JP5480743B2 - Substrate with transparent film and paint for forming transparent film - Google Patents

Description

  The present invention provides a transparent coated substrate with excellent transparency, haze, antireflection performance, strength, scratch resistance, etc., and formation of the transparent coating because whitening of the transparent coating is suppressed due to a small number of deformed silica-based hollow fine particles It is related with paint.

  Conventionally, in order to prevent reflection of the surface of a substrate such as glass, plastic sheet, plastic lens, etc., it is known to form an antireflection film on the surface, for example, by coating method, vapor deposition method, CVD method, etc. A coating of a low refractive index substance such as fluororesin or magnesium fluoride is formed on the surface of a glass or plastic substrate, or a coating liquid containing low refractive index fine particles such as silica fine particles is applied to the surface of the substrate. A method for forming an antireflection coating is known (for example, see JP-A-7-133105). At this time, in order to improve the antireflection performance, it is also known to form a high refractive index film containing fine particles of high refractive index under the antireflection coating.

  The applicant of the present invention disclosed in Japanese Patent Laid-Open No. 2001-23611 (Patent Document 1) a method for producing silica-based fine particles having cavities therein and the resulting silica-based fine particles have a low refractive index and are formed using the silica-based fine particles. It is disclosed that the transparent film has a low refractive index and excellent antireflection performance.

  Furthermore, Japanese Patent Application Laid-Open No. 2002-79616 (Patent Document 2) discloses that when such a transparent film is formed and used on the entire surface of a display device, the antireflection performance is excellent and the display performance is improved.

  However, the conventional silica-based fine particles have a high ratio of shells when the particle size is small, and the refractive index is not sufficiently low because the ratio of internal cavities is low, whereas the refractive index is low when the particle size is large. However, there is a drawback that the strength and scratch resistance of the transparent film obtained are lowered.

  Further, the applicant of the present application disclosed in Japanese Patent Application Laid-Open No. 2009-66965 (Patent Document 3) is a low refractive index having an average particle diameter (Dn) in the range of 20 to 80 nm and a particle diameter variation coefficient (CV value) of 50% or less. It is disclosed that the use of high-efficiency silica-based hollow fine particles has a low refractive index of the transparent film obtained, a smooth surface of the film, improved scratch resistance, and improved strength.

JP 2001-23611 A JP 2002-79616 A JP 2009-66965 A

  However, there is a problem that a whitening phenomenon occurs in a transparent coating using low refractive index silica-based hollow fine particles. Furthermore, there has been a demand for further improving the antireflection performance.

  As a result of intensive studies on the above problems, the present inventors have found that whitening occurs when protrusions are formed on the surface of the transparent coating. It has been found that the protrusions that cause whitening are due to irregularly shaped fine particles (for example, particles in which two or more silica-based fine particles are linked) contained in the hollow silica-based fine particles. In the production, the present invention was completed by finding that it is greatly reduced by preparing silica-based hollow fine particle precursor particles at a low concentration.

[1] a substrate;
A substrate with a transparent coating comprising a silica-based hollow fine particle and a transparent coating made of a matrix component, formed on the substrate, and having a particle size that is at least twice the average particle size (Dn) A substrate with a transparent coating, wherein the number ratio of the silica-based hollow fine particles in the silica-based hollow fine particles is 1% or less.
[2] The silica-based hollow fine particles have an average particle size in the range of 50 to 120 nm, a particle size variation coefficient (CV value) in the range of 1 to 50%, and a refractive index of 1.10 to 1.30. [1] The substrate with a transparent film in the range.
[3] The substrate with a transparent coating according to [1] or [2], wherein the content of silica-based hollow fine particles in the transparent coating is in the range of 40 to 90% by mass.
[4] The substrate with a transparent coating according to [1] to [3], wherein the refractive index of the transparent coating is in the range of 1.15 to 1.40.
[5] A coating solution for forming a transparent film comprising silica-based hollow fine particles, a matrix-forming component, and a polar solvent,
The silica-based hollow fine particles have a ratio of the number of irregular-shaped silica-based hollow fine particles having a particle size of twice or more the average particle size (Dn) of 1% or less, and an average particle size (Dn) in the range of 50 to 120 nm. A coating solution for forming a transparent film having a particle diameter variation coefficient (CV value) in the range of 1 to 50% and a refractive index in the range of 1.10 to 1.30.
[6] The concentration of the silica-based hollow fine particles in the paint is in the range of 0.4 to 54% by mass as the solid content, and the concentration of the matrix forming component is in the range of 0.1 to 36% by mass as the solid content. The paint for forming a transparent film according to [5], wherein the solid content concentration is in the range of 1 to 60 mass%.

  According to the present invention, silica-based hollow particles having a mean particle diameter in a predetermined range, having a uniform particle size distribution and having a low refractive index and having a low refractive index, the silica-based hollow particles having a size and shape far from those of the silica-based hollow fine particles. A substrate with a transparent coating excellent in antireflection performance, strength, scratch resistance, etc., in which whitening is suppressed because it does not contain fine particles, and the coating for forming a transparent coating can be provided.

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

Hereinafter, first, the transparent film-coated substrate according to the present invention will be specifically described.
The substrate with a transparent coating The substrate with a transparent coating according to the present invention comprises a substrate and a transparent coating formed on the substrate.

Base material As the base material, a conventionally known base material can be used, and in addition to glass, a cellulose-based base material such as a triacetyl cellulose film (TAC), a diacetyl cellulose film, an acetate butyrate cellulose film, Polyester base materials such as polyethylene terephthalate (PET) and polyethylene naphthalate, polyolefin base materials such as polyethylene film, polypropylene film and cyclic polyolefin film, polyamide base materials such as nylon-6 and nylon-66, polyacrylic films , Polyurethane film, polycarbonate film, polyether film, polyethersulfone film, polystyrene film, polymethylpentene film, polyetherketone film, acrylonitrile film, etc. Wood and the like.
In addition, a coated substrate in which another coating such as a hard coat film is formed on such a substrate can also be used.

The transparent coating transparent coating consists of silica-based hollow fine particles and a matrix component, and is characterized in that the thickness of the transparent coating is in the range of 80 to 120 nm.

Silica-based hollow fine particles The silica-based hollow fine particles used in the present invention are particles having silica as a main component and having cavities therein. Such silica-based hollow fine particles may contain oxides such as alumina and magnesia, and alkali metal oxides and hydroxides in addition to silica. However, in terms of the use of the transparent film, it is preferable that the film is substantially made of silica.

The average particle diameter (Dn) is preferably in the range of 50 to 120 nm, more preferably 70 to 80 nm.
If the average particle size of the silica-based hollow fine particles is too small, the shell is thick for the particle size of the silica-based hollow fine particles, and the ratio of cavities inside the particles is small, so that the refractive index is high and the refractive index is sufficiently low. May not be obtained.

  If the average particle diameter of the silica-based hollow fine particles is too large, the refractive index of the silica-based hollow fine particles is low, but the strength of the transparent film may be insufficient due to the large particle diameter. Since it is larger, the smoothness of the surface of the transparent coating may be lowered and the scratch resistance may be insufficient.

  Further, if the average particle diameter (Dn) of the silica-based hollow fine particles is within the above range, the silica-based hollow fine particles generally have a two-layer structure in the transparent film, and a transparent film having a thickness of 80 to 120 nm is formed. And a substrate with a transparent coating excellent in antireflection performance, strength, scratch resistance and the like can be obtained.

Although the thickness of the shell of the hollow fine particles depends on the size of the particles, it is preferably in the range of 3 to 20 nm, preferably 5 to 15 nm.
Conventionally, such silica-based hollow fine particles have also included irregular particles in which two or more particles are connected, but attention has not been paid to the presence of such irregular particles. Silica-based hollow microparticles are considered to have high transparency of the transparent coating because of their low refractive index. However, the transparent coating may be whitened or the scratch resistance may be insufficient. .

  In view of such problems, the present inventors have examined the cause of the problem, and as a result, have found that irregularly shaped particles contained in a very small amount in silica-based hollow fine particles have an influence. And when the number ratio of irregular-shaped silica hollow particles increases, irregular-shaped silica hollow fine particles form protrusions on the surface of the transparent coating, or normal silica-based hollow fine particles are laminated on irregular-shaped silica hollow fine particles to form protrusions. The present inventors have found that this causes whitening of the transparent coating and causes insufficient scratch resistance.

For this reason, in the present invention, the number ratio of the deformed silica-based hollow fine particles in the silica-based hollow fine particles is 1% or less, and more preferably 0.5% or less.
The irregular-shaped silica-based hollow fine particle means a silica-based hollow fine particle having a particle diameter that is at least twice the average particle diameter (Dn) and having two or more spherical silica-based hollow fine particles or spherical silica-based hollow fine particles bonded together. doing.

