Patent Application
20250179365
This application filed under 35 U.S.C. § 111 (a) claims priority benefit under 35 U.S.C. § 119 (a) of and to CN patent application No. 202311628741.X, filed Nov. 30, 2023, the entire contents of which are incorporated herein by reference in their entirety and for all purposes.
The present invention relates to Liquid Crystal on Silicon panels (LCoS panels) using liquid crystal (LC) media having negative dielectric anisotropy and to the LC media comprised therein.
The current disclosed liquid crystal medium (LC medium) has negative dielectric anisotropy and high optical anisotropy, and is particularly useful in electro-optical displays including projection systems based on vertical alignment (VA) nematic panels.
LCoS panels are used as reflective type matrix arrays in devices like projection systems, near-eye displays or beam-steering applications. In the most common mode the display modulates the orientation of polarization like most of the conventional LC displays (amplitude modulation). Some applications of LCoS make use of controlled phase modulation of coherent light in order to control spatial distribution of light beams including image projection. In view of new applications and light sources the development of LCoS panels has room for improvements in many areas.
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 in LCoS panels often consists of an inorganic alignment material which is more temperature resistant than the polyimide layers used mostly in other LC panels for desktop or TV applications. The variable alignment properties of these inorganic materials require careful testing. For LCoS panels there is demand for LC media which have high alignment property on inorganic alignment materials. In addition, these devices usually require high light stability and longer lifetime under high light intensities.
Another problem observed in prior art is that the use of conventional LC media in LCoS panels often leads to the occurrence of bubbles and finally to dark defects in the display due to the harsh temperatures and irradiation during use. It is therefore desirable to provide LC media which lead to reduced display defects after continued use. This means they must be stable in themselves and combine well with adjacent materials, e.g. the alignment layers.
Another problem observed in prior art is that LC media for use in displays, including but not limited to displays of the LCoS type, do often exhibit high viscosities and, as a consequence, long switching times.
Displays, and LC media for use in such displays, should enable a high specific resistance at the same time as a large working-temperature range, short response times, and a low threshold voltage, a multiplicity of grey shades, high contrast, have high reliability and high values for the VHR after UV exposure.
The invention is based on the object of providing novel suitable LC media for use in devices, which do not have the disadvantages indicated above or do so to a reduced extent.
The invention further has the object of providing LCoS panels which do not have the above-mentioned disadvantages, or do so only to a reduced extent, and at the same time have low viscosity, high birefringence, negative dielectric anisotropy, high transmission or reflectance and a high clearing point.
In particular, the invention is based on the object of providing LC media which reduce or prevent the occurrence of bubbles and dark defects in the display.
These objects have been achieved in accordance with the present invention by materials and processes as described in the present application. In particular, it has been found, surprisingly, that the use of liquid crystalline hosts as described hereinafter allows achieving the advantageous effects as mentioned above.
In one aspect the invention relates to an LCoS panel comprising a LC medium comprising
in which
wherein
The invention furthermore relates to a liquid crystal medium comprising
in which
wherein
in which
wherein
—O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen,
on each occurrence, identically or differently, denotes
The medium may further preferably comprise one or more compounds selected from the groups d) and e):
in which
—C≡C—, —CF2O—, —OCF2—, —OC—O— or —O—CO— in such a way that O atoms are not linked directly to one another;
in which
—C═C—, —CF2O—, —OCF2—, —CH═CH—, —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another, and in which one or more H atoms may be replaced by halogen,
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 formulae I, IV-2 and ST-1, optionally with further LC compounds and/or additives.
The invention further relates to a projection device comprising the LCoS panel according to the invention and light directing elements. The light directing elements can be chosen from lenses, mirrors, half-mirrors, prisms or similar.
The invention furthermore relates to the use of LC media according to the invention in displays. The invention further relates to an LC display comprising an LC medium according to the invention of the IPS, FFS, UB-FFS, UBplus, VA or PS-VA type. The invention furthermore relates to the use of LC media according to the invention in polymer stabilised VA or self-aligned-VA displays, and to a polymer stabilised VA displays comprising the LC medium according to the invention.
