The invention relates to a liquid-crystalline medium having a nematic phase comprising one or more furane derivative compounds of formula I wherein the parameters have the meaning given in the text below, to novel compounds under formula I, the use thereof in an electro-optical display, particularly in an active-matrix display based on the IPS or the FFS (fringe field switching) effect using dielectrically positive liquid crystals, and to displays of this type which contain a liquid-crystalline medium of this type.

For this purpose dielectrically positive liquid crystals are used, which comprise one or more compounds having at the same time a high dielectric constant parallel to the molecular director and perpendicular to the molecular director, leading to a large average dielectric constant and a high dielectric ratio and, preferably, to a relatively small dielectric anisotropy at the same time. The liquid crystalline media optionally additionally comprise dielectrically negative, dielectrically neutral compounds or both. The liquid crystalline media are used in a homogeneous (i.e. planar) initial alignment. The liquid-crystal media according to the invention have a positive dielectric anisotropy and comprise compounds having at the same time large dielectric constants parallel and perpendicular to the molecular director.

The media are distinguished by a particularly high transmission and reduced response time in respective displays, which is brought about by their unique combination of physical properties, especially by their high values of the elastic constant(s), in particular by high k ₁₁ and their excellent, low ratio (γ ₁ /k ₁₁ ) of the rotational viscosity (γ ₁ ) and the elastic constant (k ₁₁ ). This also leads to their excellent performance in the displays according to the invention.

IPS and FFS displays using dielectrically positive liquid crystals are well known in the field and have been widely adopted for various types of displays like e. g. desk top monitors and TV sets, but also for gaming, mobile, and automotive applications. However, recently, IPS and in particular FFS displays using dielectrically negative liquid crystals are widely adopted. The latter ones are sometimes also called LIB-FFS (ultra-bright FFS). Such displays are disclosed e. g. in US 20130207038 A1 . These displays are characterized by a markedly increased transmission compared to the previously used IPS- and FFS displays, which have been dielectrically positive liquid crystals. These displays using conventional, dielectrically negative liquid crystals, however, have the severe disadvantage of requiring a higher operation voltage than the respective displays using dielectrically positive liquid crystals. Liquid crystalline media used for UB-FFS have a dielectric anisotropy of -0.5 or less and preferably of -1 .5 or less.

Liquid crystalline media used for HB-FFS (high brightness FFS) have a dielectric anisotropy of 0.5 or more and preferably of 1 .5 or more. Liquid crystalline media used for HB-FFS comprising both dielectrically negative and dielectrically positive liquid crystalline compounds, respectively mesogenic compounds are disclosed e.g. in US 20130207038 A1. These media feature rather large values of already, however, their ratio of is relatively small.

According to the present application, however, the IPS or the FFS effect with dielectrically positive liquid crystalline media in a homogeneous alignment are preferred.

Industrial application of this effect in electro-optical display elements requires LC phases which have to meet a multiplicity of requirements. Particularly important here are chemical resistance to moisture, air and physical influences, such as heat, radiation in the infrared, visible and ultraviolet regions, and direct (DC) and alternating (AC) electric fields.

Furthermore, LC phases which can be used industrially are required to have a liquid-crystalline mesophase in a suitable temperature range and low viscosity.

None of the series of compounds having a liquid-crystalline mesophase that have been disclosed hitherto includes a single compound which meets all these requirements. Mixtures of two to 25, preferably three to 18, compounds are therefore generally prepared in order to obtain substances which can be used as LC phases. Matrix liquid-crystal displays (MLC displays) are known. Non-linear elements which can be used for individual switching of the individual pixels are, for example, active elements (i.e. transistors). The term “active matrix” is then used, where in general use is made of thin-film transistors (TFTs), 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 metal oxides like ZnO or TFTs based on polycrystalline and, inter alia, amorphous silicon. The latter technology currently has the greatest commercial importance worldwide.

The TFT matrix is applied to the inside of one glass plate of the display, while the other glass plate carries the transparent counter electrode on its inside. Compared with 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 fully colour-capable displays, in which a mosaic of red, green and blue filters is arranged in such a way that a filter element is located opposite each switchable pixel.

The TFT displays mostly used so far usually operate with crossed polarisers in transmission and are backlit. For TV applications, ECB (or VAN) cells or FFS cells are used, whereas monitors usually use IPS cells or TN (twisted nematic) cells, and notebooks, laptops and mobile applications usually use TN, VA or FFS cells.

The term MLC displays here encompasses any matrix display having inte- grated non-linear elements, i.e., besides the active matrix, also displays with passive elements, such as varistors or diodes (MIM = metal-insulator-metal).

MLC displays of this type are particularly suitable for TV applications, moni- tors and notebooks or for displays with a high information density, for example in automobile manufacture or aircraft construction. Besides prob- lems regarding the angle dependence of the contrast and the response times, difficulties also arise in MLC displays due to insufficiently high specific resistance of the liquid-crystal mixtures [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], With decreasing resistance, the contrast of an MLC display deteriorates. Since the specific resistance of the liquid-crystal mixture generally drops over the life of an MLC display owing to interaction with the inside surfaces of the display, a high (initial) resistance is very important for displays that have to have acceptable resistance values over a long operating period.

Displays which use the ECB effect have become established as so-called VAN (vertically aligned nematic) displays, besides IPS displays (for example: Yeo, S.D., Paper 15.3: “An LC Display for the TV Application", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pp. 758 and 759) and the long-known TN displays, as one of the three more recent types of liquid-crystal display that are currently the most important, in particular for television applications.

The most important designs may be mentioned here: MVA (multi-domain vertical alignment, for example: 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 to 9, and Liu, C.T. 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 to 753), PVA (patterned vertical alignment, for example: 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 to 763) and ASV (advanced super view, for example: 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 to 757). More modern versions of the VA effect, are the so called PAVA (photo-alignment VA) and PSVA (polymer-stabilized VA).

In general form, the technologies 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 times of modem ECB displays have already been significantly improved by addressing methods with overdrive, for example: 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 to 109, the achievement of video-compatible response times, in particular in the switching of grey shades, is still a problem which has not yet been solved to a satisfactory extent.

ECB displays, like ASV displays, use liquid-crystalline media having negative dielectric anisotropy (Δε), whereas TN and to date all conventional IPS displays use liquid-crystalline media having positive dielectric anisotropy. However, presently there is an increasing demand for IPS and FFS displays utilizing dielectrically negative liquid crystalline media.

In liquid-crystal displays of this type, the liquid crystals are used as dielec- trics, whose optical properties change reversibly on application of an elecY trical voltage.

Since in displays in general, i.e. also in displays in accordance with these mentioned effects, the operating voltage should be as low as possible, use is made of liquid-crystal media which are generally predominantly composed 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 and if possible no compounds having a sign of the dielectric anisotropy which is opposite to that of the medium are employed. In the case of liquid-crystal media having negative dielectric anisotropy e.g. for ECB or UB-FFS displays, predominantly compounds having negative dielectric anisotropy are thus em- ployed. The respective liquid-crystalline media employed generally consist predominantly of liquid-crystal compounds having negative dielectric anisotropy.

In the media used in accordance with the present application, significant amounts of dielectrically positive liquid-crystal compounds and generally only very small amounts of dielectrically negative compounds or even none at all are typically employed, since in general the liquid-crystal displays are intended to have the lowest possible addressing voltages. The low addressing voltages enables displays which are energy saving and have fast switching times. At the same time small amounts of dielectrically neutral compounds may be beneficially used.

Liquid crystalline media having a positive dielectric anisotropy for IPS and FFS displays have already been disclosed.

Compounds of the following formula and similar 2-alkyl-furan compounds are disclosed in EP 1013649 A1 as suitable for a liquid crystal material.

A 2-phenyl-5-trifluoromethyl furan and derivatives thereof are disclosed as products of a coupling reaction in the publication Y. Wang et al., Angew. Chem. Int. Ed. 2017, 56, 1810 -1814.

The phase range of the liquid-crystal mixture must be sufficiently broad for the intended application of the display. The response times of the liquid- crystal media in the displays should be as low as possible, especially for video, animated simulation and gaming applications. This is particularly important for displays for television or multimedia applications. In order to improve the response times, it has repeatedly been proposed in the past to optimise the rotational viscosity of the liquid-crystal media (γ ₁ ), i.e. to achieve media having the lowest possible rotational viscosity. However, the results achieved here are inadequate for many applications and therefore make it appear desirable to find further optimisation approaches.

Adequate stability of the media to extreme loads, in particular to UV exposure and heating, is very particularly important. In particular in the case of applications in displays in mobile equipment, such as, for example, mobile telephones, this may be crucial.

Besides their relatively poor transmission and their relatively long response times, the MLC displays disclosed hitherto, they have further disadvantages. These are e.g. their comparatively low contrast, their relatively high viewing- angle dependence and the difficulty in the reproduction of grey scales in these displays, especially when observed from an oblique viewing angle, as well as their inadequate VHR and their inadequate lifetime. The desired improvements of the transmission of the displays and of their response times are required in order to improve their energy efficiency, respectively their capacity to render rapidly moving pictures.

There thus continues to be a great demand for MLC displays having very high specific resistance at the same time as a large working-temperature range, short response times and a relatively low threshold voltage, with the aid of which various grey shades can be produced and which have, in particular, a good and stable VHR. The invention has the object of providing MLC displays, not only for monitor and TV applications, but also for mobile applications such as e.g. telephones and navigation systems, which are based on the ECB, IPS or FFS effect, do not have the disadvantages indicated above, or only do so to a lesser extent, and at the same time have very high specific resistance values. In particular, it must be ensured for mobile telephones and navigation systems that they also work at extremely high and extremely low temperatures.

