TWI399425B - Nematic liquid-crystal mixture, and displays containing same - Google Patents

Description

Nematic liquid crystal mixture and display containing the same

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to novel liquid crystal mixtures which are particularly useful in liquid crystal displays, such as torsional nematic (TN) and super-twisted nematic (very short response times and good sharpness and angular dependence). STN) The use of liquid crystal displays, and liquid crystal displays containing the novel mixture.

TN displays are known, for example, from M. Schadt and W. Heilrich, Appl. Phys. Lett., 18, 127 (1971). The STN display is represented by, for example, EP 0 131 216 B1, DE 34 23 993 A1, EP 0 098 070 A2, M. Schrader and F. Lin Hertz (Leenhouts) at the 17th Freiburg Congress on Liquid The publication of Crystals) (8.-10.04.87), K. Kawasaki et al. SID 87 Digest 391 (20.6), M. Schrader and F. Linhez SID 87 Digest 372 (20.1), K. Katoh et al., Japanese Journal of Applied Physics, Vol. 26, Chapter 11, L. L1784-L, 1786 (1987), F. Lin Hertz et al. Appl. Phys. Lett. 50 (21 ), 1468 (1987), HA Van Sprang and HG Koopman J. Appl. Phys. 62 (5), 1734 (1987), TJ Chevron and J. Nehring Appl. Phys. Lett. 45 (10), 1021 (1984), M. Schrader and F. Lin Hertz Appl. Phys. Lett. 50 (5), 236 (1987) and EP It is known from Raynes, Mol. Cryst. Liq. Cryst. Letters, Vol. 4 (1), pp. 1-8 (1986). The term STN herein includes any relatively highly torsional display element having a twist angle between 160 ^o and 360 ^o , such as, for example, according to Waters et al. (CM Watts et al., Proc .Soc.Inf.Disp. (New York) (1985) (3rd International Display Conference, Kobe, Japan), STN-LCDs (DE-A 35 03 259), SBE-LCDs (TJ Chevrolet and J. Nai) Lin, Appl. Phys. Lett. 45 (1984), 1021), OMI-LCDs (M. Schrader and F. Linhitz, Appl. Phys. Lett. 50 (1987), 236, DST-LCDs (EP- A 0 246 842) or BW-STN-LCDs (K. Kawasaki et al., SID 87 Digest 391 (20.6)).

Compared to standard TN displays, STN displays have an electro-optical characteristic line with significantly better sharpness, and a medium or relatively high multiplex rate (eg, from 32 to 64 or higher) ) The preferred contrast value. Conversely, contrast in TN displays is typically higher due to better black values, and contrast angle dependence is lower than STN displays with low multiplex rates (eg, less than 32).

Of particular interest are TN and STN displays with extremely short response times, especially at relatively low temperatures. In order to obtain a short response time, the rotational viscosities of the liquid crystal mixture have heretofore been optimized using most of the monotropic additives having a relatively high vapor pressure. However, the resulting response time does not apply to every application.

In order to achieve a sharp photoelectric characteristic line in the display according to the invention, the liquid crystal mixture should have a relatively large ratio of the elastic constant K ₃₃ /K ₁₁ and a relatively small Δ / Depreciation, where △ Is dielectric anisotropy, and ⊥ is the dielectric constant perpendicular to the longitudinal molecular axis.

In addition to optimization of contrast and response times, more important requirements constitute a mixture of this type: 1. Wide d/p window 2. High long-term chemical stability 3. High resistance 4. Low low voltage (threshold voltage) frequency and temperature dependence

The resulting combination of parameters is still not adequate, especially for high-multiplex STN displays (with multiplex rate in the range of about 1/400) and medium- and low-multiplex STN displays. (Having multiplex rates in the range of about 1/64 and 1/16, respectively) and TN displays. This is due in part to the fact that various needs are influenced by material parameters in an opposing manner.

Especially for the above requirements, liquid crystal mixtures with very short response time, high characteristic line sharpness, excellent contrast angle dependence and low low voltage are widely required in a wide operating temperature range, especially It is for medium-and low-multiplex STN displays.

WO 01/64814 discloses STN displays comprising a compound of formula IA having a terminal alkenyl group and a compound of formula IB having a terminal 4-cyano-3-fluorophenyl or 4-cyano-3,5-difluorophenyl group. However, the low voltage and frequency dependence of these mixtures is still unsatisfactory for some applications.

The invention therefore has the object of providing a liquid crystal mixture for liquid crystal displays, in particular TN and STN displays, which liquid crystal mixtures do not exhibit or exhibit only a low degree of the above disadvantages, especially in comparison with prior art mixtures It has a lower threshold voltage, an operating voltage of the same or improved frequency dependence, especially a short reaction time at low temperatures.

It has been found that this can be achieved if a nematic liquid crystal mixture consisting of one or more compounds of formula I is used, Wherein R ¹ is an alkyl group, an alkoxy group or an alkenyl group having 1 to 12 carbon atoms, and further one or two of the non-adjacent CH ₂ groups may be -O-, -CH=CH-, -CO- , -OCO- or -COO- is substituted in such a way that the O atoms are not directly interconnected; characterized in that the mixture comprises less than 10% by weight of the compound of formula IIIb ^* and less than 10% by weight of the compound of formula IIIc ^* , Wherein R is an alkyl group, an alkenyl group or an alkoxy group having 1 to 12 carbon atoms.

