JPWO2010071010A1 - Chain silica-based hollow fine particles and production method thereof, coating liquid for forming transparent film containing the fine particles, and substrate with transparent film - Google Patents

Abstract

Provided is a low refractive index chain silica-based hollow fine particle having a cavity penetrating inside an outer shell. The chain silica-based hollow fine particles have an outer shell on the outside, silica-based hollow fine particles (primary particles) having cavities inside connected in a chain, and through holes in which the cavities penetrate each other. The thickness (L) is in the range of 20 to 1500 nm, the average width (W) is in the range of 10 to 300 nm, and the refractive index is in the range of 1.10 to 1.35. The thickness (TS) of the outer shell is in the range of 2 to 100 nm, and the ratio (TS) / (W) to the average width (W) is in the range of 0.05 to 0.30.

Description

  The present invention relates to a chain silica-based hollow fine particle having a cavity penetrating inside, a method for producing the chain silica-based hollow fine particle, a coating liquid for forming a transparent film containing the chain silica-based hollow fine particle, and a chain silica-based The present invention relates to a substrate with a transparent film in which a transparent film containing hollow fine particles is formed on the surface of the substrate.

Conventionally, hollow silica particles having a particle size of about 0.1 to 300 μm are known (see Patent Document 1, Patent Document 2, etc.). Also, there is a method for producing hollow particles made of a dense silica shell by precipitating active silica from an alkali metal silicate aqueous solution on a core made of a material other than silica and removing the material without destroying the silica shell. It is publicly known (see, for example, Patent Document 3).
Furthermore, micron-sized spherical silica particles having a core-shell structure in which the outer peripheral portion is a shell, the central portion is hollow, the outer shell is denser on the outer side, and has a coarser concentration gradient structure on the inner side are known (Patent Document 4, etc.) reference).

  In addition, the applicant of the present application previously proposed that nano-sized composite oxide particles having a low refractive index can be obtained by completely covering the surface of porous inorganic oxide particles with silica or the like (Patent Document). 5), and further, a silica coating layer is formed on the core particles of the composite oxide composed of silica and an inorganic oxide other than silica, and then the inorganic oxide other than silica is removed, and silica is coated as necessary. By doing so, it has been proposed that nanometer-sized silica-based fine particles with a low refractive index having cavities inside can be obtained (see Patent Document 6).

  On the other hand, the present applicant has previously proposed to form chained silica particles by hydrothermally treating silica particles under weakly acidic conditions (see Patent Document 7). In the case of non-hollow particles, since the particle refractive index does not become 1.45 or less, in order to obtain particles having a lower refractive index, the applicant further adds an electrolyte substance in the hollow silica particle formation stage, thereby creating a chain. It has been proposed that shaped hollow silica particles are formed (see Patent Documents 8 and 9).

However, in the silica-based hollow particles according to the proposal of the applicant of the present application, a sufficient low refractive index effect may not be obtained depending on the purpose and application of the particles. That is, even if the inside of each particle is hollowed out, the hollow volume is limited from the viewpoint of particle strength, and there is a limit to lowering the refractive index, so silica-based hollow fine particles having a particle structure different from conventional ones. Was demanded.

JP-A-6-330606 Japanese Patent Laid-Open No. 7-013137 Special Table 2000-500113 JP-A-11-029318 Japanese Patent Laid-Open No. 07-133105 JP 2001-233611 A JP 2004-055298 A Special table 2004-099074 gazette JP 2005-186435 A

It is a schematic diagram of the cross section of the chain silica-based hollow fine particles of the present invention.

  The present invention has been developed based on the invention described in Patent Document 6 and aims to obtain silica-based fine particles having a low refractive index, and includes silica and inorganic oxides other than silica. Porous composite oxide particles (primary particles) consisting of the above are chained, the surface of the chained particles is covered with silica, and then inorganic oxides other than silica are removed to penetrate inside the outer shell. It is an object of the present invention to provide a method for producing chain silica-based hollow fine particles having cavities.

Another object of the present invention is to provide a coating material for forming a film, which contains the chain silica-based hollow fine particles and a matrix forming component for forming a film, and is excellent in stability, film forming property and the like.
In addition, the present invention provides a film containing the chain silica-based hollow fine particles on the surface of the base material, and has a low refractive index, adhesion to the base material, strength, scratch resistance, antireflection ability and antiglare. An object of the present invention is to provide a coated substrate having excellent performance and the like.

  The chain silica-based hollow microparticles according to the present invention have outer shells, silica-based hollow microparticles (primary particles) having cavities inside, connected in a chain, and through holes through which the cavities penetrate each other. The average length (L) is in the range of 20 to 1500 nm, the average width (W) is in the range of 10 to 300 nm, and the refractive index is in the range of 1.10 to 1.35.

The thickness (T _S ) of the outer shell is in the range of 2 to 100 nm, and the ratio (T _S ) / (W) to the average width (W) is in the range of 0.05 to 0.30. preferable.
It is preferable that (D _S ) / (W) of the ratio of the average diameter (D _S ) of the through holes to the average width (W) is in the range of 0.1 to 0.9.
An inorganic oxide other than silica and silica, the molar ratio MO _X / SiO ₂ when the inorganic oxide other than silica, expressed in MO _X is preferably in the range of 0.0001 to 0.2.

The method for producing chain silica-based hollow fine particles according to the present invention is characterized by comprising the following steps (a) to (f).
(A) An aqueous solution of a silicate and / or an acidic silicic acid solution and an aqueous solution of an alkali-soluble inorganic compound are dispersed in an alkaline aqueous solution or seed particles having a solid content concentration in the range of 0.01 to 2% by weight. The molar ratio MO _X / SiO ₂ (A) is 0.1 to ₂ when the silica is represented by SiO ₂ and the inorganic oxide other than silica is represented by MO _X. A step of preparing a composite oxide primary particle dispersion (b) a step of washing the primary particle dispersion (c) a hydrothermal treatment of the washed primary particle dispersion at 50 to 300 ° C. in the presence of an electrolyte to form a chain Step (d) of preparing a composite oxide particle dispersion (d) Step of forming a silica or silica-alumina-coated chain composite oxide particle dispersion by forming a silica or silica-alumina coating layer (e) Silica or silica Alumina coating A step (f) was obtained in which acid was added to the chain composite oxide particle dispersion to remove at least a part of elements other than silicon constituting the composite oxide particles to form a chain silica-based hollow fine particle dispersion. Process for washing the dispersion

It is preferable that the electrolyte in the step (c) is an alkaline earth metal salt.
Following the step (f), the following step (g) is preferably performed.
(G) Hydrothermal treatment of the chain silica-based hollow fine particle dispersion in the range of 50 to 300 ° C.

The step (d) is preferably any one of the following step (d-1), the following step (d-2), and the following step (d-3).
(D-1) An aqueous alkali solution and an organosilicon compound represented by the following chemical formula (1) and / or a partial hydrolyzate thereof are added to the chain complex oxide particle dispersion obtained in the step (c). Step of adding and forming a silica coating layer on the chain composite oxide particles
R _n SiX _(4-n) (1)
[However, R: unsubstituted or substituted hydrocarbon group having 1 to 10 carbon atoms, acrylic group, epoxy group, methacryl group, amino group, CF ₂ group, X: alkoxy group having 1 to 4 carbon atoms, silanol group, halogen Or hydrogen, n: an integer of 0 to 3]
(D-2) An aqueous alkali solution and an acidic silicic acid solution are added to the chain composite oxide particle dispersion obtained in the step (c) to form a silica coating layer on the chain composite oxide particles. Step (d-3) An alkali silicate aqueous solution and an aqueous aluminate solution are added to the chain composite oxide particle dispersion obtained in the step (c), and the silica-alumina coating layer is added to the chain composite oxide particles. Forming process

The coating liquid for forming a transparent film according to the present invention is characterized by comprising the chain silica-based hollow fine particles and a matrix-forming component.
The substrate with a transparent coating according to the present invention is characterized in that the transparent coating formed using the coating solution for forming a transparent coating is formed on the surface of the substrate alone or together with other coatings.

ADVANTAGE OF THE INVENTION According to this invention, the novel chain silica type hollow microparticle which has the cavity penetrated inside the outer shell can be provided. The novel chain silica-based hollow fine particles have a lower refractive index than silica-based hollow fine particles in which the hollow fine particles are connected in a chain.
According to the production method of the present invention, it is possible to provide chain silica-based hollow fine particles having a low refractive index.
Further, it is possible to provide a coating material for forming a coating film that includes the chain silica-based hollow fine particles and a matrix forming component for forming a coating film and is excellent in stability, film forming property, and the like.
In addition, a film containing the chain silica-based hollow fine particles is formed on the surface of the base material, and has a low refractive index, excellent adhesion to the base material, strength, scratch resistance, antireflection ability, etc. The substrate can be provided.

