JP2012162426A - Dispersion sol of silica-based fine particle, method for producing the dispersion sol, and coating material composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide dispersion sol of silica-based fine particles, which is extremely stable in an acidic region, a method for producing the dispersion sol, and a coating material composition including the dispersion sol.SOLUTION: The dispersion sol includes silica-based fine particles with an anisotropic shape, and a surface of the silica-based fine particle bears a negative charge, further the surface of the silica-based fine particle is modified with aluminum, wherein an amount of modification with aluminum is within a range of 0.01×10to 2.0×10mol/mper unit surface area of the silica-based fine particle in terms of AlO. An average particle size (D1) of the silica-based fine particle measured by the dynamic light scattering method is in the range of 15-70 nm, an average particle size (D2) thereof measured by the BET method is in the range of 10-50 nm, and a value of degree of heteromorphism (D1/D2) thereof is in the range of 1.55-4.00.

Description

  The present invention relates to a dispersion sol containing anisotropically shaped silica-based fine particles. The present invention also relates to a method for producing the dispersed sol and a coating composition containing the dispersed sol.

It is known that silica sol is blended in a coating film as, for example, a refractive index adjusting material or an antifouling material. However, when conventional silica sol is blended in a coating composition, the coating composition tends to become cloudy or thick. There was a problem that the transparency of the coating film was lowered.
Therefore, it has been demanded to develop a silica sol having high stability in the coating composition.
As a means for improving the stability of silica sol, a method of modifying the surface of silica particles with aluminum is known.

For example, Patent Document 1 discloses a method of adding an acidic silicic acid solution and an aluminum compound aqueous solution to a SiO ₂ -containing alkali aqueous solution or an alkali metal oxide aqueous solution, or an acidic silicic acid solution in which an aluminum compound is mixed as a SiO ₂ -containing alkaline aqueous solution or an alkali. A method is described in which an aluminum compound-containing alkaline silica sol obtained by a method of adding to an aqueous metal hydroxide solution is deionized with a cation exchange resin.

Patent Document 2 discloses a silica sol having a colloidal silica particle size of 4 to 30 millimicrons, a pH of _{2 to} 9, and an aluminum content of 0 to 0.0008 in an Al ₂ O ₃ / SiO ₂ molar ratio of Al ₂ O. ₃ / SiO ₂ molar ratio is in the range of 0.0006 to 0.004, after adding an aqueous alkali aluminate solution, heating at 80 to 250 ° C. for 0.5 to 20 hours, and then cation exchange resin or A method is described in which an acidic silica sol having a pH of 2 to 5 is obtained by contacting a cation exchange resin and an anion exchange resin.

JP-A-63-123807 Japanese Patent Laid-Open No. 06-199515

That is, the acidic silica sol obtained by the production methods described in Patent Document 1 and Patent Document 2 is a silica sol that is stable in the acidic region, but it is necessary to develop a silica sol that is further excellent in this stability, particularly at a high concentration. there were.
Furthermore, it has been desired to further improve the performance of a coating film containing silica sol.

The dispersion sol of silica-based fine particles of the present invention is a dispersion sol containing anisotropically-shaped silica-based fine particles, the surface of the silica-based fine particles has a negative charge, and the surface of the silica-based fine particles is modified with aluminum. The modification amount of the aluminum is characterized by being in the range of 0.01 × 10 ^{−6 to} 2.0 × 10 ⁻⁶ mol / m ² per unit surface area of the silica-based fine particles in terms of Al ₂ O ₃ conversion. To do.
The average particle diameter (D1) measured by the dynamic light scattering method of the silica-based fine particles is in the range of 15 to 70 nm, the average particle diameter (D2) measured by the BET method is in the range of 10 to 50 nm, The degree of irregularity (D1 / D2) is preferably in the range of 1.55 to 4.00.

  The coating composition of the present invention comprises (A) a dispersion sol of the silica-based fine particles, and (B) a binder component.

The method for producing a silica-based fine particle-dispersed sol of the present invention is a method for producing a dispersed sol containing anisotropically-shaped silica-based fine particles whose surface is modified with aluminum,
(1) An aqueous solution of aluminate in an alkaline silica sol having a pH of 9.0 to 11.5 containing anisotropic fine silica particles or fine particles containing silica as a main component, and a silicon component contained in the silica sol as SiO _2. In addition, when the aluminum contained in the aluminate is represented by Al ₂ O ₃ , the molar ratio (Al ₂ O ₃ / SiO ₂ ) is mixed at such a ratio as 0.0005 to 0.050. The process of
(2) A step of heating the mixture obtained in the above step to a temperature of 60 to 200 ° C. and stirring for 0.5 to 20 hours,
It is characterized by including.

The molar ratio (Al ₂ O ₃ / SiO ₂ ) is preferably in the range of 0.005 to 0.050.
Furthermore, the mixed solution obtained by the following step (3) and the step (2) is brought into contact with a cation exchange resin, and the alkali metal ions contained in the mixed solution are ion-exchanged to remove the pH of the mixed solution. It is preferable to include the process of adjusting to the range of 3.0-6.0.

The dispersion sol of silica-based fine particles according to the present invention has a dispersion stability even in an acidic pH region because the surface of the silica fine particles is modified with a form in which very high-density aluminum has a negative charge. It is very high, can be concentrated to a high concentration, and has excellent transparency.
The coating film obtained from the coating composition containing the silica-based fine particle-dispersed sol and the binder component has a very high film hardness and scratch resistance due to the strong dispersibility and concentration stability of the silica-based fine particles in the film. Excellent adhesion, heat resistance, impact resistance, and transparency.
Furthermore, since the silica-based fine particles have an anisotropic shape, the effect of improving the film hardness of the coating film is particularly excellent.

Hereinafter, the present invention will be specifically described.
Dispersion sol of silica-based fine particles The silica-based fine particle dispersion sol according to the present invention is a dispersion sol containing anisotropically-shaped silica-based fine particles, the surface of the silica-based fine particles having a negative charge, and the silica-based fine particle The surface of the fine particles is modified with aluminum, and the modification amount of the aluminum is 0.01 × 10 ^{−6 to} 2.0 × 10 ⁻⁶ mol / m ² per unit surface area of the silica-based fine particles in terms of Al ₂ O ₃ conversion. It is characterized by being in the range of.
Such a dispersion sol of silica-based fine particles is stable even in an acidic state, has high stability in a coating composition, and is extremely excellent in hardness, scratch resistance and transparency of the resulting coating film.

The silica-based fine particles are preferably anisotropic.
By blending the silica-based fine particles with such a shape into the coating composition, the film hardness of the obtained coating film can be remarkably improved.
Here, the anisotropic shape is a shape lacking isotropy, that is, a three-dimensional asymmetric shape, for example, a shape in which particles are stretched and / or curved in one direction, or a plurality of particles are fused. And the like.
In addition, a shape in which a part of the particle is missing, an elliptical shape, a rugby ball shape, a bell shape, a bispherical shape, a grape bunch shape, a cocoon shape, a jade shape or the like are also included.

The average particle diameter (D1) measured by the dynamic light scattering method of the silica-based fine particles is in the range of 15 to 70 nm, the average particle diameter (D2) measured by the BET method is in the range of 10 to 50 nm, The degree of irregularity (D1 / D2) is preferably in the range of 1.55 to 4.00.
By blending such silica-based fine particles into the coating composition, the film hardness of the resulting coating film is improved.
When the average particle diameter (D1) is less than 15 nm, the coating composition may thicken, and when the average particle diameter (D1) exceeds 70 nm, the transparency of the coating film may decrease. It may not be preferable.
When the average particle size (D2) is less than 10 nm, the coating composition may thicken. When the average particle size (D2) exceeds 50 nm, the transparency of the coating film may be reduced. This is not preferable.

Further, when the degree of irregularity (D1 / D2) exceeds 1.55, the film hardness may decrease, and when the degree of irregularity (D1 / D2) exceeds 4.00, the scratch resistance may decrease. Therefore, it is not preferable.
The irregularity is a scale representing the anisotropy of the three-dimensional shape of the silica-based fine particles, and means that the higher the irregularity, the larger the shape deviation in a specific direction.
Moreover, it is desirable that the anisotropic shape in the present invention does not include a chain particle in which a plurality of spherical particles are connected. The chain particles are not preferable because the irregularity may exceed 4.00.

The modification amount of aluminum modified on the surface of the silica-based fine particles is 0.01 × 10 ^{−6 to} 2.0 × 10 on an Al ₂ O ₃ conversion basis when expressed per unit surface area of the silica-based fine particles. ^It is preferably ⁻⁶ mol / m ² , more preferably in the range of 0.05 × 10 ^{−6 to} 1.8 × 10 ⁻⁶ mol / m ² . When the modification amount is less than 0.01 × 10 ⁻⁶ mol / m ² , the stability of the silica-based fine particle-dispersed sol and the film strength of the coating film are not preferable. Moreover, it is not preferable that the modification amount exceeds 2.0 × 10 ⁻⁶ mol / m ² because the transparency of the silica-based fine particle-dispersed sol may be lowered or the stability may be lowered.

The silica-based fine particles preferably have a negative charge on the surface.
The amount of negative charge existing on the surface of the silica-based fine particles is 0.01 to 1.1 μeq / m ² , more preferably 0, per specific surface area of the silica-based fine particles when the pH of the dispersion sol is 5.0. It is preferable that it is in the range of 0.05 to 1.0 μeq / m ² . When the negative charge amount is less than 0.01 μeq / m ² , the stability of the dispersion sol of silica-based fine particles may be reduced, and the hardness and scratch resistance of the coating film may be reduced. Is more than 1.1 μeq / m ² , it is not preferable because the surface charge layer of the silica-based fine particles becomes thick and the stability of the dispersed sol and the transparency of the coating film may decrease.

