Patent Application
20180223187
The present invention relates to a liquid-crystalline medium (LC medium), to the use thereof for electro-optical purposes, and to LC displays containing this medium.
Liquid crystals are used principally as dielectrics in display devices, since the optical properties of such substances can be modified by an applied voltage. Electro-optical devices based on liquid crystals are extremely well known to the person skilled in the art and can be based on various effects. Examples of such devices are cells having dynamic scattering, DAP (deformation of aligned phases) cells, guest/host cells, TN cells having a twisted nematic structure, STN (supertwisted nematic) cells, SBE (superbirefringence effect) cells and OMI (optical mode interference) cells. The commonest display devices are based on the Schadt-Helfrich effect and have a twisted nematic structure.
The liquid-crystal materials must have good chemical and thermal stability and good stability to electric fields and electromagnetic radiation. Furthermore, the liquid-crystal materials should have low viscosity and produce short addressing times, low threshold voltages and high contrast in the cells.
They should furthermore have a suitable mesophase, for example a nematic or cholesteric mesophase for the above-mentioned cells, at the usual operating temperatures, i.e. in the broadest possible range above and below room temperature. Since liquid crystals are generally used as mixtures of a plurality of components, it is important that the components are readily miscible with one another. Further properties, such as the electrical conductivity, the dielectric anisotropy and the optical anisotropy, have to satisfy various requirements depending on the cell type and area of application. For example, materials for cells having a twisted nematic structure should have positive dielectric anisotropy and low electrical conductivity.
For example, for matrix liquid-crystal displays with integrated non-linear elements for switching individual pixels (MLC displays), media having large positive dielectric anisotropy, broad nematic phases, relatively low birefringence, very high specific resistance, good UV and temperature stability and low vapour pressure are desired.
Matrix liquid-crystal displays of this type are known. Examples of non-linear elements which can be used to individually switch the individual pixels are active elements (i.e. transistors). The term “active matrix” is then used, where a distinction can be made between two types:
The use of single-crystal silicon as substrate material restricts the display size, since even modular assembly of various part-displays results in problems at the joints.
In the case of the more promising type 2, which is preferred, the electro-optical effect used is usually the TN effect. A distinction is made between two technologies: TFTs comprising compound semiconductors, such as, for example, CdSe, or TFTs based on polycrystalline or amorphous silicon. Intensive work is being carried out worldwide on the latter technology.
The TFT matrix is applied to the inside of one glass plate of the display, while the other glass plate carries the transparent counterelectrode on its inside. Compared with the size of the pixel electrode, the TFT is very small and has virtually no adverse effect on the image. This technology can also be extended to fully colour-capable displays, in which a mosaic of red, green and blue filters is arranged in such a way that a filter element is opposite each switchable pixel.
The TFT displays usually operate as TN cells with crossed polarisers in transmission and are backlit.
The term MLC displays here encompasses any matrix display with integrated non-linear elements, i.e., besides the active matrix, also displays with passive elements, such as varistors or diodes (MIM=metal-insulator-metal). MLC displays of this type are particularly suitable for TV applications (for example pocket televisions) or for high-information displays for computer applications (laptops) and in automobile or aircraft construction. Besides problems regarding the angle dependence of the contrast and the response times, difficulties also arise in MLC displays due to insufficiently high specific resistance of the liquid-crystal mixtures [TOGASHI, S., SEKIGUCHI, K., TANABE, H., YAMAMOTO, E., SORIMACHI, K., TAJIMA, E., WATANABE, H., SHIMIZU, H., Proc. Eurodisplay 84, September 1984: A 210-288 Matrix LCD Controlled by Double Stage Diode Rings, pp. 141 ff, Paris; STROMER, M., Proc. Eurodisplay 84, September 1984: Design of Thin Film Transistors for Matrix Addressing of Television Liquid Crystal Displays, pp. 145 if, Paris]. With decreasing resistance, the contrast of an MLC display deteriorates, and the problem of after-image elimination may occur. Since the specific resistance of the liquid-crystal mixture generally drops over the life of an MLC display owing to interaction with the interior surfaces of the display, a high (initial) resistance is very important in order to obtain acceptable lifetimes. In particular in the case of low-volt mixtures, it was hitherto impossible to achieve very high specific resistance values. It is furthermore important that the specific resistance exhibits the smallest possible increase with increasing temperature and after heating and/or UV exposure. The low-temperature properties of the mixtures from the prior art are also particularly disadvantageous. It is demanded that no crystallisation and/or smectic phases occur, even at low temperatures, and the temperature dependence of the viscosity is as low as possible. The MLC displays from the prior art thus do not satisfy today's requirements.
