oxygen atoms are not linked directly to one another,
  • a 3 , A 4 an alicyclic, heterocyclic, aromatic or heteroaromatic group with 4 to 20 ring atoms, which is monocyclic or polycyclic and which is optionally substituted by one or more groups L or P-Sp-,
  • R 3 or R 4 is an alkyl or alkoxy radical, i.e. where the terminal CH2 group is replaced by - O-, this may be straight-chain or branched.
  • It is preferably straight-chain, has 2, 3, 4, 5, 6, 7 or 8 carbon atoms and accordingly is preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, or octoxy, furthermore methyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy, for example.
  • Preferred compounds of formula I* and its subformulae are those wherein at least one of R 3 and R 4 , preferably both R 3 and R 4 , denote P-Sp-.
  • R 3 and R 4 are different from P-Sp-, and preferably denotes alkyl or alkoxy with 1 to 12, more preferably 1 to C atoms, and one of R 3 and R 4 may also denote F, Cl or CN.
  • a 3 and A 4 are selected from the group consisting of 1,4-phenylene, 1,3-phenylene, naphthalene-1,4-diyl, naphthalene-2,6-diyl, phenanthrene-2,7-diyl, 9,10-dihydro- phenanthrene-2,7-diyl, anthracene-2,7-diyl, anthracene-9,10-diyl, fluorene-2,7-diyl, dibenzothiophene-2, 7-diyl, dibenzofuran-2,7-diyl, benzo[1 ,2-b:4,5-b']dithiophene-2,5- diyl, indole-4, 7-diyl, benzothiophene-4, 7-diyl, coumarine, flavone, where, in addition, one or more CH
  • Very preferred compounds of formula I* and its subformulae are those wherein A 3 and A 4 are selected from the group consisting of 1 ,4-phenylene, naphthalene-1 ,4-diyl, naphthalene 2,6-diyl, 1 ,4-cyclohexylene in which, in addition, one or two non-adjacent CH2 groups may be replaced by O and/or S, 1 ,4-cyclohexenylene, 1 ,4- bicyclo(2,2,2)octylene, piperidine-1 ,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, or 1 ,2,3,4-tetrahydro-naphthalene-2,6-diyl, very preferably 1 ,4-phenylene or 1 ,4-cyclohexylene, all of which are optionally substituted by one or more groups L or P-
  • L is selected from F, Cl, CN, CH 3 , C 2 H 5 , OCH 3 , OC2H5, COCH 3 , COC2H5, CF 3 , OCF 3 , P- Sp-, in particular F, Cl, CN, CH3, C2H5, OCH3, COCH3 or OCF3 , most preferably F, CH 3 , OCH 3 or COCH 3 .
  • P is selected from the group consisting of vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxide, very preferably from acrylate and methacrylate, most preferably acrylate.
  • Further preferred compounds of formula I* and its subformulae are those wherein Sp denotes a single bond or -(CH2) P 1-, -O-(CH2) P1 -, -O-CO-(CH2) P1 , or -CO-O-(CH2) P1 , wherein p1 is an integer from 2 to 10, preferably 2, 3, 4, 5 or 6, and, if Sp is -O- (CH 2 ) P1 -, -O-CO-(CH2) P1 or -CO-O-(CH2) P1 the O-atom or CO-group, respectively, is linked to the benzene ring.
  • Further preferred compounds of formula I* and its subformulae are those wherein all polymerisable groups P that are present in the compound have the same meaning, and very preferably denote acrylate or methacrylate, most preferably acrylate.
  • Further preferred compounds of formula I* and its subformulae are those wherein at least one group Sp is different from a single bond, and is selected from -(CH2) P1 -, -O- (CH2) P1 -, -O-CO-(CH2) P1 , or -CO-O-(CH2) P 1, wherein p1 is an integer from 2 to 10, preferably 2, 3, 4, 5 or 6, and, if Sp is -O-(CH2) P1 -, -O-CO-(CH2) P1 or -CO-O-(CH2) P1 the O-atom or CO-group, respectively, is linked to the benzene ring.
  • R a or R b is a group of formula P-Sp-
  • the spacer groups on each side of the mesogenic core may be identical or different.
  • m and I are preferably 0 or 1.
  • q is preferably 0 or 1 , very preferably 0.
  • P, Sp, A 3 , A 4 , Z 3 , Z 4 and G have the meanings given for formula I* or one of their preferred meanings as described above and below
  • R* has one of the meanings of R 3 which is different from P-Sp-
  • R** has one of the meanings of R 4 which is different from P-Sp-.
  • Particularly preferred compounds of the formula l*2, I3, l*5, l*6, l*7, l*9 and 1*10 are those of the following formulae:
  • P, Sp, Z 3 , Z 4 and G have the meanings given for formula I* or one of their preferred meanings as described above and below
  • R* has one of the meanings of R 3 in formula I* which is different from P-Sp-
  • R** has one of the meanings of R 4 in formula I* which is different from P-Sp-.
  • R* and R** are independently of each other alkyl or alkoxy with 1 to 12 C atoms, or alkyl or alkoxy with 1 to 12 C atoms and the other is F, Cl or CN.
  • -Sp- is preferably alkylene or alkyleneoxy with 1 to 12 C atoms
  • P is preferably acrylate or methacrylate
  • Preferred compounds of formula I* and its subformulae are those wherein G denotes or contains a photoisomerisable group.
  • Further preferred compounds of formula I* and its subformulae are those containing an isomerisable group selected from stilbene, (1,2-difluoro-2-phenyl-vinyl)-benzene, cinnamate, a-cyanocinnamate, 4-phenylbut-3-en-2-one, Schiff base, 2-benzyliden-1- indanone, chaicone, coumarin, chromone, pentalenone or azobenzene.
  • an isomerisable group selected from stilbene, (1,2-difluoro-2-phenyl-vinyl)-benzene, cinnamate, a-cyanocinnamate, 4-phenylbut-3-en-2-one, Schiff base, 2-benzyliden-1- indanone, chaicone, coumarin, chromone, pentalenone or azobenzene.
  • chiral group G is selected or derived from dianhydrohexitol, preferably isosorbide, isomannide or isoidide, 1,1’-bi-2-naphthol (binol), 1,2-diphenyl-1 ,2-ethanediol (hydrobenzoin), 2-benzylidene-p-menthan-3-one and menthyl cinnamate ((1/ ,2S,5R)- 5-Methyl-2-(1-methylethyl)cyclohexyl (2E)-3-phenyl-2-propenoate).
  • Formula A includes the following stereoisomers based on the corresponding dianhydrohexitols:
  • X, L and q have the meanings given in formula A, and wherein Ai is based on isosorbide, Aii is based on isomannide and Aiii is based on isoidide. Especially preferred is Ai.
  • X, L and q have the meanings given in formula A or one of the preferred meanings as given above and below,
  • R 11 and R 12 independently of each other denote -(Z 4 -A 4 )i-R 4 as defined in formula I*, or R 11 and R 12 together with the O atoms form a cyclic group or a spirocyclic group which is optionally substituted by a group -(Z 4 -A 4 )i-R 4 as defined in formula I*, R 13 and R 14 independently of each other denote R 3 -(A 3 -Z 3 ) m - as defined in formula I*, a1 and a2 independently of each other are 0, 1 or 2, and the dashed lines represent a linkage to the adjacent group(s) in formula I*.
  • stereoisomers of formula l*A, l*B, l*A1 , l*A2 and l*A3 wherein the central isosorbide unit is replaced by an isomannide or isoidide unit.
  • P is preferably acrylate or methacrylate, very preferably acrylate
  • Sp is preferably -O-(CH2) P1 -, -O-CO-(CH2) P 1- or -O-(CH2) P1 - ,, very preferably -O-(CH2) P1 -, wherein the O-atom or CO-group, respectively, is linked to the benzene ring
  • p1 is an integer from 1 to 6, more preferably 2, 3, 4, 5 or 6, and R 4 is preferably P-Sp-.
  • R 16 and R 17 independently of each other denote alkyl with 1 to 12, preferably 1 to 6 C atoms, very preferably methyl, ethyl or propyl, and R 18 denotes P-Sp-, H or alkyl with 1 to 12, preferably 1 to 6 C atoms, very preferably H.
  • P is preferably acrylate or methacrylate, very preferably acrylate
  • Sp is preferably -O-(CH2) P1 -, -O-CO-(CH2) P1 - or -CO-O- (CH 2 ) P1 -, very preferably -O-(CH2) P1 -, wherein the O-atom or CO-group, respectively, is linked to the benzene ring
  • p1 is an integer from 1 to 6, more preferably 2, 3, 4, 5 or 6,
  • R* and R** are preferably, independently of each other, alkyl or alkoxy with 1 to 12, very preferably 1 to 6, C atoms.
  • the compounds of formula IA* can be prepared for example according to or in analogy to the method described in GB 2314839 A.
  • the compounds of formulae l*E1 to l*E15 can be prepared for example according to or in analogy to the method described in WO 02/40614 A1.
  • the utilized chiral isomerisable compounds have each alone or in combination with each other an absolute value of the helical twisting power (I HTP total ) of 20 pm -1 or more, preferably of 40 pm -1 or more, more preferably in the range of 60 pm -1 or more, most preferably in the range of 80 pm -1 or more to 260 pm -1 .
  • I HTP total the absolute value of the helical twisting power
  • the proportion of the chiral isomerisable compounds, especially those selected from formula I* or its subformulae, in the RM mixture according to the present invention as a whole is in the range from 0.1 to 4 % by weight, very preferably in the range from 0.2 to 3 % by weight, most preferably in the range from 0.3 to 2 % by weight.
  • the RM mixture contains, in addition to the chiral isomerisable compound, one or more, preferably exactly one, chiral compounds which are not isomerisable.
  • the configuration of the isomerisable chiral compound is selected to be different from the configuration of the non-isomerisable chiral compound.
  • the nonisomerisable chiral compound of (S) configuration is preferred and vice versa.
  • the individual values for the HTP of the individual chiral compounds with different configuration may compensate each other in terms of their individual helical twisting power to give a resulting absolute value of the HTP, hereinafter also named IHTPD I.
  • the chiral RM mixture comprises one or more chiral compounds with (S)-configuration, and additionally one or more chiral compounds with (R)-configuration, wherein at least one, preferably exactly one, of said chiral compounds either in (S) configuration or in (R) configuration is selected from isomerisable chiral compounds and the resulting IHTPD I is in the range from 0.1 pm -1 to 100 pm -1 , more preferably in the range of 0.5 pm -1 to 50 pm -1 , most preferably in the range of 1 pm -1 to 25 pm -1 .
  • non-isomerisable chiral compounds By adding one or more non-isomerisable chiral compounds it is possible to adjust the central wavelength of the reflection band of the RM mixture.
  • the additional non- isomerisable chiral compound can have the same twist sense or opposite twist sense than the chiral isomerisable compound. Accordingly the reflection waveband of the RM mixture will be shifted to shorter or longer wavelengths, respectively.
  • the isomerisable and the non-isomerisable chiral compounds have opposite handedness and, as a result, opposite twist sense.
  • the RM mixture contains one or more, preferably exactly one, chiral isomerisable compound, which is preferably polymerisable, especially selected from formula I* or its subformulae, and additionally contains one or more, preferably exactly one, non-isomerisable chiral compound, which is optionally polymerisable, and which very preferably has opposite twist sense than the chiral isomerisable compound.
  • the additional polymerisable chiral compounds have alone or in combination with each other an absolute value of the helical twisting power (I HTP to tail) of 20 pm -1 or more, preferably of 40 pm -1 or more, more preferably in the range of 60 pm -1 or more, most preferably in the range of 80 pm -1 or more to 260 pm -1 .
