Patent Application
20220298419
The present invention relates to liquid-crystalline (LC) media and to LC displays (LCDs) containing these media, in particular to LCDs of the twisted nematic (TN) mode, preferably to displays of the LCOS (LC on silicon) mode.
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 electrooptical 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 substantially perpendicular to the substrates or the LC layer. Besides these modes, there are also electro-optical modes that utilise an electric field which is substantially parallel to the substrates or the LC layer, such as, for example, the in-plane switching (IPS) mode (as disclosed, for example, in DE 40 00 451 and EP 0 588 568) and the fringe field switching (FFS) mode, in which a strong “fringe field” is present, 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 a strong horizontal component. These latter two electro-optical modes in particular are used for LCDs in modern desktop monitors and displays for TV sets and multimedia applications. The liquid crystals according to the present invention are preferably used in displays of this type. In general, dielectrically positive LC media having rather lower values of the dielectric anisotropy are used in FFS displays, but in some cases LC media having a dielectric anisotropy of only about 3 or even less are also used in IPS displays.
Especially in case of LC media for use in the expanding market of public information displays (PIDs) and automotive displays a high reliability and a wide operating range are highly important factors. For these applications LC media with high clearing temperature (Tni), good LTS (Low Temperature Stability) and high reliability are therefore desired.
LCOS is a reflective micro-display mode using a liquid crystal layer on top of a backplane made from silicon, and wherein light is reflected off this backplane while the liquid crystal layer is switched on and off. It is a combination of digital light processing (DLP) and LCD. The LCOS mode is typically a TN mode, and is often used for projection devices like e.g. projectors and projection TVs, and is also becoming widely used for different technologies like wavelength selective switching, near-eye displays and wearable devices. The LCOS mode has the advantages of light of weight, high resolution and mini-size.
However, in the LCOS mode, the reflective TN mode often shows some optical defects such as the appearance of disclination lines.
The invention has the object of providing LC media, in particular for TN and LCOS mode displays, especially for active matrix displays like those of the TFT (thin film transistor) type, which do not exhibit the disadvantages indicated above or only do so to a lesser extent and preferably exhibit one or more of a wide operating range, a high clearing temperature, a high reliability, a low threshold voltage, a high dielectric anisotropy, a good low temperature stability (LTS), a low rotational viscosity and fast response times.
This object was achieved by providing an LC medium as described and claimed hereinafter.
Thus, the inventors have found that it is possible to improve the image quality of an LCOS, TN mode display, by adding a chiral dopant to the LC medium to form a spontaneous twist in order to manage the light direction. This helps to increase the homogeneity of domain directions and to suppress the appearance of disclination lines. In addition, by varying the concentration of the chiral dopant and thus varying the chiral pitch the Voltage-Transmission (VT) curve can also be adjusted.
The displays according to the present invention are preferably addressed by an active matrix (active matrix LCDs, AMDs for short), preferably by a matrix of thin film transistors (TFTs). However, the liquid crystals according to the invention can also advantageously be used in displays having other known addressing means.
The invention relates to an LC medium with positive dielectric anisotropy, characterised in that it contains one or more compounds of formula I, one or more compounds selected from formulae II and III, and one or more chiral dopants
wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings
—CO—O— or —O—CO— in such a way that 0 atoms are not linked directly to one another, or denotes
The invention further relates to the use of an LC medium as described above and below for electro-optical purposes, in particular for the use in LC displays, preferably in LCOS, TN or TN-TFT displays.
The invention further relates to an electro-optical LC display containing an LC medium as described above and below, in particular an LCOS, TN or TN-TFT display.
The invention furthermore relates to a process for preparing an LC medium as described above and below, comprising the steps of mixing one or more compounds of formula I with one or more further LC compounds and optionally one or more additives.
In the present application, all atoms also include their isotopes. In particular, one or more hydrogen atoms (H) may be replaced by deuterium (D), which is particularly preferred in some embodiments; a high degree of deuteration enables or simplifies analytical determination of compounds, in particular in the case of low concentrations.
