Resin particles

Abstract

To provide a resin particle that has superior light diffusibility, a high specific gravity, and a reduced tendency to float even in low-viscosity liquid.SOLUTION: A resin particle comprises a resin polymerized from one or more polymerizable monomers comprising a polymerizable unsaturated bond, wherein the particle comprise one or more internal pores, and at least one of the one or more pores comprises a particle therein.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to resin particles. [Background technology]

[0002] Spherical resin particles are used as light reflectors in paints, cosmetics, etc., and as light diffusing materials in light diffusion plates for liquid crystal backlights, etc. Among these, hollow resin particles having pores inside the particles have superior light diffusing properties compared to solid resin particles without pores, and are therefore suitable for the above applications.

[0003] The following methods are known as methods for producing hollow resin particles. A method of using a combination of an oil-based surfactant and a water-soluble surfactant in suspension polymerization to complete polymerization while keeping water trapped within the monomer droplets before polymerization (Patent Document 1). A method using a special polymer surfactant (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 59-193901 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-238792 Summary of the Invention [Problem to be solved by the invention]

[0005] However, existing hollow resin particles have a problem in that they have a low specific gravity due to their hollowness, and when dispersed in a low-viscosity liquid, they tend to float due to the difference in specific gravity. An object of the present invention is to provide resin particles that have excellent light diffusibility, a high specific gravity, and are unlikely to float up even in a low-viscosity liquid. [Means for solving the problem]

[0006] The present invention has the following aspects. [1] The resin is composed of one or more polymerizable monomers having a polymerizable unsaturated bond, A resin particle having one or more pores formed therein, with a particle residing in at least one of the one or more pores. [2] The resin particles according to [1], wherein the one or more polymerizable monomers include a (meth)acrylate monomer, and the ratio of the (meth)acrylate monomer to the total mass of the one or more polymerizable monomers is 50 mass% or more. [3] Specific gravity is 0.8 g / cm 3 The resin particles according to [1] or [2] above. [4] The resin particles according to any one of [1] to [3] above, which have an average particle size of 1.0 to 200 μm. [5] Resin particles according to any one of [1] to [4] above, which have a haze of 50 to 90% as measured by the following measurement method. Measurement method: 2.0 g of the resin particles and 45 g of a 40% by mass toluene solution of a resin having the same refractive index as the resin constituting the resin particles are placed in a glass bottle and mixed for 30 minutes using a shaker. The resulting dispersion is applied to a 1 mm thick glass plate using an applicator with a gap of 150 μm, dried at 100°C for 10 minutes, and the haze of the resulting test piece is measured. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide resin particles that have excellent light diffusibility, a high specific gravity, and are unlikely to float up even in a low-viscosity liquid. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a schematic cross-sectional view of a resin particle according to one embodiment. [Figure 2] 1 is an electron microscope photograph of the surface of the resin particles obtained in Example 1. [Figure 3] 1 is an electron microscope photograph of a cross section of a resin particle obtained in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described below based on preferred embodiments. In the present invention, "(meth)acrylate" is a general term for methacrylate and acrylate. "(meth)acryloyl" is a general term for methacryloyl and acryloyl. "(meth)acrylic acid" is a general term for methacrylic acid and acrylic acid. "(meth)acrylonitrile" is a general term for methacrylonitrile and acrylonitrile. "(meth)acrylamide" is a general term for methacrylamide and acrylamide.

[0010] FIG. 1 is a schematic cross-sectional view of a resin particle 1 according to one embodiment of the present invention. As shown in Fig. 1, one or more pores 3 are provided inside a resin particle 1. Furthermore, a particle 5 is present in at least one of the one or more pores 3. The resin particles 1, including the particles 5, are made of a resin obtained by polymerizing one or more polymerizable monomers. The resin will be described in detail later.

[0011] The shape of each of the resin particles 1 and the particles 5 is not particularly limited, and may be, for example, spherical, ellipsoidal, irregular, or the like. The particles 5 may or may not be fixed to the walls of the pores 3. The number of particles 5 present in one pore 3 may be one or two or more. The pores 3 may or may not be in communication with the outside of the resin particle 1.

