Switching layer for switching elements

Abstract

The invention relates to a switching layer assembly for dimming and scattering light and to a window element comprising an arrangement of switching layers.

Description

[0001] The invention relates to a switching layer assembly for dimming and scattering light and to a window element comprising an arrangement of switching layers.

[0002] Devices for controlling or modulating the transmission of light are commonly used in display applications, but they can also be used, for example, in so-called smart window applications. R. Baetens et al., "Properties, requirements and possibilities of smart windows for dynamic daylight and solar energy control in buildings: A state-of-the-art review", Solar Energy Materials & Solar Cells, 94 (2010), pp. 87-105, review different dynamic smart windows. As described herein, smart windows can utilize several technologies for modulating the transmittance of light, such as electrochromic-based devices, liquid crystal devices, and electrophoretic or suspended particle devices.

[0003] It is also generally known that optical shutters and optical intensity modulators can be based on liquid crystals (LC).LC-based light modulators can be used in switchable windows for architectural, automotive, avionics and marine applications.

[0004] Switching between different optical states may be controlled, for example, thermally.However, in many cases it may be appropriate and even advantageous to use electrical switching.

[0005] LC-based light modulation or conditioning devices may in principle rely on either the absorption of light or the scattering of light.

[0006] In some devices, the transmission of light can be reversibly altered, wherein the intensity of incident light can be attenuated, dimmed, or colored, yet at the same time exhibiting little or no scattering or haze in different operating states. Thus, such devices can be operated in and switched between bright and dark states (i.e., a state of relatively high light transmission and a state of relatively low light transmission), wherein both states are substantially non-hazy.

[0007] Several modes or configurations can be used to provide such a reversible transmission change. For twisted nematic (TN), super twisted nematic (STN) and vertical alignment (VA) liquid crystal cells, polarizers are used to control light transmission. It is also possible to use guest-host liquid crystal cells, which are based on a liquid crystal host doped with dichroic dye molecules. These guest-host systems can be used without any polarizer to modify light transmission. However, in some embodiments and applications, guest-host liquid crystal cells are used in combination with at least one polarizer.

[0008] LC-based light modulators using light scattering include so-called polymer dispersed liquid crystal (PDLC) or encapsulated or nematic curved alignment phase liquid crystal (NCAP), polymer network liquid crystal (PNLC), cholesteric liquid crystal (CLC), polymer stabilized cholesteric textured liquid crystal (PSCT), and dynamically scattering liquid crystal devices. These scattering devices can be switched between a transparent state (i.e., optically clear or non-hazy state) and a light scattering state (i.e., translucent or hazy state).

[0009] When such a scattering device switches from a non-scattering state to a scattering state, the transmission of light is altered so as to produce a translucent or opaque appearance, which may be perceived as cloudy, turbid, diffuse or hazy.

[0010] Devices operating in a diffuse mode are particularly useful as privacy windows. In this case, a privacy mode can be provided when needed by switching the device (particularly a window element) from a clear state with possible viewing contact to a diffuse state that provides visual blocking.

[0011] In US 2014 / 0226096 A1, an optically variable device is described to adjust ambient light, particularly with regard to see-through near-eye display device applications. This device for light management is described as being able to perform both absorption and scattering. It is further described that the device can be switched between three different optical states, a low haze low tint state, a low haze high tint state, and a high haze high tint state, under different electric field conditions. In the device, a single switching layer is used, in which the LC material is mixed with a dichroic dye to provide absorption and an ionic dopant to provide so-called dynamic scattering.

[0012] J.-W.Huh et al. proposed a double-layered light shutter device using two cholesteric liquid crystal cells in “Double-layered light shutter using long-pitch cholesteric liquid crystal cells”, Applied Optics, 54 (2015), pp. 3792-3795, wherein the light shutter includes a light scattering layer using a long-pitch cholesteric LC and a light absorbing layer using a dye-doped cholesteric LC.

[0013] WO 2016 / 173693 A1 describes a switching layer for a switching element having forward scattering properties in one of the switching states and intended to adjust glare from daylight and establish privacy when required. The switching layer facilitates switching from a transparent state to a translucent or opaque state. In one embodiment, scattering is achieved by nematic liquid crystals together with a polymer component. In another embodiment, cholesteric liquid crystals are used instead. Further description In some embodiments, one or more additional switching layers can be used to provide scattering or control of light intensity or transmission.

[0014] There remains a need in the art for improved control and management of daylight transmission, particularly under certain conditions and in certain settings, such as in direct sunlight exposure or varying amounts of daylight.

[0015] It is therefore an object of the present invention to provide multilayer configurations and window elements for switchable or smart windows, in particular for architectural, automotive, avionics and marine applications, which can provide advantageous control of ambient light and can provide light conditions or lighting conditions in daylight spaces, thereby minimizing discomfort associated with, for example, blinding and glare. In addition to providing comfort and pleasant ambient conditions, switchable devices are required to provide efficiency in terms of energy and cost. Another object is to provide multilayer configurations and window elements with good stability (for example against electrical breakdown) and advantageously low operating voltages or low energy consumption, and which can exhibit fast and sufficiently effective and sufficiently uniform switching. Other objects of the present invention are immediately apparent to a person skilled in the art from the following detailed description.

[0016] This object is solved by the subject matter defined in the independent claims, while preferred embodiments are set forth in the respective dependent claims and are further described below.

[0017] The present invention particularly provides the following items, including main aspects, preferred embodiments and specific features, which individually and in combination help to solve the above objects and ultimately provide additional advantages.

[0018] A first aspect of the present invention provides a multilayer arrangement for regulating the passage of light, comprising

[0019] a first switching layer which is switchable between an optically clear state and a light-scattering state and contains a material comprising a liquid crystal medium comprising one or more mesogenic compounds and one or more chiral compounds; and a polymeric component, wherein the polymeric component is contained in the material in an amount of 5% by weight or less, based on the total content of the material, and

[0020] A switching element comprising a second switching layer, wherein the switching element is switchable between a light state and a dark state and wherein the second switching layer is a liquid crystal layer.

[0021] According to the present invention, advantageous multilayer assemblies are configured, wherein these assemblies can be advantageously used in switchable windows for architectural, automotive, avionics and marine applications. The multilayer configuration is particularly suitable and effective to provide an anti-glare effect by providing switchability (especially electrical switchability) between an optically clear and bright state and a light-scattering and dark state when desired or required.

[0022] In the present invention, it is recognized that the source of glare can come not only from the high brightness of bright light sources in absolute terms but also from large brightness contrast. Although the human eye can in principle adapt to different light intensities, its ability to handle certain ranges of brightness at a given moment or in a given adaptation state is limited.

[0023] It is further recognized that a combination of reducing the overall luminous flux and reducing the contrast between the light source brightness and the background brightness may be particularly effective in reducing discomfort due to glare, particularly in situations where daylight is perceived to be too bright and / or in an unfavorable position relative to an observer (such as an occupant of a building).

[0024] It has been unexpectedly discovered that a multilayer configuration with effective and efficient anti-glare performance can be obtained by including a first switching layer as described above and below that can provide scattering when diffuse light is required, and a switching element as described above and below that contains a second switching layer that can dim the light when a reduction in light flux or total light transmission is required. This can lead to a significant reduction in perceived glare, especially glare of daylight, by appropriately limiting and otherwise advantageously distributing the amount of light. Thus, a multilayer configuration according to the present invention can prevent or minimize glare, excessive solar heating, and illuminated areas with high intensity contrast.

[0025] In addition, the present multilayer assembly exhibits a favorable appearance. In particular, a favorable clear state with uniformly low haze and a scattering state with enhanced and uniform scattering efficiency as well as a uniform and color-neutral appearance can be obtained, wherein undesirable color effects are advantageously avoided or minimized.

[0026] Furthermore, the multi-layer configuration according to the present invention can be switched quickly while still transmitting a meaningful amount of daylight even in the dark and diffuse state. Given this benefit of still transmitting daylight, the use of artificial lighting can be limited, which leads to cost and energy savings. Additionally, the multi-layer configuration can be configured and controlled so that it permits viewing of the surroundings, at least to some extent, even in the dark and diffuse state.

[0027] In contrast, traditional mechanical solutions (such as the closing of blinds or curtains) are slow and often block or limit the transmission of daylight and require artificial lighting, while also obscuring viewing. In addition, mechanical sun protection needs to be maintained, and stresses from, for example, wind loads need to be considered.

[0028] Thus, a multi-layer configuration according to the present invention may provide improved comfort as well as energy and cost savings.

[0029] The multilayer configuration according to the invention may also result in other benefits, such as suitable reliability, durability and stability, for example with regard to electrical breakdown and light stability (especially UV light stability), as well as advantageously low switching voltages and low energy consumption. In this respect, according to the invention, liquid crystal media with improved chemical, physical and electro-optical properties may advantageously and beneficially be used, wherein the media may in particular have a broad liquid crystal phase with a suitably high clearing point, an advantageously high voltage holding ratio (VHR), good low temperature stability and suitable stability for storage.

[0030] Another aspect of the invention relates to the use of the multilayer arrangement according to the invention in an insulating glazing unit.

[0031] In a further aspect of the invention, a window element is provided which comprises a layer arrangement according to the invention and which is electrically switchable between an optically clear and bright state and a light-scattering and dark state.

[0032] The window element according to the invention is suitable for regulating or modulating the passage of light, in particular controlling the passage of daylight. The window element is particularly effective in reducing the total light intensity to a comfortable level and in reducing the contrast or intensity difference between a bright light source and its surroundings by obtaining a relatively flat angular distribution of the transmitted light of reduced intensity. The limited range of brightness and the reduced contrast difference may result in improved user comfort by avoiding or minimizing glare or dazzle.

[0033] The window element is capable of undergoing a reversible optical transition, wherein the switching is rapid, typically in less than about one second. The device can suitably be switched between states by applying a voltage.

[0034] Furthermore, window elements with minimal space requirements can be installed, which can provide clear advantages over conventional awnings or shutters, for example. The window element according to the invention can advantageously be used in windows of the facades of buildings, but it can also be used in cars, commercial vehicles, trains, airplanes, ships, etc.

[0035] The window elements can significantly reduce glare while still allowing daylight to pass through and view the outside environment, which also enables the use of artificial light sources to be minimized.

[0036] Therefore, a further aspect of the invention relates to the advantageous use of a layer arrangement or a window element according to the invention for reducing glare from solar radiation.

[0037] The present invention is illustrated below by describing in detail aspects, embodiments and specific features without thereby limiting the invention, and specific embodiments are described in more detail.

[0038] In this context, the term "liquid crystal" (LC) preferably relates to materials or media which have a liquid crystal mesophase in some temperature range (thermotropic LC). They contain mesogenic compounds.

[0039] The terms "mesogenic compound" and "liquid crystal compound" refer to compounds comprising one or more calamitic (rod-like or plate / lath-like) or discotic (disc-like) mesogenic groups (ie groups capable of inducing liquid crystal or mesophase properties).

[0040] LC compounds or materials containing mesogenic groups and mesogenic compounds or materials themselves do not necessarily have to exhibit a liquid crystal phase. They may also exhibit liquid crystal phase characteristics only in a mixture with other compounds. Such compounds include low molecular weight non-reactive liquid crystal compounds, reactive or polymerizable liquid crystal compounds and liquid crystal polymers.

[0041] Rod-like mesogenic compounds generally comprise a mesogenic core composed of one or more aromatic or non-aromatic cyclic groups directly connected to each other or connected via a linking group, optionally comprising an end group connected to the end of the mesogenic core, and optionally comprising one or more side groups connected to the long side of the mesogenic core, wherein these end groups and side groups are generally selected from, for example, carbon or hydrocarbon groups; polar groups such as halogen, nitro, hydroxyl, etc.; or polymerizable groups.

[0042] For simplicity, the term "liquid crystal" or "liquid-crystalline" material or medium is used for both liquid crystal materials or media and mesogenic materials or media and vice versa, and the term "mesogen" is used for the mesogenic group of a material.

[0043] The term "non-mesogenic compound or material" means a compound or material that does not contain a mesogenic group as defined above.

[0044] As used herein, the term "polymer" is understood to mean a molecule comprising a backbone of one or more different types of repeating units (the smallest constituent unit of a molecule), and includes the commonly known terms "oligomer," "copolymer," "homopolymer," and the like. Furthermore, it is understood that the term polymer includes, in addition to the polymer itself, residues from initiators, catalysts, and other elements accompanying the synthesis of such polymers, wherein such residues are understood to be not covalently incorporated therein. Furthermore, such residues and other elements, although typically removed during post-polymerization purification processes, are typically mixed or co-mingled with the polymer so that they are typically retained with the polymer when the polymer is transferred between containers or between solvents or dispersion media.

[0045] The term "polymerization" means a chemical process of forming a polymer by bonding together a plurality of polymerizable groups or polymer precursors (polymerizable compounds) containing such polymerizable groups.

[0046] Polymerizable compounds having one polymerizable group are also referred to as "monoreactive" compounds, compounds having two polymerizable groups are referred to as "direactive" compounds, and compounds having more than two polymerizable groups are referred to as "polyreactive" compounds. Compounds having no polymerizable groups are also referred to as "non-reactive" or "non-polymerizable" compounds.

[0047] The term "chiral" is generally used to describe an object that is not superimposable with its mirror image. In contrast, an "achiral" object is an object that is identical to its mirror image. Some of the media used according to the present invention exhibit chirality. This can be achieved by providing cholesteric liquid crystals, which are also called chiral nematic liquid crystals. Unless explicitly stated otherwise, the terms chiral nematic and cholesteric are used synonymously in this document.

[0048] In this article,

[0049]

[0050] represents trans-1,4-cyclohexylene.

[0051] In this document, all concentrations are given as percentages by weight and relate to the respective complete mixture, unless expressly stated otherwise.

[0052] All temperatures are given in degrees Celsius (Celsius, °C) and all temperature differences are given in degrees Celsius. Unless explicitly stated otherwise, all physical properties and physicochemical or electro-optical parameters were measured and are given for a temperature of 20°C.

[0053] For the purposes of the present invention, the term energy means in particular the energy of electromagnetic radiation in the UV-A, VIS and NIR regions. In particular, it means the energy of radiation that is not absorbed by the material (e.g. glass) commonly used for windows or is only absorbed to a negligible degree. In this article, the UV-A region means wavelengths in the range of 320 to 380 nm, the VIS region means wavelengths in the range of 380 nm to 780 nm, and the NIR region means wavelengths in the range of 780 nm to 2000 nm. Correspondingly, the term light generally means electromagnetic radiation with a wavelength between 320 and 2000 nm, and in particular between 380 nm and 780 nm.

[0054] The transmission and scattering of light preferably refers to the transmission and scattering of electromagnetic radiation in the spectral range of 380 nm to 780 nm.

[0055] Herein, dichroic dyes are meant to be light-absorbing compounds, wherein the absorption properties depend on the orientation of the compound relative to the polarization direction of the light. The dichroic dye compounds according to the invention generally have an elongated shape, i.e. the compound is significantly longer in one spatial direction (i.e. along the longitudinal axis) than in the other two spatial directions.

[0056] The terms "film" and "layer" include more or less rigid or flexible self-supporting or freestanding films or layers having a significant mechanical stability, as well as coatings or layers on a supporting substrate or between two substrates.

[0057] A switching layer may be arranged on a substrate or between two substrates in order to obtain a switching element which is operable and preferably electrically switchable in different optical states.

[0058] Switching according to the invention preferably means electrical switching. Electrical switching can generally be achieved by providing a substrate with electrodes, such as a glass substrate or a plastic substrate. In one embodiment, a conductive layer is provided on the substrate, wherein the conductive layer comprises or is formed by: a transparent conductive material, such as a transparent conductive oxide, preferably indium tin oxide (ITO) or SnO2:F, in particular ITO or a conductive polymer; or a thin transparent metal and / or metal oxide layer, such as silver. The conductive layer is preferably provided with electrical connections. The voltage is preferably supplied by a battery, a rechargeable battery, a supercapacitor or an external current source, more preferably by an external current source.

[0059] In one embodiment, an orientation layer, for example made of polyimide (PI), is provided on the substrate. It is particularly preferred that the conductive layer and the orientation layer are provided together on the substrate. In this case, the orientation layer or alignment layer is provided on top of the conductive layer so that the orientation layer contacts the LC medium. The orientation layer, preferably a polyimide layer, can be configured such that it provides a uniform or planar orientation or alternatively a vertical orientation of the liquid crystal medium molecules, especially at the interface. In a particular embodiment, a rubbed polyimide is used on two substrates with a 90° orientation difference as used in the so-called twisted nematic (TN) geometry. In some embodiments, a so-called pretilt angle can be set and obtained.

[0060] Alternatively and according to another preferred embodiment, a substrate without an alignment layer is used.It was surprisingly found that in some embodiments providing an alignment layer (eg a polyimide layer) as an additional layer can advantageously be avoided, while still achieving an effective and efficient switching behavior.

[0061] Alternatively and also in addition to the orientation layer, it is also possible to provide a passivation or barrier layer on the substrate, for example a passivation layer comprising, preferably consisting of, silicon oxide or silicon nitride. In case both the passivation layer and the orientation layer are provided on the substrate, they are configured so that the orientation layer is on top, i.e. in contact with the LC medium.

[0062] Therefore, according to the present invention, the first switching layer and the second switching layer are preferably each inserted between two transparent substrates, each of which supports an electrode configured as a transparent conductive layer, wherein preferably the transparent conductive layer is respectively embedded between two transparent dielectric layers (such as silicon oxide or silicon nitride layers), and wherein an optional alignment layer is further provided in direct contact with the switching layer.

