DE10123986B4 - Liquid-crystalline medium and its use in a liquid-crystal display - Google Patents

Abstract

enthält,
worin
R H, einen unsubstituierten, einen einfach durch CN oder CF₃ oder einen mindestens einfach durch Halogen substituierten Alkyl- oder Alkenylrest mit 1 bzw. 2 bis 15 C-Atomen, wobei in diesen Resten auch eine oder mehrere CH₂-Gruppen jeweils unabhängig voneinander durch -O-, -S-,

-CO-, -CO-O-, -O-CO- oder -O-CO-O- so ersetzt sein können, daß O-Atome nicht direkt miteinander verknüpft sind,

Z CH₂-CH₂, CF₂-CF₂, CH=CH, CF=CF oder eine Einfachbindung,
X H, F, CL, CF₃, CF₂CF₃, CH₂CF₃ oder CF₂H und
n 1 oder 2,
bedeuten und
eine oder mehrere Verbindung(en) ausgewählt aus der Gruppe bestehend aus den allgemeinen Formeln II bis VII enthält:

worin die einzelnen Reste die folgenden Bedeutungen haben:
R⁰ n-Alkyl,...Liquid-crystalline medium having a positive dielectric anisotropy, characterized in that it contains one or more compounds of general formula (I)

contains
wherein
R is an unsubstituted, an alkyl or alkenyl radical having 1 or 2 to 15 carbon atoms, which is monosubstituted by CN or CF ₃ or at least monosubstituted by halogen. In these radicals, one or more CH ₂ groups are each independently of one another -O-, -S-,

-CO-, -CO-O-, -O-CO- or -O-CO-O- may be replaced so that O atoms are not directly linked to one another,

Z is CH ₂ -CH ₂ , CF ₂ -CF ₂ , CH = CH, CF = CF or a single bond,
XH, F, CL, CF ₃ , CF ₂ CF ₃ , CH ₂ CF ₃ or CF ₂ H and
n 1 or 2,
mean and
one or more compound (s) selected from the group consisting of the general formulas II to VII contains:

in which the individual radicals have the following meanings:
R ⁰ n-alkyl, ...

Description

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

Liquid crystals are mainly used as dielectrics in display devices, because the optical properties of such substances by an applied Tension can be influenced. Electro-optical devices based on liquid crystals are well known to those skilled in the art and are capable of various effects based. Such devices are for example cells with dynamic scattering, DAP cells (Deformation of upright phases), guest host cells, TN cells with twisted nematic ("twisted nematic ") Structure, STN cells ("supertwisted 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 electrical stability Own fields and electromagnetic radiation. Furthermore, should the liquid crystal materials low viscosity have and in the cells short response times, low threshold voltages and give a high contrast.

Farther they should be at usual Operating temperatures, d. H. 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 usually used as mixtures of several components, it is important that the Components are readily miscible with each other. Other properties, like the electrical conductivity, the dielectric anisotropy and the optical anisotropy must each be according to cell type and field of application different requirements enough. For example, materials for cells should be twisted nematic Structure has a positive dielectric anisotropy and a low one electric conductivity exhibit.

For example are for Matrix liquid crystal displays with integrated non-linear elements for switching individual Pixels (MFK displays) Media with large positive dielectric Anisotropy, broad nematic phases, relatively low birefringence, very high resistivity, good UV and temperature stability and low Steam 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. 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) or other diodes on silicon wafer as a substrate.
• 2. Thin-film transistors (TFT) on a glass plate as a substrate.

The Use of single-crystal silicon as the substrate material restricts 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. One differentiates between two technologies: TFTs Compound semiconductors such. CdSe or TFTs based on polycrystalline or amorphous silicon. At the latter technology gets big worldwide intensity worked.

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 Images are usually extended, with a mosaic as a rule of red, green and blue filters is arranged such that each one filter element a switchable picture element opposite lies.

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

Of the Term MFK displays covers here every matrix display with integrated nonlinear elements, d. H. in addition to the active matrix also displays 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 Displays for Computer applications (laptop) and in the automotive or aircraft industry. Next Problems regarding the angular dependence of the contrast and The switching times resulting in MFK displays difficulties due by insufficient 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 Transistor for Matrix Addressing of Television Liquid Crystal Displays, p. 145 ff, Paris]. With decreasing resistance worsens the contrast of a MFK display and it may be the problem of the "old image elimination "occur. As the resistivity of the liquid crystal mixture by Interaction with the inner surfaces of the display in general over the Lifetime of an MFK display is a high (initial) resistance very important to get acceptable service life. Especially in low-volt mixtures so far it has not been possible very high specific resistances to realize. Furthermore, it is important that the specific resistance one possible slight increase with increasing temperature as well as with temperature and / or UV exposure. Particularly disadvantageous are the Low temperature properties of the blends of the prior art. It is demanded that too at low temperatures no crystallization and / or smectic Phases occur and the temperature dependence of the viscosity as possible is low. The MFK displays from the prior art thus suffice not today's requirements.

In addition to liquid crystal displays which use backlighting, ie are operated transmissively and optionally transflectively, reflective liquid crystal displays are also of particular interest. These reflective liquid crystal displays use the ambient light for information presentation. Thus, they consume significantly less energy than backlit liquid crystal displays of appropriate size and resolution. Since the TN effect is characterized by a very good contrast, such reflective displays are still easy to read even in bright ambient conditions. This is already from simple reflective TN displays, as they are in z. As watches and calculators are used known. However, the principle is also on high-quality, higher-resolution active matrix driven displays such. B. TFT displays applicable. Here, as with the general conventional transmissive TFT-TN displays, the use of liquid crystals with low birefringence (Δn) is necessary in order to achieve a small optical delay (d · Δn). This small optical delay leads to a mostly acceptable low viewing angle dependence of the contrast (cf. DE 30 22 818 ). For reflective displays, the use of liquid crystals with low birefringence is even more important than for transmissive displays, because with reflective displays the effective layer thickness through which the light passes is approximately twice that of transmissive displays with the same layer thickness.

advantages from reflective ads opposite transmissive ads are in addition to the lower power consumption (no background lighting required) the space savings, which leads to a very small overall depth and the reduction of temperature gradient problems different heating by the backlight.

A smaller birefringence allows liquid crystal cells with larger layer thickness which in turn improves the production yield.

It There is still a great need for MFK ads and in particular to reflective MFK displays with very high specificity Resistance at the same time big Working temperature range, short switching times even at low temperatures and low threshold voltage that does not have these disadvantages or only to a lesser extent demonstrate.

• – erweiterter nematischer Phasenbereich (insbesondere zu tiefen Temperaturen)
• – schnelle Schaltbarkeit bei tiefen Temperaturen
• – erhöhte Beständigkeit gegenüber UV-Strahlung (längere Lebensdauer)
• – niedrige Schwellen-(Ansteuer-)spannung
• – niedrige Doppelbrechung besonders für verbesserten Beobachtungswinkelbereich

In TN (Schadt-Helfrich) cells, media are desired which allow the following advantages in the cells:

• - extended nematic phase range (especially at low temperatures)
• - Fast switchability at low temperatures
• - increased resistance to UV radiation (longer life)
• - low threshold (drive) voltage
• - low birefringence especially for improved viewing angle range

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

For higher twisted cells (STN) media are desired, which have a higher multiplexability and / or allow smaller threshold voltages and / or wider nematic phase ranges (especially at low temperatures). For this purpose, a further expansion of the available parameter space (clearing point, transition smectic-nematic or melting point, viscosity, dielectric values, elastic sizes) is urgently desired.