The invention furthermore relates to an LC display of the VA or PSA type comprising two substrates, at least one which is transparent to light, an electrode provided on each substrate or two electrodes provided on only one of the substrates, and located between the substrates a layer of an LC medium that comprises one or more polymerisable compounds and an LC component as described above and below, wherein the polymerisable compounds are polymerised between the substrates of the display.
The invention furthermore relates to an LC display of the VA type comprising two opposing substrates, one is transparent, and one is a silicon semiconductor backplane.
The invention furthermore relates to a process for manufacturing an LCoS panel as described above and below, comprising the steps of filling or otherwise providing an LC medium as described above and below between the substrates of the panel and sealing it.
Preferred embodiments are also disclosed in the dependent claims and their combinations.
The displays according to the invention have two electrodes, preferably in the form of transparent layers, which are applied to one or both substrates. In a typical reflective display, one continuous transparent electrode is applied to the transparent substrate. The opposite electrode is formed as separately addressable pixels.
It was surprisingly found that the use of the liquid crystal medium according to the invention enables displays with fast response times, a low threshold voltage and a high birefringence, as well as high reliability when exposed to radiation and thermal stress.
In particular, the medium according to the invention is distinguished by a good alignment properties on various alignment materials.
The LC media according to the invention show the following advantageous properties when used in VA or FFS displays:
The LC media according to the invention show the following advantageous properties when used in reflective displays including projection systems:
In particular, the liquid crystal medium according to the invention shows a favourably low ratio of rotational viscosity to the splay elastic constant γ1/K1. This contributes to improved switching behaviour especially at low driving voltages which is useful to enable energy-saving displays.
In the following the essential and optional components of the LC media are disclosed in more detail, which relate to preferred embodiments of the media and the LC displays containing them.
Preferred compounds of the formulae IIA, IIB, IIC, IID and IIE are indicated below:
in which the parameter a denotes 1 or 2, alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms, and alkenyl denotes a straight-chain alkenyl radical having 2-6 C atoms, and (O) denotes an oxygen atom or a single bond, preferably an oxygen atom. Alkenyl preferably denotes any of the groups 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 compounds of the formula IID are selected from the following sub-formulae:
wherein v denotes 1, 2, 3, 4, 5 or 6.
In a preferred embodiment, the medium comprises one or more compounds of formula IID-12a
wherein the groups are defined as for formula IID above, preferably R2 denotes
in which r is 0, 1, 2, 3, 4, 5 or 6, s is 1,2 or 3.
In a preferred embodiment, the medium comprises one or more compounds of formula IIE as follows:
in which the occurring groups and parameters have the meanings given above under formula IIE.
More preferred media 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-4 and IID-10.
Very preferred media according to the invention comprise one or more compounds of formula IIB-2
in which alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms, and (O) denotes an oxygen atom or a single bond, in particular the compounds IIB-2-1 and IIB-2-2:
Preferred media according to the invention comprise at least one compound of the formula IIC-1,
in which alkyl and alkyl* have the meanings indicated above, preferably in amounts of 0.5% to 5% by weight, in particular 1% to 3% by weight.
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 or IIA-52 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:
Very preferably, the medium according to the invention comprises one or more compounds of formula IIE, in particular the compounds of the formula IIE-1-1 to IIE-1-8, and most preferably one or more of the compound of formulae IIE-1-1-1 to IIE-1-1-4:
The compounds of formula III are preferably selected from the compounds of the formula III-1, III-2 and/or III-4
in which the occurring groups have the same meanings as given under formula III above and preferably
The liquid crystal medium according to the invention preferably comprises one, two or more compounds of formula III-2. In a preferred embodiment the liquid crystal medium contains at least one compound of formula III-1 and at least one compound of formula III-2. In a further preferred embodiment the liquid crystal medium contains at least one compound of formula III-2 and at least one compound of the formula III-3.
Preferably, the compounds of the formula III-1 selected from the group of compounds of formulae III-1-1 to III-1-10, preferably of formula III-1-6,
in which
Preferably, the compounds of the formula III-2 are selected from the group of compounds of formulae III-2-1 to III-2-10, preferably of formula III-2-6,
in which
Optionally the medium comprises one or more compounds of the formula IIIA-1 and/or IIIA-2
in which L31 and L32 have the same meanings as given under formula III, (O) denotes O or a single bond,
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 which alkoxy denotes a straight-chain alkoxy radical having 1-6 C atoms or alternatively —(CH2)nF in which n is 2, 3, 4, or 5, preferably C2H4F.
