Optical element comprising chiral LC polymer film

Abstract

The present invention relates to an optical element comprising a chiral liquid crystal (LC) polymer film as a sub-class of liquid crystal materials, a method for the production thereof and the use of the optical element as a diffractive optical element in optical or electro-optical components or devices, in particular for digital optical or augmented reality or virtual reality (AR / VR) applications, such as a polarizer, an optical compensator, a reflective film, a diffraction grating or surface grating, a Bragg polarization grating (Bragg PG), a polarization volume grating (PVG), a polarization volume hologram (PVH), a Pangulam-Bell (PB) grating, a non-mechanical beam steering element, an optical waveguide, an optical coupler, an optical combiner, a polarization beam splitter, a partial mirror or a lens.

Description

TECHNICAL FIELD

[0001] The present invention relates to an optical element comprising a chiral liquid crystal (LC) polymer film (as a sub-class of liquid crystal materials), a method for its preparation and the use of the optical element as a diffractive optical element in an optical or electro-optical assembly or device, especially for digital optical or augmented or virtual reality (AR / VR) applications, such as polarizers, optical compensators, reflective films, diffractive or surface gratings, Bragg polarization gratings (Bragg PG), polarization volume gratings (PVG), polarization volume holograms (PVH), Pancharatnam-Berry (PB) gratings, non-mechanical beam steering elements, optical waveguides, optical couplers, optical combiners, polarization beam splitters, partial mirrors or lenses. BACKGROUND

[0002] In the emerging field of AR / VR (augmented reality / virtual reality), some applications such as optical waveguides require materials that display a high average refractive index (n Reactive mesogen (RM) materials have been proposed for these applications, for example for the creation of diffractive gratings such as Pancharatnam-Berry gratings (PBG) and lenses, also known as Bragg polarization gratings (Bragg PG) or polarization volume gratings (PVG). These RM materials can be polymerized into liquid crystal polymer (LCP) networks with carefully controlled properties. The optimal alignment of RMs for use in PBGs is typically achieved for chiral nematic (hereinafter also referred to as cholesteric) systems, where the chiral structure promotes self-organization of the host LC.

[0003] In particular, Bragg PGs represent a class of diffractive optical elements that offer a unique way of making gratings with high efficiency and wide angular bandwidth. These have been shown to outperform standard surface-relief gratings (SRG) and volume holographic gratings (VHG). Bragg PGs can be made by polymerizing RMs that exhibit multilayer coating capabilities. The ability to carefully control the optical properties and alignment of RMs through variations in formulation and processing conditions makes these materials extremely versatile in the production of thin, durable and customizable optical elements. However, one of the challenges faced in this field is the production of optical elements that exhibit high performance over a wide range of incident angles.

[0004] Xiang, X., Kim, J. & Escuti, M.J. Sci Rep 8, 7202 (2018) reported a possible solution to the problem of a wide acceptance angle of light and utilized two discrete sub-layers of polymer films obtained from a RM. The layers have different concentrations of chiral dopants, which results in the material adopting different amounts of cholesteric twist. This twist in combination with a variable alignment profile imparted by the photoalignment layer results in two different tilt angles occurring within the sub-layers. This change significantly improves the first order diffraction efficiency of the grating to a 40° angular bandwidth, compared to the approximately 20° previously reported at a single tilt angle in Xiao Xiang et al., Optics Express, 25(16), 19298 (2017).

[0005] Figure 1 An exemplary illustration of a double layer PBG according to the prior art is shown in the figure, which is formed from LCPs with an average refractive index and birefringence Δn on a photoalignment layer (PAL) disposed on a substrate and having a grating pitch Λ x Due to the different chiral pitches p1 and p2 in each layer, the two layer LCP PBG has layer thicknesses d1 and d2, and different tilt angles θ1 and θ2.

[0006] A significant drawback of this approach is the need for multiple layer coating, which increases production complexity and cost. Therefore, multiple RM coating steps must be performed, where a first RM layer is coated on an alignment layer, typically a photoalignment layer (PAL) or a lithographically fabricated alignment layer. The RM layer should adopt the alignment direction promoted by the alignment layer, and the material is cured to obtain an LCP. The next layer of RM is then coated directly on top of the previous LCP layer. In order to achieve good quality alignment, the coated layer must not damage the previous layer, and strong intermolecular interactions must occur between the layers to impart the alignment direction from one layer to the next.

[0007] However, in the process of preparing a multi-layer PBG using conventional RM materials, it has been found that the overcoating of RM layers is challenging, which is difficult to prevent damage in the lower RM layers. This requires good control of the degree of curing and cross-linking. Also, good intermolecular forces are required between the layers to enable good alignment transfer to subsequent layers. When RM materials with very high refractive indices are used, the alignment often does not transfer well between the layers, resulting in misaligned moire-like textures in the deposited second layer of RM.

[0008] K. Yin et al., Proc. SPIE 11708, Advances in Display Technologies XI, 1170804 (5 March 2021) report a method that is able to create continuously variable tilt angles in a single coating. This method utilizes a UV dye (azobenzene) as dopant that competes with the UV absorption of the photoinitiator, thereby reducing the amount of UV light that is able to reach the bottom of the film. Subsequently, this mixture is cured by irradiation with a low-power UV lamp over a period of 40 minutes, during which the temperature of the film slowly rises, leading to a change in the chiral pitch. As the UV dose is different throughout the film, different curing rates can be achieved, thereby polymerizing the chiral structure at different points, creating a variable chiral pitch. However, while complex structures are achieved in a single layer, this long and careful temperature-controlled curing process makes this method less attractive for commercial applications.

[0009] Therefore, there is still a need for improved chiral LC polymer films and RM materials used therein, which can be used as diffractive optical components, in particular as Bragg PGs, which do not exhibit the disadvantages of the prior art films, materials and methods, or if they do, only to a lesser extent, and which can be prepared in a simple, time- and cost-saving manner in reproducible quality and in large quantities compatible with mass production.

[0010] It is an object of the present invention to provide improved chiral LC polymer films and methods of preparing the same which meet one or more of the above needs. Other objects of the present invention will be immediately evident to a person skilled in the art from the following detailed description.

[0011] Surprisingly, the inventors of the present invention have found that by providing the chiral LC polymer films and methods of preparing the same as disclosed and claimed below, it is possible to meet, preferably simultaneously meet, one or more, preferably all, of the above needs.

[0012] In particular, it has been surprisingly found that it is possible to prepare a diffractive grating of a layer (hereinafter also referred to as “monolithic film”) containing only one chiral RM mixture containing a chiral compound having a photoisomerizable group which can undergo a photoisomerization reaction leading to a decrease of its helical twisting power (HTP). This allows for a fast photo-driven adjustment of the chiral pitch in the RM layer and results in an alignment profile with an accelerated pitch and a non-linear twist profile. Furthermore, the chiral RM mixture utilizes a RM having an extremely high birefringence. When aligning such a chiral RM mixture on a grating alignment layer, a diffractive grating with high diffraction efficiency and a wide angular bandwidth is obtained. SUMMARY

[0013] The present invention relates to an optical element, preferably a diffractive grating or a polarizing grating, comprising a monolithic film of a polymerized chiral RM mixture having a helical twist orientation, wherein the helical pitch increases or decreases in the direction of the layer thickness.

[0014] Preferably, the chiral RM mixture comprises at least one, preferably exactly one, chiral compound having one or more isomerizable groups, preferably one or more photoisomerizable groups, which is preferably polymerizable.

[0015] Further preferably, the chiral RM mixture comprises at least one RM having a birefringence of > 0.25, very preferably > 0.28.

[0016] Preferably, in the monolithic film of the polymerized chiral RM mixture having a helical twist orientation, the tilt angle between the helical axis and an axis perpendicular to the plane of the film is from 0 to 45°.

[0017] Further preferably, in the monolithic film of the polymerized chiral RM mixture having a helical twist orientation, the helical pitch is < 1200 nm, very preferably from 200 to 1200 nm.

[0018] The present invention further relates to a method of producing an optical element as described above and below.

[0019] The present invention further relates to an optical, electronic or electro-optical component or device as such comprising an optical element as described above and below. The present invention further relates to an optical, electro-optical or electronic device or component comprising an optical element as described above and below.

[0020] The component includes, but is not limited to, optical retardation films, polarizers, optical compensators, diffractive or surface gratings, such as Bragg polarization gratings (Bragg PG), polarization volume gratings (PVG) or Pancharatnam-Berry gratings (PBG), furthermore non-mechanical beam steering elements, optical waveguides, optical couplers or combiners, polarization beam splitters, partial mirrors, reflective films, alignment layers, color filters, antistatic protection sheets, electromagnetic interference protection sheets, lenses for light guiding, focusing and optical effects, polarization control lenses and IR-reflective films; for example in LC displays (LCD), organic light emitting diodes (OLED), 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 sensing optical sensing, holographic technology, spectroscopy, optical communication, polarimetry or front- / backlighting.

[0021] The device includes, but is not limited to, electro-optical displays, in particular LCDs, OLEDs, nonlinear optical (NLO) devices, autostereoscopic 3D displays, see-through near-eye displays, AR / VR systems, AR / VR application goggles, switchable windows, spatial light modulators, optical data storage devices, optical sensors, holographic devices, spectrometers, optical communication systems, polarimeters, or front- / backlighting. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Exemplary and schematic illustration of a double layer liquid crystal polymer (LCP) PBG on a photo-alignment layer (PAL) according to the prior art.

[0023] Figure 2 Exemplary and schematic illustration of different polarization states mapped on points between the equator and the ellipse on a Poincare sphere.

[0024] Figure 3 Exhibition of the spectral polarization states plotted on a Poincare sphere for a single layer polymer film according to Example 1.

[0025] Figure 4 Exhibition of the spectral polarization states plotted on a Poincare sphere for a single layer polymer film according to Comparative Example 1.

[0026] Figure 5a and Figure 5b Exhibition of the spectral polarization states plotted on a Poincare sphere for a double layer polymer film according to Comparative Example 2 when observed from the top (a) or the bottom (b), respectively.

[0027] Figure 6a and Figure 6b Schematic illustration of the fast and slow twisted regions in a single layer polymer film according to Example 1 (a) and a double layer polymer film according to Comparative Example 2 (b).

[0028] Figure 7 Exhibition of the twist profile for a double layer film according to Comparative Example 2 (a) and a single layer film according to Example 1 (b) determined by the Finite Element Method.

[0029] Figure 8 Exhibition of the diffraction efficiency as a function of the incidence angle for a double layer film based diffraction grating according to Comparative Example 2 (a) and a single layer film based diffraction grating according to Example 1 (b) determined by the Finite Element Method.

[0030] Figure 9 Exhibition of the fast axis of the single layer polymer film of Example 2 plotted on a Poincare sphere.

[0031] Figure 10Fast axis of the single layer polymer film of Example 3 plotted on a Poincare sphere.

[0032] Figure 11 Fast axis of the single layer polymer film of Example 4 plotted on a Poincare sphere.

[0033] Figure 12 Fast axis of the single layer polymer film of Example 5 plotted on a Poincare sphere.

[0034] Terms and definitions

[0035] Throughout the embodiments of the present description and the appended claims, the words "comprise" and "contain" and variations such as "comprising" and "comprises" mean "including but not limited to" and are not intended to (and do not) exclude other components.

[0036] Unless the context clearly indicates otherwise, as used herein the plural form "comprise", "comprises", "comprising", "contains" and "containing" are to be construed as meaning "including but not limited to" and not to the exclusion of other components.

[0037] The term "film" as used herein includes rigid or flexible, self-supporting or free-standing films having mechanical stability, and coatings or layers on a supporting substrate or between two substrates.

[0038] The term "monolithic film" means a one (or single) layer film consisting of a single layer of a specific material, such as the polymerized chiral RM mixture described hereinabove and hereinafter.

[0039] The terms "reactive mesogen" and "RM" as used herein are to be understood to mean a compound containing a mesogenic or liquid crystal backbone and optionally one or more functional groups suitable for polymerization, also referred to as "polymerizable groups" or "P", attached thereto via a spacer group.

[0040] The term "polymerizable compound" as used herein is to be understood to mean a polymerizable monomeric compound, unless otherwise specified.

[0041] A polymerizable compound or RM having one polymerizable group is also referred to as a "mono-reactive" compound, a polymerizable compound or RM having two polymerizable groups is referred to as a "di-reactive" compound, and a polymerizable compound or RM having more than two polymerizable groups is referred to as a "multi-reactive" compound. A compound having no polymerizable group is also referred to as a "non-reactive" compound.

[0042] The terms "liquid crystal", "mesogen" and "mesogenic compound" as used herein mean a compound which can exist as a mesophase or, in particular, as an LC phase under suitable conditions of temperature, pressure and concentration.

[0043] The term "clearing point" means the temperature at which the transition between the mesophase having the highest temperature range and the isotropic phase occurs.

[0044] The term "mesogenic group" as used herein is known to the person skilled in the art and described in the literature and means a group which contributes essentially to the generation of a liquid crystalline (LC) phase in low-molecular-weight or polymeric substances due to its anisotropy of attraction and repulsion interactions. A compound containing mesogenic groups (mesogenic compound) does not necessarily have an LC phase itself. A mesogenic compound can also exhibit LC phase properties only after mixing with other compounds and / or after polymerization. An overview of terms and definitions used in connection with mesogenic or LC compounds is given in Pure Appl. Chem. 2001, 73(5), 888 and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368.

[0045] The term "spacer group" (in the following also referred to as "Sp") as used herein is known to the person skilled in the art and described in the literature, see for example Pure Appl. Chem. 2001, 73(5), 888 and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368. The term "spacer group" or "spacer" as used herein means a flexible group, such as an alkylene group, connecting a mesogenic group and a polymerizable group in a polymerizable mesogenic compound.

[0046] The term "RM mixture" as used herein means a mixture comprising one or more, preferably two or more, more preferably two to ten, very preferably two to six RMs.

[0047] The term "RM formulation" as used herein 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 modify specific properties of the RM formulation and / or of the at least one RM therein. It is understood that the RM formulation is also the vehicle for carrying the RM to the substrate to enable formation of a layer or structure thereon. Exemplary materials include, but are not limited to, solvents, polymerization initiators, surfactants, and adhesion promoters, etc., as set out in more detail below.

[0048] The percentages of the compounds as given above and below in the RM mixture mean the weight percent of the total RM mixture, excluding solvents or additives used in the RM formulation as described above and below, unless otherwise stated.

[0049] Unless otherwise stated, the percentage of a compound as given above and below in an RM formulation means the weight percentage of all solids in the RM formulation, including the liquid additives as described below but not including the solvent.

[0050] As used herein, the term "per- and / or polyfluoroalkyl substances (PFAS)" (following the definition of OECD) means a substance or compound containing at least one fully fluorinated methyl or methylene C atom (without any H / CI / Br / I atom attached to it), i.e. a compound with at least one CF3or CF2group.

[0051] As used herein, the expression "polyfluorinated alkyl or aryl" means an alkyl or aryl group substituted with two or more F atoms, wherein the F atoms can be attached to the same or different C atoms, thus including perfluorinated carbon groups.

[0052] The term "polymer" as used herein is understood to mean a molecule encompassing a backbone of one or more different types of repeating units (the smallest constitutional unit of a molecule) and includes the commonly known terms "oligomer", "copolymer", "homopolymer" and the like. In addition, it is understood that the term polymer includes residues from initiators, catalysts and other elements accompanying the synthesis of such polymers in addition to the polymer itself, wherein these residues are understood not to be incorporated into the polymer in a covalent manner. In addition, these residues and other elements, although typically removed during the purification process after polymerization, are often mixed or blended with the polymer such that they remain with the polymer when it is transferred between vessels or between solvents or dispersion media.

[0053] The term "polymerization" means a chemical process by which a plurality of polymerizable groups or polymer precursors containing these polymerizable groups (polymerizable compounds) are joined together to form a polymer.

[0054] A "polymer network" is a network in which all polymer chains are interconnected to form a single macroscopic entity through a multitude of crosslinks.

[0055] Polymer networks can occur in the following types:

[0056] A grafted polymer molecule is a branched polymer molecule in which one or more side chains are structurally or configurational different from the main chain.

[0057] A star polymer molecule is a branched polymer molecule in which a single branching point gives rise to a plurality of linear chains or arms. If the arms are identical, the star polymer molecule is called regular. If adjacent arms are composed of different repeating subunits, the star polymer molecule is called diversified.

[0058] - Comb-like polymer molecules consist of a backbone with two or more three-way branch points and linear side chains. If the arms are identical, the comb-like polymer molecule is called regular.

[0059] - Brush-like polymer molecules consist of a backbone which is linear, unbranched side chains, and wherein one or more of the branch points have a four-way functionality or greater.

[0060] The term "chiral" is generally used to describe an object which is not superimposable on its mirror image.

[0061] An "achiral / non-chiral" object is an object which is identical to its mirror image.

[0062] The terms "chiral nematic" and "cholesteric" are used synonymously in this application, unless explicitly stated otherwise.

[0063] The term "isomerizable / photoisomerizable compound" means a compound comprising one or more isomerizable or photoisomerizable groups, respectively.

[0064] The term "isomerizable group" means a molecular functional group which causes a change in the molecular geometry (i.e. isomerization) by bond rotation, skeletal rearrangement or atom- or group transfer or by dimerization, which can be induced, for example, thermally or photochemically or by addition of a catalyst.

[0065] The term "photoisomerizable group" means a molecular functional group which causes a change in the molecular geometry (i.e. isomerization (photoisomerization)) by bond rotation, skeletal rearrangement or atom- or group transfer or by dimerization upon irradiation with light of a suitable wavelength which is absorbable by the molecule.

[0066] Examples of photoisomerizable groups are -C=C- double bonds and azo groups (-N=N-). Examples of molecular structures and substructures comprising such photoisomerizable groups are stilbenes, (1,2-difluoro-2-phenyl-vinyl)-benzene, cinnamates, a-cyanocinnamates, 4-phenylbut-3-en-2-ones, Schiff bases (i.e. groups R i R ii C=NR iii wherein R iii is different from H and is, for example, an alkyl or aryl group), 2-benzylidene-1-indanones, chalcones, coumarins, chromones, dicyclopentadienones and azobenzenes.

[0067] A chiral RM mixture of the present application can be prepared, for example, by doping a master mixture comprising one or more RMs with a chiral compound having a high twisting power.

[0068] The pitch p (in nm) of the induced cholesteric helix (in the following also referred to as "chiral pitch" or "helical pitch") is then given by the following equation from the concentration c (expressed in %) of the chiral compound and the helical twisting power HTP (expressed in nm -1 ) of the chiral compound:

[0069] p = (HTP c) -1

[0070] A low value of the pitch is in the following also referred to as "short pitch", and a high value of the pitch is in the following also referred to as "long pitch". A short pitch corresponds to a highly twisted structure (i.e. a higher twist angle), and a long pitch corresponds to a slowly twisted structure (i.e. a lower twist angle) around the helical axis within a given distance.

[0071] The twist angle Θ is defined via the thickness d by the following equation:

[0072]

[0073] where p is the pitch as defined above.

[0074] In case more than one chiral compound is used, the total HTP (HTP 总 ) of the chiral compounds having the same configuration or twist type then approximately satisfies the following equation:

[0075] HTP 总 = ∑ i c i HTP i

[0076] where c i is the concentration of each individual chiral compound and HTP i is the helical twisting power of each individual chiral compound.

[0077] The HTP (IHTP Δ I) of all chiral compounds in a mixture of different configurations or twist directions then approximately satisfies the following equation:

[0078] IHTP Δ I = (∑ s c s HTP s ) - ((∑ r c r HTP r )

[0079] where c s is the concentration of each individual chiral compound having the S configuration, HTP s is the helical twisting power of each individual chiral compound having the S configuration, and where cr is the concentration of each individual chiral compound having the R configuration, and HTP R is the helical twisting power of each individual chiral compound having the R configuration.

[0080] The birefringence Δn is defined as follows

[0081] Δn = n e - n o

[0082] where n e is the extraordinary refractive index and n o is the ordinary refractive index, and the effective average refractive index n av. is given by the following equation:

[0083] n av. = ((2n o 2 + n e 2 ) / 3) ½

[0084] The average refractive index n av. and the ordinary refractive index n o may be measured using an Abbe refractometer. Δn can then be calculated from the above equation.

[0085] The center wavelength λ and the bandwidth Δλ of the reflection band of a cholesteric RM or LC material or cholesteric polymer film are given by the pitch p of the cholesteric helix, the average refractive index n av. and the birefringence Δn of the cholesteric liquid crystal according to the following equations:

[0086] λ = n av. . p

[0087] Δλ = Δn . p

[0088] The term "visible light" means electromagnetic radiation having a wavelength in the range of about 400 nm to about 740 nm. The term "ultraviolet (UV) light" means electromagnetic radiation having a wavelength in the range of about 200 nm to about 450 nm.

[0089] According to the present application, the term "linearly polarized light" means light that is at least partially linearly polarized. Preferably, the alignment light is linearly polarized with an ellipticity greater than 5: 1. The wavelength, intensity and energy of the linearly polarized light are chosen depending on the photosensitivity of the photoalignable material. Typically, the wavelength is in the UV-A, UV-B and / or UV-C range or in the visible range. Preferably, the linearly polarized light comprises light with a wavelength of less than 450 nm, more preferably less than 420 nm, while the linearly polarized light preferably comprises light with a wavelength longer than 280 nm, preferably more than 320 nm, more preferably more than 350 nm.

[0090] Irradiance (E e ) or radiant power is defined as the power of electromagnetic radiation (dQ) per unit area (dA) incident on a surface:

[0091] E e = dQ / dA.

[0092] Radiation exposure or dose (H e ) is the irradiance or radiant power (E e ) per time (t):

[0093]

[0094] On a molecular level, the birefringence of a liquid crystal depends on the anisotropy of the polarizability (Δn) ). "Polarizability" means the ease with which the electron distribution in an atom or molecule is distorted. The polarizability increases with the number of electrons and the spread of the electron cloud. The polarizability can be calculated using the method set out in, for example, Jap. J. Appl. Phys. 42, (2003) p. 3463.

[0095] The "optical retardation" R(λ) (in nm) of a layer of liquid crystal or birefringent material at a given wavelength is defined as the product of the birefringence Δn(λ) at that wavelength and the layer thickness d (in nm) according to the following equation:

[0096] R(λ) = Δn(λ) . d

[0097] The optical retardation R represents the difference in the optical path length (in nanometers) traveled by S-polarized and P-polarized light as it passes through a birefringent material. "On-axis" retardation means the retardation at normal incidence to the surface of the sample.

[0098] The retardation (R( )) of a material can be measured using a spectroscopic ellipsometer (e.g. a M2000 spectroscopic ellipsometer manufactured by J. A. Woollam Co.). This instrument can measure the optical retardation (in nanometers) of a birefringent sample (e.g. quartz) typically over a wavelength range of 370 nm to 2000 nm. From this data the dispersion (R(450) / R(550) or Δn(450) / Δn(550)) of the material can be calculated.