Of the Invention is based on the object media in particular for such MFK, TN or STN displays, in particular for reflective MFK displays, the disadvantages mentioned above are not or only to a lesser extent Dimensions, and preferably at the same time very high resistivities and low Have threshold voltages as well as low birefringence.

It it has now been found that this Task solved can be when used in ads according to the invention media.

enthält,
worin
R H, einen unsubstituierten, einen einfach durch CN oder CF₃ oder einen mindestens einfach durch Halogen substituierten Alkyl- oder Alkenylrest mit 1 bzw. 2 bis 15 C-Atomen, wobei in diesen Resten auch eine oder mehrere CH₂-Gruppen jeweils unabhängig voneinander durch -O-, -S-,

-CO-, -CO-O-, -O-CO- oder -O-CO-O- so ersetzt sein können, daß O-Atome nicht direkt miteinander verknüpft sind,

Z CH₂-CH₂, CF₂-CF₂, CH=CH, CF=CF oder eine Einfachbindung, bevorzugt CH₂-CH₂ oder eine Einfachbindung, besonders bevorzugt eine Einfachbindung,
X H, F, Cl, CF₃, CF₂CF₃, CH₂CF₃ oder CF₂H, bevorzugt H, F, Cl, CF₃ oder CF₂CF₃ und
n 1 oder 2,
bedeuten
und eine oder mehrere Verbindung(en) ausgewählt aus der Gruppe bestehend aus den allgemeinen Formeln II bis VII:

worin die einzelnen Reste die folgenden Bedeutungen haben:
R⁰ n-Alkyl, Oxaalkyl, Fluoralkyl oder Alkenyl mit jeweils 1 bzw. 2 bis 7 C-Atomen,
X⁰ F, Cl, halogeniertes Alkyl, Alkenyl, oder Alkoxy mit 1 bzw. 2 bis 6 C-Atomen,
Y¹ und Y² jeweils unabhängig voneinander H oder F, und
r: 0 oder 1, bevorzugt 1.The invention thus relates to a liquid-crystalline medium based on a mixture of polar compounds having a positive dielectric anisotropy, characterized in that it contains one or more compounds of the general formula I.

contains
wherein
R H, an unsubstituted, a simply by CN or CF ₃ or at least one halogen-substituted alkyl or alkenyl radical having 1 or 2 to 15 carbon atoms, wherein in these radicals also one or more CH ₂ groups each independently -O-, -S-,

-CO-, -CO-O-, -O-CO- or -O-CO-O- may be replaced so that O atoms are not directly linked to one another,

Z is CH ₂ -CH ₂ , CF ₂ -CF ₂ , CH = CH, CF = CF or a single bond, preferably CH ₂ -CH ₂ or a single bond, more preferably a single bond,
X is H, F, Cl, CF ₃ , CF ₂ CF ₃ , CH ₂ CF ₃ or CF ₂ H, preferably H, F, Cl, CF ₃ or CF ₂ CF ₃ and
n 1 or 2,
mean
and one or more compound (s) selected from the group consisting of the general formulas II to VII:

in which the individual radicals have the following meanings:
R ⁰ n-alkyl, oxaalkyl, fluoroalkyl or alkenyl having in each case 1 or 2 to 7 C atoms,
X ⁰ F, Cl, halogenated alkyl, alkenyl, or alkoxy having 1 or 2 to 6 C atoms,
Y ¹ and Y ^{2 are} each independently H or F, and
r: 0 or 1, preferably 1.

Preferably, X in the compounds of the formula IH, F is CF ₃ or CF ₂ CF ₃ , preferably F or CF ₃ .

Compounds of formula I with n = 0 and X = F or Cl are made JP 63-238 030 , those with n = 0 and X = CN are off JP 60-069 059 and liquid-crystal mixtures containing such compounds of formula I with n = 0 and X = CN are made JP 09-157651 and EP 0 781 827 known.

DE 39 30 119 A1 discloses mesogenic compounds containing a cyclohexenylene-1,4-diyl ring.

If R is an alkyl radical and / or an alkoxy radical, this may be straight-chain or branched. Preferably, it is straight-chain, has 2, 3, 4, 5, 6 or 7 carbon atoms and thus preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, furthermore methyl . Octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy.

oxaalkyl preferably denotes 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-oxo-octyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl.

If R is an alkyl radical in which a CH ₂ group is replaced by -CH = CH-, this may be straight-chain or branched. It is preferably straight-chain and has 2 to 10 C atoms. It therefore 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 is an alkyl radical in which one CH ₂ group has been replaced by -O- and one by -CO-, these are preferably adjacent. Thus, they include an acyloxy group -CO-O- or an oxycarbonyl group -O-CO-. Preferably, these are straight-chain and have 2 to 6 carbon atoms.

she therefore especially acetyloxy, propionyloxy, butyryloxy, Pentanoyloxy, hexanoyloxy, acetyloxymethyl, propionyloxymethyl, Butyryloxymethyl, pentanoyloxymethyl, 2-acetyloxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 3-acetyloxypropyl, 3-propionyloxypropyl, 4-acetyloxybutyl, Methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, Pentoxycarbonyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, propoxycarbonylmethyl, Butoxycarbonylmethyl, 2- (methoxycarbonyl) ethyl, 2- (ethoxycarbonyl) ethyl, 2- (propoxycarbonyl) ethyl, 3- (methoxycarbonyl) propyl, 3- (ethoxycarbonyl) propyl, 4- (methoxycarbonyl) -butyl.

If R is an alkyl radical in which a CH ₂ group is replaced by unsubstituted or substituted -CH = CH- and an adjacent CH ₂ group by CO or COO-O or O-CO, this may be straight-chain or branched. Preferably, it is straight-chain and has 4 to 13 carbon atoms. It therefore particularly means acryloyloxymethyl, 2-acryloyloxyethyl, 3-acryloyloxypropyl, 4-acryloyloxybutyl, 5-acryloyloxypentyl, 6-acryloyloxyhexyl, 7-acryloyloxyheptyl, 8-acryloyloxyoctyl, 9-acryloyloxynonyl, 10-acryloyloxydecyl, methacryloyloxymethyl, 2-methacryloyloxyethyl, 3 Methacryloyloxypropyl, 4-methacryloyloxybutyl, 5-methacryloyloxypentyl, 6-methacryloyloxyhexyl, 7-methacryloyloxyheptyl, 8-methacryloyloxyoctyl, 9-methacryloyloxynonyl.

If R is an alkyl or alkenyl radical which is monosubstituted by CN or CF ₃ , this radical is preferably straight-chain. The substitution by CN or CF ₃ is in any position.

