Liquid crystal medium

Abstract

The invention relates to a liquid crystal (LC) material as defined in claim 1, which has a negative dielectric anisotropy, and to the use thereof for optical, electro-optical and electronic purposes, for example for LC displays, in particular energy-saving displays based on the ECB, IPS or FFS effect.

Description

Field of the Invention

[0001] The present invention relates to liquid crystal (LC) media having negative dielectric anisotropy and their use for optical, electro-optical and electronic purposes, in particular for use in LC displays. Background of the Invention

[0002] One type of liquid crystal display (LCD) currently in use is the TN ("twisted nematic") mode. However, a disadvantage of TN LCDs is that the contrast is strongly dependent on the viewing angle.

[0003] Furthermore, 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 typically has negative dielectric anisotropy. In the power-off state, the molecules of the LC layer are aligned perpendicular (homeotropically) to the electrode surfaces or have an inclined homeotropic alignment. When a voltage is applied to the two electrodes, reorientation of the LC molecules parallel to the electrode surfaces occurs.

[0004] 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 reorientation of the LC molecules in the layer plane.

[0005] 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 near 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 typically contain an LC medium with positive dielectric anisotropy and an alignment layer, typically an alignment layer of polyimide, which provides planar alignment of the molecules of the LC medium.

[0006] FFS 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 ("TFTs")), while in the case of a passive matrix display, individual pixels are typically addressed by multiplexing methods, as is known in the prior art.

[0007] In addition, FFS displays have been disclosed (see 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 those of FFS displays, 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 exhibits a more favorable director orientation, which has less tilt and more twist, and as a result, these displays have a higher transmittance. The displays also include an alignment layer, preferably polyimide 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.

[0008] 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. Disclinations, also referred to as tilt domains, may exist between these domains. A VA display having tilt domains has a greater contrast and a viewing angle independence of grey shade compared to a conventional VA display. Additionally, this type of display is easier to manufacture because no additional electrode surface treatment (such as by rubbing) is required to homogeneously align the molecules in the on state. Alternatively, the preferred direction of the tilt angle or pre-tilt angle is controlled by a special design of the electrodes.

[0009] In so-called MVA (“multi-domain vertical alignment”) displays, this is typically achieved by electrodes having protrusions that cause local pre-tilting. Thereby, upon application of a voltage, the LC molecules are aligned parallel to the electrode surfaces in different, defined cell regions in different directions. Thereby, “controlled” switching is achieved and the formation of disturbing disclination lines is prevented. While this arrangement improves the viewing angle of the display, it results in a reduction in its light transmittance. A further development of MVA uses protrusions only on one electrode side, while the opposing electrode has slits, which improves the light transmittance. The slit electrode generates a non-uniform electric field in the LC cell upon application of a voltage, meaning that controlled switching is still achieved. To further improve the light transmittance, the spacing between the slits and the protrusions 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 of the display as well as an improvement in the contrast and brightness (transmittance) of the display are required.

[0010] 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 a temperature at which the LC medium exhibits a liquid crystal phase, typically at room temperature. It has proven particularly suitable to add polymerizable mesogenic or liquid crystal compounds (also called reactive mesogens or “RMs”) to the LC mixture.

[0011] 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 very good contrast and very good transmittance.

[0012] For example, PS-VA displays are described in EP 1 170 626 A2, US 6,861,107, US 7,169,449, US 2004 / 0191428 A1, US 2006 / 0066793 A1, and US 2006 / 0103804 A1.

[0013] Especially for monitors, particularly for television applications, there is still a need to optimize the response time, as well as the contrast and brightness (and thus also the transmittance) of LC displays. The PSA method can offer significant advantages here. Especially in the case of PS-VA, PS-IPS, and PS-FFS displays, a shortened response time associated with the measurable pretilt in the test cell can be achieved without significantly adversely affecting other parameters.

[0014] Another problem observed in the prior art is that the use of conventional LC media in LC displays, including but not limited to PS(A)-type displays, often results in mura 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-mura". Thus, there is a desire to provide an LC medium that results in a reduction in ODF non-uniformity.

[0015] Another problem observed in the prior art is that LC media for PSA displays (including but not limited to PSA-type displays) often exhibit high viscosities and thus have high switching times. To reduce the viscosity and switching time of the LC media, 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 a decrease in reliability and stability, and in particular a decrease in VHR after exposure to UV radiation. This is a rather significant drawback especially when used in PSA displays, since the photopolymerization of the RM in PSA displays is typically carried out by exposure to UV radiation, which can lead to a decrease in VHR in the LC media.

[0016] Furthermore, there is a great need for PSA displays, as well as LC media and polymerizable compounds for such PSA displays, which are capable of achieving high resistivity while enabling a large operating temperature range, short response times even at low temperatures, low threshold voltages, low pretilt angles, multiple gray shades, high contrast, and wide viewing angles, with high reliability and high VHR values after UV exposure, and in the case of the polymerizable compounds, having a low melting point and high solubility in the LC host mixture. In PSA displays for mobile applications, there is a particular need for available LC media having a low threshold voltage and high birefringence.

[0017] One display trend is to achieve the fastest possible response times to obtain the best moving image quality. In this regard, media having negative dielectric anisotropy have an inherent disadvantage compared to LC media having positive dielectric anisotropy. On the other hand, mixtures having negative dielectric anisotropy are able to achieve higher transmittance in a standard FFS cell layout, and thus their use has a positive impact on power consumption and the environment. There is a need in the art to achieve both fast response times and higher transmittance. Especially when used in mobile devices, there is a great demand for displays having high transmittance, which enables the use of a lower intensity backlight, resulting in longer battery life and thus a more sustainable product. Alternatively, displays having higher brightness can be achieved, which in particular have improved contrast in ambient light. In addition, the popularity of 8K and gaming monitors has led to an increased demand for LC display panels having a higher refresh rate, and thus an increased demand for LC media having faster response times.

[0018] Another important display trend is to achieve high contrast. Contrast is described by the ratio between the bright and dark states of a display. In LCDs, especially in IPS / FFS technology, the dark state is strongly influenced by the scattering parameters and thus has a significant impact on the contrast. To improve the contrast and reduce the scattering parameters, an LC mixture with a high elastic constant is required. Here, current LC compounds and LC mixtures are limited in achieving extremely high elastic constants. Therefore, new materials need to be found to further enhance the contrast of future displays.

[0019] Therefore, there is still a great demand for VA, FFS or PSA displays and LC media optionally containing polymerizable compounds for VA, FFS or PSA displays, which do not show the above-mentioned disadvantages or show these disadvantages only to a small extent and have improved performance.

[0020] The object of the present invention is to provide novel suitable LC media which do not have the above-mentioned disadvantages or have the above-mentioned disadvantages to a reduced extent.

[0021] Surprisingly, it has now been found that by using a liquid crystal medium containing a compound of formula I, a liquid crystal medium with a suitably high negative Δε, a suitable phase range and Δn, and a high LTS can be achieved, which does not exhibit the disadvantages of the prior art materials or exhibits the above-mentioned disadvantages at least to a significantly small extent. Summary of the Invention

[0022] The present invention relates to a liquid crystal medium comprising a compound of formula I

[0023]

[0024] wherein

[0025] R 11 and R 12 independently of one another represent H, a straight-chain alkyl or alkoxy group having 1 - 15 C atoms, a straight-chain alkenyl or alkenoxy group having 2 - 15 C atoms or a branched alkyl, alkoxy, alkenyl, alkenoxy group each having 3 - 15 C atoms, where one or more CH₂ groups of these groups can each independently of one another be -CH=CH-, -C≡C-, -CF₂O-, -OCF₂-, -O-, -CO-O- or -O-CO- in such a way that the O atoms are not directly connected to one another, and where one or more H atoms can be replaced by halogen,

[0026] L 11 and L 12 one of which represents H, and

[0027] L 11 and L12 Another one in 12 represents H, F, Cl, CF3 or CHF2, preferably H or F, very preferably H;

[0028] Wherein the medium preferably comprises one or more compounds selected from the compounds of formulae IIA, IIB, IIC and IID

[0029]

[0030] Wherein

[0031] R 2A 、R 2B 、R 2C and R 2D are the same or different and represent H, a straight-chain alkyl or alkoxy group having 1-15 C atoms, a straight-chain alkenyl or alkenoxy group having 2-15 C atoms or a branched-chain alkyl, alkoxy, alkenyl, alkenoxy group each having 3-15 C atoms, wherein one or more CH2 groups in these groups may each independently of one another be -CH=CH-, -C≡C-, -CF2O-, -OCF2-, -O-, -CO-O- or -O-CO- in such a way that the O atoms are not directly connected to each other, and wherein one or more H atoms may be replaced by halogen,

[0032] L 1 and L 2 each independently of one another represent F, Cl, CF3 or CHF2,

[0033] Y represents H, F, Cl, CF3, CHF2 or CH3, preferably H or CH3, more preferably H,

[0034] Z 2 、Z 2B and Z 2D each independently of one another represent a single bond, -CH2CH2-, -CH=CH-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -COO-, -OCO-, -C2F4-, -CF=CF- or -CH=CHCH2O-,

[0035] (O) represents O or a single bond,

[0036] p represents 0, 1 or 2,

[0037] q represents 0 or 1, and

[0038] v represents an integer from 1 to 6.

[0039] The invention also relates to an LC display, which comprises an LC medium according to the invention, in particular a VA, IPS, FFS or UB-FFS or PSA display, particularly preferably an FFS, UB-FFS, VA or PS-VA display.

[0040] 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 containing an LC medium, for generating a tilt angle in the LC medium by in-situ polymerization of a polymerizable reactive mesogen (RM) in the PSA display, preferably in an electric or magnetic field.

[0041] The invention also relates to a method for preparing an LC medium as described above in the context, which comprises the steps of mixing one or more compounds of formula I with one or more compounds of formulae IIA, IIB, IIC and / or IID, and optionally with one or more chiral dopants, and optionally with one or more polymerizable compounds, and optionally with other LC compounds and / or additives.

[0042] 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.

[0043] The invention also relates to a method for manufacturing an LC display as described above in the context, which comprises the steps of filling or otherwise providing an LC medium optionally containing one or more polymerizable compounds as described above in the context between the substrates of the display and optionally polymerizing the polymerizable compounds.

[0044] The LC medium according to the invention exhibits the following advantageous properties, particularly when used in an FFS display:

[0045] - Excellent low-temperature stability (LTS)

[0046] - Improved contrast of the display,

[0047] - High transmittance of the display,

[0048] - High clear-bright temperature,

[0049] - High voltage holding ratio,

[0050] - Low rotational viscosity

[0051] - Fast switching,

[0052] - Fast response time, which enables a low-power LCD to extend the battery life of mobile devices,

[0053] - Sufficient stability to heat and / or UV, especially when used outdoors,

[0054] - High elastic constant.

[0055] According to another aspect of the present invention, there is provided a compound of formula I as described above, wherein the group L 11 and L 12 one of which represents H, and the group L 11 and L 12 the other represents F, Cl, CF3 or CHF2.

[0056] According to another aspect of the present invention, there is provided a compound of formula (3) defined in Scheme 1 below.

[0057] The compound of formula I is prepared by methods known per se as described in the literature (for example in standard works such as Houben - Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], Georg - Thieme - Verlag, Stuttgart), precisely under reaction conditions known and suitable for said reactions. Variants known per se but not mentioned in more detail herein can be used here.

[0058] If desired, the starting materials can also be formed in situ without separating them from the reaction mixture, but by immediately further reacting them to form the compound of formula I.

[0059] The compound of formula I can be synthesized analogously to the synthesis of structurally related chlorofluorinated derivatives shown in EP 1 897 928 A1.

[0060] The preferred synthetic route for preparing the compound of formula I is shown in Scheme 1.

[0061] Scheme 1:

[0062]

[0063] wherein X represents Br or I, and the other groups occurring have the meanings given above.

[0064] The compound of formula I is preferably selected from the compounds of formula I - 1 to I - 3

[0065]

[0066] wherein R 11 and R 12 have the meanings defined above for formula I, preferably represent a straight - chain alkyl group having 1 - 7 C atoms, or a straight - chain alkenyl group having 2 - 15 C atoms, wherein one or more CH2 groups in these groups can each independently of one another be Substitution.

[0067] More preferably, the medium according to the invention comprises one or more compounds of formula I-1, very preferably selected from the compounds of formulae I-1-1 to I-1-32

[0068]

[0069]

[0070]

[0071]

[0072] wherein R 11 and R 12 represent a straight-chain alkyl having 1-7 C atoms or a straight-chain alkenyl having 2-7 C atoms.

[0073] The compounds of formula I-2 are preferably selected from the compounds of formulae I-2-1 to I-2-32:

[0074]

[0075]

[0076]

[0077]

[0078]

[0079] The compounds of formula I-3 are preferably selected from the compounds of formulae I-3-1 to I-3-32:

[0080]

[0081]

[0082]

[0083]

[0084]

[0085]

[0086] Preferred compounds of formulae IIA, IIB, IIC and IID are shown below:

[0087]

[0088]

[0089]

[0090]

[0091]

[0092]

[0093]

[0094]

[0095]

[0096]

[0097]

[0098]

[0099]

[0100] wherein the parameter a represents 1 or 2, alkyl and alkyl * each independently of one another represents a straight-chain alkyl group having 1 to 6 C atoms, alkenyl and alkenyl * each independently of one another represents a straight-chain alkenyl group having 2 to 6 C atoms, and (O) represents an oxygen atom or a single bond. 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-.

