DE102005011823A1 - Liquid crystal mixture, used in electrooptical display with active matrix addressing, is based on mixture of polar compounds with negative dielectric anisotropy including compound with terminal (substituted) difluoromethoxy group - Google Patents

Abstract

Liquid crystal medium based on a mixture of polar compounds with negative dielectric anisotropy contains (a) 2-6-ring compound(s) (IA) with a terminal (substituted) difluoromethoxy substituent and (b) 4-(trans-cyclohexyl)-2',3'-difluoro-biphenyl compound(s) (IB) and/or (c) trans,trans-cyclohexylcyclohexane, 4-(trans-4-(trans-cyclohexyl)-cyclohexyl)-benzene or 4,4'-bis-(trans-cyclohexyl)-biphenyl compound(s) (IC). Liquid crystal medium based on a mixture of polar compounds with negative dielectric anisotropy contains: (a) 2-6-ring compound(s) (IA) with a terminal (substituted) difluoromethoxy substituent; (b) 4-(trans-cyclohexyl)-2',3'-difluoro-biphenyl compound(s) (IB); and/or (c) trans,trans-cyclohexylcyclohexane, 4-(trans-4-(trans-cyclohexyl)-cyclohexyl)-benzene or 4,4'-bis-(trans-cyclohexyl)-biphenyl compound(s) (IC) of the formulae; R11>, R12>, R13>, R14>H or R; R16>H, R, or, if n is 1, also F or OCF3; R : alk(en)yl with up to 15 C, optionally mono-substituted by CN or CF3 or at least mono-substituted by halogen, in which one or more CH2 groups may be replaced by -O-, -S-, 1,3-cyclobutylene, -CC-, -CO-O- or -O-CO- without directly linked O atoms; A11>, A12>, A13>(a) trans-1,4-cyclohex(en)ylene, in which 1 or more non-adjacent CH2 groups may be replaced by -O- or -S-; (b) 1,4-phenylene, in which 1 or 2 CH groups may be replaced by N; (c) piperidin-1,4-diyl, 1,4-bicyclo(2,2,2)-octylene, naphth-2,6-diyl, decahydronaphth-2,6-diyl, 1,2,3,4-tetrahydronaphth-2,6-diyl, phenanthren-2,7-diyl, fluoren-2,7-diyl, trans-1,4-silacyclohexylene, in which rings (a-c) may have halogen substituent(s) and at least one is a 2,3-difluoro-, 2-fluoro-3-trifluoromethyl-, 3-fluoro-2-trifluoromethyl or 2,3-di(trifluoromethyl)-1,4-phenylene ring; R15>2-8 C alkenyl or alkenyloxy; Z1>, Z2>-CO-O-, -O-CO-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -CH2CH2-, -(CH2)4-, -C2F4-, -CH2CF2-, -CF2CH2-, CF=CF-, -CH=CF-, -CF=CH-, -CH=CH-, -CC- or a single bond; m, n : 0, 1 or 2. [Image].

Description

• a) mindestens eine Verbindung der Formel IA,
  
• b) mindestens eine Verbindung der Formel IB,
  
  und/oder
• c) mindestens eine Verbindung der Formel IC,
  
  enthält, worin R¹¹, R¹², R¹³, R¹⁴ und R¹⁶ jeweils unabhängig voneinander H, einen unsubstituierten, oder einen einfach durch CN oder CF₃ oder mindestens einfach durch Halogen substituierten Alkyl- oder Alkenylrest mit bis zu 15 C-Atomen, wobei in diesen Resten auch eine oder mehrere CH₂-Gruppen durch -O-, -S-,
  
