Resin composition, prepreg, metal foil clad laminate, and printed substrate

Abstract

Provided are a resin composition and a prepreg which have excellent dielectric properties and reliability, and a metal foil-clad laminate and a printed circuit board which have excellent reliability. Provided is a resin composition containing: hollow particles that have a shell containing a resin and a hollow portion surrounded by the shell, have a porosity of 55% or more, have a relative dielectric constant of 1.50 or less at a frequency of 10 GHz, have reactive unsaturated bonds on the particle surface, and have an unsaturated bond amount of 0.010 mmol / m2 or more; the resin composition contains a matrix resin having a functional group as the matrix resin, and the functional group can react with the reactive unsaturated bond of the hollow particles.

Description

Technical Field

[0001] The present invention relates to a resin composition containing hollow particles, a prepreg, a metal-clad laminate, and a printed circuit board produced using the resin composition. Background Art

[0002] In recent years, in order to cope with the high-speed line trend in the communication industry, the development of resin materials with low transmission loss, that is, resin materials with low relative permittivity and low tangent of dielectric loss angle, has been underway. As methods for reducing the relative permittivity and the tangent of dielectric loss angle of resin materials, various techniques are known, such as making the resin material porous using air with a relative permittivity of 1 and a tangent of dielectric loss angle of 0, and adding hollow particles to the resin material.

[0003] For example, Patent Document 1 discloses a resin composition containing hollow particles with an average particle diameter of 0.010 to 1 μm, and the hollow particles have a shell formed of a polymer of a monomer having an aromatic ring and a plurality of reactive groups such as divinylbenzene. Patent Document 2 discloses a resin composition containing hollow particles with a shell formed of silica and an average particle diameter of 0.1 to 20 μm. It is described that these resin compositions are both made to have a lower relative permittivity and a lower tangent of dielectric loss angle by the hollow particles, and are used for prepregs, metal-clad laminates, printed circuit boards, and the like.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: International Publication No. 2022 / 202046;

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2008-31409. Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] However, in a resin composition containing hollow particles, it is necessary to further improve the dielectric properties.

[0010] In addition, in a metal-clad laminate having an insulating layer containing hollow particles, the interface between the hollow particles and the matrix resin is likely to peel off, so the adhesion between the insulating layer and the metal foil becomes insufficient, or moisture enters the interface between the hollow particles and the matrix resin, thus easily causing problems such as the occurrence of ion migration and deterioration of dielectric properties.

[0011] Since the relative permittivity of resin is lower than that of silica, there is a need for a resin composition containing hollow particles with a shell formed of resin and capable of providing an electronic device with excellent reliability.

[0012] An object of the present invention is to provide a resin composition and a prepreg having excellent dielectric properties and reliability, and to provide a metal foil-clad laminate and a printed circuit board having excellent reliability.

[0013] Means for Solving the Problems

[0014] The present inventors have found that, in a resin composition containing hollow particles having a shell formed of a resin, when the hollow particles have a specific amount or more of reactive unsaturated bonds on the surface and the matrix resin has a functional group capable of reacting with the reactive unsaturated bonds of the hollow particles, excellent reliability is exhibited, and thus the present invention has been completed.

[0015] The present invention provides a resin composition comprising hollow particles and a matrix resin,

[0016] The above-mentioned hollow particles have a shell containing a resin and a hollow portion surrounded by the shell, a porosity of 55% or more, a relative dielectric constant of 1.50 or less at a frequency of 10 GHz, have reactive unsaturated bonds on the particle surface, and the amount of unsaturated bonds per unit area calculated by the following formula (A) based on the iodine value and specific surface area of the hollow particles is 0.010 mmol / m 2 or more,

[0017] Formula (A):

[0018] Amount of unsaturated bonds (mmol / m 2 ) = Iodine value (mmol / g) / Specific surface area (m 2 / g)

[0019] The resin composition contains a matrix resin having a functional group as the above-mentioned matrix resin, and the functional group can react with the reactive unsaturated bonds possessed by the above-mentioned hollow particles.

[0020] Furthermore, the present invention provides a prepreg obtained by impregnating a base material with the resin composition of the present invention and heating and drying it.

[0021] Furthermore, the present invention provides a metal foil-clad laminate obtained by heating and pressing a laminated prepreg in which the prepregs of the present invention are stacked and a metal foil in contact with the laminated prepreg.

[0022] Furthermore, the present invention provides a metal foil-clad laminate having: an insulating layer containing a base material and a cured product of the resin composition of the present invention; and a metal foil in contact with the insulating layer, and in the cured product of the resin composition, at least a part of the above-mentioned hollow particles is crosslinked and bonded to the above-mentioned matrix resin.

[0023] Furthermore, the present invention provides a printed circuit board comprising the metal foil-clad laminate of the present invention.

[0024] Advantages of the Invention

[0025] According to the present invention as described above, a resin composition and a prepreg excellent in dielectric properties and reliability can be provided. Furthermore, the present invention can provide a metal foil-clad laminate and a printed circuit board excellent in reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A diagram showing an example of a method for manufacturing hollow particles used to illustrate the present invention.

[0027] Figure 2 A diagram showing an example of a stirring device used in the solvent removal step. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, the resin composition, resin structure, prepreg, metal foil-clad laminate, and printed circuit board of the present invention will be described in detail.

[0029] In addition, in the present invention, "~" in a numerical range means that the numerical values described before and after it are included as the lower limit value and the upper limit value.

[0030] 1. Resin Composition

[0031] The resin composition of the present invention is characterized by containing hollow particles and a matrix resin.

[0032] The above hollow particles have a shell containing a resin and a hollow portion surrounded by the shell, a porosity of 55% or more, a relative dielectric constant of 1.50 or less at a frequency of 10 GHz, and reactive unsaturated bonds on the particle surface. The amount of unsaturated bonds per unit area calculated by the following formula (A) based on the iodine value and specific surface area of the hollow particles is 0.010 mmol / m 2 Above,

[0033] Formula (A):

[0034] Amount of unsaturated bonds (mmol / m 2 ) = Iodine value (mmol / g) / Specific surface area (m 2 / g)

[0035] The resin composition contains a matrix resin having a functional group as the above matrix resin, and the functional group can react with the reactive unsaturated bonds possessed by the above hollow particles.

[0036] The resin composition of the present invention has excellent dielectric properties by containing hollow particles, and the hollow particles have a shell containing a resin and a porosity of 55% or more. The resin composition of the present invention causes the reactive unsaturated bonds on the surface of the hollow particles to react with the functional groups of the matrix resin to form covalent bonds by, for example, heat drying or hot pressing molding. Therefore, in the resin structure obtained by heat drying or hot pressing molding the resin composition of the present invention, the adhesion at the interface between the hollow particles and the matrix resin is excellent due to crosslinking and bonding of the surface of the hollow particles and the matrix resin, and the interface between the hollow particles and the matrix resin is not easily peeled off. In addition, since moisture hardly enters the interface between the hollow particles and the matrix resin, an increase in the dielectric loss tangent and ion migration caused by moisture are not likely to occur. Further, since the dielectric loss tangent is "the degree to which a part of the energy is lost as heat when an electric field is applied", by reducing the amount of moisture, energy loss can be suppressed and the dielectric loss tangent can be reduced.

[0037] In addition, in the resin structure obtained by using the resin composition of the present invention, since the hollow particles are not easily broken and the pores are easily maintained, excellent dielectric properties are exhibited. It is presumed that since a three-dimensional crosslinked structure is formed near the surface of the hollow particles after the reactive unsaturated bonds on the surface of the hollow particles react with the functional groups of the matrix resin, the hollow particles are not easily broken.

[0038] Furthermore, in the resin composition of the present invention, the hollow particles having the above reactive unsaturated bonds and the matrix resin having the above functional groups have similar polarities and high affinity, so the dispersibility of the hollow particles in the resin composition is good. Therefore, in the resin structure obtained by using the resin composition of the present invention, aggregation of the hollow particles is suppressed, the hollow particles are uniformly dispersed, and it is easy to apply pressure evenly during pressing, so that breakage of the hollow particles is further suppressed.

[0039] In addition, in the present invention, the lower the relative dielectric constant and the dielectric loss tangent, the better the dielectric properties. In addition, in the present invention, the reliability mainly refers to the reliability when used for a printed circuit board. Specifically, it is evaluated by the metal foil peel strength and the HAST test. The change amount of Df (dielectric loss tangent) before and after the water absorption test of the resin film conducted in the following examples is equivalent to a simple test of the HAST test of a metal-clad laminate.

[0040] Hereinafter, the hollow particles contained in the resin composition of the present invention, their manufacturing method, and the matrix resin will be described in detail.

[0041] [Hollow Particles]

[0042] The hollow particles used in the present invention are particles having a shell (outer shell) containing a resin and a hollow portion surrounded by the shell, and having a reactive unsaturated bond on the outer surface of the shell.

[0043] Examples of the reactive unsaturated bond include reactive unsaturated bonds contained in vinyl, (meth)acryloyl, allyl, butenyl, maleimide, nadimide, propargyl, ethynyl, etc. Among them, an olefinic unsaturated bond is preferred, and an olefinic unsaturated bond contained in at least one selected from vinyl, (meth)acryloyl, and allyl is more preferred.

[0044] In the hollow particles used in the present invention, the reactive unsaturated bond on the outer surface of the shell is preferably a reactive unsaturated bond contained in a crosslinkable monomer unit. That is, it is preferred that at least one polymerizable functional group of the crosslinkable monomer exists on the surface of the shell in an unreacted state.

[0045] The amount of unsaturated bonds per unit area of the hollow particles used in the present invention, which is calculated by the following formula (A) based on the iodine value and specific surface area, is 0.010 mmol / m 2 or more.

[0046] Formula (A):

[0047] Amount of unsaturated bonds (mmol / m 2 ) = Iodine value (mmol / g) / Specific surface area (m 2 / g)

[0048] In addition, in the present invention, the iodine value of the hollow particles is measured according to JIS K 0070.

[0049] In the present invention, the specific surface area of the hollow particles can be calculated by the following formula (B) by regarding the hollow particles as spherical, based on the volume average particle diameter of the hollow particles and the apparent density D1 of the hollow particles. In addition, the volume average particle diameter used in the following formula (B) is the value in units of "m", and the apparent density D1 is the value in units of "g / m 3 ". In addition, in the following formula (B), the values of the volume average particle diameter and the apparent density D1 are two significant figures, and the specific surface area is rounded to the third decimal place.

[0050] Formula (B):

[0051] Specific surface area (m 2 / g) = 6 / (Volume average particle diameter (m) × Apparent density D1 (g / m 3 ))

[0052] The amount of the above-mentioned unsaturated bonds can be used as an index for the amount of reactive unsaturated bonds present on the surface of the hollow particles. In the hollow particles used in the present invention, the amount of unsaturated bonds is 0.010 mmol / m 2 or more. From the viewpoint of improving reliability, it is preferably 0.030 mmol / m 2 or more, more preferably 0.050 mmol / m 2 or more, still more preferably 0.070 mmol / m 2 or more, and even more preferably 0.080 mmol / m 2 or more. In addition, when the amount of unsaturated bonds of the hollow particles is 0.165 mmol / m 2 or more, the solvent resistance of the hollow particles is improved, and when the resin composition of the present invention contains a solvent, the penetration of the solvent into the hollow particles is suppressed. In order to make the amount of unsaturated bonds of the hollow particles 0.165 mmol / m 2 or more, for example, it is effective to add a crosslinkable monomer having a solubility in water at 20 °C of 0.5 g / L to 1000 g / L during the polymerization reaction. It is presumed that by adding a crosslinkable monomer during the polymerization reaction to further carry out the polymerization reaction, the crosslinking density of the shell is increased, and as a result, the solvent resistance of the hollow particles is improved.

[0053] The upper limit of the amount of unsaturated bonds of the hollow particles is not particularly limited. From the viewpoint of improving dielectric properties, it is preferably 0.400 mmol / m 2 or less, more preferably 0.300 mmol / m 2 or less, still more preferably 0.200 mmol / m 2 or less.

[0054] In the hollow particles used in the present invention, the hollow portion is a cavity-shaped space clearly distinguishable from the shell. The shell of the hollow particles may have a porous structure, but in this case, the hollow portion has a size that can be clearly distinguished from a plurality of minute spaces uniformly dispersed in the porous structure. From the viewpoints of mechanical strength and the like, the hollow particles used in the present invention preferably have a dense shell.

[0055] In addition, from the viewpoint of exhibiting excellent dielectric properties, the hollow particles used in the present invention preferably have the hollow portion of the hollow particles filled with a gas such as air.

[0056] The hollow particles used in the present invention may have one or more than two hollow portions. From the viewpoints of maintaining a good balance between high porosity and mechanical strength and improving dielectric properties, it is preferred to have only one or two hollow portions, and more preferably only one hollow portion. Among the hollow particles used in the present invention, the proportion of the number of particles having only one or two hollow portions is preferably 90% or more, and more preferably 95% or more. Further, the proportion of the number of particles having only one hollow portion is preferably 90% or more, and more preferably 95% or more.

[0057] In addition, the shell of the hollow particles used in the present invention and the partition walls separating adjacent hollow portions in the case of having more than two hollow portions may be porous. From the viewpoint of improving dielectric properties, it is preferably dense.

[0058] The shape of the hollow particles used in the present invention may be, for example, spherical, ellipsoidal, or amorphous, etc. From the viewpoints of the dielectric properties, dispersibility, and pressure resistance of the hollow particles, it is preferably spherical.

[0059] An example of the image of the shape of the hollow particles used in the present invention is a bag formed of a thin film and inflated with gas, and its cross-sectional view is as shown in Figure 1 hollow particle 10B in (5). In this example, a thin film is provided on the outside, and its interior is filled with gas.

[0060] In addition, the hollow portion of the hollow particles can be confirmed, for example, by observing the cross-section of the particles by SEM or directly observing the particles by TEM. The shape of the hollow particles can be confirmed, for example, by observing the hollow particles by SEM or TEM.

[0061] The hollow particles used in the present invention may contain a small amount of particles with low roundness, such as broken or deformed particles, as impurities. From the viewpoint of dielectric properties, in 100% by mass of the hollow particles, the proportion of particles with a roundness of 0.85 or less is preferably 10% by mass or less, more preferably 7% by mass or less, and further preferably 4% by mass or less.

[0062] Particles with a roundness of 0.85 or less are typically particles that have undergone deformation such as indentation or cracking, and are sometimes referred to as "abnormal particles" in the present invention. Such abnormal particles have a lower porosity than spherical hollow particles, and thus have poor dielectric properties. Therefore, by reducing the proportion of abnormal particles contained in the hollow particles, the dielectric properties of the hollow particles can be improved. In addition, compared with spherical particles, abnormal particles are prone to aggregation when dispersed in a matrix resin, and there is a problem of poor dispersibility. Furthermore, abnormal particles are easily locally subjected to external pressure, and thus have a problem of poor pressure resistance compared with spherical particles. When abnormal particles are dispersed in a matrix resin, aggregates are easily formed, and external pressure is easily applied to the aggregates, resulting in further deterioration of the pressure resistance. Therefore, by reducing the proportion of abnormal particles contained in the hollow particles, the dispersibility and pressure resistance of the hollow particles can be improved.

[0063] The roundness is defined as the value obtained by dividing the diameter of a circle (equivalent circle area diameter) having the same area as the projected image of the particle by the diameter of a circle (equivalent circle circumference diameter) having the same circumference as the projected image of the particle. In the case where the particle is a perfect sphere, the roundness is 1, and the more complex the surface shape of the particle, the smaller the value of the roundness.

[0064] The average roundness of the hollow particles used in the present invention can be 0.950 to 0.995.

[0065] In the present invention, the roundness is measured using a flow particle image measuring device at an image resolution of 0.185 μm / pixel.

[0066] As the flow particle image measuring device, it is preferably possible to use, for example, the product name "IF-3200" manufactured by JASCO INTERNATIONAL CO., LTD. The measurement sample is prepared, for example, by subjecting a mixed solution obtained by adding 0.10 to 0.12 g of hollow particles to an aqueous solution of linear alkylbenzene sulfonate (concentration 0.3%) to a 5-minute dispersion treatment using an ultrasonic cleaner.

[0067] The average roundness is the average of the roundness of arbitrarily selected 1000 to 3000 particles.

[0068] The porosity of the hollow particles used in the present invention is 55% or more. Thereby, the dielectric properties of the hollow particles are excellent, and furthermore, the lightness and heat insulation properties are also excellent. The porosity of the hollow particles used in the present invention is preferably 60% or more, more preferably 65% or more.

[0069] The upper limit of the porosity of the hollow particles is not particularly limited, and from the viewpoint of suppressing a decrease in the strength of the hollow particles and being less likely to break, it is preferably 90% or less, more preferably 85% or less, and further preferably 80% or less.

[0070] The porosity of the hollow particles is calculated based on the apparent density D1 and the true density D0 of the hollow particles.

[0071] The method for measuring the apparent density D1 of the hollow particles is as follows. First, in a volumetric flask with a volume of 100 cm 3 about 30 cm 3 of hollow particles are filled, and the mass of the filled hollow particles is accurately weighed. Then, in the volumetric flask filled with hollow particles, while taking care not to mix in air bubbles, isopropanol is accurately filled up to the graduation line. The mass of the isopropanol added to the volumetric flask is accurately weighed, and the apparent density D1 (g / cm 3 ) of the hollow particles is calculated based on the following formula (I).

[0072] Formula (I

[0073] Apparent density D1 = [mass of hollow particles] / (100 - [mass of isopropanol] / [specific gravity of isopropanol at the measurement temperature])

[0074] The apparent density D1 corresponds to the specific gravity of the entire hollow particle when the hollow part is regarded as a part of the hollow particle.

[0075] The method for measuring the true density D0 of the hollow particles is as follows. After the hollow particles are crushed in advance, about 10 g of fragments of the hollow particles are filled in a volumetric flask with a volume of 100 cm 3 , and the mass of the filled fragments is accurately weighed. Then, in the same way as the measurement of the apparent density above, isopropanol is added to the volumetric flask, the mass of the isopropanol is accurately weighed, and based on the following formula (II), the true density D0 (g / cm 3 ) of the hollow particles is calculated.

[0076] Formula (II

[0077] True density D0 = [mass of fragments of hollow particles] / (100 - [mass of isopropanol] / [specific gravity of isopropanol at the measurement temperature])

[0078] The true density D0 corresponds to the specific gravity of only the shell part in the hollow particle. It is obvious from the above measurement method that when calculating the true density D0, the hollow part is not regarded as a part of the hollow particle.

[0079] The porosity (%) of the hollow particles is calculated based on the apparent density D1 and the true density D0 of the hollow particles according to the following formula (III).

[0080] Formula (III

[0081] Porosity (%) = 100 - (apparent density D1 / true density D0) × 100

[0082] The volume average particle diameter of the hollow particles used in the present invention is not particularly limited. From the viewpoints of improving the pressure resistance and excellent dispersibility due to the reduced cohesiveness between the hollow particles, the lower limit is preferably 0.1 μm or more, more preferably 0.5 μm or more, and further preferably 1 μm or more. The upper limit is preferably 10 μm or less, more preferably 8 μm or less, and further preferably 5 μm or less. If the volume average particle diameter of the hollow particles is below the above upper limit value, the particle diameter is sufficiently small, so that it can be preferably used as a substrate material for an electronic circuit board or the like, and can also be added to a small substrate with a thin thickness.