  • I HTP to tail an absolute value of the helical twisting power
  • the additional, non-isomerisable chiral compound is selected from polymerisable compounds, which are preferably mono- or direactive.
  • Suitable non-isomerisable, polymerisable chiral compounds preferably comprise one or more ring elements, linked together by a direct bond or via a linking group and, where two of these ring elements optionally may be linked to each other, either directly or via a linking group, which may be identical to or different from the linking group mentioned.
  • the ring elements are preferably selected from the group of four-, five-, six- or seven-, preferably of five- or six-, membered rings.
  • Preferred non-isomerisable, polymerisable chiral compounds are selected from the formulae CRM1 , CRM2 and CRM3: wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings P°* a polymerisable group,
  • stereoisomers of formula CRM2 wherein the central isosorbide unit is replaced by an isomannide or isoidide unit.
  • the compounds of formula CRM1 are preferably selected from the following formula: wherein A 0 , B°, Z 0 *, X 2 , P 0 *, a and b have the meanings given in formula CRMa or one of the preferred meanings given above and below, and (OCO) denotes -O-CO- or a single bond.
  • Especially preferred compounds of formula CRM are selected from the group consisting of the following subformulae:
  • R* is -X 2 -(CH2)t-P0* as defined in formula CRM1-1 , and the benzene and naphthalene rings are unsubstituted or substituted with 1, 2, 3 or 4 groups L as defined above and below.
  • concentration in the RM mixture is preferably from 0.1 to 10 %, more preferably from 0.5 to 8 % by weight of the total RM mixture.
  • the additional, non-isomerisable chiral compound is selected from non-polymerisable compounds. These chiral compounds may be non- mesogenic compounds or mesogenic compounds.
  • Preferred non-isomerisable, non-polymerisable chiral compounds are selected from the group consisting of compounds of formulae C-l to C-lll, wherein formula C-ll and C-lll include the respective (S,S) enantiomers, and wherein E and F are each independently 1 ,4-phenylene or trans-1 ,4-cyclohexylene, v is 0 or 1 , Z° is -COO-, -OCO-, -CH2CH2- or a single bond, and R c is alkyl, alkoxy or alkanoyl with 1 to 12 C atoms.
  • stereoisomers of formula C-ll wherein the central isosorbide unit is replaced by an isomannide or isoidide unit.
  • the compounds of formula C-l and their synthesis are described in EP1389199 A1.
  • the compounds of formula C-ll and their synthesis are described in W098/00428 A1.
  • the compounds of formula C-lll and their synthesis are described in GB2328207 A.
  • Additional chiral dopants are e.g. the commercially available R/S- 6011 , R/S-5011 , R/S-4011 , R/S-3011 , R/S-2011 , R/S-1011 , R/S-811 and CB-15 (from Merck KGaA, Darmstadt, Germany).
  • the amount of the non-polymerisable and non-isomerisable chiral dopants in the chiral RM mixture is preferably from 0.1 to 10 %, more preferably from 0.5 to 8 % by weight of all solids.
  • the chiral RM mixture comprises, in addition to the chiral compounds, one or more achiral RMs.
  • the RM mixture comprises one or more additional, achiral RMs having only one polymerisable functional group (monoreactive RMs) and/or one or more additional, achiral RMs having two or more polymerisable functional groups (di- or multireactive RMs).
  • Additional achiral, di- or multireactive RMs are preferably selected of formula DRM:
  • P 1 , P 2 independently of each other denote a polymerisable group
  • Sp 1 , Sp 2 independently of each other are a spacer group or a single bond
  • MG is a rod-shaped mesogenic group, which is preferably selected of formula MG
  • a 1 and A 2 denote, in case of multiple occurrence independently of one another, an aromatic or alicyclic group, which optionally contains one or more heteroatoms selected from N, O and S, and is optionally mono- or polysubstituted by L,
  • L is P-Sp-, F, Cl, Br, I, -CN, -NO 2 , -NCO, -NCS, -OCN, -SCN, -
  • R x and R y independently of each other denote H or alkyl with 1 to 12 C-atoms
  • Z 1 denotes, in case of multiple occurrence independently of one another, - single bond, preferably -COO-, -OCO- or a single bond,
  • Y 1 and Y 2 independently of each other denote H, F, Cl or CN, n is 1 , 2, 3 or 4, preferably 1 or 2, most preferably 2, n1 is an integer from 1 to 10, preferably 1 , 2, 3 or 4.
  • Preferred groups A 1 and A 2 include, without limitation, furan, pyrrol, thiophene, oxazole, thiazole, thiadiazole, imidazole, phenylene, cyclohexylene, bicyclooctylene, cyclohexenylene, pyridine, pyrimidine, pyrazine, azulene, indane, fluorene, naphthalene, tetrahydronaphthalene, anthracene, phenanthrene and dithienothiophene, all of which are unsubstituted or substituted by 1, 2, 3 or 4 groups L as defined above.
  • Particular preferred groups A 1 and A 2 are selected from 1,4-phenylene, pyridine-2,5- diyl, pyrimidine-2,5-diyl, thiophene-2, 5-diyl, naphthalene-2,6-diyl, 1,2,3,4-tetrahydro- naphthalene-2,6-diyl, indane-2, 5-diyl, bicyclooctylene or 1,4-cyclohexylene wherein one or two non-adjacent CH2 groups are optionally replaced by O and/or S, wherein these groups are unsubstituted or substituted by 1, 2, 3 or 4 groups L as defined above.
  • Preferred RMs of formula DRM are selected of formula DRMa
  • P° is, in case of multiple occurrence independently of one another, a polymerisable group, preferably an acryl, methacryl, oxetane, epoxy, vinyl, heptadiene, vinyloxy, propenyl ether or styrene group,
  • L has on each occurrence identically or differently one of the meanings given for L 1 in formula I, and is preferably, in case of multiple occurrence independently of one another, selected from F, Cl, CN or optionally halogenated alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy with 1 to 5 C atoms, r is 0, 1 , 2, 3 or 4, x and y are independently of each other 0 or identical or different integers from 1 to 12, z is 0 or 1 , with z being 0 if the adjacent x or y is 0.
  • Very preferred RMs of formula DRM are selected from the following formulae:
  • DRMa7 wherein P°, L, r, x, y and z are as defined in formula DRMa.
  • Additional achiral, monoreactive RMs are preferably selected of formula MRM:
  • R 22 denotes P-Sp-, F, Cl, Br, I, -CN, -NO 2 , -NCO, -NCS, -OCN, -SCN, -
  • X is halogen, preferably F or Cl, and R x and R y are independently of each other H or alkyl with 1 to 12 C-atoms.
  • RMs of formula MRM are selected from the following formulae.
  • R°, R 01 and R 02 are each an idependently alkyl, alkoxy, thioalkyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy with 1 or more, preferably 1 to 15 C atoms or denotes Y° or P-(CH2) y -(O) z -,
  • X° is -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR 01 -, -NR 01 -CO-, -NR 01 - CO-NR 01 -, -OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -
  • Y° is F, Cl, CN, NO 2 , OCH 3 , OCN, SCN, SF 5 , or mono- oligo- or polyfluorinated alkyl or alkoxy with 1 to 4 C atoms,
  • a 0 is, in case of multiple occurrence independently of one another, 1,4- phenylene that is unsubstituted or substituted with 1 , 2, 3 or 4 groups L, or trans-1 ,4-cyclohexylene,
  • R 01 02 are independently of each other H, R° or Y°, u and v are independently of each other 0, 1 or 2, w is O or 1, and wherein the benzene and naphthalene rings can additionally be substituted with one or more identical or different groups L.
  • MRM1 Especially preferred are compounds of formula MRM1 , MRM2, MRM3, MRM4, MRM5, MRM6, MRM7, MRM9 and MRM10, in particular those of formula MRM1 , MRM4, MRM6 and MRM7.
  • L is preferably selected from F, Cl, CN, NO2 or straight chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy with 1 to 12 C atoms, wherein the alkyl groups are optionally perfluorinated, or P-Sp-.
  • L is selected from F, Cl, CN, NO2, CH3, C2H5, C(CH3)3, CH(CH3)2, CH 2 CH(CH3)C 2 H5, OCH 3 , OC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF 3 , OCF 3 , OCHF2, OC2F5 or P-Sp-, in particular F, Cl, CN, CH 3 , C 2 H 5 , C(CH 3 ) 3 , CH(CH 3 ) 2 , OCH 3 , COCH3 or OCF3, most preferably F, Cl, CH3, C(CH3)3, OCH3 or COCH3, or P-Sp-.
  • the RM mixture comprises one or more RMs selected from formulae DRM and MRM.
  • the concentration of the di- or multireactive RMs of formula DRM and its subformulae is preferably from 15 to 75%, very preferably from 25 to 65%.
  • the concentration of the monoreactive RMs, preferably those of formula MRM, in an RM mixture according to this preferred embodiment is preferably from 1 to 50%, very preferably from 5 to 30%.
  • the chiral RM mixture comprises, in addition or alternatiely to the compounds of formula DRM and MRM, one or more achiral RMs selected from formula I: wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings
  • A, B, D, and E are selected from the group consisting of 1 ,4-phenylene, naphthalene-
  • C is selected from the group consisting of benzene-1 ,4-diyl, naphthalene-1 ,4-diyl, anthracene-9,10-diyl, fluorene-2,7-diyl, dibenzofuran-2,7-diyl, dibenzothiophene-
  • -COO-, -OCO-, -C C-, or a single bond, most preferably a single bond, n1 1 , 2, 3 or 4, r 0, 1 , 2, 3 or 4, preferably 0, 1 or 2, s 0, 1 , 2 or 3, preferably 0, 1 or 2, t 0, 1 or 2, preferably 0 or 1 , R°, R 00 H or alkyl having 1 to 12 C atoms,
  • Y 1 , Y 2 H, F, Cl, NCS, or CN n 0, 1 , 2, 3 or 4, preferably 0, 1 or 2, more preferably 0 or 1 , most preferably 0, m 0, 1 , 2, 3 or 4, preferably 0, 1 or 2, more preferably 0 or 1 , most preferably 0.
  • P is preferably selected from the group consisting of vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxide, very preferably from acrylate and methacrylate, most preferably acrylate.
  • R 11 is different from P-Sp- and is preferably selected from CN, - SCN, alkyl, alkoxy, thioalkyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy preferably with 1 to 12, preferably 1 to 6 C atoms which is optionally fluorinated.
  • Sp denotes a single bond or -(CH2) P i-, -O-(CH2) P1 -, -O-CO-(CH2) P1 , or -CO-O-(CH2) P1 , wherein p1 is 2, 3, 4, 5 or 6, and, if Sp is -O-(CH2) P1 -, -O-CO-(CH2) P1 or -CO-O-(CH2) P1 the O-atom or CO-group, respectively, is linked to the benzene ring.
  • At least one group Sp is different from a single bond, and is selected from -(CH2) P1 -, -O-(CH2) P1 -, -O-CO-(CH2) P1 , or -CO-O-(CH2) P1 , wherein p1 is an integer from 2 to 10, preferably 2, 3, 4, 5 or 6, and, if Sp is -O-(CH2) P1 -, -O-CO- (CH 2 ) P 1 or -CO-O-(CH2) P 1 the O-atom or CO-group, respectively, is linked to the benzene ring.
  • L is straight chain alkyl, alkoxy or thioalkyl having 1 to 6 C atoms, or branched or cyclic alkyl, alkoxy or thioalkyl having 3 to 8 C atoms.