[0012] Although FIG. 1 shows an example in which a plurality of pores 3 are provided inside the resin particle 1, the number of pores 3 may be one. From the viewpoint of light diffusion, the number of holes 3 is preferably 2 or more, more preferably 5 or more, and even more preferably 10 or more. The number of pores 3 is measured by observing the cross section of the resin particle with an electron microscope. Note that pores 3 that exist separately in the cross section, even if they are connected to each other in parts other than the cross section observed with the electron microscope, are counted as different pores 3.

[0013] When preparing a test piece for cross-sectional observation of resin particle 1, some particles 5 fall out of holes 3, making it difficult to accurately calculate the proportion of particles 5 contained inside resin particle 1. On the other hand, the specific gravity of resin particle 1 is considered sufficient to infer the presence of particles 5 present in holes 3. The closer the value obtained by dividing the specific gravity of resin particle 1 by the specific gravity of the resin that constitutes resin particle 1 (specific gravity of resin particle 1 / specific gravity of resin that constitutes resin particle 1) is to 1, the higher the proportion of particles 5 contained inside resin particle 1 is considered to be. The ratio of the specific gravity of resin particle 1 to the specific gravity of the resin constituting resin particle 1 is preferably 0.5 or more, more preferably 0.7 or more, from the viewpoints of specific gravity and strength. The ratio of the specific gravity of resin particle 1 to the specific gravity of the resin constituting resin particle 1 is typically less than 1, and from the viewpoint of light diffusion, is preferably 0.95 or less.

[0014] The diameter of the pores 3 in the resin particles 1 is not particularly limited, but is preferably 5 to 40% of the particle size of the resin particles 1 from the viewpoint of light diffusibility. The diameter of the pores 3 and the particle size of the resin particles 1 are measured by observing the cross section of the resin particles with an electron microscope. When a plurality of pores 3 are provided inside the resin particle 1, the diameter of the pore 3 is the diameter of each of the plurality of pores 3. Pores having diameters less than 5% or more than 40% of the particle diameter of the resin particle 1 may also coexist.

[0015] Since one or more pores 3 are provided inside the resin particle 1, the specific gravity of the resin particle 1 is lower than the specific gravity of the resin that constitutes the resin particle 1. The specific gravity of the resin is generally 0.9 to 1.2 g / cm 3 is within the range. On the other hand, particles that have pores inside them, generally called hollow particles, have a cavity inside them, and therefore have an extremely low specific gravity compared to ordinary resins. Since the particle 5 is present in at least one pore 3 of the resin particle 1, the specific gravity of the resin particle 1 is higher than when the particle 5 is not present. From the viewpoint of dispersion stability of the resin particle 1 in a low-viscosity liquid, the specific gravity of the resin particle 1 is set to 0.8 g / cm. 3More than 0.9 g / cm is preferable. 3 The above is more preferable.

[0016] The average particle size of the resin particles 1 is preferably 1.0 to 200 μm from the viewpoint of light diffusibility. The average particle size of the resin particles 1 is a volume-based value measured by a laser diffraction particle size distribution measuring device.

[0017] The haze of the resin particles 1 measured by the following measurement method is preferably 50 to 90%, more preferably 70 to 90%. If the haze is 50% or more, the light diffusion property is superior, and if it is 90% or less, the light transmittance is superior. Measurement method: 2.0 g of resin particles and 45 g of a 40% by mass toluene solution of a resin with a refractive index equivalent to that of the resin that makes up the resin particles are placed in a glass bottle and mixed for 30 minutes using a shaker. The resulting dispersion is applied to a 1 mm thick glass plate using an applicator with a gap of 150 μm, dried at 100°C for 10 minutes, and the haze of the resulting test piece is measured. Haze is measured using a haze meter.

[0018] <Resin> The resin constituting the resin particles 1 is obtained by polymerizing one or more polymerizable monomers. The polymerizable monomer has a polymerizable unsaturated bond, such as a polymerizable carbon-carbon double bond or a polymerizable carbon-carbon triple bond. Examples of the polymerizable monomer include (meth)acrylate monomers, aromatic vinyl monomers, and other polymerizable monomers.

[0019] Examples of the (meth)acrylate monomer include monofunctional (meth)acrylates having one (meth)acryloyl group and polyfunctional (meth)acrylates having two or more (meth)acryloyl groups.

[0020] Examples of monofunctional (meth)acrylates include alkyl (meth)acrylates, alkoxyalkyl (meth)acrylates, (meth)acrylates having an alicyclic structure, and (meth)acrylates having a functional group.