Compounds of formula I in particular reduce the response of TN and STN mixtures The inter- and low-limit voltages maintain or even improve (ie, reduce) the frequency dependence of the operating voltage and the low-limit voltage.

It is especially surprising that the use of compounds of formula I in TN and STN mixtures, while reducing the amount of compounds of formulas IIIb ^* and IIIc ^* , reduces response time and low voltage, while operating voltage and low voltage Frequency dependence has not been significantly impaired or even improved.

Furthermore, the mixture according to the invention is characterized by the following advantages: - short response time, in particular at low temperatures; - low rotational viscosity; - low low voltage and operating voltage; - good sharpness Photoelectric characteristic line; - frequency dependence with low operating voltage and low voltage; - can provide long life and operating time of LC display at low temperature.

The present specification therefore relates to a liquid crystal mixture containing one or more compounds of formula I, Wherein R ¹ is an alkyl group, an alkoxy group or an alkenyl group having 1 to 12 carbon atoms, and further one or two of the non-adjacent CH ₂ groups may be -O-, -CH=CH-, -CO- , -OCO- or -COO- is substituted in such a way that the O atoms are not directly interconnected; it is characterized in that the mixture comprises less than 10% by weight of the compound of the formula IIIb* and less than 10% by weight of the compound of the formula IIIc*, Wherein R is an alkyl group, an alkenyl group or an alkoxy group having 1 to 12 carbon atoms.

The invention also relates to comparable liquid crystal mixtures for use in liquid crystal displays, particularly TN and STN displays in the mid-to-high-multiplex range.

The present invention also relates to a liquid crystal display having - two outer substrates which form a cell together with a frame; - a nematic type having an anisotropy in the cell a liquid crystal mixture; - an electrode layer having an alignment layer on the inner side of the outer substrate; - an inclination angle of 0 to 30 degrees between the longitudinal axis of the outer substrate surface and the outer substrate, and - in the unit, from the alignment layer to the alignment a twist angle of a liquid crystal mixture having a value between 22.5° and 600° between layers, a nematic liquid crystal mixture composed of the following materials: a) 15-80% by weight of the liquid crystal component A , which is one or more having greater than a composition of +1.5 dielectric anisotropic; b) 20-85 weight percent of liquid crystal component B consisting of one or more compounds having a dielectric anisotropy between -1.5 and +1.5 ; c) 0-20% by weight of liquid crystal component D consisting of one or more compounds having a dielectric anisotropy of less than -1.5; and d) an optically active component C , if necessary The content is the layer thickness (interval of the outer substrate) and The ratio between the pitch of liquid crystal mixtures of natural palm nematic (natural pitch) between of from about 0.2 to 1.3; characterized in that a mixture of the present invention as described below and according to the nematic liquid crystal mixture.

Particularly preferred compounds of formula I are those wherein R ¹ is an alkyl group having from 1 to 8 carbon atoms or an alkenyl group having from 2 to 7 carbon atoms. More preferred radicals R ¹ are ethyl, n-propyl and n-pentyl, as well as vinyl and propen-1-yl.

In addition to the compound of formula I, the mixture according to the invention preferably comprises one or more alkenyl compounds of formula II, Wherein A ⁴ is 1,4-phenylene or trans-1,4-cyclohexylene, R ³ is an alkenyl group having 2 to 7 carbon atoms, and R ⁴ is a carbon having 1 to 12 carbons. An alkyl group, an alkoxy group or an alkenyl group of the atom, and further one or two of the non-adjacent CH ₂ groups may be -O-, -CH=CH-, -CO-, -OCO- or -COO- to O The atoms are not directly connected to each other, and a is 0 or 1.

A particularly preferred compound of formula II is one in which a is one.

Preferred compounds of formula II are selected from formula IIa to IIg Wherein R ^3a and R ^4a are each independently H, CH ₃ , C ₂ H ₅ or nC ₃ H ₇ , and the alkyl group is an alkyl group having 1 to 8 carbon atoms.

Particularly preferred are compounds of formula IIa wherein R ^3a and R ^4a are CH ₃ , and compounds of formula IIe, IIf, IIg, IIh and IIi wherein R ^3a is H or CH ₃ .

In the liquid crystal mixture according to the present invention, a compound of the formula II can be used to obtain a particularly low rotational viscosity value, and a TN and STN display having high sharpness and fast response time (especially at low temperatures).

In addition to the dielectrically neutral alkenyl compound of formula II, the mixture according to the invention preferably comprises one or more dielectric positive alkenyl compounds of formula II ^* Wherein R ³ is an alkenyl group having 2 to 7 carbon atoms, Q is CF ₂ , OCF ₂ , CFH, OCFH or a single bond, Y is F or Cl, and L ¹ and L ² are each independently H Or F.

Preferred compounds of formula II ^* are those wherein L ¹ and/or L ² is F and QY is F or OCF ₃ .

Further preferred compounds of formula II ^* are those wherein R ³ is 1E-alkenyl or 3E-alkenyl having 2 to 7, in particular 2, 3 or 4 carbon atoms.

Particularly preferred are compounds of formula II ^* a Wherein R ^3a is H, CH ₃ , C ₂ H ₅ or nC ₃ H ₇ , especially H or CH ₃ .

