JP2024050739A - Hollow particle and production method of the same - Google Patents

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

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 the shell that constitutes the hollow particle, and a method for producing the same. The hollow particles of the present invention are suitable for use in coating compositions, cosmetics, paper coating compositions, heat insulating compositions, light diffusing compositions, light diffusing films, etc.

Polymer particles having an internal air space (hollow particles) are used in a wide variety of fields for the purposes of reducing the weight of materials, providing pores, and imparting heat insulation, sound insulation, impact resistance, and the like.
It is known that the hollow particles scatter visible light due to the difference in refractive index between the shell and the air space partitioned by the shell, and have better light diffusion properties than polymer particles (solid particles) that do not have air spaces inside. For this reason, hollow particles have the effect of improving opacity, whiteness, gloss, etc., and are used as light diffusing agents in paints, paper coating compositions, cosmetics, sunscreen creams, etc. In particular, in recent years, from the perspective of energy saving, the application of heat-shielding paints and heat-insulating paints to the roofs of buildings has been considered, and the use of hollow particles with excellent light scattering properties as a material for improving heat-shielding and heat-insulating properties has been considered.
As hollow particles, the particles described in JP 2002-080503 A (Patent Document 1) have been proposed. In addition, WO 2002/072671 A (Patent Document 2) and JP 2017-082152 A (Patent Document 3) have proposed hollow particles whose internal morphology is made porous to improve mechanical strength.

JP 2002-080503 A International Publication No. 2002/072671 JP 2017-082152 A

The hollow particles described in Patent Document 1 do not have sufficient light scattering due to the airspace, and in particular the diffusion of visible light to near-infrared light is insufficient. As a result, they do not have sufficient performance as a material for improving heat insulation. Furthermore, the hollow particles described in Patent Documents 2 and 3 have improved light scattering compared to Patent Document 1, but the diffusion of near-infrared light is insufficient. Therefore, hollow particles with improved light diffusion have been demanded.

Thus, according to the present invention, there is provided a hollow particle having a non-porous shell and a space defined by the shell, the shell having a plurality of protrusions on an inner wall thereof, the plurality of protrusions being connected to each other,
The hollow particles are characterized in that they have a W/V ratio of 0.02 to 0.5 (W is the average width of a plurality of protrusions, and V is the volume average particle diameter of the hollow particles).
According to the present invention, there is also provided a method for producing the hollow particles, comprising the steps of:
The present invention provides a method for producing hollow particles, which comprises a 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 dispersing aid.

According to the present invention, hollow particles having excellent light diffusibility (particularly, light scattering properties of visible light and near infrared light) can be provided.
Furthermore, in any of the following cases, hollow particles having better light diffusing properties can be provided.
(1) The hollow particles have a volume average particle diameter of 1.0 to 50 μm, and the shell is composed of a crosslinked resin.
(2) The crosslinked resin is derived from a vinyl-based monofunctional monomer and a vinyl-based crosslinkable monomer, and the vinyl-based monofunctional monomer and the vinyl-based 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 an application selected from a coating composition, a cosmetic, a paper coating composition, a heat insulating composition, a light diffusing composition, and a light diffusing film.

1 shows surface photographs (3000x) and cross-sectional photographs (3000x and 1000x) of hollow particles of Examples 1 to 4. 1 shows surface photographs (3000x) and cross-sectional photographs (3000x and 1000x) of hollow particles of Examples 5 to 8. Photographs of the surface (3000x magnification) and cross-sections (3000x and 1000x magnification for Comparative Example 1, and 3000x magnification for Comparative Examples 1 and 2) of hollow particles of Example 9 and Comparative Examples 1 to 3. 1 is a graph showing the light reflectance for each wavelength of a coating film containing each hollow particle of Examples and Comparative Examples in an evaluation of ultraviolet, visible and near-infrared light reflection characteristics.

(Hollow particles)
The hollow particles have a non-porous shell and an air space defined by the shell. The shell has a plurality of protrusions on its inner wall. The protrusions are connected to each other.

(1) Shell The material constituting the shell is not particularly limited as long as it can partition the air space. The material may contain a crosslinked resin. The material may not contain an inorganic component (e.g., silica).
The type of the crosslinked resin is not particularly limited as long as it can form the shell. Examples of the crosslinked resin include resins derived from vinyl monomers, specifically, resins derived from vinyl monofunctional monomers and vinyl crosslinkable monomers. The vinyl monofunctional monomer is a monomer having one vinyl group, and the vinyl crosslinkable monomer is a monomer having two or more vinyl groups. The fact that the shell is made of a crosslinked resin can be confirmed, for example, by measuring the gel fraction.
Examples of vinyl-based monofunctional monomers include alkyl (meth)acrylic acid esters having 1 to 16 carbon atoms, 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, N-vinylcarbazole; and styrene-based monomers, such as styrene, α-methylstyrene, paramethylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, and bromostyrene. These monofunctional monomers can be used alone or in combination.

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 alone or in combination.
The vinyl monofunctional monomer and the vinyl crosslinkable monomer are preferably (meth)acrylic esters.