If R is an alkyl or at least monosubstituted by halogen Alkenyl means, this radical is preferably straight-chain and halogen is preferably F or Cl. With multiple substitution Halogen is preferably F. The resulting radicals also include perfluorinated radicals. For single substitution, the fluoro or chlorine substituent in any position, preferably however in the ω position.

links the formula I, the over for polymerization reactions suitable wing groups R have, are suitable for the preparation of liquid-crystalline Polymers.

links of the formula I with branched wing groups R can occasionally because of a better solubility in the usual liquid crystalline Base materials of importance, but especially as a chiral Dopants when they are optically active. Smectic compounds These types are suitable as components for ferroelectric materials.

branched Groups usually contain no more than one chain branch. Preferred branched radicals R are 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 is an alkyl radical in which two or more CH ₂ groups have been replaced by -O- and / or -CO-O-, this may be straight-chain or branched. Preferably, it is branched and has 3 to 12 carbon atoms. It therefore particularly denotes 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-carbo xy-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 (methoxycarbonyl) -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.

Especially preference is given to compounds of the formula I in which R is methyl, ethyl, Propyl, butyl, pentyl, vinyl, 1E-propenyl, L 1E-butenyl or 1E-pentenyl means like these compounds containing media. Especially Preferably of these compounds, the alkyl compounds are used.

The Compounds of the formula I are prepared by known methods.

object The invention also relates to the use of the media in electro-optical Displays (in particular STN or MFK displays with two plane-parallel Carrier plates, which form a cell with a border, built-in 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 specificity Resistance) containing such media and the use these media for electro-optical Purposes.

The Liquid crystal mixtures according to the invention enable a significant extension of the available parameter space.

The achievable combinations of clearing point, viscosity at low temperature, thermal and UV stability, optical Anisotropy (i.e., birefringence) and threshold voltage excel by far previous materials from the prior art.

The Demand for high clearing point, nematic phase at low temperature and low birefringence (Δn) and at the same time a low threshold voltage could only so far insufficiently fulfilled become. liquid crystal mixtures such as MLC-6476 and MLC-6625 (Merck KGaA, Darmstadt, Germany) Although comparable clarification points and low temperature stabilities however, they have both much higher Δn values of about 0.075 and a lot higher Threshold voltages of approx. 1.7 V and more.

The Liquid crystal mixtures according to the invention enable while maintaining the nematic phase to -20 ° C and preferably to -30 ° C, especially preferably to -40 ° C, clearing points above 75 ° C, preferably above 80 ° C, more preferably above 90 ° C, at the same time birefringence ≤ 0.07, preferably ≤ 0.067, particularly preferably ≦ 0.065, in particular ≤ 0.063 and most preferably ≤ 0.060 and to achieve a low threshold voltage, resulting in excellent STN and MFK displays and in particular achieved reflective MFK displays can be.

Especially the mixtures are characterized by small operating voltages. The TN thresholds are below 1.6 V, preferably below 1.5 V, more preferably <1.4 V.

• – einer Schwellenspannung von 1,50 V oder weniger sowie einem Δn von 0,065 oder weniger bevorzugt.
• – einer Schwellenspannung von 1,40 V oder weniger sowie einem Δn von 0,067 oder weniger, oder
• – einer Schwellenspannung von 1,30 oder weniger und einem Δn von 0,070 oder weniger, bevorzugt von 0,067 oder weniger, gekennzeichnet.

Particular preference is given to the mixtures according to the invention by a clearing point of 75 ° C. or more and

• A threshold voltage of 1.50 V or less and a Δn of 0.065 or less are preferred.
• A threshold voltage of 1.40 V or less and a Δn of 0.067 or less, or
• A threshold voltage of 1.30 or less and a Δn of 0.070 or less, preferably 0.067 or less.

It will be appreciated by those skilled in the art that by appropriate choice of the components of the blends of the invention, higher clearing points (e.g., above 100 ° C) at lower dielectric anisotropy values and thus higher threshold voltages or lower clearing points at higher dielectric anisotropy levels (eg> 12 ) and thus lower threshold voltages (eg <1.1 V) can be realized while preserving the other advantageous properties. Likewise, even with correspondingly low viscosities, mixtures with a larger Δε and thus lower 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], which in addition to particularly favorable electro-optical properties such. B. high slope of the characteristic and low angle dependence of the contrast ( DE-PS 30 22 818 ) at the same threshold voltage as in an analog display in the second minimum a smaller dielectric anisotropy ausrei is right. As a result, significantly higher specific resistances can be achieved using the mixtures according to the invention in the first minimum than in the case of mixtures with cyano compounds, in particular with benzonitrile compounds. By selecting the individual components and their proportions by weight, the person skilled in the art can set the birefringence required for a given layer thickness of the MFK display with simple routine methods. The requirements for reflective MFK displays have been In the Digest of Technical Papers, SID Symposium 1998, for example.

The Rotational viscosity γ1 at 20 ° C is preferably <140 mPa · s, especially preferably <120 mPas. Of the nematic phase range is preferably at least 90 degrees wide, in particular at least 100 degrees wide. Preferably, it extends this range at least from -20 ° C to + 75 ° C, especially preferably at least from -30 ° C to + 80 ° C or at least from -40 ° C to 75 ° C.

Measurements of the "Capacity Holding Ratio" also called "Voltage Holding Ratio" (also HR for short) [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 comprising compounds of the formula I have a sufficient HR for MFK displays. C or K is a crystalline, S is a smectic, S _{c is} a smectic C, S _{B is} a smectic B, N is a nematic and I is the isotropic phase.

Preferably contain the media of the invention several (preferably two or more) compounds of the formula I, d. H. the proportion of these compounds is 5-95%, preferably 10-60% and more preferably in the range of 15-50%.

The individual compounds of the formulas II to X and their sub-formulas, in the media of the invention can be used are either known or they can be analogous to the known ones Connections are made.

• a) Das Medium enthält zusätzlich eine oder mehrere Verbindung(en) ausgewählt aus der Gruppe bestehend aus den allgemeinen Formeln VIII und IX:
  
  worin die einzelnen Reste die folgenden Bedeutungen haben: R⁰: n-Alkyl, Oxaalkyl, Fluoralkyl oder Alkenyl mit jeweils 1 bzw. 2 bis 7 C-Atomen, X⁰: F, Cl, halogeniertes Alkyl, Alkenyl oder Alkoxy mit 1 bzw. 2 bis 6 C-Atomen, Z^x: CH₂O, COO, bevorzugt COO Y¹ und Y²: jeweils unabhängig voneinander H oder F, und r: 0 oder 1, bevorzugt 1. Die Verbindungen der Formel V sind vorzugsweise Verbindungen ausgewählt aus der Gruppe der Verbindungen der Formeln Va bis Vd.
  
