Silica-based hollow particles, method for producing the same, and resin composition

Abstract

To provide a silica-based particle capable of reducing the dielectric constant and dielectric loss tangent of an insulating material and not obstructing the filterability and injectability of a liquid for forming an insulating material in a manufacturing process, and a method for manufacturing the same.SOLUTION: Provided are a silica-based hollow particle having a cavity inside a nonporous outer shell and having an average particle diameter (D50) of 0.1 to 10 μm, in which when suspended in water, floating particles a are 0.5 to 7.0 mass%, suspended particles b are 0 to 4.0 mass%, and precipitated particles c are 89.0 to 99.5 mass%; and a method for producing the same.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to silica-based hollow particles useful as a filler for an insulating material of a semiconductor, a method for producing the same, and a resin composition.

Background Art

[0002] In recent years, the capacity of data communication in information communication has been increasing, and high-speed processing of communication devices has been demanded. For an insulating material in a semiconductor printed wiring board used in such a communication device, in order to realize high-speed communication, a reduction in dielectric constant (low Dk) and a reduction in dielectric tangent (low Df) are required. If the dielectric constant of the insulating material is high, it leads to dielectric loss, and if the dielectric tangent of the insulating material is high, it not only leads to dielectric loss but also may cause problems such as an increase in the amount of heat generated.

[0003] In such an insulating material for a semiconductor printed wiring board, in order to achieve a reduction in dielectric constant and a reduction in dielectric tangent, development of a resin material that is the main component of the insulating material has been carried out. As such a resin material, for example, epoxy resins, polyphenylene ether resins, fluorine-based resins, etc. have been proposed (see, for example, Patent Documents 1 to 5).

[0004] On the other hand, such resin materials are blended with fillers from the viewpoints of durability (rigidity), heat resistance, etc. As such fillers, metal oxides such as silica, boron nitride, talc, kaolin, clay, mica, alumina, zirconia, titania, etc. are used (see, for example, Patent Document 3).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0006] Among the fillers contained in the insulating material of the semiconductor, silica is excellent in terms of low dielectric constant and low dielectric tangent. However, in today's rapidly advancing large-capacity and high-speed processing of data communication, further reduction in dielectric constant and dielectric tangent is required. In addition, it is also important that the filler of the insulating material of the semiconductor does not hinder the filterability and injectability of the liquid for forming the insulating material in the manufacturing process of the insulating material.

[0007] An object of the present invention is to provide silica-based particles that enable reduction in dielectric constant and dielectric tangent of an insulating material and do not hinder the filterability and injectability of the liquid for forming the insulating material in the manufacturing process, and a method for manufacturing the same.

Means for Solving the Problems

[0008] As a result of intensive research on silica particles useful as a filler for an insulating material of a semiconductor while the large-capacity and high-speed processing of data communication are rapidly advancing, the present inventors have found that silica-based hollow particles satisfying predetermined conditions and not containing coarse particles can achieve reduction in dielectric constant and dielectric tangent of an insulating material and do not hinder the filterability and injectability of the liquid for forming the insulating material in the manufacturing process, and have thus completed the present invention.

[0009] That is, the present invention relates to silica-based hollow particles having a cavity inside a porous outer shell and having an average particle diameter (D50) of 0.1 to 10 μm, wherein when suspended in water, floating particles a are 0.5 to 7.0% by mass, suspended particles b are 0 to 4.0% by mass, and sedimented particles c are 89.0 to 99.5% by mass.

[0010] Further, the present invention relates to a method for producing silica-based hollow particles, which comprises a hollow particle preparation step of spray-drying an aqueous alkali silicate solution in a hot air stream to prepare hollow particles, an alkali removal step of neutralizing and removing the alkali contained in the prepared hollow particles with an acid, and a firing step of firing the alkali-removed hollow particles, characterized in that a classification step of classifying the hollow particles to remove coarse particles is provided between the hollow particle preparation step and the firing step.

Effects of the Invention

[0011] The silica-based hollow particles of the present invention can achieve a lower dielectric constant and a lower dielectric loss tangent of the insulating material, and thus can increase the transmission speed and reduce the transmission loss of the semiconductor. Further, the silica-based hollow particles of the present invention do not interfere with the filterability and injectability of the liquid for forming the insulating material in the manufacturing process, and excellent insulating materials can be stably manufactured.

