WO2018078078A1 - Nanocapsules comprenant un milieu à cristaux liquides - Google Patents

Nanocapsules comprenant un milieu à cristaux liquides Download PDF

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Publication number
WO2018078078A1
WO2018078078A1 PCT/EP2017/077561 EP2017077561W WO2018078078A1 WO 2018078078 A1 WO2018078078 A1 WO 2018078078A1 EP 2017077561 W EP2017077561 W EP 2017077561W WO 2018078078 A1 WO2018078078 A1 WO 2018078078A1
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Prior art keywords
nanocapsules
additives
phe
cyc
surfactant
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PCT/EP2017/077561
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English (en)
Inventor
Mariam NAMUTEBI
Rachel TUFFIN
Vicki COOK
Patricia Saxton
Kevin Adlem
Sarabjot Kaur
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Merck Patent Gmbh
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Priority to CN201780064367.1A priority Critical patent/CN109863226A/zh
Priority to DE112017005490.7T priority patent/DE112017005490T5/de
Priority to KR1020197015292A priority patent/KR20190077034A/ko
Priority to JP2019522686A priority patent/JP2019535498A/ja
Publication of WO2018078078A1 publication Critical patent/WO2018078078A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/52—Liquid crystal materials characterised by components which are not liquid crystals, e.g. additives with special physical aspect: solvents, solid particles
    • C09K19/54—Additives having no specific mesophase characterised by their chemical composition
    • C09K19/542—Macromolecular compounds
    • C—CHEMISTRY; METALLURGY
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    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K19/06—Non-steroidal liquid crystal compounds
    • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
    • C09K19/10—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings
    • C09K19/12—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings at least two benzene rings directly linked, e.g. biphenyls
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K19/06—Non-steroidal liquid crystal compounds
    • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
    • C09K19/10—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings
    • C09K19/14—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings linked by a carbon chain
    • C09K19/18—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings linked by a carbon chain the chain containing carbon-to-carbon triple bonds, e.g. tolans
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K19/06—Non-steroidal liquid crystal compounds
    • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
    • C09K19/10—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings
    • C09K19/20—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings linked by a chain containing carbon and oxygen atoms as chain links, e.g. esters or ethers
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K19/06—Non-steroidal liquid crystal compounds
    • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
    • C09K19/30—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing saturated or unsaturated non-aromatic rings, e.g. cyclohexane rings
    • C09K19/3001—Cyclohexane rings
    • C09K19/3003—Compounds containing at least two rings in which the different rings are directly linked (covalent bond)
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
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    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K2019/0444—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit characterized by a linking chain between rings or ring systems, a bridging chain between extensive mesogenic moieties or an end chain group
    • C09K2019/0466—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit characterized by a linking chain between rings or ring systems, a bridging chain between extensive mesogenic moieties or an end chain group the linking chain being a -CF2O- chain
    • C—CHEMISTRY; METALLURGY
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    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K19/06—Non-steroidal liquid crystal compounds
    • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
    • C09K19/10—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings
    • C09K19/12—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings at least two benzene rings directly linked, e.g. biphenyls
    • C09K2019/121—Compounds containing phenylene-1,4-diyl (-Ph-)
    • C09K2019/123—Ph-Ph-Ph
    • C—CHEMISTRY; METALLURGY
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    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K19/06—Non-steroidal liquid crystal compounds
    • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
    • C09K19/10—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings
    • C09K19/14—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings linked by a carbon chain
    • C09K19/18—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings linked by a carbon chain the chain containing carbon-to-carbon triple bonds, e.g. tolans
    • C09K2019/181—Ph-C≡C-Ph
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    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K19/06—Non-steroidal liquid crystal compounds
    • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
    • C09K19/10—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings
    • C09K19/14—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings linked by a carbon chain
    • C09K19/18—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings linked by a carbon chain the chain containing carbon-to-carbon triple bonds, e.g. tolans
    • C09K2019/183—Ph-Ph-C≡C-Ph
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K19/06—Non-steroidal liquid crystal compounds
    • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
    • C09K19/30—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing saturated or unsaturated non-aromatic rings, e.g. cyclohexane rings
    • C09K19/3001—Cyclohexane rings
    • C09K19/3003—Compounds containing at least two rings in which the different rings are directly linked (covalent bond)
    • C09K2019/3025—Cy-Ph-Ph-Ph
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/52—Liquid crystal materials characterised by components which are not liquid crystals, e.g. additives with special physical aspect: solvents, solid particles
    • C09K2019/528—Surfactants

Definitions

  • the present invention relates to nanocapsules which comprise a mesogenic medium as set forth hereinafter, a polymeric shell and one or more additives, to their use in electro-optical devices, and to methods for preparing the nanocapsules.
  • Liquid-crystalline (LC) media are widely used in liquid crystal displays
  • LCDs in particular in electro-optical displays having active-matrix or passive-matrix addressing, to display information.
  • active-matrix displays individual pixels are usually addressed by integrated, non-linear active elements, such as transistors, for example thin-film transistors (TFTs), while in the case of passive-matrix displays, individual pixels are usually addressed by the multiplex method, as known from the prior art.
  • TFTs thin-film transistors
  • LCDs of the TN twisted nematic
  • VA vertical aligned
  • OCB optically aligned
  • compensated bend displays which are based on a birefringence effect and have an LC layer with a so-called "bend" alignment.
  • so-called IPS in-plane switching
  • FFS far-field switching
  • displays which contain two electrodes on the same substrate, wherein one electrode is structured in a comb-shaped manner and the other is unstructured.
  • a strong, so-called “fringe field” is thereby generated, i.e. a strong electric field close to the edge of the electrodes, and, throughout the cell, an electric field which has both a strong vertical component and also a strong horizontal component.
  • PS polymer sustained
  • PSA polymer sustained alignment
  • LC medium exhibits a liquid crystal phase
  • RMs reactive mesogens
  • PDLC films In addition, displays based on polymer dispersed liquid crystal (PDLC) films have been described, see e.g. US 4,688,900.
  • PDLC films usually micrometer-sized droplets (microdroplets) of LC medium are randomly distributed in a polymer matrix.
  • the LC domains in these phase-separated systems have a size which can result in strong scattering of light.
  • PDLC films are usually prepared using methods of polymerization-induced phase separation (PIPS), wherein phase separation is reaction-induced.
  • PIPS polymerization-induced phase separation
  • PDLC films may be prepared based on temperature-induced phase separation (TIPS) or solvent-induced phase separation (SIPS).
  • TIPS temperature-induced phase separation
  • SIPS solvent-induced phase separation
  • PNLC polymer network liquid crystal
  • micrometer-sized encapsulated LC materials for use in displays have been described, wherein the microcapsules are prepared by forming an aqueous emulsion of LC material with an immiscible binder such as polyvinyl alcohol (PVA) which serves as the encapsulating medium, see e.g. US 4,435,047.
  • PVA polyvinyl alcohol
  • LCDs which include a layer comprising nanocapsules, wherein the nanocapsules contain liquid crystal molecules.
  • a configuration of an LCD device arranged with a layer which contains such nanocapsules in a so- called buffer material is described in US 2014/0184984 A1 .
  • Nanocapsules having a mean diameter of approximately 1 10 nm are prepared by adding a nematic LC to a mixture of nonionic polymeric surfactant and PVA, which serves as shell-forming polymer and water-soluble emulsifier, dissolved in aqueous solution, forming a nanoemulsion, heating up of the nanoemulsion to a cloud point and stirring to phase separate PVA around the LC nanodroplets, and crosslinking of the polymeric shell with crosslinking agents such as dialdehydes. Furthermore, a coating solution containing the prepared LC nanocapsules, hydrophilic PVA as a binder and ethylene glycol as a plasticizer is described.
  • porous nanoparticles made of crosslinked polymer which can act like a sponge to imbibe LC substances, having a possible application as phase retardation films in an LCD.
  • An object of the present invention is therefore to provide improved
  • nanocapsules comprising mesogenic media and having favourable
  • compositions and materials used in the preparation allow favourable performance during encapsulation, while further providing benefits in the resultant nanocapsules.
  • the nanocapsules such that the mesogenic media contained in the nanocapsules have suitably high ⁇ and high electrical resistance as well as suitably high ⁇ and favourable values of the electro-optical parameters, while furthermore particularly providing relatively low rotational viscosity and favourable reliability.
  • the mesogenic media comprised in the nanocapsules exhibit broad and stable LC, in particular nematic, phase ranges, low melting points and a relatively high clearing point, and a suitably high voltage holding ratio.
  • nanocapsules and composite systems comprising the nanocapsules and binder which are useful in light-modulation elements and electro-optical devices, in particular having a suitably low threshold voltage, favourably fast response times, improved low-temperature behaviour and an improvement in the operating properties at low temperatures, a minimal temperature dependence of the electro-optical parameters such as, for example, the threshold voltage, and a high contrast. It is furthermore an object to provide nanocapsules and composite systems in light-modulation elements and electro-optical devices which have a favourably wide viewing angle range and which are substantially insensitive to external forces such as from touching. Further objects of the present invention are immediately evident to the person skilled in the art from the following detailed description.
  • a first aspect of the present invention provides a method for preparing nanocapsules, wherein the method comprises (a) providing a composition, comprising
  • R and R' denote, independently of one another, a
  • CH2 groups may be, in each case independently of one another, replaced by -O-, -S-, -CO-, -COO-, -OCO-, -OCOO- or -C ⁇ C- in such a manner that oxygen atoms are not linked directly to one another,
  • a and A' denote, independently of one another, a group selected from -Cyc-, -Phe-, -Cyc-Cyc-, -Cyc-Phe-, -Phe-Phe-, -Cyc-Cyc-Cyc-Cyc-, -Cyc-Cyc-Phe-,
  • Cyc is trans-1 ,4-cyclohexylene, in which one or two non-adjacent CH2 groups may be replaced by O, and wherein Phe is 1 ,4-phenylene, in which one or two non-adjacent CH groups may be replaced by N and which may be substituted by one or two F, and
  • nanocapsules each comprising a polymeric shell and a core which contains the mesogenic medium, wherein additionally one or more additives are added
  • the additive(s) may be added to the composition or to the nanodroplets before the polymerization step is carried out.
  • the additive(s) may be added after carrying out the polymerization and forming the nanocapsules.
  • the one or more additives are added to the obtained nanocapsules in a step (d) after the polymerization according to step (c).
  • two or more surfactants are used in step (b), namely in the case where the additionally added additive(s) is (are) surfactant(s).
  • one or more further additives i.e. in addition to the
  • surfactant(s) for example, an agent may be used which influences wettability, solubility, viscosity or the osmotic pressure.
  • hydrophobic or hydrophobizing agents may preferably additionally be added before, during or also after step (b).
  • the one or more additives added in step (d) are one or more surfactants.
  • the additive(s), preferably the surfactant(s), added can be chosen such that they are matched or adapted to the surfactant(s) used in step (b), or they even may be the same. It is however also possible, and in many cases preferable, to more freely choose and use additive(s), preferably surfactant(s), in step (d), i.e. generally independent from the surfactant(s) employed in step (b).
  • nanocapsules can be provided which allow a favourable electro-optical performance with a reduced operating voltage.
  • the combined use of the additive and surfactant agents as set forth above can at the same time provide further benefits, in particular it may contribute to achieving an excellent dark state, high contrast ratio, favourably low hysteresis and suitability for film formation.
  • the amount of additive, respectively added before the polymerization or as added in step (d), with respect to the composition as provided in step (a), is preferably 5% by weight or less, more preferably is 2.5% by weight or less, and even more preferably is 1 % by weight or less.
  • the amount of additive, with respect to the composition as provided in step (a) is particularly preferably set in the range from 0.05% by weight to 1 % by weight, and even more preferably in the range from 0.1 % by weight to 1 % by weight.
  • nanocapsules which respectively comprise a polymeric shell, a core containing a mesogenic medium which comprises one or more compounds of formula I as set forth above and below, and one or more additives.
  • the one or more additives are contained in the polymeric shell. Additionally or alternatively the one or more additives may be contained in the core containing the mesogenic medium. Particularly preferably the additive, or at least part thereof, is at or close to the interface between the shell and the core. It is preferred that the additive can serve as a surfactant.
  • the nanocapsules comprise the additive(s) in an amount, based on the overall capsule composition, of 5% by weight or less, more preferably of 2.5% by weight or less, and even more preferably of 1 % by weight or less.
  • the amount of additive, based on the overall capsule composition is particularly preferably set in the range from 0.05% by weight to 1 % by weight, and even more preferably in the range from 0.1 % by weight to 1 % by weight.
  • the invention provides a method to prepare the
  • nanocapsules according to the invention, wherein the method comprises the steps of (i) providing nanocapsules which respectively comprise a polymeric shell and a core containing a mesogenic medium which comprises one or more compounds of formula I as set forth above and below, and (ii) adding one or more additives to the nanocapsules as provided.
  • a method for preparing a composite system wherein the method comprises providing nanocapsules, which respectively comprise
  • the combination of the nanocapsules with binder material(s) can suitably influence and increase the processibility and applicability of the light modulating material, in particular in view of coating, dropping or printing on substrates and film formation.
  • the one or more binders can act as both dispersant and adhesion or binding agent, and furthermore provide suitable physical and mechanical stability while maintaining or even promoting flexibility.
  • density or concentration of the capsules can advantageously be adjusted by varying the amount of binder or buffer material provided.
  • the properties of the nanocapsules in the composite system as well as the composite system on the whole can be significantly improved when one or more additives, preferably one or more surfactants, are added during the preparation of the composite system as described above.
  • one or more additives preferably one or more surfactants
  • the provided nanocapsules already comprise one or more additives, preferably surfactant(s).
  • the nanocapsules can be prepared, for example, by the method as described above, and during the preparation of the composite system one or more additives are additionally added.
  • the additive(s) added can be the same as or different from the one(s) already comprised in the nanocapsules as provided.
  • nanocapsules can, for example, be obtained by carrying out steps (a) to (c) of the method for preparing nanocapsules described above, while however leaving out the addition of the additive(s) before the
  • step (d) One or more additives, preferably surfactant(s), are then only added in the preparation of the composite system, which is an alternative to adding the additive just to the
  • This can be performed e.g. by mixing the additive with the binder, and then adding the nanocapsules to the mixture.
  • the additive can be the same as set forth under step (d) for the case of the capsule preparation.
  • the amount of additive added according to the method, based on the overall system composition as prepared is 5% by weight or less, more preferably is 2.5% by weight or less, and even more preferably is 1 % by weight or less.
  • the amount of additive added according to the method, based on the overall system composition as prepared is particularly preferably set in the range from 0.05% by weight to 1 % by weight, and even more
  • a composite system comprising the nanocapsules according to the invention, one or more binders, and one or more additives, preferably one or more surfactants, is favourably obtained by or obtainable from carrying out the method described above.
  • the one or more additives are comprised, in particular incorporated, in the nanocapsules. Additionally or alternatively the one or more additives may be comprised in the binder. Particularly preferably the additive is contained in the capsules and the binder. It is preferred that the additive can serve as a surfactant.
  • the composite system comprises the additive(s) in an amount, based on the overall composition, of 5% by weight or less, more preferably of 2.5% by weight or less, and even more preferably of 1 % by weight or less.
  • the amount of additive, based on the overall composition is particularly preferably set in the range from 0.05% by weight to 1 % by weight, and even more preferably in the range from 0.1 % by weight to 1 % by weight.
  • nanocapsules and the composite system according to the invention are particularly useful in light-modulation elements or ectro-optical devices.
  • a further aspect of the invention provides an electro-optical device which comprises the nanocapsules according to the invention or the composite system according to the invention.
  • a method for reducing the switching voltage in an electro- optical device wherein one or more additives are included in nanocapsules comprising a polymeric shell and a core containing the mesogenic medium as set forth above and below or in a composite comprising said nanocapsules and one or more binders, and wherein the obtained nanocapsules or composite are included in the device.
  • device comprises the nanocapsules according to the invention or the composite system according to the invention
  • nanoencapsulated LC medium according to the invention optionally combined with a binder material
  • an electro-optical device several significant advantages are obtainable. These include, for example, good mechanical stability, flexibility and insensitivity to external applied forces or respectively pressure such as from touch as well as further favourable properties regarding switching speed, transmittance, dark state, viewing angle behaviour and threshold voltage, in particular a reduced operating voltage and reduced hysteresis. Further advantages rest in the possible use of flexible substrates and the possibility to vary film or layer thickness and the tolerability of film thickness deviations or variance. In this respect simple dropping, coating, laminating or printing methods can be used to apply the light-modulating material to the substrate.
