JP2015051887A - Method for producing glass fine particles and glass fine particles - Google Patents

Abstract

To provide glass particles containing B2O3 having an average particle diameter of 10 to 1000 nm. An oxide (MOx) selected from the group consisting of oxides of group 2 to group 12 elements, InO1.5, SnO, PbO, SbO1.5, BiO1.5, and TeO2 is 0.5 to 0.5 in total. A uniform melt composed of a liquid phase A containing 15 mol% and containing BO1.5 in an amount of 80 to 99 mol% is prepared, and the liquid phase A is phase-separated to form a liquid medium B and a dispersoid. An emulsion which is a composition comprising liquid phase C is produced, and the emulsion is cooled to solidify liquid phase B and liquid phase C into corresponding solid phase B and solid phase C, respectively. A solid dispersion system is obtained in which a solid phase C, which is a dispersoid containing MOx at a higher molar concentration than the solid phase B, is dispersed in the solid phase B, and the solid dispersion system is treated with a solvent for the solid phase B to be solidified. Recovering solid phase C by dissolving and removing phase B Comprising a method for producing glass particles. [Selection figure] None

Description

  The present invention relates to a method for producing fine particles of inorganic oxide, and more particularly to a method for producing glass fine particles and glass fine particles that can be produced by the method.

  Various fine particles are used in various fields such as fillers and sintering aids in chemical reaction catalysts / photocatalysts, pharmaceuticals, electronic materials, and the like. As particles used for such applications, particles having various properties improved by controlling the particle size and shape are required.

  The particle production method can be roughly divided into two methods: a method by crushing a large lump of raw material (breakdown) and a method by growing from a raw material with a small molecular level (build-up). . With the breakdown method, particles of any composition can be produced as long as there is a large lump of raw material, but the sub-micron order is the technical limit for the particle size that can be reached. The lower limit of the diameter is larger than this. The build-up method can be further divided into a gas phase method and a liquid phase method. The vapor phase method uses vapor condensation / nuclear growth, and includes a CVD method and a plasma method. Depending on the physical properties such as the vapor pressure of the substance, there are materials that can be made fine particles by the gas phase method and materials that cannot be made by the gas phase method, and it is difficult to produce a large amount of particles by the gas phase method. Liquid phase methods include hydrothermal synthesis and sol-gel methods. Since the liquid phase is a fluid with a higher concentration than the gas phase, the liquid phase method is suitable for mass production, but it is difficult to stop particle growth when the particle size is small, and fine particles are used because chemical reactions are used. The materials that can be made are limited.

In recent years, glass fine particles have been used as sintering aids in the field of ceramic capacitors. In this field, in particular, in recent years, glass having a small particle size has been used in order to achieve miniaturization and high functionality of the capacitor. For example, glass fine particles having a particle size of 100 to 150 nm are used as a sintering aid. Are described in Patent Documents 1 and 2. In this document, a material capable of being sintered at a low temperature of 1100 ° C. or lower is required, and low temperature sintering cannot be performed with SiO ₂ fine particles. In addition, rare earth [Sc, Y, and lanthanoid (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)] oxides are ceramic dielectric particles. It is described that a high temperature insulation resistance characteristic of a ceramic dielectric is improved by forming a core / shell by solid solution on the surface of the ceramic (Patent Document 1), which contains a rare earth oxide when used with a ceramic dielectric. Glass is useful.

Further, Patent Document 3 discloses a multilayer ceramic electronic component including CaZrO ₃ ceramic and Li ₂ O—MgO—ZnO—B ₂ O ₃ —SiO ₂ glass. This document describes that it is preferable to be able to fire at a temperature of 1000 ° C. or lower.

  On the other hand, a phase separation phenomenon under heating is known for glass composed of a plurality of oxides (Non-Patent Document 1).

JP 2010-155768 A JP 2007-039325 A International Publication WO 2008-018407

Glass Engineering Handbook, 192-194, Asakura Shoten, (1999)

The international application PCT / JP2013 / 056239, which has not been published at the time of filing of the present invention, describes a method for producing spherical glass particles using the phase separation phenomenon of glass such as Na ₂ O—B ₂ O ₃ —SiO ₂ system. Has been. However, the particles obtained from a system containing SiO ₂ becomes a composition comprising SiO ₂ of more than 90 mol%. It is difficult to use a low-melting-point material as a sintering aid for a multilayer ceramic capacitor using BaTiO ₃ or the like, or to contain a large amount of rare earth elements.