BEST MODE FOR CARRYING OUT THE INVENTION

[Chaline silica-based hollow fine particles]
First, the chain silica-based hollow fine particles according to the present invention will be described.
The chain silica-based hollow microparticles according to the present invention have outer shells, silica-based hollow microparticles (primary particles) having cavities inside, connected in a chain, and through holes through which the cavities penetrate each other. The average length (L) is in the range of 20 to 1500 nm, the average width (W) is in the range of 10 to 300 nm, and the refractive index is in the range of 1.10 to 1.35.

Silica-based hollow fine particles (primary particles)
The chain silica-based hollow fine particles have an outer shell on the outside, and silica-based hollow fine particles (primary particles) having cavities inside are connected in a chain.
A schematic view of a cross section of the chain silica-based hollow fine particles according to the present invention is shown in FIG.

In the present invention, the size of the silica-based hollow fine particles (primary particles) is preferably in the range of about 10 to 300 nm, more preferably 15 to 200 nm.
When the size of the primary particles is less than 10 nm, there is a tendency that they are not easily chained and agglomerate, and it may be difficult to obtain desired low refractive index chain silica-based hollow fine particles.
If the size of the primary particles exceeds 300 nm, the particles are too large to be chained, and it may be difficult to obtain the desired chain silica-based hollow fine particles.

As shown in FIG. 1, the average width (W) of the chain silica-based hollow fine particles is approximately equal to or larger than the primary particle diameter, and is preferably in the range of 10 to 300 nm, more preferably 15 to 200 nm.
In the chain silica-based hollow fine particles, the primary particles are linked in a chain shape, but the average length (L) is preferably in the range of 20 to 1500 nm, more preferably 40 to 1000 nm.
When the average length (L) is less than 20 nm, it means that the primary particle having a minimum particle diameter of 10 nm is less than 2, and the average length does not become the desired low refractive index chain silica-based hollow fine particles. When (L) exceeds 1500 nm, it may be agglomerated or entangled with each other, and it may be difficult to obtain desired chain silica-based hollow fine particles.

The thickness (T _S ) of the outer shell varies depending on the primary particle diameter or average width (W), but is preferably in the range of 2 to 100 nm, more preferably 3 to 50 nm.
When the outer shell has a thickness (T _S ) of less than 2 nm, the hollow structure may not be maintained when at least a part of elements other than silicon to be described later is removed. It may be difficult to obtain.
If the thickness of the outer shell (T _S ) exceeds 100 nm, the internal voids are small, and it may be difficult to obtain a desired low-refractive chain silica-based hollow fine particle.

Further, the thickness (T _S ) of the outer shell is in the range of 0.05 to 0.30, more preferably 0.05 to 0.2, with the ratio (T _S ) / (W) to the average width (W). Preferably there is.
When (T _S ) / (W) is less than 0.05, a hollow structure may not be maintained when at least a part of elements other than silicon is removed, and chain silica-based hollow fine particles can be obtained. It can be difficult.
If (T _S ) / (W) exceeds 0.30, the internal voids are small, and it may be difficult to obtain desired low-refractive chain silica-based hollow fine particles.

The ratio (D _S ) / (W) of the average diameter (D _S ) and the average width (W) of the through holes is in the range of 0.1 to 0.9, and further 0.3 to 0.8. Preferably there is.
When (D _S ) / (W) is less than 0.1, the pores of the through-holes are small, and the degree of contribution to lowering the refractive index is small, and a desired low refractive index chain silica-based hollow fine particle is obtained. May be difficult.
It is difficult to obtain chain silica-based hollow fine particles with (D _S ) / (W) exceeding 0.9.

Such chain silica-based hollow fine particles preferably have a refractive index in the range of 1.10 to 1.35, more preferably 1.10 to 1.30.
It is difficult to obtain chain silica hollow fine particles having a refractive index of less than 1.10, and those having a refractive index of more than 1.35 are excellent in adhesion to a substrate, strength, and scratch resistance. In some cases, the antireflection ability of the object becomes insufficient.

Chain silica hollow particles according to the present invention comprises an inorganic oxide other than silica and silica, the molar ratio MO _X / SiO ₂ when the inorganic oxide other than silica, expressed in MO _X is 0.0001 to 0 Preferably it is in the range of .2.
It is difficult to obtain a chain silica-based hollow fine particle having a molar ratio MO _X / SiO ₂ of less than 0.0001, and those having a molar ratio MO _X / SiO ₂ of more than 0.2 will be described later with respect to the production method. Since there is little removal of inorganic oxides other than silica, chain silica-based hollow fine particles having a low refractive index may not be obtained.

In the chain silica-based hollow fine particles of the present invention, inorganic oxides other than silica include Al ₂ O ₃ , B ₂ O ₃ , TiO ₂ , ZrO ₂ , SnO ₂ , Ce ₂ O ₃ , P ₂ O ₅ , Sb _2. One or more of O ₃ , MoO ₃ , ZnO ₂ , WO _{3 and the} like can be mentioned. Examples of the two or more inorganic oxides include TiO ₂ —Al ₂ O ₃ and TiO ₂ —ZrO ₂ . Of these, Al ₂ O ₃ is preferred.

The average length (L) and average width (W) of the chain silica-based hollow microparticles of the present invention were obtained by taking a transmission electron micrograph (TEM) of the chain silica-based hollow microparticles and measuring 100 particles with calipers. The length and width are measured by the above, and the average value is obtained.
Further, the average thickness (T _S ) of the outer shell and the average diameter (D _S ) of the through holes can be measured by observing a transmission electron micrograph (TEM) of the particle cross section.

The refractive index is obtained by the following procedure.
(1) Take the chain silica-based hollow fine particle dispersion in an evaporator and evaporate the dispersion medium.
(2) This is dried at 120 ° C. to obtain a powder.
(3) A standard refractive index liquid having a known refractive index is dropped on a glass plate of a few drops, and the above powder is mixed therewith.
(4) The operation of (3) is performed with various standard refractive index liquids, and the refractive index of the standard refractive index liquid when the mixed liquid becomes transparent is set as the refractive index of the chain silica-based hollow fine particles.

[Method for producing silica-based fine particles]
Next, a method for producing the chain silica-based hollow fine particles of the present invention will be described.
The method for producing chain silica-based hollow fine particles according to the present invention is characterized by comprising the following steps (a) to (f).
(A) An aqueous solution of a silicate and / or an acidic silicic acid solution and an aqueous solution of an alkali-soluble inorganic compound are dispersed in an alkaline aqueous solution or seed particles having a solid content concentration in the range of 0.01 to 2% by weight. The molar ratio MO _X / SiO ₂ (A) is 0.1 to ₂ when the silica is represented by SiO ₂ and the inorganic oxide other than silica is represented by MO _X. A step of preparing a composite oxide primary particle dispersion (b) a step of washing the primary particle dispersion (c) a hydrothermal treatment of the washed primary particle dispersion at 50 to 300 ° C. in the presence of an electrolyte to form a chain Step (d) of preparing a composite oxide particle dispersion (d) Step of forming a silica or silica-alumina-coated chain composite oxide particle dispersion by forming a silica or silica-alumina coating layer (e) Silica or silica Alumina coating A step (f) was obtained in which acid was added to the chain composite oxide particle dispersion to remove at least a part of elements other than silicon constituting the composite oxide particles to form a chain silica-based hollow fine particle dispersion. Process for washing the dispersion

Step (a)
As the silicate, one or more silicates selected from alkali metal silicates, ammonium silicates and organic base silicates are preferably used. Examples of the alkali metal silicate include sodium silicate (water glass) and potassium silicate, and examples of the organic base include quaternary ammonium salts such as tetraethylammonium salt, amines such as monoethanolamine, diethanolamine, and triethanolamine. The ammonium silicate or organic base silicate includes an alkaline solution in which ammonia, quaternary ammonium hydroxide, an amine compound, or the like is added to the silicic acid solution.
As the acidic silicic acid solution, a silicic acid solution obtained by removing an alkali by treating an alkali silicate aqueous solution with a cation exchange resin or the like can be used. In particular, pH _{2 to} pH 4 and SiO ₂ concentration is about 7% by weight. The following acidic silicic acid solutions are preferred.

Examples of the inorganic oxide include Al ₂ O ₃ , B ₂ O ₃ , TiO ₂ , ZrO ₂ , SnO ₂ , Ce ₂ O ₃ , P ₂ O ₅ , Sb ₂ O ₃ , MoO ₃ , ZnO ₂ and WO ₃ . 1 type or 2 or more types can be mentioned. Examples of the two or more inorganic oxides include TiO ₂ —Al ₂ O ₃ and TiO ₂ —ZrO ₂ .
Of these, Al ₂ O ₃ is preferable because it is easy to obtain spherical primary particles and is easy to remove.

