Liquid-crystalline medium

Abstract

To provide a liquid-crystalline medium.SOLUTION: The present invention relates to liquid-crystalline media comprising one or more mesogenic compounds of formula I described in this specification and one or more dichroic dyes, as well as switching elements and window elements containing the liquid-crystalline materials. Also, the present invention relates to the use of the liquid-crystalline media in devices for regulating the passage of energy from an outside space into an inside space, for example in switchable windows for solar energy control in smart buildings and vehicles with energy efficiency and improved comfort.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a liquid-crystalline medium comprising one or more mesogenic compounds of formula I and one or more dichroic dyes, as well as to a switching element and a window element comprising said liquid-crystalline medium. The present invention further relates to the use of said liquid-crystalline medium in devices for regulating the passage of energy from an exterior space to an interior space, for example in switching windows for solar energy control in smart buildings and vehicles, which can save energy and improve comfort. [Background technology]

[0002] A review article by R. Baetens et al. ("Properties, requirements and possibilities of smart windows for dynamic daylight and solar energy control in buildings: A state-of-the-art review," Solar Energy Materials & Solar Cells, Vol. 94, 2010, pp. 87-105) describes tintable smart windows. Smart windows can utilize various technologies to adjust light transmittance, such as electrochromic, liquid crystal, electrophoretic or suspended particle devices. Liquid crystal-based devices change the orientation of liquid crystal molecules by applying an electric field between two conductive electrodes, resulting in a change in transmittance.

[0003] Light intensity modulators such as optical shutters can be based on liquid crystals (LC). In principle, such optical shutters utilize the scattering or absorption of light.

[0004] Liquid crystals are used in particular as dielectrics in display devices, since the optical properties of such materials can be influenced by an applied voltage. Electro-optical devices based on liquid crystals are known to those skilled in the art and can be based on a variety of effects. Devices of this type include, for example, cells with dynamic scattering, DAP (deformation of aligned phases) cells, TN cells with a twisted nematic structure, STN ("supertwisted nematic") cells, SBE ("superbirefringence effect") cells, OMI ("optical mode interference") cells, and guest-host cells.

[0005] Devices based on the guest-host effect were first described by Heilmeier and Zanoni (GH Heilmeier et al., Appl. Phys. Lett., 1968, vol. 13, p. 91f (Non-Patent Document 2)) and have since found widespread use, primarily in LC display elements. In guest-host systems, the LC medium contains one or more dichroic dyes in addition to liquid crystals. Due to the directional dependence of absorption by the dye molecules, the transparency of the dye-doped liquid crystal to light can be adjusted when the dye changes its orientation along with the liquid crystal.

[0006] In addition to use in LC displays, devices of this type are used as switching elements to regulate the passage of light or energy, as described, for example, in WO 2009 / 141295 and WO 2010 / 1118422.

[0007] Various technical solutions have been proposed for devices that control the passage of energy from the exterior space to the interior space.

[0008] Some devices can reversibly change their light transmittance, allowing them to attenuate, dim, or color the intensity of incident light. Thus, such devices can be operated and switched between bright and dark states, i.e., states of relatively high and relatively low light transmittance.

[0009] In one possible mode of these devices, a liquid crystal medium in combination with one or more dichroic dyes as described above can be used in the switchable layer. By applying a voltage, the orientation of the dichroic dye molecules in these switchable layers can be changed. The direction-dependent absorption allows the transmittance of the switchable layer to be changed. Corresponding devices are described, for example, in WO 2009 / 141295.

[0010] Alternatively, such a change in transmission behavior can be achieved without applying a voltage by a temperature-induced transition of the liquid crystalline medium from an isotropic to a liquid crystalline state, as described, for example, in US Patent Application Publication No. 2010 / 0259698 A1.

[0011] WO 2009 / 141295 (Patent Document 1) and WO 2010 / 1118422 (Patent Document 2) describe liquid crystal media for guest-host optical devices, which contain cyanobiphenyl derivatives and one or more dichroic dyes. Rylene dyes are described for use in the above devices, for example, in WO 2009 / 141295 (Patent Document 1), WO 2013 / 004677 (Patent Document 4), and WO 2014 / 090373 (Patent Document 5).

[0012] The use of benzothiadiazoles in the above devices is described in WO 2014 / 187529 (Patent Document 6) and WO 2020 / 104563 (Patent Document 7). The use of thiadiazoloquinoxalines in the above devices is described in WO 2016 / 177449 (Patent Document 8) and WO 2020 / 104563 (Patent Document 7).

[0013] There is still a need in the art for liquid crystal media that have improved chemical, physical and electro-optical properties, especially for use in switching elements and window elements.In particular, there is a need in the art for liquid crystal media that contain dichroic dye compounds, which provide advantages in terms of device performance and reliability.Furthermore, there is a need in the art for switching devices that can be effectively dimmed with uniform appearance, and have suitable reliability and stability, especially for solar applications. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] International Publication No. 2009 / 141295 [Patent Document 2] International Publication No. 2010 / 1118422 [Patent Document 3] US Patent Publication No. 2010 / 0259698 [Patent Document 4] International Publication No. 2013 / 004677 [Patent Document 5] International Publication No. 2014 / 090373 [Patent Document 6] International Publication No. 2014 / 187529 [Patent Document 7] International Publication No. 2020 / 104563 [Patent Document 8] International Publication No. 2016 / 177449 [Patent Document 9] International Publication No. 2020 / 104563 [Non-patent literature]

[0015] [Non-Patent Document 1] A review article by R. Baetens et al. ("Properties, requirements and possibilities of smart windows for dynamic daylight and solar energy control in buildings: A state-of-the-art review"), Solar Energy Materials & Solar Cells, Vol. 94, 2010, pp. 87-105 [Non-patent document 2] G.H. Heilmeier et al., Appl. Phys. Lett., 1968, Vol. 13, p. 91f. Summary of the Invention [Problem to be solved by the invention]

[0016] It is therefore an object of the present invention to provide improved liquid-crystalline media which have a wide and stable liquid-crystalline phase range, are particularly suitable for guest-host applications and contribute advantageously to the effective and efficient performance of switching devices.

[0017] A further object is to provide a switching medium for electro-optical applications that enables particularly advantageous performance in devices for controlling the passage of energy from an external space to an internal space, in particular smart switching windows, e.g., in terms of contrast, appearance and phase behavior, reliability and stability. Further objects of the present invention will be readily apparent to those skilled in the art from the following detailed description. [Means for solving the problem]

[0018] These objects are solved by the subject matter defined in the independent claims, while preferred embodiments are set out in the respective dependent claims and are further explained below.

[0019] The present invention provides, inter alia, the following, including main aspects, preferred embodiments and particular features, which, either alone or in combination, contribute to solving the above-mentioned objects and ultimately provide further advantages:

[0020] A first aspect of the present invention provides a liquid-crystalline medium comprising one or more compounds of formula I and one or more dichroic dyes, wherein the one or more dichroic dyes are present in an amount of at least 1% by weight, based on the total components of the medium. [ka] During the ceremony, R 1 represents a linear alkyl having 8 to 20 C atoms or a branched or cyclic alkyl having 3 to 20 C atoms, in particular a branched or cyclic alkyl having 8 to 20 C atoms, in which one or more non-adjacent CH groups may be replaced independently by O, and in which one or more H atoms may be replaced by F, Cl or Br, preferably a linear alkyl having 8 to 16 C atoms, more preferably a linear alkyl having 8 to 12 C atoms, and L 1 represents H, F, Cl or CH3, preferably H or F, more preferably H.

[0021] Preferably, the one or more dichroic dyes are contained in the medium in a total amount of 2% by weight or more, more preferably 3% by weight or more, even more preferably 4% by weight or more, even more preferably 5% by weight or more, and particularly preferably 7.5% by weight or more.

[0022] The total concentration of one or more dichroic dyes in the medium is preferably in the range of 1.5% by weight to 20% by weight, more preferably 2.5% by weight to 15% by weight, even more preferably 3% by weight to 12.5% by weight, even more preferably 4% by weight to 10% by weight, and particularly preferably 6% by weight to 8% by weight.

[0023] It has surprisingly been found that the inclusion of one or more compounds of formula I as described hereinabove and hereinafter in a liquid crystal medium containing one or more dichroic dyes in an amount of at least 1% by weight, or even significantly higher, results in a modulation medium that exhibits beneficial performance in optical and electro-optical applications, in particular in guest-host applications such as dimmable smart windows.

[0024] In addition to providing suitable light and temperature stability, including low temperature stability and stability at high operating temperatures, the media according to the present invention can advantageously contribute to effective and efficient device performance, e.g., in terms of fast and uniform switching, uniform appearance and a favorable aesthetic impression in the switching state, and favorable reliability.

[0025] In some applications it may be desirable to provide a switching element which exhibits a high contrast between the bright and dark states and which, optionally or additionally, can achieve a very effective dark state with minimal transmittance. In this respect, the liquid-crystalline media according to the invention are advantageous in that higher dye concentrations can be used, and / or a single switching layer is sufficient, and / or a smaller switching layer thickness or cell gap is sufficient to achieve the desired contrast and effective dark state.

[0026] It has thus been found that the liquid crystal media according to the invention are capable of providing stable, reliable and highly effective switching media for electro-optical applications.

[0027] Thus, in a further aspect of the present invention there is provided a switching element comprising a switching layer comprising a liquid crystal medium as described hereinabove and below, the switching layer being arranged between two substrates and an alignment layer being provided in direct contact with the liquid crystal medium.

[0028] It has been found that the media of the present invention and switching elements comprising this media in a switching layer can exhibit beneficial performance in guest-host applications, where the dye-doped mesogenic media can exhibit an appropriately wide and stable liquid crystal phase range, particularly favorable low temperature stability.

[0029] Thus, the media and switching elements according to the present invention can provide advantages in terms of performance and reliability in devices that regulate the passage of energy from an exterior space to an interior space, particularly in dimmable smart windows.

[0030] Therefore, in a further aspect there is provided a window element comprising a liquid crystal medium according to the invention or a switching element according to the invention as described herein.

[0031] The liquid crystal windows according to the invention can be used for sustainable glazing applications in buildings and vehicles, saving energy, in particular for lighting, cooling and / or heating, and having a positive impact on the life cycle, e.g. in terms of maintenance, as well as improving thermal and visual comfort.

[0032] The invention will now be illustrated, without limiting it, by detailed descriptions of aspects, embodiments and specific features, with particular embodiments being described in more detail.

[0033] The present invention relates to devices for controlling the passage of energy from an exterior space to an interior space, particularly devices for controlling the passage of energy, particularly light, especially sunlight, through areas located within structures with relatively low energy transmittance, such as walls. Energy can therefore pass through, for example, openings in the walls, particularly glass areas. These devices are therefore preferably arranged as components of windows, for example, insulating glass units.

[0034] The controlled passage of energy occurs from an exterior space, preferably an environment exposed to direct or indirect sunlight, to an interior space, such as a building, vehicle, or other unit that is substantially shielded from the environment.