Besides liquid-crystal displays which use backlighting, i.e. are operated transmissively and if desired transfiectively, reflective liquid-crystal displays are also particularly interesting. These reflective liquid-crystal displays use the ambient light for information display. They thus consume significantly less energy than backlit liquid-crystal displays having a corresponding size and resolution. Since the TN effect is characterised by very good contrast, reflective displays of this type can even be read well in bright ambient conditions. This is already known of simple reflective TN displays, as used, for example, in watches and pocket calculators. However, the principle can also be applied to high-quality, higher-resolution active matrix-addressed displays, such as, for example, TFT displays. Here, as already in the transmissive TFT-TN displays which are generally conventional, the use of liquid crystals of low birefringence (Δn) is necessary in order to achieve low optical retardation (d·Δn). This low optical retardation results in usually acceptable low viewing-angle dependence of the contrast (cf. DE 30 22 818). In reflective displays, the use of liquid crystals of low birefringence is even more important than in transmissive displays since the effective layer thickness through which the light passes is approximately twice as large in reflective displays as in transmissive displays having the same layer thickness.
In order to achieve 3D effects by means of shutter spectacles, fast-switching mixtures having low rotational viscosities and correspondingly high optical anisotropy (Δn), in particular, are employed. Electro-optical lens systems, by means of which a 2-dimensional representation of a display can be switched to a 3-dimensional autostereoscopic representation, can be achieved using mixtures having high optical anisotropy (Δn).
Thus, there continues to be a great demand for MLC displays having very high specific resistance at the same time as a large working-temperature range, short response times, even at low temperatures, and a low threshold voltage which do not exhibit these disadvantages or only do so to a lesser extent.
In the case of TN (Schadt-Helfrich) cells, media are desired which facilitate the following advantages in the cells:
The media available from the prior art do not enable these advantages to be achieved while simultaneously retaining the other parameters. Modern LCD flat-panel screens require ever-faster response times in order to be able to reproduce multimedia content, such as, for example, films and video games, realistically. These in turn require nematic liquid-crystal mixtures which have a very low rotational viscosity γ1 with high optical anisotropy Δn. In order to obtain the requisite rotational viscosities, substances are sought which have a particularly advantageous γ1/clearing point ratio at the same time as high Δn with high polarity.
In the case of supertwisted (STN) cells, media are desired which facilitate greater multiplexability and/or lower threshold voltages and/or broader nematic phase ranges (in particular at low temperatures). To this end, a further widening of the available parameter latitude (clearing point, smectic-nematic transition or melting point, viscosity, dielectric parameters, elastic parameters) is urgently desired.
In particular in the case of LC displays for TV and video applications (for example LCD-TVs, monitors, PDAs, notebooks, games consoles), a significant reduction in the response times is desired. This requires LC mixtures having low rotational viscosities and high dielectric anisotropies. At the same time, the LC media should have a broad nematic phase and the lowest possible value of the smectic-nematic phase-transition temperature or melting point.
The invention has the object of providing media, in particular for MLC, TN, STN, ECB, OCB, IPS, PS-IPS, FFS, PS-FFS or positive VA displays of this type, which do not exhibit the disadvantages indicated above or only do so to a lesser extent and preferably have fast response times and low rotational viscosities at the same time as a high clearing point, as well as high dielectric anisotropy and a low threshold voltage.
It has now been found that this object can be achieved if LC media as described below are used.