The component derived from the vinyl-based crosslinkable monomer is preferably contained in the shell in a ratio of 20 parts by weight or more per 100 parts by weight of the component derived from the vinyl-based monofunctional monomer. If the amount of the component derived from the crosslinkable monomer is less than 20 parts by weight, a shell with 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.

(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 number of protrusions in contact with the inner wall of the shell can be two or more on the cross section of the hollow particle, and can be in the range of 2 to 1600. In addition, the plurality of protrusions are connected to each other between adjacent protrusions. The mutual connection can be confirmed by a cross-sectional photograph of the hollow particle.
The protrusions have a W/V ratio (W is the average width of a plurality of protrusions, and V is the volume average particle diameter of the hollow particles) of 0.02 to 0.5 relative to the volume average particle diameter of the hollow particles. If W/V is less than 0.02 or more than 0.5, the light diffusibility 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. Although it depends 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 from 0.1 to 2.0 μm, preferably from 0.2 to 1.5 μm, and more preferably from 0.3 to 1.0 μm.
The projections may be made of the same material as the shell.

(3) Shape, etc. The shape of the hollow particles is not particularly limited, but it is preferable that the shape is as close to a sphere 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 more 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. Since the shell is non-porous, the hollow particles can maintain the air space even when used for various purposes, and the light diffusion properties of the hollow particles can be exhibited. For example, the non-porousness can be confirmed by checking whether the resin for fixing the hollow particles is present in the air space when taking a cross-sectional photograph of the hollow particles.
Within the voids, there may be particle agglomerates consisting of a plurality of particles connected to one another. The particle agglomerates of hollow particles may be connected to adjacent protrusions.

(Method of manufacturing hollow particles)
The method for producing hollow particles includes a step of polymerizing a mixture containing a vinyl-based monofunctional monomer, a vinyl-based crosslinkable monomer, a non-reactive solvent, and a polymerization initiator in an aqueous medium containing a suspension stabilizer in the presence of a dispersing aid (polymerization step).

(1) Polymerization Step In the polymerization step, a vinyl-based monofunctional monomer and a vinyl-based crosslinkable monomer are polymerized, and the resulting polymer is collected at the interface with the aqueous medium to obtain hollow particles.
In the polymerization step, first, at least a vinyl-based monofunctional monomer, a vinyl-based crosslinkable monomer, a non-reactive solvent, and a polymerization initiator are mixed to obtain a mixture. Note that the amount of the monomer used is substantially equal to the content of the monomer-derived component constituting the outer shell.
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 alone or in combination. The boiling point of the non-reactive solvent is preferably less than 100° C., since it is easy to remove from the hollow particles.
The amount of the non-reactive solvent to be added is not particularly limited, but is 40 to 250 parts by weight relative to 100 parts by weight of the total monomer. If the amount is less than 40 parts by weight, the proportion of the air space partitioned by the shell decreases, and the light diffusion property may become insufficient. If the amount exceeds 250 parts by weight, the shell is not sufficiently formed, and particles having sufficient physical strength may not be obtained.

Polymerization of the monomers is carried out in the presence of a polymerization initiator. The polymerization initiator is not particularly limited, and examples thereof include 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, dimethyl bis(tert-butylperoxy)hexane, dimethyl bis(tert-butylperoxy)hexyne-3, bis(tert-butylperoxyisopropyl)benzene, bis(tert-butylperoxy)trimethylcyclohexane, butyl-bis(tert-butylperoxy)valerate, 2-ethylhexaneperoxy acid tert-butyl, dibenzoyl peroxide, paramenthane hydroperoxide, and tert-butyl peroxybenzoate,
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(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 Examples of the polymerization initiator include azo compounds such as 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-carbonitrile), dimethyl-2,2'-azobis(2-methylpropionate), dimethyl-2,2'-azobisisobutyrate, dimethyl-2,2'-azobis(2-methylpropionate), 2-(carbamoylazo)isobutyronitrile, and 4,4'-azobis(4-cyanovaleric acid). These polymerization initiators can be used alone or in combination.
The polymerization initiator is preferably contained in the mixture in an amount of 0.05 to 5 parts by weight based on 100 parts by weight of the total monomers.
Next, the dispersed mixture is polymerized to obtain hollow particles. The polymerization is not particularly limited, and is carried out while appropriately adjusting various conditions such as polymerization temperature and polymerization time depending on the types 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 thickener may be added to the mixture. Examples of the thickener include organic thickeners such as acrylic thickeners, urethane thickeners, polyether thickeners, polyvinyl alcohols, and cellulose derivatives. Examples of the inorganic thickener include hydrophobic fumed silica and clay minerals. Only one type of these thickeners may be added, or two or more types may be added.

The mixture is added to an aqueous medium containing a suspension stabilizer.
Examples of the aqueous medium constituting the aqueous medium include water and mixtures of water and water-soluble organic solvents (for example, lower alcohols such as methanol and ethanol).
Examples of the suspension stabilizer 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. The suspension stabilizers can be used alone 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 all monomers and 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 commensurate with the amount used is not obtained, which is uneconomical in terms of cost, and is not preferred.

