Patent Application
20180002604
The invention relates to a liquid-crystalline medium based on a mixture of polar compounds comprising a self-alignment additive for vertical alignment and additionally at least one compound of formula I as described more closely within this disclosure (reactive hindered amine), especially for vertically aligned display applications.
Media of this type can be used, in particular, for electro-optical displays having active-matrix addressing based on the ECB effect.
The principle of electrically controlled birefringence, the ECB effect or also DAP (deformation of aligned phases) effect, was described for the first time in 1971 (M. F. Schieckel and K. Fahrenschon, “Deformation of nematic liquid crystals with vertical orientation in electrical fields”, Appl. Phys. Lett. 19 (1971), 3912). This was followed by papers by J. F. Kahn (Appl. Phys. Lett. 20 (1972), 1193) and G. Labrunie and J. Robert (J. Appl. Phys. 44 (1973), 4869).
The papers by J. Robert and F. Clerc (SID 80 Digest Techn. Papers (1980), 30), J. Duchene (Displays 7 (1986), 3) and H. Schad (SID 82 Digest Techn. Papers (1982), 244) showed that liquid-crystalline phases must have high values for the ratio of the elastic constants K3/K1, high values for the optical anisotropy Δn and values for the dielectric anisotropy of ΔΣ≦−0.5 in order to be suitable for use in high-information display elements based on the ECB effect. Electro-optical display elements based on the ECB effect have a homeotropic edge alignment (VA technology=vertically aligned).
Displays which use the ECB effect, as so-called VAN (vertically aligned nematic) displays, for example in the MVA (multi-domain vertical alignment, for example: Yoshide, H. et al., paper 3.1: “MVA LCD for Notebook or Mobile PCs . . . ”, SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book I, pp. 6 to 9, and Liu, C. T. et al., paper 15.1: “A 46-inch TFT-LCD HDTV Technology . . . ”, SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pp. 750 to 753), PVA (patterned vertical alignment, for example: Kim, Sang Soo, paper 15.4: “Super PVA Sets New State-of-the-Art for LCD-TV”, SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pp. 760 to 763), ASV (advanced super view, for example: Shigeta, Mitzuhiro and Fukuoka, Hirofumi, paper 15.2: “Development of High Quality LCDTV”, SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pp. 754 to 757) modes, have established themselves as one of the three more recent types of liquid-crystal display that are currently the most important, in particular for television applications, besides IPS (in-plane switching) displays (for example: Yeo, S. D., paper 15.3: “An LC Display for the TV Application”, SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pp. 758 & 759) and the long-known TN (twisted nematic) displays. The technologies are compared in general form, for example, in Souk, Jun, SID Seminar 2004, seminar M-6: “Recent Advances in LCD Technology”, Seminar Lecture Notes, M-6/1 to M-6/26, and Miller, Ian, SID Seminar 2004, seminar M-7: “LCD-Television”, Seminar Lecture Notes, M-7/1 to M-7/32. Although the response times of modem ECB displays have already been significantly improved by addressing methods with overdrive, for example: Kim, Hyeon Kyeong et al., paper 9.1: “A 57-in. Wide UXGA TFT-LCD for HDTV Application”, SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book I, pp. 106 to 109, the achievement of video-compatible response times, in particular on switching of grey shades, is still a problem which has not yet been satisfactorily solved.
Industrial application of this effect in electro-optical display elements requires LC phases, which have to satisfy a multiplicity of requirements. Particularly important here are chemical resistance to moisture, air and physical influences, such as heat, infrared, visible and ultraviolet radiation and direct and alternating electric fields.
Furthermore, industrially usable LC phases are required to have a liquid-crystalline mesophase in a suitable temperature range and low viscosity.
None of the hitherto-disclosed series of compounds having a liquid-crystalline mesophase includes a single compound which meets all these requirements. Mixtures of two to 25, preferably three to 18, compounds are therefore generally prepared in order to obtain substances which can be used as LC phases. However, it has not been possible to prepare optimum phases easily in this way since no liquid-crystal materials having significantly negative dielectric anisotropy and adequate long-term stability were hitherto available.
Matrix liquid-crystal displays (MLC displays) are known. Non-linear elements which can be used for individual switching of the individual pixels are, for example, active elements (i.e. transistors). The term “active matrix” is then used, where a distinction can be made between two types:
In the case of type 1, the electro-optical effect used is usually dynamic scattering or the guest-host effect. The use of single-crystal silicon as substrate material restricts the display size, since even modular assembly of various part-displays results in problems at the joints.
In the case of the more promising type 2, which is preferred, the electro-optical effect used is usually the TN effect.
A distinction is made between two technologies: TFTs comprising compound semiconductors, such as, for example, CdSe, or TFTs based on polycrystalline or amorphous silicon. The latter technology is being worked on intensively worldwide.
The TFT matrix is applied to the inside of one glass plate of the display, while the other glass plate carries the transparent counterelectrode on its inside. Compared with the size of the pixel electrode, the TFT is very small and has virtually no adverse effect on the image. This technology can also be extended to fully color-capable displays, in which a mosaic of red, green and blue filters is arranged in such a way that a filter element is opposite each switchable pixel.
The term MLC displays here covers any matrix display with integrated non-linear elements, i.e. besides the active matrix, also displays with passive matrix (PM displays).
MLC displays of this type are particularly suitable for TV applications (for example pocket TVs) or for high-information displays in automobile or aircraft construction. Besides problems regarding the angle dependence of the contrast and the response times, difficulties also arise in MLC displays due to insufficiently high specific resistance of the liquid-crystal mixtures [TOGASHI, S., SEKIGUCHI, K., TANABE, H., YAMAMOTO, E., SORIMACHI, K., TAJIMA, E., WATANABE, H., SHIMIZU, H., Proc. Eurodisplay 84, September 1984: A 210-288 Matrix LCD Controlled by Double Stage Diode Rings, pp. 141 ff., Paris; STROMER, M., Proc. Eurodisplay 84, September 1984: Design of Thin Film Transistors for Matrix Addressing of Television Liquid Crystal Displays, pp. 145 ff., Paris]. With decreasing resistance, the contrast of an MLC display deteriorates. Since the specific resistance of the liquid-crystal mixture generally drops over the life of an MLC display owing to interaction with the inside surfaces of the display, a high (initial) resistance is very important for displays that have to have acceptable resistance values over a long operating period.
VA displays have significantly better viewing-angle dependencies and are therefore principally used for televisions and monitors. However, there continues to be a need here to improve the response times, in particular with respect to the use of televisions having frame rates (image change frequency/repetition rates) of greater than 60 Hz. At the same time, however, the properties, such as, for example, the low-temperature stability, must not be impaired.
