Switching layer for use in window elements - Patents.com

Abstract

The present invention relates to a window element comprising two switching layers, each of which comprises a liquid crystal medium containing one or more dichroic dyes, and in one of the optical states, both switching layers have a twisted or supertwisted nematic configuration, and the twist handedness or helicity of one of the two switching layers is opposite in sense to the other switching layer.The present invention further relates to a composition for use in the window element, and to the use of the window element for energy-saving and comfort-improving building and vehicle applications.

Description

[Technical field]

[0001] The present invention relates to a window element comprising two switching layers, each of which comprises a liquid crystal medium containing one or more dichroic dyes, and in one of the optical states, both switching layers have a twisted or supertwisted nematic configuration, and the twist handedness or helicity of one of the two switching layers is opposite in sense to the other switching layer.The present invention further relates to a composition for use in the window element, and to the use of the window element for energy-saving and comfort-improving building and vehicle applications. [Background technology]

[0002] Devices for controlling or modulating the transmission of light are commonly used in display applications, but they may also be used, for example, in so-called smart window applications. R. Baetens et al., in "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, provide an overview of various dynamic smart windows. As described therein, smart windows may use several technologies for modulating the transmission of light, such as devices based on electrochromism, liquid crystal devices, and electrophoretic or suspended particle devices.

[0003] Light shutters and light intensity modulators, especially liquid crystal based light modulators, may also be used in switchable windows for architectural, automotive, railway, avionics and marine applications.

[0004] In such devices, the light transmission can be reversibly changed, where the intensity of incident light is attenuated, dimmed, or tinted. These devices can thus be operated in and switched between bright and dark states, i.e., between states of relatively higher and relatively lower light transmittance, while, however, preferably exhibiting little or no scattering or haze in the different states of operation.

[0005] While in liquid crystal based devices switching between different optical states can also be thermally controlled, it is in many cases advantageous and preferred for the device to adopt different optical states using electrical switching, where the switching is controlled by the application of a voltage. Such liquid crystal based devices in principle employ a change in the orientation of liquid crystal (LC) molecules between two conducting electrodes by the application of an electric field which results in a change in transmittance.

[0006] In principle, several modes or configurations may be adopted to provide such a reversible change in transmission. In twisted nematic (TN), super twisted nematic (STN), and vertically aligned (VA) liquid crystal cells, polarizers are commonly used to control light transmittance. It is also feasible to use guest-host liquid crystal cells based on liquid crystal hosts doped with dichroic dye molecules. These guest-host systems can be used without any polarizer to modify the light transmittance. However, in some embodiments and applications, guest-host liquid crystal cells are also used in combination with at least one polarizer.

[0007] WO 2017 / 118465 A1 describes a device for regulating the penetration of light into a room, which comprises a switchable layer containing a dichroic dye-doped liquid-crystalline medium and having a twisted configuration in one of the switching states.

[0008] WO 2014 / 180525 A1 describes a device for regulating the passage of light, which comprises two switching layers, in particular provided in a so-called double cell configuration, and in which the two switching layers each comprise a liquid-crystalline medium containing one or more dichroic dyes. In one of these embodiments, the switching layers may have a twisted configuration.

[0009] There remains a need in the art for versatile and adaptable devices for modulating the passage of light, particularly switchable windows that provide effective and efficient switching capabilities. Summary of the Invention

[0010] It is therefore an object of the present invention to provide multilayer arrangements and window elements, in particular for use in switchable or smart windows for architectural, automotive, avionics and marine applications, which may provide favourable control of ambient light and have advantageous performance during operation, in particular providing benefits in terms of electro-optical characteristics. It is a further object to provide compositions which are advantageously useful in these devices. Further objects of the present invention will be readily apparent to those skilled in the art from the following detailed description.

[0011] The object is solved by the subject matter defined in the independent claims, while preferred embodiments are presented in the respective dependent claims and are described further below.

[0012] The present invention provides, inter alia, the following including main aspects, preferred embodiments, and specific features, each of which, alone and in combination, contributes to the solution of the above objects and ultimately provides additional advantages.

[0013] A first aspect of the present invention provides a window element comprising a multilayer arrangement for modulating the passage of light and operable in and electrically switchable between a light state and a dark state, wherein the multilayer arrangement comprises a first switchable layer and a second switchable layer, each of said layers containing a liquid crystalline medium comprising one or more dichroic dyes and optionally one or more chiral compounds, wherein in one of said states the first switchable layer and the second switchable layer have a twisted nematic or supertwisted nematic configuration, and wherein the twist direction of one of the first and second switchable layers is clockwise and the twist direction of the other switchable layer is counterclockwise.

[0014] According to the present invention, advantageous multilayer assemblies including two switching layers are configured, which can be favorably used for switchable windows for architectural, automotive, avionics, and marine applications. The multilayer configuration is particularly useful and efficient in providing a change in light transmittance by ensuring switchability, especially electrical switchability, between light and dark states when desired.

[0015] In the present invention, it has been recognized that providing a combination of two switching layers in the layer arrangement of the window element can in principle advantageously provide a high transmission range, in particular a suitably large transmission difference between the optically bright and optically dark states.In addition, it has also been recognized that the switching performance can be further advantageously influenced by providing a twisted or supertwisted configuration in one of the switching states, preferably the dark state.

[0016] Moreover, it has been further recognized that each layer of the multi-layer arrangement can or will affect the optical performance of the window element, considering optical losses, for example through unwanted reflection or unwanted absorption, and therefore it is desirable to maintain or even enhance the effectiveness and efficiency of the device.

[0017] Surprisingly, it has been found that window elements comprising multilayer arrangements having effective and efficient optical, especially electro-optical, performance can be obtained by including two switching layers with twist or supertwist configurations of opposite chirality or handedness, i.e. in one of the optical states, preferably in the dark state, one of the switching layers exhibits a right-handed or, respectively, clockwise twist, whereas the other switching layer exhibits a left-handed or, respectively, counterclockwise twist.

[0018] Compared to cases in which the two switching layers have the same handedness, i.e. both layers have a clockwise twist or respectively both layers have a counterclockwise twist, it has surprisingly been found that several advantages can be obtained by providing a window element according to the present invention combining switching layers with opposite twist directions.

[0019] In particular, the window element according to the invention can achieve a larger transmission difference between the optically bright and the optically dark states, where in particular a more effective dark state with a smaller transmission can advantageously be obtained while maintaining an excellent bright state. This is particularly useful for applications where it is desired or even necessary to allow only a minimal light transmission in one of the states (for example, giving a very dark or black appearance). In addition, this provision can thus advantageously provide an improved contrast between the bright and dark states. Furthermore, the window element according to the invention can provide benefits in terms of the viewing angle dependence of both the desired contrast and color appearance, where unwanted angle dependence of contrast or color artefacts with respect to the viewing angle can be minimized or even avoided. This makes it much easier to set the contrast and chromaticity coordinates consistently, and provides design options, for example, even for curved layers and substrates. Furthermore, the window element according to the invention can provide benefits in terms of managing directional sunlight during the day, when aligned with the twist start direction.

[0020] Without wishing to be bound by theory, it is believed that when two switching layers of the same chirality or handedness are provided in sequence and light incident on the multilayer arrangement thus passes through both switching layers in succession, the desired or envisaged optical characteristics of that light are affected and influenced, for example in that a linearly polarized component of the light is unintentionally converted to an elliptically polarized component or a component that is only partially polarized, which converted component may impair the optical characteristics of the light that eventually exits the window element, thus affecting the optical performance, for example in terms of transmission characteristics, obtainable contrast and viewing angle dependence. It is further believed that when light passes through two switching layers of opposite chirality or handedness in sequence as provided in accordance with the present invention, unwanted or unintended loss of optical quality or characteristics can be minimized or even avoided, where by providing opposite handedness, the second switching layer can advantageously compensate for unwanted optical effects or artifacts caused by the first switching layer, and possibly even by other preceding layers. In this way, optical performance benefits can be obtained, including excellent dark states with reduced light transmission, while having a large transmission range in terms of the transmission of the bright state.

[0021] Given the ease of configuration and assembly, window elements according to the present invention can be provided in a convenient and robust process.

[0022] The window elements according to the invention may also provide further benefits such as good reliability, durability and stability, e.g. with respect 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 be conveniently and advantageously used, which media may inter alia have a broad liquid crystal phase with a preferably high clearing point, an advantageously high voltage holding ratio (VHR), good low temperature stability and suitable stability for storage.

[0023] In addition, the devices can exhibit fast, efficient, and uniform switching even across large device areas, which is desirable for larger windows.

[0024] Window elements according to the invention are useful for regulating or modulating the passage of light, particularly for controlling the passage of sunlight. The window elements are capable of undergoing reversible optical transitions, where such switching is fast, typically on the order of less than a second. Preferably, the devices can be conveniently switched between states by applying an electrical voltage.

[0025] Furthermore, the window element can be installed with minimal space requirements, which may ensure a significant advantage in comparison with existing awnings or blinds, for example. The window element according to the invention may be advantageously employed in windows on the exterior facades of buildings, but may also be used in cars, commercial vehicles, trains, aircraft, ships, etc.

[0026] Therefore, another aspect of the invention relates to the use of a window element according to the invention in a window of a building or vehicle.

[0027] The window elements may be used for sustainable glazing applications in buildings and vehicles, inter alia, by providing energy savings in terms of lighting, cooling and / or heating, as well as by providing improved thermal and visual comfort, while positively impacting the life cycle, e.g. in terms of maintenance.

[0028] In a further aspect of the invention, - a first liquid crystal medium having a clearing point of at least 80° C. and comprising one or more dichroic dyes and stereoisomers of a chiral dopant, preferably R-isomers, and a second liquid crystal medium having a clearing point of at least 80° C. and comprising one or more dichroic dyes and another stereoisomer of the chiral dopant, preferably the S-isomer. A set of compositions is provided, comprising:

[0029] These sets or systems comprising two separate compositions can advantageously be provided or supplied in a convenient manner as the materials to be used respectively for the two switching layers of the window element.

[0030] Without limiting the invention thereto, the invention is illustrated hereinafter by detailed descriptions of aspects, embodiments and specific features, the specific embodiments being described in more detail.

[0031] The term "liquid crystal" (LC) preferably relates here to materials or media which have a liquid crystal mesophase in some temperature range (thermotropic LC). They contain mesogenic compounds.

[0032] The terms "mesogenic compound" and "liquid crystal compound" mean compounds which contain one or more calamitic (rod-shaped or board / lath-shaped) or discotic (disc-shaped) mesogenic groups, i.e. groups capable of inducing liquid crystal or mesophase behavior.

[0033] LC compounds or materials and mesogenic compounds or materials containing mesogenic groups do not necessarily exhibit liquid crystal phases themselves. They can also show liquid crystal phase behavior only in mixtures with other compounds. This includes low molecular weight non-reactive liquid crystal compounds, reactive or polymerizable liquid crystal compounds, and liquid crystal polymers.

[0034] Rod-shaped mesogenic compounds usually comprise a mesogenic core consisting of one or more aromatic or non-aromatic cyclic groups connected to each other directly or via linking groups, optionally comprising terminal groups attached to the ends of the mesogenic core, and optionally comprising one or more side groups attached to the longitudinal sides of the mesogenic core, where these terminal and side groups are usually selected from, for example, polar groups such as carbyl or hydrocarbyl groups, halogen, nitro, hydroxy, etc., or polymerizable groups.

[0035] For simplicity, the term "liquid crystal" or "liquid crystal" material or medium is used for both liquid crystalline and mesogenic materials or media, and vice versa, and the term "mesogen" is used for the mesogenic groups of the material.

[0036] The term "non-mesogenic compound or material" means a compound or material that does not contain a mesogenic group as defined above.

[0037] The term "chiral" is generally used to describe an object that is not superimposable on its mirror image. In contrast, "achiral" (non-chiral) objects are objects that are identical to their mirror image. The media preferably used according to the present invention exhibit chirality. This can be achieved by providing cholesteric liquid crystals, also known as chiral nematic liquid crystals. The terms chiral nematic and cholesteric are used synonymously in this specification, unless expressly stated otherwise.

[0038] As used herein, 1,4-cyclohexylene and 1,4-phenylene rings are depicted as follows: [ka] [ka]

[0039] The cyclohexylene ring is a trans-1,4-cyclohexylene ring. Unless expressly stated otherwise herein, all concentrations are given in weight percent and relate to the respective complete mixtures.

[0040] All temperatures are given in degrees Celsius (°C) and all temperature differences are also given in degrees. All physical properties and physicochemical or electro-optical parameters are determined and given relative to a temperature of 20°C, unless expressly stated otherwise.

