DE102006036894A1 - Liquid-crystal medium with a negative dielectric anisotropy based on a mixture of polar compound, useful in an electro optical display comprises a bicyclohexyl compound - Google Patents

Abstract

Liquid-crystal medium with a negative dielectric anisotropy, based on a mixture of polar compounds comprises at least one bicyclohexyl compound (I) (>=30 wt.%). Liquid-crystal medium with a negative dielectric anisotropy, based on a mixture of polar compounds comprises at least one bicyclohexyl compound of formula (I) (>=30 wt.%). R 11> : 2-4C alkyl or alkenyl unsubstituted or substituted by CN or CF 3 or substituted by halogen, where the CH 2 group is substituted by -O-, -S-, 1,3-cyclobutane, -Ctriple boundC-, -CF 2O-, -OCF 2-, -OC-O- or -O-CO-; and R 12> : 2-5C alkenyl unsubstituted or substituted by CN or CF 3 or substituted by halogen, where the CH 2 group is substituted by -O-, -S-, 1,3-cyclobutane, -Ctriple boundC-, -CF 2O-, -OCF 2-, -OC-O- or -O-CO-. Where -O- are not directly connected together. Independent claims are also included for: (1) a procedure for manufacturing the liquid crystalline medium comprising mixing (I) with at least further liquid crystalline medium compound and optionally additives; and (2) an electro optical display with an active matrix-display based on the electronic code book, plasma addressed liquid crystal, fringe field switching or in-plane switching effect, as a dielectric comprising a liquid crystalline medium. [Image].

Description

worin
R¹¹ einen unsubstituierten, einen einfach durch CN oder CF₃ oder mindestens einfach durch Halogen substituierten Alkyl- oder Alkenylrest mit bis zu 4 C-Atomen, wobei in diesen Resten auch eine oder mehrere CH₂-Gruppen durch -O-, -S-,

-C≡C-, -CF₂O-, -OCF₂-, -OC-O- oder -O-CO- so ersetzt sein können, dass O-Atome nicht direkt miteinander verknüpft sind,
R¹² einen unsubstituierten, einen einfach durch CN oder CF₃ oder mindestens einfach durch Halogen substituierten Alkenylrest mit bis zu 5 C-Atomen, wobei in diesen Resten auch eine oder mehrere CH₂-Gruppen durch -O-, -S-,

-C≡C-, -CF₂O-, -OCF₂-, -OC-O- oder -O-CO- so ersetzt sein können, dass O-Atome nicht direkt miteinander verknüpft sind,
bedeuten,
in Mengen von ≥ 30 Gew.% bezogen auf das Medium,
enthält.The invention relates to a liquid-crystalline medium having negative dielectric anisotropy based on a mixture of polar compounds which comprises at least one compound of the formula I

wherein
R ^{11 is} an unsubstituted, an alkyl or alkenyl radical having up to 4 carbon atoms which is monosubstituted by CN or CF ₃ or at least simply by halogen, where one or more CH ₂ groups in these radicals are also represented by -O-, -S- .

-C≡C, -CF ₂ O-, -OCF ₂ -, -OC-O- or -O-CO- may be replaced so that O atoms are not directly linked to one another,
R ^{12 is} an unsubstituted, an alkenyl radical having up to 5 carbon atoms which is monosubstituted by CN or CF ₃ or at least simply by halogen, where one or more CH ₂ groups are also substituted by -O-, -S-,

-C≡C, -CF ₂ O-, -OCF ₂ -, -OC-O- or -O-CO- may be replaced so that O atoms are not directly linked to one another,
mean,
in amounts of ≥ 30% by weight, based on the medium,
contains.

such Media are especially for Electro-optical displays based on active matrix addressing on the ECB effect as well as for IPS Displays (In plane switching). The medium according to the invention preferably has a negative dielectric anisotropy.

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

The work of 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-crystalline phases must have high values for the ratio of the elastic constants K ₃ / K ₁ , high values for the optical anisotropy Δn and values for the dielectric anisotropy Δε ≦ -0.5 in order to be based on highly informative display elements to be used on the ECB effect. Electro-optical display elements based on the ECB effect have a homeotropic edge orientation (VA technology = Vertical Aligned). Even with displays that use the so-called IPS effect, dielectric negative liquid crystal media can be used.

Displays that use the ECB effect have become known as VAN (Vertically Aligned Nematic) displays in the MVA (Multi-Domain Vertical Alignment, eg: Yoshide, H. et al., Lecture 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., Lecture 15.1:" A 46-inch TFT-LCD HDTV Technology. ", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pp. 750-753) and PVA (Patterned Vertical Alignment, eg: Kim, Sang Soo, Lecture 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) in addition to ASV (Avanced Super View, eg: Shigeta, Mitzuhiro and Fukuoka, Hirofumi, Lecture 15.2 : "Development of High Quality LCDTV", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pp. 754-757) Displays and IPS (In Plane Switching) displays (eg: Yeo, SD, Vor 15.3: "A LC Display for the TV Application", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pp. 758 & 759), in addition to the long-known alongside TN (Twisted Nematic) displays, as one of the three most important recent types of liquid crystal displays, especially for television applications. In general, the technologies will be used eg in Souk, Jun, SIDSeminar 2004, Seminar M-6: "Recent Advances in LCD Technology", Seminar Lecture Notes, M-6/1 to M-6/26 and Miller, Ian, SIDSeminar 2004 , Seminar M-7: "LCD Television", Seminar Lecture Notes, M-7/1 to M-7/32, compared. Although the switching times of modern ECB displays have already been significantly improved by overdrive control methods, eg: Kim, Hyeon Kyeong et al., Lecture 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 switching times is still an unsatisfactory problem, especially when switching grayscale.

For the technical Application of this effect in electro-optical display elements become FK phases needed which must meet a variety of requirements. Especially important here the chemical resistance across from Moisture, air and physical influences such as heat, radiation in the infrared, visible and ultraviolet range and electric DC and Alternating fields.

Further becomes technically usable FK phases a liquid crystalline Mesophase in a suitable temperature range and a low viscosity required.

