Silica particle dispersion liquid

Abstract

The present invention provides a silica particle dispersion liquid that suppresses granulation when formed into a film and that can increase detachment strength. The silica particle dispersion liquid according to the present invention contains spherical silica particles and a solvent. The median size d50 of the spherical silica particles is 0.5-20 μm. A product A×d50 of the median size d50 (μm) and the specific surface area A (m2 / g) of the spherical silica particles is 2.7-5.0 μm·m2 / g.

Description

Silica particle dispersion

[0001] The present invention relates to a silica particle dispersion in which silica particles are dispersed in a solvent.

[0002] Silica particles have conventionally been used in a variety of applications, such as electronic materials such as printed wiring boards and package wiring boards, optical materials such as lenses and optical films, functional materials such as catalysts and catalyst carriers, and pigments for paints, cosmetics, etc. For example, silica particles have been used in electronic substrates, taking advantage of their low dielectric properties.

[0003] Silica particles tend to aggregate when used in a dry powder state, and therefore are used in the form of a dispersion in which they are dispersed in a solvent such as water or a resin depending on the intended use, and various silica particle dispersions and slurries containing such silica particle dispersions have been proposed.

[0004] For example, Patent Document 1 describes a method for producing a powder having a particle size of 100 nm to 2000 nm or a specific surface area of ​​2 m ２ / g~35m ２ / g, and the amount of water generated when heated at 200°C is ２ The present invention proposes a slurry for electronic materials, which comprises a filler for electronic materials that is a silica particle material having a surface treatment with a silane compound having a vinyl group, a phenyl group, a phenylamino group, an alkyl group having 4 or more carbon atoms, a methacryl group, or an epoxy group, and which has a silica content of 40 ppm or less per 1000 ppm of the filler, and a liquid dispersion medium that is substantially free of water.

[0005] Patent Document 2 proposes a coating liquid for forming an anti-reflection film, which comprises hollow silica particles (A) having an average particle diameter (Dpa) in the range of 30 to 200 nm, solid silica particles (B) having an average particle diameter (Dpb) in the range of 5 to 80 nm, and a solvent, wherein the concentration (CA) of the hollow silica particles (A) is in the range of 0.2 to 8 wt % as solid content, the concentration (CB) of the solid silica particles (B) is in the range of 0.2 to 8 wt % as solid content, and the weight ratio (B / A) of the hollow silica particles (A) to the solid silica particles (B) is 0.25 to 4.

[0006] Furthermore, Patent Document 3 proposes a dispersion of silica-based particles containing silica-based particles having an average particle diameter of 5 to 40 nm and a ratio of the number of hollow particles to the total number of hollow particles and solid particles (hollowness) of 70% or more.

[0007] Japanese Patent Publication No. 2020-097498 Japanese Patent Publication No. 2015-102666 Japanese Patent Publication No. 2018-123043

[0008] However, when conventional silica particle dispersions are incorporated into a resin composition to form a film, the silica particles tend to become granular, resulting in a low peel strength and making it difficult to obtain the effects expected of the silica particles. In particular, when used for the purpose of reducing dielectric constant, reducing the surface area of ​​the silica particles or increasing the particle size can achieve low dielectric constant, but the contact area between the particles increases, which tends to reduce peel strength.

[0009] The present invention has been made in view of the above problems, and an object of the present invention is to provide a silica particle dispersion liquid that can suppress granularity when a film is formed and can increase peel strength.

[0010] The present invention relates to the following (1) to (9): (1) A method for producing a dispersion medium containing spherical silica particles and a solvent, wherein the median diameter d50 of the spherical silica particles is 0.5 to 20 μm, and the specific surface area A (m ２ / g) and the median diameter d50 (μm), A×d50 is 2.7 to 5.0 μm ２ (2) The spherical silica particles have a specific surface area of ​​0.1 to 10 m ２ (3) The silica particle dispersion according to (1) above, wherein the spherical silica particles have a viscosity of 5000 mPa·s or less as measured by the following measurement method. (Measurement Method) The silica particle dispersion is dried to obtain powdery spherical silica particles, and 8 parts by mass of the obtained powdery spherical silica particles and 6 parts by mass of boiled linseed oil are mixed and kneaded at 2000 rpm for 3 minutes. The kneaded mixture is then subjected to a shear rate of 1 s using a rotational rheometer. －１The viscosity is measured for 30 seconds at 100°C, and the viscosity at 30 seconds is determined. (4) The silica particle dispersion according to any one of (1) to (3), further containing a silane compound having at least one group selected from the group consisting of a vinyl group, a phenyl group, a phenylamino group, an alkyl group having 4 or more carbon atoms, a methacryl group, and an epoxy group. (5) The silica particle dispersion according to any one of (1) to (4), further containing an organic thixotropic agent. (6) The silica particle dispersion according to any one of (1) to (5), wherein the solvent contains at least one selected from the group consisting of water, hydrocarbons, alcohols, acetate esters, ketones, cellosolves, glycol ethers, chlorinated hydrocarbons, and polar solvents. (7) The silica particle dispersion according to any one of (1) to (6), wherein the viscosity at 25°C is 20 to 20,000 mPa·s when the solids concentration of the spherical silica particles is 70% by mass. (8) A resin composition containing the silica particle dispersion liquid according to any one of (1) to (7). (9) A resin composition containing a solvent and a silica particle dispersion liquid having a median diameter d50 of 0.5 to 20 μm and a specific surface area A (m ２ / g) and the median diameter d50 (μm), A×d50 is 2.7 to 5.0 μm ２ / g of spherical silica particles, and the resulting mixture is subjected to a dispersion treatment and classified to remove agglomerates of the spherical silica particles.

[0011] In the silica particle dispersion of the present invention, the spherical silica particles are uniformly dispersed in the liquid without agglomeration, and therefore, when a resin composition containing the silica particle dispersion of the present invention is formed into a film, granulation can be suppressed and the peel strength can be increased.

[0012] The present invention will be described below, but the present invention is not limited to the examples in the following description. In this specification, the term "to" indicating a range of values ​​means that the values ​​before and after it are included as the lower and upper limits. In this specification, "mass" is synonymous with "weight."

[0013] <Silica Particle Dispersion> The silica particle dispersion of the present invention contains spherical silica particles and a solvent, and the spherical silica particles have a median diameter d50 of 0.5 to 20 μm and a specific surface area A (m２ / g) and the median diameter d50 (μm), the product A×d50 is 2.7 to 5.0 μm ２ In the silica particle dispersion of the present invention, the spherical silica particles are uniformly dispersed without aggregation, and the dispersion stability of the spherical silica particles in the dispersion is improved, so that when the spherical silica particles are incorporated into a resin composition to form a film, particle formation can be suppressed and peel strength can be increased.