[0063] Switching of a given switching layer preferably refers to switching between binary states.

[0064] According to the present invention, the first switching layer as described above and below can be switched between an optically clear state, which is non-scattering or substantially non-scattering and appears substantially transparent or clear to the human eye, and a light scattering state, which is scattering or has diffuse transmission and appears translucent or opaque to the human eye.

[0065] In the optically clear state, the first switching layer according to the invention preferably exhibits a haze, determined to ASTM D 1003, of less than 20%, more preferably less than 15%, even more preferably less than 10% and in particular less than 5%.

[0066] In the scattering state, the first switching layer according to the invention preferably produces a haze of more than 75%, more preferably more than 85%, even more preferably more than 90%, measured according to ASTM D 1003. It is particularly preferred that in the scattering state, the first switching layer according to the invention produces a haze of 95% or more, measured according to ASTM D 1003.

[0067] For the measurement of haze, a hazemeter made by BYK-Gardner can be used, in particular the haze-gard I from BYK-Gardner. It is also possible to use a spectrophotometer, for example the Lambda 1050 spectrophotometer from Perkin Elmer and a 150 mm Ulbricht sphere.

[0068] According to the invention, the switching element comprising the second switching layer can be switched between a bright state and a dark state. In this aspect, the bright state has a greater light transmittance than the dark state.

[0069] In the bright state, a switching element comprising the second switching layer according to the invention preferably has a visible light transmission determined to DIN EN 410 of more than 45%, more preferably more than 55% and even more preferably more than 65%.

[0070] In the dark state, the switching element comprising the second switching layer according to the invention preferably has a visible light transmission of less than 40%, more preferably less than 30% and even more preferably less than 20%, determined in accordance with DIN EN 410. In a preferred embodiment, in the dark state, the switching element comprising the second switching layer has a visible light transmission determined in accordance with DIN EN 410 in the range of 14% to 40% and more preferably in the range of 25% to 36%.

[0071] The multilayer arrangement and in particular the window element according to the invention is switchable, advantageously and preferably electrically, between an optically clear and bright state and a light-scattering and dark state.

[0072] In a preferred embodiment, the window element is switchable to an optically clear and bright state by applying an AC voltage V1 and to a light-scattering and dark state by applying an AC voltage V2, wherein V1>V2.

[0073] Furthermore, the multilayer arrangement and in particular the window element according to the invention is preferably further operable in an optically clear and dark state as well as in a light-scattering and bright state and is electrically switchable into an optically clear and dark state as well as into a light-scattering and bright state.

[0074] However, switching layers, multi-layer configurations and window elements may also have other switching states, in particular intermediate states.

[0075] According to the present invention, the first switching layer contains a material comprising a liquid crystal medium comprising one or more mesogenic compounds and one or more chiral compounds; and a polymeric component, wherein the polymeric component is contained in the material in an amount of 5 wt % or less based on the total content of the material.

[0076] Preferably, the polymeric component is contained in the material in an amount of 2.5 wt% or less and especially 1 wt% or less based on the total content of the material. In a preferred embodiment, the polymeric component is contained in the material in an amount ranging from 0.5 to 1.5 wt% based on the total content of the material.

[0077] In a preferred embodiment, the polymeric component comprised in the first switching layer contains one or more polymeric structures obtained or obtainable from the polymerization of one or more polymerizable mesogenic compounds.

[0078] The polymeric component is preferably obtained by exclusively polymerizing one or more polymerizable mesogenic compounds, ie the polymeric component preferably consists of one or more polymeric structures which are exclusively based on or respectively derived exclusively from one or more polymerizable mesogenic compounds as precursors.

[0079] The polymeric component is particularly preferably prepared in situ, in particular in the switching layer, by polymerizing one, two or three polymerizable mesogenic compounds, even more preferably one or two polymerizable mesogenic compounds.

[0080] The polymerizable mesogenic compounds according to the invention contain a mesogenic group and one or more polymerizable groups, ie functional groups suitable for polymerization. These compounds are also called reactive mesogens (RMs) or mesogenic monomers. RMs may be monoreactive and / or direactive or polyreactive.

[0081] Although the polymerizable compounds as used in the present invention preferably comprise only reactive mesogens, ie all reactive monomers are mesogens, in alternative embodiments one or more RMs and one or more non-mesogenic polymerizable compounds may be used.

[0082] The polymerisable compounds and mesogenic compounds may be selected in view of the polymerised components in the resulting modulation material and the refractive index of the LC medium, which advantageously contributes to an improved clear state.

[0083] Preferably, the liquid-crystalline medium contained in the first switching layer has a clearing point of 80° C. or more, more preferably 90° C. or more, even more preferably 100° C. or more and in particular 115° C. or more. Preference is given to medium having a clearing point in the range of 80° C. to 170° C. and more preferably 100° C. to 150° C.

[0084] All physical properties and physicochemical or electro-optical parameters were determined by generally known methods, in particular in accordance with “Merck Liquid Crystals, Physical Properties of Liquid Crystals”, Status November 1997, Merck KGaA, Germany.

[0085] The clearing point, in particular the phase transition temperature between the nematic phase or chiral nematic phase or cholesteric phase and the isotropic phase can be measured and determined by generally known methods, for example using a Mettler oven, a hot stage under a polarizing microscope or differential scanning calorimetry (DSC) analysis. According to the present invention, the clearing point is preferably determined using a Mettler oven.

[0086] Preferably, the liquid-crystalline medium comprised in the first switching layer exhibits a helical pitch of 0.55 μm or more in the scattering state.

[0087] Cholesteric or chiral nematic media as provided at present preferably have a relatively long helical pitch, and particularly preferably a helical pitch which gives a Bragg-type reflection of more than 780 nm. In this case, the planar texture can also give an advantageous transmission in the visible spectrum.

[0088] Pitch in this context means the pitch p of a cholesteric helix, wherein pitch p is the distance of the orientation axis (director) of the CLC that undergoes a 2π rotation. In a particularly preferred embodiment, the medium exhibits a pitch of 0.75 μm or longer, even more preferably 1.00 μm or longer, and especially 1.50 μm or longer.

[0089] The concentration of the chiral dopant(s) is preferably set so that the resulting chiral pitch is in the range of 0.55 μm to 10 μm.

[0090] According to the invention, the pitch is determined in particular by the maximum selective reflection wavelength λ at 20°C. max The pitch p is determined by NIR spectroscopy. max The measured value of λ is used in the equation max =n(λ max )×p determination, where n(λ max ) is λ max The refractive index below.

[0091] The wedge cell method known in the art for measuring the helical twisting force HTP and determining the measured pitch, particularly at 20° C., may also be used.

[0092] It is now recognized that certain additional benefits, for example with regard to the scattering efficiency or the homogeneity and appearance of the scattering effect, can be obtained when the material in the first switching layer contains a chiral nematic or cholesteric liquid-crystal medium with a relatively long pitch and advantageously a high clearing point and a polymeric component as defined herein, and in particular when a so-called polymer-stabilized cholesteric texture (PSCT) is provided.

[0093] Surprisingly, the first switching layer according to the invention can provide a scattering state with efficient and sufficiently strong scattering which has a uniform appearance to the eye, especially over large areas as required for larger windows. This uniform appearance advantageously includes a color-neutral appearance, which means that undesirable color effects or individual color artifacts can be minimized or even avoided.

[0094] It is recognized that in layers containing cholesteric materials, color effects can occur due to the inherent chiral periodicity, for example, when the material is illuminated by direct non-diffuse light, different colors can be emitted at different angles. In such cases, the transmitted light is colored when viewed off-axis, and the window element and window can appear colored when viewed off-axis, where the observed color depends on the viewing angle. This effect can be similar to a rainbow-like appearance. It is further recognized that in many applications, such color effects are undesirable.

[0095] It is believed that the material as provided in the first switching layer according to the invention can generate sufficient scattering with the desired haze, for example by scattering from material areas, in particular from boundaries, defects or irregular structures, whereas diffraction of incident light, such as that produced by periodic structures, can be substantially suppressed or avoided by sufficiently disrupting or destroying the periodicity on the relevant length scale, in particular by introducing polymeric components, which in this regard can be surprisingly effective even when only small amounts are contained.

[0096] In a preferred embodiment, the liquid crystal medium contained in the first switching layer according to the invention has a positive dielectric anisotropy. In this case, liquid crystal mixtures with a dielectric anisotropy Δε in the range of 3 to 45, more preferably in the range of 5 to 30 are preferred.

[0097] Δε represents dielectric anisotropy, where Δε=ε||-ε ⊥ The dielectric anisotropy Δε was measured at 20°C and 1 kHz.

[0098] In an alternative embodiment, however, it is also possible to provide an LC medium with a negative dielectric anisotropy. In this case, preference is given to liquid crystal mixtures having a dielectric anisotropy Δε in the range from -6 to -3.

[0099] It is particularly preferred that the liquid-crystalline medium as comprised in the first switching layer according to the invention contains at least 15% by weight, based on the total content of the medium, of one or more mesogenic compounds of the formula I

[0100]

[0101] in

[0102] R 1 and R 2 independently of one another represent a radical selected from the group consisting of F, Cl, CF3, OCF3 and straight-chain or branched alkyl or alkoxy having 1 to 15 carbon atoms or straight-chain or branched alkenyl having 2 to 15 carbon atoms, which is unsubstituted, monosubstituted by CN or CF3 or monosubstituted or polysubstituted by halogen, and in which one or more CH2 groups may in each case independently of one another be substituted by -O-, -S-, -CO-, -COO-, -OCO-, -OCOO-, -C≡C-,

[0103] A 11 express

[0104]

[0105] n represents 0 or 1, and

[0106] A21 , A 31 and A 41 Independently express

[0107]

[0108] wherein L, at each occurrence, identically or differently, is a halogen selected from F, Cl and Br.

[0109] In one embodiment, the liquid-crystalline medium contains one or more compounds of the formula I as described above and below in an amount of at least 20% by weight, preferably at least 25% by weight, more preferably at least 30% by weight and in particular at least 35% by weight, based on the total content of the medium.

[0110] In one embodiment, one or more compounds of formula I are contained in the medium in an amount ranging from 15% to 75% by weight, more preferably from 20% to 65% by weight, even more preferably from 20% to 55% by weight and in particular from 25% to 50% by weight, based on the total content of the medium.

[0111] The medium in the first switching layer therefore preferably comprises at least one compound of the formula I. In many cases, however, it may be advantageous and preferred if two, three or more compounds of the formula I are contained in the medium.

[0112] Preferably, the group A as defined in formula I 11 express

[0113]

[0114] In another embodiment, n as defined in formula I represents 0.

[0115] In a preferred embodiment, the one or more compounds of formula I are selected from compounds of formula Ia, Ib and Ic, more preferably selected from compounds of formula Ia and Ib

[0116]

[0117]

[0118] in

[0119] R 1 and R 2independently of one another represents a radical selected from the group consisting of F, Cl, CF3, OCF3 and straight-chain or branched alkyl or alkoxy radicals having 1 to 15 carbon atoms or straight-chain or branched alkenyl radicals having 2 to 15 carbon atoms, which are unsubstituted, monosubstituted by CN or CF3 or monosubstituted or polysubstituted by halogen, and in which one or more CH2 groups may in each case independently of one another be replaced by -O-, -S-, -CO-, -COO-, -OCO-, -OCOO- or -C≡C- in such a way that the oxygen atoms are not directly bonded to one another; preferably a radical selected from the group consisting of F, CF3, OCF3, straight-chain alkyl or alkoxy radicals having 1 to 9 carbon atoms or alkenyl radicals having 2 to 9 carbon atoms, and

[0120] L is, identically or differently at each occurrence, H or a halogen selected from F, Cl and Br, preferably a halogen selected from F and Cl, and more preferably is, identically or differently at each occurrence, H or F.

[0121] It is particularly preferred that in the case where the phenylene ring of the compound of formula I is substituted, the substituent is F and furthermore the terminal group R 1 and R 2 Does not contain Cl.

[0122] In a preferred embodiment, the amount of Cl-containing compounds included in the medium is limited, preferably to 55% by weight or less, more preferably to 40% by weight or less, and even more preferably to 25% by weight or less, based on the total content of the medium. In a particularly preferred embodiment, the liquid-crystalline medium contains Cl-free compounds.

[0123] Therefore, it is also preferred to limit the amount of Cl-containing compounds in the component of the LC medium consisting of compounds of the formula I as explained above and below, preferably to 55 wt.-% or less, more preferably to 40 wt.-% or less, and even more preferably to 25 wt.-% or less, based on the total content of compounds of the formula I contained in the medium. In a particularly preferred embodiment, the one or more compounds of the formula I are selected from compounds that do not contain Cl.

[0124] Furthermore, particularly preferred is ring A according to formula I 21 , A 31 and A 41 At least one of the rings A and B has at least one F substituent. 21 , A 31 and A 41 Together there are at least two F substituents.

[0125] In the medium, the use of CN-containing compounds is preferably and advantageously limited to preferably 75 wt. % or less, more preferably 50 wt. % or less, even more preferably 25 wt. % or less and in particular 15 wt. % or less, and in a particularly preferred embodiment is avoided completely.

[0126] The liquid-crystalline medium in the first switching layer preferably contains one or more further mesogenic compounds in addition to one or more compounds of the formula I. It is preferred to add these additional compounds in view of contributing to or maintaining the favourable properties of the medium, such as good VHR and favourable stability.

[0127] Preferably, the liquid-crystalline medium contained in the first switching layer according to the invention further comprises one or more mesogenic compounds selected from the group of compounds of formulae II and III

[0128]

[0129] in

[0130] R 3 , R 4 , R 5 and R 6 independently of one another represent a radical selected from the group consisting of: F, CF3, OCF3, CN and a linear or branched alkyl or alkoxy radical having 1 to 15 carbon atoms or a linear or branched alkenyl radical having 2 to 15 carbon atoms, which is unsubstituted, monosubstituted by CN or CF3 or monosubstituted or polysubstituted by halogen, and in which one or more CH2 radicals may in each case independently of one another be substituted by: -O-, -S-, -CO-, -COO-, -OCO-, -OCOO-, -C≡C-, and

[0131] L 1 , L 2 , L 3 , L 4 and L 5 represents H or F independently of each other.

[0132] In one embodiment, the liquid-crystalline medium comprises one or more mesogenic compounds of the formula II.

[0133] In a further embodiment, the liquid-crystalline medium comprises one or more mesogenic compounds of the formula III.

[0134] It is preferred that the medium contains at least 15% by weight, based on the total content of the medium, of one or more mesogenic compounds of formula I, optionally one or more photoinitiators and one or more mesogenic compounds selected from the group of compounds of formulae II and III.

[0135] It is particularly preferred that the medium comprises one or more compounds of the formula I, one or more compounds of the formula II and one or more compounds of the formula III as described above.

[0136] Preferably, the liquid-crystalline medium in the first switching layer further comprises one or more compounds of the formula IV

[0137]

[0138] in

[0139] R 7 denotes a straight-chain or branched alkyl or alkoxy radical having 1 to 15 carbon atoms, preferably 1 to 7 carbon atoms, or a straight-chain or branched alkenyl radical having 2 to 15 carbon atoms, which is unsubstituted, monosubstituted by CN or CF3 or monosubstituted or polysubstituted by halogen, and in which one or more CH2 groups may in each case be replaced independently of one another by -O-, -S-, -CO-, -COO-, -OCO-, -OCOO- or -C≡C- in such a way that the oxygen atoms are not directly connected to one another,

[0140] i is 0, 1, or 2,

[0141] L 6 and L 7 are independently H or F, and

[0142] X 1 Indicates F, CF3, OCF3 or CN.

[0143] The compounds of formula II are preferably used in a total concentration of 1% to 45% by weight, more preferably 5% to 25% by weight in the medium.

[0144] The compound of formula III is preferably used in a total concentration of 1% to 45% by weight, more preferably 5% to 25% by weight in the medium.

[0145] The compound of formula IV is preferably used in a total concentration of 1% to 45% by weight, more preferably 5% to 25% by weight in the medium.

[0146] Particularly preferred is a medium comprising one or more compounds of the formula I, one or more compounds of the formula II, one or more compounds of the formula III and one or more compounds of the formula IV as described above and below.

[0147] In a particularly preferred embodiment, one or more of the one or more compounds of formula I are selected from compounds of formula I-1 and I-2

[0148]

[0149] in

[0150] R 1 and R 2 As defined above for Formula Ia, and

[0151] L is H or F identically or differently on each occurrence.

[0152] Optionally, the medium may contain other liquid crystal compounds in order to adjust the physical properties. Such compounds are known in the art. The concentration of these compounds, which optionally further include liquid crystal compounds in the medium, is preferably from 0% to 30% by weight, more preferably from 0.1% to 20% by weight and most preferably from 1% to 15% by weight.

[0153] In one embodiment, a medium is provided which comprises one or more of the following compounds

[0154] - PGP-nm, PGP-n-mV, PGU-nF, PGIGI-nF, GGP-nF, GGP-n-Cl, in particular GGP-5-Cl, CPGP-nm, CPGP-n-OT, CPGU-n-OT, DPGU-nF, and / or

[0155] - CPP-nm, CPG-nF, CGU-nF, BCH.nFFF, in particular BCH.7.FFF, and / or

[0156] -CP-nm, CP-nN, and / or

[0157] - a compound of formula R-5011 or S-5011, and / or

[0158] - one or more reactive polymerizable compounds, and / or

[0159] - one or more polymerization initiators,

[0160] The meaning and structure of each abbreviation or acronym are explained and illustrated in the table below.

