DE4100287A1 - Super-twist liq. crystal display - has very short switching time and large operating temp. range, good contrast and low threshold voltage - Google Patents

Abstract

Supertwist LCD has 2 plane parallel substrate plates forming the cell with a rim, which is filled with a nematic liquid crystal mixt. (I) with positive dielectric anisotropy and chiral dopant(s) and electrode layers and overlying orientation layers on the inside of the plates. The angle of pitch between the longitudinal axis of the mols. w.r.t. the plate surface is ca. 1-30 deg. and the twist angle w.r.t. the orientation layer is 160-360 deg. 1. (I) contains cpd(s) (AI)-(AVI) of the given formula; and 2. the mixt. has a nematic phase range of at least 60 deg.C viscosity of max. 30 mPa.s and ratio of dielectric anisotropy to dielectric constant perpendicular to the short axis of the liquid crystal mols less than 2.0. R1 and R2 independently = R = 1-12 C alkyl, in which one or 2 non-adjacent -CH2- gps. may be replaced by -O-, -CH=CH-, -CH-, -O-CO- or -CO-O. The cpds. used are known cpds. or can be prepd. by methods analogous to those for known cpds. (No details are given in the text). The prod. of the double refraction, delta n, and the film thickness is 0.1-2.5 microns; and the perpendicular dielectric constant is at least 4, pref. at least 5, whilst the dielectric anisotropy is at least 5. USE/ADVANTAGE - The displays combine very steep gradient with a large operating temp. range short switching times and low threshold voltages.

Description

The invention relates to a supertwist liquid crystal display element With

• - two plane-parallel support plates, with a Border form a cell,
• A nematic liquid crystal mixture in the cell with positive dielectric anisotropy and with at least one chiral dopant,
• - Electrode layers with overlying alignment layers on the insides of the carrier plates,
• - An angle between the longitudinal axis of the Molecules on the surface of the backing plates and the carrier plates of about 1 degree to 30 degrees, and
• a twist angle of the liquid-crystal mixture in the cell from orientation layer to orientation layer in the amount between 160 and 360 °, characterized in that the nematic liquid-crystal mixture contains one or more compounds selected from the group consisting of Al to AVI: wherein R¹ and R² are each independently R and
  R is alkyl having 1-12 C atoms, in which also one or two non-adjacent CH₂ groups may be replaced by -O-, -CH = CH-, -CO-, -O-CO- or -CO-O- .

and the following conditions are sufficient:

• - nematic phase range of at least 60 ° C,
• Viscosity of 30 mPa · s or below, and
• Δε / ε⟂ <2.0, where Δε is the dielectric anisotropy and ε⟂ the dielectric constant in Direction of the short axis of the liquid crystal molecules means.

Supertwist liquid crystal display elements (SFK display elements) according to the preamble are known, for. B. off EP 01 31 216 B1; DE 34 23 993 A1; EP 00 98 070 A2;  M. Schadt and F. Leenhouts, 17th Freiburger Arbeitstragung Liquid crystals (8-10.04.87); K. Kawasaki et al. SID 87 Digest 391 (20.6); M. Schadt and F. Leenhouts, SID 87 Digest 372 (20.1); K. Katoh et al., Japanese Journal of Applied Physics, Vol. 26, no. 11, L 1784-L 1786 (1987); F. Leenhouts et al., Appl. Phys. Lett. 50 (21), 1468 (1987); H.A. van Sprang and H.G. Koopman, J. Appl. Phys. 62 (5), 1734 (1987); T. J. Scheffer and J. Nehring, App. Phys. Lett. 45 (10), 1021 (1984), M. Schadt and F. Leenhouts, Appl. Phys. Lett. 50 (5), 236 (1987) and E.P. Raynes, Mol. Cryst. Liq. Cryst. Letters Vol. 4 (1), pp. 1-8 (1986). The term SFK Display element here includes any higher-twist display element with a twist angle the amount after between 160 ° and 360 °, such as the display elements according to Waters et al. (C.M. Waters et al., Proc. Soc. Inf. Disp. (New York) (1985) (3rd Intern. Display Conference, Kobe, Japan), the STN-LCD's (DE OS 35 03 259), SBE-LCD's (T. J. Scheffer and J. Nehring, Appl. Phys. Lett. 45 (1984) 1021), OMI-LCD's (M. and F. Leenhouts, Appl. Phys. Lett. 50 (1987), 236, DST-LCD's (EP O2 46 842) or BW-STN-LCD's (K.Kawasaki et al., SID 87 Digest 391 (20.6)).

