Hollow particles and methods for producing the same

Abstract

To provide a hollow particle having excellent light-diffusibility.SOLUTION: The problem is solved by a hollow particle which includes a nonporous shell and a hollow region partitioned by the shell, in which the shell has a plurality of protrusions on its inside wall, the plurality of protrusions are connected together, and the hollow particle is characterized as having W / V of 0.02-0.5 (W means an average width of the plurality of protrusions and V means a volume average particle diameter of the hollow particle).SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to hollow particles and a method for producing the same. More specifically, the present invention relates to hollow particles having a plurality of protrusions on the inner wall of a shell constituting the hollow particles and a method for producing the same. The hollow particles of the present invention are suitable for applications such as paint compositions, cosmetics, paper coating compositions, heat insulating compositions, light diffusing compositions, and light diffusing films.

Background Art

[0002] Polymer particles (hollow particles) having an air space inside are used in a very wide range of fields for the purpose of imparting weight reduction, pore formation, heat insulation, sound insulation, impact resistance, etc. of materials. It is known that visible light scattering occurs due to the refractive index difference between the shell and the air space partitioned by the shell in this hollow particle, and it has better light diffusing properties than polymer particles (solid particles) without an air space inside. Therefore, hollow particles have the effect of improving opacity, whiteness, gloss, etc., and are used, for example, as light diffusing agents in paints, paper coating compositions, cosmetics, sunscreen creams, etc. In particular, in recent years, from the viewpoint of energy saving, it has been considered to apply heat shielding paints and heat insulating paints to the roofs of buildings, and the use of hollow particles having excellent light scattering properties as materials for improving heat shielding properties and heat insulating properties has been considered. As hollow particles, the particles described in JP-A-2002-080503 (Patent Document 1) have been proposed. Also, in WO 2002 / 072671 (Patent Document 2) and JP-A-2017-082152 (Patent Document 3), hollow particles having improved mechanical strength by making the internal morphology porous have been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

[0004] The hollow particles described in Patent Document 1 did not exhibit sufficient light scattering due to the air space, and in particular, the diffusion of visible light to near-infrared light was insufficient. As a result, they did not have sufficient performance as a material to improve heat shielding. Furthermore, although the hollow particles described in Patent Documents 2 and 3 showed improved light scattering compared to Patent Document 1, the diffusion of near-infrared light was insufficient. Therefore, there was a need for hollow particles with even better light diffusion. [Means for solving the problem]

[0005] Thus, according to the present invention, a non-porous shell and an air space partitioned by the shell are provided, wherein the shell has a plurality of protrusions on its inner wall, and the plurality of protrusions are hollow particles that are connected to one another. The present invention provides a hollow particle characterized in that the hollow particle has a W / V ratio of 0.02 to 0.5 (where W is the average width of the multiple protrusions and V is the volume-average particle diameter of the hollow particle). Furthermore, according to the present invention, the method for producing the above-mentioned hollow particles is as follows: A method for producing hollow particles is provided, characterized by comprising the step of polymerizing a mixture containing a vinyl monofunctional monomer, a vinyl crosslinkable monomer, a non-reactive solvent, and a polymerization initiator in an aqueous medium containing a suspension stabilizer in the presence of a dispersion aid. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide hollow particles having excellent light-diffusing properties (particularly light scattering properties for visible light and near-infrared light). Furthermore, hollow particles with superior light-diffusing properties can be provided in any of the following cases: (1) The hollow particles have a volume-average particle diameter of 1.0 to 50 μm, and the shell is made of a cross-linked resin. (2) The crosslinked resin is derived from a vinyl monofunctional monomer and a vinyl crosslinkable monomer, and the vinyl monofunctional monomer and the vinyl crosslinkable monomer are (meth)acrylic acid esters. (3) The hollow particles have the property of reflecting visible light and near-infrared light. (4) The hollow particles are used in applications selected from paint compositions, cosmetics, paper coating compositions, heat insulating compositions, light diffusing compositions and light diffusing films. [Brief explanation of the drawing]

[0007] [Figure 1] These are surface photographs (3000x magnification) and cross-sectional photographs (3000x and 1000x magnification) of the hollow particles in Examples 1-4. [Figure 2] These are surface photographs (3000x magnification) and cross-sectional photographs (3000x and 1000x magnification) of the hollow particles in Examples 5-8. [Figure 3] These are surface photographs (3000x magnification) and cross-sectional photographs (3000x and 1000x magnification for Comparative Example 1, and 3000x magnification for Comparative Examples 1 and 2) of the hollow particles in Example 9 and Comparative Examples 1-3. [Figure 4] This graph shows the light reflectance of coating films containing hollow particles for each wavelength in the examples and comparative examples for evaluation of their reflection characteristics in ultraviolet, visible, and near-infrared light. [Modes for carrying out the invention]

[0008] (hollow particles) The hollow particle comprises a non-porous shell and an air space partitioned by the shell. Furthermore, the shell has multiple protrusions on its inner wall, and these protrusions are interconnected.

[0009] (1) Shell The materials constituting the shell are not particularly limited, as long as they can partition the airspace. The materials may include cross-linked resins. The materials do not necessarily have to contain inorganic components (e.g., silica). The type of crosslinked resin is not particularly limited as long as it can form a shell. Examples of crosslinked resins include resins derived from vinyl monomers, specifically resins derived from vinyl monofunctional monomers and vinyl crosslinkable monomers. A vinyl monofunctional monomer is a monomer having one vinyl group, while a vinyl crosslinkable monomer is a monomer having two or more vinyl groups. The fact that the shell consists of a crosslinked resin can be confirmed, for example, by measuring the gel fraction. Examples of vinyl monofunctional monomers include C1-C16 alkyl(meth)acrylic acid esters such as methyl(meth)acrylate, ethyl(meth)acrylate, butyl(meth)acrylate, and cetyl(meth)acrylate; (meth)acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate, maleic anhydride, and N-vinylcarbazole; and styrene monomers such as styrene, α-methylstyrene, paramethylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, and bromostyrene. These monofunctional monomers can be used individually or in combination.

[0010] Examples of vinyl-based crosslinkable monomers include polyfunctional (meth)acrylic acid esters such as ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and glycerin tri(meth)acrylate; polyfunctional acrylamide derivatives such as N,N'-methylenebis(meth)acrylamide and N,N'-ethylenebis(meth)acrylamide; polyfunctional allyl derivatives such as diallylamine and tetraallyloxyethane; and aromatic divinyl compounds such as divinylbenzene. These crosslinkable monomers can be used individually or in combination. The vinyl monofunctional monomer and the vinyl crosslinkable monomer are preferably (meth)acrylic acid esters.

[0011] The component derived from the vinyl-based crosslinkable monomer is preferably contained in the shell at a ratio of 20 parts by weight or more with respect to 100 parts by weight of the component derived from the vinyl-based monofunctional monomer. When the amount of the component derived from the crosslinkable monomer is less than 20 parts by weight, a shell having sufficient strength may not be formed. The amount of the component derived from the vinyl-based crosslinkable monomer is more preferably 20 to 150 parts by weight, and even more preferably 80 to 130 parts by weight.

