Surface-treated spherical silica and method for producing surface-treated spherical silica

Abstract

The present invention relates to surface-treated spherical silica which has a median diameter d50 of 0.5-20 μm and a product of the BET specific surface area A (m2 / g) and the median diameter d50 (μm), A×d50, of 2.7-5.0 (μm·m2 / g) and which, in chromatography, has an amine peak area that is 70% or more of a theoretical value and a symmetry factor S of 8 or less. The present invention also relates to a method for producing the surface-treated spherical silica, the method including subjecting untreated spherical silica to a surface treatment, wherein a silane coupling agent to be used for the surface treatment has a value determined by dividing the molecular weight of the silane coupling agent by the number of Si atoms contained in one molecule of the silane coupling agent of 100-300.

Description

Surface-treated spherical silica and method for producing surface-treated spherical silica

[0001] The present invention relates to surface-treated spherical silica and a method for producing the surface-treated spherical silica.

[0002] The electrical insulating layer of a printed wiring board requires properties such as a low dielectric constant, a low dielectric loss tangent, and a low linear expansion coefficient. In recent years, resin compositions containing a thermosetting resin and silica particles have been used to manufacture electrical insulating layers for metal clad laminates that can be processed into printed wiring boards (see Patent Documents 1 and 2). Specifically, metal clad laminates are used in which a semi-cured product of the resin composition is laminated on the surface of a metal substrate layer as an electrical insulating layer. Another example is a metal clad laminate in which a glass cloth or the like impregnated with a resin composition is laminated on the surface of a metal substrate layer as an electrical insulating layer. Here, fillers (filling materials) are used as materials for prepregs using thermosetting resins, and the fillers themselves usually tend to increase the relative dielectric constant of the resulting prepreg. Among these, metal clad laminates using hollow fillers have been studied, as described in Patent Documents 1 to 3, because they can reduce the relative dielectric constant compared to those using solid fillers. Furthermore, when used in the resin composition, surface-treated silica is used, as described in Patent Document 4, and this has been studied.

[0003] Japanese Patent Publication No. 2008-31409 Japanese Patent Publication No. 2017-522580 International Publication No. 2019 / 230661 Japanese Patent No. 6347644

[0004] The present inventors have found that conventionally known surface-treated spherical silica does not provide sufficient adhesion between a resin composition, a semi-cured product thereof, a prepreg, etc. and a substrate made of metal, etc. Furthermore, they have found that if the surface treatment conditions are not optimized, silanol groups remain on the silica surface, resulting in a significant decrease in peel strength after a high-temperature, high-humidity test.

[0005] Therefore, an object of the present invention is to provide a surface-treated spherical silica which, when mixed with a resin for use in electronic applications, has excellent adhesion to the resin and which does not significantly deteriorate even when exposed to a high-temperature, high-humidity environment.

[0006] As a result of extensive investigations, the present inventors have found that the above-mentioned problems can be solved by ensuring that the median diameter, the product of the BET specific surface area and the median diameter, the peak area of ​​amines in chromatography, and the symmetry coefficient S of the surface-treated spherical silica fall within specific ranges, and have thus completed the present invention.

[0007] The present invention relates to the following: (1) A carbon nanotube having a median diameter d50 of 0.5 to 20 μm and a BET specific surface area A (m ２ / g) and the median diameter d50 (μm), the product A×d50 is 2.7 to 5.0 (μm·m ２ / g), the peak area of ​​an amine in chromatography is 70% or more of the theoretical value, and the symmetry coefficient S is 8 or less. (2) The BET specific surface area of ​​the surface-treated spherical silica is 0.1 to 3.5 m ２ / g. (3) The surface-treated spherical silica of (1) or (2) above, wherein the Ti content of the surface-treated spherical silica is 30 to 1500 ppm by mass. (4) A method for producing the surface-treated spherical silica of any one of (1) to (3) above, comprising surface-treating untreated spherical silica, wherein the molecular weight of the silane coupling agent used in the surface treatment divided by the number of Si atoms contained in one molecule of the silane coupling agent is 100 to 300. (5) The method for producing the surface-treated spherical silica of (4) above, wherein the surface treatment comprises contacting the untreated spherical silica with the silane coupling agent and then heating at a temperature of 50 to 200°C. (6) The method for producing the surface-treated spherical silica of (5) above, wherein a solvent is used during the contacting, and the amount of solvent charged per gram of the untreated spherical silica is 0.1 to 1.0 ml / g. (7) A resin composition comprising the surface-treated spherical silica according to any one of (1) to (3) above and a resin.

