Liquid crystal nano-capsule, and capsule solution, optical film, optical device, transmittance variable device using same

Abstract

The present invention relates to a liquid crystal nano-capsule and a capsule solution, an optical film, an optical device, and a transmittance variable device using same, the liquid crystal nano-capsule comprising: a core containing a liquid crystal; and a polymer shell formed on the surface of the core, wherein the sum of the onset temperature change value according to equation 1 and the peak temperature change value according to equation 2 is 37.5°C or less.

Description

Liquid crystal nanocapsules, and capsule liquid using the same, optical film, optical device, transmittance variable device

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0133749 filed on October 2, 2024, and all contents disclosed in the document of said Korean patent application are incorporated herein as part of this specification.

[0003] The present invention relates to a liquid crystal nanocapsule capable of inducing a high transmittance variability even at lower voltages by lowering the surface interaction energy of the liquid crystal enclosed inside the capsule, and to a capsule liquid, an optical film, an optical device, and a transmittance variability device using the same.

[0004] Polymer Dispersed Liquid Crystals (PDLC) films are composite materials that can be applied to high-brightness projection displays or high-contrast reflective display devices, in which liquid crystal molecules of several micrometers are dispersed within a polymer between conductive films. The operating principle of PDLC is that light incident on a polymer layer in which liquid crystals are dispersed is scattered due to the difference in refractive index between the liquid crystals and the polymer, resulting in an opaque state; however, by applying an electric field, the direction of the liquid crystals is aligned, and by changing the refractive index, the scattering and transmission of light are controlled, resulting in a transparent state.

[0005] As such, PDLC devices do not require a separate polarizer, so they do not require a polarizer structurally, and they do not require an alignment process, allowing them to be manufactured in a simple manner. This makes them applicable to smart glass and smart screens for buildings and automobiles that correspond to switchable windows, and they can also be applied as black PDLC films for transparent OLEDs. In addition, they can be manufactured in a flexible form depending on the material used as the substrate.

[0006] Specifically, liquid crystal-based smart windows refer to active windows capable of controlling transmittance using glass containing a separate liquid crystal layer; this technology is applicable not only to buildings but also to the mobility sector. Conventional polymer dispersed liquid crystal (PDLC) technology allowed for the fabrication of liquid crystal domains several micrometers in size by mixing liquid crystals with monomers capable of photo or thermal polymerization and utilizing the phase separation between the polymer and liquid crystals that occurs during polymerization. PDLC films can implement light-blocking or light-transmitting modes as the liquid crystals within the micrometer domains match or mismatch the refractive index of the polymer matrix depending on the on / off voltage application. However, it is difficult to overcome the disadvantage in PDLC that visible light is scattered due to liquid crystal domains being larger than the visible light wavelength range.

[0007] On the other hand, if the liquid crystal is domainized to a size of 380 nm or less, the scattering issue can be improved, making it possible to manufacture a liquid crystal film layer with better transmittance and haze.

[0008] In particular, when manufacturing color-modifying PDLCs containing dyes, issues arise such as the anisotropic dyes within the polymer not aligning uniformly according to the electric field, and specifically, contamination of the polymer matrix by the dyes occur. Consequently, various studies are underway on encapsulated liquid crystal composites in which the liquid crystal and anisotropic dye are encapsulated within a polymer shell, resulting in excellent mechanical properties, high uniformity, and the prevention of dye-induced contamination of the polymer matrix.

[0009] However, as the liquid crystal and anisotropic dye are encapsulated in a polymer shell, there was a limitation in that the orientation of the liquid crystal was changed only when a higher voltage was applied due to the high interaction that occurs as the contact area between the liquid crystal enclosed in the capsule and the material contained in the capsule shell increases.

[0010] The present invention aims to provide a liquid crystal nanocapsule capable of inducing a high transmittance variability even at lower voltages by lowering the surface interaction energy of the liquid crystal enclosed inside the capsule.

[0011] In addition, the present invention is intended to provide a capsule liquid, an optical film, an optical device, and a transmittance variable device manufactured using the liquid crystal nanocapsule.

[0012] To solve the above problem, the present specification provides a liquid crystal nanocapsule comprising: a core containing liquid crystal; and a polymer shell formed on the surface of the core; wherein the sum of the Onset temperature change value according to the following Equation 1 and the Peak temperature change value according to Equation 2 is 37.5 ℃ or less.

[0013] [Mathematical Formula 1]

[0014] Onset temperature change value = (Minimum temperature at which endothermic or exothermic reactions occur during DSC measurement of the above liquid crystal nanocapsule) - (Minimum temperature at which endothermic or exothermic reactions occur during DSC measurement of the above liquid crystal)

[0015] [Mathematical Formula 2]

[0016] Peak temperature change value = (Temperature at the peak where endothermic or exothermic activity is maximum during DSC measurement of the liquid crystal nanocapsule) - (Temperature at the peak where endothermic or exothermic activity is maximum during DSC measurement of the liquid crystal).

[0017] In addition to the above, a capsule solution comprising the liquid crystal nanocapsule and the solvent is provided.

[0018] In addition to the above, an optical film comprising the liquid crystal nanocapsule is provided.

[0019] The present specification also provides an optical device comprising the optical film.

[0020] The present specification also provides a transmittance variable device comprising the optical film.

[0021] The liquid crystal nanocapsule according to a specific embodiment of the invention, and the capsule liquid, optical film, optical device, and transmittance variable device using the same, will be described in more detail below.

[0022]

[0023] Unless explicitly stated otherwise in this specification, technical terms are used merely to refer to specific embodiments and are not intended to limit the invention.

[0024] The singular forms used in this specification include plural forms unless the phrases clearly indicate otherwise.

[0025] As used in this specification, the meaning of 'includes' specifies certain characteristics, regions, integers, steps, actions, elements, and / or components, and does not exclude the existence or addition of other specific characteristics, regions, integers, steps, actions, elements, components, and / or groups.

[0026] Also, in this specification, terms including ordinal numbers such as 'first' and 'second' are used for the purpose of distinguishing one component from another and are not limited by said ordinal numbers. For example, within the scope of the present invention, the first component may also be named the second component, and similarly, the second component may be named the first component.

