Patent Application
20220372371
Aspects of the present invention include liquid-crystalline (LC) media having positive dielectric anisotropy and to liquid-crystal displays (LCDs) containing these media, especially to displays addressed by an active matrix and in particular to LC displays of the TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, XB-FFS, PS-FFS, SA-HB-FFS, SA-XB-FFS, polymer stabilised SA-HB-FFS, polymer stabilised SA-XB-FFS, positive VA or positive PS-VA type.
Liquid-crystal displays (LCDs) are used in many areas for the display of information. LCDs are used both for direct-view displays and for projection-type displays. The electro-optical modes used are, for example, the twisted nematic (TN), super twisted nematic (STN), optically compensated bend (OCB) and electrically controlled birefringence (ECB) modes together with their various modifications, as well as others. All these modes utilise an electric field which is generated substantially perpendicular to the substrates and the liquid-crystal layer.
Besides these modes, there are also electro-optical modes that utilise an electric field which is substantially parallel to the substrates or the liquid-crystal layer. For example, WO 91/10936 discloses a liquid-crystal display in which the electric signals are generated in such a way that the electric fields have a significant component parallel to the liquid-crystal layer, and which has since then become known as in-plane switching IPS) display. The principles of operating such a display are described, for example, by R. A. Soref in Journal of Applied Physics, Vol. 45, No. 12, pp. 5466-5468 (1974).
IPS displays contain an LC layer between two substrates with planar orientation, where the two electrodes are arranged on only one of the two substrates and preferably have interdigitated, comb-shaped structures. On application of a voltage to the electrodes an electric field with a significant component parallel to the LC layer is generated between them. This causes realignment of the LC molecules in the layer plane.
EP 0 588 568, for example, discloses various possibilities for the design of the electrodes and for addressing an IPS display. DE 198 24 137 likewise describes various embodiments of such IPS displays.
Liquid-crystalline materials for IPS displays of this type are described, for example, in DE 195 28 104.
Furthermore, so-called “fringe-field switching” (FFS) displays have been reported (see, inter alia, S. H. Jung et al., Jpn. J. Appl. Phys., Volume 43, No. 3, 2004, 1028), which contain two electrodes on the same substrate, one of which is structured in a comb-shaped manner and the other is unstructured. A strong, so-called “fringe field” is thereby generated, i.e. a strong electric field close to the edge of the electrodes, and, throughout the cell, an electric field which has both a strong vertical component and also a strong horizontal component. FFS displays have a low viewing-angle dependence of the contrast. FFS displays usually contain an LC medium with positive dielectric anisotropy, and an alignment layer, usually of polyimide, which provides planar alignment to the molecules of the LC medium.
Liquid-crystal displays of the IPS and FFS electro-optical mode are in particular suitable for use in modern desktop monitors, TV sets and multimedia applications. The liquid-crystalline media according to the present invention are preferably used in displays of this type. In general, dielectrically positive liquid-crystalline media having rather lower values of the dielectric anisotropy are used in FFS displays, but in some cases liquid-crystalline media having a dielectric anisotropy of only about 3 or even less are also used in IPS displays.
A further improvement has been achieved by the HB-FFS mode. One of the unique features of the HB-FFS mode in contrast to the traditional FFS technology is that it enables higher transmittance which allows operation of the panel with less energy consumption.
Another recently developed mode is the XB-FFS mode, wherein the liquid-crystalline medium additionally contains a polar liquid crystal compound with low dielectric anisotropy.
Liquid-crystal compositions which are suitable for LCDs and especially for FFS and IPS displays are known in prior art, for example, from JP 07-181 439 (A), EP 0 667 555, EP 0 673 986, DE 195 09 410, DE 195 28 106, DE 195 28 107, WO 96/23 851 and WO 96/28 521. However, these compositions have certain disadvantages. Amongst other deficiencies, most of them result in disadvantageously long addressing times, have inadequate values of the resistivity and/or require excessively high operating voltages. Both an improvement in the operating properties and also in the shelf life are necessary here.
FFS and IPS displays can be operated as active-matrix displays (AMD) or passive-matrix displays (PMD). In the case of active-matrix displays individual pixels are usually addressed by integrated, non-linear active elements such as, for example, thin-film transistors (TFTs), while in the case of passive-matrix displays individual pixels are usually addressed by the multiplex method as known from the prior art.
The displays according to the present invention are preferably operated by an active matrix, preferably by a matrix of TFT. However, the liquid crystals according to the invention can also advantageously be used in displays having other known addressing means.
Typical applications of in-plane switching (IPS) and fringe field switching (FFS) technologies are monitors, notebooks, televisions, mobile telephones, tablet PCs, etc.
Both the IPS and the FFS technology have certain advantages over other LCD technologies, such as, for example, the vertical alignment (VA) technology, e.g. a broad viewing angle dependency of the contrast.
The provision of further liquid-crystalline media and the use thereof in a display having high transmission, a good black state and a high contrast ratio is a central challenge for modern FFS and IPS applications. In addition, modern applications also require good low-temperature stability and fast addressing times.
The invention has an object of providing liquid-crystalline media, in particular for FFS and IPS displays, but also for TN, positive VA or STN displays, and in particular for active-matrix displays like those addressed by TFTs, which do not exhibit the disadvantages indicated above or only do so to a lesser extent and preferably have high specific resistance, low threshold voltage, high dielectric anisotropy, a good low temperature stability (LTS), fast response times and low rotational viscosities, and enable high brightness.
This was achieved by providing liquid-crystalline media as described and claimed hereinafter.
In case of FFS displays there is a need for further optimization of response time, contrast, brightness and reliability. However, it was found that the liquid-crystalline materials of the prior art do often not achieve all these requirements at the same time.
It has now been surprisingly found that liquid-crystalline media according to the present invention which contain compounds of formula I and particularly when in combination with compounds of the formulae Z show several improvements, especially when being used in FFS mode displays, like a good solubility and a low ratio of γ1/K1, and enable fast response times.
The liquid-crystal media according to the present invention are especially suitable for use in liquid-crystal displays of the FFS, HB-FFS, XB-FFS and IPS mode based on dielectrically positive liquid crystals, and polymer stabilised variants thereof.
The invention relates, for example, to a liquid-crystalline medium, characterised in that it has positive dielectric anisotropy and comprises one or more compounds of formula I
in which the individual radicals, on each occurrence identically or differently, and each, independently of one another, have the following meaning:
—C≡C—, —CF2O—, —OCF2—, —CH═CH—, —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another,
The invention further relates to the use of a liquid-crystalline medium as described above and below for electro-optical purposes, in particular for the use in liquid-crystal displays, shutter glasses, LC windows, 3D applications, preferably in TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, XB-FFS, PS-HB-FFS, PS-XB-FFS, SA-HB-FFS, SA-XB-FFS, polymer stabilised SA-HB-FFS, polymer stabilised SA-XB-FFS, positive VA and positive PS-VA displays, very preferably in FFS, HB-FFS, IPS, PS-HB-FFS and PS-IPS displays.
The invention further relates to an electro-optical liquid-crystal display containing a liquid-crystalline medium as described above and below, in particular a TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, XB-FFS, PS-HB-FFS, PS-XB-FFS, SA-HB-FFS, SA-XB-FFS, polymer stabilised SA-HB-FFS, polymer stabilised SA-XB-FFS, positive VA or positive PS-VA display, preferably a FFS, HB-FFS, IPS, PS-HB-FFS or PS-IPS display.
In the present application, all atoms also include their isotopes. In a preferred embodiment one or more hydrogen atoms (H) are replaced by deuterium (D); a high degree of deuteration enables or simplifies analytical determination of compounds, in particular in the case of low concentrations.