  Bevorzugt wird mindestens eine Verbindung der Formel III eingesetzt. Besonders bevorzugt ist dieses eine Verbindung der Formel IIIa.
  
  in der R⁰ die oben für Formel III angegebene Bedeutung hat und X⁰ F, OCHF₂ oder OCF₃, bevorzugt jedoch R⁰ n-Alkyl und besonders bevorzugt n-Alkyl mit 2 bis 5 C-Atomen und bevorzugt X⁰ F bedeutet. Ganz besonders bevorzugt werden eine oder mehrere Verbindung(en) der Formel IIa mit X⁰ = F eingesetzt.
• b) Das Medium enthält eine oder mehrere Verbindung(en) ausgewählt aus der Gruppe bestehend aus den Verbindungen der allgemeinen Formeln VIII und IX:
  
  worin R⁰, X⁰, Y¹, Y² und r die oben bei Formel VIII bzw. IX angegebene Bedeutung haben und bevorzugt Y¹ und Y² F, r = 1 und X⁰ F bedeuten. Besonders bevorzugt werden Verbindung(en) ausgewählt aus der Gruppe der Verbindungen der Formeln Villa und IXa eingesetzt.
  
  worin R⁰ und X⁰ die oben bei Formeln II bis IX angegebene Bedeutung haben und X⁰ bevorzugt F, OCF₃ oder CHF₂, besonders bevorzugt F bedeutet.
• c) Das Medium enthält zusätzlich eine oder mehrere Verbindungen der Formel X
  
  worin R¹⁰ Alkyl oder Alkoxy mit 1 bis 7 C-Atomen oder Alkenyl, Alkenyloxy oder Alkyloxyalkyl mit 2 bis 7 C-Atomen, bevorzugt n-Alkyl, besonders bevorzugt Propyl oder Pentyl bedeutet.
• d) Das Medium enthält zusätzlich eine oder mehrere Verbindung(en) der allgemeinen Formel XI
  
  worin R¹ und R² unabhängig voneinander, Alkyl oder Alkoxy mit 1 bis 7 C-Atomen oder Alkenyl, Alkenyloxy oder Alkyloxyalkyl mit 2 bis 7 C-Atomen bedeuten. Besonders bevorzugt enthält das Medium eine oder mehrere Verbindung(en) ausgewählt aus der Gruppe der Verbindungen der Formeln XIa bis XIc.
  
  
  worin jeweils unabhängig voneinander Alkyl¹ n-Alkyl mit 1 bis 7 C-Atomen bevorzugt 1 bis 5 C-Atomen, Alkyl² n-Alkyl mit 1 bis 5 C-Atomen, bevorzugt 1, 2 oder 3 besonders bevorzugt 1 C-Atom, Alkyl³ n-Alkyl mit 1 bis 7 C-Atomen, bevorzugt mit 1 bis 5 C-Atomen, Alkyl⁴ n-Alkyl mit 1 bis 5 C-Atomen, bevorzugt mit 2 bis 4, besonders bevorzugt mit 3 C-Atomen Alkyl⁵ n-Alkyl mit 1 bis 5 C-Atomen, bevorzugt mit 3 bis 5, besonders bevorzugt mit 3 oder 5 C-Atomen Alkenyl 1E-Alkenyl mit 2 bis 5 C-Atomen, bevorzugt mit 2 bis 4, besonders bevorzugt 2 oder 3 C-Atomen bedeuten.
• e) Das Medium enthält zusätzlich eine oder mehrere Verbindungen der allgemeinen Formel XII
  
  worin R³ und R⁴ unabhängig voneinander die oben für Formel XI für R¹ und R² angegebene Bedeutung haben, bevorzugt sind R³ und R⁴ jeweils unabhängig voneinander n-Alkyl mit 1 bis 7 C-Atomen besonders bevorzugt mit 3 bis 5 C-Atomen,
  
  und m unabhängig voneinander 0 oder 1 bedeuten. Besonders bevorzugt ist der Einsatz einer oder mehrere Verbindung(en) ausgewählt aus der Gruppe der Verbindungen der Formeln XIIa bis XIIc.
  
  
  worin R³ und R⁴ jeweils unabhängig voneinander n-Alkyl mit 1 bis 7 C-Atomen bevorzugt mit 3 bis 5 C-Atomen bedeutet.
• f) Das Medium enthält zusätzlich eine oder mehrere Verbindungen der allgemeinen Formel XIII
  
  worin R⁵ und R⁶ unabhängig voneinander die oben bei Formel XII für R³ und R³ angegebene Bedeutung haben, bevorzugt sind R⁵ und R⁶ jeweils unabhängig voneinander n-Alkyl mit 1 bis 7 C-Atomen besonders bevorzugt mit 3 bis 5 C-Atomen,
  
  p 0 oder 1 bedeuten. Besonders bevorzugt ist der Einsatz einer oder mehrere Verbindung(en) ausgewählt aus der Gruppe der Verbindungen der Formeln XIIIa bis XIIIc.
  
  worin R⁵ und R⁶ jeweils unabhängig voneinander n-Alkyl mit 1 bis 7 C-Atomen bevorzugt mit 3 bis 5 C-Atomen bedeutet. Ganz besonders bevorzugt werden Verbindungen der Formel XIIIa eingesetzt.
• g) Der Anteil an Verbindungen der Formel I beträgt im Gesamtgemisch mindestens 5% bevorzugt 7% bis 40%, besonders bevorzugt 10% bis 20%
• h) Der Anteil an Verbindungen der Formeln II bis VII beträgt im Gesamtgemisch 10% bis 70%, bevorzugt 20% bis 60% und besonders bevorzugt 30% bis 55%.
• i) Der Anteil an Verbindungen der Formeln VIII und IX, besonders der Verbindungen VIIIa und IXa, a der Gesamtmischung beträgt 10% bis 60%, bevorzugt 16% bi 50%, insbesondere bevorzugt 20% bis 35%.
• j) Der Anteil an Verbindungen der Formel VIII beträgt 10% bis 45%, bevorzugt 20% bis 30%.
• k) Der Anteil an Verbindungen der Formel IX am Gesamtgemisch beträgt 0% bis 40%, bevorzugt 10–30%.
• l) Der Anteil an Verbindungen der Formel X am Gesamtgemisch beträgt 0% bis 20%, bevorzugt 2 bis 18%, besonders bevorzugt 5 bis 15%.
• m) Der Anteil an Verbindungen der Formel XI am Gesamtgemisch beträgt 0% bis 2%, bevorzugt 5% bis 20% und besonders bevorzugt 7% bis 15%.
• n) Der Anteil an Verbindungen der Formel XII am Gesamtgemisch beträgt 0% bis 20%, bevorzugt 1% bis 15%, besonders bevorzugt 2 bis 10%.
  
  besonders bevorzugt
  
• p) Das Medium enthält Verbindungen der Formeln I, III, VIII, X und XI.
• q) R⁰ ist vorzugsweise geradkettiges Alkyl oder Alkenyl mit 2 bis 7 C-Atomen
• r) Das Medium besteht im wesentlichen aus Verbindungen der Formeln I bis XI, wobei ”im wesentlichen” in dieser Anmeldung bedeutet zu mehr als 50%, bevorzugt zu 80% oder mehr und besonders bevorzugt zu 90% oder mehr.
• s) Das Medium besteht im wesentlichen aus Verbindungen der Formeln I, III VII und X bis XII.
• t) Das Medium enthält eine oder mehrere Verbindung(en) ausgewählt aus der Gruppe der Verbindungen der Formeln XIa bis XIc und XIIa bis XIIc.
• u) Das Medium enthält eine oder mehrere Verbindung(en) der Formel XId
  
  worin Alkyl⁶ n-Alkyl mit 1 bis 7 C-Atomen bevorzugt mit 3 bis 5 C-Atomen und Alkyl⁷ n-Alkyl mit 1 bis 5 C-Atomen bevorzugt mit 1 bis 3 C-Atomen bedeutet.
• v) Das Gewichtsverhältnis (I):(II bis XII) ist vorzugsweise 1:15 bis 1:1,5, besonders bevorzugt 1:13 bis 1:5 und ganz besonders bevorzugt 1:11 bis 1:4.
• w) Das Medium besteht im wesentlichen aus Verbindungen ausgewählt aus der Gruppe aus den Verbindungen der Formeln I, IIIa, VIIIa, X, IXa, XIb, XIc und XIIb.
• x) Das Medium enthält jeweils eine oder mehrere Verbindung(en) der Formeln I, III, VIII, X, XI und XII und besteht bevorzugt im wesentlichen aus diesen Verbindungen.