Compounds of formula I and compounds of formula II ^* having a dielectric anisotropy greater than +1.5 are classified in component A as defined above.

In accordance with the conditions of claim 1, component A may contain, in addition to the compound of formula I, one or more cyano compounds of the formula: Wherein R is an alkyl, alkoxy or alkenyl group having 1 to 12 carbon atoms, and further one or two of the non-adjacent CH ₂ groups may be -O-, -CH=CH-, -CO- , -OCO- or -COO- is substituted in such a manner that the O atoms are not directly bonded to each other; preferably an alkyl group or alkoxy group having 1 to 8 carbon atoms, or an alkenyl group having 2 to 7 carbon atoms. And L ^1-4 are each independently H or F, wherein in the mixture according to the invention, formulas IIIb and IIIc (wherein L ¹ and L ² are F and R is alkyl, alkenyl or alkoxy) The proportion of the compound is less than 10% in each case.

In the mixture according to the invention, the proportion of the compounds of the formulae IIIb ^* and IIIc ^* is preferably in each case 8%, especially good 5%.

Preferred compounds of formula IIIa and IIIb are as follows: Preference is given to mixtures which do not comprise the compounds of the formulae IIIb ^* and IIIc ^* . Special preference is not included wherein L ¹ is F, L ² is H or F, and R is a mixture of the compounds of formula an alkyl, alkenyl or alkoxy groups of IIIb and IIIc. More particularly preferred are mixtures which do not comprise the compounds of formula IIIb and IIIc.

In a preferred embodiment, component A comprises one or more 3,4,5-trifluorophenyl compounds of the formula: And/or one or more compounds containing a polar end group having the following chemical formula: Wherein R is as defined above, and L ³ and L ⁴ are each independently H, or F, respectively. R among these compounds is preferably an alkyl group or alkoxy group having 1 to 8 carbon atoms.

Preferred liquid crystal mixtures comprise one or more compounds of component A , preferably in a proportion of from 15% to 80%, more preferably from 20% to 70%. These compounds have △ +3, especially △ +8, better △ Dielectric anisotropy of +12.

Preferred liquid crystal mixtures comprise one or more of component B compounds, preferably in a proportion of from 20 to 85%, more preferably from 30 to 75%. Group B compounds, especially those containing alkenyl groups, are characterized by a low rotational viscosity value γ ₁ .

In addition to one or more compounds of formula II, component B preferably comprises one or more compounds selected from the group consisting of bicyclic compounds of the formula: And/or one or more compounds selected from the group consisting of tricyclic compounds of the formula: And/or one or more compounds selected from the group consisting of tetracyclic compounds of the formula: Wherein R ¹ and R ² are each independently an alkyl group, an alkoxy group or an alkenyl group having 1 to 12 carbon atoms, and further one or two of the non-adjacent CH ₂ groups may be -O-, -CH =CH-, -CO-, -OCO- or -COO- is substituted in such a way that O atoms are not directly interconnected; and L is H or F.

The 1,4-phenylene groups in IV10 to IV19 and IV23 to IV33 may also each independently be mono- or polysubstituted by fluorine.

Particularly preferred are compounds of the formulae IV27 to IV31 wherein R ¹ is an alkyl group, R ² is an alkyl group or an alkoxy group (particularly an alkoxy group), and each has 1 to 7 carbon atoms. Also preferred are compounds wherein L is a chemical formula IV27 and IV29 of F.

More particularly preferred are the compounds of the formulae IV2, IV27 and IV28.

R ¹ and R ^{2 in} the compounds of the formulae IV1 to IV33 are preferably a linear alkyl group or alkoxy group having 1 to 12 carbon atoms.

The liquid crystal mixture may optionally comprise an optically active component C in a ratio such that the ratio between the layer thickness (the spacing of the outer substrate) and the natural pitch of the palm nematic liquid crystal mixture is greater than 0.2. For this component, a variety of palm dopants can be used, some of which are commercially available, such as, for example, cholesteryl citrate, S-811 (available from Merck KGaA, Darmstadt ( Darmstadt))) and CB15 (BDH, Poole, UK). The choice of dopant itself is not very important.

The proportion of the compound of component C is preferably from 0 to 10%, especially from 0 to 5%, more preferably from 0 to 3%.

The mixture according to the invention preferably comprises one or more liquid crystal tolan compounds. Due to the high birefringence Δn of the tolan compound, a relatively small layer thickness can be used, thus significantly reducing the response time. The tolan compound is preferably selected from the group consisting of the following chemical formulas: Wherein R ¹ and R ² are as defined above; Z ⁴ is -CO-O-, -CH ₂ CH ₂ - or a single bond; and L ¹ to L ⁶ are each independently H or F, respectively.

Particularly preferred are compounds of the formulas Ta, Tb and Th.

Preferred compounds of the formula Te are those in which one, two or three of L ¹ to L ⁶ radicals are F, and the rest are H, wherein L ¹ and L ² or L ³ and L ⁴ or L ⁵ and L ⁶ Not both are F at the same time.

The proportion of the compound derived from the group containing Ta, Tb and Th is preferably from 5 to 50%, especially from 10 to 40%.

The proportion of the compound of the chemical formula Ta to Th is preferably from 2 to 55%, especially from 5 to 35%.

If necessary, the mixture according to the invention may also comprise up to 20% of one or more compounds having a dielectric anisotropy of less than -2 ( Component D ).