  As a raw material for such an inorganic oxide, an alkali-soluble inorganic compound is preferably used, and an alkali metal salt, an alkaline earth metal salt, or an ammonium salt of a metal or a non-metal oxo acid constituting the inorganic oxide described above. And quaternary ammonium salts, and more specifically, sodium aluminate, sodium tetraborate, zirconyl ammonium carbonate, potassium antimonate, potassium stannate, sodium aluminosilicate, sodium molybdate, cerium ammonium nitrate, Sodium phosphate and the like are preferred.

In order to prepare a composite oxide primary particle dispersion, an alkali aqueous solution of the inorganic compound is separately prepared in advance, or a mixed aqueous solution is prepared, and the aqueous solution other than the target silica and silica is prepared. Depending on the composite ratio of the inorganic oxide, it is gradually added with stirring to an aqueous alkali solution, preferably an aqueous alkali solution having a pH of 10 or higher.

The addition ratio of the silica raw material and the inorganic compound raw material added to the alkaline aqueous solution is such that the molar ratio MO _X / SiO ₂ is 0.01 to when the silica component is represented by SiO ₂ and the inorganic compound other than silica is represented by MO _X. 2, In particular, it is preferable to be in the range of 0.1 to 1. If the MO _X / SiO ₂ is less than 0.01, the finally obtained chain silica-based hollow fine particles do not have a sufficiently large cavity volume. On the other hand, if the MO _X / SiO ₂ exceeds 2, the spherical composite oxide It is difficult to obtain primary particles, or even if it can be done, spherical complex oxide fine particles are destroyed when elements other than silicon are removed. As a result, chain silica hollow fine particles having cavities inside are obtained. It may not be possible.
When the molar ratio MO _X / SiO ₂ is in the range of 0.01 to _2, the structure of the composite oxide primary particles is mainly a structure in which silicon and elements other than silicon are alternately bonded through oxygen. That is, oxygen atoms are bonded to the four bonds of silicon atoms, and many structures other than silica are bonded to the oxygen atoms. When removing elements other than silicon in the step (e) described later, The element M can be removed without destroying the shape of the composite oxide primary particles connected in a chain.

The average particle diameter of the composite oxide primary particles is preferably in the range of 5 to 280 nm, more preferably 10 to 200 nm.
When the average particle diameter of the composite oxide primary particles is less than 5 nm, the proportion of the outer shell of the finally obtained chain silica-based hollow fine particles increases, the proportion of the cavity volume does not increase sufficiently, and the composite oxidation If the average particle diameter of the primary particles exceeds 280 nm, it is difficult to form a chain in the step (b), or the removal of elements other than silicon is insufficient in the step (d). The cavity volume may not be sufficiently large, and it may be difficult to obtain particles with a low refractive index.

In the production method of the present invention, it is preferable to use a seed particle dispersion as a starting material when preparing a composite oxide primary particle dispersion.
Seed particles include inorganic oxides such as SiO ₂ , Al ₂ O ₃ , TiO ₂ , ZrO ₂ , SnO _2, and CeO ₂ , or composite oxides thereof such as SiO ₂ —Al ₂ O ₃ , TiO ₂ —Al. Fine particles such as ₂ O ₃ , TiO ₂ —ZrO ₂ , SiO ₂ —TiO ₂ , SiO ₂ —TiO ₂ —Al ₂ O ₃ are used, and it is usually preferable to use these sols. Such a dispersion of seed particles can be prepared by a conventionally known method. For example, it can be obtained by adding an acid or alkali to a metal salt, a mixture of metal salts, a metal alkoxide, or the like corresponding to the inorganic oxide, hydrolyzing, and aging as necessary.

In the seed particle-dispersed alkaline aqueous solution, the aqueous solution of the compound is preferably added to the seed particle-dispersed alkaline aqueous solution adjusted to a pH of 10 or more with stirring in the same manner as in the above-described method of adding the alkali solution. As described above, when the composite oxide fine particles are grown using the seed particles as seeds, it is easy to control the particle size of the grown particles, and particles having uniform particle sizes can be obtained. The addition ratio of the silica raw material and the inorganic oxide to be added to the seed particle dispersion is set to the same range as the case of adding to the aqueous alkali solution.
The silica raw material and inorganic oxide raw material described above have high solubility on the alkali side. However, when both are mixed in this highly soluble pH region, the solubility of oxo acid ions such as silicate ions and aluminate ions decreases, and these composites precipitate and grow into colloidal particles, or on the seed particles. Precipitates into particles and causes particle growth.

In the present invention, an aqueous solution of silicate and / or an acidic silicic acid solution and an alkali-soluble inorganic compound aqueous solution are added until the average particle diameter (D _P1 ) of the composite oxide primary particles becomes 5 to 280 nm. The addition may be continuous or intermittent, but it is preferable to add both at the same time.
Further, the molar ratio MO _X / SiO ₂ (A) at this time is in the range of 0.01 to ₂ , but it can be added while changing the molar ratio to be small.

In the present invention, in the step (a), the composite oxide primary particles can be prepared in the presence of an electrolyte salt as necessary.
At this time, the number of moles of the electrolyte salt (M _Ea) and SiO ₂ of moles (M _Sa) and the ratio of _{(M Ea) / (M Sa} ) from 0.1 to 10, preferably from 0.2 to 8 Can be added.
Examples of the electrolyte salt include water-soluble electrolyte salts such as sodium chloride, potassium chloride, sodium nitrate, potassium nitrate, sodium sulfate, potassium sulfate, ammonium nitrate, ammonium sulfate, magnesium chloride, and magnesium nitrate.
When an electrolyte salt is used, it is preferably added at a time point that is approximately 1/5 to 4/5 of the average particle diameter of the resulting composite oxide primary particles. You may add continuously or intermittently, adding inorganic compounds other than a metal silicate and a silica, and carrying out the particle growth of composite oxide fine particles.

The amount of electrolyte salt added depends on the concentration of the composite oxide primary particle dispersion. However, when the molar ratio (M _Ea ) / (M _Sa ) is less than 0.1, the effect of adding the electrolyte salt is ineffective. When removing at least a part of the elements other than silicon constituting the composite oxide primary particles by adding an acid in step (e), the composite oxide fine particles cannot be maintained in a spherical shape and are destroyed, and voids are formed inside. It may be difficult to obtain the chain silica-based hollow fine particles. The reason for the effect of adding such an electrolyte salt is not clear, but silica is increased on the surface of the grown composite oxide primary particles, and acid-insoluble silica acts as a protective film for the composite oxide primary particles. It is thought that it is doing.
For this reason, although the silica or silica-alumina coating layer is formed in the step (d) described later, the silica or silica-alumina coating layer to be formed can be thinned.

Even if the molar ratio (M _Ea ) / (M _Sa ) exceeds 10, the effect of adding the electrolyte is not improved, new fine particles are formed, and the economical efficiency is lowered.

Step (b)
The composite oxide primary particle dispersion prepared in step (a) is then washed to remove cations, anions and electrolytes.
The washing method is not particularly limited as long as it can remove cations, anions, and electrolytes, and a conventionally known method can be employed. In the present invention, since the particles are fine particles, the ultrafiltration membrane method and the ion exchange resin method are preferably employed. Both can be used together.
If the washing is insufficient, it is difficult to obtain the chain composite oxide primary particles in the next step (c).

Step (c)
An electrolyte is added to the composite oxide primary particle dispersion, and a hydrous heat treatment is performed at 50 to 300 ° C. and further 80 to 250 ° C. in the presence of the electrolyte to prepare a chain composite oxide particle dispersion.
The electrolyte is not particularly limited as long as the composite oxide primary particles can be chained, but in the present invention, an alkaline earth metal salt is preferable.
Examples of alkaline earth metal salts include hydrochlorides such as magnesium and calcium, nitrates, sulfates, and organic acid salts.

The concentration of the composite oxide primary particle dispersion when the electrolyte is added is preferably 0.1 to 20% by weight, more preferably 0.5 to 10% by weight, as a solid content.
When the concentration of the composite oxide primary particle dispersion is less than 0.1% by weight as a solid content, chain formation is possible but productivity is low, and the concentration of the composite oxide primary particle dispersion is 20 as a solid content. If the weight percentage is exceeded, the particles may form aggregates.

Further, the amount of electrolyte added is such that the ratio (W _EL ) / (W _P1 ) of the weight (W _P1 ) of the composite oxide primary particles in the dispersion to the weight (W _EL ) of the _electrolyte is 0.001 to 0.001. 8, more preferably in the range of 0.01 to 0.2.
If (W _EL ) / (W _P1 ) is less than 0.001, the composite oxide primary particles may not be chained, and if (W _EL ) / (W _P1 ) exceeds 0.8, composite oxidation may occur. In some cases, the primary particles of the product become aggregates.