[0101] Highly preferred compounds of formula IID are selected from the following sub-formulas:

[0102]

[0103]

[0104]

[0105]

[0106]

[0107] In a preferred embodiment, the medium comprises one or more compounds of formula IID-10a

[0108]

[0109] wherein the groups and parameters occurring therein have the meanings given under formula IID above, and

[0110] R 2 represents where r is 0, 1, 2, 3, 4, 5 or 6 and s is 1, 2 or 3.

[0111] Preferred compounds of formula IID-10a are compounds IID-10a-1 to IID-10a-14.

[0112]

[0113]

[0114]

[0115] Particularly preferred mixtures according to the invention comprise one or more compounds of formulae IIA-2, IIA-8, IIA-10, IIA-16, IIA-18, IIA-40, IIA-41, IIA-42, IIA-43, IIB-2, IIB-10, IIB-16, IIC-1, IID-4 and IID-10.

[0116] A preferred medium according to the invention comprises at least one compound of formula IIC-1

[0117]

[0118] where alkyl and alkyl * have the meanings given above.

[0119] In particular, the medium comprises one or more compounds of formula IIA-2 selected from the following sub-formulae:

[0120]

[0121]

[0122] Alternatively, preferably in addition to compounds of formulae IIA-2-1 to IIA-2-5, the medium further comprises one or more compounds of formulae IIA-2a-1 to IIA-2a-5:

[0123]

[0124] In particular, the medium comprises one or more IIA-10 compounds selected from the following sub-formulae:

[0125]

[0126] Alternatively, preferably in addition to the compounds of formulae IIA-10-1 to IIA-10-5, the medium further comprises one or more compounds of formulae IIA-10a-1 to IIA-10a-5:

[0127]

[0128]

[0129] In particular, the medium comprises one or more IIB-10 compounds selected from the following sub-formulae:

[0130]

[0131] Alternatively, preferably in addition to the compounds of formulae IIB-10-1 to IIB-10-5, the medium further comprises one or more compounds of formulae IIB-10a-1 to IIB-10a-5:

[0132]

[0133] Alternatively, preferably in addition to the compound of formula IIC-1, the medium further comprises one or more compounds of formulae IIC-1a-1 and IIC-1a-2

[0134]

[0135] wherein alkyl represents a straight-chain alkyl group having 1-7 C atoms, preferably 2-5 C atoms, and very preferably represents ethyl.

[0136] The medium according to the invention preferably comprises one or more compounds of formula III

[0137]

[0138] wherein

[0139] R 31 and R 32 each independently of one another represent H, an alkyl or alkoxy group having 1-15 C atoms, where one or more CH2 groups in these groups may each independently of one another be replaced by -CH=CH-, -C≡C-, -CF2O-, -OCF2-, -O-, -CO-O- or -O-CO- such that the O atoms are not directly connected to one another, and where one or more H atoms may be replaced by halogen,

[0140] A 31 each independently represents, each time it appears,

[0141] a) 1,4 - cyclohexenylene or 1,4 - cyclohexylene, in which one or two non - adjacent CH₂ groups may be replaced by -O- or -S-;

[0142] b) 1,4 - phenylene, in which one or two CH groups may be replaced by N, or

[0143] c) a group selected from spiro[3.3]heptane - 2,6 - diyl, 1,4 - bicyclo[2.2.2]octylene, naphthalene - 2,6 - diyl, decahydronaphthalene - 2,6 - diyl, 1,2,3,4 - tetrahydronaphthalene - 2,6 - diyl, phenanthrene - 2,7 - diyl and fluorene - 2,7 - diyl;

[0144] wherein the groups a), b) and c) may be mono - or poly - substituted by halogen atoms;

[0145] n represents 0, 1 or 2, preferably 0 or 1;

[0146] Z 31 each independently represents, each time it appears, -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, and

[0147] L 31 and L 32 each independently represents F, Cl, CF₃ or CHF₂, preferably H or F, most preferably F; and

[0148] W represents O or S.

[0149] The compound of formula III is preferably selected from the compounds of formula III - 1 and / or III - 2

[0150]

[0151] wherein the groups appearing have the same meanings as given under formula III above and preferably

[0152] R 31 and R 32 each independently has an alkyl, alkenyl or alkoxy group having at most 15 carbon atoms, more preferably one or two of them represent alkoxy groups; and

[0153] L 31and L 32 each preferably represents F.

[0154] Preferably, the compound of formula III-1 is selected from the compounds of formulae III-1-1 to III-1-10, preferably the compound of formula III-1-6,

[0155]

[0156]

[0157] wherein

[0158] alkyl and alkyl * each independently of one another represents a straight-chain alkyl having 1-6 C atoms, alkenyl and alkenyl * each independently of one another represents a straight-chain alkenyl having 2-6 C atoms, alkoxy and alkoxy * each independently of one another represents a straight-chain alkoxy having 1-6 C atoms, and L 31 and L 32 each independently of one another represents F or Cl, preferably both are F.

[0159] Preferably, the compound of formula III-2 is selected from the compounds of formulae III-2-1 to III-2-10, preferably the compound of formula III-2-6,

[0160]

[0161]

[0162] wherein

[0163] alkyl and alkyl * each independently of one another represents a straight-chain alkyl having 1-6 C atoms, alkenyl and alkenyl * each independently of one another represents a straight-chain alkenyl having 2-6 C atoms, alkoxy and alkoxy * each independently of one another represents a straight-chain alkoxy having 1-6 C atoms, and L 31 and L 32 each independently of one another represents F or Cl, preferably both are F.

[0164] Optionally, the medium comprises one or more compounds of formula IIIA-1 and / or IIIA-2

[0165]

[0166] wherein L 31 and L 32has the same meaning as given under formula III, (O) represents O or a single bond,

[0167] R IIIA represents an alkyl or alkenyl group having at most 7 C atoms, or the group Cy-C m H 2m+1 -,

[0168] m and n are the same or different and are 0, 1, 2, 3, 4, 5 or 6, preferably 1, 2 or 3, very preferably 1,

[0169] Cy represents an alicyclic group having 3, 4 or 5 ring atoms, which is optionally substituted with an alkyl or alkenyl group each having at most 3 C atoms, or with a halogen or CN, and preferably represents cyclopropyl, cyclobutyl, cyclopentyl, cyclopent-1-enyl, cyclopent-2-enyl and cyclopent-3-enyl.

[0170] The compounds of formulae IIIA-1 and / or IIIA-2 can replace the compounds of formula III or be additionally contained in the medium, preferably additionally.

[0171] Very preferred compounds of formulae IIIA-1 and IIIA-2 are as follows:

[0172]

[0173]

[0174] where alkoxy represents a straight-chain alkoxy group having 1-6 C atoms or alternatively represents –(CH2) n F, where n is 2, 3, 4 or 5, preferably C2H4F.

[0175] In a preferred embodiment of the present invention, the medium comprises one or more compounds of formula III-3

[0176]

[0177] wherein

[0178] R 31 ,R 32 are the same or different and represent H, an alkyl or alkoxy group having 1-15 C atoms, where one or more CH2 groups in these groups are optionally independently replaced by -C≡C-, -CF2O-, -OCF2-, -CH=CH-, -O-, -CO-O- or -O-CO- such that the O atoms are not directly connected to each other, and wherein additionally, one or more H atoms can be replaced by a halogen.

[0179] The compound of formula III-3 is preferably selected from formulas III-3-1 to III-3-10:

[0180]

[0181]

[0182] wherein R 32 represents an alkyl group having 1-7 C atoms, preferably ethyl, n-propyl or n-butyl, or alternatively, cyclopropylmethyl, cyclobutylmethyl or cyclopentylmethyl, or alternatively represents –(CH2) n F where n is 2, 3, 4 or 5, preferably C2H4F.

[0183] In a preferred embodiment of the present invention, the medium comprises one or more compounds of formulas III-4 to III-6, preferably formula III-5,

[0184]

[0185] wherein the parameters have the meanings given above, R 31 preferably represents a straight-chain alkyl group and R 32 preferably represents an alkoxy group, each having 1-7 C atoms.

[0186] In a preferred embodiment, the medium comprises one or more compounds of formula III selected from formulas III-7 to III-9, preferably formula III-8,

[0187]

[0188] wherein the parameters have the meanings given above, R 31 preferably represents a straight-chain alkyl group and R 32 preferably represents an alkoxy group, each having 1-7 C atoms.

[0189] In a preferred embodiment, the medium comprises one or more compounds of formula IV,

[0190]

[0191] wherein

[0192] R 41 represents an alkyl group having 1-7 C atoms or an alkenyl group having 2-7 C atoms, preferably n-alkyl, particularly preferably having 2, 3, 4 or 5 C atoms, and

[0193] R 42represents an alkyl group having 1 - 7 carbon atoms or an alkoxy group having 1 - 6 carbon atoms (both preferably having 2 - 5 carbon atoms), an alkenyl group having 2 - 7 carbon atoms, preferably having 2, 3 or 4 carbon atoms, more preferably vinyl or 1 - propenyl and especially vinyl.

[0194] The compounds of formula IV are preferably selected from formulae IV - 1 to IV - 4,

[0195]

[0196] wherein

[0197] alkyl and alkyl’ independently of one another represent an alkyl group having 1 - 7 carbon atoms, preferably having 1 - 5 carbon atoms,

[0198] alkenyl represents an alkenyl group having 2 - 5 carbon atoms, preferably having 2 - 4 carbon atoms, particularly preferably 2 carbon atoms,

[0199] alkenyl’ represents an alkenyl group having 2 - 5 carbon atoms, preferably having 2 - 4 carbon atoms, particularly preferably having 2 - 3 carbon atoms, and

[0200] alkoxy represents an alkoxy group having 1 - 5 carbon atoms, preferably having 2 - 4 carbon atoms.

[0201] The compounds of formula IV - 1 are preferably selected from the compounds of formulae IV - 1 - 1 to IV - 1 - 6

[0202]

[0203]

[0204] The compounds of formula IV - 2 are preferably selected from the compounds of formulae IV - 2 - 1 and IV - 2 - 2

[0205]

[0206] The compounds of formula IV - 3 are preferably selected from the compounds of formulae IV - 3 - 1, IV - 3 - 2 and IV - 3 - 3:

[0207]

[0208]

[0209] wherein alkyl has the meaning defined above, and the compounds of formula I are not included in formula IV - 3 - 2.

[0210] The compounds of formulae IV - 3 - 1, IV - 3 - 2 and IV - 3 - 3 are preferably selected from the following compounds:

[0211]

[0212]

[0213] Very preferably, the medium according to the invention comprises a compound of formula IV-4, in particular a compound selected from formulas IV-4-1 to IV-4-3

[0214]

[0215] The liquid crystal medium preferably additionally comprises one or more compounds of formula IVa,

[0216]

[0217] wherein

[0218] R 41 and R 42 each independently of one another represent a straight-chain alkyl, alkoxy, alkenyl, alkoxyalkyl or alkoxy group having up to 12 C atoms, and

[0219] represents

[0220] Z 4 represents a single bond, -CH2CH2-, -CH=CH-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -COO-, -OCO-, -C2F4-, -C4H8-, -CF=CF-.

[0221] Preferred compounds of formula IVa are shown below:

[0222]

[0223] wherein

[0224] alkyl and alkyl * each independently of one another represent a straight-chain alkyl group having 1-6 C atoms.

[0225] The medium according to the invention preferably comprises at least one compound of formula IVa-1 and / or formula IVa-2.

[0226] The proportion of the compound of formula IVa in the entire mixture is preferably less than 5 wt%, very preferably less than 2 wt%.

[0227] Preferably, the medium comprises one or more compounds of formulas IVb-1 to IVb-4, more preferably compounds of IVb-1 to IVb-3

[0228]

[0229] wherein

[0230] alkyl and alkyl * each independently represents a straight-chain alkyl group having 1 to 6 C atoms, and

[0231] alkenyl and alkenyl * each independently represents a straight-chain alkenyl group having 2 to 6 C atoms.

[0232] Among the compounds of formulae IVb-1 to IVb-3, the compound of formula IVb-2 is particularly preferred.

[0233] Particularly preferred biphenyls are

[0234]

[0235] wherein alkyl * represents an alkyl group having 1 to 6 C atoms and preferably represents n-propyl.

[0236] The medium according to the invention particularly preferably comprises one or more compounds of formula IVb-1-1 and / or IVb-2-3.