[0027] In this specification, derivative compounds refer to compounds that have been modified from an organic compound as a base, such as by introducing functional groups, oxidation, reduction, or substitution of atoms, to the extent that the structure and properties of the base are not significantly altered.

[0028] In this specification, the weight-average molecular weight refers to the weight-average molecular weight equivalent to polystyrene measured by the GPC method. In the process of measuring the weight-average molecular weight equivalent to polystyrene measured by the GPC method, commonly known analytical devices, detectors such as a refractive index detector, and analytical columns may be used, and commonly applied temperature conditions, solvents, and flow rates may be applied. As a specific example of the above measurement conditions, a Waters PL-GPC220 instrument is used with a Polymer Laboratories PLgel MIX-B 300 mm long column, the evaluation temperature is 160 ℃, 1,2,4-trichlorobenzene is used as the solvent, the flow rate is 1 mL / min, the sample is prepared at a concentration of 10 mg / 10 mL and supplied in an amount of 200 μL, and the value of Mw can be obtained using a calibration curve formed using a polystyrene standard. Nine types of polystyrene standards with molecular weights of 100 / 500 / 1000 / 2,000 / 10,000 / 30,000 / 70,000 / 200,000 / 700,000 were used.

[0029] The present invention will be described in more detail below.

[0030]

[0031] 1. Liquid crystal nanocapsules

[0032] According to one embodiment of the invention, a liquid crystal nanocapsule may be provided comprising: a core containing liquid crystal; and a polymer shell formed on the surface of the core, wherein the sum of the Onset temperature change value according to the following Equation 1 and the Peak temperature change value according to Equation 2 is 37.5 ℃ or less.

[0033] [Mathematical Formula 1]

[0034] Onset temperature change value = (Minimum temperature at which endothermic or exothermic reactions occur during DSC measurement of the above liquid crystal nanocapsule) - (Minimum temperature at which endothermic or exothermic reactions occur during DSC measurement of the above liquid crystal)

[0035] [Mathematical Formula 2]

[0036] Peak temperature change value = (Temperature at the peak where endothermic or exothermic activity is maximum during DSC measurement of the liquid crystal nanocapsule) - (Temperature at the peak where endothermic or exothermic activity is maximum during DSC measurement of the liquid crystal).

[0037] The inventors confirmed through experiments that, as with the liquid crystal nanocapsule of the above embodiment, the sum of the Onset temperature change value according to Equation 1 and the Peak temperature change value according to Equation 2 satisfies 37.5 ℃ or less, thereby lowering the surface interaction energy of the liquid crystal enclosed inside the capsule, and thus enabling a high transmittance variability rate even at a lower voltage, and completed the invention.

[0038] Thermotropic liquid crystals are basically materials in which a phase transition occurs due to an increase in molecular mobility caused by a rise in temperature. An example of a thermotropic liquid crystal is a liquid crystal in which nematic liquid crystals change into isotropic liquid, and the phase transition temperature at this time is referred to as Tni (Temperature from nematic to isotropic phase).

[0039] Nematic liquid crystals have the characteristic of aligning according to the surface to which they are exposed, a phenomenon referred to as the surface anchoring effect. The higher the interaction with the surface material, the more voltage is required to move the liquid crystals. Liquid crystals enclosed within a capsule have their surface anchoring energy increased by the capsule shell, requiring the application of a higher voltage to change the orientation of the liquid crystals. Therefore, if the surface anchoring energy of the liquid crystals within the capsule is lowered, a higher transmittance variability can be induced even at a lower voltage.

[0040] The Onset temperature change value according to Equation 1 and the Peak temperature change value according to Equation 2 are parameters regarding the difference value of Tni (Temperature from nematic to isotropic phase) described above. If the Onset temperature change value according to Equation 1 and the Peak temperature change value according to Equation 2 become smaller, it means that the surface anchoring energy of the liquid crystal inside the capsule is relatively low, and for this reason, the transmittance variability can increase even at low voltages. Specifically, if the Onset temperature change value according to Equation 1 and the Peak temperature change value according to Equation 2 become smaller, low-voltage driving is possible at a lower threshold voltage, and it is possible to manufacture a liquid crystal nanocapsule with a high contrast ratio and excellent transmittance variability characteristics.

[0041] Furthermore, as described below, satisfying the Onset temperature change value according to Equation 1 and the Peak temperature change value according to Equation 2 is the result of lowering the surface anchoring energy of the liquid crystal inside the capsule by mixing the emulsifier unique to the present invention with a siloxane-based additive.

[0042] Specifically, the liquid crystal nanocapsule of the above embodiment may include a core containing liquid crystal. The liquid crystal nanocapsule structure according to the present invention is characterized by containing liquid crystal inside a shell made of a polymer. This can improve the uniformity of the liquid crystal particles.

[0043] The above liquid crystal is not particularly limited, but examples include nematic liquid crystals, smectic liquid crystals, cholesteric liquid crystals, chiral nematic liquid crystals, etc. The specific type of liquid crystal compound is not limited, and various conventionally known liquid crystals can be used without restriction.The above liquid crystal is not particularly limited, but specifically (trans,trans)-4-Ethenyl-4'-propyl-1,1'-bicyclohexyl, or 1,2,3-Trifluoro-5-[(trans,trans)-4'-ethyl[1,1'-bicyclohexyl]-4-yl]benzene, or 1,2,3-Trifluoro-5-[(trans,trans)-4'-propyl[1,1'-bicyclohexyl]-4-yl]benzene, or Benzene, 1,2,3-trifluoro-5-[(trans,trans)-4-pentyl[1,1'-bicyclohexyl]-4-yl], or trans-1-Ethoxy-4-(4-propylcyclohexyl)benzene, or [trans(trans)]-1,2-Difluoro-4-(4-propyl1'-bicyclohexyl]-4-yl)benzene, or Benzene,1,2-difluoro-4-[(trans,trans)-4'-pentyl[1,1'-bicyclohexyl]-4-yl], or 2,3',4'5'-Tetrafluoro-4-[(trans,trans)-4'-propyl[bicyclohexyl]-4-yl]-1,1'-biphenyl, or 5-(Difluoro[(trans,trans)-4'-propyl[1,1'-bicyclohexyl]-4-yl]methoxy]-1,2,3-trifluorobenzene, or [1,1-Bicyclohexyl]-4-carboxylic acid,4'-propyl-, 3,4,5-trifluorophenyl ester, (trans,trans)-, or [1,1'-Bicyclohexyl]-4-carboxylic acid, 4'-pentyl-, 3,4,5-trifluorophenyl ester.(trans,trans)-, or a mixture thereof.

