DE4111015A1 - Liq. crystal mixt. with wide nematic phase range - contg. opt. substd. alkyl 1,4-cyclohexylene-phenylene cpd(s) - Google Patents

Abstract

Liq. crystal medium based on a mixt. of cpds. with positive dielectric anisotropy contains at least one cpd. of formula (I). A1 and A2 = trans-1,4-cyclohexylene, 1,4-phenylene or 3-fluoro-1,4-phenylene; Z = -CH2CH2- or a bond; L and Y = H or F; X = Cl, F, CF3, OCF3 or OCHF2; and R = alkyl, hydroxyalkyl, fluoroalkyl or alkenyl, each with up to 7C. The amt. of (I) is pref. 10-50wt.%. USE/ADVANTAGE - The medium can be used in matrix-, twisted nematic-or super-twisted nematic-cells and has, compared to liq. crystal compsns., broadened nematic phase range (esp. at low temp.), switchability at low temps. (e.g., for outdoor, automobile or avionic use), increased UV resistance, improved clear pt., lower viscosity at low temps. and improved heat stability. Viscosity at -30 deg.C is 600 m.Pd.s or less and at -40 deg.C 1800 m.Pa.s or less, while anisotropy (delta-epsilon) value is 3.5 or above and clear pt. is above 65 deg.C. The nematic phase range is -30 to +70 deg.C. (27pp Dwg.No.0/0)

Description

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

Liquid crystals are mainly displayed as dielectrics used because the optical properties of such substances is affected by an applied voltage can be. Electro-optical devices on the base of liquid crystals are well known to those skilled in the art and can be based on different effects. Such Vorrich tions are, for example, cells with dynamic scattering, DAP cells (deformation of upright phases), guest / host Cells, TN cells with twisted nematic ("twisted nema structure, STN cells ("super-twisted nematic"), SBE Cells ("super-birefringence effect") and OMI cells ("opti cal mode interference "). The most common display tions are based on the Schadt-Helfrich effect and possess a twisted nematic structure.  

The liquid crystal materials need a good chemical and thermal stability and good stability over electric fields and electromagnetic radiation Zen. Furthermore, the liquid crystal materials should be lower Have viscosity and in the cells short response times, low threshold voltages and high contrast. Furthermore, they should at normal operating temperatures, d. H. in as wide a range as possible below and above Room temperature have a suitable mesophase, for example wise for the above cells a nematic or cholesteric mesophase. Because liquid crystals usually be used as mixtures of several components, It is important that the components mix well with each other are bar. Other features, such as the electrical conduction ability, the dielectric anisotropy and the optical Anisotropy, depending on the cell type and application meet different requirements. For example should materials for cells with twisted nematic Structure a positive dielectric anisotropy and a have low electrical conductivity.

For example, are for matrix liquid crystal displays with integrated non-linear elements for switching individual Pixels (MFK displays) Media with large positive dielek trical anisotropy, broad nematic phases, relative low birefringence, very high resistivity good UV and temperature stability of the resistor and clotting gem steam pressure desired.  

Such matrix liquid crystal displays are known. When non-linear elements for individual switching of the individual For example, pixels may contain active elements (i. Transistors) can be used. One speaks then of one "active matrix", where you can distinguish two types:

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

The use of monocrystalline silicon as Substratmate rial limits the display size, as well as the modular Composition of various sub-displays at the joints too Problems leads.

In the more promising type 2, which is preferred is as electro-optical effect usually the TN effect used. There are two different technologies: TFT's Compound semiconductors such. CdSe or TFT's on the base of 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 the display is applied while the other glass plate is on the inside carries the transparent counter electrode. in the Compared to the size of the pixel electrode is the TFT very small and does not disturb the picture practically. This techno logie can also be used for fully color-capable image presentations  be extended, with a mosaic of red, green and blue filters is arranged such that each one Filterele ment is a switchable Bildemement opposite.

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

The term MFK display includes here each matrix display integrated nonlinear elements, d. H. next to the active one Matrix also displays with passive elements like varistors or diodes (MIM = metal-insulator-metal).