In the formulae above and below, halogenated means that one or more hydrogen atoms on one or more carbon atoms are replaced by a halogen atom. The halogen atoms are preferably F or Cl.
In the formulae above and below, if R0, R1 or R2 denotes an alkyl radical and/or an alkoxy radical, this may be straight-chain or branched. It is preferably straight-chain, has 2, 3, 4, 5, 6 or 7 C atoms and accordingly preferably denotes ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexyloxy or heptyloxy, furthermore methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy or tetradecyloxy. R0 preferably denotes straight-chain alkyl having 2-6 C atoms.
Oxaalkyl preferably denotes straight-chain 2-oxapropyl (=methoxymethyl), 2- (=ethoxymethyl) or 3-oxabutyl (=2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl.
If R0, R1 or R2 denotes an alkoxy or oxaalkyl group it may also contain one or more additional oxygen atoms, provided that oxygen atoms are not linked directly to one another.
In another preferred embodiment, one or more of R0, R1 and R2 are selected from the group consisting of
—S1—F, —O—S1—F, —O—S1—O—S2, wherein S1 is C1-12-alkylene or C2-12-alkenylene and S2 is H, C1-12-alkyl or C2-12-alkenyl, and very preferably one or more of R0, R1 and R2 are selected from the group consisting of
—OCH2 OCH3, —O(CH2)2OCH3, —O(CH2)3OCH3, —O(CH2)4OCH3, —O(CH2)2F, —O(CH2)3F, —O(CH2)4F.
If R0, R1 or R2 denotes an alkyl radical in which one CH2 group has been replaced by —CH═CH—, this may be straight-chain or branched. It is preferably straight-chain and has 2 to 10 C atoms. Accordingly, it denotes, in particular, vinyl, prop-1- or -2-enyl, but-1-, -2- or -3-enyl, pent-1-, -2-, -3- or -4-enyl, hex-1-, -2-, -3-, -4- or -5-enyl, hept-1-, -2-, -3-, -4-, -5- or -6-enyl, oct-1-, -2-, -3-, -4-, -5-, -6- or -7-enyl, non-1-, -2-, -3-, -4-, -5-, -6-, -7- or -8-enyl, dec-1-, -2-, -3-, -4-, -5-, -6-, -7-, -8- or -9-enyl.
If R0, R1 or R2 denotes an alkyl or alkenyl radical which is at least monosubstituted by halogen, this radical is preferably straight-chain, and halogen is preferably F or Cl. In the case of polysubstitution, halogen is preferably F.
The resultant radicals also include perfluorinated radicals. In the case of monosubstitution, the fluorine or chlorine substituent may be in any desired position, but is preferably in the ω-position.
In the formulae above and below, X0 is preferably F, Cl or a mono- or polyfluorinated alkyl or alkoxy radical having 1, 2 or 3 C atoms or a mono- or polyfluorinated alkenyl radical having 2 or 3 C atoms. X0 is particularly preferably F, Cl, CF3, CHF2, OCF3, OCHF2, OCFHCF3, OCFHCHF2, OCFHCHF2, OCF2CH3, OCF2CHF2, OCF2CHF2, OCF2CF2CHF2, OCF2CF2CHF2, OCFHCF2CF3, OCFHCF2CHF2, OCF2CF2CF3, OCF2CF2CCIF2, OCCIFCF2CF3, OCH═CF2 or CH═CF2, very particularly preferably F or OCF3, furthermore CF3, OCF═CF2, OCHF2 or OCH═CF2.
In the LC media according to the present invention the use of compounds of formula I together with compounds of formulae Z1 to Z3 or their subformulae enables to achieve an increased value of EL and at the same time a decrease of the rotational viscosity and the ratios of γ1/K2 and γ1/K1, and thus fast response times.
In the compounds of formula I and its subformulae R0 preferably denotes straight-chain alkyl or alkoxy having 1 to 6 C atoms, very preferably methyl, ethyl or propyl, most preferably n-propyl.
Preferred compounds of formula I are those wherein Y1 and Y2 denote F or Cl, very preferably F.
Very preferred compounds of formula I are those selected from the group consisting of the following subformulae
wherein Y5 is H or CH3, preferably H.
Very preferred are the compounds of formulae I1, I2, I3 and I4, most preferred is the compound formula I2.
The proportion of the compounds of formula I or its subformulae in the medium is preferably from 2 to 35%, very preferably from 3 to 30%, most preferably from 4 to 20% by weight.
Preferably the medium contains 1, 2 or 3 compounds of formula I or its subformulae.
Preferably the medium contains, in addition to the compounds of formula I, one or more compounds selected from the following formulae
wherein “alkyl” is C1-6-alkyl, and preferably denotes propyl, butyl or pentyl, very preferably propyl or butyl. Very preferred are compounds of formula Z1.
Preferred compounds of formula Z1, Z2 and Z3 are those selected from the following subformulae
Very preferred are compounds of formula Z1-1 and Z2-1.
In another preferred embodiment the medium contains one or more compounds of formula Z1 or its preferred subformulae and one or more compounds selected from formulae Z2 and Z3 or their preferred subformulae.
Preferably the total proportion of compounds of formula Z1, Z2 and Z3 or their subformulae in the medium is from 10 to 65%, very preferably from 15 to 60%, most preferably from 20 to 55% by weight.
Preferably the medium contains 1, 2 or 3 compounds selected from the formulae Z1, Z2 and Z3 or their subformulae.
In a first preferred embodiment according to the present invention, the LC medium contains, in addition to the compounds of formula I, one or more compounds selected from the formulae Y and B
in which the individual radicals, on each occurrence identically or differently, and each, independently of one another, have the following meaning:
Preferably the LC medium according to this first preferred embodiment contains one or more compounds of formula I, one or more compounds selected from formulae Z1, Z2 and Z3, and one or more compounds selected from formulae Y and B.
The LC media according to this first preferred embodiment are especially suitable for use in LC displays of the HB-FFS or PS-HB-FFS mode.
In a second preferred embodiment according to the present invention, the LC medium does not contain a compound of the formulae Y or B.
In the compounds of formula Y and its subformulae, R1 and R2 preferably denote straight-chain alkyl or alkoxy having 1 to 6 C atoms, furthermore alkenyl having 2 to 6 C atoms, in particular vinyl, 1E-propenyl, 1E-butenyl, 3-butenyl, 1E-pentenyl, 3E-pentenyl or 4-pentenyl.
In the compounds of formula Y and its subformulae, preferably both radicals L1 and L2 denote F. In another preferred embodiment of the present invention, in the compounds of formula Y and its subformulae one of the radicals L1 and L2 denotes F and the other denotes Cl.
In a preferred embodiment of the present invention the medium contains one or more compounds of formula Y selected from the following subformulae
wherein L1, L2, R1, R2, Zx, Zy, x and y have the meanings given in formula Y or one of the preferred meanings given above and below,
denotes
Preferably, in the compounds of formula Y1 and Y2 both L1 and L2 denote F or one of L1 and L2 denotes F and the other denotes Cl, or both L3 and L4 denote F or one of L3 and L4 denotes F and the other denotes Cl.
Preferably the medium comprises one or more compounds of the formula Y1 selected from the group consisting of the following subformulae
in which a denotes 1 or 2, “alkyl” and “alkyl*” each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms, and “alkenyl” denotes a straight-chain alkenyl radical having 2-6 C atoms, and (O) denotes an oxygen atom or a single bond. “alkenyl” preferably denotes CH2═CH—, CH2═CHCH2CH2—, CH3—CH═CH—, CH3—CH2—CH═CH—, CH3—(CH2)2—CH═CH—, CH3—(CH2)3—CH═CH— or CH3—CH═CH—(CH2)2—.
