CN109863226A

CN109863226A - Nano capsule comprising liquid crystal media

Info

Publication number: CN109863226A
Application number: CN201780064367.1A
Authority: CN
Inventors: M·纳姆特比; R·图芬; V·库克; P·萨克斯顿; K·阿德莱姆; S·考尔
Original assignee: Merck Patent GmbH
Current assignee: Merck Patent GmbH
Priority date: 2016-10-31
Filing date: 2017-10-27
Publication date: 2019-06-07
Also published as: KR20190077034A; WO2018078078A1; DE112017005490T5; JP2019535498A; TW201833305A

Abstract

The present invention relates to Nano capsule, it includes mesogenic media, polymer shell and one or more additives, their purposes in electro-optical device, and the method for preparing the Nano capsule.

Description

Nanocapsules comprising a liquid crystalline medium

The present invention relates to a nanocapsule comprising a mesogenic medium, a polymeric shell and one or more additives as described below, its use in an electro-optical device, and a method of preparing said nanocapsule.

Liquid Crystal (LC) media are widely used in Liquid Crystal Displays (LCDs), particularly electro-optic displays with active-matrix or passive-matrix addressing to display information. In the case of active matrix displays, individual pixels are typically addressed by integrated non-linear active elements, such as transistors, for example Thin Film Transistors (TFTs), whereas in the case of passive matrix displays, individual pixels are typically addressed by multiplexing methods as known in the art.

Also commonly used is a TN ("twisted nematic") type LCD, which however has the disadvantage of a strong viewing angle dependence of the contrast ratio. In addition, so-called VA ("vertical alignment") displays are known, which have a wide viewing angle. Furthermore, OCB ("optically compensated bend") displays are known, which are based on birefringent effects and have a so-called "bend" alignment of the LC layer. Also known are so-called IPS ("in-plane switching") displays, which comprise an LC layer between two substrates, wherein two electrodes are arranged on only one of the two substrates, and preferably have an intermeshing comb-like structure. Furthermore, so-called FFS ("fringe field switching") displays have been provided which contain two electrodes on the same substrate, one of which is constructed in a comb-like manner and the other is unstructured. This results in a strong, so-called "fringe field", i.e. a strong electric field near the edges of the electrodes, and an electric field having a strong vertical component and a strong horizontal component throughout the cell.

A further development is the so-called PS ("polymer stabilized") or PSA ("polymer sustained alignment") type of display, for which the term "polymer stabilized" is also occasionally used. Of these, a small amount (e.g. 0.3% by weight), typically < 1% by weight, of one or more polymerisable compounds (preferably polymerisable monomer compounds) is added to the LC medium and, after the LC medium is filled into the display, is polymerised or crosslinked in situ, typically by UV-photopolymerisation, optionally upon application of a voltage to the electrodes of the display. The polymerization reaction is carried out at a temperature at which the LC medium exhibits a liquid crystalline phase, typically room temperature. The addition of polymerisable mesogenic or liquid-crystalline compounds, also referred to as reactive mesogens or "RMs", to the LC mixture has proved to be particularly suitable.

In addition, displays based on Polymer Dispersed Liquid Crystal (PDLC) films have been described, see for example US 4,688,900. In such PDLC films, the LC medium droplets (microdroplets) of the LC medium in micron size are typically randomly distributed in the polymer matrix. The LC domains in these phase separated systems have dimensions that can lead to strong scattering of light. PDLC films are typically prepared using a polymerization-induced phase separation (PIPS) process, where the phase separation is reaction-induced. Alternatively, PDLC films can be prepared based on Temperature Induced Phase Separation (TIPS) or Solvent Induced Phase Separation (SIPS). In addition to PDLC films, so-called Polymer Network Liquid Crystal (PNLC) systems are known, in which the polymer network is formed in a continuous LC phase.

Furthermore, micron-sized encapsulated LC materials (microcapsules) for displays have been described, wherein the microcapsules are prepared by forming an aqueous emulsion of the LC material with an immiscible binder, such as polyvinyl alcohol (PVA) used as the encapsulation medium, see for example US 4,435,047.

A microencapsulation process using an electro-optical fluid which polymerizes at least partially soluble polymer precursors and cross-links is described in WO 2013/110564 a 1.

In addition to the above display types, LCDs including a layer containing nanocapsules, in which the nanocapsules contain liquid crystal molecules, have recently been proposed. The construction of an LCD device arranged with a layer containing such nanocapsules in a so-called buffer material is described in US 2014/0184984 a1, for example.

Another LCD device having nanocapsules arranged therein is described in US 2012/0113363 a 1.

Kang and Kim at Optics Express, 2013, volume 21, pages 15719-15727 describe optically isotropic nano-encapsulated LCs for displays based on the kerr effect and in-plane switching. Nanocapsules having an average diameter of about 110nm are prepared by adding nematic LC to a mixture of a non-ionic polymer surfactant and PVA dissolved in an aqueous solution serving as a shell-forming polymer and a water-soluble emulsifier to form a nanoemulsion, heating the nanoemulsion to the cloud point and stirring to phase separate the PVA around the LC nanodroplets, and crosslinking the polymer shell with a crosslinking agent such as dialdehyde. Furthermore, coating solutions containing the prepared LC nanocapsules, hydrophilic PVA as binder and ethylene glycol as plasticizer are described.

In WO 2009/085082 a1, porous nanoparticles made of crosslinked polymers are described, which can absorb LC substances like a sponge, with possible application as phase retardation films in LCDs.

There is a need in the art for nanocapsules having improved, and optionally adjustable, electro-optical and physical properties, particularly for use in electro-optical devices. Furthermore, there is a need for an improved, easy method, which provides for a simple manufacturing of such nanocapsules. In addition, there is a need for compositions useful in the methods.

It is therefore an object of the present invention to provide an improved method for the preparation of nanocapsules comprising a mesogenic medium, wherein the compositions and materials used in the preparation allow advantageous properties during encapsulation, while further providing the benefits of the obtained nanocapsules, in particular, it is an object of the present invention to provide nanocapsules allowing reduced operating voltages in electro-optical applications, as well as to provide a method and an improved composition for facilitating the obtaining of said nanocapsules, wherein further beneficial properties such as excellent dark state, advantageous low hysteresis and adaptability to film formation can be obtained simultaneously.

The above object is solved by the subject-matter defined in the independent claims, while preferred embodiments are set forth in the respective dependent claims and are further described below.

In particular, the present invention provides the following items including main aspects, preferred embodiments and specific features, which respectively alone and in combination contribute to solving the above objects and finally provide additional advantages.

A first aspect of the present invention provides a method of preparing a nanocapsule, wherein the method comprises:

(a) providing a composition comprising

(i) Mesogenic media comprising one or more compounds of formula I

R-A-Y-A'-R' I

Wherein,

r and R' independently of one another represent a group selected from F, CF₃，OCF₃CN and a linear or branched alkyl or alkoxy group having from 1 to 15 carbon atoms, or a linear or branched alkenyl group having from 2 to 15 carbon atoms, which is unsubstituted, substituted by CN or CF₃Mono-or poly-substituted by halogen, and wherein one or more CH₂The radicals may be replaced in each case independently of one another by-O-, -S-, -CO-, -COO-, -OCO-, -OCOO-or-C.ident.C-in such a way that oxygen atoms are not linked directly to one another,

a and A' independently of one another denote a radical selected from the group consisting of-Cyc-, -Phe-, -Cyc-Cyc-, -Cyc-Phe-, -Phe-Phe-, -Cyc-Cyc-Cyc-, -Cyc-Cyc-Phe-, -Cyc-Phe-Cyc-, -Cyc-Phe-Phe-, -Phe-Cyc-Phe-, -Phe-Phe-Phe-and the corresponding mirror images thereof,

wherein Cyc is trans-1, 4-cyclohexylene, in which one or two non-adjacent CH' s₂A group 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

y represents a single bond, -COO-, -CH₂CH₂-,-CF₂CF₂-,-CH₂O-,-CF₂O-, -CH-, -CF-or-C.ident.C-, and

(ii) one or more polymerizable compounds,

(b) the composition is dispersed as nanodroplets in an aqueous phase using a surfactant,

(C) polymerizing one or more polymerizable compounds to obtain nanocapsules, each nanocapsule comprising a polymer shell and a core comprising a mesogenic medium,

wherein the other additive or additives are

-adding to the composition or nanodroplets prior to polymerization

And/or

-adding to the obtained nanocapsules.

It has surprisingly been found that by providing a process according to the present invention comprising a combination of the above steps (a) to (c), wherein furthermore one or more additives are additionally added to or comprised in the nanodroplets prior to polymerization and/or added to the obtained nanocapsules, nanocapsules containing a mesogenic medium can be prepared in an improved and surprisingly easy way. The nanocapsules obtainable from the method exhibit advantageous properties with respect to their physical and chemical properties, in particular with respect to their electro-optical properties and their suitability in light modulation elements and electro-optical devices.

The additive(s) may be added to the composition or nanodroplets prior to performing the polymerization step. Alternatively or additionally, additives may be added after polymerization and formation of the nanocapsules.

According to one embodiment, after the polymerization according to step (c), one or more additives are added to the resulting nanocapsules in step (d).

In one embodiment, two or more surfactants are used in step (b), i.e. where the further added additive(s) is (are) surfactant(s). For example, two surfactants may be preferably used to adjust the droplet size and interfacial properties of the droplets and the formed capsules. One or more further additives, i.e. in addition to the surfactant, may also be added before, during or after the formation of the nanodroplet dispersion according to step (b). For example, agents that affect wettability, solubility, viscosity or osmotic pressure may be used. In particular, the hydrophobic or hydrophobicizing agent is preferably additionally added before, during or after step (b).

In a preferred embodiment, the one or more additives added in step (d) are one or more surfactants. The additive(s), preferably surfactant(s), added may be selected such that they match or are compatible with the surfactant(s) used in step (b), or they may even be the same. However, it is also possible and in many cases preferred to select and use the additive(s), preferably the surfactant(s), more freely in step (d), i.e. generally independently of the surfactant(s) used in step (b).

It has surprisingly been found that by using the surfactant according to step (b) in combination with the use of additives, wherein the additives are added before the polymerization or according to step (d), and in some cases even before and after the polymerization, it is possible to provide nanocapsules which allow advantageous electro-optical properties at reduced operating voltages. The combined use of additives and surfactants as described above may simultaneously provide further benefits, in particular it may contribute to achieving excellent dark state, high contrast, good low hysteresis and film formation suitability.

The amount of additive, added prior to polymerization or in step (d), respectively, is preferably 5% by weight or less, more preferably 2.5% by weight or less, and even more preferably 1% by weight or less, relative to the composition provided in step (a). In one embodiment, the amount of additive is particularly preferably set in the range of 0.05 to 1% by weight, and even more preferably in the range of 0.1 to 1% by weight, relative to the composition provided in step (a).

Another aspect of the invention relates to nanocapsules each comprising a polymeric shell, a core comprising a mesogenic medium comprising one or more compounds of formula I as described above and below, and one or more additives.

It is advantageously recognized that improved nanocapsules, particularly in view of reduced operating voltages in photovoltaic applications and other beneficial properties as described above and below, result from or are obtained from carrying out the method of the present invention. In this respect, a reduction in the operating voltage may in turn advantageously lead to a reduction in the temperature dependence of the electro-optical switching.

In one embodiment, the one or more additives are contained in the polymeric shell. Additionally or alternatively, one or more additives may be included in the core containing the mesogenic medium. Particularly preferably, the additive or at least a part thereof is located at or near the interface between the shell and the core. Preferably, additives can be used as surfactants.

Preferably, the nanocapsule comprises the additive(s) in an amount of 5% by weight or less, more preferably 2.5% by weight or less, and even more preferably 1% by weight or less, based on the total capsule composition. In one embodiment, the amount of the additive is particularly preferably set in the range of 0.05 to 1% by weight, and even more preferably in the range of 0.1 to 1% by weight, based on the total capsule composition.

In a further aspect, the present invention provides a method of preparing a nanocapsule according to the present invention, wherein the method comprises the steps of (I) providing a nanocapsule comprising a polymeric shell and a core comprising a mesogenic medium comprising one or more compounds of formula I as described above and below, respectively, and (ii) adding one or more additives to the provided nanocapsule.

In another aspect of the invention, a method of making a composite system is provided, wherein the method comprises

Providing nanocapsules, each of which comprises

A shell of a polymer, the shell comprising a polymer,

a core comprising a mesogenic medium as described above and below, and optionally one or more additives,

-adding one or more binders to the nanocapsules, and

-adding one or more additives, concomitantly or after the addition of the one or more binders.

It was found that the combination of nanocapsules and binder material(s) can suitably influence and increase the processability and applicability of the light modulating material, especially in view of coating, dripping or printing and film formation on a substrate. The binder or binders may act as a dispersant and binder or adhesive and also provide suitable physical and mechanical stability while maintaining or even promoting flexibility. Furthermore, the density or concentration of the capsules can be advantageously adjusted by varying the amount of binder or buffer material provided.

By making it possible to concentrate the nanoparticles or capsules in preparation, for example by centrifugation, filtration or drying, and redisperse them, it is possible to set or adjust the density or proportion of the particles in the film or layer independently of the concentration obtained from the original production process.

It has furthermore surprisingly been found that the properties of the nanocapsules in the composite system and of the composite system as a whole can be significantly improved when one or more additives, preferably one or more surfactants, are added in the preparation of the composite system as described above. In particular, it is thus possible to obtain systems which exhibit a reduced operating voltage, while also providing suitable or advantageous properties such as an excellent dark state, an advantageously low hysteresis and improved performance during film formation.

This improvement may be achieved when the provided nanocapsules already comprise one or more additives, preferably surfactants. In this case, the nanocapsule may be prepared, for example, by the above-described method, and one or more additives are additionally added during the preparation of the composite system. The additive added may be the same as or different from the additive already contained in the provided nanocapsule.

However, it is also possible to obtain a good composite system without providing the nanocapsules so containing additives initially. Such nanocapsules may, for example, be obtained by carrying out steps (a) to (c) of the above-described method for preparing nanocapsules, without however adding additives prior to the polymerization and according to step (d). One or more additives, preferably surfactants, are then added only during the preparation of the composite system, and this is therefore an alternative to adding only additives to the nanocapsules.

In both cases, the additive(s), preferably the surfactant(s), may be added together with the binder, e.g. PVA, at the same time. This can be done, for example, by mixing the additive with the binder and then adding the nanocapsules to the mixture. Alternatively, but also additionally, one or more additives may be added after the binder has been added or mixed with the nanocapsules.

Advantageously, the additives may be the same as described for step (d) in the case of capsule preparation.

Preferably, the amount of additive added according to the process is 5% by weight or less, more preferably 2.5% by weight or less, and even more preferably 1% by weight or less, based on the overall system composition as prepared. The amount of the additive added according to the method is particularly preferably set in the range of 0.05 to 1% by weight, and even more preferably in the range of 0.1 to 1% by weight, based on the overall system composition prepared.

In another aspect, there is thus provided a composite system comprising

-nanocapsules, each of which comprises

A polymeric shell, and

a core comprising a mesogenic medium as described hereinbefore and hereinafter,

-one or more binders, and

-one or more additives.

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 advantageously obtained or obtainable by carrying out the above-described process.

In one embodiment, the one or more additives comprise, in particular are incorporated into, the nanocapsule. Additionally or alternatively, one or more additives may be included in the binder. Particularly preferably, the additive is contained in the capsule and the binder. Preferably, the additive may be a surfactant.

Preferably, the composite system comprises the additive(s) in an amount of 5% by weight or less, more preferably 2.5% by weight or less, and even more preferably 1% by weight or less, based on the total composition. In one embodiment, the amount of additive(s) is set particularly preferably in the range of 0.05 to 1% by weight, and even more preferably in the range of 0.1 to 1% by weight, based on the total composition.

The nanocapsules and the composite systems according to the invention are particularly useful in light modulation elements or electro-optical devices.

It has been found particularly surprisingly that the use of one or more additives in the nanocapsules comprising a polymeric shell and a core comprising a mesogenic medium or in the composite comprising said nanocapsules and one or more binders according to the present invention can advantageously reduce the operating voltage. And simultaneously, further suitable product performance can be obtained.

Another aspect of the invention provides an electro-optical device comprising a nanocapsule according to the invention or a composite system according to the invention.

In another aspect, a method for reducing the switching voltage in an electro-optical device is provided, wherein one or more additives are comprised in a nanocapsule comprising a polymer shell and a core comprising a mesogenic medium as described above and below or in a composite comprising the nanocapsule and one or more binders, and wherein the obtained nanocapsule or composite is comprised in the device.

A device comprising a nanocapsule according to the invention or a composite system according to the invention.

By providing a nano-encapsulated LC medium according to the present invention, optionally in combination with a binder material, several significant advantages can be obtained in electro-optical devices. These include, for example, good mechanical stability, flexibility and insensitivity to externally applied forces or, for example, to pressure from a touch, and further advantageous properties with respect to switching speed, transmittance, dark state, viewing angle behavior and threshold voltage, in particular a reduced operating voltage and a reduced hysteresis. Further advantages are the possibility of using flexible substrates and the possibility of varying the film or layer thickness and the calibration for film thickness deviations or variances. In this regard, the light modulating material may be applied to the substrate using simple drop, coating, lamination or printing methods.

Furthermore, it is not necessary to provide an alignment layer, such as a conventionally used Polyimide (PI) alignment layer, on the substrate and/or to rub the substrate surface.

When both electrodes in the device are provided on the same substrate, e.g. in case of IPS or FFS, a single substrate may be sufficient to provide functionality and stability or support, such that the provision of opposing substrates is only optional. However, such opposing substrates may still be beneficial, for example in terms of providing other optical elements or physical or chemical protection. In view of the encapsulation and possible inclusion in the adhesive material, it may no longer be necessary to seal the layer comprising the LC material to ensure sufficient encapsulation of the material and to prevent leakage of the material from the layer.

Without limiting the invention, the invention is illustrated hereinafter by a detailed description of aspects, embodiments and specific features, and specific embodiments are described in more detail.

The term "liquid crystal" or "LC" refers to a material or medium that has a liquid crystalline mesophase over a certain temperature range (thermotropic LC) or over a certain concentration range in solution (lyotropic LC). They contain mesogenic compounds.