Surprisingly, it has been found that it is possible to achieve liquid-crystal displays which have, in particular in IPS and FFS displays, a low threshold voltage with short response times, a sufficiently broad nematic phase, favourable birefringence (Δn) and, at the same time, a high transmission, high contrast, good stability to decomposition by heating and by UV exposure, and a stable, high VHR if use is made in these display elements of nematic liquid-crystal media, which comprise at least one compound, preferably two or more compounds, of formula I, preferably additionally one or more compounds, preferably two or more compounds, selected from the group of the compounds of the formulae T, II and III, and/or one or more compounds, preferably two or more compounds selected from the group of formulae IV and/or V.

Media of this type can be used, in particular, for electro-optical displays having active-matrix addressing for IPS or FFS displays.

The media according to the present invention preferably additionally comprise a one or more compounds selected from the group of compounds of formulae T, II and III, preferably one or more compounds of formula II, more preferably in addition one or more compounds of formula III and, most preferably, additionally one or more compounds selected from the group of the compounds of formulae IV and V and, again preferably, one or more compounds selected from the group of compounds of formulae VI to IX (all formulae as defined below).

The mixtures according to the invention exhibit very broad nematic phase ranges with clearing points ≥ 70°C, very favourable values for the capacitive threshold, relatively high values for the holding ratio and at the same time good low-temperature stabilities at -20°C and -30°C, as well as very low rotational viscosities. The mixtures according to the invention are furthermore distinguished by a good ratio of clearing point and rotational viscosity and by a relatively high positive dielectric anisotropy. Now, it has been found surprisingly that LCs of the FFS type using liquid crystals with positive dielectric anisotropy may be realised using specially selected liquid crystalline media. These media are characterised by a particular combination of physical properties. Most decisive amongst these are their high values of the elastic constant(s), in particular by their excellent, low ratio (γ ₁ /k ₁₁ ) of the rotational viscosity (γ ₁ ) and the elastic constant (k ₁₁ ). Besides this, they show high leading to a good transmission.

The liquid crystalline medium of the present invention comprises a) one or more compounds of formula I, preferably in a concentration in the range from 1 % to 40 %, more preferably in the range from 2 % to 30 %, particularly preferably in the range from 3 % to 20 %, in which

R ¹ an alkyl radical having 1 to 15 C atoms, wherein one or more CH ₂ groups, including terminal C atoms, in this radical may each be replaced, independently of one another, by -C=C-, -CH=CH-,

-(CO)-O-, -O-(CO)- in such a way that 0 or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F or Cl,

A ¹ denotes

L ¹ , L ² each, independently of one another, denote F, Cl, OCF ₃ , CF ₃ , CH ₃ , OCH ₃ , CH ₂ F, CHF ₂ , preferably F,

Y CH ₃ , CH ₂ CH ₃ ,

A ⁰ , independently of one another, on each appearance, denotes phenylene-1 ,4-diyl, in which, in addition, one or two CH groups may be replaced by N and one or more H atoms may be replaced by halogen, CN, CH ₃ , CHF ₂ , CH ₂ F, OCH ₃ , OCHF ₂ or OCF ₃ , cyclohexane-1 ,4-diyl, in which, in addition, one or two non-adjacent CH ₂ groups may be replaced, independently of one another, by 0 and/or S and one or more H atoms may be replaced by F, cyclohexene-1 ,4-diyl, bicyclo[1.1.1 ]pentane-1 ,3- diyl, bicyclo[2.2.2]octane-1 ,4-diyl, spiro[3.3]heptane-2,6-diyl, tetrahydropyran-2,5-diyl or 1 ,3-dioxane-2,5-diyl,

Z° independently of one another, identically or differently, denotes a single bond, -CH ₂ O-, -(CO)O-, -CF ₂ O-, -CH ₂ CH ₂ CF ₂ O-, -CF ₂ CF ₂ -, -CH ₂ CF ₂ -, -CH ₂ CH ₂ -, -(CH ₂ ) ₄ -, -CH=CH-, -CH=CF- -CF=CF- or -C=C-, where asymmetrical bridges may be inserted in any orientation,

X ¹ F, Cl, -CF ₃ or -OCF ₃ , preferably -CF ₃ , and n denotes 0, 1 or 2, preferably 0. and preferably one or more additional compounds, selected from the groups of compounds according to the following conditions b) to f): b) one or more, preferably dielectrically neutral, compounds of formula T in which the individual radicals have the following meanings:

R ¹ and R ² denote H, F, Cl, Br, -CN or straight-chain or branched alkyl having 1 to 12 C atoms, in which, in addition, one or more CH ₂ groups, including terminal C atoms, may each be replaced, independently of one another, by -CH=CH-,

-C=C-,

-O-, -S-, -CO-, -CO-O-, -O-CO-, in such a way that O or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F or Cl,

L ¹ H or CH ₃ , preferably H, wherein the (fluoro)phenylene rings may optionally be substituted by one or two methyl and/or ethyl groups,

A ¹ , independently of one another, denotes phenylene-1 ,4-diyl, in which, in addition, one or two CH groups may be replaced by N and one or more H atoms may be replaced by halogen, CN, CH ₃ , CHF ₂ , CH ₂ F, OCH ₃ , OCHF ₂ or OCF ₃ , cyclohexane-1 ,4-diyl, in which, in addition, one or two non-adjacent CH ₂ groups may be replaced, independently of one another, by 0 and/or S and one or more H atoms may be replaced by F, cyclohexene-1 ,4- diyl, bicyclo[1.1.1]pentane-1 ,3-diyl, bicyclo[2.2.2]octane- 1 ,4-diyl, spiro[3.3]heptane-2,6-diyl, tetrahydropyran-2,5- diyl or 1 ,3-dioxane-2,5-diyl, in each case, independently of one another, denotes 0, 1 or 2, preferably 1 , c) one or more, preferably dielectrically positive, compounds selected from the group of compounds of formulae II and III, preferably of compounds having a dielectric anisotropy of greater than 3 each, preferably one or more compounds of formula II: in which an alkyl radical having 1 to 15 C atoms, wherein one or more CH ₂ groups, including terminal C atoms, in this radical may each be replaced, independently of one a such a way that 0 or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F or Cl, or H, preferably denotes alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl, fluorinated alkenyl having 2 to 7 C atoms, cycloalkyl with 3 to 5 C atoms, cyclalkylalkyl, cycloalkylalkoxy and most preferably alkyl, cyclopropyl, cyclopentyl or alkenyl, on each appearance, independently of one another, denote wherein the (fluoro)phenylene rings may optionally be substituted by one or two methyl and/or ethyl groups, preferably

L ²¹ and L ²² denote H or F,

L ^2a H or CH ₃ , preferably H,

X ² denotes halogen, halogenated alkyl or alkoxy having 1 to

3 C atoms or halogenated alkenyl or alkenyloxy 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 denotes 0, 1 , 2 or 3, preferably 1 or 2 and particularly pref- erably 2,

R ³ an alkyl radical having 1 to 15 C atoms, wherein one or more CH ₂ groups, including terminal C atoms, in this radical may each be replaced, independently of one a such a way that 0 or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F or Cl, or H, preferably denotes alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl, fluorinated alkenyl having 2 to 7 C atoms, cycloalkyl with 3 to 5 C atoms, cycloalkylalkyl, cycloalkylalkoxy and most preferably alkyl, cyclopropyl, cyclopentyl or alkenyl, on each appearance, independently of one another, are

wherein the (fluoro)phenylene rings may optionally be substituted by one or two methyl and/or ethyl groups, preferably

L ³¹ and L ³² , independently of one another, denote H or F, preferably L ³¹ denotes F,

|_3a H or CH ₃ , preferably H, X ³ denotes halogen, halogenated alkyl or alkoxy having 1 to

3 C atoms or halogenated alkenyl or alkenyloxy 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 , very preferably F, Cl, -O-CH=CF ₂ , -OCHF ₂ or -OCF ₃ ,

Z ³ denotes -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 denotes 0, 1 , 2 or 3, preferably 1 , 2 or 3 and particularly preferably 1 , d) one or more dielectrically neutral compounds selected from the group of formulae IV and V: in which

R ⁴¹ and R ⁴² , independently of one another, have the meaning indicated above for R ³ under formula III, preferably R ⁴¹ denotes alkyl and R ⁴² denotes alkyl, cyclopropyl, cyclopentyl or alkoxy or R ⁴¹ denotes alkenyl and R ⁴² denotes alkyl, also these independently of one another, denote

wherein the (fluoro)phenylene rings may optionally be substituted by one or two methyl and/or ethyl groups, preferably one or more of

Z ⁴¹ and Z ⁴² , independently of one another and, if Z ⁴¹ occurs twice, also these independently of one another, denote -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 thereof denotes/denote a single bond, p denotes 0, 1 or 2, preferably 0 or 1 , and

R ⁵¹ and R ⁵² , independently of one another, have one of the meanings given for R ⁴¹ and R ⁴² and preferably denote alkyl having 1 to 7 C atoms, preferably n-alkyl, particularly preferably n-alkyl having 1 to 5 C atoms, alkoxy having 1 to 7 C atoms, preferably n-alkoxy, particularly preferably n-alkoxy having 2 to 5 C atoms, alkoxyalkyl, alkenyl or alkenyloxy having 2 to 7 C atoms, preferably having 2 to 4 C atoms, preferably alkenyloxy, if present, each, independently of one another, denote wherein the (fluoro)phenylene rings may optionally be substituted by one or two methyl and/or ethyl groups, preferably

Z ⁵¹ to Z ⁵³ each, independently of one another, denote -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 of one another, denote 0 or 1 ,