In a preferred embodiment of the present invention, the medium comprises one or more compounds of formula III-3
in which
—O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen.
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 which R32 denotes alkyl having 1 to 7 C-atoms, preferably ethyl, n-propyl or n-butyl, or alternatively cyclopropylmethyl, cyclobutylmethyl or cyclopentylmethyl or alternatively —(CH2)nF in which n is 2,3,4, or 5, preferably C2H4F.
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 which the parameters have the meanings given above, R31 preferably denotes straight-chain alkyl having 1 to 7 C atoms and R32 preferably denotes alkoxy having 1 to 7 C atoms.
In a preferred embodiment the media according to the invention comprise one or more compounds of the formula III selected from the group of compounds of formulae III-7 to III-9, preferably of formula III-8,
in which the parameters have the meanings given above, R31 preferably denotes straight-chain alkyl having 1 to 7 C atoms and R32 preferably denotes alkoxy having 1 to 7 C atoms.
In a preferred embodiment, the medium comprises one or more compounds of the formula IV,
in which
The compounds of the formula IV are preferably selected from the group of the compounds of the formulae IV-1 to IV-4,
in which
Preferably the medium contains in addition to the compounds of formula IV-2 one or more compounds selected from the compounds of the formulae IV-1 and IV-3.
Preferably, the medium comprises one or more compounds selected from the compounds of the formulae IV-1-1 to IV-1-4
Very preferably, the medium according to the invention comprises the compound of formula IV-1-1.
Very preferably, the medium according to the invention comprises one or more compounds of the formulae IV-2-1 and/or IV-2-2
In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula IV-3,
in which very preferably alkyl denotes an alkyl radical having 1 to 7 C atoms, in particular n-ethyl or n-propyl, very particularly n-propyl, and alkenyl denotes
in which m is 0, 1 or 2, preferably 0, and n is 0, 1 or 2, preferably 0 or 1,
In a preferred embodiment, the medium comprises, in particular in addition to the compounds of the formulae IV-3-1 to IV-3-6, one or more compounds of the formulae IV-3-7 to IV-3-9
Preferably, the concentration of the compounds of the formulae IV-3-7 to IV-3-9 in the medium according to the invention is less than 5% or less than 4% or less than 3%, very preferably 0% to 1%, in particular 0%.
Very preferably, the medium according to the invention comprises one or more compounds of the formula IV-3 and one or more compounds of the formula IV-1, where the total concentration of the compounds of the formula IV-1 is in the range of from 1% to 30%.
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 to IV-4-3, in particular of the formula IV-4-3
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 1-4 in combination with one or more compounds selected from the group of compounds of the formulae IA-1 to IA-18:
The LC medium according to the invention preferably comprises one or more compounds of the formula IVa,
in which
denotes
Preferred compounds of the formula IVa are indicated below:
in which
The medium according to the invention preferably comprises at least one compound of the formula IVa-1 and/or formula IVa-2, very preferably of formula IVa-2, in particular the compounds IVa-2 in which alkyl denotes n-propyl and alkyl* denotes methyl.
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
in which
The proportion of the compounds of the formulae IV-1 to IV-3 in the mixture as a whole is preferably less than 3% by weight, in particular less than 2% by weight.
Of the compounds of the formulae IVb-1 to IVb-3, the compounds of the formula IVb-2 are particularly preferred.
Very particularly preferred biphenyls are
in which alkyl* denotes an alkyl radical having 1 to 6 C atoms and preferably denotes n-propyl or n-butyl. The medium according to the invention particularly preferably comprises one or more compounds of the formulae IVb-1-1 and/or IVb-2-3.
In the compounds of the formula IVb-1-1 alkyl denotes preferably propyl, butyl and pentyl and most preferably propyl.
In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula V
in which
denotes
denotes
The compounds of formula V are preferably selected from the compounds of the formulae V-1 to V-14:
in which R51 and R52 have the meanings indicated for formula V above.