  • an alignment layer such as conventionally used polyimide (PI) alignment layers
  • PI polyimide
  • the two electrodes in the device are provided on the same substrate such as in the case of IPS or FFS a single substrate can be sufficient to provide functionality and stability or respectively support, making the provision of an opposing substrate merely optional.
  • opposing substrate may still be beneficial, for example in terms of providing further optical elements or physical or chemical protection.
  • the sealing of the layer comprising the LC material may no longer be needed to ensure sufficient material enclosure and to prevent material leakage from the layer.
  • liquid crystal LC
  • thermotropic LCs thermotropic LCs
  • lyotropic LCs concentration ranges in solutions
  • mesogenic compound and “liquid crystal compound” mean a compound comprising one or more calamitic (rod- or board/lath-shaped) or discotic (disc-shaped) mesogenic groups, i.e. groups with the ability to induce liquid-crystalline phase or mesophase behaviour.
  • the LC compounds or materials and the mesogenic compounds or materials comprising mesogenic groups do not necessarily have to exhibit a liquid- crystalline phase themselves. It is also possible that they show liquid- crystalline phase behaviour only in mixtures with other compounds. This includes low-molecular-weight non-reactive liquid-crystalline compounds, reactive or polymerizable liquid-crystalline compounds, and liquid-crystalline polymers.
  • a calamitic mesogenic compound is usually comprising a mesogenic core consisting of one or more aromatic or non-aromatic cyclic groups connected to each other directly or via linkage groups, optionally comprising terminal groups attached to the ends of the mesogenic core, and optionally
  • lateral groups attached to the long side of the mesogenic core, wherein these terminal and lateral groups are usually selected e.g. from carbyl or hydrocarbyl groups, polar groups like halogen, nitro, hydroxy, etc., or polymerizable groups.
  • liquid crystal material or medium is used for both liquid crystal materials or media and mesogenic materials or media, and vice versa, and the term “mesogen” is used for the mesogenic groups of the material.
  • non-mesogenic compound or material means a compound or material that does not contain a mesogenic group as defined above.
  • polymer will be understood to mean a molecule that encompasses a backbone of one or more distinct types of repeating units (the smallest constitutional unit of the molecule) and is inclusive of the commonly known terms “oligomer”, “copolymer”, “homopolymer” and the like. Further, it will be understood that the term polymer is inclusive of, in addition to the polymer itself, residues from initiators, catalysts, and other elements attendant to the synthesis of such a polymer, where such residues are understood as not being covalently incorporated thereto. Further, such residues and other elements, while normally removed during post- polymerization purification processes, are typically mixed or co-mingled with the polymer such that they generally remain with the polymer when it is transferred between vessels or between solvents or dispersion media.
  • (meth)acrylic polymer includes a polymer obtained from acrylic monomers, a polymer obtainable from methacrylic monomers, and a corresponding co-polymer obtainable from mixtures of such monomers.
  • polymerization means the chemical process to form a polymer by bonding together multiple polymerizable groups or polymer precursors (polymerizable compounds) containing such polymerizable groups.
  • Polymerizable compounds with one polymerizable group are also referred to as “monoreactive” compounds, compounds with two polymerizable groups as “direactive” compounds, and compounds with more than two polymerizable groups as “multireactive” compounds.
  • Compounds without a polymerizable group are also referred to as “non-reactive” or “non-polymerizable” compounds.
  • film and layer include rigid or flexible, self-supporting or freestanding films or layers with more or less pronounced mechanical stability, as well as coatings or layers on a supporting substrate or between two substrates.
  • Visible light is electromagnetic radiation that has a wavelength in a range from about 400 nm to about 745 nm.
  • Ultraviolet (UV) light is electromagnetic radiation with a wavelength in a range from about 200 nm to about 400 nm.
  • additive which is added in addition to the one surfactant as set forth above in (b)
  • the process and the additive addition give suitable performance and suitable results even in the presence of an aqueous system or environment.
  • the invention relates to a method for preparing nanoparticles, wherein a composition is provided which comprises the mesogenic medium as described above and below and one or more polymerizable compounds, and wherein said composition is then dispersed as nanodroplets in an aqueous phase using the one surfactant.
  • the one or more polymerizable compounds are polymerized such that nanocapsules are obtained, each of which comprise a polymeric shell and a core which contains the mesogenic medium.
  • the method further comprises the addition of one or more additives.
  • a further additive may be included in the surfactant
  • nanodroplet dispersion i.e. before the polymerization is carried out. It is also possible and in some cases preferred to add the one or more additives to the formed nanocapsules, i.e. subsequent to the polymerization step. In yet another embodimemt additives are added before and after the nanocapsules are formed. It was surprisingly found that according to the invention an efficient and controlled process can be carried out, ultimately on the nanoscale, to produce nanosized containers, which typically are spherical or spheroidal, enclosing LC material.
  • nanoemulsion which is also called miniemulsion
  • nanosized phases comprising LC material and reactive, polymerizable compound(s) are dispersed in a suitable dispersion medium. It was furthermore found that the addition of one or more additives, added to the nanodroplets or to the formed nanocapsules, can further improve or adjust the properties and performance of the nanocapsules.
  • a composition comprising the mesogenic medium and one or more polymerizable compounds is provided.
  • solubilization and/or mixing optionally and preferably an organic solvent may be added to the composition, which can e.g. favourably influence phase separation during polymerization. Therefore, in a preferred embodiment the composition as provided in step (a) further comprises one or more organic solvents.
  • composition is then dispersed as nanodroplets in an aqueous phase.
  • surfactant can favourably promote formation and subsequently stabilization, in particular ionic and/or steric stabilization, of discrete nanodroplets in the dispersion medium, in particular the aqueous dispersion medium, wherein the nanodroplets comprise the LC medium and polymerizable compound(s).
  • Agitation preferably mechanical agitation, in particular high-shear mixing, can suitably yield or further effect dispersion, in particular emulsion, and homogenization, and likewise promote nanodroplet formation.
  • membrane emulsification may for example be used.
  • Both mechanical agitation and the provision of surfactant thus can play advantageous roles in obtaining nanodroplets and in turn nano-sized capsules, in particular nanocapsules with a substantially uniform size distribution or respectively low polydispersity.
  • the dispersed phase exhibits poor solubility in the dispersion medium, that means it shows low solubility or is even practically insoluble in the dispersion medium which forms the continuous phase.
  • water, water-based or aqueous solutions or mixtures are used to form the continuous or external phase.
  • the aqueous mixture can be prepared or provided in different ways.
  • a surfactant solution or mixture preferably in water, can be prepared and added to the composition comprising the mesogenic medium and the polymerizable compound(s).
  • the provided aqueous mixture is then agitated, in particular mechanically agitated, to obtain nanodroplets comprising the polymerizable compound(s) and the LC medium according to the invention dispersed in an aqueous phase. Agitation or mixing can be carried out using high-shear mixing.
  • high-performance dispersing devices using the rotor-stator principle can be used, such as commercially available Turrax (IKA).
  • IKA Turrax
  • high-shear mixing may be replaced by sonication, in particular high power ultrasound. It is also possible to combine sonication and high-shear mixing, wherein preferably sonication precedes high-shear mixing.
  • homogenizer optionally and preferably used in addition to the above described mixing, can further favourably influence the preparation of the nanodispersion, in particular nanoemulsion, by setting or adjusting and respectively reducing droplet size and by also making the droplet size distribution narrower, i.e. improving uniformity of the particle size. It is particularly preferred when the high-pressure homogenization is repeated, especially for several times such as three, four or five times.
  • a commercially available Microfluidizer Microfluidizer (Microfluidics) can be used.
  • a high-pressure homogenizer is used in step (b) of the preparation method according to the invention.
  • nanocapsules comprising a polymeric shell and a core which contains the mesogenic medium.
  • nanocapsules according to the invention is not limited thereto and which may also be prepared by other methods, e.g. by encapsulation with a preformed polymer, coacervation, solvent evaporation, or by a solute co-diffusion method, in the present invention it was
  • nanocapsules comprising LC medium can be favourably prepared by a process using in situ polymerization. Furthermore, it was recognized that, instead of providing a ready-made polymer to encapsulate LC medium, encapsulation of the mesogenic medium on the nanoscale can favourably be performed starting in situ from polymer precursors. Thus the use of a preformed polymer, and also an emulsifier specifically provided therewith, can favourably be avoided. In this respect the use of a premade polymer as given may make formation and stabilization of a nanoemulsion difficult while it furthermore may limit the adjustability of the overall process.
  • the in situ polymerization process is not particularly limited, and for example interfacial polymerization can be used. However, preferably the in situ polymerization according to the invention is in particular based on
  • the polymerizable compound(s) is (are) at least partially soluble or respectively at least partially solubilized in the phase comprising the mesogenic medium, preferably the one or more polymerizable
  • PIPS polymerization-induced phase separation
  • the provided LC medium as set forth above and below is suitably stable with respect to the encapsulation process, in particular the polymerization, and the conditions associated therewith, such as exposure to heat or UV light, e.g. from a UV lamp in the wavelength range from 300 nm to 380 nm.
  • the choice of wavelength is favourably not limited by the UV cutoff of glass, but can be rather set e.g. in view of the material properties and stability of the composition.
  • the present process conveniently utilizes in situ polymerization and is favourably and preferably based on polymerization combined with phase separation, in particular a combination of nanodispersion and PIPS.
  • the process provides significant advantages in terms of providing a controlled and adaptable preparation method.
  • the nanocapsules obtained by or respectively obtainable from this process show suitable and tunable particle size, while at the same time giving favourably high particle size uniformity, i.e. favourably low polydispersity, and in turn advantageously homogeneous product properties. It was surprisingly found that the setting of a suitable capsule nanosize while furthermore observing and achieving a low polydispersity can have a favourable influence on the operating voltage.
  • the electro- optical parameters of the obtained nanocapsules and in particular of the LC medium contained therein can be favourably set and tuned.
  • the size given by the nanodroplets sets the length scale or volume of the transformations or respectively separations, leading to polymerization induced nanophase separation.
  • the droplet interface can serve as a template for the encapsulating polymeric shell.
  • the polymer chains or networks forming or starting to form in the nanodroplets may segregate to or be driven to or accumulate at the interface with the aqueous phase, where polymerization may proceed and also terminate to form a closed
  • the forming or respectively formed polymeric shell is substantially immiscible in both the aqueous phase as well as the LC medium.
  • the polymerization can ensue, be promoted and/or continue at the interface between the aqueous phase and the phase comprising the LC medium.
  • the interface can act as a diffusion barrier and as a reaction site.
  • the characteristics, in particular the structure and the building blocks of the polymer, of the forming and formed interface of the capsules can influence the material properties, in particular LC alignment, e.g. through homeotropic anchoring, anchoring energy and switching behaviour in response to an electric field.
  • the anchoring energy or strength is reduced to favourably influence electro-optical switching, wherein e.g. the polymer surface morphology and polarity can be suitably set and adjusted.
  • the surfactant(s) used according to step (b) can be incorporated in the polymeric capsule shell, at least in part, and in particular at the interface with the LC in the interior of the capsule.
  • Such incorporated surfactant molecules at the interface may favourably influence the electro- optical performance and reduce the operating voltage, in particular by setting or tuning the interfacial properties and interactions.
  • the surfactant may favourably influence alignment of the LC molecules, e.g. promoting a homeotropic alignment resulting in a radial configuration.
  • the surfactant molecules may influence the morphology and the physicochemical attributes of the interior polymer surface such that the anchoring strength is reduced.
  • the surfactant provided according to step (b) thus not only contributes to the advantageous process according to the invention, but it may also provide benefits in the obtained nanocapsules.
  • two surfactants or a surfactant and another additive are used in step (b).
  • agents which can respectively or together contribute to influencing e.g. wettability, solubility, viscosity, polarity or hydrophobicity.
  • Such optional additives further provided in step (b) may likewise preferably reside or accumulate at the interface.
  • the combined elements of the process can favourably result in the preparation of a large multitude of individual, dispersed or respectively dispersible nanocapsules which each have a polymeric shell and a core comprising LC material, wherein the used surfactant(s) can contribute to a favourably low tendency for agglomeration.
  • phase separation and the properties of the formed polymeric shell in particular stability and immiscibility with LC component, can be advantageously influenced by optionally and preferably crosslinking the forming or respectively formed polymer chains.
  • the capsule properties can already be sufficiently good. It was recognized that the respective miscibilities, solubilities and
  • the encapsulation process is based on polymerization reaction, i.e. that a specific dynamic process is underlying the capsule formation.
  • the polymerizable compound(s) used for the encapsulation has (have) a suitable miscibility with the LC medium, while the formed capsule shell polymer exhibits a suitably low solubility with the LC material.
  • polymerization conversion or completion can be surprisingly high and the amount of residual unreacted polymerizable compound favourably low. This can ensure that the properties and performance of the LC medium in the formed capsules are not or only minimally affected by residual reactive monomers.
  • step (c) the dispersed nanodroplets are subjected to
  • the polymerizable compound(s) contained in, or respectively mixed with, the nanodroplets are polymerized.
  • this polymerization leads to PIPS.
  • the nanocapsules having a core-shell structure as described above and below are formed.
  • the obtained or respectively obtainable nanocapsules are typically spherical, substantially spherical or spheroidal. In this respect some shape asymmetry or small deformation may be beneficial, e.g. in terms of the operating voltage.
  • Polymerization in the emulsion droplets and at each droplet interface can be carried out using conventional methods.
  • the polymerization can be carried out in one or more steps.
  • polymerization of the polymerizable compound(s) in the nanodroplets is preferably achieved by exposure to heat or to actinic radiation, wherein exposure to actinic radiation means irradiation with light, like UV light, visible light or IR light, irradiation with X-rays or gamma rays, or irradiation with high-energy particles, such as ions or electrons.
  • free radical polymerization is carried out.
  • a shell having more than one layer may be prepared, e.g. a shell structure with two layers, wherein for the additional polymerization step(s) further reactive monomers are provided.
  • additional polymerization step(s) further reactive monomers are provided.
  • the shell layers may have different compositions and respectively different properties.
  • a shell may be formed with a more lipophilic inner layer facing the core and a more hydrophilic outer layer facing the exterior environment, e.g. the binder in a composite film.
  • Polymerization can be carried out at a suitable temperature.
  • polymerization is performed at a temperature below the clearing point of the mesogenic mixture. In an alternative embodiment it is however also possible to carry out the polymerization at or above the clearing point.
  • polymerization is carried out by heating the emulsion, i.e. by thermal polymerization, for example by thermal polymerization of acrylate and/or methacrylate compound(s).
  • thermal polymerization for example by thermal polymerization of acrylate and/or methacrylate compound(s).
  • thermal polymerization for example by thermal polymerization of acrylate and/or methacrylate compound(s).
  • thermally initiated free radical polymerization of the reactive polymerizable precursors leading to the nanoencapsulation of the LC material is particularly preferred.
  • polymerization is carried out by photoirradiation, i.e. with light, preferably UV light.
  • a source for actinic radiation for example a single UV lamp or a set of UV lamps can be used. When using a high lamp power the curing time can be reduced.
  • Another possible source for photoradiation is a laser, like e.g. a UV laser, a visible laser or an IR laser.
  • Suitable and conventionally used thermal initiators or photoinitiators can be added to the composition to facilitate the reaction, for example azo compounds or organic peroxides such as Luperox type initiators.
  • suitable conditions for the polymerization and suitable types and amounts of initiators are known in the art and are described in the literature.
  • a photoinitiator when polymerizing by means of UV light, a photoinitiator can be used that decomposes under UV irradiation to produce free radicals or ions that start the polymerization reaction.
  • a radical photoinitiator is used for polymerizing acrylate or methacrylate groups.
  • a cationic photoinitiator is used for polymerizing vinyl, epoxide or oxetane groups preferably a cationic photoinitiator is used.
  • a thermal polymerization initiator that decomposes when heated to produce free radicals or ions that start the polymerization.
  • Typical radical photoinitiators are for example the commercially available Irgacure® or Darocure® (Ciba Geigy AG, Basel, Switzerland).