(i + j) preferably denotes 0, 1 or 2, more preferably 0 or 1 , and e) one or more dielectrically negative compounds selected from the group of formulae VI to IX: wherein

R ⁶¹ denotes an unsubstituted alkyl radical having 1 to 7 C atoms, preferably a straight-chain alkyl radical, more preferably an n-alkyl radical, most preferably propyl or pentyl, an unsubstituted alkenyl radical having 2 to 7 C atoms, preferably a straight-chain alkenyl radical, particularly preferably having 2 to 5 C atoms, an unsubstituted alkoxy radical having 1 to 6 C atoms, an unsubstituted alkenyloxy radical having 2 to 6 C atoms or C _3-5 -cycloalkyl-(CH ₂ ) _0-1 ,

R ⁶² denotes an unsubstituted alkyl radical having 1 to 7 C atoms, an unsubstituted alkoxy radical having 1 to 6 C atoms, C _3-5 - cycloalkyloxy or an unsubstituted alkenyloxy radical having 2 to 6 C atoms, and

L ⁶¹ , L ⁶² independently H or methyl, preferably H,

I denotes 0 or 1 ,

R ⁷¹ denotes an unsubstituted alkyl radical having 1 to 7 C atoms, preferably a straight-chain alkyl radical, more preferably an n-alkyl radical, most preferably propyl or pentyl, an unsubstituted alkenyl radical having 2 to 7 C atoms, preferably a straight-chain alkenyl radical, particularly preferably having 2 to 5 C atoms or C _3-5 -cycloalkyl-(CH ₂ ) _0-1 ,

R ⁷² denotes an unsubstituted alkyl radical having 1 to 7 C atoms, preferably having 2 to 5 C atoms, an unsubstituted alkoxy radical having 1 to 6 C atoms, preferably having 1 , 2, 3 or 4 C atoms, or an unsubstituted alkenyloxy radical having 2 to 6 C atoms, preferably having 2, 3 or 4 C atoms, and

L ⁷¹ , L ⁷² independently H or methyl, preferably H,

R ⁸¹ denotes an unsubstituted alkyl radical having 1 to 7 C atoms, preferably a straight-chain alkyl radical, more preferably an n-alkyl radical, most preferably propyl or pentyl, an unsubstituted alkenyl radical having 2 to 7 C atoms, preferably a straight-chain alkenyl radical, particularly preferably having 2 to 5 C atoms or C _3-5 -cycloalkyl-(CH ₂ ) _0-1 , R ⁸² denotes an unsubstituted alkyl radical having 1 to 7 C atoms, preferably having 2 to 5 C atoms, an unsubstituted alkoxy radical having 1 to 6 C atoms, preferably having 1 , 2, 3 or 4 C atoms, an unsubstituted alkenyloxy radical having 2 to 6 C atoms, preferably having 2, 3 or 4 C atoms, or C _3-5 - cycloalkyloxy,

L ⁸¹ , L ⁸² independently H or methyl, preferably H, more preferably

Z ⁸ denotes -(C=O)-O-, -CH ₂ -O-, -CF ₂ -O- or -CH ₂ -CH ₂ -, preferably

-(C=O)-O- or -CH ₂ -O-, and o denotes 0 or 1 ,

R ⁹¹ and R ⁹² independently of one another have the meaning given for R ⁷² above,

R ⁹¹ preferably denotes an alkyl radical having 2 to 5 C atoms, preferably having 3 to 5 C atoms,

R ⁹² preferably denotes an alkyl or alkoxy radical having 2 to 5 C atoms, more preferably an alkoxy radical having 2 to 4 C atoms, or an alkenyloxy radical having 2 to 4 C atoms. p and q independently of each other denote 0 or 1 , and (p + q) preferably denotes 0 or 1 , in case preferably p = q = 1 , f) one or more compounds of formula X, preferably in a concentration in the range from 1 % to 30 %, more preferably in the range from 2 % to 20 %, particularly preferably in the range from 3 % to 10 %, in which

L independently denotes H or CH ₃ or CH ₂ CH ₃ , preferably H, denotes, in each occurrence independently of one another, preferably n denotes 1 or 2, preferably 1 ,

R ¹ denotes alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy, preferably having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms, C _3-5 -cycloalkyl, C _3-5 -cycloalkyl-alkyl, C _3-5 - cycloalkyl-alkyloxy, preferably alkyl, alkoxy, alkenyl or alkenyloxy, more preferably alkyl, alkenyl, alkoxy or alkenyloxy, and, most preferably alkyl, and

X ¹ denotes F, Cl, fluorinated alkyl, fluorinated alkenyl, fluorinated alkoxy or fluorinated alkenyloxy, the latter four groups preferably having 1 to 4 C atoms, preferably F, Cl, CF ₃ or OCF ₃ , wherein the respective rings, and preferably the phenylene rings, optionally may each be substituted by one or two alkyl groups, preferably by methyl and/or ethyl groups, preferably by one methyl group, and g) again optionally, preferably obligatory, either alternatively or additionally, one or more compounds of formula XI: in which independently denotes H or CH ₃ or CH ₂ CH ₃ , preferably H, denotes preferably

n denotes 0 or 1 ,

R ¹¹ and R ¹² independently of each other denote alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy, preferably having 1 to 7 C atoms, wherein one CH ₂ group may be replaced by a 1 ,2-cyclopropyl group, by a 1 ,3-cyclopentyl group or by a 1 ,3-cyclopentenylene group, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms and preferably alkyl, alkoxy, alkenyl or alkenyloxy, most preferably alkyl, alkoxy or alkenyloxy, wherein the respective rings, and preferably the phenylene rings, optionally may each be substituted by one or two alkyl groups, preferably by methyl and/or ethyl groups, preferably by one methyl group, and from which the compounds of formula X are excluded.

Optionally the media according to the present application comprise one or more compounds of more compounds of formula L, preferably in a concentration in the range from 1 % to 40 %, more preferably in the range from 2 % to 30 %, particularly preferably in the range from 3 % to 20 %, in which

R ^L1 and R ^L2 , independently of one another, denote, an alkyl radical having 1 to 15 C atoms, wherein one or more CH ₂ groups, preferably one CH ₂ group, in these radicals may each be replaced, independently of one another, by -C=C-, -CF ₂ O-, -OCF ₂ -, -O-, -(CO)-O-, -O-(C=O)-, cyclo-propylene, 1 ,3-cyclobutylene, 1 ,3-cyclopentylene, 1 ,3-cyclo- pentenylene in such a way that 0 atoms are not linked directly to one another, preferably by cyclopropylene or 1 ,3-cyclopentylene, an alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms, and in which one or more H atoms may be replaced by halogen, and

Y ^L1 and Y ^L2 , identically or differently, denote H, F or Cl, preferably at least one of Y ^L1 and Y ^L2 is H, preferably Y ^L2 is H, and most preferably Y ^L1 and Y ^L2 are H.

The liquid-crystalline media in accordance with the present application preferably have a nematic phase.

Throughout this application and especially for the definition of R ¹ , R ² , R ³ , R ⁴¹ , R ⁵¹ , R ^L1 , etc. and R ^L2 alkyl means an alkyl group, which may be straight- chain or branched. Each of these radicals is preferably straight-chain and preferably has 1 , 2, 3, 4, 5, 6, 7 or 8 C atoms and is accordingly preferably methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl or n-heptyl.

In case alkyl means a branched alkyl group it preferably means 2-alkyl, 2- methylalkyl or 2-(2-ethyl)-alkyl, preferably 2-butyl (=1 -methylpropyl), 2- methylbutyl, 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, in particular 2-methylbutyl, 2-methylbutoxy 4-methylhexyl, 2-hexyl, 2-octyl, 2- nonyl, 2-decyl and 2-dodecyl. Most preferred of these groups are 2-hexyl and 2-octyl.

Respective branched groups which lead to chiral compounds are also called chiral groups in this application. Particularly preferred chiral groups are 2-alkyl, 2- alkoxy, 2-methylalkyl, 2-methylalkoxy, 2-fluoroalkyl, 2-fluoroalkoxy, 2-(2-ethin)- alkyl, 2-(2-ethin)-alkoxy, 1 , 1 , 1 -trifluoro-2-alkyl and 1 ,1 ,1-trifluoro-2-alkoxy.

Particularly preferred chiral groups are 2-butyl (=1 -methylpropyl), 2- methylbutyl, 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, in particular 2-methylbutyl, 2-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 1 -methylhexoxy, 2-octyloxy, 2-oxa-3-methylbutyl, 3-oxa-4- methylpentyl, 4-methylhexyl, 2-hexyl, 2-octyl, 2-nonyl, 2-decyl, 2-dodecyl, 6- m ethoxyoctoxy, 6-m ethyloctoxy, 6-m ethyloctanoy loxy, 5- methylheptyloxycarbonyl, 2-methylbutyryloxy, 3-methylvaleroyloxy, 4- methylhexanoyloxy, 2-chlorpropionyloxy, 2-chloro-3-methylbutyryloxy, 2- chloro-4-methylvaleryloxy, 2-chloro-3-methylvaleryloxy, 2-methyl-3- oxapentyl, 2-methyl-3-oxahexyl, 1-methoxypropyl-2-oxy, 1 -ethoxypropyl-2- oxy, 1 -propoxypropyl-2-oxy, 1 -butoxypropyl-2-oxy, 2-fluorooctyloxy, 2- fluorodecyloxy, 1 ,1 ,1 -trifluoro-2-octyloxy, 1 ,1 ,1 -trif luoro-2-octy 1 , 2- fluoromethyloctyloxy for example. Very preferred are 2-hexyl, 2-octyl, 2- octyloxy, 1 ,1 , 1 -trifluoro-2-hexyl, 1 , 1 , 1 -trifluoro-2-octyl and 1 ,1 , 1 -trifluoro-2- octyloxy.