Very preferably the medium contains one or more compounds of formula Y1 selected from formulae Y1-2 and Y1-10.
Further preferably the medium comprises one or more compounds of the formula Y2 selected from the group consisting of the following subformulae:
in which “alkyl” and “alkyl*” each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms, and “alkenyl” denotes a straight-chain alkenyl radical having 2-6 C atoms, and (O) denotes an oxygen atom or a single bond. “alkenyl” preferably denotes CH2═CH—, CH2═CHCH2CH2—, CH3—CH═CH—, CH3—CH2—CH═CH—, CH3—(CH2)2—CH═CH—, CH3—(CH2)3—CH═CH— or CH3—CH═CH—(CH2)2—.
Very preferably the medium contains one or more compounds of formula Y2 selected from formulae Y2-2 and Y2-10.
The proportion of the compounds of formula Y1 or its subformulae in the medium is preferably from 1 to 10% by weight.
The proportion of the compounds of formula Y2 or its subformulae in the medium is preferably from 1 to 10% by weight.
The total proportion of the compounds of formula Y1 and Y2 or their subformulae in the medium is preferably from 1 to 20%, very preferably from 2 to 15% by weight.
Preferably the medium contains 1, 2 or 3 compounds of formula Y1 and Y2 or their subformulae, very preferably selected from formulae Y1-2, Y1-10, Y1-40, Y1-42, Y2-2 and Y2-10.
In another preferred embodiment of the present invention the medium contains one or more compounds of formula Y selected from the following subformula
wherein L1, L2, R1 and R2 have one of the meanings given in formula Y or one of the preferred meanings as given above and below.
Preferred compounds of the formula Y3 are selected from the group consisting of the following subformulae
in which, “Alkyl” and “Alkyl*” each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms, “Alkoxy” denotes a straight-chain alkoxy radical having 1-6 C atoms, “Alkenyl” and “Alkenyl*” each, independently of one another, denote a straight-chain alkenyl radical having 2-6 C atoms, and O denotes an oxygen atom or a single bond. “Alkenyl” and “Alkenyl*” preferably denote CH2═CH—, CH2═CHCH2CH2—, CH3—CH═CH—, CH3—CH2—CH═CH—, CH3—(CH2)2—CH═CH—, CH3—(CH2)3—CH═CH— or CH3—CH═CH—(CH2)2—.
Particularly preferred compounds of the formula Y3 are selected from the group consisting of following subformulae:
wherein “Alkoxy” preferably denotes straight-chain alkoxy with 3, 4, or 5 C atoms.
Preferably in the compounds of formula Y3 and its subformulae both L1 and L2 denote F. Further preferably in the compounds of formula Y3 one of the radicals L1 and L2 denotes F and the other denotes Cl.
The proportion of the compounds of formula Y3 or its subformulae in the medium is preferably from 1 to 10%, very preferably from 1 to 6% by weight.
Preferably the medium contains 1, 2 or 3 compounds of formula Y3 or its subformulae, preferably of formula Y3-6, very preferably of formula Y3-6A.
In another preferred embodiment the present invention the medium contains one or more compounds of formula Y selected from the subformula Y4
in which R1 and R2 each, independently of one another, have one of the meanings indicated above, and
each, independently of one another, denote
in which L5 denotes F or Cl, preferably F, and L6 denotes F, Cl, OCF3, CF3, CH3, CH2F or CHF2, preferably F, and preferably at least one of the rings G, I and K is different from unsubstituted benzene.
Preferred compounds of the formula Y4 are selected from the group consisting of the following sub-formulae:
in which R denotes a straight-chain alkyl or alkoxy radical having 1-7 C atoms, R* denotes a straight-chain alkenyl radical having 2-7 C atoms, (O) denotes an oxygen atom or a single bond, and m denotes an integer from 1 to 6. R* preferably denotes CH2═CH—, CH2═CHCH2CH2—, CH3—CH═CH—, CH3—CH2—CH═CH—, CH3—(CH2)2—CH═CH—, CH3—(CH2)3—CH═CH— or CH3—CH═CH—(CH2)2—.
R preferably denotes methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy or pentoxy.
The proportion of the compounds of formula Y4 or its subformulae in the medium is preferably from 1 to 10%, very preferably from 1 to 6% by weight.
Preferably the medium contains 1, 2 or 3 compounds of formula Y4 or its subformulae, preferably of formula Y4-1, Y4-2, Y4-3 or Y4-21, wherein R preferably denotes alkyl, furthermore alkoxy, each having 1-5 C atoms.
In another preferred embodiment the present invention the medium contains one or more compounds of formula Y selected from the group consisting of the following subformulae
in which R5 has one of the meanings indicated above for R1, “alkyl” denotes a straight-chain alkyl radical having 1-6 C atoms, Lx denotes H or F, X denotes F, Cl, OCF3, OCHF2 or OCH═CF2, d denotes 0 or 1, and z and m each, independently of one another, denote an integer from 1 to 6.
R5 in these compounds is particularly preferably C1-6-alkyl or -alkoxy or C2-6-alkenyl, d is preferably 1. X in these compounds is particularly preferably F.
The LC medium according to the invention preferably comprises one or more compounds of the above-mentioned formulae in amounts of ≥5% by weight.
In the compounds of formula B and its subformulae, R1 and R2 preferably denote straight-chain alkyl or alkoxy having 1 to 6 C atoms, in particular methoxy, ethoxy, propoxy or butoxy, furthermore alkenyl having 2 to 6 C atoms, in particular vinyl, 1E-propenyl, 1E-butenyl, 3-butenyl, 1E-pentenyl, 3E-pentenyl or 4-pentenyl.
In a preferred embodiment of the present invention the medium contains one or more compounds of formula B selected from the following subformulae
wherein L1, L2, R1, R3 and X1 have the meanings given in formula B or one of the preferred meanings given above and below.
Preferred compounds of formula B1 are selected from the following subformulae:
wherein “alkyl” denotes a straight-chain alkyl radical having 1-6 C atoms, and (O) denotes an oxygen atom or a single bond. Very preferred are compounds of formula B1-1 and B1-2 wherein both groups (O) denote an oxygen atom and “alkyl” is methyl, ethyl, propyl, butyl, pentyl or hexyl, which are preferably straight-chained. Very preferably one “alkyl” is ethyl and the other “alkyl” is n-pentyl.
Very preferred are compounds of formula B1-2.
The proportion of the compounds of formula B1 or its subformulae in the medium is preferably from 1 to 20%, very preferably from 1 to 15% by weight.
Preferably the medium contains 1, 2 or 3 compounds of formula B1 or its subformulae.
Preferred compounds of formula B2 are selected from the following subformulae:
The proportion of the compounds of formula B2 or its subformulae in the medium is preferably from 1 to 20%, very preferably from 1 to 15% by weight.
Preferably the LC medium contains 1, 2 or 3 compounds of formula B2 or its subformulae.
Preferred compounds of formula B3 are selected from the following subformulae:
wherein R1 has one of the meanings given in formula B3 and preferably denotes straight-chain alkyl having 1-6 C atoms, very preferably methyl, ethyl, propyl, butyl, pentyl or hexyl, more preferably ethyl or propyl, most preferably propyl, and X1 has one of the meanings given in formula B3 and preferably denotes CF3 or OCF3.
Preferred compounds of formula B3 are selected from the following subformulae:
wherein R1 has one of the meanings given in formula B3 and preferably denotes straight-chain alkyl having 1-6 C atoms, very preferably methyl, ethyl, propyl, butyl, pentyl or hexyl, more preferably ethyl or propyl, most preferably propyl.