The reliability of liquid crystal (LC) mixtures is one of the major issues in today's LCD industry. A main aspect is the stability of the liquid crystal molecules towards the light emitted from the backlight unit of the LCD. Light induced reactions of the LC material can cause display defects known as image sticking. This strongly reduces the lifetime of the LCD and is one of the main reliability criterions in LCD industry.
In conventional VA-displays a polyimide (PI) layer is needed for inducing the required homeotropic orientation of the LC. Besides of the significant costs due to its production, unfavorable interaction between PI and LC often leads to a reduction of the electric resistance of the VA-display. The number of suitable LC molecules is thus significantly reduced, at the expenses of the overall switching performances (e.g. higher switching times) of the display. Getting rid of PI is thus desirable, while providing for the required homeotropic orientation.
Thus, there is a demand to find LC mixtures which do not require a polyimide layer for the homeotropic orientation but still show a high performance and reliability.
Some self-aligning additives for inducing PI-less vertical alignment have been proposed in the publications WO 2012/038026 and EP 2918658.
The invention thus has an object of providing liquid-crystal mixtures, in particular for monitor and TV applications, which are based on the ECB effect especially for VA, PSA (polymer sustained alignment), PS-VA (polymer stabilized-VA), PVA (patterned vertical alignment), MVA (multi-domain vertical alignment), PM-VA (passive matrix-VA), HT-VA (high transmittance-VA) and VA-IPS (VA-in-plane switching) applications, which do not have the above-mentioned disadvantages or only do so to a reduced extent. In particular, it must be ensured for monitors and televisions that they also operate at extremely high and extremely low temperatures and have short response times and at the same time have improved reliability behavior, in particular have no or significantly reduced image sticking after long operating times.
It has now been found that these and other objects can be achieved if liquid-crystalline media according to the invention are used in LC displays, especially and preferred in displays without any orientation layer (polyimide layer).
The invention thus relates to a liquid crystalline medium, preferably based on a mixture of polar compounds, comprising a self-alignment additive for vertical alignment,
characterized in that it additionally contains at least one compound of the formula I, or a polymer comprising its polymerized form,
P-Sp-(A2-Z2-A1)m1-Z1-T I
wherein the individual radicals, independently of each other, and on each occurrence identically or differently, have the following meanings
The invention more specifically relates to a liquid-crystalline medium comprising
The invention preferably relates to a liquid-crystalline medium comprising
The liquid-crystalline component B) of a liquid-crystalline medium according to the present invention is hereinafter also referred to as “LC host mixture”, and preferably comprises one or more, preferably at least two mesogenic or LC compounds selected from low-molecular-weight compounds which are unpolymerizable.
The invention furthermore relates to a liquid-crystalline medium as described above and below, wherein the LC host mixture or component B) comprises at least one mesogenic or LC compound comprising an alkenyl group.
The invention furthermore relates to a liquid-crystalline medium or LC display as described above and below, wherein the compounds of formula I, or the polymerizable compounds of component A), are polymerized.
The invention furthermore relates to a process for preparing a liquid-crystalline medium as described above and below, comprising the steps of mixing one or more mesogenic or LC compounds, or an LC host mixture or LC component B) as described above and below, with a self-alignment additive and one or more compounds of formula I, and optionally with further LC compounds and/or additives.
The invention furthermore relates to the use of liquid-crystalline media according to the invention in PSA displays, in particular the use in PSA displays containing a liquid-crystalline medium, for the production of a tilt angle in the liquid-crystalline medium by in-situ polymerization of the compound(s) of the formula I in the PSA display, preferably in an electric or magnetic field.
The invention furthermore relates to an LC display comprising a liquid-crystalline medium according to the invention, in particular a PSA display, particularly preferably a PS-VA, PS-OCB (polymer stabilized-optically compensated bend), PS-IPS (polymer stabilized-in-plane switching), PS-FFS (polymer stabilized-fringe field switching), PS-UB-FFS (polymer stabilized-ultra brightness fringe field switching), PS-posi-VA (polymer stabilized-positive VA) or PS-TN display.
The invention furthermore relates to a LC display of the 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 a liquid-crystalline medium as described above and below, wherein the polymerizable compounds are polymerized between the substrates of the display.
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 a liquid-crystalline medium, which comprises one or more polymerizable compounds as described above and below, between the substrates of the display, and polymerizing the polymerizable compounds.
One category of light stabilizers for polymers consists of what are known as hindered amine light stabilizers (abbreviated as HALS). They are derivatives of 2,2,6,6-tetramethyl piperidine and are reported as stabilizers against light-induced degradation of plastics. A variety of structures, including polymerized HALS are known, see e.g. Kröhnke, Christoph et al. “Antioxidants” in Ullmann's Encyclopedia of Industrial Chemistry (2015), Wiley-VCH, DOI10.1002/14356007.a03_091.pub2.
As used herein, the terms “reactive mesogen” 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. Such groups are also referred to as “polymerizable group” or a chemical structure substituent “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 “low-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.
The term “spacer group”, hereinafter also referred to as “Sp”, 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. Whereas the mesogenic group generally contains rings, the spacer group is generally without ring systems, i.e. is in chain form, where the chain may also be branched. The term chain is applied, for example, to an alkylene group. Substitutions on and in the chain, for example by —O— or —COO—, are generally included. In functional terms, the spacer (the spacer group) is a linker between functional structural parts of a molecule which facilitates a certain spatial flexibility between these parts. In a preferred embodiment Sp denotes an alkylene or alkyleneoxy group, preferably with 2 to 5 carbon atoms.
Above and below,
denote a trans-1,4-cyclohexylene ring, and
denote a 1,4-phenylene ring.
Above and below “organic group” denotes a carbon group 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” generally denotes F, Cl, Br or I.
—CO—, —C(═O)—, —(CO)— 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 hydrocarbon 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-C30 arylalkyl, C6-C30 alkylaryloxy, C6-C30 arylalkyloxy, C2-C30 heteroaryl, C2-C30 heteroaryloxy.
Particular preference is given to C1-C4 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≡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.
Herein, 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.
The term alkoxyalkyl denotes a group of the formula -alkylenealkoxy
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″]erphenyl-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, azacarbazole, benzocarboline, phenanthridine, phenanthroline, thieno[2,3b]thiophene, thieno[3,2b]thiophene, dithienothiophene, isobenzothiophene, dibenzothiophene, benzothiadiazothiophene, or combinations of these 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— 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 L are selected from P-Sp-, F, Cl, —CN, straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy each having up to 25 C atoms, in which one or more H atoms may optionally be replaced by F or Cl.
Very preferred substituents L are, for example, F, Cl, CN, CH3, C2H5, OCH3, OC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF3, OCF3, OCHF2, OC2F5.
A substituted phenylene of formula
is preferably or
in which L has one of the meanings indicated above.