  -C≡C-, -OC-O- oder -O-CO- so ersetzt sein können, dass O-Atome nicht direkt miteinander verknüpft sind, im Fall n = 1 kann R¹⁶ auch F oder OCF₃ bedeuten, A¹¹, A¹² und A¹³ jeweils unabhängig voneinander a) einen 1,4-Cyclohexenylen- oder 1,4-Cyclohexylenrest, worin eine oder zwei nicht benachbarte CH₂-Gruppen durch -O- oder -S- ersetzt sein können, b) einen 1,4-Phenylenrest, worin eine oder zwei CH-Gruppen durch N ersetzt sein können, c) einen Rest aus der Gruppe Piperidin-1,4-diyl-, 1,4-Bicyclo[2,2,2]-octylen-, einen Naphthalin-2,6-diyl, Decahydronaphthalin-2,6-diyl, 1,2,3,4-Tetrahydronaphthalin-2,6-diyl, Phenanthren-2,7-diyl, Fluoren-2,7-diyl, trans-1,4-Silacyclohexylen, wobei die Ringe a), b) und c) ein oder mehrfach durch Halogenatome substituiert sein können, wobei mindestens einer der Ringe A¹¹, A¹² und A¹³
  
  ist, R¹⁵ Alkenyl oder Alkenyloxy mit 2 bis 8 C-Atomen, Z¹¹ und Z¹² jeweils unabhängig voneinander -CO-O-, -O-CO-, -CF₂O-, -OCF₂-, -CH₂O-, -OCH₂-, -CH₂CH₂-, -(CH₂)₄-, -C₂F₄-, -CH₂CF₂-, -CF₂CH₂-, -CF=CF-, -CH=CF-, -CF=CH-, -CH=CH-, -C≡C- oder eine Einfachbindung, und m und n jeweils unabhängig voneinander 0, 1 oder 2,

bedeuten.The invention relates to a liquid-crystalline medium based on a mixture of polar compounds with negative dielectric anisotropy, which

• a) at least one compound of the formula IA,
  
• b) at least one compound of the formula IB,
  
  and or
• c) at least one compound of the formula IC,
  
  wherein R ¹¹ , R ¹² , R ¹³ , R ¹⁴ and R ^{16 are} each independently H, an unsubstituted, or an alkyl or alkenyl radical having up to 15 C atoms, which is monosubstituted by CN or CF ₃ or at least monosubstituted by halogen in which one or more CH ₂ groups are substituted by -O-, -S-,
  
  -C≡C-, -OC-O- or -O-CO- can be replaced so that O atoms are not directly linked to one another; in the case n = 1, R ^{16 can} also be F or OCF ₃ , A ¹¹ , A ¹² and A ^{13 are} each independently a) a 1,4-cyclohexenylene or 1,4-cyclohexylene radical wherein one or two non-adjacent CH ₂ groups may be replaced by -O- or -S-, b) a 1 , 4-phenylene radical in which one or two CH groups may be replaced by N, c) a radical from the group consisting of piperidine-1,4-diyl, 1,4-bicyclo [2,2,2] octylene, a naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, phenanthrene-2,7-diyl, fluorene-2,7-diyl, trans -1,4-Silacyclohexylen, wherein the rings a), b) and c) may be substituted one or more times by halogen atoms, wherein at least one of the rings A ¹¹ , A ¹² and A ^13th
  
  R ^{15 is} alkenyl or alkenyloxy of 2 to 8 C atoms, Z ¹¹ and Z ^{12 are} each independently -CO-O-, -O-CO-, -CF ₂ O-, -OCF ₂ -, -CH ₂ O- -, -OCH ₂ -, -CH ₂ CH ₂ -, - (CH ₂ ) ₄ -, -C ₂ F ₄ -, -CH ₂ CF ₂ -, -CF ₂ CH ₂ -, -CF = CF-, - CH = CF-, -CF = CH-, -CH = CH-, -C≡C- or a single bond, and m and n are each independently 0, 1 or 2,

mean.

such Media are especially for Electro-optical displays based on active matrix addressing on the ECB effect as well as for IPS Displays (In plane switching).

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

The work of J. Robert and F. Clerc (SID 80 Digest Techn. Papers (1980), 30), J. Duchene (Displays 7 (1986), 3) and H. Schad (SID 82 Digest Techn. Papers (1982). , 244) have shown that liquid-crystalline phases must have high values for the ratio of the elastic constants K ₃ / K ₁ , high values for the optical anisotropy Δn and values for the dielectric anisotropy Δε of -0.5 to -5 in order to highly informative display elements based on the ECB effect can be used. Electro-optical display elements based on the ECB effect have a homeotropic edge orientation. Even with displays that use the so-called IPS effect, dielectric negative liquid crystal media can be used.