The silica-based hollow fine particles used in the present invention preferably have a particle diameter variation coefficient (CV value) in the range of 1 to 50%, more preferably 2 to 30%.
It is difficult to obtain particles having a small particle diameter variation coefficient (CV value) of silica-based hollow fine particles.
If the particle size variation coefficient (CV value) of the silica-based hollow fine particles is too large, the difference in the particle size of the silica-based hollow fine particles is so large that it cannot be densely packed, so that the strength of the transparent coating is lowered or the refractive index is sufficiently low. A transparent film may not be obtained.

The average particle diameter (Dn) of the silica-based hollow fine particles used in the present invention is obtained as an average value obtained by taking an electron micrograph and measuring the particle diameter of any 1000 particles.
The particle diameter variation coefficient (CV value) of the silica-based hollow fine particles used in the present invention is calculated by the following formula.
CV (%) = [particle diameter standard deviation (σ) / average particle diameter (D _n )] × 100

Ｄ_i：個々の粒子の粒子径、ｎ＝1000
本発明で使用されるシリカ系中空微粒子は内部が中空のため、単なるシリカ粒子に比べて屈折率が低く、通常、屈折率は１．１０〜１．３０、さらには１．１０〜１．２５の範囲にあることが好ましい。

D _i : particle diameter of individual particles, n = 1000
Since the silica-based hollow fine particles used in the present invention are hollow inside, the refractive index is lower than that of mere silica particles, and the refractive index is usually 1.10 to 1.30, more preferably 1.10 to 1.25. It is preferable that it exists in the range.

  When the refractive index of the silica-based hollow fine particles is less than the lower limit of the above range, it is difficult to obtain, and when the upper limit is exceeded, the obtained transparent film has a high refractive index, and the antireflection performance targeted by the present invention is insufficient. May be.

The refractive index of the silica-based hollow fine particles used in the present invention is measured by the following method.
(1) A dispersion of silica-based hollow fine particles is taken in an evaporator and the dispersion medium is evaporated.
(2) This is dried at 120 ° C. to obtain a powder.
(3) A standard refraction 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 liquids, and the refractive index of the standard refractive liquid when the mixed liquid becomes transparent is set as the refractive index of the silica-based hollow fine particles.

Production method of silica-based hollow fine particles As the silica-based hollow fine particles used in the present invention, the number ratio of the above-mentioned deformed silica-based hollow fine particles is 1% or less, and the average particle diameter, refractive index, and particle diameter variation coefficient are within the above-mentioned ranges. Although there is no particular limitation, it can be produced according to the method for producing silica-based fine particles disclosed in JP-A Nos. 2001-23611, 2004-203683, and 2006-21938.

  Specifically, the composite oxide fine particles composed of silica and an inorganic oxide other than silica are used as a core, and after forming the silica coating layer (1) as necessary, the inorganic oxide other than silica is removed, If necessary, it can be obtained by forming a silica coating layer (2) and hydrothermally treating at a high temperature if necessary, but in the step of preparing particles in the stage before removing inorganic oxides other than silica That is, the step of preparing composite oxide fine particles composed of silica and inorganic oxides other than silica, and if necessary, the concentration in the step of forming the silica coating layer (1) is reduced to a low concentration. Silica-based hollow fine particles with few silica-based hollow fine particles can be obtained.

This concentration is preferably in the range of 0.1 to 0.9% by mass, more preferably 0.2 to 0.6% by mass, with silica and an inorganic oxide other than silica as the solid content.
If this concentration is too low, the deformed silica-based hollow fine particles are eliminated or reduced, but the yield decreases and the production efficiency may decrease.
When this concentration is increased, irregular-shaped silica-based hollow fine particles increase, and protrusions are formed on the surface of the transparent coating, which may cause whitening and may have insufficient scratch resistance.

The method for producing a silica-based hollow fine particle having a small number ratio of the irregular shaped particles used in the present invention is, for example, in the main process of the method for producing a silica-based hollow fine particle described above,
(1) When a composite oxide fine particle composed of silica and an inorganic oxide other than silica is used as a nucleus, a nucleus having a uniform particle diameter is used. Specifically, the nucleus has a CV value of 100% or less, preferably Use 50% or less of core particles. The so-called seed method using seed particles is preferably used for the preparation of the core particles at this time, and it is preferable that the seed particles are slowly grown as far as possible.
(2) When carrying out the particle growth of the core particles, it is preferable to slowly add the silica source and the alumina source as much as possible. The particle growth rate at this time varies depending on the particle diameter of the core particle, but is generally in the range of 0.1 to 10 nm / hour, more preferably 0.2 to 5 nm / hour, and particularly 0.2 to 3 nm / hour. Is preferred.
(3) When forming the silica coating layer, it is preferable to slowly add the silica source as much as possible. The silica coating speed at this time varies depending on the particle diameter of the core particle, but is generally in the range of 0.1 to 10 nm / hour, more preferably 0.2 to 5 nm / hour, and particularly 0.2 to 3 nm / hour. Is preferred.
(4) In each of the above steps, it is preferable to perform aging after the particle growth and after the silica coating layer is formed. The aging at this time is preferably carried out in a range where the solid content concentration is 1 to 30% by mass, the temperature is 30 to 100 ° C., and the time is 1 to 12 hours.
(5) In each of the above steps, it is preferable to prevent aggregation or achieve high dispersion by irradiating ultrasonic waves.
(6) When there are aggregated particles and coarse particles that are difficult to disperse, it is preferable to remove them by a capsule filter, centrifugation, or the like.

The silica-based hollow fine particles used in the present invention are preferably surface-treated with an organosilicon compound represented by the following formula (1) and a hydrolyzate thereof.
_{R n -SiX 4-n (1} )
(In the formula, R is an unsubstituted or substituted hydrocarbon group having 1 to 10 carbon atoms, and may be the same or different from each other. X: an alkoxy group having 1 to 4 carbon atoms or a silanol group) , Halogen, hydrogen, n: an integer of 0 to 3)

  Examples of the organosilicon compound represented by the formula (1) include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane. , Methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (βmethoxyethoxy) silane, 3,3,3- Trifluoropropyltrimethoxysilane, methyl-3,3,3-trifluoropropyldimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxymethyltrimethoxy Silane, γ-glycidoxymethyltriexisilane, γ-glycidoxyethyltrimethoxysilane, γ-glycidoxyethyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxy Silane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltriethoxysilane, γ- (β-glycidoxyethoxy) propyltrimethoxysilane, γ- (meth) acrylooxymethyltrimethoxysilane, γ- (meth) acrylooxymethyltriethoxysilane, γ- (meth) acrylooxyethyltrimethoxysilane, γ- (meth) acryloxyethyltriethoxysilane, γ- (meth) acrylooxypropyltrimethoxy Silane, γ- (meth) acrylooxypropyltrimethoxysilane, γ- (meth) a Acryloxypropyltriethoxysilane, γ- (meth) acrylooxypropyltriethoxysilane, butyltrimethoxysilane, isobutyltriethoxysilane, hexyltriethoxysiloctyltriethoxysilane, decyltriethoxysilane, butyltriethoxysilane, Isobutyltriethoxysilane, hexyltriethoxysilane, octyltriethoxysilane, decyltriethoxysilane, 3-ureidoisopropylpropyltriethoxysilane, perfluorooctylethyltrimethoxysilane, perfluorooctylethyltriethoxysilane, perfluorooctylethyltri Isopropoxysilane, trifluoropropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β Aminoethyl) .gamma.-aminopropyltrimethoxysilane, N- phenyl--γ- aminopropyltrimethoxysilane, .gamma.-mercaptopropyltrimethoxysilane, trimethylsilanol, methyltrichlorosilane, and the like.

  When the surface treatment is performed with such an organosilicon compound, it can be uniformly dispersed in the matrix and densely filled, and a transparent film excellent in film strength and scratch resistance can be obtained.

  Surface treatment of silica-based hollow fine particles is performed by adding a predetermined amount of the above-mentioned organosilicon compound to an alcohol dispersion of fine particles, adding water thereto, and adding an acid or alkali as a hydrolysis catalyst as necessary to hydrolyze the organosilicon compound. To do.

The amount ratio of silica based hollow fine particles and the organosilicon compound at this time (the solid content of the organosilicon compound _{(R n -SiX (4-n} ) / 2 weight / weight of silica-based hollow microparticles as)) silica based hollow Although it varies depending on the average particle diameter of the fine particles, it is preferably in the range of 0.005 to 0.3, more preferably 0.01 to 0.2.

  If the weight ratio is small, the affinity with the matrix-forming component described later is low, the dispersibility and stability in the paint are insufficient, and fine particles may aggregate in the paint, resulting in a dense transparent film. In some cases, adhesion to the substrate, film strength, scratch resistance, and the like may be insufficient.

  Even if the weight ratio is too large, the dispersibility in the paint is not further improved, the refractive index of the silica-based hollow fine particles is increased, and a transparent film having a desired low refractive index may not be obtained. The antireflection performance may be insufficient.