[0083] The particle size distribution (volume average particle diameter (Dv) / number average particle diameter (Dn)) of the hollow particles is not particularly limited, and is preferably 1.1 or more and 2.5 or less, more preferably 1.1 or more and 2.0 or less. When the particle size distribution is below the above upper limit value, it tends to have excellent dielectric properties, and in addition, particles with less deviation in inter-particle properties can be obtained. In addition, when the particle size distribution is below the above upper limit value, for example, when manufacturing a sheet-like structure using the resin composition of the present invention, a product with a uniform thickness can be manufactured.

[0084] The volume average particle diameter (Dv) and number average particle diameter (Dn) of the hollow particles can be measured by a particle size distribution measuring device based on the Coulter counting method to measure the particle diameter of the hollow particles, calculate their number average and volume average respectively, and use the obtained values as the number average particle diameter (Dn) and volume average particle diameter (Dv) of the particles. The particle size distribution is the value obtained by dividing the volume average particle diameter by the number average particle diameter. The Coulter counting method is a method for measuring the particle diameter by the resistance method called the Coulter principle.

[0085] The dielectric loss tangent of the hollow particles used in the present invention at a frequency of 10 GHz is preferably 1.0×10 -3 or less, more preferably 8.0×10 -4 or less, and further preferably 6.0×10 -4 or less. The lower limit of the above dielectric loss tangent is not particularly limited, and can be, for example, 1.00×10 -4 or more.

[0086] The relative dielectric constant of the hollow particles used in the present invention at a frequency of 10 GHz is preferably 1.50 or less, more preferably 1.47 or less, further preferably 1.45 or less, and still more preferably 1.40 or less. The lower limit of the above relative dielectric constant is not particularly limited, and can be, for example, 1.00 or more.

[0087] In the present invention, the relative dielectric constant and dielectric loss tangent of the hollow particles are measured using a perturbation method measuring device.

[0088] The coefficient of thermal expansion of the hollow particles used in the present invention is preferably 1.0×10 -4 / °C or less, more preferably 8.0×10 -5 / °C or less, and still more preferably 6.0×10 -5 / °C or less. The lower limit of the above coefficient of thermal expansion is not particularly limited and is usually 1.0×10 -5 / °C or more.

[0089] In addition, in the present invention, the coefficient of thermal expansion α of the hollow particles p can be obtained from the coefficient of thermal expansion α of the molded plate composed of the matrix resin and the hollow particles c , the coefficient of thermal expansion α of the matrix resin monomer r , the volume ratio SG of the matrix resin in the above molded plate r , and the volume ratio W of the hollow particles in the above molded plate p by the following formula (IV).

[0090] α p =(α c -SG r ×α r ) / W p Formula (IV)

[0091] In addition, the coefficient of thermal expansion is measured within a specified temperature range in accordance with JIS K7197:2012.

[0092] As the matrix resin for the coefficient of thermal expansion, for example, an epoxy resin can be used.

[0093] The onset temperature of thermal decomposition of the hollow particles used in the present invention is preferably 345°C or higher, more preferably 350°C or higher. The hollow particles with the onset temperature of thermal decomposition above the above lower limit value have excellent heat resistance. The upper limit of the onset temperature of thermal decomposition of the hollow particles is not particularly limited and can be, for example, 400°C or lower.

[0094] In the present invention, the onset temperature of thermal decomposition of the hollow particles can be measured at the temperature when the weight loss is 5% by a TG-DTA apparatus in a nitrogen atmosphere under the conditions of a nitrogen flow rate of 230 mL / min and a heating rate of 10°C / min.

[0095] In addition, for the hollow particles used in the present invention, in the aqueous dispersion of hollow particles obtained by dispersing 0.35 cm 3 of hollow particles in 100 mL of ion-exchanged water, the conductivity is preferably 30 μS / cm or less.

[0096] In the aqueous dispersion obtained by dispersing hollow particles in ion exchange water, there is a tendency that the more the amount of metal or ionic surfactant dissolved from the hollow particles, the higher the conductivity. It is speculated that the metal and ionic surfactant dissolved from the hollow particles into the aqueous dispersion are attached to the particle surface in a state of being easily free from the hollow particles, and are attached to the particle surface when the particles are in a dry state. Therefore, the conductivity of the aqueous dispersion can be used as an indicator of the amount of metal and ionic surfactant attached to the surface of the hollow particles in a dry state.

[0097] When metal is attached to the surface of particles, polarization occurs when an electric field is applied, which increases the dielectric loss tangent of the particles. When surfactants are attached to the surface of particles, moisture in the air is easily absorbed, and the moisture attached to the surface of particles increases the dielectric loss tangent of the particles.

[0098] In addition, when the amount of metal and ionic surfactant dissolved from the hollow particles into the aqueous dispersion is large, there is a tendency for ion migration to occur easily in the electronic circuit substrate containing the hollow particles. In the circuit substrate containing hollow particles in the insulating resin layer, when metal or surfactant is attached to the surface of the hollow particles, in a high humidity environment, the metal or surfactant easily absorbs moisture and ionizes, thereby easily generating dendrites, and thus ion migration easily occurs. Among surfactants, especially when ionic surfactants are attached to the surface of hollow particles, ion migration is more likely to occur because they contain a large amount of ionic components, thereby further promoting the ionization of the metal.

[0099] From the viewpoint of dielectric properties and reliability, the conductivity of the aqueous dispersion of the hollow particles is more preferably 25 μS / cm or less, further preferably 20 μS / cm or less, further preferably 15 μS / cm or less, and particularly preferably 11 μS / cm or less. The lower limit of the conductivity is not particularly limited, and may be, for example, 0.5 μS / cm or more.

[0100] In the present invention, the aqueous dispersion of hollow particles for measuring electrical conductivity may further contain a dispersant if the electrical conductivity is 2 μS / cm or less in a state without containing hollow particles. The type and content of the dispersant are appropriately adjusted so that the hollow particles are uniformly dispersed. The aqueous dispersion of hollow particles for measuring electrical conductivity is in a state where no powder exists on the upper part under visual observation and all the powder is dispersed in water.

[0101] As the dispersant that can be used in the aqueous dispersion of hollow particles for measuring conductivity, a dispersant that does not change the pH and conductivity of ion exchange water when added to ion exchange water can be appropriately selected and used. For example, a nonionic surfactant (nonionic surfactant) can be used.

[0102] As the nonionic surfactant, it can be appropriately selected from known nonionic surfactants without particular limitation, and examples thereof include: polyoxyalkylene nonionic surfactants such as higher alcohol alkylene oxide adducts, alkylphenol alkylene oxide adducts, fatty acid alkylene oxide adducts, higher alkylamine alkylene oxide adducts, polyol aliphatic ester alkylene oxide adducts, polypropylene glycol ethylene oxide adducts, fatty acid amide alkylene oxide adducts, polyoxyalkylene styrenated phenyl ethers; polyol nonionic surfactants such as polyethylene oxide, fatty acid esters of glycerol, alkyl glycosides, fatty acid esters of pentaerythritol, fatty acid esters of sorbitol or sorbitan, sucrose fatty acid esters, alkyl ethers of polyols, aliphatic amides of alkanolamines; nonionic high molecular compounds having both hydrophilic groups and hydrophobic groups such as polyvinyl alcohol and polyvinylpyrrolidone. In particular, polyoxyalkylene nonionic surfactants can be preferably used.

[0103] In the aqueous dispersion of the hollow particles, the concentration of the nonionic surfactant is not particularly limited and can be, for example, 0.05% by mass to 1% by mass.

[0104] In addition, in the present invention, the hollow particles added to the aqueous dispersion for measuring the conductivity are the hollow particles just before being added to the resin composition.

[0105] In the present invention, as the hollow particles having a volume of 0.35 cm 3 , the hollow particles having a weight (g) obtained by the following formula (V) are used. In the following formula (V), the apparent density D1 of the hollow particles is the same as the apparent density D1 of the hollow particles measured when calculating the porosity described later.

[0106] Formula (V):

[0107] The weight (g) of the hollow particles having a volume of 0.35 cm 3 = the apparent density D1 (g / cm 3 ) of the hollow particles × 0.35 (cm 3 )

[0108] In addition, the content of the metal in the hollow particles used in the present invention is preferably 100 ppm or less, more preferably 70 ppm or less, further preferably 50 ppm or less, still more preferably 40 ppm or less, and particularly preferably 30 ppm or less. Here, the content of the metal is the ratio of the total mass of the metal components contained in the hollow particles to the mass of the hollow particles. The metal contained in the hollow particles used in the present invention usually comes from the dispersion stabilizer. Therefore, by sufficiently removing the dispersion stabilizer from the hollow particles, the content of the metal can be made below the above upper limit value.

[0109] When the metal content in the hollow particles is below the above upper limit value, the dielectric properties and reliability can be improved. Furthermore, in the drying process described later, the drying time can be shortened.

[0110] The metal content in the hollow particles can be measured by ICP emission spectrometry. The determination of the metal species can be carried out by X-ray fluorescence analysis (XRF). In this method, the detection limit of the metal content is usually 5 ppm.

[0111] Regarding the hollow particles used in the present invention, the total content of the surfactant and the water-soluble polymer stabilizer (hereinafter simply referred to as "surfactant, etc.") present on the particle surface is preferably 500 ppm or less, more preferably 200 ppm or less, still more preferably 100 ppm or less, and even more preferably 50 ppm or less. In addition, the water-soluble polymer stabilizer can be either organic or inorganic. When the content of the surfactant, etc. present on the surface of the hollow particles is below the above upper limit value, there is a tendency for the dielectric properties and reliability to improve. By using only an inorganic dispersion stabilizer as the dispersion stabilizer in the manufacturing process of the hollow particles described later, the content of the surfactant, etc. present on the surface of the hollow particles can be made less than the detection limit value.

[0112] In the present invention, the content of the surfactant, etc. present on the surface of the hollow particles refers to the ratio of the mass of the surfactant, etc. present on the surface of the hollow particles to the mass of the hollow particles. The surfactant, etc. present on the surface of the hollow particles can be extracted by, for example, ultrasonic treatment of the hollow particles in water. The types and masses of the surfactant, etc. extracted into the water can be determined according to 1 the peak positions and peak intensities of the 1H-NMR spectrum. In this method, the detection limit of the amount of the surfactant, etc. present on the surface of the hollow particles is usually 0.05 ppm.

[0113] In addition, in the examples of Patent Document 1, it was shown that by adding hollow particles to the insulating layer of a metal-clad laminate, the adhesion between the insulating layer and the metal foil was improved. However, in the case of manufacturing a metal-clad laminate using the resin composition disclosed in Patent Document 1, the adhesion between the insulating layer and the metal foil sometimes becomes insufficient. Since the hollow particles disclosed in Patent Document 1 are produced using a surfactant, the surfactant sometimes remains on the particle surface. When the surfactant remains on the particle surface, the interface between the hollow particles and the matrix resin is easily peeled off, so problems such as insufficient adhesion between the insulating layer and the metal foil are likely to occur, and the reliability is reduced.

[0114] The resin contained in the shell of the hollow particles used in the present invention is typically a polymer of a polymerizable monomer used in the following manufacturing method of the hollow particles. The shell of the hollow particles may further contain additives different from the resin within the range not impairing the effects of the present invention. When additives are contained, the content of the resin contained in the shell is preferably 96% by mass or more, more preferably 97% by mass or more, further preferably 98% by mass or more, and still more preferably 99% by mass or more.

[0115] In the resin composition of the present invention, the content of the hollow particles is not particularly limited. In all solid components of 100% by mass of the resin composition, as the lower limit, it is preferably 5% by mass or more, more preferably 10% by mass or more, and as the upper limit, it is preferably 50% by mass or less, more preferably 30% by mass or less, further preferably 20% by mass or less, and still more preferably 15% by mass or less. When the content of the hollow particles is at least the above lower limit value, the effects such as low dielectric loss tangent, low dielectric constant, light weight, and heat insulation of the resin composition brought by the hollow particles are excellent. When the content of the hollow particles is at most the above upper limit value, the matrix resin can be sufficiently contained in the resin composition, so that the reduction of the physical properties of the resin composition can be suppressed and the mechanical strength can be improved.

[0116] [Manufacturing method of hollow particles]

[0117] The hollow particles used in the present invention can be manufactured by, for example, the following manufacturing method based on the suspension polymerization method.

[0118] As an embodiment of the manufacturing method of the hollow particles used in the present invention, for example, a manufacturing method of hollow particles having the following steps can be cited: a step of preparing a mixed solution containing a polymerizable monomer, a hydrophobic solvent, a polymerization initiator, a dispersion stabilizer, and an aqueous medium;

[0119] A step of preparing a suspension in which droplets of a monomer composition containing the polymerizable monomer, the hydrophobic solvent, and the polymerization initiator are dispersed in the aqueous medium by suspending the above mixed solution;

[0120] A step of preparing a precursor composition in which precursor particles are dispersed in the aqueous medium by supplying the above suspension to a polymerization reaction, the precursor particles having a hollow portion surrounded by a shell containing resin and the hollow portion being filled with the hydrophobic solvent;

[0121] A step of obtaining an aqueous dispersion of hollow particles by stirring the above precursor composition in a stirring tank and blowing a gas into the above precursor composition to remove the hydrophobic solvent from the above precursor particles;

[0122] A step of performing cleaning for removing the above-described dispersion stabilizer remaining in the above-described hollow particles is carried out.

[0123] In addition, in the present invention, hollow particles in which the hollow portion is filled with a hydrophobic solvent are regarded as intermediates of hollow particles in which the hollow portion is filled with a gas, and are sometimes referred to as "precursor particles". In the present invention, a "precursor composition" refers to a composition containing precursor particles.

[0124] In the above manufacturing method, a suspension in which droplets of a monomer composition having a distribution structure in which a polymerizable monomer and a hydrophobic solvent are phase-separated, the polymerizable monomer is biased to the surface side, and the hydrophobic solvent is biased to the central portion are dispersed in an aqueous medium is prepared by suspending a mixed liquid containing a polymerizable monomer, a hydrophobic solvent, a polymerization initiator, a dispersion stabilizer, and an aqueous medium. When this suspension is supplied to a polymerization reaction, a polymer starts to precipitate on the surface of the droplets of the monomer composition, and by further performing the polymerization reaction, the surface of the droplets is solidified to form a shell, resulting in hollow particles having a hollow portion filled with a hydrophobic solvent.

[0125] By making the mixed liquid contain a crosslinkable monomer, or by adding a crosslinkable monomer to the suspension during the polymerization reaction and further performing the polymerization reaction, a reactive unsaturated bond can be introduced on the surface of the shell.

[0126] Furthermore, in the above manufacturing method, since cleaning for removing the dispersion stabilizer is carried out after removing the hydrophobic solvent from the precursor particles in the slurry, the hydrophobic solvent is removed from the hollow particles before the cleaning step, and accordingly, the remaining unreacted polymerizable monomer is also removed. When the amounts of the hydrophobic solvent and the unreacted polymerizable monomer in the aqueous dispersion of the hollow particles are large, aggregation of the hollow particles easily occurs. In the above manufacturing method, since the hydrophobic solvent and the unreacted polymerizable monomer are removed before the cleaning step, the hollow particles are less likely to aggregate during the cleaning step, and thorough cleaning of the particles can be carried out, resulting in improved cleanability.

[0127] The above manufacturing method includes a step of preparing a mixed liquid, a step of preparing a suspension, a step of supplying the suspension to a polymerization reaction, a step of removing the hydrophobic solvent from the precursor particles, and a step of performing cleaning for removing the dispersion stabilizer, and may further include other steps in addition to these. Furthermore, as long as it is technically feasible, two or more of the above steps and other additional steps can be carried out simultaneously as one step, or the order can be changed. For example, the preparation of the mixed liquid and the suspension can be carried out simultaneously in one step in such a way that the materials for preparing the mixed liquid are added while suspending.

[0128] As a preferred example of the method for manufacturing the hollow particles used in the present invention, a manufacturing method including the following steps can be cited.

[0129] (1) Mixed liquid preparation step

[0130] A step of preparing a mixed liquid containing a polymerizable monomer, a hydrophobic solvent, a polymerization initiator, a dispersion stabilizer, and an aqueous medium;

[0131] (2) Suspension step

[0132] A step of preparing a suspension in which droplets of a monomer composition containing a polymerizable monomer, a hydrophobic solvent, and a polymerization initiator are dispersed in an aqueous medium by suspending the above-mentioned mixed liquid;

[0133] (3) Polymerization step

[0134] A step of preparing a precursor composition in which precursor particles are dispersed in an aqueous medium by supplying the above-mentioned suspension to a polymerization reaction, wherein the precursor particles have a hollow portion surrounded by a shell containing a resin and the hollow portion is filled with a hydrophobic solvent;

[0135] (4) Solvent removal step

[0136] A step of removing the hydrophobic solvent from the above-mentioned precursor particles while stirring the above-mentioned precursor composition in a stirring tank and blowing a gas into the above-mentioned precursor composition to obtain an aqueous dispersion of hollow particles; and

[0137] (5) Cleaning step

[0138] A step of performing cleaning for removing the above-mentioned dispersion stabilizer remaining in the above-mentioned hollow particles.

[0139] Figure 1 is a schematic diagram showing an example of the manufacturing method of the present invention. Figure 1 (1) to (5) in correspond to the above respective steps (1) to (5). The white arrows between the respective figures indicate the order of the respective steps. In addition, Figure 1 is merely a schematic diagram for explanation, and the manufacturing method of the present invention is not limited to the manufacturing method shown in the figure. Furthermore, the structure, size, and shape of the materials used in the manufacturing method of the present invention are not limited to the structure, size, and shape of the various materials in the figure.

[0140] Figure 1 (1) of is a cross-sectional schematic diagram showing an embodiment of the mixed liquid in the mixed liquid preparation step. As shown in this figure, the mixed liquid contains an aqueous medium 1 and a low-polarity material 2 dispersed in the aqueous medium 1. Here, the low-polarity material 2 refers to a material with low polarity and difficult to mix with the aqueous medium 1. In the present invention, the low-polarity material 2 includes a polymerizable monomer, a hydrophobic solvent, and a polymerization initiator.

[0141] Figure 1 (2) is a schematic cross-sectional view showing an embodiment of the suspension in the suspension step. The suspension contains an aqueous medium 1 and droplets 3 of a monomer composition dispersed in the aqueous medium 1. The droplets 3 of the monomer composition contain a polymerizable monomer, a hydrophobic solvent, and a polymerization initiator, and the distribution within the droplets is non-uniform. The droplets 3 of the monomer composition have the following structure: the hydrophobic solvent 4a undergoes phase separation from the material 4b other than the hydrophobic solvent containing the polymerizable monomer, the hydrophobic solvent 4a tends to exist in the central portion, the material 4b other than the hydrophobic solvent tends to exist on the surface side, and a dispersion stabilizer (not shown) adheres to the surface.

[0142] Figure 1 (3) is a schematic cross-sectional view showing an embodiment of the precursor composition containing precursor particles obtained through the polymerization step, wherein the precursor particles enclose a hydrophobic solvent in the hollow portion. The precursor particles 5 have a shell 6 containing a resin and a hollow portion filled with the hydrophobic solvent 4a. The shell 6 forming the outer surface of the precursor particles 5 is formed by the polymerization of the polymerizable monomer contained in the droplets 3 of the monomer composition, and may also be formed by the further polymerization of a crosslinkable monomer added during the polymerization reaction. In Figure 1 (3), the precursor particles 5 are dispersed in the aqueous medium 1.