[0012] (2) Protrusions on the inner wall The shell has a plurality of protrusions on its inner wall. The number of protrusions is not particularly limited. For example, the protrusions contacting the inner wall of the shell can be 2 or more in the cross-section of the hollow particle, and can also be in the range of 2 to 1600. Further, the plurality of protrusions are connected to each other between adjacent protrusions. Whether they are connected to each other can be confirmed by a cross-sectional photograph of the hollow particle. The protrusions have a relationship of 0.02 to 0.5 in terms of W / V (where W is the average width of the plurality of protrusions and V is the volume-average particle diameter of the hollow particle) with respect to the volume-average particle diameter of the hollow particle. When W / V is less than 0.02 or greater than 0.5, the light diffusing property may be insufficient. W / V is preferably 0.025 to 0.4, and more preferably 0.03 to 0.3. The volume-average particle diameter V can be 1.0 to 50 μm. Depending on the application, the volume-average particle diameter is preferably 2.0 to 30 μm, and more preferably 3.0 to 25 μm. The average width W of the protrusions can be 0.1 to 2.0 μm. The average width is preferably 0.2 to 1.5 μm, and more preferably 0.3 to 1.0 μm. The protrusions may be made of the same material as the material constituting the shell.

[0013] (3) Outer shape, etc. The outer shape of the hollow particle is not particularly limited, but it is preferably as close to spherical as possible. The shell has a thickness of 0.1 to 2.0 μm. If the thickness is less than 0.1 μm, the hollow particles may be easily crushed. If the thickness is greater than 2.0 μm, the reflectivity of visible light and near-infrared light may decrease. The thickness is preferably 0.2 to 1.5 μm, and more preferably 0.3 to 1.0 μm. The shell is non-porous. Being non-porous allows the air space to be maintained even when the hollow particles are used in various applications, thus enabling the hollow particles to exhibit their light-diffusing properties. Non-porosity can be confirmed, for example, by observing whether a resin is present in the air space when taking a cross-sectional photograph of the hollow particles to fix them in place. Within the airspace, there may be particle clumps composed of multiple interconnected particles. These hollow particle clumps may be connected to adjacent protrusions.

[0014] (Method for manufacturing hollow particles) A method for producing hollow particles includes a step (polymerization step) in which a mixture containing a vinyl monofunctional monomer, a vinyl crosslinkable monomer, a non-reactive solvent, and a polymerization initiator is polymerized in an aqueous medium containing a suspension stabilizer in the presence of a dispersion aid.

[0015] (1) Polymerization process In the polymerization process, vinyl monofunctional monomers and vinyl crosslinkable monomers polymerize, and the resulting polymer accumulates at the interface with the aqueous medium, thereby obtaining hollow particles. In the polymerization process, a mixture is first obtained by mixing at least a vinyl monofunctional monomer, a vinyl crosslinkable monomer, a non-reactive solvent, and a polymerization initiator. The amount of monomer used and the content of monomer-derived components constituting the outer shell are substantially equal. Examples of non-reactive solvents include pentane, hexane, cyclohexane, heptane, decane, hexadecane, toluene, xylene, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, methyl chloride, methylene chloride, chloroform, and carbon tetrachloride. These non-reactive organic solvents can be used individually or in combination. It is preferable that the boiling point of the non-reactive solvent is less than 100°C, as this facilitates removal from hollow particles. The amount of non-reactive solvent added is not particularly limited, but is generally between 40 and 250 parts by weight per 100 parts by weight of total monomer. If the amount added is less than 40 parts by weight, the proportion of airspace partitioned by the shell will be small, which may result in insufficient light diffusion. If the amount exceeds 250 parts by weight, shell formation may be insufficient, and particles with sufficient physical strength may not be obtained.

[0016] Polymerization of monomers is carried out in the presence of a polymerization initiator. The polymerization initiator is not particularly limited and includes, for example, persulfates such as ammonium persulfate, potassium persulfate, and sodium persulfate; organic peroxides such as cumene hydroperoxide, di-tert-butyl peroxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, dimethylbis(tert-butylperoxy)hexane, dimethylbis(tert-butylperoxy)hexine-3, bis(tert-butylperoxyisopropyl)benzene, bis(tert-butylperoxy)trimethylcyclohexane, butyl-bis(tert-butylperoxy)valerate, tert-butyl 2-ethylhexaneperoxyate, dibenzoyl peroxide, paramentane hydroperoxide, and tert-butylperoxybenzoate. 2,2'-Azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-Azobis[2-(2-imidazolin-2-yl)propane] disulfate dihydrate, 2,2'-Azobis(2-amidinopropane) dihydrochloride, 2,2'-Azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate, 2,2'-Azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane} dihydrochloride, 2,2'-Azobis[2-(2-imidazolin-2-yl)propane], 2,2'-Azobis(1-imino -1-Pyrrolidino-2-ethylpropane) dihydrochloride, 2,2'-Azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}, 2,2'-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 4,4'-Azobis(4-cyanopentanoic acid), 2,2'-Azobisisobutyronitrile (2,2'-Azobis(2-methyl-butyronitrile), 2,2'-Azobis(2-isopropylbutyronitrile), 2,2'-Azobis(2,3-dimethylbutyronitrile), 2,2'-Azobis Azobis(2,4-dimethylbutyronitrile), 2,2'-azobis(2-methylcapronitrile), 2,2'-azobis(2,3,3-trimethylbutyronitrile), 2,2'-azobis(2,4,4-trimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-ethoxyvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-n-butoxyvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis[N-(2 -propenyl)-2-methylpropionamide], 2,2'-azobis(N-butyl-2-methylpropionamide), 2,2'-azobis(N-cyclohexyl-2-methylpropionamide), 1,1'-azobis(1-acetoxy-1-phenylethane), 1,1'-azobis(cyclohexane-1-carbonitride), dimethyl-2,2'-azobis(2-methylpropinate), dimethyl-2,2'-azobisisobutyrate, dimethyl-2,2'-azobis(2-methylpropinate), 2-(carbamoylazo)isobutyronitrile, 4,Examples include azo compounds such as 4'-azobis(4-cyanovaleric acid). These polymerization initiators can be used individually or in combination. The polymerization initiator is preferably present in the mixture in an amount of 0.05 to 5 parts by weight per 100 parts by weight of the total monomers. Next, the dispersed mixture is subjected to polymerization to obtain hollow particles. Polymerization is not particularly limited, and is carried out while appropriately adjusting various conditions such as polymerization temperature and polymerization time depending on the type of monomer and polymerization initiator contained in the mixture. For example, the polymerization temperature can be 30 to 80°C and the polymerization time can be 1 to 20 hours. A thickening agent may be added to the mixture. Examples of thickening agents include organic thickening agents such as acrylic thickening agents, urethane thickening agents, polyether thickening agents, polyvinyl alcohols, and cellulose derivatives. Examples of inorganic thickening agents include hydrophobic fumed silica and clay minerals. These thickening agents may be added individually or in combination of two or more.