In None of the previously known series of compounds with liquid-crystalline Mesophase there is a single compound that meets all these requirements equivalent. There are therefore usually mixtures of two to 25, preferably three to 18, compounds prepared to be used as FK phases To get substances. Optimal phases, however, were able to do this Way are not easily prepared, since so far no liquid crystal materials with clearly negative dielectric anisotropy and sufficient Long-term stability to disposal stood.

• 1. MOS (Metal Oxide Semiconductor)-Transistoren auf Silizium-Wafer als Substrat.
• 2. Dünnfilm-Transistoren (TFT) auf einer Glasplatte als Substrat.

Matrix liquid crystal displays (MFK displays) are known. As non-linear elements for individual switching of the individual pixels, for example, active elements (ie transistors) can be used. One speaks then of an "active matrix", whereby one can distinguish two types:

• 1. MOS (Metal Oxide Semiconductor) transistors on silicon wafer as a substrate.
• 2. Thin-film transistors (TFT) on a glass plate as a substrate.

at Type 1 is usually the dynamic one as an electro-optical effect Scatter or the guest host effect used. The usage of Single-crystal silicon as substrate material limits the display size, as well the modular composition of various partial displays on the Bumps to problems leads.

at the more promising type 2, which is preferred, is considered electro-optical Effect usually the TN effect used.

you distinguishes two technologies: TFTs of compound semiconductors such as e.g. CdSe or TFT's based on polycrystalline or amorphous silicon. At the latter Technology is being worked on worldwide with great intensity.

The TFT matrix is on the inside of a glass plate of the display upset while the other glass plate on the inside the transparent counter electrode wearing. Compared to the size of the pixel electrode is the TFT very small and disturbs the picture practically not. This technology can also be used for full color Image displays, with a mosaic of red, green and blue filters is arranged such that each one filter element lies opposite a switchable picture element.

The Previously known TFT displays usually work as TN cells with crossed polaristors in transmission and are from behind illuminated.

Of the Term MFK displays here includes any matrix display with built-in nonlinear elements, i. in addition to the active matrix also ads with passive elements such as varistors or diodes (MIM = metal-insulator-metal).

Such MFK displays are particularly suitable for TV applications (eg pocket TV) or for high-information displays in automotive or aircraft. In addition to problems with regard to the angle dependence of the contrast and the switching times, MFK displays are subject to difficulties due to insufficiently high resistivity 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, p. 141 ff, Paris; STROMER, M., Proc. Eurodisplay 84, Sept. 1984: Design of Thin Film Transistors for Matrix Liquid Crystal Displays, p. 145 ff, Paris]. As the resistance decreases, the contrast of a MFK display degrades. As a result of the interaction with the inner surfaces of the display, the specific resistance of the liquid-crystal mixture generally decreases over the lifetime of an MFK display A high (initial) resistance is very important for displays that must have acceptable resistance values over a long period of operation.

Of the Disadvantage of the previously known MFK TN displays is based in their comparatively low contrast, the relatively high viewing angle dependence and the difficulty in creating grayscale in these displays.

It There is still a great need for MFK ads with very high specific resistance and at the same time a large operating temperature range, short switching times and low threshold voltage, with their help different shades of gray can be generated.

Of the Invention is the object of MFK displays, in particular for monitor and TV applications based on the ECB or the IPS effect do not provide the disadvantages mentioned above or only to a lesser extent and at the same time have very high resistivities. Especially must for Monitors and TVs guaranteed be that even at extremely high and extremely low temperatures work.

Surprisingly, it has now been found that this object can be achieved by using nematic liquid-crystal mixtures containing at least one compound of the formula I in high concentrations in these display elements. Compounds of the formula I are known, for example from the EP 0 168 683 B1 and EP 0 122 389 B1 ,

object the invention is thus a liquid crystalline Medium based on a mixture of polar compounds which at least one compound of the formula I in amounts of ≥ 30% by weight contains.

enthalten, zeichnen sich dadurch aus, dass zusätzlich zur Verbesserung der Rotationsviskosität γ₁ eine Erhöhung der elastischen Konstanten K₃₃ zur Verbesserung der Schaltzeiten beiträgt.The mixtures of the invention show very broad nematic phase ranges with clearing points ≥ 70 ° C, very favorable 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 and very low rotational viscosities and low switching times. The mixtures according to the invention, in particular those which contain ≥ 30% by weight

contain, characterized in that in addition to improving the rotational viscosity γ _1, an increase in the elastic constant K ₃₃ contributes to improving the switching times.

• a) R¹¹ in Formel I bedeutet vorzugsweise Alkyl oder Alkenyl, insbesondere Ethyl, Propyl, Butyl, Vinyl, 1E-Alkenyl oder 3E-Alkenyl. R¹² in Formel I bedeutet vorzugsweise Vinyl, 1E-Alkenyl oder 3-Alkenyl, vorzugsweise CH₂=CH.
• b) Flüssigkristallines Medium, welches ein, zwei, drei, vier oder mehr, vorzugsweise ein, zwei oder drei Verbindungen der Formel I enthält,
• c) Flüssigkristallines Medium, wobei der Anteil an Verbindungen der Formel I im Gesamtgemisch mindestens 30 Gew.%, vorzugsweise mindestens 35 Gew.%, besonders bevorzugt ≥ 38 Gew.%, beträgt.
• d) Flüssigkristallines Medium, welches zusätzlich eine Verbindung der Formel
  
  enthält, vorzugsweise in Mengen von ≤ 25 Gew.%.
• e) Flüssigkristallines Medium, welches zusätzlich eine oder mehrere Verbindungen der Formeln IIA und/oder IIB enthält,
  
  
  worin R² H, einen unsubstituierten, einen einfach durch CN oder CF₃ oder mindestens einfach durch Halogen substituierten Alkyl- oder Alkenylrest mit bis zu 15 C-Atomen, wobei in diesen Resten auch eine oder mehrere CH₂-Gruppen durch -O-, -S-,
  
  -C≡C-, -CF₂O-, -OCF₂-, -OC-O- oder -O-CO- so ersetzt sein können, dass O-Atome nicht direkt miteinander verknüpft sind, p 1 oder 2, und v 1 bis 6 bedeutet.
• f) Flüssigkristallines Medium, welches zusätzlich eine oder mehrere Verbindungen der Formel III enthält,
  
  worin R³¹ und R³² jeweils unabhängig voneinander einen geradkettigen Alkyl-, Alkoxyalkyl- oder Alkoxyrest mit bis zu 12 C-Atomen, und
  
