Liquid crystal medium and electro-optical devices

Abstract

This invention relates to electro-optic devices, and more particularly to energy-efficient liquid crystal displays, which include a switchable liquid crystal layer containing a relatively small amount of one or more dichroic dyes; and to the use of liquid crystal media in such devices and the dichroic dyes in liquid crystal displays for reducing light leakage and improving contrast ratio.

Description

Technical Field

[0001] This invention relates to electro-optic devices, and more particularly to energy-efficient liquid crystal displays, comprising a switchable liquid crystal layer containing a relatively small amount of one or more dichroic dyes; and to the use of liquid crystal media in such devices and the dichroic dyes in liquid crystal displays for reducing light leakage and improving contrast ratio. Prior Technology

[0002] Since the first discovery of commercially available liquid crystal compounds, liquid crystals (LCs) have been widely used. Liquid crystal displays (LCDs) are used for information display in many fields. LCDs are used in both direct-view and projection displays.

[0003] One of the current LCD display modes is the TN ("twisted nematic") mode. However, TN LCDs have the disadvantage of strong contrast and viewing angle dependence.

[0004] Additionally, there are known VA ("vertically aligned") displays with a wider viewing angle. The LC cell of a VA display contains an LC dielectric layer between two transparent electrodes, where the LC dielectric typically exhibits negative dielectric anisotropy. In the off state, the molecules of the LC layer are aligned perpendicularly to the electrode surfaces (vertically) or have a tilted vertical alignment. When a voltage is applied to the two electrodes, a reorientation of the LC molecules parallel to the electrode surfaces occurs.

[0005] It is also known that so-called IPS ("in-plane switching") displays contain an LC layer between two substrates, wherein two electrodes are arranged on only one of the two substrates and preferably have an interlaced comb-like structure. When a voltage is applied to the electrodes, an electric field with a significant component parallel to the LC layer is generated between the electrodes. This causes the LC molecules to reorient in the layer plane.

[0006] Additionally, so-called FFS ("edge field switching") displays have been reported, notably see SH Jung et al., Jpn. J. Appl. Phys., Vol. 43, No. 3, 2004, 1028, which contain two electrodes on the same substrate, one structured in a comb-like manner and the other unstructured. This generates a strong so-called "edge field," namely a strong electric field near the electrode edge and an electric field with strong vertical and horizontal components throughout the cells. FFS displays exhibit low contrast viewing angle dependence. FFS displays typically contain an LC dielectric with positive dielectric anisotropy and an alignment layer, usually polyimide, which provides planar alignment for the LC dielectric molecules.

[0007] FFS displays can operate as active matrix or passive matrix displays. In the case of an active matrix display, individual pixels are typically addressed by integrated nonlinear active elements (e.g., transistors, such as thin-film transistors ("TFTs")), while in the case of a passive matrix display, individual pixels are typically addressed by multiplexing methods.

[0008] The typical impacts of in-plane switching (IPS) and edge field switching (FFS) electro-optical modes are found in desktop monitors, laptops, TVs, mobile phones, tablet PCs, and multimedia applications. Generally, positive dielectric liquid crystal media with a relatively low dielectric anisotropy value are used in FFS displays, but in some cases, liquid crystal media with a dielectric anisotropy of only about 3 or even lower are also used in IPS displays.

[0009] Further improvements have been achieved through the so-called "High Brightness FFS" (HB-FFS) mode. One of the advantages of the HB-FFS mode compared to traditional FFS technology is that it enables higher transmittance, which allows the panel to operate with lower energy consumption.

[0010] Furthermore, FFS displays have been described in SH Lee et al., Appl. Phys. Lett. 73(20), 1998, 2882-2883 and SH Lee et al., Liquid Crystals 39(9), 2012, 1141-1148. These displays have similar electrode designs and layer thicknesses to FFS displays, but contain an LC dielectric with negative dielectric anisotropy instead of an LC dielectric with positive dielectric anisotropy. Compared to an LC dielectric with positive dielectric anisotropy, an LC dielectric with negative dielectric anisotropy can exhibit a more favorable director orientation with less tilt and a greater torsional orientation, thereby providing higher transmittance. The display further includes an alignment layer of preferred polyimide provided on at least one of the substrates, which contacts the LC dielectric and induces planar alignment of the LC molecules in the LC dielectric. These displays are also referred to as "Ultra-Bright FFS" (UB-FFS) mode displays. These displays require highly reliable LC media.

[0011] Especially for monitor, mobile, video gaming and TV applications, there is a desire to benefit from the short response time, wide viewing angle, low power consumption, high transmittance and suitable high contrast of LC displays.

[0012] There is a particular desire to provide displays with high brightness while maintaining favorable contrast even under ambient light conditions. In this regard, improving image quality in dark states can, in principle, help increase contrast. For example, dark state quality can typically be improved by reducing inter-cell spacing and / or by reducing the optical anisotropy of the LC medium to decrease latency. However, this can adversely affect the device's transmittance or brightness. Dark state quality can also, in principle, be improved by adjusting the elastic constant of the LC medium. However, this adjustment can affect the device's operating voltage and response time.

[0013] The industry still needs LC displays with favorable electro-optical performance and reliability, which offer broad applicability under various conditions (e.g., under different temperatures or different ambient light conditions or with reduced energy consumption), and liquid crystal media suitable for such LC displays are required. Summary of the Invention

[0014] Therefore, the object of the present invention is to provide an electro-optic device and, in particular, a display with advantageous electro-optic performance, especially with high contrast ratio and good dark state, while achieving high brightness or high transmittance, low threshold voltage, fast addressing time, and advantageous reliability and stability, especially at low and high temperatures, in an optical state. Another object of the present invention is to provide a liquid crystal medium that provides benefits and advantages in such displays and is suitable for further optimization of the display. Other objects of the invention will become immediately apparent to those skilled in the art from the following detailed description.

[0015] These objectives are addressed by the subject matter defined in the independent paragraphs, while preferred embodiments are further elaborated in the respective appendices below. Implementation

[0016] The present invention particularly provides the following items, including the main features, preferred embodiments and specific characteristics, which, individually and in combination, help to solve the above objectives and ultimately provide additional advantages.

[0017] The first aspect of the present invention provides an electro-optical device comprising: - A switchable layer that is inserted between two opposing transparent substrates. Each substrate is provided with an electrode structure, or one of the substrates is provided with two electrode structures and the other substrate is not provided with electrodes. - Two polarizers and, if necessary, at least one optical retarder. The switchable layer contains a liquid crystal medium. The liquid crystal medium contains one or more dichroic dyes, and the one or more dichroic dyes are contained in the medium in a total amount of 2.0% by weight or less.

[0018] It is now recognized that light leakage, especially due to scattering, can degrade the quality of dark or dark-state images and thus affect the available contrast ratio.

[0019] It has been surprisingly found that adding one or more dichroic dyes to the liquid crystal medium in relatively small amounts, particularly 2.0% by weight or less, and even more preferably 1.0% by weight or less, can significantly reduce undesirable light leakage in the dark or dark state. Therefore, this provision of one or more dichroic dyes described herein advantageously enhances the obtainable contrast ratio of the electro-optical device of the present invention, and it has been further found that it can simultaneously maintain appropriately high transmittance or brightness, fast response time, low operating voltage and low power consumption, and wide viewing angle.

[0020] According to the present invention, one or more dichroic dyes are provided in a relatively small and limited but effective amount in the liquid crystal medium to effectively improve the dark state and overall contrast of the device, especially the display (e.g., FFS, HB-FFS and particularly UB-FFS display), without affecting the desired device transmittance or brightness or only reducing the device transmittance or brightness to a minimum or even negligible degree.

[0021] Therefore, energy-efficient electro-optical devices, and especially energy-efficient displays, are provided, which advantageously exhibit particularly high contrast while also providing favorable metric performance and fast response time.

[0022] Other aspects of the present invention relate to liquid crystal media, which include One or more dichroic dyes, in total amount of 2.0% by weight or less, preferably 1.0% by weight or less; and one or more compounds of formula IV-1. Its total amount is at least 20% by weight, preferably at least 30% by weight. In formula IV-1, R 41 and R 42 independently represent alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 carbon atoms or alkenyl, alkenoxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 carbon atoms.

[0023] It has been surprisingly found that these liquid crystal media are particularly suitable for the electro-optical device of the present invention. In particular, these media can provide benefits in achieving a modified dark state, while also advantageously contributing to enabling low operating voltage, fast response time, and reliability and stability at low and high temperatures.

[0024] Another aspect of the present invention relates to the use of one or more dyes, especially multicolor dyes or one or more pigments, especially one or more dicolor dyes, in a liquid crystal switchable layer included in an electro-optical device to reduce light leakage and improve the contrast ratio of the device.

[0025] It has been advantageously recognized that adding or doping one or more dichroic dyes to a liquid crystal medium can improve dark states and overall contrast, while appropriately maintaining other properties, including high device brightness and short response time. In this regard, the use of dyes can reduce undesirable light leakage, especially light leakage that can still occur in other ways due to scattering even in the presence of polarizers and retarders. Therefore, this use according to the invention enables the provision of liquid crystal displays with high contrast, high brightness, high transmittance, and short response time, particularly FFS, UB-FFS, HB-FFS, and IPS-mode liquid crystal displays.

[0026] Therefore, in another aspect of the invention, a method for operating the electro-optic device of the invention is provided, wherein one or more dichroic dyes are included in a switchable layer and light leakage in the dark state is reduced.

[0027] Without limiting the invention thereon, the invention will be described in detail below by way of a detailed description of various forms, embodiments and specific features, and specific embodiments will be described in more detail.

[0028] In this document, halogen is represented by F, Cl, Br or I, with F or Cl preferred, and F even more preferred.

[0029] In this invention, all atoms also include their isotopes. Specifically, one or more hydrogen atoms (H) may be replaced by deuterium (D), which is particularly preferred in some embodiments; high deuteration enables or simplifies the analysis and determination of compounds, especially in the case of low concentrations.

[0030] In this document, alkyl and / or alkoxy refer to straight-chain or branched alkyl or alkoxy groups, respectively. Preferably, they are straight-chain, having 2, 3, 4, 5, 6, or 7 carbon atoms, and therefore preferably represent ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy, or heptoxy, and also methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octyloxy, nonoxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy, or tetradecyloxy.

[0031] In this document, oxane preferably represents straight-chain 2-oxapropyl (=methoxymethyl); 2-oxabutyl (=ethoxymethyl) or 3-oxabutyl (=2-methoxyethyl); 2-, 3- or 4-oxapentyl; 2-, 3-, 4- or 5-oxahexyl; 2-, 3-, 4-, 5- or 6-oxaheptyl; 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl; 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl; 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl.

[0032] In this paper, the alkenyl group (i.e., an alkyl group with a CH2 group replaced by -CH=CH-) can be straight-chain or branched. It is preferred to be straight-chain and have 2 to 10 carbon atoms. Therefore, it particularly represents vinyl; prop-1- or -2-enyl; but-1-, -2- or -3-enyl; pent-1-, -2-, -3- or -4-enyl; hex-1-, -2-, -3-, -4- or -5-enyl; hep-1-, -2-, -3-, -4-, -5- or -6-enyl; oct-1-, -2-, -3-, -4-, -5-, -6- or -7-enyl; non-1-, -2-, -3-, -4-, -5-, -6-, -7- or -8-enyl; dec-1-, -2-, -3-, -4-, -5-, -6-, -7-, -8- or -9-enyl.

[0033] In this document, the alkyl or alkenyl group that is at least monosubstituted with a halogen is preferably straight-chain, and the halogen is preferably F or Cl. In the case of polysubstituted groups, the halogen is preferably F. The resulting groups also include perfluorinated groups. In the case of monosubstituted groups, the fluorine or chlorine substituent may be located at any desired position, but is preferably at the ω-position.