[0237] In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula V

[0238]

[0239] wherein

[0240] R 51 , R 52 represent an alkyl group having 1 to 7 C atoms, an alkoxy group having 1 to 7 C atoms or an alkoxyalkyl, alkenyl or alkenoxy group having 2 to 7 C atoms,

[0241] identically or differently represent

[0242] Z 51 , Z 52 each independently represents -CH2-CH2-, -CH2-O-, -CH=CH-, -C≡C-, -COO- or a single bond, and

[0243] n is 1 or 2,

[0244] wherein the CL compound is excluded.

[0245] The compounds of formula V are preferably selected from the compounds of formulae V-1, V-2 and V-3:

[0246]

[0247] The groups appearing therein have the meanings given above for formula V.

[0248] The compound of formula V-1 is preferably selected from the compounds of formulae V-1-1 to V-1-8;

[0249] The compound of formula V-2 is preferably selected from the compounds of formulae V-2-1 to V-2-4; and

[0250] The compound of formula V-3 is preferably selected from the compounds of formulae V-3-1 to V-3-4:

[0251]

[0252]

[0253]

[0254] wherein R 51 and R 52 have the meanings shown in formula V above.

[0255] R 51 and R 52 each preferably independently of one another represent a straight-chain alkyl group having 1-7 C atoms or an alkenyl group having 2-7 C atoms.

[0256] The highly preferred compound of formula V-2-1 is selected from the compounds of formulae V-2-1a to V-2-1g

[0257]

[0258]

[0259] The highly preferred compound of formula V-2-2 is selected from the compounds of formulae V-2-2a to V-2-2i

[0260]

[0261]

[0262] Preferably, the medium according to the invention comprises one or more compounds of formula CL

[0263]

[0264] wherein

[0265] R L represents H, a straight-chain or branched-chain alkyl or alkoxy group having 1-15 C atoms, or a straight-chain or branched-chain alkenyl group having 2-15 C atoms, where one or more CH2 groups in these groups may each independently of one another be -C≡C-, -CF2O-, -OCF2-, -CH=CH-, -O-, -CO-O- or -O-CO- are replaced in such a way that O atoms are not directly connected to each other, and in addition, one or more H atoms may be replaced by halogen,

[0266] X L represents F, Cl, CN, CHF2, CF3, OCF3, or has one of the meanings of R L as defined below,

[0267] Y L represents H, F, Cl or CH3.

[0268] The compounds of formula CL are preferably selected from the compounds of formulae CL-1, CL-2 and CL-3:

[0269]

[0270]

[0271] wherein

[0272] R L1 and R L2 , which are the same or different and have the meanings given above for formula I, preferably represent an alkyl or alkenyl group having 1-7 C atoms or 2-7 C atoms, respectively, wherein a CH2 group may be replaced by cyclopropane-1,2-diyl, and R L2 may alternatively represent an alkoxy group having 1-5 C atoms.

[0273] Very preferably, the compounds of formula CL are selected from the compounds of formulae CL-3-1 to CL-3-12:

[0274]

[0275]

[0276] In a particularly preferred embodiment, the medium according to the invention comprises the compound CL-3-1 or CLP-3-3.

[0277] In a preferred embodiment of the invention, the medium further comprises one or more compounds of formula VI,

[0278]

[0279] wherein

[0280] R 61 and R 62represents H, F, a straight-chain alkyl or alkoxy group having 1 to 15 C atoms, a straight-chain alkenyl or alkenyloxy group having 2 to 15 C atoms, or a branched alkyl, alkoxy, alkenyl, alkenyloxy group each having 3 to 15 C atoms, wherein one or more CH2 groups in these groups may each be independently replaced by -C≡C-, -CF2O-, -OCF2-, -CH=CH-, -O-, -CO-O- or -O-CO- are substituted in such a way that the O atoms are not directly connected to each other and one or more H atoms may be replaced by halogen,

[0281] X 61 , X 62 , X 63 , X 64 , X 65 and X 66 Identically or differently represent H or F, preferably X 61 , X 62 , X 63 , X 64 , X 65 and X 66 At least one of them represents F, more preferably X 61 , X 62 , X 63 , X 64 , X 65 and X 66 At least two of them represent F;

[0282] Z 61 and Z 62 Identically or differently represent CH2CH2 or a single bond.

[0283] The compound of formula VI is preferably selected from formula VI-1 and VI-2:

[0284]

[0285] The radicals occurring therein have the meanings given for formula VI.

[0286] The compound of formula VI-1 is preferably selected from the compounds of formulae VI-1-1 to VI-1-21, very preferably formula VI-1-4:

[0287]

[0288]

[0289]

[0290]

[0291] Where R6 represents a straight-chain alkyl or alkoxy group having 1 to 6 carbon atoms, (O) represents -O- or a single bond, m is 0, 1, 2, 3, 4, 5 or 6, and n is 0, 1, 2, 3 or 4.

[0292] R preferably represents methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy, pentyloxy.

[0293] In the compound of formula VI-1-4, (O) preferably represents -O-.

[0294] The compound of formula VI-2 is preferably selected from formula VI-2-1 to VI-2-15, and very preferably formula VI-2-1:

[0295]

[0296]

[0297]

[0298] wherein R 6 represents a straight-chain alkyl or alkoxy group having 1 to 6 carbon atoms, (O) represents -O- or a single bond, m is 0, 1, 2, 3, 4, 5 or 6, and n is 0, 1, 2, 3 or 4.

[0299] R preferably represents methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy, pentyloxy.

[0300] In a preferred embodiment of the present invention, the medium further comprises one or more compounds of formula VII-1 to VII-9

[0301]

[0302]

[0303] wherein

[0304] R 7 represents a straight-chain alkyl or alkoxy group having 1 to 6 carbon atoms, or a straight-chain alkenyl group having 2 to 6 carbon atoms, and

[0305] w is an integer from 1 to 6.

[0306] Preferably, the medium according to the present invention comprises one or more compounds of formula VIII:

[0307]

[0308] wherein

[0309] R 81 and R82 identically or differently represent H, halogen, CN, SCN, a straight-chain alkyl or alkoxy group having 1 to 15 C atoms, a straight-chain alkenyl or alkenyloxy group having 2 to 15 C atoms or a branched-chain alkyl, alkoxy, alkenyl or alkenyloxy group having 3 to 15 C atoms, where one or more CH2 groups in these groups may each independently of one another be -C≡C-, -CF2O-, -OCF2-, -CH=CH-, replaced by -O-, -CO-O- or -O-CO- in such a way that the O atoms are not directly linked to one another, and where one or more H atoms may be replaced by halogen,

[0310] A 0 、A 81 and A 82 each independently of one another represent 1,4-phenylene-diyl, where one or two CH groups may be replaced by N and one or more H atoms may be replaced by halogen, CN, CH3, CHF2, CH2F, CF3, OCH3, OCHF2 or OCF3, cyclohexane-1,4-diyl, where one or two non-adjacent CH2 groups may independently of one another be replaced by O and / or S and one or more H atoms may be replaced by F, cyclohexene-1,4-diyl, bicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl, tetrahydropyran-2,5-diyl or 1,3-dioxane-2,5-diyl;

[0311] Z 81 and Z 82 each independently of one another represent -CF2O-, -OCF2-, -CH2O-, -OCH2-, -CO-O-, -O-CO-, -C2H4-, -C2F4, -CF2CH2-, -CH2CF2-, -CFHCFH-, -CFHCH2-, -CH2CFH-, -CF2CFH-, -CFHCF2-, -CH=CH-, -CF=CH-, -CH=CF-, -CF=CF-, -C≡C- or a single bond;

[0312] n represents 0, 1, 2 or 3, preferably 0, 1 or 2, very preferably 0 or 1, particularly preferably 0; and

[0313] m represents 0, 1, 2 or 3, preferably 0, 1 or 2, very preferably 1 or 2, especially 1.

[0314] A in formula I 81 and A 82Preferably represents a phenylene-1,4-diyl group, which may also be mono- or poly-substituted by F, and may also represent a cyclohexane-1,4-diyl group, a cyclohexene-1,4-diyl group, a tetrahydropyran-2,5-diyl group or a 1,3-dioxane-2,5-diyl group. Very preferably, it represents a phenylene-1,4-diyl group, which may also be mono- or poly-substituted by F, or a cyclohexane-1,4-diyl group.

[0315] Z in Formula VIII 81 and Z 82 Preferably represents -CF2O-, -OCF2- or a single bond. Very preferably, it represents a single bond.

[0316] A in Formula VIII 81 and A 82 Particularly preferably represents

[0317] wherein L represents a halogen, CF3 or CN, preferably F.

[0318] In addition, preferably, the compound of Formula VIII, wherein R 81 and R 82 each independently of one another represent H, F, or an alkyl, alkoxy, alkenyl or alkynyl group having 1 - 8, preferably 1 - 5 C atoms, each of which is optionally substituted by a halogen, especially F.

[0319] R 81 and R 82 Preferably represent H, an optionally fluorinated alkyl or alkoxy group having 1 - 7 C atoms, an optionally fluorinated alkenyl or alkynyl group having 2 - 7 C atoms, an optionally fluorinated cycloalkyl group having 3 - 12 C atoms.

[0320] Preferably, at least one of R 81 and R 82 is not H. Particularly preferably, neither R 81 and R 82 is H. R 81 Very particularly preferably represents an alkyl group. R 82 Also preferably represents H, an alkyl group or fluorine. Very particularly preferably, R 81 is an alkyl group, and R 82 is H or an alkyl group. R 81 and R 82 each independently of one another very particularly preferably represent a non-branched alkyl group having 1 - 5 C atoms. If R 81 and R 82 represent a substituted alkyl, alkoxy, alkenyl or alkynyl group, then the total number of C atoms in the two groups of R 81 and R 82 is preferably less than 10.

[0321] The preferred compounds of formula VIII are selected from the compounds of formula VIIIa

[0322]

[0323] wherein R 1 and R 2 independently of one another, represent a straight-chain alkyl group having 1 to 15 C atoms, a straight-chain alkenyl group having 2 to 15 C atoms, or a branched alkyl or alkenyl group having 3 to 15 C atoms, where one or more CH2 groups in these groups may each independently of one another be replaced by and where one or more H atoms may be replaced by fluorine, preferably R 1 and R 2 both represent a straight-chain alkyl group having 1 to 6 C atoms.

[0324] The very preferred compounds of formula VIIIa are selected from the compounds of formulae VIIIa-1 to VIIIa-35:

[0325]

[0326]

[0327]

[0328]

[0329]

[0330]

[0331] where v is an integer from 1 to 6.

[0332] The further preferred compounds of formula VIII are selected from the following sub-formulae:

[0333]

[0334]

[0335] wherein R 81 、R 82 and L have the abovementioned meanings, L preferably represents F, r, s and t are independently 0, 1, 2, 3 or 4. r is preferably 1 or 2, very preferably 2, s and t are independently preferably 0 or 1, very preferably 0. R 81 and R 82 independently of one another, in particular, represent an n-alkyl group having 1 to 5 C atoms.

[0336] In a first highly preferred embodiment, the compounds of formulae VIII-1 to VIII-6 are selected from the compounds of formulae VIII-1a to VIII-6a, in particular the compound of formula VIII-3a:

[0337]

[0338] wherein R 81 、R 82 、r and s have the meanings defined above.

[0339] In a second highly preferred embodiment, the compounds of formulae VIII-1 to VIII-6 are selected from the compounds of formulae VIII-1b to VIII-6b, in particular the compound of formula VIII-3-b:

[0340]

[0341] wherein R 81 、R 82 、L, r and s have the meanings defined above.

[0342] In a third highly preferred embodiment, the compounds of formulae VIII-1 to VIII-6 are selected from the compounds of formulae VIII-1c to VIII-6c, in particular the compound of formula VIII-3-c:

[0343]

[0344]

[0345] wherein R 81 、R 82 、L, r and s have the meanings defined above.

[0346] In a fourth highly preferred embodiment, the compounds of formulae VIII-1 to VIII-6 are selected from the compounds of formulae VIII-1d to VIII-6d, in particular the compound of formula VIII-3-d:

[0347]

[0348]

[0349] wherein R 81 、R 82 、L, r and s have the meanings defined above.

[0350] In a particularly preferred embodiment, the medium according to the invention comprises one or more compounds selected from the compounds of formulae VIII-1a to VIII-6a and one or more compounds selected from the compounds of formulae VIII-1b to VIII-6b.

[0351] Very particularly preferably, the medium comprises one or more compounds selected from the compounds of formula VIII-3a, VIII-3b, VIII-3c and VIII-3d:

[0352]

[0353] wherein R 81 、R 82 、L and r have the meanings defined above, preferably r is 0.

