DE4448054B4 - Liquid-crystalline medium and its use - Google Patents

Abstract

worin
R¹ einen unsubstituierten Alkylrest mit bis zu 18 C-Atomen und
R² einen Alkoxyrest mit bis zu 17 C-Atomen bedeuten,
und
mindestens zwei Verbindungen der Formel II,

worin
R¹ und R² jeweils unabhängig voneinander
H, ein unsubstituierter Alkyl- oder Alkenylrest mit bis zu 18 C-Atomen, worin eine oder mehrere nicht benachbarte CH₂-Gruppen durch einen Rest ausgewählt aus der Gruppe -O-, -S- und -C≡C- ersetzt sein können, bedeuten,
wobei mindestens eine Verbindung der Formal II ausgewählt ist aus der Verbindung der Formel,

worin n 1-18 und m 1-17 bedeuten,
und mindestens eine Verbindung der Formel II ausgewählt ist aus der Formel,

worin n und m jeweils unabhängig voneinander 1-18 bedeuten,...Liquid-crystalline medium having a birefringence Δn between 0.04 and 0.10, based on a mixture of polar compounds with negative dielectric anisotropy, characterized in that it comprises at least one compound of the formula I,

wherein
R ^{1 is} an unsubstituted alkyl radical having up to 18 carbon atoms and
R ^{2 is} an alkoxy radical having up to 17 C atoms,
and
at least two compounds of the formula II,

wherein
R ¹ and R ^{2 are} each independently
H, an unsubstituted alkyl or alkenyl radical having up to 18 carbon atoms, wherein one or more non-adjacent CH ₂ groups may be replaced by a radical selected from the group -O-, -S- and -C≡C-, mean,
where at least one compound of the formula II is selected from the compound of the formula

where n is 1-18 and m is 1-17,
and at least one compound of the formula II is selected from the formula

where n and m are each independently 1-18, ...

Description

worin
R¹ einen unsubstituierten Alkylrest mit bis zu 18 C-Atomen und
R² einen Alkoxyrest mit bis zu 17 C-Atomen bedeuten,
und
mindestens zwei Verbindungen der Formel II,

worin
R¹ und R² jeweils unabhängig voneinander
H, ein unsubstituierter Alkyl- oder Alkenylrest mit bis zu 18 C-Atomen, worin eine oder mehrere nicht benachbarte CH₂-Gruppen durch einen Rest ausgewählt aus der Gruppe -O-, -S- und -C≡C- ersetzt sein können, bedeuten,
wobei mindestens eine Verbindung der Formel II ausgewählt ist aus der Verbindung der Formel,

worin n 1-18 und m 1-17 bedeuten,
und mindestens eine Verbindung der Formel II ausgewählt ist aus der Formel,

worin n und m jeweils unabhängig voneinander 1-18 bedeuten,
enthält,
insbesondere für elektrooptische Anzeigen mit einer Aktivmatrix-Addressierung basierend auf dem ECB-Effekt.The invention relates to a liquid-crystalline medium having a birefringence Δn of between 0.04 and 0.10 on the basis of a mixture of polar compounds having negative dielectric anisotropy, which comprises at least one compound of the formula I.

wherein
R ^{1 is} an unsubstituted alkyl radical having up to 18 carbon atoms and
R ^{2 is} an alkoxy radical having up to 17 C atoms,
and
at least two compounds of the formula II,

wherein
R ¹ and R ^{2 are} each independently
H, an unsubstituted alkyl or alkenyl radical having up to 18 carbon atoms, wherein one or more non-adjacent CH ₂ groups may be replaced by a radical selected from the group -O-, -S- and -C≡C-, mean,
wherein at least one compound of the formula II is selected from the compound of the formula

where n is 1-18 and m is 1-17,
and at least one compound of the formula II is selected from the formula

wherein n and m are each independently 1-18,
contains
especially for electro-optical displays with an active matrix addressing based on the ECB effect.

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. Lett. 19 (1971), 3912). This was followed by works by J.F. boat (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 values -0.5 and -5, for highly informative display elements based on the ECB effect can be used. Electro-optical display elements based on the ECB effect have a homeotropic edge orientation.