Such display elements are characterized in comparison to Standard TN display elements by much better Slopes of the electro-optical characteristic and thus associated better contrast levels and by a much lower angle dependence of the contrast out. Of particular interest are Supertwist display elements with very high slope. As a measure for the slope slope is generally the ratio V₅₀ / V₁₀ selected (V₅₀ = voltage at 50% contrast / V₁₀ = Tension at 10% contrast). To achieve of high characteristic slopes were so far in particular  the elastic properties of the liquid-crystal mixture optimized. However, the achieved slopes were not enough for every application.

There is thus still a great need for SFK Display elements with very high characteristic steepnesses at the same time large working temperature range, short Switching times and low threshold voltage.

The invention is based on the object, SFK display elements to provide the above-mentioned disadvantages not or only to a lesser extent and at the same time have very high slope characteristics.

It has now been found that this problem can be solved can, if one in these display elements nematic Liquid crystal mixtures used the following conditions suffice:

• - nematic phase range of at least 60 ° C,
• Viscosity of 30 mPa · s or below, and
• Δε / ε⟂ <2.0, where Δε is the dielectric anisotropy and ε⟂ is the dielectric constant in the direction of the short axis of the liquid crystal molecules, and one or more compounds selected from the group consisting of Al to AVI contains: wherein R¹ and R² are each independently R and
  R is alkyl having 1-12 C atoms, in which also one or two non-adjacent CH₂ groups may be replaced by -O-, -CH = CH-, -CO-, -O-CO- or -CO-O- ,

The subject matter of the invention is therefore a supertwist Liquid crystal display element with

• - two plane-parallel support plates, with a Border form a cell,
• A nematic liquid crystal mixture in the cell with positive dielectric anisotropy and with at least one chiral dopant,
• - Electrode layers with overlying alignment layers on the insides of the carrier plates,
• - An angle between the longitudinal axis of the Molecules on the surface of the backing plates and the carrier plates of about 1 degree to 30 degrees, and  
• a twist angle of the liquid-crystal mixture in the cell from orientation layer to orientation layer in the amount between 160 and 360 °, characterized in that the nematic liquid-crystal mixture contains one or more compounds selected from the group consisting of Al to AVI: wherein R¹ and R² are each independently R and
  R is alkyl having 1-12 C atoms, in which also one or two non-adjacent CH₂ groups may be replaced by -O-, -CH = CH-, -CO-, -O-CO- or -CO-O- .

and the following conditions are sufficient:

• - nematic phase range of at least 60 ° C,  
• Viscosity of 30 mPa · s or below, and
• Δε / ε⟂ <2.0, where Δε is the dielectric anisotropy and ε⟂ the dielectric constant in Direction of the short axis of the liquid crystal molecules means.

The invention further corresponding preferred Indicators meeting the following conditions:

• - Product of birefringence Δn and layer thickness the liquid crystal mixture between 0.1 microns and 2.5 μm,
• - dielectric constant ε⟂ greater than or equal to 4, preferably greater than or equal to 5,
• Dielectric anisotropy Δε greater than or equal to 5,
• - Liquid crystal mixture contains at least one 1,4-disubstituted 2,3-difluorobenzene compound,
• - The 2,3-difluorobenzene compound contains a 4-substituted 2,3-difluorophenoxy group,
• the 2,3-difluorobenzene compound is a compound of the formula I, wherein
  R¹ and R² are each independently of the other alkyl of 1 to 15 carbon atoms or alkenyl of 3 to 15 carbon atoms, wherein in these radicals in each case also a CH₂ group by -O-, -CO-, -CO-O- or - O-CO- may be replaced, one of R¹ and R² also F, Cl, CN, NCS, CF₃ or OCF₃,
  Each of A¹ and A² is independently
  • a) trans-1,4-cyclohexylene, in which also one or two non-adjacent CH₂ groups can be replaced by -O- and / or -S-,
  • b) 1,4-phenylene, in which also one or two CH groups can be replaced by N,
  • c) radical from the group consisting of 1,4-bicyclo (2,2,2) octylene and 1,4-cyclohexenylene,
    where the radicals b) may be monosubstituted or polysubstituted by fluorine,
• Z¹ and Z² are each independently of one another -CO-O-, -O-CO-, -CH₂O-, -OCH₂-, -CH₂CH₂- or a single bond,
  m and n are each independently 0, 1 or 2, and
  (m + n) 1, 2 or 3 means
• the liquid-crystal mixture contains at least one liquid-crystalline compound with the structural element, wherein Q¹ and Q² independently of one another are trans-1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene or 2,3-difluoro-1,4- mean phenylene,
• Liquid-crystal mixture contains at least one compound of the following formulas A to G: wherein R ^A and R ^{B are} each independently alkyl having 1 to 15 carbon atoms or alkenyl having 3 to 15 carbon atoms, wherein in each of these radicals also a CH₂ group by -O-, -CO-, -CO-O - or -O-CO- can be replaced,
• Liquid crystal mixture contains at least one compound of the following formulas H to K: wherein n is 1 or 2, in the case where n = 2, the two fluorine atoms are adjacent and R ^A and R ^{B have} the meaning given above.
• Liquid crystal mixture contains at least one liquid-crystalline tolane compound with the structural element wherein Q¹ and Q² independently of one another are 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene or 2,3-difluoro-1,4-phenylene,
• Liquid-crystal mixture contains at least one compound of the following formulas L to Q: wherein R ^A and R ^{B are} each independently alkyl having 1 to 15 carbon atoms or alkenyl having 3 to 15 carbon atoms, wherein in each of these radicals also a CH₂ group by -O-, -CO-, -CO-O - or -O-CO- may be replaced, and r is 0 or 1,
• Liquid-crystal mixture contains at least one compound of the following formulas R and / or S: in which R ^C and R ^{D are} each independently of one another n-alkyl having 1 to 10 C atoms or (trans) n-alkenyl having 3 to 10 C atoms,
• Liquid crystal mixture contains an ethyne compound of the formula II wherein
  R¹ and R² are each independently of the other alkyl of 1 to 15 carbon atoms or alkenyl of 3 to 15 carbon atoms, wherein in these radicals in each case also a CH₂ group by -O-, -CO-, -CO-O- or - O-CO- may be replaced, one of R¹ and R² also F, Cl, CN, NCS, CF₃ or OCF₃,
  Each of A¹ and A² is independently
  • a) trans-1,4-cyclohexylene, in which also one or two non-adjacent CH₂ groups can be replaced by -O- and / or -S-,
  • b) 1,4-phenylene, in which also one or two CH groups can be replaced by N,
  • c) radical from the group consisting of 1,4-bicyclo (2,2,2) octylene and 1,4-cyclohexenylene,
    where the radicals b) may be monosubstituted or polysubstituted by fluorine,
• Z¹ and Z² are each independently -CO-O-, -O-CO-, -CH₂O-, -OCH₂-, -CH₂CH₂- or a single bond, and
  m and n are each independently 0 or 1,
• - Liquid crystal mixture contains at least one liquid crystalline compound with the structural element wherein Q³ is trans-1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene or 2,3-difluoro-1,4-phenylene .
• Liquid-crystal mixture contains at least one compound of the following formulas E1 to E7: wherein R ^{E are} each n-alkyl having 1 to 10 carbon atoms or (trans) -n-alkenyl having 3 to 10 carbon atoms, R ^F n-alkyl having 1 to 10 carbon atoms, n-alkoxy having 1 to 10 C atoms, (trans) -n-alkenyl having 3 to 10 C atoms, F or CN, and X and Y are each independently H or F,
• - Liquid crystal mixture contains at least one compound of the formulas E3 and E7,
• Liquid-crystal mixture contains at least one compound of the formulas E3 to E7 in which R ^{F is} n-alkyl or n-alkenyl and X and Y are each H,
• Liquid-crystal mixture contains at least one compound of the formulas E3 to E7 in which R ^{F is} fluorine, XH and YH or fluorine,
• - Liquid crystal mixture contains at least one compound of formulas E3 to E7, wherein R ^{F is} cyano.

