DE102004020461A1 - Liquid crystalline medium for use in electro-optical displays, contains at least one compound with a 4-substituted benzene ring linked to a 1,3-dioxan-2-yl-cyclohexane system by an oxydifluoromethylene group - Google Patents

Abstract

Liquid crystalline media containing compounds in which a 4-substituted benzene ring is linked to a 4-(1,3-dioxan-2-yl)-cyclohexane system by an oxydifluoromethylene group. A liquid crystalline (LC) medium based on a mixture of polar compounds with positive dielectric anisotropy, containing one or more compounds of formula (I). [Image] R 1> : optionally halogenated 1-15C alkyl or alkoxy in which one or more CH 2 groups may be replaced by -Ctriple boundC-, -CH=CH-, -O-, -COO- or -OCO- with no direct links between oxygen atoms; X : F, Cl, CN or halogenated 1-6C alkyl, alkenyl, alkoxy or alkenyloxy; and L 1>, L 2> : H or F. Independent claims are also included for (1) electro-optical LC displays containing such media (2) eight types of compound with formula (I), i.e. new compounds of formula (I-1)-(I-8).

Description

The The present invention relates to a liquid crystalline medium, as well its use for electro-optical purposes and displays containing this medium.

Liquid crystals are mainly used as dielectrics in display devices, since the optical properties of such substances are created Voltage can be influenced. Electro-optical devices based on liquid crystals are well recognized by the expert and can have various effects based. Such devices are cells, for example dynamic scattering, DAP cells (deformation of aligned phases), Guest / host cells, TN cells with a twisted nematic structure, STN cells (super-twisted nematic), SBE cells (superbirefringence effect ") and OMI cells ("optical mode interference"). The most common Display devices are based on the Schadt-Helfrich effect and have a twisted nematic structure.

The liquid crystal materials have to good chemical and thermal stability and good stability against electrical Own fields and electromagnetic radiation. Furthermore, should the liquid crystal materials low viscosity have short response times in the cells, low threshold voltages and give a high contrast.

Farther you should at usual Operating temperatures, i.e. in the widest possible area below and have a suitable mesophase above room temperature, for example for the above cells a nematic or cholesteric mesophase. Because liquid crystals generally used as mixtures of several components, it is important that the components mix well with each other are. Other properties, such as electrical conductivity, the dielectric anisotropy and the optical anisotropy must each meet different requirements depending on the cell type and area of application. For example should materials for Cells with a twisted nematic structure have positive dielectric anisotropy and have low electrical conductivity.

For example are for Matrix liquid crystal displays with integrated non-linear elements for switching individual Pixels (MLC displays) Media with large positive dielectric Anisotropy, broad nematic phases, relatively low birefringence, very high specific resistance, good UV and temperature stability and less Vapor pressure desired.

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

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

• 1. MOS (Metal Oxide Semiconductor) or other diodes on silicon wafers as a substrate.
• 2. Thin film transistors (TFT) on a glass plate as a substrate.

The The use of single-crystal silicon as the substrate material limits the Display size, too the modular composition of various partial displays on the Bumps into problems leads.

at the more promising type 2, which is preferred, is called electro-optic Effect usually the TN effect used. A distinction is made between two technologies: TFTs made of compound semiconductors such as. CdSe or TFT's based on polycrystalline or amorphous silicon. The latter Technology is worked with great intensity worldwide.

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

The TFT displays usually work as TN cells with crossed polarizers in transmission and are backlit.

The term MFK displays here includes every matrix display with integrated non-linear elements, ie in addition to the active matrix also displays with passive elements such as varistors or diodes (MIM = Me tall-insulator-metal).

such MLC displays are particularly suitable for TV applications (e.g. pocket TVs) or for highly informative Displays for Computer applications (laptop) and in automotive or aircraft construction. Next Problems with the angle dependence of the contrast and of switching times result in difficulties with MFK 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, p. 141 ff, Paris; STROMER, M., Proc. Eurodisplay 84, Sept. 1984: Design of Thin Film Transistors for Matrix Adressing of Television Liquid Crystal Displays, p. 145 ff, Paris]. With decreasing resistance the contrast of an MLC display deteriorates and the problem of "alter image elimination" can occur. Since the resistivity of the liquid crystal mixture by interacting with the interior surfaces of the display generally across the Of an MFK display decreases, a high (initial) resistance is very important to get acceptable downtimes. Especially with low-voltage mixtures it was not possible until now very high resistivities to realize. Furthermore, it is important that the specific resistance one if possible slight increase with increasing temperature and after temperature and / or UV exposure. They are also particularly disadvantageous Low temperature properties of the mixtures from the prior art. It is required that there is no crystallization even at low temperatures and / or smectic phases occur and the temperature dependence the viscosity preferably is low. The MFK displays from the prior art are therefore sufficient not today's requirements.

In addition to liquid crystal displays which use backlighting, that is to say which are operated transmissively and possibly transflectively, are also of particular interest for reflective liquid crystal displays. These reflective liquid crystal displays use ambient light to present information. This means that they consume significantly less energy than backlit liquid crystal displays with the appropriate size and resolution. Since the TN effect is characterized by a very good contrast, such reflective displays can still be read well even in bright ambient conditions. This is already from simple reflective TN displays as they are in z. B. wristwatches and calculators are known. However, the principle is also based on high-quality, higher-resolution active matrix displays such. B. TFT displays applicable. As in the case of the generally customary transmissive TFT-TN displays, the use of liquid crystals with low birefringence (Δn) is necessary in order to achieve a low optical delay (d · Δn). This slight optical delay leads to a usually acceptable low viewing angle dependence of the contrast (cf. DE 30 22 818 ). The use of liquid crystals with small birefringence is even more important in the case of reflective displays than in the case of transmissive displays, since the effective layer thickness which the light traverses is approximately twice as large in the case of reflective displays as in the case of transmissive displays with the same layer thickness.

It there is therefore still a great need for MLC displays with a very high specific resistance and a wide working temperature range, short switching times even at low temperatures and low threshold voltage, which do not show these disadvantages or only show them to a lesser extent.

