JP2001089871A - Coated metallic sheet high in solar heat reflectibility - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a coated metallic sheet excellent in thermal shielding properties, capable of being colored into optional color and being produced inexpensively in high productivity, high in solar heat reflectibility and optimum as building exterior materials such as lightweight roof materials. SOLUTION: One side of a metallic substrate (such as a plated steel sheet) to be applied with solar radiation is provided with a coating film containing pigment of 2 to 70 mass% in which solar heat reflectibility RE/NIR in the wavelength region of 0.8 to 2.1 μm is >=10%, and the RE/NIR of the coated face is controlled to >=20%. In the case the solar heat reflectibility TE/NIR in the wavelength region of 0.8 to 2.1 μm of the coating film is high of >=20%, a metallic substrate (such as an Al plated steel sheet) whose RE/NIR is high of >=40% is used, and, reflection from the substrate is also utilized. The back side is preferably made into the one having low emissivity of <=70%, and the coating film containing flaky aluminum pigment of 0.05 to 1.5 g/m2 is suitable. When the contact angle of the surface to be applied with solar radiation to water is controlled to <=60 deg. or >=90 deg., its contamination resistance is made excellent, and the reduction of its solar heat reflectibility caused by contamination can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is excellent in solar heat reflectivity, which is suitable mainly as a building exterior material such as a roof material.
The present invention relates to a coated metal plate in which the temperature rise of a substrate when receiving solar radiation and the heat dissipation to the back side are suppressed.

[0002]

2. Description of the Related Art House structures are being strengthened from the viewpoint of improving disaster prevention and the like. Roofing materials include new ceramics, metal roofs, etc., in addition to Japanese tiles.

[0003] Metal roofs have a mass about 1/1 compared to Japanese tiles.
0, it is about 1/3 lighter than new ceramics, so it is considered to be a preferable material for promoting structural reinforcement and weight reduction. However, since metal has a higher thermal conductivity than ceramic materials, metal roofing material has the disadvantage that solar heat is easily conducted to the attic, radiated into the room from the back side, and the indoor temperature tends to increase. .

As a method of suppressing the influence of solar heat, there is a method of bonding a heat insulating material to the back surface of a metal roofing material. But,
Usually, since a method of bonding a heat insulating material after forming a metal plate is adopted, the manufacturing process of the bonding material is complicated, and the initial cost required for dedicated equipment is high, so that it is not economical. There is a problem.

[0005] There is also a method of applying a heat-shielding heat-insulating paint to a metal roofing material. The heat-insulating heat-insulating paint is a special paint that uses ceramic having a large number of hollow bubbles as a pigment.
To achieve the effect, it is necessary to increase the coating film thickness,
There are problems such as loss of economy and design. Therefore, it has not been widely adopted for general use.

Japanese Unexamined Patent Publication No. 5-293434 discloses an automobile body or automobile coated with a low-brightness solar-shielding top coat obtained by combining a plurality of pigments having a constant solar heat reflectance and additively mixing colors. Parts are disclosed.
This technology enhances solar heat reflectivity by a top coat having excellent heat reflectivity. However, it is not always possible to sufficiently secure the solar heat shielding property only by the coating film, and the color is also limited to a dark color tone with low brightness.

In the above-mentioned publication, when the solar heat shielding property is insufficient, it is better to use an aluminum base having good heat shielding property. However, aluminum has low strength, it is difficult to weld, and the material cost is very high. Therefore, there is a problem when widely adopted for general use as a roofing material. Furthermore, even if an aluminum base is adopted, the reflectance of the base may be low depending on the type and amount of the added element, the surface roughness and the oxide film thickness, and the solar heat reflectivity may be poor when the above coating is applied. .

[0008]

DISCLOSURE OF THE INVENTION The present invention is suitable for architectural exterior materials such as roofs, has excellent solar heat reflectivity, can suppress a rise in indoor temperature, and can be colored in any color.
An object of the present invention is to provide a coated metal sheet that is excellent in economic efficiency and versatile.

[0009]

Means for Solving the Problems In a building, its landscape and design are evaluated as important factors. For this reason, it is necessary for a painted metal plate used as a building exterior material to be able to be freely colored into any color or pattern.

[0010] Most of the solar heat has a wavelength of 0.3 to 2.1.
Irradiated as visible light or near infrared light of μm. Therefore, it is desirable that the coated metal plate used as the building exterior material has a high solar heat reflectance so as not to absorb solar heat as much as possible.

[0011] From the above viewpoints, the present inventors have examined in detail the influence of a substrate and a coating film on the solar heat reflectivity of a coated metal plate obtained by coating a metal substrate. As a result, the following knowledge was obtained regarding effective prevention of temperature rise due to solar heat.

A. The color, gloss and the like of the object are almost determined by the outer coating film among the coating films. In addition, since color is visually recognized, the wavelength (0.
(38 to 0.78 μm) depending on the reflectance of light from the object surface. In other words, the solar heat reflectance in the visible light region is
It depends on the color. Therefore, unless the color of the outer layer coating is changed, it is difficult to change the solar heat absorption or reflectance in the visible light region of the outer layer coating.

However, by increasing the reflectance in the near-infrared region (0.8 to 2.1 μm) outside the visible light region of the outer layer coating film, the color of the object surface can be colored in a desired color while the solar heat reflectivity can be improved. Can be improved. In order to achieve this, it is effective that the outer layer coating contains a certain amount or more of a pigment having a solar heat reflectance of 10% or more in the near infrared region. Hereinafter, such a pigment having good solar heat reflectivity is also simply referred to as “reflective pigment”, and a coating film containing this reflective pigment and having high solar heat reflectance is also referred to as “reflective coating film”.

In the coating of a metal plate, an undercoating film is provided between the outer layer coating film and the substrate for the purpose of improving the adhesion of the outer layer coating film and improving the rust-prevention property and finish of the coating as a coated metal plate. (Primer) or an intermediate coating film (hereinafter, these are collectively referred to as “inner coating film”) in some cases.