The present invention is a new production method different from the above-described conventional production method for producing glass fine particles, and in particular, B ₂ O ₃ glass fine particles having a very small particle size of 10 to 1000 nm are obtained. It is an object of the present invention to provide a manufacturing method that makes it possible.

The inventor makes use of the liquid-liquid phase separation phenomenon in a glass melt, that is, a uniform liquid phase A is phase-separated into a liquid phase B and a liquid phase C, and a spherical liquid is contained in the liquid phase B. After the phase C is dispersed and separated, the melt is cooled and solidified in this state, and the solid phase B is separated into the solid phase B, and then the solid phase B is dissolved and removed with a solvent. As a result, it was found that glass particles can be easily produced. In particular, Group 2 12 group element oxide, _{e.g., InO 1.5, SnO, PbO,} SbO 1.5, BiO 1.5, 0 oxide selected from the TeO ₂ a (MO _x) in total. When liquid phase A containing ₅ to 15 mol% and BO _1.5 to 80 to 99 mol% was used, it was found that 10 to 1000 nm glass fine particles were formed. The present invention has been completed based on these findings and provides the following.

(1) One or more oxides selected from the group consisting of Group 2 to Group 12 oxides, InO _1.5 , SnO, PbO, SbO _1.5 , BiO _1.5 , and TeO ₂ Preparing a melt which is a uniform composition comprising liquid phase A containing (MO _x ) in a total amount of 0.5 to 15 mol% and containing BO _1.5 in an amount of 80 to 99 mol%; Phase separation is caused to produce an emulsion that is a composition comprising liquid phase B that is a dispersion medium and liquid phase C that is a dispersoid, and the emulsion is cooled to form liquid phase B and liquid phase C, respectively. solidified into the corresponding solid is glass to phase B and solid phase C, whereby said solid phase is a dispersoid containing MO _x with higher mol concentration than the solid phase B in the solid phase B is a dispersion medium Obtaining a solid dispersion in which C is dispersed; and Solid phase comprising a that is treated with a solvent to dissolve and remove the solid phase B to recover the solid phase C relative to B, the production method of the glass particles.
(2) The liquid phase A further contains one or more of AlO _1.5 , GaO _1.5 and GeO ₂ , and the total amount of these components is 0.1 to 10 mol%. The manufacturing method of said (1).
(3) The production method of (1) or (2) above, wherein the solvent comprises water and / or alcohol.
(4) The method according to any one of (1) to (3) above, wherein the phase separation is performed by cooling the liquid phase A to a temperature in a temperature region not lower than the softening point and lower than the melting point.
(5) The phase separation is carried out by once cooling the melt to a temperature below the softening point and then reheating it to a temperature in the temperature region above the softening point and below the melting point. ) To (3).
(6) The method according to any one of (1) to (5) above, wherein the glass fine particles have an average particle size of 10 to 1000 nm.
(7) One or more oxides selected from the group consisting of oxides of group 2 to group 12 elements, InO _1.5 , SnO, PbO, SbO _1.5 , BiO _1.5 , and TeO ₂ (MO _x ) in total 7 to 80 mol%,
Each containing BO _1.5 in the range of 8-90 mol% and AlO _1.5 + GaO _1.5 + GeO ₂ in the range of 0 to 25 mol%,
Glass fine particles having an average particle size of 30 to 300 nm.
(8) MO _x , BO _1.5 , AlO _1.5 , GaO _1.5 , and GeO ₂
(7) The glass fine particle according to (7), wherein the total content of is 90 mol% or more.
(9) The glass fine particles according to (7) or (8) above, wherein the glass softening point is 300 to 800 ° C.
(10) The glass fine particles according to any one of (7) to (9) above, wherein the average particle diameter is 50 to 150 nm.
(11) A sintering aid for a multilayer ceramic capacitor comprising the glass fine particles according to any one of (7) to (10) above.
(12) A multilayer ceramic capacitor using the glass fine particles according to any one of (7) to (10) above.