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

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

  Examples of such resins include conventionally used thermoplastic resins such as polyester resins, polycarbonate resins, polyamide resins, polyphenylene oxide resins, thermoplastic acrylic resins, vinyl chloride resins, fluororesins, vinyl acetate resins, and silicone rubbers. , Urethane resin, melamine resin, silicon resin, butyral resin, reactive silicone resin, phenol resin, epoxy resin, unsaturated polyester resin, thermosetting acrylic resin, UV curable acrylic resin, etc., UV curable type An acrylic resin etc. are mentioned. Further, it may be a copolymer or modified body of two or more of these resins. These resins may be emulsion resins, water-soluble resins, and hydrophilic resins. Further, in the case of a thermosetting resin, it may be an ultraviolet curable type or an electron beam curable type, and in the case of a thermosetting resin, a curing catalyst may be included.

  The concept of the substrate with a transparent coating of the present invention is schematically shown in FIG. As shown in FIG. 1, when silica-based hollow fine particles having no irregular-shaped silica-based hollow fine particles and having an average particle size, refractive index, and particle size variation coefficient in the above-described ranges are used, the adhesion between the substrate and the transparent film is high. The upper surface of the transparent coating is smooth with small irregularities, and thus the transparent coating is suppressed in whitening, has excellent strength and scratch resistance, and has a low refractive index and excellent antireflection performance.

  On the other hand, the concept of a conventional substrate with a transparent coating is schematically shown in FIG. As shown in FIG. 2, when irregular-shaped silica-based hollow fine particles are present, the upper surface of the transparent film is uneven, which causes the transparent film to be whitened or to have strength and scratch resistance due to the protrusions. May decrease.

  The content of the silica-based hollow fine particles in the transparent coating is preferably in the range of 40 to 90% by mass, more preferably 50 to 90% by mass. The remaining components are matrix components. When the content of the silica-based hollow fine particles in the transparent film is small, a transparent film having a sufficiently low refractive index may not be obtained. When the content of the silica-based hollow fine particles in the transparent film exceeds 90% by mass In addition, since the content of the matrix component described later is too small, the strength and scratch resistance of the transparent film may be insufficient.

The film thickness of the transparent coating is preferably in the range of 80 to 120 nm, more preferably 90 to 110 nm.
If the transparent film is too thin, the film strength and scratch resistance may be insufficient. In addition, the film may be too thin to obtain sufficient antireflection performance. Even if the transparent film is too thick, if the content of silica-based hollow fine particles is large, cracks are likely to occur in the transparent film, and the film strength may be insufficient.

The refractive index of the transparent film is preferably in the range of 1.15 to 1.40, more preferably 1.20 to 1.35. If the refractive index of the transparent coating is lower than the above range, it is difficult to obtain from the viewpoint of coating composition, and if the refractive index is increased, the refractive index of the substrate or the lower layer of the transparent coating formed as necessary Depending on the refractive index of other films formed, the antireflection performance may be insufficient.
The refractive index of the transparent film of the present invention is measured with an ellipsometer (manufactured by ULVAC, EMS-1).

A conventionally well-known method is employable as a formation method of such a base material with a transparent film.
Specifically, the transparent film-forming paint according to the present invention described later is well known such as a dipping method, a spray method, a spinner method, a roll coating method, a bar coating method, a slit coater printing method, a gravure printing method, and a micro gravure printing method. A transparent coating film can be formed by applying to a substrate by the above method, drying, and curing by a conventional method such as ultraviolet irradiation or heat treatment.

Transparent Film Forming Paint The transparent film forming paint according to the present invention has an average particle diameter (Dn) in the range of 50 to 120 nm and a particle diameter variation coefficient (CV value) in the range of 1 to 50%. Silica-based hollow having a refractive index in the range of 1.10 to 1.30 and a number ratio of irregular-shaped hollow silica fine particles having an average particle diameter (Dn) of 2 times or more in the hollow silica fine particles of 1% or less. It is characterized by comprising fine particles, a matrix-forming component, and a polar solvent.

Silica-based hollow fine particles Silica-based hollow fine particles used in the present invention have few irregular-shaped silica-based hollow fine particles as described above, and have a predetermined average particle size, refractive index, and particle size variation coefficient (CV value). Is used.

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

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

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

  Among them, alcohols such as methanol, ethanol, propanol and 2-propanol (IPA) can uniformly disperse the surface-treated silica-based hollow fine particles, and the solvent having a carbonyl group can be obtained by treating the surface-treated silica-based hollow fine particles. Since it can disperse | distribute uniformly and the stability of a coating material is good and can form the transparent film excellent in uniformity, adhesiveness with a base material, intensity | strength, etc. with reproducibility, it can use it conveniently.

  The concentration of the silica-based hollow fine particles in the coating for forming a transparent film is preferably in the range of 0.5 to 54% by mass, more preferably 0.6 to 54% by mass as the solid content. If the silica-based hollow microparticles in the coating for forming a transparent coating are small, a transparent coating with a sufficiently low refractive index may not be obtained because the content of silica-based hollow microparticles in the transparent coating is small. Even if there are too many silica-based hollow fine particles, the strength of the transparent coating film may be insufficient because the content of the matrix-forming component is reduced.

It is preferable that the density | concentration of the matrix formation component in the coating material for transparent film formation is 0.1-30 mass% as solid content, and also exists in the range of 0.1-24 mass%.
When the concentration of the matrix-forming component is low, there are few matrix components in the obtained transparent film, and the scratch resistance, adhesion to the substrate, and the like may be insufficient. If the concentration of the matrix-forming component is too high, the content of silica-based hollow fine particles in the resulting transparent coating is reduced, the refractive index is insufficient, and the antireflection performance may be insufficient.

The total solid content concentration of the coating for forming a transparent film is preferably in the range of 1 to 60% by mass, more preferably 3 to 50% by mass.
When the total solid content concentration is too low, the film thickness of the transparent coating is too thin, the scratch resistance may be insufficient, and sufficient antireflection performance may not be obtained. on the other hand. If the total solid content is too high, the viscosity of the paint increases, the stability of the paint decreases, the coatability decreases, and it becomes difficult to form a thin film. Uniformity, adhesion to the substrate, strength, etc. may be insufficient.

A conventionally well-known method can be employ | adopted as a method of forming a transparent film using the coating material for transparent film formation which concerns on this invention.
Specifically, the transparent film-forming paint is applied to the substrate by a known method such as dipping, spraying, spinner, roll coating, bar coating, slit coater printing, gravure printing, or micro gravure printing. A transparent film can be formed by applying, drying, and curing by conventional methods such as ultraviolet irradiation, heat treatment, etc.In the present invention, roll coating, slit coater printing, gravure printing, and micro gravure printing are used. Recommended.

  A catalyst for performing a reaction such as polymerization or condensation of the matrix-forming component may be included. In addition, the component used for a well-known transparent film may be contained.

[Example]
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.

[Example 1]
Preparation of silica -based hollow fine particles (P-1) 390 g of pure water was added to 10 g of silica sol (manufactured by JGC Catalysts & Chemicals, Inc .: SI-550, average particle diameter 5 nm, CV value 17%, SiO ₂ concentration 20 mass%). While maintaining the temperature at 98 ° C., 17,000 g of a sodium silicate aqueous solution having a concentration of 0.75% by mass as SiO ₂ and 0.25% by mass of a sodium aluminate aqueous solution having a concentration of 0.25% by mass as Al ₂ O ₃ , 000 g was added in 25 hours to obtain a SiO ₂ .Al ₂ O ₃ primary particle dispersion. The pH of the reaction solution at this time was 11.8, and the solid content concentration was 0.5% by mass. Moreover, the average particle diameter was 50 nm.

Subsequently, 54,000 g of a sodium silicate aqueous solution having a concentration of 0.75% by mass as SiO ₂ and 18,000 g of a sodium silicate aqueous solution having a concentration of 0.25% by mass as Al ₂ O ₃ were added in 25 hours to form composite oxide fine particles. (1) A dispersion of (secondary particles) was obtained. At this time, the pH of the reaction solution was 11.6, and the solid content concentration was 0.6% by mass.

  The dispersion was washed with an ultrafiltration membrane to a solid content concentration of 13% by mass, and then filtered through a capsule filter having an opening of 1 μm to obtain a composite oxide fine particle (1) dispersion. At this time, the average particle size was 78 nm, and the CV value = 14.0%.

  To 500 g of the dispersion of composite oxide fine particles (1), 1,125 g of pure water was added, and concentrated hydrochloric acid (concentration 35.5% by mass) was added dropwise to adjust the pH to 1.0, followed by dealumination. Next, an aqueous dispersion of silica-based fine particles (P-1-1) having a solid content concentration of 20 mass% by separating and washing the aluminum salt dissolved in the ultrafiltration membrane while adding 10 L of hydrochloric acid aqueous solution of pH 3 and 5 L of pure water. Got.

  Next, aqueous ammonia is added to the silica-based fine particle (P-1-1) dispersion to adjust the pH of the dispersion to 10.5, and then aged at 200 ° C. for 11 hours, and then cooled to room temperature. Ion exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SK1B) is used for 3 hours, and then anion exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SA20A) is used for 3 hours. Ion exchange was performed, and 200 g of cation exchange resin (manufactured by Mitsubishi Chemical Corporation: Diaion SK1B) was used for ion exchange at 80 ° C. for 3 hours for washing, and silica-based fine particles (P An aqueous dispersion of -1-2) was obtained.

