JP6846129B2 - Method of forming a heat-shielding multi-layer coating film - Google Patents

Description

The present invention relates to a method for forming a heat-shielding multilayer coating film. More specifically, the present invention relates to a method for forming a heat-shielding multi-layer coating film for forming a transparent heat-shielding coating film on the surface of a transparent base material.

In recent years, energy saving has been required in buildings such as buildings and houses from the viewpoint of improving the living environment, reducing the environmental load, and reducing the heating and cooling costs.

In recent years, the number of buildings such as buildings and residences that have a vast glass surface in terms of daylighting and aesthetics is increasing. Since glass occupies a large proportion of the surface of the building, it is not possible to obtain a sufficient energy saving effect only by providing a heat insulating layer with glass wool or the like on the walls, floors, ceilings, etc. of the non-glass surface. , Development of energy saving method for glass surface is required. Therefore, as one of the simpler measures to replace the glass surface with double glazing or the like, a method of forming a heat-shielding coating film having high visible light transmittance and heat-shielding property on the glass surface can be considered. Such a heat-shielding coating film can be formed by applying a coating film-forming composition containing an infrared absorber as a main component on a transparent substrate that has been degreased and washed in advance and curing the coating film. It is known (see, for example, Patent Document 1 and Patent Document 2).

Japanese Unexamined Patent Publication No. 9-208863 Japanese Unexamined Patent Publication No. 2008-101111

By the way, various pollutants are attached to the glass surface of a building unless it is newly installed, and when a heat-shielding coating film is directly formed without removing such pollutants on the glass surface, it is continuous due to repellent or the like. Problems such as the formation of a coating film and the deterioration of visible light transmission due to turbidity of the coating film occur. Therefore, in the conventional methods described in Patent Document 1 and Patent Document 2, a pre-process of degreasing and cleaning, which requires a great deal of labor and time, is indispensable.

The present invention has been made in view of the above problems, and a film is formed with a surface modifier without removing contaminants on the transparent substrate in advance, and then a heat-shielding coating film is formed on the film. It is an object of the present invention to provide a method for forming a heat-shielding multi-layer coating film that eliminates the need for degreasing and cleaning work.

The present invention is a method for forming a heat-shielding multi-layer coating film for forming a heat-shielding coating film on a transparent base material, and a film is formed by applying a surface modifier (A) on the transparent base material. The surface modifier (A) comprises a first step of forming a heat-shielding coating film by applying the coating composition (B) on the substrate after the first step. Provided is a method for forming a heat-shielding multilayer coating film, which comprises a hydrolyzed organosilicate compound and has a concentration of silica contained in the surface modifier (A) of 0.1 to 20% by mass.

Further, the concentration of silica contained in the surface modifier (A) of the present invention is preferably 0.5 to 20% by mass.

The coating composition (B) of the present invention is a group consisting of a resin composition (a) made of a hydroxyl group-containing acrylic resin, a cross-linking agent (b) made of polyisocyanate, and tin, indium, tungsten, antimony and cesium. It is preferable to include metal oxide fine particles (c) having at least one metal selected from the above.

Further, in the coating composition (B) of the present invention, the content of the metal oxide fine particles (c) is 5 to 150% by mass with respect to 100 parts by mass of the total solid content of the resin composition (a) and the cross-linking agent (b). It is preferably a part.

Further, the cross-linking agent (b) of the present invention preferably comprises at least one of an aliphatic polyisocyanate and an alicyclic polyisocyanate.

The present invention is a work for degreasing and cleaning by forming a film with a surface modifier and then forming a transparent heat-shielding coating film on the film without removing contaminants on the transparent substrate in advance. It is possible to provide a method for forming a heat-shielding multi-layer coating film that eliminates the need for.

Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments.

[Method of forming a heat-shielding multi-layer coating film]
The method for forming the heat-shielding multi-layer coating film according to the present embodiment includes a first step of forming a film by applying a surface modifier (A) on a transparent substrate and a coating composition on the transparent substrate. It includes a second step of forming a heat-shielding coating film by applying the object (B).

Here, the transparent base material of the present invention is a concept including not only a completely colorless and transparent base material but also a colored transparent base material in a state in which the inside can be seen through, and is composed of an inorganic substance such as glass. Base material can be mentioned. The heat-shielding multi-layer coating film of the present embodiment is preferably applied to a window glass such as a living space.

