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

Abstract

The present invention relates to a liquid crystal capsule, and a capsule solution, an optical film, an optical device, and a transmittance-variable device using same, the liquid crystal capsule comprising: a core containing liquid crystals and an emulsifier; and a polymer shell formed on the surface of the core, wherein the emulsifier is a mixture of an acetylenic diol compound and an alkylene glycol, and the alkylene glycol content is 4 wt% or more relative to the liquid crystal.

Description

Liquid crystal capsule, 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. 10-2025-0051087 filed April 18, 2025, 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 capsule that can achieve excellent transmittance / haze variability even at lower voltages by lowering the surface interaction energy of the liquid crystal enclosed inside the capsule and prevents loss of liquid crystal even during long-term storage, as well as 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, and this technology is applicable not only to buildings but also to the mobility sector. Through conventional polymer dispersed liquid crystal (PDLC) technology, liquid crystal domains of several micrometers in size could be manufactured by mixing liquid crystals with monomers capable of photo or thermal polymerization and utilizing the phase separation between the polymer and liquid crystal that occurs during polymerization. PDLC films can implement light-blocking or transmission modes by causing the liquid crystals within the micrometer domains to have a mismatch or match in refractive index with the polymer matrix depending on the on / off switching of voltage. 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 capsule that lowers the surface interaction energy of the liquid crystal enclosed inside the capsule, thereby enabling excellent transmittance / haze variability even at lower voltages, and possesses excellent durability without loss of liquid crystal during long-term storage.

[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 capsule.

[0012] To solve the above problem, the present specification provides a liquid crystal capsule comprising: a core containing a liquid crystal and an emulsifier; and a polymer shell formed on the surface of the core, wherein the emulsifier is a mixture of an acetylenic diol-based compound and an alkylene glycol, and the content of the alkylene glycol is 4 weight% or more relative to the liquid crystal.

[0013] In addition to the above, a capsule solution comprising the liquid crystal capsule and the solvent is provided.

[0014] In addition to the above, an optical film comprising the liquid crystal capsule is provided.

[0015] The present specification also provides an optical device comprising the optical film.

[0016] The present specification also provides a transmittance variable device comprising the optical film.

[0017] A liquid crystal capsule according to a specific embodiment of the invention, and a capsule liquid, an optical film, an optical device, and a transmittance variable device using the same, will be described in more detail below.

[0018]

[0019] 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.

[0020] The singular forms used in this specification include plural forms unless the phrases clearly indicate otherwise.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] In this specification, the weight-average molecular weight refers to the weight-average molecular weight in polystyrene equivalent measured by the GPC method. In the process of measuring the weight-average molecular weight in polystyrene equivalent 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.

[0025] The present invention will be described in more detail below.

[0026]

[0027] 1. Liquid crystal capsule

[0028] According to one embodiment of the invention, a liquid crystal capsule may be provided comprising: a core containing a liquid crystal and an emulsifier; and a polymer shell formed on the surface of the core, wherein the emulsifier is a mixture of an acetylenic diol-based compound and an alkylene glycol, and the content of the alkylene glycol is 4 weight% or more relative to the liquid crystal.

[0029] The inventors confirmed through experiments that, as in the liquid crystal capsule of the above embodiment, a mixture of an acetylenic diol-based compound and an alkylene glycol is used as an emulsifier, and the content of the alkylene glycol satisfies 4% by weight or more relative to the liquid crystal, thereby lowering the surface interaction energy of the liquid crystal enclosed inside the capsule, so that a high transmittance / haze variability can be induced even at lower voltages, and the durability of the liquid crystal capsule is improved by facilitating the formation of a polymer shell by crosslinking on the core surface.

[0030] Specifically, the liquid crystal capsule of the above embodiment may include a core containing liquid crystal. The liquid crystal capsule 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.

[0031] The above liquid crystals are not particularly limited, but examples include nematic liquid crystals, smectic liquid crystals, cholesteric liquid crystals, chiral nematic liquid crystals, etc.