  • A, B, D and E in formula I are selected from the group consisting of wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings
  • L P-Sp-, -CN, F, Cl, or alkyl, alkoxy or thioalkyl which is optionally fluorinated and has 1 to 6, preferably 1 to 3, more preferably 1 or 2 C atoms, preferably P-Sp-, - CN, F, Cl, OCH 3 , SCH 3 , C 2 H 5 , OC 2 H 5 , SC 2 H 5 , r 0, 1 , 2, 3 or 4, preferably 0, 1 or 2, s 0, 1 , 2 or 3, preferably 0 or 1 , t 0, 1 or 2, preferably 0 or 1.
  • rings A, B, D and/or E in formula I are selected from the group consisting of benzene-1,4-diyl, naphthalene-1,4-diyl, naphthalene 2, 6-diyl, phenanthrene-2,7-diyl, anthracene-9,10-diyl, fluorene-2,7-diyl, dibenzofuran-2,7-diyl, dibenzothiophene-2, 7-diyl, benzo[1 ,2-b:4, 5-b']dithiophene-2, 5-diyl , indole-4, 7-diyl, benzothiophene-4, 7-diyl, all of which are optionally substituted by one or more groups L and/or P-Sp-.
  • rings A, B, D and/or E in formula I are selected from the group consisting of wherein L, on each occurrence identically or differently, denotes P-Sp-, -CN, F, Cl, or alkyl, alkoxy or thioalkyl which is optionally fluorinated and has 1 to 6, preferably 1 to 3, more preferably 1 or 2 C atoms, preferably P-Sp-, -CN, F, Cl, OCH 3 , SCH 3 , C 2 Hs, OC 2 H 5 , SC 2 H 5 .
  • L on each occurrence identically or differently, denotes P-Sp-, -CN, F, Cl, or alkyl, alkoxy or thioalkyl which is optionally fluorinated and has 1 to 6, preferably 1 to 3, more preferably 1 or 2 C atoms, preferably P-Sp-, -CN, F, Cl, OCH 3 , SCH 3 , C 2 Hs, OC 2 H 5 , SC 2 H 5
  • rings B and D are selected from the group consisting of benzene-1 ,4-diyl, naphthalene-1 ,4-diyl, naphthalene-2,6-diyl or anthracene-9,10-diyl, all of which are optionally mono- or disubstituted by L and/or P-Sp-.
  • ring C in formula I is selected from the group consisting of wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings
  • L P-Sp-, -CN, F, Cl, or alkyl, alkoxy or thioalkyl which is optionally fluorinated and has 1 to 6, preferably 1 to 3, more preferably 1 or 2 C atoms, preferably P-Sp-, - CN, F, Cl, OCH 3 , SCH 3 , C 2 H 5 , OC 2 H 5 , SC 2 H 5 , r 0, 1 , 2, 3 or 4, preferably 0, 1 or 2, s 0, 1 , 2 or 3, preferably 0 or 1 , t 0, 1 or 2, preferably 0 or 1 .
  • C in formula 1, 11 and I2 is selected from the group consisting of wherein L, on each occurrence identically or differently, denotes P-Sp-, -CN, F, Cl, or alkyl, alkoxy or thioalkyl which is optionally fluorinated and has 1 to 6, preferably 1 to 3, more preferably 1 or 2 C atoms, preferably P-Sp-, -CN, F, Cl, OCH3, SCH3, C2H5, OC2H5, SC2H5.
  • Very preferably ring C in formula I is selected from the group consisting of benzene- 1 ,4-diyl, naphthalene-1 ,4-diyl or anthracene-9,10-diyl, all of which are optionally mono- or disubstituted by L and/or P-Sp-.
  • rings B, C and D form a group selected from the following formulae or their mirror images: wherein the naphthalene and phenanthrene groups are optionally substituted with one or two groups L, and L 1 and L 2 independently of each other denote H or have one of the meanings given for L in formula I, and L and r are as defined in formula I.
  • naphthalene and phenanthrene groups are optionally substituted with one or two groups L, and P, Sp, L and r, independently of each other and on each occurrence identically or differently, have the meanings given in formula I or one of the preferred meanings given above and below, and R has one of the meanings given for R 11 in formula 11 , and preferably denotes OCH3 or SCH3, very preferably OCH3.
  • L is preferably selected from alkyl, alkoxy or thioalkyl having 1 to 6, more preferably 1 , 2 or 3 C atoms, very preferably from methyl or ethyl.
  • P is preferably acrylate.
  • - one of ring B and ring D is a single bond
  • - ring C denotes naphthalene-1 ,4-diyl or anthracene-9,10-diyl
  • - ring C denotes benzene-1 ,4-diyl which is substituted by alkyl, alkoxy or thioalkyl with 1 to 3, preferably 1 or 2 C atoms, more preferably methyl or ethyl, most preferably ethyl, and/or
  • rings B and D denotes naphthalene-1 ,4-diyl, naphthalene-2,6- diyl, or anthracene-9,10-diyl, which is optionally substituted by one or more groups L or P-Sp-, and/or
  • rings B, C and D denotes naphthalene-1 ,4-diyl, naphthalene-2,6- diyl, or anthracene-9,10-diyl, which is optionally substituted by one or more groups L or P-Sp-, and/or at least one of the rings B, C and D is benzene-1 ,4-diyl that is substituted with an ethyl group,
  • - P denotes acrylate or methacrylate and/or
  • - Sp denotes Sp”-X”, preferably, -Sp"-X"- denotes -(CH2) P1 -, -(CH2) P1 -O-, -(CH2) P1 -O- CO-, -(CH 2 ) P1 -CO-O-, -(CH 2 ) P1 -O-CO-O-, -(CH2CH 2 O) q 1-CH 2 CH2-, -CH2CH2-S-CH2CH2- , or -CH2CH2-NH-CH2CH2-, in which p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and/or
  • R 11 or R is P-Sp-, one of the groups Sp is a single bond and the other of the groups Sp is different from a single bond, and/or
  • - L is selected from methyl, ethyl, methoxy, ethoxy, thiomethyl or thiomethyl, more preferably methyl or ethyl, very preferably ethyl, and r denotes 1 , and/or
  • - L is selected from methyl, ethyl, methoxy, ethoxy, thiomethyl or thiomethyl, more preferably methyl or ethyl, very preferably ethyl, and r denotes 2, and/or
  • - ring C is substituted by one L which denotes P-Sp-, preferably acrylate, and/or
  • - R 11 is P-Sp-, or
  • R 11 is F, Cl, CN, OCH3 or SCH3, preferably OCH3 or SCH3, very preferably OCH3.
  • the compounds of formula I are characterized by a very high birefringence.
  • the synthesis of the compounds of formula I and its subformulae can be carried by methods known per se to the person skilled in the art from the literature or in analogy thereto, as described for example in WO 2022/33908A1.
  • the compounds of formula I either taken alone or in combination with other RMs in an RM mixture, exhibit in particular and preferably at the same time, a high birefringence, exhibit a good solubility in commonly known organic solvents used in mass production, show an improved alignment in the RM mixture, have favorable transition temperatures, and show high resistance against yellowing after being exposed to UV light.
  • the RM mixture contains one or more, preferably 1 to 5, very preferably 1 , 2 or 3, compounds selected from formulae I, preferably selected from formulae 1-1 to I-97, very preferably selected from formulae 11 to I76.
  • the concentration of the compounds of formula I or its subformulae in the RM mixture is preferably from 65 to 99%, very preferably from 25 to 98%.
  • the RM mixture contains only a small amount of a compound of formula I.
  • an RM mixture mainly consisting of mono-, di- and/or multireactive RMs, preferably selected from formula DRM and MRM and their subformulae, which is doped with a small amount, preferably 5 to 30% of compounds of formula I, and additionally contains one or more chiral isomerisable compounds preferably selected of formula I*.
  • the chiral RM mixture comprises at least one RM having a birefringence of >0.25, very preferably >0.28.
  • Suitable RMs with high birefringence are for example those selected of formula I and its subformulae as defined above and below.
  • the RM mixture preferably exhibits a chiral nematic LC phase, or a chiral smectic LC phase and a chiral nematic LC phase, very preferably a chiral nematic LC phase at room temperature.
  • the RM mixture preferably has a birefringence (An) in the range from 0.2 to 0.8, more preferably in the range from 0.25 to 0.7 and even more preferably in the range from 0.35 to 0.6.
  • the chiral RM mixture comprises an achiral host mixture and a chiral component.
  • the achiral host mixture preferably comprises, very preferably consists of, one or more mono- and/or direactive achiral RMs, which are preferably selected from formula DRM, MRM and I and their subformulae.
  • the chiral component preferably comprises, very preferably consists of, one or more chiral compounds, at least one of which is isomerisable, and which are preferably selected from formula I*, CRM1, CRM2 and CRM3 and their subformulae.
  • the proportion of the achiral host mixture in the chiral RM mixture is preferably from 90 to 99.7%, very preferably from 94 to 99.5%.
  • the proportion of the chiral component in the chiral RM mixure is preferably from 0.3 to 10%, very preferably from 0.5 to 6%.
  • the chiral RM mixtures for preparing two quarter- waveplates with opposite twist sense are prepared by adding to the achiral host mixture chiral components inducing opposite twst sense.
  • chiral components for example it is possible to use two chiral isomerisable compounds with opposite twist sense.
  • two chiral components wherein each chiral component comprises a first, isomerisable chiral compound and a second, non-isomerisable chiral compound which have opposte twist sense, and wherein the concentrations and HTP values of the first and second chiral compounds can be selected such that after the isomerisation process the two chiral components have opposite twist sense.
  • the chiral RM mixture for preparing the first quarter- wave plate and the chiral RM mixture for preparing the second quarter-wave plate are based on the same achiral host mixture, to which is added the (R)- or (S)-stereoisomer of the same chiral isomerisable compound, respectively, to prepare two chiral RM mixtures with opposite twist for use in the first and second quarter-wave plate, respectively.
  • the chiral RM mixture for the first quarter-wave plate is prepared by adding the (R)-stereoisomer of a chiral isomerisable compound to an achiral RM host mixture
  • the chiral RM mixture for the second quarter-wave plate is prepared by adding the corresponding (S)-stereoisomer of the said chiral isomerisable compound to the said achiral RM host mixture, or vice versa.
  • Another object of the invention is an RM formulation comprising an RM mixture as described above and below, and further comprising one or more solvents and/or additives.
  • the proportion of the RM mixture comprising, preferably consisting of, compounds selected from formulae I and I* and their subformulae, and optionally from formulae CRM1 , CRM2, CRM3, C-l, C-l I, C-lll, DRM and MRM and their subformulae, in the RM formulation is preferably from 85 to 100%, more preferably from 85 to 99%, very preferably from 90 to 99% of total solids and liquid additives, i.e., excluding the solvents.
  • the chiral RM mixture does not contain a compound of formula DRM or MRM.
  • the chiral RM mixture consists of compounds selected from formula I, I* and optionally CRM1 , CRM2, CRM3, C-l, C-ll and C-lll.
  • the RM formulation comprises optionally one or more additives selected from the group consisting of polymerisation initiators, surfactants, stabilisers, catalysts, sensitizers, inhibitors, chain-transfer agents, co-reacting monomers, reactive thinners, surface-active compounds, lubricating agents, wetting agents, dispersing agents, hydrophobing agents, adhesive agents, flow improvers, degassing or defoaming agents, deaerators, diluents, reactive diluents, auxiliaries, colourants, dyes, pigments and nanoparticles.