Throughout this application alkenyl means an alkenyl group, which may be straight-chain or branched and preferably is straight chain and preferably has 2, 3, 4, 5, 6 or 7 or 8 C atoms. Preferably it is vinyl, 1-E-alkenyl or 3-E- alkenyl, most preferably it is vinyl, 1-E-propenyl, 1-E-butenyl, 1-E-pentenyl, 3- butenyl or 3-E-pentenyl.

The compounds of the general formula I, L, T and II to X are prepared by methods known per se, as described in the literature (for example in the standard works, such as Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart), to be precise under reaction conditions which are known and are suitable for the said reactions. Use can be made here of variants which are known per se, but are not mentioned here in greater detail.

The compounds of formula I may be synthesized as disclosed in Angew. Chem. Int. Ed. 2017, 56, 1810 -1814 and as in the synthesis examples.

The compounds of general formula T are preferably synthesized as disclosed in WO 2012/013281 A1.

The invention furthermore relates to a liquid-crystal display containing a liquid-crystalline medium according to the invention, in particular an IPS or FFS display, particularly preferably a FFS or SG-FFS display. The invention furthermore relates to a liquid-crystal display of the IPS or FFS type comprising a liquid-crystal cell consisting of two substrates, where at least one substrate is transparent to light and at least one substrate has an electrode layer, and a layer, located between the substrates, of a liquid- crystalline medium comprising a polymerised component and a low- molecular-weight component, where the polymerised component is obtainable by polymerisation of one or more polymerisable compounds in the liquid-crystalline medium between the substrates of the liquid-crystal cell, preferably with application of an electrical voltage and where the low- molecular-weight component is a liquid-crystal mixture according to the invention as described above and below.

The displays in accordance with the present invention are preferably addressed by an active matrix (active matrix LCDs, AMDs for short), pref- erably by a matrix of thin-film transistors (TFTs). However, the liquid crystals according to the invention can also be used in an advantageous manner in displays having other known addressing means.

The invention furthermore relates to a process for the preparation of a liquid- crystalline medium according to the invention by mixing one or more com- pounds of formula I or its subformulae with one or more low-molecular-weight liquid-crystalline compounds, or a liquid-crystal mixture and optionally with further liquid-crystalline compounds and/or additives.

The following meanings apply above and below:

The term "FFS" is, unless indicated otherwise, used to represent FFS and SG-FFS displays.

The term "mesogenic group" is known to the person skilled in the art and is described in the literature, and denotes a group which, due to the anisotropy of its attracting and repelling interactions, essentially contributes to causing a liquid-crystalline (LC) phase in low-molecular-weight or polymeric substances. Compounds containing mesogenic groups (mesogenic com- pounds) do not necessarily have to have a liquid-crystalline phase themselves. It is also possible for mesogenic compounds to exhibit liquid- crystalline phase behaviour only after mixing with other compounds and/or after polymerisation. Typical mesogenic groups are, for example, rigid rod- or disc-shaped units. An overview of the terms and definitions used in connection with mesogenic or liquid-crystalline compounds is given in Pure Appl. Chem. 73(5), 888 (2001 ) and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368.

The term "spacer group" or “spacer” for short, also referred to as "Sp" above and below, is known to the person skilled in the art and is described in the literature, see, for example, Pure Appl. Chem. 73(5), 888 (2001) and C.

Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368. Unless indicated otherwise, the term "spacer group" or "spacer" above and below denotes a flexible group which connects the mesogenic group and the polymerisable group(s) to one another in a polymerisable mesogenic compound.

For the purposes of this invention, the term "liquid-crystalline medium" is intended to denote a medium which comprises a liquid-crystal mixture and one or more polymerisable compounds (such as, for example, reactive mesogens). The term "liquid-crystal mixture" (or "host mixture") is intended to denote a liquid-crystalline mixture which consists exclusively of unpoly- merisable, low-molecular-weight compounds, preferably of two or more liquid-crystalline compounds and optionally further additives, such as, for example, chiral dopants or stabilisers.

Particular preference is given to liquid-crystal mixtures and liquid-crystalline media which have a nematic phase, in particular at room temperature.

In a preferred embodiment of the present invention, the liquid-crystal medium comprises one or more compounds selected from formula l-A and more preferably from the group of the compounds of the formulae l-a to l-c: wherein the variables are defined as in formula I above and below.

Particular preference is given here to compounds of formula I or l-A or la/b/c in which n is 0 or is 1 , preferably 0. The group A ¹ here preferably denotes

1 ,4-phenylene, which is optionally fluorinated, particularly preferably

The group A ⁰ here preferably denotes

In the formulae I and in the related more specific formulae above and below compounds are preferred, wherein independently: n is 0 or 1 ,

X ¹ is CF ₃ or F, preferably CF ₃ ,

R ¹ is an alkyl radical having 1 to 7 C atoms, wherein one or more CH ₂ groups, including terminal C atoms, in this radical may each be replaced, independently of one another, by -C=C-, -CH=CH-, or

-0- in such a way that 0 atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F, preferably an alkyl radical having 2 to 7 C atoms.

In a preferred embodiment of the present invention the liquid crystalline medium comprises one or more compounds selected from the group of the compounds of the formulae 1-1 to I-42: wherein R ¹ , X ¹ are defined as for formula I above and below, including preferred definitions.

Preferred compounds of formula T are selected from compounds of formula wherein the groups are defined as above, and L ¹ is preferably H.

In the formula T and its more defined formulae above and below the group R ¹ preferably is straight-chain or branched alkyl having 1 to 12 C atoms, in which, in addition, one or more CH ₂ groups, including terminal C atoms, may each be replaced, independently of one another, by -CH=CH-, -C=C-,

-O-CO-, in such a way that 0 or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F or Cl, more preferably alkyl with 1 to 7 C atoms or alkenyl with 2 to 7 C atoms, cyclopentylmethyl or cyclopentyl. In the formula T and its more defined formulae above and below the group R ² preferably is straight-chain or branched alkyl having 1 to 12 C atoms, in which, in addition, one or more CH ₂ groups, including terminal C atoms, may each be replaced, independently of one another, by -CH=CH-, -C=C-,

-O-CO-, in such a way that 0 or S atoms are not linked directly to one another, a group -CF ₃ , -OCF ₃ or F, more preferably methyl, ethyl, n-propyl, n- butyl, CF ₃ or F, most preferably methyl, ethyl or propyl.

In a preferred embodiment of the present invention the liquid crystalline medium comprises one or more compounds selected from the group of the compounds of the formulae T-1 to T-4: wherein R ² is CH ₃ , CH ₂ CH ₃ , CF ₃ or F, preferably CH ₃ or CF ₃ ,

In a preferred embodiment of the present invention, the liquid-crystal medium comprises one or more, preferably dielectrically positive, compounds, preferably having a dielectric anisotropy of greater than 3, selected from the group of the compounds of the formulae 11-1 and II-2: in which the parameters have the respective meanings indicated above under formula II, and L ²³ and L ²⁴ , independently of one another, denote H or F, preferably L ²³ denotes F, and has one of the meanings given for and, in the case of formulae 11-1 and II-2, X ² preferably denotes F or OCF ₃ , particularly preferably F, and, in the case of formula II-2, and/or selected from the group of the compounds of the formulae lll-1 and HI-2: in which the parameters have the meanings given under formula III, and the media in accordance with the present invention may comprise, alternatively or in addition to the compounds of the formulae lll-1 and/or HI-2, one or more compounds of the formula HI-3 in which the parameters have the respective meanings indicated above, and the parameters L ³¹ and L ³² , independently of one another and of the other parameters, denote H or F.

The liquid-crystal medium preferably comprises compounds selected from the group of the compounds of the formulae 11-1 and 11-2 in which L ²¹ and L ²² and/or L ²⁴ and L ²⁵ both denote F.

In a preferred embodiment, the liquid-crystal medium comprises compounds selected from the group of the compounds of the formulae 11-2 in which L ²¹ , L ²² , L ²⁴ and L ²⁵ all denote F.

The liquid-crystal medium preferably comprises one or more compounds of the formula 11-1. The compounds of the formula 11-1 are preferably selected from the group of the compounds of the formulae 11-1 a to 11-1 e, preferably one or more compounds of formulaell-1 a and/or 11-1 b and/or 11-1 d, preferably of formula 11-1 a and/or 11-1 d or 11-1 b and/or 11-1 d, most preferably of formula ll-1d: in which the parameters have the respective meanings indicated above, and L ²⁵ and L ²⁶ , independently of one another and of the other parameters, denote H or F, and preferably in the formulae 11-1 a and 11-1 b,

L ²¹ and L ²² both denote F, in the formulae 11-1 c and 11-1 d,

L ²¹ and L ²² both denote F and/or L ²³ and L ²⁴ both denote F, and in formula 11-1 e, L ²¹ , L ²² and L ²³ denote F and wherein the respective rings, and preferably the phenylene rings, optionally may each be substituted by one or two alkyl groups, preferably by methyl and/or ethyl groups, preferably by one methyl group.

The liquid-crystal medium preferably comprises one or more compounds of the formula 11-2, which are preferably selected from the group of the compounds of the formulae I l-2a to I l-2k, preferably one or more compounds of formulae ll-2a and/or ll-2h and/or ll-2j and/or ll-2k: in which the parameters have the respective meanings indicated above, and L ²⁵ to L ²⁸ , independently of one another, denote H or F, preferably L ²⁷ and L ²⁸ both denote H, particularly preferably L ²⁶ denotes H, and wherein the respective rings, and preferably the phenylene rings, optionally may each be substituted by one or two alkyl groups, preferably by methyl and/or ethyl groups, preferably by one methyl group.