Such MFK displays are particularly suitable for TV users applications (eg pocket TV) or for highly informative Displays for computer applications (laptop) and in automotive or aircraft construction. Besides problems regarding the angles Depending on the contrast and the switching times result in MFK ads difficulties caused by not enough 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 Con trolled by Double Stage Diode Rings, p. 141 ff, Paris; STRO MER, 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 cons the contrast of a MFK display and worsened deteriorated the problem of "after image elimination" can occur.  

As the resistivity of the liquid crystal mixture by interacting with the internal surfaces of the display generally decreases over the lifetime of a MFK display, a high (initial) resistance is very important to accept ble to obtain service life. Especially at low-volts Mi It has not been possible to date, very specific To realize resistances. Furthermore, it is important that the specific resistance is the smallest possible increase rising temperature and after temperature and / or UV Be load shows. The MFK displays from the state of the art do not meet today's requirements.

There is thus still a great need for MFK display with very high specific resistance at the same time large working temperature range, short switching times and low threshold voltage that does not have these disadvantages or only to a lesser extent.

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

• - extended nematic phase range (in particular to low temperatures)
• - Switchability at extremely low temperatures (out-door-use, automobile, avionics)
• - Increased resistance to UV radiation (longer lifetime)

With the available from the prior art Media, it is not possible to take these advantages under the same name to receive the remaining parameters.

For higher-twisted cells (STN), media are desired a higher multiplexability and / or smaller thresholds voltages and / or broader nematic phase ranges (ins special at low temperatures). This is a further extension of the available parameters terraumes (clarification point, transition smectic-nematic or Melting point, viscosity, dielectric sizes, elastic Sizes) urgently desired.

The invention is based on the object media in particular to provide for such MFK, TN or STN displays, the disadvantages mentioned above not or only in small rem dimensions, and preferably at the same time very high specific Resistances and low threshold voltages have.

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

The invention thus relates to a liquid-crystalline Medium based on a mixture of polar compounds with positive dielectric anisotropy, characterized draws that it is one or more connections of the general NEN formula I

wherein A¹ and A² are each independently trans-1,4-cyclohexylene, 1,4-phenylene or 3-fluoro-1,4-pheny len, Z -CH₂CH₂- or a single bond, L H or F, Y is H or F, X is F, Cl, CF₃, OCF₃ or OCHF₂ and R is alkyl, oxaalkyl, Flu or alkyl or alkenyl each having up to 7 carbon atoms.

The invention also provides electro-optical displays (especially STN or MFK displays with two plane-parallel Support plates that form a cell with a border, integrated non-linear elements for switching individual Pixels on the carrier plates and one in the cell located nematic liquid crystal mixture with positi dielectric anisotropy and high specific resist stand) containing such media and the use these media for electro-optical purposes.

The liquid-crystal mixtures according to the invention make it possible a significant extension of the available Parameter space.

The achievable combinations of clearing point, viscosity at low temperature, thermal and UV stability and dielek trical anisotropy or threshold voltage excel far previous materials from the prior art.

The demand for high clearing point, nematic phase at -40 ° C and a high Δε was so far only insufficient be fulfilled. Systems such. Although ZLI-3119 have ver equivalent clearing point and comparably favorable viscosities but have a Δε of only +3.  

Other mixing systems have comparable viscosities and values of Δε, however, have only clearing points in the area from 60 ° C to.

The liquid-crystal mixtures according to the invention make it possible it at low viscosities at low temperatures (at -30 ° C600, preferably 550 mPa · s; at -40 ° C1800, preferably 1700 mPa · s) at the same time dielectric aniso tropie values Δε 3.5, preferably 4.0, clearing points above 65 °, preferably above 70 ° and a high value for the to achieve specific resistance, resulting in excellent STN and MKF displays can be achieved.

