TWI845512B - Compounds and liquid-crystalline medium - Google Patents

Abstract

The invention relates to compounds of the formula I, and to a liquid-crystalline medium, preferably having a nematic phase and negative dielectric anisotropy, which comprises a) one or more compounds of the formula I and b) one or more compounds selected from the group of compounds of formulae II and III

Description

Compounds and liquid crystal media

The invention relates to novel compounds, in particular novel compounds for use in liquid crystal media, but also to the use of such liquid crystal media in liquid crystal displays, and to such liquid crystal displays, in particular liquid crystal displays using the ECB ( electrically controlled birefringence ) effect and dielectrically negative liquid crystals with homeotropic initial alignment. The liquid crystal media according to the invention are characterized by a particularly short response time in the display according to the invention and a high voltage holding ratio (VHR or also referred to as HR).

The principle of electrically controlled birefringence (ECB effect or DAP (deformation of alignment phase) effect) was first described in 1971 (M.F. Schieckel and K. Fahrenschon, "Deformation of nematic liquid crystals with vertical orientation in electrical fields", Appl. Phys. Lett. 19 (1971), 3912). It was subsequently described in papers by J.F. Kahn (Appl. Phys. Lett. 20 (1972), 1193) and G. Labrunie and J. Robert (J. Appl. Phys. 44 (1973), 4869).

The papers by J. Robert and F. Clerc (SID 80 Digest Techn. Papers (1980), 30), J. Duchene (Displays 7 (1986), 3) and H. Schad (SID 82 Digest Techn. Papers (1982), 244) have shown that liquid crystal phases must have high values of the ratio of the elastic constants K ₃ /K ₁ , high values of the optical anisotropy Δn and high values of the dielectric anisotropy Δε ≤ -0.5 in order to be suitable for high-information display elements based on the ECB effect. Electro-optical display elements based on the ECB effect have a vertical edge alignment (VA technology = vertical alignment or also VAN = vertically aligned nematic ). Dielectrically negative liquid crystal media can also be used in displays using the so-called IPS ( in-plane switching ) effect.

Industrial applications of this effect in electro-optical display components require that the LC phase must meet multiple requirements. Of particular importance here are chemical resistance to moisture, air and physical influences such as high temperatures, radiation in the infrared, visible and ultraviolet regions, and direct and alternating electric fields.

Furthermore, industrially usable LC phases must have a liquid crystal mesophase within a suitable temperature range and with low viscosity.

None of the series of compounds having a liquid-crystalline mesophase disclosed to date include a single compound which meets all of these requirements. Therefore, mixtures of 2 to 25, preferably 3 to 18 compounds are usually prepared in order to obtain substances which can be used as LC phases.

Matrix liquid crystal displays (MLC displays) are known. Nonlinear elements that can be used for the individual switching of individual pixels are, for example, active elements (i.e. transistors). The term "active matrix" is then used, in which generally thin film transistors (TFTs) are used, which are generally arranged on a glass plate as substrate.

A distinction is made between two technologies: TFTs comprising compound semiconductors such as, for example, CdSe, or TFTs based on polycrystalline and especially amorphous silicon. The latter technology is currently of greatest commercial importance worldwide.

The TFT matrix is applied to the inside of one of the glass plates of the display, while the other glass plate carries the transparent counter electrode on its inside. Compared to the size of the pixel electrode, the TFT is very small and has virtually no adverse effect on the image. This technology can also be extended to full-color displays, where the photosensitive mosaics of red, green and blue filters are arranged in such a way that the filter elements are located opposite each switchable pixel.

The TFT displays most used to date are usually operated with crossed polarizers during transmission and are backlit. For TV applications, IPS cells or ECB (or VAN) cells are used, while monitors usually use IPS cells or TN ( twisted nematic ) cells, and notebook, laptop and mobile applications usually use TN cells.

The term MLC display here includes any matrix display with integrated nonlinear elements, that is, a display that, in addition to the active matrix, also has passive elements such as varistors or diodes (MIM = Metal-Insulator-Metal).

MLC displays of this type are particularly suitable for TV applications, monitors and notebook computers or for displays with a high information density, for example in automobile manufacturing or aircraft construction. In addition to the problems concerning the angle dependence of contrast and response time, problems also arise in MLC displays due to the insufficiently high specific resistance of the liquid crystal mixture [TOGASHI, S., SEKIGUCHI, K., TANABE, H., YAMAMOTO, E., SORIMACHI, K., TAJIMA, E., WATANABE, H., SHIMIZU, H., Proc. Eurodisplay 84, Sept. 1984: A 210-288 Matrix LCD Controlled by Double Stage Diode Rings, pp. 141 ff., Paris; STROMER, M., Proc. Eurodisplay 84, Sept. 1984: Design of Thin Film Transistors for Matrix Addressing of Television Liquid Crystal Displays, pp. 145 ff., Paris]. As the resistance decreases, the contrast of the MLC display deteriorates. Since the specific resistance of the liquid crystal mixture generally decreases gradually during the life of the MLC display due to interaction with the internal surfaces of the display, a high (initial) resistance is very important for displays that need to have acceptable resistance values over long operating cycles.

In addition to IPS displays, displays using the ECB effect have been identified as so-called VAN ( vertically aligned nematic ) displays (e.g. Yeo, SD, Paper 15.3: "An LC Display for the TV Application", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pages 758 and 759) and the long-standing TN display, as any of the three newer types of liquid crystal displays that are currently the most important, particularly for television applications.

The most important designs that may be mentioned are: MVA ( multi-domain vertical alignment , e.g. Yoshide, H. et al., paper 3.1: "MVA LCD for Notebook or Mobile PCs ...", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book I, pp. 6-9, and Liu, CT et al., paper 15.1: "A 46-inch TFT-LCD HDTV Technology ...", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pp. 750-753), PVA ( patterned vertical alignment , e.g. Kim, Sang Soo, paper 15.4: "Super PVA Sets New State-of-the-Art for LCD-TV", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pp. 760-763) and ASV ( Advanced superview , e.g., Shigeta, Mitzuhiro and Fukuoka, Hirofumi, paper 15.2: “Development of High Quality LCDTV”, SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pp. 754-757).

In a general form, the techniques are compared, for example, in Souk, Jun, SID Seminar 2004, Seminar M-6: “Recent Advances in LCD Technology”, Seminar Lecture Notes, M-6/1 to M-6/26, and Miller, Ian, SID Seminar 2004, Seminar M-7: “LCD-Television”, Seminar Lecture Notes, M-7/1 to M-7/32. Although the response time of modern ECB displays has been significantly improved by using overdrive addressing methods, e.g., Kim, Hyeon Kyeong et al., Paper 9.1: "A 57-in. Wide UXGA TFT-LCD for HDTV Application", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book I, pp. 106-109, the achievement of video-compatible response times, particularly in switching between gray shades, remains a problem that has not been solved to a satisfactory degree.

ECB displays (such as ASV displays) use a liquid crystal medium with negative dielectric anisotropy (Δε), while TN and all known IPS displays to date use a liquid crystal medium with positive dielectric anisotropy.

In this type of LCD, liquid crystal acts as a dielectric whose optical properties can be reversed when a voltage is applied.

Since in general displays, i.e. also in displays based on the effects mentioned here, the operating voltage should be as low as possible, a liquid crystal medium is used which usually consists predominantly of liquid crystal compounds, all of which have the same sign of the dielectric anisotropy and have the highest possible value of the dielectric anisotropy. In general, at most relatively small proportions of neutral compounds are employed and, if possible, compounds having a dielectric anisotropy opposite to that of the medium are not employed. In the case of liquid crystal media having a negative dielectric anisotropy for ECB displays, therefore, predominantly compounds having a negative dielectric anisotropy are employed. The liquid crystal medium employed generally consists mainly of a liquid crystal compound having negative dielectric anisotropy and often even consists essentially of a liquid crystal compound having negative dielectric anisotropy.

In the media used according to the present application, dielectrically neutral liquid crystal compounds are usually employed in at most significant amounts and generally only even very small amounts of dielectrically positive compounds or even not at all, since liquid crystal displays are generally intended to have the lowest possible addressing voltage.

For many practical applications in liquid crystal displays, known liquid crystal media are not sufficiently stable. In particular, their stability to UV irradiation, but also to conventional backlight irradiation, leads to impairments, in particular of the electrical properties. Thus, for example, the conductivity increases significantly.

The use of so-called "hindered amine light stabilizers" (HALS for short) has been proposed for stabilizing liquid crystal mixtures.

Contains a small amount of TINUVIN ^® 770 (compound of the following formula: Nematic liquid crystal mixtures with negative dielectric anisotropy as stabilizers are proposed, for example, in WO 2009/129911 A1 and in WO 2012/076105 A1. However, the corresponding liquid crystal mixtures do not have sufficient properties for some practical applications. In particular, the corresponding liquid crystal mixtures are not sufficiently stable for illumination with typical CCFL (cold cathode fluorescent lamps) and in particular typical modern LED ( light emitting diode ) backlighting.

Similar liquid-crystal mixtures are also known, for example, from EP 2 182 046 A1, WO 2008/009417 A1, WO 2009/021671 A1 and WO 2009/115186 A1. However, the use of stabilizers is not indicated therein.

According to the disclosures therein, these liquid crystal mixtures may also contain various types of stabilizers, such as, for example, phenols and sterically hindered amines ( hindered amine light stabilizers , HALS for short), if necessary. However, these liquid crystal mixtures are characterized by a relatively high threshold voltage and an optimally moderate stability. In particular, the voltage retention of these liquid crystal mixtures decreases after exposure. In addition, a yellowish discoloration usually occurs.

The use of various stabilizers in liquid crystal media is described, for example, in JP (S) 55-023169 (A), JP (H) 05-117324 (A), WO 02/18515 A1 and JP (H) 09-291282 (A).

EP 2 993 216 A1 proposes (among other things) compounds of the following formula: Used to stabilize dielectrically positive liquid crystal media.

WO 2009/129911 A1 proposes to prepare a compound: , in addition to nitrogen-doped rings, are used to stabilize dielectrically negative liquid crystal media, in addition to several other compounds as secondary stabilizers.

EP 2 514 800 A2 proposes the following compound: and Compounds in which R ¹¹ , among other things, may be O or OH, but not H, are used for stabilization purposes in liquid crystal media. However, the chemical stability of these compounds with regard to hydrolysis and in particular the solubility of these compounds in liquid crystal media is in most cases insufficient for practical use.

WO 2016/146245 A1 proposes the following compound: It is used in liquid crystal media for stabilization purposes. This compound and the following compound: DE 2016 005 083 A1 also proposes the use of alkyl ethers in liquid crystal media for stabilization purposes. However, the chemical stability, in particular with regard to hydrolysis, and especially the solubility in liquid crystal media in the case of these compounds are in most cases insufficient for practical use.

Ether-linked compounds of the following formula: In the as yet unpublished application DE 10 2016 009485.0, it is proposed to use them as stabilizers for liquid crystal mixtures.

Prior art liquid crystal media with correspondingly low addressing voltages have relatively low resistance values or low VHR and often result in undesirable flicker and/or inadequate transmission in displays. In addition, at least if such liquid crystal media have correspondingly high polarities as are necessary for low addressing voltages, they are not sufficiently stable to heat and/or UV exposure.

On the other hand, the addressing voltage of prior art displays with a high VHR is often too high, in particular for displays that are not directly connected to the power supply network or are not continuously connected to the power supply network, such as, for example, displays for mobile applications.

In addition, the phase range of the liquid crystal mixture must be wide enough for the intended application in displays. Therefore, the low temperature storage stability at -30°C in cells and preferably in bulk should be 240 h or more.

The response time of liquid crystal media in displays must be improved, i.e. reduced. This is particularly important for displays for television or multimedia applications. To improve the response time, it has been repeatedly proposed in the past to optimize the rotational viscosity (γ ₁ ) of the liquid crystal medium, i.e. to achieve a medium with the lowest possible rotational viscosity. However, the results achieved here are insufficient for many applications and therefore make it appear necessary to develop other optimization methods.

It is very particularly important that the medium is sufficiently stable to extreme loads, in particular to UV exposure and heating. This is particularly difficult to optimize the rotational viscosity at the same time. In particular in the case of applications in displays of mobile devices such as, for example, mobile phones, this can be crucial because, in particular in the case of such devices, relatively low addressing frequencies are preferably used.

The disadvantages of MLC displays disclosed to date are their relatively low contrast, relatively high viewing angle dependence and the difficulty in producing gray shading in such displays, their inadequate VHR and their inadequate lifetime.

Therefore, there is still a great need for MLC displays having a very high specific resistance, at the same time having a large operating temperature range, a short response time and a low threshold voltage, with the help of which various shades of grey can be produced and in particular which have a good and stable VHR.

The invention has the object of providing an MLC display, not only for monitor and TV applications, but also for mobile phones and navigation systems, which is based on the ECB effect, the IPS effect or on the FFS ( fringe field switching ) effect, as described in Lee, SH, Lee, SL and Kim, HY "Electro-optical characteristics and switching principle of nematic liquid crystal cell controlled by fringe-field switching", Appl. Phys. Letts., Vol. 73, No. 20, pp. 2881-2883 (1998), which does not have the disadvantages indicated above, or has the disadvantages indicated above only to a lesser extent, and at the same time has a very high specific resistance value. In particular, it must be ensured that mobile phones and navigation systems also operate at very high temperatures and very low temperatures.

Surprisingly, it has been found that if such display elements are used which comprise nematic liquid-crystal mixtures of at least one compound of the formula I and in each case at least one compound of the formula II, preferably of the subformula II-1, and/or at least one compound selected from the group of compounds of the formulae III-1 to III-4, preferably of the formula III-2 and/or of the formula B, it is possible to achieve liquid-crystal displays which have (in particular in FFS displays) a low threshold voltage and a short response time and at the same time a sufficiently broad nematic phase, advantageously a relatively low birefringence (Δn), good stability to decomposition caused by heating and by exposure to UV light, good solubility and a stable, high VHR.

This type of medium can be used, in particular, in electro-optical displays with active matrix addressing based on the ECB effect and in IPS displays and in FFS displays.

The present invention therefore relates to a liquid crystal medium based on a mixture of polar compounds comprising at least one compound of formula I and at least one compound containing one or more compounds of formula II and preferably additionally one or more compounds selected from the group of compounds of formulae III-1 to III-4, and/or a compound of formula B.

The mixture according to the invention shows a very wide nematic phase range with a clearing point ≥ 70°C, a very favorable capacitance threshold, a relatively high retention ratio value and a good low temperature stability at both -20°C and -30°C, and a very low rotational viscosity. In addition, the mixture according to the invention is characterized by a good ratio of clearing point to rotational viscosity and a high negative dielectric anisotropy.

Surprisingly, it has now been found that it is possible to achieve liquid-crystal media having a suitably high Δε, a suitable phase range and Δn which do not have the disadvantages of prior art materials or at least have them only to a significantly reduced extent.

Surprisingly, it has been found here that compounds of the formula I, even when used alone without additional thermal stabilizers, lead to a considerable (in many cases sufficient) stabilization of liquid-crystal mixtures towards UV exposure and also towards heating. This is the case, in particular in the majority of cases in which the parameter p in the compounds of the formula I used is 2 and n*p is 4 or 6. In one embodiment of the invention, therefore, compounds of the formula I in which p is 2 and n is 3 or 4 are particularly preferred, and it is particularly preferred to use precisely these compounds in the liquid-crystal mixtures according to the invention. Preference is likewise given to compounds of the formula I in which the group -Z ¹¹ -S ¹¹ -Z ¹² - represents an ω-dioxyalkylene group, i.e. -OS ¹¹ -O-.

In particular, however, adequate stabilization of the liquid crystal mixture against UV exposure and against heating can also be achieved if, in addition to the compound or compounds of the formula I, one or more further compounds, preferably phenolic resin stabilizers, are present in the liquid crystal mixture. These further compounds are suitable as thermal stabilizers.

