JP6895760B2 - Method for producing silica-based particle dispersion liquid, silica-based particle dispersion liquid, coating liquid for forming a transparent film, and base material with a transparent film - Google Patents

Description

The present invention relates to a method for producing a dispersion liquid containing silica-based hollow particles having an average particle diameter of 5 to 40 nm.

Conventionally, an antireflection film has been formed on the surface of a base material such as glass, a plastic sheet, or a plastic lens in order to prevent reflection. For example, a coating method of a substance having a low refractive index such as a fluororesin or magnesium fluoride is formed on the surface of a base material of glass or plastic by a coating method, a vapor deposition method, a CVD method or the like, or low refractive index fine particles such as silica fine particles A method of forming an antireflection film by applying a coating liquid containing the above-mentioned material to the surface of a base material is known (see, for example, Patent Document 1). At this time, it is also known to form a high refractive index film containing fine particles having a high refractive index under the antireflection film in order to enhance the antireflection performance.

On the other hand, the applicant of the present application has proposed a method for producing silica-based fine particles having cavities inside (see Patent Document 2). The silica-based fine particles obtained by this method have a low refractive index, and the transparent film formed by using the silica-based fine particles has a low refractive index and excellent antireflection performance.

Further, the applicant of the present application discloses that when such a transparent film is formed on the front surface of the display device and used, the antireflection performance is excellent and the display performance is improved (see Patent Document 3).

Furthermore, the applicant of the present application has an average particle size in the range of 50 to 120 nm, in which the number ratio of the deformed silica-based hollow fine particles having a particle size more than twice the average particle size (Dn) in the silica hollow fine particles is 1% or less. When low-refractive-index silica-based hollow fine particles having a particle size fluctuation coefficient (CV value) of 1 to 50% or less are used, whitening is suppressed, and transparency, haze, antireflection, strength, and scratch resistance are excellent. It is disclosed that a base material with a transparent film can be obtained (see Patent Document 4).

Japanese Unexamined Patent Publication No. 7-133105 Japanese Unexamined Patent Publication No. 2001-233611 JP-A-2002-079616 Japanese Unexamined Patent Publication No. 2012-30489

As shown in Patent Documents 2 to 4, it has been possible to obtain silica-based hollow particles having an average particle diameter of more than 50 nm. However, when obtaining particles having an average particle diameter smaller than 50 nm, there is a problem that the reproducibility is low and the ratio of the number of hollow particles (hollow ratio) to the total number of hollow particles and solid particles is low. It was. The film prepared by using the coating liquid containing such particles has a problem that the refractive index does not decrease sufficiently, and cannot be substantially used as an antireflection film or the like.
An object of the present invention is to provide a method for producing a silica-based particle dispersion liquid, which enables the production of silica-based hollow particles having an average particle size smaller than 50 nm at a high ratio.

The present inventors focused on the sphericity of nuclear particles prepared from silica seed particles in a study aimed at producing silica-based hollow particles having a smaller particle size. As the conventional nuclear particles, particles having a high measured value of sphericity (non-spherical), which is obtained as a ratio between the longest diameter and the shortest diameter of the particles, have been used.

However, it has been found that when such nuclear particles having a high measured value of sphericity are used, it is a cause of lowering the hollow ratio in the production of hollow particles smaller than 50 nm.

Therefore, the present inventors use nuclear particles having a low sphericity measurement value (particles that are more spherical and closer to a sphere), so that the average particle size in which hollow particles occupy 70% or more is 5 to 5. They have found that 40 nm silica-based hollow particles can be produced, and have completed the present invention.

That is, the present invention is a dispersion liquid of silica-based particles having an average particle diameter of 5 to 40 nm and a ratio (hollow ratio) of the number of hollow particles to the total number of hollow particles and solid particles of 70% or more. Regarding the method of manufacturing. This method is characterized by having the following first to fourth steps.
(1) A dispersion liquid containing silica core particles having an average particle diameter of 3 to 25 nm and a sphericity of 1.0 to 1.5, at least one of a silicate aqueous solution and an acidic silicic acid solution, and an inorganic substance containing no silicon. The first step of preparing a dispersion liquid containing composite oxide particles by adding an aqueous compound solution at the same time.
(2) A second step of adding a silica source to the dispersion liquid containing the composite oxide particles obtained in the first step to prepare a dispersion liquid containing the coated composite oxide particles coated with a layer containing silica.
(3) A third step of adding an acid to the dispersion liquid containing the coated composite oxide particles obtained in the second step to remove the element derived from the inorganic compound contained in the coated composite oxide particles.
(4) The fourth step of subjecting the dispersion liquid containing the particles obtained in the third step to hydrothermal treatment under alkaline conditions.

Further, the present invention includes silica containing silica-based particles having an average particle diameter of 5 to 40 nm and a ratio (hollow ratio) of the number of hollow particles to the total number of hollow particles and solid particles of 70% or more. Regarding the dispersion liquid of system particles.

The present invention also relates to a coating liquid for forming a transparent film containing the silica-based particles, a matrix-forming component, and a polar solvent.
Further, the present invention comprises a base material and a transparent film formed on the base material containing the silica-based particles and the matrix component, and the content of the silica-based particles in the transparent film is 20 to 80% by mass. The present invention relates to a base material with a transparent coating.

The present invention is a dispersion of silica-based particles having an average particle diameter of 5 to 40 nm and a ratio (hollow ratio) of the number of hollow particles to the total number of hollow particles and solid particles of 70% or more. Provide a manufacturing method. The transparent film-coated base material prepared of the coating liquid containing the silica-based particles has a high antireflection ability because it exhibits a sufficiently low refractive index, and has a high transparency and whitening because it is composed of relatively small particles. The phenomenon is suppressed, and it has sufficient adhesion, scratch resistance, magic resistance, water resistance, and alkali resistance.

It is the schematic which shows typically the concept of the base material with a transparent film of this invention. It is the schematic which schematically shows the concept of the base material with a transparent film using the conventional hollow particles.

[Manufacturing method of dispersion of silica-based particles]
The present invention produces a dispersion of silica-based particles having an average particle diameter of 5 to 40 nm and a ratio (hollow ratio) of the number of hollow particles to the total number of hollow particles and solid particles of 70% or more. The method is characterized by having at least the following steps. In particular, it is characterized in that the shape of the nuclear particles in the first step is adjusted.
(1) A dispersion liquid containing nuclear particles having an average particle diameter of 3 to 25 nm and a sphericity of 1.0 to 1.5, at least one of a silicate aqueous solution and an acidic silicic acid solution, and an inorganic compound aqueous solution containing no silicon. And are added at the same time to prepare a dispersion liquid containing composite oxide particles.
(2) A second step of adding a silica source to the dispersion liquid containing the composite oxide particles obtained in the first step to prepare a dispersion liquid containing the coated composite oxide particles coated with a layer containing silica.
(3) A third step of adding an acid to the dispersion liquid containing the coated composite oxide particles obtained in the second step to remove the element derived from the inorganic compound contained in the coated composite oxide particles.
(4) A fourth step in which the dispersion liquid containing the particles obtained in the third step is hydrothermally treated under alkaline conditions.

Conventionally, in the production of hollow particles having an average particle diameter smaller than 50 nm, there have been problems that the reproducibility is low and the hollow ratio is low. In the present invention, it has been found that the cause of difficulty in producing hollow particles having an average particle diameter of less than 50 nm is the sphericity of the nuclear particles, and by improving this, the ratio of the hollow particles in the whole particles is 70. % Or more silica-based particles can be produced.

<pre-process>
In order to obtain the desired range of nuclear particles of the present invention, it is preferable to adopt at least one of the following conditions (A) and (B).
(A) Nuclear particles are prepared using seed particles having an average particle diameter of 8 nm or more.
(B) The seed particles are held under the conditions of a temperature of 80 ° C. or lower and / or a pH of 12 or lower to prepare nuclear particles.
That is, (A) using relatively large seed particles to prepare nuclear particles having a measured sphericity close to 1.0, and (B) under conditions where the particle stability of the seed particles is high. It is preferable to prepare the nuclear particles, and it is particularly preferable to produce the nuclear particles under the conditions satisfying (A) and (B).

First, (A) the conditions for using seed particles having an average particle diameter of 8 nm or more will be described.
This condition is characterized in that seed particles having a relatively large particle size are used. That is, conventionally, in order to produce hollow particles having a high porosity, it is preferable that the seed particles are small, and therefore, particles having an average particle diameter of about 5 nm have been used, but under this condition, they have been used. It is characterized by applying seed particles with a large particle size. Due to the large particle size of the seed particles, the stability of the seed particles is maintained when preparing the nuclear particles, and as a result, the measured sphericity of the nuclear particles is close to 1.0 (close to true sphere). Can be formed. As long as the seed particles have this particle size, the same pH and temperature conditions as those used in the past can be applied as the conditions for preparing the nuclear particles. Further, it is preferable to apply the condition (B) in combination.
The average particle size of the seed particles is preferably 8 nm or more, more preferably 10 to 50 nm, and more preferably 10 to 30 nm, as described above, from the viewpoint of the stability of the seed particles in the preparation of nuclear particles. It is more preferably 10 to 20 nm, and particularly preferably 10 to 20 nm.