[0099] A method for carrying out this measurement was presented by N. Singh at the National Physics Laboratory (London, UK) in October 2006 and entitled "Spectroscopic Ellipsometry, Part 1 - Theory and Fundamentals, Part 2 - Practical Examples and Part 3 - measurements". The measurement procedure followed the Retardation Measurement (RetMeas) Manual (2002) and Guide to WVASE (2002) published by J. A. Woollam Co. Inc (Lincoln, NE, USA). This method was used to determine the retardation of the materials, films and devices described in the present application unless otherwise stated.

[0100] The term "director" is known in the art and refers to the preferred direction of orientation of the long molecular axis (in the case of rod-like compounds) or the short molecular axis (in the case of disc-like compounds) of a liquid crystal or RM molecule. In the case of uniaxial ordering of such anisotropic molecules, the director is the anisotropy axis.

[0101] The term "alignment" or "orientation" relates to the alignment (orientational ordering) of the anisotropic units (e.g. small molecules or fragments of large molecules) of a material in a uniform direction, referred to as the "alignment direction". In an aligned layer of a liquid crystal material or a RM material, the liquid crystal director is aligned with the alignment direction such that the alignment direction corresponds to the direction of the anisotropy axis of the material.

[0102] The term "uniform orientation" or "uniform alignment" of a liquid crystal or RM material, e.g. in a layer of the material, means that the long molecular axis (in the case of rod-like compounds) or the short molecular axis (in the case of disc-like compounds) of the liquid crystal or RM molecules is oriented substantially in the same direction. In other words, the lines of liquid crystal directors are parallel.

[0103] The term "homeotropic structure / alignment / orientation" refers to a film in which the optical axis is substantially perpendicular to the plane of the film.

[0104] The term "planar structure / alignment / orientation" refers to a film in which the optical axis is substantially parallel to the plane of the film.

[0105] All temperatures (e.g. melting point T(C,N) or T(C,S) of the liquid crystal, transition point T(S,N) from smectic (S) to nematic (N) phase and clearing point T(N,I)) are given in degrees Celsius. All temperature differences are given in Kelvin.

[0106] In case of doubt, the definitions given in C. Tschierske, G. Pelzl and S. Diele, Angew. Chem. 2004, 116, 6340-6368 shall apply.

[0107] If in the formulae shown above and below, the group R, including any variations thereof, such as R 1 , R 0 , R 00 , R 0* , R 11 , R*, R**, R C , R 3 , R 4 , etc. or L denotes an alkyl group and / or an alkoxy group, this can be linear or branched. It is preferably linear, has 2, 3, 4, 5, 6 or 7 C atoms and thus preferably denotes ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, furthermore methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy or tetradecyloxy.

[0108] If in the formulae shown above and below, the group R, including any variations thereof, such as R 1 , R 0 , R 00 , R *0 , R 11 , R 22 , R C , R 3 , R 4or L denotes alkyl and / or alkoxy, which can be straight-chain or branched. It is preferably straight- chain with 2, 3, 4, 5, 6 or 7 C atoms and thus preferably denotes ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, furthermore methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy or tetradecyloxy.

[0109] If in the formulae shown above and below the group R, including any variants thereof, such as R 1 , R 0 , R 00 , R 0* , R 11 , R 22 , R C , R 3 , R 4 and the like or L denotes alkyl and / or alkoxy, which can be straight-chain or branched. It is preferably straight- chain with 2, 3, 4, 5, 6 or 7 C atoms and thus preferably denotes ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, furthermore methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy or tetradecyloxy.

[0110] Oxaalkyl preferably denotes straight-chain 2-oxapropyl (= methoxy-methyl), 2-oxa- butyl (= ethoxymethyl) or 3-oxabutyl (= 2-methoxy-ethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5-, or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxa- octyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxa- decyl.

[0111] If in the formulae shown above and below the group R, including any variants thereof, such as R 1 , R 0 , R 00 , R *0 , R 11 , R 22 , R C , R 3 , R 4 and the like or L denotes alkyl and / or alkoxy, which can be straight-chain or branched. It is preferably straight- chain with 2, 3, 4, 5, 6 or 7 C atoms and thus preferably denotes ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, furthermore methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy or tetradecyloxy.

[0112] In a further preferred embodiment one or more of R, including any variants thereof, such as R 1 , R 0 , R 00 , R*0 11 22 C 3 4 or L is selected from the group consisting of:

[0113]

[0114] -S 1 -F, -O-S 1 -F, -O-S1-O-S2, wherein S 1 is C 1-12 alkylene or C 2-12 alkenylene, and S 2 is H, C 1-12 alkyl or C 2-12 alkenyl, and very preferably selected from the group consisting of:

[0115]

[0116] -OCH2OCH3, -O(CH2)2OCH3, -O(CH2)3OCH3, -O(CH2)4OCH3, -O(CH2)2F, -O(CH2)3F and -O(CH2)4F.

[0117] If in the formulae shown above and below, the group R, including any variations thereof, such as R 1 0 00 *0 11 22 C 3 4 or L denotes an alkyl group in which one CH2group has been replaced by -CH=CH-, this can be straight-chain or branched. It is preferably straight-chain and has 2 to 10 C atoms. Thus, in particular, it denotes vinyl, prop-1- or -2-enyl, but-1-, -2- or -3-enyl, pent-1-, -2-, -3- or -4-enyl, hex-1-, -2-, -3-, -4- or -5-enyl, hept-1-, -2-, -3-, -4-, -5- or -6-enyl, oct-1-, -2-, -3-, -4-, -5-, -6- or -7-enyl, non-1-, -2-, -3-, -4-, -5-, -6-, -7- or -8-enyl, dec-1-, -2-, -3-, -4-, -5-, -6-, -7-, -8- or -9-enyl.

[0118] If in the formulae shown above and below, the group R, including any variations thereof, such as R 1 ​​​​​​​​​​​​​​R 0 R 00 R *0 R 11 R 22 R C R 3 R 4 or L denotes at least monosubstituted alkyl or alkenyl by halogen, which radical is preferably straight-chain and the halogen is preferably F or CI. In the case of multiple substitution, the halogen is preferably F. The resulting radicals also include perfluorinated radicals. In the case of monosubstitution, the fluorine or chlorine substituent can be in any desired position, but is preferably in the omega-position.

[0119] in the context of which or denotes a trans-1,4-cyclohexylene ring, and denotes a 1,4-phenylene ring.

[0120] Halogen is preferably F or CI, very preferably F.

[0121] the radical -CR 0 =CR 00 is preferably -CH=CH-.

[0122] -OC-, -CO-, -C(=O)- and -C(O)- denote carbonyl, i.e. .

[0123] Preferred substituents L are, for example, F, CI, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, -C(=O)N(R x )2, -C(=O)Y 1 , -C(=O)R x , -N(R x )2, straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy each having 1 to 25 C atoms, optionally substituted silyl having 1 to 20 Si atoms or optionally substituted aryl having 6 to 25, preferably 6 to 15 C atoms, each of which one or more H atoms can optionally be replaced by F or CI,

[0124] in which R x denotes H, F, CI, CN or straight-chain, branched or cyclic alkyl having 1 to 25 C atoms, in which one or more non-adjacent CH2-groups are optionally replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a manner that O- and / or S-atoms are not linked directly to one another, and in which one or more H atoms are each optionally replaced by F, CI, P- or P-Sp-, and Y 1 denotes halogen.

[0125] Particularly preferred substituents L are, for example, F, CI, CN, N02, CH3, C2H5, OCH3, SCH3, OC2H5, SC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF3, OCF3, OCHF2, OC2F5, furthermore phenyl.

[0126] Preferably is , , or ,

[0127] wherein L has one of the meanings indicated above.

[0128] Throughout the application, the terms "aryl and heteroaryl" encompass groups which can be monocyclic or polycyclic, i.e. they can have one ring (e.g. phenyl) or two or more rings which can also be fused (e.g. naphthyl) or covalently linked (e.g. biphenyl), or combinations of fused and linked rings. Heteroaryl groups contain one or more heteroatoms, preferably selected from O, N, S and Se. Particularly preferred are monocyclic, bicyclic or tricyclic aryl groups having 6 to 25 C atoms and monocyclic, bicyclic or tricyclic heteroaryl groups having 2 to 25 C atoms, which optionally contain fused rings and which are optionally substituted. Further preferred are 5-, 6- or 7-membered aryl and heteroaryl groups, in addition, wherein one or more CH groups can be replaced by N, S or O in such a way that they are not directly connected to one another. Preferred aryl groups are, for example, phenyl, biphenyl, terphenyl, [1,1 ':3',1 "]terphen-2'-yl, naphthyl, anthryl, binaphthyl, phenanthryl, pyrenyl, dihydropyrenyl, phenanthryl, pyrenyl, dihydropyrenyl, chrysenyl, fluorenyl, indenyl, indenofluorenyl, spirobifluorenyl, more preferably 1,4-phenylene, 4,4'-biphenylene, 1,4-terphenylene.

[0129] Preferred heteroaryl groups are, for example, 5-membered rings, such as pyrrole, pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, tetrazole, furan, thiophene, selenophene, oxazole, isoxazole, 1,2-thiazole, 1,3-thiazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole, 1,3,4-thiadiazole, 6-membered rings, such as pyridine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, 1,2,4-triazine, 1,2,3-triazine, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine, 1,2,3,5-tetrazine, or fused ring groups, such as indole, isoindole, indolizine, indazole, benzimidazole, benzotriazole, purine, naphthoimidazole, phenanthroimidazole, pyridoimidazole, pyrazinoimidazole, quinoxalinoimidazole, benzoxazole, naphthoxazole, anthroxazole, phenanthroxazole, isoxazole, benzothiazole, benzofuran, isobenzofuran, dibenzofuran, quinoline, isoquinoline, pteridine, benzo-5,6-quinoline, benzo-6,7-quinoline, benzo-7,8-quinoline, benzoisoquinoline, acridine, phenoxazine, phenothiazine, benzopyridazine, benzopyrimidine, quinoxaline, phenazine, naphthylidine, azacarbazole, benzocarbazole, phenanthridine, phenanthroline, thieno[2,3b]thiophene, thieno[3,2b]thiophene, dithienothiophene, isobenzothiophene, dibenzothiophene, benzothiadiazolothiophene, or combinations of these groups. The heteroaryl groups can also be substituted with alkyl, alkoxy, thioalkyl, fluorine, fluoroalkyl or other aryl or heteroaryl groups.

[0130] in which the single bond shown between two ring atoms can be attached to any free position of the phenyl ring.

[0131] -OC-, -CO-, -C(=0)- and -C(O)- denote carbonyl, i.e. .

[0132] The polymerisable groups P, including any variations thereof, such as P 0 , P 1 , P 2 , P *0 , are groups suitable for polymerisation reactions, such as, for example, radical or ionic chain polymerisation, polyaddition or polycondensation, or suitable for polymer-analogous reactions, for example addition or condensation on the main polymer chain. Particularly preferred are groups for chain polymerisation, in particular those containing a C=C double bond or a -C≡C- triple bond, and groups suitable for ring-opening polymerisation, such as, for example, oxetane or epoxy groups.

[0133] Preferred groups P, including any variations thereof, such as P 0 , P 1 , P 2 , P​*0 Choose from the following groups:

[0134] CH2=CW 1 -CO-O-、CH2=CW 1 -CO-、 , , , , CH2=CW 2 -(O) k3 -、CW 1 =CH-CO-(O) k3 -、CW 1 =CH-CO-NH-、CH2=CW 1 -CO-NH-, CH3-CH=CH-O-, (CH2=CH)2CH-OCO-, (CH2=CH-CH2)2CH-OCO-, (CH2=CH)2CH-O-, (CH2=CH-CH2)2N-, (CH2=CH-CH2)2N-CO-, HO-CW 2 W 3 -、HS-CW 2 W 3 -、HW 2 N-, HO-CW 2 W 3 -NH-, CH2=CW 1 -CO-NH-, CH2=CH-(COO) k1 -Phe-(O) k2 - CH2=CH-(CO) k1 -Phe-(O) k2 -, Phe-CH=CH-, HOOC-, OCN- and W 4 W 5 W 6 Si-, where W 1 This indicates H, F, Cl, CN, CF3, phenyl, or alkyl groups having 1 to 5 carbon atoms, particularly H, F, Cl, or CH3, W 2 and W 3 Each independently represents H or an alkyl group having 1 to 5 carbon atoms, particularly H, methyl, ethyl, or n-propyl, W 4 W 5 and W 6 Each independently represents Cl, an oxaalkyl or oxacarbonylalkyl group having 1 to 5 carbon atoms, and W. 7 and W 8each independently of one another H, CI or alkyl having 1 to 5 C atoms, Phe denotes 1,4-phenylene, which is optionally substituted by one or more groups L as defined above with the exception of P-Sp-, k1, k2 and k3 each independently of one another denote 0 or 1, k3 preferably denotes 1, and k4 denotes an integer from 1 to 10.

[0135] Very preferred groups P, including any variations thereof, such as P 0 , P 1 , P 2 , P *0 are selected from the group consisting of:

[0136] CH2=CW 1 -CO-O-, 1 -CO-, , , , , CH2=CW 2 -O-, 2 -, 1 =CH-CO-, k3 -, 1 =CH-CO-NH-, 1 -CO-NH-, (CH2=CH)2CH-OCO-, (CH2=CH-CH2)2CH-OCO-, (CH2=CH)2CH-O-, (CH2=CH-CH2)2N-, (CH2=CH-CH2)2N-CO-, 1 -CO-NH-, k1 -Phe-, k2 -, k1 -Phe-, k2 -, 4 W 5 W 6 Si-, 1 denotes H, F, CI, CN, CF3, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, CI or CH3, W 2 and W 3 each independently of one another H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, W 4 , W 5 and W 6 each independently of one another CI, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms, W 7 and W8 each independently of one another H, CI or alkyl having 1 to 5 C atoms, Phe denotes 1,4-phenylene, k1, k2 and k3 each independently of one another denote 0 or 1, k3 preferably denotes 1, and k4 denotes an integer from 1 to 10.

[0137] Very particularly preferred groups P, including any variations thereof, such as P 0 , P 1 , P 2 , P *0 , are selected from the group consisting of CH2=CW 1 -CO-O-, in particular CH2=CH-CO-O-, CH2=C(CH3)-CO-O- and CH2=CF-CO-O-, furthermore CH2=CH-O-, (CH2=CH)2CH-O-CO-, , (CH2=CH)2CH-O-, and .

[0138] Other preferred polymerizable groups P, including any variations thereof, such as P 0 , P 1 , P 2 , P *0 , are selected from the group consisting of vinyloxy, acrylate, methacrylate, fluoropropenoate, chloropropenoate, oxetane and epoxy, most preferably from acrylate and methacrylate.

[0139] In another preferred embodiment of the application, in the polymerizable compounds as disclosed above and below, including the compounds of the formula I and the subformulae thereof, all polymerizable groups have the same meaning and preferably denote acrylate or methacrylate, very preferably acrylate.

[0140] Spacers, including any variations thereof, such as Sp 0 , Sp 1 , Sp 2 , Sp *0 , when different from a single bond, are preferably of the formula Sp"-X", such that the respective group P-Sp- etc. corresponds to the formula P-Sp"-X"-, wherein

[0141] Sp" denotes a straight-chain or branched alkylene radical having 1 to 20, preferably 1 to 12 C atoms, which is optionally mono- or poly-substituted by F, CI, Br, I or CN, and wherein, in addition, one or more non-adjacent CH2 groups can each be replaced, independently of each other, by -O-, -S-, -NH-, -N(R 0 )-, -Si(R 0 R 00)-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -S-CO-, -CO-S-, -N(R 00 )-CO-O-, -O-CO-N(R 0 )-, -N(R 0 )-CO-N(R 00 )-, -CH=CH- or -C≡C- instead of O and / or S atoms not directly connected to each other,

[0142] X" represents -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -CO-N(R 0 )-, -N(R 0 )-CO-, -N(R 0 )-CO-N(R 00 )-, -OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -CF2CH2-, -CH2CF2-, -CF2CF2-, -CH=N-, -N=CH-, -N=N-, -CH=CR 0 -, -CY 2 =CY 3 -, -C≡C-, -CH=CH-CO-O-, -O-CO-CH=CH- or a single bond,

[0143] R 0 and R 00 each, independently of one another, denotes H or alkyl having 1 to 20 C atoms, and

[0144] Y 2 and Y 3 each, independently of one another, denotes H, F, Cl or CN.

[0145] X" is preferably -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR 0 -, -NR 0 -CO-, -NR 0 -CO-NR 00 - or a single bond.

[0146] Typical spacer groups Sp, including any variations thereof, such as Sp 0 , Sp 1 , Sp 2 , Sp *0 and -Sp"-X"- are, for example, -(CH2) p1 -, -(CH2) p1 -O-, -(CH2) p1-O-CO-, -(CH2) p1 -CO-O-, -(CH2) p1 -O-CO-O-, -(CH2CH2O) q1 -CH2CH2-, -CH2CH2-S-CH2CH2-, -CH2CH2-NH-CH2CH2- or -(SiR 0 R 00 -O) p1 - wherein p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and R 0 and R 00 have the meanings indicated above.

[0147] Particularly preferred groups Sp, including any variations thereof, such as Sp 0 , Sp 1 , Sp 2 , Sp *0 and -Sp"-X"- are -(CH2) p1 -, -(CH2) p1 -O-, -(CH2) p1 -O-CO-, -(CH2) p1 -CO-O-, -(CH2) p1 -O-CO-O-, wherein p1 and q1 have the meanings indicated above.

[0148] 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.

[0149] In another preferred embodiment of the present application, the polymerizable compounds as disclosed above and below, including the compounds of the formula I and the subformulae thereof, contain a spacer group Sp, including any variations thereof, such as Sp 0 , Sp 1 , Sp 2 , Sp *0 which is substituted by one or more polymerizable groups P, such that the group Sp-P corresponds to Sp(P) s and s ≥ 2 (branched polymerizable groups).

[0150] Preferred polymerizable compounds according to this preferred embodiment are those in which s is 2, i.e. compounds containing the group Sp(P)2. Very preferred polymerizable compounds according to this preferred embodiment contain a group selected from the following formulae:

[0151] -X-alkyl-CHPP S1

[0152] -X-alkyl-CH((CH2) aa P)((CH2) bb P) S2

[0153] -X-N((CH2) aa P)((CH2) bb P) S3

[0154] -X-alkyl-CHP-CH2-CH2P S4

[0155] -X-alkyl-C(CH2P)(CH2P)-C aa H 2aa+1 S5

[0156] -X-alkyl-CHP-CH2P S6

[0157] -X-alkyl-CPP-C aa H 2aa+1 S7

[0158] -X-alkyl-CHPCHP-C aa H 2aa+1 S8

[0159] wherein P is as defined in formula I,

[0160] alkyl denotes a single bond or a straight-chain or branched alkylene group having 1 to 12 C atoms which is unsubstituted or mono- or poly-substituted by F, Cl or CN and in which one or more non-adjacent CH2groups can each be replaced, independently of one another, by -C(R 0 )=C(R 0 )-, -C≡C-, -N(R 0 )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and / or S atoms are not linked directly to one another, where R 0 have the meanings indicated above,

[0161] aa and bb each, independently of one another, denote 0, 1, 2, 3, 4, 5 or 6,

[0162] X has one of the meanings indicated for X", and is preferably O, CO, SO2, O-CO-, CO-O or a single bond.

[0163] Preferred spacer groups Sp(P)2are selected from formulae S1, S2 and S3.

[0164] Very preferred spacer groups Sp(P)2are selected from the following subformulae:

[0165] -CHPP S1a

[0166] -O-CHPP S1b

[0167] -CH2-CHPP S1c

[0168] -OCH2-CHPP S1d

[0169] -CH(CH2-P)(CH2-P) S2a

[0170] -OCH(CH2-P)(CH2-P) S2b

[0171] -CH2-CH(CH2-P)(CH2-P) S2c

[0172] -OCH2-CH(CH2-P)(CH2-P) S2d

[0173] -CO-NH((CH2)2P)((CH2)2P) S3a DETAILED DESCRIPTION

[0174] The optical element according to the application comprises or consists of a monolithic film of a polymerized chiral RM mixture. The chiral RM mixture is also referred to as "RM mixture (according to the application)" hereinafter. The film of the polymerized chiral RM mixture is also referred to as "polymer film (according to the application)" hereinafter.

[0175] The RM mixture used for preparing the polymer film preferably contains at least one RM and at least one chiral compound having one or more isomerizable groups, preferably one or more photoisomerizable groups (e.g. cinnamate groups). The chiral compound having one or more isomerizable groups is preferably polymerizable.

[0176] The one or more isomerizable groups in this chiral compound can undergo a photo- driven E / Z isomerization reaction and, when so proceeding, exhibit a reduction of the helical twisting power (HTP). This allows for a fast photo-driven adjustment of the chiral pitch in the RM layer and, by varying the formulation and processing conditions, a director profile with variable pitch can be generated. When aligned on a grating alignment layer, it is possible to increase the grating angular bandwidth.

[0177] Furthermore, this allows to replicate a double layer chiral RM film as described in the prior art into a single layer or monolithic film. By this, problems associated with the preparation of multi-layer films, where multiple RM layers with different pitch values have to be coated onto each other, can be avoided, which problems are e.g. insufficient alignment transfer between the RM layers, occurrence of alignment defects, damage of lower RM layers by subsequent layers or control of different pitch values and tilt angles in the individual RM layers.

[0178] In contrast, the polymer film according to the present application exhibits a non-linear twist profile with an accelerated twist through the film thickness, which can be achieved by using a photo- isomerizable chiral compound which undergoes isomerization upon partial polymerization.

[0179] In particular, the non-linear twist profile can be achieved by the method of preparing a polymer film according to the present application as described above and below. This method contains two steps of irradiating the chiral RM layer with actinic radiation, e.g. UV light, which leads to photo-isomerization of the chiral compound and photo-polymerization of the RM.

[0180] The first irradiation step involves UV irradiation of the RM layer in air instead of in an inert atmosphere, such as nitrogen. Without wishing to be bound to a particular theory, the inventors believe that the oxygen-rich environment during photo-curing inhibits radical polymerization. This effect is exploited in order to partially polymerize the RM layer with a gradient of film depth. The polymerization rate of the top of the RM layer exposed to oxygen is low, because the polymerization is partially hindered by the oxygen environment, while photo-isomerization of the chiral compound still takes place. The bottom of the film at the substrate interface is not directly affected by oxygen, so the polymerization is much less hindered by oxygen and occurs more easily.