When the metal plate has a plurality of coating films as described above, two or more coating films may be used as reflective coating films.
The most effective way to improve solar heat reflectivity is to include a reflective pigment in the outer layer coating film. However, for example, in the case where the outer layer coating film is thin and the concealing property is not sufficient even if the reflective pigment is contained, in addition to the outer layer coating film, at least one inner layer coating film may have the above-mentioned reflective pigment. In a suitable amount, a coated metal plate having sufficient solar heat reflectivity can be obtained.

The reflective pigment to be contained in the inner layer coating film whose color does not appear outside is in the visible light region (0.38
It is more effective to use a pigment having a solar heat reflectance of 10% or more at a wavelength of about 0.78 μm).

B. Some metal substrates have excellent solar heat reflectivity. When using such a substrate, if the solar heat transmittance in the near infrared region of the coating film is increased, it is possible to obtain a coated metal plate having high solar heat reflection by utilizing the solar heat reflection from the substrate. Becomes

As a coating film having a high solar heat transmittance, there is a clear coating film containing no pigment. However, since the color of the substrate appears outside the coating film, the coating metal plate lacks design and has other properties such as corrosion resistance. Tends to be inadequate. Using a pigment with low absorption in the near infrared region and high transmittance, and adjusting the film thickness and pigment content of the coating film, the pigment-containing coating film has a high solar heat transmittance in the near infrared region. A coating can be formed. By forming the coating film having high solar heat transmittance on the surface of the metal substrate having high solar heat reflectance, a coated metal plate having high solar heat reflectance can be obtained.

Specifically, a substrate having a solar thermal reflectance (R _{E / NIR} ) of 40% or more in the near infrared region is used, and a solar thermal transmittance (T _{E / NIR} ) in the near infrared region of 20% is used. % Or more, and a pigment-containing coating film having a high solar heat transmittance is formed.

A substrate having a high solar heat reflectivity (R _{E / NIR} ) of 40% or more can be easily obtained by plating a material surface with a material having excellent solar heat reflectivity. Above all, a material provided with a plating film containing 50% by mass or more of aluminum is suitable as a building material because it has good solar heat reflectivity and excellent corrosion resistance and economy.

C. When a painted metal plate is used as an exterior material for building, the solar heat absorbed by the metal plate is transferred by the convection of the indoor air and the surface on the side opposite to the solar radiation (hereinafter, the opposite side). Radiation from the surface (also referred to as the “back side”) is transmitted into the room and raises the indoor air temperature. Therefore, if the radiation from the back surface to the room is suppressed, it is possible to further suppress the rise in the indoor air temperature. For that purpose, the emissivity of the back surface may be reduced. d. The undercoat or intermediate coat as the inner coat is usually a coat containing a pigment which easily absorbs solar heat. Therefore, when the inner layer coating film is not a reflective coating film containing a reflective pigment, it is preferable that the inner layer coating film is thinner from the viewpoint of the solar heat reflectivity of the coated metal plate.

When a painted metal plate is applied to a building exterior material, the substrate is often subjected to a pre-coating treatment in order to improve long-term durability such as corrosion resistance and coating film adhesion. As a pre-coating treatment, chromate treatment, phosphate treatment and the like are generally used, but these compounds have absorption in the visible / infrared region. Therefore, it is preferable that the amount of adhesion in the pre-coating treatment is small.

E. If contaminants from the outside adhere to the surface receiving solar radiation, the reflection performance may be reduced. Therefore, it is desirable that the surface that receives solar radiation has a surface with excellent contamination resistance. To keep the surface exposed to sunlight clean, it is necessary to reduce the contact angle of the surface of the surface exposed to water with water, to increase the surface wettability, and to make it easier for contaminants to run down during rainfall. It is effective. Conversely, it is also effective to prevent the contaminants that may be contained in raindrops from adhering to the surface that receives the sunshine by making the surface of the surface receiving sunlight hydrophobic so that raindrops do not adhere during rainfall It is.

The present invention completed based on the above findings,
In the broadest sense, the solar thermal reflectance (R _{E / NIR} ) in the wavelength region of 0.8 to 2.1 μm (that is, in the near-infrared region) of a surface that receives solar radiation is a painted metal plate on a metal substrate.
It is a coated metal plate characterized by being at least 20%, in which the temperature rise of the substrate due to solar radiation is suppressed.

In one embodiment, the coated metal sheet is provided with a pigment having a solar thermal reflectance (R _{E / NIR} ) of 10% or more in a wavelength region of 0.8 to 2.1 μm (ie, a reflective pigment) At least one solar heat reflective coating containing 2-70% by mass.

In another embodiment, the coated metal plate has a solar heat reflectance (R _{E / NIR} ) of at least 40% in a wavelength region of 0.8 to 2.1 μm on a surface of the metal substrate which receives solar radiation, and has a solar heat reflectance of 40% or more. The solar thermal transmittance in the wavelength range of 0.8 to 2.1 μm (T
_{(E / NIR} ) is 20% or more.
A preferred substrate in this case is a plated metal plate provided with a plating film containing 50% by mass or more of aluminum.

The above two aspects can coexist. That is, it is possible to form a reflective coating film containing a reflective pigment in an amount of 2 to 70% by mass and having a solar heat transmittance ( _{TE / NIR} ) of 20% or more. In this case, if a substrate with a high solar thermal reflectance (R _{E / NIR} ) of 40% or more is used, the solar thermal reflectivity of the coating film and the high solar thermal reflectivity of the substrate are combined, and the solar thermal reflectance is extremely high. Thus, a coated metal plate in which heat dissipation to the back side is greatly suppressed can be obtained.

When the coated metal plate has two or more coating films, at least the outer layer is the above-mentioned solar heat reflective coating film,
It is preferable that the thickness of the coating on the inside is 200 μm or less. Preferably, the emissivity of the surface of the painted metal plate opposite to the surface that receives solar radiation is 70% or less. The outer layer coating on the opposite side preferably contains 0.05 to 1.5 g / m ^{2 of the} flaky aluminum pigment.

The surface to be exposed to sunlight has a contact angle with water of 60 ° or less or 90 ° in order to enhance the stain resistance.
It is preferable that it is above. When the surface receiving the solar radiation is a solar heat reflective coating, this coating can be a coating having a contact angle with water of 60 ° or less or 90 ° or more. Alternatively, on this solar reflective coating,
Thickness with contact angle to water less than 60 ° or more than 90 °
A coating of 0.5 to 50 μm can be overcoated to impart stain resistance.