[0161] The liquid crystal medium used according to the present invention may contain other additives in common concentrations. The total concentration of these other components is in the range of 0% to 10%, preferably 0.1% to 6%, based on the total mixture. The concentration of each compound used is preferably in the range of 0.1% to 3%. For the values ​​and ranges of the concentrations of the liquid crystal components and compounds of the liquid crystal medium, the concentrations of these and similar additives are not considered in this article. Unless explicitly indicated otherwise, this also applies to the concentration of the dichroic dye optionally used in the mixture, which is not counted when specifying the concentration of the compound or component of the main mixture. The concentration of each additive is always given relative to the final doping mixture.

[0162] Herein, all concentrations are given as weight percent unless explicitly stated otherwise.

[0163] The liquid crystal medium as used according to the present invention consists of several compounds, preferably 3 to 30, more preferably 4 to 20, and most preferably 4 to 16 compounds. These compounds are mixed in a conventional manner. Usually, the required amount of the compound used in a smaller amount is dissolved in the compound used in a larger amount. If the temperature is higher than the clearing point of the compound used in a higher concentration, it is particularly easy to observe the completion of the dissolution process. However, it is also possible to prepare the medium by other conventional means, for example using a so-called premix, which can be, for example, a homogenous mixture or a eutectic mixture of compounds, or using a so-called multi-bottle system, the components of which are themselves ready-to-use mixtures.

[0164] A variety of mesogenic compounds or mixtures thereof described above and below are commercially available. These compounds are known or can be prepared by methods known per se, specifically under reaction conditions known and suitable for the reaction, as described in the literature (e.g. in standard works such as Houben-Weyl, Methoden der Organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart). Variants known per se but not mentioned in greater detail here may also be used here. The media according to the invention are prepared in a conventional manner per se. In general, the components are preferably dissolved in one another at elevated temperatures. Suitable additives or substances may be added to improve the dielectric anisotropy, viscosity and / or orientation of the liquid-crystalline phase.

[0165] The medium may further comprise conventional additives, such as stabilizers, antioxidants, free-radical scavengers, chain transfer agents (eg thioethers) and / or plasticizers.

[0166] Furthermore, it is preferred that the medium contains one or more compounds selected from the compounds designated PCH-n as shown in Table D, in particular selected from the compounds PCH-3, PCH-5 and PCH-7.

[0167] The term "alkyl" according to the invention preferably encompasses straight-chain and branched alkyl radicals having 1 to 7 carbon atoms, especially the straight-chain radicals methyl, ethyl, propyl, butyl, pentyl, hexyl and heptyl. Radicals having 2 to 5 carbon atoms are generally preferred.

[0168] The alkoxy group may be linear or branched and it is preferably linear and has 1, 2, 3, 4, 5, 6 or 7 carbon atoms, and is therefore preferably methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy or heptyloxy.

[0169] The term "alkenyl" according to the present invention preferably includes straight and branched alkenyl groups with 2-7 carbon atoms, particularly straight chain groups. Particularly preferred alkenyl groups are C2-C7-1E-alkenyl, C4-C7-3E-alkenyl, C5-C7-4E-alkenyl, C6-C7-5E-alkenyl and C7-6E-alkenyl, particularly C2-C7-1E-alkenyl, C4-C7-3E-alkenyl and C5-C7-4E-alkenyl. The example of preferred alkenyl is vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl and 6-heptenyl. Groups having up to 5 carbon atoms are generally preferred.

[0170] Fluorinated alkyl or alkoxy groups preferably include CF3, OCF3, CFH2, OCFH2, CF2H, OCF2H, C2F5, OC2F5, CFHCF3, CFHCF2H, CFHCFH2, CH2CF3, CH2CF2H, CH2CFH2, CF2CF2H, CF2CFH2, OCFHCF3, OCFHCF2H, OCFHCFH2, OCH2CF3, OCH2CF2H, OCH2CFH2, OCHF F2CF2H, OCF2CFH2, C3F7 or OC3F7, in particular CF3, OCF3, CF2H, OCF2H, C2F5, OC2F5, CFHCF3, CFHCF2H, CFHCFH2, CF2CF2H, CF2CFH2, OCFHCF3, OCFHCF2H, OCFHCFH2, OCF2CF2H, OCF2CFH2, C3F7 or OC3F7, particularly preferably OCF3 or OCF2H. Fluoroalkyl in preferred embodiments includes straight-chain groups with terminal fluorine, i.e. fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorohexyl and 7-fluoroheptyl. However, other positions of fluorine are not excluded.

[0171] Oxaalkyl groups preferably include those of formula C n H 2n+1 -O-(CH2) m wherein n and m are each independently 1 to 6. Preferably, n=1 and m is 1 to 6.

[0172] Oxaalkyl is preferably a straight-chain 2-oxapropyl (=methoxymethyl), 2-(=ethoxymethyl) or 3-oxabutyl (=2-methoxyethyl), 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-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanononyl or 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl.

[0173] Halogen is preferably F or Cl, in particular F.

[0174] If one of the abovementioned radicals is an alkyl radical in which one CH2 group has been replaced by -CH=CH-, it can be straight-chain or branched. It is preferably straight-chain and has 2 to 10 carbon atoms. Thus, it is in particular vinyl, prop-1- or prop-2-enyl, but-1-, -2- or but-3-enyl, pent-1-, -2-, -3- or pent-4-enyl, hex-1-, -2-, -3-, -4- or hex-5-enyl, hept-1-, -2-, -3-, -4-, -5- or hept-6-enyl, oct-1-, -2-, -3-, -4-, -5-, -6- or oct-7-enyl, non-1-, -2-, -3-, -4-, -5-, -6-, -7- or non-8-enyl, dec-1-, -2-, -3-, -4-, -5-, -6-, -7-, -8- or dec-9-enyl.

[0175] If one of the abovementioned radicals is an alkyl radical in which one CH2 group has been replaced by -O- and one by -CO-, they are preferably adjacent. Thus, they contain acyloxy-CO-O- or oxycarbonyl-O-CO-. They are preferably straight-chain and have 2 to 6 carbon atoms.

[0176] Thus, they are in particular acetyloxy, propionyloxy, butyryloxy, pentanoyloxy, hexanoyloxy, acetoxymethyl, propionyloxymethyl, butyryloxymethyl, pentanoyloxymethyl, 2-acetoxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 3-acetoxypropyl, 3-propionyloxypropyl, 4-acetoxybutyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentyloxycarbonyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl, 2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl, 2-(propoxycarbonyl)ethyl, 3-(methoxycarbonyl)propyl, 3-(ethoxycarbonyl)propyl or 4-(methoxycarbonyl)butyl.

[0177] If one of the abovementioned radicals is an alkyl radical in which one CH2 group has been replaced by unsubstituted or substituted -CH=CH- and the adjacent CH2 group has been replaced by CO, CO-O or O-CO, it may be straight-chain or branched. It is preferably straight-chain and has 4 to 13 carbon atoms. Thus, it is in particular acryloyloxymethyl, 2-acryloyloxyethyl, 3-acryloyloxypropyl, 4-acryloyloxybutyl, 5-acryloyloxypentyl, 6-acryloyloxyhexyl, 7-acryloyloxyheptyl, 8-acryloyloxyoctyl, 9-acryloyloxynonyl, 10-acryloyloxydecyl, methacryloyloxymethyl, 2-methacryloyloxyethyl, 3-methacryloyloxypropyl, 4-methacryloyloxybutyl, 5-methacryloyloxypentyl, 6-methacryloyloxyhexyl, 7-methacryloyloxyheptyl, 8-methacryloyloxyoctyl or 9-methacryloyloxynonyl.

[0178] If one of the abovementioned radicals is an alkyl or alkenyl radical which is monosubstituted by CN or CF3, this radical is preferably straight-chain. The substitution by CN or CF3 is in any position.

[0179] If one of the abovementioned radicals is an alkyl or alkenyl radical which is at least monosubstituted by halogen, the radical is preferably straight-chain and the halogen is preferably F or Cl, more preferably F. In the case of polysubstitution, the halogen is preferably F. The resulting radicals also include perfluorinated radicals. In the case of monosubstitution, the fluorine or chlorine substituent may be in any desired position, but is preferably in the ω-position.

[0180] Compounds containing branched groups may occasionally be of interest because of improved solubility in some conventional liquid-crystalline base materials. However, if they are optically active, they are particularly suitable as chiral dopants.

[0181] Branched-chain groups of this type usually contain no more than one branch. Preferred branched-chain groups are isopropyl, 2-butyl (= 1-methylpropyl), isobutyl (= 2-methylpropyl), 2-methylbutyl, isopentyl (= 3-methylbutyl), 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, isopropoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexyl, 1-methylhexyloxy or 1-methylheptyloxy.

[0182] If one of the abovementioned radicals is an alkyl radical in which two or more CH2 groups have been replaced by -O- and / or -CO-O-, it may be straight-chain or branched. It is preferably branched and has 3 to 12 carbon atoms. Thus, it is in particular dicarboxymethyl, 2,2-dicarboxyethyl, 3,3-dicarboxypropyl, 4,4-dicarboxybutyl, 5,5-dicarboxypentyl, 6,6-dicarboxyhexyl, 7,7-dicarboxyheptyl, 8,8-dicarboxyoctyl, 9,9-dicarboxynonyl, 10,10-dicarboxydecyl, bis(methoxycarbonyl)methyl, 2,2-bis(methoxycarbonyl)ethyl, 3,3-bis(methoxycarbonyl)propyl, 4,4-bis(methoxycarbonyl)butyl, 5,5-bis(methoxycarbonyl)pentyl, 6,6-bis(methoxycarbonyl)hexyl, 7,7-bis(methoxycarbonyl)heptyl, 8,8-bis(methoxycarbonyl)octyl, bis(ethoxycarbonyl)methyl, 2,2-bis(ethoxycarbonyl)ethyl, 3,3-bis(ethoxycarbonyl)propyl, 4,4-bis(ethoxycarbonyl)butyl or 5,5-bis(ethoxycarbonyl)pentyl.

[0183] Advantageously, the liquid crystal medium in the first switching layer may have a suitably high optical anisotropy Δn, which is also known as birefringence. In a preferred embodiment, the liquid crystal medium comprised in the first switching layer exhibits an optical anisotropy Δn of 0.13 or more, more preferably 0.16 or more and even more preferably 0.20 or more, measured at 20° C. and 589 nm.

[0184] In the above and below, Δn represents the optical anisotropy, where Δn=n e -n o , and the optical anisotropy Δn is measured at 20° C. and a wavelength of 589.3 nm.

[0185] Besides a suitably high optical anisotropy, the liquid-crystalline medium comprised in the first switching layer according to the invention may advantageously exhibit an advantageously high voltage holding ratio (VHR) as well as good light stability and a suitably high clearing point.

[0186] The use of reactive mesogens, especially in low amounts as specified, and preferably the use of chiral dopants with high HTP which can be used in low concentrations, advantageously contributes to maintaining an advantageously high clearing point.

[0187] The liquid crystal medium in the first switching layer is a cholesteric or chiral nematic medium. Cholesteric liquid crystals (CLCs) generally contain a medium which has, for example, a flat structure reflecting light of a certain wavelength in the initial state and which can be switched to a focal conic light scattering structure, or vice versa, by applying an alternating voltage pulse. When a stronger voltage is applied, in particular a stronger voltage pulse, the CLC medium can switch to a homeotropic transparent state, relax from this homeotropic transparent state to a flat state after a rapid voltage cut-off, or relax to a focal conic state after a slow voltage cut-off.

[0188] Bragg reflection occurs in the planar texture, where the reflected light has the same handedness as the cholesteric helix.

[0189] In the focal conic state, the helical axes are randomly configured and the texture exhibits light scattering due to discontinuous spatial variations in the refractive index at the domain boundaries.

[0190] Both planar and focal conic configurations are generally stable in the absence of an external electric field. The effect of electric field driven texture transitions between the planar and focal conic states forms the basis of the operation of CLC displays, where Bragg reflections disappear when the CLC texture switches from planar to focal conic and the CLC scatters incident light because the helical axes are randomly distributed.

[0191] However, switching between these states is usually achieved only via the homeotropic state, where the cholesteric helix is ​​completely unwound by dielectric coupling between LC molecules with positive dielectric anisotropy (Δε>0) and the vertical electric field.

[0192] In one embodiment according to the present invention, the scattering state of the switching layer may be the focal conic state described above.

[0193] Alternatively, and according to a preferred embodiment, in the present invention, the scattering state is formed by a multi-domain structure. This multi-domain structure preferably produces sufficiently strong scattering, while the Bragg-type reflection characteristics remain observable at least to a certain extent. In the phases preferably consisting of multiple domains, the orientation of the helical axis usually differs between the domains, and domain boundaries usually occur. However, macroscopically, the phase can appear homogeneous to the human eye, in particular uniformly opaque or hazy, and does not contain visible defects over the entire layer area.

[0194] The multi-domain structure can be obtained, for example, using conventional alignment layers oriented in a planar or homeotropic manner, and advantageously switching to the multi-domain state can be achieved at relatively low voltages.However, multi-domain structures can also be obtained when no alignment layer is present.

[0195] Additionally, the presence of a polymeric component in the first switching layer can advantageously influence and stabilize the scattering properties.

[0196] In a preferred embodiment, the non-scattering or clear state can be formed by the homeotropic state described above. The use of this clear state can be advantageous, for example, when using components with large areas. In this respect, the advantageously high VHR currently available can be used to stabilize the component in this state to avoid self-discharge characteristics and thus maintain a state even with significantly lower refresh rates and / or lower power consumption.

[0197] Alternatively, the non-scattering or clear state may be formed by the planar texture described above.

[0198] The use of chiral nematic or cholesteric media may be beneficial in that relatively stable states, and even bistability, may be provided so that devices incorporating the media may consume less energy. In particular, each state may be retained for at least a considerable time after the electric field has been disconnected, and less frequent addressing or refreshing of the voltage may be possible.

[0199] In a preferred embodiment, the first switching layer can be switched by applying an AC voltage V i Switches to an optically transparent state and can be switched by applying an AC voltage V ii Switch to the scattering state, where V i >V ii .

[0200] In one embodiment, the switched clear state of the first switching layer, in particular the state with homeotropic alignment, is maintained by applying a voltage in the range of 15 V to 100 V, more preferably 20 V to 80 V and in particular 25 V to 50 V, while the switched scattering state of the first switching layer can be stable even at 0 V for at least a period of time.

[0201] Preferably, the switching of the first switching layer does not use dual frequency addressing, thereby simplifying the required electronics.

[0202] As stated above, the liquid-crystalline medium preferably exhibits selective reflection at wavelengths greater than 780 nm. Thus, the medium preferably reflects in the near infrared (NIR) spectral region.

[0203] Chiral compounds and in particular chiral dopants and their concentrations can be provided so that the cholesteric pitch of the liquid crystal medium is suitably set or adjusted. CLC media can be prepared, for example, by doping nematic LC media with chiral dopants having a high twisting power. The pitch p of the induced cholesteric helix is ​​then given by the concentration c of the chiral dopant and the helical twisting power HTP according to equation (1):

[0204] p=(HTP c) -1 (1)

[0205] It is also possible to use two or more dopants, for example in order to compensate for the temperature dependence of the HTP of the individual dopants and thus achieve a smaller temperature dependence of the helical pitch and the reflection wavelength of the CLC medium. 总 ), then equation (2) roughly applies:

[0206] HTP 总 =∑ i c i HTP i (2)

[0207] where c i is the concentration of each individual dopant and HTP i is the helical twisting force of each individual dopant.

[0208] The liquid crystal medium in the first switching layer contains one or more chiral compounds and in particular chiral dopants. The chiral dopant preferably has a high absolute HTP value and can usually be added to the mesogenic base mixture in a relatively low concentration and has good solubility in the achiral component. If two or more chiral compounds are used, they can have the same or opposite directions of rotation and the same or opposite temperature dependence of the distortion.

[0209] Preferably, the one or more chiral compounds contained in the liquid-crystalline medium comprised by the first switching layer preferably have a chiral density of 5 μm in the commercial liquid-crystalline mixture MLC-6828 from Merck KGaA. -1 or larger, more preferably 10 μm -1 or more, and even more preferably 15 μm -1 Particularly preferred is a helical twisting force having an absolute value of 20 μm in the commercial liquid crystal mixture MLC-6828 from Merck KGaA. -1 or larger, more preferably 40 μm -1 or larger, even more preferably 60 μm -1 or larger, and most preferably 80 μm -1 or larger up to 260μm -1 Chiral compounds with absolute values ​​of helix twisting power (HTP) in the range of 2.1 to 1.1 or less.

[0210] The content of the one or more chiral compounds in the liquid-crystalline medium is preferably 2% by weight or less, more preferably 1% by weight or less, based on the total content of the medium.

[0211] In a preferred embodiment of the invention, the chiral component consists of two or more chiral compounds all having the same HTP signature. The temperature dependence of the HTP of the individual compounds may be high or low. The temperature dependence of the pitch of the medium may be compensated by mixing compounds with different HTP temperature dependencies in corresponding ratios.

[0212] Suitable chiral dopants are known in the art, some of which are commercially available, such as cholesteryl nonanoate, R / S-811, R / S-1011, R / S-2011, R / S-3011, R / S-4011, B(OC)2C*HC-3 or CB15 (all from Merck KGaA, Darmstadt, Germany).

[0213] Particularly suitable chiral dopants are compounds which contain one or more chiral groups and one or more mesogenic groups, or one or more aromatic or alicyclic groups which form mesogenic groups with chiral groups.