[0044] More specifically, the liquid crystal may be a fluorine-based liquid crystal. The fluorine-based liquid crystal is a liquid crystal material having fluorine atoms within its molecular structure, and has low viscosity and dielectric constant, resulting in minimal introduction of ionic impurities. When a fluorine-based liquid crystal is used as a liquid crystal material, the refractive index anisotropy is relatively low, which can induce low haze. Performance degradation, such as a decrease in voltage retention rate due to impurities, is reduced, and the surface anchoring energy can be lowered when in contact with the capsule shell surface during encapsulation.

[0045] The proportion of liquid crystal contained in the liquid crystal nanocapsule of the above embodiment is not significantly limited, but, for example, may be contained in an amount of 10 mass% to 20 mass%. Within the above range, sufficient liquid crystal performance can be obtained, and at the same time, the thickness of the polymer shell becomes sufficient, thereby improving the durability of the liquid crystal nanocapsule.

[0046] The method for measuring the ratio of liquid crystal contained in the above liquid crystal nanocapsule is not limited, and various conventionally known methods can be applied without limitation. However, for example, after freeze-drying 5 mL of capsule liquid and measuring the mass to calculate the solid content per unit volume, 1 mg of the freeze-dried capsule liquid is introduced into a TGA2 instrument of METTLER TOLEDO and heated from 50°C to 700°C at a heating rate of 10°C / minute, and while confirming the mass decrease according to temperature, the liquid crystal ratio (mass%) can be obtained through the mass decrease ratio in the range of 200°C to 300°C.

[0047] Meanwhile, the core may further include an emulsifier and a siloxane-based additive. The emulsifier is a surfactant used for the formation of liquid crystal droplets, and when applied together with the siloxane-based additive, it lowers the interfacial tension of the liquid crystal within the capsule, thereby significantly lowering the surface anchoring energy of the liquid crystal.

[0048] In particular, with respect to 100 parts by weight of the emulsifier, the content of the siloxane-based additive may be 5 to 50 parts by weight, or 5 to 20 parts by weight, or 9 to 19 parts by weight, or 9.2 to 18.4 parts by weight. If the content of the siloxane-based additive is excessively reduced with respect to 100 parts by weight of the emulsifier, the effect of lowering the surface tension of the liquid crystal by the siloxane-based additive is not sufficiently realized, and there is a limitation in that the surface anchoring energy of the liquid crystal inside the capsule cannot be sufficiently lowered. In addition, if the content of the siloxane-based additive is excessively increased with respect to 100 parts by weight of the emulsifier, a problem may occur in which the liquid crystal state (mesophase state) changes into an isotropic liquid phase.

[0049] The above emulsifier is a nonionic surfactant used for forming liquid crystal droplets, and can be used without limitation as long as it is a surfactant that does not ionize in an aqueous solution. Any nonionic surfactant that is well known in the art and is known can be used without limitation. In one embodiment, the nonionic surfactant may be an amphiphilic block copolymer, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitol fatty acid ester, or glycerin fatty acid ester, but is not limited thereto. For example, nonionic surfactants include cetomacrogol 1000, cetostearyl alcohol, cetyl alcohol, cocamide DEA (cocamide diethanolamine; cocamide DEA), cocamide MEA (cocamide monoethanolamine; cocamide MEA), decyl glucoside, EGEPAL CA-630, isoceteth-20, lauryl glucoside, monolaurin, octylphenoxypolyethoxyethanol, nonoxynol-9, NP-40, octaethylene glycol monododecyl ether, N-octyl beta-D-thioglucopyranoside, octyl glucoside, oleyl alcohol, pentaethylene glycol monododecyl ether, poloxamer, polyglycerol polyricinoleate, polysorbate, sorbitan monostearate, sorbitan tristearate, stearyl alcohol, and Triton. Includes X-100, Tween 80, poly(ethylene oxide-b-propylene oxide), polyoxyethylene-b-polydimethylsiloxane, etc.

[0050] However, the above emulsifier may contain less than 0.001 mol% of ethylene oxide repeating units based on 100 mol% of the emulsifier. That is, the above emulsifier may not contain ethylene oxide repeating units or may contain them in extremely small amounts. If the content of ethylene oxide repeating units based on 100 mol% of the emulsifier increases to 0.001 mol% or more, as the van der Waals interaction between the electrophilic fluorine element in the fluorine-based liquid crystal and the ethylene oxide repeating unit increases, the Onset temperature change value according to Equation 1 and the Peak temperature change value according to Equation 2 increase, making it difficult to sufficiently lower the surface anchoring energy of the liquid crystal within the capsule.

[0051] More specifically, the emulsifier may include an acetylenic diol-based compound. The acetylenic diol-based compound may include an acetylenic diol compound or a derivative thereof.

[0052] The above acetylenic diol-based compound may have a Hydrophile Lipophile Balance (HLB) value of 2 to 4, or 2 to 3. Generally, in order to make a stable oil-in-water emulsion using a conventional emulsifier, it is necessary for the emulsifier to adsorb to the aqueous / oil phase interface to form a liquid crystal, and to this end, the Hydrophile Lipophile Balance (HLB) value of the emulsifier to be used must be carefully adjusted according to the polarity of the oil phase.

[0053] Specifically, the above HLB can be calculated using the following mathematical formula 3.

[0054] [Mathematical Formula 3]

[0055] HLB = 20*(M H / M)

[0056] In the above mathematical formula 3, M H is the molecular weight (or molar mass) of the hydrophilic group, and M is the molecular weight (or molar mass) of the emulsifier.

[0057] As a more specific example, the acetylenic diol-based compound may be 2,4,7,9-tetramethyl-5-decyn-4,7-diol. Since the acetylenic diol-based compound does not have ethylene oxide repeating units in the structure of the emulsifier, it can relatively reduce van der Waals interaction with fluorine-based liquid crystals compared to emulsifiers having ethylene oxide repeating units. For this reason, the surface anchoring energy of the liquid crystal in the capsule can be sufficiently lowered as the change in Onset temperature according to Equation 1 and the change in Peak temperature according to Equation 2 are reduced.