Embodiments for Carrying Out the Invention

[0012] [Silica-based Hollow Particles] The silica-based hollow particles of the present invention have a cavity inside a porous outer shell and an average particle diameter of 0.1 to 10 μm. When these silica-based hollow particles are suspended in water, the floating particles are 0.5 to 7.0% by mass, the suspended particles are 0 to 4.0% by mass, and the sedimented particles are 89.0 to 99.5% by mass.

[0013] Here, the silica-based means that silica is the main component, and in addition to silica, it may contain inorganic oxides such as alumina, zirconia, and titania. The content of silica in the particles is preferably 70% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably consisting essentially of only silica.

[0014] The particles of the present invention are hollow particles having a cavity inside a porous outer shell, and contain light floating particles (particles with a high porosity) that float when suspended in water. Therefore, when incorporated into a resin composition, a low dielectric constant and a low dielectric loss tangent can be achieved. In addition, since hollow particles with a high porosity generally have a large particle size, controlling the amount of these floating particles to 0.5 to 7.0% by mass of the total particles means controlling (reducing) the amount of coarse particles. Therefore, the filterability and injectability of the liquid for forming the resin composition in the manufacturing process of resin compositions such as insulating materials can be improved, and the surface smoothness after molding can be improved. At this time, the content of coarse particles exceeding 8.0 μm in particle size is preferably 10% by volume or less, more preferably 5% by volume or less, and even more preferably 1% by volume or less.

[0015] Note that light particles that float in water tend to have low particle strength because the ratio of the thickness of the outer shell to the particle size is small. Therefore, there is a risk that the particles may crack during the production of resin compositions such as insulating materials. The occurrence of such cracking of the particles hinders the reduction of the dielectric constant and the dielectric loss tangent, deteriorates the fluidity of the liquid for forming the resin composition, reduces the uniformity of the resin composition (molded product), and causes voids inside the resin composition. By controlling the amount of floating particles, cracking of the particles can be suppressed.

[0016] In the present invention, since the amount of floating particles is particularly controlled, while ensuring the preferable characteristics (particularly, reduction of the dielectric constant and the dielectric loss tangent) of particles with a high porosity, the unfavorable characteristics (particularly, occurrence of cracking) of particles with a high porosity are suppressed to such an extent that there is no problem. In addition, among the floating particles, there are small-diameter particles even with a high porosity. Such particles are less likely to crack compared to large-diameter particles in the manufacturing process, and as a whole, the unfavorable characteristics of particles with a high porosity can be suppressed as much as possible.

[0017] The content of floating particles is preferably 1.0 to 5.0% by mass, more preferably 1.0 to 4.0% by mass, and even more preferably 2.0 to 4.0% by mass. Also, the content of sedimented particles is preferably 91.0 to 99.5% by mass, more preferably 92.0 to 99.0% by mass, and even more preferably 95.0 to 98.0% by mass.

[0018] The ratios of floating particles, suspended particles, and sedimented particles when suspended in water are calculated by recovering and weighing each type of particle from the suspension. Specifically, it will be described in the examples.

[0019] In addition, the average particle diameter (D50) of the silica-based hollow particles of the present invention is in the range of 0.1 to 10 μm. Those with an average particle diameter of less than 0.1 μm are difficult to manufacture using the spray drying method. Also, silica-based particles with an average particle diameter exceeding 10 μm are not suitable for semiconductor applications. Considering semiconductor applications, the average particle diameter is preferably 0.5 to 10 μm, and more preferably 1.0 to 5.0 μm.

[0020] Also, the maximum particle diameter (D100) is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less. The maximum particle diameter (D100) is preferably 10 times or less, and preferably 8 times or less, of the average particle diameter (D50). Usually, it is 2 times or more, and may exceed 5 times as long as the requirements of the present invention are satisfied.

[0021] The average particle diameter (D50), the maximum particle diameter (D100), and the content of coarse particles are measured by the laser diffraction / scattering method. Specifically, it will be described in the examples.