[0032] The liquid crystal may contain cyano groups (-CN). As the liquid crystal contains cyano groups, the refractive index anisotropy may be increased, and depending on the on / off application of voltage, the liquid crystal within a domain of several μm size may have a mismatched or matched refractive index with the polymer matrix, thereby enabling light-blocking / transmitting modes.

[0033] Examples of liquid crystals containing cyano groups are not particularly limited, and various conventionally known cyanide-based liquid crystals can be applied without limitation. However, examples include [1,1'-Biphenyl]-4-carbonitrile,4-ethyl-; 4-n-Butyl-4'-cyanobiphenyl; [1,1'-Biphenyl]-4-carbonitrile,4'-pentyl-; Benzonitrile,4-(trans-4-propylcyclohexyl)-; [1,1'-Biphenyl]-4-carbonitrile,4-(trans-4-pentylcyclohexyl)-; Cyclohexanecarboxylic acid,4-ethyl-; 4'-cyano1,1'-biphenyl-4-yl ester, trans; or a mixture of two or more of these.

[0034] In addition, the liquid crystal may have a refractive index anisotropy (△n) of 0.2 or more, or 0.3 or less, or 0.21 or less, or 0.2 to 0.3, or 0.2 to 0.21. The refractive index anisotropy (△n) refers to the difference between the ordinary refractive index and the extraordinary refractive index. The method for measuring the refractive index anisotropy of the liquid crystal contained in the liquid crystal capsule is not limited, and various conventionally known methods can be applied without limitation.

[0035] Meanwhile, the core may further include an emulsifier. The emulsifier is a surfactant used in the formation of liquid crystal droplets, which lowers the interfacial tension of the liquid crystal within the capsule, thereby significantly lowering the surface anchoring energy of the liquid crystal.

[0036] The above emulsifier is a nonionic surfactant used for the formation of liquid crystal droplets, and can be used without limitation as long as it is a surfactant that does not ionize in an aqueous solution. The types of nonionic surfactants are well known in the art, and any known nonionic surfactant may be used without limitation.

[0037] More specifically, the emulsifier may be a mixture of an acetylenic diol-based compound and an alkylene glycol. As such, in the present invention, by using a mixture of an acetylenic diol-based compound and an alkylene glycol as an emulsifier, the density of the polymer shell is reduced by the alkylene glycol, and the critical voltage corresponding to the voltage at 10% of the maximum transmittance is reduced, thereby enabling excellent transmittance / haze variability even at lower voltages.

[0038] In particular, this effect can be maximized when the content of alkylene glycol is added at 4% by weight or more relative to the liquid crystal, or 4% to 6% by weight, or 5% to 6% by weight, or 5.2% to 5.6% by weight, or 5.3% to 5.5% by weight. The content of alkylene glycol refers to the relative ratio of alkylene glycol content when the content of the liquid crystal is 100% by weight.

[0039] Meanwhile, the above emulsifier is a mixture of an acetylenic diol-based compound and an alkylene glycol, specifically a mixed solution in which an acetylenic diol-based compound is dissolved in an alkylene glycol. That is, the liquid crystal capsule is not manufactured by separately adding the acetylenic diol-based compound and the alkylene glycol as emulsifiers, but rather by preparing a mixed solution in which an acetylenic diol-based compound is dissolved in an alkylene glycol, and then adding the mixed solution as an emulsifier.

[0040] When liquid crystal capsules are manufactured by separately adding acetylenic diol-based compounds and alkylene glycols as emulsifiers, there is a limitation in that the durability of the liquid crystal capsules is poor, such as the loss of liquid crystals during long-term storage of the liquid crystal capsules, as the polymer shell formation by crosslinking is inhibited.

[0041] The above acetylenic diol-based compound may include an acetylenic diol compound or a derivative thereof.

[0042] The above acetylenic diol-based compound may have a Hydrophile Lipophile Balance (HLB) value of 2 to 3.5, or 2.5 to 3.5. 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 droplets, 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.

[0043] Specifically, the above HLB can be calculated using the following mathematical formula 1.

[0044] [Mathematical Formula 1]

[0045] HLB = 20*(M H / M)

[0046] In the above mathematical formula 1, 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.

