Surface-treated spherical strontium titanate microparticle powder, dispersion, and resin composition

Abstract

The present invention is a surface-treated spherical strontium titanate fine particle powder characterized by having an average primary particle diameter of 50 nm or less, being surface-treated with a surface treatment agent having a surface treatment amount of 5-30 wt%, and being a fine spherical shape, thereby enabling a transparent composite film to be obtained. Furthermore, by means of the surface treatment, the solvent affinity of the surface of the microparticles is improved, thereby making it possible to produce a powder, a dispersion, and a resin composition having high dispersion stability, and thus making it possible to provide a clouding-free composite film.

Description

Technical Field

[0001] The object of the present invention is to obtain a surface-treated spherical strontium titanate fine particle powder that is most suitable as a filler. Background Art

[0002] In recent years, with the miniaturization, higher performance, and lighter weight of various electronic devices, there is an increasing demand for organic-inorganic hybrid materials that impart the functionality (refractive index, dielectric constant, electrical conductivity, magnetic properties, thermal conductivity, etc.) of inorganic fillers while maintaining the processability of organic resins.

[0003] For example, brightness-enhancing films used in displays and diffractive optical elements used in AR / MR glass require high refractive indices that cannot be achieved with a single resin component. This is to achieve properties such as high brightness, thin film thickness, and improved viewing angles. Therefore, research is underway to improve the transparency of resin films by adding inorganic fillers with high refractive indices to resins.

[0004] Required properties of inorganic fillers in such hybrid materials include transparency and dispersion stability. To achieve transparency, fine spherical particles with a good particle size distribution are required. Furthermore, dispersion stability requires that the particle surface have solvent affinity.

[0005] On the other hand, strontium titanate is a high-performance material with a perovskite structure, used in a variety of applications on its own. For example, it can be used in optical applications such as pigments with a high refractive index, reflective materials, and light-concentrating materials, or in ceramic capacitors due to its high dielectric constant. Furthermore, strontium titanate can be used in visible light photocatalysts due to its photocatalytic activity, or in semiconductors, semiconductor capacitors, thermoelectric materials, EL, and luminescent materials due to its semiconductor properties when added with other elements.

[0006] By forming a composite with resin, strontium titanate, which has such high functionality, is expected to produce new materials with functionality that cannot be achieved with resin alone.

[0007] As a method for obtaining fine strontium titanate particles, reactions in aqueous systems, such as hydrothermal reactions, are known. However, because the surface of strontium titanate particles is hydrophilic, particles adsorbed with water, which has a strong liquid cross-linking capacity, tend to aggregate. Therefore, when mixed with organic substances such as resins and solvents, interparticle aggregation is likely to occur. This poses problems with the transparency and dispersion stability of composite films formed by coating a composite liquid composed of a mixture of resin and filler.

[0008] There have been various reports on strontium titanate fine particles. Prior art literature Patent Literature

[0009] Patent Document 1: International Publication No. 2019 / 123916 Patent Document 2: Japanese Patent Application Laid-Open No. 2022-58093 Summary of the Invention -Problems to be solved by the invention-

[0010] However, although strontium titanate fine-particle powder suitable for the filler as described above is currently most desired, it has not yet been obtained.

[0011] That is, although the strontium titanate dispersion is described in Patent Document 1, the average particle size is large, 0.1 μm to 10 μm, and is insufficient as a fine particle filler having the transparency of a high refractive index material.

[0012] Furthermore, while Patent Document 2 reports fine, spherical strontium titanate particles, the addition of a third component, such as hydrazine or a hydrazide compound, is necessary. Consequently, the presence of components other than strontium titanate prevents the particles from fully utilizing their filler properties. Furthermore, particles containing the third component outside the specified amount exhibit a large average particle size and poor dispersibility, and there is no mention of the dispersion stability of these particles.

[0013] Therefore, the problem to be solved by the present invention is to produce a spherical and fine strontium titanate fine particle powder suitable for a filler in a composite material, and to achieve both transparency of the composite film and dispersion stability of the dispersion. -Solutions to solve problems--

[0014] The above technical problems can be solved by the present invention as described below.

[0015] Specifically, the present invention provides spherical strontium titanate fine particle powder, characterized in that the spherical strontium titanate fine particle powder has an average primary particle size of 50 nm or less and is surface-treated with a surface treatment agent in an amount of 5 to 30 wt% (Invention 1).

[0016] Furthermore, the present invention is the spherical strontium titanate fine particle powder according to Invention 1, wherein the surface treatment agent is a polymer dispersant (Invention 2).

[0017] Furthermore, the present invention is a dispersion containing the spherical strontium titanate fine particle powder according to Invention 1 (Invention 3).