Next, the conditions for retaining the seed particles under the conditions of (B) temperature of 80 ° C. or lower and / or pH of 12 or lower will be described.
This condition is characterized in that the seed particles generate nuclear particles under the condition that the stability as the seed particles is maintained. That is, conventionally, relatively high temperature and high pH conditions have been applied in the preparation of nuclear particles so that the particle growth of the nuclear particles proceeds rapidly. The final product manufactured under such conditions had no inconvenience as conventional hollow particles, but when hollow particles having an average particle diameter smaller than 50 nm were produced, the reproducibility was low and the hollow ratio was high. There was a problem of becoming low. Therefore, this condition (B) is a modification of this temperature and / or pH condition. This condition (B) is a lower temperature and lower pH condition than before, and the measured value of sphericity is 1. because the particle stability of the seed particles during the particle growth of the nuclear particles is maintained. Nuclear particles close to 0 (near spherical) can be formed. Under these temperature and pH conditions, desired nuclear particles can be obtained even by using conventional small particles having an average particle diameter of about 5 nm. That is, seed particles having an average particle diameter of 3 nm or more and less than 8 nm can also be used, and preferably seed particles having an average particle diameter of 5 nm or more and less than 8 nm can also be used. Further, it is preferable to apply the condition (A) in combination.

As described above, the conditions for obtaining the nuclear particles in the desired range of the present invention are preferably a temperature of 80 ° C. or lower and / or a pH of 12 or lower, but more preferably 70 ° C. or lower. It is more preferably 50 to 65 ° C. The pH is more preferably 11.5 or less, and further preferably 9.0 to 11.0. When the condition (B) is adopted in this step, it is preferable to maintain the condition (B) also in the first step of the next step.

The solid content concentration of the dispersion liquid when preparing the nuclear particles from the seed particles is preferably 0.1 to 20% by mass, more preferably 0.3 to 10% by mass. If the solid content concentration of the dispersion liquid containing the seed particles is less than 0.1% by mass, the solubility per seed particle becomes high and the formation of nuclear particles cannot be slowed down, so that the desired nuclear particles cannot be obtained. In some cases. In addition, it is not preferable because the efficiency in manufacturing is lowered. On the contrary, if the solid content concentration exceeds 20% by mass, the stability of the dispersion liquid is poor and the particles may aggregate.

<First process>
In the first step, a dispersion liquid containing silica core particles having an average particle size of 3 to 25 nm and a sphericity of 1.0 to 1.5 contains at least one of a silicate aqueous solution and an acidic silicic acid solution, and silicon. A dispersion liquid containing composite oxide particles (primary particles) is prepared by adding an aqueous solution of an inorganic compound at the same time. The nuclear particles used in this step are the nuclear particles prepared by using the seed particles in the previous step.

Here, if the average particle size of the nuclear particles is less than 3 nm, it is difficult to obtain particles having that particle size, and even if they can be obtained, they are homogeneous in the preparation of the composite oxide particle dispersion. Particle growth may not be possible. As a result, silica-based particles having a hollow ratio of 70% or more may not be obtained. On the contrary, if the average particle size of the nuclear particles exceeds 25 nm, silica-based hollow particles having a desired average particle size in the range of 5 to 40 nm may not be obtained in the subsequent steps. The average particle size of the nuclear particles is preferably 5 to 20 nm.
Further, if the sphericity of the nuclear particles is outside the range of 1.0 to 1.5, the number of non-spherical particles increases, so that silica-based particles having a desired hollow ratio of 70% or more can be obtained in the subsequent steps. I can't.

The composite oxide particle dispersion liquid in the first step is preferably prepared in a solid content concentration range of 0.1 to 0.9% by mass, more preferably 0.2 to 0.6% by mass. The solid content concentration of this dispersion is such that the addition is terminated from the time when at least one of the silicate aqueous solution and the acidic silicic acid solution and the silicon-free inorganic compound aqueous solution are simultaneously added to the dispersion containing the nuclear particles. It is preferable that it is maintained until the time when it is used.
If this concentration is lower than 0.1% by mass, the yield is lowered and the production efficiency is lowered, which is not preferable.
On the contrary, if this concentration is higher than 0.9% by mass, homogeneous particle growth is not performed, and as a result, silica-based particles having a hollow ratio of 70% or more may not be obtained.

When preparing nuclear particles, it is preferable to control the rate of particle growth within an appropriate range. The particle growth rate at this time varies depending on the particle size of the nuclear particles, but is preferably 0.1 to 10 nm / hour, more preferably 0.2 to 5 nm / hour, and further preferably 0.2 to 3 nm / hour. The range.

Means for particle growth within the above range include lowering the concentration of mother liquor and reaction solution containing nuclear particles, the concentration of silica sources such as dilute silicate aqueous solution and acidic silicate solution to be added, and the concentration of inorganic compound aqueous solution. For example, lowering the concentration, controlling the rate of addition of these added solutions to the nuclear particle dispersion, lowering the reaction temperature (temperature at the time of particle growth), and the like.

As the silicate used in this step, one or more silicates selected from alkali metal silicates, ammonium silicates and organic base silicates are preferably used.
Examples of this alkali metal silicate include sodium silicate (water glass) and potassium silicate. Examples of the organic base include quaternary ammonium salts such as tetraethylammonium salt and amines such as monoethanolamine, diethanolamine and triethanolamine. Ammonium silicates or organic base silicates include silicate solutions. Also included is an alkaline solution containing ammonia, a quaternary ammonium hydroxide, an amine compound, or the like.

The inorganic compound used in this step is substantially composed of an element other than silicon and is a compound that is soluble in acids and alkalis. Expressing this as an oxide (MOx), MOx is Al ₂ O ₃ , B ₂ O ₃ , TiO ₂ , ZrO ₂ , SnO ₂ , CeO ₂ , P ₂ O ₅ , Sb ₂ O ₃ , MoO ₃ , ZnO, One or more of WO _{3 and the like, and TiO 2-} Al ₂ O ₃ and TiO _2- ZrO _{2 and the} like can be exemplified as the composite oxide. Examples of the inorganic compound used in this step include alkali metal salts, alkaline earth metal salts, ammonium salts, and quaternary ammonium salts of metal or non-metal oxo acids constituting these inorganic oxides, and are more specific. , Sodium aluminate, sodium tetraborate, ammonium zirconium carbonate, potassium antimonate, potassium tinate, sodium aluminosilicate, sodium molybdate, ammonium cerium nitrate, sodium phosphate and the like are suitable.

In the first step, the molar ratio MO _X / SiO when silica derived from at least one of the silicate aqueous solution and the acidic silicic acid solution _{is represented by SiO 2} and the inorganic compound derived from the inorganic compound aqueous solution is _{represented by MO X as an oxide. 2} is preferably in the range of 0.15 to 3.0. When the molar ratio MO _X / SiO ₂ is in the range of 0.15 to 3.0, the structure of the composite oxide particles is mainly silicon and a structure in which elements other than silicon are alternately bonded via oxygen. That is, an oxygen atom is bonded to the four bonds of the silicon atom, and many structures in which an element M other than silicon is bonded to the oxygen atom are generated. In the second step, the inorganic compound contained in the coated composite oxide particles. When removing the element derived from, the silicon atom can also be removed as a silicic acid monomer or an oligomer in association with the element (M). Here, when MO _X / SiO ₂ is less than 0.15, the cavity volume in the hollow particles is not sufficiently large, and when MO _X / SiO ₂ exceeds 3.0, spherical composite oxide particles can be obtained. This makes it difficult, and as a result, the proportion of porosity (cavity volume) in the resulting hollow particles decreases.
The more preferable molar ratio MO _X / SiO ₂ is 0.15 to 2.0, more preferably 0.2 to 1.0.

The composite oxide particles obtained in the first step preferably have an average particle size of 3 to 35 nm and a sphericity of 1.0 to 1.5.
Here, if the average particle size of the composite oxide particles is less than 3 nm, it is difficult to obtain particles having that particle size, and even if they can be obtained, the silica content of the composite oxide particles is high. When forming a large number of coating layers, uniform particle growth is not performed, and as a result, silica-based particles having a desired hollow ratio of 70% or more may not be obtained. On the contrary, if the average particle size exceeds 35 nm, silica-based particles having a desired average particle size in the range of 5 to 40 nm may not be obtained in the subsequent steps. Further, if the sphericity of the composite oxide particles is outside the range of 1.0 to 1.5, the number of non-spherical particles increases. Therefore, in the subsequent steps, silica-based particles having a desired hollow ratio of 70% or more. Cannot be obtained.

<Second step>
In the second step, a silica source is added to the dispersion liquid containing the composite oxide particles obtained in the first step to prepare a dispersion liquid containing the coated composite oxide particles coated with a layer containing silica. Examples of the silica source include the above-mentioned aqueous silicate solution and acidic silicic acid solution, and hydrolysates thereof.

Further, in this step, in addition to the silica source, the silicon-free inorganic compound used in the first step can be added. That is, at least one of the silicate solution and an acidic silicic acid solution and an inorganic compound aqueous solution was added with a small molar ratio _MO X / SiO ₂ than the molar ratio _MO X / SiO ₂ of the first step described above, the composite oxide It is also preferable to form a coating layer containing silica and an inorganic compound other than silica in the physical particles and having a high silica content.

Here, if the molar ratio in the second step _MO X / SiO ₂ is smaller molar ratio than the molar ratio _MO X / SiO ₂ of the first step, the coating layer increases the amount of silica, the later During the acid treatment in the three steps, the element M other than silicon is removed, and a coating layer substantially made of silica is formed.

In particular, the ratio (B / A) of the molar ratio (B) _{of MO X} / SiO ₂ in the second step to the molar ratio (A) _{of MO X} / SiO _{2 in the first step is preferably 0.8 or less.} .. More preferably, the value (B / A) is 0.6 or less, and more preferably, the value (B / A) is 0.5 or less.