[0008] According to the present invention, it is possible to provide surface-treated spherical silica which, when mixed with a resin for use in electronic applications, has excellent adhesion to the resin and does not undergo a significant change in adhesion even when exposed to a harsh environment.

[0009] 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.

[0010] <Surface-treated spherical silica> The surface-treated spherical silica of the present invention has a median diameter d50 of 0.5 to 20 μm and a BET specific surface area A (m ２ / g) and the median diameter d50 (μm), the product A×d50 is 2.7 to 5.0 (μm·m ２ / g), the amine peak area in chromatography is 70% or more of the theoretical value, and the symmetry factor S is 8 or less.

[0011] Generally, silanol groups (Si—OH) on silica particles are classified into internal silanol groups present within the Si—O network inside the particle, isolated silanol groups present on the particle surface that are not bonded to water adsorbed on the silica particle, and bonded silanol groups that are bonded to water adsorbed on the silica particle or silanol on the silica surface. When silica particles are surface-treated, these silanol groups react with a surface treatment agent and are substituted with a substituent that makes the silica surface more compatible with resin. In this case, it has been found that if the raw materials and treatment conditions used in the surface treatment are not appropriately adjusted, adhesion to the resin decreases, and in addition, adhesion to the resin decreases significantly after a high-temperature, high-humidity test. Therefore, the surface-treated spherical silica of the present invention has a median diameter d50 of 0.5 to 20 μm and a BET specific surface area A (m ２ / g) and the median diameter d50 (μm), the product A×d50 is 2.7 to 5.0 (μm·m ２ / g), the peak area of ​​the amine in chromatography is 70% or more of the theoretical value, and the symmetry coefficient S is 8 or less. The median diameter d50 is 0.5 to 20 μm, and the BET specific surface area A (m ２ / g) and the median diameter d50 (μm), the product A×d50 is 2.7 to 5.0 (μm·m ２ / g), the peak area is 70% or more of the theoretical value, and the symmetry coefficient S is 8 or less, it is believed that the surface area relative to the particle size is controlled to be sufficiently small, the silanol groups on the silica particle surface are sufficiently reduced, and the silanol groups on the surface have sufficiently reacted with the silane coupling agent, and the silica surface is sufficiently covered with the silane coupling agent.As a result, excellent peel strength is obtained, and the silanol groups that interact with amines are sufficiently deactivated, and the silanol groups that interact with water molecules when exposed to high-temperature, high-humidity conditions are also deactivated, so that the decrease in peel strength after high-temperature, high-humidity testing is suppressed.Here, deactivation refers to a state in which the silanol groups react with the silane coupling agent and are less likely to interact with amines.

[0012] When the median diameter d50, which is the particle diameter at the point where the cumulative volume from the smallest point on the volume-based particle size distribution curve reaches 50%, is in the range of 0.5 μm or more, the surface area can be appropriately controlled and silanol groups can be appropriately reduced. Furthermore, an increase in viscosity of a resin composition in which surface-treated spherical silica is dispersed in a resin and a deterioration in the dispersibility of the surface-treated spherical silica in the resin can be suppressed. Furthermore, if the median diameter d50 exceeds 20 μm, when a resin composition containing spherical silica is formed into a film, for example, a sheet, the minimum thickness of the sheet becomes too large, which can cause granulation. Therefore, in the present invention, the median diameter d50 of the spherical silica is set to be in the range of 0.5 to 20 μm. The median diameter d50 is preferably 0.5 to 15 μm, more preferably 0.5 to 10 μm, even more preferably 1.0 to 5.0 μm, and particularly preferably 1.5 to 5.0 μm.