According to the present invention, it is possible to obtain B ₂ O ₃ -containing glass fine particles having an average particle diameter of 10 to 1000 nm and having a low softening point of 1000 ° C. or lower, and further 800 ° C. or lower. These are advantageous as sintering aids that facilitate downsizing in the production of multilayer ceramic capacitors. Further, the glass fine particles of the present invention containing a rare earth element can provide a multilayer ceramic capacitor having improved high-temperature insulation resistance characteristics of the ceramic dielectric and enhanced insulation performance.

1 is a drawing-substituting photograph showing an SEM observation image of fine particles separated from the glass of Example 1. FIG. FIG. 2 is a drawing-substituting photograph showing an SEM observation image of fine particles separated from the glass of Example 3.

  In the present invention, when the liquid phase and the liquid phase are separated from a uniform melt, the liquid phase on the dispersoid side becomes a spherical shape with a uniform particle size. It utilizes the phenomenon that a solid dispersion is formed in a dispersed form. Therefore, the present invention is carried out using glass of various compositions as long as phase separation occurs from a uniform melt and only a solid dispersion medium obtained by cooling and solidification can be dissolved and removed with a solvent. Can do.

  In the present specification, the term “liquid phase” for a composition or a part thereof includes not only the case where they are at a temperature higher than the melting point, but also the case where they are in the temperature range above the softening point and lower than the melting point.

In particular, in the present invention, a uniform melt (liquid phase A) containing BO _1.5 as one component is first prepared, and then phase separation is caused. By phase separation, liquid phase A is divided into a continuous phase (liquid phase B) forming a dispersion medium and a dispersoid (liquid phase C) dispersed in the continuous phase, and an emulsion is formed as a whole. This is cooled to solidify both phases (solid phases B and C, respectively) to form a solid dispersion system, and this is dissolved and removed using a solvent for the dispersion medium (solid phase B). The solid phase C that has been obtained can be obtained as glass fine particles.

In the present invention, MO _x (Group 2 to Group 12 oxide, InO _1.5 , SnO, PbO, SbO _1.5 , BiO _1.5 , and TeO ₂ is selected from one or two kinds. A uniform melt containing 0.5 to 15 mol% of the above oxide) and 80 to 99 mol% of BO _1.5 causes liquid phase-liquid phase separation due to a decrease in temperature and produces fine particles. Since the liquid phase A has a high BO _1.5 concentration and is therefore very viscous, the growth of the generated liquid phase C particles and the coalescence of two or more particles can be effectively suppressed. As a result, a dispersion in which very fine glass particles having an average particle size (number average particle size) of preferably 10 to 1000 nm, more preferably 20 to 500 nm, and particularly preferably 30 to 300 nm are dispersed in the continuous phase. Is formed.

Glass obtained The dispersion was cooled and _solidified, in a dispersion medium is a solid phase containing _{BO 1.5} at a relatively high mol% _(glass), the _{BO 1.5} relatively low mol% It is a solid dispersion system in which a dispersoid which is a spherical solid phase (glass) contained in is dispersed. Since this dispersion medium has a higher concentration (mol%) of BO _1.5 compared to the solid phase that is a dispersoid, it has high solubility in a protic polar solvent. It can be dissolved and removed by use, whereby the fine glass particles that are dispersoids can be recovered. Thus, glass fine particles having an average particle diameter of preferably 10 to 1000 nm, more preferably 20 to 500 nm, still more preferably 30 to 300 nm, and particularly preferably 50 to 150 nm are obtained.

In terms of components, according to the present invention, (i) selected from the group consisting of oxides of group 2 to group 12 elements, InO _1.5 , SnO, PbO, SbO _1.5 , BiO _1.5 , and TeO _2. One or more oxides (MO _x ) in total preferably in the range of 7-80 mol%, (ii) BO _1.5 in the range of 8-90 mol%, and (iii)
Various glass fine particles each containing one or more of AlO _1.5 , GaO _1.5 and GeO _{2 in} a total amount of preferably 0 to 25 mol% can be easily obtained.

The glass fine particles containing BO _1.5 thus obtained have a low softening point of 1000 ° C. or lower, more preferably 800 ° C. or lower, more specifically a low softening point in the range of 800 to 300 ° C.

