TW201930567A - Liquid-crystalline medium - Google Patents

Abstract

The invention relates to a liquid-crystalline medium which comprises at least one compound of the formula I, and one or more compounds selected from the group of the compounds of the formulae IIA, IIB and IIC, wherein the occurring groups and parameters have the meanings indicated in claim 1, and to the use thereof for an active-matrix display, in particular based on the VA, PSA, PA-VA, SS-VA, SA-VA, PS-VA, PALC, IPS, PS-IPS, UB-FFS, U-IPS, FFS or PS-FFS effect.

Description

Liquid crystal medium

The present invention relates to a liquid crystal medium comprising one or more compounds of formula I,

among them
R ¹¹ and R ¹² each independently denote H, an alkyl group having 1 to 15 C atoms or an alkoxy group, wherein, in addition, one or more CH ₂ groups in such groups may make the O atom not Directly linked to each other in a manner independently of each other via -C≡C-, -CF ₂ O-, -OCF ₂ -, -CH=CH-, , , -O-, -CO-O- or -O-CO-, and wherein, in addition, one or more H atoms may be replaced by halogen,
A ¹ refers to each other independently each time it appears
a) 1,4-cyclohexenylene or 1,4-cyclohexylene, wherein 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 are replaceable by N,
c) from the group piperidine-1,4-diyl, 1,4-bicyclo[2.2.2] octyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, 1 a group of 2,3,4-tetrahydronaphthalene-2,6-diyl, phenanthrene-2,7-diyl and indole-2,7-diyl groups,
Wherein the groups a), b) and c) are mono- or polysubstituted by a halogen atom,
a refers to 1 or 2, preferably 1,
Z ¹ refers to -CO-O-, -O-CO-, -CF ₂ O-, -OCF ₂ -, -CH ₂ O-, -OCH ₂ -, -CH ₂ - independently of each other at each occurrence. , -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 refer to F, Cl, CF ₃ or CHF ₂ , preferably H or F, optimally F,
And one or more compounds selected from the group of compounds of the formulae IIA, IIB and IIC

among them
R ^2A, R ^2B, and R ^2C independently of each another refers to H, without having up to 15 C atoms substituted by CN or CF ₃ at least mono-substituted by halogen or mono substituted alkyl or alkenyl group, which, in addition, One or more of the CH ₂ groups in such groups may be such that the O atoms are not directly bonded to each other via -O-, -S-, , -C≡C-, -CF ₂ O-, -OCF ₂ -, -OC-O- or -O-CO-,
L ¹ to L ⁴ each independently refer to F, Cl, CF ₃ or CHF ₂ ,
Z ² and Z ^{2 '} each independently refer to a single bond, -CH ₂ CH ₂ -, -CH=CH-, -CF ₂ O-, -OCF ₂ -, -CH ₂ O-, -OCH ₂ -, -COO-, -OCO-, -C ₂ F ₄ -, -CF=CF-, -CH=CHCH ₂ O-,
p refers to 0, 1, or 2,
q refers to 0 or 1, and
v refers to 1 to 6.

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

The principle of electrically controlled birefringence (ECB) or deformation of aligned phases (DAP) is first described in 1971 (MF Schieckel and K. Fahrenschon, "Deformation of nematic liquid crystals with Vertical orientation in electrical fields", Appl. Phys. Lett. 19 (1971), 3912). This was followed by the paper by J.F. Kahn (Appl. Phys. Lett. 20 (1972), 1193) and by G. Labrunie and J. Robert (J. Appl. Phys. 44 (1973), 4869).

J. Robert and F. Clerc's paper (SID 80 Digest Techn. Papers (1980), 30), J. Duchene's paper (Displays 7 (1986), 3) and H. Schad's thesis (SID 82 Digest Techn. Papers (1982), 244) shows that the liquid crystal phase must have a high value of the ratio of the elastic constant K ₃ /K ₁ , a high value of the optical anisotropy Δn, and a value of the dielectric anisotropy of Δε ≤ -0.5, so as to be suitable for High information display component of ECB effect. Electro-optic display elements based on the ECB effect have vertical edge alignment (VA technology = vertically aligned). Dielectric negative liquid crystal media can also be used in displays that use the so-called IPS or FFS effect.

In addition to in-plane switching (IPS) displays (eg: Yeo, SD, Paper 15.3: "An LC Display for the TV Application", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Volume II, Pages 758 and 759) Other than the well-known twisted nematic (TN) displays, for example, in multi-domain vertical alignment (MVA, for example: Yoshide, H. et al. Paper 3.1: "MVA LCD for Notebook or Mobile PCs ...", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Volume 1, pages 6 to 9, and Liu, CT et al., Paper 15.1: "A 46-inch TFT-LCD HDTV Technology ... ", SID 2004 International Symposium, Digest of Technical Papers, XXXV, book II, pages 750 to page 753), a patterned vertical alignment type (p atterned v Ertical a lignment, PVA, for example: Kim, Sang Soo, Paper 15.4: "Super PVA Sets New State-of-the-Art for LCD-TV", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Volume II, Pages 760 to 763), high Ultra viewing angle type (a dvanced s uper v iew, ASV, for example: Shigeta, Mitzuhiro and Fukuoka, Hirofumi, Paper 15.2: "Development of High Quality LCDTV", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, Pages 754 to 757) Displays that use the ECB effect in the mode, such as the so-called v ertically a ligned n ematic (VAN) display, have established itself as the three most important types of updates currently available. One of the liquid crystal displays (especially for TV applications). Such techniques are in general form, 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 2004, Seminar M-7: "LCD-Television", Seminar Lecture Notes, M-7/1 to M-7/32 for comparison. Although the response time of modern ECB displays has been significantly improved by addressing methods using overspeed driving, for example: Kim, Hyeon Kyeong et al., Paper 9.1: "A 57-in. Wide UXGA TFT-LCD for HDTV Application", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Volume 1, pages 106 to 109, but the realization of video-compatible response time, especially with regard to grayscale switching, remains a problem that has not been satisfactorily resolved.

This effect requires an LC phase for industrial applications in electro-optic display elements, which must meet a variety of requirements. Of particular importance here are chemical resistance to moisture, air and physical influences such as heat, infrared, visible and ultraviolet radiation, as well as DC and alternating electric fields.

In addition, the LC phase that can be used in industry is necessary to have a liquid crystal intermediate phase in a suitable temperature range and low viscosity.

None of the series of compounds disclosed to date having a liquid crystal mesophase includes a single compound that meets all of these requirements. Thus, a mixture of two to twenty, preferably three to eight, compounds is generally prepared to obtain a substance usable as the LC phase. However, it is impossible to easily prepare an optimum phase in this manner because liquid crystal materials having significant negative dielectric anisotropy and sufficient long-term stability have not been obtained so far.