[0017] The mixture is added to an aqueous medium containing a suspension stabilizer. Examples of aqueous media constituting an aqueous system include water, and mixtures of water and water-soluble organic solvents (e.g., lower alcohols such as methanol and ethanol). Examples of suspension stabilizers include phosphates such as calcium phosphate, magnesium phosphate, aluminum phosphate, and zinc phosphate; pyrophosphates such as calcium pyrophosphate, magnesium pyrophosphate, aluminum pyrophosphate, and zinc pyrophosphate; and poorly water-soluble inorganic compounds such as calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, and colloidal silica. Suspension stabilizers can be used individually or in combination of two or more. The suspension stabilizer is preferably used in an amount of 0.5 to 10 parts by weight per 100 parts by weight of the mixture of the total monomer and the non-reactive solvent. If the amount used is less than 0.5 parts by weight, the mixture may not be sufficiently dispersed. If the amount used is more than 10 parts by weight, the effect will not be commensurate with the amount used, making it uneconomical and therefore undesirable.

[0018] Polymerization is carried out in the presence of a dispersion aid. The dispersion aid may be present in the mixture or in an aqueous medium. Examples of dispersing agents include lauryl phosphate, polyoxyethylene(1) lauryl ether phosphate, dipolyoxyethylene(2) alkyl ether phosphate, dipolyoxyethylene(4) alkyl ether phosphate, dipolyoxyethylene(6) alkyl ether phosphate, dipolyoxyethylene(8) alkyl ether phosphate, dipolyoxyethylene(4) nonylphenyl ether phosphate, caprolactone EO modified phosphate dimethacrylate, and 2-methacryloyloxyethyl acid phosphate. (Number) indicates the number of oxyethylene repeats. EO means ethylene oxide. The amount of dispersing agent added is not particularly limited, but is generally 0.0001 to 0.5 parts by weight per 100 parts by weight of the mixture of total monomers and non-reactive solvent. If the amount added is less than 0.0001 parts by weight, the mixture may not be sufficiently dispersed. If it exceeds 0.5 parts by weight, a shell may not be formed.

[0019] The inventors believe that the uniquely shaped hollow particles of the present invention can be appropriately manufactured by controlling the interfacial tension acting at the interface between the mixture (oil phase) and the aqueous medium (aqueous phase). For example, when the interfacial tension is high, the number of protrusions tends to decrease and / or the size of the protrusions tends to increase. Conversely, when the interfacial tension is low, the number of protrusions tends to increase and / or the size of the protrusions tends to decrease. The interfacial tension between the mixture (oil phase) and the aqueous medium (aqueous phase) can be controlled, for example, by adjusting the type of non-reactive solvent used, the ratio of total monomers to non-reactive solvent, the amount of dispersant, and the amount of dispersion aid. In addition, the inventors believe that the uniquely shaped hollow particles of the present invention can also be appropriately manufactured by adjusting the viscosity of the mixture (oil phase). When the viscosity of the mixture (oil phase) is high, the number of protrusions tends to increase and / or the size of the protrusions tends to decrease. When the viscosity of the mixture (oil phase) is low, the number of protrusions tends to decrease and / or the size of the protrusions tends to increase. For example, even when the interfacial tension is high, hollow particles with a large number of protrusions and / or small protrusions can be obtained by increasing the viscosity of the mixture (oil phase). The mixture is dispersed in an aqueous medium while appropriately adjusting various conditions such as stirring speed and stirring time to obtain hollow particles of the desired particle size. (2) Other processes Hollow particles can be removed from aqueous media by centrifugation, washing, and drying, if necessary.

[0020] (Application) Hollow particles can be used in applications such as paint compositions, cosmetics, paper coating compositions, heat insulating compositions, light diffusing compositions, and light diffusing films.

[0021] (1) Paints, heat-insulating and light-diffusing compositions These compositions may include, as needed, a binder resin, a UV-curable resin, a solvent, etc. As the binder resin, an organic solvent, a water-soluble resin, or an emulsion-type aqueous resin that can be dispersed in water can be used. The amount of binder resin or UV-curable resin and hollow particles added varies depending on the film thickness of the coating, the average particle size of the hollow particles, and the coating method. The amount of hollow particles added is preferably 5 to 50% by weight relative to the total of the binder resin (solid content if an emulsion-type aqueous resin is used) and the hollow particles. A more preferable content is 10 to 50% by weight, and an even more preferable content is 20 to 40% by weight. Examples of binder resins include acrylic resins, alkyd resins, polyester resins, polyurethane resins, chlorinated polyolefin resins, and amorphous polyolefin resins. Examples of UV-curable resins include polyfunctional (meth)acrylate resins such as polyhydric alcohol polyfunctional (meth)acrylates; and polyfunctional urethane acrylate resins synthesized from diisocyanates, polyhydric alcohols, and (meth)acrylic acid esters having hydroxyl groups.

[0022] As the UV-curable resin, a polyfunctional (meth)acrylate resin is preferred, and a polyhydric alcohol polyfunctional (meth)acrylate resin having three or more (meth)acryloyl groups in one molecule is more preferred. Polyhydric alcohol polyfunctional (meth)acrylate resins having three or more (meth)acryloyl groups in one molecule include, specifically, trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, 1,2,4-cyclohexanetetra(meth)acrylate, pentagrycerol triacrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol triacrylate, dipentaerythritol pentaacrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol triacrylate, tripentaerythritol hexaacrylate, etc., which may be used individually or in combination of two or more.

[0023] When using UV-curable resins, a photopolymerization initiator is usually used in combination. The photopolymerization initiator is not particularly limited. Examples of photopolymerization initiators include acetophenones, benzoins, phosphine oxides, ketals, α-hydroxyalkylphenones, α-aminoalkylphenones, anthraquinones, thioxanthones, azo compounds, peroxides (as described in Japanese Patent Publication No. 2001-139663, etc.), 2,3-dialkyldione compounds, disulfide compounds, fluoroamine compounds, aromatic sulfoniums, onium salts, borate salts, active halogen compounds, and α-acyloxime esters. These binder resins or UV-curable resins can be appropriately selected depending on the adhesion of the paint to the substrate to be painted and the environment in which it is used.

[0024] The solvent is not particularly limited, but it is preferable to use a solvent that can dissolve or disperse the binder resin or UV-curable resin. For example, for oil-based paints, examples include hydrocarbon solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ester solvents such as ethyl acetate and butyl acetate; and ether solvents such as dioxane, ethylene glycol diethyl ether, and ethylene glycol monobutyl ether. For water-based paints, water, alcohols, etc., can be used. These solvents may be used individually or in mixtures of two or more. The solvent content in the coating material is usually about 20 to 60% by weight of the total composition.