[0214] Suitable chiral groups are, for example, chiral branched hydrocarbon groups, chiral ethylene glycol, binaphthol or dioxolane, furthermore mono- or polyvalent chiral groups selected from the group consisting of sugar derivatives, sugar alcohols, sugar acids, lactic acid, chiral substituted diols, steroid derivatives, terpenoid derivatives, amino acids or sequences of several (preferably 1 to 5) amino acids.

[0215] Preferred chiral groups are sugar derivatives, such as glucose, mannose, galactose, fructose, arabinose and dextrose; sugar alcohols, such as sorbitol, mannitol, iditol, galactitol or their dehydrated derivatives, in particular dianhydrohexitol, such as dianhydrosorbitol (1,4:3,6-dianhydro-D-sorbitol, isosorbide), dianhydromannitol (isosorbide) or dianhydroiditol (isoiditol); sugar acids, such as gluconic acid, gulonic acid and ketogulonic acid; chiral substituted diol groups, such as mono- or oligoethylene glycol or propylene glycol, in which one or more CH2 groups are substituted by alkyl or alkoxy groups; amino acids, such as alanine, valine, phenylglycine, thiazolyl glycol ... , 1-amino-2-nitropropene or 1-amino-2-nitropropene or a sequence of 2 to 5 of these amino acids; a steroid derivative, for example, a cholesteryl or cholic acid group; a terpene derivative, for example, menthyl, neomenthyl, campheyl, pineyl, terpineyl, isolongifolyl, fenchyl, carreyl, myrthenyl, nopyl, geraniyl, linaloyl, neryl, citronellyl or dihydrocitronellyl.

[0216] Suitable chiral groups and mesogenic chiral compounds are described, for example, in DE 34 25 503, DE 35 34 777, DE 35 34 778, DE 35 34 779 and DE 35 34 780, DE 43 42 280, EP 01 038 941 and DE 195 41820.

[0217] Preferred chiral compounds used according to the present invention are selected from the following group of compounds.

[0218] In one embodiment, preferred is a dopant selected from the group consisting of compounds of the following formulae AI to A-III:

[0219]

[0220] in

[0221] R a11 and R a12 are independently alkyl, oxaalkyl or alkenyl having 2 to 9, preferably up to 7, carbon atoms, and R a11 Alternatively is methyl or an alkoxy group having 1 to 9 carbon atoms, preferably both are alkyl, preferably n-alkyl,

[0222] R a21 and R a22 are independently of one another an alkyl or alkoxy radical having 1 to 9, preferably up to 7, carbon atoms, an oxaalkyl, alkenyl or alkenyloxy radical having 2 to 9, preferably up to 7, carbon atoms, preferably both are alkyl radicals, preferably n-alkyl radicals,

[0223] R a31 and R a32 are independently alkyl, oxaalkyl or alkenyl having 2 to 9, preferably up to 7, carbon atoms, and R a11 Alternatively it is methyl or an alkoxy group having 1 to 9 carbon atoms, preferably both are alkyl, preferably n-alkyl.

[0224] Particularly preferred are chiral dopants selected from the group consisting of compounds of the following formulae:

[0225]

[0226] More preferably, the doping agent is a derivative of isosorbide, isomannide or isoidide of the following formula A-IV:

[0227]

[0228] Among them yes

[0229]

[0230]

[0231] Preferably it is dianhydrosorbitan,

[0232] and chiral glycols, such as diphenyl glycol (hydrobenzoin), especially mesomorphous hydrogenated benzoin derivatives of the following formula AV:

[0233]

[0234] including (R,S), (S,R), (R,R) and (S,S) enantiomers, which are not shown,

[0235] in

[0236]

[0237] and

[0238]

[0239] L is H, F, Cl, CN or an optionally halogenated alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl or alkoxycarbonyloxy group having 1 to 7 carbon atoms,

[0240] c is 0 or 1,

[0241] Z 0 is -COO-, -OCO-, -CH2CH2- or a single bond, and

[0242] R 0 It is an alkyl group, an alkoxy group, an alkylcarbonyl group, an alkoxycarbonyl group or an alkylcarbonyloxy group having 1 to 12 carbon atoms.

[0243] Compounds of formula A-IV are described in WO 98 / 00428. Compounds of formula AV are described in GB-A-2,328,207.

[0244] In another embodiment, particularly preferred chiral dopants are chiral binaphthyl derivatives, as described in WO 02 / 94805; chiral binaphthol acetal derivatives, as described in WO 02 / 34739; chiral TADDOL derivatives, as described in WO 02 / 06265; and chiral dopants having at least one fluorinated bridging group and a terminal or central chiral group, as described in WO02 / 06196 and WO 02 / 06195.

[0245] Particularly preferred are chiral compounds of formula A-VI

[0246]

[0247] in

[0248] X 1 , X 2 , Y 1 and Y 2 Each independently of one another is F, Cl, Br, I, CN, SCN, SF5, a straight-chain or branched alkyl group having 1 to 25 carbon atoms, which may be mono- or polysubstituted by F, Cl, Br, I or CN, and wherein in addition, one or more non-adjacent CH2 groups may each independently of one another be substituted by -O-, -S-, -NH-, NR-, -S-, -NH ... 0 -, -CO-, -COO-, -OCO-, -OCOO-, -S-CO-, -CO-S-, -CH=CH- or -C≡C-substituted, polymerizable radicals or cycloalkyl or aryl radicals having up to 20 carbon atoms, which may optionally be mono- or polysubstituted by halogen, preferably F, or by polymerizable radicals,

[0249] x 1 and x 2 are each independently 0, 1 or 2,

[0250] y 1 and 2 are each independently 0, 1, 2, 3 or 4,

[0251] B 1 and B 2 each independently of one another is an aromatic or partially or fully saturated aliphatic six-membered ring, in which one or more CH groups may be replaced by an N atom and one or more non-adjacent CH2 groups may be replaced by O and / or S,

[0252] W 1 and W 2 Each independently of the other is -Z 1 -A 1 -(Z 2 -A 2 ) m -R, and one of the two is alternatively R 1 or A 3 , but they are not both H, or

[0253] yes

[0254]

[0255] U 1 and U 2 are each independently CH2, O, S, CO or CS,

[0256] V1 and V 2 Each independently of the other is (CH2) n , wherein one to four non-adjacent CH2 groups may be replaced by O and / or S, and V 1 and V 2 One of the

[0257] yes In the case

[0258] Both are single bonds,

[0259] Z 1 and Z 2 are independently -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR 0 -、-NR 0 -CO-, -O-CH2-, -CH2-O-, -S-CH2-, -CH2-S-, -CF2-O-, -O-CF2-, -CF2-S-, -S-CF2-, -CH2-CH2-, -CF2-CH2-, -CH2-CF2-, -CF2-CF2-, -CH=N-, -N=CH-, -N=N-, -CH=CH-, -CF=CH-, -CH=CF-, -CF=CF-, -C≡C-, a combination of two of these groups, wherein no two O and / or S and / or N atoms are directly bonded to each other, preferably -CH=CH-COO- or -COO-CH=CH-, or a single bond,

[0260] A 1 , A 2 and A 3 are each independently 1,4-phenylene, wherein one or two non-adjacent CH groups may be replaced by N; 1,4-cyclohexylene, wherein one or two non-adjacent CH2 groups may be replaced by O and / or S; 1,3-dioxolane-4,5-diyl, 1,4-cyclohexenylene, 1,4-bicyclo[2.2.2]octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl or 1,2,3,4-tetrahydronaphthalene-2,6-diyl, wherein each of these groups may be mono- or polysubstituted by L, and in addition A 1 is a single key,

[0261] L is a halogen atom, preferably F, CN, NO2, an alkyl group having 1 to 7 carbon atoms, an alkoxy group, an alkylcarbonyl group, an alkoxycarbonyl group or an alkoxycarbonyloxy group, wherein one or more H atoms may be replaced by F or Cl,

[0262] m is independently at each occurrence 0, 1, 2 or 3, and

[0263] R and R 1 Each is independently H, F, Cl, Br, I, CN, SCN, SF5, a linear or branched alkyl group having 1 or 3 to 25 carbon atoms, which may be optionally mono- or poly-substituted by F, Cl, Br, I or CN, and wherein one or more non-adjacent CH2 groups may be substituted by -O-, -S-, -NH-, -NR 0 -, -CO-, -COO-, -OCO-, -O-COO-, -S-CO-, -CO-S-, -CH=CH- or -C≡C-, wherein no two O and / or S atoms are directly bonded to each other, or a polymerizable group.

[0264] Particularly preferred are chiral binaphthyl derivatives of formula A-VI-1

[0265]

[0266] In particular, compounds selected from those of the following formulae A-VI-1a to A-VI-1c:

[0267]

[0268] Among them, B and Z 0 As defined for Formula A-IV, and Z 0 More preferably, it is -OCO- or a single bond, R 0 is as defined for formula A-IV or is H or an alkyl group having 1 to 4 carbon atoms, and

[0269] b is 0, 1, or 2.

[0270] Furthermore, particularly preferred are chiral binaphthyl derivatives of formula A-VI-2

[0271]

[0272] In particular, compounds selected from the following formulae A-VI-2a to A-VI-2f:

[0273]

[0274] Where R 0 is as defined for Formula A-VI, and X is H, F, Cl, CN or R 0 , preferably F.

[0275] In a particularly preferred embodiment, the chiral medium contained in the first switching layer comprises one or more compounds of formula R-5011 and S-5011 shown in Table F below. In one embodiment, the medium contains R-5011. In another embodiment, the medium contains S-5011.

[0276] The LC medium contained in the first switching layer preferably and advantageously exhibits high reliability and high resistivity. The LC medium contained in the first switching layer also preferably and advantageously exhibits a high voltage holding ratio (VHR), see S. Matsumoto et al., Liquid Crystals 5, 1320 (1989); K. Niwa et al., Proc. SID Conference, San Francisco, June 1984, p. 304 (1984); T. Jacob and U. Finkenzeller, "Merck Liquid Crystals-Physical Properties of Liquid Crystals", 1997. The VHR of the LC medium according to the present invention is preferably ≥85%, more preferably ≥90%, even more preferably ≥95% and especially preferably ≥98%. Unless otherwise described, the measurement of VHR is carried out as described in T. Jacob, U. Finkenzeller, "Merck Liquid Crystals-Physical Properties of Liquid Crystals", 1997.

[0277] It is preferred that the polymeric component comprised in the first switching layer contains one or more polymeric structures obtained or respectively obtainable from the polymerization of one or more polymerizable mesogenic compounds. Preferably, one or more of the one or more polymerizable mesogenic compounds comprises one, two or more acrylate groups and / or methacrylate groups.

[0278] Preferably, one or more polymerisable, curable or hardenable compounds, preferably one or more photocurable monomers, are provided as precursors to the polymerised components in the first switching layer in the liquid-crystalline medium and subsequently polymerised in situ.

[0279] Preferably, reactive mesogens (RMs) or mesogenic monomers are used, which contain a mesogenic group and one or more polymerizable groups, ie functional groups suitable for polymerization.

[0280] It is preferred that the polymerisable compounds used comprise only reactive mesogens, ie all reactive monomers are mesogens. Alternatively, RMs and one or more non-mesogenic polymerisable compounds may be provided. RMs may be monoreactive and / or direactive or polyreactive.

[0281] Particularly preferred is one or more of the one or more polymerizable mesogenic compounds selected from the group consisting of compounds of formula M

[0282] R Ma -A M1 -(Z M1 -A M2 )m1 -R Mb M

[0283] The definitions of the various groups are as follows:

[0284] R Ma and R Mb Each independently represents P, P-Sp-, H, F, Cl, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, SF5, or a straight or branched alkyl group having 1 to 25 carbon atoms, wherein one or more non-adjacent CH2 groups may also be independently connected to each other in a manner such that the oxygen and / or sulfur atoms are not directly connected to each other via -C(R 0 )=C(R 00 )-、-C≡C-、-N((R 00 )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, and one or more hydrogen atoms may also be replaced by F, Cl, Br, I, CN, P or P-Sp-, wherein R Ma and R Mb At least one of the groups is or contains a P or P-Sp- group;

[0285] Preferably

[0286] R Ma and R Mb Each is independently P, P-Sp-, H, halogen, SF5, NO2, alkyl, alkenyl or alkynyl, wherein R Ma and R Mb At least one of the groups is or contains a P or P-Sp- group,

[0287] P is a polymerizable group,

[0288] Sp is a spacer group or a single bond,

[0289] A M1 and A M2 are each independently an aromatic, heteroaromatic, alicyclic or heterocyclic group preferably having 4 to 25 ring atoms, preferably carbon atoms, which also contains or can contain fused rings and which can optionally be mono- or polysubstituted by L,

[0290] L is P, P-Sp-, OH, CH2OH, F, Cl, 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, optionally substituted silyl, optionally substituted aryl having 6 to 20 carbon atoms, or straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25 carbon atoms, or alkenyl or alkynyl having 2 to 25 carbon atoms, in which one or more hydrogen atoms may also be replaced by F, Cl, P or P-Sp-, preferably by P, P-Sp-, H, OH, CH2OH, halogen, SF5, NO2, alkyl, alkenyl or alkynyl,

[0291] Y 1 is halogen, preferably F,

[0292] Z M1 is -O-, -S-, -CO-, -CO-O-, -OCO-, -O-CO-O-, -OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -(CH2) n1 -, -CF2CH2-, -CH2CF2-, -(CF2) n1 -, -CH=CH-, -CF=CF-, -C≡C-, -CH=CH-, -COO-, -OCO-CH=CH-, CR 0 R 00 or single key,

[0293] R 0 and R 00 are each independently H or an alkyl group having 1 to 12 carbon atoms,

[0294] R x is P, P-Sp-, H, halogen, straight-chain, branched or cycloalkyl having 1 to 25 carbon atoms, in which one or more non-adjacent CH2 groups may also be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that the oxygen and / or sulfur atoms are not directly connected to one another, and in which one or more hydrogen atoms may also be replaced by F, Cl, P or P-Sp-, optionally substituted aryl or aryloxy having 6 to 40 carbon atoms, or optionally substituted heteroaryl or heteroaryloxy having 2 to 40 carbon atoms,

[0295] m1 is 0, 1, 2, 3, or 4, and

[0296] n1 is 1, 2, 3, or 4,

[0297] Among them, from the current R Ma , R MbAt least one substituent, preferably one, two or three substituents, and more preferably one or two substituents of the group of substituents L is a P or P-Sp- group or contains at least one P or P-Sp- group.

[0298] Particularly preferred is one in which R ma and R mb A compound of formula M wherein one or both of them are P or P-Sp-.

[0299] Suitable and preferred RMs for the liquid-crystalline media are selected, for example, from the following formulae:

[0300]

[0301]

[0302]

[0303]

[0304]

[0305] The definitions of the various groups are as follows:

[0306] P 1 To P 3 are each independently a polymerizable group, preferably having one of the definitions specified above and below for P, more preferably an acrylate, methacrylate, fluoroacrylate, oxetane, vinyloxy or epoxy group,

[0307] Sp 1 To Sp 3 Each independently is preferably a single bond or a spacer group having one of the definitions of Sp given above and below, and more preferably -(CH2) P1 -、-(CH2) P1 -O-, -(CH2) P1 -CO-O- or -(CH2) P1 -O-CO-O-, wherein p1 is an integer from 1 to 12 and wherein in the latter group the bond to the adjacent ring is via an oxygen atom, wherein P 1 -Sp 1 -、P 2 -Sp 2 - and P 3 -Sp 3 - one of the groups may also be R aa ,

[0308] R aais H, F, Cl, CN or a straight-chain or branched alkyl group having 1 to 25 carbon atoms, wherein one or more non-adjacent CH2 groups may also be independently connected to each other via C(R) in such a way that the oxygen and / or sulfur atoms are not directly connected to each other 0 )=C(R 00 )-、-C≡C-、-N(R 0 )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, and one or more hydrogen atoms may also be replaced by F, Cl, CN or P 1 -Sp 1 -substituted, more preferably, a straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl or alkylcarbonyloxy radical having 1 to 12 carbon atoms (wherein alkenyl and alkynyl radicals have at least two carbon atoms and branched radicals have at least three carbon atoms),

[0309] R 0 and R 00 is the same or different at each occurrence and is independently H or an alkyl group having 1 to 12 carbon atoms,

[0310] R y and R z are each independently H, F, CH3 or CF3,

[0311] Z 1 It is -O-, -CO-, -C(R y R z )- or -CF2CF2-,

[0312] Z 2 and Z 3 are each independently -CO-O-, -O-CO-, -CH2O-, -OCH2-, -CF2O-, -OCF2- or -(CH2) n -, where n is 2, 3, or 4,

[0313] L is identical or different on each occurrence and has the meaning given above under formula M, is preferably F, Cl, CN or a straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl or alkylcarbonyloxy radical having 1 to 12 carbon atoms, preferably F,

[0314] L' and L" are each independently H, F or Cl,

[0315] X 1 To X 3 are independently -CO-O-, -O-CO- or a single bond,

[0316] r is 0, 1, 2, 3, or 4,

[0317] s is 0, 1, 2, or 3,

[0318] t is 0, 1, or 2, and

[0319] x is either 0 or 1.

[0320] Suitable polymerizable compounds are listed, for example, in Table G. Particularly preferred reactive mesogens are compounds of formula RM-A and RM-B and RM-C as shown in Comparative Example 3 and Example 2, respectively.

