CN118369399A

CN118369399A - Liquid-crystalline medium

Info

Publication number: CN118369399A
Application number: CN202280059738.8A
Authority: CN
Inventors: 庄敏慈; R·林; 陈泽霖; 周光廷
Original assignee: Merck Patent GmbH
Current assignee: Merck Patent GmbH
Priority date: 2021-09-08
Filing date: 2022-09-06
Publication date: 2024-07-19
Also published as: WO2023036746A1; KR20240055826A; EP4399258A1; TW202328403A

Abstract

The present invention relates to chiral Liquid Crystal (LC) media comprising a) one or more compounds of formula IB) One or more compounds selected from the group consisting of compounds of formulas IIA, IIB, IIC and IID,

Description

Liquid-crystalline medium

Technical Field

The present invention relates to chiral Liquid Crystal (LC) media and the use of said liquid crystal media for optical, electro-optical and electronic purposes, in particular in LC displays, preferably in LC displays for outdoor use.

Background

One type of Liquid Crystal Display (LCD) mode currently in use is the TN ("twisted nematic") mode. However, a disadvantage of TN LCDs is that the contrast ratio has a strong dependence on viewing angle.

In addition, so-called VA (vertical alignment) displays with a wider viewing angle are known. The LC cell of a VA display contains a layer of LC medium between two transparent electrodes, where the LC medium typically has a negative dielectric anisotropy. In the off-state, the molecules of the LC layer are aligned perpendicular to the electrode surface (homeotropically) or have an inclined homeotropic alignment. When a voltage is applied to both electrodes, a realignment of LC molecules parallel to the electrode surfaces occurs.

Also known are so-called IPS ("in-plane switching") displays which contain an LC layer between two substrates, wherein the two electrodes are arranged on only one of the two substrates and preferably have an intermeshed comb structure. When a voltage is applied to the electrodes, an electric field is thereby generated between them, having a significant component parallel to the LC layer. This results in a realignment of LC molecules in the layer plane.

In addition, so-called FFS (fringe field switching) displays have been reported (see inter alia s.h.jung et al, jpn.j.appl.Phys., volume 43, stage 3, 2004,1028) which contain two electrodes on the same substrate, one of which is structured in a comb-like manner and the other of which is unstructured. A strong so-called "fringe field", i.e. a strong electric field close to the edges of the electrodes, is thereby generated, and such an electric field in the whole cartridge has both a strong vertical component as well as a strong horizontal component. FFS displays have little contrast viewing angle dependence. FFS displays typically contain an LC medium with positive dielectric anisotropy, and an alignment layer, typically a polyimide, which provides planar alignment of the molecules of the LC medium.

FFS displays may operate as active matrix or passive matrix displays. In the case of active matrix displays, individual pixels are typically addressed by integrated nonlinear active elements such as transistors (e.g. thin film transistors or "TFTs"), whereas in the case of passive matrix displays individual pixels are typically addressed according to multiplexing methods as known in the art.

Furthermore, FFS displays have been disclosed (see s.h.lee et al, appl.phys.lett.73 (20), 1998, 2882-2883 and s.h.lee et al, liquid Crystals39 (9), 2012, 1141-1148) which have similar electrode designs and layer thicknesses as FFS displays but include layers of LC media with negative dielectric anisotropy instead of LC media with positive dielectric anisotropy. LC media with negative dielectric anisotropy show a more favourable director orientation compared to LC media with positive dielectric anisotropy, which has a less tilted and more twisted orientation, as a result of which these displays have a higher transmittance. The display further comprises an alignment layer, preferably a polyimide provided on at least one substrate, which is in contact with the LC medium and induces planar alignment of LC molecules of the LC medium. These displays are also referred to as "super-bright FFS (UB-FFS)" mode displays. These displays require LC media with high reliability.

In newer types of VA displays, uniform alignment of LC molecules is limited to a plurality of relatively small domains within the LC cell. Disclination (disclination), also known as tilt domain, may exist between these domains. VA displays with tilt domains have greater contrast and viewing angle independence of gray scale (GREY SHADE) relative to conventional VA displays. In addition, this type of display is easier to produce, since no additional electrode surface treatment (e.g. by rubbing) for uniform alignment of molecules in the on-state is required. Alternatively, the preferential direction of the tilt or pretilt angle is controlled by the specific design of the electrodes.

In so-called MVA (multi-domain vertical alignment) displays, this is typically achieved by electrodes with protrusions (protrusion) that lead to local pretilt. The LC molecules are thereby aligned parallel to the electrode surfaces in different directions in different, defined cell areas upon application of a voltage. This achieves a "controlled" switching and prevents the formation of disturbing disclination lines. While this arrangement improves the viewing angle of the display, it results in a reduction in its light transmission. A further improvement of MVA uses protrusions on only one electrode side, while the opposite electrode has slits (slots), which improves light transmission. The slit electrode generates an inhomogeneous electric field in the LC cell upon application of a voltage, meaning that controlled switching is still achieved. To further improve the light transmission, the interval between the slit and the protrusion may be enlarged, but this in turn leads to an extension of the response time. In so-called PVA ("patterned VA") the protrusions are made completely superfluous, as the two electrodes are structured by slits on opposite sides, which results in increased contrast and improved light transmission, but which is technically difficult and makes the display more sensitive to mechanical influences ("tapping" etc.). However, for many applications, such as monitors and especially TV screens, there is a need to shorten the response time of the display and to improve the contrast and brightness (transmittance) of the display.

Another development is the so-called PS ("polymer stabilized") or PSA ("polymer stabilized alignment") displays, for which the term "polymer stabilized" is occasionally also employed. Of these, a small amount (e.g., 0.3 wt.%, typically <1 wt.%) of one or more polymerizable compounds, preferably polymerizable monomer compounds, is added to the LC medium and, after filling the LC medium into the display, is polymerized or crosslinked in situ (typically by UV photopolymerization) while optionally applying a voltage to the electrodes of the display. The polymerization is carried out at a temperature at which the LC medium exhibits a liquid crystal phase, typically at room temperature. The addition of polymerizable mesogenic or liquid crystalline compounds (also referred to as reactive mesogens or "RMs") to LC mixtures has proven particularly suitable.

Meanwhile, the PS (a) principle is being used in various conventional LC display modes. Thus, for example, PS-VA, PS-OCB, PS-IPS, PS-FFS, PS-UB-FFS and PS-TN displays are known. The polymerization of RM takes place in the case of PS-VA and PS-OCB displays, preferably under applied voltage, in the case of PS-IPS displays with or without, preferably without, applied voltage. As can be verified in the test cartridge, the PS (a) method results in a pre-tilt in the cartridge. In the case of PS-VA displays, this pre-tilt has a positive effect on the response time. For PS-VA displays, standard MVA or PVA pixel and electrode layouts may be used. However, in addition, it is also possible to cope with (manage) with only one structured electrode side without protrusions, for example, which significantly simplifies production and at the same time yields a very good contrast and a very good light transmission.

PS-VA displays are described in, for example, EP1 170 626A2, US 6,861,107, US7,169,449, US 2004/0191428 A1, US 2006/0066793 A1 and US 2006/0103804 A1. PS-OCB displays are described, for example, in t. -J-Chen et al, jpn.j.appl.Phys.45, 2006, 2702-2704 and s.h.kim, l. -C-Chien, jpn.j.appl.Phys.43, 2004, 7643-7647. PS-IPS-displays are described, for example, in U.S. Pat. No.3, 6,177,972 and in Appl. Phys. Lett.1999, 75 (21), 3264. PS-TN-displays are described in, for example, optics Express 2004, 12 (7), 1221.

Below the layer formed by phase separation and polymerization RM inducing the pretilt angle described above, PSA displays typically comprise an alignment layer on one or both of the substrates forming the display cell, which alignment layer provides an initial alignment of the LC molecules prior to the polymer stabilization step. The alignment layer is typically applied over the electrodes (where such electrodes are present) such that it contacts the LC medium and induces initial alignment of the LC molecules. The alignment layer may include or consist of: for example, polyimide, which may also be rubbed or may be prepared by a photoalignment method.

Similar to the conventional LC displays described above, PSA displays may operate as either active matrix or passive matrix displays. In the case of active matrix displays, individual pixels are typically addressed by integrated non-linear active elements such as transistors (e.g., thin film transistors ("TFTs")), while in the case of passive matrix displays, addressing is typically performed by multiplexing methods as known in the art.

In particular for monitors and especially TV applications, optimization of the response time of the liquid crystal display and the contrast and brightness (and thus also the transmittance) is continuously required. PSA processes may provide key advantages herein. In particular in the case of PS-VA, PS-IPS and PS-FFS displays, a reduction in response time associated with a measurable pretilt in the test cartridge can be achieved without significant detrimental effects on other parameters.

Another problem observed in the prior art is that the use of conventional LC media in LC displays, including but not limited to PSA-type displays, often results in non-uniformities in the display, especially when the LC media is filled in display cases manufactured using the One Drop Fill (ODF) method. This phenomenon is also referred to as "ODF non-uniformity". It is therefore desirable to provide LC media that result in reduced ODF non-uniformity.

Another problem observed in the prior art is that LC media used in PSA displays, including but not limited to PSA type displays, often exhibit high viscosity and, therefore, high switching times. In order to reduce the viscosity and switching time of LC media, the addition of LC compounds having alkenyl groups has been proposed in the prior art. However, it was observed that LC media containing alkenyl compounds often show reduced reliability and stability, as well as reduced VHR, especially after exposure to UV radiation. This is a considerable disadvantage, especially for use in PSA displays, because photopolymerization of RM in PSA displays is typically carried out by exposure to UV radiation, which can lead to VHR degradation in LC media.

Particularly in view of mobile devices, there is a great need for displays with high transmittance, which enables the use of backlights with lower intensity and thus leads to longer battery life. Alternatively, of course, a display with higher brightness, in particular with improved contrast under ambient light, may be achieved.

Furthermore, there is a great need for PSA displays and LC media and polymerizable compounds for such PSA displays, which enable high specific resistance at the same time as a large operating temperature range, short response times even at low temperatures and low threshold voltages, low pretilt angles, a large number of gray scales, high contrast and wide viewing angles, as well as VHR with high reliability and high values after UV exposure, and in the case of polymerizable compounds, low melting points and high solubility in LC host mixtures. In PSA displays for mobile applications, it is particularly desirable to have a useful LC medium that exhibits low threshold voltages and high birefringence.

It is an object of the present invention to provide novel suitable materials for use in LC media comprising Reactive Mesogens (RM) for PSA displays which do not have the above-mentioned disadvantages or have them to a reduced extent.

In particular, the object of the present invention is an LC medium for PSA displays containing RM which enables the display to have a high transmittance and at the same time a very high specific resistance value, a high VHR value, a high reliability, a low threshold voltage, a short response time, a high birefringence, a good UV absorption especially at longer wavelengths, a rapid and complete polymerization of the RM, a low pretilt angle which is allowed to occur (preferably as fast as possible), a high stability of the pretilt even after a longer time and/or after UV exposure, a reduction or prevention of the occurrence of "image sticking" and "ODF inhomogeneities" in the display and, in the case of RM, a polymerization as fast and complete as possible and a high solubility in LC media which are usually used as host mixtures in PSA displays.

Recently, it has also been suggested to use VA or PSA displays, such as PID (public information display), in outdoor applications. PID is one of the emerging paradigms of the display market. More and more PIDs are used to display various types of information in public areas such as train stations, streets, airports, hotels, and malls.

PID are special compared to conventional LC displays for TV or IT applications, since they are usually installed outdoors. Thus, the PID should have a higher persistence to continue to operate under various environmental conditions and should have a wider operating temperature range than conventional LC displays. Thus, the LC medium for PID should have a broad LC phase and a very high Tni value (phase transition temperature from nematic to isotropic phase, also referred to as "clearing temperature" or "clearing point"), which should preferably be 100 ℃ or higher.

However, LC media that have been proposed so far for VA or PSA displays typically have Tni values below 100 ℃.

Accordingly, there remains a great need for LC media optionally comprising polymerizable compounds for PSA displays as well as for VA or PSA displays, in particular for outdoor use, which do not show the above-mentioned drawbacks, or show them only to a lesser extent, and which have improved properties.

Disclosure of Invention

According to the present application, these objects are achieved by the materials and methods described in the present application. In particular, it has surprisingly been found that the use of a liquid crystal body as described below allows to achieve the advantageous effects as described above. These hosts are characterized by the inclusion of an optically active ingredient, also known as chiral dopants.

The invention relates to LC media comprising a) one or more compounds of formula I

Wherein the method comprises the steps of

Ar represents an aromatic or heteroaromatic hydrocarbon group having 4 to 40C atoms, preferably 6 to 30C atoms;

sp represents a spacer group;

R ^S represents H, an alkyl group having 1 to 12C atoms or an alkenyl group having 2 to 12 carbon atoms;

Z ^S represents-O-, -C (O) O-, - (CH ₂)_z -or- (CH ₂)_z O-, or single bond);

HA representation

R ^H represents H, O ^·,CH₃, OH OR OR ^S, preferably H OR O ^·;

R ^S1,R^S2,R^S3 and R ^S4, identical or different, represent an alkyl group having 1 to 6C atoms, preferably having 1 to 3C atoms, very preferably CH ₃;

G represents H or R ^S or the group Z ^S -HA;

z is an integer from 1 to 6, and

Q is 3 or 4;

And b) one or more compounds selected from the group consisting of compounds of formulas IIA, IIB, IIC and IID,

Wherein the method comprises the steps of

R ^2A,R^2B,R^2C and R ^2D each independently of one another represent H, alkyl or alkenyl having up to 15C atoms which is unsubstituted, monosubstituted by CN or CF ₃ or at least monosubstituted by halogen, where 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 linked to one another,

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

Y represents H, F, cl, CF ₃,CHF₂ or CH ₃, preferably H or methyl, very preferably H,

Z ²,Z^2B and Z ^2D each independently of one another represent a single bond ,-CH₂CH₂-,-CH＝CH-,-CF₂O-,-OCF₂-,-CH₂O-,-OCH₂-,-COO-,-OCO-,-C₂F₄-,-CF＝CF- or-ch=chch ₂ O-,

P represents a group selected from 0,1 or 2,

Q represents 0 or 1, and

V represents an integer 1,2,3,4,5 or 6;

And c) one or more chiral dopants;

and d) optionally one or more polymerizable compounds of formula R:

P-Sp-A¹-(Z¹-A²)_z-R R

Wherein each group, independently of the others and identically or differently at each occurrence, has the following meanings:

p is a polymerizable group and is preferably a polymerizable group,

Sp is a spacer group or a single bond,

A ¹,A² is an aromatic, heteroaromatic, cycloaliphatic or heterocyclic radical, preferably having from 4 to 25 ring atoms, which may also comprise fused rings and is unsubstituted, monosubstituted or polysubstituted by L,

Z ¹ is -O-,-S-,-CO-,-CO-O-,-O-CO-,-O-CO-O-,-OCH₂-,-CH₂O-,-SCH₂-,-CH₂S-,-CF₂O-,-OCF₂-,-CF₂S-,-SCF₂-,-(CH₂)_n1-,-CF₂CH₂-,-CH₂CF₂-,-(CF₂)_n1-,-CH＝CH-,-CF＝CF-,-CH＝CF-,-CF＝CH-,-C≡C-,-CH＝CH-CO-O-,-O-CO-CH＝CH-,-CH₂-CH₂-CO-O-,-O-CO-CH₂-CH₂-,-CR⁰R⁰⁰-, or a single bond,

R ⁰、R⁰⁰ is H or alkyl having 1 to 12C atoms,

R is H, L or P-Sp-,

L is F, cl, -CN, P-Sp-, or a linear, branched or cyclic alkyl having 1 to 25C atoms, wherein one or more non-adjacent CH ₂ groups are optionally replaced by-O-, -S-, -CO-O-, O-CO-, -O-CO-O-is replaced in such a way that the O-and/or S-atoms are not directly connected to one another, and wherein one or more H atoms are each optionally replaced by P-Sp-, F or Cl,

Z is 0, 1,2 or 3,

N1 is1, 2,3 or 4.