[0034] In this paper, monofluorinated or polyfluorinated alkyl or alkoxy groups having 1, 2 or 3 C atoms, or monofluorinated or polyfluorinated alkenyl groups having 2 or 3 C atoms, are preferably F, Cl, CF3, CHF2, OCF3, OCHF2, OCFHCF3, OCFHCHF2, OCFHCHF2, OCF2CH3, OCF2CHF2, OCF2CF2CHF2, OCF2CF2CHF2, OCF2CF2CHF2, OCFHCF2CF3, OCFHCF2CHF2, OCF2CF2CF3, OCF2CF2CClF2, OCClFCF2CF3, OCH=CF2 or CH=CF2, preferably F or OCF3, and also CF3, OCF=CF2, OCHF2 or OCH=CF2.

[0035] In this paper, the 1,4-extinyl cyclohexyl ring system is illustrated as follows: or ; The extended cyclohexyl ring is a trans-1,4-extended cyclohexyl ring.

[0036] In this paper, the 1,4-epenylphenyl ring system is illustrated as follows: or .

[0037] The electro-optical device of the present invention, particularly a liquid crystal-based device, can be electrically switched to adopt different optical states, wherein the application of voltage controls the switching. These devices can be used as, for example, optical blinds and light intensity modulators, particularly liquid crystal-based light modulators, wherein the transmission of light can be reversibly changed. Preferably, the electro-optical device is used for a display for displaying information, particularly an active matrix addressing display. More preferably, the liquid crystal display is a TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, UB-FFS, PS-HB-FFS, SA-HB-FFS, polymer-stabilized SA-HB-FFS, VA, or PS-VA display; even more preferably, it is an IPS, FFS, HB-FFS, or UB-FFS display.

[0038] According to the present invention, in an electro-optic device, a switchable layer is disposed between two substrates to provide, for example, an optical unit that can operate in different optical states and can be electrically switched or actuated. Suitable substrates are transparent substrates, preferably made of glass or plastic.

[0039] Voltage application and electrical switching are made possible by providing electrodes. Preferably, the device, and especially the display, has an electrode structure that provides in-plane switching or edge field switching, more preferably edge field switching. In an alternative embodiment, electrodes are provided on two substrates to provide, in particular, a VA switching mode.

[0040] In addition to the electrodes, advantageously and preferably, one or both substrates are provided with an alignment or orientation layer made of, for example, polyimide, to influence or set the alignment of the liquid crystal medium at the interface. Tribopolymer polyimide or photoalignment polyimide is preferred as the alignment layer, especially tribopolymer polyimide in applications such as FFS.

[0041] According to the present invention, the electro-optic device comprises two polarizers, particularly two polarizer layers or polarizing layers. Both absorptive and reflective polarizers can be used. Preferably, a polarizer in the form of an optical thin film is used. The polarizer is preferably a linear polarizer.

[0042] Depending on the circumstances, at least one optical retarder, particularly at least one retardation layer, is provided in the device. In a preferred embodiment, at least one optical retarder is present, more preferably two optical retarders. In this regard, a retardation layer or plate can be used to compensate for phase dispersion, thereby obtaining a wider viewing angle.

[0043] According to the present invention, the liquid crystal medium, particularly the switchable layer of an electro-optic device, contains one or more dichroic dyes in a total amount of 2.0% by weight or less. In a preferred embodiment, the total amount of the one or more dichroic dyes in the liquid crystal medium is 1.0% by weight or less. More preferably, the total amount of the one or more dichroic dyes in the liquid crystal medium is 0.5% by weight or less, and even more preferably 0.2% by weight or less.

[0044] In this document, dichroic dyes refer to light-absorbing compounds whose absorption properties depend on the orientation of the compound relative to the polarization direction of light. The dichroic dye compounds of this invention typically have an elongated shape, meaning that the compound is significantly longer in one spatial direction (i.e., along the longitudinal axis) than in the other two spatial directions. Dichroic dyes absorb or preferentially absorb light in one orientation, thus light transmission can be modulated by changing the orientation of the dichroic dye.

[0045] According to the present invention, the so-called liquid crystal substrate is doped with a relatively small, limited amount of dichroic dye molecules. Such dye-doped LC media are particularly suitable for FFS and UB-FFS modes, but other display modes described in the context can also be used.

[0046] Preferably, the dichroic dye compound is present in the liquid crystal medium in solution. Therefore, the dichroic dye molecules used in this invention preferably exhibit suitable and sufficient solubility in the liquid crystal matrix. In addition, the dye compound also advantageously promotes the stability and reliability of the medium.

[0047] Based on the total weight of the entire medium, each of one or more dichroic dyes is preferably present in the liquid crystal medium in the following proportions: 0.002 wt% to 2.0 wt%, more preferably 0.003 wt% to 1.0 wt%, still more preferably 0.005 wt% to 0.5 wt%, even more preferably 0.01 wt% to 0.3 wt%, and especially preferably 0.02 wt% to 0.2 wt%.

[0048] Preferably, one or more dichroic dyes are present in the liquid crystal medium at a total concentration in the range of 0.003 wt% to 2.0 wt%, more preferably 0.004 wt% to 1.5 wt%, still more preferably 0.005 wt% to 1.0 wt%, even more preferably 0.01 wt% to 0.5 wt%, even more preferably 0.02 wt% to 0.3 wt%, and most preferably 0.05 wt% to 0.2 wt%.

[0049] The dye concentration is advantageously selected to ensure the appropriate performance of the obtained liquid crystal material, particularly in terms of the desired reduction of light leakage in the dark state and improved black image quality and overall contrast, while appropriately maintaining other device properties such as response time, operating voltage, and brightness. The upper limit of the dye concentration is provided with particular consideration for maintaining the bright-state performance of the device, so that the transmittance is unaffected or only minimally affected.

[0050] In alternatives, such as in cases where the brightness performance is less relevant, a higher concentration of dichroic dyes may be used. For example, in such cases, one or more dichroic dyes may be present in the liquid crystal medium at a total concentration of 2.0% to 5.0% by weight, or even higher than 5.0% by weight and up to 10.0% by weight.

[0051] Dichroic dyes are preferably selected from, for example, azo dyes, anthraquinones, thiophene anthraquinones, methine compounds, methylimine compounds, anthocyanin compounds, naphthoquinones, tetraazines, pyrrolemethane dyes, malononitrile dyes, nickel dithioenes, (metallic) phthalocyanines, (metallic) phthalocyanines and (metallic) porphyrins, rylenes (especially perylene and terylenes), thiadiazole dyes, thieno-thiadiazole dyes, benzothiadiazoles, thiadiazole-quinoline and diketylpyrrole-pyrrole. Preferred species include azo compounds, anthraquinones, thiophene anthraquinones, benzothiadiazoles, especially as described in WO 2014 / 187529 and WO 2020 / 104563 A1; diketopyrrolopyrroles, especially as described in WO 2015 / 090497; thiadiazoquinoline, especially as described in WO 2016 / 177449 ​​and WO 2020 / 104563 A1; and naphthalene-benzophenones, especially as described in WO 2014 / 090373.

[0052] In a preferred embodiment, one or more dichroic dyes are selected from azo compounds, benzothiadiazoles, and thiadiazoquinoline.

[0053] The liquid crystal medium preferably contains one, two, three, four, five, six, seven, eight, nine, or ten different dichroic dyes, with two, three, four, five, or six dichroic dyes being particularly preferred. In a preferred embodiment, the medium contains at least three different dichroic dyes.

[0054] In embodiments, the absorption spectra of the dichroic dyes contained in the medium or separately switchable layers are preferably complementary to each other in a way that produces the impression of a black or separately color-neutral appearance in the eye. Preferably, two or more, more preferably three or more dichroic dyes are used in the liquid crystal medium to better cover most of the visible spectrum. Precise methods for preparing dye mixtures that appear black or gray to the eye are known to those skilled in the art and described, for example, in M. Richter, Einführung in die Farbmetrik [Introduction to Colorimetry], 2nd edition, 1981, ISBN 3 11-008209-8, Walter de Gruyter & Co.

[0055] The determination of color positions in dye mixtures is explained in the field of colorimetry. To this end, the Lambert-Beer law is used to calculate the spectrum of individual dyes to obtain the overall spectrum, and then, according to colorimetric rules, it is converted into corresponding color positions and brightness values ​​under relevant illumination, such as daylight illuminator D65. The position of the white point is fixed by the individual illuminator, such as D65, and is cited in the tables in the above references. Different color positions can be set by changing the proportions of various dyes.

[0056] According to a preferred embodiment, the medium and switchable layer comprise one or more dichroic dyes that absorb light in the visible spectrum, which is defined herein as light with wavelengths between 380 nm and 780 nm.

[0057] In embodiments, it is particularly preferred to include one or more dichroic dyes that sufficiently and effectively absorb green light.

[0058] In the embodiments, the dichroic dyes provided in the medium and the switchable layer are preferably selected from the dye classes indicated in B. Bahadur, Liquid Crystals - Applications and Uses, Volume 3, 1992, World Scientific Publishing, Part 11.2.1, and are particularly preferably selected from the exact compounds given in the table therein.

[0059] These dyes belong to the category of dichroic dyes known in the industry and described in the literature. Therefore, for example, anthraquinone dyes are described in EP 34832, EP 44893, EP 48583, EP 54217, EP 56492, EP 59036, GB 2065158, GB 2065695, GB 2081736, GB 2082196, GB 2094822, GB 2094825, JP A 55-123673, DE 3017877, DE 3040102, DE 3115147, DE 3115762, DE 3150803 and DE 3201120, naphthoquinone dyes are described in DE 3126108 and DE 3202761, and azo dyes are described in EP 43904, DE 3123519, WO 82 / 2054, GB 2079770, JP-A 56-57850, JP-A 56-104984, US 4308161, US 4308162, US 4340973, T. Uchida, C. Shishido, H. Seki and M. Wada: Mol. Cryst. Liq. Cryst. 39, 39-52 (1977) and H. Seki, C. Shishido, S. Yasui and T. Uchida: Jpn. J. Appl. Phys. 21, 191-192 (1982), and further elaborated in EP 60895, EP 68427 and WO 82 / 1191. Naphthalene-based dyes are described in, for example, EP 2166040, US 2011 / 0042651, EP 68427, EP 47027, EP 60895, DE 3110960 and EP 698649.

[0060] The compounds described herein are known, or can be prepared in a similar manner to known compounds, or can be synthesized by methods known in themselves, as described in standard works such as Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart, etc., and specifically under known and suitable reaction conditions. In this regard, known variations not detailed herein may also be utilized. Furthermore, starting materials are available through generally accessible literature procedures or are commercially available.

[0061] The liquid crystal medium used in this invention is a liquid crystal mixture that further contains one or more liquid crystal precursor compounds in addition to one or more dichroic dyes.

[0062] The liquid crystal medium used in this invention may have positive dielectric anisotropy or negative dielectric anisotropy.

[0063] In order to enable effective electrical switching, the absolute value or amplitude of the dielectric anisotropy of the liquid crystal medium is preferably 1.5 or above, more preferably 2.5 or above, and especially 3.0 or above.

[0064] In this context, ∆ε represents dielectric anisotropy, where ∆ε = ε‖ - ε ⊥. Dielectric anisotropy ∆ε is preferably measured at 20 °C and 1 kHz.

[0065] In a preferred embodiment, a liquid crystal medium having negative dielectric anisotropy is provided and used in the switchable layer. More preferably, it is a liquid crystal mixture having a dielectric anisotropy Δε in the range of -8 to -1.5, more preferably -7 to -2.5, and even more preferably -6 to -3.

[0066] In another embodiment, a liquid crystal medium having positive dielectric anisotropy is provided and used in the switchable layer. In this case, a liquid crystal mixture having a dielectric anisotropy Δε in the range of 1.5 to 30, more preferably 2.5 to 25, and even more preferably 4 to 12 is preferred.

[0067] The liquid crystal medium preferably has an optical anisotropy ∆n of 0.06 or higher, more preferably 0.08 or higher, still more preferably 0.10 or higher, and even more preferably 0.12 or higher.