[0321] The polymerizable compound has at least one polymerizable group. The polymerizable group is preferably selected from CH2=CW 1 -COO-, CH2=CW 2 -(O) k1 -, CH3-CH=CH-O-, (CH2=CH)2CH-OCO-, (CH2=CH-CH2)2CH-OCO-, (CH2=CH)2CH-O-, (CH2=CH-CH2)2N-, 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 -, Phe-CH=CH-, HOOC-, OCN-, where W 1 is H, Cl, CN, phenyl or alkyl having 1 to 5 C atoms, in particular H, Cl or CH3; W 2 and W 3 are independently H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl; Phe is 1,4-phenylene; and k1 and k2 are independently 0 or 1. The polymerizable or reactive group is preferably selected from vinyl, acrylate, methacrylate, fluoroacrylate, oxetane or epoxy, particularly preferably acrylate or methacrylate.

[0322] In one embodiment, non-mesogenic monomers are included in the medium in addition to the one or more RMs. Preferably, the one or more polymerizable compounds, the non-mesogenic monomers or the RMs or both, are selected from acrylates, methacrylates, fluoroacrylates and vinyl acetate, wherein the composition more preferably further comprises one or more di-reactive and / or tri-reactive polymerizable compounds, preferably selected from diacrylates, dimethacrylates, triacrylates and trimethacrylates.

[0323] In a particular embodiment, one or more non-mesogenic monoacrylates are provided, particularly preferably one or more compounds selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, tert-butyl acrylate, pentyl acrylate, hexyl acrylate, nonyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxybutyl acrylate and isobornyl acrylate.

[0324] Additionally or alternatively, one or more non-mesogenic monomethacrylates may be provided, particularly preferably one or more compounds selected from the group consisting of methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, tert-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, nonyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxybutyl methacrylate, isobornyl methacrylate and 1-adamantyl methacrylate.

[0325] Especially preferred is the addition of at least one crosslinker to the polymerizable composition, ie a polymerizable compound containing two or more polymerizable groups, wherein preferably di- or poly-reactive RMs are used.

[0326] In this aspect, the di-reactive and poly-reactive compounds can be used to form polymer network structures of their own and / or to cross-link polymer chains substantially formed by polymerizing the mono-reactive compounds.

[0327] Alternatively or additionally, conventional crosslinking agents known in the art may be used. It is also particularly preferred to provide di- or polyreactive acrylates and / or methacrylates. It is particularly preferred that the compound is selected from ethylene diacrylate, propylene diacrylate, butylene diacrylate, pentylene diacrylate, hexylene diacrylate, ethylene glycol diacrylate, glycerol diacrylate, pentaerythritol tetraacrylate, ethylene dimethacrylate (also known as ethylene glycol dimethacrylate), propylene dimethacrylate, butylene dimethacrylate, pentylene dimethacrylate, hexylene dimethacrylate, tripropylene glycol diacrylate, ethylene glycol dimethacrylate, glycerol dimethacrylate, trimethylolpropane trimethacrylate and pentaerythritol triacrylate.

[0328] The ratio of monoreactive monomers to direactive or polyreactive monomers can advantageously be set and adjusted to influence the properties of the resulting polymeric component.

[0329] Suitable and conventionally used thermal initiators or photoinitiators (e.g. azo compounds or organic peroxides, such as Luperox type initiators) may be added to promote the reaction. Furthermore, suitable conditions for polymerization and suitable types and amounts of initiators are known in the art and described in the literature. In the case where a polymerization initiator is included in the medium, a photoinitiator is preferably used.

[0330] For example, when polymerizing with the aid of UV light, photoinitiators can be used which decompose under UV irradiation to produce free radicals or ions which start the polymerization reaction. For polymerizing acrylate or methacrylate groups, free radical photoinitiators are preferably used. For polymerizing vinyl, epoxy or oxetane groups, cationic photoinitiators are preferably used. Thermal polymerization initiators can also be used which decompose upon heating to produce free radicals or ions which start the polymerization reaction. Typical free radical photoinitiators are commercially available, for example For example, Irgacure 651 (available from BASF, containing 2,2-dimethoxy-1,2-diphenylethan-1-one), or (Ciba Geigy AG, Basel, Switzerland). A typical cationic photoinitiator is, for example, UVI 6974 (Union Carbide). Other suitable photoinitiators include α-amino ketones (eg, Irgacure 907), coumarins, phosphine oxides (eg, Irgacure 2100), acylphosphines (eg, Irgacure 819).

[0331] In a particular embodiment, the added polymerization initiator, preferably photoinitiator, comprises, preferably consists of, one or more mesogenic polymerization initiators, preferably one or more mesogenic photoinitiators, i.e. one or more reactive compounds which can initiate polymerization and which themselves have anisotropic and mesogenic properties.

[0332] However, according to a particularly preferred embodiment, no polymerization initiator is used, in particular no photoinitiator is used. In certain cases, this can improve the VHR and reduce the tendency to generate ions in the switching layer.

[0333] To maintain and achieve a good VHR, impurities in the polymerized reaction product are preferably kept to a minimum or substantially avoided. In particular, residual reactive species and charged contaminants are suitably and preferably kept to a minimum. For example, in case of UV polymerization, in a preferred embodiment, light with a relatively long wavelength close to the visible spectrum is used, preferably advantageously UV light in the range of 340 nm to 380 nm, and even more preferably 360 nm to 380 nm is used. In this way, undesirable photodegradation or decomposition of components of the LC medium can be avoided or at least minimized. In case a photoinitiator is used, the irradiation wavelength and the photoinitiator can be appropriately matched or adjusted.

[0334] In the alternative case where no photoinitiator is used, which is preferred in some embodiments, the irradiation wavelength range can be set so that at least some of the polymerizable compounds can undergo a photoreaction and itself initiate a polymerization reaction, while in addition degradation or decomposition of non-reactive components of the LC medium can be avoided or at least minimized. Achieving and setting the desired wavelength range can be achieved by conventional methods known in the art, for example by using filters, especially edge filters.

[0335] Surprisingly it has been found that polymeric structures can advantageously be generated in situ by providing one or more polymerizable compounds and in particular polymerizable mesogenic compounds as described above and below in a medium and polymerizing them.

[0336] The polymerizable compounds in the medium may be chosen such that after the polymerization a stable system is obtained which is stable, for example, during further processing steps such as heating steps, wherein a good VHR may be maintained.

[0337] Furthermore, only relatively small amounts of (a) polymerizable compounds are used to form the polymeric components and in particular the polymeric network in the first switching layer, which can advantageously influence the stability and minimize undesired degradation.

[0338] Providing a polymeric component may be useful for stabilising one or more states or phases of the LC medium.

[0339] The polymeric component may contribute to the advantageous properties of the obtainable material in the first switching layer. For example, the polymeric component may contribute to significantly more stable scattering states, especially multi-domain states, such that such scattering states can be maintained for longer periods of time, especially up to days, without the need for refreshing or reapplying voltage.

[0340] Furthermore, the polymeric components as provided in the material containing the CLC medium according to the invention can advantageously influence the scattering efficiency and appearance, for example with regard to uniformity and viewing angle dependence. Thus, color effects that can occur at oblique viewing angles can be significantly reduced.

[0341] In a preferred embodiment, the modulation material in the first switching layer comprises a liquid crystal medium and a polymeric component, wherein the polymeric component comprises a polymer network obtained by polymerization of a reactive mesogen, wherein the reactive mesogen preferably contains at least one group selected from the group consisting of an acrylate group (particularly preferably selected from a monoacrylate group, a diacrylate group or a triacrylate group), a vinyl ether group and an epoxy group. Compounds containing acrylate groups as used herein include acrylic monomers, methacrylic monomers and mixtures of such monomers.

[0342] The polymerization can be carried out using conventional methods. The polymerization can be carried out in one or more steps. In particular, the polymerization of the polymerizable compound is preferably achieved by exposure to heat or actinic radiation, wherein exposure to actinic radiation means irradiation with light (such as UV light, visible light or IR light), irradiation with X-rays or gamma rays, or irradiation with high-energy particles (such as ions or electrons). In a preferred embodiment, free radical polymerization is carried out.

[0343] The polymerization can be carried out at a suitable temperature. In one embodiment, the polymerization is carried out at a temperature below the clearing point of the mesogenic mixture. In an alternative embodiment, however, it is also possible to carry out the polymerization at or above the clearing point.

[0344] In one embodiment, the polymerization is carried out by irradiation with light, i.e. with light, preferably UV light. As a source of actinic radiation, for example, a single UV lamp or a group of UV lamps can be used. When high lamp powers are used, the curing time can be reduced. Another possible source for optical radiation is a laser, for example a UV laser, a visible laser or an IR laser.

[0345] In one embodiment, the polymerization is performed by adding one or more polymerizable compounds, preferably comprising a direactive compound and optionally a suitable photoinitiator, to the chiral liquid crystal host mixture; and polymerizing the polymerizable compounds by exposure to UV radiation.

[0346] Preferably, the polymerization is performed in an electro-optical cell which maintains the chiral liquid crystal host mixture in a predetermined state. In a preferred embodiment, the polymerization (preferably polymerization using UV light) is performed when the medium is in a homeotropic state, wherein typically and preferably an electric field is applied.

[0347] In a preferred embodiment, the liquid crystal medium comprising one or more polymerizable compounds, in particular polymerizable mesogenic compounds, is provided as a layer between two relatively transparent substrates each provided with an electrode. Preferably, the electrodes are configured as conductive layers on the inner surface of each substrate, wherein more preferably the conductive layers are each covered by a passivation layer, and wherein an optional alignment layer is further provided in direct contact with the liquid crystal medium.

[0348] Subsequently, the one or more polymerizable compounds are polymerized, in particular in the presence of an applied electric field in the layer.

[0349] It is preferred that the polymerisation is carried out by photopolymerisation, preferably using UV light.In a particularly preferred embodiment, during the polymerisation an electric field is at least temporarily applied to induce an alignment of the medium, preferably a homeotropic alignment.

[0350] Applying a voltage to set a predetermined orientation during polymerization can advantageously influence the product properties of the switching layer and the window element. For example, inducing a homeotropic alignment during polymerization can help to obtain a uniform low haze clear state, while in addition a uniform and appropriately strong haze can be obtained in the scattering state.

[0351] It is possible to control the temperature during photopolymerization, for example in the range of 20°C to 100°C, preferably below the clearing point.

[0352] In one embodiment, the reactive mesogens are self-initiating, while in another embodiment, photoinitiators are used to trigger the polymerization.

[0353] For photopolymerization of the material in the switching layer, preferably an exposure time of 30 s to 240 min, more preferably 1 min to 120 min, is used, preferably using 0.01 mW / cm 2 Up to 100mW / cm 2 , more preferably 0.1 mW / cm 2 Up to 50mW / cm 2 And especially 1mW / cm 2 Up to 20mW / cm 2 range of irradiation intensity.

[0354] For the polymerization, several parameters such as the irradiation dose, the applied voltage, the frequency of the AC voltage, and the amount of the chiral dopant in the medium can be appropriately set or changed.

[0355] After the polymerization, especially the photopolymerization step, further treatments may be performed. Preferably, after the polymerization step, a heat treatment is performed in the presence or absence of an electric field. Heat treatment, i.e. exposure to an increased temperature relative to the previous polymerization step, may lead to further curing or further conversion or complete polymerization.

[0356] It is also possible to carry out pretreatment steps on the substrate used, for example surface treatment methods such as UV-ozone treatment or plasma treatment, which can improve the alignment and wetting properties over larger areas and contribute to improved uniformity and advantageously reduce undesirable haze in the clear state.

[0357] The methods described herein are advantageously suitable for producing window elements having advantageous durability, wherein the first switching layer can exhibit a color-neutral, low-haze clear state and an efficient and uniform scattering state.

[0358] The liquid-crystalline medium in the first switching layer may contain additional compounds, such as one or more pleochroic dyes, in particular one or more dichroic dyes, and / or other customary and suitable additives, such as stabilizers, preferably in an amount of 0.001 to 25% by weight, more preferably 0.1 to 5% by weight.

[0359] However, the first switching layer preferably does not contain any dye, which may provide a higher transmission in the clear state and give an uncolored or white appearance.

[0360] The multilayer arrangement according to the invention for regulating the passage of light further comprises, in addition to the first switching layer, a switching element comprising a second switching layer, wherein the switching element is switchable between a light state and a dark state and wherein the second switching layer is a liquid crystal layer.

[0361] This additional switching element comprising a liquid crystal based switching layer or in some implementations two liquid crystal based switching layers is provided to produce an overall reduction in light intensity when desired or needed, ie to obtain a switching capability for light attenuation or light dimming.

[0362] In a preferred embodiment, the switching element is based on one or two guest-host liquid crystal switching layers. This means that the second switching layer in this embodiment is a liquid crystal layer comprising one or more dichroic dyes. The switching element may comprise a single switching layer, i.e. the second switching layer. Alternatively, the switching element may comprise an additional switching layer. In this latter case, the two switching layers may be provided separately or individually in a so-called cell, which are then combined and configured as a so-called double cell, in particular by bonding using, for example, lamination or adhesives.

[0363] Therefore, it is preferred that the second switching layer and optionally the additional switching layers as provided in the switching element comprise at least one dichroic dye.

[0364] In the second switching layer and also in the optionally provided additional switching layers, dye-doped nematic liquid-crystalline media can be used.

[0365] Alternatively, it is also possible to include one or more chiral compounds in addition to the at least one dichroic dye in the second switching layer and also in the optional additional switching layer. Preferably, the one or more chiral compounds can be suitably selected from the chiral compounds as described for the first switching layer.

[0366] While such dye-doped cholesteric liquid-crystalline media can advantageously contribute at least to a certain extent to the scattering or diffusion of light, these media are primarily provided to achieve dimming or attenuation of light. In a preferred embodiment, the haze is kept to a minimum in the switching element, in particular in the bright state.

[0367] The switching element can be configured and arranged in different ways, especially in terms of electrode configuration, optional arrangement of alignment layers and their types and liquid crystal material, however the switching element is provided so as to obtain switching capabilities for light dimming and overall transmittance variation in a multilayer configuration.

[0368] Preferred configurations, especially for cells comprising a second switching layer, include twisted nematic (TN), antiparallel, super twisted nematic (STN) and vertically aligned - super twisted nematic (VA-STN) configurations.

[0369] In a TN configuration, the twist angle is typically 90° or about 90°. In an STN configuration, the twist angle exceeds 90° and is typically in the range of above 90° to 270°. However, it is also possible that the STN configuration of the present invention exhibits a twist angle of more than 270°.

[0370] In order to further improve the switching contrast of the switching element in the multilayer configuration, it is possible to provide two switching layers, in particular configured as a double box as described above. In this embodiment, it is preferred that two layers are provided so that they provide an overall optimized or at least increased efficiency to reduce both the parallel and perpendicular polarization components of the light.

[0371] The two switching layers of the double cell preferably comprise the same dye-doped liquid-crystalline medium, which optionally may comprise one or more chiral compounds.

[0372] In another embodiment, the switching element comprises polarization layers, wherein preferably exactly one polarizer and the second switching layer as the only switching layer are arranged in a so-called Heilmeier arrangement. This arrangement is also suitable for further improving the switching contrast of the switching element by obtaining an effective attenuation of both the parallel and perpendicular polarization components of the light.

[0373] Alternatively, it is also possible to provide more than one polarization layer, in particular two polarization layers in the switching element. In this case, the liquid crystal medium provided in the switching layer preferably does not contain any dichroic dyes. In this alternative, in which two polarizers are used, it is preferred to configure the element in a TN configuration, a STN configuration, a vertical alignment (VA) configuration, an in-plane switching (IPS) configuration or a fringe field switching (FFS) configuration. In this alternative embodiment, one or more retardation or compensation layers may optionally be further included.

[0374] Typical polarizers, especially absorbing or reflecting linear polarizers such as thin film polarizers or wire grid polarizers, and typical retarders and compensators such as uniaxial and biaxial plastic retardation films are known in the art.

[0375] It is preferred that in a multilayer configuration, in particular when the second switching layer contains one or more chiral dopants, the first switching layer is closer to the light source, i.e. the switching element is placed after the first switching layer relative to the light source. Thus, the first switching layer is preferably placed before the switching element relative to the outside facing the light source. It was surprisingly found that when the first switching layer faces the light source, in particular daylight, and the switching element is distal in this respect, further beneficial advantages with respect to the performance of the device can be obtained, such as further improved color neutrality, a favorable appearance and even better stability.

[0376] The LC host medium used in the switching element, in particular the guest-host mixture, can be identical to or different from the LC medium used in the first switching layer, in particular the nematic host mixture.

[0377] In principle, suitable host mixtures for switching elements are any dielectrically negative or dielectrically positive LC mixtures which are suitable for conventional VA, TN, STN, IPS or FFS displays.

[0378] Suitable LC mixtures are known in the art and described in the literature.LC media for VA displays having negative dielectric anisotropy are described, for example, in EP 1 378 557 A1.

[0379] Suitable LC mixtures with positive dielectric anisotropy for LCDs and in particular IPS displays are known, for example, from JP 07-181 439 (A), EP 0 667 555, EP 0 673 986, DE 195 09 410, DE 195 28 106, DE 195 28107, WO 96 / 23 851, WO 96 / 28 521 and WO 2012 / 079676.

[0380] Preferred embodiments of the liquid-crystalline media according to the invention having negative or positive dielectric anisotropy are indicated below.

