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US-12624289-B2 - Liquid-crystalline medium

US12624289B2US 12624289 B2US12624289 B2US 12624289B2US-12624289-B2

Abstract

A liquid-crystal material (LC media) containing thiophene compounds which are stabilized by sterically hindered amines or amine derivatives (HALS, hindered amine light stabilizers), where the LC media contains one or more compounds of formula 13 and one or more compounds of formula H and liquid-crystal displays (LC displays) which contain these LC materials.

Inventors

  • Atsutaka Manabe
  • Rocco Fortte
  • Harald Hirschmann

Assignees

  • MERCK PATENT GMBH

Dates

Publication Date
20260512
Application Date
20230411
Priority Date
20220412

Claims (15)

  1. 1 . An LC medium, comprising one or more compounds of the formula I-3-9 and/or I-3-10 in an amount of 1% to 40%, in which n and m independently from one another, denote an integer from 1 to 12; and 100 ppm to 1,000 ppm of compound H-10 and one or more of the following compounds in which R 3 is an alkyl radical having 1 to 15 C atoms, wherein one or more CH 2 groups, including terminal C atoms, may each be replaced, independently of one another, by —C≡C—, —CH═CH—, —O—, —S—, —(CO)—O—, or —O—(CO)— in such a way that O or S atoms are not linked directly to one another, and in which one or more H atoms may be replaced by F or Cl, or H, on each appearance, independently of one another, are L 31 and L 32 independently of one another, denote H or F, L 33 is H or CH 3 , X 3 denotes halogen, halogenated alkyl or alkoxy having 1 to 3 C atoms or halogenated alkenyl or alkenyloxy having 2 or 3 C atoms, and n denotes 0, 1, 2 or 3; and wherein the LC medium has a positive dielectric anisotropy.
  2. 2 . The LC medium according to claim 1 , further comprising one or more compounds of the following formulae in which R 1 and R 2 denote, each independently, H, F, Cl, Br, —CN, —SCN, —NCS, SF 5 or a straight-chain alkyl having 1 to 12 C atoms or a branched alkyl having 3 to 12 C atoms, in which one or more non-adjacent CH 2 groups may each be replaced, independently of one another, by —CH═CH—, —C≡C—, —O—, —CO—, —CO—O—, —O—CO—, or —O—CO—O— 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 F, Cl or Br, and L 2 to L 6 each independently denotes H or F.
  3. 3 . The LC medium according to claim 1 , additionally comprising one or more compounds of formula II and/or III, from which the compounds of formulae III-1a, III-1b, III-1e, III-1f, III-2 and III-3 are excluded: in which R 2 is an alkyl radical having 1 to 15 C atoms, wherein one or more CH 2 groups, including terminal C atoms, may each be replaced, independently of one another, by —C≡C—, —CH═CH—, —O—, —S—, —(CO)—O—, or —O—(CO)— in such a way that O or S atoms are not linked directly to one another, and in which one or more H atoms may be replaced by F or Cl, or H, on each appearance, independently of one another, denote L 21 and L 22 denote H or F, L 23 is H or CH 3 , X 2 denotes halogen, halogenated alkyl or alkoxy having 1 to 3 C atoms or halogenated alkenyl or alkenyloxy having 2 or 3 C atoms, m denotes 0, 1, 2 or 3, R 3 is an alkyl radical having 1 to 15 C atoms, wherein one or more CH 2 groups, including terminal C atoms, may each be replaced independently of one another, by —C≡C—, —CH═CH—, —O—, —S—, —(CO)—O—, or —O—(CO)— in such a way that O or S atoms are not linked directly to one another, and in which one or more H atoms may be replaced by F or Cl, or H, on each appearance, independently of one another, are L 31 and L 32 independently of one another, denote H or F, L 33 is H or CH 3 , X 31 denotes halogen, halogenated alkyl or alkoxy having 1 to 3 C atoms or halogenated alkenyl or alkenyloxy having 2 or 3 C atoms, Z 3 denotes —CH 2 CH 2 —, —CF 2 CF 2 —, —COO—, trans-CH═CH—, trans-CF═CF—, —CH 2 O— or a single bond, and n denotes 0, 1, 2 or 3.