The present invention therefore relates to compounds of formula I, and to a liquid crystal medium having a nematic phase and negative dielectric anisotropy, the liquid crystal medium comprising: a) one or more compounds of formula I, preferably in a concentration in the range of from 1 ppm to 2.500 ppm, preferably to 2.000 ppm, preferably to 1.500 ppm, particularly preferably to 1.000 ppm, preferably in a concentration in the range of from 1 ppm to 500 ppm, particularly preferably in a concentration in the range of from 1 ppm to 250 ppm, wherein R ¹¹ at each occurrence independently represents H, F, a linear or branched alkyl chain having 1 to 20 C atoms, wherein one -CH ₂ - group or, if present, a plurality of -CH ₂ - groups may be replaced by -O- or -C(=O)-, but two adjacent -CH ₂ - groups may not be replaced by -O-, and one or, if present, a plurality of -CH ₂ - groups may be replaced by -CH=CH- or -C≡C-, and wherein one H atom or a plurality of H atoms may be replaced by F, OR ¹³ , N(R ¹³ )(R ¹⁴ ) or R ¹⁵ , R ¹¹ preferably represents H or alkyl, particularly preferably alkyl, particularly preferably n-alkyl and very particularly preferably n-butyl, R ¹² represents independently at each occurrence a straight or branched alkyl chain having 1 to 20 C atoms, wherein one or more -CH ₂ - groups may be replaced by -O- or -C(=O)-, but two adjacent _{-CH 2 -} groups may not be replaced by -O-; a alkyl group containing a cycloalkyl or alkylcycloalkyl unit and wherein one or more -CH ₂ - groups may be replaced _{by -O- or -C(=O)-, but two adjacent -CH 2 -} groups may not be replaced by -O-, and wherein one or more H atoms may be replaced by F, OR ¹³ , N(R ¹³ )(R ¹⁴ ) or R or ^an aromatic or heteroaromatic alkyl group in which one or more H atoms may be replaced by F, OR ¹³ , N(R ¹³ )(R ¹⁴ ) or R ¹⁵ , R ¹² preferably represents H, an unbranched alkyl group or a branched alkyl group, particularly preferably H or an unbranched alkyl group, R ¹³ at each occurrence independently represents a straight chain or branched chain alkyl group or an acyl group having 1 to 10 C atoms, preferably a n-alkyl group, or an aromatic hydrocarbon or a carboxylic acid free radical having 6 to 12 C atoms, R ¹⁴ at each occurrence independently represents a straight chain or branched chain alkyl group or an acyl group having 1 to 10 C atoms, preferably a n-alkyl group, or an aromatic hydrocarbon or a carboxylic acid free radical having 6 to 12 C atoms, ¹⁵ represents, at each occurrence, independently of one another, a linear or branched alkyl radical having 1 to 10 C atoms, wherein one -CH ₂ - radical or multiple -CH ₂ - radicals may be replaced by -O- or -C(=O)-, but two adjacent -CH ₂ - radicals may not be replaced by -O-, S ¹¹ and S ¹² represent, at each occurrence, independently of one another, an alkylene radical having 1 to 20 C atoms, which is branched or preferably linear, preferably -(CH ₂ -) _n having 1 to 20 C atoms, preferably 1 to 10 C atoms, particularly preferably 1 to 8 C atoms, wherein one -CH ₂ - radical or, if present, multiple -CH ₂ - radicals may be replaced by -O- or -C(=O)-, but two adjacent -CH _{2 -} radicals may not be replaced by -O-, -group cannot be replaced by -O-, and one or, if present, a plurality of -CH ₂ -groups may be replaced by -CH=CH- or -C≡C- and one or a plurality of H atoms may be replaced by F, OR ¹³ , N(R ¹³ )(R ¹⁴ ) or R ¹⁵ , or represents a single bond, X ¹¹ represents C, Y ¹¹ to Y ¹⁴ each independently of one another represent methyl or ethyl, particularly preferably all represent methyl or ethyl and very particularly preferably methyl, Z ¹¹ to Z ¹⁴ each independently of one another represent -O-, -(C=O)-, -O-(C=O)-, -(C=O)-O-, -O-(C=O)-O-, -(NR ¹³ )-, -NR ¹³ -(C=O)- or a single bond, if S wherein -X ¹¹ [-R ¹¹ ] _{o - is a single bond, but Z 11 and Z 12 do not both represent -O-, and, however, if S 12 is a single bond, Z 13 and Z 14 do not both represent -O-, and, however, if -X 11 [-R 11 ] o} ^{- is a single bond ,} Z ¹² and Z ¹³ are not both -O-, Z ¹¹ preferably represents -O-, Z ¹³ preferably represents a single bond, p represents 1 or 2, o represents (3-p), n*p represents an integer from 3 to 10, preferably an integer from 3 to 8, wherein p = 1, n represents 3, 4, 5, 6 or 8, particularly preferably 4, 6 or 8, very particularly preferably 4 or 6, and m represents (10-n), and wherein p = 2, n represents an integer from 2 to 4, preferably 2 or 3, particularly preferably 3, and m represents (4-n), denotes an organic group having (m+n) binding sites, preferably having up to 4 binding sites, preferably an alkanediyl, alkanetriyl or alkanetetrayl unit having 1 to 30 C atoms, wherein, in addition to the m groups R ¹² present in the molecule, but independently thereof, another H atom can be replaced by R ¹² or a plurality of further H atoms can be replaced by R ¹² , preferably an alkanetetrayl unit having one or two valences at each of the terminal C atoms, wherein one -CH ₂ - group or a plurality of -CH ₂ - groups can be replaced by -O- or -(C═O)- in such a way that two O atoms are not directly bound to one another, or a substituted or unsubstituted aromatic or heteroaromatic hydrocarbon group having up to 10 valences, wherein, in addition to the m groups R 12 present in the molecule, but independently thereof, a further H atom can be replaced by R 12 or a plurality of further H atoms can be replaced by R 12. ¹² , but independently, another H atom may be replaced by R ¹² or a plurality of other H atoms may be replaced by R ¹² , and in the case where p = 1, -X ¹¹ [-R ¹¹ ] _o - may also represent a single bond, b) one or more compounds selected from the group of compounds of formula II and III, preferably dielectrically positive, preferably each having a dielectric anisotropy of 3 or more: wherein R ² represents H, non-fluorinated or fluorinated alkyl or non-fluorinated or fluorinated alkoxy having 1 to 17 C atoms, or non-fluorinated or fluorinated alkenyl, non-fluorinated or fluorinated alkenyloxy or non-fluorinated or fluorinated alkoxyalkyl having 2 to 15 C atoms, wherein one or more CH ₂ -groups may be , , , or substituted, preferably an alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy group having 1 to 7 C atoms, an alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl group having 2 to 7 C atoms, and preferably an alkyl or alkenyl group, and Each occurrence is expressed independently of the other , , , , , or , in which ^RL, identically or differently on each occurrence, represents H or an alkyl radical having 1 to 6 C atoms, or , , , , , , , , , , , , , , , , , , , or , better , , , , , , , , , or , better , , , , , or , L ²¹ and L ²² independently represent H or F, preferably L ²¹ represents F, X ² represents a halogen, a halogenated alkyl or alkoxy group having 1 to 3 C atoms, or a halogenated alkenyl or alkenyloxy group having 2 or 3 C atoms, preferably F, Cl, -OCF ₃ , -O-CH ₂ CF ₃ , -O-CH=CH ₂ , -O-CH=CF ₂ or -CF ₃ , very preferably F, Cl, -O-CH=CF ₂ or -OCF ₃ , m represents 0, 1, 2 or 3, preferably 1 or 2 and particularly preferably 1, R ³ has a ² , i.e. H, non-fluorinated or fluorinated alkyl or non-fluorinated or fluorinated alkoxy having 1 to 17 C atoms, or non-fluorinated or fluorinated alkenyl, non-fluorinated or fluorinated alkenyloxy or non-fluorinated or fluorinated alkoxyalkyl having 2 to 15 C atoms, wherein one or more CH ₂ -groups may be , , , or substituted, preferably an alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy group having 1 to 7 C atoms, an alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl group having 2 to 7 C atoms, and preferably an alkyl or alkenyl group, and Each occurrence has its own unique meaning for the context above. and One of the given meanings and preferably , , , , , , , , , , , , , , or , better , , , , , or , L ³¹ and L ³² independently represent H or F, preferably L ³¹ represents F, X ³ represents a halogen, a halogenated alkyl or alkoxy group having 1 to 3 C atoms, or a halogenated alkenyl or alkenyloxy group having 2 or 3 C atoms, preferably F, Cl, -OCF ₃ , -OCHF ₂ , -O-CH ₂ CF ₃ , -O-CH=CF ₂ , -O-CH=CH ₂ or -CF ₃ , very preferably F, Cl, -O-CH=CF ₂ , -OCHF ₂ or -OCF ₃ , Z ³ represents -CH ₂ CH ₂ -, -CF ₂ CF ₂ -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH ₂ O- or a single bond, preferably -CH ₂ CH ₂ -, -COO-, trans-CH=CH- or a single bond and very preferably -COO-, trans-CH=CH- or a single bond, and n represents 0, 1, 2 or 3, preferably 1, 2 or 3 and particularly preferably 1, and c) one or more compounds selected from the group of compounds of formula IV and V, preferably dielectrically neutral: wherein R ⁴¹ and R ⁴² independently have the meanings indicated above for R ² under formula II, preferably R ⁴¹ represents alkyl and R ⁴² represents alkyl or alkoxy or R ⁴¹ represents alkenyl and R ⁴² represents alkyl, and Independently of each other, and if appears twice, then these are also independent of each other and have the same meaning as above. and One of the given meanings and preferably , , , , , , , , , , , , or , better and One or more of the following indicates , Z ⁴¹ and Z ⁴² independently represent -CH ₂ CH ₂ -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH ₂ O-, -CF ₂ O-, -C≡C- or a single bond, preferably one or more of which represent ^a single bond, and p represents 0, ¹ or 2, preferably 0 or 1, R ⁵¹ and R ⁵² independently have ⁴² and preferably represents an alkyl group having 1 to 7 C atoms, preferably an n-alkyl group, particularly preferably an n-alkyl group having 1 to 5 C atoms, an alkoxy group having 1 to 7 C atoms, preferably an n-alkoxy group, particularly preferably an n-alkoxy group having 2 to 5 C atoms, an alkoxyalkyl group having 2 to 7 C atoms, an alkenyl group or an alkenyloxy group, preferably a group having 2 to 4 C atoms, preferably an alkenyloxy group, to (if any) each independently has and One of the given meanings and preferably , , , , , , , , or , better , , or , better express , and (if present) Better representation , Z ⁵¹ to Z ⁵³ each independently represent -CH ₂ -CH ₂ -, -CH ₂ -O-, -CH=CH-, -C≡C-, -COO- or a single bond, preferably -CH ₂ -CH ₂ -, -CH ₂ -O- or a single bond and particularly preferably a single bond, i and j each independently represent 0 or 1, (i + j) preferably represents 0, 1 or 2, more preferably 0 or 1 and, most preferably 1, d) again as required, alternatively or additionally, one or more compounds selected from the group of compounds of formulae VI to IX, preferably dielectrically negative: wherein R ⁶¹ , R ⁶² , R ⁷¹ , R ⁷² , R ⁸¹ and R ⁸² independently have one of the meanings given above for R ⁴¹ and R ⁴² , preferably R ⁶¹ represents an unsubstituted alkyl group having 1 to 7 C atoms, preferably a straight-chain alkyl group, more preferably a n-alkyl group, most preferably a propyl group or a pentyl group, an unsubstituted alkenyl group having 2 to 7 C atoms, preferably a straight-chain alkenyl group, particularly preferably an unsubstituted alkoxy group having 2 to 5 C atoms, an unsubstituted alkoxy group having 1 to 6 C atoms or an unsubstituted alkenyloxy group having 2 to 6 C atoms, R ⁶² represents an unsubstituted alkyl group having 1 to 7 C atoms, an unsubstituted alkoxy group having 1 to 6 C atoms or an unsubstituted alkenyloxy group having 2 to 6 C atoms, and l represents 0 or 1, R ^{R 71} represents an unsubstituted alkyl group having 1 to 7 C atoms, preferably a straight-chain alkyl group, more preferably a n-alkyl group, most preferably a propyl group or a pentyl group, or an unsubstituted alkenyl group having 2 to 7 C atoms, preferably a straight-chain alkenyl group, particularly preferably a group having 2 to 5 C atoms, R ⁷² represents an unsubstituted alkyl group having 1 to 7 C atoms (preferably a group having 2 to 5 C atoms), an unsubstituted alkoxy group having 1 to 6 C atoms (preferably a group having 1, 2, 3 or 4 C atoms), or an unsubstituted alkenyloxy group having 2 to 6 C atoms (preferably a group having 2, 3 or 4 C atoms), R ^{R 81} represents an unsubstituted alkyl group having 1 to 7 C atoms, preferably a straight-chain alkyl group, more preferably a n-alkyl group, most preferably a propyl group or a pentyl group, or an unsubstituted alkenyl group having 2 to 7 C atoms, preferably a straight-chain alkenyl group, particularly preferably a group having 2 to 5 C atoms, R ⁸² represents an unsubstituted alkyl group having 1 to 7 C atoms (preferably a group having 2 to 5 C atoms), an unsubstituted alkoxy group having 1 to 6 C atoms (preferably a group having 1, 2, 3 or 4 C atoms), or an unsubstituted alkenyloxy group having 2 to 6 C atoms (preferably a group having 2, 3 or 4 C atoms), and express , or , express , or , better or , better , Z ⁸ represents -(C=O)-O-, -CH ₂ -O-, -CF ₂ -O- or -CH ₂ -CH ₂ -, preferably -(C=O)-O- or -CH ₂ -O-, and o represents 0 or 1, R ⁹¹ and R ⁹² independently have the meanings given for R ⁷² above, R ⁹¹ preferably represents an alkyl group having 2 to 5 C atoms, preferably an alkyl group having 3 to 5 C atoms, R ⁹² preferably represents an alkyl group or alkoxy group having 2 to 5 C atoms, more preferably an alkoxy group having 2 to 4 C atoms, or an alkenyloxy group having 2 to 4 C atoms. express or , p and q independently represent 0 or 1, and (p + q) preferably represents 0 or 1, and express or, preferably, p = q = 1, e) again as required, one or more compounds of formula IN having a high dielectric constant perpendicular to the conducting plane and parallel to the conducting plane, preferably in a concentration ranging from 1% to 60%, more preferably in a concentration ranging from 5% to 40%, particularly preferably in a concentration ranging from 8% to 35%, IN where express or , express , , or , n represents 0 or 1, R ¹¹ and R ¹² independently represent preferably an alkyl group, alkoxy group, fluorinated alkyl group or fluorinated alkoxy group having 1 to 7 C atoms, an alkenyl group, alkenyloxy group, alkoxyalkyl group or fluorinated alkenyl group having 2 to 7 C atoms, preferably an alkyl group, alkoxy group, alkenyl group or alkenyloxy group, most preferably an alkyl group, alkoxy group or alkenyloxy group, and R ¹¹ represents either R ¹ and R ¹² represents either X ¹ , R ¹ represents preferably an alkyl group, alkoxy group, fluorinated alkyl group or fluorinated alkoxy group having 1 to 7 C atoms, wherein one -CH ₂ -group may be replaced by cyclopropyl, 1,3-cyclobutyl, 1,3-cyclopentyl, 1,3-cyclopentenyl, preferably by cyclopropyl or 1,3-cyclopentenyl, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms, wherein one -CH ₂ -group may be replaced by cyclopropyl, 1,3-cyclobutyl, 1,3-cyclopentyl, 1,3-cyclopentenyl, preferably by cyclopropyl or 1,3-cyclopentenyl, and preferably alkyl or alkenyl, 1,3-cyclopentenyl is selected from the formula , , , and , better , or ,optimal or and X ¹ represents F, Cl, fluorinated alkyl, fluorinated alkenyl, fluorinated alkoxy or fluorinated alkenyloxy, the latter four groups preferably have 1 to 4 C atoms, preferably F, Cl, CF ₃ or OCF ₃ , in particular for formulas I-1 and I-2, preferably F, and for formula I-4, preferably OCF ₃ and f) again as required, one or more compounds of formula B, which have a high dielectric constant perpendicular to the conducting plane and parallel to the conducting plane, preferably in a concentration ranging from 1% to 60%, more preferably in a concentration ranging from 5% to 40%, particularly preferably in a concentration ranging from 8% to 35%, B where express , express , , , , or , ^RB1 and ^RB2 independently represent an alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy group preferably having 1 to 7 C atoms, wherein one _-CH2- group may be replaced by a cyclopropyl, 1,3-cyclobutyl, 1,3-cyclopentyl or 1,3-cyclopentenyl group, preferably a cyclopropyl or 1,3-cyclopentyl group, an alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl group having 2 to 7 C atoms, wherein one _-CH2 -group may be substituted by cyclopropyl, 1,3-cyclobutyl, 1,3-cyclopentyl, 1,3-cyclopentenyl, preferably by cyclopropyl or 1,3-cyclopentyl, and preferably alkyl, alkoxy, alkenyl or alkenyloxy, most preferably alkyl, alkoxy or alkenyloxy, and n represents 0 or 1, preferably 0. g) Again, if necessary, one or more compounds of formula S having a high dielectric constant perpendicular to the conducting plane and parallel to the conducting plane, preferably in a concentration ranging from 1% to 60%, more preferably from 5% to 40%, particularly preferably from 8% to 35%, S where express , express , , , , or , R ^S1 and R ^S2 independently represent an alkyl group, an alkoxy group, a fluorinated alkyl group or a fluorinated alkoxy group, preferably having 1 to 7 C atoms, wherein one -CH ₂ - group may be replaced by a cyclopropylene, a 1,3-cyclobutylene, a 1,3-cyclopentylene, a 1,3-cyclopentenylene, preferably a cyclopropylene or a 1,3-cyclopentenylene, an alkenyl group, an alkenyloxy group, an alkoxyalkyl group or a fluorinated alkenyl group, preferably by a cyclopropylene or a 1,3-cyclopentylene, wherein one -CH ₂ The - group may be substituted by cyclopropyl, 1,3-cyclobutyl, 1,3-cyclopentyl, 1,3-cyclopentenyl, preferably substituted by cyclopropyl or 1,3-cyclopentyl, and is preferably alkyl, alkoxy, alkenyl or alkenyloxy, most preferably alkyl, alkoxy or alkenyloxy, and n represents 0 or 1, preferably 1.