[First step]
In the first step of the method for forming the heat-shielding multi-layer coating film according to the present embodiment, the surface of the transparent base material is modified using the surface modifier (A) described later. The surface modifier (A) according to the present embodiment is a transparent group that is directly applied onto a transparent substrate without degreasing the oil film on the surface or cleaning the surface in order to remove contaminants. The surface of the material is modified to a base capable of forming a heat-shielding coating film.

Here, the modified base of the present invention is a film made of the surface modifier (A). Specifically, it is a hydrophilic film described later based on the surface modifier (A).
Conventionally, unless it is newly installed, pollutants such as oxide film, oil film, and dust for surface protection are attached to the transparent base material, so heat is shielded directly on the transparent base material without removing the pollutants. The coating film could not be formed. On the other hand, on the surface of the transparent substrate modified by the surface modifier (A) of the present embodiment, a heat-shielding coating film can be formed on the substrate without removing the pollutant. it can. Further, the surface of the modified transparent base material has a high affinity with the heat-shielding coating film, and the dried heat-shielding coating film can be firmly adhered to the transparent base material.

The method of applying the surface modifier (A) in the first step is not particularly limited, and for example, a roller method, a spray method, a sponge coating method, a bar coating method, a curtain coating method (flow coating method), a spin coating method, and a doctor. Examples include the blade method and coating with a non-woven fabric.

[Surface modifier (A)]
First, the surface modifier (A) of the present embodiment will be described.
The surface modifier (A) of the present embodiment forms a transparent hydrophilic film on the surface of the transparent base material. As a result, a transparent heat-shielding coating film can be formed on this hydrophilic film by the coating composition (B) described later. As a result, the formed heat-shielding coating film is not affected by dust and oil film existing on the surface of the transparent base material. Therefore, the surface modifier (A) of the present embodiment can omit various treatments related to the surface adjustment of the transparent base material.

Here, the transparent hydrophilic coating film has a predetermined transmittance in the visible light region of the irradiated light, and the amount of dimming due to the hydrophilic coating film is suppressed as much as possible. Specifically, it is more preferable that the coating film has a wavelength of 550 nm and a spectral transmittance of 20% or more. Further, it is preferable that the hydrophilic coating film of the present embodiment has a contact angle with water adjusted to 70 degrees or less. From the viewpoint of having good performance as a substrate, the contact angle with water is particularly preferably 60 degrees or less.

The surface modifier (A) is a composition used for forming a transparent hydrophilic film on the surface of a transparent base material, and contains a dispersion medium and a silica component. The surface modifier (A) is a dispersion of hydrolyzed organosilicate that can exert a hydrophilic effect on the surface of the base material.

The dispersion medium according to the present embodiment is not limited as long as it is a solvent capable of dispersing or dissolving the silica component.

As the dispersion medium, it is preferable to use water and / or various water-soluble organic solvents.

The water-soluble organic solvent is not particularly limited, and for example, an alcohol solvent such as methanol, ethanol, isopropanol and ethylene glycol; an ether solvent such as ethylene glycol monopropyl ether, butyl glycol and 1-methoxy-2-propanol; acetone. , Ketone solvents such as diacetone alcohol; amide solvents such as dimethylacetamide and methylpyrrolidone; ester solvents such as ethylcarbitol acetate and the like. These may be used alone or in combination of two or more.

The silica component is blended in order to exert the effect of efficiently hydrophilizing the surface of the base material after application. From the viewpoint of this effect, examples of the silica component include silicate compounds such as alkyl silicate compounds and organosilicate compounds. The silica component used in the surface modifier (A) of the present embodiment is a hydrolyzed organosilicate compound from the viewpoint of adhesion to the heat-shielding coating film. From the viewpoint of adhesion to the heat-shielding coating film, it is more preferable to use colloidal silica obtained by condensation polymerization of a hydrolyzed organosilicate compound.

As used herein, the term "organosilicate" refers to a compound containing an organic group bonded to a silicon atom via an oxygen atom. Suitable organosilicates include, without limitation, an organosilane containing four organic groups bonded to a silicon atom via an oxygen atom, and a siloxane backbone ((Si—O) n) composed of the silicon atom. Organoxysiloxane having.