  • a typical cationic photoinitiator is for example UVI 6974 (Union Carbide).
  • initiators are used that are well soluble in the nanodroplets but which are water insoluble, or at least substantially water insoluble.
  • azobisisobutyronitrile AIBN
  • AIBN azobisisobutyronitrile
  • water soluble initiators may be provided, such as for example 2,2'-azobis(2-methylpropionamide) dihydrochloride (AIBA).
  • AIBA 2,2'-azobis(2-methylpropionamide) dihydrochloride
  • the polymerizable material can additionally comprise one or more additives, such as for example catalysts, sensitizers, stabilizers, inhibitors and chain transfer agents.
  • the polymerizable material may also comprise one or more stabilizers or inhibitors to prevent undesired spontaneous polymerization, like for example the commercially available Irganox® (Ciba Geigy AG, Basel, Switzerland).
  • stabilizers or inhibitors like for example the commercially available Irganox® (Ciba Geigy AG, Basel, Switzerland).
  • chain transfer agents By adding one or more chain transfer agents to the polymerizable material the properties of the obtained or respectively obtainable polymer may be modified.
  • chain transfer agents By using chain transfer agents the length of the free polymer chains and/or the length of the polymer chains between two crosslinks in the polymer can be adjusted, wherein typically the polymer chain length in the polymer decreases when the amount of the chain transfer agent is
  • Polymerization is preferably performed under an inert gas atmosphere, for example nitrogen or argon, more preferably in a heated nitrogen atmosphere. But also polymerization in air is possible. It is furthernnore preferred that polymerization is carried out in the presence of an organic solvent, wherein preferably the organic solvent is provided in the composition comprising the LC medium.
  • the use of the organic solvent for example hexadecane or 1 ,4-pentanediol, can be favourable in terms of adjusting the solubility of the reactive compound(s) with the LC material and to stabilize the nanodroplets, and it can also be beneficial in influencing phase separation. It is however preferred that the amount of organic solvent, if used at all, is limited, typically to below 25% by weight, based on the overall composition, more preferably to less than 20% by weight, and in particular to less than 15% by weight.
  • the formed polymer shell suitably exhibits low solubility, i.e. is substantially insoluble, in respect of both the LC material as well as water. Furthermore, in the process coagulation or respectively aggregation of the produced nanocapsules can suitably and favourably be limited or even avoided.
  • the forming polymer or respectively the formed polymer in the shell is crosslinked.
  • Such crosslinking can provide benefits in forming a stable polymeric shell and in giving suitable containment and barrier functionality, while maintaining sufficient mechanical flexibility.
  • the process according to the invention thus provides encapsulation and confinement of the mesogenic medium, while maintaining the electro-optical performance and in particular electric responsiveness of the LC material.
  • the composition as well as process conditions are provided such that stability of the LC material is maintained.
  • the LC can therefore exhibit in the formed nanocapsules favourable characteristics, for example suitably high ⁇ , suitably high ⁇ , a high favourable clearing point and a low melting point.
  • the LC material provided can show suitable and
  • step (d) of the present method one or more additives are added to the nanocapsules as obtained from carrying out step (c). It has surprisingly been found that even after the nanoparticles are formed their properties may still be influenced and adjusted by adding suitable additives.
  • the nanoparticles obtained through the polymerization generally already have adequate and useful properties, wherein the product characteristics are largely determined by the constitution and configuration of the LC material contained in the core and the already formed polymeric shell.
  • unexpectedly some attributes of the nanoparticles may still further be improved or changed by the additional step of adding, subsequent to preparing the encapsulated nanoparticles as such, one or more additives to the nanocapsules. Such improvement or adjustment of the nanocapsules may be especially beneficial under certain conditions or in view of specific applications.
  • the additive(s) according to the invention may be selected in view of achieving or adapting specific product characteristics.
  • agents may be used which favourably influence wettability and solubility, chemical resistance, e.g. against water, film formation and anti-foaming.
  • organic solvents or hydrophobic or hydrophobizing agents may be added.
  • the one or more additives are specifically chosen to be one or more surfactants. While these surfactants, which may be used as the additives according to step (d), can provide further benefits such as contributing to suitable film formation, a favourable dark state or suitably low hysteresis, it was
  • the one or more additives are used in combination with the one surfactant as provided in step (b).
  • the surfactant provided according to step (b) is used during the generation of the nanodroplets, and also in the following polymerization.
  • surfactant therein is useful during the process, e.g. by promoting and stabilizing the miniemulsion and also by preventing or minimizing particle agglomeration during and after the capsule formation.
  • surfactants can additionally influence the product properties such as capsule size, but also electro-optical properties as described above, e.g. by tuning the interface interactions between the shell and the core. They therefore serve several functions and should give suitable performance during the
  • the additive(s), preferably the surfactant(s), used in step (d) are only added after the capsules are formed. They can therefore generally be chosen independently from the requirements of the emulsion and polymerization steps. In one case however the additive(s), preferably surfactant(s), may be chosen in view of the surfactant, and also the optionally included additive, provided according to step (b), i.e. be matched or adjusted thereto, and may even be the same surfactant. Therefore, in an embodiment the additive according to step (d) is chosen to be the same as the surfactant as provided in step (b).
  • the surfactant according to step (d) may be chosen independently and more freely, e.g. in view of other criteria.
  • the additive of step (d) is provided in view of lowering the operating voltage. Therefore, in another embodiment the additive according to step (d) is different from the surfactant as provided in step (b). in the process stable nanocapsules are produced which are suitably dispersed. After obtaining the nanocapsules optionally and preferably the aqueous phase can be removed, or respectively the amount of water can be reduced or depleted, or alternatively the aqueous phase can be exchanged for another dispersion medium.
  • the dispersed or respectively dispersible nanocapsules are substantially or fully separated from the aqueous phase, for example by filtration or centrifugation.
  • filtration e.g. membrane filtration, dialysis, cross-flow filtration and in particular cross-flow filtration in combination with dialysis, and/or centrifugation techniques can be used.
  • Filtration and/or centrifugation can provide further benefits by, for example, removing excess or unwanted or even residual surfactant as provided in step (b). It is thus possible to not only provide concentration of the nanocapsules but also purification, e.g. by removing contaminants, impurities or unwanted ions. Preferably and favourably the amount of surface charge of the capsules is kept at a minimum. Based on the mechanical stability the nanocapsules can be subjected to the separation techniques with relative ease, e.g. using evaporation or extraction methods. It is also possible to dry the
  • drying means removing the dispersion medium but leaving the contained LC material inside the capsules.
  • Conventional techniques such as drying in air, critical point drying and freeze-drying, in particular freeze-drying can be used.
  • the one or more additives can be added to the nanocapsules before the optional further step of depleting, removing or exchanging the aqueous phase.
  • the one or more additives preferably the one or more surfactants, can be added to the nanocapsules after the optional further step of depleting, removing or exchanging the aqueous phase. It is also possible to add the additive, preferably surfactant, both before and after the depletion, removal or exchange of the aqueous phase.
  • the additive preferably surfactant
  • a suitable solvent e.g. water or an aquoues solvent, isopropanol or acetone.
  • the nanocapusles and the additive are then suitably mixed, e.g. using stirring, sonication and/or heating.
  • the additives, in particular surfactants, used according to step (b) and also to optional step (d) can each alone or in combination favourably influence the nanocapsule properties by influencing the polymeric shell and even the LC material, at least through interactions at the interior interface of the capsule wall.
  • the surfactant can adsorp to and in certain cases or under certain conditions penetrate, dissolve in or even permeate or pass through the polymeric composition that forms the capsule shell such that it can adjust the shell properties, for example with respect to charging, conductivity or permittivity.
  • the surfactant molecules may also play a role at the interface between the polymeric shell and the LC material, e.g. influence or reduce the anchoring energy of the LC material with the polymer shell surface or influence the alignment of LC molecules.
  • the elastic constants or viscosities of the material and in turn the electro-optical properties thereof may also be changed.
  • surfactant or additive molecules are located at the exterior surface of the nanocapsules interactions, such as solubility and wettability, with the environment may be changed and favourably adjusted, e.g. in view of the compatibility with a binder.
  • water or aqueous solutions are favourably used as dispersing medium.
  • the provided composition as well as the produced nanocapsules show suitable stability and chemical resistance to the presence of water, for example with respect to hydrolysis.
  • the amount of water may be reduced or even substantially minimized by providing or adding polar media, preferably non-aqueous polar media, containing for example formamide or ethylene glycol or hydrofluorocarbons.
  • the process according to the invention provides a large multitude of individual nanocapsules which are dispersible and even redispersible.
  • the capsules can thus be further used and applied to various environments with ease and flexibility. Due to their stability storing of the capsules, in particular with suitably long shelf life, before use in various applications also becomes possible. However, immediate further processing is also an option that is favourably provided. In this respect the capsules are suitably stable during processing, in particular for coating applications.
  • capsule particle size can suitably be tuned while keeping polydispersity low, for example by adjusting the amount of surfactant in the composition. It was surprisingly found that a suitably set, uniform capsule size can be particularly advantageous in view of reducing the operating voltage in electro-optical applications.
  • the additive added to the nanodroplets before the polymerization or as added in step (d) can advantageously further contribute to reducing the operating voltage.
  • the compositions provided according to step (a) of the present method show suitable behaviour and performance both during the preparation process as well as in the obtained product. This means the compositions are on the one hand well suited for
  • nanoencapsulation i.e. for the formation of nanocapsules, wherein the formed capsule shell of each capsule contains the LC medium in a nano- sized volume.
  • the formed capsule shell of each capsule contains the LC medium in a nano- sized volume.
  • they are also useful to obtain favourable product performance, e.g. in electro-optical applications.
  • compositions as provided according to the invention allow to prepare advantageous nanocapsules containing a mesogenic medium in a favourable process, in particular a process using in situ polymerization, especially a process which is based on PIPS, wherein the compositions have a favourable performance in the process.
  • these compositions allow to obtain nanocapsules which provide significant benefits in terms of their physical and chemical attributes, in particular with respect to their electro-optical properties and their suitability in electro-optical devices.
  • the inventive compositions are thus useful in the preparation of nanocapsules.
  • compositions can be provided by suitably mixing or blending the components.
  • the composition according to the invention comprises the LC medium in an amount, based on the overall composition, from 5% by weight to 95% by weight, more preferably from 15% by weight to 75% by weight, in particular from 25% by weight to 65% by weight.
  • composition according to the invention further comprises one or more organic solvents. It was found that the provision of organic solvent can provide additional benefits in the process for preparing the inventive nanocapsules.
  • the one or more organic solvents can contribute to setting or adapting the components solubilities or
  • the solvent may act as a suitable cosolvent, wherein the solvent power of other organic constituents may be enhanced or influenced. Furthermore, the organic solvent(s) can have a favourable influence during phase separation induced by the polymerization of the polymerizabe compound(s).
  • organic solvent(s) standard organic solvents can be used.
  • the solvent(s) can be selected, for example, from aliphatic hydrocarbons, halogenated aliphatic hydrocarbons, aromatic hydrocarbons, halogenated aromatic hydrocarbons, alcohols, glycols or their esters, ethers, esters, lactones, ketones, and the like, more preferably from diols, n-alkanes and fatty alcohols. It is also possible to use binary, ternary or higher mixtures of the above solvents.
  • the solvent is selected from one or more of cyclohexane, tetradecafluorohexane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, hexadecan-1 -ol, 2-isopropoxy ethanol, octyldodecanol, 1 ,2-ethanediol, 1 ,2-propanediol, 1 ,3-butanediol, 1 ,4-butanediol, pentanediol, in particular 1 ,4-pentanediol, hexanediol, in particular 1 ,6-hexanediol,
  • the organic solvent used comprises hexadecane or 1 ,4-pentanediol, in particular is hexadecane or 1 ,4-pentanediol.
  • a combination comprising hexadecane and 1 ,4-pentanediol is used.
  • the organic solvent(s), in particular hexadecane, is (are) preferably added in an amount, based on the overall composition, from 0.1 % by weight to 35% by weight, more preferably from 1 % by weight to 25% by weight, in particular from 3% by weight to 17% by weight.
  • the organic solvent can enhance solubility or respectively solubilisation, or dilute other organic components and may contribute to tuning the viscosity.
  • the organic solvent acts as a hydrophobic agent. Its addition to the dispersed phase of the nano- or miniemulsion can influence, in particular increase, the osmotic pressure in the nanodroplets. This can contribute to stabilizing the "oil-in-water" emulsion by suppressing Ostwald ripening.
  • Preferable organic solvents serving as hydrophobic agents have a solubility in water which is lower than the solubility of the liquid crystal in water, while they are soluble in the liquid crystal.
  • the organic solvent preferably the hydrophobic agent, can act as a stabilizer or co-stabilizer.
  • one or more polymenzable compounds are provided as the precursors for the polymeric shell or wall containing or respectively surrounding the LC medium.
  • the polymenzable compounds have at least one polymerizable group.
  • the one or more polymerizable compounds are chosen such that they have a suitable and sufficient solubility in the LC component or phase. Moreover, they need to be susceptible to the polymerization conditions and
  • the polymerizable compound(s) can undergo a suitable polymerization with a high conversion rate, leading to a favourably low amount of residual unreacted polymerizable compound after the reaction This can provide benefits in terms of stability and performance of the LC medium.
  • the polymerizable component is chosen such that the polymer forming therefrom is suitably phase-separating or respectively that the polymer formed thereform is phase-separated to constitute the polymeric capsule shell.
  • solubility of the LC component in the shell polymer and swelling or gelling of the formed polymer shell are favourably avoided or respectively minimized, wherein the amount and also the constitution of the LC medium remains substantially constant in the formed capsules.
  • favourably preferential solubility of any LC compound of the LC material in the wall is minimized or avoided.
  • the polymerization or curing time depends, inter alia, on the reactivity and the amount of the polymerizable material, the thickness of the formed capsule shell and, if present, the type and amount of polymerization initiator as well as the reaction temperature and/or the power of the radiation, e.g. of the UV lamp.
  • the polymerization or curing times and conditions may be chosen such as to e.g. obtain a fast process for polymerization, or
  • completeness of conversion and separation of the polymer may be beneficially influenced. It can thus be preferred to have short polymerization and curing times, for example below 5 minutes, while in an alternative embodiment longer polymerization times, such as more than one hour or even at least three hours, can be preferred.
  • non-mesogenic polymerizable compounds i.e.
  • an organic solvent is additionally provided.
  • polymerizable mesogenic or liquid-crystalline compounds also known as reactive mesogens (RMs).
  • RMs reactive mesogens
  • These compounds contain a mesogenic group and one or more polymerizable groups, i.e.
  • the polymerizabe compound(s) according to the invention comprise(s) only reactive mesogen(s), i.e. all the reactive monomers are mesogens.
  • RMs can be provided in combination with one or more non-mesogenic polymerizable compounds.
  • the RMs can be monoreactive or di- or multireactive. RMs can exhibit favourable solubility or respectively miscibility with the LC medium.
  • the polymer forming or respectively formed therefrom shows suitable phase separation behaviour.
  • Preferred polymerizable mesogenic compounds comprise at least one polymerizable group as a terminal group and a mesogenic group as a core group, further preferably comprising a spacer and/or a linking group between the polymerizable group and the mesogenic group.
  • 2-methyl-1 ,4-phenylene- bis[4[3(acryloyloxy)propyloxy]benzoate (RM 257, Merck KGaA) is used.
  • mesogenic group may also be polymerizable groups.
  • the use of mesogenic polymerizable compounds is avoided.
  • the one or more polymerizable compounds are selected from vinylchloride, vinylidenechloride, acrylnitriles, methacrylnitriles, acrylamides, methacrylamides, methyl-, ethyl-, n- or tert.- butyl-, cyclohexyl-, 2-ethylhexyl-, phenyloxyethyl-, hydroxyethyl-, hydroxypropyl-, 2-5 C- alkoxyethyl-, tetrahydrofurfurylacrylat.es or methacrylates, vinylacetates, - propionates, -acrylates, -succinates, N-vinylpyrrolidones, N-vinylcarbazoles, styrenes, divinylbenzenes, ethylenediacrylates, 1 ,6-hexan
  • tripropyleneglycoltriacrylat.es pentaerythritoltriacrylat.es,
  • the polymerizable or reactive group is preferably selected from a vinyl group, an acrylate group, a methacrylate group, a fluoroacrylate group, an oxetane group or an epoxy group, especially preferably an acrylate group or a methacrylate group.