[0035] As used herein, the term "energy" refers to electromagnetic radiation, particularly in the UV-A, VIS, and NIR regions. It particularly refers to radiation that is not absorbed, or only to a very small extent, by materials commonly used for windows, such as glass. In this specification, the UV-A region refers to the wavelength range of 320 nm to 380 nm, the VIS region refers to the wavelength range of 380 nm to 780 nm, and the NIR region refers to the wavelength range of 780 nm to 2000 nm. Similarly, the term "light" generally refers to electromagnetic radiation having a wavelength of 320 to 2000 nm, particularly 380 to 780 nm.

[0036] In this specification, "dichroic dye" is understood to mean a light-absorbing compound whose absorption properties change depending on the orientation of the compound with respect to the polarization direction of light. The dichroic dye compounds according to the present invention typically have an elongated shape, i.e., the compound is significantly longer along one spatial direction, i.e., the longitudinal direction, than along the other two spatial directions.

[0037] The term "organic group" means a carbon or hydrocarbon group.

[0038] The term "carbon group" refers to a monovalent or polyvalent organic group containing at least one carbon atom, which group contains zero or more other atoms, such as, for example, -C≡C-, or optionally contains one or more other atoms, such as N, O, S, P, Si, Se, As, Te, or Ge (e.g., carbonyl).

[0039] The term "hydrocarbon group" refers to a carbon group further containing one or more H atoms and optionally one or more heteroatoms, such as N, O, S, P, Si, Se, As, Te, or Ge.

[0040] "Halogen" refers to F, Cl, Br or I, preferably F or Cl.

[0041] The carbon or hydrocarbon group may be saturated or unsaturated. Unsaturated groups may be, for example, aryl, alkenyl, or alkynyl groups. The carbon or hydrocarbon group containing three or more atoms may be linear, branched, and / or cyclic, and may contain spiro-bonded or fused rings.

[0042] Terms such as "alkyl," "aryl," and "heteroaryl" also include multivalent radicals such as alkylene, arylene, and heteroarylene.

[0043] The term "aryl" refers to an aromatic carbon group or group derived therefrom. The term "heteroaryl" refers to an "aryl" as defined above that contains one or more heteroatoms.

[0044] Preferred carbon and hydrocarbon groups are optionally substituted alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy and alkoxycarbonyloxy having 1 to 40, preferably 1 to 25, particularly preferably 1 to 18 carbon atoms; optionally substituted aryl or aryloxy having 6 to 40, preferably 6 to 25 carbon atoms; or optionally substituted alkylaryl, arylalkyl, alkylaryloxy, arylalkyloxy, arylcarbonyl, aryloxycarbonyl, arylcarbonyloxy and aryloxycarbonyloxy having 6 to 40, preferably 6 to 25 carbon atoms.

[0045] More preferred carbon and hydrocarbon groups are C1-C 40 Alkyl, C2-C 40 Alkenyl, C2-C 40 Alkynyl, C3-C 40 Allyl, C4~C 40 Alkyldienyl, C4-C 40Polyenyl, C6-C 40 Aryl, C6-C 40 Alkylaryl, C6-C 40 Aryl alkyl, C6-C 40 Alkylaryloxy, C6-C 40 Arylalkyloxy, C2-C 40 Heteroaryl, C4-C 40 Cycloalkyl, C4-C 40 Cycloalkenyl, etc. In particular, C1-C 22 Alkyl, C2-C 22 Alkenyl, C2-C 22 Alkynyl, C3-C 22 Allyl, C4~C 22 Alkyldienyl, C6-C 12 Aryl, C6-C 20 Aryl alkyl, and C2-C 20 Heteroaryl is preferred.

[0046] Further preferred carbon and hydrocarbon groups are linear, branched or cyclic alkyl groups having 1 to 40, preferably 1 to 25, carbon atoms, which are unsubstituted or mono- or polysubstituted by F, Cl, Br, I or CN, and in which one or more non-adjacent CH groups are each, independently of one another, -C(R Z )=C(R Z )-, -C≡C-, -N(R Z )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-.

[0047] R Zpreferably represents H, halogen, or a linear, branched, or cyclic alkyl chain having 1 to 25 carbon atoms, wherein, further, one or more non-adjacent carbon atoms may be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, or -O-CO-O-, and one or more H atoms may be replaced by fluorine, an optionally substituted aryl or aryloxy group having 6 to 40 carbon atoms, or an optionally substituted heteroaryl or heteroaryloxy group having 2 to 40 carbon atoms.

[0048] Preferred alkyl groups are, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, 2-methylbutyl, n-pentyl, s-pentyl, cyclopentyl, n-hexyl, cyclohexyl, 2-ethylhexyl, n-heptyl, cycloheptyl, n-octyl, cyclooctyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, trifluoromethyl, perfluoro-n-butyl, 2,2,2-trifluoroethyl, perfluorooctyl, perfluorohexyl, and the like.

[0049] Preferred alkenyl groups are, for example, ethenyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl, cyclooctenyl, and the like.

[0050] Preferred alkynyl groups are, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl, octynyl, and the like.

[0051] Preferred alkoxy groups include, for example, methoxy, ethoxy, 2-methoxyethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy, 2-methylbutoxy, n-pentoxy, n-hexoxy, n-heptoxy, n-octoxy, n-nonoxy, n-decoxy, n-undecoxy, and n-dodecoxy.

[0052] Preferred amino groups are, for example, dimethylamino, methylamino, methylphenylamino, phenylamino, and the like.

[0053] Aryl and heteroaryl groups can be monocyclic or polycyclic, i.e., they can have one ring (such as phenyl) or two or more rings, and the rings can be fused (such as naphthyl) or covalently bonded (such as biphenyl), or can include a combination of fused and linked rings.Heteroaryl groups preferably contain one or more heteroatoms selected from O, N, S, and Se.This type of ring system can also contain individual non-conjugated units, such as in the case of a fluorene basic structure.

[0054] In particular, monocyclic, bicyclic, or polycyclic aryl groups having 6 to 50 carbon atoms and monocyclic, bicyclic, or polycyclic heteroaryl groups having 5 to 50 carbon atoms are preferred, which optionally contain fused rings and are optionally substituted.Furthermore, 5-, 6-, or 7-membered aryl and heteroaryl groups are preferred, where one or more CH groups may be replaced by N, S, or O so that the O and / or S atoms are not directly bonded to each other.This type of ring system may also contain individual non-conjugated units, such as in the case of a fluorene basic structure.

[0055] Preferred aryl groups are, for example, benzene, biphenyl, terphenyl, [1,1':3',1"]terphenyl, naphthalene, anthracene, binaphthyl, phenanthrene, pyrene, dihydropyrene, chrysene, perylene, tetracene, pentacene, benzopyrene, fluorene, indene, indenofluorene, spirobifluorene, and the like.

[0056] Preferred heteroaryl groups are, for example, five-membered rings such as pyrrole, pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, tetrazole, furan, thiophene, selenophene, oxazole, isoxazole, 1,2-thiazole, 1,3-thiazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole. , 1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole, 1,3,4-thiadiazole, 6-membered rings such as pyridine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, 1,2,4-triazine, 1,2,3-triazine, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine, 1,2,3,5-tetrazine, or fused groups such as indole, isoindole, indolizine, indazole, benzimidazole, benzotriazole, purine, naphthimidazole, phenanthrimidazole, pyridoimidazole, pyrazineimidazole, quinoxalineimidazole, benzoxazole, naphthoxazole, anthroxazole, Heteroaryl groups include thiazole, phenanthroxazole, isoxazole, benzothiazole, benzofuran, isobenzofuran, dibenzofuran, quinoline, isoquinoline, pteridine, benzo-5,6-quinoline, benzo-6,7-quinoline, benzo-7,8-quinoline, benzisoquinoline, acridine, phenothiazine, phenoxazine, benzopyridazine, benzopyrimidine, quinoxaline, phenazine, naphthyridine, azacarbazole, benzocarboline, phenanthridine, phenanthroline, thieno[2,3b]thiophene, thieno[3,2b]thiophene, dithienothiophene, dihydrothieno[3,4-b]-1,4-dioxine, isobenzothiophene, dibenzothiophene, benzothiadiazothiophene, or combinations of these groups. Heteroaryl groups may be substituted with alkyl, alkoxy, thioalkyl, fluorine, fluoroalkyl, or further aryl or heteroaryl groups.

[0057] (Non-aromatic) alicyclic and heterocyclic groups include both saturated rings, i.e., those containing only single bonds, and partially unsaturated rings, i.e., those which may contain multiple bonds. Heterocyclic rings preferably contain one or more heteroatoms selected from Si, O, N, S and Se.

[0058] (Non-aromatic) alicyclic and heterocyclic groups may be monocyclic, i.e., containing only one ring (e.g., cyclohexane), or polycyclic, i.e., containing multiple rings (e.g., decahydronaphthalene or bicyclooctane). Saturated groups are particularly preferred. Furthermore, monocyclic, bicyclic, or tricyclic groups having 3 to 25 carbon atoms are preferred, which groups optionally contain fused rings and are optionally substituted. Furthermore, 5-, 6-, 7-, or 8-membered carbocyclic groups are preferred, in which, further, one or more carbon atoms may be replaced by Si, and / or one or more CH groups may be replaced by N, and / or one or more non-adjacent CH groups may be replaced by -O- and / or -S-.

[0059] Preferred alicyclic and heterocyclic groups are, for example, 5-membered ring groups such as cyclopentane, tetrahydrofuran, tetrahydrothiofuran, pyrrolidine, 6-membered ring groups such as cyclohexane, silynan, cyclohexene, tetrahydropyran, tetrahydrothiopyran, 1,3-dioxane, 1,3-dithiane, piperidine, 7-membered ring groups such as cycloheptane, and fused groups such as tetrahydronaphthalene, decahydronaphthalene, indane, bicyclo[1.1.1]-pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl, octahydro-4,7-methanoindan-2,5-diyl.

[0060] The aryl, heteroaryl, carbon and hydrocarbon groups optionally have one or more substituents, preferably silyl, sulfo, sulfonyl, formyl, amine, imine, nitrile, mercapto, nitro, halogen, C1-C 12 Alkyl, C6-C 12Aryl, C1-C 12 It is selected from the group comprising alkoxy, hydroxyl, or a combination of these groups.

[0061] Preferred substituents are, for example, solubility-promoting groups such as alkyl or alkoxy, electron-withdrawing groups such as fluorine, nitro or nitrile, or substituents for increasing the glass transition temperature (Tg) of the polymer, especially bulky groups such as t-butyl or optionally substituted aryl groups.

[0062] Preferred substituents are, for example, F, Cl, Br, I, —CN, —NO2, —NCO, —NCS, —OCN, —SCN, —C(═O)N(R z )2, -C(=O)Y 1 , -C(=O)R z , -C(=O)OR x , -N(R z )2, where R z has the above meaning, and Y 1 denotes halogen, optionally substituted silyl or aryl having 6 to 40, preferably 6 to 20, C atoms, and linear or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25 carbon atoms, in which one or more H atoms may optionally be replaced by F or Cl.