Preferred embodiments are given below.

• a) The medium additionally contains one or more compound (s) selected from the group consisting of the general formulas VIII and IX:
  
  in which the individual radicals have the following meanings: R ⁰ : n-alkyl, oxaalkyl, fluoroalkyl or alkenyl having in each case 1 or 2 to 7 C atoms, X ⁰ : F, Cl, halogenated alkyl, alkenyl or alkoxy with 1 or 2 to 6 C atoms, Z ^x : CH ₂ O, COO, preferably COO Y ¹ and Y ² : each independently of one another H or F, and r: 0 or 1, preferably 1. The compounds of formula V are preferably selected compounds from the group of the compounds of the formulas Va to Vd.
  
  At least one compound of the formula III is preferably used. This is particularly preferably a compound of the formula IIIa.
  
  in which R ^{0 has} the meaning given above for formula III and X ⁰ denotes F, OCHF ₂ or OCF ₃ , but preferably R ⁰ n-alkyl and particularly preferably n-alkyl having 2 to 5 C atoms and preferably X ⁰ F. Very particular preference is given to using one or more compounds of the formula IIa where X ⁰ = F.
• b) The medium contains one or more compound (s) selected from the group consisting of the compounds of general formulas VIII and IX:
  
  wherein R ⁰ , X ⁰ , Y ¹ , Y ² and r have the meaning given above in the formula VIII or IX and preferably Y ¹ and Y ^{2 is} F, r = 1 and X ^{0 is} F. Particular preference is given to using compound (s) selected from the group of the compounds of the formulas VIIIa and VIIIa.
  
  wherein R ⁰ and X ^{0 have} the meaning given above for formulas II to IX and X ^{0 is} preferably F, OCF ₃ or CHF ₂ , particularly preferably F.
• c) The medium additionally contains one or more compounds of the formula X.
  
  where R ^{10 is} alkyl or alkoxy having 1 to 7 C atoms or alkenyl, alkenyloxy or alkyloxyalkyl having 2 to 7 C atoms, preferably n-alkyl, particularly preferably propyl or pentyl.
• d) The medium additionally contains one or more compound (s) of the general formula XI
  
  wherein R ¹ and R ² independently of one another are alkyl or alkoxy having 1 to 7 C atoms or alkenyl, alkenyloxy or alkyloxyalkyl having 2 to 7 C atoms. The medium particularly preferably contains one or more compounds selected from the group of the compounds of the formulas XIa to XIc.
  
  
  in which, in each case independently of one another, alkyl ^1- n-alkyl having 1 to 7 C atoms preferably 1 to 5 C atoms, alkyl ² n-alkyl having 1 to 5 C atoms, preferably 1, 2 or 3 particularly preferably 1 C atom, Alkyl ³ n-alkyl having 1 to 7 carbon atoms, preferably having 1 to 5 carbon atoms, alkyl ⁴ n-alkyl having 1 to 5 carbon atoms, preferably 2 to 4, particularly preferably 3 carbon atoms alkyl. ⁵ n-alkyl having 1 to 5 C atoms, preferably having 3 to 5, particularly preferably 3 or 5 C atoms alkenyl 1E-alkenyl having 2 to 5 carbon atoms, preferably 2 to 4, particularly preferably 2 or 3 C. -atoms mean.
• e) The medium additionally contains one or more compounds of general formula XII
  
  wherein R ³ and R ⁴ independently of one another have the meaning given above for formula XI for R ¹ and R ² , preferably R ³ and R ^{4 are} each independently of one another n-alkyl having 1 to 7 C atoms, particularly preferably having 3 to 5 C -atoms,
  
  and m independently represent 0 or 1. Particularly preferred is the use of one or more compound (s) selected from the group of compounds of the formulas XIIa to XIIc.
  
  
  wherein R ³ and R ^{4 are} each independently n-alkyl having 1 to 7 carbon atoms, preferably having 3 to 5 carbon atoms.
• f) The medium additionally contains one or more compounds of general formula XIII
  
  wherein R ⁵ and R ⁶ independently of one another have the meaning given above for formula XII for R ³ and R ³ , preferably R ⁵ and R ^{6 are} each independently of one another n-alkyl having 1 to 7 C atoms, particularly preferably having 3 to 5 C -atoms,
  
  p is 0 or 1. Particularly preferred is the use of one or more compound (s) selected from the group of compounds of formulas XIIIa to XIIIc.
  
  wherein R ⁵ and R ^{6 are} each independently n-alkyl having 1 to 7 carbon atoms, preferably having 3 to 5 carbon atoms. Very particular preference is given to using compounds of the formula XIIIa.
• g) The proportion of compounds of the formula I in the total mixture is at least 5%, preferably 7% to 40%, particularly preferably 10% to 20%
• h) The proportion of compounds of the formulas II to VII in the total mixture is 10% to 70%, preferably 20% to 60% and particularly preferably 30% to 55%.
• i) The proportion of compounds of the formulas VIII and IX, especially of the compounds VIIIa and IXa, a of the total mixture is 10% to 60%, preferably 16% bi 50%, particularly preferably 20% to 35%.
• j) The proportion of compounds of formula VIII is 10% to 45%, preferably 20% to 30%.
• k) The proportion of compounds of formula IX in the total mixture is 0% to 40%, preferably 10-30%.
• l) The proportion of compounds of formula X in the total mixture is 0% to 20%, preferably 2 to 18%, particularly preferably 5 to 15%.
• m) The proportion of compounds of formula XI in the total mixture is 0% to 2%, preferably 5% to 20% and particularly preferably 7% to 15%.
• n) The proportion of compounds of the formula XII in the total mixture is 0% to 20%, preferably 1% to 15%, particularly preferably 2 to 10%.
  
  particularly preferred
  
• p) The medium contains compounds of the formulas I, III, VIII, X and XI.
• q) R ⁰ is preferably straight-chain alkyl or alkenyl having 2 to 7 C atoms
• r) The medium consists essentially of compounds of the formulas I to XI, where "essentially" in this application means more than 50%, preferably 80% or more and more preferably 90% or more.
• s) The medium consists essentially of compounds of the formulas I, III VII and X to XII.
• t) The medium contains one or more compound (s) selected from the group of the compounds of formulas XIa to XIc and XIIa to XIIc.
• u) The medium contains one or more compound (s) of the formula XId
  
  wherein alkyl ⁶ n-alkyl having 1 to 7 carbon atoms, preferably having 3 to 5 carbon atoms and alkyl ⁷ n-alkyl having 1 to 5 carbon atoms, preferably having 1 to 3 carbon atoms.
• v) The weight ratio (I) :( II to XII) is preferably 1:15 to 1: 1.5, more preferably 1:13 to 1: 5, and most preferably 1:11 to 1: 4.
• w) The medium consists essentially of compounds selected from the group consisting of the compounds of the formulas I, IIIa, VIIIa, X, IXa, XIb, XIc and XIIb.
• x) The medium in each case contains one or more compound (s) of the formulas I, III, VIII, X, XI and XII and preferably consists essentially of these compounds.