The terms "mesogenic compound" and "liquid crystalline compound" mean a compound comprising one or more rod-like (rod-like or plate/lath-like) or disk-like (discotic) mesogenic groups, i.e. groups having the ability to induce liquid crystalline or mesophase behavior.

The LC compounds or materials comprising mesogenic groups and the mesogenic compounds or materials themselves do not necessarily have to exhibit a liquid crystalline phase. They may also exhibit liquid-crystalline phases 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.

The rod-like mesogenic groups typically comprise a mesogenic core consisting of one or more aromatic or non-aromatic cyclic groups connected to each other directly or through a linking group, optionally comprising a terminal group connected to the end of the mesogenic core, and optionally comprising one or more side groups connected to the long side of the mesogenic core, wherein these terminal and side groups are typically selected from e.g. carbon-or hydrocarbon-based, polar groups such as halogen, nitro, hydroxyl, etc., or polymerizable groups.

For simplicity, the term "liquid crystal" material or medium is used for both liquid crystal and mesogenic materials or media, and vice versa, and the term "mesogenic" is used for the mesogenic groups of the material.

The term "non-mesogenic compound or material" means a compound or material that does not contain a mesogenic group as defined above.

As used herein, the term "polymer" is understood to mean a molecule comprising a backbone of one or more different types of repeating units (the smallest structural unit of the molecule), and includes the commonly known terms "oligomer", "copolymer", "homopolymer", and the like. Furthermore, it is understood that the term polymer includes, in addition to the polymer itself, residues from initiators, catalysts and other elements accompanying the synthesis of such polymers, wherein such residues are understood not to be covalently bound thereto. In addition, these residues and other elements, while typically removed during post-polymerization purification, are typically mixed or blended with the polymer such that they typically remain with the polymer as it is transferred between vessels or between solvents or between dispersion media.

The term "(meth) acrylic polymer" as used in the present invention includes polymers obtained from acrylic monomers, polymers obtained from methacrylic monomers, and corresponding copolymers obtained from mixtures of these monomers.

The term "polymerization" means a chemical process of forming a polymer by bonding together a plurality of polymerizable groups or polymer precursors (polymerizable compounds) containing such polymerizable groups.

Polymerizable compounds having one polymerizable group are also referred to as "mono-reactive" compounds, compounds having two polymerizable groups are referred to as "di-reactive" compounds, and compounds having more than two polymerizable groups are referred to as "multi-reactive" compounds. Compounds without polymerizable groups are also referred to as "non-reactive or non-polymerizable" compounds.

The terms "film" and "layer" include rigid or flexible, self-supporting or free-standing films or layers with more or less significant mechanical stability, as well as coatings or layers on a supporting substrate or between two substrates.

Visible light is electromagnetic radiation having a wavelength in the range of about 400nm to about 745 nm. Ultraviolet (UV) light is electromagnetic radiation having a wavelength in the range of about 200nm to about 400 nm.

It has surprisingly been found that the use of additives and surfactants in the preparation of nanocapsules and nanocapsule-containing films and the inclusion of these additives in products can lead to a reduction in the operating voltage of the products in electro-optical applications. At the same time, other product properties, such as a suitable dark state, film forming ability, low hysteresis, good VHR, suitable refractive index matching and sufficient transparency and transmission, can be maintained or even improved.

Advantageously, the addition of the additive may be carried out at various stages of the manufacturing process, alternatively or additionally, in particular before or during capsule formation and processing, capsule post-processing and concentration, even during or after film formation with the binder material, in addition to the addition of a surfactant in (b) above. Furthermore, the addition of the method and additives may provide suitable performance and suitable results even in the presence of aqueous systems or environments.

In a first aspect, the present invention relates to a process for the preparation of nanoparticles, wherein a composition is provided comprising a mesogenic medium as described above and below and one or more polymerizable compounds, and wherein the composition is then dispersed as nanodroplets in an aqueous phase using a surfactant. As the nanodroplets are produced, one or more polymerizable compounds are polymerized, thereby obtaining nanocapsules, each nanocapsule comprising a polymer shell and a core containing a mesogenic medium. The method further comprises adding one or more additives. In one embodiment, in addition to the surfactant, further additives may be included in the nanodroplet dispersion, i.e., before the polymerization is carried out. It is also possible and in some cases preferable to add one or more additives to the formed nanocapsules, i.e. after the polymerization step. In another embodiment, the additives are added before and after the nanocapsule is formed.

It was surprisingly found that according to the present invention, an efficient and controlled process can be finally performed on the nanometer scale to produce nanometer-sized containers encapsulating LC material, which are typically spherical or spheroidal. The process makes use of a dispersion, in particular a nanoemulsion, which is also referred to as miniemulsion, in which a nanosized phase comprising the LC material and the reactive (one or more) polymerizable compounds is dispersed in a suitable dispersion medium. It has also been found that the addition of one or more additives to the nanodroplets or formed nanocapsules can further improve or adjust the property performance of the nanocapsules.

A composition comprising a mesogenic medium and one or more polymerizable compounds is initially provided. In order to set and influence the solubility, dissolution and/or mixing, optionally and preferably organic solvents can be added to the composition, which can for example advantageously influence the phase separation during the polymerization. Thus, in a preferred embodiment, the composition provided in step (a) further comprises one or more organic solvents.

The composition is then dispersed as nanodroplets in the aqueous phase. It has been found that the provision of a surfactant prior to polymerization can advantageously facilitate the formation and subsequent stabilization, in particular ionic and/or steric stabilization, of discrete nano-droplets in a dispersion medium, in particular an aqueous dispersion medium, wherein the nano-droplets comprise the LC medium and the polymerizable compound(s).

Stirring, preferably mechanical stirring, in particular high shear mixing, may suitably produce or further influence the dispersion, in particular emulsification and homogenization, and likewise promote the formation of nanodrops. Alternatively, membrane emulsification may be used, for example.

Thus, mechanical agitation and the provision of surfactants may play an advantageous role in obtaining nanodroplets and subsequently nanosized capsules, in particular nanocapsules having a substantially uniform size distribution or low polydispersity.

The dispersed phase exhibits poor solubility in the dispersion medium, which means that it exhibits low solubility or even is practically insoluble in the dispersion medium forming the continuous phase. Advantageously, water-based or aqueous solutions or mixtures are used to form the continuous or external phase.

The individual nano-droplets are separated from each other by dispersion in such a way that each droplet constitutes a separate nano-sized reaction volume for subsequent polymerization.

The aqueous mixture may be prepared or provided in different ways. In one embodiment, a surfactant solution or mixture may be prepared, preferably in water, and added to the composition comprising the mesogenic medium and the polymerizable compound(s). The provided aqueous mixture is then stirred, in particular mechanically stirred, to obtain nanodroplets comprising the polymerizable compound(s) and the liquid crystalline medium dispersed in the aqueous phase according to the invention. Stirring or mixing can be performed using high shear mixing. For example, a high performance dispersion apparatus using the rotor-stator principle may be used, such as the commercially available turrax (ika). Optionally, this high shear mixing may be replaced by ultrasound, in particular high power ultrasound. Sonication and high shear mixing may also be combined, with sonication preferably preceding high shear mixing.

The combination of stirring as described above with the provision of a surfactant may advantageously result in the proper formation and stabilization of the dispersion, in particular the emulsion. The use of a high-pressure homogenizer, optionally and preferably in addition to the above-described mixing, can further advantageously influence the preparation of nanodispersions, in particular nanoemulsions, by setting or adjusting and correspondingly reducing the droplet size and also by making the droplet size distribution narrower, i.e. improving the uniformity of the particle size. Particular preference is given to when the high-pressure homogenization is repeated, in particular several times, for example three, four or five times. For example, commercially available microfluidizer (microfluidics) can be used.

Therefore, in a preferred embodiment, a high-pressure homogenizer is used in step (b) of the preparation process according to the invention.

As the nanodroplets are created, one or more polymerizable compounds are polymerized. Nanocapsules are thus obtained, which comprise a polymeric shell and a core containing a mesogenic medium.

However, the preparation of the nanocapsules according to the invention is not limited thereto and they may also be prepared by other methods, for example by encapsulation with a preformed polymer, coacervation, solvent evaporation, or by solute co-diffusion, in the present invention it is advantageously realised that nanocapsules comprising an LC medium may advantageously be prepared by using a method of in situ polymerisation.

Furthermore, it has been realized that instead of providing a ready-made polymer for encapsulating the liquid crystal medium, the nanoscale encapsulation of the mesogenic matrix may advantageously be carried out in situ starting from a polymer precursor. Thus, the use of preformed polymers and particularly provided emulsifiers can advantageously be avoided. In this regard, the use of a given pre-prepared polymer may make the formation and stabilization of the nanoemulsion difficult, while it may also limit the tunability of the overall process.

The in-situ polymerization method is not particularly limited, and, for example, interfacial polymerization may be used. Preferably, however, the in situ polymerization according to the invention is based in particular on polymerization-induced phase separation.

In this process based on polymerization-induced phase separation, according to the invention, the polymerizable compound(s) are at least partially soluble or at least partially dissolved in the phase comprising the mesogenic medium, preferably the polymerizable compound(s) and the mesogenic medium are intimately mixed, in particular homogeneously mixed, wherein the mixture is nanophase-separated by polymerization, i.e. polymerization-induced phase separation (PIPS). The temperature can be set and adjusted to favorably influence the solubility.

It was advantageously observed that the provided LC media as described above and below are suitably stable in the encapsulation process, in particular in the polymerization and the conditions associated therewith, such as exposure to heat or UV light, e.g. light from a UV lamp in the wavelength range from 300nm to 380 nm. The choice of wavelength is advantageously not limited by the UV cut-off of the glass, in view of the fact that no polymerization between glass substrates is required, but can be set, for example, in view of the material properties and the stability of the composition.

The present process conveniently utilises in situ polymerisation and is advantageously and preferably based on a combination of polymerisation and phase separation, in particular a combination of nanodispersions and PIPS. This method offers significant advantages in providing a controlled and adaptable method of preparation. The nanocapsules obtained or obtainable by the process exhibit a suitable and adjustable particle size while at the same time providing an advantageously high particle size uniformity, i.e. an advantageously low polydispersity, and thereafter advantageously uniform product properties. It has surprisingly been found that setting the appropriate capsule nano-size while observing and achieving low polydispersity can have a beneficial effect on the operating voltage. The electro-optical parameters of the obtained nanocapsules, in particular of the LC medium contained therein, can advantageously be set and adjusted in view of the controllability and adaptability of the method.

The size given by the nanodroplets sets the length scale or volume of the transition or separation, resulting in polymerization-induced nanophase separation. In addition, the droplet interface can serve as a template for encapsulating the polymer shell. The polymer chains or networks formed or initially formed in the nanodroplets may segregate or be driven or accumulated at the interface with the aqueous phase, where polymerization may proceed and also terminate to form a closed encapsulation layer. In this regard, the polymer shell being formed or already formed is substantially immiscible in the aqueous phase and the LC medium.

Thus, in one aspect of the invention, the polymerization may be carried out, promoted and/or continued at the interface between the aqueous phase and the phase comprising the LC medium. In this regard, the interface may act as a diffusion barrier and a reaction site.

Furthermore, the properties of the polymer, in particular the structure and the structural units, of the forming and already forming interface of the capsule may influence the material properties, in particular the LC alignment, e.g. by homeotropic anchoring, anchoring energy and switching behavior in response to an electric field. In one embodiment, the anchoring energy or intensity is reduced to favorably affect the electro-optical switching, where, for example, the polymer surface morphology and polarity can be appropriately set and adjusted.

In one embodiment, the surfactant(s) used according to step (b) may be at least partially incorporated into the polymeric capsule shell, and in particular at the interface with the LC inside the capsule. The surfactant molecules incorporated at such interfaces can advantageously affect the electro-optic performance and reduce the operating voltage, particularly by setting or adjusting the interface properties and interactions. In one case, the surfactant may advantageously influence the alignment of the LC molecules, e.g. promote homeotropic alignment leading to a radial configuration. Additionally or alternatively, the surfactant molecules may affect the morphology and physicochemical properties of the internal polymer surface such that the anchoring strength is reduced. Thus, the surfactant provided according to step (b) not only contributes to the advantageous process according to the invention, but may also provide benefits in the obtained nanocapsules.

In a preferred embodiment, two surfactants or one surfactant and another additive are used in step (b). This way it is possible to adjust or tune properties, such as size and interface characteristics or alignment, even more efficiently and effectively. For example, it may be useful to combine agents that, individually or together, help to affect, for example, wettability, solubility, viscosity, polarity, or hydrophobicity. These optional additives further provided in step (b) may likewise preferably be present or accumulate at the interface.

The combined elements of the method may advantageously lead to the preparation of a multitude of individual, dispersed or dispersible nanocapsules each having a polymeric shell and a core comprising an LC material, wherein the surfactant(s) used may contribute to a favourably low caking tendency.

In the PIPS process, the phase separation and the properties of the formed polymer shell, in particular the stability and immiscibility with the LC component, can be advantageously influenced by optionally and preferably crosslinking the forming or already formed polymer chains. However, without such crosslinking, the capsule properties are already sufficiently good.

Recognizing the respective miscibility, solubility and compatibility, or possible lack thereof, of the various components, in particular of the LC material, the polymerizable compound or compounds as well as the dispersion medium and the forming and already formed polymer play an important role, in particular the free energy of mixing and the interaction energy of mixing and the entropy of mixing.

Furthermore, it is noted that the encapsulation process is based on a polymerization reaction, i.e. a specific dynamic process is the basis for the capsule formation. In particular, it is now generally observed that the polymerizable compound(s) used for encapsulation have a suitable miscibility with the LC medium, whereas the formed capsule shell polymer exhibits a suitably low solubility with the LC material.

In the process according to the invention, the polymerization conversion or completion can be surprisingly high and the amount of residual unreacted polymerizable compounds is advantageously low. This may ensure that the properties and performance of the LC medium in the formed capsules are not or only minimally affected by residual reactive monomers.

According to step (c), polymerizing the dispersed nanodroplets. In particular, the polymerizable compound(s) contained in or mixed with the nanodroplets is polymerized. Preferably and advantageously, the polymerization results in PIPS. The nanocapsules having a core-shell structure as described above and below are formed by polymerization. The obtained or obtainable nanocapsules are generally spherical, substantially spherical or spheroidal. In this regard, some shape asymmetry or small deformation may be beneficial, for example in terms of operating voltage.

The polymerization in the emulsion droplets and at the interface of each droplet can be carried out using conventional methods. The polymerization may be carried out in one or more steps. In particular, the polymerization of the polymerizable compound in the nanodroplets is preferably effected by exposure to heat or actinic radiation, wherein exposure to actinic radiation means irradiation with light, such as 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. In a preferred embodiment, free radical polymerization is carried out.

In case the polymerization reaction is carried out in more than one step, a shell having more than one layer may be prepared, e.g. a shell structure having two layers, wherein further reactive monomers are provided for further polymerization step(s). The shell layers may have different compositions and respective different properties depending on the polymer precursor and/or the polymerization conditions in the step. For example, a shell may be formed having a more lipophilic inner layer facing the core and a more hydrophilic outer layer facing the external environment, such as the binder in a composite membrane.

The polymerization may be carried out at a suitable temperature. In one embodiment, the polymerization is carried out at a temperature below the clearing point of the mesogenic mixture. However, in another embodiment, the polymerization may also be carried out at or above the clearing point.

In one embodiment, the polymerization is carried out by heating the emulsion, i.e. by thermal polymerization, for example by thermal polymerization of acrylate and/or methacrylate compounds. It is particularly preferred that the reactive polymerizable precursors thermally initiate free radical polymerization leading to nano-encapsulation of the LC material.

In another embodiment, the polymerization is carried out by light irradiation, i.e. with light, preferably UV light. As the source of actinic radiation, for example, a single UV lamp or a group of UV lamps can be used. When high lamp power is used, the curing time can be shortened. Another possible light radiation source is a laser, for example a UV laser, a visible laser or an IR laser.

Suitable and conventionally used thermal or photo initiators may be added to the composition to facilitate the reaction, for example azo compounds or organic peroxides such as Luperox type initiators. In addition, suitable conditions for polymerization and suitable types and amounts of initiators are known in the art and described in the literature.

For example, when polymerizing by UV light, a photoinitiator that decomposes upon UV irradiation may be used to generate radicals or ions that initiate the polymerization reaction. The use of free-radical photoinitiators is preferred for the polymerization of acrylate or methacrylate groups. For polymerizing vinyl groups, a cationic photoinitiator is preferably used for epoxy or oxetane groups. In addition, a thermal polymerization initiator that decomposes when heated to generate radicals or ions that initiate the polymerization reaction may also be used. Typical free radical photoinitiators are, for example, commercially availableOr(Ciba Geigy AG, Basel, Switzerland). Typical cationic photoinitiators are, for example, UVI6974(Union Carbide).

In one embodiment, the initiator used is well soluble in the nanodroplets but is insoluble in water, or at least substantially insoluble in water. For example, Azobisisobutyronitrile (AIBN), which in certain embodiments is further comprised in the composition according to the present invention, may be used in the method of preparing the nanocapsule.

Alternatively or additionally, a water-soluble initiator may be provided, such as 2,2' -azobis (2-methylpropionamide) dihydrochloride (AIBA).

Other additives may also be added. In particular, the polymerizable material may additionally comprise one or more additives, such as catalysts, sensitizers, stabilizers, inhibitors and chain transfer agents.

For example, the polymerizable material may also contain one or more stabilizers or inhibitors to prevent unwanted spontaneous polymerization, such as are commercially available(Ciba Geigy AG,Basel,Switzerland)。

By adding one or more chain transfer agents to the polymerizable material, the properties of the obtained or obtainable polymer can be improved. By using a chain transfer agent, the length of the free polymer chains and/or the length of the polymer chains between two cross-linking points in the polymer can be adjusted, wherein typically the length of the polymer chains in the polymer decreases when the amount of chain transfer agent increases.

The polymerization is preferably carried out under an inert gas atmosphere, such as nitrogen or argon, more preferably under a heated nitrogen atmosphere. But polymerization in air is also possible.