R51 and R52 preferably each, independently of one another, denote straight-chain alkyl having 1 to 7 C atoms or alkenyl having 2 to 7 C atoms.
Preferred media comprise one or more compounds of the formulae V-1, V-3, V-4, V-6, V-7, V-10, V-11, V-12 and/or V-14.
In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula Vb
in which
denotes
denotes
The compounds of formula Vb are preferably selected from the compounds of the formulae Vb-1 to Vb-2:
In a preferred embodiment of the present invention the medium additionally comprises one or more compounds of formula VI
in which R6 and R62 each, independently of one another, denote H, an alkyl radical having 1 to 7 C atoms or an alkenyl radical having 2 to 7 C atoms, each of which is unsubstituted, or at least monosubstituted by halogen, where one or more CH2 groups in these radicals may be replaced by —O—, —S—,
—C≡C—, —CF2O—, —OCF2—, —OC—O— or —O—CO— in such a way that O atoms are not linked directly to one another and R62 alternatively denotes F, Cl, CF3 or OCF3, preferably F, and L61, L62, L63, L64, L65, and L66 independently denote H or F, where at least one of L61, L62, L63, L64, L65, and L66 denotes F, and wherein the compounds of formula IIC and IIE are excluded.
The compounds of formula VI are preferably selected from the formulae VI-1 to VI-20, in particular from the formulae VI-1, VI-2, IV-4, VI-14, VI-19 and VI-20:
in which R6 denotes a straight-chain alkyl or alkoxy radical having 1 to 6 C atoms, (O) denotes —O— or a single bond, and m is 0, 1, 2, 3, 4, 5 or 6 and n is 0, 1, 2, 3 or 4. R6 preferably denotes methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy or pentoxy.
Particular preference is given to compounds of the formulae VI-1, VI-2, VI-4, VI-19 and VI-20.
In a preferred embodiment of the present invention the medium additionally comprises one or more compounds of formula VIA
in which R6 and R62 each, independently of one another, denote H, an alkyl radical having 1 to 7 C atoms or an alkenyl radical having 2 to 7 C atoms, each of which is unsubstituted, or at least monosubstituted by halogen, where one or more CH2 groups in these radicals may be replaced by —O—, —S—,
—C≡C—, —CF2O—, —OCF2—, —OC—O— or —O—CO— in such a way that O atoms are not linked directly to one another and R62 alternatively denotes F, Cl, CF3 or OCF3, preferably F, and L61, L62, L63, L64, L65, and L66 independently denote H or F, where at least one of L61, L62, L63, L64, L65, and L66 denotes F and
Very preferably, the medium according to the invention comprises the compound of formula VIA-1 and/or formula X
in which R6 and m have the meanings defined above and preferably R6 denotes methyl, ethyl, n-propyl, n-butyl, or n-pentyl, and m is 2, 3 or 4. In a particular preferred embodiment R6 denotes n-propyl and m denotes 2.
In a preferred embodiment of the present invention the medium additionally comprises one or more compounds of the formulae VII-1 to VII-9
in which
Particular preference is given to mixtures comprising at least one compound of the formula VII-9.
in which R has the meanings of R2A in formula IIA and alkyl denotes a straight-chain alkyl radical having 1 to 6 C atoms.
In a preferred embodiment the liquid crystal mixtures according to the present invention contain at least one compound of formula Z-8.
in which R1N and R2N each, independently of one another, have the meanings indicated for R2A, preferably denote straight-chain alkyl, straight-chain alkoxy or straight-chain alkenyl, and
in which RB1, RB2, RCR1, RCR2, R1, R2 each, independently of one another, have the meaning of R2A. c is 0, 1 or 2. R1 and R2 preferably, independently of one another, denote alkyl or alkoxy having 1 to 6 C atoms.
Particularly preferred compounds of the formulae BC and CR are the compounds BC-1 to BC-7 and CR-1 to CR-5.
in which
Very particular preference is given to mixtures comprising one, two or three compounds of the formula BC-2, BF-1 and/or BF-2.
in which
R11, R12, and R13 each, independently of one another, denote a straight-chain alkyl, alkoxy, alkoxyalkyl or alkenyl radical having 1 to 6 C atoms,
denotes
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.
in which
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.
in which R11 and R12 have one of the meanings given for R2A in formula IIA above, and L1 and L2, identically or differently, denote F or CI and L3 denotes H or CH3.