[0021] Examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, and octyl (meth)acrylate. Examples of alkoxyalkyl (meth)acrylates include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-(n-propoxy)ethyl (meth)acrylate, 2-(n-butoxy)ethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 2-(n-propoxy)propyl (meth)acrylate, and 2-(n-butoxy)propyl (meth)acrylate. Examples of the (meth)acrylate having an alicyclic structure include cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and isobornyl (meth)acrylate.

[0022] In the (meth)acrylate having a functional group, examples of the functional group include an amino group, a hydroxy group, a carboxy group, a polyoxyalkylene group, and an epoxy group. Examples of the (meth)acrylate having an amino group include dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate. Examples of the (meth)acrylate having a hydroxy group include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and glycerin mono(meth)acrylate. Examples of the (meth)acrylate having a polyoxyalkylene group include polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, and polyethylene glycol-polypropylene glycol mono(meth)acrylate. Examples of the (meth)acrylate having an epoxy group include glycidyl (meth)acrylate.

[0023] Examples of polyfunctional (meth)acrylates include (poly)ethylene glycol di(meth)acrylates having an added mole number of ethylene oxide (EO) of 1 to 9, alkylene glycol di(meth)acrylates having an alkylene group with 4 to 9 carbon atoms, and trimethylolpropane tri(meth)acrylate.

[0024] Examples of aromatic vinyl monomers include styrene-based monomers and divinylbenzene, with styrene-based monomers being preferred. Examples of the styrene-based monomer include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene.

[0025] Examples of other polymerizable monomers include (meth)acrylic acid, polymerizable monomers having an amide group, vinyl acetate, vinyl propionate, vinyl chloride, and (meth)acrylonitrile. Examples of the polymerizable monomer having an amide group include (meth)acrylamide, hydroxyethylacrylamide, dimethylacrylamide, diethylacrylamide, isopropylacrylamide, and dimethylaminopropylacrylamide. These polymerizable monomers may be used alone or in combination of two or more.

[0026] The polymerizable monomer preferably contains a (meth)acrylate monomer, since it is easy to obtain the desired structure stably. The proportion of the (meth)acrylate monomer relative to the total mass of the polymerizable monomers is preferably 50% by mass or more, more preferably 70% by mass or more, and may be 100% by mass.

[0027] From the viewpoint of polymerization stability, the (meth)acrylate monomer preferably contains a monofunctional (meth)acrylate. As the (meth)acrylate monomer, a monofunctional (meth)acrylate and a polyfunctional (meth)acrylate may be used in combination. By using a polyfunctional (meth)acrylate, a crosslinked structure is introduced into the resin, improving solvent resistance, heat resistance, etc. A (meth)acrylate monomer and an aromatic vinyl monomer may be used in combination. By using an aromatic vinyl monomer, the compatibility with the resin or solvent that serves as the dispersion medium can be adjusted, and for example, dispersibility in the medium can be improved.

[0028] The ratio of the monofunctional (meth)acrylate, polyfunctional (meth)acrylate, and aromatic vinyl monomer in the polymerizable monomer is not particularly limited, but may be, for example, 20 to 100 mass% of the monofunctional (meth)acrylate, 0 to 30 mass% of the polyfunctional (meth)acrylate, and 0 to 50 mass% of the aromatic vinyl monomer, relative to the total mass of the polymerizable monomers.

[0029] <Method of manufacturing resin particles> The resin particles 1 can be obtained, for example, by adjusting the suspending conditions in a method in which one or more polymerizable monomers are dispersed in an aqueous medium, suspended, and polymerized. For example, resin particles 1 can be produced by a production method including the following steps 1 to 3.

[0030] (Process 1) A W / O (water-in-oil) dispersion (first mixed liquid) is prepared, containing a polymerization initiator, one or more polymerizable monomers, an aqueous medium (first aqueous medium), and a first surfactant, with the one or more polymerizable monomers as a continuous phase and the first aqueous medium as a dispersed phase. Specifically, a mixture of a polymerization initiator, one or more polymerizable monomers, and a first surfactant is prepared, and the mixture is stirred using a stirrer such as a homomixer. A first aqueous medium is dispersed in the stirred mixture to prepare a first mixture. The aqueous medium, the polymerization initiator, and the first surfactant will be described in detail later. If necessary, an additive such as a chain transfer agent may be added to the first mixed liquid.