Next, an alcohol dispersion of silica-based fine particles (P-1) having a solid content concentration of 20% by mass was prepared by replacing the solvent with ethanol using an ultrafiltration membrane.
A methacrylsilane coupling agent (γ-methacryloxypropyltrimethoxysilane) (manufactured by Shin-Etsu Chemical Co., Ltd .: KBM-503, SiO ₂ ) was added to 100 g of an alcohol dispersion of silica-based fine particles (P-1) having a solid content concentration of 20% by mass. Component 81.2% by mass) 3 g of silica particles, heat-treated at 50 ° C., and again using an ultrafiltration membrane to replace the solvent with ethanol. Silica hollow fine particles having a solid content concentration of 20% by mass (P-1) An alcohol dispersion was prepared.
The average particle diameter, CV value, refractive index, and proportion of irregular silica-based hollow fine particles of the silica-based hollow fine particles (P-1) are shown in the table.

Production of antireflection transparent coating film-forming paint (1) Silica-based hollow fine particle (P-1) alcohol dispersion obtained by diluting with ethanol to a solid content concentration of 5% by mass and acrylic resin (Hitaroid 1007, Hitachi) A transparent coating film-forming paint (1) was prepared by sufficiently mixing 2.5 g of Kasei Chemical Co., Ltd.) and 37.5 g of a mixed solvent of isopropanol and n-butanol in 1/1 (weight ratio).

Preparation of coating liquid for hard coat film formation (1) Silica sol dispersion (manufactured by JGC Catalysts & Chemicals Co., Ltd .; Cataloid SI-30; average particle size 12 nm, SiO ₂ concentration 40.5% by mass, dispersion medium: isopropanol, Particle Refractive Index 1.46) 100 g is mixed with 1.88 g of γ-methacrylooxypropyltrimethoxysilane (manufactured by Shin-Etsu Silicon Co., Ltd .: KBM-503, SiO ₂ component 81.2%), and ultrapure water 3 0.1 g was added and stirred at 50 ° C. for 20 hours to obtain a surface-treated 12 nm silica sol dispersion (solid content concentration: 40.5% by mass).

Thereafter, the solvent was replaced with propylene glycol monopropyl ether (PGME) by a rotary evaporator (solid content: 40.5%).
Next, 51.85 g of a propylene glycol monopropyl ether dispersion of silica sol (1-8) having a solid content concentration of 40.5% by mass, 18.90 g of dihexaerythritol triacetate (manufactured by Kyoeisha Chemical Co., Ltd .: DPE-6A), And 1.6-hexanediol diacrylate (manufactured by Kyoeisha Chemical Co., Ltd .; light acrylate SR-238F) 2.10 g, silicone leveling agent (manufactured by Enomoto Kasei Co., Ltd .; Disparon 1610) 0.01 g and a photopolymerization initiator (Ciba Japan Co., Ltd.): Irgacure 184, dissolved in PGME to a solid content concentration of 10%) 12.60 g and PGME 14.54 g are mixed well to form a hard coating film having a solid content concentration of 42.0% by mass. A coating solution (1) was prepared.

Production of substrate (1) with transparent coating for antireflection Hard coating film forming coating solution (1) was prepared by using a TAC film (manufactured by Panac Corporation: FT-PB80UL-M, thickness: 80 μm, refractive index: 1. 51) was coated by the bar coater method (# 14), dried at 80 ° C. for 120 seconds, and then cured by irradiating with 300 mJ / cm ² of ultraviolet rays to form a hard coat film. The film thickness of the hard coat film was 6 μm.

Next, the coating solution (1) for forming an antireflection transparent film was applied by the bar coater method (bar # 4), dried at 80 ° C. for 120 seconds, and then irradiated with 600 mJ / cm ² of ultraviolet light in an N ₂ atmosphere. And cured to produce a substrate (1) with a transparent coating for antireflection. At this time, the film thickness of the antireflection transparent coating was 100 nm. Table 1 shows the total light transmittance, haze, reflectance of light having a wavelength of 550 nm, refractive index of the coating, adhesion, pencil hardness, and scratch resistance of the substrate (1) with a transparent coating for antireflection.

  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%.

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

Adhesiveness The surface of the substrate (A-1) with a transparent coating is made of 11 parallel scratches with a knife at intervals of 1 mm in length and width to make 100 squares, and cellophane tape is adhered thereto, The adhesion was evaluated by classifying the number of cells remaining after the cellophane tape was peeled off without the film being peeled into the following three stages. The results are shown in the table.
Number of remaining squares more than 90: ◎
Number of remaining squares: 85 to 89: ○
Number of remaining squares: 84 or less: △

Measurement of scratch resistance Using # 0000 steel wool, sliding 50 times at a load of 500 g / cm ² , visually observing the surface of the film, and evaluating according to the following criteria, the results are shown in the table.

Evaluation criteria:
No streak injury is found: ◎
Slight flaws are observed: ○
Many streak wounds are found: △
The surface has been cut entirely: ×

Evaluation of whitening The surface of the coating film was visually observed from an oblique direction (about 30 °), and the evaluation was evaluated in the following four stages.

Evaluation criteria:
No whitening is recognized: ◎
There is some whitening: ○
Partly whitened: △
Fully whitened: ×

[Example 2]
Preparation of antireflection transparent coating film-forming paint (2) 50 g of a dispersion of an alcohol dispersion of silica-based hollow fine particles (P-1) prepared in the same manner as in Example 1 with ethanol to a solid content concentration of 5% by mass Then, 3 g of acrylic resin (Hitaroid 1007, manufactured by Hitachi Chemical Co., Ltd.) and 47 g of a mixed solvent of isopropanol and n-butanol in 1/1 (weight ratio) are sufficiently mixed to prepare a paint (2) for forming a transparent film. did.

Production of base material with antireflection transparent coating (2) After forming a hard coat film in the same manner as in Example 1, the coating liquid for forming an antireflection transparent coating (2) was applied by the bar coater method (bar # 4). After coating and drying at 80 ° C. for 120 seconds, a substrate (2) with a transparent coating for antireflection was prepared by irradiating with an ultraviolet ray of 600 mJ / cm ² under an N ₂ atmosphere and curing. The film thickness of the antireflection transparent coating at this time was 95 nm.
The total light transmittance, haze, 550 nm light reflectance, coating refractive index, adhesion, pencil hardness, and scratch resistance of this substrate (2) with a transparent coating for antireflection are shown in the table.

[Example 3]
Preparation of antireflection transparent coating film-forming paint (3) 72 g of a dispersion of silica-based hollow fine particles (P-1) prepared in the same manner as in Example 1 diluted with ethanol to a solid content concentration of 5% by mass And 1.9 g of acrylic resin (Hitaroid 1007, manufactured by Hitachi Chemical Co., Ltd.) and 26.1 g of a 1/1 (weight ratio) mixed solvent of isopropanol and n-butanol were sufficiently mixed to form a transparent film-forming paint ( 3) was prepared.

Production of base material with antireflection transparent coating (3) After forming a hard coat film in the same manner as in Example 1, the coating liquid for forming an antireflection transparent coating (3) was applied by the bar coater method (bar # 4). After coating and drying at 80 ° C. for 120 seconds, a substrate (3) with a transparent coating for antireflection was prepared by irradiating with an ultraviolet ray of 600 mJ / cm ² in an N ₂ atmosphere and curing. At this time, the film thickness of the antireflection transparent coating was 110 nm.
The table shows the total light transmittance, haze, 550 nm light reflectance, coating refractive index, adhesion, pencil hardness, and scratch resistance of the substrate (3) with an antireflection transparent coating.

[Example 4]
Preparation of silica -based hollow fine particles (P-2) 390 g of pure water was added to 10 g of silica sol (manufactured by JGC Catalysts & Chemicals, Inc .: SI-550, average particle diameter 5 nm, CV value 17%, SiO ₂ concentration 20 mass%). While maintaining the temperature at 98 ° C., 25,500 g of an aqueous solution of sodium silicate having a concentration of 0.5% by mass as SiO ₂ and an aqueous solution of sodium aluminate having a concentration of 0.17% by mass as Al ₂ O ₃ , 000 g was added in 50 hours to obtain a SiO ₂ · Al ₂ O ₃ primary particle dispersion. The pH of the reaction solution at this time was 11.8, and the solid content concentration was 0.3% by mass. The average particle size was 49 nm.

Subsequently, 81,000 g of a sodium silicate aqueous solution with a concentration of 0.5% by mass as SiO ₂ and 26,500 g of a sodium aluminate aqueous solution with a concentration of 0.17% by mass as Al ₂ O ₃ were added over 50 hours to form composite oxide fine particles. (2) A dispersion of (secondary particles) was obtained. At this time, the pH of the reaction solution was 11.6, and the solid content concentration was 0.4% by mass.