[0041] For the purposes of the present invention, the term energy is understood to mean energy by electromagnetic radiation, especially in the UV-A, VIS and NIR regions. In particular, it is understood to mean energy by radiation that is not absorbed or is absorbed only to a negligible extent by the materials (e.g. glass) that are usually used for windows. In this specification, the UV-A region is understood to mean the wavelength range from 320 nm to 380 nm, the VIS region is understood to mean the wavelength range from 380 nm to 780 nm, and the NIR region is understood to mean the wavelength range from 780 nm to 2500 nm.

[0042] The term light is understood to mean, inter alia, electromagnetic radiation having a wavelength between 380 nm and 780 nm. Thus, the transmission and scattering of light preferably refers to the transmission and scattering of electromagnetic radiation in the spectral range between 380 nm and 780 nm.

[0043] In the present specification, dichroic dyes are understood to mean light-absorbing compounds whose absorption properties depend on the orientation of the compound relative to the polarization direction of light. Dichroic dye compounds according to the present invention typically have an elongated shape, i.e. the compound is significantly longer in one spatial direction, i.e. along its longitudinal axis, than in the other two spatial directions. Typically, dichroic dyes are dissolved in a host liquid crystal for the purpose of absorbing light, where the dye molecules are aligned with the liquid crystal and can be oriented with the liquid crystal molecules upon application of an electric field. Preferably, the dichroic dyes used herein have an absorption maximum in the visible wavelength range. Dichroic dyes are known to those skilled in the art and are well described in the literature, for example in Liquid Crystals: Applications and Uses, Volumes 1-3, edited by Birenda Bahadur, World Scientific, 1992. Chapter 11: Dichroic Liquid Crystal Displays.

[0044] The terms "film" and "layer" encompass rigid or flexible, self-supporting or freestanding films or layers having greater or lesser degrees of mechanical stability, as well as coatings or layers on a supporting substrate or between two substrates.

[0045] The window elements are preferably and suitably used as components of windows and for example together with further fittings, framing may be used to provide windows, for example for openings in buildings or vehicles and as facades or in internal partitions.

[0046] The switchable layer may be disposed on a substrate or between two substrates. The switchable layer generally contains an active material, i.e. a material that can reversibly undergo a change that affects its optical behavior, in particular the transmission behavior of light through the layer, and that is operable in different optical states and in particular is electrically switchable.

[0047] Switching according to the present invention means, inter alia, electrical switching. Electrical switching can typically be achieved by providing a substrate, for example a glass substrate or a plastic substrate, with electrodes. In an embodiment, an electrically conductive layer is provided on the substrate, where the conductive layer comprises or is formed of a transparent conductive material, for example a transparent conductive oxide, preferably indium tin oxide (ITO) or SnO2:F, especially ITO, or a conductive polymer, or a thin transparent metal layer and / or metal oxide layer, for example silver. The electrically conductive layer is preferably provided with electrical connections. The voltage is preferably provided by a battery, a rechargeable battery, a supercapacitor, or an external current source, more preferably by an external current source.

[0048] A window element according to the invention is provided which comprises a multi-layer arrangement, in particular a number of layers stacked together such that starting from the surface of the first layer which receives incident light, this light passes through all layers in succession.

[0049] The window element is operable in a light state and a dark state and is electrically switchable between the light state and the dark state, where in one of said states the first switchable layer and the second switchable layer have a twisted nematic or supertwisted nematic configuration. Preferably, the switchable layers exhibit a twisted nematic or supertwisted nematic configuration in the dark state. In this case, the dichroic compounds contained in the liquid crystal media of both switchable layers are twisted and aligned so as to absorb to a significant extent light through the device, thereby effectively softening the light transmittance.

[0050] The twisted nematic or supertwisted nematic configuration as provided according to the present invention may include the so-called twisted nematic (TN) mode, the so-called supertwisted nematic (STN) mode, and also inverted modes such as the vertically aligned-supertwisted nematic (VA-STN) mode. Switching of the window element preferably refers to switching between binary states.

[0051] According to the present invention, a window element including a switchable layer is switchable between an optically bright state and an optically dark state, in which the bright state has a greater light transmission compared to the dark state, and both the bright and dark states are preferably non-scattering or substantially non-scattering.

[0052] In the light state, a window element comprising a switchable layer according to the invention preferably has a visible light transmittance, determined according to DIN EN410, of at least 30%, more preferably at least 40%, even more preferably at least 45%.

[0053] In the dark state, a window element comprising a switchable layer according to the present invention preferably has a visible light transmission of less than 10%, more preferably less than 5%, even more preferably less than 3%, determined according to DIN EN 410. In a preferred embodiment, in the dark state, a window element comprising a switchable layer has a visible light transmission in the range from 1% to 5%, more preferably in the range from 2% to 8%, determined according to DIN EN 410.

[0054] However, for switchable layers, multi-layer arrangements and window elements it is also feasible to have further switching states, especially intermediate states.

[0055] In addition to a favourable optical anisotropy, the liquid-crystalline media contained in the switchable layer according to the invention may advantageously exhibit a favourably high voltage holding ratio (VHR) in combination with good light stability and a suitably high clearing point.

[0056] Preferably, the liquid crystal medium contained in the first switchable layer and the liquid crystal medium contained in the second switchable layer each have a clearing point of at least 80° C., more preferably at least 90° C., even more preferably at least 100° C., especially at least 115° C. Preferably, the media each have a clearing point in the range from 80° C. to 170° C., more preferably from 100° C. to 150° C.

[0057] All physical properties and physicochemical or electro-optical parameters are determined by commonly known methods, in particular according to "Merck Liquid Crystals, Physical Properties of Liquid Crystals", Status Nov. 1997, Merck KGaA, Germany.

[0058] The clearing point, especially the phase transition temperature between the nematic or chiral nematic or cholesteric phase and the isotropic phase, can be measured and determined by commonly known methods, for example using a Mettler oven or a hot stage under a polarizing microscope. The clearing point according to the present invention is preferably determined using a Mettler oven.

[0059] A high clearing point as defined can be beneficial in terms of the performance and reliability of multilayer arrangements and devices that include multilayer arrangements. In particular, the medium can maintain its functional properties over a favorable wide temperature range and even at high temperatures. This can be particularly advantageous for use in window elements for regulating the passage of sunlight, especially when the window elements are exposed to direct or persistent irradiation by sunlight. A high clearing point can also contribute to a favorably high degree of order of the liquid crystal host molecules, and therefore of the dichroic dye guest molecules, at typical operating temperatures, which can increase the contrast that can be obtained between switching states.

[0060] Preferably, the pitch of the first switchable layer differs from the pitch of the second switchable layer by no more than 25%, more preferably by no more than 10%. It is especially preferred that the pitch of the first switchable layer is the same or substantially the same as the pitch of the second switchable layer.

[0061] The provision of similar or identical pitch dimensions may advantageously contribute to efficiently compensating for unwanted optical artifacts in the layers and thus to obtaining advantageous electro-optical characteristics of the switchable window element.

[0062] By pitch is meant herein the pitch p of the cholesteric helix, where the pitch p is the distance for the orientation axis (director) of a chiral or cholesteric LC to undergo a 2π rotation.

[0063] The pitch is preferably set to the maximum selective reflection wavelength λ maxThe pitch p is determined from NIR spectroscopy at 20° C. max From the measured values ​​of max = n(λ max ) * p, where n(λ max ) is λ max is the refractive index at

[0064] It is also feasible to use the wedge cell method known in the art to measure the helical twisting power HTP, especially at 20° C., and verify the determined pitch. The cholesteric or chiral nematic medium as presently provided preferably has a relatively long pitch, in particular a pitch that gives a Bragg-type reflection above 780 nm, i.e. reflection of visible light by the cholesteric medium is advantageously avoided or eliminated.

[0065] The sense of rotation or twist of the helix may be clockwise, i.e. right-handed, or counterclockwise, i.e. left-handed, respectively. For the path of incident light passing sequentially through the two switchable layers, there is a respective handedness and helical twist or screw-like turn.

[0066] According to the present invention, the chiral or cholesteric helix of the first switchable layer exhibits opposite handedness with respect to the cholesteric helix of the second switchable layer. The absolute value of the dielectric anisotropy of the liquid crystal medium contained in the first switchable layer and the liquid crystal medium contained in the second switchable layer is preferably 2.5 or more, more preferably 3.0 or more.

[0067] Above and below, Δε denotes the dielectric anisotropy, where Δε=ε || - ε ⊥ The dielectric anisotropy Δε is determined at 20° C. and 1 kHz.

[0068] In a preferred embodiment, the liquid-crystalline media contained in the first and second switchable layers according to the invention have a positive dielectric anisotropy. In this case, preference is given to liquid-crystalline mixtures having a dielectric anisotropy Δε in the range from 3 to 45, more preferably in the range from 5 to 30.

[0069] In an alternative embodiment, however, it is also feasible to provide an LC medium with negative dielectric anisotropy, in which case preference is given to liquid crystal mixtures with a dielectric anisotropy Δε in the range from −6 to −3. The liquid crystal media according to the invention contained in the first and in the second switchable layers each contain one or more pleochroic dyes, in particular one or more dichroic dyes.

[0070] The absorption maximum of the dichroic dye(s) optionally used in the liquid crystal medium is not specifically limited, but preferably has an absorption maximum in the yellow region (Y), magenta region (M), or cyan region (C). The dichroic dye preferably used in the liquid crystal medium of the present invention may be a single compound or a combination of several dyes. When several dyes are mixed, it is preferred to use a mixture of dichroic dyes having an absorption maximum in the Y region, the M region, and the C region, respectively. Dichroic dyes are known to those skilled in the art and are reviewed, for example, in Cowling, Stephen J., Liquid Crystal Dyes, in: Handbook of Liquid Crystals, Wiley-VCH Verlag GmbH & Co. KGaA (2014). The method of displaying all colors by mixing yellow dyes, magenta dyes, and cyan dyes is specifically described in "Colour Chemistry" (by Sumio Tokita, Maruzen Company, Limited, 1982). The yellow region is in the range of 430-490 nm, the magenta region is in the range of 500-580 nm, and the cyan region is in the range of 600-700 nm.

[0071] The chromophore used in the dichroic dye is not specifically limited, but it is preferable to use azo dyes, azulene dyes, anthraquinone dyes, benzoquinone dyes, naphthoquinone dyes, benzothiazole dyes, benzothiadiazole dyes, thiadiazoloquinoxaline dyes, dithiobenzoquinone, perylene dyes, merocyanine dyes, azomethine dyes, phthaloperylene dyes, indigo dyes, azulene dyes, dioxazine dyes, tetrazine dyes, polythiophene dyes, naphthimidazo-4,9-dione dyes, and phenoxazine dyes.

[0072] The liquid crystal media each preferably comprise 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 different dichroic dyes, especially preferably 2 or 3 dichroic dyes. Preferred dyes according to the present invention are azo dyes, perylene dyes, anthraquinone dyes, benzothiazole dyes, and benzothiadiazole dyes, more preferably azo dyes and benzothiadiazole dyes, and especially benzothiadiazole dyes.

[0073] The azo dyes may contain any number of azo groups, such as monoazo dyes, bisazo dyes, trisazo dyes, tetrakisazo dyes, and pentakisazo dyes, preferably monoazo dyes, bisazo dyes, and trisazo dyes. The cyclic structure contained in the azo dye is preferably an aryl group and / or a heteroaryl group.

[0074] Preferred aryl groups are derived, for example, from the parent structures benzene, biphenyl, terphenyl, naphthalene, anthracene, phenanthrene, pyrene, dihydropyrene, chrysene, perylene, fluorene, indene, and the like.

[0075] Preferred heteroaryl groups are, for example, pyrrole, pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, furan, thiophene, oxazole, isoxazole, 1,2-thiazole, 1,3-thiazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole. , 1,3,4-thiadiazole and other five-membered rings, pyridine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, 1,2,4-triazine, 1,2,3-triazine, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine, 1,2,3,5-tetrazine and other six-membered rings, indole, benzimidazole, benzotriazole, purine, naphthimidazole, phenanthrimidazole, pyridiazole, id) imidazole, pyridine imidazole, quinoxaline imidazole, benzoxazole, naphthoxazole, anthro(anthr)oxazole, phenanthroxazole, isoxazole, benzothiazole, benzothiadiazole, benzofuran, isobenzofuran, dibenzofuran, quinoline, isoquinoline, benzo-5,6-quinoline, benzo-6,7-quinoline, benzo-7,8-quinoline, benzoisoquinoline, acridine, phenothiazoline The condensed groups may be thiophenes, phenoxazines, benzopyridazines, benzopyrimidines, quinoxalines, phenazines, naphthyridines, azacarbazoles, benzocarbolines, phenanthridines, phenanthrolines, thieno[2,3b]thiophenes, thieno[3,2b]thiophenes, dithienothiophenes, dihydrothieno[3,4-b]-1,4-dioxins, isobenzothiophenes, dibenzothiophenes, benzothiadiazothiophenes, or combinations of these groups.