  The pH of the silica-based fine particle dispersion sol is preferably in the range of 3.0 to 6.0, more preferably 3.5 to 5.0. When the pH is less than 3.0, aluminum modified with silica-based fine particles dissolves and the stability of the silica-based fine particle-dispersed sol decreases, which is not preferable. On the other hand, if the pH exceeds 6.0, the silica-based fine particle-dispersed sol tends to gel, which is not preferable.

It is preferable that at least a part of the aluminum that modifies the silica-based fine particles forms a silica-alumina-based composite oxide including a crystal structure represented by the following formula (I).
Si
｜
O
｜
Si-O-Al-X (where X is O or OH) (I)
｜
O
｜
Si
Alkali metal ions or hydrogen ions may be present in the vicinity of Al in the formula (I). When at least a part of the aluminum is in the form of the above formula (I), a negative charge can be imparted to the surface of the silica-based fine particles.

In the present invention, since the silica-alumina composite oxide is formed from a silicic acid monomer and aluminate ions, the silica-alumina composite oxide having a structure as described in (I) above is converted to silica. It can be formed on the surface of fine particles.
If the form of the aluminum that modifies the silica-based fine particles does not include the structure of the above formula (I), but takes the structure of aluminum hydroxide or aluminum oxide, the silica-alumina composite This is not preferable because the uniformity of the oxide is reduced and the surface of the silica-based fine particles has a positive charge.

The solid content concentration of the dispersion sol of the silica-based fine particles is preferably in the range of 5 to 60% by weight, more preferably 20 to 50% by weight on the basis of SiO ₂ conversion. When the solid content concentration is less than 5% by weight, the film hardness of the curable coating film obtained from the coating composition containing the dispersed sol is decreased, and when the solid content concentration exceeds 60% by weight, the dispersion sol Since stability may fall, it is not preferable.

Although the haze of the dispersion sol of the silica-based fine particles varies depending on the concentration, when the solid content concentration of the dispersion sol is 30% by weight in terms of SiO ₂ , it is preferably in the range of 0.5 to 20%. . When the haze is less than 0.5% when the solid content is 30% by weight, it is necessary to use at least ultrafine particles having an average particle diameter of less than 5 nm, and the viscosity of the silica-based fine particle-dispersed sol increases. It is not preferable. On the other hand, if the haze exceeds 20%, the transparency of the curable coating film obtained from the dispersion sol and the coating composition containing the dispersion sol may be unfavorable.

The dispersion medium of the silica-based fine particle dispersion sol according to the present invention includes water and / or alcohols such as methanol, ethanol, butanol, propanol, isopropyl alcohol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and the like. It is preferably at least one organic compound selected from ketones such as ethers, methyl ethyl ketone, and γ-butyrolactone.
In addition, as a method for producing a dispersion sol of silica-based fine particles according to the present invention, it is preferable to use the method for producing a silica fine particle water-dispersed sol and the method for producing a silica fine particle organic solvent-dispersed sol described in this specification.

Further, the silica-based fine particles contained in the dispersion sol of the silica-based fine particles may be further surface-treated with a known surface treatment agent such as a silane coupling agent.
Since the silica-based fine particle-dispersed sol according to the present invention can be used stably in the acidic region, it is a filler for ceramic fiber raw materials or binders, chromium-based surface treatment agents, acidic abrasives, various paints, and resin compositions. Can be used. Further, since it has high dispersion stability in an organic binder and is excellent in transparency and strength when formed into a film, it can be particularly suitably used as a coating for forming a curable coating film such as a hard coat film.

Method for Producing Silica-Based Fine Particle Water Dispersed Sol The method for producing a silica-based fine particle dispersed sol according to the present invention includes the following steps (1) and (2).
(1) An aqueous solution of aluminate in an alkaline silica sol having a pH of 9.0 to 11.5 containing anisotropic fine silica particles or fine particles containing silica as a main component, and a silicon component contained in the silica sol as SiO _2. In addition, when the aluminum contained in the aluminate is represented by Al ₂ O ₃ , the molar ratio (Al ₂ O ₃ / SiO ₂ ) is mixed at such a ratio as 0.0005 to 0.050. The process of
(2) The process of heating the liquid mixture obtained by the said process to the temperature of 60-200 degreeC, and stirring for 0.5 to 20 hours.

The dispersion sol of silica-based fine particles obtained by the manufacturing method including such steps has a high surface negative charge density because the surface of the silica-based fine particles is modified with high density in a form in which aluminum has a negative charge. The dispersion sol has high stability and transparency, and a coating film obtained from a coating composition containing the dispersion sol is excellent in film hardness, scratch resistance and adhesion.
Furthermore, the film hardness of the coating film can be remarkably improved by selecting an anisotropic shape as the shape of such high negative charge density silica-based fine particles.

Next, each step will be specifically described.
Step (1) : In this step, an aqueous solution of aluminate is contained in an alkaline silica sol having a pH of 9.0 to 11.5 and containing anisotropically shaped silica fine particles or fine particles mainly composed of silica. When the silicon component to be expressed is represented by SiO ₂ and the aluminum contained in the aluminate is represented by Al ₂ O ₃ , the molar ratio (Al ₂ O ₃ / SiO ₂ ) is 0.0005 to 0.050. By mixing at such a ratio, a silica / alumina composite oxide precursor is formed on the surface of the silica fine particles.

The alkaline silica sol having a pH of 9.0 to 11.5 and containing the anisotropic shaped silica fine particles or fine particles mainly composed of silica can be produced by a known method.
As an example of a method for producing a dispersed sol containing anisotropic fine silica particles, for example, a production method described in JP-A-2007-137972 or a method analogous thereto can be used.
More preferably, among the silica sol production methods described in Japanese Patent Application Laid-Open No. 2007-137972, the first production method, that is, a silica hydrogel is prepared by neutralizing an aqueous solution of silicate with an acid, It is preferable to use a method in which silica hydrogel is made into a slurry or dispersion by means or mechanical means. Here, as a chemical means, the method of adding an alkali to a silica hydrogel and heating as desired is mentioned. Moreover, as a mechanical means, the method of using apparatuses, such as a stirrer, can be mentioned. These chemical means and mechanical means may be used in combination.

At this time, the average particle diameter (D1) measured by the dynamic light scattering method of the silica fine particles contained in the alkaline silica sol or the fine particles mainly containing silica is in the range of 15 to 70 nm, and measured by the BET method. More preferably, the average particle diameter (D2) is in the range of 10 to 50 nm and the irregularity (D1 / D2) is in the range of 1.55 to 4.00.
By using an alkaline silica sol containing such silica fine particles or fine particles mainly composed of silica, silica-based fine particles having an anisotropic shape and high coating hardness are finally obtained as silica-based fine particles obtained by modifying aluminum. This is more preferable.

  The pH of the alkaline silica sol is preferably in the range of 9.0 to 11.5, more preferably 9.5 to 11.0. When the pH of the alkaline silica sol is in the range of 9.0 to 11.5, the solubility of silica is increased, and thus when the aqueous solution of aluminate is mixed, the silicate monomer present in the silica skeleton on the surface of the silica fine particles and A substitution reaction with an aluminate ion is likely to occur. In addition, silica sols in the range of pH 9.0 to 11.5 have a high silica solubility, so there is a silica component dissolved as a silicate monomer in the solvent, but when aluminate ions coexist here, The solubility of silica is locally reduced, and the complex of the silicate monomer and aluminate ions is precipitated on the surface of the silica fine particles as a precursor of the silica / alumina complex oxide. A uniform silica-alumina composite oxide precursor is formed by such a reaction, and the precursor is subjected to dehydration and polycondensation reaction in a later step, so that a larger amount of aluminum is negatively charged than before. It is possible to uniformly modify the surface of the silica fine particles in the form of having.

When the pH of the alkaline silica sol is greater than 7.0 and less than 9.0, the solubility of silica is low, and the substitution reaction between the silicate monomer and the aluminate ion does not easily occur. The acid ions are not preferable because they form a hydroxide alone and aggregate to reduce the transparency and stability of the silica-based fine particle dispersed sol. In addition, when an acidic silica sol having a pH of 7.0 or less is used instead of the alkaline silica sol, the acidic silica sol passes through an unstable neutral pH region when an aqueous solution of an alkaline aluminate is added. Absent.
Further, when the pH of the alkaline silica sol exceeds 11.5, the silica solubility becomes too high, so that it becomes difficult to form a silica-alumina composite oxide precursor on the surface of the silica fine particles, or the silica-alumina composite This is not preferable because the density of the oxide is lowered.

The alkaline silica sol preferably contains an alkali metal ion. The content of the alkali metal ion is expressed by the molar ratio (SiO ₂ ) when the alkali metal ion is represented by M ₂ O (M is an alkali metal element) and the silicon component contained in the alkaline silica sol is represented by SiO _{2. 2} / M ₂ O) is preferably in the range of 20 to 300, more preferably 30 to 200. If the molar ratio is less than 20, gelation may occur at the time of ion exchange, and if the molar ratio exceeds 300, the solubility of silica is reduced and an aqueous solution of aluminate and alkaline silica sol are mixed. This is not preferable because it may increase viscosity or gel.
Moreover, it is not preferable to use an alkaline silica sol containing amine or ammonium ions because the solubility of silica is lowered and gelation may occur when an aluminate aqueous solution is mixed.
Also, the silica sol, although the process may contain aluminum components, in that case, it is preferable to use the aluminum content is less than 0.007 in _Al 2 _O 3 / SiO ₂ molar ratio. If the Al ₂ O ₃ / SiO ₂ molar ratio exceeds 0.007, the alkali content in the silica sol is so high that gelation may occur during ion exchange, which is not preferable.