[0014] (Solvent) The solvent serving as the dispersion medium for the silica particle dispersion can be selected arbitrarily depending on the intended use, and examples thereof include water, hydrocarbons, alcohols, acetates, ketones, cellosolves, glycol ethers, chlorinated hydrocarbons, and polar solvents. The solvent preferably contains at least one selected from the group consisting of these.

[0015] Examples of hydrocarbons include toluene, methylcyclohexane, normal heptane, and m-xylene. Examples of alcohols include ethanol, isopropyl alcohol, 1-propyl alcohol, isobutyl alcohol, 1-butanol, and 2-butanol. Examples of acetates include propyl acetate, isobutyl acetate, and butyl acetate. Examples of ketones include methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. Examples of cellosolves include ethylene glycol monomethyl ether and ethylene glycol monoethyl ether. Examples of glycol ethers include 1-methoxy-2-propanol, 1-methoxypropyl-2-acetate, 1-ethoxy-2-propanol, and ethyl 3-ethoxypropionate. Examples of chlorinated hydrocarbons include trichloroethylene and tetrachloroethylene. Examples of polar solvents include N-methyl-2-pyrrolidone.

[0016] The solvent may be appropriately selected depending on the field of intended use. For example, when used for an insulating layer of a wiring substrate of an electronic device, it is preferable to use ketones or hydrocarbons, specifically methyl ethyl ketone (MEK), toluene, etc.

[0017] When the silica particle dispersion of the present invention is used in a curable composition, the liquid base resin or curing agent itself may be used as a solvent. Examples of the base resin include epoxy resin, polyphenylene ether resin, polyester resin, polyimide resin, phenol resin, and orthodivinylbenzene resin. Examples of the curing agent include polyamine-based curing agents, acid anhydride-based curing agents, phenol-based curing agents, active ester-based curing agents, and peroxides.

[0018] The solvent is preferably contained in the silica particle dispersion in a range of 15 to 90% by mass. When the solvent content is 15% by mass or more, the spherical silica particles can be uniformly dispersed, and the viscosity of the dispersion does not become too high, making it easy to handle. When the solvent content is 90% by mass or less, the dispersion is in a liquid state and can be used as is. The solvent content in the silica particle dispersion is more preferably 20% by mass or more, even more preferably 25% by mass or more, particularly preferably 30% by mass or more, most preferably 40% by mass or more, and more preferably 85% by mass or less, even more preferably 80% by mass or less, and particularly preferably 75% by mass or less.

[0019] (Spherical Silica Particles) The spherical silica particles are solid silica particles having a median diameter d50 of 0.5 to 20 μm and a specific surface area A (m ２ / g) and the median diameter d50 (μm), the product A×d50 is 2.7 to 5.0 μm ２ / g (2.7≦A×d50(μm m ２ The following physical properties of the spherical silica particles can be confirmed by drying the silica particle dispersion to obtain powdery silica particles.

[0020] When the median diameter d50 of the spherical silica particles is within the above range, the viscosity is easy to handle and the particles are less likely to granulate during coating, so that the peel strength of the resin composition is maintained at an appropriate level when used as a resin composition. Furthermore, if the median diameter is too large, the particle gauge value increases, and when a resin composition containing the spherical silica particles is formed into a sheet, for example, the minimum thickness of the sheet increases. Therefore, in the present invention, the median diameter d50 of the spherical silica particles is set to a range of 0.5 to 20 μm. The median diameter d50 is preferably 1 μm or more, and the upper limit is preferably 10 μm or less, more preferably 5 μm or less.

[0021] The median diameter d50 can be determined using a laser diffraction particle size distribution measuring device (for example, "MT3300EXII" manufactured by Microtrac Bell Co., Ltd.).

[0022] The specific surface area A of the spherical silica particles is 0.1 to 10 m ２ / g. ２ When the spherical silica particles have a particle size of 10 m / g or more, there are sufficient contact points with the resin when the spherical silica particles are contained in the resin composition, so that the particles are well-suited to the resin. ２ When the specific surface area A is 8 m / g or less, the dielectric loss tangent can be reduced and the dispersibility in the resin composition can be improved. ２ / g or less is more preferable, and ２ / g or less is more preferable, and 5m ２ / g or less is particularly preferred. ２ It is practically difficult to obtain a value less than 1 / g.

[0023] The specific surface area is determined by the BET method based on the nitrogen adsorption method using a specific surface area / pore distribution measuring device (for example, "BELSORP-mini II" manufactured by Microtrac-Bell, or "Tristar II" manufactured by Micromeritics).

[0024] The specific surface area A (m ２ / g) and the median diameter d50 (μm), A×d50 is 2.7 to 5.0 μm ２ / g, preferably 2.7 to 4.5 μm m２ / g, and more preferably 2.7 to 4.0 μm m ２ / g. The theoretical value of A × d50 is 2.7 [specific surface area = 6 / (true density of silica 2.2 (g / m ３ ) × median diameter d50 (μm)), and values ​​below this are practically impossible to achieve. ２ When the specific surface area per particle size is less than 1 / g, the dielectric loss tangent can be reduced.

[0025] The sphericity of the spherical silica particles is preferably 0.75 to 1.0. If the sphericity is too low, the contact area between the silica particles in the resin layer and the member in contact with the resin composition containing the silica particle dispersion may decrease, resulting in a decrease in peel strength. Therefore, the sphericity is preferably 0.75 or more. The sphericity can be expressed as the average value obtained by measuring the maximum diameter (DL) and the minor diameter (DS) perpendicular to the maximum diameter (DL) for each of 100 particles in a photographic projection obtained by photographing with a scanning electron microscope (SEM), and calculating the ratio (DS / DL) of the minimum diameter (DS) to the maximum diameter (DL). From the viewpoint of dispersibility, the sphericity is more preferably 0.90 or more, even more preferably 0.93 or more, and the closer to 1.0 the better.

[0026] The spherical silica particles preferably have a viscosity of 5000 mPa·s or less as measured by the following measurement method: (Measurement Method) A silica particle dispersion is dried to obtain powdered spherical silica particles, and 8 parts by mass of the obtained powdered spherical silica particles are mixed with 6 parts by mass of boiled linseed oil, and the kneaded mixture obtained by kneading at 2000 rpm for 3 minutes is measured using a rotational rheometer at a shear rate of 1 s －１ The measurement is carried out for 30 seconds, and the viscosity at the time of 30 seconds is determined.

[0027] The shear rate of the kneaded material obtained by the above measurement method is 1 s －１When the viscosity at 1000 mPa·s is 5000 mPa·s or less, the silica particles can be said to be dense, and the peel strength can be improved when the resin composition is made into a resin composition. In addition, the amount of solvent added during molding and film formation of a resin composition containing spherical silica particles can be reduced, the drying speed can be increased, and productivity can be improved. Furthermore, if the specific surface area according to the particle size of the silica particles is large, the viscosity tends to increase when added to a resin composition, but since the spherical silica particles have a small specific surface area, the viscosity increase of the resin composition can be suppressed. The viscosity of the kneaded product is more preferably 4000 mPa·s or less, and even more preferably 3500 mPa·s or less. At a shear rate of 1 s of the kneaded product, －１ The lower the viscosity at 200°C, the better the coatability of the resin composition and the higher the productivity, so there is no particular restriction on the lower limit.