[0143] Figure 1 (4) is a schematic cross-sectional view showing an embodiment of the aqueous dispersion of hollow particles obtained in the solvent removal step. In the solvent removal step, by removing the hydrophobic solvent from the precursor particles, hollow particles 10A having a shell 6 containing a resin and a hollow portion 7 filled with gas are obtained. In Figure 1 (4), the hollow particles 10A are dispersed in the aqueous medium 1.

[0144] Figure 1 (5) is a schematic cross-sectional view showing an embodiment of the hollow particles after the cleaning step. The hollow particles 10B after the cleaning step generally have a reduced amount of residual polymerizable monomer and a reduced amount of residual metal compared to the hollow particles 10A before the cleaning step.

[0145] Hereinafter, the above five steps and other steps will be described in sequence.

[0146] (1) Mixed liquid preparation step

[0147] This step is a step of preparing a mixed liquid containing a polymerizable monomer, a hydrophobic solvent, a polymerization initiator, a dispersion stabilizer, and an aqueous medium. The mixed liquid may further contain other materials within the range that does not impair the effects of the present invention.

[0148] Regarding the materials of the mixed solution, they will be described in the order of (A) polymerizable monomer, (B) hydrophobic solvent, (C) polymerization initiator, (D) dispersion stabilizer, and (E) aqueous medium.

[0149] (A) Polymerizable monomer

[0150] In the present invention, a polymerizable monomer refers to a compound having a functional group capable of addition polymerization (in the present invention, sometimes simply referred to as a polymerizable functional group). In the present invention, as the polymerizable monomer, a compound having an ethylenically unsaturated bond as the functional group capable of addition polymerization is usually used. As the polymerizable functional group, a radical polymerizable group is preferred, and from the viewpoint of excellent reactivity, at least one selected from (meth)acryloyl, vinyl, and allyl is preferred, and at least one selected from (meth)acryloyl and vinyl is more preferred.

[0151] In addition, in the present invention, a polymerizable monomer having only one polymerizable functional group is called a non-crosslinkable monomer, and a polymerizable monomer having two or more polymerizable functional groups is called a crosslinkable monomer. The crosslinkable monomer can form a crosslinking bond in the polymer through a polymerization reaction. The crosslinkable monomer becomes a crosslinkable monomer unit in the shell, and the non-crosslinkable monomer becomes a non-crosslinkable monomer unit in the shell.

[0152] In addition, in the present invention, a polymerizable monomer composed of carbon and hydrogen is called a hydrocarbon monomer, a crosslinkable monomer composed of carbon and hydrogen is called a crosslinkable hydrocarbon monomer, and a non-crosslinkable monomer composed of carbon and hydrogen is called a non-crosslinkable hydrocarbon monomer. In addition, a polymerizable monomer having (meth)acryloyl as the polymerizable functional group is called an acrylic monomer, a crosslinkable monomer having (meth)acryloyl as the polymerizable functional group is called a crosslinkable acrylic monomer, and a non-crosslinkable monomer having (meth)acryloyl as the polymerizable functional group is called a non-crosslinkable acrylic monomer. In the crosslinkable acrylic monomer, as long as at least one polymerizable functional group is (meth)acryloyl, it is preferred that all polymerizable functional groups are (meth)acryloyl.

[0153] In addition, in the present invention, (meth)acrylate represents acrylate and methacrylate, (meth)acrylic acid represents acrylic acid and methacrylic acid, and (meth)acryloyl represents acryloyl and methacryloyl.

[0154] In the present invention, by including a crosslinkable monomer as the polymerizable monomer, the above-mentioned reactive unsaturated bond can be introduced to the surface of the shell.

[0155] In addition, when a crosslinkable monomer is included as a polymerizable monomer, when the suspension is supplied to the polymerization reaction, the crosslinking density of the polymer precipitated on the surface of the droplets becomes high, and furthermore, the precipitates are crosslinked with each other, so that the crosslinking density of the shell can be increased. Therefore, it is easy to form a shell with excellent strength. In addition, the hollow particles tend to be spherical, and a hollow portion clearly distinguishable from the shell is easily formed inside the particles.

[0156] From the viewpoint of improving the dielectric properties of the hollow particles, it is more preferable to include a crosslinkable monomer and a non-crosslinkable monomer as the polymerizable monomers.

[0157] Examples of the crosslinkable monomer include aromatic divinyl monomers such as divinylbenzene, divinylbiphenyl, and divinylnaphthalene; linear or branched dienes such as butadiene, isoprene, 2,3-dimethylbutadiene, pentadiene, and hexadiene, and alicyclic dienes such as dicyclopentadiene, cyclopentadiene, and ethylidene tetracyclododecene, etc. diene-based monomers; crosslinkable macromonomers such as polybutadiene, polyisoprene, block copolymers of styrene and butadiene (SBS), and block copolymers of styrene and isoprene (SIS), etc. crosslinkable hydrocarbon monomers; crosslinkable acrylic monomers such as allyl (meth)acrylate, vinyl (meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, 3-(meth)acryloyloxy-2-hydroxypropyl (meth)acrylate, 1,3-bis(methacryloyloxy)-2-hydroxypropane, trimethylolpropane tri(meth)acrylate, bis(trimethylolpropane) tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, poly(dipentaerythritol) poly(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, bisphenol A di(meth)acrylate, and their ethoxylates; crosslinkable allyl-based monomers such as diallyl phthalate; crosslinkable macromonomers such as polyphenylene ether modified with vinyl at both ends and polyphenylene ether modified with (meth)acrylate at both ends.

[0158] These crosslinkable monomers can be used alone or in combination of two or more.

[0159] From the viewpoint of reducing the dielectric loss tangent of the hollow particles, it is preferable to contain a crosslinkable hydrocarbon monomer as the crosslinkable monomer. Among the crosslinkable hydrocarbon monomers, from the viewpoint of easily introducing a reactive unsaturated bond onto the surface of the shell, an aromatic divinyl monomer is preferable, and divinylbenzene is particularly preferable. Although not particularly limited, among divinylbenzenes, at least one selected from m-divinylbenzene and p-divinylbenzene is preferable.

[0160] Examples of the non-crosslinkable monomer include aromatic monovinyl monomers such as styrene, vinyltoluene, α-methylstyrene, p-methylstyrene, ethylvinylbenzene, ethylvinylbiphenyl, and ethylvinylnaphthalene; linear or branched monoolefins such as ethylene, propylene, and butene, and alicyclic monoolefins such as vinylcyclohexane, norbornene, tricyclodecene, and 1,4-methano-1,4,4a,9a-tetrahydrofluorene; non-crosslinkable acrylic monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, tert-butylaminoethyl (meth)acrylate, glycidyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-aminoethyl (meth)acrylate, (meth)acrylic acid, (meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, methoxypolyethylene glycol (meth)acrylate, ethoxypolyethylene glycol (meth)acrylate, propoxypolyethylene glycol (meth)acrylate, butoxypolyethylene glycol (meth)acrylate, hexyloxypolyethylene glycol (meth)acrylate, octyloxypolyethylene glycol polypropylene glycol (meth)acrylate, lauryloxypolyethylene glycol (meth)acrylate, stearyloxypolyethylene glycol (meth)acrylate, phenoxypolyethylene glycol polypropylene glycol (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol propylene glycol mono(meth)acrylate, polyethylene glycol tetramethylene glycol (meth)acrylate, propylene glycol polybutylene glycol mono(meth)acrylate, and monoethylene glycol mono(meth)acrylate; carboxylic acid vinyl ester monomers such as vinyl acetate; halogenated aromatic vinyl monomers such as halogenated styrene; halogenated vinyl monomers such as vinyl chloride; vinylidene dihalide monomers such as vinylidene dichloride; vinylpyridine; non-crosslinkable macromonomers such as polystyrene modified with (meth)acrylic acid at the end and polymethyl methacrylate modified with (meth)acrylic acid at the end.

[0161] These non-crosslinkable monomers can be used alone or in combination of two or more.

[0162] From the viewpoint of reducing the dielectric loss tangent of the hollow particles, as the non-crosslinkable monomer, non-crosslinkable hydrocarbon monomers are preferred, aromatic monovinyl monomers are more preferred, and styrene and ethyl vinylbenzene are further preferred.

[0163] The content of the polymerizable monomer in the mixed liquid is not particularly limited. From the viewpoint of the balance of the porosity, particle size, and mechanical strength of the hollow particles, it is preferably 15 to 50% by mass, more preferably 20 to 40% by mass, based on 100% by mass of the total mass of the components other than the aqueous medium in the mixed liquid.

[0164] In addition, in the obtained hollow particles, from the viewpoint of suppressing the deterioration of dielectric properties and the reduction of strength, the content of the polymerizable monomer is preferably 96% by mass or more, more preferably 97% by mass or more, based on 100% by mass of the total mass of the solid components other than the hydrophobic solvent in the material that becomes the oil phase in the mixed liquid.

[0165] In addition, in the present invention, the solid components refer to all components other than the solvent, and liquid polymerizable monomers and the like are included in the solid components.

[0166] (B) Hydrophobic solvent

[0167] The hydrophobic solvent used in the production method of the present invention is a non-polymerizable and water-insoluble organic solvent.

[0168] The hydrophobic solvent functions as a spacer material for forming a hollow portion inside the particles. In the suspension step described later, a suspension in which droplets of the monomer composition containing the hydrophobic solvent are dispersed in an aqueous medium is obtained. In the suspension step, phase separation occurs inside the droplets of the monomer composition, and as a result, the less polar hydrophobic solvent tends to aggregate inside the droplets. Finally, in the droplets of the monomer composition, the hydrophobic solvent is distributed inside according to their respective polarities, and other materials other than the hydrophobic solvent are distributed at the edges.

[0169] Moreover, in the polymerization step described later, an aqueous dispersion containing precursor particles is obtained, and the hydrophobic solvent is encapsulated inside the precursor particles. That is, the hydrophobic solvent is concentrated inside the particles, thereby forming a hollow portion filled with the hydrophobic solvent inside the obtained precursor particles.

[0170] The hydrophobic solvent can be appropriately selected from known hydrophobic solvents and is not particularly limited. Examples thereof include esters such as ethyl acetate and butyl acetate; ether esters such as propylene glycol monomethyl ether acetate and propylene glycol monoethyl ether acetate; and hydrocarbon solvents. Among them, hydrocarbon solvents are preferred, and hydrocarbon solvents having 5 to 8 carbon atoms are more preferred.

[0171] Examples of the hydrocarbon solvents include aliphatic hydrocarbons such as linear hydrocarbon solvents including pentane, hexane, heptane, octane, 2-methylbutane, 2-methylpentane, and paraffin solvents, and cyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, and cycloheptane; and aromatic hydrocarbons such as benzene, toluene, and xylene, etc.

[0172] These hydrophobic solvents can be used alone or in combination of two or more.

[0173] In the suspension step, from the viewpoint that phase separation of the polymerizable monomer and the hydrophobic solvent easily occurs in the droplets of the monomer composition, as the hydrophobic solvent, an organic solvent having a lower solubility in water than the crosslinkable monomer contained in the polymerizable monomer is preferably selected.

[0174] In addition, when the polymerizable monomer contains a hydrocarbon monomer in a proportion of more than 50% by mass, as the hydrophobic solvent, a hydrocarbon solvent is preferred, a linear hydrocarbon solvent is more preferred, a linear hydrocarbon solvent having 5 to 8 carbon atoms is further preferred, and at least one selected from pentane, hexane, heptane, and octane is still more preferred.

[0175] In addition, the boiling point of the hydrophobic solvent is not particularly limited. From the viewpoint of being easily removed in the subsequent solvent removal step, it is preferably 130 °C or lower, more preferably 100 °C or lower. On the other hand, from the viewpoint of being easily included in the precursor particles, it is preferably 50 °C or higher, more preferably 60 °C or higher.

[0176] In addition, when the hydrophobic solvent is a mixed solvent containing a plurality of hydrophobic solvents and has a plurality of boiling points, it is preferred that the boiling point of the solvent having the highest boiling point among the solvents contained in the mixed solvent is below the above upper limit value, and it is preferred that the boiling point of the solvent having the lowest boiling point among the solvents contained in the mixed solvent is above the above lower limit value.

[0177] In addition, the hydrophobic solvent preferably has a relative dielectric constant of 2.5 or less at 20 °C. The relative dielectric constant is one of the indexes indicating the polarity of a compound. It can be considered that when the relative dielectric constant of the hydrophobic solvent is sufficiently small to 2.5 or less, phase separation rapidly proceeds in the droplets of the monomer composition, and it is easy to form a hollow portion.

[0178] Examples of the hydrophobic solvent having a relative dielectric constant of 2.5 or less at 20 °C are as follows. The values in parentheses are the relative dielectric constant values.

[0179] Pentane (1.8), hexane (1.9), heptane (1.9), octane (1.9), cyclohexane (2.0).

[0180] Regarding the relative dielectric constant at 20°C, the values described in well-known literature (for example, "Chemical Handbook, Basic Volume" edited by the Chemical Society of Japan, Revised 4th Edition, Maruzen Co., Ltd., published on September 30, Heisei 5, pages II-498 to II-503) and other technical information can be referred to. As a method for measuring the relative dielectric constant at 20°C, for example, 23 according to JIS C 2101:1999, and a relative dielectric constant test performed with the measurement temperature set to 20°C can be cited.

[0181] By changing the amount of the hydrophobic solvent in the mixed solution, the porosity of the hollow particles can be adjusted. Since in the suspension process described later, the polymerization reaction is carried out in a state where the hydrophobic solvent is enclosed in the oil droplets containing the polymerizable monomer, etc., there is a tendency that the higher the content of the hydrophobic solvent, the higher the porosity of the obtained hollow particles.

[0182] In the present invention, from the viewpoints of easily controlling the particle size of the hollow particles, easily increasing the porosity while maintaining the strength of the hollow particles, and easily reducing the amount of the residual hydrophobic solvent in the particles, it is preferable that the content of the hydrophobic solvent in the mixed solution is 100 parts by mass or more and 650 parts by mass or less relative to 100 parts by mass of the polymerizable monomer. The content of the hydrophobic solvent in the mixed solution is more preferably 120 parts by mass or more and 500 parts by mass or less, and further preferably 140 parts by mass or more and 300 parts by mass or less relative to 100 parts by mass of the polymerizable monomer.

[0183] (C) Polymerization initiator

[0184] In the production method of the present invention, the mixed solution preferably contains an oil-soluble polymerization initiator as the polymerization initiator. The oil-soluble polymerization initiator is not particularly limited as long as it is a lipophilic polymerization initiator having a solubility in water of 0.2% by mass or less, and examples thereof include organic peroxides such as benzoyl peroxide, lauroyl peroxide, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxy diethylacetate, and tert-butyl peroxy pivalate; azo compounds such as 2,2'-azobis(2,4-dimethylvaleronitrile), azobisisobutyronitrile, and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile). Among them, from the viewpoint of easily improving the dielectric properties of the hollow particles, it is preferable to use an organic peroxide as the oil-soluble polymerization initiator. When an organic peroxide is used as the oil-soluble polymerization initiator, it is easy to reduce the amount of the unreacted polymerizable monomer remaining in the shell. In addition, when the decomposition product of the polymerization initiator remains in the shell, there is a tendency to increase the molecular motion of the shell, but the decomposition product of the organic peroxide is easily removed. Therefore, when an organic peroxide is used as the polymerization initiator, the amount of the unreacted polymerizable monomer and the decomposition product of the polymerization initiator remaining in the shell can be reduced, and the increase in the molecular motion of the shell can be suppressed.

[0185] The content of the polymerization initiator is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 7 parts by mass, and still more preferably 1 to 5 parts by mass with respect to 100 parts by mass of the polymerizable monomer in the mixed liquid. When the content of the polymerization initiator is at least the above lower limit value, the polymerization reaction can proceed sufficiently. When it is at most the above upper limit value, the possibility of the polymerization initiator remaining after the polymerization reaction is small, and the possibility of unexpected side reactions occurring is also small.

[0186] (D)Dispersion stabilizer

[0187] The dispersion stabilizer is a preparation for dispersing the droplets of the monomer composition in the aqueous medium in the suspension step. Examples of the dispersion stabilizer include inorganic dispersion stabilizers, water-soluble polymer stabilizers of organic or inorganic systems, and surfactants.

[0188] In the present invention, from the viewpoints of easily controlling the particle diameter of the droplets in the suspension and easily removing the dispersion stabilizer through the cleaning process, and suppressing the shell from becoming too thin and suppressing the reduction in the strength of the hollow particles, it is preferable to use an inorganic dispersion stabilizer as the dispersion stabilizer.

[0189] Examples of the inorganic dispersion stabilizer include sulfates such as barium sulfate and calcium sulfate; carbonates such as barium carbonate, calcium carbonate, and magnesium carbonate; phosphates such as calcium phosphate; metal oxides such as alumina and titanium oxide; metal hydroxides such as aluminum hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, and iron hydroxide; and inorganic compounds such as silicon dioxide. These inorganic dispersion stabilizers can be used alone or in combination of two or more.

[0190] As the inorganic dispersion stabilizer, a water-insoluble inorganic dispersion stabilizer can be particularly preferably used. Here, water-insoluble means that the solubility in water at 25 °C is preferably less than 1 g / L.

[0191] Among them, as the water-insoluble inorganic dispersion stabilizer, metal hydroxides are preferred, and magnesium hydroxide is more preferred.

[0192] In the present invention, it is particularly preferable to use the water-insoluble inorganic dispersion stabilizer in a state of being dispersed in the aqueous medium in the form of colloidal particles, that is, in a colloidal dispersion containing colloidal particles of the water-insoluble inorganic dispersion stabilizer. Thereby, the inorganic dispersion stabilizer can be easily removed through the cleaning process described later.

[0193] The colloidal dispersion containing colloidal particles of the water-insoluble inorganic dispersion stabilizer can be prepared, for example, by reacting at least one selected from alkali metal hydroxides and alkaline earth metal hydroxides with a water-soluble polyvalent metal salt (excluding alkaline earth metal hydroxides) in an aqueous medium.

[0194] Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide and the like. Examples of the alkaline earth metal hydroxide include barium hydroxide, calcium hydroxide and the like.

[0195] Examples of the water-soluble polyvalent metal salt include magnesium metal salts such as magnesium chloride, magnesium phosphate, magnesium sulfate; calcium metal salts such as calcium chloride, calcium nitrate, calcium acetate, calcium sulfate; aluminum metal salts such as aluminum chloride, aluminum sulfate; barium salts such as barium chloride, barium nitrate, barium acetate; zinc salts such as zinc chloride, zinc nitrate, zinc acetate and the like, as long as they are water-soluble polyvalent metal salts other than the compounds belonging to the above-mentioned alkaline earth metal hydroxides. Among these, magnesium metal salts, calcium metal salts and aluminum metal salts are preferred, magnesium metal salts are more preferred, and magnesium chloride is particularly preferred.