  Subsequently, after washing with an ultrafiltration membrane to obtain a solid content concentration of 13% by mass, the mixture was filtered through a capsule filter having an opening of 1 μm to obtain a composite oxide fine particle (2) dispersion. At this time, the average particle diameter was 76 nm, and the CV value = 11.0%.

  To 500 g of the composite oxide fine particle (2) dispersion, 1,125 g of pure water was added, and concentrated hydrochloric acid (concentration 35.5% by mass) was added dropwise to adjust the pH to 1.0, followed by dealumination. Next, an aqueous dispersion of silica-based fine particles (P-2-1) having a solid content concentration of 20 mass% by separating and washing the aluminum salt dissolved in the ultrafiltration membrane while adding 10 L of hydrochloric acid aqueous solution of pH 3 and 5 L of pure water. Got.

  Next, aqueous ammonia is added to the silica-based fine particle (P-2-1) dispersion to adjust the pH of the dispersion to 10.5, and then aged at 200 ° C. for 11 hours, and then cooled to room temperature. Ion exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SK1B) is used for 3 hours, and then anion exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SA20A) is used for 3 hours. Ion exchange was performed, and 200 g of cation exchange resin (manufactured by Mitsubishi Chemical Corporation: Diaion SK1B) was used for ion exchange at 80 ° C. for 3 hours for washing, and silica-based fine particles (P An aqueous dispersion of -2-2) was obtained.

Next, an alcohol dispersion of silica-based fine particles (P-2) having a solid content concentration of 20% by mass, in which the solvent was replaced with ethanol using an ultrafiltration membrane, was prepared.
A methacrylsilane coupling agent (γ-methacryloxypropyltrimethoxysilane) (manufactured by Shin-Etsu Chemical Co., Ltd .: KBM-503, SiO ₂ ) was added to 100 g of an alcohol dispersion of silica-based fine particles (P-2) having a solid content concentration of 20% by mass. (81.9 mass% component) 3 g was added, heat-treated at 50 ° C., and again the alcohol of silica-based hollow fine particles (P-2) having a solid content concentration of 20 mass%, where the solvent was replaced with ethanol using an ultrafiltration membrane. A dispersion was prepared.
The average particle diameter, CV value, refractive index, and proportion of irregular silica-based hollow fine particles of the silica-based hollow fine particles (P-2) are shown in the table.

Production of transparent coating for antireflection coating (4) In the same manner as in Example 1, except that an alcohol dispersion of silica-based hollow fine particles (P-2) having a solid content concentration of 20% by mass was used. A paint (4) was prepared.

Preparation of base material with antireflection transparent coating (4) After forming a hard coat film in the same manner as in Example 1, the coating liquid for forming an antireflection transparent coating (4) was applied by the bar coater method (bar # 4). After coating and drying at 80 ° C. for 120 seconds, a substrate (4) with a transparent coating for antireflection was prepared by irradiating with an ultraviolet ray of 600 mJ / cm ² under an N ₂ atmosphere and curing. At this time, the film thickness of the antireflection transparent coating was 100 nm.
The total light transmittance, haze, reflectance of 550 nm light, refractive index of the coating, adhesion, pencil hardness, and scratch resistance of this substrate (4) with a transparent coating for antireflection are shown in the table.

[Example 5]
Preparation of silica -based hollow fine particles (P-3) 390 g of pure water was added to 10 g of silica sol (manufactured by JGC Catalysts & Chemicals Co., Ltd .: SI-550, average particle diameter 5 nm, CV value 17%, SiO ₂ concentration 20 mass%). While maintaining the temperature at 98 ° C., 10,500 g of a sodium silicate aqueous solution having a concentration of 1.2% by mass as SiO ₂ and a sodium aluminate aqueous solution having a concentration of 0.4% by mass as Al ₂ O ₃ , 500 g was added in 25 hours to obtain a SiO ₂ .Al ₂ O ₃ primary particle dispersion. The pH of the reaction solution at this time was 11.8, and the solid content concentration was 0.8% by mass. Moreover, the average particle diameter was 51 nm.

Subsequently, 33,560 g of a sodium silicate aqueous solution having a concentration of 1.2% by mass as SiO ₂ and 11,190 g of a sodium aluminate aqueous solution having a concentration of 0.4% by mass as Al ₂ O ₃ were added in 25 hours to form composite oxide fine particles. (3) A dispersion of (secondary particles) was obtained. At this time, the pH of the reaction solution was 11.6, and the solid content concentration was 0.9% by mass.

  The dispersion was washed with an ultrafiltration membrane to a solid content concentration of 13% by mass, and then filtered through a capsule filter having an opening of 1 μm to obtain a composite oxide fine particle (3) dispersion. At this time, the average particle size was 78 nm, and the CV value = 28.0%.

  To 500 g of the composite oxide fine particle (3) dispersion, 1,125 g of pure water was added, and concentrated hydrochloric acid (concentration 35.5% by mass) was added dropwise to adjust the pH to 1.0, followed by dealumination. Next, an aqueous dispersion of silica-based fine particles (P-3-1) having a solid content concentration of 20 mass% by separating and washing the aluminum salt dissolved in the ultrafiltration membrane while adding 10 L of hydrochloric acid aqueous solution of pH 3 and 5 L of pure water. Got.

  Next, aqueous ammonia is added to the silica-based fine particle (P-3-1) dispersion to adjust the pH of the dispersion to 10.5, and then aged at 200 ° C. for 11 hours, and then cooled to room temperature. Ion exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SK1B) is used for 3 hours, and then anion exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SA20A) is used for 3 hours. Ion exchange was performed, and 200 g of cation exchange resin (manufactured by Mitsubishi Chemical Corporation: Diaion SK1B) was used for ion exchange at 80 ° C. for 3 hours for washing, and silica-based fine particles (P An aqueous dispersion of -3-2) was obtained.

Next, an alcohol dispersion of silica-based fine particles (P-3) having a solid content concentration of 20% by mass was prepared by replacing the solvent with ethanol using an ultrafiltration membrane.
A methacrylsilane coupling agent (γ-methacryloxypropyltrimethoxysilane) (manufactured by Shin-Etsu Chemical Co., Ltd .: KBM-503, SiO ₂ ) was added to 100 g of an alcohol dispersion of silica-based fine particles (P-3) having a solid content concentration of 20% by mass. 3 g of component 81.9% by mass), heat-treated at 50 ° C., and again using an ultrafiltration membrane, the solvent was replaced with ethanol. Silica-based hollow fine particles having a solid content concentration of 20% by mass (P-3) An alcohol dispersion was prepared.
The average particle diameter, CV value, refractive index, and proportion of irregular silica-based hollow fine particles of the silica-based hollow fine particles (P-3) are shown in the table.

Production of transparent coating for antireflection coating (5) In Example 1, except for using an alcohol dispersion of silica-based hollow fine particles (P-3) with a solid content concentration of 20% by mass, for transparent coating formation A paint (5) was prepared.

Preparation of substrate with antireflection transparent coating (5) After forming a hard coat film in the same manner as in Example 1, the coating liquid for forming an antireflection transparent coating (5) was applied by the bar coater method (bar # 4). After coating and drying at 80 ° C. for 120 seconds, the substrate (5) with a transparent coating for antireflection was produced by irradiating and curing an ultraviolet ray of 600 mJ / cm ² in an N ₂ atmosphere. At this time, the film thickness of the antireflection transparent coating was 100 nm.
The total light transmittance, haze, 550 nm light reflectance, coating refractive index, adhesion, pencil hardness, and scratch resistance of this substrate (5) with a transparent coating for antireflection are shown in the table.

[Example 6]
Preparation of silica -based hollow fine particles (P-4) 390 g of pure water was added to 10 g of silica sol (manufactured by JGC Catalysts & Chemicals Co., Ltd .: SI-550, average particle diameter 5 nm, CV value 17%, SiO ₂ concentration 20 mass%). While heating to 98 ° C. and maintaining this temperature, 45,200 g of a sodium silicate aqueous solution having a concentration of 0.75% by mass as SiO ₂ and a sodium aluminate aqueous solution 45 having a concentration of 0.25% by mass as Al ₂ O ₃ , 200 g was added in 25 hours to obtain a SiO ₂ .Al ₂ O ₃ primary particle dispersion. The pH of the reaction solution at this time was 11.8, and the solid content concentration was 0.5% by mass. Moreover, the average particle diameter was 70 nm.

Subsequently, 138,600 g of a sodium silicate aqueous solution having a concentration of 0.75% by mass as SiO ₂ and 46,200 g of a sodium silicate aqueous solution having a concentration of 0.25% by mass as Al ₂ O ₃ were added in 25 hours to form composite oxide fine particles. (4) A dispersion of (secondary particles) was obtained. At this time, the pH of the reaction solution was 11.6, and the solid content concentration was 0.6% by mass.

  Subsequently, after washing with an ultrafiltration membrane to a solid content concentration of 13% by mass, the mixture was filtered through a capsule filter having an opening of 1 μm to obtain a composite oxide fine particle (4) dispersion. At this time, the average particle size was 95 nm, and the CV value was 11.5%.