In the present invention, an acidic silicic acid solution can be added in addition to the electrolyte. The acidic silicic acid liquid is an acidic silicic acid liquid similar to the acidic silicic acid liquid used in the step (d-2) to be described later. The amount of the acidic silicic acid liquid is the same as the weight (W _P1 ) of the composite oxide primary particles in the dispersion. The ratio (W _S ) / (W _P1 ) of the acidic silicic acid solution to the weight (W _S ) of SiO ₂ is preferably in the range of 0.01 to 1, more preferably 0.02 to 0.5.
When (W _S ) / (W _P1 ) is less than 0.01, although depending on the particle diameter of the composite oxide primary particles, chain formation is promoted or chains of the composite oxide primary particles are formed. In some cases, when (W _S ) / (W _P1 ) exceeds 1, it may be difficult to remove elements other than silicon in step (e) to be described later. In some cases, a through hole in which cavities in chain particles penetrate each other may not be formed.

When the hydrothermal treatment temperature is lower than 50 ° C., chaining does not proceed, and a large amount of monodispersed composite oxide primary particles remain, and when the hydrothermal treatment temperature exceeds 300 ° C., aggregated particles tend to increase.
The hydrothermal treatment time is generally 1 to 24 hours, although it varies depending on the temperature.

Step (d)
Next, a silica or silica-alumina coating layer is formed.
There are three methods for forming a silica or silica-alumina coating layer.
The first method is the step (d-1), and an aqueous alkali solution and an organosilicon compound represented by the following chemical formula (1) are added to the chain complex oxide particle dispersion obtained in the step (c). And / or a partial hydrolyzate thereof.
R _n SiX _(4-n) (1)
[However, R: unsubstituted or substituted hydrocarbon group having 1 to 10 carbon atoms, acrylic group, epoxy group, methacryl group, amino group, CF ₂ group, X: alkoxy group having 1 to 4 carbon atoms, silanol group, halogen Or hydrogen, n: an integer of 0 to 3]

  Specific examples of the organosilicon compound include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, and dimethyldiethoxy. Silane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (βmethoxyethoxy) silane, 3,3,3-trifluoropropyltrimethoxysilane, methyl- 3,3,3-trifluoropropyldimethoxysilane, β- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxytripropyltrimethoxysilane, -Glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ- Methacryloxypropyltriethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltriethoxy Silane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, trimethylsilanol, methyltrichlorosilane Examples include orchid, methyldichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, vinyltrichlorosilane, trimethylbromosilane, and diethylsilane.

The second method is step (d-2) in which an aqueous alkali solution and an acidic silicic acid solution are added to the chain composite oxide particle dispersion obtained in step (c).
As the acidic silicate solution, an alkaline silicate aqueous solution, for example, an acidic silicate solution obtained by dealkalizing water glass with an ion exchange resin is used. Such an acidic silicic acid solution has a concentration of 0.1 to 7% by weight as SiO ₂ and a pH of 0.1 to 4.

  The third method is step (d-3), in which an aqueous alkali silicate solution and an aqueous aluminate solution are added to the chain composite oxide particle dispersion obtained in step (c).

In the above, the addition amount of the organosilicon compound or acidic silicic acid solution used for forming the silica coating layer is in the range of 10 to 2000% by weight, more preferably 20 to 1000% by weight of the chain complex oxide particles as the solid content. .
When the addition amount of the organosilicon compound or the acidic silicic acid solution is less than 10% by weight of the chain composite oxide particles as a solid content, the coating layer is thin, so that elements other than silicon are removed in the step (e). In some cases, the chained particles may collapse or become chained silica-based hollow fine particles having cavities open to the outside.
If the addition amount of the organosilicon compound or the acidic silicic acid solution exceeds 2000% by weight of the chain composite oxide particles as a solid content, it is difficult to remove elements other than silicon, or the outer shell is too thick and the desired low In some cases, chain silica hollow fine particles having a refractive index cannot be obtained.

Moreover, it is preferable to add alkaline aqueous solution so that pH of a chain | strand-shaped complex oxide particle dispersion liquid may be maintained at 7-13.5, Furthermore, 10-13.
When the pH of the chain complex oxide particle dispersion is less than 7, the chain complex oxide particles may aggregate to form a uniform coating layer or particle growth.
When the pH of the chain composite oxide particle dispersion exceeds 13.5, the silica and alumina are highly soluble, so formation of the silica layer and silica / alumina layer and particle growth become difficult. Hollow fine particles may not be obtained.

In addition, when an alkali silicate aqueous solution and an aluminate aqueous solution are added to the formation of the silica / alumina coating layer in the step (d-3), the molar ratio Al ₂ O ₃ / SiO ₂ is 0.01 to 0.5, Furthermore, it is preferable that it exists in the range of 0.05-0.3.
When the molar ratio Al ₂ O ₃ / SiO is less than 0.01, there is no difference from the formation of the silica layer, and the ease of removing elements other than silicon by the formation of the silica / alumina coating layer is reduced.
When the molar ratio Al ₂ O ₃ / SiO exceeds 0.5, there is too much alumina in the coating layer, and when the elements other than silicon are removed in step (e), the coating layer cannot be maintained, In some cases, it becomes a chain silica-based hollow fine particle having an open cavity.

The addition amount in the case of adding the alkali silicate aqueous solution and the aluminate aqueous solution to the formation of the silica / alumina coating layer is 10 to 2000% by weight of the chain composite oxide particles as the silica / alumina solid content, and further 20 to 1000%. It is preferably in the range of wt%.
When the addition amount of the alkali silicate aqueous solution and the aluminate aqueous solution is less than 10% by weight of the chain composite oxide particles as a solid content, elements other than silicon are removed in step (e) because the coating layer is thin. In some cases, the chained particles may collapse or become chained silica-based hollow fine particles having cavities open to the outside.
When the addition amount of the alkali silicate aqueous solution and the aluminate aqueous solution exceeds 2000% by weight of the chain composite oxide particles as a solid content, it is difficult to remove elements other than silicon, or the outer shell is too thick and the desired low In some cases, chain silica hollow fine particles having a refractive index cannot be obtained.

The concentration of the chain composite oxide particle dispersion when forming the silica layer and the silica-alumina layer is preferably in the range of 0.5 to 20% by weight, more preferably 1 to 10% by weight as the solid content.
When the concentration of the chain complex oxide particle dispersion is less than 0.5% by weight as the solid content, the productivity is low, and when it exceeds 20% by weight, the particles may be aggregated.

The temperature at which the silica or silica-alumina coating layer is formed is preferably 30 to 150 ° C, more preferably 50 to 100 ° C.
If the temperature at which the silica or silica-alumina coating layer is formed is less than 30 ° C., it may take a long time to form the silica-alumina coating layer, or a coating layer having a desired thickness may not be formed.
When the temperature at the time of forming the silica or silica-alumina coating layer exceeds 150 ° C., the chain composite oxide particles may be aggregated depending on the concentration.

Step (e)
A chain silica-based hollow fine particle dispersion in which an acid is added to the silica or silica-alumina-coated composite oxide particle dispersion to remove at least a part of elements other than silicon constituting the silica or silica-alumina-coated composite oxide particles. And
When removing elements other than silicon, for example, it is removed by dissolution by adding mineral acid or organic acid, ion exchange removal by contacting with a cation exchange resin, or a combination of these methods. To do.

  The concentration of silica or silica / alumina-coated composite oxide particles in the dispersion of silica or silica-alumina-coated composite oxide particles when removing elements other than silicon varies depending on the treatment temperature, but is 0 in terms of oxide. 0.1 to 50% by weight, particularly 0.5 to 25% by weight is preferred. When the concentration of the silica-coated composite oxide particles is less than 0.1% by weight, the production efficiency is low. When the concentration exceeds 50% by weight, the composite oxide particles having a large content of elements other than silicon are uniform or efficient. May not be removed in a small number of times.

The removal of the above elements is preferably carried out until the MO _X / SiO ₂ of the chain silica-based hollow fine particles obtained for the above-described reason is 0.0001 to 0.2, particularly 0.001 to 0.1. .

Step (f)
The chain silica-based hollow fine particle dispersion obtained in the step (e) mainly contains an acid, a cation of an element other than silicon, and dissolved silica.
The cleaning method is the same as in step (b). The washing is preferably performed until the acid, cations of elements other than silicon, and dissolved silica are substantially eliminated.

Step (g)
The chain silica-based hollow fine particle dispersion is hydrothermally treated at 50 to 300 ° C, more preferably at 80 to 250 ° C.
In the present invention, the chain silica-based hollow fine particles obtained in the step (f) can be used as they are, but it is preferable to perform a hydrothermal treatment after the step (f).