A matrix liquid crystal display (MLC display) is known. Non-linear elements that can be used for individual switching of individual pixels are, for example, active elements (i.e., transistors). Then use the term "active matrix" where there can be differences between the following two types:
1. A metal oxide semiconductor (MOS) transistor on a germanium wafer is used as a substrate
2. Thin-film transistors (TFTs) on the glass plate are used as the substrate.

In the case of Type 1, the electro-optic effect used is typically a dynamic scattering or a guest-host effect. The use of single crystal germanium as the substrate material limits the size of the display because even the module assemblies of various partial displays create problems at the joint.

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

The following two techniques are distinguished: a TFT containing a compound semiconductor such as, for example, CdSe, or a TFT based on polycrystalline or amorphous germanium. The latter technology is widely used throughout the world.

The TFT matrix is applied to one of the glass plates of the display while the other glass plate carries transparent counter electrodes therein. Compared to the size of the pixel electrode, the TFT is extremely small and has almost no adverse effect on the image. This technique can also be extended to a fully colour-capable display in which a mosaic of red, green and blue light filters is arranged in a manner that the filter elements oppose the respective convertible pixels.

Here, the term MLC display encompasses any matrix display having an integrated nonlinear element, that is, in addition to an active matrix, a display having a passive component, such as a varistor or a diode (MIM = metal-insulator-metal).

This type of MLC display is particularly suitable for TV applications (such as pocket TV) or high information displays in car or aircraft construction. In addition to the problem of the angular dependence of contrast and the response time, the specific resistance due to the liquid crystal mixture is not high enough, which also causes difficulties in the MLC display [TOGASHI, S., SEKIGUCHI, K., TANABE, H., YAMAMOTO, E., SORIMACHI, K., TAJIMA, E., WATANABE, H., SHIMIZU, H., Proc. Eurodisplay 84, September 1984: A 210-288 Matrix LCD Controlled by Double Stage Diode Rings, page 141 and Following, Paris; STROMER, M., Proc. Eurodisplay 84, September 1984: Design of Thin Film Transistors for Matrix Addressing of Television Liquid Crystal Displays, page 145 and below, Paris]. 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 due to interaction with the inner surface of the display, high (initial) resistance is extremely important for displays that must have acceptable resistance values over long periods of operation.

There is still a large demand for MLC displays having a very high specific resistance while having a large operating temperature range, a short response time, and a low threshold voltage, by which various gradations can be produced.

A disadvantage of the commonly used main MLC-TN displays is their relatively low contrast, relatively high viewing angle dependence, and the difficulty of producing grayscale in such displays.

The market for VA, PS-VA, IPS, FFS and UB-FFS applications is looking for LC blends with fast response times and extremely high reliability. One method for achieving fast response times is to identify highly polar LC materials with low rotational viscosity that promote the desired effect in the LC mixture. However, the use of this type of highly polar LC material, especially after exposure, has an adverse effect on the reliability parameters.

The present invention is based on the object of providing a specific liquid crystal mixture based on ECB, UB-FFS, IPS or FFS effect for monitors and TV applications, which liquid crystal mixtures have no disadvantages indicated above, or only have a degree of reduction The shortcomings indicated above. In particular, it must be ensured that monitors and TVs work equally well at very high and low temperatures, while having extremely short response times and improved reliability behavior, in particular, without image retention or rendering after long operating times. Significantly reduced image retention.

a compound of the formula

It is mentioned as a component of a liquid crystal medium in European Patent Application No. EP 17161352.4. Also reveal the following

and
.
However, only a single compound

In the medium used in the literature, where n is 2 and m is 5.

Thus, the present invention relates to a liquid crystal medium comprising at least one compound of the formula I and one or more compounds selected from the group of compounds of the formulae IIA, IIB and IIC. These media are particularly well-suited for liquid crystal displays that exhibit fast response times and good voltage retention, as well as memory storage for excellent stability at deep temperatures for many applications.

The mixture according to the invention preferably exhibits a very broad nematic phase range (where the clear point is ≥ 70 ° C, preferably ≥ 75 ° C, specifically ≥ 80 ° C), a very favorable capacitance threshold, a relatively high retention Rate and excellent low temperature stability at -20 ° C and -30 ° C, as well as very low rotational viscosity and short response time. Further, in addition to improvement of rotational viscosity γ _1, distinguished by the mixtures according to the present invention may be observed that a relatively high spring constant for improved response time of the K ₃₃ value. The use of a compound of formula I in an LC mixture, preferably an LC mixture having a negative dielectric anisotropy, reduces the ratio of rotational viscosity γ ₁ and elastic constant K _i .

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

In the compounds of formula I, R ¹¹ and R ^{12 are} preferably each independently of one another: straight-chain alkyl, in particular CH ₃ , n -C ₂ H ₅ , n -C ₃ H ₇ , n -C ₄ H ₉ , n -C ₅ H ₁₁ , n -C ₆ H ₁₃ - or n -C ₇ H ₁₅ ; linear alkoxy group, specifically CH ₃ -O, n -C ₂ H ₅ -O, n - C ₃ H ₇ -O, n -C ₄ H ₉ -O, n -C ₅ H ₁₁ -O or n -C ₆ H ₁₃ -O; further, an alkenyl group, specifically CH ₃ =CH, CH ₃ CH =CH, CH ₃ CH=CHCH ₂ or CH ₃ CH ₂ CH=CH; branched alkoxy group, specifically (CH ₃ ) ₂ CH(CH ₂ ) ₃ O; and alkenyloxy group, specifically CH ₂ =CHO, CH ₂ =CH ₂ CHO, CH ₃ CH ₂ =CHCHO or O CH ₂ CH ₂ CH=CHCH ₂ O.

R ¹¹ particularly preferably refers to a linear alkyl group having 1 to 7 C atoms, and R ¹² particularly preferably refers to a linear alkoxy group having 1 to 6 C atoms, specifically methoxy, B. Oxy, propoxy, butoxy, pentyloxy or hexyloxy.

L ¹¹ and L ^{12 in} formula I preferably all refer to F.

The parameter "a (a)" in the formula I preferably denotes 1.

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


Wherein the parameters have the meanings given above, R ¹¹ refers to a linear alkyl group, and R ¹² preferably refers to an alkoxy group, and L ¹¹ and L ¹² preferably both refer to F.

In a preferred embodiment, the medium comprises a group of compounds selected from the group consisting of Formulas IO-1 through IO-3, and preferably one or more compounds of Formula I of the compound of Formula IO-2

Wherein the parameters have the meanings given above.

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

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 compounds of formulas IO-1 to IO-3 and one or a group selected from the group consisting of compounds of formulas IS-1 to IS-3. A variety of compounds.