• – erweiterter nematischer Phasenbereich (insbesondere zu tiefen Temperaturen)
• – lagerstabil, auch bei extrem tiefen Temperaturen
• – Schaltbarkeit bei extrem tiefen Temperaturen (out-door-use, Automobil, Avionik)
• – erhöhte Beständigkeit gegenüber UV-Strahlung (längere Lebensdauer)

With TN (Schadt-Helfrich) cells, media are desired that enable the following advantages in the cells:

• - extended nematic phase range (especially at low temperatures)
• - stable in storage, even at extremely low temperatures
• - Switchability at extremely low temperatures (out-door use, automotive, avionics)
• - increased resistance to UV radiation (longer life)

With it is the media available from the prior art not possible, realize these advantages while maintaining the other parameters.

at twisted higher Cells (STN) are media desirable the one higher Multiplexability and / or smaller threshold voltage and / or broader nematic phase ranges (especially at low temperatures) enable. This requires a further expansion of the available parameter space (clearing point, transition smectic-nematic or melting point, viscosity, dielectric sizes, elastic sizes) urgently he wishes.

The invention has for its object media in particular for such MFK, TN or To provide STN displays that do not have the disadvantages indicated above or only to a lesser extent, and preferably at the same time have very high resistivities and low threshold voltages.

It has now been found that this object can be achieved if media according to the invention are used in advertisements. The media according to the invention are distinguished by large dielectric anisotropies and very low optical anisotropies. At the same time, the media have very low threshold voltages and very low rotational viscosities γ ₁ .

enthält,
worin
R¹ einen halogenierten oder unsubstituierten Alkyl- oder Alkoxyrest mit 1 bis 15 C-Atomen, wobei in diesen Resten auch eine oder mehrere CH₂-Gruppen jeweils unabhängig voneinander durch -C≡C-, -CH=CH-, -O-, -CO-O- oder -O-CO- so ersetzt sein können, dass O-Atome nicht direkt miteinander verknüpft sind,
X F, Cl, CN, SF₅, halogenierter Alkylrest, halogenierter Alkenylrest, halogenierter Alkoxyrest oder halogenierter Alkenyloxyrest mit bis zu 6 C-Atomen, und
L¹ und L² jeweils unabhängig voneinander H oder F
bedeuten.The invention thus relates to a liquid-crystalline medium based on a mixture of polar compounds with positive dielectric anisotropy, characterized in that it contains one or more compounds of the formula I.

contains
wherein
R ^{1 is} a halogenated or unsubstituted alkyl or alkoxy radical having 1 to 15 carbon atoms, one or more CH ₂ groups in these radicals also being each independently of one another by —C≡C-, -CH = CH-, -O-, -CO-O- or -O-CO- can be replaced so that O atoms are not directly linked,
XF, Cl, CN, SF ₅ , halogenated alkyl radical, halogenated alkenyl radical, halogenated alkoxy radical or halogenated alkenyloxy radical with up to 6 carbon atoms, and
L ¹ and L ^{2 are} each independently H or F
mean.

The compounds of formula I are protected by Chisso EP 0 881 221 A1 and EP 0 844 229 A1 includes.

The Mixtures mentioned in this property right have the disadvantage that they have very high thresholds and a relatively low clearing point Connection with a high Δn value have or low thresholds and at the same time low clearing points exhibit.

task The present invention is liquid crystalline mixtures with relatively high clearing points, low ones Thresholds, preferably ≤ 1.3 V, especially <1.25 and very particularly preferably <1.00 V to provide. The Δn values should preferably be in the range of 0.06-0.12.

It has surprisingly been found that liquid-crystalline mixtures comprising compounds of the formula I have high clearing points and low thresholds. The invention also relates to compounds of the formula I. Particularly preferred are compounds in which L ¹ = L ² = F, furthermore in which L ¹ = L ² = H. Compounds in which L ¹ = L ² = F and X = F or OCHF ₂ are very particularly preferred. X preferably denotes CN, F, SF ₅ , OCHF ₂ , OC ₂ F ₅ , OC ₃ F ₇ , OCHFCF ₃ , OCF ₂ CHFCF ₃ , OCF ₃ .

The Compounds of the formula I have a wide range of applications. Dependent on From the selection of the substituents, these compounds can be considered Base materials serve from which liquid-crystalline media predominantly Part are composed; it can but also compounds of the formulas I liquid-crystalline base materials from other classes of compounds, for example the dielectric and / or to influence the optical anisotropy of such a dielectric and / or to optimize its threshold voltage and / or its viscosity.

The In the pure state, compounds of the formulas I are colorless and form liquid crystalline Mesophases in one for the electro-optical use cheap located temperature range. Chemically, thermally and against light they are stable.

If R ¹ in formula I is an alkyl radical and / or an alkoxy radical, this can be straight-chain or branched. It is preferably straight-chain, has 2, 3, 4, 5, 6 or 7 carbon atoms and accordingly preferably means ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, also methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradedoxy.

oxaalkyl preferably means straight-chain 2-oxapropyl (= methoxymethyl), 2 - (= ethoxymethyl) or 3-oxabutyl (= 2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6-, or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadexyl.

If R ^{1 is} an alkyl radical in which a CH ₂ group has been replaced by -CH = CH-, this can be straight-chain or branched. It is preferably straight-chain and has 2 to 10 carbon atoms. Accordingly, it means especially vinyl, prop-1-, or prop-2-enyl, but-1-, 2- or but-3-enyl, pent-1-, 2-, 3- or pent-4-enyl, hex -1-, 2-, 3-, 4- or hex-5-enyl, hept-1-, 2-, 3-, 4-, 5- or hept-6-enyl, oct-1-, 2-, 3-, 4-, 5-, 6- or oct-7-enyl, non-1-, 2-, 3-, 4-, 5-, 6-, 7- or non-8-enyl, Dec-1 -, 2-, 3-, 4-, 5-, 6-, 7-, 8- or Dec-9-enyl.

If R ^{1 is} an alkyl radical in which one CH ₂ group has been replaced by -O- and one has been replaced by -CO-, these are preferably adjacent. Thus, these include an acyloxy group -CO-O- or an oxycarbonyl group -O-CO-. These are preferably straight-chain and have 2 to 6 carbon atoms.

she accordingly mean especially acetyloxy, propionyloxy, butyryloxy, Pentanoyloxy, hexanoyloxy, acetyloxymethyl, propionyloxymethyl, Butyryloxymethyl, pentanoyloxymethyl, 2-acetyloxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 2-acetyloxypropyl, 3-propionyl-oxypropyl, 4-acetyl-oxybutyl, Methoxycarbonyl, ethoxycarbonyl, propoxy-carbonyl, butoxycarbonyl, Pentoxycarbonyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, propoxycarbonylmethyl, Butoxycarbonylmethyl, 2- (methoxycarbonyl) ethyl, 2- (ethoxycarbonyl) ethyl, 2- (propoxycarbonyl) ethyl, 3- (methoxycarbonyl) propyl, 3- (ethoxycarbonyl) propyl or 4- (methoxycarbonyl) butyl.