It is furthermore preferred that the polymerization is carried out in the presence of an organic solvent, wherein the organic solvent is preferably provided in the composition comprising the LC medium. The use of an organic solvent, such as hexadecane or 1, 4-pentanediol, is advantageous in adjusting the solubility of the reactive compound(s) with the LC material and in stabilizing the nano-droplets, and it may also be beneficial in influencing the phase separation. However, it is preferred that the amount of organic solvent, if used, is limited, typically below 25% by weight, more preferably below 20% by weight and especially below 15% by weight based on the total composition.

The formed polymer shell suitably exhibits low solubility, i.e. is substantially insoluble, in terms of the LC material and water. Furthermore, in this method, it is possible to suitably and advantageously limit or even avoid the coagulation or aggregation of the produced nanocapsules.

It is also preferred to crosslink the polymer being formed or already formed in the shell. Such crosslinking may facilitate the formation of a stable polymer shell and provide suitable containment and barrier functions while maintaining sufficient mechanical flexibility.

The method according to the present invention thus provides for encapsulation and confinement of mesogenic media while maintaining the electro-optical properties, in particular the electrical responsiveness, of the LC material, in particular provides for compositions and process conditions such that the stability of the LC material is maintained LC may thus exhibit advantageous properties in the formed nanocapsules, such as a suitably high △ epsilon, a suitably high △ n, a high advantageous clearing point and a low melting point.

According to optional, and in some cases preferred, step (d) of the present process, one or more additives are added to the nanocapsules obtained in carrying out step (c). It was surprisingly found that even after the nanoparticles have been formed, their properties can still be influenced and adjusted by adding suitable additives. The nanoparticles obtained by polymerization generally already have sufficient and useful properties, wherein the properties of the product are to a large extent determined by the composition and configuration of the LC material contained in the core and in the formed polymer shell. However, unexpectedly, some properties of the nanoparticles can still be further improved or altered by the additional step of adding one or more additives to the nanocapsules after preparation of the encapsulated nanoparticles. Such improvements or adjustments of the nanocapsules may be particularly beneficial under certain conditions or in view of specific applications.

The additives according to the invention may be selected with a view to achieving or adapting to specific product properties. For example, agents that facilitate wetting and solubility, chemical resistance such as water repellency, film formation, and defoaming may be used. In one embodiment, an organic solvent or hydrophobic or hydrophobizing agent may be added. In a preferred embodiment of the invention, however, the one or more additives are specifically selected to be one or more surfactants. Although these surfactants, which may be used as additives according to step (d), may provide further benefits such as facilitating suitable film formation, a favourable dark state or a suitably low hysteresis, it is advantageously recognised that these additives may be used to reduce the operating voltage when the nanocapsules are used in electro-optical devices.

According to the present invention, one or more additives are used in combination with one of the surfactants provided in step (b). In this respect, the surfactant provided according to step (b) is used during the generation of the nanodroplets and also in the subsequent polymerization. As noted above, the surfactants therein are useful in the process, for example, by promoting and stabilizing the microemulsion and preventing and minimizing particle aggregation during and after capsule formation. Furthermore, the surfactant may additionally influence product properties such as capsule size, as well as electro-optical properties as described above, for example by modulating the interfacial interaction between the shell and the core. They therefore have a variety of functions and should provide suitable properties during the preparation of capsules from precursor materials.

The additive(s), preferably the surfactant(s), used in step (d) are added only after capsule formation. Thus, they can generally be selected independently of the requirements of the emulsification and polymerization steps. However, the additive(s), preferably surfactant(s), in one case may be selected in view of, i.e. matched to or adjusted to, the surfactant(s) provided according to step (b), and the optionally included additives, and may even be the same surfactant. Thus, in one embodiment, the additive of step (d) is selected to be the same as the surfactant provided in step (b).

In another case, the surfactant according to step (d) may be selected independently and more freely, for example taking into account other criteria. In a preferred embodiment, the additive of step (d) is provided in view of lowering the operating voltage. Thus, in another embodiment, the additive according to step (d) is different from the surfactant provided in step (b).

In the method, suitably dispersed stable nanocapsules are produced. After obtaining the nanocapsule, optionally and preferably, the aqueous phase may be removed, or the amount of water may be reduced or depleted, or alternatively, the aqueous phase may be exchanged for another dispersion medium.

In one embodiment, the dispersed or dispersible nanocapsules are substantially or completely separated from the aqueous phase, for example by filtration or centrifugation. Conventionally used filtration, such as membrane filtration, dialysis, cross-flow filtration, and in particular cross-flow filtration in combination with dialysis, and/or centrifugation techniques may be used. Filtration and/or centrifugation may provide further benefits by, for example, removing excess or unwanted or even residual surfactant provided in step (b). Thus, not only concentration of the nanocapsules, but also purification can be provided, for example, by removing contaminants, impurities or unwanted ions.

Preferably and advantageously, the surface charge of the capsule is kept at a minimum. Based on mechanical stability, nanocapsules can be relatively easily subjected to separation techniques, for example using evaporation or extraction methods. The nanocapsules may also be dried, wherein drying refers to removing the dispersion medium but retaining the LC material contained within the capsules. Conventional techniques such as drying in air, critical point drying and freeze drying, particularly freeze drying, may be used. Other conventional solvent removal, isolation, purification, concentration and work-up, such as chromatography or fractionation, may also be carried out.

In the process according to the invention, one or more additives, preferably one or more surfactants, may be added to the nanocapsules before the optional further step of depleting, removing or exchanging the aqueous phase. Alternatively, one or more additives, preferably one or more surfactants, may be added to the nanocapsule after an optional further step of depleting, removing or exchanging the aqueous phase. Additives, preferably surfactants, may also be added before and after the aqueous phase is depleted, removed or exchanged.

Depending on the material properties and the respective circumstances, additives, preferably surfactants, can be added directly or as a solution using suitable solvents, for example water or aqueous solvents, isopropanol or acetone. The nanocapsules and the additive are then suitably mixed, for example using stirring, sonication and/or heating.

The additives, in particular surfactants, used according to step (b) and optional step (d), may advantageously influence the properties of the nanocapsules, respectively alone or in combination, by influencing the polymer shell or even the LC material, at least by interactions at the inner interface of the capsule wall. It is believed that the surfactant may adsorb to and in some cases or under certain conditions permeate into, dissolve in or even penetrate or pass through the polymer composition forming the capsule shell, so that it may adjust the properties of the shell, for example in terms of charging, conductivity or dielectricity. The surfactant molecules may also act at the interface between the polymer shell and the LC material, for example to influence or reduce the anchoring energy of the LC material to the polymer shell surface or to influence the alignment of the LC molecules. In case a part of the surfactant or additive is mixed with the LC material, the elastic constant or viscosity of the material as well as its electro-optical properties may also be changed. Furthermore, when the surfactant or additive molecules are located on the outer surface of the nanocapsule interaction, e.g. solubility and wettability with the environment can be altered and advantageously adjusted, e.g. in view of compatibility with the adhesive.

In this process, water or an aqueous solution is advantageously used as the dispersion medium. However, it was further observed in this respect that the provided compositions as well as the produced nanocapsules show suitable stability and chemical resistance to the presence of water, e.g. with respect to hydrolysis. In one embodiment, the amount of water can be reduced or even substantially minimized by providing or adding a polar medium, preferably a non-aqueous polar medium, containing, for example, formamide or ethylene glycol or a hydrofluorocarbon.

Advantageously, the process according to the invention provides a large number of individual nanocapsules which are dispersible and even redispersible. Therefore, they can be further easily and flexibly used and applied to various environments. Due to their stability, it also becomes possible to store the capsules before use in various applications, in particular with a suitably long shelf life. However, immediate further processing is also an advantageously provided option. In this regard, the capsules are suitably stable during processing, particularly for coating applications.

The method as described above provides a convenient way of producing nanocapsules in a controlled and adaptive manner. In particular, the capsule particle size can be suitably varied while keeping the polydispersity low, for example by adjusting the amount of surfactant in the composition. It has surprisingly been found that a suitably set uniform capsule size may be particularly advantageous in view of reducing the operating voltage in electro-optical applications. In addition, the additives added to the nanodroplets prior to polymerization or in step (d) may advantageously further contribute to the reduction of the operating voltage.

It has furthermore been found that step (a) of the process according to the invention provides compositions which exhibit suitable behaviour and properties during the preparation as well as in the resulting product. This means that the composition is on the one hand very suitable for nano-encapsulation, i.e. the formation of nano-capsules, wherein the capsule shell of each capsule formed comprises a nano-sized volume of the LC medium. On the other hand, they can also be used to obtain advantageous product properties, for example in electro-optical applications.

In particular, the compositions provided according to the invention allow the preparation of advantageous nanocapsules containing a mesogenic medium in an advantageous process, in particular using an in situ polymerisation process, in particular a PIPS-based process, wherein the composition has advantageous properties in the process. Furthermore, these compositions allow to obtain nanocapsules which offer significant benefits in terms of physical and chemical properties, in particular in terms of their electro-optical properties and their suitability for use in electro-optical devices. The compositions of the present invention are therefore useful in the preparation of nanocapsules.

The composition may be provided by appropriate mixing or blending of the components.

In a preferred embodiment, the composition according to the invention comprises an LC medium in an amount of from 5 to 95% by weight, more preferably from 15 to 75% by weight, in particular from 25 to 65% by weight, based on the total composition.

In a preferred embodiment, the composition according to the invention further comprises one or more organic solvents. It was found that the provision of an organic solvent may provide additional benefits in the process of preparing the nanocapsules of the present invention. In particular, the one or more organic solvents may help to set or adjust the solubility or miscibility of the components. Solvents may be suitable co-solvents, wherein the solvent power of the other organic components may be enhanced or influenced. Furthermore, the organic solvent(s) may have a favourable effect during the phase separation caused by the polymerization of the polymerizable compound(s).

In this regard, as the organic solvent(s), standard organic solvents may be used. The solvent(s) may be selected from, for example, 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 glycols, n-alkanes and aliphatic alcohols. Binary, ternary or higher mixtures of the above solvents may also be used.

In one embodiment, 1, 5-dimethyltetralin, 3-phenoxytoluene, cyclohexane or 5-hydroxy-2-pentanone may be added.

In a preferred embodiment, the solvent is selected from one or more of cyclohexane, tetradecafluorohexane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, hexadecane-1-ol, 2-isopropoxyethanol, octyldodecanol, 1, 2-ethanediol, 1, 2-propanediol, 1, 3-butanediol, 1, 4-butanediol, pentanediol, especially 1, 4-pentanediol, hexanediol, especially 1, 6-hexanediol, heptanediol, octanediol, triethanolamine, ethyl acetate, ethyl hexanoate and butyl acetate. Particularly preferably, the organic solvent used comprises hexadecane or 1, 4-pentanediol, in particular hexadecane or 1, 4-pentanediol. In another embodiment, a combination comprising hexadecane and 1, 4-pentanediol is used.

The organic solvent, especially hexadecane, is preferably added in an amount of from 0.1 to 35% by weight, more preferably from 1 to 25% by weight, especially from 3 to 17% by weight, based on the total composition.

In one embodiment, the amount of hexadecane used in the preparation of the nanocapsule is not considered to constitute an additional additive according to the present invention.

The organic solvent(s) may enhance solubility or solubilization, or dilute other organic components and may help to adjust viscosity.

In one embodiment, the organic solvent acts as a hydrophobic agent. Its addition to the dispersed phase of the nano-or micro-emulsion can influence, in particular increase, the osmotic pressure in the nano-droplets. This can help stabilize "oil in water" emulsions by inhibiting Ostwald ripening. Preferred organic solvents for use as hydrophobicizing agents have a solubility in water which is lower than the solubility of the liquid crystal in water, whereas they are soluble in the liquid crystal. Organic solvents, preferably hydrophobic agents, may act as stabilizers or co-stabilizers.

In the composition according to the invention, one or more polymerisable compounds are provided as precursors for the polymer shell or wall containing or surrounding the LC medium.

The polymerizable compound has at least one polymerizable group. The polymerisable group is preferably selected from CH₂＝CW¹-COO-,CH₂＝CW²-(O)_k1-,CH₃-CH＝CH-O-,(CH₂＝CH)₂CH-OCO-,(CH₂＝CH-CH₂)₂CH-OCO-,(CH₂＝CH)₂CH-O-,(CH₂＝CH-CH₂)₂N-,HO-CW²W³-,HS-CW²W³-,HW²N-,HO-CW²W³-NH-,CH₂＝CW¹-CO-NH-,CH₂＝CH-(COO)_k1-Phe-(O)_k2-, Phe-CH- ═ CH-, HOOC-, OCN-, where W is¹Is H, Cl, CN, phenyl or alkyl having 1 to 5C atoms, in particular H, Cl or CH₃，W²And W³Independently of one another, H or alkyl having 1 to 5C atoms, in particular H, methyl, ethyl or n-propyl, Phe is 1, 4-phenylene and k₁And k₂Independent of each otherAnd ground is 0 or 1.

One or more polymerizable compounds are selected such that they have suitable and sufficient solubility in the LC component or phase. Furthermore, they need to be susceptible to polymerization conditions and the environment. In particular, the polymerizable compound(s) can be suitably polymerized at a high conversion rate, resulting in a favorable small amount of residual unreacted polymerizable compound after the reaction. This may provide benefits in terms of stability and performance of the LC medium. Further, the polymerizable components are selected such that the polymers formed therefrom phase separate or the polymers formed phase separate as appropriate to constitute the polymeric capsule shell. In particular, the solubility of the LC component in the shell polymer and the swelling or gelling of the formed polymer shell are advantageously avoided or minimized, wherein the amount and composition of the LC medium in the formed capsules remains substantially constant. Thus, an advantageous preferential solubility of any LC compound of the LC material in the wall is minimized or avoided.

By providing a suitably tough polymer shell, swelling or even rupture of the nanocapsules and undesired leakage of the LC material from the capsules is advantageously minimized or even completely avoided.

The polymerization or curing time depends, inter alia, on the reactivity and amount of the polymerizable material, the thickness of the capsule shell formed and, if present, the amount and type of polymerization initiator and the reaction temperature and/or the radiation power, for example of an ultraviolet lamp. The time and conditions of polymerization or curing may be selected, for example, to obtain a fast process for polymerization, or alternatively, for example, to obtain a slow process, however, where the integrity of the conversion and separation of the polymer may be favorably affected. It is therefore preferred to have short polymerization and curing times, for example less than 5 minutes, while in another alternative embodiment, longer polymerization times may be preferred, for example more than 1 hour or even at least 3 hours.

In one embodiment, non-mesogenic polymerizable compounds, i.e. compounds which do not contain mesogenic groups, are used. However, they exhibit sufficient and suitable solubility or miscibility with the LC component. In a preferred embodiment, an organic solvent is additionally provided.

In another aspect, polymerizable mesogenic or liquid crystalline compounds, also referred to as Reactive Mesogens (RMs), are used. These compounds contain a mesogenic group and one or more polymerizable groups, i.e. functional groups suitable for polymerization.

Optionally, in one embodiment, the polymerizable compound(s) according to the invention comprise only reactive mesogens, i.e. all reactive monomers are mesogens. Alternatively, the RM may be provided in combination with one or more non-mesogenic polymerizable compounds. The RM may be mono-reactive, or di-or poly-reactive. The RMs may exhibit advantageous solubility or miscibility with the LC medium. However, the polymers formed or formed therefrom are further designed to exhibit suitable phase separation behavior. Preferred polymerizable mesogenic compounds comprise at least one polymerizable group as end group and a mesogenic group as core group, further preferably comprising a spacer and/or a linking group between the polymerizable group and the mesogenic group. In one embodiment 2-methyl-1, 4-phenylene-bis [4- [3- (acryloyloxy) propoxy ] benzoate (RM 257, Merck KGaA) is used. Alternatively or additionally, one or more lateral substituents of the mesogenic group may also be polymerizable groups.

In another embodiment, the use of mesogenic polymerizable compounds is avoided.

In a preferred embodiment, the polymerizable compound or compounds are selected from the group consisting of vinyl chloride, vinylidene chloride, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, methyl-, ethyl-, N-or tert-butyl-, cyclohexyl-, 2-ethylhexyl-, phenoxyethyl-, hydroxyethyl-, hydroxypropyl-, 2-5C-alkoxyethyl-, tetrahydrofurfuryl acrylate or methacrylate, vinyl acetate, propionate, acrylate, succinate, N-vinylpyrrolidone, N-vinylcarbazole, styrene, divinylbenzene, ethylene glycol diacrylate, 1, 6-hexanediol acrylate, bisphenol-A-diacrylate and dimethacrylate, trimethylolpropane diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, triethylene glycol diacrylate, ethylene glycol dimethacrylate, tripropylene glycol triacrylate, pentaerythritol tetraacrylate, ditrimethylpropane tetraacrylate or dipentaerythritol penta-or hexaacrylate. Thiol-olefins are also preferred, for example, the commercially available product Norland 65(Norland Products).

The polymerizable or reactive groups are preferably selected from vinyl, acrylate, methacrylate, fluoroacrylate, oxetane or epoxy groups, particularly preferably acrylate or methacrylate groups.

Preferably, the one or more polymerizable compounds are selected from the group consisting of acrylates, methacrylates, fluoroacrylates, and vinyl acetates, wherein the composition more preferably further comprises one or more di-and/or tri-reactive polymerizable compounds, preferably selected from the group consisting of diacrylates, dimethacrylates, triacrylates, and trimethacrylates.

In one embodiment, the one or more polymerizable compounds (ii) as described above comprise one, two or more polymerizable groups selected from acrylate, methacrylate and vinyl acetate groups, wherein said compounds are preferably non-mesogenic compounds.

In a preferred embodiment, the composition according to the invention comprises one or more monoacrylates, preferably added in an amount of from 0.1% to 75% by weight, more preferably from 0.5% to 50% by weight, in particular from 2.5% to 25% by weight, based on the total composition. Particularly preferred mono-reactive compounds are selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, tert-butyl acrylate, pentyl acrylate, hexyl acrylate, nonyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxybutyl acrylate, 2, 3-dihydroxypropyl acrylate and glycidyl acrylate.

Additionally or alternatively, vinyl acetate may be added.