[0022] The porosity of the silica-based hollow particles of the present invention is preferably 5% by volume or more, more preferably 8% by volume or more, and still more preferably 10% by volume or more. On the upper limit side, it is preferably 50% by volume or less, more preferably 35% by volume or less, still more preferably 25% by volume or less, and most preferably 20% by volume or less. With such a porosity, it is possible to achieve a lower dielectric constant and a lower dielectric tangent, and at the same time, the particle strength can be maintained at a predetermined level or higher to effectively suppress cracking of the particles. Here, the porosity is calculated from the particle density. Specifically, it will be described in the examples.

[0023] The silica-based hollow particles of the present invention are preferably used as a filler for insulating materials of electronic materials such as semiconductors. Specifically, it can be incorporated into copper-clad laminates, prepregs, build-up films, etc. for forming printed wiring boards (including rigid substrates and flexible substrates). In addition, it can be incorporated into semiconductor package-related materials such as mold resins, mold underfills, and underfills, and adhesives for flexible substrates.

[0024] [Resin composition] The resin composition of the present invention contains the above-described silica-based hollow particles of the present invention. Such a resin composition can be used for the applications of the above-described silica-based hollow particles, such as insulating materials of electronic materials such as semiconductors.

[0025] As the resin contained in the resin composition (liquid for forming resin composition) of the present invention, a curable resin generally used for electronic materials such as semiconductors can be used. A photocurable resin may be used, but a thermosetting resin is preferred. Examples of such curable resins include epoxy resins, polyphenylene ether resins, fluorine resins, polyimide resins, bismaleimide resins, acrylic resins, methacrylic resins, silicone resins, BT resins, cyanate resins, and the like. Specific examples of epoxy resins include bisphenol type epoxy resins, novolak type epoxy resins, triphenolalkane type epoxy resins, epoxy resins having a biphenyl skeleton, epoxy resins having a naphthalene skeleton, dicyclopentadiene phenol novolak resins, phenol aralkyl type epoxy resins, glycidyl ester type epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, halogenated epoxy resins, and the like. These resins may be used alone or in combination of two or more.

[0026] Regarding the content of silica-based hollow particles in the resin composition (liquid for forming resin composition) of the present invention, the mass ratio (A / B) of silica-based hollow particles A to curable resin B is preferably 10 / 100 to 95 / 100, and more preferably 30 / 100 to 80 / 100. With such a mass ratio, the characteristics of the liquid for forming resin composition such as fluidity can be maintained, and the function as a filler can be sufficiently exerted.

[0027] The resin composition (liquid for forming resin composition) of the present invention preferably contains a curing agent such as a phenol compound, an amine compound, and an acid anhydride. When an epoxy resin is used as the curable resin, examples of the curing agent include phenol resins such as bisphenol type resins, novolak resins, triphenolalkane type resins, resol type phenol resins, phenol aralkyl resins, biphenyl type phenol resins, naphthalene type phenol resins, and cyclopentadiene type phenol resins, which have two or more phenolic hydroxyl groups in one molecule, and acid anhydrides such as methylhexahydrophthalic acid, methyltetrahydrophthalic acid, and methylnadic anhydride.

[0028] In the resin composition (liquid for forming a resin composition), various additives such as a colorant, a stress reliever, an antifoaming agent, a leveling agent, a coupling agent, a flame retardant, and a curing accelerator can be added as necessary.

[0029] The resin composition of the present invention can be obtained by a conventionally known method. For example, a thermosetting resin, silica-based hollow particles, a curing agent, additives, etc. are mixed and kneaded with a roll mill or the like to prepare a coating liquid (liquid for forming a resin composition), and after coating on a substrate, it can be obtained by curing with heat, ultraviolet rays, etc.

[0030] [Method for producing silica-based particles] The method for producing silica-based hollow particles of the present invention includes a hollow particle preparation step of spray-drying an aqueous alkali silicate solution in a hot air stream to prepare hollow particles, an alkali removal step of neutralizing and removing the alkali contained in the prepared hollow particles with an acid, and a firing step of firing the alkali-removed hollow particles. A classification step for classifying the hollow particles to remove coarse particles is provided between the hollow particle preparation step and the firing step. Note that other steps such as a drying step may be provided between each step.

[0031] By the production method of the present invention, for example, the silica-based hollow particles of the present invention as described above can be produced. That is, according to the production method of the present invention, it is possible to reduce the dielectric constant and the dielectric loss tangent of the insulating material, and it is also possible to produce silica-based particles that do not interfere with the filterability and injectability of the liquid for forming an insulating material in the production process.