[0031] (Process 2) After step 1, a mixture (second mixture) of a second surfactant or dispersant and an aqueous medium (second aqueous medium) is added to the first mixture while stirring with a stirrer, thereby causing a phase inversion (dispersed phase inversion) in which the continuous phase is the aqueous medium and the dispersed phase is one or more polymerizable monomers, thereby preparing a W / O / W (water in oil in water) suspension. The aqueous medium, the second surfactant, and the dispersant will be described in detail later. In step 2, when the second mixed liquid is added to the first mixed liquid, the first mixed liquid is stirred using a stirrer equipped with a rotor blade so that the peripheral speed at the tip of the rotor blade (stirring peripheral speed) is 4.3 to 17.6 m / s. By setting the stirring peripheral speed within the above range, the desired structure is easily obtained. The stirring peripheral speed is preferably 5.1 to 16.9 m / s, and more preferably 5.9 to 16.1 m / s. An example of an agitator equipped with a rotor is a high-speed shear disperser.

[0032] (Step 3) After step 2, the suspension is polymerized, thereby producing resin particles 1, and a dispersion in which the resin particles 1 are dispersed in an aqueous medium is obtained. After step 3, the resin particles 1 may be recovered from the dispersion, if necessary. There are no particular limitations on the recovery method, and any known method can be used.

[0033] In this production method, when the aqueous medium is added in two separate steps, it is referred to as the "first aqueous medium" and the "second aqueous medium" to make it easier to understand which step the aqueous medium is added in. The first aqueous medium and the second aqueous medium may be the same or different. The same applies to the surfactant.

[0034] (aqueous medium) The "aqueous medium" is a medium containing water, and may consist of only water, or may further contain an organic solvent within a range that does not impair the objects and effects of the present invention. As the water, known water such as ion-exchanged water can be used. The organic solvent may be any solvent that is miscible with water, and examples thereof include alcohols such as methanol, ethanol, and isopropyl alcohol. The proportion of water relative to the total mass of the aqueous medium is not particularly limited, but may be 50% by mass or more, 70% by mass or more, 90% by mass or more, or even 100% by mass.

[0035] (Polymerization initiator) As the polymerization initiator, known polymerization initiators can be used, and examples thereof include peroxide-based initiators such as benzoyl peroxide and lauroyl peroxide, and oil-soluble azo-based polymerization initiators such as 2,2'-azobis(2-methylbutyronitrile) and 2,2'-azobis(isobutyronitrile).

[0036] The amount of polymerization initiator used may be, for example, 0.05 to 3.0 parts by mass, preferably 0.1 to 2.0 parts by mass, and more preferably 0.2 to 1.5 parts by mass, per 100 parts by mass of the total of one or more polymerizable monomers. If the amount of polymerization initiator used is 0.05 parts by mass or more, the proportion of unreacted polymerizable monomers during polymerization can be reduced. On the other hand, if the amount of polymerization initiator used is 3.0 parts by mass or less, decomposition products of the polymerization initiator can be prevented from remaining as impurities.

[0037] (First surfactant) The first surfactant contains surfactant A represented by the following formula (1). When the first surfactant contains surfactant A, the desired structure is easily obtained. The reason for this is thought to be that when the polymerizable monomer is suspended in the presence of surfactant A at the above-mentioned predetermined stirring peripheral speed, water droplets containing fine droplets of the polymerizable monomer are incorporated into the droplets of the polymerizable monomer. T 1 O-(RO) n (EO) m -T 2 … (1)

[0038] In formula (1), T 1 is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or an alkenyl group having 2 to 18 carbon atoms, and T 2 is a hydrogen atom, a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylate group, a phosphoric acid group, a phosphate group, an amino group, or an ammonium group; RO is an oxyalkylene group having 3 to 18 carbon atoms; n is an integer of 1 to 50; EO is an oxyethylene group; and m is an integer of 0 to 200. T is advantageous in that it can suppress bleeding when surfactants remain in the resin particles. 1 is preferably an alkenyl group.