The liquid-crystal medium preferably comprises compounds selected from the group of the compounds of the formulae I l-2a to I l-2k in which L ²¹ and L ²² both denote F and/or L ²³ and L ²⁴ both denote F.

In a preferred embodiment, the liquid-crystal medium comprises compounds selected from the group of the compounds of the formulae I l-2a to I l-2k in which L ²¹ , L ²² , L ²³ and L ²⁴ all denote F.

Especially preferred compounds of the formula 11-2 are the compounds of the following formulae, particularly preferred of formulae ll-2a-1 and/or ll-2h-1 and/or ll-2k-2:

in which R ² and X ² have the meanings indicated above, and X ² preferably denotes F.

The liquid-crystal medium preferably comprises one or more compounds of the formula lll-1. The compounds of the formula lll-1 are preferably selected from the group of the compounds of the formulae lll-1 a to lll-1 j, preferably from formulae lll-1 d, lll-1 e, lll-1 g, lll-1 h, lll-1j, lll-1 k and lll-1 m:

in which the parameters have the meanings given above and preferably in which

X ³ denotes F, Cl, halogenated alkyl or alkoxy having 1 to 3 C atoms or halogenated alkenyl or alkenyloxy 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 , preferably denotes F, -OCF ₃ , or -CF ₃ ,

L ³³ and L ³⁴ , independently of one another, denote H or F,

L ³⁵ and L ³⁶ , independently of one another, denote H or F, preferably H.

The liquid-crystal medium preferably comprises one or more compounds of the formula lll-1 c, which are preferably selected from the group of the compounds of the formulae lll-1 c-1 to lll-1 c-5, preferably of formulae lll-1 c-1 and/or lll-1 c-2, most preferably of formula lll-1 c-1 : in which R ³ has the meaning indicated above and wherein the respective rings, and preferably the phenylene rings, optionally may each be substituted by one or two alkyl groups, preferably by methyl and/or ethyl groups, preferably by one methyl group.

The liquid-crystal medium preferably comprises one or more compounds of the formula III-1 d, which are preferably selected from the group of the compounds of the formulae III-1 d-1 to III-1 d-2, preferably of formulae III-1 d-1 : in which R ³ is defined as above, and X ³ is CF ₃ , F or OCF ₃ , preferably CF ₃ .

The liquid-crystal medium preferably comprises one or more compounds of the formula lll-1 g, which are preferably selected from the group of the compounds of the formulae lll-1 g-1 to lll-1g-6, preferably of formulae lll-1 g-1 and/or lll-1 g-2 and/or lll-1 g-3 and /or lll-1 g-6, more preferably of formula lll-1 g-3 and/or lll-1 g-6, more preferably of formula lll-1 g-6: in which R ³ has the meaning indicated above and wherein the respective rings, and preferably the phenylene rings, optionally may each be substituted by one or two alkyl groups, preferably by methyl and/or ethyl groups, preferably by one methyl group.

The liquid-crystal medium preferably comprises one or more compounds of the formula III-1 g, which are preferably selected from the group of the compounds of the formulae III-1 h-1 to III-1 h-5, preferably of formula III-1 h-3: in which R ³ has the meaning indicated above and wherein the respective rings, and preferably the phenylene rings, optionally may each be substituted by one or two alkyl groups, preferably by methyl and/or ethyl groups, preferably by one methyl group.

The liquid-crystal medium preferably comprises one or more compounds selected from the formulae lll-1j, lll-1 k and lll-1 m, which are preferably selected from the group of the compounds of the formulae lll-1 j-1 , lll-1 k-1 , III- 1 m-1 , preferably of the formula lll-1 i-1 : in which the parameters have the meanings given above, and X ³ preferably denotes F or -OCF ₃ .

The liquid-crystal medium preferably comprises one or more compounds of the formula lll-1 k, which are preferably selected from the group of the compounds of the formulae lll-1 m-1 and lll-1 m-2, preferably of the formula lll-1 m-1 : in which the parameters have the meanings given above and wherein the respective rings, and preferably the phenylene rings, optionally may each be substituted by one or two alkyl groups, preferably by methyl and/or ethyl groups, preferably by one methyl group.

The liquid-crystalline media in accordance with the present invention pref- erably comprise one or more dielectrically neutral compounds having a dielectric anisotropy in the range from -1 .5 to 3, preferably selected from the group of the compounds of the formulae VI, VII, VIII and IX.

In the present application, the elements all include their respective isotopes. In particular, one or more H in the compounds may be replaced by D, and this is also particularly preferred in some embodiments. An increased degree of deuteration of the corresponding compounds enables, for example, detection and recognition of the compounds.

In the present application, alkyl particularly preferably denotes straight-chain alkyl, in par- ticular 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 denotes 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 further preferred embodiment, the medium comprises one or more compounds of formula IV, preferably of formula IVa IVa in which

R ⁴¹ denotes an unsubstituted alkyl radical having 1 to 7 C atoms or an unsubstituted alkenyl radical having 2 to 7 C atoms, preferably an n-alkyl radical, particularly preferably having 2, 3, 4 or 5 C atoms, and

R ⁴² denotes an unsubstituted alkyl radical having 1 to 7 C atoms, an unsubstituted alkenyl radical having 2 to 7 C atoms, or an unsubstituted alkoxy radical having 1 to 6 C atoms, both preferably having 2 to 5 C atoms, an unsubstituted alkenyl radical preferably having 2, 3 or 4 C atoms, more preferably a vinyl radical or 1 -propenyl radical and in particular a vinyl radical.

In a particularly preferred embodiment, the medium comprises one or more compounds of formula IV selected from the group of the compounds of the formulae IV-1 to IV-5, preferably of formula IV-1 , in which alkyl and alkyl’, independently of one another, denote alkyl having 1 to 7 C atoms, preferably having 2 to 5 C atoms, alkenyl and alkenyl’, independently of one another, denote alkenyl having 2 to 5 C atoms, preferably having 2 to 4 C atoms, particularly preferably 2 C atoms, alkenyl’ preferably denotes alkenyl having 2 to 5 C atoms, preferably having 2 to 4 C atoms, particularly preferably having 2 to 3 C atoms, and alkoxy denotes alkoxy having 1 to 5 C atoms, preferably having 2 to 4 C atoms.

In a particularly preferred embodiment, the media according to the invention comprise one or more compounds of formula IV-1 and/or one or more compounds of formula IV-2.

In a further preferred embodiment, the medium comprises one or more compounds of formula IV, selected from the group of the compounds of the formulae IV-2 and IV-3, in which alkyl and alkyl’, independently of one another, denote alkyl having 1 to 7 C atoms, preferably having 2 to 5 C atoms, alkoxy denotes alkoxy having 1 to 5 C atoms, preferably hav- ing 2 to 4 C atoms.

In a further preferred embodiment, the medium comprises one or more compounds of formula V. In this further preferred embodiment, the medium comprises one or more compounds of formula V selected from the group of the compounds of the formulae V-1 to V-5, preferably one or more of formulae V-1 , V-3, V-4 and V-5, V-1

in which the parameters have the meanings given above under formula V, and preferably

R ⁵¹ denotes alkyl having 1 to 7 C atoms or alkenyl having 2 to 7

C atoms, and

R ⁵² denotes 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.

In a further preferred embodiment the medium comprises one or more compounds of the formula V-1 in which at least one of the R ⁵¹ and R ⁵² radicals is alkenyl having 2 to 6 carbon atoms, preferably those selected from the following formula: V-1 a wherein alkenyl preferably denotes alkenyl having 2 to 5 C atoms, preferably having 2 to 4 C atoms, particularly preferably vinyl or 3-buten-1 -yl, and R ⁵² is defined as above, and preferably is methyl or ethyl.

In a further preferred embodiment the medium comprises one or more compounds of the formula V-3 in which at least one of the R ⁵¹ and R ⁵² radicals is alkenyl having 2 to 6 carbon atoms, preferably those selected from the following formulae:

in which "Alkyl" has the definition given above, and is preferably methyl or ethyl. Particular preference is given to compounds of the formula V-3d.

In a further preferred embodiment, the medium comprises one or more compounds of formula V-4 selected from the group of the compounds of the formulae V-4a to V-4c, in which alkyl and alkyl* are each independently straight-chain alkyl radical having 1 to 6 carbon atoms, especially methyl, ethyl, n-propyl and pentyl.

The liquid crystalline medium preferably comprises two, three or more compounds selected from the group of compounds of formulae V-4a, V-4b and V-4c.

In a further preferred embodiment, the medium comprises one or more compounds of formula V-5 selected from the group of the compounds of the formulae V-5a to V-5c, preferably V-5a: in which alkyl and alkyl* are each independently straight-chain alkyl radical having 1 to 6 carbon atoms, especially methyl, ethyl or n-propyl, and alkenyl preferably denotes alkenyl having 2 to 5 C atoms, preferably having 2 to 4 C atoms, particularly preferably vinyl.

The media according to the invention preferably comprise the following compounds in the total concentrations indicated:

1 - 30 % by weight of one or more compounds selected from the group of the compounds of formula I and

2 - 60 % by weight of one or more compounds of formula II, preferably selected from the group of the compounds of the formulae II- 1 and II-2 and/or

1 - 60 % by weight of one or more compounds of formula III, and/or

20 - 80 % by weight of one or more compounds of formula IV, and/or 0 - 20 % by weight of one or more compounds of formula T, and/or 0 - 50 % by weight of one or more compounds of formula V, and/or 0 - 20 % by weight of one or more compounds of formula VI, and/or 0 - 20 % by weight of one or more compounds of formula VII, and/or 0 - 20 % by weight of one or more compounds of formula VIII, preferably selected from the group of the compounds of the formulae VI 11-1 and VIII-2 and/or

0 - 20 % by weight of one or more compounds of formula IX, and/ or

0 - 30 % by weight of one or more compounds selected from the group of the compounds of formula X where the total content of all compounds of formula I, T, of formulae II to IX and of formula X, which are present in the medium, preferably is 95 % or more, more preferably 97 % or more and, most preferably, 100 %, but always not more than 100 %.

