CN119752457A

CN119752457A - Liquid crystal medium

Info

Publication number: CN119752457A
Application number: CN202411931106.3A
Authority: CN
Inventors: M·恩格尔; L·利曹
Original assignee: Merck Patent GmbH
Current assignee: Merck Patent GmbH
Priority date: 2017-12-08
Filing date: 2018-12-05
Publication date: 2025-04-04
Also published as: WO2019110636A1; TW201928025A; CN111433324A; TWI884906B; DE112018006224T5

Abstract

The invention relates to liquid-crystalline media comprising at least one compound of formula (I),And one or more compounds selected from the group consisting of the compounds of formulae (IIA), (IIB) and (IIC),

Description

Liquid-crystalline medium

The application is a divisional application of patent application number 201880078751.1.

The present invention relates to liquid-crystalline media comprising one or more compounds of the formula I:

Wherein,

R ¹¹ and R ¹² each independently of one another represent H, alkyl or alkoxy having 1 to 15C atoms, where, in addition, one or more CH ₂ groups of these radicals can each, independently of one another, be replaced by-C.ident.C-, -CF ₂O-、-OCF₂ -, -ch=ch-,-O-, -CO-O-, -O-CO-is replaced in such a way that O atoms are not directly connected to each other, and wherein, in addition, one or more H atoms may be replaced by halogen,

A ¹ at each occurrence independently of one another

A) 1, 4-cyclohexenylene or 1, 4-cyclohexylene, in which one or two non-adjacent CH ₂ groups may be replaced by-O-or-S-,

B) 1, 4-phenylene, in which one or two CH groups may be replaced by N,

C) Selected from the group consisting of piperidine-1, 4-diyl, 1, 4-bicyclo [2.2.2] -octylene, naphthalene-2, 6-diyl, decalin-2, 6-diyl, 1,2,3, 4-tetrahydronaphthalene-2, 6-diyl, phenanthrene-2, 7-diyl and fluorene-2, 7-diyl,

Wherein the radicals a), b) and c) may be monosubstituted or polysubstituted by halogen atoms,

Z ¹ in each occurrence independently of one another represents -CO-O-、-O-CO-、-CF₂O-、-OCF₂-、-CH₂O-、-OCH₂-、-CH₂-、-CH₂CH₂-、-(CH₂)₄-、-CH＝CH-CH₂O-、-C₂F₄-、-CH₂CF₂-、-CF₂CH₂-、-CF＝CF-、-CH＝CF-、-CF＝CH-、-CH＝CH-、-C≡C- or a single bond, and

L ¹¹ and L ¹² each independently of one another represent F, cl, CF ₃ or CHF ₂, preferably H or F, more preferably F,

And

One or more compounds selected from the group consisting of compounds of formulas IIA, IIB and IIC,

Wherein,

R ^2A,R^2B and R ^2C independently of one another denote H, unsubstituted, alkyl or alkenyl having up to 15C atoms which is monosubstituted by CN or CF ₃ or at least monosubstituted by halogen, where, in addition, one or more CH ₂ groups of these radicals may be replaced by-O-, -S-C.ident.C-, -CF ₂O-、-OCF₂ -, -OC-O-or-O-CO-is replaced in such a way that the O atoms are not directly connected to one another,

L ¹ to L ⁴ each independently of one another represent F, cl, CF ₃ or CHF ₂,

Z ² and Z ^2' each independently of the other represent a single bond 、-CH₂CH₂-、-CH＝CH-、-CF₂O-、-OCF₂-、-CH₂O-、-OCH₂-、-COO-、-OCO-、-C₂F₄-、-CF＝CF-、-CH＝CHCH₂O-,

P represents 0, 1 or 2

Q represents 0 or 1, and

V represents 1-6.

This type of medium can be used in particular for electro-optical displays with active matrix addressing based on the ECB effect, as well as IPS (in plane switching) or FFS (fringe field switching) displays.

In 1971, the principle (M.F.Schieckel and K.Fahrenschon,"Deformation of nematic liquid crystals with vertical orientation in electrical fields",Appl.Phys.Lett.19(1971),3912). of electric field controlled birefringence, i.e. the ECB effect or the DAP (phase distortion) effect, was first proposed, followed by J.F.Kahn (appl. Phys. Lett.20 (1972), 1193) and G.Labrunie and J.Robert (J.appl. Phys.44 (1973), 4869) published papers.

The papers published by J.Robert and F.Clerc (SID 80Digest Techn.Papers (1980), 30), J.Duche (Displays 7 (1986), 3) and H.Schad (SID 82Digest Techn.Papers (1982), 244) show that the liquid crystal phase must have a high ratio of elastic constants K ₃/K₁, a high value of optical anisotropy Δn and dielectric anisotropy Δε.ltoreq.0.5 in order to be suitable for use in high information display elements based on the ECB effect. Electro-optical display elements based on the ECB effect have homeotropic edge alignment (VA technology = vertical alignment). The negatively charged liquid crystal media can also be used in displays of the so-called IPS or FFS effect.

Displays using the ECB effect, such as so-called VAN (vertically aligned nematic) displays, for example in MVA (Multi-domain vertical alignment, for example: yoshide, H. Etc., papers 3.1:"MVA LCD for Notebook or Mobile PCs...",SID 2004International Symposium,Digest of Technical Papers,XXXV,Book I,pp.6-9, and Liu, C.T. etc., papers 15.1:"A46-inch TFT-LCD HDTV Technology...",SID 2004International Symposium,Digest of Technical Papers,XXXV,Book II,pp.750 -753)、PVA( pattern vertical alignment, for example: kim, sang Soo, paper 15.4:"Super PVA Sets New State-of-the-Art for LCD-TV",SID 2004International Symposium,Digest of Technical Papers,XXXV,Book II,pp.760-763)、ASV( super viewing angle, for example: shigeta, mitzuhiro and Fukuoka, hirofumi, paper 15.2:"Development of High Quality LCDTV",SID 2004International Symposium,Digest of Technical Papers,XXXV,Book II,pp.754-757) modes, besides IPS (in-plane switching) displays (for example: yeo, S.D., paper 15.3:"An LC Display for the TV Application",SID 2004International Symposium,Digest of Technical Papers,XXXV,Book II,pp.758&759) and TN (twisted nematic) displays known for a long time), have each developed itself into one of three recent, currently most important liquid crystal displays, especially for use in Television, for example, in Souk,Jun,SID Seminar 2004,seminar M-6:"Recent Advances in LCD Technology",Seminar Lecture Notes,M-6/1 to M-6/26, and Miller, ian, SID SEMINAR, seminar M-7: "LCD-Television", seminar Lecture Notes, M-7/1 to M-7/32 have improved the response time of such ECB displays in a conventional manner compared to that the above-mentioned displays have been used, in particular, but the response time to the current shadow has been improved, particularly in 38 has been a satisfactory manner, although the response to the current shadow has been still not been improved, especially in 38.

