JP2004339483A - Liquid crystal medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a twisted nematic (TN) and super twisted nematic (STN) liquid crystal display having a very short response time and good steepness and angular dependance. <P>SOLUTION: The liquid crystal medium contains one kind or a plurality of a compound of formula 1 and a compound of formula T1. (Wherein, R<SP>1</SP>and R<SP>2</SP>are each an alkyl group having 1-12 carbon atoms; R<SP>3</SP>is an alkenyl group having 2-9 carbon atoms; L<SP>1</SP>-L<SP>4</SP>are each independently H or F; at least one of L<SP>1</SP>, L<SP>2</SP>, L<SP>3</SP>and L<SP>4</SP>is F). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid crystal medium and a liquid crystal display including the same, particularly to a twisted nematic (TN) and super twisted nematic (STN) liquid crystal display having a very short response time, good sharpness and good angle dependence.

  The TN display is described in Non-Patent Document 1, for example. STN displays are described in Patent Literatures 1 to 3 and Non-Patent Literatures 2 to 10, for example. The term STN is used herein to refer to, for example, display elements by Waters et al. (Non-Patent Documents 11 and 12), STN-LCD (Patent Document 4), SBE-LCD (Non-Patent Document 13), and OMI-LCD (Non-Patent Document 13). Reference 14), any relatively highly twisted display having a twist angle with a value between 160 ° and 360 °, such as a DST-LCD (Patent Document 5) or a BW-STN-LCD (Non-Patent Document 15). Contains the element.

  Compared to standard TN displays, STN displays are characterized by a much better steepness of the electro-optical characteristic line and associated better contrast values, and a much lower angular dependence of the contrast.

European Patent 0,131,216 German publication 34 23 993 European Patent Publication 0,098,070 German Patent Publication No. 35 03 259 European Patent Publication No. 0,246,842 German Offenlegungsschrift 38 07 801 German Offenlegungsschrift 38 07 861 German Offenlegungsschrift 38 07 863 German Offenlegungsschrift 38 07 864 German Offenlegungsschrift 38 07 908 WO 88/07514 pamphlet Published German Application No. 32 31 707 German publication 34 07 013 International Publication No. 92/19695 pamphlet U.S. Pat. U.S. Pat. No. 5,453,863 U.S. Pat. No. 6,172,720 U.S. Pat. No. 5,661,533 WO 98/00428 Pamphlet UK Patent 2328207 International Publication No. 02/94805 pamphlet WO 02/34739 pamphlet WO 02/06265 pamphlet WO 02/06196 pamphlet WO 02/06195 pamphlet M. Schadt and W.C. Helfrich, Appl. Phys. Lett. , Vol. 18, p. 127, published in 1971 M. Schadt and F.S. 17th Freiburg Congress on Liquid Crystal, by Leeenouts (8-10.4.87) K. Kawasaki et al., SID 87 Digest 391 (20.6) M. Schadt and F.S. By Leenouts, SID 87 Digest 372 (20.1) K. Katoh et al., Japanese Journal of Applied Physics, Vol. 26, No. 11, L1784-L1786, 1987 F. See Leenhouts et al., Appl. Phys. Lett. 50, No. 21, p. 1468, 1987 H. A. van Sprang and H.M. G. FIG. Koopman, J.M. Appl. Phys. , Vol. 62, No. 5, pp. 1734, 1987 T. J. Scheffer and J.M. Nehring, Appl. Phys. Lett. 45, No. 10, pp. 1021, 1984 M. Schadt and F.S. Leenhouts, Appl. Phys. Lett. , Vol. 50, No. 5, 236 pages, 1987 E. FIG. P. Raynes, Mol. Cryst. Liq. Cryst. Letters, Volume 4, Issue 1, Pages 1-8, 1986 C. M. Waters et al., Proc. Soc. Inf. Disp. , New York, 1985 3rd Intern. Display Conference, Kobe, Japan T. J. Scheffer and J.M. Nehring, Appl. Phys. Lett. 45, 1021 pages, 1984 M. Schadt and F.S. Leenhouts, Appl. Phys. Lett. , 50, 236, 1987 K. Kawasaki et al., SID 87 Digest 391 (20.6)