[0063] More preferred substituents include, for example, F, Cl, CN, NO2, CH3, C2H5, OCH3, OC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF3, OCF3, OCHF2, OC2F5, and also phenyl.

[0064] In this specification, the substituents represented by L in each occurrence are the same or different and are preferably F, Cl, CN, SCN, SF5, or linear or branched, in each case optionally fluorinated, alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy, or alkoxycarbonyloxy having 1 to 12 C atoms.

[0065] Preferably, in each occurrence, L, identical or different, denotes F or linear or branched, in each case optionally fluorinated, alkyl or alkoxy having 1 to 7 C atoms.

[0066] "Substituted silyl or aryl" preferably includes halogen, -CN, R y1 , -OR y1 , -CO-R y1 , -CO-OR y1 , -O-CO-R y1 or -O-CO-OR y1 (In the formula, R y1 means replaced by (which has the meaning given above).

[0067] In this specification, a 1,4-cyclohexylene ring and a 1,4-phenylene ring are represented as follows: [ka]

[0068] The cyclohexylene ring is a trans-1,4-cyclohexylene ring.

[0069] Unless otherwise specified, all concentrations herein are given as weight percent and are relative to the respective total mixture.

[0070] All temperatures are given in degrees Celsius (°C) and all temperature differences are given in degrees Celsius. All physical properties and physicochemical or electro-optical parameters are measured and given at a temperature of 20°C unless otherwise stated.

[0071] The liquid-crystalline media according to the invention comprise one or more compounds of formula I as defined above and below.

[0072] In Formula I, R 1 The group is preferably a linear alkyl having 8 to 12 C atoms, more preferably a linear alkyl having 8 to 10 C atoms. 1 The group is preferably H or CH3, more preferably H.

[0073] In one embodiment, the one or more compounds of formula I used according to the invention are selected from the group of compounds of formula Ii, I-ii and I-iii: [ka]

[0074] In the formula, R 1 has the meaning given for formula I above and preferably denotes a straight-chain alkyl having 8 to 16 C atoms, more preferably a straight-chain alkyl having 8 to 12 C atoms.

[0075] R 1 particularly preferably represents n-octyl, n-nonyl or n-decyl, more preferably n-octyl or n-nonyl.

[0076] In a preferred embodiment, the liquid crystal medium comprises one or more compounds of formula Ii, preferably two or more compounds of formula Ii, more preferably at least three compounds of formula Ii.

[0077] In a preferred embodiment, the one or more compounds of formula I used according to the present invention are selected from the compounds of formulae I-1 to I-12: [ka] [ka]

[0078] The liquid crystal medium preferably comprises one or more compounds of the formulae I-1, I-2, I-3, I-4 and I-5.

[0079] It is particularly preferred that the liquid-crystalline medium comprises one or more compounds of the formulae I-1, I-2 and I-3, more preferably two or more compounds of the formulae I-1, I-2 and I-3, in particular all three compounds of the formulae I-1, I-2 and I-3.

[0080] In a preferred embodiment, the liquid crystal medium comprises a compound of the formula I-1 and / or a compound of the formula I-2.

[0081] Preferably, the liquid crystal medium comprises compounds of the formulae I-1 and I-2.

[0082] In another embodiment the liquid crystal medium comprises a compound of formula I-2 and / or a compound of formula I-3.

[0083] The liquid-crystalline media according to the invention preferably contain one or more compounds of formula I, in particular of formulae Ii, I-ii and I-iii and I-1 to I-12, in a total amount of at least 1% by weight, more preferably at least 3% by weight, even more preferably at least 5% by weight, even more preferably at least 10% by weight, in particular at least 15% by weight. In one embodiment, the liquid-crystalline media according to the invention contain one or more compounds of formula I, in particular of formulae Ii, I-ii and I-iii and I-1 to I-12, in a total concentration in the range from 3% to 35% by weight, preferably from 5% to 30% by weight, more preferably from 10% to 25% by weight.

[0084] In embodiments in which the liquid crystal medium comprises two or more compounds of formula I, in particular compounds of formulae Ii, I-ii and I-iii and I-1 to I-12, each individual compound of formula I is preferably present in the medium in a concentration of at least 0.5% by weight, preferably at least 2.5% by weight, more preferably at least 5% by weight, even more preferably in the range from 1% to 15% by weight, especially in the range from 4% to 12% by weight.

[0085] A further aspect of the present invention provides one or more compounds of formula I, particularly formula Ii, wherein R 1 is selected from n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl and n-octadecyl, preferably from n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl and n-hexadecyl, in particular from n-decyl, n-undecyl and n-dodecyl. One or more compounds can be suitably used in the medium according to the invention.

[0086] In one embodiment, the medium further comprises a compound of formula II. [ka]

[0087] In another embodiment, the medium does not include a compound of formula II. [ka]

[0088] The liquid-crystalline media according to the invention can be advantageously provided both as media with a positive dielectric constant and as media with a negative dielectric constant.

[0089] In the above and below, Δε denotes the dielectric anisotropy, and Δε = ε ∥ -ε ⊥ The dielectric anisotropy Δε is preferably measured at 20° C. and 1 kHz.

[0090] In a preferred embodiment, the liquid-crystalline medium has a positive dielectric anisotropy Δε, in particular a dielectric anisotropy of +0.5 or more.

[0091] The liquid crystal medium preferably has a dielectric anisotropy Δε of +0.5 or more, more preferably +1.5 or more, and even more preferably +2.5 or more.The liquid crystal medium particularly preferably has a dielectric anisotropy Δε in the range of +1.5 to +20, more preferably +3.0 to +12, still more preferably +4.0 to +8.0, and particularly preferably +4.5 to +6.0.

[0092] In a preferred embodiment, the liquid crystal medium further comprises one or more compounds of the formula III. [ka]

[0093] During the ceremony, R 3 is an unsubstituted or halogenated linear alkyl or alkoxy group having 1 to 15 C atoms or an unsubstituted or halogenated branched alkyl or alkoxy group having 3 to 15 C atoms, in which one or more CH groups, independently of one another, are connected in such a way that O atoms are not directly linked to one another, [ka] optionally substituted by -C≡C-, -CF2O-, -CH=CH-, -O-, -CO-O- or -O-CO-; [ka] L 31 and L 32 are, independently of one another, H or F, Y 3 represents H or CH3, preferably H, X 3 represents a halogen, a halogenated alkyl or halogenated alkoxy having 1 to 3 C atoms, or a halogenated alkenyl or halogenated alkenyloxy having 2 or 3 C atoms, Z 3represents -CH2CH2-, -CF2CF2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CHO- or a single bond, preferably a single bond; n and o each independently represent 0 or 1;

[0094] The medium preferably comprises one or more compounds of formula III in a total amount of at least 5% by weight, more preferably at least 10% by weight, even more preferably at least 20% by weight, even more preferably at least 30% by weight, especially at least 40% by weight.

[0095] The compound of formula III is preferably selected from the group of compounds of formulae III-i to III-v: [ka]

[0096] In the formula, R 3 , L 31 , L 32 and X 3 have the meanings shown in formula III, and L 33 and L 34 are each independently H or F.

[0097] In one embodiment the liquid crystalline medium comprises one or more compounds of formula III-iv, preferably L 31 , L 32 and L 33 represents F, and L 34 is preferably H, and X 3 is preferably F, the total amount of which is preferably at least 2% by weight, more preferably at least 4% by weight, especially at least 6% by weight.

[0098] In a preferred embodiment, the one or more compounds of formula III are selected from one or more compounds of formula III-a: [ka]

[0099] In the formula, L 1 , L 2 and L 3 are each independently H or F, R 3 and X 3 has the meaning given in formula III.

[0100] In a particularly preferred embodiment, the liquid crystal medium comprises one or more compounds selected from the group of the compounds of the formulae III-a-1 and III-a-2: [ka]

[0101] During the ceremony, base R 3 has the meaning given in formula III.

[0102] The medium preferably contains one or more compounds of formula III-a, in particular of formula III-a-1 and III-a-2, in a total amount of at least 5% by weight, more preferably at least 10% by weight, even more preferably at least 15% by weight, even more preferably at least 20% by weight, and in particular at least 30% by weight.

[0103] In a preferred embodiment, the liquid crystal medium further comprises one or more compounds of formula IV. [ka]

[0104] During the ceremony, R 11 represents a linear alkyl group having 1 to 12 carbon atoms, a branched or cyclic alkyl group having 3 to 12 carbon atoms, or a linear alkenyl group having 2 to 12 carbon atoms, a branched alkenyl group having 3 to 12 carbon atoms, or a cyclic alkenyl group having 5 to 12 carbon atoms, in which one or more H atoms may be substituted by fluorine, and is preferably a linear alkyl group having 1 to 8 carbon atoms; R 12represents a linear alkyl group or alkoxy group having 1 to 12 carbon atoms, or a branched or cyclic alkyl group or alkoxy group having 3 to 12 carbon atoms, or a linear alkenyl group having 2 to 12 carbon atoms, a branched alkenyl group having 3 to 12 carbon atoms, or a cyclic alkenyl group having 5 to 12 carbon atoms, in which one or more H atoms may be substituted by fluorine, and is preferably a linear alkoxy group having 1 to 8 carbon atoms.

[0105] The medium preferably comprises one or more compounds of formula IV in a total amount of at least 2% by weight, more preferably at least 4% by weight, even more preferably at least 6% by weight, even more preferably at least 8% by weight, especially at least 10% by weight.

[0106] The compound of formula IV is preferably selected from the group of compounds of formulae IV-1 to IV-4, more preferably from the group of compounds of formula IV-2. [ka]

[0107] During the ceremony, alkyl and alkyl' independently represent alkyl having 1 to 7 carbon atoms, preferably 2 to 5 carbon atoms; alkoxy represents an alkoxy having 1 to 5 carbon atoms, preferably 2 to 4 carbon atoms; alkenyl represents an alkenyl group having 2 to 5 carbon atoms, preferably 2 to 4 carbon atoms, particularly preferably 2 carbon atoms; "Alkeny'" represents an alkenyl group having 2 to 5 carbon atoms, preferably 2 to 4 carbon atoms, and particularly preferably 2 to 3 carbon atoms.

[0108] In a particularly preferred embodiment, the medium comprises one or more compounds of formula IV-2 in a total amount of at least 2% by weight, more preferably at least 6% by weight, even more preferably at least 10% by weight, in particular at least 12% by weight.

[0109] In another preferred embodiment, the medium comprises a compound of formula IV-3, more preferably a compound designated CC-3-V, in a total amount of at least 2% by weight, more preferably at least 5% by weight, even more preferably at least 10% by weight, in particular at least 15% by weight.

[0110] In a preferred embodiment, the liquid crystal medium further comprises one or more compounds of formula V [ka]

[0111] In the formula, R 51 , R 52 are independently of one another alkyl having 1 to 7 C atoms, alkoxy having 1 to 7 C atoms, or alkoxyalkyl, alkenyl or alkenyloxy having 2 to 7 C atoms, [ka] Z 51 and Z 52 represent, independently of one another, -CH2CH2-, -C2O-, -CH=CH-, -C≡C-, -COO- or a single bond, preferably -COO- or a single bond, p is 1 or 2.