The polymerization is carried out in the presence of a dispersing aid, which may be present in the mixture or in the aqueous medium.
Examples of the dispersion aid 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 dimethacrylate phosphate, and 2-methacryloyloxyethyl acid phosphate. (Number) means the number of oxyethylene repeats. EO means ethylene oxide.
The amount of the dispersion aid to be added is not particularly limited, but is 0.0001 to 0.5 parts by weight based on 100 parts by weight of the mixture of all monomers and the non-reactive solvent. If the amount is less than 0.0001 part by weight, the mixture may not be sufficiently dispersed. If the amount exceeds 0.5 part by weight, the shell may not be formed.

The inventors believe that the hollow particles of the present invention having a unique shape can be appropriately produced by controlling the interfacial tension acting on the interface between the mixture (oil phase) and the aqueous medium (aqueous phase). For example, when the interfacial tension is large, the number of protrusions tends to decrease and/or the size of the protrusions tends to increase. On the other hand, when the interfacial tension is small, 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 the total monomer to the non-reactive solvent, the amount of the dispersant, and the amount of the dispersion aid.
In addition, the inventors believe that the hollow particles of the present invention having a unique shape can also be appropriately produced 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 having 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 so as to obtain hollow particles having a desired particle size.
(2) Other Steps The hollow particles can be taken out from the aqueous medium through centrifugation, washing with water and drying, if necessary.

(Application)
The hollow particles can be used in applications such as coating compositions, cosmetics, paper coating compositions, heat insulating compositions, light diffusing compositions, and light diffusing films.

(1) Paint, heat insulating and light diffusing composition These compositions contain, as necessary, a binder resin, a UV curable resin, a solvent, etc. As the binder resin, a resin soluble in an organic solvent or water, or an emulsion-type water-based resin dispersible in water can be used.
The amount of binder resin or UV curable resin and hollow particles added varies depending on the thickness of the coating film to be formed, 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 based on the total amount of the binder resin (solid content when an emulsion-type aqueous resin is used) and the hollow particles. The more preferred content is 10 to 50% by weight, and the even more preferred content is 20 to 40% by weight.
Examples of the binder resin include acrylic resin, alkyd resin, polyester resin, polyurethane resin, chlorinated polyolefin resin, and amorphous polyolefin resin. Examples of the UV-curable resin 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.

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. Specific examples of polyhydric alcohol polyfunctional (meth)acrylate resins having three or more (meth)acryloyl groups in one molecule include trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, 1,2,4-cyclohexane tetra(meth)acrylate, pentaglycerol triacrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol triacrylate, dipentaerythritol pentaacrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol triacrylate, and tripentaerythritol hexaacrylate, and may be used alone or in combination of two or more.

When a UV-curable resin is used, a photopolymerization initiator is usually used in combination. The photopolymerization initiator is not particularly limited.
Examples of the photopolymerization initiator include acetophenones, benzoins, benzophenones, phosphine oxides, ketals, α-hydroxyalkylphenones, α-aminoalkylphenones, anthraquinones, thioxanthones, azo compounds, peroxides (described in JP-A No. 2001-139663, etc.), 2,3-dialkyldione compounds, disulfide compounds, fluoroamine compounds, aromatic sulfonium compounds, 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 coating material to the substrate to be coated, the environment in which the coating material is used, and the like.

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, 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 can be used. For water-based paints, water, alcohols, etc. can be used. These solvents may be used alone or in combination of two or more. The solvent content in the coating material is usually about 20 to 60% by weight based on the total amount of the composition.

The composition may contain, as necessary, known coating surface conditioners, flowability conditioners, ultraviolet absorbers, light stabilizers, curing catalysts, extender pigments, coloring pigments, metal pigments, mica powder pigments, dyes, etc.
The method of forming a coating film using the composition is not particularly limited, and any known method can be used. For example, spray coating, roll coating, brush coating, and other methods, and coating reverse roll coating, gravure coating, die coating, comma coating, and spray coating methods can be used to coat a substrate such as a film as a thin layer. The composition may be diluted to adjust the viscosity as necessary. 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 alone or in combination of two or more.
The coating film can be formed by applying the coating composition to any coating surface of a substrate, drying the coating film, and then curing the coating film as necessary. The coating film using the coating composition is used by coating various substrates, including but not limited to metal, wood, glass, plastics, etc. The coating composition can also be used by coating transparent substrates such as polyethylene terephthalate (hereinafter abbreviated as PET), polyethylene carbonate (hereinafter abbreviated as PC), and acrylic.

(2) Cosmetics The cosmetics preferably contain hollow particles in the range of 1 to 40% by weight.
Examples of cosmetics include cleansing cosmetics such as soap, body shampoo, facial cleansing cream, and facial scrub cleanser; lotions, creams, milky lotions, face packs, powders, foundations, lipstick, lip balm, blush, eyebrow cosmetics, nail polish, hair washing cosmetics, hair dyes, hair styling products, aromatic cosmetics, toothpaste, bath additives, antiperspirants, sunscreen products, tanning products, body cosmetics such as body powder and baby powder; and lotions such as shaving cream, pre-shave lotion, after-shave lotion, and body lotion.