[0032] Also, when performing classification during the production of fired particles, it is generally considered preferable to perform it at the final stage after firing in order to adjust the final particles. However, in the production method of the present invention, it is deliberately performed before the firing step. If the firing step is performed without performing the classification step, coarse particles with a high porosity that should originally be removed will remain. Since these coarse particles with a high porosity are prone to cracking, there is a risk of cracking due to the stress of shrinkage during heating. And the fragments generated by this cracking have a smaller particle size, so they cannot be removed in the subsequent classification step. Also, since they are dense silica without voids, they hinder the reduction of the dielectric constant and the dielectric loss tangent. By performing the classification step before firing as in the production method of the present invention, such inconveniences can be avoided, and the reduction of the dielectric constant and the dielectric loss tangent of the produced particles can be more reliably achieved, and particles corresponding to the recent high-speedization of data communication can be obtained.

[0033] (Hollow particle preparation step) In the hollow particle preparation step, an aqueous solution of alkali silicate is spray-dried in a hot air stream to prepare hollow particles.

[0034] As the alkali silicate, sodium silicate and potassium silicate that are usually soluble in water are generally used, but sodium silicate is preferable. The SiO 2 / M 2 O molar ratio (where M represents an alkali metal) is preferably 1 to 5, and more preferably 2 to 4. When the SiO 2 / M 2 O molar ratio of the alkali silicate is less than 1, not only is it difficult to perform acid washing in the alkali removal step because the amount of alkali is too large, but also the deliquescence of the spray-dried product becomes remarkable, and thus the desired silica-based hollow particles may not be obtained. When the SiO 2 / M 2 O molar ratio of the alkali silicate exceeds 5, the solubility of the alkali silicate decreases, it is difficult to prepare an aqueous solution, and even if an aqueous solution can be prepared, the desired silica-based hollow particles may not be obtained by spray drying.

[0035] The SiO of the aqueous alkali silicate solution 2The concentration as such is preferably 1 to 30% by mass, more preferably 5 to 28% by mass. Although production is possible even if it is less than 1% by mass, the productivity is significantly reduced. If it exceeds 30% by mass, the stability as an aqueous alkali silicate solution is significantly reduced and it becomes highly viscous, making spray drying difficult. Even if it can be spray-dried, there is a risk that the particle size distribution, the thickness of the outer shell, etc. will become extremely non-uniform, and the use of the final particles may be restricted.

[0036] As the spray drying method, for example, conventionally known methods such as the rotary disk method, the pressure nozzle method, and the two-fluid nozzle method can be adopted. Here, the two-fluid nozzle method is preferable.

[0037] In spray drying, the inlet temperature in the spray dryer is preferably 300 to 600 °C, more preferably 350 to 550 °C. Also, the outlet temperature is preferably 120 to 300 °C, more preferably 130 to 250 °C. By having the inlet temperature and the outlet temperature within the above ranges, hollow particles having cavities inside can be stably obtained.

[0038] (Alkali removal step) In the alkali removal step, the alkali contained in the prepared hollow particles is neutralized and removed with an acid.

[0039] As the acid, mineral acids such as hydrochloric acid, nitric acid, and sulfuric acid, organic acids such as acetic acid, tartaric acid, and malic acid, etc. can be used. Among these, mineral acids such as hydrochloric acid, nitric acid, and sulfuric acid are preferably used, and sulfuric acid is particularly preferable from the viewpoint of valence.

[0040] The treatment in this step is not particularly limited as long as it is a treatment using an acid, and a treatment of immersing the prepared hollow particles in an acid solution is preferable.

[0041] M in the hollow particles when immersing the hollow particles in an aqueous acid solution 2 The molar ratio (Ma) / (Msp) of the number of moles of M 2Since the amount of acid is too small relative to O, the silicification of the silica skeleton of silicic acid, which is considered to occur along with the removal of alkali, does not proceed, and the hollow particles may be partially dissolved, or the dissolved alkali silicate may gel. Even if the molar ratio exceeds 4.7, the silicification of the silica skeleton does not proceed further, and the acid is excessive and uneconomical.

[0042] Also, the concentration of the hollow particles when immersed in the aqueous acid solution is preferably 1 to 30% by mass, more preferably 5 to 25% by mass, expressed as SiO 2 If it is less than 1% by mass, there is no problem with alkali removal or detergency, but the production efficiency decreases. If it exceeds 30% by mass, the concentration may be too high and the alkali removal and washing efficiency may decrease.