The solid content of the alkaline silica sol is preferably in the range of 10 to 50 wt% in terms of SiO ₂ based. When the solid content concentration is less than 10% by weight, the productivity of silica-based fine particles decreases, which is not preferable. Moreover, since the viscosity of alkaline silica sol will become high when the said density | concentration exceeds 50 weight%, it is unpreferable.

The amount of the aqueous solution of aluminate mixed with the alkaline silica sol is represented by SiO ₂ as the silicon component contained in the silica sol, and Al ₂ O ₃ as the aluminum contained in the aluminate. When the molar ratio (Al ₂ O ₃ / SiO ₂ ) is in the range of 0.0005 to 0.050, more preferably 0.005 to 0.050, and still more preferably 0.010 to 0.050. preferable.
If the molar ratio is less than 0.0005, the amount of modification of aluminum on the surface of the silica-based fine particles is small, so the stability of the silica-based fine particle-dispersed sol decreases, and the stability of the coating composition and the hardness of the curable coating film And scratch resistance and transparency are also unfavorable. On the other hand, when the molar ratio exceeds 0.050, the stability and transparency of the silica-based fine particle-dispersed sol are deteriorated, and the hardness, scratch resistance, and transparency of the curable coating film are not preferable.

The aluminate is preferably sodium aluminate and / or potassium aluminate.
Moreover, it is preferable that the solid content concentration of the aqueous solution of the aluminate is in the range of 0.5 to 30% by weight in terms of Al ₂ O ₃ conversion.
When the concentration based on Al ₂ O ₃ is less than 0.5% by weight, the aluminate is easily hydrolyzed to form a hydroxide, and when the concentration exceeds 30% by weight, the local pH In addition, silica and aluminum components may be aggregated due to an increase in salt concentration.

Further, the _M 2 _O / _Al 2 O ₃ molar ratio of the aqueous solution of aluminate (M is an alkali metal element) is preferably in the range of 1.0 to 1.5. When the molar ratio is less than 1.0, the aluminate is easily hydrolyzed to form a hydroxide, and when the molar ratio exceeds 1.5, the precursor of the silica-alumina composite oxide. Since a body may become difficult to form, it is not preferable.

Next, process (2) is demonstrated.
Process (2) : The liquid mixture obtained by the said process (1) is heated to the temperature of 60-200 degreeC, and is stirred for 0.5 to 20 hours.
When the substitution reaction of silicic acid monomer and aluminate ion on the surface of the silica fine particles or the precipitation reaction of silica and aluminate dissolved in the silica sol on the surface of the silica fine particles is not sufficiently performed only in the step (1) In this step, the substitution reaction and the precipitation reaction are sufficiently performed. Furthermore, by this process, the surface of silica fine particles is modified with aluminum by dehydrating and condensing polymerization of the silica-alumina composite oxide precursor formed on the surface of the silica fine particles to stabilize the surface of the silica fine particles. To do.

  If the heating temperature of the mixed solution is less than 60 ° C., the silica-alumina composite oxide precursor is not sufficiently dehydrated and polycondensed, and the stability and high concentration of the silica-based fine particle-dispersed sol are deteriorated. Further, when the heating temperature exceeds 200 ° C., the solubility of silica becomes too high, so that the density of the silica / alumina composite oxide is lowered, and the stability and high concentration of the silica-based fine particle dispersed sol are lowered. This is not preferable.

The heating can be performed using a known apparatus and method. The heating may be performed under normal pressure or under pressure. When heating is performed under pressure using an autoclave apparatus or the like, the stability of the silica-based fine particle dispersed sol is further improved.
The stirring time is preferably in the range of 0.5 to 20 hours. When the stirring time is less than 0.5 hours, the dehydration / condensation polymerization reaction does not occur sufficiently, and the stability of the silica-based fine particle dispersed sol may be lowered. When the stirring time exceeds 20 hours, although there is no technical problem in particular, it is not preferable because the manufacturing time becomes long and it is not economical.

Furthermore, the dispersion sol of silica-based fine particles obtained from the step (2) can be subjected to the following step (3).
Step (3) : The mixed solution obtained in the step (2) is brought into contact with a cation exchange resin, and the alkali metal ions contained in the mixed solution are removed by ion exchange, so that the pH of the mixed solution is 3 Adjust to the range of .0 to 6.0.
Through this step, a dispersion sol of acidic silica-based fine particles can be produced. This dispersion sol is stable even in the acidic region, and is excellent in the effect of improving the hardness, scratch resistance, and adhesion of the coating film obtained when blended in the coating composition.
When the pH is less than 3.0, a part of the modified aluminum is dissolved on the surface of the silica-based fine particles and is ion-exchanged and removed by the cation resin, and the stability and film hardness of the silica-based fine particle dispersed sol are lowered. This is not preferable. On the other hand, if the pH exceeds 6.0, the silica-based fine particle-dispersed sol may become unstable and gel.

As a method of bringing the mixed solution into contact with the cation exchange resin, a batch method (resin circulation method), a column method (resin filling method), and other known methods can be used.
Moreover, in the said process (3), when the said liquid mixture is heated and it is made to contact with the said cation exchange resin on 60-95 degreeC temperature conditions, the ion exchange removal effect of an alkali metal ion can be improved more.

By performing these steps (1) to (3), silica-based fine particles having an average particle diameter of 5 to 50 nm obtained by modifying the surface of the silica fine particles with aluminum and having a pH of 3.0 to 6.0 are contained. A silica-based fine particle water-dispersed sol in the acidic range can be obtained.
Furthermore, between the step (1) and the step (2),
Step (1.1): A step of heating the mixed liquid obtained in the step (1) to a temperature of 60 to 95 ° C. and stirring for 0.2 to 10 hours.
Step (1.2): The mixed solution obtained in the step (1.1) is brought into contact with a cation exchange resin, and at least a part of alkali metal ions contained in the mixed solution is removed by ion exchange. Adjusting the pH of the mixture to a range of 7 to 10,
It is preferable to contain.

By performing the step (1.1) and the step (1.2), the denseness of the silica-alumina composite oxide formed on the surface of the silica fine particles is further increased, and the hardness of the curable coating film is increased. be able to. In addition, when the steps (1.1) and (1.2) are not performed, the silica component dissolved in the solvent of the silica-based fine particle water-dispersed sol may remain. Depending on the conditions, these may reduce the stability when the silica-based fine particle water-dispersed sol is concentrated to a high concentration, but the silica dissolved in the solvent of the silica-based fine particle water-dispersed sol by this step All components can be deposited on the surface of silica fine particles as a silica-alumina composite oxide.
The silica component deposited as a precursor of such a silica / alumina composite oxide hardly dissolves again in the mixed solution even when heated under the condition of high silica solubility in the subsequent step (3).

By such a process, the silica-alumina composite oxide becomes denser, and the stability when the obtained silica-based fine particle water-dispersed sol is concentrated to a high concentration is further improved.
The silica-based fine particle water-dispersed sol obtained by the above steps can be concentrated by a known method such as an ultrafiltration method, an evaporator, or evaporation as necessary.
Further, the silica-based fine particle organic solvent-dispersed sol can be obtained by replacing the dispersion medium of the silica-based fine particle water-dispersed sol obtained in the above step with an organic solvent by a known method such as an ultrafiltration method or an evaporator. it can.
Further, the silica-based fine particle water-dispersed sol and the silica-based fine particle organic solvent-dispersed sol may be further subjected to a surface treatment using a known surface treating agent such as a silane coupling agent, if necessary.

Next, the coating composition according to the present invention will be described.
The application of the coating composition according to the present invention is not particularly limited, and can be used as a hard coat material, a sealing material, an adhesive material, a filler for a resin composition, and the like. The curable coating film obtained from the coating composition according to the present invention is particularly suitable as a coating composition for forming a hard coat layer or a primer layer provided on the surface of an optical lens substrate because of high film strength, transparency and scratch resistance. Can be used for

The coating composition according to the present invention comprises:
(A) a dispersion sol of silica-based fine particles according to the present invention;
(B) A binder component is included.