In addition, ingredients commonly used in cosmetics can be blended according to purpose, so 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, moisturizers, surfactants, polymeric compounds, coloring materials, fragrances, preservatives and germicides, antioxidants, ultraviolet absorbers, and specially blended ingredients.
Examples of oils, fats, and waxes include avocado oil, almond oil, olive oil, cacao butter, beef tallow, sesame oil, wheat germ oil, safflower oil, shea butter, turtle oil, camellia oil, persic oil, castor oil, grape oil, macadamia nut oil, mink oil, egg yolk oil, Japan wax, coconut oil, rosehip oil, hardened oil, silicone oil, orange roughy oil, carnauba wax, candelilla wax, whale wax, jojoba oil, montan wax, beeswax, and lanolin.
Examples of the hydrocarbons include liquid paraffin, petrolatum, paraffin, ceresin, microcrystalline wax, squalane, etc. Examples of the higher fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, behenic acid, undecylenic acid, oxystearic acid, linoleic acid, lanolin fatty acid, and synthetic fatty acids.

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 cyclic alcohol fatty acid esters such as 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, tri(caprylic/capric acid)glycerin, propylene glycol dioleate, glyceryl triisostearate, glyceryl triisooctanoate, cetyl lactate, myristyl lactate, diisostearyl malate, cholesteryl isostearate, and cholesteryl 12-hydroxystearate.

Examples of the metal soap include zinc laurate, zinc myristate, magnesium myristate, zinc palmitate, zinc stearate, aluminum stearate, calcium stearate, magnesium stearate, and zinc undecylenate.
Examples of moisturizing agents 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 the surfactant include anionic surfactants such as higher fatty acid soaps, higher alcohol sulfates, N-acylglutamates, and phosphate salts; cationic surfactants such as amine salts and quaternary ammonium salts; amphoteric surfactants such as betaine, amino acid, imidazoline, 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.

Examples of polymer compounds include natural polymer compounds such as gum arabic, gum tragacanth, 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, cross-linked polystyrene particles, silicone particles, urethane particles, polyethylene particles, and silica particles.

Coloring materials include inorganic pigments such as iron oxide, ultramarine, konjou, chromium oxide, chromium hydroxide, carbon black, manganese violet, titanium oxide, 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.

Here, the powder raw materials such as the polymer compounds and coloring raw materials may be surface-treated in advance. Conventional surface treatment techniques can be used as the surface treatment method. For example, oil treatment with hydrocarbon oil, ester oil, lanolin, etc., silicone treatment with dimethylpolysiloxane, methylhydrogenpolysiloxane, methylphenylpolysiloxane, etc., fluorine compound treatment with perfluoroalkyl group-containing ester, perfluoroalkylsilane, perfluoropolyether, polymer having perfluoroalkyl group, etc., silane coupling agent treatment with 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, etc., titanium coupling agent treatment with isopropyltriisostearoyltitanate, isopropyltris(dioctylpyrophosphate)titanate, etc., metal soap treatment, amino acid treatment with acylglutamic acid, etc., lecithin treatment with hydrogenated egg yolk lecithin, etc., collagen treatment, polyethylene treatment, moisture retention treatment, inorganic compound treatment, mechanochemical treatment, etc. can be mentioned.

Examples of the fragrance include natural fragrances such as lavender oil, peppermint oil, lime oil, etc., and synthetic fragrances such as ethyl phenyl acetate, geraniol, p-tert-butylcyclohexyl acetate, etc. Examples of the preservative/bactericide include methylparaben, ethylparaben, propylparaben, benzalkonium, benzethonium, etc.
Examples of the antioxidant include dibutylhydroxytoluene, butylhydroxyanisole, propyl gallate, tocopherol, etc. Examples of the ultraviolet absorbing agent include inorganic absorbing agents such as fine titanium oxide, fine zinc oxide, fine cerium oxide, fine iron oxide, fine zirconium oxide, etc., and organic absorbing agents such as benzoic acid, paraaminobenzoic acid, anthranilic acid, salicylic acid, cinnamic acid, benzophenone, dibenzoylmethane, etc.

Specially formulated ingredients include hormones such as estradiol, estrone, ethinyl estradiol, 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, aluminum chlorhydroxyl allantoin, zinc paraphenolsulfonate, and zinc sulfate; hair growth promoters such as cantharides tincture, capsicum tincture, ginger tincture, Swertia japonica extract, garlic extract, hinokitiol, carpronium chloride, pentadecanoic acid glyceride, vitamin E, estrogen, and photosensitizers; and skin whitening agents such as magnesium L-ascorbyl phosphate and kojic acid.