The commercial application of this effect in electro-optical display elements requires LC phases, which have to meet the diversity of requirements. Of particular importance are chemical resistance to moisture, air and physical effects such as heat, infrared, visible light, and ultraviolet and direct and alternating electric fields.

Furthermore, LC phases that are industrially usable are required to have a liquid crystalline mesophase and a low viscosity in a suitable temperature range.

None of the series of compounds with liquid crystalline mesophase disclosed so far contains a single compound capable of satisfying all of these requirements. Thus, mixtures of 2 to 25, preferably 3 to 18, compounds are generally prepared in order to obtain substances which can be used as LC phases. However, it is not possible to easily prepare the most suitable phase in this way, since no liquid crystal material having a significantly negative dielectric anisotropy and sufficient long-term stability has been available to date.

Matrix liquid crystal displays (MLC displays) are known. The nonlinear element that can be used for individual switching of a single pixel is for example an active element (e.g. a transistor). The term "active matrix" is used below, wherein there is a distinction between two types:

1. MOS (metal oxide semiconductor) transistor on silicon wafer as substrate

2. Thin Film Transistors (TFTs) on a glass plate as a substrate.

In the case of type 1, the electro-optical effect used is typically dynamic scattering or guest-host effect. The use of monocrystalline silicon as substrate material limits the display size, as the integration of modules of different parts of the display can also lead to problems at the joints.

In the case of the preferred more promising type 2, the electro-optical effect used is generally the TN effect.

The two techniques differ in TFTs containing compound semiconductors such as CdSe or TFTs based on polysilicon or amorphous silicon. The latter technique is intensively studied worldwide.

The TFT matrix is applied to the inside of one glass plate of the display, while the other glass plate carries a transparent counter electrode therein. The TFT is very small compared to the size of the pixel electrode and there is little adverse effect in the image. The technique can also be extended to full color functional displays where mosaic of red, green and blue filters are arranged such that the filter element is arranged in an opposing manner to each switchable pixel.

The term MLC display here includes any matrix display with integrated nonlinear elements, i.e. in addition to active matrices, displays with passive elements, such as varistors or diodes (mim=metal-insulator-metal).

Such MLC displays are particularly suitable for TV applications (e.g. pocket TV) or for high-information displays in automobile or aircraft construction. In addition to the problem of angular dependence with respect to contrast and response time, problems [TOGASHI,S.,SEKIGUCHI,K.,TANABE,H.,YAMAMOTO,E.,SORIMACHI,K.,TAJIMA,E.,WATANABE,H.,SHIMIZU,H.,Proc.Euro-display 84,Sept.1984:A210-288Matrix LCD Controlled by Double Stage Diode Rings,, page 141ff, .,Paris;STROMER,M.,Proc.Eurodisplay 84,Sept.1984:Design of Thin Film Transistors for Matrix Addressing of Television Liquid Crystal Displays,, page 145ff, paris, are also caused in MLC displays by insufficiently high specific resistances of the liquid crystal mixtures. As the resistance decreases, the contrast of the MLC display deteriorates. Since the specific resistance of the liquid crystal mixture generally decreases with the lifetime of the MLC display as a result of interactions with the internal surfaces of the display, a high (initial) resistance is very important for the display and therefore has to have an acceptable resistance value after long-term operation.

Thus, there remains a great need for MLC displays with very high resistivity, with a large operating temperature range, short response times and low threshold voltages, with the aid of which a multiplicity of gray scales can be produced.

The disadvantage of the MLC-TN displays frequently used is their comparatively low contrast ratio, relatively high viewing angle dependence and the difficulty in generating gray scales in these displays.

The markets for VA, PS-VA, IPS, FFS and UB-FFS applications are looking for LC mixtures with fast response times and very high reliability. One way to achieve a fast response time is to identify a highly polar LC material with low rotational viscosity, the use of which in LC mixtures contributes to the desired effect. However, the use of this type of highly polar LC material has an adverse effect on the reliability parameters, especially after exposure to light.

The object of the present invention is to provide liquid-crystalline mixtures based on the ECB, UB-FFS, IPS or FFS effect, in particular for monitor and TV applications, which do not have the disadvantages described above or only have them to a small extent. In particular, it has to be determined for monitors and televisions that they also operate at very high and very low temperatures and at the same time have a very short response time and at the same time have an improved reliability behavior, in particular exhibiting no image sticking or a significantly reduced image sticking after a long run time.

Compounds of the general formula

In European patent application EP 17161352.4, it is mentioned as a component of a liquid-crystalline medium. Also discloses

However, only a single compound is used in the medium of this document

Where n is 2 and m is 5.

Accordingly, the present invention relates to liquid-crystalline media comprising at least one compound of the formula I and one or more compounds selected from the group consisting of compounds of the formulae IIA, IIB and IIC. These media are particularly suitable for obtaining liquid crystal displays having a fast response time at low temperatures and good voltage retention and excellent storage stability. Sufficient for many applications.

The mixtures according to the invention preferably exhibit a very broad nematic phase range and a clear point of ≡70 ℃, preferably ≡75 ℃, in particular ≡80 ℃, very advantageous values of capacitance threshold, relatively high retention values and at the same time very good low temperature stability at-20 ℃ and-30 ℃ and very low rotational viscosity values and short response times. The mixture according to the invention is further characterized in that in addition to an improved rotational viscosity gamma ₁, a relatively high value of the elastic constant K ₃₃ is observed for improved response times. The ratio of the rotational viscosity gamma ₁ to the elastic constant K _i is reduced by using the compounds of the formula I in LC mixtures which preferably have negative dielectric anisotropy.

Some preferred embodiments of the mixture according to the invention are set forth below.

In the compounds of the formula I, R ¹¹ and R ¹² preferably each independently of one another represent a linear alkyl radical, in particular CH₃、n-C₂H₅、n-C₃H₇、n-C₄H₉、n-C₅H₁₁、n-C₆H₁₃- or n-C ₇H₁₅, a linear alkoxy radical, in particular CH₃-O、n-C₂H₅-O、n-C₃H₇-O、n-C₄H₉-O、n-C₅H₁₁-O or n-C ₆H₁₃ -O, and an alkenyl radical, in particular CH ₃＝CH、CH₃CH＝CH、CH₃CH＝CHCH₂ or CH ₃CH₂ ch=ch, a branched alkoxy radical, in particular, (CH ₃)₂CH(CH₂)₃ O), and an alkenyloxy radical, in particular CH ₂＝CHO、CH₂＝CH₂CHO、CH₃CH₂ =chcho or OCH ₂CH₂CH＝CHCH₂ O.

R ¹¹ particularly preferably represents a straight-chain alkyl radical having 1 to 7C atoms. R ¹² particularly preferably represents a linear alkoxy radical having 1 to 6C atoms, in particular methoxy, ethoxy, propoxy, butoxy, pentoxy or hexoxy.

Preferably, both L ¹¹ and L ¹² in the compound of formula I represent F.

Preferred compounds of the formula I present in the medium are compounds of the formulae I-1 to I-3, preferably of the formula I-2,

Wherein,

The parameters have the meanings given above, R ¹¹ represents a linear alkyl group, R ¹² preferably represents an alkoxy group, and L ¹¹ and L ¹² preferably both represent F.

