JP3376949B2 - Solar heat reflective surface treated metal plate - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated metal plate having excellent solar heat reflectivity, which is suitable mainly as a building exterior material such as a roof material.

[0002]

2. Description of the Related Art Reinforcement of the structure of houses has been promoted from the viewpoint of improving disaster prevention, and as a part of this, reduction in the weight of roofing materials is desired. As roofing materials, in addition to Japanese roof tiles, there are new ceramic systems, metal roofs, etc., but the weight of metal roofs is about 1/10 that of Japanese roof tiles, and about 1/3 of that of new ceramic systems. Since it is lightweight, 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, the problem with metal roofing materials is that solar heat is easily conducted to the attic and the indoor temperature tends to rise.

As a method of suppressing the influence of solar heat, there is a method of attaching a heat insulating material to the back of a metal roof material. However, since a method of bonding a heat insulating material after forming a metal plate is usually adopted, the manufacturing process of the bonding material is complicated, and the initial cost required for dedicated equipment is high, which is economical. There is a problem of chipping.

There is also a method of applying a heat-shielding heat-insulating paint to a metal roofing material, but the heat-shielding heat-insulating paint is a special paint that uses a ceramic having a large number of hollow bubbles as a pigment.
It is necessary to increase the coating thickness in order to bring out the effect.
There are problems such as impairing economy and design. Therefore, it has not been widely adopted for general use.

Japanese Unexamined Patent Publication (Kokai) No. 5-293434 discloses an automobile body or an automobile part coated with a low-brightness solar heat-shielding topcoat paint obtained by additively mixing a plurality of pigments having a constant solar heat reflectance. Is disclosed. This technique enhances the solar heat reflectivity by a top coat coating having excellent heat reflectivity. However, the coating film alone may not have sufficient solar heat shielding properties.

In the above publication, it is advisable to use an aluminum underlayer in such a case, but aluminum has problems that it has low strength and is difficult to weld, and that the material cost becomes very high. There is a problem in widespread adoption. Further, even with an aluminum base, the reflectance may be low depending on the type and amount of the additive element, the surface roughness and the oxide film thickness, and the solar heat reflectivity may be poor when used as a coating material.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides a surface-treated metal plate suitable for exterior materials for building materials such as roofs, which is excellent in economic efficiency, versatile, and excellent in solar heat reflectivity. It is in.

[0009]

[Means for solving the problem] In a building, its landscape and design are evaluated as important factors. Therefore, it is necessary that the exterior material for construction can be easily painted in any color or pattern. Most of the solar heat has a wavelength of 0.3-
It is irradiated as visible light or near infrared rays of 2.5 μm. Therefore, a material having a high solar heat reflectance is desirable as the building exterior material. As a result of detailed research on the influence of the metal plate and the coating film on the solar heat reflectivity of the metal roofing material, the present inventors have obtained the following findings regarding a method for effectively preventing a temperature rise due to solar heat.

A. The color, gloss, etc. of an object are almost determined by the outer layer coating of the coating. In addition, since the color is visually recognized, the wavelength in the visible light region (38
0 to 780 nm) depending on the reflectance of light from the object surface. That is, the reflectance of solar heat in the visible light region is determined according to the type of color. Therefore, unless the color of the outer coating film is changed, it is difficult to change the solar heat absorption amount or reflectance in the visible light region of the outer coating film.

However, by increasing the reflectance in the near-infrared region (800 to 2100 nm), which is outside the visible light region of the outer layer coating, the color of the object surface is colored in a desired color while the solar heat reflection from the surface is reflected. It is possible to improve the sex. In order to do so, it is effective that the outer coating film contains a predetermined amount or more of the pigment having a solar heat reflectance of 20% or more in the near infrared region. Hereinafter, such a pigment having good solar heat reflectivity will be simply referred to as "reflective pigment", and a coating film containing a predetermined amount of solar heat reflective pigment will also be referred to as "reflective coating film".

[0012] When coating a metal plate, an undercoating film (primer coating film) (primer film) is provided between the outer coating film and the substrate for the purpose of enhancing the adhesion of the outer coating film and improving the rust prevention as a surface-treated metal plate and the finish of the coating. ) Or an intermediate coating film (hereinafter collectively referred to simply as “inner layer coating film”) and the like. When the metal plate has a plurality of coating films, two or more coating films may be reflective coating films.