It was found that already a relatively low proportion of compounds of the formula I in admixture with conventional Liquid crystal materials, but especially with one or more compounds of the formulas III, VIII, IX and / or X significantly reduce the Values for the birefringence and low threshold voltages leads, where at the same time broad nematic phases with low transition temperatures be observed smectic-nematic, which improves the storage stability becomes.

The term "alkyl" preferably includes 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 of 2-5 carbon atoms are generally preferred.

The term "alkenyl" preferably includes straight-chain and branched alkenyl groups having 2-7 carbon atoms, especially the straight-chain groups. Particularly preferred alkenyl groups are C ₂ -C ₇ -1E-alkenyl, C ₄ -C ₇ -E-alkenyl, C ₅ -C ₇ -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 further 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.

Of the The term "fluoroalkyl" preferably includes straight-chain groups with terminal Fluorine, d. H. Fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorohexyl and 7-fluoroheptyl. Other positions However, the fluorine are not excluded.

The term "oxaalkyl" preferably includes straight-chain radicals of the formula C _n H _{2n + 1} -O- (CH ₂ ) _m , wherein n and m are each independently 1 to 6. Preferably, n = 1 and m is 1 to 6.

By suitably selecting the meanings of R ⁰ and X ⁰ , the response times, the threshold voltage, the transconductance of the transmission characteristics etc. can be modified in the desired manner. For example, 1E-alkenyl radicals, 3E-alkenyl radicals, 2E-alkenyloxy radicals 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) compared to alkyl or alkoxy. 4-Alkenyl radicals, 3-alkenyl radicals and the like generally give lower threshold voltages and smaller values of k ₃₃ / k ₁₁ in comparison to alkyl and alkoxy radicals.

A -CH ₂ CH ₂ group generally results in higher values of k ₃₃ / k ₁₁ compared to a single covalent bond. Higher values of k ₃₃ / k ₁₁ allow z. B. flatter transmission characteristics in TN cells with 90 ° twist (to achieve shades of gray) and steeper transmission characteristics in STN, SBE and OMI cells (higher multiplexability) and vice versa.

The optimal ratio the compounds of formulas I and II to IX depends largely on the desired Properties of the choice of compounds of formulas I to XII and the choice of other optional components from. Suitable proportions within the range given above can be easy from case to case be determined.

The Total amount of compounds of the formulas I to X in the mixtures according to the invention is not very critical. The mixtures can therefore one or more other components are included to optimize various properties. The observed effect on the response times and the threshold voltage however, the larger the higher the rule Total concentration of compounds of formulas I to X is.

In a particularly preferred embodiment, the media according to the invention comprise compounds of the formulas II to VII, wherein X ⁰ is F, OCF ₃ or OCHF ₂ group. A favorable synergistic effect with the compounds of the formula I leads to particularly advantageous properties. In particular, mixtures comprising compounds of the formula I and of the formula IIIa are distinguished by their low threshold voltages and by their small birefringence.

mixtures, in addition to compounds of the formula I and the formula IIIa compounds of the formula VIII, in particular Villa, or the formula XI, in particular the formula XIa and especially the formula Villa and the formula XIa are characterized by good threshold voltages.

Of the Structure of the STN or MFK display from polarizers, electrode base plates and electrodes with surface treatment corresponds to the for Such ads usual Construction. The term of the usual construction is here far collected and includes also all the modifications and modifications of the MFK display, in particular also matrix display elements based on poly-Si TFT or MIM and whole particularly reflective displays.

One significant difference of the ads to the usual however, based on the twisted nematic cell, there exists the choice of liquid crystal parameters the liquid crystal layer.

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, the mixtures on other conventional Species, e.g. B. by using premixes z. B. mixtures from homologous compounds or using so-called "multi-bottle" systems, typically consisting of four corner blends, each one distinguish in pairs only in a physical property, manufacture.

The liquid-crystal media can also further, known in the art and described in the literature additions contain. For example, you can 0-15% preferably 0-10%, added pleochroic dyes and / or chiral dopants become. The individual added compounds are in concentrations from 0.01 to 6%, and preferably from 0.1 to 3%. It will be however, the concentration data of the other constituents of the liquid-crystal mixtures So the liquid crystalline or mesogenic compounds, without regard to concentration indicated these additives.

• – Prozentangaben bedeuten Gewichtsprozent,
• – Temperaturangaben sind in °C angegeben,
• – Temperaturdifferenzen sind in Differenzgrad Celsius (kurz Grad) angegeben,
• – alle physikalischen Eigenschaften sind für 20°C angegeben,
• – der Ausdruck ”im wesentlichen bestehen aus” bedeutet zu 50% oder mehr, bevorzugt zu 80% oder mehr und besonders bevorzugt zu 90% oder mehr bestehen aus,
• – der Begriff ”Verbindungen” ohne weitere Einschränkungen, zur Verdeutlichung meist als Verbindung(en) geschrieben, bedeutet eine Verbindung oder bevorzugt mehrere Verbindungen und
  
  bedeuten trans-1,4-Cyclohexenylen.

Above and below, unless explicitly stated otherwise:

• - percentages mean weight percent,
• - temperature data are given in ° C,
• - temperature differences are in degrees Celsius (short degrees),
• - all physical properties are given at 20 ° C,
• The term "consisting essentially of" means 50% or more, preferably 80% or more and more preferably 90% or more,
• - The term "compounds" without further limitations, for clarity usually written as compound (s), means a compound or preferably several compounds and
  
  mean trans-1,4-cyclohexenylene.

In the present application and in the following examples, the structures of the liquid crystal compounds are indicated by acronyms, wherein the transformation into chemical formulas according to following Tables A and B takes place. All radicals C _n H _{2n + 1} and C _m H _{2m + 1} are straight-chain alkyl radicals having n or m C atoms, where n and m independently of one another preferably denote an integer from 1 to 7. The coding according to Table B is self-evident. In Table A, only the acronym for the main body is given. In the individual case, a code for the substituents R ¹ , R ² , L ¹ and L ² follows separately from the acronym for the main body with a dash: Code for R ¹ , R ² , L ¹ , L ² R ¹ R ² L ¹ L ² nm C _n H _{2n + 1} C _m H _{2m + 1} H H n Om C _n H _{2n + 1} OC _m H _{2m + 1} H H nO.m OC _n H _{2n + 1} C _m H _{2m + 1} H H nm C _n H _{2n + 1} C _m H _{2m + 1} H H n Om C _n H _{2n + 1} OC _m H _{2m + 1} H H nO.m OC _n H _{2n + 1} C _m H _{2m + 1} H H n C _n H _{2n + 1} CN H H nN.F C _n H _{2n + 1} CN H F nN.FF C _n H _{2n + 1} CN F F nF C _n H _{2n + 1} F H H nOF OC _n H _{2n + 1} F H H n Cl C _n H _{2n + 1} Cl H H nCl.F C _n H _{2n + 1} Cl H F nCl.FF C _n H _{2n + 1} Cl F F nF C _n H _{2n + 1} F H H nF.F C _n H _{2n + 1} F H F nF.FF C _n H _{2n + 1} F F F nCF ₃ C _n H _{2n + 1} CF ₃ H H nOCF ₃ C _n H _{2n + 1} OCF ₃ H H nOCF ₃ .F C _n H _{2n + 1} OCF ₃ F H nOCF ₃ .FF C _n H _{2n + 1} OCF ₃ F F nOCF ₂ C _n H _{2n + 1} OCHF ₂ H H nOCF ₂ .F C _n H _{2n + 1} OCHF ₂ H F nOCF ₂ .FF C _n H _{2n + 1} OCHF ₂ F F nS C _n H _{2n + 1} NCS H H RVSN C _r H _{2r + 1} -CH = CH-C _s H _2s - CN H H rESn C _r H _{2r + 1} -OC _s H _2s - CN H H nAm C _n H _{2n + 1} COOC _m H _{2m + 1} H H nOCCF ₂ .FF C _n H _{2n + 1} OCH ₂ CF ₂ H F F

preferred Mixture components are given in Tables A and B.