In another preferred embodiment, the composition according to the invention, optionally in addition to the above-mentioned monoacrylates, preferably incorporates one or more monomethacrylates in an amount of 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, based on the total composition. Particularly preferred mono-reactive compounds are selected from the group consisting of methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, tert-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, nonyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxybutyl methacrylate, 2, 3-dihydroxypropyl methacrylate and glycidyl methacrylate, stearyl methacrylate, adamantyl methacrylate and isobornyl methacrylate.

It is particularly preferred to add at least one crosslinking agent, i.e. a polymerizable compound containing two or more polymerizable groups, to the composition. Crosslinking of the polymer shell in the prepared particles may provide additional benefits, particularly in further improving stability and containment, and adjusting or reducing sensitivity to swelling, particularly due to solvent-induced swelling. In this regard, di-and multi-reactive compounds may be used to form their own polymer networks and/or to crosslink polymer chains formed substantially from polymerizing mono-reactive compounds.

Conventional crosslinking agents known in the art may be used. It is particularly preferred to additionally provide di-or multireactive acrylates and/or methacrylates, preferably in amounts of from 0.1 to 75% by weight, more preferably from 0.5 to 50% by weight, in particular from 2.5 to 25% by weight, based on the total composition. Particularly preferred compounds are selected from the group consisting of ethylene diacrylate, propylene diacrylate, butylene diacrylate, pentylene diacrylate, hexylene diacrylate, ethylene glycol diacrylate, glycerol diacrylate, pentaerythritol tetraacrylate, ethylene dimethacrylate, also known as ethylene glycol dimethacrylate, propylene dimethacrylate, butylene dimethacrylate, pentylene dimethacrylate, hexylene dimethacrylate, tripropylene glycol diacrylate, ethylene glycol dimethacrylate, glycerol dimethacrylate, trimethylpropane trimethacrylate and pentaerythritol triacrylate.

The ratio of mono-reactive monomer and di-or multireactive monomer can be advantageously set and adjusted to affect the polymer composition of the shell and its properties.

According to step (b) of the method, the composition is dispersed as nanodroplets in an aqueous solution using a surfactant. In one embodiment, the surfactant may be mixed and included in the composition provided in step (a). Alternatively, the surfactant is added after step (a), preferably in the form of an aqueous mixture. In this case, the surfactant is provided in an aqueous phase and then mixed with the composition provided in (a).

Thus, according to a preferred embodiment, the surfactant may be prepared or provided separately in an initial step and then added to the other components. In particular, the surfactant may be prepared or provided as an aqueous mixture or composition, which is then added to the other components comprising the mesogenic medium and the polymerizable compound(s) as described above and below. Particularly preferably, the one surfactant is provided as an aqueous surfactant.

Surfactants are useful in lowering surface or interfacial tension and facilitating emulsification and dispersion.

Conventional surfactants known in the art may be used, including anionic surfactants such as sulfate, e.g., sodium lauryl sulfate, sulfonate, phosphate and carboxylate surfactants, cationic surfactants such as secondary or tertiary amine and quaternary ammonium salt surfactants, zwitterionic surfactants such as betaine, sultaine and phospholipid surfactants, and nonionic surfactants such as long chain alcohols and phenols, ethers, esters or amides.

In a preferred embodiment according to the invention, a nonionic surfactant is used. The use of nonionic surfactants can provide benefits in the preparation of nanocapsules, particularly in the formation and stabilization of dispersions and PIPS. It is further recognized that it may be advantageous to avoid charged surfactants in the case of inclusion of surfactants, such as residual surfactants, in the formed nanocapsules. Thus, the use of nonionic surfactants and avoidance of ionic surfactants is beneficial in the stability, reliability and electro-optic characteristics and performance of nanocapsules, as well as in composite systems and electro-optic devices.

Polyethoxylated nonionic surfactants are particularly preferred. Preferred compounds are selected from polyoxyethylene glycol alkyl ether surfactants, polyoxypropylene glycol alkyl ether surfactants, glucoside alkyl ether surfactants, polyoxyethylene glycol octylphenol ether surfactants such as Triton^TMX-100, polyoxyethylene glycol alkylphenol ether surfactants, glycerol alkyl ester surfactants, polyoxyethylene glycol sorbitan alkyl ester surfactants such as polysorbitols, sorbitan alkyl ester surfactants, cocamide monoethanol-amine, cocamide diethanolamine, and dodecyl dimethylamine oxide.

In a particularly preferred embodiment, the surfactant(s) used are selected from polyoxyethylene glycol alkyl ether surfactants, including commercially available surfactantsReagents (from Sigma-Aldrich). Particularly preferred are surfactants comprising, more preferably consisting of, behenyl triethylene glycol dodecyl ether. In a very particularly preferred embodiment, use is made of commercially availableL23(Sigma-Aldrich), also known as Brij 35 or polyoxyethylene (23) lauryl ether. In a further embodiment, commercially available are preferred58, also known as polyethylene glycol cetyl ether or polyoxyethylene (20) cetyl ether, or preferably commercially availableL4, also known as polyethylene glycol dodecyl ether or polyoxyethylene (4) lauryl ether.

In another embodiment, preference is given to using alkylaryl polyether alcohols, preferably commercially available Triton^TMX-100, and in particular 4- (1,1,3, 3-tetramethylbutyl) phenyl-polyethylene glycol and of the formula C₁₄H₂₂O(C₂H₄O)_nH, wherein n is 9 and 10. Alternatively or additionally, octyl phenol ethoxylate surfactants such as ECOSURF^TMSurfactants (commercially available from Dow), e.g. ESOSURF^TMEH-9 (90%), orSurfactants (commercially available from Dow), for example15-S-9 can be preferably used.

In another embodiment, it is preferred to use organosiloxanes, such as polyether siloxanes and polyether siloxane copolymers, for example, commercially availableAdditive (Evonik), preferablyWet270, and particularly, comprises, preferably consists of 3- [ methyl-bis (trimethylsiloxy) silyl]Propyl-polySurfactants consisting of ethylene glycol, or preferablyWet 280. In addition to this, the present invention is,WET 260 andsiloxane surfactants described in Wet KL 245 and US 7,618,777 can preferably be used, for example H₃CSi(CH₃)₂OSiO(CH₃)(CH₂CH₂CH₂O(CH₂CH₂O)₇CH₃)Si(CH₃)₃。

In another embodiment, fluorosurfactant(s), preferably FluorN 322, are preferably used and in particular, surfactants consisting of 2- [ [ 2-methyl-5- (3,3,4,4,5,5,6,6,7,7,8,8, 8-tridecafluorooxycarbonylamino) phenyl ] carbamoyloxy ] ethyl-polypropylene glycol are included, more preferably. Other fluorosurfactants, such as commercially available FluorN561 and FluorN 562(Cytonix), can also be preferably used.

In another embodiment, poloxamer copolymers are preferably used, preferably copolymers comprising polyethylene oxide and polypropylene oxide units, more preferably triblock copolymers consisting of a central hydrophobic block of polypropylene glycol flanked by two hydrophilic blocks of polyethylene glycol, and in particular the commercially available poloxamers 407 orF-127(BASF) or Synperonic PE/F127 (Croda). Alternatively or additionally, othersAdditives, e.g.10R5, may be preferably used.

The surfactant is preferably provided in an amount of less than 30% by weight, more preferably less than 25% by weight, even more preferably less than 20% by weight, and especially less than 15% by weight relative to the composition provided in step (a).

According to a preferred embodiment, when 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 excluded in this respect.

Also in the method for preparing nanocapsules according to the present invention, a polymer surfactant or a surface active polymer or a block copolymer may be used.

However, in certain embodiments, the use of such polymeric surfactants or surface active polymers is avoided.

According to one aspect of the present invention, a polymerizable surfactant, i.e., a surfactant comprising one or more polymerizable groups, may be used.

Such polymerizable surfactants can be used alone, i.e., as the sole surfactant provided, or in combination with non-polymerizable surfactants. In one embodiment, a polymerizable surfactant is additionally provided and combined with a non-polymerizable surfactant. The provision of such optional polymerizable surfactants can provide the combined benefits of facilitating suitable droplet formation and stabilization and forming a stable polymeric capsule shell. Thus, these compounds act as both a surfactant and a polymerizable compound. Polymerizable nonionic surfactants, in particular nonionic surfactants additionally having one or more acrylate and/or methacrylate groups, are particularly preferred. This embodiment, which includes the use of a polymerizable surfactant, may have the following advantages: the template properties at the amphiphilic interface can be maintained particularly well during polymerization. Furthermore, the polymerizable surfactant may not only participate in the polymerization reaction, but may advantageously be incorporated into the polymer shell as a building block, and more preferably may also be incorporated at the surface of the shell, so that it may advantageously affect the interfacial interactions. In a particularly preferred embodiment, a silicone polyether acrylate is used as the polymerizable surfactant, more preferably a crosslinkable silicone polyether acrylate. In another embodiment, PEG methyl ether methacrylate is used.

In this process, the composition is added to an aqueous mixture, wherein the composition is dispersed in an aqueous phase. In this regard, the surfactant(s) provided may advantageously aid in forming and stabilizing dispersions, particularly emulsions, and facilitate homogenization.

Where an aqueous mixture is provided, the amount of water is not considered to contribute to the overall composition in terms of weight, i.e. water is excluded in this respect.

Preferably, the water is provided as purified water, in particular deionized water.

According to the invention, the composition provided in step (a) is then dispersed as nanodroplets in an aqueous phase.

The composition may contain further compounds, such as one or more pleochroic dyes, in particular dichroic dye(s), one or more chiral compounds and/or other conventional and suitable additives.

The pleochroic dye is preferably a dichroic dye, and may be selected from, for example, azo dyes and thiadiazole dyes.

Suitable chiral compounds are, for example, standard chiral dopants, such as R-or S-811, R-or S-1011, R-or S-2011, R-or S-3011, R-or S-4011, R-or S-5011, or CB15 (all available from Merck KGaA, Darmstadt, Germany), sorbitol as described in WO 98/00428, hydrobenzoin as described in GB 2,328,207, chiral binaphthol as described in WO 02/94805, chiral binaphthol acetal as described in WO 02/34739, chiral TADDOL as described in WO02/06265, or chiral compounds having a fluorinated linking group as described in WO 02/06196 or WO 02/06195.

Furthermore, substances may be added to modify the dielectric anisotropy, the optical anisotropy, the viscosity and/or the temperature dependence of the electro-optical parameters of the LC material.

The mesogenic medium according to the invention comprises one or more compounds of formula I as described above.

In a preferred embodiment, the liquid 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 formula I according to the invention. The medium preferably comprises a low molecular weight liquid-crystalline compound selected from the group consisting of nematic or nematic substances, for example the known azoxybenzenes, benzylideneanilines, biphenyls, terphenyls, phenyl-or cyclohexylbenzoates, phenyl-or cyclohexyl esters of cyclohexylcarboxylic acids, phenyl-or cyclohexyl esters of cyclohexylbenzoic acids, phenyl-or cyclohexyl esters of cyclohexylcyclohexanecarboxylic acids, cyclohexylphenyl esters of benzoic acids, cyclohexylphenyl esters of cyclohexanecarboxylic acids, cyclohexylphenyl esters of cyclohexylcyclohexanecarboxylic acids, phenylcyclohexanes, cyclohexyl-biphenyls, phenylcyclohexylcyclohexanes, cyclohexylcyclohexanes, cyclohexylcyclohexenes, 1, 4-dicyclohexylbenzenes, 4,4' -dicyclohexylbiphenyls, phenyl-or cyclohexylpyrimidines, phenyl-or cyclohexylpyridines, phenyl-or cyclohexylpyridazines, phenyl-or cyclohexyl-diAlkanes, phenyl-or cyclohexyl-1, 3-dithianes, 1, 2-diphenyl-ethane, 1, 2-dicyclohexylethane, 1-phenyl-2-cyclohexylethane, 1-cyclohexyl-2- (4-phenylcyclohexyl) -ethane, 1-cyclohexyl-2-biphenyl-ethane, 1-phenyl-2-cyclohexyl-phenylethane, optionally halogenated stilbenes, benzyl phenyl ether, tolane, substituted cinnamic acid types and other types of nematic or nematic substances. The 1, 4-phenylene groups in these compounds can also be laterally mono-or difluorinated. The liquid-crystal mixtures are preferably based on achiral compounds of this type.

In a preferred embodiment, the LC host mixture is a nematic LC mixture, preferably without a chiral liquid crystal phase therein.

Suitable LC mixtures may have positive dielectric anisotropy. Such mixtures are described, for example, in JP 07-181439(A), EP 0667555, EP 0673986, DE 19509410, DE 19528106, DE 19528107, WO 96/23851, WO 96/28521 and WO 2012/079676.

In another embodiment, the LC medium has a negative dielectric anisotropy. Such media are described, for example, in EP 1378557 a 1.

In a particularly preferred embodiment, one or more compounds of the formula I are selected from the group consisting of compounds of the formulae Ia, Ib, Ic and Id

Wherein,

R¹，R²，R³，R⁴，R⁵and R⁶Independently of one another, a straight-chain or branched alkyl or alkoxy radical having 1 to 15 carbon atoms, preferably 1 to 7 carbon atoms, or a straight-chain or branched alkenyl radical having 2 to 15 carbon atoms, which is unsubstituted, substituted by CN or CF₃Mono-or poly-substituted by halogen, and wherein one or more CH₂The radicals may be replaced in each case independently of one another by-O-, -S-, -CO-, -COO-, -OCO-, -OCOO-or-C.ident.C-in such a way that oxygen atoms are not bonded directly to one another,

X¹and X²Independently of one another, F, CF₃，OCF₃Or the CN group is selected from the group consisting of,

L¹，L²，L³，L⁴and L⁵Independently of one another, are H or F,

i is 1 or 2, and

j and k are independently of each other 0 or 1.

The additive or additives according to the invention are agents which may serve an advantageous or suitable function in the preparation process and may in particular impart or at least contribute to one or more advantageous or useful properties on the obtained product. Additives may be used, for example, to adjust material properties, solubility or miscibility, or to provide benefits in film forming ability.

The additive may be provided prior to the polymerisation step or according to step (d).

Preferably, the additive(s) according to the present invention, in particular as provided in step (d), are surfactant(s). The surfactant is a surface active agent. The agent may reduce the surface or interfacial tension between liquids or between a liquid and a solid. The surfactants herein may include or be used as detergents, wetting agents, emulsifiers, foaming agents and dispersing agents.

In the method for preparing nanocapsules according to the present invention, one or more surfactants are used in step (b). The surfactants herein may facilitate or contribute to the formation of nano-droplets and the stabilization of nano-emulsions. It can also be used to set or adjust the size and size distribution of the droplets and the nanocapsules produced.

The surfactant added according to step (d) may in one case be the same as that used in step (b). However, the additive according to step (d) is added after the capsules are so formed. At this stage, other factors, i.e. factors other than the stability of the droplets and the setting of the particle size, may be specifically addressed or taken into account. Thus, additives may be used which also have different or additional functions or influence other or further properties. In another case, the surfactant added according to step (d) may thus be different from the surfactant used in step (b), i.e. another or second surfactant. In addition, combinations of additives, such as surfactants and film formers, may also be used.

According to a preferred embodiment, the additive in step (d) is a surfactant. In this embodiment in step (d) conventional surfactants known in the art may be used, including anionic surfactants such as sulphate, e.g. sodium lauryl sulphate, sulphonate, phosphate and carboxylate surfactants, cationic surfactants such as secondary or tertiary amines and quaternary ammonium salt surfactants, zwitterionic surfactants such as betaines, sulphobetaines and phospholipid surfactants, and nonionic surfactants such as long chain alcohols and phenols, ethers, esters or amides nonionic surfactants, particularly alkyl polyethers and polyethoxy alcohols.

In a preferred embodiment according to the invention, a nonionic surfactant is used. The use of non-ionic surfactants and the avoidance of ionic surfactants is also beneficial in the stability, reliability and electro-optic characteristics and performance of nanocapsules, also in composite systems and electro-optic devices.

Especially preferred are polyethoxylated nonionic surfactants. Preferred compounds are selected from the group consisting 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 polysorbitan, sorbitan alkyl ester surfactants, cocamide monoethanol-amine, cocamide diethanolamine and dodecyldimethylamine oxide.

In a particularly preferred embodiment, the surfactant(s) used are selected from polyoxyethylene glycol alkyl ether surfactants, including commercially available surfactantsReagents (Sigma-Aldrich). Particularly preferred are surfactants comprising, more preferably consisting of, behenyl triethylene glycol dodecyl ether. In a very particularly preferred embodimentIn the case of using commercially availableL23(Sigma-Aldrich), also known as Brij 35 or polyoxyethylene (23) lauryl ether. In a further embodiment, commercially available are preferred58, also known as polyethylene glycol cetyl ether or polyoxyethylene (20) cetyl ether, or preferably commercially availableL4, also known as polyethylene glycol dodecyl ether or polyoxyethylene (4) lauryl ether.

In another embodiment, preference is given to using alkylaryl polyether alcohols, preferably commercially available Triton X-100, and in particular 4- (1,1,3, 3-tetramethylbutyl) phenyl-polyethylene glycol and the compound of the formula C₁₄H₂₂O(C₂H₄O)_nH, wherein n is 9 and 10. Alternatively or additionally, octyl phenol ethoxylate surfactants such as ECOSURF^TMSurfactants (commercially available from Dow), e.g. ESOSURF^TMEH-9 (90%), orSurfactants (commercially available from Dow), for example15-S-9 can be preferably used.

In another embodiment, it is preferred to use organosiloxanes, such as polyether siloxanes and polyether siloxane copolymers, for example, commercially availableAdditive (Evonik), preferablyWet270, and particularly comprises, preferably consists of 3- [ methyl-bis (trimethylsiloxy) silyl]Surfactant composition of propyl-polyethylene glycol, or preferablyWet 280. In addition to this, the present invention is,WET 260 andthe silicon surfactants described in Wet KL 245 and US 7,618,777 can preferably be used, for example H₃CSi(CH₃)₂OSiO(CH₃)(CH₂CH₂CH₂O(CH₂CH₂O)₇CH₃)Si(CH₃)₃。

In another embodiment, fluorosurfactant(s), preferably FluorN 322, are preferably used, and in particular, surfactants comprising and more preferably consisting of 2- [ [ 2-methyl-5- (3,3,4,4,5,5,6,6,7,7,8,8, 8-tridecafluorooxycarbonylamino) phenyl ] carbamoyloxy ] ethyl-polypropylene glycol. Other fluorosurfactants (one or more) can also preferably be used, such as commercially available FluorN561 and FluorN 562 (Cytonix).

