Patent Application
20240067879
The present invention relates to liquid-crystal (LC) media and to the use thereof for optical, electro-optical and electronic purposes, in particular in LC displays.
One of the liquid-crystal display (LCD) modes used at present is the TN (“twisted nematic”) mode. However, TN LCDs have the disadvantage of a strong viewing-angle dependence of the contrast.
In addition, so-called VA (“vertically aligned”) displays are known which have a broader viewing angle. The LC cell of a VA display contains a layer of an LC medium between two transparent electrodes, where the LC medium usually has a negative dielectric anisotropy. In the switched-off state, the molecules of the LC layer are aligned perpendicular to the electrode surfaces (homeotropically) or have a tilted homeotropic alignment. On application of an electrical voltage to the two electrodes, a realignment of the LC molecules parallel to the electrode surfaces takes place.
Also known are so-called IPS (“in-plane switching”) displays, which contain an LC layer between two substrates, where the two electrodes are arranged on only one of the two substrates and preferably have intermeshed, comb-shaped structures. On application of a voltage to the electrodes, an electric field which has a significant component parallel to the LC layer is thereby generated between them. This causes realignment of the LC molecules in the layer plane.
Furthermore, so-called FFS (“fringe-field switching”) 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 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.
FFS displays can be operated as active-matrix or passive-matrix displays. In the case of active-matrix displays, individual pixels are usually addressed by integrated, non-linear active elements, such as, for example, transistors (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.
Furthermore, FFS displays have been disclosed (see S. H. Lee et al., Appl. Phys. Lett. 73(20), 1998, 2882-2883 and S. H. Lee et al., Liquid Crystals 39(9), 2012, 1141-1148), which have similar electrode design and layer thickness as FFS displays but comprise a layer of an LC medium with negative dielectric anisotropy instead of an LC medium with positive dielectric anisotropy. The LC medium with negative dielectric anisotropy shows a more favorable director orientation that has less tilt and more twist orientation compared to the LC medium with positive dielectric anisotropy, as a result of which these displays have a higher transmission. The displays further comprise an alignment layer, preferably of polyimide provided on at least one of the substrates that is in contact with the LC medium and induces planar alignment of the LC molecules of the LC medium. These displays are also known as “Ultra Brightness FFS (UB-FFS)” mode displays. These displays require an LC medium with high reliability.
In VA displays of the more recent type, uniform alignment of the LC molecules is restricted to a plurality of relatively small domains within the LC cell. Disclinations may exist between these domains, also known as tilt domains. VA displays having tilt domains have, compared with conventional VA displays, a greater viewing-angle independence of the contrast and the grey shades. In addition, displays of this type are simpler to produce since additional treatment of the electrode surface for uniform alignment of the molecules in the switched-on state, such as, for example, by rubbing, is no longer necessary. Instead, the preferential direction of the tilt or pretilt angle is controlled by a special design of the electrodes.
In so-called MVA (“multidomain vertical alignment”) displays, this is usually achieved by the electrodes having protrusions which cause a local pretilt. As a consequence, the LC molecules are aligned parallel to the electrode surfaces in different directions in different, defined regions of the cell on application of a voltage. “Controlled” switching is thereby achieved, and the formation of interfering disclination lines is prevented. Although this arrangement improves the viewing angle of the display, it results, however, in a reduction in its transparency to light. A further development of MVA uses protrusions on only one electrode side, while the opposite electrode has slits, which improves the transparency to light. The slitted electrodes generate an inhomogeneous electric field in the LC cell on application of a voltage, meaning that controlled switching is still achieved. For further improvement of the transparency to light, the separations between the slits and protrusions can be increased, but this in turn results in a lengthening of the response times. In so-called PVA (“patterned VA”) displays, protrusions are rendered completely superfluous in that both electrodes are structured by means of slits on the opposite sides, which results in increased contrast and improved transparency to light but is technologically difficult and makes the display more sensitive to mechanical influences (“tapping”, etc.). For many applications, such as, for example, monitors and especially TV screens, however, a shortening of the response times and an improvement in the contrast and luminance (transmission) of the display are demanded.
A further development are displays of the so-called PS (“polymer sustained”) or PSA (“polymer sustained alignment”) type, for which the term “polymer stabilized” is also occasionally used. In these, a small amount (for example 0.3% by weight, typically <1% by weight) of one or more polymerizable, compound(s), preferably polymerizable monomeric compound(s), is added to the LC medium and, after filling the LC medium into the display, is polymerized or crosslinked in situ, usually by UV photopolymerization, optionally while a voltage is applied to the electrodes of the display. The polymerization is carried out at a temperature where the LC medium exhibits a liquid crystal phase, usually at room temperature. The addition of polymerizable mesogenic or liquid-crystalline compounds, also known as reactive mesogens or “RMs”, to the LC mixture has proven particularly suitable.
In the meantime, the PS(A) principle is being used in various conventional LC display modes. Thus, for example, PS-VA, PS-OCB, PS-IPS, PS-FFS, PS-UB-FFS and PS-TN displays are known. The polymerization of the RMs preferably takes place with an applied voltage in the case of PS-VA and PS-OCB displays, and with or without, preferably without, an applied voltage in the case of PS-IPS displays. As can be demonstrated in test cells, the PS(A) method results in a pretilt in the cell. In the case of PS-VA displays, the pretilt has a positive effect on response times. For PS-VA displays, a standard MVA or PVA pixel and electrode layout can be used. In addition, however, it is also possible, for example, to manage with only one structured electrode side and no protrusions, which significantly simplifies production and at the same time results in very good contrast and in very good transparency to light.
PS-VA displays are described, for example, in EP 1 170 626 A2, U.S. Pat. Nos. 6,861,107, 7,169,449, US 2004/0191428 A1, US 2006/0066793 A1 and US 2006/0103804 A1. PS-OCB displays are described, for example, in T.-J-Chen et al., Jpn. J. Appl. Phys. 45, 2006, 2702-2704 and S. H. Kim, L.-C-Chien, Jpn. J. Appl. Phys. 43, 2004, 7643-7647. PS-IPS displays are described, for example, in U.S. Pat. No. 6,177,972 and Appl. Phys. Lett. 1999, 75(21), 3264. PS-TN displays are described, for example, in Optics Express 2004, 12(7), 1221.
Below the layer formed by the phase-separated and polymerized RMs which induce the above mentioned pretilt angle, the PSA display typically contains an alignment layer on one or both of the substrates forming the display cell, that provides the initial alignment of the LC molecules before the polymer stabilization step. The alignment layer is usually applied on the electrodes (where such electrodes are present) such that it is in contact with the LC medium and induces initial alignment of the LC molecules. The alignment layer may comprise or consist of, for example, a polyimide, which may also be rubbed, or may be prepared by a photoalignment method.
Like the conventional LC displays described above, PSA displays can be operated as active-matrix or passive-matrix displays. In the case of active-matrix displays, individual pixels are usually addressed by integrated, non-linear active elements, such as, for example, transistors (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.
In particular for monitor and especially TV applications, optimization of the response times, but also of the contrast and luminance (thus also transmission) of the LC display continues to be demanded. The PSA method can provide significant advantages here. In particular in the case of PS-VA, PS-IPS and PS-FFS displays, a shortening of the response times, which correlate with a measurable pretilt in test cells, can be achieved without significant adverse effects on other parameters. Another problem observed in prior art is that the use of conventional LC media in LC displays, including but not limited to displays of the PSA type, often leads to the occurrence of mura in the display, especially when the LC medium is filled in the display cell manufactured using the one drop filling (ODF) method. This phenomenon is also known as “ODF mura”. It is therefore desirable to provide LC media which lead to reduced ODF mura.
Another problem observed in prior art is that LC media for use in PSA displays, including but not limited to displays of the PSA type, do often exhibit high viscosities and, as a consequence, high switching times. In order to reduce the viscosity and switching time of the LC medium, it has been suggested in prior art to add LC compounds with an alkenyl group. However, it was observed that LC media containing alkenyl compounds often show a decrease of the reliability and stability, and a decrease of the VHR especially after exposure to UV radiation. Especially for use in PSA displays this is a considerable disadvantage because the photo-polymerization of the RMs in the PSA display is usually carried out by exposure to UV radiation, which may cause a VHR drop in the LC medium.
Especially in view of mobile devices there is great demand for displays with high transmission, which enable the use of less intensive backlight, which, therefore, leads to longer battery lifetime, hence, more sustainable products. Alternatively, displays with higher brightness can be achieved having improved contrast especially under ambient light.
In addition there is a great demand for PSA displays, and LC media and polymerizable compounds for use in such PSA displays, which enable a 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, a low pretilt angle, a multiplicity of grey shades, high contrast and a broad viewing angle, have high reliability and high values for the VHR after UV exposure, and, in case of the polymerizable compounds, have low melting points and a high solubility in the LC host mixtures. In PSA displays for mobile applications, it is especially desired to have available LC media that show low threshold voltage and high birefringence.
One display trend is to achieve fastest possible response time to have best motion picture quality. In this respect, media with negative dielectric anisotropy have an intrinsic disadvantage compared to LC media with positive dielectric anisotropy. On the other hand, mixtures with negative dielectric anisotropy enable a higher transmittance in standard FFS cell layouts and therefore its use has a positive impact on the power consumption and the environment. There is a need in the art to achieve both, fast response time and higher transmittance.