[0181] At the same time, due to the presence of at least one photo-isomerizable chiral compound, photo-isomerization occurs during the first UV irradiation step and the photo-reactive chiral compound decreases its helical twist power (HTP) upon exposure to UV light. In areas where the polymer density is higher, the change in the chiral structure is physically resisted. As described above, due to the lower polymer density at the top or surface of the RM layer, the chiral structure and helical pitch can be modified more freely. At the bottom of the film adjacent to the substrate, where more photo-polymerization takes place, the polymer density is higher, so the change in the chiral structure and helical pitch is hindered. This leads to the presence of a pitch gradient in the film, where the chiral rotation angle gradually increases or decreases through the film thickness (depending on the viewing direction).

[0182] Thus, after performing the method as described above, the polymerized 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.

[0183] The second irradiation step is carried out in an inert gas atmosphere, for example nitrogen, which also completes the polymerization process in the upper region of the RM layer, so that the RM layer is completely polymerized to a polymer film with a locked non-linear twist.

[0184] Preferably, the polymer film according to the application contains only one layer of a polymerized chiral RM mixture.

[0185] In addition to the advantageous effects as described above and below, the polymer film according to the application and the method for its production can also provide the following advantages:

[0186] - the chiral RM mixture can be easily aligned into the desired orientation, for example on a planar alignment layer or on a PB grating,

[0187] - by the addition of only a small amount of a chiral compound with a high HTP, a helical twist is induced in the direction of the entire film thickness.

[0188] - the vertically homeotropic alignment can be provided in a single film and using only one RM mixture, which makes the material costs low and improves the market competitiveness,

[0189] - a helical pitch gradient in the polymer film has already been achieved by the application of low intensity UV light,

[0190] - compared to the method for producing a conventional single planarly aligned RM film, the method for producing the polymer film requires only one additional method step,

[0191] - the additional method step is a low intensity UV exposure in air to induce photoisomerization of the chiral compound, and no inert gas atmosphere or additional heating or cooling of the film is required.

[0192] The RM mixture preferably comprises at least one RM with a birefringence of > 0.25, very preferably > 0.28. Suitable RMs with a high birefringence are, for example, those selected from the group of the RMs of the formula I and the subformulae thereof as defined below.

[0193] Preferably, the RM mixture comprises one or more compounds of the formula I or RMs:

[0194] wherein each radical, independently of the others and on each occurrence identically or differently, has the following meanings:

[0195] P is a polymerizable group,

[0196] Sp is a spacer group or a single bond,

[0197] R 11H, F, CI, CN, optionally fluorinated alkyl, alkoxy, thioalkyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 15, preferably having 1 to 5 C atoms, or P-Sp,

[0198] A, B, D and E are selected from the group consisting of 1,4-phenylene, naphthalene-1,4-diyl, naphthalene-2,6-diyl, phenanthrene-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']bithiophene-2,5-diyl, indol-4,7-diyl, benzothiophene-4,7-diyl, 9,10-dihydro-phenanthrene-2,7-diyl, 1,2,3,4-tetrahydronaphthalene-5,8-diyl or indan-2,5-diyl, wherein in addition one or more CH groups in these radicals can be replaced by N, all of the above optionally substituted by one or more groups L or P-Sp.

[0199] 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-2,7-diyl, benzo[1,2-b:4,5-b']bithiophene-2,5-diyl, indol-4,7-diyl, benzothiophene-4,7-diyl, all of the above optionally substituted by one or more groups L or P-Sp.

[0200] and one of the rings C and D can also denote a single bond,

[0201] L is F, CI, -CN, -SCN, P-Sp- or straight-chain, branched or cyclic alkyl with 1 to 25 C atoms, wherein one or more non-adjacent CH2-groups are optionally replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, CR 0 =CR 00 -, -C≡C-, instead,

[0202] in such a way that O- and / or S-atoms are not directly attached to one another, and wherein one or more H atoms are each optionally replaced by P-Sp-, F or CI, or two substituents L attached to directly adjacent C atoms can also form a cycloalkyl or cycloalkenyl group with 5, 6, 7 or 8 C atoms,

[0203] Z 11 , Z 12 is -O-, -S-, -CO-, -COO-, -OCO-, -S-CO-, -CO-S-, -O-COO-, -CO-NR0 -CO-, -NR 0 -CO-, -NR 0 -CO-NR 00 -CO-, -NR 0 -CO-O-, -O-CO-NR 0 -, -OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -CH2CH2-, -(CH2) n1 -, -CF2CH2-, -CH2CF2-, -CF2CF2-, -CH=N-, -N=CH-, -N=N-, -CH=CR 0 -, -CY 1 =CY 2 -, -C≡C-, -CH=CH-COO-, -OCO-CH=CH- or a single bond, preferably -COO-, -OCO-, -C≡C- or a single bond, most preferably a single bond,

[0204] n1 is 1, 2, 3 or 4,

[0205] r is 0, 1, 2, 3 or 4, preferably 0, 1 or 2,

[0206] s is 0, 1, 2 or 3, preferably 0, 1 or 2,

[0207] t is 0, 1 or 2, preferably 0 or 1,

[0208] R 0 , R 00 is H or alkyl with 1 to 12 C atoms,

[0209] Y 1 , Y 2 is H, F, CI, NCS or CN,

[0210] n is 0, 1, 2, 3 or 4, preferably 0, 1 or 2, more preferably 0 or 1, most preferably 0,

[0211] m is 0, 1, 2, 3 or 4, preferably 0, 1 or 2, more preferably 0 or 1, most preferably 0.

[0212] In the compounds of the formula I and its subformulae as described above and below, P is preferably selected from the group consisting of vinyloxy, acrylate, methacrylate, fluorinated acrylate, chlorinated acrylate, oxetane and epoxide, very preferably from acrylate and methacrylate, most preferably acrylate.

[0213] More preferred are compounds of formula I and the subformulae thereof as described above and below, wherein all polymerisable groups P present in the compounds have the same meaning and very preferably denote acrylate or methacrylate, most preferably acrylate.

[0214] More preferred are compounds of formula I and the subformulae thereof as described above and below, which contain one, two, three or four groups P-Sp, very preferably two or three groups P-Sp.

[0215] More preferred are compounds of formula I and the subformulae thereof as described above and below, wherein R 11 is P-Sp-.

[0216] More preferred are compounds of formula I and the subformulae thereof as described above and below, wherein R 11 is different from P-Sp- and is preferably selected from CN, -SCN, optionally fluorinated alkyl, alkoxy, thioalkyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy, preferably having 1 to 12, preferably 1 to 6 C atoms.

[0217] More preferred are compounds of formula I and the subformulae thereof as described above and below, wherein Sp denotes a single bond or -(CH2) p1 -, -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 , then the O-atom or the CO-group, respectively, is bound to the phenyl ring.

[0218] More preferred are compounds of formula I and the subformulae thereof as described above and below, wherein at least one group Sp is a single bond.

[0219] More preferred are compounds of formula I and the subformulae thereof as described above and below, wherein at least one group Sp is a single bond and at least one group Sp is different from a single bond.

[0220] More preferred are compounds of formula I and the subformulae thereof as described above and below, 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) p1wherein pi is an integer from 2 to 10, preferably 2, 3, 4, 5 or 6, and if Sp is -0-(CH2) p1 -0-CO-(CH2) p1 or -CO-O-(CH2) p1 then the O-atom or the CO-group is respectively bound to the phenyl ring.

[0221] More preferably, compounds of formula I and its subformulae as described above and below, wherein L is P-Sp-, -CN or straight-chain, branched or cyclic alkyl having 1 to 25 C atoms, wherein one or more non-adjacent CH2-groups are optionally replaced by -0-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, CR 0 =CR 00 - -C≡C-, instead,

[0222] in such a way that O-atoms and / or S-atoms are not directly attached to each other, and wherein one or more H atoms are each optionally replaced by P-Sp-, F or CI, or two substituents L attached to directly adjacent C atoms can also form a cycloalkyl or cycloalkenyl group having 5, 6, 7 or 8 C atoms.

[0223] Very preferably, compounds of formula I and its subformulae as described above and below, wherein 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.

[0224] More preferably, compounds of formula I and its subformulae as described above and below, wherein Z 11 and Z 12 denote -COO-, -OCO-, -C≡C- or a single bond, more preferably -C≡C- or a single bond, most preferably a single bond.

[0225] Preferably, A, B, D and E in formula I are selected from the group consisting of:

[0226] , , , , ,

[0227] , , , ,

[0228] , ,

[0229] wherein each radical, independently of each other and on each occurrence, has the following meanings identically or differently:

[0230] L is P-Sp-, -CN, F, CI or an alkyl, alkoxy or sulfanyl group, optionally fluorinated and having 1 to 6, preferably 1 to 3, more preferably 1 or 2 C atoms, preferably P-Sp-, -CN, F, CI, OCH3, SCH3, C2H5, OC2H5, SC2H5,

[0231] r is 0, 1, 2, 3 or 4, preferably 0, 1 or 2,

[0232] s is 0, 1, 2 or 3, preferably 0 or 1,

[0233] t is 0, 1 or 2, preferably 0 or 1.

[0234] More preferably, one, two, three, four or more of the rings A, B, D and / or E in formula I are selected from the group consisting of benzo-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']bithiophene-2,5-diyl, indol-4,7-diyl, benzo- thiophene-4,7-diyl, all of which are optionally substituted by one or more groups L and / or P-Sp-.

[0235] Very preferably, one, two, three, four or more of the rings A, B, D and / or E in formula I are selected from the group consisting of:

[0236] wherein L, on each occurrence, identically or differently, denotes P-Sp-, -CN, F, CI or an alkyl, alkoxy or sulfanyl group, optionally fluorinated and having 1 to 6, preferably 1 to 3, more preferably 1 or 2 C atoms, preferably P-Sp-, -CN, F, CI, OCH3, SCH3, C2H5, OC2H5, SC2H5.

[0237] Especially preferred are compounds of formula I, in particular wherein n = m = 0, wherein rings B and D are selected from the group consisting of benzo-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-.

[0238] Preferably, ring C in formula I is selected from the group consisting of:

[0239] , , and

[0240] wherein each radical, independently of one another and on each occurrence, has the following meanings, identically or differently:

[0241] L is P-Sp-, -CN, F, CI or an alkyl, alkoxy or thioalkyl group, optionally fluorinated and having 1 to 6, preferably 1 to 3, more preferably 1 or 2 C atoms, preferably P-Sp-, -CN, F, CI, OCH3, SCH3, C2H5, OC2H5, SC2H5,

[0242] r is 0, 1, 2, 3 or 4, preferably 0, 1 or 2,

[0243] s is 0, 1, 2 or 3, preferably 0 or 1,

[0244] t is 0, 1 or 2, preferably 0 or 1.

[0245] More preferably, C in formulae I, I1 and I2 is selected from the group consisting of:

[0246] wherein L, on each occurrence, identically or differently, denotes P-Sp-, -CN, F, CI or an alkyl, alkoxy or thioalkyl group, optionally fluorinated and having 1 to 6, preferably 1 to 3, more preferably 1 or 2 C atoms, preferably P-Sp-, -CN, F, CI, OCH3, SCH3, C2H5, OC2H5, SC2H5.

[0247] 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-.

[0248] More preferably are compounds of formula I, preferably those wherein n = m = 0, wherein rings B, C and D form a group selected from the following formulae or their mirror images:

[0249] wherein the naphthalene and phenanthrene groups are optionally substituted by one or two groups L, and L 1 and L 2 independently of one another denote H or one of the meanings given for L in formula I, and L and r are as defined in formula I.

[0250] In the formulae T1 to T28, preferably, L, on each occurrence, identically or differently, denotes P-Sp-, -CN, F, CI or an alkyl, alkoxy or thioalkyl group, optionally fluorinated and having 1 to 6, preferably 1 to 3, more preferably 1 or 2 C atoms, very preferably P-Sp-, methyl, ethyl, methoxy, ethoxy, thiomethyl or thioethyl, most preferably methyl or ethyl, and r is preferably 0, 1, 2 or 3, very preferably 0, 1 or 2.

[0251] Especially preferred are groups of the formulae T1 to T7.

[0252] Very preferred compounds of the formula I are selected from the following subformulae:

[0253] wherein the naphthalene and phenanthrene radicals are optionally substituted by one or two groups L, and P, Sp, L and r, independently of each other and on each occurrence identically or differently, have one of 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 one of the meanings given in formula I1, and preferably denotes OCH3or SCH3, very preferably OCH3. L is preferably selected from alkyl, alkoxy or thioalkyl groups having 1 to 6, more preferably 1, 2 or 3 C atoms, very preferably from methyl or ethyl. P is preferably acrylate.

[0254] More preferred are compounds of the formulae I1 and I1-1 to I1-103, wherein one of the two groups Sp is a single bond and the other group Sp is different from a single bond.

[0255] More preferred compounds of the formulae I and I-1 to I1-103 are selected from the following preferred embodiments (including any combination thereof):

[0256] - n = m = 0, or

[0257] - n = 1 and m = 0, or

[0258] - n = m = 1, and / or

[0259] - one of the rings B and D is a single bond, and / or - one of the rings B and D is a single bond, and / or

[0260] - ring C represents naphthalene-1,4-diyl or anthracene-9,10-diyl, or

[0261] - ring C represents phen-1,4-diyl, which is substituted with alkyl, alkoxy or thioalkyl having 1 to 3, preferably 1 or 2 C atoms, more preferably methyl or ethyl, most preferably ethyl, and / or

[0262] - at least one of rings B and D represents naphthalene-1,4-diyl, naphthalene-2,6-diyl or anthracene-9,10-diyl, which is optionally substituted with one or more groups L or P-Sp-, and / or

[0263] - at least one of rings B, C and D represents naphthalene-1,4-diyl, naphthalene-2,6-diyl or anthracene-9,10-diyl, which is optionally substituted with one or more groups L or P-Sp-, and / or at least one of rings B, C and D is phen-1,4-diyl substituted with ethyl,

[0264] - P represents acrylate or methacrylate, and / or

[0265] - Sp represents Sp"-X", preferably -Sp"-X"- represents -(CH2) p1 - -(CH2) p1 - O-, -(CH2) p1 - O-CO-, -(CH2) p1 - CO-O-, -(CH2) p1 - O-CO-O-, -(CH2CH2O) q1 - CH2CH2-, -CH2CH2-S-CH2CH2- or -CH2CH2-NH-CH2CH2-, wherein p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and / or

[0266] - if R 11 or R is P-Sp-, both groups P-Sp- are identical, or

[0267] - if R 11 or R is P-Sp-, one of the groups Sp is a single bond and the other one of the groups Sp is different from a single bond, and / or

[0268] - L is selected from methyl, ethyl, methoxy, ethoxy or thiomethyl, more preferably methyl or ethyl, very preferably ethyl, and r represents 1, and / or

[0269] - L is selected from methyl, ethyl, methoxy, ethoxy or thiomethyl, more preferably methyl or ethyl, very preferably ethyl, and r represents 2, and / or

[0270] - ring C is substituted by one L, which denotes P-Sp-, preferably acrylate, and / or

[0271] - R 11 is P-Sp-, or

[0272] - R 11 is F, CI, CN, OCH3or SCH3, preferably OCH3or SCH3 ， very preferably OCH3.

[0273] Very preferred compounds of formula I are listed below:

[0274] Especially preferred are compounds of formula I-3, I-19, I-21, I-24, I-25, I-30, I-47, I-50, I-53, I-59, I-67, I-69, I-70, I-72 and I-73.

[0275] The synthesis of compounds of formula I and its subformulae can be carried out by methods known per se to the person skilled in the art from the literature or in an analogous manner, as described in WO 2022 / 33908 A1.

[0276] The compounds of formula I taken alone or in combination with other RMs in an RM mixture especially and preferably exhibit simultaneously a high birefringence, a good solubility in commonly known organic solvents used in mass production, an improved alignment in the RM mixture, a favorable transition temperature and a higher resistance against yellowing after exposure to UV light.

[0277] Preferably, the RM mixture contains one or more, preferably 1 to 5, very preferably 1, 2 or 3 compounds selected from formula I, preferably from formulae I-1 to I-97, very preferably from formulae I1 to I76.

[0278] The concentration of the compounds of formula I or its subformulae in the RM mixture is preferably 65 to 99%, very preferably 25 to 98%.

[0279] In addition to the polymerizable compounds of the formula I or subformulae thereof, the RM mixture according to the application additionally comprises one or more chiral isomerizable compounds, preferably selected from chiral photoisomerizable compounds.

[0280] The chiral isomerizable compounds can be polymerizable or non-polymerizable. They can be non-mesogenic compounds or mesogenic compounds. If the chiral isomerizable compounds are polymerizable, they can be mono- or polyreactive.

[0281] In a preferred embodiment, the RM mixture according to the application comprises one or more polymerizable chiral isomerizable compounds.

[0282] In another preferred embodiment, the RM mixture according to the application contains exactly one chiral isomerizable compound.

[0283] More preferably, the RM mixture contains only polymerizable chiral isomerizable compounds, preferably selected from mono- or di-reactive chiral isomerizable compounds.

[0284] More preferably, the RM mixture contains no chiral compounds which do not contain isomerizable groups, in particular no photoisomerizable groups.

[0285] In another preferred embodiment, the RM mixture according to the application contains no further chiral compounds in addition to the one or more chiral isomerizable compounds.

[0286] Suitable polymerizable chiral isomerizable compounds preferably comprise one or more ring elements which are linked together by direct bonds or via linking groups, and wherein two of these ring elements are optionally linked to each other directly or via linking groups, which can be the same or different from the mentioned linking groups. The ring elements are preferably selected from 4-, 5-, 6- or 7-, preferably 5- or 6-membered ring groups.

[0287] The preferred chiral isomerizable compounds are selected from the formula I*:

[0288] R 3 -(A 3 -Z 3 ) m -G(-(Z 4 -A 4 ) l -R 4 ) k I*

[0289] wherein each of the radicals independently of the others and on each occurrence identically or differently has the following meanings:

[0290] R 3 , R 4H, F, CI, CN, P-Sp- or alkyl having up to 25 C atoms which can be unsubstituted, mono- or poly-substituted by halogen or CN, it being also possible for one or more non-adjacent CH2groups to be replaced, in each case independently from one another, by -0-, -S-, -NH-, -N(CH3)-, -CO-, -COO-, -OCO-, -OCO-O-, -S-CO-, -CO-S- or -C=C- in such a way that O atoms are not linked directly to one another,

[0291] P is a polymerisable group,

[0292] Sp is a spacer group or a single bond,

[0293] Z 3 , Z 4 -CO-O-, -O-CO-, -CH2CH2-, -OCH2-, -CH2O-, -CH=CH-, -CH=CH-CO-O-, -O-CO-CH=CH-, -CH=C(CN)-CO-O-, -O-CO-C(CN)=CH-, -N=N-, -CH=N-, -N=CH-, -C≡C- or a single bond,

[0294] A 3 , A 4 is an alicyclic, heterocyclic, aromatic or heteroaromatic group having 4 to 20 ring atoms which is monocyclic or polycyclic and is optionally substituted by one or more groups L or P-Sp-,

[0295] G is a chiral group,

[0296] L is F, CI, -CN, -SCN, P-Sp- or straight-chain, branched or cyclic alkyl having 1 to 25 C atoms, in which one or more non-adjacent CH2-groups are optionally replaced, in each case independently from one another, by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, CR 0 =CR 00 -, -C≡C-, , , , , or in such a way that O and / or S atoms are not linked directly to one another, and in which one or more H atoms are each optionally replaced by P-Sp-, F or CI, or two substituents L attached to directly adjacent C atoms can also form a cycloalkyl or cycloalkenyl group having 5, 6, 7 or 8 C atoms,

[0297] m, I are independently of one another 0, 1, 2 or 3,

[0298] k is 0, 1 or 2,

[0299] wherein the compound contains at least one isomerizable group, which is preferably a photoisomerizable group.

[0300] In the compounds of the formula I* and the subformulae thereof as set forth above and below, if R 3 or R 4 is alkyl or alkoxy (i.e. wherein the terminal CH2group is replaced by -O-), it can be straight-chain or branched. It is preferably straight-chain, has 2, 3, 4, 5, 6, 7 or 8 carbon atoms and is thus preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy or octoxy, furthermore, for example, methyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradoxy.

[0301] Oxaalkyl (i.e. wherein one CH2group is replaced by -O-) is preferably, for example, straight-chain 2-oxapropyl (= methoxymethyl); 2-oxa- butyl (= ethoxymethyl) or 3-oxa-butyl (= 2-methoxyethyl); 2-, 3- or 4-oxapentyl; 2-, 3-, 4- or 5-oxahexyl; 2-, 3-, 4-, 5-, 6- or 7-oxaheptyl; 2-, 3-, 4-, 5-, 6-, 7- or 8-oxa- nonyl or 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl.

[0302] Preferred compounds of the formula I* and the subformulae thereof are those in which at least one of R 3 and R 4 , preferably both R 3 and R 4 , denote P-Sp-.

[0303] Further preferred compounds of the formula I* and the subformulae thereof are those in which at least one of R 3 and R 4 , preferably both R 3 and R 4 , are different from P-Sp- and preferably denote alkyl or alkoxy having 1 to 12, more preferably 1 to 6, C atoms, one of R 3 and R 4 may also denote F, CI or CN.

[0304] Further preferred compounds of the formula I* and the subformulae thereof are those in which A 3 and A 4those 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, indol-4,7-diyl, benzothiophene-4,7-diyl, coumarin, flavone, wherein, additionally, one or more CH groups in these radicals can be replaced by N, cyclohexane-1,4-diyl, wherein, additionally, one or more non-adjacent CH2 groups can be replaced by O and / or S, 1,4-cyclohexenylene, bicyclo[1.1.1 ]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl, hexahydropyridine-1,4-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, indane-2,5-diyl, octahydro-4,7-methylenedihydroinden-2,5-diyl, 2-benzylidene-1 -indanone, chalcone, chromone and dicyclopentadienone, all of which radicals are optionally substituted by one or more groups L or P-Sp-.

[0305] Very preferred compounds of formula I* and its subformulae are those wherein A 3 and A 4 selected from the group consisting of 1,4-phenylene, naphthalene-1,4-diyl, naphthalene-2,6-diyl, 1,4-cyclohexylene, wherein, additionally, one or two non-adjacent CH2 groups can be replaced by O and / or S, 1,4-cyclohexenylene, 1,4-bicyclo(2,2,2)octylene, hexahydropyridine-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 radicals are optionally substituted by one or more groups L or P-Sp-.

[0306] Further preferred compounds of formula I* and its subformulae are those wherein Z 3 and Z 4 independently of one another represent -CO-O-, -O-CO- or a single bond.

[0307] Further preferred compounds of formula I* and its subformulae are those wherein L is selected from F, CI, CN, CH3, C2H5, OCH3, OC2H5, COCH3, COC2H5, CF3, OCF3, P-Sp-, in particular F, CI, CN, CH3, C2H5, OCH3, COCH3 or OCF3, most preferably F, CH3, OCH3 or COCH3.