In the formation of the coating layer containing silica in the second step, the solid content concentration of the dispersion liquid containing the composite oxide particles is in the range of 0.1 to 0.9% by mass, and further in the range of 0.2 to 0.6% by mass. It is preferable to carry out with.
If this concentration is lower than 0.1% by mass, the yield is lowered and the production efficiency is lowered, which is not preferable.
On the contrary, if this concentration is higher than 0.9% by mass, homogeneous particle growth is not performed, and as a result, silica-based particles having a hollow ratio of 70% or more may not be obtained.

When forming the coating layer containing silica, it is preferable to control the formation rate of the coating layer within an appropriate range. The formation rate at this time varies depending on the particle size of the primary particles of the composite oxide particles, but is preferably 0.1 to 10 nm / hour, more preferably 0.2 to 5 nm / hour, and further preferably 0.2 to 0.2 to 5 nm / hour. It is in the range of 3 nm / hour.

As a means for forming the coating layer within the above range, the concentration of the mother liquor or reaction solution containing the composite oxide particles is lowered, the organic silicon compound solution to be added, the dilute silicate aqueous solution or the acidic silicate solution is silica. Reduce the concentration of the source, the concentration of the inorganic compound aqueous solution containing no silicon, control the rate of addition of these added solutions to the composite oxide particle dispersion, and reduce the reaction temperature (temperature at the time of forming the coating layer). Examples of things to do.

In the first step and / or the second step, it is preferable to carry out aging by hydrothermal treatment after the particle growth and / or the formation of the coating layer containing silica. The aging at this time is preferably carried out in the range of a solid content concentration of 1 to 30% by mass, a temperature of 30 to 100 ° C., and a time of 1 to 12 hours.

In the first step and / or the second step, it is preferable to prevent aggregation by irradiating ultrasonic waves or the like to achieve high dispersion. If agglomerated particles or coarse particles that are difficult to disperse are present, it is preferable to remove them by a capsule filter, centrifugation or the like.

The coated composite oxide particles obtained in the second step preferably have an average particle size of 5 to 40 nm and a sphericity of 1.0 to 1.5.
Here, if the average particle size of the coated composite oxide particles is less than 5 nm, it is difficult to obtain particles having that particle size, and even if they can be obtained, the desired average particles are obtained in the subsequent steps. In some cases, silica-based particles having a diameter in the range of 5 to 40 nm cannot be obtained. Further, in the subsequent steps, silica-based particles having a desired hollow ratio of 70% or more may not be obtained. On the contrary, even if the average particle size exceeds 40 nm, silica-based particles having a desired average particle size in the range of 5 to 40 nm may not be obtained in the subsequent steps, which is not preferable.
Further, if the sphericity of the coated composite oxide particles is outside the range of 1.0 to 1.5, the number of non-spherical particles increases. Therefore, in the subsequent steps, a silica-based particle having a desired hollow ratio of 70% or more is used. No particles can be obtained.

<Third step>
In the third step, an acid is added to the dispersion liquid containing the coated composite oxide particles obtained in the second step to remove the element derived from the inorganic compound contained in the coated composite oxide particles. That is, hollow particles having cavities inside are produced by removing the metal elements constituting the silicon-free inorganic compound added in the first step (second step if necessary) from the coated composite oxide particles. To do.

Examples of the method for removing the element derived from the inorganic compound contained in the coated composite oxide particles include a method for dissolving and removing using at least one of a mineral acid and an organic acid. Further, a method of contacting with a cation exchange resin to remove the ion exchange, or a method of using these in combination can be exemplified.

The concentration of the coated composite oxide particles in the coated composite oxide particle dispersion at this time varies depending on the treatment temperature, but is 0.1 to 50% by mass in terms of oxide, particularly 0.5 to 25% by mass. It is preferable that it is in the range of. If it is less than 0.1% by mass, dissolution of silica in the silica coating layer may occur, and at the same time, the treatment efficiency is poor due to the low concentration. Further, when the concentration of the coated composite oxide particles exceeds 50% by mass, it becomes difficult to remove the desired amount of the element derived from the inorganic compound contained in the coated composite oxide particles in a small number of times.

The removal of the element derived from the above-mentioned inorganic compound may _{be carried out until the molar ratio MO X} / SiO ₂ of the obtained silica-based particles is 0.0001 to 0.2, particularly 0.0001 to 0.1. preferable. The dispersion liquid from which the elements have been removed can be washed by a known washing method such as ultrafiltration. In this case, if a part of alkali metal ions, alkaline earth metal ions, ammonium ions and the like in the dispersion liquid is removed in advance and then ultrafiltration is performed, a sol in which particles having high dispersion stability are dispersed can be obtained. An organic solvent-dispersed sol can be obtained by substituting with an organic solvent if necessary. The silica-based particles dispersed in the dispersed sol thus obtained have an outer shell composed of a porous silica layer and having cavities inside. In addition, if the nuclear particles are not completely removed, a porous substance remains in the cavity. Therefore, the obtained hollow particles have a low refractive index, and the film formed by using the hollow particles has a low refractive index, so that a film having excellent antireflection performance can be obtained.

<4th process>
In the fourth step, the dispersion liquid containing the particles obtained in the third step is aged by hydrothermal treatment under alkaline conditions. By this step, hollow particles having an excellent dispersion stability and a hollow ratio of 70% or more can be produced.

This hydrothermal treatment is preferably performed in the range of solid content concentration of 1 to 30% by mass, pH of 9.0 or more, temperature of 30 to 300 ° C., and time of 1 to 72 hours.
The silica-based particles aged by this hydrothermal treatment can also be solvent-substituted with an organic solvent. The type of the organic solvent is not particularly limited as long as it does not adversely affect the silica-based particles. Examples of usable organic solvents include alcohols, glycols, esters, ketones, nitrogen compounds, aromatics and the like. The method of solvent substitution is not particularly limited as long as the solvent is substituted, and a conventionally known method such as using an ultrafiltration membrane or a rotary evaporator may be used.

<Fifth step>
The production method of the present invention includes a fifth step of surface-treating the hollow particles that have undergone the first to fourth steps with an organic silicon compound represented by the following formula (1) or a hydrolyzate thereof. Is preferable.

R _n −SiX _4-n (1)
(However, in the formula, R is an unsubstituted or substituted hydrocarbon group having 1 to 10 carbon atoms, and may be the same or different from each other. X is an alkoxy group or a silanol group having 1 to 4 carbon atoms. , Halogen, hydrogen, n is an integer from 0 to 3)

Examples of the organic silicon compound represented by the formula (1) include tetramethoxysilane, tetraethoxysilane, tetrapropoxysisilane, tetrabutoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, and diphenyldimethoxy. Silane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (βmethoxyethoxy) silane, 3,3,3 -Trifluoropropyltrimethoxysilane, methyl-3,3,3-trifluoropropyldimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxymethyltrimethoxysilane, γ-gly Sidoxymethyltrioxysilane, γ-glycidoxyethyltrimethoxysilane, γ-glycidoxyethyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-( β-Glysidoxyethoxy) Propyltrimethoxysilane, γ- (meth) acryloximethyltrimethoxysilane, γ- (meth) acryloximethyltrioxysilane, γ- (meth) acryloxiethyltrimethoxysilane, γ- (Meta) Acryloxyethyltriethoxysilane, γ- (meth) Acryloxypropyltrimethoxysilane, γ- (meth) acryloxipropyltrimethoxysilane, γ- (meth) acryloxipropyltriethoxysilane, γ- (meth) ) Acryloxipropyltriethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltriethoxysilaoctyltriethoxysilane, decyltriethoxysilane, butyltriethoxysilane, isobutyltriethoxysilane, hexyltriethoxysilane, octyltriethoxysilane Silane, decyltriethoxysilane, 3-ureidoisopropylpropyltriethoxysilane, perfluorooctylethyltrimethoxysilane, perfluorooctylethyltriethoxysilane, perfluorooctylethyltriisopropoxysilane, trifluoropropyltrimethoxysilane, N- β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoki Examples thereof include sisilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, trimethylsilanol, and methyltrichlorosilane.

When the silica-based particles are surface-treated with such an organic silicon compound, they can be uniformly dispersed and densely packed in the matrix to obtain a transparent film having excellent film strength and scratch resistance. Can be done.

For the surface treatment of silica-based particles, a predetermined amount of the above-mentioned organic silicon compound is added to the alcohol dispersion of the particles, water is added thereto, and if necessary, an acid or alkali is added as a hydrolysis catalyst to add the organic silicon compound. Disassemble. More preferably, it is then heat treated and aged.

At this time, the mass ratio of the silica-based particles to the organic silicon compound (mass as the solid content of the organic silicon compound (R _n −SiX _{(4-n) / 2} ) / mass of the silica-based particles) is that of the silica-based particles. Although it depends on the average particle size, it is preferably in the range of 0.005 to 3.0, more preferably 0.05 to 1.0.

If the mass ratio is smaller than 0.005, the affinity with the matrix-forming component described later is low, the dispersibility and stability in the paint are insufficient, and the particles may aggregate in the paint. A dense transparent film may not be obtained, and the adhesion to the substrate, the strength of the film, the scratch resistance, etc. may be insufficient.

On the contrary, when the mass ratio is larger than 30.0, the dispersibility in the coating material is not further improved, the refractive index of the silica-based particles is increased, and a transparent film having a desired low refractive index is obtained. It may not be possible, and the antireflection performance may be insufficient.

[Dispersion of silica-based particles]
The dispersion liquid of silica-based particles of the present invention has an average particle diameter of 5 to 40 nm, and the ratio of the number of hollow particles (hollow ratio) to the total number of hollow particles and solid particles is 70% or more. It contains system particles. This can be produced by the production method described above. Conventionally, it has been difficult to produce small silica-based hollow particles having an average particle diameter of 5 to 40 nm, but in the present invention, production has been realized at a high hollow ratio of 70% or more.