[0043] The conditions for the immersion treatment in the aqueous acid solution are not particularly limited as long as the alkali can be removed to a desired amount. Usually, the treatment temperature is 5 to 100 °C and the treatment time is 0.5 to 24 hours. After the immersion treatment, it is preferable to wash by a conventionally known method. For example, filtration washing with pure water may be sufficient. In addition, if necessary, the above acid treatment and washing may be repeated.

[0044] The remaining amount (mass ratio) of the alkali (M) after the alkali removal step is preferably 300 ppm or less, more preferably 200 ppm or less, still more preferably 100 ppm or less, and particularly preferably 50 ppm or less. By sufficiently removing the alkali in this step, it is possible to prevent the particles from sticking together in the subsequent steps and to prevent the generation of sintered particles in the firing step. Also, it is known that the remaining amount (content) of the alkali affects the dielectric properties. By sufficiently removing the alkali in this step, it is possible to obtain silica-based hollow particles that enable low dielectric constant and low dielectric tangent even when an aqueous alkali silicate solution is used as the raw material.

[0045] Note that the alkali amount of the final product (silica-based hollow particles) is also preferably in the above range, and usually, the alkali amount of the final product is the same as the alkali amount after the alkali removal step.

[0046] The remaining amount of alkali is measured by using an atomic absorption photometer to measure Na or K, with the sample being the particles dissolved in acid. When using sodium silicate, Na is measured, and when using potassium silicate, K is measured. Specifically, it will be described in the examples.

[0047] (Firing step) The firing step is a step of firing the hollow particles from which alkali has been removed. The firing temperature is preferably 600 to 1200 °C, more preferably 900 to 1100 °C. When the firing temperature is less than 600 °C, the remaining amount of SiOH groups is large, the dielectric tangent of the particles becomes high, and it is difficult to obtain the effect of reducing the dielectric tangent even when compounded with a resin. When the firing temperature exceeds 1200 °C, the hollow particles are likely to sinter together, resulting in particles of irregular shapes and coarse particles, which causes a decrease in the filterability and injectability of the liquid for forming the resin composition.

[0048] (Classification step) In the classification step, the hollow particles are classified to remove coarse particles. This classification step is carried out between the hollow particle preparation step and the firing step. When the classification treatment is carried out after the preparation of the hollow particles, it is necessary to carry out the classification treatment immediately after granulation in order to prevent the hollow particles from absorbing moisture (deliquescence) and aggregating or coalescing. Therefore, in actual production, it is preferable to carry out the classification treatment after the alkali removal step. Also, when the classification treatment is carried out after the alkali removal step, the classification treatment may be carried out continuously after the alkali removal treatment, or may be carried out after a drying treatment is carried out after the alkali removal treatment. To better enjoy the effects of the present invention, it is preferable to carry out the treatment after the drying treatment.

[0049] In the classification step, it is preferable that the amount of coarse particles having a particle diameter exceeding 8.0 μm is 10% by volume or less, more preferably 5% by volume or less, and even more preferably 1% by volume or less. By this classification step, the floating particle ratio of the silica-based hollow particles of the present invention can be controlled within a predetermined range.

[0050] The classification in the classification step of the present invention means particle size classification for separating powders according to particle size for the purpose of making the particle sizes of the powders uniform. As an operation of this particle size classification, fluid classification can be mentioned, and fluid classification can be classified into dry classification and wet classification. Since wet classification requires classification treatment in a state where particles are suspended in water, and SiOH groups may be generated on the particle surface, which may have an adverse effect on the dielectric properties, dry classification is preferred.

[0051] When classifiers used for dry classification are classified in principle, they can be roughly classified into gravitational classifiers, inertial classifiers, and centrifugal classifiers. Any classifier may be used within the range where the object of the present invention can be achieved, but from the viewpoint of enabling more precise classification, it is preferable to use an inertial classifier that classifies using the inertial force of particles or a centrifugal classifier. In particular, since the hollow particles of the present invention are light and it is difficult to apply centrifugal force to the particles, a classifier that can exhibit characteristics even for such particles is preferable. Examples of such classifiers include the Elbow Jet manufactured by Nippon Steel Mining Co., Ltd., the SG Separator manufactured by 3M Japan Limited, the Aerofine Classifier manufactured by Nisshin Engineering Co., Ltd., and the Micro Spin manufactured by Nippon Pneumatic Mfg. Co., Ltd. Among these, since light hollow particles can be precisely classified, the Elbow Jet manufactured by Nippon Steel Mining Co., Ltd. and the Aerofine Classifier manufactured by Nisshin Engineering Co., Ltd. are preferable.

