Liquid crystal medium

Abstract

The invention relates to a liquid crystal medium comprising a liquid crystal host consisting of a liquid crystal component H) containing one or more mesogenic or liquid crystal compounds and an optically active component D), and optionally a polymerizable component P) containing one or more polymerizable compounds; the invention further relates to the use of the polymerizable compounds and the liquid crystal media for optical, electro-optical and electronic purposes, in particular in liquid crystal displays, in particular in liquid crystal displays of the polymer-stabilized alignment type.

Description

[0001] This application is a divisional application of the patent application with the application number 201811560527.4. Technical Field

[0002] The present invention relates to liquid crystal media (LC media) and to the use of such liquid crystal media for optical, electro-optical and electronic purposes, in particular in liquid crystal displays, especially in polymer-stabilized aligned liquid crystal displays. Background Art

[0003] One of the currently used liquid crystal display (LCD) modes is the TN (twisted nematic) mode. However, TN LCDs have the disadvantage of strong contrast viewing angle dependence.

[0004] In addition, so-called VA (vertical alignment) displays with a wider viewing angle are known. The LC cell of a VA display contains a layer of LC medium between two transparent electrodes, where the LC medium usually has a negative dielectric anisotropy. In the power-off state, the molecules of the LC layer are aligned perpendicular to the electrode surface (vertically) or have an inclined vertical alignment. When a voltage is applied to the two electrodes, realignment of the LC molecules parallel to the electrode surface occurs.

[0005] Also known are so-called IPS ("in-plane switching") displays, which contain an LC layer between two substrates, where the two electrodes are arranged on only one of the two substrates and preferably have an intermeshing 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 therebetween. This causes realignment of the LC molecules in the layer plane.

[0006] In addition, so-called FFS (fringe field switching) displays have been reported (see in particular S.H. Jung et al., Jpn. J. Appl. Phys., Vol. 43, No. 3, 2004, 1028), which contain two electrodes on the same substrate, one of which is structured in a comb-like manner and the other is unstructured. This results in a strong so-called "fringe field", i.e., a strong electric field close to the electrode edges, and such an electric field throughout the cell, which has both a strong vertical component and a strong horizontal component. FFS displays have a small contrast viewing angle dependence. FFS displays usually contain an LC medium with a positive dielectric anisotropy and an alignment layer, usually an alignment layer of polyimide, which provides planar alignment of the molecules of the LC medium.

[0007] The FFS display can operate as an active matrix or a passive matrix display. In the case of an active matrix display, individual pixels are typically addressed through integrated non-linear active elements such as transistors (e.g., thin film transistors or "TFTs"), while in the case of a passive matrix display, individual pixels are typically addressed according to multiplexing methods known in the prior art.

[0008] In addition, FFS displays have been disclosed (cf. S.H. Lee et al., Appl. Phys. Lett. 73(20), 1998, 2882 - 2883 and S.H. Lee et al., Liquid Crystals 39(9), 2012, 1141 - 1148), which have an electrode design and layer thickness similar to the FFS display, but include a layer with an LC medium having negative dielectric anisotropy instead of a layer with an LC medium having positive dielectric anisotropy. Compared with an LC medium having positive dielectric anisotropy, an LC medium having negative dielectric anisotropy shows a more favorable director orientation, which has less tilt and more twist orientation, and as a result, these displays have a higher transmittance. The display also includes an alignment layer, preferably a polyimide alignment layer provided on at least one substrate, which contacts the LC medium and induces planar alignment of the LC molecules of the LC medium. These displays are also referred to as "Ultra Bright FFS (UB - FFS)" mode displays. These displays require an LC medium with high reliability.

[0009] The term "reliability" as used hereinafter means the quality of the performance of the display during a period of time and under different stress loads, such as light load, temperature, humidity, voltage, and includes display effects such as image sticking (surface and line image sticking), color mura, non-uniformity (yogore), etc., which are known to those skilled in the art of LC displays. As a standard parameter for classifying reliability, the voltage holding ratio (VHR) value is typically used, which is a measure for maintaining a constant voltage in the test display. Among other factors, a high VHR value is a prerequisite for high reliability of the LC medium.

[0010] In a newer type of VA display, the homogeneous alignment of the LC molecules is limited to a plurality of relatively small domains within the LC cell. There can be disclinations, also called tilt domains, between these domains. A VA display with tilt domains has a greater contrast and a viewing angle independence of gray levels compared to a conventional VA display. Additionally, this type of display is easier to manufacture because no additional electrode surface treatment (e.g., by rubbing) for homogeneous alignment of the molecules in the on state is required. Instead, the preferred director of the tilt angle or pre-tilt angle is controlled by a special design of the electrodes.

[0011] In so-called MVA (multi-domain vertical alignment) displays, this is typically achieved by electrodes having protrusions that cause local pre-tilting. Thereby, when a voltage is applied, the LC molecules are aligned parallel to the electrode surface in different, defined cell regions in different directions. Thereby, "controlled" switching is achieved and the formation of disturbing rotational displacement lines is prevented. Although such an arrangement improves the viewing angle of the display, however, this results in a reduction in its light transmittance. A further improvement of MVA uses protrusions only on one electrode side, while the opposite electrode has slits, which improves the light transmittance. The slit electrode generates a non-uniform electric field in the LC cell when a voltage is applied, meaning that controlled switching is still achieved. To further improve the light transmittance, the spacing between the slit and the protrusion can be increased, but this in turn results in an extension of the response time. In so-called PVA ("patterned VA"), the protrusions are made completely redundant, since both electrodes are structured by slits on opposite sides, which results in increased contrast and improved light transmittance, but this is technically difficult and makes the display more sensitive to mechanical influences ("tapping", etc.). However, for many applications, such as monitors and especially TV screens, a shortening of the response time as well as an improvement in the contrast and brightness (transmittance) of the display are required.

[0012] Another development is the so-called PS ("polymer stabilized") or PSA ("polymer stabilized alignment") display, for which the term "polymer stabilization" is also occasionally used. In these, a small amount (e.g. 0.3 wt%, typically <1 wt%) of one or more polymerizable compounds, preferably polymerizable monomer compounds, is added to the LC medium, and after the LC medium has been filled into the display, it is polymerized or crosslinked in situ (usually by UV photopolymerization), while optionally applying a voltage to the electrodes of the display. The polymerization is carried out at the temperature at which the LC medium exhibits a liquid crystal phase, typically at room temperature. Adding polymerizable mesogens or liquid crystal compounds (also called reactive mesogens or "RMs") to the LC mixture has proven to be particularly suitable.

[0013] Unless otherwise stated, the term "PSA" is used hereinafter when referring to displays of the generally polymer stabilized alignment type, and the term "PS" is used when referring to specific display modes (such as PS-VA, PS-TN, etc.).

[0014] Furthermore, unless otherwise stated, the term "RM" is used hereinafter when referring to polymerizable mesogens or liquid crystal compounds.

[0015] At the same time, the PS(A) principle is being used in various conventional LC display modes. Thus, for example, PS-VA, PS-OCB, PS-IPS, PS-FFS, PS-UB-FFS, and PS-TN displays are known. The aggregation of the RM preferably occurs under the applied voltage in the case of PS-VA and PS-OCB displays, and occurs with or without, preferably without, the applied voltage in the case of PS-IPS displays. As can be verified in a test cell, the PS(A) method results in a pretilt in the cell. In the case of PS-VA displays, this pretilt has a positive effect on the response time. For PS-VA displays, standard MVA or PVA pixel and electrode layouts can be used. However, alternatively, for example, it is also possible to manage with only one structured electrode side without protrusions, which significantly simplifies production and at the same time results in excellent contrast, as well as excellent light transmittance.

[0016] PS-VA displays are described, for example, in EP1 170 626A2, US 6,861,107, US 7,169,449, US2004 / 0191428 A1, US2006 / 0066793 A1, and US 2006 / 0103804A1. PS-OCB displays are described, for example, in T.-J-Chen et al., Jpn.J.Appl.Phys.45, 2006, 2702-2704 and S.H.Kim, L.-C-Chien, Jpn.J.Appl.Phys.43, 2004, 7643-7647. PS-IPS-displays are described, for example, in US 6,177,972 and Appl.Phys.Lett.1999, 75(21), 3264. PS-TN-displays are described, for example, in Optics Express 2004, 12(7), 1221.

[0017] Under the layer formed by the phase separation and aggregation of the RM, which introduces the above-mentioned pretilt angle, PSA displays typically contain an alignment layer, for example composed of polyimide, which provides an initial alignment of the LC molecules, followed by a polymer stabilization step.

[0018] Rubbed polyimide has been used as an alignment layer for a long time. However, the rubbing process causes many problems, such as color difference, contamination, problems with electrostatic discharge, debris, etc. Therefore, instead of the rubbed polyimide layer, it is proposed to use a polyimide layer prepared by photoalignment, arranging the alignment surface using photoinitiated orientation. This can be achieved by photodecomposition, photodimerization, or photoisomerization with the aid of polarized light.

[0019] However, there is still a need for a suitably derivatized polyimide layer that contains photoreactive groups. Generally, the effort and expense of producing such a polyimide layer, processing the polyimide, and improving with bumps or polymer layers are relatively large.

[0020] In addition, it has been observed that the adverse interaction of polyimide alignment layers with specific liquid crystal medium compounds typically results in a reduction in the display resistance. The number of suitable and available liquid crystal compounds is thus significantly reduced, at the expense of display parameters such as viewing angle dependence, contrast, and response time, which are intended to be improved using such liquid crystal compounds. Therefore, it is desirable to eliminate the polyimide alignment layer.

[0021] For some display modes, this is achieved by adding a self-aligning agent or additive to the liquid crystal medium, which introduces the desired alignment, for example, homeotropic or planar alignment in situ by a self-assembly mechanism. Thereby, the alignment layer can be eliminated on one or both of the substrates.

[0022] These display modes are also known as "self-aligned" or "self-aligning" (SA) modes.

[0023] In SA displays, the self-aligning additive is added to the liquid crystal medium in a small amount, typically in an amount of 0.1 to 2.5%. Suitable self-aligning additives are, for example, compounds having an organic core group and one or more polar anchoring groups attached to the organic core group, which are capable of interacting with the substrate surface, causing the additive to align on the substrate surface and introducing the desired alignment in the liquid crystal molecules. Preferred self-aligning additives contain, for example, mesogenic groups and straight-chain or branched-chain alkyl side chains, which are capped with one or more polar anchoring groups, such as selected from hydroxyl, carboxyl, amino, or thiol groups. The self-aligning additive can also contain one or more polymerizable groups, which can be polymerized under conditions similar to those of the RM used in the PSA method.

[0024] SA-VA displays and SA-FFS displays have been disclosed to date. Suitable self-aligning additives for introducing homeotropic alignment, especially for SA-VA mode displays, are disclosed in US 2013 / 0182202 A1, US 2014 / 0838581A1, US 2015 / 0166890A1, and US 2015 / 0252265 A1.

[0025] The SA mode can also be used in combination with the PSA mode. Thus, the liquid crystal medium for such a combined mode contains both one or more RMs and one or more self-aligning additives.

[0026] Similar to the above-described conventional LC displays, PSA displays can be operated as active matrix or passive matrix displays. In the case of an active matrix display, individual pixels are typically addressed by integrated non-linear active elements such as transistors (e.g., thin film transistors "TFT"), while in the case of a passive matrix display, they are typically addressed by multiplexing methods known in the prior art.

[0027] The PSA display also includes an alignment layer on one or both substrates forming the display cell. The alignment layer is typically applied to the electrodes (where such electrodes exist) such that it contacts the LC medium and induces an initial alignment of the LC molecules. The alignment layer also comprises or consists of, for example, polyimide, which can also be rubbed or can be prepared by photo-alignment methods.

[0028] Especially for monitors and particularly for TV applications, there is a continuous requirement for the optimization of the response time as well as the contrast and brightness (and thus also the transmittance) of liquid crystal displays. The PSA method can provide key advantages here. Especially in the case of PS-VA, PS-IPS, and PS-FFS displays, a shortening of the response time related to the pre-tilt measurable in a test cell can be achieved without a significant detrimental effect on other parameters.

[0029] The prior art has proposed using optionally fluorinated biphenyl diacrylate or biphenyl dimethacrylate as the RM in PSA displays.

[0030] However, problems have arisen in that not all combinations consisting of an LC mixture and one or more RMs are suitable for PSA displays, because for example, an insufficient tilt or no tilt at all is established, or because for example, the VHR is insufficient for TFT display applications. Furthermore, it has been found that when used in PSA displays, LC mixtures and RMs known from the prior art still have some disadvantages. Thus, not every known RM soluble in the LC mixture is suitable for PSA displays. In addition, it is often difficult to find suitable selection criteria for the RM, apart from directly measuring the pre-tilt in the PSA display. If polymerization is desired by means of UV light without adding a photoinitiator (which may be advantageous for certain applications), the selection of a suitable RM becomes even smaller.

[0031] In addition, the selected LC host mixture / RM combination should have as low a rotational viscosity as possible and as optimal electrical properties as possible. In particular, it should have as high a VHR as possible. In PSA displays, a high VHR after UV light irradiation is particularly needed because UV exposure is an essential part of the display production process and also occurs as normal exposure during the operation of the manufactured display.

[0032] In particular, it is desirable to provide novel materials that are available for PSA displays that produce particularly small pretilt angles. Here, preferred materials are those that produce a lower pretilt angle than previously known materials for the same exposure time during polymerization, and / or by using them, the (higher) pretilt angle that previously known materials have been able to achieve can also be achieved after a shorter exposure time. Thereby, the production time ("takt time") of the display can be shortened and the cost of the production process can be reduced.

[0033] Another problem in the production of PSA displays is the presence or removal of residual amounts of unpolymerized RM, especially after the polymerization step used to produce the pretilt angle in the display. For example, such unreacted RM may detrimentally affect the properties of the display by, for example, polymerizing in an uncontrolled manner during operation after the display is made.

[0034] Thus, PSA displays known in the prior art often exhibit an undesirable effect called "image sticking" or "image burn-in", i.e., an image generated by the brief addressing of individual pixels in an LC display remains visible even after the electric field in these pixels has been turned off or after other pixels have been addressed.

[0035] If an LC host mixture with a low VHR is used, this "image sticking" can occur on the one hand. The UV component of sunlight or backlight may trigger an undesired decomposition reaction of the LC molecules and thereby the generation of ionic or radical impurities. These can accumulate, especially at the electrodes or alignment layers, where they can reduce the effectively applied voltage. This effect can also be observed in conventional LC displays without polymer components.

[0036] In addition, an additional "image sticking" effect caused by the presence of unpolymerized RM is often observed in PSA displays. The uncontrolled polymerization of the residual RM is triggered here by UV light from the environment or the backlight. In the switched regions of the display, after a plurality of addressing cycles, this changes the tilt angle. As a result, transmittance changes can occur in the switched regions, while remaining unchanged in the unswitched regions.

[0037] Therefore, it is desirable that the polymerization of RM proceeds as completely as possible during the production of PSA displays and that the presence of unpolymerized RM in the display is excluded as much as possible or reduced to a minimum. Therefore, RM and LC mixtures are needed that enable or support highly efficient and complete polymerization of RM. In addition, a controlled reaction of the residual RM amount is desirable. It would be simpler if RM polymerizes faster and more effectively than previously known materials.

[0038] Another problem observed in the operation of PSA displays is the stability of the pretilt angle. Thus, it has been observed that the pretilt angle, which is generated during the manufacture of displays by polymerizing RM as described above, does not remain constant but deteriorates after the display is subjected to voltage stress during its operation. This can have a negative impact on display performance, for example by increasing the transmittance in the black state and thus reducing the contrast ratio.

[0039] Another problem to be solved is that RMs of the prior art often have a high melting point and indeed only show limited solubility in many currently common LC mixtures and thus often tend to crystallize out spontaneously from the mixture. In addition, the risk of spontaneous polymerization prevents the LC host mixture from being warmed to dissolve the polymerizable components, which means that the best solubility that can be achieved is necessary even at room temperature. In addition, there is a risk of separation, for example when introducing the LC medium into an LC display (chromatographic effects), which can greatly impair the uniformity of the display. This is further increased by the fact that the LC medium is usually introduced at low temperature to reduce the risk of spontaneous polymerization (see above), which in turn has an adverse effect on solubility.

[0040] Another problem observed in the prior art is that the use of conventional LC media in LC displays, including but not limited to PSA-type displays, often results in color differences occurring in the display, especially when the LC medium is filled in a display cell manufactured using the one-drop filling (ODF) method. This phenomenon is also referred to as "ODF color difference". Thus, it is desirable to provide an LC medium that results in reduced ODF color difference.

[0041] Another problem observed in the prior art is that LC media used in PSA displays, including but not limited to PSA-type displays, often indeed exhibit high viscosity and thus high switching times. In order to reduce the viscosity and switching time of the LC medium, it has been proposed in the prior art to add LC compounds having alkenyl groups. However, it has been observed that LC media containing alkenyl compounds often show reduced reliability and stability, as well as reduced VHR, especially after exposure to UV radiation. Especially for use in PSA displays, this is a considerable disadvantage because the photopolymerization of RM in PSA displays is usually carried out by exposure to UV radiation, which can lead to a decrease in VHR in the LC medium.

[0042] Therefore, there continues to be a great demand for PSA displays and for LC media and polymerizable compounds for such displays that do not exhibit the disadvantages described above or exhibit these disadvantages only to a small extent and have improved properties.

[0043] Particularly in the case of mobile devices, there is a huge demand for high transmittance, which enables the use of less intense backlighting and thus results in longer battery life. Alternatively, of course, it is possible to achieve a display with higher brightness, which has improved contrast, especially in ambient light.

[0044] Furthermore, there is a great demand for PSA displays and for LC media and polymerizable compounds for such PSA displays, which enable high specific resistance over a large operating temperature range, short response times even at low temperatures, low threshold voltages, low pretilt angles, a large number of gray levels, high contrast, and wide viewing angles, as well as high reliability and high values of "voltage holding ratio" (VHR) after UV exposure, and in the case of polymerizable compounds, low melting points and high solubility in the LC host mixture. In PSA displays for mobile applications, in particular, an LC medium that exhibits a low threshold voltage and high birefringence is desirable.

[0045] The object on which the present invention is based is to provide novel suitable materials for LC media containing reactive mesogens (RM) in PSA displays, which do not have the disadvantages described above or have these disadvantages to a reduced extent.

[0046] In particular, the object on which the present invention is based is to provide an RM-containing LC medium for PSA displays, which enables the display to have the following properties: high transmittance while having a very high specific resistance value, high VHR value, high reliability, low threshold voltage, short response time, high birefringence, exhibiting good UV absorption (especially at longer wavelengths), enabling rapid and complete polymerization of the RM, allowing preferably as fast as possible the generation of a low pretilt angle, enabling high stability of the pretilt (even after a long time and / or after UV exposure), reducing or preventing "image sticking" and "ODF color difference" from occurring in the display, and in the case of the RM, polymerizing as fast and completely as possible and showing high solubility in the LC medium, which is typically used as the host mixture in PSA displays.

[0047] These objects have been achieved according to the invention by the materials and methods described in the present invention. In particular, it has surprisingly been found that the use of the liquid crystal hosts described below allows the achievement of the advantageous effects described above. These hosts are characterized by containing optically active components, also known as chiral dopants.

[0048] In the field of liquid crystals, it is known to add a chiral dopant to, for example, a nematic liquid crystal host mixture. At low concentrations of the chiral dopant, a chiral-nematic phase, also known as a cholesteric phase, is obtained. In the field of twisted nematic liquid crystal displays, the addition of a dopant is required to achieve a uniform twist direction and thus avoid rotational displacement lines. Higher concentrations are used to achieve the desired shorter pitch, for example in supertwisted LCDs (STN displays).

