JP3400548B2 - Method for producing high-purity spherical silica - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] The present invention relates to a high-purity spherical silica and
And its manufacturing method. The high-purity spherical silicon according to the present invention
Mosquito has excellent surface smoothness and high sphericity.
Resin compositions for sealing integrated circuit electronic components (hereinafter referred to as sealing materials)
) Is suitably used as the filler. [0002] 2. Description of the Related Art In recent years, as the density of integrated circuits has increased, sealing has been increasing.
As the percentage of chip area in the material increases,
Cages are becoming thinner. Hold the chip with a thin encapsulant
Requirements for the quality of the encapsulant
It is getting better. Silicon chip and encapsulant
Thermal stress is generated by the difference in thermal expansion coefficient, so that the
Thermal stress properties are required. Therefore, the thermal expansion coefficient of the sealing
To get as close as possible to that of the recon chip,
Use silica with a low elongation as the filler
The method of raising and adding to resin is taken. [0003] Conventionally, silica as a filler has been crushed.
Manufactured shredded body with irregular shape and sharp corners
Mosquitoes were used. However, the filling rate of crushed silica
The increased encapsulant has a high flow rate during molding due to its increased viscosity.
Quality, and obtain a homogeneous package with the required characteristics.
I can't. In addition, crushed silica with sharp corners is molded
Wear the metal mold and project the protective coating on the chip surface.
There is a danger that the aluminum wiring on the chip will be damaged by breakthrough.
For this reason, the fluidity of the sealing material is reduced.
High-purity spherical silica with few sharp edges
Was. Conventionally, as a method for producing high-purity spherical silica,
Is; 1) A method of melting crushed high-purity silica in a flame.
(For example, JP-A-58-145613). 2) Sol form obtained by hydrolysis of alkyl silicate
The solution is sprayed into a heating medium, granulated and dried, and then
How to melt with. (For example, JP-A-58-2233). 3) Part obtained by hydrolyzing silicon alkoxide
After removing the alcohol from the condensate sol,
A method in which the precipitated silica gel is calcined. (For example,
JP-A-63-225538). And so on. These conventional technologies
In the firing of mosquitoes, the hydrophobicity of silica and the strength of the fired body
In consideration of the above, complete until the pore volume becomes 0.01 ml / g or less.
The conditions under which firing all proceeds were adopted. [0005] In addition, the software
Of filler used for sealing material to prevent
Higher purity is required. What meets these demands
But alkali metal, alkaline earth metal, halogen, radiation
High purity spherical silica with low content of impurities such as volatile substances
It is. [0006] SUMMARY OF THE INVENTION
Each of the above conventional methods has the following problems.
I have. The particles obtained by the method 1) have poor sphericity,
It is not effective for improving mobility. In the method of 2), the state of the sol liquid
The size of silica particles generated during spraying differs depending on the state
Difficult to obtain spherical silica particles of the desired particle size.
No. Further, spherical silica particles obtained by the method of 2) or 3)
When baking, it shrinks greatly and causes irregularities on the surface,
The particles have poor smoothness. A decrease in surface smoothness is caused by fluidity
It is not preferable because it causes a decrease. Also, 2) and 3)
In this method, the raw materials used are expensive, and
Wastewater containing organic matter is generated and needs to be treated. [0007] Spherical silica according to the conventional method is used in sealing materials.
Deterioration of the fluidity of the sealing material caused by increasing the filling rate
Can be prevented to some extent compared to crushed silica
However, the effect is not enough. Because of this, sealing
Spherical shape and surface smoothness desirable as filler for materials
There is a strong need for superior spherical silica. An object of the present invention is to fill a sealing resin.
Even if blended in the range of 60 to 90% by weight, the fluidity of the sealing material
Low reduction, radioactive and ionic
Low in the content of impurities, a filler for electronic components
Provide a suitable high-purity spherical silica and a method for producing the same
It is in. [0009] Means for Solving the Problems The present inventors have proposed a conventional method.