[0013] d50 is the volume-based cumulative 50% diameter determined using a laser diffraction particle size distribution analyzer (for example, "MT3300EXII" manufactured by Microtrac-Bell Co., Ltd.). That is, particle size distribution is measured by a laser diffraction / scattering method, and a cumulative curve is calculated from the smaller volume, assuming the total volume of the surface-treated spherical silica to be 100%, and d50 is the particle diameter at the point on the cumulative curve where the cumulative volume is 50%.

[0014] BET specific surface area A (m ２The product A×d50 of the specific surface area (specific surface area = 6 / (true density of silica 2.2 (g / cm ３ ) × median diameter d50 (μm)], and values ​​less than this are practically impossible to achieve. The larger the value of A × d50, the smaller the specific surface area per particle size, and the fewer silanol groups there are on the silica particle surface, suppressing the decrease in peel strength after high-temperature, high-humidity testing. The product A × d50 is 5.0 or less, preferably 4.5 or less, and most preferably 4.0 or less.

[0015] The theoretical peak area of ​​an amine in chromatography is 100%, so it is theoretically impossible for it to exceed 100%. The peak area is 70% or more of the theoretical value, preferably 80% or more, more preferably 90% or more, and most preferably 95% or more.

[0016] The theoretical value of the symmetry coefficient S is 1 at the minimum, and therefore, it is theoretically impossible to make it less than 1. The symmetry coefficient S is 8 or less, preferably 3 or less, more preferably 2.5 or less, even more preferably 2 or less, and most preferably 1.5 or less.

[0017] The method for measuring the peak area and symmetry factor of the amine in the above-mentioned chromatography is as follows. The surface-treated spherical silica is wet-packed into a stainless steel column with an inner diameter of 4.6 mm and a length of 100 mm, and this column is loaded into a chromatography apparatus "Prominence (manufactured by Shimadzu Corporation)" and measured under the following conditions: Eluent: MeOH / 20 mM phosphate buffer (pH 7.0) = 82 / 18 Flow rate: 0.5 mL / min Temperature: 25°C Detector: UV at 254 nm Sample: Propranolol hydrochloride The obtained peak is analyzed based on JIS K0124:2011 to obtain the peak area and symmetry factor. Note that the theoretical value of the peak area is the peak area when a similar measurement is performed without packing the surface-treated spherical silica.

[0018] The peak area and symmetry factor S of amines in chromatography of surface-treated spherical silica can be adjusted by the type and amount of surface treatment agent, the amount of solvent used during surface treatment, the temperature of surface treatment, etc.

[0019] The surface-treated spherical silica of the present invention is spherical, and its average circularity is preferably 0.90 or more. When the average circularity is 0.90 or more, the particles are essentially spherical, so the specific surface area of ​​the particles can be reduced, and the active surface is not exposed because the protrusions are not broken by vibration of the particles, so the silica particles can have a low dielectric constant. The average circularity is more preferably 0.92 or more, and particularly preferably 0.95 or more. Furthermore, the closer to a perfect sphere the more desirable it is, so 1.00 is most preferred.

[0020] The circularity can be determined by photographing particles with a scanning electron microscope (for example, "JCM-7000" manufactured by JEOL Ltd.), determining the area and perimeter of the particles using image analysis software, for example, image analysis software attached to a particle image analyzer (for example, "Morphologi4" manufactured by Malvern Instruments), and applying it to the following formula for calculation. The average value of the circularities of 20 particles is taken as the average circularity. Circularity = perimeter of a circle with the same projected area / perimeter of a particle Circumference of a circle with the same projected area: When a particle is observed from directly above, the area of ​​the shadow of the particle projected on a flat surface below is determined, and a circle equal to this area is calculated, and the length of the outline of that circle Particle perimeter: When a particle is observed from directly above, the length of the outline of the shadow of the particle projected on a flat surface below is calculated

[0021] The surface-treated spherical silica of the present invention has a BET specific surface area of ​​0.1 to 3.5 m ２ / g. The BET specific surface area is preferably 0.1 m ２ It is practically difficult to make the BET specific surface area less than 3.5 m / g. ２ When the BET specific surface area is 0.1 to 3.5 m / g or less, the increase in viscosity when the surface-treated spherical silica is dispersed in a resin to form a resin composition can be suppressed, and the dispersibility in the resin composition will not be deteriorated. ２ / g is preferred, and 0.2 to 3.0 m ２ / g is more preferable, and 0.5 to 3.0 m ２ / g is more preferable, and 0.8 to 2.8 m ２ / g is particularly preferred.