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

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

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

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

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

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

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

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

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

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

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

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

such MFK displays are particularly suitable for TV applications (e.g., pocket televisions) or for highly informative Displays in automotive or Aircraft construction. In addition to problems with the angle dependence the contrast and the switching times result in MFK displays difficulties due to a not sufficiently high specific resistance the liquid crystal mixtures [TOGASHI, S., SEKIGUCHI, K., TANABE, H., YAMAMOTO, E., SORIMACHI, K., TAJIMA, E., WATANABE, N., 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. Because the specific resistance of the liquid crystal mixture by interacting with the inner surfaces of the display in general over the Lifetime of an MFK display is a high (initial) resistance very important for Display the acceptable resistance values over a long period of operation must have.

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

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

Of the Invention is based on the object, MFK displays which on the ECB or based on the IPS effect to provide the above indicated disadvantages or only to a lesser extent and at the same time very high specific resistances exhibit.

It It has now been found that this task can be solved when in uses nematic liquid-crystal mixtures for these display elements, the at least one compound of the formula IA and at least one Compound of formula IB and / or IC included.

The invention thus relates to a liquid-crystalline medium based on a mixture of polar compounds having negative dielectric anisotropy, which contains at least one compound of the formula IA and at least one compound of the formula IB and / or IC. In the compound of formula IA is preferably at least one of the rings A ¹¹ , A ¹² , A ^13th

Compounds of the formula IA are known, for example, from JP 2002-308814. The mixtures according to the invention exhibit relatively high clearing points, low rotational viscosities γ ₁ and high negative dielectric anisotropies Δε.

• a) Flüssigkristallines Medium, welches zusätzlich eine oder mehrere Verbindungen der Formeln IIA und/oder IIB enthält,
  
  worin R² und R²* jeweils unabhängig voneinander die Bedeutung von R¹¹ hat, p 1 oder 2, und v 1 bis 6 bedeutet.
• b) Flüssigkristallines Medium, welches zusätzlich eine oder mehrere Verbindungen der Formel III enthält,
  
  worin R³¹ und R³² jeweils unabhängig voneinander einen geradkettigen Alkylrest mit bis zu 12 C-Atomen, wobei eine CH₂-Gruppe auch durch -O-, -OC-O- oder -COO- ersetzt sein kann,
  
  bedeuten. Vorzugsweise bedeutet R³¹ und/oder R³² Alkyl oder Alkoxy. Bevorzugte Verbindungen sind ausgewählt aus den Formeln IIIa bis IIId:
  
  
  worin Alkyl und Alkyl* jeweils unabhängig voneinander einen geradkettigen Alkylrest mit 1-6 C-Atomen, bedeuten.
• c) Flüssigkristallines Medium, welches ein, zwei, drei, vier oder mehr, vorzugsweise ein oder zwei Verbindungen der Formel IA enthält.
• d) Flüssigkristallines Medium, worin R¹¹ in Formel IA vorzugsweise folgende Bedeutungen hat: geradkettiges Alkyl, vorzugsweise CH₃ oder C₂H₅.
• e) Flüssigkristallines Medium, wobei der Anteil an Verbindungen der Formel IA im Gesamtgemisch mindestens 5 Gew.%, vorzugsweise mindestens 10 Gew.%, beträgt. Vorzugsweise enthält das Medium 10-35 Gew.%
• f) Flüssigkristallines Medium, wobei der Anteil an Verbindungen der Formeln IIA und/oder IIB im Gesamtgemisch mindestens 20 Gew.-% beträgt.
• g) Flüssigkristallines Medium, wobei der Anteil den Verbindungen der Formel III im Gesamtgemisch mindestens 5 Gew.-% beträgt.
• h) Flüssigkristallines Medium, welches mindestens eine Verbindung ausgewählt aus den Teilformeln IA-1 bis IA-18 enthält:
  