[0068] In this context, ∆n represents optical anisotropy, where ∆n = n e- no, and the preferred optical anisotropy ∆n is measured at 20 °C and a wavelength of 589.3 nm. The liquid crystal medium preferably has an optical anisotropy Δn in the range of 0.03 to 0.30, more preferably 0.04 to 0.27, even more preferably 0.06 to 0.21, and particularly 0.09 to 0.16.

[0069] In addition, liquid crystal media exhibits superior low-temperature stability without visible crystallization or decomposition, especially with a long storage life of over 200 hours measured at -40°C.

[0070] All physical properties and physicochemical or electro-optic parameters have been determined by commonly known methods, specifically according to "Merck Liquid Crystals, Physical Properties of Liquid Crystals", Status November 1997, Merck KGaA, Germany, and unless otherwise explicitly stated, are given at a temperature of 20°C.

[0071] In this document, unless otherwise explicitly stated, all concentrations are given as weight percentages and pertain to the individual complete compounds. All temperatures are indicated in degrees Celsius.

[0072] Preferably, the liquid crystal medium contained in the liquid crystal medium, especially the switchable layer of the electro-optic device, comprises one or more compounds of formula IV-1. in R 41 and R 42 independently represent alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 carbon atoms or alkenyl, alkenoxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 carbon atoms.

[0073] Preferably, one or more compounds of form IV-1 are contained in the liquid crystal medium in a total amount of at least 20% by weight, more preferably at least 30% by weight, even more preferably at least 40% by weight, or even more preferably at least 50% by weight.

[0074] In a preferred embodiment, the liquid crystal medium comprises one or more compounds selected from the group consisting of compounds of formulas B-1, B-2, and B-3. in R11 and R12 represent, respectively, H or a straight-chain alkyl or alkoxy group having 1 to 15 C atoms, wherein one or more of these CH2 groups are independently connected to each other in a manner where the O atoms are not directly linked to each other via -C≡C-, -CF2O-, -OCF2-, -CH=CH-, The alkoxy group is substituted with -O-, -CO-O-, or -O-CO-, and one or more of the H atoms may be substituted with halogens, preferably having a straight-chain alkoxy group with 1 to 7 C atoms.

[0075] The compounds of formula B-1 are preferably selected from the group of compounds of formulas B-1-a to B-1-e. R11 and R12 represent, respectively, alkyl groups having 1 to 7 carbon atoms, preferably ethyl, n-propyl, n-butyl, or n-pentyl.

[0076] The compounds of formula B-2 are preferably selected from the group of compounds of formulas B-2-a to B-2-e. R11 and R12 represent alkyl groups having 1 to 12 carbon atoms, or different from each other, preferably alkyl groups having 1 to 7 carbon atoms.

[0077] The compounds of formula B-3 are preferably selected from the group of compounds of formulas B-3-a to B-3-j. R 12 represents an alkyl group having 1 to 7 carbon atoms, preferably ethyl, n-propyl, or n-butyl.

[0078] In a preferred embodiment, one or more compounds selected from the group consisting of formulas B-1, B-2, and B-3 are selected from the group consisting of compounds BA to BJ. .

[0079] One or more compounds selected from the group of compounds of formula B-1, B-2 and B-3, especially formula B-2, are preferably included in the liquid crystal medium in a total amount of 0.5% to 20% by weight, more preferably 4% by weight or more, and even more preferably 8% by weight or more.

[0080] In a preferred embodiment, the medium of the present invention comprises one or more compounds of formula Y. Some of these groups have the following meanings: and express or R1 and R2 independently represent unsubstituted or halogenated straight-chain, branched, or cyclic alkyl or alkoxy groups having 1 to 15 carbon atoms, wherein one or more of these CH2 groups may be independently connected to each other via -C≡C-, -CF2O-, or -CH=CH-, where the O atoms are not directly linked. Replace with -O-, -CO-O-, or -O-CO-. Zx and Zy independently represent -CH2CH2-, -CH=CH2O2, -OCF2O2, -OCH2, -CO-O2CO2, -O-CO2, -C2F4, -CF=CF2, -CH=CH-CH2O2, or single bonds, preferably single bonds. L1, L2, L3, and L4 independently represent H, F, or Cl, with H or F preferred, F even better, and x and y represent 0, 1, or 2 independently, where x + y ≤ 3.

[0081] Preferably, the compound of formula Y contains at least one substituent of F or Cl, preferably F, L1-4, and more preferably at least two substituents of F, L1-4.

[0082] In compounds of formula Y and its sub-formulas, R1 and R2 preferably represent alkyl or alkoxy groups having 1 to 6 carbon atoms in a straight chain, and alkenyl groups having 2 to 6 carbon atoms, especially vinyl, 1E-propenyl, 1E-butenyl, 3-butenyl, 1E-pentenyl, 3E-pentenyl or 4-pentenyl.

[0083] In compounds of formula Y and its sub-formulas, preferably both L1 and L2 represent F. In another preferred embodiment of the invention, in compounds of formula Y and its sub-formulas, one of the groups L1 and L2 represents F and the other represents Cl.

[0084] In the embodiments, in the compounds of formula Y, each ring, preferably an extended phenyl ring, may be substituted with one or two alkyl groups, preferably with methyl and / or ethyl groups, preferably with one methyl group, as appropriate.

[0085] In a preferred embodiment of the present invention, the medium contains one or more compounds selected from formula Y. Where R1, R2, Zx, Zy, L1, and L2 have one of the meanings given in equation Y or one of the preferred meanings given in the context. 'a' represents 0, 1, or 2, with 1 or 2 being preferred. b represents 0, 1, or 2, preferably 1 or 2. express or , L3 and L4 represent F or Cl independently, with F being preferred.

[0086] Preferably, in compounds of formulas Y1 and Y2, both L1 and L2 represent F, or one of L1 and L2 represents F and the other represents Cl, or both L3 and L4 represent F or one of L3 and L4 represents F and the other represents Cl.

[0087] In the embodiments, in the compounds of formula Y1 and Y2, each ring, preferably an extended phenyl ring, may be substituted with one or two alkyl groups, preferably with methyl and / or ethyl groups, preferably with one methyl group, as appropriate.

[0088] Preferably, the medium comprises one or more compounds of formula Y1 selected from the group consisting of the following formulas. Where a represents 1 or 2, alkyl and alkyl* each independently represent a straight-chain alkyl group having 1 to 6 carbon atoms, and alkenyl represents a straight-chain alkenyl group having 2 to 6 carbon atoms, and (O) represents an O atom or a single bond. Alkenyl preferably represents CH 2=CH-, CH 2=CHCH 2CH 2-, CH 3-CH=CH-, CH 3-CH 2-CH=CH-, CH 3-(CH 2) 2-CH=CH-, CH 3-(CH 2) 3-CH=CH- or CH 3-CH=CH-(CH 2) 2-.

[0089] Preferably, the medium contains one or more compounds of formula Y1 selected from formulas Y1-2 and Y1-10.

[0090] In certain embodiments, the medium comprises one or more compounds of formulas Y1A-1 to Y1A-10: .

[0091] Preferably, the medium comprises one or more Y2 compounds selected from the group consisting of the following formulas: Wherein alkyl and alkyl* each independently represent a straight-chain alkyl group having 1 to 6 carbon atoms, and alkenyl represents a straight-chain alkenyl group having 2 to 6 carbon atoms, and (O) represents an oxygen atom or a single bond. Alkenyl preferably represents CH 2=CH-, CH 2=CHCH 2CH 2-, CH 3-CH=CH-, CH 3-CH 2-CH=CH-, CH 3-(CH 2) 2-CH=CH-, CH 3-(CH 2) 3-CH=CH- or CH 3-CH=CH-(CH 2) 2-.

[0092] Preferably, the medium contains one or more compounds of formula Y2 selected from Y2-2 and Y2-10, especially one or more compounds of formula Y2-10.

[0093] The proportion of the compound of formula Y1 or its sub-formula in the medium is preferably 1 to 10 by weight.

[0094] The proportion of compounds of formula Y2 or its sub-formulas, especially formula Y2-10, in the medium is preferably 1% to 15% by weight, more preferably 2% to 10% by weight.

[0095] The total proportion of compounds of formula Y1 and Y2 or their sub-formulas in the medium is preferably 0 to 20%, very preferably 1 to 15%, and most preferably 1 to 10 by weight.

[0096] In a particular embodiment, the medium contains one, two, or three compounds of formula Y1 and Y2 or their sub-formulas, preferably selected from formulas Y1-2, Y1-10, Y2-2, and Y2-10.

[0097] In certain embodiments, the medium comprises one or more compounds of formulas Y2A-1 to Y2A-5: .

[0098] Preferably, the medium comprises one or more compounds of formula Y selected from the following formulas. in R1, R2, L1, L2, ring X, x, and Zx have the meanings given in formula Y, wherein at least one of ring X is an extended cyclohexenyl group. If x is 2, then preferably one ring X is an extended cyclohexyl-1,4-diyl group and the other ring X is an extended cyclohexyl-1,4-diyl group or a cyclohexane-1,4-diyl group.

[0099] Preferably, in formula LY, x is 1 or 2, and express Furthermore, in the case where x is 2, a group Another option indicates .

[0100] Preferably, both groups L1 and L2 represent F. In an alternative embodiment, one of groups L1 and L2 represents F and the other represents Cl.

[0101] Compounds of formula LY are preferably selected from the group consisting of the following formulas: Wherein R1 has the meaning indicated by the formula LY above, (O) represents an oxygen atom or a single bond, and v represents an integer from 1 to 6. R1 preferably represents a straight-chain alkyl group having 1 to 6 carbon atoms or a straight-chain alkenyl group having 2 to 6 carbon atoms, especially CH3, C2H5, nC3H7, nC4H9, nC5H11, CH2=CH-, CH2=CHCH2CH2-, CH3-CH=CH-, CH3-CH2-CH=CH-, CH3-(CH2)2-CH=CH-, CH3-(CH2)3-CH=CH- or CH3-CH=CH-(CH2)2-.

[0102] Preferably, the medium contains one, two, or three compounds of formula LY. The proportion of compounds of formula LY or its derivatives in the medium is preferably 0 to 15% by weight.

[0103] Preferably, the medium contains one or more compounds of formula LY4, wherein the proportion of the compound of formula LY4 in the medium is preferably 1% to 15% by weight, more preferably 5% to 10% by weight.

[0104] In an embodiment, the medium comprises one or more compounds selected from the group consisting of compounds of formulas Y4-1 to Y4-24. Wherein R has 1 to 7 carbon atoms, it represents a straight-chain alkyl or alkoxy group; R* represents a straight-chain alkenyl group, it represents an oxygen atom or a single bond; and m represents an integer from 1 to 6. R* preferably represents CH 2=CH-, CH 2=CHCH 2CH 2-, CH 3-CH=CH-, CH 3-CH 2-CH=CH-, CH 3-(CH 2) 2-CH=CH-, or CH 3-(CH 2) 3-CH=CH- or CH 3-CH=CH-(CH 2) 2-. R preferably represents methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy, or pentoxy.

[0105] In a particular embodiment, the medium contains one or more compounds of formula Y4-5, preferably 0.5% by weight or more, more preferably 1% by weight or more.

[0106] Preferably, the total proportion of compounds of formula Y, and especially of its individual sub-forms, in the medium is 5% by weight or more, more preferably 15% by weight or more, and even more preferably 25% by weight or more.