Preferred compounds of the formula IIA-Y are selected from the group consisting of the following sub-formulae
in which alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms; alkoxy denotes a straight-chain alkoxy radical having 1-6 C atoms; alkenyl and alkenyl* each, independently of one another, denote a straight-chain alkenyl radical having 2-6 C atoms, and O denotes an oxygen atom or a single bond. alkenyl and alkenyl* preferably denote CH2═CH—, CH2═CHCH2CH2—, CH3—CH═CH—, CH3—CH2—CH═CH—, CH3—(CH2)2—CH═CH—, CH3—(CH2)3—CH═CH— or CH3—CH═CH—(CH2)2—.
Particularly preferred compounds of the formula IIA-Y are selected from the group consisting of following sub-formulae:
in which alkoxy and alkoxy* have the meanings defined above and preferably denote methoxy, ethoxy, n-propyloxy, n-butyloxy or n-pentyloxy.
in which
—C≡C—, —CF2O—, —OCF2—, —OC—O— or —O—CO— in such a way that O atoms are not linked directly to one another;
Preferred compounds of the formulae P1 to P4 are listed in the following:
wherein
The compounds of formula P-1 have stabilizing properties for the liquid crystal medium. In a preferred embodiment the medium according to the invention comprises at least one compound of formula P-1, more preferably of formula P-1a, preferably in an amount from 0.1 to 5% by weight, more preferably 0.4 to 2.5% by weight.
in which
R2 and R3 denote a straight-chain or branched alkyl or alkoxy radical that is unsubstituted or halogenated and has 1 to 15 C atoms, where one or more CH2 groups in these radicals may each be replaced, independently of one another, by
—C═C—, —CF2O—, —CH═CH—, —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another,
identically or differently, denote
preferably
Preferred compounds of the formula PIII are of formula PIII-1
in which
—C═C—, —CF2O—, —CH═CH—, —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another,
Preferably in PIII and PIII-1 the groups independently denote one or more of:
Preferably, the liquid crystal medium according to the invention comprises one or more compounds of the formula H
in which
In formula H, aryl preferably 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 optionally replaced with alkyl or alkoxy having 1 to 6 C atoms or alkenyl having 2 to 6 C atoms, or with CN, CF3 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 aliphatic groups are alkylene, cycloalkylene, more preferably
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.
The compounds of formula H are described in EP 3354710 A1 and EP 3354709 A1.
The compounds of formula H are preferably applied in a range of 0.1 to 0.3% (by weight).
In a preferred embodiment the medium comprises one or more compounds of formula H selected from compounds of formula H-A
wherein
The group Aa preferably denotes
wherein
The compounds of formula H are preferably selected from the compounds of the formulae H-1, H-2 and H-3:
in which RH has the meanings given above and preferably denote H or O·, and
Preferred compounds of formula H-10 are selected from the compounds of the formula H-10-1.
in which RH has the meanings given above and preferably denotes H or O·, and n is an integer from 0 to 12, preferably 5, 6, 7, 8 or 9, very preferably 7.
Preferred compounds of formula H-11 are selected from the compounds of the formula H-11-1:
in which RH has the meanings given above and preferably denotes H or O·, and n2, on each occurrence identically or differently, preferably identically, is an integer from 1 to 12, preferably 2, 3, 4, 5, or 6, very preferably 3, and R$ on each occurrence identically or differently, preferably identically, denotes alkyl having 1 to 6 C atoms, preferably n-butyl.
Preferred compounds of formula H-12 are selected from the compounds of the formula H-12-1:
in which RH has the meanings given above and preferably denotes H or O·, and
Preferred stabilizers H are the following:
Preferably, the medium according to the invention comprises a compound selected from the group of compounds of the formulae ST-1 to ST-12:
in which
—O—, —CO—O—, —O—CO— in such a way that O atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen, preferably alkyl with 1-7 C atoms or cyclopentyl,
on each occurrence, identically or differently, denotes
Of the compounds of the formula ST, special preference is given to the compounds of the formulae ST-1 and ST-3 and in particular to any of the following:
in which n=1, 2, 3, 4, 5, 6 or 7, preferably n=3
in which n=1, 2, 3, 4, 5, 6 or 7, preferably n=1 or 7
in which n=1, 2, 3, 4, 5, 6 or 7, preferably n=3
Very particularly preferred mixtures according to the invention comprise one or more stabilizers from the group of the compounds of the formulae ST-1a, ST-1b-1 and ST-1c-1:
The compounds of the formulae ST-1 to ST-12 are preferably each present in the liquid-crystal mixtures according to the invention in amounts of 0.1 to 0.5%, based on the mixture.