The organic group bonded to the silicon atom via the oxygen atom in the organosilicate is not limited, and may include, for example, a linear alkyl group, a branched alkyl group, or a cyclic alkyl group. Specific examples of organic groups that can be attached to a silicon atom via an oxygen atom in an organosilicate are unlimited: methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl. , N-Pentyl, i-Pentyl, Neopentyl, Hexyl, Octyl and the like. Of these alkyl groups, C1-C4 alkyl groups are often used. Examples of other suitable organic groups may include aryl, xylyl, naphthyl and the like. Organosilicates can contain two or more different types of organic groups.

Specific examples of the organoxysiloxane include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetraisobutoxysilane, tetra-sec-butoxysilane, and tetra-. Examples thereof include condensates of one kind or a combination of two or more kinds such as t-butoxysilane, tetraphenoxysilane, and dimethoxydiethoxysilane.

Hydrolysis of the organosilicate can be carried out in the presence of one or more hydrolysis catalysts. Specific examples of suitable catalysts include, but are not limited to, inorganic acids (eg, hydrochloric acid, sulfuric acid, nitrate and phosphoric acid, among others); organic acids (eg, acetic acid, benzenesulfonic acid, toluenesulfonic acid, among others, among others). Xylene sulfonic acid, ethylbenzene sulfonic acid, benzoic acid, phthalic acid, maleic acid, formic acid, citric acid, and oxalic acid); alkaline catalysts (eg, sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia), and organic amines. Compounds, organic metal compounds or metal alkoxide compounds other than organosilicates (eg, organic tin compounds (eg, dibutyltin dilaurate, dibutyltin dioctate, and dibutyltin diacetate), organic aluminum compounds (eg, aluminum tris (acetylacetonate)), Aluminum Monoacetylacetate Bis (Ethylacet Acetate), Aluminum Tris (Ethylacet Acetate), and Aluminum Ethylacetacetate Diisopropirate, Organic Titanium Compounds (eg Titanium Tetrax (Acetylacetate), Titanium Bis (Butoxy) Bis (acetylacetonate) and titanium tetra-n-butoxide), as well as organic zirconium compounds (eg, zirconium tetrakis (acetylacetonate), zirconium bis (butoxy) -bis (acetylacetonate), zirconium (isopropoxy) -bis (Acetylacetonate) and zirconium tetra-n-butoxide), and boron compounds (eg, boron tri-n-butoxide and boric acid) and the like.

The organosilicate condensate can be produced by a conventional method. It can also be obtained by combining the above-mentioned organosilicate condensate alone or in combination of two or more, partially hydrolyzing using the above-mentioned hydrolysis catalyst, and then condensing. In the polymerization reaction of the organosilicate, it is preferable to proceed with the polymerization reaction of silicic acid in the reaction medium to produce a condensate of the organosilicate of a predetermined size.

Further, it is preferable to produce spherical colloidal silica by, for example, growing the average particle size to a range not exceeding 100 nm by utilizing the condensation reaction of the organosilicate.
Colloidal silica has the effect of increasing the hydrophilicity of the film obtained from the uneven shape. If the average particle size exceeds 100 nm, agglomerates having a large particle size may be generated in the treatment agent, which may reduce the coating workability.

The hydrolyzed organosilicate dispersion can be produced by a conventional method. After washing the colloidal silica made of the organosilicate, the silica is charged into a dispersion medium so that the silica concentration is 0.1 to 20% by mass. Then, the hydrolyzed organosilicate dispersion is produced by stirring under normal temperature and pressure. From the viewpoint of adhesion to the heat-shielding coating film, the silica concentration in the dispersion medium is more preferably 0.5 to 20% by mass.

[Second step]
In the second step of the method for forming a heat-shielding multi-layer coating film according to the present embodiment, the coating composition (B) described later is applied on a modified base (film), and a transparent shield is applied on the base material. Form a thermal coating. Specifically, the coating composition (B) is applied to the surface (base) of the transparent base material that has been modified by the first step, and dried to obtain the modified base (film). A transparent heat-shielding coating film is formed on the surface.