[0049] Surprisingly, it has been found that in VA or PS-VA displays, the use of these liquid crystal hosts and liquid crystal media containing them endows the displays with the following properties: improved transmittance while maintaining excellent performance in terms of process-related parameters, i.e., in the case of PSA displays, especially in the range of 300 - 380 nm and especially at longer UV wavelengths above 320 nm, enabling rapid and complete UV photopolymerization even in the absence of a photoinitiator, rapid generation of a large and stable pretilt angle, reduced image sticking and ODF color difference in the display, high reliability and high VHR values after UV photopolymerization, especially in the case of LC host mixtures containing LC compounds with alkenyl groups, and generally fast response times, low threshold voltages, and high birefringence. Summary of the Invention

[0050] The present invention relates to a liquid crystal medium comprising

[0051] - a liquid crystal host, which consists of a liquid crystal component H) and an optically active component D), wherein the liquid crystal component H) comprises one or more mesogenic or liquid crystal compounds,

[0052] - optionally a polymerizable component P), which comprises one or more polymerizable compounds,

[0053] - optionally a self-aligning additive for vertical alignment (hereinafter referred to as SA-VA additive),

[0054] wherein the liquid crystal component H) comprises one or more compounds selected from the group consisting of formula CY and / or PY,

[0055]

[0056] wherein each group has the following meanings:

[0057] a represents 1 or 2,

[0058] b represents 0 or 1,

[0059] represents

[0060] R 1 and R 2each independently represents an alkyl group having 1 to 12 C atoms, where one or more H atoms may be replaced by F, and where one or two non-adjacent CH2 groups may be replaced by -O-,-CH=CH-,-CO-,-O-CO- or -CO-O- provided that the O atoms are not directly connected to each other,

[0061] Z x represents -CH=CH-,-CH2O-,-OCH2-,-CF2O-,-OCF2-,-O-,-CH2-,-CH2CH2- or a single bond, preferably a single bond,

[0062] L 1-4 each independently represents F, Cl, OCF3, CF3, CH3, CH2F, CHF2; preferably L 1 and L 2 both represent F or L 1 and L 2 one represents F and the other represents Cl, or L 3 and L 4 both represent F or L 3 and L 4 one represents F and the other represents Cl,

[0063] L 5 represents H or has one of the meanings given for L 1-4 preferably represents H or CH3, particularly preferably H,

[0064] and where the optional polymerizable component, component P), comprises one or more compounds of the formula R,

[0065] P-Sp-A 1 -(Z 1 -A 2 ) z -R R

[0066] where each group, each independently of the others and each time it occurs, has the following meaning, which may be the same or different:

[0067] P is a polymerizable group,

[0068] Sp is a spacer group or a single bond,

[0069] A 1 ,A 2 is an aromatic, heteroaromatic, cycloaliphatic or heterocyclic group, preferably having 4 to 25 ring atoms, which may also include fused rings, and which is unsubstituted, mono-substituted or multi-substituted by L,

[0070] Z 1is O-,-S-,-CO-,-CO-O-,-O-CO-,-O-CO-O-,-OCH2-,-CH2O-,-SCH2-,-CH2S-,-CF2O-,-OCF2-,-CF2S-,-SCF2-,-(CH2) n1 -,-CF2CH2-,-CH2CF2-,-(CF2) n1 -,-CH=CH-,-CF=CF-,-CH=CF-,-CF=CH-,-C≡C-,-CH=CH-CO-O-,-O-CO-CH=CH-,-CH2-CH2-CO-O-,-O-CO-CH2-CH2-,-CR 0 R 00 - or a single bond,

[0071] R 0 ,R 00 is H or an alkyl group having 1 to 12 C atoms,

[0072] R is H, L, or P-Sp-,

[0073] L is F, Cl, -CN, P-Sp- or a straight-chain, branched-chain or cyclic alkyl group having 1 to 25 C atoms, where one or more non-adjacent CH2 groups are optionally replaced by -O-,-S-,-CO-,-CO-O-,-O-CO-,-O-CO-O- in such a way that O- and / or S atoms do not directly connect to each other, and where one or more H atoms are each optionally replaced by P-Sp-, F or Cl,

[0074] z is 0, 1, 2 or 3,

[0075] n1 is 1, 2, 3 or 4,

[0076] The liquid-crystalline component H) of the liquid-crystalline medium according to the invention is also referred to hereinafter as "LC host mixture" and preferably contains one or more, preferably at least two mesogenic or LC compounds, which are selected from non-polymerizable low-molecular-weight compounds.

[0077] The invention also relates to an LC display comprising the above LC medium.

[0078] The invention also relates to an LC medium or an LC display as described above, wherein the compound of formula R or the polymerizable compound of component P) is polymerized.

[0079] The invention also relates to a method for preparing an LC medium as described in the context, comprising the steps of: mixing one or more mesogenic or LC compounds or an LC host mixture or LC component H) as described in the context, with one or more chiral dopants (component D)) and optionally with one or more compounds of formula R and with other LC compounds and / or additives.

[0080] The invention also relates to the use of an LC medium according to the invention in a PSA display, in particular in a PSA display comprising an LC medium, for generating a tilt angle in the LC medium by in-situ polymerization of one or more compounds of formula R (preferably in an electric or magnetic field) in the PSA display.

[0081] The invention also relates to an LC display comprising an LC medium according to the invention, in particular a VA or PSA display, particularly preferably a VA or PS-VA display.

[0082] The invention also relates to the use of an LC medium according to the invention in a polymer-stabilized SA-VA display, and to a polymer-stabilized SA-VA display comprising an LC medium according to the invention.

[0083] The invention also relates to an LC display of the VA or PSA type, which comprises two substrates (at least one of which is transparent to light), electrodes arranged on each substrate or two electrodes arranged only on one of the substrates, and a layer of an LC medium located between the substrates, said LC medium optionally containing one or more polymerizable compounds and LC components as described in the context, wherein the polymerizable compounds are polymerized between the substrates of the display.

[0084] The invention also relates to a method for manufacturing an LC display as described in the context, which comprises the steps of: filling or otherwise providing an LC medium between the substrates of the display, and optionally polymerizing polymerizable compounds, said LC medium optionally containing one or more polymerizable compounds as described in the context.

[0085] A PSA display according to the invention has two substrates, preferably in the form of a transparent layer, which are applied to one or both substrates. In some displays, for example in a PS-VA display, an electrode is applied to one of the two substrates.

[0086] In a preferred embodiment, the polymerizable component is polymerized in the LC display while a voltage is applied to the electrodes of the display.

[0087] The polymerizable compounds of the polymerizable component are preferably polymerized by photopolymerization, particularly preferably by UV photopolymerization.

[0088] When used in a VA display, the LC medium according to the invention exhibits the following advantageous properties:

[0089] - Improved display transmittance,

[0090] - High voltage holding ratio,

[0091] - Fast switching,

[0092] - Good tilt stability,

[0093] - Sufficient stability against heat,

[0094] When used in a PSA display, the LC medium according to the invention exhibits the following advantageous properties:

[0095] - Improved display transmittance,

[0096] - Generation of suitable tilt within certain processing windows,

[0097] - Fast polymerization, resulting in minimal RM residue after UV treatment,

[0098] - High voltage holding ratio after UV treatment,

[0099] - Good tilt stability,

[0100] - Sufficient stability against heat,

[0101] - Fast switching.

[0102] The use of chiral dopants in nematic liquid crystals is known to those skilled in the art. For a review, see, for example, A. Taugerbeck, Ch. Booth, 2013, Design and Synthesis of Chiral Nematic Liquid Crystals, Handbook of Liquid Crystals. 3:III:14:1–63.

[0103] It should be noted here that, as a first approximation, the HTP of a mixture of chiral compounds (i.e., conventional chiral dopants and chiral reactive mesogens) can be approximated by adding their individual HTP values, weighted by their respective concentrations in the medium.

[0104] The cholesteric pitch of the modulating medium in the cholesteric phase (also known as the chiral nematic phase) can be reproduced to a first approximation by equation (1).

[0105] P = (HTP·c) -1 (1)

[0106] where P represents the cholesteric pitch,

[0107] c represents the concentration of the chiral component D), and

[0108] HTP (helical twisting power) is a constant that characterizes the twisting power of the chiral substance and depends on the chiral substance (component D)) and the achiral component H).

[0109] If a more precise determination of the pitch is desired, equation (1) can be changed accordingly. For this purpose, an expansion of the cholesteric pitch in the form of a polynomial (2) is usually used.

[0110] P = (HTP·c) -1 +(α1·c) -2 +(α2·c) -3 +... (2)

[0112] where the parameters are defined as in equation (1) above, and

[0113] α1 and α2 represent constants that depend on the chiral component (D) and the achiral component (H).

[0114] The polynomial can be continued to a certain degree that can achieve the desired accuracy.

[0115] Typically, the parameters of the polynomial HTP (sometimes also called α1, α2, α3, etc.) depend very strongly on the type of chiral dopant and, to a certain extent, also on the specific liquid crystal mixture used.

[0116] Obviously, they also do depend on the enantiomeric excess of the respective chiral dopant. They have their respective maximum absolute values for the pure enantiomers and are zero for the racemate. In this application, the given values are those for the pure enantiomers with an enantiomeric excess of 98% or more, unless otherwise explicitly stated.

[0117] If the optically active component D) consists of two or more compounds, equation (1) is changed to obtain equation (3).

[0118] P = [Σ i (HTP(i)·c i )] -1 (3)

[0119] where P represents the cholesteric pitch,

[0120] c i represents the concentration of the i-th compound of the chiral compound D), and

[0121] HTP(i) represents the HTP of the i-th compound of the optically active component D) in the achiral liquid crystal component (H).

[0122] The temperature dependence of HTP is usually expressed in a polynomial expansion (4), however for practical purposes it can usually be truncated after a linear factor (β1).

[0123] HTP(T) = HTP(T0) + β1·(T - T0) + β2·(T - T0) 2 +...(4)

[0124] where the parameters are as defined above for equation (1), and

[0125] T represents temperature,

[0126] T0 represents the reference temperature,

[0127] HTP(T) represents the HTP at temperature T,

[0128] HTP(T0) represents the HTP at temperature T0, and

[0129] β1 and β2 represent constants which depend on the chiral component (D) and the achiral LC component (H).

[0130] As used herein, the terms "active layer" and "switchable layer" denote, in an electro-optical display, for example in an LC display, a layer comprising one or more molecules (e.g. LC molecules) having structural and optical anisotropy, which molecules change their orientation when subjected to an external stimulus such as an electric or magnetic field, which results in a change in the transmittance of the layer for polarized or non-polarized light.

[0131] As used herein, the terms "tilt" and "tilt angle" are to be understood as denoting a tilted alignment of the LC molecules of the LC medium with respect to the cell surface in an LC display (here preferably a PSA display). Here the tilt angle represents the average angle (<90°) between the longitudinal molecular axis of the LC molecules (LC director) and the outer plate parallel to the plane forming the LC cell. Here a low value of the tilt angle (i.e. a large deviation from the 90° angle) corresponds to a large tilt. Suitable methods for measuring the tilt angle are given in the examples. Unless otherwise stated, the tilt angle values disclosed in the context relate to this measurement method.

[0132] As used herein, the terms "reactive mesogen" and "RM" are to be understood as denoting a compound comprising a mesogenic or liquid crystalline backbone, and one or more polymerizable functional groups attached thereto, and said functional groups are also referred to as "polymerizable groups" or "P".

[0133] Unless otherwise stated, the term "polymerizable compound" as used herein is to be understood as a polymerizable monomeric compound.

[0134] As used herein, the term "low molecular weight compound" is understood to mean monomeric and / or compounds not prepared by a polymerization reaction, as opposed to "polymeric compounds" or "polymers".

[0135] As used herein, the term "non-polymerizable compound" is understood to mean a compound that does not contain functional groups suitable for polymerization under the conditions normally applied to RM polymerization.

[0136] As used herein, the term "mesogenic group" is known to those skilled in the art and is described in the literature, and it means a group that substantially contributes to the generation of a liquid crystal (LC) phase in low molecular weight or polymeric materials due to the anisotropy of its attractive and repulsive interactions. Compounds containing mesogenic groups (mesogenic compounds) do not necessarily have an LC phase themselves. Mesogenic compounds can also exhibit LC phase behavior only after mixing with other compounds and / or after polymerization. Typical mesogenic groups are, for example, rigid rod-like or disc-like units. A review of the terms and definitions used in connection with mesogenic or LC compounds is given in Pure Appl. Chem. 2001, 73(5), 888 and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340 - 6368.

[0137] As used herein, the terms "optically active" and "chiral" are synonyms for materials that are capable of introducing a helical pitch into a nematic host material and are also referred to as "chiral dopants".

[0138] As used herein, the term "spacer group" (also referred to hereinafter as "Sp") is known to those skilled in the art and is described in the literature, see, for example, Pure Appl. Chem. 2001, 73(5), 888 and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340 - 6368. As used herein, the term "spacer group" or "spacer" means a flexible group, for example, an alkylene group, which is connected to a mesogenic group or a polymerizable group(s) in a polymerizable mesogenic compound.

[0139] In the context, represents a trans - 1,4 - cyclohexylene ring, and represents a 1,4 - phenylene ring.

[0140] In the group the single bond shown between two ring atoms can be connected to any free position of the benzene ring.

[0141] The "organic group" in the context means a carbon or hydrocarbon group.

[0142] "Carbon group" means a mono- or polyvalent organic group containing at least one carbon atom, where the group does not contain other atoms (such as -C≡C-) or optionally contains one or more other atoms, such as N, O, S, B, P, Si, Se, As, Te, or Ge (such as a carbonyl group, etc.). The term "hydrocarbyl group" means a carbon group that additionally contains one or more H atoms and optionally one or more heteroatoms, such as N, O, S, B, P, Si, Se, As, Te, or Ge.

[0143] "Halogen" means F, Cl, Br, or I, preferably F or Cl.

[0144] -CO-, -C(=O)-, and -C(O)- represent a carbonyl group, i.e.,

[0145] The carbon or hydrocarbyl group can be a saturated or unsaturated group. Unsaturated groups are, for example, aryl, alkenyl, or alkynyl groups. A carbon or hydrocarbyl group having more than 3 C atoms can be straight-chain, branched, and / or cyclic and can also contain spiro linkages or fused rings.

[0146] The terms "alkyl", "aryl", "heteroaryl", etc. also include polyvalent groups, such as alkylene, arylene, heteroarylene, etc.

[0147] The term "aryl" means an aromatic carbon group or a group derived therefrom. The term "heteroaryl" means an "aryl" as defined above that contains one or more heteroatoms (preferably selected from N, O, S, Se, Te, Si, and Ge).

[0148] Preferred carbon and hydrocarbyl groups are optionally substituted, straight-chain, branched, or cyclic alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy, and alkoxycarbonyloxy groups having 1 to 40, preferably 1 to 20, very preferably 1 to 12 C atoms, optionally substituted aryl or aryloxy groups having 5 to 30, preferably 6 to 25 C atoms, or optionally substituted alkylaryl, aralkyl, alkylaryloxy, arylalkyloxy, arylcarbonyl, aryloxycarbonyl, arylcarbonyloxy, and aryloxycarbonyloxy groups having 5 to 30, preferably 6 to 25 C atoms, where one or more C atoms can also be replaced by heteroatoms (preferably selected from N, O, S, Se, Te, Si, and Ge).

[0149] Further preferred carbon and hydrocarbyl groups are C1-C 20 alkyl, C2-C 20 alkenyl, C2-C 20 alkynyl, C3-C 20 allyl, C4-C 20 alkyl diene group, C4-C 20Polyenyl, C6-C 20 Cycloalkyl, C4-C 15 Cycloalkenyl, C6-C 30 Aryl, C6-C 30 Alkylaryl, C6-C 30 Arylalkyl, C6-C 30 Alkylaryloxy, C6-C 30 Arylalkyloxy, C2-C 30 Heteroaryl, C2-C 30 Heteroaryloxy.

[0150] Particularly preferred are C1-C 12 alkyl, C2-C 12 alkenyl, C2-C 12 alkynyl, C6-C 25 aryl and C2-C 25 heteroaryl.

[0151] Further preferred carbon-based and hydrocarbon-based groups are straight-chain, branched-chain or cyclic alkyl groups having 1-20, preferably 1-12 C atoms, which are unsubstituted or mono- or poly-substituted by F, Cl, Br, I or CN, and in which one or more non-adjacent CH2 groups may each independently of one another be replaced by -C(R x )=C(R x )-, -C≡C-, -N(R x )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and / or S atoms are not directly linked to one another.

[0152] R x preferably represents H, F, Cl, CN, a straight-chain, branched-chain or cyclic alkyl chain having 1 to 25 C atoms, in which furthermore one or more non-adjacent C atoms may be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, and in which one or more H atoms may be replaced by F or Cl, or represents an optionally substituted aryl or aryloxy group having 6 to 30 C atoms, or an optionally substituted heteroaryl or heteroaryloxy group having 2 to 30 C atoms.

[0153] Preferred alkyl groups are, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 2-methylbutyl, n-pentyl, sec-pentyl, cyclopentyl, n-hexyl, cyclohexyl, 2-ethylhexyl, n-heptyl, cycloheptyl, n-octyl, cyclooctyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, dodecyl, trifluoromethyl, perfluorobutyl, 2,2,2-trifluoroethyl, perfluorooctyl, perfluorohexyl, etc.

[0154] Preferred alkenyl groups are, for example, vinyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl, cyclooctenyl, and the like.

[0155] Preferred alkynyl groups are, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl, octynyl, and the like.

[0156] Preferred alkoxy groups are, for example, methoxy, ethoxy, 2 - methoxyethoxy, n - propoxy, isopropoxy, n - butoxy, isobutoxy, sec - butoxy, tert - butoxy, 2 - methylbutoxy, n - pentyloxy, n - hexyloxy, n - heptyloxy, n - octyloxy, n - nonyloxy, n - decyloxy, n - undecyloxy, n - dodecyloxy, and the like.

[0157] Preferred amino groups are, for example, dimethylamino, methylamino, methylphenylamino, phenylamino, and the like.

[0158] Aryl and heteroaryl groups can be monocyclic or polycyclic, i.e., they can contain one ring (e.g., phenyl) or two or more rings, which can also be fused (e.g., naphthyl) or covalently bonded (e.g., biphenyl), or contain a combination of fused and linked rings. Heteroaryl contains one or more heteroatoms, preferably selected from O, N, S, and Se.

[0159] Particularly preferred are mono -, bi - or tricyclic aryls having 6 - 25 C atoms and mono -, bi - or tricyclic heteroaryls having 5 - 25 ring atoms, which optionally contain fused rings and are optionally substituted. Further preferred are 5 -, 6 - or 7 - membered aryl and heteroaryl groups, wherein, in addition, one or more CH groups can be replaced by N, S, or O in such a way that O atoms and / or S atoms are not directly connected to each other.

[0160] Preferred aryl groups are, for example, phenyl, biphenyl, terphenyl, [1,1':3',1”] - terphenyl - 2'-yl, naphthyl, anthracenyl, binaphthyl, phenanthryl, 9,10 - dihydro - phenanthryl, pyrene, dihydropyrene, picene, tetracene, pentacene, benzopyrene, fluorene, indene, indenofluorene, spirobifluorene, and the like.

[0161] Preferred heteroaryl groups are, for example, 5-membered rings such as pyrrole, pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, tetrazole, furan, thiophene, selenophene, oxazole, isoxazole, 1,2-thiazole, 1,3-thiazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole, 1,3,4-thiadiazole, 6-membered rings such as pyridine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, 1,2,4-triazine, 1,2,3-triazine, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine, 1,2,3,5-tetrazine or fused groups such as indole, isoindole, indene, indazole, benzimidazole, benzotriazole, purine, naphthimidazole, phenanthrimidazole, pyridinimidazole, pyrazinimidazole, quinoxalinimidazole, benzoxazole, naphthoxazole, anthroxazole, phenanthroxazole, isoxazole, benzothiazole, benzofuran, isobenzofuran, dibenzofuran, quinoline, isoquinoline, pteridine, benzo-5,6-quinoline, benzo-6,7-quinoline, benzo-7,8-quinoline, benzoisoquinoline, acridine, phenothiazine, phenoxazine, benzopyridazine, benzopyrimidine, quinoxaline, phenazine, naphthyridine, azacarbazole, benzocarbazole, phenanthridine, phenanthroline, thiophene[2,3b]thiophene, thiophene[3,2b]thiophene, dithienothiophene, isobenzothiophene, dibenzothiophene, benzothiadiazolethiophene, or combinations of these groups.