However, the total proportion of the compounds of the formulae ST-1 to ST-12, based on the mixture according to the invention, should not exceed 2%.
The medium according to the invention preferably has negative dielectric anisotropy.
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 categorising 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.
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.
Unless indicated otherwise, the term LC display is used herein when referring to an information display based on switchable liquid crystals. It includes back-lit and reflective displays, for direct or indirect view, for virtual or augmented reality systems or projection systems. The size ranges from microdisplays to large screens. The addressing can be realized in that the LC display comprises simple electrodes on a substrate, an array of thin-film-transistors with electrodes for each pixel, or a structured silicon semiconductor as backplane, the latter of which is preferred.
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”.
Throughout the patent application, 1,4-cyclohexylene rings and 1,4-phenylene rings are depicted as follows:
The cyclohexylene rings are trans-1,4-cyclohexylene rings.
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.
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.
Herein, alkyl is straight-chain or branched and has 1 to 15 C atoms, is preferably straight-chain and has, unless indicated otherwise, 1, 2, 3, 4, 5, 6 or 7 C atoms and is accordingly preferably methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl or n-heptyl.
Herein, branched alkyl is alkyl having a secondary and/or tertiary, preferably secondary, carbon atom and is preferably isopropyl, s-butyl, isobutyl, isopentyl, 2-methylhexyl or 2-ethylhexyl, 2-methylpropyl, 2-pentyl, 3-pentyl, 2-methylbutyl, 3-methylbutyl.
Herein, a cyclic alkyl group is taken to mean a cycloaliphatic radical or an alkyl group in which a methylene group is replaced with a cycloaliphatic group (i.e. a cycloalkylalkyl or alkylcycloalkylalkyl), which may be saturated or partially unsaturated, and preferably denotes cyclopropyl, methylcyclopropyl, cyclobutyl, methylcyclobutyl, cyclopentyl, methylcyclopentyl, cyclopent-1-enyl, cyclopropylmethyl, cyclopropylethyl, cyclobutylmethyl, cyclobutylethyl, cyclopentylmethyl, cyclopentylethyl, cyclopent-1-enylmethyl.
Herein, an alkoxy radical is straight-chain or branched and contains 1 to 15 C atoms. It is preferably straight-chain and has, unless indicated otherwise, 1, 2, 3, 4, 5, 6 or 7 C atoms and is accordingly preferably methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, n-hexoxy or n-heptoxy.
Herein, an alkenyl radical is preferably an alkenyl radical having 2 to 15 C atoms, which is straight-chain or branched and contains at least one C—C double bond. It is preferably straight-chain and has 2 to 7 C atoms. Accordingly, it is preferably 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. If the two C atoms of the C—C double bond are substituted, the alkenyl radical can be in the form of E and/or Z isomer (trans/cis). In general, the respective E isomers are preferred. Of the alkenyl radicals, prop-2-enyl, but-2-and-3-enyl, and pent-3-and-4-enyl are particularly preferred.
Herein, alkynyl is taken to mean an alkynyl radical having 2 to 15 C atoms, which is straight-chain or branched and contains at least one C—C triple bond. 1- and 2-propynyl and 1-, 2- and 3-butynyl are preferred.
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-C30 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—, —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 be replaced by —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O— and in which one or more H atoms may 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 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-2′-yl, 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 be replaced by Si and/or one or more CH groups may be replaced by N and/or one or more non-adjacent CH2 groups may 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.
“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 R0 denotes H or alkyl with 1 to 20 C atoms.
Particularly preferred substituents L are, for example, F, Cl, CN, NO2, CH3, C2H5, OCH3, OC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF3, OCF3, OCHF2, OC2F5, furthermore phenyl.