(3) Light Diffusion Film The light diffusion film is a film in which a light diffusion layer is formed by the light diffusion composition on the surface of a substrate such as a plastic sheet, a plastic film, a plastic lens, a plastic panel, etc., such as glass, polycarbonate, acrylic resin, PET, triacetyl cellulose (TAC), etc., a cathode ray tube, a fluorescent display tube, a liquid crystal display panel, etc. Depending on the application, the coating is formed alone or on the substrate in combination with a protective film, a hard coat film, a flattening film, a high refractive index film, an insulating film, a conductive resin film, a conductive metal fine particle film, a conductive metal oxide fine particle film, or other primer film used as necessary. Note that when used in combination, the light diffusion layer does not necessarily have to be formed on the outermost surface.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these. First, the measurement methods used in the examples will be described.
(Volume average particle size)
The volume average particle diameter of the hollow particles was measured by a Coulter Multisizer ^™ 3 (a measuring device manufactured by Beckman Coulter, Inc.) using an aperture calibrated according to the Multisizer ^™ 3 User's Manual published by Beckman Coulter, Inc.
The aperture used for the measurement was appropriately selected such that, when the assumed volume average particle diameter of the particles to be measured was 1 μm or more and 10 μm or less, an aperture having a size of 50 μm was selected, when the assumed volume average particle diameter of the particles to be measured was more than 10 μm and 30 μm or less, an aperture having a size of 100 μm was selected, when the assumed volume average particle diameter of the particles was more than 30 μm and 90 μm or less, an aperture having a size of 280 μm was selected, when the assumed volume average particle diameter of the particles was more than 90 μm and 150 μm or less, an aperture having a size of 400 μm was selected, etc. If the volume average particle diameter after measurement was different from the assumed volume average particle diameter, the aperture was changed to an aperture having an appropriate size and the measurement was performed again.

In addition, when an aperture having a size of 50 μm was selected, Current (aperture current) was set to −800 and Gain was set to 4. When an aperture having a size of 100 μm was selected, Current (aperture current) was set to −1600 and Gain was set to 2. When apertures having sizes of 280 μm and 400 μm were selected, Current (aperture current) was set to −3200 and Gain was set to 1.
The measurement sample was prepared by dispersing 0.1 g of particles in 10 ml of a 0.1 wt % aqueous solution of a nonionic surfactant using a touch mixer (manufactured by Yamato Scientific Co., Ltd., "TOUCHMIXER MT-31") and an ultrasonic cleaner (manufactured by Vervoclear, "ULTRASONICCLEANER VS-150") to prepare a dispersion. During the measurement, the inside of the beaker was gently stirred to an extent that no air bubbles were introduced, and the measurement was terminated when 100,000 particles were measured. The volume average particle diameter of the particles was taken as the arithmetic average in the volume-based particle size distribution of 100,000 particles.

(Morphological Observation)
Conductive tape was attached to the sample stage, and the particles were placed on the tape. The particles were coated using a sputtering device "Auto Fine Coater JFC-1300" manufactured by JEOL Ltd. The particles were then photographed using a secondary electron detector of a scanning electron microscope "SU1510" manufactured by Hitachi High-Technologies Corporation.

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

(Average width of multiple protrusions)
During the above cross-sectional observation, the lengths of the protrusions arising from the shell were measured using images taken at 3000x and/or 5000x magnification, using a length measurement function attached to a scanning electron microscope "SU1510" manufactured by Hitachi High-Technologies Corporation. Length measurements were performed on 30 random protrusions, and the arithmetic average value was taken as the average width of the protrusions.

(Viscosity of Oil Phase)
The viscosity of the oil phase, whose temperature was adjusted in a thermostatic bath at 25°C, was measured using a tuning fork type vibration viscometer SV-10 (manufactured by A&D Co., Ltd.). The viscosity value displayed on the device (unit: mPa·s×g/cm ³ ) was divided by the density of the oil phase to determine the viscosity of the mixed liquid (unit: mPa·s). The density of the oil phase was determined by adding the oil phase to a 25 mL pycnometer and dividing the weight (g) of the added oil phase by the capacity (mL) of the pycnometer.

(Example 1: Hollow particles having an internal structure in which multiple protrusions are connected)
100g of methyl methacrylate (MMA) as a vinyl monofunctional monomer, 100g of ethylene glycol dimethacrylate (EGDMA) as a vinyl crosslinkable monomer, 150g of cyclohexane (CH) and 50g of ethyl acetate (EA) as non-reactive solvents, 2g of 2,2'-azobis (2,4-dimethylvaleronitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.; product name V-65) as a polymerization initiator, and 0.16g of lauryl phosphoric acid as a dispersion aid were mixed and dissolved to prepare a mixture (oil phase) (viscosity 0.69 mPa s) (monomer: solvent = 50: 50, MMA: EGDMA = 50: 50, CH: EA = 75: 25). In addition, 1200g of ion-exchanged water as an aqueous medium and 24g of magnesium pyrophosphate as a suspension stabilizer were mixed to prepare an aqueous medium (aqueous phase).
The oil phase was added to this aqueous phase, and emulsification and dispersion treatment was 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 2L pressure vessel equipped with an agitator, and polymerization was allowed to proceed by heating at 50°C for 4 hours while stirring with the agitator at 250 rpm. Thereafter, the reaction system was cooled to room temperature, and the suspension stabilizer magnesium pyrophosphate was decomposed with hydrochloric acid. The solid content was separated by dehydration through filtration, purified by repeated washing with water, and then dried at 100°C to obtain hollow particles.
The surface photograph (3000x) and cross-sectional photograph (3000x and 1000x) of the obtained hollow particles are shown in Figure 1. It was confirmed that the hollow particles had a plurality of protrusions on the inner wall of the shell, and the plurality of protrusions on the inner wall of the shell had a structure in which they were connected to each other. The volume average particle size was 13.1 μm. The average width of the protrusions was 0.75 μm, and W/V was 0.057.