[0162] The aryl and heteroaryl groups mentioned in the context may also be substituted by alkyl, alkoxy, thioalkyl, fluorine, fluoroalkyl or other aryl or heteroaryl groups.

[0163] (Non-aromatic) alicyclic groups and heterocyclic groups include both saturated rings, i.e., rings containing only single bonds, and partially unsaturated rings, i.e., those that may also contain multiple bonds. Heterocycles contain one or more heteroatoms, preferably selected from Si, O, N, S and Se.

[0164] (Non-aromatic) alicyclic groups and heterocyclic groups may be monocyclic, i.e., containing only one ring (such as cyclohexane), or polycyclic, i.e., containing multiple rings (such as decalin or bicyclooctane). Saturated groups are particularly preferred. Also preferred are mono-, bi- or tricyclic groups having 5-25 ring atoms, which optionally contain fused rings and are optionally substituted. Further preferred are 5-, 6-, 7- or 8-membered carbocyclic groups, wherein in addition, one or more C atoms may be replaced by Si and / or one or more CH groups may be replaced by N and / or one or more non-adjacent CH2 groups may be replaced by -O- and / or -S-.

[0165] Preferred alicyclic and heterocyclic groups are, for example, 5-membered groups such as cyclopentane, tetrahydrofuran, tetrahydrothiophene, pyrrolidine; 6-membered groups such as cyclohexane, silinane, cyclohexene, tetrahydropyran, tetrahydrothiopyran, 1,3-dioxane, 1,3-dithiane, piperidine; 7-membered groups such as cycloheptane; and fused groups such as tetralin, decalin, indane, bicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl, octahydro-4,7-methanoindane-2,5-diyl.

[0166] Preferred substituents are, for example, solubility promoting groups such as alkyl or alkoxy; electron-withdrawing groups such as fluorine, nitro or nitrile; or substituents for increasing the glass transition temperature (Tg) of the polymer, in particular bulky groups such as tert-butyl or optionally substituted aryl.

[0167] Preferred substituents, hereinafter also referred to as “L” S ” are, for example, F, Cl, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, -C(=O)N(R x )2, -C(=O)Y 1 , -C(=O)R x , -N(R x )2, straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 - 25 C atoms, where one or more H atoms may optionally be replaced by F or Cl, optionally substituted silyl having 1 to 20 Si atoms, or optionally substituted aryl having 6 to 25, preferably 6 to 15 C atoms.

[0168] where R x represents H, F, Cl, CN, or straight-chain, branched or cyclic alkyl having 1 to 25 C atoms, where one or more non-adjacent CH2-groups are optionally replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O- and / or S-atoms are not directly connected to each other, and where one or more H atoms are each optionally replaced by F, Cl, P- or P-Sp-, and

[0169] Y 1 represents halogen.

[0170] “Substituted silyl or aryl” preferably means that it is substituted by halogen, -CN, R 0 , -OR 0 , -CO-R 0 , -CO-O-R 0, -O-CO-R 0 or -O-CO-O-R 0 is substituted, where R 0 represents H or an alkyl group having 1 to 20 C atoms.

[0171] Particularly preferred substituents L S are, for example, F, Cl, CN, NO2, CH3, C2H5, OCH3, OC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF3, OCF3, OCHF2, OC2F5, and in addition phenyl.

[0172] are preferably

[0173] wherein L has one of the meanings indicated above.

[0174] The polymerizable group P is a group suitable for polymerization reactions (such as free radical or ionic chain polymerization, addition polymerization or condensation polymerization), or a group suitable for polymer-analogous reactions (such as addition or condensation on the polymer backbone). Particularly preferred are groups for chain polymerization, especially those containing a C═C double bond or a -C≡C- triple bond, and groups suitable for ring-opening polymerization, such as oxetanyl or epoxy groups.

[0175] Preferred groups P are selected from the group consisting of: CH2═CW 1 -CO-O-, CH2═CW 1 -CO-,

[0176] CH2═CW 2 -(O) k3 -,

[0177] CW 1 ═CH-CO-(O) k3 -, CW 1 ═CH-CO-NH-, CH2═CW 1 -CO-NH-, CH3-CH═CH-O-,

[0178] (CH2═CH)2CH-OCO-, (CH2═CH-CH2)2CH-OCO-, (CH2═CH)2CH-O-, (CH2═CH-CH2)2N-, (CH2═CH-CH2)2N-CO-, HO-CW 2 W 3 -, HS-CW 2 W 3 -, HW 2N-, HO-CW 2 W 3 -NH-, CH2=CW 1 -CO-NH-, CH2=CH-(COO) k1 -Phe-(O) k2 -, CH2=CH-(CO) k1 -Phe-(O) k2 -, Phe-CH=CH-, HOOC-, OCN- and W 4 W 5 W 6 Si-, where W 1 represents H, F, Cl, CN, CF3, phenyl or an alkyl group having 1 to 5 C atoms, especially H, F, Cl or CH3, W 2 and W 3 each independently of one another represent H or an alkyl group having 1 to 5 C atoms, especially H, methyl, ethyl or n-propyl, W 4 , W 5 and W 6 each independently of one another represent Cl, an oxaalkyl group or an oxacarbonylalkyl group having 1 to 5 C atoms, W 7 and W 8 each independently of one another represent H, Cl or an alkyl group having 1 to 5 C atoms, Phe represents 1,4-phenylene, which is optionally substituted by one or more groups L different from P-SP- as defined above, k1, k2 and k3 each independently of one another represent 0 or 1, k3 preferably represents 1, and k4 represents an integer from 1 to 10.

[0179] Very preferred groups P are selected from the group consisting of: CH2=CW 1 -CO-O-, CH2=CW 1 -CO-, CH2=CW 2 -O-, CH2=CW 2 -, CW 1 =CH-CO-(O) k3 -, CW 1 =CH-CO-NH-, CH2=CW 1 -CO-NH-, (CH2=CH)2CH-OCO-, (CH2=CH-CH2)2CH-OCO-, (CH2=CH)2CH-O-, (CH2=CH-CH2)2N-, (CH2=CH-CH2)2N-CO-, CH2=CW 1 -CO-NH-, CH2=CH-(COO) k1 -Phe-(O) k2 -, CH2=CH-(CO)k1 -Phe-(O) k2 -, Phe-CH=CH-, and W 4 W 5 W 6 Si-, where W 1 represents H, F, Cl, CN, CF3, phenyl, or an alkyl group having 1 to 5 C atoms, especially H, F, Cl, or CH3, and W 2 and W 3 each independently of one another represent H or an alkyl group having 1 to 5 C atoms, especially H, methyl, ethyl, or n-propyl, and W 4 , W 5 and W 6 each independently of one another represent Cl, an oxaalkyl group having 1 to 5 C atoms, or an oxacarbonylalkyl group, and W 7 and W 8 each independently of one another represent H, Cl, or an alkyl group having 1 to 5 C atoms, Phe represents 1,4-phenylene, k1, k2, and k3 each independently of one another represent 0 or 1, k3 preferably represents 1, and k4 represents an integer from 1 to 10.

[0180] A very preferred group P is selected from the group consisting of: CH2=CW 1 -CO-O-, especially CH2=CH-CO-O-, CH2=C(CH3)-CO-O-, and CH2=CF-CO-O-, and also CH2=CH-O-, (CH2=CH)2CH-O-CO-, (CH2=CH)2CH-O-,

[0181] Other particularly preferred polymerizable groups P are selected from vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetanyl, and epoxy groups, and most preferably from acrylate and methacrylate groups.

[0182] If the spacer group Sp is different from a single bond, it is preferably of the formula Sp"-X" such that each group P-Sp- conforms to the formula R-Sp"-X"-, where

[0183] Sp" represents a straight-chain or branched alkylene group having 1 to 20, preferably 1 to 12 C atoms, which is optionally mono- or polysubstituted by F, Cl, Br, I, or CN, and wherein furthermore, one or more non-adjacent CH2 groups are each independently of one another replaced by -O-, -S-, -NH-, -N(R 0 ), -, Si(R 0 R 00 ), -, CO-, -CO-O-, -O-CO-, -O-CO-O-, -S-CO-, -CO-S-, -N(R00 )-CO-O-, -O-CO-N(R 0 )-, -N(R 0 )-CO-N(R 00 )-, -CH=CH- or -C≡C- are replaced in such a way that O and / or S atoms are not directly connected to each other,

[0184] X" represents -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -CO-N(R 0 )-, -N(R 0 )-CO-, -N(R 0 )-CO-N(R 00 )-, -OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -CF2CH2-, -CH2CF2-, -CF2CF2-, -CH=N-, -N=CH-, -N=N-, -CH=CR 0 -, -CY 2 =CY 3 -, -C≡C-, -CH=CH-CO-O-, -O-CO-CH=CH- or a single bond,

[0185] R 0 and R 00 each independently of one another represent H or an alkyl group having 1 - 20 C atoms, and

[0186] Y 2 and Y 3 each independently of one another represent H, F, Cl or CN.

[0187] X" is preferably -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR 0 -, -NR 0 -CO-, -NR 0 -CO-NR 00 - or a single bond.

[0188] Typical spacer groups Sp and -Sp"-X"- are for example -(CH2) p1 -, -(CH2) p1 -O-, -(CH2) p1 -O-CO-, -(CH2) p1 -CO-O-, -(CH2) p1 -O-CO-O-, -(CH2CH2O) q1-CH2CH2-, -CH2CH2-S-CH2CH2-, -CH2CH2-NH-CH2CH2- or -(SiR 0 R 00 -O) p1 -, where p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and R 0 and R 00 has the meaning indicated above.

[0189] Particularly preferred groups Sp and -Sp"-X"- are -(CH2) p1 -, -(CH2) p1 -O-, -(CH2) p1 -O-CO-, -(CH2) p1 -CO-O-, -(CH2) p1 -O-CO-O-, where p1 and q1 have the meaning indicated above.

[0190] Particularly preferred groups Sp" are in each case a straight-chain ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethylenethioethylene, ethyl-N-methylimino-ethylene, 1-methylalkylene, vinyl, propenyl and butenyl.

[0191] In a preferred embodiment of the present invention, the compound of formula R and its sub-formulas contain a spacer group Sp substituted by one or more polymerizable groups P such that the group Sp-P corresponds to Sp(P) s , where s is ≥2 (branched polymerizable group).

[0192] Preferred compounds of formula R according to this preferred embodiment are those where s = 2, i.e., compounds containing the group Sp(P)2. Very preferred compounds of formula R according to this preferred embodiment contain a group selected from the following formulas:

[0193] -X-alkyl-CHPP S1

[0194] -X-alkyl-CH((CH2) aa P)((CH2) bb P) S2

[0195] -X-N((CH2) aa P)((CH2) bb P) S3

[0196] -X-alkyl-CHP-CH2-CH2P S4

[0197] -X-alkyl-C(CH2P)(CH2P)-C aa H 2aa+1 S5

[0198] -X-alkyl-CHP-CH2P S6

[0199] -X-alkyl-CPP-C aa H 2aa+1 S7

[0200] -X-alkyl-CHPCHP-C aa H 2aa+1 S8

[0201] wherein P is as defined in formula R,

[0202] alkyl represents a single bond or a straight-chain or branched alkylene having 1 to 12 C atoms, which is unsubstituted or mono- or polysubstituted by F, Cl or CN, wherein one or more non-adjacent CH2 groups may each independently of one another be replaced by -C(R 0 )=C(R 0 )-, -C≡C-, -N(R 0 )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and / or S atoms are not directly linked to one another, wherein R 0 has the meaning as described above.

[0203] aa and bb each independently of one another represent 0, 1, 2, 3, 4, 5 or 6,

[0204] X has one of the meanings given for X", and is preferably O, CO, SO2, O-CO-, CO-O or a single bond.

[0205] The preferred spacer group Sp(P)2 is selected from formulae S1, S2 and S3.

[0206] The very preferred spacer group Sp(P)2 is selected from the following sub-formulae:

[0207] -CHPP S1a

[0208] -O-CHPP S1b

[0209] -CH2-CHPP S1c

[0210] -OCH2-CHPP S1d

[0211] -CH(CH2-P)(CH2-P) S2a

[0212] -OCH(CH2-P)(CH2-P) S2b

[0213] -CH2-CH(CH2-P)(CH2-P) S2c

[0214] -OCH2-CH(CH2-P)(CH2-P) S2d

[0215] -CO-NH((CH2)2P)((CH2)2P) S3a

[0216] In the compounds of formula R and its sub-formulas as described in the context, P is preferably selected from vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetanyl and epoxy group, and most preferably selected from acrylate and methacrylate groups.

[0217] Further preferred are the compounds of formula R and its sub-formulas as described in the context, wherein all polymerizable groups P present in the compound have the same meaning, and very preferably represent acrylate and methacrylate groups, and most preferably methacrylate group.

[0218] In the compounds of formula R and its sub-formulas as described in the context, R preferably represents P-Sp-.

[0219] Further preferred are the compounds of formula R and its sub-formulas as described in the context, wherein Sp represents a single bond or -(CH2) p1 -,-O-(CH2) p1 -,-O-CO-(CH2) p1 or -CO-O-(CH2) p1 , where p1 is 2, 3, 4, 5 or 6, and if Sp is -O-(CH2) p1 -,-O-CO-(CH2) p1 or -CO-O-(CH2) p1 , then the O-atom or the CO-group is attached to the benzene ring, respectively.

[0220] Further preferred are the compounds of formula R and its sub-formulas as described in the context, wherein at least one group Sp is a single bond.

[0221] Further preferred are the compounds of formula R and its sub-formulas as described in the context, wherein at least one group Sp is different from a single bond, and is preferably selected from -(CH2) p1 -,-O-(CH2) p1 -,-O-CO-(CH2) p1 or -CO-O-(CH2) p1 , where p1 is 2, 3, 4, 5 or 6, and if Sp is -O-(CH2)p1 -,-O-CO-(CH2) p1 or -CO-O-(CH2) p1， then the O-atom or the CO-group is attached to the benzene ring, respectively.

[0222] In formula R, the very preferred group -A 1 -(Z 1 -A 2 ) z - is selected from the following formulas

[0223]

[0224] wherein at least one benzene ring is substituted by at least one group L 11 and the benzene ring is also optionally substituted by one or more groups L or P-Sp-.

[0225] The preferred compounds of formula R and II and their sub-formulas are selected from the following preferred embodiments, including any combination thereof:

[0226] - all groups P in the compound have the same meaning: -A 1 -(Z-A 2 ) z - is selected from formulas A1, A2 and A5,

[0227] - the compound contains exactly two polymerizable groups (represented by group P),

[0228] - the compound contains exactly three polymerizable groups (represented by group P),

[0229] - P is selected from acrylate group, methacrylate group and oxetanyl, very preferably acrylate group or methacrylate group,

[0230] - P is methacrylate group,

[0231] - all groups are single bonds,

[0232] - at least one of the groups Sp is a single bond, and at least one of the groups Sp is different from a single bond,

[0233] - Sp, when different from a single bond, is -(CH2) p2 -,-(CH2) p2 -O-,-(CH2) p2 -CO-O-,-(CH2) p2 -O-CO-, where p2 is 2, 3, 4, 5 or 6, and the O-atom or the CO-group is attached to the benzene ring, respectively.

[0234] - Sp is a single bond or represents -(CH2) p2-,-(CH2) p2 -O-,-(CH2) p2 -CO-O-,-(CH2) p2 -O-CO-, where p2 is 2, 3, 4, 5 or 6, and the O-atom or the CO-group is attached to the benzene ring respectively

[0235] -Sp(P)2 is selected from sub-formulas S11 - S31

[0236] -R represents P-Sp-

[0237] -R does not represent or contain a polymerizable group

[0238] -R does not represent or contain a polymerizable group and represents a straight-chain, branched-chain or cyclic alkyl group having 1 to 25 C atoms, where one or more non-adjacent CH2-groups are optionally replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that the O- and / or S-atoms do not directly connect to each other, and where one or more H atoms are each optionally replaced by F, Cl or L a replaced

[0239] -L or L’, when different from L 11 represents F, Cl or CN

[0240] -L' is F

[0241] -r1, r2 and r3 represent 0 or 1

[0242] -r1, r2, r3, r4, r5 and r6 represent 0 or 1

[0243] -One of r1 and r6 is 0 and the other is 1

[0244] -r1 is 1 and r2 and r3 are 0

[0245] -r3 is 1 and r1 and r2 are 0

[0246] -One of r4 and r5 is 0 and the other is 1

[0247] -r1 and r4 are 0 and r3 is 1

[0248] -r1 and r3 are 0 and r4 is 1

[0249] -r3 and r4 are 0 and r1 is 1

[0250] For the production of PSA displays, the polymerizable compounds contained in the LC medium are polymerized or crosslinked (if a compound contains two or more polymerizable groups) by in-situ polymerization in the LC medium (between the substrates of the LC display), optionally while applying a voltage to the electrodes simultaneously.

[0251] The structure of the PSA display according to the invention corresponds to the usual geometry of PSA displays as described in the prior art cited at the beginning. A geometry without protrusions is preferred, wherein in addition, in particular those in which the electrodes on the color filter side are unstructured and only the electrodes on the TFT side have slots. A particularly suitable and preferred electrode structure for PS-VA displays is described, for example, in US2006 / 0066793A1.

[0252] The preferred PSA type LC display of the invention comprises:

[0253] - A first substrate comprising pixel electrodes defining pixel regions (the pixel electrodes being connected to switching elements arranged in each pixel region and optionally comprising a micro-slit pattern), and optionally a first alignment layer arranged on the pixel electrodes,

[0254] - A second substrate comprising a common electrode layer (which may be arranged over the entire part of the second substrate facing the first substrate), and optionally a second alignment layer,

[0255] - An LC layer arranged between the first and second substrates and comprising an LC medium, the LC medium containing a polymerizable component P) as described in the context and a liquid crystal component H) containing a chiral component D), wherein the polymerizable component P) may also be polymerized.

[0256] The first and / or second alignment layer controls the alignment direction of the LC molecules of the LC layer. For example, in a PS-VA display, the alignment layer is selected such that it imparts a homeotropic (or vertical) alignment (i.e., perpendicular to the surface) or an inclined alignment to the LC molecules. Such an alignment layer may, for example, comprise polyimide, which may also be rubbed, or may be prepared by a photo-alignment method.

[0257] The LC layer having the LC medium can be deposited between the substrates of the display by methods conventionally used by display manufacturers (such as the so-called one-drop filling (ODF) method). The polymerizable component of the LC medium is then polymerized, for example, by UV photopolymerization. This polymerization can be carried out in one step or in two or more steps.

[0258] The PSA display may include other elements, such as color filters, black matrices, passivation layers, optical retardation layers, transistor elements for individual pixel addressing, etc., all of which are well known to those skilled in the art and can be used without creative skills.

[0259] Those skilled in the art can design the electrode structure depending on the type of a single display. For example, for a PS-VA display, the multi-domain alignment of LC molecules can be induced by providing an electrode having slits and / or bumps or protrusions so as to generate two, four or more different tilt alignment directions.

[0260] After polymerization, the polymerizable compound forms a crosslinked polymer, which results in a certain pretilt of LC molecules in the LC medium. Without wishing to be bound by a specific theory, it is believed that at least a part of the crosslinked polymer formed by the polymerizable compound phase-separates or precipitates from the LC medium and forms a polymer layer on the substrate or the electrode, or on the alignment layer provided thereon. Microscopic measurement data (such as SEM and AFM) have confirmed that at least a part of the formed polymer accumulates at the LC / substrate interface.

[0261] The polymerization can be carried out in one step. It is also possible to first carry out the polymerization in a first step (optionally while applying a voltage) so as to generate a pretilt angle, and then polymerize or crosslink the compounds that have not reacted in the first step in a second polymerization step without applying a voltage (“final curing”).