[0039] Commercially available surfactants A can be used. For example, commercially available anionic surfactants A include Aqualon KH series and Hiteno XJ-630S manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., and Latemul PD-104 manufactured by Kao Corporation. Commercially available nonionic surfactants A include Noigen XL series manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., Latemul-420, 430, 450 manufactured by Kao Corporation, Emulgen LS series, Emulgen MS series, and Emulgen PP series manufactured by Aoki Oil & Fat Co., Ltd., and Finesurf NDB series, IDEP series, Wondersurf NDR series, ID series, and S series manufactured by Aoki Oil & Fat Co., Ltd. The surfactant A may be used alone or in combination of two or more.

[0040] The amount of surfactant A used in step 1 is preferably 0.05 to 5.0 parts by mass per 100 parts by mass of the total of one or more polymerizable monomers. When the amount of surfactant A used is within the above range, resin particles 1 are likely to be formed stably. If the amount of surfactant A used is less than 0.05 parts by mass, the structure will be incomplete, and if it exceeds 5.0 parts by mass, the properties of the resin constituting the resin particles may be impaired.

[0041] The first surfactant may further contain a surfactant different from surfactant A (another surfactant) to the extent that the effects of the present invention are not impaired. As the other surfactant, known surfactants can be used, and examples thereof include the anionic surfactants and cationic surfactants shown below.

[0042] Specific examples of anionic surfactants include higher fatty acid salts such as sodium oleate and sodium stearate; alkyl (or aryl) sulfonates such as sodium dodecylbenzenesulfonate and disodium dodecyldiphenylethersulfonate; alkyl (or alkenyl) sulfates such as sodium lauryl sulfate and sodium oleyl sulfate; polyoxyethylene alkyl (or alkenyl) ether sulfates such as sodium polyoxyethylene lauryl ether sulfate, ammonium polyoxyethylene oleyl ether sulfate, and ammonium polyoxyethylene styrenated phenyl ether sulfate; polyoxyethylene alkylaryl ether sulfates such as sodium polyoxyethylene nonylphenyl ether sulfate; alkyl sulfosuccinate esters such as sodium monooctyl sulfosuccinate, sodium di-2-ethylhexyl sulfosuccinate, sodium dioctyl sulfosuccinate, and sodium polyoxyethylene lauryl sulfosuccinate; and derivatives thereof. These anionic surfactants may be used alone or in combination of two or more.

[0043] Specific examples of cationic surfactants include quaternary ammonium salts such as alkylbenzylmethylammonium salts such as dodecylbenzylmethylammonium chloride, alkyltrimethylammonium salts such as dodecyltrimethylammonium chloride, stearyltrimethylammonium chloride, and cetyltrimethylammonium chloride, dialkyldimethylammonium salts such as didecyldimethylammonium chloride and distearyldimethylammonium chloride, and alkylbenzyldimethylammonium salts such as dodecylbenzyldimethylammonium chlorite. These cationic surfactants may be used alone or in combination of two or more.

[0044] (Second surfactant) The second surfactant is used to improve the stability of the polymerization. The second surfactant is not particularly limited, and for example, surfactant A may be used, or another surfactant may be used, or these may be used in combination. The second surfactant may be used alone or in combination of two or more.

[0045] (dispersant) The dispersant, like the second surfactant, is used for the purpose of improving the stability of the polymerization. Examples of the dispersant include organic dispersants and inorganic dispersants. Examples of organic dispersants include polyvinyl alcohol, cellulose, and polyvinylpyrrolidone. Examples of inorganic dispersants include calcium phosphate tribasic and calcium carbonate. These dispersants may be used alone or in combination of two or more.

[0046] (Other additives) In the present invention, other additives may be used as long as they do not impair the properties of the resin particles. Examples of other additives include chain transfer agents such as organic sulfur compounds, preservatives, and antioxidants. In addition, pigments or dyes for coloring the particles, and metal particles, inorganic fine particles, or organic fine particles for the purpose of modifying the particles may also be added.

[0047] <Action and effect> The resin particle 1 described above has one or more holes 3 inside, and the difference in refractive index between the hole 3 part (air) and the resin part causes light to be scattered at the interface between them, resulting in excellent light diffusion properties. Furthermore, since the resin particle 1 has a particle 5 present in at least one pore 3, its specific gravity is close to that of a solid resin particle without pores 3, and it is less likely to float up even in low-viscosity liquids (aqueous media, low-viscosity organic solvents, low-viscosity resin solutions, etc.).

[0048] Although the resin particles of the present invention have been described above by showing embodiments, the present invention is not limited to the above embodiments. Each configuration and combination thereof in the above embodiments is an example, and addition, omission, substitution, and other modifications of the configuration are possible within the scope of the present invention.