It is understood that by suitable choice of the components the mixtures according to the invention also have higher clearing points (eg above 90 °) at higher threshold voltage or lower Clarification points at lower threshold voltages while preserving the other advantageous properties are realized can. The MFK displays according to the invention work preferential wise in the first transmission minimum after Gooch and Tarry [C. H. Gooch and H.A. Tarry, Electron. Lett. 10, 2-4, 1974; C.H. Gooch and H.A. Tarry, Appl. Phys., Vol. 8, 1575-1584, 1975], whereby here in addition to particularly favorable electro-optical Properties such. B. high slope of the characteristic and low angular 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 is sufficient. This can be done using the Mixtures according to the invention clearly in the first minimum  realize higher specific resistances than with Mischun with cyano compounds. The skilled person can by suitable Choice of the individual components and their proportions by weight simple routine methods for a given layer Set the thickness of the MFK display required birefringence len.

The viscosity at 20 ° C is preferably 25 mPa · s. The nematic phase range is preferably at least 70 °, in particular at least 80 °. Preferably, it extends this range at least from -30 ° to + 70 °.

Measurements of the Voltage Holding Ratio (HR) [p. Matsumoto et al., Liquid Crystals 5, 1320 (1989); K. Niwa et al., Proc. SID Conference, San Francisco, June 1984, p. 304 (1984); G. Weber et al., Liquid Crystals 5, 1381 (1989)] have shown that inventive mixtures containing compounds of Formula I a much smaller decrease in HR with increasing Have temperature as analogous mixtures containing provide the compounds of the formula I Cyanophenylcyclohexane the formula

The UV stability of the mixtures according to the invention is also considerably better, d. H. they show a much smaller one Decrease in HR under UV exposure.  

The achieved threshold voltages (V _th ) are generally 1.8 volts, preferably in the range 1.4 to 1.7 volts.

The media of the invention are also unusual wide nematic phase range also by extraordinary high elastic constants at very favorable viscosity which, in particular when used in STN displays There are clear advantages over media from the state of the art Technology result.

Preferably, the media of the invention are based on several ren (preferably two or more) compounds of formula I, d. H. the proportion of these compounds is 25%, preferably 40%.

The individual compounds of formulas I to XII and their Sub-formulas used in the media of the invention are either known, or they can be analog be prepared to the known compounds.

Preferred embodiments are given below:

• - Medium additionally contains one or more compounds selected from the group consisting of the general formulas II, III and IV: wherein the individual radicals have the following meanings: R: alkyl, oxaalkyl, fluoroalkyl or alkenyl having in each case up to 7 C atoms
  X: F, Cl, CF₃, OCF₃ or OCHF₂
  L: H or F
  Y: H or F
  r: 0 or 1.
• - Medium additionally contains one or more compounds selected from the group consisting of the general formulas V to VIII: wherein R, R, L, X and Y each independently have one of the meanings given in claim 2.
• - Medium additionally contains one or more compounds selected from the group consisting of the general formulas IX to XII: wherein R, L, X and Y each independently have one of the meanings given in claim 2.
• - The proportion of compounds of formulas I to IV together is at least 50% by weight in the total mixture
• - The proportion of compounds of formula I is in Total mixture 10 to 50% by weight
• the proportion of compounds of the formulas II to IV in the total mixture is 30 to 70% by weight
• - The medium contains compounds of formulas II and III or IV
• R is straight-chain alkyl or alkenyl with 2 to 7 C atoms
• - The medium consists essentially of compounds of formulas I to IV
• the medium contains further compounds, preferably selected from the following group:
• The weight ratio I: (II + III + IV) is preferred wise 1: 4 to 1: 1.
• - Medium consists essentially of compounds, selected from the group consisting of the general Formulas I to XII.

It was found that already a relatively small proportion of Compounds of formula I in admixture with conventional liquid crystal materials, but in particular with one or several compounds of formula II, III and / or IV to a considerable improvement in response times and too low gene threshold voltages leads, while wide nematic phases with low transition temperatures smectic observed nematic. The compounds of the formulas I to IV are colorless, stable and with each other and with others Liquid crystal materials readily miscible.

The term "alkyl" 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 in the generally preferred.