[0381] In a preferred embodiment of the present invention, the LC medium in the switching layer of the switching element contains an LC host mixture having a negative dielectric anisotropy. Therefore, in a preferred embodiment, the mesogenic medium comprises a component selected from the following item a):

[0382] a) a mesogenic medium comprising one or more compounds selected from the group of compounds of formula CY, PY and AC:

[0383]

[0384] in

[0385] a means 1 or 2,

[0386] b represents 0 or 1,

[0387] c is 0, 1, or 2,

[0388] d is 0 or 1,

[0389] express

[0390]

[0391] And express

[0392]

[0393] and

[0394] express

[0395]

[0396] R 1 and R 2

[0397] R AC1 and R AC2 each independently of one another represents an alkyl radical having 1 to 12 C atoms, wherein one or two non-adjacent CH2 groups may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that the O atoms are not directly connected to one another; preferably an alkyl radical or alkoxy radical having 1 to 6 C atoms,

[0398] Z x and Z y each independently represents -CH2CH2-, -CH=CH-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -CO-O-, -O-CO-, -C2F4-, -CF=CF-, -CH=CH-CH2O- or a single bond, preferably a single bond,

[0399] L 1-4 Each independently represents F, Cl, CN, OCF3, CF3, CH3, CH2F, CHF2,

[0400] The various groups have the following meanings:

[0401] each independently of one another represents an alkyl radical having 1 to 12 C atoms, wherein one or two non-adjacent CH2 groups may be replaced by -O-, -CH=CH-, -CO-, -O-CO- or -CO-O- in such a way that the O atoms are not directly connected to one another,

[0402] Z AC represents -CH2CH2-, -CH=CH-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -CO-O-, -O-CO-, -C2F4-, -CF=CF-, -CH=CH-CH2O- or a single bond, preferably a single bond, and

[0403] Preferably, L 1 and L 2 Both represent F or L 1 and L 2 One of them represents F and the other represents Cl, or L 3 and L 4 Both represent F or L 3 and L 4 One of them represents F and the other represents Cl.

[0404] The compound of formula CY is preferably selected from the group consisting of the following sub-formulae:

[0405]

[0406]

[0407]

[0408]

[0409] wherein a represents 1 or 2, alkyl and alkyl* each independently represent a straight-chain alkyl group having 1 to 6 C atoms, and alkenyl represents a straight-chain alkenyl group having 2 to 6 C atoms, and (O) represents an oxygen atom or a single bond. Alkenyl preferably represents CH2=CH-, CH2=CHCH2CH2-, CH3-CH=CH-, CH3-CH2-CH=CH-, CH3-(CH2)2-CH=CH-, CH3-(CH2)3-CH=CH- or CH3-CH=CH-(CH2)2-.

[0410] The compound of formula PY is preferably selected from the group consisting of the following sub-formulae:

[0411]

[0412]

[0413]

[0414] wherein alkyl and alkyl* each independently represent a straight-chain alkyl group having 1 to 6 C atoms, and alkenyl represents a straight-chain alkenyl group having 2 to 6 C atoms, and (O) represents an oxygen atom or a single bond. Alkenyl preferably represents CH2=CH-, CH2=CHCH2CH2-, CH3-CH=CH-, CH3-CH2-CH=CH-, CH3-(CH2)2-CH=CH-, CH3-(CH2)3-CH=CH- or CH3-CH=CH-(CH2)2-.

[0415] The compound of formula AC is preferably selected from the group of compounds of the following sub-formulae:

[0416]

[0417]

[0418] Where R 3 and R 4 With R as described above AC1 and R AC2 meaning.

[0419] In a preferred embodiment of the present invention, the LC medium in the switching layer of the switching element contains an LC host mixture having positive dielectric anisotropy. Therefore, in other preferred embodiments, the mesogenic medium according to the present invention comprises a component selected from the following items b) to c):

[0420] b) a mesogenic medium comprising one or more compounds selected from the group of compounds of formulae IIA to VIII, in particular formulae IIA and IIIA, as described below

[0421]

[0422] in

[0423] R 20 each identically or differently represents a halogenated or unsubstituted alkyl or alkoxy radical having 1 to 15 C atoms, wherein one or more CH2 radicals in these radicals may each independently of one another be substituted by -C≡C-, -CF2O-, -CH=CH-, -C≡C-, -C≡O-, -C≡ ...C-, -C -O-, -CO-O- or -O-CO-,

[0424] X 20 each identically or differently represents F, Cl, CN, SF5, SCN, NCS, each a halogenated alkyl, halogenated alkenyl, halogenated alkoxy or halogenated alkenyloxy group having up to 6 C atoms, and

[0425] Y 20-24each identically or differently represents H or F;

[0426] Each independently expresses

[0427]

[0428] The compound of formula IIA is preferably selected from the following formulae:

[0429]

[0430] Where R 20 and X 20 has the meaning indicated above.

[0431] R 20 Preferably, X represents an alkyl radical having 1 to 6 C atoms. 20 Preferably X represents F. Particularly preferred are compounds of the formulae IIAa and IIAb, in particular compounds of the formulae IIAa and IIAb wherein X represents F.

[0432] The compound of formula IIIA is preferably selected from the following formulae:

[0433]

[0434] Where R 20 and X 20 has the meaning indicated above.

[0435] R 20 Preferably, X represents an alkyl radical having 1 to 6 C atoms. 20 Preferably it represents F. Particularly preferred are compounds of the formulae IIIAa and IIIAe, in particular compounds of the formula IIIAa.

[0436] c) a mesogenic medium which alternatively or additionally comprises one or more compounds selected from the following formulae:

[0437]

[0438] in

[0439] R 20 , X 20 and Y 20-23 has the meaning indicated above, and

[0440] Z 20 represents -C2H4-, -(CH2)4-, -CH=CH-, -CF=CF-, -C2F4-, -CH2CF2-, -CF2CH2-, -CH2O-, -OCH2-, -COO- or -OCF2-, and also represents a single bond in formulas V and VI, and also represents -CF2O- in formulas V and VIII,

[0441] r represents 0 or 1, and

[0442] s represents 0 or 1;

[0443] - The compound of formula IVA is preferably selected from the following formulae:

[0444]

[0445]

[0446] Where R 20 and X 20 has the meaning indicated above.

[0447] R 20 Preferably, X represents an alkyl radical having 1 to 6 C atoms. 20 Preferably it represents F, CN or OCF3, furthermore OCF═CF2 or Cl.

[0448] - The compound of formula V is preferably selected from the following formulae:

[0449]

[0450]

[0451] Where R 20 and X 20 has the meaning indicated above.

[0452] R 20 Preferably, X represents an alkyl radical having 1 to 6 C atoms. 20 Preferably, F and OCF3 are represented, furthermore OCHF2, CF3, OCF=CF2 and OCH=CF2.

[0453] - The compound of formula VI is preferably selected from the following formulae:

[0454]

[0455]

[0456] Where R 20 and X 20 has the meaning indicated above.

[0457] R 20 Preferably, X represents an alkyl radical having 1 to 6 C atoms. 20 Preferably represents F, in addition OCF3, CF3, CF=CF2, OCHF2 and OCH=CF2;

[0458] - The compound of formula VII is preferably selected from the following formulae:

[0459]

[0460] Where R 20 and X 20 has the meaning indicated above.

[0461] R 20 Preferably, X represents an alkyl radical having 1 to 6 C atoms. 20 Preferably it represents F, in addition OCF3, OCHF2 and OCH=CF2.

[0462] In the case where the medium used in the switching element has negative dielectric anisotropy, the value of the dielectric anisotropy (Δε) is preferably in the range of -2.0 to -8.0, more preferably in the range of -3.0 to -6.0 and particularly preferably in the range of -3.5 to -5.0.

[0463] In the case of a medium used in the switching element having a positive dielectric anisotropy, the value of Δε is preferably in the range of 3.0 to 60.0, more preferably in the range of 5.0 to 30.0 and particularly preferably in the range of 8.0 to 15.0.

[0464] The liquid-crystalline medium used in the switching element preferably has a clearing point of 70° C. or more, more preferably 80° C. or more, even more preferably 90° C. or more, yet more preferably 105° C. or more and especially preferably 110° C. or more. In one embodiment, the liquid-crystalline medium used in the switching element has a clearing point in the range of 70° C. to 170° C.

[0465] A higher clearing point as defined may be beneficial with respect to the performance and reliability of the multilayer configuration and devices comprising the multilayer configuration. In particular, the medium may maintain its functional properties over a suitably wider temperature range and also at elevated temperatures. This may be particularly advantageous for use in window elements for regulating the passage of daylight, especially when the window elements are exposed to direct or prolonged irradiation of daylight. A high clearing point may also contribute to an advantageously high degree of ordering of the liquid crystal host molecules and thus to the dichroic dye guest molecules at typical operating temperatures, which may increase the achievable contrast between the switching states.

[0466] In a preferred embodiment, the birefringence (Δn) of the liquid crystal medium used in the switching element is in the range of 0.040 or more to 0.080 or less, more preferably in the range of 0.045 or more to 0.070 or less and most preferably in the range of 0.050 or more to 0.060 or less. In this embodiment, the dielectric anisotropy is positive or negative, preferably negative.

[0467] In another preferred embodiment, the Δn of the liquid-crystal medium used in the switching element is in the range of 0.075 or more to 0.130 or less, more preferably in the range of 0.090 or more to 0.125 or less and most preferably in the range of 0.095 or more to 0.120 or less.

[0468] In yet another preferred embodiment, the Δn of the liquid-crystal medium used in the switching element is in the range of 0.100 or more to 0.200 or less, more preferably in the range of 0.110 or more to 0.180 or less and most preferably in the range of 0.120 or more to 0.160 or less.

[0469] In a preferred embodiment, the second switching layer and optionally the additional switching layer of the switching element comprise one or more pleochroic dyes, in particular one or more dichroic dyes. Preferably, the medium comprises two, three, four, five, six, seven or eight dichroic dyes. It is particularly preferred that the medium comprises at least three dichroic dyes.

[0470] Preferably, the dichroic compound is present in the liquid-crystalline medium in the form of a solution.

[0471] Each of the one or more dichroic dyes is preferably present in the liquid-crystalline medium in a proportion of 0.01% to 10% by weight, more preferably 0.025% to 7.5% by weight, even more preferably 0.05% to 5% by weight, furthermore even more preferably 0.1% to 2.5% by weight and particularly preferably 0.25% to 1% by weight, based on the total weight of the entire medium.

[0472] Preferably, the one or more dichroic compounds are present in the total liquid-crystalline medium in a total concentration in the range from 0.05 to 15% by weight, more preferably from 0.1 to 10% by weight and even more preferably from 0.5 to 5% by weight.

[0473] Dichroic compounds preferably exhibit a relatively high dichroic ratio, a favourable colour purity and a relatively large extinction coefficient, especially in the VIS and / or NIR region of light, and additionally suitable light fastness and suitable solubility in liquid-crystalline media.

[0474] The dichroic compounds and the amounts of the individual compounds are advantageously selected and mixed so that the desired color effect for a given application can be obtained.

[0475] In one embodiment, the dichroic compound contained in the LC medium has red, green and blue colors, respectively. In a preferred embodiment, the dichroic compound in the LC medium has an absorption that completely covers the entire visible spectrum. In this way, a color-neutral or black appearance can be obtained. This color-neutral appearance can be advantageous in applications where color artifacts or residual colors should be minimized or avoided, such as in certain smart window applications.

[0476] It has further been found that it may be advantageous to include one or more near infrared dyes in the composition. This provision may advantageously facilitate minimizing or even avoiding residual fluorescence in the visible spectrum, such that undesirable color artifacts, such as red glow, may be avoided or at least substantially reduced.

[0477] In a particularly preferred embodiment, the LC medium of the switching element comprises at least one violet dye, at least one blue dye, at least one yellow dye, at least one red dye and at least one near-infrared dye.

[0478] It is particularly preferred that the absorption spectra of the dichroic dyes in the LC medium complement one another in the switching layer, in such a way that the eye has the impression of black. The dyes of the liquid-crystalline medium preferably cover a large part of the visible spectrum, more preferably the entire part and most preferably a further part of the NIR spectrum. The precise manner in which dye mixtures which appear black or grey to the eye can be prepared is known in the art and is described, for example, in M. Richter, Einführung in die Farbmetrik [Introduction to Colorimetry], 2nd edition, 1981, ISBN 3-11-008209-8, Walter de Gruyter & Co.

[0479] The setting of the color position of the dye mixture is described in the colorimetric area. For this purpose, the spectra of the individual dyes are calculated according to the Lambert-Beer law to obtain the total spectrum and converted into the corresponding color position and brightness values ​​according to the colorimetric rules under the relevant illumination, for example the daylight illuminant D65. The position of the white point is fixed by the individual illuminants (for example D65) and is given in the table, for example in the above references. Different color positions can be set by changing the ratio of the different dyes.

[0480] The dichroic compound is preferably a positive dichroic dye, ie a dye having a positive degree of anisotropy R.

[0481] The degree of anisotropy R of an LC mixture comprising a dye is determined from the values ​​of the extinction coefficients of the molecules aligned parallel and perpendicular to the polarization direction of the light.

[0482] According to the invention, the degree of anisotropy R is preferably greater than 0.4, more preferably greater than 0.6, even more preferably greater than 0.7 and in particular greater than 0.8.

[0483] The absorption preferably reaches a maximum when the polarization direction of the light is parallel to the direction of the longest molecular extension of the dichroic compound and it preferably reaches a minimum when the polarization direction of the light is perpendicular to the direction of the longest molecular extension of the dichroic compound.

[0484] In one embodiment, the dichroic dye is preferably selected from the classes of dyes indicated in B. Bahadur, Liquid Crystals—Applications and Uses, Vol. 3, 1992, World Scientific Publishing, Chapter 11.2.1, and particularly preferably from the explicit compounds given in the table presented therein.

[0485] Dichroic dyes may generally belong to the class of dichroic dyes known in the art and described in the literature. Thus, for example, anthraquinone dyes are described in EP 34832, EP 44893, EP 48583, EP 54217, EP 56492, EP 59036, GB 2065158, GB 2065695, GB 2081736, GB 2082196, GB 2094822, GB 2094825, JP-A 55-123673, DE 3017877, DE 3040102, DE 3115147, DE 3115762, DE 3150803 and DE 3201120, naphthoquinone dyes in DE 3126108 and DE 3202761, azo dyes in EP 43904; DE 3123519; WO 3123519. 82 / 2054; GB 2079770; JP-A 56-57850; JP-A 56-104984; US 4308161; US ​​4308162; US4340973; T. Uchida, C. Shishido, H. Seki and M. Wada: Mol. Cryst. Lig. Cryst. 39, 39-52 (1977) and H. Seki, C. Shishido, S. Yasui and T. Uchida: Jpn. J. Appl. Phys. 21, 191-192 (1982), and perylene is described in EP 60895, EP 68427 and WO 82 / 1191. Rylene dyes are described, for example, in EP 2166040, US 2011 / 0042651, EP 68427, EP 47027, EP 60895, DE 3110960 and EP 698649.

[0486] Dichroic dyes can be preferably selected from, for example, azo dyes, anthraquinones, methine compounds, azomethine compounds, merocyanidin compounds, naphthoquinones, tetrazines, pyrromethene dyes, malononitrile dyes, rylenes (especially perylene and terylene), thiadiazole dyes, thienothiadiazole dyes, benzothiadiazoles, thiadiazoloquinoxaline, pyrromethene and diketopyrrolopyrroles. Particularly preferred are azo compounds, anthraquinones, benzothiadiazoles, especially as described in WO 2014 / 187529; diketopyrrolopyrroles, especially as described in WO 2015 / 090497; rylenes, especially as described in WO 2014 / 090373; and thiadiazoloquinoxaline derivatives, especially as described in WO 2016 / 177449. Particularly preferred are dichroic dyes selected from azo dyes, benzothiadiazoles and / or thiadiazoquinoxalines.

[0487] Examples of preferred dichroic dyes that may be present in the LC medium of the switching element in a multilayer configuration are shown below

[0488]

[0489]

[0490]

[0491]

[0492]

[0493]

[0494]

[0495]

[0496]

[0497] The liquid-crystalline media may additionally comprise suitable additives and auxiliary materials, for example stabilizers and quenchers.

[0498] It is preferred that the liquid-crystalline medium used in the second switching layer and optionally the additional switching layer in a switching element as in a multilayer configuration contains no polymerizable compounds, in particular no polymerizable mesogenic compounds.

[0499] The LC media according to the invention are prepared in a manner conventional per se. In general, the components are preferably dissolved in one another at elevated temperature. Mixing is preferably carried out under an inert gas, for example under nitrogen or argon. Subsequently, the optional dye is added, preferably at elevated temperature, more preferably at above 40° C. and particularly preferably at above 50° C. In general, the desired amount of the component used in smaller amounts is dissolved in the component constituting the main constituent. It is also possible to mix solutions of the components in organic solvents, for example in acetone, toluene, chloroform or methanol, and to remove the solvent again after mixing, for example by distillation.

[0500] In one aspect of the invention, the layer arrangement is included in a window element that is electrically switchable between an optically clear and bright state and a light scattering and dark state.

[0501] Preferably, the window element is further operable in an optically clear and dark state and a light-scattering and bright state and is electrically switchable to the optically clear and dark state and the light-scattering and bright state.

[0502] The window element preferably has a width greater than 0.5 m 2 , more preferably greater than 1m 2 And even more preferably greater than 3m 2 In one embodiment, the window element has a size of 0.10 m 2 Up to 10m 2 within the range of 0.5 m 2 Up to 10m 2 The area within the range.

[0503] The window element according to the invention allows light to pass through it. It can be advantageously used and included in windows, glazing units, including insulating glazing units, facade elements, room dividers, partition walls, etc., and it can be used herein as a component that provides different switching states as required and thus provides anti-glare control as required.

[0504] Window elements as switchable devices can be used to regulate or modulate the passage of light from an exterior space to an interior space, for example into the interior of a building (such as a residential building, an office building or a building for commercial purposes) or a vehicle. Window elements can also be used to regulate or modulate the passage of light from an interior space to another interior space, in particular in structural components that separate different functional areas or rooms.