[0047] 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 lacks repeating ethylene oxide units in its molecular structure, it can reduce interactions with cyano groups within the liquid crystal. For this reason, it can sufficiently lower the surface anchoring energy of the liquid crystal within the capsule, thereby inducing a high transmittance / haze variability even at lower voltages. Additionally, the formation of a polymer shell by crosslinking on the core surface, which occurs due to hydrophobic adsorption as the temperature increases, becomes easier, thereby improving the durability of the liquid crystal capsule.

[0048] That is, the acetylenic diol-based compound may contain less than 0.001 mol% of ethylene oxide repeating units based on 100 mol% of the acetylenic diol-based compound. In other words, the acetylenic diol-based compound may not contain ethylene oxide repeating units or may contain them in extremely small amounts. If the ethylene oxide repeating unit content of the acetylenic diol-based compound increases to 0.001 mol% or more based on 100 mol% of the acetylenic diol-based compound, as the interaction between polar cyano groups within the liquid crystal and ethylene oxide repeating units increases, it becomes difficult to sufficiently lower the surface anchoring energy of the liquid crystal within the capsule, and it becomes difficult to sufficiently form a polymer shell by crosslinking on the core surface caused by hydrophobic adsorption.

[0049] The above alkylene glycol is a compound in which hydroxyl groups are bonded to both ends of an alkylene group, and examples of alkylene groups are not particularly limited. It may be a divalent functional group derived from an alkane, in a straight-chain or branched form, such as methylene, ethylene, propylene, isobutylene, sec-butylene, tert-butylene, pentylene, hexylene, etc. However, as a specific example, the above alkylene glycol may be ethylene glycol.

[0050] Additionally, the core may further include an anisotropic dye. The dye is not particularly limited as long as it is a dopable anisotropic dye, and specifically, an azo compound containing an intramolecular azo group may be used.

[0051] Meanwhile, the liquid crystal capsule of the above embodiment may include a polymer shell formed on the surface of the core. 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 improved at the same time.

[0052] The polymer shell may include a polymer crosslinked with a crosslinking agent. The specific examples of the polymer are not particularly limited, but may be, for example, one polymer selected from polyvinyl alcohol, polyurea, polyurethane, polyamide including nylon, polyacetal, and polyester.

[0053] The above-mentioned crosslinking agent is a material used for polymer crosslinking, and while specific examples are not particularly limited, glyoxal may be used as an example. The content of the above-mentioned crosslinking agent may be 10% to 30% by weight relative to the weight of the liquid crystal. That is, when the content of the liquid crystal is 100% by weight, the content ratio of the crosslinking agent may be 10% to 30% by weight.

[0054] As 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 can be appropriately selected depending on the purpose. Glyoxal is used as the crosslinking agent for crosslinking the PVA.

[0055] Meanwhile, when the liquid crystal capsule of the above embodiment is heated from 50°C to 700°C at a heating rate of 10°C / min, the final decomposition temperature measured by TGA may be 450°C to 550°C, or 480°C to 520°C, or 490°C to 510°C, or 495°C to 505°C. The final decomposition temperature measured by TGA refers to the temperature at the point where decomposition can be evaluated as complete because there is no further mass loss during TGA measurement. Since the final decomposition temperature of the above embodiment is high, the polymer shell is polymerized to the extent that liquid crystal loss occurs during long-term storage of the liquid crystal capsule, thereby improving the durability of the liquid crystal capsule.

[0056] The average diameter of the liquid crystal capsule may be 400 nm to 5 μm. If the average diameter of the liquid crystal capsule is reduced excessively, there is a problem that the driving voltage increases and power consumption increases. In addition, if the average diameter of the liquid crystal capsule is increased excessively, visible light is scattered and the haze increases.

[0057] The liquid crystal capsule may be a group of individual particles having an average diameter of 400 nm to 5 μm, and the individual particles included in this group may have an average diameter of 400 nm to 5 μm. More specifically, 95% or 99% of the individual particles included in the group may have a diameter of 400 nm to 5 μm.

[0058] 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.