[0196] The method for reacting at least one selected from the above-mentioned alkali metal hydroxides and alkaline earth metal hydroxides with the above-mentioned water-soluble polyvalent metal salt in an aqueous medium is not particularly limited. For example, an aqueous solution of at least one selected from alkali metal hydroxides and alkaline earth metal hydroxides may be mixed with an aqueous solution of the water-soluble polyvalent metal salt.

[0197] In addition, colloidal silica can also be used as the colloidal dispersion liquid containing water-insoluble inorganic dispersion stabilizer colloidal particles.

[0198] Examples of the organic water-soluble polymer stabilizer include polyvinyl alcohol, polycarboxylic acids (such as polyacrylic acid), celluloses (such as hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose), polyvinylpyrrolidone, polyacrylimide, polyethylene oxide, poly(hydroxystearic acid-g-methyl methacrylate-co-methacrylic acid) copolymer and the like.

[0199] Examples of the inorganic water-soluble polymer stabilizer include sodium tripolyphosphate and the like.

[0200] A surfactant refers to a compound having both a hydrophilic group and a hydrophobic group in one molecule, and examples thereof include well-known ionic surfactants such as anionic surfactants, cationic surfactants and amphoteric surfactants, and nonionic surfactants and the like.

[0201] In addition, the water-soluble polymer stabilizer and the surfactant usually have a solubility of 1 g / L or more in water at 25 °C.

[0202] The content of the dispersion stabilizer is not particularly limited, and is preferably 0.5 to 15 parts by mass, more preferably 1 to 10 parts by mass, based on 100 parts by mass of the total mass of the polymerizable monomer and the hydrophobic solvent. By making the content of the dispersion stabilizer above the above lower limit value, the droplets of the monomer composition can be sufficiently dispersed in the suspension without aggregating into one body. On the other hand, by making the content of the dispersion stabilizer below the above upper limit value, an increase in the viscosity of the suspension during granulation can be prevented, and an adverse situation of blockage of the suspension in the granulator can be avoided.

[0203] In addition, the content of the dispersion stabilizer is preferably 0.5 to 15 parts by mass, more preferably 0.5 to 10 parts by mass, based on 100 parts by mass of the aqueous medium.

[0204] In the hollow particles of the present invention, from the viewpoints of suppressing deterioration of dielectric properties and reliability, the less the residual amount of the dispersion stabilizer, the more preferable, and it is most preferable not to contain a dispersion stabilizer, and in particular, it is preferably not to contain a water-soluble polymer stabilizer and a surfactant. By using only an inorganic dispersion stabilizer as the dispersion stabilizer, hollow particles in which both the water-soluble polymer stabilizer and the surfactant are less than the detection limit value can be obtained.

[0205] (E) Aqueous medium

[0206] In the present invention, the aqueous medium refers to a medium selected from water, a hydrophilic solvent, and a mixture of water and a hydrophilic solvent.

[0207] In the case of using a mixture of water and a hydrophilic solvent, from the viewpoint of forming droplets of the monomer composition, it is important not to make the polarity of the whole mixture too low. In this case, for example, the mass ratio of water to the hydrophilic solvent (water: hydrophilic solvent) can be 99:1 to 50:50.

[0208] The hydrophilic solvent in the present invention is not particularly limited as long as it is a hydrophilic solvent that is sufficiently mixed with water without phase separation. Examples of the hydrophilic solvent include alcohols such as methanol and ethanol; tetrahydrofuran (THF); dimethyl sulfoxide (DMSO), etc.

[0209] The content of the aqueous medium is not particularly limited. From the viewpoint of making the particle diameter and porosity of the hollow particles within the preferred ranges described below, as the lower limit, it is preferably 200 parts by mass or more, more preferably 400 parts by mass or more, further preferably 600 parts by mass or more, and as the upper limit, it is preferably 1000 parts by mass or less, more preferably 800 parts by mass or less, based on 100 parts by mass of the polymerizable monomer contained in the mixed liquid.

[0210] The mixed liquid may further contain other materials different from the above materials (A) to (E) within the range that does not impair the effects of the present invention.

[0211] A mixed solution is obtained by mixing the above-described respective materials and other materials as needed and appropriately stirring them, etc. In this mixed solution, an oil phase containing the above-described (A) polymerizable monomer, (B) hydrophobic solvent, and (C) polymerization initiator and other lipophilic materials is dispersed in an aqueous phase containing (D) dispersion stabilizer and (E) aqueous medium, etc., in the form of particles having a size of about several mm. The dispersion state of these materials in the mixed solution can also be observed with the naked eye depending on the type of the materials.

[0212] In the mixed solution preparation step, the above-described respective materials and other materials as needed can be mixed and appropriately stirred, etc., to obtain a mixed solution. From the viewpoint of easily making the shell uniform, it is preferable to separately prepare in advance an oil phase containing a polymerizable monomer, a hydrophobic solvent, and a polymerization initiator, and an aqueous phase containing a dispersion stabilizer and an aqueous medium, and mix them to prepare a mixed solution. In the present invention, a colloidal dispersion in which a water-insoluble inorganic dispersion stabilizer is dispersed in the form of colloidal particles in an aqueous medium can be preferably used as the aqueous phase.

[0213] By mixing the oil phase and the aqueous phase separately prepared in advance in this way, hollow particles having a uniform composition in the shell part can be manufactured, and the control of the particle size of the hollow particles is also made easy.

[0214] (2) Suspension step

[0215] The suspension step is a step of preparing a suspension in which droplets of a monomer composition containing a hydrophobic solvent are dispersed in an aqueous medium by suspending the above-described mixed solution.

[0216] The suspension method for forming droplets of the monomer composition is not particularly limited, and a known suspension method can be adopted. As a disperser used in preparing the suspension, for example, horizontal or vertical pipeline dispersers such as MILDER manufactured by Taiheiyo Kiko Co., Ltd., CAVITRON manufactured by Eurotec Co., Ltd., and pipeline type dispersers manufactured by IKA (for example, DISPAX-REACTOR (registered trademark) DRS); emulsifying dispersers such as Homomixer MARK II series manufactured by Primix Corporation, etc. can be used.

[0217] In the dispersion for preparing the suspension, from the viewpoint of making the particle size of the hollow particles fall within the above-described preferred range, the tip speed of the rotating part of the disperser is preferably 5 m / s or more, more preferably 10 m / s or more, and further preferably 15 m / s or more. On the other hand, from the viewpoint of reducing the proportion of abnormal particles, it is preferably 90 m / s or less, more preferably 89 m / s or less, and further preferably 88 m / s or less.

[0218] In the suspension prepared in the suspension step, droplets of the monomer composition containing the above lipophilic material and having a particle size of about 0.1 to 10 μm are uniformly dispersed in the aqueous medium. Such droplets of the monomer composition are difficult to observe with the naked eye and can be observed, for example, using a known observation instrument such as an optical microscope.

[0219] In the suspension step, due to phase separation occurring in the droplets of the monomer composition, the less polar hydrophobic solvent aggregates inside the droplets. As a result, in the obtained droplets, the hydrophobic solvent is distributed inside and the materials other than the hydrophobic solvent are distributed at the edges.

[0220] The droplets of the monomer composition dispersed in the aqueous medium are formed by surrounding the oil-soluble monomer composition with a dispersion stabilizer. The droplets of the monomer composition contain an oil-soluble polymerization initiator, a polymerizable monomer, and a hydrophobic solvent.

[0221] The droplets of the monomer composition are micro oil droplets, and the oil-soluble polymerization initiator generates polymerization initiating radicals inside the micro oil droplets. Therefore, the micro oil droplets will not grow excessively, and precursor particles with the target particle size can be manufactured.

[0222] In the suspension polymerization method using such an oil-soluble polymerization initiator, there is no opportunity for the polymerization initiator to contact the polymerizable monomer dispersed in the aqueous medium. Therefore, by using an oil-soluble polymerization initiator, it is possible to suppress the generation of unnecessary resin particles such as dense particles with a smaller particle size as by-products, other than the resin particles having a hollow portion as the target.

[0223] (3) Polymerization step

[0224] This step is a step of supplying the suspension obtained through the above suspension step to a polymerization reaction to prepare a precursor composition containing precursor particles, where the precursor particles have a hollow portion surrounded by a shell containing resin and the hollow portion is filled with the hydrophobic solvent.

[0225] In this step, since polymerization occurs in the shell portion of the droplets of the monomer composition containing the hydrophobic solvent inside, a hollow portion filled with the hydrophobic solvent is formed inside the obtained precursor particles.

[0226] In this step, during the polymerization reaction, a crosslinkable monomer may also be added to the suspension to further carry out the polymerization reaction. In particular, a crosslinkable monomer having a solubility in water at 20 °C of 0.5 g / L to 1000 g / L is more preferably added during the polymerization reaction than during the mixed solution preparation step. Thereby, more reactive unsaturated bonds can be introduced onto the outer surface of the shell, and the amount of unsaturated bonds in the hollow particles can be increased. In addition, during the polymerization reaction, a crosslinkable monomer having the above solubility is added to the suspension to further carry out the polymerization reaction, whereby the solvent resistance of the hollow particles can be improved.

[0227] The solubility of the crosslinkable monomer added during the polymerization reaction in water at 20 °C is preferably greater than that of the above hydrophobic solvent and is 0.5 g / L to 1000 g / L, more preferably 0.5 g / L to 80 g / L. By adding a crosslinkable monomer having a solubility in water at 20 °C within the above range during the polymerization reaction, the crosslinkable monomer easily enters the surface of the shell, and reactive unsaturated bonds can be efficiently introduced onto the surface of the shell. Regarding the solubility of the crosslinkable monomer added during the polymerization reaction in water at 20 °C, as the upper limit, it is further preferably 50 g / L or less, more preferably 20 g / L or less, particularly preferably 10 g / L or less, and as the lower limit, it is more preferably 1.0 g / L or more, further preferably 2.0 g / L or more.

[0228] In addition, from the viewpoint of easily entering the surface of the shell, the molecular weight of the crosslinkable monomer added during the polymerization reaction is preferably 300 or less, more preferably 200 or less. In addition, the lower limit of the above molecular weight is not particularly limited and is usually 50 or more.

[0229] As the crosslinkable monomer added during the polymerization reaction, for example, crosslinkable acrylic monomers such as allyl (meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,3-bis(methacryloyloxy)-2-hydroxypropane, etc. can be preferably used.

[0230] When adding a crosslinkable monomer to the suspension during the polymerization reaction, regarding the timing of this addition, from the viewpoint of efficiently introducing reactive unsaturated bonds onto the surface of the shell, as the upper limit of the polymerization conversion rate of the polymerizable monomer in the suspension, it is preferably 80% by mass or less, more preferably 60% by mass or less, further preferably 40% by mass or less, and as the lower limit, it is preferably 10% by mass or more.

[0231] In addition, the polymerization conversion rate when adding a crosslinkable monomer to the suspension during the polymerization reaction is determined by the following formula (VI) based on the mass of the polymerizable monomer contained in the suspension before the addition and the mass of the unreacted polymerizable monomer contained in the suspension immediately before the addition. In addition, the mass of the polymerizable monomer contained in the suspension before the addition refers to the total mass of the polymerizable monomer and the unreacted polymerizable monomer after the polymerization reaction.

[0232] Formula (VI):

[0233] Polymerization conversion rate (mass %) = 100 - (mass of unreacted polymerizable monomer / mass of polymerizable monomer contained in the suspension) × 100

[0234] When adding a crosslinkable monomer to the suspension during the polymerization reaction, from the viewpoint of efficiently introducing a reactive unsaturated bond to the surface of the shell, the amount of the crosslinkable monomer added during the polymerization reaction is preferably 1 part by mass or more, more preferably 2 parts by mass or more, per 100 parts by mass of the polymerizable monomer in the mixed solution. From the viewpoint of suppressing the deterioration of dielectric properties, it is preferably 10 parts by mass or less, more preferably 8 parts by mass or less.

[0235] In the present invention, from the viewpoints of introducing a sufficient amount of reactive unsaturated bonds to the surface of the shell to improve reliability, improving the strength of the shell, and making it easy for the hollow particles to maintain a high porosity and for the dielectric properties to be easily improved, the content of the crosslinkable monomer in 100% by mass of the polymerizable monomers added up to the polymerization step is preferably 50% by mass or more, more preferably 60% by mass or more, further preferably 70% by mass or more, still more preferably 80% by mass or more, and particularly preferably 90% by mass or more. On the other hand, when a combination containing a crosslinkable monomer and a non-crosslinkable monomer is used as the polymerizable monomer, the tangent of the dielectric loss angle of the hollow particles is likely to decrease. From the viewpoint of reducing the tangent of the dielectric loss angle of the hollow particles, the content of the crosslinkable monomer in 100% by mass of the polymerizable monomers added up to the polymerization step is preferably 80% by mass or less, more preferably 70% by mass or less.

[0236] In 100% by mass of the polymerizable monomers added up to the polymerization step, from the viewpoint of improving the dielectric properties of the hollow particles, the content of the hydrocarbon monomer is preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more. The above polymerizable monomer may be composed of hydrocarbon monomers. There is a tendency that the dielectric properties of the hollow particles are more improved as the proportion of the hydrocarbon monomer in the polymerizable monomer increases. On the other hand, from the viewpoint of efficiently introducing a reactive unsaturated bond to the surface of the shell using a crosslinkable monomer containing a heteroatom, the content of the hydrocarbon monomer may be 98% by mass or less, may be 95% by mass or less, or may be 90% by mass or less.

[0237] In addition, the content of each monomer in 100% by mass of the polymerizable monomers added up to the polymerization step corresponds to the content of each monomer unit in all monomer units of 100% by mass of the polymer contained in the shell.

[0238] In the polymerization step, the polymerization method is not particularly limited, and known polymerization methods such as batch (batch) type, semi-continuous type, and continuous type can be employed.

[0239] The polymerization temperature is not particularly limited. From the viewpoint of allowing the polymerization reaction to proceed sufficiently, it is preferably 60 °C or higher, more preferably 70 °C or higher, and further preferably 80 °C or higher. From the viewpoint of suppressing the evaporation of the aqueous medium, it is preferably 95 °C or lower.

[0240] The reaction time of the polymerization is not particularly limited. From the viewpoint of allowing the polymerization reaction to proceed sufficiently, it is preferably 5 hours or longer, more preferably 10 hours or longer. From the viewpoint of production efficiency, it is preferably 60 hours or shorter, more preferably 48 hours or shorter, and further preferably 36 hours or shorter.

[0241] When a crosslinkable monomer is added to the suspension during the polymerization reaction, the reaction time of the polymerization reaction until the addition of the crosslinkable monomer is preferably 10 minutes to 3 hours, more preferably 30 minutes to 2 hours, and the reaction time of the polymerization reaction after the addition of the crosslinkable monomer is preferably 1 to 48 hours, more preferably 2 to 24 hours.

[0242] The suspension in the polymerization reaction is usually stirred. The stirring power for this stirring is not particularly limited. From the viewpoint of promoting the polymerization reaction, it is preferably 0.01 kW / m 3 or higher, more preferably 0.02 kW / m 3 or higher, further preferably 0.03 kW / m 3 or higher, and from the viewpoint of reducing the proportion of irregularly shaped particles, it is preferably 0.20 kW / m 3 or lower, more preferably 0.10 kW / m 3 or lower, and further preferably 0.05 kW / m 3 or lower.

[0243] (4) Solvent removal step

[0244] This step is a step of removing the hydrophobic solvent from the precursor particles by blowing a gas into the precursor composition while stirring the precursor composition in a stirring tank, thereby obtaining an aqueous dispersion of hollow particles. Through this step, an aqueous dispersion of hollow particles in which the hollow portion is filled with the blown gas can be obtained.

[0245] The introduction of gas into the precursor composition can be carried out, for example, by directly introducing the gas into the precursor composition, that is, by directly blowing the gas into the precursor composition. Alternatively, it can also be carried out by stirring the precursor composition in a stirring tank having a liquid phase part and a gas phase part containing the precursor composition, and introducing the gas in the gas phase part into the precursor composition. Among them, from the viewpoint of efficiently removing the hydrophobic solvent encapsulated in the precursor particles and the unreacted polymerizable monomers remaining in the precursor particles, etc., it is preferred to introduce gas into the precursor composition by directly introducing the gas into the precursor composition while stirring the precursor composition in a stirring tank having a gas phase part. In addition, the gas phase part in the stirring tank is preferably filled with the gas introduced into the precursor composition in advance.

[0246] The gas introduced into the precursor composition is preferably selected from at least one of inert gases and air, and more preferably an inert gas. Examples of the inert gas include nitrogen, argon, helium, etc., and nitrogen is particularly preferred.

[0247] In this step, from the viewpoint of efficiently removing the hydrophobic solvent encapsulated in the precursor particles and the unreacted polymerizable monomers remaining in the precursor particles, etc., the treatment time for introducing gas into the precursor composition is preferably 2 hours or more, more preferably 5 hours or more, further preferably 10 hours or more, and still more preferably 15 hours or more. From the viewpoint of manufacturing efficiency, it is preferably 72 hours or less, more preferably 60 hours or less.

[0248] On the other hand, when the polymerization reaction time in the above polymerization step is 50 hours or more, even if the time of the gas blowing treatment in the solvent removal step is less than 2 hours, it is possible to sufficiently remove the hydrophobic solvent encapsulated in the precursor particles and the unreacted polymerizable monomers contained in the precursor particles. When the polymerization reaction time in the above polymerization step is 50 hours or more, the time of the gas blowing treatment in the solvent removal step is preferably 20 minutes or more, more preferably 30 minutes or more.

[0249] In this step, the stirring power when stirring the precursor composition is not particularly limited. From the viewpoint of efficiently removing the hydrophobic solvent encapsulated in the precursor particles and the unreacted polymerizable monomers remaining in the precursor particles, etc., it is preferably 0.01 kW / m 3 or more, more preferably 0.02 kW / m 3 or more, further preferably 0.03 kW / m 3 or more. From the viewpoint of reducing the proportion of abnormal particles and suppressing the foaming of the precursor composition, it is preferably 0.60 kW / m 3 or less, more preferably 0.55 kW / m 3 or less, further preferably 0.50 kW / m 3Hereinafter, it is more preferably 0.20 kW / m 3 Hereinafter, it is particularly preferably 0.10 kW / m 3 Hereinafter, it may also be 0.05 kW / m 3 Hereinafter.

[0250] In this step, from the viewpoint of efficiently removing the hydrophobic solvent encapsulated in the precursor particles and the unreacted polymerizable monomers remaining in the precursor particles, etc., introducing gas into the precursor composition is preferably carried out at a pressure of 20 kPa or more and 300 kPa or less, more preferably at a pressure of 40 kPa or more and 200 kPa or less. In addition, when at a pressure above the above lower limit value, it is preferred from the viewpoint of being able to improve the yield, and when at a pressure below the above upper limit value, it is preferred from the viewpoint of being able to reduce the proportion of abnormal-shaped particles. Among them, from the viewpoint of excellent removal efficiency of the hydrophobic solvent, introducing gas into the precursor composition is preferably carried out at a pressure below atmospheric pressure, more preferably at a reduced pressure of 60 kPa or less. On the other hand, from the viewpoint of suppressing foaming of the precursor composition, it is preferably carried out under a pressure of 150 kPa or more. By suppressing foaming of the precursor composition during gas introduction, the yield of hollow particles is increased. In addition, the above pressure can be the internal pressure of the stirring tank.