[0262] Suitable and preferred polymerization methods are, for example, thermal or photopolymerization, preferably photopolymerization, especially UV-induced photopolymerization, which can be achieved by exposing the polymerizable compound to UV radiation.

[0263] Optionally, one or more polymerization initiators are added to the LC medium. Suitable conditions for polymerization and suitable types and amounts of initiators are known to those skilled in the art and are described in the literature. Suitable for free radical polymerization are, for example, commercially available photoinitiators or (Ciba AG). If a polymerization initiator is used, its proportion is preferably 0.001 to 5% by weight, particularly preferably 0.001 to 1% by weight.

[0264] The polymerizable compound according to the present invention is also suitable for polymerization without an initiator, which is accompanied by a number of advantages, such as lower material costs and especially less contamination of the LC medium caused by possible residual amounts of the initiator or its degradation products. The polymerization can thus be carried out without adding an initiator. In a preferred embodiment, the LC medium thus does not contain a polymerization initiator.

[0265] The LC medium can also contain one or more stabilizers to prevent the spontaneous polymerization of undesired RMs, for example during storage or transportation. Suitable types and amounts of stabilizers are known to those skilled in the art and are described in the literature. Particularly suitable are, for example, commercially available from Stabilizers of series (Ciba AG), such as 1076. If stabilizers are used, based on the total amount of RM or polymerizable components (component P), their proportion is preferably 10 - 500000 ppm, particularly preferably 50 - 50000 ppm.

[0266] The polymerizable compounds of formula R do particularly show good UV absorption and are thus particularly suitable for the production method of PSA displays comprising one or more of the following features:

[0267] - The polymerizable medium in the display is exposed to UV light in a two-step process, which includes a first UV exposure step ("UV-1 step") to generate an inclination angle, and a second UV exposure step ("UV-2 step") to complete the polymerization.

[0268] - The polymerizable medium in the display is exposed to UV light generated by energy-saving UV lamps (also called "green UV lamps"). These lamps are characterized by a relatively low intensity in their absorption spectrum of 300 - 380 nm (1 / 100 - 1 / 10 of conventional UV1 lamps), and they are preferably used in the UV2 step, but they are also optionally used in the UV1 step when it is necessary to avoid high intensity for the method.

[0269] - The polymerizable medium in the display is exposed to UV light generated by a UV lamp, which has a radiation spectrum shifted to longer wavelengths (preferably 340 nm or longer) to avoid short UV light exposure in the PS-VA method.

[0270] Both low-intensity and longer-wavelength-shifted UV are used to protect the organic layer from damage that may be caused by UV light.

[0271] A preferred embodiment of the present invention relates to a method for preparing a PSA display as described in the context, which includes one or more of the following features:

[0272] - The polymerizable LC medium is exposed to UV light in a two-step process, which includes a first UV exposure step ("UV-1 step") to generate an inclination angle, and a second UV exposure step ("UV-2 step") to complete the polymerization.

[0273] - The polymerizable LC medium is exposed to UV light with an intensity of 0.5 mW / cm 2 to 10 mW / cm 2 in the wavelength range of 300 - 380 nm generated by a UV lamp, preferably used in the UV2 step and optionally also used in the UV1 step.

[0274] - The polymerizable LC medium is exposed to UV light having a wavelength of 340 nm or longer, and preferably 400 nm or shorter.

[0275] This preferred method is carried out, for example, by using a desired UV lamp, or by using a band-pass filter and / or a cut-off filter, which is substantially transmissive to UV light having respective desired wavelength(s) and substantially blocks UV light having respective undesired wavelengths. For example, when radiation of UV light having a wavelength λ in the range of 300 - 400 nm is desired, the UV exposure can be carried out using a broadband-pass filter that is substantially transmissive to wavelengths of 300 nm < λ < 400 nm. When radiation of UV light having a wavelength λ greater than 340 nm is desired, the UV exposure can be carried out using a cut-off filter that is substantially transmissive to wavelengths of λ > 340 nm.

[0276] "Substantially transmissive" means that the filter transmits most, preferably at least 50%, of the intensity of the incident light of the desired wavelength(s). "Substantially blocks" means that the filter does not transmit most, preferably at least 50%, of the intensity of the incident light of the undesired wavelength. "Desired (undesired) wavelength" means, for example, in the case of a band-pass filter, a wavelength within (outside) a given λ range, and in the case of a cut-off filter, a wavelength higher (lower) than a given λ value.

[0277] This preferred method makes it possible to manufacture a display by using a longer UV wavelength, thereby reducing or even avoiding the harmful and damaging effects of short UV light components.

[0278] The UV radiation energy is generally 6 to 100 J, depending on the production method conditions.

[0279] Preferably, the LC medium according to the present invention essentially consists of a polymerizable component P) or a compound of one or more polymerizable formulas R as described in the context, an LC component H) or an LC host mixture, and an optically active component D) containing one or more chiral dopants. However, the LC medium may additionally contain one or more other components or additives, preferably selected from the list including but not limited to the following: comonomers, polymerization initiators, inhibitors, stabilizers, surfactants, wetting agents, lubricants, dispersants, water repellents, adhesives, flow improvers, defoamers, degassing agents, diluents, reactive diluents, auxiliaries, colorants, dyes, pigments, and nanoparticles.

[0280] Particularly preferred is an LC medium containing one, two, or three chiral dopants, and very preferably one chiral dopant.

[0281] Particularly preferred is an LC medium containing one, two, or three polymerizable compounds of formula R.

[0282] Furthermore preferred are LC media in which the polymerizable component (P) contains only polymerizable compounds of the formula R.

[0283] Furthermore preferred are LC media in which the liquid-crystalline component (H) or the LC host mixture has a chiral nematic LC phase.

[0284] The LC component (H) or the LC host mixture is preferably a nematic LC mixture.

[0285] Preferably, the proportion of the polymerizable component (P) in the LC medium is >0 to <5%, very preferably from >0 to <1%, and most preferably 0.01 to 0.5%.

[0286] Preferably, the proportion of the compound of the formula R in the LC medium is >0 to <5%, very preferably >0 to <1%, and most preferably 0.01 to 0.5%.

[0287] Preferably, the LC component (H) comprising one or more mesogenic or liquid-crystalline compounds and the optically active component (D), the proportion thereof in the LC medium being 95 to <100%, very preferably 99 to <100%.

[0288] In a preferred embodiment, the polymerizable compounds of the polymerizable component (H) are selected only from the formula R.

[0289] Preferred compounds of the formula R are selected from the following formulae:

[0290]

[0291]

[0292]

[0293]

[0294]

[0295] In which, each group has the following meanings:

[0296] P 1 、P 2 and P 3 each independently of one another represents an acrylate group or a methacrylate group,

[0297] Sp 1 、Sp 2 and Sp 3 each independently of one another represents a single bond or a spacer group (having one of the meanings as described for Sp in the context), and particularly preferably represents -(CH2) p1 -、-(CH2) p1 -O-、-(CH2) p1-CO-O-, -(CH2) p1 -O-CO- or -(CH2) p1 -O-CO-O-, where p1 is an integer from 1 to 12, and in addition where the group P 1 -Sp 1 -, P 1 -Sp 2 - and P 3 -Sp 3 - one or more of which may represent R aa , provided that the group P 1 -Sp 1 -, P 2 -Sp 2 - and P 3 -Sp 3 - at least one of which is different from R aa ,

[0298] R aa represents H, F, Cl, CN or a straight-chain or branched alkyl group having 1 to 25 C atoms, where in addition one or more non-adjacent CH2 groups may each independently of one another also be replaced by C(R 0 )=C(R 00 )-, -C≡C-, -N(R 0 )-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that the O and / or S atoms are not directly connected to one another, and where in addition one or more H atoms may be replaced by F, Cl, CN or P 1 -Sp 1 -, particularly preferably a straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy group having 1 to 12 C atoms (where the alkenyl and alkynyl groups have at least two C atoms and the branched groups have at least three C atoms),

[0299] R 0 , R 00 each independently of one another and each time they occur the same or different, represent H or an alkyl group having 1 to 12 C atoms,

[0300] R y and R z each independently of one another represent H, F, CH3 or CF3,

[0301] X 1 、X 2 and X 3 each independently of one another represent -CO-O-, -O-CO- or a single bond,

[0302] Z1 represents -O-, -CO-, -C(R y R z )- or -CF2CF2-,

[0303] Z 2 and Z 3 each independently of one another represents -CO-O-, -O-CO-, -CH2O-, -OCH2-, -CF2O-, -OCF2- or -(CH2) n -, where n is 2, 3 or 4,

[0304] L, each occurrence being the same or different, represents F, Cl, CN or a straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy group having 1 to 12 C atoms, preferably F,

[0305] L' and L'' each independently of one another represent H, F or Cl,

[0306] r represents 0, 1, 2, 3 or 4,

[0307] s represents 0, 1, 2 or 3,

[0308] t represents 0, 1 or 2,

[0309] x represents 0 or 1.

[0310] Particularly preferred are the compounds of the formulas R2, R13, R17, R22, R23, R24 and R30.

[0311] Further preferred are the tri-reactive compounds R17 to R31, in particular R17, R18, R19, R22, R23, R24, R25, R26, R30 and R31.

[0312] In the compounds of the formulas R1 to R31, the groups

[0313] are preferably

[0314]

[0315] Wherein L, each time it appears, independently has one of the meanings given by the context, preferably F, Cl, CN, NO2, CH3, C2H5, C(CH3)3, CH(CH3)2, CH2CH(CH3)C2H5, OCH3, OC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF3, OCF3, OCHF2, OC2F5 or P-Sp-, very preferably F, Cl, CN, CH3, C2H5, OCH3, COCH3, OCF3 or P-Sp-, more preferably F, Cl, CH3, OCH3, COCH3 or OCF3, especially F or CH3.

[0316] In addition to the above-mentioned polymerizable compounds, the LC medium for an LC display according to the invention further comprises an LC mixture ("host mixture") which contains one or more, preferably two or more, LC compounds selected from non-polymerizable low-molecular-weight compounds. These LC compounds are selected such that they are stable or non-reactive towards the polymerization reaction under the polymerization conditions applied to the polymerizable compounds.

[0317] In principle, any LC mixture suitable for a conventional display is suitable as the host mixture. Suitable LC mixtures are known to the person skilled in the art and are described in the literature, for example the mixtures in VA displays in EP 1 378 557.

[0318] The polymerizable compounds of formula R are particularly suitable for use in an LC host mixture which contains one or more mesogenic or LC compounds containing an alkenyl group (hereinafter also referred to as "alkenyl compounds"), wherein the alkenyl group is stable towards the polymerization reaction under the polymerization conditions for the polymerization of the compounds of formula R and for the polymerization of the other polymerizable compounds contained in the LC medium. Compared to the RM known from the prior art, the compounds of formula R in such an LC host mixture do indeed exhibit improved properties, such as solubility, reactivity or the ability to generate a tilt angle.

[0319] Thus, in addition to the polymerizable compounds of formula R, the LC medium according to the invention further comprises one or more mesogenic or liquid-crystalline compounds containing an alkenyl group ("alkenyl compounds"), wherein the alkenyl group is stable towards the polymerization reaction under the polymerization conditions for the polymerization of the polymerizable compounds of formula R or for the polymerization of the other polymerizable compounds contained in the LC medium.

[0320] The alkenyl group in the alkenyl compound is preferably selected from linear, branched or cyclic alkenyl groups, in particular having 2 to 25 C atoms, particularly preferably having 2 to 12 C atoms, wherein in addition one or more non-adjacent CH2 groups can be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and / or S atoms are not directly connected to each other, and wherein in addition one or more H atoms can be replaced by F and / or Cl.

[0321] Preferred alkenyl groups are linear alkenyl groups having 2 to 7 C atoms and cyclohexenyl groups, in particular vinyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, 1,4-cyclohexen-1-yl and 1,4-cyclohexen-3-yl.

[0322] The concentration of the alkenyl-containing compound in the LC host mixture (i.e., without any polymerizable compounds) is preferably 5% to 100%, very preferably 20% to 60%.

[0323] Particularly preferred is an LC mixture containing 1 to 5, preferably 1, 2 or 3 compounds having an alkenyl group.

[0324] The mesogenic and LC compounds containing an alkenyl group are preferably selected from the formulas AN and AY defined below.

[0325] In addition to the above-mentioned polymerizable component P), the LC medium according to the invention further comprises an LC component H) or an LC host mixture which comprises one or more, preferably two or more, LC compounds selected from non-polymerizable low molecular weight compounds. These LC compounds are selected such that they are stable and / or non-reactive towards the polymerization reaction under the polymerization conditions applied to the polymerizable compounds.

[0326] The medium according to the invention comprises one or more chiral dopants. Preferably, these chiral dopants have an absolute value of the helical twisting power (abbreviation: HTP) of 1 μm -1 to 150 μm -1 preferably 10 μm -1 to 100 μm -1 If the medium comprises two or more chiral dopants, they can have opposite signs of their HTP values. This condition is preferred for some specific embodiments because it allows the chiral compensation of the respective compounds to a certain extent and can thus be used to compensate for various temperature-dependent properties of the medium obtained in the device. However, generally most preferably, all chiral compounds preferably present in the medium according to the invention have the same sign as their HTP values. Preferably, the chiral dopants present in the medium according to the present application are mesogenic compounds and they most preferably exhibit their own mesophase.

[0327] In a preferred embodiment according to the invention, the chiral component D) consists of two or more chiral compounds, all of which have the same algebraic sign as HTP.

[0328] The temperature dependence of the HTP of the individual compounds can be high or low. The temperature dependence of the pitch of the medium can be compensated by mixing compounds with different HTP temperature dependencies in corresponding proportions.

[0329] For the optically active components, most chiral dopants, some of which are commercially available, are known to the person skilled in the art, for example cholesteryl nonanoate, R- and S-811, R- and S-1011, R- and S-2011, R- and S-3011R- and S-4011, B(OC)2C*HC-3 or CB15 (all Merck KGaA, Darmstadt).

[0330] Particularly suitable dopants are compounds which comprise one or more chiral groups and one or more mesogenic groups, or one or more aromatic or cycloaliphatic groups which form a mesogenic group with the chiral group.

[0331] Suitable chiral groups are, for example, chiral branched hydrocarbon groups, chiral ethylene glycol, binaphthol or dioxolane, as well as mono- or polyvalent chiral groups selected from sugar derivatives, sugar alcohols, sugar acids, lactic acid, chiral substituted diols, steroid derivatives, terpenoid derivatives, amino acids or a sequence, preferably 1-5 amino acids.

[0332] Preferred chiral groups are sugar derivatives, such as glucose, mannose, galactose, fructose, arabinose and glucose; sugar alcohols, such as sorbitol, mannitol, edetol, galactitol or their anhydrous derivatives, in particular dihydrohexanols, such as dihydrosorbitol (1,4:3,6-dihydro-D-sorbitol, isosorbide), dihydromannitol (isosorbide) or dihydroiditol (isoiditol); sugar acids, such as gluconic acid, gulonic acid and ketogulonic acid; chiral substituted diol groups, For example, mono- or oligoethylene glycol or propylene glycol, in which one or more CH2 groups are substituted by alkyl or alkoxy groups; amino acids, such as alanine, valine, phenylglycine or phenylalanine, or 1 to 5 of their sequences of these amino acids; steroid derivatives, such as cholesterol or cholic acid; terpene derivatives, such as mint, mint, lettuce, rosin, pine oil, isostearyl, fenugreek, carthene, myristoyl, nonyl, geranyl, linalool, neroli, citronellol or dihydrocitronellol.

[0333] The optically active component D) preferably consists of chiral dopants selected from known chiral dopants. Suitable chiral groups and mesogenic chiral compounds are described, for example, in DE 34 25 503, DE 35 34 777, DE 35 34 778, DE 35 34 779 and DE 35 34 780, DE 43 42 280, EP 01 038 941 and DE 195 41 820. Examples are also the compounds listed in Table B below.

[0334] The chiral compounds preferably used according to the invention are selected from the following formulae.

[0335] Particularly preferred are the following chiral dopants selected from the compounds of the formulae A-I to A-III and Ch:

[0336]

[0337]

[0338] where

[0339] R a11 , R a12 and R b12 , independently of one another, represent an alkyl group having 1 to 15 C atoms, where furthermore one or more non-adjacent CH2 groups can each independently of one another be replaced by -C(R z )=C(R z )-,-C≡C-,-O-,-S-,-CO-,-CO-O-,-O-CO- or -O-CO-O- in such a way that O and / or S atoms are not directly linked to one another, and where furthermore one or more H atoms can be replaced by F, Cl, Br, I or CN, preferably an alkyl group, more preferably a normal alkyl group, provided that R a12 is different from R b12 ,

[0340] R a21 and R a22 , independently of one another, represent an alkyl group having 1 to 15 C atoms, where furthermore one or more non-adjacent CH2 groups can each independently of one another be replaced by -C(R z )=C(R z )-,-C≡C-,-O-,-S-,-CO-,-CO-O-,-O-CO- or -O-CO-O- in such a way that O and S atoms are not directly linked to one another, and where furthermore one or more H atoms can be replaced by F, Cl, Br, I or CN, preferably an alkyl group, more preferably a normal alkyl group,

[0341] R a31 , R a32 and Rb32 , independently of one another, represent a straight-chain or branched alkyl group having 1 to 15 carbon atoms, wherein in addition, one or more non-adjacent CH2 groups may each independently of one another be replaced by -C(R z )=C(R z )-, -C≡C-, -O-, -S-, -CO-, -CO-O-, -O-CO- or -O-CO-O- in such a way that O and / or S atoms are not directly connected to each other, and wherein in addition, one or more H atoms may be replaced by F, Cl, Br, I or CN, preferably an alkyl group, more preferably a normal alkyl group, provided that R a32 is different from R b32 .

[0342] R z represents H, CH3, F, Cl or CN, preferably H or F,

[0343] R 8 has one of the meanings given for R a11 above, preferably an alkyl group, more preferably a normal alkyl group having 1 to 15 carbon atoms,

[0344] Z 8 represents -C(O)O-, CH2O, CF2O or a single bond, preferably -C(O)O-,

[0345] A 11 is as defined by A 12 below, or alternatively represents

[0346]

[0347] A 12 represents

[0348]

[0349] preferably

[0350]

[0351] wherein L 11 each independently of one another, in each occurrence, has one of the meanings given above for formula R

[0352] shown, preferably Me, Et, Cl or F, particularly preferably F.

[0353] A 21 represents

[0354]

[0355] A 22 has the meaning given for A 12 above,

[0356] A 31 has the meaning given for A 11 and, alternatively, represents

[0357]

[0358]

[0359] A 32 has the meaning given for A 12 and,

[0360] n2 is the same or different and is 0, 1 or 2 each time it appears, and

[0361] n3 is 1, 2 or 3.

[0362] Particularly preferred are dopants selected from compounds of the formula

[0363]

[0364]

[0365] wherein

[0366] m is the same or different and is an integer from 1 to 9 each time it appears,

[0367] n is the same or different and is an integer from 2 to 9 each time it appears,

[0368] Particularly preferred compounds of formula A are compounds of formula A-III.

[0369] Further preferred dopants are derivatives of isosorbide, isomannide or isoidide of the formula A-IV

[0370]

[0371] where the group is

[0372] (dianhydro sorbitol),

[0373] (dianhydro mannitol), or

[0374] (dianhydro iditol),

[0375] preferably dianhydro sorbitol,

[0376] and chiral ethylene glycols, such as diphenyl ethylene glycol (hydrobenzoin), in particular derivatives of mesogenic hydrobenzoin of the formula A-V

[0377]

[0378] including the (R,S), (S,R), (R,R) and (S,S) enantiomers, not shown.

[0379] wherein,

[0380]

[0381] and

[0382] each independently of one another is 1,4-phenylene, which may also be mono-, di- or trisubstituted by L, or 1,4-cyclohexylene, and L is H, F, Cl, CN or an alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl or alkylcarbonyloxy group having 1 to 7 C atoms which may be optionally halogenated,

[0383] c is 0 or 1,

[0384] Z 0 is -COO-, -OCO-, -CH2CH2- or a single bond, and

[0385] R 0 is an alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl or alkylcarbonyloxy group having 1 to 12 C atoms,

[0386] Examples of the compounds of formula IV are:

[0387]

[0388]

[0389] The compounds of formula A-IV are described in WO 98 / 00428. The compounds of formula A-V are described in GB-A-2,328,207.