[0028] The dielectric loss tangent of the spherical silica particles in powder form is preferably 0.0020 or less at a frequency of 1 GHz, more preferably 0.0010 or less, and even more preferably 0.0008 or less. In particular, when measuring the dielectric loss tangent and dielectric constant of powders, the sample space becomes small and measurement accuracy deteriorates at frequencies of 10 GHz or higher, so in the present invention, measurements at a frequency of 1 GHz are used. When the dielectric loss tangent of the spherical silica particles at a frequency of 1 GHz is 0.0020 or less, an excellent dielectric loss suppression effect is obtained, resulting in substrates and sheets with improved high-frequency characteristics. The smaller the dielectric loss tangent, the more the circuit transmission loss is suppressed, so the lower limit is not particularly limited.

[0029] The dielectric loss tangent can be measured by a perturbation resonator method using a dedicated device (for example, "Vector Network Analyzer E5063A" manufactured by Keycom Corporation).

[0030] 3746 cm originating from isolated silanol groups on the surface of spherical silica particles －１ The IR peak intensity around 0.1 or less is preferably 0.08 or less, and more preferably 0.06 or less. Isolated silanol groups are silanol (Si-OH) groups that are not bonded to water or the like adsorbed on silica particles. The amount of isolated silanol (Si-OH) groups on the surface of silica particles can be obtained by IR measurement. Specifically, the IR spectrum is measured at 800 cm －１ Normalized to 3800 cm－１ After adjusting the baseline, 3746 cm －１ If there are many isolated silanol groups on the particle surface, the dielectric loss tends to increase when the material mixed with resin is used for electronic applications. －１ When the IR peak intensity in the vicinity is 0.1 or less, the dielectric loss can be reduced.

[0031] In addition, the 3300 to 3700 cm 2 derived from the bonded silanol groups on the surface of the spherical silica particles －１ The maximum IR peak intensity at 800 cm is preferably 0.2 or less, more preferably 0.17 or less, and even more preferably 0.15 or less. The bonded silanol group is a silanol (Si-OH) group that is bonded to water adsorbed on the silica particles or silanol on the silica surface. The amount of bonded silanol (Si-OH) groups on the silica particle surface can be obtained by IR measurement. Specifically, the IR spectrum is measured at 800 cm －１ Normalized to 3800 cm －１ After adjusting the baseline, 3300-3700 cm －１ The relative value of the bond Si—OH peak intensity is calculated from the maximum peak among the peaks in the range of 3300 to 3700 cm. If there are many bond silanol groups on the particle surface, the dielectric loss tends to increase when the material mixed with the resin is used for electronic applications. －１ When the maximum IR peak intensity at 1.0 is 0.2 or less, the dielectric loss can be reduced.

[0032] The spherical silica particles are preferably non-porous particles. Porous particles tend to increase the oil absorption, leading to an increase in viscosity in the resin, an increase in surface area, and an increase in the number of silanol (Si—OH) groups on the silica particle surface, resulting in a deterioration in the dielectric loss tangent. Specifically, the oil absorption is preferably 100 ml / 100 g or less, more preferably 70 ml / 100 g or less, and most preferably 50 ml / 100 g or less. There is no particular restriction on the lower limit, but it is practically difficult to achieve an oil absorption of 20 ml / 100 g or less.

[0033] The spherical silica particles preferably contain titanium (Ti) in the range of 30 to 1500 ppm, more preferably 100 to 1000 ppm, and even more preferably 100 to 500 ppm. Ti is a component that is optionally added during the production of spherical silica particles. If fine powder is generated due to cracking of silica particles during the production of spherical silica particles, the fine powder will adhere to the surface of the base particle, increasing the specific surface area of ​​the particles. By adding Ti during the production of spherical silica particles, they are more likely to be thermally compacted during firing. This makes them less likely to crack during post-treatment after firing, thereby suppressing the generation of fine powder and reducing the number of particles adhering to the surface of the silica base particle, thereby suppressing the increase in specific surface area. By including 30 ppm or more of Ti, the material is easily thermally compacted during firing, thereby suppressing the generation of fine powder due to cracking. When the Ti content is 1500 ppm or less, the above effect can be obtained, and an increase in the amount of silanol groups can be suppressed, thereby suppressing a deterioration in the dielectric loss tangent.

[0034] The spherical silica particles may contain impurity elements other than titanium (Ti) as long as the effects of the present invention are not impaired. Examples of impurity elements include Na, K, Mg, Ca, Al, and Fe, in addition to Ti. The total content of alkali metals and alkaline earth metals among the impurity elements is preferably 2000 ppm or less, more preferably 1000 ppm or less, and even more preferably 200 ppm or less.

[0035] The spherical silica particles may be treated with a silane coupling agent. Treating the surfaces of the spherical silica particles with a silane coupling agent reduces the amount of remaining silanol groups on the surfaces, making the surfaces hydrophobic and suppressing moisture adsorption, improving dielectric loss, and also improving affinity with resins when used in a resin composition, improving dispersibility and strength after resin film formation.

[0036] The conditions for the surface treatment are not particularly limited, and general surface treatment conditions may be used, and a wet treatment method or a dry treatment method may be used. From the viewpoint of uniform treatment, the wet treatment method is preferred.

[0037] Examples of the silane coupling agent include aminosilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, silane coupling agents, organosilazane compounds, etc. One type of silane coupling agent may be used alone, or two or more types may be used in combination.