(A) Dispersion sol of silica-based fine particles according to the present invention As described above, the dispersion sol of silica-based fine particles according to the present invention is a dispersion sol containing anisotropic-shaped silica-based fine particles, The surface has a negative charge, and the surface of the silica-based fine particles is modified with aluminum. The modification amount of the aluminum is 0.01 × 10 ⁻⁶ per unit surface area of the silica-based fine particles in terms of Al ₂ O ₃ conversion. It is a dispersion sol of silica-based fine particles in a range of ˜2.0 × 10 ⁻⁶ mol / m ² .
By blending such a dispersion sol of silica-based fine particles into the coating composition, the film hardness, scratch resistance and adhesion of the resulting coating film are remarkably improved.
Furthermore, the average particle diameter (D1) measured by the dynamic light scattering method of the silica-based fine particles is in the range of 15 to 70 nm, and the average particle diameter (D2) measured by the BET method is in the range of 10 to 50 nm. Yes, the degree of irregularity (D1 / D2) is preferably in the range of 1.55 to 4.00. Use of such silica-based fine particles is preferable because the hardness of the coating film is remarkably improved.
Such a dispersion sol of silica-based fine particles can be obtained by the production method as described above.
In addition, the dispersion sol of silica-based fine particles as the component (A) may be water or an organic solvent.
(B) Binder component The binder component can be appropriately selected from conventionally known ones or those currently under development depending on the purpose of use of the coating composition.
Examples of the binder component include an organosilicon compound represented by the following formula (II) and / or a hydrolyzate thereof.
R ¹ _a R ² _b Si (OR ³ ) _{4- (a + b)} (II)
(In the formula, R ¹ is an alkyl group having 1 to 6 carbon atoms, an organic group having 8 or less carbon atoms containing a vinyl group, an organic group having 8 or less carbon atoms containing an epoxy group, and 8 carbon atoms containing a methacryloxy group. The following organic group, an organic group having 1 to 5 carbon atoms containing a mercapto group or an organic group having 1 to 5 carbon atoms containing an amino group, R ² is an alkyl group having 1 to 3 carbon atoms, an alkylene group, A cycloalkyl group, a halogenated alkyl group or an allyl group, R ³ is an alkyl group having 1 to ³ carbon atoms, an alkylene group or a cycloalkyl group, a is an integer of 0 or 1, b is 0, 1 Or an integer of 2.)

  As the organosilicon compound represented by the general formula (II), an alkoxysilane compound can be given as a representative example, and specifically, tetraethoxysilane, methyltrimethoxysilane, vinyltrimethoxysilane, γ-methacryloxypropyl. Trimethoxysilane, trimethylchlorosilane, α-glycidoxymethyltrimethoxysilane, α-glycidoxyethyltrimethoxysilane, β-glycidoxyethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycyl Sidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-γ-glycidoxypropylmethyldiethoxysilane, β- (3,4-epoxycyclohexyl) -ethyltrimethoxysilane, β- (3 4-epoxycyclohexyl) -Ethyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β (aminoethyl) -γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) -γ-aminopropyl And methyldiethoxysilane. These may be used alone or in combination of two or more.

Such an organosilicon compound and / or a hydrolyzate thereof is particularly preferable as a binder for a hard coat film-forming coating material such as an optical substrate.
In order to prepare a coating composition according to the present invention using such an organosilicon compound as a binder component, the organosilicon compound is used in the absence of a solvent or in a polar organic solvent such as alcohol in the presence of an acid or water. It is preferably mixed with the silica-based fine particle dispersed sol after partial hydrolysis or hydrolysis. However, after the organosilicon compound and the silica-based fine particle dispersed sol are mixed, they may be partially hydrolyzed or hydrolyzed.

The mixing of the silica-based fine particle-dispersed sol with the organosilicon compound and / or a hydrolyzate thereof represents the weight of the organosilicon compound in terms of SiO ₂ as X, and the silica contained in the silica-based fine particle dispersed sol When the weight of the system fine particles is represented by Y, the weight ratio (X / Y) is preferably 30/70 to 90/10, preferably 35/65 to 80/20. Here, if the weight ratio is less than 30/70, adhesion to the substrate or other coating film may be lowered, and if the weight ratio exceeds 90/10, the coating film is scratch resistant. This is not preferable because the properties may be lowered.

Examples of the binder component include a thermosetting organic resin or a thermoplastic organic resin. The thermosetting organic resin is preferably at least one selected from urethane resins, epoxy resins and melamine resins.
More specifically, examples of the urethane resin include a reaction product of a block-type polyisocyanate such as hexamethylene diisocyanate and an active hydrogen-containing compound such as polyester polyol and polyether polyol, and the epoxy resin. Examples of the resin include a polyalkylene ether-modified epoxy resin and an epoxy group-containing compound in which a flexible skeleton (soft segment) is introduced into a molecular chain.

Furthermore, examples of the melamine-based resin include cured products of etherified methylol melamine, polyester polyol, and polyether polyol. Among these, it is preferable to use a urethane-based resin that is a cured product of a block type isocyanate and a polyol. Moreover, these thermosetting organic resins may use not only one type but also two or more types.
The thermoplastic organic resin as the binder component used in the present invention is preferably at least one selected from an acrylic resin, a urethane resin, and an ester resin, and more preferably a self-emulsifying aqueous emulsion resin. It is more preferable that

  More specifically, examples of the acrylic resin include a water-based emulsion obtained from a (meth) acrylic acid alkyl ester monomer and a polymer emulsion obtained by copolymerizing the monomer with styrene, acrylonitrile, and the like. Examples of the urethane resin include water-based emulsions obtained by reacting a polyol compound such as polyester polyol, polyether polyol, and polycarbonate polyol with polyisocyanate. Further, examples of the ester resin include hard segments. Examples include polyester, water-dispersed elastomer of a multi-block copolymer using polyether or polyester as a soft segment. Among these, it is preferable to use a water-dispersed urethane resin obtained from polyester polyol or polyether polyol and polyisocyanate. Moreover, these thermoplastic organic resins may use not only one type but also two or more types.

A coating composition using such a thermosetting organic resin and the thermoplastic resin as a binder component is prepared by mixing the resin and a silica-based fine particle-dispersed sol, and the mixing ratio is R based on the weight of the resin. When the weight of the silica-based fine particles contained in the silica-based fine particle dispersed sol is represented by S, the weight ratio (R / S) is 90/10 to 30/70, more preferably 80/20 to 35/65. It is preferable to do so.
Here, if the weight ratio is less than 30/70, the adhesion to the substrate and other coating films and the impact resistance of the substrate may be lowered, and the weight ratio exceeds 90/10. And the refractive index and heat resistance of the coating film may decrease, which is not preferable.
The coating composition is preferably a coating composition for an optical substrate, more preferably a coating composition for forming a hard coat layer film.

The coating composition of the present invention may further contain one or more of various uncrosslinked epoxy compounds, surfactants, leveling agents and / or ultraviolet absorbers, light stabilizers, diluent solvents, and the like.
Further, as a binder component of the coating composition according to the present invention, a metal alkoxide such as titanium alkoxide, a compound such as an ultraviolet curable compound (for example, a polyfunctional acrylic compound having an acryloyloxy group), and the thermosetting organic resin In place of the thermoplastic resin, a compound such as the ultraviolet curable compound may be used.

Next, the coating film according to the present invention will be described.
The coating film according to the present invention is a coating film having high transparency, film strength, and scratch resistance, which can be obtained by applying the coating composition according to the present invention on a substrate.
As a coating method of the coating composition, a known method such as a dipping method or a spin coating method can be used.
When the coating film which consists of the said coating composition apply | coated on the base material using such a method is thermosetted, the curable coating film which concerns on this invention is formed. This thermosetting is performed by heat-processing at 80-130 degreeC for 0.5 to 5 hours. The film thickness of the cured coating film thus obtained is 1.0 to 5.0 μm, preferably 1.5 to 4.0 μm.
The substrate can be suitably used for substrates such as lenses such as plastic and glass, plastic films, plastic sheets, plastic panels, and metals.
Examples of the plastic include resin compounds such as polystyrene resin, allyl resin, polycarbonate resin, polythiourethane resin, polythioepoxy resin, PMMA resin, ABS resin, epoxy resin, polysulfone resin, PET, TAC, and acrylic resin.

[Measurement method and evaluation test method]
Next, the measurement methods and evaluation test methods used in the examples and others of the present invention will be specifically described as follows.

(1) Measuring method of specific surface area The specific surface area of the silica-based fine particles according to the present invention was measured by a nitrogen adsorption method (BET method).
50 ml of dispersion sol containing silica fine particles (dispersion medium may be water or organic solvent) is adjusted to pH 3.5 with HNO ₃ , 40 ml of 1-propanol is added and dried at 110 ° C. for 16 hours. It was. The obtained sample was pulverized in a mortar and then baked at 500 ° C. for 1 hour in a muffle furnace to obtain a measurement sample. About the obtained measurement sample, the nitrogen adsorption amount is measured by a nitrogen adsorption method (BET method) using a specific surface area measuring device (manufactured by Yuasa Ionics, model number Multisorb 12), and the obtained adsorption amount is determined by the BET one-point method. The specific surface area was calculated. Specifically, 0.5 g of a sample is taken in a measurement cell, degassed for 20 minutes at 300 ° C. in a mixed gas stream of nitrogen 30 vol% / helium 70 vol%, and then the sample is placed in the mixed gas stream At a liquid nitrogen temperature, nitrogen was adsorbed on the sample by equilibrium. Next, the sample temperature is gradually raised to room temperature while flowing the above mixed gas, the amount of nitrogen desorbed during that time is detected, and the specific surface area (m ² / g) of the fine particles is calculated using a calibration curve prepared in advance. did.

(2) Measuring method of average particle diameter D2 The average particle diameter D2 calculated | required by BET method of the silica type fine particle was calculated | required with the following method.
The value of the specific surface area (m ² / g) of the silica-based fine particles determined by the above-described specific surface area measurement method was applied to the following formula to determine the average particle diameter (nm).
Average particle diameter (nm) = 6000 / [specific surface area (m ² / g) × density (ρ)]
Here, the density (ρ) used was a silica density of 2.2.
It should be noted that for spherical particles, the average particle size determined by the BET method and the average particle size determined from the transmission electron micrograph are substantially the same.