If R ^{1 is} an alkyl radical in which a CH ₂ group has been replaced by unsubstituted or substituted -CH = CH- and an adjacent CH ₂ group has been replaced by CO or CO-O or O-CO, this can be straight-chain or branched , It is preferably straight-chain and has 4 to 12 carbon atoms. Accordingly, it means especially acryloyloxymethyl, 2-acryloyloxyethyl, 3-acryloyloxypropyl, 4-acryloyloxybutyl, 5-acryloyloxypentyl, 6-acryloyloxyhexyl, 7-acryloyloxyheptyl, 8-acryloyloxyoctyl, 9-acryloyloxynonyl, 10-acryloyloxoyloxydoxymyl, Methacryloyloxypropyl, 4-methacryloyloxybutyl, 5-methacryloyloxypentyl, 6-methacryloyloxyhexyl, 7-methacryloyloxyheptyl, 8-methacryloyloxyoctyl, 9-methacryloyloxynonyl.

If R ^{1 is} an alkyl or alkenyl radical which is simply substituted by CN or CF ₃ , this radical is preferably straight-chain. The substitution by CN or CF ₃ is in any position.

If R ^{1 is} an alkyl or alkenyl radical which is at least monosubstituted by halogen, this radical is preferably straight-chain and halogen is preferably F or Cl. In the case of multiple substitution, halogen is preferably F. The resulting residues also include perfluorinated residues. In the case of single substitution, the fluorine or chlorine substituent can be in any position, but preferably in the ω position.

Compounds with branched wing groups R ¹ can occasionally be important because of their better solubility in the usual liquid-crystalline base materials, but in particular as chiral dopants if they are optically active. Smectic compounds of this type are suitable as components for ferroelectric materials.

Branched groups of this type usually contain no more than one chain branch. Branched radicals R ¹ are preferably isopropyl, 2-butyl (= 1-methylpropyl), isobutyl (= 2-methylpropyl), 2-methylbutyl, isopentyl (= 3-methylbutyl), 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, isopropoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 1-methylhexoxy, 1-methylheptoxy.

If R ^{1 represents} an alkyl radical in which two or more CH ₂ groups have been replaced by -O- and / or -CO-O-, this can be straight-chain or branched. It is preferably branched and has 3 to 12 carbon atoms. Accordingly, it means especially bis-carboxy-methyl, 2,2-bis-carboxy-ethyl, 3,3-bis-carboxy-propyl, 4,4-bis-carboxy-butyl, 5,5-bis-carboxy-pentyl, 6,6-bis-carboxy-hexyl, 7,7-bis-carboxy-heptyl, 8,8-bis-carboxy-octyl, 9,9-bis-carboxy-nonyl, 10,10-bis-carboxy-decyl, Bis- (methoxycarbonyl) methyl, 2,2-bis (methoxycarbonyl) ethyl, 3,3-bis (methoxycarbonyl) propyl, 4,4-bis (methoxycarbonyl) butyl, 5, 5-bis (methoxy-carbo nyl) pentyl, 6,6-bis (methoxycarbonyl) hexyl, 7,7-bis (methoxycarbonyl) heptyl, 8,8-bis (methoxycarbonyl) octyl, bis (ethoxycarbonyl) methyl , 2,2-bis (ethoxycarbonyl) ethyl, 3,3-bis (ethoxycarbonyl) propyl, 4,4-bis (ethoxycarbonyl) butyl, 5,5-bis (ethoxycarbonyl) hexyl.

The Compounds of the formulas I are made by methods known per se presented as they are in the literature (e.g. in the standard works such as Houben-Weyl, Methods of Organic Chemistry, Georg-Thieme-Verlag, Stuttgart) are described, namely under reaction conditions for the above Implementations are known and suitable. You can also start from confessed, not closer here mentioned variants Make use. The compounds of formula I can, for. B. made as follows become.

Scheme 1

object The invention also includes electro-optical displays (in particular STN or MFK displays with two plane-parallel carrier plates with a border form a cell, integrated non-linear elements for switching individual pixels on the carrier plates and a nematic liquid crystal mixture in the cell with positive dielectric anisotropy and high specific Resistance) that contain such media as well as their use of this media for electro-optical purposes.

The liquid crystal mixtures according to the invention enable a significant expansion of the available parameter space. The achievable combinations of clearing point, viscosity at low temperature, thermal and UV stability and dielectric anisotropy by far previous materials from the prior art.

The Demand for high clearing point, nematic phase at low temperature and a low Δn so far only insufficiently fulfilled become. Systems such as ZLI-3119 have comparable clearing point and comparably cheap viscosities on, but have a Δε of only +3. Other mixing systems have comparable viscosities and Have values of Δε however, only clearing points in the area of 60 ° C on.

The liquid crystal mixtures according to the invention enable it while maintaining the nematic phase down to -20 ° C and preferred down to -30 ° C, particularly preferred down to -40 ° C, clearing point above 60 ° C, preferably above 70 ° C, particularly preferably above 80 ° C, at the same time dielectric anisotropy values Δε> 8, preferably ≥ 10 and a high value for the specific Reach resistance, creating excellent STN and MFK displays can be achieved. In particular, the mixtures are due to small operating voltages characterized. The TN thresholds are below 1.3 V, preferably below 1.25 V, particularly preferably <1.0 V.