[0308] Other preferred compounds of formula I* and the subformulae thereof are those wherein P is selected from the group consisting of vinyloxy, propenoate, methacrylate, fluoropropenoate, chloropropenoate, oxetane and epoxide, very preferably from propenoate and methacrylate, most preferably propenoate.

[0309] Other preferred compounds of formula I* and the subformulae thereof are those wherein Sp represents a single bond or -(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-(CH2) p1 or -CO-O-(CH2) p1 , then the O atom or the CO- group, respectively, is attached to the phenyl ring.

[0310] Other preferred compounds of formula I* and the subformulae thereof are those wherein all polymerizable groups P present in the compound have the same meaning and very preferably represent propenoate or methacrylate, most preferably propenoate.

[0311] Other preferred compounds of formula I* and the subformulae thereof are those wherein one, two, three or four groups P-Sp are present, very preferably two or three groups P-Sp.

[0312] Other preferred compounds of formula I* and the subformulae thereof are those wherein at least one group Sp is a single bond.

[0313] Other preferred compounds of formula I* and the subformulae thereof are those wherein at least one group Sp is a single bond and at least one group Sp is different from a single bond.

[0314] Other preferred compounds of formula I* and the subformulae thereof 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) 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-(CH2) p1 or -CO-O-(CH2) p1 , then the O atom or the CO- group, respectively, is attached to the phenyl ring.

[0315] In Ra or R b In case of a group of the formula P-Sp-Group, the spacer groups on each side of the mesogenic core can be the same or different.

[0316] In the compounds of the formula I* and the subformulae thereof as set forth above and below, m and l are preferably 0 or 1.

[0317] In the compounds of the formula I* and the subformulae thereof as set forth above and below, q is preferably 0 or 1, very preferably 0.

[0318] The following compounds of the formula I* are particularly preferred:

[0319] R*-G-R ** I*1

[0320] R*-A 3 -Z 3 -G-R** I*2

[0321] R*-A 3 -Z 3 -G-Z 4 -A 4 -R** I*3

[0322] P-Sp-G-R ** I*4

[0323] P-Sp-A 3 -Z 3 -G-R** I*5

[0324] P-Sp-G-Z 4 -A 4 -R** I*6

[0325] P-Sp-A 3 -Z 3 -G-Z 4 -A 4 -R** I*7

[0326] P-Sp-G-Sp-P I*8

[0327] P-Sp-A 3 -Z 3 -G-Sp-P I*9

[0328] P-Sp-A 3 -Z 3 -G-Z 4 -A 4 -Sp-P I*10

[0329] P-Sp-A 3 -Z 3-A 3 -Z 3 -G-Z 4 -A 4 -Sp-P I*11

[0330] P-Sp-A 3 -Z 3 -A 3 -Z 3 -G-Z 4 -A 4 -Z 4 -A 4 -Sp-P I*12

[0331] wherein P, Sp, A 3 , A 4 , Z 3 , Z 4 and G have the meaning given in formula I* as set forth above and below or one of its preferred meanings, R* has one of the meanings of R 3 different from R 4 of P-Sp- and R** has one of the meanings of R 3 different from R 3 of P-Sp-.

[0332] Among these preferred compounds, especially preferred are those of formulae I*8 to I*10, very especially preferred are those of formula I*8.

[0333] A smaller group of especially preferred compounds of formulae I*1 to I*10 is listed below. For reasons of conciseness, Phe is 1,4-phenylene optionally substituted at the 2- and / or 3-position by L and Cyc is 1,4-cyclohexylene.

[0334] Especially preferred compounds of formulae I*2, I3, I*5, I*6, I*7, I*9 and I*10 are those of the following formulae:

[0335] R*-Phe-Z 3 -G-R** I*2-1

[0336] R*-Cyc-Z 3 -G-R** I*2-2

[0337] R*-Phe-Z 3 -G-Z 4 -Phe-R** I*3-1

[0338] R*-Cyc-Z 3 -G-Z 4 -Cyc-R** I*3-2

[0339] R*-Phe-Z 3 -G-Z 4-Cyc-R** I*3-3

[0340] P-Sp-Cyc-Z 3 -G-R** I*5-1

[0341] P-Sp-Phe-Z 3 -G-R** I*5-2

[0342] P-Sp-G-Z 4 -Phe-R** I*6-1

[0343] P-Sp-G-Z 4 -Cyc-R** I*6-2

[0344] P-Sp-Phe-Z 3 -G-Z 4 -Phe-R** I*7-1

[0345] P-Sp-Cyc-Z 3 -G-Z 4 -Cyc-R** I*7-2

[0346] P-Sp-Phe-Z 3 -G-Z 4 -Cyc-R** I*7-3

[0347] P-Sp-Cyc-Z 3 -G-Z 4 -Phe-R** I*7-4

[0348] P-Sp-Cyc-Z 3 -G-Sp-P I*9-1

[0349] P-Sp-Phe-Z 3 -G-Sp-P I*9-2

[0350] P-Sp-Phe-Z 3 -G-Z 4 -Phe-Sp-P I*10-1

[0351] P-Sp-Cyc-Z 3 -G-Z 4 -Cyc-Sp-P I*10-2

[0352] P-Sp-Phe-Z 3 -G-Z 4 -Cyc-Sp-P I*10-3

[0353] P-Sp-Phe-Z 3-Phe-Z 3 -G-Z 4 -Phe-Sp-P I*11-1

[0354] P-Sp-Phe-Z 3 -Cyc-Z 3 -G-Z 4 -Phe-Sp-P I*11-2

[0355] P-Sp-Cyc-Z 3 -Phe-Z 3 -G-Z 4 -Phe-Sp-P I*11-3

[0356] P-Sp-Phe-Z 3 -Phe-Z 3 -G-Z 4 -Cyc-Sp-P I*11-4

[0357] P-Sp-Phe-Z 3 -Cyc-Z 3 -G-Z 4 -Cyc-Sp-P I*11-5

[0358] P-Sp-Cyc-Z 3 -Phe-Z 3 -G-Z 4 -Cyc-Sp-P I*11-6

[0359] P-Sp-Cyc-Z 3 -Cyc-Z 3 -G-Z 4 -Cyc-Sp-P I*11-7

[0360] P-Sp-Phe-Z 3 -Phe-Z 3 -G-Z 4 -Phe-Z 4 -Phe-Sp-P I*12-1

[0361] P-Sp-Phe-Z 3 -Cyc-Z 3 -G-Z 4 -Phe-Z 4 -Phe-Sp-P I*12-2

[0362] P-Sp-Cyc-Z 3 -Phe-Z 3 -G-Z 4 -Phe-Z 4P-Sp-P I*12-3

[0363] P-Sp-Phe-Z 3 -Cyc-Z 3 -G-Z 4 -Cyc-Z 4 P-Sp-P I*12-4

[0364] P-Sp-Cyc-Z 3 -Phe-Z 3 -G-Z 4 -Phe-Z 4 -Cyc-Sp-P I*12-5

[0365] P-Sp-Phe-Z 3 -Phe-Z 3 -G-Z 4 -Cyc-Z 4 -Cyc-Sp-P I*12-6

[0366] P-Sp-Cyc-Z 3 -Phe-Z 3 -G-Z 4 -Cyc-Z 4 -Cyc-Sp-P I*12-7

[0367] P-Sp-Phe-Z 3 -Cyc-Z 3 -G-Z 4 -Cyc-Z 4 -Cyc-Sp-P I*12-8

[0368] P-Sp-Cyc-Z 3 -Cyc-Z 3 -G-Z 4 -Cyc-Z 4 -Cyc-Sp-P I*12-9

[0369] wherein P, Sp, Z 3 , Z 4 and G have the meaning given in formula I* as set out above and below or one of its preferred meanings, R* has one of the meanings of R in formula I* different from P-Sp- 3 , and R** has one of the meanings of R in formula I* different from P-Sp- 4 .

[0370] In the compounds of the formulae I*2-1 to I*10-6, preferably, R*and R**independently of one another are alkyl or alkoxy having 1 to 12 C atoms or are alkyl or alkoxy having 1 to 12 C atoms and the other is F, CI or CN. Furthermore, -Sp- is preferably alkylene or alkyleneoxy having 1 to 12 C atoms, P is preferably acrylate or methacrylate and Z 3 and Z 4 independently of one another denote -CO-O-, -O-CO-, -CH=CH-CO-O-, -O-CO-CH=CH-, -CH=C(CN)-CO-O-, -O-CO-C(CN)=CH-, -CH=N-, -N=CH-, -N=N- or a single bond, more preferably -CO-O-, -O-CO- or a single bond.

[0371] Preferred compounds of the formula I* and the subformulae thereof are those in which G denotes or contains a photoisomerizable group.

[0372] Other preferred compounds of the formula I* and the subformulae thereof are those in which Z 3 and / or Z 4 independently of one another denote -CH=CH-CO-O-, -O-CO-CH=CH-, -CH=C(CN)-CO-O-, -O-CO-C(CN)=CH-, -CH=N-, -N=CH- or -N=N-.

[0373] Other preferred compounds of the formula I* and the subformulae thereof are those containing an isomerizable group selected from the following: stilbene, (1,2-difluoro-2-phenyl-vinyl)-benzene, cinnamate, a-cyanocinnamate, 4-phenylbut-3-en-2-one, Schiff base, 2-benzylidene-1-indanone, chalcone, coumarin, chromone, di-pericyclopentadiketone or azobenzene.

[0374] Other preferred compounds of the formula I* and the subformulae thereof are those in which the chiral group G is selected from or derived from the following: dianhydrohexitol, preferably isosorbide, isomannide or isoidide, 1,1 '-bis-2-naphthol (binol), 1,2-diphenyl-1,2-ethanediol (benzoin), 2-benzylidene-p-menthane-3-one and menthyl cinnamate ((2E)-3-phenyl-2-propenoic acid (1 R,2S,5R)-5-methyl-2-(1 -methylethyl)cyclohexyl ester).

[0375] Very preferred compounds of the formula I* and the subformulae thereof are those in which the chiral group G is selected from the formula A:

[0376] wherein X is -CO-O-, -CH=CH-CO-O-, -CH=C(CN)-CO-O-, wherein the ester O atom of each is attached to the furan ring or -N=N-, q is 0, 1, 2, 3 or 4, and L has the meaning of formula I* or one of its preferred meanings as given above and below.

[0377] Formula A comprises the following stereoisomers based on the respective dianhydrohexitol:

[0378] wherein X, L and q have the meanings as 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.

[0379] Other preferred compounds of formula I* and its subformulae are those wherein Z 3 and Z 4 one or both of which independently of one another represent -CH=CH-CO-O-, -O-CO-CH=CH-, -CH=C(CN)-CO-O-, -O-CO-C(CN)=CH-, -CH=N-, -N=CH- or -N=N- and / or wherein G is formula A (preferably Ai) and X represents -CH=CH-CO-O-, -CH=C(CN)-CO-O- or -N=N-.

[0380] Other preferred compounds of formula I* and its subformulae are those wherein G is formula A (preferably formula Ai) and X represents -CH=CH-CO-O-, -CH=C(CN)-CO-O- or -N=N-, very preferably -CH=CH-CO-O-.

[0381] Other preferred compounds of formula I* and its subformulae are those wherein the chiral group G is selected from the following formulae:

[0382] wherein

[0383] X, L and q have the meanings as given in formula A or one of its preferred meanings as given above and below,

[0384] R 11 and R 12 independently of one another represent -(Z 4 -A 4 ) l -R 4 ,

[0385] or R 11 and R 12 together with the O atom form an optionally substituted group -(Z 4 -A4 ) l -R 4 substituted cyclic or spirocyclic group,

[0386] R 13 and 14 independently of one another, R 3 -(A 3 -Z 3 ) m -,

[0387] a1and a2independently of one another are 0, 1 or 2,

[0388] and the dotted line represents a bond to the adjacent group in formula I*.

[0389] Preference is given to compounds of the formula I* selected from the following subformulae:

[0390] in which R 3 , R 4 , Z 4 , A 4 , L and q have one of the meanings or preferred meanings given in formula I* as given above and below, 1 1 is 0, 1 or 2, R 13 , R 14 , a1and a2have one of the meanings or preferred meanings given in formula G as given above and below, R 15 denote R 4 -A 4 ) l -R 4 and X 11 and X 12 denote -O-CO-CH=CH-.

[0391] Very particular preference is given to compounds of the formula I* A selected from the following subformulae:

[0392] in which P, Sp, L and q have one of the meanings or preferred meanings given in formula I* as given above and below, R* has one of the meanings of R 3 in formula I* other than P-Sp-, and R** has one of the meanings of R 4 in formula I* other than P-Sp-.

[0393] Particular preference is given to compounds of the formula I* A3.

[0394] Further preferred are the stereoisomers of formula I*A, I*B, I*A1, I*A2 and I*A3, wherein the central isosorbide unit is replaced by an isomannide or an isoidide unit.

[0395] In the compounds of formula I*A, I*B, I*A1, I*A2 and I*A3, P is preferably an acrylate or methacrylate, very preferably an acrylate, Sp is preferably -0-(CH2) p1 -, -0-CO-(CH2) p1 - or -CO-0-(CH2) p1 -, very preferably -0-(CH2) p1 -, wherein the O atom or the CO- group, respectively, is attached to the phenyl ring, p1 is an integer from 1 to 6, more preferably 2, 3, 4, 5 or 6, and R 4 is preferably P-Sp-.

[0396] Further preferred compounds of formula I* and its subformulae are selected from the following formulae:

[0397] wherein P, Sp, R*, R**, L and q have one of the meanings or preferred meanings as given in formula I* and I*A1 above and below, R 16 and R 17 independently of one another denote alkyl having 1 to 12, preferably 1 to 6 C atoms, very preferably methyl, ethyl or propyl, and R 18 denotes P-Sp-, H or alkyl having 1 to 12, preferably 1 to 6 C atoms, very preferably H.

[0398] In the compounds of formula I*C1 to I*G1, P is preferably an acrylate or methacrylate, very preferably an acrylate, Sp is preferably -0-(CH2) p1 -, -0-CO-(CH2) p1 - or -CO-0-(CH2) p1 -, very preferably -0-(CH2) p1 -, wherein the O atom or the CO- group, respectively, is attached to the phenyl ring, p1 is an integer from 1 to 6, more preferably 2, 3, 4, 5 or 6, R* and R** independently of one another are preferably alkyl or alkoxy having 1 to 12, very preferably 1 to 6 C atoms.

[0399] The compounds of the formula IA* can be prepared, for example, according to or analogously to the methods set out in GB 2314839 A. The compounds of the formulae I*E1 to I*E15 can be prepared, for example, according to or analogously to the methods set out in WO 02 / 40614 A1.

[0400] The chiral isomerizable compounds used preferably have a helical twist power (IHTP 总 I) in the range of 20 pm -1 or more, preferably 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 .

[0401] In the case where the RM mixture contains two or more chiral isomerizable compounds, the compounds can have the same or opposite twist direction.

[0402] In a preferred embodiment, the RM mixture contains only one chiral isomerizable compound, which is preferably polymerizable (i.e. contains at least one group P-Sp-), which is very preferably selected from the formula I* or a subformula thereof.

[0403] In another preferred embodiment, the RM mixture contains no other chiral compounds than those of the formula I*.

[0404] Preferably, the proportion of chiral isomerizable compounds, in particular of chiral isomerizable compounds selected from the formula I* or a subformula thereof, in the RM mixture according to the application is generally in the range of 0.1 to 4% by weight, very preferably in the range of 0.2 to 3% by weight, most preferably in the range of 0.3 to 2% by weight.

[0405] In another preferred embodiment, the RM mixture contains one or more chiral compounds which are not isomerizable in addition to the chiral isomerizable compounds.

[0406] By adding one or more chiral compounds which are not isomerizable, the center wavelength of the reflection band of the RM mixture can be adjusted. The additional chiral compounds which are not isomerizable can have the same twist direction or the opposite twist direction as the chiral isomerizable compounds. The reflection band of the RM mixture will thus be shifted to shorter or longer wavelengths, respectively.

[0407] In another preferred embodiment, the RM mixture contains one or more, preferably exactly one, chiral isomerizable and polymerizable compound, especially selected from the group of compounds of the formula I* or subformulae thereof, and additionally one or more, preferably exactly one, non-isomerizable and very preferably polymerizable chiral compound having an opposite twist direction to the chiral isomerizable and polymerizable compound.

[0408] Preferably, the additional polymerizable chiral compound(s) have an absolute value of the helical twist power (IHTP -1 ) of 20 pm -1 or more, preferably 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 总 .

[0409] The additional polymerizable chiral compound is preferably selected from mono- or di- reactive compounds.

[0410] Suitable polymerizable chiral compounds preferably comprise one or more ring elements which are linked together by a direct bond or via a linking group, and wherein two of these ring elements are optionally linked to each other directly or via a linking group, which linking group can be the same or different from the mentioned linking group. The ring elements are preferably selected from the group of four-, five-, six- or seven-membered rings, preferably five- or six-membered rings.

[0411] Preferred polymerizable chiral compounds are selected from the group of the formulae CRM1, CRM2 and CRM3:

[0412] wherein each group, independently of the others and on each occurrence identically or differently, has the following meanings,

[0413] P 0* is a polymerizable group,

[0414] Sp 0* is a spacer group or a single bond,

[0415] R 0* is F, CI, CN, alkyl, alkoxy, thioalkyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 15, preferably 1 to 6, C atoms, 0* - or P 0* - Sp * -,

[0416] A 0 , B 0 , E 0 , F0 1,4-phenylene, which is unsubstituted or substituted by 1, 2, 3 or 4 groups L, or trans-1,4-cyclohexylene,

[0417] L is F, CI, CN, P-Sp- or alkyl, alkoxy, thioalkyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 5 C atoms which is optionally fluorinated,

[0418] X 1 , X 2 is -O-, -COO-, -OCO-, -O-CO-O- or a single bond,

[0419] Z 0* -COO-, -OCO-, -O-CO-O-, -OCH2-, -CH2O-, -CF2O-, -OCF2-, -CH2CH2-, -(CH2)4-, -CF2CH2-, -CH2CF2-, -CF2CF2-, -CºC-, -CH=CH-, -CH=CH-COO-, -OCO-CH=CH- or a single bond, preferably -COO-, -OCO- or a single bond,

[0420] a0 is 0, 1 or 2, preferably 0 or 1,

[0421] b0 is 0 or an integer from 1 to 12, preferably from 1 to 6,

[0422] t0 is 0, 1, 2 or 3,

[0423] z0 is 0 or 1, preferably 1,

[0424] and wherein the naphthalene ring can additionally be substituted by one or more identical or different groups L.

[0425] Further preferred are stereoisomers of formula CRM2, wherein the central isosorbide unit is replaced by an isomannide or isoidide unit.

[0426] The compounds of formula CRM1 are preferably selected from the following formulae:

[0427] wherein A 0 , B 0 , Z 0* , X 2 , P 0* , a and b have the meanings given in formula CRM a or one of the preferred meanings given in context, and (OCO) denotes -O-CO- or a single bond.

[0428] Especially preferred compounds of formula CRM are selected from the group consisting of the following subformulae:

[0429] wherein R* is -X as defined in formula CRM1-1 2 -(CH2) t -P 0 *, and the benzene and naphthalene rings are unsubstituted or substituted with 1, 2, 3 or 4 groups L as defined above and below.

[0430] In the presence of one or more polymerizable chiral compounds, their concentration in the RM mixture is preferably from 0.1 to 10 % by weight, more preferably from 0.5 to 8 % by weight, of the total RM mixture.

[0431] In another preferred embodiment, the RM mixture comprises one or more further RMs which are different from formulae I CRM1 to CRM3 and their subformulae. Preferably, the RM mixture comprises one or more further RMs which are selected from RMs having only one polymerizable functional group (single-reactive RMs) and / or one or more further RMs having two or more polymerizable functional groups (double- or multi-reactive RMs).

[0432] The further double- or multi-reactive RMs are preferably selected from formulae DRM,

[0433] P 1 -Sp 1 -MG-Sp 2 -P 2 DRM

[0434] wherein

[0435] P 1 , P 2 independently of one another represent a polymerizable group,

[0436] Sp 1 , Sp 2 independently of one another are a spacer group or a single bond, and

[0437] MG is a rod-like mesogenic group which is preferably selected from formulae MG,

[0438] -(A 1 -Z 1 ) n -A 2 - MG

[0439] wherein

[0440] A 1 and A 2independently of one another in each occurrence, denote an aromatic or alicyclic radical, which optionally contains one or more heteroatoms from the group consisting of N, O and S, and is optionally mono- or poly-substituted by L,

[0441] L is P-Sp-, F, Cl, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, -C(=O)NR x R y , -C(=O)OR x , -C(=O)R x , -NR x R y , -OH, -SF5, optionally substituted silyl, aryl or heteroaryl having 1 to 12, preferably 1 to 6, C atoms, and straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12, preferably 1 to 6, C atoms, in which one or more H atoms are optionally replaced by F or Cl,

[0442] R x and R y independently of one another denote H or alkyl having 1 to 12 C atoms,

[0443] Z 1 independently of one another in each occurrence, denote -O-, -S-, -CO-, -COO-, -OCO-, -S-CO-, -CO-S-, -O-COO-, -CO-NR 00 -, -NR 00 -CO-, -NR 00 -CO-NR 000 , -NR 00 -CO-O-, -O-CO-NR 00 -, -OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -CH2CH2-, -(CH2) n1 -, -CF2CH2-, -CH2CF2-, -CF2CF2-, -CH=N-, -N=CH-, -N=N-, -CH=CR 00 -, -CY 1 =CY 2 -, -C≡C-, -CH=CH-COO-, -OCO-CH=CH- or a single bond, preferably -COO-, -OCO- or a single bond,

[0444] Y 1 and Y 2 independently of one another denote H, F, Cl or CN,

[0445] n is 1, 2, 3 or 4, preferably 1 or 2, most preferably 2,

[0446] n1 is an integer from 1 to 10, preferably 1, 2, 3 or 4.

[0447] Preferred groups A 1 and A 2 including but not limited to furan, pyrrole, thiophene, oxazole, thiazole, thiadiazole, imidazole, phenylene, cyclohexylene, bis-cyclooctylene, 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 described above.

[0448] Especially 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, bis-cyclooctylene or 1,4-cyclohexylene, wherein one or two non-adjacent CH2groups 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.