[0505] The window element and the window as a whole comprising the window element preferably do not contain any light source. Therefore, any light transmitted through the window originates from an external light source, such as daylight or household lighting, in particular daylight.

[0506] According to the invention, the state of the switching layer and the window element is controlled using an electric field applied by means of electrodes. The electrodes are preferably transparent electrodes arranged on the substrate in the form of a coating. The coating is usually applied to the side or surface of the substrate facing the switching layer.

[0507] Preferably, the electrode is not patterned and / or structured so that it is continuous. Thus, the entire switchable area is simultaneously addressed and switched by applying an electric field. In an alternative embodiment, the electrode may be patterned to form individual addressable areas that can be switched independently from other areas by applying an electric field. In this case, the electrode is preferably patterned so that there are 2 to 10 independently addressable areas.

[0508] Preferably, the first switching layer and the switching element with the second switching layer can be matched to facilitate switching by electronically driven switching voltages. Advantageously, relatively low switching voltages can be useful and effective, wherein preferably, a switching voltage of 48V or less is used.

[0509] In one embodiment, the window element is switchable to an optically clear and bright state by applying an AC voltage V1 and to a light scattering and dark state by applying an AC voltage V2, wherein V1>V2.

[0510] In a window element, preferably in a window comprising a window element for controlling and regulating the passage of light, a first switching layer providing a scattering pattern and a switching element comprising a second switching layer and providing switchable light dimming can be appropriately configured and combined, for example by lamination or using an adhesive, and also separated by using, for example, one or more intermediate substrates or sheets, panes or panels, wherein optionally the panes can be further separated by a vacuum or gas-filled space.

[0511] In one embodiment, the first switching layer and the second switching layer included in the switching element are assembled in an insulating glazing unit, wherein the two layers are separated in particular by a vacuum or gas-filled space and wherein optionally one or more of the substrate or carrier panes, in particular one or more glazing sheets, have a low-e coating. In this case, it is preferred to place the first switching layer facing the outer side of the window element, i.e. the side facing the light source and in particular the daylight, and the switching element with the second switching layer facing the inner side, i.e. the switching element is on the far side of the light source.

[0512] The switching layer according to the invention preferably has a thickness in the range of 1 μm to 100 μm, more preferably 2 μm to 50 μm, even more preferably 4 μm to 40 μm and in particular 10 μm to 25 μm.

[0513] To maintain the appropriate thickness of the switching layer, a spacer may be included in the cell gap of the switching layer. Typically, the spacer has a spherical shape with a diameter within the cell gap. For example, a non-conductive spacer made of a polymer or glass having a spherical shape with a predetermined diameter may be used. In some embodiments, it may be suitable to provide a viscous spacer, i.e., a spacer having some inherent adhesive characteristics to better adhere to the surface. It may also be suitable to use a black spacer, for example to avoid or minimize unwanted light leakage. In some embodiments, the use of a black and viscous spacer may be particularly beneficial. Alternatively, the cell thickness may be set or maintained by other suitable means, for example, by using a column spacer. Column spacers may also be formed to obtain compartments, thereby optionally allowing a freely cuttable structure. In some embodiments, the switching layer may therefore include compartments each containing a liquid crystal medium, for example, using a rectangular or honeycomb structure.

[0514] The switching layer according to the invention can be arranged between two substrates, in particular two transparent substrates. The substrate can comprise, preferably consist of, glass or a polymer, in particular glass; polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyvinyl butyral (PVB), polymethyl methacrylate (PMMA), polycarbonate (PC), polyimide (PI), COP (cyclic olefin polymer) or TAC (triacetyl cellulose). In a particularly preferred embodiment, a glass substrate is used. In an alternative embodiment, a plastic substrate is used.

[0515] Preferably, an alignment layer is used in the device of the present invention, wherein for this purpose the alignment layer can be any desired layer known to the person skilled in the art. Preferred are polyimide layers, particularly preferably layers comprising rubbed polyimide. In one embodiment, a planar alignment is provided, wherein more preferably a slight pretilt angle can be set. In an alternative embodiment, a vertical alignment is provided, wherein more preferably a high pretilt angle is set.

[0516] In a preferred embodiment, the device according to the invention is a component of a window, more preferably a window element comprising at least one glass surface, especially preferably a component of an insulating glazing unit.

[0517] The window element may be suitably integrated into the window, for example by lamination or gluing, preferably lamination into a pane or glazing unit.

[0518] Here, a window means in particular a structure in a building, a car, a commercial vehicle, a ship, a train, an airplane, etc., which comprises a frame and at least one substrate or pane, such as a plastic substrate or a glass pane, surrounded by the frame. In a preferred embodiment, in particular for architectural applications, the window preferably comprises an insulating frame and two or more glass panes, i.e., a multi-pane insulating glass.

[0519] According to a preferred embodiment, the device according to the invention is applied directly to the glass surface of a window (for example by lamination), particularly preferably in the gap between two glass panes of a multi-pane insulating glass.

[0520] The window element according to the invention or a window in which the window element can be integrated, for example configured as a switchable glazing unit and in particular an insulating glazing unit, preferably comprises one or more layers that block UV light. In particular, the window element preferably comprises one or more layers that do not allow or only allow a very small proportion of light with a wavelength of less than 350 nm, preferably extending to less than 360 nm, particularly preferably even extending to less than 380 nm to pass through. In addition, a low-e coating can preferably be applied to one or more of the lamellae.

[0521] The window may be part of a building, container, vehicle or other substantially enclosed space. The use of the window element for interior spaces is particularly preferred, which are subject to strong and / or strongly varying insolation from an exterior location.

[0522] Advantageously, the window element can be operated so that even in a dark and diffuse state a meaningful amount of daylight can be transmitted, including direct and diffuse light. This means that enough daylight can pass through so that the use of artificial lighting can be limited or even avoided entirely, resulting in cost and energy savings.

[0523] Preferably, in the light-scattering and dark state, the window element according to the invention exhibits a transmittance (preferably direct transmittance) of visible light, preferably light having a wavelength of 550 nm, of less than 40%, preferably less than 36%, more preferably less than 30% and in particular less than 20%. In one embodiment, in the light-scattering and dark state, the transmittance of the window element according to the invention is in the range of 14% to 36%.

[0524] By providing dimming and scattering together in a switchable device as currently configured, it is possible to distribute daylight more evenly in an interior space (e.g. a building), wherein scattering preferably occurs over a wide range of angles so that a more even distribution of light can be achieved at all angles. This form of light modulation can advantageously result in effective reduction of glare from daylight radiation and comfortable lighting conditions.

[0525] This favorable transmission behavior of multilayer configurations and window elements can be determined using the Bidirectional Transmission Distribution Function (BTDF).

[0526] Preferably, for a normally incident collimated light beam from a white light source, in a light-scattering and dark state, the window element according to the invention exhibits a ratio of the average intensity of light transmitted into a radiation angle of -3° to +3° to the average intensity of light transmitted into a radiation angle of -60° to +60° of 15 or less, more preferably 10 or less, even more preferably 5 or less, still more preferably 3.5 or less and especially 2 or less. Preferably, viewing angle dependence measurements, especially BTDF measurements, are performed using a viewing angle photometer based on Fourier optics, especially the EZLite 120R instrument from Eldim, using a white light source and normal incidence angle of light, to determine the angular dependence of the brightness of the transmitted light and the ratio of the average intensity of light transmitted into different radiation angle ranges or viewing cones.

[0527] In the present invention and in particular in the following examples, the structures of the mesogenic compounds are indicated with the aid of abbreviations (also referred to as acronyms). In these acronyms, the chemical formulae are abbreviated as follows using Tables A to C below. All C n H 2n+1 , C m H 2m+1 and C l H 2l+1 or C n H 2n-1 , C m H 2m-1 and C l H 2l-1 The radical represents a straight chain alkyl or alkenyl, preferably a 1-E-alkenyl, each of which has n, m and 1 C atoms, respectively. Table A lists the codes for the ring elements of the core structure of the compound, while Table B shows the linking groups. Table C gives the meaning of the codes for the left or right end groups. The acronyms consist of the following: the code for the ring element with the optional linking group, followed by the first hyphen and the code for the left end group, and the second hyphen and the code for the right end group. Table D shows the illustrative structures of the compounds and their respective abbreviations.

[0528] Table A: Ring elements

[0529]

[0530]

[0531] Table B: Linking Groups

[0532]

[0533] Table C: End Groups

[0534]

[0535]

[0536] Use with each other and with others

[0537]

[0538] wherein n and m each represent an integer, and the triple dots "..." are placeholders for other abbreviations from this table.

[0539] The following table shows illustrative structures and their respective abbreviations. These are shown to illustrate the meaning of the abbreviation rules. In addition, they represent compounds that can be preferably used.

[0540] Table D: Illustrative structure

[0541]

[0542]

[0543]

[0544]

[0545]

[0546]

[0547]

[0548]

[0549]

[0550]

[0551]

[0552]

[0553]

[0554]

[0555]

[0556]

[0557]

[0558]

[0559]

[0560] wherein n, m and l preferably represent 1 to 7 independently of one another.

[0561] The following table shows illustrative compounds that can be used as stabilizers in the media according to the present invention.

[0562] Table E

[0563] Table E shows possible stabilizers which can be added to the LC media according to the invention, wherein n represents an integer from 1 to 12, preferably 1, 2, 3, 4, 5, 6, 7 or 8.

[0564]

[0565]

[0566]

[0567]

[0568]

[0569]

[0570] The LC medium preferably comprises 0 to 10% by weight, in particular 1 ppm to 5% by weight, particularly preferably 1 ppm to 1% by weight, of stabilizer.

[0571] Table F below shows illustrative compounds that can preferably be used as chiral dopants in the mesogenic medium according to the present invention.

[0572] Table F

[0573]

[0574]

[0575]

[0576] In a preferred embodiment of the present invention, the mesogenic medium comprises one or more compounds selected from the compounds shown in Table F.

[0577] The mesogenic medium according to the present invention preferably comprises two or more, preferably four or more compounds selected from the compounds presented in Tables D to F above.

[0578] In one embodiment, the LC media according to the present invention preferably comprise three or more, more preferably five or more, compounds shown in Table D.

[0579] Table G

[0580] Table G collates example compounds which can be used in the LC media according to the invention, preferably as reactive mesogenic compounds. Preferably, one initiator or a mixture of two or more initiators is added for the polymerization. The initiator or initiator mixture is preferably added in an amount of 0.001% to 2% by weight, based on the mixture. Suitable initiators are, for example 651 (from BASF).

[0581]

[0582]

[0583]

[0584]

[0585]

[0586]

[0587]

[0588]

[0589]

[0590]

[0591]

[0592]

[0593]

[0594]

[0595]

[0596]

[0597]

[0598] In a preferred embodiment of the present invention, the mesogenic medium comprises one or more compounds selected from the group of compounds from Table G.

[0599] The liquid-crystalline medium according to the invention preferably comprises four or more, more preferably six or more, even more preferably seven or more and especially preferably eight or more compounds selected from the group of compounds of Table D, preferably three or more compounds of different formulae selected from the group of formulae of Table D. The medium particularly preferably additionally contains one, two or more compounds selected from the group of formulae of Table E. Even more preferably, the medium further contains one, two or more than two compounds selected from the group of formulae of Table G.

[0600] The following examples are merely illustrative of the present invention and should not be construed as limiting the scope of the present invention in any way. In view of the present invention, the embodiments and their modifications or other equivalents will become apparent to those skilled in the art.

[0601] However, the physical properties and compositions presented below illustrate which properties can be achieved and within what range they can be modified. Therefore, especially the combination of different properties which can be preferably achieved is fully defined. Example

[0602] In an embodiment,

[0603] V o represents the threshold voltage at 20°C, capacitive [V],

[0604] n e represents the extraordinary refractive index at 20°C and 589nm,

[0605] n o represents the ordinary refractive index at 20°C and 589nm,

[0606] Δn represents the optical anisotropy at 20°C and 589 nm,

[0607] ε || represents the dielectric constant parallel to the director at 20°C and 1kHz,

[0608] ε ⊥ represents the dielectric constant perpendicular to the director at 20°C and 1kHz,

[0609] Δε represents the dielectric anisotropy at 20°C and 1kHz,

[0610] cl.p.,T(N,I) represents the clearing point [℃],

[0611] γ1 represents the rotational viscosity [mPa·s] measured at 20°C, determined by the rotation method in a magnetic field,

[0612] K1 is the elastic constant, the “bending” deformation at 20°C [pN],

[0613] K2 represents the elastic constant, "torsion" deformation at 20°C [pN],

[0614] K3 represents the elastic constant, "bending" deformation at 20°C [pN],

[0615] Unless otherwise explicitly stated, the term "threshold voltage" of the present invention relates to the capacitive threshold (V0). In an embodiment, as usual, the optical threshold may also be for a 10% relative contrast ratio (V 10 ) pointed out.

[0616] Liquid crystal mixtures and composite systems are realized with compositions and properties as given below. Their properties and optical performances are studied.

[0617] Reference Example 1

[0618] A liquid crystal base mixture B-1 was prepared and characterized by its general physical properties, having the composition and properties indicated in the following table.

[0619]

[0620]

[0621] Reference Example 2

[0622] A liquid crystal base mixture B-2 was prepared and characterized by its general physical properties, having the composition and properties indicated in the following table.

[0623]

[0624]

[0625] Reference Example 3

[0626] A liquid crystal base mixture B-3 was prepared and characterized by its general physical properties, having the composition and properties as indicated in the following table.

[0627]

[0628] The bulk mixture H-3 was prepared by mixing 99.97% of the mixture B-3 with 0.03% of the compound of the formula below, which will be referred to as ST-1 hereinafter.

[0629] Reference Example 4

[0630] Liquid crystal base mixture B-4 was prepared and characterized by its general physical properties, having the composition and properties as indicated in the following table.

[0631]

[0632] Host mixture H-4 was prepared by mixing 99.97% of mixture B-4 with 0.03% of compound ST-1 as demonstrated in Reference Example 3 above.

[0633] Reference Example 5

[0634] Liquid crystal base mixture B-5 was prepared and characterized by its general physical properties, having the composition and properties as indicated in the following table.

[0635]

[0636]

[0637] Reference Example 6

[0638] Liquid crystal base mixture B-6 was prepared and characterized for its general physical properties, having the composition and properties as indicated in the following table.

[0639]

[0640] Reference Example 7

[0641] Liquid crystal base mixture B-7 was prepared and characterized for its general physical properties, having the composition and properties as indicated in the following table.

[0642]

[0643]

[0644] Reference Example 8

[0645] Liquid crystal base mixture B-8 was prepared and characterized for its general physical properties, having the composition and properties as indicated in the following table.

[0646]

[0647]

[0648] Comparative Example 1

[0649] Mixture M-1 was prepared by mixing 98.877% of mixture B-1 as described in Reference Example 1 with 0.470% of chiral dopant R-5011 commercially available from Merck KGaA, Darmstadt, Germany and shown in Table F above, 0.129% of a compound of formula DD-1

[0650]

[0651] 0.244% of the compound of formula DD-2

[0652]

[0653] and 0.280% of the compound of formula DD-3

[0654]

[0655] Mixture M-1 was filled by vacuum filling into a cell with a glass substrate having an ITO electrode and a polyimide alignment layer (AL-1054, planar, TN from Japan Synthetic Rubber) with a cell gap of 25 μm and the filling port was sealed. Wires were applied to the cell by soldering.

[0656] The obtained cell had a clear state with 3% haze and 64.5% transmittance at 48 V. Furthermore, at 5 V, the cell had a dark privacy state with 83% haze and 22% transmittance.

[0657] When viewed from the side, undesirable off-axis color effects are observed.

[0658] Bidirectional transmission distribution function (BTDF) measurements were performed with an EZLite 120R instrument from Eldim using a white light source and normal incidence angle of the light.

[0659] The ratio of the average intensity of light transmitted in the radiation angle of -3° to +3° to the average intensity of light transmitted in the radiation angle of -60° to +60° (<I -3°＜θ＜3° > / <I -60°＜θ＜60° >) is 15.7.

[0660] While the box effectively dims the overall light intensity, the light is not sufficiently diffused. The box does not sufficiently reduce the contrast of bright light sources and therefore does not reliably prevent glare from, for example, sunlight.

[0661] Comparative Example 2

[0662] Mixture M-2 was prepared by mixing 98.72% of mixture H-3 as described in Reference Example 3 with 0.05% of chiral dopant S-811 commercially available from Merck KGaA, Darmstadt, Germany and shown in Table F above, 0.24% of the compound of formula DD-1 as shown in Comparative Example 1 above, 0.46% of the compound of formula DD-2 as shown in Comparative Example 1 above, and 0.53% of the compound of formula DD-3 as shown in Comparative Example 1 above.

[0663] Mixture M-2 was filled by vacuum filling into a cell with a glass substrate having an ITO electrode and a polyimide alignment layer (AL-1054, planar, TN from Japan Synthetic Rubber) with a cell gap of 25 μm and the filling port was sealed. Wires were applied to the cell by soldering.

[0664] The obtained cell had a clear state with a transmittance of 49% at 12 V. Furthermore, at 0 V, the cell had a dark state with a transmittance of 25%.

[0665] Bidirectional transmission distribution function (BTDF) measurements were performed with an EZLite 120R instrument from Eldim using a white light source and normal incidence angle of the light.

[0666] The ratio of the average intensity of light transmitted in the radiation angle of -3° to +3° to the average intensity of light transmitted in the radiation angle of -60° to +60° (<I -3°＜θ＜3° > / <I -60°＜θ＜60° >) is 18.7.