[0076] The aryl and heteroaryl groups may also be substituted by alkyl, cycloalkyl, alkoxy, thioalkyl, alkylamino, dialkylamino, fluorine, fluoroalkyl, or by further aryl or heteroaryl groups.

[0077] In a preferred embodiment, the liquid crystal medium comprises one or more dichroic dyes selected from the group of compounds represented by the formulae Dye-1, Dye-2 and Dye-3: [ka]

[0078] Additionally or alternatively, other types of dyes known to have equivalent effects to those described above may also preferably be used.

[0079] Each of the one or more dichroic dyes is preferably present in each liquid crystal medium in a proportion of 0.005% to 12.5% ​​by weight, more preferably 0.01% to 10% by weight, even more preferably 0.025% to 7.5% by weight, even more preferably 0.05% to 5% by weight, even more preferably 0.1% to 2.5% by weight, and especially preferably 0.25% to 1% by weight, based on the total weight of the entire medium.

[0080] Preferably, the one or more dichroic dyes are present in each liquid crystal medium in a total concentration ranging from 0.01% to 30% by weight, more preferably from 0.025% to 25% by weight, even more preferably from 0.05% to 15% by weight, even more preferably from 0.1% to 10% by weight, and especially preferably from 0.5% to 5% by weight.

[0081] The concentration of the dye(s) is preferably chosen to ensure proper performance of the resulting modulating material, especially in terms of the desired color and / or photochromic effect.

[0082] In some embodiments, the absorption spectra of the dichroic dyes optionally contained in the medium or in each switchable layer are preferably complementary to each other so that the impression of black color is produced to the eye. Preferably, two or more, more preferably three or more, dichroic dyes are used in the liquid crystal medium, preferably to cover a large part of the visible spectrum. The exact manner in which mixtures of dyes that appear black or gray to the eye can be prepared is known in the art and is described, for example, in M. Richter, Einfuehrung in die Farbmetrik [Introduction to Colorimetry], 2nd Edition, 1981, ISBN 3 11-008209-8, Walter de Gruyter & Co.

[0083] In another embodiment, different color settings, for example red, green, or blue, are implemented.

[0084] The determination of the color location of a mixture of dyes is described in the field of colorimetry. For this purpose, the spectra of the individual dyes are calculated taking into account the Beer-Lambert law to give the entire spectrum, which is converted according to the rules of colorimetry into the corresponding color location and luminance value under the relevant illumination (e.g. illuminant D65 for daylight). The position of the white point is fixed by the respective illuminant, e.g. D65, and is cited in tables, e.g. in the above references. Different color locations can be set by varying the proportions of the various dyes.

[0085] Preferably, the dichroic compound is present in solution in the liquid crystal medium. The dichroic compounds preferably exhibit a high dichroic ratio, favourable colour purity and a large extinction coefficient, especially in the VIS and / or NIR region of light, as well as good light fastness and good solubility in liquid-crystalline media.

[0086] In a preferred embodiment, the dichroic compounds in the LC medium have absorptions that collectively cover the entire visible spectrum.In this way, a color-neutral or black appearance may be obtained.Such a color-neutral appearance may be advantageous in applications where color artifacts or residual colors should be minimized or avoided, for example in some smart window applications.

[0087] 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 contribute to minimizing or even avoiding residual fluorescence in the visible spectrum, so that unwanted color artifacts (e.g., red emission) may be avoided or at least substantially reduced.

[0088] In a more particularly preferred embodiment, the LC medium of the window 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. The dichroic compound is preferably a positive dichroic dye, i.e. a dye having a positive degree of anisotropy R.

[0089] The degree of anisotropy R is determined for a dye-containing LC mixture from the values ​​of the extinction coefficients for the parallel and perpendicular alignment of the molecules compared to the direction of the light polarization. The degree of anisotropy R according to the invention is preferably greater than 0.4, more preferably greater than 0.6, even more preferably greater than 0.7, especially greater than 0.8.

[0090] 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.

[0091] In one embodiment, the dichroic dye is preferably selected from the dye classes indicated in B. Bahadur, Liquid Crystals - Applications and Uses, Vol. 3, 1992, World Scientific Publishing, Section 11.2.1, and more preferably from the explicit compounds given in the tables present herein.

[0092] In a preferred embodiment, the dichroic dye is selected from azo dyes, anthraquinones, methine compounds, azomethine compounds, merocyanine compounds, naphthoquinones, tetrazines, pyrromethene dyes, malononitrile dyes, rylenes, especially perylenes and terylenes, thiadiazole dyes, thienothiadiazole dyes, benzothiadiazoles, thiadiazoloquinoxalines, pyrromethenes, and diketopyrrolopyrroles. Particularly preferred are azo compounds, anthraquinones, benzothiadiazoles, especially those as described in WO 2014 / 187529, diketopyrrolopyrroles, especially those as described in WO 2015 / 090497, rylenes, especially those as described in WO 2014 / 090373, and thiadiazoloquinoxaline derivatives, especially those as described in WO 2016 / 177449. It is especially preferred that the dichroic dye is selected from azo dyes, benzothiadiazoles, and / or thiadiazoloquinoxalines.

[0093] Examples of particularly preferred dichroic dyes which may be present in the LC medium are shown below: [ka]

[0094] [ka]

[0095] [ka]

[0096] [ka]

[0097] The liquid crystal medium as contained in the first and second switchable layers according to the invention has at least 15% by weight of the compound of formula I, based on the total content of the medium. [ka] It is particularly preferred that the mesogenic compound contains one or more mesogenic compounds of the formula R 1 and R 2 represent, independently of one another, a radical selected from F, Cl, CF3, OCF3 and a straight-chain or branched alkyl or alkoxy having 1 to 15 carbon atoms or a straight-chain or branched alkenyl having 2 to 15 carbon atoms, said alkyl / alkoxy / alkenyl being unsubstituted, mono- or polysubstituted by CN or CF3 or mono- or polysubstituted by halogen, and in which one or more CH2 groups are in each case independently of one another selected from -O-, -S-, -CO-, -COO-, -OCO-, -OCOO-, -C≡C ... [ka] may be replaced by A 11 teeth, [ka] represents n represents 0 or 1, and A 21 , A 31 , and A 41 are mutually independent, [ka] wherein L at each occurrence, identically or differently, is a halogen selected from F, Cl, and Br, or methyl.

[0098] In one embodiment, the liquid crystal medium each contains one or more compounds of formula I as depicted 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, especially at least 35% by weight, based on the total content of the medium.

[0099] In some embodiments, one or more compounds of formula I are contained in each 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 especially from 25% to 50% by weight, based on the total content of the medium.

[0100] The media in the first and second switchable layers each therefore preferably contain at least one compound of formula I. In many cases, however, it may be beneficial and preferred for two, three or more compounds of formula I to be contained in each medium.

[0101] Preferably, the group A 11 is as defined in formula I, [ka] Represents.

[0102] In another embodiment, n represents 0, as defined in formula I. In a preferred embodiment, one or more compounds according to formula I are represented by formulas Ia, Ib, and Ic [ka] [ka] and more preferably selected from the compounds of formula Ia and Ib, R 1 and R 2 represent, independently of one another, a radical selected from F, Cl, CF3, OCF3, and a linear or branched alkyl or alkoxy having 1 to 15 carbon atoms or a linear or branched alkenyl having 2 to 15 carbon atoms, said alkyl / alkoxy / alkenyl being unsubstituted, monosubstituted by CN or CF3 or mono- 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-, -C≡C-, such that the oxygen atoms are not directly linked to one another, preferably a radical selected from F, CF3, OCF3, a linear alkyl or alkoxy having 1 to 9 carbon atoms or an alkenyl having 2 to 9 carbon atoms, and L, at each occurrence, identically or differently, is H or a halogen selected from F, Cl, and Br, preferably F and Cl, more preferably at each occurrence, identically or differently, is H or F.

[0103] In the case where the phenylene ring of the compound of formula I is substituted, the substituent(s) may be F and further the terminal group R 1 and R 2 It is especially preferred that the catalyst does not contain Cl.

[0104] In a preferred embodiment, the amount of Cl-containing compounds contained in the medium is limited, preferably to 55% by weight or less, more preferably to 40% by weight or less, even more preferably to 25% by weight or less, based on the total content of the medium. In a particularly preferred embodiment, the liquid crystal medium contains non-Cl-containing compounds.

[0105] Consequently, it is also preferred to limit the amount of Cl-containing compounds in the LC medium components consisting of the compounds of formula I as described above and below to preferably 55% by weight or less, more preferably 40% by weight or less, even more preferably 25% by weight or less, based on the total content of the compounds of formula I contained in the medium.In a particularly preferred embodiment, one or more compounds of formula I are selected from compounds that do not contain Cl.

[0106] Ring A according to Formula I 21 , A 31 , and A 41 It is further particularly preferred that at least one of the rings A according to formula I has at least one F substituent. 21 , A 31 , and A 41 It is furthermore especially preferred that together have at least two F substituents.

[0107] In certain embodiments, the use of CN-containing compounds in the medium is preferably limited to 75% by weight or less, more preferably 50% by weight or less, even more preferably 25% by weight or less, especially 15% by weight or less, and in specific embodiments is avoided entirely.

[0108] In addition to one or more compounds of formula I, the liquid crystal medium in the first switchable layer preferably contains one or more further mesogenic compounds. With a view to contributing to or maintaining favorable properties of the medium, such as good VHR and favorable stability, it is preferred that these additional compounds are also added.

[0109] Preferably, the liquid crystal media contained in the first and second switchable layers according to the invention preferably contain, in addition to one or more compounds of formula I, compounds of formula II and III [ka] The present invention includes one or more mesogenic compounds selected from the group of compounds represented by the formula R 3 , R4 , R 5 , and R 6 represent, independently of one another, a radical selected from F, CF3, OCF3, CN and a straight-chain or branched alkyl or alkoxy having 1 to 15 carbon atoms or a straight-chain or branched alkenyl having 2 to 15 carbon atoms, said alkyl / alkoxy / alkenyl being unsubstituted, mono- or polysubstituted by CN or CF3 or mono- or polysubstituted by halogen, and in which one or more CH2 groups may, in each case independently of one another, be selected from -O-, -S-, -CO-, -COO-, -OCO-, -OCOO-, -C≡C ... [ka] may be replaced by L 1 , L 2 , L 3 , L 4 , and L 5 represent, independently of one another, H or F, and L 6 and L 7 represent, independently of one another, H or methyl.

[0110] In one embodiment the liquid crystal media each comprise one or more mesogenic compounds of formula II. In another embodiment the liquid crystal media each comprise one or more mesogenic compounds of formula III.

[0111] Each medium preferably contains at least 15% by weight, based on the total content of the medium, of one or more mesogenic compounds of formula I and one or more mesogenic compounds selected from the group of compounds of formulae II and III. It is particularly preferred that each medium comprises one or more compounds of formula I, one or more compounds of formula II, and one or more compounds of formula III as described above.

[0112] Preferably, the liquid crystal medium in the first and second switchable layers has the formula IV [ka] and further comprising one or more compounds represented by the formula R 7 represents a straight-chain or branched alkyl or alkoxy having 1 to 15 carbon atoms, preferably 1 to 7 carbon atoms, or a straight-chain or branched alkenyl having 2 to 15 carbon atoms, which is unsubstituted or mono- or polysubstituted by CN or CF3 or mono- or polysubstituted by halogen, and in which one or more CH2 groups may be replaced, in each case 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 linked to one another, i is 0, 1, or 2; L 6 and L 7 are, independently of each other, H or F; and X 1 represents F, CF3, OCF3, or CN.

[0113] The compounds of formula II are preferably used in a total concentration of from 1% to 45% by weight, more preferably from 5% to 25% by weight, in the respective medium. The compounds of formula III are preferably used in a total concentration of from 1% to 45% by weight, more preferably from 5% to 25% by weight, in the respective medium.

[0114] The compounds of formula IV are preferably used in a total concentration of from 1% to 45% by weight, more preferably from 5% to 25% by weight, in the respective medium. It is particularly preferred that the medium comprises one or more compounds of formula I, one or more compounds of formula II, one or more compounds of formula III, and one or more compounds of formula IV as described above and below.