[0107] In another preferred embodiment, the liquid crystal medium comprises one or more compounds selected from the group consisting of compounds of formulas II-1 and II-2. in R 2 represents an alkyl, alkoxy, fluorinated alkyl, or fluorinated alkoxy group having 1 to 7 carbon atoms, or an alkenyl, alkenoxy, alkoxyalkyl, or fluorinated alkenyl group having 2 to 7 carbon atoms. Depending on the circumstances, one or more CH2 groups can be processed independently of each other. or Alternative, and Independent of each other or L 21, L 22, L23 and L24 independently represent H or F, L 25 represents H or CH 3, and X 2 represents a halogen, preferably F, a halogenated alkyl or alkoxy group having 1 to 3 carbon atoms, or a halogenated alkenyl or alkenyloxy group having 2 or 3 carbon atoms.

[0108] The medium preferably comprises one or more compounds of formula II-1 and / or II-2 in a total amount of 5% or more, more preferably 10% or more.

[0109] In equations II-1 and II-2, L 21 and L 22 or L 23 and L 24 are preferred, both of which are F.

[0110] In another preferred embodiment, in formulas II-1 and II-2, L 21, L 22, L 23 and L 24 all represent F.

[0111] The compound of formula II-1 is preferably selected from the compound of formula II-1-a. The groups appearing therein have the meaning given with respect to Formula II-1, and the preferred X2 series F is preferred.

[0112] Preferably, the medium comprises one or more compounds of formula II-1-a-1. R2 has the meaning as explained in Equation II-1.

[0113] One or more compounds of formula II-1-a-1 are preferably contained in the liquid crystal medium in a total amount of 5% by weight or more, more preferably 10% by weight or more.

[0114] In another embodiment, the liquid crystal medium comprises one or more compounds selected from formulas II-1-b to II-1-h. R2 has the meaning given in Equation II-1.

[0115] The compounds of formula II-2 are preferably selected from the group of compounds of formula II-2-a, II-2-b, II-2-c and II-2-d. The parameters have the specific meanings given above for Equation II-2, and the preferred X 2 series F.

[0116] In a preferred embodiment of the present invention, the medium comprises a compound of formula II-2-b, wherein all of L21, L22, L23 and L24 are F, and the total amount thereof is preferably 5% by weight or more.

[0117] Preferably, the medium comprises one or more compounds selected from those of formula II-2-d.

[0118] Preferred compounds of formula II-2 are compounds of formulas II-2-i, II-2-ii, II-2-iii and II-2-iv. R 2 has the meaning given above for Equation II-2.

[0119] In a preferred embodiment, the medium contains at least one compound of formula II-2-iii, preferably in an amount of 2.5% by weight or more, more preferably 5% by weight or more.

[0120] In another embodiment, the liquid crystal medium comprises one or more compounds selected from formulas II-2-A to II-2-L. R 2 has the meaning given above for Equation II-2.

[0121] In the embodiments, the liquid crystal medium comprises one or more compounds selected from the group consisting of compounds of formulas III-1 to III-32. R3 has the same meaning as R2 given in Equation II-2 above.

[0122] In the embodiments, the liquid crystal medium preferably comprises at least one compound of formula III-1 in an amount of at least 2% by weight, more preferably at least 5% by weight.

[0123] Preferably, the medium of the present invention comprises one or more compounds of formula IV. in R 41 and R 42 independently represent an alkyl, alkoxy, fluorinated alkyl, or fluorinated alkoxy group having 1 to 7 carbon atoms, or an alkenyl, alkenyloxy, alkoxyalkyl, or fluorinated alkenyl group having 2 to 7 carbon atoms. Preferably, R 41 is an alkyl group having 1 to 7 carbon atoms and R 42 is an alkyl group having 1 to 7 carbon atoms or an alkoxy group having 1 to 7 carbon atoms, or R 41 is an alkenyl group having 2 to 7 carbon atoms and R 42 is an alkyl group having 1 to 7 carbon atoms. and The same or different meanings each time it appears. or better location and At least one of them Tie Z 41 and Z 42, each time appearing, represent the same or different forms of -CH 2CH 2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH 2O-, -CF 2O-, -C≡C-, or a single bond, preferably a single bond. p is 0, 1 or 2, preferably 0 or 1, even better 0.

[0124] Preferably, the liquid crystal medium of the present invention, especially the switchable layer of an electro-optic device, comprises one or more compounds of formula IV selected from the group of compounds of formula IV-1 to IV-5. R 41 and R 42 have the respective meanings given above under Formula IV, and in Formulas IV-1, IV-4 and IV-5, R 41 is preferably alkyl or alkenyl, preferably alkenyl, and R 42 is preferably alkyl or alkenyl, preferably alkyl; in Formula IV-2, R 41 and R 42 are preferably alkyl, and in Formula IV-3, R 41 is preferably alkyl or alkenyl, preferably alkyl, and R 42 is preferably alkyl or alkoxy, preferably alkoxy.

[0125] More preferably, the medium of the present invention comprises one or more compounds of formula IV-1 and one or more compounds of formula IV-4.

[0126] Preferably, the medium further comprises one or more compounds of formula IV selected from the group of formulas IV-6 to IV-13. in R 41 and R 42 independently represent alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy, alkenyl, alkenoxy, alkoxyalkyl or fluorinated alkenyl having 1 to 7 carbon atoms, and L4 represents H or F.

[0127] In a preferred embodiment, the liquid crystal medium comprises one or more compounds of formula IV-13, wherein L4 is an F-type compound.

[0128] In embodiments, the medium may comprise one or more compounds of formula V. in R5 series comprises alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy groups having 1 to 7 carbon atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl groups having 2 to 7 carbon atoms, and preferably alkyl groups having 1 to 7 carbon atoms or alkenyl groups having 2 to 7 carbon atoms. to Independent of each other or L51 and L52 independently represent H or F, with L51 preferably representing F. X 5 represents a halogen, a halogenated alkyl or alkoxy group having 1 to 3 carbon atoms, or a halogenated alkenyl or alkenyloxy group having 2 or 3 carbon atoms, preferably F, Cl, -OCF 3 or -CF 3, most preferably F, Cl or -OCF 3. Z 5 represents -CH 2CH 2-, -CF 2CF 2-, -COO-, trans-CH=CH-, trans-CF=CF-, or -CH 2O, with -CH 2CH 2-, -COO-, or trans-CH=CH- being preferred, and -COO- or -CH 2CH 2- being the most optimal. q represents 0 or 1.

[0129] Preferably, the medium of the present invention comprises one or more compounds of formula V selected from the group consisting of compounds of formula V-1 and V-2. The parameters have the individual meanings given above for formula V, and parameters L53 and L54 are independently H or F, and preferably Z5 is -CH2-CH2-.

[0130] Preferably, the compound of formula V-1 is selected from the group of compounds of formulas V-1a and V-1b. R5 has the meaning given above for formula V.

[0131] Preferably, the compound of formula V-2 is selected from the group of compounds of formulas V-2a to V-2d. R5 has the meaning given above for formula V.

[0132] Preferably, the liquid crystal medium of the present invention further comprises one or more compounds of formula VI. in R 61 represents an alkyl, alkoxy, fluorinated alkyl, or fluorinated alkoxy group having 1 to 7 carbon atoms, or an alkenyl, alkenoxy, alkoxyalkyl, or fluorinated alkenyl group having 2 to 7 carbon atoms, preferably an alkyl group having a maximum of 7 carbon atoms. R 62 represents F, an alkyl, alkoxy, fluorinated alkyl, or fluorinated alkoxy group having 1 to 7 carbon atoms, or an alkenyl, alkenoxy, alkoxyalkyl, or fluorinated alkenyl group having 2 to 7 carbon atoms. to The same or different meanings each time it appears. Z 61 and Z 62, in each occurrence, represent, in the same or different ways, -CH 2CH 2-, -COO-, trans-CH=CH-, trans-CF=CF-, -CH 2O-, -CF 2O-, or a single bond, preferably at least one of which is a single bond, and r can be 0, 1, or 2, with 0 or 1 being preferred.

[0133] Preferably, the compound of formula VI is selected from the group of compounds of formulas VI-1 to VI-4. R 61 and R 62 have the respective meanings given above for formula VI. R 61 is preferably an alkyl group with 1 to 7 carbon atoms, and in formula VI-1, R 62 is preferably an alkenyl group with up to 7 carbon atoms, more preferably -(CH 2) 2-CH=CH-CH 3, and in formula VI-2, R 62 is preferably an alkenyl group with up to 7 carbon atoms, more preferably -(CH 2) 2-CH=CH 2, and in formulas VI-3 and VI-4, R 62 is preferably an alkyl group with 1 to 7 carbon atoms.

[0134] Preferably, the liquid crystal medium comprises one or more compounds of form VI-1, the total amount of which is preferably at least 2.5% by weight, more preferably at least 4% by weight, and especially at least 7.5% by weight.

[0135] In the embodiments, the medium comprises one or more compounds of formula VI-2, preferably at least 5% by weight, more preferably at least 10% by weight, and especially at least 15% by weight.

[0136] In a preferred embodiment, the liquid crystal medium comprises a compound of the following formula. The abbreviation used below, as explained in Tables A through C, is also designated as compound CLP-V-1.

[0137] The liquid crystal medium of the present invention preferably maintains the nematic phase at temperatures as low as -20°C, more preferably as low as -30°C, and even more preferably as low as -40°C. Preferably, the liquid crystal medium of the present invention has a clarifying point of ≥ 75°C, more preferably ≥ 80°C, and particularly ≥ 85°C. Furthermore, the liquid crystal medium preferably exhibits a rotational viscosity γ1 of ≤ 110 mPa⋅s, and particularly preferably ≤ 100 mPa⋅s, wherein the rotational viscosity is measured at 20°C. Therefore, an LC display with a fast response time can be advantageously provided.

[0138] The rotational viscosity γ1 of the liquid crystal medium is preferably ≤ 80 mPa s, more preferably ≤ 70 mPa s, and even more preferably ≤ 60 mPa s.

[0139] The ratio γ1 / K11 of the liquid crystal medium (where γ1 is the rotational viscosity and K11 is the elastic constant of the warp deformation) is preferably ≤ 4.5 mPa. [, . , ]s / pN, preferably ≤ 4.2 mPa [, . , ]s / pN, optimal ≤ 4.0 mPa [, . , ]s / pN.

[0140] The nematic phase range of the liquid crystal medium of the present invention preferably has a width of at least 90°C, more preferably at least 100°C, and particularly at least 110°C. This range preferably extends at least from -25°C to +80°C.

[0141] It has been surprisingly found that the liquid crystal media currently available can advantageously contribute to achieving favorable electro-optical device performance, for example, in terms of contrast and high brightness transmittance, while also exhibiting functionality and reliability at both high and low temperatures.

[0142] The electro-optical device preferably includes a light source. For example, the backlight commonly used in LC displays can be used for illumination, such as LED backlighting or cold cathode fluorescent lamp backlighting.

[0143] Preferably, the polarizer used in the electro-optic device is a linear polarizer. In principle, a linear polarizer is used to linearly polarize light, so that the electric field of the light is confined to a single plane in the direction of propagation. In this regard, a linear polarizer has a transmission axis, also called a polarization axis, in which the polarizer selectively transmits light that is linearly polarized (i.e., aligned along this orientation) parallel to this axis.

[0144] In an embodiment, the two polarizers used in the electro-optic device are linear polarizers with a cross configuration, wherein the polarizers are configured such that the polarization axes are orthogonal to each other.

[0145] In a preferred embodiment, the electro-optical device is operable in at least a bright state and a dark state and is electrically switchable between the bright state and the dark state, and the device comprises in the following order: - Light source, - First linear polarizer, - As described in this article, switchable layers, and - Second linear polarizer, In the dark state, the absorption axis of one or more dichroic dyes as described herein is parallel to the transmission axis of the second linear polarizer, or the absorption axis of one or more dichroic dyes as described herein and the transmission axis of the second linear polarizer are arranged at an angle of 25° or less.

[0146] The state of the switchable layer, and therefore the optical state of the device, can be controlled by electrical switching, wherein an electric field can be applied via electrodes. Although the switchable layer may have other switching states, especially intermediate states, the device preferably switches between an optically bright state and an optically dark state, wherein the bright state has a greater degree of light transmission compared to the dark state. Specifically, although intermediate or so-called grayscale transmission states can be provided, the bright state provides the maximum light transmission and the dark state provides the minimum light transmission.