The term "alkenyl" includes straight-chain and branched Alkenyl groups with 2-7 carbon atoms, in particular the straight-chain groups. Especially alkenyl groups are C₂-C₇-1E- Alkenyl, C₄-C₇-3E-alkenyl, C₅-C₇-4-alkenyl, C₆-C₇-5-alkenyl and C₇-6 alkenyl, in particular C₂-C₇-1E-alkenyl, C₄-C₇-3E-alkenyl  and C₅-C₇-4 alkenyl. Examples of preferred alkenyl groups are Vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl and the like. Groups of up to 5 carbon Atoms are generally preferred.

The term "fluoroalkyl" preferably includes straight chain Fluorine-terminated groups, d. H. Fluoromethyl, 2-fluoro ethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluoro hexyl and 7-fluoroheptyl. Other positions of the fluorine are but not excluded.

The term "oxaalkyl" preferably includes straight-chain radicals of the formula C _n H _{2n + 1} -O- (CH₂) _m , wherein n and m are each independently 1 to 6. Preferably, n = 1 and m is 1 to 6.

By suitable choice of the meanings of R, X and Y can the response times, the threshold voltage, the slope of the Transmission characteristics etc. modified in the desired manner become. For example, 1E-alkenyl radicals, 3E-alkenylre ste, 2E-alkenyloxy radicals and the like, as a rule shorter response times, improved nematic tendencies and a higher ratio of the elastic constant k₃₃ (bend) and k₁₁ (splay) compared to Alkl- or alkoxy residues. 4-alkenyl radicals, 3-alkenyl radicals and the like result ben generally lower threshold voltages and smaller Values of k₃₃ / k₁₁ compared to alkyl and alkoxy.  

A group -CH₂CH₂- in Z¹ or Z² generally leads to higher values of k₃₃ / k₁₁ compared to a simple Covalent bond. Higher values of k₃₃ / k₁₁ allow z. B. shallower transmission characteristics in TN cells with 90 ° Ver Drilling (to achieve shades of gray) and steeper Transmis sion characteristics in STN, SBE and OMI cells (higher multi plexibility) and vice versa.

The optimum ratio of the compounds of the formulas I and II + III + IV largely depends on the desired eigen of the choice of the components of the formulas I, II, III and / or IV and the choice of others, if any dener components. Suitable proportions within of the above range may be easy from case to case be determined.

The total amount of compounds of formulas I to XII in the mixtures according to the invention is not critical. The mixtures may therefore contain one or more other components for the purpose of optimizing various properties. The observer tete effect on the response times and the threshold voltage However, in general, the higher the Gesamtkon is concentration of compounds of formulas I to XII.

In a particularly preferred embodiment, the Media of the invention compounds of the formula II, III, V and / or VII (preferably II and / or III), wherein X is CF₃, OCF₃  or X is OCHF₂. A favorable synergistic effect with the compounds of formula I leads to particularly advantageous stick properties.

The media according to the invention preferably contain compounds the above formulas II to VII wherein X, L and Y are the same early F mean.

For STN applications, the media preferably contains verbin selected from the group consisting of the formulas V to VIII, wherein X is preferably OCHF₂.

The media according to the invention may further comprise a component A. Contain one or more compounds with a dielectric anisotropy of -1.5 to +1.5 of the general my formula I '

wherein
R¹ and R² are each independently of one another n-alkyl, n-alkoxy ω-fluoroalkyl or n-alkenyl having up to 9 C atoms,
the rings A¹, A² and A³ are each independently of one another 1,4-phenylene, 2- or 3-fluoro-1,4-phenylene, trans-1,4-cyclohexylene or 1,4-cyclohexenylene,
Each of Z¹ and Z² independently represents -CH₂CH₂-, -C≡C-, -CO-O-, -O-CO-, or a single bond, and
m is 0, 1 or 2.

Component A preferably contains one or more compounds selected from the group consisting of II1 to II7:

wherein R¹ and R² have the meaning given in formula I '.