For example, a compound of formula I can be prepared as described in US 2005/0258399 or WO 02/055463 A1.

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 compound of the formula I is preferably used in the liquid-crystalline medium in an amount of ≥ 1% by weight, preferably ≥ 3% by weight, based on the mixture as a whole. More preferably, it is a liquid-crystalline medium comprising from 1 to 40% by weight, preferably from 2 to 30% by weight, of one or more compounds of the formula I.

In a preferred embodiment, the medium comprises one or more compounds of formula I ^I

Wherein the parameters have the same meaning as the respective meanings given above according to formula I, and preferably
R ¹¹ and R ¹² each independently denote an alkyl group or alkoxy group having 1 to 15 C atoms, more preferably one or both of them refer to an alkoxy group, and
L ¹¹ and L ¹² each preferably refer to F.

In a preferred embodiment, the medium comprises a group of compounds selected from the group consisting of Formula I ^I- O-1 to I ^I -O-10, preferably one or more compounds of Formula I ^I , of a compound of Formula I ^I- O-6,


Wherein alkyl and alkyl* each independently denote a straight-chain alkyl group having 1 to 6 C atoms, and alkenyl and alkenyl* each independently mean a linear alkenyl group having 2 to 6 C atoms And alkoxy and alkoxy* each independently mean a linear alkoxy group having 1 to 6 C atoms, and each of L ¹ and L ² independently of F or Cl.

In another preferred embodiment, alternatively or additionally, the medium comprising one or more compounds selected from the group of compounds of formula I ^I -O-10 of the -O-1 to I ^I, one or more compounds of formula I ^I Where X1 is S, preferably selected from the group of compounds of the formula I ^I -S-1 to I ^I -S-10, preferably a compound of the formula I ^I -S-6 having the same number of formulas The corresponding structures of the corresponding compounds of I ^I -O-1 to I ^I -O-10, the only exception being that the bridging atom (i.e., X ¹ ) is an S atom instead of an O atom.

Preferred embodiments of the liquid crystal medium according to the present invention are indicated below:
a) a liquid crystal medium further comprising one or more compounds selected from the group of compounds of the formulae IIA, IIB and IIC,

In the compounds of formula IIA and IIB, Z ² may have the same 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 denote an alkyl group having 1 to 6 C atoms, in particular CH ₃ , C ₂ H ₅ , n -C ₃ H ₇ , n -C ₄ H ₉ , n -C ₅ H ₁₁ .

IIA and IIB compounds of the ^{formula, L 1, L 2, L} 3 and L ⁴ are preferably refers L ¹ = L ² = F, and L ³ = L ⁴ = F, in addition L ¹ = F, L and ² = Cl, L ¹ = Cl, and L ² = F, L ³ = F, and L ⁴ = Cl, L ³ = Cl, and L ⁴ = F. Z ² and Z ² ' in the formulae IIA and IIB preferably each independently refer to a single bond, in addition to a -C ₂ H ₄ - bridge.

In Formula IIB, if Z ² = -C ₂ H ₄ - or -CH ₂ O-, Z ^{2 ' is} preferably a single bond, or if Z ^{2 '} = -C ₂ H ₄ - or -CH ₂ O- Then, Z ^{2 is} preferably a single bond. In the compounds of the formulae IIA and IIB, (O)C _v H _2v+1 preferably denotes OC _v H _2v+1 , in addition to C _v H _2v+1 . In the compound of formula IIC, (O)C _v H _2v+1 preferably denotes C _v H _2v+1 . In the compounds of formula IIC, L ³ and L ⁴ are preferably each refer to F.

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









Wherein alkyl and alkyl* each independently denote a straight-chain alkyl group having 1 to 6 C atoms, and the alkenyl group and the alkenyl group each independently represent a linear olefin having 2 to 6 C atoms base.

A particularly preferred mixture according to the invention comprises one or more of formulas IIA-2, IIA-8, IIA-14, IIA-26, II-28, IIA-33, IIA-39, IIA-45, IIA-46, IIA- 47. Compounds of IIA-50, IIB-2, IIB-11, IIB-16 and IIC-1.

The proportion of the compound of the formula IIA and/or IIB in the mixture as a whole is preferably at least 20% by weight.

A particularly preferred medium according to the invention comprises at least one compound of the formula IIC-1,

Wherein alkyl and alkyl* have the meaning indicated above, preferably in an amount of > 3% by weight, specifically > 5% by weight and especially preferably from 5 to 25% by weight.

b) a liquid crystal medium additionally comprising one or more compounds of the formula III,

among them
R ³¹ and R ³² each independently of one another mean a straight-chain alkyl, alkoxy, alkenyl, alkoxyalkyl or alkoxy group having up to 12 C atoms, and
Refers to
Z ³ refers to a single bond, -CH ₂ CH ₂ -, -CH=CH-, -CF ₂ O-, -OCF ₂ -, -CH ₂ O-, -OCH ₂ -, -COO-, -OCO-, -C ₂ F ₄ -, -C ₄ H ₈ -, -CF=CF-.

Preferred compounds of formula III are indicated below:

Wherein alkyl and alkyl* each independently of one another mean a straight-chain alkyl group having from 1 to 6 C atoms.

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

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

c) A liquid crystal medium additionally containing a compound of the formula:
And/or
And/or
,
It is preferably in a total amount of ≥ 5% by weight, specifically ≥ 10% by weight.

Further, a mixture according to the present invention comprising the following compound (abbreviation: CC-3-V1) is preferred
,
It is preferably in an amount of from 2 to 15% by weight.

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 the compound of the formula (abbreviation: CC-3-V)
.

Further, a mixture comprising a compound of the formula (abbreviation: CC-3-V) is preferred.

And compounds of the formula (abbreviation: CC-3-V1)
,
It is preferably in an amount of 10 to 60% by weight.

d) a liquid crystal medium further comprising one or more tetracyclic compounds of the formula


among them
R ^7-10 each independently of one another has one of the meanings indicated for R ^{2A in} claim 5, and
w and x each independently refer to 1 to 6.

More preferably, it is a mixture comprising at least one compound of the formula V-9.

e) a liquid crystal medium further comprising one or more compounds of the formulae Y-1 to Y-6,


Wherein R ¹⁴ to R ¹⁹ each independently denote an alkyl group or alkoxy group having 1 to 6 C atoms; z and m each independently refer to 1 to 6; x means 0, 1, 2 or 3 .

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

f) a liquid crystal medium further comprising one or more fluorinated terphenyls of the formula T-1 to T-21,



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

R preferably denotes methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy, pentyloxy.