In a preferred embodiment, the medium comprises one or more compounds of the formula I selected from the group consisting of compounds of the formulae I-O-1 to I-O-3, preferably compounds of the formula I-O-2,

Wherein the parameters have the meanings given above,

In another preferred embodiment, the medium comprises one or more compounds of the formula I selected from the group consisting of compounds of the formulae I-S-1 to I-S-3, preferably of the formula I-S-2,

Wherein the parameters have the meanings given above.

In a preferred embodiment of the invention, the medium comprises one or more compounds selected from the group consisting of the formulae I-O-1 to I-O-3 and one or more compounds selected from the group consisting of the formulae I-S-1 to I-S-3.

The compounds of formula I may be prepared, for example, as described in US2005/0258399 or WO 02/055463A 1.

The medium according to the invention preferably comprises one, two, three, four or more, preferably one, two or three, compounds of the formula I.

The amount of the compounds of the formula I in the liquid-crystalline medium is preferably not less than 1% by weight, preferably not less than 3% by weight, based on the entire mixture. Particular preference is given to liquid-crystalline media which comprise from 1 to 40% by weight, very particular preference from 2 to 30% by weight, of one or more compounds of the formula I.

Preferred embodiments of the liquid-crystalline medium according to the invention are shown below:

a) A liquid-crystalline medium which additionally comprises one or more compounds selected from the group consisting of compounds of formulae IIA, IIB and IIC,

In the compounds of formulae IIA and IIB, Z ² can have identical or different meanings. In the compounds of formula IIB, Z ² and Z ²' may have the same or different meanings.

In the compounds of the formulae IIA, IIB and IIC, R ^2A,R^2B and R ^2C each preferably represent alkyl having 1 to 6C atoms, in particular ,CH₃、C₂H₅、n-C₃H₇、n-C₄H₉、n-C₅H₁₁.

In the compounds of formulae IIA and IIB, L ¹、L²、L³ and L ⁴ preferably represent L ¹＝L² =f and L ³＝L⁴ =f, and also L ¹ =f and L ²＝Cl,L¹ =cl and L ²＝F,L³ =f and L ⁴＝Cl,L³ =cl and L ⁴ =f. Z ² and Z ²' in the formulae IIA and IIB preferably each independently of one another represent a single bond and also represent a C ₂H₄ -bridge.

If in formula IIB Z ²＝-C₂H₄ -or-CH ₂O-,Z^2' is preferably a single bond, or if Z ²'＝-C₂H₄ -or-CH ₂O-,Z² is preferably a single bond. Of the compounds of formulae IIA and IIB, (O) C _vH_2v+1 preferably denotes OC _vH_2v+1 and also C _vH_2v+1. In the compounds of the formula IIC, (O) C _vH_2v+1 preferably denotes C _vH_2v+1. In the compounds of formula IIC, L ³ and L ⁴ preferably each represent F.

Preferred compounds of formulae IIA, IIB and IIC are shown below:

Wherein,

The alkyl and alkyl ^* each independently of the other represent a straight-chain alkyl radical having 1 to 6C atoms, and

Each of alkinyl and alkinyl ^*, independently of the other, represents a straight-chain alkenyl group having 2 to 6C atoms.

Particularly preferred mixtures according to the invention comprise one or more compounds of the formulae IIA-2, IIA-8, IIA-14, IIA-26, II-28, IIA-33, IIA-39, IIA-45, IIA-46, IIA-47, IIA-50, IIB-2, IIB-11, IIB-16 and IIC-1.

The proportion of the compounds of the formulae IIA and/or IIB in the overall mixture is preferably at least 20% by weight.

Particularly preferred media according to the invention comprise at least one compound of the formula IIC-1,

Wherein alkyl and alkyl ^* have the meaning as described above, preferably in an amount of > 3% by weight, in particular > 5% by weight, and particularly preferably 5-25% by weight.

B) A liquid-crystalline medium, additionally comprising one or more compounds of the formula III,

Wherein,

R ³¹ and R ³² each independently of one another represent straight-chain alkyl, alkoxy, alkenyl, alkoxyalkyl or alkoxy having up to 12C atoms, and

D represents en represents o

Z ³ represents a single bond 、-CH₂CH₂-、-CH＝CH-、-CF₂O-、-OCF₂-、-CH₂O-、-OCH₂-、-COO-、-OCO-、-C₂F₄-、-C₄H₈-、-CF＝CF-.

Preferred compounds of formula III are shown below:

Wherein,

The alkyl and alkyl ^* each independently of the other represent a straight-chain alkyl group having 1 to 6C atoms.

The medium according to the invention preferably comprises at least one compound of formula IIIa and/or IIIb.

The proportion of the compound of the formula III in the entire mixture is preferably at least 5% by weight.

C) A liquid-crystalline medium, additionally comprising a compound of the formula,

And/or

The total amount is preferably not less than 5% by weight, in particular not less than 10% by weight.

It is further preferred that the mixture according to the invention comprises the following compounds

(Abbreviation: CC-3-V1),

The preferred amount is 2-15 wt.%.

Preferred mixtures comprise from 5 to 60% by weight, preferably from 10 to 55% by weight, in particular from 20 to 50% by weight, of compounds of the formula (abbreviation: CC-3-V)

Further preferred are compounds comprising the formula (abbreviation: CC-3-V)

And a compound of the formula (abbreviation: CC-3-V1)

Is used in the preparation of a mixture of (a),

The preferred amount is 10 to 60% by weight.

D) A liquid-crystalline medium, additionally comprising one or more tetracyclic compounds of the formula,

Wherein,

R ^7-10 each independently of the other has one of the meanings described for R ^2A in claim 5, and w and x each independently of the other represent 1 to 6.

Particularly preferred are mixtures comprising at least one compound of the formula V-9.

E) Liquid-crystalline medium additionally comprising one or more compounds of the formulae Y-1 to Y-6

Wherein R ¹⁴-R¹⁹ each independently of the other represents an alkyl group or an alkoxy group having 1 to 6C atoms, and z and m each independently of the other represent 1 to 6;x represent 0,1, 2 or 3.

The medium according to the invention particularly preferably comprises one or more compounds of the formulae Y-1 to Y-6, preferably in an amount of.gtoreq.5% by weight.

F) Liquid-crystalline medium additionally comprising one or more fluorinated terphenyl of the formulae T-1 to T-21

Wherein,

R represents a linear alkyl or alkoxy group having 1 to 6C atoms, and m=0, 1,2, 3, 4, 5 or 6 and n represents 0,1, 2, 3 or 4.

R preferably represents methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy, pentoxy.

The media according to the invention preferably comprise the terphenyl of the formulae T-1 to T-21 in an amount of 2 to 30% by weight, in particular 5 to 20% by weight.

Particularly preferred are compounds of the formulae T-1, T-2, T-4, T-20 and T-21. In these compounds, R preferably represents alkyl as well as alkoxy, each having 1 to 5C atoms. In the compounds of the formula T-20, R preferably represents alkyl or alkenyl, in particular alkyl. In the compounds of formula T-21, R preferably represents alkyl.