In another embodiment, poloxamer copolymers are preferably used, preferably copolymers comprising polyethylene oxide and polypropylene oxide units, more preferably triblock copolymers consisting of a central hydrophobic block of polypropylene glycol flanked by two hydrophilic blocks of polyethylene glycol, and in particular the commercially available poloxamers 407 or poloxamer 407F-127(BASF) or Synperonic PE/F127 (Croda).

In some cases it is preferred to provide the nonionic, partially water soluble surfactant with a low molecular weight or oligomeric formula.

Surprisingly, already relatively small amounts of additives are sufficient to favorably influence the product properties. Preferably, the additive 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 capsule. It is further preferred that the capsules contain additives in an amount of at least 0.01% by weight, more preferably at least 0.05% by weight of the total capsule weight.

In a preferred embodiment, the amount of additive added prior to the polymerization step (c) or in step (d) is limited to 10% by weight or less, preferably 5% by weight or less, more preferably 2.5% by weight or less, and even more preferably 1% by weight or less, relative to the composition provided in step (a). In one embodiment, the amount of additive is particularly preferably set in the range of 0.05 to 1% by weight, and even more preferably in the range of 0.1 to 1% by weight, relative to the composition provided in step (a).

Another aspect of the invention relates to nanocapsules, each comprising a polymeric shell, a core comprising a mesogenic medium comprising one or more compounds of formula I as described above and below, and one or more additives. Preferably and advantageously, the nanocapsules are obtained or obtainable by implementing the method according to the invention.

It is advantageously realized that an improved nanocapsule, in particular in view of a reduced operating voltage in electro-optical applications and further advantageous properties as described above and below, is obtained or obtainable by carrying out the method according to the invention.

Furthermore, it has surprisingly been found that stable and reliable nanocapsules can be provided, which contain a mesogenic medium with advantageous electro-optical properties and suitable reliability, while also incorporating one or more additives, preferably one or more surfactants, which can provide or contribute to the same and/or further benefits, such as a reduction of the operating voltage.

It is further recognized that the nanocapsules according to the invention can be obtained or obtainable by a process based on in situ polymerization and in particular on PIPS in a nanoemulsion. Thus, surprisingly, it is possible to provide a light modulating material comprising nanosized droplets (nanodroplets) of LC as core encapsulated by a polymeric shell, wherein the nanocapsule as a whole and the mesogenic medium comprised therein have suitable and even improved properties.

As mentioned above, the properties of the nanocapsules can be further influenced and adjusted by the addition, preferably incorporation, of additive(s), preferably surfactant(s). It has surprisingly been found that even after the nanocapsule itself is prepared or provided, the subsequent introduction of the additive(s) may still contribute to and under certain conditions even further improve the properties and performance of the nanocapsule.

By providing nanocapsules according to the invention, it is possible to confine discrete amounts of LC material in a nano-volume, which is stably contained and individually addressable and which can be installed or dispersed in different environments. LC material nano-encapsulated by a polymer shell can be easily applied onto and supported by a single substrate, which may be flexible, and in which the layer or film thickness may be variable or varied. The LC medium surrounded, i.e. encapsulated, by the polymer walls operates in at least two states.

However, providing LC. in only a relatively small volume per nanodroplet is currently achieved to preferably and advantageously provide an LC composition having a suitably large △ n while also exhibiting good transmittance and good reliability, in particular including a suitable Voltage Holding Ratio (VHR) and thermal and UV stability as well as a relatively small rotational viscosity.

It is furthermore advantageously recognized that in nanocapsules the interfacial area between the LC core and the polymer shell is relatively large compared to the provided nano-volume, and therefore the respective properties of the polymer shell component and the LC core component and their interrelationship need to be taken into particular account. In the nanocapsules according to the invention, the interaction between the polymer and the LC component can be advantageously and suitably set and adjusted, which is mainly obtained due to the control and adaptability of the nano-encapsulated compositions provided according to the invention and of the preparation processes provided. Furthermore, additives, preferably surfactants, may further influence or modify these interactions.

For example, the interfacial interactions may facilitate or prevent the formation of any alignment or orientation in the LC nanodroplets.

Given the small size of the nanocapsules, which may be sub-wavelength of visible light and even smaller than λ/4 of visible light, the capsules may advantageously be only very weak scatterers of visible light.

Furthermore, in the absence of an electric field and depending on interfacial interactions, LC media can in one instance form disordered phases with little or no orientation in nano-sized volumes, particularly isotropic phases, which can, for example, provide excellent viewing angle behavior. Furthermore, having an essentially isotropic phase in the passive or non-addressed state may be advantageous in device applications, since a very good dark state may be achieved, especially when polarizers are used.

In contrast to the occurrence of, for example, radial or bipolar orientation, it is believed that in one instance, such orientation may not occur or at least be limited due to the small volume provided in the nanocapsule.

Alternatively, and as preferred in particular embodiments, alignment may occur, wherein in particular the interface(s) corresponding effect(s) may be used to induce or influence alignment or orientation in the LC medium, e.g. by setting or adjusting the anchoring strength to the capsule wall. In this case, homogeneous, planar, radial or bipolar alignment may occur. When such nanocapsules with separate or individual LC orientation or alignment are randomly dispersed, optical isotropy can be observed as a whole.

The spherical or spheroidal geometry, together with the curvature, sets the constraints or boundary conditions for the nematic configuration, as well as the alignment of the liquid crystal molecules, which may further depend on the anchoring of the LC on the capsule surface, the elastic properties and volume and surface energy, and the size of the capsule. The electro-optic response depends on the ordering and alignment of the LC in the nanocapsule.

Furthermore, any possible absence or presence of alignment or orientation of the encapsulated LC medium is independent of the substrate, so that no alignment layer needs to be provided on the substrate.

In particular, nanocapsules are substantially optically isotropic or exhibit pseudo-isotropic optical properties when the LC in the capsule has a radial configuration and particle size is below the wavelength of light. This allows an excellent dark state to be achieved when two crossed polarizers are used. Upon switching with an electric field, in particular in-plane switching, an optically isotropic axial configuration can be obtained, wherein the induced birefringence leads to the transmission of light. Thus, in a preferred embodiment, the LC material contained in the nanocapsule has a radial configuration.

For switching, in particular based on birefringence induced in the IPS configuration, it is advantageous to use dielectrically positive or dielectrically negative liquid-crystalline media.

The present invention provides advantageous nanocapsules, i.e. the capsule formation has a polymeric shell, which is optionally and preferably cross-linked, filled with nanocapsules of LC material. The nanocapsule further comprises one or more additives as described above. Capsules are individual and divided, i.e., discrete and dispersible granules having a core-shell structure. The capsules may function individually but may also function together as a light regulating material. They can be applied in various environments and can be re-dispersed in different media depending on the dispersion medium. For example, they may be dispersed in water or an aqueous phase, dried and dispersed in a binder, preferably a polymeric binder.

Nanocapsules may also be referred to as nanoparticles. In particular, the nanoparticles comprise a nanoscale LC material surrounded by a polymeric shell. These nano-encapsulated liquid crystals may optionally be additionally embedded in a polymeric binder.

In other cases, where the phase separation is less pronounced or less complete, a polymer network may form inside the droplets, such that the resulting capsules exhibit a spongy or porous interior, in which the LC material fills the voids. In this case, the LC material fills the pores in the sponge-like structure or network, while the shell encapsulates the LC material.

In another alternative, the separation between the LC material and the polymer may be at an intermediate level, where the interface or boundary between the LC interior and the wall is only less pronounced and shows a gradient behavior.

However, it is preferred to obtain an efficient and complete separation of the shell polymer and the LC material, in particular to give a shell with a smooth inner surface.

Optionally, the included mesogenic medium may further contain one or more chiral dopants and/or one or more pleochroic dyes and/or other conventional additives.

Advantageously, the nanocapsules according to the invention are obtained or obtainable by polymerization of a composition as described above, in particular by an efficient and controlled process as described herein. Surprisingly, in nanocapsules, a shell polymer can be provided, in particular by polymerizing the above-mentioned precursor compound(s), which is well matched to the LC component and compatible with the LC properties. Preferably, the electrical impedance of the capsule polymer is at least equal to and more preferably greater than the electrical impedance (electrical impedance) of the LC material. In this regard, additives may be used to appropriately adjust the properties and characteristics.

In addition, the shell polymer may be advantageous in terms of dispersibility and avoidance of undesirable aggregation. In addition, the shell polymer can be combined with a binder and function well, for example in film-forming composite systems, and in particular in electro-optic applications. In this connection, the additives may also advantageously influence the capsule properties, for example with a view to avoiding aggregation or improving film formation.

The capsules according to the invention, in which the liquid crystals are encapsulated by a shell material component, are characterized in that they are of nanometric size. Nanocapsules having an average size of not more than 400nm are preferred.

Preferably, the nanocapsules have an average size of no greater than 400nm, more preferably no greater than 300nm, even more preferably no greater than 250nm, as determined by dynamic light scattering analysis. Dynamic Light Scattering (DLS) is a generally known technique that can be used to determine the size and size distribution of particles in the submicron region. For example, commercially available zetasizer (malvern) may be used for DLS analysis.

Even more preferably, the average size of the nanocapsules is below 200nm, in particular not more than 150nm, preferably determined by DLS. In a particularly preferred embodiment, the average nanocapsule size is below the wavelength of visible light, in particular below λ/4 of visible light. It has advantageously been found that the nanocapsules according to the invention can be very weak scatterers of visible light in at least one state, in particular with a suitable LC alignment or configuration, i.e. they do not or substantially do not scatter visible light. In this case, the capsule can be used to modulate the phase shift, i.e. the phase retardation, between the two polarization components of the light without exhibiting or substantially without exhibiting undesired scattering of light in any state.

In one embodiment, the retardation is set to approximately λ/2, in particular λ/2 for a wavelength of 550 nm. This can be achieved by, for example, providing the appropriate type and amount of nanocapsules in the membrane and setting the appropriate membrane thickness.

For electro-optic applications, the polymer encapsulated mesogenic medium preferably exhibits a confinement dimension of from 15nm to 400nm, more preferably from 50nm to 250nm and especially from 75nm to 150 nm.

If the capsule size becomes very small, in particular close to the molecular size of the LC molecules, the function of the capsule may become less effective in view of the reduced amount of encapsulated LC material and the mobility of the LC molecules becoming more limited.

The thickness of the polymer shells or walls forming the discrete individual structures is selected such that it effectively contains and stably confines the contained LC medium, while allowing for relative flexibility and still enabling excellent electrical responsiveness of the LC material. In view of capacitance and electro-optical performance, the shell should preferably be as thin as possible while still providing sufficient containment strength. Typical capsule shells or wall thicknesses are therefore below 100 nm. Preferably, the polymeric shell has a thickness of less than 50nm, more preferably less than 25nm, and in particular less than 15 nm. In a preferred embodiment, the polymeric shell has a thickness of from 1nm to 15nm, more preferably from 3nm to 10nm, and in particular from 5nm to 8 nm.

Microscopy techniques, in particular SEM and TEM, can be used to observe the size, structure and morphology of the nanocapsules. The wall thickness can be determined on a freeze-fractured sample, for example by TEM. Alternatively, neutron scattering techniques may be used. Furthermore, techniques such as AFM, NMR, ellipsometry and sum frequency generation can be used to study nanocapsule structures. The nanocapsules according to the invention generally have a spherical or spheroidal shape, wherein a hollow spherical or spheroidal shell is filled with or contains the LC medium according to the invention.

Accordingly, the present invention provides a plurality of discrete spherical or spheroidal or particulate LCs, each of which is nano-encapsulated by a polymeric shell, and each of which is individually but collectively operable in at least two states in an electro-optic device.

In a preferred embodiment, the LC medium according to the invention has a birefringence of △ n ≧ 0.15, more preferably ≧ 0.20 and most preferably ≧ 0.25.

Surprisingly, by providing and setting the birefringence and the dielectric anisotropy according to the invention appropriately, even small nanosomes of the LC are sufficient to modulate light efficiently and effectively, wherein only moderate electric fields or moderate driving voltages can be used to influence or change the alignment of the LC molecules in the nanocapsules.

Furthermore, another advantage of the present invention lies in the possibility of obtaining substantially uniform capsule sizes, i.e. achieving low polydispersities. Such uniformity may advantageously provide uniform electro-optic performance of the capsule in device applications.

Furthermore, the capsules obtained or obtainable by the controlled and adaptive method according to the invention can be adjusted and adapted in terms of capsule size, which in turn allows to adjust the electro-optical properties as desired, in particular based on the kerr effect.

The small and uniform size of the nanocapsules is beneficial in obtaining a fast and uniform switching in response to an applied electric field, preferably giving a response time of low milliseconds or even sub-milliseconds.

It was found that the combination of nanocapsules and binder material(s) can suitably influence and increase the processability and applicability of the light modulating material, especially in view of coating, dripping or printing and film formation on a substrate. Accordingly, another aspect of the present invention provides a method for preparing such a composite system comprising nanocapsules and an adhesive. Furthermore, the method is designed such that the resulting system further comprises one or more additives, preferably one or more surfactants as described above. Additives incorporated into the system, preferably at least to some extent into the nanocapsules, can provide further improved or tailored product properties, in particular with regard to operating voltage, but also, for example, with regard to excellent dark states, advantageously low hysteresis and film formation. Advantageously, the method of making the composite system provides useful flexibility in when and how to add the additive(s).

In this method, nanocapsules may be provided which themselves already contain one or more additives. However, in another embodiment, the nanocapsules initially provided do not comprise one or more additives. The nanocapsules are suitably mixed with one or more binders, to which one or more additives as described above are additionally added. In particular, the additives used in step (d) of capsule preparation may also be advantageously used for preparing the composite system according to the invention. The addition of additives, preferably surfactants, can be carried out simultaneously with and/or after the addition of the binder. However, it is preferable that the additive is added together with the binder so that the components including the nanocapsule can be more easily and more largely mixed.

The binder or binders may act as a dispersant and binder or binders and also provide suitable physical and mechanical stability while maintaining or even promoting flexibility. Furthermore, the density or concentration of the capsules can be advantageously adjusted by varying the amount of binder or buffer material provided.

The present invention therefore provides a composite system comprising nanocapsules according to the present invention, one or more binders and one or more additives, wherein said system is preferably and advantageously obtainable by carrying out a process as described above and below.

It has been found that the discrete nanocapsules can be mixed with a binder material, wherein the mixed nanocapsules substantially retain, preferably completely retain, their integrity in the composite, while, however, they are bound, retained or disposed in the binder. In this regard, the binder material may be the same material as the polymeric shell material or a different material. Thus, according to the present invention, the nanocapsules may be dispersed in a binder made of the same material as the nanocapsule shell or a different material. Preferably, the binder is a different or at least modified material. Furthermore, according to the invention, one or more additives, preferably surfactants, are incorporated, which suitably influence the properties of the resulting system.

The binder may be useful because it can disperse the nanocapsules, wherein the amount or concentration of the capsules can be set and adjusted. Surprisingly, by providing the capsules and a suitable binder separately, the amount of capsules in the combined composite can not only be adjusted, but if desired, particularly very high or also very low content of capsules can be obtained. Typically, the nanocapsules are included in the composite in a proportion of about 2% to about 95% by weight. Preferably, the composite contains 10 to 85% by weight, more preferably 30 to 70% by weight of nanocapsules. In a preferred embodiment, approximately the same amount of binder and nanocapsule is used. The amount of additive in the composite system is generally considerably less than the amount of nanocapsule or binder. Preferably, the amount of additive in the resulting system is 5% by weight or less, more preferably 2.5% by weight or less, and even more preferably 1% by weight or less, based on the total system composition. The amount of the additive in the composite system is particularly preferably set in the range of 0.05 to 1% by weight, and even more preferably in the range of 0.1 to 1% by weight, based on the entire system composition.

The binder material, preferably also additives or a combination of both, may improve or influence the coatability or printability and film forming ability and properties of the capsules. Preferably, the adhesive can provide mechanical support while maintaining suitable flexibility, and it can serve as a matrix. The adhesive also exhibited suitable and sufficient transparency.

In one embodiment, the binder may be selected from, for example, an inorganic glass monolith, as described in US 4,814,211, or other inorganic material.

Preferably, however, the binder is a polymeric material. Suitable materials may be synthetic resins, such as epoxy resins and polyurethanes, which are, for example, thermosetting. Furthermore, vinyl compounds and acrylates, in particular polyethylene acrylates and polyvinyl acetates, can be used. In addition, polymethyl methacrylate, polyurea, polyurethane, urea-formaldehyde, melamine-urea-formaldehyde may be used or added. In some embodiments, acrylates and methacrylates are used as the adhesive.

Particularly preferably used are water-soluble polymers such as polyvinyl alcohol (PVA), starch, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, polyvinyl pyrrolidine, gelatin, alginates, casein, gum arabic, or latex-like emulsions. For example, the binder may be selected in consideration of setting the corresponding hydrophobicity or hydrophilicity.

In one embodiment, the adhesive, particularly a dry adhesive, absorbs little or no water.

In a particularly preferred embodiment, the one or more binders comprise polyvinyl alcohol, including partially and fully hydrolyzed PVA. Advantageously, water solubility and hydrophilicity can be adjusted by varying the degree of hydrolysis. Water absorption can be controlled or reduced. The properties of the PVA, such as mechanical strength or viscosity, can be set advantageously by, for example, adjusting the molecular weight, the degree of hydrolysis or by chemical modification of the PVA.

Crosslinking of the adhesive may also advantageously affect the properties of the adhesive. Thus, particularly when PVA is provided as a binder, in one embodiment the binder is cross-linked, preferably by cross-linking agents such as dialdehydes, e.g. glutaraldehyde, formaldehyde and glyoxal. Such crosslinking may, for example, advantageously reduce any tendency for undesirable crack formation.