  To 500 g of the composite oxide fine particle (4) dispersion, 1,125 g of pure water was added, and concentrated hydrochloric acid (concentration 35.5% by mass) was added dropwise to adjust the pH to 1.0, followed by dealumination. Next, an aqueous dispersion of silica-based fine particles (P-4-1) having a solid content concentration of 20 mass% by separating and washing the aluminum salt dissolved in the ultrafiltration membrane while adding 10 L of hydrochloric acid aqueous solution of pH 3 and 5 L of pure water. Got.

  Next, aqueous ammonia is added to the silica-based fine particle (P-4-1) dispersion to adjust the pH of the dispersion to 10.5, and then aged at 200 ° C. for 11 hours, and then cooled to room temperature. Ion exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SK1B) is used for 3 hours, and then anion exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SA20A) is used for 3 hours. Ion exchange was performed, and 200 g of cation exchange resin (manufactured by Mitsubishi Chemical Corporation: Diaion SK1B) was used for ion exchange at 80 ° C. for 3 hours for washing, and silica-based fine particles (P An aqueous dispersion of -4-2) was obtained.

Next, an alcohol dispersion of silica-based fine particles (P-4) having a solid content concentration of 20% by mass was prepared by replacing the solvent with ethanol using an ultrafiltration membrane.
A methacrylsilane coupling agent (γ-methacryloxypropyltrimethoxysilane) (manufactured by Shin-Etsu Chemical Co., Ltd .: KBM-503, SiO ₂ ) was added to 100 g of an alcohol dispersion of silica-based fine particles (P-4) having a solid content concentration of 20% by mass. Ingredient 81.9% by mass) 3 g was added, heat-treated at 50 ° C., and again using an ultrafiltration membrane to replace the solvent with ethanol. Silica-based hollow fine particles having a solid content concentration of 20% by mass (P-4) An alcohol dispersion was prepared.
The average particle diameter, CV value, refractive index, and proportion of irregular silica-based hollow fine particles of the silica-based hollow fine particles (P-4) are shown in the table.

Production of transparent coating for antireflection coating (6) In Example 1, except that an alcohol dispersion of silica-based hollow fine particles (P-4) having a solid content of 20% by mass was used. A paint (6) was prepared.

Preparation of base material with antireflection transparent coating (6) After forming a hard coat film in the same manner as in Example 1, the coating liquid for forming an antireflection transparent coating (6) was applied by the bar coater method (bar # 4). After coating and drying at 80 ° C. for 120 seconds, a substrate (6) with a transparent coating for antireflection was prepared by irradiating with an ultraviolet ray of 600 mJ / cm ² in an N ₂ atmosphere and curing. At this time, the film thickness of the antireflection transparent coating was 100 nm.
The total light transmittance, haze, 550 nm light reflectance, coating refractive index, adhesion, pencil hardness, and scratch resistance of this substrate (6) with a transparent coating for antireflection are shown in the table.

[Example 7]
Preparation of silica -based hollow fine particles (P-5) 390 g of pure water was added to 10 g of silica sol (manufactured by JGC Catalysts & Chemicals, Inc .: SI-550, average particle diameter 5 nm, CV value 17%, SiO ₂ concentration 20 mass%). While maintaining the temperature at 98 ° C., 13,000 g of a sodium silicate aqueous solution having a concentration of 0.75% by mass as SiO ₂ and a sodium aluminate aqueous solution having a concentration of 0.25% by mass as Al ₂ O ₃ , 000 g was added in 25 hours to obtain a SiO ₂ .Al ₂ O ₃ primary particle dispersion. The pH of the reaction solution at this time was 11.8, and the solid content concentration was 0.5% by mass. The average particle size was 42 nm.

Subsequently, 40,000 g of a sodium silicate aqueous solution having a concentration of 0.75% by mass as SiO ₂ and 13,000 g of a sodium silicate aqueous solution having a concentration of 0.25% by mass as Al ₂ O ₃ were added in 25 hours to form composite oxide fine particles. (5) A dispersion of (secondary particles) was obtained. At this time, the pH of the reaction solution was 11.6, and the solid content concentration was 0.6% by mass.

  Subsequently, after washing with an ultrafiltration membrane to obtain a solid content concentration of 13% by mass, the mixture was filtered through a capsule filter having an opening of 1 μm to obtain a composite oxide fine particle (5) dispersion. At this time, the average particle diameter was 61 nm, and the CV value was 16%.

  1,500 g of pure water was added to 500 g of the dispersion of the composite oxide fine particles (5), and concentrated hydrochloric acid (concentration 35.5% by mass) was added dropwise to adjust the pH to 1.0, followed by dealumination. Next, an aqueous dispersion of silica-based fine particles (P-5-1) having a solid content concentration of 20 mass% by separating and washing the aluminum salt dissolved in the ultrafiltration membrane while adding 10 L of hydrochloric acid aqueous solution of pH 3 and 5 L of pure water. Got.

  Next, aqueous ammonia is added to the silica-based fine particle (P-5-1) dispersion to adjust the pH of the dispersion to 10.5, and after aging at 200 ° C. for 11 hours, it is cooled to room temperature. Ion exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SK1B) is used for 3 hours, and then anion exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SA20A) is used for 3 hours. Ion exchange was performed, and 200 g of cation exchange resin (manufactured by Mitsubishi Chemical Corporation: Diaion SK1B) was used for ion exchange at 80 ° C. for 3 hours for washing, and silica-based fine particles (P An aqueous dispersion of -5-2) was obtained.

Then, an alcohol dispersion of silica-based fine particles (P-5) having a solid content concentration of 20% by mass was prepared by replacing the solvent with ethanol using an ultrafiltration membrane.
A methacrylsilane coupling agent (γ-methacryloxypropyltrimethoxysilane) (manufactured by Shin-Etsu Chemical Co., Ltd .: KBM-503, SiO ₂ ) was added to 100 g of an alcohol dispersion of silica-based fine particles (P-5) having a solid content concentration of 20% by mass. Ingredient 81.9% by mass) 3 g was added, heat-treated at 50 ° C., and the solvent was replaced with ethanol again using an ultrafiltration membrane. An alcohol dispersion was prepared.
The average particle diameter, CV value, refractive index, and proportion of irregular silica-based hollow fine particles of the silica-based hollow fine particles (P-5) are shown in the table.

Preparation of transparent coating for antireflection coating (7) Preparation of transparent coating in the same manner as in Example 1 except that an alcohol dispersion of silica-based hollow fine particles (P-5) having a solid content of 20% by mass was used. A paint (7) was prepared.

Preparation of base material with antireflection transparent coating (7) After forming a hard coat film in the same manner as in Example 1, the coating liquid for forming an antireflection transparent coating (7) was applied by the bar coater method (bar # 4). After coating and drying at 80 ° C. for 120 seconds, a substrate (7) with a transparent coating for antireflection was prepared by irradiating with an ultraviolet ray of 600 mJ / cm 2 under an N ₂ atmosphere and curing. At this time, the film thickness of the antireflection transparent coating was 100 nm.
The table shows the total light transmittance, haze, 550 nm light reflectance, coating refractive index, adhesion, pencil hardness, and scratch resistance of the substrate (7) with an antireflection transparent coating.

[Comparative Example 1]
Preparation of silica -based hollow fine particles (RP-1) 390 g of pure water was added to 10 g of silica sol (manufactured by JGC Catalysts & Chemicals Co., Ltd .: SI-550, average particle size 5 nm, CV value 17%, SiO ₂ concentration 20 mass%). While maintaining the temperature at 98 ° C., 4,200 g of a sodium silicate aqueous solution having a concentration of 3.0% by mass as SiO ₂ and a sodium aluminate aqueous solution having a concentration of 1.0% by mass as Al ₂ O ₃ , 200 g was added in 25 hours to obtain a SiO ₂ .Al ₂ O ₃ primary particle dispersion. The pH of the reaction solution at this time was 11.8, and the solid content concentration was 1.9% by mass. The average particle size was 53 nm.

Next, 13,400 g of a sodium silicate aqueous solution having a concentration of 3.0% by mass as SiO ₂ and 4,500 g of a sodium aluminate aqueous solution having a concentration of 1.0% by mass as Al ₂ O ₃ were added over 25 hours to form composite oxide fine particles. A dispersion of (R1) (secondary particles) was obtained. At this time, the pH of the reaction solution was 11.6, and the solid content concentration was 2.3% by mass.

  Subsequently, after washing with an ultrafiltration membrane to obtain a solid content concentration of 13% by mass, the mixture was filtered through a capsule filter having an opening of 1 μm to obtain a composite oxide fine particle (R1) dispersion. At this time, the average particle size was 77 nm, and the CV value was 56%.

  1,500 g of pure water was added to 500 g of the dispersion of composite oxide fine particles (R1), and concentrated hydrochloric acid (concentration 35.5% by mass) was added dropwise to adjust the pH to 1.0, followed by dealumination. Next, an aqueous dispersion of silica-based fine particles (RP-1-1) having a solid content concentration of 20 mass% by separating and washing the aluminum salt dissolved in the ultrafiltration membrane while adding 10 L of hydrochloric acid aqueous solution of pH 3 and 5 L of pure water. Got.