If the Δn value of the mixture is ≡0.1, terphenyl is preferably used in the mixture according to the invention. Preferred mixtures comprise from 2 to 20% by weight of one or more terphenyl compounds selected from the group consisting of compounds T-1 to T-21.

G) A liquid-crystalline medium, additionally comprising one or more biphenyls of the formulae B-1 to B-3,

Wherein,

The proportion of biphenyls of the formulae B1 to B3 in the overall mixture is preferably at least 3% by weight, in particular.gtoreq.5% by weight.

Of the compounds of the formulae B1 to B3, the compounds of the formula B-2 are particularly preferred.

Particularly preferred biphenyls are

Wherein alkyl ^* represents an alkyl group having 1 to 6C atoms. The medium according to the invention particularly preferably comprises one or more compounds of the formulae B-1a and/or B-2 c.

H) A liquid-crystalline medium comprising at least one compound of the formulae Z-1 to Z-7,

Wherein R and alkyl have the meanings indicated above.

I) The liquid-crystalline medium additionally comprises at least one compound of the formulae O-1 to O-18,

Wherein R ¹ and R ² have the meanings described for R ^2A. R ¹ and R ² preferably each independently of one another represent a linear alkyl or alkenyl radical.

Preferred media comprise one or more compounds of the formulae O-1, O-3, O-4, O-6, O-7, O-10, O-11, O-12, O-14, O-15, O-16 and/or O-17.

Particularly preferred are compounds comprising one or more compounds selected from the group consisting of the formula O-17,

Very particular preference is given to mixtures according to the invention which comprise compounds of the formulae O-10, O-12, O-16 and/or O-17, in particular in amounts of from 5 to 30%.

Preferred compounds of formulae O-10 and O-17 are shown below:

the medium according to the invention particularly preferably comprises a tricyclic compound of the formula O-10a and/or O-10b, and one or more bicyclic compounds of the formulae O-17a to O-17 d. The total proportion of the compounds of the formulae O-10a and/or O-10b and of one or more compounds selected from the group consisting of the bicyclic compounds of the formulae O-17a to O-17d is from 5 to 40%, very particularly preferably from 15 to 35%.

Very particularly preferred mixtures include the compounds O-10a and O-17a:

the compounds O-10a and O-17a are preferably present in the mixture in a concentration of from 15 to 35%, particularly preferably from 15 to 25% and particularly preferably from 18 to 22%, based on the entire mixture.

Very particularly preferred mixtures comprise the compounds O-10b and O-17a:

The compounds O-10b and O-17a are preferably present in the mixture in a concentration of from 15 to 35%, particularly preferably from 15 to 25% and particularly preferably from 18 to 22%, based on the entire mixture.

Very particularly preferred mixtures comprise the following three compounds:

The compounds O-10a, O-10b and O-17a are preferably present in the mixture in a concentration of from 15 to 35%, particularly preferably from 15 to 25% and particularly preferably from 18 to 22%, based on the entire mixture.

Preferred mixtures comprise at least one compound selected from the group consisting of

Wherein R ¹ and R ² have the meanings as described above. Preferably, in the compounds O-6, O-7 and O-17, R ¹ represents an alkyl or alkenyl group having 1 to 6 or 2 to 6C atoms respectively and R ² represents an alkenyl group having 2 to 6C atoms.

Preferred mixtures comprise at least one compound of the formulae O-6a, O-6b, O-7a, O-7b, O-17e, O-17f, O-17g and O-17 h:

wherein alkyl represents an alkyl group having 1 to 6C atoms.

The compounds of the formulae O-6, O-7 and O-17e-h are preferably present in the mixtures according to the invention in amounts of from 1 to 40% by weight, preferably from 2 to 35% by weight and very particularly preferably from 2 to 30% by weight.

J) Preferred liquid-crystalline media according to the invention comprise one or more substances containing tetrahydronaphthyl or naphthyl units, for example compounds of the formulae N-1 to N-5,

Wherein R ^1N and R ^2N each independently of one another have the meaning indicated for R ^2A, preferably denote a linear alkyl, linear alkoxy or linear alkenyl radical, and

Z ¹ and Z ² each independently of one another represent -C₂H₄-、-CH＝CH-、-(CH₂)₄-、-(CH₂)₃O-、-O(CH₂)₃-、-CH＝CHCH₂CH₂-、-CH₂CH₂CH＝CH-、-CH₂O-、-OCH₂-、-COO-、-OCO-、-C₂F₄-、-CF＝CF-、-CF＝CH-、-CH＝CF-、-CF₂O-、-OCF₂-、-CH₂- or a single bond.

K) Preferred mixtures comprise one or more compounds selected from the group consisting of difluorodibenzochroman compounds of formula BC, chromans of formula CR, fluorophenanthrenes of formulae PH-1 and PH-2, fluorodibenzofurans of formulae BF-1 and BF-2,

Wherein R ^B1、R^B2、R^CR1、R^CR2、R¹、R² each independently of one another have the meaning of R ^2A. c is 0, 1 or 2 and d represents 1 or 2.R ¹ and R ² preferably represent, independently of one another, alkyl or alkoxy having 1 to 6C atoms. The compounds of formulae BF-1 and BF-2 should not be identical to one or more of the compounds of formula I.

The mixtures according to the invention preferably comprise compounds of the formulae BC, CR, PH-1, PH-2 and/or BF in an amount of from 3 to 20% by weight, in particular in an amount of from 3 to 15% by weight.

Particularly preferred compounds of the formulae BC and CR are the compounds BC-1 to BC-7 and CR-1 to CR-5,

Wherein,

Very particular preference is given to mixtures comprising one, two or three compounds of the formulae BC-2, BF-1 and/or BF-2.

L) preferred mixtures comprise one or more indane compounds of formula In,

Wherein the method comprises the steps of

R ¹¹、R¹²、R¹³ each independently of the other represents a straight-chain alkyl, alkoxy, alkoxyalkyl or alkenyl radical having 1 to 6C atoms,

R ¹² and R ¹³ additionally represent halogen, preferably F,

Representation of

I represents 0,1 or 2.

Preferred compounds of formula In are compounds of the formulae In-1 to In-16 shown below:

particularly preferred are compounds of the formulae In-1, in-2, in-3 and In-4.

The compounds of the formulae In and sub-formulae In-1 to In-16 are preferably used In the mixtures according to the invention In concentrations of ≡5 wt.%, in particular 5 to 30 wt.% and very particularly preferably 5 to 25 wt.%.

M) the preferred mixtures additionally comprise one or more compounds of the formulae L-1 to L-11,

Wherein,

R, R ¹ and R ² each independently of one another have the meaning indicated for R ^2A in claim 5, and alkyl represents alkyl having 1 to 6C atoms. s represents 1 or 2.

Particular preference is given to compounds of the formulae L-1 and L-4, in particular L-4.