In the present invention, the solar thermal reflectance used for the surface of the coated metal plate which receives the solar radiation, the pigment, and the substrate is determined in consideration of the intensity of the spectrum in the wavelength region calculated from the spectral reflectance (Rλ). The solar thermal reflectance.
Solar thermal reflectance in the wavelength range from 0.8 to 2.1 μm (R _{E / NIR} )
Is calculated by the following equation (1).

[0031]

(Equation 1) RE _{/ NIR} : Solar thermal reflectance in the wavelength range of 0.8 to 2.1 μm
(%), Eλ: spectral intensity of solar heat, Rλ: spectral reflectance (measured with a spectrophotometer).

The solar heat transmittance of a coating film is a solar heat transmittance in consideration of the intensity of the spectrum in the wavelength region calculated from the spectral transmittance (Tλ) of the coating film. 0.8-2.1 μm
The solar thermal transmittance (T _{E / NIR} ) of the coating film in the wavelength range of
It is obtained by equation (2).

[0033]

(Equation 2) TE _{/ NIR} : solar heat transmittance (%) of the coating film in the wavelength region of 0.8 to 2.1 μm, Eλ: spectral intensity of solar heat, Rλ: spectral transmittance (measured by a spectrophotometer).

In the present invention, the emissivity of the back surface is 4.5 to
This emissivity is calculated from the spectral reflectance (Rλ) of the back surface in the wavelength region of 25 μm and taking into account the relative value when the absolute temperature is 293 K in Planck's thermal emission spectrum distribution. The emissivity α is obtained by the following equation (3).

[0035]

(Equation 3) α: emissivity (%), Gλ: relative value when the absolute temperature is 293 K in the plank thermal radiation spectrum distribution, Rλ: spectral reflectance (measured by a spectrophotometer).

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION The coated metal plate of the present invention is obtained by coating at least one surface of a metal substrate which receives solar radiation, and has a surface having a solar radiation (hereinafter also referred to as a solar radiation surface) of 0.8 to 0.8.
The solar thermal reflectance (R _{E / NIR} ) in the wavelength region of 2.1 μm (= near infrared region) is 20% or more. R _{/ NIR on the} solar surface
If it is less than 20%, the effect of suppressing the temperature rise of the substrate as a solar heat reflective coated metal plate is reduced. RE _{/ NIR} of the solar radiation surface is preferably 30% or more.

In one embodiment, the coated metal sheet contains at least 2 to 70% by mass of a pigment (ie, a reflective pigment) having a solar heat reflectance (R _{E / NIR} ) of 10% or more in the near infrared region. It may be one provided with one reflective coating film on the solar radiation surface. When the painted metal plate has a plurality of coating films on the solar radiation surface, it is preferable that at least the outer layer coating film is a reflective coating film. That is, only the outer coating film may be a reflective coating film, or a part or all of the inner coating film may be a reflective coating film. In the case where the outer layer coating film is thin and the concealing property is not sufficient even if the reflective pigment is contained, the inner layer coating film may also contain the reflective pigment.

The outer layer coating film in the present invention means a coating film applied in a coating step for determining the color of a coated metal plate.
For the purpose of improving performance such as stain resistance, a clear film may be further provided on the outer layer coating film, but the clear film is not considered to be the outer layer coating film in the present invention.

In another embodiment, the coating film on the solar radiation surface is 0.8 to 2.
20% solar heat transmittance (T _{E / NIR} ) in the 1 μm wavelength region
Above, is a pigment-containing coating film having a high solar heat transmittance,
0.8 to 2.1 μm of at least the surface of the metal substrate that receives solar radiation
The solar thermal reflectance (R _{E / NIR} ) in the wavelength region of is as high as 40% or more. In this case, since the solar heat reflected from the substrate is reflected to the outside through the coating film, the coated metal plate can exhibit high solar heat reflectivity.

In the present invention, the reflectance of the solar radiation surface of the coated metal plate, the reflectance of the reflective pigment used in the coating film, and the solar heat transmittance of the coating film are all in the near infrared region.
Solar thermal reflectance for wavelengths in the 0.8-2.1 μm wavelength range
(R _{E / NIR} ) or solar heat transmittance (T _{E / NIR} ) is because the solar heat reflectance and the solar heat transmittance with respect to the wavelength in the visible light region are determined depending on colors. If the solar heat reflectance and the solar heat transmittance are specified for the wavelength in the visible light region, the degree of freedom of the color of the coated metal plate is lost, and the metal plate is not suitable as a building exterior material. According to the present invention, it is possible to remarkably suppress the rise in the substrate temperature when receiving solar radiation simply by defining the solar heat reflectance and the solar heat transmittance with respect to the wavelength in the near infrared region. Coating : (1) Reflective coating The reflective coating provided on the solar radiation surface of the coated metal plate is a reflective pigment having a solar heat reflectance of 10% or more in the near infrared region as described above in a mass of 2 to 70 mass. % (The same applies hereinafter based on the dry weight of the coating film). If the content of the reflective pigment (when two or more reflective pigments are used in combination) is less than 2% by mass in the coating film, the metal plate should have sufficient solar thermal reflectivity. In addition, a thick film coating is required to obtain a desired color due to insufficient coloring power. This content is preferably at least 5% by mass. When the content of the reflective pigment exceeds 70% by mass in the coating film, the processability of the coating film is impaired. The upper limit of the content is preferably 60% by mass.

The reflective pigment contained in the reflective coating film need not be limited to one kind, and one or more kinds of pigments satisfying the above conditions are optionally selected in consideration of hue, weather resistance and color stability. Can be selected. When two or more reflective pigments are used, their total content may be within the above range.

The reflective pigment used in the coated metal sheet of the present invention is preferably one that is safe, has excellent water resistance and weather resistance, and maintains the heat shielding effect for a long time. Above all, it is preferable to use pigments selected from metal compounds such as metal oxides, sulfides and chromates, insoluble dyes (dye pigments), lake pigments and the like.