  • the one or more polymerizable compounds are selected from acrylates, methacrylates, fluoroacrylates and vinyl acetate, wherein the composition more preferably further comprises one or more direactive and/or trireactive polymerizable compounds, preferably selected from diacrylates, dimethacrylates, triacrylates and trimethacrylates.
  • the one or more polymerizable compounds (ii) as set forth above comprise polymerizable groups selected from one, two or more acrylate, methacrylate and vinyl acetate groups, wherein the compounds preferably are non-mesogenic compounds.
  • the composition according to the invention comprises one or more monoacrylates, preferably added in an amount, based on the overall composition, from 0.1 % by weight to 75% by weight, more preferably from 0.5% by weight to 50% by weight, in particular from 2.5% by weight to 25% by weight.
  • Particularly preferred monoreactive compounds are selected from methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, nonyl acrylate, 2-ethyl-hexyl acrylate, 2-hydroxy-ethyl acrylate, 2- hydroxy-butyl acrylate, 2,3-dihydroxypropyl acrylate and glycidyl acrylate. Additionally or alternatively vinyl acetate may be added.
  • composition according to the invention comprises, optionally in addition to the above monoacrylates, one or more monomethacrylates, preferably added in an amount, based on the overall composition, from 0.1 % by weight to 75% by weight, more preferably from 0.5% by weight to 50% by weight, in particular from 2.5% by weight to 25% by weight.
  • Particularly preferred monoreactive compounds are selected from methyl methacrylate, ethyl methacrylate, propyl methacrylate, ispropyl methacrylate, butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, nonyl methacrylate, 2-ethyl-hexyl methacrylate, 2- hydroxy-ethyl methacrylate, 2-hydroxy-butyl methacrylate, 2,3- dihydroxypropyl methacrylate, glycidyl methacrylate, stearyl methacrylate, adamantyl methacrylate and isobornyl methacrylate.
  • At least one crosslinking agent is added to the composition, i.e. a polymerizable compound containing two or more polymerizable groups.
  • Crosslinking of the polymeric shell in the prepared particle can provide additional benefits, especially with respect to further improve stability and containment, and to tune or respectively reduce susceptibility to swelling, in particular swelling due to solvent.
  • direactive and multireactive compounds can serve to form polymer networks of their own and/or to crosslink polymer chains formed substantially from polymerizing monoreactive compounds.
  • crosslinkers known in the art can be used. It is particularly preferred to additionally provide direactive or multireactive acrylates and/or methacrylates, preferably added in an amount, based on the overall composition, from 0.1 % by weight to 75% by weight, more preferably from 0.5% by weight to 50% by weight, in particular from 2.5% by weight to 25% by weight.
  • Particularly preferred compounds are selected from ethylene diacrylate, propylene diacrylate, butylene diacrylate, pentylene diacrylate, hexylene diacrylate, glycol diacrylate, glycerol diacrylate, pentaerythritol tetraacrylate, ethylene dimethacrylate, also known as ethyleneglycol dimethacrylate, propylene diamethcrylate, butylene dimethacrylate, pentylene dimethacrylate, hexylene dimethacrylate, tripropylene glycol diacrylate, glycol dimethacrylate, glycerol dimethacrylate, trimethylpropane trimethacrylate and pentaerythritol triacrylate.
  • the ratio of monoreactive monomers and di- or multireactive monomers can be favourably set and adjusted to influence the polymer make-up of the shell and its properties.
  • step (b) of the present method the one surfactant is used to disperse the composition as nanodroplets in an aqueous
  • this surfactant may be mixed and included in the composition as provided in step (a).
  • the surfactant is added subsequent to step (a), preferably as an aqueous mixture.
  • the surfactant is provided in the aqueous phase and then mixed with the composition as provided in (a).
  • the surfactant can be prepared or provided separately in an initial step, and then added to the other components.
  • the surfactant can be prepared or provided as an aqueous mixture or composition, which is then added to the other
  • the one surfactant is provided as aqueous surfactant.
  • the surfactant can be useful in lowering the surface or interfacial tension and in promoting emulsifying and dispersion.
  • Conventional surfactants known in the art can be used, including anionic surfactants, for example sulfate, e.g. sodium lauryl sulfate, sulfonate, phosphate and carboxylate surfactants, cationic surfactants, for example secondary or tertiary amine and quaternary ammonium salt surfactants, zwitterionic surfactants, for example betaine, sultaine and phospholipid surfactants, and nonionic surfactants, for example long chain alcohol and phenol, ether, ester or amide nonionic surfactants.
  • anionic surfactants for example sulfate, e.g. sodium lauryl sulfate, sulfonate, phosphate and carboxylate surfactants
  • cationic surfactants for example secondary or tertiary amine and quatern
  • nonionic surfactant is used.
  • the use of nonionic surfactant can provide benefits during the process of preparing the nanocapsules, in particular with respect to dispersion formation and stabilization as well as in PIPS. It was furthermore recognized that it can be advantageous to avoid charged surfactants in case surfactant, for example residual surfactant, is comprised in the formed nanocapsules.
  • the use of nonionic surfactant and the avoidance of ionic surfactant can thus be beneficial in terms of stability, reliability and the electro-optical
  • Preferable compounds are selected from the group of polyoxyethylene glycol alkyl ether surfactants, polyoxypropylene glycol alkyl ether surfactants, glucoside alkyl ether surfactants, polyoxyethylene glycol octylphenol ether surfactants such as TritonTM X-100, polyoxyethylene glycol alkylphenol ether surfactants, glycerol alkyl ester surfactants, polyoxyethylene glycol sorbitan alkyl ester surfactants such as polysorbate, sorbitan alkyl ester surfactants, cocamide monoethanol-amine, cocamide diethanolamine and
  • the used surfactant(s) is (are) selected from polyoxyethylene glycol alkyl ether surfactants, which comprise commercially available Brij ® agents (from Sigma-Aldrich). Particular preference is given to a surfactant which comprises, more preferably consists of, tricosaethylene glycol dodecyl ether.
  • the commercially available Brij ® L23 (Sigma-Aldrich), also referred to as Brij 35 or polyoxyethylene (23) lauryl ether, is used.
  • Brij ® 58 also known as polyethylene glycol hexadecyl ether or polyoxyethylene (20) cetyl ether
  • Brij ® L4 also known as polyethylene glycol dodecyl ether or polyoxyethylene (4) lauryl ether
  • alkylaryl polyether alcohol preferably commercially available TritonTM X-100, and in particular 4-(1 ,1 ,3,3- tetramethylbutyl)phenyl-polyethylene glycol and compounds of the formula Ci 4 H22O(C 2 H 4 O)nH where n is 9 and10.
  • octylphenol ethoxylates surfactants such as ECOSURFTM surfactants
  • TERGITOL ® surfactants (commercially available from Dow), e.g. TERGITOL ® 15-S-9 can preferably be used.
  • organosilicones such as polyethersiloxanes and polyether siloxane copolymers, e.g commercially available TEGO ® additives (Evonik), preferably TEGO ® Wet 270, and in particular a surfactant comprising, preferably consisting of, 3-[methyl-bis (trimethylsilyloxy)silyl]propyl-polyethylene glycol, or preferably TEGO ® Wet 280.
  • TEGO ® WET 260 and TEGO ® Wet KL 245 and the silicone surfactants described in US 7,618,777 can be preferably used, e.g.
  • fluorosurfactant(s) preferably FluorN 322, and in particular a surfactant comprising and more preferably consisting of 2-[[2-methyl-5-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro- octoxycarbonylamino)phenyl]carbamoyloxy]ethyl-polypropylene glycol.
  • fluorosurfactant(s) such as commercially available FluorN 561 and FluorN 562 (Cytonix) can also preferably be used.
  • poloxamer copolymers preferably copolymers comprising units of polyethylene oxide and
  • polypropylene oxide more preferably a triblock copolymer consisting of a central hydrophobic block of polypropylene glycol flanked by two hydrophilic blocks of polyethylene glycol, and in particular commercially available poloxamer 407 or Pluronic ® F-127 (BASF) or Synperonic PE/F127 (Croda).
  • Pluronic ® additves e.g. Pluronic ® 10R5
  • Pluronic ® 10R5 may preferably be used
  • the surfactant is preferably provided in an amount, relative to the
  • composition as provided in step (a) of less than 30% by weight, more preferably less than 25% by weight, even more preferably less than 20% by weight, and in particular less than 15% by weight.
  • the surfactant is provided as a prepared aqueous mixture
  • the amount of water is not considered to contribute to the overall composition in terms of weight, i.e. water is excepted in this respect.
  • polymeric surfactants or surface active polymers or block copolymers can be used.
  • polymerizable surfactant i.e.
  • surfactant comprising one or more polymerizable groups
  • Such polymerizable surfactant can be used alone, i.e. as the only surfactant provided, or in combination with non-polymerizable surfactant.
  • a polymerizable surfactant is provided in addition and in combination with a non-polymerizable surfactant.
  • This optional provision of polymerizable surfactant can provide the combined benefits of contributing to suitable droplet formation and stabilization as well as to the formation of stable polymeric capsule shells. Therefore, these compounds act at the same time as surfactant and polymerizable compound.
  • This embodiment which includes the use of polymerizable surfactant can have an advantage in that the template properties at the amphiphilic interface may be particularly well preserved during polymerization.
  • the polymerizable surfactant may not only take part in the polymerization reaction, but may be favourably incorporated as a building block into the polymer shell, and more preferably also at the shell surface such that it may advantageously influence the interface interactions.
  • silicone polyether acrylate is used as polymerizable surfactant, more preferably cross-linkable silicone polyether acrylate.
  • PEG methyl ether methacrylate is used.
  • the composition is added to an aqueous mixture, wherein the composition is dispersed in an aqueous phase.
  • the provided surfactant(s) can favourably contribute to form and stabilize the dispersion, in particular emulsion, and to promote homogenization.
  • the amount of water is not considered to contribute to the overall composition in terms of weight, i.e. water is excepted in this respect.
  • water is provided as purified water, in particular deionized water.
  • the composition as provided in step (a) is then dispersed as nanodroplets in an aqueous phase.
  • the composition may contain additional compounds such as one or more pleochroic dyes, in particular dichroic dye(s), one or more chiral compounds and/or other customary and suitable additives.
  • Pleochroic dyes preferably are dichroic dyes and can be selected from for example azo dyes and thiadiazol dyes.
  • Suitable chiral compounds are for example standard chiral dopants like R- or S-81 1 , R- or S-101 1 , R- or S-201 1 , R- or S-301 1 , R- or S-401 1 , R- or S-501 1 , or CB 15 (all available from Merck KGaA, Darmstadt, Germany), sorbitols as described in WO 98/00428, hydrobenzoins as described in GB 2,328,207, chiral binaphthols as described in WO 02/94805, chiral binaphthol acetals as described in WO 02/34739, chiral TADDOLs as described in WO 02/06265, or chiral compounds having fluorinated linkage groups as described in WO 02/06196 or WO 02/06195.
  • substances can be added to change the dielectric anisotropy, the optical anisotropy, the viscosity and/or the temperature dependence of electro-optical parameters of the LC material.
  • the mesogenic medium according to the invention comprises one or more compounds of the formula I as set forth above.
  • the liquid-crystalline medium consists of 2 to 25, preferably 3 to 20 compounds, at least one of which is a compound of formula I.
  • the medium preferably comprises one or more, more preferably two or more, and most preferably three or more compounds of the formula I according to the invention.
  • the medium preferably comprises low molecular weight liquid-crystalline compounds selected from nematic or nematogenic substances, for example from the known classes of the azoxybenzenes, benzylidene-anilines, biphenyls, terphenyls, phenyl or cyclohexyl benzoates, phenyl or cyclohexyl esters of cyclohexanecarboxylic acid, phenyl or cyclohexyl esters of cyclohexylbenzoic acid, phenyl or cyclohexyl esters of cyclohexylcyclohexanecarboxylic acid, cyclohexylphenyl esters of benzoic acid, of cyclohexanecarboxylic acid and of cyclohexylcyclohexanecarboxylic acid, phenylcyclohexanes, cyclohexyl-biphenyls, phenyl
  • the 1 ,4-phenylene groups in these compounds may also be laterally mono- or difluorinated.
  • the liquid-crystalline mixture is preferably based on achiral compounds of this type.
  • the LC host mixture is a nematic LC mixture, which preferably does not have a chiral LC phase.
  • Suitable LC mixtures can have positive dielectric anisotropy. Such mixtures are described, for example, in JP 07-181 439 (A), EP 0 667 555, EP
  • the LC medium has negative dielectric anisotropy.
  • Such media are described in for example EP 1 378 557 A1 .
  • the one or more compounds of formula I are selected from the compounds of formulae la, lb, lc and Id
  • R 1 , R 2 , R 3 , R 4 , R 5 and R 6 denote, independently of one another, straight- chain or branched alkyl or alkoxy having 1 to 15 carbon atoms, preferably 1 to 7 carbon atoms, or straight-chain or branched alkenyl having 2 to 15 carbon atoms which is unsubstituted, monosubstituted by CN or CF3 or mono- or polysubstituted by halogen and wherein one or more CH2 groups may be, in each case independently of one another, replaced by -O-, -S-, -CO-, -COO-, -OCO-, -OCOO- or -C ⁇ C- in such a manner that oxygen atoms are not linked directly to one another,
  • X 1 and X 2 denote, independently of one another, F, CF3, OCF3 or
  • L 1 , L 2 , L 3 , L 4 and L 5 are, independently of one another, H or F, i is 1 or 2, and j and k are, independently of one another, 0 or 1 .
  • the one or more additives according to the invention are agents which may serve a favourable or suitable function during the preparation and especially can impart one or more advantageous or useful properties on the obtained product, or at least contribute thereto.
  • the additive may for example be useful to adjust material properties, solubilities or miscibilities, or provide benefits in terms of film forming capabilities.
  • the additive(s) may be provided before the polymerization step or according to step (d).
  • the additive(s) according to the invention is (are) (a) surfactant(s).
  • a surfactant is a surface active agent. This agent can lower the surface or interfacial tension between liquids or a liquid and a solid.
  • Surfactants herein can include, or respectively act as, detergents, wetting agents, emulsifiers, foaming agents and dispersants.
  • one or more surfactants are used.
  • the surfactant herein can promote or contribute to nandroplet formation and stabilization of the nanoemulsion. It may also be useful in setting or adjusting the size and size distribution of the droplets, and also of the produced nanocapsules.
  • the surfactant added according to step (d) can in one case be the same as used in step (b). However, this additive according to step (d) is added after the capsules are formed as such. At this stage other factors, i.e. factors which are different from droplet stabilization and setting of particle size, may be particularly addressed or considered. Therefore, additives serving also different or additional functions or influencing other or further properties may be used. In another case the surfactant added according to step (d) can thus be different from the surfactant as used in step (b), i.e. be another or second surfactant. Furthermore, also combinations of additives may be employed, such as a surfactant and a film forming agent.
  • additive in step (d) means surfactant.
  • conventional surfactants known in the art can be used, including anionic surfactants, for example sulfate, e.g. sodium lauryl sulfate, sulfonate, phosphate and carboxylate surfactants, cationic
  • surfactants for example secondary or tertiary amine and quaternary ammonium salt surfactants, zwitterionic surfactants, for example betaine, sultaine and phospholipid surfactants, and nonionic surfactants, for example long chain alcohol and phenol, ether, ester or amide nonionic surfactants, in particular alkyl polyethers and polyethoxy alcohols.
  • nonionic surfactant is used.
  • the use of nonionic surfactant and the avoidance of ionic surfactant can be beneficial in terms of stability, reliability and the electro-optical characteristics and performance of the nanocapsules, also in the composite system and electro-optical devices. Particular preference is given to polyethoxylated nonionic surfactant.
  • Preferable compounds are selected from the group of polyoxyethylene glycol alkyl ether surfactants, polyoxypropylene glycol alkyl ether surfactants, glucoside alkyl ether surfactants, polyoxyethylene glycol octylphenol ether surfactants such as Triton X-100, polyoxyethylene glycol alkylphenol ether surfactants, glycerol alkyl ester surfactants, polyoxyethylene glycol sorbitan alkyl ester surfactants such as polysorbate, sorbitan alkyl ester surfactants, cocamide monoethanol-amine, cocamide diethanolamine and
  • the used surfactant(s) is (are) selected from polyoxyethylene glycol alkyl ether surfactants, which comprise commercially available Brij ® agents (Sigma-Aldrich). Particular preference is given to a surfactant which comprises, more preferably consists of, tricosaethylene glycol dodecyl ether.