  4. 4 . The LC medium according to claim 1 , additionally comprising one or more compounds of the following formulae, in which R 41 and R 42 each, independently of one another, is an alkyl radical having 1 to 15 C atoms, wherein one or more CH 2 groups, including terminal C atoms, may each be replaced, independently of one another, by —C≡C—, —CH═CH—, —O—, —S—, —(CO)—O—, or —O—(CO)— in such a way that O or S atoms are not linked directly to one another, and in which one or more H atoms may be replaced by F or Cl, or H, independently of one another and, if occurs twice, also these independently of one another, denote Z 41 and Z 42 each, independently of one another and, if Z 41 occurs twice, also these independently of one another, denotes —CH 2 CH 2 —, —COO—, trans-CH═CH—, trans-CF═CF—, —CH 2 O—, —CF 2 O—, —C≡C— or a single bond, p denotes 0, 1 or 2, and R 51 and R 52 each, independently of one another, is an alkyl radical having 1 to 15 C atoms, wherein one or more CH 2 groups, including terminal C atoms, may each be replaced, independently of one another, by —C≡C—, —CH═CH—, —O—, —S—, —(CO)—O—, or —O—(CO)— in such a way that O or S atoms are not linked directly to one another, and in which one or more H atoms may be replaced by F or Cl, or H, if present, each, independently of one another, denote Z 51 to Z 53 each, independently of one another, denotes —CH 2 —CH 2 —, —CH 2 —O—, —CH═CH—, —C≡C—, —COO— or a single bond, i and j each, independently of one another, denotes 0 or 1, (i+j) denotes 0, 1 or 2, wherein the rings optionally may each be substituted by one or two alkyl groups.
  5. 5 . The LC medium according to claim 1 , additionally comprising one or more compounds of the following formulae, wherein R 61 denotes an unsubstituted alkyl radical having 1 to 7 C atoms, R 62 denotes an unsubstituted alkyl radical having 1 to 7 C atoms, an unsubstituted alkoxy radical having 1 to 6 C atoms, C 3-5 -cycloalkyloxy or an unsubstituted alkenyloxy radical having 2 to 6 C atoms, L 61 , L 62 are independently H or methyl, 1 denotes 0 or 1, R 71 denotes an unsubstituted alkyl radical having 1 to 7 C atoms, R 72 denotes an unsubstituted alkyl radical having 1 to 7 C atoms, L 71 , L 72 are independently H or methyl, independently denote R 81 denotes an unsubstituted alkyl radical having 1 to 7 C atoms, or an unsubstituted alkoxy radical having 1 to 6 C atoms, R 82 denotes an unsubstituted alkyl radical having 1 to 7 C atoms, or an unsubstituted alkoxy radical having 1 to 6 C atoms, L 81 , L 82 are independently H or methyl, denotes Z 8 denotes —(C═O)—O—, —CH 2 —O—, —CF 2 —O— or —CH 2 —CH 2 —, denotes 0 or 1, R 91 and R 92 independently of one another denote an unsubstituted alkyl radical having 1 to 7 C atoms, R 91 denotes an alkyl radical having 2 to 5 C atoms, R 92 denotes an alkyl or alkoxy radical having 2 to 5 C atoms, or an alkenyloxy radical having 2 to 4 C atoms, denotes p and q independently of each other denote 0 or 1.
  6. 6 . The LC medium according to claim 1 , further comprising one or more compounds of formula IVa in which R 41 denotes an unsubstituted alkyl radical having 1 to 7 C atoms or an unsubstituted alkenyl radical having 2 to 7 C atoms, and R 42 denotes an unsubstituted alkyl radical having 1 to 7 C atoms, an unsubstituted alkenyl radical having 2 to 7 C atoms, or an unsubstituted alkoxy radical having 1 to 6 C atoms.
  7. 7 . The LC medium according to claim 1 , wherein the total concentration of the one or more compounds of formula I-3-9 and/or I-3-10 in the medium as a whole is 1% to 25%.
  8. 8 . The LC medium according to claim 1 , wherein the total concentration of the compound of formula H-10 in the LC medium is 1,000 ppm.
  9. 9 . An electro-optical device comprising an LC display comprising an LC medium according to claim 1 .
  10. 10 . An LC display containing the LC medium according to claim 1 .
  11. 11 . The display according to claim 10 , which is based on an IPS or FFS effect.
  12. 12 . A process for preparing the LC medium according to claim 1 , comprising mixing one or more compounds of formula I-3-9 and/or I-3-10 with the compound of formula H-10 and with one or more compounds of formula III-1a, III-1b, III-1e, III-1f, III-2 and/or III-3.
  13. 13 . The LC medium according to claim 1 , wherein the total concentration of the one or more compounds of formula I-3-9 and/or I-3-10 in the medium as a whole is 5% to 25%.
  14. 14 . The LC medium according to claim 1 , which has a positive dielectric anisotropy of 2.0 to 20.
  15. 15 . The LC medium according to claim 1 , which comprises one or more compounds of formulae