[0147] In a preferred embodiment, a dark state is provided, wherein the absorption axes of one or more dichroic dyes are parallel or substantially parallel to the transmission axis of the second linear polarizer, particularly when the first and second polarizers intersect each other. In this regard, the second polarizer is the polarizer located far from the light source. Although ideally the absorption and transmission axes are parallel, in some cases a substantially parallel configuration deviating somewhat from the parallel arrangement can be provided, which is still effective and suitable in this embodiment. In this case, the absorption axes of the one or more dichroic dyes described herein and the transmission axis of the second linear polarizer are arranged at an angle of 25° or less, particularly an azimuth angle, preferably an angle of 15° or less, even more preferably an angle of 5° or less, and particularly at an angle close to or approximately 0°.

[0148] In this embodiment, it is particularly preferred that the liquid crystal medium has a planar or horizontal alignment in the dark state.

[0149] For dichroic dyes, the light absorption properties depend on the orientation of the compound relative to the polarization direction of light. Dichroic dye compounds typically have elongated shapes, where the longitudinal or principal molecular axis is significantly longer than the other two spatial dimensions. For positive dichroic dyes, the absorption axis, and especially the transition dipole moment, is parallel to or at least substantially parallel to this longitudinal axis. For negative dichroic dyes, the absorption axis, and especially the transition dipole moment, is perpendicular to or at least substantially perpendicular to or transverse to this longitudinal axis. Therefore, the absorption axis is defined as the orientation or direction in which light absorption, especially visible light absorption, occurs within the molecular framework.

[0150] The term "light" in this document preferably refers to visible light, especially electromagnetic radiation with wavelengths from 380 nm to 780 nm.

[0151] The orientation of one or more dichroic dyes contained in the liquid crystal medium, and therefore the direction or orientation of the dye absorption axis, are given in this paper as spatial and temporal averages.

[0152] The desired orientation of the dichroic dyes, and therefore the direction of the dye absorption axis, especially in the dark state, can be provided and controlled by using a suitable alignment layer and / or switching appropriate electrical control at the cell substrate interface. Preferably, in the dark state, the dichroic dye molecules in the liquid crystal medium contained in the switchable layer are aligned parallel to the substrate and thus exhibit parallel or planar alignment.

[0153] It has been found that even in electro-optic devices using two polarizers, undesirable light leakage can still occur to some extent in the dark. When a dichroic dye is included in the switchable layer of the present invention, and the absorption axes of the dye molecules are set and aligned with regard to the second polarizer, particularly aligned parallel to or at least substantially parallel to the transmission axis of the second polarizer, undesirable light leakage can be effectively and significantly reduced or even avoided. Therefore, setting the absorption and transmission axes to be parallel can help further improve the dark state and the achievable contrast.

[0154] In another embodiment, the absorption axis of one or more dichroic dyes described herein and the transmission axis of the second linear polarizer are configured at angles greater than 25° and up to and including 90°. In this case, the use of one or more dichroic dyes of the present invention can still appropriately contribute to beneficial effects on dark states and contrast, compared to cases where the switchable layer does not include dyes.

[0155] In the embodiments, the medium may contain one or more additives, particularly one or more stabilizers, one or more chiral dopants, one or more polymerizable compounds and / or one or more self-aligning additives.

[0156] The term "alkyl" or "alkyl*" herein refers to straight-chain and branched alkyl groups having 1 to 6 carbon atoms, particularly straight-chain groups methyl, ethyl, propyl, butyl, pentyl, and hexyl. Groups having 2 to 5 carbon atoms are generally preferred.

[0157] The branched alkyl group may be selected from the second and / or third alkyl group, preferably the second alkyl group.

[0158] The term "alkenyl" or "alkenyl*" refers to preferably straight-chain and branched alkenyl groups having 2 to 6 carbon atoms, especially straight-chain groups. Preferred alkenyl groups are C2-C7-1E-alkenyl and C4-C6-3E-alkenyl, especially C2-C6-1E-alkenyl. Examples of particularly preferred alkenyl groups are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl, and 5-hexenyl. Groups having up to 5 carbon atoms are particularly preferred, especially CH2=CH and CH3CH=CH.

[0159] The term "fluoroalkyl" preferably encompasses a straight-chain group with a terminal fluorine fluoride, namely fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorohexyl, and 7-fluoroheptyl. However, other positions of fluorine are not excluded.

[0160] The terms "oxaalkyl" or "alkoxy" preferably cover a straight-chain group having the formula CnH2n+1-O-(CH2)m, wherein n and m each independently represent 1 to 6. m may also represent 0. Preferably, n=1 and m=1-6, or m=0 and n=1-3.

[0161] In embodiments of the present invention, the liquid crystal medium further comprises one or more polymerizable compounds, for example, to provide a PS-VA mode device. Preferably, the liquid crystal medium of the present invention comprises one or more polymerizable compounds selected from Table G below.

[0162] Preferably, the proportion of the polymerizable compound selected from Table G in the liquid crystal medium is 0.01 to 5%, very preferably 0.05 to 1%, and most preferably 0.1 to 0.5%.

[0163] Adding one or more polymerizable compounds (e.g., selected from Table G) to a liquid crystal medium can produce advantageous properties, such as fast response time. This liquid crystal medium is particularly suitable for PSA displays, which exhibit low image retention, fast and complete polymerization, rapid generation of low pretilt angles (stable after UV exposure), high reliability, high VHR value after UV exposure, and high birefringence. By appropriately selecting polymerizable compounds, the absorption of the liquid crystal medium at longer UV wavelengths can be increased, allowing these longer UV wavelengths to be used for polymerization, which is advantageous for display manufacturing processes.

[0164] The preferred type is a liquid crystal medium with a nematic liquid crystal phase and preferably without a chiral liquid crystal phase.

[0165] This invention also relates to the use of the liquid crystal medium of the present invention as described in the context for electro-optical purposes, particularly for shutter glasses, for 3D applications, for TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, UB-FFS, HB-FFS, PS-FFS, VA and PS-VA displays, and to electro-optical displays containing the liquid crystal medium of the present invention as described in the context, particularly of the types mentioned above, especially IPS, FFS, HB-FFS and UB-FFS displays.

[0166] Preferably, the electro-optical device of the present invention is used as or applied to desktop monitors, laptops, TVs, mobile phones, tablet PCs, and other multimedia applications. In embodiments, the device is an AR or VR device, particularly a VR display with extremely high resolution.

[0167] This invention also relates to an electro-optic display, such as an STN or MLC display, having two planar parallel outer plates forming a unit together with a frame, an integrated nonlinear element for switching individual pixels on the outer plates, and a nematic liquid crystal mixture located in the unit having negative or positive dielectric anisotropy and high specific resistance, wherein the nematic liquid crystal mixture is the liquid crystal medium of this invention as described in the context.

[0168] The liquid crystal medium of this invention can significantly expand the dimensions of available parameters. The combination of clearing point, low-temperature viscosity, thermal and UV stability, and high optical anisotropy is superior to that of previous materials from the prior art.

[0169] Comparative measurements of voltage retention rate (VHR) are shown, for example, in S. Matsumoto et al., Liquid Crystals. [5], 1320 (1989); K. Niwa et al., Proc. SID Conference, San Francisco, June 1984, p. 304 (1984); G. Weber et al., Liquid Crystals [5], 1381 (1989).

[0170] The MLC display of this invention, with its polarizer, electrode substrate, and surface-treated electrodes, corresponds to a common design for this type of display. The term "common design" has a broad meaning herein and also encompasses all derivatives and modifications of MLC displays, specifically including matrix display elements based on multi-Si TFTs or MIMs.

[0171] The liquid crystal medium that can be used according to the invention is prepared in a conventional manner, for example, by mixing a liquid crystal precursor compound and, where appropriate, additives. Generally, it is advantageous to dissolve the desired amount of a component used in a smaller quantity in the component constituting the main component at an elevated temperature. The solution of these components can also be mixed in an organic solvent (e.g., acetone, chloroform, or methanol), and the solvent is removed, for example, by distillation, after thorough mixing.

[0172] Liquid crystal media may also contain other additives known to those skilled in the art and described in the literature, such as polymerization inhibitors, inhibitors, surfactants, stabilizers, antioxidants (e.g., BHT, TEMPOL), microparticles, free radical scavengers, nanoparticles, etc. For example, pleochroic dyes or chiral dopants may be added. Suitable stabilizers and dopants are mentioned in Tables E and F below.

[0173] In one embodiment, the liquid crystal medium preferably contains one or more chiral dopants at a concentration of 0.01% to 1% by weight, and most preferably 0.05% to 0.5% by weight. The chiral dopants are preferably selected from the group consisting of compounds listed in Table E below, and most 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.

[0174] In another embodiment, the liquid crystal medium contains racemic components other than one or more chiral dopants, which are preferably selected from the chiral dopants mentioned in the preceding paragraphs.

[0175] In another embodiment, the LC medium of the present invention preferably contains a self-aligning (SA) additive at a concentration of 0.1% to 2.5% by weight. The LC medium of this embodiment is particularly suitable for polymer-stabilized SA-FFS, SA-UB-FFS, or SA-HB-FFS displays.

[0176] In a preferred embodiment, the SA-FFS, SA-UB-FFS, or SA-HB-FFS display of the present invention does not contain a polyimide alignment layer. In another preferred embodiment, the SA-FFS, SA-UB-FFS, or SA-HB-FFS display contains a polyimide alignment layer.

[0177] The preferred SA additive used in this embodiment is selected from compounds containing a liquid crystal precursor group and a straight-chain or branched alkyl side chain capped with one or more polar anchoring groups selected from hydroxyl, carboxyl, amino or thiol groups.

[0178] Other preferred SA additives include one or more polymerizable groups, which, where appropriate, are linked to the liquid crystal precursor group via spacer groups. These polymerizable SA additives can be polymerized in an LC medium under conditions similar to those applied to the RM in a PSA process.

[0179] Suitable SA additives for inducing vertical alignment, particularly for SA-VA mode displays, are described in, for example, US 2013 / 0182202 A1, US 2014 / 0838581 A1, US 2015 / 0166890 A1 and US 2015 / 0252265 A1.

[0180] In another preferred embodiment, the LC media or polymer-stabilized SA-FFS, SA-UB-FFS or SA-HB-FFS display of the present invention contains one or more self-aligning additives selected from Table H below.

[0181] In addition, nanoparticles, conductive salts to improve conductivity, preferably ethyl dimethyl dodecyl ammonium 4-hexyloxybenzoate, tetrabutylammonium tetraphenylborate, or crown ether chelates (see, for example, Haller et al., Mol. Cryst. Liq. Cryst. 24, 249-258 (1973)), or substances to modify dielectric anisotropy, viscosity, and / or nematic phase alignment can be added to the liquid crystal medium. Such substances are described, for example, in DE-A 22 09 127, 22 40 864, 23 21 632, 23 38 281, 24 50 088, 26 37 430, and 28 53 728.

[0182] The display of the present invention is preferably addressed by an active matrix, and more preferably by a matrix addressing of TFTs. However, the liquid crystal of the present invention can also be advantageously used in displays having other known addressing methods.

[0183] In this invention, and particularly in the following examples, the structures of the liquid crystal proto-compounds are represented by abbreviations (also known as acronyms). In these acronyms, the chemical formulas are abbreviated using Tables A to C below. All groups CnH2n+1, CmH2m+1, and ClH2l+1 or CnH2n-1, CmH2m-1, and ClH2l-1 represent straight-chain alkyl or alkenyl groups, preferably 1 E-alkenyl groups, having n, m, and l carbon atoms respectively, wherein n, m, and l independently represent integers from 1 to 9, preferably 1 to 7, or 2 to 9, preferably 2 to 7. CoH2o+1 represents a straight-chain alkyl group having 1 to 7, preferably 1 to 4 carbon atoms, or a branched alkyl group having 1 to 7, preferably 1 to 4 carbon atoms.