In order to improve the solar heat reflectivity, it is effective to include a reflective pigment in the outer coating film. For example, the outer coating film is thin, and the hiding property is sufficient even if the reflective pigment is contained. In other cases, it is preferable that the inner coating film also contains a reflective pigment.

As the reflective pigment contained in the inner coating film, it is effective to contain a predetermined amount or more of a pigment having a solar heat reflectance of 20% or more at a wavelength in the visible light region in addition to the near infrared region.

Here, the solar heat reflectance referred to in the present invention is
It is the solar heat reflectance in consideration of the intensity of the spectrum in the wavelength region calculated from the spectral reflectance (Rλ) of the surface.
Solar thermal reflectance R _{E in} the wavelength range of 350 to 2100 nm
Is calculated by the following formula (1) and is 800 to
Solar reflectance R of pigment in the wavelength range of 2100 nm
_{E / NIR} shall be _calculated by the following equation (2). The spectral reflectance (Rλ) for obtaining these solar heat reflectances can be measured using a spectrophotometer.

[0016]

[Equation 1]

However, R _E : wavelength 350 to 2100 n
Solar heat reflectance (%) in the region of m, Eλ: spectral intensity of solar heat, Rλ: spectral reflectance.

[0018]

[Equation 2]

However, R _{E / NIR} : wavelength is 800 to 210
Solar heat reflectance (%) in the region of 0 nm, Eλ: solar heat spectral intensity, Rλ: spectral reflectance.

B. Even a plate provided with a solar heat reflective coating film as described above may lack sufficient hiding power of the coating film, and may not have sufficient reflectivity as a surface-treated metal plate. In such a case, it is effective to use a substrate having good solar heat reflectivity.

A substrate having a good solar heat reflectivity is one having a solar heat reflectivity of 40% or more in the wavelength region of 350 to 2100 nm, which is the visible light region plus the near infrared region. The reflectivity of the substrate can be easily obtained by plating the surface of the material with excellent reflectivity. Among them, materials having a plating film containing 50% by weight or more of aluminum are suitable as building materials because they have good solar heat reflectivity, corrosion resistance, and economy.

Further, the solar heat reflectivity of the substrate is affected by the roughness of the substrate surface, and when the surface roughness is excessively rough, the reflectivity of the substrate decreases, so that a smoother surface is preferred. Further, since the metal oxide easily absorbs solar heat, when the oxide film is present on the surface of the substrate, the thinner the thickness, the better.

C. The undercoating film or the intermediate coating film, which is the interior coating film, usually contains a pigment that easily absorbs solar heat. Therefore, when the inner coating film does not contain the predetermined reflective pigment, it is desirable that the inner coating film is thin.

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

The present invention has been completed based on the newly obtained knowledge as described above, and the gist thereof is the solar heat reflective surface described in any of the following (1) to (9). It is on a treated metal plate.

(1) Aluminum-zinc alloy plating film
In the provided substrate surface solar reflectance in the wavelength region of 350~2100nm (R _E) is 60% or more, 800
Solar thermal reflectance (RE _{/ NIR} ) in the wavelength range of 2100 nm
Is provided with a coating film containing 20 to 20% by weight of a pigment in an amount of 2 to 70% by weight.

(2) Aluminum-zinc alloy plating film
The equipped, solar reflectance in the wavelength region of 350~2100nm the (R _E) is more than 60% of the substrate surface, and an outer layer coating 1
The above inner layer coating film is provided, and the outer layer coating film has a thickness of 800 to 21.
Solar thermal reflectance (RE _{/ NIR} ) in the wavelength range of 00 nm is 2
A surface-treated metal plate, which contains 2 to 70% by weight of 0% or more of a pigment.

(3) At least one inner layer coating is 350
Solar reflectance in the wavelength region of ~2100nm (R _E) is solar heat reflective surface treated metal sheet according to (2), characterized in that those containing 20% or more pigments 2-70 wt% .

(4) The surface-treated metal plate as described in (2) or (3) above, wherein the at least one inner coating film contains 2 to 20% by weight of a scaly aluminum pigment.