[0449] Preferred RMs of formula DRM are selected from formula DRMa

[0450] wherein

[0451] P 0 in each occurrence independently of one another are polymerisable groups, preferably acryloyl, methacryloyl, oxetane, epoxy, vinyl, heptadiene, vinyloxy, propenyl ether or styryl,

[0452] Z 0 is -COO-, -OCO-, -CH2CH2-, -CF2O-, -OCF2-, -C≡C-, -CH=CH-, -OCO-CH=CH-, -CH=CH-COO- or a single bond,

[0453] L is in each occurrence the same or different as L 1 as given for L in formula I, and preferably in each occurrence independently of one another is selected from F, CI, CN or an optionally halogenated alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy group having 1 to 5 C atoms,

[0454] r is 0, 1, 2, 3 or 4,

[0455] x and y independently of one another are 0 or an identical or different integer from 1 to 12,

[0456] z is 0 or 1 and, if adjacent x or y is 0, then z is 0.

[0457] Very preferred RMs of the formula DRM are selected from the following formulae:

[0458] wherein P 0 , L, r, x, y and z are defined as in formula DRM a.

[0459] Especially preferred are compounds of the formulae DRMa1, DRMa2 and DRMa3, in particular those of the formula DRMa1.

[0460] In another preferred embodiment, the RM mixture comprises, in addition to the compound of the formula I, one or more monoreactive RMs. These further monoreactive RMs are preferably selected from the formulae MRM:

[0461] P 1 -Sp 1 -MG-R 22 MRM

[0462] wherein P 1 , Sp 1 and MG have the meanings given in formula DRM,

[0463] R 22 denote P-Sp-, F, CI, Br, I, -CN, -N02, -NCO, -NCS, -OCN, -SCN, -C(=0)NR x R y , -C(=0)X, -C(=0)OR x , -C(=0)R y , -NR x R y , -OH, -SF5, optionally substituted silyl, straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy with 1 to 12, preferably 1 to 6 C atoms, in which one or more H atoms are optionally replaced by F or CI,

[0464] X is halogen, preferably F or CI, and

[0465] R x and R y are independently of one another H or alkyl with 1 to 12 C atoms.

[0466] Preferred RMs of the formula MRM are selected from the following formulae,

[0467] wherein P 0 , L, r, x, y and z are defined as in formula DRMa,

[0468] R 0 , R 01 and R 02 are each independently alkyl, alkoxy, thioalkyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 or more, preferably 1 to 15 C atoms or represent Y 0 or P-(CH2) y -(O) z -,

[0469] X 0 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-, -CF2S-, -SCF2-, -CF2CH2-, -CH2CF2-, -CF2CF2-, -CH=N-, -N=CH-, -N=N-, -CH=CR 01 -, -CF=CF-, -C≡C-, -CH=CH-COO-, -OCO-CH=CH- or a single bond,

[0470] Y 0 is F, Cl, CN, NO2, OCH3, OCN, SCN, SF5 or a monofluorinated, oligofluorinated or polyfluorinated alkyl or alkoxy group having 1 to 4 C atoms,

[0471] Z 0 is -COO-, -OCO-, -CH2CH2-, -CF2O-, -OCF2-, -CH=CH-, -OCO-CH=CH-, -CH=CH-COO- or a single bond,

[0472] A 0 in each occurrence is independently 1,4-phenylene which is unsubstituted or substituted by 1, 2, 3 or 4 groups L or trans-1,4-cyclohexylene,

[0473] R 01、02 are each independently H, R 0 or Y0 ,

[0474] u and v independently of one another are 0, 1 or 2,

[0475] w is 0 or 1,

[0476] and wherein the benzene and naphthalene rings can additionally be substituted by one or more identical or different groups L.

[0477] Especially preferred are compounds of formulae MRM1, MRM2, MRM3, MRM4, MRM5, MRM6, MRM7, MRM9 and MRM10, in particular those of formulae MRM1, MRM4, MRM6 and MRM7.

[0478] In formulae DRM, MRM and their preferred subformulae, L is preferably selected from F, CI, CN, NO2 or straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms, where the alkyl groups are optionally perfluorinated, or P-Sp-.

[0479] Very preferably, L is selected from F, CI, CN, NO2, CH3, C2H5, C(CH3)3, CH(CH3)2, CH2CH(CH3)C2H5, OCH3, OC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF3, OCF3, OCHF2, OC2F5 or P-Sp-, in particular from F, CI, CN, CH3, C2H5, C(CH3)3, CH(CH3)2, OCH3, COCH3 or OCF3, most preferably from F, CI, CH3, C(CH3)3, OCH3 or COCH3 or P-Sp-.

[0480] The concentration of the additional di- or multireactive RM, preferably of formula DRM and its subformulae, in the RM mixture is preferably 1 to 50 %, very preferably 2 to 30 %.

[0481] The concentration of the additional monoreactive RM, preferably of formula MRM, in the RM mixture is preferably 1 to 40 %, very preferably 2 to 20 %.

[0482] In a further preferred embodiment, the RM mixture contains only a small amount of compounds of formula I. Thus, it is possible to provide RM mixtures consisting mainly of monoreactive, di- and / or multireactive RMs, preferably selected from the group of RMs of formulae DRM and MRM and their subformulae, which are doped with a small amount, preferably 5 to 30 %, of compounds of formula I and additionally contain one or more chiral isomerizable compounds, preferably selected from formula I*.

[0483] In the RM mixture according to this preferred embodiment, the concentration of the di- or multireactive RMs of the formula DRM and its subformulae is preferably from 15 to 75 %, very preferably from 25 to 65 %. In the RM mixture according to this preferred embodiment, the concentration of the mono-reactive RMs, preferably the mono-reactive RMs of the formula MRM, is preferably from 1 to 50 %, very preferably from 5 to 30 %.

[0484] 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.

[0485] The birefringence (Δn) of the RM mixture is preferably in the range of from 0.2 to 0.8, more preferably in the range of from 0.25 to 0.7, and even more preferably in the range of from 0.35 to 0.6.

[0486] A further object of the present application is a RM formulation comprising the RM mixture as described above and below, and further comprising one or more solvents and / or additives.

[0487] The proportion of the RM mixture comprising, preferably consisting of, compounds selected from the group of the formulae I and I* and their subformulae, and optionally from the group of the formulae CRM1, CRM2, CRM3, 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 the total solids and liquid additives (i.e. not including solvents).

[0488] In a further preferred embodiment of the present application, the chiral RM mixture does not contain compounds of the formulae DRM or MRM. In a further preferred embodiment, the chiral RM mixture consists of compounds selected from the group of the formulae I and I*.

[0489] In a further preferred embodiment, the RM mixture of the present application additionally comprises one or more non-polymerizable and non-isomerizable chiral compounds. These chiral compounds can be non-mesogenic compounds or mesogenic compounds.

[0490] The further chiral compounds can have the same twist direction or the opposite twist direction as the chiral isomerizable compounds. Thus, the reflection band of the RM mixture can be shifted towards shorter or longer wavelengths as set out above.

[0491] The preferred non-polymerizable chiral compounds are selected from the group of the formulae C-I to C-III,

[0492] wherein the formulae C-II and C-III include the respective (S,S) enantiomer, and wherein E and F are each independently 1,4-phenylene or trans-1,4- cyclohexylene, v is 0 or 1, Z 0is -COO-, -OCO-, -CH2CH2- or a single bond, and R c is an alkyl, alkoxy or alkanoyl group having 1 to 12 C atoms.

[0493] Further preferred are stereoisomers of formula C-II, wherein the central isosorbide unit is replaced by an isomannide or isoidide unit.

[0494] Compounds of formula C-I and their synthesis are described in EP 1389199 A1. Compounds of formula C-II and their synthesis are described in WO 98 / 00428 A1. Compounds of formula C-III and their synthesis are described in GB 2328207 A.

[0495] Other preferred further chiral dopants are e.g. 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).

[0496] The amount of the non-polymerizable chiral dopant in the RM formulation is preferably 0.1 to 10 % by weight of all solids, more preferably 0.5 to 8 % by weight.

[0497] In another preferred embodiment, the RM formulation optionally comprises one or more additives selected from the group consisting of polymerization initiators, surfactants, stabilizers, catalysts, sensitizers, inhibitors, chain transfer agents, co-reacting monomers, reactive diluents, surface-active compounds, lubricants, wetting agents, dispersants, hydrophobing agents, adhesive agents, flow improvers, degasing or antifoam agents, gas scavengers, diluents, reactive diluents, auxiliaries, colorants, dyes, pigments and nanoparticles.

[0498] In another preferred embodiment of the present application, the RM mixture and / or the RM formulation is free of compounds having at least one CF3 or CF2 group (PFAS), and very preferably the RM mixture and / or the RM formulation is free of compounds having polyfluorinated alkyl or aryl groups or perfluorocarbon groups. More preferably, the RM mixture and / or the RM formulation is free of compounds having fluorinated aliphatic C atoms, most preferably the RM mixture and / or the RM formulation is free of compounds having fluorinated C atoms. Thus, the RM mixture and the RM formulation of this preferred embodiment are indeed able to reduce perfluorocarbon compounds.

[0499] The RM mixture and / or the RM formulation as set forth above and below, which is free of PFAS, more preferably free of perfluorocarbon compounds, very preferably free of compounds having polyfluorinated C atoms and most preferably free of compounds having fluorinated C atoms, is another object of the present application.

[0500] In another preferred embodiment, the RM formulation comprises one or more specific antioxidant additives, preferably selected from the Irganox® series, such as the antioxidants Irganox® 1076 and Irganox® 1010, commercially available from Ciba, Switzerland.

[0501] In another preferred embodiment, the RM formulation comprises one or more, more preferably two or more, combinations of photoinitiators, such as selected from the commercially available Irgacure® or Darocure® (Ciba AG) series (in particular Irgacure 127, Irgacure 184, Irgacure 369, Irgacure 651, Irgacure 817, Irgacure 907, Irgacure 1300, Irgacure, Irgacure 2022, Irgacure 2100, Irgacure 2959 or Darcure TPO) and 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).

[0502] The concentration of the one or more polymerization initiators in the RM formulation is generally preferably in the range of 0.1 to 6%, very preferably in the range of 0.3 to 4%, more preferably in the range of 0.7 to 2%.

[0503] In another preferred embodiment, the ratio between the concentration of the photoinitiator and the concentration of the chiral compound in the chiral RM mixture is generally in the range of 2:1 to 1:5, more preferably in the range of 2:1 to 1:4, even more preferably in the range of 2:1 to 1:3.

[0504] In another embodiment, the RM formulation optionally comprises one or more additives selected from polymerizable non-mesogenic compounds (reactive viscosity reducers). The amount of these additives in the RM formulation is preferably in the range of 0 to 30%, very preferably in the range of 0 to 25%.

[0505] The reactive viscosity reducers used are not only substances which are referred to as reactive viscosity reducers in the practical sense, but also the auxiliary compounds mentioned above which contain one or more additional reactive units (e.g. hydroxyl, thiol- or amino groups) via which a reaction with the polymerizable units of the liquid-crystalline compounds can take place.

[0506] Generally photopolymerisable substances include, for example, mono-, di- or polyfunctional compounds which comprise at least one olefinic double bond. Examples thereof are vinyl esters of carboxylic acids, for example of lauric acid, myristic acid, palmitic acid and stearic acid, and of dicarboxylic acids, for example of succinic acid, adipic acid, allyl and vinyl ethers and methacrylic acid and acrylic acid esters of monofunctional alcohols, for example of lauryl alcohol, myristyl alcohol, palmityl alcohol and stearyl alcohol, and of difunctional alcohols, for example of ethylene glycol and 1,4-butanediol, diallyl ethers and divinyl ethers.

[0507] Also suitable are, for example, methacrylic acid and acrylic acid esters of polyfunctional alcohols, in particular those which comprise no further functional groups in addition to the hydroxyl groups or at most ether groups. Examples of such alcohols are difunctional alcohols, such as ethylene glycol, propylene glycol and their more highly condensed representatives, for example diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol and the like, butylene glycol, pentanediol, hexanediol, neopentyl glycol, alkoxylated phenolic compounds, such as ethoxylated and propoxylated bisphenols, cyclohexanedimethanol, tri- and polyfunctional alcohols, such as glycerol, trimethylolpropane, butanetriol, trimethylolethane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, sorbitol, mannitol, and the corresponding alkoxylated, in particular ethoxylated and propoxylated, alcohols.

[0508] Other suitable reactive viscosity reducers are polyester (meth)acrylates which are (meth)acrylates of polyesterols.

[0509] Examples of suitable polyesterols are those which can be prepared by esterification of a polybasic carboxylic acid, preferably a dicarboxylic acid, using a polyhydric alcohol, preferably a diol. Starting materials for such hydroxyl-containing polyesters are known to the person skilled in the art. Dicarboxylic acids which can be used are succinic acid, glutaric acid, adipic acid, sebacic acid, phthalic acid and its isomers and hydrogenation products, and esterifiable or ester group transferable derivatives of the said acids, for example anhydrides and dialkyl esters. Suitable polyhydric alcohols are the alcohols mentioned above, preferably ethylene glycol, 1,2- and 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, cyclohexanedimethanol and polyglycols of ethylene glycol and propylene glycol.

[0510] Furthermore, suitable reactive viscosity reducers are 1,4-divinylbenzene, triallyl cyanurate, the acrylate of the tricyclodecenyl alcohol of the formula

[0511]

[0512] Also known as dihydridodicyclopentadienyl acrylate, and allyl esters of acrylic acid, methacrylic acid and cyanoacrylic acid.

[0513] Among the reactive tackifiers mentioned by way of example, in particular and taking into account the preferred compositions mentioned above, those comprising a photopolymerisable group are used.

[0514] The group includes, for example, diols and polyols, such as ethylene glycol, propylene glycol and its more highly condensed representatives, such as diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, etc., butylene glycol, pentanediol, hexanediol, neopentyl glycol, cyclohexanedimethanol, glycerol, trimethylolpropane, butanetriol, trihydroxyethylmethane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, sorbitol, mannitol and the corresponding alkoxylated, in particular ethoxylated and propoxylated, alcohols.

[0515] Furthermore, the group also includes, for example, alkoxylated phenolic compounds, such as ethoxylated and propoxylated bisphenols.

[0516] Furthermore, these reactive tackifiers can be, for example, epoxy or urethane (meth)acrylates.

[0517] For example, epoxy (meth)acrylates are those obtainable by reacting an epoxidised alkene or a poly- or di-glycidyl ether, such as bisphenol A diglycidyl ether, with (meth)acrylic acid.

[0518] In particular, urethane (meth)acrylates are likewise known to the person skilled in the art, the products of the reaction of (meth)acrylic acid hydroxyalkyl esters with poly- or di-isocyanates.

[0519] Such epoxy and urethane (meth)acrylates are included in the compounds listed above as "hybrid forms".

[0520] If reactive tackifiers are used, their amount and properties must be matched to the respective conditions, so that on the one hand the desired effects, such as the desired colour of the composition according to the application, are achieved, but on the other hand the phase behaviour of the liquid crystal composition is not excessively impaired. For example, a low-crosslinking (high-crosslinking) liquid crystal composition can be prepared using a corresponding reactive tackifier having a relatively low (high) number of reactive units per molecule.

[0521] For example, the group of diluents includes:

[0522] C1-C4-alcohols, such as methanol, ethanol, n-propanol, isopropanol, butanol, isobutanol, sec-butanol, and in particular C5-C12-alcohols, n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonyl alcohol, n-decanol, n-undecanol and n-dodecanol and their isomers, glycols, such as 1,2-ethanediol, 1,2- and 1,3-propanediol, 1,2-, 2,3- and 1,4-butanediol, di- and tri-ethanediol and di- and tri-propanediol, ethers, such as methyl tert-butyl ether, 1,2-ethanediol mono- and di-methyl ether, 1,2-ethanediol mono- and di-ethyl ether, 3-methoxypropanol, 3-isopropoxypropanol, tetrahydrofuran and dioxane, ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone and diacetone alcohol (4-hydroxy-4-methyl-2-pentanone), C1-C5-alkyl esters, such as methyl acetate, ethyl acetate, propyl acetate, butyl acetate and amyl acetate, aliphatic and aromatic hydrocarbons, such as pentane, hexane, heptane, octane, isooctane, petroleum ether, toluene, xylene, ethylbenzene, tetralin, decalin, dimethylnaphthalene, white spirit, Shellsol® and Solvesso® mineral oils, such as gasoline, kerosene, diesel and heating oil, and also natural oils, such as olive oil, soybean oil, rapeseed oil, linseed oil and sunflower oil.

[0523] Mixtures of these diluents can of course also be used in the compositions according to the application.

[0524] The diluents can also be mixed with water, provided that at least partial miscibility is present. Examples of suitable diluents here are C1-C4-alcohols, such as methanol, ethanol, n-propanol, isopropanol, butanol, isobutanol and sec-butanol, glycols, such as 1,2-ethanediol, 1,2- and 1,3-propanediol, 1,2-, 2,3- and 1,4-butanediol, di- and tri-ethanediol and di- and tri-propanediol, ethers, such as tetrahydrofuran and dioxane, ketones, such as acetone, methyl ethyl ketone and diacetone alcohol (4-hydroxy-4-methyl-2-pentanone), and C1-C4-alkyl esters, such as methyl acetate, ethyl acetate, propyl acetate and butyl acetate.

[0525] The diluents are optionally used 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.

[0526] The defoamers and air release agents (c1 ), the lubricants and flow aids (c2), the thermal or radiation curing aids (c3), the substrate wetting aids (c4), the wetting and dispersing aids (c5), the hydrophobizing agents (c6), the adhesion promoters (c7) and the aids for promoting scratch resistance (c8) cannot be strictly delimited from one another by their action.

[0527] For example, lubricants and flow aids are also often used as defoamers and / or degassing agents and / or as aids to promote scratch resistance. Radiation-curing aids can also be used as lubricants and flow aids and / or as degassing agents and / or as aids to wet the substrate. In each case, some of these aids can also fulfill the function of adhesion promoters (c8).

[0528] Corresponding to the above, certain additives can be classified into the following groups c1 ) to c8) described below.

[0529] Defoamers in the group c1 ) include both silicon-free and silicon-containing polymers. 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.

[0530] Degassing agents in the group c1 ) include, for example, organic polymers, such as polyethers and polyacrylates, dialkylpolysiloxanes, in particular dimethylpolysiloxanes, organomodified polysiloxanes, such as arylalkyl-modified polysiloxanes, and fluorosilicones.

[0531] The action of defoamers is based essentially on preventing the formation of foam or destroying already formed foam. In the medium to be degassed, for example the composition according to the application, the defoamers act essentially by promoting the coalescence of finely divided gas or air bubbles to give larger bubbles and thus accelerate the escape of gas (or air). Since defoamers can often also be used as degassing agents and vice versa, these additives have been included in the group c1 ) as a whole.

[0532] For example, such assistants can be obtained 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® Antifoam 14, TEGO® Antifoam 28, TEGO® Antifoam 81, TEGO® Antifoam D 90, TEGO® Antifoam 93, TEGO® Antifoam 200, TEGO® Antifoam 201, TEGO® Antifoam 202, TEGO® Antifoam 793, TEGO® Antifoam 1488, TEGO® Antifoam 3062, TEGOPREN® 5803, TEGOPREN® 5852, TEGOPREN® 5863, TEGOPREN® 7008, TEGO® Antifoam 1-60, TEGO® Antifoam 1-62, TEGO® Antifoam 1-85, TEGO® Antifoam 2-67, TEGO® Antifoam WM 20, TEGO® Antifoam 50, TEGO® Antifoam 105, TEGO® Antifoam 730, TEGO® Antifoam MR 1015, TEGO® Antifoam MR 1016, TEGO® Antifoam 1435, TEGO® Antifoam N, TEGO® Antifoam KS 6, TEGO® Antifoam KS 10, TEGO® Antifoam KS 53, TEGO®Antifoam KS 95, TEGO® Antifoam KS 100, TEGO® Antifoam KE 600, TEGO® Antifoam KS 911, TEGO® Antifoam MR 1000, TEGO® Antifoam KS 1100, Tego® Airex 900, Tego® Airex 910, Tego® Airex 931, Tego® Airex 935, Tego® Airex 936, Tego® Airex 960, Tego® Airex 970, Tego® Airex 980 and Tego® Airex 985 are commercially available and from BYK under BYK® -011, BYK® -019, BYK® -020, BYK® -021, BYK® -022, BYK® -023, BYK® -024, BYK® -025, BYK® -027, BYK® -031, BYK® -032, BYK® -033, BYK® -034, BYK® -035, BYK® -036, BYK® -037, BYK® -045, BYK® -051, BYK® -052, BYK® -053, BYK® -055, BYK® -057, BYK® -065, BYK® -066, BYK® -070, BYK® -080, BYK® -088, BYK® -141 and BYK® -A 530.

[0533] The adjuvants in group c1) are optionally used in a proportion of about 0 to 3.0 % by weight, preferably about 0 to 2.0 % by weight, based on the total weight of the RM formulation.

[0534] In group c2) the lubricants and flow adjuvants generally include both silicon-free and silicon-containing polymers, such as polyacrylates or modifiers, low-molecular-weight polydialkylsiloxanes. The modification consists in that some of the alkyl groups have been replaced by a broad variety of organic groups. These are, for example, polyether, polyester or even long-chain alkyl groups, the former being most frequently used.

[0535] The polyether groups in the correspondingly modified polysiloxanes are generally composed of ethylene oxide and / or propylene oxide units. Generally, the higher the proportion of these alkylene oxide units in the modified polysiloxanes, the higher the hydrophilicity of the resulting product.

[0536] For example, such assistants are 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 defoaming and air release agent), TEGO® Flow ATF, TEGO® Flow 300, TEGO® Flow 460, TEGO® Flow 425 and TEGO® Flow ZFS 460. Suitable radiation-curable lubricants and flow assistants, 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 available from TEGO.

[0537] For example, such assistants are available from BYK as BYK®-300 BYK®-306, BYK®-307, BYK®-310, BYK®-320, BYK®-333, BYK®-341, Byk® 354, Byk® 361, Byk® 361N, BYK® 388.

[0538] The assistants in group c2) are optionally used in an amount of from about 0 to 3.0 wt.%, preferably from about 0 to 2.0 wt.%, based on the total weight of the RM formulation.

[0539] In group c3), the radiation-curing assistants include, in particular, polysiloxanes having terminal double bonds, for example components whose terminal double bonds are acrylate groups. Such assistants can be crosslinked by actinic or, for example, electronic radiation. These assistants generally combine several properties together. In the uncrosslinked state, they can be used as defoaming, air release, lubricating and flow assistants and / or as substrate wetting assistants, while in the crosslinked state they, in particular, improve the scratch resistance of coatings or films which can be produced, for example, using the composition according to the application. The improvement in, for example, the gloss properties of those coatings or films is essentially attributed to the action of these assistants as defoaming, air release and / or lubricating and flow assistants in the uncrosslinked state.

[0540] Examples of suitable radiation-curing adjuvants are the products TEGO® Rad 2100, TEGO® Rad 2200, TEGO® Rad 2500, TEGO® Rad 2600 and TEGO® Rad 2700 available from TEGO and the products BYK®-371 available from BYK.