If R0 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 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 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.
Particular preference is given to compounds in which X0 denotes F or OCF3, preferably F.
In the non-addressed or off-state (a), i.e. with no voltage applied, the LC molecules (8) of the LC layer (5) exhibit a planar, twisted nematic alignment (induced by the chiral dopant). In the addressed or on-state (b), i.e. upon application of a voltage, the LC molecules (8) reorient into vertical alignment.
In the LC media and displays according to the present invention, a chiral dopant is added to the LC medium to form a spontaneous twist in order to manage the light direction. The control of the twist angle and thus the pitch length is important to prevent under/over twist and to reach the best optical performance.
The threshold voltage (Vth) of the 900 TN-LCD is given by the equation (1) wherein pitch>λ (wavelength of light propagating inside a LC material):
Here the (p/d) ratio represent the chiral pitch-to-cell gap, Δε and γ1 represent the dielectric anisotropy and rotational viscosity; K11, K22, K33 represent elastic constants of the splay, twist, and bend deformations respectively.
From equation (1) above it follows that a shorter pitch will lead to a right shift of the VT curve, whereas a longer pitch will lead to a left shift of the VT curve with better contrast ratio. However, a longer pitch will also increase the risk of disclination lines appearing, caused by weak domain direction.
The chiral dopants are preferably selected from the group consisting of compounds from Table C below, very preferably from the group consisting of R- or S-1011, R- or S-2011, R- or S-3011, R- or S-4011, and R- or S-5011:
Very preferred are chiral dopants of formula S-4011.
Preferably the LC medium contains one or two, more preferably one, chiral dopants, in a concentration from 0.01 to 1% by weight, preferably in a concentration from 0.1 to 0.72%, more preferably from 0.2 to 0.72% by weight and very preferably from 0.35 to 0.72% by weight.
The helical twisting power and amount of the chiral dopant in the LC medium are preferably selected such that the ratio d/p in the display according to the present invention preferably from 0.015 to 0.2, more preferably from 0.03 to 0.2, and very preferably from 0.05 to 0.2.
Preferably the twist angle of the helical twist induced in the LC medium by the chiral dopants (before applying a voltage) is from 60 to 120°, more preferably from 80 to 100°, very preferably 90°.
Preferably the pitch of the helical twist induced in the LC medium by the chiral dopants is from 15 to 100 μm, more preferably from 15 to 50 μm, and very preferably from 15 to 30 μm.
Preferably the ratio d/p in a display according to the present invention is from 0.015 to 0.2, more preferably from 0.03 to 0.2, most preferably from 0.05 to 0.2.
In the compounds of formula I R1 and R2 are preferably selected from ethyl, propyl, butyl and pentyl, all of which are straight-chain.
Preferably the LC medium comprises one or more compounds of formula I selected from the group consisting of the following subformulae
wherein “alkyl” has the meaning given in formula I and preferably denotes C2H5, n-C3H7, n-C4H9 or n-C5H11, in particular n-C3H7.
Very preferably the LC medium comprises one or more compounds of formula I selected from the group consisting of the following subformulae:
Very preferred are compounds of formula Ia1, Ib1 and Ic1.
The concentration of the compounds of formula I and its subformulae in the LC medium is preferably from 15 to 70%, very preferably from 20 to 60%.
Preferably the LC medium contains 1, 2 or 3 compounds of formula I or its subformulae.
In the compounds of formulae II and III and their subformulae R0 preferably denotes straight-chain alkyl having 1 to 6 C atoms, in particular methyl, ethyl or propyl, furthermore alkenyl having 2 to 6 C atoms, in particular vinyl, 1E-propenyl, 1E-butenyl, 3-butenyl, 1E-pentenyl, 3E-pentenyl or 4-pentenyl.