The invention further provides a method for Production of corresponding display elements, wherein one a nematic liquid crystal mixture in the cell filled, the following conditions are sufficient:

• - nematic phase range of at least 60 ° C,  
• Viscosity of 30 mPa · s or below, and
• Δε / ε⟂ <2.0, where Δε is the dielectric anisotropy and ε⟂ the dielectric constant in Direction of the short axis of the liquid crystal molecules means.

The invention finally also corresponding Liquid crystal mixtures for use in SFK display elements.

Nematic liquid crystal mixtures, two of the meet three specified conditions are known and become commercial in various embodiments used. It is further known that by use high proportions of phenyl benzoates corresponding to DE-PS 21 67 252 or of strongly dielectric negative liquid crystals (For example, according to DE-OS 32 31 707) values of Δε / ε⟂ <2.0 can be realized. These liquid crystal mixtures However, they are characterized by high viscosities from, with the values at 20 ° C often between 40 and 50 mPa · s or higher. Corresponding SFK Display elements have for a commercial application thus clearly too long switching times.

The liquid-crystal mixtures according to the invention make it possible however, at low viscosities at the same time to achieve a lower value for Δε / ε⟂, thereby in SKF display elements excellent slopes of the electro-optical characteristic can be achieved. The Liquid crystal mixtures according to the invention preferably have a ε⟂ ≧ 4, in particular ε⟂ ≧ 5 or ≧ 6. Δε / ε⟂ is preferably <1.5, in particular ≦ 1.3. Let it  However, in particular with the help of the compounds of Formula I also reach values for Δε / ε⟂ ≦ 1.1 or even ≦ 0.9. Such embodiments are also preferred. The viscosity at 20 ° C is preferably ≦ mPa · s. The nematic phase range is preferred at least 70 °, in particular at least 80 °. Preferably this range extends at least from -20 ° C to + 70 ° C.

The individual compounds of the formulas I, II, A to Q and E1 to E7, in the SFK display elements according to the invention can be used are either known or they can be analogous to the known compounds getting produced.

Preferred liquid crystal mixtures which can be used according to the invention contain a total of preferably 5-60%, in particular 10-40% of compounds of the formula I. Particularly preferred are liquid crystal mixtures, the in addition to dielectrically negative compounds of the formula I. also at least one compound of formula I with positive contain dielectric anisotropy (wherein a R¹ and R² are F, Cl, CN, NCS, CF₃ or OCF₃, preferably CN or F means). They contain a total of preferably 10-30, especially 12-20 components. Especially preferred are liquid crystal mixtures, the known liquid crystalline esters of p-fluorophenol and / or liquid crystalline tolan derivatives. The latter are characterized by a high birefringence and high values for K₃ / K₁. The use of tolane derivatives allows the transition to SFK display elements with smaller layer thicknesses (about 5 to 6 microns), which significantly shorter switching times result.  

The proportion of Tolanderivate is preferably included 5% to 35%, more preferably 10% to 30%. Preferred tolan derivatives are given below:

wherein R¹ and R² are the meanings given for formula I. to have. R¹ is preferably n-alkyl having 1 to 7 carbon atoms or n-alkyl having 3 to 7 carbon atoms. R² is preferably n-alkoxy or n-alkyl each having 1 to 7 carbon atoms or n-alkenyl or n-alkenyloxy each having 3 to 7 C-atoms. Q is 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene or 2,3-difluoro-1,4-phenylene. Preferably, the mixtures according to the invention contain one or more compounds of the formulas T1, T2 and T3, wherein Q is 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene or 2,3-difluoro-1,4-phenylene, especially preferred 2,3-difluoro-1,4-phenylene.