  • the commercially available Brij ® L23 also referred to as Brij 35 or polyoxyethylene (23) lauryl ether, is used.
  • Brij ® 58 also known as polyethylene glycol hexadecyl ether or polyoxyethylene (20) cetyl ether
  • Brij ® L4 also known as polyethylene glycol dodecyl ether or polyoxyethylene (4) lauryl ether.
  • alkylaryl polyether alcohol preferably commercially available Triton X-100, and in particular 4-(1 ,1 ,3,3- tetramethylbutyl)phenyl-polyethylene glycol and compounds of the formula Ci 4 H22O(C 2 H 4 O)nH where n is 9 and10.
  • octylphenol ethoxylates surfactants such as ECOSURFTM surfactants
  • TERGITOL® surfactants commercially available from Dow, e.g.
  • TERGITOL® 15-S-9 can preferably be used.
  • organosilicones such as polyethersiloxanes and polyether siloxane copolymers, e.g commercially available TEGO ® additives (Evonik), preferably TEGO ® Wet 270, and in particular a surfactant comprising, preferably consisting of, 3-[methyl-bis (trimethylsilyloxy)silyl]propyl-polyethylene glycol, or preferably TEGO ® Wet 280.
  • TEGO ® WET 260 and TEGO ® Wet KL 245 and the silicone surfactants described in US 7,618,777 can be preferably used, e.g. H3CSi(CH3)2OSiO(CH3)(CH2CH2CH2O(CH2CH 2 O)7CH3)Si(CH3)3.
  • fluorosurfactant(s) preferably FluorN 322, and in particular a surfactant comprising and more preferably consisting of 2-[[2-methyl-5-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro- octoxycarbonylamino)phenyl]carbamoyloxy]ethyl-polypropylene glycol.
  • fluorosurfactant(s) such as commercially available FluorN 561 and FluorN 562 (Cytonix) can also preferably be used.
  • poloxamer copolymers preferably copolymers comprising units of polyethylene oxide and
  • polypropylene oxide more preferably a triblock copolymer consisting of a central hydrophobic block of polypropylene glycol flanked by two hydrophilic blocks of polyethylene glycol, and in particular commercially available poloxamer 407 or Pluronic ® F-127 (BASF) or Synperonic PE/F127 (Croda).
  • BASF Pluronic ® F-127
  • Synperonic PE/F127 Croda
  • the capsules constitutes less than 10% by weight, more preferably less than 5% by weight, and in particular less than 2.5% by weight of the finally obtained capsules. It is furthermore preferred that the capsules contain the additive in an amount of at least 0.01 % by weight, more preferably at least 0.05% by weight based on the overall capsule weight.
  • composition as provided in step (a) is limited to an amount of 10% by weight or less, preferably is 5% by weight or less, more preferably is 2.5% by weight or less, and even more preferably is 1 % by weight or less.
  • the amount of additive, with respect to the composition as provided in step (a) is particularly preferably set in the range from 0.05% by weight to 1 % by weight, and even more preferably in the range from 0.1 % by weight to 1 % by weight.
  • nanocapsules which respectively comprise a polymeric shell, a core containing a mesogenic medium which comprises one or more compounds of formula I as set forth above and below, and one or more additives.
  • a polymeric shell a core containing a mesogenic medium which comprises one or more compounds of formula I as set forth above and below, and one or more additives.
  • nanocapsules are obtained by or are obtainable from carrying out the method according to the present invention. It was advantageously recognized that improved nanocapsules, in particular in view of a reduced operating voltage in electro-optical applications along with further beneficial properties as described above and below, are obtained by or obtainable from carrying out the method according to the present invention. Moreover, it has surprisingly been found that stable and reliable
  • nanocapsules can be provided which contain a mesogenic medium with favourable electro-optical properties as well as suitable reliability, while furthermore one or more additives, preferably one or more surfactants, can be incorporated which can provide or contribute to same and/or further benefits, such as lowering of the operating voltage.
  • nanocapsules according to the invention can be obtained by or respectively are obtainable from a process based on in situ polymerization, and in particular based on PIPS in a nanoemulsion.
  • a light modulating material which comprises nano-sized droplets (nanodroplets) of LC as a core encapsulated by a polymeric shell can be provided, wherein the nanocapsules as a whole and also the mesogenic medium contained therein have suitable and even improved properties.
  • the properties of the nanocapsules can be further influenced and adjusted by adding, preferably incorporating, the additive(s), preferably surfactant(s), as described above. It was surprisingly found that even after nanocapsules are prepared or provided as such the subsequent introduction of additive(s) may still contribute to and under certain conditions even further improve the characteristics and performance of the nanocapsules.
  • nanocapsules By providing the nanocapsules according to the invention it is possible to confine discrete amounts of LC material in nanovolumes, which are stably contained and individually addressable and which can be mounted or dispersed in different environments.
  • the LC material nanoencapsulated by a polymeric shell can be easily applied to and supported from a single substrate, which may be flexible and wherein the layer or film thickness can be variable or respectively varied.
  • the LC medium which is surrounded, i.e. enclosed by a polymeric wall is operable in at least two states.
  • the nanodroplets each provide only a comparatively small volume of LC. It was thus presently realized to preferably and favourably provide the LC component having a suitably large ⁇ , while furthermore exhibiting good transmission and good reliability, including in particular a suitable voltage holding ratio (VHR) and thermal and UV stability as well as relatively small rotational viscosity. Furthermore, the LC component can favourably be provided with suitable and reasonably high values for the dielectric
  • anisotropy ⁇ to obtain relatively small threshold voltages in electro-optical device applications.
  • the use of the surfactant as described above can further suitably reduce the operating voltage.
  • the interface area between the LC core and the polymeric shell is relatively large compared to the provided nanovolume and that therefore the respective properties of the polymeric shell component and the LC core component and their interrelations need to be particularly taken into consideration.
  • the interactions between the polymer and the LC component can favourably and suitably be set and adjusted, which is primarily obtainable on account of the provided
  • composition for nanoencapsulation according to the invention as well as the control and adaptability of the provided process of preparation.
  • the additive preferably surfactant, may further influence or change these interactions.
  • the interface interactions can favour or discourage the formation of any alignment or orientation in the LC nanodroplets.
  • the capsules may advantageously be only very weak scatterers of visible light.
  • the LC medium may in one case form a disordered phase with little or no orientation in the nanosized volumes, in particular an isotropic phase, which can for example provide excellent viewing angle behaviour.
  • having intrinsically an isotropic phase in the unpowered or non-addressed state can be advantageous in device applications in that a very good dark state may be realized, in particular when using polarizers.
  • polarizers As opposed to an occurence of for example a radial or bipolar orientation, it is believed that in one case such orientation may not happen, or at least be limited, on account of the small volume provided in the nanocapsules.
  • arrangement may occur, wherein in particular the interface interaction(s) can be used to induce or influence alignment and orientation in the LC medium, for example by setting or adjusting anchoring strengths with the capsule wall.
  • uniform, planar, radial or bipolar alignment may occur.
  • nanocapsules having respectively and individually LC orientation or alignment are randomly dispersed, overall an optical isotropy may be observed.
  • the spherical or spheroidal geometry along with curvature set a constraint or boundary condition for the nematic configuration as well as the alignment of the liquid crystal molecules, which can further depend on the anchoring of the LC at the capsule surface, the elastic properties and the bulk and surface energetics as well as the size of the capsules.
  • the electro-optical response in turn is dependent on the LC ordering and orientation in the nanocapsules.
  • any possible absence or presence of alignment and orientation of the encapsulated LC medium is independent of the substrate such that there is no need to provide an alignment layer on the substrate.
  • the nanocapsules are substantially optically isotropic or respectively show pseudo-isotropic optical properties. This allows to realize an excellent dark state when two crossed polarizers are used. Upon switching with an electric field, in particular in- plane switching, an axial configuration which is optically anisotropic can be obtained, where the induced birefringence causes transmission of light.
  • the LC material comprised in the nanocapsules has a radial configuration.
  • dielectrically positive or dielectrically negative LC media may be used.
  • the present invention provides favourable nanocapsules, i.e. capsules constituting nanocontainers having a polymeric shell, which optionally and preferably is crosslinked, filled with the LC material.
  • the nanocapsules furthermore comprise one or more additives as set forth above.
  • the capsules are individual and separate, i.e. discrete and dispersible particles having a core-shell structure.
  • the capsules can act individually but also collectively as light modulating material.
  • They can be applied to various environments and, depending on the dispersion medium, can be redispersed in different media.
  • they may be dispersed in water or an aqueous phase, dried, and dispersed in a binder, preferably a polymer binder.
  • the nanocapsules can also be referred to as nanoparticles.
  • the nanoparticles comprise nanoscale LC material surrounded by a polymer shell.
  • These nanoencapsulated liquid crystals may optionally additionally be embedded in a polymeric binder.
  • phase separation is less pronounced or less complete it can be possible that a polymer network is forming in the droplet interior such that capsules are obtained that exhibit a sponge-like or porous interior, wherein the LC material fills the voids.
  • the LC material is filling the pores in the sponge-like structure or network, while a shell encloses the LC material.
  • the separation between the LC material and the polymer may be at an intermediate level wherein the interface or boundary between the LC interior and the wall is only less pronounced and shows a gradient behaviour.
  • the comprised mesogenic medium can further contain one or more chiral dopants and/or one or more pleochroic dyes and/or other customary additives.
  • the nanocapsules according to the invention are obtained by or obtainable from polymerization of the composition as set forth above, and in particular from the efficient and controlled process described herein.
  • a shell polymer in particular by polymerizing the precursor compound(s) described above, which is well matched with respect to the LC component and which is compatible with the LC performance. It is preferred that the electrical impedance of the capsule polymer is at least equal to and more preferably larger than that of the LC material.
  • the additive may be useful to suitably adjust properties and performance in this regard.
  • the shell polymer can be advantageous in terms of dispersibility and avoidance of unwanted aggregation.
  • the shell polymer can be combined and function well with a binder, for example in a film-forming composite system and in particular in electro-optical applications.
  • the additive can also favourably influence the capsule properties in this regards, e.g. in view of avoiding aggregation or improving film forming.
  • nanocapsules encapsulated by a shell material component are characterized in that they are nano-sized. Preference is given to nanocapsules having an average size of not greater than 400 nm.
  • the nanocapsules have an average size, as determined by dynamic light scattering analysis, of not greater than 400 nm, more preferably of not greater than 300 nm, even more preferably of not greater than 250 nm.
  • Dynamic light scattering is a commonly known technique which is useful for determining the size as well as the size distribution of particles in the submicron region.
  • a commercially available Zetasizer (Malvern) may be used for the DLS analysis.
  • the average size of the nanocapsules is below
  • the average nanocapsule size is below the wavelength of visible light, in particular smaller than ⁇ /4 of visible light. It is advantageously found that the nanocapsules according to the invention in at least one state, in particular with appropriate LC alignment or configuration, can be very weak scatterers of visible light, i.e. that they do not, or substantially not, scatter visible light. In this case the capsules can be useful in modulating the phase shift between the two polarization
  • phase retardation while not showing or substantially not showing unwanted scattering of light in any state.
  • the retardation is set to be approximatey ⁇ /2, in particular to be ⁇ /2 for a wavelength of 550 nm. This can be achieved by e.g. providing suitable types and amounts of nanocapsules in a film and setting an appropriate film thickness.
  • the polymer-encapsulated mesogenic medium preferably exhibits a confinement size from 15 nm to 400 nm, more preferably from 50 nm to 250 nm and in particular from 75 nm to 150 nm.
  • the functionality of the capsules may become less efficient, considering that the amount of enclosed LC material decreases and also the mobility of the LC molecules becomes more limited.
  • the thickness of the polymeric shell or respectively wall, which forms a discrete individual structure, is chosen such that it effectively contains and stably confines the contained LC medium, while at the same time allowing for relative flexibility and still enabling excellent electric responsiveness of the LC material.
  • the shell should preferably be as thin as possible while still providing adequate strength for containment. Therefore, the typical capsule shell or wall thickness is below 100 nm.
  • the polymeric shell has a thickness of less than 50 nm, more preferably below 25 nm, and in particular below 15 nm. In a preferred embodiment, the polymeric shell has a thickness from 1 nm to 15 nm , more preferably from 3 nm to 10 nm, and in particular from 5 nm to 8 nm.
  • Microscopy techniques in particular SEM and TEM can be used to observe the nanocapsule size, structure and morphology.
  • Wall thickness can e.g. be determined by TEM on freeze-fractured samples.
  • neutron scattering techniques may be used.
  • AFM, NMR, ellipsometric and sum-frequency generation techniques can be useful to study the nanocapsule structure.
  • the nanocapsules according to the invention typically have spherical or spheroidal shape, wherein the hollow spherical or spheroidal shells are filled with or respectively contain the LC medium according to the invention.
  • the present invention thus provides a plurality of discrete spherical or spheroidal bodies or particles of LC which are each nanoencapsulated by a polymeric shell and which each individually but also collectively are operable in electro-optical devices in at least two states.
  • the LC component provides the beneficial chemical, physical and electro- optical characteristics as described above, such as good reliability and stability and low rotational viscosity.
  • the LC medium according to the invention has a birefringence of ⁇ 0.15, more preferably ⁇ 0.20 and most preferably ⁇ 0.25. It is even more preferred when the LC medium according to the invention additionally has a dielectric anisotropy of ⁇ 10.
  • Another advantage of the invention rests in the possibility to obtain substantially uniform capsule sizes, i.e. to achieve low polydispersity. This uniformity can favourably provide a uniform electro-optical performance of the capsules in device applications.
  • the capsules obtained by or respectively obtainable from the controlled and adaptable process according to the invention can be adjusted and tuned in terms of capsule size, which in turn allows to tune the electro- optical performance as desired, in particular based on the Kerr effect.
  • the small and uniform size of the nanocapsules can be beneficial in terms of obtaining fast and uniform switching in response to an applied electric field, preferably giving low millisecond or even sub-millisecond response times.
  • the present invention provides a method for preparing such a composite system comprising the nanocapsules and binder.
  • the method is devised such that the obtained system furthermore comprises one or more additives, preferably one ore more surfactants as set forth abobve.
  • the additive incorporated into the system preferably at least to an extent into the nanocapsules, can give further improved or adjusted product properties, in particular with respect to the operating voltage, but also e.g. related to an excellent dark state, favourably low hysteresis and film formation.
  • the method for preparing the composite system offers useful flexibility in terms of when and how the additive(s) can be added.
  • nanocapsules can be provided which already as such comprise one or more additives.
  • the nanocapsules as initially provided do not comprise the one or more additives.
  • the nanocapsules are suitable mixed with one or more binders, wherein in addition the one or more additives as set forth above are furher added.
  • the additive as used in step (d) of the capsule preparation can favourably also be used in the preparation of the composite system
  • the addition of the additive preferably surfactant, can be carried out simultaneously with the addition of the binder and/or after the addition of the binder. It is however preferred that the additive is added together with the binder such that the components, including the
  • nanocapsules can be mixed more easily and to a greater extent.
  • the one or more binders can act as both dispersant and adhesion or binding agent, and furthermore provide suitable physical and mechanical stability while maintaining or even promoting flexibility.
  • density or concentration of the capsules can advantageously be adjusted by varying the amount of binder or buffer material provided.
  • the invention thus provides a composite system which comprises the nanocapsules according to the invention, one or more binders and one or more additives, wherein the system is preferably and favourably obtainable from carrying out the method as set forth above and below.
  • the discrete nanocapsules can be mixed with a binder material, wherein the mixed nanocapsules substantially maintain, preferably fully maintain, their integrity in the composite while however being bound, held or mounted in the binder.
  • the binder material can be the same material as the polymeric shell material or a different material.
  • the nanocapsules can be dispersed in a binder made from the same material as or a different material from that of the nanocapsule shell.
  • the binder is a different or at least modified material.
  • one or more additives, preferably a surfactant, are incorporated which suitably influence the properties of the obtained system.