The invention relates to a liquid-crystalline medium, characterised in that it comprises
one or more compounds of the formula 1,
and one or more compounds of the formula 2,
and one or more compounds selected from the compounds of the formulae 3, 4 and 5,
in which the individual radicals, in each case independently of one another and identically or differently on each occurrence, have the following meanings:
Surprisingly, it has been found that LC media comprising one or more compounds selected from the formulae 1-5 have high dielectric anisotropy Δε, high birefringence Δn, low rotational viscosity γ1 and a low smectic-nematic phase-transition temperature or melting point. They are therefore particularly suitable for achieving liquid-crystal mixtures having low γ1 and high Δn. In addition, the compounds of the formulae 1-5 exhibit good solubility and very good phase behaviour in LC media.
LC media according to the invention comprising compounds of the formulae 1-5 have low rotational viscosity, fast response times, a high clearing point, very high positive dielectric anisotropy, relatively high birefringence and a broad nematic phase range. They are therefore particularly suitable for mobile telephones, TV and video applications.
The compounds of the formulae 1-5 have a broad range of applications. Depending on the choice of substituents, they can serve as base materials of which liquid-crystalline media are predominantly composed; however, liquid-crystalline base materials from other classes of compound can also be added to the compounds of the formulae 1-5 in order, for example, to modify the dielectric and/or optical anisotropy of a dielectric of this type and/or to optimise its threshold voltage and/or its viscosity.
The compounds of the formulae 1-5 have relatively low melting points, exhibit good phase behaviour, are colourless in the pure state and form liquid-crystalline mesophases in a temperature range which is favourably located for electro-optical use. They are stable chemically, thermally and to light.
In the formulae above and below, an alkyl radical 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. RA and RB each preferably denote 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.
An alkenyl radical 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 an alkyl or alkenyl radical 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 co-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.
Particular preference is given to compounds of the formula 1 in which “alkenyl” denotes vinyl, prop-1-enyl, prop-2-enyl or but-3-enyl.
Preference is furthermore given to compounds of the formula 1 in which Rx denotes methyl, ethyl, n-propyl, n-butyl or n-pentyl.
Particular preference is given to compounds of the formula 2 in which L denotes F.
Preference is furthermore given to compounds of the formula 2 in which “alkyl” denotes methyl, ethyl, n-propyl, n-butyl or n-pentyl.
Preference is furthermore given to compounds of the formula 2 in which “alkenyl” denotes vinyl, prop-1-enyl, prop-2-enyl or but-3-enyl, particularly preferably but-3-enyl.
Particular preference is given to compounds of the formula 4 in which L denotes F.
Particular preference is given to compounds of the formula 5 in which L denotes H.
Preference is furthermore given to compounds of the formulae 3, 4 and 5 in which “alkyl” denotes ethyl, n-propyl or n-pentyl.
The compounds of the formula 1 are preferably selected from the following formulae:
in which “alkyl” has the meaning indicated in formula 1 and particularly preferably denotes methyl, ethyl, n-propyl, n-butyl or n-pentyl.
Particular preference is given to compounds of the formulae 1a and 1b, in particular those in which “alkyl” denotes n-propyl.
The compounds of the formula 2 are preferably selected from the following formulae:
The compounds of the formula 3 are preferably selected from the following formulae:
Particular preference is given to compounds of the formula 3b.
The compounds of the formula 4 are preferably selected from the following formulae:
Particular preference is given to compounds of the formula 4b.
The compounds of the formula 5 are preferably selected from the following formulae:
Particular preference is given to compounds of the formula 5c.
Particularly preferred media are described below:
Medium comprising in each case one or more compounds of the formulae 1, 2 and 3.
Medium comprising in each case one or more compounds of the formulae 1, 2 and 4.
Medium comprising in each case one or more compounds of the formulae 1, 2 and 5.
Medium comprising one or more compounds of formula 1, one or more compounds of the formula 2 and one or more compounds of the formula 3 or 5.