[0390] Very particularly preferred dopants are chiral binaphthyl derivatives as described in WO 02 / 94805, chiral binaphthol acetal derivatives as described in WO 02 / 34739, chiral TADDOL derivatives as described in WO 02 / 06265, and chiral dopants having at least one fluorinated bridging group and a terminal or central chiral group as described in WO 02 / 06196 and WO 02 / 06195.

[0391] Particularly preferred are chiral compounds of formula A-VI

[0392]

[0393] wherein

[0394] X 1 , X 2 , Y1 and Y 2 each independently of one another is F, Cl, Br, I, CN, SCN, SF5, a straight-chain or branched alkyl group having 1 to 25 carbon atoms, which may be mono- or polysubstituted by F, Cl, Br, I or CN, and in which furthermore one or more non-adjacent CH2 groups are each independently of one another replaced by -O-, -S-, -NH-, NR 0 -,-CO-,-COO-,-OCO-,-OCOO-,-S-CO-,-CO-S-,-CH=CH- or -C≡C- in such a way that O and / or S atoms are not directly connected to one another, a polymerizable group or a cycloalkyl or aryl group having up to 20 carbon atoms, which may optionally be mono- or polysubstituted by halogen, preferably F, or by a polymerizable group,

[0395] x 1 and x 2 each independently of one another is 0, 1 or 2,

[0396] y 1 and y 2 each independently of one another is 0, 1, 2, 3 or 4,

[0397] B 1 and B 2 each independently of one another is an aromatic or partially or fully saturated aliphatic six-membered ring in which one or more CH groups may be replaced by N atoms and one or more non-adjacent CH2 groups may be replaced by O and / or S,

[0398] W 1 and W 2 each independently of one another is -Z 1 -A 1 -(Z 2 -A 2 ) m -R, and one of the two is alternatively R 1 or A 3 , but the two are not both H, or

[0399] is

[0400]

[0401] U 1 and U 2 each independently of one another is CH2, O, S, CO or CS,

[0402] V 1 and V 2 each independently of one another is (CH2) n, where one to four non-adjacent CH2 groups can be replaced by O and / or S, and V 1 and V 2 One of them is a single bond and in

[0403] is is a single bond in all cases,

[0404] Z 1 and Z 2 are each independently of one another -O-,-S-,-CO-,-COO-,-OCO-,-O-COO-,-CO-NR 0 -,-NR 0 -CO-,-O-CH2-,-CH2-O-,-S-CH2-,-CH2-S-,-CF2-O-,-O-CF2-,-CF2-S-,-S-CF2-,-CH2-CH2-,-CF2-CH2-,-CH2-CF2-,-CF2-CF2-,-CH=N-,-N=CH-,-N=N-,-CH=CH-,-CF=CH-,-CH=CF-,-CF=CF-,-C≡C-, combinations of two of these groups, where no two O and / or S and / or N atoms are linked to one another, preferably -CH=CH-COO- or -COO-CH=CH-, or a single bond,

[0405] A 1 ,A 2 and A 3 are each independently of one another 1,4-phenylene, where one or two non-adjacent CH groups can be replaced by N, 1,4-cyclohexylene, where one or two non-adjacent CH2 groups can be replaced by O and / or S, 1,3-di alkane-4,5-diyl, 1,4-cyclohexenylene, 1,4-bicyclo[2.2.2]octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl or 1,2,3,4-tetrahydronaphthalene-2,6-diyl, where each of these groups can be mono- or polysubstituted by L, and furthermore A 1 is a single bond,

[0406] L is a halogen atom, preferably F, CN, NO2, an alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkoxycarbonyloxy group having 1 to 7 carbon atoms, where one or more H atoms can be replaced by F or Cl,

[0407] m is independently in each case 0, 1, 2 or 3, and

[0408] R and R 1Each is independently of the others H, F, Cl, Br, I, CN, SCN, SF5, a straight-chain or branched alkyl group having 1 or 3 to 25 C atoms, which may optionally be mono- or polysubstituted by F, Cl, Br, I or CN, and in which one or more non-adjacent CH2 groups may be replaced by -O-, -S-, -NH-, -NR 0 -,-CO-,-COO-,-OCO-,-O-COO-,-S-CO-,-CO-S-,-CH=CH- or -C≡C-, where no two O and / or S atoms are directly linked to one another, or a polymerizable group.

[0409] Particularly preferred are the chiral binaphthyl derivatives of formula A-VI-1,

[0410]

[0411] in particular those selected from formulas A-VI-1a to A-VI-1c:

[0412]

[0413] wherein ring B and Z 0 are as defined for formula A-IV, and

[0414] R 0 is as defined for formula A-iV, or H or an alkyl group having 1 to 4 carbon atoms, and

[0415] b is 0, 1 or 2, and Z 0 is in particular OCO- or a single bond.

[0416] Also particularly preferred are the chiral binaphthyl derivatives of formula A-VI-2,

[0417]

[0418] in particular those selected from formulas A-VI-2a to A-VI-2f:

[0419]

[0420] wherein R 0 is as defined for formula A-VI, and X is H, F, Cl, CN or R 0 , preferably F.

[0421] The concentration of one or more chiral dopants in the LC medium is preferably from 0.001% to 20%, more preferably from 0.05% to 5%, even more preferably from 0.1% to 2%, and most preferably from 0.5% to 1.5%. These preferred concentration ranges are particularly suitable for the chiral dopants S-4011 or R-4011 (both from Merck KGaA) and chiral dopants having the same or similar HTP. For chiral dopants having a higher or lower absolute value of HTP compared to S-4011, these preferred concentrations must be proportionally reduced or increased respectively in accordance with the ratio of their HTP values relative to the HTP value of S-4011.

[0422] The pitch p of the LC medium or host mixture according to the invention is preferably from 5 to 50 μm, more preferably from 8 to 30 μm, and particularly preferably from 10 to 20 μm.

[0423] The cell thickness d of the display according to the invention or the thickness of the LC layer is preferably in the range from 2 μm to 10 μm, more preferably in the range from 3 μm to 5 μm. Based on this, according to the invention, the preferred range of the ratio d / p of the cell thickness d to the chiral pitch p is set to 0.04 to 2, preferably 0.1 to 1, and very preferably 0.2 to 0.3.

[0424] The term "alignment for vertical alignment" (hereinafter simply referred to as "aligning agent") refers to certain substances as disclosed, for example, in WO2012 / 038026 and EP2918658, WO2016 / 015803 or WO2017 / 045740. The aligning agent may optionally have one, two or more polymerizable groups attached to its structure. Herein, the alignment additive is preferably a molecular compound having two or more rings and polar anchoring groups (such as -OH, -SH, -NH2), where if the molecular compound has one, two or more polymerizable groups, it can become part of a polymer during its use. In the present disclosure, unless otherwise indicated, the term aligning agent refers to the molecule of the reagent and any polymeric form.

[0425] The self-aligning additive for vertical alignment is preferably selected from the formula SA

[0426] MES-R A SA

[0427] where

[0428] MES is a mesogenic group containing one or more rings (which are directly or indirectly connected to each other) and optionally one or more polymerizable groups (which are directly or through a spacer connected to MES),

[0429] and

[0430] R Ais a polar anchoring group, preferably comprising at least one -OH, -SH or primary or secondary amine functional group. More preferably, R A is a group R more precisely defined as follows a , including the definition for formula SAa.

[0431] Preferably, the polar anchoring group R A is a straight-chain or branched-chain alkyl group having 1 to 12 carbon atoms, wherein any -CH2- is optionally replaced by -O-, -S-, -NR 0 -, or -NH-, and which is substituted by one, two or three polar groups selected from -OH, -NH2 or -NR 0 H, wherein R 0 is an alkyl group having 1 to 10 carbon atoms. More preferably, R A is a group R defined as follows a .

[0432] More preferably, the self-aligning additive for vertical alignment is preferably selected from formula SAa

[0433] R 1 -[A 2 -Z 2 m -A 1 -R a SAa

[0434] wherein

[0435] A 1 , A 2 each independently of one another represent an aromatic, heteroaromatic, alicyclic or heterocyclic group, which may also contain fused rings, and which may also be monosubstituted or polysubstituted by any of the groups L and -Sp-P,

[0436] L in each case, independently of one another, represents H, F, Cl, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, -C(=O)N(R 0 )2, -C(=O)R 0 , an optionally substituted silyl group, an optionally substituted aryl or cycloalkyl group having 3 to 20 C atoms, or a straight-chain or branched-chain alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy group having 1 to 25 C atoms, wherein additionally, one or more H atoms may be replaced by F or Cl,

[0437] P represents a polymerizable group,

[0438] Sp represents a spacer group or a single bond,

[0439] Z 2 ​Each independently represents a single bond, -O-, -S-, -CO-, -CO-O-, -OCO-, -O-CO-O-, -OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -(CH2) n1 -, -CF2CH2-, -CH2CF2-, -(CF2) n1 -, -CH=CH-, -CF=CF-, -C≡C-, -CH=CH-COO-, -OCO-CH=CH-, -(CR 0 R 00 ) n1 -, -CH(-Sp-P)-, -CH2CH-(-Sp-P)-, -CH(-Sp-P)CH(-Sp-P)-,

[0440] n1 represents 1, 2, 3 or 4,

[0441] m represents 1, 2, 3, 4, 5 or 6, preferably 2, 3 or 4,

[0442] R 0 In each case, independently of one another, represents an alkyl group having 1 to 12 C atoms,

[0443] R 00 In each case, independently of one another, represents H or an alkyl group having 1 to 12 C atoms,

[0444] R 1 Each independently represents H, halogen, a straight-chain, branched-chain or cyclic alkyl group having 1 to 25 C atoms, wherein additionally, one or more non-adjacent CH2 groups may be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and / or S atoms are not directly connected to one another, and wherein additionally, one or more H atoms may be replaced by F or Cl, or the group -Sp-P, and

[0445] R a represents a polar anchoring group having at least one group selected from -OH, -NH2, NHR 11 , -SH, C(O)OH and -CHO, wherein R 11 represents an alkyl group having 1 to 12 C atoms.

[0446] The anchoring group R of the self-aligning additive a or R A is preferably defined as

[0447] R a is an anchoring group of the following formula

[0448]

[0449] wherein

[0450] p represents 1 or 2,

[0451] q represents 2 or 3,

[0452] B represents a substituted or unsubstituted ring system or fused ring system, preferably selected from the ring systems of benzene, pyridine, cyclohexane, di ane or tetrahydropyran,

[0453] Y each independently represents -O-, -S-, -C(O)-, -C(O)O-, -OC(O)-, -NR 11 -, or a single bond,

[0454] o represents 0 or 1,

[0455] X 1 each independently represents H, alkyl, fluoroalkyl, OH, NH2, NHR 11 , NR 11 2, -SH, OR 11 , C(O)OH, -CHO, wherein at least one group X 1 represents a group selected from -OH, -NH2, NHR 11 , -SH, C(O)OH and –CHO,

[0456] R 11 represents an alkyl group having 1 to 12 C atoms,

[0457] Sp a , Sp c , Sp d each independently represents a spacer group or a single bond, and

[0458] Sp b represents a trivalent or tetravalent group, preferably CH, N or C.

[0459] The SA / SAa compounds optionally include polymerizable compounds. In the present disclosure, "a medium containing a compound of formula SA" means a medium containing a compound of formula SA, and optionally, both the compound in its polymeric form associated with the medium.

[0460] In the compounds of formula SAa, Z 1 and Z 2 preferably represent a single bond, -C2H4-, -CF2O- or -CH2O-. In a particularly preferred embodiment, Z 1 and Z 2 each independently represent a single bond.

[0461] In the formula SAa compound, L 1 and L 2 each independently preferably represents F or an alkyl group, preferably F, CH3, C2H5 or C3H7.

[0462] In the formula SAa compound, A 1 is preferably a 1,4-phenylene ring, optionally substituted by one or two groups -Sp-P and / or one, two or more groups L.

[0463] Preferred formula SA / SAa compounds are illustrated by the following sub-formulas SA-A to SA-I

[0464]

[0465]

[0466] wherein R 1 , R a , A 2 , Z 1 , Z 2 , Sp and P independently have the meanings defined for the above formula SAa,

[0467] L 1 , L 2 are independently defined as L in the above formula SA, and

[0468] r1, r2 are independently 0, 1, 2, 3 or 4, preferably 0, 1 or 2.

[0469] In a preferred embodiment, r2 represents 1 and / or r1 represents 0.

[0470] The polymerizable group P preferably has the preferred meaning provided for P in formula I, most preferably a methacrylate group.

[0471] In the above formula SA or SA-A to SA-I, Z 1 and Z 2 preferably independently represent a single bond or -CH2CH2-, and very particularly represent a single bond.

[0472] In the formula SA / SAa and its sub-formulas, the group R A / R a preferably represents a partial group selected from the following

[0473]

[0474] where p = 1, 2, 3, 4, 5 or 6, and

[0475] R 22is H, methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, CH2CH2-tert-butyl or n-pentyl,

[0476] and * represents the point of attachment of the group,

[0477] especially

[0478]

[0479]

[0480] In the sub-formulas of formula SA / SAa and formula SA or SAa, R 1 preferably represents a straight-chain alkyl or branched-chain alkyl having 1-8 C atoms, preferably a straight-chain alkyl. In the compounds of formula SA or SAa, R 1 more preferably represents CH3, C2H5, n-C3H7, n-C4H9, n-C5H 11 , n-C6H 13 or CH2CH(C2H5)C4H9. R 1 can also represent an alkenyloxy group, especially OCH2CH=CH2, OCH2CH=CHCH3, OCH2CH=CHC2H5 or an alkoxy group, especially OC2H5, OC3H7, OC4H9, OC5H 11 and OC6H 13 . Particularly preferred R 1 represents a straight-chain alkyl residue, preferably C5H 11 .

[0481] Particularly preferred compounds of formula SA are selected from the compounds of sub-formulas SA-1 to SA-79,

[0482]

[0483]

[0484]

[0485]

[0486]

[0487]

[0488]

[0489]

[0490]

[0491]

[0492]

[0493]

[0494]

[0495] wherein R 1 ,L 1 ,L 2 ,Sp,P and R a have the meanings given above, and L 3 is defined as L 2 .

[0496] The mixture according to the invention very particularly preferably contains a self-aligning additive which is at least one compound selected from the sub-formulae of formula SA of the following formulae:

[0497]

[0498]

[0499]

[0500]

[0501]

[0502]

[0503]

[0504]

[0505]

[0506]

[0507]

[0508]

[0509]

[0510]

[0511]

[0512]

[0513]

[0514]

[0515]

[0516]

[0517]

[0518] wherein R a represents an anchoring group as described in the context, one of its preferred meanings, or a group of a preferred formula

[0519]

[0520] wherein R 22 is H, methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, CH2CH2-, tert-butyl or n-pentyl, most preferably H,

[0521] and R 1 has the meaning given in formula SAa above, preferably represents a straight-chain alkyl group having 1-8 carbon atoms, preferably C2H5, n-C3H7, n-C4H9, n-C5H 11 , n-C6H1 or n-C7H 15 , most preferably n-C5H 11 .

[0522] The preferred LC mixture according to the invention contains at least one compound of formula SA or its preferred formula.

[0523] The self-aligning additive of formula SA is preferably used in the liquid crystal medium in an amount of ≥0.01% by weight, preferably 0.1-5% by weight, based on the entire mixture. Particularly preferred is a liquid crystal medium containing 0.1-5% by weight, preferably 0.2-3% by weight, of one or more self-aligning additives based on the total mixture.

[0524] Using one or more compounds of formula SA in a preferably 0.2-3% by weight amount results in a completely vertical alignment of the LC layer for a conventional LC thickness (3 to 4 μm) and the substrate materials used in the display industry. Special surface treatments can significantly reduce the amount of the compound(s) of formula SA to an amount in a lower range.

[0525] The preferred mixture contains:

[0526] - at least one self-aligning additive selected from the compounds of formula SA-1c or SA-8i

[0527]

[0528] Its amount is preferably 0.1 - 5% by weight, especially 0.2 - 2% by weight.

[0529] Preferably, the medium according to the invention comprises a stabilizer selected from the compounds of formulae ST-1 to ST-18.

[0530]

[0531]

[0532]

[0533]

[0534] wherein

[0535] R ST represents H, an alkyl or alkoxy group having 1 to 15 C atoms, wherein additionally, one or more CH2 groups in these groups may be independently replaced by -C≡C-, -CF2O-, -OCF2-, -CH=CH-, -O-, -CO-O-, -O-CO- in such a way that O atoms are not directly connected to each other, and wherein additionally, one or more H atoms may be replaced by halogen,

[0536] represents

[0537]

[0538]

[0539] Z ST each independently of one another represents -CO-O-, -O-CO-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -CH2-, -CH2CH2-, -(CH2)4-, -CH=CH-CH2O-, -C2F4-, -CH2CF2-, -CF2CH2-, -CF=CF-, -CH=CF-, -CF=CH-, -CH=CH-, -C≡C- or a single bond,

[0540] L 1 and L 2 each independently of one another represents F, Cl, CF3 or CHF2,

[0541] p represents 1 or 2,

[0542] q represents 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0543] Among the compounds of formula ST, the compounds of the following formula are particularly preferred

[0544]

[0545]

[0546] where n = 1, 2, 3, 4, 5, 6 or 7, preferably n = 1 or 7

[0547]

[0548] where n = 1, 2, 3, 4, 5, 6 or 7, preferably n = 3

[0549]

[0550] where n = 1, 2, 3, 4, 5, 6 or 7, preferably n = 3

[0551]

[0552]

[0553]

[0554] In the compounds of formulae ST-3a and ST-3b, n preferably represents 3. In the compounds of formula ST-2a, n preferably represents 7.

[0555] A very particularly preferred mixture according to the invention comprises a stabilizer which is one or more compounds selected from the compounds of formulae ST-2a-1, ST-3a-1, ST-3b-1, ST-8-1, ST-9-1 and ST-12:

[0556]

[0557]

[0558] The compounds of formulae ST-1 to ST-18 are preferably each present in the liquid crystal mixture according to the invention in an amount of 0.005 - 0.5% based on the mixture.

[0559] If the mixture according to the invention comprises two or more compounds selected from the compounds of formulae ST-1 to ST-18, then in the case of two compounds, this concentration is increased accordingly to 0.01 - 1% based on the mixture

[0560] However, based on the mixture according to the invention, the total proportion of the compounds of formulae ST-1 to ST-18 should not exceed 2%.

[0561] The LC medium contains an LC component H) or an LC host mixture based on a compound having negative dielectric anisotropy. Such an LC medium is particularly suitable for PS-VA and PVA displays. Particularly preferred embodiments of such an LC medium are those of parts a)-hh) below, where the acronyms used are explained in Table A below.

[0562] a) An LC medium, wherein one or more compounds selected from the formulas CY and PY according to claim 1 are preferably selected from the following sub-formulas:

[0563]

[0564]

[0565]

[0566]

[0567]

[0568] where a represents 1 or 2, alkyl and alkyl * each independently of one another represents a straight-chain alkyl group having 1-6 C atoms, and alkenyl represents a straight-chain alkenyl group having 2-6 C atoms, and (O) represents an oxygen atom or a single bond. Alkenyl preferably represents CH2=CH-, CH2=CHCH2CH2-, CH3-CH=CH-, CH3-CH2-CH=CH-, CH3-(CH2)2-CH=CH-, CH3-(CH2)3-CH=CH- or CH3-CH=CH-(CH2)2-.