[0354] The most preferred compounds of formula VIII particularly include one or more of the following:

[0355]

[0356]

[0357] Alternatively or additionally, the following compounds of formula VIII can be used:

[0358]

[0359]

[0360]

[0361]

[0362] In a preferred embodiment, the medium comprises one or more compounds of formula IX

[0363]

[0364] wherein

[0365] R 1 and R 2 independently of one another represent H, halogen, a straight-chain alkyl or alkoxy group having 1 - 15 C atoms, a straight-chain alkenyl or alkenoxy group having 2 - 15 C atoms or a branched-chain alkyl, alkoxy, alkenyl or alkenoxy group each having 3 - 15 C atoms, where one or more CH2 groups in these groups can each independently of one another be -C≡C-, -CF2O-, -OCF2-, -CH=CH-, replaced by -O-, -CO-O- or -O-CO- in such a way that the O atoms are not directly linked to one another, and where one or more H atoms can be replaced by halogen,

[0366] L 11 and L 12 each independently of one another represent F, Cl, CF3 or CHF2,

[0367] L 13 and L 14 each independently represent H, F, Cl, CF3 or CHF2,

[0368] Y 1 represents H, F, Cl, CF3, CHF2 or CH3, preferably H or CH3, and

[0369] n is 0 or 1.

[0370] Preferably, the LC medium contains a compound of formula IX, where n is 0, Y represents H or CH3, more preferably H, and L 11 and L 12 represent F.

[0371] Highly preferred compounds of formula IX are selected from compounds of formulae IX-1 to IX-35

[0372]

[0373]

[0374]

[0375]

[0376]

[0377]

[0378] In a preferred embodiment of the present invention, the medium contains one or more compounds of formula X

[0379]

[0380] wherein

[0381] represents

[0382] represents

[0383] R X represents a straight-chain or branched-chain alkyl or alkoxy group having 1-15 C atoms, where one or more CH2 groups in these groups may each independently be replaced by -C≡C-, -CF2O-, -OCF2-, -CH=CH-, -O-, -CO-O- or -O-CO- in such a way that O atoms are not directly connected to each other, and wherein, furthermore, one or more H atoms may be replaced by halogen, preferably by F,

[0384] X X represents F, Cl, CN, SF5, SCN, NCS, haloalkyl or haloalkoxy each having 1 - 6 C atoms, or haloalkenyl or haloalkenyloxy each having 2 - 6 C atoms.

[0385] Z X represents -C2H4-, -CH2O-, CF2O, -CH=CH- or a single bond.

[0386] In the compound of formula X, R X preferably represents alkyl having 1 - 6 C atoms or alkenyl having 2 - 6 C atoms, which is preferably straight-chain.

[0387] In the compound of formula X, X X is preferably F, Cl or mono- or polyfluoroalkyl or alkoxy having 1, 2 or 3 C atoms, or mono- or polyfluoroalkenyl having 2 or 3 C atoms. X X More preferably, it is F, Cl, CF3, CHF2, OCF3, OCHF2, OCFHCF3, OCFHCHF2, OCFHCHF2, OCF2CH3, OCF2CHF2, OCF2CHF2, OCF2CF2CHF2, OCF2CF2CHF2, OCFHCF2CF3, OCFHCF2CHF2, OCF2CF2CF3, OCF2CF2CClF2, OCClFCF2CF3, OCH=CF2 or CH=CF2, very preferably F or OCF3, in addition CF3, OCF=CF2, OCHF2 or OCH=CF2, very particularly preferably F, OCF3 or CF3, and most preferably F.

[0388] Preferred compounds of formula X are selected from the following sub-formulas:

[0389]

[0390]

[0391] wherein R X has one of the meanings given in formula X, preferably represents straight-chain alkyl having 1 - 6 C atoms, very preferably ethyl, propyl or butyl, or straight-chain alkenyl having 2 - 6 C atoms, very preferably vinyl or 1-propenyl, and most preferably vinyl, and X X has one of the meanings given in formula X, preferably represents F, CF3 or OCF3, and very preferably F.

[0392] Very preferred compounds of formula X are selected from the following sub-formulas:

[0393]

[0394]

[0395]

[0396]

[0397]

[0398] Preferably, the LC medium contains one or more compounds selected from formulas X1-1, X1-3, X2-1 and X2-3.

[0399] The following are further preferred embodiments:

[0400] a) A liquid crystal medium comprising at least one compound of formulas Z-1 to Z-8, preferably compounds of formulas Z-2, Z-4 and Z-6, and very preferably the compound of Z-4

[0401]

[0402]

[0403] wherein R Z has the meaning of the above R 2A and preferably represents an alkyl group having 1-7 C atoms or an alkenyl group having 2-7 C atoms.

[0404] (O) represents O or a single bond, and alkyl represents an alkyl group having 1-7 C atoms.

[0405] b) A preferred liquid crystal medium according to the present invention contains one or more substances containing a tetrahydronaphthyl or naphthyl unit, such as compounds of formulas N-1 to N-5.

[0406]

[0407] wherein R 1N and R 2N each independently of one another have the meaning as described above for R 2A and preferably represent a straight-chain alkyl group, a straight-chain alkoxy group or a straight-chain alkenyl group, and

[0408] Z 1 and Z 2Each independently represents -C2H4-, -CH=CH-, -(CH2)4-, -(CH2)3O-, -O(CH2)3-, -CH=CHCH2CH2-, -CH2CH2CH=CH-, -CH2O-, -OCH2-, -COO-, -OCO-, -C2F4-, -CF=CF-, -CF=CH-, -CH=CF-, -CF2O-, -OCF2-, -CH2- or a single bond.

[0409] c) Preferred mixtures comprise one or more compounds selected from compounds of formula BC dithienyldibenzofulvenes, compounds of formula CR fulvenes, and compounds of formula PH-1 and PH-2 fluorophenanthrenes,

[0410]

[0411] wherein

[0412] R B1 ,R B2 ,R CR1 ,R CR2 ,R P1 ,R P2 each independently has the meaning of R of formula III. c is 0, 1 or 2. R 31 and R 1 and R 2 preferably independently of each other represent an alkyl or alkoxy group having 1-6 C atoms.

[0413] Particularly preferred compounds of formula BC, CR and PH-1 are compounds BC-1 to BC-7, CR-1 to CR-5 and BP-1 to BP-7

[0414]

[0415]

[0416]

[0417] wherein

[0418] alkyl and alkyl * each independently represent a straight-chain alkyl group having 1-6 C atoms, and

[0419] alkenyl and alkenyl * each independently represent a straight-chain alkenyl group having 2-6 C atoms.

[0420] More preferably, the mixture comprises one, two or three compounds of formula BC-2, BC-3, BP-2 and / or BP-3, very preferably BP-2 and / or BP-3, especially BP-3.

[0421] d) The preferred mixture contains one or more indane compounds of the formula In

[0422]

[0423] wherein

[0424] R 11 、R 12 and R 13 each independently of one another represent a straight-chain alkyl, alkoxy, alkoxyalkyl or alkenyl having 1 to 6 C atoms.

[0425] R 12 and R 13 alternatively represent halogen, preferably F,

[0426] represents

[0427]

[0428] i represents 0, 1 or 2.

[0429] The preferred compounds of the formula In are the compounds of the formulae In-1 to In-16 described below:

[0430]

[0431]

[0432] Particularly preferred are the compounds of the formulae In-1, In-2, In-3 and In-4.

[0433] e) The preferred mixture additionally contains one or more compounds of the formulae L-1 to L-5

[0434]

[0435] wherein

[0436] R, R 1 and R 2 each independently of one another have the meanings described above for R 2A in formula IIA, and alkyl represents an alkyl having 1 to 6 C atoms. The parameter s represents 1 or 2.

[0437] The compounds of the formulae L-1 to L-9 are preferably used at a concentration of 5 to 15 wt%, in particular 5 to 12 wt% and very particularly preferably 8 to 10 wt%.

[0438] f) The preferred mixture additionally contains one or more compounds of the formula IA-Y

[0439]

[0440] wherein R 11 and R 12 have one of the meanings given above for R in formula IIA, and L 2A and L 1 and L 2 independently of one another represent F or Cl, either identically or differently.

[0441] Preferred compounds of formula IIA-Y are selected from the following sub-formulae

[0442]

[0443]

[0444] wherein Alkyl and Alkyl * each independently of one another represent a straight-chain alkyl group having 1-6 C atoms, Alkoxy represents a straight-chain alkoxy group having 1-6 C atoms, Alkenyl and Alkenyl * each independently of one another represent a straight-chain alkenyl group having 2-6 C 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-.

[0445] Particularly preferred compounds of formula IIA-Y are selected from the following sub-formulae:

[0446]

[0447] wherein Alkoxy and Alkoxy * have the meanings defined above and preferably represent methoxy, ethoxy, n-propoxy, n-butoxy or n-pentyloxy.

[0448] Preferably, the medium according to the invention comprises a compound selected from formulae ST-1 to ST-18, very preferably the compound of formula ST-3:

[0449]

[0450]

[0451]

[0452]

[0453] wherein

[0454] R ST represents H, an alkyl or alkoxy group having 1 - 15 C atoms, wherein, in addition, one or more CH₂ groups in these groups may each independently of one another be 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, in addition, one or more H atoms may be replaced by halogen,

[0455] represents, each time it occurs, the same or differently

[0456] 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,

[0457] L 1 and L 2 each independently of one another represents F, Cl, CH₃, CF₃ or CHF₂,

[0458] p represents 0, 1 or 2,

[0459] q represents 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0460] In the ST compounds, compounds of the following formula are particularly preferred

[0461]

[0462] wherein n = 1, 2, 3, 4, 5, 6 or 7, preferably n = 1

[0463] or 7

[0464]

[0465] wherein n = 1, 2, 3, 4, 5, 6 or 7, preferably n = 3

[0466]

[0467] wherein n = 1, 2, 3, 4, 5, 6 or 7, preferably n = 3

[0468]

[0469]

[0470] In the compounds of formulae ST-3a and ST-3b, n preferably represents 3. In the compound of formula ST-2a, n preferably represents 7.

[0471] A very particularly preferred mixture according to the invention comprises one or more stabilizers selected from the compounds of formulae ST-2a-1, ST-3a-1, ST-3b-1, ST-8-1, ST-9-1 and ST-12:

[0472]

[0473]

[0474] Preferably, the medium comprises one or more compounds of formula S

[0475]

[0476] wherein

[0477] Ar represents a methylene group or an aromatic hydrocarbon group having 6 to 40 C atoms or a heteroaromatic hydrocarbon group having 4 to 40 C atoms; preferably an aromatic hydrocarbon group having 6 to 40 C atoms;

[0478] Sp represents a spacer group;

[0479] R S represents H, an alkyl group having 1 to 12 C atoms or an alkenyl group having 2 to 12 C atoms;

[0480] Z S represents -O-, -C(O)O-, -(CH2) z - or -(CH2) z O- or a single bond;

[0481] HA represents

[0482] R H represents H, O · , CH3, OH or OR S ;

[0483] R S1 , R S2 , R S3 and R S4 independently of one another represent an alkyl group having 1 to 6 C atoms, preferably having 1 to 3 C atoms, very preferably CH3;

[0484] G represents H or R Sor group Z S -HA;

[0485] z is an integer from 1 to 6; and

[0486] q is 2, 3 or 4, preferably 3 or 4.

[0487] In formula S, Ar represents an aromatic or heteroaromatic hydrocarbon group having 4 to 40 C atoms, which contains one, two, three or four aromatic rings, including fused rings which may be directly linked or linked via an alkylene linking group having 1 to 12 C atoms, wherein one or more H atoms are optionally replaced by an alkyl or alkoxy group having 1 to 6 C atoms or an alkenyl group having 2 to 6 C atoms, or by CN, CF3 or halogen, and wherein one or more CH2 groups may each independently of one another be replaced by -O-, -S-, -NH-, -N(C1-C4-alkyl)-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -CH=CH- or -C≡C- in such a way that O or S atoms are not directly linked to one another.

[0488] Preferred aryl groups are phenyl, naphthyl, anthryl, biphenyl, m-terphenyl, p-terphenyl and (phenylalkyl)phenyl, where the alkyl group is a straight-chain alkyl group having 1 to 12 C atoms.

[0489] In a preferred embodiment, the medium according to the invention comprises a compound of formula S, in which the parameter q is 3 and G represents the group

[0490] Z S -HA.

[0491] In another preferred embodiment, the medium according to the invention comprises a compound of formula S, in which the parameter q is 4 and G represents H or R S .

[0492] The compounds of formula S are preferably selected from the compounds of formulae S-1, S-2 and S-3:

[0493]

[0494]

[0495] wherein R H has the above meaning and preferably represents H or O · ,

[0496] Sp is the same or different each time it appears and represents a spacer group, and

[0497] W represents a straight-chain or branched-chain optionally unsaturated alkylene group having 1 to 12 C atoms, in which one or more non-adjacent -CH2- groups may be replaced by -O-.

[0498] The preferred compound of formula S-1 is selected from the compounds of formula S-1-1:

[0499]

[0500] wherein R H has the meaning given above and preferably represents H or O · , and n is an integer from 0 to 12, preferably 5, 6, 7, 8 or 9, very preferably 7.

[0501] The preferred compound of formula S-2 is selected from the compounds of formula S-2-1:

[0502]

[0503] wherein R H has the meaning given above and preferably represents H or O · , and n2 is the same or different each time it appears, preferably the same, and is an integer from 1 to 12, preferably 2, 3, 4, 5 or 6, very preferably 3, and R S is the same or different each time it appears, preferably the same, and represents an alkyl group having 1 to 6 C atoms, preferably n-butyl.