There is thus still a great demand for VA, FFS or PSA displays, and LC media optionally comprising polymerizable compounds for use in VA, FFS or PSA displays, which do not show the drawbacks as described above, or only do so to a small extent, and have improved properties.
The invention is based on the object of providing novel suitable LC media, which do not have the disadvantages indicated above or do so to a reduced extent.
Surprisingly, it has now been found that liquid crystalline media with a suitably high negative Δε, a suitable phase range and Δn and high LTS can be realized which do not exhibit the drawbacks of the materials of the prior art or at least do exhibit them to a significantly lesser degree by using liquid crystalline media comprising one or more compounds of formula I defined below.
The invention relates to a liquid crystal medium comprising
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 the formula I with one or more compounds of the formulae IIA, IIB, IIC and/or IID, and optionally with one or more chiral dopants, and optionally with one or more polymerizable compounds and optionally with further LC compounds and/or additives.
The invention furthermore relates to the use of the LC media according to the invention for electro-optical purposes, preferably in displays, very preferably in displays of the VA, IPS or FFS type, in particular of the UB-FFS type.
The invention furthermore relates to the use of the LC media according to the invention in PSA displays, in particular to the use in PSA displays containing an LC medium, for the production of a tilt angle in the LC medium by in-situ polymerization of polymerizable reactive mesogens (RM) in the PSA display, preferably in an electric or magnetic field.
The invention furthermore relates to an LC display comprising an LC medium according to the invention, in particular a VA, IPS, FFS or UB—FFS or PSA display, particularly preferably an FFS, UB-FFS, VA or a PS-VA display.
The invention furthermore relates to the use of LC media according to the invention in polymer stabilized SA-VA displays, and to a polymer stabilized SA-VA display comprising the LC medium according to the invention.
The invention furthermore relates to a process for manufacturing an LC display as described above and below, comprising the steps of filling, or otherwise providing an LC medium, which optionally comprises one or more polymerizable compounds as described above and below, between the substrates of the display, and optionally polymerizing the polymerizable compounds.
The LC media according to the invention show the following advantageous properties, in particular when used in UB-FFS displays:
In particular, the medium according to the invention is distinguished by high elastic constants K1 and K3, which enables displays with improved contrast and by a favorably low ratio γ1/K1, resulting in fast switching and short response times.
The medium further enables the production of LC displays without the occurrence of ODF mura, in particular when used in a display with inverted-staggered type thin-film transistors.
The medium is further distinguished by a high stability against any change of the liquid crystal composition by evaporation of a liquid crystal compound in the manufacture of a liquid crystal display element using a one-drop-filling (ODF) process.
Preferred compounds of the formula I are selected from the following sub-formulae:
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 preferred media comprise a compound of the formula I-2, in particular the compound of formula I-2 in which alkyl denotes propyl and alkyl* denotes ethyl.
Preferred compounds of the formulae IIA, IIB, IIC and IID are indicated below:
Very preferred compounds of the formula IID are selected from the following sub-formulae:
In a preferred embodiment, the medium comprises one or more compounds of formula IID-7a
Preferred compounds of formula IID-7a are the compounds IID-7a-1 to IID-7a-14.
Particularly preferred mixtures according to the invention comprise one or more compounds of the formulae IIA-2, IIA-8, IIA-10, IIA-16, IIA-18, IIA-40, IIA-41, IIA-42, IIA-43, IIB-2, IIB-10, IIB-16, IIC-1, IID-1 and IID-7.
Preferred media according to the invention comprise at least one compound of the formula IIC-1,
In particular, the medium comprises one or more compounds of the formula IIA-2 selected from the following sub-formulae:
Alternatively, preferably in addition to the compounds of the formulae IIA-2-1 to IIA-2-5, the medium comprises one or more compounds of the formulae IIA-2a-1 to IIA-2a-5:
In particular, the medium comprises one or more compounds of the formula IIA-10 selected from the following sub-formulae:
Alternatively, preferably in addition to the compounds of the formulae IIA-10-1 to IIA-10-5, the medium comprises one or more compounds of the formulae IIA-10a-1 to IIA-10a-5:
In particular, the medium comprises one or more compounds of the formula IIB-10 selected from the following sub-formulae:
Alternatively, preferably in addition to the compounds of the formulae IIB-10-1 to IIB-10-5, the medium comprises one or more compounds of the formulae IIB-10a-1 to IIB-10a-5:
The medium according to the invention preferably comprises one or more compounds of formula III
The compounds of formula III are preferably selected from the compounds of the formula III-1 and/or III-2
Preferably, the compounds of the formula III-1 are selected from the group of compounds of the formulae III-1-1 to III-1-11, preferably of formula III-1-6,
Preferably, the compounds of the formula III-2 are selected from the group of compounds of the formulae III-2-1 to III-2-10, preferably of formula III-2-6,
Optionally the medium comprises one or more compounds of the formula IIIA-1 and/or IIIA-2
The compounds of formula IIIA-1 and/or IIIA-2 are contained in the medium either alternatively or in addition to the compounds of formula III, preferably additionally.
Very preferred compounds of the formulae IIIA-1 and IIIA-2 are the following:
In a preferred embodiment of the present invention, the medium comprises one or more compounds of formula III-3
The compounds of formula III-3 are preferably selected from the group of compounds of the formulae III-3-1 to III-3-10:
In a preferred embodiment of the present invention, the medium comprises one or more compounds of the formulae III-4 to III-6, preferably of formula III-5,
In a preferred embodiment the medium comprises one or more compounds of the formula I selected from the group of compounds of formulae III-7 to III-9, preferably of formula III-8,
In a preferred embodiment, the medium comprises one or more compounds of the formula IV,
The compounds of the formula IV are preferably selected from the group of the compounds of the formulae IV-1 to IV-4,
In a preferred embodiment of the present invention, the medium comprises one or more compounds of formula IV-1 and one or more compounds of formula IV-3.
The compounds of the formula IV-1 are preferably selected from the group of the compounds of the formulae IV-1-1 to IV-1-5
The compounds of the formula IV-2 are preferably selected from the compounds of the formulae IV-2-1 and IV-2-2
The compounds of the formula IV-3 are preferably selected from the group of the compounds of the formulae IV-3-1 and IV-3-2:
The compounds of the formula IV-3-1 and IV-3-2 are preferably selected from the following compounds:
Very preferably, the medium according to the invention comprises a compound of formula IV-4, in particular selected from the compounds of the formulae IV-4-1 and IV-4-2
In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula I selected from the compounds of the formulae I-1 to I-4 in combination with one or more compounds selected from the group of compounds of the formulae IA-1 to IA-9:
The liquid-crystalline medium preferably additionally comprises one or more compounds of the formula Iva,
Preferred compounds of the formula Iva are indicated below:
The medium according to the invention preferably comprises one or more compounds of the formula Iva-1 and/or formula Iva-2.
The proportion of compounds of the formula Iva in the mixture as a whole is preferably less than 5% by weight, very preferably less than 2% by weight.
Preferably, the medium comprises one or more compounds of formula Ivb-1 to Ivb-3
Of the compounds of the formulae Ivb-1 to Ivb-3, the compounds of the formula Ivb-2 are particularly preferred.
Particularly preferred biphenyls are
In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula V
The compounds of formula V are preferably selected from the compounds of the formulae V-1 to V-16:
Preferred media comprise one or more compounds of the formulae V-1, V-5, V-6, V-8, V-9, V-10, V-11, V-12, V-14, V-15, and/or V-16, very preferably V-5 and/or V-6 and/or V-8.
Preferably, the medium according to the invention comprises one or more compounds of the formula CL
The compounds of formula CL are preferably selected form the group of compounds of the formulae CL-1, CL-2 and CL-3
Very preferred compounds of the formula I are selected from the compounds of the formulae CL-3-1 to CL-3-12:
In a preferred embodiment, the medium according to the invention comprises the compound CL-3-1.
In a preferred embodiment of the present invention the medium additionally comprises one or more compounds of the formulae VI-1 to VI-21,
In a preferred embodiment of the present invention the medium additionally comprises one or more compounds of the formulae VII-1 to VII-9
Preferably, the medium according to the invention comprises one or more compounds of the formula VIII:
Preference is furthermore given to compounds of the formula VIII in which R81 and R82 each, independently of one another, denote H, F, or alkyl, alkoxy, alkenyl or alkynyl having 1 to 8, preferably 1 to 5, C atoms, each of which is optionally substituted by halogen, in particular by F.
R81 and R82 preferably denote H, optionally fluorinated alkyl or alkoxy having 1 to 7 C atoms, optionally fluorinated alkenyl or alkynyl having 2 to 7 C atoms, optionally fluorinated cycloalkyl having 3 to 12 C atoms.
Preferably, at least one of R81 and R82 is not H, particularly preferably both of R81 and R82 are not H. R81 is very particularly preferably alkyl. R82 is furthermore preferably H, alkyl or fluorine. Very particularly preferably, R81 is alkyl and R82 is H or alkyl. R81, R82 each, independently of one another, very particularly preferably denote unbranched alkyl having 1 to 5 C atoms. If R81 and R82 denote substituted alkyl, alkoxy, alkenyl or alkynyl, the total number of C atoms in the two groups R81 and R82 is preferably less than 10.