As a result of conducting research to improve problems in
An emulsion containing an aqueous solution of rukarisilicate as a dispersed phase
Mixing with an emulsion containing a mineral acid aqueous solution as a dispersed phase
To produce spherical silica gel, and the resulting spherical silica gel
Is treated with mineral acid to obtain spherical hydrous silica, which is heat-treated
Sphericity and surface smoothness of spherical silica
High purity suitable for sealing material filler
They found that spherical silica was obtained and completed the present invention.
Was. [0010] The first invention is directed to an aqueous solution of an alkali silicate.
High-purity spherical silica obtained from
With an influx of 1 ppb or less, the electricity of the extraction water obtained by boiling and leaching silica
Air conductivity is less than 10μS / cm, sphericity is 0.9 ~ 1.0
The content of certain particles is 90% or more,
Specific surface by the BET method for the corresponding theoretical surface area
A high-purity spherical silica having a product magnification of 3 or less. "
Is the gist. [0011] The second invention is directed to an "alkali silicate aqueous solution.
Water-in-oil type (W / O) dispersed as fine particles as a disperse phase
Type) Emulsion and finely divided form using mineral acid aqueous solution as dispersed phase
And a water-in-oil (W / O) emulsion dispersed in
To form a spherical silica gel.
Drying spherical hydrous silica obtained by treating Rica gel with mineral acid
Production of high-purity spherical silica characterized by firing
Method. ”. The high-purity spherical silica of the present invention is an alkali silica.
Spherical silica obtained from an aqueous solution of
Extraction by boiling and leaching silica with a content of less than 1 ppb
The electrical conductivity of the water is 10 μS / cm or less, and
If the content of particles with a sphericity of 0.9 to 1.0 is 90% or more,
Yes, the measured value of the specific surface area by the BET method
The value is not more than three times the theoretical value of the corresponding specific surface area. The radioactive substances usually contained in silica are U, Th
However, in the high-purity spherical silica of the present invention,
Is preferably small, more than 1 ppb
Not be. If it exceeds 1 ppb, a soft error will occur.
It is not preferable because it causes. On the other hand, alkali metals such as Na, K, and Li;
Alkaline earth metals such as a and Mg and ionic properties such as Cl
Impurities can corrode aluminum wiring
In the high-purity spherical silica of the present invention, these impurities
Desirably, it is not substantially contained. The content of these impurities is determined by an appropriate analytical method.
Although it can be measured directly by a step, in the present invention,
Electrical Conductivity Measured for Extracted Water from Boiling and Leaching Lica
Was used as an index of the ionic impurity content. This is the product
Can be directly used as the quality characteristics of the product and analyzed directly
It is simpler and clearer than it is.
This is a very strict method. Electric conductivity of the extraction water obtained by boiling and leaching silica
Add 10.0 g of sample silica to 100 ml of pure water and add
Extracted water obtained by boiling at 60 ° C for 20 hours
Measure in ° C. High purity spherical silica of the present invention
Therefore, this value needs to be 10 μS / cm or less.
You. The sphericity defined in the present invention is one
By the ratio of the smallest diameter to the largest diameter in silica particles
Is expressed. The value of sphericity is determined by electron microscopy of silica particles.
In the mirror photo, randomly select 20 particles
Calculate by measuring the maximum and minimum diameter of each. The high-purity spherical silica of the present invention has a sphericity of
Of particles having a value of 0.9 to 1.0 in a range of 90% or less
Above. Particles with a sphericity of less than 0.9 should be
Even if you look at the pictures, the deviation from the true sphere is large. Such a series
The encapsulant using particles as fillers has a high fluidity during molding.
Is not good. In the present invention, the high-purity spherical silica of the present invention is used.
The specific surface area is used as a measure of the smoothness of the particle surface.
Generally, a sphere having a diameter of d (μm) and no pores
The specific surface area SA of the body, when its true specific gravity is D,
It can be represented by the formula (I). Formula (I): SA, (m^Two/ G) = 6 / (d × D) From equation (I), the diameter is d (μm) and the true
Specific surface area SA of silica sphere having a specific gravity of 2.2 (m^Two
/ G) is represented by the following formula (II).