Those required to obtain small values for Δε / ε⟂ Components of formulas I to II are in the following German Offenlegungsschriften DE-OS 38 07 801, 38 07 861, 38 07 863, 38 07 864 and 38 07 908 or in the International Patent Application PCT / DE 88/00133. Preferably, the proportion of these compounds chosen such that ε⟂ the Total mix at least 4.0, preferably at least 5.0 is. The compounds of the formulas I and II Suitable for this purpose in an ideal way, since by their Add the viscosity of the total mixture surprising  remains low while strongly dielectrically negative Prior art compounds, such as Derivatives of 2,3-dicyanhydroquinone or cyclohexane derivatives with the structural element

to one in many cases unacceptable increase in viscosity to lead.

Preferably, a mixture contains one or more dielectrically negative compounds (Δε <-1.5), the simultaneously a high optical anisotropy (Δn <-0.15) respectively. Preferably, compounds of the formula II used.

Preferably, the mixtures according to the invention contain Ester compounds with the structural element

wherein Q¹ and Q² independently of one another are trans-1,4-cyclohexylene, 1,4-phenylene, 2- or 3-fluoro-1,4-phenylene or 2,3-difluoro-1,4-phenylene. Ask the latter preferred compounds of the formula I.

Particularly preferred are mixtures containing one or more Ester compounds of the formulas A to G, wherein Compounds of the formulas B, C, D and E are particularly preferred are. Further preferred ester compounds are those of the formulas

wherein R ^A and R ^{B have} the meaning given in formulas A to G. G1 is particularly preferred. The proportion of these ester compounds can be up to about 60%, in particular about 10% to 40%.

In a particularly preferred embodiment included the mixtures one or more compounds with the structural element

wherein Q³ is trans-1,4-cyclohexylene, 1,4-phenylene, 2- or 3-fluoro-1,4-phenylene or 2,3-difluoro-1,4-phenylene. The latter are preferred compounds of Formula I. The proportion of these compounds is preferably 10% to 45%, especially preferably approx. 10% to 35%. Particularly preferred are the compounds the formulas E1 to E7, including in particular E3 and E6.

The compounds of the invention contain one or several compounds with Δε <1.5. The selection of this In large numbers known compounds is not critical. The expert can do without inventive step and kind Proportion of these compounds to achieve the desired Set threshold voltage. The proportion is preferred about 30% to 70%, particularly preferably 40% to 60%. Preferably, also dielectrically positive compounds of the formula I and / or II (one of the radicals R¹ and R² is F, Cn, CF₃ or OCF₃) besides conventional ones Components such. B.  

wherein R ^{A has} the meaning given in formulas A to G, x is 1 or 2, X¹ is CN or F and X² is H or F.

The choice of chiral dopants is not per se critical. The expert can without inventive step Type and amount of chiral component to achieve the desired ratio between layer thickness and natural pitch of the total mixture (eg between 0.3 and 1.3).  

The displays of the invention show next to very good Characteristic slopes also very low angle dependence of contrast, d. H. the value

is particularly low.

The mixtures according to the invention show at the same time favorable elastic properties, d. H. in particular for K₃ / K₁.

The mixtures according to the invention can also be used still highly clarifying additives (clarification point <180 ° C) included. The proportion of these compounds is preferably about 5% to 20%. Suitable compounds are those skilled in the art known. Particularly preferred are those below specified compounds:

wherein R ^A and R ^{B have} the meaning given in formulas A to G.

The structure of the liquid crystal display elements according to the invention from polarizers, electrode base plates and Electrodes with such a surface treatment, that the preference orientation (director) of each adjacent liquid crystal molecules of the  one to the other electrode usually by amount 160 ° to 360 ° is rotated against each other, corresponds the usual for such display elements construction. The term of the usual construction is here far and includes all modifications known from the literature and modifications of the supertwist cell, in particular also matrix display elements. The surface angle on the two carrier plates can be the same or to be different. Same tilt angles are preferred.

A significant difference of the display elements of the invention to the usual on the basis of However, twisted nematic cell exists in the choice the liquid crystal parameter of the liquid crystal layer.