[0025] The composition may optionally contain known surface modifiers, flow modifiers, ultraviolet absorbers, light stabilizers, curing catalysts, extender pigments, coloring pigments, metal pigments, mica powder pigments, dyes, etc. The method for forming a coating film using the composition is not particularly limited, and any known method can be used. For example, methods such as spray coating, roll coating, and brush coating are available, and for coating a substrate such as a film as a thin layer, methods such as coating reverse roll coating, gravure coating, die coating, comma coating, and spray coating are available. The composition may be diluted as needed to adjust its viscosity. Examples of diluents include hydrocarbon solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ester solvents such as ethyl acetate and butyl acetate; ether solvents such as dioxane and ethylene glycol diethyl ether; water; and alcohol solvents. These diluents may be used individually or in mixtures of two or more. A coating can be formed by applying the coating to any surface, such as a substrate, to create a coating film, drying the coating film, and then curing it as needed. The coating film using the paint composition can be used to coat various substrates, and is not particularly limited to metals, wood, glass, plastics, etc. It can also be used to coat transparent substrates such as polyethylene terephthalate (hereinafter abbreviated as PET), polyethylene carbonate (hereinafter abbreviated as PC), and acrylic.

[0026] (2) Cosmetics The cosmetic composition preferably contains hollow particles in an amount ranging from 1% to 40% by weight. Cosmetics include cleansing products such as soap, body wash, facial cleansing cream, and scrub cleanser; lotions, creams, emulsions, face masks, face powders, foundations, lipstick, lip balm, blush, eyebrow cosmetics, nail polish, hair washing products, hair dyes, hair styling products, fragrances, toothpaste, bath products, antiperspirants, sunscreens, suntan products, body cosmetics such as body powder and baby powder; and lotions such as shaving cream, pre-shave lotion, aftershave lotion, and body lotion.

[0027] Furthermore, ingredients commonly used in cosmetics can be incorporated as needed, as long as they do not impair the effects of the present invention. Examples of such ingredients include water, lower alcohols, oils and waxes, hydrocarbons, higher fatty acids, higher alcohols, sterols, fatty acid esters, metal soaps, humectants, surfactants, polymer compounds, colorants, fragrances, preservatives and disinfectants, antioxidants, UV absorbers, and special formulation ingredients. Examples of oils and waxes include avocado oil, almond oil, olive oil, cocoa butter, beef tallow, sesame oil, wheat germ oil, safflower oil, shea butter, turtle oil, camellia oil, peach oil, castor oil, grape oil, macadamia nut oil, mink oil, egg yolk oil, Japanese wax, coconut oil, rosehip oil, hydrogenated oil, silicone oil, orange roughy oil, carnauba wax, candelilla wax, whale wax, jojoba oil, montan wax, beeswax, and lanolin. Examples of hydrocarbons include liquid paraffin, petrolatum, paraffin, ceresin, microcrystalline wax, and squalane. Examples of higher fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, behenic acid, undecylenic acid, oxystearic acid, linoleic acid, lanolinic acid, and synthetic fatty acids.

[0028] Examples of higher alcohols include lauryl alcohol, cetyl alcohol, cetostearyl alcohol, stearyl alcohol, oleyl alcohol, behenyl alcohol, lanolin alcohol, hydrogenated lanolin alcohol, hexyldecanol, octyldecanol, isostearyl alcohol, jojoba alcohol, and decyltetradecanol. Examples of sterols include cholesterol, dihydrocholesterol, and phytocholesterol. Examples of fatty acid esters include ethyl linoleate, isopropyl myristate, isopropyl lanolate, hexyl laurate, myristyl myristate, cetyl myristate, octyldodecyl myristate, decyl oleate, octyldodecyl oleate, hexadecyl dimethyloctanoate, cetyl isooctanoate, decyl palmitate, glyceryl trimyristate, caprylic / capric triglyceride, propylene glycol dioleate, glyceryl triisostearate, glyceryl triisooctanoate, cetyl lactate, myristyl lactate, cyclic alcohol fatty acid esters such as diisostearyl malate, cholesteryl isostearate, and cholesteryl 12-hydroxystearate.

[0029] Examples of metallic soaps include zinc laurate, zinc myristate, magnesium myristate, zinc palmitate, zinc stearate, aluminum stearate, calcium stearate, magnesium stearate, and zinc undecylenate. Examples of humectants include glycerin, propylene glycol, 1,3-butylene glycol, polyethylene glycol, sodium dl-pyrrolidone carboxylate, sodium lactate, sorbitol, sodium hyaluronate, polyglycerin, xylitol, and maltitol. Examples of surfactants include anionic surfactants such as higher fatty acid soaps, higher alcohol sulfates, N-acyl glutamates, and phosphate ester salts; cationic surfactants such as amine salts and quaternary ammonium salts; amphoteric surfactants such as betaine-type, amino acid-type, imidazoline-type, and lecithin; and nonionic surfactants such as fatty acid monoglycerides, propylene glycol fatty acid esters, sorbitan fatty acid esters, sucrose fatty acid esters, polyglycerin fatty acid esters, and ethylene oxide condensates.

[0030] Examples of polymer compounds include natural polymer compounds such as gum arabic, tragacanth gum, guar gum, locust bean gum, karaya gum, iris moss, quince seed, gelatin, shellac, rosin, and casein; semi-synthetic polymer compounds such as sodium carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, ethylcellulose, sodium alginate, ester gum, nitrocellulose, hydroxypropylcellulose, and crystalline cellulose; and synthetic polymer compounds such as polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylate, carboxyvinyl polymer, polyvinyl methyl ether, polyamide resin, silicone oil, nylon particles, polymethyl methacrylate particles, crosslinked polystyrene particles, silicone particles, urethane particles, polyethylene particles, silica particles, and other resin particles.

[0031] Examples of colorants include inorganic pigments such as iron oxide, ultramarine, chromium oxide, chromium hydroxide, carbon black, manganese violet, titanium dioxide, zinc oxide, talc, kaolin, mica, calcium carbonate, magnesium carbonate, mica, aluminum silicate, barium silicate, calcium silicate, magnesium silicate, silica, zeolite, barium sulfate, calcined calcium sulfate (calcined gypsum), calcium phosphate, hydroxyapatite, and ceramic powder, as well as tar dyes such as azo, nitro, nitroso, xanthene, quinoline, anthraquinoline, indigo, triphenylmethane, phthalocyanine, and pyrene.

[0032] Here, the powder raw materials such as the polymer compounds and colorant raw materials may be pre-treated. Conventional known surface treatment techniques can be used as surface treatment methods. For example, treatment methods include oil treatment with hydrocarbon oils, ester oils, lanolin, etc.; silicone treatment with dimethylpolysiloxane, methylhydrogenpolysiloxane, methylphenylpolysiloxane, etc.; fluorine compound treatment with perfluoroalkyl group-containing esters, perfluoroalkyl silanes, perfluoropolyethers, polymers having perfluoroalkyl groups, etc.; silane coupling agent treatment with 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, etc.; titanium coupling agent treatment with isopropyltriisostearoyl titanate, isopropyltris(dioctyl pyrophosphate) titanate, etc.; metal soap treatment; amino acid treatment with acyl glutamic acid, etc.; lecithin treatment with hydrogenated egg yolk lecithin, etc.; collagen treatment; polyethylene treatment; moisturizing treatment; inorganic compound treatment; and mechanochemical treatment.