The latter condition holds for all media according to the present application.

In a further preferred embodiment, the media in accordance with the present invention in addition to the compounds of formula I or the preferred sub- formulae thereof, preferably comprise one or more dielectrically neutral compounds selected from the group of compounds of formulae IV and V preferably in a total concentration in the range from 5 % or more to 90 % by weight or less, preferably from 10 % or more to 80 % or less, particularly preferably from 20 % or more to 70 % or less.

The medium according to the invention in a particularly preferred embodiment comprises independently one or more compounds of formula I in a total concentration in the range from 3 % or more to 30 % or less, preferably in the range from 5 % or more to 25 % or less, and/or one or more compounds of formula T in a total concentration in the range from 1 % or more to 40 % or less, preferably in the range from 5 % or more to 25 % or less, and/or one or more compounds of formula II in a total concentration in the range from 5 % or more to 50 % or less, preferably in the range from 10 % or more to 40 % or less, and/or one or more compounds of formula III in a total concentration in the range from 5 % or more to 50 % or less, preferably in the range from 10 % or more to 40 % or less, and/or one or more compounds of formula IV-1 and IV-2 in a total concentration in the range from 5 % or more to 55 % or less, preferably in the range from 25 % or more to 50 % or less, and/or one or more compounds of formula V in a total concentration in the range from 3 % or more to 30 % or less, preferably in the range from 20 % or more to 30 % or less.

All percentages (%) of mixture components within this disclosure are to be understood in % by weight.

Preferably the concentration of the compounds of formula I in the media according to the invention is in the range from 1 % or more to 20 % or less, more preferably from 1 .5 % or more to 20 % or less, most preferably from 2 % or more to 12 % or less.

In a preferred embodiment of the present invention the concentration of the compounds of formula II in the media is in the range from 3 % or more to 60 % or less, more preferably from 5 % or more to 55 % or less, more preferably from 10 % or more to 50 % or less and, most preferably, from 15 % or more to 45 % or less.

In a preferred embodiment of the present invention the concentration of the compounds of formula I, T and V altogether in the media is in the range from 30 % or more to 55 % or less, more preferably from 35 % or more to 45 % or less.

In a preferred embodiment of the present invention the concentration of the compounds of formula IV-1 , IV-2 and V-1 altogether in the media is in the range from 45 % or more to 75 % or less, more preferably from 55 % or more to 70 % or less.

In a preferred embodiment of the present invention the concentration of the compounds of formula lll-1 d and V-5 altogether in the media is in the range from 4 % or more to 25 % or less, more preferably from 8 % or more to 20 % or less.

In a preferred embodiment of the present invention the concentration of the compounds of formula V-1 a and V-5, preferably V-5a, altogether in the media is in the range from 12 % or more to 30 % or less, more preferably from 18 % or more to 28 % or less.

The present invention also relates to electro-optical displays or electro-optical components which contain liquid-crystalline media according to the invention. Preference is given to electro-optical displays which are based on the FFS, IPS, 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.

Accordingly, the present invention likewise relates to the use of a liquid- crystalline medium according to the invention in an electro-optical display or in an electro-optical component, and to a process for the preparation of the liquid-crystalline media according to the invention, characterised in that one or more compounds of formula I are mixed with one or more additional mesogenic compounds and optionally one ore more additives.

Besides compounds of the formulae I, T, II to X and L, other constituents 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 media according to the invention may optionally also comprise di- electrically negative compounds, whose total concentration is preferably 20 % or less, more preferably 10 % or less, based on the entire medium.

In a preferred embodiment, the liquid-crystal media according to the invention comprise in total, based on the mixture as a whole,

1 % or more to 30 % or less, preferably 1.5 % or more to 20 % or less, par- ticularly preferably 2 % or more to 10 % or less, of the compound of formula I, and/or

1 % or more to 35 % or less, preferably 2 % or more to 30 % or less, par- ticularly preferably 5 % or more to 25 % or less, of the compound of formula T, and/or

3 % or more to 50 % or less, preferably 4 % or more to 45 % or less, par- ticularly preferably 5 % or more to 40 % or less, of compounds of formulae II and/or III, and/or

40 % or more to 70 % or less, preferably 50 % or more to 65 % or less, par- ticularly preferably 55 % or more to 65 % or less, of compounds of formulae IV and/ or V, and/or 0 % or more to 30 % or less 0 % or more to 20 % or less, preferably 0 % or more to 15 % or less of compounds of the formulae VI and/or VII and/or VIII and/or IX.

The liquid-crystal media in accordance with the present invention may comprise one or more chiral compounds.

Particularly preferred embodiments of the present invention meet one or more of the following conditions, where the acronyms (abbreviations) are explained in Tables A to C and illustrated by examples in Table D.

Preferably the media according to the present invention fulfil one or more of the following conditions. i. The liquid-crystalline medium has a birefringence of 0.060 or more, par- ticularly preferably 0.070 or more. ii. The liquid-crystalline medium has a birefringence of 0.200 or less, par- ticularly preferably 0.180 or less. iii. The liquid-crystalline medium has a birefringence in the range from 0.090 or more to 0.180 or less. iv. The liquid-crystalline medium comprises one or more particularly pre- ferred compounds of formula I, preferably selected from the (sub-) formulae l-A or la to Ic. v. The liquid-crystalline medium comprises one or more particularly pre- ferred compounds of formula T, preferably selected from the (sub-) formulae T-1 to T-53, most preferably of (sub-)formula T-6. vi. The total concentration of the compounds of formula II in the mixture as a whole is 0.5 % or more, preferably 1 % or more, and preferably 14 % or less, particularly preferably 9 % or less, and very particularly preferably in the range from 1 % or more to 6 % or less. vii. The liquid-crystalline medium comprises one or more compounds of formula IV selected from the group of the compounds of the following formulae: CC-n-V and/or CC-n-Vm and/or CC-n-nVm and/or CC-V-V and/or CC-V-Vn and/or CC-nV-Vn, particularly preferably CC-3-V, preferably in a concentration of up to 60 % or less, particularly preferably up to 50 % or less, and optionally additionally to CC-3-V the compound(s) CC-3-V1 , preferably in a concentration of up to 15 % or less, and/or CC-3-2V1 , preferably in a concentration of up to 15 % or less, and/or CC-4-V, preferably in a concentration of up to 40 % or less, particularly preferably up to 30 % or less, and/or CC-5-V, preferably in a concentration of up to 20 % or less. viii. The media comprise the compound of formula CC-n-V, preferably CC-3-V, preferably in a concentration of 1 % or more to 60 % or less, more preferably in a concentration of 20 % or more to 55 % or less. ix. The liquid-crystalline medium comprises one or more compounds of formula IV, preferably of the formulae IV-1 and/or IV-2, preferably in a total concentration of 20 % or more, in particular 30 % or more, and very particularly preferably 40 % or more, and is preferably in the range from 46 % to 55 % of compounds of formula IV-1 . x. The total concentration of the compounds of formula V in the mixture as a whole is 15 % or more, preferably 20 % or more, and is preferably in the range from 15 % or more to 40 % or less, particularly preferably in the range from 20 % or more to 30 % or less. xi. The total concentration of the compounds of formula V-3 in the mixture as a whole preferably is 5 % or more to 25 % or less, preferably 5 % or more to 15 % or less. xii. The total concentration of the compounds of formula V-4, preferably V- 4a to V-4c, in the mixture as a whole preferably is 3 % or more to 30 % or less, preferably 10 % or more to 25 % or less. xiii. The total concentration of the compounds selected from formula V-5, preferably V-5-a, and lll-1 d, preferably lll-1 d-1 , in the mixture as a whole preferably is 2 % or more to 20 % or less, preferably 4 % or more to 15 % or less.

The invention furthermore relates to an electro-optical display having active- matrix addressing based on the IPS, FFS or UB -FFS effect, characterised in that it contains, as dielectric, a liquid-crystalline medium in accordance with the present invention.

The liquid-crystal mixture preferably has a nematic phase range having a width of at least 70 degrees. The rotational viscosity γ ₁ is preferably 350 mPa-s or less, preferably 250 mPa-s or less and, in particular, 150 mPa-s or less.

The mixtures according to the invention are suitable for all IPS and FFS-TFT applications using dielectrically positive liquid crystalline media, such as, e.g. XB-FFS.

The liquid-crystalline media according to the invention preferably virtually completely consist of 4 to 15, in particular 5 to 12, and particularly preferably 10 or less, compounds. These are preferably selected from the group of the compounds of the formulae I, T, II, III, IV, V, VI, VII, VIII and IX.

The liquid-crystalline media according to the invention may optionally also comprise more than 18 compounds. In this case, they preferably comprise 18 to 25 compounds.

In a preferred embodiment, the liquid-crystal media according to the invention predominantly comprise, preferably essentially consist of and, most preferably, virtually completely consist of compounds, which do not comprise a cyano group.

In a preferred embodiment, the liquid-crystal media according to the invention comprise compounds selected from the group of the compounds of the formulae I, T, II, III, and IV and V, preferably selected from the group of the compounds of the formulae la, T-1/-2, 11-1 , II-2, lll-1 , HI-2, IV, and V; they preferably consist predominantly, particularly preferably essentially and very particularly preferably virtually completely of the compounds of the said formulae.