[0018] Furthermore, the present invention provides a resin composition comprising the spherical strontium titanate fine particle powder according to Invention 1 (Invention 4). -Effects of the Invention-

[0019] According to the present invention, by surface-treating spherical strontium titanate particles, their surface can be modified to have solvent affinity, thereby being dispersed in various solvents. Even after surface treatment, the particles are finely spherical, thus showing transparency and exhibiting little cohesion in the dispersion solvent. Therefore, the composite film containing the particles is transparent and free of turbidity. In addition, the resulting dispersion does not settle over time, and is therefore also suitable for storage and transportation, resulting in an industrially advantageous spherical strontium titanate particle powder that can have both transparency and dispersion stability. DETAILED DESCRIPTION

[0020] The structure of the present invention is described in detail below.

[0021] First, the surface-treated spherical strontium titanate fine particle powder according to the present invention will be described.

[0022] The surface-treated spherical strontium titanate fine particle powder of the present invention has an average primary particle size of 50 nm or less. If the average primary particle size exceeds 50 nm, the coating may become turbid and lack transparency. The average primary particle size is more preferably 40 nm or less, and even more preferably 30 nm or less. The lower limit is not particularly limited, but is approximately 8 nm.

[0023] The surface-treated spherical strontium titanate particle powder of the present invention is obtained by coating and modifying a part or all of the particle surface with a surface treatment agent.

[0024] The surface treatment amount of the surface treatment agent of the present invention is 5 to 30% by weight, more preferably 7 to 27% by weight, and even more preferably 9 to 25% by weight, relative to the spherical strontium titanate fine-particle powder. If the surface treatment amount of the surface treatment agent is less than 5% by weight, the amount of dispersant is insufficient, and the spherical strontium titanate fine-particle powder cannot be fully coated, resulting in a possibility of not achieving dispersion stability. On the other hand, if the surface treatment amount of the surface treatment agent exceeds 30% by weight, the amount of dispersant is excessive, and the dispersant layer may be damaged, resulting in a possibility of not achieving dispersion stability.

[0025] The surface treatment agent of the present invention is not particularly limited, and examples thereof include surfactants, wetting agents, and dispersants. Depending on the compatibility with the dispersion solvent or resin and the intended use, one or more surface treatment agents may be used or a mixture of two or more surface treatment agents may be used. When a coupling agent is used as the surface treatment agent, a hydrolysis step is required to achieve bonding via a chemical reaction. On the other hand, when a surfactant or dispersant is used as the surface treatment agent, the particle surface and the surface treatment agent are hydrogen bonded, and surface adsorption and surface treatment can be performed as long as the particle surface is in contact with the dispersant, which is more preferred.

[0026] The surfactant of the present invention is not particularly limited, and examples thereof include anionic surfactants such as fatty acid salts, sulfates, sulfonates, and phosphates; nonionic surfactants such as polyethylene glycol nonionic surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene aryl ethers, and polyol nonionic surfactants such as sorbitan fatty acid esters; cationic surfactants such as amine salt cationic surfactants and quaternary ammonium salt cationic surfactants; alkyl betaines such as alkyl dimethylaminoacetic acid betaine, and amphoteric surfactants such as alkyl imidazolines.

[0027] Dispersant of the present invention is not particularly limited, and can list polymer dispersants, low molecular weight dispersants etc. Because the molecular weight of dispersant is higher (polymer), then can ensure stable steric hindrance more, easily obtain dispersion stabilization effect, therefore preferably use polymer dispersant.As polymer dispersant, can use the alkanolammonium copolymer containing acid group, acrylic polymer, block copolymer, styrene-acrylic acid copolymer, styrene-maleic acid copolymer, polycarboxylic acid and its salt etc., preferably have the polymer dispersant of the molecular weight 800~2000 or so of acrylic acid group or methacrylic acid group, as structure, preferably block type or graft type polymer.In addition, the polymer dispersant of acid number more than 5 has the tendency with the affinity and reactivity high of this particle surface, so preferred.

[0028] The surface treatment agent has particularly good adsorption properties on the surface of hydrophilic spherical strontium titanate fine particles. It forms steric hindrance by adhering, adsorbing and binding to the surface of the fine particles, thereby suppressing desorption and achieving dispersion stability.

[0029] The particle shape of the surface-treated spherical strontium titanate particle powder described in the present invention is spherical, and its circularity is preferably above 0.80. As long as the circularity of the particles is within the above range, the surface treatment can be uniformly performed with a small amount of surface treatment agent. In addition, since the filling property of solvents, resins, etc. is also good, it is suitable as a filler. The more preferred circularity is above 0.85, and further preferably 0.88 to 1.00. It should be noted that the circularity is determined by (4v×area) / perimeter of the particles measured by electron microscope photographs. 2 express.

[0030] Next, the spherical strontium titanate fine-particle powder before surface treatment of the present invention will be described.

[0031] The average primary particle size of the spherical strontium titanate fine particles of the present invention, before surface treatment, is preferably 50 nm or less. By ensuring that the average primary particle size of the spherical strontium titanate fine particles before surface treatment is within this range, the particles can be uniformly dispersed in the film, thereby obtaining a transparent composite film. The average primary particle size is preferably 40 nm or less, and more preferably 30 nm or less. The lower limit is not particularly limited, but is approximately 8 nm.