[0059] The method for manufacturing the above liquid crystal capsule is not significantly limited, and various conventionally known methods for manufacturing liquid crystal capsules 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 liquid crystal, an emulsifier, 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 capsule containing liquid crystal within a polymer shell by crosslinking the polyvinyl alcohol (PVA) using a crosslinking agent to form a polymer shell surrounding the liquid crystal.

[0060] In the process of preparing a mixed solution by mixing the above (1) liquid crystal, emulsifier, 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. If necessary, additional additives may be added.

[0061] In the process of preparing a mixed solution by mixing the above (1) liquid crystal, emulsifier, and polyvinyl alcohol (PVA) with a solvent, examples of methods for mixing the liquid crystal, emulsifier, polyvinyl alcohol (PVA), and additive with the solvent are not significantly limited, and various methods used in conventionally known emulsification reactions can be applied without limitation. However, as an example, a method of mixing the liquid crystal with a solution containing the solvent, emulsifier, and polyvinyl alcohol can be used, but is not limited thereto.

[0062] 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.

[0063] One method for preparing the above droplets is to produce droplets using a dispersion-type emulsification device.

[0064] 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.

[0065] 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.

[0066] In addition, a more preferred embodiment of the droplet preparation process may be a droplet preparation process in which droplets are prepared using a dispersion-type emulsification device.

[0067] There are no particular restrictions on the dispersion emulsification device 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.

[0068] In the process of placing polyvinyl alcohol (PVA) around the above (3) droplets, coacervation can proceed in which the PVA gathers around the liquid crystal composition 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 room temperature or higher.

[0069] In the process of manufacturing a liquid crystal capsule 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.

[0070]

[0071] 2. Capsule solution

[0072] Meanwhile, according to another embodiment of the invention, a capsule solution comprising a liquid crystal capsule and a solvent of the first embodiment may be provided. The details regarding the liquid crystal capsule include the details described above with respect to the first embodiment.

[0073] 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.

[0074] The above capsule solution contains liquid crystal capsules dispersed in a solvent. That is, the above capsule solution may be a liquid crystal capsule 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 applying the capsule solution onto a support substrate to form a film.

[0075] The above-mentioned capsule liquid may contain a mass ratio of liquid crystals ranging from 60 mass% to 80 mass%, or 65 mass% to 75 mass%, or 69 mass% to 72 mass%, or 69 mass% to 70 mass%, or 71 mass% to 72 mass%. The above-mentioned mass ratio of liquid crystals refers to the relative mass ratio of liquid crystals when the mass of the capsule liquid is 100 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 capsule.

[0076] The method for measuring the mass ratio of liquid crystal based on the above capsule liquid 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 ℃ to 700 ℃ at a heating rate of 10 ℃ minutes, and while confirming the mass decrease according to temperature, the mass ratio (mass%) of the liquid crystal based on the capsule liquid can be obtained through the mass decrease ratio in the range of 200 ℃ to 500 ℃.

[0077]

[0078] 3. Optical film

[0079] Meanwhile, according to another embodiment of the invention, an optical film comprising a liquid crystal capsule of the first embodiment may be provided. The details regarding the liquid crystal capsule include the details described above with respect to the first embodiment.

[0080] The optical film may comprise a polymer and a liquid crystal capsule of the above embodiment dispersed within the polymer. Although the polymer is not particularly limited, for example, a transparent material may be used. Although specific examples of the polymer are not particularly limited, for example, it may be selected from polyvinylpyrrolidone, polyvinyl alcohol, polyurea, polyurethane, polyamide including nylon, polyacetal, and polyester.

[0081] For a more specific example, the optical film may be formed by applying the capsule liquid of the other embodiment onto a support substrate to form a film. Additionally, the optical film may be formed by applying a mixture of the capsule liquid of the other embodiment and a polymer onto a support substrate to form a film.

[0082] 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.

[0083] However, for example, the above optical film can be used in a transmittance variable film.

[0084] In addition, the thickness of the optical film may be 10 μm to 30 μm. The optical film has the advantage of being able to achieve excellent transmittance / haze variability even at a low thickness of 10 μm to 30 μm.