Most preferred are compounds of formulae B3-1-1 and B3-2-2.
In a preferred embodiment the medium contains one or more compounds of formula B or its subformulae B1, B2, B3, B1-1, B1-2, B2-1, B2-2, B2-3, B3-1, B3-2, B3-1-1, B3-1-2, B3-2-1 and B3-2-2 wherein the dibenzofuran or dibenzothiophene group is substituted by a methyl or methoxy group, preferably by a methyl group, preferably in p-position to the substituent L1 or L2, very preferably in p-position to the substituent L2 (i.e. in m-position to the terminal group R2 or X1).
The proportion of the compounds of formula B3 or its subformulae in the LC medium is preferably from 1 to 20%, very preferably from 1 to 10% by weight.
Preferably the LC medium contains 1, 2 or 3 compounds of formula B3 or its subformulae.
Preferably the total proportion of compounds of formula Y and B or their subformulae in the medium is from 2 to 25%, very preferably from 3 to 20% by weight.
Further preferred embodiments are indicated below:
wherein R1, R2, L1, L2, X, x and Zx have the meanings given in formula Y, and wherein at least one of the rings X is cyclohexenylene.
Preferably, both radicals L1 and L2 denote F. Further preferably one of the radicals L1 and L2 denotes F and the other denotes Cl.
The compounds of the formula LY are preferably selected from the group consisting of the following sub-formulae:
in which R1 has the meaning indicated above, (O) denotes an oxygen atom or a single bond, and v denotes an integer from 1 to 6. R1 preferably denotes straight-chain alkyl having 1 to 6 C atoms or straight-chain alkenyl having 2 to 6 C atoms, in particular CH3, C2H5, n-C3H7, n-C4H9, n-C5H11, CH2═CH—, CH2═CHCH2CH2—, CH3—CH═CH—, CH3—CH2—CH═CH—, CH3—(CH2)2—CH═CH—, CH3—(CH2)3—CH═CH— or CH3—CH═CH—(CH2)2—.
Very preferred are compounds of formula LY4.
Preferably the medium contains 1, 2 or 3 compounds of formula LY, very preferably of formula LY4.
The proportion of the compounds of formula LY or its subformulae in the medium is preferably from 1 to 10% by weight.
wherein R1, R2, L1, L2, Y, y and Zy have the meanings given in formula Y, and wherein at least one of the rings Y is tetrahydropyrane.
The compounds of the formula AY are preferably selected from the group consisting of the following sub-formulae:
in which R1 has the meaning indicated above, “alkyl” denotes a straight-chain alkyl radical having 1-6 C atoms, (O) denotes an oxygen atom or a single bond, and v denotes an integer from 1 to 6. R1 preferably denotes straight-chain alkyl having 1 to 6 C atoms or straight-chain alkenyl having 2 to 6 C atoms, in particular CH3, C2H5, n-C3H7, n-C4He, n-C5H11, CH2═CH—, CH2═CHCH2CH2—, CH3—CH═CH—, CH3—CH2—CH═CH—, CH3—(CH2)2—CH═CH—, CH3—(CH2)3—CH═CH— or CH3—CH═CH—(CH2)2—.
wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings
Preferred compounds of formula II and III are those wherein Y0 is H.
Further preferred compounds of formula II and III are those wherein R0 denotes alkyl having 1 to 6 C atoms, very preferably ethyl or propyl, and X0 denotes F or OCF3, very preferably F.
in which R0 and X0 have the meanings given in formula II or one of the preferred meanings given above and below.
Preferred compounds are those of formula II1, II2 and II3, very preferred those of formula II and II2.
In the compounds of formulae II1 to II7 R0 preferably denotes alkyl having 1 to 6 C atoms, very preferably ethyl or propyl, and X0 preferably denotes F or OCF3, very preferably F.
in which R0 and X0 have the meanings given in formula II or one of the preferred meanings given above and below.
Preferred compounds are those of formula IIA1, IIA2 and IIA3, very preferred those of formula IIA1 and IIA2.
In the compounds of formulae IIA1 to IIA7 R0 preferably denotes alkyl having 1 to 6 C atoms, very preferably ethyl or propyl, and X0 preferably denotes F or OCF3, very preferably F.
in which R0 and X0 have the meanings given in formula II or one of the preferred meanings given above and below.
Preferred compounds are those of formula III1, III4, III6, III16, III19 and III20.
In the compounds of formulae III1 to III21 R0 preferably denotes alkyl having 1 to 6 C atoms, very preferably ethyl or propyl, X0 preferably denotes F or OCF3, very preferably F, and Y2 preferably denotes F.
in which R0 and X0 have the meanings given in formula III or one of the preferred meanings given above and below.
Preferred compounds are those of formula IIIA1, IIIA4, IIIA6, IIIA16, IIIA19 and IIIA20.
In the compounds of formulae IIIA1 to IIIA21 R0 preferably denotes alkyl having 1 to 6 C atoms, very preferably ethyl or propyl, X0 preferably denotes F or OCF3, very preferably F, and Y2 preferably denotes F.
in which
in which R0 and X0 have the meanings indicated above.
in which R0 has the meanings indicated above and is preferably propyl or pentyl.
in which R0 has the meanings indicated above and is preferably propyl or pentyl.
The compound(s) of the formula IVc, in particular of the formula IVc1, is (are) preferably employed in the mixtures according to the invention in amounts of 1-20% by weight, particularly preferably 2-15% by weight.
in which R0 and X0 have the meanings indicated above.
R0 preferably denotes alkyl having 1 to 6 C atoms. X0 preferably denotes F and OCF3, furthermore OCHF2, CF3, OCF═CF2 and OCH═CF2;
in which R0 and X0 have the meanings indicated above.
R0 preferably denotes alkyl having 1 to 6 C atoms. X0 preferably denotes F, furthermore OCF3, CF3, CF═CF2, OCHF2 and OCH═CF2;
in which R0 and X0 have the meanings indicated above.
R0 preferably denotes alkyl having 1 to 6 C atoms. X0 preferably denotes F, furthermore OCF3, OCHF2 and OCH═CF2.
in which X0 has the meanings indicated above, and
wherein “alkyl” has the meaning given in formula IX, “alkyl*” is methyl, butyl, pentyl or hexyl and “alkyl**” is butyl, pentyl or hexyl.
Particular preference is given to the compounds of the formulae IXa, Xb, Xc, XIa, XIb, XIIa and XIIla. In the formulae IXb and IX, “alkyl” preferably, independently of one another, denotes n-C3H7, n-C4H9 or n-C5H11, in particular n-C3H7.
Very preferred are compounds of formula Xb2;
in which L1 and L2 have the meanings indicated above, and R1 and R2 each, independently of one another, denote n-alkyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyl, each having up to 6 C atoms, and preferably each, independently of one another, denote alkyl having 1 to 6 C atoms, and the compounds of formula XIV are different from those of formula P; in the compound of the formula XIV, at least one of the radicals R1 and R2 preferably denotes alkenyl having 2 to 6 C atoms.
in which “alkyl” has the meaning indicated above, and preferably denotes methyl, ethyl or propyl;
Very preferred are compounds of formula XIVd1;
in which R1 and R2 have the meanings indicated above and preferably each, independently of one another, denote alkyl having 1 to 6 C atoms. L denotes H or F.