If the average particle size of the pigment exceeds 50 μm, the solar heat reflectivity is poor, so that the average particle size of the reflective pigment is preferably 50 μm or less. From the viewpoint of stain resistance, weather resistance, and color stability, the average particle size of the reflective pigment is more preferably 20 μm.
m, more preferably 10 μm or less.

In addition to the above-mentioned reflective pigments, the reflective coating film may further include a coloring pigment, a rust-preventive pigment, and a binder necessary for obtaining a desired color, concealing property, corrosion resistance and other coating properties. Organic resin (for example, polyester resin, fluorine-based resin, etc.), to increase the cohesive strength of the coating film itself, or to improve the concealment and brightness of the base, for example, silica, alumina, calcium carbonate, Barium sulfate,
Kaolin, clay, talc, nepheline, sinite,
An extender pigment such as mica or a bubble-containing pigment may be contained.

As a binder for retaining a pigment, yellowing, discoloration, reduction in gloss, and chalking are unlikely to occur even when exposed to sunlight. It is preferable to use an organic resin that can be maintained for a long time.

As such a resin, an acrylic resin,
Various organic resins such as a polyester resin, a polyolefin resin, and a fluorine-based resin may be used. Any one of them may be used, but a mixture of two or more may be used. The content of these organic resins is preferably in the range of 10 to 90% by mass of the coating film as a solid content.

In the resin, synthetic powder silica, organic bentonite, carboxymethylcellulose, a thickener such as polyvinyl alcohol, melamine, benzoguanamine,
A crosslinking agent such as an isocyanate type, a dispersant such as polyacrylic acid and polyacrylate, and a photocatalyst for antifouling may be contained.

The thickness of the reflective coating is preferably in the range of 3 to 200 μm. A coating film thinner than 3 μm may not have stable hue. The thickness of this coating film is more preferably 7 μm or more. If the thickness of the coating film exceeds 200 μm, peeling or cracking of the coating film may occur at the time of processing, and a plurality of coating operations are required, resulting in poor economy. More preferably, it is 50 μm or less.

The undercoat or intermediate coat as the inner coat usually contains a pigment which easily absorbs solar heat. Therefore, when the content of the reflective pigment in the inner layer coating film is less than 2%, the thickness is preferably thinner and not more than 200 μm so as not to hinder solar heat reflectivity. More preferably, it is 50 μm or less.

The outer coating film of the coated metal plate of the present invention may be formed into a metallic coating film by mixing aluminum flakes (flaky aluminum pigment) with the coating material to be used, or may be formed into a matte coating film by mixing a matting agent. , Any design can be imparted. Also, the reflective coating is preferably provided as the outer layer coating of the coated metal plate of the present invention, that is, as the uppermost layer. For example, in the case of a metallic coating containing aluminum flakes, the reflective coating is optionally provided. A clear layer containing no pigment or a translucent layer containing a small amount of pigment may be provided on the film. (2) Coating film with solar heat transmittance (T _{E / NIR} ) of 20% or more In order to secure T _{E / NIR} of 20% or more, the coating film in this case has a solar heat in the near infrared region of 0.8 to 2.1 μm. It is basically the same as the above-mentioned solar heat reflective coating film, except that the coating film is constituted so that the absorptance does not increase.

As the pigment, there are pigments of the kind listed for the reflective pigment. Among them, pigments having a low light absorption in the near infrared region and a high transmittance may be used. If the average particle size of the pigment or the coating thickness is too large, the solar heat transmittance of the coating decreases, so the average particle size of the pigment is 20 μm.
The following range is preferable, and the thickness of the coating film is preferably in the range of 1 to 100 μm. It is preferable that the organic resin used as the binder and the additive to be present in the coating film are selected so as not to hinder the solar heat transmittance of the coating film in the near infrared region.

As described above, even with a reflective coating film containing 2 to 70% by mass of a reflective pigment, the type and particle size of the pigment,
If the thickness of the coating film and other conditions are appropriately selected, _{TE / NIR}
A coating film having a solar heat permeability of 20% or more can be obtained. (3) Stain-Resistant Coating As described above, if a contaminant adheres to the insolated surface of the coated metal plate of the present invention and becomes contaminated, the solar heat reflectivity decreases and the intended heat shielding performance also decreases. Therefore, it is advantageous to impart stain resistance to the surface of the solar radiation surface for long-term performance retention.

Most of the contaminants adhering to painted metal plates used outdoors are hydrophobic substances. Therefore, in order to suppress contamination of the solar radiation surface, it is preferable to improve the water wettability of the surface of the solar radiation surface so that hydrophobic contaminants are hardly attached. If the surface has good water wettability, hydrophobic contaminants cannot strongly adhere to the surface and are easily washed away during rainfall, so that no contaminants accumulate. In order to ensure such wettability, the contact angle of the surface of the solar radiation surface with water must be adjusted.
What is necessary is just to make it 60 degrees or less. Contact angle with water
A hydrophilic coating film of 60 ° or less can be obtained by using a hydrophilic organic resin having a polar group such as a hydroxyl group or a carbonyl group as a part or all of a binder. In order to adjust the contact angle, the type and amount of the polar group of the resin may be changed, or two or more resins may be used in combination.

Conversely, in order to prevent contaminants which may be contained in raindrops during rainfall from adhering to the insolation surface, the surface of the insolation surface is made hydrophobic so that it is difficult for the raindrops to adhere to the insolation surface. This is also an effective method for preventing contamination of the solar radiation surface. For this purpose, it is preferable that the contact angle of the surface of the solar radiation surface with water is 90 ° or more. A hydrophobic coating film having a water contact angle of 90 ° or more can be obtained by using a non-polar organic resin such as a polyolefin resin or a fluororesin as a binder.

When the stain resistance is imparted to the coated metal sheet of the present invention by the above-mentioned means, the binder resin of the outer layer of the solar reflective coating which appears on the surface is made hydrophilic or hydrophobic resin,
The water may have a contact angle of 60 ° or less or 90 ° or more with respect to water. That is, stain resistance is imparted to the outer solar reflective coating film itself. However, in this method, the kind of the binder resin used for the solar heat reflective coating film is limited, so that the cost may be increased and other performances such as workability and corrosion resistance may not reach desired levels.