  • additives selected from the group consisting of polymerisation initiators, surfactants, stabilisers, catalysts, sensitizers, inhibitors, chain-transfer agents, co-reacting monomers, reactive thinners, surface-active compounds, lubricating agents, wetting agents, dispersing agents, hydrophobing agents, adhesive agents, flow improvers, degassing or defoaming agents, deaerators, dil
  • the RM mixture and/or RM formulation do not contain a compound with at least one CF3 or CF2 group (PFAS), and very preferably the RM mixture and/or RM formulation do not contain a compound with a polyfluorinated alkyl or aryl group or a perfuorocarbon group. More preferably the RM mixture and/or RM formulation do not contain a compound with a fluorinated aliphatic C atom, most preferably the RM mixture and/or RM formulation do not contain a compound with a fluorinated C atom.
  • the RM mixtures and RM formulations according to this preferred embodiment do thus enable a reduction of perfluorocarbons.
  • RM mixture and/or RM formulation as described above and below which do not contain a PFAS, more preferably do not contain a perfluorocarbon compound, very preferably do not contain compound with a polyfluorinated C atom, and most preferably do not contain a compound with a fluorinated C atom, are another object of the invention.
  • the RM formulation comprises one or more specific antioxidant additives, preferably selected from the Irganox® series, e.g. the commercially available antioxidants lrganox®1076 and lrganox®1010, from Ciba, Switzerland.
  • the RM formulation comprises a combination of one or more, more preferably of two or more photoinitiators, for example, selected from the commercially available Omnirad® or Darocur® series (from IGM Resins), in particular, Omnirad 127, Omnirad 184, Omnirad 369, Omnirad 651, Omnirad 817, Omnirad 907, Omnirad 1300, Omnirad, Omnirad 2022, Omnirad 2100, Omnirad 2959, or Darocur TPO, further selected from the commercially available OXE02 (Ciba AG), NCI 930, N1919T (Adeka), SPI-03 or SPI-04 (Samyang), TR-PBG 304 or TR-PGB 345 (Tronly).
  • Omnirad® or Darocur® series from IGM Resins
  • the concentration of the polymerisation initiator(s) as a whole in the RM formulation is preferably from 0.1 to 6%, very preferably from 0.3 to 4%, more preferably from 0.7 to 2%.
  • the ratio between the concentration of the photoinitiator and the concentration of the chiral compounds as a whole is in the range from 2:1 to 1 :5, more preferably in the range from 2:1 to 1:4, even more preferably in the range from 2:1 to 1 :3.
  • the RM formulation optionally comprises one or more additives selected from polymerisable non-mesogenic compounds (reactive thinners).
  • the amount of these additives in the RM formulation is preferably from 0 to 30 %, very preferably from 0 to 25 %.
  • the reactive thinners used are not only substances which are referred to in the actual sense as reactive thinners, but also auxiliary compounds already mentioned above which contain one or more complementary reactive units, for example hydroxyl, thiol-, or amino groups, via which a reaction with the polymerisable units of the liquid- crystalline compounds can take place.
  • the substances which are usually capable of photopolymerisation include, for example, mono-, bi- and polyfunctional compounds containing at least one olefinic double bond.
  • examples thereof are vinyl esters of carboxylic acids, for example of lauric, myristic, palmitic and stearic acid, and of dicarboxylic acids, for example of succinic acid, adipic acid, allyl and vinyl ethers and methacrylic and acrylic esters of monofunctional alcohols, for example of lauryl, myristyl, palmityl and stearyl alcohol, and diallyl and divinyl ethers of bifunctional alcohols, for example ethylene glycol and 1 ,4-butanediol.
  • methacrylic and acrylic esters of polyfunctional alcohols are also suitable, for example, methacrylic and acrylic esters of polyfunctional alcohols, in particular those which contain no further functional groups, or at most ether groups, besides the hydroxyl groups.
  • examples of such alcohols are bifunctional alcohols, such as ethylene glycol, propylene glycol and their more highly condensed representatives, for example diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol etc., butanediol, pentanediol, hexanediol, neopentyl glycol, alkoxylated phenolic compounds, such as ethoxylated and propoxylated bisphenols, cyclohexanedimethanol, trifunctional and polyfunctional alcohols, such as glycerol, trimethylolpropane, butanetriol, trimethylolethane, pentaerythritol, ditrimethylolpropane, dipenta
  • polyester (meth)acrylates which are the (meth)acrylic ester of polyesterols.
  • polyesterols examples are those which can be prepared by esterification of polycarboxylic acids, preferably dicarboxylic acids, using polyols, preferably diols.
  • the starting materials for such hydroxyl-containing polyesters are known to the person skilled in the art.
  • Dicarboxylic acids which can be employed are succinic, glutaric acid, adipic acid, sebacic acid, o-phthalic acid and isomers and hydrogenation products thereof, and esterifiable and transesterifiable derivatives of said acids, for example anhydrides and dialkyl esters.
  • Suitable polyols are the abovementioned alcohols, preferably ethyleneglycol, 1,2- and 1,3-propylene glycol, 1,4-butanediol, 1,6- hexanediol, neopentyl glycol, cyclohexanedimethanol and polyglycols of the ethylene glycol and propylene glycol type.
  • Suitable reactive thinners are furthermore 1,4-divinylbenzene, triallyl cyanurate, acrylic esters of tricyclodecenyl alcohol of the following formula also known under the name dihydrodicyclopentadienyl acrylate, and the allyl esters of acrylic acid, methacrylic acid and cyanoacrylic acid.
  • This group includes, for example, dihydric and polyhydric alcohols, for example ethylene glycol, propylene glycol and more highly condensed representatives thereof, for example diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol etc., butanediol, pentanediol, hexanediol, neopentyl glycol, cyclohexanedimethanol, glycerol, trimethylolpropane, butanetriol, trimethylolethane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, sorbitol, mannitol and the corresponding alkoxylated, in particular ethoxylated and propoxylated alcohols.
  • dihydric and polyhydric alcohols for example ethylene glycol, propylene glycol and more highly condensed representatives thereof, for example diethylene glycol, triethylene glycol, dipropylene
  • the group furthermore also includes, for example, alkoxylated phenolic compounds, for example ethoxylated and propoxylated bisphenols.
  • These reactive thinners may furthermore be, for example, epoxide or urethane (meth)acrylates.
  • Epoxide (meth)acrylates are, for example, those as obtainable by the reaction, known to the person skilled in the art, of epoxidized olefins or poly- or diglycidyl ether, such as bisphenol A diglycidyl ether, with (meth)acrylic acid.
  • Urethane (meth)acrylates are, in particular, the products of a reaction, likewise known to the person skilled in the art, of hydroxylalkyl (meth)acrylates with poly- or diisocyanates.
  • Such epoxide and urethane (meth)acrylates are included amongst the compounds listed above as “mixed forms”.
  • the low-crosslinking (high-crosslinking) liquid-crystalline compositions can be prepared, for example, using corresponding reactive thinners which have a relatively low (high) number of reactive units per molecule.
  • the group of diluents include, for example:
  • C1-C4-alcohols for example methanol, ethanol, n-propanol, isopropanol, butanol, isobutanol, sec-butanol and, in particular, the C5-C12-alcohols n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol, n-undecanol and n-dodecanol, and isomers thereof, glycols, for example 1 ,2-ethylene glycol, 1 ,2- and 1 ,3-propylene glycol, 1 ,2-, 2,3- and 1 ,4-butylene glycol, di- and triethylene glycol and di- and tripropylene glycol, ethers, for example methyl tert-butyl ether, 1 ,2-ethylene glycol mono- and dimethyl ether, 1 ,2-ethylene glyco
  • these diluents can also be mixed with water.
  • suitable diluents are C1-C4-alcohols, for example methanol, ethanol, n-propanol, isopropanol, butanol, isobutanol and sec-butanol, glycols, for example 1,2-ethylene glycol, 1,2- and 1,3-propylene glycol, 1,2-, 2,3- and 1,4-butylene glycol, di- and triethylene glycol, and di- and tripropylene glycol, ethers, for example tetra hydrofuran and dioxane, ketones, for example acetone, methyl ethyl ketone and diacetone alcohol (4-hydroxy-4-methyl-2-pentanone), and C1-C4-alkyl esters, for example methyl, ethyl esters, for example methyl, ethyl esters, for example methyl, ethyl esters, for example methyl, eth
  • the diluents are optionally employed in a proportion of from about 0 to 10.0% by weight, preferably from about 0 to 5.0% by weight, based on the total weight of the RM formulation.
  • the antifoams and deaerators (c1 )), lubricants and flow auxiliaries (c2)), thermally curing or radiation-curing auxiliaries (c3)), substrate wetting auxiliaries (c4)), wetting and dispersion auxiliaries (c5)), hydrophobicizing agents (c6)), adhesion promoters (c7)) and auxiliaries for promoting scratch resistance (c8)) cannot strictly be delimited from one another in their action.
  • lubricants and flow auxiliaries often also act as antifoams and/or deaerators and/or as auxiliaries for improving scratch resistance.
  • Radiation-curing auxiliaries can also act as lubricants and flow auxiliaries and/or deaerators and/or as substrate wetting auxiliaries. In individual cases, some of these auxiliaries can also fulfil the function of an adhesion promoter (c8)).
  • a certain additive can therefore be classified in a number of the groups c1) to c8) described below.
  • the antifoams in group c1) include silicon-free and silicon-containing polymers.
  • the silicon-containing polymers are, for example, unmodified or modified polydialkylsiloxanes or branched copolymers, comb or block copolymers comprising polydialkylsiloxane and polyether units, the latter being obtainable from ethylene oxide or propylene oxide.
  • the deaerators in group c1) include, for example, organic polymers, for example polyethers and polyacrylates, dialkylpolysiloxanes, in particular dimethylpolysiloxanes, organically modified polysiloxanes, for example arylalkyl-modified polysiloxanes, and fluorosilicones.
  • organic polymers for example polyethers and polyacrylates
  • dialkylpolysiloxanes in particular dimethylpolysiloxanes
  • organically modified polysiloxanes for example arylalkyl-modified polysiloxanes
  • fluorosilicones fluorosilicones.
  • the action of the antifoams is essentially based on preventing foam formation or destroying foam that has already formed.
  • Antifoams essentially work by promoting coalescence of finely divided gas or air bubbles to give larger bubbles in the medium to be deaerated, for example the compositions according to the invention, and thus accelerate escape of the gas (of the air). Since antifoams can frequently also be employed as deaerators and vice versa, these additives have been included together under group c1).
  • auxiliaries are, for example, commercially available from Tego as TEGO® Foamex 800, TEGO® Foamex 805, TEGO® Foamex 810, TEGO® Foamex 815, TEGO® Foamex 825, TEGO® Foamex 835, TEGO® Foamex 840, TEGO® Foamex 842, TEGO® Foamex 1435, TEGO® Foamex 1488, TEGO® Foamex 1495, TEGO® Foamex 3062, TEGO® Foamex 7447, TEGO® Foamex 8020, Tego® Foamex N, TEGO® Foamex K 3, TEGO® Antifoam 2-18, TEGO® Antifoam 2-18, TEGO® Antifoam 2-57, TEGO® Antifoam 2-80, TEGO® Antifoam 2-82, TEGO® Antifoam 2-89, TEGO® Antifoam 2-92, TEGO® Antif
  • the lubricants and flow auxiliaries typically include silicon-free, but also silicon-containing polymers, for example polyacrylates or modifiers, low-molecular- weight polydialkylsiloxanes.
  • the modification consists in some of the alkyl groups having been replaced by a wide variety of organic radicals. These organic radicals are, for example, polyethers, polyesters or even long-chain alkyl radicals, the former being used the most frequently.