The composition of the uniform glass melt in the present invention will be described in more detail below.
One or more oxides (MO _x ) selected from Group 2 to Group 12 element oxides, InO _1.5 , SnO, PbO, SbO _1.5 , BiO _1.5 , TeO ₂ are BO. _1.5 is a component that forms glass, and is a component that causes phase separation in a liquid phase containing more than 80 mol% of BO _1.5 , and constitutes a solid phase that is hardly soluble in solvents such as water. It is an ingredient. If the content of MO _x in the uniform liquid phase A obtained by melting the raw material is too large, the speed of phase separation will increase, resulting in an excessively large particle size and an average particle size of 10 to 1000 nm. Of fine particles cannot be obtained. Conversely, if the MO _x content in the liquid phase A is too small, the yield of the insoluble phase will be low. Therefore, the total amount of MO _{x in} the liquid phase A (and therefore in the raw material) is preferably 0.5 to 15 mol%, more preferably 0.7 to 10 mol%, and still more preferably 0.8 to 8 mol%, particularly preferably 0.9 to 6 mol%.

Further, when selecting MO _x , it is particularly preferable to contain at least one component that easily forms glass with BO _1.5 and gives glass that is hardly soluble in water. Such particularly preferred components in MO _x include, for example, MgO, BaO, MnO ₂ , YO _1.5 , ZrO ₂ , NbO _2.5 , TiO ₂ , WO ₃ , VO _2.5 , FeO _1.5 , Examples include ZnO ₂ and rare earth metal oxides such as lanthanoid oxides such as DyO _1.5 and HoO _1.5 , and PbO, SbO _1.5 , BiO _1.5 and TeO ₂ . In addition, although there exists what has a some valence in said MO _X , the valence of said oxide is an illustration. In other words, “MO _X ” is merely a notation for determining the number of cations, and includes valences other than those specifically shown above.

BO _1.5 is a main component constituting a solid phase B that is soluble in a solvent. The content of BO _1.5 in the liquid phase A is preferably 80 to 99 mol%, more preferably 85 to 99 mol%, still more preferably 90 to 99 mol%.

AlO _1.5 , GaO _1.5 , and GeO ₂ , which are optional components that can be contained in the liquid phase A, increase the compatibility of MO _x and BO _1.5 to produce a uniform liquid phase A. It has the effect of facilitating the prevention and the effect of suppressing phase separation in a short time in which the liquid phase A is rapidly cooled to produce glass flakes. Accordingly, in order to reduce the particle size while increasing the yield of the glass particles by increasing the content of MO _{x is,} AlO _{1.5, GaO} 1.5, 1 kind of GeO ₂ or active two or more It is preferable to make it contain. However, since these components are finally contained in the solid phase C, it is preferable to determine the content in consideration of the thermophysical properties of the glass fine particles. When AlO _1.5 + GaO _1.5 + GeO ₂ is contained, the content is preferably 0.1 to 10 mol%, more preferably 0.5 to 7 mol%, and still more preferably 1 to 5 mol%.

As an optional component, the liquid phase A may contain one or more of alkali metal oxides LiO _0.5 , NaO _0.5 , and KO _0.5 . These components remain in the solid phase C and lower the softening point of the glass particles. However, in order to reduce the water resistance of the glass fine particles at the same time, their content should be preferably 5 mol% or less, more preferably 3 mol% or less, and still more preferably 1 mol% or less.

Also, MO _x , BO _1.5 , AlO _1.5 , GaO _1.5 , and GeO ₂
The total content is preferably 90 mol% or more, more preferably 95% or more, as an optional component, to the extent that does not substantially affect the phase separation of the dispersoid containing MO _x, the other liquid phase A A small amount of a component such as SiO ₂ may be contained.

  The liquid phase A may contain, as an optional component, metal oxides other than those described above and metal salts such as metal halides (fluoride, chloride, bromide or iodide). At least a part of these optional components in the liquid phase A is also contained in the insoluble solid phase C, and as a result, multicomponent spherical glass fine particles are obtained. This provides a means for adding new functions such as optical properties and catalytic properties to the glass fine particles through adjustment of the types and combinations of optional components to be contained and their amounts.