[0058] In addition, the emulsifier may include a silicone polyether copolymer containing propylene oxide. The silicone polyether copolymer containing propylene oxide may have a weight-average molecular weight of 1000 g / mol or more, or 1000 g / mol to 50000 g / mol, or 1000 g / mol to 10000 g / mol, or 1000 g / mol to 5000 g / mol, or 2000 g / mol to 3000 g / mol, or 2800 g / mol to 3000 g / mol.

[0059] The above silicone polyether copolymer containing propylene oxide may have a Hydrophile Lipophile Balance (HLB) value of 0 to 1. Generally, in order to make a stable oil-in-water emulsion using a conventional emulsifier, it is necessary for the emulsifier to adsorb to the aqueous / oil phase interface to form a liquid crystal, and to this end, the Hydrophile Lipophile Balance (HLB) value of the emulsifier to be used must be carefully adjusted according to the polarity of the oil phase.

[0060] Specifically, the above HLB can be calculated using the following mathematical formula 3.

[0061] [Mathematical Formula 3]

[0062] HLB = 20*(M H / M)

[0063] In the above mathematical formula 3, M H is the molecular weight (or molar mass) of the hydrophilic group, and M is the molecular weight (or molar mass) of the emulsifier.

[0064] As a more specific example, the silicon polyether copolymer containing propylene oxide may be a dimethicone graft copolymer of the following formula a (weight-average molecular weight 3,000; HLB: 0; CAS number 68550-66-4) or a dimethicone linear copolymer of the following formula b (weight-average molecular weight 2,800; HLB: 0; CAS number 161755-53-9).

[0065] [Chemical formula a]

[0066]

[0067] In the above chemical formula a, x is an integer from 1 to 100, y is an integer from 1 to 100, and n is an integer from 0 to 20.

[0068] [Chemical formula b]

[0069]

[0070] In the above chemical formula b, p is an integer from 0 to 20, q is an integer from 1 to 100, and r is an integer from 0 to 20.

[0071] The above-mentioned silicon polyether copolymer containing propylene oxide can sufficiently lower the surface anchoring energy of the liquid crystal within the capsule as the Onset temperature change value according to Equation 1 and the Peak temperature change value according to Equation 2 are lowered, because the above-mentioned silicon polyether copolymer increases the surface energy contacted by the liquid crystal and induces vertical orientation of the liquid crystal.

[0072] The above siloxane-based additive is an additive capable of lowering the interfacial tension of the liquid crystal. Accordingly, the liquid crystal nanocapsule containing the above siloxane-based additive and the liquid crystal together in the core can sufficiently lower the surface anchoring energy of the liquid crystal within the capsule.

[0073] The above siloxane-based additive may have a molar mass of 500 g / mol or less, or 100 g / mol to 500 g / mol. The above siloxane-based additive may include a trisiloxane-based compound. The above trisiloxane-based compound may include a trisiloxane compound or a derivative thereof. As a specific example, the above siloxane-based additive may be octamethyltrisiloxane or hexamethylcyclotrisiloxane.

[0074] Additionally, the core may further include an anisotropic dye. The anisotropic dye is not particularly limited as long as it is a dopable anisotropic dye, and specifically may be S-428, M-483, M412 (Mitsui FineChemical), etc.

[0075] Meanwhile, the liquid crystal nanocapsule of the above embodiment may include a polymer shell formed on the core surface. The shell may be a single-layer shell made of a single polymer material, or a double-layer shell or a multi-layer shell made of different polymer materials to achieve improved mechanical properties and particle uniformity. Accordingly, the uniformity of the liquid crystal particles can be improved, and the problem of contamination by dye can be addressed.

[0076] The material forming the shell has the same refractive index as the matrix polymer in which the liquid crystal composite is dispersed, and while specific examples are not particularly limited, it may be selected from polyvinyl alcohol, polyurea, polyurethane, polyamide including nylon, polyacetal, and polyester.

[0077] However, to give a specific example, the polymer shell formed on the surface of the core may be made of polyvinyl alcohol (PVA) resin crosslinked with glyoxal. There are no particular restrictions on the type of PVA, and various types of PVA with different molecular weights or saponification rates may be appropriately selected depending on the purpose. Glyoxal is used as the crosslinking agent for crosslinking the PVA.

[0078] Meanwhile, the liquid crystal nanocapsule of the above embodiment may have an Onset temperature change value according to the following Equation 1 and a Peak temperature change value according to Equation 2 such that the sum of these values ​​is 37.5 ℃ or less, or 37 ℃ or less, or 36 ℃ or less, or 35 ℃ or less, or 1 ℃ or more, or 1 ℃ to 37.5 ℃, or 1 ℃ to 37 ℃, or 1 ℃ to 36 ℃, or 1 ℃ to 35 ℃.

[0079] [Mathematical Formula 1]

[0080] Onset temperature change value = (Minimum temperature at which endothermic or exothermic reactions occur during DSC measurement of the above liquid crystal nanocapsule) - (Minimum temperature at which endothermic or exothermic reactions occur during DSC measurement of the above liquid crystal)

[0081] [Mathematical Formula 2]

[0082] Peak temperature change value = (Temperature at the peak where endothermic or exothermic activity is maximum during DSC measurement of the liquid crystal nanocapsule) - (Temperature at the peak where endothermic or exothermic activity is maximum during DSC measurement of the liquid crystal).

[0083] In the liquid crystal nanocapsule of the above embodiment, as the Onset temperature change value according to Equation 1 and the Peak temperature change value according to Equation 2 decrease together, the sum of the Onset temperature change value according to Equation 1 and the Peak temperature change value according to Equation 2 also tends to decrease.

[0084] Specifically, if the sum of the Onset temperature change value according to Equation 1 and the Peak temperature change value according to Equation 2 decreases, it implies that the surface anchoring energy of the liquid crystal within the capsule is relatively low, and consequently, the transmittance variability can increase even at low voltages. Specifically, if the sum of the Onset temperature change value according to Equation 1 and the Peak temperature change value according to Equation 2 decreases, it is possible to manufacture a liquid crystal nanocapsule that enables low-voltage driving at a lower threshold voltage, while having a high contrast ratio and excellent transmittance variability characteristics.