Preferably the LC medium comprises one or more compounds of formula II wherein Y0 is H, preferably selected from the group consisting of the following subformulae
in which R0 and X0 have the meanings given above.
Preferred compounds are those of formula I11, I12 and I13, very preferred those of formula II1 and II2.
In the compounds of formulae II1 to II7R0 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 another preferred embodiment the LC medium comprises one or more compounds of formula II wherein Y0 is CH3, preferably selected from the group consisting of the following subformulae
in which R0 and X0 have the meanings given above.
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 IIA7R0 preferably denotes alkyl having 1 to 6 C atoms, very preferably ethyl or propyl, and X0 preferably denotes F or OCF3, very preferably F.
Further preferably the LC medium comprises one or more compounds of formula III wherein Y0 is H, preferably selected from the group consisting of the following subformulae
in which R0 and X0 have the meanings given above.
Preferred compounds are those of formula III1, III4, III6, III16, III19 and III20.
In the compounds of formulae III1 to III21R0 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 another preferred embodiment the LC medium comprises one or more compounds of formula III wherein Y0 is CH3, preferably selected from the group consisting of the following subformulae
in which R0 and X0 have the meanings given above
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.
The concentration of an individual compound of formula II and its subformulae in the LC medium is preferably from 1 to 15% by weight. The total concentration of the compounds of formula II in the LC medium is preferably from 5 to 25% by weight.
The concentration of an individual compound of formula III in the LC medium s is preferably from 1 to 15% by weight. The total concentration of the compounds of formula III is preferably from 2 to 25% by weight.
Preferably the LC medium contains 1 to 8 compounds of formula II and/or formula III or their subformulae.
Preferably the LC medium contains at least one compound of formula II or its subformulae and at least one compound of formula II or its subformulae.
Further preferred embodiments are indicated below, including any combination thereof:
Particular preference is given to the compounds of the formulae IXa, IXb, IXc, Xa, Xb, XIa and XIIa. In the formula IXa the groups “alkyl” preferably, independently of one another, denote C2H5, n-C3H7, n-C4H9 or n-C5H11, very preferably C2H5 or n-C3H7. In the formulae XIa and XIb “alkyl” preferably denotes CH3, C2H5 or n-C3H7, very preferably CH3.
Preferred compounds of formula XIII are those wherein L1 and L2 are H.
Further preferred compounds of formula XIII are those wherein L1 and L2 are F.
Further preferred compounds of formula XIII are those wherein R1 is alkyl with 1 to 6 C atoms, preferably methyl, ethyl or propyl, and R2 is alkoxy with 1 to 6 C atoms, preferably methoxy, ethoxy or propoxy.
in which R1 and R2 independently of each other denote alkyl having 1 to 6 C atoms.
Preferred compounds of the formula XIV are selected from the following subformulae.
Particularly preferred compounds of the formula XVI are those of the sub-formulae
Very preferably the mixture according to the invention comprises one or more compounds of the formula XXIa,
Further preferably the mixture according to the invention comprises one or more compounds of the formula XXIIIa,
denotes
R0 preferably denotes alkyl having 1 to 6 C atoms. X0 preferably denotes F;
is preferably
Preferred compounds of formula XXX are those of formula XXXa
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.
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 LC 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 LC 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 IA, IIA, IB and IIB results in particularly advantageous properties. In particular, mixtures comprising compounds of the formulae IA or IIA and IB or IIB 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 LC 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, TN 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 LC mixture having positive dielectric anisotropy and high specific resistance located in the cell, wherein the a nematic LC mixture is an LC medium according to the present invention as described above and below.
The LC 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.
The LC media according to the invention are suitable for mobile applications and TFT applications, such as, for example, mobile telephones and PDAs.
Furthermore, the LC media according to the invention are particularly suitably for use in FFS and IPS displays.
The LC media according to the invention preferably retain the nematic phase down to −20° C. very preferably down to −30° C., most preferably down to −40° C. The LC media according to the invention preferably have a clearing point ≥85° C., very preferably 95° C., most preferably 105° C.