If the spacer group Sp is different from a single bond, it is preferably selected of the formula Sp″-X″, so that the respective radical P-Sp- conforms to the formula P-Sp″-X″—, wherein
X″ is preferably —O—, —S—, —CO—, —COO—, —OCO—, —O—COO—, —CO—NR0—, —NR0—CO—, —NR0—CO—NR00— or a single bond.
Typical spacer groups Sp and -Sp″-X″— are, for example, —(CH2)p1-, —(CH2CH2O)q1—CH2CH2—, —CH2CH2—S—CH2CH2—, —CH2CH2—NH—CH2CH2— or —(SiR0R00—O)p1—, in which p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and R0 and R00 have the meanings indicated above.
Particularly preferred groups Sp and -Sp″-X″— are —(CH2)p1—, —(CH2)p1—O—, —(CH2)p1—O—CO—, —(CH2)p1—CO—O—, —(CH2)p1—O—CO—O—, in which p1 and q1 have the meanings indicated above.
Particularly preferred groups Sp″ are, in each case straight-chain, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethylenethioethylene, ethylene-N-methyliminoethylene, 1-methylalkylene, ethenylene, propenylene and butenylene.
Preferably Ra-d in formulae 1-3 are selected, independently of each other, from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, very preferably methyl.
Preferably Ra, Rb, Rc and Rd in formulae 1-3 have the same meaning.
Preferably m1 in formula I is 0 or 1.
Preferably Z1 in formula I denotes —CO—O—, —O—CO— or a single bond, very preferably —CO—O— or a single bond.
Preferably Z2 and Z3 in formula I denote —CO—O—, —O—CO— or a single bond, very preferably a single bond.
Preferably P in formula I is an acrylate or methacrylate group.
Preferably Sp in formula I is a single bond.
Preferably A3 in formula I denotes an aromatic or heteroaromatic group with 6 to 24 ring atoms, which may also contain fused rings, and is optionally substituted by one or more groups L.
Very preferably A3 in formula I denotes benzene or naphthalene, which is optionally substituted by one or more groups L.
Preferably A1 and A2 in formula I denote an aromatic or heteroaromatic group with 6 to 24 ring atoms, which may also contain fused rings, and is optionally substituted by one or more groups L or R-(A3-Z3)m2—, or A1 is a single bond.
Very preferably A1 and A2 in formula I denote benzene, cyclohexylene, naphthalene, phenanthrene or anthracene, which is optionally substituted by one or more groups L or R-(A3-Z3)m2—, or A1 is a single bond.
Preferably -(A2-Z2-A1)m1- in formula I denotes benzene, biphenylene, p-terphenylene (1,4-diphenylbenzene), m-terphenylene (1,3-diphenylbenzene), naphthylene, 2-phenyl-naphthylene, phenanthrene or anthracene, all of which are optionally substituted by one or more groups L.
Very preferably -(A2-Z2-A1)m1- denotes biphenylene, p-terphenylene or m-terphenylene, all of which are optionally substituted by one or more groups L.
Preferred groups -(A2-Z2-A1)m1- are selected from the following formulae
wherein L is as defined in formula I or has one of the preferred meanings as described above and below, r is 0, 1, 2, 3 or 4, s is 0, 1, 2 or 3, t is 0, 1 or 2, and u is 0, 1, 2, 3, 4 or 5.
Particular preference is given to the groups of formula A1, A2, A3, A4 and A5.
Preferred compounds of formula I are selected from the following subformulae
wherein P, Sp, Ra-d, Z1, L and R are as defined in formula I or have one of the preferred meanings as described above and below,
Re is alkyl having 1 to 12 C atoms,
r is 0, 1, 2, 3 or 4,
s is 0, 1, 2 or 3,
t is 0, 1, or 2.
Preferably Z1 in formulae I and I-1 to I-45 is —CO—O—, —O—CO—, or a single bond, very preferably —CO—O— or a single bond.
Preferably P in formulae I and I-1 to I-45 is acrylate or methacrylate.
Preferably Sp in formulae I and I-1 to I-45 is a single bond.
Preferably Ra, Rb, Rc and Rd in formulae I and I-1 to I-45 are methyl.
Preferably R9 in formula I is H.
Further preferred compounds of formula I and its subformulae I-1 to I-45 are independently selected from the following preferred embodiments, including any combination thereof:
The liquid-crystalline media according to the invention are highly suitable for the use in displays which do not contain any orientation layer. Liquid crystal display devices, in general have a structure in which a liquid crystal mixture is sealed between a pair of insulating substrates, such as glass substrates, in such a manner that the liquid crystal molecules thereof are orientated in a predetermined direction, and an orientation film is formed on the respective substrates on the side of the liquid crystal mixture. As a material of an orientation film there is usually used a polyimide (PI). Homeotropic orientation of the LC molecules is especially necessary for LC modes like PVA, PS-VA, VA, etc., and can be achieved by the use of self-aligning additives, without the need of an orientation film. The mixtures according to the invention show an improved light and temperature stability compared to LC mixtures without compound of formula I. The media according to the invention are also suitable for liquid-crystalline base mixtures comprising different kinds of alkenyl compounds, which may provide advantageous properties. Finally, problems summarized as image sticking can thus be avoided by the use of media according to the invention as the self-aligning VA medium.
In a preferred embodiment, the LC medium according to the invention contains at least one additional polymerizable compound (also called reactive mesogen, RM) or contains a polymer comprising its polymerized form. Such kind of LC mixtures are highly suitable for PI-free PS (polymer stabilized)-VA displays or PSA (polymer sustained alignment) displays. The alignment of the LC molecules is induced by the self-aligning additives and the induced orientation (pre-tilt) may be additionally tuned or stabilized by the polymerization of the reactive mesogens (RMs), under conditions suitable for a multidomain switching. By the tuning of the UV-curing conditions it is possible in one single step to improve simultaneously SWT and contrast ratio. Reliability of the mixture (VHR) after light stress (both UV-curing and Backlight (BLT)) is improved compared to LC mixtures without any self-aligning additive filled in a “classic” PI-coated test cell. Furthermore, the UV-curing may be performed by using cut-filters at a wavelength by which the polymerization of the RMs is still reasonably fast and the VHR values are on an acceptable level.
The media according to the invention preferably exhibit very broad nematic phase ranges having clearing points≧70° C., preferably ≧75° C., in particular ≧80° C., very favorable values for the capacitive threshold, relatively high values for the holding ratio and at the same time very good low-temperature stabilities at −20° C. and −30° C., as well as very low rotational viscosities and short response times.
The media according to the invention preferably exhibit a voltage holding ratio (VHR) of 98.0% or more, more preferably of 98.5% or more, and most preferably of 99.0% or more under the methods indicated throughout this disclosure, e.g. typically at 60° C. and a cell thickness d˜4.0 μm, ITO coating on both sides, no additional layers.