For the technical application of this effect in electro-optical display elements FK phases are needed, which must meet a variety of requirements. Particularly important here are the chemical resistance to moisture, air and physical influences such as heat, radiation in the infrared, visible and ultraviolet range and electrical alternating and alternating fields. Furthermore, technically usable LC phases require a liquid-crystalline mesophase in a suitable temperature range and a low viscosity.

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 FK phases to obtain usable substances. Optimal phases, however, could can not be easily prepared in this way, 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. There are two technologies: TFTs made of compound semiconductors such as 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 a switchable picture element opposite lies.

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, d. H. 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 highly informative Dis-plays in automotive or Aircraft construction. In addition to problems with the angle dependence the contrast and the switching times result in MFK displays Difficulties due to not sufficiently 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, p. 141 ff, Paris; STROMER, M., Proc. Eurodisplay 84, Sept. 1984: Design of Thin Film Transistors for Matrix Addressing Television Liquid Crystal Displays, p. 145 ff, Paris]. With decreasing resistance, the contrast deteriorates a MFK display. As the resistivity of the liquid crystal mixture by Interaction with the inner surfaces of the display in general over the Lifetime of a MFK display decreases, a high (initial) resistance is very important for ads the acceptable resistance values over have to have a long service life.

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.

From the EP 0 474 062 and DE 42 23 059 MFK ads based on the ECB effect known. The FK mixtures described there based on 2,3-difluorophenyl derivatives which have an ester, ether or ethyl bridge and have low values of the "voltage holding ratio" (HR) after UV exposure on.

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 based on the object, MFK displays which on the ECB effect based provide the above-mentioned disadvantages not or only to a lesser extent and at the same time have very high resistivities.

aufweist.It has now been found that this object can be achieved if one uses in these display elements nematic liquid-crystal mixtures containing at least one compound of formula

having.

• a) Medium, welches zusätzlich eine oder mehrere Verbindungen der Formel III enthält:
  
  worin R¹ und R² jeweils unabhängig voneinander eine der in Anspruch 1 für Formel 4 angegebene Bedeutung haben.
• b) Medium, welches im wesentlichen aus 4 oder mehr Verbindungen ausgewählt aus den Formeln I und II, und zwei oder mehr Verbindungen der Formel III besteht.
• c) Medium, welches mindestens 2 Verbindungen der Formel I enthält.
• d) Medium, wobei der Anteil an Verbindungen der Formel I im Gesamtgemisch mindestens 15 Gew.-% beträgt.
• e) Medium, wobei der Anteil an Verbindungen der Formel II im Gesamtgemisch mindestens 30 Gew.-% beträgt.
• f) Medium, wobei der Anteil an Verbindungen der Formel III im Gesamtgemisch 10 bis 50 Gew.-% beträgt.
• g) Flüssigkristallines Medium, welches mindestens 2 Verbindungen ausgewählt aus den Formeln IIIa und IIIb enthält
  
  worin alkyl C_1-6-Alkyl bedeutet, insbesondere enthaltend 1 Verbindung der Formel IIIa und mindestens 1 Verbindung der Formel IIIb
• h) Flüssigkristallines Medium, welches im wesentlichen aus: 15–30 Gew.-% einer oder mehrerer Verbindungen der Formel I, 30–70 Gew.-% zwei oder mehrerer Verbindungen der Formel II und 10–50 Gew.-% einer oder mehrerer Verbindungen der Formel III besteht.

The invention thus relates to a liquid-crystalline medium based on a mixture of polar compounds with negative dielectric anisotropy according to claim 1. Preferred embodiments are:

• a) medium which additionally contains one or more compounds of the formula III:
  
  wherein R ¹ and R ² each independently have one of the meanings given in claim 1 for formula 4.
• b) medium which consists essentially of 4 or more compounds selected from the formulas I and II, and two or more compounds of formula III.
• c) medium containing at least 2 compounds of formula I.
• d) medium, wherein the proportion of compounds of formula I in the total mixture is at least 15 wt .-%.
• e) medium, wherein the proportion of compounds of formula II in the total mixture is at least 30 wt .-%.
• f) medium, wherein the proportion of compounds of formula III in the total mixture is 10 to 50 wt .-%.
• g) liquid-crystalline medium containing at least 2 compounds selected from the formulas IIIa and IIIb
  
  wherein alkyl is C _1-6 -alkyl, in particular containing 1 compound of formula IIIa and at least 1 compound of formula IIIb
• h) liquid-crystalline medium which consists essentially of: 15-30% by weight of one or more compounds of the formula I, 30-70% by weight of two or more compounds of the formula II and 10-50% by weight of one or more Compounds of formula III is.