In addition to one or more additives, preferably surfactants, as described above, the compound may also comprise conventional additives, such as stabilizers, antioxidants, radical scavengers and/or plasticizers.

For adhesives, particularly PVA, ethylene glycol may be used as a preferred plasticizer. Glycerol may also be used, or alternatively or additionally 1-octanol.

In one embodiment, the nanocapsule is mixed with PVA and glycerol, more preferably with PVA, glycerol and 1-octanol, and even more preferably with PVA, glycerol,wet270 and optionally 1-octanol.

In addition, film formers such as polyacrylic acid and defoamers may be added in order to favorably influence the film-forming properties.

These agents are useful for improving film formation and substrate wetting. Optionally, degassing and/or filtration of the coating composition may be performed to further improve the membrane properties. Likewise, setting and adjusting the viscosity of the binder can have a beneficial effect on film formation or the resulting film.

Humectants or drying agents may also be added to the adhesive.

The binder may be provided as a liquid or paste, wherein the carrier medium or solvent, e.g. water, aqueous or organic solvent, may be removed from the composite mixture, e.g. during or after film formation, in particular by evaporation at elevated temperature.

The binder is preferably well mixed or bound with the nanocapsules, and additives may suitably contribute to this in some cases. Furthermore, the aggregation of the capsules is suitably avoided or reduced, so that for example light leakage can be avoided or reduced, which in turn may enable a very good dark state. Furthermore, the binder may be selected such that a high density of nanocapsules may be provided in the composite, for example in a film formed from the composite. Furthermore, in composites, the structural and mechanical advantages of the binder can be combined with the advantageous electro-optical properties of the LC capsules. Additives may be used to further improve these properties.

For the prepared film comprising nanocapsules and binder, a top coat outer coating can be applied using, for example, cellulose or cellulose derivatives, polysiloxanes or thioolefins as coating.

The nanocapsules according to the invention can be applied in a number of different environments, in particular by (re) dispersing them. They may advantageously be dispersed as a plurality of capsules in the binder or mixed with the binder. The binder can improve not only the film-forming property but also the film property, wherein particularly the binder can hold the capsules with respect to the substrate. Typically, the capsules are randomly distributed or randomly aligned in the binder. Due to the alignment of the LC in the capsules, in particular in the case of radial alignment, and/or due to the random distribution of the capsules, an optically isotropic, or at least substantially optically isotropic on a macroscopic scale, overall material can be obtained.

The composite comprising the adhesive material and the nanocapsules themselves may be suitably applied or laminated to a substrate. For example, the composite or just the nanocapsules may be applied to the substrate by conventional coating techniques such as spin coating, knife coating or drop coating. Alternatively, they may also be applied to the substrate by conventional and known printing methods, such as inkjet printing. The capsules or complexes may also be dissolved in a suitable solvent. The solution is then coated or printed onto a substrate, for example by spin coating or printing or other known techniques, and the solvent is evaporated. In many cases, it is suitable to heat the mixture to facilitate evaporation of the solvent. As solvent, it is possible to use, for example, water, aqueous mixtures or standard organic solvents.

Preferably the material applied to the substrate is a composite, i.e. it also contains a binder. The film formed generally has a thickness of less than 25 μm, preferably less than 15 μm. In a preferred embodiment, the membrane made of the composite has a thickness of 0.5 μm to 10 μm, very preferably 1 μm to 7 μm, in particular 2 μm to 5 μm. In a particularly preferred embodiment, the layer thickness is in the range of 2 μm to 4 μm, more preferably 3 μm to 4 μm, and even more preferably 3.5 μm to 4.0 μm.

As the substrate, for example, glass, silicon, a quartz plate, or a plastic film can be used. It is also possible to place a second substrate on top of the applied, preferably coated or printed, material. Isotropic or birefringent substrates may be used. Optical coatings, particularly optical adhesives, may also be applied.

In a preferred embodiment, the substrate may be a flexible material. Given the flexibility provided by the composite, a generally flexible system or device may be obtained.

Suitable and preferred plastic substrates are, for example, polyester films, such as polyethylene terephthalate (PET) orPolyethylene naphthalate (PEN), polyvinyl alcohol (PVA), Polycarbonate (PC) or triacetyl cellulose (TAC), more preferably PET or TAC film. As the birefringent substrate, for example, a uniaxially stretched plastic film can be used. PET films are available, for example, from DuPont Teijinfilms under the trade name MelCommercially available.

The substrate may be transparent and transmissive or reflective. For electro-optical addressability, the substrate may have electrode(s). In a typical embodiment, a glass substrate having an ITO electrode is provided.

The electrical and optical properties of the LC material, the polymeric capsule shell and the adhesive may advantageously and preferably be matched or aligned in terms of compatibility and in terms of the respective application. The compound according to the invention may provide suitable and advantageous electro-optical behaviour and performance. In this regard, the additives may suitably influence the behavior and performance.

Furthermore, excellent physical and chemical stability can be obtained, for example by preferably and advantageously reducing water absorption. In particular, good stability and resistance to thermal or mechanical stresses may be achieved while still providing suitable mechanical flexibility.

In view of the electrical responsiveness of the LC and a suitable dielectric constant close to the dielectric constant of the LC material to limit charging at the interface, preferably the adhesive, preferably also the polymer shell, has a relatively large impedance. The dielectric constant of the binder was observed to be high enough to ensure efficient application of an electric field throughout the LC medium in the capsule. It is preferred to minimize any charge or ionic content in these materials to keep the conductivity very low. In this respect, it has been found that the properties of the provided binder, preferably PVA, may be improved by purification, in particular by removing or reducing the amount of impurities and charged contaminants. For example, the binder, in particular PVA, can be dissolved and washed in deionized water or alcohol, and it can be treated by dialysis or soxhlet purification.

Furthermore, the refractive indices of the LC material, the polymeric capsule shell and the adhesive are advantageously and preferably matched or aligned for optimal performance in various applications. In particular, the refractive indices of the LC material and the adhesive are matched. In particular, the refractive index of the binder, and possibly also of the encapsulating polymer, may take into account the extraordinary refractive index (n) of the LC_e) Ordinary refractive index (n) of LC_o) Or the average refractive index (n) of LC_avg) But set or adjusted. In particular, the refractive indices of the binder and of the shell polymer may be matched to the n of the LC material_e，n_o，n_avgAnd (4) closely matching.

In one embodiment, the nanocapsules are dispersed in an adhesive, wherein the capsules in the adhesive exhibit random orientation with respect to each other. Such random orientation of the capsules with respect to each other may result in the LC material as a whole giving the observed average refractive index (n) irrespective of whether there is any possible alignment or orientation of the LC material within each individual capsule_avg). In view of the nano-size of the capsules and their advantageous potential as very weak scatterers of light, in this embodiment, the application of an electric field, wherein the electric field force (re) aligns the LC material, can modulate the phase shift or retardation of transmitted or reflected light without altering the apparent scattering, if any. In this case, in particular when the size of the capsules is significantly smaller than the wavelength of the light, the refractive index of the binder and preferably of the polymeric capsule shell can be adjusted, for example, appropriately and advantageously or with respect to n of the LC material_avgAnd (6) matching. Thus, nanocapsules can behave as effective nanoscale phase modifiers.

Given the nano-size of the capsules and in the absence of an electric field, light scattering can be substantially suppressed, preferably completely suppressed, especially for sizes less than 400 nm. Furthermore, scattering and refraction can be controlled by matching or adjusting the refractive indices of the LC material and the polymer material(s).

When the agent capsules and the corresponding LC directors are randomly oriented in the binder, in one embodiment, the phase shift may be polarization-independent for the normally incident light.

In another embodiment, the capsules are aligned or oriented in the binder.

The composite system according to the invention advantageously allows a high degree of flexibility and several degrees of freedom in setting and adjusting, in particular with a view to adjusting electro-optical properties and functions, for example, the layer or film thickness can be set, adjusted or varied, while the density of the nano-sized LC material in the film can be independently varied, wherein also the size of the nanocapsules, i.e. the amount of LC material in each individual capsule can be predetermined or adjusted, furthermore, the LC medium can be selected to have specific properties, for example a high value of △ epsilon and △ n as appropriate.

In a preferred embodiment, the amount of LC in the composition, nanocapsule and composite is suitably maximized to achieve advantageous high electro-optic performance.

According to the present invention, it is advantageously possible to provide a composite having a relative ease of production and high processability, which can achieve good transmittance, low operating voltage, improved VHR and good dark state. Surprisingly, a strong, effective and efficient system can be obtained, which can be applied to a single substrate without any alignment layer or surface rubbing, and which can show a relative insensitivity to layer thickness deviations or external forces, such as touch, i.e. with respect to light leakage. In addition, a wide viewing angle can be obtained without providing an alignment layer or an additional retardation layer.

Preferably and advantageously, the provided nanocapsules and composite systems exhibit sufficient processability such that aggregation during concentration and filtration of the capsules, mixing with binders, film formation and optional film drying is kept to a minimum.

The nanocapsules and the composite systems according to the invention are useful in optical and electro-optical applications, especially in light modulation elements or electro-optical devices, and especially in displays. For display applications, fast response and switching times may be obtained, such that fast video and/or sequential color capabilities may be obtained, for example.

In particular, nanocapsules containing an LC medium, preferably mixed with a binder, are suitable for efficient control and modulation of light. They can be used, for example, in optical filters, adjustable polarizers and lenses, and phase plates. As phase modulators, they can be used in photonic devices, optical communications and information processing, and three-dimensional displays. A further use is switchable smart windows or privacy windows.

The present invention therefore advantageously provides a light modulation element and an electro-optic modulator. These elements and modulators comprise nanocapsules according to the invention, wherein preferably the capsules are mixed and dispersed in a binder. The use of one or more additives in the nanocapsules and/or in the composite system according to the invention advantageously reduces the operating voltage. At the same time, further suitable product properties can be achieved, apart from a favorable influence on the threshold value and the switching voltage.

Furthermore, an electro-optical device, in particular an electro-optical display, is provided, which makes advantageous use of the nanocapsules and/or the composite system as described above and below. In the device, a plurality of nanocapsules is provided.

Many mesogenic compounds or mixtures as described above and below are commercially available. All these compounds are known or can be prepared by Methods known per se, as described in the literature (for example in standard works such as Houben-Weyl, Methodender Organic Chemistry [ Methods of Organic Chemistry ], Georg-Thieme-Verlag, Stuttgart), in particular under reaction conditions which are known and suitable for the reaction in question. Known variants, which are known per se but not mentioned in detail herein, can be used here.

The media according to the invention are prepared in a manner conventional per se. Generally, the components are dissolved in each other, preferably at elevated temperatures. By means of suitable additives, the liquid-crystalline phases of the 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). For example, pleochroic dyes may be added for producing colored guest-host systems, or substances may be added to improve the dielectric anisotropy, viscosity and/or alignment of the nematic phase.

The term "alkyl" according to the present invention preferably includes straight-chain and branched alkyl groups having 1 to 7 carbon atoms, in particular the straight-chain groups methyl, ethyl, propyl, butyl, pentyl, hexyl and heptyl. Groups having 2 to 5 carbon atoms are generally preferred.

The alkoxy group may be linear or branched, and it is preferably linear and has 1,2,3,4,5,6 or 7 carbon atoms, and is therefore preferably methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy or heptyloxy.

The term "alkenyl" according to the present invention preferably includes straight-chain and branched alkenyl groups having 2 to 7 carbon atoms, in particular straight-chain groups. Particularly preferred alkenyl is C₂-C₇-1E-alkenyl, C₄-C₇-3E-alkenyl, C₅-C₇-4E-alkenyl, C₆-C₇-5E-alkenyl and C₇-6E-alkenyl, especially C₂-C₇-1E-alkenyl, C₄-C₇-3E-alkenyl and C₅-C₇-4E-alkenyl. Examples of preferred alkenyl groups are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl and 6-heptenyl. Groups having up to 5 carbon atoms are generally preferred.

Fluorinated alkyl or alkoxy groups preferably include CF₃,OCF₃,CFH₂,OCFH₂,CF₂H,OCF₂H,C₂F₅,OC₂F₅,CFHCF₃,CFHCF₂H,CFHCFH₂,CH₂CF₃,CH₂CF₂H,CH₂CFH₂,CF₂CF₂H,CF₂CFH₂,OCFHCF₃,OCFHCF₂H,OCFHCFH₂,OCH₂CF₃,OCH₂CF₂H,OCH₂CFH₂,OCF₂CF₂H,OCF₂CFH₂,C₃F₇Or OC₃F₇In particular CF₃,OCF₃,CF₂H,OCF₂H,C₂F₅,OC₂F₅,CFHCF₃,CFHCF₂H,CFHCFH₂,CF₂CF₂H,CF₂CFH₂,OCFHCF₃,OCFHCF₂H,OCFHCFH₂,OCF₂CF₂H,OCF₂CFH₂,C₃F₇Or OC₃F₇Particularly preferred is OCF₃Or OCF₂H. In a preferred embodiment fluoroalkyl includes straight chain groups having a terminal fluorine, i.e., fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorohexyl and 7-fluoropentyl. However, other locations for fluorine are not excluded.

The oxaalkyl group preferably comprises the formula C_nH_2n+1-O-(CH₂)_mWherein n and m are each independently of the other from 1 to 6. Preferably, n-1 and m is 1 to 6.

Oxaalkyl is preferably straight-chain 2-oxapropyl (═ methoxymethyl), 2- (═ ethoxymethyl) or 3-oxabutyl (═ 2-methoxyethyl), 2-, 3-or 4-oxapentyl, 2-, 3-, 4-or 5-oxahexyl, 2-, 3-, 4-, 5-or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6-or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7-or 8-oxanonyl or 2-, 3-, 4-, 5-, 6-, 7-, 8-or 9-oxadecyl.

Halogen is preferably F or Cl, in particular F.

If one of the above radicals is alkyl, one of the radicals CH₂The group is replaced by-CH ═ CH-, which may be straight-chain or branched. Preferably straight-chain and having from 2 to 10 carbon atoms. Thus, in particular vinyl, prop-1-or prop-2-enyl, but-1-, -2-or but-3-enyl, pent-1-, -2-, -3-or pent-4-enyl, hex-1-, -2-, -3-, -4-or hex-5-enyl, hept-1-, -2-, -3-, -4-, -5-or hept-6-enyl, oct-1-, -2-, -3-, -4-, -5-, -6-or oct-7-enyl, non-1-, -2-, -3-, -4-, -5-, -6-, -7-or-8-alkenyl, dec-1-, -2-, -3-, -4-, -5-, -6-, -7-, -8-or-9-alkenyl.

If one of the above radicals is alkyl, one of the radicals CH₂The groups are replaced by-O-and one by-CO-, these preferably being adjacent. These therefore contain acyloxy groups-CO-O-or oxycarbonyl groups-O-CO-. They are preferably straight-chain and have 2 to 6 carbon atoms.

They are therefore in particular acetoxy, propionyloxy, butyryloxy, pentanoyloxy, hexanoyloxy, acetoxymethyl, propionyloxymethyl, butyryloxymethyl, pentanoyloxymethyl, 2-acetoxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 3-acetoxypropyl, 3-propionyloxypropyl, 4-acetoxybutyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl, 2- (methoxycarbonyl) ethyl, 2- (ethoxycarbonyl) ethyl, 2- (propoxycarbonyl) ethyl, 3- (methoxycarbonyl) propyl, 3- (ethoxycarbonyl) propyl or 4- (methoxycarbonyl) butyl.

If one of the above radicals is alkyl, one of the radicals CH₂The radicals being substituted by unsubstituted or substituted-CH ═ CH-and adjacent CH₂The groups are replaced by CO, CO-O or O-CO, which may be straight-chain or branched. Preferably straight chain and having from 4 to 13 carbon atoms. Thus, in particular acryloyloxymethyl, 2-acryloyloxyethyl, 3-acryloyloxypropyl, 4-acryloyloxybutyl, 5-acryloyloxypentyl, 6-acryloyloxyhexyl, 7-acryloyloxyheptyl, 8-acryloyloxyoctyl, 9-acryloyloxynonyl, 10-acryloyloxydecyl, methacryloyloxymethyl,2-methacryloyloxyethyl, 3-methacryloyloxypropyl, 4-methacryloyloxybutyl, 5-methacryloyloxypentyl, 6-methacryloyloxyhexyl, 7-methacryloyloxyheptyl, 8-methacryloyloxyoctyl or 9-methacryloyloxynonyl.

If one of the above radicals is alkyl or alkenyl, it is substituted by CN or CF₃Monosubstituted, the radical is preferably straight-chain. CN or CF₃In any position.

If one of the above radicals is alkyl or alkenyl, which is at least mono-substituted by halogen, this radical is preferably straight-chain and halogen is preferably F or Cl, more preferably F. In the case of polysubstitution, halogen is preferably F. The resulting groups also include perfluorinated groups. In the case of monosubstitution, the fluorine or chlorine substituent may be in any desired position, but is preferably in the ω -position.

Compounds containing branched groups may occasionally be important because of better solubility in some conventional liquid crystal base materials. However, they are particularly suitable as chiral dopants if they are optically active.

Branched groups of this type generally contain no more than one branch. Preferred branched radicals are isopropyl, 2-butyl (═ 1-methylpropyl), isobutyl (═ 2-methylpropyl), 2-methylbutyl, isopentyl (═ 3-methylbutyl), 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, isopropoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methylbutoxy, 2-methylpentyloxy, 3-methylpentyloxy, 2-ethylhexyloxy, 1-methylhexyloxy or 1-methylheptyloxy.

If one of the above radicals is alkyl, in which two or more CH groups₂The radicals are replaced by-O-and/or-CO-, which may be linear or branched. Preferably branched and having 3 to 12 carbon atoms. Thus, in particular dicarboxymethyl, 2, 2-dicarboxyethyl, 3, 3-dicarboxypropyl, 4, 4-dicarboxybutyl, 5, 5-dicarboxypentyl, 6, 6-dicarboxyhexyl, 7, 7-dicarboxyheptyl, 8, 8-di-carboxylic acidCarboxyoctyl, 9, 9-dicarboxynonyl, 10, 10-dicarboxydecyl, di (methoxycarbonyl) methyl, 2, 2-di (methoxycarbonyl) ethyl, 3, 3-di (methoxycarbonyl) propyl, 4, 4-di (methoxycarbonyl) butyl, 5, 5-di (methoxycarbonyl) pentyl, 6, 6-di (methoxycarbonyl) hexyl, 7, 7-di (methoxycarbonyl) heptyl, 8, 8-di (methoxycarbonyl) octyl, di (ethoxycarbonyl) methyl, 2, 2-di (ethoxycarbonyl) ethyl, 3, 3-di (ethoxycarbonyl) propyl, 4, 4-di (ethoxycarbonyl) butyl or 5, 5-di (ethoxycarbonyl) pentyl.