Here, the transparent heat-shielding coating film of the present invention preferably has a shielding coefficient of 0.8 or less. The shielding coefficient defined in the present invention is a value indicating the degree of light shielding with respect to the total amount of light when natural light is applied to the transparent base material on which the heat shielding coating film is formed. That is, the shielding coefficient represents the shielding ability for the irradiated light including ultraviolet light to infrared light. In the present embodiment, the shielding coefficient is preferably 0.8 or less because it is excellent in visible light transmittance and heat shielding property. In particular, the transparent heat-shielding coating film of the present invention preferably has a light transmittance of 20% or more at a wavelength of 550 nm.

The coating method of the coating composition (B) in the second step according to the present embodiment is not particularly limited, and is, for example, a brush coating method, a roller method, a spray method, a sponge coating method, a bar coating method, and a curtain coating method (flow coating). Method), spin coating method, doctor blade method, etc. can be mentioned. Further, when painting on the existing window glass, the spray method, the sponge coating method, the brush coating method, the roller method, and when painting on the line of a factory or the like, the curtain coating method and the spin coating method are preferable.

[Coating composition (B)]
The coating composition (B) of the present embodiment contains a resin composition (a), a cross-linking agent (b), and metal oxide fine particles (c).

As the resin composition (a), an acrylic resin having a crosslinkable functional group (for example, a hydroxyl group, an epoxy group, a carboxyl group, an alkoxysilane group, etc.), a vinyl resin, a polyester resin, an alkyd resin, a urethane resin and the like are preferable. In particular, from the viewpoint of affinity with the surface modifier (A), it is preferable to use a hydroxyl group-containing acrylic resin that has been properly adjusted.

Examples of the monomer composition suitable for producing the acrylic resin of the resin composition (a) include a hydroxyl-containing acrylic acid hydroxy ester such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate; methacrylic acid. It contains at least one of a hydroxyl-containing methacrylic acid hydroxy ester, such as 2-hydroxyethyl acid, 4-hydroxybutyl methacrylate; and, if necessary, acrylic acid; methyl acrylate, butyl acrylate. , Acrylic acids such as isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, isobolonyl acrylate; methacrylic acid; methyl methacrylate, butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate , Methacrylic acid esters such as 2-ethylhexyl methacrylate, lauryl methacrylate, isobolonyl methacrylate; ethylenically unsaturated monomers having an aromatic ring such as styrene; and the like. The composition of the monomer composition may be appropriately adjusted according to various physical properties required for the hydroxyl group-containing acrylic resin.

The monomer composition may be polymerized using a solvent such as butyl acetate, and the polymerization conditions such as the type of the solvent, the concentration of the monomer composition at the time of polymerization, the type and amount of the polymerization initiator, the polymerization temperature and the polymerization time can be determined. , It may be appropriately adjusted according to various physical properties required for the hydroxyl group-containing acrylic resin, and is not particularly limited.

The composition ratio of each monomer constituting the acrylic resin of the resin composition (a) is preferably adjusted so that the hydroxyl value (OHV) of the acrylic resin is 1 to 300 mgKOH / g, and the hydroxyl value (OHV) is 10. It is more preferable that the content is in the range of ~ 200 mgKOH / g. If the hydroxyl value of the acrylic resin is less than 1 mgKOH / g, it tends to be difficult to secure the curability of the obtained coating film, and if it exceeds 300 mgKOH / g, the water resistance of the coating film tends to decrease.

The weight average molecular weight (Mw) of the acrylic resin of the resin composition (a) is preferably in the range of 1000 to 2000000, and if it is below the lower limit, the coating film hardness tends to be insufficient, and if it exceeds the upper limit, it tends to be insufficient. There is a risk that unevenness and agglomerates may cause lumps and deteriorate the appearance of the coating film. In particular, it is more preferable that the weight average molecular weight (Mw) is 1500 to 15000000.

The glass transition point (Tg) of the acrylic resin of the resin composition (a) is preferably −50 to 150 ° C. If the glass transition temperature (Tg) is lower than -50 ° C, the coating film is softened by heat generated by sunlight when it is applied to the exterior surface of a building, and sufficient coating film strength cannot be obtained, resulting in swelling of the coating film. If the temperature is higher than 150 ° C., the film-forming property of the coating film is poor, and even if the film can be formed, the flexibility of the coating film becomes insufficient and the coating film cracks. It tends to be easier. The glass transition temperature (Tg) of the resin composition (a) is more preferably −50 to 100 ° C.