(3) Measuring method of average particle diameter D1 The average particle diameter D1 of the silica type fine particle calculated | required by the dynamic light scattering method was calculated | required with the following method.
A sample with a solid content of 0.15% prepared by mixing 19.90 g of pure water with 0.10 g of an aqueous dispersion sol of silica-based fine particles (solid content of 30% by weight) was 1 cm in length, 1 cm in width, In a quartz cell having a height of 5 cm, the particle size distribution of the particle group is measured using an ultrafine particle size analyzer (model ELS-Z2 manufactured by Otsuka Electronics Co., Ltd.) using a dynamic light scattering method. In addition, the average particle diameter as used in the field of this invention shows the value computed by cumulant analysis of this measurement result.

(4) Method for calculating degree of irregularity The average particle diameter (D1) of silica-based fine particles measured by the dynamic light scattering method is the average particle diameter (D2) of silica-based fine particles calculated from the specific surface area obtained from the BET method. It calculated | required as the value (D1) / (D2) which remove | divided.

(5) pH measurement method A pH meter in which a cell containing 50 ml of a sample has been corrected with standard solutions of pH 4, 7 and 9 in a thermostatic bath maintained at a temperature of 25 ° C. (manufactured by Horiba, F22) A glass electrode was inserted to measure the pH value.
At this time, a sample with a solid concentration of 30% by weight was used as the sample for the aqueous dispersion sol, and a silica-based fine particle organic solvent dispersion sol with a solid content of 30% by weight was diluted 10 times with distilled water. A sample having a solid content concentration of 3.0% by weight was used as a sample.

(6) Method for measuring content of silicon, aluminum and sodium contained in silica sol or silica-based fine particle dispersed sol (a) Content of silicon Silica sol or silica-based fine particle dispersed sol (dispersion medium may be water or an organic solvent) 2 ml of 50% sulfuric acid aqueous solution is added to 10 g and evaporated to dryness on a platinum pan. The obtained solid is baked at 1000 ° C. for 1 hour, cooled and weighed. Next, dissolve the weighed solid in a small amount of 50% aqueous sulfuric acid, add 20 ml of hydrofluoric acid, evaporate to dryness on a platinum pan, bake at 1000 ° C. for 15 minutes, and cool. Weigh. These weight differences were defined as the silicon content (wt% based on SiO ₂ conversion) contained in the silica sol, silica-based fine particle water-dispersed sol, or silica-based fine particle organic solvent-dispersed sol.

(B) Aluminum content 1) 1 g of silica sol or silica-based fine particle dispersion sol (the dispersion medium may be water or an organic solvent) is collected in a platinum dish and weighed to 0.1 mg.
2) Add 20 ml of hydrofluoric acid, heat on a sand bath and evaporate to dryness.
3) After cooling the sample obtained in 2) above to room temperature, 5 ml of hydrochloric acid and about 50 ml of water are added and heated on a sand bath to dissolve.
4) After cooling the sample obtained in 3) above to room temperature, it is used in a 200 ml capacity flask and diluted to 200 ml with water to prepare a sample solution.
5) The amount of aluminum contained in the sample solution obtained in 4) above was measured with an inductively coupled plasma emission spectroscopic analyzer (manufactured by Shimadzu Corporation, ICPS-8100, detection wavelength 396.153 nm), and Al ₂ The weight% based on O ₃ conversion standard was determined.

(C) Content of sodium 1) 1 g of silica sol or silica-based fine particle dispersion sol (dispersion medium may be water or organic solvent) is collected in a platinum dish and weighed to 0.1 mg.
2) Add 20 ml of hydrofluoric acid, heat on a sand bath and evaporate to dryness.
3) After cooling the sample obtained in 2) above to room temperature, 5 ml of hydrochloric acid and about 50 ml of water are added and heated on a sand bath to dissolve.
4) After cooling the sample obtained in 3) above to room temperature, it is used in a 200 ml capacity flask and diluted to 200 ml with water to prepare a sample solution.
5) Atomic absorption spectrophotometer (manufactured by Hitachi, Ltd., Z-5300, measurement mode: amount of sodium contained in the sample solution obtained in 4) above on the basis of Na ₂ O ₃ conversion; atomic absorption, measurement wavelength Range; 190-900 nm). This measurement method is a method in which the sample solution is atomized by the flame method, the atomic vapor layer is irradiated with light of an appropriate wavelength, and the element concentration in the sample solution is measured by the intensity of light absorbed by the atoms. . The detection wavelength of sodium was 589.0 nm.

(7) Method for measuring surface negative charge 1.67 g of silica-based fine particle dispersion sol (dispersion medium may be water or organic solvent) having a solid content concentration of 30% by weight was collected, and distilled water 98. 53 g was added to prepare 100.00 g of a mixed solution having a solid content concentration of 0.5% by weight. A hydrochloric acid aqueous solution or an ammonia aqueous solution was added to the obtained mixed solution to prepare a measurement aqueous solution having a pH adjusted to 5.0 at 25 ° C., and 20.00 g was fractionated therefrom to obtain a streaming potential measuring device (MUUTEK). PCD-T3, manufactured by the company, and using a Poly-Dadmac as a cation standard titrant, the flow potential titration value obtained by measuring the cation streaming potential titration value was defined as the surface negative charge amount.
The value obtained by the above measurement is the amount of negative surface charge (μeq / g) per 1 g of silica fine particles or silica-based fine particles. A value obtained by dividing this value by the specific surface area (m ² / g) of the silica-based fine particles was defined as the negative charge amount existing per unit specific surface area of the silica-based fine particles.

(8) Method for measuring haze of silica-based fine particle-dispersed sol Silica-based fine particle-dispersed sol (dispersion medium may be water or an organic solvent) having a solid content concentration of 30% by weight in a quartz cell having an optical path length of 33 mm. The turbidity (haze) was measured using a color difference / turbidity measuring device (Nippon Denshoku Industries Co., Ltd., COH-300A).

(9) Calculation method of modification amount of aluminum contained in silica-based fine particles The silicon content (% by weight on the basis of SiO ₂ conversion) of the silica-based fine particle-dispersed sol obtained by the measurement method (6) is defined as C _SiO2 , When the aluminum content (weight% on the basis of Al ₂ O ₃ conversion) is C _Al2O3 and the alkali metal content (weight% on the basis of M ₂ O conversion) is C _M2O , the following formula is used per 1 g of silica-based fine particles. The amount of aluminum modification (number of moles in terms of Al ₂ O ₃ ) was determined. The molecular weight of Al ₂ O ₃ was 102.
Aluminum modification amount per 1 g of silica-based fine particles (mol / g) = [C _{2 Al 2 O 3} / (C _{3 SiO 2} + C _{Al 2 O 3} + C _M2O )] / 102
A value obtained by dividing this amount by the specific surface area (m ² / g) of the silica-based fine particles was used as the aluminum modification amount per unit surface area of the silica-based fine particles.
However, when the silica-based fine particles according to the present invention are produced using alkaline silica sol containing fine particles mainly composed of silica, the amount of aluminum contained in the fine particles mainly composed of silica is subtracted from C _{Al2O3 in} advance. It shall be calculated.

(10) Viscosity measurement method Weigh 20 ml each of silica-based fine particle dispersion sol (dispersion medium may be water or organic solvent) having a solid content concentration of 30% by weight and measure viscometer (Toki Sangyo Co., Ltd.) The viscosity was measured at a temperature of 25 ° C. using a TV-10M manufactured by company. At this time, the rotor of the viscometer rotates at 60 rpm when the viscosity of the sample is in the range of 1.0 to 10.0 mPa · s, and when the viscosity is in the range of 10.0 to 20.0 mPa · s. When the viscosity was in the range of 30 rpm and 20.0 to 50.0 mPa · s, the rotational speed was 12 rpm, and when the viscosity was in the range of 50.0 to 100.0 mPa · s, the rotational speed was 6 rpm.

(11) Test Method of Film Hardness (Bayer Test Value) A lens to be tested prepared in the preparation example of the example using an abrasion tester BTM (manufactured by Colts, USA) and a haze value measuring device (NDH2000 manufactured by NIPPON DENSGKUKU) Then, the Bayer value is measured by the change in the haze value with respect to the reference lens. The reference lens uses a CR39 base material (diethylene glycol bisallyl carbonate), and first, the respective haze values are measured. The initial haze value of the reference lens is D (std0), and the initial haze value of the lens under test is D (test0). Each lens is placed in an abrasion resistance tester pan, filled with 500 g of abrasive (exclusive sand), and vibrated 600 times to the left and right for testing. Assume that the initial haze value of the reference lens after the test is D (stdf) and the initial haze value of the lens under test is D (testf). The Bayer test value (R) is calculated from the following equation.
R = [D (stdf) -D (std0)] / [D (testf) -D (test0)]
In the evaluation of the film hardness of the present invention, the film hardness (Bayer test value) is good if it is 2.5 or more, and less than 2.5 is regarded as bad.

(12) Abrasion resistance test of coating film The surface of the test piece prepared in the preparation example of the example is subjected to a load of 1 kg on Bonstar steel wool # 0000 (manufactured by Nippon Steel Wool Co., Ltd.), and a distance of 3 cm is applied. After rubbing under conditions of 50 reciprocations / 100 seconds, the degree of damage was visually determined and evaluated according to the following criteria.
A: Almost no flaws B: Some flaws enter C: Some flaws enter D: Most flawed areas are scratched.