[0022] The specific surface area is determined by a multipoint BET method based on a 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).

[0023] The surface-treated spherical silica of the present invention is surface-treated with a silane coupling agent. Surface treatment with the silane coupling agent forms a strong bond between the functional group of the silane coupling agent and the silanol group, preventing the bond from being broken when the surface-treated spherical silica is mixed with a resin. Furthermore, the bond is less susceptible to moisture severance, even in high-temperature, high-humidity environments. Furthermore, bonding of organic functional groups to the silica surface by the silane coupling agent reduces the amount of remaining silanol groups on the surface, making the surface hydrophobic and improving affinity with the resin in the resin composition. This improves the dispersibility of the surface-treated spherical silica in the resin and the strength of the resin film formed. Furthermore, moisture adsorption is suppressed, thereby improving the decrease in peel strength after high-temperature, high-humidity testing. Examples of silane coupling agents include aminosilane coupling agents, allylsilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, alkylsilane coupling agents, fluorine-containing silane coupling agents, and organosilazane compounds. The silane coupling agents may be used alone or in combination of two or more.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; allylsilane-based coupling agents such as methyltrimethoxysilane, vinyltrimethoxysilane, octadecyltrimethoxysilane, phenyltrimethoxysilane, metachloroxypropyl trimethoxysilane, imidazole silane, and triazine silane; and glycidoxypropyl trimethoxysilane and glycidoxypropyl trimethoxysilane. Epoxysilane-based coupling agents such as ethoxysilane, glycidoxypropylmethyldiethoxysilane, glycidylbutyltrimethoxysilane, and (3,4-epoxycyclohexyl)ethyltrimethoxysilane; mercaptosilane-based coupling agents such as mercaptopropyltrimethoxysilane and mercaptopropyltriethoxysilane; alkylsilane-based coupling agents such as methyltrimethoxysilane, ethyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, octadecyltrimethoxysilane, dimethyldimethoxysilane, and octyltriethoxysilane; 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 ２ Si(CH ３ ) Cl ２ , C.F.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 fluorine-containing silane coupling agents such as hexamethyldisilazane, hexaphenyldisilazane, trisilazane, cyclotrisilazane, 1,1,3,3,5,5-hexamethylcyclotrisilazane, and other organosilazane compounds.

[0024] The amount of the silane coupling agent to be used 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, relative to 100 parts by mass of the spherical silica, and is preferably 5 parts by mass or less, more preferably 2 parts by mass or less. When two or more types of silane coupling agents are used in combination, the amount of the silane coupling agent to be used refers to the total amount of the silane coupling agents to be used.

[0025] Examples of methods for treating with a silane coupling agent include a dry method in which the silane coupling agent is sprayed onto spherical silica 1 before surface treatment, and a wet method in which spherical silica 1 is dispersed in a solvent and then a silane coupling agent is added to cause a reaction. (Here, "spherical silica 1" refers to untreated spherical silica before surface treatment.)

[0026] The fact that the surface of the surface-treated spherical silica has 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. The carbon content can be measured by a combustion method using a SUMIGRAPH NC-80 (manufactured by Sumika Chemical Analysis Center Co., Ltd.).

[0027] The surface treatment is preferably carried out under wet treatment conditions in order to achieve uniform treatment, and examples of the solvent used include hydrocarbon organic solvents.

[0028] Furthermore, the value obtained by dividing the molecular weight of the silane coupling agent by the number of Si atoms contained in one molecule of the silane coupling agent is preferably 100 or more and 300 or less. This value corresponds to the molecular weight of the group to which the silane coupling agent is bonded when it is bonded to the surface of the silica particles. When this value is 100 or more, the volatility of the silane coupling agent is suppressed, preventing it from evaporating during the reaction. When this value is 300 or less, steric hindrance can be prevented, preventing the phenomenon of silanol groups remaining. This value is preferably 100 or more, more preferably 150 or more, and most preferably 180 or more. Furthermore, it is preferably 300 or less, more preferably 270 or less, and most preferably 260 or less. When two or more silane coupling agents are used in combination, it is preferable that the value for each silane coupling agent is 100 or more and 300 or less.