[0251] The flow rate of the gas introduced into the stirring tank is not particularly limited. From the viewpoint of efficiently removing the hydrophobic solvent encapsulated in the precursor particles and the unreacted polymerizable monomers remaining in the precursor particles, etc., as the flow rate per unit time, it is preferably 4 L / min or more, more preferably 8 L / min or more, and further preferably 10 L / min or more. As the flow rate per unit volume, it is preferably 200 L / (min·m 3 ) or more, more preferably 8000 L / (min·m 3 ) or more, and further preferably 10000 L / (min·m 3 ) or more. From the viewpoint of cost reduction, the upper limit of the gas flow rate can be, for example, 10000 L / min or less as the flow rate per unit time, and 500000 L / (min·m 3 ) or less as the flow rate per unit volume.

[0252] In addition, when using a stirring tank with a capacity of 3 to 15000 L, the gas flow rate is preferably within the above range.

[0253] In this step, it is preferred that there is a liquid phase part and a gas phase part containing the precursor composition in the stirring tank. This is because when there is a gas phase part in the stirring tank, the hydrophobic solvent encapsulated in the precursor particles and the unreacted polymerizable monomers contained in the precursor particles, etc., can transfer to the gas phase part, and thus their removal efficiency is excellent.

[0254] From the viewpoint of efficiently removing the hydrophobic solvent encapsulated in the precursor particles and unreacted polymerizable monomers remaining in the precursor particles, etc., the proportion of the liquid phase part with respect to the whole inside the stirring tank is preferably 30% by volume or more and less than 80% by volume.

[0255] As a method of directly introducing a gas into the precursor composition, for example, it is preferable to directly introduce the gas into the precursor composition in the stirring tank from the side or bottom of the stirring tank, and more preferably to introduce the gas from the bottom of the stirring tank. Here, the bottom of the stirring tank refers to the part of the stirring tank that can be observed looking up in the usage state. The stirring tank is typically columnar, and in the columnar stirring tank, the bottom surface on the lower side in the direction of gravity is the bottom, which is the deepest part.

[0256] When directly introducing a gas into the precursor composition, the closer the gas introduction part is to the deepest part of the stirring tank, the easier it is for the gas to be evenly bubbled into the precursor composition, and thus it is preferable. When the gas is evenly bubbled into the precursor composition, the hydrophobic solvent and unreacted polymerizable monomers removed from the precursor particles are likely to move upward to the gas phase part, and thus their removal efficiency is excellent.

[0257] In addition, from the viewpoint of easy and uniform bubbling of the gas in the precursor composition, the introduction of the gas into the precursor composition is preferably carried out at the center of the area occupied by the precursor composition in the stirring tank. That is, when introducing the gas from the bottom of the stirring tank, it is preferable to introduce the gas in the direction opposite to the direction of gravity.

[0258] In addition, in the present invention, the direction of gravity means a direction that is not necessarily on the same straight line as the direction of gravity and allows an axis deviation of, for example, within 30 degrees.

[0259] On the other hand, sometimes the gas is not directly introduced into the precursor composition, but only by introducing the gas into the gas phase part in the stirring tank and stirring the precursor composition in the stirring tank, the gas in the gas phase part is bubbled into the precursor composition, thereby enabling an increase in the yield of hollow particles.

[0260] This step can be carried out using, for example Figure 2 the stirring device shown. In addition, Figure 2 is only a schematic diagram for illustration, and the stirring device used in the solvent removal step of the present invention is not limited to the device shown in the figure. In addition, the structure, size, shape, etc. of the stirring device used in the solvent removal step of the present invention are not limited to Figure 2 the structure, size, shape, etc. shown.

[0261] In Figure 2In the stirring device shown, when the precursor composition as the slurry liquid is injected into the supply tank 12, the precursor composition is supplied from the supply tank 12 to the inside of the stirring tank 11 via the supply pipeline 16. The supply method of the precursor composition is not particularly limited, and examples thereof include a method using a liquid feed pump. The precursor composition is supplied into the stirring tank 11 via an inner nozzle (not shown). The precursor composition 20 in the stirring tank 11 is stirred by rotating a rotor (not shown) provided in the stirring tank 11.

[0262] Gas can be introduced into the stirring tank 11 from the gas inlets 13a, 13b or 13c provided in the stirring tank 11. The gas inlet 13a is provided at the bottom of the stirring tank 11, and the gas inlet 13b is provided on the side surface of the stirring tank 11. When gas is introduced from the gas inlet 13a or 13b, gas can be directly blown into the precursor composition 20 in the stirring tank 11 for aeration. The gas inlet 13c is provided at the upper part of the stirring tank 11. When gas is introduced from the gas inlet 13c, the gas is blown into the gas phase part 21 in the stirring tank 11. By stirring the precursor composition 20 in the stirring tank 11, the gas in the gas phase part 21 is aerated into the precursor composition 20.

[0263] In Figure 2 In the stirring device shown, by returning the precursor composition 20 stirred in the stirring tank 11 from the outlet 14 to the stirring tank 11 via the circulation pipeline 17a, the supply tank 12 and the supply pipeline 16, the precursor composition 20 can be circulated in the stirring device.

[0264] Figure 2 The stirring device shown further has a spraying mechanism 15. In Figure 2 In the stirring device shown, a part of the precursor composition 20 stirred in the stirring tank 11 can be supplied from the outlet 14 to the spraying mechanism 15 via the circulation pipeline 17b and sprayed onto the liquid surface 20a of the precursor composition 20 located in the stirring tank 11.

[0265] In addition, by adjusting the flow rate of the precursor composition discharged from the stirring tank 11, the internal pressure of the stirring tank 11 can be adjusted.

[0266] In this step, during the period of aerating gas into the precursor composition, it is preferable to repeatedly perform the operation of supplying the precursor composition from the supply tank to the stirring tank, stirring in the stirring tank, and then discharging it to the supply tank for circulation in the stirring device. Thereby, the hydrophobic solvent encapsulated in the precursor particles and the unreacted polymerizable monomers contained in the precursor particles can be efficiently removed. In addition, the flow rate of this circulation is not particularly limited.

[0267] In this step, when blowing gas into the precursor composition, it is preferable to supply a part of the precursor composition from the stirring tank to the spraying mechanism and spray it onto the liquid surface of the precursor composition in the stirring tank. Thereby, it is possible to efficiently remove the hydrophobic solvent encapsulated in the precursor particles and the unreacted polymerizable monomers contained in the precursor particles, etc., and thus the treatment time for blowing can be shortened.

[0268] The spraying of the precursor composition can be carried out continuously or intermittently during the blowing of gas into the precursor composition, and it is particularly preferable to carry it out continuously. In the case of intermittently spraying the precursor composition, it is preferable to appropriately spray the precursor composition until the foaming disappears when the precursor composition foams and the liquid level rises. In addition, the spraying amount in the case of spraying the precursor composition is not particularly limited.

[0269] Furthermore, from the viewpoint of reducing the residual amount of the hydrophobic solvent, the temperature when blowing gas into the precursor composition is preferably a temperature equal to or higher than the temperature obtained by subtracting 35°C from the boiling point of the hydrophobic solvent, more preferably a temperature equal to or higher than the temperature obtained by subtracting 30°C from the boiling point of the hydrophobic solvent, and further preferably a temperature equal to or higher than the temperature obtained by subtracting 20°C from the boiling point of the hydrophobic solvent. Here, when the above hydrophobic solvent is a mixed solvent containing a plurality of hydrophobic solvents and has a plurality of boiling points, the boiling point of the hydrophobic solvent in the solvent removal step refers to the boiling point of the solvent with the highest boiling point among the solvents contained in the mixed solvent, that is, the highest boiling point among the plurality of boiling points.

[0270] Furthermore, the temperature when blowing gas into the precursor composition is usually set to a temperature equal to or higher than the polymerization temperature in the above polymerization step.

[0271] The temperature when blowing gas into the precursor composition is not particularly limited and can be 50 to 100°C.

[0272] (5) Cleaning step

[0273] The above manufacturing method has a cleaning step after the above solvent removal step. The cleaning step is a step for removing the dispersion stabilizer remaining in the hollow particles obtained by the above solvent removal step.

[0274] The cleaning process is preferably carried out, for example, by repeating the following series of operations more than twice: adding an acid or a base to the aqueous dispersion of hollow particles obtained through the solvent removal process, thereby dissolving the dispersion stabilizer contained in the hollow particles in the aqueous medium, then separating the hollow particles from the aqueous medium, and then, after dispersing the separated hollow particles in ion-exchanged water and re-slurrying them, separating the hollow particles. From the viewpoint of removing more of the dispersion stabilizer remaining in the hollow particles and easily reducing the dielectric loss tangent of the hollow particles, it is preferable to repeat the series of operations of dispersing the hollow particles separated after adding an acid or a base in ion-exchanged water and re-slurrying them and then separating the hollow particles more than 3 times in the cleaning process. The number of times of performing this operation is more preferably 4 times or more, and further preferably 5 times or more. There is no particular limitation on the upper limit. From the viewpoint of ease of manufacture, for example, it can be 10 times or less, or can be 8 times or less.

[0275] When the dispersion stabilizer used is an inorganic dispersion stabilizer soluble in an acid, it is preferable to add an acid. When the dispersion stabilizer used is an inorganic dispersion stabilizer soluble in a base, it is preferable to add a base.

[0276] When the dispersion stabilizer used is an inorganic dispersion stabilizer soluble in an acid, an acid is added to the aqueous dispersion of hollow particles, and it is preferable to adjust the pH to 6.5 or less, more preferably 6 or less. As the acid to be added, inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid, and organic acids such as formic acid and acetic acid can be used. From the viewpoints of high removal efficiency of the dispersion stabilizer and small burden on manufacturing equipment, sulfuric acid is particularly preferable.

[0277] The method for separating the hollow particles from the aqueous medium is not particularly limited, and examples thereof include a centrifugation method, a filtration method, and static separation. Among them, from the viewpoints of simple operation and high removal efficiency of the dispersion stabilizer, the filtration method is preferable. In addition, when separating the hollow particles from the aqueous medium, it is preferable to dehydrate the hollow particles obtained by a method such as the filtration method by a known method.

[0278] As the filtration method, any method such as natural filtration (atmospheric pressure filtration), vacuum filtration, pressure filtration, and centrifugal filtration can be used. Among them, from the viewpoint of efficiently removing the dispersion stabilizer remaining in the hollow particles, pressure filtration is preferable.

[0279] In the manufacturing method of the present invention, in the cleaning process, the operation of separating the hollow particles from the aqueous medium is performed multiple times. It is preferable to perform pressure filtration at least once, and it is more preferable to always perform pressure filtration in the operation of separating the hollow particles from the aqueous medium.

[0280] (6) Drying process

[0281] The drying process is a process of drying and removing the moisture remaining in the hollow particles obtained through the above-described cleaning process.

[0282] The hollow particles obtained through the above-described cleaning process are usually in the form of a filter cake, and in this process, the dewatered filter cake of the hollow particles is usually dried.

[0283] The water content of the hollow particles before drying used in the drying process is usually 40 to 80%. In addition, in the present invention, the water content can be calculated by the following formula (VII).

[0284] Formula (VII)

[0285] Water content (%) = {(w1 - w2) / w1} × 100

[0286] In the above formula (VII), w1 represents the mass of the test sample, and w2 represents the mass after cooling the test sample to 25°C after drying at 200°C for 12 hours.

[0287] The method of drying and removing the moisture remaining in the hollow particles is not particularly limited, and a known method can be adopted. As such a method, for example, a vacuum drying method, a heat drying method, a fluidized bed drying method, or a combination of these methods can be cited.

[0288] Especially in the case of using the heat drying method, it is necessary to be below the maximum temperature at which the shell structure is not damaged. Therefore, depending on the composition of the shell, for example, the heating temperature can be set to 50 to 200°C, or can be set to 70 to 200°C, or can be set to 100 to 200°C.

[0289] In addition, pre-drying can also be carried out in the drying process. The pre-drying can be carried out, for example, by drying the hollow particles after the cleaning process using a drying device such as a dryer or a drying tool such as a hand dryer.

[0290] The drying atmosphere is not particularly limited and can be appropriately selected according to the use of the hollow particles. As the drying atmosphere, for example, air, oxygen, nitrogen, argon, etc. can be considered. In addition, once the inside of the hollow particles is filled with gas, through vacuum drying, hollow particles with a temporarily vacuum inside can also be obtained.

[0291] (7) Others

[0292] As a process other than the above (1) to (6), for example, a replacement process inside the particles can also be added. The replacement process inside the particles is a process of replacing the gas and liquid inside the hollow particles with other gases and liquids. By such replacement, the environment inside the hollow particles can be changed, or molecules can be selectively enclosed inside the hollow particles, or the chemical structure inside the hollow particles can be modified according to the use.

[0293] Matrix resin

[0294] The resin composition of the present invention contains a matrix resin having a functional group as the matrix resin, and the functional group can react with the reactive unsaturated bond on the surface of the hollow particles to form a covalent bond. In addition, the reaction between the reactive unsaturated bond of the hollow particles and the functional group of the matrix resin only needs to be a reaction to form a covalent bond, and can be, for example, an addition reaction.

[0295] The functional group of the matrix resin is not particularly limited. From the viewpoint of reactivity, it is preferably at least one selected from (meth)acryloyl group, vinyl group, allyl group, mercapto group, and maleimide group, and more preferably at least one selected from (meth)acryloyl group and vinyl group.

[0296] From the viewpoint of improving reliability, the iodine value of the matrix resin having an ethylenic unsaturated bond such as (meth)acryloyl group, vinyl group, allyl group or maleimide group is preferably 1 g / 100 g or more, and more preferably 10 g / 100 g or more. The upper limit of the iodine value of the matrix resin having an ethylenic unsaturated bond is not particularly limited, and can be, for example, 1000 g / 100 g or less.

[0297] From the viewpoint of improving reliability, the mercaptan value of the matrix resin having a mercapto group such as a mercaptan resin is preferably 0.5% or more, and more preferably 1% or more. The upper limit of the mercaptan value of the mercaptan resin is not particularly limited, and can be, for example, 100% or less. In addition, the mercaptan value can be obtained by the following formula.

[0298] Mercaptan value (%) = {(molecular weight of mercapto group × number of mercapto groups in one molecule) / molecular weight of mercaptan compound} × 100 As the matrix resin having the above functional group, for example, it is preferably at least one selected from bismaleimide resin, hydrocarbon resin, unsaturated polyester resin, modified polyphenylene ether resin, allyl resin, mercaptan resin, and raw material compounds of these resins. Among them, from the viewpoint of excellent dielectric properties and reliability, a modified polyphenylene ether resin is particularly preferably used.

[0299] As the modified polyphenylene ether resin, for example, a resin obtained by end-modifying a known polyphenylene ether resin containing a polyphenylene ether skeleton can be used. Among them, from the viewpoint of excellent reactivity with hollow particles, a modified polyphenylene ether resin end-modified with a substituent containing an ethylenic unsaturated bond such as styrene-modified polyphenylene ether resin and (meth)acrylic acid-modified polyphenylene ether resin is preferably used.

[0300] As the polyphenylene ether resin, there is no particular limitation, and examples thereof include: poly(2,6-dimethyl-1,4-phenylene) ether, an alloyed polymer of poly(2,6-dimethyl-1,4-phenylene) ether and polystyrene, an alloyed polymer of poly(2,6-dimethyl-1,4-phenylene) ether and a styrene-butadiene copolymer, etc.

[0301] From the viewpoint of excellent reactivity with the hollow particles, the number-average molecular weight of the modified polyphenylene ether resin is preferably 500 or more and 5000 or less, more preferably 1000 or more and 3000 or less.

[0302] As the bismaleimide resin, examples thereof include: 4,4'-diphenylmethane bismaleimide, m-phenylene bismaleimide, bisphenol A diphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, 4-methyl-1,3-phenylene bismaleimide, 1,6'-bismaleimide-(2,2,4-trimethyl)hexane, etc.

[0303] In addition, as the resin containing a maleimide group, polymers having a maleimide group such as "MIR-3000-70MT" or "MIR-5000-60T" manufactured by Nippon Kayaku Co., Ltd. can be used.

[0304] As the hydrocarbon resin, examples thereof include polyfunctional styrene compounds and their polymers, and cyclic olefin polymers, etc. In addition, the polymer of the polyfunctional styrene compound can be any one of a homopolymer or copolymer of the polyfunctional styrene compound, or a copolymer of the polyfunctional styrene compound and other monomers. The cyclic olefin polymer can be any one of a homopolymer or copolymer of a cyclic olefin, or a copolymer of a cyclic olefin and other monomers.

[0305] As the polyfunctional styrene compound, examples thereof include: divinylbenzene, divinylnaphthalene, divinylbiphenyl, 1,2-bis(p-vinylphenyl)ethane, 1,2-bis(m-vinylphenyl)ethane, 1-(p-vinylphenyl)-2-(m-vinylphenyl)ethane, bis(p-vinylphenyl)methane, bis(m-vinylphenyl)methane, p-vinylphenyl-m-vinylphenylmethane, 1,4-bis(p-vinylphenyl)benzene, 1,4-bis(m-vinylphenyl)benzene, 1-(p-vinylphenyl)-4-(m-vinylphenyl)benzene, 1,3-bis(p-vinylphenyl)benzene, 1,3-bis(m-vinylphenyl)benzene, 1-(p-vinylphenyl)-3-(m-vinylphenyl)benzene, 1,6-bis(p-vinylphenyl)hexane, 1,6-bis(m-vinylphenyl)hexane, 1-(p-vinylphenyl)-6-(m-vinylphenyl)hexane, and a divinylbenzene polymer (oligomer) having a vinyl group in the side chain, etc.

[0306] As cyclic olefins, examples include: norbornene, methanooctalin, dimethanooctalin, dimethandodecahydroanthracene, dimethandecahydroanthracene, trimethandodecahydroanthracene, dicyclopentadiene, 2,3-dihydrocyclopentadiene, methanodecahydrobenzindene, dimethanodecahydrobenzindene, methanododecahydrobenzindene, dimethanododecahydrobenzindene, methanooctahydrofluorene, dimethanooctahydrofluorene, their substituents, and the like.

[0307] In addition, even if a hydrocarbon resin having a tertiary carbon generates free radicals by being deprived of the tertiary carbon by a crosslinking agent described later, it reacts with the reactive unsaturated bonds possessed by the hollow particles.

[0308] As the unsaturated polyester resin, for example, an esterified product of an unsaturated dibasic acid and a dibasic acid component and a polyol component that may contain a saturated dibasic acid as required can be used. Within the range not impairing the effects of the present invention, an unsaturated polyester resin modified with a dicyclopentadiene-based compound or the like can also be used.

[0309] As the unsaturated dibasic acid, examples include: maleic acid, maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride, and the like.

[0310] As the saturated dibasic acid, examples include: aliphatic dibasic acids such as adipic acid, aromatic dibasic acids such as phthalic acid and phthalic anhydride, halogenated saturated dibasic acids, and the like.

[0311] As the polyol, examples include: dihydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, cyclohexanediol, and p-xylene glycol; dihydric alcohols such as adducts of dihydric phenols such as hydrogenated bisphenol A, cyclohexanedimethanol, bisphenol A, bisphenol F, bisphenol S, and tetrabromobisphenol A and alkylene oxides represented by propylene oxide or ethylene oxide; alcohols having three or more hydroxyl groups such as 1,2,3,4-tetrahydroxybutane, glycerin, trimethylolpropane, and pentaerythritol.