The liquid-crystal media according to the invention preferably have a nematic phase from in each case at least -10°C or less to 70°C or more, particularly preferably from -20°C or less to 80°C or more, very particularly preferably from -30°C or less to 85°C or more and most preferably from -40°C or less to 90°C or more.

The expression "have a nematic phase" here means on the one hand that no smectic phase and no crystallisation are observed at low temperatures at the corresponding temperature and on the other hand that no clearing occurs on heating out of the nematic phase. The investigation at low temperatures is carried out in a flow viscometer at the corresponding temperature and checked by storage in test cells having a cell thickness corresponding to the electro-optical application for at least 100 hours. If the storage stability at a temperature of -20°C in a corresponding test cell is 1 ,000 h or more, the medium is regarded as 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 capillaries by conventional methods.

In a preferred embodiment, the liquid-crystal media according to the invention are characterised by optical anisotropy values in the moderate to low range. The birefringence values are preferably in the range from 0.075 or more to 0.130 or less, particularly preferably in the range from 0.085 or more to 0.120 or less and very particularly preferably in the range from 0.090 or more to 0.115 or less.

Preferably the liquid-crystalline media according to the present invention, on the one hand, have a value of the dielectric anisotropy of 1 .5 or more, preferably of 2.5 or more. At the other hand, they preferably have a dielectric anisotropy of 26 or less, preferably of 15 or less and most preferably of 10 or less.

In this embodiment, the liquid-crystal media according to the invention have a positive dielectric anisotropy Δε, which preferably is in the range from 2.0 or more to 20 or less, more preferably to 15 or less, more preferably from 2.0 or more to 10 or less, particularly preferably from 2.0 or more to 9.0 or less and very particularly preferably from 2.5 or more to 8.0 or less.

The liquid-crystal media according to the invention preferably have relatively low values for the threshold voltage (Vo) in the range from 1 .0 V or more to 5.0 V or less, preferably to 2.5 V or less, preferably from 1 .2 V or more to 2.2 V or less, particularly preferably from 1 .3 V or more to 2.0 V or less.

In addition, the liquid-crystal media according to the invention have high values for the VHR in liquid-crystal cells.

In general, liquid-crystal media having a low addressing voltage or threshold voltage here have a lower VHR than those having a higher addressing voltage or threshold voltage, and vice versa.

These preferred values for the individual physical properties are preferably also in each case maintained by the media according to the invention in combination with one another. In the present application, the term "compounds", also written as "com- pound(s)", means both one and also a plurality of compounds, unless explicitly indicated otherwise.

For the present invention, the following definitions apply in connection with the specification of the constituents of the compositions, unless indicated otherwise in individual cases:

- "comprise": the concentration of the constituents in question in the com- position is preferably 5% or more, particularly preferably 10% or more, very particularly preferably 20% or more,

- "predominantly consist of": the concentration of the constituents in ques- tion in the composition is preferably 50% or more, particularly preferably 55% or more and very particularly preferably 60% or more,

- "essentially consist of": the concentration of the constituents in question in the composition is preferably 80% or more, particularly preferably 90% or more and very particularly preferably 95% or more, and

- "virtually completely consist of': the concentration of the constituents in question in the composition is preferably 98% or more, particularly preferably 99% or more and very particularly preferably 100.0%.

This applies both to the media as compositions with their constituents, which can be groups of compounds as well as individual compounds, and also to the groups of compounds with their respective constituents, the compounds. Only in relation to the concentration of an individual compound relative to the medium as a whole does the term comprise mean: the concentration of the compound or compounds in question is preferably 1 % or more, particularly preferably 2% or more, very particularly preferably 4% or more.

For the present invention, "<" means less than or equal to, preferably less than, and "≥" means greater than or equal to, preferably greater than.

For the present invention denote trans-1 ,4-cyclohexylene, denotes a mixture of both cis- and trans-1 ,4-cyclohexylene and denote 1 ,4-phenylene.

Throughout this application 1 ,3-cyclopentenylene is a moiety selected from the group of the formulae preferably most preferably

For the present invention, the expression "dielectrically positive compounds" means compounds having a Δε of > 1 .5, the expression "dielectrically neutral compounds" means compounds having -1 .5 ≤ Δε ≤ 1 .5 and the expression "dielectrically negative compounds” means compounds having Δε < -1.5. The dielectric anisotropy of the compounds is determined here by dissolving 10 % by weight of the compounds in a liquid-crystalline host and determining the capacitance of the resultant mixture in each case in at least one test cell having a cell thickness of 20 pm with homeotropic and with homogeneous surface alignment at 1 kHz. The measurement voltage is typically 0.5 V to 1.0 V, but is always lower than the capacitive threshold of the respective liquid-crystal mixture investigated. The host mixture used for dielectrically positive and dielectrically neutral compounds is ZLI-4792 and that used for dielectrically negative compounds is ZLI-2857, both from Merck KGaA, Germany. The values for the respective compounds to be investigated are obtained from the change in the dielectric constant of the host mixture after addition of the compound to be investigated and extrapolation to 100% of the compound employed. The compound to be investigated is dissolved in the host mixture in an amount of 10 % by weight. If the solubility of the substance is too low for this purpose, the concentration is halved in steps until the investigation can be carried out at the desired temperature.

The liquid-crystal media according to the invention may, if necessary, also comprise further additives, such as, for example, stabilisers and/or pleo- chroitic, e.g. dichroitic, dyes and/or chiral dopants in the usual amounts. The amount of these additives employed is preferably in total 0 % or more to 10 % by weight or less, based on the amount of the entire mixture, particularly preferably 0.1 % or more to 6 % or less. The concentration of the individual compounds employed is preferably 0.1 % or more to 3 % or less. The concentration of these and similar additives is generally not taken into account when specifying the concentrations and concentration ranges of the liquid-crystal compounds in the liquid-crystal media.

In a preferred embodiment, the liquid-crystal media according to the invention comprise a polymer precursor which comprises one or more reactive compounds, preferably reactive mesogens, and, if necessary, also further additives, such as, for example, polymerisation initiators and/or polymeri- sation moderators, in the usual amounts. The amount of these additives employed is in total 0 % or more to 10 % by weight or less, based on the amount of the entire mixture, preferably 0.1 % or more to 2 % by weight or less. The concentration of these and similar additives is not taken into account when specifying the concentrations and concentration ranges of the liquid-crystal compounds in the liquid-crystal media.

The compositions consist of a plurality of compounds, preferably 3 or more to 30 or fewer, particularly preferably 6 or more to 20 or fewer and very particularly preferably 10 or more to 16 or fewer compounds, which are mixed in a conventional manner. In general, the desired amount of the compounds used in lesser amount is dissolved in the compounds making up the principal constituent of the mixture. This is advantageously carried out at elevated temperature. If the selected temperature is above the clearing point of the principal constituent, completion of the dissolution operation is particularly easy to observe. However, it is also possible to prepare the liquid- crystal mixtures in other conventional ways, for example using pre-mixes or from a so-called "multi-bottle system".

The mixtures according to the invention exhibit very broad nematic phase ranges having clearing points of 65°C or more, very favourable values for the capacitive threshold, relatively high values for the holding ratio and at the same time very good low-temperature stabilities at -30°C and -40°C. Furthermore, the mixtures according to the invention are distinguished by low rotational viscosities γ ₁ .

It goes without saying to the person skilled in the art that the media according to the invention for use in VA, IPS, FFS or PALC displays may also comprise compounds in which, for example, H, N, 0, Cl, F have been replaced by the corresponding isotopes.

The structure of the FFS liquid-crystal displays according to the invention corresponds to the usual geometry, as described, for example, in US 2002/0041354 A1.

The liquid-crystal phases according to the invention can be modified by means of suitable additives in such a way that they can be employed in any type of, for example, IPS and FFS LCD display that has been disclosed to date.

Table E below indicates possible dopants which can be added to the mix- tures according to the invention. If the mixtures comprise one or more dopants, it is (they are) employed in amounts of 0.01 % to 4 % by weight, preferably 0.1 % to 1 .0 %.

Stabilisers which can be added, for example, to the mixtures according to the invention, preferably in amounts of 0.01 % to 6 % by weight, in particular 0.1 % to 3 %, are shown below in Table F.

For the purposes of the present invention, all concentrations are, unless explicitly noted otherwise, indicated in per cent by weight and relate to the corresponding mixture as a whole or mixture constituents, again a whole, unless explicitly indicated otherwise. In this context the term “the mixture” describes the liquid crystalline medium. 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 all temperature differences are correspondingly indicated in differential degrees (° or degrees), unless explicitly indicated otherwise.

For the present invention, the term "threshold voltage" relates to the capaci- tive threshold (Vo), also known as the Freedericks threshold, unless explicitly indicated otherwise.

All physical properties are and have been determined in accordance with "Merck Liquid Crystals, Physical Properties of Liquid Crystals", status Nov. 1997, Merck KGaA, Germany, and apply for a temperature of 20°C, and Δn is determined at 436 nm, 589 nm and at 633 nm, and Δε at 1 kHz, unless explicitly indicated otherwise in each case.

The electro-optical properties, for example the threshold voltage (Vo) (capacitive measurement), are, as is the switching behaviour, determined in test cells produced at Merck Japan. The measurement cells have soda-lime glass substrates and are constructed in an ECB or VA configuration with polyimide alignment layers (SE-1211 with diluent **26 (mixing ratio 1 :1 ), both from Nissan Chemicals, Japan), which have been rubbed perpendicularly to one another and effect homeotropic alignment of the liquid crystals. The surface area of the transparent, virtually square ITO electrodes is 1 cm ² .