  Z Einfachbindung, -CH₂CH₂-, -CH=CH-, -CF₂O-, -OCF₂-, -CH₂O-, -OCH₂-, -COO-, -OCO-, -C₂F₄-, -CF=CF- bedeuten.
• g) Flüssigkristallines Medium, wobei der Anteil an Verbindungen der Formeln IIA und/oder IIB im Gesamtgemisch mindestens 20 Gew.% beträgt.
• h) Flüssigkristallines Medium, wobei der Anteil der Verbindungen der Formel III im Gesamtgemisch mindestens 5 Gew.% beträgt.
• i) Flüssigkristallines Medium, welches mindestens eine Verbindung ausgewählt aus den Teilformeln I1 bis I9 enthält:
  
  
  Besonders bevorzugte erfindungsgemäße Medien enthalten eine Verbindung der Formel
  
  vorzugsweise in Mengen von 30-60 Gew.%, insbesondere 35-60 Gew.% und/oder eine Verbindung der Formel
  
  vorzugsweise in Mengen von 30-40 Gew.%, insbesondere von 35-40 Gew.%. Sofern die erfindungsgemäße sowohl eine Verbindung der Formel
  
  und eine Verbindung der Formelenthält, beträgt die Gesamtkonzentration dieser beiden Verbindungen in der Mischung ≥ 40 Gew.%, vorzugsweise ≥ 45 Gew.%, insbesondere ≥ 50 Gew.%.
• j) Flüssigkristallines Medium, welches mindestens eine oder mehrere Verbindungen aus der Gruppe
  
  
  enthält.
• k) Flüssigkristallines Medium, welches zusätzlich eine oder mehrere Verbindungen ausgewählt aus den Formeln IIIa bis IIIh enthält:
  
  
  worin Alkyl und Alkyl* jeweils unabhängig voneinander einen geradkettigen Alkylrest mit 1-6 C-Atomen, und bedeuten. Vorzugsweise enthält das erfindungsgemäße Medium mindestens eine Verbindung der Formel IIIa, Formel IIIb und/oder Formel IIId.
• l) Flüssigkristallines Medium, welches 30-80 Gew.% einer oder mehrerer Verbindungen der Formel I und 20-70 Gew.% einer oder mehrerer Verbindungen der Formeln IIA und/oder IIB enthält bzw. daraus besteht, wobei die Gesamtmenge der Verbindungen der Formeln I und IIA und/oder IIB ≤ 100 Gew.% beträgt.
• m) Flüssigkristallines Medium, welches zusätzlich eine oder mehrere Vierkernverbindungen der Formeln,
  
  worin R⁷ und R⁸ jeweils unabhängig voneinander eine der in Anspruch 2 für R² angegebenen Bedeutung haben, und w und x jeweils unabhängig voneinander 1 bis 6 bedeuten, enthält.
• n) Flüssigkristallines Medium, welches zusätzlich eine oder mehrere Verbindungen der Formeln Y-1 bis Y-11
  
  
  enthält, worin R¹³-R²⁰ jeweils unabhängig voneinander, die für R² angegebenen Bedeutungen haben, und z und m jeweils unabhängig voneinander 1-6 bedeuten. R^E bedeutet H, CH₃, C₂H₅ oder n-C₃H₇. x bedeutet 0, 1, 2 oder 3. Insbesondere bevorzugt enthält das erfindungsgemäße Medium eine oder mehrere Verbindungen der Formeln Y-2, Y-3 und/oder Y-11 mit einer Alkenylseitenkette, vorzugsweise in Mengen von ≥ 5 Gew.%.
• o) Flüssigkristallines Medium, welches zusätzlich eine oder mehrere Verbindungen der Formeln
  
  vorzugsweise in Mengen von > 3 Gew.%, insbesondere ≥ 5 Gew.%, und ganz besonders bevorzugt von 5-25 Gew.% enthält, wobei R²¹ die für R² angegebenen Bedeutungen hat und m 1-6 bedeutet.
• p) Flüssigkristallines Medium enthaltend zusätzlich ein oder mehrere fluorierte Terphenyle der Formeln T-1 bis T-22,
  
  
  
  worin R die für R² angegebenen Bedeutungen hat. Vorzugsweise ist R geradkettiges Alkyl, Alkoxy oder Alkoxyalkyl mit jeweils 1-6 C-Atomen, Alkenyl oder Alkenyloxy mit 2-6 C-Atomen. Vorzugsweise bedeutet R Methyl, Ethyl, Propyl, Butyl, Pentyl, Hexyl Methoxy, Ethoxy, Propoxy, Butoxy, Pentoxy. Das erfindungsgemäße Medium enthält die Terphenyle der Formeln T-1 bis T-22 vorzugsweise in Mengen von 2-30 Gew.%, insbesondere von 5-20 Gew.%. Besonders bevorzugt sind Verbindungen der Formeln T-1, T-2, T-3 und T-22. In diesen Verbindungen bedeutet R vorzugsweise Alkyl, ferner Alkoxy jeweils mit 1-5 C-Atomen. Vorzugsweise werden die Terphenyle in Mischungen mit einem Δn ≥ 0,10 in Kombination mit den Verbindungen der Formeln I, IIA, IIB und III eingesetzt. Bevorzugte Mischungen enthalten 2-20 Gew.% Terphenyle und 5-60 Gew.% der Verbindungen der Formel IIA und/oder IIB.
• q) Flüssigkristallines Medium enthaltend zusätzlich ein oder mehrere Biphenyle der Formeln B-1 bis B-4,
  
  worin Alkyl und Alkyl* jeweils unabhängig voneinander einen geradkettigen Alkylrest mit 1-6 C-Atomen, und Alkenyl und Alkenyl* jeweils unabhängig voneinander einen geradkettigen Alkenylrest mit 2-6 C-Atomen bedeuten. Der Anteil der Biphenyle der Formeln B-1 bis B-4 der Gesamtmischung beträgt vorzugsweise mindestens 3 Gew.%, insbesondere ≥ 5 Gew.%. Von den Verbindungen der Formeln B-1 bis B-4 sind die Verbindungen der Formeln B-1 und B-4 insbesondere bevorzugt. Besonders bevorzugte Biphenyle sind
  