[0184] Table A lists the codes for ring elements used in the core structure of the compounds, while Table B shows the linking groups. Table C gives the meaning of the codes used for left-handed or right-handed end groups. Table D shows the illustrative structure of the compounds and their individual abbreviations. [, , ] [] [surface] [A] [Ring Elements] [, , ] [, , ] [] [surface] [B] [:linking group] [E] -CH 2CH 2- [Z] -CO-O- [V] -CH=CH- [ZI] -O-CO- [X] -CF=CH- [O] -CH 2-O- [XI] -CH=CN- [OI] -O-CH 2- [B] -CF=CF- [Q] -CF 2-O- [T] -C≡C- [QI] -O-CF 2- [W] -CF 2CF 2- [] [surface] [C] [Terminal group] [Left side] [Right-hand side] [Use alone] [-n-] C nH 2n+1- [-n] -C nH 2n+1 [-nO-] C nH 2n+1-O- [-On] -OC nH 2n+1 [-V-] CH 2=CH- [-V] -CH=CH 2 [-nV-] C nH 2n+1-CH=CH- [-nV] -C nH 2n-CH=CH 2 [-Vn-] CH 2=CH-C nH 2n+1- [-Vn] -CH=CH-C nH 2n+1 [-nVm-] C nH 2n+1-CH=CH-C mH 2m- [-nVm] -C nH 2n-CH=CH-C mH 2m+1 [-N-] N≡C- [-N] -C≡N [-S-] S=C=N- [-S] -N=C=S [-F-] F- [-F] -F [-Cl-] Cl- [-Cl] -Cl [-M-] CFH 2- [-M] -CFH 2 [-D-] CF 2H- [-D] -CF 2H [-T-] CF 3- [-T] -CF 3 [-MO-] CFH 2O- [-OM] -OCFH 2 [-DO-] CF 2HO- [-OD] -OCF 2H [-TO-] CF 3O- [-OT] -OCF 3 [-OXF-] CF 2=CH-O- [-OXF] -O-CH=CF 2 [-A-] H-C≡C- [-A] -C≡C-H [-nA-] C nH 2n+1-C≡C- [-An] -C≡C-C nH 2n+1 [-NA-] N≡C-C≡C- [-AN] -C≡C-C≡N [Used together with others] [-…A…-] -C≡C- [-…A…] -C≡C- [-…V…-] CH=CH- [-…V…] -CH=CH- [-…Z…-] -CO-O- [-…Z…] -CO-O- [-…ZI…-] -O-CO- [-…ZI…] -O-CO- [-…K…-] -CO- [-…K…] -CO- [-…W…-] -CF=CF- [-…W…] -CF=CF- Where n and m each represent integers, and the three dots "..." are placeholders for other abbreviations from this table.

[0185] The table below shows illustrative structures and their individual abbreviations. These structures are shown to explain the meaning of the abbreviation rules. They also represent compounds that are preferred for use.

[0186] [surface] [D] [:descriptive structure] [] The illustrative structure shows that the compound is particularly well-suited for use.

[0187] Where k, l, m and n are each an integer from 1 to 9, and more preferably from 1 to 7, which are independent of each other.

[0188] [surface] [E] Table E indicates possible chiral dopants to be added to the liquid crystal medium of the present invention, as appropriate. These liquid crystal media preferably contain 0-10% by weight, particularly 0.01-5% by weight, and even more preferably 0.01-3% by weight of chiral dopants.

[0189] [surface] [F] [] It is preferable to add 0.005-3% by weight of the stabilizer to the liquid crystal medium, as shown below.

[0190] [surface] [G] Table G shows illustrative reactive liquid crystal precursor compounds (RMs) that can be used in the liquid crystal media of this invention.

[0191] In a preferred embodiment, the liquid crystal medium of the present invention comprises one or more polymerizable compounds preferably selected from polymerizable compounds of formulas RM-1 to RM-145. Among these, compounds RM-1, RM-4, RM-8, RM-17, RM-19, RM-35, RM-37, RM-39, RM-40, RM-41, RM-48, RM-52, RM-54, RM-57, RM-64, RM-74, RM-76, RM-88, RM-102, RM-103, RM-109, RM-117, RM-120, RM-121, and RM-122 are particularly preferred.

[0192] [surface] [H] Table H shows self-aligning additives for vertical alignment, which may be used, as appropriate, together with polymerizable compounds, in the LC media of the SA-VA and SA-FFS displays of this invention.

[0193] In a preferred embodiment, the LC medium comprises one or more SA additives selected from SA-1 to SA-34, more preferably SA-14 to SA-34, more preferably SA-20 to SA-28, and most preferably SA-20, especially in combination with one or more RMs.

[0194] The following examples are merely illustrative of the invention and should not be construed as limiting the scope of the invention in any way. These examples, their modifications, or other equivalents will become apparent to those skilled in the art based on this disclosure.

[0195] However, the physical properties and composition described below illustrate which properties can be achieved and to what extent they can be modified. This fully defines the various combinations of properties that can be achieved, especially well.

[0196] [Work Example] Unless otherwise indicated, parts or percentage data are expressed as parts by weight or weight percentage of the mixture as a whole.

[0197] Symbols and abbreviations have the following meanings: The capacitive Freedericksz threshold voltage at 020℃ [V] V is the voltage transmitted at 1010% [V]. The extraordinary refractive index of ne was measured at 20°C and 589 nm. The ordinary refractive index measured at 20℃ and 589 nm. Optical anisotropy of Δn measured at 20℃ and 589 nm ε is the dielectric susceptibility (or "dielectric constant") perpendicular to the longitudinal axis of the molecule at 20 °C and 1 kHz. ε‖ is the dielectric susceptibility (or "dielectric constant") parallel to the longitudinal axis of the molecule at 20℃ and 1 kHz. Dielectric anisotropy of Δε at 20℃ and 1 kHz cl.p. or T(N,I) Clarity point [°C] ν is the flow viscosity [mm²·s⁻¹] measured at 20°C. γ1 rotational viscosity [mPa·s] measured at 20℃ Elastic constant of "bend" deformation at K 1120℃ [pN] The elastic constant [pN] of torsional deformation at K 2220℃. Elastic constant [pN] for bending deformation at K 3320℃. The overall low-temperature stability of the phase determined by LTS, and VHR (Voltage Holding Rate)

[0198] Unless otherwise explicitly indicated, for the purposes of this invention, the term "threshold voltage" refers to the capacitive threshold value (V0). In such instances, by common practice, the optical threshold value may also be indicated, for example, as 10% relative contrast (V10).

[0199] [Example of a reference mixture] Nematic host mixtures H1 to H13 were prepared as follows.

[0200] [Reference Mixture] [H1] CC-3-V 47.50% Clarification point [°C]: 74.8 CC-3-V1 7.50% Δn [589 nm, 20℃]: 0.1220 CLP-3-T 7.00% ne[589 nm, 20℃]: 1.6125 CPGU-3-OT 2.00% no[589 nm, 20℃]: 1.4905 PGP-2-2V 16.00% Δε [1 kHz, 20℃]: 4.9 PGU-2-F 11.00% [1 kHz, 20℃]: 2.9 PGUQU-3-F 6.00% γ 1[mPa s, 20℃]: 53 PP-1-2V1 2.00% PPGU-3-F 1.00% Σ 100.0%

[0201] [Reference Mixture] [H2] [] B(S)-2O-O4 4.00% Clarification point [°C]: 91.9 B(S)-2O-O5 4.00% Δn [589 nm, 20℃]: 0.0982 CC-3-V 41.00% ne[589 nm, 20℃]: 1.5814 CC-3-V1 3.50% no[589 nm, 20℃]: 1.4832 CCP-3-1 4.50% Δε [1 kHz, 20℃]: -3.4 CCY-3-O1 5.00% ε‖ [1 kHz, 20℃]: 3.4 CCY-3-O2 7.00% [1 kHz, 20℃]: 6.8 CLY-3-O2 6.50% CLY-3-O3 6.00% CPY-3-O2 10.00% CY-3-O2 7.00% PGIY-2-O4 1.50% Σ 100.0%

[0202] [Reference Mixture] [H3] [] The following compound B-2-b corresponds to the compound of formula B-2-b as specified and shown in the description above, wherein R 12 is an ethyl group. Compound B-2-b 4.00% Clarification point [°C]: 90.5 B(S)-2O-O5 4.00% CC-3-V 41.00% CC-3-V1 3.50% CCP-3-1 4.50% CCY-3-O1 5.00% CCY-3-O2 7.00% CLY-3-O2 6.50% CLY-3-O3 6.00% CPY-3-O2 10.00% CY-3-O2 7.00% PGIY-2-O4 1.50% Σ 100.0%

[0203] [Reference Mixture] [H4] [] CY-3-O2 9.00% Clarification point [°C]: 110.5 CY-3-O4 9.00% Δn [589 nm, 20℃]: 0.1322 CY-5-O2 12.00% ne[589 nm, 20℃]: 1.6212 CY-5-O4 8.00% Δε [1 kHz, 20℃]: -4.9 CCY-3-O2 5.00% [1 kHz, 20℃]: 8.8 CCY-3-O3 5.00% CCY-4-O2 5.00% CPY-2-O2 7.00% CPY-3-O2 6.00% PYP-2-3 12.00% CCP-V-1 6.00% CCZPC-3-3 3.00% CCZPC-3-4 3.00% CGPC-3-3 5.00% CGPC-5-3 5.00% Σ100.00%

[0204] [Reference Mixture] [H5] [] CPG-3-F 8.00% Clarification point [°C]: 114 CPG-5-F 8.00% Δn [589 nm, 20℃]: 0.1298 CPU-5-F 14.00% n e[589 nm, 20℃]: 1.6241 CPU-7-F 11.00% Δε [1 kHz, 20℃]: 10.0 CP-5-N 18.00% [1 kHz, 20℃]: 4.0 CP-7-N 13.00% CCGU-3-F 7.00% CC-3-O3 2.00% CGPC-3-3 4.00% CGPC-5-3 4.00% CGPC-5-5 3.00% CCZPC-3-3 3.00% CCZPC-3-4 3.00% CCZPC-3-5 2.00% Σ100.00%

[0205] [Reference Mixture] [H6] [] CPP-3-2 5.50% Clarification point [°C]: 75.3 CPP-5-2 2.50% Δn [589 nm, 20℃]: 0.1036 CC-3-V 21.00% ne[589 nm, 20℃]: 1.5884 CC-2-3 10.00% Δε [1 kHz, 20℃]: -3.0 CCP-3-1 3.00% [1 kHz, 20℃]: 6.6 CCY-3-O2 9.00% CLY-3-O2 1.00% CPY-2-O2 8.00% CPY-3-O2 10.00% CY-3-O2 13.00% CY-3-O4 11.50% PYP-2-3 3.50% PYP-2-4 2.00% Σ100.00%

[0206] [Reference Mixture] [H7] [] The following compounds Y2A-1 and Y1A-5 correspond to the compounds of formula Y2A-1 and Y1A-5 as specified and shown in the description above. CPP-3-2 5.50% Clarification point [°C]: 74.0 CPP-5-2 2.50% CC-3-V 21.00% CC-2-3 10.00% CCP-3-1 3.00% CCY-3-O2 9.00% CLY-3-O2 1.00% Compound Y2A-1 8.00% CPY-3-O2 10.00% CY-3-O2 13.00% Compound Y1A-5 11.50% PYP-2-3 3.50% PYP-2-4 2.00% Σ100.00%