Another object of the invention is the use of a liquid-crystalline medium according to one of claims 1 to 11 as a dielectric in an electro-optical display with an active matrix Addres based on the ECB effect.

Preferably indicates the liquid crystal mixture a nematic phase range of at least 60 K and a maximum viscosity 30 mPa · s at 20 ° C on.

The Inventive liquid-crystal mixture has a Δε of about -0.5 to -5, in particular from about -3.0 to -4.5 on, wherein Δε the dielectric Anisotropy means.

The Birefringence Δn in the liquid crystal mixture is between 0.04 and 0.10, preferably between 0.05 and 0.09 and the dielectric constant e || bigger or equal to 3, preferably 3.2 to 8.5.

• – mindestens eine Verbindung der Formel I,
• – mindestens zwei Verbindungen der Formel II, und
• – mindestens eine Verbindung ausgewählt aus den Formeln V und VI:
  
  worin R¹ und R² die die für Formel II in Anspruch 1 angegebene Bedeutung besitzen, und m und n jeweils 0 oder 1 bedeuten.

In a further preferred embodiment, the media according to the invention contain

• At least one compound of the formula I,
• At least two compounds of formula II, and
• At least one compound selected from the formulas V and VI:
  
  wherein R ¹ and R ² have the meaning given for formula II in claim 1, and m and n are each 0 or 1.

• – einer oder mehreren Verbindungen der Formel I,
• – zwei oder mehreren Verbindungen der Formel II,
• – einer oder mehreren Verbindungen der Formel V, und
• – einer oder mehreren Verbindungen der Formel VI.

In particular, these media essentially consist of

• One or more compounds of the formula I,
• Two or more compounds of the formula II,
• - One or more compounds of the formula V, and
• - One or more compounds of formula VI.

media containing compounds of the formula V, wherein m is 0, and compounds of Formula V wherein m is 1 are particularly preferred.

In a particularly preferred embodiment, the media according to the invention consist essentially of:
10-25% by weight of one or more compounds of the formula I,
20-40% by weight of two or more compounds of the formula II,
20-40 wt .-% of one or more compounds of the formula V and
15-35% by weight of one or more compounds of the formula VI.

The dielectrics may also contain further additives known to the person skilled in the art and described in the literature. For example, 0-15% of pleochroic dyes may also be added, furthermore conductive salts, preferably ethyldimethyldodecylammonium-4-hexoxybenzoate, tetrabutylammonium tetraphenylboranate or complex salts of crown ethers (cf., for example, Haller et al., Mol , Pages 249-258 (1973)) for improving the conductivity or substances for changing the dielectric anisotropy, the viscosity and / or the orientation of the nematic phases. Such substances are z. Tie DE-OS 22 09 127 . 22 40 864 . 23 21 632 . 23 38 281 . 24 50 088 . 26 37 430 and 28 53 728 described.

The individual components of the formula I to III of the liquid crystal phases according to the invention are either known or their manufacturing methods are for the skilled person to derive readily from the prior art, since they are based on in based on the literature described standard methods.

Corresponding compounds of the formulas I and II are described, for example, in WHERE 89-08633 ,

Corresponding compounds of the formula III are described, for example, in DE 33 21 373 ,

Corresponding compounds of the Formal V are described in the WO 88/07514 described.

The compounds of formula VI are known, for. B. from the DE 26 36 684 (n = 0) or the DE 29 27 277 (n = 1).

The nematic according to the invention liquid crystal mixtures The ads preferably contain at least 10% of compounds of the formula I, particularly preferably 15 to 30% of compounds of Formula I.

The nematic according to the invention liquid crystal mixtures the ads usually contain two components A and B, which in turn consist of one or more individual links.

The Component A has a distinctly negative dielectric anisotropy and gives the nematic phase a dielectric anisotropy from ≤ -0.3. she contains preferably compounds of the formulas I and II.

Of the Proportion of component A is between 45 and 100%.

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

The component B has a pronounced nematogeneity and a 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 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 mixed with in each case different materials with high nematogeneity, the degree of suppression of smectic phases achieved 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 compounds of the formulas I, II and III, or I, II, V and VI.