  
  Besonders bevorzugte Medien enthalten eine oder mehrere Verbindungen ausgewählt aus der Gruppe der Verbindungen der Formeln
  
  
  
  
  worin Alkyl und Alkyl* jeweils unabhängig voneinander einen geradkettigen Alkylrest mit 1-6 C-Atomen, und Alkenyl und Alkenyl* jeweils unabhängig voneinander einen geradkettigen Alkenylrest mit 2-8 C-Atomen bedeuten.
• i) Flüssigkristallines Medium, welches mindestens eine Verbindung ausgewählt aus den Teilformeln IC-1 bis IC-5 enthält,
  
  
  worin Alkyl einen geradkettigen Alkylrest mit 1-6 C-Atomen, und Alkenyl und Alkenyl* jeweils unabhängig voneinander einen geradkettigen Alkenylrest mit 2-8 C-Atomen bedeutet. Vorzugsweise enthält das erfindungsgemäße Medium mindestens eine Verbindung der Formel IC-1 und/oder IC-3. Besonders bevorzugte Verbindungen der Formeln IC-1 und IC-2 werden nachfolgend genannt:
  
  
• j) Flüssigkristallines Medium, welches 5-35 Gew.% einer oder mehrerer Verbindungen der Formel IA, 20-70 Gew.% einer oder mehrerer Verbindungen der Formeln IB und/oder IC, und 10-40 Gew.% einer oder mehrerer Verbindungen der Formeln IIA und/oder IIB enthält.
• k) Flüssigkristallines Medium, welches zusätzlich eine oder mehrere Vierkernverbindungen der Formeln,
  
  worin R⁷, R⁸ und R⁸ jeweils unabhängig voneinander eine der in Anspruch 1 für R¹¹ angegebenen Bedeutung haben, und w, x und z jeweils unabhängig voneinander 1 bis 6 bedeuten, enthält.
• l) Flüssigkristallines Medium, welches zusätzlich eine oder mehrere Verbindungen der Formeln
  
  
  
  enthält, worin R¹³-R²⁸ jeweils unabhängig voneinander, die für R¹¹ angegebenen Bedeutungen haben, und z und m jeweils unabhängig voneinander 1-6 bedeuten. R^E bedeutet H, CH₃, C₂H₅ oder n-C₃H₇.
• m) Flüssigkristallines Medium enthaltend zusätzlich ein oder mehrere Verbindungen der Formeln,
  
  worin R Alkyl, Alkenyl, Alkoxy, Alkylalkoxy, Alkenyloxy mit 1 bzw. 2 bis 6 C-Atomen bedeutet und Alkenyl die oben angegebene Bedeutung hat.

Some preferred embodiments are mentioned below:

• a) liquid-crystalline medium which additionally contains one or more compounds of the formulas IIA and / or IIB,
  
  wherein R ² and R ² * each independently has the meaning of R ¹¹ , p is 1 or 2, and v is 1 to 6.
• b) liquid-crystalline medium which additionally contains one or more compounds of the formula III,
  
  in which R ³¹ and R ^{32 are} each independently a straight-chain alkyl radical having up to 12 C atoms, where a CH ₂ group may also be replaced by -O-, -OC-O- or -COO-,
  
  mean. Preferably, R ³¹ and / or R ^{32 is} alkyl or alkoxy. Preferred compounds are selected from the formulas IIIa to IIId:
  
  
  wherein alkyl and alkyl * each independently represent a straight-chain alkyl radical having 1-6 C atoms.
• c) liquid-crystalline medium which contains one, two, three, four or more, preferably one or two, compounds of the formula IA.
• d) liquid-crystalline medium, wherein R ¹¹ in formula IA preferably has the following meanings: straight-chain alkyl, preferably CH ₃ or C ₂ H ₅ .
• e) Liquid-crystalline medium, wherein the proportion of compounds of the formula IA in the total mixture is at least 5% by weight, preferably at least 10% by weight. Preferably, the medium contains 10-35% by weight.
• f) liquid-crystalline medium, wherein the proportion of compounds of the formulas IIA and / or IIB in the total mixture is at least 20% by weight.
• g) liquid-crystalline medium, wherein the proportion of the compounds of formula III in the total mixture is at least 5 wt .-%.
• h) Liquid-crystalline medium which contains at least one compound selected from the sub-formulas IA-1 to IA-18:
  