The liquid crystal medium according to the present application preferably has a nematic phase.

In the compounds of formula I, the group N(R ¹³ )(R ¹⁴ ) may preferably also be an amine.

The following embodiments are preferred: p is 2, is an organic group with 4 binding sites, preferably an alkanetetrayl unit with 1 to 30 C atoms, wherein, in addition to the m groups R ¹² present in the molecule, but independently thereof, another H atom can be replaced by R ¹² or a plurality of other H atoms can be replaced by R ¹² , preferably an alkanetetrayl unit with one or two valences at each of the two terminal C atoms, wherein one -CH ₂ - group or a plurality of -CH ₂ - groups can be replaced by -O- or -(C=O)- in such a way that the two O atoms are not directly bound to one another, or a substituted or unsubstituted aromatic or heteroaromatic hydrocarbon group with up to 8 valences, wherein, in addition to the m groups R ¹² present in the molecule, but independently thereof, another H atom can be replaced by R ¹² or a plurality of other H atoms can be replaced by R ¹² , express , (Biphenyl-1,1',3,3'-tetrayl), (benzene-1,2,4,5-tetrayl), >CH-[CH ₂ ] _r -CH< (where r {0, 1, 2, 3, 4, 5 to 18}, -CH ₂ -(CH-)-[CH ₂ ] _q -(CH-)-CH ₂ -< (where q {0, 1, 2, 3, 4, 5 to 16}, express (Benzene-1,3,5-triyl), (benzene-1,2,4-triyl) or >CH-[CH ₂ ] _r -CH ₂ - (where r {0, 1, 2, 3, 4, 5 to 18}) or represents -CH ₂ -[CH ₂ ] _r -CH ₂ - (where r {0, 1, 2, 3, 4, 5 to 18}), octane-1,8-diyl, heptane-1,7-diyl, hexane-1,6-diyl, pentane-1,5-diyl, butane-1,4-diyl, propane-1,3-diyl, ethane-1,2-diyl, or (1,4-phenylene), (1,3-phenylene), (1,2-phenylene) or (1,4-cyclohexylene).

In an alternative preferred embodiment, p represents 1.

In the present application, the elements all include their individual isotopes. In particular, one or more H in the compounds may be replaced by D, and this is also particularly preferred in some embodiments. The corresponding high degree of deuteration of the corresponding compounds makes it possible, for example, to detect and identify these compounds. This is very helpful in some cases, in particular in the case of compounds of formula I.

In the present application, alkyl particularly preferably represents a straight chain alkyl, specifically CH ₃ -, C ₂ H ₅ -, n-C ₃ H ₇ -, n-C ₄ H ₉ - or n-C ₅ H ₁₁ -, and alkenyl particularly preferably represents CH ₂ =CH-, E-CH ₃ -CH=CH-, CH ₂ =CH-CH ₂ -CH ₂ -, E-CH ₃ -CH=CH-CH ₂ -CH ₂ - or E-(n-C ₃ H ₇ )-CH=CH-.

The liquid crystal medium according to the present application preferably comprises a total of 1 ppm to 2500 ppm, preferably 1 ppm to 1500 ppm, preferably 1 to 600 ppm, even more preferably 1 to 250 ppm, preferably to 200 ppm and very particularly preferably 1 ppm to 100 ppm of the compound of formula I.

In a preferred embodiment of the present invention, in the compound of formula I, express , (biphenyl-1,1',3,3'-tetrayl) or (Benzene-1,2,4,5-tetrayl), express (Benzene-1,3,5-triyl) or (Benzene-1,2,4-triyl), represents -(CH ₂ -) ₂ , -(CH ₂ -) ₃ , -(CH ₂ -) ₄ , -(CH ₂ -) ₅ , -(CH ₂ -) ₆ , -(CH ₂ -) ₇ , -(CH ₂ -) ₈ , that is, ethane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, (1,4-phenylene), (1,3-phenylene), (1,2-phenylene) or (trans-1,4-cyclohexylene), and/or -Z ¹² -S ¹¹ -Z ¹¹ - independently represents -O-, S ¹¹ -O-, -OS ¹¹ -O-, -(C=O)-OS 11 -O-, -O-(C=O)-S ¹¹ -O-, -O-(C=O)-S ¹¹ -(C=O)-O-, -OS ¹¹ -(C=O)-O-, -(C=O)-OS ¹¹ -C, -(C=O)-OS ¹¹ -O-(C=O)- or -(NR ¹³ )-S ¹¹ -O-, -(NR ¹³ -C(=O)-S ¹¹ -(C=O)-O or a single bond at each occurrence, preferably -O-, -S ^{11 -O-} , -OS ¹¹ -O-, -(C=O)-OS ¹¹ -O-, -O-(C=O)-S ¹¹ -O- or -OS ¹¹ -(C=O)-O-, and/or S ¹¹ preferably represents an alkylene group having 1 to 20 C atoms, and/or R ¹¹ (if present) represents alkyl, alkoxy or H, preferably H or alkyl, and/or R ¹² represents H, methyl, ethyl, propyl, isopropyl or 3-heptyl or cyclohexyl.

In one preferred embodiment of the present application, in the compound of formula I, Indicates the selected , , , , , or A group of compounds.

In one preferred embodiment of the present application, in the compound of formula I, Indicates the selected , or The base group of the group.

In a preferred embodiment of the present application, in the compound of formula I, wherein p preferably represents 1, express , preferably -OS ¹¹ -O-, -S ¹¹ -O- or -OS ¹¹ -, particularly preferably -OS ¹¹ -O- or -S ¹¹ -O-.

In another preferred embodiment of the present application, in the compound of formula I, the group Preferred expression selection , , , or The base group of the group.

In another preferred embodiment of the present application, wherein p is 2, which may be the same as or different from those described above, in the compound of formula I, Preferred expression selection , and The base group of the group.

In another preferred embodiment of the present invention, which may be the same as or different from those described above, in the compound of formula I, the group Each occurrence is expressed independently of the other , , or , better or .

In a particularly preferred embodiment of the present invention, in the compound of formula I, all groups present have the same meaning.

These compounds are highly suitable as stabilizers in liquid crystal mixtures. In particular, the compounds stabilize the VHR of the mixtures against UV exposure.

In a preferred embodiment of the invention, the medium according to the invention comprises in each case one or more compounds of the formula I selected from the group of compounds of the following formulae I-1 to I-13, preferably from the group of compounds of the formulae I-3, I-5, I-6, I-7, I-8, I-9, I-10, I-12 and I-13, particularly preferably from the group of compounds of the formulae I-6 to I-10 and very particularly preferably from the group of compounds of the formula I-10, I-1 I-2 I-3 I-4 I-5 I-6 I-7 and I-8 I-9 I-10 I-11 I-12 I-13.

In an even better embodiment of the invention, the medium according to the invention comprises in each case one or more compounds of the formula I selected from the group of compounds of the following formulae I-1 and/or I-3 to I-8 and/or I-9 and/or I-10.

In an even more preferred embodiment of the invention, the medium according to the invention comprises in each case one or more compounds of the formula I selected from the group of compounds of the following formulae I-9 and/or I-10.

In addition to the compound of formula I or its preferred subformulae, the medium according to the present invention preferably contains one or more compounds of formula II in a total concentration ranging from 1% or more to 90% or less, preferably from 10% or more to 80% or less, particularly preferably from 20% or more to 70% or less.

In a preferred embodiment of the present invention, the liquid crystal medium comprises one or more preferably dielectrically positive compounds, preferably compounds having 3 or more dielectric anisotropies, selected from the group of compounds of formula II-1 and II-2: II-1 II-2 wherein the parameters have the respective meanings indicated above under formula II, and L ²³ and L ²⁴ independently of one another represent H or F, preferably L ²³ represents F, and Targeted Any of the meanings given, and in the case of formula II-1 and II-2, X ² preferably represents F or OCF ₃ , particularly preferably F, and in the case of formula II-2, and Better representation independently or .

In addition to the compound of formula I or its preferred subformulae, the medium according to the present invention preferably contains one or more compounds of formula III in a total concentration ranging from 1% or more to 40% or less, preferably from 3% or more to 20% or less, particularly preferably from 4% or more to 10% or less.

The compound of formula III is preferably selected from the group of compounds of formula III-1 and III-2: III-1 III-2 wherein the parameters have the meanings given under formula III, and the medium according to the invention may comprise, alternatively or in addition to compounds of formula III-1 and/or III-2, one or more compounds of formula III-3 III-3 wherein the parameters have the individual meanings indicated above, and the parameters L ³¹ and L ³² independently of each other and independently of the other parameters represent H or F.

The liquid crystal medium preferably comprises a compound selected from the group of compounds of formulae II-1 and II-2, wherein L ²¹ and L ²² and/or L ²³ and L ²⁴ both represent F.

In a preferred embodiment, the liquid crystal medium comprises a compound selected from the group of compounds of formulae II-1 and II-2, wherein L ²¹ , L ²² , L ²³ and L ²⁴ all represent F.

The liquid crystal medium preferably comprises one or more compounds of formula II-1. The compound of formula II-1 is preferably selected from the group of compounds of formula II-1a to II-1e, preferably one or more compounds of formula II-1a and/or II-1b and/or II-1d, preferably compounds of formula II-1a and/or II-1d or II-1b and/or II-1d, and most preferably compounds of formula II-1d: II-1a II-1b II-1c II-1d II-1e, wherein the parameters have the individual meanings indicated above, and L ²⁵ and L ²⁶ independently of each other and independently of the other parameters represent H or F, and preferably in formulas II-1a and II-1b, L ²¹ and L ²² both represent F, in formulas II-1c and II-1d, L ²¹ and L ²² both represent F and/or L ²³ and L ²⁴ both represent F, and in formula II-1e, L ²¹ , L ²² and L ²³ represent F.

The liquid crystal medium preferably comprises one or more compounds of formula II-2, which are preferably selected from the group of compounds of formula II-2a to II-2k, preferably each having one or more compounds of formula II-2a and/or II-2h and/or II-2j: II-2a II-2b II-2c II-2d II-2e II-2f II-2g II-2h II-2i II-2j II-2k wherein the parameters have the individual meanings indicated above, and L ²⁵ to L ²⁸ independently of one another represent H or F, preferably L ²⁷ and L ²⁸ both represent H, particularly preferably L ²⁶ represents H.

The liquid crystal medium preferably comprises a compound selected from the group of compounds of formulae II-1a to II-1e, wherein L ²¹ and L ²² both represent F and/or L ²³ and L ²⁴ both represent F.

In a preferred embodiment, the liquid crystal medium comprises a compound selected from the group of compounds of formulae II-2a to II-2k, wherein L ²¹ , L ²² , L ²³ and L ²⁴ all represent F.

Particularly preferred compounds of formula II-2 are compounds of the following formula, and particularly preferred compounds are compounds of formula II-2a-1 and/or II-2h-1 and/or II-2k-2: II-2a-1 II-2c-1 II-2d-1 II-2e-1 II-2f-1 II-2h-1 II-2i-1 II-2i-2 II-2j-1 II-2k-1 II-2k-2 wherein R ² and X ² have the meanings indicated above, and X ² preferably represents F.

The liquid crystal medium preferably comprises one or more compounds of formula III-1. The compound of formula III-1 is preferably selected from the group of compounds of formula III-1a to III-1j, preferably selected from compounds of formula III-1c, III-1f, III-1g and III-1j: III-1a III-1b III-1c III-1d III-1e III-1f III-1g III-1h III-1i III-1j wherein the parameters have the meanings given above and preferably wherein the parameters have the individual meanings indicated above, parameters L ³⁵ and L ³⁶ independently of one another and independently of the other parameters denote H or F, and parameters L ³⁵ and L ³⁶ independently of one another and independently of the other parameters denote H or F.

The liquid crystal medium preferably comprises one or more compounds of formula III-1c, which are preferably selected from the group of compounds of formula III-1c-1 to III-1c-5, preferably compounds of formula III-1c-1 and/or III-1c-2, and most preferably compounds of formula III-1c-1: III-1c-1 III-1c-2 III-1c-3 III-1c-4 III-1c-5 wherein R ³ has the meaning indicated above.

The liquid crystal medium preferably comprises one or more compounds of formula III-1f, which are preferably selected from the group of compounds of formula III-1f-1 to III-1f-6, preferably compounds of formula III-1f-1 and/or III-1f-2 and/or III-1f-3 and/or III-1f-6, more preferably compounds of formula III-1f-3 and/or III-1f-6, more preferably compounds of formula III-1f-6: III-1f-1 III-1f-2 III-1f-3 III-1f-4 III-1f-5 III-1f-6 wherein R ³ has the meaning indicated above.

The liquid crystal medium preferably comprises one or more compounds of formula III-1g, which are preferably selected from the group consisting of compounds of formula III-1g-1 to III-1g-5, preferably compounds of formula III-1g-3: III-1g-1 III-1g-2 III-1g-3 III-1g-4 III-1g-5 wherein R ³ has the meaning indicated above.

The liquid crystal medium preferably comprises one or more compounds of formula III-1h, which are preferably selected from the group consisting of compounds of formula III-1h-1 to III-1h-3, preferably compounds of formula III-1h-3: III-1h-1 III-1h-2 III-1h-3 wherein the parameters have the meanings given above, and X ³ preferably represents F.

The liquid crystal medium preferably comprises one or more compounds of formula III-1i, which are preferably selected from the group of compounds of formula III-1i-1 and III-1i-2, preferably compounds of formula III-1i-2: III-1i-1 III-1i-2 wherein the parameters have the meanings given above, and X ³ preferably represents F.

The liquid crystal medium preferably comprises one or more compounds of formula III-1j, which are preferably selected from the group of compounds of formula III-1j-1 and III-1j-2, preferably the compound of formula III-1j-1: III-1j-1 III-1j-2 where the parameters have the meanings given above.