The LC media according to the invention preferably have a rotational viscosity γ1 of 130 mPa·s, very preferably 115 mPa·s, enabling excellent MLC displays having fast response times to be achieved. The rotational viscosities are determined at 20° C.
In a preferred embodiment, the dielectric anisotropy Δε of the LC media according to the invention at 20° C. is preferably ≥+4, very preferably ≥+6, most preferably ≥+8.
The birefringence Δn of the LC media according to the invention at 20° C. is preferably in the range of from 0.080 to 0.150, more preferably from 0.090 to 0.140, particularly preferably 0.100 to 0.130.
The nematic phase range of the LC media according to the invention preferably has a width of at least 100°, more preferably of at least 110° C., in particular at least 130°. This range preferably extends at least from −25° to +105° C.
It goes without saying that, through a suitable choice of the components of the LC 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 LC 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 LC 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 LC 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 LC 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 LC parameters of the LC layer.
The LC 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 IV-XXXI or with further LC 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 500 ppm, very preferably from 20 to 100 ppm.
In another preferred embodiment an LC medium contains one or more polymerisable compounds, preferably selected from polymerizable mesogenic compounds. These LC media are suitable for use in displays of the polymer stabilized (PS) mode, like the PS-TN mode.
Another preferred embodiment of the present invention thus relates to a PS-TN display comprising an LC medium as described above and below.
Preferably the LC medium according to this preferred embodiment contains one or more polymerisable compounds of 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 M 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 0 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.
The polymerizable group P is a group which is suitable for a polymerization reaction, such as, for example, free-radical or ionic chain polymerization, 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 polymerization, in particular those containing a C═C double bond or —C≡C— triple bond, and groups which are suitable for polymerization 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═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, Cl 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═CW2—O—, CH2═CW2—, CW1═CH—CO—(O)k3—, CW1═CH—CO—NH—, CH2═CW1—CO—NH—, (CH2═CH)2CH—OCO—, (CH2═CH—CH2)2CH—OCO—, (CH2═CH)2CH—O—, (CH2═CH—CH2)2N—, (CH2═CH—CH2)2N—CO, CH2═CW1—CO—NH—, CH2═CH—(COO)k1-Phe-(O)k2—, CH2═CH—(CO)k1-Phe(O)k2—, Phe-CH═CH— and 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, Cl 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 polymerizable 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
Typical spacer groups Sp and -Sp″-X″— are, for example, —(CH2)p1—, —(CH2CH2O)p1—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.
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:
Very preferred are compounds of formulae M2 and M13, especially direactive compounds containing exactly two polymerizable groups P1 and P2.
Further preferred are compounds selected from formulae M17 to M32, in particular from formulae M20, M22, M24, M27, M30 and M32, especially trireactive compounds containing exactly three polymerizable groups P1, P2 and P3.
In the compounds G 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, most preferably F or OCH3.
Preferred compounds of formulae M1 to M32 are those wherein P1, P2 and P3 denote an acrylate, methacrylate, oxetane or epoxy group, very preferably an acrylate or methacrylate group, most preferably a methacrylate group.
Further preferred compounds of formulae M1 to M32 are those wherein Sp1, Sp2 and Sp3 are a single bond.
Further preferred compounds of formulae M1 to M32 are those wherein one of Sp1, Sp2 and Spa is a single bond and another one of Sp1, Sp2 and Spa is different from a single bond.
Further preferred compounds of formulae M1 to M32 are those wherein those groups Sp1, Sp2 and Spa 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.
Further preferred compounds of formula M are those selected from Table E below, especially those selected from the group consisting of formulae RM1, RM-4, RM-8, RM-17, RM-19, RM-35, RM-37, RM-39, RM-40, RM-41, RM48, RM-52, RM-54, RM-57, RM-64, RM-74, RM-76, RM-88, RM-92, RM102, RM-103, RM-109, RM-116, RM-117, RM-120, RM-121, RM-122, RM139, RM-142, RM-153, RM-155, RM-158 and RM-159.