Medium comprising one or more compounds selected from the formulae 1a and 1b, two or more compounds selected from the formulae 2a to 2d, and a compound of the formula 3b or 4b or 5c.
Medium comprising
one or more compounds selected from the formulae 1a and 1b, two or more compounds selected from the formulae 2a to 2d, and a compound of the formula 3b or 5c.
The proportion of compounds of the formula 1 in the mixture as a whole is preferably 20 to 65% by weight, particularly preferably 25 to 60% by weight.
The proportion of compounds of the formula 2 in the mixture as a whole is preferably 5 to 35% by weight, particularly preferably 5 to 25% by weight.
The proportion of compounds of the formula 3 in the mixture as a whole is preferably 2 to 20% by weight, particularly preferably 2 to 15% by weight.
The proportion of compounds of the formula 4 in the mixture as a whole is preferably 2 to 20% by weight, particularly preferably 2 to 15% by weight.
The proportion of compounds of the formula 5 in the mixture as a whole is preferably 2 to 20% by weight, particularly preferably 2 to 15% by weight.
Particular preference is given to media comprising
The compounds of the formulae 1-5 are prepared by methods known per se, as described in the literature (for example in the standard works, such as Houben-Weyl, Methoden der Organischen Chemie (Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart), to be precise under reaction conditions which are known and suitable for the said reactions. Use can also be made here of variants known per se which are not mentioned in greater detail here.
Preferred embodiments for the mixtures according to the invention are indicated below:
—O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another,
each, independently of one another, denote
each, independently of one another, denote
denotes
—O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another,
denotes
is preferably
Further preferred embodiments are indicated below:
It has been found that the use of compounds of the formulae 1-5 as described above in a mixture with conventional liquid-crystal materials, but in particular with one or more compounds of the formulae II to XXX, results in a significant increase in the light stability and in relatively high birefringence values, with broad nematic phases with low smectic-nematic transition temperatures being observed at the same time, improving the shelf life. At the same time, the mixtures exhibit very low threshold voltages, very good values for the VHR on exposure to UV, and very high clearing points.
The term “alkyl” or “alkyl*” in this application encompasses straight-chain and branched alkyl groups having 1-6 carton 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 carton 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.
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 mixtures 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 mixture is generally greater, the higher the total concentration of compounds of the above-mentioned formulae.
In a particularly preferred embodiment, the media according to the invention comprise compounds of the formulae II to VIII (preferably II, III, IV and V, in particular IIa and IIa) in which X0 denotes F, OCF3, OCHF2, OCH═CF2, OCF═CF2 or OCF2—CF2H.
The individual compounds of the above-mentioned formulae and the sub-formulae thereof which can be used in the media according to the invention are either known or can be prepared analogously to the known compounds.
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 mixture having positive dielectric anisotropy and high specific resistance located in the cell, which contain media of this type, and to the use of these media for electro-optical purposes.
The liquid-crystal mixtures 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.
The mixtures according to the invention are particularly suitable for mobile applications and TFT applications, such as, for example, mobile telephones and PDAs. Furthermore, the mixtures according to the invention can be used in FFS, HB-FFS, VA-IPS, OCB and IPS displays.
The liquid-crystal mixtures 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-crystal mixtures according to the invention at 20° C. is preferably ≥+7, particularly preferably ≥+8, especially preferably ≥10. In addition, the mixtures are characterised by low operating voltages. The threshold voltage of the liquid-crystal mixtures according to the invention is preferably ≤2.0 V. The birefringence Δn of the liquid-crystal mixtures according to the invention at 20° C. is preferably ≥0.09, particularly preferably ≥0.10.
The nematic phase range of the liquid-crystal mixtures according to the invention preferably has a width of at least 90°, in particular at least 100°. This range preferably extends at least from −25° to +70° C.
It goes without saying that, through a suitable choice of the components of the mixtures 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 mixtures 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 mixtures 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 mixtures according to the invention comprising one or more compounds of the formula IA 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 one or more compounds of the formula IA.