[0085] On the other hand, if the sum of the Onset temperature change value according to the above mathematical formula 1 and the Peak temperature change value according to the above mathematical formula 2 increases excessively to more than 37.5 ℃, the surface anchoring energy of the liquid crystal inside the capsule increases, and thus a higher voltage must be applied to change the orientation of the liquid crystal, and more voltage is required to move the liquid crystal.

[0086] Examples of DSC measurement methods in the above mathematical formulas 1 and 2 are not significantly limited, and conventionally known DSC measurement equipment, conditions, and methods can be applied without limitation. However, for example, using the DSC3 equipment from METTLER TOLEDO, the minimum temperature at which endothermic and exothermic reactions occur can be measured while increasing the temperature from 25°C to 200°C at a heating rate of 5°C / minute.

[0087] More specifically, the liquid crystal nanocapsule of the above embodiment may have an Onset temperature change value according to the above mathematical formula 1 of 18.5 ℃ or less, or 18 ℃ or less, or 17 ℃ or less, or 16 ℃ or less, or 15 ℃ or less, or 14 ℃ or less, or 1 ℃ or more, or 1 ℃ to 18.5 ℃, or 1 ℃ to 18 ℃, or 1 ℃ to 17 ℃, or 1 ℃ to 16 ℃, or 1 ℃ to 15 ℃, or 1 ℃ to 14 ℃.

[0088] In addition, the liquid crystal nanocapsule of the above embodiment may have a peak temperature change value according to the following mathematical formula 2 that is 21.5 ℃ or less, or 21 ℃ or less, or 20 ℃ or less, or 19 ℃ or less, or 1 ℃ or more, or 1 ℃ to 21.5 ℃, or 1 ℃ to 21 ℃, or 1 ℃ to 20 ℃, or 1 ℃ to 19 ℃.

[0089] The average diameter of the liquid crystal nanocapsules may be 200 nm to 300 nm. If the average diameter of the liquid crystal nanocapsules decreases excessively, there is a problem that the driving voltage increases and power consumption increases. In addition, if the average diameter of the liquid crystal nanocapsules increases excessively, there is a problem that visible light is scattered and haze increases.

[0090] The liquid crystal nanocapsules may be a group of individual particles having an average diameter of 200 nm to 300 nm, and the individual particles included in this group may have an average diameter of 200 nm to 300 nm. More specifically, 95% or 99% of the individual particles included in the group may have a diameter of 200 nm to 300 nm.

[0091] The present application also provides uses for the liquid crystal capsule. The liquid crystal capsule of the present application can be used in various optical modulation devices applicable to liquid crystals. Accordingly, the present application provides an optical modulation device having a substrate; and a liquid crystal layer formed on one surface of the substrate and comprising the liquid crystal capsule. The manufacturing method and type of the optical modulation device are well known in the art and can be manufactured using known manufacturing methods without limitation. The optical modulation device includes, but is not limited to, a smart window, an isotropic film, a polarization control film, or a flexible LCD, etc.

[0092] The method for manufacturing the above liquid crystal nanocapsule is not significantly limited, and various conventionally known methods for manufacturing liquid crystal nanocapsules may be applied without limitation. However, for example, the method comprises: (1) a process of preparing a mixed solution formed by mixing a mixed material containing a liquid crystal, an emulsifier, a siloxane-based additive, and polyvinyl alcohol (PVA) in a solvent; (2) a process of forming a droplet from the mixed solution; (3) a process of placing polyvinyl alcohol (PVA) around the droplet; and (4) a process of manufacturing a liquid crystal nanocapsule containing the liquid crystal within the polymer shell by crosslinking the polyvinyl alcohol (PVA) using a crosslinking agent to form a polymer shell surrounding the liquid crystal.

[0093] In the process of preparing a mixed solution by mixing the above (1) liquid crystal, emulsifier, siloxane-based additive and polyvinyl alcohol (PVA) with a solvent, the solvent is not particularly limited and can be appropriately selected according to the purpose, and examples include pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, distilled water, or ultrapure water.

[0094] In the process of forming droplets from the above (2) mixed solution, the droplets are dispersed in a dispersion medium, and more specifically, the droplets are dispersed in a dispersion medium in a state where an emulsifier covers the liquid crystal.

[0095] One method for preparing the above droplets is to produce droplets using a dispersion-type emulsification device.

[0096] As for the dispersion-type emulsification device, there are no particular restrictions as long as droplets of the desired particle size are obtained, and it can be appropriately selected according to the purpose; for example, a homomixer, which is a device for mixing liquids, or a homogenizer, which is a device for finely and uniformly grinding particles, can be used. Furthermore, there are no particular restrictions on the dispersion method; for example, any dispersion method such as stirring, ultrasound, or high pressure can be used.

[0097] In the present invention, as a dispersion emulsification device, various dispersion emulsification devices such as a high-speed homogenizer, an ultrasonic homogenizer, a high-pressure homogenizer, and a homo mixer may be used.

[0098] In addition, a more preferred embodiment of the droplet preparation process may include a droplet preparation process comprising a first preparation process for preparing droplets using a first dispersion emulsification device and a second preparation process for preparing droplets smaller than the particle size obtained in the first preparation process using a second dispersion emulsification device.

[0099] As for the first and second dispersion emulsification devices, there are no particular restrictions as long as droplets of the desired particle size are obtained, and various dispersion emulsification devices such as the high-speed homogenizer, ultrasonic homogenizer, high-pressure homogenizer, and homo mixer described above can be appropriately combined and used.

[0100] In the process of placing polyvinyl alcohol (PVA) around the above (3) droplets, coacervation in which the PVA gathers around the liquid crystal composition can proceed under a droplet dispersion at a predetermined temperature. For example, it is preferable to set the solution temperature of the droplet dispersion in the coacervation process to 40°C or higher.

[0101] In the process of manufacturing a liquid crystal nanocapsule containing a liquid crystal within a polymer shell by crosslinking polyvinyl alcohol (PVA) using the above (4) crosslinking agent to form a polymer shell surrounding the liquid crystal, the crosslinking reaction is preferably carried out under acidic conditions. As for the acidic conditions, it is preferable that the pH be in the range of 1 to 5, and more preferable that the pH be about 3.