Preferably, component A additionally contains one or more Other compounds selected from the group consisting of II8 to II20:  

wherein R¹ and R² have the meaning given in formula I ' and the 1,4-phenylene groups in II8 to II17 each unab dependent on one another also by fluorine one or more times sub can be stituiert.  

Furthermore, component A preferably additionally contains one or several compounds selected from the group consisting of II21 to II25:

wherein R¹ and R² have the meaning given in formula I ' and the 1,4-phenylene groups in II21 to II25, respectively independently of one another by fluorine one or more times may be substituted.

Finally, such mixtures are preferred, whose compo A is one or more compounds selected from the Group consisting of II26, II27 and II28 contains:

wherein C _r H _{2r + 1 is} a straight-chain alkyl group having up to 7 C atoms.

In some cases, the addition of compounds proves the formula

wherein
R¹ and R² have the meaning given in formula I 'and
Z⁰ a single bond,

means
for the suppression of smectic phases as advantageous, although thereby the resistivity can be lowered. To achieve optimum parameter combinations for the application, the person skilled in the art can easily determine whether and, if so, in what quantity these compounds can be added. Normally, less than 15%, especially 5-10% are used.

Further preferred are liquid-crystal mixtures which have a or more compounds selected from the group from III 'and IV' contain:

wherein R¹ and R² have the meaning given in formula I '.

The type and amount of polar compounds with positive Dielectric anisotropy is not critical per se. The Specialist can be known among a wide range and in many cases also commercially available components and Basic mixtures in simple routine experiments suitable mate select the materials. Preferably, the invention contain According to the media one or more compounds of the formula I ''

wherein Z¹, Z² and m are as defined for formula I ', Q¹ and Q² are each independently 1,4-phenylene, trans-1,4-cyclohexylene or 3-fluoro-1,4-phenylene or one of Q¹ and Q² also denotes trans-1,3-dioxane-2,5-diyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or 1,4-cyclohexenylene,
R⁰ is n-alkyl, n-alkenyl, n-alkoxy or n-oxaalkyl each having up to 9 C atoms, LH or F, YH or F and X 'is CN, halogen, CF₃, OCF₃ or OCHF₂.

In a preferred embodiment, the invention are based appropriate media for STN or TN applications on connections of the formula I "in which X 'is CN. It is understood that also smaller or larger proportions of other compounds of formula I '' (X '≠ CN) come into question. For MFK applications preferably contain only the media of the invention to about 10% of nitriles of the formula I '' (preferably, however no nitriles of the formula I ", but compounds of the formula I ' with X '= halogen, CF₃, OCF₃ or OCHF₂). These media are preferably based on the compounds of the formulas II to XII.

The structure of the STN or MFK display according to the invention Polarizers, electrode base plates and electrodes with Surface treatment is the same as for such displays usual construction. The term is the usual construction Wise here, and includes all variations and Modifications of the MFK display, in particular Matrix-An Display elements based on poly-Si TFT or MIM.

An essential difference of the displays according to the invention to the usual on the basis of the twisted nemati However, the cell consists of the choice of liquid crystal parameter of the liquid crystal layer.  

The preparation of the liquid used in the invention crystal mixtures is carried out in a conventional manner. In the Usually, the desired amount of ver in lesser quantity ver used components in the main constituent Components dissolved, expedient at elevated temperature. It is also possible solutions of the components in an organi rule solvent, for. In acetone, chloroform or metha nol, to mix and the solvent after mixing to remove again, for example by distillation.

The dielectrics may also be further known to those skilled in the art and additives described in the literature. at For example, 0-15% pleochroic dyes or chiral dopants are added.

C is a crystalline, S is a smectic, S _{B is} a smectic B, N is a nematic and I is the isotropic phase.

V₁₀ denotes the voltage for 10% transmission (View direction perpendicular to the plate surface). t _on denotes the switch-on time and t _off the switch-off time at an operating voltage corresponding to 2.5 times the value of V₁₀ · Δn denotes the optical anisotropy and n _o the refractive index. Δε denotes the dielectric anisotropy (Δε = ε _∥ -ε _⟂ , where ε _{∥ denotes} the dielectric constant parallel to the _longitudinal molecular _axes and ε _senk the dielectric constant _{perpendicularly} to it The electrooptical data were determined in a TN cell in the first minimun (ie at a d · Δn value of 0.5) at 20 ° C unless expressly stated otherwise Optical data were measured at 20 ° C unless expressly stated otherwise.