[0038] Specific examples of the silane coupling agent include aminosilane-based coupling agents such as aminopropyl methoxysilane, aminopropyl triethoxysilane, ureidopropyl triethoxysilane, N-phenylaminopropyl trimethoxysilane, and N-2(aminoethyl)aminopropyl trimethoxysilane; epoxysilane-based coupling agents such as glycidoxypropyl trimethoxysilane, glycidoxypropyl triethoxysilane, glycidoxypropyl methyldiethoxysilane, glycidyl butyl trimethoxysilane, and (3,4-epoxycyclohexyl)ethyl trimethoxysilane; mercaptosilane-based coupling agents such as mercaptopropyl trimethoxysilane and mercaptopropyl triethoxysilane; silane-based coupling agents such as methyltrimethoxysilane, vinyltrimethoxysilane, octadecyltrimethoxysilane, phenyltrimethoxysilane, metachloroxypropyl trimethoxysilane, imidazole silane, and triazine silane; and CF ３ (CF ２ ) ７ CH ２ CH ２ Si(OCH ３ ) ３ , C.F. ３ (CF ２ ) ７ CH ２ CH ２ SiCl ３ , C.F. ３ (CF ２ ) ７ CH ２ CH ２ Si(CH ３ ) (OCH ３ ) ２ , C.F. ３ (CF ２ ) ７ CH ２ CH ２Si (CH ３ )C1 ２ 、CF ３ (CF ２ ) ５ CH ２ CH ２ SiCS ３ 、CF ３ (CF ２ ) ５ CH ２ CH ２ Si (OCH ３ ) ３ 、CF ３ CH ２ CH ２ SiCS ３ 、CF ３ CH ２ CH ２ Si (OCH ３ ) ３ 、C ８ F １７ SO ２ N (C ３ H ７ )CH ２ CH ２ CH ２ Si (OCH ３ ) ３ 、C ７ F １５ [NNHCH ２ CH ２ CH ２ Si (OCH ３ ) ３ 、C ８ F １７ CO ２ CH ２ CH ２ CH ２ Si (OCH ３ ) ３ 、C ８ F １７ -O-CF(CF ３ )CF ２ -O-C ３ H ６ SiCS ３ 、C ３ F ７ -O-(CF(CF ３ )CF ２ -O) ２ -CF(CF ３ )CONNH-(CH ２) ３ Si(OCH ３ ) ３ and organosilazane compounds such as hexamethyldisilazane, hexaphenyldisilazane, trisilazane, cyclotrisilazane, and 1,1,3,3,5,5-hexamethylcyclotrisilazane.

[0039] The amount of the silane coupling agent attached is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, and even more preferably 0.10 parts by mass or more, per 100 parts by mass of the spherical silica particles, and is more preferably 5 parts by mass or less, and even more preferably 2 parts by mass or less.

[0040] The fact that the surfaces of the spherical silica particles have been treated with a silane coupling agent can be confirmed by detecting a peak due to a substituent of the silane coupling agent by IR. The amount of the silane coupling agent attached can be measured by the carbon content.

[0041] The spherical silica particles are preferably contained in the silica particle dispersion in a range of 10 to 85% by mass. When the content of spherical silica particles is 10% by mass or more, the desired peel strength can be imparted with a small amount of silica particle dispersion added to the resin composition, and when it is 85% by mass or less, the viscosity of the dispersion does not increase too much, making it easy to handle. The content of spherical silica particles in the silica particle dispersion is more preferably 15% by mass or more, even more preferably 20% by mass or more, particularly preferably 25% by mass or more, more preferably 80% by mass or less, even more preferably 75% by mass or less, particularly preferably 70% by mass or less, and most preferably 60% by mass or less.

[0042] (Silane compound) The silica particle dispersion of the present invention preferably contains a silane compound having at least one group selected from the group consisting of a vinyl group, a phenyl group, a phenylamino group, an alkyl group having 4 or more carbon atoms, a methacryl group and an epoxy group.By containing the silane compound, when the silica particle dispersion is contained in a resin composition, the surface of the spherical silica particles is adapted to the resin, so that the peel strength of the resin composition can be further improved.In addition, when the spherical silica particles are treated with a silane coupling agent, it is not necessarily necessary to add a silane compound.

[0043] Examples of the silane compound include vinyl silane, phenyl silane, phenylamino silane, hexyl silane, decyl silane, 3-methacryloxypropyl trimethoxy silane, and aminopropyl silane. These may be used alone or in combination of two or more. Among these, from the viewpoint of interaction with the resin, silane compounds containing a vinyl group, a phenyl group, a methacryl group, an epoxy group, or a phenylamino group are preferred, silane compounds containing a vinyl group, a phenyl group, a methacryl group, or a phenylamino group are more preferred, and silane compounds containing a phenyl group or a methacryl group are even more preferred. In this case, the dispersibility of the silica particles in the kneaded product described below and the silica particle dispersion of the present invention is improved, and it is particularly easy to maintain a balance between the viscosity and the peel strength of a molded product formed therefrom.

[0044] The silane compound is preferably contained in the silica particle dispersion in a range of 0.01 to 5% by mass. When the silane compound content is 0.01% by mass or more, when the silica particle dispersion is incorporated into a resin composition, the compatibility between the spherical silica particles and the resin is improved, thereby increasing the peel strength of the resin composition. When the silane compound content is 5% by mass or less, the silane compound is prevented from remaining in the composition, thereby reducing its impact on the physical properties of the resin composition. The content of the silane compound in the silica particle dispersion is more preferably 0.02% by mass or more, even more preferably 0.04% by mass or more, particularly preferably 0.05% by mass or more, and more preferably 4% by mass or less, particularly preferably 3% by mass or less.

[0045] (Organic Thixotropic Agent) The silica particle dispersion of the present invention preferably further contains an organic thixotropic agent, which is added to suppress aggregation and precipitation of the spherical silica particles in the silica particle dispersion and the resin composition or slurry containing the silica particle dispersion, and to improve the wettability of the flux to the cured resin composition or slurry.

[0046] Examples of organic thixotropic agents include fatty acid amides (amide wax-based) synthesized from vegetable oil fatty acids and amines; surfactants such as fatty acid esters, polyethers, sulfated oils, and higher alcohol sulfates; polycarboxylic acid esters; polycarboxylic acid amides; and urea-modified compounds, but do not include hydrogenated castor oil-based agents known as castor oil waxes or oxidized polyethylene-based waxes obtained by oxidizing polyethylene and introducing polar groups. One type of organic thixotropic agent may be used alone, or two or more types may be used in combination.

[0047] Organic thixotropic agents are commercially available, for example, BYK (registered trademark)-R606, BYK (registered trademark)-405, BYK (registered trademark)-R605, BYK (registered trademark)-R607, BYK (registered trademark)-410, BYK (registered trademark)-411, BYK (registered trademark)-415, BYK (registered trademark)-430, BYK (registered trademark)-431, BYK (registered trademark)-7410ET, and BYK (registered trademark)-7411E. S (all manufactured by BYK Japan), TALEN 1450, TALEN 2000, TALEN 2200A, TALEN 7200-20, TALEN 8200-20, TALEN 8300-20, TALEN 8700-20, TALEN BA-600, FLOWNON SH-290, FLOWNON SH-295S, FLOWNON SH-350, FLOWNON HR-2, FLOWNON HR-4AF (all manufactured by Kyoeisha Chemical Co., Ltd.).

[0048] The organic thixotropic agent is preferably contained in the silica particle dispersion in a range of 0.01 to 5% by mass. When the organic thixotropic agent content is 0.01% by mass or more, aggregation of the spherical silica particles in the dispersion is suppressed, and when the silica particle dispersion is incorporated into a resin composition, accumulation of resin between the spherical silica particles can be suppressed. This increases the peel strength of the resin composition. Furthermore, when the organic thixotropic agent content is 5% by mass or less, residue in the composition can be suppressed, reducing the impact on the physical properties of the resin composition. The content of the organic thixotropic agent in the silica particle dispersion is more preferably 0.02% by mass or more, even more preferably 0.04% by mass or more, particularly preferably 0.05% by mass or more, and more preferably 4% by mass or less, even more preferably 3% by mass or less, and particularly preferably 2.5% by mass or less.