[0085]

[0086] 4. Optical device

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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 opposing surfaces of each of the set of substrates, a liquid crystal capsule liquid of the present invention disposed between the substrates and formed by applying the liquid crystal capsule liquid of the present invention alone or together with a polymer, and a means for applying an electric field to the liquid crystal capsule of the present invention in the liquid crystal layer through the electrode.

[0091] The above optical device may have a threshold voltage of 25 V or less, 22 V or less, 20 V or less, 1 V or more, 1 V to 25 V, 1 V to 22 V, or 1 V to 20 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 to the film through a function generator.

[0092] Additionally, the optical device may have a saturation voltage of 200 V or less, or 180 V or less, or 170 V or less, or 160 V or less, or 150 V or less, or 120 V or less, or 100 V or less, or 1 V or more, or 1 V to 200 V, or 1 V to 180 V, or 1 V to 170 V, or 1 V to 160 V, or 1 V to 150 V, or 1 V to 120 V, or 1 V to 100 V. The saturation voltage refers to the minimum voltage at which haze becomes saturated, and as the optical device has a saturation voltage within the range described above, the optical device may be able to operate at a lower voltage. The method for measuring the saturation 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, voltage can be applied to the film through a function generator and measured using a haze meter (Nippon Denshoku, NDH7000).

[0093] In addition, the optical device may have a contrast of 3 or more, or 3.2 or more, or 3.5 or more, or 3.9 or more, or 6.5 or more, or 7 or more, or 7.1 or more, or 40 or less, or 3 to 40, or 3.2 to 40, or 3.5 to 40, or 3.9 to 40, or 6.5 to 40, or 7 to 40, or 7.1 to 40. The contrast refers to the ratio between the transmittance at a voltage of 100 V and the transmittance at a voltage of 0 V, and as the optical device has a contrast within the range described above, the optical device can achieve an excellent transmittance variability even at lower voltages. The method for measuring the contrast 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, voltage can be applied to the film through a function generator and measured using a haze meter (Nippon Denshoku, NDH7000).

[0094] In addition, the optical device may have a △Haze value, which is the difference between the haze at an applied voltage of 100V and the haze at an applied voltage of 0V, of -65% or less, or -66% or less, or -67% or less, or -68% or less, or -70% or less, or -80% or less, or -84% or less, or -99% or more, or -99% to -65%, or -99% to -66%, or -99% to -67%, or -99% to -68%, or -99% to -70%, or -99% to -80%, or -99% to -84%. As the optical device has a △Haze value within the range described above, the optical device can achieve an excellent haze variability even at lower voltages. The method for measuring the haze 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, voltage can be applied to the film through a function generator and measured using a haze meter (Nippon Denshoku, NDH7000).

[0095]

[0096] 5. Variable transmittance device

[0097] 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.

[0098] 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.

[0099] 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.

[0100] According to the present invention, a liquid crystal capsule having excellent durability that enables excellent transmittance / haze variability even at lower voltages by lowering the surface interaction energy of the liquid crystal enclosed inside the capsule and prevents loss of liquid crystal even during long-term storage, and a capsule liquid, an optical film, an optical device, and a transmittance variability device using the same can be provided.

[0101] 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.

[0102]

[0103] <Example: Preparation of Liquid Crystal Capsule and Capsule Solution>

[0104] Example 1

[0105] 0.249 g of an emulsifier (0.5 wt% based on the weight of the aqueous solution) was added to an aqueous solution mixed with 0.65 g of polyvinyl alcohol (PVA) and 46.8 g of water, and stirred to dissolve it. As the emulsifier, 0.249 g of a mixed solution (0.5 wt% based on the weight of the aqueous solution) was used, in which 0.125 g of 2,4,7,9-tetramethyl-5-decyn-4,7-diol (HLB: 3) was dissolved in 0.124 g of ethylene glycol (5.4 wt% based on the weight of the liquid crystal).