  • polyether radicals in the correspondingly modified polysiloxanes are usually built up from ethylene oxide and/or propylene oxide units. Generally, the higher the proportion of these alkylene oxide units in the modified polysiloxane, the more hydrophilic is the resultant product.
  • auxiliaries are, for example, commercially available from Tego as TEGO® Glide 100, TEGO® Glide ZG 400, TEGO® Glide 406, TEGO® Glide 410, TEGO® Glide 411 , TEGO® Glide 415, TEGO® Glide 420, TEGO® Glide 435, TEGO® Glide 440, TEGO® Glide 450, TEGO® Glide A 115, TEGO® Glide B 1484 (can also be used as antifoam and deaerator), TEGO® Flow ATF, TEGO® Flow 300, TEGO® Flow 460, TEGO® Flow 425 and TEGO® Flow ZFS 460.
  • Suitable radiation-curable lubricants and flow auxiliaries which can also be used to improve the scratch resistance, are the products TEGO® Rad 2100, TEGO® Rad 2200, TEGO® Rad 2500, TEGO® Rad 2600 and TEGO® Rad 2700, which are likewise obtainable from TEGO.
  • Such-auxiliaries are available, for example, from BYK as BYK®-300 BYK®-306, BYK®-307, BYK®-310, BYK®-320, BYK®-333, BYK®-341, Byk® 354, Byk®361, Byk®361 N, BYK®388.
  • the auxiliaries in group c2) are optionally employed in a proportion of from about 0 to 3.0% by weight, preferably from about 0 to 2.0% by weight, based on the total weight of the RM formulation.
  • the radiation-curing auxiliaries include, in particular, polysiloxanes having terminal double bonds which are, for example, a constituent of an acrylate group.
  • Such auxiliaries can be crosslinked by actinic or, for example, electron radiation. These auxiliaries generally combine a number of properties together. In the uncrosslinked state, they can act as antifoams, deaerators, lubricants and flow auxiliaries and/or substrate wetting auxiliaries, while, in the crosslinked state, they increase, in particular, the scratch resistance, for example of coatings or films which can be produced using the compositions according to the invention.
  • Suitable radiation-curing auxiliaries are the products TEGO® Rad 2100, TEGO® Rad 2200, TEGO® Rad 2500, TEGO® Rad 2600 and TEGO® Rad 2700 available from TEGO and the product BYK®-371 available from BYK.
  • Thermally curing auxiliaries in group c3) contain, for example, primary OH groups which are able to react with isocyanate groups, for example of the binder.
  • thermally curing auxiliaries which can be used are the products BYK®- 370, BYK®-373 and BYK®-375 available from BYK.
  • the auxiliaries in group c3) are optionally employed in a proportion of from about 0 to 5.0% by weight, preferably from about 0 to 3.0% by weight, based on the total weight of the RM formulation.
  • the substrate wetting auxiliaries in group c4) serve, in particular, to increase the wettability of the substrate to be printed or coated, for example, by printing inks or coating compositions, for example compositions according to the invention.
  • the generally attendant improvement in the lubricant and flow behaviour of such printing inks or coating compositions has an effect on the appearance of the finished (for example crosslinked) print or coating.
  • auxiliaries are commercially available, for example from Tego as TEGO® Wet KL 245, TEGO® Wet 250, TEGO® Wet 260 and TEGO® Wet ZFS 453 and from BYK as BYK®-306, BYK®-307, BYK®-310, BYK®-333, BYK®-344, BYK®-345, BYK®-346 and Byk®-348.
  • the auxiliaries in group c4) are optionally employed in a proportion of from about 0 to 3.0% by weight, preferably from about 0 to 1.5% by weight, based on the total weight of the liquid-crystalline composition.
  • the wetting and dispersion auxiliaries in group c5) serve, in particular, to prevent the flooding and floating and the sedimentation of pigments and are therefore, if necessary, suitable in particular in pigmented compositions according to the invention.
  • auxiliaries stabilize pigment dispersions essentially through electrostatic repulsion and/or steric hindrance of the pigment particles containing these additives, where, in the latter case, the interaction of the auxiliary with the ambient medium (for example binder) plays a major role.
  • Such wetting and dispersion auxiliaries are commercially available, for example from Tego, as TEGO® Dispers 610, TEGO® Dispers 610 S, TEGO® Dispers 630, TEGO® Dispers 700, TEGO® Dispers 705, TEGO® Dispers 710, TEGO® Dispers 720 W, TEGO® Dispers 725 W, TEGO® Dispers 730 W, TEGO® Dispers 735 W and TEGO® Dispers 740 W and from BYK as Disperbyk®, Disperbyk®-107, Disperbyk®-108, Disperbyk®-110, Disperbyk®-111 , Disperbyk®-115, Disperbyk®-130, Disperbyk®- 160, Disperbyk®-161 , Disperbyk®-162, Disperbyk®-163, Disperbyk®-164, Disperbyk®-165, Disperbyk®-166, Disperbyk®- 167, Disperbyk®
  • auxiliaries which can be allocated to group c2), c4) or c5), includes wetting-, flow- and leveling agents, in particular based on non-ionic fluorosurfactants, which are commercially available from Synthomer under the PolyfoxTM series, for example PolyfoxTMPF-656.
  • the hydrophobicizing agents in group c6) can be used to give water-repellent properties to prints or coatings produced, for example, using compositions according to the invention. This prevents or at least greatly suppresses swelling due to water absorption and thus a change in, for example, the optical properties of such prints or coatings.
  • the composition is used, for example, as a printing ink in offset printing, water absorption can thereby be prevented or at least greatly reduced.
  • Such hydrophobicizing agents are commercially available, for example, from Tego as Tego® Phobe WF, Tego® Phobe 1000, Tego® Phobe 1000 S, Tego® Phobe 1010, Tego® Phobe 1030, Tego® Phobe 1010, Tego® Phobe 1010, Tego® Phobe 1030, Tego® Phobe 1040, Tego® Phobe 1050, Tego® Phobe 1200, Tego® Phobe 1300, Tego® Phobe 1310 and Tego® Phobe 1400.
  • the auxiliaries in group c6) are optionally employed in a proportion of from about 0 to 5.0% by weight, preferably from about 0 to 3.0% by weight, based on the total weight of the RM formulation.
  • Adhesion promoters from group c7) serve to improve the adhesion of two interfaces in contact. It is directly evident from this that essentially the only fraction of the adhesion promoter that is effective is that located at one or the other or at both interfaces. If, for example, it is desired to apply liquid or pasty printing inks, coating compositions or paints to a solid substrate, this generally means that the adhesion promoter must be added directly to the latter or the substrate must be pre-treated with the adhesion promoters (also known as priming), i.e. this substrate is given modified chemical and/or physical surface properties.
  • the substrate has previously been primed with a primer
  • the adhesion properties between the substrate and the primer, but also between the substrate and the printing ink or coating composition or paint play a part in adhesion of the overall multilayer structure on the substrate.
  • Adhesion promoters in the broader sense which may be mentioned are also the substrate wetting auxiliaries already listed under group c4), but these generally do not have the same adhesion promotion capacity.
  • the multiplicity of adhesion promoter systems is not surprising.
  • Adhesion promoters based on silanes are, for example, 3- aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3- aminopropylmethyldiethoxysilane, N-aminoethyl-3-aminopropyltrimethoxysilane, N- aminoethyl-3-aminopropylmethyldimethoxysilane, N-methyl-3- aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3- methacryloyloxypropyltrimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3- mercaptopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane and vinyltrimethoxysilane.
  • silanes are commercially available from Huis, for example under the tradename DYNASILAN®.
  • additives are to be added as auxiliaries from group c7) to the RM formulations according to the invention, their proportion optionally corresponds to from about 0 to 5.0% by weight, based on the total weight of the RM formulation.
  • concentration data serve merely as guidance, since the amount and identity of the additive are determined in each individual case by the nature of the substrate and of the printing/coating composition. Corresponding technical information is usually available from the manufacturers of such additives for this case or can be determined in a simple manner by the person skilled in the art through corresponding preliminary experiments.
  • the auxiliaries for improving the scratch resistance in group c8) include, for example, the abovementioned products TEGO® Rad 2100, TEGO® Rad 2200, TEGO® Rad 2500, TEGO® Rad 2600 and TEGO® Rad 2700, which are available from Tego.
  • the amount data given for group c3) are likewise suitable, i.e. these additives are optionally employed in a proportion of from about 0 to 5.0% by weight, preferably from about 0 to 3.0% by weight, based on the total weight of the liquid-crystalline composition.