The theoretical value of the specific surface area of a silica sphere having a
0.27 m^Two/ G. Formula (II): SA = 2.73 / d Spherical silicon used as a filler for a sealing material
Mosquitoes are usually subjected to pore closing treatment by firing.
Therefore, the deviation of the measured value of the specific surface area from the theoretical value is large.
The smoothness can be evaluated by the size. For example, a flame
On the surface of the spherical silica particles prepared by the melting method,
Formed by recondensation of Si vapor evaporated by hot flame
There are many microspheres or uneven surface
Specific surface area of molten particles is 1m^Two/ G, usually about 2
m^Two/ G. These particles are used as fillers
However, the flowability of the sealing material during molding is still insufficient. The specific surface area of the spherical silica of the present invention is a theoretical value.
3 times or less of that of
It turns out that it is excellent in property. The spherical silica of the present invention as a filler
The sealing material used has extremely good fluidity during molding.
is there. In the present invention, the specific surface area of the spherical silica is BET.
It is measured by the method. The BET method is based on multilayer adsorption.
Using the adsorption isotherm (BET equation)
Calculate the surface area of the solid from the layer adsorption amount and the molecular cross-sectional area of the adsorbate
This is a well-known method. The method for producing the high-purity spherical silica of the present invention comprises:
It includes the following three steps. ・ Step-1: <Preparation step of spherical silica gel particles> Emulsion containing alkali silicate aqueous solution as dispersed phase
And emulsion containing mineral acid aqueous solution as dispersed phase
And let them react to form porous spherical silica gel particles.
Step of preparing. ・ Step-2: <Step of extracting and removing impurities from spherical silica gel> Treating the spherical silica gel particles obtained in step-1 with a mineral acid,
Extraction and removal of contained impurities, high purity and porous
Obtaining spherical hydrous silica particles. ・ Step-3: <Sintering step for spherical hydrous silica particles> Baking the spherical hydrous silica particles obtained in step-2
A step of imparting the physical properties specified in the above. Hereinafter, each of the above steps will be sequentially described. 1> Step of preparing spherical silica gel particles (Step-1). 1-1) Preparation of emulsion In the method of the present invention, the aqueous alkali silicate solution is dispersed.
Phase containing emulsion and mineral acid aqueous solution
And containing emulsions are respectively prepared. Preferably
Is immiscible with aqueous alkali silicate solutions and aqueous mineral acids.
Liquid as a continuous phase, and an aqueous solution of alkali silicate
Mineral acid aqueous solution and fine particles separately as a dispersed phase
Water-in-oil type (W / O type)
Generate a marjon. Continuous with alkali silicate aqueous solution
Mix the phase forming liquid and the emulsifier and use an emulsifier
Emulsified and contain aqueous alkali silicate solution as dispersed phase
 Prepare a W / O emulsion. On the other hand,
Mix the continuous phase forming liquid and the emulsifier, and
W / O emulsion containing mineral acid aqueous solution as dispersed phase
Prepare John. The alkali silicate used is sodium silicate
, Potassium silicate, lithium silicate, etc.
Sodium silicate is commonly used. Alkali silicate
Silica concentration in aqueous solution (SiO_Two1) to 40% by weight
Is more preferable, more preferably 15 to 30% by weight.
It is. The mineral acids used are sulfuric acid, nitric acid, hydrochloric acid, etc.
However, it is preferable to use sulfuric acid or nitric acid.
The acid concentration ranges from 1 to 30% by weight, preferably from 3 to 15% by weight.