The invention also relates to an LC display comprising an LC medium as described above.

The invention also relates to an LC medium or LC display as described above, wherein the compound of formula R is polymerized.

The invention also relates to a process for preparing an LC medium as described above and below, comprising the step of mixing one or more compounds of formula IIA, IIB, IIC and/or IID with one or more chiral dopants and one or more compounds of formula I, and optionally with one or more compounds of formula R, and optionally with other LC compounds and/or additives.

The invention also relates to the use of the LC medium according to the invention in PSA displays, in particular PSA displays containing LC media, for producing tilt angles in LC media by polymerizing the compounds of formula R in situ in the PSA display, preferably in an electric or magnetic field.

The invention also relates to LC displays, in particular VA or PSA displays, particularly preferably VA or PS-VA displays, comprising an LC medium according to the invention.

The invention also relates to the use of the LC medium according to the invention in a polymer stabilized SA-VA display, and to a polymer stabilized SA-VA display comprising the LC medium according to the invention.

The invention also relates to a VA or PSA type LC display comprising two substrates, at least one of which is transparent to light, an electrode provided on each substrate or only two electrodes provided on one of the substrates, and an LC medium layer between the substrates optionally comprising one or more polymerisable compounds and an LC component as described above and below, wherein the polymerisable compounds polymerise between the substrates of the display.

The invention also relates to a method of manufacturing an LC display as described above and below, comprising the steps of: an LC medium is filled or otherwise provided between the substrates of the display, optionally including one or more polymerizable compounds as described above and below, and optionally polymerizing the polymerizable compounds.

The PSA display according to the invention has two electrodes, preferably in the form of transparent layers, which are applied to one or both substrates. In some displays, such as PS-VA displays, one electrode is applied to each of the two substrates.

In a preferred embodiment, the polymerisable component polymerizes in the LC display with simultaneous application of a voltage to the electrodes of the display.

The polymerizable compound of the polymerizable component is preferably polymerized by photopolymerization, and very preferably polymerized by UV photopolymerization.

In the liquid crystal field, it is basically known to add chiral dopants to, for example, nematic liquid crystal host mixtures. At low concentrations of chiral dopants, chiral nematic phases, also known as cholesteric phases, can be obtained. In the field of twisted nematic liquid crystal displays, it is necessary to add dopants to achieve a uniform twist direction, so as to avoid disclination lines. The increased concentration is used to achieve the shorter pitch required for example in a super twisted LCD (STN display).

Surprisingly it was found that the use of the liquid crystal hosts according to the invention and LC media comprising them in VA or PS-VA displays enables the displays to have improved transmittance while maintaining excellent properties with respect to process related parameters, i.e. fast and complete UV photopolymerization in the case of PSA displays (especially at longer UV wavelengths in the range of 300-380nm, especially above 320nm, even without the addition of photoinitiators), fast generation of large and stable pretilt angles, reduced image sticking and ODF inhomogeneities in the display, high reliability and high VHR values after UV photopolymerization (especially in the case of LC host mixtures containing LC compounds with alkenyl groups), and generally fast response times, low threshold voltages and high birefringence, and high reliability when exposed to the environment when used outdoors.

When used in VA displays, the LC medium according to the invention shows the following advantageous properties:

An improved transmittance of the display device is provided,

A high-definition temperature at which the light-off temperature,

A high voltage holding rate and a high voltage holding rate,

A fast-switching-over of the switching-over,

A good stability of the inclination,

Sufficient heat and/or UV stability, especially when used outdoors.

When used in PSA displays, LC media according to the invention exhibit the following advantageous properties:

An improved transmittance of the display device is provided,

A high-definition temperature at which the light-off temperature,

A suitable tilt within a specific process window,

Rapid polymerization results in minimal residual RM after UV process,

High voltage retention after UV process,

A good stability of the inclination,

Sufficient heat resistance and/or UV stability, especially when used outdoors,

Fast switching.

In formula I, aryl represents an aromatic or heteroaromatic hydrocarbon radical having 4 to 40C atoms, including one, two, three or four aromatic rings comprising condensed rings which may be directly linked or linked by alkylene linking groups having 1 to 12 carbon atoms, wherein one or more H atoms are optionally replaced by alkyl or alkoxy groups having 1 to 6C atoms or alkenyl groups having 2 to 6 carbon atoms, or are optionally replaced by CN, CF ₃ or halogen, and wherein one or more CH ₂ groups may each be replaced independently of one another by-O-, -S-, -NH-, -N (C ₁-C₄ -alkyl) -, -CO-O-, -O-CO-, -ch=ch-, or-c≡c-, in such a way that O or S atoms are not directly linked to one another.

Preferred aryl groups are benzene, naphthalene, anthracene, biphenyl, m-terphenyl, p-terphenyl and (phenylalkyl) benzene, wherein the alkyl group is a straight chain alkyl group having 1 to 12C atoms.

Compounds of formula I are described in EP3354710A1 and EP3354709A 1. The compound of formula I is preferably selected from the group consisting of compounds of formulas I-1, I-2 and I-3:

wherein R ^H has the meaning given above and preferably denotes H or O ^·, and

N is an integer from 0 to 12, preferably 5, 6, 7, 8 or 9, very preferably 7, and

Sp represents a spacer group, preferably an alkylene group having 1 to 12C atoms, wherein one or more non-adjacent-CH ₂ -groups may be replaced by-O-.

Preferred compounds of formula I-1 are selected from compounds of formula I-1-1:

Wherein R ^H has the meaning given above and preferably denotes H or O ^·, and n is an integer from 0 to 12, preferably 5,6,7,8 or 9, very preferably 7.

Preferred compounds of formula I-2 are selected from compounds of formula I-2-1:

Wherein R ^H has the meaning given above and preferably represents H or O ^·, and n2, identically or differently at each occurrence, preferably identically is an integer from 1 to 12, preferably 2,3,4,5, or 6, very preferably 3, and R ^S, identically or differently at each occurrence, preferably identically represents an alkyl group having from 1 to 6C atoms, preferably n-butyl.

Preferred compounds of formula I-3 are selected from compounds of formula I-3-1:

Preferably, the medium according to the invention comprises a compound selected from the group consisting of compounds of formulae ST-1 to ST-18:

Wherein the method comprises the steps of

R ^ST represents H, alkyl or alkoxy having 1 to 15C atoms, wherein, in addition, one or more CH ₂ groups of these radicals may 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,

At each occurrence, identically or differently, represent

Z ^ST each independently of the other 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,

L ¹ and L ² each independently of one another represent F, cl, CH ₃,CF₃ or CHF ₂,

P represents a group selected from 0,1 or 2,

Q represents 1,2,3,4,5,6,7,8,9 or 10.

Of the compounds of formula ST, particular preference is given to compounds of formula ST-3, and in particular:

Where n=1, 2,3,4,5,6 or 7, preferably n=3

Wherein n=1, 2,3,4,5,6 or 7, preferably n=1 or 7

In the compounds of the formulae ST-3a and ST-3b, n preferably denotes 3. In the compounds of the formula ST-2a, n preferably represents 7.

Very particularly preferred mixtures according to the invention comprise one or more stabilizers selected from the group consisting of the compounds of the formulae ST-2a-1, ST-3b-1, ST-8-1, ST-9-1 and ST-12:

The compounds of the formulae ST-1 to ST-18 are preferably each present in the liquid-crystal mixtures according to the invention in an amount of from 0.005 to 0.5%, based on the mixture.

If the mixture according to the invention comprises two or more compounds of the formulae ST-1 to ST-18, the concentration increases accordingly to 0.01 to 1% in the case of the two compounds, based on the mixture.

However, the total proportion of the compounds of the formulae ST-1 to ST-18 should not exceed 2%, based on the mixture according to the invention.

The use of chiral dopants in nematic liquid crystals is known to the person skilled in the art. For an overview, please see, e.g. A.Taugerbeck,Ch.Booth,2013.Design and Synthesis of Chiral Nematic Liquid Crystals.Handbook of Liquid Crystals.3:III:14:1-63.

The medium according to the invention comprises one or more chiral dopants. Preferably, the absolute value of the Helical Twisting Power (HTP) of these chiral dopants is in the range of 1 μm ^-1 to 150 μm ^-1, preferably in the range of 10 μm ^-1 to 100 μm ^-1. Where the medium comprises two or more chiral dopants, these may have opposite signs of their HTP values. For some embodiments, this condition is preferred because it allows to compensate to some extent the chirality of the corresponding compound and, therefore, can be used to compensate various temperature dependent properties of the resulting medium in the device. However, in general, it is preferred that most, preferably all, of the chiral compounds present in the medium according to the invention have HTP values of their same sign.

Preferably, the chiral dopants present in the medium according to the application are mesogenic compounds and most preferably they themselves exhibit a mesogenic phase.

In a preferred embodiment of the invention, the chiral component D) consists of two or more chiral compounds which all have the same algebraic sign of HTP.

The temperature dependence of the HTP of the respective compounds may be high or low. The temperature dependence of the pitch of the medium can be compensated by mixing compounds having different temperature dependence of the HTP in respective ratios.

For optically active components, a variety of chiral dopants are available to those skilled in the art, some of which are commercially available, for example, cholesteryl pelargonate, R-and S-811, R-and S-1011, R-and S-2011, R-and S-3011, R-and S-4011, B (OC) 2 C.times.H-C-3 or CB15 (all from MERCK KGAA, darmstadt).

Particularly suitable dopants are compounds containing one or more chiral groups and one or more mesogenic groups, or one or more aromatic or cycloaliphatic groups which form mesogenic groups with the chiral groups.

Suitable chiral groups are, for example, chiral branched hydrocarbon groups, chiral ethylene glycol, binaphthol or dioxolane, and also monovalent or polyvalent chiral groups selected from the group consisting of: sugar derivatives, sugar alcohols, sugar acids, lactic acids, chiral substituted diols, steroid derivatives, terpenoid derivatives, amino acids or sequences of several (preferably 1 to 5) amino acids.

Preferred chiral groups are sugar derivatives such as glucose, mannose, galactose, fructose, arabinose and dextrose; sugar alcohols, for example sorbitol, mannitol, iditol, galactitol or dehydrated derivatives thereof, in particular dianhydrohexitols, such as dianhydrosorbitol (1, 4:3, 6-dianhydro-D-sorbitol, isosorbide), dianhydromannitol (isosorbide) or dianhydroiditol (isoiditol); sugar acids, such as, for example, gluconic acid, gulonic acid, and ketogulonic acid; a chiral substituted diol group, for example mono-or oligoethylene glycol or propylene glycol, in which one or more CH ₂ groups are substituted by alkyl or alkoxy groups; amino acids, for example alanine, valine, phenylglycine or phenylalanine or a sequence of 1 to 5 of these amino acids; steroid derivatives, such as, for example, cholesteryl or cholic acid groups; terpene derivatives, for example, menthyl, neomenthyl, camphene (campheyl), pinenyl (pineyl), terpinen (terpineyl), isolongifolia (isolongifolyl), fenchyl, methylene dichloride (carreyl), myrtenyl (myrthenyl), nopyl (nopyl), geranyl (geraniyl), linalool (linaloyl), neryl (neryl), citronellyl (citronellyl) or dihydrocitronellyl.

The optically active component D) preferably consists of chiral dopants, which are selected from the group of known chiral dopants. Suitable chiral groups and mesogenic chiral compounds are described, for example, in DE 34 25 503,DE 35 34 777,DE 35 34 778,DE 35 34 779 and DE 35 34 780,DE 43 42 280,EP 01 038 941 and DE 195 41 820. Examples are also the compounds listed in table B below.

The chiral compounds preferably used according to the invention are selected from the formulae shown below.