  worin R Alkyl, Alkenyl, Alkoxy, Alkoxyalkyl, Alkenyloxy mit 1 bzw. 2 bis 6 C-Atomen bedeutet und Alkenyl die oben angegebene Bedeutung hat. Insbesondere bevorzugt enthält das erfindungsgemäße Medium eine oder mehrere Verbindungen der Formeln B-1a und/oder B-2c.
• r) Flüssigkristallines Medium, welches zusätzlich eine oder mehrere Verbindungen der Formeln
  
  vorzugsweise in Mengen von > 3 Gew.%, insbesondere ≥ 5 Gew.%, und ganz besonders bevorzugt von 5-25 Gew.%, enthält, wobei R^22-23 die für R¹¹ angegebenen Bedeutungenen haben und R²⁴ CH₃, C₂H₅ oder n-C₃H₇ und q 1 oder 2 bedeutet.
• s) Flüssigkristallines Medium enthaltend mindestens eine Verbindung der Formeln Z-1 bis Z-22,
  
  
  
  
  worin R und Alkyl die oben angegebenen Bedeutungen haben und p 1 oder 2 ist, vorzugsweise in Mengen von ≥ 5 Gew.%, insbesondere ≥ 10 Gew.%. Insbesondere bevorzugt sind Medien, die eine, zwei oder mehr Verbindungen der Formeln Z-1 bis Z-9 enthalten und zusätzlich eine, zwei oder mehr Verbindungen der Formel II. Vorzugsweise enthalten derartige Mischungen ≥ 10 Gew.% an Verbindungen der Formel II.
• t) Flüssigkristallines Medium enthaltend mindestens eine Verbindung der Formeln 0-1 bis 0-12,
  
  
  worin R¹ und R² die für R² angegebenen Bedeutungen haben, vorzugsweise bedeuten R¹ und R² jeweils unabhängig voneinander geradkettiges Alkyl, ferner Alkenyl.
• u) Bevorzugte erfindungsgemäße flüssigkristalline Medien enthalten eine oder mehrere Substanzen, die eine Tetrahydronaphthyl- oder Naphthyl-Einheit aufweisen, wie z.B. die Verbindungen der Formeln N-1 bis N-5,
  
  worin R^1N und R^2N jeweils unabhängig voneinander die für R² angegebenen Bedeutungen haben, vorzugsweise geradkettiges Alkyl, geradkettiges Alkoxy oder geradkettiges Alkenyl bedeuten, und Z, Z¹ und Z² jeweils unabhängig voneinander -C₂H₄-, -CH=CH-, -(CH₂)₄-, -(CH₂)₃O-, -O(CH₂)₃-, -CH=CHCH₂CH₂-, -CH₂CH₂CH=CH-, -CH₂O-, -OCH₂-, -COO-, -OCO-, -C₂F₄-, -CF=CF-, -CF=CH-, -CH=CF-, -CF₂O-, -OCF₂-, -CH₂- oder eine Einfachbindung bedeuten.
• v) Bevorzugte Mischungen enthalten eine oder mehrere Difluorbenzochroman-Verbindungen der Formel BC
  
  worin R^B1 und R^B2 jeweils unabhängig voneinander die Bedeutung von R² aufweisen, vorzugsweise in Mengen von 3 bis 20 Gew.%, insbesondere in Mengen von 3 bis 15 Gew.%. Besonders bevorzugte Verbindungen der Formel BC sind die Verbindungen BC-1 bis BC-7,
  
  
  worin Alkyl und Alkyl* jeweils unabhängig voneinander einen geradkettigen Alkylrest mit 1-6 C-Atomen, und Alkenyl und Alkenyl* jeweils unabhängig voneinander einen geradkettigen Alkenylrest mit 2-6 C-Atomen, bedeuten. Ganz besonders bevorzugt sind Mischungen enthaltend eine, zwei oder drei Verbindungen der Formel BC-2.

Some preferred embodiments of the mixtures according to the invention are mentioned below:

• a) R ¹¹ in formula I is preferably alkyl or alkenyl, in particular ethyl, propyl, butyl, vinyl, 1E-alkenyl or 3E-alkenyl. R ¹² in formula I is preferably vinyl, 1E-alkenyl or 3-alkenyl, preferably CH ₂ = CH.
• b) liquid-crystalline medium which contains one, two, three, four or more, preferably one, two or three compounds of the formula I,
• c) Liquid-crystalline medium, wherein the proportion of compounds of the formula I in the total mixture is at least 30% by weight, preferably at least 35% by weight, particularly preferably ≥ 38% by weight.
• d) liquid-crystalline medium which additionally contains a compound of the formula
  
  contains, preferably in amounts of ≤ 25 wt.%.
• e) liquid-crystalline medium which additionally contains one or more compounds of the formulas IIA and / or IIB,
  
  
  in which R ² denotes H, an unsubstituted alkyl or alkenyl radical having up to 15 C atoms, which is monosubstituted by CN or CF ₃ or at least simply by halogen, where one or more CH ₂ groups in these radicals are also represented by -O-, -S-,
  
  -C≡C-, -CF ₂ O-, -OCF ₂ -, -OC-O- or -O-CO- may be replaced so that O atoms are not directly linked together, p 1 or 2, and v 1 to 6 means.
• f) liquid-crystalline medium which additionally contains one or more compounds of the formula III,
  
  wherein R ³¹ and R ³² each independently represent a straight-chain alkyl, alkoxyalkyl or alkoxy radical having up to 12 C atoms, and
  
  Z single bond, -CH ₂ CH ₂ -, -CH = CH-, -CF ₂ O-, -OCF ₂ -, -CH ₂ O-, -OCH ₂ -, -COO-, -OCO-, -C ₂ F ₄ -, -CF = CF- mean.
• g) liquid-crystalline medium, wherein the proportion of compounds of the formulas IIA and / or IIB in the total mixture is at least 20% by weight.
• h) liquid-crystalline medium, wherein the proportion of the compounds of the formula III in the total mixture is at least 5% by weight.
• i) Liquid-crystalline medium which contains at least one compound selected from the sub-formulas I1 to I9:
  