[0541] The thermal curing adjuvants in group c3) comprise, for example, primary OH groups, which are capable of reacting with isocyanate groups of, for example, the binder.

[0542] Examples of useful thermal curing adjuvants are the products BYK®-370, BYK®-373 and BYK®-375 available from BYK.

[0543] The adjuvants in group c3) are optionally used in a proportion of about 0 to 5.0 % by weight, preferably about 0 to 3.0 % by weight, based on the total weight of the RM formulation.

[0544] The substrate wetting adjuvants in group c4) are used in particular to improve the wettability of the substrate to be printed or coated, for example, by a printing ink or coating composition, for example a composition according to the application. The generally accompanying improvement in the lubrication and flow behaviour of such printing inks or coating compositions has an influence on the appearance of the finished (for example crosslinked) print or coating.

[0545] A wide variety of such adjuvants 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.

[0546] The adjuvants in group c4) are optionally used in a proportion of about 0 to 3.0 % by weight, preferably about 0 to 1.5 % by weight, based on the total weight of the liquid-crystalline composition.

[0547] The wetting and dispersing adjuvants in group c5) are used in particular to prevent colour floatation and blooming of pigments and to deposit, and are therefore particularly suitable, if necessary, in pigmented compositions according to the application.

[0548] These adjuvants stabilize the pigment dispersion essentially by electrostatic repulsion of the pigment particles comprising these additives and / or steric hindrance, in which case, in the latter case, the interaction of the adjuvant with the surrounding medium, for example the binder, plays an important role.

[0549] The selection of suitable wetting and dispersing aids of this type is generally not any difficult for the person skilled in the art if they are used at all, since the use of such wetting and dispersing aids is common practice, for example, in the field of printing inks and paints technology.

[0550] Such wetting and dispersing aids 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®-170, Disperbyk®-174, Disperbyk®-180, Disperbyk®-181, Disperbyk®-182, Disperbyk®-183, Disperbyk®-184, Disperbyk®-185, Disperbyk®-190, Anti-Terra®-U, Anti-Terra®-U 80, Anti-Terra®-P, Anti-Terra®-203, Anti-Terra®-204, Anti-Terra®-206, BYK®-151, BYK®-154, BYK®-155, BYK®-P 104 S, BYK®-P 105, Lactimon®, Lactimon®-WS and Bykumen®.

[0551] The amount of the aids in group c5) is used with the average molecular weight of the aid. In any case, preliminary experiments are advisable, but this can be easily done by the person skilled in the art.

[0552] Another preferred group of auxiliaries which can be assigned to the groups c2), c4) or c5) comprises wetting agents, flow agents and levelling agents, in particular based on non-ionic fluorine surfactants, which are commercially available from Synthomer under the trade name Polyfox TM series, for example Polyfox TM PF-656 are commercially available.

[0553] The hydrophobizing agents in the group c6) can be used to impart water-repellent properties to, for example, printed matter or coatings produced using the compositions according to the application. This prevents or at least greatly inhibits swelling due to water uptake and thus, for example, changes in the optical properties of such printed matter or coatings. Furthermore, when the compositions are used as printing inks, for example in offset printing, water uptake can thereby be prevented or at least greatly reduced.

[0554] Such hydrophobizing agents are commercially available, for example, from Tego under the trade names 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.

[0555] The auxiliaries in the group c6) are optionally used 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.

[0556] The adhesion promoters from the group c7) serve to improve the adhesion of the two interfaces in contact. It is immediately apparent therefrom that essentially the only part of an effective adhesion promoter is the part which is located at one or the other interface or at both interfaces. If, for example, it is desired to apply a liquid or pasty printing ink, coating composition or lacquer to a solid substrate, this generally means that the adhesion promoter must either be added directly to the latter or the substrate must be pretreated with the adhesion promoter, i.e. an upper primer, which imparts altered chemical and / or physical surface properties to the substrate.

[0557] If the substrate has been primed beforehand with a primer, this means that the interfaces in contact are on the one hand the interface of the primer and on the other hand the interface of the printing ink or coating composition or lacquer. In this case, not only the adhesion properties between the substrate and the primer, but also the adhesion properties between the substrate and the printing ink or coating composition or lacquer, play a role in the adhesion of the overall multilayer structure on the substrate.

[0558] The adhesion promoters in a broader sense that can be mentioned are also the substrate wetting aids already listed in group c4), but these generally do not have the same adhesion promoting ability.

[0559] In view of the wide variety of physical and chemical properties of the substrates and of the printing inks, coating compositions and lacquers intended for their printing or coating, for example, the diversity of adhesion promoter systems is not surprising.

[0560] Silane-based adhesion promoters 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. These and other silanes are commercially available, for example, from Huls under the trade name DYNASILAN®.

[0561] In general, the corresponding technical information from the manufacturer of such additives should be used, or this information can be obtained in a simple manner by the person skilled in the art by corresponding preliminary experiments.

[0562] However, if these additives are to be added as auxiliaries from group c7) to the RM formulation according to the application, their proportion optionally corresponds to about 0 to 5.0% by weight, based on the total weight of the RM formulation. These concentration data are merely a guide, since the amount and identity of the additives are determined in each individual case by the properties of the substrate and the printing / coating composition. For this case, the corresponding technical information is generally available from the manufacturer of such additives, or can be determined in a simple manner by the person skilled in the art by corresponding preliminary experiments.

[0563] The auxiliaries for improving the scratch resistance in group c8) include, for example, the products TEGO® Rad 2100, TEGO® Rad 2200, TEGO® Rad 2500, TEGO® Rad 2600 and TEGO® Rad 2700 mentioned above, which are available from Tego.

[0564] The data given for the amounts of group c3) likewise apply to these auxiliaries, i.e. these additives are optionally used in a proportion of about 0 to 5.0% by weight, preferably about 0 to 3.0% by weight, based on the total weight of the liquid-crystalline composition.

[0565] Examples of light, heat and / or oxidation stabilizers that can be mentioned are the following substances:

[0566] 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-(alpha-methylcyclohexyl)-4,6- dimethylphenol, 2,6-dioctadecyl-4-methylphenol, 2,4,6-tricyclohexylphenol, 2,6-di-tert- butyl-4-methoxymethylphenol, nonylphenols which are linear or branched in the alkyl chain, such as 2,6-di-nonyl-4-methylphenol, 2,4-dimethyl-6-(1'-methylundec-1'-yl)phenol, 2,4- dimethyl-6-(1'-methylheptadec-1'-yl)phenol, 2,4-dimethyl-6-(1'-methyltridec-1'-yl)phenol and mixtures thereof, alkylthiomethylphenols, such as 2,4-dioctylthiomethyl-6-tert-butylphenol, 2,4- dioctylthiomethyl-6-methylphenol, 2,4-dioctylthiomethyl-6-ethylphenol and 2,6-di(dodecyl)thiomethyl- 4-nonylphenol,

[0567] hydroquinones and alkylated hydroquinones, such as 2,6-di-tert-butyl-4-methoxyphenol, 2,5-di-tert- butylhydroquinone, 2,5-di-tert-amylhydroquinone, 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,

[0568] tocopherols, such as alpha-tocopherol, beta-tocopherol, gamma-tocopherol, delta-tocopherol and mixtures thereof, and tocopherol derivatives, such as tocopherol acetate, tocopherol succinate, tocopherol nicotinate and tocopherol polyoxyethyl succinate ("tocofersolate"),

[0569] hydroxylated thiodiphenyl ethers, 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-di-methyl-4-hydroxyphenyl) disulfide,

[0570] Alkylidenebisphenols, for example 2,2'-methylenebis(6-tert-butyl-4-methylphenol), 2,2'- methylenebis(6-tert-butyl-4-ethylphenol), 2,2'-methylenebis[4-methyl-6-(α-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-(α- methylbenzyl)-4-nonylphenol], 2,2'-methylenebis[6-(α,α-dimethylbenzyl)-4-nonylphenol], 4,4'- methylenebis(2,6-di-tert-butylphenol), 4,4'-methylenebis(6-tert-butyl-2-methylphenol), 1,1 - bis(5-tert-butyl-4-hydroxy-2-methylphenyl)butane, 2,6-bis(3-tert-butyl-5-methyl-2- hydroxybenzyl)-4-methylphenol, 1,1,3-tris(5-tert-butyl-4-hydroxy-2-methylphenyl)butane, 1,1 - bis(5-tert-butyl-4-hydroxy-2-methylphenyl)-3-n-dodecylmercapto-butane, ethylene glycol bis[3,3- bis(3'-tert-butyl-4'-hydroxyphenyl)butyrate], bis(3-tert-butyl-4-hydroxy-5-methyl- phenyl)dicyclopentadiene, bis[2-(3'-tert-butyl-2'-hydroxy-5'-methylbenzyl)-6-tert-butyl-4- methylphenyl]isophthalate, 1,1 -bis(3,5-dimethyl-2-hydroxyphenyl)butane, 2,2-bis(3,5-di-tert- butyl-4-hydroxyphenyl)propane, 2,2-bis(5-tert-butyl-4-hydroxy-2-methylphenyl)-4-n- dodecylmercapto-butane and 1,1,5,5-tetra(5-tert-butyl-4-hydroxy-2-methylphenyl)pentane,

[0571] O-, N- and S-benzyl compounds, such as 3,5,3',5'-tetra-tert-butyl-4,4'-dihydroxydibenzyl ether, 4-hydroxy-3,5-di-methylbenzyl mercaptan octadecylate, 4-hydroxy-3,5-di-tert- butylbenzyl mercaptan tridecylate, tris(3,5-di-tert-butyl-4-hydroxybenzyl)amine, bis(4-tert- butyl-3-hydroxy-2,6-dimethylbenzyl) dithiophtalate, bis(3,5-di-tert-butyl-4-hydroxybenzyl) sulfide and isooctyl-3,5-di-tert-butyl-4-hydroxybenzyl mercaptan,

[0572] Aromatic hydroxybenzyl compounds, such as 1,3,5-tris(3,5-di-tert-butyl-4- hydroxybenzyl)-2,4,6-trimethyl-benzene, 1,4-bis(3,5-di-tert-butyl-4- hydroxybenzyl)-2,3,5,6-tetramethyl-benzene and 2,4,6-tris(3,5-di-tert-butyl-4- hydroxybenzyl)phenol,

[0573] 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-3-hydroxy-2,6-dimethylbenzyl) isocyanurate, 2,4,6-tris(3,5-di-tert-butyl-4-hydroxyphenylethyl)-1,3,5-triazine, 1,3,5-tris-(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)hexahydro-1,3,5-triazine, 1,3,5-tris(3,5-dicyclohexyl-4-hydroxybenzyl)isocyanurate and 1,3,5-tris(2- hydroxyethyl)isocyanurate,

[0574] Benzylphosphonates, such as 2,5-di-tert-butyl-4-hydroxybenzylphosphonic acid dimethyl ester, 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid diethyl ester, 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid di(octadecyl) ester and 5-tert-butyl-4- hydroxy-3-methylbenzylphosphonic acid di(octadecyl) ester,

[0575] Acylaminophenols, such as 4-hydroxylauranilide, 4-hydroxystearanilide and N-(3,5-di-tert-butyl-4-hydroxyphenyl)octylcarbamate,

[0576] Propionic and acetic acid 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)oxamide, 3-thiaundecanol, 3-thiapentadecanol, trimethyl hexanediol, trimethylolpropane and 4-hydroxymethyl-1 -phospha-2,6,7-trioxabicyclo[2.2.2]-octane,

[0577] 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.

[0578] Ascorbic acid (vitamin C) and ascorbic acid derivatives, such as ascorbate palmitate, ascorbate laurate, and ascorbate stearate, as well as ascorbate sulfate and ascorbate phosphate.

[0579] amine, 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'-phenyl-p- phenylenediamine, N-(1 -methylheptyl)-N'-phenyl-p-phenylenediamine, N- cyclohexyl-N'-phenyl-p-phenylenediamine, 4-(p-toluenesulfamoyl)diphenylamine, N,N'-dimethyl-N,N'-di-sec-butyl-p-phenylenediamine, diphenylamine, N-allyldiphenylamine, 4-isopropoxydiphenylamine, N-phenyl-1 -naphthylamine, N-(4-tert-octylphenyl)-1 -naphthylamine, N-phenyl-2-naphthylamine, octyl- substituted diphenylamines, such as p,p'-di-tert-octyldiphenylamine, 4-n- butylaminophenol, 4-butyrylaminophenol, 4-nonanoylaminophenol, 4- dodecanoylaminophenol, 4-octadecanoylaminophenol, bis(4- methoxyphenyl)amine, 2,6-di-tert-butyl-4-dimethylamino-methylphenol, 2,4- diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, N,N,N',N'-tetramethyl- 4,4'-diaminodiphenylmethane, 1,2-bis[(2-methylphenyl)amino]ethane, 1,2- bis(phenylamino)propane, (o-tolyl)biguanide, bis[4-(1 ',3'-dimethylbutyl)phenyl]amine, tert-octyl-substituted N-phenyl-1 -naphthylamine, mixtures of mono- and di-alkylated tert-butyl / tert-octyl diphenyl amines, mixtures of mono- and di-alkylated nonyl diphenyl amines, mixtures of mono- and di-alkylated dodecyl diphenyl amines, mixtures of mono- and di-alkylated isopropyl / isohexyl diphenyl amines, mixtures of mono- and di-alkylated tert-butyl diphenyl amines, 2,3-dihydro-3,3-dimethyl-4H-1,4- benzothiazine, phenothiazine, mixtures of mono- and di-alkylated tert- butyl / tert-octyl phenothiazines, mixtures of mono- and di-alkylated tert-octyl phenothiazines, N-allylphenothiazine, N,N,N',N'-tetraphenyl-1,4- diamino but-2-ene, N,N-bis(2,2,6,6-tetramethylpiperid-4-yl)hexamethylenediamine, bis(2,2,6,6-tetramethylpiperid-4-yl)sebacate, 2,2,6,6-tetramethylpiperid-4-one and 2,2,6,6-tetramethylpiperid-4-ol,

[0580] phosphines, phosphites and phosphonites such as triphenylphosphine, triphenylphosphite, diphenylalkylphosphite, phenyldialkylphosphite, tris(nonylphenyl)phosphite, trilaurylphosphite, trioctadecylphosphite, 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, diisodecyloxypentaerythritol diphosphite, bis(2,4-di-tert-butyl-6-methylphenyl)pentaerythritol diphosphite, bis(2,4,6-tri-tert-butylphenyl)pentaerythritol diphosphite, tristearyl sorbitol triphosphite, tetrakis(2,4-di-tert-butylphenyl)4,4'-diphenylene diphosphonite, 6-isooctyloxy-2,4,8,10-tetra-tert-butyl-12H-dibenzo[d,g]-1,3,2-dioxaphosphocine, 6-fluoro-2,4,8,10-tetra-tert-butyl-12-methyl-dibenzo[d,g]-1,3,2-dioxaphosphocine, bis(2,4-di-tert-butyl-6-methylphenyl)methylphosphite and bis(2,4-di-tert-butyl-6-methylphenyl)ethylphosphite,

[0581] 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'-octyloxyphenyl)benzotriazole, 2-(3',5'- di-tert-amyl-2'-hydroxyphenyl)benzotriazole, 2-(3,5'-bis-(a,a-dimethylbenzyl)-2'- hydroxyphenyl)benzotriazole, mixtures of the following: 2-(3'-tert-butyl-2'-hydroxy-5'-(2- octyloxycarbonyl)ethyl)phenyl)-5-chlorobenzotriazole, 2-(3'-tert-butyl-5'-[2-(2- ethylhexyloxy)carbonyl]ethyl)-2'-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3'-tert-butyl- 2'-hydroxy-5'-(2-methoxycarbonyl)ethyl)phenyl)-5-chlorobenzotriazole, 2-(3'-tert-butyl- 2'-hydroxy-5'-(2-methoxycarbonyl)ethyl)phenyl)benzotriazole, 2-(3'-tert-butyl-2'- hydroxy-5'-(2-octyloxycarbonyl)ethyl)phenyl)benzotriazole, 2-(3'-tert-butyl-5'-[2-(2- ethylhexyloxy)carbonyl]ethyl)-2'-hydroxyphenyl)benzotriazole, 2-(3'-dodecyl-2'- hydroxy-5'-methylphenyl)benzotriazole and 2-(3'-tert-butyl-2'-hydroxy-5'-(2- isooctyloxycarbonyl)ethyl)phenylbenzotriazole, 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-benzotriazol-2-ylphenol]; the fully esterified product of 2-[3'-tert-butyl-5'-(2- methoxycarbonyl)ethyl)-2'-hydroxyphenyl]-2H-benzotriazole with polyethylene glycol 300;

[0582] Sulfur-containing peroxide scavengers and sulfur-containing antioxidants, such as esters of 3,3'-thiodipropionic acid, for example, the lauryl, stearyl, myristyl and tridecyl esters, mercaptobenzimidazole and zinc salt of 2-mercaptobenzimidazole, dibutylthiuram disulfide, dioctadecyl dithiomerthane and pentaerythritol tetrakis(β-dodecylmercapto)propionate,

[0583] 2-hydroxybenzophenones, such as 4-hydroxy, 4-methoxy, 4-octyloxy, 4-decyl- oxy, 4-dodecyloxy, 4-benzyloxy, 4,2',4'-trihydroxy and 2'-hydroxy-4,4'-dimethoxy derivatives,

[0584] esters of unsubstituted and substituted benzoic acids, such as 4-tert-butylphenyl salicylate, phenyl salicylate, octylphenyl salicylate, dibenzoyl resorcinol, bis(4-tert- butylbenzoyl)resorcinol, benzoyl resorcinol, 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,

[0585] Acrylates, such as ethyl α-cyano-β,β-diphenylacrylate, isooctyl α-cyano-β,β-diphenylacrylate, methyl α-methoxycarbonylcinnamate, methyl α-cyano-β-methyl-p-methoxycinnamate, butyl-α-cyano-β-methyl-p-methoxycinnamate, and methyl-α-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, and bis(1-octoxy-2,2,6,6-tetramethylpiperidin-4-yl) sebacate. Sebacic acid ester, bis(1,2,2,6,6-pentamethylpiperidin-4-yl)-n-butyl-3,5-di-tert-butyl-4-hydroxybenzylmalonic acid ester, condensation product of 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid, condensation product of N,N′-bis(2,2,6,6-tetramethylpiperidin-4-yl)hexamethylenediamine and 4-tert-octylamino-2,6-dichloro-1,3,5-triazine, tris(2,2,6,6-tetramethylpiperidin-4-yl)hydantoin triacetate, tetra(2,2,6,6-tetramethylpiperidin-4-yl)1,2,3,4-butanetetracarboxylate, 1,1′-(1,2-ethylidene) ) bis(3,3,5,5-tetramethylpiperazinone), 4-benzoyl-2,2,6,6-tetramethylpiperidine, 4-stearyloxy-2,2,6,6-tetramethylpiperidine, bis(1,2,2,6,6-pentamethylpiperidin-4-yl)2-n-butyl-2-(2-hydroxy-3,5-di-tert-butylbenzyl)malonate, 3-n-octyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione, bis(1-octoxy-2,2,6,6-tetramethylpiperidin-4-yl)sepiacetate, bis(1-octoxy-2,2,6,6-tetramethylpiperidin-4-yl)succinate, N,N′-bis(2 The condensation product of 2,6,6-tetramethylpiperidin-4-yl)hexamethylenediamine and 4-morpholino-2,6-dichloro-1,3,5-triazine, the condensation product of 2-chloro-4,6-bis(4-n-butylamino-2,2,6,6-tetramethylpiperidin-4-yl)-1,3,5-triazine and 1,2-bis(3-aminopropylamino)ethane, the condensation product of 2-chloro-4,6-bis(4-n-butylamino-1,2,2,6,6-pentamethylpiperidin-4-yl)-1,3,5-triazine and 1,2-bis(3-aminopropylamino)ethane, and 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4].5]-Decane-2,4-dione, 3-dodecyl-1-(2,2,6,6-tetramethylpiperidin-4-yl)pyrrolidine-2,5-dione, 3-dodecyl-1-(1,2,2,6,6-pentamethylpiperidin-4-yl)pyrrolidine-2,5-dione, a mixture of 4-hexadecyloxy- and 4-stearyloxy-2,2,6,6-tetramethylpiperidine, a condensation product of N,N′-bis(2,2,6,6-tetramethylpiperidin-4-yl)hexamethylenediamine and 4-cyclohexylamino-2,6-dichloro-1,3,5-triazine, a condensation product of 1,2-bis(3-aminopropylamino)ethane and 2,4,6-trichloro-1,3,5-triazine, 4-butylamino-2,2,6,6-tetramethyl The condensation products of piperidine, N-(2,2,6,6-tetramethylpiperidin-4-yl)-dodecylsuccinimide, N-(1,2,2,6,6-pentamethylpiperidin-4-yl)-dodecylsuccinimide, 2-undecyl-7,7,9,9-tetramethyl-1-oxa-3,8-diaza-4-oxo-spiro[4.5]decane, 7,7,9,9-tetramethyl-2-cycloundecyl-1-oxa-3,8-diaza-4-oxospiro[4.5]decane and epichlorohydrin, and the condensation products of 4-amino-2,2,6,6-tetramethylpiperidine with tetrahydroxymethylethynyl diurea and poly(methoxypropyl-3-oxy)-[4(2,2,6,6-tetramethyl)piperidinyl]-siloxane.

[0586] Oxalides, such as 4,4′-dioctyloxyoxalaniline, 2,2′-diethoxyoxalaniline, 2,2′-dioctyloxy-5,5′-di-tert-butoxalaniline (butoxanilide), 2,2′-di(dodecyloxy)-5,5′-di-tert-butoxalaniline, 2-ethoxy-2′-ethyloxalaniline, N,N′-bis(3-dimethylaminopropyl)oxalamide, 2-ethoxy-5-tert-butyl-2′-ethoxalaniline (ethoxanilide) and mixtures thereof with 2-ethoxy-2′-ethyl-5,4′-di-tert-butoxalaniline, and mixtures thereof of o-, p-methoxy-disubstituted oxalanilines and mixtures thereof of o- and p-ethoxy-disubstituted oxalanilines, and

[0587] 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)-1,3,5-triazine, 2-(2-hydroxy-4-tridecyloxyphenyl)-4,6-bis(2,4- dimethylphenyl)-1,3,5-triazine, 2-[2-hydroxy-4-(2-hydroxy-3-butyloxypropoxy)- phenyl]-4,6-bis(2,4-dimethyl)-1,3,5-triazine, 2-[2-hydroxy-4-(2-hydroxy-3- octyloxypropoxy)phenyl]-4,6-bis(2,4-dimethyl)-1,3,5-triazine, 2-[4- (dodecyloxy / tridecyloxy-2-hydroxypropoxy)-2-hydroxyphenyl]-4,6-bis(2,4- dimethylphenyl)-1,3,5-triazine, 2-[2-hydroxy-4-(2-hydroxy-3- dodecyloxypropoxy)phenyl]-4,6-bis-(2,4-dimethylphenyl)-1,3,5-triazine, 2-(2- hydroxy-4-hexyloxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4- methoxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2,4,6-tris[2-hydroxy-4-(3-butyloxy- 2-hydroxypropoxy)phenyl]-1,3,5-triazine and 2-(2-hydroxyphenyl)-4-(4- methoxyphenyl)-6-phenyl-1,3,5-triazine.