Particularly preferred compounds of the formula XVI are those of the sub-formulae
in which
Particular preference is given to the compounds of the formulae XVIb, XVIc and XVIg. Very particular preference is given to the compounds of the following subformulae
Very preferred are compounds of formula XVIc2, XVIg1 and XVIg2;
in which R1 and R2 have the meanings indicated above and preferably each, independently of one another, denote alkyl having 1 to 6 C atoms. L denotes H or F. Very preferred are compounds of formula XVIIa wherein L is H Very preferred are compounds of formula XVIIb wherein L is F.
in which R0 and X0 each, independently of one another, have one of the meanings indicated above, and Y1-4 each, independently of one another, denote H or F and Y5 denotes H or CH3, preferably H. X° is preferably F, Cl, CF3, OCF3 or OCHF2. R0 preferably denotes alkyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyl, each having up to 6 C atoms.
Very preferably the medium according to the invention comprises one or more compounds of the formula XXa,
in which R0 has the meanings indicated above. R0 preferably denotes straight-chain alkyl, in particular ethyl, n-propyl, n-butyl or n-pentyl and very particularly preferably n-propyl.
The compound(s) of the formula XX, in particular of the formula XXa, is (are) preferably employed in the mixtures according to the invention in amounts of 1-15% by weight, particularly preferably 2-10% by weight.
Very preferably the medium according to the invention comprises one or more compounds of the formula XXIa,
in which R0 has the meanings indicated above. R0 preferably denotes straight-chain alkyl, in particular ethyl, n-propyl, n-butyl or n-pentyl and very particularly preferably n-propyl.
The compound(s) of the formula XXI, in particular of the formula XXIa, is (are) preferably employed in the mixtures according to the invention in amounts of 1-15% by weight, particularly preferably 2-10% by weight.
Further preferably the medium according to the invention comprises one or more compounds of the formula XXIIIa,
in which R0 has the meanings indicated above. R0 preferably denotes straight-chain alkyl, in particular ethyl, n-propyl, n-butyl or n-pentyl and very particularly preferably n-propyl.
The compound(s) of the formula XXIII, in particular of the formula XXIIIa, is (are) preferably employed in the mixtures according to the invention in amounts of 0.5-5% by weight, particularly preferably 0.5-2% by weight.
in which R0, X0 and Y1-6 have the meanings indicated in formula I, s denotes 0 or 1, and
denotes
In the formula XXIV, X0 may also denote an alkyl radical having 1-6 C atoms or an alkoxy radical having 1-6 C atoms. The alkyl or alkoxy radical is preferably straight-chain.
R0 preferably denotes alkyl having 1 to 6 C atoms. X0 preferably denotes F;
in which R0, X0 and Y1 have the meanings indicated above. R0 preferably denotes alkyl having 1 to 6 C atoms. X0 preferably denotes F, and Y1 is preferably F;
is preferably
in which R1 and X0 have the meanings indicated above. R1 preferably denotes alkyl having 1 to 6 C atoms. X0 preferably denotes F or Cl. In the formula XXIV, X0 very particularly preferably denotes Cl.
in which R1 and X0 have the meanings indicated above. R1 preferably denotes alkyl having 1 to 6 C atoms. X0 preferably denotes F. The medium according to the invention particularly preferably comprises one or more compounds of the formula XXIX in which X0 preferably denotes F.
The compound(s) of the formulae XXVI-XXIX is (are) preferably employed in the mixtures according to the invention in amounts of 1-20% by weight, particularly preferably 1-15% by weight. Particularly preferred mixtures comprise at least one compound of the formula XXIX.
Very preferably the medium according to the invention comprises one or more compounds of the formula XXIXa,
in which R1 has the meanings indicated above, and preferably denotes straight-chain alkyl, in particular ethyl, n-propyl, n-butyl or n-pentyl and very particularly preferably n-propyl.
The compound(s) of the formula XXIXa is (are) preferably employed in the mixtures according to the invention in amounts of 1-15% by weight, particularly preferably 2-10% by weight.
in which R1 and X0 have the meanings indicated above. R1 preferably denotes alkyl having 1 to 6 C atoms. X0 preferably denotes F. The medium according to the invention particularly preferably comprises one or more compounds of the formula XXX1, in which X0 preferably denotes F. The compound(s) of the formulae XXX1 to XXX3 is (are) preferably employed in the mixtures according to the invention in amounts of 1-20% by weight, particularly preferably 1-15% by weight.
in which R0 and X0 and Y1-4 have the meanings indicated above with X0 being different from F
X0 is preferably Cl, CF3, OCF3 or OCHF2. Y1-4 each, independently of one another, preferably denote H or F. R0 preferably denotes alkyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyl, each having up to 6 C atoms.
Very preferably the medium according to the invention comprises one or more compounds of the formula XXXa,
in which R0 has the meanings indicated above. R0 preferably denotes straight-chain alkyl, in particular ethyl, n-propyl, n-butyl or n-pentyl and very particularly preferably n-propyl.
The compound(s) of the formula XXX, in particular of the formula XXXa, is (are) preferably employed in the mixtures according to the invention in amounts of 1-15% by weight, particularly preferably 2-10% by weight.
Further preferred LC media are selected from the following preferred embodiments, including any combination thereof:
The term “alkyl” or “alkyl*” in this application encompasses straight-chain and branched alkyl groups having 1-6 carbon atoms, in particular the straight-chain groups methyl, ethyl, propyl, butyl, pentyl and hexyl. Groups having 2-5 carbon atoms are generally preferred.
The term “alkenyl” or “alkenyl*” encompasses straight-chain and branched alkenyl groups having 2-6 carbon atoms, in particular the straight-chain groups. Preferred alkenyl groups are C2-C7-1E-alkenyl, C4-C6-3E-alkenyl, in particular C2-C6-1E-alkenyl. Examples of particularly preferred alkenyl groups are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl and 5-hexenyl. Groups having up to 5 carbon atoms are generally preferred, in particular CH2═CH, CH3CH═CH.
The term “fluoroalkyl” preferably encompasses straight-chain groups having a terminal fluorine, i.e. fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorohexyl and 7-fluoroheptyl. However, other positions of the fluorine are not excluded.
The term “oxaalkyl” or “alkoxy” preferably encompasses straight-chain radicals of the formula CnH2n+1—O—(CH2)m, in which n and m each, independently of one another, denote 1 to 6. m may also denote 0. Preferably, n=1 and m=1-6 or m=0 and n=1-3. Further preferably the alkoxy or oxaalkyl group can also contain one or more further O atoms such that oxygen atoms are not directly linked to one another.
Through a suitable choice of the meanings of R0 and X0, the addressing times, the threshold voltage, the steepness of the transmission characteristic lines, etc., can be modified in the desired manner. For example, 1E-alkenyl radicals, 3E-alkenyl radicals, 2E-alkenyloxy radicals and the like generally result in shorter addressing times, improved nematic tendencies and a higher ratio between the elastic constants k33 (bend) and k11 (splay) compared with alkyl and alkoxy radicals. 4-Alkenyl radicals, 3-alkenyl radicals and the like generally give lower threshold voltages and lower values of k33/k11 compared with alkyl and alkoxy radicals. The mixtures according to the invention are distinguished, in particular, by high Δε values and thus have significantly faster response times than the mixtures from the prior art.
The optimum mixing ratio of the compounds of the above-mentioned formulae depends substantially on the desired properties, on the choice of the components of the above-mentioned formulae and on the choice of any further components that may be present.
Suitable mixing ratios within the range indicated above can easily be determined from case to case.
The total amount of compounds of the above-mentioned formulae in the liquid-crystalline media according to the invention is not crucial. The mixtures can therefore comprise one or more further components for the purposes of optimisation of various properties. However, the observed effect on the desired improvement in the properties of the medium is generally greater, the higher the total concentration of compounds of the above-mentioned formulae.