  Of particular interest are TN and STN displays, which have very short response times, especially at relatively low temperatures. In order to achieve short response times, the rotational viscosity of the liquid-crystal mixture has hitherto been optimized using near-monotropic additives with a relatively high vapor pressure. However, the response times obtained were not sufficient for all applications.

In order to achieve a steep electro-optical characteristic line in the display according to the invention, the liquid crystal mixture must have a relatively large elastic constant ratio K ₃₃ / K _{11 and a} relatively small value of Δε / ε⊥, Here, Δε is a dielectric anisotropy, and ε⊥ is a dielectric constant in a direction perpendicular to a molecular axis which is a long axis.

In addition to optimizing contrast and response time, such mixtures also have the following important requirements:
1. a wide d / p window,
2. High long-term chemical stability,
3. High electrical resistance,
4. Low frequency and temperature dependence of threshold voltage.

  The realized parameter combinations are particularly high multiplex STN displays (with a multiplex ratio in the region of about 1/400), as well as medium and low multiplex STN displays (in the region of about 1/64 and 1/16, respectively). Is still far from sufficient for TN displays. This is due in part to the fact that various requirements are adversely affected by important parameters.

  Therefore, TN and STN displays, especially those satisfying the above requirements, have a very short response time, a wide operating temperature range, high characteristic line steepness, good contrast angle dependence, and low threshold voltage. There is a continuing need for medium and low multiplex STN displays.

  Furthermore, modern applications such as telecommunications require liquid crystal mixtures with a high positive dielectric anisotropy Δε in order to achieve the required low threshold voltage. However, as the threshold voltage decreases, the response time often increases. For this reason, it is necessary to provide a liquid crystal mixture having a high positive value of Δε and at the same time a fast response time.

  The present invention does not have the above-mentioned drawbacks, or has a low degree of presence, and at the same time, Δε is a high positive value, the threshold voltage is low, the response time is short especially at low temperatures, and the sharpness is very good It has the object of providing new compounds and liquid crystal media, especially for TN and STN displays.

  It has now been found that this object can be achieved by using the liquid crystal medium according to the invention.

  According to the present invention, one or more compounds of formula I:

One or more compounds of the formula T1

A liquid crystal medium is provided, comprising:

Where,
R ¹ and R ² are an alkyl group having 1 to 12 carbon atoms, and may be unsubstituted, monosubstituted with CN or CF ₃ , or at least monosubstituted with halogen; Or a plurality of CH ₂ groups are each independently —O—, —S—, —CH ＝ CH—, —C≡C—, —CO—, —CO—O—, —O—CO—, or O-CO-O- may be substituted so that the O atoms are not directly linked to each other;
R ³ is an alkenyl group having 2 to 9 carbon atoms,
L ¹ to L ⁴ are each independently H or F, and at least one of L ¹ , L ² , L ³ and L ⁴ is F.

The use of compounds of Formulas I and T1 in mixtures for TN and STN displays of the present invention results in the following:
・ Higher steepness of the electro-optical characteristic line,
Lower temperature dependence of the operating voltage due to improved frequency dependence,
Faster response times, especially at low temperatures
Is obtained.

  The compounds of the formula I in particular significantly reduce the response time of TN and STN mixtures, while at the same time increasing the dielectric anisotropy and the steepness and reducing the temperature dependence of the threshold voltage.

The mixtures according to the invention are further characterized by the following advantages;
-Low viscosity,
Low threshold voltage and operating voltage;
-Achieve a long useful life of the display at low temperatures.