[0112] The compound of formula V is preferably selected from the group of compounds of formulae V-1 to V-7, preferably from the group of compounds of formulae V-1 and V-2. [ka]

[0113] In the formula, the group R 51 and R 52 has the meaning shown in formula V, and preferably each independently represents a straight-chain alkyl having 1 to 7 carbon atoms or an alkenyl having 2 to 7 carbon atoms.

[0114] The medium preferably contains one or more compounds of formula V, in particular of formulae V-1 and V-2, in a total amount of at least 2% by weight, more preferably at least 5% by weight, even more preferably at least 10% by weight, even more preferably at least 15% by weight, in particular at least 20% by weight.

[0115] In certain embodiments, the medium comprises one or more compounds of formula V-5, preferably R 51 is alkenyl having 2 to 7 C atoms, and R 52 is alkyl having 1 to 7 C atoms, more preferably methyl, and the total amount thereof is preferably 5% by weight or more, more preferably 10% by weight or more, even more preferably 15% by weight or more, even more preferably 20% by weight or more, in particular 25% by weight or more.

[0116] In a particular embodiment, the medium comprises the compound designated CCG-VF, preferably in an amount of 5% by weight or more, more preferably 10% by weight or more, in particular 15% by weight or more.

[0117] The liquid-crystalline medium preferably has an optical anisotropy Δn, measured in particular at a wavelength of 589 nm, of 0.04 or more, more preferably 0.06 or more, even more preferably 0.08 or more, even more preferably 0.10 or more.

[0118] In the above and below, Δn indicates the optical anisotropy, and Δn=n e -n o Preferably, the optical anisotropy Δn is measured at 20° C. and at a wavelength of 589 nm.

[0119] The liquid crystal medium preferably has an optical anisotropy in the range of 0.04 to 0.20, more preferably 0.06 to 0.15, and particularly preferably 0.08 to 0.12.

[0120] The media according to the present invention are particularly useful for guest-host applications such as dimmable smart windows, and the dye-doped liquid crystal media can exhibit an appropriately wide and stable liquid crystal phase range, particularly favorable low temperature stability.

[0121] The liquid-crystalline media according to the invention preferably have a clearing point of at least 70° C., more preferably at least 80° C., even more preferably at least 90° C., even more preferably at least 105° C., and particularly preferably at least 110° C. In one embodiment, the liquid-crystalline media according to the invention have a clearing point in the range from 70° C. to 170° C., preferably from 80° C. to 150° C.

[0122] Such a high clearing point can be beneficial in terms of the performance and reliability of devices using the liquid crystal medium. In particular, the medium can maintain its functional properties over a suitably wide temperature range and even at high temperatures. This is particularly advantageous for use in window elements to control solar transmission, especially when the window element is exposed to direct or prolonged sunlight. A high clearing point also contributes to good high order of the liquid crystal host molecules, and therefore the dichroic dye guest molecules, at typical operating temperatures, which can enhance the contrast between switching states.

[0123] The clearing point, particularly the phase transition temperature between the nematic and isotropic phases, can be measured and determined by well-known methods such as a Mettler oven, a hot stage under a polarizing microscope, or differential scanning calorimetry (DSC) analysis. According to the present invention, the clearing point is preferably determined using a Mettler oven.

[0124] The nematic phase of the medium according to the present invention preferably has a temperature range of at least -10° C. to 70° C. A wider nematic phase range is more preferred, particularly up to 85° C. or higher, more preferably at least -20° C. to 100° C. or higher, and particularly preferably 30° C. to 110° C. or higher.

[0125] The LC media according to the invention are preferably nematic liquid crystals.

[0126] The medium according to the present invention is prepared by conventional methods. Generally, the components are dissolved in each other and mixed, preferably at high temperature. Mixing is preferably carried out under an inert gas, for example, nitrogen or argon. Subsequently, one or more dyes are added, preferably at high temperature, more preferably at 40°C or higher, particularly preferably at 50°C or higher. Generally, the desired amount of a component used in a small amount is dissolved in the component that constitutes the main component. It is also possible to mix solutions of each component in an organic solvent, such as acetone, toluene, chloroform, or methanol, and then remove the solvent again after mixing, for example by distillation.

[0127] The present invention further relates to a method for producing the mesogenic medium according to the invention.

[0128] The invention further relates to the use of an LC medium comprising at least one dichroic dye in a guest-host liquid crystal device, in particular a window component or a display, in which the medium according to the invention is preferably provided in one or more switchable layers.

[0129] In a preferred embodiment, the device, in particular the window element, comprises only a single switching layer.

[0130] In another embodiment, the device, in particular the window element, comprises two switching layers, preferably arranged in a so-called double cell.

[0131] The invention further relates to the use of a mixture comprising a liquid-crystalline medium and one or more dichroic dyes as defined above in a device for controlling the passage of energy from an external space to an internal space.

[0132] The medium according to the invention comprises one or more dichroic dyes, especially in the minimum amounts mentioned above.

[0133] In this regard, the one or more dichroic dyes are preferably provided in an amount useful and effective to provide the desired contrast between switching states in optical and electro-optical devices, particularly an appropriate transmittance difference between the bright and dark states, and preferably an effective dark state with minimal transmittance as desired.

[0134] Surprisingly, it has been found that the medium according to the present invention is particularly suitable for containing and providing a relatively high concentration of dichroic dyes. In a preferred embodiment, the one or more dichroic dyes are present in the medium in an amount of at least 4% by weight, preferably at least 5% by weight, more preferably at least 6% by weight, even more preferably at least 7.5% by weight, and especially at least 10% by weight. In a particularly preferred embodiment, the one or more dichroic dyes are present in the medium in an amount of 5% by weight or more.

[0135] By providing the liquid crystal medium according to the present invention, modulation media can be obtained that can exhibit beneficial performance in optical and electro-optical applications, particularly in guest-host applications such as dimmable smart windows. In this regard, the ease of providing dichroic dyes at high concentrations is particularly beneficial in that it improves the contrast between the bright and dark states and allows for a highly effective dark state with minimal transmittance. This means that, depending on the application, it may be possible to achieve the desired device characteristics with a single switching layer and / or to achieve the desired contrast and effective dark state with a thinner switching layer thickness, i.e., a thinner cell gap.

[0136] It has surprisingly been found that the medium according to the invention can offer advantages with respect to solubility and effects related to, for example, viscosity, elastic constant, phase behavior and phase stability, in particular with respect to the possibility of achieving high concentrations of dichroic dye in the medium, in which favorable phase behavior and phase stability can be achieved both with respect to changes in dye concentration and with respect to changes in temperature.

[0137] Particularly surprising is the fact that, in particular, R 1It has been found that providing one or more compounds of formula I containing, as a group, longer alkyl chains, such as linear alkyl groups having 8 to 12 carbon atoms, particularly groups such as n-octyl and n-nonyl, can advantageously contribute to obtaining modulation media having switching states with uniform appearance and good aesthetic impression, as well as to effective and efficient device performance, e.g., with respect to fast and uniform switching. Such uniformity can be advantageously achieved at low and high temperatures, even at relatively high dye concentrations.

[0138] In one embodiment, the medium is completely free of compounds of formula IA or contains no more than 2% by weight, preferably no more than 1% by weight, more preferably no more than 0.1% by weight of compounds of formula IA. [ka]

[0139] In the formula, R 2 denotes a straight-chain alkyl having 1 to 6 C atoms, in particular a straight-chain alkyl having 1 to 5 C atoms.

[0140] Compared with the compounds of Formula I of the present invention, compounds of Formula IA having relatively short, linear alkyl groups, such as propyl or pentyl groups, have surprisingly been found to have fewer advantages in terms of phase behavior or stability under certain conditions or circumstances. It is currently believed that these compounds of Formula IA may be less suitable for favorably influencing phase behavior and phase retention, for example, at low temperatures or high dye concentrations, because they are less effective at suppressing undesirable phase transitions or phase heterogeneity, or undesirable textures, such as fan-like, focal conic, or pseudofocal conic textures, or heterogeneous appearances. In particular, switching between optical states may be slower, and heterogeneity, such as grainy textures, may occur.

[0141] The one or more dichroic dyes preferably have suitable solubility, stability, and reliability in the liquid crystal medium, and further preferably exhibit an extinction coefficient of a suitable magnitude, preferably within the visible and / or near-infrared spectrum, especially within the visible spectrum.

[0142] The dye preferably exhibits an absorption maximum at a wavelength in the visible or near infrared spectrum, more preferably in the visible spectrum.

[0143] The dichroic dyes can be suitably used as guest compounds in liquid crystal host mixtures, and therefore in a preferred embodiment the dyes are dissolved in the liquid crystal medium.

[0144] In one embodiment, the one or more dichroic dyes are positive dichroic dyes, i.e., dyes with a positive anisotropy R.

[0145] The degree of anisotropy R is determined from the values of the extinction coefficients for the parallel and perpendicular orientations of the molecules with respect to the polarization direction of light for a liquid crystal mixture containing a dye.

[0146] According to the invention, the degree of anisotropy R is preferably greater than 0.5, more preferably greater than 0.6, even more preferably greater than 0.7, in particular greater than 0.8.

[0147] The absorption is preferably maximized when the polarization direction of the light is parallel to the direction of the longest molecular extension of the dichroic dye compound, and is preferably minimized when the polarization direction of the light is perpendicular to the direction of the longest molecular extension of the dichroic dye compound.

[0148] According to the invention, the liquid-crystalline medium comprises at least one dichroic dye, preferably 1, 2, 3, 4, 5, 6, 7 or 8 dichroic dyes, more preferably at least 3 dichroic dyes.

[0149] The absorption spectrum of dichroic dyes preferably complement each other, and the visual change is such that they appear black, or relatively gray, or colorless.Preferably two or more, more preferably three or more dichroic dyes in the liquid crystal medium of the present invention preferably cover most of the visible spectrum, more preferably cover the entire visible spectrum.The exact method of preparing the dye mixture that appears black or gray visually is known in the art, and is described, for example, in M.Richter's "Einfuhrung in die Farbmetrik [Introduction to Colorimetry]", 2nd edition, 1981, ISBN3-11-008209-8, Walter de Gruyter & Co.

[0150] Determining the color position of a dye mixture is explained in the field of colorimetry. To do this, the spectra of the individual dyes are calculated taking into account the Beer-Lambert law to obtain the overall spectrum. This is then converted to the color position and luminance value under the corresponding illuminant, e.g., daylight illuminant D65, according to the rules of colorimetry. The position of the white point is determined by the respective illuminant (e.g., D65) and is shown, for example, in the tables in the references mentioned above. Different color positions can be determined by varying the proportions of the various dyes.