[0033] Examples of fragrances include natural fragrances such as lavender oil, peppermint oil, and lime oil, and synthetic fragrances such as ethylphenyl acetate, geraniol, and p-tert-butylcyclohexyl acetate. Examples of preservatives and disinfectants include methylparaben, ethylparaben, propylparaben, benzalkonium, and benzethonium. Examples of antioxidants include dibutylhydroxytoluene, butylhydroxyanisole, propyl gallate, and tocopherol. Examples of UV absorbers include inorganic absorbers such as fine-particle titanium dioxide, fine-particle zinc oxide, fine-particle cerium oxide, fine-particle iron oxide, and fine-particle zirconium oxide, as well as organic absorbers such as benzoic acid, para-aminobenzoic acid, anthranic acid, salicylic acid, cinnamic acid, benzophenone, and dibenzoylmethane.

[0034] Special ingredients include hormones such as estradiol, estrone, ethinylestradiol, cortisone, hydrocortisone, and prednisone; vitamins such as vitamin A, vitamin B, vitamin C, and vitamin E; skin astringents such as citric acid, tartaric acid, lactic acid, aluminum chloride, aluminum potassium sulfate, allantoin chlorohydroxyaluminum, zinc paraphenolsulfonate, and zinc sulfate; hair growth stimulants such as cantharis tincture, capsicum tincture, ginger tincture, swertia japonica extract, garlic extract, hinokitiol, carpronium chloride, pentadecanoic acid glyceride, vitamin E, estrogen, and photosensitizer; and whitening agents such as magnesium L-ascorbate phosphate and kojic acid.

[0035] (3) Light diffusing film Light-diffusing films are formed by forming a light-diffusing layer with the aforementioned light-diffusing composition on the surface of substrates such as glass, polycarbonate, acrylic resin, PET, triacetylcellulose (TAC), plastic sheets, plastic films, plastic lenses, plastic panels, cathode ray tubes, fluorescent display tubes, and liquid crystal display boards. Depending on the application, the coating may be formed alone or in combination with a protective film, hard coat film, planarization film, high refractive index film, insulating film, conductive resin film, conductive metal microparticle film, conductive metal oxide microparticle film, or other primer film as needed on the substrate. When used in combination, the light-diffusing layer does not necessarily need to be formed on the outermost surface. [Examples]

[0036] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. First, the measurement methods used in the examples will be explained. (Volume-average particle size) The volume-average particle diameter of hollow particles is determined by the Coulter Multisizer TM Measurements were taken using a Beckman Coulter measuring device (3). The measurements were performed using the Multisizer issued by Beckman Coulter. TM 3. The procedure was performed using an aperture calibrated according to the user manual. The aperture used for measurement was selected as appropriate, for example, if the assumed volume-average particle size of the particles to be measured was between 1 μm and 10 μm, an aperture with a size of 50 μm was selected; if the assumed volume-average particle size of the particles to be measured was greater than 10 μm and 30 μm or less, an aperture with a size of 100 μm was selected; if the assumed volume-average particle size of the particles was greater than 30 μm and 90 μm or less, an aperture with a size of 280 μm was selected; and if the assumed volume-average particle size of the particles was greater than 90 μm and 150 μm or less, an aperture with a size of 400 μm was selected. If the volume-average particle size after measurement differed from the assumed volume-average particle size, the aperture was changed to one with an appropriate size and the measurement was repeated.

[0037] Furthermore, when an aperture with a size of 50 μm was selected, the Current (aperture current) was set to -800 and the Gain to 4; when an aperture with a size of 100 μm was selected, the Current (aperture current) was set to -1600 and the Gain to 2; and when apertures with sizes of 280 μm and 400 μm were selected, the Current (aperture current) was set to -3200 and the Gain to 1. For the measurement sample, 0.1 g of particles were dispersed in 10 ml of a 0.1 wt% nonionic surfactant aqueous solution using a touch mixer (Yamato Scientific Co., Ltd., "TOUCHMIXER MT-31") and an ultrasonic cleaner (Velvo-Clear Co., Ltd., "ULTRASONICCLEANER VS-150") to obtain a dispersion. During the measurement, the contents of the beaker were gently stirred to prevent the introduction of air bubbles, and the measurement was terminated when 100,000 particles had been measured. The volume-average particle size was calculated as the arithmetic mean of the volume-based particle size distribution of 100,000 particles.

[0038] (Morphological observation) Conductive tape was attached to the sample stage, and particles were placed on top of it. The particles were coated using a JEOL Ltd. "Auto Fine Coater JFC-1300" sputtering system. Next, the particles were photographed using the secondary electron detector of a Hitachi High-Technologies Corporation "SU1510" scanning electron microscope.

[0039] (Cross-sectional observation) After the washing process, the particles, dried at 100°C, were mixed with photocurable resin D-800 (manufactured by JEOL Ltd.), and a cured product was obtained by irradiation with ultraviolet light. The cured product was then cut with nippers, the cut surface was smoothed using a cutter, and the sample was coated using a JEOL Ltd. "Auto Fine Coater JFC-1300" sputtering device. Next, the sample was photographed using the secondary electron detector of a Hitachi High-Technologies Corporation "SU1510" scanning electron microscope.

[0040] (Average width of multiple protrusions) During the cross-sectional observation described above, the lengths of the protrusions emanating from the shell were measured using the length-measuring function attached to the Hitachi High-Technologies Corporation "SU1510" scanning electron microscope, on images taken at 3000x and / or 5000x magnification. The lengths were measured for 30 arbitrary protrusions, and the arithmetic mean was taken as the average width of the protrusions.

[0041] (Viscosity of the oil phase) The viscosity of the oil phase, temperature-controlled in a 25°C constant temperature bath, was measured using a tuning fork type vibrating viscometer SV-10 (manufactured by A&D Co., Ltd.). The viscosity displayed on the instrument (unit: mPa·s × g / cm²) 3 The viscosity of the mixture (unit: mPa·s) was determined by dividing the value of the mixture by the density of the oil phase. The density of the oil phase was determined by adding 25 mL of the oil phase to a pycnometer and dividing the weight of the added oil phase (g) by the volume of the pycnometer (mL).