Further according to the invention,
-Two skins forming a cell with the frame;
-A nematic liquid crystal mixture of positive dielectric anisotropy located in the cell;
-An electrode layer having an alignment film inside the outer plate,
A tilt angle between 0 ° and 30 ° between the long axis of the molecule on the skin surface and the skin;
A twist angle between 22.5 ° and 600 ° between the alignment films of the liquid crystal mixture in the cell;
-A) 15 to 75% by mass of a liquid crystal component A comprising one or more compounds having a dielectric anisotropy greater than +1.5,
b) 25-85% by mass of a liquid crystal component B composed of one or more compounds having a dielectric anisotropy of -1.5 to +1.5,
c) 0 to 20% by mass of a liquid crystal component D composed of one or more compounds having a dielectric anisotropy smaller than -1.5,
d) optionally a nematic comprising an amount of optically active component C in which the ratio between the layer thickness (separation between the skins) and the natural pitch of the chiral nematic liquid crystal mixture is from 0.2 to 1.3. Having a liquid crystal mixture,
A liquid crystal display is provided wherein the nematic liquid crystal mixture comprises at least one compound of the formula I above and below and at least one compound of the formula T1.

  Furthermore, according to the present invention, there are provided TN and STN displays comprising a liquid crystal mixture, especially medium and low multiplex STN displays.

  The use of the compounds of the formulas I and T1 in the liquid-crystal mixtures according to the invention results in TN and STN displays with particularly low values of rotational viscosity, high steepness and particularly fast response times at low temperatures.

Compounds of formula I wherein one or both of L ¹ and L ² are F are particularly preferred.

  Further preferred compounds of formula I are compounds selected from

Wherein R ³ is as defined in Formula I.

  In particular, compounds of the formulas Ib, Id, Ie, Ig and Ih are preferred.

Formula I, particularly Ih (R ³ from formula Ia above, 1E- alkenyl or 3E-alkenyl, more preferably vinyl, 1E- propenyl, 1E--butenyl, 3E-butenyl or 3E-pentenyl, and most preferably 1E- butenyl Is particularly preferred.

Particularly preferred compounds of the formula T1 are those in which R ¹ and R ² are alkyl or alkoxy having 1 to 8 carbon atoms, in particular alkyl having 1 to 5 carbon atoms.

  In addition to the compounds of the formulas I and T1, the liquid-crystal mixtures according to the invention preferably additionally comprise one or more alkenyl compounds of the formula II.

Where,
A is 1,4-phenylene or trans-1,4-cyclohexylene;
a is 0 or 1;
R ³ is an alkenyl group having 2 to 9 carbon atoms,
R ⁴ is as defined for R ¹ in formula T1.

  Particularly preferred compounds of formula II are those selected from:

However, in the formula, R ^3a and R ^4a are each independently H, CH ₃ , C ₂ H ₅ or nC ₃ H ₇ , and alkyl is an alkyl group having 1 to 8 carbon atoms. .

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

  Compounds of formulas T1 and II with a dielectric anisotropy of -1.5 to +1.5 ("dielectric neutral") are part of component B as defined above.

In addition to the compounds of the formulas I and T1, the liquid-crystal mixtures according to the invention preferably additionally comprise one or more compounds of the formula II ^* having a positive dielectric anisotropy.

Where,
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;
L ¹ and L ² are independently H or F.

Compounds of formula II ^* in which L ¹ and / or L ² are F and QY is F or OCF ₃ are particularly preferred.

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

Compounds of formula II ^* a are highly preferred.

However, in the formula, R ^3a is H, CH ₃ , C ₂ H ₅ or nC ₃ H ₇ , particularly H or CH ₃ .

Polar compounds of formula II ^* having a dielectric anisotropy of more than +1.5 are part of component A as defined above.

  Preferred liquid crystal mixtures comprise one or more compounds of component A, preferably in a proportion of from 15% to 75% by weight, more preferably from 20% to 65% by weight. These compounds preferably have a dielectric anisotropy of Δε ≧ + 3, more preferably Δε ≧ + 8, most preferably Δε ≧ + 12.