The cross-linking agent (b) is a polyisocyanate compound, but is not particularly limited, and is a fat such as trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate (HDI), or trimethylhexamethylene diisocyanate having a free isocyanate group. Group isocyanate; alicyclic isocyanates such as 1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate, 1,2-cyclohexane diisocyanate, isophorone diisocyanate (IPDI), norbornan diisocyanate methyl; xylylene diisocyanate (XDI), 2, Aromatic isocyanates such as 4-tolylene diisocyanate (TDI) and 2,6-tolylene diisocyanate; and multimers such as these burettes and nurates can be mentioned as examples. These polyisocyanate compounds can be used alone or in combination of two or more. Among them, the hexamethylene diisocyanate multimer and the isophorone diisocyanate multimer are preferable because they can secure sufficient fluidity even when no solvent is used, and when these two multimers are used in combination, the coating film hardness and other coating film physical properties, for example, It is particularly preferable because it can improve water resistance and chipping resistance.

As the cross-linking agent (b), it is preferable to use an aliphatic polyisocyanate or an alicyclic polyisocyanate, which is good for an acrylic resin having many hydroxyl groups. Commercially available products can be used as these polyisocyanate compounds. For example, it is preferable to use "Duranate 50M-HDI" manufactured by Asahi Kasei Chemicals Co., Ltd. as the aliphatic polyisocyanate compound, and "VESTANAT IPDI" manufactured by Ebonic Japan Co., Ltd. as the alicyclic polyisocyanate compound.

The cross-linking agent (b) is preferably contained in the coating composition (B) according to the present embodiment in an amount of 1 to 50% by mass. More preferably, it is 2 to 40% by mass.

The metal oxide fine particles (c) preferably have at least one metal selected from the group consisting of tin, indium, tungsten, antimony and cesium. More specifically, it is preferably an infrared absorbing inorganic compound containing these metals.

Here, the infrared absorbing inorganic compound used in the present embodiment is an inorganic compound that satisfactorily absorbs near infrared rays (wavelength: 700 to 2500 nm) among infrared rays. Further, it is preferable that the infrared absorbing inorganic compound absorbs near infrared rays well, whereas the absorption of visible light (wavelength: 360 to 700 nm) is low. Infrared-absorbing Inorganic compounds absorb near-infrared rays well and do not absorb visible light as much as possible, so that a heat-shielding coating film having a small shielding coefficient can be formed on the surface of the base material while maintaining transparency.

Examples of the infrared absorbing inorganic compound include cesium-indium-tin mixed oxide, antimon-tungsten-tin mixed oxide, cesium-tungsten mixed oxide, antimon-containing tin oxide (ATO), and indium-containing tin oxide (ITO). , Aluminum-added zinc oxide (AZO), titanium oxide, zinc oxide, cerium oxide, ruthenium oxide and the like. From the viewpoint of increasing the shielding coefficient, a cesium-indium-tin mixed oxide, an antimony-tungsten-tin mixed oxide, and a cesium-tungsten mixed oxide are more preferable.

The metal oxide fine particles (c) are dispersed in a solvent such as toluene, methyl ethyl ketone, butyl acetate, propylene glycol monomethyl ether, and ethylene glycol monobutyl ether acetate, and these solvents are appropriately selected and used alone or mixed. Can be used. Considering the compatibility with the acrylic resin, it is preferable to use butyl acetate as the solvent.

The concentration of the metal oxide fine particles (c) at the time of dispersion is preferably 5 to 150 parts by mass with respect to the solvent. In particular, the coating composition (B) contains 2 to 50 parts by mass of metal oxide fine particles (c) from the viewpoint of ensuring a good shielding coefficient and ensuring the transparency of the heat-shielding coating film. Is more preferable.

[Other components of coating composition (B)]
The coating composition (B) of the present embodiment is not limited to each of the above components, and may further contain a solvent in which an ultraviolet absorber is dissolved or dispersed.

Hereinafter, the present invention will be described in more detail with reference to Examples. Further, in the examples, "part" means "part by mass" unless otherwise specified, and "%" means "mass%" unless otherwise specified.