It is an enclosure. The required amount of mineral acid is one emulsion
Adjust according to the amount of alkali in the alkali silicate aqueous solution
You. When the amount ratio of mineral acid / alkali is represented by molar ratio,
 Adjust the amount of mineral acid to be in the range of 0.1-2. As the liquid for forming a continuous phase, alkali silicate
Does not react with and does not mix with salt aqueous solutions and mineral acid aqueous solutions
Use a good liquid. The type is not particularly limited,
From the viewpoint of chemical treatment, the boiling point is 100 ° C or higher and the specific gravity is
It is preferred to use an oil that is 0.9 or less. Al
Quantitative ratio of potassium silicate aqueous solution to oil, mineral acid aqueous solution
The weight ratio of oil to oil is 8: 2 to 2:
8 range. The oil as the liquid for forming the continuous phase is
For example, n-octane, gasoline, kerosene, iso
Aliphatic hydrocarbons such as paraffinic hydrocarbon oils,
Alicyclic hydrocarbons such as rononane and cyclodecane,
Ene, xylene, ethylbenzene, tetralin, etc.
Aromatic hydrocarbons and the like can be used. As an emulsifier, a W / O emulsion may be used.
There is no particular limitation as long as it has a stabilizing function.
Of polyvalent metal salts and poorly water-soluble cellulose ethers
Strongly oily surfactants can be used. Post-processing
From the point of view, it is preferable to use a nonionic surfactant.
No. Specific examples include sorbitan monolaurate, sorbitan
Tanmonopalmitate, Sorbitan monostearate,
Sorbitan fatty acid esthetics such as sorbitan monooleate
, Polyoxyethylene sorbitan monolaurate,
Polyoxyethylene sorbitan monopalmitate, poly
Oxyethylene sorbitan monostearate, polyoxy
Polyoxyethylene such as ethylene sorbitan monooleate
Tylene sorbitan fatty acid esters, polyoxyethylene
Monolaurate, polyoxyethylene monopalmitate
G, polyoxyethylene monostearate, polyoxy
Polyoxyethylene fatty acids such as ethylene monooleate
Esters, stearic acid monoglyceride, oleic acid
Glycerin fatty acid esters such as monoglyceride, etc.
Can be mentioned. The amount of emulsifier
For a certain alkali silicate aqueous solution or mineral acid aqueous solution,
Each ranges from 0.1 to 5% by weight. 1-2) Preparation of spherical silica gel particles An aqueous solution containing the prepared aqueous alkali silicate solution as a dispersed phase
Emuljo containing marjon and aqueous solution of mineral acid as dispersed phase
And under stirring. Reaction between mineral acid and alkali silicate
In response, a spherical porous silica gel is formed. The present invention
In the method of the above, the porous silica formed at this stage
The gel only needs to have at least the surface of the particles solidified,
The inside is not fully solidified with residual alkali components
It may be in a state. There is no limitation on the order of mixing.
Emulsion containing silicate aqueous solution contains mineral acid aqueous solution
Emulsions that may be added to emulsions or containing aqueous mineral acids
Rejuvenation into emulsion containing aqueous alkali silicate solution
May be added. Moreover, you may add both simultaneously. this
The emulsion containing the aqueous mineral acid and the alkali silicate
The present invention is to contact an emulsion containing an aqueous solution.
Is a mandatory requirement. Emuls containing alkali silicate aqueous solution
John is added to the non-emulsified aqueous solution of mineral acid.
When it is obtained, the sphericity and smoothness aimed at by the present invention
Excellent and solid spherical particles cannot be obtained. 1-3) Demulsification treatment To demulsify the emulsion after the reaction, for example,
The reaction solution may be heated by adding a mineral acid aqueous solution. This way
According to this, extraction and removal of impurities can be performed together with demulsification.
You. The demulsification treatment is usually carried out at a temperature of 60 to 120 ° C., preferably
Performing in the temperature range of 80-100 ° C, processing time is about 1 minute to 5 hours
However, the time and temperature conditions are changed in relation to the process-2 described below.
It is desirable to decide. With this process,
The reaction solution in the form of an oil is composed of an oil phase and silica gel particles dispersed mineral acid.
The layers are separated into aqueous phases. Oil phase that constitutes the upper layer
Can be separated and recovered by standard methods and used repeatedly.
it can. 2> Extraction and removal of impurities from spherical silica gel particles
Removal process (process-2). The spherical porous silica gel obtained in the above-mentioned step-1 is converted into an acid.