In a particularly preferred embodiment, the liquid-crystalline media according to the invention comprise compounds of the formulae IV to VIII (preferably IV and V) in which X0 denotes F, OCF3, OCHF2, OCH═CF2, OCF═CF2 or OCF2—CF2H. A favourable synergistic action with the compounds of the formulae I, II and III results in particularly advantageous properties. In particular, mixtures comprising compounds of the formulae I, II and III are distinguished by their low threshold voltage.
The individual compounds of the above-mentioned formulae and the subformulae thereof which can be used in the liquid-crystalline media according to the invention are either known or can be prepared analogously to the known compounds.
The invention also relates to a process for the preparation of a liquid-crystalline medium as described above and below, by mixing one or more compounds of the formula I with one or more compounds of the formulae Y1, Y2 or Y3, one or more compounds of formula B, and one or more compounds selected from the group consisting of formulae II, III, IV, VI, IX, X, XIV, XII, XVI, XVIIa, XVIIb, XVIIc, XX, XXIII, XXIX, XXXI and XXXIV.
In another preferred embodiment of the present invention the liquid-crystalline medium additionally comprises one or more polymerisable compounds. The polymerisable compounds are preferably selected from formula M
Ra—B1—(Zb—B2)m—Rb M
in which the individual radicals, on each occurrence identically or differently, and each, independently of one another, have the following meaning:
Particularly preferred compounds of the formula I are those in which B1 and B2 each, independently of one another, denote 1,4-phenylene, 1,3-phenylene, naphthalene-1,4-diyl, naphthalene-2,6-diyl, phenanthrene-2,7-diyl, 9,10-dihydro-phenanthrene-2,7-diyl, anthracene-2,7-diyl, fluorene-2,7-diyl, coumarine, flavone, where, in addition, one or more CH groups in these groups may be replaced by N, cyclohexane-1,4-diyl, in which, in addition, one or more non-adjacent CH2 groups may be replaced by O and/or S, 1,4-cyclohexenylene, bicycle[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl, piperidine-1,4-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, indane-2,5-diyl or octahydro-4,7-methanoindane-2,5-diyl, where all these groups may be unsubstituted or mono- or polysubstituted by L as defined above.
Particularly preferred compounds of the formula M are those in which B1 and B2 each, independently of one another, denote 1,4-phenylene, 1,3-phenylene, naphthalene-1,4-diyl or naphthalene-2,6-diyl,
Very preferred compounds of formula M are selected from the following formulae:
in which the individual radicals, on each occurrence identically or differently, and each, independently of one another, have the following meaning:
Especially preferred are compounds of formulae M2 and M13.
Further preferred are trireactive compounds M15 to M31, in particular M17, M18, M19, M22, M23, M24, M25, M30 and M31.
In the compounds of formulae M1 to M31 the group
is preferably
wherein L on each occurrence, identically or differently, has one of the meanings given above or below, and is 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, CH3, C2H5, OCH3, COCH3, OCF3 or P-Sp-, more preferably F, Cl, CH3, OCH3, COCH3 or OCF3, especially F or CH3.
Preferred compounds of formulae M1 to M31 are those wherein P1, P2 and P3 denote an acrylate, methacrylate, oxetane or epoxy group, very preferably an acrylate or methacrylate group.
Further preferred compounds of formulae M1 to M31 are those wherein Sp1, Sp2 and Sp3 are a single bond.
Further preferred compounds of formulae M1 to M31 are those wherein one of Sp1, Sp2 and Sp3 is a single bond and another one of Sp1, Sp2 and Sp3 is different from a single bond.
Further preferred compounds of formulae M1 to M31 are those wherein those groups Sp1, Sp2 and Sp3 that are different from a single bond denote —(CH2)s1—X″—, wherein s1 is an integer from 1 to 6, preferably 2, 3, 4 or 5, and X″ is X″ is the linkage to the benzene ring and is —O—, —O—CO—, —CO—O—, —O—CO—O— or a single bond.
Particular preference is given to liquid-crystalline media comprising one, two or three polymerisable compounds of formula M, preferably selected from formulae M1 to M31.
Further preferably the liquid-crystalline media according to the present invention comprise one or more polymerisable compounds selected from Table E below.
Preferably the proportion of polymerisable compounds in the liquid-crystalline medium, preferably selected from formula M and Table E, is from 0.01 to 5%, very preferably from 0.05 to 1%, most preferably from 0.1 to 0.5%.
It was observed that the addition of one or more polymerisable compounds to the liquid-crystalline medium, like those selected from formula M and Table E, leads to advantageous properties like fast response times. Such a liquid-crystalline medium is especially suitable for use in PSA displays where it shows low image sticking, a quick and complete polymerisation, the quick generation of a low pretilt angle which is stable after UV exposure, a high reliability, high VHR value after UV exposure, and a high birefringence.
By appropriate selection of the polymerisable compounds it is possible to increase the absorption of the liquid-crystalline medium at longer UV wavelengths, so that it is possible to use such longer UV wavelengths for polymerisation, which is advantageous for the display manufacturing process.
The polymerisable group P is a group which is suitable for a polymerisation reaction, such as, for example, free-radical or ionic chain polymerisation, polyaddition or polycondensation, or for a polymer-analogous reaction, for example addition or condensation onto a main polymer chain. Particular preference is given to groups for chain polymerisation, in particular those containing a C≡C double bond or —C≡C— triple bond, and groups which are suitable for polymerisation with ring opening, such as, for example, oxetane or epoxide groups.
Preferred groups P are selected from the group consisting of CH2═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 W4W5W6Si—, in which W1 denotes H, F, Cl, CN, CF3, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, Cl or CH3, W2 and W3 each, independently of one another, denote H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, W4, W5 and W6 each, independently of one another, denote Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms, W7 and W8 each, independently of one another, denote H, C1 or alkyl having 1 to 5 C atoms, Phe denotes 1,4-phenylene, which is optionally substituted by one or more radicals L as defined above which are other than P-Sp-, k1, k2 and k3 each, independently of one another, denote 0 or 1, k3 preferably denotes 1, and k4 denotes an integer from 1 to 10.
Very preferred groups P are selected from the group consisting of CH2═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═CHCH2)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 W4W5W6Si—, in which W1 denotes H, F, Cl, CN, CF3, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, Cl or CH3, W2 and W3 each, independently of one another, denote H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, W4, W5 and W6 each, independently of one another, denote Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms, W7 and W8 each, independently of one another, denote H, C1 or alkyl having 1 to 5 C atoms, Phe denotes 1,4-phenylene, k1, k2 and k3 each, independently of one another, denote 0 or 1, k3 preferably denotes 1, and k4 denotes an integer from 1 to 10.
Very particularly preferred groups P are selected from the group consisting of CH2═CW1—CO—O—, in particular CH2═CH—CO—O—, CH2═C(CH3)—CO—O— and CH2═CF—CO—O—, furthermore CH2═CH—O—, (CH2═CH)2CH—O—CO—, (CH2═CH)2CH—O—,
Further preferred polymerisable groups P are selected from the group consisting of vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxide, most preferably from acrylate and methacrylate.
If Sp is different from a single bond, it is preferably of the formula Sp″-X″, so that the respective radical P-Sp- conforms to the formula P-Sp″-X″—, wherein
X″ is preferably —O—, —S—, —CO—, —COO—, —OCO—, —O—COO—, —CO—NRO—, —NROCO—, —NR0—CO—NR00— or a single bond.
Typical spacer groups Sp and -Sp″-X″— are, for example, —(CH2)p1—, —(CH2CH2O)q1—CH2CH2—, —CH2CH2—S—CH2CH2—, —CH2CH2—NH—CH2CH2— or —(SiR0R00—O)p1—, in which p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and R0 and R00 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—, in which 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, ethyleneoxyethylene, methyleneoxybutylene, ethylenethioethylene, ethylene-N-methyliminoethylene, 1-methylalkylene, ethenylene, propenylene and butenylene.