(Example 2: Hollow particles having a more complicated internal structure than 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). Surface photographs (3000x) and cross-sectional photographs (3000x and 1000x) of the obtained hollow particles are shown in FIG. 1. It was confirmed that the hollow particles had a plurality of protrusions on the inner wall of the shell, and that the plurality of protrusions on the inner wall of the shell had a structure in which they were connected to each other. The volume average particle size was 9.7 μm. The average width of the protrusions was 0.49 μm, and W/V was 0.051.

(Example 3: Changing the crosslinkable monomer ratio, hollow particles having an internal structure in which multiple protrusions are connected)
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 cross-linking monomer (monomer:solvent=50:50, MMA:EGDMA=45:55, CH:EA=75:25, viscosity of oil phase 0.68 mPa·s). Surface photographs (3000x) and cross-sectional photographs (3000x and 1000x) of the obtained hollow particles are shown in FIG. 1. It was confirmed that the hollow particles had a plurality of protrusions on the inner wall of the shell, and that the plurality of protrusions on the inner wall of the shell had a structure in which they were connected to each other. The volume average particle size was 9.8 μm. The average width of the protrusions was 0.68 μm, and W/V was 0.070.

(Example 4: Change in crosslinkable monomer ratio, hollow particles having a more complicated internal structure than 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) and cross-sectional photographs (3000x and 1000x) of the obtained hollow particles are shown in FIG. 1. It was confirmed that the hollow particles had a plurality of protrusions on the inner wall of the shell, and that the plurality of protrusions on the inner wall of the shell had a structure in which they were connected to each other. The volume average particle size was 9.9 μm. The average width of the protrusions was 0.37 μm, and W/V was 0.037.

(Example 5: Change of dispersing agent)
Hollow particles were obtained in the same manner as in Example 3, except that lauryl phosphoric acid as a dispersing agent was changed to 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) and cross-sectional photographs (3000x and 1000x) of the obtained hollow particles are shown in FIG. 2. It was confirmed that the hollow particles had a plurality of protrusions on the inner wall of the shell, and that the plurality of protrusions on the inner wall of the shell had a structure in which they were connected to each other. The volume average particle size was 10.2 μm. The average width of the protrusions was 0.86 μm, and W/V was 0.084.

Example 6: Use of a single solvent
Hollow particles were obtained in the same manner as in Example 1, except that 108 g of methyl methacrylate (MMA) was used as a vinyl monofunctional monomer, 132 g of ethylene glycol dimethacrylate (EGDMA) was used as a vinyl crosslinkable monomer, 2.4 g of 2,2'-azobis(2,4-dimethylvaleronitrile) was used as an initiator, and 160 g of cyclohexane was used as a non-reactive solvent, and no ethyl acetate was used (monomer:solvent=60:40, MMA:EGDMA=45:55, cyclohexane was used alone, viscosity of oil phase was 0.68 mPa·s). Surface photographs (3000x) and cross-sectional photographs (3000x and 1000x) of the obtained hollow particles are shown in FIG. 2. It was confirmed that the hollow particles had a structure in which a plurality of protrusions on the inner wall of the shell were connected to each other. The volume average particle size was 9.9 μm. The average width of the protrusions was 1.11 μm, and W/V was 0.112.

(Example 7: Use of a single solvent, hollow particles having a more complicated internal structure than Example 6)
Hollow particles were obtained in the same manner as in Example 1, except that 112.5 g of methyl methacrylate (MMA) was used as a vinyl monofunctional monomer, 137.5 g of ethylene glycol dimethacrylate (EGDMA) was used as a vinyl crosslinkable monomer, 2.5 g of 2,2'-azobis (2,4-dimethylvaleronitrile) was used as an initiator, and 150 g of cyclohexane was used as a non-reactive solvent, and no ethyl acetate was used (monomer:solvent=62:38, MMA:EGDMA=45:55, cyclohexane was used alone, viscosity of oil phase was 0.67 mPa·s). Surface photographs (3000x) and cross-sectional photographs (3000x and 1000x) of the obtained hollow particles are shown in FIG. 2. It was confirmed that the hollow particles had a structure in which a plurality of protrusions on the inner wall of the shell were connected to each other. The volume average particle size was 11.4 μm. The average width of the protrusions was 0.61 μm, and W/V was 0.054.

(Example 8: Change of dispersing agent)
Hollow particles were obtained in the same manner as in Example 7, except that 0.40 g of "KAYAMER (registered trademark) PM-21" (manufactured by Nippon Kayaku Co., Ltd.) lauryl phosphoric acid was used as a 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) and cross-sectional photographs (3000x and 1000x) of the obtained hollow particles are shown in FIG. 2. It was confirmed that the hollow particles had a plurality of protrusions on the inner wall of the shell, and that the plurality of protrusions on the inner wall of the shell had a structure in which they were connected to each other. The volume average particle size was 11.5 μm. The average width of the protrusions was 0.76 μm, and W/V was 0.066.