The medium according to the invention preferably comprises terphenyls of the formulae T-1 to T-21 in an amount of from 2 to 30% by weight, in particular from 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 denotes an alkyl group (in addition to an alkoxy group) each having 1 to 5 C atoms. In the compound of the formula T-20, R preferably denotes an alkyl or alkenyl group, in particular an alkyl group. In the compound of formula T-21, R preferably denotes an alkyl group.

If the Δn value of the mixture is ≥ 0.1, terphenyl is preferably used in the mixture according to the invention. A preferred mixture comprises from 2 to 20% by weight of one or more biphenyl compounds selected from the group of T-1 to T-21 compounds.

g) a liquid crystal medium additionally comprising one or more biphenyls of the formulae B-1 to B-3,

Wherein alkyl and alkyl* each independently denote a straight-chain alkyl group having 1 to 6 C atoms, and the alkenyl group and the alkenyl group each independently represent a linear olefin having 2 to 6 C atoms base.

The proportion of biphenyl of the formulae B-1 to B-3 in the mixture as a whole is preferably at least 3% by weight, specifically ≥ 5% by weight.

Among the compounds of the formulae B-1 to B-3, the compound of the formula B-2 is particularly preferred.

Especially good biphenyl is

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

h) a liquid crystal medium comprising at least one compound of the formula Z-1 to Z-7,

Wherein R and alkyl have the meanings indicated above.

i) a liquid crystal medium further comprising at least one compound of the formulae O-1 to O-18,



Wherein R ¹ and R ² have the meanings indicated for R ^2A . R ¹ and R ² each preferably independently of each other refer to a linear alkyl or alkenyl group.

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

A preferred medium comprises one or more compounds selected from the group of compounds of formula O-17.

The mixture according to the invention very preferably comprises a compound of the formula O-10, O-12, O-16 and/or O-17, in particular in an amount of from 5% to 30%.

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

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

A very preferred mixture comprises 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 mixture as a whole.

A very preferred mixture comprises 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 mixture as a whole.

A very preferred mixture contains the following three compounds:
.

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

A preferred mixture comprises at least one compound selected from the group of compounds below
,
Wherein R ¹ and R ² have the meanings indicated 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 6 C atoms, respectively, and R ^{2 is} represented by 2 Alkenyl to 6 C 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-17h:


Wherein alkyl refers to an alkyl group having from 1 to 6 C atoms.

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

j) a preferred liquid-crystalline medium according to the invention comprises one or more substances containing tetrahydronaphthyl or naphthyl units, such as, for example, compounds of the formulae N-1 to N-5,

Wherein R ^1N and R ^2N each independently have the meaning indicated for R ^2A , preferably a straight-chain alkyl group, a linear alkoxy group or a linear alkenyl group, and
Z ¹ and Z ² each independently refer to -C ₂ H ₄ -, -CH=CH-, -(CH ₂ ) ₄ -, -(CH ₂ ) ₃ O-, -O(CH ₂ ) ₃ -, -CH=CHCH ₂ CH ₂ -, -CH ₂ CH ₂ CH=CH-, -CH ₂ O-, -OCH ₂ -, -COO-, -OCO-, -C ₂ F ₄ -, -CF=CF- , -CF=CH-, -CH=CF-, -CF ₂ O-, -OCF ₂ -, -CH ₂ - or a single bond.

k) The preferred mixture comprises a difluorodibenzochroman compound of the formula BC, a color of the formula CR, a fluorinated phenanthrene of the formula PH-1 and PH-2, a fluorine of the formula BF-1 and BF-2 One or more compounds of the group of dibenzofurans,

among them
R ^B1 , R ^B2 , R ^CR1 , R ^CR2 , R ¹ and R ² each have the meaning of R ^2A independently of each other. c is 0, 1 or 2, and d refers to 1 or 2. R ¹ and R ² preferably independently of each other refer to an alkyl or alkoxy group having 1 to 6 C atoms. Compounds of formula BF-1 and BF-2 should not be equivalent to one or more compounds of formula I.

The mixture according to the invention preferably comprises a compound of the formula BC, CR, PH-1, PH-2 and/or BF in an amount of from 3 to 20% by weight, in particular from 3 to 15% by weight.

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


Wherein alkyl and alkyl* each independently denote a straight-chain alkyl group having 1 to 6 C atoms, and the alkenyl group and the alkenyl group each independently represent a linear olefin having 2 to 6 C atoms base.

Very preferably one, two or three mixtures of compounds comprising formula BC-2, BF-1 and/or BF-2.

l) a preferred mixture comprising one or more indane compounds of the formula In,

among them
R ¹¹ , R ¹² ,
R ¹³ each independently means, independently of one another, a linear alkyl group, alkoxy group, alkoxyalkyl group or alkenyl group having 1 to 6 C atoms.
R ¹² and R ¹³ additionally denote halogen, preferably F,
Refers to
,
i refers to 0, 1, or 2.

Preferred compounds of the formula In are compounds of the formula In-1 to In-16 as indicated below:

.

Particularly preferred are compounds of the formulas In-1, In-2, In-3 and In-4.

The compounds of the formula In and sub-forms In-1 to In-16 are preferably used in the mixture according to the invention in a concentration of ≥ 5% by weight, in particular 5 to 30% by weight and very preferably 5 to 25% by weight.

m) a preferred mixture additionally comprising one or more compounds of the formulae L-1 to L-11,


,
among them
R, R ¹ and R ² each independently have the meaning as indicated for R ^{2A in} the embodiment 5, and the alkyl group means an alkyl group having 1 to 6 C atoms. s refers to 1 or 2.

It is especially preferred to be a compound of the formula L-1 and L-4, specifically L-4.

The compound of the formulae L-1 to L-11 is preferably used in a concentration of 5 to 50% by weight, specifically 5 to 40% by weight and preferably 10 to 40% by weight.

The preferred mixture concept is indicated below: (The abbreviations used are explained in Table A. Here n and m each independently refer to 1 to 15, preferably 1 to 6).

The mixture according to the invention preferably comprises
- one or more compounds of the formula I, wherein L ¹¹ = L ¹² = F, R ¹ = alkyl and R ^1* = alkoxy;
And/or
-CPY-n-Om, in particular CPY-2-O2, CPY-3-O2 and/or CPY-5-O2, the concentration of which is preferably 5%, in particular 10%, to the mixture as a whole 30%,
And/or
-CY-n-Om, preferably CY-3-O2, CY-3-O4, CY-5-O2 and/or CY-5-O4, the concentration of which is preferably > 5%, as a whole, specific 15% to 50%,
And/or
-CCY-n-Om, preferably CCY-4-O2, CCY-3-O2, CCY-3-O3, CCY-3-O1 and/or CCY-5-O2, the concentration of which is preferably as a mixture of the whole > 5%, specifically 10% to 30%,
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%, as a whole mixture %.