  • alkylated monophenols such as 2,6-di-tert-butyl-4-methylphenol, 2-tert-butyl-4,6- dimethylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,6-di-tert-butyl-4-n-butylphenol, 2,6-di- tert-butyl-4-isobutylphenol, 2,6-dicyclopentyl-4-methylphenol, 2-(a-methylcyclohexyl)- 4,6-dimethylphenol, 2,6-dioctadecyl-4-methylphenol, 2,4,6-tricyclohexylphenol, 2,6-di- tert-butyl-4-methoxymethylphenol, nonylphenols which have a linear or branched side chain, for example 2,6-dinonyl-4-methylphenol, 2, 4-dimethyl-6-(1
  • Hydroquinones and alkylated hydroquinones such as 2,6-di-tert-butyl-4- methoxyphenol, 2,5-di-tert-butylhydroquinone, 2,5-di-tert-amylhydrocrainone, 2,6- diphenyl-4-octadecyloxyphenol, 2,6-di-tert-butylhydroquinone, 2,5-di-tert-butyl-4- hydroxyanisole, 3,5-di-tert-butyl-4-hydroxyanisole, 3,5-di-tert-butyl-4-hydroxyphenyl stearate and bis(3,5-di-tert-butyl-4-hydroxyphenyl)adipate,
  • Tocopherols such as a-tocopherol, ⁇ -tocopherol, y-tocopherol, b-tocopherol and mixtures of these compounds, and tocopherol derivatives, such as tocopheryl acetate, succinate, nicotinate and polyoxyethylenesuccinate (“tocofersolate”), hydroxylated diphenyl thioethers, such as 2,2'-thiobis(6-tert-butyl-4-methylphenol), 2,2'-thiobis(4-octylphenol), 4,4'-thiobis(6-tert-butyl-3-methylphenol), 4,4'-thiobis(6-tert-butyl-2-methylphenol), 4,4'-thiobis(3,6-di-sec-amylphenol) and 4,4'-bis(2,6-dimethyl-4- hydroxyphenyl)disulfide,
  • tocopherol derivatives such as tocopheryl acetate, succinate, nico
  • Alkylidenebisphenols such as 2,2'-methylenebis(6-tert-butyl-4-methylphenol), 2,2'- methylenebis(6-tert-butyl-4-ethylphenol), 2,2'-methylenebis[4-methyl-6-(a- methylcyclohexyl)phenol], 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 2,2'- methylenebis(6-nonyl-4-methylphenol), 2,2'-methylenebis(4,6-di-tert-butylphenol), 2,2- ethylidenebis(4,6-di-tert-butylphenol), 2,2'-ethylidenebis(6-tert-butyl-4-isobutylphenol), 2,2'-methylenebis[6-(a-methylbenzyl)-4-nonylphenol], 2,2'-methylenebis[6-(a,a- dimethylbenzyl)-4-nonylphenol
  • O-, N- and S-benzyl compounds such as 3,5,3',5'-tetra-tert-butyl-4,4'- dihydroxydibenzyl ether, octadecyl 4-hydroxy-3,5-dimethylbenzylmercaptoacetate, tridecyl 4-hydroxy-3,5-di-tert-butylbenzylmercaptoacetate, tris(3,5-di-tert-butyl-4- hydroxybenzyl)amine, bis(4-tert-butyl-3-hydroxy-2,6- dimethylbenzyl)dithioterephthalate, bis(3,5-di-tert-butyl-4-hydroxybenzyl)sulfide and isooctyl-3,5-di-tert-butyl-4-hydroxybenzylmercaptoacetate, aromatic hydroxybenzyl compounds, such as 1 ,3,5-tris(3,5-di-tert-butyl-4- hydroxybenz
  • Triazine compounds such as 2,4-bis(octylmercapto)-6-(3,5-di-tert-butyl-4- hydroxyanilino)-1,3,5-triazine, 2-octylmercapto-4,6-bis(3,5-di-tert-butyl-4- hydroxyanilino)-1,3,5-triazine, 2-octylmercapto-4,6-bis(3,5-di-tert-butyl-4- hydroxyphenoxy)-1 , 3, 5-triazine, 2,4,6-tris(3,5-di-tert-butyl-4-hydroxyphenoxy)-1 ,2,3- triazine, 1 ,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate, 1 , 3, 5-tris(4-tert-butyl-
  • Benzylphosphonates such as dimethyl 2,5-di-tert-butyl-4-hydroxybenzylphosphonate, diethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, dioctadecyl 3,5-di-tert-butyl-4- hydroxybenzylphosphonate and dioctadecyl 5-tert-butyl-4-hydroxy-3- methylbenzylphosphonate,
  • Acylaminophenols such as 4-hydroxylauroylanilide, 4-hydroxystearoylanilide and octyl N-(3,5-di-tert-butyl-4-hydroxyphenyl)carbamate
  • Propionic and acetic esters for example of monohydric or polyhydric alcohols, such as methanol, ethanol, n-octanol, i-octanol, octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol, 1,2-propanediol, neopentyl glycol, thiodiethylene glycol, diethylene glycol, triethylene glycol, pentaerythritol, tris(hydroxyethyl)isocyanurate, N,N'- bis(hydroxyethyl)oxalamide, 3-thiaundecanol, 3-thiapentadecanol, trimethyl
  • Propionamides based on amine derivatives such as N,N'-bis(3,5-di-tert-butyl-4- hydroxyphenylpropionyl)hexamethylenediamine, N,N'-bis(3,5-di-tert-butyl-4- hydroxyphenylpropionyl)trimethylenediamine and N,N'-bis(3,5-di-tert-butyl-4- hydroxyphenylpropionyl)hydrazine,
  • Ascorbic acid (Vitamin C) and ascorbic acid derivatives, such as ascorbyl palmitate, laurate and stearate, and ascorbyl sulfate and phosphate,
  • Antioxidants based on amine compounds such as N,N'-diisopropyl-p- phenylenediamine, N,N'-di-sec-butyl-p-phenylenediamine, N, N'-bis(1 ,4- dimethylpentyl)-p-phenylenediamine, N,N'-bis(1-ethyl-3-methylpentyl)-p- phenylenediamine, N,N'-bis(1-methylheptyl)-p-phenylenediamine, N,N'-dicyclohexyl-p- phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-bis(2-naphthyl)-p- phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1 ,3-dimethylbutyl)- N'
  • Phosphines, phosphites and phosphonites such as triphenylphosnine triphenylphosphite, diphenyl alkyl phosphite, phenyl dialkyl phosphite, tris(nonylphenyl)phosphite, trilauryl phosphite, trioctadecyl phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl)phosphite, diisodecyl pentaerythritol diphosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, diisodecyloxy pentaery
  • 2-(2'-Hydroxyphenyl)benzotriazoles such as 2-(2'-hydroxy-5'- methylphenyl)benzotriazole, 2-(3',5'-di-tert-butyl-2'-hydroxyphenyl)benzotriazole, 2-(5'- tert-butyl-2'-hydroxyphenyl)benzotriazole, 2-(2'-hydroxy-5'-(1 ,1,3,3- tetramethylbutyl)phenyl)benzotriazole, 2-(3',5'-di-tert-butyl-2'-hydroxyphenyl)-5- chlorobenzotriazole, 2-(3'-tert-butyl-2'-hydroxy-5'-methylphenyl)-5-chlorobenzotriazole, 2-(3'-sec-butyl-5'-tert-butyl-2'-hydroxyphenyl)benzotriazole, 2-(2'-hydroxy-4'- octyloxyphen
  • 2-hydroxybenzophenones such as the 4-hydroxy, 4-methoxy, 4-octyloxy, 4-decycloxy, 4-dodecyloxy, 4-benzyloxy, 4, 2 ',4 '-tri hydroxy and 2'-hydroxy-4,4'-dimethoxy derivatives,
  • Esters of unsubstituted and substituted benzoic acids such as 4-tert-butylphenyl salicylate, phenyl salicylate, octylphenyl salicylate, dibenzoylresorcinol, bis(4-tert- butylbenzoyl)resorcinol, benzoylresorcinol, 2,4-di-tert-butylphenyl 3,5-di-tert-butyl-4- hydroxybenzoate, hexadecyl-3, 5-di-tert-butyl-4-hydroxybenzoate, octadecyl-3, 5-di-tert- butyl-4-hydroxybenzoate and 2-methyl-4,6-di-tert-butylphenyl-3,5-di-tert-butyl-4- hydroxybenzoate,
  • Acrylates such as ethyl a-cyano-p,p-diphenylacrylate, isooctyl a-cyano-p,p- diphenylacrylate, methyl a-methoxycarbonylcinnamate, methyl a-cyano-p-methyl-p- methoxycinnamate, butyl-a-cyano-p-methyl-p-methoxycinnamate and methyl-a- methoxycarbonyl-p-methoxycinnamate, sterically hindered amines, such as bis(2,2,6,6-tetramethylpiperidin-4-yl)sebacate, bis(2,2,6,6-tetramethylpiperidin-4- yl)succinate, bis(1,2,2,6,6-pentamethylpiperidin-4-yl)sebacate, bis(1-octyloxy-2, 2,6,6- tetramethylpiperidin-4-yl)sebacate, bis
  • Oxalamides such as 4,4'-dioctyloxyoxanilide, 2,2'-diethoxyoxanilide, 2,2'-dioctyloxy- 5,5'-di-tert-butoxanilide, 2,2'-didodecyloxy-5,5'-di-tert-butoxanilide, 2-ethoxy-2'- ethyloxanilide, N,N'-bis(3-dimethylaminopropyl)oxalamide, 2-ethoxy-5-tert-butyl-2'- ethoxanilide and its mixture with 2-ethoxy-2'-ethyl-5,4'-di-tert-butoxanilide, and mixtures of ortho-, para-methoxy-disubstituted oxanilides and mixtures of ortho- and para-ethoxy-disubstituted oxanilides, and
  • 2-(2-hydroxyphenyl)-1 ,3,5-triazines such as 2,4,6-tris-(2-hydroxy-4-octyloxyphenyl)- 1 ,3,5-triazine, 2-(2-hydroxy-4-octyloxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1 ,3,5- triazine, 2-(2,4-dihydroxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1 ,3,5-triazine, 2,4-bis(2- hydroxy-4-propyloxyphenyl)-6-(2,4-dimethylphenyl)-1 ,3,5-triazine, 2-(2-hydroxy-4- octyloxyphenyl)-4,6-bis(4-methylphenyl)-1 ,3,5-triazine, 2-(2-hydroxy-4- dodecyloxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1 ,
  • the RM formulation is dissolved in a suitable solvent, which are preferably selected from organic solvents.
  • the solvents are preferably selected from ketones such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone or cyclohexanone; acetates such as methyl, ethyl or butyl acetate or methyl acetoacetate; alcohols such as methanol, ethanol or isopropyl alcohol; aromatic solvents such as toluene or xylene; alicyclic hydrocarbons such as cyclopentane or cyclohexane; halogenated hydrocarbons such as di- or trichloromethane; glycols or their esters such as PGMEA (propyl glycol monomethyl ether acetate), ⁇ -butyrolactone. It is also possible to use binary, ternary or higher mixtures of the above solvents. In particular, for multilayer applications, methyl iso butyl ketone is the preferred utilized solvent
  • the total concentration of all solids, including the RMs, in the solvent(s) is preferably from 5 to 60%, more preferably from 10 to 50%, in particular from 10 to 35%.
  • the RM formulation comprises, besides one or more compounds or formula I and the chiral isomerisable compounds: a) optionally one or more multi - or direactive polymerisable mesogenic compounds, preferably selected from compounds of formula DRM and corresponding subformulae, and/or b) optionally one or more additional polymerisable chiral compounds, preferably selected from formulae CRM or its subformulae, and/or c) optionally one or more additional non-polymerisable chiral compounds, preferably selected from formulae C-l, C-ll and C-lll, and/or d) optionally one or more monoreactive mesogens, preferably selected from compounds of formula MRM and corresponding subformulae, and/or e) optionally one or more photoinitiators, and/or f) optionally one or more antioxidative additives, and/or g) optionally one or more adhesion promotors, and/or h) optionally one or more surfactants, and
  • the RM formulation comprises: a) one or more compounds of formula I, or its corresponding preferred subformulae, b) one or more chiral isomerisable compounds, preferably selected from formula I*, more preferably from formula l*A, or their corresponding preferred subformulae, c) optionally one or more, preferably two or more, direactive polymerisable mesogenic compounds, preferably selected from the compounds of formula DRMa-1, d) optionally one or more, preferably two or more, monoreactive polymerisable mesogenic compounds, preferably selected from compounds of formulae MRM-1 , and/or MRM-4, and/or MRM-6, and/or MRM-7, e) optionally one or more additional polymerisable chiral compounds, preferably selected from formulae CRM or its subformulae, f) optionally one or more additional non-polymerisable chiral compounds, preferably selected from formulae C-l, C-ll and C-lll, g) optionally
  • the RM mixture and RM formulation can be prepared in a manner conventional per se, for example by mixing one or more of the above-mentioned chiral isomerisable compounds with one or more RMs as defined above, and optionally with further additives.
  • the invention further relates to a process of preparing an individual polymer film comprising, preferably consisting of, the steps of p1) providing a first layer of an RM mixture or RM formulation as described above and below onto a substrate, which is optionally provided with an alignment layer capable of inducing a planar alignment to the adjacent layer of the RM mixture, p2) optionally removing any solvents, if present, p3) optionally annealing the RM mixture (i.e.
  • a first step of irradiation of the RM mixture with actinic radiation preferably with UV radiation, in air (1 st UV step)
  • p5) optionally annealing the RM mixture preferably at a temperature where it is in the chiral nematic phase
  • p6) a second step of irradiation of the RM mixture with actinic radiation preferably with UV radiation, in an inert gas atmosphere (2 nd UV step).
  • the process of preparing an individual polymer film according to the present invention comprises the following steps: p11) providing a layer of an RM mixture or RM formulation as described above and below, or a solution thereof, onto a substrate, which is preferably equipped with an alignment layer inducing planar alignment layer, for example a rubbed polyimide layer or a photo alignment layer, for example by spin-coating or printing methods, and optionally removing any solvents present, p22) optionally removing any solvents, if present, p33) optionally annealing the layer of the RM mixture (i.e., without solvent), preferably at a temperature where it is in the chiral nematic phase, p44) exposing the layer of the RM mixture (i.e., without solvent) to UV light, which causes photoisomerisation of the chiral compound comprising the photoisomerisable group and provides the chiral structure with the biased helical pitch, preferably to unpolarised UV light, very preferably to unpolarised
  • UV light which causes photopolymerisation of the RMs, preferably to unpolarised UV light, very preferably to unpolarised UVA light, for example with a dose of 200 to 2000 mJ/cm 2 cm 2 , preferably in an inert gas atmosphere, e.g. nitrogen and at ambient temperature ("2 nd UV step").