Antireflection films are generally wavelength-dependent and are often designed to be λ / 4 with respect to wavelength λ, usually having the lowest reflectance at a wavelength of 550 nm, which is highly sensitive to humans. Since it is designed, it is generally used as a thin film having a film thickness of about 100 nm.
In the present invention, since silica-based hollow particles having a relatively small particle size of 5 to 40 nm can be produced, the antireflection film containing the hollow particles has the hollow particles sufficiently embedded in the thin film. Become. As a result, the smoothness of the particle surface is also improved, and the magic resistance, water resistance, and alkali resistance of the thin film can be improved. Moreover, since the hollow ratio is high, high antireflection performance can be exhibited. Further, even when the blending amount of the particles is relatively high, since the particle size is small, scattering by the particles is suppressed, and a highly transparent film can be formed.

The silica-based particles according to the dispersion liquid of the present invention are silica-based particles having an average particle diameter of 5 to 40 nm as a main component. In addition to silica, the silica-based particles may contain oxides such as alumina and magnesia, oxides of alkali metals, and hydroxides. However, in terms of the use of the transparent coating, it is preferably substantially made of silica.

<< Measurement of average particle size >>
The average particle size is determined by taking an electron micrograph, measuring the longest and shortest diameters of each particle, and using the average value as the particle size of the particles, measuring the particle size of any 100 particles and averaging them. It was obtained as a value.

If the average particle size of the silica-based particles is less than 5 nm, it is difficult to obtain particles having that particle size, and in particular, it is difficult to obtain silica-based hollow particles. Even if silica-based hollow particles having this particle size are obtained, the particle size itself is small, so the proportion of cavities inside the particles is small, that is, the porosity is small, so the refractive index is high, and sufficient antireflection ability is provided. The transparent film to have may not be obtained. Further, silica-based particles having a hollow ratio of 70% or more cannot be obtained.
On the contrary, when the average particle size exceeds 40 nm, the particles are large and are not sufficiently embedded in the surface of the transparent film when blended in the thin film. As a result, particles may be exposed on the surface of the transparent coating film, which may induce external scattering on the surface of the coating film to reduce the transparency, or the smoothness of the surface of the transparent coating film may be lowered, resulting in insufficient scratch resistance and the like.
A more preferable average particle size is 5 to 35 nm, still more preferably 8 to 30 nm.

Further, in the silica-based particles according to the dispersion liquid of the present invention, the ratio (hollow ratio) of the number of hollow particles to the total number of hollow particles and solid particles is 70% or more. Here, the hollow particles mean particles having cavities inside and have a porosity of 3% or more, and the solid particles mean particles having a porosity of less than 3%.

<< Measurement of porosity of individual particles >>
Porosity is defined as the ratio of cavities in a particle to the particle. Specifically, a transmission electron micrograph of the particles is taken. At this time, the hollow portion of the hollow particle has a low density, and the contrast of that portion is low in the transmission electron micrograph, so that the hollow portion of the hollow particle has a contrast ratio with that of the outer shell portion of the hollow particle in the transmission electron micrograph. The hollow part can be confirmed. First, the longest diameter and the shortest diameter of the particles are measured, and the average value is used as the particle diameter of the particles to obtain _{the volume (VQ) assuming that the particle shape is a true sphere.} Next, the longest diameter and the shortest diameter of the cavity of the particle are measured, and the average value is used as the diameter of the cavity to obtain _{the volume (VP) assuming that the shape of the cavity is spherical.} Porosity, expressed as a percentage of the volume _{(V P)} to the volume _{(V Q).}

《Measurement of hollow ratio》
For the hollow ratio, 100 particles are confirmed on the TEM image, and the ratio of the number of hollow particles to the total number of particles of the hollow particles (porosity of 3% or more) and the solid particles (porosity of less than 3%) is determined. ..

When the hollow ratio is less than 70%, the refractive index of the transparent film cannot be sufficiently lowered, which is sufficient, although it depends on the content of silica-based particles in the transparent film, the particle size, or the sphericity. Anti-reflection performance may not be exhibited. The hollow ratio is preferably 75% or more, more preferably 80% or more, still more preferably 90% or more, particularly preferably 95% or more, and most preferably 100%.

The porosity of the entire silica-based particles according to the dispersion liquid of the present invention is preferably 3 to 50%, more preferably 15 to 50%, still more preferably 25 to 48%.
<< Porosity of the entire silica-based particles >>
The porosity of the entire silica-based particles in the dispersion liquid of the present invention is obtained by calculating the porosity of the individual particles obtained as described above for any 100 particles and obtaining the average value thereof. The higher the porosity, the lower the refractive index. When such particles having a high porosity are blended in a transparent film, a film having high antireflection performance can be obtained.

The silica-based particles according to the dispersion liquid of the present invention preferably have a sphericity of 1.0 to 1.5. If the sphericity of the silica-based particles is in this range, the particle shape becomes close to a sphere. Therefore, the transparent film having a thin film thickness can be uniformly filled, and a thin film transparent film can be formed while maintaining the smoothness of the film surface, that is, the silica-based particles are not exposed to the outside from the film surface. As a result, a film having a low refractive index and sufficient strength can be obtained, which is preferable. Further, since it is easy to obtain a transparent film in which silica-based particles are not exposed to the outside from the surface of the film, whitening and scratch resistance are unlikely to occur. Further, the number ratio of so-called irregularly shaped particles having a sphericity of more than 1.5 is preferably 1% or less.
A more preferable sphericity is 1.0 to 1.4, and even more preferably 1.0 to 1.2.

《Measurement of sphericity》
Spheroidity is defined as the ratio of the longest diameter to the shortest diameter of a particle. Specifically, a transmission electron micrograph is taken, the longest diameter and the shortest diameter of each particle are measured, and the ratio (ratio of the longest diameter to the shortest diameter) is obtained for any 100 particles, and the average value thereof is obtained. I got it as. The closer to a spherical spherical shape, the less the difference between the longest diameter and the shortest diameter, and the ratio (that is, sphericity) approaches 1.0.

<< Measurement of the number ratio of irregularly shaped particles >>
In the above-mentioned measurement of sphericity, the ratio of the number of particles having sphericity exceeding 1.5 to any 100 particles is obtained.

Further, the silica-based particles according to the dispersion liquid of the present invention preferably have a refractive index of 1.10 to 1.41. Since these silica-based particles contain hollow particles and have a hollow ratio of 70% or more, the refractive index is lower than that of those composed of only ordinary silica-based solid particles.

Those with a refractive index of less than 1.10 are difficult to obtain. On the contrary, if the refractive index is higher than 1.41, the refractive index of the transparent film containing the silica-based particles is also high, so that the antireflection performance may be insufficient. A more preferable refractive index is 1.10 to 1.30, and even more preferably 1.10 to 1.25.

<< Measurement of refractive index >>
The refractive index of the silica-based particles used in the present invention is measured by the following method.
[1] A dispersion of silica-based particles is taken on an evaporator to evaporate the dispersion medium.
[2] This is dried at 120 ° C. to obtain a powder.
[3] A few drops of a standard refracting liquid having a known refractive index are dropped onto a glass plate, and the above powder is mixed thereto.
[4] The operation of the above [3] is performed with various standard refracting liquids, and the refractive index of the standard refracting liquid when the mixed liquid becomes transparent is defined as the refractive index of the silica-based particles.

Further, the silica-based particles of the present invention preferably have an organic group directly bonded to a silicon atom on the surface thereof. That is, the one subjected to the surface treatment of the fifth step in the production method of the present invention is preferable. As for the type of organic group, a binder for preparing a composition for forming a transparent film, particularly one having an affinity with an organic resin is preferable. The transparent film-coated substrate obtained by curing this transparent film-forming composition on the substrate is not limited as long as it does not cause whitening of the transparent film and does not impair scratch resistance and adhesion. Absent. For example, it may be a hydrocarbon group or a hydrocarbon group containing a carbon atom or a foreign atom other than a hydrogen atom. The hydrocarbon group may be an aliphatic group, an aromatic group, a saturated hydrocarbon group, or an unsaturated hydrocarbon group. Further, it may contain a double bond or a triple bond, or may have an ether bond.

Preferable examples of the organic group directly bonded to the silicon atom include an organic group selected from a saturated or unsaturated hydrocarbon group having 1 to 18 carbon atoms and a halogenated hydrocarbon group having 1 to 18 carbon atoms. it can. Specifically, 3-methacryloxypropyl group, 3-acryloxypropyl group, 3,3,3-trifluoropropyl group, methyl group, phenyl group, isobutyl group, vinyl group, γ-glycidoxytripropyl group, γ-methacryloxypropyl group, N-β (aminoethyl) γ-aminopropyl group, N-β (aminoethyl) γ-aminopropyl group, γ-aminopropyl group, N-phenyl-γ-aminopropyl group, etc. It can be mentioned, but it is not limited to these.

<Preferable Aspects of Silica Particles and Organic Groups <1>>
From the viewpoint of adhesion of the transparent coating film containing the silica-based particles of the present invention to the substrate, prevention of whitening of the coating film, and scratch resistance, the silica-based particles of the present invention have the following formula (2) or the following formula ( Those having the organic group of 3) and showing a weight loss of 1.5% by mass or more in the temperature range of 200 ° C. to 500 ° C. by thermal weight measurement (TG) are preferable.
-R-OC (= O) CCH ₃ = CH ₂ ... (2)
(However, R is a divalent hydrocarbon group having 1 to 12 carbon atoms)
-R-OC (= O) CH = CH ₂ ... (3)
(However, R is a divalent hydrocarbon group having 1 to 12 carbon atoms)

<Preferable Aspects of Silica-based Hollow Particles and Organic Groups <2>>
Further, for the same reason as described above, it is preferable that the silica-based particles of the present invention have an organic group of the following formula (4).
_{-R-C n F a H b} ··· (4)
(However, a + b = 2n + 1, n is an integer of 1 to 3, R is a divalent hydrocarbon group having 1 to 12 carbon atoms)

The silica-based particles of the present invention are usually dispersed in a dispersion medium. The silica concentration of 1 to 70% by mass is preferable from the viewpoint of stability, and more preferably 3 to 40% by mass is recommended.