If the mixture comprises a compound of component D , it is preferably one or more compounds containing structural units 2,3-difluoro-1,4-phenylene, for example according to DE-A 38 07 801, 38 07 861, 38 07 863, 38 07 864 or 38 07 908 compounds. Particular preference is given to tolans containing this structural unit in accordance with International Patent Application No. PCT/DE 88/00133.

Further known compounds of component D are, for example, derivatives or structural units according to DE-A 32 31 707 or DE-A 34 07 013, 2,3-dicyanohydroquinone or a cyclohexane derivative.

The liquid crystal display according to the present invention is preferably free of the compound of component D.

The term "alkenyl" in the definition of R, R ¹ , R ² , R ³ and R ⁴ encompasses straight-chain and branched alkenyl groups having 2 to 12 carbon atoms in R, R ¹ and R ² , When R ³ and R ⁴ have 2 to 7 carbon atoms, they are mainly linear groups. Preferred alkenyl groups are C ₂ -C ₇ -1E-alkenyl, C ₄ -C ₇ -3E-alkenyl, C ₅ -C ₇ -4-alkenyl, C ₆ -C ₇ -5-alkenyl and C ₇ -6-alkenyl, especially C ₂ -C ₇ -1E-alkenyl, C ₄ -C ₇ -3E-alkenyl and C ₅ -C ₇ --4-alkenyl.

Examples of preferred alkenyl groups are ethenyl, 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 analog. Groups having up to 5 carbon atoms are generally preferred.

Individual compounds of formulas I, II, III, IV, V, VI and T which may be used in the TN and STN displays according to the invention, or sub-formulae and other compounds thereof, are known or may be similar It is manufactured by knowing the compound.

In a preferred embodiment, the mixture comprises: - one, two or three compounds of formula I; - from 3 to 45%, especially from 5 to 35%, more preferably from 10 to 30% or a variety of compounds of formula I;- 8%, preferably 5%, more preferably free of compounds of formula IIIb ^* ;- 8%, preferably 5%, more preferably free of compounds of formula IIIb wherein L ¹ is F, L ² is H or F and R is alkyl, alkenyl or alkoxy; 8%, preferably 5%, more preferably free of the compound of formula IIIb wherein R is alkyl, alkenyl or alkoxy; 8%, preferably 5%, more preferably free of the compound of formula IIIc ^* ;- 8%, preferably 5%, more preferably free of the compound of formula IIIc wherein L ¹ is F, L ² is H or F and R is alkyl, alkenyl or alkoxy; 8%, preferably 5%, more preferably free of the compound of formula IIIc wherein R is alkyl, alkenyl or alkoxy; - from 3 to 40%, especially from 6 to 35%, more preferably from 8 to 25% a compound of one or more of the formulae Ta, Tb and Th; - an alkenyl compound of from 25 to 75%, in particular from 35 to 65%, of one or more of formula II, II ^* , IV9 and IV24; - one or more selected from Alkenyl compounds of the formulae IIf, IIg, IIh, IIi and II ^* , wherein the alkyl group is an alkyl group having from 1 to 8 carbon atoms, and R ^3a is H or CH ₃ ; one or more of formulas IV9 and / Or a compound of IV24 (wherein R ¹ is an alkenyl group having 2 to 7 carbon atoms, and R ² is as defined above, especially an alkyl group or alkoxy group having 1 to 6 carbon atoms), particularly one or a variety of compounds of formula IV9a and / or IV24a

Wherein R ^3a is H, CH ₃ , C ₂ H ₅ or nC ₃ H ₇ , especially H or CH ₃ , and R ² is as defined above, preferably having from 1 to 6 carbon atoms, especially 1, An alkyl or alkoxy group of 2 or 3 carbon atoms, more preferably a methoxy group, an ethoxy group or a n-propoxy group. The proportion of these compounds in the liquid crystal mixture is preferably from 2 to 30%, especially from 3 to 20%; one or more compounds of the formula IV2, wherein R ¹ and R ² preferably have from 1 to 6 An alkyl or alkoxy group of a carbon atom, especially wherein R ¹ is an alkyl group and R ² is an alkoxy group having from 1 to 6 carbon atoms; - one or more compounds of the formula IV27 and/or IV28, wherein the formula IV27 L in the middle is H or F, preferably F. The proportion of these compounds in the liquid crystal mixture is preferably from 10 to 45%, especially from 15 to 40%; - more than 20% has positive dielectric anisotropy, especially with Δ +12 compound.

Particularly for use in TN and STN displays having a higher layer thickness, the mixture according to the invention has the characteristic of a very low total response time (t _s =t _on +t _off ).

The liquid crystal mixture used for the TN and STN units according to the present invention has Δ Positive dielectric anisotropy of 1. Especially preferred is △ 3, especially △ 5 liquid crystal mixture.

The liquid crystal mixture according to the invention has an advantageous low limit voltage value V _10/0/20 and a rotational viscosity value γ ₁ . If the optical path difference d. The value of Δn is predetermined, and the value of the layer thickness d is determined by optical anisotropy Δn. Especially at relatively high d. At Δn values, it is generally preferred to use a liquid crystal mixture according to the invention having a relatively high optical anisotropy value, since a relatively small value of d can be selected to produce a better response time value. However, even if the liquid crystal display according to the present invention contains the liquid crystal mixture having a smaller ?n value according to the present invention, it still has a characteristic of an advantageous response time value.