[0569] The compounds of the formula PY are preferably selected from the group consisting of the following sub-formulas:

[0570]

[0571]

[0572]

[0573]

[0574] where alkyl and alkyl *Each independently of one another represents a straight-chain alkyl group having 1 to 6 C atoms, and alkenyl represents a straight-chain alkenyl group having 2 to 6 C atoms, and (O) represents an oxygen atom or a single bond. Alkenyl preferably represents CH2=CH-, CH2=CHCH2CH2-, CH3-CH=CH-, CH3-CH2-CH=CH-, CH3-(CH2)2-CH=CH-, CH3-(CH2)3-CH=CH- or CH3-CH=CH-(CH2)2-.

[0575] b) an LC medium, wherein component H) or the LC host mixture comprises one or more mesogenic or LC compounds containing an alkenyl group (hereinafter also referred to as "alkenyl compound"), wherein the alkenyl group is stable to the polymerization reaction under the polymerization conditions of the polymerizable compounds contained in the LC medium.

[0576] Preferably, component H) or the LC host mixture comprises one or more alkenyl compounds selected from the formulas AN and AY

[0577]

[0578] wherein each group, each occurrence being the same or different and independently of one another, has the following meanings:

[0579]

[0580]

[0581] R A1 is an alkenyl group having 2 to 9 C atoms, or if at least one of X, Y and Z represents cyclohexenyl, then R A1 also has one of the meanings of R A2 and

[0582] R A2 is an alkyl group having 1 to 12 C atoms, wherein in addition one or two non-adjacent CH2 groups are replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that the O atoms are not directly connected to one another,

[0583] Z x is -CH2CH2-, -CH=CH-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -CO-O-, -O-CO-, -C2F4-, -CF=CF-, -CH=CH-CH2O- or a single bond, preferably a single bond,

[0584] L 1,2 is H, F, Cl, OCF3, CF3, CH3, CH2F or CHF2H, preferably H, F or Cl,

[0585] x is 1 or 2,

[0586] z is 0 or 1.

[0587] Preferred compounds of the formulas AN and AY are those in which R A2 is selected from vinyl, propenyl, butenyl, pentenyl, hexenyl, and heptenyl.

[0588] In a preferred embodiment, component (H) or the LC host mixture comprises one or more compounds of formula AN selected from the following sub-formulas:

[0589]

[0590]

[0591] where alkyl and alkyl * each independently of one another represent straight-chain alkyl groups having 1-6 C atoms, and alkenyl and alkenyl * each independently of one another represent straight-chain alkenyl groups having 2-7 C atoms. Alkenyl and alkenyl * preferably represent 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-.

[0592] Preferably, component (H) or the LC host mixture comprises one or more compounds selected from formulas AN1, AN2, AN3, and AN6, very preferably one or more compounds of formula AN1.

[0593] In another preferred embodiment, component (H) or the LC host mixture comprises one or more compounds of formula AN selected from the following sub-formulas:

[0594]

[0595] where m represents 1, 2, 3, 4, 5, or 6, i represents 0, 1, 2, or 3, and R b1 represents H, CH3, or C2H5.

[0596] In another preferred embodiment, component (H) or the LC host mixture comprises one or more compounds selected from the following sub-formulas:

[0597]

[0598]

[0599] Most preferred are the compounds of formulae AN1a2 and AN1a5.

[0600] In another preferred embodiment, component H) or the LC host mixture comprises one or more compounds of formula AY selected from the following sub-formulae:

[0601]

[0602]

[0603]

[0604]

[0605]

[0606] wherein alkyl and alkyl * each independently of one another represent straight-chain alkyl groups having 1 - 6 C atoms, "(O)" represents an O-atom or a single bond, and alkenyl and alkenyl * each independently of one another represent straight-chain alkenyl groups having 2 - 7 C atoms. alkenyl and alkenyl * preferably represent 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-.

[0607] In another preferred embodiment, component H) or the LC host mixture comprises one or more compounds of formula AY selected from the following sub-formulae:

[0608]

[0609]

[0610] wherein m and n each independently of one another represent 1, 2, 3, 4, 5 or 6, and alkenyl represents CH2=CH-, CH2=CHCH2CH2-, CH3-CH=CH-, CH3-CH2-CH=CH-, CH3-(CH2)2-CH=CH-, CH3-(CH2)3-CH=CH- or CH3-CH=CH-(CH2)2-.

[0611] Preferably, the proportion of the compounds of formulae AN and AY in the LC medium is 2 - 70 wt%, very preferably 5 - 60 wt%, and most preferably 10 - 50 wt%.

[0612] Preferably, the LC medium or the LC host mixture contains 1 to 5, preferably 1, 2 or 3 compounds selected from the compounds of formula AN and AY.

[0613] In another preferred embodiment of the present invention, the LC medium contains one or more compounds of formula AY14, very preferably AY14a. The proportion of the compound of formula AY14 or AY14a in the LC medium is preferably 3 - 20 wt%.

[0614] Adding an alkenyl compound of formula AN and / or AY enables the reduction of the viscosity and response time of the LC medium.

[0615] c) an LC medium, wherein component H) or the LC host mixture contains one or more compounds of the following formula:

[0616]

[0617] wherein each group has the following meanings:

[0618] represents

[0619]

[0620] represents

[0621] R 3 and R 4 each independently of one another represents an alkyl group having 1 to 12 C atoms, and in addition, one or two non-adjacent CH2 groups may also be replaced by -O-, -CH=CH-, -CO-, -O-CO- or -CO-O- in such a way that the O atoms are not directly connected to each other.

[0622] Z y represents -CH2CH2-, -CH=CH-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -CO-O-, -O-CO-, -C2F4-, -CF=CF-, -CH=CH-CH2O- or a single bond, preferably a single bond.

[0623] The compounds of formula ZK are preferably selected from the group consisting of the following sub-formulas:

[0624]

[0625]

[0626] where alkyl and alkyl *Each independently of one another represents a straight-chain alkyl group having 1 to 6 C atoms, and alkenyl represents a straight-chain alkenyl group having 2 to 6 C atoms. Alkenyl preferably represents CH2=CH-, CH2=CHCH2CH2-, CH3-CH=CH-, CH3-CH2-CH=CH-, CH3-(CH2)2-CH=CH-, CH3-(CH2)3-CH=CH- or CH3-CH=CH-(CH2)2-.

[0627] Particularly preferred are the compounds of formula ZK1.

[0628] Particularly preferred compounds of formula ZK are selected from the following sub-formulas:

[0629]

[0630]

[0631] wherein propyl, butyl and pentyl are straight-chain groups.

[0632] Most preferred are the compounds of formula ZK1a.

[0633] d) an LC medium, wherein component H) or the LC host mixture additionally contains one or more compounds of the following formula:

[0634]

[0635] wherein each group, each time it occurs, independently of one another has the following meanings:

[0636] R 5 and R 6 each independently of one another represents an alkyl group having 1 to 12 C atoms, wherein in addition one or two non-adjacent CH2 groups may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that the O atoms are not directly linked to one another, preferably an alkyl group or an alkoxy group having 1 to 6 C atoms,

[0637] represents

[0638] represents and e represents 1 or 2.

[0639] Compounds of formula DK are preferably selected from the group consisting of the following sub-formulas:

[0640]

[0641]

[0642]

[0643] wherein alkyl and alkyl * each independently of one another represents a straight-chain alkyl group having 1 to 6 C atoms, and alkenyl represents a straight-chain alkenyl group having 2 to 6 C atoms. Alkenyl preferably represents CH2=CH-, CH2=CHCH2CH2-, CH3-CH=CH-, CH3-CH2-CH=CH-, CH3-(CH2)2-CH=CH-, CH3-(CH2)3-CH=CH- or CH3-CH=CH-(CH2)2-.

[0644] e) an LC medium, wherein component H) or the LC host mixture additionally comprises one or more compounds of the following formula:

[0645]

[0646] wherein each group has the following meanings:

[0647] e represents note

[0648]

[0649] wherein at least one ring F is different from cyclohexylene.

[0650] f represents 1 or 2,

[0651] R 1 and R 2 each independently of one another represents an alkyl group having 1 to 12 C atoms, wherein in addition one or two non-adjacent CH2 groups may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that the O atoms are not directly connected to one another,

[0652] Z x represents -CH2CH2-, -CH=CH-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -CO-O-, -O-CO-, -C2F4-, -CF=CF-, -CH=CH-CH2O- or a single bond, preferably a single bond,

[0653] L 1 and L 2 each independently of one another represents F, Cl, OCF3, CF3, CH3, CH2F, CHF2.

[0654] Preferably, the two groups L 1 and L 2 represent F, or the group L1 and L 2 One of them represents F and the other represents Cl.

[0655] The compound of formula LY is preferably selected from the group consisting of the following sub-formulas:

[0656]

[0657]

[0658]

[0659]

[0660] wherein R 1 has the meaning given above, alkyl represents a straight-chain alkyl group having 1 to 6 C atoms, (O) represents an oxygen atom or a single bond, and v represents an integer from 1 to 6. R 1 preferably represents a straight-chain alkyl group having 1 to 6 C atoms or a straight-chain alkenyl group having 2 to 6 C atoms, especially CH3, C2H5, n-C3H7, n-C4H9, n-C5H 11 , 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-.

[0661] f) An LC medium, wherein component H) or the LC host mixture further comprises one or more compounds selected from the group consisting of the following formulas:

[0662]

[0663] wherein alkyl represents C 1-6 alkyl, L x represents H or F, and X represents F, Cl, OCF3, OCHF2 or OCH=CF2. Compounds of formula G1 are particularly preferred, wherein X represents F.

[0664] g) An LC medium, wherein component H) or the LC host mixture further comprises one or more compounds selected from the group consisting of the following formulas:

[0665]

[0666]

[0667]

[0668] wherein R 5Having one of the meanings given above for R 1 As used herein, "alkyl" means a C 1-6 -alkyl group, "d" represents 0 or 1, and "z" and "m" each independently represent an integer from 1 to 6. In these compounds, R 5 is particularly preferably a C 1-6 -alkyl or -alkoxy group or a C 2-6 -alkenyl group, and "d" is preferably 1. The LC medium according to the invention preferably contains one or more compounds of the above formula in an amount of ≥ 5% by weight.

[0669] h) An LC medium, wherein component H) or the LC host mixture further contains one or more biphenyl compounds selected from the group consisting of the following formulas:

[0670]

[0671] wherein "alkyl" and "alkyl" * each independently represent a straight-chain alkyl group having 1 to 6 carbon atoms, and "alkenyl" and "alkenyl" * each independently represent a straight-chain alkenyl group having 2 to 6 carbon atoms. "Alkenyl" and "alkenyl" * preferably represent 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-.

[0672] The proportion of the biphenyls of formulas B1 to B3 in the LC host mixture is preferably at least 3% by weight, particularly ≥ 5% by weight.

[0673] The compound of formula B2 is particularly preferred.

[0674] The compounds of formulas B1 to B3 are preferably selected from the group consisting of the following sub-formulas:

[0675]

[0676] wherein "alkyl" * represents an alkyl group having 1 to 6 carbon atoms. The medium according to the invention particularly preferably contains one or more compounds of formulas B1a and / or B2c.

[0677] i) An LC medium, wherein component H) or the LC host mixture further contains one or more terphenyl compounds of the following formula:

[0678]

[0679] wherein R5 and R 6 each independently has one of the meanings shown above, and

[0680] each other independently represents:

[0681]

[0682] wherein L 5 represents F or Cl, preferably F, and L 6 represents F, Cl, OCF3, CF3, CH3, CH2F or CHF2, preferably F.

[0683] The compound of formula T is preferably selected from the group consisting of the following sub-formulas:

[0684]

[0685]

[0686]

[0687] wherein R represents a straight-chain alkyl or alkoxy group having 1-7 C atoms, R * represents a straight-chain alkenyl group having 2-7 C atoms, (O) represents an oxygen atom or a single bond, and m represents an integer from 1 to 6. R * preferably represents CH2=CH-, CH2=CHCH2CH2-, CH3-CH=CH-, CH3-CH2-CH=CH-, CH3-(CH2)2-CH=CH-, CH3-(CH2)3-CH=CH- or CH3-CH=CH-(CH2)2-.

[0688] R preferably represents methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy or pentyloxy.

[0689] The LC host mixture according to the invention preferably contains terphenyls of formula T and its preferred sub-formulas, in an amount preferably of 0.5-30% by weight, in particular 1-20% by weight.

[0690] The compounds of formula T1, T2, T3 and T21 are particularly preferred. In these compounds, R preferably represents an alkyl group, and also an alkoxy group, each having 1-5 C atoms.

[0691] If the Δn value of the mixture ≥ 0.1, terphenyls are preferably used in the LC medium according to the invention. The preferred LC medium contains 2-20% by weight of one or more terphenyl compounds of formula T, preferably selected from compounds T1 to T22.

[0692] k) An LC medium, wherein the component H) or the LC host mixture further comprises one or more terphenyl compounds selected from the group consisting of the following formula:

[0693]

[0694] wherein

[0695] R Q is an alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C atoms, or an alkenyl or alkenyloxy having 2 to 9 C atoms, all of which are optionally fluorinated,

[0696] X Q is F, Cl, a haloalkyl or alkoxy having 1 to 6 C atoms, or a haloalkenyl or alkenyloxy having 2 to 6 C atoms,

[0697] L Q1 to L Q6 are each independently H or F, where at least one of L Q1 to L Q6 is F.

[0698] Preferred compounds of formula Q are those in which R Q represents a straight-chain alkyl having 2 to 6 C atoms (very preferably ethyl, n-propyl or n-butyl).

[0699] Preferred compounds of formula Q are those in which L Q3 and L Q4 are F. Further preferred compounds of formula Q are those in which one or two of L Q3 、L Q4 as well as L Q1 and L Q2 are F.

[0700] Preferred compounds of formula Q are those in which X Q represents F or OCF3 (very preferably F).

[0701] Compounds of formula Q are preferably selected from the following sub-formulas

[0702]

[0703] wherein R Q has one of the meanings of formula Q or one of its preferred meanings given by the context, and is preferably ethyl, n-propyl or n-butyl.

[0704] Particularly preferred are compounds of formula Q1, especially those in which R Q is n-propyl.

[0705] Preferably, the proportion of the compound of formula Q in the LC host mixture is from >0 to ≤5% by weight, very preferably from 0.1 to 2% by weight, and most preferably from 0.2 to 1.5% by weight.

[0706] Preferably, the LC host mixture contains 1 to 5, preferably 1 or 2, compounds of formula Q.

[0707] Adding a terphenyl compound of formula Q to the LC host mixture can reduce the ODF color difference while maintaining high UV absorption, enable fast and complete polymerization, enable strong and fast tilt angle generation, and increase the UV stability of the LC medium.

[0708] Furthermore, adding a compound of formula Q having positive dielectric anisotropy to an LC medium having negative dielectric anisotropy allows better control of the dielectric constant ε || and ε ⊥ values, in particular enabling a high value of the dielectric constant ε || while keeping the dielectric anisotropy Δη constant, thereby reducing the kickback voltage and reducing image sticking.

[0709] l) an LC medium, wherein component H) or the LC host mixture further comprises one or more compounds of formula C:

[0710]

[0711] wherein

[0712] R C represents an alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C atoms, or an alkenyl or alkenyloxy having 2 to 9 C atoms, all of which are optionally fluorinated,

[0713] X C represents F, Cl, a haloalkyl or alkoxy having 1 to 6 C atoms, or a haloalkenyl or alkenyloxy having 2 to 6 C atoms,

[0714] L C1 、L C2 independently of one another represent H or F, where at least one of L C1 and L C2 is F.

[0715] Preferred compounds of formula C are those in which R C represents a straight-chain alkyl having 2 to 6 C atoms (very preferably ethyl, n-propyl or n-butyl).

[0716] Preferred compounds of formula C are those in which L C1 and L C2 are F.

[0717] Preferred compounds of formula C are those in which X C represents F or OCF3 (very preferably F).

[0718] Preferred compounds of formula C are selected from the following formulas

[0719]

[0720] wherein R C has one of the meanings of formula C or one of its preferred meanings given by the context, and is preferably ethyl, n-propyl or n-butyl, very preferably n-propyl.

[0721] Preferably, the proportion of the compound of formula C in the LC host mixture is >0 to ≤10% by weight, very preferably 0.1% to 8% by weight, and most preferably 0.2 to 5% by weight.

[0722] Preferably, the LC host mixture contains 1 to 5, preferably 1, 2 or 3 compounds of formula C.

[0723] Adding a compound of formula C having positive dielectric anisotropy to an LC medium having negative dielectric anisotropy allows better control of the dielectric constants ε || and ε ⊥ values, in particular enabling a high dielectric constant ε || value while keeping the dielectric anisotropy Δη constant, thereby reducing the kickback voltage and reducing image sticking. In addition, adding the compound of formula C can reduce the viscosity and response time of the LC medium.

[0724] m) LC medium, wherein component H) or the LC host mixture further contains one or more compounds selected from the group consisting of the following formulas

[0725]

[0726]

[0727] wherein R 1 and R 2 have the meanings shown above and are preferably each independently of the other a straight-chain alkyl having 1 to 6 C atoms or a straight-chain alkenyl having 2 to 6 C atoms.

[0728] Preferred media contain one or more compounds selected from formulas O1, O3 and O4.

[0729] n) LC medium, wherein component H) or the LC host mixture further contains one or more compounds of the following formulas

[0730]

[0731] wherein

[0732] represents

[0733]

[0734] R 9 represents H, CH3, C2H5 or n-C3H7, (F) represents an optional fluorine substituent, and q represents 1, 2 or 3, and R 7 has one of the meanings indicated for R 1 and preferably in an amount of > 3% by weight, in particular ≥ 5% by weight, very particularly preferably 5 - 30% by weight.

[0735] Particularly preferred compounds of formula FI are selected from the group consisting of the following sub-formulas:

[0736]

[0737]

[0738] wherein R 7 preferably represents a straight-chain alkyl group, and R 9 represents CH3, C2H5 or n-C3H7. Particularly preferred are the compounds of formulas FI1, FI2 and FI3.

[0739] o) LC medium, wherein component H) or the LC host mixture additionally contains one or more compounds selected from the group consisting of the following formulas:

[0740]

[0741] wherein R 8 has the meaning indicated for R 1 and alkyl represents a straight-chain alkyl group having 1 - 6 C atoms.

[0742] p) LC medium, wherein component H) or the LC host mixture additionally contains one or more compounds containing a tetrahydronaphthyl or naphthyl unit, for example compounds selected from the group consisting of the following formulas:

[0743]

[0744]

[0745] wherein

[0746] R 10 and R 11each independently represents an alkyl group having 1 to 12 carbon atoms, wherein one or two non-adjacent CH2 groups can be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that the O atoms are not directly connected to each other, preferably an alkyl group or an alkoxy group having 1 to 6 carbon atoms

[0747] and R 10 and R 11 preferably represents a straight-chain alkyl group or alkoxy group having 1 to 6 carbon atoms, or a straight-chain alkenyl group having 2 to 6 carbon atoms, and

[0748] Z 1 and Z 2 each independently represents -C2H4-, -CH=CH-, -(CH2)4-, -(CH2)3O-, -O(CH2)3-, -CH=CH-CH2CH2-, -CH2CH2CH=CH-, -CH2O-, -OCH2-, -CO-O-, -O-CO-, -C2F4-, -CF=CF-, -CF=CH-, -CH=CF-, -CH2- or a single bond

[0749] q) an LC medium, wherein component H) or the LC host mixture further contains one or more difluorodibenzochromans and / or chromans of the following formula:

[0750]

[0751] wherein

[0752] R 11 and R 12 each independently has one of the meanings indicated above for R 11 pointed out,

[0753] ring M is trans-1,4-cyclohexylene or 1,4-phenylene,

[0754] Z m is -C2H4-, -CH2O-, -OCH2-, -CO-O- or -O-CO-,

[0755] c is 0, 1 or 2,

[0756] preferably in an amount of 3-20 wt%, particularly in an amount of 3-15 wt%.