Furthermore, preferred is a mixture according to the invention comprising:
(n and m each independently refer to 1 to 6 respectively.)
a compound of the formula I, preferably a compound of the formulae I-1 to I-3, ie a formula IO-1 to IO-3 and/or IS-1 to IS-3, in particular LB-3-O4 and/or LB ( a compound of S)-4-O3 in a concentration ranging from 1 to 20% by weight, more preferably from 2 to 15% by weight, particularly preferably from 3 to 12% by weight and very preferably from 4 to 11% by weight
- CPY-n-Om and CY-n-Om, the concentration of which is preferably from 10% to 80% in terms of a mixture as a whole,
And/or
- CPY-n-Om and CK-nF, the concentration of which is preferably from 10% to 70% in terms of a mixture as a whole,
And/or
-CPY-n-Om and PY-n-Om, preferably CPY-2-O2 and/or CPY-3-O2 and PY-3-O2, the concentration of which is preferably from 10% to 45% in terms of a mixture as a whole. ,
And/or
- CPY-n-Om and CLY-n-Om, the concentration of which is preferably from 10% to 80% in terms of a mixture as a whole,
And/or
-CCVC-nV, preferably CCVC-3-V, preferably having a concentration of 2% to 10% as a mixture of the whole,
And/or
-CCC-nV, preferably CCC-2-V and/or CCC-3-V, preferably having a concentration of 2% to 10% by weight of the mixture as a whole,
And/or
-CC-VV, the concentration of which is preferably from 5% to 50% in terms of a mixture as a whole.

In a preferred embodiment of the invention, the medium comprises one or more compounds of the formula B-nO-Om and/or (B(S)-nO-Om, in particular the compound B-2O-O5, at a higher concentration Preferably, the range is from 2% to 8%, and the concentration is from 25% to 35% of the compound CC-3-V, and the concentration is from 8% to 12% of the compound CC-3-V1.

The present invention further relates to an electro-optic display having active matrix addressing based on ECB, VA, PS-VA, PA-VA, IPS, PS-IPS, FFS or PS-FFS effects, characterized in that it contains according to claim 1 The liquid crystal medium of one or more of 11 is used as a dielectric.

The liquid crystal medium according to the present invention preferably has a nematic phase of ≤ -20 ° C to ≥ 70 ° C, particularly preferably ≤ -30 ° C to ≥ 80 ° C, and preferably ≤ -40 ° C to ≥ 90 ° C.

The expression "having a nematic phase" means herein that, on the one hand, no smectic phase and crystallization are observed at a lower temperature at a corresponding temperature, and on the other hand, a clear phenomenon does not occur from the nematic phase upon heating. The study at low temperatures was carried out in a flow-type viscometer at the corresponding temperature and was verified by storage in a test unit having a layer thickness corresponding to the electro-optical use for at least 100 hours. If the storage stability at a temperature of -20 ° C in the corresponding test unit is 1000 hours or longer, the medium is said to be stable at this temperature. At -30 ° C and -40 ° C, the corresponding time is 500 h and 250 h. At high temperatures, clear points are measured in the capillary using conventional methods.

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

The value of the birefringence Δn in the liquid crystal mixture is usually between 0.07 and 0.16, preferably between 0.08 and 0.13.

The liquid crystal mixture according to the invention has a Δ ε of -0.5 to -8.0, in particular -2.5 to -6.0, wherein Δ ε denotes dielectric anisotropy. The rotational viscosity γ ₁ at 20 ° C is preferably ≤ 150 mPa·s, specifically ≤ 120 mPa·s.

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

For the present invention, unless specifically indicated otherwise, the term "threshold voltage" system on a capacitive threshold (V _0), also known as Frederick threshold (Freedericks threshold).

Further, the liquid crystal medium according to the present invention has a high voltage holding ratio value in the liquid crystal cell.

In general, liquid crystal media having a low address voltage or a threshold voltage exhibit a lower voltage hold ratio than a liquid crystal medium having a higher address voltage or threshold voltage, and vice versa.

For the purposes of the present invention, the term "dielectric positive compound" refers to a compound having a Δ ε > 1.5, the term "dielectric neutral compound" refers to a compound of -1.5 ≤ Δε ≤ 1.5, and the term "dielectric negative compound" Refers to their compounds of Δε < -1.5. Herein, the dielectric anisotropy of a compound is determined by dissolving 10% of the compound in a liquid crystal host, and measuring the capacitance of the resulting mixture in at least one test cell, the layer thickness of the test cell being in each case 20 μm and surface alignment at 1 kHz with a vertical and a creeping surface. The measurement voltage is typically 0.5 V to 1.0 V, but is always below the capacitance threshold of the individual liquid crystal mixtures studied.

All temperature values indicated for the present invention are in °C.

The mixture according to the invention is suitable for use in all VA-TFT applications such as, for example, VAN, MVA, (S)-PVA, ASV, polymer sustained VA (PSA) and polymer stabilized VA (polymer stabilized VA, PS-VA). It is also applicable to in-plane switching (IPS) and fringe field switching (FFS) applications with negative Δε.

The nematic liquid crystal mixture in the display according to the invention typically comprises two components: A and B, which themselves consist of one or more individual compounds.

Component A has a significant negative dielectric anisotropy and provides a dielectric anisotropy of nematic phase ≤ -0.5. In addition to one or more compounds of formula I, it preferably comprises a compound of formula IIA, IIB and/or IIC, in addition to one or more compounds of formula O-17.

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

For component A, one (or more) individual compounds having a Δε value ≤ -0.8 are preferably selected. It must be that the more negative this value is, the less the ratio A is in the mixture as a whole.

Component B has a nematic clear state, and at 20 ℃, the flow viscosity of not greater than 30 mm ² · s ^-1, preferably not more than 25 mm ² · s ^-1.

A wide variety of suitable materials are known to those skilled in the art from the literature. It is especially preferred to be a compound of formula O-17.

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

Component B is a unimorphic or tautomeric nematic, has no smectic phase and is capable of preventing the appearance of a smectic phase in the liquid crystal mixture when dropped to very low temperatures. For example, if various high nematic materials are added to the smectic liquid crystal mixture, the nematic state of the materials can be compared via the degree of inhibition of the smectic phase achieved.

The mixture may also optionally comprise component C comprising a compound having a dielectric anisotropy of Δε ≥ 1.5. These so-called positive compounds are usually present in the mixture of negative dielectric anisotropies in an amount of ≤ 20% by weight, based on the mixture as a whole.