  • the binder can be useful in that it can disperse the nanocapsules, wherein the amount or concentration of the capsules can be set and adjusted.
  • the amount of the capsules in the combined composite cannot only be tuned, but especially a very high content, and alternatively also a very low content, of the capsules is obtainable if desired.
  • the nanocapsules are contained in the composite in a proportion from about 2% by weight to about 95% by weight.
  • the composite contains the nanocapsules in a range from 10% by weight to 85% by weight, more preferably from 30% by weight to 70% by weight.
  • the amounts of binder and nanocapsules used are approximately the same.
  • the amount of additive in the composite system is typically considerably smaller than the amount of the nanocapsules or binder.
  • the amount of additive in the obtained system, based on the overall system composition is 5% by weight or less, more preferably is 2.5% by weight or less, and even more preferably is 1 % by weight or less.
  • the amount of additive in the composite system, based on the overall system composition is particularly preferably set in the range from 0.05% by weight to 1 % by weight, and even more preferably in the range from 0.1 % by weight to 1 % by weight.
  • the binder material can improve or influence the coatabilty or printability of the capsules and the film forming ability and performance.
  • the binder can provide mechanical support while maintaining a suitable degree of flexibility, and it can serve as a matrix.
  • the binder furthermore exhibits suitable and adequate transparency.
  • the binder can be selected from, for example, inorganic glass monoliths, as described e.g. in US 4,814,21 1 , or other inorganic materials.
  • the binder is a polymeric material. Suitable materials may be synthetic resins such as, for example, epoxy resins and polyurethanes which, for example, are thermally curable. Furthermore, vinyl compounds and acrylates, in particular polyvinyl acrylates and polyvinyl acetates may be used. Furthermore, polymethyl methacrylate, polyurea, polyurethane, urea formaldehyde, melamine formaldehyde, melamine urea formaldehyde can be used or added. In some embodiments acrylates and methacrylates are used as binder.
  • water-soluble polymers are used, such as, for example, polyvinyl alcohol (PVA), starch, carboxyl methyl cellulose, methyl cellulose, ethyl cellulose, polyvinyl pyrrolidine, gelatin, alginate, casein, gum arabic, or latex-like emulsions.
  • PVA polyvinyl alcohol
  • the binder can for example be chosen in view of setting the respective hydrophobicity or hydrophilicity.
  • the binder in particular the dried binder, absorbs little or no water.
  • the one or more binders comprise polyvinyl alcohol, which includes partially and fully hydrolyzed PVA.
  • water solubility and hydrophilicity can be adjusted by varying the degree of hydrolysis.
  • water uptake may be controlled or reduced.
  • the properties, such as mechanical strength or viscosity, of the PVA may be favourably set by e.g. adjusting the molecular weight, the degree of hydrolysis or by chemical modification of the PVA.
  • the binder properties can also be favourably influenced by cross-linking the binder. Therefore, in particular when PVA is provided as the binder, in an embodiment the binder is cross-linked, preferably by cross-linking agents such as dialdehydes, e.g. glutaraldehyde, formaldehyde and glyoxal. Such cross-linking may e.g. favourably reduce any tendency for undesirable crack- formation.
  • the composite may further comprise customary additives such as stabilizers, antioxidants, free radical scavengers and/or plasticizers.
  • ethylene glycol can be used as a preferable plasticizer. It is also possible to use glycerol, and alternatively or additionally 1 -octanol.
  • the nanocapsules are mixed with PVA and glycerol, more preferably with PVA, glycerol and 1 -octanol, and even more preferably with PVA, glycerol, TEGO ® Wet 270 and optionally 1 -octanol.
  • film-forming agents for example polyacrylic acid, and anti-foaming agents may be added. Such agents may be used to improve film formation and substrate wettability.
  • degassing and/or filtration of the coating composition can be carried out to further improve film properties.
  • setting and adjusting binder viscosity can have a favourable influence on the forming or
  • the binder can be provided as a liquid or paste, wherein a carrier medium or solvent, such as water, aqueous solvent or organic solvent, can be removed from the composite mixture, for example during or after film formation, in particular by evaporation at an elevated temperature.
  • a carrier medium or solvent such as water, aqueous solvent or organic solvent
  • the binder preferably mixes and combines well with the nanocapsules, to which the additive may in some cases suitably contribute. Furthermore, aggregation of capsules is suitably avoided or minimized, such that e.g. light leakage can be avoided or minimized, which in turn can make a very good dark state possible. Moreover, the binder can be chosen such that a high density of nanocapsules can be provided in the composite, for example in a film formed of the composite. Furthermore, in the composite the structural and mechanical advantages of the binder can be combined with the favourable electro-optical properties of the LC capsules. The additive can be useful in further improving these properties.
  • a top coating or an overcoat may be applied, using e.g. cellulose or cellulose derivatives, polysiloxanes or thiolenes as such coating.
  • the nanocapsules according to the invention can be applied to a large variety of different environments, in particular by (re)dispersing them. They can be favourably dispersed as a plurality of capsules in or respectively mixed with the binder.
  • the binder cannot only improve film forming behviour but also film properties, wherein in particular the binder can hold the capsules relative to a substrate.
  • the capsules are randomly distributed or respectively randomly oriented in the binder. Owing to the LC alignment in the capsules, in particular in case of radial aligment, and/or due to the random distribution of the capsules overall a material which is optically isotropic, or at least substantially optically isotropic, on the macroscopic scale can be obtained.
  • the composite comprising the binder material, but also the nanocapsules on their own, may be suitably applied or laminated to a substrate.
  • the composite or just the nanocapsules can be applied onto the substrate by conventional coating techniques such as spin coating, blade coating or drop coating. Alternatively they can also be applied to the substrate by
  • solvents for example water, aqueous mixtures or standard organic solvents can be used.
  • the material applied to the substrate is the composite, i.e. that it also contains binder.
  • films are formed having a thickness of below 25 ⁇ , preferably below 15 ⁇ .
  • a film made of the composite has a thicknes of from 0.5 ⁇ to 10 ⁇ , very
  • the layer thickness is in a range from 2 ⁇ to 4 ⁇ , more preferably from 3 ⁇ to 4 ⁇ , and even more preferably from 3.5 ⁇ to 4.0 ⁇ .
  • substrate for example glass, silicon, quartz sheets or plastic films can be used. It is also possible to put a second substrate on top of the applied, preferably coated or printed, material. Isotropic or birefringent substrates can be used. It is also possible to apply an optical coating, in particular with optical adhesive.
  • the substrate can be a flexible material. Given the flexibility as provided by the composite, overall a flexible system or device is thus obtainable.
  • Suitable and preferred plastic substrates are for example films of polyester such as polyethyleneterephthalate (PET) or polyethylenenaphthalate (PEN), polyvinylalcohol (PVA), polycarbonate (PC) or triacetylcellulose (TAC), more preferably PET or TAC films.
  • PET films are commercially available for example from DuPont Teijin Films under the trade name Melinex ® .
  • the substrates can be transparent and transmissive or reflective. For electro- optical addressability the substrates can exhibit electrode(s). In a typical embodiment a glass substrate with ITO electrodes is provided.
  • the electrical and optical properties of the LC material, the polymeric capsule shell and the binder are favourably and preferably matched or aligned in terms of compatibility and in view of the respective applications.
  • the composite according to the invention can provide suitable and advantageous electro-optical behaviour and performance.
  • the additive can suitably influence the behaviour and performance.
  • the binder and preferably also the polymer shell, has a relatively large impedance in view of the electric responsiveness of the LC as well as a suitable dielectric constant close to that of the LC material to limit charging at the interfaces. It is observed that the dielectric constant of the binder is sufficiently high to ensure that an electric field is efficiently applied across the LC medium in the capsules. Any charge or ionic content in these materials is preferably minimized to keep conductivity very low. In this respect it was found that the properties of the provided binder, preferably PVA, can be improved by purification, in particular by removing or decreasing the amount of impurities and charged contaminants.
  • the binder in particular PVA, may be dissolved and washed in deionized water or alcohol, and it may be treated by dialysis or soxhlet purification.
  • the refractive indices of the LC material, the polymeric capsule shell and the binder are favourably and preferably matched or aligned in view of optimum performance in the respective applications.
  • the refractive indices of the LC material and the binder are coordinated.
  • the refractive index of the binder can be set or adjusted in view of the extraordinary refractive index (n e ) of the LC, the ordinary refractive index (n 0 ) of the LC, or the average refractive index (n avg ) of the LC.
  • the refractive index of the binder, and also of the shell polymer can be matched closely to n e , n 0 or n avg of the LC material.
  • the nanocapsules are dispersed in the binder, wherein the capsules in the binder exhibit a random orientation relative to each other. Regardless of any possible absence or presence of alignment or orientation of the LC material within each individual capsule, this random orientation of the capsules with respect to each other can result in the LC material as a whole giving an observed average refractive index (n avg ).
  • the application of an electric field wherein the electric field forces (re)alignment of the LC material, can modulate the phase shift, or retardation, of the transmitted, or reflected, light, without however changing the apparent scattering, if at all present.
  • the refractive index of the binder, and preferably also the polymeric capsule shell can e.g. suitably and advantageously be adjusted or matched with respect to n avg of the LC material.
  • nanocapsules can thus behave as efficient nanoscale phase modulators.
  • light scattering may be substantially suppressed, preferably completely suppressed, in particular for sizes smaller than 400 nm.
  • scattering and refraction may be controlled by matching or adjusting the refractive indices of the LC material and of the polymeric material(s).
  • the phase shift can be polarization-independent for normally incident light.
  • the capsules are aligned or oriented in the binder.
  • the composite systems according to the invention advantageously allow for a high degree of adaptability and for setting and adjusting several degrees of freedom, especially in view of tuning the electro-optical properties and functionality.
  • the layer or film thickness can be set, adapted or varied while being able to independently vary the density of the nano-sized LC material in the film, wherein furthermore the size of the nanocapsules, i.e. the amount of LC material in each individual capsule can be preset and thus also adjusted.
  • the LC medium can be chosen to have specific properties, e.g. suitably high values of ⁇ and ⁇ .
  • the amount of LC in the composition, in the nanocapsules and in the composite is suitably maximized to achieve favourably high electro-optical performance.
  • a composite can favourably be provided, with relative production ease and high processibility, that can make good transmittance, low operating voltages, improved VHR and a good dark state possible.
  • a robust, effective and efficient system is obtainable, which is applicable to a single substrate without any alignment layer or without surface rubbing and which can exhibit relative insensitivity to layer thickness deviations or to external forces such as touching, also in terms of light leakage.
  • a wide viewing angle can be obtainable without providing an alignment layer or an additional retardation layer.
  • the nanocapsules and composite systems as provided show sufficient processibility such that aggregation during
  • nanocapsules and the composite system according to the invention are useful in optical and electro-optical applications, in particular in light- modulation elements or ectro-optical devices, and especially in displays. For display applications, fast response and switching times and thus e.g. fast video and/or sequential colour capabilities may be obtainable.
  • the nanocapsules containing the LC medium are suitable for efficient control and modulation of light. They may be used, for example, in optical filters, tunable polarizers and lenses, and phase plates. As phase modulators they may be useful for photonic devices, optical communications and information processing, and three- dimensional displays. A further use is in smart windows or privacy windows which are switchable.
  • the invention thus advantageously provides light-modulation elements and electro-optical modulators. These elements and modulators comprise the nanocapsules according to the invention, wherein preferably the capsules are mixed and dispersed in the binder.
  • the use of one or more additives according to the invention in the nanocapsules and/or the composite systems can beneficially reduce the operating voltage. At the same time further suitable product properties, in addition to the favourable influence on threshold and switching voltage, can be obtained.
  • an electro-optical device in particular an electro-optical display, which makes advantageous use of the nanocapsules and/or the composite system as described above and below.
  • the device a plurality of the nanocapsules are provided.
  • the media according to the invention are prepared in a manner conventional per se.
  • the components are dissolved in one another, preferably at elevated temperature.
  • the liquid-crystalline phases of the present invention can be modified in such a way that they can be used in liquid-crystal display elements.
  • Additives of this type are known to the person skilled in the art and are described in detail in the literature (H. Kelker/ R. Hatz, Handbook of Liquid Crystals, Verlag Chemie, Weinheim, 1980).
  • pleochroic dyes can be added for the production of coloured guest-host systems or substances can be added in order to modify the dielectric anisotropy, the viscosity and/or the alignment of the nematic phases.
  • alkyl preferably encompasses straight-chain and branched alkyl groups having 1 -7 carbon atoms, particularly the straight-chain groups methyl, ethyl, propyl, butyl, pentyl, hexyl and heptyl. Groups having 2-5 carbon atoms are generally preferred.
  • alkoxy can be straight-chain or branched, and it preferably is straight- chain and has 1 , 2, 3, 4, 5, 6 or 7 carbon atoms, and accordingly is preferably methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy.
  • alkenyl according to the present invention preferably
  • alkenyl groups having 2-7 carbon atoms, in particular the straight-chain groups.
  • Particularly preferred alkenyl groups are C 2 -C 7 -1 E-alkenyl, C 4 -C 7 -3E-alkenyl, C 5 -C 7 -4E-alkenyl,
  • alkenyl groups are vinyl, 1 E-propenyl, 1 E-butenyl, 1 E-pentenyl, 1 E-hexenyl,
  • Fluorinated alkyl or alkoxy preferably comprises CF3, OCF3, CFH2, OCFH2, CF 2 H, OCF 2 H, C 2 F 5 , OC 2 F 5 , CFHCFs, CFHCF 2 H, CFHCFH 2 , CH 2 CF 3 , CH 2 CF 2 H, CH 2 CFH 2 , CF 2 CF 2 H, CF 2 CFH 2 , OCFHCF3, OCFHCF 2 H,
  • OCFHCFH 2 OCH 2 CF 3 , OCH 2 CF 2 H, OCH 2 CFH 2 , OCF 2 CF 2 H, OCF 2 CFH 2 , C3F7 or OC3F7, in particular CF 3 , OCF 3 , CF 2 H, OCF 2 H, C 2 F 5 , OC 2 F 5 ,
  • CFHCFs CFHCF 2 H, CFHCFH 2 , CF 2 CF 2 H, CF 2 CFH 2 , OCFHCF3,
  • OCFHCF 2 H OCFHCFH 2 , OCF 2 CF 2 H, OCF 2 CFH 2 , C3F7 or OC3F7, particularly preferably OCF3 or OCF 2 H.
  • embodiment encompasses straight-chain groups with terminal fluorine, i.e. fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl,
  • Halogen is preferably F or CI, in particular F.
  • non-8-enyl dec-1 -, -2-, -3-, -4-, -5-, -6-, -7-, -8- or dec-9-enyl.
  • one of the above mentioned groups is an alkyl group in which one CH 2 group has been replaced by -O- and one has been replaced by -CO-, these are preferably adjacent. These thus contain an acyloxy group -CO-O- or an oxycarbonyl group -O-CO-. These are preferably straight-chain and have 2 to 6 carbon atoms.
  • propoxycarbonylmethyl butoxycarbonyl methyl, 2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl, 2-(propoxycarbonyl)ethyl, 3-(methoxy- carbonyl)propyl, 3-(ethoxycarbonyl)propyl or 4-(methoxycarbonyl)butyl.
  • one of the above mentioned groups is an alkyl or alkenyl group which is monosubstituted by CN or CF3, this group is preferably straight-chain. The substitution by CN or CF3 is in any position.
  • one of the above mentioned groups is an alkyl or alkenyl group which is at least monosubstituted by halogen, this group is preferably straight-chain and halogen is preferably F or CI, more preferably F.
  • halogen is preferably F or CI, more preferably F.
  • halogen is preferably F.
  • the resulting groups also include perfluorinated groups.
  • the fluoro or chloro substituent can be in any desired position, but is preferably in the co-position.
  • Compounds containing branched groups may occasionally be of importance owing to better solubility in some conventional liquid-crystalline base materials. However, they are particularly suitable as chiral dopants if they are optically active.
  • Branched groups of this type generally contain not more than one chain branch.
  • one of the above mentioned groups is an alkyl group in which two or more CH2 groups have been replaced by -O- and/or -CO-O-, this can be straight- chain or branched. It is preferably branched and has 3 to 12 carbon atoms. Accordingly, it is in particular biscarboxymethyl, 2,2-biscarboxyethyl,
  • the LC medium according to the present invention preferably has a nematic phase range between -10°C and +70°C.