[0030] (5) that solar heat reflectance in the wavelength region of 350~2100nm (R _E) is the thickness of the inner layer coating content of more than 20% of the pigment is less than 2% by weight is 10μm or less The surface-treated metal plate according to any one of (2) to (4) above, which is characterized.

[0031]

( 6 ) The surface-treated metal as described in any one of (1) to ( 5 ) above, wherein the plated steel sheet is used as a substrate and the thickness of the oxide film on the surface of the plated film is 0.30 μm or less. Board.

( 7 ) The surface treatment as described in any one of (1) to ( 6 ) above, wherein the substrate surface has a centerline average roughness Ra of 0.05 to 2.0 μm. Metal plate.

( 8 ) The substrate is provided with a chromate treatment film equivalent to 5 to 200 mg / m ^{2 in} terms of metallic chromium or a phosphate treatment film of 0.2 to 5.0 g / m ^{2 as} a pretreatment film for coating. The surface-treated metal plate according to any one of (1) to ( 7 ) above.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail.
It

[0036] Substrate: a substrate for use in solar reflective surface treated metal sheet of the present invention, solar heat reflectance in the wavelength region of 350~2100nm calculated from the spectral reflectance of the surface (R _E) is more than 40% belongs to.

The target wavelength is limited as described above. Since most of the solar heat is included in the above wavelength range, defining the reflectance in this wavelength range is sufficient for the evaluation of solar heat reflectivity. This is because it has accuracy. R _E is 40%
If it does not satisfy the above condition, the reflectivity of the entire solar heat reflective surface-treated metal plate is lowered. Preferably R _E is at least 60%, more preferably at least 70%.

The substrate may be a metal plate having the above-mentioned properties, and its kind and chemical composition are arbitrary. For example, a low carbon steel, a high carbon steel, a steel plate made of a low alloy steel used for a high-strength steel plate, or the like, or a base plate of these steel plates, and a plated steel plate plated with a metal having excellent solar heat reflectivity It is preferable because it is excellent in economic efficiency. However, the type of substrate need not be limited to these, and may be a stainless steel plate or an aluminum plate.

The plating type of the plated steel sheet is not particularly limited, but Al-Zn type, Al-Mn type, Al type are used because of their good reflectivity to sunlight and economical efficiency of plating work.
-Si type and the like are preferable. Among them, 50 aluminum
The one provided with a plating film containing at least wt% is preferable. Pure aluminum plating may be used. For the plating film,
Further, an appropriate amount of alloying element such as Ni, Cr, Fe, Co may be contained. Such a plating film has high solar heat reflectivity and also has excellent corrosion resistance and economical efficiency of the substrate.

The amount of the plating film deposited is arbitrary, but it is 0.
It is preferable to have a plating film with a thickness of 01 μm or more because the solar heat reflectivity becomes good. The method of providing the plating film is arbitrary, and the electroplating method, the hot dipping method,
The plating can be performed by a known plating method such as a molten salt electrolytic plating method and a vapor deposition plating method.

In order to further improve the solar heat reflectivity of the substrate, the roughness of the substrate surface (the plating film surface in the case of having a plating film) is a center line average roughness Ra of 0.05 to
2 μm is preferable. Ra is better to be smaller, but 0.
Manufacturing a film having a thickness of less than 05 μm may increase the cost and impair the economical efficiency. When Ra exceeds 2 μm,
The reflectivity of the substrate may decrease.

Substrate surface (when it has a plating film,
If an oxide is attached to the surface of the plating film, it is easy to absorb solar heat. Therefore, even if the oxide film is provided, the oxide film thickness is preferably 0.30 μm or less. The thickness of this oxide film can be measured using X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), secondary ion mass spectrometry (SIMS), or the like.

In order to improve long-term durability such as corrosion resistance and coating film adhesion of the coated metal plate, in addition to the inner layer film, a coating type, a reaction type chromate treatment film, a phosphate treatment film, etc. are used for the substrate. Alternatively, a known coating pretreatment film may be provided. However, since these pretreatment films have the effect of impairing the solar heat reflectivity, the smaller the amount of the coating pretreatment film to be deposited is in the range where the effect of improving the adhesion and the like can be obtained.