The liquid crystal medium preferably comprises one or more compounds of formula III-2. The compound of formula III-2 is preferably selected from the group consisting of compounds of formula III-2a and III-2b, preferably the compound of formula III-2b: III-2a III-2b wherein the parameters have the individual meanings indicated above, and the parameters L ³³ and L ³⁴ independently of each other and independently of the other parameters denote H or F.

The liquid crystal medium preferably comprises one or more compounds of formula III-2a, which are preferably selected from the group consisting of compounds of formulae III-2a-1 to III-2a-6: III-2a-1 III-2a-2 III-2a-3 III-2a-4 III-2a-5 III-2a-6 wherein R ³ has the meaning indicated above.

The liquid crystal medium preferably comprises one or more compounds of formula III-2b, which are preferably selected from the group consisting of compounds of formulae III-2b-1 to III-2b-4, preferably compound III-2b-4: III-2b-1 III-2b-2 III-2b-3 III-2b-4 wherein R ³ has the meaning indicated above.

Alternatively or in addition to the compounds of formula III-1 and/or III-2, the medium according to the invention may comprise one or more compounds of formula III-3: III-3 wherein the parameters have the respective meanings indicated above under formula III.

These compounds are preferably selected from the group consisting of formula III-3a and III-3b: III-3a III-3b wherein R ³ has the meaning indicated above.

The liquid crystal medium according to the present invention preferably comprises one or more dielectrically neutral compounds, preferably having a dielectric anisotropy in the range from -1.5 to 3, preferably selected from the group of compounds of formulae VI, VII, VIII and IX.

In the present application, the elements all include their individual isotopes. In particular, one or more H in the compounds may be replaced by D, and this is also particularly preferred in some embodiments. The corresponding high degree of deuteration of the corresponding compounds makes it possible, for example, to detect and identify these compounds. This is very helpful in some cases, in particular in the case of compounds of formula I.

In the present application, alkyl particularly preferably represents a straight chain alkyl, specifically CH ₃ -, C ₂ H ₅ -, n-C ₃ H ₇ -, n-C ₄ H ₉ - or n-C ₅ H ₁₁ -, and alkenyl particularly preferably represents CH ₂ =CH-, E-CH ₃ -CH=CH-, -CH ₂ =CH-CH ₂ -CH ₂ -, E-CH ₃ -CH=CH-CH ₂ -CH ₂ - or E-(n-C ₃ H ₇ )-CH=CH-.

In a preferred embodiment of the present invention, the medium according to the present invention comprises one or more compounds of formula B, preferably compounds of formula B-1, preferably in a concentration of 1% to 20%, particularly preferably 2% to 15% and very particularly preferably 3% to 9%, B-1 in which the parameters have the respective meanings given above under formula B and preferably ^RB1 and ^RB2 in each case independently of one another represent unsubstituted alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 7 C atoms, or alkenyl or alkenyloxy having 2 to 7 C atoms, preferably both represent alkoxy, and ^LB1 and ^LB2 in each case independently of one another represent F or Cl, preferably F.

In a particularly preferred embodiment, the medium according to the present invention comprises one or more compounds selected from the group of compounds of formula OH-1 to OH-6, OH-1 OH-2 OH-3 OH-4 OH-5 OH-6 These compounds are highly suitable for stabilizing media against thermal loads.

In another preferred embodiment of the invention, in which the medium according to the invention comprises (in particular) one or more compounds of formula I, in which p is 2 and n is 2, 3 or 4, preferably 2 or 3, particularly preferably 3, these media have excellent stability.

In a further preferred embodiment of the invention, the media according to the invention comprise in each case at least one or more compounds of the formula I, in which p is 1 and n is 3, 4, 5 or 6, preferably 4, and the group -Z ¹¹ -S ¹¹ -Z ¹² - represents ω-bisoxyalkylene, i.e. -OS ¹¹ -O-. Such media have excellent stability.

The invention also relates to an electro-optical display or an electro-optical component containing a liquid crystal medium according to the invention. Preference is given to electro-optical displays based on the IPS, FFS, VA or ECB effect, preferably on the IPS or FFS effect, and in particular those which are addressed by means of an active matrix addressing device.

Therefore, the present invention also relates to the use of the liquid crystal medium according to the present invention in an electro-optical display or an electro-optical component, and to a method for preparing the liquid crystal medium according to the present invention, characterized in that one or more compounds of formula I are mixed with one or more compounds of formula II, preferably with one or more compounds of sub-formula II-1, and with one or more other compounds, preferably selected from the group of compounds of formula III and IV and/or V and/or VI to IX and/or IN and/or B and/or S.

Furthermore, the present invention relates to a method for stabilizing a liquid crystal medium comprising one or more compounds of formula II and one or more compounds selected from the group of compounds of formulae III to IX, B, S and IN, characterized in that one or more compounds of formula I are added to the medium.

In a particularly preferred embodiment, the medium comprises one or more compounds of formula IV, which are selected from the group consisting of compounds of formula IV-1 to IV-4, preferably compounds of formula IV-1 and/or IV-2: wherein alkyl and alkyl' independently represent an alkyl group having 1 to 7 C atoms, preferably 2 to 5 C atoms, alkenyl and alkenyl' independently represent an alkenyl group having 2 to 5 C atoms, preferably 2 to 4 C atoms, particularly preferably 2 C atoms, alkenyl' represents an alkenyl group having 2 to 5 C atoms, preferably 2 to 4 C atoms, particularly preferably 2 to 3 C atoms, and alkoxy represents an alkoxy group having 1 to 5 C atoms, preferably 2 to 4 C atoms.

In a particularly preferred embodiment, the medium according to the present invention comprises one or more compounds of formula IV-1 and/or one or more compounds of formula IV-2. Particularly preferred compounds of formula IV-1 are selected from the group consisting of the following compounds: wherein alkyl has the meaning given above and preferably, in each case independently of one another, denotes alkyl having 1 to 6, preferably 2 to 5, C atoms and particularly preferably n-alkyl.

Particularly preferred compounds of formula IV are selected from the group consisting of compounds of the following formulae:

In another preferred embodiment, the medium comprises one or more compounds of formula V, which are selected from the group of compounds of formula V-1 to V-11, preferably selected from the group of compounds of formula V-1 to V-5: wherein the parameters have the meanings given above under formula V, and Y ⁵ represents H or F, and preferably R ⁵¹ represents alkyl having 1 to 7 C atoms or alkenyl having 2 to 7 C atoms, and R ⁵² represents alkyl having 1 to 7 C atoms, alkenyl having 2 to 7 C atoms or alkoxy having 1 to 6 C atoms, preferably alkyl or alkenyl, particularly preferably alkenyl.

In another preferred embodiment, the medium comprises one or more compounds of formula V-1 selected from the group consisting of compounds of formula V-1a and V-1b, preferably compounds of formula V-1b: wherein alkyl and alkyl' independently represent an alkyl group having 1 to 7 C atoms, preferably 2 to 5 C atoms, and alkoxy represents an alkoxy group having 1 to 5 C atoms, preferably 2 to 4 C atoms.

In another preferred embodiment, the medium comprises one or more compounds of formula V-3 selected from the group consisting of compounds of formula V-3a and V-3b: wherein alkyl and alkyl' independently represent an alkyl group having 1 to 7 C atoms, preferably 2 to 5 C atoms, and alkenyl represents an alkenyl group having 2 to 7 C atoms, preferably 2 to 5 C atoms.

In another preferred embodiment, the medium comprises one or more compounds of formula V-4 selected from the group consisting of compounds of formula V-4a and V-4b: wherein alkyl and alkyl' independently represent an alkyl group having 1 to 7 C atoms, preferably 2 to 5 C atoms.

In another preferred embodiment, the medium comprises one or more compounds of formula V-5 selected from the group consisting of compounds of formula V-5a to V-5d, preferably compounds of formula V-5a and/or V-5b: wherein alkyl and alkyl' independently represent an alkyl group having 1 to 7 C atoms, preferably 2 to 5 C atoms, and alkenyl and alkenyl' independently represent an alkenyl group having 2 to 5 C atoms, preferably 2 to 4 C atoms, particularly preferably 4 C atoms.

The liquid crystal medium according to the present invention may comprise one or more chiral compounds.

Particularly preferred embodiments of the present invention satisfy one or more of the following conditions, wherein the abbreviations are explained in Tables A to C and illustrated by the examples in Table D. i. The liquid crystal medium has a birefringent index of 0.060 or more, particularly preferably 0.070 or more. ii. The liquid crystal medium has a birefringent index of 0.130 or less, particularly preferably 0.120 or less. iii. The liquid crystal medium has a birefringent index in the range of from 0.090 or more to 0.120 or less. iv. The liquid crystal medium has a negative dielectric anisotropy having a value of 2.0 or more, particularly preferably 3.0 or more. v. The liquid crystal medium has a negative dielectric anisotropy having a value of 5.5 or less, particularly preferably 5.0 or less. vi. The liquid crystal medium has a negative dielectric anisotropy having a value in the range of 3.6 or more to 5.2 or less. vii. The total concentration of the compound of formula II in the mixture as a whole is 25% or more, preferably 30% or more, and preferably in the range of 25% or more to 49% or less, particularly preferably in the range of 29% or more to 47% or less, and very particularly preferably in the range of 37% or more to 44% or less. viii. The liquid crystal medium comprises one or more compounds of formula IV selected from the group of compounds of the following formulae: CC-n-V and/or CC-n-Vm, particularly preferably CC-3-V, preferably in a concentration of up to 50% or less, particularly preferably up to 42% or less, and optionally additionally CC-3-V1, preferably in a concentration of up to 15% or less, and/or CC-4-V, preferably in a concentration of up to 20% or less, particularly preferably up to 10% or less. ix. The total concentration of the compounds of formula CC-3-V in the mixture as a whole is 20% or more, preferably 25% or more. x. The proportion of the compounds of formula II and III in the mixture as a whole is 10% or more and preferably 75% or less. xi. The liquid crystal medium is essentially composed of compounds of formula I, II, III, IV, V and B and/or S, preferably of compounds of formula I, II, III, IV, V and S.

Furthermore, the invention relates to an electro-optical display with active matrix addressing based on the VA or ECB effect, which is characterized in that it contains a liquid crystal medium according to the invention as dielectric.

The liquid crystal mixture preferably has a nematic phase range having a width of at least 80 degrees and a flow viscosity ν ₂₀ of at most 30 mm ² · s ^-1 at 20°C.

The liquid crystal mixtures according to the invention have a Δε, where Δε denotes the dielectric anisotropy, of -0.5 to -8.0, in particular -1.5 to -6.0 and very particularly preferably -2.0 to -5.0.

The rotational viscosity _γ1 is preferably 150 mPa·s or less, particularly 120 mPa·s or less and very particularly preferably 120 mPa·s or less.

The mixtures according to the invention are suitable for all IPS and FFS-TFT applications. Furthermore, they are suitable for all VA applications, such as, for example, VAN, MVA, (S)-PVA and ASV applications, and PALC applications with negative Δε.

The nematic liquid crystal mixture in the display according to the invention generally comprises two components A and B, which themselves consist of one or more individual compounds.

The liquid crystal medium according to the present invention preferably comprises 4 to 15, in particular 5 to 12, and particularly preferably 10 or less compounds, which are preferably selected from the group of compounds of formula I, II and III-1 to III-4, and/or IV and/or V.

The liquid crystal medium according to the present invention may also contain more than 18 compounds as required. In this case, it preferably contains 18 to 25 compounds.

In addition to the compounds of formulae I to V, further components may also be present, for example in an amount of up to 45%, but preferably up to 35%, in particular up to 10% of the mixture as a whole.

The medium according to the present invention may also contain a dielectrically positive component as needed, the total concentration of which is preferably 10% or less based on the entire medium.

In a preferred embodiment, the liquid crystal medium according to the present invention contains a total of 100 ppm or more to 2500 ppm or less, preferably 300 ppm or more to 2000 ppm or less, particularly preferably 500 ppm or more to 1500 ppm or less and very particularly preferably 700 ppm or more to 1200 ppm or less of the compound of formula I, 20% or more to 60% or less, preferably 25% or more to 50% or less, particularly preferably 30% or more to 45% or less of the compound of formula II, and 50% or more to 70% or less of the compound of formula I to IX and/or IN and/or B and or S, based on the mixture as a whole.

In a preferred embodiment, the liquid crystal medium according to the present invention comprises one or more compounds selected from the group of compounds of formula II, III, IV, V, VI, VII, VIII and IX, preferably selected from the group of compounds of formula II and/or III and/or IV and/or V, which contain one or more rings independent of each other, which are selected from the following groups: substituted 1,4-phenylene, , , and .

In a particularly preferred embodiment of the preferred embodiments above, the liquid crystal medium according to the present invention comprises one or more compounds selected from the group consisting of the following compounds: .

In a preferred embodiment, the liquid crystal medium according to the invention comprises one or more compounds selected from the group of compounds of formulae II, III, IV, V, VI, VII, VIII and IX, preferably selected from the group of compounds of formulae II and/or III and/or IV and/or V, which comprise one terminal group or, if present, two terminal groups, preferably one terminal group, selected from the group of terminal groups: 3-fluoro-propyl, cyclopropyl, cyclopropylmethyl, 2-cyclopropylethyl, cyclobutyl, cyclobutylmethyl, cyclopentyl and cyclopentylmethyl, preferably selected from 3-fluoro-propyl, cyclopropyl, cyclopropylmethyl, 2-cyclopropylethyl, cyclobutylmethyl and cyclopentylmethyl.

In a particularly preferred embodiment of the preferred embodiments above, the liquid crystal medium according to the present invention comprises one or more compounds selected from the group consisting of the following compounds: .

In a preferred embodiment, the liquid crystal medium according to the present invention comprises a compound selected from the group of compounds of formula I, II, III, IV, V, In, B and S, preferably selected from the group of compounds of formula I, II and/or III and/or B and/or S; preferably, it mainly consists of compounds of said formula, particularly preferably, it is essentially composed of compounds of said formula and very particularly preferably, it is actually completely composed of compounds of said formula.

The liquid crystal medium according to the invention preferably has a nematic phase in each case from at least -20°C or lower to 70°C or higher, particularly preferably from -30°C or lower to 80°C or higher, very particularly preferably from -40°C or lower to 85°C or higher and most preferably from -40°C or lower to 90°C or higher.

The expression "having a nematic phase" here means on the one hand that at low temperatures no smectic phase and no crystallization is visible at the corresponding temperature and on the other hand that no clearing occurs on heating of the nematic phase. The investigations at low temperatures are carried out in a flow viscometer at the corresponding temperature and checked by storage for at least 100 hours in a test cell having a cell thickness corresponding to that for optoelectronic applications. If the storage stability at a temperature of -20°C in a corresponding test cell is 1000 h or more, the medium is considered stable at this temperature. At temperatures of -30°C and -40°C, the corresponding times are 500 h and 250 h, respectively. At high temperatures, the clearing point is measured in a capillary by known methods. In addition, the shelf life of bulk (1 mL sample) at low temperature is measured in glass vials at -20°C or -30°C. At these temperatures, preferably at -30°C, the stable shelf life is preferably 120 h or more, particularly preferably more than 240 h.

In a preferred embodiment, the liquid crystal medium according to the invention is characterized by an optical anisotropy value in the medium to low range. The birefringence value is preferably in the range from 0.065 or more to 0.130 or less, particularly preferably in the range from 0.080 or more to 0.120 or less and very particularly preferably in the range from 0.085 or more to 0.110 or less.

In this embodiment, the liquid crystal medium according to the present invention has a negative dielectric anisotropy and a relatively high absolute value of dielectric anisotropy (|Δε|), which are preferably in the range of from 2.7 or greater to 5.3 or less, preferably to 4.5 or less, preferably from 2.9 or greater to 4.5 or less, particularly preferably from 3.0 or greater to 4.0 or less and very particularly preferably from 3.5 or greater to 3.9 or less.

The liquid crystal medium according to the present invention has a relatively low value of the threshold voltage (V 0 ) in the range from 1.7 V or more to 2.5 V or less, preferably from 1.8 V or more to 2.4 V or less, particularly preferably from 1.9 V or more to 2.3 V or less and very particularly preferably from 1.95 V or more to _2.1 V or less.