In another embodiment, a stain-resistant coating having a surface having a contact angle with water of 60 ° or less or 90 ° C. or more can be separately formed on the solar heat reflective coating. This stain-resistant coating film can be formed using a hydrophilic or hydrophobic binder resin as described above. In this case, the thickness of the stain-resistant coating film is preferably 0.5 to 50 μm. If the thickness is less than 0.5 μm, the effect of improving contamination resistance is small, and if it exceeds 50 μm, solar heat reflectivity may be impaired. The stain-resistant coating film may be a clear coating film containing no pigment, but may contain a pigment as long as the solar heat reflection property or the solar heat permeability is not impaired. (4) Coating Film on Back Side The coated metal plate of the present invention only needs to have the above-mentioned reflective coating film or solar heat permeable coating film on only one side of the substrate that is to be the solar radiation surface. There is no particular limitation on the surface (rear surface) of the substrate that faces the room and is opposite to the solar radiation surface. This back surface does not necessarily need to be a painted surface, but is preferably a surface having an emissivity of 70% or less.

When a painted metal plate is used as a building exterior material, the absorbed solar heat is transmitted into the room by conduction due to convection of room air and radiation from the back surface, thereby increasing the room air temperature. Therefore, if the radiation from the back surface to the room is suppressed, it is possible to suppress an increase in the indoor air temperature. That is, the emissivity of the back surface may be reduced.

The emissivity is obtained by measuring the spectral reflectance and the above equation.
(3). If the emissivity of the back side exceeds 70%, the temperature rise will be remarkable.
It is advantageous to make it 70% or less, especially 50% or less.

In order to reduce the emissivity of the back surface, a clear coating is applied to the metal surface of the back surface, or
2 to 70% by mass in total of one or more of the above-mentioned reflective pigments
It is effective to apply a contained coating (that is, the same coating as the solar radiation side) or an aluminum paint.

The aluminum paint is a paint containing a flaky aluminum pigment, and a coating containing 2 to 30% by mass of the flaky aluminum pigment is suitable. Scaly aluminum pigments can be less radioactive than other pigments when compared at the same content.
The thickness of the coating film having a small emissivity is preferably in the range of 1 to 20 μm. In that case, the content of the flaky aluminum pigment in the coating film is preferably in the range of 0.05 to 1.5 g / m ² . If the content is less than 0.05 g / m ² , a sufficiently low emissivity cannot be obtained, and if it exceeds 1.5 g / m ² , peeling or cracking of the coating film may occur during processing.

The coating film on the back side having a low emissivity may contain a coloring pigment, a rust-preventive pigment, or an extender pigment in addition to the above-mentioned pigments as described for the reflective coating film. . Further, as the binder for holding the pigment, it is preferable to use the same organic resin as the reflective coating film. Further, an additive such as a dispersant may be contained similarly to the reflective coating film. Substrate : As the metal substrate, any metal plate having characteristics required for the intended use can be used, and its type and chemical composition are not particularly limited. For example, a steel plate made of a low alloy steel used for a low carbon steel, a high carbon steel, a high tensile steel plate, or the like, a plated steel plate using these steel plates as a base material, a stainless steel plate, an aluminum plate, and the like are exemplified.

When the coating film formed on the solar radiation surface of the substrate is a reflective coating film, it is possible to obtain a coated metal plate having high solar heat reflection regardless of the type of the substrate. Therefore, corrosion resistance,
The substrate may be selected in consideration of characteristics required for the coated metal plate such as strength. In this case, preferred substrates are plated steel sheets, particularly Zn-based plated steel sheets (pure Zn-plated or Zn-based alloy plated steel sheets) and Al-based plated steel sheets having excellent corrosion resistance. However, as described later, the _{TE / NIR} of the reflective coating is 20%.
In the case of the above, if a substrate having a high solar heat reflectance is selected as a substrate, a coated metal plate having a higher solar heat reflectivity can be obtained.

Even when a coating film containing a reflective pigment is formed on the solar radiation surface of the substrate, the hiding power of the coating film in the near infrared region is insufficient depending on the thickness of the coating film and the content of the pigment. In some cases, the solar heat reflective coated metal plate has insufficient solar heat reflectivity. This is because near infrared rays have higher transmittance of the coating film than visible light rays. In such a case, use a substrate with good near-infrared solar heat reflectivity,
It is effective to increase the reflectivity of the painted metal plate by utilizing the solar heat reflectivity from the substrate. As described above, when a metal plate with high solar heat reflection is used to obtain a coated metal plate with high solar heat reflection using reflection from the substrate, the coating film has a solar heat transmittance _{TE / NIR} of 20%. The above coating film is used. When this coating is solar heat reflective, the solar heat reflectivity of the coated metal plate is further enhanced.

Specifically, 0.8% of the coating film formed on the solar radiation surface was used.
Solar heat transmittance (T _{E / NIR} ) in the wavelength range of ~ 2.1 μm
If it is more than 20%, the solar heat reflectivity is greatly influenced by the reflectivity of the substrate. In that case, 0.8-2.
40% solar thermal reflectance (R _{E / NIR} ) in the 1 μm wavelength region
When the above substrate is used, a coated metal plate having high solar heat reflection on the solar radiation surface is obtained. When _{RE / NIR} is less than 40%, the reflectivity of the painted surface on the solar radiation side decreases. Preferably, the _{RE / NIR} of the substrate is at least 50%, more preferably 60%
That is all.

When the substrate is a plated steel plate, the type of plating is not particularly limited. However, the substrate has good reflectivity to sunlight, the _{RE / NIR of the} substrate is 40% or more, and the plating is economical. Thus, Al-Zn-based, Al-Mn-based, and Al-Si-based are preferred. Among them, those provided with a plating film containing 50% by mass or more of aluminum are preferable, and pure aluminum plating may be used. In addition to the plating film,
Alloy elements such as Ni, Cr, Fe, and Co may be contained.
Such plating films have high solar heat reflectivity,
It has the feature that the substrate is also excellent in corrosion protection and economic efficiency.
In addition, even in the case of a Zn-based plated steel sheet, _{RE / NIR} may be 40% or more.