The LC medium according to the invention preferably has a nematic phase range of between-10 ℃ and +70 ℃. The LC medium may even more suitably have a nematic phase range between-20 ℃ and +80 ℃. More advantageously, the liquid-crystalline medium according to the invention has a nematic phase range of between-20 ℃ and +90 ℃.

The LC medium according to the invention preferably has a birefringence of △ n.gtoreq.0.15, more preferably △ n.gtoreq.0.20, and most preferably △ n.gtoreq.0.25.

The LC medium according to the invention preferably has a dielectric anisotropy of △ ε ≧ 10, more preferably △ ε ≧ 15, and most preferably △ ε ≧ 20.

The LC medium according to the invention preferably and advantageously exhibits high reliability and high resistivity, also referred to as Specific Resistivity (SR). The SR value of the liquid-crystalline medium according to the invention is preferably ≧ 1X 10¹³W cm, very preferably ≥ 1X 10¹⁴W cm. Unless otherwise stated, measurement of SR is performed as described in G.Weber et al, Liquid Crystals 5,1381 (1989).

The LC media according to the invention also preferably and advantageously exhibit a high Voltage Holding Ratio (VHR), see S.Matsumoto et al, Liquid Crystals 5,1320 (1989); niwa et al, proc.sid Conference, SanFrancisco, June 1984, p.304 (1984); T.Jacob and U.S. Finkenzeller in "Merck Liquid Crystals-Physical Properties of Liquid Crystals", 1997. The VHR of the liquid-crystalline medium according to the invention is preferably & gt, 85%, more preferably & gt, 90% and even more preferably & gt, 95%. Unless otherwise stated, VHR measurements were made as described in T.Jacob, U.S. Finkenzeller in "Merck Liquid Crystals-Physical Properties of Liquid Crystals", 1997.

Herein, all concentrations are given in weight percent and relative to the corresponding complete mixture, except for the aqueous solvent or phase as described above, unless explicitly stated otherwise.

All temperatures are given in degrees Celsius (C.,. degree. C.) and all temperature differences are given in degrees Celsius. All Physical Properties and physicochemical or electrooptical parameters are determined by generally known methods, in particular in accordance with "Merck Liquid Crystals, Physical Properties of Liquid Crystals", Status Nov.1997, Merck KGaA, Germany and are given for temperatures of 20 ℃ unless explicitly stated otherwise.

In this context, △ n denotes optical anisotropy, where △ n ═ n_e-n_oAnd △ epsilon represents dielectric anisotropy, wherein △ epsilon | -_⊥Dielectric anisotropy △ epsilon was determined at 20 ℃ and 1kHz optical anisotropy △ n was determined at 20 ℃ and a wavelength of 589.3 nm.

△ n and △ ε values and rotational viscosity (. gamma.) of the compounds according to the invention₁) Obtained by linear extrapolation from a liquid-crystal mixture consisting of 5% to 10% of the corresponding compound according to the invention and 90% to 95% of a commercially available liquid-crystal mixture ZLI-2857 or ZLI-4792 (both mixtures from Merck KGaA).

In addition to the usual and well-known abbreviations, the following abbreviations are used: c: a crystalline phase; n: a nematic phase; sm: a smectic phase; i: an isotropic phase. The numbers between these symbols represent the transition temperatures of the relevant substances.

In the present invention, in particular in the following examples, the structure of the mesogenic compounds is indicated by an abbreviation, also known as acronym. In these acronyms, the chemical formulae are abbreviated as follows using the following tables a to C. All radicals C_nH_2n+1,C_mH_2m+1And C_lH_2l+1Or C_nH_2n-1,C_mH_2m-1Or C_lH_2l-1Represents a straight-chain alkyl group orAlkenyl, preferably 1-E-alkenyl, each having n, m and l C atoms, respectively. Table a lists the codes for the ring elements used in the core structure of the compounds, while table B shows the linking groups. Table C gives the meaning of the left-hand or right-hand end-base codes. The acronym consists of a ring code and an optional linking group followed by a first hyphen and left-hand end code and a second hyphen and right-hand end code. Table D shows exemplary structures of the compounds, and their respective abbreviations.

Table a: ring element

Table B: linking group

Table C: terminal group

Where n and m each represent an integer and the three points are placeholders for other abbreviations in the table.

The following table shows exemplary structures with respective abbreviations. These are shown to illustrate the meaning of the abbreviation rules. They also represent compounds which can be used preferably.

Table D: exemplary Structure

Wherein n, m, l and z preferably represent, independently of one another, 1 to 7.

The following table shows exemplary compounds that may be used as further stabilizers in the mesogenic medium according to the invention.

Table E.

Table E shows possible stabilizers which may be added to the LC media according to the invention, wherein n represents an integer from 1 to 12, preferably 1,2,3,4,5,6,7 or 8, the terminal methyl group not being shown.

The liquid-crystalline medium preferably comprises from 0 to 10% by weight, in particular from 1ppm to 5% by weight, particularly preferably from 1ppm to 1% by weight, of the stabilizer.

Table F below shows exemplary compounds that can preferably be used as chiral dopants in the mesogenic media according to the invention.

TABLE F

In a preferred embodiment of the invention, the mesogenic medium comprises one or more compounds selected from the group shown in table F.

The mesogenic medium according to the invention preferably comprises two or more, preferably four or more compounds selected from the compounds shown in tables D to F above.

The LC media according to the invention preferably comprise three or more, more preferably five or more compounds shown in table D.

The following examples are merely illustrative of the present invention and they should not be construed as limiting the scope of the invention in any way. Embodiments and modifications or other equivalents will become apparent to those skilled in the art in view of this disclosure.

Examples

In an embodiment of the present invention,

V_odenotes the threshold voltage, capacitance [ V ] at 20 deg.C]，

n_eRepresenting the extraordinary refractive index at 20 c and 589nm,

n_oindicating the ordinary refractive index at 20 c and 589nm,

△ n represents the optical anisotropy at 20 ℃ and 589nm

ε_||Represents the dielectric constant parallel to the director at 20 c and 1kHz,

ε_⊥represents the dielectric constant perpendicular to the director at 20 c and 1kHz,

△ epsilon represents the dielectric anisotropy at 20 ℃ and 1kHz,

p. and T (N, I) represents clearing point [ ° C ],

γ₁represents the rotational viscosity [ mPas ] measured at 20 DEG C]Determined by a rotation method in a magnetic field,

K₁the elastic constant [ pN ] representing the "unfolding" deformation at 20 ℃]，

K₂The elastic constant [ pN ] representing the "distortion" at 20 ℃ of the strain]，

K₃The elastic constant [ pN ] representing the "bending" deformation at 20 ℃]，

The term "threshold voltage" of the present invention relates to the capacitance threshold (V) unless explicitly stated otherwise₀). In an embodiment, the optical threshold may also be expressed as a relative contrast (V) of 10%, as commonly used₁₀)。

Reference example 1

A liquid-crystal mixture B-1 having the composition and properties shown in the following table was prepared and its general physical properties were characterized.

Base mixture B-1

Reference example 2

A liquid-crystal mixture B-2 having the composition and properties shown in the following table was prepared and its general physical properties were characterized.

Base mixture B-2

Reference example 3

A liquid-crystal mixture B-3 having the composition and properties shown in the following table was prepared and its general physical properties were characterized.

Base mixture B-3

Reference example 4

A liquid-crystal mixture B-4 having the composition and properties shown in the following table was prepared and its general physical properties were characterized.

Base mixture B-4

Reference example 5

A liquid-crystal mixture B-5 having the composition and properties shown in the following table was prepared and its general physical properties were characterized.

Base mixture B-5

Reference example 6

A liquid-crystal mixture B-6 having the composition and properties shown in the following table was prepared and its general physical properties were characterized.

Base mixture B-6

Reference example 7

A liquid-crystal mixture B-7 having the composition and properties shown in the following table was prepared and its general physical properties were characterized.

Base mixture B-7

Reference example 8

A liquid-crystal mixture B-8 having the composition and properties shown in the following table was prepared and its general physical properties were characterized.

Base mixture B-8

Reference example 9

A liquid-crystal mixture B-9 having the composition and properties shown in the following table was prepared and its general physical properties were characterized.

Base mixture B-9

Example 1

Preparation of nanocapsules

LC mixture B-1(1.00g), hexadecane (175mg), methyl methacrylate (100mg), hydroxyethyl methacrylate (40mg) and ethylene glycol dimethacrylate (300mg) were weighed into a 250ml beaker.

Will be provided withL23(50mg) (from Sigma Aldrich) was weighed into a 250ml Erlenmeyer flask and water (150g) was added. The mixture is then sonicated in a sonication bath for 5 to 10 minutes.

Will be provided withThe aqueous L23 surfactant solution was poured directly into a beaker containing the organics. The mixture was mixed at turrax for 5 minutes at 10,000 rpm. Once turrax mixing is complete, the crude emulsion is passed through a high pressure homogenizer four times at 30,000 psi.

The mixture was charged into a flask and equipped with a condenser, and then heated to 70 ℃ for 3 hours after addition of AIBN (35 mg). The reaction mixture was cooled, filtered and then the size analysis of the material was performed on a Zetasizer (malvern Zetasizer Nano zs) instrument.

The resulting capsules had an average size of 213nm as determined by Dynamic Light Scattering (DLS) analysis (Zetasizer).

Addition of additives

From the resulting nanocapsule samples, two portions each containing 0.21g nanocapsules in 20ml solution were added to a centrifuge tube, respectively.

0.01g ofL23 and Triton X-100(Sigma Aldrich) were added to 0.1ml of water in a centrifuge tube, respectively. 0.01g ofL4(Sigma Aldrich) andwet270 (from Evonik) was added separately to 0.1ml of isopropyl alcohol (IPA) in a centrifuge tube. A 20ml portion (0.21g) of the resulting nanocapsule sample was added to four centrifuge tubes containing the additive accordingly.

Six tubes were placed on a roller for 48 hours.

The corresponding particle suspension was then concentrated by centrifugation, wherein the centrifuge tube was placed in a centrifuge (ThermoFisher Biofuge stands) and centrifuged at 6,500rpm for 10 minutes and then at 15,000rpm for 20 minutes. The pellets obtained were redispersed in 1ml of the supernatant liquid, respectively.

Preparation of 30% solids PVA Binder

The PVA (molecular weight M of PVA) was first washed in a Soxhlet apparatus_w: 31K; 88% hydrolysis) for 3 days to remove ions.

46.66 grams of deionized water was added to a 150ml bottle, a large magnetic stir bar was added, the bottle was placed on a 50 ℃ stir hotplate and allowed to reach temperature. 20.00g of solid washed 31k PVA was weighed into a beaker. A vortex was established in the bottle and gradually added over about 5 minutesPVA, stopped to allow floating PVA to disperse into the mixture. The heating plate was raised to 90 ℃ and stirring was continued for 2-3 hours. The bottles were placed in an oven at 80 ℃ for 20 hours. The mixture was filtered while still warm through a 50 μm cloth filter under an air pressure of 0.5 bar. The filter was replaced with a Millipore 5 μm SVPP filter and filtration was repeated.

The solids content of the filtered binder was determined 3 times and averaged, calculated by: empty DSC pans were weighed using a DSC microbalance, approximately 40mg of the binder mixture was added to the DSC pan and the mass recorded, the pan was placed on a 60 ℃ hot plate for 1 hour followed by a 110 ℃ hot plate for 10 minutes, the pan was removed from the hot plate and cooled, the mass of the dry pan was recorded and the solids content calculated.

Preparation of the composite System

The six nanocapsule samples obtained were first examined microscopically for unwanted agglomeration or coalescence, and also after film formation. The solid content of the corresponding concentrated nanocapsule suspension was measured, wherein the solid content of each sample was measured 3 times, and the average value was calculated. The samples were weighed into empty DSC pans using a DSC microbalance, wherein the respective samples were added to the DSC pans and the mass was recorded. The plate was placed on a 60 ℃ hot plate for 1 hour, followed by a 110 ℃ hot plate for 10 minutes. The disk was removed from the hot plate and cooled. The mass of the dried disc was recorded and the solids content was calculated.

The prepared PVA was added to the corresponding concentrated nanocapsule samples, wherein approximately 30% washed 31KPVA mixture was added to a 2.5ml volumetric flask and then the corresponding nanocapsules were added to the volumetric flask. The weight ratio of PVA to capsules was 50: 50. Deionized water was added to make the total solids content 20%. The mixture was stirred using a vortex stirrer and placed on a roller overnight to disperse the PVA.

Preparation of a film on a substrate

The substrate used was IPS (in-plane switching) glass with ITO-coated interdigitated electrodes, electrode width 4 μm and gap 8 μm. The substrates were placed in racks and plastic boxes for cleaning. Deionized water was added and the sample was placed in the ultrasound for 10 minutes. The substrate was removed from the water and wiped with a paper towel to remove excess water. The washing was repeated with acetone, 2-propanol (IPA) and finally water to be suitable for ion chromatography. The substrate was then dried using a compressed air gun. The substrate was treated with UV-ozone for 10 minutes.

Six composite systems containing the respective nanocapsules and binder were then each coated on a substrate. A Coater (K Control Coater, RK Printcoat Instruments, K bar 1 bar, coating speed 7) was used to coat 40. mu.L of the mixture into a film. The sample was dried on a hot plate at 60 ℃ for 10 minutes and dried under a lid to prevent air flow and to prevent contaminants from falling onto the membrane. The appearance of the film was recorded. The prepared film was stored in a dry box between measurements.

Film thickness was measured by removing the film from over the electrical contacts with a razor blade. The film thickness was measured in the region in the middle of the electrodes using a surface profiler (Dektak XT surface profiler, Bruker) with a 5mg pen contact force and a scan length of 3000nm and a time of 30 s.

Measurement of electro-optical characteristics

The uniformity of appearance and defects of each film were checked by naked eyes. Two electrodes are welded to the glass. The voltage-transmission curve was measured using Dynamic Scattering Mode (DSM).

Images of dark and light states at voltages required for 0% or 10% and 90% transmission were also recorded using a microscope.

The switching speed was measured at 40 ℃ and 25 ℃, 150Hz modulation frequency and, where appropriate, also at 10 Hz.

The measured electro-optical parameters of the prepared film comprising nanocapsules and binder are given in the table below. In this and the following examples, at V₅₀The hysteresis is determined next.

The electro-optical properties shown in the table below were measured on a display test system (Autronic-Melchers), where the backlight intensity was taken as 100% transmission T and the dark state between crossed polarizers as 0% transmission T and where the switching was done at 1kHz and 24 ℃.

Among other advantages, in particular improved dark state and reduced hysteresis, it was found that additives can suitably contribute to the reduction of the operating voltage.

Example 2

Will be provided with58(50 mg) (Sigma-Aldrich) was weighed into a 250ml Erlenmeyer flask and water (150g) was added. The mixture was then sonicated for 5 to 10 minutes.

Will be provided with58 aqueous surfactant solution was poured directly into a beaker containing the organics. The mixture was mixed at turrax for 5 minutes at 10,000 rpm. Once turrax mixing is complete, the crude emulsion is passed through a high pressure homogenizer four times at 30,000 psi.

The mixture was then further processed and studied as described above in example 1.

Example 3

LC mixture B-1(2.01g), hexadecane (358mg), ethylene glycol dimethacrylate (597mg), 2-hydroxyethyl methacrylate (80mg) and methyl methacrylate (190mg) were weighed into a 400ml beaker.

58(100mg) was weighed into a 400ml Erlenmeyer flask and water (250g) was added. The mixture was then sonicated for 5 to 10 minutes.

The Brij surfactant aqueous solution was poured directly into a beaker containing the organics. The mixture was mixed at turrax for 10 minutes at 10,000 rpm. Once turrax mixing is complete, the crude emulsion is passed through a high pressure homogenizer four times at 30,000 psi.

The mixture was charged into a flask and equipped with a condenser, and after adding AAPH (20mg), it was heated to 73 ℃ for 4 hours. The reaction mixture was cooled, filtered and then the material was subjected to size analysis on a Zetasizer instrument.

The resulting capsules had an average size of 230nm and a polydispersity of 0.051 as determined by Dynamic Light Scattering (DLS) analysis (Zetasizer).

The samples were concentrated before further use. This was done by passing the sample through a cross-flow filtration device (Vivaflow 200 from Sartorius, a membrane with a cut-off weight of 100,000 Da) at a flow rate of 100ml per minute until the volume was reduced by half. The samples were then transferred to a water tank with a lid with a suitable vacuum and used with a sample consisting of 450ml of water and58(200mg) were washed in the same apparatus.

After washing the sample, the device was operated in the concentration mode and continued at a rate of 100ml per minute until it reached a minimum volume. The sample is removed from the filtration device and is suitable for further use.

The solids content of this sample was measured to be 19%.

A composite system with adhesive and coating film was then prepared as described in example 1, however with a weight ratio of capsules to PVA of 60: 40.

The coated sample had a V of 41V₉₀And a dark state transmission of 1.25%.

Example 4

Preparation of nanocapsules

LC mixture B-8(2.00g), methyl methacrylate (165mg), hydroxyethyl methacrylate (75mg) and ethylene glycol dimethacrylate (660mg) were weighed into a 250ml beaker.

Will be provided withL23(150mg) was weighed into a 250ml Erlenmeyer flask and water (150g) was added. The mixture was then sonicated for 5 to 10 minutes.

The mixture was charged into a flask and equipped with a condenser, and after AIBN (35mg) was added, it was heated to 70 ℃ for 3 hours. The reaction mixture was cooled, filtered and then the size analysis of the material was performed on a Zetasizer (malvern Zetasizer Nano zs) instrument.