Chiral dopants selected from the following compounds of the formulae A-I to A-III and Ch are particularly preferred:

Chiral dopants selected from the following compounds of the formulae A-I to A-III and A-Ch are particularly preferred:

Wherein the method comprises the steps of

R ^a11、R^a12 and R ^b12 independently of one another represent alkyl having 1 to 15C atoms, where, in addition, one or more non-adjacent CH ₂ groups can each be replaced independently of one another by-C (R ^z)＝C(R^z) -, -C.ident.C-, -O-, -S-, -CO-, -CO-O-, -O-CO-or-O-CO-O-is replaced in such a way that O and/or S atoms are not directly linked to each other, and wherein, in addition, one or more H atoms may each be replaced by F, cl, br, I or CN, preferably alkyl, more preferably n-alkyl, provided that R ^a12 is different from R ^b12,

R ^a21 and R ^a22 independently of one another represent alkyl having 1 to 15C atoms, where, in addition, one or more non-adjacent CH ₂ groups can each be replaced independently of one another by-C (R ^z)＝C(R^z) -, -C.ident.C-, -O-, -S-, -CO-, -CO-O-, -O-CO-or-O-CO-O-is replaced in such a way that O and/or S atoms are not directly linked to each other, and wherein, in addition, one or more H atoms may be replaced by F, cl, br, I or CN, preferably both are alkyl groups, more preferably n-alkyl groups,

R ^a31、R^a32 and R ^b32 independently of one another represent straight-chain and branched alkyl having 1 to 15C atoms, where, in addition, one or more non-adjacent CH ₂ groups can each be replaced independently of one another by-C (R ^z)＝C(R^z) -, -C.ident.C-, -O-, -S-, -CO-, -CO-O-, -O-CO-or-O-CO-O-is replaced in such a way that O and/or S atoms are not directly linked to each other, and wherein, in addition, one or more H atoms may be replaced by F, cl, br, I or CN, preferably alkyl, more preferably n-alkyl, provided that R ^a32 is different from R ^b32,

R ^z represents H, CH ₃, F, cl or CN, preferably H or F,

R ⁸ has one of the meanings given above for R ^a11, preferably alkyl, more preferably n-alkyl having 1 to 15C atoms,

Z ⁸ represents-C (O) O-, CH ₂O,CF₂ O or a single bond, preferably-C (O) O-,

As defined in A ¹² below, or alternatively represent

Representation of

Preferably

Wherein L ¹² in each case independently of one another represents halogen, CN, or alkyl, alkenyl, alkoxy or alkenyloxy having up to 12C atoms and wherein one or more H atoms are optionally replaced by halogen, preferably methyl, ethyl, cl or F, particularly preferably F,

Representation of

With a target ofThe meaning of the terms is given in,

With a target ofGiven meaning, or alternatively, represent

With a target ofThe meaning of the terms is given in,

N2 is, identically or differently, at each occurrence, 0, 1 or 2,

N3 is 1,2 or 3, and

R is 0, 1,2, 3 or 4.

Particularly preferred are dopants selected from the group consisting of compounds of the formula:

Wherein the method comprises the steps of

M is the same or different at each occurrence an integer from 1 to 9, and

N is an integer from 2 to 9, identically or differently, at each occurrence.

Particularly preferred compounds of formula A are compounds of formulae A-III.

Further preferred dopants are derivatives of isosorbide, isomannide or isoidide of the following formulae A-IV:

Wherein the radicals are Is that

(Dianhydrosorbitol),

(Dianhydromannitol), or

(Dianhydroiditol),

Preferably it is di-sorbitan which,

And chiral glycols, such as diphenylethylene glycol (hydrobenzoin), in particular mesogenic hydrobenzoin derivatives of the following formulae a to V:

including the (S, S) enantiomer not shown,

Wherein the method comprises the steps ofEach independently of the others is 1, 4-phenylene (which may also be mono-, di-or trisubstituted by L) or 1, 4-cyclohexylene,

L is H, F, cl, CN or an optionally halogenated alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl or alkoxycarbonyloxy group having 1 to 7 carbon atoms,

C is either 0 or 1 and,

X is CH ₂ or-C (O) -,

Z ⁰ is-COO-, -OCO-, -CH ₂CH₂ -, or a single bond, and

R ⁰ is alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl or alkylcarbonyloxy having 1 to 12 carbon atoms.

Examples of compounds of formula IV are:

Compounds of the formulae A to IV are described in WO 98/00428. Compounds of the formulase:Sub>A A-V are described in GB-A-2,328,207.

Very particularly preferred dopants are chiral binaphthyl derivatives as described in WO 02/94805, chiral binaphthol acetal derivatives as described in WO 02/34739, chiral TADDOL derivatives as described in WO 02/06265, and chiral dopants having at least one fluorinated bridging group and a terminal or central chiral group as described in WO 02/06196 and WO 02/06195.

Chiral compounds of the formulae A to VI are particularly preferred

Wherein the method comprises the steps of

X ¹、X²、Y¹ and Y ² are each, independently of one another, F, cl, br, I, CN, SCN, SF ₅, straight-chain or branched alkyl having from 1 to 25 carbon atoms, which is unsubstituted or monosubstituted or polysubstituted by F, cl, br, I or CN, and wherein, furthermore, one or more non-adjacent CH ₂ groups may each independently be represented by-O-, -S-, -NH-, NR ^x -, -CO-, -COO-, -OCO-, -OCOO-, -S-CO-, -CO-S-, -CH=CH-, or-C≡C-, respectively, alternatively O and/or S atoms are not directly bonded to each other, a polymerizable group, or a cycloalkyl or aryl group having up to 20 carbon atoms, which may optionally be monosubstituted or polysubstituted by halogen (preferably F) or a polymerizable group,

X ¹ and x ² are each, independently of one another, 0, 1 or 2,

Y ¹ and y ² are each, independently of one another, 0, 1,2, 3 or 4,

B ¹ and B ² are each, independently of one another, an aromatic or partially or fully saturated aliphatic six-membered ring in which one or more CH groups can each be replaced by N and one or more non-adjacent CH ₂ groups can each be replaced by O or S,

W ¹ and W ² are each independently of the other-Z ¹-A¹-(Z²-A²)_m -R, and either is instead R ¹ or A ³, but not both are H, or

Is that

U ¹ and U ² are each, independently of one another, CH ₂, O, S, CO or CS,

V ¹ and V ² are each, independently of one another, (CH ₂)_n, where one to four nonadjacent CH ₂ groups may each be replaced by O or S, and one of V ¹ and V ² is a single bond, and inIs thatIn which case V ¹ and V ² are both single bonds,

N is 1, 2 or 3,

Z ¹ and Z ² are each, independently of one another, -O-、-S-、-CO-、-COO-、-OCO-、-O-COO-、-CO-NR^x-、-NR^x-CO-、-O-CH₂-、-CH₂-O-、-S-CH₂-、-CH₂-S-、-CF₂-O-、-O-CF₂-、-CF₂-S-、-S-CF₂-、-CH₂-CH₂-、-CF₂-CH₂-、-CH₂-CF₂-、-CF₂-CF₂-、-CH＝N-、-N＝CH-、-N＝N-、-CH＝CH-、-CF＝CH-、-CH＝CF-、-CF＝CF- or-C.ident.C-or a combination of two of these groups, wherein no two O and/or S and/or N atoms are directly bonded to each other, preferably-ch=ch-COO-, or-COO-ch=ch-, or a single bond,

R ^x represents an alkyl group having 1 to 6C atoms,

A ¹、A² and A ³ are each, independently of one another, 1, 4-phenylene, in which one or two non-adjacent CH groups may each be replaced by N, 1, 4-cyclohexylene, in which one or two non-adjacent CH ₂ groups may each be replaced by O or S, 1, 3-dioxolan-4, 5-diyl, 1, 4-cyclohexenylene, 1, 4-bicyclo [2.2.2] octylene, piperidine-1, 4-diyl, naphthylene-2, 6-diyl, decalin-2, 6-diyl or 1,2,3, 4-tetrahydronaphthalene-2, 6-diyl, in which each of these groups may be monosubstituted or polysubstituted by L and furthermore A ¹ may be a single bond,

L is a halogen atom, preferably F, CN, NO ₂, alkyl having 1 to 7 carbon atoms, alkoxy, alkylcarbonyl, alkoxycarbonyl or alkoxycarbonyloxy, wherein one or more H atoms may each be replaced by F or Cl,

M is independently in each occurrence 0, 1,2 or 3, and

R and R ¹ are each, independently of one another, H, F, cl, br, I, CN, SCN, SF ₅, straight-chain or branched alkyl having in each case 1 or 3 to 25 carbon atoms, which may optionally be monosubstituted or polysubstituted by F, cl, br, I or CN, and wherein one or more non-adjacent CH ₂ groups may each be interrupted by-O-, -S-, -NH-, -NR ^x -, -CO-, -COO-, -OCO-, -O-COO-, -S-CO-, -CO-S-, -CH=CH-, or-C≡C-, wherein no two O and/or S atoms are directly bonded to each other, or a polymerizable group.

Chiral binaphthyl derivatives of the formula A-VI-1 are particularly preferred

Wherein ring B and Z ⁰ have the meanings defined for formulae A-IV and A-V, R ⁰ represents alkyl having 1 to 7C atoms, and B is 0,1 or 2,

In particular those selected from the following formulae A-VI-1a to A-VI-1 c:

wherein R ⁰ and Z ⁰ have the meanings defined for the formula A-VI-1, and preferably R ⁰ represents H or alkyl having 2 to 5 carbon atoms, and

Z ⁰ is in particular-OC (O) -or a single bond.

The concentration of the one or more chiral dopants in the LC medium is preferably in the range of 0.001% to 20%, preferably 0.05% to 5%, more preferably 0.1% to 2%, and most preferably 0.5% to 1.5%. These preferred concentration ranges are particularly applicable to chiral dopants S-4011 or R-4011 (both from MERCK KGAA) and chiral dopants having the same or similar HTPs. For chiral dopants with higher or lower absolute HTP values than S-4011, these preferred concentrations must be reduced or increased proportionally according to their ratio of HTP values relative to the HTP value of S-4011.

The pitch p of the LC medium or host mixture according to the invention is preferably in the range from 5 to 50 μm, more preferably from 8 to 30 μm and particularly preferably from 10 to 20 μm.

The cell gap d, or the thickness of the LC layer, of the display according to the invention is preferably in the range of 2 μm to 10 μm, more preferably 3 μm to 5 μm. Based on this, according to the present invention, the preferred range of the ratio d/p between the cell gap d and the chiral pitch p is set to 0.04 to 2, preferably 0.1 to 1, and very preferably 0.2 to 0.3.

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

Wherein parameter a represents 1 or 2, alkyl and alkyl each independently of the others represent a linear alkyl group having 1 to 6C atoms, and alkinyl represents a linear or branched alkenyl group having 2 to 6C atoms, and (O) represents an oxygen atom or a single bond. The alkinyl preferably represents CH₂＝CH-,CH₂＝CHCH₂CH₂-,CH₃-CH＝CH-,CH₃-CH₂-CH＝CH-,CH₃-(CH₂)₂-CH＝CH-,CH₃-(CH₂)₃-CH＝CH- or CH ₃-CH＝CH-(CH₂)₂ -.

Highly preferred compounds of formula IID are selected from the following subformulae:

highly preferred compounds of formula I are compounds I-1 to I-14.

In a preferred embodiment, the medium comprises one or more compounds of the formula IID-10a

Wherein the radicals and parameters present have the meanings given above under formula IID, and

R ² representsWhere r is 0,1,2,3,4,5 or 6 and s is 1,2 or 3.

Preferred compounds of formula IID-10a are compounds IID-10a-1 to IID-10a-14.

Particularly preferred mixtures of the invention include one or more compounds of the formulae IIA-2, IIA-8, IIA-10, IIA-16, IIA-18, IIA-40, IIA-41, IIA-42, IIA-43, IIB-2, IIB-10, IIB-16, IIC-1, IID-4 and IID-10.

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

Wherein alkyl and alkyl have the above meaning, the preferred amount is 0.5 to 5 wt%, especially 1 to 3 wt%.

In particular, the medium comprises one or more compounds of formula IIA-2 selected from the following subformulae:

or preferably, in addition to the compounds of formulae IIA-2-1 to IIA-2-5, the medium comprises one or more compounds of formulae IIA-2a-1 to IIA-2 a-5:

In particular, the medium comprises one or more compounds of formula IIA-10 selected from the following subformulae:

Or preferably, the medium comprises, in addition to the compounds of formulae IIA-10-1 to IIA-10-5, one or more compounds of formulae IIA-10a-1 to IIA-10 a-5:

In particular, the medium comprises one or more compounds of formula IIB-10 selected from the following subformulae:

or preferably, the medium comprises, in addition to the compounds of the formulae IIB-10-1 to IIB-10-5, one or more compounds of the formulae IIB-10a-1 to IIB-10 a-5:

The medium according to the invention optionally comprises one or more compounds of formula III

Wherein the method comprises the steps of

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

C) A group selected from: spiro [3.3] heptane-2, 6-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,

N represents 0,1 or 2, preferably 0 or 1,

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 denote F, cl, CF ₃ or CHF ₂, preferably H or F, most preferably F, and

W represents O or S.

The compound of formula III is preferably selected from the group consisting of compounds of formulas III-1 and/or III-2

Wherein the radicals present have the same meanings as given in the above formula III, and are preferably

R ¹¹ and R ¹² are each, independently of one another, alkyl, alkenyl or alkoxy having up to 15C atoms, more preferably one or both of them represent alkoxy, and

L ¹¹ and L ¹² each preferably represent F.

Preferably, the compound of formula III-1 is selected from the group consisting of compounds of formulas III-1-1 to III-1-11, preferably formula III-1-6

Wherein the method comprises the steps of

Each of alkyl and alkyl independently of the other represents a linear alkyl group having 1 to 6C atoms, each of alkinyl and alkinyl independently of the other represents a linear alkenyl group having 2 to 6C atoms, each of alkoxy and alkoxy independently of the other represents a linear alkoxy group having 1 to 6C atoms, and L ¹¹ and L ¹² each independently of the other represent F or Cl, preferably both F.

The compound of formula III-2 is preferably selected from the group consisting of compounds of formulas III-2-1 to III-2-10, preferably formula III-2-6,

Wherein the method comprises the steps of

Each of alkyl and alkyl independently of the other represents a linear alkyl group having 1 to 6C atoms, each of alkinyl and alkinyl independently of the other represents a linear alkenyl group having 2 to 6C atoms, each of alkoxy and alkoxy independently of the other represents a linear alkoxy group having 1 to 6C atoms, and L ¹ and L ² each independently of the other represent F or Cl, preferably both F.

Optionally, the medium comprises one or more compounds of formula IIIA-1 and/or IIIA-2

Wherein L ¹¹ and L ¹² have the same meaning as given under formula III, (O) represents O or a single bond,

R ^IIIA represents an alkyl or alkenyl group having up to 7C atoms or a group Cy-C _mH_2m+1 -,

M and n are identical or different and are 0,1,2,3,4,5 or 6, preferably 1,2 or 3, very preferably 1,

Cy represents a cycloaliphatic group having 3, 4 or 5 ring atoms, optionally substituted with: an alkyl or alkenyl group each having up to 3C atoms, or halogen or CN, and preferably represents cyclopropyl, cyclobutyl or cyclopentyl.