  Component A preferably contains one or more cyano compounds selected from the following formulas.

Where,
R is an alkyl, alkoxy or alkenyl group having from 1 to 12 carbon atoms, and one or more CH ₂ groups are also each independently of the other -O-,-so that the O atoms are not directly linked to each other. CH = CH-, -CO-, -OCO- or -COO-,
L ¹ , L ² , L ³ and L ⁴ are each independently H or F.

  R in these compounds is preferably alkyl or alkoxy having 1 to 8 carbon atoms or alkenyl having 2 to 7 carbon atoms.

Very particular preference is given to mixtures comprising one or more compounds of the formulas IIIb and / or IIIc, wherein L ¹ and / or L ² are F, and also IIIf.

Preferred liquid-crystal mixtures comprise one or more compounds of component B, preferably in a proportion of from 25 to 85% by weight. Compounds from the group B are particularly characterized by the value of rotational viscosity gamma ₁ is low.

  Component B preferably comprises, in addition to one or more compounds of the formulas I and II, one or more compounds selected from the group consisting of the bicyclic compounds of the following formulas:

  Further, it is preferable to include one or more compounds selected from the group consisting of the tricyclic compounds of the following formulas.

  In addition, it is preferable to include one or more compounds selected from the group consisting of tetracyclic compounds of the following formula.

As described above, in the formula, R ¹ and R ² independently of one another have 1 to 12 carbon atoms and are unsubstituted, monosubstituted with CN or CF ₃ , or at least monosubstituted with halogen. And one or more CH ₂ groups of these groups are also each independently of the other, such that —O—, —S—, —CH よ う CH—, -C≡C-, -CO-, -CO-O-, -O-CO- or -O-CO-O-,
L is H or F;
The 1,4-phenylene groups of the formulas IV10 to IV19 and IV23 to IV33 are optionally mono- or polysubstituted by F.

Particular preference is given to compounds of the formulas IV27 to IV33, wherein R ¹ is alkyl and R ² is alkyl or alkoxy, in particular alkoxy (each having 1 to 7 carbon atoms). Further, compounds of formulas IV27 and IV33, wherein L is F, are preferred.

  Compounds of the formulas IV27 and IV29 are particularly preferred.

It is particularly preferred that R ¹ and R ² of the compounds of the formulas IV1 to IV33 are straight-chain alkyl or alkoxy having 1 to 12 carbon atoms.

  Particular preference is given to compositions according to the invention which comprise one or more compounds of the formulas IV24a and / or IV24b.

However, in the formula, R ^3a is as defined above.

  This mixture preferably comprises 2 to 25% by weight, in particular 2 to 15% by weight, of a compound of the formulas IV24a and / or IV24b.

  In a further preferred embodiment, the liquid-crystal mixture comprises, in addition to the compound of the formula T1, one or more tolane compounds selected from the group consisting of the formulas Ta to Th.

Wherein R ¹ and R ² are as defined in the above formula IV,
Z ⁴ is —CO—O—, —CH ₂ CH ₂ — or a single bond;
L ¹ to L ⁶ are each independently H or F.

  Compounds of the formulas Ta and Tb are particularly preferred.

  The proportion of compounds from the group consisting of the formulas Ta and Tb is preferably from 1 to 30% by weight, particularly preferably from 3 to 20% by weight. The proportion of compounds from the group consisting of the formulas Ta to Th is preferably from 2 to 55% by weight, particularly preferably from 3 to 35% by weight.

  In a further preferred embodiment, component A or the liquid-crystal mixture according to the invention preferably additionally comprises one or more 3,4,5-trifluorophenyl compounds selected from the following formulas:

  Further, it is preferable to additionally include one or more compounds having a polar terminal group selected from the following formula.