In addition to one or more compounds of the formula I, the phases preferably comprise from 4 to 15, in particular 5 to 12 and especially preferably <10 compounds of the formula IIA, IIB and/or IIC and optionally one of Or a plurality of 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, the other constituents may, for example, be at most 45%, but preferably at most 35%, in particular at most 35%, in particular at most 10% of the amount exists.

The other component is preferably selected from the group consisting of a nematic or a nematic primordial substance, in particular a known substance selected from the group consisting of azobenzene, benzylidene aniline, biphenyl, terphenyl, benzoic acid. Phenyl ester or cyclohexyl benzoate, phenyl cyclohexanecarboxylate or cyclohexyl cyclohexanecarboxylate, phenylcyclohexane, cyclohexylbiphenyl, cyclohexylcyclohexane, cyclohexylnaphthalene, 1,4-bicyclic Hexylbiphenyl or cyclohexylpyrimidine, phenyldioxane or cyclohexyldioxane, optionally halogenated hydrazine, benzylphenyl ether, diphenylacetylene and substituted cinnamate.

The most important compound suitable as a component of this type of liquid crystal phase can be characterized by the following formula IV
R ²⁰ -LGER ²¹ IV
Wherein L and E each represent a carbocyclic or heterocyclic ring system derived from a group consisting of 1,4-disubstituted benzene rings and cyclohexane rings, 4,4'-disubstituted biphenyls, phenyl rings Hexane and cyclohexylcyclohexane systems, 2,5-disubstituted pyrimidines and 1,3-dioxane rings, 2,6-disubstituted naphthalenes, dihydronaphthalenes and tetrahydronaphthalenes, quinazolines and four Hydroquinazoline,
Or a CC single bond, Q refers to a halogen, preferably refers to chloro or -CN, and R ²⁰ and R ²¹ each represent an alkyl, alkenyl, alkane having up to 18, preferably up to 8 carbon atoms. An oxy, alkoxyalkyl or alkoxycarbonyloxy group, or one of such groups, refers to CN, NC, NO ₂ , NCS, CF ₃ , SF ₅ , OCF ₃ , 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 group or an alkoxy group. Other variations of the proposed substituents are also common. Many such materials or mixtures thereof are also commercially available. All such materials can be prepared by methods known from the literature.

It is self-evident to those skilled in the art that the VA, IPS or FFS mixture according to the invention may also comprise compounds in which, for example, H, N, O, Cl and F are replaced by corresponding isotopes.

Furthermore, polymerizable compounds (so-called reactive mesogens (RM), as disclosed, for example, in US Pat. No. 6,861,107, may be added in a concentration of preferably from 0.01 to 5% by weight, particularly preferably from 0.2 to 2% by weight, based on the mixture. To the mixture according to the invention. Such mixtures may also optionally comprise an initiator, as described, for example, in US 6,781,665. Preferably, an initiator (for example Irganox-1076 from BASF) is added in an amount of from 0% to 1%. A mixture comprising a polymerizable compound. Mixtures of this type can be used in the so-called polymer-stabilized VA mode (PS-VA) or PSA (polymer-supported VA), wherein it is intended to carry out polymerization of reactive liquid crystal primaries in a liquid crystal mixture. The prerequisite is that the liquid crystal compound of the LC main body does not react under the polymerization conditions of the reactive liquid crystal primordium (that is, usually when exposed to UV in the wavelength range of 320 to 360 nm). A liquid crystal compound such as, for example, CC-3-V does not exhibit a reaction (UV polymerization) under polymerization conditions for RM.

The mixture according to the invention may further comprise customary additives such as, for example, stabilizers, antioxidants, UV absorbers, nanoparticles, microparticles and the like.

The structure of a liquid crystal display according to the invention corresponds to a common geometry as described, for example, in EP-A 0 240 379.

The following examples are intended to illustrate the invention without limiting it. Above and below, percentage data refers to weight percent; all temperatures are indicated in degrees Celsius.

Throughout the patent application, the 1,4-cyclohexylene ring and the 1,4-phenylene ring are depicted as follows:
;
.

Unless otherwise specifically mentioned, the cyclohexyl ring is a trans-1,4-extended cyclohexyl ring.

In the entire patent application and working examples, the structure of the liquid crystal compound is indicated by means of an abbreviation. Conversion to the chemical formula was carried out according to Tables 1 to 3 unless otherwise indicated. All groups C _n H2 _n+1 , C _m H _2m+1 and C _{m '} H _{2m ' +1} or C _n H _2n and C _m H _2m are respectively n, m, m' or in each case a linear alkyl group or an alkyl group of z C atoms. n, m, m', z each independently of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, preferably 1, 2, 3, 4, 5 or 6. In Table 1, the ring elements of the respective compounds are encoded, in Table 2, the bridge member is listed, and in Table 3, the meaning of the symbols of the left or right side chain of the compound is indicated.

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 compounds from the compounds mentioned hereinafter in Table A.

Table A
Use the following abbreviation:
(n, m, m', z: each independently of 1, 2, 3, 4, 5 or 6; (O) C _m H _2m+1 means OC _m H _2m+1 or C _m H _{2m+ 1} ))

Liquid crystal mixtures which can be used in accordance with the invention are prepared in a manner known per se. In general, it is preferred to dissolve the components in the required amounts in a relatively small amount in the components constituting the main component at a high temperature. 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 again, for example, by distillation after thorough mixing.

By means of suitable additives, the liquid crystal phase according to the invention can be modified in a manner that can be used in any type of display (e.g., ECB, VAN, IPS, GH or ASM-VA LCD display) that has been disclosed to date.

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

For example, 0% to 15% of a polychromatic dye may be added, and in addition, a conductive salt may be added, preferably 4-hexyloxybenzoic acid ethyldimethyldodecyl ammonium, tetraphenylhydroboration tetra a mis-synthesis salt of butylammonium or a crown ether (see, for example, Haller et al., Mol. Cryst. Liq. Cryst., Vol. 24 , pp. 249-258 (1973)) in order to improve conductivity, or to add substances To change the dielectric anisotropy, viscosity and/or alignment of the nematic phase. Substances of this type are described, for example, in DE-A 22 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 indicates possible dopants that can be added to the mixture according to the invention. If the mixture contains a dopant, it is added in an amount of from 0.01 to 4% by weight, preferably from 0.01 to 3% by weight.

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

Table C
The indication below can be added to the stabilizer, for example a mixture according to the invention, in an amount of from 0 to 10% by weight, preferably from 0.001 to 5% by weight, in particular from 0.001 to 1% by weight.

Working example:
The following examples are intended to illustrate the invention without limiting it. In the examples, mp refers to the melting point (in degrees Celsius) of the liquid crystal material and C refers to the clear point (in degrees Celsius) of the liquid crystal material; the boiling point temperature is denoted by mp. In addition: C refers to the crystalline solid state, S refers to the smectic phase (index refers to the phase type), N refers to the nematic state, Ch refers to the cholesteric liquid crystal phase, I refers to the isotropic phase, T _g refers to Glass transfer temperature. The number between the two symbols indicates the conversion temperature in degrees Celsius.