Therefore, the adhesion amount of the pretreatment film is 200 mg / m ^{2 in} terms of metal chromium in the case of the chromate treatment film.
The following is more preferable and 100 mg / m ² or less is preferable. In the case of a phosphate treatment film, the adhesion amount is 5.0 g /
m ² or less, and more preferably 3.0 g / m ² or less. If it exceeds this value, the solar heat reflectivity will be impaired and
When processing the metal plate, the coating film may be cracked or peeled off, which is not preferable.

In order to obtain the effect of improving the adhesion, the adhesion amount of the pretreatment film is 5 mg / m ^{2 in} the case of chromate treatment.
As described above, more preferably 20 mg / m ² or more. In the case of the phosphate treatment, the amount is preferably 0.2 g / m ² or more, more preferably 0.5 g / m ² or more.

Even when the substrate is a stainless steel plate or an aluminum plate, it is preferable that the adhesion amount is within the above range even if a known chromate treatment is performed in order to improve the adhesion with the coating film.

Coating film: The surface-treated metal plate of the present invention comprises a reflective coating film containing 2 to 70% by weight of a reflective pigment on the above-mentioned substrate. When the metal plate has a plurality of coating films, two or more coating films may be reflective coatings. The outer coating film defined in the present invention means a coating film applied in a coating process that determines the color of a coated metal plate. In some cases, a clear film or the like is further applied on the outer layer coating film, but in the present invention, the clear film is not considered to be the outer layer coating film. When the outer coating film is thin and the hiding property is not sufficient even when the reflective pigment is contained, it is preferable that the inner coating film also contains the reflective pigment.

The wavelength defining the reflectance of the pigment of the outer coating film is limited to the solar heat reflectance (RE _{/ NIR} ) in the wavelength region of 800 to 2100 nm, which is the near infrared region, with respect to the wavelength of the visible light region. This is because the solar heat reflectance of the pigment is determined by the color applied to the substrate. When the R _{E / NIR of the} pigment contained in the coating film is less than 20%, the reflectivity of the entire solar heat reflective surface-treated metal plate is lowered. It is preferably 30% or more, more preferably 40% or more.

Coloring is performed when the content of the reflective pigment (when a plurality of reflective pigments are used in combination, the total of them) is less than 2% by weight based on the weight of the coating film to be treated. It is not good because it lacks strength and requires thick film coating to obtain the desired color. It is preferably at least 5% by weight.
The pigment content is 70% by weight with respect to the target coating film weight.
If it exceeds, the workability of the coating film will be impaired, so the upper limit is 7
It is 0% by weight. It is preferably 60% by weight or less.

The reflective pigment to be contained in the reflective coating is not limited to one kind, and a pigment satisfying the above conditions can be arbitrarily selected in consideration of hue, weather resistance and color stability.
When a plurality of types of reflective pigments are used, the total content thereof should be in the range of 2 to 70% by weight.

The reflective pigment used in the coating material of the present invention is preferably a component which is safe, has excellent water resistance and weather resistance and maintains a heat shielding effect for a long period of time. Among them, it is preferable to use metal compounds such as metal oxides, sulfides and chromates, and pigments such as insoluble dyes (color pigments) and lake pigments.

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

In addition to the above-mentioned reflective pigments, the reflective coating film may be composed of a color pigment, a rust preventive pigment, a substrate surface and a binder necessary for obtaining desired coating properties such as color, hiding property and corrosion resistance. For the purpose of improving the adhesiveness with a certain organic resin (for example, polyester resin, fluorine-based resin, etc.), the cohesive strength of the coating film itself, or the concealing property and brightness of the base, silica, alumina, calcium carbonate, An extender pigment such as barium sulfate, kaolin clay , talc, nepheline sinite, mica, and a bubble-containing pigment may be contained.

As a binder for holding the pigment, it is unlikely to cause yellowing, discoloration, loss of gloss, and chalking even when exposed to sunlight, and it is excellent in maintaining aesthetics even when used for many years and has a long-lasting effect of hiding sunlight. It is preferable to use an organic resin that can be maintained for a period of time.

As this resin, any one of various organic resins such as acrylic resin, polyester resin, polyolefin resin, and fluorine resin may be used, but two or more kinds may be mixed and used. . The content of these organic resins is preferably in the range of 10 to 90% by weight based on the dry weight of the coating film.