[0052] (Drying step) In the production method of the present invention, a drying step can be provided as appropriate. The drying step can be provided, for example, between the alkali removal step and the classification step, between the classification step and the firing step, or both. It may be provided multiple times as necessary.

[0053] As the drying method, heat drying is preferable. The drying temperature is preferably 50 to 400°C, more preferably 50 to 200°C. Specifically, examples include a method of drying over a long time at a low temperature of about 50 to 200°C, a method of gradually increasing the temperature for drying, and a method of changing the temperature in several stages for drying.

[0054] (Screening Process) It is preferable to provide a screening process for screening particle agglomerates after the drying process and / or the firing process. Note that the particle agglomerates refer to, for example, foreign substances with a particle size exceeding 50 μm. In this process, a sieve with an appropriate mesh size (number of meshes) capable of removing such particle agglomerates is used as appropriate.

Example

[0055] Hereinafter, examples of the present invention will be specifically described.

[0056] [Example 1] An aqueous sodium silicate solution (SiO 2 / Na 2 O molar ratio 3.2, SiO 2 concentration 24% by mass) 30000 g was used. One of the two-fluid nozzles was sprayed with hot air at an inlet temperature of 400 °C at a flow rate of 0.62 kg / hr, and the other nozzle was sprayed with air at a flow rate of 31800 L / hr (air / liquid volume ratio 63600) to obtain silica hollow particles. At this time, the outlet temperature was 150 °C (hollow particle preparation process).

[0057] Next, 5000 g of silica hollow particles were immersed in 32000 g of a sulfuric acid aqueous solution with a concentration of 10% by mass and stirred for 15 hours. At this time, the solid content (SiO 2 ) concentration was 10.2% by mass, the temperature of the dispersion was 35 °C, and the pH was 3.0. Also, the molar ratio (Ma) / (Msp) with the number of moles of acid (Ma) was 1.2. After the immersion treatment, filtration and washing were performed with pure water (alkali removal process).

[0058] Next, it was dried in a dryer at 120 °C for 24 hours (drying process). After drying, it was crushed and sieved through a sieve with a mesh size of 75 μm to remove coarse particles.

[0059] Next, using a company-made cyclone, dry centrifugal classification was performed with the flow velocity in the powder transport line set to 5 m / s (classification process). The particles that passed through without being collected by the cyclone were recovered with a bag filter.

[0060] Finally, the classified particles were heat-treated at 1000 °C for 10 hours to obtain the silica-based hollow particles (A1) according to the target example (firing step). After firing, lumps of particles (foreign substances) were removed with a sieve having an opening of 150 μm.

[0061] In addition, the produced silica-based hollow particles (A1) were blended with the liquid acid anhydride "Ricacid MH700" manufactured by Shin Nippon Rika Co., Ltd. and the imidazole-based epoxy resin curing agent "2PHZ-PW" manufactured by Shikoku Kasei Co., Ltd. into the liquid epoxy resin "ZX-1059" manufactured by Nippon Steel Chemical & Material Co., Ltd. After preliminary kneading with a planetary mill, they were kneaded with a three-roll mill to prepare a liquid for forming a resin composition. Here, "ZX-1059" was blended at a ratio of 100 parts by mass, "Ricacid MH700" was 86 parts by mass, and "2PHZ-PW" was 1 part by mass. In addition, the silica-based hollow particles (A1) were blended so that the proportion in the resin composition was 35% by volume. The prepared liquid for forming the resin composition was heated and cured at 170 °C for 2 hours to obtain a plate-shaped resin composition (A1R) according to the example of 50 mm × 50 mm × 1 mm.