<Preparation of transparent base material (test plate)>
A glass plate used as a window glass for a living space was cut out in a range of 200 mm × 300 mm × 3 mm to prepare a test plate. After applying the following surface modifier (A) to this test plate, the coating composition (B) was applied to form a heat-shielding multi-layer coating film on the test plate.

[Raw materials, etc.]
In the following Examples and Comparative Examples, the following raw materials and the like were used.
(1) Dispersion medium: Methanol "Methanol" manufactured by Mitsubishi Gas Chemical Company, Inc.
(2) Silica component: Colloidal silica (organosilicate condensate) "Snowtex N" manufactured by Nissan Chemical Industries, Ltd.,
(3) Hydrolysis catalyst: "TVS # Tin Lau" manufactured by Nitto Kasei Co., Ltd.,
(4) Resin composition (a): Acrylic resin BASF's "Joncryl 507 (Mw = 12500, NV80%, OH-V140 mgKOH / g)",
(5) Crosslinking agent (b-1): 100% aliphatic polyisocyanate compound "Duranate 50M-HDI" manufactured by Asahi Kasei Chemicals Co., Ltd.,
(6) Crosslinking agent (b-2): 100% alicyclic polyisocyanate compound "VESTANAT IPDI" manufactured by Evonik Japan, Inc.
(7) Solvent: Butyl acetate "Butyl acetate" manufactured by Mitsubishi Chemical Corporation.
(8) Metal oxide fine particles (c-1): Cesium / indium / tin composite oxide (9) Metal oxide fine particles (c-2): Tungsten / cesium composite oxide (10) Metal oxide fine particles (c-) 3): Indium tin oxide composite oxide (ITO)
(11) Metal oxide fine particles (c-4): Antimony tin composite oxide (ATO)

[Example 1]
(A) First step Adjustment of surface modifier (A): Colloidal silica "Snowtex N" (manufactured by Nissan Chemical Industries, Ltd.) is used as a dispersion medium (manufactured by Nissan Chemical Industries, Ltd.) so that the silica concentration becomes 2% by mass under normal temperature and pressure. It was dissolved in methanol) to obtain a surface modifier (A).
Surface modification treatment: The test plate was spray-treated with the surface modifier (A) for 30 seconds so that the coating amount was 10 g / m ^2. As a result, a highly transparent hydrophilic film was formed on the test plate.
(B) Second Step Preparation of Coating Composition (B): Under normal temperature and pressure, the acrylic resin (a) shown in Table 1 has a solid content of 30 parts by mass, and the aliphatic polyisocyanate (b-1) has a solid content. Acrylic resin "Joncryl 507" (manufactured by BASF) dissolved in 30% butyl acetate (manufactured by Mitsubishi Chemical Co., Ltd.) and aliphatic polyisocyanate "Duranate 50M" using a conventional method so as to have 10 parts by mass in conversion. -HDI "(manufactured by Asahi Kasei Chemicals Co., Ltd.) was mixed. Further, when the sum of the solid content of the acrylic resin (a) and the solid content of the aliphatic polyisocyanate (b-1) is 100 parts by mass, the solid content is 12.5 parts by mass. A 20% dispersion of a cesium / indium / tin composite oxide (dispersion medium: butyl acetate (manufactured by Mitsubishi Chemical Corporation)) was mixed so as to obtain a coating composition (B).
Heat-shielding film forming step: The coating composition (B) is applied to a test plate on which a hydrophilic film is formed obtained through the first step with a roller and dried at 25 ° C. , A test plate on which a heat-shielding multi-layer coating film having a thickness of 10 μm was formed was obtained.

[Examples 2 to 13 and Comparative Examples 1 to 3]
The composition of the raw materials of the surface modifier (A) and the coating composition (B) was changed as shown in Table 1, respectively. Other than that, the heat-shielding multi-layer coating film was formed on the test plate by the same procedure as the method for forming the heat-shielding multi-layer coating film of Example 1.

<Evaluation of shielding coefficient>
A spectrum having a wavelength of 250 nm to 2500 nm is measured with a spectrophotometer, and the measured value is obtained by multiplying each wavelength by the wavelength distribution of sunlight. The ratio of the measured values of the glass plate on which the heat-shielding multi-layer coating film was formed when the measured value of the glass plate was 1 was defined as the shielding coefficient. Here, with the shielding coefficient = 0.8 as the threshold value, the one having the shielding coefficient of 0.8 or less was set to 1, and the one having the shielding coefficient exceeding 0.8 was set to 0. The evaluation results are shown in Table 1.