[0042] (Example 1: Hollow particle having an internal structure in which multiple protrusions are connected) A mixture (oil phase) (viscosity 0.69 mPa·s) was prepared by mixing and dissolving 100 g of methyl methacrylate (MMA) as a vinyl monofunctional monomer, 100 g of ethylene glycol dimethacrylate (EGDMA) as a vinyl crosslinkable monomer, 150 g of cyclohexane (CH) and 50 g of ethyl acetate (EA) as non-reactive solvents, 2 g of 2,2'-azobis(2,4-dimethylvaleronitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.; product name V-65) as a polymerization initiator, and 0.16 g of lauryl phosphate as a dispersion aid. (Monomer:solvent = 50:50, MMA:EGDMA = 50:50, CH:EA = 75:25). In addition, an aqueous medium (aqueous phase) was prepared by mixing 1200 g of deionized water as an aqueous medium and 24 g of magnesium pyrophosphate as a suspension stabilizer. The above oil phase was added to this aqueous phase, and emulsification and dispersion were performed for 5 minutes at 5500 rpm using a Polytron homogenizer PT10-35 (manufactured by Central Science Trading Co., Ltd.). The resulting emulsion was placed in a 2 L pressure vessel with a stirring blade, and polymerization was carried out by heating at 50°C for 4 hours while stirring with the blade at 250 rpm. After that, the reaction system was cooled to room temperature, and the suspension stabilizer, magnesium pyrophosphate, was decomposed with hydrochloric acid. The solid components were separated by dehydration by filtration, and after purification by repeated washing with water, hollow particles were obtained by drying at 100°C. Figure 1 shows surface photographs (3000x magnification) and cross-sectional photographs (3000x and 1000x magnification) of the obtained hollow particles. It was confirmed that the hollow particles had multiple protrusions on the inner wall of the shell, and that the multiple protrusions on the inner wall of the shell were interconnected. The volume-average particle diameter was 13.1 μm. The average width of the protrusions was 0.75 μm, and the W / V ratio was 0.057.

[0043] (Example 2: Hollow particles with a more complex interconnected internal structure than in Example 1) Hollow particles were obtained in the same manner as in Example 1, except that 140 g of cyclohexane and 60 g of ethyl acetate were used as non-reactive solvents (monomer:solvent = 50:50, MMA:EGDMA = 50:50, CH:EA = 70:30, viscosity of oil phase 0.68 mPa·s). Figure 1 shows surface photographs (3000x magnification) and cross-sectional photographs (3000x and 1000x magnification) of the obtained hollow particles. It was confirmed that the hollow particles had multiple protrusions on the inner wall of the shell, and that the multiple protrusions on the inner wall of the shell had a structure in which they were interconnected. The volume-average particle diameter was 9.7 μm. The average width of the protrusions was 0.49 μm, and the W / V ratio was 0.051.

[0044] (Example 3: Modified crosslinkable monomer ratio, hollow particles having an internal structure with multiple interconnected protrusions) Hollow particles were obtained in the same manner as in Example 1, except that 90 g of methyl methacrylate (MMA) was used as the vinyl monofunctional monomer and 110 g of ethylene glycol dimethacrylate (EGDMA) was used as the vinyl crosslinkable monomer (monomer:solvent = 50:50, MMA:EGDMA = 45:55, CH:EA = 75:25, viscosity of oil phase = 0.68 mPa·s). Surface photographs (3000x magnification) and cross-sectional photographs (3000x and 1000x magnification) of the obtained hollow particles are shown in Figure 1. It was confirmed that the hollow particles had multiple protrusions on the inner wall of the shell, and that the multiple protrusions on the inner wall of the shell had a structure in which they were interconnected. The volume-average particle diameter was 9.8 μm. The average width of the protrusions was 0.68 μm, and the W / V ratio was 0.070.

[0045] (Example 4: Changed crosslinkable monomer ratio, hollow particles with a more complexly linked internal structure than in Example 3) Hollow particles were obtained in the same manner as in Example 3, except that 140 g of cyclohexane and 60 g of ethyl acetate were used as non-reactive solvents (monomer:solvent = 50:50, MMA:EGDMA = 45:55, CH:EA = 70:30, viscosity of oil phase = 0.68 mPa·s). Surface photographs (3000x magnification) and cross-sectional photographs (3000x and 1000x magnification) of the obtained hollow particles are shown in Figure 1. It was confirmed that the hollow particles had multiple protrusions on the inner wall of the shell, and that the multiple protrusions on the inner wall of the shell had a structure in which they were interconnected. The volume-average particle diameter was 9.9 μm. The average width of the protrusions was 0.37 μm, and the W / V ratio was 0.037.

[0046] (Example 5: Change in dispersing agent) Hollow particles were obtained in the same manner as in Example 3, except that the lauryl phosphate used as a dispersant was replaced with 0.40 g of "KAYAMER(registered trademark) PM-21" (manufactured by Nippon Kayaku Co., Ltd.) (monomer:solvent = 50:50, MMA:EGDMA = 45:55, CH:EA = 75:25, viscosity of oil phase 0.68 mPa·s). Surface photographs (3000x magnification) and cross-sectional photographs (3000x and 1000x magnification) of the obtained hollow particles are shown in Figure 2. It was confirmed that the hollow particles had multiple protrusions on the inner wall of the shell, and that the multiple protrusions on the inner wall of the shell had a structure in which they were interconnected. The volume-average particle diameter was 10.2 μm. The average width of the protrusions was 0.86 μm, and the W / V ratio was 0.084.

[0047] (Example 6: Using a single solvent) Hollow particles were obtained in the same manner as in Example 1, except that methyl methacrylate (MMA) was used as a vinyl monofunctional monomer, ethylene glycol dimethacrylate (EGDMA) as a vinyl crosslinkable monomer, 2.4 g of 2,2'-azobis(2,4-dimethylvaleronitrile) as an initiator, and 160 g of cyclohexane as a non-reactive solvent, with ethyl acetate not being used (monomer:solvent = 60:40, MMA:EGDMA = 45:55, cyclohexane used alone, oil phase viscosity 0.68 mPa·s). Surface photographs (3000x magnification) and cross-sectional photographs (3000x and 1000x magnification) of the obtained hollow particles are shown in Figure 2. It was confirmed that the hollow particles had multiple protrusions on the inner wall of the shell, and that the multiple protrusions on the inner wall of the shell had a structure in which they were interconnected. The volume-average particle diameter was 9.9 μm. The average width of the protrusions was 1.11 μm, and the W / V ratio was 0.112.

[0048] (Example 7: Hollow particles with a more complex interconnected internal structure than in Example 6, using a single solvent) Hollow particles were obtained in the same manner as in Example 1, except that methyl methacrylate (MMA) was used as a vinyl monofunctional monomer, ethylene glycol dimethacrylate (EGDMA) as a vinyl crosslinkable monomer, 2.5 g of 2,2'-azobis(2,4-dimethylvaleronitrile) as an initiator, and 150 g of cyclohexane as a non-reactive solvent, with ethyl acetate not being used (monomer:solvent = 62:38, MMA:EGDMA = 45:55, cyclohexane used alone, oil phase viscosity 0.67 mPa·s). Surface photographs (3000x magnification) and cross-sectional photographs (3000x and 1000x magnification) of the obtained hollow particles are shown in Figure 2. It was confirmed that the hollow particles had multiple protrusions on the inner wall of the shell, and that the multiple protrusions on the inner wall of the shell had a structure in which they were interconnected. The volume-average particle diameter was 11.4 μm. The average width of the protrusions was 0.61 μm, and the W / V ratio was 0.054.

[0049] (Example 8: Change in dispersing agent) Hollow particles were obtained in the same manner as in Example 7, except that 0.40 g of "KAYAMER® PM-21" (manufactured by Nippon Kayaku Co., Ltd.) was used as the dispersing agent (monomer:solvent = 65:35, MMA:EGDMA = 45:55, CH / EA = 100 / 0, viscosity of oil phase 0.67 mPa·s). Surface photographs (3000x magnification) and cross-sectional photographs (3000x and 1000x magnification) of the obtained hollow particles are shown in Figure 2. It was confirmed that the hollow particles had multiple protrusions on the inner wall of the shell, and that the multiple protrusions on the inner wall of the shell had a structure in which they were interconnected. The volume-average particle diameter was 11.5 μm. The average width of the protrusions was 0.76 μm, and the W / V ratio was 0.066.