[0029] Furthermore, in the surface treatment, the heating temperature after contacting the spherical silica 1 with the silane coupling agent is preferably 50 to 200°C. A high heating temperature increases the remaining proportion of the silane coupling agent, but if the heating temperature is too high, partial decomposition begins, and silanol groups are regenerated. A low heating temperature also reduces the reaction rate, making it easier for silanol groups to remain, which in turn deteriorates the peel strength of the resin, particularly after high-temperature, high-humidity testing. The heating temperature is more preferably 60°C or higher, even more preferably 70°C or higher, and most preferably 80°C or higher. The heating temperature is more preferably 170°C or lower.

[0030] Furthermore, in the surface treatment, the amount of solvent charged per gram of spherical silica is preferably 0.1 to 1.0 ml / g. By setting the amount of solvent charged per gram of spherical silica to 0.1 ml / g or more, an amount of solvent sufficient to sufficiently cover the surface of the spherical silica 1 is ensured, making it difficult for silanol groups to remain, and preventing a decrease in peel strength, particularly after a high-temperature, high-humidity test. Furthermore, by setting the amount of solvent charged to 1.0 ml / g or less, the amount of solvent distilled off is reduced, resulting in excellent productivity. The amount of solvent charged is preferably 0.1 ml / g or more, more preferably 0.2 ml / g or more, and most preferably 0.3 ml / g or more. Furthermore, it is preferably 1.0 ml / g or less, more preferably 0.8 ml / g or less, and most preferably 0.6 ml / g or less.

[0031] The surface-treated spherical silica of the present invention preferably contains titanium (Ti) in the range of 30 to 1500 ppm by mass. The Ti content is more preferably 80 ppm by mass or more, even more preferably 100 ppm by mass or more, and more preferably 1000 ppm by mass or less, even more preferably 500 ppm by mass or less. The Ti content can be measured by inductively coupled plasma (ICP) emission spectrometry after adding perchloric acid and hydrofluoric acid to the silica, igniting the mixture to remove the main component silicon.

[0032] Ti is an optional component that can be included in the production of surface-treated spherical silica. If fine powder is generated due to cracking of silica particles during the production of surface-treated spherical silica, the fine powder will adhere to the surface of the base particles, increasing the specific surface area of ​​the particles. By including Ti during the production of surface-treated spherical silica, densification during firing is facilitated. This makes the silica less susceptible to cracking 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 particles, thereby suppressing an increase in the specific surface area. By including 30 ppm by mass or more of Ti, densification during firing is facilitated, thereby suppressing the generation of fine powder due to cracking. When the Ti content is 1500 ppm by mass or less, the above effects can be achieved, and an increase in the amount of silanol groups can be suppressed, thereby suppressing a deterioration in the dielectric loss tangent.

[0033] The surface-treated spherical silica of the present invention 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, in addition to Ti, Na, K, Mg, Ca, Al, and Fe. The total content of alkali metals and alkaline earth metals among the impurity elements is preferably 2000 mass ppm or less, more preferably 1000 mass ppm or less, and even more preferably 200 mass ppm or less. The total is preferably 1 mass ppm or more, more preferably 2 mass ppm or more, and even more preferably 5 mass ppm or more.

[0034] <Spherical Silica 1> Spherical silica 1, i.e., untreated spherical silica before surface treatment, can be obtained by a conventionally known production method. Examples of the production method include a dry method and a wet method. Alternatively, commercially available spherical silica 1 may be used. Spherical silica 1 may be appropriately selected depending on the properties required for the surface-treated spherical silica.

[0035] The BET specific surface area and median diameter d50 of spherical silica 1 generally coincide with those of the surface-treated spherical silica. Therefore, the characteristics of spherical silica 1 may be appropriately selected based on the characteristics desired for the surface-treated spherical silica.