[0757] Particularly preferred compounds of the formulas BC, CR and RC are selected from the group consisting of the following sub-formulas:

[0758]

[0759]

[0760]

[0761]

[0762] wherein alkyl and alkyl * each independently of one another represents a straight-chain alkyl group having 1 to 6 C atoms, (O) represents an oxygen atom or a single bond, c is 1 or 2, and alkenyl and alkenyl * each independently of one another represents a straight-chain alkenyl group having 2 to 6 C atoms. alkenyl and alkenyl * preferably represents CH2=CH-, CH2=CHCH2CH2-, CH3-CH=CH-, CH3-CH2-CH=CH-, CH3-(CH2)2-CH=CH-, CH3-(CH2)3-CH=CH- or CH3-CH=CH-(CH2)2-.

[0763] A very particularly preferred LC host mixture comprises one, two or three compounds of formula BC-2.

[0764] r) an LC medium, wherein component H) or the LC host mixture additionally comprises one or more fluorinated phenanthrenes and / or dibenzofurans and / or dibenzothiophenes of the following formula:

[0765]

[0766]

[0767] wherein R 11 and R 12 each independently of one another have one of the meanings indicated above for R 11 and b represents 0 or 1, L represents F, and r represents 1, 2 or 3.

[0768] Particularly preferred compounds of formula PH, BF and BT are selected from the group consisting of the following sub-formulas:

[0769]

[0770] wherein R and R' each independently of one another represent a straight-chain alkyl or alkoxy group having 1 to 7 C atoms.

[0771] s) an LC medium, wherein component H) or the LC host mixture additionally comprises one or more monocyclic compounds of the following formula

[0772]

[0773] wherein

[0774] R1 and R 2 each independently represent an alkyl group having 1 to 12 carbon atoms, wherein in addition one or two non-adjacent CH2 groups may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that the O atoms are not directly connected to each other, preferably an alkyl group or an alkoxy group having 1 to 6 carbon atoms

[0775] L 1 and L 2 each independently represent F, Cl, OCF3, CF3, CH3, CH2F, CHF2

[0776] Preferably, L 1 and L 2 both represent F, or one of L 1 and L 2 represents F and the other represents Cl

[0777] The compound of formula Y is preferably selected from the group consisting of the following sub-formulas:

[0778]

[0779]

[0780] wherein, Alkyl and Alkyl * each independently represent a straight-chain alkyl group having 1-6 carbon atoms, Alkoxy represents a straight-chain alkoxy group having 1-6 carbon atoms. Alkenyl and Alkenyl * each independently represent a straight-chain alkenyl group having 2-6 carbon atoms, and O represents an oxygen atom or a single bond. Alkenyl and Alkenyl * preferably represent 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-

[0781] Particularly preferred compounds of formula Y are selected from the group consisting of the following sub-formulas:

[0782]

[0783] wherein Alkoxy preferably represents a straight-chain alkoxy group having 3, 4 or 5 carbon atoms

[0784] t) an LC medium which, in addition to the polymerizable compounds as described in the context, does not contain compounds having a terminal vinyloxy group (-O-CH=CH2)

[0785] u) An LC medium, wherein component H) or the LC host mixture contains one or more compounds of formula PY, with a total concentration of 5 - 60%, more preferably 15 - 50%, particularly preferably 20 - 45%.

[0786] v) An LC medium, wherein component H) or the LC host mixture contains 1 to 8, preferably 1 to 5 compounds of formula CY1, CY2, PY1, and / or PY2. The proportion of these compounds in the entire LC host mixture is preferably 5 - 60%, particularly preferably 10 - 40%. The content of each of these compounds is preferably 2 - 20% in each case.

[0787] w) An LC medium, wherein component H) or the LC host mixture contains one or more compounds of formula PY2, preferably with a total concentration of 3 - 30%, more preferably 3 - 25%, especially 10 - 25%. The compounds of formula PY2 are preferably selected from the compounds PY - 1 - O2, PY - 3 - O2, PY - 1 - O4, PY - 4 - O2.

[0788] x) An LC medium, wherein component H) or the LC host mixture contains 1 - 8, preferably 1 - 5 compounds of formula CY9, CY10, PY9, and / or PY10. The proportion of these compounds in the entire LC host mixture is preferably 5 - 60%, particularly preferably 10 - 35%. The content of each of these compounds is preferably 2 - 30% in each case.

[0789] y) An LC medium, wherein component H) or the LC host mixture contains one or more compounds of formula PY10, with a total concentration of 5 - 30%, more preferably 7 - 25%, particularly preferably 10 - 30%. Highly preferred compounds are CPY - 2 - O2 and / or CPY - 3 - O2.

[0790] z) An LC medium, wherein component H) or the LC host mixture contains 1 - 10, preferably 1 - 8 compounds of formula ZK, especially compounds of formula ZK1, ZK2, and / or ZK6. The proportion of these compounds in the entire LC host mixture is preferably 3 - 45%, more preferably 5 - 40%, particularly preferably 10 - 35%. The content of each of these compounds is preferably 2 - 20% in each case.

[0791] aa) An LC medium, wherein the proportion of the compounds of formula CY, PY, and ZK in the entire LC host mixture is greater than 70%, preferably greater than 80%.

[0792] bb) LC medium, wherein component H) or the LC host mixture contains one or more, preferably 1 to 5, compounds selected from formulas PY1 - PY8 (very preferably formula PY2). The proportion of these compounds in the entire LC host mixture is preferably 1 - 55%, particularly preferably 15 - 50%, and very preferably 20 - 45%. The content of each of these compounds is preferably 1 - 20% in each case.

[0793] cc) LC medium, wherein the LC host mixture contains one or more compounds selected from formulas CY and PY, and one or more compounds selected from formula T.

[0794] dd) LC medium, wherein component H) or the LC host mixture contains one or more, preferably 1, 2 or 3, compounds selected from formulas T1, T2 and T5, very preferably selected from formula T2. The proportion of these compounds in the entire LC host mixture is preferably 1 - 30%, more preferably 5 - 25%, and particularly preferably 10 - 22%.

[0795] ee) LC medium, wherein component H) or the LC host mixture contains one or more compounds of formula DK, especially compounds of formula DK1 and / or DK4. The proportion of these compounds in the entire LC host mixture is preferably 1 - 30%, more preferably 2 - 25%, and particularly preferably 2 - 20%.

[0796] ff) LC medium, wherein component H) or the LC host mixture contains one or more, preferably 1 to 3, compounds of formula BT, especially compound of formula BT1. The proportion of these compounds in the entire LC host mixture is preferably 0.5 - 25%, more preferably 1 - 20%, and particularly preferably 2 - 15%.

[0797] gg) LC medium, wherein component H) or the LC host mixture contains one or more, preferably 1 to 3, compounds of formula B, especially compound of formula B2c. The proportion of these compounds in the entire LC host mixture is preferably 0.5 - 20%, more preferably 1 - 15%, and particularly preferably 3 - 15%.

[0798] hh) LC medium, wherein component H) or the LC host mixture contains one or more compounds of formula CPY - n - Om, one or more compounds of formula PY - n - Om, and one or more compounds of formula PYP - nm, and their total concentration is 45 - 70%.

[0799] The combination of the compounds of the above preferred embodiments with the above polymerized compounds causes a low threshold voltage, low rotational viscosity and very good low temperature stability in the LC medium according to the invention, while causing a continuously high clearing point and a high HR value, and allowing a particularly low pretilt angle to be established quickly in a PSA display. In particular, compared with the media from the prior art, the LC medium shows a significantly shortened response time, especially the gray scale response time, in a PSA display.

[0800] The LC medium and the LC host mixture according to the invention preferably have a nematic phase range of at least 80 K, particularly preferably at least 100 K, and a rotational viscosity of ≤250 mPa·s, preferably ≤200 mPa·s at 20 °C.

[0801] In the VA type display according to the invention, the molecules in the LC medium layer in the off state are aligned perpendicular to the electrode surface (vertically) or have an inclined vertical alignment. When a voltage is applied to the electrodes, reorientation of the LC molecules occurs and the longitudinal molecular axis is parallel to the electrode surface.

[0802] The LC medium according to the invention based on the compounds with negative dielectric anisotropy according to the first preferred embodiment, in particular for PS-VA and PS-UB-FFS type displays, has a negative dielectric anisotropy Δε, preferably from -0.5 to -10, particularly from -2.5 to -7.5, at 20 °C and 1 kHz.

[0803] In another preferred embodiment, the LC medium according to the invention has a negative dielectric anisotropy Δε, preferably from -1.5 to -6.0, particularly from -2.0 to -4.0, and very preferably from -2.5 to -3.5, at 20 °C and 1 kHz.

[0804] The birefringence Δn in the LC medium according to the invention for PS-VA and PS-UB-FFS type displays is preferably 0.16 or lower, in the range from 0.06 to 0.16, preferably in the range from 0.110 to 0.150, more preferably from 0.120 to 0.140, particularly preferably from 0.125 to 0.137.

[0805] In the OCB type display according to the invention, the molecules in the LC medium layer have a "bent" alignment. When a voltage is applied, reorientation of the LC molecules occurs and the longitudinal molecular axis is perpendicular to the electrode surface.

[0806] The LC media according to the invention for PS-IPS and PS-FFS type displays are preferably those based on the compounds with positive dielectric anisotropy according to the second preferred embodiment and preferably have a positive dielectric anisotropy Δε from +4 to +17 at 20 °C and 1 kHz.

[0807] For the LC medium for a PS-OCB type display according to the present invention, the birefringence Δn is preferably from 0.14 to 0.22, particularly preferably from 0.16 to 0.22.

[0808] For the LC medium for a PS-IPS- or PS-FFS type display according to the present invention, the birefringence Δn is preferably from 0.07 to 0.15, particularly preferably from 0.08 to 0.13.

[0809] The LC medium according to the present invention may also contain other additives known to those skilled in the art and described in the literature, such as polymerization initiators, inhibitors, stabilizers, surface-active substances or chiral dopants. These may be polymerizable or non-polymerizable. Polymerizable additives are thus assigned to the polymerizable components or component P). Non-polymerizable additives are thus assigned to the non-polymerizable components or component H).

[0810] In another preferred embodiment, the LC medium contains a racemate of one or more chiral dopants, which are preferably selected from the chiral dopants mentioned in the previous paragraph.

[0811] Furthermore, for example, 0 to 15% by weight of a polychromatic dye can be added to the LC medium, and furthermore, nanoparticles, conductive salts, preferably ethyl dimethyldodecylammonium 4-hexyloxybenzoate, tetrabutylammonium tetraphenylborate or complex salts of crown ethers (see, for example, Haller et al., Mol. Cryst. Liq. Cryst. 24 , 249-258 (1973)) can be added for improving conductivity, or substances for changing the dielectric anisotropy, the viscosity of the nematic phase and / or the alignment. Substances of this type are described, for example, in DE-A 22 09 127, 22 40864, 23 21 632, 23 38 281, 24 50 088, 26 37 430 and 28 53 728.

[0812] The individual components of the preferred embodiments a)-z) of the LC medium according to the present invention are known or their preparation methods can be readily obtained by those skilled in the relevant art from the prior art, since they are based on standard methods described in the literature. Compounds of the corresponding formula CY are described, for example, in EP-A-0 364 538. Compounds of the corresponding formula ZK are described, for example, in DE-A-26 36 684 and DE-A-33 21 373.

[0813] The LC media that can be used according to the present invention are prepared in a conventional manner, for example, by mixing one or more of the above compounds with one or more polymerizable compounds as defined above, and optionally with additional liquid crystal compounds and / or additives. Generally, the required amounts of the components to be used in smaller amounts are dissolved in the components constituting the main component, advantageously at an elevated temperature. The solutions of the components can also be mixed in an organic solvent, such as acetone, chloroform or methanol, and the solvent is removed again after thorough mixing, for example, by distillation. The present invention also relates to a method for preparing an LC medium according to the present invention.

[0814] It is self-evident to those skilled in the art that the LC media according to the present invention can also contain compounds in which, for example, H, N, O, Cl, F have been replaced by the corresponding isotopes such as deuterium, etc.

[0815] The following examples illustrate the present invention without limiting it. However, the examples show to those skilled in the art the preferred mixture concepts, as well as the preferred compounds to be employed and their respective concentrations and their combinations with each other. Additionally, the examples illustrate which properties and combinations of properties are achievable.

[0816] The preferred mixture components are shown in Table A below.

[0817] Table A

[0818] In Table A, m and n are independently of each other integers from 1 to 12, preferably 1, 2, 3, 4, 5 or 6, k is 0, 1, 2, 3, 4, 5 or 6, and (O)C m H 2m+1 means C m H 2m+1 or OC m H 2m+1 .

[0819]

[0820]

[0821]

[0822]

[0823]

[0824]

[0825]

[0826]

[0827]

[0828]

[0829]

[0830]

[0831]

[0832]

[0833]

[0834]

[0835]

[0836]

[0837]

[0838]

[0839]

[0840]

[0841] In a first preferred embodiment of the present invention, the LC medium according to the present invention, in particular those having positive dielectric anisotropy, comprises one or more compounds selected from the compounds from Table A1.

[0842] In a second preferred embodiment of the present invention, the LC medium according to the present invention, in particular those having negative dielectric anisotropy, comprises one or more compounds selected from the compounds from Table A2.

[0843] Table B

[0844] Table B shows the chiral dopants that can be added to the LC medium according to the present invention.

[0845]

[0846]

[0847]

[0848]

[0849]

[0850] Table C

[0851] Table C shows the possible stabilizers that can be added to the LC medium according to the present invention. Where n represents an integer from 1 to 12, preferably 1, 2, 3, 4, 5, 6, 7 or 8, and the terminal methyl groups are not shown.

[0852]

[0853]

[0854]

[0855]

[0856]

[0857]

[0858] The LC medium preferably contains 0 to 10% by weight, in particular 1 ppm to 5% by weight, and particularly preferably 1 ppm to 1% by weight of the stabilizer. The LC medium preferably contains one or more stabilizers selected from the compounds from Table C.

[0859] Table D

[0860] Table D shows illustrative reactive mesogenic compounds of formula R that can be used in the LC medium according to the present invention.

[0861]

[0862]

[0863]

[0864]

[0865]

[0866]

[0867]

[0868]

[0869]

[0870]

[0871]

[0872]

[0873]

[0874]

[0875]

[0876]

[0877]

[0878] In a preferred embodiment, the mixture according to the invention comprises one or more polymerizable compounds, preferably selected from the polymerizable compounds of the formulas RM-1 to RM-131. Among these, the compounds RM-1, RM-4, RM-8, RM-17, RM-19, RM-35, RM-37, RM-43, RM-47, RM-49, RM-51, RM-59, RM-69, RM-71, RM-83, RM-97, RM-98, RM-104, RM-112, RM-115, RM-116 and RM-128 are particularly preferred. Detailed Description of the Invention

[0879] Example

[0880] The following examples illustrate the invention without limiting it. However, the examples show those skilled in the art the preferred mixture concept, as well as the preferred compounds employed and their respective concentrations and their combinations with one another. In addition, the examples illustrate which properties and combinations of properties are achievable.

[0881] In addition, the following abbreviations and symbols are used:

[0882] V0 represents the threshold voltage at 20 °C, capacitive [V],

[0883] n e represents the extraordinary refractive index at 20 °C and 589 nm,

[0884] n o represents the ordinary refractive index at 20 °C and 589 nm,

[0885] Δn represents the optical anisotropy at 20 °C and 589 nm,

[0886] ε ⊥ represents the dielectric constant perpendicular to the director at 20 °C and 1 kHz,

[0887] ε ||denotes the dielectric constant parallel to the director at 20 °C and 1 kHz,

[0888] Δε denotes the dielectric anisotropy at 20 °C and 1 kHz,

[0889] cl.p., T(N,I) denotes the clearing point [°C],

[0890] γ1 denotes the rotational viscosity [mPa·s] at 20 °C,

[0891] K1 denotes the elastic constant at 20 °C, "tilt" deformation [pN],

[0892] K2 denotes the elastic constant at 20 °C, "twist" deformation [pN],

[0893] K3 denotes the elastic constant at 20 °C, "bend" deformation [pN].

[0894] Unless otherwise explicitly stated, all concentrations in this application are quoted in weight % and relative to the respective entire mixture, including all solid or liquid crystal components, and excluding solvents.

[0895] Unless otherwise specified, all temperature values indicated in this application, such as the melting point T(C,N), the transition from the smectic phase (S) to the nematic phase (N) T(S,N), and the clearing point T(N,I), are expressed in degrees Celsius (°C). M.p. denotes the melting point, cl.p. = clearing point. In addition, C = crystalline state, N = nematic phase, S = smectic phase, and I = isotropic phase. The data between these symbols represent the transition temperatures.

[0896] All physical properties are and have been determined according to "Merck Liquid Crystals, Physical Properties of Liquid Crystals" Status November 1997, Merck KGaA, Germany, and apply to a temperature of 20 °C, and Δn is measured at 589 nm and Δε is measured at 1 kHz, unless otherwise explicitly stated in each case.

[0897] The term "threshold voltage" used in this invention refers to the capacitive threshold (V0), which is also referred to as the Freedericks threshold, unless otherwise stated. In the examples, the optical threshold is also given as usual for a relative contrast of 10% (V 10 )

[0898] Unless otherwise stated, the method of polymerizing the polymerizable compound in the PSA display as described in the context is carried out at a temperature at which the LC medium exhibits a liquid crystal phase, preferably a nematic phase, and most preferably at room temperature.

[0899] Unless otherwise specified, the method of preparing the test cells and measuring their electro-optical and other properties is carried out by the method described below or a similar method thereto.

[0900] The display for measuring the capacitive threshold voltage consists of two parallel planar glass outer plates spaced 25 μm apart, each outer plate having an electrode layer on the inner side and an unrubbed polyimide alignment layer on the top, which results in a homeotropic edge alignment of the liquid crystal molecules.

[0901] The display or test cell for measuring the tilt angle consists of two parallel planar glass outer plates spaced 4 μm apart, each outer plate having an electrode layer on the inner side and a polyimide alignment layer on the top, where the two polyimide layers are rubbed in reverse parallel to each other and achieve a homeotropic edge alignment of the liquid crystal molecules.

[0902] The polymerizable compound is polymerized in the display or test cell by irradiating with UV light of a defined intensity for a preset time while applying a voltage to the display (usually an alternating current of 10 V to 30 V, 1 kHz). In the examples, unless otherwise indicated, a fluorescent lamp and an intensity of 0 - 20 mW / cm 2 are used for polymerization. The intensity is measured using a standard meter (Ushio Accumulate UV meter, central wavelength 313 nm).

[0903] The transmittance measurement is carried out in a test cell having a fishbone electrode arrangement (from Merck Ltd., Japan; 1 pixel fishbone electrode (ITO, 10 x 10 mm, 47.7° angle fishbone, 3 μm line / 3 μm pitch), 3.2 μm cell thickness, AF - glass, tilt angle 1°) Mixture Example

[0904] The nematic LC host mixtures N1 to N14 are formulated as follows: Mixture N1

[0905]

[0906] Mixture N2

[0907]

[0908] Mixture N3

[0909]

[0910] Mixture N4

[0911]

[0912] Mixture N5

[0913]

[0914] Mixture N6

[0915]

[0916] Mixture N7

[0917]

[0918] Mixture N8

[0919]

[0920] Mixture N9

[0921]

[0922] Mixture N10

[0923]

[0924] Mixture N11

[0925]

[0926] Mixture N12

[0927]

[0928] Mixture N13

[0929]

[0930] Mixture N14

[0931]

[0932] Prepared as follows Comparative Mixture Example C1: Mixture C1

[0933]

[0934]

[0935] Comparative Mixture Example C2

[0936] The comparative mixture C2 consists of 99.7% of the mixture C1 and 0.3% of RM3.

[0937] Chiral Nematic Mixture

[0938] The chiral nematic mixtures in Table 1 are prepared from the above nematic host mixtures N1 to N4 by adding the chiral dopants S-811, S-2011 or S-4011 (in the amounts given in Table 1), respectively:

[0939]

[0940] Table 1: Chiral Nematic Mixture

[0941]

[0942]

[0943]

[0944] The following mixtures Ch40 to Ch105 additionally contain the stabilizer as described above. The amounts of the host mixture and the stabilizer given in the table add up to 100 wt%.