  • the LC medium even more suitably may have a nematic phase range between -20°C and +80°C. It is even more advantageous when the LC medium according to the present invention has a nematic phase range between -20°C and +90°C.
  • the LC medium according to the present invention preferably has a birefringence of ⁇ 0.15, more preferably ⁇ is ⁇ 0.20, and most preferably ⁇ is ⁇ 0.25.
  • the LC medium according to the present invention preferably has a dielectric anisotropy ⁇ +10, more preferably ⁇ is ⁇ +15, and most preferably ⁇ is > +20.
  • the LC medium according to the present invention preferably and favourably exhibits a high reliability and a high electric resistivity, also known as specific resistivity (SR).
  • SR value of an LC medium according to the invention is preferably ⁇ 1 x10 13 W cm, very preferably ⁇ 1x10 14 W cm. Unless described otherwise, the measurement of the SR is carried out as described in
  • the LC medium according to the present invention also preferably and favourably exhibits a high voltage holding ratio (VHR), see S. Matsumoto et al., Liquid Crystals 5, 1320 (1989); K. Niwa et al., Proc. SID Conference, San Francisco, June 1984, p. 304 (1984); T. Jacob and U. Finkenzeller in "Merck Liquid Crystals - Physical Properties of Liquid Crystals", 1997.
  • the VHR of an LC medium according to the invention is preferably ⁇ 85 %, more preferably ⁇ 90 %, and even more preferably ⁇ 95 %. Unless described otherwise, the measurement of the VHR is carried out as described in T. Jacob, U. Finkenzeller in "Merck Liquid Crystals - Physical Properties of Liquid Crystals", 1997.
  • ⁇ and ⁇ values and the rotational viscosity ( ⁇ ) of the compounds according to the invention are obtained by linear extrapolation from liquid- crystalline mixtures consisting of 5% to 10% of the respective compound according to the invention and 90% to 95% of the commercially available liquid-crystal mixtures ZLI-2857 or ZLI-4792 (both mixtures from Merck KGaA).
  • C crystalline phase
  • N nematic phase
  • Sm smectic phase
  • I nematic phase
  • C m H 2m+1 and C l H 21+1 or C n H 2n-1 denote straight-chain alkyl or alkenyl, preferably 1 -E-alkenyl, each having n, m and I C atoms respectively.
  • Table A lists the codes used for the ring elements of the core structures of the compounds, while Table B shows the linking groups.
  • Table C gives the meanings of the codes for the left-hand or right-hand end groups. 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.
  • n and m each denote integers, and the three dots are place
  • n, m, I and z preferably, independently of one another, denote 1 to 7.
  • Table E shows possible stabilizers which can be added to the LC media according to the invention, wherein n denotes an integer from 1 to 12, preferably 1 , 2, 3, 4, 5, 6, 7 or 8, terminal methyl groups are not shown.
  • the LC media preferably comprise 0 to 10% by weight, in particular 1 ppm to 5% by weight, particularly preferably 1 ppm to 1 % by weight, of stabilizers.
  • Table F below shows illustrative compounds which can preferably be used as chiral dopants in the mesogenic media according to the present invention.
  • the mesogenic media comprise one or more compounds selected from the compounds shown in Table F.
  • the mesogenic media according to the present invention preferably comprise two or more, preferably four or more, compounds selected from the compounds shown in the above tables D to F.
  • the LC media according to the present invention preferably comprise three or more, more preferably five or more compounds shown in Table D.
  • Table D The following examples are merely illustrative of the present invention and they should not be considered as limiting the scope of the invention in any way. The examples and modifications or other equivalents thereof will become apparent to those skilled in the art in the light of the present disclosure.
  • Vo denotes threshold voltage, capacitive [V] at 20°C,
  • n e denotes extraordinary refractive index at 20°C and 589 nm
  • n 0 denotes ordinary refractive index at 20°C and 589 nm
  • ⁇ denotes optical anisotropy at 20°C and 589 nm
  • ⁇ 11 denotes dielectric permittivity parallel to the director at 20°C and
  • ⁇ denotes dielectric permittivity perpendicular to the director at
  • ⁇ denotes dielectric anisotropy at 20°C and 1 kHz
  • T(N,I) denotes clearing point [°C]
  • ⁇ denotes rotational viscosity measured at 20°C [mPa s]
  • Ki denotes elastic constant
  • splay deformation at 20°C [pN]
  • K2 denotes elastic constant
  • twist deformation at 20°C [pN]
  • K3 denotes elastic constant, "bend” deformation at 20°C [pN],
  • threshold voltage for the present invention relates to the capacitive threshold (Vo), unless explicitly indicated otherwise.
  • the optical threshold can also be indicated for 10% relative contrast (V10).
  • Reference Example 1 A liquid-crystal mixture B-1 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.
  • a liquid-crystal mixture B-2 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.
  • a liquid-crystal mixture B-3 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.
  • a liquid-crystal mixture B-4 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.
  • a liquid-crystal mixture B-5 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.
  • a liquid-crystal mixture B-6 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.
  • Reference Example 7 A liquid-crystal mixture B-7 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.
  • a liquid-crystal mixture B-8 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.
  • a liquid-crystal mixture B-9 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.
  • dimethacrylate 300 mg are weighed into a 250 ml tall beaker.
  • Brij ® L23 50 mg (from Sigma Aldrich) is weighed into a 250 ml conical flask and water (150 g) is added. This mixture is then sonicated in an ultrasound bath for 5 to 10 minutes.
  • the Brij ® L23 aqueous surfactant solution is poured directly into the beaker containing the organics.
  • the mixture is turrax mixed for 5 minutes at 10,000 rpm. Once turrax mixing is complete, the crude emulsion is passed through a high-pressure homogenizer at 30,000 psi four times.
  • the mixture is charged into a flask and fitted with a condenser, and after adding AIBN (35 mg) is heated to 70°C for three hours.
  • AIBN 35 mg
  • the reaction mixture is cooled, filtered, and then size analysis of the material is carried out on a Zetasizer (Malvern Zetasizer Nano ZS) instrument.
  • the obtained capsules have an average size of 213 nm, as determined by dynamic light scattering (DLS) analysis (Zetasizer).
  • DLS dynamic light scattering
  • the PVA (molecular weight M w of PVA: 31 k; 88% hydrolysed) is first washed to remove ions in a Soxhlet apparatus for 3 days. 46.66 g of deionized water are added to a 150 ml bottle, a large magnetic stirrer bar is added and the bottle is placed on a 50°C stirrer hotplate and allowed to come to temperature. 20.00 g of the solid washed 31 k PVA are weighed into a beaker. A vortex is created in the bottle and gradually the 31 k PVA is added over approximately 5 minutes, stopping to allow the floating PVA to disperse into the mixture. The hotplate is turned up to 90°C and stirring is continued for 2-3 hours.
  • the bottle is placed in oven at 80°C for 20 hours.
  • the mixture is filtered whilst still warm through a 50 ⁇ cloth filter under an air pressure of 0.5 bar.
  • the filter is replaced with a Millipore 5 ⁇ SVPP filter and the filtration is repeated.
  • the solid content of the filtered binder is measured 3 times and the average is calculated by weighing an empty DSC pan using a DSC microbalance, adding approximately 40 mg of the binder mixture to the DSC pan and recording the mass, placing the pan on a 60°C hotplate for 1 hour followed by 1 10°C hotplate for 10 min, removing the pan from the hotplate and allowing to cool, recording the mass of the dry pan, and calculating the solid content.
  • the obtained six nanocapsule samples are initially checked by microscopy for unwanted clumping or lumping, and also after film forming.
  • the solid content of the respective concentrated nanocapsule suspensions are measured, wherein the solid content of each sample is measured 3 times and the average is calculated.
  • the samples are weighed in an empty DSC pan using the DSC microbalance, wherein the respective sample is added to the DSC pan and the mass is recorded.
  • the pan is placed on a 60°C hotplate for 1 hour followed by 1 10°C hotplate for 10 min. The pan is removed from the hotplate and allowed to cool. The mass of the dry pan is recorded, and the solid content is calculated.
  • the prepared PVA is added to the respective concentrated nanocapsule samples, wherein the approximately 30% washed 31 k PVA mixture is added in 2.5 ml vials, and then the respective nanocapsules are added to the vials.
  • the weight ratio of PVA to capsules is 50:50.
  • Deionized water is added to give a total solids content of 20%. The mixtures are stirred using a vortex stirrer and leaving the mixtures on a roller overnight to allow the PVA to disperse.
  • the substrates used are IPS (in-plane switching) glass having ITO coated interdigitated electrodes with an electrode width of 4 ⁇ and a gap of 8 ⁇ .
  • the substrates are placed in a rack and plastic box for washing. Deionised water is added and the samples are placed in a sonicator for 10 minutes. The substrates are removed from the water and blotted with a paper towel to remove the excess water. Washing is repeated with acetone, 2-propanol (IPA) and finally water for ion-chromatography. The substrates are then dried using a compressed air gun. The substrates are treated with UV-ozone for 10 minutes.
  • IPS in-plane switching
  • the six composite systems comprising the respective nanocapsules and the binder are then coated on a substrate each.
  • 40 ⁇ _ of mixture are coated as a film using a coating machine (K Control Coater, RK PrintCoat Instruments, bar coating with k bar 1 , coating speed of 7).
  • the sample is dried at 60 °C for 10 minutes on a hotplate, under a lid to prevent draughts and stop contaminants falling onto the film. The appearance of the film is recorded. Prepared films are stored in a dry box between measurements.
  • Film thickness is measured by removing the film from above the electrical contacts with a razor blade.
  • the film thickness is measured in the region of the middle electrode using a profilometer (Dektak XT surface profiler, Bruker) with a stylus force of 5 mg and a scan length of 3000 nm and a time of 30 s.
  • a profilometer Dektak XT surface profiler, Bruker
  • Switching speeds are measured at 40°C and 25°C at 150 Hz modulation frequency, and also at 10 Hz as appropriate.
  • the measured electro-optical parameters for the prepared film comprising the nanocapsules and the binder are given in the following Table. In this Example and the following Examples hysteresis is determined at V50.
  • the electro-optical properties shown in the following Table are determined on a Display Measurement System (Autronic-Melchers), wherein the intensity of the back light is taken as 100% transmission T and the dark state between crossed polarizers is taken as 0% transmission T and wherein switching is performed at 1 kHz and 24 °C.
  • the additives can suitably contribute to reducing the operating voltage.
  • dimethacrylate 300 mg are weighed into a 250 ml tall beaker.
  • Brij ® 58 50 mg (Sigma-Aldrich) is weighed into a 250 ml conical flask and water (150 g) is added. This mixture is then sonicated for 5 to 10 minutes.
  • the Brij ® 58 aqueous surfactant solution is poured directly into the beaker containing the organics.
  • the mixture is turrax mixed for 5 minutes at 10,000 rpm. Once turrax mixing is complete, the crude emulsion is passed through a high-pressure homogenizer at 30,000 psi four times.
  • LC mixture B-1 (2.01 g), hexadecane (358 mg), ethylene dimethacrylate (597mg), 2-hydroxyethyl methacrylate (80 mg) and methyl methacrylate (190 mg) are weighed into a 400 ml tall beaker.
  • Brij ® 58 (100 mg) is weighed into a 400 ml conical flask and water (250 g) is added. This mixture is then sonicated for 5 to 10 minutes.
  • the Brij aqueous surfactant solution is poured directly into the beaker containing the organics.
  • the mixture is turrax mixed for 10 minutes at 10,000 rpm. Once turrax mixing is complete, the crude emulsion is passed through a high-pressure homogenizer at 30,000 psi four times.
  • the mixture is charged into a flask and fitted with a condenser, and after adding AAPH (20 mg) is heated to 73°C for four hours.
  • the reaction mixture is cooled, filtered, and then size analysis of the material is carried out on a Zetasizer instrument.
  • the obtained capsules have an average size of 230 nm, as determined by dynamic light scattering (DLS) analysis (Zetasizer) and a polydispersity of 0.051 .
  • the sample is concentrated before further use. This is carried out by passing the sample through a cross flow filtration apparatus (Vivaflow 200 from
  • the sample is removed from the filtration apparatus and is suitable for further use.
  • Example 1 The solid content of this sample is measured to be at 19%.
  • a composite system with binder and a coated film are then prepared as described in Example 1 , wherein however the weight ratio of capsules to PVA is 60:40.
  • the coated sample has a V90 of 41 V and a dark state transmission of 1 .25%.
  • LC mixture B-8 (2.00 g), methyl methacrylate (165 mg), hydroxyethyl methacrylate (75 mg) and ethylene glycol dimethacrylate (660 mg) are weighed into a 250 ml tall beaker.
  • Brij ® L23 (150 mg) is weighed into a 250 ml conical flask and water (150 g) is added. This mixture is then sonicated for 5 to 10 minutes. The Brij ® L23 aqueous surfactant solution is poured directly into the beaker containing the organics. The mixture is turrax mixed for 5 minutes at 10,000 rpm. Once turrax mixing is complete, the crude emulsion is passed through a high-pressure homogenizer at 30,000 psi four times.
  • the mixture is charged into a flask and fitted with a condenser, and after adding AIBN (35 mg) is heated to 70°C for three hours.
  • AIBN 35 mg
  • the reaction mixture is cooled, filtered, and then size analysis of the material is carried out on a Zetasizer (Malvern Zetasizer Nano ZS) instrument.
  • the obtained capsules have an average size of 167 nm, as determined by dynamic light scattering (DLS) analysis (Zetasizer).
  • DLS dynamic light scattering
  • Triton X-100 0.019 g is added to 0.1 ml of water in a centrifuge tube.
  • 0.019 g of Brij ® L4, 0.019 g FluorN 561 (from Cytonix) and 0.019 g TEGO ® Wet 270 are respectively added to 0.1 ml of isopropanol (IPA) in centrifuge tubes.
  • IPA isopropanol
  • the respective particle suspensions are then concentrated by centrifugation, wherein the centrifuge tubes are placed in a centrifuge (ThermoFisher Biofuge Stratos) and centrifuged at 6,500 rpm for 10 minutes and at
  • Switching speeds are measured at 40°C and 25°C at 150 Hz modulation frequency, and also at 10 Hz as appropriate.
  • the measured electro-optical parameters for the prepared film comprising the nanocapsules and the binder are given in the following Table.
  • the electro-optical properties shown in the following Table are determined on a Display Measurement System (Autronic-Melchers), wherein the intensity of the back light is taken as 100% transmission T and the dark state between crossed polarizers is taken as 0% transmission T and wherein switching is performed at 1 kHz and 24 °C.
  • the additives can suitably contribute to reducing the operating voltage.
  • hydroxyethyl methacrylate (510 mg) and ethylene glycol dimethacrylate (2000 mg) are weighed into a 250 ml tall beaker.
  • Brij ® L23 (450 mg) is weighed into a 250 ml conical flask and water (150 g) is added. This mixture is then sonicated for 5 to 10 minutes. The Brij ® L23 aqueous surfactant solution is poured directly into the beaker containing the organics. The mixture is turrax mixed for 5 minutes at 10,000 rpm. Once turrax mixing is complete, the crude emulsion is passed through a high-pressure homogenizer at 30,000 psi four times.
  • the mixture is charged into a flask and fitted with a condenser, and after adding AIBN (75 mg) is heated to 70°C for three hours.
  • AIBN 75 mg
  • the reaction mixture is cooled, filtered, and then size analysis of the material is carried out on a Zetasizer (Malvern Zetasizer Nano ZS) instrument.
  • the obtained capsules have an average size of 173 nm, as determined by dynamic light scattering (DLS) analysis (Zetasizer).
  • DLS dynamic light scattering
  • the obtained nanoparticle suspension is concentrated by centrifugation, wherein the centrifuge tubes are placed in a centrifuge (ThermoFisher Biofuge Stratos) and centrifuged at 6,500 rpm for 10 minutes and at 15,000 rpm for 20 minutes.
  • a centrifuge ThermoFisher Biofuge Stratos
  • the PVA binder, the composite systems and the films are prepared as described for Example 1 . Measurement of Electro-optical Properties
  • the appearance of the respective films is checked by eye for uniformity and defects.
  • Two electrodes are soldered to the glass.