[0504] The preferred compound of formula S-3 is selected from the compounds of formula S-3-1:

[0505]

[0506] wherein R H has the meaning given above and preferably represents H or O · , and n is an integer from 0 to 12, preferably 5, 6, 7, 8 or 9, very preferably 7.

[0507] The compounds of formula S and ST-1 to ST-18 preferably each are present in the liquid crystal mixture according to the invention in an amount of 0.005 - 0.5% based on the mixture.

[0508] If the mixture according to the invention contains two or more compounds selected from formula S and ST-1 to ST-18, then in the case of two compounds, the concentration is correspondingly increased to 0.01 - 1% based on the mixture.

[0509] However, based on the mixture according to the invention, the total proportion of the compounds of formula S and ST-1 to ST-18 should not exceed 2%.

[0510] The liquid crystal medium according to the invention, also referred to herein as the liquid crystal host mixture, is suitable for polymer-stabilized displays. For this purpose, the medium according to the invention optionally contains one or more polymerizable compounds of formula P

[0511] P-Sp-A 1 -(Z 1 -A 2 ) z -RP

[0512] wherein, independently of one another and each time they occur identically or differently,

[0513] P represents a polymerizable group,

[0514] Sp represents a spacer group or a single bond,

[0515] A 1 、A 2 represents an aromatic, heteroaromatic, cycloaliphatic or heterocyclic group, preferably having 4-25 ring atoms, which may also contain fused rings, and which is unsubstituted, or mono- or polysubstituted by L,

[0516] 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,

[0517] R 0 、R 00 represents H or an alkyl group having 1-12 C atoms,

[0518] R represents H, L or P-Sp-,

[0519] L represents F, Cl, -CN, P-Sp- or a straight-chain, branched or cyclic alkyl group having 1-25 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 are not directly connected to each other, and wherein one or more H atoms are each optionally replaced by P-Sp-, F or Cl,

[0520] z is 0, 1, 2 or 3, and

[0521] n1 is 1, 2, 3 or 4.

[0522] As used herein, the term "reliability" means the quality of the performance of a display over 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 usually used, which is a measure of the amount of voltage maintained constant in a test display. Among other factors, a high VHR is a prerequisite for high reliability of the LC medium.

[0523] Unless otherwise specified, the term "PSA" is generally used hereinafter to refer to a polymer stabilized alignment type display, and the term "PS" is used to refer to a specific display mode, such as PS-VA, PS-TN, etc.

[0524] As used herein, the terms "active layer" and "switchable layer" denote a layer in an electro-optical display, such as in an LC display, containing one or more molecules (e.g., LC molecules) having structural and optical anisotropy, which 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.

[0525] As used herein, the terms "tilt" and "tilt angle" should be understood to denote the tilted alignment of the LC molecules of the LC medium with respect to the cell surface in an LC display (preferably a PSA display herein). The tilt angle herein represents the average angle (<90°) between the longitudinal molecular axis (LC director) of the LC molecules and the planar parallel outer plate surface forming the LC cell. A low value of the tilt angle herein (i.e., a large deviation from the 90° angle) corresponds to a large tilt. A suitable method for measuring the tilt angle is given in the examples. Unless otherwise specified, the tilt angle values disclosed in the context are related to this measurement method.

[0526] As used herein, the terms "reactive mesogen" and "RM" will be understood to refer to a compound containing a mesogenic or liquid crystal backbone, and one or more polymerizable functional groups (also referred to as "polymerizable groups" or "P") attached thereto.

[0527] Unless otherwise specified, as used herein, the term "polymerizable compound" will be understood to refer to a polymerizable monomer compound.

[0528] As used herein, the term "low molecular weight compound" will be understood to refer to a compound that is monomeric and / or not prepared by a polymerization reaction, as opposed to a "polymerized compound" or "polymer".

[0529] 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 typically used for RM polymerization.

[0530] As used herein, the term "mesogenic group" is known to those skilled in the art and has been described in the literature, and it denotes a group that substantially contributes to the formation 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 per se. Mesogenic compounds can 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. Terms and definitions related to mesogenic or LC compounds are given in PureAppl.Chem.2001,73(5),888 and C. Tschierske, G. Pelzl, S. Diele, Angew.Chem.2004,116,6340 - 6368.

[0531] As used herein, the terms "optically active" and "chiral" are synonyms for materials that can induce a helical pitch in a nematic host material, also referred to as "chiral dopants".

[0532] As used herein, the term "spacer group" (also referred to as "Sp" in the context) is known to those skilled in the art in the prior art and has been described in the literature, see, for example, PureAppl.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" denotes a flexible group, for example, an alkylene group, which is connected to a mesogenic group or a polymerizable group in a polymerizable mesogenic compound.

[0533] Similarly, in the compounds of formula I, the spacer group connects the central hydrocarbon group to the photosensitive, stable hindered amine functional group.

[0534] In the context, represents a trans - 1,4 - cyclohexylene ring.

[0535] In the group the single bond between the two ring atoms can be connected to any free position of the benzene ring.

[0536] The "organic group" in the context means a carbon group or a hydrocarbon group.

[0537] "Carbon group" means a monovalent or polyvalent organic group containing at least one C 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 carbonyl, 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.

[0538] "Halogen" means F, Cl, Br or I, preferably F or Cl.

[0539] -CO-, -C(=O)- and -C(O)- represent a carbonyl group, i.e.

[0540] The carbon group or hydrocarbyl group can be a saturated or unsaturated group. Unsaturated groups are, for example, aryl, alkenyl or alkynyl groups. The carbon group 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.

[0541] The terms "alkyl", "aryl", "heteroaryl", etc. also include polyvalent groups, such as alkylene, arylene, heteroarylene, etc.

[0542] 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).

[0543] Preferred carbon groups and hydrocarbyl groups are optionally substituted, straight-chain, branched or cyclic alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy and alkoxycarbonyloxy having 1 to 40, preferably 1 to 20, very preferably 1 to 12 C atoms, optionally substituted aryl or aryloxy having 5 to 30, preferably 6 to 25 C atoms, or optionally substituted alkylaryl, aralkyl, alkylaryloxy, arylalkyloxy, arylcarbonyl, aryloxycarbonyl, arylcarbonyloxy and aryloxycarbonyloxy 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).

[0544] Further preferred carbon groups 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, C4-C 20 polyene, C6-C 20Naphthenyl, 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.

[0545] Particularly preferred are C1-C 12 alkyl, C2-C 12 alkenyl, C2-C 12 alkynyl, C6-C 25 aryl and C2-C 25 heteroaryl.

[0546] 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 can each be independently of one another 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.

[0547] 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 additionally one or more non-adjacent C atoms can be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, and in which one or more H atoms can 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.

[0548] 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.

[0549] Preferred alkenyl groups are, for example, vinyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl, cyclooctenyl, and the like.

[0550] Preferred alkynyl groups are, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl, octynyl, and the like.

[0551] 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.

[0552] Preferred amino groups are, for example, dimethylamino, methylamino, methylphenylamino, phenylamino, and the like.

[0553] Aryl groups 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.

[0554] 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 aryls and heteroaryls, wherein, additionally, 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.

[0555] 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.

[0556] 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, dithiophenothiophene, isobenzothiophene, dibenzothiophene, benzothiophene, benzothiadiazolethiophene, or combinations of these groups.

[0557] Aryl and heteroaryl groups mentioned in the context may also be substituted by alkyl, alkoxy, thioalkyl, fluorine, fluoroalkyl or other aryl or heteroaryl groups.

[0558] (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.

[0559] (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 additionally, 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-.

[0560] 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.

[0561] Preferred substituents are, for example, solubility promoting groups such as alkyl or alkoxy groups; 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 groups.

[0562] Preferred substituents, also referred to hereinafter 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 to 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.

[0563] 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 linked to one another, and where one or more H atoms are each optionally replaced by F, Cl, P- or P-Sp-, and

[0564] Y 1 represents halogen.

[0565] “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-R0 or -O-CO-O-R 0 is substituted, where R 0 represents H or an alkyl group having 1 to 20 C atoms.

[0566] Particularly preferred substituents L are, for example, F, Cl, CN, NO2, CH3, C2H5, OCH3, OC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF3, OCF3, OCHF2, OC2F5, and in addition phenyl.

[0567] A 1 and A 2 very preferably represents where L has the meaning described above and r represents 0, 1, 2, 3 or 4, in particular

[0568] represents

[0569] The polymerizable group P is suitable for polymerization reactions, such as free radical or ionic chain polymerization, addition polymerization or condensation polymerization, or for reactions similar to polymers, 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.

[0570] Preferred P groups are selected from the group: CH2═CW 1 -CO-O-, CH2═CW 1 -CO-, CH2═CW 2 -(O) k3 -, CW 1 ═CH-CO-(O) k3 -, CW 1 ═CH-CO-NH-, CH2═CW 1 -CO-NH-, CH3-CH═CH-O-, (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 2 N-, 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 represents H or an alkyl group having 1 - 5 C atoms, especially H, methyl, ethyl or n-propyl, W 4 , W 5 and W 6 each independently of one another represents Cl, an oxaalkyl group or an oxacarbonylalkyl group having 1 to 5 C atoms, W 7 and W 8 each independently of one another represents 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 of the above-defined groups L, where the group L is not P-Sp-, k1, k2 and k3 each independently of one another represent 0 or 1, k3 preferably represents 1, and k4 represents an integer from 1 - 10.

[0571] Very preferably, the P groups 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 W5 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 represents 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 represents Cl, an oxaalkyl group or an oxacarbonylalkyl group having 1 to 5 C atoms, and W 7 and W 8 each independently of one another represents 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.

[0572] Very particularly preferred P groups are 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 CH2 = CH-O-, (CH2 = CH)2CH-O-CO-, (CH2 = CH)2CH-O-,

[0573] Further preferred polymerizable groups P are selected from the group consisting of: vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetanyl and epoxy, and most preferably from acrylate and methacrylate.

[0574] If the spacer group Sp is different from a single bond, it is preferably of the formula Sp"-X", so that the corresponding group P-Sp- conforms to the formula R-Sp"-X", where,

[0575] Sp" represents a straight-chain or branched alkylene group having 1 to 20 C atoms, preferably 1 to 12 C atoms, which is optionally mono- or polysubstituted by F, Cl, Br, I or CN, and where, in addition, one or more non-adjacent CH2 groups can each independently of one another be 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(R 00 )-CO-O-, -O-CO-N(R 0 )-, -N(R 0)-CO-N(R 00 )-, -CH=CH-, or -C≡C- in such a way that the O and / or S atoms are not directly connected to each other,

[0576] 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,

[0577] R 0 and R 00 each independently of one another represent H or an alkyl group having 1 to 20 C atoms, and

[0578] Y 2 and Y 3 each independently of one another represent H, F, Cl, or CN.

[0579] 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.

[0580] Typical spacers 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, R 0 and R 00 have the above meanings.

[0581] 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 above meanings.

[0582] Particularly preferred groups Sp" are in each case 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.

[0583] In a preferred embodiment of the present invention, the compound of formula P and its sub-formula contains 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 ≥ 2 (branched polymerizable group).

[0584] According to this preferred embodiment, preferred compounds of formula P are those in which s is 2, i.e., compounds containing the group Sp(P)2. According to this preferred embodiment, very preferred compounds of formula P contain a group selected from the following formulae:

[0585] -X-alkyl-CHPP S1

[0586] -X-alkyl-CH((CH2) aa P)((CH2) bb P) S2

[0587] -X-N((CH2) aa P)((CH2) bb P) S3

[0588] -X-alkyl-CHP-CH2-CH2P S4

[0589] -X-alkyl-C(CH2P)(CH2P)-C aa H 2aa+1 S5

[0590] -X-alkyl-CHP-CH2P S6

[0591] -X-alkyl-CPP-C aa H 2aa+1 S7

[0592] -X-alkyl-CHPCHP-C aa H 2aa+1 S8

[0593] wherein P is as defined in formula P,

[0594] alkyl represents a single bond or a straight-chain or branched-chain alkylene group having 1 to 12 C atoms, which is unsubstituted or mono- or polysubstituted by F, Cl or CN, and 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 connected to each other, where R 0 has the above meaning,

[0595] aa and bb each independently of one another represent 0, 1, 2, 3, 4, 5 or 6,

[0596] X has one of the meanings indicated by X", preferably O, CO, SO2, O-CO-, CO-O or a single bond.

[0597] The preferred spacer group Sp(P)2 is selected from formulae S1, S2 and S3.

[0598] The very preferred spacer group Sp(P)2 is selected from the following sub-formulae:

[0599] -CHPP S1a

[0600] -O-CHPP S1b

[0601] -CH2-CHPP S1c

[0602] -OCH2-CHPP S1d

[0603] -CH(CH2-P)(CH2-P) S2a

[0604] -OCH(CH2-P)(CH2-P) S2b

[0605] -CH2-CH(CH2-P)(CH2-P) S2c

[0606] -OCH2-CH(CH2-P)(CH2-P) S2d

[0607] -CO-NH((CH2)2P)((CH2)2P) S 3a

[0608] Among the compounds of formula P and its sub-formulas described in the context, P is preferably selected from ethenyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetanyl, and epoxy group, and most preferably selected from acrylate and methacrylate groups.