The compounds of formula IIIA-1 and/or IIIA-2 may alternatively or in addition to the compound of formula III, preferably additionally be included in the medium.

Highly preferred compounds of formulae IIIA-1 and IIIA-2 are as follows:

Wherein alkoxy represents a linear alkoxy group having 1 to 6C atoms or alternatively- (CH ₂)_n F, wherein n is 2,3, 4, or 5, preferably C ₂H₄ F).

In a preferred embodiment of the invention, the medium comprises one or more compounds of formula III-3

Wherein the method comprises the steps of

R ¹¹,R¹² identical or different represent H, alkyl or alkoxy having 1 to 15C atoms, wherein one or more CH ₂ groups of these groups are optionally replaced independently of one another by-C.ident.C-, -CF ₂O-,-OCF₂ -, -ch=ch-, -O-, -CO-O-or-O-CO-in such a way that the O atoms are not directly connected to each other, and wherein, in addition, one or more H atoms may be replaced by halogen.

The compound of formula III-3 is preferably selected from the compounds of formulas III-3-1 to III-3-10:

Wherein R ¹² represents an alkyl group having 1 to 7C atoms, preferably ethyl, n-propyl or n-butyl, or alternatively cyclopropylmethyl, cyclobutylmethyl or cyclopentylmethyl, or alternatively- (CH ₂)_n F, wherein n is 2,3, 4 or 5, preferably C ₂H₄ F).

In a preferred embodiment of the invention, the medium comprises one or more compounds of the formulae III-4 to III-6, preferably III-5,

Wherein the parameters have the meanings given above, R ¹¹ preferably represents a straight-chain alkyl group and R ¹² preferably represents an alkoxy group, each having 1 to 7C atoms.

In a preferred embodiment, the medium comprises one or more compounds of the formula I selected from the group consisting of the compounds of the formulae III-7 to III-9, preferably of the formula III-8,

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

Wherein the method comprises the steps of

R ⁴¹ represents unsubstituted alkyl having 1 to 7C atoms or unsubstituted alkenyl having 2 to 7C atoms, preferably n-alkyl, particularly preferably having 2,3,4 or 5C atoms, and

R ⁴² represents an unsubstituted alkyl group having 1 to 7C atoms or an unsubstituted alkoxy group having 1 to 6C atoms (each preferably having 2 to 5C atoms), an unsubstituted alkenyl group having 2 to 7C atoms, preferably having 2,3 or 4C atoms, more preferably vinyl or 1-propenyl, especially vinyl.

The compound of formula IV is preferably selected from compounds of formulae IV-1 to IV-4,

Wherein the method comprises the steps of

Alkyl and alkyl', independently of each other, represent an alkyl group having 1 to 7C atoms, preferably having 2 to 5C atoms,

Alkinyl represents an alkenyl group having 2 to 5C atoms, preferably having 2 to 4C atoms, particularly preferably 2C atoms,

Alkinyl' denotes alkenyl having 2 to 5C atoms, preferably having 2 to 4C atoms, particularly preferably having 2 to 3C atoms, and

Alkoxy means an alkoxy group having 1 to 5C atoms, preferably having 2 to 4C atoms.

Preferably, the medium comprises one or more compounds selected from the group consisting of formulas IV-1-1 to IV-1-5:

Very preferably, the medium according to the invention comprises one or more compounds of the formulae IV-2-1 and/or IV-2-2

Very preferably, the medium according to the invention comprises compounds of the formula IV-3, in particular compounds selected from the group consisting of the formulae IV-3-1 to IV-3-5

Very preferably, the medium according to the invention comprises compounds of the formula IV-4, in particular compounds selected from the group consisting of the formulae IV-4-1 and IV-4-2

In one embodiment, a medium according to the present invention comprises a combination of one or more compounds of formula I selected from the group consisting of compounds of formulas I-1 through I-4 and one or more compounds selected from the group consisting of compounds of formulas IA-1 through IA-18:

Wherein alkyl represents methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or n-pentyl.

The liquid-crystalline medium preferably additionally comprises one or more compounds of the formula IVa,

Wherein the method comprises the steps of

R ⁴¹ and R ⁴² each independently of one another represent straight-chain alkyl, alkoxy, alkenyl, alkoxyalkyl or alkoxy having up to 12C atoms, and

Representation of

Z ⁴ represents a single bond ,-CH₂CH₂-,-CH＝CH-,-CF₂O-,-OCF₂-,-CH₂O-,-OCH₂-,-COO-,-OCO-,-C₂F₄-,-C₄H₈-,-CF＝CF-.

Preferred compounds of formula IVa are shown below:

Wherein the method comprises the steps of

The alkyl and alkyl each independently represent a straight chain alkyl group having 1 to 6C atoms.

The medium according to the invention preferably comprises at least one compound of the formula IVa-1 and/or IVa-2.

The proportion of the compounds of the formula IVa in the overall mixture is preferably less than 5% by weight, very preferably less than 2% by weight.

Preferably, the medium comprises one or more compounds of formulae IVb-1 to IVb-3

Wherein the method comprises the steps of

Alkyl and alkyl each independently of the other represent a linear 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.

The proportion of biphenyls of the formulae IV-1 to IV-3 in the overall mixture is preferably less than 3% by weight, in particular less than 2% by weight.

Of the compounds of the formulae IVb-1 to IVb-3, compounds of the formula IVb-2 are particularly preferred.

Particularly preferred biphenyls are

Wherein alkyl represents an alkyl group having 1 to 6C atoms and preferably represents an n-propyl group. The medium according to the invention particularly preferably comprises one or more compounds of the formulae IVb-1-1 and/or IVb-2-3.

In a preferred embodiment, the medium according to the invention comprises one or more compounds of the formula V

Wherein the method comprises the steps of

R ⁵¹,R⁵² represents an alkyl group having 1 to 7C atoms, an alkoxy group having 1 to 7C atoms, or an alkoxyalkyl, alkenyl or alkenyloxy group having 2 to 7C atoms,

Identically or differently, denote

Z ⁵¹,Z⁵², independently of one another, represents-CH ₂-CH₂-,-CH₂ -O-, -ch=ch-, -c≡c-, -COO-, or a single bond, and

N is 1 or 2, and the number of the N is 1 or 2,

Preferably, the compound of formula V is selected from the following formulae:

The compound of formula V is preferably selected from compounds of formulae V-1 to V-16:

Wherein R ⁵¹ and R ⁵² have the meaning indicated by formula V above.

R ⁵¹ and R ⁵² preferably each independently of one another represent a straight-chain alkyl radical having 1 to 7C atoms or an alkenyl radical having 2 to 7C atoms.

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

In a preferred embodiment of the invention, the medium additionally comprises one or more compounds of the formulae VI-1 to VI-21,

Wherein R ⁶ represents a straight-chain alkyl or alkoxy group having 1 to 6C atoms, (O) represents-O-or a single bond, and m is 0,1,2,3,4,5 or 6 and n is 0,1,2,3 or 4.

R ⁶ preferably represents methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy, pentoxy.

In a preferred embodiment of the invention, the medium additionally comprises one or more compounds of the formulae VII-1 to VII-9

Wherein the method comprises the steps of

R ⁷ represents a linear alkyl or alkoxy group having 1 to 6C atoms, or a linear alkenyl group having 2 to 6C atoms, and

W is an integer of 1 to 6.

Mixtures comprising at least one compound of the formula V-9 are particularly preferred.

Particular preference is given to compounds of the formulae VI-1, VI-2, VI-4, VI-20 and VI-21. In these compounds, R ⁶ preferably represents alkyl, but also alkoxy, each having 1 to 5C atoms. In the compounds of the formula VI-20, R ⁶ preferably represents alkyl or alkenyl, in particular alkyl. In the compounds of the formula VI-21, R ⁶ preferably represents alkyl.

Further preferred embodiments are listed below:

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

Wherein R and alkyl have the meaning of formula III above.

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

Wherein R ^1N and R ^2N each independently of the other have the meaning indicated for R ^2A, preferably represent a linear alkyl, linear alkoxy or linear alkenyl group, 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.

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

Wherein R ^B1,R^B2,R^CR1,R^CR2,R¹,R² each independently of the other has the meaning of R ^2A and c is 0,1 or 2.R ¹ and R ² preferably represent, independently of one another, alkyl or alkoxy having 1 to 6C atoms.

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

Wherein the method comprises the steps of

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

D) Preferred mixtures comprise one or more indane compounds of formula In,

Wherein the method comprises the steps of

R ¹¹,R¹² and R ¹³ each independently of one another represent a linear alkyl, alkoxy, alkoxyalkyl or alkenyl radical having 1 to 6C atoms,

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

Representation of

I represents 0,1 or 2.

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

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

E) Preferred mixtures additionally comprise one or more compounds of the formulae L-1 to L-5,

Wherein the method comprises the steps of

R, R ¹ and R ² each independently of one another have the meanings described above for R ^2A in formula IIA, and alkyl represents alkyl having 1 to 6C atoms. The parameter s represents 1 or 2.

The compounds of the formulae L-1 to L-9 are preferably used in concentrations of 5 to 15% by weight, in particular 5 to 12% by weight and very particularly preferably 8 to 10% by weight.

F) Preferred mixtures additionally comprise one or more compounds of the formula IIA-Y

Wherein R ¹¹ and R ¹² have one of the meanings given above for R ^2A in formula IIA, and L ¹ and L ², identically or differently, represent F or Cl,

Preferred compounds of formula IIA-Y are selected from the following subformulae

Wherein, alkyl and Alkyl each independently of the other represent a linear Alkyl group having 1 to 6C atoms, alkoxy represents a linear alkoxy group having 1 to 6C atoms, alkenyl and Alkenyl each independently of the other represent a linear alkenyl group having 2 to 6 carbon atoms, and O represents an oxygen atom or a single bond. Alkenyl and Alkenyl preferably represent CH₂＝CH-,CH₂＝CHCH₂CH₂-,CH₃-CH＝CH-,CH₃-CH₂-CH＝CH-,CH₃-(CH₂)₂-CH＝CH-,CH₃-(CH₂)₃-CH＝CH- or CH ₃-CH＝CH-(CH₂)₂ -.

Particularly preferred compounds of formula IIA-Y are selected from the following subformulae:

Wherein Alkoxy and Alkoxy have the meanings defined above and preferably represent methoxy, ethoxy, n-propyloxy, n-butyloxy or n-pentyloxy.

The term "reliability" as used herein means the quality of the performance of the display during time and under different stress loads (stress loads), such as light load, temperature, humidity, voltage, and includes display effects such as image sticking (face and line image sticking), non-uniformity (mura), smudging (yogore), etc., which are known to those skilled in the art of LC displays. As a standard parameter for classifying reliability, a Voltage Holding Ratio (VHR) value, which is a measure for maintaining a constant voltage in a test display, is generally used. Among other factors, high VHR is a precondition for high reliability of LC media.

The term "PSA" is used hereinafter when referring generally to polymer sustained alignment type displays, and the term "PS" is used when referring to specific display modes (e.g., PS-VA, PS-TN, etc.), unless otherwise indicated.

Furthermore, the term "RM" is used hereinafter to refer to a polymerizable mesogenic or liquid crystalline compound, unless otherwise indicated.

As used herein, the terms "active layer" and "switchable layer" refer to a layer comprising one or more molecules (e.g., LC molecules) having structural and optical anisotropy that change their orientation when subjected to an external stimulus, such as an electric or magnetic field, in an electro-optic display, such as an LC display, which results in a change in the transmittance of the layer for polarized or unpolarized light.

As used herein, the terms "tilt" and "tilt angle" are understood to mean the tilt alignment of LC molecules of the LC medium relative to the cell surface in an LC display (here preferably a PSA display). The tilt angle here means the average angle (< 90 °) between the longitudinal molecular axis of the LC molecules (LC director) and the plane-parallel outer plates forming the LC cell. Where a low value of the tilt angle (i.e. a large deviation from the 90 angle) corresponds to a large tilt. Suitable methods of measuring tilt angle are given in the examples. The tilt angle values disclosed in the context relate to such measurement methods, unless otherwise indicated.

As used herein, the terms "reactive mesogen" and "RM" are understood to mean a compound comprising a mesogen or liquid crystal backbone, and one or more functional groups suitable for polymerization attached thereto, and said functional groups are also referred to as "polymerizable groups" or "P".

The term "polymerizable compound" as used herein is understood to mean a polymerizable monomer compound unless otherwise indicated.

As used herein, the term "low molecular weight compound" is understood to mean a compound that is monomeric and/or is not prepared by polymerization, as opposed to "polymeric compound" or "polymer".

As used herein, the term "non-polymerizable compound" is understood to mean a compound that does not contain functional groups suitable for polymerization under the conditions typically applied to RM polymerization.

As used herein, the term "mesogenic group" is known to those skilled in the art and described in the literature, and refers to a group that substantially contributes to the creation of a Liquid Crystal (LC) phase in a low molecular weight or polymeric species due to the anisotropy of its attractive and repulsive interactions. The compound containing mesogenic groups (mesogenic compound) does not necessarily have to have an LC phase per se. The mesogenic compounds may also exhibit LC phase behaviour only after mixing with other compounds and/or after polymerization. Typical mesogenic groups are for example rigid rod-like or disk-like units. The terms and definitions used in connection with mesogenic or LC compounds are given in Pure appl.chem.2001, 73 (5), 888 and C.Tschierske, G.Pelzl, S.Diele, angew.Chem.2004,116,6340-6368.

As used herein, the terms "optically active" and "chiral" are synonymous with material, which can induce a helical pitch in a nematic host material, also referred to as a "chiral dopant".

As used herein, the term "spacer group" (hereinafter also referred to as "Sp") is known to those skilled in the art and is described in the literature, see, e.g., pure appl. Chem.2001, 73 (5), 888 and C.Tschierske, G.Pelzl, S.Diele, angew.Chem.2004,116,6340-6368. As used herein, the term "spacer group" or "spacer group" means a flexible group, e.g., it is an alkylene group that connects the mesogenic group and the polymerizable group(s) in the polymerizable mesogenic compound.

In the context of the present context, it is intended that,Represents a trans-1, 4-cyclohexylidene ring.

At a groupThe single bond shown between the two ring atoms may be attached to any free position of the benzene ring.

"Organic group" in this context means a carbon or hydrocarbon group.