[0115] In a particularly preferred embodiment, one or more of the compounds of formula I are represented by the formulae I-1 and I-2 [ka] The compound is selected from compounds represented by the formula R 1 and R 2 is as defined for formula Ia above, and L, identically or differently, is H or F at each occurrence.

[0116] Optionally, the medium may contain additional liquid crystal compounds to adjust physical properties. Such compounds are known in the art. The concentration of these optional additional liquid crystal compounds in the medium is preferably 0% to 30% by weight, more preferably 0.1% to 20% by weight, and most preferably 1% to 15% by weight.

[0117] In one embodiment, the respective liquid crystal medium when used according to the present invention preferably has the formula CY, PY and AC [ka] [ka] The compound includes one or more compounds selected from the group of compounds represented by the formula a represents 1 or 2; b represents 0 or 1; c represents 0, 1 or 2; d represents 0 or 1; [ka] teeth, [ka] represents, and [ka] teeth, [ka] represents [ka] teeth, [ka] represents R 1 , R 2 , R AC1 , and R AC2 each independently of the other represents an alkyl having 1 to 12 C atoms, where in addition, one or two non-adjacent CH groups are not directly linked to each other, such that [ka] may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO-, preferably represents alkyl or alkoxy having 1 to 6 C atoms, Z x , Z y , and Z AC each independently of the others is -CHCH-, -CH=CH-, -CFO-, -OCF-, -CHO-, -OCH-, -CO-O-, -O-CO-, -CF-, -CF=CF-, -CH=CH-CHO- or a single bond, preferably a single bond; and L 1~4 each independently of the others represents F, Cl, CN, OCF3, CF3, CH3, CH2F, or CHF2, preferably F.

[0118] Preferably, L 1 and L 2 Both of them represent F or L 1 and L 2 one of represents F and the other represents Cl, and L 3 and L 4 Both of them represent F or L 3and L 4 One of these represents F and the other represents Cl.

[0119] It is particularly preferred that the liquid crystal medium, when used according to the present invention, contains one or more compounds selected from the compounds of the formulae CY, PY and AC in an amount of at least 20% by weight, more preferably at least 25% by weight, even more preferably at least 30% by weight, even more preferably at least 35% by weight, even more preferably at least 40% by weight and especially preferably at least 50% by weight, based on the total content of the medium.

[0120] The compound of formula AC preferably has the following formula: [ka] wherein R 3 and R 4 is R as described above. AC1 and R AC2 It has the meaning:

[0121] The liquid-crystalline medium when used according to the invention may contain further additives in customary concentrations. The total concentration of these further constituents is in the range of 0% to 10%, preferably 0.1% to 6%, based on the total mixture. The concentration of each individual compound used is preferably in the range of 0.1% to 3%. In this specification, the values ​​and ranges of the concentrations of the liquid-crystalline components and compounds of the liquid-crystalline medium do not take into account the concentrations of these and similar additives. Unless expressly indicated otherwise, this also applies to the concentrations of dichroic dyes optionally used in the mixture, which do not count when the concentrations of the individual compounds of the host mixture components are specified. The concentration of each additive is always a given relative value to the final dope mixture.

[0122] Unless expressly stated otherwise herein, all concentrations are given in weight percent.

[0123] The liquid crystal medium, when used according to the invention, consists of several compounds, preferably 3 to 30, more preferably 4 to 20, most preferably 4 to 16 compounds. These compounds are mixed in a conventional manner. As a rule, the required amount of the compound used in a smaller amount is dissolved in the compound used in a larger amount. In the case where the temperature is above 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 feasible to prepare the medium by other conventional methods, for example using so-called pre-mixtures (which can be, for example, homogeneous or eutectic mixtures of compounds) or using so-called multi-bottle systems (the constituents of which are ready-to-use mixtures themselves).

[0124] Many of the mesogenic compounds described above and below or their mixtures are commercially available. These compounds are either known or can be prepared by methods known per se, precisely under known and suitable reaction conditions, 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). Here, the use of variants known per se may also be made, but are not mentioned here in more detail. The medium according to the invention is prepared per se in a conventional manner. In general, the components are dissolved in each other, preferably at high temperature. Suitable additives or substances can be added to modify the dielectric anisotropy, viscosity and / or alignment of the liquid crystal phase.

[0125] The medium may further contain conventional additives such as stabilizers, antioxidants, free radical scavengers, chain transfer agents, e.g. thioethers, and / or plasticizers.

[0126] The term "alkyl" according to the invention preferably covers straight-chain and branched alkyl radicals having 1 to 7 carbon atoms, in particular the straight-chain radicals methyl, ethyl, propyl, butyl, pentyl, hexyl and heptyl. Radicals having 2 to 5 carbon atoms are generally preferred.

[0127] Alkoxy may be straight chain or branched, and is preferably straight chain and has 1, 2, 3, 4, 5, 6, or 7 carbon atoms, and is thus preferably methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy, or heptoxy.

[0128] The term "alkenyl" according to the invention preferably covers straight-chain and branched alkenyl groups having 2 to 7 carbon atoms, especially 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, especially C2-C7-1E-alkenyl, C4-C7-3E-alkenyl and C5-C7-4E-alkenyl. Examples of preferred alkenyl groups are 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.

[0129] The fluorinated alkyl or alkoxy is preferably CF3, OCF3, CFH2, OCFH2, CF2H, OCF2H, C2F5, OC2F5, CFHCF3, CFHCF2H, CFHCFH2, CH2CF3, CH2CF2H, CH2CFH2, CF2CF2H, CF2CFH2, OCFHCF3, OCFHCF2H, OCFHCFH2, OCH2CF3, OCH2CF2H, OCH2CFH2, OC F2CF2H, OCF2CFH2, C3F7, or OC3F7, especially CF3, OCF3, CF2H, OCF2H, C2F5, OC2F5, CFHCF3, CFHCF2H, CFHCFH2, CF2CF2H, CF2CFH2, OCFHCF3, OCFHCF2H, OCFHCFH2, OCF2CF2H, OCF2CFH2, C3F7, or OC3F7, especially preferably OCF3 or OCF2H. Fluoroalkyl in a preferred embodiment encompasses linear 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.

[0130] The oxaalkyl is preferably of the formula C n H 2n+1 -O-(CH2) m where n and m are each, independently of one another, from 1 to 6. Preferably, n=1, and m is 1-6.

[0131] Oxaalkyl is preferably 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-oxanonyl or 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl. Halogen is preferably F or Cl, especially F.

[0132] If one of the above mentioned groups is an alkyl group in which one CH2 group is replaced by -CH=CH-, it can be linear or branched. It is preferably linear and has 2 to 10 carbon atoms. It is consequently especially 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.

[0133] If one of the above mentioned groups is an alkyl group in which one CH2 group is replaced by -O- and one by -CO-, then these are preferably adjacent. They thus contain an acyloxy group -CO-O- or an oxycarbonyl group -O-CO-. They are preferably linear and have 2 to 6 carbon atoms.

[0134] They are therefore especially acetyloxy, propionyloxy, butyryloxy, pentanoyloxy, hexanoyloxy, acetyloxymethyl, propionyloxymethyl, butyryloxymethyl, pentanoyloxymethyl, 2-acetyloxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 3-acetyloxypropyl, 3-propionyloxypropyl, 4-acetyloxybutyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl, 2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl, 2-(propoxycarbonyl)ethyl, 3-(methoxycarbonyl)propyl, 3-(ethoxycarbonyl)propyl or 4-(methoxycarbonyl)butyl.

[0135] If one of the above mentioned groups is an alkyl group in which one CH2 group is replaced by unsubstituted or substituted -CH=CH- and the adjacent CH2 group is replaced by CO, CO-O or O-CO, it may be linear or branched. It is preferably linear and has 4 to 13 carbon atoms. Consequently, it is especially 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.

[0136] When one of the above mentioned groups is an alkyl or alkenyl group monosubstituted by CN or CF3, this group is preferably linear. The substitution by CN or CF3 can be in any position.

[0137] When one of the above mentioned groups is an alkyl or alkenyl group which is at least monosubstituted by halogen, this group is preferably linear and the halogen is preferably F or Cl, more preferably F. In the case of polysubstitution, the halogen is preferably F. The resulting groups also include perfluorinated groups. In the case of monosubstitution, the fluoro or chloro substituent can be in any desired position, but is preferably in the ω position.

[0138] Compounds containing branched groups are sometimes of interest due to their better solubility in some conventional liquid crystal matrices, but they are particularly suitable as chiral dopants if they are optically active.

[0139] Branched groups of this type generally contain not more than one chain branch. Preferred branched 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-ethylhexoxy, 1-methylhexoxy, or 1-methylheptoxy.

[0140] When one of the above mentioned radicals is an alkyl radical in which two or more CH2 groups are replaced by -O- and / or -CO-O-, this can be linear or branched. It is preferably branched and has 3 to 12 carbon atoms. As a result, it is especially preferred for use as biscarboxymethyl, 2,2-biscarboxyethyl, 3,3-biscarboxypropyl, 4,4-biscarboxybutyl, 5,5-biscarboxypentyl, 6,6-biscarboxyhexyl, 7,7-biscarboxyheptyl, 8,8-biscarboxyoctyl, 9,9-biscarboxynonyl, 10,10-biscarboxydecyl, bis(methoxycarbonyl)methyl, 2,2-bis(methoxycarbonyl)ethyl, 3,3-bis(methoxycarbonyl)propyl, ... 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.

[0141] The first and second switchable layers each have a thickness of 20 μm or less, preferably 15 μm or less, in particular 10 μm or less. Surprisingly, advantageous optical performances may also be obtained, especially in the case of relatively small layer thicknesses, providing efficient dimming, especially in the dark state. It is particularly preferred that the first and second switchable layers have the same thickness, and even more preferred that the same layer thickness is set in combination with the same pitch size. This provision may advantageously contribute to achieving efficient compensation of optical artifacts.

[0142] In an embodiment, the switchable layer according to the present invention preferably has a thickness, also represented herein as d, in the range of from 1 μm to 30 μm, more preferably from 2 μm to 25 μm, even more preferably from 3 μm to 18 μm, especially from 4 μm to 12 μm.

[0143] To maintain the appropriate thickness of the switchable layer, spacers may be included within the cell gap of the switchable layer. Typically the spacers have a spherical shape with a diameter in the range of the cell gap. For example, non-conductive spacers made of polymer or glass with a spherical shape with a predetermined diameter may be used. In some embodiments, it may be useful to provide sticky spacers, i.e. spacers with some inherent adhesive characteristics that allow better adhesion to the surface. It may also be useful to use black spacers, for example to avoid or minimize undesired light leakage. In some embodiments, it may be particularly beneficial to use black and sticky spacers. Alternatively, the cell thickness may be set or maintained by other suitable means, for example by using column spacers. The column spacers may also be formed to provide compartments, thus optionally allowing free-cuttable structures. In some embodiments, the switchable layer may thus include isolated compartments, each containing a liquid crystal medium, for example using rectangular or honeycomb structures.

[0144] The liquid crystal medium in the first and second switchable layers preferably exhibits a suitable optical anisotropy Δn, also known as birefringence. In a preferred embodiment, the liquid crystal medium contained in the first and second switchable layers exhibits an optical anisotropy Δn, determined at 20° C. and 589 nm, in the range from 0.03 to 0.30, more preferably from 0.04 to 0.20, even more preferably from 0.05 to 0.13.

[0145] Above and below, Dn represents the optical anisotropy, where Δn = ne -n o , and the optical anisotropy Dn are determined at 20° C. and a wavelength of 589.3 nm.

[0146] For each of the first and second switchable layers, the following relationships: d*Δn<3.0μm where d is the respective thickness of each switching layer and Δn is the respective optical anisotropy of the liquid crystal medium contained in each switching layer, in particular said optical anisotropy determined at 589.3 nm and 20° C. is particularly preferably applied.

[0147] Surprisingly, it has been found that setting defined upper limits for the layer thickness and optical anisotropy of the product can advantageously contribute to obtaining an excellent dark state while in addition providing a large switching range. Even more preferred is d*Δn<2.0 μm, especially d*Δn<1.5 μm, for each of the first and second switchable layers.

[0148] In a further embodiment, the first and second switchable layers are provided such that d*Δn for each of both layers is 3.0 μm or more, for example in the range of 3.0 μm to 7.0 μm. It has been found that for larger layer thicknesses, further performance benefits may also be obtained, for example by compensating for or mitigating device differences or deviations with respect to irregularities such as unwanted cell thickness or gap variations or cell substrate defects or glass waviness.

[0149] A window element including two liquid crystal based switching layers, in particular so-called dye-doped or guest-host liquid crystal switching layers, is provided to produce an overall reduction in light intensity where desired or required, i.e. to provide switching capability to reduce light or dim light while still minimizing or even avoiding haze.