  • Voltage-transmission curves are measured using the dynamic scattering mode (DSM).
  • Switching speeds are measured at 40°C and 25°C at 150 Hz modulation frequency, and also at 10 Hz as appropriate.
  • the measured electro-optical parameters for the prepared film comprising the nanocapsules and the binder are given in the following Table.
  • the electro-optical properties shown in the following Table are determined on a Display Measurement System (Autronic-Melchers), wherein the intensity of the back light is taken as 100% transmission T and the dark state between crossed polarizers is taken as 0% transmission T and wherein switching is performed at 1 kHz and 24 °C.
  • the additives can suitably contribute to reducing the operating voltage.
  • dimethacrylate (303 mg) are weighed into a 250 ml tall beaker.
  • Brij ® L23 (50 mg) is weighed into a 250 ml conical flask and water (150 g) is added. This mixture is then sonicated for 5 to 10 minutes.
  • the Brij ® L23 aqueous surfactant solution is poured directly into the beaker containing the organics.
  • the mixture is turrax mixed for 5 minutes at
  • the obtained capsules have an average size of 167 nm, as determined by dynamic light scattering (DLS) analysis (Zetasizer).
  • the obtained nanoparticle suspension is concentrated by centrifugation, wherein the centrifuge tubes are placed in a centrifuge (ThermoFisher Biofuge Stratos) and centrifuged at 6,500 rpm for 10 minutes and at
  • the PVA binder is prepared as described for Example 1 .
  • 0.2 ⁇ ⁇ _ of TEGO ® Wet 270 in 0.02 g of acetone and 0.2 ⁇ ⁇ _ of TEGO ® Wet 280 (from Evonik) in 0.02 g of isopropanol (IPA) are respectively added to separate bottles. The solvent is evaporated over the next 24 h. To each bottle, a 0.20 g portion of the prepared PVA and nanocapsules mixture is added.
  • the mixtures containing TEGO ® Wet 270 or respectively TEGO ® Wet 280 are further mixed for 24 hours.
  • the films are prepared as described for Example 1 .
  • the appearance of the respective films is checked by eye for uniformity and defects.
  • Two electrodes are soldered to the glass.
  • Voltage-transmission curves are measured using the dynamic scattering mode (DSM).
  • the measured electro-optical parameters for the prepared film comprising the nanocapsules and the binder are given in the following Table.
  • the electro-optical properties shown in the following Table are deternnined on a Display Measurement System (Autronic-Melchers), wherein the intensity of the back light is taken as 100% transmission T and the dark state between crossed polarizers is taken as 0% transmission T and wherein switching is performed at 1 kHz and 24 °C.
  • the additives can suitably contribute to reducing the operating voltage.
  • nanocapsules composite systems with binder and coated films.
  • Example 16 LC mixture B-1 is treated as described above in Example 1 to prepare nanocapsules, composite systems with binder and coated films, where instead of hexadecane respectively 1 ,4-pentanediol (Example 15.1 ), dodecane (Example 15.2) or tetradecane (Example 15.3) are used.
  • Example 16
  • LC mixture B-3 (1 .0 g), ethylene dimethacrylate (0.34 g), 2-hydroxy ethylmethacrylate (0.07 g) and hexadecane (0.25 g) are weighed into a 250 ml tall beaker.
  • Example 17 This mixture is treated and investigated as described above in Example 1 .
  • Example 17 This mixture is treated and investigated as described above in Example 1 .
  • LC mixture B-1 (1 .00 g), hexadecane (175 mg), methyl methacrylate (100 mg), hydroxyethyl methacrylate (40 mg) and ethylene glycol dimethacrylate (300 mg) are weighed into a 250 ml tall beaker.
  • Brij ® L23 (50 mg) is weighed into a 250 ml conical flask and water (150 g) is added. This mixture is then sonicated for 5 to 10 minutes. The aqueous surfactant solution is poured directly into the beaker containing the organics. The mixture is turrax mixed for 5 minutes at 10,000 rpm. Once turrax mixing is complete, the crude emulsion is passed through a high- pressure homogenizer at 30,000 psi four times. The mixture is charged into a flask and fitted with a condenser, and after adding AIBN (35 mg) is heated to 70°C for three hours. The reaction mixture is cooled, filtered, and then size analysis of the material is carried out on a Zetasizer (Malvern Zetasizer Nano ZS) instrument.
  • Zetasizer Mervern Zetasizer Nano ZS
  • the obtained capsules have an average size of 167 nm, as determined by dynamic light scattering (DLS) analysis (Zetasizer).
  • DLS dynamic light scattering
  • the obtained nanoparticle suspension is concentrated by centrifugation, wherein the centrifuge tubes are placed in a centrifuge (ThermoFisher Biofuge Stratos) and centrifuged at 6,500 rpm for 10 minutes and at
  • Example 18.1 is repeated, wherein however in addition to Brij ® L23 (50 mg) respectively 50 mg of TEGO ® Wet 270 (Example 18.2), 50 mg of Triton X-100 (Example 18.3) or 50 mg of Brij ® L4 (Example 18.4) are weighed into a 250 ml conical flask.
  • Brij ® L23 50 mg respectively 50 mg of TEGO ® Wet 270 (Example 18.2), 50 mg of Triton X-100 (Example 18.3) or 50 mg of Brij ® L4 (Example 18.4) are weighed into a 250 ml conical flask.
  • the PVA binder is prepared as described for Example 1 .
  • the four mixtures are stirred using a vortex stirrer and leaving the mixtures on a roller over night.
  • Electro-optical Properties The appearance of the respective films is checked by eye for uniformity and defects. Two electrodes are soldered to the glass. Voltage-transmission curves are measured using the dynamic scattering mode (DSM).
  • DSM dynamic scattering mode
  • Switching speeds are measured at 40°C and 25°C at 150 Hz modulation frequency, and also at 10 Hz as appropriate.
  • the measured electro-optical parameters for the prepared film comprising the nanocapsules and the binder are given in the following Table.
  • the electro-optical properties shown in the following Table are determined on a Display Measurement System (Autronic-Melchers), wherein the intensity of the back light is taken as 100% transmission T and the dark state between crossed polarizers is taken as 0% transmission T and wherein switching is performed at 1 kHz and 24 °C.
  • the additives can suitably contribute to reducing the operating voltage.
  • LC mixture B1 (2.00 g), 1 ,4-pentanediol (102 mg), ethylene dimethacrylate (658 mg), 2-hydroxyethyl methacrylate (77 mg) and methyl methacrylate (162 mg) are weighed into a 250 ml tall beaker.
  • Brij ® L23 (100 mg) is weighed into a 250 ml conical flask and water (100 g) is added. This mixture is then sonicated for 5 to 10 minutes.
  • the Brij aqueous surfactant solution is poured directly into the beaker containing the organics.
  • the mixture is turrax mixed for 10 minutes at 10,000 rpm. Once turrax mixing is complete, the crude emulsion is circulated through a high-pressure homogenizer at 30,000 psi for eight minutes.
  • the mixture is charged into a flask and fitted with a condenser, and after adding AAPH (20 mg) is heated to 70°C for four hours.
  • the reaction mixture is cooled, filtered, and then size analysis of the material is carried out on a Zetasizer instrument.
  • the obtained capsules have an average size of 180 nm, as determined by dynamic light scattering (DLS) analysis (Zetasizer).
  • the obtained sample is then further treated as described in Example 1 .
  • Brij ® L23 (300 mg) is weighed into a 250 ml conical flask and water (100 g) is added. This mixture is then sonicated for 5 to 10 minutes. The Brij ® L23 aqueous surfactant solution is poured directly into the beaker containing the organics. The mixture is turrax mixed for 5 minutes at
  • 0.01 g of Triton X-100 is added to 0.1 ml of water in a centrifuge tube.
  • 0.01 g of Brij ® L4, 0.01 g FluorN 322 and 0.01 g TEGO ® Wet 270 are respectively added to 0.1 ml of isopropanol (IPA) in centrifuge tubes.
  • IPA isopropanol
  • the five centrifuge tubes are placed on a roller for 48 hours.
  • the respective particle suspensions are then concentrated by centrifugation, wherein the centrifuge tubes are placed in a centrifuge (ThermoFisher Biofuge Stratos) and centrifuged at 6,500 rpm for 10 minutes and at
  • Electro-optical Properties The appearance of the respective films is checked by eye for uniformity and defects. Two electrodes are soldered to the glass. Voltage-transmission curves are measured using the dynamic scattering mode (DSM).
  • DSM dynamic scattering mode
  • Switching speeds are measured at 40°C and 25°C at 150 Hz modulation frequency, and also at 10 Hz as appropriate.
  • the measured electro-optical parameters for the prepared film comprising the nanocapsules and the binder are given in the following Table.
  • the electro-optical properties shown in the following Table are determined on a Display Measurement System (Autronic-Melchers), wherein the intensity of the back light is taken as 100% transmission T and the dark state between crossed polarizers is taken as 0% transmission T and wherein switching is performed at 1 kHz and 24 °C.
  • the additives can suitably contribute to reducing the operating voltage.
  • Brij ® L23 (50 mg) is weighed into a first 250 ml conical flask and water (150 g) is added. Into three more 250 ml conical flasks Brij ® L23 (50 mg), water (150 g) and respectively Brij ® L4 (50mg), TEGO ® Wet 270 (50mg) or Triton X-100 (50mg) are added. These mixtures are then sonicated for 5 to 10 minutes.
  • the four aqueous solutions are poured directly into the four beakers containing the organics.
  • the mixtures are turrax mixed for 5 minutes at 10,000 rpm. Once turrax mixing is complete, the crude emulsions are respectively passed through a high-pressure homogenizer at 30,000 psi four times.
  • the four mixtures are respectively charged into flasks and fitted with condensers, and after adding AIBA (20 mg) are heated to 70°C for three hours.
  • the reaction mixtures are cooled, filtered, and then size analysis of the respectively obtained materials is carried out on a Zetasizer (Malvern Zetasizer Nano ZS) instrument.
  • the obtained capsules of Compative Example 21 .1 (Brij ® L23 only) have an average size of 129 nm, as determined by dynamic light scattering (DLS) analysis (Zetasizer).
  • the obtained capsules of Example 21 .2 (additional Brij ® L4) have an average size of 192 nm, as determined by dynamic light scattering (DLS) analysis (Zetasizer).
  • the obtained capsules of Example 21 .3 (additional TEGO ® Wet 270) have an average size of 200 nm, as determined by dynamic light scattering (DLS) analysis (Zetasizer).
  • the obtained capsules of Example 21 .4 (additional Triton X-100) have an average size of 180 nm, as determined by dynamic light scattering (DLS) analysis (Zetasizer).
  • Electro-optical properties are measured as described in Example 1 .
  • the measured electro-optical parameters for the prepared films comprising the nanocapsules and the binder are given in the following Table.
  • the additives can suitably contribute to reducing the operating voltage.
  • LC mixture B-1 is treated as described above in Example 1 to prepare nanocapsules, composite systems with binder and coated films, where instead of 175 mg of hexadecane respectively 100 mg of hexadecane and 75 mg of 1 ,5-dimethyltetraline (Example 22.1 ), 100 mg of hexadecane and 75 mg of 3-phenoxytoluene (Example 22.2), 100 mg of hexadecane and 75 mg of cyclohexane (Example 22.3) or 100 mg of hexadecane and 75 mg of 5-hydroxy-2-pentanone (Example 22.4) are used.
  • 175 mg of hexadecane respectively 100 mg of hexadecane and 75 mg of 1 ,5-dimethyltetraline (Example 22.1 ), 100 mg of hexadecane and 75 mg of 3-phenoxytoluene (Example 22.2), 100 mg of hexadecan
  • Example 23 LC mixture B-1 (1 .00 g), hexadecane (125 mg), methyl methacrylate (100 mg), hydroxyethyl methacrylate (40 mg) and ethylene glycol dimethacrylate (300 mg) are weighed into a 250 ml tall beaker. In addition, 50 mg of PEG methyl ether methacrylate are added.
  • Brij ® L23 (50 mg) is weighed into a 250 ml conical flask and water (150 g) is added. This mixture is then sonicated for 5 to 10 minutes.
  • the Brij ® L23 aqueous surfactant solution is poured directly into the beaker containing the organics.
  • the mixture is turrax mixed for 5 minutes at
  • the obtained capsules have an average size of 21 1 nm as determined by dynamic light scattering (DLS) analysis (Zetasizer).
  • a composite system and film containing the nanocapsules sample is then prepared as described in Comparative Example 1 .1 .
  • Electro-optical properties are measured as described in Example 1 .
  • LC mixture B-1 (1 .00 g), hexadecane (100 mg), methyl methacrylate (16 mg), hydroxyethyl methacrylate (89 mg) and ethylene glycol dimethacrylate (250 mg) are weighed into a 250 ml tall beaker. In addition, 100 mg of stearyl methacrylate are added.
  • Brij ® L23 (75 mg) is weighed into a 250 ml conical flask and water (150 g) is added. This mixture is then sonicated for 5 to 10 minutes.
  • the Brij ® L23 aqueous surfactant solution is poured directly into the beaker containing the organics.
  • the mixture is turrax mixed for 5 minutes at
  • the mixture is charged into a flask and fitted with a condenser, and after adding AIBA (20 mg) is heated to 70°C for three hours.
  • the reaction mixture is cooled, filtered, and then size analysis of the material is carried out on a Zetasizer (Malvern Zetasizer Nano ZS) instrument.
  • the obtained capsules have an average size of 178 nm as determined by dynamic light scattering (DLS) analysis (Zetasizer).
  • a composite system and film containing the nanocapsules sample is then prepared as described in Comparative Example 1 .1 .
  • Electro-optical properties are measured as described in Example 1 .

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  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing Of Micro-Capsules (AREA)
  • Liquid Crystal (AREA)
  • Liquid Crystal Substances (AREA)
  • Polymerisation Methods In General (AREA)

Abstract

La présente invention concerne des nanocapsules qui comprennent un milieu mésogène, une enveloppe polymère et un ou plusieurs additifs, leur utilisation dans des dispositifs électro-optiques, et des procédés pour préparer les nanocapsules.
PCT/EP2017/077561 2016-10-31 2017-10-27 Nanocapsules comprenant un milieu à cristaux liquides WO2018078078A1 (fr)

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CN201780064367.1A CN109863226A (zh) 2016-10-31 2017-10-27 包含液晶介质的纳米胶囊
DE112017005490.7T DE112017005490T5 (de) 2016-10-31 2017-10-27 Nanokapseln enthaltend ein fluessigkristallines medium
KR1020197015292A KR20190077034A (ko) 2016-10-31 2017-10-27 액정 매질을 포함하는 나노캡슐
JP2019522686A JP2019535498A (ja) 2016-10-31 2017-10-27 液晶媒体を含むナノカプセル

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EP3399006A3 (fr) * 2017-04-13 2019-03-20 LG Display Co., Ltd. Dispositif d'affichage à cristaux liquides comprenant une capsule à cristaux liquides et son procédé de fabrication
EP3467074A1 (fr) * 2017-10-05 2019-04-10 Merck Patent GmbH Compositions comprenant de l'alcool polyvinylique fonctionnalisé et nanocapsules contenant un milieu à base de cristaux liquides
WO2019079507A1 (fr) * 2017-10-18 2019-04-25 The Regents Of The University Of California Mousse solide incorporant des nanoparticules fonctionnalisées par un ligand mésogène, leurs procédés de fabrication et d'utilisation
EP3599266A1 (fr) * 2018-07-24 2020-01-29 Merck Patent GmbH Lentille à cristaux liquides
GB2587254A (en) * 2019-05-28 2021-03-24 Merck Patent Gmbh Compositions comprising waterborne polyurethane dispersion and nanocapsules containing a liquid-crystalline medium
CN116515340A (zh) * 2023-03-06 2023-08-01 北京印刷学院 一种胆甾相液晶/高分子复合体系微胶囊及其制备方法

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CN111205912B (zh) * 2020-01-19 2021-03-30 清华大学 一种智能存储型纳米颗粒的制备方法
WO2021166746A1 (fr) * 2020-02-18 2021-08-26 日産化学株式会社 Nanocapsules de cristaux liquides et procédé de production associé, liquide de dispersion de nanocapsule de cristaux liquides et élément d'affichage à cristaux liquides contenant chacun lesdites nanocapsules de cristaux liquides

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