[0050] (Example 9: Using a thickener, using a single solvent) Reference example Hollow particles were obtained in the same manner as in Example 1, except that 90 g of methyl methacrylate (MMA) was used as a vinyl monofunctional monomer, 110 g of ethylene glycol dimethacrylate (EGDMA) was used as a vinyl crosslinkable monomer, and 200 g of cyclohexane was used as a non-reactive solvent, ethyl acetate was not used, and 16 g of hydrophobic fumed silica R972 (EVONIK) was added as a thickener (monomer:solvent = 50:50, MMA:EGDMA = 45:55, cyclohexane used alone). The viscosity of the oil phase was 1.73 mPa·s. Surface photographs (3000x magnification) and cross-sectional photographs (3000x and 1000x magnification) of the obtained hollow particles are shown in Figure 3. It was confirmed that the hollow particles had multiple protrusions on the inner wall of the shell, and that the multiple protrusions on the inner wall of the shell had a structure in which they were interconnected. The volume-average particle diameter was 11.7 μm. The average width of the protrusions was 0.58 μm, and the W / V ratio was 0.050.

[0051] (Comparative Example 1: Internal structure without protrusions, single hollow particle) A mixture (oil phase) was prepared by mixing and dissolving 100g of DVB-810 (Nippon Steel Chemical Co., Ltd., divinylbenzene mixture), a mixture of vinyl monofunctional monomers and vinyl crosslinkable monomers, 100g of hexadecane as a non-reactive solvent, and 2g of benzoyl peroxide (BPO) as a polymerization initiator (monomer:solvent = 50:50). In addition, an aqueous medium (aqueous phase) was prepared by mixing 590g of ion-exchanged water as an aqueous medium and 10g of polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Co., Ltd.; product name Gosenol GL-05) as a suspension stabilizer. The above oil phase was added to this aqueous phase, and emulsification and dispersion were performed at 6000 rpm for 5 minutes using a Polytron homogenizer PT10-35 (Central Science Trading Co., Ltd.). The resulting emulsion was placed in a 1 L glass container with a stirring blade, and polymerization was carried out by heating at 70°C for 24 hours under a nitrogen atmosphere while stirring with the blade at 100 rpm. After that, the reaction system was cooled to room temperature, and the solid components of the resulting dispersion were separated by dehydration by filtration. Polyvinyl alcohol, which acts as a suspension stabilizer, was removed by repeated washing with water, and then hexadecane, which acts as a non-reactive solvent, was removed by repeated washing with ethanol. After that, hollow particles were obtained by drying at 100°C. Surface photographs (3000x magnification) and cross-sectional photographs (3000x and 1000x magnification) of the obtained particles are shown in Figure 3. Many of the hollow particles had smooth inner shell walls without protrusions, confirming that they were single hollow particles. The volume-average particle diameter was 14.5 μm. In this specification, "smooth" means that the W / V ratio is less than 0.01.

[0052] (Comparative Example 2: Porous shell, porous particle) Particles were obtained in the same manner as in Example 1, except that cyclohexane was not used as a non-reactive solvent and 200 g of ethyl acetate was used (monomer:solvent = 50:50, MMA:EGDMA = 50:50, ethyl acetate alone used, viscosity of oil phase 0.65 mPa·s). Surface photographs (3000x magnification) and cross-sectional photographs (3000x magnification) of the obtained particles are shown in Figure 3. It was confirmed that the hollow particles did not have a clear shell and were porous particles. The volume-average particle diameter was 10.2 μm.

[0053] (Comparative Example 3: Hollow particles with a more complexly interconnected internal structure than in Example 2) Particles were obtained in the same manner as in Example 1, except that 100 g of methyl methacrylate (MMA) was used as a vinyl monofunctional monomer, 100 g of ethylene glycol dimethacrylate (EGDMA) was used as a vinyl crosslinkable monomer, and 120 g of cyclohexane and 80 g of ethyl acetate were used as non-reactive solvents (monomer:solvent = 50:50, MMA:EGDMA = 50:50, CH:EA = 60:40, viscosity of oil phase 0.68 mPa·s). Figure 3 shows a surface photograph (3000x) and a cross-sectional photograph (3000x) of the obtained particles. It was confirmed that the hollow particles had multiple protrusions on the inner wall of the shell, and that the multiple protrusions on the inner wall of the shell had a structure in which they were interconnected. The volume-average particle diameter was 12.1 μm. The average width of the protrusions was 0.23 μm, and the W / V ratio was 0.019. Table 1 summarizes the raw materials used to produce the particles in the above examples and comparative examples, as well as the amount used (g).

[0054] [Table 1]

[0055] (Evaluation of reflection characteristics of ultraviolet, visible, and near-infrared light) To 10g of commercially available water-based paint (Asahi Paint Co., Ltd., product name: Water-based Multipurpose Color Clear), 2.5g each of the particles obtained from the examples and comparative examples were added, and the mixture was defoamed and stirred using a planetary agitator and defoamer (KURABO Co., Ltd., Mazelstar KK-250) to prepare the paint for evaluation. The evaluation coating was applied to the black side of the opacity test paper using an applicator set to a wet thickness of 250 μm, and then thoroughly dried at room temperature to obtain a sample plate for light reflectivity evaluation. The reflectance of the sample plate to ultraviolet light, visible light, and near-infrared light was evaluated in the following order. A Shimadzu UV-3600Plus ultraviolet-visible-near-infrared spectrophotometer was used to measure reflectance, and the reflectance characteristics of the coated surface of the sample plate in the ultraviolet to near-infrared range (wavelength 300-2500 nm) were measured as reflectance (%). The measurements were performed using a 60 mmΦ integrating sphere and barium sulfate as the standard white plate. The above measurements were performed on the particles of the examples and comparative examples. The results obtained are shown in Figure 4. Figure 4 also shows the results for the case without particle addition. Furthermore, the reflectance at a wavelength of 1500 nm is shown in Table 2.

[0056] [Table 2]

[0057] Figure 4 and Table 2 show that the hollow particles of the example have a higher reflectivity than the comparative particles at almost all wavelengths from ultraviolet to near-infrared light. In particular, they exhibit high reflectivity in the wavelength range of 500 to 2500 nm. This confirms that the hollow particles of the example have the property of reflecting visible light and near-infrared light, and impart high visible light to near-infrared light reflection performance to the paint. Furthermore, it can be confirmed that the hollow particles in the examples impart higher visible light to near-infrared light reflectivity to the paint compared to the porous particles without a shell in Comparative Example 2. Furthermore, it can be confirmed that the particles in the example impart higher visible light to near-infrared light reflection performance to the paint compared to the particles in Comparative Example 3, where the W / V ratio, calculated from the average width (W) of multiple protrusions on the inner wall of the shell and the volume-average particle diameter (V) of the hollow particles, was less than 0.02.