Next Compounds of the formulas I to VI may also contain other constituents be present, for. In an amount of up to 45% of the total mixture, but preferably up to 34%, 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 cyclohexyldioxanes, optionally halogenated stilbenes, benzylphenyl ethers, tolans and substituted ones Cinnamic acids.

The most important compounds which can be considered as constituents of such liquid-crystal phases can be characterized by the formula IV R ³ -LGER ⁴ 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 or a CC single bond, Q is halogen, preferably chlorine, or -CN, and R ³ and R ^{4 are} each alkyl, alkoxy, alkanoyloxy or alkoxycarbonyloxy having up to 18, preferably up to 8 carbon atoms, or one of these radicals also CN, NC, NO ₂ , CF ₃ , F, Cl or Br mean.

In most of these compounds R ³ and R ⁴ 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.

The inventive media can furthermore contain one or more dyes.

The structure of the liquid crystal displays according to the invention corresponds to the usual geometry, as z. In EP-OS 0 240 379 is described.

The The following examples are intended to illustrate the invention without limiting it. Above and below, percentages are by weight; all Temperatures are given in degrees Celsius.

The following abbreviations are used:

The given threshold voltage values V (0,0), V (10,0), V (90,0) were in a standard ECB cell with a layer thickness of 5 microns at 20 ° C measured.

Δn

die optische Anisotropie gemessen bei 20°C und 589 nm

Δε

die dielektrische Anisotropie bei 20°C

cp

Klärpunkt [°C]

S

Steilheit der Kennlinie

HR (20) Voltage holding ratio bei 20°C [%] HR (100) Voltage holding ratio bei 100°C [%] HR (UV) Voltage holding ratio nach UV-Belastung [%] Furthermore, mean: V (0,0) Threshold voltage [V] 0% transmission Viewing angle 0 ° V (10,0) Threshold voltage [V] 10% transmission Viewing angle 0 ° V (90,0) Threshold voltage [V] 90% transmission Viewing angle 0 °

.DELTA.n

the optical anisotropy measured at 20 ° C and 589 nm

Δε

the dielectric anisotropy at 20 ° C

cp

Clearing point [° C]

S

Slope of the characteristic

HR (20) Voltage holding ratio at 20 ° C [%] HR (100) Voltage holding ratio at 100 ° C [%] HR (UV) Voltage holding ratio after UV exposure [%]

The The display used to measure the threshold voltage has two plane-parallel Carrier plates, at a distance of 5 μm and electrode layers with overlying Orientation layers of lecithin on the insides of the carrier plates which cause a homeotropic orientation of the liquid crystals.

example 1

You make a mixture consisting of PCH-302FF 9:00 PCH-502FF 9:00 CCP 302FF 12:00 CCP 502FF 14:00 CCP 32FF 25.00 CCH-34 10:00 CCH-32 5:00 CCH 301 5:00 CCH 303 6:00 am CCH 501 5:00 whose physical data can be found in Table I. Table 1 cp + 86 ° C .DELTA.n +0.0766 Δε -3.4 ε || 3.4 ε⏊ 6.8 V (10,0) 2.24 (DAP) HR (20) 98.4 HR (100) 83.3 HR (UV) 86.4

Example 2

A liquid-crystalline phase is formed PCH-302FF 12:00 PCH-502FF 11:00 CCP 302FF 14:00 CCP 502FF 15:00 CCP 32FF 24.00 CCH-34 6:00 am CCH-32 5:00 CCH 301 4:00 CCH 303 5:00 CCH 501 4:00 whose physical data can be found in Table II. Table II cp + 86 ° C .DELTA.n .0804 Δε -4.0 ε || 3.6 ε⏊ 7.6 V (10,0) 2.08 (DAP) HR (20) 97.6 HR (100) 80.1 HR (UV) 91.6

Comparative Example 1

A liquid-crystalline phase is prepared consisting of D-302FF 8:00 D-402FF 8:00 D-502FF 8:00 PCH-301 10:00 CCH 303 15:00 CCH 501 12:00 CP-402FF 4:00 CP-502FF 4:00 CH-33 4:00 CH-35 4:00 CH-43 4:00 CH-45 4:00 BCN-55 11:00 their physical data can be found in Table III. Table III cp + 98 ° C .DELTA.n 0.0678 Δε -3.5 ε || 3.5 ε⏊ 7.0 V (10,0) 2.32 (DAP) HR (20) 97.3 HR (100) 67.2 HR (UV) 74.4