In another preferred embodiment, the liquid crystal medium according to the present invention preferably has a relatively low value of the average dielectric anisotropy (ε _av. ≡ (ε _|| + 2ε _┴ )/3), which is preferably in the range of from 5.0 or greater to 7.0 or less, preferably from 5.5 or greater to 6.5 or less, still more preferably from 5.7 or greater to 6.4 or less, particularly preferably from 5.8 or greater to 6.2 or less and very particularly preferably from 5.9 or greater to 6.1 or less.

In addition, the liquid crystal medium according to the present invention has a high VHR value in the liquid crystal cell.

In freshly filled cells at 20° C. in the cell these are preferably greater than or equal to 95%, preferably greater than or equal to 97%, particularly preferably greater than or equal to 98% and very particularly preferably greater than or equal to 99%, and after 5 minutes in an oven at 100° C. in the cell these are greater than or equal to 90%, preferably greater than or equal to 93%, particularly preferably greater than or equal to 96% and very particularly preferably greater than or equal to 98%.

In general, liquid crystal media having low addressing voltages or threshold voltages here have lower VHRs than those having higher addressing voltages or threshold voltages, and vice versa.

These preferred values for the individual physical properties are preferably also maintained in each case by the media according to the invention in combination with one another.

In this application, unless otherwise expressly indicated, the term "compounds" (also written as "compound(s)") means one or more compounds.

Unless otherwise indicated, the individual compounds are generally used in a mixture in a concentration of from 1% or more to 30% or less, preferably from 2% or more to 30% or less and particularly preferably from 3% or more to 16% or less.

In a preferred embodiment, the liquid crystal medium according to the invention comprises one or more compounds of formula I and one or more compounds of formula IV, which are preferably selected from the group of compounds of formula CC-n-V and CC-n-Vm, preferably CC-3-V, CC-3-V1, CC-4-V and CC-5-V, particularly preferably selected from the group of compounds CC-3-V, CC-3-V1 and CC-4-V, very particularly preferably compound CC-3-V, and optionally further compounds CC-4-V and/or CC-3-V1.

In a preferred embodiment, the liquid crystal medium according to the present invention comprises: one or more compounds of formula I and/or one or more compounds of formula II, preferably compounds of formula PUQU-n-F, CDUQU-n-F, APUQU-n-F, DPUQU-n-F and PGUQU-n-F, and/or one or more compounds of formula III, preferably compounds of formula CCG-n-FCCP-n-OT, CLP-n-T, CGG-n-F, CGG-n-OD and PPGU-n-F and/or one or more compounds of formula IV, preferably compounds of formula CC-n-V, CC-n-Vm, CC-n-m, CC-V-V, CCVC-n-V and/or one or more compounds of formula V, preferably compounds of formula Compounds of formula CP-n-Om, CCP-n-m, CCP-V-n, CCP-V2-n, CLP-V-n, CCVC-n-V, CGP-n-m, PGP-n-m, PGP-n-mV and CPGP-n-m and/or, preferably, if necessary, one or more compounds of formula VI, preferably compounds of formula Y-n-Om, Y-nO-Om and/or CY-n-Om, which are selected from the group of compounds of formula Y-3-O1, Y-4O-O4, CY-3-O2, CY-3-O4, CY-5-O2 and CY-5-O4, and/or, preferably, if necessary, one or more compounds of formula VII-1, which are preferably selected from the group of compounds of formula CCY-n-m and C A group of compounds of formula CY-n-Om, preferably a compound of formula CCY-n-Om, which is preferably selected from the group of compounds of formula CCY-3-O2, CCY-2-O2, CCY-3-O1, CCY-3-O3, CCY-4-O2, CCY-3-O2 and CCY-5-O2, and/or, as necessary, preferably mandatory, one or more compounds of formula VII-2, preferably a compound of formula CLY-n-Om, which is preferably selected from the group of compounds of formula CLY-2-O4, CLY-3-O2, CLY-3-O3, and/or one or more compounds of formula VIII, preferably compounds of formula CZY-n-On and CCOY-n-m and/or one or more compounds of formula IX, which are preferably selected From the group of compounds of the formula PYP-n-m and PGIY.n-Om and/or one or more compounds of the formula B and/or one or more compounds of the formula S and/or, if necessary, preferably mandatory, one or more compounds of the formula IV, which are preferably selected from the group of compounds of the formula CC-n-V, CC-n-Vm and CC-nV-Vm, preferably CC-3-V, CC-3-V1, CC-4-V, CC-5-V and CC-V-V, which are particularly preferably selected from the group of compounds CC-3-V, CC-3-V1, CC-4-V and CC-V-V, very particularly preferably compound CC-3-V, and, if necessary, further compounds CC-4-V and/or CC-3-V1 and/or CC-V-V.

In a particularly preferred embodiment of the invention, the medium according to the invention comprises one or more compounds of the formula PPGU-n-F. Compounds of the formula PPGU-n-F are also highly suitable as stabilizers in liquid crystal mixtures.

In a particularly preferred embodiment of the present invention, the medium according to the invention comprises one or more compounds of formula IX.

The compounds of formula IX are also highly suitable as stabilizers in liquid crystal mixtures, especially in the case of p = q = 1 and ring A ⁹ = 1,4-phenylene. In particular, they stabilize the VHR of these mixtures against UV exposure.

In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula IX, which are selected from the group of formulae IX-1 to IX-4, very preferably one or more of the group of compounds of formulae IX-1 to IX-3, wherein the parameters have the meanings given under formula IX and F/H means F or H.

In another preferred embodiment, the medium comprises one or more compounds of formula IX-3, preferably compounds of formula IX-3-a: wherein alkyl and alkyl' independently represent an alkyl group having 1 to 7 C atoms, preferably 2 to 5 C atoms.

In case the compounds of formula IX are used in the liquid crystal medium according to the present application, they are preferably present in a concentration of 20% or less, more preferably 10% or less, and most preferably 5% or less, and in case of individual, i.e. (homologous) compounds, they are preferably present in a concentration of 10% or less, and more preferably 5% or less.

For the purposes of the present invention, unless otherwise indicated in individual cases, the following definitions of the description of the composition of the combination apply: - "comprising": the concentration of the said component in the composition is preferably 5% or more, particularly preferably 10% or more, very particularly preferably 20% or more, - "consisting mainly of": the concentration of the said component in the composition is preferably 50% or more, particularly preferably 55% or more and very particularly preferably 60% or more, - "consisting essentially of": the concentration of the said component in the composition is preferably 80% or more, particularly preferably 90% or more and very particularly preferably 95% or more, and - “Consisting substantially entirely of…”: The concentration of the ingredient in the composition is preferably 98% or greater, particularly preferably 99% or greater and very particularly preferably 100.0%.

This applies both to the medium in which the composition is present and its components (which may be components and compounds), and also to the components and their components (compounds). With regard only to the concentration of the individual compound relative to the medium as a whole, the term inclusive means that the concentration of the compound is preferably 1% or more, particularly preferably 2% or more, very particularly preferably 4% or more.

In the context of the present invention, “≤” means less than or equal to, preferably less than, and “≥” means greater than or equal to, preferably greater than.

In the context of the present invention, , and represents trans-1,4-cyclohexylene, represents 1,4-cyclohexylene, preferably trans-1,4-cyclohexylene, and and It represents 1,4-phenylene.

For the purposes of the present invention, the expression "dielectrically positive compounds" means compounds having a Δε> 1.5, the expression "dielectrically neutral compounds" generally means those for which -1.5 ≤ Δε ≤ 1.5 and the expression "dielectrically negative compounds" means those for which Δε < -1.5. The dielectric anisotropy of the compounds is determined herein by dissolving 10% of the compound in a liquid crystal host and measuring the capacitance of the resulting mixture in each case in at least one test cell with a cell thickness of 20 µm with homeotropic and uniform surface alignment at a temperature of 20° C. and a frequency of 1 kHz. The measuring voltage is typically 1.0 V, but is always below the capacitance threshold for the individual liquid crystal mixtures investigated.

The host mixtures used for dielectrically positive and dielectrically neutral compounds were ZLI-4792 and for dielectrically negative compounds were ZLI-2857, both from Merck KGaA, Germany. The values for the individual compounds to be investigated were obtained from the change in the dielectric constant of the host mixture after addition of the compound to be investigated and extrapolated to 100% of the compound employed. The compound to be investigated was dissolved in the host mixture in an amount of 10%. If the solubility of the substance was too low for this purpose, the concentration was halved stepwise until the investigation could be carried out at the desired temperature.

The compounds of formula I according to the invention or to be employed according to the invention can advantageously be prepared according to the following reaction schemes.

Synthesis Scheme 1 Herein, n is preferably 2, 3 or 4, particularly preferably 3 or 4.

Synthesis Scheme 2 Herein, n is preferably 2, 3 or 4, particularly preferably 3 or 4.

Synthesis Scheme 3 Here, m represents an integer from 3 to 6, and is particularly preferably 4 or 6.

In the above reaction scheme, Pg represents a protecting group and Rg represents a free group and the parameter n has the meaning given in the case of formula I, furthermore ^R1 has the meaning given for ^R11 in the case of formula I, the ring structure has the meaning given for ZG in the case of formula I, ^Sp1 and ^Sp2 have the meanings given for ^S1 and ^S2 , respectively, in the case of formula I, and preferably n represents 3 or 4, the ring structure represents an aromatic or aliphatic group, ^Sp1 and ^Sp2 represent a single bond or an alkylene group having 1 to 8 C atoms and ^R1 represents an alkyl group having 1 to 8 C atoms.

For the purposes of the present invention, the following definitions apply to the description of the components of a combined composition, unless otherwise indicated in individual cases: - "comprising": the concentration of the component in question in the composition is preferably 5% or more, particularly preferably 10% or more, very particularly preferably 20% or more, - "consisting mainly of": the concentration of the component in question in the composition is preferably 50% or more, particularly preferably 55% or more and very particularly preferably 60% or more, - "consisting essentially of": the concentration of the component in question in the composition is preferably 80% or more, particularly preferably 90% or more and very particularly preferably 95% or more, and - "Consists substantially entirely of": the concentration of the ingredient in the composition is preferably 98% or more, particularly preferably 99% or more and very particularly preferably 100.0%. This applies both to the medium in which the composition is present and its ingredients (which may be components and compounds), and to the components and their ingredients (compounds). With respect only to the concentration of the individual compound relative to the overall medium, the term includes the meaning that the concentration of the compound is preferably 1% or more, particularly preferably 2% or more, very particularly preferably 4% or more.

In the context of the present invention, “≤” means less than or equal to, preferably less than, and “≥” means greater than or equal to, preferably greater than.

In the context of the present invention, , and represents trans-1,4-cyclohexylene, and and It represents 1,4-phenylene.

For the purposes of the present invention, the expression "dielectrically positive compounds" means compounds having a Δε> 1.5, the expression "dielectrically neutral compounds" means those for which -1.5 ≤ Δε ≤ 1.5 and the expression "dielectrically negative compounds" means those for which Δε < -1.5. The dielectric anisotropy of the compounds is determined by dissolving 10% of the compound in a liquid crystal host and measuring the capacitance of the resulting mixture at 1 kHz in each case at least one test cell with a cell thickness of 20 µm with a homeotropic and uniform surface alignment. The measuring voltage is typically 0.5 V to 1.0 V, but is always below the capacitance threshold for the individual liquid crystal mixtures investigated.

The host mixtures used for dielectrically positive and dielectrically neutral compounds were ZLI-4792 and for dielectrically negative compounds were ZLI-2857, both from Merck KGaA, Germany. The values for the individual compounds to be investigated were obtained from the change in the dielectric constant of the host mixture after addition of the compound to be investigated and extrapolated to 100% of the compound employed. The compound to be investigated was dissolved in the host mixture in an amount of 10%. If the solubility of the substance was too low for this purpose, the concentration was halved stepwise until the investigation could be carried out at the desired temperature.

The liquid crystal medium according to the invention may (if necessary) also contain other additives such as stabilizers and/or pleochroic dyes and/or chiral dopants in the usual amounts. The amount of these additives used is preferably 0% or more to 10% or less in total, particularly preferably 0.1% or more to 6% or less, based on the amount of the entire mixture. The concentration of the individual compounds used is preferably 0.1% or more to 3% or less. When specifying the concentration and concentration range of the liquid crystal compounds in the liquid crystal medium, the concentration of these additives and similar additives is generally not taken into account.

In a preferred embodiment, the liquid crystal medium according to the present invention comprises a polymer precursor containing one or more reactive compounds, preferably reactive mesogens, and optionally other additives such as polymerization initiators and/or polymerization moderators in a usual amount. The amount of these additives used is a total of 0% or more to 10% or less, preferably 0.1% or more to 2% or less, based on the amount of the entire mixture. The concentrations of these additives and similar additives are not taken into account when specifying the concentrations and concentration ranges of the liquid crystal compounds in the liquid crystal medium.

The composition consists of a plurality of compounds, preferably 3 or more to 30 or less, particularly preferably 6 or more to 20 or less and very particularly preferably 10 or more to 16 or less, which are mixed in a known manner. In general, the required amount of the component used in a smaller amount is dissolved in the component constituting the main component of the mixture. This dissolution is advantageously carried out at high temperature. If the selected temperature is above the clearing point of the main component, the completion of the dissolution operation is particularly easy to observe. However, it is also possible to prepare the liquid crystal mixture in other known ways, for example using premixes or from the so-called "multi-bottle system".

The mixtures according to the invention show a very broad nematic phase range with a clearing point of 65° C. or more, very favorable capacitance threshold values, relatively high retention ratio values and very good low temperature stability at both -30° C. and -40° C. Furthermore, the mixtures according to the invention are characterized by a low rotational viscosity γ ₁ .

Those skilled in the art will appreciate that the medium according to the present invention for use in VA, IPS, FFS or PALC displays may also include compounds in which, for example, H, N, O, Cl, F have been correspondingly isotopically substituted.

The structure of the liquid crystal display according to the invention corresponds to the customary geometric structure, as described, for example, in EP-A 0 240 379.

The liquid-crystalline phases according to the invention can be modified by means of suitable additives in such a way that they can be used, for example, in any of the types of ECB, VAN, IPS, GH or ASM-VA LCD displays disclosed to date.

Table E below indicates possible dopants that can be added to the mixtures according to the invention. If the mixtures contain one or more dopants, they are used in an amount of 0.01 to 4%, preferably in an amount of 0.1 to 1.0%.

Stabilizers which can be added, for example, to the mixture according to the invention preferably in an amount of 0.01 to 6%, in particular in an amount of 0.1 to 3%, are shown in Table F below.

For the purposes of the present invention, unless expressly indicated otherwise, all concentrations are indicated as percentages by weight and relate to the corresponding mixture or components of a mixture unless expressly indicated otherwise.

All temperature values indicated in the present application, such as for example the melting point T(C,N), the smectic (S) to nematic (N) phase transition T(S,N) and the clearing point T(N,I), are indicated in degrees Celsius (°C) and, unless expressly indicated otherwise, all temperature differences are correspondingly indicated in differential degrees (° or degrees).

For the purposes of the present invention, unless expressly indicated otherwise, the term "threshold voltage" refers to the capacitance threshold (V ₀ ), also known as the Freedericks threshold.

All physical properties were and have been measured according to "Merck Liquid Crystals, Physical Properties of Liquid Crystals", status Nov. 1997, Merck KGaA, Germany, and apply to a temperature of 20°C and, unless expressly indicated otherwise in each case, Δn was measured at 589 nm and Δε at 1 kHz.

As well as the switching behaviour, the electro-optical properties, such as the threshold voltage (V ₀ ) (capacitance measurement), were determined in a test cell produced by Merck Japan. The test cell had a sodium calcium glass substrate and was constructed with polyimide alignment layers (SE-1211 and diluent**26 (mixing ratio 1:1), both from Nissan Chemicals, Japan) in ECB or VA configuration, which were rubbed perpendicular to each other and achieved homeotropic alignment of the liquid crystal. The surface area of the transparent, practically square ITO electrodes was 1 cm ² .