[0032] The BET specific surface area of ​​the spherical strontium titanate fine particles before surface treatment of the present invention is preferably 23.4 m 2 / g or more. If the BET specific surface area is less than 23.4m 2 / g, the average particle size of the spherical strontium titanate fine particles will be greater than 50nm. The more preferred BET specific surface area is 30.0m 2 / g or more, more preferably 35.0m 2 / g or more. The upper limit of BET specific surface area is 120.0m 2 / g or so.

[0033] The ratio of the average primary particle size of the spherical strontium titanate fine particles before surface treatment of the present invention to the BET converted particle size (6000 / (BET×5.13)) (average primary particle size before surface treatment / BET converted particle size) is preferably 0.85 to 1.25. If the ratio is within the above range, a spherical strontium titanate fine particles powder with fewer particle defects and a narrow particle size distribution can be obtained. On the other hand, if the ratio is outside the above range, the stability of the composition may not be obtained, and the dispersion may gel or settle, etc., and dispersion stability may not be obtained. If the ratio is less than 0.85, the BET specific surface area is low relative to the average particle size, so there are many coarse particles and the distribution is poor. If the above ratio is greater than 1.25, the BET specific surface area is high relative to the average particle size, so particle defects such as low crystallinity increase. A more preferred range is 0.86 to 1.23, and even more preferably 0.87 to 1.20.

[0034] The particle shape of the spherical strontium titanate fine particles of the present invention before surface treatment is spherical, and its circularity is preferably greater than 0.80. If the circularity of the spherical strontium titanate fine particles is less than 0.80, the shape is rectangular, etc., and the packing density may sometimes decrease. In addition, spherical particles with a circularity within the above range have a smaller specific surface area than rectangular particles, so the amount of dispersant used can be reduced, thereby improving the refractive index and transparency during composite formation. A more preferred circularity is greater than 0.82, and even more preferably 0.84 to 1.00.

[0035] The Sr / Ti ratio of the spherical strontium titanate fine particles of the present invention, before surface treatment, is preferably 0.90 to 1.10. By controlling the Sr / Ti ratio within this range, various properties of strontium titanate, such as its high refractive index, can be utilized. A more preferred Sr / Ti ratio is 0.95 to 1.05, and even more preferably, 0.98 to 1.02.

[0036] The refractive index of the spherical strontium titanate fine particles before surface treatment of the present invention is preferably 2.080 or higher, more preferably 2.187 or higher. When the refractive index is within the above range, a transparent thin film can be produced.

[0037] The surface-treated spherical strontium titanate fine powder of the present invention is spherical and fine, and thus can make a composite film transparent. By surface-treating the hydrophilic portion of the surface with a surface treatment agent, the solvent compatibility of the particle surface is improved, and the dispersion stability in resins and the like is also improved. Therefore, the composite film is free of turbidity. In addition, the surface-treated spherical strontium titanate fine powder of the present invention can be formed into fillers with high compatibility and dispersion stability with various solvents, and is suitable for optical and electronic applications. Furthermore, by surface-treating the high-crystallinity, high-refractive-index spherical strontium titanate fine powder with small particles and small particle defects such as composition fluctuations, high transparency can be obtained, and industrially excellent particles with small fluctuations in shape and characteristics during processing can be obtained.

[0038] Next, a dispersion containing the surface-treated spherical strontium titanate fine particle powder according to the present invention will be described.

[0039] The dispersion containing the surface-treated spherical strontium titanate fine particles of the present invention can be subjected to solid-liquid separation by centrifugation, standing, or the like. The average dispersed particle size in the supernatant is preferably 80 nm or less, more preferably 70 nm or less, and even more preferably 60 nm or less. If the average dispersed particle size exceeds 80 nm, sedimentation may occur in the dispersion, resulting in poor dispersion stability and loss of transparency in the resulting composite film. The lower limit is not particularly limited, but is approximately 8 nm.

[0040] The dispersion reach of the surface-treated spherical strontium titanate fine powder in the dispersion of the present invention is represented by the ratio of the average dispersed particle size in the dispersion to the average primary particle size of the surface-treated spherical strontium titanate fine powder (average dispersed particle size in the dispersion / average primary particle size of the surface-treated spherical strontium titanate fine powder). The dispersion reach of the dispersion of the present invention is preferably 5.0 or less, more preferably 3.5 or less, and further preferably 2.0 or less. If within the above range, the agglomerates contained in the dispersion are small, so the dispersion stability is excellent, and the transparency of the composite film can also be obtained, thereby obtaining a turbidity-free film.

[0041] The circularity of the dispersed particles contained in the dispersion is preferably 0.80 or greater, more preferably 0.84 or greater, and even more preferably 0.88 to 1.00. If the circularity is less than 0.80, the particles may aggregate due to changes in shape caused by cracks, etc., and dispersion stability may not be achieved.