[0102]

[0103] 2. Capsule solution

[0104] Meanwhile, according to another embodiment of the invention, a capsule solution comprising a liquid crystal nanocapsule and a solvent of the first embodiment may be provided. The details regarding the liquid crystal nanocapsule include the details described above with respect to the first embodiment.

[0105] The above solvent is not particularly limited and can be appropriately selected according to the purpose, and examples include pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, distilled water, or ultrapure water.

[0106] The above capsule solution contains liquid crystal nanocapsules dispersed in a solvent. That is, the above capsule solution may be a liquid crystal nanocapsule dispersion. The above capsule solution is used as a coating solution for forming a liquid crystal layer. For example, a liquid crystal layer is formed by depositing the capsule solution onto a support substrate.

[0107]

[0108] 3. Optical film

[0109] Meanwhile, according to another embodiment of the invention, an optical film comprising the liquid crystal nanocapsules of the first embodiment may be provided. The details regarding the liquid crystal nanocapsules include the details described above with respect to the first embodiment.

[0110] The optical film may include a matrix and liquid crystal capsules of the above embodiment dispersed within the matrix. Although the content of the matrix is ​​not particularly limited, for example, the matrix may be a transparent material. Although specific examples of the matrix are not particularly limited, for example, it may be selected from polyvinyl alcohol, polyurea, polyurethane, polyamide including nylon, polyacetal, and polyester.

[0111] For a more specific example, the optical film may be formed by applying the capsule liquid of the other embodiment onto a supporting substrate to form a film.

[0112] Specific details regarding the above optical film can be applied without limitation to various conventionally known optical films. For example, regarding the structure, composition, manufacturing method, physical properties, and applications of the optical film, various details widely known in the conventional film field can be applied without limitation.

[0113] However, for example, the above optical film can be used in a transmittance variable film.

[0114]

[0115] 4. Optical device

[0116] Meanwhile, according to another embodiment of the invention, an optical device comprising an optical film of the other embodiment may be provided. The details regarding the optical film include the details described above regarding the other embodiment.

[0117] The content regarding the above optical device can be applied without limitation to various conventionally known optical devices. For example, regarding the specific structure, size, manufacturing method, physical properties, and applications of the optical device, various contents widely known in the conventional display field can be applied without limitation.

[0118] However, for example, the optical device may be a light modulation device including an optical film of the other embodiment. Specific examples of the light modulation device are not particularly limited, but may include, for example, a smart window, an isotropic film, a polarization control film, or a liquid crystal display, an organic electroluminescent display, etc.

[0119] More specifically, examples of the above optical device include a liquid crystal display element having a set of opposing substrates, an electrode formed on one or both sides of the opposing surface of each of the set of substrates, a liquid crystal layer formed by applying a liquid crystal nanocapsule solution of the present invention disposed between the substrates, and a means for applying an electric field to the liquid crystal nanocapsules of the present invention in the liquid crystal layer through the electrode.

[0120] The above optical device may have a threshold voltage of 64 V or less, or 63 V or less, or 61 V or less, or 1 V or more, or 1 V to 64 V, or 1 V to 63 V, or 1 V to 61 V, or 60 V to 63 V, or 60 V to 61 V. The above threshold voltage refers to the voltage at 10% transmittance of the maximum transmittance, and as the optical device has a threshold voltage within the range described above, the optical device may be able to operate at a lower voltage. The method for measuring the above threshold voltage is not limited, and various methods widely known in the field of conventional liquid crystal-containing optical devices may be applied without limitation. However, for example, it may be measured using a haze meter (Nippon Denshoku, NDH7000) while applying voltage through a function generator.

[0121] In addition, the optical device may have a contrast ratio of 10 or more, or 11 or more, or 20 or less, or 10 to 20, or 11 to 20, or 11.1 to 16.5. The contrast ratio refers to the ratio between the transmittance at a voltage of 100 V and the transmittance at a voltage of 0 V. As the optical device has a contrast ratio within the range described above, the optical device can achieve excellent transmittance variability even at lower voltages. The method for measuring the contrast ratio is not limited, and various methods widely known in the field of conventional liquid crystal-containing optical devices can be applied without limitation. However, for example, it can be measured using a haze meter (Nippon Denshoku, NDH7000) while applying voltage through a function generator.

[0122]

[0123] 5. Variable transmittance device

[0124] Meanwhile, according to another embodiment of the invention, a transmittance variable device comprising an optical film of the other embodiment may be provided. Details regarding the optical film include details described above regarding the other embodiment.

[0125] The above description regarding the variable transmittance device may apply various conventionally known variable transmittance devices without limitation. For example, regarding the specific structure, size, manufacturing method, physical properties, and applications of the variable transmittance device, various contents widely known in the field of conventional liquid crystal capsules may be applied without limitation. However, as an example, the variable transmittance device may include a polarization layer and a variable transmittance layer, and the polarization layer or the variable transmittance layer may contain the dichroic dye of the above embodiment as a light modulating material.

[0126] The transmittance variable device of the present application can be applied to any device to which transmittance variation can be applied. For example, the transmittance variable device of the present application can be applied to a sunroof, automotive glass, goggles, sunglasses, or helmet, etc., to provide a transmittance variable device. As long as the transmittance variable device includes the transmittance variable device of the present application, other parts or structures, etc., are not particularly limited, and all contents known in the art may be appropriately applied.

[0127] According to the present invention, a liquid crystal nanocapsule capable of inducing a high transmittance variability even at a lower voltage by lowering the surface interaction energy of the liquid crystal enclosed inside the capsule, and a capsule liquid, an optical film, an optical device, and a transmittance variability device using the same may be provided.

[0128] The invention is described in more detail in the following examples. However, the following examples are merely illustrative of the invention, and the scope of the invention is not limited by the following examples.

[0129]

[0130] <Example: Preparation of Liquid Crystal Nanocapsules and Capsule Solution>

[0131] Example 1

[0132] 0.125 g of an emulsifier (2,4,7,9-tetramethyl-5-decyn-4,7-diol, HLB: 3) (0.25 wt% based on the total weight of the aqueous solution) was added to an aqueous solution mixed with 0.7 g of polyvinyl alcohol (PVA) and 49.3 g of water, and dissolved by stirring. Subsequently, 2.2 g of liquid crystal (1,2,3-Trifluoro-5-[(trans,trans)-4'-ethyl[1,1'-bicyclohexyl]-4-yl]benzene; manufactured by TCI), 0.11 g of an anisotropic dye (Sudan Black B), and 0.023 g of octamethyltrisiloxane (1 wt%) based on the total weight of the mixture of liquid crystal and anisotropic dye were added, and primary emulsification was performed for 1 hour at 18,000 rpm using an IKA homogenizer T25. Afterwards, secondary emulsification was performed 5 times at 10,000 psi using a microfluidizer to form droplets.