Unless otherwise indicated, no chiral dopants are added to the liquid-crystal mixture used, but the latter is also particularly suitable for applications in which doping of this type is necessary.

The VHR was determined in a test cell produced by Merck Japan. The measuring cell had a sodium calcium glass substrate and was constructed with a polyimide alignment layer (e.g. AL-3046 from Japan Synthetic Rubber, Japan unless otherwise indicated) with a layer thickness of 50 nm or with the alignment layers described in the examples, which had been rubbed perpendicularly to each other. The layer thickness was uniformly 6.0 µm. The surface area of the transparent ITO electrode was 1 cm ² .

VHR was determined at 20° C. (VHR ₂₀ ) and after 5 minutes in an oven at 100° C. (VHR ₁₀₀ ) in a commercial instrument from Autronic Melchers, Germany. The voltage used had a frequency of 60 Hz or where indicated in the examples.

The accuracy of the VHR measurement depends on the individual value of the VHR. The accuracy decreases as the individual value decreases. The deviations that are usually seen in the case of values within various magnitude ranges are compiled in the table below in equal magnitudes.

The stability to UV irradiation was investigated in a "Suntest CPS" (commercial instrument from Heraeus, Germany). The sealed test cells were irradiated for 2.0 h without additional heating. The irradiation power in the wavelength range from 300 nm to 800 nm was 765 W/m ² V, or as indicated in the examples. A UV "cut-off" filter with a edge wavelength of 310 nm was used to simulate the so-called window glass mode. In each series of experiments, at least four test cells were investigated for each condition, and the individual results are indicated as the average value of the corresponding individual measurements.

The drop in voltage holding ratio (ΔVHR) caused by exposure, such as UV radiation or LCD backlighting, is usually determined according to the following equation (1): (1).

The relative stability (S _rel ) of the LC mixture to loading duration t was determined according to the following equation, Equation (2): (2), where “reference” refers to the corresponding unstable mixture.

Besides VHR, another characteristic quantity which can characterize the conductivity of a liquid crystal mixture is the ion density. High ion density values generally lead to the occurrence of display malfunctions such as image sticking and flicker. The ion density is preferably determined in test cells produced by Merck Japan Ltd. The test cells have a substrate made of sodium calcium glass and are provided with a polyimide alignment layer with a polyimide layer thickness of 40 nm (e.g. AL-3046 from Japan Synthetic Rubber, Japan unless otherwise indicated). The layer thickness of the liquid crystal mixture is uniformly 6.0 µm. The area of the round, transparent ITO electrodes, which are additionally equipped with protective rings, is 1 cm ² . The accuracy of the measurement method is about ± 15%. The cells were dried in an oven at 120°C overnight and then filled with the relevant liquid crystal mixture.

The ion density is measured using a commercial instrument from TOYO, Japan. The measurement method is essentially similar to that of cyclic voltammetry, as described in M. Inoue, "Recent Measurement of Liquid Crystal Material Characteristics", Proceedings IDW 2006, LCT-7-1,647. In this method, the applied DC voltage is varied between a positive maximum and a negative maximum according to a predefined triangular profile. A complete run through the entire profile thus forms one measurement cycle. If the applied voltage is large enough so that the ions in the electric field can move to the individual electrodes, an ion current is formed due to the discharge of the ions. The amount of charge transferred here is typically in the range from a few pC to a few nC. This necessitates a highly sensitive detection, which is ensured by the instrumentation mentioned above. The results are plotted as current/voltage curves. The ionic current is evidenced here by the appearance of a peak at voltages less than the critical voltage of the liquid-crystal mixture. The integration of the peak area yields the value of the ionic density of the mixture under investigation. Four test cells are measured every minute. Depending on the magnitude of the dielectric anisotropy of the relevant mixture, the repetition frequency of the triangular voltage is 0.033 Hz, the measuring temperature is 60 °C and the maximum voltage is between ± 3 V and ± 10 V.

The rotational viscosity was determined using the rotating permanent magnet method and the flow viscosity was determined in a modified Oodel viscometer. For the liquid crystal mixtures ZLI-2293, ZLI-4792 and MLC-6608, all products from Merck KGaA, Darmstadt, Germany, the rotational viscosity values measured at 20°C were 161 mPa·s, 133 mPa·s and 186 mPa·s, respectively, and the flow viscosity values (ν) were 21 mm ² ·s ^-1 , 14 mm ² ·s ^-1 and 27 mm ² ·s ^-1 , respectively.

Unless expressly indicated otherwise, the following symbols are used: _{V0capacitance} threshold voltage at 20℃ [V], _ne extraordinary refractive index measured at 20℃ and 589 nm, _n oordinary refractive index measured at 20℃ and 589 nm, Δn optical anisotropy measured at 20℃ and 589 nm, _{ε┴dielectric} perpendicu- lar to the conducting plane at 20℃ and 1 kHz, ε _|| dielectric permeability parallel to the conducting plane at 20℃ and 1 kHz, Δε dielectric anisotropy at 20℃ and 1 kHz, cl.p. or T(N,I) clearing point [℃], ν kinematic viscosity measured at 20℃ [ ^mm2 ·s ^-1 ], _γ1 rotational viscosity measured at 20℃ [mPa·s], K ₁ elastic constant, "opening" deformation at 20°C [pN], K ₂ elastic constant, "twist" deformation at 20°C [pN], K ₃ elastic constant, "bend" deformation at 20°C [pN], and LTS low temperature stability of the phase measured in the test unit, VHR voltage holding ratio , ΔVHR reduction of the voltage holding ratio, S _rel relative stability of VHR.

The following examples illustrate the present invention but do not limit it. However, these examples show the skilled person the concept of using preferred mixtures of compounds to be employed and their individual concentrations and their combinations with each other. In addition, these examples illustrate the properties and property combinations that can be obtained.

For the purposes of the present invention and in the following examples, the structures of the liquid crystal compounds are indicated by means of the prefixes and the conversion of the chemical formulae occurs according to the following Tables A to C. All groups C _n H _2n+1 , C _m H _2m+1 and C _l H _2l+1 or C _n H _2n , C _m H _2m and C _l H _2l are linear alkyl or alkylene groups, in each case with n, m and l C atoms, respectively. Table A shows the codes for the ring elements of the atomic nuclei of the compounds, Table B lists the bridging units and Table C lists the meanings of the symbols for the left-hand and right-hand terminal groups of the molecules. The prefix consists of the code of the ring element with an optional linking group, followed by the first hyphen and the code for the left terminal group, and the second hyphen and the code for the right terminal group. Table D shows illustrative structures of compounds together with their individual abbreviations. Table A : Ring Elements C D DI A AI P G GI U UI Y P(F, Cl)Y P(Cl,F)Y np n3f n3I th tI H2 HkDJ o2f oF i dh B K KI L LI F FI B(S) P(n,m) where m = 1, 2, 3, 4, 5, or 6 and n = 1, 2, 3, 4, 5, or 6 P(o) PI(o) Where o = 1, 2, 3, 4, 5, or 6 Where o = 1, 2, 3, 4, 5, or 6 P(i3) PI(ic3) P(t4) PI(t4) P(c3) PI(c3) P(c4) PI(c4) P(c5) PI(c5) P(e5) PI(e5) P(c6) PI(c6) P(e6) PI(e6) GI(o) G(o) Where o = 1, 2, 3, 4, 5, or 6 Where o = 1, 2, 3, 4, 5, or 6 GI(i3) G(i3) GI(t4) G(t4) GI(c3) G(c3) GI(c4) G(c4) GI(c5) G(c5) GI(e5) G(e5) GI(c6) G(c6) GI(e6) G(e6) Np(1,4) Th Table B : Bridge Unit Table C : End Groups Where n and m are integers, and the three dots "..." are placeholders for other abbreviations from this table.

In addition to the compounds of the formula I, the mixtures according to the invention preferably comprise one or more of the compounds mentioned below.

The following abbreviations are used: (n, m and Z are each independently integers, preferably 1 to 6). Table D

Table E shows the preferred chiral dopants for use in the mixture according to the present invention. Table E

In a preferred embodiment of the present invention, the medium according to the present invention comprises one or more compounds selected from the group of compounds from Table E.

Table F shows stabilizers which can preferably be used in the mixtures according to the invention in addition to the compounds of formula I. The parameter n here represents an integer in the range from 1 to 12. In particular, the phenol derivatives shown here can be used as additional stabilizers, since they act as antioxidants. Table F

In a preferred embodiment of the present invention, the medium according to the present invention comprises one or more compounds selected from the group of compounds from Table F, in particular one or more compounds selected from the group of compounds having the following two chemical formulae:

Examples The following examples illustrate the invention without limiting it in any way. However, the physical properties make it clear to the person skilled in the art which properties can be achieved and the extent to which these properties can be modified. In particular, the combination of various properties that can be preferably achieved for the person skilled in the art is therefore clearly defined.

Material Examples The following substances are preferred substances of Formula I according to this application or preferred substances of Formula I to be used according to this application.

The following examples illustrate the present invention but do not limit it in any way. However, the physical properties make it clear to the skilled person which properties can be achieved and the extent to which these properties can be modified. In particular, the combination of various properties that can be preferably achieved for the skilled person is therefore clearly defined.

Synthetic Example 1 : Synthesis of 2-{3-[2,5-bis({4-butyl-5-[(2,2,6,6-tetramethylpiperidin-4-yl)oxy]-4-{[(2,2,6,6-tetramethylpiperidin-4-yl)oxy]carbonyl}-5-oxopentyl})phenyl]propyl}-2-butylmalonate bis(2,2,6,6-tetramethylpiperidin-4-yl) ester 1 (Material Example 1) Step 1.1: Synthesis of 3-[3,4-bis(3-hydroxypropyl)phenyl]propan-1-ol A

51.34 g (484.0 mmol) of anhydrous sodium carbonate are dissolved in 171.7 ml of water. A solution of 25.0 g (79.0 mmol) of 1,2,4-tribromobenzene and 67.70 g (476.0 mmol) of 2-butoxy-1,2-oxaborane in 965.2 ml of tetrahydrofuran (THF) is added, 1.65 ml (11.9 mmol) of triethylamine is added, and the mixture is stirred and degassed using a stream of hydrogen for 30 min. 1.40 g (7.49 mmol) of palladium(II) chloride (59% palladium, anhydrous) and 1.85 g (3.97 mmol) of 2-dicyclohexylphosphino-2',6'-di-isopropoxy-1,1'-biphenyl are added, and the reaction mixture is stirred under reflux for 18 h. The reaction mixture is allowed to cool to room temperature (RT), water and methyl tert-butyl ether (MTBE) are added, and the phases are separated. The aqueous phase is extracted with MTBE, and the combined organic phases are washed with saturated NaCl solution, dried over sodium sulfate, filtered and evaporated in vacuo. The product is obtained as a pale yellow oil and filtered through silica gel with a mixture of ethyl acetate (EA) and methanol (9:1). The product fractions were combined and evaporated in vacuo to yield the reaction product as a light yellow oil. The product was characterized by means of NMR spectroscopy. ¹ H NMR (500 MHz, DMSO-d6) δ = 1.66 (m _c , 6H, CH ₂ ), 2.42 – 2.69 (m _{( overlapped with DMSO )} , 6H, CH ₂ ,), 3.36 – 3.49 (m, 6H, CH ₂ ), 4.44 (t, J = 5.15 Hz, 1H), 4.48 (m _c , 2H), 6.92 (dd, J = 1.7, 7.72 Hz, 1H), 6.95 (d, J = 1.53 Hz, 1H), 7.03 (d, J = 7.7 Hz, 1 H).

Step 1.2: Synthesis of 1,2,4-tris(3-iodopropyl)benzene B

30.2 ml (138 mmol) of triphenylphosphine are dissolved in 513 ml of acetonitrile and a solution of 34.92 g (138.0 mmol) of iodine in 513 ml of acetonitrile is added dropwise and cooled gently. During this addition an orange suspension is formed. When the addition is complete, the mixture is stirred for a further 10 min. 13.3 g (197 mmol) of imidazole are added and then a solution of 10.0 g (39.3 mmol) of triol A in 100 ml of acetonitrile is added dropwise (a clear yellow solution is formed during this addition). The reaction solution is stirred at room temperature for 3 hours (h) and poured carefully into a cold sodium thiosulfate solution (decolorization occurs) and heptane is added. After washing, the phases are separated by stirring, the aqueous phase is extracted with heptane, and the combined organic phases are washed with water, dried over sodium sulfate, filtered and evaporated in vacuo. The crude product is filtered through silica gel with heptane (H) and ethyl acetate (8:2), and the product fraction is evaporated to give the product as a colorless oil. The product is characterized by mass spectrometry. MS (EI) = 582.0.

Step 1.3: Synthesis of 2-butylmalonyl dichloride C

76.00 g (474.5 mmol) 2-butylmalonic acid are first introduced into the reaction apparatus and the temperature is raised to 40° C. Then, in the course of about 30 min, 90.00 ml (1.240 mol) thionyl chloride are added dropwise (caution, gas evolution), and the mixture is stirred for a further 5 hours (h) at room temperature (RT). During this time span, the gas evolution decreases significantly. The reaction solution is then stirred at 50° C. for 18 h and then at 70° C. for 5 h. With each increase in temperature, a slight evolution of gas occurs again. The reaction mixture was then cooled to room temperature and taken up in 300 ml of anhydrous toluene, and the excess thionyl chloride was separated off by distillation with toluene (8 mbar and maximum bath temperature from room temperature to 80° C.), yielding the crude product as a brown liquid which was used directly in the next synthetic step.

Step 1.4: Synthesis of 2-butylmalonate (1-oxy-2,2,6,6-tetramethylpiperidin-4-yl) D

45.3 g (262.9 mmol) 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (free radical) and 40.1 ml (289.15 mmol) triethylamine are dissolved in 419 ml dichloromethane (DCM) and cooled to -11 ° C. Then a solution of 25.9 g (131.4 mmol) acyl chloride C in 252 ml DCM is added dropwise over the course of 1.5 hours (h) at -11 ° C to -6 ° C. The reaction mixture is stirred for about 3 h at maximum 0 ° C, allowed to thaw slowly and stirred at room temperature (RT) for 18 h. Saturated NaHCO ₃ solution is added at 3 to 6 ° C and cooled, the mixture is stirred briefly and the phases are separated. The aqueous phase was extracted with DCM, and the organic phases were combined, washed with saturated NaCl solution, dried over sodium sulfate, filtered and evaporated in vacuo. The crude product obtained (orange solid) was filtered through silica gel with DCM/MTBE (9:1), and the product fraction was evaporated in vacuo to give an orange crystalline product.

Step 1.5: Synthesis of 2-{3-[2,5-bis({4-butyl-5-[(1-oxy-2,2,6,6-tetramethylpiperidin-4-yl)oxy]-4-{[(1-oxy-2,2,6,6-tetramethylpiperidin-4-yl)oxy]carbonyl}-5-oxopentyl})phenyl]propyl}-2-butylmalonate bis(1-oxy-2,2,6,6-tetramethylpiperidin-4-yl) ester 1'

0.31 g (7.87 mmol) of sodium hydride (60% suspension in paraffin) is suspended in 9.7 ml of N,N-dimethylformamide (DMF). A solution of 3.75 g (7.87 mmol) of diradical D dissolved in 29.0 ml of DMF is added dropwise and gently cooled (gas evolution), and the mixture is stirred at room temperature for 1 hour. 1.40 g (2.39 mmol) of triiodide B is added dropwise to the reaction solution (temperature rise of 5°C in 5 minutes), and the mixture is stirred at room temperature for 3 h. The reaction mixture is carefully added to the ammonium chloride solution and extracted with MTBE. The phases were separated, the aqueous phase was extracted with MTBE, washed with saturated NaCl solution, dried over sodium sulfate, filtered and evaporated in vacuo. The orange crude product obtained was filtered through silica gel with ethyl acetate/heptane (1:1) and the product fraction was evaporated in vacuo to give the product as an orange solid which foamed in a glassy manner. The product had the following properties. Phase: Glass transition temperature (TG) = 23.5°C, decomposition from 150°C MS (APCI) = 1605.1 [M + H ⁺ ].