(Example 9: Use of thickener, use of single solvent) Reference Example 90 g of methyl methacrylate (MMA) as a vinyl monofunctional monomer, 110 g of ethylene glycol dimethacrylate (EGDMA) as a vinyl crosslinkable monomer, 200 g of cyclohexane as a non-reactive solvent, no ethyl acetate, and 16 g of hydrophobic fumed silica R972 (EVONIK) as a thickener were used, but hollow particles were obtained in the same manner as in Example 1 (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) and cross-sectional photographs (3000x and 1000x) of the obtained hollow particles are shown in FIG. 3. It was confirmed that the hollow particles had a structure in which a plurality of protrusions on the inner wall of the shell were connected to each other. The volume average particle size was 11.7 μm. The average width of the protrusions was 0.58 μm, and W/V was 0.050.

(Comparative Example 1: Internal structure without protrusions, single hollow particle)
A mixture (oil phase) was prepared by mixing and dissolving 100 g of DVB-810 (Nippon Steel Chemical Co., Ltd., divinylbenzene mixture) as a mixture of vinyl monofunctional monomers and vinyl crosslinkable monomers, 100 g of hexadecane as a non-reactive solvent, and 2 g of benzoyl peroxide (BPO) as a polymerization initiator (monomer:solvent=50:50).Furthermore, an aqueous medium (aqueous phase) was prepared by mixing 590 g of ion-exchanged water as an aqueous medium and 10 g of polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., product name Gohsenol GL-05) as a suspension stabilizer.
The oil phase was added to this aqueous phase, and emulsification and dispersion treatment was performed for 5 minutes at 6000 rpm using a Polytron homogenizer PT10-35 (manufactured by Central Science Trading Co., Ltd.). The obtained emulsion was placed in a 1 L glass container with stirring blades, and polymerization was allowed to proceed by heating at 70 ° C. for 24 hours while stirring the stirring blades at 100 rpm under a nitrogen atmosphere. Thereafter, the reaction system was cooled to room temperature, and the obtained dispersion was dehydrated by filtration to separate the solid content, and the polyvinyl alcohol as a suspension stabilizer was removed by repeatedly washing with water, and then the hexadecane as a non-reactive solvent was removed by repeatedly washing with ethanol. Then, hollow particles were obtained by drying at 100 ° C. Surface photographs (3000 times) and cross-sectional photographs (3000 times and 1000 times) of the obtained particles are shown in FIG. 3. It was confirmed that many hollow particles had no protrusions on the inner shell wall and were smooth, and were single hollow particles. The volume average particle size was 14.5 μm. In this specification, "smooth" means that W/V is less than 0.01.

(Comparative Example 2: Porous Shell, Porous Particles)
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 was used, viscosity of oil phase was 0.65 mPa·s). A surface photograph (3000 times) and a cross-sectional photograph (3000 times) of the obtained particles are shown in FIG. 3. It was confirmed that the hollow particles did not have a clear shell and were porous particles. The volume average particle size was 10.2 μm.

(Comparative Example 3: Hollow particles having a more complicated internal structure than 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). A surface photograph (3000 times) and a cross-sectional photograph (3000 times) of the obtained particle are shown in FIG. 3. It was confirmed that the hollow particles had a plurality of protrusions on the inner wall of the shell, and that the plurality of protrusions on the inner wall of the shell had a structure in which they were connected to each other. The volume average particle size was 12.1 μm. The average width of the protrusions was 0.23 μm, and W/V was 0.019.
The raw materials used in the production of the particles in the above Examples and Comparative Examples and the amounts (g) used are summarized in Table 1.

(Evaluation of UV, visible and near infrared light reflection characteristics)
To 10 g of a commercially available water-based paint (trade name: Water-based Multi-Purpose Color Clear, manufactured by Asahipen Co., Ltd.), 2.5 g of the particles obtained in each of the Examples and Comparative Examples were added, and the mixture was defoamed and stirred using a planetary mixing defoamer (MAZERSTAR KK-250, manufactured by KURABO Corporation) to prepare a paint for evaluation.
The paint for evaluation was applied to the black side of the hiding power test paper with an applicator set to a wet thickness of 250 μm, and then thoroughly dried at room temperature to obtain a sample plate for evaluating light reflectivity. The reflectance of the sample plate to ultraviolet light, visible light, and near infrared light was evaluated in the following order of points.
The reflectance was measured using a Shimadzu UV-3600Plus ultraviolet-visible near-infrared spectrophotometer, and the reflectance characteristics of the coated surface of the sample plate from ultraviolet light to near-infrared light (wavelength 300 to 2500 nm) were measured as reflectance (%). The measurements were performed using a 60 mmΦ integrating sphere and barium sulfate as a standard white plate.
The above measurements were carried out for the particles of the examples and the comparative examples. The results are shown in Figure 4. The results for the case where no particles were added are also shown in Figure 4. Furthermore, the reflectance at a wavelength of 1500 nm is shown in Table 2.