  
  Particularly preferred media contain one or more compounds selected from the group of compounds of the formulas
  
  
  
  
  wherein alkyl and alkyl * each independently represent a straight-chain alkyl radical having 1-6 C atoms, and alkenyl and alkenyl * each independently represent a straight-chain alkenyl radical having 2-8 C atoms.
• i) liquid-crystalline medium which contains at least one compound selected from the sub-formulas IC-1 to IC-5,
  
  
  wherein alkyl is a straight-chain alkyl radical having 1-6 C atoms, and alkenyl and alkenyl * each independently a straight-chain alkenyl radical having 2-8 C atoms. The medium according to the invention preferably contains at least one compound of the formula IC-1 and / or IC-3. Particularly preferred compounds of the formulas IC-1 and IC-2 are mentioned below:
  
  
• j) liquid-crystalline medium which 5-35 % By weight of one or more compounds of the formula IA, 20-70 % By weight of one or more compounds of the formulas IB and / or IC, and 10-40 % By weight of one or more compounds of the formulas IIA and / or IIB contains.
• k) liquid-crystalline medium which additionally contains one or more four-nucleus compounds of the formulas,
  
  wherein R ⁷ , R ⁸ and R ⁸ each independently have one of the meanings given in claim 1 for R ¹¹ , and w, x and z are each independently 1 to 6, contains.
• l) liquid-crystalline medium which additionally contains one or more compounds of the formulas
  
  
  
  wherein R ¹³ -R ²⁸ each independently of one another have the meanings given for R ¹¹ , and z and m are each independently 1-6. R ^E is H, CH ₃ , C ₂ H ₅ or nC ₃ H ₇ .
• m) liquid-crystalline medium additionally containing one or more compounds of the formulas,
  
  wherein R is alkyl, alkenyl, alkoxy, alkylalkoxy, alkenyloxy having 1 or 2 to 6 carbon atoms and alkenyl has the meaning given above.

One Another object of the invention is an electro-optical display with an active matrix addressing based on the ECB effect, characterized in that it is a liquid-crystalline dielectric Medium according to one of the claims 1 to 9 contains.

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

The liquid-crystal mixture according to the invention has a Δε of about -0.5 to -8.0, in particular of about -3.0 to -6.0, where Δ∈ denotes the dielectric anisotropy. The rotational viscosity γ ₁ is preferably <150 mPa · s, in particular <140 mPa · s.

The Birefringence Δn in the liquid crystal mixture is, as a rule, between 0.07 and 0.16, preferably between 0.08 and 0.11.

The mixtures according to the invention are for all VA TFT applications are suitable, e.g. MVA, PVA, ASV. Farther are they for IPS and PALC applications suitable with negative Δε.

The Compounds of the formula IA can for example, as described in JP 2002-308814 described.

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

The Component A has a distinctly negative dielectric anisotropy and gives the nematic phase a dielectric anisotropy from ≤ -0.3. It contains preferably compounds of the formulas IA and IB and / or IC, II and III.

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

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

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

The liquid-crystal mixture according to the invention has a Δε of about -0.5 to -8.0, in particular of about -3.0 to -6.0, where Δ∈ denotes the dielectric anisotropy. The rotational viscosity γ ₁ is preferably <200 mPa · s, in particular <180 mPa · s, very particularly preferably <150 mPa · s.

The Birefringence Δn in the liquid crystal mixture is, as a rule, between 0.07 and 0.18, preferably between 0.08 and 0.11.

The mixtures according to the invention are for all VA TFT applications are suitable, e.g. MVA, PVA, ASV. Farther are they for IPS and PALC applications suitable with negative Δε.

The compounds of the formula IA can be prepared, for example, as follows, as described in JP 2002-308814.