[0150] The switchable window element thus has a layer structure comprising at least two switchable layers, where the first and second switchable layers each comprise one or more dichroic dyes, preferably containing the same dye(s). The window element can be arranged and configured in various ways, especially in terms of electrode configurations, optionally provided with alignment layers and their types and liquid crystal materials, however where the window element is provided to provide an overall change in transmittance and switching ability to dim light in a multi-layer arrangement.

[0151] In particular, the first and second switchable layers can be provided separately or individually in so-called cells, which are then combined and arranged as a so-called double cell, for example by lamination or bonding using an adhesive, in particular. In this case, each cell comprises two substrates. Alternatively, the first and second switchable layers can be provided stacked, where both switchable layers share a common substrate arranged between the switchable layers.

[0152] Thus, in one embodiment, the multi-layer arrangement of window elements may be in this order: - first transparent base material, - first electrode layer, - a first alignment layer, - a first switchable layer; - a second alignment layer, - second electrode layer, - second transparent base material, - optionally a bonding, adhesive or laminating layer, - third transparent base material, - third electrode layer, - the third alignment layer, - a second switchable layer; - 4th alignment layer, - a fourth electrode layer, and - 4th transparent base material Includes.

[0153] In this embodiment, two switchable optical cells are combined to form a so-called dual cell, where the dual cell has twist or supertwist switching layers exhibiting opposite twist senses.

[0154] The provision of a tie, adhesive or laminating layer is preferred to provide improved mechanical stability and to reduce possible optical losses by suitably matching the refractive index. The electrode layer is preferably and advantageously arranged as a transparent conductive layer.

[0155] In this case, the first switching layer and the second switching layer are each preferably interposed between two respective transparent substrates supporting an electrode arranged as a transparent conductive layer, wherein the transparent conductive layers are preferably embedded between two transparent dielectric layers, such as layers of silicon oxide or silicon nitride, respectively, and wherein an alignment layer in direct contact with the switching layers is further provided.

[0156] In an alternative embodiment, the multi-layer arrangement of window elements may be in this order: - first transparent base material, - first electrode layer, - a first alignment layer, - a first switchable layer; - a second alignment layer, - second electrode layer, - second transparent base material, - third electrode layer, - the third alignment layer, - a second switchable layer; - 4th alignment layer, - a fourth electrode layer, and - Third transparent base material wherein the second alignment layer and the second electrode layer are disposed or positioned on a first surface of the second transparent substrate, and wherein the third electrode layer and the third alignment layer are disposed or positioned on a second surface of the second transparent substrate.

[0157] The switchable optical cells as described above are electrically switchable, in that in the presence or absence of an electric field the switchable layers have a twisted or supertwisted configuration, and in particular in the dark state the switchable layer materials exhibit a twisted nematic phase or respectively a supertwisted nematic phase.

[0158] An alignment layer or orientation layer, for example made of polyimide (PI), is preferably provided on the substrate. It is particularly preferred that the electrically conductive layer and the alignment layer are provided together on the substrate. In this case, the alignment layer or orientation layer is provided on top of the conductive layer such that the alignment layer is in contact with the LC medium. The alignment layer, preferably a polyimide layer, may be arranged to provide a uniform or planar alignment or alternatively a homotropic alignment of the molecules of the liquid crystal medium, especially at the interface.

[0159] In some embodiments, rubbed polyimide is used on both substrates with a difference in orientation, especially at or around 90°, when used in a so-called twisted nematic (TN) geometry. In some embodiments, a so-called pre-tilt angle can be set and obtained as desired. In a TN configuration, the twist angle is typically at or around 90°. Alternatively, the configuration can be set in a super twisted nematic (STN) configuration, where the twist angle is greater than 90°, typically ranging from greater than 90° to 270°. However, the STN configuration is also feasible to exhibit a twist angle greater than 270°. It is especially preferred for the STN configuration that the twist angle is at or around 180°.

[0160] Preferred configurations for the first and second switchable layers are the TN, STN, vertically aligned-twisted nematic (VA-TN) and vertically aligned-supertwisted nematic (VA-STN) configurations, in which the twist angle for TN and VA-TN may range from greater than 0° up to and including 90°, and for STN and VA-STN the twist angle is greater than 90°.

[0161] Preferably, the first, second, third and fourth alignment layers comprise polyimide, and are preferably made from rubbed polyimide.

[0162] It is especially preferred, especially for the TN configuration, that the rubbing directions of the second and third alignment layers are mutually orthogonal. This provision can advantageously contribute to an overall optimized or at least increased efficiency of softening both the parallel and the perpendicular polarization components of light.

[0163] Alternatively, it is however also feasible for the angle between the rubbing direction of the second alignment layer and the rubbing direction of the third alignment layer to be different from 90° (for example an angle closer to 0°, in particular 0°).

[0164] It is also feasible to provide a passivation layer or a barrier layer on the substrate, but alternatively, in addition to the alignment layer, a passivation layer, for example comprising silicon oxide or silicon nitride, preferably consisting of silicon oxide or silicon nitride. In the case where both a passivation layer and an alignment layer are provided on the substrate, they are arranged such that the alignment layer is on top, i.e. in contact with the LC medium.

[0165] The liquid crystal medium contained in the first switchable layer and the second switchable layer each preferably comprises one or more chiral compounds. The liquid crystal medium is thus preferably a cholesteric or a chiral nematic medium. In addition to providing an alignment layer, the chiral compound may contribute to establishing a desired twist in the switchable layer as well as a desired twist sense.

[0166] It is particularly preferred that the liquid crystal medium contained in the first switchable layer and the liquid crystal medium contained in the second switchable layer each comprise a chiral dopant, preferably a chiral dopant having a relatively high helix twisting power (HTP), for example a medium to high HTP. This provision allows the incorporation of the chiral compound(s) in low concentrations into the medium.

[0167] The liquid crystal medium contained in each of the first and second switchable layers preferably comprises the chiral dopant in a concentration of 0.01% to 5% by weight, more preferably from 0.03% to 2.50% by weight, even more preferably from 0.05% to 1.00% by weight.

[0168] According to the invention, the twist senses in the first and second switchable layers are opposite to each other, and the chiral compounds are chosen so that, as a result, the twist of one of the layers is set clockwise and the twist of the other layer is set counterclockwise.

[0169] In a preferred embodiment, the chiral dopants used in the two switchable layers are each other's stereoisomers, especially enantiomers. In a particularly preferred embodiment, the two switchable layers each contain the R-isomer and the S-isomer of the chiral dopant. It is also feasible to use suitable or corresponding enantiomers. It is particularly preferred that the dopant concentration of each isomer used in the medium is the same. This provision can facilitate the preparation of both liquid crystal media in that they can be identical except for the chirality of the chiral dopant, i.e. the form of isomer or enantiomer. Using the same concentration of corresponding isomer or enantiomer can also advantageously contribute to achieving effective and efficient compensation of unwanted optical artifacts.

[0170] In this respect, it is particularly preferred that the two switchable layers have the same thickness and that the two media contain the same dichroic dye, preferably in the same concentration, and the same enantiomer of the chiral dopant, preferably in the same concentration.

[0171] Chiral or cholesteric media can be prepared, for example, by doping a nematic LC medium with a chiral dopant having a high twisting power. The pitch p of the induced cholesteric helix then depends on the concentration c of the chiral dopant and the helix-inducing power HTP, as given by equation (1): p = (HTP c) -1 (1) is given according to

[0172] For example, it is also feasible to use two or more dopants to compensate for the temperature dependence of the HTP of the individual dopants, and thus achieve a smaller temperature dependence of the helical pitch. 合計 ), we thus obtain approximately equation (2): HTP 合計 = Σ i c i HTP i (2) holds true, and in the formula, c i are the individual dopant concentrations, and HTP i is the helical induction power of each of the individual dopants.

[0173] The liquid crystal medium in the first and second switchable layers preferably contains one or more chiral compounds and especially chiral dopants. The chiral dopants preferably have a high absolute value of HTP, can generally be added to mesogen-based mixtures and also to dye-doped mixtures in relatively low concentrations, and have good solubility in the achiral component. If two or more chiral compounds are employed, they may have the same or opposite senses of rotation and the same or opposite temperature-dependent twist.

[0174] Preferably, the one or more chiral compounds contained in the liquid crystal media contained in the first switchable layer and in the second switchable layer each have a chromaticity of less than 5 μm, preferably in the commercial liquid crystal mixture MLC-6828 from Merck KGaA. -1 More preferably, 10 μm -1 More preferably still, 15 μm -1 Especially preferred is a liquid crystal mixture having an absolute value of the helical twisting power of 20 μm or more, preferably in the commercial liquid crystal mixture MLC-6828 from Merck KGaA. -1 More preferably, 40 μm or more -1 More preferably still, 60 μm -1 More than 80 μm, most preferably -1 More than ~260μm -1 These are chiral compounds having absolute values ​​of helical twisting power (HTP) in the following ranges:

[0175] In one embodiment, the one or more chiral compounds are contained in the liquid crystal medium in an amount of not more than 2% by weight, more preferably not more than 1% by weight, based on the total content of the medium.

[0176] In a preferred embodiment of the present invention, the chiral component consists of two or more chiral compounds that all have the same sign of HTP. The temperature dependence of the HTP of each individual compound may be high or low. The temperature dependence of the pitch of the medium can be compensated by mixing compounds with different temperature dependence of HTP in the corresponding ratio.

[0177] Suitable chiral dopants are known in the art and some of them are commercially available, such as, for example, cholesteryl nonanoate, R / S-811, R / S-1011, R / S-2011, R / S-3011, R / S-4011, R / S-5011, B(OC)2C*HC-3, or CB15 (all from Merck KGaA, Darmstadt, Germany).

[0178] More particularly suitable chiral dopants are compounds which contain one or more chiral radicals and one or more mesogenic groups or one or more aromatic or alicyclic groups which form a mesogenic group together with the chiral radical.

[0179] Suitable chiral radicals are, for example, monovalent or polyvalent chiral radicals selected from the group consisting of chiral branched hydrocarbon radicals, chiral ethanediols, binaphthols or dioxolanes, furthermore sugar derivatives, sugar alcohols, sugar acids, lactic acids, chiral substituted glycols, steroid derivatives, terpene derivatives, amino acids or sequences of a small number of, preferably 1 to 5, amino acids.

[0180] Preferred chiral radicals are sugar derivatives, such as glucose, mannose, galactose, fructose, arabinose, and dextrose; sugar alcohols, such as, for example, sorbitol, mannitol, iditol, galactitol, or their anhydro derivatives, especially dianhydrohexitols, such as dianhydrosorbide (1,4:3,6-dianhydro-D-sorbide, isosorbide), dianhydromannitol (isosorbitol), or dianhydroiditol (isoiditol); sugar acids, such as, for example, gluconic acid, gulonic acid, and ketogulonic acid; chiral substituted glycol radicals, such as, for example, mono- or oligoethylene glycol or propylene glycol, in which one or more CH groups are replaced by alkyl or alkoxy; For example, amino acids such as alanine, valine, phenylglycine, or phenylalanine, or sequences of two to five of these amino acids; steroid derivatives, such as, for example, cholesteryl or cholic acid radicals; terpene derivatives, such as, for example, menthyl, neomenthyl, campheyl, pineyl, terpineyl, isolongifolyl, fenchyl, carreyl, myrthenyl, nopyl, geraniyl, linaloyl, neryl, citronellyl, or dihydrocitronellyl.

[0181] Suitable chiral radicals 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 41 820. Preferred chiral compounds for use in accordance with the present invention are selected from the following group of compounds:

[0182] In one embodiment, preferred are dopants selected from the group consisting of compounds represented by the following formulae AI to A-III: [ka] [ka] During the ceremony R a11 and R a12 are each independently an alkyl, oxaalkyl, or alkenyl having from 2 to 9, preferably up to 7, carbon atoms, and R a11 is alternatively methyl or alkoxy having from 1 to 9 carbon atoms, preferably both are alkyl, preferably n-alkyl; R a21 and R a22 are each independently an alkyl or alkoxy having from 1 to 9, preferably up to 7, carbon atoms, an oxaalkyl, alkenyl, or alkenyloxy having from 2 to 9, preferably up to 7, carbon atoms, preferably both of which are alkyl, preferably n-alkyl; R a31 and R a32 are each independently an alkyl, oxaalkyl, or alkenyl having from 2 to 9, preferably up to 7, carbon atoms, and R a11 is alternatively methyl or alkoxy having from 1 to 9 carbon atoms, preferably both are alkyl, preferably n-alkyl.