The host mixture used to determine the optical anisotropy Δn of the compound of formula I is the commercially available mixture ZLI-4792 (Merck KGaA). The dielectric anisotropy Δ ε was determined using a commercially available mixture ZLI-2857. The physical data of the compound to be studied are obtained from the change in the dielectric constant of the host mixture after the addition of the compound to be studied and extrapolation to 100% of the compound used. In general, depending on the solubility, 10% of the compound to be studied is dissolved in the host mixture.

Parts or percentages indicate weight parts by weight or percentage by weight unless otherwise indicated.

Above and below:
V _o refers to the capacitance threshold voltage [V] at 20 ° C,
n _e refers to the anomalous refractive index at 20 ° C and 589 nm,
n _o refers to the ordinary refractive index at 20 ° C and 589 nm,
Δn refers to optical anisotropy at 20 ° C and 589 nm.
ε _⊥ refers to the dielectric permittivity perpendicular to the director at 20 ° C and 1 kHz,
ε _|| refers to the dielectric permittivity parallel to the director at 20 ° C and 1 kHz,
Δε refers to the dielectric anisotropy at 20 ° C and 1 kHz,
Cl.p., T(N,I) refers to the clear point [°C],
γ ₁ refers to the rotational viscosity [mPa·s] measured at 20 ° C, which is measured in a magnetic field by a rotation method.
K ₁ refers to the elastic constant, the "tilt" deformation at 20 ° C [pN],
Refers to an elastic constant K _2, temperature is 20 ℃ at "torsional" modification [pN],
K ₃ refers to the elastic constant, the "bending" deformation at 20 ° C [pN], and
LTS refers to low temperature stability (nematic phase) as determined in a test unit or block as specified.

Unless otherwise expressly indicated, in this application it is directed to, for example, the melting point T(C,N), the transition from the smectic (S) to the nematic (N) phase T(S,N), and the clearing point T(N, All values indicated by the temperature of I) or cl.p. are indicated in degrees Celsius (°C). M.p. indicates the melting point. In addition, Tg = glassy state, C = crystalline state, N = nematic phase, S = smectic phase and I = isotropic phase. The number between these symbols indicates the transfer temperature.

Unless specifically indicated otherwise, the terms of the present invention, "threshold voltage" system on a capacitive threshold (V _0), also known as Frederick threshold. In an example, as commonly used, also indicates the optical threshold for 10% relative contrast (V _10).

The display for measuring the capacitance threshold voltage consists of two plane-parallel glass outer plates with a pitch of 20 μm, each having an electrode layer on the inner side and an unfriction polyimine alignment layer on the top, which causes The vertical edges of the liquid crystal molecules are aligned.

The display or test unit for measuring the tilt angle consists of two plane-parallel glass outer plates with a pitch of 4 μm, each having an electrode layer on the inner side and a polyimine alignment layer on the top, of which two are The quinone imine layers rub against each other in antiparallel and cause vertical edge alignment of the liquid crystal molecules.

Unless otherwise indicated, the VHR was measured in a commercially available instrument model 6254 from TOYO Corporation of Japan at 5 ° C (VHR ₂₀ ) and after 5 minutes in an oven at 100 ° C (VHR ₁₀₀ ). Unless otherwise indicated, the voltage used has a frequency ranging from 1 Hz to 60 Hz.

The accuracy of the VHR measurements depends on the individual VHR values. The accuracy decreases as the value decreases. The deviations observed in the case of values in the various magnitude ranges are compiled in the following table in their order of magnitude.

The stability of UV irradiation was investigated in a commercially available instrument "Suntest CPS" from Heraeus, Germany. Unless otherwise indicated, the sealed test unit will be illuminated for between 30 minutes and 2.0 hours without additional heating. The illumination power in the 300 nm to 800 nm wavelength range is 765 W/m ² V. A UV "cutoff" filter with an edge wavelength of 310 nm is used in order to simulate the so-called glazing mode. In each series of experiments, at least four test cells were studied for each condition, and the individual results were indicated as corresponding to the average of the individual measurements.

The decrease in voltage holding ratio (ΔVHR) usually caused by exposure (for example, by UV irradiation or by LCD backlight) is determined according to the following equation (1):
.

For the study of low temperature stability, also known as "LTS", that is, the stability of the LC mixture against the occurrence of spontaneous crystallization or smectic phase of individual components in the bulk at low temperatures, as the case may be, each containing A number of sealed bottles of about 1 g of material are stored at one or more of a given temperature, typically -10 ° C, -20 ° C, -30 ° C, and / or -40 ° C, and the phase is visually inspected at regular intervals to see if the phase is observed. change. Once the first of the samples shows a change at a given temperature, the time is noted. The time until no change was observed until the last test was indicated as the respective LTS.

The ion density was measured using a commercially available LC material characteristic measurement system model 6254 from Toyo Corporation, Japan, using a VHR test unit (JSR Corp., Japan, having a cell gap of 3.2 μm), and the resistivity was calculated therefrom. . The measurement was carried out 5 minutes after storage in an oven at 60 ° C or 100 ° C.

The so-called "HTP" refers to the optically active or helical torsion force (in μm) of the palm material in the LC medium. Unless otherwise indicated, HTP was measured in a commercially available nematic LC host mixture MLD-6260 (Merck KGaA) at a temperature of 20 °C.

All concentrations in this application are indicated by weight percent, and are meant to be a corresponding mixture (no solvent) as a whole comprising all solid or liquid crystal components, unless explicitly stated otherwise. All physical properties are determined according to "Merck Liquid Crystals, Physical Properties of Liquid Crystals", Status, November 1997, Merck KGaA, Germany, and are applicable to temperatures of 20 ° C unless otherwise expressly indicated.

The following examples of mixtures having negative dielectric anisotropy are particularly suitable for liquid crystal displays having at least one planar alignment layer, such as, for example, IPS and FFS displays, especially UB-FFS (=Super Bright FFS), and are suitable for VA displays.

Mixture examples and comparative examples
The comparative mixture C1 was prepared as follows:

This mixture had a relatively poor response time, but had a VHR value of 95.7% with a preferred VHR value measured at 60 °C at 1 V, 1 Hz.

The comparative mixture C2 was prepared as follows:

This mixture exhibited a modified response time compared to Comparative Example 1, mainly due to its reduced γ ₁ , but exhibited a lower VHR. The VHR measured at 1 Hz and 1 V at 60 ° C was 94.2%.