[0312] As the allyl resin, it can be a polymer and oligomer obtained by using a compound containing two or more allyl groups in one molecule, and examples include diallyl phthalate resin, allylphenol resin, allyl ester resin, and the like.

[0313] In addition, as the allyl resin, a compound containing two or more allyl groups in one molecule such as triallyl isocyanurate can also be used.

[0314] As the thiol resin, polyphenylene sulfide resin is preferably used. As the polyphenylene sulfide resin, known resins containing a polyphenylene sulfide skeleton can be used, and there is no particular limitation. Polymers homologous to polyphenylene sulfide (for example, polyphenylene sulfide ketone PPSK, polyphenylene sulfide sulfone PPSS, poly(phenylenesulfide) PBPS, etc.) are also included in the polyphenylene sulfide resin.

[0315] In addition, as the thiol resin, the following thiol compounds can be used: trimethylolpropane tris(3-mercaptopropionate), 3-mercaptopropionate of pentaerythritol, dipentaerythritol hexa(3-mercaptopropionate), tris-[(3-mercaptopropionyloxy)-ethyl]-isocyanurate, polyethylene glycol bis(3-mercaptopropionate), pentaerythritol tetrapropyl mercaptan, etc.

[0316] The resin composition of the present invention may further contain a matrix resin that does not have the above functional groups as the matrix resin. As the matrix resin that does not have the above functional groups, it is preferably used, for example: cyanate resin, polysiloxane resin, polyphenylene ether resin, epoxy resin, benzoxazine resin, polyimide resin, polyester resin, liquid crystalline polymer (LCP), and modified polyolefin resin, etc.

[0317] In the resin composition of the present invention, the content of the matrix resin is not particularly limited. In all solid components of 100% by mass of the resin composition, as the lower limit, it is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more. As the upper limit, it is preferably 95% by mass or less, more preferably 90% by mass or less. When the content of the matrix resin is above the above lower limit value, the decrease in the physical properties of the resin composition can be suppressed, the moldability can be improved, and in addition, the mechanical strength can be improved. When the content of the matrix resin is below the above upper limit value, the hollow particles can be sufficiently contained, so the effects such as the reduction of the dielectric loss tangent, the reduction of the dielectric constant, the light weight, and the heat insulation of the resin composition brought by the hollow particles are excellent.

[0318] In addition, from the viewpoint of improving the adhesion between the matrix resin and the hollow particles, in 100% by mass of the matrix resin, the content of the matrix resin having the above functional groups is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 90% by mass or more.

[0319] In addition, the matrix resins can be used alone or in combination of two or more.

[0320] [Crosslinking agent]

[0321] The resin composition of the present invention preferably contains a crosslinking agent for initiating or promoting the curing reaction of the matrix resin, or the reaction between the reactive unsaturated bonds of the hollow particles and the functional groups of the matrix resin. The crosslinking agent is appropriately selected according to the type of the functional group and is not particularly limited.

[0322] When the base resin contains a radically polymerizable group as a functional group, it is preferable to contain a radical polymerization initiator as a crosslinking agent. Examples of the radical polymerization initiator include organic peroxides such as benzoyl peroxide, di-tert-butyl peroxide, dicumyl peroxide, 3,3,5-trimethylhexanoyl peroxide, di-2-ethylhexyl peroxydicarbonate, methyl ethyl ketone peroxide, tert-butyl o-phthalate peroxide, tert-butyl benzoate peroxide, di-tert-butyl peroxyacetate, tert-butyl isobutyrate peroxide, tert-butyl 2-hexanoate peroxide, tert-butyl 2-ethylhexanoate peroxide, tert-butyl 3,5,5-trimethylhexanoate peroxide, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, tert-butyl peroxide, di-tert-amyl peroxide; inorganic peroxides such as ammonium persulfate, potassium persulfate, sodium persulfate; azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 4,4'-azobis(4-cyanovaleric acid), etc.

[0323] The content of the crosslinking agent is appropriately adjusted according to the types of the crosslinking agent and the base resin and is not particularly limited.

[0324] [Others]

[0325] The resin composition of the present invention may further contain a solvent. As the solvent, known solvents can be used and appropriately selected according to the type of the base resin.

[0326] Within the range not impairing the effects of the present invention, the resin composition of the present invention may further contain additives such as a curing accelerator, a filler, a coupling agent, a low-stress agent, an antifoaming agent, a leveling agent, an ultraviolet absorber, a foaming agent, an antioxidant, a coloring agent, a heat stabilizer, a flame retardant, etc. as needed.

[0327] [Manufacturing method of resin composition]

[0328] The resin composition of the present invention can be obtained by mixing the above-mentioned hollow particles, base resin, and other components added as needed. The mixing method is not particularly limited, and methods using known mixing devices such as a planetary mixer, a ball mill, a bead mill, a planetary mixer, a roll mill, etc. can be adopted. The resin composition of the present invention obtained using such a mixing device is usually a liquid resin composition (resin varnish).

[0329] [Uses of resin composition]

[0330] Examples of the use of the resin composition of the present invention include components such as low dielectric materials, heat insulating materials, sound insulating materials, light reflecting materials, anti-glare films, light diffusing films or light diffusing plates, etc. for various fields such as automobiles, electrics, electronics, construction, aviation, and space; food containers, footwear such as sports shoes and sandals; home appliance components, automotive components, stationery, tools, filaments for 3D printers, buoyancy materials such as composite foams, etc. Among them, since the resin composition of the present invention has excellent dielectric properties and reliability, it is preferably used in the electrical or electronic field. For example, the resin composition of the present invention is preferably used as an electronic circuit board material. In addition, the resin composition of the present invention is also preferably used as: interlayer insulating materials, dry film resists, solder resists, bonding wires, magnet wires, semiconductor encapsulating materials, epoxy encapsulating materials, mold underfill, underfill, die bond paste, buffer coating materials, copper-clad laminates, flexible substrates and other semiconductor materials, or semiconductor materials for high-frequency device modules, antenna modules, automotive radars, etc. Among them, it is preferably used as interlayer insulating materials, solder resists, magnet wires, semiconductor encapsulating materials, epoxy encapsulating materials, underfill materials, buffer coating materials, copper-clad laminates, flexible substrates and other semiconductor materials, or semiconductor materials for high-frequency device modules, antenna modules, automotive radars, etc. In addition, the resin composition of the present invention is not limited to being used for semiconductor materials and can be used for various electronic materials.

[0331] In addition, the resin composition of the present invention is also preferably used for insulating resin sheets used in the manufacture of electronic components such as printed circuit boards. The insulating resin sheet can be manufactured, for example, by coating and drying the resin composition of the present invention on one or both sides of a sheet-like substrate, extrusion molding, or transfer printing, etc. to form it into a sheet shape. When the resin or elastomer contained in the insulating resin sheet has adhesiveness, the insulating resin sheet can be used as an adhesive sheet, and specifically, it can be used as, for example, a bonding sheet. The bonding sheet is used as an insulating adhesive layer forming material for bonding a conductor layer and an organic insulating layer in the case of manufacturing a multi-layer printed circuit board.

[0332] 2. Resin structure

[0333] The resin structure of the present invention is characterized by containing a semi-cured product or a cured product of the above resin composition of the present invention, and in the semi-cured product or cured product, at least a part of the hollow particles is crosslinked and bonded to the matrix resin. In addition, when curing the resin structure, usually when curing a thermosetting resin, it is preferably cured in an inert environment. By curing in an inert environment, changes in dielectric properties can be suppressed.

[0334] The resin structure of the present invention is a structure obtained by molding the resin composition of the present invention under the condition that at least a part of the reactive unsaturated bonds of the hollow particles contained in the resin composition of the present invention reacts with the functional groups of the matrix resin. The resin structure of the present invention can be obtained, for example, by heating and drying the resin composition of the present invention or by hot pressing and molding. The prepreg, the insulating layer contained in the metal-clad laminate, and the insulating layer contained in the printed circuit board described below are the resin structures of the present invention, but the resin structure of the present invention is not limited to these.

[0335] Since the resin structure of the present invention contains hollow particles, it is imparted with properties such as low dielectric loss tangent, low dielectric constant, light weight, and heat insulation.

[0336] When the resin structure is obtained by heating and drying the resin composition of the present invention, the method of heating and drying is not particularly limited, and it can be carried out using, for example, an oven. The heating temperature is not particularly limited, and it can be, for example, 20°C to 200°C, 50°C to 200°C, 100°C to 180°C, or 150°C to 170°C. The heating time is not particularly limited, and it can be, for example, 1 minute to 1 hour, 1 minute to 30 minutes, or 3 minutes to 10 minutes. In addition, the heating and drying can also be carried out in stages by changing the temperature.

[0337] When the resin structure is obtained by hot pressing and molding the resin composition of the present invention, the method of hot pressing and molding is not particularly limited, and it can be carried out using, for example, a hot press. The temperature, pressure, and time during hot pressing and molding are not particularly limited, and can be appropriately set according to the thickness of the metal-clad laminate to be manufactured and the composition of the resin composition of the prepreg, etc. For example, the temperature can be set to 150°C to 250°C, or 170°C to 220°C, the pressure can be set to 1.0 MPa to 7.0 MPa, or 1.5 MPa to 5.0 MPa, and the time can be set to 1 minute to 5 hours, or 1 hour to 3 hours.

[0338] The shape of the resin structure of the present invention is not particularly limited, and it can be various shapes that can be molded, and can be, for example, a sheet shape, a film shape, or a plate shape, or any shape such as a tubular shape and other various three-dimensional shapes.

[0339] In addition, the resin structure of the present invention can be a structure in which the hollow particles of the present invention are added to a fiber-reinforced plastic. The reinforcing fiber used for the fiber-reinforced plastic is not particularly limited, and known organic or inorganic reinforcing fibers such as carbon fiber, glass fiber, aramid fiber, polyethylene fiber, cellulose nanofiber, and liquid crystalline polymer (LCP) fiber can be used. The reinforcing fiber contained in the resin structure of the present invention can be used as the base material of the prepreg or can be contained as a filler.

[0340] In the resin structure of the present invention, the content of the hollow particles is not particularly limited. As the lower limit, it is preferably 10% by volume or more, more preferably 20% by volume or more. As the upper limit, it is preferably 70% by volume or less, more preferably 60% by volume or less. When the content of the hollow particles is at least the above lower limit value, the effects such as low dielectric loss tangent, low dielectric constant, light weight, and heat insulation of the resin structure brought by the hollow particles are excellent. When the content of the hollow particles is at most the above upper limit value, the matrix resin can be sufficiently contained in the resin structure, so that the reduction of the physical properties of the resin structure can be suppressed and the mechanical strength can be improved.

[0341] In the resin structure of the present invention, the content of the matrix resin is not particularly limited. From the viewpoint of suppressing the reduction of the physical properties of the resin structure and improving the mechanical strength, it is preferably 30% by volume or more, more preferably 40% by volume or more. From the viewpoint of sufficiently containing the hollow particles, it is preferably 90% by volume or less, more preferably 80% by volume or less.

[0342] In addition, when the matrix resin contained in the resin composition of the present invention is cured by additives such as crosslinking agents, the matrix resin contained in the resin structure of the present invention may also contain such additives as crosslinking agents.

[0343] The dielectric loss tangent of the resin structure of the present invention at a frequency of 10 GHz is preferably 4.00×10 -3 or less, more preferably 3.00×10 -3 or less, and further preferably 2.00×10 -3 or less. The lower limit of the above dielectric loss tangent is not particularly limited and may be, for example, 1.00×10 -4 or more.

[0344] The relative dielectric constant of the resin structure of the present invention at a frequency of 10 GHz is preferably 2.50 or less, more preferably 2.30 or less, and further preferably 2.20 or less. The lower limit of the above relative dielectric constant is not particularly limited and may be, for example, 1.00 or more.

[0345] In the present invention, the relative dielectric constant and the dielectric loss tangent of the resin structure are measured using a perturbation method measuring device.

[0346] 3. Prepreg

[0347] The prepreg of the present invention is a prepreg obtained by impregnating a base material with the above resin composition of the present invention and heating and drying it. The prepreg of the present invention contains a semi-cured product of the above resin composition of the present invention, and in this semi-cured product, at least a part of the hollow particles is crosslinked and bonded to the matrix resin.

[0348] The substrate used in the prepreg is not particularly limited, and examples thereof include substrates composed of inorganic fibers such as carbon fiber, glass fiber, metal fiber, and ceramic fiber, or organic synthetic fibers such as polyamide fiber, polyester fiber, polyolefin fiber, and Novoloid fiber. The form of the substrate is not limited, and fabrics, non-woven fabrics, etc. can be used. Among them, from the viewpoint of mechanical strength, etc., a glass cloth (glass fiber) is preferred.

[0349] As the thickness of the substrate, a thickness of, for example, 0.04 mm to 0.3 mm can generally be used.

[0350] The method of impregnating the resin composition into the substrate is not particularly limited, and examples thereof include a method of impregnating the substrate into the resin composition and a method of coating the resin composition on the substrate. The impregnation can be repeated several times as needed.

[0351] The method of heat drying only needs to be a method in which the matrix resin becomes a semi-cured state (B-stage state), and can be the same as the method of heat drying in the case of obtaining the above resin structure.

[0352] 4. Metal-clad laminate

[0353] The metal-clad laminate of the present invention is characterized by having an insulating layer containing a cured product of the resin composition of the present invention and a substrate, and a metal foil in contact with the insulating layer.

[0354] Examples of the substrate including the insulating layer include the same substrates as those contained in the above prepreg.

[0355] In the cured product of the resin composition contained in the insulating layer of the metal-clad laminate of the present invention, at least a part of the hollow particles is crosslinked and bonded to the matrix resin.

[0356] The metal-clad laminate of the present invention can be a metal-clad laminate formed by heating and pressing a laminated prepreg in which the above prepreg of the present invention is stacked and a metal foil in contact with the laminated prepreg. In this case, the cured product of the laminated prepreg becomes the insulating layer. Heating and pressing the laminated prepreg and the metal foil in contact with the laminated prepreg can be heating and pressing a laminate including the laminated prepreg and the metal foil in contact with the laminated prepreg.

[0357] In addition, in the metal-clad laminate of the present invention, it is sufficient that the metal foil is in contact with at least one surface of the insulating layer, and metal foils can also be arranged on both surfaces of the insulating layer.

[0358] In the case where the insulating layer is a cured product of a laminated prepreg, the number of prepreg sheets contained in the laminated prepreg is not particularly limited, and may be, for example, 1 to 50 sheets, 2 to 40 sheets, 2 to 30 sheets, 2 to 20 sheets, or 2 to 10 sheets.

[0359] Examples of the metal foil include copper foil, silver foil, and gold foil. From the viewpoints of cost and conductivity, copper foil is preferably used. The thickness of the metal foil is not particularly limited, and may be, for example, 9 μm to 70 μm.

[0360] The method of hot press molding for obtaining the metal foil-clad laminate may be the same as the method of hot press molding for obtaining the resin structure described above. By hot press molding, the matrix resin contained in the insulating layer is completely cured.

[0361] In the metal foil-clad laminate of the present invention, the peel strength between the insulating layer and the metal foil is preferably 0.5 N / mm or more, more preferably 0.6 N / mm or more, and further preferably 0.7 N / mm or more.

[0362] In addition, in the present invention, the peel strength between the insulating layer and the metal foil is measured according to JIS C 6481.

[0363] 5. Printed Circuit Board

[0364] The printed circuit board of the present invention is characterized by including the above-described metal foil-clad laminate of the present invention.

[0365] The printed circuit board of the present invention can be manufactured, for example, by forming a circuit on the above-described metal foil-clad laminate of the present invention. For example, a conductor pattern can be formed by etching away the metal foil on the surface of the metal foil-clad laminate, thereby obtaining a printed circuit board. In addition, this printed circuit board can also be used as a core material to manufacture a multilayer printed wiring board.

[0366] Examples

[0367] Hereinafter, examples and comparative examples are given to illustrate the present invention more specifically, but the present invention is not limited to these examples. In addition, unless otherwise specified, parts and % are based on mass.

[0368] [Production Example 1]

[0369] 1. Preparation of Hollow Particles

[0370] (1) Mixed Liquid Preparation Step

[0371] First, the following materials are mixed to form an oil phase.

[0372] 37.2 parts of divinylbenzene (DVB) (a mixture of m-divinylbenzene and p-divinylbenzene)

[0373] 1.5 parts of ethyl vinylbenzene (EVB)

[0374] 0.89 parts of tert-butyl peroxyethylhexanoate

[0375] 61.3 parts of hydrophobic solvent (heptane)

[0376] Next, in a stirring tank, an aqueous solution of 19.59 parts of magnesium chloride (water-soluble polyvalent metal salt) dissolved in 225 parts of ion-exchanged water was slowly added with stirring to an aqueous solution of 13.72 parts of sodium hydroxide (alkali metal hydroxide) dissolved in 55 parts of ion-exchanged water to prepare a magnesium hydroxide colloid (water-insoluble metal hydroxide colloid) dispersion (10 parts of magnesium hydroxide), forming an aqueous phase.

[0377] The obtained aqueous phase and oil phase were mixed to prepare a mixed solution.

[0378] (2) Suspension process

[0379] The mixed solution obtained in the above mixed solution preparation process was stirred for 1 minute using an emulsifying disperser (manufactured by Primix Corporation, product name: homogenizing mixer) under the condition that the front-end speed of the rotating part was 88 m / s, thereby performing a suspension treatment to prepare a suspension in which droplets of a monomer composition containing a hydrophobic solvent were dispersed in water.

[0380] (3) Polymerization process

[0381] The suspension obtained in the above suspension process was heated to 80 °C in a nitrogen atmosphere, and the stirring power of the stirring blade was set to 0.04 kW / m 3 , and stirred for 24 hours to perform a polymerization reaction. Through this polymerization reaction, a slurry liquid, i.e., a precursor composition, in which precursor particles containing a hydrophobic solvent and having reactive unsaturated bonds on the surface were dispersed in water was obtained.

[0382] (4) Solvent removal process

[0383] The solvent removal process is carried out using the stirring device shown in Figure 2 through the following steps. In addition, a stirring tank with a capacity of 3.6 L was used as the stirring tank, and the inside of the stirring tank was in a nitrogen atmosphere when supplying the precursor composition.

[0384] 2.6 L of the precursor composition obtained in the above polymerization process was supplied from the supply tank to the stirring tank. The stirring power of the stirring blade provided in the stirring tank was set to 0.04 kW / m 3 , while stirring the precursor composition in the stirring tank, the precursor composition was heated to 95 °C and the inside of the stirring tank was depressurized to 40 kPa, while from the gas inlet located at the bottom of the stirring tank ( Figure 2The gas inlet 13a) in 3 blows nitrogen directly into the precursor composition at a flow rate of 10 L / min in a direction opposite to the direction of gravity (since the gas phase part is 1 L, the flow rate per unit volume is 10000 L / (min·m

[0385] (5) Cleaning process

[0386] In an environment at 25°C, dilute sulfuric acid is added to the aqueous dispersion of hollow particles obtained in the above solvent removal process and stirred for 10 minutes to obtain a pH-adjusted slurry with a pH adjusted to 5.5 or less. The obtained pH-adjusted slurry is directly pressure-filtered and dehydrated at 25°C to obtain a dehydrated filter cake of hollow particles. A series of processes of washing the obtained dehydrated filter cake with 400 parts of ion-exchanged water, pressure-filtering, and dehydrating are repeated 6 times.