The liquid crystal mixture according to the present invention still has an advantageous photoelectric characteristic line sharpness value and can be operated at a high multiplex rate (especially at a temperature higher than 20 ° C). Further, the liquid crystal mixture according to the present invention has high stability and a high frequency dependence of a resistance value and a low voltage limit. The liquid crystal display according to the present invention has a large working-temperature range and a good contrast angle dependency.

A polarizing plate (polarisers), and the surface-treated electrode substrate to the adjacent electrodes to the liquid crystal molecules in each case the Priority (guide shaft (Director)) between the one electrode to the other electrode is usually 720 to 160 ^o rotation The construction of the liquid crystal display element according to the present invention of the electrode of the value of ^o is equivalent to the conventional construction of this type of display element. The term "conventional construction" is used broadly herein and encompasses all derivatives and modifications of TN and STN units, and in particular also includes matrix display elements and display elements containing additional magnets.

The surface inclination angles of the two outer substrates may be the same or different, and the same inclination angle is preferable. A preferred TN display has an angle of inclination of from 0 ^o to 7 ^o , preferably from 0.01 ^o to 5 ^o , more preferably from 0.1 ^o to 2 ^o , between the longitudinal axis of the molecules of the outer substrate surface and the outer substrate. In the STN display, the tilt angle is from 1 ^o to 30 ^o , preferably from 1 ^o to 12 ^o , and more preferably from 3 ^o to 10 ^o .

The twist angle of the TN mixture within the unit has a value between 22.5 ^o and 170 ^o , preferably 45 ^o and 130 ^o , and more preferably between 80 ^o and 115 ^o . The twist angle of the STN mixture in the unit from the alignment layer to the alignment layer has a value between 100 ^o and 600 ^o , preferably between 170 ^o and 300 ^o , and more preferably between 180 ^o and 270 ^o .

The liquid crystal mixtures usable according to the invention are produced in a conventionally known manner. Usually, the required amount of the component which is used in a small amount is dissolved in the component constituting the main component, preferably at a high temperature. It is also possible to mix the solutions of the components in an organic solvent such as acetone, chloroform or methanol, and then, after mixing, remove the solvent by, for example, distillation.

The liquid crystal mixtures according to the invention are also suitable for liquid crystal media in cholesterol phase liquid crystal (CLC) displays, in particular SSCT (surface stable cholesterol structures) and PSCT (polymer stable cholesterol structure) displays, as for example in WO 92/19695. US 5,384,067, US 5,453,863, US 6,172,720 or US 5,661,533. CLC displays typically contain a CLC medium consisting of a nematic component and an optically active component that is added as needed. Compared to TN and STN displays, CLC displays have significantly larger helical turns (helical). Twist) and exhibits selective reflection of circularly polarized light. The reflection wavelength corresponds to the product of the pitch of the cholesterol helix and the average refractive index of the CLC medium.

For this purpose, one or more pairs of palm dopants may be added to the liquid crystal mixture according to the invention, wherein the twisting power and concentration of the dopant are selected such that the liquid crystal medium has a room temperature The cholesteric liquid crystal phase, and preferably has a reflection wavelength in the visible, UV or IR region of the electromagnetic spectrum, especially between 400 and 800 nm.

Suitable dopants are known to those skilled in the art and are commercially available, such as, for example, cholesteryl phthalate (CN), CB15, R/S-811, R/S-1011, R/. S-2011, R/S-3011 or R/S-4011 (Merck KGaA, Darmstadt). Particularly preferred are high-torsional dopants containing palmitic free radicals, especially dianhydrohexitol derivatives such as, for example, isosorbitol, isomannitol or iso-idu A derivative of a sugar alcohol, preferably a sorbitol derivative as described in WO 98/00428. Preferred are 1,2-derivatives (benzylene glycol, diphenylethylene glycol) of palmitic glycol derivatives such as diphenyl-1,2-dihydroxyethane. Preferably, a mesogenic diphenyl glycol derivative as described in GB-A-2,328,207. The most preferred dopant is a palladium naphthalene derivative as described in WO 02/94805, as described in WO 02/34739, as described in WO 02/34739, as in WO 02/06265 The palmar TADDOL derivative described herein, with at least one fluorinated bridging group as described in WO 02/06196 and WO 02/06195, and a terminal or intermediate pair of palms Agent.

If two or more dopants are added, they may have the same or opposite directions of rotation and the same or opposite torsional temperature dependence.

The present invention is also directed to a CLC medium comprising a liquid crystal mixture according to the present invention as a nematic component, and one or more pair of palm dopants as an optically active component. The invention also relates to CLC displays containing CLC media as described above, particularly SSCT and PSCT displays.

The dielectrics may also comprise other additives known to those skilled in the art or described in the literature. For example, 0-15% multicolor dye can be added (pleochroic dyes).

In the present specification and the following examples, the structure of the liquid crystal compound is represented in the form of a headline, which is converted into a chemical formula according to Tables A and B below. All of the radicals C _n H _2n+1 and C _m H _2m+1 are linear alkyl radicals having n and m carbon atoms, respectively. The alkenyl radical has a trans configuration. The code in Table B is self-explanatory; in Table A, only the head words of the parent structure are marked. In individual cases, the substituents R ¹ , R ² , L ¹ , L ² and L ³ are separated from the head of the parent structure by a solid line following the designations given in the table below.