The compounds of the formulae L-1 to L-11 are preferably used in concentrations of from 5 to 50% by weight, in particular from 5 to 40% by weight and very particularly preferably from 10 to 40% by weight.

The particularly preferred mixture concept is set forth below (abbreviations used are explained in Table A. Where n and m each independently of one another represent from 1 to 15, preferably from 1 to 6).

The mixture according to the invention preferably comprises,

-One or more compounds of formula I wherein L ¹¹＝L¹² =f and R ¹ =alkyl, R ^1* =alkoxy, and/or

CPY-n-Om, in particular CPY-2-O2, CPY-3-O2 and/or CPY-5-O2, preferably with a concentration of >5%, in particular 10-30%, based on the total mixture,

And/or

-CY-n-Om, preferably CY-3-O2, CY-3-O4, CY-5-O2 and/or CY-5-O4, preferably with a concentration of >5%, in particular 15-50%, based on the whole mixture,

And/or

CCY-n-Om, preferably CCY-4-O2, CCY-3-O3, CCY-3-O1 and/or CCY-5-O2, preferably in a concentration of >5%, in particular 10-30%, based on the total mixture,

And/or

CLY-n-Om, preferably CLY-2-O4, CLY-3-O2 and/or CLY-3-O3, preferably having a concentration of >5%, in particular 10 to 30%, based on the total mixture,

Further preferred are mixtures according to the invention comprising:

(n and m each independently represent 1 to 6.)

The compounds of the formula I, preferably the compounds of the formulae I-1 to I-3, i.e. the formulae I-O-1 to I-O-3 and/or I-S-1 to I-S-3, in particular LB-3-O4 and/or LB (S) -4-O3, are present in a concentration of 1 to 20% by weight, more preferably 2 to 15% by weight, particularly preferably 3 to 12% by weight, very particularly preferably 4 to 11% by weight.

-CPY-n-Om and CY-n-Om, preferably in a concentration of 10-80% based on the whole mixture, and/or

CPY-n-Om and CK-n-F, preferably in a concentration of 10 to 70% based on the total mixture and/or

CPY-n-Om and PY-n-Om, preferably CPY-2-O2 and/or CPY-3-O2 and PY-3-O2, preferably in a concentration of 10 to 45% based on the total mixture,

And/or

-CPY-n-Om and CLY-n-Om, preferably in a concentration of 10-80% based on the whole mixture, and/or

CCVC-n-V, preferably CCVC-3-V, preferably with a concentration of 2 to 10% based on the total mixture,

And/or

CCC-n-V, preferably CCC-2-V and/or CCC-3-V, preferably with a concentration of 2-10% based on the total mixture,

And/or

CC-V-V, preferably in a concentration of 5 to 50% based on the whole mixture.

In a particularly preferred embodiment of the invention, the medium comprises compound B-2O-O5 in a concentration of 2 to 8%, compound CC-3-V in a concentration of 25 to 35% and compound CC-3-V1 in a concentration of 8 to 12%.

The invention further relates to an electro-optic display with active matrix addressing based on ECB, VA, PS-VA, PA-VA, IPS, PS-IPS, FFS or PS-FFS effect, characterized in that it contains as dielectric a liquid-crystalline medium according to one or more of claims 1-11.

The liquid-crystalline media according to the invention preferably have a nematic phase of from.ltoreq.20℃to.gtoreq.70℃and particularly preferably from.ltoreq.30℃to.gtoreq.80℃and very particularly preferably from.ltoreq.40℃to.gtoreq.90 ℃.

The expression "having a nematic phase" here means on the one hand that no smectic phase and no crystallization are observed at the respective temperatures at low temperatures and on the other hand that heating from the nematic phase does not become clear. The low temperature study was performed in a flow viscometer at the corresponding temperature and verified by storage in a test box having a layer thickness corresponding to at least 100 hours of electro-optic use. If the storage stability in the corresponding test cartridge is 1000 hours or more at a temperature of-20 ℃, the medium is said to be stable at that temperature. At temperatures of-30 ℃ and-40 ℃, the corresponding times were 500 hours and 250 hours, respectively. The clearing point is measured in a capillary tube by conventional methods at elevated temperature.

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

The birefringence Δn in the liquid crystal mixture is usually 0.07 to 0.16, preferably 0.08 to 0.13.

The liquid-crystal mixtures according to the invention have a Δεof from-0.5 to-8.0, in particular from-2.5 to-6.0, where Δεrepresents the dielectric anisotropy. The rotational viscosity gamma ₁ at 20℃is preferably < 150 mPas, in particular < 120 mPas.

The liquid-crystalline medium according to the invention has a relatively low threshold voltage value (V ₀). The preferred range is from 1.7V to 3.0V, particularly preferably 2.5V and very particularly preferably 2.3V.

For the purposes of the present invention, unless explicitly stated otherwise, the term "threshold voltage" refers to a capacitance threshold (V ₀), also known as the Freedericks threshold.

In addition, the liquid-crystalline medium according to the invention has a high voltage retention value in the liquid-crystalline cell.

In general, liquid crystal media with low addressing voltages or threshold voltages exhibit lower voltage retention than those with higher addressing voltages or threshold voltages, and vice versa.

For the purposes of the present invention, the term "positive dielectric compound" means compounds having a Δε >1.5, the term "neutral dielectric compound" means those having a Δε of-1.5.ltoreq.Δε.ltoreq.1.5 and the term "negative dielectric compound" means those having a Δε < -1.5. Here, the dielectric anisotropy of the compounds is determined by dissolving 10% of the compounds in the liquid-crystalline host in at least one test cell and measuring the capacitance of the resulting mixture, the test cell in each case having a layer thickness of 20 μm and having homeotropic and faceted surface alignment at 1 kHz. The measurement voltage is typically 0.5V-1.0V, but always below the capacitance threshold of the respective liquid crystal mixture under investigation.

All temperature values described herein are expressed in terms of degrees celsius.

The mixtures according to the invention are suitable for all VA-TFT applications, for example VAN, MVA, (S) -PVA, ASV, PSA (Polymer stabilized VA) and PS-VA (Polymer stabilized VA). They are also suitable for IPS (in-plane switching) and FFS (fringe field switching) applications with negative Δ∈.

The nematic liquid-crystal mixtures in the displays according to the invention generally comprise two components A and B, which consist of one or more individual compounds.

Component A has a significantly negative dielectric anisotropy and gives a nematic phase a dielectric anisotropy of < 0.5. In addition to one or more compounds of the formula I, it preferably comprises compounds of the formulae IIA, IIB and/or IIC, and also one or more compounds of the formula O-17.

The proportion of component A is preferably 45 to 100%, in particular 60 to 100%.

For component A, it is preferable to select one (or more) of the individual compounds having a value of Δε.ltoreq.0.8. The smaller the proportion of A in the overall mixture, the more negative this value must be.

Component B has a pronounced nematic (nematogeneity) and a flow viscosity of not more than 30mm ²·s^-1, preferably not more than 25mm ²·s^-1, at 20 ℃.

A variety of suitable substances are known from the literature to those skilled in the art. Particularly preferred are compounds of formula O-17.