  
  Particularly preferred media according to the invention contain a compound of the formula
  
  preferably in amounts of 30-60 wt.%, In particular 35-60 wt.% And / or a compound of formula
  
  preferably in amounts of 30-40% by weight, in particular of 35-40% by weight. If the inventive both a compound of formula
  
  and a compound of the formula contains, the total concentration of these two compounds in the mixture ≥ 40 wt.%, Preferably ≥ 45 wt.%, In particular ≥ 50 wt.%.
• j) liquid-crystalline medium containing at least one or more compounds from the group
  
  
  contains.
• k) Liquid-crystalline medium which additionally contains one or more compounds selected from the formulas IIIa to IIIh:
  
  
  wherein alkyl and alkyl * each independently represent a straight-chain alkyl radical having 1-6 C atoms, and mean. The medium according to the invention preferably contains at least one compound of the formula IIIa, formula IIIb and / or formula IIId.
• l) liquid-crystalline medium which contains 30-80% by weight of one or more compounds of the formula I and 20-70% by weight of one or more compounds of the formulas IIA and / or IIB, wherein the total amount of the compounds of the formulas I and IIA and / or IIB ≤ 100% by weight.
• m) liquid-crystalline medium which additionally contains one or more quaternary compounds of the formulas,
  
  wherein R ⁷ and R ⁸ each independently have one of the meanings given in claim 2 for R ² , and w and x are each independently 1 to 6, contains.
• n) Liquid-crystalline medium which additionally contains one or more compounds of the formulas Y-1 to Y-11
  
  
  wherein R ¹³ -R ²⁰ each independently of one another have the meanings given for R ² , and z and m are each independently 1-6. R ^E is H, CH ₃ , C ₂ H ₅ or nC ₃ H ₇ . x is 0, 1, 2 or 3. Particularly preferably, the medium according to the invention contains one or more compounds of the formulas Y-2, Y-3 and / or Y-11 with an alkenyl side chain, preferably in amounts of ≥ 5% by weight.
• o) liquid-crystalline medium which additionally contains one or more compounds of the formulas
  
  preferably in amounts of> 3% by weight, in particular ≥ 5% by weight, and very particularly preferably of 5-25% by weight, where R ^{21 has} the meanings given for R ² and m is 1-6.
• p) liquid-crystalline medium additionally containing one or more fluorinated terphenyls of the formulas T-1 to T-22,
  
  
  
  wherein R has the meanings given for R ² . Preferably, R is straight-chain alkyl, alkoxy or alkoxyalkyl each having 1-6 C atoms, alkenyl or alkenyloxy having 2-6 C atoms. Preferably R is methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy, pentoxy. The medium according to the invention contains the terphenyls of the formulas T-1 to T-22, preferably in amounts of 2-30% by weight, in particular of 5-20% by weight. Particular preference is given to compounds of the formulas T-1, T-2, T-3 and T-22. In these compounds R preferably denotes alkyl, furthermore alkoxy in each case with 1-5 C atoms. The terphenyls are preferably used in mixtures with a Δn ≥ 0.10 in combination with the compounds of the formulas I, IIA, IIB and III. Preferred mixtures contain 2-20% by weight of terphenyls and 5-60% by weight of the compounds of the formula IIA and / or IIB.
• q) liquid-crystalline medium additionally containing one or more biphenyls of the formulas B-1 to B-4,
  
  wherein alkyl and alkyl * each independently represent a straight-chain alkyl radical having 1-6 C atoms, and alkenyl and alkenyl * each independently of one another denote a straight-chain alkenyl radical having 2-6 C atoms. The proportion of the biphenyls of the formulas B-1 to B-4 of the total mixture is preferably at least 3% by weight, in particular ≥ 5% by weight. Of the compounds of the formulas B-1 to B-4, the compounds of the formulas B-1 and B-4 are particularly preferred. Particularly preferred biphenyls are
  
  wherein R is alkyl, alkenyl, alkoxy, alkoxyalkyl, alkenyloxy having 1 or 2 to 6 carbon atoms and alkenyl has the meaning given above. With particular preference, the medium according to the invention contains one or more compounds of the formulas B-1a and / or B-2c.
• r) liquid-crystalline medium which additionally contains one or more compounds of the formulas
  
  preferably in amounts of> 3% by weight, in particular ≥ 5% by weight, and very particularly preferably of 5-25% by weight, where R ^{22-23 have} the meanings given for R ¹¹ and R ^{24 is} CH ₃ , C ₂ H ₅ or nC ₃ H ₇ and q is 1 or 2.
• s) liquid-crystalline medium containing at least one compound of the formulas Z-1 to Z-22,
  
  
  
  
  wherein R and alkyl have the meanings given above and p is 1 or 2, preferably in amounts of ≥ 5 wt.%, In particular ≥ 10 wt.%. Particular preference is given to media which contain one, two or more compounds of the formulas Z-1 to Z-9 and additionally one, two or more compounds of the formula II. Preferably, such mixtures contain ≥ 10% by weight of compounds of the formula II.
• t) liquid-crystalline medium comprising at least one compound of the formulas 0-1 to 0-12,
  
  
  wherein R ¹ and R ^{2 have} the meanings given for R ² , preferably R ¹ and R ^{2 are} each independently of the other straight-chain alkyl, further alkenyl.
• u) Preferred liquid-crystalline media according to the invention contain one or more substances which have a tetrahydronaphthyl or naphthyl unit, for example the compounds of the formulas N-1 to N-5,
  
  wherein R ^1N and R ^2N each independently of one another have the meanings given for R ² , preferably straight-chain alkyl, straight-chain alkoxy or straight-chain alkenyl, and Z, Z ¹ and Z ² each independently of one another represent -C ₂ H ₄ -, -CH = CH -, - (CH ₂ ) ₄ -, - (CH ₂ ) ₃ O-, -O (CH ₂ ) ₃ -, -CH = CHCH ₂ CH ₂ -, -CH ₂ CH ₂ CH = CH-, -CH ₂ O, -OCH ₂ -, -COO-, -OCO-, -C ₂ F ₄ -, -CF = CF-, -CF = CH-, -CH = CF-, -CF ₂ O-, -OCF ₂ -, -CH ₂ - or mean a single bond.
• v) Preferred mixtures contain one or more difluorobenzochroman compounds of the formula BC
  
  wherein R ^B1 and R ^B2 each independently have the meaning of R ² , preferably in amounts of 3 to 20 wt.%, In particular in amounts of 3 to 15 wt.%. Particularly preferred compounds of the formula BC are the compounds BC-1 to BC-7,
  
  
  wherein alkyl and alkyl * each independently represent a straight-chain alkyl radical having 1-6 C atoms, and alkenyl and alkenyl * each independently a straight-chain alkenyl radical having 2-6 C atoms. Very particular preference is given to mixtures containing one, two or three compounds of the formula BC-2.