Unless indicated otherwise, a chiral dopant is not added to the liquid-crystal mixtures used, but the latter are also particularly suitable for applications in which doping of this type is necessary.

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

The dispersion of the materials may for practical purposes be conveniently characterized in the following way, which is used throughout this application unless explicitly stated otherwise. The values of the birefringence are determined at a temperature of 20°C at several fixed wavelengths using a modified Abbe refractometer with homeotropically aligning surfaces on the sides of the prisms in contact with the material. The birefringence values are determined at the specific wavelength values of 436 nm (respective selected spectral line of a low pressure mercury lamp), 589 nm (sodium “D” line) and 633 nm (wavelength of a HE-Ne laser (used in combination with an attenuator/diffusor in order to prevent damage to the eyes of the observers. In the following table Δn is given at 589 nm and A(Δn) is given as A(Δn) = Δn(436 nm) - Δn(633 nm).

The following symbols are used, unless explicitly indicated otherwise:

V ₀ threshold voltage, capacitive [V] at 20°C, n _e extraordinary refractive index measured at 20°C and 589 nm, n ₀ ordinary refractive index measured at 20°C and 589 nm,

Δn optical anisotropy measured at 20°C and 589 nm, λ wavelength λ [nm],

Δn(X) optical anisotropy measured at 20°C and wavelength λ, Δ(Δn) change in optical anisotropy defined as:

Δn(20°C, 436 nm) - Δn(20°C, 633 nm),

Δ(Δn*) “relative change in optical anisotropy” defined as: A(Δn)/Δn(20°C, 589 nm), dielectric susceptibility perpendicular to the director at 20°C and

1 kHz, dielectric susceptibility parallel to the director at 20°C and

1 kHz, Δε dielectric anisotropy at 20°C and 1 kHz,

T(N, I) or clp. clearing point [°C],

K _av . average eleastic constant at 20°C [pN] defined here as

LTS low-temperature stability of the phase, determined in test cells, VHR voltage holding ratio,

AVHR decrease in the voltage holding ratio, and Srei relative stability of the VHR, The following examples explain the present invention without limiting it. However, they show the person skilled in the art preferred mixture concepts with compounds preferably to be employed and the respective con- centrations thereof and combinations thereof with one another. In addition, the examples illustrate the properties and property combinations that are accessible.

For the present invention and in the following examples, the structures of the liquid-crystal compounds are indicated by means of acronyms, with the transformation into chemical formulae taking place in accordance with Tables A to C below. All radicals C _n H _2n+1 , C _m H _2m+1 and C _I H _2I+1 or C _n H _2n , C _m H _2m and CiH2i are straight-chain alkyl radicals or alkylene radicals, in each case having n, m and I C atoms respectively. Preferably n, m and I are independently of each other 1 , 2, 3, 4, 5, 6, or 7. Table A shows the codes for the ring elements of the nuclei of the compound, Table B lists the bridging units, and Table C lists the meanings of the symbols for the left- and right- hand end groups of the molecules. The acronyms are composed of the codes for the ring elements with optional linking groups, followed by a first hyphen and the codes for the left-hand end group, and a second hyphen and the codes for the right-hand end group. Table D shows illustrative structures of compounds together with their respective abbreviations.

Table A: Ring elements On the left individually or in combi- On the right individually or in com- nation bination

-cp- cyclopentyl -cp cyclopentyl

-cpr- cyclopropyl -cpr cyclopropyl On the left only in combination On the right only in combination -...n...- -CnH2n- -...n... “CnH2n“

-...M...- -CFH- -...M... -CFH-

-...D...- -CF ₂ - -...D... -CF ₂ -

-...V...- -CH=CH- -...V... -CH=CH-

-...Z...- -CO-O- -...Z... -CO-O-

-...Zl...- -O-CO- -...Zl... -O-CO-

-...K...- -CO- -...K... -CO-

-...W...- -CF=CF- -...W... -CF=CF-

-...0...- -0- -...0...- -0- in which n and m are each integers, and the three dots are placeholders for other abbreviations from this table.

Besides the compounds of formula B, the mixtures according to the invention preferably comprise one or more compounds of the compounds mentioned below.

The following abbreviations are used:

(n, m, k and I are, independently of one another, each an integer, preferably 1 to 9 preferably 1 to 7, k and I possibly may be also 0 and preferably are 0 to 4, more preferably 0 or 2 and most preferably 2, n preferably is 1 , 2, 3, 4 or 5, in the combination “-nO-” it preferably is 1 , 2, 3 or 4, preferably 2 or 4, m preferably is 1 , 2, 3, 4 or 5, in the combination “-Om” it preferably is 1 , 2, 3 or 4, more preferably 2 or 4. The combination “-IVm” preferably is “2V1”.)

Table D

Exemplary, preferred dielectrically positive compounds

CCG-n-OT

CCEU-n-F CGG-n-OD

Exemplary, preferred dielectrically neutral compounds

CC-V-IV LGP-n-m

PUS-cprn-m

LBh-n-T

Exemplary compounds having a high s±:

Exemplary, preferred dielectrically negative compounds CCY-nV-m

CPY-nV-m

CVY-V-n

PY-n-Om

CPY-n-m

CP(F,CI)-n-Om

CLY n Om

Table E shows chiral dopants which are preferably employed in the mixtures according to the invention.

Table E



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

Table F shows stabilisers which can preferably be employed in addition in the mixtures according to the invention. The parameter n here denotes an integer in the range from 1 to 12. In particular, the phenol derivatives shown can be employed as additional stabilisers since they act as antioxidants.

Table F





In a preferred embodiment of the present invention, the media according to the invention comprise one or more compounds selected from the group of the compounds from Table F, in particular one or more compounds selected from the group of the compounds of the following two formulae

Examples

The following examples explain the present invention without restricting it in any way. However, the physical properties make it clear to the person skilled in the art what properties can be achieved and in what ranges they can be modified. In particular, the combination of the various properties which can preferably be achieved is thus well defined for the person skilled in the art.

Synthesis Examples

Synthesis Example 1 (PO-3-T)

Synthesis of 2-(4-propylphenyl)-5-(trifluoromethyl)furan

A mixture of 1 -bromo-4-propylbenzene (1) (CAS 588-93-2, 1.3 g, 7 mmol) and [5-(trifluoromethyl)-2-furyl]boronic acid (2) (CAS 1308354-99-5, 1.3 g, 7 mmol) in acetone (40 mL) is treated with bis(dibenzylidene-acetone)- palladium(O) (15 mg, 26 pmol) and tris-(o-tolyl)phosphine (40 mg, 131 pmol) at 50°C under argon atmosphere. Aqueous sodium hydroxide (2 A/, 6.5 mL, 13 mmol) is slowly added at reflux temperature, and the reaction mixture is heated at reflux temperature for 2 h. Then it is allowed to cool to room temperature and quenched with dist. water/hydrochloric acid (2 A/) and diluted with MTB ether. The aqueous phase is separated and extracted with MTB ether. The combined organic phases are washed with dist. water and brine, dried (sodium sulfate) and concentrated in vacuo. The residue is purified by silica gel chromatography (solvent heptane) to give 2-(4- propylphenyl)-5-(trifluoromethyl)furan (3) as a colorless oil.

Compound (3) has the following phase characteristics:

K 11 °C I Δε: 0.5

Δn: 0.038 γ ₁ : 5 mPa s

Synthesis Example 2 (YO-2O-T)

Synthesis of 2-(4-ethoxy-2,3-difluorophenyl)-5-(trifluoromethyl)furan

A mixture of 1 -bromo-4-ethoxy-2,3-difluoro-benzene (4) (CAS 156573-09-0, 1.8 g, 8 mmol) and potassium carbonate (1.6 g, 12 mmol) in THF (40 mL) and dist. water (8 mL) is treated with tris(dibenzylidene-acetone)palladium(0) (35 mg, 38 pmol) and di(1 -adamantyl)-n-butylphosphine (25 mg, 70 pmol) at 60°C under argon atmosphere. A solution of [5-(trifluoromethyl)-2- furyl]boronic acid (2) (CAS 1308354-99-5, 1 .5 g, 8 mmol) in THF (10 mL) is slowly added at reflux temperature, and the reaction mixture is heated at reflux temperature for 5 h. Then it is allowed to cool to room temperature and quenched with dist. water/hydrochloric acid (2 A/) and diluted with MTB ether. The aqueous phase is separated and extracted with MTB ether. The combined organic phases are washed with dist. water and brine, dried (sodium sulfate) and concentrated in vacuo. The residue is purified by silica gel chromatography (solvent heptane) and crystallization (ethanol) to give white crystals of 2-(4-ethoxy-2,3-difluoro-phenyl)-5-(trifluoromethyl)furan (5). Compound (5) has the following phase characteristics: K 98°C I.

Further Compound Examples

In the following table the following abbreviations for the end groups are used

Further exemplary compounds: Mixture Examples

In the following exemplary mixtures are disclosed. All % values are % by weight.

This mixture has an advantageously low rotational viscosity γ ₁ of 54 mPa s.

Mixture Examples 1.1 to 1.4

Alternatively, 0.05 % of the compounds of one of the following formulae

wherein the two 0 atoms bonded to the N atoms indicate radicals, and are added to the mixture M-1. The resultant mixtures M-1.1 , M-1.2, M-1.3 and M-1 .4 respectively are characterized by an improved stability against severe conditions, especially against exposure to light. 1

The following mixture (C-1 ) is prepared and investigated. It is made analogously to Mixture Example 1 , but without PO-3-T and adjustments, so that the parameters T(N , I), Δn and Δε are balanced to about the same target values in both mixtures.

Table 1 : Comparison of mixtures C-1 and M-1

The mixture M-1 according to the invention has 9% improvement in γ ₁ over mixture C-1 .