[0667] While the box effectively dims the overall light intensity, the light is not sufficiently diffused. The box does not sufficiently reduce the contrast of bright light sources and therefore does not reliably prevent glare from, for example, sunlight.

[0668] Comparative Example 3

[0669] The cholesteric mixture C-1 was prepared by mixing 98.61% of the mixture B-2 as described in Reference Example 2 with 0.64% of the chiral dopant R-5011 commercially available from Merck KGaA, Darmstadt, Germany and shown in Table F above and 0.75% of the compound of formula RM-A

[0670]

[0671] Mixture C-1 was filled by vacuum filling into a cell with a glass substrate having an ITO electrode and a polyimide alignment layer (AL-1054, planar, TN from Japan Synthetic Rubber) with a cell gap of 25 μm and the filling port was sealed. Wires were applied to the cell by soldering.

[0672] Subsequently, the cells were exposed to UV light (UVA and UVB, 3.5 mW / cm 2 The polymerization is carried out by irradiating the box with light intensity (ratio of light intensity to light intensity).

[0673] After polymerization, the obtained cell had a clear state with 6.6% haze and 88% transmittance at 60 V. Furthermore, at 0 V, the cell had a privacy (diffusing) state with 99% haze and 72% transmittance.

[0674] The transmission in the privacy state is still too high to reliably eliminate the glare from sunlight experienced by the user.

[0675] Example 1

[0676] The cartridges prepared according to Comparative Example 3 were combined with the cartridges prepared according to Comparative Example 1 to configure a stack of cartridges.

[0677] This assembly of the combined boxes had a transparent state with 7.7% haze and 57% transmittance at 63 V. In addition, the assembly of the boxes at 5 V had an anti-glare state with 100% haze and 12% transmittance. In addition, in the privacy state (where the scattering box according to Comparative Example 3 was operated at 5 V and the dye-doped box according to Comparative Example 1 was operated at 63 V), the assembly had 99% haze and 46% transmittance.

[0678] Bidirectional transmission distribution function (BTDF) measurements were performed with an EZLite 120R instrument from Eldim for the combined cells in the anti-glare state, using a white light source and normal incidence angle of the light.

[0679] In the anti-glare state, the ratio of the average intensity of light transmitted in the radiation angle of -3° to +3° to the average intensity of light transmitted in the radiation angle of -60° to +60° (<I -3°＜θ＜3° > / <I -60°＜θ＜60° >) is 3.0.

[0680] The combination of boxes effectively reduces the overall transmission of light while also distributing the transmitted light more evenly into wider angles. The combination of boxes provides excellent anti-glare properties, especially against sunlight.

[0681] Additionally, no undesirable off-axis color effects were observed.

[0682] Example 2

[0683] The cholesteric mixture C-2 was prepared by mixing 98.640% of the mixture B-1 as described in Reference Example 1 with 0.423% of the chiral dopant R-5011 commercially available from Merck KGaA, Darmstadt, Germany, 0.450% of the compound of formula RM-B

[0684]

[0685] 0.450% of the compound of formula RM-C

[0686]

[0687] and 0.037% photoinitiator 651 (hereinafter abbreviated as IRG-651)

[0688] It is commercially available from Ciba, Switzerland.

[0689] Mixture C-2 was filled by vacuum filling into a cell with a glass substrate having an ITO electrode and a polyimide alignment layer (AL-1054, planar, TN from Japan Synthetic Rubber) with a cell gap of 25 μm and the filling port was sealed. Wires were applied to the cell by soldering.

[0690] Subsequently, the cells were exposed to UV light (UVA and UVB, 3.5 mW / cm 2 The polymerization is carried out by irradiating the box with light intensity (ratio of light intensity to light intensity).

[0691] The obtained cartridge was arranged together with the cartridge prepared according to Comparative Example 2 in a stacked manner.

[0692] This assembly of the combined box has a transparent state with 17.6% haze and 46.3% transmittance at 48V. In addition, the assembly of the box at 0V has an anti-glare state with 100% haze and 18% transmittance. In addition, in the privacy state (wherein the scattering box as prepared herein is operated at 0V and the box of the doped dye according to Comparative Example 2 is operated at 12V), the assembly has 100% haze and 26% transmittance, and in the solar intensity control state (wherein the scattering box as prepared herein is operated at 48V and the box of the doped dye according to Comparative Example 2 is operated at 0V), the assembly has 24% haze and 22% transmittance. In addition, by changing the voltage of the box of the doped dye, grayscale switching is possible.

[0693] Bidirectional transmission distribution function (BTDF) measurements were performed with an EZLite 120R instrument from Eldim for the combined cells in the anti-glare state, using a white light source and normal incidence angle of the light.

[0694] In the anti-glare state, the ratio of the average intensity of light transmitted in the radiation angle of -3° to +3° to the average intensity of light transmitted in the radiation angle of -60° to +60° (<I -3°＜θ＜3° > / <I -60°＜θ＜60° >) is 1.6.

[0695] The combination of boxes effectively reduces the overall transmission of light while also distributing the transmitted light more evenly into wider angles. The combination of boxes provides excellent anti-glare properties, especially against sunlight.

[0696] Additionally, no undesirable off-axis color effects were observed.

[0697] Example 3

[0698] Cholesteric mixture C-3 was prepared by mixing 98.764% of mixture B-2 as described in Reference Example 2 with 0.486% of chiral dopant R-5011 commercially available from Merck KGaA, Darmstadt, Germany and shown in Table F above and 0.750% of a compound of formula RM-A as shown in Comparative Example 3.

[0699] Mixture C-3 was filled by vacuum filling into a cell with a glass substrate having an ITO electrode and a polyimide alignment layer (AL-1054, planar, TN from Japan Synthetic Rubber) with a cell gap of 25 μm and the filling port was sealed. Wires were applied to the cell by soldering.

[0700] Subsequently, the cells were exposed to UV light (UVA and UVB, 3.5 mW / cm 2 The polymerization is carried out by irradiating the box with light intensity (ratio of light intensity to light intensity).

[0701] Mixture M-3 was prepared by mixing 99.559% of mixture H-3 as described in Reference Example 3 with 0.050% of chiral dopant S-811 commercially available from Merck KGaA, Darmstadt, Germany and shown in Table F above, 0.077% of the compound of formula DD-1 as shown in Comparative Example 1 above, 0.146% of the compound of formula DD-2 as shown in Comparative Example 1 above, and 0.168% of the compound of formula DD-3 as shown in Comparative Example 1 above.

[0702] Mixture M-3 was filled individually by vacuum filling into two test cells each having a glass substrate with an ITO electrode and a polyimide alignment layer (AL-1054, planar, TN from Japan Synthetic Rubber), wherein the cell gap of each cell was 25 μm, and the filling port was sealed. The two dye-doped cells were configured as a double cell, wherein the first dye-doped cell was oriented so that its absorption principal axis was orthogonal to the absorption principal axis of the second dye-doped cell. Wires were applied to the cells by soldering.

[0703] The stack of cells was configured by combining a polymer stabilized cholesteric scattering cell with a dye doped double cell configuration.

[0704] This assembly of combined boxes had a transparent state with 9.5% haze and 46% transmittance, where the diffuser box was operated at 48V and the two dye-doped boxes were operated at 12V. In addition, the assembly of boxes at 0V had an anti-glare state with 99% haze and 8.5% transmittance. In addition, in the privacy state (where the diffuser box was operated at 0V and the dye-doped box was operated at 12V), the assembly had 99% haze and 38.5% transmittance, and in the solar intensity control state (where the diffuser box was operated at 48V and the dye-doped box was operated at 0V), the assembly had 11% haze and 10% transmittance.

[0705] The combination of cells provides excellent anti-glare performance, especially against sunlight. In addition, no undesirable off-axis color effects are observed.

[0706] Example 4

[0707] Mixture M-3 as shown in Example 3 above was filled into an electrically switchable cell with a Heilmeier configuration using an ITOS XP-40HT polarizer, an antiparallel polyimide planar alignment layer and a switching layer thickness of 12 μm.

[0708] The cholesteric mixture C-4 was prepared by mixing 98.89% of the mixture B-2 as described in Reference Example 2 with 0.33% of the chiral dopant R-5011 commercially available from Merck KGaA, Darmstadt, Germany and shown in Table F above, 0.75% of the compound of formula RM-A as shown in Comparative Example 3 and 0.03% of the compound of formula ST-1 as shown in Reference Example 3.

[0709] The mixture C-4 was filled into a cell having a glass substrate with an ITO electrode and no alignment layer by vacuum filling, wherein the cell gap was 25 μm, and the filling port was sealed. Wires were applied to the cell by soldering.

[0710] Subsequently, the cells were exposed to UV light (UVA and UVB, 3.5 mW / cm 2 The polymerization is carried out by irradiating the box with light intensity (ratio of light intensity to light intensity).

[0711] The stack was configured by combining two boxes. The combination provided excellent anti-glare performance, especially for sunlight. In addition, no undesirable off-axis color effects were observed.

[0712] Example 5

[0713] The procedure as described in Example 4 was repeated, however, instead of mixture C-4, mixture C-5 having the following composition was prepared and used:

[0714] 98.78% of mixture B-2 as described in Reference Example 2, 0.44% of chiral dopant R-5011 commercially available from Merck KGaA, Darmstadt, Germany and shown in Table F above, 0.75% of the compound of formula RM-A as shown in Comparative Example 3 and 0.03% of the compound of formula ST-1 as shown in Reference Example 3.

[0715] Example 6

[0716] The procedure as described in Example 4 was repeated, however, instead of mixture M-3, mixture M-6 having the following composition was prepared and used:

[0717] 97.77% of the mixture H-3 as described in Reference Example 3, 0.34% of the compound of formula DD-1 as shown in Comparative Example 1 above, 0.72% of the compound of formula DD-2 as shown in Comparative Example 1 above, 0.87% of the compound of formula DD-3 as shown in Comparative Example 1 above, 0.15% of the compound of formula ST-1 as shown in Reference Example 3, and 0.15% of the compound of formula ST-2

[0718]

[0719] Example 7

[0720] The procedure as described in Example 4 was repeated, however, instead of mixture M-3, mixture M-7 having the following composition was prepared and used:

[0721] 95.55% of the mixture H-3 as described in reference example 3, 1.20% of the compound of formula DD-4

[0722]

[0723] 0.35% of the compound of formula DD-5

[0724]

[0725] 0.50% of the compound of formula DD-6

[0726]

[0727] 1.20% of the compound of formula DD-7

[0728]

[0729] and 1.20% of the compound of formula DD-8

[0730]

[0731] Example 8

[0732] Mixture M-8 was prepared by mixing 99.95% of mixture H-4 as described in Reference Example 4 with 0.05% of chiral dopant S-811 available from Merck KGaA, Darmstadt, Germany and shown in Table F above.

[0733] Two VA cells VA-1 and VA-2 used glass substrates with 3° pre-tilt with ITO electrodes and rubbed polyimide vertical alignment layer, with a cell gap of 25 μm; a thin film polarizer was applied on the first substrate of each cell and a thin film polarizer with a retarder (for optical compensation for improved viewing angle dependence) was applied on the other substrate of each cell, both from Polatechno. For VA-1, the two polarizers were arranged at 0° relative to each other, and for VA-2, the two polarizers were arranged at 90° relative to each other.

[0734] The mixture M-8 was filled into the boxes VA-1 and VA-2 accordingly.

[0735] Scattering cell SC was prepared using mixture C-3 and conditions as described in Example 3 above.

[0736] Combining VA-1 and SC and / or VA-2 and SC to configure two stacks. Using the following operating voltages, the following different applicable optical stack modes can be obtained:

[0737] Stack 1

[0738] VA-1 SC model 0V 48V Transparent and bright 0V 0V Bright scattering 12V 48V Transparent Dark 12V 0V Anti-glare (diffuse darkness)

[0739] Stack 2

[0740]

[0741]

[0742] Examples 9 to 11

[0743] The procedure as described in Example 3 was repeated, however, instead of using the dye-doped mixture M-3, mixtures M-9, M-10 and M-11 were prepared and used respectively, wherein M-9, M-10 and M-11 had the following compositions.

[0744]

[0745] Example 12

[0746] The procedure as described in Example 1 was repeated, however wherein the base mixture B-6 as shown in Reference Example 6 was used instead of the mixture B-1 to prepare the mixture M-12 and the dye-doped kit based on this mixture M-12.

[0747] Examples 13 and 14

[0748] The procedure as described in Example 1 was repeated, wherein the box was prepared according to Comparative Example 2, but instead of using mixture H-3, basic mixture B-7 as described in Reference Example 7 and basic mixture B-8 as described in Reference Example 8 were used to prepare the corresponding mixtures M-13 and M-14, respectively.

Claims

1. A multilayer arrangement for regulating the passage of light, comprising: a first switching layer which is switchable between an optically clear state and a light-scattering state and contains a material comprising a liquid crystal medium comprising one or more mesogenic compounds and one or more chiral compounds; and a polymeric component, wherein the polymeric component is contained in the material in an amount of 5% by weight or less, based on the total content of the material, and a switching element comprising a second switching layer, wherein the switching element is switchable between a light state and a dark state and wherein the second switching layer is a liquid crystal layer, wherein the second switching layer comprises one or more dichroic dyes and one or more chiral compounds, wherein the first switching layer is placed in front of the switching element relative to the outside facing the light source, The liquid crystal medium contained in the first switching layer has a clearing point of 80° C. or higher.

2. A multilayer arrangement according to claim 1, wherein the first switching layer and the second switching layer are each inserted between two transparent substrates, each of which supports an electrode configured as a transparent conductive layer, and wherein an optional alignment layer is further provided in direct contact with the switching layer.

3. The multilayer arrangement according to claim 2, wherein the transparent conductive layer is respectively embedded between two transparent dielectric layers.

4. The multilayer arrangement according to claim 1, wherein the switching element comprises a further switching layer which is a liquid crystal layer and contains at least one dichroic dye and one or more chiral compounds.

5. A multilayer arrangement according to any one of claims 1 to 3, wherein the switching element further comprises at least one polarisation layer and optionally at least one retardation layer.

6. The multilayer arrangement according to claim 1 , wherein the liquid-crystalline medium contained in the first switching layer exhibits a helical pitch of 0.55 μm or more in the scattering state and wherein the polymeric component contained in the first switching layer contains one or more polymeric structures obtained or obtainable by polymerization of one or more polymerizable mesogenic compounds.

7. The multilayer arrangement according to claim 1 , wherein the liquid-crystalline medium contained in the first switching layer contains at least 15% by weight of one or more mesogenic compounds of the formula I, based on the total content of the medium. in R 1 and R 2 independently of one another represent a radical selected from the group consisting of F, Cl, CF3, OCF3 and straight-chain or branched alkyl or alkoxy having 1 to 15 carbon atoms or straight-chain or branched alkenyl having 2 to 15 carbon atoms, which is unsubstituted, monosubstituted by CN or CF3 or monosubstituted or polysubstituted by halogen, and in which one or more CH2 groups may in each case independently of one another be substituted by -O-, -S-, -CO-, -COO-, -OCO-, -OCOO-, -C≡C-, A 11 express n represents 0 or 1, and A 21 , A 31 and A 41 Independently express wherein L, at each occurrence, identically or differently, is a halogen selected from F, Cl and Br.

8. The multilayer arrangement according to any one of claims 1 to 3, wherein the liquid-crystalline medium contained in the first switching layer further comprises one or more mesogenic compounds selected from the group of compounds of formulae II and III in R 3 , R 4 , R 5 and R 6 independently of one another represent a radical selected from the group consisting of: F, CF3, OCF3, CN and a linear or branched alkyl or alkoxy radical having 1 to 15 carbon atoms or a linear or branched alkenyl radical having 2 to 15 carbon atoms, which is unsubstituted, monosubstituted by CN or CF3 or monosubstituted or polysubstituted by halogen, and in which one or more CH2 radicals may in each case independently of one another be substituted by: -O-, -S-, -CO-, -COO-, -OCO-, -OCOO-, -C≡C-, and L 1 , L 2 , L 3 , L 4 and L 5 represents H or F independently of each other.

9. The multilayer arrangement according to any one of claims 1 to 3, wherein the liquid-crystalline medium comprised in the first switching layer exhibits an optical anisotropy Δn measured at 20° C. and 589 nm of 0.13 or more, and The one or more chiral compounds contained in the liquid crystal medium in the first switching layer have a -1 Or greater absolute value of the helical twisting force.

10. Use of a multilayer arrangement according to any one of claims 1 to 9 in an insulating glazing unit.

11. A window element comprising a multilayer arrangement according to any one of claims 1 to 9 and being electrically switchable between an optically clear and bright state and a light-scattering and dark state.

12. The window element according to claim 11, which is switchable to the optically clear and bright state by applying an AC voltage V1 and to the light-scattering and dark state by applying an AC voltage V2, wherein V1>V2.

13. A window element according to claim 11 or 12, which is further operable in an optically clear and dark state and a light-scattering and bright state and is electrically switchable to the optically clear and dark state and the light-scattering and bright state.

14. A window element according to claim 11 or 12, which exhibits in a light-scattering and dark state: - a visible light transmission of less than 40%, and / or - For a normally incident collimated beam from a white light source, the ratio of the average intensity of light transmitted into a radiation angle of -3° to +3° to the average intensity of light transmitted into a radiation angle of -60° to +60° is 5 or less.

15. Use of a multilayer arrangement according to any of claims 1 to 9 or a window element according to any of claims 11 to 14 for reducing glare from solar radiation.

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