Preferred compounds of the formula VIII are selected from the following sub-formulae, more preferably from the compounds of the formula VIII-3:
In a first very preferred embodiment, the compounds of the formulae VIII-1 to VIII-6 are selected from the compounds of the formula VIII-1a to VIII-6a, in particular of the formula VIII-3a:
In a second very preferred embodiment, the compounds of the formulae VIII-1 to VIII-6 are selected from the compounds of the formula VIII-2b to VIII-6b, in particular of the formula VIII-3b:
In a third very preferred embodiment, the compounds of the formulae VIII-1 to VIII-6 are selected from the compounds of the formula VIII-1c to VIII-6c, in particular of the formula I3-c:
In a fourth very preferred embodiment, the compounds of the formulae VIII-1 to VIII-6 are selected from the compounds of the formula VIII-1d to VIII-6d, in particular of the formula VIII-3d:
In a particularly preferred embodiment, the medium according to the invention comprises one or more compounds selected from the group of the formulae VIII-1a to VIII-6a and one or more compounds selected from the group of the formulae VIII-2b to VIII-6b.
Very particularly preferably the medium comprises one or more compounds selected from the group of compounds of the formulae VIII-3a, VIII-3b, VIII-3c and VIII-3d:
Most preferred compounds of formula I include, in particular, one or more of the following:
Alternatively, or additionally, the following compounds of formula I can be used:
Further preferred embodiments are listed below:
Particularly preferred compounds of the formulae BC and CR are the compounds BC-1 to BC-7 and CR-1 to CR-5,
Very particular preference is given to mixtures comprising one, two or three compounds of the formula BC-2.
Preferred compounds of the formula In are the compounds of the formulae In-1 to In-16 indicated below:
Particular preference is given to the compounds of the formulae In-1, In-2, In-3 and In-4.
The compounds of the formulae L-1 to L-11 are preferably employed in concentrations of 5 to 15% by weight, in particular 5 to 12% by weight and very particularly preferably 8 to 10% by weight.
Preferred compounds of the formula IIA-Y are selected from the group consisting of the following sub-formulae
Particularly preferred compounds of the formula IIA-Y are selected from the group consisting of following sub-formulae:
The medium according to the invention preferably comprises one or more compounds selected from the group of compounds of the formulae PI and PII
The compounds of formula PI are preferably selected from the group of compounds of formulae PI-1 to PI-3, very preferably from the group of compounds of formulae PI-1 and PI-3, in particular PI-3:
In formulae PI-1, PI-2 and PI-3, L21 and L22 or L23 and L24 are preferably both F.
In another preferred embodiment in formulae PI-1 and PI-2, all of L21, L22, L23 and L24 denote F.
The compounds of formula PI-1 are preferably selected from the group of compounds of formulae PI-1a to PI-1 h
In a preferred embodiment of the present invention the medium comprises one or more compounds selected from the group of compounds of the formulae PI-1a to PI-1 h wherein L21 and L22, and/or L23 and L24 are both F, respectively.
In another preferred embodiment the medium comprises one or more compounds selected from the group of compounds of formulae PI-1a to PI-1 h, in which L21, L22, L23 and L24 all denote F.
Very preferred compounds of formula PI-1 are
Preferably the compounds of formula PI-2 are selected from the group of compounds of formulae PI-2a to PI-2c
Preferably the compounds of formula PI-3 are selected from the group of compounds of formulae PI-3a to PI-3e
Very preferred compounds of formula PI-3 are
Alternatively, or in addition to the preferred compounds of formula PI above, the medium optionally comprises one or more compounds of formula PI selected from the compounds of the formulae PIA-1 to PIA-7:
Preferred compounds are those of formula PIA-1, PIA-2 and PIA-3, very preferred are those of formula PIA-1 and PIA-2, furthermore PIA-8, PIA-11, PIA-13, PIA-23, PIA-26 and PIA-27.
In the compounds of formulae PIA-1 to PIA-28 R2 preferably denotes alkyl having 1 to 6 C atoms, very preferably ethyl or propyl, X2 preferably denotes F or OCF3, very preferably F.
In another preferred embodiment of the present invention the medium comprises one or more compounds of formula PII preferably selected from the group of formulae PII-1 and PII-2, preferably of formula PII-2:
Preferably the compounds of formula PII-1 are selected from the group of compounds of formulae PI-11a and PII-1b
The compounds of formula PII-1a are preferably selected from the group of compounds of formulae PII-1a-1 to PII-1a-6
Preferably the compounds of formula PII-2 are selected from the group of compounds of formulae PII-2a to PII-2m
Preferably, the compounds of formula PII-2a are selected from the group of compounds of formulae PII-2a-1 to PII-2a-4
The compounds of formula PII-2b are preferably selected from the group of compounds of formulae PII-2b-1 and PII-2b-2, preferably PII-2b-2
The compounds of formula PII-2c are preferably selected from the group of compounds of formulae PII-2c-1 to PII-2c-5
The compounds of formulae PII-2d and PII-2e are preferably selected from the group of compounds of formulae PII-2d-1 and PII-2e-1
The compounds of formula PII-2f are preferably selected from the group of compounds of formulae PII-2f-1 to PII-2f-4
The compounds of formula PII-2g are preferably selected from the group of compounds of formulae PII-2g-1 to PII-2g-7
The compounds of formula PII-2h are preferably selected from the group of compounds of formulae PII-2h-1 to PII-2h-5
The compounds of formula PII-2i are preferably selected from the group of compounds of formulae PII-2i-1 to PII-2i-3
The compounds of formula PII-2j are preferably selected from the group of compounds of formulae PII-2j-1 to PII-2j-3
The compounds of formula PII-2k are preferably selected from the group of compounds of formulae PII-2k-1 to PII-2k-6
The compounds of formula PII-21 are preferably selected from the group of compounds of formulae PII-21-1 to PII-21-6
The compounds of formula PII-2m are preferably selected from the compounds of formula PII-2m-1
Alternatively, or in addition to the compounds of the formulae PII-1 and/or PII-2 the media according to the present invention optionally comprise one or more compounds of formula PII-3,
Preferably, the medium according to the invention comprises a compound selected from the group of compounds of the formulae ST-1 to ST-19, very preferably of the formula ST-3:
or
Of the compounds of the formula ST, special preference is given to the compounds of the formulae ST-3 and in particular:
In the compounds of the formulae ST-3a and ST-3b, n preferably denotes 3. In the compounds of the formula ST-3c, n preferably denotes 7.
Very particularly preferred mixtures according to the invention comprise one or more stabilizers from the group of the compounds of the formulae ST-3a-1, ST-3b-1, ST-3c-1, ST-8-1, ST-9-1, ST-12a-1, ands ST-12b-1:
Preferably, the medium comprises one or more compounds of the formula S
In formula S, aryl denotes an aromatic or heteroaromatic hydrocarbon group having 4 to 40 C atoms, comprising one, two, three or four aromatic rings including condensed rings that may be linked directly or via an alkylene linking group having 1 to 12 C atoms, in which one or more H atoms are each optionally replaced with alkyl or alkoxy having 1 to 6 C atoms or alkenyl having 2 to 6 C atoms, or with CN, CFs or halogen, and in which one or more CH2 groups may each, independently of one another, be replaced by —O—, —S—, —NH—, —N(C1-C4-alkyl)-, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CH═CH— or —C≡C— in such a way that O or S atoms are not linked directly to one another.
Preferred aryl groups are benzene, naphthalene, anthracene, biphenyl, m-terphenyl, p-terphenyl, and (phenylalkyl)benzene in which alkyl is straight chain alkyl having 1 to 12 C atoms.
In a preferred embodiment, the medium according to the invention comprises a compound of the formula S in which the parameter q is 3 and G denotes a group ZS-HA.
In another preferred embodiment, the medium according to the invention comprises a compound of the formula S in which the parameter q is 4 and G denotes H or RS.
The compounds of formula S are preferably selected from the compounds of the formulae S-1, S-2 and S-3:
Preferred compounds of formula S-1 are selected from the compounds of the formula S-1-1:
Preferred compounds of formula S-2 are selected from the compounds of the formula S-2-1:
Preferred compounds of formula S-3 are selected from the compounds of the formula S-3-1:
The compounds of the formulae ST-1 to ST-18 are preferably each present in the liquid-crystal mixtures according to the invention in amounts of 0.005-0.5%, based on the mixture.
If the mixtures according to the invention comprise two or more compounds from the group of the compounds of the formulae ST-1 to ST-18, the concentration correspondingly increases to 0.01-1% in the case of two compounds, based on the mixtures.
However, the total proportion of the compounds of the formulae ST-1 to ST-18, based on the mixture according to the invention, should not exceed 2%.