"Carbon group" means a mono-or polyvalent organic group containing at least one carbon atom, wherein the group contains no other atoms (e.g., -C≡C-) or optionally one or more other atoms, such as N, O, S, B, P, si, se, as, te or Ge (e.g., carbonyl, etc.). The term "hydrocarbyl group" means a carbon group that additionally contains one or more H atoms and optionally one or more heteroatoms, such as N, O, S, B, P, si, se, as, te or Ge.

"Halogen" means F, cl, br or I, preferably F or Cl.

-CO-, -C (=o) -and-C (O) -represent carbonyl groups, i.e.

The carbon or hydrocarbon group may be a saturated or unsaturated group. The unsaturated group is, for example, an aryl, alkenyl or alkynyl group. The carbon or hydrocarbon group having more than 3C atoms may be linear, branched, and/or cyclic and may also contain spiro or fused rings.

The terms "alkyl", "aryl", "heteroaryl" and the like also include multivalent groups such as alkylene, arylene, heteroarylene and the like.

The term "aryl" means an aromatic carbon group or a group derived therefrom. The term "heteroaryl" denotes an "aryl" group as defined above comprising one or more heteroatoms (preferably selected from N, O, S, se, te, si and Ge).

Preferred carbon and hydrocarbon groups are optionally substituted, straight-chain, branched or cyclic alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy and alkoxycarbonyloxy having from 1 to 40, preferably from 1 to 20, very preferably from 1 to 12, C atoms, optionally substituted aryl or aryloxy having from 5 to 30, preferably from 6 to 25, C atoms, or optionally substituted alkylaryl, arylalkyl, alkylaryl, arylalkyloxy, arylcarbonyl, aryloxycarbonyl, arylcarbonyloxy and aryloxycarbonyloxy having from 5 to 30, preferably from 6 to 25, C atoms, wherein one or more C atoms may also be replaced by heteroatoms, preferably selected from N, O, S, se, te, si and Ge.

Further preferred carbon and hydrocarbon groups are C ₁-C₂₀ alkyl, C ₂-C₂₀ alkenyl, C ₂-C₂₀ alkynyl, C ₃-C₂₀ allyl, C ₄-C₂₀ alkyldienyl, C ₄-C₂₀ polyalkenyl, C ₆-C₂₀ cycloalkyl, C ₄-C₁₅ cycloalkenyl, C ₆-C₃₀ aryl, C ₆-C₃₀ alkylaryl, C ₆-C₃₀ aralkyl, C ₆-C₃₀ alkylaryl oxy, C ₆-C₃₀ arylalkoxy, C ₂-C₃₀ heteroaryl, C ₂-C₃₀ heteroaryloxy.

Particularly preferred are C ₁-C₁₂ alkyl, C ₂-C₁₂ alkenyl, C ₂-C₁₂ alkynyl, C ₆-C₂₅ aryl and C ₂-C₂₅ heteroaryl.

Further preferred carbon and hydrocarbon radicals are straight-chain, branched or cyclic alkyl radicals having 1 to 20, preferably 1 to 12, C atoms, which are unsubstituted or mono-or polysubstituted by F, cl, br, I or CN, and wherein one or more non-adjacent CH ₂ groups may each be, independently of one another, represented by-C (R ^x)＝C(R^x)-、-C≡-、-N(R^x) -, -O-, -S-, -CO-, -CO-O-, -O-CO-O-is replaced in such a way that the O and/or S atoms are not directly connected to each other.

R ^x preferably represents H, F, cl, CN, a straight, branched or cyclic alkyl chain having 1 to 25C atoms, where in addition, one or more non-adjacent C atoms may be replaced by-O-, -S-, -CO-, -CO-O-, -O-CO-O-substitution, and wherein one or more H atoms may be replaced by F or Cl, or represents an optionally substituted aryl or aryloxy group having 6 to 30C atoms, or an optionally substituted heteroaryl or heteroaryloxy group having 2 to 30C atoms.

Preferred alkyl groups are, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 2-methylbutyl, n-pentyl, sec-pentyl, cyclopentyl, n-hexyl, cyclohexyl, 2-ethylhexyl, n-heptyl, cycloheptyl, n-octyl, cyclooctyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, trifluoromethyl, perfluoro-n-butyl, 2-trifluoroethyl, perfluoro-octyl, perfluorohexyl and the like.

Preferred alkenyl groups are, for example, ethenyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl, cyclooctenyl and the like.

Preferred alkynyl groups are, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl, octynyl and the like.

Preferred alkoxy groups are, for example, methoxy, ethoxy, 2-methoxyethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, 2-methylbutoxy, n-pentoxy, n-hexoxy, n-heptoxy, n-octoxy, n-nonoxy, n-decoxy, n-undecoxy, n-dodecoxy and the like.

Preferred amino groups are, for example, dimethylamino, methylamino, methylphenylamino, phenylamino, and the like.

Aryl and heteroaryl groups may be monocyclic or polycyclic, i.e., they may contain one ring (e.g., phenyl) or two or more rings, which may also be fused (e.g., naphthyl) or covalently bonded (e.g., biphenyl), or comprise a combination of fused and linked rings. Heteroaryl contains one or more heteroatoms, preferably selected from O, N, S and Se.

Particularly preferred are mono-, bi-or tricyclic aryl groups having 6 to 25C atoms and mono-, bi-or tricyclic heteroaryl groups having 5 to 25 ring atoms, which optionally contain fused rings and are optionally substituted. Further preferred are 5-, 6-or 7-membered aryl and heteroaryl groups, wherein, in addition, one or more CH groups may be replaced by N, S or O in such a way that O atoms and/or S atoms are not directly connected to one another.

Preferred aryl groups are, for example, phenyl, biphenyl, terphenyl, [1,1':3', 1' ] -terphenyl-2 ' -yl, naphthyl, anthryl, binaphthalenyl, phenanthryl, 9, 10-dihydro-phenanthryl, pyrene, dihydropyrene,Perylene, tetracene, pentacene, benzopyrene, fluorene, indene, indenofluorene, spirobifluorene (spirobifluorene), and the like.

Preferred heteroaryl groups are, for example, 5-membered rings, such as pyrrole, pyrazole, imidazole, 1,2, 3-triazole, 1,2, 4-triazole, tetrazole, furan, thiophene, selenophene, oxazole, isoxazole, 1, 2-thiazole, 1, 3-thiazole, 1,2, 3-oxadiazole, 1,2, 4-oxadiazole, 1,2, 5-oxadiazole, 1,3, 4-oxadiazole, 1,2, 3-thiadiazole, 1,2, 4-thiadiazole, 1,2, 5-thiadiazole, 1,3, 4-thiadiazole, 6-membered rings, such as pyridine, pyridazine, pyrimidine, pyrazine, 1,3, 5-triazine, 1,2, 4-triazine, 1,2, 3-triazine, 1,2,4, 5-tetrazine, 1,2,3, 4-tetrazine, 1,2,3, 5-tetrazine or fused groups, such as indole, isoindole, indolizine, indazole, benzimidazole, benzotriazole, purine, naphthazole, phenanthroimidazole, pyridoimidazole, pyrazinoimidazole, quinoxalinoimidazole, benzoxazole, naphthazole, anthraoxazole, phenanthroazole, isoxazole, benzothiazole, benzofuran, isobenzofuran, dibenzofuran, quinoline, isoquinoline, pteridine, benzo-5, 6-quinoline, benzo-6, 7-quinoline, benzo-7, 8-quinoline, benzisoquinoline, acridine, phenothiazine, phenoxazine, benzopyridazine, benzopyrimidine, quinoxaline, phenazine, naphthyridine, azacarbazole, benzocarboline, phenanthridine, phenanthroline, thieno [2,3b ] thiophene, thieno [3,2b ] thiophene, dithienothiophene, isobenzothiophene, dibenzothiophene, benzothiophene, benzothiadiazole, or a combination of these groups.

The aryl and heteroaryl groups mentioned in the context may also be substituted by alkyl, alkoxy, thioalkyl, fluoro, fluoroalkyl or other aryl or heteroaryl groups.

(Non-aromatic) alicyclic groups and heterocyclic groups comprise both saturated rings, i.e. rings containing only single bonds, and partially unsaturated rings, i.e. those which may also contain multiple bonds. The heterocyclic ring contains one or more heteroatoms, preferably selected from Si, O, N, S and Se.

The (non-aromatic) alicyclic and heterocyclic groups may be monocyclic, i.e. contain only one ring (e.g. cyclohexane), or polycyclic, i.e. contain multiple rings (e.g. decalin or bicyclooctane). Saturated groups are particularly preferred. Preference is furthermore given to mono-, bi-or tricyclic groups having 5 to 25 ring atoms which optionally contain fused rings and are optionally substituted. Further preferred are 5-, 6-, 7-or 8-membered carbocyclic groups in which, in addition, one or more C atoms may be replaced by Si and/or one or more CH groups may be replaced by N and/or one or more non-adjacent CH ₂ groups may be replaced by-O-and/or-S-.

Preferred cycloaliphatic and heterocyclic groups are, for example, 5-membered groups, such as cyclopentane, tetrahydrofuran, tetrahydrothiophene, pyrrolidine; 6-membered radicals, such as cyclohexane, silacyclohexane (silinane), cyclohexene, tetrahydropyran, tetrahydrothiopyran, 1, 3-dioxane, 1, 3-dithiane, piperidine; 7-membered groups such as cycloheptane; and condensed groups such as tetrahydronaphthalene, decalin, indane, bicyclo [1.1.1] pentane-1, 3-diyl, bicyclo [2.2.2] octane-1, 4-diyl, spiro [3.3] heptane-2, 6-diyl, octahydro-4, 7-methanoindan-2, 5-diyl.

Preferred substituents are, for example, solubility promoting groups, such as alkyl or alkoxy groups; electron withdrawing groups such as fluorine, nitro or nitrile; or substituents for increasing the glass transition temperature (Tg) of the polymer, in particular bulky groups such as tert-butyl or optionally substituted aryl.

Preferred substituents, hereinafter also referred to as "L ^S", are, for example, F、Cl、Br、I、-CN、-NO₂、-NCO、-NCS、-OCN、-SCN、-C(＝O)N(R^x)₂、-C(＝O)Y¹、-C(＝O)R^x、-N(R^x)₂, straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy groups having 1 to 25C atoms, where one or more H atoms may optionally be replaced by F or Cl, optionally substituted silyl (silyl) having 1 to 20 Si atoms or optionally substituted aryl having 6 to 25, preferably 6 to 15C atoms.

Wherein R ^x represents H, F, cl, CN, or a linear, branched or cyclic alkyl group having 1 to 25C atoms, wherein one or more non-adjacent CH ₂ -groups are optionally replaced by-O-, -S-, -CO-O-, O-CO-, -O-CO-O-is replaced in such a way that O-and/or S-atoms are not directly linked to one another, and wherein one or more H atoms are each optionally replaced by F, cl, P-or P-Sp-, and

Y ¹ represents halogen.

"Substituted silyl or aryl" preferably means that it is substituted by halogen, -CN, R ⁰、-OR⁰、-CO-R⁰、-CO-O-R⁰、-O-CO-R⁰ or-O-CO-O-R ⁰, where R ⁰ represents H or alkyl having 1 to 20C atoms.

Particularly preferred substituents L are, for example, F、Cl、CN、NO₂、CH₃、C₂H₅、OCH₃、OC₂H₅、COCH₃、COC₂H₅、COOCH₃、COOC₂H₅、CF₃、OCF₃、OCHF₂、OC₂F₅, and also phenyl.

A ¹ and A ² very preferably representWherein L has one of the above meanings and r represents 0,1,2,3 or 4, in particular

Representation of

The polymerizable group P is a group suitable for polymerization (e.g., radical or ionic chain polymerization, addition polymerization or condensation polymerization) or a group suitable for polymer-analogous reactions (e.g., addition or condensation on the polymer backbone). Particularly preferred are groups for chain polymerization, in particular those comprising a c=c double bond or-c≡c-triple bond, and groups suitable for ring-opening polymerization, such as oxetanyl or epoxy groups.

Preferred groups P are selected from the group consisting of: CH ₂＝CW¹-CO-O-、CH₂＝CW¹ -CO-, CH₂＝CW²-(O)_k3-、CW¹＝CH-CO-(O)_k3-、CW¹＝CH-CO-NH-、CH₂＝CW¹-CO-NH-、CH₃-CH＝CH-O-、(CH₂＝CH)₂CH-OCO-、(CH₂＝CH-CH₂)₂CH-OCO-、(CH₂＝CH)₂CH-O-、(CH₂＝CH-CH₂)₂N-、(CH₂＝CH-CH₂)₂N-CO-、HO-CW²W³-、HS-CW²W³-、HW²N-、HO-CW²W³-NH-、CH₂＝CW¹-CO-NH-、CH₂＝CH-(COO)_k1-Phe-(O)_k2-、CH₂＝CH-(CO)_k1-Phe-(O)_k2-、Phe-CH＝CH-、HOOC-、OCN- And W ⁴W⁵W⁶ Si-, wherein W ¹ represents H, F, cl, CN, CF ₃, phenyl or alkyl having 1 to 5C atoms, in particular H, F, cl or CH ₃,W² and W ³ each independently of the other represent H or alkyl having 1 to 5C atoms, in particular H, methyl, ethyl or n-propyl, W ⁴、W⁵ and W ⁶ each independently of the other represent Cl, oxaalkyl having 1 to 5C atoms or oxacarbonylalkyl, W ⁷ and W ⁸ each independently of the other represent H, cl or alkyl having 1 to 5C atoms, phe represents 1, 4-phenylene, which is optionally substituted by one or more groups L other than P-SP-, as defined above, k ₁、k₂ and k ₃ each independently of the other represent 0 or 1, k ₃ preferably represents 1, and k ₄ represents an integer from 1 to 10.