In the display elements of the invention are liquid crystalline Phases used in which the liquid crystal temperature ensures the steepest possible electro-optical characteristic is, along with a maximum contrast and a minimal angle dependence in a nematic one Phase range of at least 60 ° and a viscosity of 30 mPa · s or below.

The preparation of the liquid crystal mixtures which can be used according to the invention takes place in a conventional manner. Usually, the desired amount is in lesser Quantity of used components in the main component solved components, expedient at elevated Temperature. It is also possible solutions of Components in an organic solvent, eg. In Acetone, chloroform or methanol, and mix Remove solvent after thorough mixing, for example by distillation.  

All components of the mixtures according to the invention are known or can in analogy to known compounds be prepared according to known methods.

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

The following examples are intended to illustrate the invention, without limiting it.

It means:

SN phase transition temperature smectic-nematic,
Klp. clearing point,
Visc. Viscosity at 20 ° C (m Pa · s),
V₅₀ / V₁₀ Slope of the characteristic of an SFK display element at 20 ° C.

Above and below, all temperatures are given in ° C. The percentages are by weight. The physical data are each referenced to 20 ° C.

Example 1

An SFK display element with the following parameters:

Twist | 180 ° angle of attack 1 ° d / p (layer thickness / pitch) 0.35 d · Δn 1.06

containing a liquid crystal mixture consisting of

5% p-trans-4-ethylcyclohexylbenzonitrile,
15% p-trans-4-propylcyclohexylbenzonitrile,
11% p-trans-4-butylcyclohexylbenzonitrile,
11% p-trans-4-pentylcyclohexylbenzonitrile,
7% trans-4-propylcyclohexanecarboxylic acid (2,3-difluoro-4-ethoxyphenyl ester),
6% trans-4-pentylcyclohexanecarboxylic acid (2,3-difluoro-4-ethoxyphenyl ester),
7% trans-4- (trans-4-propylcyclohexyl) cyclohexanecarboxylic acid (2,3-difluoro-r-4-ethoxyphenyl ester),
5% 4 '- (trans-4-propylcyclohexyl) -2,3-difluoro-4-ethoxytolane,
5% 4 '- (trans-4-pentylcyclohexyl) -2,3-difluoro-4-ethoxytolane,
6% 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -2- (5-propylpyridin-2-yl) -ethane,
6% 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -2- (5-pentylpyridin-2-yl) -ethane,
4% 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -2- (p-cyanophenyl) ethane,
6% 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -2- (p -fluorophenyl) -ethane and
shows a high slope.

example 2

A nematic liquid-crystal mixture is prepared consisting of

5% p-trans-4-ethylcyclohexylbenzonitrile,
15% p-trans-4-propylcyclohexylbenzonitrile,
11% p-trans-4-butylcyclohexylbenzonitrile,
11% p-trans-4-pentylcyclohexylbenzonitrile,
10% 4-pentyl-2 ', 3'-difluoro-4'-ethoxytolane,
8% 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -2- (5-methylpyridin-2-yl) -ethane,
8% 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -2- (5-ethylpyridin-2-yl) -ethane,
8% 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -2- (5-propylpyridin-2-yl) -ethane,
8% 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -2- (5-pentylpyridin-2-yl) -ethane;
8% 1- [trans-4- (trans-4-propylcyclohexyl) -cyclohexyl] -2- (p-cyanophenyl) -ethane and
8% 1- [trans-4- (trans-4-propylcyclohexyl) cyclohexyl] -2- (p-fluorophenyl) -ethane.

After suitable doping, this mixture is suitable for displays according to the invention.