[0151] According to a preferred embodiment, the medium contains one or more dichroic dyes that absorb light in the red and near-infrared region, i.e., in the wavelength range of 600 nm to 2000 nm, preferably 600 nm to 1800 nm, particularly preferably 650 nm to 1300 nm.

[0152] Preferably, the one or more dichroic dyes are selected from azo dyes, anthraquinones, methine compounds, azomethine compounds, merocyanine compounds, naphthoquinones, tetrazines, perylenes, terrylenes, quaterrylenes, higher rylenes, pyrromethenes, thiadiazoles, benzothiadiazoles, nickel dithiolenes, (metal)phthalocyanines, (metal)naphthalocyanines, and (metal)porphyrins, of which azo dyes, thiadiazoles, and benzothiadiazoles are particularly preferred.

[0153] In one embodiment, the dichroic dye is preferably selected from the dye classes described in B. Bahadur, "Liquid Crystals - Applications and Uses," Vol. 3, 1992, World Scientific Publishing, Section 11.2.1, and particularly preferably selected from the compounds specified in the tables therein.

[0154] The dyes belong to the class of dichroic dyes known in the art and described in the literature.For example, anthraquinone dyes are described in EP 34832, EP 44893, EP 48583, EP 54217, EP 56492, EP 59036, GB 2065158, GB 2065695, GB 2081736, GB 2082196, GB 2094822, and naphthoquinone dyes are described in German Patent Nos. 3,126,108 and 3,201,120. 761, and azo dyes are described in European Patent No. 43904, German Patent No. 3123519, International Publication No. 82 / 2054, British Patent No. 2079770, Japanese Patent Application Laid-Open No. 56-57850, Japanese Patent Application Laid-Open No. 56-104984, U.S. Pat. No. 4308161, U.S. Pat. No. 4308162, U.S. Pat. No. 4340973, T. Uchida, C. Shishido, H.S. Seki and M. Wada: Mol. Cryst. Lig. Cryst. 39, 39-52 (1977), and H. Seki, C. Shishido, S. Yasui and T. Uchida: Jpn. J. Appl. Phys. 21, 191-192 (1982), and perylenes are described in EP 60895, EP 68427 and WO 82 / 1191. For example, rylene dyes are described in EP 2166040, U.S. Patent Publication No. 2011 / 0042651, EP 68427, EP 47027, EP 60895, DE 3110960, and EP 698649.

[0155] In a preferred embodiment, benzothiadiazoles, as described in particular in WO 2014 / 187529 and WO 2020 / 104563, and / or thiadiazoloquinoxalines, as described in WO 2016 / 177449 and WO 2020 / 104563, are used as dichroic dyes.

[0156] Preferably, the medium comprises a combination of one or more benzothiadiazole derivatives and one or more thiadiazoloquinoxaline derivatives, and more preferably, a combination of two or more benzothiadiazole derivatives and two or more thiadiazoloquinoxaline derivatives.

[0157] In a particularly preferred embodiment, the liquid-crystalline medium comprises at least one compound selected from the group of compounds of the following formulae D-1 to D-10: [ka] [ka] [ka]

[0158] Preferably, the medium comprises one or more compounds selected from the group of compounds of formulae D-1, D-2, D-3, D4 and D-5, more preferably two or more compounds selected from the group of compounds of formulae D-1, D-2, D-3, D4 and D-5.

[0159] In one embodiment, the medium preferably comprises one or more compounds selected from the group of compounds of formulae D-6, D-7, D-8, D9 and D-10, more preferably two or more compounds selected from the group of compounds of formulae D-6, D-7, D-8, D9 and D-10.

[0160] Particularly preferably, the medium comprises one or more compounds selected from the group of compounds of the formulae D-1, D-2, D-3, D-4 and D-5 and one or more compounds selected from the group of compounds of the formulae D-6, D-7, D-8, D-9 and D-10, more preferably two or more compounds selected from the group of compounds of the formulae D-1, D-2, D-3, D-4 and D-5 and two or more compounds selected from the group of compounds of the formulae D-6, D-7, D-8, D-9 and D-10.

[0161] In one embodiment, the one or more dichroic dyes have a chromophore comprising a substituted phenylene or at least two fused rings, at least one of which is unsubstituted or substituted phenylene. Preferably, the one or more dichroic dyes have a chromophore comprising at least two fused rings, at least one of which is phenylene.

[0162] In certain embodiments, the medium according to the present invention comprises one or more quenching compounds, which is preferred when the device according to the present invention comprises one or more fluorescent dyes in the medium and in the switchable layer.

[0163] A quenching compound is a compound that quenches fluorescence. It can absorb the electronic excitation energy of an adjacent molecule in the switching layer, such as a fluorescent dye, and in the process transition to an electronically excited state. This converts the quenched fluorescent dye to its electronic ground state, preventing it from emitting fluorescence or undergoing any subsequent reactions. The quenching compound itself returns to its ground state through radiationless inactivation or photoemission, making it available again for quenching.

[0164] The quenching compound can have various functions in the medium and the switching layer of the device according to the present invention. First, the quenching compound can contribute to extending the lifetime of the dye system by deactivating the electronic excitation energy. Second, the quenching compound can eliminate additional color effects that may be aesthetically undesirable, such as colored emission emitted into the interior space from fluorescent dyes in the switching layer.

[0165] To achieve effective quenching, the quenching compound must be matched to each dye system, particularly the longest absorbing dye in the dye combination, as is known in the art.

[0166] Suitable quenching compounds are listed, for example, in Table 8.1 of "Principles of Fluorescence Spectroscopy" by J.R. Lakowicz, 3rd Edition, 2010, ISBN 10:0387-31278-1, Springer Science+Business Media LLC, p. 279. Furthermore, classes of compounds, such as so-called dark quenchers or black hole quenchers, are known in the art. Examples include azo dyes and aminoanthraquinones. The quenching compounds used in the switching layer of the device according to the present invention may be non-fluorescent dyes or dyes that fluoresce only in the near-infrared range.

[0167] Preferably, any quenching compounds present are selected such that fluorescence in the visible region of the spectrum is suppressed.

[0168] The liquid crystal medium may contain further additives known to those skilled in the art and described in the literature, such as polymerization initiators, polymerization inhibitors, surfactants, stabilizers, antioxidants (e.g., BHT, TEMPOL), microparticles, free radical scavengers, nanoparticles, etc. Suitable stabilizers and dopants are listed in Tables E and F below.

[0169] In one embodiment, the liquid-crystalline medium comprises additives or further compounds, in particular one or more stabilizers, preferably two or more stabilizers, and / or one or more polymerizable compounds, preferably one or more polymerizable mesogenic compounds.

[0170] In a preferred embodiment, the liquid crystal medium comprises one or more chiral compounds, preferably one or more chiral dopants.

[0171] Preferably, the liquid-crystalline medium comprises one or more chiral dopants in a concentration of 0.01 to 2% by weight, more preferably 0.05 to 1% by weight, even more preferably 0.1 to 0.5% by weight. The chiral dopants are preferably selected from the group consisting of the compounds of Table E below, more preferably from the group consisting of R- or S-811, R- or S-1011, R- or S-2011, R- or S-3011, R- or S-4011, and R- or S-5011.

[0172] It is particularly preferred that the medium comprises a chiral compound of the following formula: [ka]

[0173] Preferably it is the R-stereoisomer, and R a denotes alkyl having 1 to 8 C atoms, preferably having 2 to 5 C atoms, in particular compounds of the following formulae, preferably the R-stereoisomers: [ka]

[0174] Chiral or cholesteric media can be created, for example, by doping a nematic liquid crystal medium with a chiral dopant with high twisting power. The pitch p of the induced cholesteric helix is given by the concentration c of the chiral dopant and the helical twisting power HTP according to equation (1):

number

[0175] In this specification, the pitch refers to the pitch p of the cholesteric helix, and the pitch p is the distance that the alignment axis (director) of the chiral or cholesteric liquid crystal rotates by 2π.

[0176] It is also possible to use two or more dopants, for example, to compensate for the temperature dependence of the HTP of each dopant and achieve a low temperature dependence of the helical pitch. total ), the following equation holds approximately:

[0177]

number

[0178] c in the formula i are the concentrations of the individual dopants, and HTP i are the helical twisting powers of the respective individual dopants.

[0179] The liquid crystal medium preferably comprises one or more chiral compounds, particularly chiral dopants.Chiral dopants preferably have high absolute values of HTP, and can generally be added to mesogen-based mixtures, even dye-doped mixtures, at relatively low concentrations, and also have good solubility in achiral components.When two or more chiral compounds are used, their rotational direction and twist temperature dependence can be the same or opposite.

[0180] Preferably, the one or more chiral compounds optionally contained in the liquid crystal medium have a chromaticity of 5 μm, preferably in the commercially available liquid crystal mixture MLC-6828 from Merck. -1 More preferably, 10 μm -1 More preferably, 15 μm or more -1 Particularly preferred is a liquid crystal mixture having an absolute value of helical twisting power (HTP) of 20 μm or more, preferably in the commercially available liquid crystal mixture MLC-6828 manufactured by Merck. -1 More than 40 μm, preferably -1 More preferably, 60 μm or more -1 More than 80 μm, most preferably -1 More than 260μm -1 Chiral compounds within the following range:

[0181] The present invention further relates to a switching element comprising a switching layer containing the liquid-crystalline medium. The switching layer can be arranged on a substrate or between two substrates, preferably between two substrates. The switching layer comprises an active material, i.e., a material that can undergo a reversible change that affects its optical behavior, in particular the transmission behavior of light passing through the layer, and can operate in different optical states, in particular be electrically switchable. Preferably, the substrate is provided with an alignment layer or film that is in direct contact with the liquid-crystalline medium.

[0182] The medium and switching element are suitable for use in a device for controlling the passage of energy in the form of sunlight from the environment to an interior space, where the passage of energy to be controlled occurs from the environment, i.e., the exterior space, to the interior space.

[0183] An interior space herein can be any space that is substantially isolated from the environment, such as a building, a vehicle, or a container.

[0184] However, the device can also be used for aesthetic interior design, e.g. light and color effects, etc. For example, doors or wall elements containing a device according to the invention in grey or color can be switched to transparent.

[0185] Additionally, the device may include a white or colored planar backlight that is luminance modulated, or a yellow planar backlight that is color modulated by a blue guest-host display.When glass substrates are used in the device, one or both sides of a device according to the invention may be provided with textured or structured glass for light extraction and / or for creating optical effects.

[0186] Therefore, the liquid crystal medium according to the present invention is preferably used in architectural windows or automobiles, for example the sunroof of automobiles.In particular, switchable optical device can be incorporated into the window of building or facade.Device according to the present invention can also be applied to commercial vehicles, ships, trains or airplanes.

[0187] The medium and the switching element are preferably incorporated into a window element, which is preferably and suitably used as a component of a window, and can be used, for example, in combination with further accessories and a frame, to provide windows in openings, facades or interior partitions of buildings or vehicles.

[0188] In yet another application, the device is used to regulate light incidence on the eye, for example in protective goggles, visors or sunglasses, where one switching state allows less light to enter the eye and another switching state allows slightly less light to enter.