  Next, aqueous ammonia is added to the dispersion of silica-based fine particles (RP-1-1) to adjust the pH of the dispersion to 10.5, then aging at 200 ° C. for 11 hours, and then cooled to room temperature. Ion exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SK1B) is used for 3 hours, and then anion exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SA20A) is used for 3 hours. After ion exchange, 200 g of cation exchange resin (manufactured by Mitsubishi Chemical Corporation: Diaion SK1B) was used for ion exchange at 80 ° C. for 3 hours for washing, and silica-based fine particles (RP An aqueous dispersion of -1-2) was obtained.

Next, an alcohol dispersion of silica-based fine particles (RP-1) having a solid content concentration of 20% by mass was prepared by replacing the solvent with ethanol using an ultrafiltration membrane.
A methacrylsilane coupling agent (γ-methacryloxypropyltrimethoxysilane) (manufactured by Shin-Etsu Chemical Co., Ltd .: KBM-503, SiO ₂ ) was added to 100 g of an alcohol dispersion of silica-based fine particles (RP-1) having a solid content concentration of 20% by mass. Ingredient 81.9% by mass) 3 g was added, heat-treated at 50 ° C., and the solvent was replaced with ethanol again using an ultrafiltration membrane. An alcohol dispersion was prepared.
The average particle diameter, CV value, refractive index, and proportion of irregular silica-based hollow fine particles of the silica-based hollow fine particles (RP-1) are shown in the table.

Production of transparent coating film (R1) for antireflection coating In Example 1, except for using an alcohol dispersion of silica-based hollow fine particles (RP-1) having a solid content concentration of 20% by mass, a transparent coating film is formed. A paint (R1) was prepared.

Preparation of base material with antireflection transparent coating (R1) After forming a hard coat film in the same manner as in Example 1, the coating liquid for forming an antireflection transparent coating (R1) was applied by the bar coater method (bar # 4). After coating and drying at 80 ° C. for 120 seconds, a substrate (R1) with a transparent coating for antireflection was prepared by irradiating with an ultraviolet ray of 600 mJ / cm ² under an N ₂ atmosphere and curing. At this time, the film thickness of the antireflection transparent coating was 100 nm.
The total light transmittance, haze, 550 nm light reflectance, coating refractive index, adhesion, pencil hardness, and scratch resistance of this substrate (R1) with an antireflection transparent coating are shown in the table.

[Comparative Example 2]
Preparation of silica -based hollow fine particles (RP-2) 390 g of pure water was added to 10 g of silica sol (manufactured by JGC Catalysts & Chemicals Co., Ltd .: SI-550, average particle diameter 5 nm, CV value 17%, SiO ₂ concentration 20 mass%). While maintaining the temperature at 98 ° C., 11,300 g of a sodium silicate aqueous solution having a concentration of 3.0% by mass as SiO ₂ and a sodium aluminate aqueous solution having a concentration of 1.0% by mass as Al ₂ O ₃ , 300 g was added in 25 hours to obtain a SiO ₂ .Al ₂ O ₃ primary particle dispersion. The pH of the reaction solution at this time was 11.8, and the solid content concentration was 1.9% by mass. The average particle size was 78 nm.

Next, 34,650 g of a sodium silicate aqueous solution having a concentration of 3.0% by mass as SiO ₂ and 11,550 g of a sodium aluminate aqueous solution having a concentration of 1.0% by mass as Al ₂ O ₃ were added in 25 hours to form composite oxide fine particles. (4) A dispersion of (secondary particles) was obtained. At this time, the pH of the reaction solution was 11.6, and the solid content concentration was 2.3% by mass.

  Subsequently, after washing with an ultrafiltration membrane to a solid content concentration of 13% by mass, the mixture was filtered through a capsule filter having an opening of 1 μm to obtain a composite oxide fine particle (4) dispersion. At this time, the average particle size was 97 nm, and the CV value was 52%.

  To 500 g of the composite oxide fine particle (4) dispersion, 1,125 g of pure water was added, and concentrated hydrochloric acid (concentration 35.5% by mass) was added dropwise to adjust the pH to 1.0, followed by dealumination. Next, an aqueous dispersion of silica-based fine particles (P-4-1) having a solid content concentration of 20 mass% by separating and washing the aluminum salt dissolved in the ultrafiltration membrane while adding 10 L of hydrochloric acid aqueous solution of pH 3 and 5 L of pure water. Got.

  Next, aqueous ammonia is added to the silica-based fine particle (P-4-1) dispersion to adjust the pH of the dispersion to 10.5, and then aged at 200 ° C. for 11 hours, and then cooled to room temperature. Ion exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SK1B) is used for 3 hours, and then anion exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SA20A) is used for 3 hours. Ion exchange was performed, and 200 g of cation exchange resin (manufactured by Mitsubishi Chemical Corporation: Diaion SK1B) was used for ion exchange at 80 ° C. for 3 hours for washing, and silica-based fine particles (P An aqueous dispersion of -4-2) was obtained.

Next, an alcohol dispersion of silica-based fine particles (P-4) having a solid content concentration of 20% by mass was prepared by replacing the solvent with ethanol using an ultrafiltration membrane.
A methacrylsilane coupling agent (γ-methacryloxypropyltrimethoxysilane) (manufactured by Shin-Etsu Chemical Co., Ltd .: KBM-503, SiO ₂ ) was added to 100 g of an alcohol dispersion of silica-based fine particles (P-4) having a solid content concentration of 20% by mass. Ingredient 81.9% by mass) 3 g was added, heat-treated at 50 ° C., and again using an ultrafiltration membrane to replace the solvent with ethanol. Silica-based hollow fine particles having a solid content concentration of 20% by mass (P-4) An alcohol dispersion was prepared.
The average particle diameter, CV value, refractive index, and proportion of irregular silica-based hollow fine particles of the silica-based hollow fine particles (RP-2) are shown in the table.

Production of anti-reflection transparent coating (R2) coating Example 1 In the same manner as in Example 1, except that an alcohol dispersion of silica-based hollow fine particles (RP-2) having a solid content concentration of 20% by mass was used. A paint (R2) was prepared.

Preparation of base material with antireflection transparent coating (R2) After forming a hard coat film in the same manner as in Example 1, the coating liquid for forming an antireflection transparent coating (R2) was applied by the bar coater method (bar # 4). After coating and drying at 80 ° C. for 120 seconds, a substrate (R2) with a transparent coating for antireflection was prepared by irradiating with an ultraviolet ray of 600 mJ / cm ² in an N ₂ atmosphere and curing. At this time, the film thickness of the antireflection transparent coating was 110 nm.
The total light transmittance, haze, 550 nm light reflectance, coating refractive index, adhesion, pencil hardness, and scratch resistance of this substrate (R2) with an antireflection transparent coating are shown in the table.
[Comparative Example 3]

Preparation of silica -based hollow fine particles (RP-3) 390 g of pure water was added to 10 g of silica sol (manufactured by JGC Catalysts & Chemicals, Inc .: SI-550, average particle diameter 5 nm, CV value 17%, SiO ₂ concentration 20% by mass). While maintaining the temperature at 98 ° C., 5,200 g of a sodium silicate aqueous solution having a concentration of 0.75% by mass as SiO ₂ and a sodium aluminate aqueous solution having a concentration of 0.25% by mass as Al ₂ O ₃ 200 g was added in 25 hours to obtain a SiO ₂ .Al ₂ O ₃ primary particle dispersion. The pH of the reaction solution at this time was 11.8, and the solid content concentration was 0.5% by mass. Moreover, the average particle diameter was 23 nm.

Subsequently, 11,300 g of a sodium silicate aqueous solution having a concentration of 0.75% by mass as SiO ₂ and 3,800 g of an aqueous solution of sodium aluminate having a concentration of 0.25% by mass as Al ₂ O ₃ were added over 25 hours to form composite oxide fine particles. A dispersion of (R3) (secondary particles) was obtained. At this time, the pH of the reaction solution was 11.6, and the solid content concentration was 0.6% by mass.

  Subsequently, after washing with an ultrafiltration membrane to obtain a solid content concentration of 13% by mass, the mixture was filtered through a capsule filter having an opening of 1 μm to obtain a composite oxide fine particle (R3) dispersion. At this time, the average particle size was 34 nm, and the CV value was 13%.

  To 500 g of the composite oxide fine particle (R3) dispersion, 1,125 g of pure water was added, and concentrated hydrochloric acid (concentration 35.5% by mass) was added dropwise to adjust the pH to 1.0, followed by dealumination. Next, an aqueous dispersion of silica-based fine particles (RP-3-1) having a solid content concentration of 20% by mass by separating and washing the aluminum salt dissolved in the ultrafiltration membrane while adding 10 L of hydrochloric acid aqueous solution of pH 3 and 5 L of pure water. Got.