The TN and STN displays preferably comprise a liquid crystal mixture comprised of one or more compounds selected from Tables A and B.

The following examples are intended to illustrate the invention, without limitation. The following abbreviations are used: Cl.p. phase-setting temperature (nematic-isotropic phase transition temperature) SN layer-nematic phase transition temperature Δn optical anisotropy (589 nm, 20 ° C ) n _o ordinary (refractive) refractive index (589 nm, 20 ° C) △ Dielectric Anisotropy (1 kHz, 20 °C) S Characteristic Line Sharpness = V ₉₀ /V ₁₀ V ₁₀ Low Limit Voltage = Characteristic Voltage at 10% Relative Contrast (unless otherwise stated) at a frequency of 80 Hz) V ₉₀ t characteristic voltage at a relative contrast of 90% of the self-turn _on until 90% of the maximum contrast t _off the time required until the self-closing time required for 10% of the maximum contrast of t _Tot total response time t _on +t _off

All temperatures above and below are expressed in °C. Unless otherwise stated, all percentages are by weight and all values are related to 20 ° C; unless otherwise stated, the display is at a 1/128 multiplex rate and a 1/12 maximum voltage (bias) Under processing. Unless otherwise stated, the twist is 240 ^o .

Comparative example 1

A mixture of TN and STN (mixture V1) according to Example 2, available from WO 01/64814, having a composition of ME2N.F 8.00% Cl.p.: 86.5 °C ME3N.F 9.00% Δn: 0.1376 ME4N.F 12.00% V ₁₀ :CC-3-V1 3.00% CCG-VF 15.00% CCP-V-1 6.00% CCPC-33 5.00% CCPC-34 5.00% CCPC-35 5.00% CBC-33F 4.00% CBC-53F 4.00% PPTUI-3 -2 6.00% PCH-3N.FF 10.00% (Chemical Formula IIIb ^* ) DU-5-N 8.00% (Formula I)

Example 1

A mixture of TN and STN according to the invention (mixture M1) having a composition of ME2N.F 8.00% Cl.p.: 85.0 °C ME3N.F 9.00% Δn: 0.1307 ME4N.F 6.00% CC-3-V1 3.00% CCG-VF 15.00% CCP-V-1 6.00% CCPC-33 5.00% CCPC-34 5.00% CCPC-35 5.00% CBC-33F 4.00% CBC-53F 4.00% PPTUI-3-2 6.00% PCH-3N.FF 5.00 % (Chemical Formula IIIb ^* ) DU-5-N 8.00% (Formula I) DU-2-N 6.00% (Formula I) DU-3-N 5.00% (Formula I)

For mixtures V1 and M1, the lower limit voltage V ₁₀ is measured as a function of the frequency f of the rectangular voltage (dV ₁₀ /df). The results are shown in Figure 1.

It is clear from Figure 1 that the mixture M1 according to the invention has a significantly lower low voltage and a significantly lower frequency dependence of the lower limit voltage compared to the control mixture V1 while still maintaining other preferred properties such as, for example, the phase transition temperature. And birefringence.

In addition, the control mixture V1 appears low at relatively high frequencies (>5 kHz) The formation of the temperature region thus produces a result that the low voltage cannot be measured at these frequencies. In contrast, the mixture M1 according to the present invention does not exhibit a low temperature region even at a frequency of 10 kHz.

Comparative example 2

A mixture of TN and STN (V2) having a composition of PCH-301 16.00% Cl.p.: 79.5 ° C CCP-V-1 12.00% Δn: 0.1466 CCP-V2-1 12.00% n _o : 1.5036 CVCP-V- 1 5.00% V ₁₀ : 1.92 V CVCP-V-O1 5.00% S: 1.042 CVCP-1V-O1 5.00% t _tot : 304 ms PPTUI-3-2 20.00% PCH-2N.FF 25.00% (Chemical Formula IIIb ^* )

Example 2

A mixture of TN and STN (M2) according to the invention, the composition of which is PCH-301 16.00% Cl.p.: 85.0 ° C CCP-V-1 12.00% Δn: 0.1502 CCP-V2-1 12.00% n _o : 1.5002 CVCP-V-1 5.00% V ₁₀ :1.56 V CVCP-V-O1 5.00% S:1.058 CVCP-1V-O1 5.00% t _tot :252 ms PPTUI-3-2 20.00% DU-2-N 25.00% (Chemical formula I)

Compared with the mixture V2, it has a significantly higher phase transition temperature, significantly more Low low voltage, large sharpness and faster total response time.

Comparative example 3

A mixture of TN and STN (V3) having a composition of PCH-301 16.00% Cl.p.: 93.5 ° C CCP-V-1 12.00% Δn: 0.1552 CCP-V2-1 12.00% n _o : 1.5009 CVCP-V- 1 5.00% V ₁₀ :2.07 V CVCP-V-O1 5.00% S:1.040 CVCP-1V-O1 5.00% t _tot :243 ms PPTUI-3-2 20.00% PCH-3N.FF 25.00% (Chemical Formula IIIb ^* )

Example 3

A mixture of TN and STN (M3) according to the invention, having a composition of PCH-301 16.00% Cl.p.: 92.5 ° C CCP-V-1 12.00% Δn: 0.1561 CCP-V2-1 12.00% n _o : 1.4996 CVCP-V-1 5.00% V ₁₀ : 1.72 V CVCP-V-O1 5.00% S:1.061 CVCP-1V-O1 5.00% t _tot :228 ms PPTUI-3-2 20.00% DU-3-N 25.00% (Chemical formula I)

Compared to the mixture V3, it has a significantly higher phase transition temperature, a significantly lower lower limit voltage, a larger sharpness, and a faster total response time.