[0189] The device according to the present invention is preferably placed in an opening of a relatively large two-dimensional structure, the two-dimensional structure itself allowing little or no energy to pass through, and the opening having a relatively high energy transmittance. The two-dimensional structure is preferably a wall or other boundary separating an interior space from the outside. Furthermore, the two-dimensional structure preferably covers an area at least as large as the opening in which the device according to the present invention is placed, particularly preferably an area at least twice as large as the opening.

[0190] The device, in particular the window element, preferably has a thickness of at least 0.05 mm 2 , preferably at least 0.1 m 2 , particularly preferably at least 0.5 m 2 , very preferably at least 1.0 m 2 In the case of a window equipped with the device, the device area is preferably 0.1 m 2 ~10m 2 , more preferably 0.5 m 2 ~5m 2 , particularly preferably 1 m 2 ~3m 2 The range is.

[0191] The device is preferably housed in an opening in a building, container, vehicle, or other substantially enclosed space that has a relatively high energy transmittance, as described above. The device can generally be used in any interior space that has a light-transmitting interface, particularly one that has limited air exchange with the environment and allows energy input from the outside in the form of light energy. It is particularly preferred to use the device in interior spaces that are heavily insulated via light-transmitting areas, such as window areas.

[0192] The device according to the invention is switchable, where switching refers to a change in the path of energy, particularly light, passing through the device. Preferably, the device according to the invention is electrically switchable, as described, for example, in WO 2009 / 141295 and WO 2014 / 090373.

[0193] If the device is electrically switchable, it preferably comprises two or more electrodes, preferably located on both sides of the switching layer. The electrodes preferably consist of ITO or a thin, preferably transparent metal and / or metal oxide layer, such as silver, FTO (fluorine-doped tin oxide), or alternative materials known in the art for this application. The electrodes are preferably provided with electrical connections. The voltage is preferably supplied by a battery, a rechargeable battery, or an external power source, particularly an external power source.

[0194] In the case of electrical switching, the switching action is caused by (re)orientation of the molecules of the liquid crystal medium by application of a voltage.

[0195] In one embodiment, the device is converted from a state of high absorption, i.e., low light transmittance, in the absence of an applied voltage to a state of lower absorption, i.e., high light transmittance. The liquid crystal medium of the switchable layer is preferably in a nematic phase in both states. The state of no applied voltage is preferably characterized by the molecules of the liquid crystal medium, and thus the dichroic compound, being oriented parallel to the plane of the switchable layer. This is preferably achieved by a correspondingly selected alignment layer. The state of applied voltage is preferably characterized by the molecules of the liquid crystal medium, and thus the dye molecules, being oriented perpendicular to the plane of the switchable layer.

[0196] In another embodiment, the device is switchable from a state of low absorption, i.e. high light transmittance, which exists in the absence of an applied voltage, to a state of high absorption, i.e. low light transmittance, and the liquid crystal medium of the switchable layer is preferably nematic in both states.

[0197] In a particular embodiment, a switching element is provided in which the switchable layer has a non-twisted nematic configuration and has a switching state in which the liquid crystal medium in the switchable layer has positive dielectric anisotropy and homogeneous alignment.

[0198] In one embodiment, the switching element and window element are configured to operate in the so-called electrically controlled birefringence mode.

[0199] In a further embodiment, a switching element is provided in which the switchable layer has at least one switching state with a twisted nematic configuration, a supertwisted nematic configuration, or a highly twisted nematic configuration, preferably a highly twisted nematic configuration.

[0200] In this case, the switchable layer has a chiral or twisted configuration in one switching state, particularly in the presence or absence of an electric field, and the twist or rotation angle of the cholesteric helix can be set as desired.

[0201] For example, in a twisted nematic (TN) configuration, the twist angle can typically be set at or about 90°. Alternatively, the element can be configured in a supertwisted nematic (STN) configuration, in which the twist angle is greater than 90°, typically in the range of 90° to 270°, such as at or about 180°. Furthermore, the twist of the cholesteric helix can be set to angles greater than 270°, or even greater than 360°, to obtain a highly twisted nematic (HTN) configuration.

[0202] A device according to the invention preferably has the following layer order, although further layers may be present: The layers shown below are preferably immediately adjacent to each other in the device.

[0203] - a substrate layer (preferably comprising glass or a polymer) - a conductive transparent layer (preferably containing ITO) -Alignment layer - a switching layer containing a liquid crystal medium -Alignment layer - a conductive transparent layer (preferably containing ITO) - a substrate layer (preferably comprising glass or a polymer)

[0204] In another embodiment, the device comprises two switching layers, which may be arranged in a so-called double cell. In this case, two switchable optical cells are combined to form a multilayer structure of the window element. In this embodiment, the switching element therefore comprises two switching layers containing liquid crystal media.

[0205] The alignment layer can be any desired layer known to those skilled in the art for this purpose, preferably a polyimide layer, and particularly preferably a layer comprising rubbed polyimide. In one embodiment, planar alignment is provided, and more preferably a slight pretilt angle may be set.

[0206] Furthermore, by using a polymer obtained by a polarized light exposure process as an alignment layer, the compounds of the liquid crystal medium can be aligned along an alignment axis, ie, photoalignment can be achieved.

[0207] The switching layer in the device according to the invention is preferably disposed between or surrounded by two substrate layers. The substrates are preferably optically transparent. The substrate layers can be made of, for example, glass or polymer, preferably an optically transparent polymer.

[0208] Suitable glass substrates include, for example, float glass, down-draw glass, chemically or heat-treated tempered glass, borosilicate glass, and aluminosilicate glass.

[0209] Suitable polymer substrates include, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyvinyl butyral (PVB), polymethyl methacrylate (PMMA), polycarbonate (PC), polyimide (PI), cyclic olefin polymer (COP), and cellulose triacetate (TAC).

[0210] The two substrates are arranged as a cell, and a gap is formed between the two substrates. The size of the gap, i.e., the thickness of the switching layer, is preferably 1 μm to 100 μm, preferably 2 μm to 50 μm, more preferably 3 μm to 25 μm, and most preferably 5 μm to 10 μm. The cell is usually sealed by an adhesive layer disposed at or near the edge. In a preferred embodiment, the cell gap is 25 μm or less, preferably 10 μm or less, and more preferably 6 μm or less.

[0211] The device, in particular the window element, is preferably characterized in that it does not contain a polymer-based polarizer, particularly preferably does not contain a polarizer in a solid material phase, and very particularly preferably does not contain a polarizer at all.

[0212] However, in alternative embodiments, the device may include one or more polarizers, in which case the polarizers are preferably linear polarizers.

[0213] In a preferred embodiment, the window element is a component of a window, more preferably a window part comprising at least one glass surface, and particularly preferably a part of an insulating glass unit.

[0214] In the present invention, and in particular in the following examples, the structures of mesogenic compounds are represented by abbreviations (also called acronyms). In these abbreviations, chemical formulas are abbreviated as follows using the following Tables A to C: n H 2n+1 , C m H 2m+1 , and C l H 2l+1 , or C n H 2n-1 , C m H 2m-1 , and C l H 2l-1 All groups in the above table represent straight-chain alkyl or alkenyl, preferably 1E-alkenyl, having n, m, and l C atoms, respectively. Table A shows the codes used for the ring elements of the core structure of the compounds, and Table B shows the linking groups. Table C shows the meaning of the codes representing the leftmost or rightmost group. The acronyms consist of the code for the ring element with any linking group, the code for the first hyphen and the leftmost group, and the code for the second hyphen and the rightmost group. Table D shows examples of compound structures and their respective abbreviations.

[0215] <Table A: Ring elements>

[0216] [Table 1]

[0217] [Table 2]

[0218] [Table 3]

[0219] <Table B: Crosslinking group>

[0220] [Table 4]

[0221] <Table C: Terminal group>

[0222] [Table 5]

[0223] In the table, n and m are each integers, and the three dots "..." are places for other abbreviations from this table.

[0224] The following table shows exemplary structures and their respective abbreviations, which are provided to explain the meaning of the abbreviation rules and represent compounds that are preferably used:

[0225] Table D: Exemplary Structures

[0226] [Table 6]

[0227] [Table 7]

[0228] [Table 8]

[0229] [Table 9]

[0230]

Table 10

[0231]

Table 11

[0232]

Table 12

[0233]

Table 13

[0234]

Table 14

[0235]

Table 15

[0236] Table 16

[0237]

Table 17

[0238]

Table 18

[0239]

Table 19

[0240] Table 20

[0241] [Table 21]

[0242] [Table 22]

[0243] [Table 23]

[0244] [Table 24]

[0245] [Table 25]

[0246] In the formula, n, m and l preferably represent 1 to 7 independently of each other.

[0247] The following table, Table E, gives examples of compounds that can optionally be used as stabilizers in the mesogenic media according to the present invention.

[0248]

[0249] Table E shows examples of stabilizers which can be added to the liquid-crystalline media according to the invention, in which n is an integer from 1 to 12, preferably 1, 2, 3, 4, 5, 6, 7 or 8. [Table 26]

[0250] [Table 27]

[0251] [Table 28]

[0252] [Table 29]

[0253] [Table 30]

[0254] [Table 31]

[0255] [Table 32]

[0256] The liquid-crystalline medium preferably comprises 0 to 10% by weight, in particular 1 ppm to 5% by weight, particularly preferably 1 ppm to 1% by weight, of stabilizers.

[0257] Table F below shows exemplary compounds which can be preferably used as chiral dopants in the mesogenic media according to the present invention.

[0258] [Table 33]

[0259] [Table 34]

[0260] [Table 35]

[0261] In a preferred embodiment of the present invention, the mesogenic medium comprises one or more compounds selected from the group of compounds in Table F.

[0262] The mesogenic medium of the present invention preferably comprises two or more, preferably four or more compounds selected from the group of compounds in Tables D, E and F above.

[0263] The liquid-crystalline media according to the invention preferably comprise at least 7, preferably at least 8, individual compounds selected from the group of compounds of Table D, preferably compounds having at least 3, particularly preferably at least 4, different formulae selected from the formulae shown in Table D.

[0264] The LC media according to the invention may for example comprise compounds in which H, C, N, O, Cl or F has been replaced by the corresponding isotopes.

[0265] All percentage data and quantitative ratios given herein are percent by weight unless otherwise stated.

[0266] All physical properties are measured in accordance with "Merck Liquid Crystals, Physical Properties of Liquid Crystals" (published November 1997, Merck, Germany) and apply to a temperature of 20°C unless otherwise stated. In each case, Δn values are measured at 589 nm and Δε values at 1 kHz unless otherwise stated. e and n o are the refractive indices of the extraordinary and ordinary rays under the above conditions, respectively.