The liquid crystal medium according to the invention, herein also referred to as liquid crystal host mixture, is suitable for the use in polymer stabilized displays. To this end, the medium according to the invention optionally comprises one or more polymerizable compounds of formula P
P-Sp-A1-(Z1-A2)z-R P
The term “reliability” as used herein means the quality of the performance of the display during time and with different stress loads, such as light load, temperature, humidity, voltage, and comprises display effects such as image sticking (area and line image sticking), mura, yogore etc. which are known to the skilled person in the field of LC displays. As a standard parameter for categorizing the reliability usually the voltage holding ration (VHR) value is used, which is a measure for maintaining a constant electrical voltage in a test display. Among other factors, a high VHR is a prerequisite for a high reliability of the LC medium.
Unless indicated otherwise, the term “PS” is used hereinafter when referring to displays of the polymer sustained alignment type in general, and the term “P” is used when referring to specific display modes, like PS-VA, PS-TN, and the like.
As used herein, the terms “active layer” and “switchable layer” mean a layer in an electrooptical display, for example an LC display, that comprises one or more molecules having structural and optical anisotropy, like for example LC molecules, which change their orientation upon an external stimulus like an electric or magnetic field, resulting in a change of the transmission of the layer for polarized or unpolarized light.
As used herein, the terms “tilt” and “tilt angle” will be understood to mean a tilted alignment of the LC molecules of an LC medium relative to the surfaces of the cell in an LC display (here preferably a PSA display). The tilt angle here denotes the average angle (<90°) between the longitudinal molecular axes of the LC molecules (LC director) and the surface of the plane-parallel outer plates which form the LC cell. A low value for the tilt angle (i.e., a large deviation from the 90° angle) corresponds to a large tilt here. A suitable method for measurement of the tilt angle is given in the examples. Unless indicated otherwise, tilt angle values disclosed above and below relate to this measurement method.
As used herein, the terms “reactive mesogens” and “RM” will be understood to mean a compound containing a mesogenic or liquid crystalline skeleton, and one or more functional groups attached thereto which are suitable for polymerization and are also referred to as “polymerizable group” or “P”.
Unless stated otherwise, the term “polymerizable compound” as used herein will be understood to mean a polymerizable monomeric compound.
As used herein, the term “ow-molecular-weight compound” will be understood to mean to a compound that is monomeric and/or is not prepared by a polymerization reaction, as opposed to a “polymeric compound” or a “polymer”.
As used herein, the term “unpolymerizable compound” will be understood to mean a compound that does not contain a functional group that is suitable for polymerization under the conditions usually applied for the polymerization of the RMs.
The term “mesogenic group” as used herein is known to the person skilled in the art and described in the literature, and means a group which, due to the anisotropy of its attracting and repelling interactions, essentially contributes to causing a liquid-crystal (LC) phase in low-molecular-weight or polymeric substances. Compounds containing mesogenic groups (mesogenic compounds) do not necessarily have to have an LC phase themselves. It is also possible for mesogenic compounds to exhibit LC phase behavior only after mixing with other compounds and/or after polymerization. Typical mesogenic groups are, for example, rigid rod- or disc-shaped units. An overview of the terms and definitions used in connection with mesogenic, or LC compounds is given in Pure Appl. Chem. 2001, 73(5), 888 and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368.
As used herein, the terms “optically active” and “chiral” are synonyms for materials that are able to induce a helical pitch in a nematic host material, also referred to as “chiral dopants”.
The term “spacer group”, above and below also referred to as “S”, as used herein is known to the person skilled in the art and is described in the literature, see, for example, Pure Appl. Chem. 2001, 73(5), 888 and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368. As used herein, the terms “spacer group” or “spacer” mean a flexible group, for example an alkylene group, which connects the mesogenic group and the polymerizable group(s) in a polymerizable mesogenic compound.
Likewise, in the compounds of formula S, a spacer group connects a central hydrocarbon group with a photoactive, stabilizing hindered amine functional group.
Above and below
denotes a trans-1,4-cyclohexylene ring.
In a group
the single bond shown between the two ring atoms can be attached to any free position of the benzene ring.
Above and below “organic group” denotes a carbon or hydrocarbon group.
“Carbon group” denotes a mono- or polyvalent organic group containing at least one carbon atom, where this either contains no further atoms (such as, for example, —C≡C—) or optionally contains one or more further atoms, such as, for example, N, O, S, B, P, Si, Se, As, Te or Ge (for example carbonyl, etc.). The term “hydrocarbon group” denotes a carbon group which additionally contains one or more H atoms and optionally one or more heteroatoms, such as, for example, N, O, S, B, P, Si, Se, As, Te or Ge.
“Halogen” denotes F, Cl, Br, or I, preferably F or Cl. —CO—, —C(≡O)— and —C(O)— denote a carbonyl group, i.e.,
A carbon or hydrocarbon group can be a saturated or unsaturated group. Unsaturated groups are, for example, aryl, alkenyl or alkynyl groups. A carbon or hydrocarbon radical having more than 3 C atoms can be straight-chain, branched and/or cyclic and may also contain spiro links or condensed rings.
The terms “alkyl”, “aryl”, “heteroaryl”, etc., also encompass polyvalent groups, for example alkylene, arylene, heteroarylene, etc.
The term “aryl” denotes an aromatic carbon group, or a group derived therefrom. The term “heteroaryl” denotes “aryl” as defined above, containing one or more heteroatoms, preferably selected from N, O, S, Se, Te, Si and Ge.
Preferred carbon and hydrocarbon groups are optionally substituted, straight-chain, branched or cyclic, alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy and alkoxycarbonyloxy having 1 to 40, preferably 1 to 20, very preferably 1 to 12, C atoms, optionally substituted aryl or aryloxy having 5 to 30, preferably 6 to 25, C atoms, or optionally substituted alkylaryl, arylalkyl, alkylaryloxy, arylalkyloxy, arylcarbonyl, aryloxycarbonyl, arylcarbonyloxy and aryloxycarbonyloxy having 5 to 30, preferably 6 to 25, C atoms, wherein one or more C atoms may also be replaced by hetero atoms, preferably selected from N, O, S, Se, Te, Si and Ge.
Further preferred carbon and hydrocarbon groups are C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C3-C20 allyl, C4-C20 alkyldienyl, C4-C20 polyenyl, C6-C20 cycloalkyl, C4-C15 cycloalkenyl, C6-C30 aryl, C6-C30 alkylaryl, C6-C0 arylalkyl, C6-C30 alkylaryloxy, C6-C30 arylalkyloxy, C2-C30 heteroaryl, C2-C30 heteroaryloxy.
Particular preference is given to C1-C12 alkyl, C2-C12 alkenyl, C2-C12 alkynyl, C6-C25 aryl and C2-C25 heteroaryl.
Further preferred carbon and hydrocarbon groups are straight-chain, branched or cyclic alkyl having 1 to 20, preferably 1 to 12, C atoms, which are unsubstituted or mono- or polysubstituted by F, Cl, Br, I or CN and in which one or more non-adjacent CH2 groups may each be replaced, independently of one another, by —C(Rx)═C(Rx)—, —C≡—, —N(Rx)—, —O—, —S—, —CO—, —CO—O—, —O—CO—, or —O—CO—O— in such a way that O and/or S atoms are not linked directly to one another.
Rx preferably denotes H, F, Cl, CN, a straight-chain, branched or cyclic alkyl chain having 1 to 25 C atoms, in which, in addition, one or more non-adjacent C atoms may each be replaced by —O—, —S—, —CO—, —CO—O—, —O—CO—, or —O—CO—O— and in which one or more H atoms may each be replaced by F or Cl, or denotes an optionally substituted aryl or aryloxy group with 6 to 30 C atoms, or an optionally substituted heteroaryl or heteroaryloxy group with 2 to 30 C atoms.
Preferred alkyl groups are, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, 2-methylbutyl, n-pentyl, s-pentyl, cyclopentyl, n-hexyl, cyclohexyl, 2-ethylhexyl, n-heptyl, cycloheptyl, n-octyl, cyclooctyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, dodecanyl, trifluoromethyl, perfluoro-n-butyl, 2,2,2-trifluoroethyl, perfluorooctyl, perfluorohexyl, etc.
Preferred alkenyl groups are, for example, ethenyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl, cyclooctenyl, etc.
Preferred alkynyl groups are, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl, octynyl, etc.
Preferred alkoxy groups are, for example, methoxy, ethoxy, 2-methoxyethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy, 2-methylbutoxy, n-pentoxy, n-hexoxy, n-heptoxy, n-octoxy, n-nonoxy, n-decoxy, n-undecoxy, n-dodecoxy, etc.
Preferred amino groups are, for example, dimethylamino, methylamino, methylphenylamino, phenylamino, etc.
Aryl and heteroaryl groups can be monocyclic or polycyclic, i.e., they can contain one ring (such as, for example, phenyl) or two or more rings, which may also be fused (such as, for example, naphthyl) or covalently bonded (such as, for example, biphenyl), or contain a combination of fused and linked rings. Heteroaryl groups contain one or more heteroatoms, preferably selected from O, N, S and Se.
Particular preference is given to mono-, bi- or tricyclic aryl groups having 6 to 25 C atoms and mono-, bi- or tricyclic heteroaryl groups having 5 to 25 ring atoms, which optionally contain fused rings and are optionally substituted. Preference is furthermore given to 5-, 6- or 7-membered aryl and heteroaryl groups, in which, in addition, one or more CH groups may each be replaced by N, S or O in such a way that O atoms and/or S atoms are not linked directly to one another.