[0049] The use of the resin particles of the present invention is not particularly limited, but for example, they can be used as light reflecting materials or matting materials in paints, cosmetics, etc., and light diffusing materials in light diffusing plates for liquid crystal backlights, etc. For example, when the resin particles of the present invention are incorporated as a light reflecting material or a matting material into a paint or the like, they exhibit an excellent light reflecting effect or a matting effect.When the resin particles of the present invention are incorporated as a light diffusing material into a light diffusing plate for a liquid crystal backlight or the like, they exhibit an excellent light diffusing effect. [Example]

[0050] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. "Parts" means "parts by mass".

[0051] Example 1 (Preparation of Resin Particles) According to the formulation shown in Table 1, resin particles according to Example 1 were prepared. In preparing the resin particles, a suspension was prepared in which the continuous phase consisted of a polymerization initiator, a polymerizable monomer, and a surfactant, and the dispersion layer consisted of water. A mixture of a dispersant and water was added to the suspension while stirring with a stirrer, to obtain a suspension in which the continuous phase consisted of water and the dispersion layer consisted of the polymerizable monomer. Then, polymerization was carried out to obtain the resin particles. The details are as follows. A liquid mixture of 60 parts of methyl methacrylate (MMA), 30 parts of styrene (St), and 10 parts of ethylene glycol dimethacrylate (EGDMA) as polymerizable monomers (100 parts in total), 2.0 parts of Emulgen PP-290 as a surfactant, and 30 parts of water was poured into a container equipped with a homomixer and mixed with the homomixer to obtain a first mixed liquid. Separately, 1.0 part of polyvinyl alcohol as a dispersant and 270 parts of water were mixed to obtain a second mixed liquid. The second mixed liquid was added to the first mixed liquid while stirring at a peripheral stirring speed of 14.7 m / s, thereby obtaining a W / O / W (water in oil in water) suspension. The obtained suspension was placed in a four-neck flask equipped with a stirrer, a condenser, a thermometer, and a nitrogen inlet tube, and the temperature was raised to 75°C under nitrogen encapsulation, and the reaction was carried out for 4 hours at 75°C. Thereafter, the obtained resin particle dispersion was filtered, and the collected resin particles were washed with 500 parts of water and dried at 60°C for 12 hours to recover the resin particles. The recovered resin particles were evaluated as follows.

[0052] (shape) The surface and cross-section of resin particles were observed using a scanning electron microscope (SEM, manufactured by JEOL Ltd.). To observe the cross-section of resin particles, resin particles were dispersed in a UV-curable resin, which was then cured by irradiating it with UV light. The cured material was then cut using a microtome to create sections. As a result, a porous structure was confirmed inside the resin particles, and the presence of pores containing particles within the porous structure was observed. Figure 2 shows a scanning electron microscope photograph of the surface of a resin particle, and Figure 3 shows a scanning electron microscope photograph of the cross section of a resin particle.

[0053] (Average particle size) 0.1 g of the recovered resin particles was mixed with 100 g of a dilute aqueous solution of a surfactant, and the resin particles were dispersed in the medium using an ultrasonic irradiator. The volumetric particle size distribution of the resulting resin particle dispersion was measured using a laser diffraction particle size distribution analyzer (Shimadzu Corporation), and the average particle diameter was determined. The average particle diameter of the resin particles was found to be 3.1 μm.

[0054] (specific gravity) The specific gravity of the resin particles was determined by immersion in methanol, and the results are shown in Table 1. The methanol immersion was carried out according to the following procedure. Five grams of resin particles were weighed out and placed in a 50 mL volumetric flask. Methanol was then added to the volumetric flask, and the volume of the volumetric flask was adjusted to 50 mL while the resin particles were allowed to soak in the methanol. The combined mass (A) of the volumetric flask and its contents was weighed out, and the previously measured tare weight (B) of the volumetric flask and the mass (C) of the resin particles were subtracted from this mass to calculate the mass (D) of the methanol added. The calculated mass (D) of methanol was then added to the specific gravity of methanol at 20°C, 0.792 g / cm. 3 The volume of methanol (E) in the volumetric flask was calculated by dividing by 1. The volume of the contents of the volumetric flask (50 mL) was subtracted by the volume of methanol (E) to calculate the volume of the resin particles (F). The specific gravity of the resin particles was calculated by dividing the mass of the resin particles (C) by the resulting volume of the resin particles (F).