[0207] [Reference Mixture] [H8] [] CC-3-V 46.60% Clarification point [°C]: 75.9 CC-3-O3 4.40% Δn [589 nm, 20℃]: 0.1176 CCP-V-1 7.20% ne[589 nm, 20℃]: 1.6068 CCVC-3-V 2.00% no[589 nm, 20℃]: 1.4892 CPGU-3-OT 5.00% Δε [1 kHz, 20℃]: 3.9 PGP-2-2V 15.00% ε‖ [1 kHz, 20℃]: 6.9 PGP-2-3 6.10% [1 kHz, 20℃]: 3.0 PPGU-3-F 1.00% PUQU-2-F 5.00% PUQU-3-F 7.70% Σ 100.0%

[0208] [Reference Mixture] [H9] [] CC-3-2V1 1.50% Clarification point [°C]: 80.1 CC-3-V 37.50% Δn [589 nm, 20℃]: 0.1374 CC-3-V1 8.00% ne[589 nm, 20℃]: 1.6338 CCVC-3-V 3.00% Δε [1 kHz, 20℃]: 3.3 CLP-3-T 2.00% [1 kHz, 20℃]: 2.9 CLP-V-1 1.50% DGUQU-4-F 5.00% PGP-1-2V 7.50% PGP-2-2V 14.00% PGP-3-2V 2.50% PGU-2-F 6.00% PP-1-2V1 10.50% PPGU-3-F 1.00% Σ100.00%

[0209] [Reference Mixture] [H10] [] APUQU-2-F 6.00% Clarification point [°C]: 80.8 APUQU-3-F 8.00% Δn [589 nm, 20℃]: 0.1125 CC-3-V 26.00% ne[589 nm, 20℃]: 1.6002 CCP-V-1 14.00% Δε [1 kHz, 20℃]: 10.5 CCP-V2-1 12.00% [1 kHz, 20℃]: 5.1 DGUQU-4-F 5.00% DPGU-4-F 5.00% PGP-2-2V 4.50% PGUQU-3-F 5.00% PGUQU-4-F 3.00% PPGU-3-F 0.50% Y-4O-O4 11.00% Σ100.00%

[0210] [Reference Mixture] [H11] [] B(S)-2O-O4 4.00% Clarification point [°C]: 115.4 B(S)-2O-O5 3.00% Δn [589 nm, 20℃]: 0.0987 B(S)-2O-O6 2.00% ne[589 nm, 20℃]: 1.5804 CC-3-V 10.50% n o[589 nm, 20℃]: 1.4817 CC-3-V1 7.00% Δε [1 kHz, 20℃]: -4.4 CC-3-4 8.00% ε‖[1 kHz, 20℃]: 3.4 CC-3-5 10.00% CCP-V2-1 1.50% CCZPC-3-5 3.00% CCY-3-O1 4.00% CCY-3-O2 6.00% CCY-3-O3 4.00% CCY-4-O2 4.00% CCY-5-O2 4.00% CLY-2-O4 3.00% CLY-3-O2 6.00% CLY-3-O3 4.00% CLY-4-O2 3.00% CLY-5-O2 3.00% CPY-3-O2 3.00% CY-3-O2 3.00% CY-3-O4 4.00% Σ 100.0%

[0211] [Reference Mixture] [H12] [] CPP-3-2 9.00% Clarification point [°C]: 102.8 CC-3-V 30.00% Δn [589 nm, 20°C]: 0.1117 CC-3-V1 1.00% n e[589 nm, 20°C]: 1.6022 CCP-3-1 10.00% Δε [1 kHz, 20°C]: 5.8 CCP-V-1 10.50% [1 kHz, 20°C]: 2.8 CCZPC-3-3 3.00% CLU-3-F 20.00% PGUQU-3-F 5.00% PGUQU-4-F 7.00% PP-1-2V1 4.50% Σ100.00%

[0212] [Reference Mixture] [H13] [] CC-3-V 32.30% Clarification point [°C]: 110 CC-3-V1 6.00% Δn [589 nm, 20℃]: 0.1239 CCP-V-1 15.00% ne[589 nm, 20℃]: 1.6168 CCP-V2-1 4.00% no[589 nm, 20℃]: 1.4929 CCVC-3-V 6.00% Δε [1 kHz, 20℃]: 3.6 CDUQU-3-F 3.00% ε‖[1 kHz, 20℃]: 6.3 CLP-V-1 5.00% CPGP-4-3 1.50% CPGU-3-OT 2.00% DGUQU-4-F 3.50% CP-3-O2 1.50% PGP-2-2V 5.00% PGUQU-3-F 3.20% PPGU-3-F 1.00% PUS-3-2 11.00% Σ 100.0%

[0213] [Reference Dye Mixture] [DM1] [] Provide a dichroic dye mixture DM1 containing the following: 18% of Dye-1 Dye-1, 38% of Dye-2 Dye-2 and 44% of Dye-3 Dye-3.

[0214] [Examples and Comparative Examples] [] [Example] [M1.1] [、] [M1.2] [、] [M1.3] [、] [M1.4] [、] [M1.5] [and] [M1.6] [and comparative examples] [CM1.1] [and] [CM1.2] [] Add 0.040% of the following compound to the reference mixture H1 as shown above. It will be referred to as ST-1 below to obtain mixture M1.

[0215] The dye mixture DM1 as shown above was added to mixture M1 in the amounts shown in the table below to obtain mixtures M1.1, M1.2, M1.3, M1.4, M1.5 and M1.6, and comparative mixtures CM1.1 and CM1.2, respectively. Add the amount of DM1 to M1 CM1.1 - M1.1 0.01% by weight M1.2 0.05% by weight M1.3 0.1% by weight M1.4 0.2% by weight M1.5 0.5% by weight M1.6 1.0% by weight CM1.2 2.5% by weight

[0216] Compared to the comparative mixture CM1.1, which contains no dichroic dye, mixtures M1.1 to M1.6 have the same or very similar values ​​of optical anisotropy, dielectric anisotropy, elastic constant, and rotational viscosity. For the comparative mixture CM1.2, which contains 2.5% by weight of dichroic dye, the optical anisotropy is significantly altered.

[0217] Mixtures M1.1, M1.2, M1.3, M1.4, M1.5 and M1.6, and comparative mixtures CM1.1 and CM1.2 were filled into FFS electro-optic units and their electro-optic performance was evaluated.

[0218] Compared with the units containing mixtures M1.1 to M1.6 and the comparative mixture CM1.1 respectively, the unit containing the comparative mixture CM1.2 exhibits a less favorable operating voltage and reaction time.

[0219] The color coordinates differ very little between all FFS units.

[0220] Compared to the unit containing the comparative mixture CM1.1, all other units have improved dark states, reduced scattering, and reduced light leakage.

[0221] However, compared with the units containing mixtures M1.1 to M1.6 respectively, the unit containing the comparative mixture CM1.2 showed a significantly reduced transmittance in the bright state.

[0222] Units containing mixtures M1.1 to M1.6 exhibit favorable bright-state transmittance, favorable contrast ratio, and favorable reaction time.

[0223] [Example] [M2.1] [、] [M2.2] [、] [M2.3] [、] [M2.4] [、] [M2.5] [and] [M2.6] [and comparative examples] [CM2.1] [and] [CM2.2] [] Add 0.040% of compound ST-1 as shown above and 0.005% of the following compound to the reference mixture H2 as shown above. It will be referred to as ST-2 below to obtain mixture M2.

[0224] The dye mixture DM1 as shown above was added to mixture M2 in the amounts shown in the table below to obtain mixtures M2.1, M2.2, M2.3, M2.4, M2.5 and M2.6, and comparative mixtures CM2.1 and CM2.2, respectively. Add the amount of DM1 to M2 CM2.1 - M2.1 0.01% by weight M2.2 0.05% by weight M2.3 0.1% by weight M2.4 0.2% by weight M2.5 0.5% by weight M2.6 1.0% by weight CM2.2 2.5% by weight

[0225] Compared to the comparative mixture CM2.1, which contains no dichroic dye, mixtures M2.1 to M2.6 have the same or very similar values ​​of optical anisotropy, dielectric anisotropy, elastic constant, and rotational viscosity. For the comparative mixture CM2.2, which contains 2.5% by weight of dichroic dye, the optical anisotropy is significantly altered.

[0226] Mixtures M2.1, M2.2, M2.3, M2.4, M2.5 and M2.6, and comparative mixtures CM2.1 and CM2.2 were filled into FFS cells and their electro-optical properties were evaluated.

[0227] Compared with the units containing mixtures M2.1 to M2.6 and the comparative mixture CM2.1 respectively, the unit containing the comparative mixture CM2.2 exhibits a less favorable operating voltage and reaction time.

[0228] The color coordinates differ very little between all FFS units.

[0229] Compared to the unit containing the comparative mixture CM2.1, all other units have improved dark states and reduced scattering and light leakage.

[0230] However, compared with the units containing mixtures M2.1 to M2.6 respectively, the unit containing the comparative mixture CM2.2 showed a significantly reduced transmittance in the bright state.

[0231] Units containing mixtures M2.1 to M2.6 exhibit favorable bright-state transmittance, favorable contrast ratio, and favorable reaction time.

[0232] [Example] [M3.1] [、] [M3.2] [、] [M3.3] [、] [M3.4] [、] [M3.5] [and] [M3.6] [and comparative examples] [CM3.1] [and] [CM3.2] [] Mixtures M3.1, M3.2, M3.3, M3.4, M3.5 and M3.6 and comparative mixtures CM3.1 and CM3.2 are prepared as described above, similar to mixtures M2.1, M2.2, M2.3, M2.4, M2.5 and M2.6 and comparative mixtures CM2.1 and CM2.2, wherein reference mixture H3 as shown above is used instead of reference mixture H2.

[0233] Mixtures M3.1, M3.2, M3.3, M3.4, M3.5 and M3.6 provide favorable device performance, especially favorable contrast, transmittance and response time of the display.

[0234] [Example] [4] [] Add 0.08% of the following compound to the reference mixture H4 as shown above. It will be referred to as ST-3 below to obtain mixture B4.

[0235] Mixture M4 was obtained by adding 0.16% of Dye-1 as described above, 0.35% of Dye-2 as described above, and 0.43% of Dye-3 as described above to mixture B4.

[0236] Mixture M4 provides favorable device performance, especially for displays with favorable contrast, transmittance and response time.

[0237] [Example] [5] [] Add 0.025% of compound ST-2 and 0.150% of compound ST-3 as shown above to the reference mixture H5 as shown above to obtain mixture B5.

[0238] Mixture M5 was obtained by adding 0.047% of Dye-1 as described above, 0.092% of Dye-2 as described above, and 0.110% of Dye-3 as described above to mixture B5.

[0239] Mixture M5 provides favorable device performance, especially for displays with favorable contrast, transmittance, and response time.

[0240] [Example] [6] [] Add the following to the reference mixture H5 as shown above: 0.100% of compound ST-3 as shown above, and 0.032% of Dye-4. Dye-4, 0.063% of Dye-5 Dye-5, 0.077% of Dye-6 Dye-6, 0.060% of Dye-7 Dye-7, 0.073% of Dye-8 Dye-8 and 0.037% Dye-9 Dye-9 To obtain mixture M6.

[0241] Mixture M6 provides favorable device performance, especially for displays with favorable contrast, transmittance, and response time.

[0242] [Reference dye mixture] [DM2] [] DM2 is a mixture of dichroic dyes containing 9% Dye-4, 20% Dye-5, 17% Dye-6, 26% Dye-7 and 28% Dye-8.

[0243] [Example] [7.1] [and] [7.2] [and comparative examples] [7] [] Add 0.2% of dye mixture DM2 to mixture M1 as shown above to obtain mixture M7.

[0244] According to Comparative Example 7, a dye-free mixture M1 was filled into an electro-optic unit (a glass substrate coated with an ITO layer having a polyimide alignment layer), wherein the unit further includes a first linear polarizer facing the light source and a second linear polarizer facing away from the light source and oriented perpendicular to the first linear polarizer. Visible light transmission in the dark was measured, and residual light leakage was observed.