Comparative example 4

A mixture of TN and STN (V4) having a composition of PCH-301 16.00% Cl.p.: 97.5 ° C CCP-V-1 12.00% Δn: 0.1554 CCP-V2-1 12.00% n _o : 1.4992 CVCP-V- 1 5.00% V ₁₀ : 2.16 V CVCP-V-O1 5.00% S: 1.041 CVCP-1V-O1 5.00% t _tot :261 ms PPTUI-3-2 20.00% PCH-5N.FF 25.00% (Chemical Formula IIIb ^* )

Example 4

A mixture of TN and STN (M4) according to the invention, having a composition of PCH-301 16.00% Cl.p.: 90.0 ° C CCP-V-1 12.00% Δn: 0.1512 CCP-V2-1 12.00% n _o : 1.5003 CVCP-V-1 5.00% V ₁₀ :1.86 V CVCP-V-O1 5.00% S:1.062 CVCP-1V-O1 5.00% t _tot :273 ms PPTUI-3-2 20.00% DU-5-N 25.00% (Chemical formula I)

Compared to the mixture V4, it has a significantly lower low voltage and a greater sharpness.

Comparative example 5

A mixture of TN and STN (V5) having a composition of CC-3-V 21.00% Cl.p.: 96.5 ° C CCG-VF 5.00% Δn: 0.1314 CCP-V-1 14.00% n _o : 1.4954 CCP-V2- 1 15.00% V ₁₀ :2.13 V CVCP-1V-O1 5.00% S:1.054 CVCP-V-O1 5.00% t _tot :275 ms PPTUI-3-2 14.00% PZU-V2-N 5.00% (Chemical Formula IIIc ^* ) PCH -2N.FF 8.00% (chemical formula IIIb ^* ) PCH-3N.FF 8.00% (chemical formula IIIb ^* )

Example 5

A mixture of TN and STN (M5) according to the invention having a composition of CC-3-V 21.50% Cl.p.: 98.0 °C CCG-VF 3.00% Δn: 0.1308 CCP-V-1 14.00% n _o : 1.4944 CCP-V2-1 15.00% V ₁₀ :2.02 V CVCP-1V-O1 5.00% S:1.059 CVCP-V-O1 5.00% t _tot :278 ms PPTUI-3-2 14.50% CCPC-33 2.00% PZU-V2- N 4.00% (chemical formula IIIc ^* ) PCH-2N.FF 8.00% (chemical formula IIIb ^* ) DU-2-N 8.00% (chemical formula I)

Compared to the mixture V5, it has a higher phase transition temperature, a lower lower limit voltage and a larger sharpness, and has a comparable total response time.

Figure 2 shows the frequency dependence of the low limit voltages of M5 and V5. The mixture M5 according to the invention has a significantly lower frequency dependence than V5.

Comparative example 6

A mixture of TN and STN (V6) having a composition of CP-1V-N 10.00% Cl.p.: 91.5 ° C CC-3-V 16.00% Δn: 0.1425 CCP-V-1 12.00% n _o : 1.4970 CCP- V2-1 13.50% V ₁₀ : 1.72 V CVCP-1V-O1 5.00% S: 1.071 PPTUI-3-2 15.50% t _tot :278 ms CCPC-33 5.00% PCH-2N.FF 15.00% (Formula IIIb ^* ) PZU -V2-N 8.00% (Formula IIIc ^* )

Example 6a

A mixture of TN and STN (M6a) according to the invention having a composition of CP-1V-N 10.00% Cl.p.: 87.0 ° C CC-3-V 20.00% Δn: 0.1406 CC-5-V 9.00% n _o :1.4921 CCP-V2-1 4.00% V ₁₀ :1.72 V CVCP-V-1 5.00% S:1.061 CVCP-V-O1 5.00% t _tot :251 ms CVCP-1V-O1 5.00% PPTUI-3-2 19.00% CCPC-33 5.00% PZU-V2-N 3.00% (Chemical Formula IIIc ^* ) DU-2-N 15.00% (Formula I)

Compared to the mixture V6, it has a faster total response time and has the same lower limit voltage.

Example 6b

A mixture of TN and STN (M6b) according to the invention, having a composition of CP-1V-N 10.00% Cl.p.: 92.5 ° C CC-3-V 20.00% Δn: 0.1400 CC-5-V 10.00% n _o :1.4932 CCP-V2-1 6.00% V ₁₀ :1.76 V CVCP-V-1 5.00% S:1.071 CVCP-V-O1 5.00% t _tot :238 ms CVCP-1V-O1 5.00% PPTUI-3-2 17.00% CCPC-33 5.00% PZU-V2-N 8.00% (Chemical Formula IIIc ^* ) DU-2-N 9.00% (Formula I)

Compared to the mixture V6, it has a significantly faster total response time and a higher phase transition temperature with a relatively lower voltage limit.