When the hydrothermal treatment temperature is lower than 50 ° C., densification of the outer shell of the obtained chain silica-based hollow fine particles is insufficient, and depending on the usage of the chain silica-based hollow fine particles, a solvent or a matrix-forming component for forming a transparent film May enter the cavity and the low refractive index effect may not be obtained. In addition, the content of impurities such as alkali metals or ammonia in the obtained chain silica-based hollow fine particles cannot be effectively reduced, and the stability of the coating liquid for forming a film becomes insufficient. May be insufficient in strength.
When the hydrothermal treatment temperature exceeds 300 ° C., an aggregate of chain silica-based hollow fine particles may be formed.

After the hydrothermal treatment, washing can be performed as necessary in the same manner as in the step (b).
By washing, alkali and / or ammonia eluted by hydrothermal treatment can be further reduced.

In the method for producing the chain silica-based hollow fine particles of the present invention, the obtained chain silica-based hollow fine particle dispersion is replaced with an organic solvent using an ultrafiltration membrane, a rotary evaporator, or the like, to thereby obtain an organic solvent-dispersed sol. Can be obtained.
The obtained chain silica-based hollow fine particles can also be used after being treated with a silane coupling agent or the like by a conventionally known method.
Moreover, in the manufacturing method of the chain | strand-shaped silica type hollow microparticles of this invention, after washing | cleaning, it can dry and it can bake as needed.

[Transparent coating solution]
Next, the coating liquid for forming a transparent film will be described.
The coating liquid for forming a transparent film according to the present invention contains the chain silica-based hollow fine particles and a matrix-forming component.

A conventionally well-known dispersion medium can be used as a dispersion medium of a dispersion medium coating liquid, and specifically, water and various organic solvents are mentioned.
The organic solvent used in the present invention is not particularly limited as long as it can dissolve or disperse a matrix-forming component, which will be described later, and a polymerization initiator used as necessary, and can uniformly disperse the chain silica-based hollow fine particles described above. A known dispersion medium can be used.
Specifically, alcohols such as methanol, ethanol, propanol, 2-propanol (IPA), butanol, diacetone alcohol, furfuryl alcohol, tetrahydrofurfuryl alcohol, ethylene glycol, hexylene glycol, isopropyl glycol; methyl acetate , Esters such as ethyl acetate, butyl acetate; diethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol isopropyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl Ethers such as ether and propylene glycol monoethyl ether; Acetone, methyl ethyl ketone, methyl isobutyl ketone, butyl methyl ketone, cyclohexanone, methyl cyclohexanone, dipropyl ketone, methyl pentyl ketone, diisobutyl ketone, isophorone, acetylacetone, ketones such as acetoacetate, toluene, xylene and the like. These may be used alone or in combination of two or more.

Polymerization initiator The coating liquid of the present invention may contain a polymerization initiator together with the chain silica-based hollow fine particles and the matrix-forming component. As the polymerization initiator, known ones can be used without particular limitation. 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- Examples include cyclohexyl-phenyl-ketone and 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one.

Chain silica-based hollow fine particles As the chain silica-based hollow fine particles, the chain silica-based hollow fine particles are used.
The coating liquid of the present invention may contain inorganic oxide fine particles other than the chain silica-based hollow fine particles as necessary.
Examples of the inorganic oxide fine particles include conventionally known low refractive index inorganic oxide fine particles, high refractive index inorganic oxide fine particles, and conductive inorganic oxide fine particles.

  The matrix-forming component is a dispersion of the fine particles, and refers to a component that can form a film on the surface of the substrate. The matrix-forming component is selected from resins that meet conditions such as adhesion to the substrate, hardness, and coatability. For example, conventionally used polyester resin, acrylic resin, urethane resin, vinyl chloride resin, epoxy resin, melamine resin, fluororesin, silicone resin, butyral resin, phenol resin, vinyl acetate resin, UV curable resins, electron beam curable resins, emulsion resins, water-soluble resins, hydrophilic resins, mixtures of these resins, and coating resins such as copolymers and modified products of these resins, or hydrolysis of alkoxysilanes, etc. Organic organosilicon compounds and partial hydrolysates thereof.

The total concentration of the matrix-forming component and the chain silica-based hollow fine particles in the coating solution for forming a transparent film is preferably in the range of 1 to 60% by weight, more preferably 2 to 50% by weight as the solid content.
When the solid content concentration of the coating liquid for forming a transparent film is less than 1% by weight, a necessary film thickness may not be obtained by a single application. For this reason, if coating and drying are repeated, adhesion and the like are insufficient. It is disadvantageous in economic efficiency.
When the solid content concentration exceeds 60% by weight, the film thickness of the obtained transparent film may become non-uniform or cracks may occur.

The concentration of the chain silica-based hollow fine particles in the coating liquid for forming a transparent film is such that the content of the chain silica-based hollow fine particles in the obtained transparent film is 5 to 80% by weight, further 10 to 50% by weight as the solid content. The range is used.
When the content of the chain silica-based hollow fine particles in the transparent film is less than 5% by weight as the solid content, a transparent film having a desired low refractive index may not be obtained, and the chain silica-based hollow of the present invention may not be obtained. Other conventionally known low refractive index particles may be used regardless of the fine particles.
If the content of the chain silica hollow fine particles in the transparent coating exceeds 80% by weight as the solid content, the transparency and strength of the film may be insufficient.
In addition, when using inorganic oxide fine particles other than the chain silica-based hollow fine particles as necessary, the total concentration of the particles is preferably in the same range as described above.

  The concentration of the matrix-forming component in the coating solution for forming a transparent coating is such that the content of the matrix component in the resulting transparent coating is in the range of 20 to 95% by weight, further 50 to 90% by weight as the solid content. Used for.

More specifically, the concentration of the chain silica-based hollow fine particles in the coating solution for forming a transparent film is in the range of 0.05 to 48% by weight, further 0.1 to 30% by weight as the solid content. preferable.
The concentration of the matrix-forming component in the coating liquid for forming a transparent film is preferably in the range of 0.2 to 57% by weight, more preferably 0.5 to 54% by weight as the solid content.

The above-mentioned coating liquid for forming a transparent film is applied to a substrate by a known method such as a dipping method, a spray method, a spinner method, a roll coating method, a bar coating method, a gravure printing method, or a micro gravure printing method, dried, and then irradiated with ultraviolet rays. A transparent film can be formed by curing by conventional methods such as irradiation and heat treatment.
The film thickness of the obtained transparent coating is preferably in the range of 200 nm to 20 μm.

[Base material with transparent film]
Next, the substrate with a transparent coating will be described.
In the substrate with a transparent coating according to the present invention, the transparent coating formed using the coating solution for forming a transparent coating is formed on the surface of the substrate alone or together with other coatings.

Base materials such as glass, polycarbonate, acrylic resin, plastic sheets such as PET and TAC, plastic films, plastic lenses, plastic panels, and other substrates, cathode ray tubes, fluorescent display tubes, liquid crystal display plates, etc. A coating film is formed on the surface. Depending on the application, the coating film is used alone or on a substrate. A protective film, a hard coat film, a planarizing film, a high refractive index film, an insulating film, a conductive resin film, a conductive metal It is formed in combination with a fine particle film, a conductive metal oxide fine particle film, and a primer film used as necessary. In addition, when using in combination, it is preferable that the film of this invention is formed in the outermost surface.

  Such a transparent coating is prepared by applying the coating solution for forming the transparent coating to a substrate by a known method such as a dipping method, a spray method, a spinner method, or a roll coating method, drying, and heating or It can be obtained by curing by ultraviolet irradiation or the like.

The refractive index of the transparent film formed on the surface of the base material varies depending on the mixing ratio of the chain silica hollow fine particles and the matrix components and the refractive index of the matrix used, but is as low as 1.15 to 1.42. Refractive index. In addition, the refractive index of the chain silica-based hollow fine particles of the present invention is 1.10 to 1.35.
This is because the chain silica-based hollow fine particles of the present invention have cavities inside, matrix forming components such as resin remain outside the particles, and the cavities inside the chain silica-based hollow fine particles are retained.

  Furthermore, in the above-mentioned substrate with a transparent coating, when the refractive index of the substrate is 1.60 or less, a coating having a refractive index of 1.60 or more on the surface of the substrate (hereinafter sometimes referred to as an intermediate coating). It is recommended to form a transparent film containing the chain silica-based hollow fine particles of the present invention. If the refractive index of the intermediate coating is 1.60 or more, the difference between the refractive index of the transparent coating containing the chain silica-based hollow fine particles of the present invention is large, and a substrate with a transparent coating having more excellent antireflection performance is obtained. It is done. The refractive index of the intermediate coating can be adjusted by the refractive index of the metal oxide fine particles used for increasing the refractive index of the intermediate coating, the mixing ratio of the metal oxide fine particles and the resin, and the refractive index of the resin used.

The coating solution for forming an intermediate coating is a mixed solution of metal oxide particles and a matrix for forming a coating, and an organic solvent is mixed as necessary. As the film forming matrix, the same film as that containing the silica-based fine particles of the present invention can be used. By using the same film forming matrix, the coated substrate having excellent adhesion between the two films Is obtained.
The following examples further illustrate the present invention.