One Another object of the invention is an electro-optical display with an active matrix addressing based on the ECB effect, characterized in that it is a liquid-crystalline dielectric Medium according to one of the claims 1 to 10 contains.

The Inventive liquid-crystalline Medium preferably has a nematic phase of ≤ 20 ° C to ≥ 70 ° C, especially preferably from ≤ 30 ° C to ≥ 80 ° C, especially preferably from ≤ 40 ° C to ≥ 90 ° C on.

in this connection means the term "one have nematic phase "on the one hand, that at low temperatures at the corresponding temperature no smectic phase and no crystallization is observed and on the other hand, that when heating up from the nematic phase, no clarification yet. The investigation at low temperatures is done in a flow viscometer carried out at the appropriate temperature and by storage in Test cells of the electro-optic application corresponding layer thickness for at least 100 hours checked. If the storage stability at a temperature of -20 ° C in a corresponding test cell is 1,000 hours or more the medium is said to be stable at this temperature. At temperatures from -30 ° C or -40 ° C the corresponding times are 500 h or 250 h. At high temperatures becomes the clearing point according to usual Methods measured in capillaries.

The liquid-crystal mixture preferably has a nematic phase range of at least 60 K and a flow viscosity ν ₂₀ of at most 30 mm ² · s ^-1 at 20 ° C.

The liquid-crystal mixture according to the invention has a Δ∈ of -0.5 to -8.0, in particular of -3.0 to -6.0, where Δ∈ denotes the dielectric anisotropy. The rotational viscosity γ ₁ is preferably <200 mPa · s, in particular <170 mPa · s.

The Values of birefringence Δn in the liquid crystal mixture are usually between 0.07 and 0.16, preferably between 0.08 and 0.12.

The Liquid-crystal media according to the invention have a negative dielectric anisotropy and have relative high values of the amount of dielectric anisotropy (| Δε |), the preferably in the range of ≥ 2.7 to ≥ 5.3 lie.

The liquid-crystal media according to the invention have relatively small values for the threshold voltage (V ₀ ). Preferably, they are in the range of 1.7V to 2.5V, more preferably ≤ 2.3V, and most preferably ≤ 2.2V.

In addition, show the liquid-crystal media according to the invention high values for the voltage holding ratio in liquid crystal cells on. These are in freshly filled Cells at 20 ° C in the cells ≥ 95 %, preferably ≥ 97 %, and most preferably ≥ 99 % and after 5 minutes in the oven at 100 ° C in the cells ≥ 90%, preferably ≥ 93% and most preferably ≥ 98 %.

In usually have liquid crystal media with a low drive voltage or threshold voltage a lower voltage holding ratio than those with a larger drive voltage or threshold voltage and vice versa.

For the present Invention means the terms "dielectrically positive links "such Compounds with a Δε> 1.5, "dielectrically neutral Compounds "such with -1.5 ≤ Δε ≤ 1.5 and "dielectrically negative" compounds such with Δε <-1.5. This is determines the dielectric anisotropy of the compounds by 10 % of the compounds in a liquid-crystalline Host solved and from the resulting mix the capacity in at least one test cell each with 20 μm Layer thickness with homeotropic and with homogeneous surface orientation at 1 kHz is determined. The measuring voltage is typically 0.5 V to 1.0V, but always lower than the capacitive threshold the respective examined liquid crystal mixture.

When Host mix for becomes dielectrically positive and dielectrically neutral compounds ZLI-4792 and for dielectrically negative compounds ZLI-2857, both from Merck KGaA, Germany, used. From the change the dielectric constant the host mixture after addition of the compound to be investigated and Extrapolation to 100% of the compound used will be the values for the obtained respective compounds to be examined. The to be examined Compound is 10% dissolved in the host mix. If the solubility the substance is too low, the concentration is gradual halved until the examination at the desired Temperature can be done.

All specified values for Temperatures for the present invention is in ° C.

The term "threshold voltage" for the present invention refers to the capacitive threshold (V ₀ ), also called Freedericksz threshold, unless explicitly stated otherwise. Also, in the examples, the optical threshold for 10% relative contrast (V ₁₀ ) is determined and reported, as is common practice.

The electro-optical properties, eg the threshold voltage (V ₀ ) (capacitive measurement) and the optical threshold (V ₁₀ ), as well as the switching behavior, are determined in test cells manufactured at Merck KGaA. The measuring cells have substrates of sodium glass (sodalime glass) and are in an ECB or VA configuration with polyimide orientation layers (SE-1211 with thinner ** 26 (mixing ratio 1: 1) both from Nissan Chemicals, Japan) which are perpendicular to each other are rubbed, executed. The area of the transparent, nearly square electrodes made of ITO is 1 cm ² . The layer thickness of the test cells used is selected according to the birefringence of the investigated liquid crystal mixture so that the optical retardation is (0.33 ± 0.01) μm. The polarizers, one of which is located in front of and behind the cell, form with their absorption axes an angle of 90 ° to each other and are parallel to the rubbing direction at their respective adjacent substrate with these axes. The layer thickness is usually about 4.0 microns. The cells are filled under normal pressure by capillarity and examined unsealed. The liquid crystal mixtures used are not mixed with a chiral dopant unless otherwise stated, but they are also particularly suitable for applications in which such a doping is required.