The LC medium according to the invention may additionally comprise one or more further components or additives, preferably selected from the list including but not limited to co-monomers, polymerisation initiators, inhibitors, stabilizers, surfactants, wetting agents, lubricating agents, dispersing agents, hydrophobing agents, adhesive agents, flow improvers, defoaming agents, deaerators, diluents, reactive diluents, auxiliaries, colourants, dyes, pigments and nanoparticles.
The LC media according to the invention may comprise one, two or three chiral dopants, preferably one chiral dopant.
Preferred embodiments, taken alone or in combination with one another, are listed below. The medium according to the invention preferably comprises
The mixtures according to the invention preferably comprise
It is advantageous for the LC medium according to the invention to preferably have a nematic phase from ≤−20° C. to ≥90° C., particularly preferably from ≤−30° C. to ≥100° C., very particularly preferably from ≤−40° C. to ≥105° C.
In a preferred embodiment, the medium according to the invention has a clearing temperature (clearing point) of 90° C. or more, more preferably of 100° C. or more, and in particular of 105° C. more.
Herein, the expression “to have a nematic phase” at a given temperature means that no smectic phase and no crystallisation is observed at low temperatures and on the other hand that clearing (phase transition to the isotropic phase) does not occur on heating of a nematic phase at a given temperature. 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 storage 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 nematic phase range of at least 60 K and a flow viscosity v20 of at most 30 mm2·s−1 at 20° C.
The mixture is nematic at a temperature of −20° C. or less, preferably at −30° C. or less, very preferably at −40° C. or less.
The medium according to the invention has a birefringence in the range of from 0.085 to 0.170, preferably from 0.13 to 0.16, in particular from 0.14 to 0.16.
In a preferred embodiment, the medium has a birefringence in the range of from 0.1480 to 0.155, preferably from 0.147 to 0.153, in particular from 0.158 to 0.152.
In a preferred embodiment, the medium according to the invention has a dielectric anisotropy Δε of −2.5 to −6.0, preferably of −2.8 to −4.7, in particular −3.5 to −4.5.
In a very preferred embodiment, the liquid-crystal mixture according to the invention has a dielectric anisotropy Δε of −3.8 to −4.2.
The rotational viscosity γ1 at 20° C. is preferably in the range of from 90 to 300 mPa·s, more preferably from 100 to 290 mPa s.
The medium according to the invention has an elastic constant K1 in the range of from 16 to 20 pN.
In a preferred embodiment, the medium according to the invention has a ratio of the rotational viscosity to the splay elastic constant γ1/K1 of 15 mPa·s pN−1 or less.
The liquid-crystal media according to the invention have relatively low values for the threshold voltage (V0). They are preferably in the range from 1.7 V to 3.0 V, particularly preferably ≤2.6 V and very particularly preferably ≤2.4 V.
For the present invention, the term “threshold voltage” relates to the capacitive threshold (V0), also called the Freedericks threshold, unless explicitly indicated otherwise.
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.
The mixtures are also particularly suitable for VA-TFT application of the LCoS type, more preferably LCoS microdisplays. LCoS microdisplays are reflective displays which typically contain a liquid-crystal layer having a nematic structure between a silicon backplane and a cover glass. The silicon backplane is an array of pixels, each of which has a mirrored surface which at the same time acts as electrical conductor. Each pixel comprises a stationary mirror covered by an active liquid-crystal layer having a twisted nematic alignment which can be switched between homeotropic and homogeneous alignment by application of a voltage. LCoS microdisplays are small, with a diagonal of typically less than 1.0″, but enable high resolutions nevertheless.
Owing to the small pixel size, LCoS displays also have a very small cell thickness, which is typically about 1 micron. The liquid-crystalline phases used in these displays therefore have to have, in particular, high values for the optical anisotropy Δ n, in contrast to conventional reflective-type LC displays, which usually require LC phases of low Δn.
In an preferred embodiment, the LCoS panel according to the invention comprises inorganic alignment layers, more preferably vertical alignment layers for vertical alignment of the liquid crystal medium. Most preferred are SiOx alignment layers. Such inorganic alignment layers are especially suitable for LCoS panels.