The following examples are intended to illustrate the invention, without to limit them. Before and below are all temperatures indicated in ° C. The percentages are by weight.

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 residual C _n H _{2n + 1} are straight-chain alkyl radical with n or m C atoms. The coding according to Table B is self-evident. In Table A, only the acronym for the main body is given. In individual cases, followed by the acronym for the main body with a dash followed by a code for the substituents R¹, R², L¹, L² and L³:

example 1 PCH-3 9% EBCH-3F 10% EBCH-3F · F 12% Bech-3F · F 9% CCP 2OCF₃ 5% CCP 3OCF₃ 13% CCP 4OCF₃ 5% CCP 5OCF₃ 12% CCB-3F · F 2% CCB-5F · F 3% PCH-5F 10% PCH-6F 10% _Tc = 70 ° C @ .DELTA.n = 0.09

Example 2 PCH-3-CI 15% PCH 5Cl 10% PCH 3 Cl · F 10% Bech-3F · F 10% CCP 2F · F 10% CCP-3F · F 12% CCP-5F · F 12% CCB 3 · FF 3% CCB 5 × FF 3%

Example 3 PCH-3-CI 12% PCH 5Cl 10% PCH 3 Cl · F 10% Bech-3F · F 8th% CCP 2F · F 8th% CCP-3F · F 12% CCP-5F · F 12% CCB 3 · FF 3% CCB 5 × FF 3% BCH-3F · F 12% BCH-5F · F 10%

Example 4 EPCH-3F · F 10% EPCH-5F · F 8th% B-3F · F 8th% B-5F · F 7% CCP 2F · F 15% CCP-3F · F 12% CCP-5F · F 12% BCH-3F · F 10% BCH-5F · F 10% CCEB-3F · F 4% CCEB-5F · F 4%

Example 5 EPCH-3 Cl · F 5% EPCH-5 Cl · F 5% PCH-5F 11% PCH-7F 13% CCP 2OCF₃ 9% CCP 3OCF₃ 12% CCP 4OCF₃ 7% CCP 5OCF₃ 12% BCH-3 · FCF₃ 5% BCH-5 · FCF₃ 5% CCB-2 · FF 3% BCH-5F · F 13% _Tc = 66 ° C @ .DELTA.n = 0.08 @ η ₂₀ = 14 mPa · s @ V _th = 1.6V

Example 6 PCH-7F 10% EPCH-5F · F 9% EPCH-7F · F 8th% CCP 2OCF₃ 9% CCP 3OFC₃ 12% CCP 4OCF₃ 7% CCP 5OCF₃ 12% BCH-3F · F 12% BCH-5F · F 10% BCH-3 · FCF₃ 5% CCB 3 · FF 3% CCB 5 × FF 3%

Example 7 PCH-5F 10% PCH-7F 15% EPCH-7F · F 5% EPCH-5F · F 5% CCP 20CF₃ 9% CCP 30CF₃ 12% CCP 50CF₃ 12% BCH-3F · F 13% BCH 3OCF₂ · F 8th% BCH-3 · FOCF₂ 7% CCB 3 · FF 4% _Tc = 65 ° C @ .DELTA.n = 0.10 @ V _th = 1.7V

Example 8 B-3F · F 10% B-5F · F 8th% PCH-3-CI 8th% PCH 5Cl 10% CCP 2F · F 10% CCP-3F · F 12% CCP-5F · F 12% BCH-3 · FCI 8th% BCH-3 · FCI 10% CCB 3 · FF 3% CCB 5 × FF 3% CCP 30CF₃ 6%