[0106] Subsequently, 2.3 g of a cyanide-based liquid crystal (a mixture of 1,1'-Biphenyl]-4-carbonitrile,4-ethyl-, 4-n-Butyl-4'-cyanobiphenyl; [1,1'-Biphenyl]-4-carbonitrile,4'-pentyl-; Benzonitrile,4-(trans-4-propylcyclohexyl)-; [1,1'-Biphenyl]-4-carbonitrile,4-(trans-4-pentylcyclohexyl)-; Cyclohexanecarboxylic acid,4-ethyl-, 4'-cyano1,1'-biphenyl-4-yl ester, trans) and 0.161 g of an azo-based anisotropic dye were added, and emulsification was carried out for 1 hour at 4,000 rpm using an IKA homogenizer T25.

[0107] Afterwards, the solution was heated to 40°C under stirring and PVA was adsorbed onto the droplet surface for 18 hours.

[0108] 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.

[0109] After concentrating the solution with a rotary evaporator for 1 hour, the supernatant was recovered by centrifuging at 5000 rpm for 5 minutes to remove unencapsulated liquid crystals, thereby obtaining a capsule solution containing liquid crystal capsules.

[0110]

[0111] Examples 2 and 3

[0112] A liquid crystal capsule and a capsule solution were prepared in the same manner as in Example 1, except that 1.2 g of a 40% aqueous glyoxal solution was added as the crosslinking agent instead of 0.8 g of a 40% aqueous glyoxal solution.

[0113]

[0114] <Comparative Example: Preparation of Liquid Crystal Capsule and Capsule Solution>

[0115] Comparative Example 1

[0116] A liquid crystal capsule and a capsule solution were prepared in the same manner as in Example 1, except that 0.25 g (0.5 wt%) of a mixed solution (2.7 wt%) based on the weight of the liquid crystal) was added by dissolving 0.1875 g of 2,4,7,9-tetramethyl-5-decyn-4,7-diol (HLB: 3) in 0.0625 g of ethylene glycol (2.7 wt%) based on the weight of the liquid crystal) as the emulsifier.

[0117]

[0118] Comparative Example 2

[0119] A liquid crystal capsule and a capsule solution were prepared in the same manner as in Example 1, except that 0.25 g (0.5 wt%) of Ethoxylated tetramethyl decynediol (ethylene oxide content: 20 wt%; HLB: 4) was added as the emulsifier.

[0120]

[0121] Comparative Example 3

[0122] 0.25 g of the emulsifier ethoxylated tetramethyl decynediol (ethylene oxide content: 20 wt%; HLB: 4) (0.5 wt% based on the 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, 0.25 g of ethylene glycol (5.4 wt% based on the weight of the liquid crystal) was additionally added as an additive.

[0123] Subsequently, 2.3 g of a cyanide-based liquid crystal (a mixture of 1,1'-Biphenyl]-4-carbonitrile,4-ethyl-, 4-n-Butyl-4'-cyanobiphenyl; [1,1'-Biphenyl]-4-carbonitrile,4'-pentyl-; Benzonitrile,4-(trans-4-propylcyclohexyl)-; [1,1'-Biphenyl]-4-carbonitrile,4-(trans-4-pentylcyclohexyl)-; Cyclohexanecarboxylic acid,4-ethyl-, 4'-cyano1,1'-biphenyl-4-yl ester, trans) and 0.161 g of an azo-based anisotropic dye were added, and emulsification was carried out for 1 hour at 4,000 rpm using an IKA homogenizer T25.

[0124] Afterwards, the solution was heated to 40°C under stirring and PVA was adsorbed onto the droplet surface for 18 hours.

[0125] 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.

[0126] After concentrating the solution with a rotary evaporator for 1 hour, the supernatant was recovered by centrifuging at 5000 rpm for 5 minutes to remove unencapsulated liquid crystals, thereby obtaining a capsule solution containing liquid crystal capsules.

[0127]

[0128] Comparative Example 4

[0129] A liquid crystal capsule and a capsule solution were prepared in the same manner as in Example 1, except that 0.25 g (0.5 wt%) of Ethoxylated tetramethyl decynediol (ethylene oxide content: 40 wt%; HLB: 8) was added as the emulsifier.