The average size of the resulting capsules was determined to be 167nm by Dynamic Light Scattering (DLS) analysis (Zetasizer)

Addition of additives

From the resulting nanocapsule sample, a portion containing 0.40g nanocapsules in 20ml of solution was added to a centrifuge tube.

0.019g of Triton X-100 was added to 0.1ml of water in a centrifuge tube. Mixing 0.019g ofL4,0.019g FluorN561 (from Cytonix) and 0.019gWet270 was added separately to 0.1ml of isopropyl alcohol (IPA) in a centrifuge tube. A20 ml portion (0.40g) of the resulting nanocapsule sample was added to four centrifuge tubes containing additives, respectively.

Five centrifuge tubes were placed on a roller for 48 hours.

The corresponding particle suspension was then concentrated by centrifugation, wherein the centrifuge tube was placed on a centrifuge (ThermoFisher Biofuge stands) and centrifuged at 6,500rpm for 10 minutes and then at 15,000rpm for 20 minutes. The pellets obtained were redispersed in 0.7ml of the supernatant liquid, respectively.

Preparation of PVA binder and composite system, and preparation of film on substrate

PVA binder, composite system and film were prepared as described in example 1.

Measurement of electro-optical characteristics

The measured electro-optical parameters of the prepared film comprising nanocapsules and binder are given in the table below.

The electro-optical properties shown in the table below were measured on a display test system (Autronic-Melchers), where the backlight intensity was taken as 100% transmission T and the dark state between crossed polarizers as 0% transmission T and where switching was done at 1kHz and 24 ℃.

Example 5

Preparation of nanocapsules

LC mixture B-1(6.00g), hexadecane (300mg), methyl methacrylate (225mg), hydroxyethyl methacrylate (510mg) and ethylene glycol dimethacrylate (2000mg) were weighed into a 250ml beaker.

Will be provided withL23(450mg) was weighed into a 250ml Erlenmeyer flask andwater (150g) was added. The mixture was then sonicated for 5 to 10 minutes.

The mixture was charged into a flask and equipped with a condenser, and after AIBN (75mg) was added, it was heated to 70 ℃ for 3 hours. The reaction mixture was cooled, filtered and then the size analysis of the material was performed on a Zetasizer (malvern Zetasizer Nano zs) instrument.

The mean size of the resulting capsules was determined to be 173nm by Dynamic Light Scattering (DLS) analysis (Zetasizer).

The resulting nanoparticle suspension was concentrated by centrifugation, with the centrifuge tube placed on a centrifuge (thermo fisher biofuge stands) and centrifuged at 6,500rpm for 10 minutes and then at 15,000rpm for 20 minutes.

Addition of additives

0.32g of the pellets obtained are redispersed in 1ml of supernatant and placed in a 2.5ml glass bottle.

0.01g ofL23，Triton X-100，Wet270 and FluorN 322 were added to 0.99g of acetone in 2.5ml glass vials, respectively. The acetone was then evaporated on a hot plate at 40 ℃ for 10 minutes. A1 ml portion (0.32g) of the resulting nanocapsules was added to 4 2.5ml glass bottles containing the additive respectively.

Five glass bottles were placed on the roller for 48 hours.

PVA binder, composite system and film were prepared as described in example 1.

Measurement of electro-optical characteristics

The electro-optical properties shown in the table below were measured on a display test system (Autronic-Melchers), where the backlight intensity was taken as the transmission T of 100% and the dark state between crossed polarizers was taken as the transmission T of 0% and where the switching was done at 1kHz and 24 ℃.

Example 6

Preparation of nanocapsules

LC mixture B-1(1.00g), hexadecane (179mg), methyl methacrylate (102mg), hydroxyethyl methacrylate (40mg) and ethylene glycol dimethacrylate (303mg) were weighed into a 250ml beaker.

Will be provided withL23(50mg) was weighed into a 250ml Erlenmeyer flask and water (150g) was added. The mixture was then sonicated for 5 to 10 minutes.

The average size of the resulting capsules was determined to be 167nm by Dynamic Light Scattering (DLS) analysis (Zetasizer).

Preparation of PVA Binder

A PVA binder was prepared as described in example 1.

Composite bodyPreparation of the lines

0.22 grams of the prepared nanocapsules in 1.5ml of solution and 0.33 grams of the prepared PVA in 1.2ml of aqueous solution were mixed to obtain a PVA to capsule weight ratio of 60: 40.

The mixture was stirred with a vortex stirrer and placed on a roller overnight to disperse the PVA.

Three separate fractions were prepared from the mixture. One of these fractions was used for film formation without further addition of additives, and for the other two additives were added as follows.

Addition of additives

0.2. mu.L of 0.02g of acetoneWet270 and 0.2. mu.L in 0.02g Isopropanol (IPA)Wet280 (from Evonik) was added separately to separate bottles. The solvent was evaporated over the next 24 hours. A 0.20g portion of the prepared mixture of PVA and nanocapsules was added to each bottle.

Will containWet270 orThe mixture of Wet280 was further mixed for 24 hours.

In thatPreparation of a film on a substrate

Membranes were prepared as described in example 1.

Measurement of electro-optical characteristics

Examples 7 to 14

Instead of B-1, the LC mixtures B-2, B-3, B-4, B-5, B-6, B-7, B-8 and B-9 were each treated as described above in example 1 to prepare nanocapsules, composite systems with binders and coated films.

Example 15

The LC mixture B-1 was processed as described above in example 1 to prepare nanocapsules, composite systems with binder and coated films, using 1, 4-pentanediol (example 15.1), dodecane (example 15.2) or tetradecane (example 15.3), respectively, instead of hexadecane.

Example 16

LC mixture B-3(1.0g), ethylene glycol dimethacrylate (0.34g), 2-hydroxyethyl methacrylate (0.07g) and hexadecane (0.25g) were weighed into a 250ml beaker.

The mixture was processed and studied as described above in example 1.

Example 17

LC mixture B-1(2.66g), hexadecane (0.66g) and methyl methacrylate (3.30g) were weighed into a 250ml beaker.

The mixture was processed and studied as described in example 4 above.

Example 18

Preparation of nanocapsules

Comparative example 18.1

L23(50mg) was weighed into a 250ml Erlenmeyer flask and water (150g) was added. The mixture was then sonicated for 5 to 10 minutes.

The aqueous surfactant solution was poured directly into a beaker containing the organics. The mixture was mixed at turrax for 5 minutes at 10,000 rpm. Once turrax mixing is complete, the crude emulsion is passed through a high pressure homogenizer four times at 30,000 psi.

The resulting nanoparticle suspension was concentrated by centrifugation, with the centrifuge tube placed on a centrifuge (thermo fisher biofuge stands) and centrifuged at 6,500rpm for 10 minutes and then at 15,000rpm for 20 minutes. The solid content was measured three times in a DSC pan and approximately 40 μ Ι _ of concentrated nanocapsules were kept on a hot plate at 40 ℃ for 10 minutes.

Examples 18.2,18.3 and 18.4

The preparation of nanocapsules as described in comparative example 18.1 was repeated except that50mg of L23(50mg) in each caseWet270 (example 18.2), 50mg of TritonX-100 (example 18.3) or 50mg ofL4 (example 18.4) was weighed into a 250ml Erlenmeyer flask.

Preparation of PVA Binder

A PVA binder was prepared as described in example 1.

Preparation of the composite System

A 0.5g centrifuged suspension containing 15% by weight of the corresponding prepared nanocapsules was mixed with PVA to obtain a PVA to capsule weight ratio of 60: 40.

The four mixtures were stirred using a vortex stirrer and the mixture was placed on a roller overnight.

In thatPreparation of a film on a substrate

Membranes were prepared as described in example 1.

Measurement of electro-optical characteristics

Example 19

LC mixture B1(2.00g), 1, 4-pentanediol (102mg), ethylene glycol dimethacrylate (658mg), 2-hydroxyethyl methacrylate (77mg), and methyl methacrylate (162mg) were weighed into a 250ml beaker.

L23(100mg) was weighed into a 250ml Erlenmeyer flask and water (100g) was added. The mixture was then sonicated for 5 to 10 minutes.

The Brij surfactant aqueous solution was poured directly into a beaker containing the organics. The mixture was mixed at turrax for 10 minutes at 10,000 rpm. Once turrax mixing is complete, the crude emulsion is passed through a high pressure homogenizer eight times at 30,000 psi.

The mixture was charged into a flask and charged with a condenser, and after adding AAPH (20mg), it was heated to 70 ℃ for 4 hours. The reaction mixture was cooled, filtered and then the material was subjected to size analysis on a Zetasizer instrument.

The average size of the resulting capsules was determined to be 180nm by Dynamic Light Scattering (DLS) analysis (Zetasizer).

The resulting sample was then further processed as described in example 1.

Example 20

LC mixture B-9(2.00g), hexadecane (100mg), methyl methacrylate (100mg), hydroxyethyl methacrylate (130mg) and ethylene glycol dimethacrylate (198mg) were weighed into a 250ml beaker.

Will be provided withL23(300mg) was weighed into a 250ml Erlenmeyer flask and water (100g) was added. The mixture was then sonicated for 5 to 10 minutes.

The mixture was charged into a flask and charged with a condenser, and after AIBA (20mg) was added, it was heated to 70 ℃ for 3 hours. The reaction mixture was cooled, filtered and then the size analysis of the material was performed on a Zetasizer (malvern Zetasizer Nano zs) instrument.

The average size of the resulting capsules was determined to be 129nm by Dynamic Light Scattering (DLS) analysis (Zetasizer).

Addition of additives

From the resulting nanocapsule sample, a portion containing 0.28g nanocapsules in 20ml of solution was added to a centrifuge tube.

0.01g of Triton X-100 was added to 0.1ml of water in a centrifuge tube. 0.01g ofL4,0.01g FluorN332 and 0.01gWet270 was added separately to 0.1ml of isopropyl alcohol (IPA) in a centrifuge tube. A20 ml portion (0.28g) of the resulting nanocapsule sample was added to four centrifuge tubes containing additives, respectively.

Five centrifuge tubes were placed on a roller for 48 hours.

Preparation of PVA binder and composite system and preparation of film on substrate

PVA binders, composite systems and films were prepared as described in example 1.

Measurement of electro-optical characteristics

Example 21

LC mixture B-1(1.00g), hexadecane (175mg), methyl methacrylate (100mg), hydroxyethyl methacrylate (40mg) and ethylene glycol dimethacrylate (300mg) were weighed into each of four 250ml beaker beakers.

Will be provided withL23(50mg) was weighed into a first 250ml Erlenmeyer flask and water (150g) was added. Into three other 250ml conical flasksL23(50mg), water (150g) and the correspondingL4(50mg)，Wet270(50mg) or Triton X-100(50 mg). These mixtures were then sonicated for 5 to 10 minutes.

The 4 aqueous solutions were poured directly into 4 beakers containing the organics. The mixture was mixed at turrax for 5 minutes at 10,000 rpm. Once turrax mixing is complete, the crude emulsion is passed through a high pressure homogenizer four times at 30,000 psi.

The 4 mixtures were charged into flasks, respectively, and loaded with a condenser, and after AIBA (20mg) was added, the mixture was heated to 70 ℃ and held for 3 hours. The reaction mixture was cooled, filtered and then the size analysis of the material was performed separately on a Zetasizer (malvern Zetasizer Nano zs) instrument.

Comparative example 21.1 (Zetasizer only) determined by Dynamic Light Scattering (DLS) analysis (Zetasizer)L23) the mean size of the capsules obtained was 129 nm. Example 21.2 (additional) was determined by Dynamic Light Scattering (DLS) analysis (Zetasizer)L4) the mean size of the capsules obtained was 192 nm. Example 21.3 (additional) was determined by Dynamic Light Scattering (DLS) analysis (Zetasizer)Wet 270) the mean size of the capsules obtained was 200 nm. The mean size of the capsules obtained in example 21.4 (additional Triton X-100) was determined to be 180nm by Dynamic Light Scattering (DLS) analysis (Zetasizer).

The composite system and film containing the four nanocapsule samples were then prepared as described in comparative example 1.1.

The electrooptical properties were measured as described in example 1. The measured electro-optical parameters of the prepared film comprising nanocapsules and binder are given in the table below.

Example 22

LC mixture B-1 was treated as described in example 1 above to prepare nanocapsules, composite systems with binder and coating films in which instead of 175mg of hexadecane, 100mg of hexadecane and 75mg of 1, 5-dimethyltetralin (example 22.1), 100mg of hexadecane and 75mg of 3-phenoxytoluene (example 22.2), 100mg of hexadecane and 75mg of cyclohexane (example 22.3) or 100mg of hexadecane and 75mg of 5-hydroxy-2-pentanone (example 22.4) were used, respectively.

Example 23

LC mixture B-1(1.00g), hexadecane (125mg), methyl methacrylate (100mg), hydroxyethyl methacrylate (40mg) and ethylene glycol dimethacrylate (300mg) were weighed into a 250ml beaker. In addition 50mg of PEG methyl ether methacrylate were added.

The average size of the resulting capsules was determined to be 211nm by Dynamic Light Scattering (DLS) analysis (Zetasizer).

Composite systems and films containing nanocapsule samples were then prepared as described in comparative example 1.1.

Trueness ofThe electro-optic properties were measured as described in example 1. The measured electrooptical parameters of the prepared film (3.42 μm) were: v₉₀＝51.5V；V₉₀T of (c) 13.8%; v₀T of (1.07%); hysteresis 1.1V.

Example 24

LC mixture B-1(1.00g), hexadecane (100mg), methyl methacrylate (16mg), hydroxyethyl methacrylate (89mg) and ethylene glycol dimethacrylate (250mg) were weighed into a 250ml beaker. 100mg of stearyl methacrylate are additionally added.

L23(75mg) was weighed into a 250ml Erlenmeyer flask and water (150g) was added. The mixture was then sonicated for 5 to 10 minutes.

The average size of the resulting capsules was determined to be 178nm by Dynamic Light Scattering (DLS) analysis (Zetasizer).

The electro-optical properties were measured as described in example 1. The measured electrooptical parameters of the prepared film (4.70 μm) were: v₉₀＝64.5V；V₉₀T of (b) 14.3%; v₀T of (b) 0.59%; hysteresis 4.8V.

Claims

1. A method of making a nanocapsule, wherein the method comprises

(a) Providing a composition comprising

(i) Mesogenic media comprising one or more compounds of formula I

R-A-Y-A'-R' I

Wherein,

r and R' independently of one another represent a group selected from F, CF₃，OCF₃A radical of CN and a linear or branched alkyl or alkoxy radical having from 1 to 15 carbon atoms or a linear or branched alkenyl radical having from 2 to 15 carbon atomsWhich is unsubstituted, is substituted by CN or CF₃Mono-or poly-substituted by halogen, and wherein one or more CH₂The radicals may be replaced in each case independently of one another by-O-, -S-, -CO-, -COO-, -OCO-, -OCOO-or-C.ident.C-in such a way that oxygen atoms are not linked directly to one another,

(ii) one or more polymerizable compounds,

wherein the other additive or additives are

-adding to the composition or nanodroplets prior to polymerization

And/or

-adding to the obtained nanocapsules.

2. The process according to claim 1, wherein the one or more additives are added to the obtained nanocapsules in step (d) after the polymerization according to step (c).

3. The process according to claim 2, wherein after obtaining the nanocapsules, the aqueous phase is depleted, removed or exchanged in a further step, and

wherein the addition of one or more additives according to step (d) is carried out before and/or after the further step of depleting, removing or exchanging the aqueous phase.

4. The process according to one or more of claims 1 to 3, wherein the one or more additives additionally added, preferably the one or more additives added to the obtained nanocapsules, are one or more surfactants.

5. The process according to one or more of claims 1 to 4, wherein the composition provided in (a) further comprises one or more organic solvents.

6. The method according to one or more of claims 1 to 5, wherein the one or more polymerizable compounds of claim 1 comprise one, two or more polymerizable groups selected from acrylate, methacrylate and vinyl acetate groups.

7. The process according to one or more of claims 1 to 6, wherein the one or more compounds of formula I comprised in the mesogenic medium of claim 1 are selected from compounds of formulae Ia, Ib, Ic and Id,

wherein,

R¹，R²，R³，R⁴，R⁵and R⁶Independently of one another, a linear or branched alkyl radical having from 1 to 15 carbon atomsOr alkoxy, or straight-chain or branched alkenyl having 2 to 15 carbon atoms, which is unsubstituted, substituted by CN or CF₃Mono-or poly-substituted by halogen, and wherein one or more CH₂The radicals may be replaced in each case independently of one another by-O-, -S-, -CO-, -COO-, -OCO-, -OCOO-or-C.ident.C-in such a way that oxygen atoms are not bonded directly to one another,

L¹，L²，L³，L⁴and L⁵Independently of one another, are H or F,

i is 1 or 2, and

j and k are independently of each other 0 or 1.

8. Nanocapsules obtained or obtainable by carrying out a process according to one or more of claims 1 to 7.

9. Nanocapsules, each of which comprises

A shell of a polymer, the shell comprising a polymer,

a core comprising the mesogenic medium of claim 1 or 7, and,

one or more additives.

10. A method of making a composite system, wherein the method comprises:

providing nanocapsules, each of which comprises

A shell of a polymer, the shell comprising a polymer,

a core comprising the mesogenic medium of claim 1 or 7, and,

optionally one or more additives selected from the group consisting of,

-adding one or more binders to the nanocapsules, and

11. The method of claim 10, wherein the one or more binders comprise polyvinyl alcohol.

12. Composite system obtained or obtainable by carrying out a process according to claim 10 or 11.

13. A composite system comprising

-nanocapsules, each of which comprises

A polymeric shell, and

a core comprising the mesogenic medium of claim 1 or 7,

-one or more binders, and

-one or more additives.

14. Use of a nanocapsule according to claim 8 or 9 or of a composite system according to claim 12 or 13 in a light modulation element or an electro-optical device.

15. Electro-optical device comprising a nanocapsule according to claim 8 or 9 or a composite system according to claim 12 or 13.

16. Use of one or more additives in a nanocapsule comprising a polymer shell and a core comprising a mesogenic medium according to claim 1 or 7 or in a composite comprising the nanocapsule and one or more binders for reducing the switching voltage.