Wherein R is as defined in Formula III, and L ³ and L ⁴ are independently H or F. Preferably, R in these compounds is alkyl or alkoxy having 1 to 8 carbon atoms.

  Compounds of the formulas Va, Vb, Vc, Vd, Vm, Vn and VIm, especially compounds of the formulas Va, Vm, Vn and VIm, are particularly preferred.

  In a further preferred embodiment, the liquid-crystal mixture comprises one or more, particularly preferably one, two or three, heterocyclic compounds of the formula VIIa and / or VIIb.

Wherein R ⁶ and R ⁷ are as defined for R in Formula III, and Y is F or Cl.

  The proportion of compounds from the group consisting of VIIa and VIIb is preferably from 2 to 35% by weight, in particular from 5 to 20% by weight.

  If desired, the liquid crystal mixture comprises an amount of optically active component C in which the ratio between the layer thickness (separation between skins) and the natural pitch of the chiral nematic liquid crystal mixture is greater than about 0.2. Various chiral dopants (some are commercially available) such as, for example, cholesteryl nonanoate, S-811, S-1011, S-2011, S-3011, S-4011 and CB15 from Merck KGaA (Darmstadt) are: It is available to those skilled in the art as a component. The choice of the dopant itself is not critical.

  The proportion of compounds of component C is preferably from 0 to 10% by weight, in particular from 0 to 5% by weight, particularly preferably from 0 to 3% by weight.

  The mixtures according to the invention can, if desired, contain up to 20% by weight of one or more compounds having a dielectric anisotropy of less than −2 (component D).

  When the mixture comprises compounds of component D, these may be one or more compounds, including the structural units 2,3-difluoro-1,4-phenylene, for example the compounds described in US Pat. preferable. Tranes containing this structural unit described in Patent Document 11 are particularly preferred.

  Further known compounds of component D are described, for example, in US Pat.

Or

2,3-dicyanohydroquinone derivative or cyclohexane derivative containing the structural unit of

  Preferably, the liquid crystal display according to the invention does not contain a compound of component D.

The term “alkenyl” in the definition of R and R ¹ to R ⁷ includes straight-chain and branched alkenyl groups, in particular straight-chain groups. Particularly preferred alkenyl groups, 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, in particular C ₂ -C _{7-1E-alkenyl,} C ₄ -C ₇ -3E-alkenyl and C ₅ -C _7-4-alkenyl.

  Preferred alkenyl groups include vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3E-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z- Hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl and the like. Groups having up to 5 carbon atoms are generally preferred.

In a particularly preferred embodiment, the liquid crystal mixture comprises
One or more compounds selected from formulas Ia to Ih,
One or more compounds selected from formulas IIa to IIi,
One or more compounds of the formula II ^* a,
One or more compounds selected from formulas IIIb, IIIc and IIIf,
One or more compounds selected from formulas IV27 and / or IV32,
4 to 30% by weight, preferably 6 to 20% by weight, of a compound of the formula I
2 to 35% by weight, preferably 4 to 25% by weight, of a compound of the formula T1;
10 to 55% by weight, preferably 15 to 45% by weight, of a compound of the formula II and / or II ^*
5 to 30% by weight, preferably 7 to 25% by weight, of a compound of the formula IV27 and / or IV32.
15 to 50% by weight, preferably 25 to 45% by weight, of compounds of the formulas IIIa to IIIh
including.

Individual compounds of the formulas I to VII, II ^* , T1, Ta to Th and their subformulas or other compounds which can be used in the mixtures according to the invention or in TN and STN displays are also known or known. Can be prepared in the same manner as in the above compound.

The mixtures according to the invention are distinguished by very low total response times (t _sum = t _on + t _off ), especially when used in TN and STN displays with high layer thickness.

  The liquid crystal mixture used in the TN and STN cells according to the invention is dielectrically positive and Δε ≧ 1. Liquid crystal mixtures with Δε ≧ 5, more preferably Δε ≧ 10, most preferably Δε ≧ 15, especially Δε ≧ 20 are preferred.