[0130]

[0131] Comparative Example 5

[0132] A liquid crystal capsule and a capsule solution were prepared in the same manner as in Example 1, except that 0.25 g of [2,4,7,9-tetramethyl-5-decyn-4,7-diol (HLB: 3) (0.5 wt%) based on the weight of the aqueous solution] was added as the emulsifier.

[0133]

[0134] <Experimental Example>

[0135] For the liquid crystal capsules 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.

[0136]

[0137] 1. Physical properties of liquid crystal capsules

[0138] (1) Capsule size in capsule liquid

[0139] Using a Malvern Zetasizer zs, the average capsule diameter (nm) and standard deviation of 4 mL of capsule solution diluted (water and capsule solution mixed in a 4:1 weight ratio) were measured under RI: 1.5 and 25 ℃ conditions.

[0140] (2) Liquid crystal ratio (mass%) in capsule solution

[0141] 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 500 ℃.

[0142] (3) TGA final decomposition temperature (°C)

[0143] 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 introduced into a TGA2 instrument from METTLER TOLEDO and heated from 50 ℃ to 700 ℃ at a heating rate of 10 ℃ / min. The mass decrease according to temperature was then checked, and the final temperature at which decomposition was completed was set as the TGA final decomposition temperature.

[0144] (4) Whether the liquid crystal is lost

[0145] The capsule liquids obtained in the above examples and comparative examples were stored for 2 weeks to check whether liquid crystal was lost from the liquid crystal capsules, and evaluated under the following criteria.

[0146] Defect: Liquid crystal loss in capsule solution

[0147] Good: No liquid crystal loss in the capsule solution

[0148]

[0149] 2. Physical properties of liquid crystal capsule films

[0150] (1) Thickness (㎛)

[0151] 0.8 mL of capsule solution and 0.2 mL of a 50 wt% aqueous solution of polyvinylpyrrolidone (PVP; Mw=55,000) were mixed, coated onto the ITO of a PET-ITO film using a Mayer bar, and then dried at 70°C for 2 hours to produce a liquid crystal capsule film. (However, Comparative Examples 3, 4, and 5, in which liquid crystal was lost from the capsule solution, were not evaluated as film production was impossible.) The thickness of the liquid crystal capsule film was measured using an Alpha step (KLA TENCOR).

[0152] (2) T off (%), Haze off (%)

[0153] After laminating the ITO surface of a PET-ITO film (GMP EXCELAM-SMART 655) onto the upper surface of the liquid crystal capsule film, an electrode tape was attached to the ITO surface.

[0154] T, which is the transmittance of a liquid crystal capsule film with no applied voltage (transmittance at an applied voltage of 0V). off , and Haze of a liquid crystal capsule film with no applied voltage (haze at an applied voltage of 0V) off It was measured using a haze meter (Nippon Denshoku, NDH7000).

[0155] (3) Critical voltage (V), saturation voltage (V)

[0156] T of (2) above off (%), Haze off Under conditions identical to the (%) measurement conditions, voltage was applied to the liquid crystal capsule film through a function generator.

[0157] In addition, the critical voltage, which is the voltage at 10% transmittance of the maximum transmittance, and the saturation voltage, which is the minimum voltage at which the variation in Haze value according to voltage becomes 1%, were measured using a haze meter (Nippon Denshoku, NDH7000).

[0158] (4) CR, ΔHaze

[0159] T of (2) above off (%), Haze off Under conditions identical to the (%) measurement conditions, voltage was applied to the liquid crystal capsule film through a function generator.

[0160] And, transmittance at a voltage of 100 V and transmittance at a voltage of 0 V The contrast (CR), which is the ratio between them, was measured using a haze meter (Nippon Denshoku, NDH7000).

[0161] In addition, haze at an applied voltage of 0V and The haze at an applied voltage of 100V was measured using a haze meter (Nippon Denshoku, NDH7000), and ΔHaze = haze at an applied voltage of 100V (%) - haze at an applied voltage of 0V (%) was calculated.