Tabelle B:

The mixtures according to the invention preferably contain at least one of the compounds of the formulas given in Table B. Table A:

Table B:

The following examples are intended to illustrate the invention without limiting it. All temperatures are in degrees Celsius. Mp means melting point, bp. Clearing point. Δn means optical anisotropy (589 nm, 20 ° C), Δε is the dielectric anisotropy (1 kHz, 20 ° C) and the viscosity γ ₁ (mPa · s) was determined at 20 ° C.

The physical properties of the liquid crystal mixtures were after "Physical Properties of Liquid Crystals "Ed. M. Becker, Merck KGaA, as of Nov. 1997, unless explicitly stated stated otherwise.

V ₁₀ denotes the voltage for 10% relative contrast (viewing direction perpendicular to the plate surface). t _on denotes the switch-on time and t _off the switch-off time at a given operating voltage. Δn denotes the optical anisotropy, and n ₀ denotes the ordinary refractive index at 589 nm, unless otherwise specified. Δε denotes the dielectric anisotropy (Δε = ε _|| - ε _⊥ , where ε _|| the dielectric constant parallel to the _longitudinal molecular _axes and ε _⊥ the dielectric constant perpendicular to it). Δn is determined at 589 nm and 20 ° C and Δε at 1 kHz and 20 ° C, unless expressly stated otherwise. The electro-optical data were measured in a TN cell (twist 90 °, angle of attack 1 °) in the 1st minimum (ie at a d · Δn value of 0.5 microns) at 20 ° C, unless expressly stated otherwise ,

The stability the nematic phase at low temperatures became at fixed temperatures both in the flow viscometer as well as in sealed bottles in the refrigerator. Additionally were filled, with Glue sealed TN cells stored in the refrigerator. The used TN cells corresponded to the the electro-optical examinations used cells. There were for each Storage test at given temperature at least five samples used. As stable Storage time was given at the last at none of the Samples a change had been observed.

Of the Value of rotaton viscosity for ZLI-4792 included with the calibrated self-made rotational visimeter at 20 ° C 133 mPas.

The The following examples are intended to illustrate the invention without limiting it. They do, however, give an overview of possible compositions the media as well as over the achievable physical properties, especially on their Combinations.

example 1

A liquid crystal composition having the following composition was prepared, its properties were determined, and TN liquid crystal cells were prepared and tested. Connection abbreviation Concentration / mass% Physical Properties CL-5-F 6.0 Clearing point (T (N, I)) = 77.5 ° C Transition smectic nematic (T (S, N)) <-40 ° C n ₀ (20 ° C, 589 nm) = 1.469 Δn (20 ° C, 589 nm ) = 0.066 Δε = 7.1 γ ₁ (20 ° C) = 118 mPa · s V ₁₀ (20 ° C, 1 kHz) = 1.37 VV ₉₀ (20 ° C, 1 kHz) = 2.13 V CCH 3CF3 6.0 CCH-34 6.0 CC V-5 8.0 CCP 2F.FF 12.0 CCP 3F.FF 11.0 CCP 5F.FF 6.0 CCP 40CF3 7.0 CCP 20CF3.F 10.0 CCZU-2-F 5.0 CCZU-3-F 16.0 CCZU-5-F 5.0 CCPC-34 2.0 Σ 100.0

The so realized TN cells are characterized in particular by their low drive voltage (threshold voltage and saturation voltage) in combination with excellent stability during deep storage Temperatures off.

Comparative Example 1

A liquid crystal composition having the following composition was prepared, its own and TN-liquid crystal cells made and examined with it. Connection abbreviation Concentration / mass% Physical Properties CCH 5CF3 10.0 Clearing point (T (N, I)) = 79.5 ° C transition smectic nematic (T (S, N)) <-30 ° C n ₀ (20 ° C, 589 nm) = 1.468 Δn (20 ° C, 589 nm ) = 0.065 V ₁₀ (20 ° C, 1 kHz) = 1.58 VV ₉₀ (20 ° C, 1 kHz) = 2.40V CCH-34 5.0 CC V-5 16.0 CCP 2F.FF 12.0 CCP 3F.FF 10.0 CCP 5F.FF 7.0 CCP 20CF3.F 12.0 CCZU-2-F 5.0 CCZU-3-F 16.0 CCZU-5-F 5.0 CCPC-34 2.0 Σ 100.0

in the Comparison to Example 1 shows the TN cell of this comparative example both unfavorable, higher characteristic Tensions up as well as a less favorable one Low-temperature behavior.

Example 2

A liquid crystal composition having the following composition was prepared, its properties were determined, and TN liquid crystal cells were prepared and tested. Connection abbreviation Concentration / mass% Physical Properties CL-5-F 6.0 Clearing point (T (N, I)) = 74.6 ° C Transition smectic nematic (T (S, N)) <-40 ° C n ₀ (20 ° C, 589 nm) = 1.472 Δn (20 ° C, 589 nm ) = 0.067 Δε = 7.5 γ ₁ (20 ° C) = 99 mPa · s V ₁₀ (20 ° C, 1 kHz) = 1.30 VV ₉₀ (20 ° C, 1 kHz) = 1.98 V CCH 3CF3 6.0 CCH-34 6.0 CC V-5 8.0 CCP 2F.FF 12.0 CCP 3F.FF 11.0 CCP 5F.FF 6.0 CCP 40CF3 7.0 CCP 20CF3.F 10.0 CCZU-2-F 5.0 CCZU-3-F 16.0 CPZU-2-F 3.0 CPZU-3-F 2.0 CCPC-34 2.0 Σ 100.0

The so realized TN cells are characterized in particular by their low drive voltage (threshold voltage and saturation voltage) in combination with excellent stability during deep storage Temperatures off.

Example 3

A liquid crystal composition having the following composition was prepared, its properties were determined, and TN liquid crystal cells were prepared and tested. Connection abbreviation Concentration / mass% Physical Properties CL-5-H 10.0 Clearing point (T (N, I)) = 75.2 ° C transition smectic nematic (T (S, N)) <-40 ° C n _e (20 ° C, 589 nm) = 1.5650 Δn (20 ° C, 589 nm) = 0.0847 ε _|| (20 ° C, 1 kHz) = 7.3 Δε (20 ° C, 1 kHz) = 4.3 ν (20 ° C) = 13 mm ² s ^-1 PCH-5F 9.0 PCH-6F 7.2 PCH-7F 5.4 BCH 3F.F 10.8 BCH 5F.F 9.0 ECCP 3OCF3 4.5 ECCP 5OCF3 4.5 CCP 2OCF3 7.2 CCP 3OCF3 10.8 CCP 4OCF3 6.3 CCP 5OCF3 9.9 CBC-33F 1.8 CBC-53F 1.8 CBC-55F 1.8 Σ 100.0

The so realized TN cells are characterized in particular by their low drive voltage (threshold voltage and saturation voltage) in combination with excellent stability during deep storage Temperatures off.