[0387] (6) Drying process

[0388] The dehydrated filter cake (with a moisture content of 67% and a thickness of 2 cm) after the above cleaning process is pre-dried by drying with a dryer at a temperature of 40°C, and then the moisture remaining in the particles is removed by heat treatment with a vacuum dryer at 200°C and a vacuum condition of 4 kPa for 12 hours to obtain the hollow particles 1 of Production Example 1.

[0389] [Production Example 2]

[0390] In Production Example 1, in the above-mentioned “(1) Mixed solution preparation process”, the addition amounts of DVB and EVB are changed according to Table 1. In the above-mentioned “(3) Polymerization process”, the temperature is raised to 80°C in a nitrogen atmosphere, and the stirring power of the stirring blade is set to 0.04 kW / m 3 , and stirring is carried out for 1 hour to carry out the first polymerization reaction. Then, 2.0 parts of allyl methacrylate (solubility in water at 20°C: 2.2 g / L) is added to the stirring tank, and stirring is carried out for 23 hours under the same conditions as the first polymerization reaction to carry out the second polymerization reaction. Except for this, the hollow particles 2 of Production Example 2 are manufactured in the same steps as Production Example 1.

[0391] [Production Example 3]

[0392] In Production Example 2, the first polymerization reaction was carried out for 0.5 hours and the second polymerization reaction was carried out for 23.5 hours. Except for this, the hollow particles 3 of Production Example 3 were produced in the same steps as in Production Example 2.

[0393] [Production Examples 4 to 10]

[0394] In Production Example 1, in the above-mentioned “(1) Mixed solution preparation step”, the types and addition amounts of the polymerizable monomers were changed according to Table 1. Except for this, the hollow particles 4 to 10 of Production Examples 4 to 10 were produced in the same steps as in Production Example 1.

[0395] In addition, “before suspension” in the addition timing shown in the table means addition to the oil phase in the above-mentioned “(1) Mixed solution preparation step”.

[0396] <Measurement of polymerization conversion rate>

[0397] In the polymerization steps of Production Examples 2 and 3, 50 g of the suspension just before adding the crosslinkable monomer (allyl methacrylate) was collected, the pH of the suspension was adjusted to 5 to 6, and then pressure filtration was carried out to separate the precipitate of the polymer contained in the suspension (including water and hydrophobic solvent). After removing water and hydrophobic solvent by drying at 200 °C for 2 hours, the mass of the precipitate of the polymer was accurately weighed as the mass of the polymerizable monomer contained in the suspension (the total mass of the polymerizable monomer after the polymerization reaction and the unreacted polymerizable monomer). The precipitate of the polymer was dispersed in ethyl acetate, and 2 μL of the obtained dispersion was collected as a measurement sample. Under the following conditions, the mass of the unreacted polymerizable monomer in the measurement sample was quantified by gas chromatography (GC), and the mass of the unreacted polymerizable monomer contained in the suspension was calculated. Based on the mass of the polymerizable monomer contained in the suspension, that is, the mass of the precipitate of the polymer, and the mass of the unreacted polymerizable monomer contained in the suspension, that is, the mass of the unreacted polymerizable monomer measured by GC, the polymerization conversion rate was calculated by the following formula (VI).

[0398] Alternatively, in the case where no precipitate of the polymer is formed, the suspension with a pH of 5 to 6 is phase-separated to separate the oil phase. 2 μL of the obtained oil phase was collected as a measurement sample, and the polymerizable monomer after the polymerization reaction or the unreacted polymerizable monomer in the measurement sample was quantitatively determined by gas chromatography (GC) under the following conditions, and the mass of the polymerizable monomer after the polymerization reaction or the unreacted polymerizable monomer contained in the oil phase was calculated respectively. At this time, by dividing (dividing) the non-reactive encapsulating solvent (hydrophobic solvent) contained in the oil phase, the mass of the unreacted polymerizable monomer contained only in the oil phase can be calculated. Based on the mass of the polymerizable monomer contained in the suspension, that is, the total mass of the polymerizable monomer after the polymerization reaction and the unreacted polymerizable monomer contained in the suspension, and the mass of the unreacted polymerizable monomer contained in the suspension, the polymerization conversion rate was calculated by the following formula (VI).

[0399] Formula (VI):

[0400] Polymerization conversion rate (mass %) = 100 - (mass of unreacted polymerizable monomer / mass of polymerizable monomer contained in the suspension) × 100

[0401] (GC conditions)

[0402] Chromatographic column: TC - WAX (0.25 mm × 30 m)

[0403] Column temperature: 80 °C

[0404] Injection temperature: 200 °C

[0405] FID detection side temperature: 200 °C

[0406] [Comparative Production Example 1]

[0407] Comparative Production Example 1 corresponds to Example 1 of Patent Document 1.

[0408] Mix pure water, 0.25 part of sodium dodecylbenzenesulfonate, 50 parts of divinylbenzene, 50 parts of hexadecane, and 3 parts of benzoyl peroxide to obtain an emulsion.

[0409] Put the emulsion into a detachable flask, heat it up to 70 °C in a nitrogen atmosphere, and carry out a polymerization reaction at 70 °C for 9 hours.

[0410] Next, mix 1.25 parts of benzoyl peroxide, 17 parts of toluene, 0.09 part of sodium dodecylbenzenesulfonate, and pure water to prepare a dispersion. Divide the prepared dispersion into 3 parts. First, put 1 / 3 of the amount into the reaction solution in the detachable flask. Then, after 1.5 hours, put 1 / 3 of the amount of this dispersion into the reaction solution in the detachable flask. Furthermore, after 1.5 hours, put 1 / 3 of the amount of this dispersion into the reaction solution in the detachable flask. Then continue stirring for 2 hours to carry out a polymerization reaction to obtain latex - like core - shell particles.

[0411] In another detachable flask, 100 parts of the latex-like core-shell particles obtained above and 100 parts of acetone were charged. After stirring at room temperature for 5 minutes, the mixture was stirred at 40 °C for 30 minutes. Stirring was stopped, and the reaction solution in the detachable flask was allowed to stand. The reaction solution separated into a coagulated particle layer and a transparent solvent layer was filtered by natural filtration using filter paper. The recovered coagulated particles were further dispersed in a mixed solvent of acetone and hexane, and the mixed solvent was stirred at 40 °C for 30 minutes. Stirring was stopped, and the mixed solvent was allowed to stand. The mixed solution separated into a coagulated particle layer and a transparent solvent layer was filtered by natural filtration using filter paper. The recovered coagulated particles were dispersed in acetone, and the core was replaced with a low-boiling organic solvent from hexadecane, whereby an acetone dispersion liquid in which hollow particles encapsulating an organic solvent in the core were dispersed was obtained.

[0412] 526 parts of methyl ethyl ketone was added to 100 parts of the above acetone dispersion liquid, and volatile components were removed under reduced pressure at 70 °C to remove the acetone and hexane used above, whereby a methyl ethyl ketone dispersion liquid in which hollow particles were dispersed was obtained.

[0413] Furthermore, after adding 250 parts of pure water to 100 parts of the methyl ethyl ketone dispersion liquid, the dispersion liquid separated into coagulated particles and a transparent solvent was filtered using gauze. Pure water was added to and mixed with the coagulated particles, and then methyl ethyl ketone was added and stirred. Subsequently, the mixed liquid separated into coagulated particles and a transparent solvent was filtered using gauze. Methyl ethyl ketone was added to the recovered coagulated particles to obtain a methyl ethyl ketone dispersion liquid in which hollow particles were dispersed.

[0414] Next, after transferring the above methyl ethyl ketone dispersion liquid to an eggplant-shaped flask, 264 parts of methyl ethyl ketone was added to 100 parts of the methyl ethyl ketone dispersion liquid. By removing the volatile components under reduced pressure at 70 °C, the pure water used above was removed, whereby a methyl ethyl ketone dispersion liquid in which hollow particles were dispersed was obtained. The methyl ethyl ketone dispersion liquid was dried to obtain the hollow particles C1 of Comparative Production Example 1.

[0415] [Table 1]

[0416]

[0417] [Measurement and Evaluation of Hollow Particles]

[0418] The hollow particles obtained in each production example were subjected to the following measurement and evaluation. The results are shown in Tables 2 to 3. In addition, in the table, for simplicity, the values of the dielectric loss tangent and the coefficient of thermal expansion are expressed using the exponents specified in JIS X 0210. For example, "5.60×10 -4 " is marked as "5.60E-04".

[0419] 1. Observation of Hollow Particles

[0420] Wipe the hollow particles fixed on the carbon tape with a cotton swab to intentionally break the hollow particles. Observe the interiors of 100 of these broken particles using SEM, determine the number of hollow parts in each particle, and calculate the percentage of the number of particles having only one hollow part.

[0421] 2. Ratio of irregular particles

[0422] Add 0.10 - 0.12 g of hollow particles to an aqueous solution of sodium linear alkylbenzene sulfonate (concentration 0.3%) to prepare a mixed solution. Disperse the obtained mixed solution using an ultrasonic cleaner for 5 minutes to prepare a measurement sample. Using a flow particle image measurement device (manufactured by JASCO Corporation, product name: IF-3200), measure the roundness of each particle contained in the measurement sample under the following measurement conditions. Calculate the mass-based ratio of particles with a roundness of 0.85 or less as the ratio of irregular particles.

[0423] In addition, the smaller the particle size, the larger the number of particles contained in the measurement sample, and the number is in the range of 1000 - 3000 for each example and each comparative example.

[0424] (Measurement conditions)

[0425] Thickness of the flow cell spacer: 50 μm

[0426] Telecentric zoom lens magnification: 4.5 times

[0427] Total magnification: 9.0 times

[0428] Measurement volume: 0.5 mL

[0429] Image resolution: 0.185 μm / pixel

[0430] Detection algorithm: Ghost detection

[0431] Threshold: 15%

[0432] 3. Particle size and particle size distribution

[0433] Use a particle size distribution measuring machine based on the Coulter counting method (product name: Multisizer 4e, manufactured by Beckman Coulter, Inc.) to measure the particle size of the hollow particles, calculate their number average and volume average respectively, and obtain the number average particle size (Dn) and volume average particle size (Dv). In addition, by dividing the volume average particle size by the number average particle size, obtain the particle size distribution (Dv / Dn).

[0434] The measurement conditions are set as follows: pore diameter: 50 μm, dispersion medium: ISOTON II (product name), concentration: 10%, number of measured particles: 100,000. Specifically, take 0.2 g of the particle sample into a beaker, and add an aqueous surfactant solution (product name: DRIWEL, manufactured by Fujifilm Corporation) as a dispersant thereto. Further add 2 ml of the dispersion medium thereto, wet the particles, then add 10 ml of the dispersion medium, disperse it with an ultrasonic disperser for 1 minute, and then measure it with the above particle size distribution analyzer.

[0435] 4. Porosity

[0436] 4-1. Measurement of the apparent density of hollow particles

[0437] First, fill about 30 cm 3 of hollow particles into a volumetric flask with a volume of 100 cm 3 . Accurately weigh the mass of the filled hollow particles. Then, while taking care not to mix in air bubbles, accurately fill isopropyl alcohol up to the graduation line in the volumetric flask filled with hollow particles. Accurately weigh the mass of the isopropyl alcohol added to the volumetric flask, and calculate the apparent density D1 (g / cm 3 ) of the hollow particles based on the following formula (I).

[0438] Formula (I)

[0439] Apparent density D1 = [mass of hollow particles] / (100 - [mass of isopropyl alcohol] / [specific gravity of isopropyl alcohol at the measurement temperature])

[0440] 4-2. Measurement of the true density of hollow particles

[0441] Pre-crush the hollow particles, and then fill about 10 g of fragments of the hollow particles into a volumetric flask with a volume of 100 cm 3 . Accurately weigh the mass of the filled fragments.

[0442] Then, add isopropyl alcohol to the volumetric flask in the same manner as the measurement of the apparent density above, accurately weigh the mass of the isopropyl alcohol, and calculate the true density D0 (g / cm 3 ) of the hollow particles based on the following formula (II).

[0443] Formula (II)

[0444] True density D0 = [mass of fragments of hollow particles] / (100 - [mass of isopropyl alcohol] / [specific gravity of isopropyl alcohol at the measurement temperature])

[0445] 4-3. Calculation of porosity

[0446] Calculate the porosity of the hollow particles based on the apparent density D1 and the true density D0 of the hollow particles according to the following formula (III).

[0447] Formula (III)

[0448] Porosity (%) = 100 - (Apparent density D1 / True density D0) × 100

[0449] 5. Measurement of relative dielectric constant (Dk) and dielectric loss tangent (Df) of hollow particles

[0450] Using a measurement device (manufactured by AET Co., Ltd., model: ADMS01Nc) in a perturbation mode, measure the relative dielectric constant and dielectric loss tangent of the hollow particles under the conditions of a frequency of 10 GHz, a temperature of 23 °C, and a humidity of 50%.

[0451] 6. Measurement of the amount of unsaturated bonds

[0452] 6-1. Measurement of iodine value

[0453] Measure the iodine value of the hollow particles according to JIS K 0070. The specific measurement method is as described below.

[0454] Add 0.7 - 2 g of hollow particles and 10 mL of chloroform to a 300 mL iodine flask, and then add 25 mL of Wij's solution as the reaction solution. Gently stir and seal, and let it stand in the dark at 25 °C for 60 minutes. Then, add 20 mL of 100 g / L potassium iodide solution and 100 mL of purified water and stir. Titrate with a titrant (0.1 mol / L sodium thiosulfate solution) using a burette. When the solution becomes light yellow, add an indicator (1% starch solution), continue titrating, and take the point where the blue color disappears as the end point. Different from this test, perform a blank test on the solution without adding hollow particles, and calculate the iodine value of the hollow particles using the following formula. In addition, the iodine value is the value obtained by converting the amount of halogen bonded when reacting 100 g of the sample with halogen into grams of iodine.

[0455] Iodine value (g / 100 g) = {(V0 - V1) × f × 1.269} / S

[0456] S: Mass of the sample (g)

[0457] V1: Volume of the titrant in this test (mL)

[0458] V0: Volume of the titrant in the blank test (mL)

[0459] f: Factor of the titrant

[0460] 6-2. Measurement of specific surface area

[0461] Calculate the specific surface area (m of the hollow particles from the volume average particle diameter and apparent density D1 of the hollow particles measured above using the following formula (B) 2 / g).

[0462] Formula (B):

[0463] Specific surface area (m 2 / g) = 6 / (volume average particle size (m) × apparent density D1 (g / m 3 ))

[0464] 6 - 3. Calculation of the amount of unsaturated bonds

[0465] Based on the value obtained by converting the iodine value (g / 100g) of the hollow particles measured above to iodine value (mmol / g) and the specific surface area of the hollow particles, the amount of unsaturated bonds per unit area (mmol / m 2 ) of the hollow particles is calculated by the following formula (A).

[0466] Formula (A):

[0467] Amount of unsaturated bonds (mmol / m 2 ) = iodine value (mmol / g) / specific surface area (m 2 / g)

[0468] In addition, following Rule B of JIS Z8401:1999, as the iodine value and specific surface area, values rounded to the third decimal place are used, and the amount of unsaturated bonds is a value rounded to the third decimal place.

[0469] 7. Coefficient of thermal expansion

[0470] 7 - 1. Preparation of the molded plate for measurement

[0471] Add 50 parts of epoxy resin (manufactured by Daicel Corporation, product number: EHPE3150CE), 24.9 parts of curing agent (manufactured by DIC Corporation, product number: LF6161), 0.1 part of 2 - ethyl - 4 - methylimidazole (manufactured by Nacalai Tesque, 2E4MZ) as a curing catalyst, and 26 parts of methyl ethyl ketone (MEK), and stir for 30 minutes. After stirring, add 16.6 parts of hollow particles and stir for an additional 1 hour to prepare a resin composition. Place 15 g of the resin composition on a copper foil, and use a vacuum dryer at 130°C to defoam until no more foaming occurs, and cure it in a hot air circulation oven at 110°C for 2 hours. Then, start heating and pressing at 0.5 MPa in a press at 110°C and then raise the temperature (4°C / min) until 205°C, and hold for 1 hour to make a molded plate. Cut the molded plate into a shape of 20 mm × 40 mm × 0.5 mm as the test specimen for measurement.

[0472] 7 - 2. Measurement of the coefficient of thermal expansion of the hollow particles

[0473] According to JIS K 7197:2012, the coefficient of thermal expansion of the molded plate produced was measured in the range of 23 to 250 °C in tensile mode using a TMA apparatus (manufactured by Rigaku Corporation, model: TMA-8311).

[0474] In the temperature range of 23 to 100 °C, based on the coefficient of thermal expansion α of the above-mentioned molded plate c , the coefficient of thermal expansion α of the epoxy resin monomer r , the volume ratio SG of the epoxy resin in the above-mentioned molded plate r , and the volume ratio W of the hollow particles in the above-mentioned molded plate p , the coefficient of thermal expansion α of the hollow particles was obtained by the following formula (IV). p .

[0475] α p = (α c - SG r × α r ) / W p Formula (IV)

[0476] 8. Conductivity of the aqueous dispersion of hollow particles

[0477] In 100 mL of an aqueous solution (conductivity 1 μS / cm or less) of ion-exchanged water in which a nonionic surfactant (product name: SN DEFOAMER180, manufactured by San Nopco Ltd., polyether type) was dissolved at a concentration of 0.1% by mass, 0.35 cm 3 of hollow particles was added, and the mixture was stirred at 300 rpm for 3 hours at 25 °C to obtain an aqueous dispersion of hollow particles. The conductivity of the obtained aqueous dispersion of hollow particles was measured. In addition, the obtained aqueous dispersion of hollow particles was in a state where no powder was present visually on the upper part and all the powder was dispersed in water. Furthermore, as the hollow particles with a volume of 0.35 cm 3 , the hollow particles obtained by measuring the weight (g) of the hollow particles obtained by the following formula (V) were used.

[0478] Formula (V):

[0479] Weight (g) of hollow particles with a volume of 0.35 cm 3 = apparent density D1 (g / cm 3 ) × 0.35 (cm 3 )

[0480] 9. Residual metal content

[0481] Using a microwave digestion apparatus (manufactured by PerkinElmer, Multiwave 3000), 10 g of the hollow particles accurately weighed were wet-decomposed, and the resulting decomposition product was subjected to ICP emission analysis using an ICP emission analysis device (manufactured by PerkinElmer, Optima 2100DV type) to measure the total mass of the metals. In addition, the determination of the metal species was carried out by elemental analysis based on fluorescence X-ray analysis (XRF). The ratio of the total mass of the metals in the decomposition product to the mass of the hollow particles was calculated as the residual metal amount in the hollow particles.