Treat with the contained solution. The acids used are sulfuric acid and hydrochloric acid
・ Use mineral acid such as nitric acid, but use sulfuric acid or nitric acid
Is preferred. As a treatment liquid, the acid
In practice, an aqueous solution containing one kind is preferable. Processing liquid
The acid concentration is not more than 30% by weight, preferably 5 to 20% by weight.
It is an enclosure. The acid treatment operation in this step is performed in one stage.
Although it is possible to adopt a method of
To extract and remove, the processing operation is divided into at least two stages.
Multi-stage processing to update the processing solution used for each stage
You can do it too. The process of this step is performed while stirring.
It is desirable. The treatment temperature is not particularly limited, but is not less than 50 ° C.
The extraction operation is preferably performed at a temperature. At normal pressure of processing solution
When processed under pressure at a temperature higher than the boiling point, impurity extraction
Required time can be shortened. Temperature during pressure extraction
The higher the degree, the better, but acid corrosion of equipment and energy
-Considering the cost, 100-150 ° C, preferably 110
A range of ~ 140 ° C is practical. The acid treatment time is 30 minutes in the case of a batch type.
About 20 hours, or 30 seconds to 20 hours for continuous type
It is about. Spherical hydrous silica particles obtained by acid treatment
The child is then washed with water at the desired temperature and
And a combination of filtration and deacidification / dehydration treatment. In addition,
The acid used in the method of the present invention may be purified or electronic grade
High-purity products, and dilution of raw materials and acids used
Or water used for washing silica, etc.
It is preferable to use pure water. By the treatment in this step, the release in the silica particles
The content of impurities containing radioactive elements becomes extremely low. Acid treatment
After processing, the impurity content of the silica
Metal and alkaline earth metals such as Mg and Ca
Element is less than 1ppm each, U and Th radioactivity
Elements can be reduced to 1 ppb or less. Ma
In addition, the electric conductivity of the extraction water obtained by boiling and leaching silica was 10μ
S / cm or less. 3> Drying / firing treatment of spherical hydrous silica particles
Process (process-3). Spherical hydrous silica particles from which impurities were extracted and removed in step-2
Moisture is still retained in the offspring. This moisture is
It is divided into landing water and combined water. Normally, adhesion water is 100 ℃ before
It can be easily removed by heating at a later temperature, but the combined water is 400 ° C
It is difficult to completely remove even at the above temperatures. Adhesion
Perform a drying process to remove water and remove bound water
Baking process to remove and densify the silica particles.
Do the work. The drying conditions for removing the adhering water are as follows:
Temperature should be in the range of 50-500 ° C, practically 100-300 ° C
Is good. Processing time is 1 minute to 40 minutes, depending on the drying temperature.
What is necessary is just to select suitably in the range of time. Obtained by the method of the present invention
The silica particles have a particle size distribution in the range of 1 to 100 μm,
Although it is a fine spherical silica with an average particle size of about 10 to 15 μm,
As it has high sphericity and excellent surface smoothness,
Can be dried without agglomeration. In addition,
When drying, use a decompression method or a flow method.
Can also be. The surface of the silica particles obtained by the wet method has a large amount.
Number of silanol groups (≡Si-OH)
Combines with water to form the bound water. This silanol group
Fires the silica obtained in step-2 at a temperature of 1000 ° C or higher.
It can be removed by processing. This process
Can obtain dense spherical silica with a small specific surface area.
Can be. Low moisture absorption, large bulk density, specific surface area
The firing conditions for obtaining small silica particles are the firing temperature.
The temperature should be 1000 ° C or higher, especially in the range of 1050 to 1200 ° C.
Is good. The firing time is from 1 minute to 1 hour depending on the firing temperature.
What is necessary is just to select suitably within the range of 20 hours. The atmosphere for performing the firing treatment is oxygen.
Or carbon dioxide gas, or if necessary, nitrogen or
An inert gas such as gon can also be used. Practically
Should be air. The silica particles obtained by the method of the present invention
Because of its high sphericity and excellent surface smoothness,
Even if the silica particles are not kept in a fluid state,
Can be fired without sintering, and when firing
The equipment used for the treatment is to treat the silica particles in a stationary state.