Particularly preferred are LC media comprising one, two or three polymerizable compounds of formula M.
Further preferred are LC media comprising two or more direactive polymerizable compounds of formula M, preferably selected from formulae M1 to M16, very preferably selected from formulae M2 and M13.
Further preferred are LC media comprising one or more direactive polymerizable compounds of formula M, preferably selected from formulae M1 to M16, very preferably from formulae M2 and M13, and one or more trireactive polymerizable compounds of formula M, preferably selected from formulae M17 to M32, very preferably from formulae M20, M22, M24, M27, M30 and M32.
Further preferred are LC media comprising one or more polymerizable compounds of formula M wherein at least one r is not 0, or at least one of s and t is not 0, very preferably selected from formulae M2, M13, M22, M24, M27, M30 and M32, and wherein L is selected from the preferred groups shown above, most preferably from F and OCH3.
Further preferred are polymerizable compounds, preferably selected from formula M, very preferably from formulae M1 to M32, most preferably from the group consisting of the above-mentioned formulae from Table E, which show absorption in the wavelength range from 320 to 380 nm.
Preferably the proportion of the polymerizable compounds in the LC medium is from 1 to <3%, more preferably from 2 to <3%, very preferably from 2 to 2.5%, most preferably from 2 to 2.2%.
In another preferred embodiment the LC medium contains one or more polymerization initiators.
Suitable conditions for polymerization and suitable types and amounts of initiators are known to the person skilled in the art and are described in the literature. Suitable for free-radical polymerization are, for example, the commercially available photoinitiators Irgacure651@, Irgacure184@, Irgacure907®, Irgacure369@ or Darocure1173@ (Ciba AG).
If a polymerization initiator is added to the LC medium, its proportion is preferably from 0.001 to 1% by weight, particularly preferably from 0.001 to 0.5% by weight.
Furthermore, it is possible to add to the LC 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 LC 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.
Particular preference is given to LC media which, besides the compounds of the formula I, comprise at least one, two, three, four or more compounds from Table B.
In a preferred embodiment, the mixtures according to the invention comprise one or more polymerisable compounds, preferably selected from the polymerisable compounds of the formulae RM-1 to RM-144. 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, RM88, RM-92, RM-102, RM-103, RM-109, RM-116, RM-117, RM-120, RM-121, RM-122, RM-139, RM-142, RM-153, RM-155, RM-158 and RM-159 are particularly preferred.
The following examples are intended to explain the invention without limiting it. Above and below, unless explicitly noted otherwise, all percentage data denote percent by weight, and relate to the corresponding mixture as a whole, comprising all solid or liquid-crystalline components, without solvents. Furthermore, unless explicitly noted otherwise, all temperatures are indicated in in degrees Celsius (° C.). 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.
In addition, the following abbreviations and symbols are used:
All physical properties are and have been 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 in each case.
The term “threshold voltage” for the present invention relates to the capacitive threshold (V0), also known as the Freedericks threshold, unless explicitly indicated otherwise. In the examples, the optical threshold may also, as generally usual, be quoted for 10% relative contrast (Via).
The LC mixture N1 is formulated as follows:
To 99.28% of the mixture N1 are added 0.72% of the chiral dopant S-4011.
The LC mixture N2 is formulated as follows:
To 99.75% of the mixture N2 are added 0.22% of the chiral dopant S-4011 and 0.03% of the stabiliser S1-1.
The LC mixture N3 is formulated as follows:
To 99.888% of the mixture N3 are added 0.04% of the stabiliser S2-1 and 0.108% of the chiral dopant S-4011.
| Number | Date | Country | Kind |
|---|---|---|---|
| 19194534.4 | Aug 2019 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/073791 | 8/26/2020 | WO |