[Coating liquid for forming a transparent film]
The coating liquid for forming a transparent film according to the present invention is characterized by containing the above-mentioned silica-based particles having an average particle diameter of 5 to 40 nm and a hollow ratio of 70% or more, a matrix-forming component, and a polar solvent.

<Silica particles>
As the silica-based particles used in the present invention, the above-mentioned silica-based particles are used.

<Matrix forming component>
As the matrix-forming component, a silicone-based (sol-gel-based) matrix-forming component, an organic resin-based matrix-forming component, or the like is used.

As the silicone-based matrix-forming component, a hydrolyzed polycondensate of an organic silicon compound similar to the above-mentioned formula (1) is preferably used.
Examples of the organic resin matrix forming component include thermosetting resins, thermoplastic resins, and electron beam curable resins known as paint resins.

As such resins, for example, thermoplastic resins such as conventionally used polyester resins, polycarbonate resins, polyamide resins, polyphenylene oxide resins, thermoplastic acrylic resins, vinyl chloride resins, fluororesins, vinyl acetate resins, and silicone rubbers. , Urethane resin, melamine resin, silicon resin, butyral resin, reactive silicone resin, phenol resin, epoxy resin, unsaturated polyester resin, thermosetting acrylic resin, thermosetting resin such as UV curable acrylic resin, UV curable Acrylic resin and the like can be mentioned. Furthermore, it may be a copolymer or a modified product of two or more kinds of these resins. These resins may be emulsion resins, water-soluble resins, and hydrophilic resins. Further, in the case of a thermosetting resin, it may be an ultraviolet curable type or an electron beam curable type, and in the case of a thermosetting resin, a curing catalyst may be contained.

<Polymerization initiator, etc.>
When the matrix-forming component is the above-mentioned organic resin, if the resin is an ultraviolet curable resin, a photopolymerization initiator may be contained, and if the resin is a thermosetting resin, a curing catalyst may be contained. Good. These are not treated as matrix-forming components as constituent substances of the coating liquid.

The polymerization initiator is not particularly limited as long as the matrix-forming component can be cured, and conventionally known ones can be used. For example, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) 2,4,4-trimethyl-pentylphosphine oxide, 2-hydroxy-methyl-2-methyl- Phenyl-Propane-1-ketone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-methyl-1- [4- (methylthiophenyl] -2) -Morphorinopropane-1-one and the like can be mentioned.

Examples of the curing catalyst include inorganic acids such as nitric acid, hydrochloric acid and sulfuric acid, organic acids such as formic acid, acetic acid and itaconic acid, and basic substances such as ammonia, ethylamine and ethanolamine.

<Polar solvent>
The polar solvent used in the present invention is not particularly limited as long as it can dissolve or disperse the matrix-forming component and the polymerization initiator used as needed and uniformly disperse the silica-based hollow particles, and a conventionally known solvent is used. Can be done.

Specifically, alcohols such as water, methanol, ethanol, propanol, 2-propanol (IPA), butanol, diacetone alcohol, furfuryl alcohol, tetrahydrofurfuryl alcohol, ethylene glycol, hexylene glycol, isopropyl glycol; acetic acid. Esters such as methyl ester, ethyl acetate ester, butyl acetate; ethers such as diethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether ; Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acetyl acetone, acetoacetic acid ester, methyl cellosolve, ethyl cellosolve, butyl cellosolve, toluene, cyclohexanone, isophorone and the like can be mentioned.

Among them, alcohols such as methanol, ethanol, propanol and 2-propanol (IPA) can uniformly disperse the surface-treated silica-based fine particles, and the solvent having a carbonyl group uses the surface-treated silica-based particles. It can be uniformly dispersed and the stability of the paint is good. Therefore, a transparent film having excellent uniformity, adhesion to a base material, strength, and the like can be formed with good reproducibility, so that it can be preferably used.

The concentration of the silica-based fine particles in the coating liquid for forming a transparent film is preferably in the range of 0.4 to 54% by mass, more preferably 0.6 to 54% by mass as a solid content. If the amount of silica-based particles in the coating liquid for forming a transparent film is small, the content of silica-based particles in the transparent film is low and a transparent film having a sufficiently low refractive index may not be obtained. On the contrary, if the amount of silica-based particles is too large, the strength of the transparent film may be insufficient because the content of the matrix-forming component is reduced.

The concentration of the matrix-forming component in the coating liquid for forming a transparent film is preferably in the range of 0.1 to 36% by mass, more preferably 0.1 to 24% by mass as a solid content.
When the concentration of the matrix-forming component is low, the amount of the matrix component in the obtained transparent film is small, and scratch resistance, adhesion to the substrate, and the like may be insufficient. If the concentration of the matrix-forming component is too high, the content of silica-based particles in the obtained transparent film may be low, the refractive index may be insufficient, and the antireflection performance may be insufficient.

The transparent film-forming coating may contain a catalyst for carrying out a reaction such as polymerization or condensation of the matrix-forming component. In addition, other components used in known transparent coatings may be contained.

The total solid content concentration of the coating liquid for forming a transparent film is preferably in the range of 1 to 60% by mass, more preferably 3 to 50% by mass.
If the total solid content concentration is lower than 1% by mass, the film thickness of the transparent film may be too thin, the scratch resistance may be insufficient, and sufficient antireflection performance may not be obtained. .. On the other hand, when the total solid content concentration is higher than 60% by mass, the viscosity of the coating liquid becomes high, and the stability of the coating liquid decreases or the coatability deteriorates. Further, it becomes difficult to form a thin film, and further, the uniformity of the obtained transparent film, the adhesion to the substrate, the strength and the like may be insufficient.

As a method for forming a transparent film using the coating liquid for forming a transparent film according to the present invention, a conventionally known method can be adopted.
Specifically, the coating liquid for forming a transparent film is applied to a base material by a well-known method such as a dip method, a spray method, a spinner method, a roll coating method, a bar coating method, a slit coater printing method, a gravure printing method, or a microgravure printing method. A transparent film can be formed by applying it to a cloth, drying it, and curing it by a conventional method such as ultraviolet irradiation and heat treatment. In the present invention, a roll coating method, a slit coater printing method, a gravure printing method, and a microgravure printing method are recommended.

[Base material with transparent film]
The substrate with a transparent coating according to the present invention is characterized by containing silica-based particles having an average particle diameter of 5 to 40 nm and a hollow ratio of 70% or more, and a matrix component.

<Base material>
As the base material used in the present invention, conventionally known ones can be used without particular limitation. Examples thereof include plastic sheets such as glass, plastic, polycarbonate, acrylic resin, polyethylene terephthalate (PET), triacetyl cellulose (TAC), cyclopolyolefin and norbornene, plastic films and the like, and plastic panels and the like.

<Silica particles>
As the silica-based particles used in the present invention, the silica-based hollow particles having the above-mentioned predetermined average particle diameter and hollow ratio are used.

<Matrix component>
As the matrix component, a silicone-based (sol-gel-based) matrix component, an organic resin-based matrix component, or the like is used.

The concept of the substrate with a transparent coating of the present invention is schematically shown in FIG. As shown in FIG. 1, when silica-based hollow particles having the above-mentioned predetermined average particle diameter and hollow ratio are used, a homogeneous transparent film can be easily obtained, and the adhesion between the base material and the transparent film is improved. Further, since the upper surface of the transparent film has small irregularities and becomes smooth, external scattering on the surface can be suppressed. Further, since the particle size is small, the internal scattering of the coating film due to the particles dispersed in the coating film can be suppressed. Therefore, the transparent film is suppressed from whitening, has excellent scratch resistance, magic resistance, water resistance, and alkali resistance, and has a low refractive index and excellent antireflection performance.

The above-mentioned silica-based particles are silica-based particles having a hollow ratio of 70% or more, and the hollow particles are excellent in transparency and antireflection performance because the inside is composed only of gas or gas and a porous substance. .. Therefore, it is also useful as a base material that requires transparency, such as a display board and a lighting device.

On the other hand, the conventional concept of a substrate with a transparent coating is schematically shown in FIG. As shown in FIG. 2, some conventional products have a low particle hollow ratio and a large particle size. Further, the unevenness of the upper surface of the film is larger than that of the present invention, and the external scattering due to the unevenness on the film surface is increased as compared with the present invention. Further, since the light scattering due to the particle size of the particles blended in the coating film becomes larger than that of the present invention, the internal scattering of the transparent coating film increases. Therefore, the transparent film may be whitened or the scratch resistance, magic resistance, water resistance, and alkali resistance may be lowered. In addition, the desired refractive index and antireflection performance may not be obtained.

The content of the silica-based particles in the transparent film is preferably in the range of 20 to 80% by mass, more preferably 30 to 70% by mass. The remaining components are matrix components. If the content of silica-based particles in the transparent film is less than 20% by mass, a transparent film having a sufficiently low refractive index may not be obtained. On the contrary, when the content of the silica-based particles in the transparent film exceeds 80% by mass, the strength and scratch resistance of the transparent film may be insufficient because the content of the matrix component described later is too small.