[0042] The polydispersity index in the present invention is an index representing the particle size distribution of the dispersed particles contained in the dispersion, and the lower its value means that the deviation of the average dispersed particle size is smaller. The polydispersity index of the dispersed particles contained in the dispersion of the present invention is preferably 0.35 or less, more preferably 0.30 or less, and further preferably 0.29 or less. If the polydispersity index is greater than 0.35, the characteristics during composite formation may have deviations. The lower limit of the polydispersity index is 0.

[0043] Next, the method for producing the spherical strontium titanate fine-particle powder before surface treatment according to the present invention will be described.

[0044] The strontium titanate microparticle powder of the present invention can be obtained as follows: using an aqueous strontium hydroxide solution as an alkaline aqueous solution to neutralize an aqueous titanium tetrachloride solution as a titanium raw material to obtain a hydrous titanium hydroxide slurry (neutralization reaction); after heating, the hydrous titanium hydroxide slurry is washed with water, added to the aqueous strontium hydroxide solution, and a wet reaction is carried out in a temperature range of 60 to 200°C.

[0045] The addition ratio (Sr / Ti) of the titanium raw material to the alkaline aqueous solution during the neutralization reaction is preferably 1.1 to 1.8. If the addition ratio is less than 1.1, the yield of strontium titanate core particles decreases, while if the addition ratio exceeds 1.8, the distribution of the primary strontium titanate particles deteriorates. A more preferred addition ratio is 1.25 to 1.65.

[0046] The reaction solution for producing strontium titanate microparticles preferably has a concentration of 0.05 to 0.7 mol / L, calculated as a titanium compound. If the concentration is less than 0.05 mol / L, the yield is low, making industrialization unsuitable. On the other hand, if the concentration is greater than 0.7 mol / L, the amount of strontium hydroxide in the reaction solution exceeds its solubility, causing Sr(OH)2 to precipitate and making a uniform liquid-phase reaction difficult.

[0047] After the neutralization reaction, the mixture is washed with water and then an aqueous strontium hydroxide solution is added. The amount of the aqueous strontium hydroxide solution added is such that the Sr / Ti ratio reaches 1.5 to 3.0 relative to the Ti in the reaction solution.

[0048] Preferably, nitrogen is introduced during the reaction to prevent the strontium compound from reacting with carbon dioxide in the air.

[0049] The reaction temperature for the wet process is preferably 60-300°C. If the reaction temperature is lower than 60°C, it is difficult to obtain dense, spherical strontium titanate particles. If the reaction temperature is higher than 300°C, it is difficult to design a hydrothermal container. The reaction temperature is preferably 65-250°C.

[0050] The particles after the wet reaction can be washed with water according to conventional methods and dispersed in water to obtain a suspension, or dried after washing to obtain a dry powder. Washing with water can remove excess strontium. It can also simultaneously remove impurities such as Na, K, and Cl.

[0051] In the present invention, the desired strontium titanate fine particle powder can be obtained by controlling the reaction concentration, Sr / Ti during neutralization, and Sr / Ti during wet reaction.

[0052] In addition, in the present invention, the dry powder can be subjected to pulverization and crushing treatment.

[0053] Next, the method for producing the surface-treated spherical strontium titanate fine particle powder and dispersion according to the present invention is described. This method is a stepwise dispersion method that performs a first step and a second step.

[0054] The spherical strontium titanate fine particle powder before surface treatment in the present invention can be directly used as a suspension by washing the reaction filter cake with water, or can be used after increasing the concentration of strontium titanate by suction filtration or centrifugal filtration, or can be used as a dry powder after drying.

[0055] As the first operation, spherical strontium titanate fine powder of the present invention is pre-dispersed in a dispersion solvent. As the dispersion machine used in the first operation, it is not particularly limited, preferably the powder layer can be applied to a device of shearing force, impact force, compressive force and / or frictional force, for example, a roller mill, a high-speed rotary mill (high-speed rotation mill), a classifier built-in high-speed rotary mill, a ball mill, a medium stirring mill (medium stirring mill), an air flow pulverizer, a consolidation shearing mill (consolidation shearing mill), a colloid mill (colloid mill), a rolling crusher (rollmill) etc. can be used.

[0056] When a medium stirring mill is used in the first process, as the crushing medium, steel balls made of stainless steel, steel, etc.; ceramic beads made of alumina, talc, zirconia, zircon, silica, silicon carbide, silicon nitride, etc.; glass beads made of soda glass, HiBea, etc.; super hard beads made of WC, etc., etc. can be used, depending on the material of the mill. The size is preferably in the range of 0.05 to 2.0 mm, and more preferably in the range of 0.1 to 1.5 mm.

[0057] In the second step, the dispersion containing the spherical strontium titanate fine particles obtained in the first step of the present invention is stirred with a medium. As the disperser used in the second step, a media stirring mill can be suitably used, and a vertical bead mill is particularly preferred.

[0058] As the grinding medium used in the second step, depending on the material of the mill, steel balls made of stainless steel, steel, etc.; ceramic beads made of alumina, talc, zirconia, zircon, silica, silicon carbide, silicon nitride, etc.; glass beads made of soda glass, HiBea, etc.; super hard beads made of WC, etc., etc. can be used, and their size is preferably less than 100 μm, more preferably less than 50 μm, and the lower limit is preferably 1 μm.