[0133] Afterwards, the solution was heated to 40°C under stirring and PVA was adsorbed onto the droplet surface for 18 hours.

[0134] Subsequently, 0.8 g of a 40% aqueous glyoxal solution was added as a crosslinking agent, and the pH of the solution was adjusted to 3, and the adsorbed PVA was crosslinked at 40 ℃ for 18 hours.

[0135] After concentrating the solution with a rotary evaporator for 1 hour, the supernatant was recovered by centrifuging at 5000 rpm for 30 minutes to remove unencapsulated liquid crystals, thereby obtaining a capsule solution containing liquid crystal nanocapsules.

[0136]

[0137] Example 2

[0138] Liquid crystal nanocapsules and capsule solution were prepared in the same manner as in Example 1, except that 0.25 g of Dimethicone graft copolymer of the following formula a (weight average molecular weight 3,000; HLB: 0; CAS number 68550-66-4) (0.5 wt% based on the total weight of the aqueous solution) was added instead of 0.125 g of 2,4,7,9-tetramethyl-5-decyn-4,7-diol (0.25 wt% based on the total weight of the aqueous solution) as the emulsifier.

[0139] [Chemical formula a]

[0140]

[0141] In the above chemical formula a, x is an integer from 1 to 100, y is an integer from 1 to 100, and n is an integer from 0 to 20.

[0142]

[0143] Example 3

[0144] Liquid crystal nanocapsules and capsule solution were prepared in the same manner as in Example 1, except that 0.25 g of Dimethicone linear copolymer of the following formula b (weight average molecular weight 2,800; HLB: 0; CAS number 161755-53-9) (0.5 wt% based on the total weight of the aqueous solution) was added as the emulsifier instead of 0.125 g of 2,4,7,9-tetramethyl-5-decyn-4,7-diol (0.25 wt% based on the total weight of the aqueous solution).

[0145] [Chemical formula b]

[0146]

[0147] In the above chemical formula b, p is an integer from 0 to 20, q is an integer from 1 to 100, and r is an integer from 0 to 20.

[0148]

[0149] <Comparative Example: Preparation of Liquid Crystal Nanocapsules and Capsule Solution>

[0150] Comparative Example 1

[0151] Liquid crystal nanocapsules and capsule solutions were prepared in the same manner as in Example 1, except that octamethyltrisiloxane was not used.

[0152]

[0153] Comparative Example 2

[0154] Liquid crystal nanocapsules and capsule solutions were prepared in the same manner as in Example 2 above, except that octamethyltrisiloxane was not used.

[0155]

[0156] Comparative Example 3

[0157] Liquid crystal nanocapsules and capsule solutions were prepared in the same manner as in Example 3 above, except that octamethyltrisiloxane was not used.

[0158]

[0159] Comparative Example 4

[0160] Liquid crystal nanocapsules and capsule solution were prepared in the same manner as in Example 1, except that 0.25 g of Ethoxylated tetramethyl decynediol (EO 1.3 mol; CAS number: 9014-85-1) (0.50 wt% based on the total weight of the aqueous solution) was added instead of 0.125 g of 2,4,7,9-tetramethyl-5-decyn-4,7-diol (0.25 wt% based on the total weight of the aqueous solution) as the emulsifier.

[0161]

[0162] <Experimental Example>

[0163] For the liquid crystal nanocapsules or capsule liquids obtained in the above examples and comparative examples, physical properties were measured by the following method, and the results are shown in Table 1.

[0164]

[0165] 1. Physical properties of liquid crystal nanocapsules

[0166] (1) Average diameter of capsule in capsule solution (nm)

[0167] Using a Malvern Zetasizer zs, the average diameter (nm) of 4 mL of capsule solution diluted (water and capsule solution mixed in a 4:1 weight ratio) was measured under conditions of RI: 1.5 and 25 ℃.

[0168] (2) Liquid crystal ratio (mass%) in capsule solution

[0169] After freeze-drying 5 mL of capsule liquid, the mass was measured to calculate the solid content per unit volume. 1 mg of freeze-dried capsule liquid was placed into a TGA2 instrument from METTLER TOLEDO and heated from 50 ℃ to 700 ℃ at a heating rate of 10 ℃ / min, after which the mass decrease according to temperature was checked. The liquid crystal ratio (mass%) in the capsule liquid was determined through the mass decrease ratio in the range of 200 ℃ to 300 ℃.

[0170]

[0171] 2. Physical properties of liquid crystal nanocapsule films

[0172] (1) Thickness (㎛)

[0173] A liquid crystal nanocapsule film was prepared by coating 1 mL of capsule solution onto the ITO of a PET-ITO film using a 200 μm film applicator and drying at 70 °C for 2 hours. The thickness of the liquid crystal nanocapsule film was measured using an Alpha step (KLA TENCOR).

[0174] (2) T off (%), Haze off (%), critical voltage (V), CR

[0175] After laminating the ITO surface of a PET-ITO film (GMP EXCELAM-SMART 655) onto the upper surface of the liquid crystal nanocapsule film, an electrode tape was attached to the ITO surface.

[0176] T, which is the transmittance of a liquid crystal nanocapsule film with no applied voltage (transmittance at an applied voltage of 0V). off , and Haze (transmittance at an applied voltage of 0V) of a liquid crystal nanocapsule film to which no voltage is applied off It was measured using a haze meter (Nippon Denshoku, NDH7000).

[0177] Then, while applying voltage through a function generator, the threshold voltage, which is the voltage at 10% of the maximum transmittance, and the contrast ratio (CR), which is the ratio between the transmittance at 100 V and the transmittance at 0 V, were measured using a haze meter (Nippon Denshoku, NDH7000).