Preparation of chain silica-based hollow fine particles (P-1) Silica-alumina sol (manufactured by JGC Catalysts & Chemicals Co., Ltd .: USBB-120, average particle size 25 nm, SiO ₂ · Al ₂ O ₃ concentration 20 wt%, solid content in Al ₂ O ₃ content 27 wt%) was added to deionized water 3900g was warmed to 98 ° C. to 100 g, while maintaining this temperature, concentration of 1.5 wt% aqueous solution of sodium silicate 1750g as SiO ₂ and Al ₂ O ₃ As a result, 1750 g of a sodium aluminate aqueous solution having a concentration of 0.5% by weight was added over 6 hours to obtain a dispersion of primary particles of SiO ₂ .Al ₂ O ₃ (P-1). The molar ratio at this time was MO _X / SiO ₂ = 0.2. Further, the pH of the reaction solution at this time was 12.0. The average primary particle diameter of this dispersion was 35 nm. (Process (a))

Next, the SiO ₂ · Al ₂ O ₃ primary particle (P-1) dispersion is washed by the ultrafiltration membrane method and concentrated to obtain a SiO ₂ · Al ₂ O ₃ primary particle (P- 1) A dispersion was obtained. (Process (b))
Separately, an aqueous solution prepared by mixing 136 g of an acidic silicic acid solution having a concentration of 2% by weight as SiO ₂ and 5.4 g of an aqueous solution of Ca (NO ₃ ) ₂ having a concentration of 10% by weight as an electrolyte for chain formation is prepared. After mixing 300 g of 5 wt% SiO ₂ · Al ₂ O ₃ primary particle (P-1) dispersion and adding 9 g of 2 wt% NaOH aqueous solution to this, hydrothermal treatment at 150 ° C. for 3 hours. Then, a chain composite oxide particle (P-1) dispersion having a solid content concentration of 5% by weight was prepared. Then it was cooled to room temperature. The pH of the dispersion at this time was 10.9. (Process (c))

Then, the solid content concentration of 5 wt% of a chain-like composite oxides particles (P-1) dispersion liquid was added to deionized water 3900g was warmed to 98 ° C. to 300 g, while maintaining this temperature, concentration as SiO ₂ 1. 1530 g of 5 wt% sodium silicate aqueous solution and 500 g of 0.5 wt% sodium aluminate aqueous solution as Al ₂ O ₃ were added over 17 hours, and silica-alumina coated chain composite oxide particles (P-1) A dispersion was obtained. (Process (d))

  Subsequently, 1,125 g of pure water was added to 500 g of the silica / alumina-coated chain composite oxide particle (P-1) dispersion which was washed by the ultrafiltration membrane method and concentrated to a solid content concentration of 13% by weight. Concentrated hydrochloric acid (concentration 35.5% by weight) was added dropwise to adjust the pH to 1.0, and dealumination was performed. Subsequently, the aluminum salt dissolved while adding 10 L of hydrochloric acid aqueous solution of pH 3 and 5 L of pure water is separated and washed with an ultrafiltration membrane, and water dispersion of the chain silica hollow particles (P-1) having a solid content concentration of 20% by weight is performed. A liquid was obtained. (Step (e)) (Step (f))

For the obtained chain silica-based hollow fine particles (P-1), the average width, average length, outer shell thickness, average diameter of through-holes, MO _X / SiO ₂ (molar ratio) and refractive index were measured, The results are shown in Table 1. The same measurement was performed in the following examples and comparative examples, and the results are shown in Table 1.
Here, the average particle diameter was measured by a dynamic light scattering method, and the refractive index was measured by the above-described method using Series A and AA manufactured by CARGILL as a standard refractive liquid. MO _X is measured with an ICP emission spectrophotometer (Shimadzu Corporation: ICPS-8100), and SiO ₂ is a value obtained by removing the weight of MO _X and Na ₂ O from the weight of the residual solid when calcined at 1000 ° C. Using.

Production of substrate with transparent coating (A- 1) The aqueous dispersion of chain silica-based hollow microparticles (P-1) having a solid content concentration of 20% by weight obtained above was used to remove the solvent using an ultrafiltration membrane. Substitution with ethanol was performed to prepare an alcohol dispersion of chain silica-based hollow fine particles (P-1) having a solid concentration of 20% by weight.
50 g of an alcohol dispersion of chain silica hollow fine particles (P-1) diluted with ethanol to a solid concentration of 5% by weight, 3 g of acrylic resin (Hitaroid 1007, manufactured by Hitachi Chemical Co., Ltd.), isopropanol and n -A coating solution was prepared by thoroughly mixing 47 g of a butanol 1/1 (weight ratio) mixed solvent.
This coating solution was applied to a PET film by a bar coater method and dried at 80 ° C. for 1 minute to obtain a substrate with transparent coating (A-1) having a transparent coating thickness of 100 nm. Table 2 shows the total light transmittance, haze, reflectance of light having a wavelength of 550 nm, refractive index of the coating, adhesion, scratch resistance, and pencil hardness of the substrate with transparent coating (A-1). In the following examples and comparative examples, the same measurement was performed, and the results are shown in Table 2.

  The total light transmittance and haze were measured with a haze meter (manufactured by Suga Test Instruments Co., Ltd.), and the reflectance was measured with a spectrophotometer (JASCO Corporation, Ubest-55). Moreover, the refractive index of the film was measured with an ellipsometer (manufactured by ULVAC, EMS-1). The uncoated PET film had a total light transmittance of 90.7%, a haze of 2.0%, and a reflectance of light having a wavelength of 550 nm of 7.0%.

  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 coating surface, a predetermined load was applied, and the film was pulled at a constant speed, and the presence or absence of scratches was observed.

In addition, 11 parallel scratches were made on the surface of the substrate (A-1) with a transparent coating at intervals of 1 mm in length and width with a knife to make 100 squares, cellophane tape was adhered to this, and then cellophane tape was attached. Adhesion was evaluated by classifying the number of cells remaining without peeling off when the film was peeled into the following three stages.
Number of remaining squares more than 90: ◎
Number of remaining squares: 85 to 89: ○
Number of remaining squares: 84 or less: △

The scratch resistance was evaluated by the following criteria using # 0000 steel wool, sliding 50 times at a load of 500 g / cm ² , visually observing the surface of the film.
No streak injury is found: ◎
Slightly scratched streak: ○
Many scratches are found in the streak: △
The surface has been cut entirely: ×

Preparation of chain silica-based hollow fine particles (P-2) In Example 1, a solid content concentration of 20% by weight was similarly used except that 2.7 g of a Ca (NO ₃ ) ₂ aqueous solution having a concentration of 10% by weight was mixed as an electrolyte. An aqueous dispersion of chain silica-based hollow fine particles (P-2) was obtained.
In the same manner as in Production Example 1 of substrate with transparent coating (A-2), except that an aqueous dispersion of chain silica-based hollow fine particles (P-2) having a solid content concentration of 20% by weight was used. And the base material (A-2) with a transparent film whose film thickness of a transparent film is 100 nm was obtained.

Preparation of chain silica-based hollow fine particles (P-3) In Example 1, a chain with a solid content of 20% by weight was prepared in the same manner except that 54 g of an aqueous Ca (NO ₃ ) ₂ solution having a concentration of 10% by weight was mixed as the electrolyte. An aqueous dispersion of silica-based hollow fine particles (P-3) was obtained.
In the same manner as in Production Example 1 of substrate with transparent coating (A-3), except that an aqueous dispersion of chain silica hollow particles (P-3) having a solid content concentration of 20% by weight was used, the coating solution And the base material (A-3) with a transparent film whose film thickness of a transparent film is 100 nm was obtained.

Preparation of chain silica-based hollow fine particles (P-4) In Example 1, a solid content concentration of 20 wt% was similarly obtained except that 4.9 g of an Mg (NO ₃ ) ₂ aqueous solution having a concentration of 10 wt% was mixed as the electrolyte. An aqueous dispersion of chain silica-based hollow fine particles (P-4) was obtained.
In the same manner as in Production Example 1 of substrate with transparent coating (A-4), except that an aqueous dispersion of chain silica-based hollow fine particles (P-4) having a solid content concentration of 20% by weight was used. And the base material (A-4) with a transparent film whose film thickness of a transparent film is 100 nm was obtained.