[0059] The spherical strontium titanate fine particles contained in the dispersion of the present invention are surface-treated with a surface treatment agent. Besides being added directly to the dispersion solvent in the first and / or second steps, the surface treatment agent may be pre-treated with the spherical strontium titanate fine particles, or may be added to the dispersion solvent first. According to the above method, the surface treatment agent may be applied to a portion or the entire surface of the spherical strontium titanate fine particles. Therefore, a method in which the spherical strontium titanate fine particles are crushed and mixed with the surface treatment agent for surface treatment is preferred.

[0060] The surface treatment time of the present invention is not particularly limited, but is preferably carried out by stirring and mixing at room temperature for about 30 minutes.

[0061] The dispersion of the present invention may be centrifuged or filtered to remove coarse particles and impurities.

[0062] Alternatively, the surface-treated spherical strontium titanate fine-particle powder can be dried to remove the solvent from the dispersion to obtain a dry powder. Drying methods include, but are not limited to, a heat dryer, a reduced-pressure dryer, an evaporator, and a vacuum-type stirring dryer, as long as the method provides a spherical strontium titanate fine-particle powder surface-treated with a surface treatment agent.

[0063] The dispersion containing surface-treated spherical strontium titanate fine powder of the present invention can be obtained by redispersing the dry powder obtained in the previous stage in a solvent, or can be obtained by not undergoing the drying process of the previous stage and containing surface-treated spherical strontium titanate. As a constituent substrate of the dispersion containing the fine powder, in addition to the above-mentioned fine powder, a dispersant, an additive (resin, defoamer, auxiliary agent, etc.) can also be added as needed. The dispersion time is not particularly limited, and is preferably more than 1 hour. The upper limit is not particularly limited, and there is no problem with more than 10 hours.

[0064] The solvent used in the surface treatment step and / or dispersion of the present invention may be an aqueous solvent or a solvent-based solvent, and one kind or a mixture of two or more kinds may be used depending on the purpose and application.

[0065] As the aqueous solvent, water, alcoholic solvents such as methanol, ethanol, propanol, isopropanol, and butanol; glycol ether solvents such as methyl cellosolve, ethyl cellosolve, propyl cellosolve, and butyl cellosolve; ethylene oxide or propylene oxide addition polymers such as diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, and polypropylene glycol; alkylene glycols such as ethylene glycol, propylene glycol, and 1,2,6-hexanetriol; and water-soluble organic solvents such as glycerol and 2-pyrrolidone can be used. These dispersing solvents used in aqueous dispersions can be used alone or in combination of two or more, depending on the intended use.

[0066] As solvents, aromatic hydrocarbons such as toluene and xylene; ketones such as methyl ethyl ketone and cyclohexanone; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; alcohol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether; ether acetates such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; acetates such as ethyl acetate, butyl acetate, and isobutyl acetate; lactic acid esters such as methyl lactate, ethyl lactate, and propyl lactate; cyclic esters such as ethylene carbonate, propylene carbonate, and γ-butyrolactone; and various monomers can be used. These solvents can be used alone or in combination, depending on the intended use.

[0067] The solubility parameter (SP value) of the solvent of the present invention is expressed in units of (cal / cm 3 ) 1 / 2 The SP value of the solvent of the present invention is preferably 5 to 25 (cal / cm 3 ) 1 / 2 , more preferably 6 to 20 (cal / cm 3 ) 1 / 2 , more preferably 7 to 15 (cal / cm 3 ) 1 / 2 As SP value 5~25(cal / cm 3 ) 1 / 2 Solvents such as dimethylcyclohexane can be used as SP values ​​of 6 to 20 (cal / cm 3 ) 1 / 2 Solvents such as n-pentane and formamide can be listed as SP values ​​of 7 to 15 (cal / cm 3 ) 1 / 2Examples of suitable solvents include n-hexane, methyl ethyl ketone, propylene glycol monomethyl ether acetate, and 2-methoxyethanol. When the SP value of the solvent is within the above range, the surface treatment agent can be fully dissolved in the solvent, and when mixed with the fine particles, the surface of the fine particles can be coated, which is preferable. Furthermore, the dispersion stability of the dispersion can be improved, resulting in a stable dispersion without fine particle sedimentation.

[0068] The solid content of the dispersion of the present invention, i.e., the concentration of the surface-treated spherical strontium titanate fine particles, is not particularly limited as long as it maintains fluidity without sedimentation, separation, solidification, or gelation. However, it is preferably approximately 10 to 60% by weight relative to the total weight. If the solid content is less than 10% by weight, productivity is low when used in the next step. If the solid content is greater than 60% by weight, the dispersion may not be fluid.