[0062] [Example 2] Except for the classification step, the same procedure as in Example 1 was carried out to produce the silica-based hollow particles (A2) and the plate-shaped resin composition (A2R) according to the example. In the classification step, dry inertial classification treatment was performed using the Elbow Jet (EJ-15) manufactured by Nippon Steel Mining Co., Ltd. In this apparatus, by classification, the powder can be divided into three types: F powder (fine powder), M powder (fine powder), and G powder (coarse powder). Among them, the F-edge distance was adjusted so that the coarse particles exceeding 8.0 μm contained in the F powder (fine powder) were 5% by volume or less, and they were collected with a bag filter and used in the subsequent steps.

[0063] [Example 3] In Example 2, except that the F-edge distance was adjusted so that the coarse particles exceeding 8.0 μm contained in the F powder (fine powder) were 1% by volume or less in the classification step, the silica-based hollow particles (A3) and the plate-shaped resin composition (A3R) according to the example were produced in the same manner.

[0064] [Example 4] In Example 1, silica-based hollow particles (A4) and plate-shaped resin composition (A4R) according to the example were produced in the same manner except that in the classification step, dry centrifugal (semi-free vortex) classification treatment was performed using an Aerofine classifier manufactured by Nissin Engineering Co., Ltd. The classification was carried out by adjusting the blade angle and the like so that the coarse particles exceeding 8.0 μm contained in the recovered powder were 1% by volume or less.

[0065] [Comparative Example 1] In Example 1, in the alkali removal step, the immersion stirring time was changed from 15 hours to 1.5 hours, and silica-based hollow particles (B1) and plate-shaped resin composition (B1R) according to the comparative example were produced in the same manner except that the classification treatment (classification step) was not performed.

[0066] [Comparative Example 2] In Example 1, in the hollow particle preparation step, the inlet temperature of the spray dryer was set to 250°C, and silica-based hollow particles (B2) and plate-shaped resin composition (B2R) according to the comparative example were produced in the same manner except that the classification step was not performed.

[0067] [Comparative Example 3] In Example 1, silica-based hollow particles (B3) and plate-shaped resin composition (B3R) according to the comparative example were produced in the same manner except that the classification step was performed after the firing step (with the same classification conditions).

[0068] The properties of the silica-based hollow particles and resin compositions according to the above-produced examples and comparative examples were evaluated. Each evaluation was performed as follows.

[0069] (1) Average particle diameter (D50), maximum particle diameter (D100), and amount of coarse particles of silica-based hollow particles Measured by the laser diffraction / scattering method. Specifically, the apparatus used was a laser micron size analyzer (LMS-3000) manufactured by Seishin Enterprise Co., Ltd., and the measurement was performed in a dry state. The amount of coarse particles was calculated as the volume ratio of particles exceeding 8.0 μm.

[0070] (2) Residual amount of Na in silica-based hollow particles It was measured by atomic absorption spectrometry. Specifically, for the residual amount of Na, after pre-treating the silica-based hollow particles with sulfuric acid and hydrofluoric acid, they were dissolved in hydrochloric acid, and the amount of Na was measured using an atomic absorption spectrophotometer (Z-2310 manufactured by Hitachi).

[0071] (3) Particle density of silica-based hollow particles It was measured by the gas pycnometer method. Specifically, the particle density was measured using Ultrapyc1200e manufactured by Quantachrome Instruments. Nitrogen gas was used as the gas.

[0072] (4) Porosity of silica-based hollow particles It was calculated from the above particle density. Specifically, for the porosity, using the density of silica = 2.2 g / cm 3 it was calculated using the following formula (1). Porosity (%) = [2.2 - (particle density of silica-based hollow particles)] / 2.2 × 100 ··· Formula (1)

[0073] (5) Dielectric constant (Dk) and dielectric tangent (Df) of silica-based hollow particles It was measured by the cavity resonator perturbation method. Specifically, the dielectric constant (Dk) and dielectric tangent (Df) of the silica-based particles were measured using a network analyzer (MS46122B manufactured by Anritsu) and a cavity resonator (1 GHz). This measurement was carried out in accordance with ASTM D2520 (JIS C2565).

[0074] (6) Ratios of floating particles a, suspended particles b, and sedimented particles c when suspended in water Each type of particle was recovered from the suspension and weighed, and their ratios were calculated. Specifically, first, silica-based hollow particles and water were mixed to a concentration of 0.5% by mass, and ultrasonic treatment was performed for 10 minutes to prepare a dispersion. After allowing this dispersion to stand at 25°C for 24 hours, floating particles a, suspended particles b, and sedimented particles c were each collected. Subsequently, each type of particle was dried at 105°C for 24 hours and then weighed, and the ratio was calculated.