Preparation of chain silica-based hollow fine particles (P-5) Silica-alumina sol (manufactured by JGC Catalysts & Chemicals Co., Ltd .: USBB-120, average particle size 25 nm, SiO ₂ · Al ₂ O ₃ concentration 20 wt%, solid content in Al ₂ O ₃ content 27 wt%) was added to deionized water 3900g was warmed to 98 ° C. to 100 g, while maintaining this temperature, concentration of 1.5 wt% aqueous solution of sodium silicate 405g as SiO ₂ and Al ₂ O ₃ 405 g of a sodium aluminate aqueous solution having a concentration of 0.5% by weight was added over 6 hours to obtain a dispersion of primary particles of SiO ₂ .Al ₂ O ₃ (P-5). The molar ratio at this time was MO _X / SiO ₂ = 0.2. Further, the pH of the reaction solution at this time was 12.0. The average primary particle diameter of this dispersion was 28 nm. (Process (a))

Next, the SiO ₂ · Al ₂ O ₃ primary particles (P-5) dispersion was washed by the ultrafiltration membrane method and concentrated to concentrate SiO ₂ · Al ₂ O ₃ primary particles (P- 5) A dispersion was obtained. (Process (b))
Separately, an aqueous solution prepared by mixing 136 g of an acidic silicic acid solution having a concentration of 2% by weight as SiO ₂ and 5.4 g of an aqueous solution of Ca (NO ₃ ) ₂ having a concentration of 10% by weight as an electrolyte for chain formation is prepared. After mixing 300g of 5% by weight SiO ₂ · Al ₂ O ₃ primary particle (P-5) dispersion and adding 9g of 2% by weight NaOH aqueous solution, hydrothermal treatment at 150 ° C for 3 hours. Then, a chain composite oxide particle (P-5) dispersion having a solid content concentration of 5% by weight was prepared. Then it was cooled to room temperature. The pH of the dispersion at this time was 10.9. (Process (c))

Then, a chain-like composite oxide of a solid concentration of 5 wt% particles (P-5) was heated to 98 ° C. Pure water was added to 3900g to the dispersion 300 g, while maintaining this temperature, concentration as SiO ₂ 1. 1530 g of 5 wt% sodium silicate aqueous solution and 500 g of 0.5 wt% sodium aluminate aqueous solution as Al ₂ O ₃ were added over 17 hours, and silica-alumina coated chain composite oxide particles (P-5) A dispersion was obtained. (Process (d))

  Next, 1,125 g of pure water was added to 500 g of the silica / alumina-coated chain composite oxide particle (P-5) dispersion which was washed by the ultrafiltration membrane method and concentrated to a solid content concentration of 13% by weight. Concentrated hydrochloric acid (concentration 35.5% by weight) was added dropwise to adjust the pH to 1.0, and dealumination was performed. Subsequently, the aluminum salt dissolved while adding 10 L of hydrochloric acid aqueous solution of pH 3 and 5 L of pure water is separated and washed with an ultrafiltration membrane, and water dispersion of the chain silica hollow particles (P-5) having a solid content concentration of 20% by weight is performed. A liquid was obtained. (Step (e)) (Step (f))

In the same manner as in Production Example 1 of substrate with transparent coating (A-5), except that an aqueous dispersion of chain silica hollow particles (P-5) having a solid content of 20% by weight was used, the coating solution And the base material (A-5) with a transparent film whose film thickness of a transparent film is 100 nm was obtained.

Preparation of chain silica-based hollow fine particles (P-6) Silica-alumina sol (manufactured by JGC Catalysts & Chemicals Co., Ltd .: USBB-120, average particle size 25 nm, SiO ₂ · Al ₂ O ₃ concentration 20 wt%, solid content in Al ₍ 2O ₃ content 27 wt%) 100 g of pure water 3900 g was added and heated to 98 ° C., and while maintaining this temperature, 20,900 g of 1.5 wt% sodium silicate aqueous solution as SiO ₂ and Al ₂ An aqueous solution of sodium aluminate having a concentration of 0.5% by weight as O ₃ was added in 6 hours to obtain a dispersion of primary particles of SiO ₂ · Al ₂ O ₃ (P-6). The molar ratio at this time was MO _X / SiO ₂ = 0.2. Further, the pH of the reaction solution at this time was 12.0. The average primary particle diameter of this dispersion was 70 nm. (Process (a))

Next, the SiO ₂ · Al ₂ O ₃ primary particles (P-6) dispersion was washed by the ultrafiltration membrane method and concentrated to obtain a SiO ₂ · Al ₂ O ₃ primary particles (P- 6) A dispersion was obtained. (Process (b))
Separately, an aqueous solution prepared by mixing 136 g of an acidic silicic acid solution having a concentration of 2% by weight as SiO ₂ and 5.4 g of an aqueous solution of Ca (NO ₃ ) ₂ having a concentration of 10% by weight as an electrolyte for chain formation is prepared. After mixing 300 g of 5% by weight SiO ₂ · Al ₂ O ₃ primary particle (P-6) dispersion and adding 9 g of 2% by weight NaOH aqueous solution to this, hydrothermal treatment at 150 ° C for 3 hours. Then, a chain composite oxide particle (P-6) dispersion having a solid content concentration of 5% by weight was prepared.

Then it was cooled to room temperature. The pH of the dispersion at this time was 10.9. (Process (c))
Next, 3900 g of pure water was added to 300 g of the chain composite oxide particle (P-6) dispersion having a solid content concentration of 5% by weight and heated to 98 ° C., and while maintaining this temperature, the concentration of SiO ₂ was 1. 2,000 g of 5 wt% sodium silicate aqueous solution and 700 g of 0.5 wt% sodium aluminate aqueous solution as Al ₂ O ₃ were added over 17 hours to form silica-alumina coated chain-like composite oxide particles (P -6) A dispersion was obtained. (Process (d))

  Next, 1,125 g of pure water was added to 500 g of the silica / alumina-coated chain composite oxide particle (P-6) dispersion which was washed by the ultrafiltration membrane method and concentrated to a solid content concentration of 13% by weight. Concentrated hydrochloric acid (concentration 35.5% by weight) was added dropwise to adjust the pH to 1.0, and dealumination was performed. Subsequently, the aluminum salt dissolved while adding 10 L of hydrochloric acid aqueous solution of pH 3 and 5 L of pure water is separated and washed with an ultrafiltration membrane to disperse water of chain silica hollow fine particles (P-6) having a solid content concentration of 20% by weight. A liquid was obtained. (Step (e)) (Step (f))

In the same manner as in Production Example 1 of substrate with transparent coating (A-6), except that an aqueous dispersion of chain silica hollow fine particles (P-6) having a solid concentration of 20% by weight was used, the coating solution And the base material (A-6) with a transparent film whose film thickness of a transparent film is 100 nm was obtained.

Production of transparent coated substrate (A-7) In Example 1, 36.6 g of a dispersion obtained by diluting an alcohol dispersion of chain silica-based hollow fine particles (P-1) with ethanol to a solid content concentration of 5% by weight; Coating film and transparent coating film in the same manner except that 3.7 g of acrylic resin (Hitaroid 1007, manufactured by Hitachi Chemical Co., Ltd.) and 58 g of 1/1 (weight ratio) mixed solvent of isopropanol and n-butanol were used. A substrate with a transparent coating (A-7) having a thickness of 100 nm was obtained.

Production of substrate with transparent coating (A-8) In Example 1, 55 g of a dispersion obtained by diluting an alcohol dispersion of chain silica hollow fine particles (P-1) with ethanol to a solid content concentration of 5% by weight, and acrylic Coating liquid and transparent coating film in the same manner except that 2.75 g of resin (Hitaroid 1007, manufactured by Hitachi Chemical Co., Ltd.) and 43.1 g of a 1: 1 (weight ratio) mixed solvent of isopropanol and n-butanol were used. A substrate with a transparent coating (A-8) having a thickness of 100 nm was obtained.

Preparation of chain silica-based hollow fine particles (P-7 ) Dispersion of silica-alumina-coated chain composite oxide particles (P-1) washed by ultrafiltration membrane method and concentrated to a solid content concentration of 13% by weight 1,500 g of pure water was added to 500 g, and concentrated hydrochloric acid (concentration 35.5% by weight) was added dropwise to adjust the pH to 0.5, followed by dealumination. Next, the aluminum salt dissolved while adding 25 L of a hydrochloric acid aqueous solution of pH 3.0 and 10 L of pure water was separated and washed with an ultrafiltration membrane to form a chain silica hollow fine particle (P-7) having a solid content concentration of 20% by weight. An aqueous dispersion was obtained. (Step (e)) (Step (f))

In the same manner as in Production Example 1 of substrate with transparent coating (A-9), except that an aqueous dispersion of chain silica hollow particles (P-7) having a solid concentration of 20% by weight was used, the coating solution And the base material (A-9) with a transparent film whose film thickness of a transparent film is 100 nm was obtained.