(13) Appearance of the coating film (cloudy)
A fluorescent lamp “trade name: Mellow 5N” (manufactured by Toshiba Lighting & Technology Co., Ltd., three-wavelength daylight white fluorescent lamp) is mounted in a box whose inner wall is black and has a hard coat layer film containing the metal oxide fine particles. The sample substrate is placed vertically directly under the fluorescent lamp, and the transparency (degree of cloudiness) is visually confirmed and evaluated according to the following criteria.
A: No haze B: Slight haze C: Clear haze D: Significant haze

(14) Adhesion test of coating film Cut the surface of the test piece prepared in the preparation example of the embodiment with a knife at intervals of 1 mm to form 100 squares of 1 mm square, and strongly adhere the cellophane adhesive tape. After pressing, the plastic lens substrate was suddenly pulled in the direction of 90 degrees with respect to the in-plane direction of the plastic lens substrate, this operation was performed a total of 5 times, the number of squares not to be peeled was counted, and evaluated according to the following criteria.
Good: The number of cells not peeled is 95 or more. Bad: The number of cells not peeled is less than 95.

(15) Hot water resistance test of coating film After immersing the test piece prepared in the preparation example of the example in 90 ° C. hot water for 120 minutes, the same test as the above-mentioned adhesion test was performed, and the following criteria were used. evaluated.
Good: The number of cells not peeled is 95 or more. Bad: The number of cells not peeled is less than 95.

(16) Weather-resistant adhesion test of coating film In the present invention, the weather-resistant adhesion means that there is little change over time in the adhesion of the coating film, particularly the deterioration of the adhesion with time under outdoor use conditions such as under ultraviolet irradiation. This means the effect of suppressing the above. The weather resistance adhesion according to the present invention was evaluated by the following method.
The sample substrate on which the hard coat layer film was formed was subjected to an exposure test with a xenon weather meter (X-75 type, manufactured by Suga Test Instruments Co., Ltd.), and then the appearance test and the same test as the adhesion test were performed. Evaluation based on the criteria. The exposure time is 200 hours for a substrate having an antireflection film and 50 hours for a substrate not having an antireflection film.
Good: The number of cells not peeled is 95 or more. Bad: The number of cells not peeled is less than 95.

[Example 1]
Preparation of water-dispersed sol containing anisotropic shaped silica-based fine particles (1)
(Preparation of anisotropic shaped silica fine particles)
A sodium silicate aqueous solution having a SiO ₂ concentration of 24% by weight (SiO ₂ / Na ₂ O molar ratio: 3.1) 33.4 g was diluted with 126.6 kg of pure water, and a sodium silicate aqueous solution having a SiO ₂ concentration of 5% by weight. 160 kg of (pH 11) was prepared. The aqueous solution of sodium silicate was neutralized by adding an aqueous sulfuric acid solution having a sulfuric acid concentration of 25% so that the pH of the aqueous solution of sodium silicate was 4.5, and was aged by maintaining at room temperature for 5 hours to prepare a silica hydrogel.
This silica hydrogel was sufficiently washed with pure water (equivalent to about 120 times the SiO ₂ solid content) using a filter with a filter cloth, to remove salts contained in the silica hydrogel. The sodium sulfate concentration in the silica hydrogel after washing was less than 0.01% by weight based on the SiO ₂ solid content of the silica hydrogel.

This silica hydrogel was dispersed in pure water to prepare a dispersion having a SiO ₂ concentration of 3% by weight, and the mixture was stirred using a powerful stirrer until it became a fluid slurry.
Ammonia water having a concentration of 15% was added so that the pH of the slurry-like hydrosilica gel dispersion was 10.5, and stirring was continued at 95 ° C. for 1 hour to perform a deflocculation operation of the silica hydrogel. Obtained.
After the obtained silica sol is stabilized by heating at 150 ° C. for 1 hour, the silica sol is used with an ultrafiltration membrane (SIP-1013, manufactured by Asahi Kasei Corporation) until the SiO ₂ concentration becomes 13% by weight. Concentrated. Next, the solution was concentrated to 30% by weight with a rotary evaporator and then filtered with a 44 μm mesh nylon filter to obtain 24.02 kg of an anisotropic silica sol having a SiO ₂ concentration of 30% by weight.
The specific surface area of the obtained silica fine particles was 97 m ² / g, and the average particle diameter (D2) determined from the specific surface area by the BET method was 28 nm. Moreover, the average particle diameter (D1) measured by the dynamic light scattering method was 50.3 nm, and the value of the degree of irregularity (D1 / D2) was 1.79.

Process (1)
4,000 g of the alkaline anisotropic silica sol (CP-1) obtained above was supplied to a 13-liter SUS reaction vessel equipped with a stirrer and a heating device, and converted to Al ₂ O ₃ while stirring at a temperature of 25 ° C. 2712 g of 0.9% by weight sodium aluminate aqueous solution was added at a constant rate over 80 minutes to obtain a mixed solution. At this time, Al ₂ O ₃ / SiO ₂ (mixing molar ratio) was 0.012, and the addition rate of the sodium aluminate aqueous solution was 1.5 × 10 ⁻² g / Hr.

Step (1.1)
The resulting mixed solution was heated to 95 ° C. with stirring, and then stirred for 6.0 hours while maintaining the temperature at 95 ° C. The pH of this mixed solution was 10.9, the solid content concentration based on SiO ₂ was 24.2% by weight, and the solid content concentration based on Al ₂ O ₃ was 0.36% by weight.
Step (1.2)
A cation exchange resin (Mitsubishi Chemical Corporation Diaion SK1BH) was added to the mixed solution obtained in the above step to adjust the pH to 9.
Process (2)
After separating and removing the resin from the mixed solution obtained in the above step, heat treatment was performed at 165 ° C. for 1 hour in an autoclave to obtain an aqueous dispersion sol of alkaline silica-based fine particles.

Step (3)
Next, after cooling the aqueous dispersion sol of the alkaline silica-based fine particles obtained in the above step to room temperature, a cation exchange resin (Mitsubishi Chemical Corporation Diaion SK1BH) was added and adjusted to pH 3.5. The resin was not separated and aged for 7 hours while maintaining at 80 ° C. with stirring.
Thereafter, the cation exchange resin was separated and removed to obtain an aqueous dispersion sol containing anisotropically shaped silica-based fine particles in an acidic region having a solid content concentration of 24.2% by weight and a pH of 4.9 on the basis of SiO ₂ conversion.
The acidic anisotropically shaped silica-based fine particle water-dispersed sol obtained above is concentrated using an ultrafiltration membrane, and a silica-based fine particle water-dispersed sol (hereinafter referred to as “CPA-1”) having a solid content concentration of 30% by weight. ) 5400 g was obtained. This silica-based fine particle water-dispersed sol has an SiO ₂ concentration of 29.93 wt%, an Al ₂ O ₃ concentration of 0.41 wt%, an Na ₂ O concentration of 0.16 wt%, and an Al ₂ O ₃ / SiO ₂ molar ratio. Of 8.1 × 10 ⁻³ and pH of 5.4. Further, the silica-based fine particles contained in the silica-based fine particle water-dispersed sol have an anisotropic shape, the average particle size determined by the dynamic light scattering method is 50.1 nm, the BET specific surface area is 93 m ² / g, The amount of negative charge existing per unit specific surface area was 0.24 μeq / m ² .
The modification amount of aluminum contained in the silica-based fine particles was 1.4 × 10 ⁻⁶ mol / m ² in terms of unit surface area.
The average particle diameter of the silica-based fine particles contained in the silica-based fine particle aqueous dispersion sol determined by the BET method was 29.3 nm, and the degree of irregularity was 1.71.

Preparation of methanol-dispersed sol containing anisotropic shaped silica-based fine particles (1)
5400 g of the aqueous dispersion sol (CPA-1) containing the anisotropically-shaped silica-based fine particles obtained in the above process is used as a dispersion medium using an ultrafiltration membrane device (a filtration membrane manufactured by Asahi Kasei Corporation, SIP-1013). The water was replaced with methanol (Mayashi Junyaku Co., Ltd., methyl alcohol concentration: 99.9% by weight).
The water content of the methanol-dispersed sol (hereinafter referred to as “CPM-1”) containing the anisotropically shaped silica-based fine particles thus obtained is about 0.5% by weight, and the solid content concentration is 30% by weight. %, The solid content concentration on the basis of SiO ₂ conversion was 29.93 wt%, and the pH when diluted 10-fold with distilled water was 5.8. The silica-based fine particles contained in the methanol-dispersed sol had an average particle size of 29.3 nm determined by the BET method and an average particle size of 50.1 nm measured by the dynamic light scattering method. The amount of aluminum formed was 1.4 × 10 ⁻⁶ mol / m ² in terms of unit surface area based on Al ₂ O _{3, and the} amount of negative charge existing per unit specific surface area of the silica-based fine particles was 0.24 μeq / m ² . there were.

Preparation of coating composition (H1) for forming a hard coat layer film 180 g of γ-glycidoxypropyltrimethoxysilane (Z-6040, manufactured by Toray Dow Corning Co., Ltd.) and methanol (produced by Hayashi Junyaku Co., Ltd., methyl alcohol) (Concentration: 99.9% by weight) A plurality of containers containing 90 g of a mixed solution were prepared, and 86 g of a 0.01N hydrochloric acid aqueous solution was dropped into these mixed solutions while stirring. Furthermore, this liquid mixture was stirred at room temperature all day and night to hydrolyze the silane compound.
Subsequently, 333 g of silica-based fine particle water-dispersed sol (CPA-1) containing anisotropic shaped silica-based fine particles having a solid content concentration of 30% by weight in a container containing these hydrolyzed solutions, and further propylene glycol monomethyl ether (Dow Chemical) Manufactured) 303 g, Tris (2,4-pentanedionato) aluminum III (manufactured by Tokyo Chemical Industry Co., Ltd.) 1.5 g and a silicone surfactant as a leveling agent (manufactured by Toray Dow Corning Co., Ltd., L-7604) 0.6 g was added and stirred at room temperature all day and night to prepare a coating composition (H1) for forming a hard coat layer film as a coating composition for an optical substrate.