Further, synthetic fine powder silica, organic bentonite, carboxymethyl cellulose, polyvinyl alcohol and other thickeners, melamine-based, benzoguanamine-based, isocyanate-based cross-linking agents, polyacrylic acid, polyacrylic acid salts and other dispersants, etc. It may be contained.

The thickness of the reflective coating film is preferably 3 to 200 μm. If it is less than 3 μm, the hue may not be stable. More preferably, it is 10 μm or more. If the thickness of the coating film exceeds 200 μm, peeling or cracking of the coating film may occur during processing, and more than one coating work will be required, resulting in poor economic efficiency. Therefore, the thickness is 200 μm or less. Is good. More preferably, it is 30 μm or less.

[0058] The undercoating film or the intermediate coating film as the coating film is usually tends pigment absorbs solar heat is contained. Therefore, in a case where the content of the solar heat reflecting pigments of these inner coating film is less than 2%, in order not to inhibit the solar reflectivity, the thickness thereof thinner is preferable, and its thickness is 10μm or less It is good to say More preferably 7
μm or less.

The paint used in the present invention may be blended with aluminum flakes for use as a metallic coating film, or may be blended with a matting agent for use as a matting coating film. Also,
The solar heat reflective coating film is preferably provided on the uppermost layer of the surface-treated metal plate of the present invention, but, for example, in the case of a metallic coating containing aluminum flakes, the above solar heat reflective coating film may be added as necessary. A clear layer containing no pigment or a semi-transparent layer containing a small amount of pigment may be provided.

Aluminum paint containing a scaly aluminum pigment has been known as a solar heat shielding paint. However, this aluminum paint has a hue limitation that it is difficult to color other than white.

[0061] The flake aluminum pigment is contained in the inner layer coating film as solar reflecting pigments, by applying an outer layer coating film thereon, it is possible to achieve both the desired color and solar reflective. The content of the scaly aluminum pigment in this case can be provided with solar heat reflectivity by containing 2 to 30% by weight, but 10% by weight or less is required to maintain good interlayer adhesion to the outer layer coating film. Is desirable.

Production Method: The method for producing the solar-heat-reflecting surface-treated metal plate of the present invention is not particularly limited, but the above-mentioned pigment and organic resin are dispersed in a solvent to prepare a coating composition, and the coating composition is applied to the substrate surface. It is preferable to manufacture by forming a reflective layer by coating on and drying.

The solvent to be added to the coating material is not particularly limited, and may be appropriately selected and used from commonly used solvents according to the organic resin. As the solvent, a commonly used solvent such as water, toluene, xylene, cyclohexanone, methyl ethyl ketone may be appropriately selected and used. The extender pigment, the cross-linking agent, the dispersant, and the like described above can be added to the coating composition.

The coating composition may be applied by a known method, for example, spray coating, roll coating, curtain flow coating, bar coating, or the like.
After the coating, when the substrate is a metal plate, it may be dried by a known method such as a hot air oven or an induction heating oven and cooled by a known method. These treatments can be performed using known coating equipment.

[0065]

Example 1 As a substrate, a hot-dip galvanized steel sheet (hereinafter, referred to as “GI”) defined in JIS-G3302, which is a base material of a cold-rolled steel sheet having a thickness of 0.80 mm, and hot-dip zinc are used. -5% aluminum alloy plated steel sheet (hereinafter referred to as "5% Al-Z
n ”), molten zinc-5 specified in JIS-G3321
5% aluminum alloy plated steel sheet (hereinafter referred to as "55%"
Al-Zn " ) was used. Also, using the same base material,
75% Al-25% Mn Molten Salt Electroplating and 12%
Any one of Ni-88% Zn alloy electroplating was applied. Further, as a comparative example, 10% Fe-90% Z
N-alloy electroplated steel sheets were also manufactured. The oxide film on the surface of each of the plated steel sheets was 0.01 μm as a result of measurement by X-ray photoelectron spectroscopy. Further, all the plated steel sheets were subjected to temper rolling by using a rolling roll in which the roughness of the rolling roll was adjusted after plating, and the roughness of the plating surface was adjusted to Ra of 0.6 μm .