It goes without saying that, by a suitable choice of the components of the mixtures according to the invention, higher clearing points (for example above 110 ° C.) at higher threshold voltages or lower clearing points at lower threshold voltages can be achieved while maintaining the other advantageous properties. Likewise, with correspondingly little increased viscosities, mixtures with a larger Δε and thus low thresholds can be obtained. The MFK displays according to the invention preferably operate in the first transmission minimum according to Gooch and Tarry [CH Gooch and HA Tarry, Electron. Lett. 10, 2-4, 1974; CH Gooch and HA Tarry, Appl. Phys., Vol. 8, 1575-1584, 1975], where in addition to particularly favorable elec trooptic properties, such as high slope of the characteristic and low angle dependence of the contrast ( DE-PS 30 22 818 ) with the same threshold voltage as in an analog display in the second minimum, a smaller dielectric anisotropy is sufficient. As a result, significantly higher specific resistances can be achieved using the mixtures according to the invention than with mixtures with cyan compounds. The person skilled in the art can set the birefringence required for a given layer thickness of the MLC display by means of suitable routine selection of the individual components and their proportions by weight.

The flow viscosity ν ₂₀ at 20 ° C. is preferably <60 mm ² · s ^-1 , particularly preferably <50 mm ² · s ^-1 . The rotational viscosity γ _{1 of} the mixtures according to the invention at 20 ° C. is preferably <220 mPa · s, particularly preferably <200 mPa · s. The nematic phase range is preferably at least 90 °, in particular at least 100 °. This range preferably extends at least from -20 ° to + 80 °.

A short switching time is desirable for liquid crystal displays. This is especially true for ads that are capable of video playback. Switching times (total: t _on + t _off ) of maximum 25 ms are required for such displays. The upper limit of the switching time is determined by the refresh rate. In addition to the rotational viscosity γ ₁ , the tilt angle also influences the switching time. In particular, mixtures with 20 20% of the compounds of the formula I have a tilt angle of> 2.5 °, preferably> 3.0 °, in comparison to the sales product ZLI-4792 from Merck KGaA.

oder Ester der Formel

Measurements of the "Voltage Holding Ratio" (HR) [p. Matsumoto et al., Liquid Crystals 5, 1320 (1989); K. Niwa et al., Proc. SID Conference, San Francisco, June 1984, p. 304 (1984); G. Weber et al., Liquid Crystals 5, 1381 (1989) have shown that mixtures according to the invention containing compounds of the formula I exhibit a significantly smaller decrease in HR with increasing temperature than analogous mixtures containing instead of the compounds of the formula I cyanophenylcyclohexanes of the formula

or esters of the formula

Also the UV stability of the mixtures according to the invention is significantly better, i.e. they show a significantly smaller decrease of HR under UV exposure.

worin R¹ die in Formel I angegebene Bedeutung hat.Particularly preferred compounds of the formula I are compounds of the formulas I-1 to I-10:

wherein R ^{1 has} the meaning given in formula I.

Of these preferred compounds are particularly preferably those of the formulas I-1, I-2, I-3 and I-4, in particular those of the formulas I-1 and I-2.

worin
Alkyl CH₃, C₂H₅, n-C₃H₇, n-C₄H₉, n-C₅H₁₁ oder n-C₆H₁₃ bedeutet.The invention further relates to the compounds of the formulas I-1 to I-8, in which R ^{1 has} the meaning given above. R ¹ preferably denotes straight-chain alkyl or alkenyl with up to 6 C atoms. The connection is particularly preferred,

wherein
Alkyl CH ₃ , C ₂ H ₅ , nC ₃ H ₇ , nC ₄ H ₉ , nC ₅ H ₁₁ or nC ₆ H ₁₃ .

• – Das Medium enthält ein, zwei oder mehr Verbindungen der Formeln I-1 bis I-9;
• – Das Medium enthält zusätzlich eine oder mehrere Verbindungen ausgewählt aus der Gruppe bestehend aus den allgemeinen Formeln II bis VI:
  
  worin die einzelnen Reste die folgenden Bedeutungen haben: R⁰ n-Alkyl, Alkoxy, Oxaalkyl, Fluoralkyl oder Alkenyl mit jeweils bis zu 9 C-Atomen, X⁰ F, Cl, halogeniertes Alkyl, halogeniertes Alkenyl, halogeniertes Oxalkyl, halogeniertes Alkenyloxy oder halogeniertes Alkoxy mit bis zu 6 C-Atomen, Z⁰ -C₂F₄-, -CF=CF-, -C₂H₄-, -(CH₂)₄-, -OCH₂-, -CH₂O-, -CF₂O- oder -OCF₂-, Y¹ bis Y⁴ jeweils unabhängig voneinander H oder F, r 0 oder 1.

Preferred embodiments are given below:

• - The medium contains one, two or more compounds of the formulas I-1 to I-9;
• The medium additionally contains one or more compounds selected from the group consisting of the general formulas II to VI:
  
  wherein the individual radicals have the following meanings: R ⁰ n-alkyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyl, each having up to 9 carbon atoms, X ⁰ F, Cl, halogenated alkyl, halogenated alkenyl, halogenated oxalkyl, halogenated alkenyloxy or halogenated Alkoxy with up to 6 carbon atoms, Z ⁰ -C ₂ F ₄ -, -CF = CF-, -C ₂ H ₄ -, - (CH ₂ ) ₄ -, -OCH ₂ -, -CH ₂ O-, -CF ₂ O- or -OCF ₂ -, Y ¹ to Y ⁴ each independently of one another H or F, r 0 or 1.

• – Das Medium enthält zusätzlich eine oder mehrere Verbindungen ausgewählt aus der Gruppe bestehend aus den allgemeinen Formeln VII bis XIII:
  
  
  worin R⁰, X⁰ und Y^1-4 jeweils unabhängig voneinander eine der in Anspruch 3 angegebenen Bedeutungen haben. X⁰ ist vorzugsweise F, Cl, CF₃, OCF₃ oder OCHF₂. R⁰ bedeutet vorzugsweise Alkyl, Alkoxy, Oxaalkyl, Fluoralkyl oder Alkenyl mit jeweils bis zu 6 C-Atomen.
• – Das Medium enthält zusätzlich eine oder mehrere Verbindungen der Formeln Ea bis Ed
  
  worin R⁰ die in Anspruch 3 angegebenen Bedeutungen hat;
• – Der Anteil der Verbindungen der Formeln Ea bis Ed ist vorzugsweise 10-30 Gew.%, insbesondere 15-25 Gew.%;
• – Der Anteil an Verbindungen der Formeln I bis VI zusammen beträgt im Gesamtgemisch mindestens 50 Gew.%;
• – Der Anteil an Verbindungen der Formel I beträgt im Gesamtgemisch 0,5 bis 40, besonders bevorzugt 1 bis 30 Gew.%;
• – Der Anteil an Verbindungen der Formeln II bis VI im Gesamtgemisch beträgt 30 bis 80 Gew.%;
  