For the production of PSA displays, the polymerisable compounds contained in the liquid-crystalline medium are polymerised or crosslinked (if one compound contains two or more polymerisable groups) by in-situ polymerisation in the liquid-crystalline medium between the substrates of the LC display, optionally while a voltage is applied to the electrodes.
The structure of the PSA displays according to the invention corresponds to the usual geometry for PSA displays, as described in the prior art cited at the outset. Geometries without protrusions are preferred, in particular those in which, in addition, the electrode on the colour filter side is unstructured and only the electrode on the TFT side has slots. Particularly suitable and preferred electrode structures for PS-VA displays are described, for example, in US 2006/0066793 A1.
The combination of compounds of the preferred embodiments mentioned above with the polymerised compounds described above causes low threshold voltages, low rotational viscosities and very good low-temperature stabilities in the liquid-crystalline media according to the invention at the same time as constantly high clearing points and high VHR values.
The use of liquid-crystalline media containing polymerisable compounds allows the rapid establishment of a particularly low pretilt angle in PSA displays. In particular, the liquid-crystalline media exhibit significantly shortened response times, in particular also the grey-shade response times, in PSA displays compared with the media from the prior art.
Preference is generally given to liquid-crystalline media which have a nematic liquid-crystalline phase, and preferably have no chiral liquid crystal phase.
The invention also relates to the use of a liquid-crystalline medium according to the present invention as described above and below for electro-optical purposes, in particular for the use is in shutter glasses, for 3D applications, in TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, XB-FFS, PS-FFS, positive VA and positive PS-VA displays, and to electro-optical displays, in particular of the aforementioned types, containing a liquid-crystalline medium according to the present invention as described above and below, in particular a TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, XB-FFS, PS-FFS, positive VA (vertically aligned) or positive PS-VA display.
The invention also relates to electro-optical displays, such as, for example, STN or MLC displays, having two plane-parallel outer plates, which, together with a frame, form a cell, integrated non-linear elements for switching individual pixels on the outer plates, and a nematic liquid-crystal medium having positive dielectric anisotropy and high specific resistance located in the cell, wherein the a nematic liquid-crystal medium is a liquid-crystalline medium according to the present invention as described above and below.
The liquid-crystalline media according to the invention enable a significant broadening of the available parameter latitude. The achievable combinations of clearing point, viscosity at low temperature, thermal and UV stability and high optical anisotropy are far superior to previous materials from the prior art.
In particular, the combination of compounds of formula I with compounds of formula Y and/or B, and additionally with compounds selected from formulae II-XXXIV or their subformulae, leads to liquid-crystalline media which show a moderate positive dielectric anisotropy and at the same time an increased dielectric constant EL perpendicular to the longitudinal axes of the liquid-crystalline molecules, while maintaining a low rotational viscosity and a low value of the ratio γ1/K1. This enables liquid-crystalline displays, especially of the FFS, HB-FFS, XB-FFS and IPS mode, with high brightness and transmission and low response times.
The liquid-crystalline media according to the invention are suitable for mobile applications and TFT applications, such as, for example, mobile telephones and PDAs. Furthermore, the liquid-crystalline media according to the invention are particularly suitably for use in FFS, HB-FFS, XB-FFS and IPS displays based on dielectrically positive liquid crystals.
The liquid-crystalline media according to the invention, while retaining the nematic phase down to −20° C. and preferably down to −30° C., particularly preferably down to −40° C., and the clearing point ≥75° C., preferably ≥80° C., at the same time allow rotational viscosities γ1 of ≤110 mPa·s, particularly preferably ≤100 mPa·s, to be achieved, enabling excellent MLC displays having fast response times to be achieved. The rotational viscosities are determined at 20° C.
The dielectric anisotropy Δε of the liquid-crystalline media according to the invention at 20° C. and 1 kHz is preferably ≥+1.5, very preferably from +2 to +3.
The birefringence Δn of the liquid-crystalline media according to the invention at 20° C. is preferably from 0.08 to 0.12, very preferably from 0.09 to 0.11.
The rotational viscosity γ1 of the liquid-crystalline media according to the invention is preferably ≤80 mPa s, more preferably ≤70 mPa s, very preferably ≤60 mPa s.
The ratio γ1/K1 (wherein γ1 is the rotational viscosity γ1 and K1 is the elastic constant for splay deformation) of the liquid-crystalline media according to the invention is preferably ≤4.6 mPa·s/pN, very preferably ≤4.2 mPa·s/pN, most preferably ≤4.0 mPa·s/pN.
The nematic phase range of the liquid-crystalline media according to the invention preferably has a width of at least 90°, more preferably of at least 100° C., in particular at least 110°. This range preferably extends at least from −25° to +80° C.
Through a suitable choice of the components of the liquid-crystalline media according to the invention, it is also possible for higher clearing points (for example above 100° C.) to be achieved at higher threshold voltages or lower clearing points to be achieved at lower threshold voltages with retention of the other advantageous properties. At viscosities correspondingly increased only slightly, it is likewise possible to obtain liquid-crystalline media having a higher Δε and thus low thresholds. The MLC displays according to the invention preferably operate at the first Gooch and Tarry transmission minimum [C. H. Gooch and H. A. Tarry, Electron. Lett. 10, 2-4, 1974; C. H. Gooch and H. A. Tarry, Appl. Phys., Vol. 8, 1575-1584, 1975], where, besides particularly favourable electro-optical properties, such as, for example, high steepness of the characteristic line and low angle dependence of the contrast (German patent 30 22 818), lower dielectric anisotropy is sufficient at the same threshold voltage as in an analogous display at the second minimum. This enables significantly higher specific resistance values to be achieved using the mixtures according to the invention at the first minimum than in the case of liquid-crystalline media comprising cyano compounds. Through a suitable choice of the individual components and their proportions by weight, the person skilled in the art is able to set the birefringence necessary for a pre-specified layer thickness of the MLC display using simple routine methods.
Measurements of the voltage holding ratio (HR) [S. Matsumoto et al., Liquid Crystals 5, 1320 (1989); K. Niwa et al., Proc. SID Conference, San Francisco, June 1984, p. 304 (1984); G. Weber et al., Liquid Crystals 5, 1381 (1989)] have shown that liquid-crystalline media according to the invention comprising compounds of the formulae ST-1, ST-2, RV, IA and IB exhibit a significantly smaller decrease in the HR on UV exposure than analogous mixtures comprising cyanophenylcyclohexanes of the formula
or esters of the formula
instead of the compounds of the formulae I ST-1, ST-2, RV, IA and IB.
The light stability and UV stability of the liquid-crystalline media according to the invention are considerably better, i.e. they exhibit a significantly smaller decrease in the HR on exposure to light, heat or UV.
The construction of the MLC display according to the invention from polarisers, electrode base plates and surface-treated electrodes corresponds to the usual design for displays of this type. The term usual design is broadly drawn here and also encompasses all derivatives and modifications of the MLC display, in particular including matrix display elements based on poly-Si TFTs or MIM.
A significant difference between the displays according to the invention and the hitherto conventional displays based on the twisted nematic cell consists, however, in the choice of the liquid-crystal parameters of the liquid-crystal layer.
The liquid-crystalline media which can be used in accordance with the invention are prepared in a manner conventional per se, for example by mixing one or more compounds of Claim 1 with one or more compounds of the formulae II-XXXIV or with further liquid-crystalline compounds and/or additives. In general, the desired amount of the components used in lesser amount is dissolved in the components making up the principal constituent, advantageously at elevated temperature. It is also possible to mix solutions of the components in an organic solvent, for example in acetone, chloroform or methanol, and to remove the solvent again, for example by distillation, after thorough mixing.