[0588] In a preferred embodiment, the RM formulation is dissolved in a suitable solvent, which is preferably selected from organic solvents.

[0589] The solvent is preferably selected from ketones such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone or cyclohexanone; acetic acid esters such as methyl acetate, ethyl acetate or butyl acetate or methyl acetoacetate; alcohols such as methanol, ethanol or isopropanol; aromatic solvents such as toluene or xylene; alicyclic hydrocarbons such as cyclopentane or cyclohexane; halogenated hydrocarbons such as dichloromethane or trichloromethane; glycols or esters thereof such as PGMEA (propylene glycol monomethyl ether acetate), gamma-butyrolactone. It is also possible to use binary, ternary or higher mixtures of the above mentioned solvents. In particular, for multi-layer applications, methyl isobutyl ketone is the preferred solvent to be used.

[0590] In case the RM formulation contains one or more solvents, the total concentration of all solids, including the RMs, in the solvent is preferably from 5 to 60 %, more preferably from 10 to 50 %, in particular from 10 to 35 %.

[0591] Preferably, the RM formulation comprises, in addition to one or more compounds of formula I and a chiral isomerizable compound,

[0592] a) optionally one or more multi- or di-reactive polymerizable mesogenic compounds, which are preferably selected from compounds of formula DRM and the corresponding subformulae, and / or

[0593] b) optionally one or more additional polymerizable chiral compounds, which are preferably selected from formula CRM or subformulae thereof, and / or

[0594] c) optionally one or more additional non-polymerizable chiral compounds, which are preferably selected from formulae C-I, C-II and C-III, and / or

[0595] d) optionally one or more mono-reactive mesogens, which are preferably selected from compounds of formula MRM and the corresponding subformulae, and / or

[0596] e) optionally one or more photoinitiators, and / or

[0597] f) optionally one or more antioxidants, and / or

[0598] g) optionally one or more adhesion promoters, and / or

[0599] h) optionally one or more surfactants, and / or

[0600] i) optionally one or more mono-, di- or multi-reactive polymerizable non-mesogenic compounds, and / or

[0601] j) optionally one or more dyes showing a maximum absorption at the wavelength used to initiate photopolymerization, and / or

[0602] k) optionally one or more chain transfer agents, and / or

[0603] l) optionally one or more (UV) stabilizers, and / or

[0604] m) optionally one or more lubricants and flow aids, and

[0605] n) optionally one or more diluents, and / or

[0606] o) optionally non-polymerizable nematic components, and / or

[0607] p) optionally one or more organic solvents.

[0608] More preferably, the RM formulation comprises:

[0609] a) one or more compounds of formula I or its corresponding preferred subformulae,

[0610] b) one or more chiral isomerizable compounds, preferably selected from formula I*, more preferably from formula I*A or its corresponding preferred subformulae,

[0611] c) optionally one or more, preferably two or more di-reactive polymerizable mesogenic compounds, preferably selected from compounds of formula DRMa-1,

[0612] d) optionally one or more, preferably two or more mono-reactive polymerizable mesogenic compounds, preferably selected from compounds of formula MRM-1 and / or MRM-4 and / or MRM-6 and / or MRM-7,

[0613] e) optionally one or more additional polymerizable chiral compounds, preferably selected from formula CRM or its subformulae,

[0614] f) optionally one or more additional non-polymerizable chiral compounds, preferably selected from formulae C-I, C-II and C-III,

[0615] g) optionally one or more antioxidant additives,

[0616] h) optionally one or more photoinitiators,

[0617] i) optionally one or more organic solvents.

[0618] The RM mixture and the RM formulation can be prepared in the usual manner per se, for example by mixing one or more of the above-mentioned chiral isomerizable compounds with one or more RMs as defined above, and optionally with other additives.

[0619] The present application further relates to a method of preparing an optical element, comprising, preferably consisting of, the following steps:

[0620] - providing a layer of a RM mixture or RM formulation as described above and below onto a substrate, which is optionally equipped with an alignment layer capable of inducing planar alignment of adjacent layers of the RM mixture,

[0621] - optionally removing any solvent, if present,

[0622] - optionally annealing the RM mixture (i.e. without solvent), preferably at a temperature at which it is in the chiral nematic phase,

[0623] - a first step of irradiation of the RM mixture with actinic radiation, preferably with UV radiation, in air (first UV step),

[0624] - optionally annealing the RM mixture, preferably at a temperature at which it is in the chiral nematic phase, and

[0625] - a second step of irradiation of the RM mixture with actinic radiation, preferably with UV radiation, in an inert gas atmosphere (second UV step).

[0626] The present application further relates to an optical element obtainable by this method.

[0627] More preferably, the method of preparing an optical element according to the present application comprises the following steps:

[0628] - providing a layer of the RM mixture or RM formulation as described hereinbefore and hereinafter or a solution thereof onto a substrate, preferably equipped with an alignment layer inducing a planar alignment layer (e.g. a rubbed polyimide layer or a photoalignment layer), e.g. by spin coating or a printing method, and optionally removing any solvent present,

[0629] - optionally annealing the layer of the RM mixture (i.e. without solvent), preferably at a temperature at which it is in the chiral nematic phase,

[0630] - exposing the layer of the RM mixture (i.e. without solvent) to UV light, preferably in an air atmosphere at ambient temperature, which causes photoisomerization of the chiral compounds comprising photoisomerizable groups and provides a chiral structure with biased helical pitch, preferably exposing the layer of the RM mixture to unpolarized UV light, very preferably to unpolarized UVA light, e.g. at a dose of 40 to 500 mJ / cm 2 ("first UV step"),

[0631] - optionally annealing the RM mixture, preferably at a temperature at which it is in the chiral nematic phase,

[0632] - exposing the layer of the RM mixture to UV light, preferably in an inert gas atmosphere (e.g. nitrogen) and at ambient temperature, which causes photopolymerization of the RM, preferably exposing the layer of the RM mixture to unpolarized UV light, very preferably to unpolarized UVA light, e.g. at a dose of 200 to 2000 mJ / cm 2 ("second UV step").

[0633] Preferably, in the method according to the present application, 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 a heat treatment during or between the irradiation or UV exposure steps.

[0634] The first irradiation step or first UV step causes photoisomerization of the chiral compound comprising a photoisomerizable group and provides a chiral structure with a biased helical pitch. The second irradiation step or second UV step causes photopolymerization of the polymerizable mesogenic compound and thereby fixes the chiral structure.

[0635] Without wishing to be bound by a particular theory, the inventors believe that the presence of oxygen in air during the first UV step inhibits radical polymerization. This effect provides several advantages.

[0636] Firstly, this effect also allows the use of RMs having an absorption maximum in the same UV wavelength range as the photoisomerizable chiral compound and thus will polymerize unless hindered. Since it is often difficult to find suitable RMs with very high birefringence as well as suitable chiral photoisomerizable compounds, this allows a wider selection of suitable mixture components so that the chiral RM mixture composition can more easily be adapted to the specific requirements of the end use of the polymer film as an optical element.

[0637] Secondly, this effect can be advantageously used for a film that is only partially polymerized and has a gradient in the film thickness direction. Thus, the RMs at the top of the film that are exposed to oxygen have a lower polymerization rate, while the RMs at the bottom of the film (at the substrate interface) are much less hindered by oxygen and thus can polymerize more easily.

[0638] Due to the presence of the photoisomerizable chiral compound, photoisomerization occurs during the first UV step and the photoisomerizable chiral compound has a reduced helical twisting power (HTP) upon exposure to UV light. In regions where the polymer density is higher, the changes in the chiral structure are hindered by the physical resistance. At the top or surface of the film, the polymer density is low, so the chiral structure can be modified more freely. However, at the bottom of the film adjacent to the substrate (where more photopolymerization occurs), the polymer density is higher, so the changes in the chiral structure are hindered. This results in a gradient of chiral pitch in the film. Thus, after performing the method as described above, the polymerized RM mixture exhibits an accelerated chiral rotation in the direction to the main plane of the polymer film or the film thickness. Preferably, the polymerized RM mixture exhibits a biased pitch so that the chiral rotation angle gradually increases or decreases through the film thickness.

[0639] The RM mixture or RM formulation can be coated or printed onto a substrate, for example by spin coating, printing or other known techniques, and the solvent evaporated off before polymerization. In most cases, it is appropriate to heat the mixture to facilitate evaporation of the solvent.

[0640] The RM mixture or RM formulation can be applied to the substrate by conventional coating techniques such as spin coating, bar coating or blade coating. It can also be applied to the substrate by conventional printing techniques known to the expert, such as for example screen printing, offset printing, roll-to-roll printing, letterpress printing, gravure printing, rotogravure printing, flexographic printing, intaglio printing, pad printing, heat-seal printing, inkjet printing or printing by means of a stamp or printing plate.

[0641] Suitable substrate media and substrates are known to the expert and described in the literature, for example conventional substrates for the optical film industry, such as glass or plastic. Particularly suitable and preferred substrates for polymerization are polyesters, such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), polyvinyl alcohol (PVA), polycarbonate (PC), triacetyl cellulose (TAC), a cyclic olefin polymer (COP) or generally known filter materials, preferably triacetyl cellulose (TAC), a cyclic olefin polymer (COP) or generally known filter materials.

[0642] In another preferred embodiment, the substrate has a surface grating or surface pattern. In another preferred embodiment, the substrate is prepared from a photoalignment layer (PAL) which is patterned by laser interference to produce a grating pattern with a defined pitch.

[0643] The Friedel-Creagh-Kmetz law can be used to predict whether the mixture will adopt planar or perpendicular alignment by comparing the surface energy (γ RM ) of the RM layer with the surface energy (γ s ) of the substrate:

[0644] If γ RM > γ s , the reactive mesogens will exhibit perpendicular alignment, and if γ RM < γ s , the reactive mesogens will exhibit planar alignment.

[0645] Without wishing to be bound by a particular theory, when the surface energy of the substrate is relatively low, the intermolecular forces between the reactive mesogens are stronger than the forces across the RM-substrate interface, and thus, the reactive mesogens align perpendicular to the substrate (perpendicular alignment) in order to maximize the intermolecular forces. Therefore, an additional alignment layer is required which is able to induce planar alignment with the adjacent RM mixture.

[0646] When the surface tension of the substrate is greater than the surface tension of the RM, the forces across the interface dominate. If the reactive mesogens align parallel to the substrate, the interfacial energy is minimized, and thus the long axis of the RM can interact with the substrate. Unidirectional planar alignment can be promoted by coating the substrate with a polyimide layer and subsequently rubbing the alignment layer with a velvet cloth.

[0647] Other suitable planar alignment layers are known in the art, such as rubbed polyimide or alignment layers prepared by photo-alignment, as described, for example, in US 5,602,661, US 5,389,698 or US 6,717,644.

[0648] In general, a review of alignment techniques is given, for example, by I. Sage in "Thermotropic Liquid Crystals" (G. W. Gray, Ed., John Wiley & Sons, 1987, pages 75-77); and by T. Uchida and H. Seki in "Liquid Crystals - Applications and Uses Vol. 3" (B. Bahadur, Ed., World Scientific Publishing, Singapore 1992, pages 1-63). Another review of alignment materials and alignment techniques is given by J. Cognard, Mol. Cryst. Liq. Cryst. 78, Supplement 1 (1981), pages 1-77.

[0649] In a preferred embodiment, the process of the present application comprises a process step allowing the RM mixture to rest for a certain time to allow the RM mixture to redistribute evenly onto the substrate (herein referred to as "annealing").

[0650] In a preferred embodiment, the layer stack is annealed between 10 seconds and 1 hour, preferably between 20 seconds and 10 minutes and most preferably between 30 seconds and 2 minutes after the RM mixture or RM formulation has been provided onto the substrate. Annealing is preferably carried out at room temperature.

[0651] The RM mixture preferably consists of compounds that self-align when deposited as a mixture onto the substrate. Thus, preferably the LC medium is not subjected to a heat treatment to align the mesogenic or liquid crystalline compounds prior to UV exposure.

[0652] If desired, the layer stack can be cooled to room temperature after annealing at elevated temperature. Cooling can be carried out actively with the help of cooling aids or passively by just leaving the layer stack at rest for a given time.

[0653] In a preferred embodiment, the RM mixture is exposed to actinic radiation in the first UV step as set out, for example, in WO 01 / 20394, GB 2,315,072 or WO 98 / 04651.

[0654] Actinic radiation means irradiation with light (such as 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). Preferably, the first UV step is carried out by light irradiation, in particular with UV light, especially with UVA light.

[0655] As a source of actinic radiation, one can use for example a single UV lamp or a set of UV lamps. When using higher lamp power, the curing time can be reduced. Another possible source of light radiation is a laser, for example a UV laser, an IR laser or a visible laser.

[0656] The curing time depends, inter alia, on the reactivity of the photoreactive compound, the thickness of the coated layer and the power and the selected wavelength of the UV lamp. The curing time is preferably < 5 minutes, very preferably < 3 minutes, most preferably < 1 minute. For large-scale production, a short curing time of < 30 seconds is preferred.

[0657] The suitable UV radiation power in the first UV step is preferably in the range of 5 to 300 mWcm -2 , more preferably in the range of 50 to 250 mWcm -2 and most preferably in the range of 100 to 180 mWcm -2 .

[0658] With regard to the applied UV radiation and over time, the suitable UV dose is preferably in the range of 20 to 1000 mJcm -2 , more preferably in the range of 30 to 800 mJcm -2 , very preferably in the range of 40 to 500 mJcm -2 , most preferably in the range of 40 to 200 mJcm -2 .

[0659] The first irradiation step or the first UV step is preferably carried out in air.

[0660] The first irradiation step or the first UV step is preferably carried out at room temperature.

[0661] The photopolymerization in the second irradiation step of the RM mixture is preferably achieved by exposing it to actinic radiation. Actinic radiation means irradiation with light (such as 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). Preferably, the polymerization is carried out by light irradiation, in particular with UV light. As a source of actinic radiation, one can use for example a single UV lamp or a set of UV lamps. When using higher lamp power, the curing time can be reduced. Another possible source of light radiation is a laser, for example a UV laser, an IR laser or a visible laser.

[0662] The curing time of the photopolymerization depends, inter alia, on the reactivity of the RM mixture, the thickness of the coated layer, the type of polymerization 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.

[0663] The suitable UV radiation power for the photopolymerization is preferably in the range of 100 to 1000 mWcm -2 , more preferably in the range of 200 to 800 mWcm -2 and most preferably in the range of 300 to 600 mWcm -2 .

[0664] The suitable UV dose with respect to the applied UV radiation and over time is preferably in the range of 25 to 16500 mJcm -2 , more preferably in the range of 50 to 7200 mJcm -2 , very preferably in the range of 100 to 3500 mJcm -2 , most preferably in the range of 200 to 2000 mJcm -2 .

[0665] The photopolymerization (second irradiation step or second UV step) is preferably carried out under an inert gas atmosphere, preferably in a nitrogen atmosphere.

[0666] The photopolymerization (second irradiation step or second UV step) is preferably carried out at room temperature.

[0667] The preferred thickness of the polymerized LC film according to the present application is determined by the required optical properties of the film or end product.

[0668] For optical applications of the polymer film, the thickness is preferably 0.1 to 10 pm, very preferably 0.1 to 2 pm, in particular 0.1 to 1 pm.

[0669] As mentioned above, due to the photoisomerization of the chiral compounds during the first UV step, the HTP is reduced and the helical pitch is extended to larger values, wherein this effect is stronger at the top or surface of the film than at the bottom of the polymer film adjacent to the substrate, resulting in a pitch gradient in the film, wherein the helical pitch gradually increases or decreases through the film thickness, depending on the direction of observation.

[0670] Preferably, in the polymer film according to the present application, the minimum helical pitch is < 1200 nm, very preferably in the range of 200 to 1200 nm. More preferably, the helical pitch increases in the entire thickness direction from the side of the polymer film close to the substrate on which the polymer film is prepared.

[0671] In a preferred embodiment, the polymer film of the present application exhibits planar alignment, i.e. the LC molecules are oriented parallel to the film plane and the helix axis is oriented substantially perpendicular to the film plane.

[0672] In another preferred embodiment, the polymer film of the present application exhibits tilted alignment, i.e. the LC molecules are oriented at an angle (also referred to as tilt angle) to the film plane and the helix axis is oriented at an angle to the film plane. In tilted films, the tilt angle between the helix axis and an axis perpendicular to the film plane is in the range of 5° to 45°, very preferably 15° to 45°.

[0673] In another preferred embodiment, the tilt angle between the helix axis and an axis perpendicular to the film plane is in the range of 0 to 15°, very preferably 0 to 5°.

[0674] Planar alignment can be induced, for example, by providing a alignment layer (e.g. a polyimide alignment layer) to the substrate as set forth 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).

[0675] The optical retardation (δ(λ)) of a polymer film as a function of the wavelength (λ) of the incident light beam is given by the following equation (7):

[0676]

[0677] where (Δn) is the birefringence of the film, (d) is the thickness of the film and λ is the wavelength of the incident light beam.

[0678] The birefringence and the corresponding optical retardation depend on the thickness of the film and the tilt angle of the optical axes in the film (see Berek compensator). Thus, the skilled person realizes that different optical retardations or different birefringences can be induced by adjusting the orientation of the liquid crystal molecules in the polymer film.

[0679] The optical retardation as a function of the thickness of the polymer film according to the present application is less than 200 nm, preferably less than 180 nm and even more preferably less than 150 nm.

[0680] The birefringence (Δn) of the polymer film according to the present application is preferably in the range of 0.20 to 0.60, more preferably 0.25 to 0.55, very preferably 0.30 to 0.50.

[0681] After photopolymerization, the resulting polymer film can be removed from the substrate and combined with other substrates or optical films by lamination processes known to the skilled person. Suitable substrates and optical films are given above and include, inter alia, polarizers (in particular linear polarizers), photo-alignment layers or diffractive gratings (e.g. PB gratings).

[0682] The inventive polymer LC films have good adhesion to plastic substrates, in particular to TAC, COP and color filters. Thus, they can be used as adhesion agents or primer layers for subsequent LC layers which cannot adhere sufficiently to the substrate as such.

[0683] The inventive polymer films can also be used as alignment films or substrates for other liquid crystal or RM materials. The inventors have found that the polymer films obtainable from the RM formulations as described above and below are particularly suitable for multilayer applications due to their improved dewetting properties. In this way, stacks of optical films or preferably polymerized LC films can be prepared.

[0684] The present invention further relates to an optical, electro-optical or electronic device or component comprising an optical element as described above and below.

[0685] Preferably, the component is a diffraction grating, very preferably a PBG or Bragg PG, comprising an optical element obtained from the RM mixture or RM formulation according to the present invention as described above and below.

[0686] In summary, the inventive polymer films and RM mixtures can be used for optical elements such as polarizers, compensators, alignment layers, circular polarizers or color filters in liquid crystal displays or projection systems, for the preparation of liquid crystals or effect pigments and especially for reflective films with spatially varying reflective color (e.g. as multicolor images for decorative, information storage or security purposes, e.g. non-forgable documents such as identity cards or credit cards, banknotes, etc.).

[0687] The inventive polymer films can be used in transmissive or reflective displays. They can be used in conventional OLED displays or LCDs, in particular LCDs.

[0688] The present invention is described above and below by way of preferred embodiments. It will be understood that various changes and modifications can be made without departing from the spirit and scope of the invention.

[0689] Many of the compounds mentioned above and below or mixtures thereof are commercially available. All these compounds are known or can be prepared by methods known per se, in particular under reaction conditions known and suitable for the reaction, as described in the literature (for example, in standard works such as Houben-Weyl, Methoden der Organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart). Variations can also be used here which are known per se but are not mentioned here.

[0690] It will be appreciated that variations to the foregoing embodiments of the application can be made and will be apparent to those skilled in the art, without departing from the scope of the application. Such variations are not to be regarded as a departure from the scope of the application, and all such modifications as would be recognized by one skilled in the art to those field to those disclosed herein are to be included as further embodiments of the present application. Accordingly, no limitation is placed on the scope of the application by the description of the preferred embodiments which follows. The use of the terms "include", "includes" or "including" in the description above and in the following claims are not meant to be construed as specifying that there are no other elements other than the ones expressly named in such specifications or claims. Nor are such terms intended to exclude the presence of other elements or steps. It is to be understood that where the application, or any embodiment thereof, is dependent on any one of a plurality of options, this is intended to mean that the application, or any embodiment thereof, is equally dependent on each of the individual options.

[0691] In addition to combinations of at least some of such features and / or steps exclusive of each other, all features disclosed in this specification can be combined in any combination. In particular, preferred features of the application are applicable to all aspects of the application and can be used in any combination. Likewise, features described in non-essential combinations can also be used separately (not in combination).

[0692] It will be appreciated that many of the features described above, particularly preferred embodiments, are themselves inventive and can be sought independent protection. In addition to, or instead of, any application presently claimed, these features can be sought independent protection.

[0693] Unless explicitly stated otherwise, all temperature values indicated in this application such as, for example, melting point T(K,N), transition from smectic (S) to nematic (N) phase T(S,N) and clearing point T(N,I) are quoted in degrees Celsius (°C). Furthermore, K denotes the crystalline state, N denotes the nematic phase and I denotes the isotropic phase. The values between these symbols denote the transition temperatures.

[0694] All physical properties have been and are determined according to "Merck Liquid Crystals, Physical Properties of Liquid Crystals", Status Nov. 1997, Merck KGaA, Germany and are given for a temperature of 20 °C.

[0695] In the foregoing and hereinafter, percentages are percent by weight. All temperatures are given in degrees Celsius.

[0696] In the foregoing and hereinafter, m.p. denotes melting point, cl.p. denotes clearing point, T g denotes glass transition temperature. Furthermore, C denotes the crystalline state, N denotes the nematic phase, S A , S B etc. denote smectic A phase, smectic B phase etc., S X denotes a smectic phase not further identified, X denotes an intermediate phase not further identified and I denotes the isotropic phase. The values between these symbols denote the transition temperatures in °C. Δn denotes the optical anisotropy or birefringence (Δn = n e - n o , wherein no represents the refractive index perpendicular to the longitudinal molecular axis and n e represents the refractive index parallel to it), at 589 nm and 20°C. Unless explicitly stated otherwise, optical and electro-optical data are measured at 20°C. "Clearing point" and "clearing temperature" mean the temperature at which the LC phase transforms into the isotropic phase.