The pigment contained in the coating film is 800 to 2
Spectral reflectance R _{E / NIR in} the wavelength region of 100 nm is 45
%, Insoluble monoazo pigment having an average particle size of 0.4 μm (manufactured by Dainippon Ink and Chemicals, SYMULER FAST YELLOW 41
92) (hereinafter referred to as “PY154”), R _{E / NIR} is 25
%, An inorganic pigment having an average particle diameter of 0.5 μm (Kamaike Dye Industry Co., Ltd., Permaero 1650S) (hereinafter referred to as “PY3”).
4 "), and _{RE / NIR} of 15% and an average particle size of 0.
5 μm of lead chromate (manufactured by Dainichiseika Kogyo KK, 325 Chrome Yellow 7G) (hereinafter referred to as “7G”) was used.

40 parts by weight of the above pigment, 60 parts by weight of polyester resin as a binder, and a melamine-based cross-linking agent as the rest of the dry solid content were dispersed and mixed with a proper amount of cyclohexanone as a solvent using a ball mill. A coating composition (paint) was obtained.

These coatings were applied to the above-mentioned various substrates by 2
An amount of a dry film thickness of 0 μm was applied by a roll coating method, and a baking treatment was performed at 240 ° C. for 60 seconds to obtain a solar heat reflective surface-treated metal plate of the present invention. Table 1 shows the constitution of the obtained surface-treated metal plate.

[0069]

[Table 1]

Length from the above treated metal plate: 150 mm,
Width: cut out samples of 200 mm, affixed to the opening of the insulated container having an opening shown in FIG. 1, exposing the sample surface to solar radiation, it was investigated temperature Rise of the steel sheet back surface.

In FIG. 1, the heat insulating container 6 is constructed so that the side walls other than the opening have good heat insulating properties, and the sample is attached to the opening so that the sample surface is exposed to the solar radiation at the same angle. A device that follows the solar radiation so that it is illuminated (not shown)
Disposed on top. A thermocouple 4 is attached to the back surface of the sample, and the temperature change on the back surface of the sample can be measured by connecting the thermocouple 4 to a recorder 5 provided outside. The results obtained are shown graphically in FIG. In addition, Table 1 shows the maximum temperature.

As can be seen from Table 1 and FIG. 2, in the range defined by the present invention, the maximum temperature reached on the back surface of the steel sheet was low, and good solar heat reflectivity was exhibited. Sample 4 showed the best performance. On the other hand, those which deviated from the conditions defined by the present invention were not preferable.

(Example 2) As a substrate, the 55% Al-Zn plated steel sheet described in Example 1 was used. A part of them was subjected to AC anodic oxidation in a dilute sulfuric acid aqueous solution to variously change the thickness of the oxide layer on the plating surface. These plated steel sheets were subjected to temper rolling by using a rolling roll in which the roughness of the rolling roll was adjusted after plating, to prepare substrates in which the roughness of the plating surface was variously changed. On these substrates, the pigment PY15 used in Example 1 was added.
A coating material containing 40 parts by weight of No. 4 and 60 parts by weight of a polyester resin as a binder was prepared by the same method as described in Example 1. These paints were applied to the above substrate and dried so as to obtain a dry film thickness of 20 μm.
The resulting coated plate in the same manner as in Example 1, was investigated temperature Rise of the steel sheet back surface. The results obtained are shown in Table 2.

[0074]

[Table 2]

As can be seen from Table 2, in the test numbers 21, 22 and 24 in which the thickness of the oxide film on the plated surface is 0.30 μm or less and the surface roughness Ra is 2 μm or less,
It was found that the maximum temperature reached on the back surface of the steel sheet was particularly low and that it had extremely excellent reflectivity. Test number 23 in which the surface roughness of the plating film was rough and test number 2 in which the oxide film was thick
In No. 5, the reflectance was a little low and the maximum temperature reached was a little high.

Example 3 As a substrate, the hot-dip galvanized steel sheet (GI) described in Example 1, hot-dip zinc-5% aluminum alloy-plated steel sheet (5% Al-Zn), hot-dip zinc-55% aluminum alloy plating. A steel plate (55% Al-Zn ) was used. The pigment PY154 described in Example 1 was used as the pigment contained in the coating film for solar heat reflection, and the pigment 7G was used as the comparative example.
20 parts by weight of any of the above pigments for topcoating,
80 parts by weight of a polyester resin as a binder, a melamine-based cross-linking agent as the balance of the dry solid content, and an appropriate amount of cyclohexanone as a solvent were dispersed and mixed using a ball mill to obtain a top coating composition (paint). .