<Evaluation of transparency>
The transparency of the obtained heat-shielding multi-layer coating film was visually evaluated. The presence or absence of turbidity and cracks in the heat-shielding multi-layer coating film was examined. No turbidity was observed in the coating film 3, the case where the volume of the turbid part in the coating film was 30% or less was 2, and the case where the volume of the turbid part in the coating film was larger than 30% was 1. .. The evaluation results are shown in Table 1.

<Appearance evaluation of heat-shielding multi-layer coating film>
The appearance (design) of the obtained heat-shielding multi-layer coating film was visually evaluated. In the heat-shielding multi-layer coating film, abnormalities in the coating film such as wrinkles, unevenness, repelling, bumps, blisters, and peeling were investigated. The one with a very good coating film appearance was rated as 3, the one with a good coating film appearance was rated as 2, and the one with an abnormal coating film appearance was rated as 1. The evaluation results are shown in Table 1.

Comparing Examples 1 to 4 and 8 with Example 13 in which the content of the metal oxide fine particles (c) is low, Examples 1 to 4 and Examples 1 to 4 in which the content of the metal oxide fine particles (c) is 5.0 or more. It was found that 8 has an excellent heat shielding coefficient.

Comparing Examples 1 to 4 and 8 with Example 12 having a high content of the metal oxide fine particles (c), Examples 1 to 4 and 8 having a metal oxide fine particle (c) content of 125 or less are It was found to be excellent in transparency and appearance. In particular, it was found that the heat-shielding multi-layer coating film described in Examples 1 and 2 was excellent in transparency.

In Comparative Example 1 in which the surface modifier (A) was not used, the heat-shielding coating film adhered poorly, and the heat-shielding coating film could not be formed on the test plate. Further, in Comparative Example 2 in which the surface modifier (A) containing a low concentration of silica is used, the coating composition (B) is repelled on the hydrophilic film, and a uniform heat-shielding multi-layer coating film can be formed. There wasn't. On the other hand, in Comparative Example 3 in which the surface modifier (A) containing a high concentration of silica is used, agglomerates are formed in the heat-shielding coating film on the hydrophilic film to form a uniform heat-shielding multi-layer coating film. could not.
Therefore, in the present invention, a film is formed with the surface modifier (A) without removing the contaminants on the transparent substrate in advance, and then a heat-shielding coating film is formed on the film for degreasing and cleaning. It is possible to provide a novel method for forming a heat-shielding multi-layer coating film that does not require the work for the above. In particular, for the surface modifier (A), it is preferable to adjust the silica concentration so that it is at least more than 0.05% and less than 30%.

Claims (4)

A method for forming a heat-shielding multi-layer coating film that forms a heat-shielding coating film having a shielding coefficient of 0.8 or less on glass.
The first step of forming a film by applying the surface modifier (A) on the glass, and
A second step of forming a heat-shielding coating film by applying the coating composition (B) on the film of the glass on which the film is formed after the first step is included.
The surface modifier (A) comprises a hydrolyzed organosilicate compound.
The concentration of silica contained in the surface modifier (A) is Ri 0.1-20% by mass,
The coating composition (B) is
A resin composition (a) composed of a hydroxyl group-containing acrylic resin and
A cross-linking agent (b) composed of polyisocyanate and
A method for forming a heat-shielding multilayer coating film , which comprises metal oxide fine particles (c) having at least one metal selected from the group consisting of tin, indium, tungsten, antimony and cesium. The method for forming a heat-shielding multi-layer coating film according to claim 1, wherein the concentration of silica contained in the surface modifier (A) is 0.5 to 20% by mass. The coating composition (B) contains 5 to 150 parts by mass of the metal oxide fine particles (c) with respect to 100 parts by mass of the total solid content of the resin composition (a) and the cross-linking agent (b). The method for forming a heat-shielding multilayer coating film according to claim 1 or 2. The method for forming a heat-shielding multi-layer coating film according to any one of claims 1 to 3, wherein the cross-linking agent (b) comprises at least one of an aliphatic polyisocyanate and an alicyclic polyisocyanate.