The adhesion amount of the plating film is optional,
A plating film having a thickness of not less than μm is preferable because the solar heat reflectivity is improved. The plating method is arbitrary, and any known plating method such as an electroplating method, a hot-dip plating method, a molten salt electrolytic plating method, and a vapor deposition plating method can be adopted.

In order to improve the long-term durability of the coated metal plate, such as the corrosion resistance and the adhesion of the coating film, the substrate is not limited to an inner coating film (eg, an undercoat, an intermediate coating), and may be a coating type, a reaction type or the like. A known coating pretreatment film such as a treatment film or a phosphate treatment film may be formed. However, these pretreatment films tend to impair the solar heat reflectivity and increase the emissivity. Therefore, the adhesion amount of the coating pretreatment film is preferably as small as possible within a range where the effect of improving adhesion and the like can be obtained.

The amount of the pretreatment film to be applied is preferably 200 mg / m ² or less, more preferably 100 mg / m ² or less in terms of chromium metal, if it is a chromate treatment film. Deposition amount in the case of phosphating coating, 5.0 g / m ² or less, more preferably 3.
It is good to be 0 g / m ² or less. Exceeding this is not preferred because the solar heat reflectivity is impaired and the coating film may be cracked or peeled off when processing the metal plate.

In order to obtain an effect such as improvement in adhesion, the amount of the pretreatment film to be applied is preferably 5 mg / m ² or more in the case of chromate treatment, more preferably 20 mg / m ² or more. In the case of phosphate treatment, 0.2 g / m ² or more, more preferably 0.5 g / m ²
m ² or more is preferable.

When the substrate is a stainless steel plate or an aluminum plate, a known chromate treatment may be applied in order to enhance the adhesion to the coating film. In this case, the amount of adhesion may be within the above range. Production method : The method for producing the solar heat-reflective coated metal plate of the present invention is not particularly limited, but a paint containing the above-described reflective pigment and an organic resin as a binder in a solvent is applied to one or both surfaces of a substrate. It is preferable to manufacture it by drying and, if necessary, heat-curing to form a reflective coating film.

The solvent used for the paint is not particularly limited, and may be appropriately selected from conventional solvents according to the organic resin. Examples of the solvent include, but are not limited to, water, toluene, xylene, cyclohexanone, and methyl ethyl ketone. The resin may be dissolved in a solvent or may be dispersed or suspended in a solvent such as an emulsion resin. In the paint,
The above-mentioned extender, cross-linking agent, dispersant and the like can be blended.

The method of applying the paint may be a known method, for example, a method such as spray coating, roll coating, curtain flow coating, bar coating and the like can be applied. After coating, drying and cooling may be performed by a known method such as a hot air oven or an induction heating oven. These treatments can be performed using known coating equipment.

Before applying the coating material to the substrate, as described above, the substrate may be appropriately subjected to a pre-coating treatment, an undercoat, an intermediate coating, or a part or all thereof may be omitted.
Furthermore, it is also possible to include a reflective pigment in the intermediate coating.

The back side may be coated with the same paint as that of the solar radiation side, or may be coated with another paint. It is preferable to select a pigment used for another coating that lowers the emissivity on the back side as described above. The back side can be coated in the same manner as described above.

As described above, the coated metal sheet of the present invention is most suitable as a building exterior material such as a roof material and an outer wall material, and is excellent in workability. To make a product.

[0076]

(Example 1) As a substrate, a base material of a cold-rolled steel sheet having a thickness of 0.80 mm was electroplated with 12% Ni-88% Zn alloy (adhesion amount: 30 g / m ² ), 10% Fe- 90% Zn alloy electroplating (Coating weight
Three types of double-sided plated steel sheets (adhesion amount per one side) coated with 30 g / m ² ) or 55% Al-45% Zn alloy hot-dip (adhesion amount 60 g / m ² ) were used. 0.8-2.1 of these substrates
Table 1 shows the results of measuring the spectral reflectance in the wavelength region of μm with a spectrophotometer and determining the solar thermal reflectance _{RE / NIR} .

As pigments to be contained in the coating film on the solar radiation side of the substrate, (1) Carbon black MA-100 having a RE _{/ NIR} of 2% and an average particle diameter of 0.02 μm [manufactured by Mitsubishi Chemical] (symbol “CB”) ),
(2) Iron black BL-100 having a RE _{/ NIR} of 5% and an average particle size of 3 μm
[Manufactured by Titanium Industry] (symbol “FB”), (3) _{RE / NIR} 15%,
Composite oxide pigment with an average particle diameter of 0.5 μm, Tyroxide Side Brown # 9290 (manufactured by Dainichi Seika Kogyo Co., Ltd.) (symbol “TB”), and (4) 15% of _{RE / NIR} and an average particle diameter of 0.3 μm Four kinds of black pigments of organic pigment Chromo Fine Black A1103 (manufactured by Dainichi Seika Kogyo Co., Ltd.) (symbol “AB”) were prepared. Of these, (3) and (4) are reflective pigments, and (1) and (2) are pigments for comparison.

40 parts by weight of any of the above pigments, 60 parts by weight of a polyester resin as a binder, and 10 parts by weight of a melamine-based cross-linking agent are mixed and dispersed and mixed together with an appropriate amount of a solvent, cyclohexanone, using a ball mill. A paint was prepared.

These paints were applied to the above-mentioned various substrates by a roll coating method so as to have a dry film thickness shown in Table 1, and were baked at 240 ° C. for 60 seconds to form a coating film on the solar radiation side. . No undercoat or intermediate coat was performed. Each of the coating films on the solar radiation side had a black appearance with the Munsell symbol N-1.5.

0.8 to 2.1 μm of each coating film applied to the solar radiation surface
Solar heat transmittance T in the wavelength region of m_{E / NIR}The isolated coating
Determined from the spectral transmittance measured with a spectrophotometer using the film
Was. To isolate the coating, immerse the painted metal plate in acid and
Performed by dissolution. In addition, each coating on the plated steel sheet
Solar thermal reflectance R in the wavelength range of 0.8 to 2.1 μm on the surface of the film
_{E / NIR}Is determined from the spectral reflectance measured with a spectrophotometer.
Was. Table 1 also shows the measurement results.