  The clearing point of the liquid crystal mixture according to the invention is preferably above 70 ° C., more preferably above 80 ° C.

The liquid-crystal mixtures according to the invention have preferred values of the threshold voltage V _10/0/20 and the rotational viscosity γ ₁ . When the value of the optical path difference d · Δn is specified in advance, the value of the layer thickness d is determined by the optical anisotropy Δn. Particularly at relatively high values of d · Δn, the use of the liquid-crystal mixtures according to the invention with relatively high values of the optical anisotropy is generally preferred. This is because the value of d can be selected to be relatively small, so that a more favorable value of the response time can be obtained. However, the liquid-crystal displays according to the invention comprising the liquid-crystal mixtures according to the invention with smaller values of Δn are also characterized by advantageous values of the response time.

  The liquid-crystal mixtures according to the invention are furthermore characterized by an abrupt value of the electro-optical characteristic line and can operate at high multiplex ratios, especially at temperatures above 20 ° C. Furthermore, the liquid-crystal mixtures according to the invention have a high stability, and the values of the electrical resistance and the frequency dependence of the threshold voltage are preferred. The liquid crystal display according to the present invention has a wide operating temperature range and good angle dependence of contrast.

  Polarization in which the surface is treated such that in each case the preferred orientation (orienter) of the liquid crystal molecules adjacent thereto is usually twisted from one electrode to the other by a value of 160 ° to 720 °. The configuration of the liquid crystal display element according to the invention from the element, the electrode substrate and the electrodes corresponds to the usual structure of a display element of this type. The term "conventional structure" herein has a broad meaning and encompasses all derivatives and variants of TN and STN cells, especially matrix display elements and display elements including additional magnets.

  The tilt angles of the surfaces of the two outer plates may be the same or different. The same tilt angle is preferred. Preferred TN displays are those wherein the pretilt angle between the long axis of the molecules on the surface of the skin and the skin is from 0 ° to 7 °, preferably from 0.01 ° to 5 °, especially from 0.1 ° to 2 °. It is. For STN displays, the pretilt angle is between 1 ° and 30 °, preferably between 1 ° and 12 °, especially between 3 ° and 10 °.

  The value of the twist angle of the TN mixture in the cell is between 22.5 ° and 170 °, preferably between 45 ° and 130 °, in particular between 80 ° and 115 °. The value of the twist angle between the alignment films of the STN mixture in the cells from the alignment films is from 100 ° to 600 °, preferably from 170 ° to 300 °, especially from 180 ° to 270 °.

  The liquid-crystal mixtures according to the invention are also suitable, for example, as liquid-crystal media for use in cholesteric liquid-crystal displays as described in Patent Documents 14 to 18, in particular in SSCT (Surface Stabilized Cholesteric Texture) and PSCT (Polymer-Stabilized Cholesteric Texture) displays. Cholesteric liquid crystal displays typically include a cholesteric liquid crystal medium consisting of a nematic component and an optically active component, exhibit a significantly higher helical twist as compared to TN and STN displays, and selectively reflect circularly polarized light. This reflection wavelength is the product of the pitch of the cholesteric helix and the average refractive index of the cholesteric liquid crystal medium.

  For this purpose, one or more chiral dopants are added to the liquid-crystal mixture according to the invention, wherein the torsional force and the concentration of the dopant are such that the resulting liquid-crystal medium has a cholesteric phase at room temperature, preferably in the electromagnetic spectrum. Are selected to have a reflection wavelength in the visible, UV or IR region, especially in the region of 400 to 800 nm.