[0049] The silica particle dispersion of the present invention may contain other optional components, such as other inorganic fillers such as alumina, curing compositions, etc., as long as the effects of the present invention are not impaired.

[0050] (Physical Properties of Silica Particle Dispersion) The silica particle dispersion of the present invention preferably has a viscosity of 20 to 20,000 mPa·s at 25°C when the solids concentration of spherical silica particles is 70% by mass. If the viscosity of a silica particle dispersion with a solids concentration of spherical silica particles of 50% by mass at 25°C is 20 mPa·s or more, sedimentation (floating) separation of the silica can be prevented, and if it is 20,000 mPa·s or less, the dispersion state of the silica can be maintained while it is usable. The viscosity is more preferably 50 mPa·s or more, even more preferably 75 mPa·s or more, particularly preferably 100 mPa·s or more, and most preferably 500 mPa·s or more. It is more preferably 15,000 mPa·s or less, even more preferably 12,000 mPa·s or less, and particularly preferably 10,000 mPa·s or less.

[0051] <Method for producing silica particle dispersion> The silica particle dispersion of the present invention is obtained by dispersing a powder of spherical silica particles in a solvent. The spherical silica particles may be obtained by manufacturing, or commercially available spherical silica particles may be used. Below, a method for producing spherical silica particles and a method for producing a silica particle dispersion using the same will be described.

[0052] (Method for producing spherical silica particles) Examples of methods for producing spherical silica particles include a method of forming a spherical silica precursor by a wet method and obtaining spherical silica particles from this precursor. The wet method refers to a method that includes a step of using a liquid silica source and gelling it to obtain a raw material for spherical silica particles. Since spherical silica particles can be formed using a wet method, there is no need to adjust the particle shape by grinding or the like, and as a result, particles with a small specific surface area can be obtained. In addition, the wet method is less likely to produce particles that are significantly smaller than the average particle diameter, and the specific surface area tends to be small after firing. In addition, in the wet method, the amount of impurity elements such as titanium can be adjusted by adjusting the impurities in the silica source, and the aforementioned impurity elements can be uniformly dispersed in the particles.

[0053] Examples of wet methods include spraying and emulsion gelation. The emulsion gelation method involves, for example, emulsifying a dispersed phase containing a silica precursor with a continuous phase, and gelling the resulting emulsion to obtain a spherical silica precursor. A preferred emulsification method involves supplying a dispersed phase containing a silica precursor to a continuous phase through a micropore or porous membrane to produce an emulsion. This produces an emulsion with uniform droplet size, resulting in spherical silica with a uniform particle size. Examples of such emulsification methods include a micromixer method and a membrane emulsification method. For example, the micromixer method is disclosed in International Publication No. 2013 / 062105.

[0054] The pore volume of the spherical silica precursor obtained by the wet method is preferably 0.3 to 2.2 ml / g. When the pore volume of the silica precursor is 0.3 ml / g or more, the silica particles shrink sufficiently during calcination, allowing the specific surface area to be reduced. The pore volume of the silica precursor is preferably 0.3 ml / g or more, more preferably 0.6 ml / g or more, and even more preferably 0.7 ml / g or more. Furthermore, when the pore volume of the silica precursor is 2.2 ml / g or less, the bulk density of the charge before calcination can be prevented from becoming too high, thereby improving productivity. The pore volume of the silica precursor is preferably 2.2 ml / g or less, more preferably 1.8 ml / g or less, and most preferably 1.5 ml / g or less.

[0055] The pore volume is determined by the BJH method based on the nitrogen adsorption method using a specific surface area / pore distribution measuring device (for example, "BELSORP-mini II" manufactured by Microtrac-Bell, or "Tristar II" manufactured by Micromeritics).

[0056] The ignition loss of the silica precursor obtained by the wet method is preferably 5.0 to 15.0% by mass. The ignition loss is the sum of the water adhering to the silica precursor and the water generated by condensation of silanol groups contained in the silica precursor. When the silica precursor has an appropriate number of silanol groups, condensation progresses during calcination, making it easier for the silanol groups to be reduced. If the ignition loss is too high, the yield during calcination decreases and productivity deteriorates. Therefore, the ignition loss of the silica precursor is preferably 15.0% by mass or less, more preferably 13.0% by mass or less, and most preferably 12.0% by mass or less. If the ignition loss is too low, silanol groups are more likely to remain during calcination. Therefore, the ignition loss of the silica precursor is preferably 5.0% by mass or more, more preferably 6.0% by mass or more, and most preferably 7.0% by mass or more.

[0057] Here, the ignition loss is determined in accordance with JIS K0067 as the mass loss when 1 g of silica precursor is heated and dried at 850° C. for 0.5 hours.

[0058] The spherical silica particles are obtained by heat-treating the spherical silica precursor. In the heat treatment, the spherical silica particles are sintered to densify the shell, reduce the amount of silanol groups on the surface, and lower the dielectric loss tangent. The heat treatment temperature is preferably 700°C or higher, more preferably 800°C or higher, and most preferably 900°C or higher. If the temperature is too high, the particles tend to aggregate and the particle size in the resin composition increases, so the heat treatment temperature is preferably 1600°C or lower, more preferably 1500°C or lower, and most preferably 1400°C or lower. In other words, the heat treatment is preferably performed in the range of 700 to 1600°C.

[0059] The heat treatment method is not particularly limited, but examples thereof include a stationary heat treatment, a rotary kiln heat treatment, and a spray combustion heat treatment.

[0060] The spherical silica particles obtained by the above steps may be aggregated due to the drying or calcination steps, so they may be crushed to make the aggregate size easier to handle, but in the present invention, the silica particle dispersion is obtained by mixing the particles directly with a solvent. Examples of crushing methods include a method using a mortar, a method using a dry or wet ball mill, a method using a shaking sieve, or a method using a crusher such as a pin mill, a cutter mill, a hammer mill, a knife mill, a roller mill, or a jet mill.

[0061] In this manner, the spherical silica particles used in the silica particle dispersion of the present invention are obtained.

[0062] (Preparation of Silica Particle Dispersion) The obtained spherical silica particles are mixed with a solvent to obtain a silica particle dispersion. The method for producing a silica particle dispersion of the present invention includes mixing a solvent with a powder of spherical silica particles, dispersing the mixture, and classifying it to remove agglomerates of the spherical silica particles. The spherical silica particles have a median diameter d50 of 0.5 to 20 μm and a specific surface area A (m ２ / g) and the median diameter d50 (μm), the product A×d50 is 2.7 to 5.0 μm ２ The type and amount of the solvent and other physical properties of the spherical silica particles are as described above.