[0697] Unless stated otherwise, the percentage of a solid component in an RM mixture or RM formulation as described above and below refers to the total amount of solids in the mixture or formulation, i.e. without any solvent.

[0698] Unless stated otherwise, all optical, electro-optical properties and physical parameters, such as birefringence, dielectric constant, conductivity, resistivity and sheet resistance refer to a temperature of 20°C.

[0699] The application will now be described in more detail with reference to the following working examples, which are illustrative only and do not limit the scope of the application.

[0700] Example 1

[0701] The following chiral RM mixture was prepared:

[0702] The additive Irganox® 1076 is commercially available from CIBA, Switzerland. The photoinitiator NCI-930 is commercially available from Adeka. The Polyfox® 2000 is a dispersant commercially available from Elementis. TM PF-656 is a surfactant commercially available from Synthomer.

[0703] The compound I25 has a high birefringence of 0.292.

[0704] A unilayer polymer film with a non-linear twist was prepared from the mixture M1 by the following method:

[0705] The mixture was dissolved in a solvent blend MIBK:PGMEA at 25% solid content. The solution was subsequently spin-coated at 900 rpm on a polyimide coated glass slide. The wet layer was heated on a hot plate at 75°C for 60 seconds to evaporate the solvent and to anneal the RM layer.

[0706] In a first irradiation step (isomerization step), the RM layer was exposed to non-polarized UV-A light (40-50 mJ / cm 2 ) at room temperature in an air atmosphere. Since the UV wavelength is inside the absorption band of the chiral isomerizable compound, it causes isomerization of the compound, leading to a decrease of its helical twist force.

[0707] In the second irradiation step (polymerization step), the RM layer is exposed to unpolarized UV-A light (200-6000 mJ / cm²) in an N₂ environment at room temperature. 2 This causes complete polymerization of the RM layer and fixes the helical twisted structure. The polymerized film thickness is 1.4–1.5 μm.

[0708] Comparative Example 1

[0709] For comparative purposes, a monolayer film with linear distortion was prepared from mixture M1 by the method described in Example 1, but the first UV irradiation step in an air atmosphere was omitted.

[0710] Comparative Example 2

[0711] For further comparative purposes, a bilayer membrane as disclosed in the prior art was prepared from mixtures M2 and M3 by the following method:

[0712] Mixtures M2 and M3 were dissolved in solvent blend MIBK:PGMEA at solid contents of 25% and 20%, respectively.

[0713] For the first layer, the solution from M2 was spin-coated onto a polyimide-coated glass slide at 3600 rpm. The wet layer was heated on a hot plate at 75°C for 60 seconds to evaporate the solvent and anneal the first RM layer.

[0714] The first RM layer was exposed to unpolarized UV-A light (200-600 mJ / cm²) in an N2 environment at room temperature. 2 This causes complete polymerization of the RM layer and fixes the helical twisted structure. The polymerized film thickness is approximately 0.78 μm.

[0715] For the second layer, the solution from M3 was spin-coated onto the first layer at 2300 rpm. The wet layer was heated on a hot plate at 30°C for 60 seconds to evaporate the solvent and anneal the second RM layer.

[0716] The second RM layer was exposed to unpolarized UV-A light (200-600 mJ / cm²) at room temperature in an N2 environment. 2 This causes complete polymerization of the RM layer and fixes the helical twisted structure. The polymerized film thickness is approximately 0.66 μm.

[0717] The parameters of the two sublayers in the bilayer membrane have been customized to replicate the membrane in the prior art reference Xiang, X., Kim, J. & Escuti, MJ Sci Rep 8, 7202 (2018), and are summarized in Table 1.

[0718] Table 1: Parameters of sub-layers 1 and 2 according to comparative example 2

[0719] Optical results

[0720] The prepared films were measured on an Axoscan (Axometrics) to obtain and compare their optical properties. The Axoscan measures the fast axis of birefringent films as well as the linear and circular retardation of the films. The fast axis represents the polarization state that propagates fastest through the optical film. The fast axis is plotted using a Poincare sphere.

[0721] The Poincare sphere is a convenient way of mapping all possible polarization states onto the surface of a sphere. Each polarization state is represented using a longitude and latitude coordinate: the latitude on the sphere represents the amount of ellipticity, while the longitude represents the angle of the ellipse. In particular, the north and south poles of the sphere represent left and right circular polarization, while the equator represents all possible states of linear polarization, with all orientations represented by the longitude coordinate. Elliptical polarization states are mapped on points between the equator and the poles, as shown in Figure 2 Details on the Poincare sphere can be found in, for example, J. E. Bigelow and R. A. Kashnow, APPLIED OPTICS / Vol. 16, No. 8 / August 1977.

[0722] The behavior of the fast axis polarization states represented on the Poincare sphere is directly related to the twist profile of the film.

[0723] Thus, from a general observation of the Poincare sphere, it can be seen that the fast axis of a film with a linear twist passes through the poles, while the fast axis of a film exhibiting a non-linear twist does not pass through the poles.

[0724] Furthermore, if two anisotropic films have the same fast axis as the fast axis plotted on the Poincare sphere, the two anisotropic films are optically identical.

[0725] Figure 3 The fast axis of the single layer polymer film of example 1 plotted on the Poincare sphere is shown when observed from the top (measuring the film with the top up). The polarization ellipses vary with each wavelength, but each has a right handed rotation.

[0726] It can be seen that the single layer polymer film of example 1 has a non-linear, asymmetric twist profile, with the twist rate decreasing from the bottom to the top. Thus, when light passes into the bottom of the film, it first travels through a region of fast twist. When light passes into the top of the film, it first travels through a region of slow twist. Furthermore, due to the asymmetry of the twist in the z direction, the film does not act reversibly.

[0727] Figure 4The fast axis of the single layer film of Comparative Example 1 plotted on a Poincare sphere is shown. It can be seen that the film exhibits a uniform and linear twist through the thickness of the film. The twist measured using Axoscan software was 488°. The polarization state can be clearly observed to be centered on the pole towards the equator, which exhibits a linear behavior of the twist through the z-axis, unlike the case of the perpendicular polarization profile observed in the non-linear twist using the film of Example 1.

[0728] Figure 5a The fast axis of the double layer polymer film of Comparative Example 2 plotted on a Poincare sphere is shown when viewed from the top. Figure 5b The fast axis of the double layer polymer film of Comparative Example 2 plotted on a Poincare sphere is shown when viewed from the bottom.

[0729] It can be seen that the double layer polymer film of Comparative Example 2 has a non-linear, asymmetric twist profile. Due to the asymmetry of the twist in the z-direction, the double layer film does not act reversibly. When light passes into the top of the double layer film, it first travels through a region of fast twist (a; measured upwards from the film). When light passes into the bottom of the film, it first travels through a region of slow twist (b; measured downwards from the film). Figure 5a Figure 5b

[0730] For clarity, Figure 6a and Figure 6b The regions of fast and slow twist in the single layer polymer film of Example 1 (a) and the double layer polymer film of Comparative Example 2 (b) are schematically illustrated.

[0731] From Figure 3 , Figure 4 , Figure 5a and Figure 5b It can be seen that the twist profile formed by the single layer film of Example 1 according to the present application exhibits fast twist at the bottom of the substrate and slow twist at the top of the substrate. This is similar to the double layer film (of Comparative Example 2), where it twists slowly near the substrate and fast away from the substrate when measured downwards from the film. The Poincare configuration is similar in both cases for the wavelength of light incident on the film.

[0732] Thus, the single layer film according to the present application exhibits a similar polarization state to the double layer film according to the comparative example when measured on Axoscan, demonstrating similar behavior to that achieved in the double layer film.

[0733] This demonstrates that a single layer film with an asymmetric twist profile can be used in place of a double layer film with different twist angles, which exhibits similar optical behavior and can be made using the materials and methods according to the present application as described above and below.

[0734] ​​In contrast, the single layer film prepared according to the method of comparative example 1 did not exhibit an asymmetric non-linear twist without a separate UV exposure step under air atmosphere, but rather a uniform and linear twist across the film thickness.

[0735] Diffraction efficiency

[0736] To demonstrate that a single layer RM film with a non-linear twist profile according to example 1 can exhibit similar diffraction efficiency when used as a diffraction grating as a double layer multi-tilt RM film according to comparative example 2, the diffraction efficiency of a grating with a given twist profile was determined using the finite element method. The model was set up using Comsol Multiphysics.

[0737] The first model was based on a double layer grating with two RM sub-layers, each sub-layer having a linear twist profile but different twist angles, prepared according to the method described in comparative example 2. The thicknesses and twist angles of the two RM sub-layers were 0.78 pm and 0.66 pm and -113.5° and -242°, respectively, as shown in Table 1 above.

[0738] The second model was based on a single layer grating with one RM film having a non-linear twist profile, prepared according to the method described in example 1. The film had a total thickness of 1.44 pm and a non-linear twist with a parabolic profile (quadratic model) and a total twist angle of -355.5°.

[0739] Figure 7 The twist profiles of the double layer film (a) and the single layer film (b) are shown in Figure 2.

[0740] The parameters were as follows: the refractive indices of the RM material were 1.81 (n e ) and 1.55 (n o ), the grating periodicity was 400 nm and the light wavelength was 550 nm.

[0741] Figure 8 The first order diffraction efficiency of the double layer film (a) and the single layer film (b) as a function of the incidence angle is shown in Figure 3. Both films exhibited a high first order diffraction efficiency with an angular bandwidth of about 40 o .

[0742] The above results show that a single layer grating with an asymmetric (here: quadratic) twist profile based on a single chiral RM film that can be prepared according to the method described in example 1 has comparable angular performance, a high first order diffraction efficiency and a wide angular bandwidth as a double layer grating based on two chiral RM sub-layers with a linear twist profile that can be prepared according to the method described in comparative example 2.

[0743] Examples 2 to 5

[0744] The following mixture was formulated:

[0745] The photoinitiator SPI-03 was purchased from Samyang, the photoinitiator N1919T was purchased from Adeka, the photoinitiator TR-PBG304 was purchased from Tronly and the photoinitiator Irgacure® 651 was purchased from Ciba.

[0746] A unilayer polymer film with an asymmetric non-linear twist profile was prepared as described in Example 1.

[0747] Figure 9 The fast axis of the unilayer polymer film of Example 2 plotted on a Poincare sphere when viewed from the top is shown.

[0748] Figure 10 The fast axis of the unilayer polymer film of Example 3 plotted on a Poincare sphere when viewed from the top is shown.

[0749] Figure 11 The fast axis of the unilayer polymer film of Example 4 plotted on a Poincare sphere when viewed from the top is shown.

[0750] Figure 12 The fast axis of the unilayer polymer film of Example 5 plotted on a Poincare sphere when viewed from the top is shown.

[0751] It can be seen that all the unilayer polymer films of Examples 2 to 5 have an asymmetric twist profile with a twist rate decreasing from the bottom to the top, similar to the unilayer film of Example 1.

Claims

1. The present invention relates to optical elements, preferably to diffractive or polarizing gratings, comprising a monolithic film of a polymerized chiral RM mixture with a helically twisted orientation, wherein the helical pitch increases or decreases in the direction of the layer thickness.

2. An optical element according to claim 1, characterised in that The chiral RM mixture comprises at least one, preferably exactly one chiral compound with one or more isomerizable groups, preferably one or more photoisomerizable groups, which is preferably polymerizable.

3. An optical element according to claim 1 or 2, characterised in that The chiral RM mixture comprises at least one RM with a birefringence > 0.25, very preferably > 0.

28.

4. Optical element according to one or more of claims 1 to 3, characterized in that The chiral reactive mesogenic mixture comprises one or more compounds of formula I: wherein each group independently of the others and on each occurrence identically or differently has the following meanings: P is a polymerizable group, Sp is a spacer group or a single bond, R 11 H, F, CI, CN, optionally fluorinated alkyl having 1 to 15, preferably having 1 to 5 C atoms, alkoxy, thioalkyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy, or P-Sp, A, B, D and E are selected from the group consisting of 1,4-phenylene, naphthalene-1,4-diyl, naphthalene-2,6-diyl, phenanthrene-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']bithiophene-2,5-diyl, indol-4,7-diyl, benzothiophene-4,7-diyl, 9,10-dihydro-phenanthrene-2,7-diyl, 1,2,3,4-tetrahydronaphthalene-5,8-diyl or indan-2,5-diyl, where in addition one or more CH groups in these radicals can be replaced by N, all of the above optionally substituted by one or more groups L or P-Sp-, 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-2,7-diyl, benzo[1,2-b:4,5-b']bithiophene-2,5-diyl, indol-4,7-diyl, benzothiophene-4,7-diyl, all of the above optionally substituted by one or more groups L or P-Sp-, and one of the rings C and D can also denote a single bond, L is F, CI, -CN, -SCN, P-Sp- or straight-chain, branched or cyclic alkyl with 1 to 25 C atoms, wherein one or more non-adjacent CH2-groups are optionally replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, CR 0 =CR 00 -, -C≡C-, Alternatively, it is replaced in such a way that the O- and / or S-atoms are not directly connected to one another, and wherein one or more H atoms are each optionally replaced by P-Sp-, F or CI, or two substituents L attached to directly adjacent C atoms can also form a cycloalkyl or cycloalkenyl group with 5, 6, 7 or 8 C atoms, Z 11 , Z 12 -O-, -S-, -CO-, -COO-, -OCO-, -S-CO-, -CO-S-, -O-COO-, -CO-NR 0 -, -NR 0 -CO-, -NR 0 -CO-NR 00 -, -NR 0 -CO-O-, -O-CO-NR 0 -, -OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -CH2CH2-, -(CH2) n1 -, -CF2CH2-, -CH2CF2-, -CF2CF2-, -CH=N-, -N=CH-, -N=N-, -CH=CR 0 -, -CY 1 =CY 2 -, -C≡C-, -CH=CH-COO-, -OCO-CH=CH- or a single bond, preferably -COO-, -OCO-, -C≡C- or a single bond, most preferably a single bond, n1 is 1, 2, 3 or 4, r is 0, 1, 2, 3 or 4, preferably 0, 1 or 2, s is 0, 1, 2 or 3, preferably 0, 1 or 2, t is 0, 1 or 2, preferably 0 or 1, R 0 , R 00 is H or alkyl having 1 to 12 C atoms, Y 1 , Y 2 H, F, CI, NCS or CN, n is 0, 1, 2, 3 or 4, preferably 0, 1 or 2, more preferably 0 or 1, most preferably 0, m is 0, 1, 2, 3 or 4, preferably 0, 1 or 2, more preferably 0 or 1, most preferably 0.

5. An optical element according to claim 4, characterised in that In the compounds of the formula I, the 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']bithiophene-2,5-diyl, indol-4,7-diyl, benzothiophene-4,7-diyl, all of the above optionally substituted by one or more groups L and / or P-Sp-.

6. An optical element according to claim 4 or 5, characterised in that In the compound of formula I, ring C is selected from the group consisting of benzo-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-.

7. Optical element according to one or more of claims 4 to 6, characterized in that In the compound of formula I, n = m = 0 and the 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 by one or two groups L, and L 1 and L 2 independently of one another, denote H or one of the meanings given for L in claim 3, and L and r are as defined in claim 3.

8. Optical element according to one or more of claims 4 to 7, characterized in that In this compound of formula I, P is an acrylate or a methacrylate, preferably an acrylate, and Sp is -(CH2). p1 -、-(CH2) p1 -O-、-(CH2) p1 -O-CO-、-(CH2) p1 -CO-O- or -(CH2) p1 -O-CO-O-, where p1 is an integer from 1 to 6.

9. Optical element according to one or more of claims 1 to 8, characterized in that The chiral RM mixture contains a isomerizable chiral compound selected from formula I*: R 3 -(A 3 -Z 3 ) m -G(-(Z 4 -A 4 ) l -R 4 ) k I* wherein each group independently of each other and on each occurrence identically or differently has the following meaning: R 3 , R 4 is H, F, CI, CN, P-Sp- or alkyl with up to 25 C atoms, it being possible for the alkyl to be unsubstituted, mono- or multiply-substituted with halogen or CN, one or more non-adjacent CH2groups are also possible and are in each case independently from one another replaced by -O-, -S-, -NH-, -N(CH3)-, -CO-, -COO-, -OCO-, -OCO-O-, -S-CO-, -CO-S- or -C=C-, in such a way that oxygen atoms are not directly linked to one another, P is a polymerizable group, Sp is a spacer group or a single bond, Z 3 , Z 4 -CO-O-, -O-CO-, -CH2CH2-, -OCH2-, -CH2O-, -CH=CH-, -CH=CH-CO-O-, -O-CO-CH=CH-, -CH=C(CN)-CO-O-, -O-CO-C(CN)=CH-, -N=N-, -CH=N-, -N=CH-, -C≡C- or a single bond, A 3 , A 4 is an alicyclic, heterocyclic, aromatic or heteroaromatic radical having 4 to 20 ring atoms which is monocyclic or polycyclic and which is optionally substituted by one or more groups L or P-Sp-, G is a chiral group, L is F, CI, -CN, -SCN, P-Sp- or straight-chain, branched or cyclic alkyl with 1 to 25 C atoms, wherein one or more non-adjacent CH2-groups are optionally replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, CR 0 =CR 00 -, -C≡C-, Alternatively, it is replaced in such a way that the O- and / or S-atoms are not directly connected to one another, and wherein one or more H atoms are each optionally replaced by P-Sp-, F or CI, or two substituents L attached to directly adjacent C atoms can also form a cycloalkyl or cycloalkenyl group with 5, 6, 7 or 8 C atoms, m, 1 independently of each other are 0, 1, 2 or 3, k is 0, 1 or 2, wherein the compound contains at least one isomerizable group, which is preferably a photoisomerizable group.

10. An optical element according to claim 9, characterised in that The compounds of the formula I* contain an isomerizable group selected from stilbene, (1,2-difluoro-2-phenyl-vinyl)-benzene, cinnamate, a-cyanocinnamate, 4-phenylbut-3-en-2-one, 2-benzylidene-1-indanone, Schiff base, chalcone, coumarine, chromone, norcaradienone or azo-phenyl group, and / or Z 3 and / or Z 4 independently of one another -CH=CH-CO-O-, -O-CO-CH=CH-, -CH=C(CN)-CO-O-, -O-CO-C(CN)=CH-, -CH=N-, -N=CH- or -N=N-.

11. An optical element according to claim 9 or 10, characterised in that In the compound of formula I*, the chiral group G is selected from or derived from a dianhydrohexitol, preferably isosorbide, isomannide or isoidide, a 1,1'-bi-2-naphtol or a 1,2-diphenyl-1,2-ethanediol group.

12. Optical element according to one or more of claims 9 to 11, characterized in that In the compound of formula I*, G is selected from the following formulae: wherein X is -CO-O-, -CH=CH-CO-O-, -CH=C(CN)-CO-O-, in each of which the ester O-atom is bonded to the furan ring, or -N=N-, q is 0, 1, 2, 3 or 4, L has the meaning of claim 9, R 11 and R 12 independently of one another represent R 3 -(A 3 -Z 3 ) m - or R 11 and R 12 together with the O atom form an optionally substituted cyclic group or spirocyclic group, which is 4 -A 4 ) l -R 4 substituted with a group -Z R 13 and R 14 independently of one another represent R 3 -(A 3 -Z 3 ) m - a1 and a2 independently of each other are 0, 1 or 2, and the dotted line indicates a bond to one or more adjacent groups in formula I*.

13. Optical element according to one or more of claims 9 to 12, characterized in that The compound of formula I* is selected from the following subformulae: in which P, Sp, L and q have the meanings given in claim 9, R* has a meaning different from P-Sp- in claim 9, R** has a meaning different from P-Sp- in claim 9, R 3 and R 4 independently of one another denote alkyl having 1 to 12, preferably 1 to 6 C atoms, very preferably methyl, ethyl or propyl, and R 16 and R 17 independently of one another denote alkyl having 1 to 12, preferably 1 to 6 C atoms, very preferably methyl, ethyl or propyl, and R 18 denote P-Sp-, H or alkyl having 1 to 12, preferably 1 to 6 C atoms, very preferably H.

14. Optical element according to one or more of claims 9 to 13, characterized in that In the compounds of the formula I* or its subformulae, P is an acrylate or methacrylate, Sp is -0-(CH2) p1 - or -CO-O-(CH2) p1 - or -CO-O-(CH2) p1 - wherein the O-atom or CO-group is bound to the phenyl ring, respectively, pi is an integer from 1 to 6 and R 4 is P-Sp-.

15. Optical element according to one or more of claims 4 to 14, characterized in that The chiral RM mixture additionally comprises one or more RMs having only one polymerizable functional group, and / or one or more RMs having two or more polymerizable functional groups, which are different from formula I.

16. A method of manufacturing an optical element according to one or more of claims 1 to 15, comprising the steps of, Preferably consisting of the following steps: - providing a layer of a chiral reactive mesogenic mixture as defined in one or more of claims 1 to 15 onto a substrate, which is optionally equipped with an alignment layer capable of inducing planar alignment of adjacent layers of the chiral reactive mesogenic mixture, - optionally removing any solvent, if present, - optionally annealing the layer of the chiral reactive mesogenic mixture, preferably at a temperature at which it is in a chiral nematic phase, - irradiating the chiral reactive mesogenic mixture in air with actinic radiation, preferably with UV radiation, in a first step (first UV step), - optionally annealing the layer of the chiral reactive mesogenic mixture, preferably at a temperature at which it is in the chiral nematic phase, and - irradiating the chiral reactive mesogenic mixture in an inert gas atmosphere with actinic radiation, preferably with UV radiation, in a second step (second UV step).

17. The method according to claim 16, wherein the substrate has a surface grating or pattern.

18. An optical, electro-optical or electronic device or component thereof comprising an optical element according to one or more of claims 1 to 15.

19. The assembly according to claim 18, selected from the group consisting of optical retardation films, polarizers, optical compensators, diffraction or surface gratings, Bragg polarization gratings (Bragg PG), polarization volume gratings (PVG) or Pancharatnam-Berry (PB) gratings, in addition to non-mechanical beam steering elements, optical waveguides, optical couplers or combiners, polarization beam splitters, partial mirrors, reflective films, alignment layers, color filters, anti-static protection sheets, electromagnetic interference protection sheets, lenses for light guiding, focusing and optical effects, polarization control lenses and IR reflective films.

20. The device according to claim 18, selected from the group consisting of liquid crystal displays, organic light emitting diodes, autostereoscopic 3D displays, see-through near-eye displays, AR / VR systems, AR / VR application goggles, switchable windows, spatial light modulators, optical data storage devices, optical sensors, holographic devices, spectrometers, optical communication systems, polarimeters or front light / back light.

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