The film thickness of the transparent film is preferably in the range of 80 to 120 nm, more preferably 90 to 110 nm.
If the transparent film is too thin, the strength and scratch resistance of the film may be insufficient. In addition, the film may be too thin to obtain sufficient antireflection performance. If the transparent film is too thick, the desired antireflection performance may not be obtained.

The refractive index of the transparent film is preferably in the range of 1.15 to 1.40, more preferably 1.20 to 1.35. If the refractive index of the transparent film is lower than the above range, it is difficult to obtain it in terms of the film composition, and if the refractive index is large, the refractive index of the base material or the lower layer of the transparent film formed as needed. Although it depends on the refractive index of other films formed on the surface, the antireflection performance may be insufficient.

Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples.

[Example 1]
<Preparation of silica-based particles (1)>
After adding 946.4 g of pure water to 53.6 g of an aqueous dispersion of seed particles (manufactured by JGC Catalysts and Chemicals Co., _{Ltd .: SI-550, SiO 2} concentration 20.5% by mass), 1% by mass of sodium hydroxide was added. The pH was adjusted to 11.0 by addition. Then, the mixture was heated to 60 ° C. and held for about 30 minutes to obtain an aqueous dispersion of the nuclear particles (1). The average particle size of the nuclear particles (1) was 5 nm, and the sphericity was 1.1.
While holding the aqueous dispersion of the nuclear particles (1) at 60 ° C., 28.6 kg of an aqueous sodium silicate solution having a concentration of 0.75% by mass as _{SiO 2} and sodium aluminate having a concentration of 0.25% by mass as _{Al 2} O ₃ 28.6 kg of an aqueous solution was added over 16 hours to obtain a primary particle dispersion of _{a composite oxide (SiO 2} · Al ₂ O _3). The pH of the reaction solution at this time was 11.1. The average particle size was 15 nm.
Then, 129.4 kg of a sodium silicate aqueous solution having a concentration of 0.75 mass% as _{SiO 2} and 43.12 kg of a sodium aluminate aqueous solution having a concentration of 0.25 mass% as _{Al 2} O _{3 were added in 8 hours to cover the composite oxide.} A dispersion of particles was obtained. At this time, the pH of the reaction solution was 11.0.
Then, it was washed with an ultrafiltration membrane to a solid content concentration of 13% by mass, and then filtered with a capsule filter having an opening of 1 μm to obtain a coated composite oxide particle (1) dispersion liquid. At this time, the average particle size was 22 nm.
1,125 g of pure water was added to 500 g of the dispersion liquid of the coated composite oxide particles (1), and concentrated hydrochloric acid (concentration: 35.5% by mass) was further added dropwise to adjust the pH to 1.0, and dealumination treatment was performed. Next, while adding 10 L of a hydrochloric acid aqueous solution having a pH of 3 and 5 L of pure water, the aluminum salt dissolved in the ultrafiltration membrane was separated and washed to obtain an aqueous dispersion of silica-based particles (1-1) having a solid content concentration of 20% by mass. It was.
Next, aqueous ammonia was added to the silica-based particle (1-1) dispersion to adjust the pH of the dispersion to 10.5, then aged at 80 ° C. for 11 hours, cooled to room temperature, and cations. Ion exchange for 3 hours using 400 g of exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SK1B), and then ion exchange for 3 hours using 200 g of anion exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SA20A). Then, using 200 g of a cation exchange resin (manufactured by Mitsubishi Chemical Corporation: Diaion SK1B), ion exchange was performed at 80 ° C. for 3 hours for washing, and silica-based particles (1-2) having a solid content concentration of 20% by mass were used. ) Was obtained.
Then, an alcohol dispersion of silica-based particles (1-2) having a solid content concentration of 20% by mass was prepared by substituting ethanol for the solvent using an ultrafiltration membrane.
Add 6 g of 3-methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Industry Co., Ltd .: KBM-503) to 100 g of an alcohol dispersion of silica-based particles (1-2) having a solid content concentration of 20% by mass, and at 50 ° C. The heat treatment was carried out for 36 hours, and an alcohol dispersion of silica-based particles (1) having a solid content concentration of 20% by mass was prepared by substituting the solvent with ethanol again using an ultrafiltration membrane.
Table 1 shows each preparation step of the silica-based particles (1). Table 2 shows the physical properties of the average particle size, hollowness, sphericity, number ratio of irregularly shaped particles, refractive index and void ratio of the silica-based particles (1). Each measurement was carried out by the method shown in "Forms for Carrying Out the Invention".

<Manufacturing of paint (1) for forming a transparent film for antireflection>
50 g of the dispersion liquid obtained by diluting the alcohol dispersion liquid of the silica-based particles (1) with ethanol to a solid content concentration of 5% by mass, 1.67 g of an acrylic resin (Hitaroid 1007, manufactured by Hitachi Chemical Co., Ltd.), isopropanol and n-butanol. A coating material (1) for forming a transparent film was prepared by sufficiently mixing 52.6 g of a 1/1 (mass ratio) mixed solvent. The coating material (1) for forming a transparent film is shown in Table 3.

<Preparation of coating liquid for forming hard coat film>
Silica sol dispersion (manufactured by JGC Catalysts and Chemicals Co., Ltd .; Cataloid SI-30; average particle diameter 12 nm, SiO ₂ concentration 40.5% by mass, dispersion medium: isopropanol, particle refractive index 1.46) γ-meth 1.88 g of acrylooxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Industry Co., Ltd .: KBM-503, SiO ₂ concentration 81.2% by mass) is mixed, 3.1 g of ultrapure water is added, and the mixture is stirred at 50 ° C. for 20 hours. A 12 nm silica sol dispersion was surface-treated (solid content concentration: 40.5% by mass).
Then, the solvent was replaced with propylene glycol monopropyl ether (PGME) by a rotary evaporator (solid content concentration: 40.5% by mass).
Next, 51.85 g of this propylene glycol monopropyl ether dispersion of silica sol having a solid content concentration of 40.5% by mass, and 18.90 g of dihexaerythritol triacetate (manufactured by Kyoeisha Chemical Co., Ltd .: DPE-6A), 1.6. -Hexanediol diacrylate (manufactured by Kyoeisha Chemical Co., Ltd .; light acrylate SR-238F) 2.10 g, silicone leveling agent (manufactured by Kusumoto Kasei Co., Ltd .; Disparon 1610) 0.01 g, and photopolymerization initiator (Ciba Japan (Ciba Japan) Manufactured by: Irgacure 184, dissolved in 10% by mass of solid content with PGME) 12.60 g and 14.54 g of PGME were sufficiently mixed to prepare a coating liquid for forming a hard coat film having a solid content of 42.0% by mass. ..

<Manufacturing of base material with transparent coating for antireflection (1)>
The coating liquid for forming a hard coat film is applied to a TAC film (manufactured by Panac Co., Ltd .: FT-PB80UL-M, thickness: 80 μm, refractive index: 1.51) by the bar coater method (# 18), and the temperature is 80 ° C. After drying for 120 seconds, a hard coat film was formed by irradiating with ultraviolet rays of ^{300 mJ / cm 2 and curing.} The film thickness of the hard coat film was 8 μm.
Then, the reflection preventive transparent film-forming coating liquid (1) was coated with a bar coater method (# 4), and was dried for 120 seconds at 80 ° C., and irradiated with ultraviolet rays of 600 mJ / cm ² under _{N 2} It was cured to prepare a base material (1) with a transparent film for antireflection. The film thickness of the antireflection transparent film at this time was 100 nm. Total light transmittance, haze, light reflectance of light having a wavelength of 550 nm, refractive index of the film, adhesion and pencil hardness, scratch resistance, whitening, magic resistance, and water resistance of the base material (1) with a transparent film for antireflection. Table 4 shows the evaluation results of the property and alkali resistance. The total light transmittance and haze were measured by a haze meter (manufactured by Suga Test Instruments Co., Ltd.), and the reflectance was measured by a spectrophotometer (JASCO Corporation, Ubest-55). The refractive index of the coating film was measured by an ellipsometer (EMS-1 manufactured by ULVAC, Inc.).

《Adhesion》
When 11 parallel scratches are made on the surface of the transparent coating base material (1) with a knife at intervals of 1 mm in length and width to make 100 squares, cellophane tape is adhered to the squares, and then the cellophane tape is peeled off. The adhesion was evaluated by classifying the number of squares in which the coating film did not peel off and remained in the following three stages. The results are shown in the table.
Number of remaining squares 90 or more: ◎
Number of remaining squares 85-89: ○
Number of remaining squares 84 or less: △

"Pencil hardness"
The pencil hardness was measured with a pencil hardness tester according to JIS K 5400. That is, a pencil was set at an angle of 45 degrees with respect to the surface of the transparent coating film, a predetermined load was applied, and the pencil was pulled at a constant speed to observe the presence or absence of scratches.