A firing furnace can be used. In addition, silica particles
For baking while keeping the fluid state, for example,
Use a fluidized kiln, rotary kiln, flame kiln, etc.
You can also. Electric heating or combustion gas as heating source
Etc. can be used. [0044] According to the method of the present invention, an alkali silicate
Using aqueous solutions as raw materials, non-metals containing radioactive elements such as uranium
High purity with extremely low pure content and surface smoothness
Obtaining high-purity spherical silica particles with excellent sphericity
Can be. High-purity spherical silica particles obtained by the method of the present invention
The child is higher in purity and
It has excellent surface smoothness and high sphericity.
Suitable as a filler for resin compositions for encapsulating electronic components
Can be. [0045] The present invention will now be described with reference to Examples and Comparative Examples.
This will be described more specifically. The present invention is not limited to the following embodiments.
However, the present invention is not limited to this. Example 1. 1> Preparation of spherical silica gel particles 1-1) Preparation of emulsion Sorbitan monooleate ("Rheodor SP
-O10 ", manufactured by Kao), isoparaffin as a liquid for continuous phase formation
-Based hydrocarbon oils (Isosol 400, Nippon Oil
Product) and water glass (JIS K-1408, No. 3 equivalent)
The mixture was mixed at a ratio of 1:44:55 in a volume ratio, and was mixed using an emulsifier.
Stir at 000 rpm for 1 minute to disperse the aqueous alkali silicate solution
268 g of water-in-oil type (W / 0 type) emulsion containing
Prepared. On the other hand, the above surfactant and oil and fivefold
% Sulfuric acid aqueous solution mixed at a weight ratio of 1:44:55
And treated under the same conditions as above using an emulsifier,
842g of W / 0 emulsion containing aqueous solution as dispersed phase
Prepared. [0046] 1-2) Preparation and demulsification of spherical silica gel particles While stirring the sulfuric acid aqueous solution emulsion,
A water glass emulsion was added. After completion of addition, at room temperature
The stirring was further continued for 1 hour. Then, the reaction solution was added at 16% by weight.
Add 1,000g of sulfuric acid aqueous solution and heat to 100 ℃ for 1 hour
Stirred. By this treatment, the emulsion reaction liquid becomes oily
Phase (upper layer) and aqueous phase (lower layer) in which silica gel particles are dispersed
Separated. Silica gel particles in the aqueous phase, excluding the oil phase
Was filtered and washed by a conventional method. [0047] 2> Impurity extraction of spherical silica gel particles The silica gel particles obtained were mixed with a newly prepared 16% by weight sulfuric acid.
Impregnated by immersing in an aqueous acid solution and stirring at 100 ° C for 1 hour
And then use pure water 10 times the weight of silica gel.
And washed twice. Repeat the above extraction and washing operations twice
The silica gel particles obtained by using
After washing until H is 4, dehydrate using Nutsche
Thus, spherical hydrous silica particles were obtained. 3> Firing treatment of spherical hydrous silica particles The obtained hydrous silica particles were dried at a temperature of 120 ° C. overnight,
g of dried silica particles were obtained. This dried silica particles are quartz
Into a beaker (1 liter) made at 1,100 ℃ for 30 minutes
Fired. Analysis of silica particles obtained by firing
Alkali metals such as Na, K, Li, Ca, Mg
Which alkaline earth metals and transition metals such as Cr, Fe, Cu
Of each element is 1 ppm or less.
And the total of the radioactive elements of Th was 1 ppb or less. Ma
Boiling leaching extraction of silica particles, measured by the method described above
The electric conductivity of water was 1.8 μS / cm. The average particle size of the obtained silica particles was 11.5 μm.
m, the true specific gravity was 2.20. Ratio table measured by BET method
The area is 0.5 m^Two/ G was 2.1 times the theoretical value. Soshi
If the content of particles with a sphericity of 0.9 or more is 90% or more,
Some spherical silica particles, judged by electron micrograph
Both sphericity and smoothness were good. In addition, the particle cross-section
According to the observation of the electron micrograph, no spherical particles were found.