[0036] <Resin Composition> The surface-treated spherical silica of the present invention has excellent adhesion to resins, and therefore excellent mixability with resin compositions. The resin composition according to this embodiment contains the surface-treated spherical silica of the present invention and a resin. The content of the surface-treated spherical silica per 100 parts by mass of resin is preferably 10 to 400 parts by mass, more preferably 50 to 300 parts by mass, and even more preferably 70 to 250 parts by mass. In particular, when a high loading of silica particles is desired, the content of the silica particles is preferably 80 parts by mass or more, more preferably 90 parts by mass or more. When the content of the surface-treated spherical silica is 10 parts by mass or more, a sufficient reduction in dielectric constant is obtained, and when it is 400 parts by mass or less, adhesion between the resin composition and the metal substrate is maintained.

[0037] Examples of the resin include epoxy resin, silicone resin, phenol resin, melamine resin, urea resin, unsaturated polyester resin, fluororesin, polyamide resin such as polyimide resin, polyamideimide resin, and polyetherimide; polyester resin such as polybutylene terephthalate and polyethylene terephthalate; polyphenylene ether resin, polyphenylene sulfide resin, orthodivinylbenzene resin, aromatic polyester resin, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide-modified resin, ABS (acrylonitrile butadiene styrene) resin, AAS (acrylonitrile-acrylic rubber styrene) resin, AES (acrylonitrile ethylene propylene diene rubber styrene) resin, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-ethylene copolymer (ETFE). One or more of these may be used. 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 into consideration.

[0038] The resin preferably contains a thermosetting resin. One type of thermosetting resin may be used, or two or more types may be used. Examples of the thermosetting resin include epoxy resin, polyphenylene ether resin, polyimide resin, phenol resin, and orthodivinylbenzene resin. From the viewpoints of adhesion, heat resistance, and the like, the thermosetting resin is preferably an epoxy resin, polyphenylene ether resin, or orthodivinylbenzene resin.

[0039] From the viewpoint of adhesion, dielectric properties, etc., the weight average molecular weight of the thermosetting resin is preferably 1000 to 7000, more preferably 1000 to 5000, and even more preferably 1000 to 3000. The weight average molecular weight is determined using gel permeation chromatography (GPC) in terms of polystyrene.

[0040] The particle size distribution of the surface-treated spherical silica contained in the resin composition is preferably unimodal, which can be confirmed by the presence of a single peak in the particle size distribution measured by laser diffraction / scattering.

[0041] The resin composition may contain any component other than the resin and medium (e.g., toluene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.) Examples of the optional component include a dispersing aid, a surfactant, and a filler other than silica particles.

[0042] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these. In the following description, the same components are used in common. <Test Example 1> (Spherical Silica A) Silica 1 (manufactured by AGC Si-Tech Co., Ltd.: H-31, d50 = 3.5 μm) produced by a wet method was used as the spherical silica precursor. The titanium (Ti) content of Silica 1 was measured and found to be 300 ppm by mass. 15 g of Silica 1 was filled 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 passed through a vibrating sieve with 150 μm openings to obtain spherical silica A.

[0043] (Spherical Silica B) Spherical silica B was obtained by the same treatment as for spherical silica A, except that silica 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. The Ti content of silica 2 used as the spherical silica precursor was measured and found to be 300 ppm by mass.

[0044] (Spherical Silica C) Spherical Silica C was obtained by the same treatment as for Spherical Silica A, except that Silica 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. The Ti content of Silica 3 used as the spherical silica precursor was measured and found to be 300 ppm by mass.

[0045] (Spherical Silica D) Spherical silica D was obtained by the same treatment as for spherical silica A, except that silica 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. The Ti content of silica 4 used as the spherical silica precursor was measured and found to be 300 ppm by mass.

[0046] (Spherical Silica E) Spherical silica E was obtained by the same treatment as for spherical silica A, except that silica 6 (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. The Ti content of silica 6 used as the spherical silica precursor was measured and found to be 1,450 ppm by mass.

[0047] (Spherical Silica F) Spherical silica F was obtained by the same treatment as for spherical silica A, except that silica 7 (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. The Ti content of silica 7 used as the spherical silica precursor was measured and found to be 35 ppm by mass.