Some preferred embodiments of the media according to the invention are indicated below.
The self-alignment additive for vertical alignment is preferably selected of formula II
MES-R2 II
in which
Preferably the polar anchor group R2 is a linear or branched alkyl group with 1 to 12 carbon atoms, wherein any —CH2— is optionally replaced by —O—, —S—, —NR0— or —NH—, and which is substituted with one, two or three polar groups selected from —OH, —NH2 or —NR0H, wherein R0 is alkyl with 1 to 10 carbon atoms. More preferably R2 is a group Ra as defined below.
More preferably the self-alignment additive for vertical alignment is preferably selected of formula IIa
R1-[A2-Z2]m-A1-Ra (IIa)
in which
The anchor group Ra of the self-alignment additive is preferably defined as
wherein
Formulae II and IIa optionally include polymerizable compounds. Within this disclosure the “medium comprising a compound of formula II/IIa” refers to both, the medium comprising the compound of formula II/IIa and, alternatively, to the medium comprising the compound in its polymerized form.
In the compounds of the formulae IIa, and subformulae thereof, Z1 and Z2 preferably denote a single bond, —C2H4—, —CF2O— or —CH2O—. In a specifically preferred embodiment Z1 and Z2 each independently denote a single bond.
In the compounds of the formula IIa, L, in each case independently, preferably denotes F or alkyl, preferably CH3, C2H5 or C3H7.
Preferred compounds of the formula II are illustrated by the following sub-formulae II-A to II-D
in which R1, Ra, A2, Z1, Z2, Sp, and P have the meanings as defined for formula IIa above,
In the compounds of the formulae II-A to II-D, L1 and L2, in each case independently, preferably denote F or alkyl, preferably CH3, C2H5 or C3H7.
In a preferred embodiment, r2 denotes 1 and/or r1 denotes 0.
The polymerizable group P of formulae II, IIA, and II-A to II-D preferably has the preferred meanings provided for P in formula I, most preferably methacrylate.
In the above formulae IIa or II-A to II-D Z1 and Z2 preferably independently denote a single bond or —CH2CH2—, and very particularly a single bond.
Ra denotes preferably
wherein p=1, 2, 3, 4, 5 or 6, and
R22 is H, methyl, ethyl, n-propyl, i-propyl, n-butyl, tert-butyl, n-pentyl, or —CH2CH2-tert-butyl
in particular
In the formula IIa and in the sub-formulae of the formula IIa R1 preferably denotes a straight-chain alkyl or branched alkyl radical having 1-8 C atoms, preferably a straight-chain alkyl radical. In the compounds of the formulae IIa or II-A to II-D R1 more preferably denotes CH3, C2H5, n-C3H7, n-C4H9, n-C5H11, n-C6H13 or CH2CH(C2H5)C4H9. R1 furthermore may denote alkenyloxy, in particular OCH2CH═CH2, OCH2CH═CHCH3, OCH2CH═CHC2H5, or alkoxy, in particular OC2H5, OC3H7, OC4H9, OC5H11 and OC6H13. Particularly preferable R1 denotes a straight chain alkyl residue, preferably C5H11.
In particular preferred compounds of the formula IIa are selected from the compounds of the sub-formulae II-1 to II-79,
in which R1, L1, L2, Sp, P and Ra have the meanings as given above, and L3 is defined as L2.
The mixtures according to the invention very particularly contain at least one self-aligning additive selected from the following group of compounds of the sub-formulae II-1a to II-1 h, II-8a to II-8h, II-10a to II-10h, II-16a to II-16h, II-23a to II-23h, II-62a to II-62d, II-67a to II-67d, II-68a to II-68d, II-69a to II-69d, II-70a to II-70d, II-71a to II-71d, II-72a to II-72d, and II-76a to II-76d:
in which Ra denotes an anchor group as described above and below, one of its preferred meanings, or preferably a group of formula
wherein R22 is H, methyl, ethyl, n-propyl, i-propyl, n-butyl, tert-butyl, n-pentyl, or —CH2CH2-tert-butyl, most preferably H,
and R1 has the meanings given in formula IIa, preferably denotes a straight-chain alkyl radical having 1 to 8 carbon atoms, preferably C2H5, n-C3H7, n-C4H9, n-C5H11, n-C6H13 or n-C7H15, most preferably n-C5H11.
Preferred LC mixtures according to the present invention contain at least one compound of the formulae II, IIa or their preferred subformulae.
In the compounds of the formula IIa and in the sub-formulae of the compounds of the formula IIa the group Ra preferably denotes
The compounds of the formulae II and IIa can be prepared by methods known per se, which are described in standard works for organic chemistry as such, for example, Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag, Stuttgart.
The compounds of the formula II can be prepared for example as follows:
The media according to the invention preferably contain one, two, three, four or more, preferably one, self-aligning additive.
The self-aligning additives of the formula II and IIa are preferably employed in the liquid-crystalline medium in amounts of ≧0.01% by weight, preferably 0.1-5% by weight, based on the mixture as a whole. Particular preference is given to liquid-crystalline media which contain 0.1-5%, preferably 0.2-3%, by weight of one or more self-aligning additives, based on the total mixture.
The use of preferably 0.2 to 3% by weight of one or more compounds of the formula II or IIa results in a complete homeotropic alignment of the LC layer for conventional LC thickness (3 to 4 μm) and for the substrate materials used in display industry. Special surface treatment may allow to significantly reduce the amount of the compound(s) of the formula II or IIa to amounts in the lower range.
The polymerizable compounds and components of the present invention are especially suitable for use in an LC host mixture that comprises one or more mesogenic or LC compounds comprising an alkenyl group (hereinafter also referred to as “alkenyl compounds”), wherein the alkenyl group is stable to a polymerization reaction under the conditions used for polymerization of the compounds of formula I and of the other polymerizable compounds contained in the liquid-crystalline medium.
Thus, in a preferred embodiment of the present invention, the liquid-crystalline medium comprises one or more low-molecular compounds comprising an alkenyl group, (“alkenyl compound”), where this alkenyl group is preferably stable to a polymerization reaction under the conditions used for the polymerization of the polymerizable compounds of formula I and of the other polymerizable compounds contained in the liquid-crystalline medium.
The alkenyl groups in the alkenyl compounds are preferably selected from straight-chain, branched or cyclic alkenyl, in particular having 2 to 25 C atoms, particularly preferably having 2 to 12 C atoms, in which, in addition, one or more non-adjacent CH2 groups may each be replaced by —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, and in which, in addition, one or more H atoms may each be replaced by F or Cl.
Preferred alkenyl groups are straight-chain alkenyl having 2 to 7 C atoms and cyclohexenyl, in particular ethenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, 1,4-cyclohexen-1-yl and 1,4-cyclohexen-3-yl.