Step 1.6: Synthesis of 2-{3-[2,5-bis({4-butyl-5-[(2,2,6,6-tetramethylpiperidin-4-yl)oxy]-4-{[(2,2,6,6-tetramethylpiperidin-4-yl)oxy]carbonyl}-5-oxopentyl})phenyl]propyl}-2-butylmalonate bis(2,2,6,6-tetramethylpiperidin-4-yl) ester 1

1.5 g (0.1 mmol) of hexaradical 1' are dissolved in 20 ml of THF and 1.5 g of sponge nickel (Johnson-Matthey A-7000) are added. The mixture is stirred at 5 bar of hydrogen pressure and 50° C. for 17 h. The reaction solution is allowed to cool to room temperature, filtered and evaporated in vacuo. The crude product obtained is purified by column chromatography on basic alumina (RediSep Rf) in a CombiFlash apparatus with dichloromethane/methanol (95:5), and the product fractions are combined and evaporated in vacuo. The product is dried in a bulb apparatus at 50° C. and 3.2 *10 ^-1 mbar for 3 h, yielding the product as a foaming glassy solid. Phase: T _g (glass transition temperature) 39° C (melting point) 41° C I (isotropic). MS (APCI) = 1515.1 [M+H] ⁺ . ¹ H NMR (500 MHz, CDCl ₃ ) δ = 0.54 – 0.99 (m _{( overlay )} ,16H, 6 X NH, CH ₂ ), 1.09 – 1.40 (m _{( overlay )} 97H, CH ₃ , CH ₂ ), 1.48 (m _c , 6H, CH ₂ ), 1.82 – 2.02 (m _{( overlay )} , 24H, CH ₂ ), 2.57 (t, J = 7.63 Hz, 6 H), 5.24 (m _c , 6H, CH(CH ₂ ) ₂ ), 6.93 (d _{( overlay with singlet )} , J = 7.87 Hz, 2H), 7.04 (d, J = 7.72 Hz, 1 H).

Synthetic Example 2 : Synthesis of 2-(3-{3,5-bis[({4-butyl-5-[(1-oxy-2,2,6,6-tetramethylpiperidin-4-yl)oxy]-4-{[(1-oxy-2,2,6,6-tetramethylpiperidin-4-yl)oxy]carbonyl}-5-oxopentyl}oxy)-carbonyl]benzoyloxy}propyl)-2-butylmalonate bis(1-oxy-2,2,6,6-tetramethylpiperidin-4-yl) ester 2 Step 2.1: Synthesis of 2-butyl-2-[3-(oxan-2-yloxy)propyl]malonate bis(1-oxy-2,2,6,6-tetramethylpiperidin-4-yl) E

3.20 g (80.01 mmol) of sodium hydride (60% suspension in paraffin oil) was suspended in 30 ml of DMF. A solution of 32.40 g (69.14 mmol) of diradical D (from the synthesis of compound 1) in 300 ml of DMF was added dropwise to the reaction solution and gently cooled (gas evolution), and the mixture was stirred at room temperature for 1 h. Then a solution of 19.0 g (85.16 mmol) of 2-(3-bromopropoxy)tetrahydropyran in 200 ml of DMF was added dropwise at room temperature (temperature rise of 0.5°C). To deaerate the reaction mixture before the temperature increase, a gentle flow of argon was passed through the reaction mixture by means of an immersed Pasteur pipette for 30 minutes, and the mixture was then stirred at 35°C for 18 h. The reaction solution was allowed to cool to room temperature, added to a saturated NaCl solution and extracted with MTBE, and the phases were separated. The aqueous phase was extracted with MTBE, and the organic phases were combined, washed with a saturated NaCl solution, dried over sodium sulfate, filtered and evaporated in vacuo to give a crude product as a red oil, which was purified by filtering it through silica gel with DCM/MTBE (9:1) to give a product as a red oil.

Step 2.2: Synthesis of 2-butyl-2-(3-hydroxypropyl)malonate (1-hydroxy-2,2,6,6-tetramethylpiperidin-4-yl) F

36.5 g (56.1 mmol) of diradical E and 9.50 g (55.2 mmol) of toluene-4-sulfonic acid monohydrate are dissolved in a mixture of 500 ml of methanol and 50 ml of water, and the mixture is stirred at 40° C. for 5 h. The reaction solution is cooled to room temperature and adjusted to pH = 9 using NaHCO ₃ solution and cooled and evaporated in vacuo. The aqueous residue is extracted with MTBE, and the combined organic phases are washed with saturated NaCl solution, dried over sodium sulfate, filtered and evaporated in vacuo to give a red oil, which is dissolved in 250 ml of DCM, 6.00 g (55.6 mmol) of MnO ₂ are added, and the mixture is stirred at room temperature for 1 h. (In case of removal of the THP protecting group, the free radical is in some cases also converted to an OH compound, which is reversed using MnO ₂ ). The reaction mixture is filtered through silica gel with DCM and evaporated in vacuo. The crude product obtained is filtered through silica gel with DCM/MTBE (7:3) and the product fraction is evaporated in vacuo to yield a red oil.

Step 2.3: Synthesis of 2-(3-{3,5-bis[({4-butyl-5-[(1-oxy-2,2,6,6-tetramethylpiperidin-4-yl)oxy]-4-{[(1-oxy-2,2,6,6-tetramethylpiperidin-4-yl)oxy]carbonyl}-5-oxopentyl}oxy)carbonyl]-benzoyloxy}propyl)-2-butylmalonate bis(1-oxy-2,2,6,6-tetramethylpiperidin-4-yl) ester 2'

6.70 g (11.7 mmol) of F and 50.0 mg (0.41 mmol) of 4-(dimethylamino)pyridine are dissolved in 100 ml of dichloromethane at room temperature and the mixture is cooled to 4° C. 5.00 ml (36.1 mmol) of triethylamine are then added and then a solution of 1.00 g (3.77 mmol) of 1,3,5-benzenetrimethylol chloride in 10 ml of DCM is added dropwise at 3 to 4° C. When the exotherm is complete, the mixture is allowed to warm to room temperature and is then stirred at room temperature for 18 h. The ammonium chloride solution is then added and cooled, the mixture is stirred briefly, the phases are separated and the aqueous phase is extracted with DCM. The combined organic phases were washed with a dilute NaCl solution (better phase separation), dried over sodium sulfate, filtered and evaporated in vacuo to give a red solidified foam reaction product. For further purification, the product was filtered through silica gel with DCM/MTBE (9:1 to 85:15) and the product fraction was evaporated in vacuo. The reaction product was obtained as a red solidified foam. The reaction product had the following properties. Phase: _Tg (glass transition temperature) 52°C, C (melting point) 57°C I, decomposition> 175°C. MS (APCI) = 1734.

The following compounds were prepared analogously to the synthetic sequences described herein.

Substance / Synthetic Example 2' :

Substance / Synthetic Example 2 : (Formula I-7)

Substance / Synthetic Example 3' : Phase: T_g (Glass transition temperature) -3℃ I (isotropic), decomposition > 100℃.

Substance / Synthetic Example 3 :

Substance / Synthetic Example 4' : Phase: T_g (Glass transition temperature) 5℃ I (isotropic), decomposition＞ 180℃.

Substance / Synthetic Example 4 : (Formula I-9)

Substance / Synthetic Example 5' : Phase: T_g (Glass transition temperature) 5℃ I (isotropic), decomposition＞ 170℃.

Substance / Synthetic Example 5 :

Substance / Synthetic Example 6' : (Formula I-13) Phase: T_g (Glass transition temperature) 27℃ I (isotropic).

Substance / Synthetic Example 6 : (Formula I-12)

Substance / Synthetic Example 7’ :

Substance / Synthetic Example 7 : (Formula I-3) Phase: (Glass transition temperature) 14℃ I (isotropic).

Substance / Synthetic Example 8' : (Formula I-6)

Substance / Synthetic Example 8 : Phase: T_g (Glass transition temperature) -3℃ I (isotropic).

Substance / Synthetic Example 9' :

Substance / Synthetic Example 9 : (Formula I-5) Phase: T_g (Glass transition temperature) -3℃ I (isotropic).

Substance / Synthetic Example 10 : Synthesis of 4-(3-{3-[3,5-bis({3-[(2,2,6,6-tetramethylpiperidin-4-yl)oxy]propoxy})phenyl]-5-{3-[(2,2,6,6-tetramethylpiperidin-4-yl)oxy]propoxy}phenoxy}propoxy)-2,2,6,6-tetramethylpiperidine Step 10.1: Synthesis of 1-benzyl-2,2,6,6-tetramethylpiperidin-4-ol A

37.80 ml (318.2 mmol) of benzyl bromide and 100.0 g (635.9 mmol) of 2,2,6,6-tetramethylpiperidin-4-ol are dissolved in 500 ml of N,N-dimethylformamide (DMF) and the mixture is stirred at 120° C. for 18 hours (h). The reaction solution is cooled to room temperature (RT) and stirred in a mixture of water and ice. The mixture is stirred for 30 min and the precipitated solid is filtered off with suction and extracted with methyl tert-butyl ether (MTB ether). The product solution is washed several times with saturated sodium chloride solution and the organic phase is dried over sodium sulfate, filtered and evaporated in vacuo. The crystalline crude product obtained was recrystallized from heptane/isopropanol (5:1) at 5° C., and the crystals were filtered off with suction and dried in vacuo at 40° C. for 18 h, yielding the reaction product as a colorless crystalline solid.

Step 10.2: Synthesis of 1-benzyl-2,2,6,6-tetramethyl-4-[3-(oxan-2-yloxy)propoxy]piperidine B

35.00 g (141.5 mmol) of tetramethylpiperidine A, 47.20 g (211.5 mmol) of 2-(3-bromopropoxytetrahydropyran) and 20.00 g (62.04 mmol) of tetra-n-butylammonium bromide are suspended in 270 ml of toluene and 110 ml (2.10 mol) of sodium hydroxide solution (50%) are added dropwise rapidly at room temperature (RT). The reaction mixture is stirred at 60° C. for 16 hours (h) and then allowed to cool to room temperature. The reaction mixture is carefully added to a mixture of ice-water and toluene and the phases are separated. The aqueous phase is extracted with toluene, and the combined organic phases are washed with saturated sodium chloride solution, dried over sodium sulfate, filtered and evaporated in vacuo to give a yellow, partially crystalline crude product, to which 300 ml of heptane are added, and the mixture is stirred and filtered. The reaction product is obtained in the mother liquor as a yellow oil, which is filtered through silica gel with toluene/ethyl acetate (9:1 to 3:1). The product fractions are combined and evaporated in vacuo to give the product as a slightly yellow oil.

Step 10.3: Synthesis of 3-[(1-benzyl-2,2,6,6-tetramethylpiperidin-4-yl)oxy]propan-1-ol C

34.60 g (80.91 mmol) of B and 20.00 g (116.1 mmol) of toluene-4-sulfonic acid monohydrate are dissolved in 700 ml of methanol and 100 ml of water are added at room temperature (exotherm/ 7 K). The reaction solution is stirred at 40°C for 1 h, then evaporated in vacuo and diluted with methyl tert-butyl ether (MTBE). The mixture is carefully washed with saturated NaHCO ₃ solution and the phases are separated. The organic phase is washed with saturated NaCl solution, dried over sodium sulfate, filtered and evaporated in vacuo to give the crude product as a yellow oil, which is filtered through silica gel with dichloromethane (DCM) and MTBE (3:1). The product fractions are combined to give the reaction product as a virtually colorless oil.

Step 10.4: Synthesis of 1-benzyl-4-[3-(3-{3-[(1-benzyl-2,2,6,6-tetramethylpiperidin-4-yl)oxy]propoxy}-5-bromophenoxy)propoxy]-2,2,6,6-tetramethylpiperidine D

5.80 g (30.7 mmol) of 5-bromobenzene-1,3-diol, 21.50 g (70.4 mmol) of alcohol C from the previous step and 18.51 g (70.58 mmol) of triphenylphosphine are dissolved in 120 ml of tetrahydrofuran (THF) and cooled to 0° C. 14.70 ml (70.58 mmol) of diisopropyl azodicarboxylate are added dropwise to the reaction solution, and the mixture is stirred at room temperature for 16 h. The reaction mixture is evaporated in vacuo, 200 ml of heptane are added, and the mixture is stirred vigorously. The precipitated triphenylphosphine oxide is filtered off, and the mother liquor is washed with 100 ml of heptane and evaporated in vacuo. The crude product obtained was filtered through silica gel with heptane/MTBE (7:3) and the combined product fractions were evaporated in vacuo to yield the reaction product as a viscous oil.

Step 10.5: Synthesis of 1-benzyl-4-[3-(3-{3-[(1-benzyl-2,2,6,6-tetramethylpiperidin-4-yl)oxy]propoxy}-5-[3,5-bis({3-[(1-benzyl-2,2,6,6-tetramethylpiperidin-4-yl)oxy]propoxy})-phenyl]phenoxy)propoxy]-2,2,6,6-tetramethylpiperidine E

14.60 g (19.11 mmol) of bromide D from the previous step, 2.54 g (10.0 mmol) of bis(pinacolato)diboron and 2.81 g (28.7 mmol) of potassium acetate are first introduced into 150 ml of dioxane and degassed under an atmosphere of hydrogen for 30 min. 220.00 mg (0.30 mmol) of PdCl ₂ -dppf are added, and the reaction mixture is stirred at 100° C. for 1 h. The reaction mixture is then cooled to below the boiling point, a further 220.00 mg (0.30 mmol) of PdCl ₂ -dppf and 25 ml (50 mmol) of sodium carbonate solution (2 M) are added, and the mixture is stirred at 100° C. for 20 h. The reaction mixture was allowed to cool to room temperature, water and MTBE were added, and the phases were separated. The aqueous phase was extracted with MTBE, and the organic phases were combined, washed with water, dried over sodium sulfate, filtered and evaporated in vacuo. The crude product was obtained as a black oil and filtered through silica gel with heptane/MTBE (8:2 to 7:3). The combined product fractions were evaporated in vacuo to give a reaction product as a yellow resin. MS (APCI) = 1367.9 [M] ⁺ . ¹ H NMR (500 MHz, CDCl ₃ ) δ = 0.99 (s, 24H, CH ₃ ), 1.13 (s, 24H, CH ₃ ), 1.45 (t, J = 11.7 Hz, 8H, CH ₂ ), 1.94 (dd, J = 12.25, 3.84 Hz, 4H, CH ₂ ), 2.09 (quintet, J = 6.16 Hz, 4 H, CH ₂ ), 3.71 (t _{( with multiplet overlap )} , J = 6.21 Hz, 6 H, CH ₂ , CH), 3.83 (s, 8H, CH ₂ ), 4.15 (t, 6.15 Hz), 6.53 (t, 2.06 Hz, 2H), 6.76 (d, J = 2.12 Hz, 4H), 7.16 (t, 7.26 Hz, 4H), 7.28 (t, 7.72 Hz, 8H), 7.43 (d, J = 7.49 Hz, 8H).

Step 10.6: Synthesis of 4-(3-{3-[3.5-bis({3-[(2,2,6,6-tetramethylpiperidin-4-yl)oxy]propoxy})phenyl]-5-{3-[(2,2,6,6-tetramethylpiperidin-4-yl)oxy]propoxy}phenoxy}propoxy)-2,2,6,6-tetramethylpiperidine 10

8.50 g (6.21 mmol) of product E from the previous step are dissolved in 107 ml tetrahydrofuran, 3.00 g 5% Pd/C (50% water, Degussa) are added and the mixture is stirred under hydrogen atmosphere at atmospheric pressure and room temperature (RT) for 17 h. The reaction mixture is filtered and evaporated in vacuo. The residue is dissolved in 100 ml MTBE, 50 ml 2 N hydrochloric acid is added and the phases are separated. The aqueous phase is extracted with MTBE and then adjusted to pH 12 to 13 using 32% sodium hydroxide solution and extracted with MTBE ether. The combined organic phases are washed with saturated sodium chloride solution, dried over sodium sulfate, filtered and evaporated in vacuo. The crude product obtained was filtered through Al ₂ O ₃ ("basic aluminum oxide") with dichloromethane/methanol, and the product fractions were combined and evaporated in vacuo to give the product as a yellowish oil which solidified. Phase: T _g (glass transition temperature) -4°C, T(C,I) (melting point) 64°C I (isotropic). MS (APCI) = 1007.7 [M+H] ⁺ . ¹ H NMR (500 MHz, CDCl ₃ ) δ = 0.62 (s _{( wide )} , 4H, NH), 1.02 (t, J = 11.76, 8H), 1.15 (s, 24H, CH ₃ ), 1.19 (s, 24H, CH ₃ ), 1.98 (dd, 12.49, 3.9 Hz 8H), 2.07 (quintet, 6.13 Hz, 8H), 3.69 (t _{( overlapping )} , J = 5.8 Hz, 12H), 4.12 (t, J = 6.1 Hz, 8 H), 6.50 (s _{( wide )} = 2H), 6.73 (d, J = 2.1 Hz, 4H).