  Next, aqueous ammonia is added to the dispersion of silica-based fine particles (RP-3-1) to adjust the pH of the dispersion to 10.5, then aging at 200 ° C. for 11 hours, and then cooled to room temperature. Ion exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SK1B) is used for 3 hours, and then anion exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SA20A) is used for 3 hours. After ion exchange, 200 g of cation exchange resin (manufactured by Mitsubishi Chemical Corporation: Diaion SK1B) was used for ion exchange at 80 ° C. for 3 hours for washing, and silica-based fine particles (RP An aqueous dispersion of -3-2) was obtained.

Next, an alcohol dispersion of silica-based fine particles (RP-3) having a solid content concentration of 20% by mass was prepared by replacing the solvent with ethanol using an ultrafiltration membrane.
A methacrylsilane coupling agent (γ-methacryloxypropyltrimethoxysilane) (manufactured by Shin-Etsu Chemical Co., Ltd .: KBM-503, SiO ₂ ) was added to 100 g of an alcohol dispersion of silica-based fine particles (RP-3) having a solid content concentration of 20% by mass. Ingredient 81.9% by mass) 3 g was added, heat-treated at 50 ° C., and the solvent was replaced with ethanol using an ultrafiltration membrane again. Silica-based hollow fine particles (RP-3) having a solid content concentration of 20% by mass An alcohol dispersion was prepared.
The average particle diameter, CV value, refractive index, and proportion of irregular silica-based hollow fine particles of the silica-based hollow fine particles (RP-3) are shown in the table.

Production of transparent coating film (R3) for antireflection coating In the same manner as in Example 1, except that an alcohol dispersion of silica-based hollow fine particles (RP-3) having a solid content concentration of 20% by mass was used. A paint (R3) was prepared.

Production of base material with antireflection transparent coating (R3) After forming a hard coat film in the same manner as in Example 1, the coating liquid for forming an antireflection transparent coating (R3) was applied by the bar coater method (bar # 4). After coating and drying at 80 ° C. for 120 seconds, a substrate (R3) with a transparent coating for antireflection was prepared by irradiating with an ultraviolet ray of 600 mJ / cm ² under an N ₂ atmosphere and curing. At this time, the film thickness of the antireflection transparent coating was 100 nm.
The total light transmittance, haze, 550 nm light reflectance, coating refractive index, adhesion, pencil hardness, and scratch resistance of this substrate (R3) with an antireflection transparent coating are shown in the table.

[Comparative Example 4]
Preparation of silica -based hollow fine particles (RP-4) 390 g of pure water was added to 10 g of silica sol (manufactured by JGC Catalysts & Chemicals, Inc .: SI-550, average particle diameter 5 nm, CV value 17%, SiO ₂ concentration 20 mass%). While maintaining the temperature at 98 ° C., while maintaining this temperature, the sodium silicate aqueous solution 102, 200 g having a concentration of 0.75% by mass as SiO ₂ and the sodium aluminate aqueous solution 102 having a concentration of 0.25% by mass as Al ₂ O ₃ , 200 g was added in 25 hours to obtain a SiO ₂ .Al ₂ O ₃ primary particle dispersion. The pH of the reaction solution at this time was 11.8, and the solid content concentration was 0.5% by mass. The average particle size was 115 nm.

Subsequently, 535,700 g of a sodium silicate aqueous solution having a concentration of 0.75% by mass as SiO ₂ and 178,560 g of a sodium silicate aqueous solution having a concentration of 0.25% by mass as Al ₂ O ₃ were added over 25 hours to form composite oxide fine particles. A dispersion of (R4) (secondary particles) was obtained. At this time, the pH of the reaction solution was 11.6, and the solid content concentration was 0.6% by mass.

  Subsequently, after washing with an ultrafiltration membrane to obtain a solid content concentration of 13% by mass, the mixture was filtered through a capsule filter having an opening of 1 μm to obtain a composite oxide fine particle (R4) dispersion. At this time, the average particle size was 152 nm and the CV value was 9%.

  1,500 g of pure water was added to 500 g of this dispersion of composite oxide fine particles (R4), and concentrated hydrochloric acid (concentration 35.5% by mass) was added dropwise to adjust the pH to 1.0, followed by dealumination. Next, an aqueous dispersion of silica-based fine particles (RP-4-1) having a solid content of 20% by mass by separating and washing the aluminum salt dissolved in the ultrafiltration membrane while adding 10 L of hydrochloric acid aqueous solution of pH 3 and 5 L of pure water. Got.

  Next, aqueous ammonia is added to the dispersion of silica-based fine particles (RP-3-1) to adjust the pH of the dispersion to 10.5, then aging at 200 ° C. for 11 hours, and then cooled to room temperature. Ion exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SK1B) is used for 3 hours, and then anion exchange resin (Mitsubishi Chemical Co., Ltd .: Diaion SA20A) is used for 3 hours. After ion exchange, 200 g of cation exchange resin (manufactured by Mitsubishi Chemical Corporation: Diaion SK1B) was used for ion exchange at 80 ° C. for 3 hours for washing, and silica-based fine particles (RP An aqueous dispersion of -4-2) was obtained.

Next, an alcohol dispersion of silica-based fine particles (RP-4) having a solid content concentration of 20% by mass was prepared by replacing the solvent with ethanol using an ultrafiltration membrane.
A methacrylsilane coupling agent (γ-methacryloxypropyltrimethoxysilane) (manufactured by Shin-Etsu Chemical Co., Ltd .: KBM-503, SiO ₂ ) was added to 100 g of an alcohol dispersion of silica-based fine particles (RP-3) having a solid content concentration of 20% by mass. Ingredient 81.9% by mass) 3 g was added, heat-treated at 50 ° C., and the solvent was replaced with ethanol using an ultrafiltration membrane again. Silica-based hollow fine particles (RP-3) having a solid content concentration of 20% by mass An alcohol dispersion was prepared.
Table 1 shows the average particle diameter, CV value, refractive index, and proportion of irregular silica-based hollow fine particles of the silica-based hollow fine particles (RP-4).

Production of transparent coating film for antireflection coating (R4) In Example 1, except for using an alcohol dispersion of silica-based hollow fine particles (RP-4) with a solid content concentration of 20% by mass, for transparent coating formation A paint (R4) was prepared.

Production of substrate with antireflection transparent coating (R4) After forming a hard coat film in the same manner as in Example 1, the coating solution for forming an antireflection transparent coating (R3) was applied by the bar coater method (bar # 4). After coating and drying at 80 ° C. for 120 seconds, a substrate (R3) with a transparent coating for antireflection was prepared by irradiating with an ultraviolet ray of 600 mJ / cm ² under an N ₂ atmosphere and curing. At this time, the film thickness of the antireflection transparent coating was 160 nm.
The total light transmittance, haze, 550 nm light reflectance, coating refractive index, adhesion, pencil hardness, and scratch resistance of the substrate (R4) with an antireflection transparent coating are shown in the table.

Claims (5)

A substrate;
The average particle size (Dn) formed on the substrate is in the range of 50 to 120 nm, the particle size variation coefficient (CV value) is in the range of 1 to 50%, and the refractive index is 1.10 to 1. A substrate with a transparent coating comprising a silica-based hollow fine particle in the range of 30 and a transparent coating composed of a matrix component, wherein the particle size is at least twice the average particle size (Dn) of the silica-based hollow fine particle. The number ratio of the deformed silica-based hollow fine particles in the silica-based hollow fine particles is 1% or less, and the silica-based hollow fine particles are prepared by preparing composite oxide fine particles composed of silica and an inorganic oxide other than silica. In the process of preparing silica-based hollow fine particles comprising removing substances, the composite oxide fine particle dispersion is prepared by maintaining the solid content concentration in the range of 0.1 to 0.6% by mass. Base material with coating. 2. The substrate with a transparent coating according to claim 1 , wherein the content of the silica-based hollow fine particles in the transparent coating is in the range of 40 to 90 mass%. The refractive index of the transparent film is you being in the range of 1.15 to 1.40 according to claim 1 or 2 with a transparent film substrate according to. A coating liquid for forming a transparent film comprising silica-based hollow fine particles, a matrix-forming component, and a polar solvent,
The silica-based hollow fine particles have a ratio of the number of irregular-shaped silica-based hollow fine particles having a particle size of twice or more the average particle size (Dn) of 1% or less, and an average particle size (Dn) in the range of 50 to 120 nm. The particle diameter variation coefficient (CV value) is in the range of 1 to 50%, the refractive index is in the range of 1.10 to 1.30 ,
In the preparation step of the silica-based hollow fine particles, in which the silica-based hollow fine particles are prepared by preparing the composite oxide fine particles composed of silica and an inorganic oxide other than silica, and then removing the inorganic oxide. A coating solution for forming a transparent film, characterized in that it is prepared while maintaining a solid content concentration of 0.1 to 0.6 mass% . The concentration of the silica-based hollow fine particles in the paint is in the range of 0.4 to 54% by mass as the solid content, the concentration of the matrix forming component is in the range of 0.1 to 36% by mass as the solid content, and the total solid content concentration The paint for forming a transparent film according to claim 4 , wherein is in the range of 1 to 60% by mass.

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