Example 4

A liquid crystal composition having the following composition was prepared, its properties were determined, and TN liquid crystal cells were prepared and tested. Connection abbreviation Concentration / mass% Physical Properties CL-5-H 10.0 Clearing point (T (N, I)) = 66.6 ° C transition smectic nematic (T (S, N)) <-40 ° C n _e (20 ° C, 589 nm) = 1.5624 Δn (20 ° C, 589 nm) = 0.0820 ε _|| (20 ° C, 1 kHz) = 7.6 Δε (20 ° C, 1 kHz) = 4.5 PCH-5F 9.0 PCH-6F 7.2 PCH-7F 5.4 BCH 3F.F 10.8 BCH 5F.F 9.0 CECU-3-F 4.5 CECU-5-F 4.5 CCP 2OCF3 7.2 CCP 3OCF3 10.8 CCP 4OCF3 6.3 CCP 5OCF3 9.9 CBC-33F 1.8 CBC-53F 1.8 CBC-55F 1.8 Σ 100.0

The so realized TN cells are characterized in particular by their low drive voltage (threshold voltage and saturation voltage) in combination with excellent stability during deep storage Temperatures off.

Example 5

A liquid crystal composition having the following composition was prepared, its properties were determined, and TN liquid crystal cells were prepared and tested. Connection abbreviation Concentration / mass% Physical Properties CL-5-DT 10.0 Clearing point (T (N, I)) = 79.1 ° C transition smectic nematic (T (S, N)) <-40 ° C n _e (20 ° C, 589 nm) = 1.5634 Δn (20 ° C, 589 nm) = 0.0881 ε _|| (20 ° C, 1 kHz) = 8.4 Δε (20 ° C, 1 kHz) = 5.2 PCH-5F 9.0 PCH-6F 7.2 PCH-7F 5.4 BCH 3F.F 10.8 BCH 5F.F 9.0 ECCP 3OCF3 4.5 ECCP 5OCF3 4.5 CCP 2OCF3 7.2 CCP 3OCF3 10.8 CCP 4OCF3 6.3 CCP 5OCF3 9.9 CBC-33F 1.8 CBC-53F 1.8 CBC-55F 1.8 Σ 100.0

The so realized TN cells are characterized in particular by their low drive voltage (threshold voltage and saturation voltage) in combination with excellent stability during deep storage Temperatures off.

Example 6

A liquid crystal composition having the following composition was prepared, its properties were determined, and TN liquid crystal cells were prepared and tested. Connection abbreviation Concentration / mass% Physical Properties CL-DT-5 10.0 Clearing point (T (N, I)) = 80.8 ° C Transition smectic nematic (T (S, N)) <-40 ° C Δn (20 ° C, 589 nm) = 0.0760 ε _|| (20 ° C, 1 kHz) = 8.1 Δε (20 ° C, 1 kHz) = 5.0 PCH-5F 9.0 PCH-6F 7.2 PCH-7F 5.4 CCP 3F.F 10.8 CCP 5F.F 9.0 ECCP 3F.F 4.5 ECCP 5OCF3 4.5 CCP 2OCF3 7.2 CCP 3OCF3 10.8 CCP 4OCF3 6.3 CCP 5OCF3 9.9 CBC-33F 1.8 CBC-53F 1.8 CBC-55F 1.8 Σ 100.0

The so realized TN cells are characterized in particular by their low drive voltage (threshold voltage and saturation voltage) in combination with excellent stability during deep storage Temperatures off.

Example 7

A liquid crystal composition having the following composition was prepared, its properties were determined, and TN liquid crystal cells were prepared and tested. Connection abbreviation Concentration / mass% Physical Properties CL-5-F 20.0 Clearing point (T (N, I)) = 74.0 ° C ε _|| (20 ° C, 1 kHz) = 10.4 Δε (20 ° C, 1 kHz) = 6.4 k ₁ (20 ° C) = 8.7 pN k ₁ / k ₃ (20 ° C) = 1.53 PCH-5F 3.2 CCP 2OCF2.FF 17.0 CCP 3OCF2.FF 16.0 CCP 5OCF2.FF 17.0 CUP 2F.F 5.4 CUP 3F.F 5.3 CBC-33F 5.4 CBC-53F 5.4 CBC-55F 5.3 Σ 100.0

The so realized TN cells are characterized in particular by their low drive voltage (threshold voltage and saturation voltage) out.

Claims (8)

Liquid-crystalline medium having a positive dielectric anisotropy, characterized in that it contains one or more compounds of general formula (I)

in which R is H, an unsubstituted, an alkyl or alkenyl radical having 1 or 2 to 15 C atoms, which is monosubstituted by CN or CF ₃ or at least one halogen, where one or more CH ₂ groups are also present in these radicals independently of each other by -O-, -S-,

-CO-, -CO-O-, -O-CO- or -O-CO-O- may be replaced so that O atoms are not directly linked to one another,

Z is CH ₂ -CH ₂ , CF ₂ -CF ₂ , CH = CH, CF = CF or a single bond, X is H, F, CL, CF ₃ , CF ₂ CF ₃ , CH ₂ CF ₃ or CF ₂ H and n is 1 or 2, and one or more compound (s) selected from the group consisting of the general formulas II to VII contains:

wherein the individual radicals have the following meanings: R ⁰ n-alkyl, oxaalkyl, fluoroalkyl or alkenyl each having up to 9 C atoms, X ⁰ F, Cl, halogenated alkyl, alkenyl, or alkoxy with 1 or 2 to 6 C. Atoms, Y ¹ and Y ^{2 are} each independently H or F; and r: 0 or 1. Medium according to claim 1, characterized in that it additionally contains one or more compound (s) selected from the group of compounds of formulas VIII and IX:

wherein R ⁰ X ⁰ , Y ¹ , Y ² and r have the meaning given in claim 1 in formula V and Z ^{x is} CH ₂ O or COO. Medium according to claim 1 or 2, characterized that the Proportion of compound (s) of the formula I in the total mixture at least 5 wt .-% is. Medium according to at least one of claims 1 to 3, characterized in that the Proportion of compounds of the formulas II to VII together in the total mixture 10% to 70% by weight. Medium according to claim 2, characterized in that it contains a compound of formula VIII '

wherein R ⁰ , X ⁰ , Y ² and r have the meaning given in claim. Medium according to claim 5, characterized in that X ⁰ denotes F or OCF ₃ and Y ² denotes H or F. Medium according to at least one of Claims 1 to 6, characterized in that it contains one or more compound (s) of the formula III

wherein X ⁰ F, OCHF ₂ or OCF ₃ , Y ¹ and Y ^{2 are} each independently H or F and R ⁰ n-alkyl, oxaalkyl or fluoroalkyl each having up to 7 carbon atoms. Use of the liquid-crystalline Medium according to at least one of claims 1 to 7 for electro-optical Purposes.