Preferred aryl groups are, for example, phenyl, biphenyl, terphenyl, [1,1′:3′,1″ ]-terphenyl, naphthyl, anthracene, binaphthyl, phenanthrene, 9,10-dihydro-phenanthrene, pyrene, dihydropyrene, chrysene, perylene, tetracene, pentacene, benzopyrene, fluorene, indene, indenofluorene, spirobifluorene, etc.
Preferred heteroaryl groups are, for example, 5-membered rings, such as pyrrole, pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, tetrazole, furan, thiophene, selenophene, oxazole, isoxazole, 1,2-thiazole, 1,3-thiazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole, 1,3,4-thiadiazole, 6-membered rings, such as pyridine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, 1,2,4-triazine, 1,2,3-triazine, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine, 1,2,3,5-tetrazine, or condensed groups, such as indole, isoindole, indolizine, indazole, benzimidazole, benzotriazole, purine, naphthimidazole, phenanthrimidazole, pyridimidazole, pyrazinimidazole, quinoxalinimidazole, benzoxazole, naphthoxazole, anthroxazole, phenanthroxazole, isoxazole, benzothiazole, benzofuran, isobenzofuran, dibenzofuran, quinoline, isoquinoline, pteridine, benzo-5,6-quinoline, benzo-6,7-quinoline, benzo-7,8-quinoline, benzoisoquinoline, acridine, phenothiazine, phenoxazine, benzopyridazine, benzopyrimidine, quinoxaline, phenazine, naphthyridine, aza-carbazole, benzocarboline, phenanthridine, phenanthroline, thieno[2,3b]thiophene, thieno[3,2b]thiophene, dithienothiophene, isobenzothiophene, dibenzothiophene, benzothiophene, benzothiadiazothiophene, or combinations of these groups.
The aryl and heteroaryl groups mentioned above and below may also be substituted by alkyl, alkoxy, thioalkyl, fluorine, fluoroalkyl or further aryl or heteroaryl groups.
The (non-aromatic) alicyclic and heterocyclic groups encompass both saturated rings, i.e., those containing exclusively single bonds, and also partially unsaturated rings, i.e., those which may also contain multiple bonds. Heterocyclic rings contain one or more heteroatoms, preferably selected from Si, O, N, S and Se.
The (non-aromatic) alicyclic and heterocyclic groups can be monocyclic, i.e., contain only one ring (such as, for example, cyclohexane), or polycyclic, i.e., contain a plurality of rings (such as, for example, decahydronaphthalene or bicyclooctane).
Particular preference is given to saturated groups. Preference is furthermore given to mono-, bi- or tricyclic groups having 5 to 25 ring atoms, which optionally contain fused rings and are optionally substituted. Preference is furthermore given to 5-, 6-, 7- or 8-membered carbocyclic groups, in which, in addition, one or more C atoms may each be replaced by Si and/or one or more CH groups may each be replaced by N and/or one or more non-adjacent CH2 groups may each be replaced by —O— and/or -S—.
Preferred alicyclic and heterocyclic groups are, for example, 5-membered groups, such as cyclopentane, tetrahydrofuran, tetrahydrothiofuran, pyrrolidine, 6-membered groups, such as cyclohexane, silinane, cyclohexene, tetrahydropyran, tetrahydrothiopyran, 1,3-dioxane, 1,3-dithiane, piperidine, 7-membered groups, such as cycloheptane, and fused groups, such as tetrahydronaphthalene, decahydronaphthalene, indane, bicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl, octahydro-4,7-methanoindane-2,5-diyl.
Preferred substituents are, for example, solubility-promoting groups, such as alkyl or alkoxy, electron-withdrawing groups, such as fluorine, nitro or nitrile, or substituents for increasing the glass transition temperature (Tg) in the polymer, in particular bulky groups, such as, for example, t-butyl or optionally substituted aryl groups. Preferred substituents, hereinafter also referred to as “L”, are, for example, F, Cl, Br, I, —CN, —NO2, —NCO, —NCS, —OCN, —SCN, —C(═O)N(Rx)2, —C(═O)Y1, —C(═O)Rx, —N(Rx)2, straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy each having 1 to 25 C atoms, in which one or more H atoms may optionally be replaced by F or C, optionally substituted silyl having 1 to 20 Si atoms, or optionally substituted aryl having 6 to 25, preferably 6 to 15, C atoms,
“Substituted silyl or aryl” preferably means substituted by halogen, —CN, R0, —OR0, —CO—R0, —CO—O—R0, —O—CO—R0, or —O—CO—O—R0, wherein R00 denotes H or alkyl with 1 to 20 C atoms.
Particularly preferred substituents L are, for example, F, C, CN, NO2, CH3, C2H5, OCH3, OC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF3, OCF3, OCHF2, OC2F5, furthermore phenyl.
A1 and A2 very preferably denote
in which L has one of the meanings indicated above and r denotes 0, 1, 2, 3 or 4, in particular
denotes
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═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, 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═CW1—CO—,
CH2═CW2—O—, CH2═CW2—, CW1═CH—CO—(O)k3—, CW1═CH—CO—NH—, CH2═CW1—CO—NH—, (CH2═CH)2CH—OCO—, (CH2═CH—CH2)2CH—OCO—, (CH2═CH)2CH—O—, (CH2═CH—CH2)2N—, (CH2═CH—CH2)2N—CO—, CH2═CW1—CO—NH—, CH2═CH—(COO)k1-Phe-(O)k2—, CH2═CH—(CO)k1-Phe-(O)k2—, Phe-CH═CH— and 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 oxa-carbonylalkyl 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 the spacer group 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—, —(CH2)p1—O—, —(CH2)p1—O—CO—, —(CH2)p1—CO—O—, —(CH2)p1—O—CO—O—, —(CH2CH2O)q1—CH2CH2—, —CH2CH2—S—CH2CH2—, —CH2CH2—NH—CH2CH2— or —(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 has the meaning 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.
In a preferred embodiment of the invention the compounds of formula P and its subformulae contain a spacer group Sp that is substituted by one or more polymerizable groups P, so that the group Sp-P corresponds to Sp(P)s, with s being >2 (branched polymerizable groups).
Preferred compounds of formula P according to this preferred embodiment are those wherein s is 2, i.e., compounds which contain a group Sp(P)2. Very preferred compounds of formula P according to this preferred embodiment contain a group selected from the following formulae:
—X-alkyl-CHPP S1
—X-alkyl-CH((CH2)aaP)((CH2)bbP) S2
—X—N((CH2)aaP)((CH2)bbP) S3
—X-alkyl-CHP—CH2—CH2P S4
—X-alkyl-C(CH2P)(CH2P)—CaaH2aa+1 S5
—X-alkyl-CHP—CH2P S6
—X-alkyl-CPP-CaaH2aa+i S7
—-X-alkyl-CHPCHP-CaaH2aa+1 S8
Preferred spacer groups Sp(P)2 are selected from formulae S1, S2 and S3.
Very preferred spacer groups Sp(P)2 are selected from the following subformulae:
—CHPP S1a
—O—CHPP S1b
—CH2—CHPP S1c
—OCH2—CHPP S1d
—CH(CH2—P)(CH2—P) S2a
—OCH(CH2—P)(CH2—P) S2b
—CH2—CH(CH2—P)(CH2—P) S2c
—OCH2—CH(CH2—P)(CH2—P) S2d
—CO—NH((CH2)2P)((CH2)2P) S3a
In the compounds of formula P and its subformulae as described above and below, P is preferably selected from the group consisting of vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxide, most preferably from acrylate and methacrylate.
Further preferred are compounds of formula P and its subformulae as described above and below, wherein all polymerizable groups P that are present in the compound have the same meaning, and very preferably denote acrylate or methacrylate, most preferably methacrylate.
In the compounds of formula P and its subformulae as described above and below, R preferably denotes P-Sp-.
Further preferred are compounds of formula P and its subformulae as described above and below, wherein Sp denotes a single bond or —(CH2)p1—, —O—(CH2)p1—, —O— CO—(CH2)p1, or —CO—O—(CH2)p1, wherein p1 is 2, 3, 4, 5 or 6, and, if Sp is —O—(CH2)p1—, —O—CO—(CH2)p1 or —CO—O—(CH2)p1 the O-atom or CO-group, respectively, is linked to the benzene ring.
Further preferred are compounds of formula P and its subformulae as described above and below, wherein at least one group Sp is a single bond.
Further preferred are compounds of formula P and its subformulae as described above and below, wherein at least one group Sp is different from a single bond, and is preferably selected from —(CH2)p1—, —O—(CH2)p1—, —O—CO—(CH2)p1, or —CO—O—(CH2)p1, wherein p1 is 2, 3, 4, 5 or 6, and, if Sp is —O—(CH2)p1—, —O—CO—(CH2)p1 or —CO—O—(CH2)p1 the O-atom or CO-group, respectively, is linked to the benzene ring.
Very preferred groups -A1-(Z-A2)z- in formula P are selected from the following formulae
Preferred compounds of formula P and their subformulae are selected from the following preferred embodiments, including any combination thereof:
Very preferred compounds of formula P are selected from the following formulae:
Very preferred are compounds of formulae P2, P13 and P32, especially direactive compounds containing exactly two polymerizable groups P1 and P2.