• – Das Medium enthält Verbindungen der Formeln II, III, IV, V und/oder VI;
• – R⁰ ist geradkettiges Alkyl oder Alkenyl mit 2 bis 7 C-Atomen;
• – Das Medium besteht im wesentlichen aus Verbindungen der Formeln I bis VI und XIII;
• – Das Medium enthält weitere Verbindungen, vorzugsweise ausgewählt aus der folgenden Gruppe bestehend aus den allgemeinen Formeln XIV bis XVIII:
  
  worin R⁰ und X⁰ die oben angegebenen Bedeutungen haben. Die 1,4-Phenylenringe können zusätzlich durch CN, Chlor oder Fluor substituiert sein. Vorzugsweise sind die 1,4-Phenylenringe ein- oder mehrfach durch Fluoratome substituiert.
• – Das Medium enthält zusätzlich ein, zwei, drei oder mehr, vorzugsweise zwei oder drei Verbindungen der Formeln,
  
  worin "Alkyl" und "Alkyl*" die nachfolgend angegebene Bedeutung haben. Der Anteil der Verbindungen der Formeln O1 und/oder O2 in den erfindungsgemäßen Mischungen beträgt vorzugsweise 5-10 Gew.%, insbesondere 1-12 Gew.% und ganz besonders bevorzugt 3-10 Gew.%.
• – Das Medium enthält vorzugsweise 5-35 Gew.% der Verbindung IVa.
• – Das Medium enthält vorzugsweise ein, zwei oder drei Verbindungen der Formel IVa, worin X⁰ F oder OCF₃ bedeutet.
• – Das Medium enthält vorzugsweise ein oder mehrere Verbindungen der Formeln IIa bis IIg,
  
  
  worin R⁰ die oben angegebenen Bedeutungen hat. In den Verbindungen der Formeln IIa-IIg bedeutet R⁰ vorzugsweise Methyl, Ethyl, n-Propyl, n-Butyl und n-Pentyl.
• – Das Medium enthält vorzugsweise ein oder mehrere Verbindungen der Formeln,
  
  
  
  worin R⁰ die oben angegebenen Bedeutungen hat.
• – Weiterhin bevorzugt enthält das erfindungsgemäße Medium ein oder mehrere Verbindungen der Formeln DD-1 und/oder DD-2,
  
  worin R^a-d jeweils unabhängig voneinander geradkettiges Alkyl oder Alkoxy mit 1 bis 6 C-Atomen bedeuten. Der Anteil der Verbindungen der Formeln DD-1 und/oder DD-2 in den erfindungsgemäßen Mischungen beträgt vorzugsweise 0-10 Gew.%, insbesondere 0,1-8 Gew.% und besonders bevorzugt 0,5-4 Gew.%.
• – Das Gewichtsverhältnis (I) : (II + III + IV + V + VI) ist vorzugsweise 1 : 10 bis 10 : 1.
• – Das Medium besteht im wesentlichen aus Verbindungen ausgewählt aus der Gruppe bestehend aus den allgemeinen Formeln I bis XIII.
• – Der Anteil der Verbindungen der Formel IVb und/oder IVc, worin X⁰ Fluor und R⁰ CH₃, C₂H₅, n-C₃H₇, n-C₄H₉ oder n-C₅H₁₁ bedeutet, beträgt im Gesamtgemisch 2 bis 20 Gew.%, insbesondere 2 bis 15 Gew.%.
• – Das Medium enthält vorzugsweise Verbindungen der Formeln II bis VI, worin R⁰ Methyl bedeutet. Insbesondere bevorzugt enthält das erfindungsgemäße Medium Verbindungen der Formeln
  
• – Das Medium enthält vorzugsweise ein, zwei oder mehr, vorzugsweise ein oder zwei, Dioxon-Verbindungen der Formeln,
  
  worin R⁰ die oben angegebenen Bedeutungen hat. Der Anteil der Dioxon-Verbindungen D-1 und/oder D-2 in den erfindungsgemäßen Mischungen beträgt vorzugsweise 0-30 Gew.%, insbesondere 5-25 Gew.% und ganz besonders bevorzugt 8-20 Gew.%.
• – Das Medium enthält vorzugsweise ein, zwei oder mehr, vorzugsweise ein oder zwei Pyranverbindungen der Formeln P-1 bis P-4,
  
  
  worin R⁰ die oben angegebenen Bedeutungen hat.
• – Das Medium enthält zusätzlich ein, zwei oder mehr Zweikern-Verbindungen der Formeln Z1 bis Z7,
  
  worin R^1a und R^2a jeweils unabhängig voneinander H, CH₃, C₂H₅ oder n-C₃H₇ bedeuten. R⁰, Alkyl und Alkyl* besitzen die in Anspruch 3 bzw. nachfolgend angegebenen Bedeutungen. Von den genannten Zweikern-Verbindungen sind besonders bevorzugt die Verbindungen Z-1, Z-2, Z-5 und Z-6.
• – Das Medium enthält zusätzlich ein, zwei oder mehr Verbindungen mit annellierten Ringen der Formeln ANN1 bis AN11:
  
  
  worin R⁰ die oben angegebenen Bedeutungen hat;
• – Die erfindungsgemäßen Mischungen zeichnen sich insbesondere dadurch aus, dass sie Klärpunkte von > 75°C und Schwellen von < 1,2 V aufweisen.