Example 3

A liquid-crystalline phase is prepared: PCH-302FF 10:00 cp + 86 ° C PCH-502FF 10:00 .DELTA.n 0.0765 CCP 302FF 12:00 Δε -3.3 CCP 502FF 13:00 ε⏊ 6.6 CCP 21FF 4:00 ε || 3.4 CCP 22ff 4:00 CH-33 5:00 CH-35 5:00 CH-43 5:00 CCH-34 5:00 CCH-35 5:00 CCH 301 6:00 am CCH 303 6:00 am PCH-301 5:00 PCH-302 5:00

Comparative Example 2

A liquid-crystalline phase is prepared: PCH-302FF 8.00% PCH-502FF 8.00% CCP 302FF 12.00% CCP 502FF 8.00% CCP 21FF 5.00% CCP 31ff 5.00% PCH-302 10.00% CPTP-302FF 5.00% CPTP-502FF 5.00% PTP-302FF 9.00% PTP-502FF 9.00% BCH-32 6.00% PCH-53 10.00% whose physical properties can be found in Table IV: Table IV cp + 85 ° C .DELTA.n +0.1501 Δε -4.21 ε || 3.74 ε⏊ 7.95 V (10,0) 2.24 (DAP)

Claims (12)

Liquid-crystalline medium having a birefringence Δn between 0.04 and 0.10, based on a mixture of polar compounds with negative dielectric anisotropy, characterized in that it comprises at least one compound of the formula I,

wherein R ^{1 is} an unsubstituted alkyl radical having up to 18 C atoms and R ^{2 is} an alkoxy radical having up to 17 C atoms, and at least two compounds of the formula II,

wherein R ¹ and R ^{2 are} each independently H, an unsubstituted alkyl or alkenyl radical having up to 18 carbon atoms, wherein one or more non-adjacent CH ₂ groups are selected from the group consisting of -O-, -S- and -C≡C- may be replaced, wherein at least one compound of the formula II is selected from the compound of the formula

wherein n is 1-18 and m is 1-17, and at least one compound of formula II is selected from the formula

wherein n and m are each independently 1-18. Liquid-crystalline medium according to Claim 1, characterized in that it additionally contains one or more compounds of the formula III,

wherein R ¹ and R ² each independently have one of the meanings given in claim 1 for formula II. liquid-crystalline Medium according to claim 1 or 2, characterized in that it is in consisting essentially of 4 or more compounds selected from the formulas I and II, and two or more compounds of the formula III exists. liquid-crystalline Medium according to one or more of claims 1 to 3, characterized in that it is at least Contains 2 compounds of formula I. liquid-crystalline Medium according to one or more of claims 1 to 4, characterized in that the proportion to compounds of the formula I in the overall mixture at least 15% by weight is. liquid-crystalline Medium according to one or more of claims 1 to 5, characterized in that the proportion at compounds of the formula II in the total mixture at least 30 wt .-% is. liquid-crystalline Medium according to one or more of claims 1 to 6, characterized in that the proportion to compounds of the formula III in the total mixture 10 to 50% by weight is. Liquid-crystalline medium according to one or more of Claims 1 to 7, characterized in that it contains at least 2 compounds selected from the formulas IIIa and IIIb,

wherein alkyl is C _1-6 -alkyl. liquid-crystalline Medium according to one or more of claims 1 to 8, characterized in that it is at least a compound of formula IIIa and at least one compound of Formula IIIb contains. liquid-crystalline Medium according to one or more of claims 1 to 9, characterized in that it is in essential 15-30 % By weight of one or more compounds of the formula I, 30-70% by weight two or more compounds of formula II, and 10-50% by weight one or more compounds of the formula III consists. Liquid-crystalline medium according to one or more of claims 1 to 10, characterized in that it additionally contains one or more compounds selected from the formulas V and VI,

wherein R ¹ and R ^{2 have} the meaning given for formula II in claim 1 and m and n are each 0 or 1. Use of a liquid-crystalline medium after one or more of the claims 1 to 11 in a matrix liquid crystal display based on the ECB effect.