[0183] Especially preferred are chiral dopants selected from the group consisting of compounds represented by the following formula: [ka] [ka]

[0184] More preferred dopants are those of formula A-IV: [ka] A derivative of isosorbide, isomannitol, or isoiditol represented by the formula: [ka] teeth, [ka] and preferably dianhydrosorbitol, and chiral ethanediols, such as, for example, diphenylethanediol (hydrobenzoin), especially those of the formula: [ka] mesogenic hydrobenzoin derivatives of the formula: (not shown but including the (R,S), (S,R), (R,R), and (S,S) enantiomers); During the ceremony [ka] are each, independently of one another, 1,4-phenylene (which may also be mono-, di-, or trisubstituted by L), or 1,4-cyclohexylene; L is H, F, Cl, CN, or an optionally halogenated alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, or alkoxycarbonyloxy having 1 to 7 carbon atoms; c is 0 or 1; Z 0 is -COO-, -OCO-, -CH2CH2-, or a single bond, and R 0 is an alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, or alkylcarbonyloxy having 1 to 12 carbon atoms.

[0185] Compounds of formula A-IV are described in WO 98 / 00428. Compounds of formula AV are described in GB-A-2,328,207.

[0186] In another embodiment, particularly preferred chiral dopants are chiral binaphthyl derivatives, chiral binaphthyl derivatives as described in WO 02 / 94805, chiral binaphthol acetal derivatives, chiral binaphthol acetal derivatives as described in WO 02 / 34739, chiral TADDOL derivatives, 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, said chiral dopants as described in WO 02 / 06196 and WO 02 / 06195.

[0187] Particularly preferred are compounds of formula A-VI [ka] A chiral compound represented by the formula: X 1 , X 2 , Y 1 , and Y 2 each independently represent F, Cl, Br, I, CN, SCN, SF5, linear or branched alkyl having 1 to 25 carbon atoms, which may be mono- or polysubstituted by F, Cl, Br, I, or CN, and in said alkyl, in addition, one or more non-adjacent CH2 groups each independently represent -O-, -S-, -NH-, -NR2-, -NH-, -NR1-, -NR2-, -NR3-, -NR4-, -NR5-, -NR6-, -NR7-, -NR8-, -NR9-, -NR10-, -NR11-, -NR12-, -NR13-, -NR14-, -NR15-, -NR16-, -NR17-, -NR18-, -NR19-, -NR20-, -NR21-, -NR22-, -NR23-, -NR24-, -NR25-, -NR36-, -NR37-, -NR38-, -NR39-, -NR40-, -NR41-, -NR52-, -NR39-, -NR42-, -NR53-, -NR54-, -NR60-, -NR71-, -NR82-, -NR19-, -NR10-, -NR11-, -NR12-, -NR13-, -NR25-, -NR36- 0 -, -CO-, -COO-, -OCO-, -OCOO-, -S-CO-, -CO-S-, -CH=CH- or -C≡C-), a polymerizable group or a cycloalkyl or aryl having up to 20 carbon atoms, which may optionally be mono- or polysubstituted by halogen, preferably F, or by polymerizable groups, x1 and x 2 are each, independently of one another, 0, 1, or 2; y 1 and y 2 are each, independently of one another, 0, 1, 2, 3, or 4; B 1 and B. 2 are each, independently of one another, 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 CH groups may be replaced by O and / or S, W 1 and W 2 are each independently -Z 1 -A 1 -(Z 2 -A 2 ) m -R, and one of the two is alternatively R 1 Or A 3 But neither of them are H at the same time, or [ka] teeth, [ka] or [ka] and U 1 and U 2 are each, independently of one another, CH, O, S, CO, or CS; V 1 and V 2 are each independently (CH2) n where n is 0, 1, 2, 3, 4, or 5, and where one or more non-adjacent CH groups may be replaced by O and / or S, and V 1 and V 2と one of, and [ka] but, [ka] In the case where both are single bonds, Z 1 and Z 2 each independently represents -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, in which two O and / or S and / or N atoms are not directly bonded to one another and are preferably -CH=CH-COO- or -COO-CH=CH- or a single bond, A 1 , A 2 , and A 3 are each, independently of one another, 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 CH 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, where each of these groups may be mono- or polysubstituted by L, and in addition A 1 is a single bond, L is a halogen atom, preferably F, CN, NO2, alkyl having 1 to 7 carbon atoms, alkoxy, alkylcarbonyl, alkoxycarbonyl, or alkoxycarbonyloxy, in which one or more H atoms may be replaced by F or Cl; m, in each occurrence, is independently 0, 1, 2, or 3; and R and R 1 are each, independently of one another, H, F, Cl, Br, I, CN, SCN, SF5, linear or branched alkyl having 1 or from 3 to 25 carbon atoms, which may optionally be mono- or polysubstituted by F, Cl, Br, I, or CN, and in which one or more non-adjacent CH groups are -O-, -S-, -NH-, -NR 0 -, -CO-, -COO-, -OCO-, -O-COO-, -S-CO-, -CO-S-, -CH=CH-, or -C≡C-, where the two O and / or S atoms are not directly bonded to each other), or a polymerizable group.

[0188] Particularly preferred are compounds of formula A-VI-1 [ka] and in particular chiral binaphthyl derivatives of the following formulae A-VI-1a to A-VI-1c: [ka] where B and Z are selected from 0 is as defined for formula A-IV, and Z 0 is more preferably -OCO- or a single bond, R 0 is as defined for formula A-IV, or H, or alkyl having 1 to 4 carbon atoms; and b is 0, 1, or 2.

[0189] Particularly preferred are those of formula A-VI-2 [ka] and in particular chiral binaphthyl derivatives of the following formulae A-VI-2a to A-VI-2f: [ka] [ka] where R 0 is as defined for formula A-VI, and X is H, F, Cl, CN, or R 0 , preferably F.

[0190] In a particularly preferred embodiment, the liquid crystal medium contained in one of the first and second switchable layers comprises the compound R-5011 and the liquid crystal medium contained in the other switchable layer comprises the compound S-5011, both shown below in Table F. It is particularly preferred that R-5011 and S-5011, respectively, are the only chiral compounds contained in the media.

[0191] In another especially preferred embodiment, the liquid crystal medium contained in one of the first and second switchable layers comprises compound S-811 and the liquid crystal medium contained in the other switchable layer comprises compound R-811, both as shown below in Table F. It is especially preferred that S-811 and R-811, respectively, are the only chiral compounds contained in the media.

[0192] In one embodiment, for each of the first and second switchable layers, the following relationship is satisfied: p*Δn<20.0μm It is preferred to apply where p is the respective pitch of each of the switchable layers and Δn is the optical anisotropy of each of the liquid crystal media contained in each of the switchable layers, in particular said optical anisotropy determined at 589.3 nm and 20° C. For each of the first and second switchable layers, it is preferred that p*Δn<15.0 μm, even more preferred that p*Δn<10.0 μm, in particular even more preferred that p*Δn<5.0 μm.

[0193] The LC medium contained in the switching layer preferably and advantageously exhibits high reliability and high electrical resistivity. The LC medium 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 in "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 stated, the measurement of VHR is carried out as described in T. Jacob, U. Finkenzeller in "Merck Liquid Crystals - Physical Properties of Liquid Crystals", 1997.

[0194] In a preferred embodiment, the window element does not include a polarizer. Even in the absence of any polarizer, advantageous electro-optical performance, e.g., in terms of switching contrast and transmission reduction, has been found, especially by providing two switching layers, and a dye-doped LC material, and especially one or more dichroic dyes as presently defined.

[0195] The LC host medium for the guest-host mixture, especially the nematic host mixture, when used in the first and second switchable layers may be the same or different. However, it is preferred that the LC host medium for the guest-host mixture when used in the first and second switchable layers is the same in consideration of simplifying the material supply. It is also preferred to use the same dichroic dye, preferably at the same concentration.

[0196] In principle, suitable host mixtures for use in the switching elements are either dielectrically negative or positive LC mixtures suitable for use in conventional VA, TN, STN, VA-STN, IPS or FFS displays.

[0197] Suitable LC mixtures are known in the art and described in the literature: LC media for VA displays with negative dielectric anisotropy are described, for example, in EP 1 378 557 A1. Suitable LC mixtures with positive dielectric anisotropy which are suitable for LCD displays, 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 28 107, WO 96 / 23 851, WO 96 / 28 521, and WO2012 / 079676.

[0198] Preferred embodiments of the liquid-crystalline media according to the invention having negative or positive dielectric anisotropy are indicated below.

[0199] In a preferred embodiment of the present invention, the LC medium used in the switching layer of the window element contains an LC host mixture of positive dielectric anisotropy. Consequently, in a further preferred embodiment, the mesogenic medium according to the present invention comprises a component selected from the following a) and b): a) Formulae IIA to VIII as shown below, in particular formulae IIA and IIIA [ka] During the ceremony R 20 each represents, identically or differently, a halogenated or unsubstituted alkyl or alkoxy radical having 1 to 15 C atoms, in which in addition, one or more CH groups in these radicals can each be independently selected from -C≡C-, -CF2O-, -CH=CH ... [ka] may be replaced by -O-, -CO-O-, or -O-CO-; X 20 each represents, identically or differently, F, Cl, CN, SF5, SCN, NCS, a halogenated alkyl radical, a halogenated alkenyl radical, a halogenated alkoxy radical, or a halogenated alkenyloxy radical, each having up to 6 C atoms, and Y 20~24 each represents, identically or differently, H or F; [ka] are each, independently of the other, [ka] Represents, A mesogenic medium comprising one or more compounds selected from the group of compounds represented by:

[0200] The compound of formula IIA preferably has the following formula: [ka] [ka] wherein R is selected from 20 and X 20 has the meaning indicated above.

[0201] R 20 preferably represents alkyl having 1 to 6 C atoms. 20 preferably denotes F. Especially preferred are compounds of the formulae IIAa and IIAb, especially compounds of the formulae IIAa and IIAb, in which X denotes F.

[0202] The compound of formula IIIA preferably has the following formula: [ka] [ka] wherein R is selected from 20 and X 20 has the meaning indicated above.

[0203] R 20 preferably represents alkyl having 1 to 6 C atoms. 20 preferably denotes F. Especially preferred are compounds of the formulae IIIAa and IIIAe, especially compounds of the formula IIIAa.

[0204] In a further embodiment the liquid crystal medium has the formula IIIA-1-b to IIIA-1-h [ka] [ka] wherein R 2 is R as given in formula IIIA 20 It has the meaning:

[0205] b) Alternatively or additionally, a compound of the formula: [ka] [ka] During the ceremony R 20 , X 20 , and Y 20~23 has the meaning indicated above, and Z 20 represents -C2H4-, -(CH2)4-, -CH=CH-, -CF=CF-, -C2F4-, -CH2CF2-, -CF2CH2-, -CHO-, -OCH2-, -COO-, or -OCF2-, and also represents a single bond in formulae V and VI, and also represents -CF2O- in formulae V and VIII, r represents 0 or 1, and s represents 0 or 1; a mesogenic medium comprising one or more compounds selected from

[0206] The compound of formula IVA preferably has the following formula: [ka] wherein R is selected from 20 and X 20 has the meaning indicated above. R 20 preferably represents alkyl having 1 to 6 C atoms. 20 preferably represents F, CN or OCF3, furthermore also OCF=CF2 or Cl.

[0207] The compound of formula V preferably has the following formula: [ka] [ka] wherein R is selected from 20 and X 20 has the meaning indicated above. R 20 preferably represents alkyl having 1 to 6 C atoms. 20preferably represents F and OCF3, furthermore also OCHF2, CF3, OCF=CF2 and OCH=CF2.

[0208] The compound of formula VI preferably has the following formula: [ka] wherein R is selected from 20 and X 20 has the meaning indicated above. R 20 preferably represents alkyl having 1 to 6 C atoms. 20 preferably represents F, and also OCF3, CF3, CF=CF2, OCHF2, and OCH=CF2;

[0209] The compound of formula VII preferably has the following formula: [ka] [ka] wherein R is selected from 20 and X 20 has the meaning indicated above. R 20 preferably represents alkyl having 1 to 6 C atoms. 20 preferably represents F, furthermore also OCF3, OCHF2, and OCH=CF2.

[0210] The liquid-crystalline media may additionally comprise suitable additives and auxiliary materials, such as stabilizers and quenchers. It is preferred that the liquid crystal medium used in the first and second switchable layers does not contain any polymerisable compounds, in particular no polymerisable mesogenic compounds.