Description

The present invention relates to a liquid-crystal material (LC media) comprising thiophene derivatives which are stabilised by sterically hindered amines or amine derivatives (HALS, hindered amine light stabilisers), and to liquid-crystal displays (LC displays) which contain these LC materials. Liquid crystals are used principally as dielectrics in display devices, since the optical properties of such substances can be modified by an applied voltage. Electro-optical devices based on liquid crystals are extremely well known to the person skilled in the art and can be based on various effects. Examples of such devices are cells having dynamic scattering, DAP (deformation of aligned phases) cells, guest/host cells, TN cells having a twisted nematic structure, STN (supertwisted nematic) cells, SBE (super-birefringence effect) cells and OMI (optical mode interference) cells. The commonest display devices are based on the Schadt-Helfrich effect and have a twisted nematic structure. In addition, there are also cells which work with an electric field parallel to the substrate and liquid-crystal plane, such as, for example, IPS (in-plane switching) cells. The principle of electrically controlled birefringence, the ECB (electrically controlled birefringence) effect or 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). Papers by J. F. Kahn (Appl. Phys. Lett. 20 (1972), 1193) and G. Labrunie and J. Robert (J. Appl. Phys. 44 (1973), 4869) followed. 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) have shown that liquid-crystalline phases must have high values for the ratio between the elastic constants K3/K1, high values for the optical anisotropy Δn, and values for the dielectric anisotropy Δε of ≤−0.5 in order to be suitable for use for 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). Dielectrically negative liquid-crystal media can also be used in displays which use the IPS or FFS effect. TN, VA, IPS and FFS cells, in particular, are currently areas of application of commercial interest for the media according to the invention. The liquid-crystal materials must have good chemical and thermal stability and good stability to electric fields and electromagnetic radiation. Furthermore, the liquid-crystal materials should have low viscosity and give rise to short addressing times, low threshold voltages and high contrast in the cells. They should furthermore have a suitable mesophase, for example a nematic mesophase for the above-mentioned cells, at the usual operating temperatures, i.e. in the broadest possible range above and below room temperature. Since liquid crystals are generally used as mixtures of a plurality of components, it is important that the components are readily miscible with one another. Further properties, such as the electrical conductivity, the dielectric anisotropy and the optical anisotropy, have to satisfy various requirements depending on the cell type and area of application. For example, materials for cells having a twisted nematic structure should have positive dielectric anisotropy and low electrical conductivity. For example, for matrix liquid-crystal displays with integrated non-linear elements for switching individual pixels (MLC displays), media having large positive dielectric anisotropy, broad nematic phases, relatively low birefringence, very high specific resistance, good UV and temperature stability and low vapour pressure are desired. Matrix liquid-crystal displays of this type are known. Examples of non-linear elements which can be used to individually switch the individual pixels are active elements (i.e. transistors). The term “active matrix” is then used, where a distinction can be made between two types: 1. MOS (metal oxide semiconductor) or other diodes on silicon wafers as substrate.2. Thin-film transistors (TFTs) on a glass plate as substrate. The TFT matrix is applied to the inside of one glass plate of the display, while the other glass plate carries the transparent counter electrode on its inside. Compared with the size of the pixel electrode, the TFT is very small and has virtually no adverse effect on the image. This technology can also be extended to fully colour-capable displays, in which a mosaic of red, green and blue filters is arranged in such a way that a filter element is opposite each switchable pixel. The TFT displays usually operate as TN cells with crossed polarisers in transmission and are backlit. The term MLC displays here encompasses any matrix display with integrated non-linear elements, i.e., besides the acti