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

Component B is a unidirectionally transformed or interconverted nematic phase, does not have a smectic phase and is capable of preventing the occurrence of a smectic phase when brought down to very low temperatures in a liquid crystal mixture. For example, if a plurality of high nematic materials are added to a smectic liquid crystal mixture, the nematic properties of these materials can be compared by the degree of suppression of the smectic phase achieved.

The mixture may also optionally comprise component C, which comprises compounds having a dielectric anisotropy of Δε.gtoreq.1.5. These so-called positive compounds are generally present in the negative dielectric anisotropic mixture in an amount of.ltoreq.20% by weight based on the whole mixture.

In addition to one or more compounds of the formula I, the phase preferably comprises 4 to 15, in particular 5 to 12, particularly preferably <10 compounds of the formulae IIA, IIB and/or IIC and optionally one or more compounds of the formula O-17.

In addition to the compounds of the formula I and the compounds of the formulae IIA, IIB and/or IIC and optionally O-17, it is also possible to add further components beforehand, for example in amounts of up to 45% of the total mixture, but preferably up to 35% and in particular up to 10%.

The other components are preferably selected from nematic or nematic substances, in particular from the known substances, from the group consisting of azoxybenzene, benzanilide, biphenyl, terphenyl, phenylbenzoate or cyclohexylbenzoate, phenylcyclohexane carboxylate or cyclohexylcyclohexane carboxylate, phenylcyclohexane, cyclohexylbiphenyl, cyclohexylcyclohexane, cyclohexylnaphthalene, 1, 4-dicyclohexylbiphenyl or cyclohexylpyrimidine, phenylbiphenylAlkane or cyclohexyl diAlkanes, optionally halogenated stilbenes, benzyl phenyl ethers, diphenylacetylenes and substituted cinnamic acid esters.

The most important compounds suitable as components of this type of liquid crystal phase can be characterized by the formula IV

R²⁰-L-G-E-R²¹ IV

Wherein L and E each represent a member selected from the group consisting of 1, 4-disubstituted benzene and cyclohexane rings, 4' -disubstituted biphenyls, phenylcyclohexane and cyclohexylcyclohexane systems, 2, 5-disubstituted pyrimidines and 1, 3-disubstituted pyrimidinesCarbocycle or heterocyclic ring systems of an alkane ring, of a 2, 6-disubstituted naphthalene, of a di-and tetrahydronaphthalene, of a quinazoline and of a tetrahydroquinazoline,

G represents-CH=CH-N (O) =N-

-CH=CQ--CH=N(O)-

-C≡C--CH₂-CH₂-

-CO-O--CH₂-O-

-CO-S--CH₂-S-

-CH=N--COO-Phe-COO-

-CF₂O--CF=CF-

-OCF₂--OCH₂-

-(CH₂)₄--(CH₂)₃O-

Or a C-C single bond, Q represents halogen, preferably chlorine, or-CN, and R ²⁰ and R ²¹ each represent alkyl, alkenyl, alkoxy, alkoxyalkyl or alkoxycarbonyloxy having up to 18, preferably up to 8, carbon atoms, or one of these groups represents, instead, CN, NC, NO ₂、NCS、CF₃、SF₅、OCF₃, F, cl or Br.

In most of these compounds, R ²⁰ and R ²¹ are different from each other, and one of these groups is usually an alkyl or alkoxy group. Other variations of the proposed substituents are also conventional. Many such materials or mixtures thereof are commercially available. All of these materials can be prepared by methods known in the literature.

It is obvious to the person skilled in the art that VA, IPS or FFS mixtures according to the invention may also comprise compounds in which, for example, H, N, O, cl and F have been replaced by the corresponding isotopes.

The polymerizable compounds, so-called Reactive Mesogens (RMs), as disclosed for example in U.S. Pat. No. 6,861,107, can furthermore be added to the mixtures according to the invention in concentrations of preferably 0.01 to 5% by weight, particularly preferably 0.2 to 2% by weight, based on the mixture. These mixtures may also optionally contain an initiator, as described in U.S.6,781,665. An initiator, such as Irganox-1076 from BASF, is preferably added to the mixture containing the polymerizable compound in an amount of 0-1%. Mixtures of this type can be used in so-called polymer stabilized VA modes (PS-VA) or PSA (polymer stabilized VA), where the polymerization of the reactive mesogens is intended to take place in the liquid crystal mixture. A prerequisite for this is that the liquid crystal compounds of the LC host do not react under the polymerization conditions of the reactive mesogens, i.e. typically when exposed to UV in the wavelength range 320-360 nm. The liquid crystal compound containing alkenyl side chains, for example, CC-3-V, does not react under the polymerization conditions of RM (UV polymerization).

The mixture according to the invention may further comprise conventional additives, such as stabilizers, antioxidants, UV absorbers, nanoparticles, microparticles, etc.

The structure of the liquid crystal display according to the invention corresponds to the usual geometry as described, for example, in EP-a 0 240379.

The following examples are intended to illustrate the invention without limiting it. In this context, percent data represents weight percent and all temperatures are in degrees celsius.

Throughout the present application, the 1, 4-cyclohexylene ring and the 1, 4-phenylene ring are depicted below:

Unless otherwise indicated, cyclohexylidene ring is a trans-1, 4-cyclohexylidene ring.

The structure of the liquid crystal compounds is expressed by means of abbreviations throughout the present application and working examples. The conversion to chemical formula is according to tables 1-3, unless otherwise indicated. All radicals C _nH_2n+1、C_mH_2m+1 and C _m'H_2m'+1 or C _nH_2n and C _mH_2m are straight-chain alkyl or alkylene radicals having n, m' or z C atoms, respectively, in each occurrence. n, m', z each independently of one another represent 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, preferably 1,2, 3, 4, 5 or 6. The ring elements encoding each compound are shown in table 1, and the bridging members are shown in table 2 and the symbolic meanings of the left-hand side chains or right-hand side chains of the compounds are set forth in table 3.

TABLE 1 Ring elements

TABLE 2 bridge Member

TABLE 3 side chain

In addition to one or more compounds of the formula I, the mixtures according to the invention preferably comprise one or more of the compounds mentioned in Table A below.

Table A

The following abbreviations are used:

(n, m, m', z: in each case independently of one another 1,2,3,4,5 or 6; O) C _mH_2m+1 means OC _mH_2m+1 or C _mH_2m+1

The liquid-crystal mixtures used according to the invention are prepared in a manner customary per se. In general, the desired amount of the components used in minor amounts is dissolved in the components constituting the main component, advantageously at elevated temperatures. It is also possible to mix solutions of the components in an organic solvent, for example in acetone, chloroform or methanol, and to remove the solvent after thorough mixing, for example by distillation.

The liquid crystal phases according to the invention can be modified by suitable additives so that they can be used in any type, for example ECB, VAN, IPS, GH or ASM-VA LCD displays, which have been disclosed hitherto.