Example 9 PCH 5Cl 10% PCH 3 Cl · F 8th% PCH-5 Cl · F 8th% CCP 20CF₂ · F 10% CCP 30CF₂ · F 12% CCP 50CF₂ · F 12% BCH-3 · FF 6% BCH-3 · FCF₃ 8th% BCH-3F · F 10% CCB-2F · F 3% CCB-3F · F 3% CBC-33F 3% CCB-53F 4% CBC-55F 3%

Example 10 PCH 30CF₂ 10% PCH 50CF₂ 8th% PCH-5F 10% PCH-6F 5% PCH-7F 5% CCP 20CF₂ · F 8th% CCP 30CF₂ · F 12% CCP 40CF₂ · F 7% CCP 50CF₂ · F 10% BCH-3 · FCI 8th% BCH-5 · FCI 8th% CCB-2 · FF 3% CBC-33F 3% CBC-53F 3%

Example 11 PCH-3-CI 10% PCH 5Cl 10% B-3F · F 6% B-5F · F 6% CCP 2F · F 8th% CCP-3F · F 12% CCP-5F · F 12% BCH-3F · F 14% BCH-5F · F 10% CCEB-3F · F 4% CCEB-5F · F 4% CCB 3 · FF 2% CCB 5 × FF 2%

Example 12 PCH-3-CI 11% PCH 4Cl 10% PCH 5Cl 16% CCP 20CF₃ 8th% CCP 30CF₃ 12% CCP 40CF₃ 7% CCP 50CF₃ 10% BCH-3F · F 10% BCH-5F · F 10% CCB 3 · FF 3% CCB 5 × FF 3% _Tc = 80 ° C @ .DELTA.n = 0.10 @ h₂₀ = 14 cst. @ V _th = 1.6V

Example 13 PCH 3 Cl · F 12% PCH-5 Cl · F 10% EPCH-3F · F 10% EPCH-5F · F 10% CCP-3F · F 15% CCP-5F · F 12% BCH-3F · F 12% BCH 30CF₃ 8th% CCB 3 · FF 3% CCB 5FF 3% CBC-33F 3% CBC-55F 2%

Example 14 PCH 7F · F 10% PCH-5F · F 12% B-3F · F 6% B-5F · F 6% CCP 2F · F 10% CCP-3F · F 12% CCP-5F · F 12% BCH-3F · F 10% BCH-5F · F 10% CCEB-3F · F 3% CCEB-5F · F 3% CBC-33F 3% CBC-53F 3%

Example 15 PCH 3 Cl · F 11% PCH-5 Cl · F 10% PCH-7F 10% CCP 20CF₃ 9% CCP 20CF₃ 12% CCP 40CF₃ 7% CCP 50CF₂ 12% BCH-3F · F 10% BCH-5F · F 8th% BCH-3 · FCF₃ 5% CCB 3 · FF 3% CCB 5 × FF 3% _Tc = 71 ° C @ .DELTA.n = 0.09 @ η₂₀ = 18 mPa · s @ V _th = 1.6V

Example 16 B-3F · F 9% B-5F · F 6% PCH-3-CI 15% PCH 5Cl 15% CCP-2F 8th% CCP-3F 8th% CCP 2F · F 14% BCH-3F · F 15% CCEB-3F · F 5% CCEB-5F · F 5%

Example 17 PCH-5F 7% PCH-7F 15% EPCH-5F · F 7% EPCH-5 Cl · F 5% CCP-3F 6% CCP-5F 4% BCH-3F · F 11% BCH 3OCF₃ 11% CCB 3 · FF 4% CCP 2OCF₃ 6% CCP 3OCF₃ 12% CCP 5OCF₃ 12% T _c = 73 ° C @ .DELTA.n = 0.10 @ V _th = 1.7V

Example 18 B-3F · F 9% B-5F · F 6% PCH-3-CI 15% PCH 5Cl 15% CCP 2F · F 12% CCP-3F · F 10% CCP-5F · F 8th% BCH-3F · F 15% CCEB-3F · F 5% CCEB-2F · F 5%