For undercoating, 40 parts by weight of PY154 or 7G and 60 parts of polyester resin as a binder are used.
The weight parts and the like were adjusted in the same manner as the above-mentioned top coating material to obtain a bottom coating material. Furthermore, as a paint for undercoat,
Flake shaped aluminum powder (manufactured by Toyo Aluminum Co., Ltd., 0
700 M) (hereinafter, referred to as “Al powder”) by 5 parts by weight, polyester resin as a binder by 95 parts by weight, and other adjustments were performed in the same manner as the topcoating paint to obtain an undercoating paint.

These coating materials were applied to the above-mentioned various substrates by a roll coating method in an amount such that a predetermined dry film thickness for undercoating and a dry film thickness of 20 μm for topcoating were obtained.
A baking treatment was carried out at 60 ° C. for 60 seconds to obtain a solar heat reflective surface-treated metal plate according to the present invention having an undercoat coating film (inner layer coating film) and an overcoat coating film (outer layer coating film). Table 3 shows the constitution of the obtained surface-treated metal plate.

[0079]

[Table 3]

Length from the treated metal plate: 150 mm,
Width: cut out samples of 200 mm, affixed to the opening of the insulated container having an opening shown in FIG. 1, exposing the sample surface to solar radiation, the temperature Rise of the steel sheet back surface in a manner similar to that described in Example 1 The temperature was investigated, and the temperature when 1 hour passed from the start of the test is also shown in Table 3 as the maximum reached temperature.

As can be seen from Table 3, in the range defined by the present invention, the maximum temperature reached on the back surface of the steel sheet was low, and good solar heat reflectivity was exhibited. Test No. 36, 38, 40 and 45 showed particularly good results. On the other hand, the results that were out of the conditions specified by the present invention were not favorable.

Example 4 As a substrate, the same hot-dip galvanized steel sheet (GI) as that described in Example 3 and 55% A were used.
An l-Zn plated steel plate was used. As a pretreatment, a part of the GI was subjected to a zinc phosphate treatment using a commercially available chemical solution so as to obtain a predetermined adhesion amount (hereinafter referred to as “PB”).
Further, a part of 55% Al-Zn was subjected to a coating type chromate treatment as a pretreatment by using a commercially available chemical solution so that a predetermined adhesion amount could be obtained (hereinafter, referred to as "CR"). A paint containing 20 parts by weight of the pigment PY154 described in Example 1 and 80 parts by weight of a polyester resin as a binder is used in Example 3.
A top coating composition was prepared in the same manner as described in 1.
Similarly, a coating material containing 40 parts by weight of the pigment PY154 and 60 parts by weight of a polyester resin as a binder was prepared in Example 3.
An undercoat paint was prepared in the same manner as described in 1.
These paints were applied to the above pretreated substrate so that the dry film thickness was 10 μm for the undercoat and 20 μm for the overcoat, and dried.

[0083]

[Table 4]

Length from the treated metal plate: 150 mm,
Width: cut out samples of 200 mm, and investigated for the temperature Rise of the steel sheet back surface by the same method described in Example 1 to obtain the temperature at which one hour has elapsed after the start of the test as a maximum temperature. Further, the bendability and corrosion resistance of the test piece obtained from the treated metal plate were investigated by the following methods.

Bendability: 18 at 23 ° C. with the coated surface outside
0 ° bending is performed, and the presence or absence of cracks in the coating film at the bent portion is observed with a magnifying glass 10 times to find the minimum number of plate sandwiches (T) in which no cracks are recognized (plate sandwiching number 0T means close bending). It was evaluated according to the following criteria. 4T or less: ⊚, 5T: ◯, 6T: Δ, 7T or more: ×.

Corrosion resistance: Corrosion resistance was evaluated by a salt spray test specified in JIS-Z2371. Put a cross-cut to reach the base of the plated steel plate in the test piece and spray with salt water to 50
The coating film bulge width (maximum value) from the cut portion after application for 0 hour was measured and evaluated according to the following criteria. 1 mm or less: ⊚, 2 mm: ◯, 3 mm: Δ, 4 mm or more: ×.