The compound of formula IV is preferred

• The medium additionally contains one or more compounds selected from the group consisting of the general formulas VII to XIII:
  
  
  wherein R ⁰ , X ⁰ and Y ^1-4 each independently have one of the meanings given in claim 3. X ⁰ is preferably F, Cl, CF ₃ , OCF ₃ or OCHF ₂ . R ⁰ preferably denotes alkyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyl, each having up to 6 carbon atoms.
• - The medium additionally contains one or more compounds of the formulas Ea to Ed
  
  wherein R ^{0 has} the meanings given in claim 3;
• - The proportion of the compounds of the formulas Ea to Ed is preferably 10-30% by weight, in particular 15-25% by weight;
• - The proportion of compounds of the formulas I to VI together is at least 50% by weight in the total mixture;
• - The proportion of compounds of the formula I in the mixture as a whole is 0.5 to 40, particularly preferably 1 to 30,% by weight;
• - The proportion of compounds of the formulas II to VI in the mixture as a whole is 30 to 80% by weight;
  
• - The medium contains compounds of the formulas II, III, IV, V and / or VI;
• - R ⁰ is straight-chain alkyl or alkenyl with 2 to 7 C atoms;
• - The medium consists essentially of compounds of the formulas I to VI and XIII;
• The medium contains further compounds, preferably selected from the following group consisting of the general formulas XIV to XVIII:
  
  wherein R ⁰ and X ^{0 have} the meanings given above. The 1,4-phenylene rings can additionally be substituted by CN, chlorine or fluorine. The 1,4-phenylene rings are preferably substituted one or more times by fluorine atoms.
• The medium additionally contains one, two, three or more, preferably two or three, compounds of the formulas
  
  wherein "alkyl" and "alkyl *" have the meaning given below. The proportion of the compounds of the formulas O1 and / or O2 in the mixtures according to the invention is preferably 5-10% by weight, in particular 1-12% by weight and very particularly preferably 3-10% by weight.
• - The medium preferably contains 5-35% by weight of compound IVa.
• The medium preferably contains one, two or three compounds of the formula IVa, in which X ^{0 is} F or OCF ₃ .
• The medium preferably contains one or more compounds of the formulas IIa to IIg,
  
  
  wherein R ^{0 has} the meanings given above. In the compounds of the formulas IIa-IIg, R ⁰ preferably denotes methyl, ethyl, n-propyl, n-butyl and n-pentyl.
• The medium preferably contains one or more compounds of the formulas
  
  
  
  wherein R ^{0 has} the meanings given above.
• The medium according to the invention further preferably contains one or more compounds of the formulas DD-1 and / or DD-2,
  
  wherein R ^ad each independently represent straight-chain alkyl or alkoxy having 1 to 6 carbon atoms. The proportion of the compounds of the formulas DD-1 and / or DD-2 in the mixtures according to the invention is preferably 0-10% by weight, in particular 0.1-8% by weight and particularly preferably 0.5-4% by weight.
• - The weight ratio (I): (II + III + IV + V + VI) is preferably 1:10 to 10: 1.
• - The medium consists essentially of compounds selected from the group consisting of the general formulas I to XIII.
• - The proportion of compounds of the formula IVb and / or IVc wherein X ⁰ is fluorine and R ⁰ is CH _3, C ₂ H _5, nC ₃ H _7, nC ₄ H ₉ or nC ₅ H _11, in the total mixture 2 to 20 % By weight, in particular 2 to 15% by weight.
• - The medium preferably contains compounds of the formulas II to VI, in which R ^{0 is} methyl. The medium according to the invention particularly preferably contains compounds of the formulas
  
• The medium preferably contains one, two or more, preferably one or two, dioxone compounds of the formulas
  
  wherein R ^{0 has} the meanings given above. The proportion of the dioxone compounds D-1 and / or D-2 in the mixtures according to the invention is preferably 0-30% by weight, in particular 5-25% by weight and very particularly preferably 8-20% by weight.
• The medium preferably contains one, two or more, preferably one or two pyran compounds of the formulas P-1 to P-4,
  
  
  wherein R ^{0 has} the meanings given above.
• The medium additionally contains one, two or more two-core compounds of the formulas Z1 to Z7,
  
  wherein R ^1a and R ^2a each independently represent H, CH ₃ , C ₂ H ₅ or nC ₃ H ₇ . R ⁰ , alkyl and alkyl * have the meanings given in claim 3 or below. Of the two-core compounds mentioned, the compounds Z-1, Z-2, Z-5 and Z-6 are particularly preferred.
• - The medium additionally contains one, two or more compounds with fused rings of the formulas ANN1 to AN11:
  
  
  wherein R ^{0 has} the meanings given above;
• The mixtures according to the invention are distinguished in particular by the fact that they have clearing points of> 75 ° C. and thresholds of <1.2 V.

It it was found that a relatively low proportion of compounds of the formulas I in a mixture with usual Liquid crystal materials, in particular, however, with one or more compounds of the formulas II, III, IV, V and / or VI to a considerable reduction in the Threshold voltage and leads to low values for birefringence, where at the same time broad nematic phases with low transition temperatures can be observed smectically-nematically, which improves the storage stability becomes.

The term "alkyl" or "alkyl *" encompasses straight-chain and branched alkyl groups having 1-7 carbon atoms, in particular the straight-chain groups methyl, ethyl, propyl, butyl, pentyl, hexyl and heptyl. Groups with 1-5 carbon atoms are generally preferred.

The term "alkenyl" encompasses straight-chain and branched alkenyl groups with 2-7 carbon atoms, in particular the straight-chain groups. Preferred alkenyl groups are C ₂ -C ₇ -1E-alkenyl, C ₄ -C ₇ -3E-alkenyl, C ₅ -C ₇ -4-alkenyl, C ₆ -C ₇ -5-alkenyl and C ₇ -6-alkenyl, in particular C ₂ -C ₇ -1E-alkenyl, C ₄ -C ₇ -3E-alkenyl and C ₅ -C ₇ -4-alkenyl. Examples of particularly preferred alkenyl groups are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl , 4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl and the like. Groups of up to 5 carbon atoms are generally preferred.

The The term "fluoroalkyl" preferably includes straight chain groups with terminal Fluorine, i.e. Fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorhexyl and 7-fluoroheptyl. Other positions of fluorine are not excluded.

The term "oxaalkyl" or "alkoxy" preferably includes straight-chain radicals of the formula C _n -C _{2n + 1} -O- (CH ₂ ) _m , in which n and m each independently represent 1 to 6. m can also mean 0. Preferably n = 1 and m 1-6 or m = O and n = 1-3.

The response times, the threshold voltage, the steepness of the transmission characteristics, etc. can be modified as desired by suitable choice of the meanings of R ⁰ and X ⁰ . For example, 1E-alkenyl residues, 3E-alkenyl residues, 2E-alkenyloxy residues and the like generally lead to shorter response times, improved nematic tendencies and a higher ratio of the elastic constants k ₃₃ (bend) and k ₁₁ (splay) in comparison to alkyl or alkoxy. 4-alkenyl residues, 3-alkenyl residues and the like generally give lower threshold voltages and smaller values of k ₃₃ / k ₁₁ compared to alkyl and alkoxy residues.