[0482] [Example 1]

[0483] (1) Preparation of the resin composition

[0484] 100 parts of a 65% toluene solution of modified polyphenylene ether (modified PPE) modified with a vinyl group-containing functional group (manufactured by Mitsubishi Gas Chemical Company, Inc., product name: OPE-1200, iodine value: 43 g / 100 g, number average molecular weight: 1200) were measured in a cup, 11 parts of the hollow particles 1 obtained in Production Example 1 were added, and further 0.63 parts of dicumyl peroxide (manufactured by NOF Corporation, product name: PERCUMYL D) were added and uniformly dispersed using a planetary stirring and degassing device (manufactured by Kurabo Industries Ltd., product name: MAZERUSTAR), thereby preparing the resin composition of Example 1.

[0485] (2) Production of the resin film

[0486] An aluminum foil was pasted on a glass plate without wrinkles, and the resin composition obtained in the above (1) was coated on the aluminum foil using a bar coater No. 75 to form a coating film. The coating film was heated and cured in a nitrogen atmosphere in the order of heating at 80°C for 1 hour, heating at 120°C for 30 minutes, heating at 160°C for 30 minutes, and heating at 200°C for 1 hour to form a resin film on the aluminum foil. By immersing the laminate of the resin film and the aluminum foil in a 1N hydrochloric acid aqueous solution overnight, only the resin film was obtained by removing the aluminum foil. The obtained resin film was washed with ion-exchanged water and dried, thereby obtaining the resin film. In the obtained resin film, the content of the hollow particles was 40% by volume with respect to 100% by volume of the resin film.

[0487] (3) Production of the prepreg

[0488] The resin composition obtained in the above (1) was impregnated into a glass cloth (manufactured by Nitto Boseki Co., Ltd., product name: WEA116E), and then heated and dried at 150 to 170°C for 3 to 10 minutes to remove the solvent, thereby obtaining a prepreg. The obtained prepreg contained a semi-cured product of the resin composition, and the content of the hollow particles in the semi-cured product was 40% by volume with respect to 100% by volume of the semi-cured product.

[0489] (4) Production of Metal-Clad Laminate

[0490] Copper foils with a thickness of 18 μm are arranged on both sides of the obtained prepreg above, and are formed by heating and pressing under the curing conditions of 200 °C, 2 hours, and a pressure of 2.94 MPa (30 kg / cm 2 ) in a nitrogen atmosphere, to obtain a double-sided copper-clad laminate with a copper foil thickness of 0.10 mm on both sides of the cured product of the prepreg.

[0491] [Examples 2 to 10 and Comparative Example 1]

[0492] In Example 1, the hollow particles 2 to 10 obtained in Production Examples 2 to 10 or the hollow particle C1 obtained in Comparative Production Example 1 are used to replace the hollow particle 1 obtained in Production Example 1. Except for this, the resin compositions, resin films, prepregs, and metal-clad laminates of Examples 2 to 10 and Comparative Example 1 are produced in the same steps as in Example 1.

[0493] [Comparative Example 2]

[0494] In Example 1, no hollow particles are added to the resin composition. Except for this, the resin composition, resin film, prepreg, and metal-clad laminate of Comparative Example 2 are produced in the same steps as in Example 1.

[0495] [Comparative Example 3]

[0496] In Example 1, silica particles (product name: SC2500-SXJ) manufactured by Admatechs Company are used to replace the hollow particle 1 obtained in Production Example 1. Except for this, the resin composition, resin film, prepreg, and metal-clad laminate of Comparative Example 3 are produced in the same steps as in Example 1.

[0497] [Comparative Example 4]

[0498] In Example 1, hollow glass particles (product name: CellSpheres (registered trademark) NF) manufactured by Taiheiyo Cement Corporation are used to replace the hollow particle 1 obtained in Production Example 1. Except for this, the resin composition, resin film, prepreg, and metal-clad laminate of Comparative Example 4 are produced in the same steps as in Example 1.

[0499] [Comparative Example 5]

[0500] In Example 1, hollow polyurethane particles (product name: H-600T) manufactured by Koken Sangyo Co., Ltd. were used in place of the hollow particles 1 obtained in Production Example 1. Except for this, a resin composition, a resin film, a prepreg, and a metal-clad laminate of Comparative Example 5 were produced in the same steps as in Example 1.

[0501] [Example 11]

[0502] The modified polyphenylene ether (modified PPE) modified with methacryloyl group (manufactured by SABIC, product name: NORYL SA9000, iodine value: 29 g / 100 g, number average molecular weight: 1700) was dissolved in toluene so that the concentration became 50%. 100 parts of this solution was measured in a cup, 8.7 parts of the hollow particles 1 obtained in Production Example 1 was added, and further, 0.5 part of diisopropylbenzene peroxide (manufactured by NOF Corporation, product name: PERCUMYL D) was added, and it was uniformly dispersed using a planetary stirring and degassing device (manufactured by Kurashiki Boseki Co., Ltd., product name: MAZERUSTAR), whereby the resin composition of Example 11 was prepared.

[0503] Using the resin composition obtained above, except for this, the resin film, prepreg, and metal-clad laminate of Example 11 were obtained in the same manner as in Example 1.

[0504] In the obtained resin film, the content of the hollow particles was 40% by volume with respect to 100% by volume of the resin film. Further, in the obtained prepreg, the content of the hollow particles was 40% by volume with respect to the semi-cured product of 100% by volume of the resin composition.

[0505] [Comparative Example 6]

[0506] In Example 11, no hollow particles were added to the resin composition. Except for this, a resin composition, a resin film, a prepreg, and a metal-clad laminate of Comparative Example 6 were produced in the same steps as in Example 11.

[0507] [Example 12]

[0508] Measure 86 parts of a 65% toluene solution of modified polyphenylene ether (modified PPE) modified with a vinyl-functional group (manufactured by Mitsubishi Gas Chemical Company, Inc., product name: OPE-1200, iodine value: 43 g / 100 g, number average molecular weight: 1200), 14 parts of triallyl isocyanurate (manufactured by Mitsubishi Chemical Corporation, product name: TAIC, iodine value: 305 g / 100 g) in a cup, add 12.3 parts of the hollow particles 1 obtained in Production Example 1, and further add 0.7 parts of dicumyl peroxide (manufactured by NOF Corporation, product name: PERCUMYL D), and uniformly disperse with a planetary stirring and degassing device (manufactured by Kurabo Industries Ltd., product name: MAZERUSTAR) to prepare the resin composition of Example 12.

[0509] Using the resin composition obtained above, in addition, the resin film, prepreg, and metal-clad laminate of Example 12 were obtained in the same manner as in Example 1.

[0510] In the obtained resin film, the content of the hollow particles is 40% by volume with respect to 100% by volume of the resin film. In addition, in the obtained prepreg, the content of the hollow particles is 40% by volume with respect to 100% by volume of the semi-cured product of the resin composition.

[0511] [Comparative Example 7]

[0512] In Example 12, the hollow particles were not added to the resin composition, and in addition, the resin composition, resin film, prepreg, and metal-clad laminate of Comparative Example 7 were produced in the same steps as in Example 12.

[0513] [Example 13]

[0514] Measure 100 parts of a 70% MEK solution of maleimide resin (manufactured by Nippon Kayaku Co., Ltd., product name: MIR-3000-70MT, number average molecular weight: 1200) in a cup, add 12.3 parts of the hollow particles 1 obtained in Production Example 1, and further add 0.7 parts of dicumyl peroxide (manufactured by NOF Corporation, product name: PERCUMYL D), and uniformly disperse with a planetary stirring and degassing device (manufactured by Kurabo Industries Ltd., product name: MAZERUSTAR) to prepare the resin composition of Example 13.

[0515] Using the resin composition obtained above, in addition, the resin film, prepreg, and metal-clad laminate of Example 13 were obtained in the same manner as in Example 1.

[0516] In the obtained resin film, the content of the hollow particles is 40% by volume with respect to 100% by volume of the resin film. Further, in the obtained prepreg, the content of the hollow particles is 40% by volume with respect to 100% by volume of the semi-cured product of the resin composition.

[0517] [Comparative Example 8]

[0518] In Comparative Example 8, hollow particles were not added to the resin composition, and except for this, a resin composition, a resin film, a prepreg, and a metal-clad laminate were produced in the same steps as in Example 13.

[0519] [Evaluation of Resin Film]

[0520] The resin film was cut into a width of 3 mm and a length of 80 mm to obtain a measurement sample. In the obtained measurement sample, according to JIS R 1641, the relative permittivity and the tangent of the dielectric loss angle of the resin film were measured under the conditions of a frequency of 10 GHz, 23°C, and a humidity of 50% using a measurement device of the perturbation method (manufactured by AET Co., Ltd., model: ADMS01Nc).

[0521] The above-mentioned measured measurement sample was immersed in ion-exchanged water at 25°C for 24 hours, and then the water on the surface of the measurement sample was gently wiped off with a paper towel. The relative permittivity and the tangent of the dielectric loss angle were measured for this measurement sample in the same manner as above, as the relative permittivity and the tangent of the dielectric loss angle of the resin film after the water absorption test.

[0522] The change amount of the tangent of the dielectric loss angle (Df) before and after the water absorption test was calculated in the following manner.

[0523] Change amount of Df before and after water absorption test = Df after water absorption test - Df before water absorption test

[0524] In addition, the physical properties of the resin film of each example and comparative example correspond to the physical properties of the insulating layer of the metal-clad laminate of each example and comparative example.

[0525] [Evaluation of Metal-Clad Laminate]

[0526] (1) Copper Foil Peel Strength

[0527] According to JIS C 6481, the peel strength (N / mm) when peeling the copper foil from the metal-clad laminate at a speed of 50 mm / minute was measured using a tensile testing machine.

[0528] (2) Reliability Test

[0529] Using a highly accelerated life test device (manufactured by ESPEC Corporation), a HAST test was performed on the metal-clad laminate under the conditions of 110°C, 85% RH, and treatment for 100 hours. After the test, a voltage of 50V was applied to the metal-clad laminate for a specified time, the resistance value was measured, and any abnormalities were confirmed. Evaluation was carried out according to the following evaluation criteria. In addition, a change in the resistance value was regarded as an abnormality. The change in the resistance value was considered to be caused by ion migration.

[0530] (Evaluation Criteria)

[0531] AA: No abnormality was observed even after applying voltage for 400 hours.

[0532] A: No abnormality was observed even after applying voltage for 300 hours, but an abnormality occurred when the voltage application time reached 400 hours.

[0533] B: No abnormality was observed even after applying voltage for 200 hours, but an abnormality occurred when the voltage application time reached 300 hours.

[0534] C: An abnormality occurred when the voltage application time reached 200 hours.

[0535] [Table 2]

[0536]

[0537] [Table 3]

[0538]

[0539] [Table 4]

[0540]

[0541] [Discussion]

[0542] The hollow particles used in Comparative Example 1 had a low porosity and a high relative dielectric constant. Therefore, the resin film made from the resin composition of Comparative Example 1 had a high relative dielectric constant. In addition, the change in Df before and after the water absorption test of the resin film made from the resin composition of Comparative Example 1 was large, and the reliability was poor. The copper foil peel strength of the metal-clad laminate made from the resin composition of Comparative Example 1 was low, and abnormalities were likely to occur in the reliability test, and the reliability was poor. It was considered that the hollow particles used in Comparative Example 1 retained sodium dodecylbenzenesulfonate, and it was speculated that the cross-linking reaction between the matrix resin and the hollow particles could not be carried out, resulting in poor reliability.

[0543] Since hollow particles were not used in Comparative Example 2, there is no reduction in reliability caused by hollow particles in the resin film and metal-clad laminate produced using the resin composition of Comparative Example 2, and the relative dielectric constant and dielectric loss tangent of the resin film produced using the resin composition of Comparative Example 2 are high.

[0544] In Comparative Example 3, commercially available silica particles without a hollow portion were used instead of hollow particles. Since the relative dielectric constant of these silica particles is high, the relative dielectric constant of the resin film produced using the resin composition of Comparative Example 3 is high.

[0545] In Comparative Example 4, commercially available hollow glass particles were used as the hollow particles. These hollow glass particles have a high relative dielectric constant and dielectric loss tangent and a small amount of unsaturated bonds. Therefore, the relative dielectric constant and dielectric loss tangent of the resin film produced using the resin composition of Comparative Example 4 are high. In addition, the change in Df before and after the water absorption test is large, and the reliability is poor. The copper foil peel strength of the metal-clad laminate produced using the resin composition of Comparative Example 4 is low, and abnormalities are likely to occur in the reliability test, and the reliability is poor.

[0546] In Comparative Example 5, commercially available hollow polyurethane particles were used instead of hollow particles. Since these hollow polyurethane particles have a low porosity, a high relative dielectric constant and dielectric loss tangent, and a small amount of unsaturated bonds, the relative dielectric constant and dielectric loss tangent of the resin film produced using the resin composition of Comparative Example 5 are high. In addition, the change in Df before and after the water absorption test is large, and the reliability is poor. The copper foil peel strength of the metal-clad laminate produced using the resin composition of Comparative Example 5 is low, and abnormalities are likely to occur in the reliability test, and the reliability is poor.

[0547] In contrast, the resin compositions of the respective examples contain hollow particles having a porosity of 55% or more, a relative dielectric constant of 1.50 or less, reactive unsaturated bonds on the particle surface, and an unsaturated bond amount of 0.010 mmol / m 2 or more, and having a low relative dielectric constant and dielectric loss tangent, and contain a modified polyphenylene ether resin having vinyl groups capable of reacting with the reactive unsaturated bonds possessed by the hollow particles as the matrix resin. Therefore, the relative dielectric constant and dielectric loss tangent of the resin film produced using the resin compositions of the respective examples are low, the change in Df before and after the water absorption test is small, the dielectric properties and reliability are excellent, the copper foil peel strength of the metal-clad laminate produced using the resin compositions of the respective examples is large, abnormalities are not likely to occur in the reliability test, and the reliability is excellent.

[0548] Among them, when using hollow particles with an unsaturated bond amount of 0.070 mmol / m 2In the above embodiments of the hollow particles, the reliability of the resin film and the metal-clad laminate is excellent, and the amount of unsaturated bonds is 0.080 mmol / m 2 In the above embodiments of the hollow particles, the reliability of the resin film and the metal-clad laminate is even more excellent.

[0549] The resin compositions of Examples 11, 12, and 13 contain the hollow particles 1 in the same manner as in Example 1, and the type of the matrix resin is different from that of the resin composition of Example 1. The resin compositions of Comparative Examples 6, 7, and 8 do not contain hollow particles, and are otherwise the same as the resin compositions of Examples 11, 12, and 13, respectively. Although the resin films made from the resin compositions of Examples 11, 12, and 13 have a higher relative dielectric constant and a higher tangent of the dielectric loss angle than those of Example 1 due to the influence of the matrix resin, they have a lower relative dielectric constant and a lower tangent of the dielectric loss angle than the resin films of Comparative Examples 6, 7, and 8 that do not contain hollow particles and use the same matrix resin. Thus, the resin films of Examples 11, 12, and 13 have a reduced relative dielectric constant and a reduced tangent of the dielectric loss angle by containing hollow particles. In addition, the change amount of Df before and after the water absorption test of the resin films made from the resin compositions of Examples 11, 12, and 13 is small, and the reliability is excellent. The copper foil peel strength of the metal-clad laminates made from the resin compositions of Examples 11, 12, and 13 is large, and abnormalities are not likely to occur in the reliability test, and the reliability is excellent. Further, since hollow particles are not used in Comparative Examples 6, 7, and 8, there is no reduction in reliability caused by hollow particles in the resin films and metal-clad laminates made from the resin compositions of Comparative Examples 6, 7, and 8.

[0550] Description of Reference Numerals

[0551] 1: Aqueous medium; 2: Low-polarity material; 3: Droplets of the monomer composition; 4a: Hydrophobic solvent;

[0552] 4b: Materials other than the hydrophobic solvent; 5: Precursor particles; 6: Shell; 7: Hollow portion; 10A: Hollow particles after the solvent removal step; 10B: Hollow particles after the cleaning step; 11: Stirring tank; 12: Supply tank; 13a, 13b, 13c: Gas inlets; 14: Outlet; 15: Spraying mechanism; 16: Supply pipeline to the stirring tank; 17a, 17b: Circulation pipelines; 20: Precursor composition; 21: Gas phase part.

Claims

1. A resin composition comprising hollow particles and a matrix resin, The hollow particles have a shell containing a resin and a hollow portion surrounded by the shell, a porosity of 55% or more, a relative dielectric constant of 1.50 or less at a frequency of 10 GHz, reactive unsaturated bonds on the particle surface, and the amount of unsaturated bonds per unit area calculated by the following formula (A) based on the iodine value and specific surface area of the hollow particles is 0.010 mmol / m 2 or more. Formula (A): Unsaturated bond amount (mmol / m 2 ) = Iodine value (mmol / g) / Specific surface area (m 2 / g) The resin composition contains a matrix resin having a functional group that can react with the reactive unsaturated bond of the hollow particles as the matrix resin.

2. The resin composition according to claim 1, wherein The functional group of the matrix resin is at least one selected from (meth)acryloyl group, vinyl group, allyl group, mercapto group, and maleimide group.

3. The resin composition according to claim 1 or 2, wherein, The total content of the surfactant and the water-soluble polymer stabilizer present on the surface of the hollow particles is 500 ppm or less.

4. The resin composition according to claim 1 or 2, wherein The shell of the hollow particles contains a polymer as the resin, and the polymer contains 50% by mass or more of crosslinkable monomer units.

5. The resin composition according to claim 4, wherein, The polymer contains 70% by mass or more of hydrocarbon monomer units.

6. The resin composition according to claim 1 or 2, wherein The dielectric loss tangent of the hollow particles at a frequency of 10 GHz is 1.0×10 -3 or less.

7. The resin composition according to claim 1 or 2, wherein The thermal expansion coefficient of the hollow particles at 23 to 100 °C is 1.0×10 -4 / °C or less.

8. The resin composition according to claim 1 or 2, wherein The volume average particle diameter of the hollow particles is 0.1 to 10.0 μm.

9. The resin composition according to claim 1 or 2, wherein, The matrix resin contains at least one selected from bismaleimide resins, hydrocarbon resins, unsaturated polyester resins, modified polyphenylene ether resins, allyl resins, thiol resins, and raw material compounds of these resins.

10. A prepreg obtained by impregnating a substrate with the resin composition according to any one of claims 1 to 9 and heating and drying it, the prepreg contains a semi-cured product of the resin composition, and in this semi-cured product, at least a part of the hollow particles is crosslinked and bonded to the matrix resin.

11. A metal-clad laminate obtained by heating and pressing a laminated prepreg in which the prepreg according to claim 10 is stacked and a metal foil in contact with the laminated prepreg, the metal-clad laminate contains a cured product of the laminated prepreg, and in this cured product, at least a part of the hollow particles is crosslinked and bonded to the matrix resin.

12. The metal foil-clad laminate according to claim 11, wherein, The peel strength between the cured product of the laminated prepreg and the metal foil is 0.5 N / mm or more.

13. A metal-clad laminate having: an insulating layer comprising a substrate and a cured product of the resin composition according to any one of claims 1 to 9; and a metal foil in contact with the insulating layer, and in the cured product of the resin composition, at least a part of the hollow particles is crosslinked and bonded to the matrix resin.

14. The metal foil-clad laminate according to claim 13, wherein, The peel strength between the insulating layer and the metal foil is 0.5 N / mm or more.

15. A printed circuit board comprising the metal-clad laminate according to claim 11.

16. A printed circuit board comprising the metal-clad laminate according to claim 13.

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