These were also solid, and the existence of hollow spheres was not recognized. Example 2.3 No. 2.3 Water glass was diluted with pure water.
Silica concentration (SiO_Two20), 15,10% by weight respectively
Alkali silicate aqueous solution using water glass aqueous solution prepared in advance
Example 1 was repeated except that an emulsion containing a liquid was prepared.
Thus, spherical silica particles were obtained. Silica particles obtained
The results of various measurements and observations for
It was a cage. Example 3 The sulfuric acid concentrations were 15, 15, and 3, respectively.
Including sulfuric acid aqueous solution using sulfuric acid aqueous solution adjusted to wt%
Except for preparing the emulsion, the procedure was the same as in Example 1.
Thus, spherical silica particles were obtained. About the obtained silica particles
The results of various measurements and observations are as described below.
there were. Example 4 Emulsion in Example 1
By changing the method of adding
Same as Example 1 except that an aqueous acid solution emulsion was added.
Thus, spherical silica particles were obtained. Silica particles obtained
The results of various measurements and observations for
It was a cage. Comparative Example 1. Sulfur not emulsified
In sulfuric acid aqueous solution with acid concentration of 3, 5, 10% by weight respectively
Other than adding a water glass aqueous solution emulsion
In the same manner as in Example 1, silica particles were obtained. Silica obtained
The results of various measurements and observations on particles are described below.
It was as follows. The samples obtained in Examples 2 to 4 and Comparative Example 1
Impurity content of Lica particles,
Each measurement result of air conductivity, average particle size, specific surface area, and
States such as sphericity and solidness by observing electron micrographs
Was as follows. About the obtained spherical silica particles
And analysis showed that all were Na, K, Li, Ca, Mg, Cr
The concentration of each element of Cu and Cu is 0.1 ppm or less, respectively.
Fe was 0.8 ppm. In addition, U is 0.1ppb
 Th is in the range of 0.4 to 0.6 ppb, with no significant difference.
It did not fit. In addition, silica measured by the above method, silica
The measurement result of the electric conductivity of the boiling leaching extraction water of particles is 1.7
No significant difference was observed in the range of 2.22.2 μS / cm. Electron microscope for the obtained silica particles
The states such as sphericity and solidness by observing the photographs are
In Nos. 2 to 4, particles containing sphericity of 0.9 or more were included.
Spherical silica particles with a predominance of 90% or more, sphericity and smoothness
Everything was good. In addition, all spherical particles are solid
There was no hollow sphere. In contrast
The silica particles obtained in Comparative Example 1 were all spherical.
Is less than 90%, and the content of particles having a
In addition, many hollow spheres were observed. Next, the average particle size of each of the obtained silica particles,
 The specific surface area measured by the BET method and the equation
To the theoretical value of the specific surface area corresponding to each particle size calculated by
The magnification of the measured values is as shown in Tables 1 and 2.
Was. The true specific gravity of each silica particle is 2.20.
Was. [0058] [Table 1] [0059] [Table 2]

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-230422 (JP, A) JP-A-2-59416 (JP, A) JP-A-2-13311 (JP, A) JP-A-3-230 131511 (JP, A) JP-A-3-159912 (JP, A) JP-A-4-154605 (JP, A) JP-A-1-275438 (JP, A) JP-A-61-40811 (JP, A) JP-A-60-180911 (JP, A) JP-A-2-14807 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C01B 33/00-39/54 H01L 23/10

Claims (1)

(57) [Claims 1] A water-in-oil (W / O) emulsion in which an aqueous alkali silicate solution is finely dispersed as a dispersion phase, and a mineral acid aqueous solution as a dispersion phase. Dispersed in granules,
A water-in-oil type (W / O type) emulsion is mixed to form a spherical silica gel, the obtained spherical silica gel is treated with a mineral acid, and the obtained spherical hydrous silica is dried and fired. A method for producing high-purity spherical silica.