[Example 2]
Preparation of water-dispersed sol containing anisotropic silica-based fine particles (2)
In step (1) of Example 1, the amount of sodium aluminate aqueous solution (concentration: 0.9 wt%) added to 4000 g of alkaline anisotropically shaped silica sol (CP-1) was changed from 2712 g to 1532 g, and the addition time was changed. A silica-based fine particle water-dispersed sol (CPA-2) containing anisotropic-shaped silica-based fine particles was obtained using the same method as in Example 1 except that the time was changed from 80 minutes to 46 minutes.
At this time, the Al ₂ O ₃ / SiO ₂ molar ratio when the aqueous solution of sodium aluminate was mixed with the alkaline silica sol in the process was 0.007.

The silica-based fine particle water-dispersed sol thus obtained has a SiO ₂ concentration of 30.09% by weight, an Al ₂ O ₃ concentration of 0.14% by weight, a Na ₂ O concentration of 0.10% by weight, and Al ₂ O. _{The 3} / SiO ₂ molar ratio was 2.7 × 10 ⁻³ and the pH was 5.2. Further, the silica-based fine particles contained in the silica-based fine particle water-dispersed sol have an anisotropic shape, the average particle size determined by the dynamic light scattering method is 50.2 nm, the BET specific surface area is 91 m ² / g, The amount of negative charge existing per unit specific surface area was 0.22 μeq / m ² .
Moreover, the modification amount of aluminum contained in the silica-based fine particles was 5.0 × 10 ⁻⁷ mol / m ² in terms of unit surface area.
Moreover, the average particle diameter calculated | required from the BET method of the silica type fine particle contained in the said silica type fine particle water dispersion sol was 30.0 nm, and the deformity was 1.68.

Preparation of methanol-dispersed sol containing anisotropic shaped silica-based fine particles (2)
The anisotropically shaped silica-based fine particles described in Example 1 except that the silica-based fine particle water-dispersed sol (CPA-2) produced in this example was used instead of the silica-based fine particle water-dispersed sol (CPA-1). Preparation of a methanol-dispersed sol containing a methanol-dispersed sol (hereinafter referred to as “CPM-2”) containing anisotropically-shaped silica-based fine particles was prepared in the same manner as in (1).
The water content of the methanol-dispersed sol (CPM-2) is about 0.5% by weight, the solid content concentration is 30% by weight, the solid content concentration based on SiO ₂ is 30.09% by weight, and 10% in distilled water. The pH when diluted twice was 5.8. The silica-based fine particles contained in the methanol-dispersed sol have a mean particle size of 30.0 nm determined by the BET method and a mean particle size of 50.2 nm measured by the dynamic light scattering method. The amount of aluminum formed is 0.5 × 10 ⁻⁶ mol / m ² in terms of unit surface area based on Al ₂ O _{3, and the} amount of negative charge existing per unit specific surface area of the silica-based fine particles is 0.22 μeq / m ² . there were.

Preparation of coating composition (H2) for forming a hard coat layer film Except for using an anisotropic shaped silica-based fine particle water-dispersed sol (CPA-2) instead of the anisotropic shaped silica-based fine particle water-dispersed sol (CPA-1) A hard coat layer film-forming coating composition (H2) was prepared in the same manner as the preparation of the hard coat layer film-forming coating composition (H1) described in Example 1.

[Example 3]
Preparation of water-dispersed sol containing anisotropic silica-based fine particles (3)
In the step (1) of Example 1, the amount of the sodium aluminate aqueous solution (concentration: 0.9% by weight) added to 4000 g of the alkaline anisotropic silica sol (CP-1) was changed from 2712 g to 9158 g, and the addition time was changed. A silica-based fine particle water-dispersed sol (CPA-3) containing anisotropic-shaped silica-based fine particles was obtained using the same method as in Example 1 except that the time was changed from 80 minutes to 4.5 hours.
At this time, the Al ₂ O ₃ / SiO ₂ molar ratio when the aqueous solution of sodium aluminate was mixed with the alkaline silica sol in the process was 0.040.

The silica-based fine particle water-dispersed sol thus obtained has a SiO ₂ concentration of 28.86% by weight, an Al ₂ O ₃ concentration of 0.55% by weight, a Na ₂ O concentration of 0.38% by weight, and Al ₂ O. _{The 3} / SiO ₂ molar ratio was 1.1 × 10 ⁻² and the pH was 5.6. The silica-based fine particles contained in the silica-based fine particle water-dispersed sol have an anisotropic shape, the average particle size determined by the dynamic light scattering method is 50.0 nm, the BET specific surface area is 95 m ² / g, The amount of negative charge existing per unit specific surface area was 0.26 μeq / m ² .
The modification amount of aluminum contained in the silica-based fine particles was 1.9 × 10 ⁻⁶ mol / m ² on a unit surface area conversion basis.
Moreover, the average particle diameter calculated | required from the BET method of the silica type fine particle contained in the said silica type fine particle water dispersion sol was 28.7 nm, and the deformity was 1.74.

Preparation of methanol-dispersed sol containing anisotropic shaped silica-based fine particles (3)
The anisotropically shaped silica-based fine particles described in Example 1 except that the silica-based fine particle water-dispersed sol (CPA-3) produced in this example was used instead of the silica-based fine particle water-dispersed sol (CPA-1). Preparation of a methanol-dispersed sol containing a methanol-dispersed sol (hereinafter referred to as “CPM-3”) containing anisotropically-shaped silica-based fine particles by the same method as in (1).
The water content of the methanol-dispersed sol (CPM-3) is about 0.5% by weight, the solid content concentration is 30% by weight, the solid content concentration based on SiO ₂ is 28.89% by weight, and 10% in distilled water. The pH after doubling was 5.9. The silica-based fine particles contained in the methanol-dispersed sol have an average particle size of 28.7 nm determined by the BET method and an average particle size of 50.0 nm measured by the dynamic light scattering method. The amount of aluminum formed was 1.9 × 10 ⁻⁶ mol / m ² in terms of unit surface area based on Al ₂ O _{3, and the} amount of negative charge existing per unit specific surface area of the silica-based fine particles was 0.26 μeq / m ² . there were.

Preparation of coating composition (H3) for forming a hard coat layer film Except for using an anisotropic shaped silica-based fine particle water-dispersed sol (CPA-3) instead of the anisotropic shaped silica-based fine particle water-dispersed sol (CPA-1) A hard coat layer film-forming coating composition (H3) was prepared in the same manner as the preparation of the hard coat layer film-forming coating composition (H1) described in Example 1.

[Comparative Example 1]
Preparation of water-dispersed sol containing spherical silica-based fine particles In step (1) of Example 1, instead of using 4000 g of alkaline anisotropic-shaped silica sol (CP-1), alkaline silica sol in which spherical colloidal silica fine particles are dispersed ( Cataloid SI-40 manufactured by JGC Catalysts & Chemicals Co., Ltd., SiO ₂ concentration 40 wt%, Na ₂ O concentration 0.40 wt%, pH 9.5, BET average particle diameter 17 nm, Al ₂ O ₃ / SiO ₂ (molar ratio) = 0.0006) A silica-based fine particle water-dispersed sol (RCPA-1) in which spherical silica-based fine particles were dispersed in a solid content concentration of 30% by weight was obtained in the same manner as in Example 1 except that 3000 g was used. .
At this time, the Al ₂ O ₃ / SiO ₂ molar ratio when the sodium aluminate aqueous solution was mixed with the alkaline silica sol in step (1) was 0.012.

The silica-based fine particle water-dispersed sol (RCPA-1) thus obtained has a SiO ₂ concentration of 29.34% by weight, an Al ₂ O ₃ concentration of 0.42% by weight, and a Na ₂ O concentration of 0.24% by weight. %, Al ₂ O ₃ / SiO ₂ molar ratio was 8.4 × 10 ⁻³ , and pH was 4.8.
The silica-based fine particles contained in the silica-based fine particle water-dispersed sol are spherical, the average particle size determined by the dynamic light scattering method is 25.5 nm, the BET specific surface area is 162 m ² / g, and the unit ratio of the silica-based fine particles The amount of negative charge present per surface area was 0.90 μeq / m ² .
Further, the modification amount of aluminum contained in the silica-based fine particles was 8.5 × 10 ⁻⁷ mol / m ² in terms of unit surface area.
Moreover, the average particle diameter calculated | required from BET method of the silica type fine particle contained in the said silica type fine particle water dispersion sol was 16.8 nm, and the deformity was 1.51.

Preparation of methanol-dispersed sol containing spherical silica-based fine particles Water-dispersed sol containing spherical silica-based fine particles (RCPA) prepared in this comparative example instead of water-dispersed sol (CPA-1) containing anisotropic-shaped silica-based fine particles The methanol dispersion sol containing silica fine particles (RCPM-1) using the same method as the preparation (1) of methanol dispersion sol containing anisotropic silica fine particles described in Example 1 except that -1) was used ) Was prepared.
The methanol-dispersed sol (RCPM-1) thus obtained contains spherical silica-based fine particles, has a water content of about 0.5% by weight, and has a solid content concentration of 29.32 on the basis of SiO ₂ conversion. The pH when diluted 10 times with wt% distilled water was 5.3. The average particle size of the spherical silica-based fine particles contained in this methanol-dispersed sol, determined by the BET method, is 16.8 nm, the average particle size measured by the dynamic light scattering method is 25.5 nm, and the unit specific surface area The amount of aluminum modified per unit area was 8.5 × 10 ⁻⁷ mol / m ² , and the amount of negative charge existing per unit specific surface area was 0.9 μeq / m ² .