  Suitable chiral dopants are known to the expert, for example cholesteryl nonanoate (CN), CB15, R / S-811, R / S-1011, R / S-2011, R / S-3011 and R / S -4011 (Merck KGaA, Darmstadt) and the like are commercially available. Particularly preferred are dopants with a high torsion power, including derivatives of chiral sugar groups, in particular sorbitol, mannitol or iditol, very preferably the sorbitol derivatives disclosed in US Pat. The hydrobenzoin group described in Patent Document 20, the chiral binaphthol derivative described in Patent Document 21, the chiral binaphthol acetal derivative described in Patent Document 22, the chiral TADDOL derivative described in Patent Document 23, and the chiral TADDOL derivative described in Patent Documents 24 and 25 More preferred is a dopant comprising a chiral dopant having at least one fluorinated bridging group and a terminal or central chiral group.

  When two or more dopants are used, they can exhibit the same or opposite twist directions as well as the same or opposite signs of the linear temperature coefficient of twist.

  A cholesteric liquid crystal medium comprising a liquid crystal mixture according to the invention as a nematic component and one or more chiral dopants as an optically active component is another object of the invention. Yet another object of the present invention is a cholesteric liquid crystal display comprising the above cholesteric liquid crystal medium, especially SSCT and PSCT displays.

  The liquid-crystal mixtures which can be used according to the invention are prepared in a manner customary per se. In general, the desired amount of the components used in smaller amounts is dissolved in the components forming the main constituents, advantageously at elevated temperatures. The solution of the components can be mixed with an organic solvent, such as acetone, chloroform, or methanol, and after thorough mixing, the solvent can be removed again, for example, by distillation.

  The dielectric may also include further additives known to those skilled in the art and described in the literature. For example, a polychromatic dye, a stabilizer, an antioxidant, a UV absorber and the like may be added in an amount of 0 to 15% by mass.

In the present application and the following examples, the structures of the liquid crystal compounds are indicated by abbreviations converted into chemical formulas according to Tables A and B. All groups C _n H _{2n + 1} and C _m H _{2m + 1} are straight-chain alkyl groups having n and m carbon atoms, respectively. An alkenyl group has a trans configuration. The codes in Table B are self-evident. In Table A, only parent structure abbreviations are shown. In each case, the abbreviations of the parent structures follow, separated by a dash and follow the codes given in the table below for the substituents R ¹ , R ² , L ¹ , L ² and L ³ .

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

  Table C shows the dopants preferably used in the mixtures according to the invention.

  For example, stabilizers which can be added to the mixtures according to the invention are given below.

  The following examples are intended to illustrate the invention without limitation.

Use the following abbreviations:
clp. Clearing point (nematic isotropic phase transition temperature),
SN smectic-nematic phase transition temperature,
v ₂₀ flow viscosity (mm ² / s, at 20 ° C., unless otherwise specified)
Δn optical anisotropy (589 nm, 20 ° C.)
Δε dielectric anisotropy (1 kHz, 20 ° C),
γ ₁ rotational viscosity (mPa · s at 20 ° C.),
S characteristic line steepness = V ₉₀ / V _10,
V ₁₀ threshold voltage = characteristic voltage at a relative contrast of 10%
V ₉₀ Characteristic voltage at 90% relative contrast,
t _ave (t _on + t _off ) / 2, average response time,
t _sum t _on + t _off ,
time from turning _{on the} power until reaching 90% of the maximum contrast,
time from turning _{off the} power until reaching 10% of the maximum contrast,
mux multiplex ratio,
t _store low temperature storage stability for several hours (-20 ° C, -30 ° C, -40 ° C).

  Above and below, all temperatures are given in ° C. Percentages are weight percentages. Unless otherwise noted, all values are at 20 ° C. Unless otherwise stated, the display has a 240 ° twist and is considered at a multiplex ratio of 1/64 and a bias of 1/7.