The concentration of compounds containing an alkenyl group in the LC host mixture (i.e. without any polymerizable compounds) is preferably from 5% to 100%, very preferably from 20% to 60%.
Especially preferred are LC mixtures containing 1 to 5, preferably 1, 2 or 3 compounds having an alkenyl group.
The mesogenic and LC compounds containing an alkenyl group are preferably selected from the following formulae:
in which the individual radicals, on each occurrence identically or differently, each, independently of one another, have the following meaning:
RA2 is preferably straight-chain alkyl or alkoxy having 1 to 8 C atoms or straight-chain alkenyl having 2 to 7 C atoms.
The liquid-crystalline medium preferably comprises no compounds containing a terminal vinyloxy group (—O—CH═CH2), in particular no compounds of the formula AN or AY in which RA1 or RA2 denotes or contains a terminal vinyloxy group (—O—CH═CH2).
Preferably, L1 and L2 denote F, or one of L1 and L2 denotes F and the other denotes Cl, and L3 and L4 preferably denote F, or one of L3 and L4 denotes F and the other denotes Cl.
The compounds of the formula AN are preferably selected from the following sub-formulae:
in which alkyl denotes a straight-chain alkyl radical having 1-6 C atoms, and alkenyl and alkenyl* each, independently of one another, denote a straight-chain alkenyl radical having 2-7 C atoms. 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—.
Very preferred compounds of the formula AN are selected from the following sub-formulae:
in which m denotes 1, 2, 3, 4, 5 or 6, i denotes 0, 1, 2 or 3, and Rb1 denotes H, CH3 or C2H5.
Very particularly preferred compounds of the formula AN are selected from the following sub-formulae:
Most preferred are compounds of formula AN1a2 and AN1a5.
The compounds of the formula AY are preferably selected from the following sub-formulae:
in which (O) is O or a single bond, 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 2-7 C atoms. 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 compounds of the formula AY are selected from the following sub-formulae:
in which m and n each, independently of one another, denote 1, 2, 3, 4, 5 or 6, and alkenyl 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—.
Further preferred embodiments of the liquid-crystalline medium according to the invention are indicated below:
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 the compounds of the formulae CY and PY, Z2 may have identical or different meanings. In the compounds of the formula PY, Z2 and Z2 may have identical or different meanings.
In the compounds of the formulae CY, PY and PYP, R2A, R2B and R2C each preferably denote alkyl having 1-6 C atoms, in particular CH3, C2H5, n-C3H7, n-C4H9, n-C5H11.
In the compounds of the formulae CY and PY, L1, L2, L3 and L4 preferably denote L1=L2=F and L3=L4=F, furthermore L1=F and L2=Cl, L1=Cl and L2=F, L3=F and L4=Cl, L3=Cl and L4=F. Z2 and Z2′ in the formulae CY and PY preferably each, independently of one another, denote a single bond, furthermore a —C2H4— or —CH2O—bridge.
If in the formula PY Z2═—C2H4— or —CH2O—, Z2′ is preferably a single bond or, if Z2′═—C2H4— or —CH2O—, Z2 is preferably a single bond. In the compounds of the formulae CY and PY, (O)CvH2v+1, preferably denotes OCvH2v+1, furthermore CvH2v+1. In the compounds of the formula PYP, (O)CvH2v+1 preferably denotes CvH2v+1. In the compounds of the formula PYP, L3 and L4 preferably each denote F.
Preferred compounds of the formulae CY, PY and PYP are indicated below:
in which alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms.
Particularly preferred mixtures according to the invention comprise one or more compounds of the formulae CY-2, CY-8, CY-14, CY-29, CY-74, PY-2, PY-11 and PYP-1.
The proportion of compounds of the formulae CY and/or PY in the mixture as a whole is preferably at least 10% by weight.
Particularly preferred media according to the invention comprise at least one compound of the formula PYP-1,
in which alkyl and alkyl* have the meanings indicated above, preferably in amounts of ≧3% by weight, in particular ≧5% by weight and particularly preferably 5-25% by weight.
in which
Preferred compounds of the formula III are indicated below:
in which
The medium according to the invention preferably comprises at least one compound of the formula IIIa and/or formula IIIb.
The proportion of compounds of the formula III in the mixture as a whole is preferably at least 5% by weight.
in which
Particular preference is given to mixtures comprising at least one compound of the formula V-8.
in which R14-R19 each, independently of one another, denote an alkyl or alkoxy radical having 1-6 C atoms; and z and m each, independently of one another, denote 1-6.
The medium according to the invention particularly preferably comprises one or more compounds of the formulae Y-1 to Y-6, preferably in amounts of ≧5% by weight.
in which
R preferably denotes methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy, pentoxy.
The medium according to the invention preferably comprises the terphenyls of the formulae T-1 to T-21 in amounts of 2-30% by weight, in particular 5-20% by weight.
Particular preference is given to compounds of the formulae T-1, T-2, T-20 and T-21. In these compounds, R preferably denotes alkyl, furthermore alkoxy, each having 1-5 C atoms. In the compounds of the formula T-20, R preferably denotes alkyl. In the compound of the formula T-21, R preferably denotes alkyl.
The terphenyls are preferably employed in the mixtures according to the invention if the Δn value of the mixture is to be ≧0.1. Preferred mixtures comprise 2-20% by weight of one or more terphenyl compounds selected from the group of the compounds T-1 to T-21.
in which
The proportion of the biphenyls of the formulae B-1 to B-3 in the mixture as a whole is preferably at least 3% by weight, in particular ≧5% by weight.
Of the compounds of the formulae B-1 to B-3, the compounds of the formula B-2 are particularly preferred.
Particularly preferred biphenyls are
in which alkyl* denotes an alkyl radical having 1-6 C atoms. The medium according to the invention particularly preferably comprises one or more compounds of the formulae B-1a and/or B-2c.
in which R denotes a straight-chain alkyl or alkoxy radical having 1-7 C atoms, (O) denotes O or a single bond, and alkyl denotes a straight-chain alkyl radical having 1-6 C atoms.
in which R1 and R2 have the meanings indicated for R2A in formula CY. R1 and R2 preferably each, independently of one another, denote straight-chain alkyl or alkenyl having up to 6 carbon atoms.
Mixtures according to the invention very particularly preferably comprise the compounds of the formula O-5, O-7, O-9, O-10 and/or O-11, in particular in amounts of 5-30%.
Preferred compounds of the formulae O-5 and O-10 are indicated below:
The medium according to the invention particularly preferably comprises the tricyclic compounds of the formula O-5a and/or of the formula O-5b in combination with one or more bicyclic compounds of the formulae O-10a to O-10d. The total proportion of the compounds of the formulae O-5a and/or O-5b in combination with one or more compounds selected from the bicyclic compounds of the formulae O-10a to O-10d is 5-40%, very particularly preferably 15-35%.