Very preferred groups P are selected from the group consisting of: CH ₂＝CW¹-CO-O-、CH₂＝CW¹ -CO-, CH₂＝CW²-O-、CH₂＝CW²-、CW¹＝CH-CO-(O)_k3-、CW¹＝CH-CO-NH-、CH₂＝CW¹-CO-NH-、(CH₂＝CH)₂CH-OCO-、(CH₂＝CH-CH₂)₂CH-OCO-、(CH₂＝CH)₂CH-O-、(CH₂＝CH-CH₂)₂N-、(CH₂＝CH-CH₂)₂N-CO-、CH₂＝CW¹-CO-NH-、CH₂＝CH-(COO)_k1-Phe-(O)_k2-、CH₂＝CH-(CO)_k1-Phe-(O)_k2-、Phe-CH＝CH- And W ⁴W⁵W⁶ Si-, wherein W ¹ represents H, F, cl, CN, CF ₃, phenyl or alkyl having 1 to 5C atoms, in particular H, F, cl or CH ₃,W² and W ³ each independently of the other represent H or alkyl having 1 to 5C atoms, in particular H, methyl, ethyl or n-propyl, W ⁴、W⁵ and W ⁶ each independently of the other represent Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5C atoms, W ⁷ and W ⁸ each independently of the other represent H, cl or alkyl having 1 to 5C atoms, phe represents 1, 4-phenylene, k ₁、k₂ and k ₃ each independently of the other represent 0 or 1, k ₃ preferably represents 1, and k ₄ represents an integer from 1 to 10.

Very preferred groups P are selected from the group consisting of: CH ₂＝CW¹ -CO-O-, in particular CH ₂＝CH-CO-O-、CH₂＝C(CH₃) -CO-O-and CH ₂ =cf-CO-O-, also CH ₂＝CH-O-、(CH₂＝CH)₂CH-O-CO-、(CH₂＝CH)₂ CH-O-,

Other particularly preferred polymerizable groups P are selected from ethyleneoxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxy groups, most preferably from acrylate and methacrylate groups.

If the spacer group Sp is different from a single bond, it is preferably of the formula Sp "-X" such that the individual groups P-Sp-correspond to the formula R-Sp "-X" -, where

Sp' represents a linear or branched alkylene radical having from 1 to 20, preferably from 1 to 12, C atoms, which is optionally mono-or polysubstituted by F, cl, br, I or CN, and wherein, in addition, one or more non-adjacent CH ₂ groups are each, independently of one another, replaced by -O-、-S-、-NH-、-N(R⁰)-、-Si(R⁰R⁰⁰)-、-CO-、-CO-O-、-O-CO-、-O-CO-O-、-S-CO-、-CO-S-、-N(R⁰⁰)-CO-O-、-O-CO-N(R⁰)-、-N(R⁰)-CO-N(R⁰⁰)-、-CH＝CH- or-C.ident.C-in such a way that O and/or S atoms are not directly linked to one another,

X' represents -O-、-S-、-CO-、-CO-O-、-O-CO-、-O-CO-O-、-CO-N(R⁰)-、-N(R⁰)-CO-、-N(R⁰)-CO-N(R⁰⁰)-、-OCH₂-、-CH₂O-、-SCH₂-、-CH₂S-、-CF₂O-、-OCF₂-、-CF₂S-、-SCF₂-、-CF₂CH₂-、-CH₂CF₂-、-CF₂CF₂-、-CH＝N-、-N＝CH-、-N＝N-、-CH＝CR⁰-、-CY²＝CY³-、-C≡C-、-CH＝CH-CO-O-、-O-CO-CH＝CH- or a single bond,

R ⁰ and R ⁰⁰ each independently of one another represent H or alkyl having 1 to 20C atoms, and

Y ² and Y ³ each independently represent H, F, cl or CN.

X' is preferably-O-, -S-; -CO-, -COO-, -OCO-, -O-COO-, -CO-NR ⁰-、-NR⁰-CO-、-NR⁰-CO-NR⁰⁰ -, or a single bond.

Typical spacer groups Sp and-Sp "-X" -are for example -(CH₂)_p1-、-(CH₂)_p1-O-、-(CH₂)_p1-O-CO-、-(CH₂)_p1-CO-O-、-(CH₂)_p1-O-CO-O-、-(CH₂CH₂O)_q1-CH₂CH₂-、-CH₂CH₂-S-CH₂CH₂-、-CH₂CH₂-NH-CH₂CH₂- or- (SiR ⁰R⁰⁰-O)_p1 -, where p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and R ⁰ and R ⁰⁰ have the meanings indicated above.

Particularly preferred groups Sp and-Sp "-X" -are -(CH₂)_p1-、-(CH₂)_p1-O-、-(CH₂)_p1-O-CO-、-(CH₂)_p1-CO-O-、-(CH₂)_p1-O-CO-O-, wherein p1 and q1 have the meanings indicated above.

Particularly preferred groups Sp' are in each case straight-chain ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxy ethylene, methyleneoxy butylene, ethylenethio ethylene, ethylene-N-methylimino-ethylene, 1-methylalkylene, ethylene, propylene and butylene.

In a preferred embodiment of the invention, the compounds of formula P and its subformulae contain a spacer group Sp substituted with one or more polymerizable groups P, so that the group Sp-P corresponds to Sp (P) _s and s is ≡2 (branched polymerizable groups).

Preferred compounds of formula P according to this preferred embodiment are those in which s is 2, i.e. compounds containing the group Sp (P) ₂. Very preferred compounds of formula P according to this preferred embodiment contain a group selected from the following formulae:

-X-alkyl-CHPP S1

-X-alkyl-CH((CH₂)_aaP)((CH₂)_bbP) S2

-X-N((CH₂)_aaP)((CH₂)_bbP) S3

-X-alkyl-CHP-CH₂-CH₂P S4

-X-alkyl-C(CH₂P)(CH₂P)-C_aaH_2aa+1 S5

-X-alkyl-CHP-CH₂P S6

-X-alkyl-CPP-C_aaH_2aa+1 S7

-X-alkyl-CHPCHP-C_aaH_2aa+1 S8

Wherein P is as defined in formula P,

Alkyl represents a single bond or a straight-chain or branched alkylene radical having 1 to 12C atoms, which is unsubstituted or monosubstituted or polysubstituted by F, cl or CN, and wherein one or more non-adjacent CH ₂ groups may each be, independently of one another, interrupted by-C (R ⁰)＝C(R⁰)-、-C≡C-、-N(R⁰) -, by-O-, -S-, -CO-O-, -O-CO-O-substitution, wherein R ⁰ has the meaning indicated above, aa and bb each independently of the others represent 0, 1,2, 3,4, 5 or 6,

X has one of the meanings indicated for X ", and is preferably O, CO, SO ₂, O-CO-, CO-O, or a single bond.

Preferred spacer groups Sp (P) ₂ are selected from formulas S1, S2 and S3.

Very preferred spacer groups Sp (P) ₂ are selected from the following subformulae:

-CHPP S1a

-O-CHPP S1b

-CH₂-CHPP S1c

-OCH₂-CHPP S1d

-CH(CH₂-P)(CH₂-P) S2a

-OCH(CH₂-P)(CH₂-P) S2b

-CH₂-CH(CH₂-P)(CH₂-P) S2c

-OCH₂-CH(CH₂-P)(CH₂-P) S2d

-CO-NH((CH₂)₂P)((CH₂)₂P) S3a

In the compounds of formula P and its subformulae as described above and below, P is preferably selected from the group consisting of: vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxy groups, most preferably selected from acrylate and methacrylate groups.

More preferred are compounds of formula P and its subformulae as described hereinabove and hereinbelow, wherein all polymerizable groups P present in the compound have the same meaning, and very preferred represent acrylate or methacrylate groups, most preferred methacrylate groups.

In the compounds of formula P and its subformulae as described above and below, R preferably represents P-Sp-.

More preferred are compounds of formula P and its subformulae as described hereinabove and hereinbelow, wherein Sp represents a single bond or- (CH ₂)_p1-、-O-(CH₂)_p1-、-O-CO-(CH₂)_p1 or-CO-O- (CH ₂)_p1), wherein P1 is 2, 3, 4, 5 or 6, and if Sp is-O- (CH ₂)_p1-、-O-CO-(CH₂)_p1 or-CO-O- (CH ₂)_p1), then the O-atom or CO-group, respectively, is attached to the benzene ring.

More preferred are compounds of formula P and its subformulae as described hereinabove and hereinbelow, wherein at least one group Sp is a single bond.

More preferred are compounds of formula P and its subformulae as described hereinabove and hereinbelow, wherein at least one group Sp is different from a single bond, and is preferably selected from- (CH ₂)_p1-、-O-(CH₂)_p1-、-O-CO-(CH₂)_p1 or-CO-O- (CH ₂)_p1), wherein P1 is 2, 3, 4, 5 or 6, and if Sp is-O- (CH ₂)_p1-、-O-CO-(CH₂)_p1 or-CO-O- (CH ₂)_p1), then the O-atom or CO-group, respectively, is attached to the benzene ring.

Very preferred radicals-A ¹-(Z-A²)_z -in the formula P are selected from the following formulae

Wherein at least one benzene ring is substituted with at least one group L and the benzene ring is optionally further substituted with one or more groups L or P-Sp-.

Preferred compounds of formula P and sub-formulae thereof are selected from the following preferred embodiments, including any combination thereof:

all groups P in the compounds have the same meaning,

- -A ¹-(Z-A²)_z - -is selected from the group consisting of formulae A1, A2 and A5,

The compound contains exactly two polymerizable groups (represented by the group P),

The compound contains exactly three polymerizable groups (represented by the group P),

P is selected from the group consisting of acrylate, methacrylate and oxetane groups, very preferably acrylate or methacrylate groups,

-P is a methacrylate group and,

All the groups Sp are single bonds,

At least one of the groups Sp being a single bond and at least one of the groups Sp being different from a single bond,

Sp, when different from a single bond, is -(CH₂)_p2-、-(CH₂)_p2-O-、-(CH₂)_p2-CO-O-、-(CH₂)_p2-O-CO-, where p2 is 2, 3, 4, 5 or 6, and an O atom or CO-group, respectively, is attached to the benzene ring,

Sp is a single bond or represents -(CH₂)_p2-、-(CH₂)_p2-O-、-(CH₂)_p2-CO-O-、-(CH₂)_p2-O-CO-, wherein p2 is 2,3, 4, 5 or 6, and an O atom or CO-group, respectively, is attached to the benzene ring,

-R represents P-Sp-,

R does not represent or contains a polymerizable group,

R does not represent or contain a polymerizable group and represents a linear, branched or cyclic alkyl group having 1 to 25C atoms, wherein one or more non-adjacent CH ₂ groups are optionally interrupted by-O-, -S-, -CO-O-, O-CO-, -O-CO-O-is replaced in such a way that O and/or S atoms are not directly connected to one another, and wherein one or more H atoms are each optionally replaced by F, cl or L ^a,

L or L' represents F, cl or CN,

-L is F.

Suitable and preferred compounds of formula P are selected from the following formulae:

wherein the individual radicals have the following meanings:

P ¹、P² and P ³ each independently of one another represent an acrylate group or a methacrylate group,

Sp ¹、Sp² and Sp ³ each independently of one another represent a single bond or a spacer group which has one of the meanings described for Sp in the context, and particularly preferably represent -(CH₂)_p1-,-(CH₂)_p1-O-,-(CH₂)_p1-CO-O-,-(CH₂)_p1-O-CO- or- (CH ₂)_p1 -O-CO-O-, where P1 is an integer from 1 to 12, where, in addition, one or more of the radicals P ¹-Sp¹-、P²-Sp² and P ³-Sp³ may represent R ^aa, provided that at least one of the radicals P ¹-Sp¹-、P²-Sp² and P ³-Sp³ present is different from R ^aa,

R ^aa represents H, F, cl, CN or a linear or branched alkyl group having 1 to 25C atoms and, furthermore, wherein one or more non-adjacent CH ₂ groups can each be replaced independently of one another by-C (R ⁰)＝C(R⁰⁰)-,-C≡C-,-N(R⁰) -, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-being replaced in such a way that O and/or S atoms are not directly connected to one another, and wherein one or more further H atoms can be replaced by F, cl, CN or P ¹-Sp¹ -, particularly preferred are straight-chain or branched, optionally mono-or polyfluoro, alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy groups having from 1 to 12C atoms, where alkenyl and alkynyl groups have at least two C atoms and branched groups have at least three C atoms,

R ⁰、R⁰⁰, independently of one another and identically or differently on each occurrence, represents H or alkyl having 1 to 12C atoms,

R ^y and R ^z each independently of one another represent H, F, CH ₃ or CF ₃,

X ¹、X² and X ³ each independently of the other represent-CO-O-; -O-CO-or a single bond,

Z ¹ represents-O, -CO-; -C (R ^yR^z) -or-CF ₂CF₂ -,

Z ² and Z ³ each independently of one another represent-CO-O-, -O-CO-, -CH ₂O-,-OCH₂-,-CF₂O-,-OCF₂ -or- (CH ₂)_n -, where n is 2, 3 or 4,

L represents identically or differently on each occurrence F, cl, CN or a straight-chain or branched chain having 1 to 12C atoms, optionally mono-or polyfluoro alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy, preferably F,

L 'and L' each independently of one another represent H, F or Cl,

K represents either 0 or 1 and,

R represents 0, 1, 2, 3 or 4,

S represents 0,1, 2 or 3,

T represents 0,1 or 2,

X represents 0 or 1.

Particularly preferred are compounds of the formulae R2, R13, R17, R22, R23, R24, R30, R31 and R32.

Further preferred are the three reactive compounds R15 to R30, in particular R17, R18, R19, R22, R23, R24, R25, R26, R30, R31 and R32.

Of the compounds of the formulae P1 to P32

Preferably is

Wherein L, identically or differently, at each occurrence, has one of the meanings given above or below, and preferably F,Cl,CN,NO₂,CH₃,C₂H₅,C(CH₃)₃,CH(CH₃)₂,CH₂CH(CH₃)C₂H₅,OCH₃,OC₂H₅,COCH₃,COC₂H₅,COOCH₃,COOC₂H₅,CF₃,OCF₃,OCHF₂,OC₂F₅ or P-Sp-, very preferably F, cl, CN, CH ₃,C₂H₅,OCH₃,COCH₃,OCF₃ or P-Sp-, more preferably F, cl, CH ₃,OCH₃,COCH₃ or OCF ₃, most preferably F or CH ₃.

In order to produce a PSA display, the polymerisable compounds contained in the LC medium are polymerised or cross-linked (if one compound contains two or more polymerisable groups) by in situ polymerisation in the LC medium (between the substrates of the LC display, optionally with the application of a voltage to the electrodes).