The light stability and UV stability of the mixtures according to the invention are considerably better, i.e. they exhibit a significantly smaller decrease in the HR on exposure to light 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-crystal mixtures 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 the formulae 1-5 with one or more compounds of the formulae II-XXX 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 dielectrics may also comprise further additives known to the person skilled in the art and described in the literature, such as, for example, UV stabilisers, such as Tinuvin®, e.g. Tinuvin® 770, from Ciba Chemicals, antioxidants, e.g. TEMPOL, microparticles, free-radical scavengers, nanopartides, etc. For example, 0-15% of pleochroic dyes or chiral dopants can be added. Suitable stabilisers and dopants are mentioned below in Tables B and C.
Polymerisable compounds, so-called reactive mesogens (RMs), for example as disclosed in U.S. Pat. No. 6,861,107, may furthermore be added to the mixtures according to the invention in concentrations of preferably 0.12-5% by weight, particularly preferably 0.2-2% by weight, based on the mixture. These mixtures may optionally also comprise an initiator, as described, for example, in U.S. Pat. No. 6,781,665. The initiator, for example Irganox-1076 from Ciba, is preferably added to the mixture comprising polymerisable compounds in amounts of 0-1%. Mixtures of this type can be used for so-called polymer-stabilised (PS) modes, in which polymerisation of the reactive mesogens is intended to take place in the liquid-crystalline mixture, for example for PS-IPS, PS-FFS, PS-TN, PS-VA-IPS. The prerequisite for this is that the liquid-crystal mixture does not itself comprise any polymerisable components.
In a preferred embodiment of the invention, the polymerisable compounds are selected from the compounds of the formula M
RMa-AM1-(ZM1-AM2)m1-RMb M
in which the individual radicals have the following meanings:
Particularly preferred compounds of the formula M are those in which
Very particular preference is given to compounds of the formula M in which one of RMa and RMb or both denote(s) P or P-Sp-.
Suitable and preferred RMs for use in liquid-crystalline media and PS mode displays according to the invention are selected, for example, from the following formulae:
in which the individual radicals have the following meanings:
Suitable polymerisable compounds are listed, for example, in Table D.
The liquid-crystalline media in accordance with the present application preferably comprise in total 0.01 to 3%, preferably 0.1 to 1.0%, particularly preferably 0.1 to 0.5%, of polymerisable compounds.
Particular preference is given to the polymerisable compounds of the formulae M2, M13, M17, M22, M23, M24 and M30.
Preference is furthermore given to the polymerisable compounds of the formulae M15 to M31, in particular M17, M18, M19, M22, M23, M24, M25, M26, M30 and M31.
The present invention thus also relates to the use of the mixtures according to the invention in electro-optical displays and to the use of the mixtures according to the invention in shutter spectacles, in particular for 3D applications, and in TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, PS-FFS and PS-VA-IPS displays.
Throughout the patent application and in the working examples, the structures of the liquid-crystal compounds are indicated by means of acronyms. Unless indicated otherwise, the transformation into chemical formulae takes place in accordance with Tables 1-3. All radicals CnH2n+1 and CmH2m+1 or CnH2n and CmH2m are straight-chain alkyl radicals or alkylene radicals having n and m C atoms each. n, m and k each, independently of one another, denote 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, preferably 0, 1, 2, 3, 4, 5 or 6. In Table 1 the ring elements of the respective compound are coded, in Table 2 the bridging elements are listed and in Table 3 the meanings of the symbols for the left-hand or right-hand side chains of the compounds are indicated.
Preferred mixture components are found in Table A.
Besides one or more compounds of the formulae 1 to 5, the mixtures according to the invention preferably comprise at least one compound selected from the compounds shown below in Table A.
Particular preference is given to liquid-crystalline mixtures which, besides the compounds of the formulae 1 to 5, comprise at least one, two, three, four or more compounds from Table A.
In a preferred embodiment of the present invention, the mesogenic media comprise one or more compounds selected from the group of the compounds from Table D.
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,
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2015 010 116.1 | Aug 2015 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/001278 | 7/22/2016 | WO | 00 |