[0063] The spherical silica particle powder is preferably mixed in the silica particle dispersion at a ratio of 10 to 85% by mass. If the ratio of spherical silica particles is too low, productivity in the subsequent concentration step decreases, while if it is too high, the viscosity of the silica particle dispersion increases too much, which may decrease productivity in the dispersion treatment. Therefore, the range of 10 to 85% by mass is preferable. The amount of spherical silica particles used is more preferably 15% by mass or more, even more preferably 20% by mass or more, particularly preferably 25% by mass or more, more preferably 80% by mass or less, even more preferably 75% by mass or less, particularly preferably 70% by mass or less, and most preferably 60% by mass or less.

[0064] For the dispersion treatment of the mixed liquid containing the solvent and spherical silica particles, a dispersing device used for pigment dispersion etc. can be used. For example, mixers such as a Disper, Homomixer, Planetary Mixer, homogenizers (M Technique's "Clearmix", PRIMIX, etc., and Silverson's "Abramix", etc.), paint conditioners (Red Devil), colloid mills (PUC Colloid Mill, PUC, IKA, Colloid Mill MK), cone mills (IKA, I ... Examples of suitable dispersers include media-type dispersers such as a wet jet mill (such as the "Dynomill" manufactured by Shinmaru Enterprises), an attritor, a pearl mill (such as the "DCP Mill" manufactured by Eirich), and a Coball mill; media-less dispersers such as the wet jet mill (such as the "Zenus PY" manufactured by Genus, the "Starburst" manufactured by Sugino Machine, and the "Nanomizer" manufactured by Nanomizer), the "Clear SS-5" manufactured by M Technique, and the "MICROS" manufactured by Nara Kikai; and other roll mills and kneaders. Among these, those that do not use grinding media (such as balls and beads) are preferred. This is because the use of grinding media raises concerns about contamination from worn media. Specifically, media-less dispersers such as the wet jet mill (such as the "Zenus PY" manufactured by Genus, the "Starburst" manufactured by Sugino Machine, and the "Nanomizer" manufactured by Nanomizer), the "Clear SS-5" manufactured by M Technique, and the "MICROS" manufactured by Nara Kikai are preferred.

[0065] The temperature during dispersion treatment is preferably 0 to 100°C. Here, the temperature during dispersion treatment refers to the temperature range before and after treatment. By performing dispersion treatment within this temperature range, the viscosity of the solvent is maintained at an appropriate level, productivity is maintained, and evaporation of the solvent is suppressed, making it possible to easily control the solid content. The treatment temperature is more preferably 5°C or higher, even more preferably 10°C or higher, and more preferably 90°C or lower, and even more preferably 80°C or lower.

[0066] The time for the dispersion treatment may be appropriately set depending on the dispersion device used so as not to cause particle destruction, but is preferably 0.5 to 60 minutes, more preferably 0.5 to 10 minutes, and even more preferably 0.5 to 5 minutes.

[0067] Thereafter, the agglomerates of spherical silica particles that remain after the dispersion treatment are subjected to wet classification. Examples of wet classification include classification using a sieve or centrifugal force. When using a sieve, classification is preferably performed using a sieve with a mesh size of 100 μm or less. As the sieve, for example, a metal sieve with a dense lattice structure, such as an electroformed sieve, is preferably used.

[0068] The sieve opening is preferably 100 μm or less, more preferably 75 μm or less, even more preferably 50 μm or less, and particularly preferably 35 μm or less. The lower limit of the sieve opening is preferably 0.2 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more. That is, the sieve opening is preferably in the range of 0.2 to 100 μm.

[0069] Thereafter, the mixture may be diluted or concentrated as necessary to adjust the concentration to an appropriate level. Concentration methods include evaporation concentration and solid-liquid separation.

[0070] In the method for producing a silica particle dispersion of the present invention, a silane coupling agent may be added to the mixture of the solvent and the spherical silica particles. Examples of the silane coupling agent include the silane coupling agents described above.

[0071] <Resin Composition> The silica particle dispersion of the present invention can be mixed with a resin to form a resin composition. The resin composition preferably contains spherical silica particles in an amount of 5 to 70% by mass, more preferably 10 to 50% by mass.

[0072] Examples of resins that can be used include epoxy resins, silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyamides such as polyimides, polyamideimides, and polyetherimides; polyesters such as polybutylene terephthalate and polyethylene terephthalate; polyphenylene sulfide, aromatic polyesters, polysulfones, liquid crystal polymers, polyethersulfones, polycarbonates, maleimide-modified resins, ABS resins, AAS (acrylonitrile-acrylic rubber-styrene) resins, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resins, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA), tetrafluoroethylene-hexafluoropropylene copolymers (FEP), and tetrafluoroethylene-ethylene copolymers (ETFE). The dielectric loss tangent of a resin composition also depends on the properties of the resin, so the resin to be used should be selected taking these factors into consideration.

[0073] The resin composition may contain optional components other than the resin and medium, such as a dispersing aid, a surfactant, and a filler other than silica.

[0074] When a resin film is produced using the resin composition of the present invention, its dielectric loss tangent is preferably 0.012 or less at a frequency of 10 GHz, more preferably 0.010 or less, and even more preferably 0.009 or less. If the dielectric loss tangent at a frequency of 10 GHz of the resin film is 0.012 or less, the resin film has excellent electrical properties and can be expected to be used in electronic devices, communication devices, etc. The smaller the dielectric loss tangent, the more the circuit transmission loss can be suppressed, so the lower limit is not particularly limited.

[0075] The dissipation factor can be measured using a split post dielectric resonator (SPDR) (eg, manufactured by Agilent Technologies).

[0076] The resin film preferably has an average linear expansion coefficient of 10 to 50 ppm / °C. When the average linear expansion coefficient is within this range, it is close to the thermal expansion coefficient of copper foil, which is widely used as a substrate, and therefore has excellent electrical properties. The average linear expansion coefficient is more preferably 12 ppm / °C or higher, even more preferably 15 ppm / °C or higher, and more preferably 40 ppm / °C or lower, even more preferably 30 ppm / °C or lower.

[0077] The average linear expansion coefficient can be determined by using a thermomechanical analyzer (for example, "TMA-60" manufactured by Shimadzu Corporation) to heat the resin film under a load of 5 N at a temperature increase rate of 2°C / min, measuring the dimensional change of the sample from 30°C to 150°C, and calculating the average.