A -CH ₂ CH ₂ group generally leads to higher values of k ₃₃ / k ₁₁ compared to a simple covalent bond. Higher values of k ₃₃ / k ₁₁ enable, for example, flatter transmission characteristics in TN cells with 90 ° twist (to achieve gray tones) and steeper transmission characteristics in STN, SBE and OMI cells (higher multiplexability) and vice versa.

The optimal quantity ratio The compounds of formulas I and II + III + IV + V + VI depend largely of the ones you want Properties, from the choice of components of formulas I, II, III, IV, V and / or VI and the choice of any other available ones Components.

suitable proportions within the above range may vary slightly from case to case be determined.

The Total amount of compounds of the formulas I to XIII in the mixtures according to the invention is not critical. The mixtures can therefore be one or more contain further components for the purpose of optimizing various properties. The observed effect on the response times and the threshold voltage however, the higher the Total concentration of compounds of the formulas I to XIII are.

In a particularly preferred embodiment, the media according to the invention contain compounds of the formulas II to VI (preferably II, III and / or IV, in particular IVa), in which X ⁰ F, OCF ₃ , OCHF ₂ , OCH = CF ₂ , OCF = CF ₂ or OCF ₂ -CF ₂ H. A favorable synergistic effect with the compounds of the formulas I leads to particularly advantageous properties. Mixtures containing compounds of the formula I and the formula IVa in particular are notable for their low threshold voltage.

The individual compounds of the formulas I to XVIII and their sub-formulas, those in the media according to the invention can be used are either known or they can be analogous to the known compounds getting produced.

The Structure of the MFK display according to the invention made of polarizers, electrode base plates and electrodes with surface treatment corresponds to that for such advertisements usual Construction. The concept of conventional construction is wide here summarized and includes all modifications and modifications of the MFK display, in particular also matrix display elements based on poly-Si TFT or MIM.

A significant difference between the advertisements according to the invention and the previously used ones However, the twisted nematic cell consists in the choice of the liquid crystal parameters of the liquid crystal layer.

The Production of the usable according to the invention liquid crystal mixtures takes place in a more usual way Wise. Usually the one you want Amount of components used in smaller quantities in the Main constituent components dissolved, expedient at elevated temperature. It is also possible solutions the components in an organic solvent, e.g. in acetone, Chloroform or methanol, mix and the solvent after mixing to remove again, for example by distillation.

The dielectrics can also other additives known to the person skilled in the art and described in the literature, such as, for. B. UV stabilizers such as Tinuvin ^® from Ciba, antioxidants, radical scavengers, etc. contain. For example, 0-15% pleochroic dyes or chiral dopants can be added. Suitable stabilizers and dopants are listed in Tables C and D below.

C means a crystalline, S a smectic, S _c a smectic C, N a nematic and I the isotropic phase.

V ₁₀ denotes the voltage for 10% transmission (viewing direction perpendicular to the plate surface). t _on denotes the switch-on time and t _off the switch-off time for an operating voltage corresponding to 2.0 times the value of V ₁₀ . Δn denotes the optical anisotropy. Δε denotes the dielectric anisotropy (Δε = ε _∥ - ε _⊥ , where ε _{∥ means} the dielectric constant parallel to the _{longitudinal axes of} the molecule and ε _{⊥ means} the dielectric constant perpendicular to it). The electro-optical data are measured in a TN cell at the 1st minimum (ie at a Δn value of 0.5 μm) at 20 ° C, unless expressly stated otherwise. The optical data are measured at 20 ° C, unless expressly stated otherwise.

In the present application and in the following examples, the structures of the liquid crystal compounds are indicated by acronyms, the transformation into chemical formulas taking place according to Tables A and B below. All residues C _n H _{2n + 1} and C _m H _{2m + 1} are straight-chain alkyl residues with n or m C atoms; n and m are integers and are preferably 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12. The coding according to Table B goes without saying. In Table A is only specified the acronym for the base body. In individual cases, a code for the substituents R ^{1 *} , R ^{2 *} , L ^{1 *} and L ^{2 *} follows separately for the basic body with a rope:

preferred Mixing components can be found in Tables A and B.

Table A

Table B

Especially liquid crystalline are preferred Mixtures which, in addition to the compounds of the formulas I at least contain one, two, three or four compounds from Table B.

Table C.

In Table C becomes possible Dopants specified, which are generally the mixtures according to the invention be added. The mixtures preferably contain 0-10% by weight, in particular 0.01-5% by weight and particularly preferably 0.01-3% by weight Dopants.

Table D

stabilizers, which are added, for example, to the mixtures according to the invention can become called below.

The following examples are intended to illustrate the invention without limiting it. Percentages above and below mean percentages by weight. All temperatures are given in degrees Celsius. Mp. Means melting point, Kp. = Clearing point. Furthermore, K = crystalline state, N = nematic phase, S = smectic phase and I = isotropic phase. The information between these symbols represents the transition temperatures. Δn means optical anisotropy (589 nm, 20 ° C), Δε the dielectric anisotropy (1 kHz, 20 ° C). The flow viscosity ν ₂₀ (mm ² / sec) and the rotational viscosity γ ₁ (mPa · s) were each determined at 20 ° C.

n-BuLi

1,6 molare Lösung von n-Butyllithium in n-Hexan

DMAP

4-(Dimethylamino)-pyridin

THF

Tetrahydrofuran

DCC

N,N'-Dicyclohexylcarbodiimid

LDA

Lithiumdimethylamid

TsOH

Toluolsulfonsäure

RT

Raumtemperatur

"Customary work-up" means: water is optionally added to the reaction mixture, extracted with dichloromethane, diethyl ether, methyl tert-butyl ether or toluene, separated, the organic phase is dried, evaporated and the product is purified by distillation under reduced pressure or crystallization and / or chromatography. The following abbreviations are used in the examples as well as in the synthesis and reaction schemes.

n-BuLi

1.6 molar solution of n-butyllithium in n-hexane

DMAP

4- (dimethylamino) pyridine

THF

tetrahydrofuran

DCC

N, N'-dicyclohexylcarbodiimide

LDA

lithium dimethylamide

TsOH

toluenesulphonic

RT

room temperature

example

0.054 mol of propyl propanediol and 0.054 mol of the corresponding cyclohexanaldehyde are heated in 200 ml of toluene with 0.0055 mol of p-toluenesulfonic acid monohydrate on a water separator under reflux. The cooled reaction solution is then extracted with aqueous NaHCO ₃ solution in order to remove the p-toluenesulfonic acid. After drying with Na ₂ SO ₄ and evaporation, the organic phase gives a residue which is filtered through a 1: 1 by volume mixture of toluene / heptane over silica gel. After evaporation and recrystallization of the evaporation residue of 19.0 g from 60 ml of heptane at -20 ° C., the filtrate gives 7.4 g of the pure dioxane derivative.

hergestellt.