Very particularly preferred mixtures comprise compounds O-5a and O-10a:
Compounds O-5a and O-10a are preferably present in the mixture in a concentration of 15-35%, particularly preferably 15-25% and especially preferably 18-22%, based on the mixture as a whole.
Very particularly preferred mixtures comprise compounds O-5b and O-10a:
Compounds O-5b and O-10a are preferably present in the mixture in a concentration of 15-35%, particularly preferably 15-25% and especially preferably 18-22%, based on the mixture as a whole.
Very particularly preferred mixtures comprise the following three compounds:
Compounds O-5a, O-5b and O-10a are preferably present in the mixture in a concentration of 15-35%, particularly preferably 15-25% and especially preferably 18-22%, based on the mixture as a whole.
in which R1N and R2N each, independently of one another, have the meanings indicated for R2A in formula CY, preferably denote straight-chain alkyl, straight-chain alkoxy or straight-chain alkenyl, and
in which
The mixtures according to the invention preferably comprise the compounds of the formulae BC, CR, PH-1, PH-2, BF-1, BF-2, BS-1 and/or BS-2 in amounts of 3 to 20% by weight, in particular in amounts of 3 to 15% by weight.
Particularly preferred compounds of the formulae BC, CR, BF-1, BF-2, BS-1, and BS-2 are the compounds BC-1 to BC-7 and CR-1 to CR-5, BF-1a to BF-1e, BF2a to BF-2b, BS-1a to BS-1e, and BS-2a to BS-2b:
in which
Mixtures comprising a compound of formula BF-1c are especially preferred, and alkyl and alkyl* are independently methyl, ethyl, propyl, butyl of pentyl or hexyl, which are preferably straight-chained.
in which
In the case that R12 and/or R13 denote halogen, halogen is preferably F.
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 formula In and the sub-formulae In-1 to In-16 are preferably employed in the mixtures according to the invention in concentrations≧5% by weight, in particular 5-30% by weight and very particularly preferably 5-25% by weight. m) Preferred mixtures additionally comprise one or more compounds of the formulae L-1 to L-11,
in which
Particular preference is given to the compounds of the formulae L-1 and L-4, in particular L-4.
The compounds of the formulae L-1 to L-11 are preferably employed in concentrations of 5-50% by weight, in particular 5-40% by weight and very particularly preferably 10-40% by weight.
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 each be replaced by halogen,
Preferred compounds of the formulae To-1 and To-2 are the compounds of the formula
in which
In particular, the following compounds of the formula To-1 are preferred:
where
Particularly preferred mixture concepts are indicated below: (the acronyms used are explained in Table A. n and m here each denote, independently of one another, 1-6).
The preferred mixtures contain:
preferably in amounts of 0.1-5 wt. %, in particular 0.2-2 wt. %.
Preference is furthermore given to mixtures according to the invention which comprise the following mixture concepts:(n and m each denote, independently of one another, 1-6.)
The invention furthermore relates to an electro-optical display, preferably a PI-free display, having either passive- or active-matrix addressing (based on the ECB, VA, PS-VA, PSA, IPS, HT-VA, PM (passive matrix)-VA characterized in that it contains, as dielectric, a liquid-crystalline medium according to one or more of the Claims.
The liquid-crystalline medium according to the invention preferably has a nematic phase from ≦−20° C. to ≧70° C., particularly preferably from ≦−30° C. to ≧80° C., very particularly preferably from ≦−40° C. to ≧90° C.
The expression “have a nematic phase” here 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 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 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 values of the birefringence Δn in the liquid-crystal mixture are generally between 0.07 and 0.16, preferably between 0.08 and 0.13.
The liquid-crystal mixture according to the invention has a & of −0.5 to −8.0, in particular −2.5 to −6.0, where & denotes the dielectric anisotropy. The rotational viscosity γ1 at 20° C. is preferably ≦165 mPa·s, in particular ≦140 mPa·s.
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 s 2.5 V and very particularly preferably s 2.3 V.
For the present invention, the term “threshold voltage” relates to the capacitive threshold (V0), also known as the Freedericks threshold, unless explicitly indicated otherwise.
Importantly, 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 Δ∈≧1.5, the term “dielectrically neutral compounds” denotes those having −1.5≦Δ∈≦1.5 and the term “dielectrically negative compounds” denotes those having Δ∈≦−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 (super patterned vertical alignment), ASV (advanced super view), PSA (polymer sustained VA) and PS-VA (polymer stabilized VA), as well as for PM-VA, HT (high transmission)-VA and VA-IPS applications.
The nematic liquid-crystal mixtures in the displays according to the invention generally comprise two components A and B, which themselves consist of one or more individual compounds.
Component A has significantly negative dielectric anisotropy and gives the nematic phase a dielectric anisotropy of ≦−1.5. Preferably component A comprises the compounds of the formulae CY, PY and/or PYP, furthermore compounds of the formula III.
The proportion of component A is preferably between 45 and 100%, in particular between 60 and 100%.
For component A, one (or more) individual compound(s) which has (have) a value of Δ∈≦−0.8 is (are) preferably selected. This value must be more negative, the smaller the proportion A in the mixture as a whole.
Component B has pronounced nematogeneity and a flow viscosity of not greater than 30 mm2·s−1, preferably not greater than 25 mm2·s−1, at 20° C.
Particularly preferred individual compounds in component B are extremely low-viscosity nematic liquid crystals having a flow viscosity of not greater than 18 mm2·s−1, preferably not greater than 12 mm2·s−1, at 20° C.
Component B is monotropically or enantiotropically nematic, has no smectic phases and is able to prevent the occurrence of smectic phases down to very low temperatures in liquid-crystal mixtures. For example, if various materials of high nematogeneity are added to a smectic liquid-crystal mixture, the nematogeneity of these materials can be compared through the degree of suppression of smectic phases that is achieved.
The mixture may optionally also comprise a component C, comprising compounds having a dielectric anisotropy of Δ∈≧1.5. These so-called positive compounds are generally present in a mixture of negative dielectric anisotropy in amounts of ≦20% by weight, based on the mixture as a whole.
Besides compounds of the formula II and the compounds of the formulae CY, PY and/or PYP and optionally III, other constituents may also be present, for example in an amount of up to 45% of the mixture as a whole, but preferably up to 35%, in particular up to 10%.
The other constituents are preferably selected from nematic or nematogenic substances, in particular known substances, from the classes of the azoxybenzenes, benzylideneanilines, biphenyls, terphenyls, phenyl or cyclohexyl benzoates, phenyl or cyclohexyl cyclohexanecarboxylates, phenylcyclohexanes, cyclohexylbiphenyls, cyclohexylcyclohexanes, cyclohexylnaphthalenes, 1,4-biscyclohexylbiphenyls or cyclohexylpyrimidines, phenyl- or cyclohexyldioxanes, optionally halogenated stilbenes, benzyl phenyl ethers, tolans and substituted cinnamic acid esters.