[0075] (7) Filterability of the liquid for forming the resin composition Using a filter manufactured by ROKITEK Co., Ltd. (SHP type: 30 μm), evaluation was carried out based on the liquid flow rate per unit area until the filter became clogged.

[0076] The evaluation criteria are as follows. ◎: ≧ 1 g / cm 2 〇: 0.5 g / cm 2 above 1.0 g / cm 2 less than △: 0.3 g / cm 2 above 0.5 g / cm 2 less than ×: < 0.3 g / cm 2

[0077] (8) Injectability of the liquid for forming the resin composition Injection was carried out between glass plates having a 20-μm gap, and evaluation was performed based on the time required to fill 25 mm.

[0078] The evaluation criteria are as follows. ◎: within 200 seconds 〇: exceeding 200 seconds and within 400 seconds △: exceeding 400 seconds and within 600 seconds ×: exceeding 600 seconds

[0079] (9) Dielectric constant (Dk) and dissipation factor (Df) of the resin composition The dielectric constant (Dk) and dissipation factor (Df) of a plate-shaped molded body (resin composition) measuring 50 mm × 50 mm × 1 mm were measured at 9.4 GHz using a network analyzer (manufactured by Anritsu Corporation, MS46122B) and a coaxial resonator.

[0080] The evaluation was conducted by comparison with a resin composition not containing silica-based hollow particles (fillers). The evaluation criteria are as follows.

[0081] Reduction rate of dielectric constant (Dk) (%) = (Dielectric constant without filler - Dielectric constant with filler) / Dielectric constant without filler × 100

[0082] 〇: Reduction rate > 0 △: Reduction rate = 0 ×: Reduction rate < 0

[0083] Reduction rate of dielectric tangent (Df) (%) = (Dielectric tangent without filler - Dielectric tangent with filler) / Dielectric tangent without filler × 100

[0084] ◎: Reduction rate 50% or more 〇: Reduction rate 30% or more and less than 50% △: Reduction rate 20% or more and less than 30% ×: Reduction rate less than 20%

[0085] The above results are shown in Table 1.

[0086]

Table 1

[0087] As shown in Table 1, the silica-based hollow particles according to the examples and the resin composition containing the same achieve a lower dielectric constant and a lower dielectric tangent. In addition, the liquid for forming a resin composition containing the silica-based hollow particles according to the examples is also excellent in filterability and injectability.

Industrial Applicability

[0088] Since the silica-based hollow particles of the present invention can be used as a filler for an insulating material of a semiconductor, they are industrially useful.

Claims

1. Silica-based hollow particles having a cavity inside a porous outer shell and an average particle diameter (D50) of 0.1 to 10 μm, when suspended in water, having floating particles of 0.5 to 7.0% by mass, suspended particles of 0 to 4.0% by mass, and sedimented particles of 89.0 to 99.5% by mass, and a content of coarse particles having a particle diameter exceeding 8.0 μm being 10% by volume or less. Silica-based hollow particles characterized by this.

2. A resin composition characterized by containing the silica-based hollow particles according to Claim 1.

3. A hollow particle preparation step of preparing hollow particles by spray-drying an aqueous alkali silicate solution in a hot air stream, an alkali removal step of neutralizing and removing the alkali contained in the prepared hollow particles with an acid, a firing step of firing the alkali-removed hollow particles at 600 to 1200°C, A method for producing silica-based hollow particles having these steps, characterized by having a classification step of classifying the hollow particles between the alkali removal step and the firing step to make the content of coarse particles having a particle diameter exceeding 8.0 μm 10% by volume or less. A method for producing silica-based hollow particles.

4. The method for producing silica-based hollow particles according to Claim 3, characterized in that in the alkali removal step, the amount of alkali contained in the hollow particles is reduced to 200 ppm or less.

5. The method for producing silica-based hollow particles according to Claim 3 or 4, characterized in that the classification step is performed after drying the alkali-removed hollow particles.

6. The method for producing silica-based hollow particles according to any one of Claims 3 to 5, characterized in that the classification treatment in the classification step is a dry classification treatment.

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