[0267] The anisotropy R is determined from the values of the extinction coefficient E(p) (the extinction coefficient of the mixture when the molecules are aligned parallel to the polarization direction of the light) and the extinction coefficient E(s) of the mixture (the extinction coefficient of the mixture when the molecules are aligned perpendicular to the polarization direction of the light) at the maximum wavelength of the absorption band of each dye. If a dye has multiple absorption bands, the strongest absorption band is usually selected. The orientation of the molecules in the mixture is achieved by an alignment layer, as is known in the art. To eliminate the influence of the liquid crystal medium, other absorptions, or reflections, each measurement is performed on the same mixture without the dye, and the obtained values are subtracted.

[0268] Measurements are performed using linearly polarized light whose vibration direction is parallel to the alignment direction (measurement of E(p)) or perpendicular to the alignment direction (measurement of E(s)). This can be achieved by using a linear polarizer, which is then rotated relative to the device to achieve two different polarization directions. Thus, measurements of E(p) and E(s) are performed by rotating the polarization direction of the incident polarized light.

[0269] The degree of anisotropy R is calculated from the obtained values of E(s) and E(p) according to the following formula: R=[E(p)-E(s)] / [E(p)+2*E(s)] This formula is described in particular in "Polarized Light in Optics and Spectroscopy" by D.S.K. Liger et al., Academic Press, 1990. A detailed description of the method for measuring the anisotropy of liquid crystal media containing dichroic dyes is also given in "Liquid Crystals - Applications and Uses" by B. Bahadur, Vol. 3, 1992, World Scientific Publishing, Section 11.4.2.

[0270] The following examples are merely illustrative of the present invention and are not intended to limit the scope of the present invention in any way. These examples, modifications thereof, or other equivalents will be apparent to those of skill in the art in light of this disclosure. [Example]

[0271] In the example, V o is the capacitance threshold voltage [V] at 20°C, n e is the extraordinary refractive index at 20°C and 589 nm, n o is the normal refractive index at 20°C and 589 nm, Δn is the optical anisotropy at 20°C and 589 nm, ε ∥ is the dielectric constant parallel to the director at 20°C and 1 kHz, ε ⊥ Permittivity perpendicular to the director at 20℃ and 1kHz Δε is the dielectric anisotropy at 20°C and 1 kHz. cl.p., T(N,I) is the clearing point [℃], gamma 1 is the rotational viscosity [mPa s] at 20°C measured by the magnetic field rotation method, K1 is the elastic constant for "splay" deformation at 20°C [pN]. K2 is the elastic constant for "twist" deformation at 20°C [pN], K3 represents the elastic constant [pN] for "bend" deformation at 20°C.

[0272] The term "threshold voltage" in the present invention relates to the capacitance threshold (V0) unless otherwise specified. In the examples, it is generally common to refer to the 10% relative contrast (V 10 ) may also be given as the optical threshold.

[0273] <Reference example 1> A liquid crystal host mixture H-1 was prepared and characterized with respect to its general physical properties having the composition and properties shown in the table below.

[0274] [Table 36]

[0275] <Reference example 2> A liquid crystal host mixture H-2 was prepared and characterized with respect to its general physical properties having the composition and properties shown in the table below.

[0276] [Table 37]

[0277] <Reference example 3> A liquid crystal host mixture H-3 was prepared and characterized with respect to its general physical properties having the composition and properties shown in the table below.

[0278] [Table 38]

[0279] <Reference example 4> A liquid crystal host mixture H-4 was prepared and characterized with respect to its general physical properties having the composition and properties shown in the table below.

[0280] [Table 39]

[0281] <Reference example 5> A liquid crystal host mixture H-5 was prepared and characterized with respect to its general physical properties having the composition and properties shown in the table below.

[0282] [Table 40]

[0283] <Reference example 6> A liquid crystal host mixture H-6 was prepared and characterized with respect to its general physical properties having the composition and properties shown in the table below.

[0284] [Table 41]

[0285] <Reference example 7> A liquid crystal host mixture H-7 was prepared and characterized with respect to its general physical properties having the composition and properties shown in the table below.

[0286] [Table 42]

[0287] <Reference example 8> A liquid crystal host mixture H-8 was prepared and characterized with respect to its general physical properties having the composition and properties shown in the table below.

[0288] [Table 43]

[0289] <Reference example 9> A liquid crystal host mixture H-9 was prepared and characterized with respect to its general physical properties having the composition and properties shown in the table below.

[0290] [Table 44]

[0291] <Reference example 10> A liquid crystal host mixture H-10 was prepared and characterized with respect to its general physical properties having the composition and properties shown in the table below: Compound I-8 corresponds to the compound of formula I-8.

[0292] [Table 45]

[0293] <Reference example 11> A liquid crystal host mixture H-11 was prepared and characterized with respect to its general physical properties having the composition and properties shown in the table below.

[0294] [Table 46]

[0295] <Reference example 12> A liquid crystal host mixture H-12 was prepared and characterized with respect to its general physical properties having the composition and properties shown in the table below.

[0296] [Table 47]

[0297] <Reference example 13> A liquid crystal host mixture H-13 was prepared and characterized with respect to its general physical properties having the composition and properties shown in the table below.

[0298] [Table 48] <Reference example 14> A liquid crystal host mixture H-14 was prepared and characterized with respect to its general physical properties having the composition and properties shown in the table below.

[0299] [Table 49] <Comparative Example 1> Comparative mixture CM-1 contains 89.65% of mixture H-1 described in Reference Example 1 above and 0.10% of a compound of the formula: [ka] (hereinafter referred to as ST-1), 0.95% of the formula [ka] (hereinafter referred to as D-1), 1.90% of the compound of the formula [ka] (hereinafter referred to as D-2), 2.30% of the compound of formula [ka] (hereinafter referred to as D-3), 1.80% of the compound of formula [ka] (hereinafter referred to as D-6), 2.20% of the compound of formula [ka] (hereinafter referred to as D-9), 1.10% of the compound of formula [ka] (hereinafter referred to as D-10) is mixed.

[0300] Comparative mixture CM-1.1 is prepared by mixing 99.618% of mixture CM-1 with 0.382% of the compound of formula R-5011 set forth in Table F above.

[0301] Comparative mixture CM-1.2 is prepared by mixing 99.847% of mixture CM-1 with 0.153% of the compound of formula R-5011 set forth in Table F above.

[0302] Mixtures CM-1.1 and CM-1.2 are filled into HTN cells with a cell thickness of 15 μm and planar polyimide alignment layers.

[0303] In the absence of an applied field, at temperatures below room temperature, especially below 15 °C, especially at 0 °C and -10 °C, the cells, instead of exhibiting a cholesteric structure, exhibit a non-uniform appearance with a granular, pseudo-focal conic structure. This can lead to undesirable light leakage in the dark state, reducing the effectiveness of the dark state and degrading switching performance.

[0304] <Comparative Example 2> Comparative mixture CM-2 contained 95.377% of mixture H-1 described in Reference Example 1 above, 0.050% of compound ST-1 described in Comparative Example 1 above, 0.473% of compound D-1 described in Comparative Example 1 above, 0.970% of compound D-2 described in Comparative Example 1 above, 0.819% of compound D-3 described in Comparative Example 1 above, and a compound of the formula [ka] (hereinafter referred to as D-5) in an amount of 0.683% and the compound D-9 shown in Comparative Example 1 in an amount of 1.628%.

[0305] The mixture CM-2 was filled into two cells, each with a cell thickness of 8 μm and a planar polyimide alignment layer, and the two cells were arranged as a double cell in a cross configuration.

[0306] At temperatures below 0°C, especially at -20°C and -30°C, the double cells have slow switching characteristics and the transitions between optical states appear non-uniform or uneven.

[0307] <Comparative Example 3> Comparative mixture CM-3 is prepared by mixing 94.786% of mixture H-1 described in Reference Example 1 above, 0.061% of compound ST-1 described in Comparative Example 1 above, 0.375% of compound D-1 described in Comparative Example 1 above, 1.031% of compound D-2 described in Comparative Example 1 above, 1.030% of compound D-3 described in Comparative Example 1 above, 1.125% of compound D-6 described in Comparative Example 1 above, 0.702% of compound D-9 described in Comparative Example 1 above, and 0.890% of compound D-10 described in Comparative Example 1 above.

[0308] The mixture CM-3 was filled into two cells, each with a cell thickness of 8 μm and a planar polyimide alignment layer, and the two cells were arranged as a double cell in a cross configuration.

[0309] At temperatures below 0°C, especially at -20°C and -30°C, the switching performance of the double cell deteriorates and the transitions between optical states appear non-uniform or uneven.

[0310] <Comparative Examples 4 to 7> Comparative mixtures CM-4, CM-5, CM-6, and CM-7 are prepared and further processed according to Comparative Example 2 above, except that mixture H-1 is replaced with mixtures H-2, H-3, H-4, and H-5, respectively, described in Reference Examples 2 to 5 above.

[0311] At low temperatures, the switching performance of the cell deteriorates and the transitions between optical states appear non-uniform or uneven.

[0312] <Example 1> Mixture M-1 is prepared by mixing 90.68% of mixture H-6 described in Reference Example 6 above with 0.10% of compound ST-1 described in Comparative Example 1 above, 1.05% of compound D-1 described in Comparative Example 1 above, 1.63% of compound D-2 described in Comparative Example 1 above, 2.10% of compound D-3 described in Comparative Example 1 above, 1.64% of compound D-6 described in Comparative Example 1 above, 0.60% of compound D-9 described in Comparative Example 1 above, and 2.20% of compound D-10 described in Comparative Example 1 above.

[0313] Mixture M-1.1 is prepared by mixing 0.344% of the compound of formula R-5011 described in Table F above with 99.656% of mixture M-1.

[0314] Mixture M-1.1 was filled into an HTN cell, which had a cell thickness of 15 μm and a planar polyimide alignment layer.

[0315] In the absence of an applied field, the cell exhibits a cholesteric structure with a uniform appearance and maintains a good dark state even at temperatures well below room temperature, particularly at 0°C, -10°C, and -20°C. The cell has fast switching characteristics, and the transitions between optical states are uniform in appearance.

[0316] <Example 2> Mixture M-2 is prepared by mixing 89.65% of mixture H-7 described in Reference Example 7 above with 0.10% of compound ST-1 described in Comparative Example 1 above, 0.95% of compound D-1 described in Comparative Example 1 above, 1.90% of compound D-2 described in Comparative Example 1 above, 2.30% of compound D-3 described in Comparative Example 1 above, 1.80% of compound D-6 described in Comparative Example 1 above, 2.20% of compound D-9 described in Comparative Example 1 above, and 1.10% of compound D-10 described in Comparative Example 1 above.

[0317] Mixture M-2.1 is prepared by mixing 0.382% of the compound of formula R-5011 described in Table F above with 99.618% of mixture M-2.

[0318] Mixture M-2.2 is prepared by mixing 99.847% of Mixture M-2 with 0.153% of the compound of formula R-5011 set forth in Table F above.

[0319] Mixtures M-2.1 and M-2.2 are filled into HTN cells with a cell thickness of 15 μm and planar polyimide alignment layers.

[0320] In the absence of an applied electric field, the cell exhibits a cholesteric structure with a uniform appearance and exhibits a good dark state even at temperatures well below room temperature, particularly at 0 °C, -10 °C, and -20 °C. The cell has fast switching performance, and the transitions between optical states are uniform in appearance.