Mixture M1 was prepared as follows:

Mixture M2 was prepared as follows:

The storage test at deep temperature was performed with the above mixture in a 1 ml glass vial.

This mixture has a preferred VHR and at the same time has an improved response time, primarily due to its preferred (γ ₁ /K ₁ ) value relative to CM1 as compiled in the table below.
Table 1: VHR values
(Note: *All VHR values are measured at 1V, 1 Hz and at 60 °C.)

Mixture M3 was prepared as follows:

The VHR measured at 1 Hz and 1 V at 60 ° C was 94.2%.

Mixture M4 was prepared as follows:

The VHR measured at 1 Hz, 1 V at 60 ° C was 94.3%.

Mixture M5 was prepared as follows:

The VHR measured at 1 Hz, 1 V at 60 ° C was 94.3%.

Mixture M6 was prepared as follows:

The VHR measured at 1 Hz and 1 V at 60 ° C was 93.0%.

Mixture M7 was prepared as follows:

The VHR measured at 1 Hz, 1 V at 60 ° C was 92.9%.

The mixture M8 was prepared as follows:

The VHR measured at 1 Hz, 1 V at 60 ° C was 95.4%.

Mixture M9 was prepared as follows:

The VHR measured at 1 Hz and 1 V at 60 ° C was 93.0%.

These results clearly indicate that the use of B(S)-nO-Om instead of B-nO-Om produces a medium with improved rotational viscosity while VHR does not decrease so much.

In particular, in combination with LB-n-Om and/or LB(S)-n-Om, B(S)-nO-m can be used, and the rotational viscosity of the medium can be reduced even without further sacrificing VHR, which can be maintained. Constant.

Claims (15)

A liquid crystal medium characterized by comprising one or more compounds of formula I, Wherein R ¹¹ and R ¹² each independently refer to H, an alkyl group having 1 to 15 C atoms or an alkoxy group, wherein, in addition, one or more CH ₂ groups of such groups may be O atoms. Directly linked to each other in a manner independently of each other via -C≡C-, -CF ₂ O-, -OCF ₂ -, -CH=CH-, , , -O-, -CO-O-, -O-CO-substitution, and wherein, in addition, one or more H atoms may be replaced by halogen, and A ¹ independently of each other refers to a) 1,4 - cyclohexene or 1,4-cyclohexylene, wherein one or two non-adjacent CH ₂ groups may be replaced by -O- or -S-, b) 1,4-phenylene, one of which Or two CH groups may be substituted by N, c) from the group piperidine-1,4-diyl, 1,4-bicyclo[2.2.2] octyl, naphthalene-2,6-diyl, ten a group of a group of hydrogen naphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, phenanthrene-2,7-diyl and anthracene-2,7-diyl a group wherein the groups a), b) and c) are mono- or polysubstituted by a halogen atom, and Z ¹¹ is referred to each other independently at each occurrence: -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 refer to F, Cl, CF ₃ or CHF ₂ , X ¹ refers to O or S, and a refers to 1 or 2, and a compound selected from the group consisting of Formulas IIA, IIB and IIC a group of one or more compounds, Wherein R ^2A , R ^2B and R ^2C each independently denote H, an unsubstituted alkyl group having up to 15 C atoms, a single or a single alkyl group substituted by CN or CF _{3 ,} or an at least one monosubstituted by halogen, wherein , one or more of the CH ₂ groups in such groups may be such that the O atoms are not directly bonded to each other via -O-, -S-, , -C≡C-, -CF ₂ O-, -OCF ₂ -, -OC-O- or -O-CO-, L ¹ to L ⁴ each independently refer to F or Cl, Z ² and Z ^{2 '} each independently refers to a single bond, -CH ₂ CH ₂ -, -CH=CH-, -CF ₂ O-, -OCF ₂ -, -CH ₂ O-, -OCH ₂ -, -COO-, -OCO-, -C ₂ F ₄ -, -CF=CF-, -CH=CHCH ₂ O-, p means 0, 1 or 2, q means 0 or 1, and v means 1 to 6. The liquid crystal medium of claim 1, wherein the medium comprises one or more compounds selected from the group of compounds of Formulas I-1 to I-3, Wherein the parameter has the meaning as given in claim 1. A liquid crystal medium according to claim 1 or 2, which comprises one or more compounds selected from the group consisting of compounds of formulas IO-1 to IO-3: Wherein the parameters have such meanings as given in claim 1. A liquid crystal medium according to one or more of claims 1 to 3, wherein it comprises one or more compounds selected from the group of compounds of the formula IS-1 to I-SO-3: Wherein the parameters have such meanings as given in claim 1. A liquid crystal medium according to one or more of claims 1 to 4, wherein it comprises one or more compounds of the formula IIA: Wherein the parameters have such meanings as given in claim 1. A liquid crystal medium according to one or more of claims 1 to 5, which additionally comprises one or more compounds of the formula IIB, Wherein the parameters have such meanings as given in claim 1. A liquid crystal medium according to one or more of claims 1 to 6, wherein the medium comprises one or more compounds of the formula IIC, Wherein the parameters have such meanings as given in claim 1. A liquid crystal medium according to one or more of claims 1 to 7, wherein the medium additionally comprises one or more compounds selected from the group consisting of compounds of formulae O-1 to O-18, Wherein R ¹ and R ² each independently have the meaning as indicated for R ^{2A in} claim 6 independently of each other. A liquid crystal medium according to one or more of claims 1 to 8, wherein the medium additionally comprises one or more compounds selected from the group of compounds of the formulae T-1 to T-21, Wherein R denotes a linear alkyl or alkoxy group having 1 to 6 C atoms, and m = 0, 1, 2, 3, 4, 5 or 6 and n means 0, 1, 2, 3 or 4. A liquid crystal medium according to one or more of items 1 to 9, wherein the ratio of the compound of the formula I in the mixture as a whole is from 1 to 40% by weight. A liquid crystal medium according to one or more of claims 1 to 10, wherein the ratio of the compound of the formula IIA to IIC in the medium as a whole is in the range of 10% to 70%. A process for the preparation of a liquid-crystalline medium according to one or more of claims 1 to 11, characterized by one or more compounds of the formula I and one or more compounds selected from the group of compounds of the formulae IIA to IIC and one or more of Compounds are mixed. A use of a liquid crystal medium according to one or more of claims 1 to 11 for use in an electro-optic display. An electro-optic display having active matrix addressing, characterized in that the electro-optic display contains a liquid crystal medium as one or more of claims 1 to 11 as a dielectric. The electro-optic display of claim 14, wherein the electro-optic display is VA, PSA, PA-VA, SS-VA, SA-VA, PS-VA, PALC, IPS, PS-IPS, FFS, UB-FFS, U-IPS Or PS-FFS display.