[0048] (Spherical Silica G) Silica 1 (manufactured by AGC Si-Tech Co., Ltd.: H-31, d50 = 3.5 μm) produced by a wet method was used as the spherical silica precursor. The Ti content of Silica 1 was measured and found to be 300 ppm by mass. 15 g of Silica 1 was filled into an alumina crucible and heat-treated at an electric furnace temperature of 1050°C for 6 hours. After the heat treatment, the mixture was cooled to room temperature and passed through a vibrating sieve with 150 μm openings to obtain Spherical Silica G.

[0049] (Surface Treatment) 2000 g of spherical silica particles were placed in a 3.5 L planetary mixer (Hibismix 3L-5, manufactured by PRIMIX Corporation). 3.0 g of the silane coupling agent listed in Table 1 was added to hexane, the amount of solvent per gram of spherical silica having been adjusted to the value in Table 1, and the mixture was stirred for 5 minutes with a magnetic stirrer to prepare a solution. The prepared solution was added to the planetary mixer containing the spherical silica, and nitrogen was passed through for 10 minutes while stirring at 60 rpm. The mixture was then heated to 80°C at a rate of 2°C / min while passing nitrogen through, and held at 80°C for 1 hour. After being cooled to 50°C and taken out into the atmosphere, surface-treated spherical silica was obtained. Surface-treated spherical silica of Examples 2 to 12 and 18 to 25 was obtained in this manner. In Example 1, spherical silica A was used as is without surface treatment. In addition, in Examples 13 to 17, the heating temperature was changed from 80°C to the temperature shown in Table 1, and surface-treated hollow silica was prepared in the same manner as in Example 1. In Example 26, the amount of silane coupling agent shown in Table 1 was changed to 0.5 g, in Example 27, to 1.0 g, in Example 28, to 12.0 g, and in Example 29, to 30.0 g of the silane coupling agent shown in Table 1, and surface-treated spherical silica was prepared in the same manner as in Example 1. Hereinafter, the spherical silica of Example 1 and the surface-treated spherical silica of Examples 2 to 29 may be collectively referred to as "spherical silica."

[0050] The following measurements were carried out on the spherical silica obtained in Examples 1 to 29. The results are shown in Table 1.

[0051] (Measurement by chromatography) For each example of spherical silica, the peak area and symmetry factor of the amine in chromatography were measured by the following measurement method, and the results are shown in Table 1. The spherical silica was wet-packed into a stainless steel column with an inner diameter of 4.6 mm and a length of 100 mm, and this column was loaded into a chromatography apparatus "Prominence (manufactured by Shimadzu Corporation)" and measured under the following conditions. Eluent: MeOH / 20 mM phosphate buffer (pH 7.0) = 82 / 18 Flow rate: 0.5 mL / min Temperature: 25 ° C. Detector: UV at 254 nm Sample: Propranolol hydrochloride The obtained peak was analyzed based on JIS K0124:2011 to obtain the peak area and symmetry factor. Note that the theoretical value of the peak area was the peak area when a similar measurement was performed without packing spherical silica. In Table 1, the symmetry coefficient S is "-" indicates that the amine was adsorbed to the hollow silica and could not be detected.

[0052] (Method for measuring BET specific surface area of ​​spherical silica) The spherical silica used in each example was 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 using nitrogen gas by the multi-point BET method with a Micromeritics automatic specific surface area and pore distribution analyzer "Tristar II". The results are shown in Table 1.

[0053] (Method for measuring d50 of spherical silica) The d50 of the spherical silica used in each example was measured by a laser diffraction / scattering method using a particle size distribution analyzer (MT3300EXII, manufactured by Microtrac-Bell). Specifically, measurement was performed after dispersing secondary particles of spherical silica by irradiating with ultrasonic waves for 120 seconds, and the value at which the cumulative distribution of the particle sizes obtained reached 50% was taken as d50. The results are shown in Table 1. In addition, the BET specific surface area (m ２ / g) and the median diameter (μm) ２ / g) are also shown in Table 1.