[0609] Further preferably, the compounds of formula P and its sub-formulas described in the context are such that all polymerizable groups P present in the compound have the same meaning, very preferably represent acrylate or methacrylate groups, and most preferably methacrylate groups.

[0610] Among the compounds of formula P and its sub-formulas described in the context, R preferably represents P-Sp-.

[0611] Further preferably, the compounds of formula P and its sub-formulas are as described in the context, where 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.

[0612] Further preferably, the compounds of formula P and its sub-formulas are as described in the context, where at least one group Sp is a single bond.

[0613] Further preferably, the compounds of formula P and its sub-formulas are as described in the context, where 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.

[0614] A very preferred group -A in formula P 1 -(Z-A 2 )Z - selected from the following formulae

[0615]

[0616] wherein at least one benzene ring is substituted by at least one group L, and the benzene ring is optionally further substituted by one or more groups L or P-Sp-

[0617] Preferred compounds of formula P and its sub-formulae are selected from the following preferred embodiments, including any combination thereof:

[0618] - all groups P in the compound have the same meaning

[0619] --A 1 -(Z-A 2 ) Z - selected from formulae A1, A2 and A5

[0620] - the compound contains exactly two polymerizable groups (represented by group P)

[0621] - the compound contains exactly three polymerizable groups (represented by group P)

[0622] - P is selected from acrylate group, methacrylate group and oxetanyl group, very preferably acrylate group or methacrylate group

[0623] - P is methacrylate group

[0624] - all groups Sp are single bonds

[0625] - 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

[0626] - when Sp is different from a single bond, Sp 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 CO-group is respectively connected to the benzene ring

[0627] - 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 CO-group is respectively connected to the benzene ring

[0628] - R represents P-Sp-

[0629] -R does not represent or contain a polymerizable group,

[0630] -R does not represent or contain a polymerizable group, represents a straight-chain, branched-chain or cyclic alkyl group having 1 to 25 C atoms, in which 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 linked to each other, and in which one or more H atoms are each optionally replaced by F, Cl or L a is replaced,

[0631] -L or L’ represents F, Cl or CN,

[0632] -L is F.

[0633] Suitable and preferred compounds of formula P are selected from the following formulas:

[0634]

[0635]

[0636]

[0637]

[0638]

[0639]

[0640] wherein each group has the following meanings:

[0641] P 1 、P 2 、P 3 each independently of one another represents an acrylate group or a methacrylate group,

[0642] Sp 1 、Sp 2 and Sp 3 each independently of one another represents a single bond or a spacer group having the meaning 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, and wherein, furthermore, the group P 1 -Sp 1 -、P2 -Sp 2 - and P 3 -Sp 3 - one or more of which may also represent R aa provided that the group P present 1 -Sp 1 -, P 2 -Sp 2 and P 3 -Sp 3 - at least one of which is different from R aa ,

[0643] 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 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 each other, 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 monofluorinated 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),

[0644] R 0 ,R 00 each independently of one another and, each time they occur, identically or differently represent H or an alkyl group having 1 to 12 C atoms,

[0645] R y and R z each independently represent H, F, CH3 or CF3,

[0646] X 1 、X 2 and X 3 each independently represent -CO-O-, -O-CO- or a single bond,

[0647] Z 1 represents -O-, -CO-, -C(R y R z )- or -CF2CF2-,

[0648] Z 2 and Z3 each independently represents -CO-O-, -O-CO-, -CH2O-, -OCH2-, -CF2O-, -OCF2- or -(CH2) n -, where n is 2, 3 or 4,

[0649] L, each time it appears, is the same or different and represents F, Cl, CN or a straight-chain or branched-chain alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy group having 1 to 12 C atoms, optionally mono- or poly-fluorinated, preferably F,

[0650] L' and L" each independently represent H, F or Cl,

[0651] k represents 0 or 1,

[0652] r represents 0, 1, 2, 3 or 4,

[0653] s represents 0, 1, 2 or 3,

[0654] t represents 0, 1 or 2,

[0655] x represents 0 or 1.

[0656] Particularly preferred are the compounds of formulae P2, P13, P17, P22, P23, P24, P30, P31 and P32.

[0657] Further preferred are the tri-reactive compounds P15 to P31, especially P17, P18, P19, P22, P23, P24, P25, P26, P30, P31 and P32.

[0658] In the compounds of formulae P1 to P32, the group

[0659] is preferably

[0660]

[0661] where L, each time it appears, is the same or different and has one of the meanings given in the context, and is 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.

[0662] The very particularly preferred compounds of formula P are selected from Table E below.

[0663] For the production of PSA displays, the polymerizable compounds comprised in the liquid-crystalline medium are polymerized or crosslinked (if a compound comprises two or more polymerizable groups) in the liquid-crystalline medium between the substrates of the LC display by in-situ polymerization, optionally while applying a voltage to the electrodes.

[0664] The structure of the PSA displays 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, in particular those in which additionally the electrodes on the color filter side are unstructured and only the electrodes on the TFT side have grooves. Particularly suitable and preferred electrode structures for PS-VA displays are described, for example, in US 2006 / 0066793 A1.

[0665] Preferred PS-type LC displays according to the invention comprise:

[0666] - a first substrate which comprises pixel electrodes defining pixel regions and optionally a first alignment layer provided on the pixel electrodes, the pixel electrodes being connected to switching elements provided in each pixel region and optionally comprising a micro-slit pattern,

[0667] - a second substrate which comprises a common electrode layer and optionally a second alignment layer, the common electrode layer being able to be provided over the entire part of the second substrate facing the first substrate,

[0668] - an LC layer which is provided between the first and second substrates and comprises an LC medium which contains a polymerizable component and a liquid-crystalline host, the polymerizable component comprising one or more compounds of formula R, the liquid-crystalline host comprising as described in context, where the polymerizable component can also be polymerized.

[0669] The first and / or second alignment layer controls the alignment direction of the LC molecules of the LC layer. For example, in PS-VA displays, the alignment layer is chosen such that it imparts a homeotropic (or perpendicular) alignment (i.e. perpendicular to the surface) or an inclined alignment to the LC molecules. Such an alignment layer can, for example, comprise polyimide, which can also be rubbed, or can be prepared by a photo-alignment method.

[0670] The LC layer having the LC medium can be deposited between the substrates of the display by methods customarily 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. The polymerization can be carried out in one step or in two or more steps.

[0671] The PSA display may include other elements such as color filters, black matrices, passivation layers, optical retardation layers, transistor elements for addressing individual pixels, etc., all of which are well known to those skilled in the art and can be used without creative skills.

[0672] The electrode structure can be designed by those skilled in the art according to each display type. For example, for a PS-VA display, a multi-domain alignment of LC molecules can be induced by providing an electrode having slits and / or bumps or protrusions to produce two, four or more different tilt alignment directions.

[0673] After polymerization, the polymerizable compound forms a crosslinked polymer, which causes a certain pretilt of the LC molecules in the LC medium. Without wishing to be bound by a particular theory, it is believed that at least a portion of the crosslinked polymer formed by the polymerizable compound will phase separate or precipitate from the LC medium and form a polymer layer on the substrate or on the alignment layer provided thereon. Microscopic measurement data (such as SEM and AFM) confirm that at least a portion of the formed polymer accumulates at the LC / substrate interface.

[0674] The polymerization can be carried out in one step. It is also possible to first optionally carry out the polymerization while applying a voltage in a first step to produce a pretilt angle, and subsequently in a second step of polymerization without applying a voltage, polymerize or crosslink the unreacted compounds in the first step ("final curing").

[0675] Suitable and preferred polymerization methods are, for example, thermal polymerization or photopolymerization, preferably photopolymerization, especially UV-induced photopolymerization, which can be achieved by exposing the polymerizable compound to UV radiation.

[0676] Optionally, one or more polymerization initiators are added to the LC medium. Suitable conditions for polymerization as well as 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 - 5 wt%, particularly preferably 0.001 - 1 wt%.

[0677] The polymerizable compound according to the invention is also suitable for polymerization without an initiator, which has considerable advantages such as lower material costs, especially less possible contamination of the LC medium by the initiator or its degradation products. Therefore, the polymerization can also be carried out without adding an initiator. Thus, in a preferred embodiment, the LC medium does not contain a polymerization initiator.

[0678] The LC medium may also contain one or more stabilizers to prevent the unwanted spontaneous polymerization of the RM during, for example, 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 stabilizers of the series (Ciba AG), such as

[0679] The polymerizable compounds of formula P particularly exhibit good UV absorption and are thus particularly suitable for a method for preparing a PSA display, which method comprises one or more of the following features:

[0680] - The polymerizable medium is exposed to UV light in a two-step process in the display, including a first UV exposure step ("UV-1 step") that generates an inclination angle and a second UV exposure step ("UV-2 step") that completes the polymerization,

[0681] - The polymerizable medium is exposed to UV light generated by energy-saving UV lamps (also known as "green UV lamps") in the display. These lamps are characterized by having a relatively low intensity in the absorption spectrum of 300 - 380 nm (1 / 100 - 1 / 10 of a conventional UV1 lamp), and are preferably used for the UV2 step, but are also optionally used for the UV1 step when the process requires avoiding high intensity.

[0682] - The polymerizable medium is exposed to UV light generated by a UV lamp, the radiation spectrum of which is shifted to longer wavelengths, preferably 340 nm or longer, to avoid short UV light exposure in the PS-VA process.

[0683] Using both lower intensity and UV shifted to longer wavelengths can protect the organic layer from damage that may be caused by UV light.

[0684] A preferred embodiment of the present invention relates to a method for preparing a PSA display as described in the context, comprising one or more of the following features:

[0685] - The polymerizable LC medium is exposed to UV light in a 2-step process, including a first UV exposure step ("UV-1 step") that generates an inclination angle and a second UV exposure step "UV-2 step" that completes the polymerization,

[0686] - The polymerizable LC medium is exposed to UV light generated by a UV lamp, which UV light has 0.5 mW / cm 2 to 10 mW / cm 2The intensity is preferably used for the UV2 step and optionally also for the UV1 step.

[0687] - The polymerizable LC medium is exposed to UV light having a wavelength of 340 nm or greater, preferably 400 nm or less.

[0688] This preferred process can be achieved, for example, by using the required UV lamp or by using band-pass filters and / or cut-off filters that are substantially transmissive to UV light having the corresponding required wavelength and substantially block light having the corresponding undesired wavelength. For example, when UV light with a wavelength λ of 300 - 400 nm is required for irradiation, a broadband pass filter that is substantially transmissive to wavelengths 300 nm < λ < 400 nm can be used for UV exposure. When UV light with a wavelength λ greater than 340 nm is required for irradiation, a cut-off filter that is substantially transmissive to wavelengths λ > 340 nm can be used for UV exposure.

[0689] "Substantially transmissive" means that the filter transmits most of the incident light of the desired wavelength, preferably at least 50% of the intensity. "Substantially blocking" means that the filter does not transmit most of the incident light of the undesired wavelength, preferably at least 50% of the intensity. "Desired (undesired) wavelength", for example, in the case of a band-pass filter, refers to the wavelength(s) within (outside) a given λ range, and in the case of a cut-off filter, refers to the wavelength(s) above (below) a given λ value.

[0690] This preferred process enables the manufacture of displays using longer UV wavelengths, thereby reducing or even avoiding the dangerous and damaging effects of short UV components.

[0691] The UV radiation energy is typically 6 - 100 J, depending on the manufacturing process conditions.

[0692] Preferably, as described in the context, the LC medium according to the present invention substantially consists of a polymerizable component P) containing one or more polymerizable compounds of formula P, an LC host mixture, and an optically active component containing one or more chiral dopants. However, the LC medium can 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.

[0693] Particularly preferred is an LC medium containing one, two, or three polymerizable compounds of formula P.

[0694] Preferably, the proportion of the compound of formula P in the LC medium is >0 to <5%, very preferably >0 to <1%, and most preferably 0.01 - 0.5%.

[0695] In a preferred embodiment, the medium according to the invention preferably comprises one or more compounds of formula S, the total concentration of which is in the range of 10 ppm to 2000 ppm, more preferably 100 ppm to 1000 ppm, still more preferably 150 ppm to 500 ppm, very preferably 200 ppm to 400 ppm, especially 250 - 300 ppm.

[0696] In another preferred embodiment, the medium according to the invention preferably comprises one or more compounds of formula S, the total concentration of which is in the range of 1000 ppm to 5000 ppm, more preferably more than 1000 ppm to 5000 ppm, still more preferably 1200 ppm to 4500 ppm, very preferably 2000 ppm to 4000 ppm, especially 2500 - 3500 ppm.

[0697] The medium according to the invention preferably has negative dielectric anisotropy.

[0698] The liquid crystal mixture according to the invention is preferably nematic at -20 °C or lower, preferably at -30 °C or lower, very preferably at -40 °C or lower.