Comparative Example 1

Preparation of silica -based hollow fine particles (RP-1) Silica-alumina sol (manufactured by JGC Catalysts & Chemicals Co., Ltd .: USBB-120, average particle size 25 nm, SiO ₂ · Al ₂ O ₃ concentration 20 wt%, solid content of Al ₂ O ₃ content 27 wt%) 100 g of pure water 3900 g was added and heated to 98 ° C., and while maintaining this temperature, 1750 g of sodium silicate aqueous solution having a concentration of 1.5 wt% as SiO ₂ and Al ₂ O ₃ An aqueous solution of sodium aluminate having a concentration of 0.5% by weight was added over 6 hours to obtain a dispersion of primary particles of SiO ₂ .Al ₂ O ₃ (P-1). The molar ratio at this time was MO _X / SiO ₂ = 0.2. Further, the pH of the reaction solution at this time was 12.0. The average primary particle diameter of this dispersion was 35 nm. (Process (a))

Next, the SiO ₂ · Al ₂ O ₃ primary particle (P-1) dispersion is washed by the ultrafiltration membrane method and concentrated to obtain a SiO ₂ · Al ₂ O ₃ primary particle (P- 1) A dispersion was obtained. (Process (b))
Then, warmed to 98 ° C. Pure water was added to 3900g solids concentration of 5% by weight of SiO ₂ · Al ₂ O ₃ primary particles (P-1) dispersion liquid 300 g, while maintaining this temperature, a SiO ₂ 1530 g of a sodium silicate aqueous solution having a concentration of 1.5% by weight and 500 g of a sodium aluminate aqueous solution having a concentration of 0.5% by weight as Al ₂ O ₃ were added over 17 hours, and silica-alumina coated composite oxide particles (RP-1 ) A dispersion was obtained.

  Next, 1,125 g of pure water was added to 500 g of the silica / alumina-coated composite oxide particle (RP-1) dispersion that had been washed by the ultrafiltration membrane method and concentrated to a solid content concentration of 13% by weight. Hydrochloric acid (concentration 35.5% by weight) was added dropwise to adjust the pH to 1.0, and dealumination was performed. Next, the aluminum salt dissolved while adding 10 L of hydrochloric acid aqueous solution of pH 3 and 5 L of pure water was separated and washed with an ultrafiltration membrane, and the water of monodispersed silica-based hollow fine particles (RP-1) having a solid concentration of 20 wt% was obtained. A dispersion was obtained. The silica-based hollow fine particles (RP-1) in the aqueous dispersion were neither chained nor aggregated.

In the same manner as in Production Example 1 of substrate with transparent coating (RA-1), except that an aqueous dispersion of silica-based hollow fine particles (RP-1) having a solid content concentration of 20% by weight was used, the coating solution and transparent A substrate with a transparent film (RA-1) having a film thickness of 100 nm was obtained.

Comparative Example 2

Preparation of chain silica-based hollow fine particles (RP-2) In Example 1, step (c) was carried out in the same manner except that 140 g of a Ca (NO ₃ ) ₂ aqueous solution having a concentration of 10% by weight as an electrolyte was mixed. At this time, aggregated particles were obtained, so the subsequent steps were not performed.

Comparative Example 3

Preparation of chain silica-based hollow fine particles (RP-3) In Example 1, a solid content concentration of 20 wt% was similarly obtained except that 0.1 g of a Ca (NO ₃ ) ₂ aqueous solution having a concentration of 10 wt% was mixed as an electrolyte. An aqueous dispersion of chain silica-based hollow fine particles (RP-3) was obtained. However, many of them were monodispersed silica-based hollow fine particles as in Comparative Example 1. Physical properties of some chain silica-based hollow fine particles (RP-3) were measured in the same manner as in Example 1, and the results are shown in Table 1.

In the same manner as in Production Example 1 of substrate with transparent coating (RA-3), except that an aqueous dispersion of chain silica-based hollow fine particles (RP-3) having a solid content of 20% by weight was used, the coating solution And the base material (RA-3) with a transparent film whose film thickness of a transparent film is 100 nm was obtained.

Comparative Example 4

Manufacture of substrate with transparent coating (RA-4) Silica sol ( manufactured by JGC Catalysts & Chemicals Co., Ltd .: Cataloid-SI-45P, average particle size 45 nm, SiO ₂ concentration 40% by weight) using ultrafiltration membrane as solvent A silica organosol having a solid content concentration of 5% by weight was prepared by substituting ethanol with ethanol.
50 g of a silica organosol having a solid content concentration of 5% by weight, 3 g of an acrylic resin (Hitaloid 1007, manufactured by Hitachi Chemical Co., Ltd.) and 47 g of a mixed solvent of 1/1 (weight ratio) of isopropanol and n-butanol were sufficiently mixed. A coating solution was prepared.
This coating solution was applied to a PET film by a bar coater method and dried at 80 ° C. for 1 minute to obtain a substrate with transparent coating (RA-4) having a transparent coating thickness of 100 nm.

Claims (12)

  Silica-based hollow fine particles (primary particles) having an outer shell on the outside and cavities inside are connected in a chain, the cavities have through-holes penetrating each other, and an average length (L) of 20 to 1500 nm A chain silica-based hollow fine particle characterized by being in the range, having an average width (W) in the range of 10 to 300 nm and a refractive index in the range of 1.10 to 1.35. The thickness (T _S ) of the outer shell is in the range of 2 to 100 nm, and the ratio (T _S ) / (W) to the average width (W) is in the range of 0.05 to 0.30. 2. The chain silica-based hollow fine particles according to claim 1, wherein The ratio (D _S ) / (W) of the average diameter (D _S ) and the average width (W) of the through holes is in the range of 0.1 to 0.9. 2. The chain silica-based hollow fine particles according to 2. An inorganic oxide other than silica and silica, the molar ratio MO _X / SiO ₂ when the inorganic oxide other than silica, expressed in MO _X is lies in the range of 0.0001 to claims Item 4. The chain silica-based hollow fine particles according to any one of Items 1 to 3. A method for producing chain silica-based hollow fine particles comprising the following steps (a) to (f).
(A) An aqueous solution of a silicate and / or an acidic silicic acid solution and an aqueous solution of an alkali-soluble inorganic compound are dispersed in an alkaline aqueous solution or seed particles having a solid content concentration in the range of 0.01 to 2% by weight. The molar ratio MO _X / SiO ₂ (A) is 0.1 to ₂ when the silica is represented by SiO ₂ and the inorganic oxide other than silica is represented by MO _X. A step of preparing a composite oxide primary particle dispersion (b) a step of washing the primary particle dispersion (c) a hydrothermal treatment of the washed primary particle dispersion at 50 to 300 ° C. in the presence of an electrolyte to form a chain Step (d) of preparing a composite oxide particle dispersion (d) Step of forming a silica or silica-alumina-coated chain composite oxide particle dispersion by forming a silica or silica-alumina coating layer (e) Silica or silica Alumina coating A step (f) was obtained in which acid was added to the chain composite oxide particle dispersion to remove at least a part of elements other than silicon constituting the composite oxide particles to form a chain silica-based hollow fine particle dispersion. Process for washing the dispersion   6. The method for producing chain silica-based hollow fine particles according to claim 5, wherein the electrolyte in the step (c) is an alkaline earth metal salt. The method for producing chain silica-based hollow fine particles according to claim 5 or 6, wherein the following step (g) is carried out following the step (f).
(G) Hydrothermal treatment of the chain silica-based hollow fine particle dispersion in the range of 50 to 300 ° C. The method for producing chain silica-based hollow fine particles according to any one of claims 5 to 7, wherein the step (d) is the following step (d-1).
(D-1) To the chain complex oxide particle dispersion obtained in the step (c), an alkaline aqueous solution and an organosilicon compound represented by the following chemical formula (1) and / or a partial hydrolyzate thereof are added. Step of adding and forming a silica coating layer on the chain composite oxide particles
R _n SiX _(4-n) (1)
[However, R: unsubstituted or substituted hydrocarbon group having 1 to 10 carbon atoms, acrylic group, epoxy group, methacryl group, amino group, CF ₂ group, X: alkoxy group having 1 to 4 carbon atoms, silanol group, halogen Or hydrogen, n: an integer of 0 to 3] The method for producing chain silica-based hollow fine particles according to any one of claims 5 to 7, wherein the step (d) is the following step (d-2).
(D-2) An aqueous alkali solution and an acidic silicic acid solution are added to the chain composite oxide particle dispersion obtained in the step (c) to form a silica coating layer on the chain composite oxide particles. Process The method for producing chain silica-based hollow fine particles according to any one of claims 5 to 7, wherein the step (d) is the following step (d-3).
(D-3) An alkali silicate aqueous solution and an aluminate aqueous solution are added to the chain complex oxide particle dispersion obtained in the step (c) to form a silica coating layer on the chain complex oxide particles. Process   A coating solution for forming a transparent film, comprising the chain silica-based hollow fine particles according to claim 1 and a matrix-forming component.   The base material with a transparent film by which the transparent film formed using the coating liquid for transparent film formation of Claim 11 was formed on the base-material surface independently or with another film.

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