[0211] The LC medium according to the present invention is prepared in a conventional manner per se. In general, the components are dissolved in each other, preferably at high temperature. Mixing is preferably carried out under inert gas, for example under nitrogen or argon. Any dye is subsequently added, preferably at high temperature, more preferably at a temperature above 40°C, especially preferably at a temperature above 50°C. Generally, the desired amount of the component used in a smaller amount is dissolved in the component that constitutes the main constituent. It is also possible to mix the solutions of the components in an organic solvent, for example acetone, toluene, chloroform or methanol, and remove the solvent again after mixing, for example by distillation.

[0212] The window elements are preferably 0.5 m 2 Larger, preferably 1m 2 Larger, even more preferably 3m 2 In one embodiment, the window element has a size greater than 0.10 mm. 2 ~10m 2 More preferably, in the range of 0.5 m 2 ~10m 2 The area is in the range of

[0213] The window element according to the invention allows light to pass through it. It can advantageously be used in or be included in windows, glazing units, including insulating glazing units, facade elements, partitions, dividing walls, etc. It can be used therein as an element which has different switching states on demand, thus providing anti-glare control when desired.

[0214] Window elements as switchable devices can be used to regulate or modulate the passage of light from an exterior space into an interior space, for example into the interior of a building such as a house, an office building or a building used for commercial purposes, or into a vehicle. Window elements can also be used to regulate or modulate the passage of light from an interior space into another interior space, especially in structural elements that separate various functional areas or rooms.

[0215] The window element also does not include the window as a whole that contains the window element, and preferably does not include any light source, so that any light passing through the window originates from an external light source, such as the sun or a domestic lighting device, in particular the sun.

[0216] According to the invention, the state of the switchable layer and the window element is controlled using an electric field applied by means of an electrode. The electrode is preferably a transparent electrode arranged on the substrate in the form of a coating. The coating is typically applied to the substrate side or surface facing the switching layer.

[0217] Preferably, the electrodes are not patterned and / or structured so that they are continuous. Thus, all switchable areas are simultaneously addressed and switched by applying an electric field. In an alternative embodiment, the electrodes may be patterned to form individually addressable areas that may be switched independently from other areas by applying an electric field. In this case, the electrodes are preferably patterned so that there are between 2 and 500 independently addressable areas. Such patterns may be useful, for example, to generate a permeability gradient across the device area.

[0218] Preferably, to facilitate electronic actuation, the switching voltages for switching the first and second switchable layers may be coordinated. Advantageously, relatively low switching voltages may be useful and effective, where a switching voltage of 48V or less is preferably used.

[0219] In a window element, preferably a window including a window element that controls and regulates the passage of light, the switchable layer and any further layers may be suitably positioned and joined, for example by lamination or the use of adhesives, but may be separated, for example by the use of one or more intervening substrates or sheets, panes, or panels, where optionally the panes may be further separated by a vacuum or gas filled space.

[0220] In one embodiment, the multilayer arrangement is assembled into an insulating glazing unit, where the layers are separated, inter alia, by a vacuum or gas-filled space, and where optionally one or more of the substrates or carrier panes, particularly one or more of the glazing sheets, have a low-emissivity (low-e) coating. The laminated or adhesive materials may include, for example, ionoplast, ethylene vinyl acetate (EVA), polyvinyl butyral (PVB), or polyurethane, for example thermoplastic polyurethane (TPU), or optically clear adhesives.

[0221] The switchable layer according to the invention may be arranged between substrates, in particular transparent substrates, which may comprise, preferably consist of, glass or a polymer.

[0222] Suitable glass materials include, for example, float glass or downdraw glass. The glass may also be subjected to pre-treatment steps such as tempering, toughening, and / or coating or sputtering. The glass may be, for example, soda-lime glass, borosilicate glass, or aluminosilicate glass. In some embodiments, alkali-free or chemically strengthened glass is used. Suitable alkali-free glasses include borosilicate or aluminosilicate glasses with low or even no alkali content in the glass recipe. Such glasses are available, for example, from Corning under the trade names Eagle 2000 glass or EAGLE XG Slim glass, and from Schott under the trade names AF32 or BOROFLOAT. Suitable chemically strengthened glasses are available, for example, from Corning under the trade name Gorilla, and from Asahi Glass Corporation (AGC) under the trade name Dragontrail.

[0223] Suitable polymeric materials include, for example, 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.

[0224] Preferably, an alignment layer is used in the device according to the invention, where the alignment layer can be any desired layer known to the skilled person for this purpose. Preferred is a polyimide layer, particularly preferably a layer comprising rubbed polyimide. In one embodiment, planar alignment is provided, where more preferably a slight pretilt angle may be set. In an alternative embodiment, homotropic alignment is provided, where more preferably a high pretilt angle is set.

[0225] In a preferred embodiment, the device according to the invention is a component of a window, more preferably a window component comprising at least one glass surface, most especially preferably a component of an insulating glazing unit.

[0226] The window elements may be suitably assembled into the window, for example by lamination or gluing, preferably by lamination to the window frame or glazing unit, for example using an optically clear adhesive. In an embodiment, the window element, particularly or only the window, includes first and second switchable layers as switchable layers.

[0227] In an alternative embodiment, in addition to the first and second switchable layers, the multilayer arrangement may also comprise one or more further switchable layers. In a specific embodiment, the multilayer arrangement contains a third switchable layer, which is switchable between an optically transparent state and a scattering state. In this case, this switchable layer of scattering type preferably contains a liquid crystal medium with a so-called polymer stabilized cholesteric texture (PSCT).

[0228] A window is taken here to mean a structure, especially in a building, car, commercial vehicle, boat, train, aircraft, etc., that includes a frame and at least one substrate or pane, e.g., a plastic substrate or glass pane, surrounded by the frame. In a preferred embodiment, especially for architectural applications, the window preferably includes an insulating frame and two or more panes, i.e., multipane insulating glass.

[0229] According to a preferred embodiment, the device according to the invention is applied directly to the glass surface of the window, for example by lamination, especially preferably in the gap between two panes of a multi-pane insulating glass.

[0230] The window element according to the invention, or the window in which it may be incorporated (for example arranged) as a switchable glazing unit, 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 the passage of light having a wavelength below 350 nm, preferably extending down to below 360 nm, and even more preferably extending down to below 380 nm, or that allow the passage of said light only to a very small extent. In addition, a low-emissivity (low-e) coating may preferably be applied to one or more of the sheets.

[0231] The window, and particularly the window element, may also include one or more anti-reflective layers or coatings. In cases where a laminate layer is present, it is preferred that a UV blocking laminate layer is used, where preferably the laminate faces the light source.

[0232] The window may be part of a building, a vessel, a vehicle, or another substantially enclosed space. The use of window elements for interior spaces that are subject to strong and / or strongly fluctuating solar radiation from the exterior space is particularly preferred.

[0233] In the present invention, and in particular in the following examples, the structures of the mesogenic compounds are designated using abbreviations, also called acronyms. In these acronyms, the chemical formulae are abbreviated as follows, using the tables A to C below: 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-1represents a linear alkyl or alkenyl, preferably 1-E-alkenyl, each with n, m and l C atoms, respectively. Table A lists the codes used for the ring elements of the core structure of the compounds, while Table B shows the linking groups. Table C gives the meaning of the codes for the left- or right-hand end groups. The initial letter consists of the code for the ring element with the optional linking group, followed by the first hyphen, the code for the left-hand end group, the second hyphen and the code for the right-hand end group. Table D shows exemplary structures of compounds together with their respective abbreviations.

[0234] Table A: Ring elements [Table A-1]

[0235] [Table A-2]

[0236] [Table A-3]

[0237] Table B: Linking groups [Table B]

[0238] Table C: End groups [Table C-1]

[0239] [Table C-2] where n and m each represent an integer, and the three dots "..." are substitutes for other abbreviations from this table.

[0240] The following table shows exemplary structures together with their respective abbreviations. These are presented to illustrate the meaning of the abbreviation rules. They also represent compounds which may be preferably used.

[0241] Table D: Exemplary Structures [Table D-1]

[0242] [Table D-2]

[0243] [Table D-3]

[0244] [Table D-4]

[0245] [Table D-5]

[0246] [Table D-6]

[0247] [Table D-7]

[0248] [Table D-8]

[0249] [Table D-9]

[0250] [Table D-10]

[0251] [Table D-11]

[0252] [Table D-12]

[0253] [Table D-13]

[0254] [Table D-14]

[0255] [Table D-15]

[0256] [Table D-16]

[0257] [Table D-17] In the formula, n, m, and l preferably each independently represent 1 to 9, more preferably 1 to 7.

[0258] The following table shows exemplary compounds which may be used as stabilizers in the media according to the invention. Table E Table E shows possible stabilizers which can be added to the LC medium according to the invention, where n represents an integer from 1 to 12, preferably 1, 2, 3, 4, 5, 6, 7 or 8. [Table E-1]

[0259] [Table E-2]

[0260] [Table E-3]

[0261] [Table E-4]

[0262] [Table E-5]

[0263] [Table E-6]

[0264] The LC medium preferably comprises 0 to 10% by weight, in particular 1 ppm to 5% by weight, especially preferably 1 ppm to 1% by weight, of a stabilizer.

[0265] Table F below shows exemplary compounds which may preferably be used as chiral dopants in the mesogenic media according to the present invention. Table F [Table F-1]

[0266] [Table F-2]

[0267] [Table F-3]

[0268] In a preferred embodiment of the invention, the mesogenic medium comprises one or more compounds selected from the compounds shown in Table F.

[0269] The mesogenic medium according to the invention preferably comprises two or more, preferably four or more compounds selected from the compounds shown in Tables D to F above. In one embodiment, the LC medium according to the invention preferably comprises 3 or more, more preferably 5 or more, compounds as shown in Table D.

[0270] The liquid crystal medium according to the invention preferably comprises 4 or more, more preferably 6 or more, even more preferably 7 or more, especially preferably 8 or more compounds selected from the group of compounds of table D, preferably compounds of 3 or more different formulae selected from the group of formulae of table D. It is especially preferred that the medium additionally contains 1, 2 or more compounds selected from the group of formulae of table E.

[0271] 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. The examples and modifications or other equivalents thereof will be apparent to those of skill in the art in light of this disclosure.

[0272] However, the physical properties and compositions given below are illustrative of what properties can be achieved and to what extent they can be modified. In particular, the combinations of various properties that can be preferably achieved are thus well defined.

[0273] example In the example, V o represents the threshold voltage, capacitive [V] at 20°C, n e represents the extraordinary refractive index at 20° C. and 589 nm, n o represents the ordinary refractive index at 20° C. and 589 nm, Δn represents the optical anisotropy at 20° C. and 589 nm; ε || represents the dielectric constant parallel to the director at 20°C and 1 kHz, ε ⊥ is the dielectric constant perpendicular to the director at 20°C and 1 kHz, Δε denotes the dielectric anisotropy at 20 ° C and 1 kHz, cl.p., T(N,I) represents the clearing point [℃], γ1 represents the rotational viscosity measured at 20°C [mPa s] and is determined by the rotation method in a magnetic field. K1 is the elastic constant, the "splay" deformation at 20°C [pN], K2 is the elastic constant, or "twist" deformation, at 20°C [pN]. K3 represents the elastic constant, the "bend" deformation at 20°C [pN].

[0274] The term "threshold voltage" according to the present invention relates to the capacitive threshold (V0), unless explicitly indicated otherwise. In the examples, as is generally customary, the optical threshold is also determined at a relative contrast of 10% (V 10 ) can also be indicated. Liquid crystal mixtures and composite systems are realized with compositions and properties as given below. Their properties and optical performances are investigated.

[0275] Reference example 1 A liquid crystal based mixture B-1 was prepared and characterized in terms of its general physical properties, having the composition and properties as indicated in the table below. [Table 1]

[0276] Reference example 2 A liquid crystal based mixture B-2 was prepared and characterized in terms of its general physical properties, having the composition and properties as indicated in the table below. [Table 2]

[0277] Host mixture H-2 is 99.97% mixture B-2 with 0.03% of the formula [ka] and a compound represented by the formula:

[0278] Comparative Example 1 Mixture M-1 was prepared by mixing 95.935% of mixture B-1 as described in Reference Example 1 with 0.050% of compound ST-1 as described in Reference Example 2 above, 0.070% of chiral dopant S-811 available from Merck KGaA, Darmstadt, Germany and shown in Table F above, 0.408% of the compound of formula DD-1 [ka] 0.837% of the compound represented by the formula DD-2 [ka] 0.707% of the compound represented by the formula DD-3 [ka] 0.589% of the compound represented by the formula DD-4 [ka] and 1.404% of the compound represented by the formula DD-5 [ka] The compound is prepared by mixing with a compound represented by the formula:

[0279] Mixture M-1 is filled into two TN cells each having two glass substrates (alkali-free glass, 0.7 mm thick) with ITO electrodes (sheet resistance 100 ohms / square) and polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar, TN, 90° twist), where the cell gap is 7.8 μm, and the filling port is sealed. Electrical wiring is applied to the cells by soldering. Both TN cells have a counterclockwise twist.