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

The Component A has a distinctly negative dielectric anisotropy and gives the nematic phase a dielectric anisotropy from ≤ -0.3. It contains preferably compounds of the formulas IA and IB and / or IC, II and III.

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

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

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

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

component B is monotropic or enantiotropic nematic, has no smectic Phases and can in liquid crystal mixtures the occurrence of smectic phases up to very low temperatures prevent. For example, if a smectic liquid-crystal mixture is added each with different materials with high nematogeneity, so can the degree of suppression achieved smectic phases compared the nematogeneity of these materials become.

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

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

Preferably contain the phases 4 to 15, in particular 5 to 12 compounds Formulas IA and IB and / or IC, IIA and / or IIB and optional III.

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

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

oder eine C-C-Einfachbindung, Q Halogen, vorzugsweise Chlor, oder -CN, und R¹⁰ und R¹¹ jeweils Alkyl, Alkenyl, Alkoxy, Alkanoyloxy oder Alkoxycarbonyloxy mit bis zu 18, vorzugsweise bis zu 8 Kohlenstoffatomen, oder einer dieser Reste auch CN, NC, NO₂, NCS, CF₃, SF₅, OCF₃, F, Cl oder Br bedeuten.The most important compounds which can be considered as constituents of such liquid-crystal phases can be characterized by the formula IV R ¹⁰ -LGER ¹¹ IV wherein each of L and E is a carbo- or heterocyclic ring system of the 1,4-disubstituted benzene and cyclohexane rings, 4,4'-disubstituted biphenyl, phenylcyclohexane and cyclohexylcyclohexane systems, 2,5-disubstituted pyri (mi) din- and 1,3-dioxane rings, 2,3-difluoro-1,4-phenylene, trans-1,4-silacyclohexylene, tetrahydropyran, 1,3-dithiane or tetrahydrothiopyran group, 2,6-disubstituted naphthalene, di- and Tetrahydronaphthalene, quinazoline and tetrahydroquinazoline formed group,

or a CC single bond, Q is halogen, preferably chlorine, or -CN, and R ¹⁰ and R ^{11 are} each alkyl, alkenyl, alkoxy, alkanoyloxy or alkoxycarbonyloxy having up to 18, preferably up to 8 carbon atoms, or one of these radicals also CN, Mean NC, NO ₂ , NCS, CF ₃ , SF ₅ , OCF ₃ , F, Cl or Br.

In most of these compounds R ¹⁰ and R ¹¹ are different from each other, wherein one of these radicals is usually an alkyl or alkoxy group. Other variants of the proposed substituents are in use. Many such substances or mixtures thereof are commercially available. All these substances can be prepared by literature methods.

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

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

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

Preferably contain the mixtures according to the invention in addition to the compounds of formulas IA and IB and / or IC one or several compounds of the compounds listed below.

The following abbreviations are used:
(n, m = 1-6, z = 1-6)

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

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

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

In Table A becomes possible Indicated dopants, which are added to the mixtures of the invention can. If the mixtures contain a dopant, it is in quantities from 0.01-4% by weight, preferably 0.1-1.0 wt.% Used.

Table A

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

Table B (n = 1-12)

V_o

Schwellenspannung, kapazitiv [V] bei 20°C

Δn

die optische Anisotropie gemessen bei 20°C und 589 nm

Δε

die dielektrische Anisotropie bei 20°C und 1 kHz

cp.

Klärpunkt [°C]

γ₁

Rotationsviskosität gemessen bei 20°C [mPa·s]

LTS

Low temperature stability, bestimmt in Testzellen

The following examples are intended to illustrate the invention without limiting it. Above and below mean

V _o

Threshold voltage, capacitive [V] at 20 ° C

.DELTA.n

the optical anisotropy measured at 20 ° C and 589 nm

Δε

the dielectric anisotropy at 20 ° C and 1 kHz

cp.