[0069] The surface-treated spherical strontium titanate fine particles of the present invention are obtained by physically attaching or adsorbing, or chemically bonding, a surface treatment agent to the surface of a spherical and fine high-crystallinity spherical strontium titanate fine particle powder. The particles have a high degree of crystallinity before surface treatment, so they can be evenly coated with a surface treatment agent that is compatible with solvents and resins while maintaining their roundness, thereby modifying the particle surface to be solvent-affinity. The surface-treated spherical strontium titanate fine particles with steric hindrance on the surface can maintain a spherical shape even in resins and solvents, and exist in a fine state without excessive agglomeration, so that a transparent film without turbidity can be formed. Furthermore, the surface treatment agent is used to impart steric hindrance to the spherical and fine surface of the particles, thereby obtaining a dispersion with high dispersion stability that does not settle. In addition, the surface-treated spherical strontium titanate fine particles of the present invention have uniform particle size, less drying agglomeration, easy redispersion, and reduced dispersion cost and dispersion energy.

[0070] Next, the resin composition containing the surface-treated spherical strontium titanate fine particle powder according to the present invention will be described.

[0071] The resin of the present invention is not particularly limited, and thermosetting resins, photocurable resins, etc. can be listed. Acrylic resins; acrylate or methacrylate polymers, polycarbonate resins, polystyrene resins, polyester resins, polyimide resins, polymethyl methacrylate (PMMA) resins, AS resins, silicone resins, fluororesins, etc. can be used.

[0072] The solid content of the resin composition of the present invention, i.e., the concentration of the surface-treated strontium titanate fine particles, is not particularly limited as long as it is dispersed in the resin, but is preferably approximately 10 to 60% by weight. If the solid content of the resin composition is less than 10% by weight, productivity is low when used in the next step. If the solid content exceeds 60% by weight, the resin composition may not have adequate fluidity.

[0073] The surface-treated spherical strontium titanate fine particle powder, dispersion and resin composition described in the present invention may appropriately contain various conventional additives such as monomers or oligomers not contained in the above-mentioned resins, dispersants, polymerization initiators, antistatic agents, refractive index regulators, antioxidants, ultraviolet absorbers, light stabilizers, leveling agents, defoaming agents, inorganic fillers, preservatives, plasticizers, flow regulators, thickeners, pH regulators, polymerization initiators, etc., within the scope that does not impair the effects of the present invention.

[0074] The manufacture method of the resin combination of the present invention is not particularly limited, and can be manufactured by mixing the surface-treated spherical strontium titanate fine powder or / and a dispersion containing the surface-treated spherical strontium titanate fine powder with a resin. The mixing method can be enumerated by a propeller stirrer, a disperser, an ultrasonic wave, etc. The mixing time is not particularly limited as long as it can fully stir and mix, and is preferably about 1 hour. The viscosity of the resin combination is as long as it does not impair the operability. [Example]

[0075] Examples of the present invention are described below, but the present invention is not limited thereto.

[0076] [Average primary particle size] Transmission electron microscopy (JEM-F200, manufactured by JEOL Ltd.) was used to observe photographs (25,000x magnification) of spherical strontium titanate fine particles before and after surface treatment, and the average primary particle size of approximately 50 particles was measured. The average primary particle size herein refers to the particle size obtained by averaging the diameter of a circle having the same area as that determined from the photograph for each particle, relative to all particles measured. Particle shape was also determined based on the electron micrographs.

[0077] [Circularity] The circularity of the granular powder and the dispersed particles was determined by the ratio (4v×area) / perimeter of the particles as determined from the electron micrographs above. 2 express.

[0078] [Average dispersed particle size and polydispersity index] The average dispersed particle size was determined by measuring each dispersion using dynamic light scattering (FPAR-1000, manufactured by Otsuka Electronics Co., Ltd.) and cumulant analysis. The polydispersity index, which represents the particle size distribution, was also determined using histogram analysis.

[0079] [Dispersion Sedimentation Test] A dispersion sedimentation test was performed to evaluate dispersion stability. A dispersion containing surface-treated spherical strontium titanate fine particles was stored at 25°C and visually observed for sedimentation after one month. Dispersions with no sedimentation were rated as ◯, while those with sedimentation were rated as ×.

[0080] [Specific surface area and BET-converted particle size] The specific surface area value is determined by the BET method (m 2 / g). In addition, the BET-converted particle size (nm) is calculated by the relationship: 6000 / (BET specific surface area × 5.13). It should be noted that 5.13 is the density of strontium titanate (g / cm 3 The ratio of the average primary particle size and the BET-converted particle size was calculated (average primary particle size / BET-converted particle size).

[0081] [Particle density] The particle density was measured using a particle density measuring apparatus BELPYCNO (manufactured by Microtrac Bell Co., Ltd.).

[0082] [Refractive index of dispersion] 2 g of each strontium titanate fine particle powder was mixed with 8 g of 2-methoxypropanol for 120 minutes to prepare a dispersion having a solid content of 20 wt%. The refractive index of the dispersion was measured using an Abbe refractometer RX-7000α (manufactured by Atago Co., Ltd.).