Claims (11)

One or more compounds of formula I;

One or more compounds of the formula T1

A liquid crystal medium characterized by containing (wherein,
R ¹ and R ² are an alkyl group having 1 to 12 carbon atoms, and may be unsubstituted, monosubstituted with CN or CF ₃ , or at least monosubstituted with halogen; Or a plurality of CH ₂ groups are each independently —O—, —S—, —CH ＝ CH—, —C≡C—, —CO—, —CO—O—, —O—CO—, or O-CO-O- may be substituted so that the O atoms are not directly linked to each other;
R ³ is an alkenyl group having 2 to 9 carbon atoms,
L ¹ to L ⁴ are independently H or F, and at least one of L ¹ , L ² , L ³ and L ⁴ is F). 2. A liquid crystal medium according to claim 1, comprising at least one compound of the formula I selected from the following formulas:

(Wherein, R ³ is as defined in claim 1). 3. The liquid crystal medium according to claim 1, comprising at least one compound of the formula II.

(However, in the formula,
A is 1,4-phenylene or trans-1,4-cyclohexylene;
a is 0 or 1;
R ³ is an alkenyl group having 2 to 9 carbon atoms,
R ⁴ is ^one of the meanings of R ¹ as defined in claim 1). 4. The liquid crystal medium according to claim 1, comprising at least one compound of the formula II ^*.

(However, in the formula,
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;
L ¹ and L ² are independently H or F). 5. The liquid crystal medium according to claim 1, comprising at least one compound selected from the following formulas.

(However, in the formula,
R is an alkyl, alkoxy or alkenyl group having 1 to 12 carbon atoms, and one or a plurality of CH ₂ groups each independently represent —O—, —CH ＝ CH—, —CO—, OCO- or -COO- may be substituted so that the O atoms are not directly linked to each other;
L ¹ and L ² are independently H or F). 6. The liquid crystal medium according to claim 1, comprising at least one compound selected from the following formulas.

(However, in the formula,
R ¹ and R ² are as defined in claim 1,
L is H or F). One or more compounds selected from formula Ia to formula Ih,
One or more compounds selected from Formula IIa to Formula IIi,
-Optionally, one or more compounds of formula II ^* a,
One or more compounds selected from formula IIIb, formula IIIc and formula IIIf;
The liquid crystal medium according to any one of claims 1 to 6, comprising at least one compound of formula IV27 and formula IV32. From 4 to 30% by weight of a compound of formula I,
From 2 to 35% by weight of the compound of the formula T1;
-From 10 to 55% by weight of a compound of formula II and / or formula II ^* ;
-From 5 to 30% by weight of a compound of at least one of formulas IV27 and IV32;
8. The liquid-crystal medium according to claim 1, comprising from 15 to 50% by weight of at least one compound selected from the formulas IIIa to IIIh.   9. The liquid crystal medium or compound according to claim 1, which is used for electro-optical purposes.   An electro-optical liquid crystal display comprising the liquid crystal medium or the compound according to claim 1. -Two skins forming a cell with the frame;
-A nematic liquid crystal mixture of positive dielectric anisotropy located in the cell;
-An electrode layer having an alignment film inside the outer plate,
A tilt angle between 0 ° and 30 ° between the long axis of the molecule on the skin surface and the skin;
A twist angle between 22.5 ° and 600 ° between the alignment films of the liquid crystal mixture in the cell;
-A) 15 to 75% by mass of a liquid crystal component A comprising one or more compounds having a dielectric anisotropy greater than +1.5,
b) 25-85% by mass of a liquid crystal component B composed of one or more compounds having a dielectric anisotropy of -1.5 to +1.5,
c) 0 to 20% by mass of a liquid crystal component D composed of one or more compounds having a dielectric anisotropy smaller than -1.5,
d) optionally a nematic comprising an amount of optically active component C in which the ratio between the layer thickness (separation between skins) and the natural pitch of the chiral nematic liquid crystal mixture is from 0.2 to 1.3. Having a liquid crystal mixture,
TN or STN liquid crystal display, characterized in that the nematic liquid crystal mixture is as defined in any of claims 1 to 8.