[0280] The two dye-doped TN cells are placed one after the other into a double cell using an optically clear adhesive. The resulting dual cell, with two switchable layers, exhibits a dark state of 6.5% transmission and a bright state of 45.5% transmission.

[0281] Example 1 Mixture M-2 is prepared according to mixture M-1 as described in Comparative Example 1, except that instead of S-811, 0.070% of chiral dopant R-811, available from Merck KGaA, Darmstadt, Germany, and shown in Table F above, is used. Mixture M-1 as described in Comparative Example 1 is filled into TN cell 1 according to Comparative Example 1. The TN cell 1 has a counterclockwise twist.

[0282] Mixture M-2 was filled into a TN cell 2 with two alkali-free glass substrates (0.7 mm thick) with an ITO electrode (sheet resistance 100 ohms / square) as well as a polyimide alignment layer (AL-1054 from Japan Synthetic Rubber, planar, clockwise TN), where the cell gap is 7.8 μm. The TN cell 2 has a clockwise twist. The two dye-doped TN cells 1 and 2 are sequentially placed into a double cell using an optically clear adhesive.

[0283] The resulting dual cell, with two switchable layers, exhibits a dark state of 5.4% transmission and a bright state of 45.5% transmission. Compared to the dual cell of Comparative Example 1, which is identical except for the twist sense of the second switchable layer, the dual cell, having two optical cells with opposite twist senses, exhibits an improved dark state. The dual cell also exhibits excellent behavior in terms of contrast and chromaticity coordinates over a wide range of viewing angles.

[0284] Comparative Example 2 Mixture M-3 is prepared by mixing 96.005% mixture B-1 as described in Reference Example 1 with 0.050% compound ST-1 as described in Reference Example 2 above, 0.537% chiral dopant S-811, 0.408% compound represented by formula DD-1 as described in Comparative Example 1, 0.837% compound represented by formula DD-2 as described in Comparative Example 1, 0.707% compound represented by formula DD-3 as described in Comparative Example 1, 0.589% compound represented by formula DD-4 as described in Comparative Example 1, and 1.404% compound represented by formula DD-5 as described in Comparative Example 1. Mixture M-3 was filled into two STN cells (180° twist) with two glass substrates each, together with ITO electrodes as well as a polyimide alignment layer, where the cell gap is 7.7 μm.

[0285] Both STN cells have a counterclockwise twist. The two dye-doped TN cells are placed one after the other into a double cell using an optically clear adhesive. The resulting dual cell, with two switchable layers, exhibits a dark state of 8.3% transmission and a bright state of 47.1% transmission.

[0286] Example 2 Mixture M-4 is prepared according to mixture M-3 as described in Comparative Example 2, but using 0.537% of the chiral dopant R-811 instead of S-811. Mixture M-3 described in Comparative Example 2 is filled into STN cell 1 (180° twist, cell gap 7.7 μm).

[0287] The STN cell 1 has a counterclockwise twist. Mixture M-4 is filled into STN cell 2 (180° twist, cell gap 7.7 μm). The STN cell 2 has a clockwise twist.

[0288] The two dye-doped TN cells 1 and 2 are sequentially placed into a double cell using an optically clear adhesive. The resulting dual cell, with two switchable layers, exhibits a dark state of 5.4% transmission and a bright state of 47.1% transmission.

[0289] Compared to the dual cell of Comparative Example 2, which is identical except for the twist sense of the second switchable layer, the dual cell, having two optical cells with opposite twist senses, exhibits an improved dark state. The dual cell also exhibits excellent behavior in terms of contrast and chromaticity coordinates over a wide range of viewing angles.

[0290] Example 3 Mixture M-5 was prepared by mixing 90.128% of mixture H-2 as described in Reference Example 2 with 1.160% of a compound represented by formula DD-1, 1.919% of a compound represented by formula DD-2, 1.800% of a compound represented by formula DD-3, 0.853% of a compound represented by formula DD-4, 0.730% of a compound represented by formula DD-5, 1.300% of a compound represented by formula DD-6, [ka] and 2.110% of the compound represented by the formula DD-7 [ka] The compound is prepared by mixing with a compound represented by the formula:

[0291] Mixture M-5-1 is prepared by mixing 99.236% of mixture M-5 with 0.764% of the chiral dopant S-811. Mixture M-5-2 is prepared by mixing 99.236% of mixture M-5 with 0.764% of chiral dopant R-811.

[0292] Mixture M-5-1 is filled into the first switchable layer of a VA-STN dual cell, and Mixture M-5-2 is filled into the second switchable layer of the same dual cell. The dual cell exhibits excellent dark state, favorable transmission range, and excellent viewing angle performance.

[0293] Example 4 Mixture M-6-1 was prepared by mixing 98.877% of mixture B-1 as described in Reference Example 1 with 0.470% of chiral dopant R-5011, 0.129% of phenylalanine, 0.20% of phenylalanine, 0.25% of phenylalanine, 0.17% of phenylalanine, 0.26% of phenylalanine, 0.27% of phenylalanine, 0.31% of phenylalanine, 0.32% of phenylalanine, 0.470% of phenylalanine, 0.26% of phenylalanine, 0.32% of phenylalanine, 0.27 ...32% [ka] 0.244% of the compound represented by the formula DD-9 [ka] and 0.280% of the compound represented by the formula DD-10 [ka] The compound is prepared by mixing with a compound represented by the formula:

[0294] Mixture M-6-2 is prepared according to mixture M-6-1, but using, instead of R-5011, the chiral dopant S-5011 available from Merck KGaA, Darmstadt, Germany and shown in Table F above. The series of mixtures M-6-1 and M-6-2 are used in a window element comprising a layer arrangement comprising two optical cells, where M-6-1 is used in the switchable layer of the first cell and M-6-2 is used in the switchable layer of the second cell.

Claims

1. a window element comprising a multilayer arrangement for regulating the passage of light and operable in and electrically switchable between a light state and a dark state; wherein the multi-layer arrangement comprises a first switchable layer and a second switchable layer, each of said layers containing a liquid crystalline medium comprising one or more dichroic dyes and optionally one or more chiral compounds, wherein in one of said states the first switchable layer and the second switchable layer have a twisted nematic or supertwisted nematic configuration; and The window element, wherein the twist direction of one of the first and second switchable layers is clockwise and the twist direction of the other switchable layer is counterclockwise.

2. the liquid-crystalline medium contained in the first switchable layer and the liquid-crystalline medium contained in the second switchable layer each comprise a chiral dopant, preferably in a concentration of 0.01% to 5% by weight, Window element according to claim 1, wherein the respective chiral dopants are stereoisomers, in particular enantiomers, of one another.

3. For each of the first and second switchable layers, the following relationships: d * Δn<3.0μm where d is the respective thickness of each of the switchable layers and Δn is the optical anisotropy of the respective liquid crystal medium contained in each of the switchable layers, is applied, 3. A window element according to claim 1 or 2, wherein preferably d*Δn<2.0 μm, and more preferably d*Δn<1.5 μm.

4. the pitch of the first switchable layer differs from the pitch of the second switchable layer by no more than 25%, preferably no more than 10%, and 3. A window element according to claim 1 or 2, wherein the pitch of the first switchable layer is the same as the pitch of the second switchable layer.

5. Multi-layer arrangement, in this order - first transparent base material, - first electrode layer, - a first alignment layer, - a first switchable layer; - a second alignment layer, - second electrode layer, - second transparent base material, - optionally a bonding, adhesive or laminating layer, - third transparent base material, - third electrode layer, - the third alignment layer, - a second switchable layer, - 4th alignment layer, - a fourth electrode layer, and - 4th transparent base material 3. A window element according to claim 1 or 2, comprising:

6. Multi-layer arrangement, in this order - first transparent base material, - first electrode layer, - a first alignment layer, - a first switchable layer; - a second alignment layer, - second electrode layer, - second transparent base material, - third electrode layer, - the third alignment layer, - a second switchable layer, - 4th alignment layer, - a fourth electrode layer, and - Third transparent base material Including, wherein a second alignment layer and a second electrode layer are disposed on a first surface of a second transparent substrate; and 3. A window element according to claim 1 or 2, wherein the third electrode layer and the third alignment layer are disposed on the second surface of the second transparent substrate.

7. the first, second, third, and fourth alignment layers comprise polyimide, preferably made from rubbed polyimide; and More preferably still, the rubbing directions of the second and third alignment layers are perpendicular to each other.

8. 3. A window element according to claim 1, wherein the liquid-crystalline medium contained in the first switchable layer and the liquid-crystalline medium contained in the second switchable layer each have a clearing point of at least 80°C.

9. 3. A window element according to claim 1, wherein the liquid-crystalline medium contained in the first switchable layer and the liquid-crystalline medium contained in the second switchable layer each have an absolute value of the dielectric anisotropy of 2.5 or more.

10. The liquid-crystalline medium contained in the first switchable layer and the liquid-crystalline medium contained in the second switchable layer each have a structure of formula I, based on the total content of the medium. 【Chemical 1】 and containing at least 15% by weight of one or more mesogenic compounds represented by the formula R 1 and R 2 are, independently of each other, F, Cl, CF 3 , OCF 3 and a straight or branched alkyl or alkoxy having 1 to 15 carbon atoms or a straight or branched alkenyl having 2 to 15 carbon atoms, wherein said alkyl / alkoxy / alkenyl is unsubstituted or is selected from CN or CF 3 or mono- or polysubstituted by halogen, wherein one or more CH 2 The groups may in each case independently be -O-, -S-, -CO-, -COO-, -OCO-, -OCOO-, -C≡C ... 【Chemistry 2】 may be replaced by A 11 teeth, 【Chemistry 3】 represents n represents 0 or 1, and A 21 , A 31 , and A 41 are mutually independent, 【Chemistry 4】 wherein L, at each occurrence, whether identical or different, is a halogen selected from F, Cl, and Br, or methyl; Window element according to claim 1 or 2.

11. The liquid-crystalline medium contained in the first switchable layer and the liquid-crystalline medium contained in the second switchable layer are of the formulae II and III, respectively. 【Chemistry 5】 and further comprising one or more mesogenic compounds selected from the group of compounds represented by the formula R 3 , R 4 , R 5 , and R 6 are mutually independent, F, CF 3 , OCF 3 , CN, and a straight or branched alkyl or alkoxy having 1 to 15 carbon atoms or a straight or branched alkenyl having 2 to 15 carbon atoms, wherein said alkyl / alkoxy / alkenyl is unsubstituted or is CN or CF 3 or mono- or polysubstituted by halogen, wherein one or more CH 2 The groups may in each case independently be -O-, -S-, -CO-, -COO-, -OCO-, -OCOO-, -C≡C ... 【Chemistry 6】 may be replaced by L 1 , L 2 , L 3 , L 4 , and L 5 represent, independently of one another, H or F, and L 6 and L 7 are, independently of one another, H or methyl, Window element according to claim 1 or 2.

12. 3. A window element according to claim 1 or 2, wherein the thickness of the first switchable layer and the second switchable layer is each 20 μm or less, preferably 15 μm or less, and in particular 10 μm or less.

13. 3. The window element according to claim 1, wherein the one or more dichroic dyes are selected from azo dyes, anthraquinones, methine compounds, azomethine compounds, merocyanine compounds, naphthoquinones, tetrazines, pyrromethene dyes, malononitrile dyes, rylenes, especially perylenes and terrylenes, thiadiazole dyes, thienothiadiazole dyes, benzothiadiazoles, thiadiazoloquinoxalines, pyrromethenes, and diketopyrrolopyrroles, preferably from azo dyes, anthraquinones, benzothiadiazoles, diketopyrrolopyrroles, rylenes, and thiadiazoloquinoxalines, and more preferably from azo dyes, benzothiadiazoles, and thiadiazoloquinoxalines.

14. 3. The window element of claim 1, wherein the window element does not include a polarizer.

15. 3. The window element according to claim 1, wherein the window element in the dark state has a visible light transmittance, determined in accordance with DIN EN 410, of less than 10%, preferably less than 5%, and more preferably less than 3%.

16. Use of a window element according to claim 1 or 2 in a window of a building or vehicle.

17. a first liquid-crystalline medium having a clearing point of at least 80° C. and comprising one or more dichroic dyes and stereoisomers, preferably R-isomers, of a chiral dopant, and a second liquid-crystalline medium having a clearing point of at least 80°C and comprising one or more dichroic dyes and another stereoisomer of the chiral dopant, preferably the S-isomer. A set of compositions comprising:

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