  • an inert gas atmosphere e.g. nitrogen and at ambient temperature
  • the invention further relates to a process of process of preparing a half-wave plate comprising, preferably consisting of, the steps of: p1) forming a first quarter-wave plate by a process comprising, preferably consisting of, the following steps p11) providing a layer of a chiral RM mixture as described above and below onto a substrate, which is optionally provided with an alignment layer capable of inducing a planar alignment to the adjacent layer of the chiral reactive mesogen mixture, p12) optionally removing any solvents, if present, p13) optionally annealing the layer of the chiral reactive mesogen mixture, preferably at a temperature where it is in the chiral nematic phase, p14) a first step of irradiation of the chiral reactive mesogen mixture with actinic radiation, preferably with UV radiation, in air (1 st UV step), p15) optionally annealing the layer of the chiral reactive mesogen mixture, preferably at a
  • the first and second quarter-wave plate can be combined with each other for example by laminating the films onto each other.
  • the second quarter-wave plate can be prepared directly on top of the first quarter-wave plate serving as a substrate. Lamination or coating of the films can also be done in a roll-to-roll process.
  • all irradiation or UV exposure steps are carried out at room temperature, and the layer of the RM mixture or RM formulation is not subjected to heat treatment during or between the irradiation or UV exposure steps.
  • the first irradiation or 1 st UV step causes photoisomerisation of the chiral compound comprising the photoisomerisable group and provides the chiral structure with the biased helical pitch.
  • the second irradiation or 2 nd UV step causes photopolymerisation of the polymerisable mesogenic compounds and thereby fixes the chiral structure.
  • this effect allows to use also RMs which have an absorption maximum in the same UV wavelength range as the photoisomerisable chiral compound, and would therefore polymerise unless being hindered. Since it is often difficult to find suitable RMs with very high birefringence as well as suitable chiral photoisomerisable compounds, this allows a broader choice of suitable mixture components, so that the chiral RM mixture composition can be more easily adapted to the specific requirements for the final use of the polymer film as half-wave plate.
  • this effect can be advantageously used to polymerise the film only partially, with a gradient in the film thickness direction.
  • the RMs at the top of the film, which are exposed to oxygen have a lower rate of polymerisation, whereas the RMs at the bottom of the film, at the substrate interface, are far less exposed to an hindered by oxygen so that they can polymerise more easily.
  • the polymerised RM mixture exhibits an accelerated chiral rotation in direction to the main plane of the polymer film or the film thickness.
  • the polymerised RM mixture exhibits a biased pitch, such that the chiral rotation angle increases or decreases incrementally through the film thickness.
  • the RM mixture or RM formulation can be coated or printed onto the substrate, for example by spin-coating, printing, or other known techniques, and the solvent is evaporated off before polymerisation. In most cases, it is suitable to heat the mixture in order to facilitate the evaporation of the solvent.
  • the RM mixture or RM formulation can be applied onto a substrate by conventional coating techniques like spin coating, bar coating or blade coating. It can also be applied to the substrate by conventional printing techniques which are known to the expert, like for example screen printing, offset printing, reel-to-reel printing, letter press printing, gravure printing, rotogravure printing, flexographic printing, intaglio printing, pad printing, heat-seal printing, ink-jet printing or printing by means of a stamp or printing plate.
  • Suitable substrate mediums and substrates are known to the expert and described in the literature, as for example conventional substrates used in the optical films industry, such as glass or plastic.
  • Especially suitable and preferred substrates for polymerisation are polyester such as polyethyleneterephthalate (PET) or polyethylenenaphthalate (PEN), polyvinylalcohol (PVA), polycarbonate (PC), triacetylcellulose (TAC), cyclo-olefin polymers (COP), or commonly known color filter materials, preferably triacetylcellulose (TAC), cyclo-olefin polymers (COP), or commonly known colour filter materials.
  • PET polyethyleneterephthalate
  • PEN polyethylenenaphthalate
  • PVA polyvinylalcohol
  • PC polycarbonate
  • TAC triacetylcellulose
  • COP cyclo-olefin polymers
  • color filter materials preferably triacetylcellulose (TAC), cyclo-olefin polymers (COP), or commonly known colour filter materials.
  • the substrate has a surface grating or surface pattern.
  • the substrate is prepared from a photoalignment layer (PAL) which is patterned by laser interferometry to create a grating pattern with a defined pitch.
  • PAL photoalignment layer
  • the Friedel-Creagh-Kmetz rule can be used to predict whether a mixture will adopt planar or homeotropic alignment, by comparing the surface energies of the RM layer ( ⁇ RM) and the substrate (y s ):
  • planar alignment layers are known in the art, like for example rubbed polyimide or alignment layers prepared by photoalignment as described in US 5,602,661 , US 5,389,698 or US 6,717,644.
  • the process according to the invention contains a process step where the RM mixture is allowed to rest for a period of time in order to evenly redistribute the RM mixture on the substrate (herein referred to as “annealing”).
  • the layer stack is annealed for a time between 10 seconds and 1 hour, preferably between 20 seconds and 10 minutes and most preferably between 30 seconds and 2 minutes.
  • the annealing is preferably performed at room temperature.
  • the RM mixture preferably consists of compounds that align spontaneously when being deposited as a mixture onto the substrate. Therefore, preferably the LC medium is not subjected to heat treatment to align the mesogenic or liquid-crystalline compounds before the UV exposure.
  • the layer stack can be cooled down to room temperature after annealing at an elevated temperature.
  • the cooling can be performed actively with the help of cooling aids or passively just by letting the layer stack rest for a given time.
  • the RM mixture in the 1 st UV step is exposed to actinic radiation as described for example in WO 01/20394, GB 2,315,072 or WO 98/04651.
  • Actinic radiation means irradiation with light, like UV light, IR light or visible light, irradiation with X-rays or gamma rays, or irradiation with high-energy particles, such as ions or electrons.
  • the 1 st UV step is carried out by photo irradiation, in particular with UV light, especially with UVA light.
  • a source for actinic radiation for example a single UV lamp or a set of UV lamps can be used. When using a high lamp power the curing time can be reduced.
  • a laser like e.g. a UV laser, an IR laser, or a visible laser.
  • the curing time is dependent, inter alia, on the reactivity of the photoreactive compounds, the thickness of the coated layer, and the power and selected wavelength of the UV lamp.
  • the curing time is preferably ⁇ 5 minutes, very preferably ⁇ 3 minutes, most preferably ⁇ 1 minute. For mass production, short curing times of ⁇ 30 seconds are preferred.
  • a suitable UV radiation power in the 1 st UV step is preferably in the range from 5 to 300 mWcm’ 2 , more preferably in the range from 50 to 250 mWcm’ 2 and most preferably in the range from 100 to 180 mWcm -2 .
  • a suitable UV dose is preferably in the range from 20 to 1000 mJcnr 2 , more preferably in the range from 30 to 800 mJcnr 2 , very preferably in the range from 40 to 500 mJcnr 2 , most preferably in the range from 40 to 200 mJcnr 2 .
  • the first irradiation step or 1 st UV step are preferably performed in air.
  • the first irradiation step or 1 st UV step are preferably performed at room temperature.
  • Photopolymerisation in the second irradiation step of the RM mixture is preferably achieved by exposing it to actinic radiation.
  • Actinic radiation means irradiation with light, like UV light, IR light or visible light, irradiation with X-rays or gamma rays, or irradiation with high-energy particles, such as ions or electrons.
  • polymerisation is carried out by photo irradiation, in particular with UV light.
  • a source for actinic radiation for example a single UV lamp or a set of UV lamps can be used. When using a high lamp power the curing time can be reduced.
  • Another possible source for photo radiation is a laser, like e.g. a UV laser, an IR laser, or a visible laser.
  • the curing time for the photopolymerisation is dependent, inter alia, on the reactivity of the RM mixture, the thickness of the coated layer, the type of polymerisation initiator and the power of the UV lamp.
  • the curing time is preferably ⁇ 5 minutes, very preferably ⁇ 3 minutes, most preferably ⁇ 1 minute. For mass production, short curing times of ⁇ 30 seconds are preferred.
  • a suitable UV radiation power for the photopolymerisation is preferably in the range from 100 to 1000 mWcm-2, more preferably in the range from 200 to 800 mWcnr 2 and most preferably in the range from 300 to 600 mWcm’ 2 .
  • a suitable UV dose is preferably in the range from 25 to 16500 mJcnr 2 , more preferably in the range from 50 to 7200 mJcnr 2 , very preferably in the range from 100 to 3500 mJcnr 2 and most preferably in the range from 200 to 2000 mJcnr 2 .
  • Photopolymerisation (the second irradiation step or 2 nd UV step) is preferably performed under an inert gas atmosphere, preferably in a nitrogen atmosphere.
  • Photopolymerisation (the second irradiation step or 2 nd UV step) is preferably performed at room temperature.
  • the preferred thickness of a polymer film according to the present invention is determined by the optical properties desired from the film or the final product.
  • the polymer film preferably has a thickness of from 0.1 to 10 pm, very preferably from 0.2 to 5 pm, in particular from 0.3 to 3 pm.
  • the minimum helical pitch is ⁇ 1200 nm, very preferably from 200 to 1200 nm.
  • the helical pitch increases from the side of the polymer film close to the substrate on which it is prepared throughout the thickness direction.
  • the polymer film according to the present invention shows planar alignment, i.e. , the LC molecules are oriented parallel to the film plane and the helical axis is oriented substantially perpendicular to the film plane.
  • the polymer film according to the present invention shows tilted alignment, i.e., the LC molecules are oriented at an angle to the film plane and the helical axis is oriented at an angle to the film plane, also referred as tilt angle.
  • the tilt angle between the helix axis and the axis normal to the film plane is from 5° to 45°, very preferably from 15° to 45°.
  • the tilt angle between the helix axis and the axis normal to the film plane is from 0 to 15°, very preferably from 0 to 5°.
  • Planar alignment can be induced for example by providing an alignment layer on the substrate, for example a polyimide alignment layer, as described above.
  • Tilted alignment can be achieved for example by adding an alignment additive to the chiral RM mixture, or by using a substrate with a surface grating or pattern, e.g. a PB grating.
  • the birefringence (An) of the polymer film according to the present invention is preferably in the range from 0.20 to 0.60, more preferably from 0.25 to 0.55, very preferably from 0.30 to 0.50.
  • the birefringence and accordingly optical retardation depends on the thickness of a film and the tilt angle of optical axis in the film (cf. Berek’s compensator). Therefore, the skilled expert is aware that different optical retardations or different birefringence can be induced by adjusting the orientation of the liquid-crystalline molecules in the polymer film.
  • the optical retardation as a function of the thickness of the polymer film according to the present invention is less than 200 nm, preferable less than 180 nm and even more preferable less than 150 nm.
  • the optical retardation as a function of the thickness of the polymer film according to the present invention is in the range from 110 nm to 170 nm, very preferably from 130 nm to 150 nm.
  • the minimum twist angle is 0°.
  • the maximum twist angle is in the range from 70 to 150°, very preferably from 80 to 120°, most preferably from 90 to 110°.
  • the twist angle varies from 0° to 150°, very preferably from 0° to 120°, most preferably from 0° to 110° in the direction of the film thickness.
  • the lower twist value is at the side of the polymer film adjacent to the substrate on which it is prepared.
  • the average twist angle in the polymer film is preferably in the range from 10 to 40°, very preferably from 15 to 35°, most preferably from 20 to 30°.