The structure of the PSA display according to the invention corresponds to the usual geometry of PSA displays, as described in the prior art cited at the outset. The geometry without protrusions is preferred, wherein in addition, in particular, the electrodes on the color filter side are unstructured and only the electrodes on the TFT side have slots (slots). A particularly suitable and preferred electrode structure for PS-VA displays is described, for example, in US2006/0066793 A1.

The preferred PSA-type LC display of the present invention comprises:

A first substrate comprising pixel electrodes defining pixel areas, which pixel electrodes are connected to switching elements arranged in each pixel area and optionally comprise a micro slit pattern, and optionally a first alignment layer arranged on the pixel electrodes,

A second substrate comprising a common electrode layer (which may be arranged on the whole part of the second substrate facing the first substrate), and optionally a second alignment layer,

-An LC layer disposed between the first and second substrates and comprising an LC medium comprising a polymerisable component comprising one or more compounds of formula R and a chiral nematic liquid crystal host comprising a compound of formula R as described above and below, wherein the polymerisable component may also be polymerised.

The first and/or second alignment layers control the alignment direction of LC molecules of the LC layer. For example, in a PS-VA display, the alignment layer is selected to impart homeotropic (or homeotropic) alignment (i.e., normal to the surface) or tilt alignment to the LC molecules. Such an alignment layer may for example comprise polyimide, which may also be rubbed or may be prepared by a photoalignment method.

The LC layer with LC medium may be deposited between the substrates of the display by methods conventionally used by display manufacturers, such as the so-called drop fill (ODF) method. The polymerisable component of the LC medium is then polymerised, for example by UV photopolymerization. The polymerization may be carried out in one step or in two or more steps.

PSA displays may include other elements such as color filters, black matrices, passivation layers, optical retardation layers, transistor elements for single pixel addressing, etc., all of which are well known to those skilled in the art and may be used without the inventive skill.

One skilled in the art can design the electrode structure depending on the individual display type. For example, for PS-VA displays, the multi-domain orientation of LC molecules may be induced by providing electrodes with slits and/or protrusions (bumps) or projections in order to create two, four or more differently tilted alignment directions.

After polymerization, the polymerizable compounds form crosslinked polymers, which lead to a certain pretilt of the LC molecules in the LC medium. Without wishing to be bound by a particular theory, it is believed that at least a portion of the crosslinked polymer formed by the polymerizable compound will separate or precipitate out of the LC medium and form a polymer layer on the substrate or electrode, or on an alignment layer provided thereon. Microscopic measurement data (such as SEM and AFM) have demonstrated that at least a portion of the formed polymer accumulates at the LC/substrate interface.

The polymerization may be carried out in one step. It is also possible to first carry out the polymerization in a first step (optionally with simultaneous application of voltage) in order to produce a pretilt angle and then to polymerize or crosslink the compounds which have not reacted in the first step in a second polymerization step in which no voltage is applied ("final cure").

Suitable and preferred polymerization methods are, for example, thermal or photopolymerization, preferably photopolymerization, in particular UV-induced photopolymerization, which can be achieved by exposing the polymerizable compound to UV radiation.

Optionally, one or more polymerization initiators are added to the LC medium. Suitable conditions for the polymerization and suitable types and amounts of initiator are known to the person skilled in the art and are described in the literature. Suitable for free-radical polymerization are, for example, commercially available photoinitiatorsOr (b)(Ciba AG). If a polymerization initiator is used, the proportion thereof is preferably from 0.001 to 5% by weight, particularly preferably from 0.001 to 1% by weight.

The polymerizable compounds according to the invention are also suitable for polymerization without initiator, which is accompanied by considerable advantages, such as low material costs and in particular less contamination of the LC medium by possible residual amounts of initiator or degradation products thereof. The polymerization can also be carried out without addition of initiator. In a preferred embodiment, the LC medium thus contains no polymerization initiator.

The LC medium may also contain one or more stabilizers in order to prevent undesired spontaneous polymerization of the RM, for example during storage or transport. Suitable types and amounts of stabilizers are known to the person skilled in the art and are described in the literature. Particularly suitable are, for example, those commercially available fromSeries (Ciba AG) stabilizers, e.g.1076. If stabilizers are used, their proportion is preferably from 10 to 500,000ppm, particularly preferably from 50 to 50,000ppm, based on the total amount of RM or polymerizable components (component P).

The polymerizable compounds of formula R do in particular show good UV absorption and are therefore particularly suitable for use in a process for the production of PSA displays comprising one or more of the following features:

Exposing the polymerizable medium to UV light in a 2-step process in a display, the process comprising a first UV exposure step ("UV-1 step") to produce a tilt angle, and a second UV exposure step ("UV-2 step") to complete the polymerization,

In the display the polymerizable medium is exposed to UV light generated by an energy saving UV lamp (also called "green UV lamp"). These lamps are characterized by a relatively low intensity in their absorption spectrum of 300-380nm (1/100-1/10 of conventional UV1 lamps) and are preferably used in the UV2 step, but are optionally also used in the UV1 step when high intensities are to be avoided for the process.

The polymerizable medium is exposed to UV light generated by a UV lamp in the display, which has a radiation spectrum shifted to longer wavelengths (preferably 340nm or longer) to avoid short UV light exposure in the PS-VA process.

Both low intensity and UV shifted to longer wavelengths are used to protect the organic layer from damage that may be caused by UV light.

Preferred embodiments of the present invention relate to a method of making a PSA display as described above and below, comprising one or more of the following features:

exposing the polymerizable LC medium to UV light in a 2-step process comprising a first UV exposure step ("UV-1 step") to produce a tilt angle and a second UV exposure step ("UV-2 step") to complete the polymerization,

The polymerizable LC medium is exposed to UV light in the wavelength range of 300-380nm with an intensity of 0.5mW/cm ² to 10mW/cm ² generated by a UV lamp, preferably for the UV2 step and optionally also for the UV1 step,

The polymerizable LC medium is exposed to UV light having a wavelength of 340nm or more, and preferably 400nm or less.

Such a preferred method is performed, for example, by using a desired UV lamp, or by using a bandpass filter and/or a cutoff filter that is substantially transmissive to UV light having the respective desired wavelength and substantially blocking UV light having the respective undesired wavelength. For example, when radiation of UV light having a wavelength λ of 300-400nm is desired, UV exposure may be performed using a broadband pass filter substantially transmissive for wavelengths of 300nm < λ <400 nm. When radiation of UV light having a wavelength lambda greater than 340nm is desired, UV exposure may be performed using a cut-off filter that is substantially transmissive to wavelengths lambda >340 nm.

By "substantially transmissive" is meant that the filter transmits a substantial portion, preferably at least 50%, of the intensity of incident light of the desired wavelength. By "substantially blocked" is meant that the filter does not transmit a substantial portion, preferably at least 50%, of the intensity of incident light of the undesired wavelength. "desired (undesired) wavelength", for example, means a wavelength within (outside) a given lambda range in the case of a band-pass filter, and a wavelength higher (lower) than a given lambda value in the case of a cut-off filter.

This preferred method makes it possible to manufacture displays by using longer UV wavelengths, thereby reducing or even avoiding the deleterious and damaging effects of short UV light components.

The UV radiation energy is typically 6 to 100J, depending on the production process conditions.

Preferably, the LC medium according to the invention essentially consists of a polymerizable component P) comprising one or more polymerizable compounds of formula R and LC host mixture as described above and below, and an optically active component comprising one or more chiral dopants. However, the LC medium may additionally comprise one or more other components or additives, preferably selected from the list including, but not limited to: comonomers, polymerization initiators, inhibitors, stabilizers, surfactants, wetting agents, lubricants, dispersants, hydrophobing agents, binders, flow improvers, defoamers, deaerators, diluents, reactive diluents, auxiliaries, colorants, dyes, pigments and nanoparticles.

The LC medium according to the invention comprises one, two or three chiral dopants, very preferably one chiral dopant.

LC media comprising one, two or three polymerizable compounds of formula R are particularly preferred.

LC media having chiral nematic LC phases are further preferred.

Preferably the proportion of the compound of formula R in the LC medium is >0 to <5%, very preferably >0 to <1%, most preferably 0.01 to 0.5%.

In a preferred embodiment, the medium according to the invention comprises, alone or in combination with one another, one or more compounds of the formula IIA in a total concentration in the range from 25% to 50%, more preferably from 30% to 45%, very preferably from 32% to 40%;

-one or more compounds of formula IIA-2 in a total concentration in the range of 5% to 20%, more preferably 8% to 18%, very preferably 10% to 15%;

-one or more compounds of formula IIA-10 in a total concentration ranging from 17% to 38%, more preferably from 19% to 30%, very preferably from 20% to 26%;

-one or more compounds of formula IIB, preferably IIB-10, in a total concentration ranging from 5% to 25%, more preferably from 9% to 22%, very preferably from 12% to 20%;

-one or more compounds of formula IIA and one or more compounds of formula IIB in a total concentration of 50% or more, more preferably 55% or more and very preferably 60% or more;

-one or more compounds of formula IIA and one or more compounds of formula IIB and one or more compounds of formula V in a total concentration of 60% or more, more preferably 65% or more, very preferably 70% or more, in particular 73% or 74% or more;

-one or more compounds of formula IV in a total concentration of less than 30%, preferably less than 29%, more preferably less than 28% or 27% or 26%;

-one or more compounds of formula IV in a total concentration ranging from 15% to 45%, more preferably from 18% to 38%, still more preferably from 21% to 30%, very preferably from 22% to 28%, or from 22% to 26%;

-one or more compounds of formula IV-2 in a total concentration ranging from 1% to 8%, more preferably from 2% to 7%, still more preferably from 3% to 6%, very preferably from 4% to 5%;

-one or more compounds of formula IV-3, preferably IV-3-4 and IV-3-1, in a total concentration in the range of 10% to 35%, more preferably 12% to 32%, still more preferably 16% to 28%, very preferably 18% to 22%;

-a compound of formula IV-3-4 in a total concentration in the range of 5% to 25%, more preferably 10% to 22%, very preferably 13% to 17%;

-a compound of formula IV-3-1, having a total concentration in the range of 1% to 12%, more preferably 2% to 10%, very preferably 3% to 7%;

-one or more compounds of formula V in a total concentration ranging from 15% to 40%, more preferably from 17% to 38%, still more preferably from 19% to 30%, very preferably from 20% to 26%;

-one or more compounds of formula V-3 in a total concentration ranging from 1% to 12%, more preferably from 2% to 10%, still more preferably from 3% to 9%, very preferably from 4% to 8%;

-one or more compounds of formula V-10 in a total concentration ranging from 5% to 30%, more preferably from 10% to 25% and very preferably from 12% to 18%.

As liquid-crystalline media according to the invention, it is advantageous to have nematic phases of from.ltoreq.20℃to.gtoreq.100℃and particularly preferably from.ltoreq.30℃to.gtoreq.110℃and very particularly preferably from.ltoreq.40℃to.gtoreq.120 ℃.

The medium according to the invention has a clearing temperature of 90 ℃ or more, preferably 100 ℃ or more, more preferably 105 ℃ or more and in particular 110 ℃ or more.

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 the heating from the nematic phase does not yet clear (phase transition to isotropic phase). The low temperature study was performed in a flow viscometer at the corresponding temperature and tested by storage in a test box having a layer thickness corresponding to the electro-optic application for at least 100 hours. 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. The response times were 500 hours and 250 hours at temperatures of-30℃and-40℃respectively. At elevated temperature, the clearing point is measured in a capillary tube by conventional methods.

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 mixture is nematic at a temperature of-20 ℃ or less, preferably-30 ℃ or less, and very preferably-40 ℃ or less.

In a preferred embodiment of the invention, the medium has a birefringence in the range of 0.085 to 0.110, preferably 0.090 to 0.105, in particular 0.095 to 0.100.

The liquid-crystalline mixtures according to the invention have a dielectric anisotropy Δεof from-2.5 to-5.0, preferably from-2.8 to-4.0, in particular from-3.0 to-3.5.

The rotational viscosity gamma ₁ at 20℃preferably ranges from 150 to 250mPas, more preferably from 170 to 210 mPas.

The liquid-crystalline medium according to the invention has a relatively low value of the threshold voltage (V ₀). They are preferably in the range from 1.7V to 3.0V, particularly preferably 2.8V or less, very particularly preferably 2.6V or less.

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

Furthermore, 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 "dielectrically positive compounds" means compounds having a Δε >1.5, the term "dielectrically neutral compounds" means those having a Δε of-1.5.ltoreq.Δε.ltoreq.1.5 and the term "dielectrically negative compounds" 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 according to the invention are expressed in degrees celsius.

Preferably, the liquid-crystalline medium according to the invention has a negative dielectric anisotropy (Δε).

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

It will be apparent to those 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 are replaced by the corresponding isotopes.

The compounds according to the invention can be synthesized by known methods or analogously to what is described in the literature (for example in standard works, for example Houben-Weyl,Methoden der Organischen Chemie[Methods of Organic Chemistry],Georg-Thieme-Verlag,Stuttgart), under reaction conditions which are known and are suitable for the reaction in question, variants which are known per se can also be used here but are not mentioned here.

Other mesogenic compounds not explicitly mentioned above may also optionally and advantageously be used in the medium according to the invention. Such compounds are known to those skilled in the art.

Detailed Description

For the present invention and in the following examples, the structures of the liquid crystal compounds are indicated by abbreviations, which are converted into chemical formulas according to tables a to C below. All radicals C _mH_2m+1、C_nH_2n+1 and C _lH_2l+1 or C _mH_2m-1、C_nH_2n-1 and C _lH_2l-1 are straight-chain alkyl radicals or alkylene radicals, in each case having n, m and l C atoms. Preferably, n, m and l are each independently 1,2,3,4,5,6 or 7. Table A shows the codes for the ring elements of the compound core, table B lists the bridging units, and Table C lists the symbolic meanings of the left-hand and right-hand end groups of the molecule. The abbreviation consists of a code of ring elements with optional linking groups, followed by a first hyphen and a left-hand end code, and a second hyphen and a right-hand end code. Table D shows exemplary structures of compounds and their respective abbreviations.

Table a: ring element

Table B: bridging unit

Table C: end group

Where n and m are each integers, and three points ".." is a placeholder for other abbreviations from the table.

In addition to the compounds of formulae I, IIA, IIB, IIC and/or IID, IVa, IVb and V, the mixtures of the invention optionally comprise one or more of the following compounds.