[0083] [Refractive index of particles] The refractive index of strontium titanate fine-particle powder is calculated according to the following formula using the particle density of the fine-particle powder, the refractive index of the dispersion, and the solid content of the dispersion. When the dispersion is considered to be a composite of a solvent and a filler (powder), the refractive index of the dispersion, n, is calculated using the following formula (1). V1 is the volume fraction of the filler, n1 is the refractive index of the filler, V2 is the volume fraction of the solvent, and n2 is the refractive index of the solvent. That is, the refractive index of the filler can be calculated from the measured refractive index and the volume fractions of each component in the dispersion. [Number 1] n=V1×n1+V2×n2…(1)

[0084] The refractive index n1 of the filler is given by the following equation (2). Since volume fractions in dispersions are difficult to measure, they are converted from the weight fractions w1 (filler) and w2 (solvent) of the components, which are easily measured, and the densities d1 (filler) and d2 (solvent), respectively, to the following equations (3) and (4). Substituting equations (3) and (4) into equation (2) yields the refractive index of the filler. [Number 2] [Number 3] [Number 4]

[0085] [Solid content in dispersion] The solid content in the dispersion was calculated by calcining the strontium titanate dispersion in a muffle furnace at 300° C. for 1 hour using the formula (5) and expressed in wt %. [Number 5]

[0086] [Sr / Ti molar ratio] Sr / Ti was measured using a fluorescent X-ray analyzer (ZSX Primus II manufactured by Rigaku Corporation).

[0087] [Total light transmittance and film haze evaluation] The total light transmittance of each coating film was measured using a turbidimeter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.). The light transmittance measured in air was considered 100% for evaluation, and the total light transmittance of each coating film was preferably 90% or higher. Film haze was evaluated by visual inspection of each coating film, with films without haze rated as ◯ and films with haze rated as ×.

[0088] Example 1 An aqueous solution of titanium tetrachloride is mixed with water so that the molar concentration of Ti reaches 2.10 mol / 1 to prepare a mixed solution. A 20 wt% aqueous solution of strontium hydroxide is added to the mixed solution so that the Sr / Ti molar ratio reaches 1.32 to obtain a titanium hydroxide slurry, which is then washed with water. The obtained titanium hydroxide slurry is placed in an aqueous solution of strontium hydroxide that has been dissolved in advance in a reaction vessel. At this time, the Sr / Ti molar ratio of the strontium hydroxide aqueous solution is adjusted to 2.0. In addition, the concentration during the reaction is 0.28 mol / 1 in terms of strontium titanate concentration. Then, a hydrothermal reaction is carried out at 260°C with continuous stirring for 8 hours. After the reaction, the mixture is cooled to room temperature, then washed with water, filtered, and dried to obtain a white powder of strontium titanate particles.

[0089] The obtained spherical strontium titanate fine particle powder is a spherical particle with a primary average particle size of 22.12 nm, a circularity of 0.92, an Sr / Ti ratio of 0.978, a particle density of 4.71 g / cc, and a BET specific surface area of ​​45.9 m 2 / g, a BET-converted particle size of 25.5 nm, and a ratio of average primary particle size to BET-converted particle size of 0.87. Furthermore, the dispersion prepared for calculation of the particle refractive index had a solids content of 19.72% by weight, a refractive index of 1.440, and a calculated particle refractive index of 2.196.

[0090] As the first step of dispersion, 10.5 g of the spherical strontium titanate fine particle powder obtained in the previous step was added to 59.5 g of 2-methoxyethanol in a 200 mL screw bottle. ZrO2 beads (zirconia balls YTZ series manufactured by Nikkato Corporation) were dispersed using a paint shaker (manufactured by Toyo Seiki Seisaku-sho, Ltd.) for 1 hour, and then the ZrO2 beads were removed to obtain a dispersion having a solid content of 15% by weight.

[0091] Next, as the second dispersion step, a new screw-cap bottle was prepared, and 10 wt% of strontium titanate fine particles were added to the dispersion containing the spherical strontium titanate fine particles obtained in the previous step and the surface treatment agent (Disperbyk-180 manufactured by BYK-Chemie). ZrO2 beads (Nikkato Corporation zirconia balls YTZ series) were added and dispersed again using a paint shaker (Toyo Seiki Seisaku-sho, Ltd.) for 4 hours. The ZrO2 beads were removed to obtain a dispersion containing surface-treated spherical strontium titanate fine particle powder.

[0092] The mixture was dried at 80° C. for 12 hours using a high temperature constant temperature machine to obtain a surface-treated spherical strontium titanate fine particle powder.

[0093] Table 1 shows various properties of the spherical strontium titanate fine particles before surface treatment, Table 2 shows the surface treatment conditions and various properties of the surface-treated spherical strontium titanate fine particles, and Table 3 shows various properties and effects of the dispersion.

[0094] [Table 1]

[0095] [Table 2]

[0096] [Table 3]

[0097] Examples 2 to 5 A dispersion containing surface-treated spherical strontium titanate fine particles and surface-treated spherical strontium titanate fine particles were obtained by the same procedures as in Example 1 except that the surface treatment conditions shown in Table 2 were variously changed.