  • the resulting polymer film can be removed from the substrate and combined with other substrates or optical films by a laminating process known by the skilled person.
  • Suitable substrates and optical films are given above and include especially polarisers, in particular linear polarisers, photoalignment layers, or diffraction gratings, for example PB gratings.
  • the polymer film according to the present invention has good adhesion to plastic substrates, in particular to TAG, COP, and colour filters. Accordingly, it can be used as adhesive or base coating for subsequent LC layers which otherwise would not well adhere to the substrates.
  • two polymer films each representing a quarter-wave plate, are combined into a bilayer.
  • the two quarter-wave plates can be cobined by laminating one quarter-wave plate directly onto the other quarter wave plate.
  • the second quarter-wave plate is directly prepared on the first quarter-wave plate which serves as a substrate.
  • the invention thus further relates to a process of preparing a half-wave plate, wherein two quarter-wave plates having a pitch gradient are formed by a process as described above and below comprising, preferably consisting of, process steps p1) to p6), preferably of process steps p11) to p66), and wherein the first quarter-wave plate is laminated onto the second quarter-wave plate or vice versa.
  • the invention further relates to a process of preparing a half-wave plate, wherein a first quarter-wave plate having a pitch gradient is formed by a process as described above and below comprising, preferably consisting of, process steps p1) to p6), preferably of process steps p11) to p66), and a second quarter-wave plate is formed by a process as described above and below, wherein the first quarter-wave plate is used as the substrate.
  • the two quarter-wave plates are combined such that their surfaces with the higher twist are facing each other (inner sufarces), and their surfaces with the lower twist represent the outer surfaces of the bilayer thus formed. Since the low twist corresponds to a long pitch (i.e. a high pitch value) and the high twist corresponds to a short pitch (i.e. a low pitch value), this means that the two quarter-wave plates in the half-wave plate of this preferred embodiment are combined such that their surfaces with the shorter pitch are facing each other.
  • Fig. 2. shows the twist profile in a half-wave plate according to the present invention consisting of two quarter-wave plates L1 and L2, each formed by a layer of a polymerised chiral RM mixture with helically twisted structure and a pitch gradient.
  • the black line indicates the boundary between the inner surfaces of the two layers L1 and L2.
  • the polymer film of the present invention can also be used as alignment film or substrate for other liquid-crystalline or RM materials.
  • the inventors have found that the polymer film obtainable from a RM formulation as described above and below, is in particular useful for multilayer applications due to its improved dewetting characteristics. In this way, stacks of optical films or preferably polymer films can be prepared.
  • the invention further relates to an optical, electrooptical or electronic device or a component comprising a half-wave plate as described above and below.
  • the component is a diffraction grating, very preferably a PBG, PBL or Bragg PG, comprising a half-wave plate obtained from an RM mixture or RM formulation according to the present invention as described above and below.
  • the polymer films and RM mixtures according to the present invention are useful in optical elements like polarisers, compensators, alignment layer, circular polarisers or colour filters in liquid crystal displays or projection systems, decorative images, for the preparation of liquid crystal or effect pigments, and especially in reflective films with spatially varying reflection colours, e.g. as multicolour image for decorative, information storage or security uses, such as non-forgeable documents like identity or credit cards, banknotes etc..
  • the polymer film according to the present invention can be used in displays of the transmissive or reflective type. It can be used in conventional OLED displays or LCDs, in particular LCDs.
  • m.p. denotes the melting point
  • cl.p. denotes the clearing point
  • T g glass transition temperature.
  • C denotes the crystalline state
  • N denotes the nematic phase
  • SA, SB etc. denotes the smectic A phase
  • Sx denotes an unidentified smectic phase
  • X denotes an unidentified mesophase
  • I denotes the isotropic phase.
  • the values between these symbols represent the transition temperature in °C.
  • the optical and electro optical data are measured at 20°C, unless expressly stated otherwise.
  • “Clearing point” and “clearing temperature” mean the temperature of the transition from an LC phase into the isotropic phase.
  • the percentages of solid components in an RM mixture or RM formulation as described above and below refer to the total amount of solids in the mixture or formulation, i.e. without any solvents.
  • optical, electro optical properties and physical parameters like birefringence, permittivity, electrical conductivity, electrical resistivity and sheet resistance, refer to a temperature of 20°C.
  • Omnirad®907 is a photoinitiator, being commercially available (IGM Resins).
  • BYK®-388 is c surfactant, being commercially available (BYK, Germany).
  • the achromaticity of a half-waveplate according to the present invention when put between two crossed polarizers, is compared with the achromaticity of a half- waveplate of prior art.
  • a half-waveplate between crossed polarizers will allow a maximum of 50% light through the top polarizer. Any reduction in light intensity across the wavelength range will be a reduction in performance and render the polarizer less suitable for this application. Thus, in this example any reduction in light intensity less than 49% is considered as a failure.
  • the achromaticity of a film stack S1 as shown in Table 1 below, including a half- waveplate according to the present invention between two crossed polarizers, is determined using DIMOS 1D software.
  • the half-wave plate in Table 1 consists of two layers L1 and L2 of polymerized mixture M2, each layer having a varying twist with a calculated asymmetric twist profile as shown in Table 2 below and having quarter- wave retardation.
  • Fig. 2. shows the twist profile in the half-wave plate according to the present invention consisting of the two layers L1 and L2 with asymmetric twist profile.
  • the black line indicates the boundary between the inner surfaces of the two layers L1 and L2.
  • the achromaticity of a film stack CS1 as shown in Table 3 below, including a half-waveplate according to prior art between two crossed polarizers, is determined using DI MOS 1D software.
  • the half-wave plate in Table 3 consists of a non-twisted layer C1 of polymerized mixture M2 having half-wave retardation.
  • the achromaticity is determined for unpolarized light input (400-700nm in 1nm steps), with the light detected after it exits the full stack including polarizers.
  • Fig. 3(a) and Table 4 show the transmission vs. wavelength for the film stack S1 of Example 1 with a half-wave plate according to the present invention, consisting of two quarter-wave plates L1 and L2 with an asymmetric twist profile, between crossed polarizers (b).
  • Fig. 3(b) and Table 5 show the transmission vs. wavelength for the film stack CS1 of Comparison Example 1 with a standard half-wave plate between crossed polarizers.
  • the film stack S1 according to the invention with the half- wave plate consisting of two layers with asymmetric twist profile, has a much higher achromaticity than the film stack CS1 according to prior art, with the standard half- wave plate.
  • the film stack CS1 with the standard half- wave plate of prior art shows a 49% transmission only at a wavelength of 550nm.
  • the film stack S1 with the variable twist half-wave plate of the invention has a spectral bandwidth of more than 200nm, and thus exhibits significantly improved performance over the full visible spectrum.
  • the half-waveplate of Example 1 according to the present invention is compared with a half-waveplate of prior art made by stacking two untwisted RM films on top of each other with precise angular control.
  • the achromaticity of the film stack of Example 1 with a half-waveplate according to the invention is determined using DIMOS 1D software.
  • Fig. 4(a) and Table 7 show the transmission vs. wavelength for the film stack S1 of Example 1 with a half-wave plate according to the present invention, consisting of two quarter-wave plates with an asymmetric twist profile, between crossed polarizers.
  • the half-wave plate in stack CS2 consists of two fractional waveplates, each consisting of a non-twisted layer C2 or C3, respectively, of polymerized mixture M2 having quarter-wave retardation.
  • the achromaticity is determined for unpolarized light input (400-700nm in 1nm steps), with the light detected after it exits the full stack including polarizers.
  • Fig. 4(a) and Table 7 show the transmission vs. wavelength for the film stack S1 of Example 1 with a half-wave plate according to the present invention, consisting of two quarter-wave plates L1 and L2 with an asymmetric twist profile, between crossed polarizers.
  • Fig. 4(b) and Table 8 show the transmission vs. wavelength for the film stack CS2 of Comparison Example 2 with a standard half-wave plate, consisting of two non-twisted quarter-wave plates C2 and C3, between crossed polarizers.
  • the film stack S1 of the invention with a half-wave plate consisting of two layers with asymmetric twist profile, has a much higher achromaticity, with a spectral bandwidth of more than 200nm and good performance over the full visible spectrum, compared to the film stack CS2 of prior art with a half-wave plate consisting of two non-twisted fractional quarter-wave plates.
  • the half-wave plate of the invention also has the advantage of simpler manufacture.
  • the first RM layer L1 can act as an alignment layer for the second RM layer L2, and vice versa. Using this approach it is very easy to build an RM film stack by coating an extra layer on top of an already cured RM film.
  • the following chiral RM mixture is prepared: . % % % %
  • DRMal b lrganox®1076 is a stabilizer, being commercially available (Ciba AG, Basel, Switzerland).
  • NCI®-930 is a photoinitiator, being commercially available (Adeka Coorporation, Japan).
  • BYK®-310 is a surfactant being commercially available (BYK, Germany).
  • RM formulation F1 is prepared by dissolving mixture M1 at 36% solids in a solvent blend of toluene: cyclohexanone (7:3).
  • a polymer film is prepared from formulation F1 by the following process:
  • An alignment layer is prepared on a TAC substrate with 60pm thickness by barcoating Nissan PAL HSPA-152 with an MB#3 bar, baking the coated substrate at 110°C for 60 seconds and exposed to polarised UV light utilizing a wire grid polariser and a high pressure mercury lamp (LH6 fusion) with 67 mW/cm 2 and 12 mJ/cm 2 UVA.
  • the formulation F1 is barcoated onto the alignment layer using a MB#6 bar, and annealed at 60°C for 60 seconds, followed by a first exposure step in an air atmosphere to UV light utilizing a high pressure mercury lamp (LH6 fusion) with 180 mW/cm 2 and 40 mJ/cm 2 UVA.
  • LH6 fusion high pressure mercury lamp
  • the sample is purged with nitrogen for 60 seconds and in a second step exposed to UV light utilizing a high pressure mercury lamp (LH6 fusion) with 520 mW/cm 2 and 220 mJ/cm 2 UVA.
  • LH6 fusion high pressure mercury lamp
  • the resulting polymer film P1 is measured with an Axometrics Axostep, once film up (Light source, Substrate, Polymer Film Detector) and once film down (Light source, Polymer Film, Substrate, Detector).
  • the spectral polarisation states are plotted on a Poincare sphere.
  • the polarisation ellipse varies for each wavelength, but each has left-handed rotation. Due to the asymmetry of the twist in the z direction the film does not act reversibly.

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  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
  • Liquid Crystal (AREA)
  • Polarising Elements (AREA)

Abstract

L'invention concerne une lame demi-onde comprenant deux couches d'un polymère à cristaux liquides (LC) chiraux ayant un gradient de pas (sous la forme d'une sous-catégorie de matériau à cristaux liquides), son procédé de préparation, et son utilisation en tant qu'élément optique diffractif dans des composants ou dispositifs optiques ou électrooptiques, en particulier pour des optiques numériques ou des applications de réalité augmentée ou de réalité virtuelle (AR/VR) comme des polariseurs, des compensateurs optiques, des films réfléchissants, des réseaux de diffraction ou de surface, des réseaux de polarisation de Bragg (Bragg PG), des réseaux de volume de polarisation (PVG), des hologrammes de volume de polarisation (PVH), des réseaux de Pancharatnam Berry (PB), des éléments d'orientation de faisceau non mécanique, des guides d'ondes optiques, des coupleurs optiques, des combineurs optiques, des diviseurs de faisceau de polarisation, des miroirs partiels ou des lentilles.
PCT/EP2024/066836 2023-06-20 2024-06-17 Lame demi-onde Pending WO2024260930A1 (fr)

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