[0078] The silica particle dispersion of the present invention can be used as various fillers, and is particularly suitable as a filler for resin compositions used in the production of electronic substrates for electronic devices such as personal computers, notebook computers, and digital cameras, and communication devices such as smartphones and game consoles. Specifically, the silica particle dispersion of the present invention is expected to be applied to resin compositions, prepregs, metal foil-clad laminates, printed wiring boards, resin sheets, adhesive layers, adhesive films, solder resists, bump reflow materials, rewiring insulating layers, die bond materials, encapsulants, underfills, mold underfills, and laminated inductors, etc., in order to reduce dielectric loss tangent, transmission loss, moisture absorption, and improve peel strength.

[0079] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following description, the same components are used. Examples 1 to 7 are examples, and Examples 8 to 10 are comparative examples.

[0080] Test Example 1 In Test Example 1, spherical silica particles were prepared, and a silica particle dispersion was prepared using the obtained spherical silica particles.

[0081] Example 1: Silica powder 1 (AGC Si-Tech Co., Ltd.: H-31, d50 = 3.5 μm) produced by a wet process was used as the spherical silica precursor. 150 g of silica powder 1 was charged into an alumina crucible and heat-treated at a temperature of 1200°C in an electric furnace for 1 hour. After the heat treatment, the mixture was cooled to room temperature and crushed in an agate mortar to obtain a spherical silica powder, which is an aggregate of spherical silica particles.

[0082] 100 g of the obtained spherical silica powder and 43 g of methyl ethyl ketone (MEK) were placed in a 250 ml polyvinyl chloride bottle and stirred at 30 rpm for 2 hours using a mix rotor. The resulting mixture was sprayed three times from a φ0.1 mm nozzle using a wet microparticulation device (Starburst Mini, manufactured by Sugino Machine Co., Ltd., model number: HJP-25001) at a pressure of 100 MPa. The resulting slurry was passed through an electroformed sieve with 10 μm openings to obtain a silica particle dispersion with a solids content of 70 mass %.

[0083] Example 2 A silica particle dispersion was obtained by the same treatment as in Example 1, except that silica powder 2 (manufactured by AGC Si-Tech Co., Ltd.: H-51, d50 = 5.5 μm) produced by a wet method was used as the spherical silica precursor.

[0084] Example 3 A silica particle dispersion was obtained by the same treatment as in Example 1, except that silica powder 3 (manufactured by AGC Si-Tech Co., Ltd.: H-121, d50 = 13 μm) produced by a wet method was used as the spherical silica precursor and the slurry was passed through an electroformed sieve with a mesh size of 30 μm.

[0085] Example 4 A silica particle dispersion was obtained by the same treatment as in Example 1, except that silica powder 4 (manufactured by AGC Si-Tech Co., Ltd.: H-201, d50=20 μm) produced by a wet method was used as the spherical silica precursor and the slurry was passed through an electroformed sieve with a mesh size of 40 μm.

[0086] Example 5: 100 g of the spherical silica powder obtained in Example 4, 43 g of methyl ethyl ketone (MEK), and 0.10 g of KBM-503 (3-methacryloxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.) were placed in a 250 ml polyvinyl chloride bottle and stirred at 30 rpm for 2 hours using a mix rotor. The resulting mixture was heated at 80°C for 1 hour, cooled, and then sprayed three times from a φ0.1 mm nozzle at a pressure of 100 MPa using a wet microparticulation device (Starburst Mini, manufactured by Sugino Machine Co., Ltd., model number: HJP-25001). The resulting slurry was passed through an electroformed sieve with 10 μm openings to obtain a silica particle dispersion with a solids content of 70% by mass.

[0087] Example 6: 100 g of the spherical silica powder obtained in Example 4, 43 g of methyl ethyl ketone (MEK), and 0.10 g of BYK (registered trademark)-R606 (polyhydroxycarboxylic acid ester, manufactured by BYK-Chemie) were placed in a 250 ml plastic bottle and stirred at 30 rpm for 2 hours using a mix rotor. The resulting mixture was sprayed three times from a φ0.1 mm nozzle using a wet microparticulation device (Starburst Mini, manufactured by Sugino Machine Co., Ltd., model number: HJP-25001) at a pressure of 100 MPa. The resulting slurry was passed through an electroformed sieve with 10 μm openings to obtain a silica particle dispersion with a solids content of 70% by mass.

[0088] Example 7 A silica particle dispersion was obtained in the same manner as in Example 5, except that KBM-503 was changed to 0.10 g of KBM-103 (trimethoxyphenylsilane, manufactured by Shin-Etsu Chemical Co., Ltd.).

[0089] Example 8 Spherical silica powder 5 (manufactured by Denka: FB-5D) produced from raw material silica produced by a dry method was used. 150 g of spherical silica powder 5 was charged into an alumina crucible and heat-treated at a temperature of 1300°C in an electric furnace for 1 hour. After the heat treatment, the mixture was cooled to room temperature and crushed in an agate mortar to obtain spherical silica powder. Using the obtained spherical silica powder, a silica particle dispersion was obtained in the same manner as in Example 1.

[0090] Example 9 A silica particle dispersion was obtained in the same manner as in Example 1, except that spherical silica powder 6 (manufactured by Admatechs Co., Ltd.: SC-04) produced from raw material silica produced by the VMC method was used.

[0091] Example 10 10 g of the spherical silica powder obtained in Example 4 was used as it was.

[0092] The spherical silica powders prepared in the above examples were measured for specific surface area, median diameter, viscosity when kneaded, and viscosity of a 70% by mass dispersion by the following methods. The results are shown in Table 1.

[0093] 1. Specific Surface Area The spherical silica particles were dried under reduced pressure at 230°C to completely remove moisture, and used as a sample. The specific surface area of ​​this sample was determined by the multipoint BET method using nitrogen gas with a Micromeritics automatic specific surface area and pore distribution measuring device "Tristar II."

[0094] 2. Median diameter The median diameter was measured using a laser diffraction particle size distribution analyzer (MT3300EXII manufactured by Microtrac-Bell). The spherical silica particles were dispersed in the analyzer by irradiating them with ultrasonic waves three times for 60 seconds, and then the measurement was carried out. The measurement was carried out twice for 60 seconds each, and the average value was calculated.

[0095] 3. Viscosity of the kneaded product 6 parts by mass of boiled linseed oil (manufactured by Yamakei Sangyo Co., Ltd.) and 8 parts by mass of spherical silica particles were mixed and kneaded for 3 minutes at 2000 rpm using a rotation-revolution type mixer, Awatori Rentaro (manufactured by Thinky Corporation) to prepare a kneaded product. The obtained kneaded product was measured using a rotational rheometer at a shear rate of 1 s －１ The viscosity at the time of 30 seconds was determined. The viscosity measured for boiled linseed oil alone was 46 mPa·s.