The dielectric may also contain other additives known to those skilled in the art and described in the literature, such as UV absorbers, antioxidants, nanoparticles and radical scavengers. For example, 0-15% of a polychromatic dye, a stabilizer, such as phenol, HALS (hindered amine light stabilizer) or chiral dopant, may be added. Stabilizers suitable for the mixtures according to the invention are in particular those listed in Table C.

For example, 0-15% of a polychromatic dye may be added, as well as a conductive salt, preferably ethyl dimethyl dodecyl ammonium 4-hexyloxybenzoate, tetrabutylammonium tetraphenyl borate or a complex salt of a crown ether (see, for example, haller et al mol. Cryst. Liq. Cryst., volume 24, pages 249-258 (1973)), to improve conductivity or substances may be added to alter dielectric anisotropy, viscosity and/or alignment of the nematic phase. Such a substance is described, for example, in DE-A22 09 127,22 40 864,23 21 632,23 38 281,24 50 088,26 37 430 and 28 53 728.

Table B

Table B shows possible dopants which are typically added to the mixtures according to the invention. If the mixture contains a dopant, it is used in an amount of 0.01 to 4% by weight, preferably 0.01 to 3% by weight.

The mixture according to the invention comprises at least one stabilizer from table C below.

Table C

For example, stabilizers which can be added to the mixtures according to the invention in amounts of from 0 to 10% by weight, preferably from 0.001 to 5% by weight, in particular from 0.001 to 1% by weight, are as follows:

Working examples:

The following examples are intended to illustrate the invention but not to limit it. In the examples, m.p. represents the melting point, C represents the clearing point of the liquid crystal substance in degrees celsius, and boiling temperature is in m.p.. And C represents a crystalline solid state, S represents a smectic phase (index represents a phase type), N represents a nematic state, ch represents a cholesteric phase, I represents an isotropic phase, and T _g represents a glass transition temperature. The number between the two symbols represents the switching temperature in degrees celsius.

The host mixture used to determine the optical anisotropy Δn of the compounds of formula I is the commercial mixture ZLI-4792 (MERCK KGAA). The dielectric anisotropy Δεof the commercial mixture ZLI-2857 was determined. Physical data for the compound to be investigated are obtained from the change in dielectric constant of the host mixture after addition of the compound to be investigated and extrapolated to 100% of the compound used. Typically, depending on the solubility, 10% of the compound to be investigated is dissolved in the host mixture.

Unless otherwise indicated, parts or percentages data refer to parts or percentages by weight.

In the context of the present context, it is intended that,

V _o represents the threshold voltage, capacitance at 20 ℃ [ V ]

N _e represents the extraordinary refractive index at 20 ℃ and 589nm,

N _o represents the ordinary refractive index at 20 ℃ and 589nm,

Δn represents the optical anisotropy measured at 20℃and 589nm

Epsilon _⊥ represents the dielectric constant perpendicular to the director at 20C and 1kHz,

Epsilon _|| represents the dielectric constant parallel to the director at 20C and 1kHz,

Delta epsilon represents the dielectric anisotropy at 20 ℃ and 1kHz

Cl.p., T (N, I) represents a clearing point [ DEGC ]

Gamma ₁ represents the rotational viscosity [ mpa·s ] at 20 ℃ as determined by the rotation in magnetic field method

K ₁ represents the elastic constant, "expansion" deformation at 20 ℃ [ pN ]

K ₂ represents the elastic constant, the "twist" deformation [ pN ] at 20 ℃,

K ₃ represents the elastic constant, the "bending" deformation at 20℃pN,

And

LTS means low temperature stability (nematic) as measured in a test cartridge or block sample as described.

Unless explicitly stated otherwise, all values of temperature indicated in the present application, e.g., melting point T (C, N), transition from smectic (S) phase to nematic (N) phase T (S, N) and clearing point T (N, I) or cl.p., are expressed in degrees celsius (C). M.p. represents the melting point. And, tg=glassy state, c=crystalline state, n=nematic phase, s=smectic phase and i=isotropic phase. The data between these symbols represents the transition temperature.

For purposes of the present invention, the term "threshold voltage" refers to a capacitive threshold (V ₀), also known as Freedericksz threshold, unless explicitly indicated otherwise. In an embodiment, as is generally usual, an optical threshold (V ₁₀) for a relative contrast of 10% may also be given.

The display for measuring the capacitive threshold voltage consists of two plane-parallel glass outer plates spaced 20 μm apart, each of which has an electrode layer on the inside and a top, non-rubbed polyimide alignment layer, which results in homeotropic edge alignment of the liquid crystal molecules.

The display or test cell for measuring tilt angle consists of two plane parallel glass outer plates spaced 4 μm apart, each of which has an electrode layer on the inside and a polyimide alignment layer on top, wherein the two polyimide layers rub against each other antiparallel (antarallel) and cause homeotropic edge alignment of the liquid crystal molecules.

Unless otherwise indicated, VHR was measured at 20 ℃ (VHR ₂₀) and after 5 minutes in an oven at 100 ℃ (VHR ₁₀₀) in a commercially available instrument Model 6254 from TOYO Corporation, japan. Unless more precisely indicated, the voltages used have frequencies in the range from 1Hz to 60 Hz.

The accuracy of the VHR measurement depends on the corresponding value of VHR. The accuracy decreases with decreasing value. The deviations generally observed for the values within the various value ranges are written in their orders of magnitude in the following table.

Stability to UV radiation was studied in a commercial instrument "Suntest CPS" from Heraeus, germany. Unless explicitly stated otherwise, the sealed test cartridges were irradiated for 30 minutes to 2.0 hours without additional heating. The irradiation power in the wavelength range of 300nm to 800nm was 765W/m ² V. A UV "cut-off" filter with an edge wavelength of 310nm was used to simulate the so-called glazing mode. In each series of experiments, at least four test cartridges were studied for each condition, and the corresponding results are expressed as the average of the corresponding individual measurements.

The decrease in voltage holding ratio (avhr) typically caused by exposure, e.g., UV illumination or LCD backlight, is determined according to the following equation (1):

ΔVHR(t)=VHR(t)-VHR(t=0) (1)

to investigate the low temperature stability, also known as "LTS", i.e. the stability of the LC mixture in the block against spontaneous crystallization of the individual components or possibly smectic phases at low temperature, several sealed bottles each containing about 1g of material are stored at one or more given temperatures, typically-10 ℃, -20 ℃, -30 ℃ and/or-40 ℃, and visually inspected at regular time intervals for phase changes. Once the first sample at a given temperature shows a change, the time is recorded. Until the last check, the time when no change was observed was recorded as the corresponding LTS.

Ion density to calculate resistivity was measured using commercially available LC material property measurement system 6254 type from Toyo Corporation, japan, using a VHR test cartridge of AL16301 polyimide (JSR corp., japan) with a 3.2 μm cell gap. Measurements were made after 5 minutes of storage in an oven at 60 ℃ or 100 ℃.

By "HTP" is meant the helical twisting power (in μm) of an optically active or chiral substance in an LC medium. HTP was measured at a temperature of 20℃in a commercially available nematic LC host mixture MLD-6260 (MERCK KGAA) unless otherwise specified.