Clearing point [° C]

γ ₁

Rotational viscosity measured at 20 ° C [mPa · s]

LTS

Low temperature stability, determined in test cells

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

Examples mix

Example M1

Example M2

Example M3 CC-3-V1 9.00% CC-5-V 14.00% CCH-34 8.00% CY-3-O4 14.00% CY-5-O4 9.00% CCY-3-O2 10.00% CCY-5-O2 10.00% CCY-3-1 10.00% PY-2DO-O2 8.00% PY-3DO O2 8.00%

Example M4

Claims (10)

Liquid-crystalline medium based on a mixture of polar compounds having a negative dielectric anisotropy, characterized in that it comprises a) at least one compound of the formula IA,

b) at least one compound of the formula IB,

and / or c) at least one compound of the formula IC,

wherein R ¹¹ , R ¹² , R ¹³ , R ¹⁴ and R ^{16 are} each independently H, an unsubstituted or substituted by CN or CF ₃ or at least simply by halogen substituted alkyl or alkenyl radical having up to 15 carbon atoms, where in these radicals also one or more CH ₂ groups is represented by -O-, -S-,

-C≡C-, -OC-O- or -O-CO- can be replaced so that O atoms are not directly linked to one another; in the case n = 1, R ^{16 can} also be F or OCF ₃ , A ¹¹ , A ¹² and A ^{13 are} each independently a) a 1,4-cyclohexenylene or 1,4-cyclohexylene radical wherein one or two non-adjacent CH ₂ groups may be replaced by -O- or -S-, b) a 1 , 4-phenylene radical in which one or two CH groups may be replaced by N, c) a radical from the group consisting of piperidine-1,4-diyl, 1,4-bicyclo [2,2,2] octylene, a naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, phenanthrene-2,7-diyl, fluorene-2,7-diyl, trans -1,4-Silacyclohexylen, wherein the rings a), b) and c) may be substituted one or more times by halogen atoms, wherein at least one of the rings A ¹¹ , A ¹² and A ^13th

is. R ¹⁵ alkenyl or alkenyloxy having 2 to 8 C atoms Z ¹¹ and Z ^{12 are} each independently of one another -CO-O-, -O-CO-, -CF ₂ O-, -OCF ₂ -, -CH ₂ O-, - OCH ₂ -, -CH ₂ CH ₂ -, - (CH ₂ ) ₄ -, -C ₂ F ₄ -, -CH ₂ CF ₂ -, -CF ₂ CH ₂ -, -CF = CF-, -CH = CF -, -CF = CH-, -CH = CH-, -C≡C- or a single bond, and m and n are each independently 0, 1 or 2, mean. Liquid-crystalline medium according to Claim 1, characterized in that it additionally contains one or more compounds of the formulas IIA and / or IIB:

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

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

in which R ³¹ and R ^{32 are} each independently a straight-chain alkyl radical having up to 12 C atoms, where a CH ₂ group may also be replaced by -O-, -OC-O- or -COO-,

mean, contains. liquid-crystalline Medium according to one of the claims 1 to 3, characterized in that it is one, two, three, four or contains more compounds of the formula IA. liquid-crystalline Medium according to one of the claims 1 to 4, characterized in that the proportion of compounds of the formula IA in the total mixture is at least 5% by weight. liquid-crystalline Medium according to one of the claims 1 to 5, characterized in that the proportion of compounds of the formulas IIA and / or IIB in the overall mixture at least 20% by weight. is. liquid-crystalline Medium according to one of the claims 1 to 6, characterized in that the proportion of compounds of the formula III in the total mixture is at least 5% by weight. A liquid-crystalline medium according to any one of claims 1 to 7, characterized in that it comprises at least one compound selected from the formulas IA-1 to IA-18,

wherein R ¹¹ and R ^{12 have} the meanings given in claim 1 contains. liquid-crystalline Medium according to one of the claims 1 to 8, characterized in that it consists essentially of 5-35 % By weight of one or more compounds of the formula IA, 20-70 % By weight of one or more compounds of the formulas IB and / or IC, and 10-40% by weight of one or more compounds of the formulas IIA and / or IIB contains. Electro-optical display with active matrix addressing based on the ECB, PALC or IPS effect, characterized that they are a liquid crystalline dielectric Medium according to one of the claims 1 to 9 contains.