[0699] Advantageously, the liquid crystal medium according to the invention preferably has a nematic phase of ≤ -20 °C to ≥ 90 °C, particularly preferably from ≤ -30 °C to ≥ 100 °C, very particularly preferably from ≤ -40 °C to ≥ 108 °C.

[0700] The expression "having a nematic phase" here means on the one hand that no smectic phase and no crystallization are observed at the corresponding temperature at low temperature and on the other hand that it does not become clear (phase transition to the isotropic phase) when heated from the nematic phase. The low temperature studies are carried out in a flow viscometer at the corresponding temperature and are checked by storing in a test cell having a layer thickness corresponding to electro-optical use for at least 100 hours. If the storage stability in the corresponding test cell at -20 °C is 1000 hours or more, the medium is called stable at this temperature. At -30 °C and -40 °C, the corresponding times are 500 hours and 250 hours respectively. At high temperature, the clearing point is measured in a capillary by conventional methods.

[0701] In a first preferred embodiment, the medium according to the invention has a clearing temperature of 90 °C or higher, preferably 100 °C or higher, more preferably 105 °C or higher, especially 108 °C or higher.

[0702] In a preferred embodiment, the liquid crystal mixture according to the invention has a dielectric anisotropy Δε of -2.0 to -6.0, preferably -2.2 to -5.0, especially -2.4 to -4.3.

[0703] The rotational viscosity γ1 at 20 °C is preferably in the range of 100 - 250 mPas, more preferably 120 - 230 mPas.

[0704] The medium according to the invention comprises a compound of formula I in a concentration in the range of 0.1% - 10%, preferably 0.5% - 8%, more preferably 1% - 7%, very preferably 1.5% - 6%.

[0705] Preferred embodiments, either alone or in combination with each other, are as follows.

[0706] The medium preferably comprises:

[0707] - one or more compounds of formula IIA, preferably IIA - 10, more preferably one or more compounds CCY - n - Om, in particular CCY - 4 - O2, CCY - 3 - O2, CCY - 3 - O3, CCY - 3 - O1 and / or CCY - 5 - O2, preferably in a total concentration in the range of 3 - 25%, more preferably 6 - 20%, particularly preferably 8 - 15%;

[0708] - one or more compounds of formula IID, preferably selected from compounds of formula IID - 4 and IID - 10, preferably in a total concentration in the range of 2 - 40%, more preferably 15 - 35%, particularly preferably 20 - 30%,

[0709] and / or

[0710] - one or more compounds of formula IID - 4, preferably CLY - n - Om, in particular CLY - 2 - O4, CLY - 3 - O2 and / or CLY - 3 - O3, preferably in a total concentration in the range of 3 - 38%, more preferably 8 - 25%, particularly preferably 10 - 20%;

[0711] and / or

[0712] - one or more compounds of formula IID - 10, preferably CLOY - n - Om, in particular CLOY - 3 - O2, preferably in a total concentration in the range of 2 - 35%, more preferably 4 - 30%, particularly preferably 6 - 26%;

[0713] and / or

[0714] - one or more compounds of formula IIB in an amount less than 5%, more preferably less than 3%, very preferably less than 1%;

[0715] and / or

[0716] - one or more compounds of formula IIC in an amount less than 5%, more preferably less than 3%, very preferably less than 1%;

[0717] and / or

[0718] -One or more compounds of formula III, preferably compounds of formula III-2 and / or III-3, more preferably compounds of formula III-2-6 and / or III-3, especially one or more compounds B(S)-nO-Om and / or COB(S)-n-Om, very especially B(S)-2O-O4, B(S)-2O-O5, B(S)-2O-O6 and / or COB(S)-2-O4, preferably with a total concentration in the range of 1-20%, more preferably 2-17%, very preferably 4-15%;

[0719] and / or

[0720] -One or more compounds of formula III and / or PH-1, preferably compounds of formula III-2 and / or BP-3, more preferably compounds of formula III-2-6, especially selected from B(S)-2O-O4, B(S)-2O-O5 and B(S)-2O-O6, preferably with a total concentration in the range of 1-12%, more preferably 2-11%, very preferably 3-10%;

[0721] and / or

[0722] -One or more compounds of formula III, preferably formula III-2 and III-3, more preferably compounds of formula III-2-6 and III-3, especially one or more compounds B(S)-nO-Om and COB(S)-n-Om, very especially B(S)-2O-O4, B(S)-2O-O5, B(S)-2O-O6 and COB(S)-2-O4, preferably with a total concentration in the range of 4-20%, more preferably 6-14%, very preferably 8-12%;

[0723] and / or

[0724] -One or more compounds of formula IV, preferably with a total concentration in the range of 25-70%, more preferably 30-60%, especially preferably 35-55%;

[0725] and / or

[0726] -One or more compounds of formula VI-1, preferably IV-1-6, preferably with a total concentration in the range of 1-20%, more preferably 2-18%, very preferably 3-15%;

[0727] and / or

[0728] -One or more compounds of formula CC-3-V1 and / or CC-4-V1, with a total concentration in the range of 5-35%, more preferably 10-28%, especially preferably 12-26%,

[0729] and / or

[0730] -One or more compounds of formula IV-3-1, preferably CC-3-V and / or CC-4-V, preferably in a total concentration in the range of 1-25%, more preferably 2-22%, very preferably 3-20%;

[0731] and / or

[0732] -One or more compounds of formula IVa, more preferably compounds of formula IVa-2, especially CP-3-O2, in a total concentration in the range of 0.5-8%, more preferably 1-6%, very preferably 2-5%;

[0733] and / or

[0734] -One or more compounds of formula V, more preferably compounds selected from formula V-2-1 and V-2-2, especially CCP-n-m and / or CCP-Vn-m and / or CPP-n-m, very particularly selected from CCP-3-1, CCP-V-1, CCP-V2-1 and CPP-3-2, preferably in a total concentration in the range of 1-20%, more preferably 2-17%, very preferably 3-14%;

[0735] and / or

[0736] -One or more compounds selected from formula V-1-1 and V-1-6, especially CCC-n-m and / or CCC-n-V, very especially CCC-3-V and / or CCC-V-V, preferably in a total concentration in the range of 1-20%, more preferably 2-17%, very preferably 3-14%;

[0737] and / or

[0738] One or more compounds of formula CL, more preferably compounds of formula CL-3, very preferably selected from the compounds CLP-V-m, CLP-V-Om, CLP-n-m and CLP-n-Om, where n and m are independently 1, 2, 3, 4 or 5, preferably in a total concentration in the range of 1-12%, more preferably 2-10%, very preferably 3-7%,

[0739] and / or

[0740] One or more compounds of formula COYOIC-n-m

[0741] and / or

[0742] One or more compounds of formula CCOY-n-Om

[0743] and / or

[0744] 0.1-3% of the compound PPGU-3-F.

[0745] The liquid crystal medium of the present invention has a high voltage holding ratio value in the liquid crystal cell.

[0746] Generally, liquid crystal media with a low addressing voltage or threshold voltage exhibit a lower voltage holding ratio than those LC media with a higher addressing voltage or threshold voltage, and vice versa.

[0747] As used herein, the term "dielectrically positive compound" denotes a compound having Δε > 1.5, the term "dielectrically neutral compound" denotes those having -1.5 ≤ Δε ≤ 1.5 and the term "dielectrically negative compound" denotes those having Δε < -1.5. Here, the dielectric anisotropy of the compound is determined by dissolving 10% of the compound in a liquid crystal host in at least one test cell and measuring the capacitance of the resulting mixture, each test cell having a layer thickness of 20 μm and homeotropic and planar surface alignments at 1 kHz. The measurement voltage is typically 0.5 V - 1.0 V, but always below the capacitance threshold of the respective liquid crystal mixture under investigation.

[0748] All temperature values described in the present invention are in °C.

[0749] The mixtures according to the invention are suitable for all VA-TFT applications, such as VAN, MVA, (S)-PVA, ASV, PSA (polymer stabilized VA) and PS-VA (polymer stabilized VA). In addition, they are also suitable for IPS (in-plane switching) and FFS (fringe field switching) applications with negative Δε, in particular UB-FFS.

[0750] It goes without saying for a person skilled in the art that the VA, IPS or FFS mixtures according to the invention can also contain, for example, compounds in which H, N, O, Cl and F are replaced by the corresponding isotopes.

[0751] The compounds according to the invention can be synthesized by known methods described in the literature (for example in standard works such as Houben-Weyl, Methoden der Organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart) or analogous methods under reaction conditions known and suitable for the said reaction. Variants which are known per se but not mentioned here can also be used. In particular, they can be prepared as described in the following reaction schemes or analogous methods. Other methods for preparing the compounds of the invention can be obtained from the examples.

[0752] Other mesogenic compounds not explicitly mentioned above can also optionally and advantageously be used in the media according to the invention. These compounds are known to a person skilled in the art.

[0753] For the present invention and in the following examples, the structures of the liquid crystal compounds are represented by acronyms and converted into chemical formulas according to Tables A to C below. All groups C m H 2m+1 、C n H 2n+1 and C l H 2l+1 or C m H 2m-1 、C n H 2n-1 and C l H 2l-1 are straight-chain alkyl or alkylene groups, each having n, m, and l carbon atoms in each case. Preferably, n, m, and l independently of one another represent 1, 2, 3, 4, 5, 6, or 7. Table A shows the codes for the ring elements of the compound nucleus, Table B lists the bridging units, and Table C lists the symbolic meanings of the left- and right-hand end groups of the molecule. The acronyms consist of the code for the ring element with an optional linking group, followed by a first hyphen and the left-hand end group code, and a second hyphen and the right-hand end group code. Table D shows the exemplary structures of the compounds and their respective abbreviations.

[0754] Table A: Ring Elements

[0755]

[0756]

[0757]

[0758] Table B: Bridging Units

[0759]

[0760]

[0761] Table C: End Groups

[0762]

[0763]

[0764] where n and m are each integers and the three dots "..." are placeholders for other abbreviations from the table.

[0765] In addition to the compounds of Formulas I, IIA, IIB, IIC, and / or IID, IVa, IVb, and V, the mixtures according to the invention optionally contain one or more of the following compounds.

[0766] The following abbreviations are used:

[0767] (n, m, k, and l are each independently integers, preferably 1 - 9, more preferably 1 - 7. k and l can also be 0, preferably 0 - 4, more preferably 0 - 2, most preferably 2. n is preferably 1, 2, 3, 4, or 5, and in the combination "-nO-", it is preferably 1, 2, 3, or 4, very preferably 2 or 4. m is preferably 1, 2, 3, 4, or 5, and in the combination "-Om", it is preferably 1, 2, 3, or 4, more preferably 2 or 4. The combination "-lVm" is preferably "2V1".)

[0768] Table D

[0769]

[0770]

[0771]

[0772]

[0773]

[0774]

[0775]

[0776]

[0777]

[0778]

[0779]

[0780]

[0781]

[0782]

[0783]

[0784]

[0785]

[0786]

[0787]

[0788]

[0789]

[0790]

[0791] Table E

[0792] Table E shows exemplary reactive mesogenic compounds that can be used for the LC medium according to the present invention.

[0793]

[0794]

[0795]

[0796]

[0797]

[0798]

[0799]

[0800]

[0801]

[0802]

[0803]

[0804]

[0805]

[0806]

[0807]

[0808]

[0809]

[0810]

[0811]

[0812]

[0813]

[0814] In a preferred embodiment, the mixture according to the invention comprises one or more polymerizable compounds, preferably selected from the polymerizable compounds of formulas RM-1 to RM-182. Among them, the compounds RM-1, RM-4, RM-8, RM-17, RM-19, RM-35, RM-37, RM-39, RM-40, RM-41, RM-48, RM-52, RM-54, RM-57, RM-58, RM-64, RM-74, RM-76, RM-88, RM-91, RM-102, RM-103, RM-109, RM-116, RM-117, RM-120, RM-121, RM-122, RM-139, RM-140, RM-142, RM-143, RM-145, RM-146, RM-147, RM-149, RM-156 to RM-163, RM-169, RM-170 and RM-171 to RM-184 are particularly preferred. Detailed Description of the Invention

[0815] Examples

[0816] The present invention will be described in detail by the following non-limiting working examples.

[0817] The following abbreviations and symbols are used:

[0818] V0 represents the threshold voltage at 20 °C, capacitive [V],

[0819] n e represents the extraordinary refractive index at 20 °C and 589 nm,

[0820] n o represents the ordinary refractive index at 20 °C and 589 nm,

[0821] Δn represents the optical anisotropy at 20 °C and 589 nm,

[0822] ε ⊥ represents the dielectric constant perpendicular to the director at 20 °C and 1 kHz,

[0823] ε|| represents the dielectric constant parallel to the director at 20 °C and 1 kHz,

[0824] Δε represents the dielectric anisotropy at 20 °C and 1 kHz,

[0825] cl.p., T(N, I) represents the clearing point [°C],

[0826] γ1 represents the rotational viscosity [mPa·s] at 20°C,

[0827] K1 represents the elastic constant at 20°C, "tilt" deformation [pN],

[0828] K2 represents the elastic constant at 20°C, "twist" deformation [pN],

[0829] K3 represents the elastic constant at 20°C, "bend" deformation [pN].