All concentrations in the present application are expressed in weight percent unless explicitly stated otherwise and refer to the corresponding whole mixture, which contains all solid or liquid crystalline components, without solvent. All physical properties were determined according to "Merck Liquid Crystals,Physical Properties of Liquid Crystals",Status November 1997,Merck KGaA,Germany", and were applicable to temperatures of 20 ℃, unless explicitly stated otherwise.

The following mixture embodiments with negative dielectric anisotropy are particularly suitable for liquid crystal displays with at least one in-plane alignment layer, such as IPS and FFS displays, in particular UB-FFS (=superbright FFS), and VA displays.

Mixture examples and comparative examples

Comparative mixture C1 was prepared as follows

The mixture has a rather poor response time but good VHR values.

Comparative mixture C2 was prepared as follows:

The mixture showed improved response time compared to the mixture of comparative example 1, mainly due to its reduced gamma ₁, but lower VHR.

The mixture M1 was prepared as follows:

The mixture M2 was prepared as follows

The above mixture was used for storage testing at low temperature in a test cartridge having an appropriate thickness.

The good VHR, and simultaneously improved response time, is mainly due to its good (gamma ₁/K₁) value compared to CM1, as shown in the table below.

TABLE 1 VHR values

(Note: all VHR values were measured at 1v,1hz and 60 ℃).

Claims

1. A liquid-crystalline medium, characterized in that it comprises one or more compounds of formula I,

in,

R ¹¹ and R ¹² , each independently of one another, represent H, alkyl or alkoxy having 1 to 15 C atoms, wherein in addition, one or more CH ₂ groups in these groups may each independently of one another be replaced by -C≡C-, -CF ₂ O-, -OCF ₂ -, -CH=CH-, -O-, -CO-O-, -O-CO- are substituted in such a way that the O atoms are not directly connected to one another, and wherein in addition one or more H atoms may be replaced by halogen,

A ¹¹ represents each independently of the other at each occurrence

a) 1,4-cyclohexenylene or 1,4-cyclohexylene, in which one or two non-adjacent _CH2 groups may be replaced by -O- or -S-,

b) 1,4-phenylene, in which one or both CH groups may be replaced by N,

c) is selected from piperidine-1,4-diyl, 1,4-bicyclo[2.2.2]-octylene, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, phenanthrene-2,7-diyl and fluorene-2,7-diyl,

wherein the groups a), b) and c) may be mono- or poly-substituted by halogen atoms,

Z ¹¹ represents, at each occurrence, independently of one another, -CO-O-, -O-CO-, -CF ₂ O-, -OCF ₂ -, -CH ₂ O-, -OCH ₂ -, -CH ₂ CH ₂ -, -(CH ₂ ) ₄ -, -CH＝CH-CH ₂ O-, -C ₂ F ₄ -, -CH ₂ CF ₂ -, -CF _{2 CH 2} _- , -CF＝CF-, -CH＝CF-, -CF＝CH-, -CH＝CH-, -C≡C- or a single bond, and

L ¹¹ and L ¹² each independently represent F, Cl, CF ₃ or CHF ₂ ,

X ¹ represents O or S, and

a represents 1 or 2, preferably 1,

and one or more compounds selected from the group consisting of compounds of formula IIA, IIB and IIC,

in,

R ^2A , R ^2B and R ^2C each independently represent H, unsubstituted, monosubstituted by CN or CF ₃ or at least monosubstituted by halogen, alkyl or alkenyl with up to 15 C atoms, wherein in addition one or more CH ₂ groups in these radicals may be replaced by -O-, -S-, -C≡C-, -CF ₂ O-, -OCF ₂ -, -OC-O- or -O-CO- are substituted in such a way that the O atoms are not directly connected to each other,

^L1 to ^L4 each independently represent F or Cl,

^Z2 and Z2 ^' each independently represent a single bond, _-CH2CH2- , _-CH =CH-, _-CF2O- , _-OCF2- , _-CH2O- , _-OCH2- , -COO-, -OCO-, _-C2F4- _, -CF=CF-, -CH= _CHCH2O- ,

p means 0, 1 or 2

q represents 0 or 1, and

v means 1-6.

2. The liquid crystal medium according to claim 1, characterized in that the medium comprises one or more compounds selected from the group consisting of compounds of formulae I-1 to I-3,

The parameters have the meanings given in claim 1.

3. A liquid crystal medium according to claim 1 or 2, characterized in that it comprises one or more compounds selected from the group consisting of formulae I-0-1 to I-0-3,

The parameters have the meanings given in claim 1.

4. Liquid-crystalline medium according to one or more of claims 1 to 3, characterised in that it comprises one or more compounds selected from the group consisting of compounds of the formulae I-S-1 to I-SO-3,

The parameters have the meanings given in claim 1.

5. Liquid-crystalline medium according to one or more of claims 1 to 4, characterised in that it comprises one or more compounds of the formula IIA,

The parameters have the meanings given in claim 1.

6. Liquid-crystalline medium according to one or more of claims 1 to 5, characterised in that it further comprises one or more compounds of the formula IIB,

The parameters have the meanings given in claim 1.

7. Liquid-crystalline medium according to one or more of claims 1 to 6, characterised in that the medium comprises one or more compounds of the formula IIC,

The parameters have the meanings given in claim 1.

8. Liquid-crystalline medium according to one or more of claims 1 to 7, characterised in that the medium further comprises one or more compounds selected from the group consisting of compounds of the formulae O-1 to O-18,

in,

R ¹ and R ² each independently have the meanings given for R ^2A in claim 6.

9. Liquid-crystalline medium according to one or more of claims 1 to 8, characterised in that the medium further comprises one or more compounds selected from the group consisting of compounds of the formulae T-1 to T-21,

in,

R represents a straight-chain alkyl or alkoxy group having 1-6 C atoms, and m=0, 1, 2, 3, 4, 5 or 6, and n represents 0, 1, 2, 3 or 4.

10 . Liquid-crystalline medium according to claim 1 , characterised in that the proportion of the compound of the formula I in the mixture as a whole is from 1 to 40% by weight.

11 . Liquid-crystalline medium according to claim 1 , characterised in that the proportion of compounds of the formulae IIA to IIC in the medium as a whole is from 10% to 70%.

12. Process for preparing a liquid-crystalline medium according to one or more of claims 1 to 11, characterised in that one or more compounds of the formula I are mixed with one or more compounds selected from the group consisting of compounds of the formulae IIA to IIC and one or more compounds of the formula.

13. Use of a liquid-crystalline medium according to one or more of claims 1 to 11 in electro-optical displays.

14. Electro-optical display with active-matrix addressing, characterized in that it comprises a liquid-crystalline medium according to one or more of claims 1 to 11 as dielectric.

15. The electro-optic display of claim 15, wherein the electro-optic display is a VA, PSA, PA-VA, SS-VA, SA-VA, PS-VA, PALC, IPS, PS-IPS, FFS, UB-FFS, U-IPS, or PS-FFS display.