4 and Table 2, it can be seen that the hollow particles of the examples have a higher reflectance than the particles of the comparative examples in almost all wavelengths from ultraviolet light to near infrared light. In particular, it can be seen that they have a high reflectance in the wavelength range of 500 to 2500 nm. This confirms that the hollow particles of the examples have the property of reflecting visible light and near infrared light, and impart high light reflecting performance from visible light to near infrared light to the paint.
It can also be confirmed that the hollow particles of the Examples impart higher light reflectance from visible light to near infrared light to the paint than the porous particles of Comparative Example 2 that do not have a shell.
Furthermore, it can be confirmed that the particles of the examples impart high light reflecting performance from visible light to near infrared light to the paint, compared to the particles of Comparative Example 3, in which the W/V ratio calculated from the average width (W) of the 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.

(Paint composition production example 1)
A coating composition was obtained by mixing 2 parts by weight of the hollow particles obtained in Example 1 and 20 parts by weight of a commercially available acrylic water-based glossy coating material (manufactured by Campe Papio, product name Super Hit) for 3 minutes using a stirring and defoaming device and defoaming for 1 minute.
The resulting coating composition was applied onto an ABS resin (acrylonitrile-butadiene-styrene resin) plate using a coating device equipped with a blade with a clearance of 75 μm, and then dried to obtain a coating film.

(Light-diffusing composition and light-diffusing film manufacturing example 1)
7.5 parts by weight of the hollow particles obtained in Example 1, 30 parts by weight of an acrylic resin (manufactured by DIC Corporation, product name ACRYDIC A811), 10 parts by weight of a crosslinking agent (manufactured by DIC Corporation, product name VM-D), and 50 parts by weight of butyl acetate as a solvent were mixed for 3 minutes using a stirring and defoaming device and defoamed for 1 minute to obtain a light diffusing composition.
The obtained light diffusing composition was applied onto a PET film having a thickness of 125 μm using a coating device equipped with a blade having a clearance of 50 μm, and then dried at 70° C. for 10 minutes to obtain a light diffusing film.

(Cosmetic formulation examples)
(Formulation Example 1)
Preparation and blending amount of powder foundation Hollow particles obtained in Example 1 10.0 parts by weight Red iron oxide 3.0 parts by weight Yellow iron oxide 2.5 parts by weight Black iron oxide 0.5 parts by weight 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 Preparation method Hollow particles, red iron oxide, yellow iron oxide, black iron oxide, titanium oxide, mica, and talc are mixed in a Henschel mixer, and a mixture of liquid paraffin, octyldodecyl myristate, vaseline, and preservative is added and mixed uniformly. Fragrance is added and mixed, then crushed and passed through a sieve. This is compression molded into a metal plate to obtain a powder foundation.

(Formulation Example 2)
Preparation and blending amount of cosmetic emulsion Hollow particles obtained in Example 1 10.0 parts by weight 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 moles) monooleate 2.0 parts by weight Polyethylene glycol 1500 3.0 parts by weight Triethanolamine 1.0 parts by weight Purified water 64.5 parts by weight Fragrance 0.5 parts by weight Preservative Appropriate amount and preparation method First, stearic acid, cetyl alcohol, vaseline, liquid paraffin, and polyethylene monooleate are heated and dissolved, and hollow particles are added and mixed thereto, and the mixture is kept at 70°C (oil phase). Polyethylene glycol and triethanolamine are added to purified water, heated and dissolved, and the mixture is kept at 70°C (water phase). The oil phase is added to the water phase, and pre-emulsified, then uniformly emulsified using a homogenizer. After emulsification, the mixture is cooled to 30° C. while stirring to obtain a cosmetic emulsion.

Claims (6)

A hollow particle having a non-porous shell and a space defined by the shell, the shell having a plurality of protrusions on an inner wall thereof, the plurality of protrusions being connected to each other,
The hollow particles have a W/V ratio of 0.02 to 0.5 (W is the average width of a plurality of protrusions, and V is the volume average particle diameter of the hollow particles). The hollow particles according to claim 1, wherein the hollow particles have a volume average particle diameter of 1.0 to 50 μm, and the shell is made of a crosslinked resin. The hollow particles according to claim 2, wherein the cross-linked resin is derived from a vinyl monofunctional monomer and a vinyl cross-linkable monomer, and the vinyl monofunctional monomer and the vinyl cross-linkable monomer are (meth)acrylic acid esters. The hollow particles according to any one of claims 1 to 3, wherein the hollow particles have the property of reflecting visible light and near infrared light. The hollow particles according to any one of claims 1 to 4, which are used for an application selected from a coating composition, a cosmetic, a paper coating composition, a heat insulating composition, a light diffusing composition, and a light diffusing film. A method for producing hollow particles according to any one of claims 1 to 5,
A method for producing hollow particles, comprising a step of polymerizing a mixture containing a vinyl-based monofunctional monomer, a vinyl-based 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.