The electro-optical properties and the switching times of the test cells are determined in a measuring device DMS 301 from the company Autronic-Melchers, Karlsruhe, Germany, at a temperature of 20 ° C. The drive waveform used is a square wave with a frequency of 60 Hz. The voltage is given as V _rms (root mean square). When measuring the switching times, the voltage is increased from 0 V to twice the optical threshold (2V ₁₀ ) and vice versa. The specified switching times apply to the entire time that elapses from the change in the voltage until 90% of the respective total change in light intensity has been reached, ie τ _on ≡t (0% to> 90%) and τ _off ≡t (100%). to> 10%), so include the respective dead times (delay times). Since the individual switching times depend on the control voltage, the sum of the two individual switching times (Σ = τ _on + τ _off ) or the mean switching time (τ _av = (τ _on + τ _off ) / 2) are also improved to improve the comparability of the results _. specified.

The Voltage Holding Ratio is determined in the test cells produced at Merck KGaA. The measuring cells have substrates made of sodium glass (sodalime glass) and are made with polyimide orientation layers (AL-3046 from Japan Synthetic Rubber, Japan) with a layer thickness of 50 nm, which are rubbed perpendicular to each other. The layer thickness is uniformly 6.0 microns. The area of the transparent electrodes made of ITO is 1 cm ² .

The mixtures according to the invention are for all VA TFT applications are suitable, e.g. VAN, MVA, (S) -PVA, ASV. Furthermore, they are for IPS (in-plane switching), FFS (fringe field switching) and PALC applications suitable with negative Δε.

The nematic liquid-crystal mixtures in the displays of the invention usually contain two components A and B, which in turn consist of one or more individual connections.

The Component A has a distinctly negative dielectric anisotropy and gives the nematic phase a dielectric anisotropy from ≤ -0.5. It contains preferably compounds of the formulas I, IIA, IIB and / or III.

Of the Proportion of component A is preferably between 45 and 100%, in particular between 60 and 100%.

For component A is preferably one (or more) individual compounds selected) have a value of Δε ≤ -0.8. This value must be the more negative, the smaller the proportion A is the total mixture is.

The component B has a pronounced nematogeneity and a flow viscosity of not more than 30 mm ² .s ^-1 , preferably not more than 25 mm ² .s ^-1 , at 20 ° C.

Particularly preferred individual compounds of component B are extremely low-viscosity nematic liquid crystals having a flow viscosity of not more than 18, preferably not more than 12 mm ² · s ^-1 , at 20 ° C.

Component B is monotropic or enantiotropic nematic, has no smectic phases and can prevent the occurrence of smectic phases in liquid crystal mixtures up to very low temperatures. If, for example, a smectic liquid-crystal mixture is added, each with different Ma With high nematogeneity, the degree of suppression of smectic phases can be used to compare the nematogeneity of these materials.

the The skilled person is from the literature a variety of suitable materials known. Particular preference is given to compounds of the formula III.

Besides can these liquid crystal phases also more than 18 components, preferably 18 to 25 components, contain.

Preferably contain the phases 4 to 15, in particular 5 to 12, and especially preferably <10, compounds of the formulas I, IIA and / or IIB and optionally III.

Next Compounds of formulas I, IIA and / or IIB and III may also still other ingredients to be present, for. B. in an amount of up to 45% of the total mixture, but preferably up to 35%, in particular up to 10 %.

The Other ingredients are preferably selected from the nematic or nematogenic substances, in particular the known substances from the classes of azoxybenzenes, benzylideneanilines, biphenyls, terphenyls, Phenyl or cyclohexyl benzoates, cyclohexane-carboxylic acid phenyl or cyclohexyl esters, phenylcyclohexanes, cyclohexylbiphenyls, cyclohexylcyclohexanes, Cyclohexylnaphthalenes, 1,4-biscyclohexylbiphenyls or cyclohexylpyrimidines, Phenyl or cyclohexyl dioxanes, optionally halogenated stilbenes, Benzylphenyl ethers, tolans and substituted cinnamic acid esters.

The most important compounds which can be considered as constituents of such liquid-crystal phases can be characterized by the formula IV R ⁹ -LGER ¹⁰ IV wherein L and E are each a carbo- or heterocyclic ring system of the 1,4-disubstituted benzene and cyclohexane rings, 4,4'-disubstituted biphenyl, phenylcyclohexane and cyclohexylcyclohexane systems, 2,5-disubstituted pyrimidine and 1,3- Dioxane rings, 2,6-disubstituted naphthalene, di- and tetrahydronaphthalene, quinazoline and tetrahydroquinazoline, G -CH = CH- -N (O) = N- -CH = CQ -CH = N (O) - -C≡C- -CH ₂ -CH ₂ - -CO-O- -CH ₂ -O- -CO-S- -CH ₂ -S- -CH = N- -COO-Phe-COO- -CF ₂ O- CF = CF -OCF ₂ - -OCH ₂ - - (CH ₂ ) ₄ - - (CH ₂ ) ₃ O- or a C-C single bond, Q is halogen, preferably chlorine, or -CN, and R ⁹ and R ^{10 are} each alkyl, alkenyl, alkoxy, alkoxyalkyl or alkoxycarbonyloxy having up to 18, preferably up to 8 carbon atoms, or one of these radicals also CN, Mean NC, NO ₂ , NCS, CF ₃ , OCF ₃ , F, Cl or Br.

In most of these compounds R ⁹ and R ¹⁰ are different from each other, wherein one of these radicals is usually an alkyl or alkoxy group. Other variants of the proposed substituents are in use. Many such substances or mixtures thereof are commercially available. All these substances can be prepared by literature methods.

It goes without saying the person skilled in the art that the inventive VA, IPS, FFS or PALC mixture may also contain compounds in which, for example, H, N, O, Cl, F are replaced by the corresponding isotopes.

Of the Structure of the liquid crystal displays according to the invention corresponds to the usual Geometry, as e.g. in EP-OS 0 240 379, is described.

The following examples are intended to illustrate the invention without limiting it. Before and after percentages are by weight; All temperatures are in degrees Celsius.

Preferably contain the mixtures according to the invention in addition to the compounds of the formulas I one or more compounds the following compounds.