[0058] (Coating composition manufacturing example 1) Two parts by weight of the hollow particles obtained in Example 1 and 20 parts by weight of a commercially available acrylic water-based gloss paint (manufactured by Kanpe Papio Co., Ltd., product name Super Hit) were mixed for 3 minutes using a stirring and defoaming device, and then defoamed for 1 minute to obtain a paint composition. The obtained coating composition was applied to an ABS resin (acrylonitrile-butadiene-styrene resin) plate using a coating apparatus equipped with a blade with a clearance of 75 μm, and then dried to obtain a coating film.

[0059] (Example 1 of manufacturing a light-diffusing composition and light-diffusing film) A light-diffusing composition was obtained by mixing 7.5 parts by weight of the hollow particles obtained in Example 1 with 30 parts by weight of acrylic resin (DIC Corporation, product name Acrydic A811), 10 parts by weight of crosslinking agent (DIC Corporation, product name VM-D), and 50 parts by weight of butyl acetate as a solvent using a stirring and defoaming apparatus for 3 minutes and then defoaming for 1 minute. The obtained light-diffusing composition was applied to a 125 μm thick PET film using a coating apparatus equipped with a blade with a clearance of 50 μm, and then dried at 70°C for 10 minutes to obtain a light-diffusing film.

[0060] (Example of cosmetic formulation) (Combination example 1) Powder foundation manufacturing ·Containing amount 10.0 parts by weight of hollow particles obtained in Example 1 Red iron oxide 3.0 parts by weight Yellow iron oxide 2.5 parts by weight 0.5 parts by weight of black iron oxide Titanium oxide 10.0 parts by weight Mica 20.0 parts by weight Talc 44.0 parts by weight Liquid paraffin 5.0 parts by weight Octyldodecyl myristate 2.5 parts by weight Vaseline 2.5 parts by weight Preservative (appropriate amount) Fragrance (appropriate amount) ·Manufacturing method Hollow particles, red iron oxide, yellow iron oxide, black iron oxide, titanium dioxide, mica, and talc are mixed in a Henschel mixer. A mixture of liquid paraffin, octyldodecyl myristate, petrolatum, and a preservative is added and mixed until uniform. Fragrance is added and mixed, then the mixture is ground and sieved. This is then compressed and molded into a metal tray to obtain powder foundation.

[0061] (Combination example 2) Manufacturing of cosmetic lotions ·Containing amount 10.0 parts by weight of hollow particles obtained in Example 1 Stearic acid 2.5 parts by weight Cetyl alcohol 1.5 parts by weight Vaseline 5.0 parts by weight Liquid paraffin 10.0 parts by weight Polyethylene (10 mol) monooleate ester 2.0 parts by weight Polyethylene glycol 1500 3.0 parts by weight Triethanolamine 1.0 part by weight Purified water 64.5 parts by weight Fragrance 0.5 part by weight Preservatives: Appropriate amount and manufacturing method First, stearic acid, cetyl alcohol, petrolatum, liquid paraffin, and polyethylene monooleate are heated and dissolved, then hollow particles are added and mixed, and the mixture is kept warm at 70°C (oil phase). Also, polyethylene glycol and triethanolamine are added to purified water, heated and dissolved, and the mixture is kept warm at 70°C (aqueous phase). The oil phase is added to the aqueous phase, preliminary emulsification is performed, then the mixture is homogenized uniformly, and after emulsification, it is cooled to 30°C while stirring to obtain a cosmetic emulsion.

Claims

1. A non-porous shell and an air space partitioned by the shell, wherein the shell has a plurality of protrusions on its inner wall, and the plurality of protrusions are hollow particles connected to one another. The hollow particles have a W / V ratio of 0.03 to 0.3 (where W is the average width of multiple protrusions ranging from 0.3 to 1.0 μm, and V is the volume-average particle diameter of the hollow particles ranging from 1.0 to 50 μm), and do not contain silica. The method for producing hollow particles involves adding 2.5 g of the hollow particles to 10 g of a transparent aqueous paint containing 35-45% by mass of silicone acrylic resin, 1.8% by mass of diethylene glycol monomethyl ether, and 50-60% by mass of water, with a density of 1.04 g / mL at 23°C, and stirring to remove foam to obtain a paint; coating the obtained paint onto the black side of opacity test paper with an applicator set to a wet thickness of 250 μm; drying at room temperature to obtain a sample plate; and measuring the reflectance (%) of the coated surface of the obtained sample plate from ultraviolet to near-infrared light (wavelength 300-2500 nm) using a UV-Vis-Near-Infrared spectrophotometer, a 60 mmΦ integrating sphere, and barium sulfate on a standard white plate, and determining that the reflectance at a wavelength of 1500 nm is 50% or more. The process includes polymerizing a mixture containing a vinyl monofunctional monomer, a vinyl crosslinkable monomer, a non-reactive solvent, and a polymerization initiator in an aqueous medium containing a suspension stabilizer in the presence of a dispersion aid. The dispersing agent is at least one selected from lauryl phosphate, polyoxyethylene (1) lauryl ether phosphate, dipolyoxyethylene (2) alkyl ether phosphate, dipolyoxyethylene (4) alkyl ether phosphate, dipolyoxyethylene (6) alkyl ether phosphate, dipolyoxyethylene (8) alkyl ether phosphate, dipolyoxyethylene (4) nonylphenyl ether phosphate, caprolactone EO modified phosphate dimethacrylate, and 2-methacryloyloxyethyl acid phosphate (where (number) means the number of oxyethylene repeats and EO means ethylene oxide). The suspension stabilizer is at least one selected from phosphates selected from calcium phosphate, magnesium phosphate, aluminum phosphate, and zinc phosphate; pyrophosphates selected from calcium pyrophosphate, magnesium pyrophosphate, aluminum pyrophosphate, and zinc pyrophosphate; and poorly water-soluble inorganic compounds selected from calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, and barium sulfate. A method for producing hollow particles, characterized by the following:

2. The method for producing hollow particles according to claim 1, wherein the amount of the nonreactive solvent added is 40 to 250 parts by weight with respect to 100 parts by weight of the total monomers of the vinyl monofunctional monomer and the vinyl crosslinkable monomer.

3. A method for producing hollow particles according to claim 1 or 2, wherein the shell is made of a crosslinked resin.

4. A method for producing hollow particles according to any one of claims 1 to 3, wherein the crosslinked resin is derived from a vinyl monofunctional monomer and a vinyl crosslinkable monomer, and the vinyl monofunctional monomer and the vinyl crosslinkable monomer are (meth)acrylic acid esters.

5. A method for producing hollow particles according to any one of claims 1 to 4, wherein the hollow particles have the property of reflecting visible light and near-infrared light.

6. A method for producing hollow particles according to any one of claims 1 to 5, wherein the hollow particles are used in applications selected from paint compositions, cosmetics, paper coating compositions, heat insulating compositions, light diffusing compositions, and light diffusing films.

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