Further preferred are compounds selected from formulae P17 to P31, in particular from formulae P20, P22, P26, P29 and P31, especially trireactive compounds containing exactly three polymerizable groups P1, P2 and P3.
In the compounds of formulae P1 to P32 the group
is preferably
Preferred compounds of formulae P1 to P32 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 P1 to P32 are those wherein Sp1, Sp2 and Sp3 are a single bond.
Further preferred compounds of formulae P1 to P32 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 P1 to P32 are those wherein those groups Sp1, Sp2 and Sp3 that are different from a single bond denote —(CH2)s1—X″—, wherein si 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—0, or —O—CO—O— or a single bond.
Further preferred polymerizable compounds are selected from Table E below, especially selected from the group consisting of formulae 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-58, RM-64, RM-74, RM-76, RM-88, RM-91, RM-102, RM-103, RM-109, RM-116, RM-117, RM-120, RM-121, RM-122, RM-139, RM-140, RM-142, RM-143, RM-145, RM-146, RM-147, RM-149, RM-156 to RM-163, RM-169, RM-170 and RM-171 to RM-183.
Particularly preferred are LC media comprising one, two or three polymerizable compounds of formula P.
Further preferred are LC media comprising two or more direactive polymerizable compounds of formula P, preferably selected from formulae P1 to P16 and P32, very preferably selected from formulae P2, P13 and P32.
Further preferred are LC media comprising one or more direactive polymerizable compounds of formula P, preferably selected from formulae P1 to P16 and P32, very preferably from formulae P2, P13 and P32, and one or more trireactive polymerizable compounds of formula P, preferably selected from formulae P17 to P22 and P24 to P32, very preferably from formulae P20, P22, P26, P29 and P31.
Further preferred are LC media comprising one or more polymerizable compounds of formula P wherein at least one r is not 0, or at least one of s and t is not 0, very preferably selected from formulae P2, P13, P22, P24, P27, P29, P31 and P32, and wherein L is selected from the preferred groups shown above, most preferably from F, OCH3 and SCH3.
Further preferred are LC media comprising one or more polymerizable compounds which show absorption in the wavelength range from 320 to 380 nm, preferably selected from formula P, very preferably from formulae P1 to P32.
Particular preference is given to LC media comprising one, two or three polymerizable compounds selected from formula P or formulae P1 to P32.
For use in PSA displays the total proportion of the polymerizable compounds, like those of formula P or P1 to P32, in the LC medium is preferably from 0.01 to 2.0%, very preferably from 0.1 to 1.0%, most preferably from 0.2 to 0.8%.
For use in SA-VA displays the total proportion of the polymerizable compounds, like those of formula P or P1 to P32, in the LC medium is preferably from >0 to <3%, very preferably from >0 to <2%, more preferably from 0.05 to 2.0, most preferably from 0.05 to 1.0%.
For the production of PSA displays, the polymerizable compounds contained in the LC medium are polymerized or crosslinked (if one compound contains two or more polymerizable groups) by in-situ polymerization in the LC 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 color 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.
A preferred PSA type LC display of the present invention comprises:
The first and/or second alignment layer controls the alignment direction of the LC molecules of the LC layer. For example, in PS-VA displays the alignment layer is selected such that it imparts to the LC molecules homeotropic (or vertical) alignment (i.e., perpendicular to the surface) or tilted alignment. Such an alignment layer may for example comprise a polyimide, which may also be rubbed, or may be prepared by a photoalignment method.
The LC layer with the LC medium can be deposited between the substrates of the display by methods that are conventionally used by display manufacturers, for example the so-called one-drop-filling (ODF) method. The polymerizable component of the LC medium is then polymerized for example by UV photopolymerization. The polymerization can be carried out in one step or in two or more steps.
The PSA display may comprise further elements, like a color filter, a black matrix, a passivation layer, optical retardation layers, transistor elements for addressing the individual pixels, etc., all of which are well known to the person skilled in the art and can be employed without inventive skill.
The electrode structure can be designed by the skilled person depending on the individual display type. For example, for PS-VA displays a multi-domain orientation of the LC molecules can be induced by providing electrodes having slits and/or bumps or protrusions in order to create two, four or more different tilt alignment directions.
Upon polymerization the polymerizable compounds form a crosslinked polymer, which causes a certain pretilt of the LC molecules in the LC medium. Without wishing to be bound to a specific theory, it is believed that at least a part of the crosslinked polymer, which is formed by the polymerizable compounds, will phase-separate or precipitate from the LC medium and form a polymer layer on the substrates or electrodes, or the alignment layer provided thereon. Microscopic measurement data (like SEM and AFM) have confirmed that at least a part of the formed polymer accumulates at the LC/substrate interface.
The polymerization can be carried out in one step. It is also possible firstly to carry out the polymerization, optionally while applying a voltage, in a first step in order to produce a pretilt angle, and subsequently, in a second polymerization step without an applied voltage, to polymerize or crosslink the compounds which have not reacted in the first step (“end curing”).
Suitable and preferred polymerization methods are, for example, thermal or photopolymerization, preferably photopolymerization, in particular UV induced photopolymerization, which can be achieved by exposure of the polymerizable compounds to UV radiation.
Optionally one or more polymerization initiators are added to the LC medium. Suitable conditions for the polymerization and suitable types and amounts of 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 employed, its proportion is preferably 0.001 to 5% by weight, particularly preferably 0.001 to 1% by weight.
The polymerizable compounds according to the invention are also suitable for polymerization without an initiator, which is accompanied by considerable advantages, such, for example, lower material costs and in particular less contamination of the LC medium by possible residual amounts of the initiator or degradation products thereof. The polymerization can thus also be carried out without the addition of an initiator. In a preferred embodiment, the LC medium thus does not contain a polymerization initiator.
The LC medium may also comprise one or more stabilizers in order to prevent undesired spontaneous polymerization of the RMs, for example during storage or transport. Suitable types and amounts of stabilizers are known to the person skilled in the art and are described in the literature. Particularly suitable are, for example, the commercially available stabilizers from the Irganox® series (Ciba AG), such as, for example, Irganox®1076. If stabilizers are employed, their proportion, based on the total amount of RMs or the polymerizable component (component P), is preferably 10-500,000 ppm, particularly preferably 50-50,000 ppm.
The polymerizable compounds of formula P in particular show good UV absorption in, and are therefore especially suitable for, a process of preparing a PSA display including one or more of the following features:
Both using lower intensity and a UV shift to longer wavelengths protect the organic layer against damage that may be caused by the UV light.
A preferred embodiment of the present invention relates to a process for preparing a PSA display as described above and below, comprising one or more of the following features:
This preferred process can be carried out for example by using the desired UV lamps or by using a band pass filter and/or a cut-off filter, which are substantially transmissive for UV light with the respective desired wavelength(s) and are substantially blocking light with the respective undesired wavelengths. For example, when irradiation with UV light of wavelengths λ of 300-400 nm is desired, UV exposure can be carried out using a wide band pass filter being substantially transmissive for wavelengths 300 nm<λ<400 nm. When irradiation with UV light of wavelength k of more than 340 nm is desired, UV exposure can be carried out using a cut-off filter being substantially transmissive for wavelengths k>340 nm.
“Substantially transmissive” means that the filter transmits a substantial part, preferably at least 50% of the intensity, of incident light of the desired wavelength(s). “Substantially blocking” means that the filter does not transmit a substantial part, preferably at least 50% of the intensity, of incident light of the undesired wavelengths. “Desired (undesired) wavelength” e.g., in case of a band pass filter means the wavelengths inside (outside) the given range of k, and in case of a cut-off filter means the wavelengths above (below) the given value of k.
This preferred process enables the manufacture of displays by using longer UV wavelengths, thereby reducing or even avoiding the hazardous and damaging effects of short UV light components.
UV radiation energy is in general from 6 to 100 J, depending on the production process conditions.
Preferably the LC medium according to the present invention essentially consist of a polymerizable component P) comprising or one or more polymerizable compounds of formula P, and an LC host mixture, and an optically active component comprising one or more chiral dopants, as described above and below. However, the LC medium may additionally comprise one or more further components or additives, preferably selected from the list including but not limited to co-monomers, polymerization initiators, inhibitors, stabilizers, surfactants, wetting agents, lubricating agents, dispersing agents, hydrophobing agents, adhesive agents, flow improvers, defoaming agents, deaerators, diluents, reactive diluents, auxiliaries, colorants, dyes, pigments, and nanoparticles.
Particular preference is given to LC media comprising one, two or three polymerizable compounds of formula P.
Preferably the proportion of compounds of formula P in the LC medium is from >0 to <5%, very preferably from >0 to <1%, most preferably from 0.01 to 0.5%.
In an embodiment, the media according to the present invention comprise one or more chiral dopants. Preferably these chiral dopants have an absolute value of the helical twisting power (HTP) in the range of from 1 μm−1 to 150 μm−1, preferably in the range of from 10 μm−1 to 100 μm−1. In case the media comprise two or more chiral dopants, these may have opposite signs of their HTP-values. This condition is preferred for some specific embodiments, as it allows to compensate the chirality of the respective compounds to some degree and, thus, may be used to compensate various temperature dependent properties of the resulting media in the devices. Generally, however, it is preferred that most, preferably all of the chiral compounds present in the media according to the present invention have the same sign of their HTP-values.