Claims (28)

1. Supertwist liquid crystal display element with

• two plane-parallel carrier plates, which form a cell with a border,
• an in-cell nematic liquid-crystal mixture having positive dielectric anisotropy and having at least one chiral dopant,
• Electrode layers with overlying orientation layers on the insides of the carrier plates,
• an angle of attack between the longitudinal axis of the molecules on the surface of the carrier plates and the carrier plates of about 1 degree to 30 degrees, and
• a twist angle of the liquid-crystal mixture in the cell from orientation layer to orientation layer in the amount between 160 and 360 °,

characterized in that the nematic liquid-crystal mixture contains one or more compounds selected from the group consisting of Al to AVI: wherein R¹ and R² are each independently R and
R is alkyl having 1-12 C atoms, in which also one or two non-adjacent CH₂ groups may be replaced by -O-, -CH = CH-, -CO-, -O-CO- or -CO-O- , and the following conditions are sufficient:

• - nematic phase range of at least 60 ° C,
• Viscosity of 30 mPa · s or below, and
• Δε / ε⟂ <2.0, where Δε is the dielectric anisotropy and ε⟂ is the dielectric constant in the direction of the short axis of the liquid crystal molecules.

2. Display element according to claim 1, characterized in that that the product of birefringence Δn and the Layer thickness of the liquid crystal mixture between 0.1 μm and 2.5 μm. 3. Display element according to at least one of claims 1 and 2, characterized in that the dielectric constant ε⟂ is greater than or equal to 4. 4. Display element according to at least one of claims 1 to 3, characterized in that the dielectric Anisotropy Δε is greater than or equal to 5. 5. Display element according to at least one of claims 1 to 4, characterized in that the dielectric constant ε⟂ is greater than or equal to 5. 6. Display element according to at least one of claims 1 to 5, characterized in that the liquid-crystal mixture at least one 1,4-disubstituted Contains 2,3-difluorobenzene compound. 7. Display element according to claim 6, characterized that the 2,3-difluorobenzene compound is a 4-substituted Contains 2,3-difluorophenoxy group. 8. Display element according to claim 6, characterized in that the 2,3-Difluorbenzolverbindung is a compound of formula I, wherein
R¹ and R² are each independently of the other alkyl of 1 to 15 carbon atoms or alkenyl of 3 to 15 carbon atoms, wherein in these radicals in each case also a CH₂ group by -O-, -CO-, -CO-O- or - O-CO- may be replaced, one of R¹ and R² also F, Cl, CN, NCS, CF₃ or OCF₃,
Each of A¹ and A² is independently

• a) trans-1,4-cyclohexylene, in which also one or two non-adjacent CH₂ groups can be replaced by -O- and / or -S-,
• b) 1,4-phenylene, in which also one or two CH groups can be replaced by N,
• c) radical from the group consisting of 1,4-bicyclo [2.2.2] octylene and 1,4-cyclohexenylene,
  where the radicals b) may be monosubstituted or polysubstituted by fluorine,

Z¹ and Z² are each independently of one another -CO-O-, -O-CO-, -CH₂O-, -OCH₂-, -CH₂CH₂- or a single bond,
m and n are each independently 0, 1 or 2, and
(m + n) is 1, 2 or 3. 9. Display element according to at least one of claims 6 to 8, characterized in that the liquid-crystal mixture at least one liquid-crystalline compound with the structural element wherein Q¹ and Q² independently of one another are trans-1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene or 2,3-difluoro-1, 4-phenylene mean. 10. Display element according to claim 9, characterized in that the liquid-crystal mixture contains at least one compound of the following formulas A to G: wherein R ^A and R ^{B are} each independently alkyl having 1 to 15 carbon atoms or alkenyl having 3 to 15 carbon atoms, wherein in these radicals in each case also a CH₂ group by -O-, -CO-, -CO-O - or -O-CO- may be replaced. 11. Display element according to at least one of claims 9 and 10, characterized in that the liquid-crystal mixture contains at least one compound of the following formulas H to K: wherein n is 1 or 2, in the case where n = 2, the two fluorine atoms are adjacent and R ^A and R ^{B have} the meaning given in claim 9. 12. Display element according to at least one of claims 6 to 11, characterized in that the liquid-crystal mixture at least one liquid-crystalline tolane compound with the structural element wherein Q¹ and Q² independently represent 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene or 2,3-difluoro-1,4-phenylene. 13. A display element according to claim 12, characterized in that the liquid-crystal mixture contains at least one compound of the following formulas L to Q: wherein R ^A and R ^{B are} each independently alkyl having 1 to 15 carbon atoms or alkenyl having 3 to 15 carbon atoms, wherein in each of these radicals also a CH₂ group by -O-, -CO-, -CO-O - or -O-CO- may be replaced, and r is 0 or 1. 14. Display element according to at least one of claims 12 and 13, characterized in that the liquid-crystal mixture contains at least one compound of the following formulas R and / or S: wherein R ^C and R ^{D are} each independently n-alkyl having 1 to 10 carbon atoms or (trans) -n-alkenyl having 3 to 10 carbon atoms. 15. Display element according to claim 6, characterized in that it contains an ethyne compound of the formula II, wherein
R¹ and R² are each independently of the other alkyl of 1 to 15 carbon atoms or alkenyl of 3 to 15 carbon atoms, wherein in these radicals in each case also a CH₂ group by -O-, -CO-, -CO-O- or - O-CO- may be replaced, one of R¹ and R² also F, Cl, CN, NCS, CF₃ or OCF₃,
Each of A¹ and A² is independently