Substance / Synthetic Example 11 : Synthesis of This compound was prepared similarly to produce a colorless oil. Stage: T_g (Glass transition temperature) -118℃.¹ H NMR (500 MHz, CDCl₃ ) δ = 6.35 (dd, J = 13.3, 2.2 Hz, 6H), 4.05 (t, J = 6.1 Hz, 8H), 3.81 – 3.51 (m, 12), 2.57 – 2.48 (m, 4H), 2.04 (p, J = 6.2 Hz, 8H), 1.98 (dd, J = 12.5, 3.9 Hz, 8H), 1.67 – 1.56 (m, 4H), 1.36 (d, J = 4.1 Hz, 6H), 1.18 (d J = 19.7 Hz, 48H), 1.02 (t, J = 11.7 Hz, 8H), 0.69 (s, 4H).

Mixture Examples Liquid crystal mixtures having the composition and properties indicated in the following table were prepared and investigated. The improved stability of the mixtures comprising the compound of formula I is shown by comparison with an unstable alkaline mixture as reference (Ref).

Examples 1 And corresponding comparative examples The following mixture (M-1) was prepared and studied.

First, the stability of the voltage retention of the mixture (M-1) itself was determined. In a test cell with an alignment material for planar alignment, a layer thickness of 6.0 µm and a flat ITO electrode, the stability of the mixture M-1 to irradiation with a backlight was investigated. To this end, the mixture or mixtures were subjected to a test for exposure to a backlight. To this end, the stability of the corresponding test cell to irradiation with an LED ( light-emitting diode ) backlight for LCDs was investigated. To this end, the corresponding test cells were filled and sealed. These cells were then exposed to irradiation for various times using a commercial LCD backlight. No additional heating was applied, except for the heat generated by the backlight. In each case, the "voltage retention" was then determined after 5 minutes at a temperature of 100°C. The results are compiled in the table below (Table 1a).

Here, as below, six test cells were filled and investigated for each individual mixture. The values indicated here are the average of six individual values.

The relative deviation of the "voltage holding ratio" values in various measurement series is usually in the range of about 3% to 4%.

100 ppm, 500 ppm, and 1.000 ppm of reference compound R-1 were added Add to one of the three other parts of the mixture M-1, and 100 ppm, 500 ppm, and 1.000 ppm of compound I-10 The stability of each of the three other parts added to the mixture M-1, and the resulting mixtures (C-1.1, C-1.2 and C-1.3, and M-1.1, M-1.2 and M-1.3) was investigated as described above. The results are shown in the following tables, Tables 1a to 1c. Table 1a Table 1b Table 1c

Examples 2 And corresponding comparative examples The following mixture (M-2) was prepared and studied.

This mixture (mixture M-2) was investigated below with regard to its stability in voltage retention to irradiation with ultraviolet radiation. For this purpose, this mixture was also divided into several parts.

First, the stability of the mixture (M-2) itself was determined. To this end, the stability of the mixture M-1 to UV exposure was investigated in test cells with a suitable polyimide as alignment material for planar alignment, a layer thickness of 6.0 µm and flat ITO electrodes. To this end, the corresponding test cells were irradiated for 30 min in the Suntest. The voltage retention was then determined in each case after 5 minutes at a temperature of 100°C. Unless otherwise specified in the text, the addressing frequency (or measuring frequency) here was 60 Hz. The results are compiled in Table 2a.

Then, for comparison, 100 ppm, 500 ppm or 1.000 ppm of the reference compound R-1 were added to three portions of the mixture M-2, and the resulting mixtures (C-2.1, C-2.2 and C-2.3.) were studied as described above.

And then, in each case 100 ppm, 500 ppm or 1.000 ppm of any one of the compounds I-9 was added to the three parts of the mixture M-2, and the resulting mixtures (M-2.1, M-2.2 and M-2.3.) were studied as described above.

Examples 3 The following mixture (M-3) was prepared and studied.

As described in Examples 1 and 2, mixture M-3 was also divided into several parts and its stability to LCD backlight and exposure to UV source was studied in a test cell with alignment material for planar alignment and flat ITO electrodes, likewise and with various added compounds.

Examples 4 The following mixture (M-4) was prepared and studied.

As described in Examples 1 to 3, mixture M-4 was also divided into several parts and its stability to LCD backlight and exposure to UV sources was studied in a test cell with alignment material for planar alignment and flat ITO electrodes, likewise and with various added compounds.

Examples 5 The following mixture (M-5) was prepared and studied.

As described in Examples 1 to 4, mixture M-5 was also divided into several parts and its stability to LCD backlight and exposure to UV sources was studied in a test cell with alignment material for planar alignment and flat ITO electrodes, likewise and with various added compounds.

Examples 6 The following mixture (M-6) was prepared and studied.

As described in Examples 1 to 5, mixture M-6 was also divided into several parts and its stability to LCD backlight and exposure to UV sources was studied in a test cell with alignment material for planar alignment and flat ITO electrodes, likewise and with various added compounds.

Claims (14)

A liquid crystal medium, characterized in that it comprises: a) 1 wt ppm or more to 2000 wt ppm or less of one or more compounds of formula I

wherein R ¹¹ at each occurrence independently represents H, F, a linear or branched alkyl chain having 1 to 20 C atoms, wherein one -CH ₂ - group or, if present, a plurality of -CH ₂ - groups may be replaced by -O- or -C(=O)-, but two adjacent -CH _{2 - groups may not be replaced by -O-, and one or, if present, a plurality of -CH 2} - groups may be replaced by -CH=CH- or -C≡C-, and wherein one or a plurality of H atoms may be replaced by F, OR ¹³ , N(R 13 )(R 14 ) or R 15, R ¹² at each occurrence independently represents ^H , a linear or branched alkyl chain having 1 to 20 C atoms, wherein one -CH ₂ - group or a plurality of -CH 2 - groups may be replaced by -O- or -C(= ^O )-, but two ^adjacent -CH 2 - groups may not be replaced by -O-, and one or, if present, a plurality of -CH _{2 -} groups may be replaced by -CH=CH- or -C≡C-, and wherein one or a plurality of H atoms may be replaced by F, OR 13 , N(R 13 )(R 14 ) or R 15 -group may be replaced by -O- or -C(=O)-, but two adjacent -CH ₂ -groups cannot be replaced by -O-; a alkyl group containing a cycloalkyl or alkylcycloalkyl unit and _{wherein one or more -CH 2 -groups may be replaced by -O- or -C(=O)-, but two adjacent -CH 2 -groups cannot} be replaced by -O-, and wherein one or more H atoms may be replaced by F, OR ¹³ , N(R ¹³ )(R ¹⁴ ) or R ¹⁵ ; or an aromatic or heteroaromatic alkyl group wherein one or more H atoms may be replaced by OR ¹³ , N(R ¹³ )(R ¹⁴ ) or R ¹⁵ , R R ¹³ at each occurrence independently represents a straight-chain or branched alkyl or acyl group having 1 to 10 C atoms, or an aromatic hydrocarbon or a carboxylic acid radical having 6 to 12 C atoms, R ¹⁴ at each occurrence independently represents a straight-chain or branched alkyl or acyl group having 1 to 10 C atoms, or an aromatic hydrocarbon or a carboxylic acid radical having 6 to 12 C atoms, R ¹⁵ at each occurrence independently represents a straight-chain or branched alkyl group having 1 to 10 C atoms, wherein one or more -CH ₂ - groups may be replaced by -O- or -C(=O)-, but two adjacent -CH ₂ - groups may not be replaced by -O-, -Z ¹² -S 11 -Z 11 - at each occurrence independently represents -S 11 -O-, -OS ₁₁ -, -S 11 -O-, -OS 11 -, -S 11 -O-, -OS 11 -O-, -S 11 -O-, -OS 11 -O-, -S ¹¹ -O-, -OS ¹¹ -O-, -S ¹¹ -O-, -OS 11 -O-, -S 11 -O-, -OS wherein S ¹¹ represents an alkylene group having 1 to 20 C atoms; S ¹² represents ^, at each occurrence, an alkylene group having 1 to 20 C atoms, wherein one ^-CH ₂ - group or, if present, a plurality of -CH ² _- groups may be replaced by -O- or -C(=O)-, but two adjacent -CH ₂ - groups may not be replaced by -O-, and wherein one H atom or a plurality of H atoms may be replaced by F, OR ¹³ , N(R ¹³ )(R ¹⁴ ) or R ¹⁵ , or represents a single bond, Y ¹¹ to Y 14 each represent, independently of one another, a methyl group or an ethyl group, and Z ¹¹ to Z ¹⁴ represent, independently of one another, a methyl group or an ethyl group. ¹⁴ represents -O-, -(C=O)-, -O-(C=O)-, -(C=O)-O-, -O-(C=O)-O-, -(NR ¹³ )-, -NR ¹³ -(C=O)- or a single bond at each occurrence, if S ¹¹ is a single bond, but Z ¹¹ and Z ¹² do not both represent -O-, and if S ¹² is a single bond, then Z ¹³ and Z ¹⁴ do not both represent -O-, and if -X ¹¹ [-R ¹¹ ] _o - is a single bond, then Z ¹² and Z ¹³ do not both represent -O-, X ¹¹ represents C, p represents 1 or 2, o represents (3-p), n*p represents an integer from 3 to 10, and in the case where p=1, n represents 3, 4, 5, 6 or 8, and m represents (10-n), and in the case where p=2, n represents an integer from 2 to 4, and m represents (4-n), and

represents an organic group having (m+n) binding sites, and, in the case where p=1, -X ¹¹ [-R ¹¹ ] _o - may also represent a single bond, and b) 1% by weight or more to 90% by weight or less of one or more compounds selected from the group of compounds of formula II and/or 1% by weight or more to 40% by weight or less of one or more compounds selected from the group of compounds of formula III

wherein R ² represents H, non-fluorinated or fluorinated alkyl or non-fluorinated or fluorinated alkoxy having 1 to 17 C atoms, or non-fluorinated or fluorinated alkenyl, non-fluorinated or fluorinated alkenyloxy or non-fluorinated or fluorinated alkoxyalkyl having 2 to 15 C atoms, wherein one or more CH ₂ -groups may be

,

,

,

or

substituted, alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms,

and

Each occurrence is expressed independently of the other

wherein ^RL represents, identically or differently on each occurrence, H or an alkyl radical having 1 to 6 C atoms or

L ²¹ and L ²² independently represent H or F, X ² represents a halogen, a halogenated alkyl or alkoxy group having 1 to 3 C atoms, or a halogenated alkenyl or alkenyloxy group having 2 or 3 C atoms, m represents 0, 1, 2 or 3, R ³ represents H, a non-fluorinated or fluorinated alkyl group having 1 to 17 C atoms, or a non-fluorinated or fluorinated alkenyl group, a non-fluorinated or fluorinated alkenyloxy group, or a non-fluorinated or fluorinated alkoxyalkyl group having 2 to 15 C atoms, wherein one or more CH ₂ -groups may be substituted or substituted by a fluorinated alkyl group.

,

,

,

or

Replacement,

and

Each occurrence is expressed independently of the other

wherein ^RL, identically or differently on each occurrence, represents H or alkyl having 1 to 6 C atoms; or

L ³¹ and L ³² independently represent H or F, X ³ represents a halogen, a halogenated alkyl or alkoxy group having 1 to 3 C atoms, or a halogenated alkenyl or alkenyloxy group having 2 or 3 C atoms, F, Cl, -OCF ₃ , -OCHF ₂ , -O-CH ₂ CF ₃ , -O-CH=CF ₂ , -O-CH=CH ₂ or -CF ₃ , Z ³ represents -CH ₂ CH ₂ -, -CF ₂ CF ₂ -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH ₂ O- or a single bond, and n represents 0, 1, 2 or 3. The medium of claim 1, wherein the compound of formula I is selected from the group consisting of compounds of the following formulae:

A medium as claimed in claim 1, wherein the medium comprises one or more compounds of formula II. A medium as claimed in claim 1, wherein the medium comprises one or more compounds of formula III. The medium of any one of claims 1 to 4, wherein the medium comprises one or more compounds selected from the group of formulas B and S:

in

express

,

express

,

,

,

R ^B1 and R ^B2 independently represent alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy, wherein one -CH ₂ - group may be replaced by cyclopropyl, 1,3-cyclobutyl, 1,3-cyclopentyl or 1,3-cyclopentenyl, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms, wherein one -CH ₂ - group may be replaced by cyclopropyl, 1,3-cyclobutyl, 1,3-cyclopentyl or 1,3-cyclopentenyl, n represents 0 or 1,

express

,

express

,

,

,

^RS1 and ^RS2 independently represent alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy, wherein one _-CH2- group may be replaced by cyclopropyl, 1,3-cyclobutyl, 1,3-cyclopentyl or 1,3-cyclopentenyl, alkenyl having 2 to 7 C atoms, alkenyloxy, alkoxyalkyl or fluorinated alkenyl, wherein one _-CH2- group may be replaced by cyclopropyl, 1,3-cyclobutyl, 1,3-cyclopentyl or 1,3-cyclopentenyl, and n represents 0 or 1. The medium of any one of claims 1 to 4, wherein the medium comprises one or more compounds selected from the group consisting of formula IV and V:

wherein R ⁴¹ and R ⁴² independently have the meanings indicated above for R ² in claim 1,

and

Independently of each other, and if

appears twice, then these independently, if any, each independently have the

and

One of the given meanings,

Z ⁴¹ and Z ⁴² independently of one another and, if Z ⁴¹ occurs twice, also independently of one another represent -CH ₂ CH ₂ -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH ₂ O-, -CF ₂ O-, -C≡C- or a single bond, and p represents 0, 1 or 2, R ⁵¹ and R ⁵² independently of one another have one of the meanings given for R ⁴¹ and R ⁴² , respectively,

to

, if any, then each has independently the same

and

^Z51 to ^Z53 each independently represent _{-CH2- CH2-} , _-CH2 -O-, -CH=CH-, -C≡C-, -COO- or a single bond, and i and j each independently represent 0 or 1. A medium as claimed in any one of claims 1 to 4, wherein the medium additionally comprises one or more chiral compounds. An electro-optical display or electro-optical component, characterized in that it contains a liquid crystal medium as claimed in any one of claims 1 to 7. A display as claimed in claim 8, wherein the display is based on IPS, FFS, VA or ECB effect. A display as claimed in claim 8 or 9, wherein the display comprises an active matrix addressing device. A use of a compound of formula I as given in claim 1, which is used in a liquid crystal medium. A use of a liquid crystal medium as claimed in any one of claims 1 to 7, which is used in an electro-optical display or an electro-optical component. A method for preparing a liquid crystal medium as claimed in any one of claims 1 to 7, characterized in that one or more compounds of formula I as claimed in any one of claims 1 to 7 are mixed with one or more compounds of formula II as claimed in claim 1 and/or one or more compounds selected from the group of compounds of formula III as claimed in claim 1. A method for stabilizing a liquid crystal medium, characterized in that one or more compounds of the formula I as given in claim 1 and, if necessary, one or more compounds selected from the group of compounds of the formulae OH-1 to OH-6 are added to the mixture.

Add to this medium.