[0055] The value of "specific gravity of resin particles / specific gravity of resin constituting resin particles" was calculated from the specific gravity of the resin particles and the specific gravity of a resin having the same refractive index as the resin component constituting the resin particles. The results are shown in Table 1 as "particle specific gravity / resin specific gravity." In this example, the refractive index of the acrylic component making up the resin particles was set to 1.49 for PMMA, and the refractive index of the styrene component was set to 1.59 for polystyrene. The copolymerization ratio of methyl methacrylate and styrene was calculated so that the refractive index would be equivalent to that of the resin component making up the resin particles, and a copolymer with this copolymerization ratio was produced and used as a resin with a refractive index equivalent to that of the resin component making up the resin particles.

[0056] (Haze) As an index of the light diffusibility of the resin particles, haze was measured by the following procedure. The results are shown in Table 1. 2.0 g of the recovered resin particles and 45 g of a 40% by weight toluene solution of a resin with a refractive index equivalent to that of the resin component constituting the resin particles were placed in a glass bottle and mixed for 30 minutes using a shaker to obtain a resin particle dispersion. The resulting resin particle dispersion was applied to a 1 mm thick glass plate using an applicator with a 150 μm gap and dried at 100 °C for 10 minutes to obtain a test piece. The haze of the obtained test piece was measured using a haze meter (manufactured by Murakami Color Research Laboratory).

[0057] <Examples 2 to 7, Comparative Examples 2 and 4> The same operations as in Example 1 (Preparation of Resin Particles) were carried out, except that the stirring peripheral speed or monomer composition when obtaining the W / O / W type suspension was changed as shown in Table 1, and the obtained resin particles were evaluated in the same manner as in Example 1. The results are shown in Table 1. In Comparative Example 2, the polymer formed agglomerates and was not granulated, so no evaluation was carried out.

[0058] [Table 1]

[0059] The abbreviations in Table 1 represent the following: MMA: methyl methacrylate. nBA: n-butyl acrylate. EMA: ethyl methacrylate. EGDMA: ethylene glycol dimethacrylate. St: styrene. nBMA: n-butyl methacrylate. AMBN: 2,2'-azobis(2-methylbutyronitrile). PP-290: Kao Corporation's "Emulgen PP-290", polyoxyethylene (160) polyoxypropylene (30) glycol, 100% solids. D-3-D: "Emeral D-3-D" manufactured by Kao Corporation, an aqueous solution of sodium polyoxyethylene alkyl ether sulfate, solids content 26%. PVA: Polyvinyl alcohol, average degree of polymerization 3500.

[0060] In Table 1, "porous with particles" in "shape" indicates that a porous structure was confirmed inside the resin particle and that pores containing particles were observed within the porous structure. "Spherical" indicates that the particle has a spherical appearance and no pores exist in the particle cross section.

[0061] The resin particles of Examples 1 to 7 had a high haze of 50% or more on the test pieces and were excellent in light diffusion properties. 3 The viscosity was high, and it was difficult for the particles to float up even in low viscosity liquids. [Explanation of symbols]

[0062] 1 resin particle, 3 holes, 5 particles

Claims

1. The resin is formed by polymerizing one or more polymerizable monomers having a polymerizable unsaturated bond, two or more holes are provided therein, and particles are present in at least one of the two or more holes; the particles are made of a resin obtained by polymerizing one or more polymerizable monomers, The average particle size is 1.0 to 200 μm, Resin particles having a specific gravity of 0.8 g / cm 3 or more.

2. The resin particles according to claim 1, wherein the one or more polymerizable monomers include a (meth)acrylate monomer, and the proportion of the (meth)acrylate monomer to the total mass of the one or more polymerizable monomers is 50 mass% or more.

3. 3. The resin particles according to claim 1, wherein the haze measured by the following measurement method is 50 to 90%. Measurement method: 2.0 g of the resin particles and 45 g of a 40% by mass toluene solution of a resin having the same refractive index as the resin constituting the resin particles are placed in a glass bottle and mixed for 30 minutes using a shaker. The resulting dispersion is applied to a 1 mm thick glass plate using an applicator with a gap of 150 μm, dried at 100° C. for 10 minutes, and the haze of the resulting test piece is measured.

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