• a) trans-1,4-cyclohexylene, in which also one or two non-adjacent CH₂ groups can be replaced by -O- and / or -S-,
• b) 1,4-phenylene, in which also one or two CH groups can be replaced by N,
• c) radical from the group consisting of 1,4-bicyclo (2,2,2) octylene and 1,4-cyclohexenylene,
  where the radicals b) may be monosubstituted or polysubstituted by fluorine,

Z¹ and Z² are each independently -CO-O-, -O-CO-, -CH₂O-, -OCH₂-, -CH₂CH₂- or a single bond and
m and n are each independently 0 or 1. 16. Display element according to at least one of claims 1 to 15, characterized in that the liquid-crystal mixture at least one liquid-crystalline compound with the structural element wherein Q³ is trans-1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene or 2,3-difluoro-1,4-phenylene , 17. A display element according to claim 16, characterized in that the liquid-crystal mixture contains at least one compound of the following formulas E1 to E7: wherein R ^{E are} each n-alkyl having 1 to 10 carbon atoms or (trans) -n-alkenyl having 3 to 10 carbon atoms, R ^F n-alkyl having 1 to 10 carbon atoms, n-alkoxy having 1 to 10 C atoms, (trans) -n-alkenyl having 3 to 10 C atoms, F or CN, and X and Y are each independently H or F. 18. Display element according to claim 17, characterized in that the liquid-crystal mixture is at least contains a compound of formulas E3 to E7. 19. A display element according to claim 18, characterized in that in at least one compound of the formulas E3 to E7 R ^F n-alkyl or n-alkenyl and X and Y are each H. 20. Display element according to claim 18 or 19, characterized in that in at least one compound of the formulas E3 to E7 R ^{F is} fluorine, XH and YH or fluorine. 21. Display element according to at least one of claims 18 to 20, characterized in that in at least one compound of the formulas E3 to E7 R ^F means cyano. 22. Liquid-crystal mixture in one of the claims 1 to 21 defined composition. 23. A method for producing a high-slope and high-slope supertwist liquid crystal display element

• two plane-parallel carrier plates, which form a cell with a border,
• an in-cell nematic liquid-crystal mixture having positive dielectric anisotropy and having at least one chiral dopant,
• Electrode layers with overlying orientation layers on the insides of the carrier plates,
• an angle of attack between the longitudinal axis of the molecules on the surface of the carrier plates and the carrier plates of about 1 degree to 30 degrees, and
• a twist angle of the liquid-crystal mixture in the cell from orientation layer to orientation layer in the amount between 160 and 360 °, characterized in that a nematic liquid-crystal mixture comprising one or more compounds selected from the group consisting of Al to AVI: wherein R¹ and R² are each independently R and
  R is alkyl having 1-12 C atoms, in which also one or two non-adjacent CH₂ groups may be replaced by -O-, -CH = CH-, -CO-, -O-CO- or -CO-O- .

and the following conditions are sufficient:

• - nematic phase range of at least 60 ° C,
• Viscosity of 30 mPa · s or below, and
• Δε / ε⟂ <2.0, where Δε is the dielectric anisotropy and ε⟂ is the dielectric constant in the direction of the short axis of the liquid crystal molecules,

filled in the cell.