Preferably the chiral dopants present in the media according to the instant application are mesogenic compounds and most preferably they exhibit a mesophase on their own.
In a preferred embodiment of the present invention, the medium comprises two or more chiral compounds which all have the same algebraic sign of the HTP.
The temperature dependence of the HTP of the individual compounds may be high or low. The temperature dependence of the pitch of the medium can be compensated by mixing compounds having different temperature dependencies of the HTP in corresponding ratios.
For the optically active component, a multitude of chiral dopants, some of which are commercially available, is available to the person skilled in the art, such as, for example, cholesteryl nonanoate, R- and S-811, R- and S-1011, R- and S-2011, R- and S-3011, R- and S-4011, or CB15 (all Merck KGaA, Darmstadt).
Particularly suitable dopants are compounds which contain one or more chiral groups and one or more mesogenic groups, or one or more aromatic or alicyclic groups which form a mesogenic group with the chiral group.
Suitable chiral groups are, for example, chiral branched hydrocarbon radicals, chiral ethane diols, binaphthols or dioxolanes, furthermore mono- or polyvalent chiral groups selected from the group consisting of sugar derivatives, sugar alcohols, sugar acids, lactic acids, chiral substituted glycols, steroid derivatives, terpene derivatives, amino acids or sequences of a few, preferably 1-5, amino acids.
Preferred chiral groups are sugar derivatives, such as glucose, mannose, galactose, fructose, arabinose and dextrose; sugar alcohols, such as, for example, sorbitol, mannitol, iditol, galactitol or anhydro derivatives thereof, in particular dianhydrohexitols, such as dianhydrosorbide (1,4:3,6-dianhydro-D-sorbide, isosorbide), dianhydromannitol (isosorbitol) or dianhydroiditol (isoiditol); sugar acids, such as, for example, gluconic acid, gulonic acid and ketogulonic acid; chiral substituted glycol radicals, such as, for example, mono- or oligoethylene or propylene glycols, in which one or more CH2 groups are substituted by alkyl or alkoxy; amino acids, such as, for example, alanine, valine, phenylglycine or phenylalanine, or sequences of from 1 to 5 of these amino acids; steroid derivatives, such as, for example, cholesteryl or cholic acid radicals; terpene derivatives, such as, for example, menthyl, neomenthyl, campheyl, pineyl, terpineyl, isolongifolyl, fenchyl, carreyl, myrthenyl, nopyl, geraniyl, linaloyl, neryl, citronellyl or dihydrocitronellyl.
The media according to the present invention preferably comprise chiral dopants which are selected from the group of known chiral dopants. Suitable chiral groups and mesogenic chiral compounds are described, for example, in DE 34 25 503, DE 35 34 777, DE 35 34 778, DE 35 34 779 and DE 35 34 780, DE 43 42 280, EP 01 038 941 and DE 195 41 820. Examples are also compounds listed in Table F below.
Chiral compounds preferably used according to the present invention are selected from the group consisting of the formulae shown below.
Particular preference is given to chiral dopants selected from the group consisting of compounds of the following formulae A-I to A-III and A-Ch:
A12 denotes
Particular preference is given to dopants selected from the group consisting of the compounds of the following formulae:
Particularly preferred compounds of formula A are compounds of formula A-III. Further preferred dopants are derivatives of the isosorbide, isomannitol or isoiditol of the following formula A-IV:
Examples of compounds of formula IV are:
The compounds of the formula A-IV are described in WO 98/00428. The compounds of the formula A-V are described in GB-A-2,328,207.
Very particularly preferred dopants are chiral binaphthyl derivatives, as described in WO 02/94805, chiral binaphthol acetal derivatives, as described in WO 02/34739, chiral TADDOL derivatives, as described in WO 02/06265, and chiral dopants having at least one fluorinated bridging group and a terminal or central chiral group, as described in WO 02/06196 and WO 02/06195.
Particular preference is given to chiral compounds of the formula A-VI
Particular preference is given to chiral binaphthyl derivatives of the formula A-VI-1
The concentration of the one or more chiral dopant(s), in the LC medium is preferably in the range from 0.001% to 20%, preferably from 0.05% to 5%, more preferably from 0.1% to 2%, and, most preferably from 0.5% to 1.5%. These preferred concentration ranges apply in particular to the chiral dopant S-4011 or R-4011 (both from Merck KGaA) and for chiral dopants having the same or a similar HTP. For Chiral dopants having either a higher or a lower absolute value of the HTP compared to S-4011 these preferred concentrations have to be decreased, respectively increased proportionally according to the ratio of their HTP values relatively to that of S-4011.
The pitch p of the LC media or host mixtures according to the invention is preferably in the range of from 5 to 50 μm, more preferably from 8 to 30 m and particularly preferably from 10 to 20 μm.
The medium according to the invention preferably comprises one or more compounds of formula S in a total concentration in the range of from 1000 ppm to 5000 ppm, more preferably from more than 1000 ppm to 5000 ppm, still more preferably from 1200 ppm to 4500 ppm, very preferably from 2000 ppm to 4000 ppm and in particular from 2500 to 3500 ppm.
The medium according to the invention preferably has negative dielectric anisotropy.
Preferred embodiments, take alone or in combination with one another, are the following (acronyms are explained in table D):
The medium according to the invention preferably comprises
A medium comprising one or more compounds of the formulae I-2 and IIA-2 and IIA-10 and IIB-2 and IIB-10 is particularly preferred and has the advantage of a high LTS.
In a preferred embodiment, the medium contains the compound IV-3-1a (CC-3-V) in a concentration of 10% or more, more preferably 20% or more, very preferably 30% or more.
In a preferred embodiment, the medium contains the compound IV-3-1a (CC-3-V) in a concentration of 9% or less, more preferably 19% or less, very preferably 29% or less.
Preferably, the medium according to the invention comprises a stabilizer, more preferably two or more stabilizers, very preferably tree or more stabilizers. Said stabilizers are preferably selected from the compounds of the formulae ST-1 to ST-18 and S.
Preferably, the medium according to the invention comprises one or more, more preferably two or more reactive mesogens of formula P, still more preferably from the sub-formulae listed in Table E below.
Very preferably, the medium comprises one, two or three, in particular two compounds selected from the group consisting of the formulae RM-1, RM-17, RM-35, RM-64, RM-145, RM-163 and RM-171.
In another preferred embodiment the medium according to the invention comprises one, two or more reactive mesogens of formula P and a chiral dopant.
It is advantageous for the liquid-crystalline medium according to the invention to preferably have a nematic phase from −20° C. to >70° C., particularly preferably from <−30° C. to >72° C., very particularly preferably from −40° C. to >74° C.
In a first preferred embodiment, the medium according to the invention has a clearing temperature of 70° C. or more, preferably of 72° C. or more, more preferably of 73° C. or more and in particular of 74° C. or more.
The expression “have a nematic phase” herein means on the one hand that no smectic phase and no crystallization are observed at low temperatures at the corresponding temperature and on the other hand that clearing (phase transition to the isotropic phase) still does not occur on heating from the nematic phase. The investigation at low temperatures is carried out in a flow viscometer at the corresponding temperature and checked by storage in test cells having a layer thickness corresponding to the electro-optical use for at least 100 hours. If the stor-age stability at a temperature of −20° C. in a corresponding test cell is 1000 h or more, the medium is referred to as stable at this temperature. At temperatures of −30° C. and −40° C., the corresponding times are 500 h and 250 h respectively. At high temperatures, the clearing point is measured by conventional methods in capillaries.
The liquid-crystal mixture preferably has a flow viscosity ν20 of at most 30 mm2·s−1 at 20° C.
The liquid crystal mixture according to the invention is nematic, preferably at a temperature of −20° C. or less, preferably at −30° C. or less, very preferably at −40° C. or less.
In a preferred embodiment of the present invention, the medium has a birefringence of 0.1060 or less.
In a preferred embodiment of the present invention, the medium has a birefringence in the range of from 0.085 to 0.120, more preferably from 0.088 to 0.110, very preferably from 0.090 to 0.108 and in particular from 0.091 to 0.106.
In a preferred embodiment, the liquid-crystal mixture according to the invention has a dielectric anisotropy Δε of −2.0 to −5.0, preferably of −2.8 to −4.5, in particular −3.3 to −4.1.
The rotational viscosity γ1 at 20° C. is preferably 210 mPas or less.
The rotational viscosity γ1 at 20° C. is preferably in the range of from 60 to 250 mPas, more preferably from 100 to 210 mPa s.
Very preferably, the rotational viscosity γ1 at 20° C. is in the range of from 80 to 140 mPas, more preferably from 90 to 120 mPa s.
In a preferred embodiment, the elastic constant K1 and K3 is preferably in the range of from 17.0 to 25.0, more preferably from 18.0 to 22.0, in particular from 18.5 to 21.0, and
In another preferred embodiment, the elastic constant K1 is preferably in the range of from 22.0 to 29.0, more preferably from 24.0 to 28.0, in particular from 25.0 to 27.0, and the elastic constant K3 is preferably in the range of from 19.0 to 26.0, more preferably from 21.0 to 23.0, in particular from 22.0 to 24.0.