[0830] K av represents the average elastic constant at 20°C, defined as

[0831] Unless otherwise explicitly stated, all concentrations in this application are given as weight percentages and relate to the respective entire mixture, which includes all solid or liquid crystal components (without solvent).

[0832] Unless otherwise explicitly stated, 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. represents the melting point, cl.p. = clearing point. Additionally, C = crystalline phase, N = nematic phase, S = smectic phase, and I = isotropic phase. The data between these symbols represent transition temperatures.

[0833] 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.

[0834] The term "threshold voltage" used in this invention relates 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 10% relative contrast (V 10 ) as given.

[0835] Unless otherwise stated, the method of polymerizing polymerizable compounds in a 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.

[0836] Unless otherwise specified, the methods for preparing the test cells and measuring their electro-optical and other properties are carried out by the methods described below or similar methods thereto.

[0837] 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 alignment of the liquid crystal molecules.

[0838] The display or test cell for measuring the tilt angle consists of two parallel planar glass outer plates spaced 4 μm apart, each of the outer plates having an electrode layer on the inner side and a polyimide alignment layer on the top, where the two polyimide layers are rubbed antiparallel to each other and result in a homeotropic edge alignment of the liquid crystal molecules.

[0839] The polymerizable compound is polymerized in the display or test cell by irradiating with UV light of a defined intensity for a predetermined time while applying a voltage (usually 10 V - 30 V alternating current, 1 kHz) to the display. In the examples, unless otherwise specified, 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, center wavelength 313 nm).

[0840] The transmittance measurement is carried out in a test cell with a fishbone electrode layout (from Merck Ltd., Japan; 1 - pixel fishbone electrode (ITO, 10 x 10 mm, fishbone angle 47.7°, 3 μm line / 3 μm space), 3.2 μm cell gap, AF glass, tilt angle 1°).

[0841] The storage stability of the medium according to the present invention in the bulk (LTS 本体 ) at a given temperature T is determined by visual inspection. 2 g of the medium of interest is loaded into a closed glass container (bottle) of appropriate size, and the container is placed in a refrigerator at a predetermined temperature. The bottles are checked at regular time intervals for the appearance of the smectic phase or crystallization. Two bottles are stored for each material and each temperature. If crystallization or the appearance of the smectic phase is observed in at least one of the two corresponding bottles, the test is terminated, and the time of the last check before the appearance of the higher - order phase is observed is recorded as the corresponding storage stability.

[0842] Compound Example 1: 1 - (4 - ethylcyclohexyl) - 4 - [4 - (4 - propylcyclohexyl)cyclohex - 1 - en - 1 - yl]benzene

[0843]

[0844] 1-(4-Ethylcyclohexyl)-4-[4-(4-propylcyclohexyl)cyclohex-1-en-1-yl]benzene is prepared by adding [4-(4-ethylcyclohexyl)phenyl]magnesium bromide to 4'-propyl-[1,1'-bicyclohexyl]-4-one to obtain the intermediate 4-[4-(4-ethylcyclohexyl)phenyl]-4'-propyl-[1,1'-bicyclohexyl]-4-ol, and then removing water.

[0845] Phase sequence: K 239N 290I

[0846] Δε = 0.5

[0847] Δn = 0.1352

[0848] Compound Example 2: 1-(4-Ethylcyclohexyl)-2-fluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-en-1-yl]benzene

[0849]

[0850] Similar to Compound Example 1, 1-(4-ethylcyclohexyl)-2-fluoro-4-[4-(4-propylcyclohexyl)cyclohex-1-en-1-yl]benzene in the form of colorless crystals was obtained.

[0851] Phase sequence: K 68SmB 163SmA 188N 272.0I.

[0852] Δε = 2.3

[0853] Δn = 0.1348

[0854] Mixture Example

[0855] Comparing Mixture Example C1 and Mixture Examples M1 to M15 and P1 to P10 have the compositions and properties given in the following table. The amounts in the table are expressed as weight percentages.

[0856] Comparative Mixture Example C1

[0857]

[0858]

[0859] Mixture Example M1

[0860]

[0861] The following table summarizes the key parameters of Mixtures C1 and M1.

[0862] Δε Δn <![CDATA[K av [pN]]]> <![CDATA[γ1[mPas]]]> <![CDATA[γ1 / K1[mPas / pN]]]> C1 -3.6 0.1030 23.9 209 7.3 M1 -3.7 0.1019 24.8 202 6.8

[0863] Surprisingly, by using the compound of formula I in Mixture Example 1, a favorable low rotational viscosity (γ1) can be achieved despite the high clearing temperature, and at the same time a very low ratio of γ1 / K1 can be achieved, which improves the response time of the display.

[0864] Mixture Example M2

[0865]

[0866]

[0867] Mixture Example M3

[0868]

[0869] Mixture Example M4

[0870]

[0871]

[0872] Mixture Example M5

[0873]

[0874] Mixture Example M6

[0875]

[0876] Mixture Example M7

[0877]

[0878]

[0879] Mixture Example M8

[0880]

[0881] Mixture Example M9

[0882]

[0883]

[0884] Mixture Example M10

[0885]

[0886]

[0887] Mixture Example M11

[0888]

[0889] Mixture Example M12

[0890]

[0891]

[0892] Mixture Example M13

[0893]

[0894] Mixture Example M14

[0895]

[0896] Mixture Example M15

[0897]

[0898]

[0899] Mixture Example M15

[0900]

[0901] Polymerizable Mixture

[0902] The polymerizable mixtures P1 to P9 are prepared from the nematic mixtures given in Table 1 by adding a reactive mesogen (RM) selected from the compounds of the formulas RM-1, RM-17, RM-35, RM-64 and RM-171 in the amounts (%) RM given in Table 1.

[0903]

[0904]

[0905] Table 1: Polymerizable mixtures

[0906]

[0907]

[0908] Mixture Example P11

[0909] The polymerizable mixture P11 consists of 99.434% of the mixture Example M1, 0.300% of RM-1, 0.200% of RM-145, 0.050% of RM-163, 0.001% of 1076 and 0.015% of the compound ST-3a-1.

[0910]

Claims

1. A liquid crystal medium comprising one or more compounds of formula I in R 11 and R 12 Identically or differently represent H, straight-chain alkyl or alkoxy groups having 1 to 15 C atoms, straight-chain alkenyl or alkenyloxy groups having 2 to 15 C atoms, or branched alkyl, alkoxy, alkenyl, alkenyloxy groups each having 3 to 15 C atoms, wherein one or more CH2 groups in these groups can each be independently replaced by -CH=CH-, -C≡C-, -CF2O-, -OCF2-, -O-, -CO-O- or -O-CO- are substituted in such a way that the O atoms are not directly connected to each other, and wherein one or more H atoms may be replaced by halogen, L 11 and L 12 One of the two represents H, and L 11 and L 12 The other of represents H, F, Cl, CF3 or CHF2.

2. A liquid crystal medium according to claim 1, wherein the medium comprises one or more compounds selected from the group consisting of compounds of the formulae IIA, IIB, IIC and IID in R 2A , R 2B , R 2C and R 2D Identically or differently represent H, straight-chain alkyl or alkoxy groups having 1 to 15 C atoms, straight-chain alkenyl or alkenyloxy groups having 2 to 15 C atoms, or branched alkyl, alkoxy, alkenyl, alkenyloxy groups each having 3 to 15 C atoms, wherein one or more CH2 groups in these groups can each be independently replaced by -CH=CH-, -C≡C-, -CF2O-, -OCF2-, -O-, -CO-O- or -O-CO- are substituted in such a way that the O atoms are not directly connected to each other, and wherein one or more H atoms may be replaced by halogen, L 1 and L 2 each independently represents F, Cl, CF3 or CHF2, Y represents H, F, Cl, CF3, CHF2 or CH3, Z 2 , Z 2B and Z 2D each independently represents a single bond, -CH2CH2-, -CH=CH-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -COO-, -OCO-, -C2F4-, -CF=CF- or -CH=CHCH2O-, (O) represents O or a single bond, p represents 0, 1 or 2, q represents 0 or 1, and v represents an integer from 1 to 6.

3. A liquid-crystalline medium according to claim 1 or 2, wherein the medium comprises one, two or more compounds of the formula IID as defined in claim 2.

4. Liquid-crystalline medium according to one or more of claims 1 to 3, wherein the medium comprises one or more compounds of the formula III in R 31 and R 32 independently of one another represent H, alkyl or alkoxy having 1 to 15 C atoms, wherein one or more CH2 groups in these radicals can each independently of one another be -CH=CH-, -C≡C-, -CF2O-, -OCF2-, -O-, -CO-O- or -O-CO- are substituted in such a way that the O atoms are not directly connected to one another, and wherein one or more H atoms may be replaced by halogen, A 31 Each occurrence represents independently of each other a) 1,4-cyclohexylene or 1,4-cyclohexenylene, in which one or two non-adjacent CH2 groups may be replaced by -O- or -S-, b) a 1,4-phenylene group in which one or both CH groups may be replaced by N, or c) a radical selected from the group consisting of spiro[3.3]heptane-2,6-diyl, 1,4-bicyclo[2.2.2]octane-2,6-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, phenanthrene-2,7-diyl and fluorene-2,7-diyl, wherein the groups a), b) and c) may be mono- or poly-substituted by halogen atoms, Z 31 Each occurrence independently 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, L 31 and L 32 each independently represents F, Cl, CF3 or CHF2, W means O or S, and n represents 0, 1, or 2.

5. Liquid-crystalline medium according to one or more of claims 1 to 4, wherein the medium comprises one or more compounds selected from the group consisting of compounds of the formulae BC, CR, PH-1 and PH-2 in R B1 , R B2 , R CR1 , R CR2 , R P1 and R P2 each independently of one another represents H, alkyl or alkoxy having 1 to 15 C atoms, wherein one or more CH2 groups in these radicals can each independently of one another be -CH=CH-, -C≡C-, -CF2O-, -OCF2-, -O-, -CO-O- or -O-CO- are substituted in such a way that the O atoms are not directly connected to each other, and wherein, One or more H atoms may be replaced by halogen, and c is 0, 1 or 2.

6. Liquid-crystalline medium according to one or more of claims 1 to 5, wherein the medium comprises one or more compounds of the formula IV in R 41 represents an alkyl group having 1 to 7 C atoms or an alkenyl group having 2 to 7 C atoms, R 42 represents an alkyl group having 1 to 7 C atoms, an alkoxy group having 1 to 6 C atoms, or an alkenyl group having 2 to 7 C atoms.

7. Liquid-crystalline medium according to one or more of claims 1 to 6, wherein the medium comprises one or more compounds of the formula V in R 51 , R 52 represents, identically or differently, an alkyl radical having 1 to 7 C atoms, an alkoxy radical having 1 to 7 C atoms or an alkoxyalkyl radical, an alkenyl radical or an alkenyloxy radical each having 2 to 7 C atoms, Same or different Z 51 and Z 52 represent, identically or differently, -CH2-CH2-, -CH2-O-, -CH=CH-, -C≡C-, -COO- or a single bond, and n is 1 or 2, The compounds of formula I according to claim 1 are excluded.

8. Liquid-crystalline medium according to one or more of claims 1 to 7, wherein the medium comprises polymerizable compounds.

9. Liquid-crystalline medium according to one or more of claims 1 to 8, wherein the medium has a clearing temperature of 100°C or more.

10. A process for preparing a liquid-crystalline medium according to any one of claims 1 to 9, comprising the step of mixing one or more compounds of the formula I with one or more compounds selected from the group consisting of formulae IIA, IIB, IIC and IID, and optionally with polymerizable compounds or other liquid-crystalline compounds or additives.

11. A liquid crystal display comprising a liquid crystal medium according to any one of claims 1 to 9.

12. The liquid crystal display of claim 11, wherein the display is a VA, IPS, FFS, PS-VA, PS-IPS or PS-FFS type display.

13. Compounds of formula I in R 11 and R 12 Identically or differently represent H, straight-chain alkyl or alkoxy groups having 1 to 15 C atoms, straight-chain alkenyl or alkenyloxy groups having 2 to 15 C atoms, or branched alkyl, alkoxy, alkenyl, alkenyloxy groups each having 3 to 15 C atoms, wherein one or more CH2 groups in these groups can each be independently replaced by -CH=CH-, -C≡C-, -CF2O-, -OCF2-, -O-, -CO-O- or -O-CO- are substituted in such a way that the O atoms are not directly connected to each other, and wherein one or more H atoms may be replaced by halogen, L 11 and L 12 One of them represents H, And L 11 and L 12 The other one of them represents F, Cl, CF3 or CHF2.

14. The method for preparing the compound of formula (I) according to claim 13, which comprises at least the step of dehydrating the compound of formula (3) Where R 11 ,R 12 ,L 11 and L 12 has the meaning given for formula I in claim 13.

15. A compound of formula (3) as defined in claim 14.

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