  In the present invention, the phase separation is performed in such a manner that the melt, which is a uniform composition composed of the liquid phase A in a state in which the raw materials are mixed at a high temperature, is melted into a temperature range above the softening point and below the melting point (hereinafter referred to as “phase separation temperature range” It can also be caused by cooling to the temperature within. The rate of cooling can be selected as appropriate. For example, the composition may be allowed to cool naturally from the melt state, and simply pass through the phase separation temperature region, and the composition may be within the phase separation temperature region. The composition may be kept at a constant temperature for an appropriate time, and may be reheated to raise the temperature of the composition as long as it is within the phase separation temperature range. If the time for putting the liquid phase A in the phase separation temperature region is long, the growth of fine particles is promoted and the particle size is easily increased.

  In phase separation, the composition is rapidly cooled from a uniform melt state to a temperature lower than the softening point (for example, room temperature), and then heated again to the phase separation temperature region and maintained in the phase separation temperature region for an appropriate time. Can also be awakened. Just by rapidly cooling from the melt state to a temperature below the softening point, the higher the cooling rate, the more difficult the phase separation occurs. Even if it occurs, the solidified product (glass) obtained in this way is negligible. By reheating to a temperature within the phase separation temperature region, phase separation can be advanced, and generation of liquid phase C (particles) and particle growth can be promoted.

  A combination of the two methods described above may also be used for phase separation. That is, the melt, which is a uniform composition composed of the liquid phase A in which the raw materials are mixed at a high temperature, is cooled to a temperature within the phase separation temperature region to cause phase separation, and then cooled (for example, at room temperature). The glass that has been solidified by heating to the phase separation temperature region may be heated again at an appropriate time to further promote particle growth.

The time required for the phase separation varies depending on the glass composition, the temperature at the time of phase separation, and the target particle size, but usually heat treatment for several minutes to several hours may be performed.

In the present invention, the term “solvent for the dispersion medium (solid phase B)” is a solvent that can substantially dissolve only the dispersion medium and later leave the fine particles as the dispersoid (solid phase C) in the solution. I just need it.
The solvent for dissolving the dispersion medium of the solid dispersion system is not particularly limited as long as it is a solvent that can dissolve only the dispersion medium without substantially dissolving the dispersoid. Preferable is a protic polar solvent, and in particular, water, alcohol or a mixture thereof can be suitably used. When the solid phase C (fine particles) contains a lot of water-soluble oxides, it is preferable to use alcohol. Also, selective dissolution of the dispersoid can be promoted by heating the solvent to increase the solubility of BO _1.5 .

  Although it does not necessarily limit as said alcohol, A C1-C4 alcohol is preferable. Monoalcohol or polyalcohol may be used, and examples of the polyalcohol include glycols. An example of a preferable alcohol for handling is ethanol.

  Furthermore, the pH can be adjusted by adding an acid or a base to the solvent so that the solubility of the solid phase C becomes low.

  Extraction of fine particles from a solution in which fine particles obtained by treating a solid dispersion with a solvent are dispersed can be performed using an appropriate solid-liquid separation means such as centrifugation.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not intended to be limited to these examples.

[Examples 1 to 16]
After the raw materials mixed so as to give the compositions shown in Tables 1 to 3 were melted at a melting temperature shown in the table in a platinum crucible, the melt was quenched with a stainless steel cooling roll to obtain a thickness of 0. 2-0.3 mm glass flakes were prepared. The glass flakes were clear or slightly cloudy. This glass flake was heat-treated under the conditions shown in the table to cause phase separation. The glass after the heat treatment was deformed and fused by softening. This was analyzed by powder X-ray diffraction, and it was confirmed that amorphous B ₂ O ₃ was contained in the amorphous material. A continuous phase containing BO _1.5 at a relatively high mol% was dissolved in water at 80 ° C. to obtain a cloudy aqueous solution. The aqueous solution was centrifuged to precipitate fine particles. As a washing step, water was added again to the precipitated fine particles, dispersed by ultrasonic waves, and subjected to a second centrifugation to precipitate the fine particles. Water was further added to the precipitated microparticles and dispersed ultrasonically, followed by freeze drying to collect the microparticles. The collected fine particles were confirmed to be amorphous by powder X-ray diffraction. The particle diameter was measured by observation with a scanning electron microscope (SEM). The average particle diameter (number average particle diameter) determined from the electron microscope image is shown in the table. The particles were examined for glass transition point, yield point, and softening point by DTA. That is, about 20 to 50 mg of a powdery sample of each glass composition is put in a platinum cell, and using a differential thermal analyzer (model name “TG-8120”, manufactured by Rigaku Corporation), alumina powder is used as a standard sample. A DTA curve was obtained at a heating rate of 20 ° C./min from room temperature to 1000 ° C. in an air atmosphere. The first endothermic peak start point (extrapolated point) was the glass transition point, the endothermic minimum temperature was the yield point, and the second endothermic peak start point (extrapolated point) was the glass softening point.