[0162]

[0163] 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 Comparative Example 5 Liquid Crystal Capsule Size (㎛) 0.762 ± 0.270 0.756 ± 0.383 0.756 ± 0.383 0.767 ± 0.227 0.728 ± 0.203 0.838 ± 0.676 0.937 ± 0.345 1.208 ± 0.383 Liquid Crystal Ratio (Mass%) 69.37 2.07 2.07 2.87 6.57 5.07 3.472 TGA Final Decomposition Temperature (°C) 500 500 500 500 500 400 500 520 Liquid Crystal Loss Status Good Good Good Good Good Poor Poor Poor Liquid Crystal Capsule Film thickness (㎛) 29.3 18.5 15.8 29.9 29.7--_T off (%)5.6 10.8 15.2 5.4 5.6---Haze off(%)89.193.291.694.895.0---Critical Voltage(V)2020203030---Saturation Voltage(V)100170150170150---CR @100V7.13.93.25.06.1---ΔHaze (%)-84-66-68-52-73---

[0164] As shown in Table 1 above, the liquid crystal capsule of the example had good characteristics with high durability and no loss of liquid crystal. On the other hand, it was confirmed that the liquid crystal capsules of Comparative Examples 3 to 5 had poor durability due to the loss of liquid crystal. Meanwhile, the liquid crystal capsule film of Example 1 was measured to have a threshold voltage of 20 V and a saturation voltage of 100 V, which is lower than that of the Comparative Example. It was confirmed that transmittance / haze variability characteristics can be realized at lower voltages, and that the contrast and haze changes according to voltage application were greater than those of the Comparative Example, thereby enabling a superior transmittance variability rate at lower voltages.

[0165] In addition, through the liquid crystal capsule films of Examples 2 and 3, it was confirmed that even when the film thickness was lowered to 15.8 μm to 18.5 μm, a lower threshold voltage was exhibited compared to the comparative example, and the saturation voltage or the change in contrast and haze according to the application of voltage was maintained at an equivalent level compared to the comparative example.

Claims

1. A core containing a liquid crystal and an emulsifier; and A polymer shell formed on the surface of the core; comprising The above emulsifier is a mixture of an acetylenic diol-based compound and an alkylene glycol, and A liquid crystal capsule having a content of 4 weight percent or more relative to the liquid crystal of the above-mentioned alkylene glycol.

2. In Paragraph 1, A liquid crystal capsule having a content of 4% to 6% by weight relative to the liquid crystal of the above alkylene glycol.

3. In Paragraph 1, A liquid crystal capsule having a content of 40% to 60% by weight relative to the emulsifier for the alkylene glycol.

4. In Paragraph 1, The above emulsifier is a liquid crystal capsule, which is a mixed solution of an acetylenic diol-based compound dissolved in alkylene glycol.

5. In Paragraph 1, The above acetylenic diol-based compound is a liquid crystal capsule having an ethylene oxide repeating unit content of less than 0.001 mol% based on 100 mol% of the acetylenic diol-based compound.

6. In Paragraph 1, The above acetylenic diol-based compound is a liquid crystal capsule having an HLB (Hydrophile Lipophile Balance) value of 2 to 3.

5.

7. In Paragraph 1, The above liquid crystal is a liquid crystal capsule containing a cyano group.

8. In Paragraph 1, A liquid crystal capsule having an average diameter of 400 nm to 5 μm.

9. In Paragraph 1, A liquid crystal capsule having a final decomposition temperature of 450°C to 550°C as measured by TGA when the liquid crystal capsule is heated from 50°C to 700°C at a heating rate of 10°C / min.

10. In Paragraph 1, The above core is a liquid crystal capsule further comprising an anisotropic dye.

11. In Paragraph 1, The above polymer shell is a liquid crystal capsule comprising a polymer crosslinked with a crosslinking agent.

12. A capsule solution comprising the liquid crystal capsule and solvent of claim 1.

13. In Paragraph 12, A capsule liquid having a mass ratio of liquid crystal based on the above capsule liquid of 60 mass% to 80 mass%.

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

15. In Paragraph 14, An optical film having a thickness of 10 μm to 30 μm.

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

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