The LC media may also comprise further additives known to the person skilled in the art and described in the literature, such as, for example, polymerisation initiators, inhibitors, surface-active substances, light stabilisers, antioxidants, e.g. BHT, TEMPOL, microparticles, free-radical scavengers, nanoparticles, etc. For example, 0-15% of pleochroic dyes or chiral dopants or initiators like Irgacure651@ or Irgacure907® can be added. Suitable stabilisers and dopants are mentioned below in Tables C and D.
In a preferred embodiment of the present invention the LC media contain one or more further stabilisers, preferably selected from the group consisting of the following formulae
wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings
Preferred stabilisers of formula S3 are selected from formula S3A
wherein n2 is an integer from 1 to 12, and wherein one or more H atoms in the group (CH2)n2 are optionally replaced by methyl, ethyl, propyl, butyl, pentyl or hexyl.
Very preferred stabilisers are selected from the group consisting of the following formulae
In a preferred embodiment the LC medium comprises one or more stabilisers selected from the group consisting of formulae S1-1, S2-1, S3-1, S3-1 and S3-3.
In a preferred embodiment the LC medium comprises one or more stabilisers selected from Table D.
Preferably the proportion of stabilisers, like those of formula S1-S3, in the LC medium is from 10 to 2000 ppm, very preferably from 30 to 1000 ppm.
In another preferred embodiment the LC medium according to the present invention contains a self-aligning (SA) additive, preferably in a concentration of 0.1 to 2.5%. An LC medium according to this preferred embodiment is especially suitable for use in polymer stabilised SA-FFS, SA-HB-FFS or SA-XB-FFS displays.
In a preferred embodiment the SA-FFS, SA-HB-FFS or SA-XB-FFS display according to the present invention does not contain a polyimide alignment layer. In another preferred embodiment the SA-FFS, SA-HB-FFS or SA-XB-FFS display according to preferred embodiment contains a polyimide alignment layer.
Preferred SA additives for use in this preferred embodiment are selected from compounds comprising a mesogenic group and a straight-chain or branched alkyl side chain that is terminated with one or more polar anchor groups selected from hydroxy, carboxy, amino or thiol groups.
Further preferred SA additives contain one or more polymerisable groups which are attached, optionally via spacer groups, to the mesogenic group.
These polymerisable SA additives can be polymerised in the LC medium under similar conditions as applied for the RMs in the PSA process.
Suitable SA additives to induce homeotropic alignment, especially for use in SA-VA mode displays, are disclosed for example in US 2013/0182202 A1, US 2014/0838581 A1, US 2015/0166890 A1 and US 2015/0252265 A1.
In another preferred embodiment an LC medium or a polymer stabilised SA-FFS, SA-HB-FFS or SA-XB-FFS display according to the present invention contains one or more self-aligning additives selected from Table F below.
Furthermore, it is possible to add to the liquid-crystalline media, for example, 0 to 15% by weight of pleochroic dyes, furthermore nanoparticles, conductive salts, preferably ethyldimethyldodecylammonium 4-hexoxybenzoate, tetrabutylammonium tetraphenylborate or complex salts of crown ethers (cf., for example, Haller et al., Mol. Cryst. Liq. Cryst. 24, 249-258 (1973)), for improving the conductivity, or substances for modifying the dielectric anisotropy, the viscosity and/or the alignment of the nematic phases. Substances of this type are described, for example, in DE-A 22 09 127, 22 40 864, 23 21 632, 23 38 281, 24 50 088, 26 37 430 and 28 53 728. In the present application and in the examples below, the structures of the liquid-crystal compounds are indicated by means of acronyms, the transformation into chemical formulae taking place in accordance with Table A. All radicals CnH2n+1 and CmH2m+1 are straight-chain alkyl radicals having n and m C atoms respectively; n, m and k are integers and preferably denote 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12. The coding in Table B is self-evident. In Table A, only the acronym for the parent structure is indicated. In individual cases, the acronym for the parent structure is followed, separated by a dash, by a code for the substituents R1*, R2*, L1* and L2*:
Preferred mixture components are shown in Tables A and B.
In the following formulae, n and m each, independently of one another, denote 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, in particular 2, 3, 5, furthermore 0, 4, 6.
Particular preference is given to liquid-crystalline media which, besides the compounds of the formulae IA, IIA, IB and IIB, comprise at least one, two, three, four or more compounds from Table B.
Table C indicates possible dopants which are generally added to the liquid-crystalline media according to the invention. The liquid-crystalline media
preferably comprise 0-10% by weight, in particular 0.01-5% by weight and particularly preferably 0.01-3% by weight of dopants.
Stabilisers, which can additionally be added, for example, to the liquid-crystalline media according to the invention in amounts of 0-10% by weight, are mentioned below.
Table E shows illustrative reactive mesogenic compounds (RMs) which can be used in the liquid-crystalline media in accordance with the present invention.
In a preferred embodiment, the liquid-crystalline media according to the invention comprise one or more polymerisable compounds, preferably selected from the polymerisable compounds of the formulae RM-1 to RM-143. Of these, compounds RM-1, RM-4, RM-8, RM-17, RM-19, RM-35, RM-37, RM-39, RM-40, RM-41, RM-48, RM-52, RM-54, RM-57, RM-64, RM-74, RM-76, RM-88, RM-102, RM-103, RM-109, RM-117, RM-120, RM-121 and RM-122 are particularly preferred.
Table E shows self-alignment additives for vertical alignment which can be used in LC media for SA-FFS, SA-HB-FFS and SA-XB-FFS displays according to the present invention, optionally together with the polymerizable compounds of formula I:
In a preferred embodiment, the LC media, SA-FFS, SA-HB-FFS and SA-XB-FFS displays according to the present invention comprise one or more SA additives selected from formulae SA-1 to SA-34, preferably from formulae SA-14 to SA-34, very preferably from formulae SA-20 to SA-28, most preferably of formula SA-20, in combination with one or more RMs of formula I. Very preferred is a combination of polymerizable compound 1, 2 or 3 of Example 1 below, very preferably of polymerizable compound 3 of Example 1, with an SA additive of formula SA-20 to SA-28, very preferably of formula SA-20.
The following mixture examples are intended to explain the invention without limiting it.
Above and below, percentage data denote percent by weight. All temperatures are indicated in degrees Celsius. m.p. denotes melting point, cl.p.=clearing point. Furthermore, C≡crystalline state, N=nematic phase, S=smectic phase and I=isotropic phase. The data between these symbols represent the transition temperatures. Furthermore, the following symbols are used
All physical properties are determined in accordance with “Merck Liquid Crystals, Physical Properties of Liquid Crystals”, status November 1997, Merck KGaA, Germany, and apply for a temperature of 20° C., unless explicitly indicated otherwise.
The following liquid-crystalline medium is formulated:
The medium does not contain a compound of formula I.
The following liquid-crystalline medium is formulated:
The medium does not contain a compound of formula I.
The following liquid-crystalline medium is formulated:
The medium contains compound CLU-3-F of formula I and shows a lower value of γ1/K1 than the medium of Comparison Example 1 or 2.
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The medium does not contain a compound of formula I.
The following liquid-crystalline medium is formulated:
The medium contains compound CLU-3-F of formula I and shows a lower value of γ1/K1 and a higher LTS than the medium of Comparison Example 3.
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
The following liquid-crystalline medium is formulated:
Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.
The entire disclosure[s] of all applications, patents and publications, cited herein and of corresponding EP Patent Application No. 20168884.3, filed Apr. 9, 2020. is [are] incorporated by reference herein.
The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.
From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20168884.3 | Apr 2020 | EP | regional |