[0098] Comparative Example 1 Strontium titanate fine powder (Strontium titanate 517011-50G manufactured by Sigma-Aldrich, average particle size 38.5 nm) was used as the first step of dispersion. 2.25 g of the strontium titanate fine powder was added to 12.75 g of methyl cellosolve in a 30 mL sample bottle. ZrO2 beads (zirconia balls YTZ series manufactured by Nikkato Corporation) were dispersed using a paint shaker (manufactured by Toyo Seiki Seisaku-sho, Ltd.) for 1 hour.

[0099] Next, as the second dispersion step, a new sample bottle is prepared and the dispersion containing the spherical strontium titanate fine particle powder obtained in the previous step and ZrO2 beads (zirconia balls YTZ series manufactured by Nikkato Corporation) were added and dispersed again using a paint shaker (manufactured by Toyo Seiki Seisaku-sho, Ltd.) for 2 hours. The ZrO2 beads were then removed to obtain a dispersion with a solid content of 15% by weight, and the same steps as in Example 1 were used to obtain granular powder.

[0100] The dispersion adjusted for calculating the particle refractive index had a solid content of 19.43% by weight, a refractive index of 1.439, and a calculated particle refractive index of 2.186.

[0101] Comparative Examples 2 and 3 A dispersion containing surface-treated spherical strontium titanate fine particles and surface-treated spherical strontium titanate fine particles were obtained by the same procedures as in Example 1 except that the surface treatment conditions described in Table 2 were variously changed.

[0102] Comparative Example 4 An aqueous strontium hydroxide solution and an aqueous titanium tetrachloride solution were added to achieve a molar ratio of S1 to Ti of 1.6, and a neutralization reaction was carried out. Then, an aqueous strontium hydroxide solution and the titanium hydroxide slurry obtained above were added to the reaction vessel to achieve a molar ratio of Sr to Ti of 1.5. The reaction was then carried out at 90°C for 3 hours to obtain a white powder of strontium titanate particles.

[0103] A dispersion containing surface-treated spherical strontium titanate fine particles and surface-treated spherical strontium titanate fine particles were obtained by the same procedures as in Example 1 except that the surface treatment conditions described in Table 2 were variously changed.

[0104] The dispersion adjusted for calculating the particle refractive index had a solid content of 19.66% by weight, a refractive index of 1.437, and a calculated particle refractive index of 2.075.

[0105] Next, the preparation of a coating film for evaluating total light transmittance and film haze will be described.

[0106] In a 30 mL sample bottle, 2 g of the dispersion prepared in the previous step, a mixed resin (CN2283 (polyester acrylate, manufactured by Sartomer) / SR833 (tricyclodecanedimethanol diacrylate, manufactured by Sartomer), and 3 g of a photopolymerization initiator (Omnirad 380 (phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, manufactured by IGMRESINS)) were mixed to prepare a coating solution for each strontium titanate fine particle (9% solid content). This coating solution was applied to a PET film (Lumirror, manufactured by Toray Industries, Inc.) at a thickness of 12 μm using a Khandcoater manufactured by RKPRINTCOATINSTRUMENTS, and cured using an area irradiator (for UV curing) manufactured by CCS Inc. to form a coating film.

[0107] As shown in Table 3, the coating films using the strontium titanate fine-particle powders obtained in Examples 1 to 5 were confirmed to have no turbidity and excellent transparency. In addition, the dispersions were also confirmed to have no sedimentation and excellent dispersion stability. -Industrial Applicability-

[0108] Spherical strontium titanate particulate powder of the present invention is fine spherical, therefore can obtain transparent composite film.In addition, by surface treatment, the solvent affinity of the surface of this particulate is improved, therefore can make powder, dispersion and resin combination with little cohesion and high dispersion stability, and dispersion stability is also very high.And then, owing to be the spherical strontium titanate particulate powder with few particle defects and high crystallinity, therefore dispersion stability is improved, can obtain dispersion without sediment.Spherical strontium titanate particulate powder of the present invention can control average particle diameter according to purpose, owing to be spherical, therefore easily improve filler packing density in composite.Therefore, spherical strontium titanate particulate powder of the present invention is most suitable for the resin combination of the diffraction optical element used for the brightness enhancement film used for display, XR (AR, MR, VR) glass etc., for the high refractive index inorganic filler of high refractive indexization or can be used for the high dielectric inorganic filler of the high dielectric resin composition of electronic components such as thin film transistor (TFT).

Claims

1. A spherical strontium titanate fine particle powder, characterized in that: The spherical strontium titanate fine particle powder has an average primary particle size of 50 nm or less and is surface-treated with 5 to 30% by weight of a surface treatment agent.

2. The spherical strontium titanate fine particle powder according to claim 1, characterized in that The surface treatment agent is a polymer dispersant.

3. A dispersion, characterized in that The dispersion contains the spherical strontium titanate fine particle powder according to claim 1.

4. A resin composition, characterized in that The resin composition contains the spherical strontium titanate fine particle powder according to claim 1.

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