Preparation of coating composition (C1) for forming a hard coat layer film Water-dispersed sol containing spherical silica-based fine particles prepared in this comparative example instead of water-dispersed sol (CPA-1) containing anisotropic-shaped silica-based fine particles A hard coat layer film-forming coating composition (C1) was prepared in the same manner as the hard coat layer film-forming coating composition (H1) described in Example 1 except that (RCPA-1) was used.

[Comparative Example 2]
Preparation of water-dispersed sol containing anisotropically-shaped silica-based fine particles In step (1) of Example 1, an aqueous sodium aluminate solution (concentration: 0.9% by weight) added to 4000 g of alkaline anisotropically-shaped silica sol (CP-1) The silica-based fine particle water-dispersed sol (RCPA-2) containing anisotropically-shaped silica-based fine particles was obtained using the same method as in Example 1 except that the amount of was changed so as not to be added from 2712 g.

The silica-based fine particle aqueous dispersion sol (RCPA-2) thus obtained has a SiO ₂ concentration of 30.27 wt%, an Al ₂ O ₃ concentration of 0.002 wt%, and a Na ₂ O concentration of 0.21 wt%. %, Al ₂ O ₃ / SiO ₂ molar ratio was 3.9 × 10 ⁻⁴ , and pH was 5.3.
Further, the silica-based fine particles contained in the silica-based fine particle water-dispersed sol have an anisotropic shape, the average particle size determined by the dynamic light scattering method is 170.5 nm, the BET specific surface area is 93 m ² / g, The amount of negative charge existing per unit specific surface area was 0.13 μeq / m ² .
Further, the modification amount of aluminum contained in the silica-based fine particles was 7.0 × 10 ⁻⁹ mol / m ² in terms of unit surface area.
The average particle diameter of the silica-based fine particles contained in the silica-based fine particle water-dispersed sol was 29.3 nm as determined from the BET method, and the degree of irregularity was 5.82.

Preparation of methanol-dispersed sol containing anisotropic silica-based fine particles Water-dispersed sol containing silica-based fine particles (RCPA-) prepared in this comparative example instead of water-dispersed sol (CPA-1) containing anisotropic-shaped silica-based fine particles Methanol-dispersed sol containing silica-based fine particles (RCPM-2) using the same method as in preparation of methanol-dispersed sol containing anisotropically-shaped silica-based fine particles described in Example 1 except that 2) was used (RCPM-2) Was prepared.
The methanol-dispersed sol (RCPM-2) thus obtained contains anisotropically shaped silica-based fine particles, the water content is about 0.5% by weight, and the solid content concentration on the basis of SiO ₂ is 30%. The pH when diluted 10-fold with distilled water at 27% by weight was 5.3. The average particle size of the silica-based fine particles contained in this methanol-dispersed sol determined by the BET method is 29.3 nm, the average particle size measured by the dynamic light scattering method is 50.8 nm, The amount of aluminum modified was 7.0 × 10 ⁻⁹ mol / m ² , and the amount of negative charge per unit specific surface area was 0.13 μeq / m ² .

Preparation of Hard Coat Layer Film Forming Coating Composition (C2) Water containing anisotropic shaped silica fine particles prepared in this comparative example instead of water dispersed sol (CPA-1) containing anisotropic shaped silica fine particles A coating composition (C2) for forming a hard coat layer film was prepared in the same manner as the coating composition (H1) for forming a hard coat layer film described in Example 1, except that the dispersion sol (RCPA-2) was used. .

  Table 1 shows the properties of the silica-based fine particle water-dispersed sol (solid content concentration 30% by weight) and silica-based fine particles prepared in Examples 1 to 3 and Comparative Examples 1 and 2.

[Preparation of paint composition for forming primer coat layer]
[Preparation Example 1]
Preparation of coating composition 200 g of commercially available water-dispersed polyurethane resin (Daiichi Kogyo Seiyaku Co., Ltd. “Superflex 460: solid content concentration: 38%”) 200 g was mixed with pure water 100 g, 500 g of methanol with stirring, and leveling agent 2 g of a silicone surfactant (“L-7604” manufactured by Toray Dow Corning Co., Ltd.) is added and stirred at room temperature all day and night to form a primer coating layer-forming coating composition (hereinafter referred to as “primer coating”). ) Was prepared.

[Preparation of test piece]
[Preparation Example 2]
Pretreatment of plastic lens substrate Prepare the required number of commercially available plastic lens substrates CR-39 (using PPG monomer) and immerse them in a 10 wt% KOH aqueous solution kept at 40 ° C. for 3 minutes. Etching treatment was performed. Further, these were taken out, washed with water, and then sufficiently dried.

Formation of primer layer The plastic lens substrate obtained as described above was coated with the primer paint according to the combinations shown in Table 2 to form a coating film. In addition, application | coating of this coating composition was performed using the dipping method (lifting speed 100mm / min).
Next, the said coating film was heat-processed at 100 degreeC for 10 minute (s), and the coating film (primer layer) was pre-hardened.
The film thickness of the primer layer thus formed after preliminary curing was approximately 0.5 μm.

Formation of Hard Coat Layer According to the combinations shown in Table 2 on the surface of the plastic lens substrate or primer coat layer, the hard coat layer forming coating composition (that is, the hard coat paint obtained in Examples 1 to 3) H1 to H3 and hard coat paints C1 to C2) obtained in Comparative Examples 1 and 2 were respectively applied to form a coating film. In addition, application | coating of this coating composition was performed using the dipping method (pickup speed 230mm / min).
Next, after the coating film was dried at 100 ° C. for 10 minutes, the coating film (hard coat layer) was cured by heat treatment at 100 ° C. for 2 hours. At this time, the main curing of the primer layer was also performed at the same time.
Moreover, the film thickness after hardening of the said hard-coat layer formed in this way was 3.0-3.5 micrometers in general.

Formation of Antireflection Film Layer An inorganic oxide component having the following constitution was deposited on the surface of the cured hard coat layer according to the combinations shown in Table 2 by a vacuum deposition method. Laminated in the order of SiO ₂ : 0.06λ, ZrO ₂ : 0.15λ, SiO ₂ : 0.04λ, ZrO ₂ : 0.25λ, and SiO ₂ : 0.25λ from the hard coat layer side to the atmosphere side. A layer of antireflection film was formed. The design wavelength λ was 520 nm.

The test pieces 1 to 9 thus obtained were evaluated for film hardness, scratch resistance, transparency (degree of cloudiness), adhesion, hot water resistance, and weather resistance adhesion by the methods shown above. Shown in
As is clear from this result, the test piece obtained by applying the coating composition prepared in the example, that is, the coating composition containing the dispersed sol of anisotropic silica-based fine particles, was modified with aluminum on the surface. It was found that a coating film having excellent film hardness, scratch resistance, transparency, hot water resistance and weather resistance adhesion as compared with a coating composition containing an anisotropic silica sol which is not present, and excellent adhesion can be formed. Furthermore, it was found that a coating film having excellent coating film hardness can be formed as compared with a coating composition containing a spherical silica sol whose surface is modified with aluminum.

Claims (6)

Dispersion sol containing anisotropically shaped silica-based fine particles, the surface of the silica-based fine particles has a negative charge, and the surface of the silica-based fine particles is modified with aluminum, and the amount of modification of the aluminum is Al A dispersion sol of silica-based fine particles, characterized in that it is in the range of 0.01 × 10 ^{−6 to} 2.0 × 10 ⁻⁶ mol / m ² per unit surface area of the silica-based fine particles on a ₂ O ₃ conversion basis.   The average particle diameter (D1) measured by the dynamic light scattering method of the silica-based fine particles is in the range of 15 to 70 nm, the average particle diameter (D2) measured by the BET method is in the range of 10 to 50 nm, The dispersion sol of silica-based fine particles according to claim 1, wherein the degree of irregularity (D1 / D2) is in the range of 1.55 to 4.00. (A) a dispersion sol of silica-based fine particles according to claim 1 or 2,
(B) A coating composition comprising a binder component. A method for producing a dispersion sol comprising anisotropically shaped silica-based fine particles whose surface is modified with aluminum,
(1) An aqueous solution of aluminate in an alkaline silica sol having a pH of 9.0 to 11.5 containing anisotropic fine silica particles or fine particles containing silica as a main component, and a silicon component contained in the silica sol as SiO _2. In addition, when the aluminum contained in the aluminate is represented by Al ₂ O ₃ , the molar ratio (Al ₂ O ₃ / SiO ₂ ) is mixed at such a ratio as 0.0005 to 0.050. The process of
(2) A step of heating the mixture obtained in the above step to a temperature of 60 to 200 ° C. and stirring for 0.5 to 20 hours,
A method for producing a silica-based fine particle-dispersed sol, comprising: Method for producing a silica-based fine particle dispersion sol of claim 4, wherein the molar ratio _{(Al 2 O 3 / SiO 2} ) is characterized in that in the range of 0.005 to 0.050. Furthermore, the mixed solution obtained by the following step (3) and the step (2) is brought into contact with a cation exchange resin, and the alkali metal ions contained in the mixed solution are ion-exchanged to remove the pH of the mixed solution. The method for producing a silica-based fine particle-dispersed sol according to any one of claims 4 to 5, comprising a step of adjusting the pH to a range of 3.0 to 6.0.