The most important compounds which are suitable as constituents of liquid-crystal phases of this type can be characterized by the formula IV
R20-L-G-E-R21 IV
in which L and E each denote a carbo- or heterocyclic ring system from the group formed by 1,4-disubstituted benzene and cyclohexane rings, 4,4′-disubstituted biphenyl, phenylcyclohexane and cyclohexylcyclohexane systems, 2,5-disubstituted pyrimidine and 1,3-dioxane rings, 2,6-disubstituted naphthalene, di- and tetrahydronaphthalene, quinazoline and tetrahydroquinazoline,
—CF2O— —CF═CF—
In most of these compounds, R20 and R21 are different from one another, one of these radicals usually being an alkyl or alkoxy group. Other variants of the proposed substituents are also common. Many such substances or also mixtures thereof are commercially available. All these substances can be prepared by methods known from the literature.
It goes without saying for the person skilled in the art that the VA 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.
Additional polymerizable compounds, so-called reactive mesogens (RMs), may furthermore be added to the mixtures according to the invention in concentrations of preferably 0.1-5% by weight, particularly preferably 0.2-2% by weight, based on the mixture. These are also referred to as co-monomers below. Mixtures of this type can be used for so-called polymer-stabilized VA modes (PS-VA) or PSA (polymer sustained VA), in which polymerization of the reactive mesogens is intended to take place in the liquid-crystalline mixture.
In a preferred embodiment of the invention, the additional polymerizable compounds (monomers) are selected from the compounds of the formula M,
RMa-AM1-(ZM1-AM2)m1-RMb M
in which the individual radicals have the following meanings:
Particularly preferred compounds of the formula M are those in which
Very particular preference is given to compounds of the formula M in which one of RMa and RMb or both denote(s) P or P-Sp-.
Suitable and preferred mesogenic comonomers, particularly for use in PSA displays, are selected, for example, from the following formulae:
in which the individual radicals have the following meanings:
In the compounds of formulae M1 to M41
is preferably
wherein L on each occurrence, identically or differently, has one of the meanings given above or below, and is preferably F, Cl, CN, NO2, CH3, C2H5, C(CH3)3, CH(CH3)2, CH2CH(CH3)C2H5, OCH3, OC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF3, OCF3, OCHF2, OC2F5 or P-Sp-, very preferably F, Cl, CN, CH3, C2H5, OCH3, COCH3, OCF3 or P-Sp-, more preferably F, Cl, CH3, OCH3, COCH3 or OCF3, especially F or CH3.
Suitable polymerizable compounds are furthermore listed, for example, in Table D. LC mixtures containing at least one polymerizable compound listed in Table D are especially preferred.
The liquid-crystalline media in accordance with the present application preferably comprise in total 0.1 to 10%, preferably 0.2 to 4.0%, particularly preferably 0.2 to 2.0%, of polymerizable compounds.
The combination of at least two liquid crystalline compounds, at least one self-aligning additive, a compound of formula I and preferably with at least one polymerizable compound selected from the formula M and/or the formulae M1 to M41, produces low threshold voltages, low rotational viscosities, very good low temperature stabilities (LTS) in the media but at the same time high clearing points and high VHR values, and enables the setting or a pretilt angle in VA displays without the need of any alignment layer, e.g., a polyimide layer.
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 polymerase 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 liquid-crystalline 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 and components according to the invention are also suitable for polymerization without an initiator, which is accompanied by advantages, such, for example, lower material costs and in particular less contamination of the liquid-crystalline 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 liquid-crystalline medium thus does not contain a polymerization initiator.
The liquid-crystalline 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 A), is preferably 10-500,000 ppm, particularly preferably 50-50,000 ppm.
However, the liquid-crystalline medium may additionally comprise one or more further components or additives, preferably selected from the list including but not limited to co-monomers, chiral dopants, 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.
The structure of the liquid-crystal displays according to the invention corresponds to the usual geometry, as described, for example, in EP 0 240 379.
The following examples are intended to explain the invention without limiting it. Above and below, percent data denote percent by weight; all temperatures are indicated in degrees Celsius.
Throughout the patent application and in the working examples, the structures of the liquid-crystalline compounds are indicated by means of acronyms. Unless indicated otherwise, the transformation into chemical formulae is carried out in accordance with Tables 1-3. All radicals CnH2n+1, CmH2m+1 and Cm′H2m′+1 or CnH2n and CmH2m or —(CH2)z— are straight-chain alkyl radicals or alkylene radicals in each case having n, m, m′ or z C atoms respectively. n, m, m′, z each denote, independently of one another, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, preferably 1, 2, 3, 4, 5 or 6. In Table 1 the ring elements of the respective compound are coded, in Table 2 the bridging members are listed and in Table 3 the meanings of the symbols for the left-hand or right-hand side chains of the compounds are indicated.
In a preferred embodiment the mixtures according to the invention contain at least one compound of formula I and at least two compounds selected from the compounds listed in Table A.
The liquid-crystal mixtures which can be used in accordance with the invention are prepared in a manner which is conventional per se. In general, the desired amount of the components used in lesser amount is dissolved in the components making up the principal constituent, advantageously at elevated temperature. It is also possible to mix solutions of the components in an organic solvent, for example in acetone, chloroform or methanol, and to remove the solvent again, for example by distillation, after thorough mixing.
By means of suitable additives, the liquid-crystal phases according to the invention can be modified in such a way that they can be employed in any type of, for example, ECB, VAN, GH or ASM-VA, PS-VA, PM-VA, HT-VA, VA-IPS LCD display that has been disclosed to date.
The dielectrics may also comprise further additives known to the person skilled in the art and described in the literature, such as, for example, UV absorbers, antioxidants, nanoparticles and free-radical scavengers. For example, 0-15% of pleochroic dyes, stabilizers or chiral dopants may be added. Suitable stabilizers for the mixtures according to the invention are, in particular, those listed in Table C.
For example, 0-15% of pleochroic dyes may be added, furthermore conductive salts, preferably ethyldimethyldodecylammonium 4-hexoxybenzoate, tetrabutylammonium tetraphenylboranate or complex salts of crown ethers (cf., for example, Haller et al., Mol. Cryst. Liq. Cryst. Volume 24, pages 249-258 (1973)), may be added in order to improve the conductivity or substances may be added in order to modify the dielectric anisotropy, the viscosity and/or the alignment of the nematic phases. Substances of this type are described, for example, in DE-A 22 09 127, 22 40 864, 23 21 632, 23 38 281, 24 50 088, 26 37 430 and 28 53 728.