《Measurement of scratch resistance》
Using # 0000 steel wool, the film was slid 50 times under a load of 1,000 g / cm ² , the surface of the film was visually observed, evaluated according to the following criteria, and the results are shown in the table.
Evaluation criteria:
No streaky scratches: ◎
Slight streaks are seen: ○
Many streaky scratches are observed: △
The entire surface has been scraped: ×

<< Evaluation of bleaching >>
The surface of the coating film was visually observed from an angle (about 20 °), and the evaluation was evaluated in the following four stages.
Evaluation criteria:
No bleaching: ◎
There is some bleaching: ○
Partially whitened: △
Fully whitened: ×

《Evaluation of magic resistance》
Draw a line on the surface of the coating film with an oil-based magic to a length of 3 cm, leave it for 1 minute, and then visually check the traces when wiping it off.
Evaluation criteria:
I can't see the magic marks: ◎
Almost no magic marks can be seen: ○
Part of the magic mark can be seen: △
Magic marks can be seen on the entire surface: ×

<< Evaluation of water resistance >>
Drop a drop of pure water on the surface of the coating film with a dropper, leave it for 3 hours, wipe off the water droplets, and visually check if any traces remain where the water droplets were.
Evaluation criteria:
No traces of water drops: ○
Some water droplets are observed: △
Water droplets can be clearly seen: ×

<< Evaluation of alkali resistance >>
Drop a drop of 1% NaOH aqueous solution on the surface of the coating film with a dropper, leave it for 1 hour, wipe off the water droplets, and visually check if any marks remain where the water droplets were.
Evaluation criteria:
No traces: ○
Some traces are observed: △
Traces can be clearly seen: ×

[Example 2]
<Preparation of silica-based particles (2)>
300 g of a cation exchange resin (manufactured by Mitsubishi Chemical Corporation: Diaion SK1B) was added to 1000 g of an aqueous sodium silicate solution having a concentration of 3.5 mass% as SiO _{2, and the mixture was stirred at room temperature for 1 hour, and then the ion exchange resin was separated.} , Aqueous silicate solution was obtained. Next, 4.2 g of an aqueous silicic acid solution, 62.5 g of pure water, and 13.1 g of sodium silicate were mixed and aged at 70 ° C. for 1 hour, and then 141.4 g of an aqueous silicic acid solution was added over 6 hours while being maintained at 70 ° C. The addition gave seed particles (2) having an average particle diameter of 3 nm. 1.1% by mass of seed particles (2) The pH was adjusted to 11.0 by adding 1% by mass of sodium hydroxide to 1.0 kg of the aqueous dispersion. Then, the mixture was heated to 60 ° C. and held for about 30 minutes to obtain an aqueous dispersion of the nuclear particles (2). The average particle size of the nuclear particles (2) was 3 nm, and the sphericity was 1.2.
While holding the aqueous dispersion of the nuclear particles (2) at 60 ° C., 4.0 kg of an aqueous sodium silicate solution having a concentration of 0.75% by mass as _{SiO 2} and sodium aluminate having a concentration of 0.25% by mass as _{Al 2} O ₃ 4.0 kg of an aqueous solution was added in 18 hours to obtain a primary particle dispersion of _{a composite oxide (SiO 2} · Al ₂ O _3). The pH of the reaction solution at this time was 11.0. The average particle size was 5 nm.
Then, 78.4 kg of a sodium silicate aqueous solution having a concentration of 0.75 mass% as _{SiO 2} and 26.1 kg of a sodium aluminate aqueous solution having a concentration of 0.25 mass% as _{Al 2} O _{3 were added in 8 hours to cover the composite oxide.} A dispersion of particles was obtained. At this time, the pH of the reaction solution was 11.0.
Then, it was washed with an ultrafiltration membrane to a solid content concentration of 13% by mass, and then filtered with a capsule filter having an opening of 1 μm to obtain a coated composite oxide particle (2) dispersion. At this time, the average particle size was 12 nm.
Then, silica-based particles (2) were obtained in the same manner as in Example 1 except that the coated composite oxide particles (2) were used.
A coating material for forming a transparent film (2) and a base material with a transparent film for antireflection (2) were produced in the same manner as in Example 1 except that silica-based particles (2) were used.

[Example 3]
<Preparation of silica-based particles (3)>
After adding 963.9 g of pure water to 36.1 g of an aqueous dispersion of seed particles (manufactured by JGC Catalysts and Chemicals Co., _{Ltd .: SI-30, SiO 2} concentration 30.5% by mass), 1% by mass of sodium hydroxide was added. The pH was adjusted to 11.0 by addition. Then, the mixture was heated to 60 ° C. and held for about 30 minutes to obtain an aqueous dispersion of the nuclear particles (3). The average particle size of the nuclear particles (3) was 12 nm, and the sphericity was 1.0.
While holding the aqueous dispersion of the nuclear particles (3) at 60 ° C., 7.7 kg of an aqueous solution of sodium silicate having a concentration of 0.75% by mass as _{SiO 2} and sodium aluminate having a concentration of 0.25 mass% as _{Al 2} O ₃ 7.7 kg of an aqueous solution was added in 18 hours to obtain a primary particle dispersion of _{a composite oxide (SiO 2} · Al ₂ O _3). The pH of the reaction solution at this time was 11.2. The average particle size was 24 nm.
Then, 38.3 kg of a sodium silicate aqueous solution having a concentration of 0.75 mass% as _{SiO 2} and 12.8 kg of a sodium aluminate aqueous solution having a concentration of 0.25 mass% as _{Al 2} O _{3 were added in 8 hours to cover the composite oxide.} A dispersion of particles was obtained. At this time, the pH of the reaction solution was 11.0.
Then, it was washed with an ultrafiltration membrane to a solid content concentration of 13% by mass, and then filtered with a capsule filter having an opening of 1 μm to obtain a coated composite oxide particle (3) dispersion liquid. At this time, the average particle size was 12 nm.
Then, silica-based particles (3) were obtained in the same manner as in Example 1 except that the coated composite oxide particles (3) were used.
A coating material for forming a transparent film (3) and a base material with a transparent film for antireflection (3) were produced in the same manner as in Example 1 except that silica-based particles (3) were used.

[Example 4]
<Preparation of silica-based particles (4)>
After adding 946.4 g of pure water to 53.6 g of an aqueous dispersion of seed particles (manufactured by JGC Catalysts and Chemicals Co., _{Ltd .: SI-550, SiO 2} concentration 20.5% by mass), 1% by mass of sodium hydroxide was added. The pH was adjusted to 11.0 by addition. Then, the mixture was heated to 60 ° C. and held for about 30 minutes to obtain an aqueous dispersion of nuclear particles (4). The average particle size of the nuclear particles (4) was 5 nm, and the sphericity was 1.0.
While holding the aqueous dispersion of the nuclear particles (4) at 60 ° C., 28.6 kg of an aqueous sodium silicate solution having a concentration of 0.75% by mass as _{SiO 2} and sodium aluminate having a concentration of 0.25% by mass as _{Al 2} O ₃ 28.6 kg of an aqueous solution was added in 18 hours to obtain a primary particle dispersion of _{a composite oxide (SiO 2} · Al ₂ O _3). The pH of the reaction solution at this time was 11.2. The average particle size was 15 nm.
Then, 141.6 kg of an aqueous sodium silicate solution having a concentration of 0.75% by mass as _{SiO 2} and 75.0 kg of an aqueous solution of sodium aluminate having a concentration of 0.25% by mass as _{Al 2} O _{3 were added in 8 hours to cover the composite oxide.} A dispersion of particles was obtained. At this time, the pH of the reaction solution was 11.0.
Then, it was washed with an ultrafiltration membrane to a solid content concentration of 13% by mass, and then filtered with a capsule filter having an opening of 1 μm to obtain a coated composite oxide particle (4) dispersion. At this time, the average particle size was 26 nm.
Then, silica-based particles (4) were obtained in the same manner as in Example 1 except that the coated composite oxide particles (4) were used.
A coating material for forming a transparent film (4) and a base material with a transparent film for antireflection (4) were produced in the same manner as in Example 1 except that silica-based particles (4) were used.

[Example 5]
<Preparation of silica-based particles (5)>
After adding 946.4 g of pure water to 53.6 g of an aqueous dispersion of seed particles (manufactured by JGC Catalysts and Chemicals Co., _{Ltd .: SI-550, SiO 2} concentration 20.5% by mass), 1% by mass of sodium hydroxide was added. The pH was adjusted to 11.0 by addition. Then, the mixture was heated to 80 ° C. and held for about 30 minutes to obtain an aqueous dispersion of nuclear particles (5). The average particle size of the nuclear particles (5) was 5 nm, and the sphericity was 1.4.
Silica-based particles (5) were obtained in the same manner as in Example 1 except that the nuclear particles (5) were used.
A coating material for forming a transparent film (5) and a base material with a transparent film for antireflection (4) were produced in the same manner as in Example 1 except that silica-based particles (5) were used.

[Example 6]
<Preparation of silica-based particles (6)>
After adding 946.4 g of pure water to 53.6 g of an aqueous dispersion of seed particles (manufactured by JGC Catalysts and Chemicals Co., _{Ltd .: SI-550, SiO 2} concentration 20.5% by mass), 1% by mass of sodium hydroxide was added. The pH was adjusted to 11.0 by addition. Then, the mixture was heated to 60 ° C. and held for about 30 minutes to obtain an aqueous dispersion of nuclear particles (6). The average particle size of the nuclear particles (6) was 5 nm, and the sphericity was 1.0.
While holding the aqueous dispersion of the nuclear particles (6) at 60 ° C., 5.3 kg of an aqueous sodium silicate solution having a concentration of 0.75 mass% as _{SiO 2} and aluminate having a concentration of 0.25 mass% as _{Al 2} O ₃ 5.3 kg of an aqueous sodium solution was added over 18 hours to obtain a primary particle dispersion of _{a composite oxide (SiO 2} , Al ₂ O _3). The pH of the reaction solution at this time was 11.2. The average particle size was 9 nm.
Then, 148.6 kg of a sodium silicate aqueous solution having a concentration of 0.75 mass% as _{SiO 2} and 78.7 kg of a sodium aluminate aqueous solution having a concentration of 0.25 mass% as _{Al 2} O _{3 were added in 8 hours to cover the composite oxide.} A dispersion of particles was obtained. At this time, the pH of the reaction solution was 11.0.
Then, it was washed with an ultrafiltration membrane to a solid content concentration of 13% by mass, and then filtered with a capsule filter having an opening of 1 μm to obtain a coated composite oxide particle (6) dispersion. At this time, the average particle size was 26 nm.
Then, silica-based particles (6) were obtained in the same manner as in Example 1 except that the coated composite oxide particles (6) were used.
A coating material for forming a transparent film (6) and a base material with a transparent film for antireflection (6) were produced in the same manner as in Example 1 except that silica-based particles (6) were used.