The following abbreviations are used:
(n, m, z: each independently 1, 2, 3, 4, 5 or 6)

The Preparation of the invention usable liquid crystal mixtures takes place in per se usual Wise. In general, the desired Amount of components used in lesser amount in the Main component making up components solved, expedient at elevated temperature. It is also possible, solutions the components in an organic solvent, e.g. in acetone, Chloroform or methanol, to mix and the solvent after mixing to remove again, for example by distillation.

The Dielectrics can also further, known in the art and described in the literature Additives, such as. As UV absorbers, antioxidants, nanoparticles, radical scavengers included. For example, 0-15 % pleochroic dyes, stabilizers or chiral dopants be added.

For example can 0-15% pleochroic dyes are added, further conductive salts, preferably ethyldimethyldodecylammonium 4-hexoxybenzoate, tetrabutylammonium tetraphenylboranate or complex salts of crown ethers (see, e.g., Haller et al., Mol. Cryst. Liq. Cryst. Volume 24, pages 249-258 (1973)) for improvement the conductivity or substances for change dielectric anisotropy, viscosity and / or orientation the nematic phases. Such substances are z. B. in the DE-OS 22 09 127, 22 40 864, 23 21 632, 23 38 281, 24 50 088, 26 37 430 and 28 53 728.

In Table A becomes possible Indicated dopants, which are added to the mixtures of the invention can. If the mixtures contain a dopant, it is in quantities from 0.01-4% by weight, preferably 0.1-1, 0 wt.% Used.

Table A

stabilizers, which are added, for example, the mixtures of the invention can become hereinafter referred to in Table B.

Table B (n = 1-12)

The following examples are intended to illustrate the invention without limiting it. Above and below mean
V _o threshold voltage, capacitive [V] at 20 ° C
Δn is the optical anisotropy measured at 20 ° C and 589 nm
Δε the dielectric anisotropy at 20 ° C and 1 kHz
cp. Clearing point [° C]
K ₁ elastic constant, "Splay" deformation at 20 ° C, [pN]
K ₃ elastic constant, "Bend" deformation at 20 ° C, [pN]
γ ₁ Rotational viscosity measured at 20 ° C [mPa · s], determined by the rotation method in a magnetic field
LTS low temperature stability (nematic phase), determined in test cells

The The display used to measure the threshold voltage has two plane parallel support plates in Distance of 20 μm and electrode layers with overlying Orientation layers from SE-1211 (Nissan Chemicals) on the insides the carrier plates on which a homeotropic Orientation of liquid crystals cause.

Mixing Examples Example 1

Example 2

Example 3

Example 4

Example 5

Example 6

Example 7

Example 8

Claims (12)

Liquid-crystalline medium having negative dielectric anisotropy based on a mixture of polar compounds which comprises at least one compound of the formula I,

wherein R ^{11 is} an unsubstituted, a simply by CN or CF ₃ or at least simply substituted by halogen alkyl or alkenyl radical having up to 4 carbon atoms, wherein in these radicals also one or more CH ₂ groups by -O-, -S -

-C≡C-, -CF ₂ O-, -OCF ₂ -, -OC-O- or -O-CO- can be replaced so that O atoms are not directly linked, R ^{12 is} an unsubstituted, a simple by CN or CF ₃ or at least monosubstituted by halogen alkenyl radical having up to 5 carbon atoms, wherein in these radicals also one or more CH ₂ groups by -O-, -S-,

-C≡C-, -CF ₂ O-, -OCF ₂ -, -OC-O- or -O-CO- may be replaced so that O atoms are not directly linked to each other, in amounts of ≥ 30 % By weight based on the medium contains. Liquid-crystalline medium according to Claim 1, characterized in that it additionally contains one or more compounds of the formulas IIA and / or IIB,

wherein R ^{2 is} an unsubstituted, an alkyl or alkenyl radical having up to 15 carbon atoms which is monosubstituted by CN or CF ₃ or at least monosubstituted by halogen, where one or more CH ₂ groups in these radicals are each independently of one another denoted by -O- , -S-,

-C≡C-, -CO- -CO-O-, -O-CO- or -O-CO-O- may be replaced so that O atoms are not directly linked together, p 1 or 2, and v 1 to 6 means. Liquid-crystalline medium according to claim 1 or 2, characterized in that it additionally contains one or more compounds of the formula III,

wherein R ³¹ and R ³² each independently represent a straight-chain alkyl, alkoxyalkyl or alkoxy radical having up to 12 C atoms, and

Z single bond, -CH ₂ CH ₂ -, -CH = CH-, -CF ₂ O-, -OCF ₂ -, -CH ₂ O-, -OCH ₂ -, -COO-, -OCO-, -C ₂ F ₄ -, -CF = CF- mean, contains. liquid-crystalline Medium according to one or more of claims 1 to 3, characterized in that it contains one, two, three, four or more compounds of formula I. liquid-crystalline Medium according to one or more of claims 1 to 4, characterized in that the proportion of compounds of formula I in the total mixture at least 35% by weight. liquid-crystalline Medium according to one or more of claims 1 to 5, characterized in that the proportion of compounds of the formulas IIA and / or IIB in the total mixture at least 20% by weight. liquid-crystalline Medium according to one or more of claims 1 to 6, characterized in that the proportion of compounds of formula III in the total mixture at least 3% by weight. Liquid-crystalline medium according to one or more of claims 1 to 7, characterized in that it comprises at least one compound selected from the formulas I1 to I9,

contains. liquid-crystalline Medium according to one or more of claims 1 to 8, characterized in that it 30-80% by weight of one or more compounds of the formula I and 20-70% by weight of one or more compounds of the formulas IIA and / or IIB contains in which the total amount of the compounds of formulas I and IIA and / or IIB ≤ 100 % By weight. Liquid-crystalline medium according to one or more of claims 1 to 9, characterized in that it is a compound of formula

and / or a compound of the formula

contains. Process for the preparation of a liquid-crystalline Medium according to one or more of claims 1 to 10, characterized that one or more compounds of the formula I having at least one further liquid crystalline Blend compound and optionally added additives. Electro-optical display with active matrix addressing based on the ECB, PALC, FFS or IPS effect, thereby in that it has a liquid-crystalline medium as a dielectric after a or more of the claims 1 to 10 contains.