Table B shows possible dopants which can be added to the mixtures according to the invention. If the mixtures comprise a dopant, it is employed in amounts of 0.01-4% by weight, preferably 0.1-1.0% by weight.
Stabilizers which can be added, for example, to the mixtures according to the invention in amounts of up to 10% by weight, based on the total amount of the mixture, preferably 0.01 to 6% by weight, in particular 0.1 to 3% by weight, are shown below in Table C. Preferred stabilizers are, in particular, BHT derivatives, for example 2,6-di-tert-butyl-4-alkylphenols, and Tinuvin® 770, as well as Tunuvin® P and Tempol.
Preferred reactive mesogens (polymerizable compounds) for use in the mixtures according to the invention, preferably in PSA and PS-VA applications are shown in Table D below:
The following examples are intended to explain the invention without restricting it. In the examples, m.p. denotes the melting point and C denotes the clearing point of a liquid-crystalline substance in degrees Celsius; boiling points are denoted by b.p. Furthermore:
C denotes crystalline solid state, S denotes smectic phase (the index denotes the phase type), N denotes nematic state, Ch denotes cholesteric phase, I denotes isotropic phase, Tg denotes glass transition temperature. The number between two symbols indicates the conversion temperature in degrees Celsius.
The additive is prepared as provided in WO 2017/041893.
In the following examples
The display used for measurement of the threshold voltage has two plane-parallel outer plates at a separation of 20 μm and electrode layers with overlying alignment layers of JALS-2096 on the insides of the outer plates, which effect a homeotropic alignment of the liquid crystals.
All concentrations in this application relate to the corresponding mixture or mixture component, unless explicitly indicated otherwise. All physical properties are determined as described in “Merck Liquid Crystals, Physical Properties of Liquid Crystals”, status November 1997, Merck KGaA, Germany, and apply for a temperature of 20° C., unless explicitly indicated otherwise.
Unless indicated otherwise, parts or percent data denote parts by weight or percent by weight.
The polymerizable compounds are polymerized in the display or test cell by irradiation with UVA 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 metal halide lamp and an intensity of 100 mW/cm2 is used for polymerization. The intensity is measured using a standard UVA meter (Hoenle UV-meter high end with UVA sensor).
The tilt angle is determined by crystal rotation experiment (Autronic-Melchers TBA-105). A low value (i.e. a large deviation from the 90° angle) corresponds to a large tilt here.
The VHR value is measured as follows: 0.3% of a polymerizable monomeric compound is added to the LC host mixture, and the resultant mixture is introduced into VA-VHR test cells. The VHR value is determined after 5 min at 60° C. before and after UV exposure at 1 V, 60 Hz, 64 ρs pulse (measuring instrument: Autronic-Melchers VHRM-105).
For the production of the examples according to the present invention the following host mixtures H1 to H34 are used:
stabilized with 0.01% of the compound of the formula
stabilized with 0.03% of
Together with the above host mixtures the following polymerizable stabilizers (polymerizable HALS) are used:
The following alignment additives are used:
(prepared as described in EP 2918658)
all prepared analogously to compound II-2 (see Example 1).
A polymerizable base mixture C1 or C2 respectively is prepared by adding the direactive monomer RM-1 (see Table D above) in an amount of 0.3% by weight and an alignment additive of formula II-1 or II-2 respectively in an amount of 0.3% by weight to the nematic LC host mixture H1.
Polymerizable mixtures (P) according to the present invention are prepared by adding 100 ppm (0.01%) of the polymerizable compounds RH-1, RH-2 or RH-3 to the base mixtures C1 or C2 (the latter as described in Comparative Mixture Examples C1, C2).
The compositions of the resulting polymerizable mixtures are shown in Table 1 below.
The resulting mixtures are homogenized and filled into “alignment-free” test cells (cell thickness d˜4.0 μm, ITO coating on both sides (structured ITO in case of a multi-domain switching), no alignment layer and no passivation layer).
The LC-mixtures show a spontaneous homeotropic (vertical) orientation with respect to the surface of the substrates. The orientation is stable to elevated temperatures until the clearing point of the respective host mixture H1. The resulting VA-cell can be reversibly switched. Crossed polarizers are applied to visualize the switching operation.
By using alignment additives like the compound of the formula II-1 to II-3, no alignment layer (e.g. no PI coating) is required for vertical orientation for any kind of display technologies.
The resulting VA-cell is polymerized with UV-light in a two-step process (step 1: high-pressure mercury lamp, 50 mW/cm2 for 120 s (6 J) for pre-tilt generation; step 2: Fluorescent lamp (Type C) for 80 min for polymer stabilization). The polymerizable derivative polymerizes and, consequently, the homeotropic self-orientation is stabilized and the tilt of the mixture is tuned. The resulting PSA-VA-cell can be reversibly switched even at high temperatures. The switching times are reduced compared to the non-polymerized system.
Additives like Irganox® 1076 (BASF) may be added (e.g. 0.001%) for preventing spontaneous polymerization. UV-cut filter may be used during polymerization for preventing damage of the mixtures (e.g. 340 nm cut-filter).
As above for the non-polymerized cell, no alignment layer is required to maintain vertical alignment.
The voltage-holding ratio (VHR) of the polymer-stabilized test cells is measured before and after intensive light load (120 min). The irradiated light is equivalent to 500 h of a typical white CCFL backlight for displays.
By using additives like the compound of the formula RH-1 in combination with RM-1, the VHR drop after backlight load is avoided. The test cells (P1.1, P2.1) show no decrease of VHR, while the comparative cells without any HALS additive (C1, C2) show a small VHR drop.
In addition, the reliability of a display improves by the addition of a reactive HALS additive. The display based on the mixture shows little image sticking.
Based on the host mixture H7 a base mixture is composed by adding the direactive monomer RM-1 (see Table D above) in an amount of 0.3% by weight and an alignment additive of formula II-3 in an amount of 0.3% by weight. This mixture is used as a comparative mixture.
Polymerizable mixtures according to the present invention are prepared by adding 100 ppm (0.01%) of the polymerizable compounds RH-1, RH-2 or RH-3 to the base mixtures C3 as described in the Comparative Mixture Example C3 above.
The compositions of the polymerizable mixtures C3 and P3 are shown in Table 2 below.
The voltage-holding ratio (VHR) of the polymer-stabilized test cells is measured before and after the polymer stabilization process.
By using additives like the compound of the formula RH-2 or RH-3 in combination with RM-1, a VHR gain after the UV polymerization process is achieved. The test cells (P3.2, P3.3) show high values of the voltage-holding ratio VHR after the final UV curing step.
The entire disclosures of all applications, patents and publications, cited herein and of corresponding European Application No. EP 16177392.4, filed Jun. 30, 2016 are incorporated by reference herein.
Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.
The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.
From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 16177392.4 | Jun 2016 | EP | regional |