[Examples 17 and 18]
The point that the solvent for dissolving the continuous phase containing BO _1.5 at a relatively high mol% and the solvent used for the washing step are absolute ethanol, and that the solvent is dried by heating to 70 ° C. instead of freeze drying. Except for the above, glass fine particles were produced in the same manner as in Example 1.

  As can be seen from Tables 1 to 3, glass fine particles having a low softening point of 800 ° C. or less and an average particle diameter of several tens to several hundreds of nm were obtained.

The present invention makes it possible to produce glass fine particles having an average particle size of 10 to 1000 nm containing BO _1.5 and having a low softening point of 1000 ° C. or lower, further 800 ° C. or lower, and such glass. Since it is possible to obtain fine particles containing a rare earth element, which is particularly advantageous when used with a ceramic dielectric, it is highly useful as a sintering aid in the production of ceramic capacitors.

Claims (12)

One or more oxides selected from the group consisting of oxides of Group 2 to 12 elements, InO _1.5 , SnO, PbO, SbO _1.5 , BiO _1.5 , and TeO ₂ (MO _x ) In a total composition of 0.5 to 15 mol% and BO _1.5 of 80 to 99 mol%, and preparing a melt that is a uniform composition comprising liquid phase A, and subjecting liquid phase A to phase separation. Causing an emulsion which is a composition comprising liquid phase B as a dispersion medium and liquid phase C as a dispersoid, and cooling the emulsion so that liquid phase B and liquid phase C respectively correspond to glass in it solidified to a solid phase B and solid phase C, whereby a dispersoid containing MO _x with higher mol concentration than the solid phase B in the solid phase B is a dispersion medium solid phase C is dispersed To obtain a solid dispersion of the form It was treated with a solvent to dissolve and remove the solid phase B comprises and recovering the solid phase C relative method of glass particles. The liquid phase A further contains one or more of AlO _1.5 , GaO _1.5 and GeO ₂ , and the total amount of these components is 0.1 to 10 mol%. Manufacturing method.   The method according to claim 1 or 2, wherein the solvent comprises water and / or alcohol.   The production method according to any one of claims 1 to 3, wherein the phase separation is performed by cooling the liquid phase A to a temperature in a temperature region not lower than the softening point and lower than the melting point.   The phase separation is performed by once cooling the melt to a temperature below the softening point, and then reheating it to a temperature in the temperature region above the softening point and below the melting point. Any manufacturing method.   The manufacturing method in any one of Claims 1-5 whose average particle diameter of this glass microparticle is 10-1000 nm. One or more oxides selected from the group consisting of oxides of Group 2 to 12 elements, InO _1.5 , SnO, PbO, SbO _1.5 , BiO _1.5 , and TeO ₂ (MO _x ) In total 7 to 80 mol%,
Each containing BO _1.5 in the range of 8-90 mol% and AlO _1.5 + GaO _1.5 + GeO ₂ in the range of 0 to 25 mol%,
Glass fine particles having an average particle size of 30 to 300 nm. MO _x , BO _1.5 , AlO _1.5 , GaO _1.5 , and GeO ₂
The glass fine particles according to claim 7, wherein the total content of is 90 mol% or more.   The glass fine particles according to claim 7 or 8, wherein the glass softening point is 300 to 800 ° C.   The glass particle according to any one of claims 7 to 9, wherein an average particle diameter is 50 to 150 nm.   A sintering aid for a multilayer ceramic capacitor, comprising the glass fine particles according to claim 7. A multilayer ceramic capacitor using the glass fine particles according to claim 7.