Figure 3 shows the frequency dependence of the lower limit voltages of M6a, M6b and V6. The mixtures M6a and M6b according to the invention have a significantly lower frequency dependence than V6.

Figure 1 shows a mixture (M1) according to the invention and a control mixture (V1) The frequency dependence of the low limit voltage.

Figure 2 shows the frequency dependence of the low limit voltage of the mixture (M5) and the control mixture (V5) according to the invention.

Figure 3 shows the frequency dependence of the lower limit voltages of the two mixtures (M6a and M6b) and the control mixture (V6) according to the invention.

(no component symbol description)

Claims (12)

A liquid crystal mixture comprising greater than 10% to 30% by weight of at least one compound of Formula I, Wherein R ¹ is an alkyl group, an alkoxy group or an alkenyl group having 1 to 12 carbon atoms, and further one or two of the non-adjacent CH ₂ groups may be -O-, -CH=CH-, -CO- , -OCO- or -COO- is substituted in such a way that the O atoms are not directly interconnected; it is characterized in that the mixture comprises 8 weight percent of the compound of formula IIIb*, 8 weight percent of a compound of formula IIIc* and at least one compound of formula IV31, Wherein R is an alkyl group, an alkenyl group or an alkoxy group having 1 to 12 carbon atoms, and R ¹ and R ² are each independently as defined above for R ¹ . The liquid crystal mixture of claim 1, which is characterized in that it comprises at least one compound of the formula II and/or II*, Wherein A ⁴ is 1,4-phenylene or trans-1,4-cyclohexylene, R ³ is an alkenyl group having 2 to 7 carbon atoms, and R ⁴ is a carbon atom having 1 to 12 carbon atoms. An alkyl group, an alkoxy group or an alkenyl group, and further one or two of the non-adjacent CH ₂ groups may be used as -O-, -CH=CH-, -CO-, -OCO- or -COO- as an O atom. Instead of a direct interconnection, a is 0 or 1, L ¹ and L ² are each independently H or F, Q is CF ₂ , OCF ₂ , CFH, OCFH or a single bond, and Y is F or Cl. A liquid crystal mixture according to claim 1 or 2 which is characterized in that it comprises one or more compounds of the formula: Wherein R ^3a is H, CH ₃ , C ₂ H ₅ or nC ₃ H ₇ , and R ² is as defined for R ^{1 in} Formula I. A liquid crystal mixture according to claim 1 or 2 which is characterized in that it comprises one or more compounds of the formula: Wherein R ¹ and R ² are each independently, as defined for R ^{1 in} Formula I, respectively. A liquid crystal mixture according to claim 1 or 2, which is characterized in that it comprises one or more compounds selected from the group consisting of: Wherein R ^3a are each independently H, CH ₃ , C ₂ H ₅ or _n -C ₃ H ₇ , and the alkyl group is an alkyl group having 1 to 8 carbon atoms. A liquid crystal mixture according to claim 1 or 2, characterized in that the ratio of the compounds of the formulae IIIb* and IIIc* is in each case 5 wt%. A liquid crystal mixture according to claim 1 or 2, characterized in that it comprises one or more compounds of formula IV2: Wherein R ¹ 'and R ² 'is an alkyl group or alkoxy group having 1 to 6 carbon atoms. A liquid crystal mixture according to claim 1 or 2, characterized in that it comprises one or more compounds of the formula IV27 and/or IV28: Wherein R ¹ and R ² are each independently an alkyl group, an alkoxy group or an alkenyl group having 1 to 12 carbon atoms, and further one or two of the non-adjacent CH ₂ groups may be -O-, -CH =CH-, -CO-, -OCO- or -COO- is substituted in such a way that O atoms are not directly interconnected; and L is H or F. A liquid crystal display comprising the liquid crystal mixture of any one of claims 1 to 8. A TN or STN liquid crystal display having two outer substrates which form a unit together with a frame; a nematic liquid crystal mixture having a positive dielectric anisotropy in the unit; on the outer substrate An inner side, an electrode layer having an alignment layer; a tilt angle of 0 to 30 degrees between a longitudinal axis of the outer substrate surface and the outer substrate, and In the unit, the twist angle of the liquid crystal mixture having a value between 22.5° and 600° between the alignment layer and the alignment layer, a nematic liquid crystal mixture composed of the following materials: a) 15-80% by weight of the liquid crystal component A, It consists of one or more compounds having a dielectric anisotropy greater than +1.5; b) 20-85 weight percent of liquid crystal component B, which is composed of one or more having between -1.5 and +1.5 Composition of an electrically anisotropic compound; c) 0-20% by weight of liquid crystal component D consisting of one or more compounds having a dielectric anisotropy of less than -1.5; and d) an optically active Component C, the content of which is such that the ratio between the layer thickness (the spacing of the outer substrate) and the natural pitch of the palm nematic liquid crystal mixture is between about 0.2 and 1.3; characterized by the nematic type The liquid crystal mixture is a liquid crystal mixture according to any one of claims 1 to 8. A cholesteric liquid crystal display comprising one or more of a palm-doping agent as an optically active component, and a liquid crystal mixture according to any one of claims 1 to 8 as a nematic liquid crystal component. A cholesterol liquid crystal display according to claim 11, which is an SSCT or PSCT display.