[0054] (Measurement of Peel Strength of Resin Composition Using Spherical Silica) [Example 1] 25 parts by mass of polyphenylene ether resin, 50 parts by mass of butadiene-styrene random copolymer, 0.75 parts by mass of α,α'-di(t-butylperoxy)diisopropylbenzene, 225 parts by mass of spherical silica A, and 50 parts by mass of toluene were placed in a planetary centrifugal mixer (Thinky Mixer ARE-310) and mixed at 2000 rpm for 30 minutes to obtain a resin composition. The obtained resin composition was vacuum dried at 120°C for 1 hour, and then 5 g of the composition was sampled and placed in a square mold measuring 0.3 mmt x 80 mm squares. Low-profile copper foil (thickness: 18 μm, Rz: 3.5 μm, Mitsui Kinzoku Co., Ltd., 3EC-M3-V-18) was laminated on top and bottom. The resulting laminate was heated to 200°C at a heating rate of 5°C / min and held at a pressure of 10 MPa for 120 minutes for heat molding to obtain a resin-coated metal substrate. The peel strength between the cured prepreg and the copper foil was measured for the resulting resin-coated metal substrate in accordance with IPC-TM650-2.4.8. In Table 1, this peel strength is referred to as "Peel (PPE)." Furthermore, the peel strength after a high-temperature, high-humidity test was similarly measured after the resulting resin-coated metal substrate was left in a constant-temperature, constant-humidity chamber set at 85°C and 85% RH for 24 hours. In Table 1, the peel strength after the high-temperature, high-humidity test is referred to as "High-Temperature, High-Humidity Peel." The obtained resin-coated metal substrate was etched with an etching solution (H-1000A, manufactured by Sanhayato Corporation) and dried in an oven at 100°C for 1 hour, after which the relative permittivity and dielectric loss tangent were measured using a split post dielectric resonator (SPDR) (manufactured by Agilent Technologies). The measurement results are summarized in Table 1.

[0055] [Examples 2 to 29] Resin compositions, prepregs, and resin-coated metal substrates were produced in the same manner as in Example 1, except that spherical silica A was changed to the surface-treated spherical silica shown in Table 1, and measurements similar to those in Example 1 were carried out.

[0056]

[0057] It was found that the surface-treated spherical silica of Examples 3 to 29 all had higher peel strength and peel strength after high-temperature, high-humidity testing than the comparative examples (Examples 1 and 2), and were excellent in both adhesion to resin and its reliability. On the other hand, the surface-treated spherical silica of Comparative Examples 1 and 2 had low peel strength and a significant decrease in peel strength after the high-temperature, high-humidity testing, indicating that they were inferior in adhesion to resin and its reliability.

[0058] Although the present invention has been described in detail 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. 2023-099442) filed on June 16, 2023, the entirety of which is incorporated by reference.

Claims

1. The median diameter d50 is 0.5 to 20 μm, and the BET 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), the amine peak area in chromatography is 70% or more of the theoretical value, and the symmetry factor S is 8 or less.

2. The BET specific surface area of ​​the surface-treated spherical silica is 0.1 to 3.5 m ２ The surface-treated spherical silica according to claim 1, wherein the molecular weight of the surface-treated spherical silica is 1 / g.

3. The surface-treated spherical silica according to claim 1, wherein the Ti content of the surface-treated spherical silica is 30 to 1,500 ppm by mass.

4. A method for producing the surface-treated spherical silica according to any one of claims 1 to 3, comprising subjecting untreated spherical silica to a surface treatment, wherein the molecular weight of a silane coupling agent used in the surface treatment is 100 to 300 when divided by the number of Si atoms contained in one molecule of the silane coupling agent.

5. The method for producing surface-treated spherical silica according to claim 4, wherein the surface treatment comprises contacting the untreated spherical silica with the silane coupling agent and then heating the resultant at a temperature of 50 to 200°C.

6. The method for producing surface-treated spherical silica according to claim 5, wherein a solvent is used during the contacting, and the amount of the solvent charged per gram of the untreated spherical silica is 0.1 to 1.0 ml / g.

7. A resin composition comprising the surface-treated spherical silica according to any one of claims 1 to 3 and a resin.

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