[0321] <Example 3> Mixture M-3 is prepared by mixing 94.600% of mixture H-6 described in Reference Example 6 above, 0.050% of compound ST-1 described in Comparative Example 1 above, 0.496% of compound D-1 described in Comparative Example 1 above, 0.973% of compound D-2 described in Comparative Example 1 above, 0.925% of compound D-3 described in Comparative Example 1 above, 1.526% of compound D-6 described in Comparative Example 1 above, 0.667% of compound D-9 described in Comparative Example 1 above, and 0.763% of compound D-10 described in Comparative Example 1 above.

[0322] Mixture M-3 was filled into two cells, each with a cell thickness of 8 μm and a planar polyimide alignment layer, and the two cells were arranged as a double cell in a cross configuration.

[0323] At room temperature and temperatures much lower than room temperature, especially at -20°C and -30°C, the double cell exhibits fast switching performance and the transition between optical states is uniform in appearance.

[0324] <Example 4> Mixture M-4 is prepared by mixing 95.377% of mixture H-8 described in Reference Example 8 with 0.050% of compound ST-1 shown in Comparative Example 1 above, 0.473% of compound D-1 shown in Comparative Example 1 above, 0.970% of compound D-2 shown in Comparative Example 1 above, 0.819% of compound D-3 shown in Comparative Example 1 above, 0.683% of compound D-5 shown in Comparative Example 2 above, and 1.628% of compound D-9 shown in Comparative Example 1 above.

[0325] Mixture M-4 was filled into two cells with a cell thickness of 8 μm and a planar polyimide alignment layer, which were arranged as a double cell in a cross configuration.

[0326] At room temperature and temperatures much lower than room temperature, particularly at -20°C and -30°C, the double cell exhibits fast switching characteristics, and the transitions between optical states are uniform in appearance.

[0327] <Example 5> Mixture M-5 is prepared by mixing 94.90% of mixture H-6 described in Reference Example 6 with 0.52% of compound D-1 shown in Comparative Example 1 above, 1.02% of compound D-2 shown in Comparative Example 1 above, 0.97% of compound D-3 shown in Comparative Example 1 above, 1.22% of compound D-6 shown in Comparative Example 1 above, 0.81% of compound D-9 shown in Comparative Example 1 above, and 0.56% of compound D-10 shown in Comparative Example 1 above.

[0328] Mixture M-5 was filled into two cells with 8 μm-thick planar polyimide alignment films. The two cells were arranged as a cross-shaped double cell.

[0329] At room temperature and temperatures much lower than room temperature, especially at −20° C. and −30° C., the double cell exhibits fast switching performance and the transitions between optical states are uniform in appearance.

[0330] <Examples 6, 7 and 8> Mixtures M-6, M-7, and M-8 are prepared and further processed according to Example 5 above, except that Mixture H-6 is replaced with Mixtures H-9, H-10, and H-11 described in Reference Examples 9, 10, and 11 above, respectively.

[0331] At low temperatures, the cells exhibit fast switching performance and the transitions between optical states are uniform in appearance.

[0332] <Example 9> Mixture M-9 is prepared by mixing 91.68% of mixture H-12 described in Reference Example 12 above with 0.67% of compound D-1, 1.50% of compound D-2, 2.23% of compound D-3, 1.75% of compound D-6, 0.64% of compound D-9, 1.14% of compound D-10, 0.09% of compound ST-1, and 0.30% of the compound of formula R-5011.

[0333] Mixture M-9 is filled into an HTN cell with a cell thickness of 15 μm and a planar polyimide alignment layer.

[0334] The cell exhibits an excellent dark state with uniform appearance, and has fast switching capability with uniform appearance of the transitions between optical states.

[0335] <Example 10> Mixture M-10 is prepared by mixing 91.67% of mixture H-13 described in Reference Example 13 above with 0.67% of compound D-1, 1.50% of compound D-2, 2.23% of compound D-3, 1.75% of compound D-6, 0.64% of compound D-9, 1.14% of compound D-10, 0.09% of compound ST-1, and 0.31% of the compound of formula R-5011.

[0336] Mixture M-10 is filled into an HTN cell with a cell thickness of 15 μm and a planar polyimide alignment layer.

[0337] The cell exhibits an excellent dark state with uniform appearance, and has fast switching capability with transitions between optical states that are uniform in appearance.

[0338] <Example 11> Mixture M-11 is prepared by mixing 95.007% of mixture H-14 described in Reference Example 14 above with 0.883% of compound D-1, 0.817% of compound D-2, 0.990% of compound D-3, 1.500% of compound D-6, 0.572% of compound D-9, 0.181% of compound D-10, and 0.050% of compound ST-1.

[0339] Mixtures M-1 to M-11 are highly suitable for use in devices for regulating the passage of energy from an exterior space to an interior space, such as windows, especially at low temperatures.

Claims

1. A liquid-crystalline medium comprising one or more compounds of formula I and one or more dichroic dyes, wherein the one or more dichroic dyes are contained in an amount of 1% by weight or more in the medium. 【Chemical 1】 (In the formula, R １ represents a linear alkyl having 8 to 20 C atoms or a branched or cyclic alkyl having 3 to 20 C atoms, and further comprises one or more non-adjacent CH ２ groups may each be independently replaced by O, and one or more H atoms may be replaced by F, Cl or Br; and L １ is H, F, Cl or CH ３ Represents.)

2. 2. The liquid crystal medium according to claim 1, wherein the one or more dichroic dyes are contained in the medium in an amount of 2% by weight or more, preferably 3% by weight or more, more preferably 4% by weight or more, even more preferably 5% by weight or more, in particular 7.5% by weight or more.

3. R １ denotes a linear alkyl having 8 to 12 C atoms, preferably a linear alkyl having 8 to 10 C atoms, and / or L １ is H or CH ３ 3. The liquid-crystalline medium according to claim 1, wherein R is H, preferably H.

4. 4. Liquid-crystalline medium according to claim 1, wherein the medium comprises one or more chiral compounds, preferably one or more chiral dopants, more preferably chiral compounds of the formula: 【Chemistry 2】

5. 5. Liquid-crystalline medium according to claim 1, wherein the medium has a positive dielectric anisotropy Δε and / or an optical anisotropy Δn at 589 nm of 0.04 or more.

6. 6. Liquid-crystalline medium according to claim 1, wherein the medium comprises one or more compounds selected from the group of compounds of the formulae III, IV and V 【Chemistry 3】 (In the formula, R ３ is an unsubstituted or halogenated, straight-chain or branched alkyl or alkoxy group having 1 to 15 C atoms, in which one or more CH ２ The groups may be independently selected such that the O atoms are not directly linked to each other. 【Chemistry 4】 -C≡C-, -CF ２ optionally substituted by -O-, -CH=CH-, -O-, -CO-O- or -O-CO-; 【Chemistry 5】 L ３１ and L ３２ are, independently of one another, H or F, Y ３ is H or CH ３ represents X ３ represents halogen, a halogenated alkyl or halogenated alkoxy having 1 to 3 C atoms, or a halogenated alkenyl or halogenated alkenyloxy having 2 or 3 C atoms, Z ３ is -CH ２ CH ２ -, -CF ２ CF ２ -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH ２ represents O— or a single bond, preferably a single bond, n and o each independently represent 0 or 1; R １１ represents a linear alkyl group having 1 to 12 C atoms, a branched or cyclic alkyl group having 3 to 12 C atoms, or a linear alkenyl group having 2 to 12 C atoms, a branched alkenyl group having 3 to 12 C atoms, or a cyclic alkenyl group having 5 to 12 C atoms (one or more H atoms may optionally be substituted by fluorine), R １２ is a linear alkyl or alkoxy group having 1 to 12 C atoms, or a branched or cyclic alkyl or alkoxy group having 3 to 12 C atoms, or a linear alkenyl group having 2 to 12 C atoms, a branched alkenyl group having 3 to 12 C atoms, or a cyclic alkenyl group having 5 to 12 C atoms, in which one or more H atoms may optionally be replaced by fluorine, R ５１ , R ５２ are independently of one another alkyl having 1 to 7 C atoms, alkoxy having 1 to 7 C atoms or alkoxyalkyl, alkenyl or alkenyloxy having 2 to 7 C atoms, 【Chemistry 6】 Z ５１ and Z ５２ are each independently —CH ２ CH ２ -, -CH ２ represents O—, —CH═CH—, —C≡C—, —COO—, or a single bond; p is 1 or 2.

7. Liquid-crystalline medium according to any one of claims 1 to 6, wherein the medium comprises one or more compounds of the formula III-a 【Chemistry 7】 During the ceremony, L １ , L ２ and L ３ are, independently of one another, H or F, R ３ and X ３ has the meaning as defined in claim 6.

8. Liquid-crystalline medium according to any one of claims 1 to 7, wherein the medium comprises one or more, preferably two or more, compounds of the formulae I-1, I-2 and I-3. 【Chemistry 8】

9. 9. Liquid-crystalline medium according to claim 1, wherein the medium is free of compounds of the formula IA or contains at most 2% by weight, preferably at most 1% by weight, of compounds of the formula IA. 【Chemistry 9】 (In the formula, R ２ is a linear alkyl having 1 to 6 C atoms, preferably a linear alkyl having 1 to 5 C atoms.

10. The liquid-crystalline medium according to any one of claims 1 to 9, wherein the one or more dichroic dyes have a chromophore comprising a substituted phenylene or at least two fused rings, at least one of the fused rings being unsubstituted or substituted phenylene; and preferably the one or more dichroic dyes are selected from benzothiadiazoles and thiadiazoloquinoxalines.

11. 11. Liquid-crystalline medium according to claim 1, wherein the medium contains one or more compounds of formula I in a total amount of at least 3% by weight, preferably at least 5% by weight, more preferably at least 10% by weight, in particular at least 15% by weight.

12. 12. Liquid-crystalline medium according to claim 1, wherein the medium comprises one or more stabilizers, preferably two or more stabilizers, and / or one or more polymerizable compounds, preferably one or more polymerizable mesogenic compounds.

13. A switching element comprising a switchable layer comprising a liquid-crystalline medium according to any one of claims 1 to 12, the switchable layer being arranged between two substrates and provided with an alignment layer in direct contact with the liquid-crystalline medium.

14. 14. A switching element according to claim 13, wherein in at least one switching state the switchable layer has a twisted nematic, supertwisted nematic or highly twisted nematic structure, preferably a highly twisted nematic structure.

15. 14. A switching element according to claim 13, wherein in the switched state the switchable layer has a non-twisted nematic structure and the liquid crystal medium has positive dielectric anisotropy and homogeneous alignment.

16. 16. Switching element according to any one of claims 13 to 15, wherein the switching element has two switchable layers comprising a liquid-crystalline medium according to any one of claims 1 to 12.

17. A window element comprising a liquid-crystalline medium according to any one of claims 1 to 12 or a switching element according to any one of claims 13 to 16.

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