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 ClH2l+1 or CmH2m−1, CnH2n−1 and ClH2l−1 are straight-chain alkyl radicals or alkylene radicals, in each case having n, m and l 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.
in which n and m are each integers, and the three dots “ . . . ” are placeholders for other abbreviations from this table.
Apart from the compounds of formula IV-2, I and ST-1 the mixtures according to the invention optionally comprise one or more compounds of the compounds listed in Table D.
The following abbreviations are used:
Table E shows chiral dopants which are preferably employed in the mixtures according to the invention.
In a preferred embodiment of the present invention, the media according to the invention comprise one or more compounds selected from the group of the compounds from Table E.
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 Δn 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, 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.
Unless indicated otherwise, the VHR is determined at 20° C. (VHR20) and after 5 minutes in an oven at 100° C. (VHR100) in a commercially available instrument Model LCM-1 (O0004) from TOYO Corporation, Japan. The voltage used has a frequency of in a range from 1 Hz to 60 Hz, unless indicated more precisely.
The stability to UV irradiation is investigated in a “Suntest CPS+”, a commercial instrument from Heraeus, Germany, using a Xenon lamp NXE1500B. The sealed test cells are irradiated for 2.0 h, unless explicitly indicated, without additional heating. The irradiation power in the wavelength range from 300 nm to 800 nm is 765 W/m2 V. A UV “cut-off” filter having an edge wavelength of 310 nm is used in order to simulate the so-called window glass mode. In each series of experiments, at least four test cells are investigated for each condition, and the respective results are indicated as averages of the corresponding individual measurements.
In order to investigate the low-temperature stability, also known as “LTS”, i.e. the stability of the LC mixture in the bulk against spontaneous crystallisation of individual components at low temperatures or the occurrence of smectic phases, as the case may be, several sealed bottles, each containing about 1 g of the material, are stored at one or more given temperatures, typically of −10° C., −20° C., −30° C. and/or −40° C. and it is inspected at regular intervals visually, whether a phase transition is observed or not. As soon as the first one of the samples at a given temperature shows a change time is noted. The time until the last inspection, at which no change has been observed, is noted as the respective LTS.
The ion density from which the resistivity is calculated is measured using the commercially available LC Material Characteristics Measurement System Model 6254 from Toyo Corporation, Japan, using VHR test cells with AL16301 Polyimide (JSR Corp., Japan) having a 3.2 μm cell gap. The measurement is performed after 5 min of storage in an oven at 60° C. or 100° C.
The clearing point is measured using the Mettler Thermosystem FP900. The optical anisotropy (Δn) is measured using an Abbe Refractometer H005 (Natrium-spectral lamp Na10 at 589 nm, 20° C.). The dielectric anisotropy (Δε) is measured using an LCR-Meter E4980A/Agilent (G005) at 20° C. (ε-parallel-cells with JALS 2096-R1). The turn on voltage (V0) is measured using an LCR-Meter E4980A/Agilent (G005) at 20° C. (ε-parallel-cells with JALS 2096-R1). The rotational viscosity (γ1) is measured using a TOYO LCM-2 (0002) at 20° C. (gamma 1 negative cells with JALS-2096-R1). The elastic constant (K1, splay) is measured using an LCR-Meter E4980A/Agilent (G005) at 20° C. (ε parallel-cells with JALS 2096-R1). K3: The elastic constant (K3, bend) is measured using an LCR-Meter E4980A/Agilent (G005) at 20° C. (ε-parallel-cells with JALS 2096-R1).
The following mixture examples having negative dielectric anisotropy are suitable, in particular, for vertically aligned liquid crystal displays.
The following stabilizing compounds are used and described with the acronyms as follows:
The nematic LC mixtures M1 to M41 have the composition and physical properties given in the following tables:
The above Example Mixtures are subjected to test cells with inorganic alignment (SiOx) layers or to analogous LCoS panels. The devices are tested under enforced temperature and illumination (stress test blue light, >45 W/cm2, 70° C.). Occurrence of bubbles and dark stains is avoided over prolonged time. Alignment of the mixtures is found to be stable over prolonged time under these conditions. Stability for practical use in LCoS of the mixtures is improved over conventional mixtures.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202311628741.X | Nov 2023 | CN | national |