[Example 7]
<Preparation of silica-based particles (7)>
After adding 946.4 g of pure water to 53.6 g of an aqueous dispersion of seed particles (manufactured by JGC Catalysts and Chemicals Co., _{Ltd .: SI-550, SiO 2} concentration 20.5% by mass), 1% by mass of sodium hydroxide was added. The pH was adjusted to 11.0 by addition. Then, the mixture was heated to 60 ° C. and held for about 30 minutes to obtain an aqueous dispersion of nuclear particles (7). The average particle size of the nuclear particles (7) was 5 nm, and the sphericity was 1.0.
While holding the aqueous dispersion of the nuclear particles (7) at 60 ° C., 236.5 kg of an aqueous sodium silicate solution having a concentration of 0.75% by mass as _{SiO 2} and 0.25% by mass of sodium aluminate as _{Al 2} O ₃ 236.5 kg of an aqueous solution was added in 18 hours to obtain a primary particle dispersion of _{a composite oxide (SiO 2} · Al ₂ O _3). The pH of the reaction solution at this time was 11.2. The average particle size was 30 nm.
Then, 369.0 kg of a sodium silicate aqueous solution having a concentration of 0.75 mass% as _{SiO 2} and 195.4 kg of an aqueous sodium aluminate solution having a concentration of 0.25 mass% as _{Al 2} O _{3 were added in 8 hours to cover the composite oxide.} A dispersion of particles was obtained. At this time, the pH of the reaction solution was 11.4.
Then, it was washed with an ultrafiltration membrane to a solid content concentration of 13% by mass, and then filtered with a capsule filter having an opening of 1 μm to obtain a coated composite oxide particle (7) dispersion. At this time, the average particle size was 40 nm.
Then, silica-based particles (7) were obtained in the same manner as in Example 1 except that the coated composite oxide particles (7) were used.
A coating material for forming a transparent film (7) and a base material with a transparent film for antireflection (7) were produced in the same manner as in Example 1 except that silica-based particles (7) were used.

[Example 8]
<Preparation of silica-based particles (8)>
After adding 963.9 g of pure water to 36.1 g of an aqueous dispersion of seed particles (manufactured by JGC Catalysts and Chemicals Co., _{Ltd .: SI-30, SiO 2} concentration 30.5% by mass), 1% by mass of sodium hydroxide was added. Addition was added to adjust the pH to 12.5. Then, the mixture was heated to 95 ° C. and held for about 30 minutes to obtain an aqueous dispersion of nuclear particles (8). The average particle size of the nuclear particles (8) was 12 nm, and the sphericity was 1.3.
Then, silica-based particles (8) were obtained in the same manner as in Example 3 except that the nuclear particles (8) were used.
A coating material for forming a transparent film (8) and a base material with a transparent film for antireflection (8) were produced in the same manner as in Example 1 except that silica-based particles (8) were used.

[Comparative Example 1]
<Preparation of silica-based particles (R1)>
After adding 946.4 g of pure water to 53.6 g of an aqueous dispersion of seed particles (manufactured by JGC Catalysts and Chemicals Co., _{Ltd .: SI-550, SiO 2} concentration 20.5% by mass), 1% by mass of sodium hydroxide was added. Addition was made to adjust the pH to 12.5. Then, the mixture was heated to 95 ° C. and held for about 30 minutes to obtain an aqueous dispersion of nuclear particles (R1). The average particle size of the nuclear particles (R1) was 5 nm, and the sphericity was 1.8.
Silica-based particles (R1) were obtained in the same manner as in Example 1 except that the nuclear particles (R1) were used.
A coating material for forming a transparent film (R1) and a base material with a transparent film for antireflection (R1) were produced in the same manner as in Example 1 except that silica-based particles (R1) were used.

[Reference example 1]
<Preparation of silica-based particles (E1)>
After adding 946.4 g of pure water to 53.6 g of an aqueous dispersion of seed particles (manufactured by JGC Catalysts and Chemicals Co., _{Ltd .: SI-550, SiO 2} concentration 20.5% by mass), 1% by mass of sodium hydroxide was added. The pH was adjusted to 11.0 by addition. Then, the mixture was heated to 60 ° C. and held for about 30 minutes to obtain an aqueous dispersion of nuclear particles (E1). The average particle size of the nuclear particles (E1) was 5 nm, and the sphericity was 1.0.
While holding the aqueous dispersion of the nuclear particles (E1) at 60 ° C., 562.1 kg of an aqueous sodium silicate solution having a concentration of 0.75 mass% as _{SiO 2} and sodium aluminate having a concentration of 0.25 mass% as _{Al 2} O ₃ 562.1 kg of an aqueous solution was added in 18 hours to obtain a primary particle dispersion of _{a composite oxide (SiO 2} · Al ₂ O _3). The pH of the reaction solution at this time was 11.2. The average particle size was 40 nm.
Then, coated complex oxide was added as SiO ₂ concentration 0.25 wt% of an aqueous sodium aluminate solution 540.5kg as concentration 0.75 wt% aqueous solution of sodium silicate 1021.0kg and _Al 2 _{O 3} at 8 hours A dispersion of particles was obtained. At this time, the pH of the reaction solution was 11.5.
Then, it was washed with an ultrafiltration membrane to a solid content concentration of 13% by mass, and then filtered with a capsule filter having an opening of 1 μm to obtain a coated composite oxide particle (E1) dispersion. At this time, the average particle size was 40 nm.
Then, silica-based particles (E1) were obtained in the same manner as in Example 1 except that the coated composite oxide particles (E1) were used.
A coating material for forming a transparent film (E1) and a base material with a transparent film for antireflection (E1) were produced in the same manner as in Example 1 except that silica-based particles (E1) were used.

Claims (10)

The average particle size is 5 to 40 nm , the sphericity is 1.0 to 1.5, the porosity is 15 to 50% , and the ratio of the number of hollow particles to the total number of hollow particles and solid particles (hollow). A method for producing a dispersion of silica-based particles having a porosity of 70% or more.
Start of addition to a dispersion containing silica nuclei having an average particle size of 3 to 25 nm and a sphericity of 1.0 to 1.5, which are maintained at a temperature of 70 ° C. or lower and a pH of 11.5 or lower. The solid content concentration of the dispersion liquid from to the end is maintained at 0.1 to 0.9% by mass, and the particle growth rate from the nuclear particles to the composite oxide particles is performed at 0.1 to 10 nm / hour. As described above, the first step of preparing a dispersion liquid containing composite oxide particles by simultaneously adding at least one of a silicate aqueous solution and an acidic silicic acid solution and an inorganic compound aqueous solution containing no silicon.
A second step of adding a silica source to the dispersion liquid containing the composite oxide particles obtained in the first step to prepare a dispersion liquid containing the coated composite oxide particles coated with a layer containing silica.
The third step of adding an acid to the dispersion liquid containing the coated composite oxide particles obtained in the second step to remove the element derived from the inorganic compound contained in the coated composite oxide particles, and the third step.
The fourth step of hydrothermally treating the dispersion liquid containing the particles obtained in the third step under alkaline conditions, and
A method for producing a silica-based particle dispersion liquid. The method for producing a silica-based particle dispersion liquid according to claim 1, wherein the composite oxide particles have an average particle diameter of 3 to 35 nm and a sphericity of 1.0 to 1.5. In the first step, the molar ratio MO _X / SiO ₂ when the silica derived from the silicate aqueous solution and the acidic silicic acid solution is _{represented by SiO 2} and the inorganic compound derived from the inorganic compound aqueous solution is _{represented by MO X} as an oxide is obtained. The method for producing a silica-based particle dispersion according to claim 1 or 2 , wherein the content is 0.15 to 3.0. The second step is characterized in that at least one of a silicate aqueous solution and an acidic silicic acid solution and an inorganic compound aqueous solution containing no silicon are added to form a coating layer containing silica in the composite oxide particles. The method for producing a dispersion of silica-based particles according to any one of 1 to 3. In the second step, the coating layer containing silica is formed on the composite oxide particles at a solid content concentration of 0.1 to 0.9% by mass, and the formation rate of the coating layer on the composite oxide particles is 0.1. The method for producing a dispersion liquid of silica-based particles according to any one of claims 1 to 4 , wherein the operation is carried out at 10 nm / hour. The average particle size is 5 to 40 nm , the sphericity is 1.0 to 1.5, the void ratio is 15 to 50% , and the ratio of the number of hollow particles to the total number of hollow particles and solid particles (hollow). A dispersion liquid of silica-based particles, which comprises silica-based particles having a ratio) of 70% or more. The dispersion liquid of silica-based particles according to claim 6 , wherein the silica-based particles have an organic group directly bonded to a silicon atom on the surface thereof. A coating liquid for forming a transparent film, which comprises the silica-based particles according to claim 6 or 7, a matrix-forming component, and a polar solvent. The concentration of the silica-based particles is 0.4 to 54% by mass as a solid content.
The concentration of the matrix-forming component is 0.1 to 36% by mass, and the concentration is 0.1 to 36% by mass.
The coating liquid for forming a transparent film according to claim 8 , wherein the total solid content concentration is 1 to 60% by mass. A base material with a transparent coating having a base material and a transparent coating film formed on the base material and containing the silica-based particles according to claim 6 or 7 and a matrix component.
A base material with a transparent coating, wherein the content of silica-based particles in the transparent coating is 20 to 80% by mass.

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