On the other hand, as a pigment to be contained in the coating film on the back side of the coated metal plate, (5) a white titanium oxide pigment
-90 (Ishihara Sangyo, average particle diameter 0.4 μm) (symbol “TI”),
And (6) Scale-like aluminum powder 0700M [made by Toyo Aluminum] (symbol “AL”) was used.

In the case of the white pigment (5), 40 parts by weight of this pigment, 60 parts by weight of a polyester resin as a binder, and 10 parts by weight of a melamine crosslinking agent are blended, and a ball mill is used together with an appropriate amount of a solvent of cyclohexanone. The mixture was dispersed and mixed to prepare a paint. This paint was applied to various substrates by a roll coating method so as to have a dry film thickness of 5 μm, and was baked at 240 ° C. for 60 seconds to form a white paint film on the back side.

About 5 parts by weight of the flaky aluminum powder (6), polyester resin 100 was used as a binder.
Parts by weight and 10 parts by weight of a melamine-based crosslinking agent were mixed and dispersed and mixed together with an appropriate amount of a solvent, cyclohexanone, using a ball mill to prepare a coating material. This paint is applied to various substrates by a roll coating method so that the content of aluminum powder (aluminum pigment) becomes the amount shown in Table 1.
After baking for 2 seconds, a metallic color coating film on the back side was formed.

Table 1 shows the composition of the coating film on the substrate, the solar radiation surface and the back surface of the obtained coated metal plate. For the back side of this coated metal plate, measure the spectral reflectance in the wavelength range of 4.5 to 25 μm, and use the relative value when the absolute temperature is 293 K in Planck's thermal radiation spectrum distribution specified in JIS R3106. The emissivity of the back surface was determined. This value is also shown in Table 1.

From the above coated metal plate, length: 150 mm, width:
A 200 mm sample was cut out and, as shown in FIG. 1, the solar radiation surface was attached to the opening of the thermal insulation container having an opening, and the effect of the sample on the temperature rise inside the thermal insulation container by exposing the sample to solar radiation was shown. investigated.

The heat retaining container 6 shown in FIG. 1 is configured so that the side walls other than the opening have good heat insulating properties. The sample is attached to the opening, and the sunlight is irradiated on the sample surface at the same angle outdoors. It is arranged on a device (not shown) that follows the solar radiation so that it is irradiated with the light. A thermocouple 4 is installed inside the heat retaining container 6, and the thermocouple 4 is connected to a recorder 5 provided outside so that a temperature change inside the heat retaining container 6 can be measured. Table 1 shows the measured maximum temperatures.

[0087]

[Table 1] As can be seen from Table 1, in the coated metal plate of the present invention in which the reflective pigment was contained in the outer layer of the coating film on the solar radiation side, the inside of the heat insulating container 6 was higher than in the comparative example in which the pigment was not solar heat reflective. The temperature reached a maximum of about 10 ° C or lower, indicating good solar heat reflectivity. Among them, the solar heat transmittance _{TE / NIR of} the coating film
Is as high as 25% and the solar thermal reflectance R _{E / NIR of the} substrate is 73%
And Sample 7, which was very high, showed the best performance.

The amount of the pigment added to the coating film on the back side was such that titanium oxide (TI) was 40 parts by weight, flaky aluminum pigment (AL)
5 parts by weight, the latter being much less. Therefore, AL
The emissivity of the back surface of Samples 8 and 9 with a very small amount of adhesion is smaller than that of Samples 1 to 7, but the emissivity of 70% or less is obtained when the amount of adhesion of the AL pigment is 0.05 g / m ² or more. Was. AL
If the amount of pigment attached was sufficient at 1.2 g / m ² , the emissivity was extremely low at 10%, even though the amount of pigment attached was smaller than that of TI.

(Example 2) In this example, based on the coated metal plate shown in Table 1 as Test No. 7 (Example of the present invention) or Test No. 2 (Comparative Example) in Example 1, a solar reflective coating was prepared. The stain resistance was investigated by changing the binder resin of the membrane and / or forming a stain resistant coating thereon. The test materials manufactured in this example are as follows.

(1) Test No. 7 except that the amount of the polar group in the polyester resin of the binder was adjusted to form a solar heat reflective coating film having a contact angle to water of 55 °, 65 ° or 85 °. A coated metal plate comprising the same coating film and substrate was produced. These are designated as Test Nos. 11 to 13 (contact angles are 55, 65 and 85 ° in order).

(2) A coated metal plate comprising a coating film and a substrate was prepared in the same manner as in Test No. 7 except that a fluororesin was used instead of the polyester resin as the organic resin for the binder.
(Test number 14). The contact angle of this coating surface to water is 95
°.

(3) A polyester resin paint capable of forming a film having a contact angle to water of 55 ° was applied on the solar heat reflective coating film obtained in Test No. 7 so that the dry film thickness became 3 μm, and dried. To form a clear coating film (Test No. 15)
.

(4) A fluororesin paint was applied on the solar heat reflective coating film obtained in Test No. 7 so as to have a dry film thickness of 3 μm, dried, and cleared to a water contact angle of 95 °. A coating was formed (Test No. 16).

(5) By adjusting the amount of the polar group of the polyester resin as the binder, the contact angle with water is 55 ° or 65 °.
Test No. 2 except that a solar heat reflective coating was
A coated metal plate comprising the same coating film and substrate was prepared. These are designated as Test Nos. 17 and 18.

The test materials of the coated metal plates of Test Nos. 11 to 18 were exposed at an angle of 45 ° from the horizontal surface to the outside for 3 months, and then exposed without any surface dirt. As shown in FIG. 1, the heat-insulating container 6 was attached to the upper surface of the heat-insulating container 6, and exposed to sunlight outdoors to measure the temperature rise in the container as described in Example 1. Table 2 shows the maximum temperature together with the reflectance of the coated metal plate.

[0096]

[Table 2] As can be seen from Table 2, the coated metal plates of Test Nos. 11 to 16 based on Test No. 7 of the present invention were the same as those of Test No. 7 irrespective of the contact angle of the surface with water. In addition, the solar heat reflection was high, the temperature rise in the thermal insulation container was low, and the heat insulation was excellent. On the other hand, the coated metal plate based on Test No. 2 which is a comparative example had low solar heat reflectivity and was inferior in heat shield similarly to Test No. 2. That is,
Changing the binder resin to impart stain resistance or overcoating the clear coating does not significantly affect the solar heat reflectivity.