[0945] Table 2: Chiral nematic mixtures containing stabilizer

[0946]

[0947]

[0948]

[0949]

[0950] Polymerizable Chiral Nematic Mixture

[0951] The following polymerizable chiral nematic mixtures are prepared from the chiral nematic mixtures given in Table 1 by adding a reactive mesogen (RM) selected from RM1, RM2 and RM3 (in the amounts (%RM) given in Table 4).

[0952]

[0953] Table 4: Polymerizable chiral nematic mixtures.

[0954]

[0955]

[0956]

[0957]

[0958]

[0959] The polymerizable mixtures PCh1 to PCh117 preferably contain a stabilizer for the chiral nematic mixture at the same concentrations given in Table 2.

[0960] The following mixtures PCh118 to PCh183 additionally contain the stabilizer as described above. The amounts of the host mixture and the stabilizer given in the table add up to 100 wt%.

[0961] Table 5: Polymerizable chiral nematic mixtures containing a stabilizer.

[0962]

[0963]

[0964]

[0965] Transmittance Measurement

[0966] The transmittance values of the above mixtures are exemplified below.

[0967] For the transmittance measurement, a Zeiss AxioScope measurement system was used to measure the voltage-transmittance curve (frequency: 60 Hz; range: 0 - 10 V, increment 0.1 V) at a temperature of 25 °C. The results are shown in Tables 6 and 7.

[0968] The transmittance of the chiral nematic mixture was measured in a VA test cell.

[0969] Table 6. Transmittance values of the chiral nematic mixtures

[0970]

[0971] A test cell for the transmittance measurement of the polymerizable chiral nematic mixture was prepared as follows:

[0972] The test cell with the fishbone electrode arrangement indicated above was filled with the polymerizable chiral nematic mixture and then irradiated (UV fluorescent lamp, 5.1 mW / cm 2 with an applied voltage (20 V AC, square waveform, 1 kHz) at 313 nm and then post-cured (UV intensity 2.6 mW / cm 2 at 313 nm) for 2 hours. The transmittance values were determined as described above and are shown in Table 6.

[0973] Table 7. Transmittance values of the polymerizable chiral nematic mixtures

[0974]

[0975]

[0976] In the on-state, the mixtures Ch5, Ch8, Ch9, Ch18, Ch21, Ch22 according to the invention show an improved transmittance compared to the mixture C1 from the prior art.

[0977] In the on-state, the mixtures PCh5, PCh86, PCh87, PCh18, PCh99, PCh100 according to the invention show an improved transmittance compared to the mixture C2 from the prior art.

[0978] The following table (Table 8) shows the transmittance values of the nematic host mixtures N5, N8 and N9 and the corresponding mixtures Ch5, Ch8 and Ch9 containing the chiral dopant S-4011. It can be seen that the transmittance of Ch5, Ch8 and Ch9 is clearly improved compared to the mixtures without chiral dopant. The same applies to the mixtures Ch18, Ch21 and Ch22 (not shown here, see Table 6 above), which contain the chiral dopant S-811.

[0979] Table 8.

[0980]

[0981]

[0982] The transmittance values of the polymerizable chiral nematic mixtures shown above (Table 7) are also improved compared to the transmittance of the host mixtures N5, N8 and N9.

[0983] Self-Aligning Mixture

[0984] Alignment Additive Example 1

[0985]

[0986] The additives are prepared as described in WO 2017 / 041893.

[0987] Phase: T g -33K 26I

[0988] The following alignment additives are used together with the above host mixtures:

[0989]

[0990] (prepared as described in EP 2918658)

[0991]

[0992]

[0993]

[0994] All are similar to the preparation of compound SA-2.

[0995] The self-aligning LC medium according to the present invention is prepared by using each of the above host mixtures Ch1 to Ch105 according to the following table, by adding one or more of the indicated alignment additives and reactive mesogens (RM), and then by homogenization.

[0996] Table 9. Composition of mixture examples SM1 to SM1365 (all percentages are weight % based on the whole mixture)

[0997] Mixture Number LC Host [wt%] Alignment Additive RM SM1-SM105 Ch1 to Ch105 (99.4%) SA-1 (0.3%) RM1 (0.3%) SM106 to SM210 Ch1 to Ch105 (99.4%) SA-2 (0.3%) RM1 (0.3%) SM211 to SM315 Ch1 to Ch105 (99.4%) SA-3 (0.3%) RM1 (0.3%) SM316 to SM420 Ch1 to Ch105 (99.4%) SA-4 (0.3%) RM1 (0.3%) SM421 to SM525 Ch1 to Ch105 (99.4%) SA-5 (0.3%) RM1 (0.3%) SM526 to SM630 Ch1 to Ch105 (99.4%) SA-6 (0.3%) RM1 (0.3%) SM631 to SM735 Ch1 to Ch105 (99.4%) SA-7 (0.3%) RM1 (0.3%) SM736 to SM840 Ch1 to Ch105 (99.4%) SA-8 (0.3%) RM1 (0.3%) SM841 to SM945 Ch1 to Ch105 (99.4%) SA-9 (0.3%) RM1 (0.3%) SM946 to SM1050 Ch1 to Ch105 (99.4%) SA-10 (0.3%) RM1 (0.3%) SM1051 to SM1155 Ch1 to Ch105 (99.4%) SA-11 (0.3%) RM1 (0.3%) SM1156 to SM1260 Ch1 to Ch105 (99.4%) SA-12 (0.3%) RM1 (0.3%) SM1261 to SM1365 Ch1 to Ch105 (99.4%) SA-13 (0.3%) RM1 (0.3%)

[0998] The resulting mixture is homogenized and filled into a "non-aligned" test cell (cell thickness d ~ 4.0 μm, ITO coating on both sides (structured ITO in the case of multi-domain switching), no alignment layer and no passivation layer).

[0999] The LC-mixture shows a spontaneous homeotropic (vertical) alignment with respect to the substrate surface. The alignment is stable for elevated temperatures (up to the clearing points of the respective host mixtures Ch1 to Ch105). The resulting VA cell can be switched reversibly. Orthogonal polarizers are applied to visualize the switching operation.

[1000] By using alignment additives (such as compounds of formula SA-1 to SA-13), for any type of display technology, a vertical alignment does not require an alignment layer (e.g., no PI coating). Additionally, the transmittance values of the test cells produced using mixtures SA1 to SA1165 are comparable to those given in Table 6 above (where test cells with polyimide were used).

Claims

1. A liquid crystal (LC) medium, characterized in that, The liquid crystal medium comprises a liquid crystal host consisting of an LC component H) and an optically active component D), and the LC component H) comprises one or more mesogenic or liquid crystal compounds. Among them, the component H comprises one or more compounds selected from the compounds of formula CY and / or PY. Among them, each group has the following meanings: a represents 1 or 2. b represents 0 or 1. indicate R 1 and R 2 each independently of one another represents an alkyl group having 1 to 12 C atoms, where one or more H atoms may be replaced by fluorine, and where one or two non-adjacent CH2 groups may be replaced by -O-,-CH=CH-,-CO-,-O-CO- or -CO-O-, Z x represents -CH=CH-, -CH2O-, -OCH2-, -CF2O-, -OCF2-, -O-, -CH2-, -CH2CH2- or a single bond, L 1-4 each independently represents F, Cl, OCF3, CF3, CH3, CH2F, CHF2, L 5 represents H or has one of the meanings given for L 1-4 given; And the medium comprises one or more compounds of formula ZK1. wherein alkyl and alkyl * each independently of one another represents a straight-chain alkyl group having 1 to 6 C atoms.

2. The LC medium according to claim 1, wherein the compound of formula ZK1 is selected from the compounds of formula ZK1a to formula ZK1d: wherein the propyl, butyl and pentyl groups are straight-chain groups.

3. The LC medium according to claim 1, wherein the liquid crystal host has a helical pitch in the range of 5 to 50 μm.

4. The LC medium according to claim 1, wherein the optically active component (D) comprises one or more compounds selected from the compounds of the following formulae, wherein, R a11 , R a12 and R b12 , each independently represents an alkyl group having 1 to 15 C atoms, wherein in addition, one or more non-adjacent CH2 groups may each independently of one another be replaced by -C(R z )=C(R z )-, -C≡C-, -O-, -S-, -CO-, -CO-O-, -O-CO- or -O-CO-O- in such a way that O and / or S atoms are not directly linked to one another, wherein in addition, one or more H atoms may be replaced by F, Cl, Br, I or CN, The condition is R a12 is different from R b12 , R a21 and R a22 , independently of one another, represent an alkyl group having 1 to 15 C atoms, where, furthermore, one or more non-adjacent CH2 groups can each independently of one another be replaced by -C(R z )=C(R z )-, -C≡C-, -O-, -S-, -CO-, -CO-O-, -O-CO- or -O-CO-O- in such a way that O and / or S atoms are not directly linked to one another, and where, furthermore, one or more H atoms can be replaced by F, Cl, Br, I or CN, R a31 , R a32 and R b32 , each independently represents a straight-chain or branched alkyl group having 1 to 15 C atoms, wherein in addition, one or more non-adjacent CH2 groups may each independently be replaced by -C(R z )=C(R z )-, -C≡C-, -O-, -S-, -CO-, -CO-O-, -O-CO- or -O-CO-O- in such a way that O and / or S atoms are not directly connected to each other, and wherein in addition, one or more H atoms may be replaced by F, Cl, Br, I or CN, The condition is R a32 is different from R b32 , R z represents H, CH3, F, Cl or CN, R 8 having one of the meanings given above for R a11 as given above Z 8 represents -C(O)O-, -CH2O-, -CF2O- or a single bond A 11 as defined below in A 12 or alternatively represents, A 12 indicate Preferably wherein L 11 , each independently has, upon each occurrence, one of the meanings of L given for formula R in claim 12 A 21 indicate A 22 having one of the meanings given for A 12 given one of the meanings for A 31 having one of the meanings given for A 11 as given Optionally represents A 32 having one of the meanings given for A 12 given one of the meanings for n2 is the same or different each time it appears and is 0, 1 or 2, and n3 is 1, 2 or 3.

5. The LC medium according to any one of claims 1 to 4, wherein the liquid crystal host or LC component H) comprises one or more compounds selected from the compounds of the following formula, wherein R 11 and R 12 each independently of one another represent an alkyl group having 1 to 12 C atoms, where one or two non-adjacent CH2 groups may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that the O atoms are not directly linked to one another, L represents F, b represents 0 or 1, and r represents 1, 2 or 3.

6. The LC medium according to any one of claims 1 to 4, wherein the liquid crystal host or LC component H) additionally comprises one or more compounds selected from the following formula, wherein, alkyl and alkyl * each independently of one another represents a straight-chain alkyl group having 1 to 6 C atoms, and alkenyl and alkenyl * each independently of one another represents a straight-chain alkenyl group having 2 to 6 C atoms.

7. The LC medium according to any one of claims 1 to 4, wherein the liquid crystal host or LC component H) additionally comprises one or more compounds of the following formula, wherein R 5 and R 6 each independently of one another represent an alkyl group having 1 to 12 C atoms, furthermore wherein, One or two non-adjacent CH2 groups can be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that the O atoms are not directly connected to each other. Each represents independently of one another. where L 5 represents F or Cl, and L 6 represents F, Cl, OCF3, CF3, CH3, CH2F or CHF2.

8. An LC medium according to any one of claims 1 to 4, wherein the LC medium additionally comprises one or more self-aligning additives of formula SA, MES-R A SA wherein MES represents a mesogenic group comprising one or more rings and optionally one or more polymerizable groups, and R A is a polar anchoring group.

9. An LC medium according to claim 8, wherein one or more self-aligning additives of formula SA are selected from compounds of formula SAa R 1 -[A 2 -Z 2 m -A 1 -R a SAa wherein A 1 ,A 2 each independently of one another represents an aromatic, heteroaromatic, cycloaliphatic or heterocyclic group, which may also contain fused rings, and which may also be mono- or polysubstituted by either group L and -Sp-P, L in each case independently of one another represents H, F, Cl, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, -C(=O)N(R 0 )2, -C(=O)R 0 , an optionally substituted silyl group, an optionally substituted aryl or cycloalkyl group having 3 - 20 C atoms, or a straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy group having 1 - 25 C atoms, where additionally, one or more H atoms may be replaced by F or Cl, P represents a polymerizable group, Sp represents a spacer group or a single bond, Z 2 in each case independently of one another represents a single bond, -O-, -S-, -CO-, -CO-O-, -OCO-, -O-CO-O-, -OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -(CH2) n1 -, -CF2CH2-, -CH2CF2-, -(CF2) n1 -, -CH=CH-, -CF=CF-, -C≡C-, -CH=CH-COO-, -OCO-CH=CH-, -(CR​0 R 00 ) n1 -, -CH(-Sp-P)-, -CH2CH(-Sp-P)-, -CH(-Sp-P)CH(-Sp-P)-, n1 represents 1, 2, 3 or 4, m represents 1, 2, 3, 4, 5 or 6, preferably 2, 3 or 4, R 0 In each case, independently of one another, represents an alkyl group having 1 to 12 C atoms, R 00 In each case, independently of one another, represents H or an alkyl group having 1 to 12 C atoms, R 1 Independently of one another represent H, halogen, a straight-chain, branched or cyclic alkyl group having 1 to 25 C atoms, where furthermore one or more non-adjacent CH2 groups can be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and / or S atoms do not directly connect to each other, where furthermore one or more H atoms can be replaced by F or Cl, or a -Sp-P group, and R a Represents a polar anchoring group having at least one selected from -OH, -NH2, NHR 11 , -SH, C(O)OH and -CHO groups, where R 11 Represents an alkyl group having 1 to 12 C atoms.

10. The LC medium according to claim 9, wherein the polar anchoring group R of the self-aligning additive a or R A Is defined as follows: R a Is an anchoring group of the following formula Where p represents 1 or 2, q represents 2 or 3, Represents a substituted or unsubstituted ring system or fused ring system, preferably a ring system selected from benzene, pyridine, cyclohexane, di Alkane or tetrahydropyran ring systems, Y, each time it appears, represents the same or differently -O-, -S-, -C(O)-, -C(O)O, -OC(O)-, -NR 11 -, or a single bond, o represents 0 or 1, X 1 Each time it appears, represents the same or differently H, alkyl, fluoroalkyl, OH, NH2, NHR 11, NR 11 2, -SH, OR 11 , C(O)OH, -CHO, where at least one group X 1 represents a group selected from -OH, -NH2, NHR 11 , -SH, C(O)OH and -CHO, R 11 represents an alkyl group having 1 to 12 C atoms, Sp a , Sp c , Sp d each independently of one another represents a spacer group or a single bond, and Sp b represents a trivalent or tetravalent group, preferably CH, N or C.

11. The LC medium according to any one of claims 1 to 4 or 8, wherein the LC medium additionally comprises a polymerizable component (P) which contains one or more polymerizable compounds.

12. The LC medium according to claim 11, wherein one or more polymerizable compounds are selected from compounds of formula R, P-Sp-A 1 -(Z 1 -A 2 ) z -R R where each group independently of one another and each occurrence may be the same or different and has the following meanings: P is a polymerizable group, Sp is a spacer group or a single bond, A 1 , A 2 is an aromatic, heteroaromatic, cycloaliphatic or heterocyclic group preferably having 4 to 25 ring atoms, which may also contain fused rings, and which may also be unsubstituted or mono- or polysubstituted by L, Z 1 represents -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -(CH2) n1 -,-CF2CH2-,-CH2CF2-,-(CF2) n1 -,-CH=CH-,-CF=CF-,-CH=CF-,-CF=CH-,-C≡C-,-CH=CH-CO-O-,-O-CO-CH=CH-,-CH2-CH2-CO-O-,-O-CO-CH2-CH2-,-CR 0 R 00 - or a single bond, R 0 ,R 00 represents an alkyl group having 1 to 12 C atoms for H, R represents H, L, or P-Sp-, L represents F, Cl, -CN, P-Sp- or a linear, branched or cyclic alkyl group having 1 to 25 C atoms, wherein one or more non-adjacent CH2 groups are optionally replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O- and / or S-atoms do not directly connect to each other, and wherein one or more H atoms are each optionally replaced by P-Sp-, F or Cl, z represents 0, 1, 2 or 3, n1 represents 1, 2, 3 or 4.

13. The LC medium according to claim 12, wherein one or more polymerizable compounds are selected from the compounds of formulas M1 to M31, wherein P 1 ,P 2 and P 3 each independently of one another represent an acrylate group or a methacrylate group, Sp 1 ,Sp 2 and Sp 3 each independently of one another represent a single bond or a spacer group, said spacer group having one of the meanings as defined for Sp in the context, and particularly preferably represents -(CH2) p1 -,-(CH2) p1 -O-,-(CH2) p1 -CO-O-,-(CH2) p1 -O-CO- or -(CH2) p1 -O-CO-O-, where p1 is an integer from 1 to 12, wherein in addition P 1 -Sp 1 -,P 1 -Sp 2 - and P 3 -Sp 3 - of one or more may represent R aa , provided that the group P 1 -Sp 1 -,P 2 -Sp2 and P 3 -Sp 3 - at least one different from R aa , R aa represents H, F, Cl, CN or a straight-chain or branched alkyl group having 1 to 25 C atoms, wherein furthermore, one or more non-adjacent CH2 groups can each independently of one another be replaced by C(R 0 )=C(R 00 )-,-C≡C-,-N(R 0 )-,-O-,-S-,-CO-,-CO-O-,-O-CO-,-O-CO-O- in such a way that O and / or S atoms are not directly connected to one another, wherein furthermore, one or more H atoms can be replaced by F, Cl, CN or P 1 -Sp 1 - instead, particularly preferably a straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy group having 1 to 12 C atoms (wherein the alkenyl and alkynyl groups have at least two C atoms and the branched groups have at least three C atoms), R 0 ,R 00 each independently of one another and identically or differently each time they occur represent H or an alkyl group having 1 to 12 C atoms, R y and R z each independently of one another represent H, F, CH3 or CF3, X 1 ,X 2 and X 3 each independently of one another represent -CO-O-,-O-CO- or a single bond, Z 1 represents -O-,-CO-,-C(R y R z )- or -CF2CF2-, Z 2 and Z 3 each independently of one another represent -CO-O-,-O-CO-,-CH2O-,-OCH2-,-CF2O-,-OCF2- or -(CH2) n -, where n is 2, 3 or 4, L each time it occurs identically or differently represents F, Cl, CN or a straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy group having 1 to 12 C atoms, preferably F, L' and L" each independently of the other represent H, F or Cl, r represents 0, 1, 2, 3 or 4, s represents 0, 1, 2 or 3, t represents 0, 1 or 2, x represents 0 or 1.

14. The LC medium according to any one of claims 11 to 13, wherein the polymerizable compound is polymerized.

15. A method of preparing an LC medium according to one or more of claims 1 to 13, comprising the steps of: One or more mesogenic or liquid crystal compounds or the liquid crystal component H) as defined in claims 1 to 7 are mixed with one or more chiral dopants or optically active components D), optionally with one or more polymerizable compounds as defined in claims 11 to 13, optionally with one or more self-aligning additives as defined in claims 8 to 10, and optionally with other liquid crystal compounds and / or additives.

16. An LC display comprising an LC medium as defined in one or more of claims 1 to 14.

17. The LC display according to claim 16, wherein the display is a VA display.

18. An LC display comprising an LC medium as defined in one or more of claims 8 to 10, wherein the display is a SA-VA display.

19. An LC display comprising an LC medium as defined in any one of claims 11 to 14, wherein the display is a PS-VA display or a polymer-stabilized SA-VA display.

20. The LC display according to one or more of claims 16 to 19, wherein the display comprises two substrates, at least one of which is optically transparent, electrodes disposed on each substrate or two electrodes disposed on only one of the substrates, and a layer of an LC medium located between the substrates, the LC medium comprising one or more polymerizable compounds as defined in any one of claims 11 to 13, wherein the polymerizable compound is polymerized between the substrates of the display.

21. The LC display according to one or more of claims 16 to 20, wherein the thickness of the cell gap is from 2 μm to 10 μm.

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