[0178]

[0179] 3. Tni Analysis of Liquid Crystals

[0180] A pan was placed inside the DSC3 instrument of METTLER TOLEDO, and 0.5 mL of capsule solution was added. The temperature was increased from 25°C to 200°C at a heating rate of 5°C / minute, and the onset temperature, which is the minimum temperature at which endothermic and exothermic reactions begin to be observed, and the peak temperature, at which endothermic and exothermic reactions occur most actively, were measured.

[0181] In addition, the onset temperature (121 ℃) of the free liquid crystal not enclosed in the capsule was measured, and the change value of the onset temperature (△Onset) was calculated by the following mathematical formula 1.

[0182] [Mathematical Formula 1]

[0183] Onset temperature change value = (Minimum temperature at which endothermic or exothermic reactions occur during DSC measurement of the above liquid crystal nanocapsule) - (Minimum temperature at which endothermic or exothermic reactions occur during DSC measurement of the above liquid crystal)

[0184] In addition, the peak temperature (125 ℃) of the free liquid crystal not enclosed in the capsule was measured, and the peak temperature change value (△Peak) was calculated by the following mathematical formula 2.

[0185] [Mathematical Formula 2]

[0186] Peak temperature change value = (Temperature at the peak where endothermic or exothermic activity is maximum during DSC measurement of the above liquid crystal nanocapsule) - (Temperature at the peak where endothermic or exothermic activity is maximum during DSC measurement of the above liquid crystal)

[0187]

[0188] Measurement Results of Experimental Examples of Examples and Comparative Examples Classification Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Emulsifier 2,4,7,9-tetramethyl-5-decyn-4,7-diol Dimethicone graft copolymer Dimethicone linear copolymer 2,4,7,9-tetramethyl-5-decyn-4,7-diol Dimethicone graft copolymer Dimethicone linear copolymer Ethoxylated tetramethyl decynediol Additive Octamethyltrisiloxane Octamethyltrisiloxane Octamethyltrisiloxane---Octamethyltrisiloxane Liquid Crystal Nanocapsule Average Diameter (nm) 268.0 291.5 281.2 284.4 304.8 290.1 ​​148.7 Liquid Crystal Ratio (Mass%) 17.1 14.0 14.8 17.3 11.4 15.0 16.7 Liquid Crystal Nanocapsule Film thickness (㎛) 14.8 16.2 15.6 15.3 16.5 15.3 14.4T off (%) 1.8 1.9 1.9 0.9 1.0 1.6 0.5 Haze off(%) 33.6 35.6 31.1 37.4 34.7 34.7 11.3 Critical Voltage (V) 60 60 63 65 80 75 80 CR @ 100V 16.5 12.1 11.1 16.9 10.6 9.8 10.0 Tni Analysis of Liquid Crystal Onset Temperature (°C) 135 137 139 140 140 140 140 Peak Temperature (°C) 146 146 145 147 144 149 150 Absorption / Exothermic Amount (J / g) 110 7.5 99 3.4 120 1.0 97 8.3 94 1.3 124 3.2 15 57.1 △Onset 14 16 18 19 19 19 19 △Peak 21 21 19 22 19 24 25 (△Onset + △Peak)35373741384344

[0189] As shown in Table 1 above, the liquid crystal nanocapsule of the example was measured to have a (△Onset + △Peak) value of 35°C to 37°C, which is lower than that of the comparative example. Accordingly, the liquid crystal nanocapsule film of the example was measured to have a threshold voltage of 60°V to 63°V, which is lower than that of the comparative example, confirming that it can be operated even at lower voltages. In addition, the liquid crystal nanocapsule film of the example was measured to have a contrast ratio of 11.1 to 16.5, which is equivalent to or higher than that of the comparative example, confirming that it can achieve excellent transmittance variability even at lower voltages.

Claims

1. A core containing a liquid crystal; and A polymer shell formed on the surface of the core; comprising A liquid crystal nanocapsule in which the sum of the Onset temperature change value according to Equation 1 below and the Peak temperature change value according to Equation 2 below is 37.5 ℃ or less: [Mathematical Formula 1] Onset temperature change value = (Minimum temperature at which endothermic or exothermic reactions occur during DSC measurement of the above liquid crystal nanocapsule) - (Minimum temperature at which endothermic or exothermic reactions occur during DSC measurement of the above liquid crystal) [Mathematical Formula 2] Peak temperature change value = (Temperature at the peak where endothermic or exothermic activity is maximum during DSC measurement of the liquid crystal nanocapsule) - (Temperature at the peak where endothermic or exothermic activity is maximum during DSC measurement of the liquid crystal).

2. In Paragraph 1, A liquid crystal nanocapsule having an onset temperature change value of 18.5 ℃ or less according to the above mathematical formula 1.

3. In Paragraph 1, A liquid crystal nanocapsule having a peak temperature change value of 21.5 ℃ or less according to the following mathematical formula 2.

4. In Paragraph 1, The above core is a liquid crystal nanocapsule further comprising an emulsifier and a siloxane-based additive.

5. In Paragraph 4, The above emulsifier is a liquid crystal nanocapsule having an ethylene oxide repeating unit content of less than 0.001 mol% based on 100 mol% of the emulsifier.

6. In Paragraph 4, The above emulsifier comprises a liquid crystal nanocapsule containing an acetylenic diol-based compound or a silicon polyether copolymer containing propylene oxide.

7. In Paragraph 4, The above siloxane-based additive is a liquid crystal nanocapsule having a molar mass of 500 g / mol or less.

8. In Paragraph 4, The above siloxane-based additive is a liquid crystal nanocapsule containing a trisiloxane-based compound.

9. In Paragraph 4, Liquid crystal nanocapsules in which the above siloxane-based additive is octamethyltrisiloxane or hexamethylcyclotrisiloxane.

10. In Paragraph 4, A liquid crystal nanocapsule having a siloxane-based additive content of 5 to 50 parts by weight per 100 parts by weight of the above emulsifier.

11. In Paragraph 1, The above liquid crystal is a liquid crystal nanocapsule, which is a fluorine-based liquid crystal.

12. In Paragraph 1, A liquid crystal nanocapsule having an average diameter of 200 nm to 300 nm.

13. A capsule solution comprising the liquid crystal nanocapsule of claim 1 and a solvent.

14. An optical film comprising the liquid crystal nanocapsule of claim 1.

15. An optical device comprising the optical film of claim 14.

16. A transmittance variable device comprising the optical film of claim 14.

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