The following abbreviations are used:

(n, m, k and l are each independently of the other integers, preferably from 1 to 9, preferably from 1 to 7,k and l may also be 0 and preferably from 0 to 4, more preferably 0 or 2 and most preferably 2, n is preferably 1,2,3,4 or 5, in combination "-nO-" it is preferably 1,2,3 or 4, preferably 2 or 4, m is preferably 1,2,3,4 or 5, in combination "-Om" it is preferably 1,2,3 or 4, more preferably 2 or 4, combination "-lVm" is preferably "2V 1").

Table D

CC-n-m

CC-n-Om

CC-n-V

CC-n-Vm

CC-n-lV

CC-n-lVm

CC-V-V

CC-V-lV

CC-V-Vm

CC-Vk-lV

CC-nV-lV

CC-nV-Vm

CC-n-VV

CC-n-VVm

CVC-n-V

CVC-n-Vm

CP-n-m

CP-n-Om

PP-n-m

PP-n-Om

CCP-n-m

CCP-n-Om

CCP-V-m

CCP-nV-m

CCP-Vl-m

CCP-nVl-m

CCOC-n-m

CCZC-n-m

CCVC-n-m

CCVC-n-V

CCVC-n-lV

CLP-n-m

CLP-V-n

CPP-n-m

CPG-n-m

CGP-n-m

PGP-n-m

PGP-n-lV

PGP-n-lVm

CCZPC-n-m

CPPC-n-m

CGPC-n-m

CPGP-n-m

CY-V-n

CY-V-On

CY-nV-m

CY-nV-Om

CY-Vl-m

CY-Vl-Om

CY-nVl-m

CY-nVl-Om

PY-V-n

PY-V-On

PY-nV-m

PY-nV-Om

PY-Vl-m

PY-Vl-Om

PY-nVl-m

PY-nVl-Om

CCY-V-n

CCY-V-On

CCY-nV-m

CCY-nV-Om

CCY-Vl-m

CCY-Vl-Om

CCY-nVl-m

CCY-nVl-Om

CPY-V-n

CPY-V-On

CPY-nV-m

CPY-nV-Om

CPY-Vl-m

CPY-Vl-Om

CPY-nVl-k

CPY-nVl-Om

CY-n-m

CY-n-Om

CVY-n-m

CVY-V-n

CZY-n-Om

COY-n-m

COY-n-Om

Y-n-m

Y-n-Om

Y-nO-Om

PY-n-m

PY-n-Om

CCY-n-m

CCY-n-Om

CCY-n-mOl

CCZY-n-Om

CCOY-n-m

CCOY-n-Om

CPY-n-m

CPY-n-Om

PYP-n-m

PYP-n-V

PYP-n-lV

PYP-n-Vm

PYP-n-lVm

CP(F,Cl)-n-Om

CLY-n-m

CLY-n-Om

CK-n-F

B-n-m

B-n-lV

B-Vn-lV

B-n-Om

B-nO-Om

CB-n-Om

PB-n-Om

B(S)-nO-Om

COB(S)-n-Om

B(S)-(c3)nO-Om

B(S)-(c5)nO-Om

B(S)-(c5)nO-Om(c3)

CCY-n-Om(c3)

Examples

The invention is illustrated in detail by the following non-limiting working examples.

The following abbreviations and symbols are used:

v _o represents the threshold voltage at 20 c, the capacitance 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 optical anisotropy 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 20 c and 1kHz,

Delta epsilon represents the dielectric anisotropy at 20 deg.c and 1kHz,

Cl.p., T (N, I) represents a clear light spot [. Degree.C ],

Gamma ₁ represents the rotational viscosity at 20 c [ mpa·s ],

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

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

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

Unless explicitly stated otherwise, all concentrations in the present application are expressed in weight percent and relate to the corresponding mixture as a whole, including all solid or liquid crystal components, without solvent.

All temperature values indicated in the present application, e.g. melting point T (C, N), transition from smectic phase (S) to nematic phase (N) T (S, N) and clearing point T (N, I) are all referred to in degrees celsius (°c), unless otherwise indicated. M.p. represents melting point, cl.p. =clearing point. Further, c=crystalline, n=nematic, s=smectic and i=isotropic phases. The data between these symbols represents the transition temperature.

Unless otherwise indicated, all physical properties were and have been determined in accordance with "Merck Liquid Crystals, physical Properties of Liquid Crystals", status nov 1997, MERCK KGAA, germany, and applied to temperatures of 20 ℃, and Δn at 589nm and Δε at 1kHz in each case.

The term "threshold voltage" as used in the present invention relates to a capacitive threshold (V ₀), which is also referred to as Freedericks threshold unless otherwise indicated. In an embodiment, as usual, the optical threshold may also be referenced to a relative contrast of 10% (V ₁₀).

The process of polymerizing the polymerizable compounds in PSA displays as described above and as described below, unless otherwise indicated, is carried out at a temperature at which the LC medium exhibits a liquid crystal phase, preferably a nematic phase, and most preferably at room temperature.

Unless otherwise specified, the methods of preparing the test cartridge and measuring its electro-optic and other properties should be performed using methods described below or similar thereto.

The display for measuring the capacitive threshold voltage consists of two plane-parallel glass outer plates at a distance of 25 μm, each having an electrode layer on the inside and an unwarped polyimide alignment layer on top, which results in homeotropic alignment of the liquid crystal molecules.

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

The polymerizable compound is polymerized in the display or the test cartridge by irradiating with UV light of a defined intensity for a predetermined time while applying a voltage (typically 10V-30V alternating current, 1 kHz) to the display. In the examples, unless otherwise indicated, polymerization was carried out using a fluorescent lamp and an intensity of 0 to 20mW/cm ². The intensity was measured using a standard instrument (Ushio Accumulate UV instrument (UV meter) with a center wavelength of 313 nm).

Transmittance (transmission) measurements (from Merck ltd., japan;1 pixel fishbone electrode (ITO, 10x10mm, fishbone angle 47.7 °,3 μm line/3 μm space), 3.2 μm cell gap, AF-glass, tilt 1 °) were performed in a test cartridge with a fishbone electrode layout.

Examples

Nematic LC host mixtures H1 to H9 were formulated as follows:

Mixture H1

Mixture H2

Mixture H3

Mixture H4

Mixture H5

Mixture H6

Mixture H7

Mixture H8

Mixture H9

Chiral nematic mixtures

Chiral nematic mixtures are prepared from the above nematic host mixtures H1 by adding chiral dopants S-811, S-2011 or S-4011, respectively.

Stabilizers of the following formula I are used:

in addition to the compounds of formula I, the following stabilizers are used:

Examples of mixtures

Using the host mixtures H1 to H9, the following LC mixtures Ch-1 to Ch-10 according to the invention were obtained, which have the physical properties shown in the following table.

Mixture Ch-1

Mixture Ch-2

Mixture Ch-3

Mixture Ch-4

Mixture Ch-5

Mixture Ch-6

Mixture Ch-7

Mixture Ch-8

Mixture Ch-9

Mixture Ch-10

Polymerizable chiral nematic mixtures

By adding Reactive Mesogens (RMs) selected from the group of compounds of formulae RM1, RM2, RM3 and RM4 in the amounts (%rm) given in table 4, the following polymerizable chiral nematic mixtures were prepared from the chiral nematic mixtures given in table 1:

table 4: polymerizable chiral nematic mixtures

Mixture of	LC body	RM	％RM
				PCh1	Ch1	RM1	0.3
PCh2	Ch1	RM2	0.3
				PCh3	Ch1	RM3	0.4
PCh4	Ch1	RM4	0.3
				PCh5	Ch2	RM1	0.2
PCh6	Ch2	RM2	0.25
				PCh7	Ch2	RM3	0.25
PCh8	Ch2	RM4	0.25

Claims

1. A liquid crystalline medium comprising

A) One or more compounds of formula I

Wherein the method comprises the steps of

Ar represents an aromatic or heteroaromatic hydrocarbon group having 4 to 40C atoms;

sp represents a spacer group;

HA representation

R ^H represents H, O ^·,CH₃, OH OR OR ^S;

R ^S1,R^S2,R^S3 and R ^S4, which are identical or different, represent alkyl groups having 1 to 6C atoms;

G represents H or R ^S or the group Z ^S -HA;

z is an integer from 1 to 6, and

Q is 3 or 4;

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

Wherein the method comprises the steps of

R ^2A,R^2B,R^2C and R ^2D each independently of one another represent H, alkyl or alkenyl having up to 15C atoms, which is unsubstituted, monosubstituted by CN or CF ₃ or at least monosubstituted by halogen, where 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 linked to one another,

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

y represents H, F, cl, CF ₃,CHF₂ or CH ₃;

Z ²,Z^2B and Z ^2D each independently of one another represent a single bond ,-CH₂CH₂-,-CH＝CH-,-CF₂O-,-OCF₂-,-CH₂O-,-OCH₂-,-COO-,-OCO-,-C₂F₄-,-CF＝CF- or-ch=chch ₂ O-;

p represents a group selected from 0,1 or 2,

Q represents 0 or 1, and

V represents an integer 1,2,3,4,5 or 6;

And

C) One or more chiral dopants.

2. The liquid-crystalline medium according to claim 1, wherein the one or more compounds of formula I are selected from the group consisting of compounds of formula I-1, I-2 and I-3:

Wherein R ^H has the meaning given in claim 1, n is an integer from 0 to 12, and Sp represents a spacer group.

3. A liquid-crystalline medium according to claim 1 or2, wherein the radical R ^H represents H or O ^·.

4. A liquid-crystalline medium according to one or more of claims 1 to 3, wherein the medium comprises one or more compounds of formula ST-3

Wherein the method comprises the steps of

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

At each occurrence, identically or differently, represent

Z ^ST 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

P represents 0,1 or 2.

5. Liquid-crystalline medium according to one or more of claims 1 to 4, wherein the medium comprises one or more compounds of formula V

Wherein the method comprises the steps of

R ⁵¹ and R ⁵², which are identical or different, represent alkyl having 1 to 7C atoms, alkoxy having 1 to 7 carbon atoms, or alkoxyalkyl, alkenyl or alkenyloxy having 2 to 7C atoms,

The same or different expressions

Z ⁵¹,Z⁵² each independently of the other represents-CH ₂CH₂-,-CH₂ O-, -ch=ch-, -c≡c-, -COO-, or a single bond, and

N is 1 or 2.

6. Liquid-crystalline medium according to one or more of claims 1 to 5, wherein the medium comprises one or more compounds of the formulae V-1 to V-16

Wherein R ⁵¹ and R ⁵² represent a linear alkyl group having 1 to 7C atoms or an alkenyl group having 2 to 7 carbon atoms.

7. The liquid-crystalline medium according to one or more of claims 1 to 6, wherein the medium comprises one or more chiral dopants selected from compounds of the formulae a-I to a-III and a-Ch:

Wherein the method comprises the steps of

R ^a11、R^a12 and R ^b12 independently of one another represent alkyl having 1 to 15C atoms, wherein one or more non-adjacent CH ₂ groups can each be replaced independently of one another by-C (R ^z)＝C(R^z) -, -C.ident.C-, -O-, S-, -CO-O-, -O-CO-, or-O-CO-O-is replaced in such a manner that O and/or S atoms are not directly linked to each other, and wherein, in addition, one or more H atoms may each be replaced by F, cl, br, I or CN, provided that R ^a12 is different from R ^b12,

R ^a21 and R ^a22 independently of one another represent alkyl having 1 to 15C atoms, wherein one or more non-adjacent CH ₂ groups can each be replaced independently of one another by-C (R ^z)＝C(R^z) -, -C.ident.C-, -O-, S-, -CO-O-, -O-CO-, or-O-CO-O-is replaced in such a manner that O and/or S atoms are not directly linked to each other, and wherein, in addition, one or more H atoms may be replaced by F, cl, br, I or CN,

R ^a31、R^a32 and R ^b32 independently of one another represent a linear or branched alkyl radical having 1 to 15C atoms, where, in addition, one or more non-adjacent CH ₂ groups can each be replaced independently of one another by-C (R ^z)＝C(R^z) -, -C.ident.C-, -O-, -S-, -CO-, -CO-O-, -O-CO-or-O-CO-O-is replaced in such a way that O and/or S atoms are not directly linked to each other, and wherein additionally one or more H atoms may be replaced by F, cl, br, I or CN, provided that R ^a32 is different from R ^b32,

R ^z represents H, CH ₃, F, cl or CN,

R ⁸ has one of the meanings given above for R ^a11,

Z ⁸ represents-C (O) O-, CH ₂O,CF₂ O or a single bond,

As defined in A ¹² below, or alternatively represent

Representation of

Wherein L ¹² in each case independently of one another represents halogen, CN, or alkyl, alkenyl, alkoxy or alkenyloxy having up to 12C atoms and wherein one or more H atoms are optionally replaced by halogen,

Representation of

With a target ofThe meaning of the terms is given in,

With a target ofGiven meaning, or alternatively, represent

With a target ofThe meaning of the terms is given in,

N2 is, identically or differently, at each occurrence, 0, 1 or 2,

N3 is 1,2 or 3, and

R is 0, 1,2, 3 or 4.

8. The liquid-crystalline medium according to one or more of claims 5 to 7, wherein the medium comprises one or more compounds of formula IIA and one or more compounds of formula IIB and one or more compounds of formula V in a total concentration of 60% or more.

9. Liquid-crystalline medium according to one or more of claims 1 to 8, wherein the helical pitch of the medium is in the range of 5 μm to 50 μm.

10. The liquid-crystalline medium according to one or more of claims 1 to 9, wherein the medium has a clearing temperature of 100 ℃ or more.

11. The liquid-crystalline medium according to one or more of claims 1 to 10, wherein the medium further comprises a polymerizable compound.

12. A liquid crystal display comprising a liquid crystal medium as defined in any one of claims 1 to 11.

13. The liquid crystal display of claim 12, wherein the display is a VA, IPS or FFS type display.

14. Use of a liquid-crystalline medium according to one or more of claims 1 to 11 in VA, IPS, FFS, PS-VA, PS-IPS or PS-FFS displays.

15. A process for the preparation of a liquid-crystalline medium according to any one of claims 1 to 11, comprising the step of mixing one or more compounds of formula I as defined in claim 1 with one or more compounds selected from the group consisting of compounds of formulae IIA, IIB, IIC and IID, and with one or more chiral dopants, and optionally with a polymerisable compound or other liquid-crystalline compound or additive.