Beispiel M1

Beispiel M2

Beispiel M3

Beispiel M4

Beispiel M5

Beispiel M6

Beispiel M7

Beispiel M8

Beispiel M9

Beispiel M10

Beispiel M11

Beispiel M12

Beispiel M13

Beispiel M 14 CCP-2F.F.F 8,00% CCP-3F.F.F 9,00% CCP-5F.F.F 6,00% CCP-3OCF₃ 7,00% CCP-4OCF₃ 6,00% CC-3-V1 5,00% CDU-2-F 9,00% CDU-5-F 9,00% CGU-3-F 6,00% CCGU-3-F 8,00% DCQU-1-F 6,00% DCQU-2-F 7,00% DCQU-3-F 7,00% DCQU-5-F 7,00% Beispiel M 15 CCP-1F.F.F 4,00% CCP-2F.F.F 6,00% CCP-3F.F.F 8,00% CCP-5F.F.F 5,00% CCQU-2-F 10,00% CCQU-3-F 13,00% CCQU-5-F 8,00% DCQU-1-F 5,00% DCQU-2-F 7,00% DCQU-3-F 7,00% DCQU-5-F 7,00% CC-4-V 4,00% CC-3-V1 9,00% CCOC-3-3 3,00% CCOC-4-3 4,00% The following compounds of the formula become analogous

manufactured.

Example M1

Example M2

Example M3

Example M4

Example M5

Example M6

Example M7

Example M8

Example M9

Example M10

Example M11

Example M12

Example M13

Example M 14 CCP 2F.FF 8.00% CCP 3F.FF 9.00% CCP 5F.FF 6.00% CCP-3OCF ₃ 7.00% CCP-4OCF ₃ 6.00% CC-3-V1 5.00% CDU-2-F 9.00% CDU-5-F 9.00% CGU-3-F 6.00% CCGU-3-F 8.00% DCQU-1-F 6.00% DCQU-2-F 7.00% DCQU-3-F 7.00% DCQU-5-F 7.00% Example M 15 CCP 1F.FF 4.00% CCP 2F.FF 6.00% CCP 3F.FF 8.00% CCP 5F.FF 5.00% CCQU-2-F 10.00% CCQU-3-F 13.00% CCQU-5-F 8.00% DCQU-1-F 5.00% DCQU-2-F 7.00% DCQU-3-F 7.00% DCQU-5-F 7.00% CC-4-V 4.00% CC-3-V1 9.00% CCOC-3-3 3.00% CCOC-4-3 4.00%

Claims (12)

Liquid-crystalline medium based on a mixture of polar compounds with positive dielectric anisotropy, characterized in that it contains one or more compounds of the formula I.

contains in which R ^{1 is} a halogenated or unsubstituted alkyl or alkoxy radical having 1 to 15 carbon atoms, one or more CH ₂ groups in these radicals also being each independently of one another by —CC-, -CH = CH-, -O- , -CO-O- or -O-CO- can be replaced so that O atoms are not directly linked to one another, XF, Cl, CN, halogenated alkyl radical, halogenated alkenyl radical, halogenated alkoxy radical or halogenated alkenyloxy radical with up to 6 C- Atoms, and L ¹ and L ² each independently represent H or F. Liquid-crystalline medium according to Claim 1, characterized in that it contains one, two or more compounds of the formulas I-1 to I-10:

wherein R ^{1 has} the meaning given in claim 1. Liquid-crystalline medium according to claim 1 or 2, characterized in that it additionally contains one or more compounds selected from the group consisting of the general formulas II, III, IV, V and VI:

wherein the individual radicals have the following meanings: R ⁰ n-alkyl, oxaalkyl, fluoroalkyl or alkenyl, each with up to 9 C atoms, X ⁰ F, Cl, halogenated alkyl, halogenated alkenyl, halogenated alkenyloxy or halogenated alkoxy with up to 6 C atoms, Z ⁰ -C ₂ F ₄ -, -CF = CF-, -C ₂ H ₄ -, - (CH ₂ ) ₄ -, -OCH ₂ -, -CH ₂ O-, CF ₂ O- or -OCF ₂ -, Y ¹ to Y ⁴ each independently of one another H or F, r 0 or 1. liquid-crystalline Medium according to claim 3, characterized in that the portion of compounds of the formulas I to VI together in the total mixture at least Is 50% by weight. Liquid-crystalline medium according to at least one of Claims 1 to 4, characterized in that it additionally contains one or more compounds of the formulas Ea to Ed,

wherein R ^{0 has} the meanings given in claim 3, contains. Liquid-crystalline medium according to at least one of claims 1 to 5, characterized in that it is one or more compounds of the formulas IIa to IIg,

wherein R ^{0 has} the meanings given in claim 3, contains. Liquid-crystalline medium according to one of Claims 1 to 6, characterized in that it comprises one or more compounds of the formulas O1 and O2,

wherein alkyl and alkyl * each independently represent a straight-chain or branched alkyl group having 1-7 carbon atoms. Liquid-crystalline medium according to one of Claims 1 to 7, characterized in that it contains one or more dioxane compounds of the formulas D1 and / or D2,

wherein R ^{0 has} the meanings given in claim 3, contains. liquid-crystalline Medium according to at least one of claims 1 to 8, characterized in that the proportion of compounds of formula I in the total mixture 0.5 to Is 40% by weight. Use of the liquid crystalline medium after at least one of the claims 1 to 9 for electro-optical purposes. Containing electro-optical liquid crystal display a liquid crystalline Medium according to at least one of claims 1 to 9. Compounds of the formulas I-1 to I-8

wherein R ^{1 has} the meanings given in claim 1.