In addition, the liquid-crystal media according to the invention have high values for the voltage holding ratio in liquid-crystal cells.
In general, liquid-crystal media having a low addressing voltage or threshold voltage exhibit a lower voltage holding ratio than those having a higher addressing voltage or threshold voltage and vice versa.
For the present invention, the term “dielectrically positive compounds” denotes compounds having a Δε>1.5, the term “dielectrically neutral compounds” denotes those having −1.5≤Δε≤1.5 and the term “dielectrically negative compounds” denotes those having Δε<−1.5. The dielectric anisotropy of the compounds is determined here by dissolving 10% of the compounds in a liquid-crystalline host and determining the capacitance of the resultant mixture in at least one test cell in each case having a layer thickness of 20 μm with homeotropic and with homogeneous surface alignment at 1 kHz. The measurement voltage is typically 0.5 V to 1.0 V but is always lower than the capacitive threshold of the respective liquid-crystal mixture investigated.
All temperature values indicated for the present invention are in ° C.
The mixtures according to the invention are suitable for all VA-TFT applications, such as, for example, VAN, MVA, (S)-PVA, ASV, PSA (polymer sustained VA) and PS-VA (polymer stabilized VA). They are furthermore suitable for IPS (in-plane switching) and FFS (fringe field switching) applications having negative Δε, in particular UB-FFS.
It goes without saying for the person skilled in the art that the VA, IPS or FFS mixture according to the invention may also comprise compounds in which, for example, H, N, O, Cl and F have been replaced by the corresponding isotopes. The compounds according to the present invention can be synthesized by or in analogy to known methods 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), under reaction conditions which are known and suitable for said reactions. Use may also be made here of variants which are known per se but are not mentioned here. In particular, they can be prepared as described in or in analogy to the following reaction schemes. Further methods for preparing the inventive compounds can be taken from the examples.
Other mesogenic compounds which are not explicitly mentioned above can optionally and advantageously also be used in the media in accordance with the present invention. Such compounds are known to the person skilled in the art.
For the present invention and in the following examples, the structures of the liquid-crystal compounds are indicated by means of acronyms, with the transformation into chemical formulae taking place in accordance with Tables A to C below. All radicals CmH2m+1, CnH2n+1, and ClH2+1 or CmH2m−1, CnH2n−1 and ClH2l−1 are straight-chain alkyl radicals or alkylene radicals, in each case having n, m and I C atoms respectively.
Preferably n, m and l are independently of each other 1, 2, 3, 4, 5, 6, or 7. Table A shows the codes for the ring elements of the nuclei of the compound, Table B lists the bridging units, and Table C lists the meanings of the symbols for the left- and right-hand end groups of the molecules. The acronyms are composed of the codes for the ring elements with optional linking groups, followed by a first hyphen and the codes for the left-hand end group, and a second hyphen and the codes for the right-hand end group. Table D shows illustrative structures of compounds together with their respective abbreviations.
Apart from the compounds of formula I, IIA, IIB, IIC and/or IID, IVa, IVb and V, the mixtures according to the invention optionally comprise one or more compounds of the compounds mentioned below.
The following abbreviations are used: (n, m, k and l are, independently of one another, each an integer, preferably 1 to 9 preferably 1 to 7, k and l possibly may be also 0 and preferably are 0 to 4, more preferably 0 or 2 and most preferably 2, n preferably is 1, 2, 3, 4 or 5, in the combination “-nO-” it preferably is 1, 2, 3 or 4, preferably 2 or 4, m preferably is 1, 2, 3, 4 or 5, in the combination “—Om” it preferably is 1, 2, 3 or 4, more preferably 2 or 4. The combination “-IVm” preferably is “2V1”.)
In a preferred embodiment, the mixtures according to the invention comprise one or more polymerizable compounds, preferably selected from the polymerizable compounds of the formulae RM-1 to RM-182. 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-58, RM-64, RM-74, RM-76, RM-88, RM-91, RM-102, RM-103, RM-109, RM-116, RM-117, RM-120, RM-121, RM-122, RM-139, RM-140, RM-142, RM-143, RM-145, RM-146, RM-147, RM-149, RM-156 to RM-163, RM-169, RM-170 and RM-171 to RM-183 are particularly preferred.
The present invention is illustrated in detail by the following non-restrictive working examples.
The following abbreviations and symbols are used:
Unless explicitly noted otherwise, all concentrations in the present application are quoted in percent by weight and relate to the corresponding mixture as a whole, comprising all solid or liquid-crystalline components, without solvents.
Unless explicitly noted otherwise, all temperature values indicated in the present application, such as, for example, for the melting point T(C,N), the transition from the smectic (S) to the nematic (N) phase T(S,N) and the clearing point T(N,I), are quoted 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.
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., and An is determined at 589 nm and Δε at 1 kHz, 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 (V10).
Unless stated otherwise, the process of polymerizing the polymerizable compounds in the PSA displays as described above and below is carried out at a temperature where the LC medium exhibits a liquid crystal phase, preferably a nematic phase, and most preferably is carried out at room temperature.
Unless stated otherwise, methods of preparing test cells and measuring their electrooptical and other properties are carried out by the methods as described hereinafter or in analogy thereto.
The display used for measurement of the capacitive threshold voltage consists of two plane-parallel glass outer plates with a distance of 25 μm, each of which has on the inside an electrode layer and an unrubbed polyimide alignment layer on top, which effect homeotropic alignment of the liquid-crystal molecules.
The display or test cell used for measurement of the tilt angles consists of two plane-parallel glass outer plates at a separation of 4 μm, each of which has on the inside an electrode layer and a polyimide alignment layer on top, where the two polyimide layers are rubbed antiparallel to one another and effect a homeotropic edge alignment of the liquid-crystal molecules.
The polymerizable compounds are polymerized in the display or test cell by irradiation with UV light of defined intensity for a prespecified time, with a voltage simultaneously being applied to the display (usually 10 V to 30 V alternating current, 1 kHz). In the examples, unless indicated otherwise, a fluorescent lamp and an intensity of 0 to 20 mW/cm2 is used for polymerization. The intensity is measured using a standard meter (Ushio Accumulate UV meter with central wavelength of 313 nm).
The transmission measurements are performed in test cells with fishbone electrode layout (from Merck Ltd., Japan; 1 pixel fishbone electrode (ITO, 10×10 mm, 47.7° angle of fishbone with 3 μm line/3 μm space), 3.2 μm cell gap, AF-glass, tilt angle 1°).
The storage stability in the bulk (LTSbulk) of the media according to the invention at a given temperature T is determined by visual inspection. 2 g of the media of interest are filled into a closed glass vessel (bottle) of appropriate size placed in a refrigerator at a predetermined temperature. The bottles are checked at defined time intervals for the occurrence of smectic phases or crystallization. For every material and at each temperature two bottles are stored. If crystallization or the appearance of a smectic phase is observed in at least one of the two correspondent bottles the test is terminated and the time of the last inspection before the one at which the occurrence of a higher ordered phase is observed is recorded as the respective storage stability.
Mixture Examples M1 to M142, P1 to P9, Ch1 and PCh1 have the compositions and physical properties indicated in the following tables:
Mixture example M15 consists of 99.985% of Mixture Example M6 and 0.015% of the compound ST-3a-1
The mixture example M17 consists of 99.98% of the Mixture example M1 and 0.02% of a compound of the formula ST-12b-1
The mixture example M18 consists of 99.985% of the Mixture example M1 and 0.015% of a compound of the formula S1-1a
Mixture Example M19 contains 225 ppm of the compound of the formula ST-19
The mixture M409 contains 300 ppm of the compound ST-3a-1.
The mixture M410 contains 300 ppm of the compound ST-3a-1.
The mixture M411 contains 300 ppm of the compound ST-3a-1.
Polymerizable Mixtures
The following polymerizable mixtures are prepared from the nematic mixtures given in Table 1 by adding a reactive mesogen (RM) selected from the group of compounds of the formulae RM-1, RM-17, RM-35, RM-64 and RM-171, respectively, in the amount given in Table 1 (% RM).
Chiral Nematic Mixtures
Chiral Nematic Mixtures are prepared by adding the chiral dopant S-811, S-2011 or S-4011, respectively:
Mixture Example Ch1 consists of 99.09% of Mixture Example M14 and 0.91% of the chiral dopant S-4011.
Mixture Example Ch2 consists of 99.12% of Mixture Example M315 and 0.88% of the chiral dopant S-4011.
Chiral polymerizable mixtures
The chiral polymerizable mixture PCh1 consists of 99.434% of Mixture Example Ch1, 0.300% of RM-1, 0.200% of RM-145, 0.050% of RM-163, 0.001% of Irganox 1076 and 0.015% of the compound ST-3a-1.
The chiral polymerizable mixture PCh2 consists of 99.434% of Mixture Example Ch2, 0.300% of RM-1, 0.200% of RM-145, 0.050% of RM-163, 0.001% of Irganox 1076 and 0.015% of the compound ST-3a-1.
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/CN2022/104920 | Jul 2022 | WO | international |