Example 19 PCH-5F 11% PCH-7F 12% EPCH-5F · F 5% EPCH-5 Cl · F 5% CCP 3 Cl · F 6% CCP-3F · F 6% BCH-3F · F 10% BCH-5F · F 8th% BCH 3OCF₃ 5% CCB 3 · FF 4% CCP 2OCF₃ 9% CCP 3OCF₃ 12% CCP 4OCF₃ 7% _Tc = 70 ° C @ .DELTA.n = 0.09 @ V _th = 1.7V

Example 20 PCH-5F 10% PCH-6F 7% PCH-7F 10% BCH 3CL · F 12% BCH 5CL · F 10% BCH 2Cl * F * F 10% BCH-3 Cl * F * F 14% BCH-5 Cl · F · F 11% CCB-3F · F 5% CCB-4F · F 5% CCB-5F · F 6% _Tc = 70 ° C @ .DELTA.n = 0.143 @ V _th = 2.7 V @ η₂₀ = 21 mPa · s

Example 21 PCH-5F 6% PCH-7F 7% PCH-302 4% CCP 2F · F 6% CCP-3F · F 10% CCP-5F · F 7% CCP 2F * F * F 8th% CCP-3F • F • F 10% CCP-5F * F * F 9% CCP 3CF3 * F * F 12% CCP 5CF3 * F * F 11% CCECP-3F · F 5% CCECP-5F · F 5% T _c = 87 ° C @ .DELTA.n = 0.082 @ V _th = 1.55 V @ η₂₀ = 17 mPa · s

Example 22 PCH-5F 8.00 PCH-7F 6.00 CCP 3OCF₂ 8.00 CCP 4OCF₃ 4.00 CCP 5OCF₃ 9.00 CCP 3CL * F * F 10.00 CCP 5CL * F * F 9.00 CCP 3CL · F 11.00 CCP 5CL · F 9.00 BCH-3F · F 12,00 BCH-5F · F 10.00 CCB 3 · FF 2.00 CCB 5 × FF 2.00 T _c = 98 ° C @ .DELTA.n = 0.107 @ V _th = 2.10 V @ η₂₀ = 22 mPa · s

Claims (9)

1. Liquid-crystalline medium based on a mixture of polar compounds having positive dielectric anisotropy, characterized in that it comprises one or more compounds of general formula I. in which A¹ and A² each independently of one another are trans-1,4-cyclohexylene, 1,4-phenylene or 3-fluoro-1,4-phenylene, Z is -CH₂CH₂ or a single bond, LH or F, YH or F, XF, Cl, CF₃, OCF₃ or OCHF₂ and R is alkyl, oxalkyl, fluoroalkyl or alkenyl, each having up to 7 carbon atoms. 2. Medium according to claim 1, characterized in that it additionally contains one or more compounds selected from the group consisting of the general formulas II, III and IV: in which the individual radicals have the following meanings:
R: alkyl, oxaalkyl, fluoroalkyl or alkenyl, each having up to 7 carbon atoms
X: F, Cl, CF₃, OCF₃ or OCHF₂
L: H or F
Y: H or F
r: 0 or 1. 3. Medium according to claim 1 or 2, characterized in that it additionally contains one or more compounds selected from the group consisting of the general formulas V to VIII: wherein R, R, L, X and Y each independently have one of the meanings given in claim 2. 4. Medium according to claim 2, characterized in that the Proportion of compounds of the formulas I to IV together in Total mixture is at least 50 wt .-%. 5. Medium according to claim 1 or 2, characterized that the proportion of compounds of formula I in the total mixture 10 to 50 wt .-% is. 6. Medium according to at least one of claims 2 to 4, characterized in that the proportion of compounds of the formulas II to IV in the total mixture 30 to 70% by weight is.   7. Medium according to at least one of claims 1 to 4, characterized in that it consists essentially of Compounds selected from the group consisting of consists of the general formulas I to XII. 8. Use of the liquid-crystalline medium according to Claim 1 for electro-optical purposes. 9. Electro-optical liquid crystal display, comprising a Liquid-crystalline medium according to Claim 1.