Regarding the stain resistance, Test Nos. 11, 14 and 14 in which the contact angle of water on the surface was 60 ° or less or 90 ° or more.
In comparison with the basic test number 7 in Table 1 (for test numbers 11 to 16 in Table 2) or test number 2 (for test numbers 17 to 18 in Table 2), It can be seen that the decrease in heat insulation after outdoor exposure was small and the contamination resistance was good, so that there was little adhesion of contaminants, and the solar heat reflection, and hence the heat insulation, was small. On the other hand, in Test Nos. 12, 13, and 18 in which the contact angle was 65 ° or 85 °, it was found that the heat-shielding property after outdoor exposure was significantly reduced, and the stain resistance was inferior to that described above.

[0098]

EFFECT OF THE INVENTION The coated metal sheet having high solar heat reflectivity of the present invention is most suitable as an exterior material for building materials such as roofs, and is excellent in lightness and heat shielding properties required for roofs, and can be colored in any color. It can be manufactured with good productivity and at low cost.
In addition, by imparting contamination resistance to the solar radiation surface, a decrease in solar heat reflectivity due to contamination can be suppressed, and heat insulation is maintained for a long time.

[Brief description of the drawings]

FIG. 1 is a sectional view of an apparatus for measuring the reflectivity of a surface-treated metal plate.

[Explanation of symbols]

1: sunlight, 2: reflective layer, 3: substrate, 4: thermocouple, 5:
Recorder, 6: Insulated container

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[Procedure amendment]

[Submission date] November 21, 2000 (200.11.
21)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0055

[Correction method] Change

[Correction contents]

When the stain resistance is imparted to the coated metal sheet of the present invention by the above-mentioned means, the binder resin of the outer layer of the solar reflective coating which appears on the surface is made hydrophilic or hydrophobic resin,
The water may have a contact angle of 60 ° or less or 90 ° or more with respect to water. That is, stain resistance is imparted to the outer solar reflective coating film itself. However, in this method, the kind of the binder resin used for the solar heat reflective coating film is limited, so that the cost may be increased and other performances such as workability and corrosion resistance may not reach desired levels.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0056

[Correction method] Change

[Correction contents]

In another embodiment, a stain-resistant coating having a surface having a contact angle with water of 60 ° or less or 90 ° or more can be separately formed on the solar heat reflective coating. This stain-resistant coating film can be formed using a hydrophilic or hydrophobic binder resin as described above. In this case, the thickness of the stain-resistant coating film is preferably 0.5 to 50 μm. If the thickness is less than 0.5 μm, the effect of improving contamination resistance is small, and if it exceeds 50 μm, solar heat reflectivity may be impaired. The stain-resistant coating film may be a clear coating film containing no pigment, but may contain a pigment as long as the solar heat reflection property or the solar heat permeability is not impaired. (4) Coating Film on Back Side The coated metal plate of the present invention only needs to have the above-mentioned reflective coating film or solar heat permeable coating film on only one side of the substrate that is to be the solar radiation surface. There is no particular limitation on the surface (rear surface) of the substrate that faces the room and is opposite to the solar radiation surface. This back surface does not necessarily need to be a painted surface, but is preferably a surface having an emissivity of 70% or less.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) B32B 15/08 B32B 15/08 G C23C 28/00 C23C 28/00 A E04D 3/35 E04D 3/35 B (72) Inventor Kenji Ikishima 4-5-33 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture Within Sumitomo Metal Industries, Ltd. (72) Inventor Sayo Matsuo 1-21, Fuso-cho, Amagasaki-shi, Hyogo (72) Inventor Minoru Tomohiro 1-21 Fuso-cho, Amagasaki City, Hyogo Prefecture Sumitomo Metal Construction Materials Co., Ltd.

Claims (10)

[Claims] 1. A coated metal plate obtained by applying a coating to a metal substrate and having a solar heat reflectance (R _{E / NIR} ) of 20% or more in a wavelength region of 0.8 to 2.1 μm on a surface to receive solar radiation. Characterized by painted metal sheet with solar heat reflection. 2. A solar radiation-reflecting surface comprising at least one layer containing at least 2 to 70% by mass of a pigment having a solar thermal reflectance (R _{E / NIR} ) of 10% or more in a wavelength region of 0.8 to 2.1 μm on a surface receiving solar radiation. The coated metal sheet according to claim 1, further comprising a coating film. 3. The surface of the metal substrate, which receives the solar radiation, has a thickness of 0.8 to 2.1.
The solar thermal reflectance (R _{E / NIR} ) in the wavelength region of μm is 40% or more, and the solar thermal transmittance (TE _{/ NIR} ) in the wavelength region of 0.8 to 2.1 μm is 20% or more on the surface. 3. The coated metal sheet according to claim 1, which has a pigment-containing coating film. 4. The coated metal plate according to claim 3, wherein the metal substrate is a plated metal plate having a plating film containing 50% by mass or more of aluminum. 5. The coated metal plate comprises two or more coating films, at least the outer coating film is the solar heat reflective coating film, and the thickness of the inner coating film is 200 μm or less. A coated metal plate according to any one of the above. 6. The emissivity of the surface opposite to the surface receiving solar radiation is
The coated metal sheet according to any one of claims 1 to 5, which is 70% or less. 7. The coated metal sheet according to claim 6, wherein the outer layer coating film on the opposite side contains 0.05 to 1.5 g / m ^{2 of} flaky aluminum pigment. 8. The coated metal sheet according to claim 1, wherein a contact angle of the surface receiving the solar radiation with water is 60 ° or less or 90 ° or more. 9. The method according to claim 2, wherein the surface of the surface receiving the solar radiation comprises a solar heat reflective coating, and the coating has a contact angle with water of 60 ° or less or 90 ° or more. Painted metal plate. 10. The method according to claim 1, wherein the contact angle with water is 60 ° or less or 90 ° or more, and the thickness is 0.5 to 50 μm.
The coated metal sheet according to any one of claims 2 to 7, which has a coating of (1).