[0096] 4. Viscosity of Silica Particle Dispersion 42 g of spherical silica particles and 18 g of methyl ethyl ketone (MEK) were placed in a 100 ml plastic bottle (solids concentration: 70% by mass) and stirred at 30 rpm for 2 hours using a mix rotor. The resulting mixture was sprayed three times from a 0.1 mm diameter nozzle using a wet atomization device (Starburst Mini, model HJP-25001, manufactured by Sugino Machine Co., Ltd.) at a pressure of 50 MPa. The resulting slurry was adjusted to 25°C, and its viscosity was measured for 30 seconds using a rotational rheometer (Modular Rheometer Physica MCR-301, manufactured by Anton Paar) at a shear rate of 1 rpm. The viscosity at 30 seconds was determined.

[0097] Test Example 2 (Preparation of Evaluation Sample A (Resin Film)) A resin film was prepared using the silica particle dispersions of Examples 1 to 9 and the spherical silica powder of Example 10. 25 parts by mass of biphenyl-type epoxy resin (epoxy equivalent: 276, "NC-3000" manufactured by Nippon Kayaku Co., Ltd.) was heated and dissolved in 13 parts by mass of methyl ethyl ketone (MEK) while stirring. After cooling to room temperature, 32 parts by mass of an active ester curing agent ("HP8000-65T" manufactured by DIC Corporation, active group equivalent 223, toluene solution with 65% by mass of non-volatile components) was mixed therein and kneaded for 5 minutes at 2000 rpm using a foaming mixer. 0.9 parts by mass of 4-dimethylaminopyridine (DMAP) and 1.6 parts by mass of 2-ethyl-4-methylimidazole ("2E4MZ" manufactured by Shikoku Chemicals Corporation) were then mixed as curing accelerators, and the mixture was mixed for 5 minutes at 2000 rpm using a homodisper. A silica particle dispersion or spherical silica powder was weighed and mixed therein so as to obtain 90 parts by mass of particle powder, and the mixture was mixed for 5 minutes at 2000 rpm using a homodisper.

[0098] Next, a release-treated transparent polyethylene terephthalate (PET) film ("PET5011 550" manufactured by Lintec Corporation, thickness 50 μm) was prepared. The obtained varnish was applied to the release-treated surface of this PET film using an applicator so that the thickness after drying would be 40 μm, and after drying for 10 minutes in a gear oven at 100 ° C, it was cut to produce an uncured laminate film comprising an uncured resin film (B-stage film) measuring 200 mm in length x 200 mm in width x 40 μm in thickness. The obtained uncured laminate film was heated for 90 minutes in a gear oven set at 190 ° C to cure the uncured resin film, and a cured film was produced.

[0099] (Preparation of Evaluation Sample B (Laminate)) (1) Lamination Process: A single-sided roughened copper foil (F0-WS, thickness 18 μm, surface roughness Rz = 1.2 μm, manufactured by Furukawa Electric Co., Ltd.) was prepared. Using a batch vacuum laminator MVLP-500-IIA manufactured by Meiki Seisakusho Co., Ltd., the uncured laminate film prepared above was laminated onto this copper foil so that the surface of the uncured resin film (B-stage film) faced the roughened surface of the copper foil, thereby obtaining a laminate structure consisting of copper foil / B-stage film / PET film. The lamination conditions were as follows: the pressure was reduced for 30 seconds to a pressure of 13 hPa or less, and then the laminate was pressed at 100 ° C and a pressure of 0.8 MPa for 30 seconds. (2) Film Peeling Process: The PET film of the laminate structure was peeled off. (3) Curing Process: The laminate was placed in a gear oven with an internal temperature of 180 ° C for 30 minutes, and the B-stage film was cured to form an insulating layer.

[0100] (Evaluation) 1. Measurement of peel strength A 1 cm wide rectangular cut was made on the copper foil side of Evaluation Sample B. The substrate was set in a 90° peel tester, and the end of the copper plating where the cut had been made was picked up with a gripping tool, and the copper plating was peeled off by 20 mm to measure the peel strength (N / cm).

[0101] 2. Granularity of the coating film The appearance of the uncured laminate film was observed to evaluate the granularity of the coating film. The evaluation criteria are as follows. A and B ratings were judged to be practical. [Evaluation criteria] A (good): No granularity. B (fair): Fine irregularities were observed after coating. C (unfair): Streaks were observed due to adhesion of coarse particles during coating.

[0102] The test results are shown in Table 1.

[0103]

[0104] From Table 1, it can be seen that Examples 1 to 7 had higher peel strength and stronger adhesive strength than Examples 8 to 10. Furthermore, Examples 1 to 7 also had good coating film graininess, making all of them suitable for practical use. In contrast, Examples 8 to 10 had low peel strength and coating film graininess was also observed.

[0105] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2022-077093) filed on May 9, 2022, the contents of which are incorporated herein by reference.

Claims

1. The present invention comprises spherical silica particles and a solvent, the median diameter d50 of the spherical silica particles being 0.5 to 20 μm, and the specific surface area A (m ２ / g) and the median diameter d50 (μm), the product A×d50 is 2.7 to 5.0 μm ２ / g of silica particle dispersion.

2. The spherical silica particles have a specific surface area of ​​0.1 to 10 m ２ The silica particle dispersion according to claim 1 , wherein the silica particle dispersion has a molecular weight of 1000 to 10000.

3. 2. The silica particle dispersion according to claim 1, wherein the spherical silica particles have a viscosity of 5000 mPa·s or less as measured by the following measurement method. (Measurement method) The silica particle dispersion liquid is dried to obtain powdered spherical silica particles, and 8 parts by mass of the obtained powdered spherical silica particles and 6 parts by mass of boiled linseed oil are mixed and kneaded at 2000 rpm for 3 minutes. The kneaded product is subjected to a shear rate of 1 s －１ The measurement is carried out for 30 seconds, and the viscosity at the 30 second point is calculated.

4. The silica particle dispersion liquid according to claim 1 , further comprising a silane compound having at least one group selected from the group consisting of a vinyl group, a phenyl group, a phenylamino group, an alkyl group having 4 or more carbon atoms, a methacryl group, and an epoxy group.

5. The silica particle dispersion according to claim 1 , further comprising an organic thixotropic agent.

6. 2. The silica particle dispersion liquid according to claim 1, wherein the solvent comprises at least one selected from the group consisting of water, hydrocarbons, alcohols, acetates, ketones, cellosolves, glycol ethers, chlorinated hydrocarbons, and polar solvents.

7. 2. The silica particle dispersion according to claim 1, wherein the silica particle dispersion has a viscosity of 20 to 20,000 mPa·s at 25° C. when the solid content concentration of the spherical silica particles is 70% by mass.

8. A resin composition comprising the silica particle dispersion according to any one of claims 1 to 7.

9. A solvent and a solvent having a median diameter d50 of 0.5 to 20 μm and a specific surface area A (m ２ / g) and the median diameter d50 (μm), the product A×d50 is 2.7 to 5.0 μm ２ / g of spherical silica particles, and the mixture is subjected to a dispersion treatment and classified to remove agglomerates of the spherical silica particles.