[0245] According to Example 7.1, mixture M7 was filled into an electro-optic unit with a cross-polarized linear polarizer, wherein in the dark state, the absorption axis of the dichroic dye is parallel to the transmission axis of the first linear polarizer facing the light source. Visible light transmission in the dark state was measured. Compared to the unit in Comparative Example 7, light leakage in the dark state was reduced, and the transmission was only 81% relative to the dark state transmission of the unit in Comparative Example 7.

[0246] According to Example 7.2, mixture M7 was filled into an electro-optic unit with a cross-polarized linear polarizer, wherein in the dark state, the absorption axis of the dichroic dye is parallel to the transmission axis of the second linear polarizer facing away from the light source, i.e., parallel to the polarizer located far from the light source. Visible light transmission in the dark state was measured. Compared with the unit in Comparative Example 7, light leakage in the dark state was further reduced, and the transmission was only 74% relative to the dark state transmission of Comparative Example 7.

[0247] [Example] [8.1] [and] [8.2] [and comparative examples] [8] [] Add 0.2% of dye mixture DM2 to mixture M2 as shown above to obtain mixture M8.

[0248] According to Comparative Example 8, a dye-free mixture M2 was filled into an electro-optic unit with a cross-polarizer. Visible light transmission in the dark was measured, and residual light leakage was observed.

[0249] According to Example 8.1, mixture M8 was filled into an electro-optic unit with a cross-polarizer, wherein in the dark state, the absorption axis of the dichroic dye is parallel to the transmission axis of the first linear polarizer facing the light source. Visible light transmission in the dark state was measured. Compared with the unit of Comparative Example 8, light leakage in the dark state was reduced, and the transmission was only 76% relative to the dark state transmission of Comparative Example 8.

[0250] According to Example 8.2, mixture M8 was filled into an electro-optic unit with a cross-polarizer, wherein in the dark state, the absorption axis of the dichroic dye is parallel to the transmission axis of the second linear polarizer facing away from the light source. Visible light transmission in the dark state was measured. Compared with the unit of Comparative Example 8, light leakage in the dark state was further reduced, and the transmission was only 70% relative to the dark state transmission of Comparative Example 8.

[0251] [Example] [9.1] [and] [9.2] [and comparative examples] [9] [] Add 0.04% of compound ST-1 and 0.02% of compound ST-2 as shown above to the reference mixture H10 as shown above to obtain mixture B9.

[0252] Add 0.2% dye mixture DM2 to mixture B9 to obtain mixture M9.

[0253] According to Comparative Example 9, a dye-free mixture B9 was filled into an electro-optic unit with a cross-polarizer. Visible light transmission in the dark was measured, and residual light leakage was observed.

[0254] According to Example 9.1, mixture M9 was filled into an electro-optic unit with a cross-polarizer, wherein in the dark state, the absorption axis of the dichroic dye is parallel to the transmission axis of the first linear polarizer facing the light source. Visible light transmission in the dark state was measured. Compared with the unit of Comparative Example 9, light leakage in the dark state was reduced, and the transmission was only 80% relative to the dark state transmission of Comparative Example 9.

[0255] According to Example 9.2, mixture M9 was filled into an electro-optic unit with a cross-polarizer, wherein in the dark state, the absorption axis of the dichroic dye is parallel to the transmission axis of a second linear polarizer facing away from the light source. Visible light transmission in the dark state was measured. Compared to the unit of Comparative Example 9, light leakage in the dark state was further reduced, and the transmission was only 72% relative to the dark state transmission of Comparative Example 9.

[0256] [Example] [10.1] [and] [10.2] [and comparative examples]

[10] [] Add 0.04% of compound ST-3 as described above to the reference mixture H11 as shown above to obtain mixture B10.

[0257] Add 0.10% of dye mixture DM2 to mixture B10 to obtain mixture M10.

[0258] According to Comparative Example 10, a dye-free mixture B10 was filled into an electro-optic unit with a cross-polarizer. Visible light transmission in the dark was measured, and residual light leakage was observed.

[0259] According to Example 10.1, mixture M10 was filled into an electro-optic unit with a cross-polarizer, wherein in the dark state, the absorption axis of the dichroic dye is parallel to the transmission axis of the first linear polarizer facing the light source. Visible light transmission in the dark state was measured. Compared with the unit of Comparative Example 10, light leakage in the dark state was reduced, and the transmission was only 97% relative to the dark state transmission of Comparative Example 10.

[0260] According to Example 10.2, mixture M10 was filled into an electro-optic unit with a cross-polarizer, wherein in the dark, the absorption axis of the dichroic dye is parallel to the transmission axis of a second linear polarizer facing away from the light source. Visible light transmission in the dark was measured. Compared with the unit of Comparative Example 10, light leakage in the dark was further reduced, and the transmission was only 79% relative to the dark transmission of Comparative Example 10.

[0261] [Example]

[11] [] Add 0.050% of compound ST-1 as described above to the reference mixture H12 as shown above to obtain mixture M12.

[0262] M12 is treated similarly to mixture M1 as described above.

[0263] [Example]

[12] [] Add 0.050% of compound ST-1 as shown above and 0.015% of the following compound to the reference mixture H13 as shown above. It will be referred to as ST-4 below to obtain mixture M13.

[0264] M13 was then processed in a manner similar to that of mixture M1, as described above.

[0265] [Example]

[13] [] Mixture M14 is prepared by including 0.25% Dye-5, 0.50% Dye-6 and 0.25% Dye-7 in the reference mixture H1 as shown above.

[0266] The mixture M14 provides favorable device performance, especially for displays with favorable contrast, transmittance and response time.

[0267] [Example]

[14] [] Mixture M15 is prepared by including 1.00% Dye-6 and 1.00% Dye-7 in the reference mixture H1 as shown above.

[0268] The M15 mixture provides favorable device performance, especially for displays with favorable contrast, transmittance and response time.

Claims

1. An electro-optic device comprising: a switchable layer inserted between two opposing transparent substrates, wherein each substrate is provided with an electrode structure, or one of the substrates is provided with two electrode structures and the other substrate is not provided with electrodes; two polarizers and, if applicable, at least one optical retarder; wherein the switchable layer comprises a liquid crystal medium; wherein the liquid crystal medium comprises one or more dichroic dyes, wherein the one or more dichroic dyes are contained in the medium in a total amount of 2.0% by weight or less; and one or more compounds of formula IV-1, wherein R41 and R42 independently represent alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 carbon atoms or alkenyl, alkenoxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 carbon atoms, wherein the one or more compounds of formula IV-1 are contained in the liquid crystal medium in a total amount of at least 30% by weight.

2. The electro-optical device of claim 1, wherein the one or more dichroic dyes are contained in the liquid crystal medium in a total amount of 1.0% by weight or less.

3. The electro-optical apparatus of claim 1, wherein the one or more dichroic dyes are selected from azo compounds, anthraquinones, thiophene anthraquinones, methine compounds, methylimine compounds, anthocyanin compounds, naphthoquinones, tetraazines, pyrromethene dyes, malononitrile dyes, nickel dithiolenes, phthalocyanines, naphthophthalocyanines, porphyrins, rylenes, thiadiazole dyes, thieno-thiadiazole dyes, benzothiadiazoles, thiadiazole-quinoline, and diketylpyrrolopyrrole.

4. An electro-optical device as described in any of claims 1 to 3, wherein the device is a liquid crystal display.

5. An electro-optical device as claimed in any one of claims 1 to 3, wherein the device is operable in at least a bright state and a dark state and is electrically switchable between at least the bright state and the dark state, and wherein the device comprises, in the following order: a light source, a first linear polarizer, the switchable layer, and a second linear polarizer, wherein, In the dark state, the absorption axis of the one or more dichroic dyes is parallel to the transmission axis of the second linear polarizer, or the absorption axis of the one or more dichroic dyes and the transmission axis of the second linear polarizer are arranged at an angle of 25° or less.

6. An electro-optical device as claimed in any of claims 1 to 3, wherein the compound of one or more of the form IV-1 is contained in the liquid crystal medium in a total amount of at least 40% by weight.

7. An electro-optic device according to any one of claims 1 to 3, wherein the liquid crystal medium comprises one or more compounds selected from the group of compounds of formula B-1, B-2 and B-3, wherein R11 and R12 represent H or straight-chain alkyl or alkoxy groups having 1 to 15 C atoms, wherein one or more CH2 groups among such groups are, as appropriate, independently substituted with -C≡C-, -CF2O-, -OCF2-, -CH=CH-, -O-, -CO-O- or -O-CO- in a manner in which O atoms are not directly connected to each other, and wherein one or more H atoms may be substituted with halogens.

8. An electro-optic device according to any one of claims 1 to 3, wherein the liquid crystal medium comprises one or more compounds selected from the group of compounds of formula Y1, Y2 and LY, wherein R1 and R2 independently represent unsubstituted or halogenated straight-chain, branched or cyclic alkyl or alkoxy groups having 1 to 15 C atoms, wherein one or more CH2 groups among these groups may be independently substituted by -C≡C-, -CF2O-, -CH=CH-, -O-, -CO-O- or -O-CO- in a manner in which O atoms are not directly connected to each other, Zx and Zy independently represent -CH2CH2-, -CH=CH-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -CO-O-, -O-CO-, -C2F4-, -CF=CF-, -CH=CH-CH2O- or single bonds, and L1, L2, L3, L4 H, F, or Cl are represented independently of each other; a and b are either 0, 1, or 2, and x is 1 or 2.

9. An electro-optic device as claimed in any one of claims 1 to 3, wherein the liquid crystal medium comprises one or more compounds of formula VI, wherein R61 represents an alkyl, alkoxy, fluorinated alkyl, or fluorinated alkoxy having 1 to 7 C atoms, or an alkenyl, alkenoxy, alkoxyalkyl, or fluorinated alkenyl having 2 to 7 C atoms, R62 represents F, an alkyl, alkoxy, fluorinated alkyl, or fluorinated alkoxy having 1 to 7 C atoms, or an alkenyl, alkenoxy, alkoxyalkyl, or fluorinated alkenyl having 2 to 7 C atoms, Z61 and Z62, in each occurrence, represent -CH2CH2-, -COO-, trans--CH=CH-, trans---CF=CF-, -CH2O-, -CF2O-, or a single bond, and r is 0, 1, or 2.

10. An electro-optic device according to any one of claims 1 to 3, wherein the liquid crystal medium comprises one or more compounds selected from the group of compounds of formulas II-1 and II-2, wherein R2 represents an alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 carbon atoms or an alkenyl, alkenoxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 carbon atoms, wherein one or more CH2 groups may be independently substituted for each other, L21, L22, L23 and L24 independently represent H or F, L25 represents H or CH3, and X2 represents a halogen, a halogenated alkyl or alkoxy having 1 to 3 carbon atoms or a halogenated alkenyl or alkenoxy having 2 or 3 carbon atoms.

11. A liquid crystal medium comprising one or more dichroic dyes, the total amount of which is 2.0% by weight or less, and one or more compounds of formula IV-1, the total amount of which is at least 30% by weight, wherein R41 and R42 independently represent alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 carbon atoms or alkenyl, alkenoxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 carbon atoms.

12. The liquid crystal medium of claim 11, wherein the one or more dichroic dyes are selected from azo compounds, anthraquinones, thiophene anthraquinones, methine compounds, methylimine compounds, anthocyanin compounds, naphthoquinones, tetraazines, pyrrolemethane dyes, malononitrile dyes, nickel dithioenes, phthalocyanines, naphthocyanins, porphyrins, naphthalene-phenylene oxides, thiadiazole dyes, thieno-thiadiazole dyes, benzothiadiazoles, thiadiazole-quinoline, and diketopyrrolopyrroles.

13. The liquid crystal medium of claim 11 or 12, wherein the medium contains at least three different dichroic dyes.

14. The liquid crystal medium of claim 11 or 12, wherein the medium contains one or more stabilizers, one or more chiral dopants, one or more polymerizable compounds and / or one or more self-aligning additives.