The results are also shown in Table 4. As can be seen from Table 4, test number 5 with appropriate pretreatment
In Nos. 2 and 55, the performance (bending workability and corrosion resistance) as the exterior coated metal plate was particularly good, as well as the solar heat reflectivity.

[0088]

The highly-reflective surface-treated metal sheet of the present invention can be used mainly as an exterior material for building materials such as roofs, and is excellent in the required lightness and heat-shielding properties of roofs, and has high productivity. Since it is expensive, an inexpensive material can be provided.

[Brief description of drawings]

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

FIG. 2 is a graph showing the results of measuring the temperature rise situation on the back surface of a steel sheet.

[Explanation of symbols]

1 ... sunlight, 2 ... reflection layer, 3 ... substrate, 4 ...
..Thermocouple, 5 ... Recorder, 6 ... Insulation container

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Ikishima 4-53-3 Kitahama, Chuo-ku, Osaka City Sumitomo Metal Industries, Ltd. (56) Reference JP-A-10-37404 (JP, A) JP 55-71548 (JP, A) JP-A-4-246478 (JP, A) JP-A-10-128232 (JP, A) JP-A-4-224668 (JP, A) JP-A-4-280953 (JP , A) JP-A-4-254588 (JP, A) JP-A-5-202485 (JP, A) Rust prevention management, Japan, Japan Society for Corrosion Protection, July 1, 1983, Vol. 27, No. 7. , 205-215 (58) Fields investigated (Int.Cl. ⁷ , DB name) B05D 7/14 B05D 5/06 B05D 7/24 303 B32B 15/08 G02B 5/08

Claims (10)

(57) [Claims] As claimed in claim 1] substrate, aluminum - with a zinc alloy plating film on the substrate surface solar reflectance in the wavelength region of 350~2100nm (R _E) is 60% or more,
Solar thermal reflectance (R in the wavelength range of 800 to 2100 nm (R
A solar-heat-reflecting surface-treated metal plate having a coating film containing 2 to 70% by weight of pigment whose _{E / NIR} is 20% or more. 2. A substrate made of an aluminum-zinc alloy
Equipped with a plating film, in the wavelength range of 350-2100 nm
On the substrate surface having a solar heat reflectance (R _E ) of 60% or more,
Solar thermal reflectance (R in the wavelength range of 800 to 2100 nm (R
_{E / NIR} ) contains 2 to 70% by weight of pigment of 20% or more
It is characterized by having a coating film colored in the desired color
Solar heat reflective surface treated metal plate. 3. A color pigment other than the pigment is not contained.
The solar heat reflective surface treated gold according to claim 2, characterized in that
Generic plate . As wherein the substrate, an aluminum - with a zinc alloy plating film solar reflectance in the wavelength region of 350~2100nm the (R _E) is more than 60% of the substrate surface, the outer coating and one or more inner coating And an outer coating film of 80
Solar heat reflectivity in the wavelength range of 0 to 2100 nm (R
_{E / NIR} ) contains 2 to 70% by weight of a pigment of 20% or more, a solar heat reflective surface-treated metal plate. 5. At least one inner layer coating comprises 350-2.
The solar heat reflectance (R _E ) in the wavelength range of 100 nm is 20.
% Or more of the pigment is contained in an amount of 2 to 70% by weight, and the solar heat-reflecting surface-treated metal plate according to claim 4, which is characterized in that. 6. The solar heat-reflecting surface-treated metal plate according to claim 4, wherein at least one inner coating film contains 2 to 20% by weight of a scaly aluminum pigment. 7. The thickness of the inner coating film having a pigment content of 20% or more in the solar heat reflectance (R _E ) in the wavelength range of 350 to 2100 nm of less than 2% by weight and 10 μm or less. The solar heat reflective surface-treated metal plate according to any one of claims 4 to 6. 8. The solar heat-reflecting surface-treated metal sheet according to claim 1, wherein the plated steel sheet is used as a substrate, and the thickness of the oxide film on the surface of the plated film is 0.30 μm or less. . 9. The roughness of the substrate surface is the center line average roughness Ra.
It is 0.05-2.0 micrometers, The solar heat reflective surface treatment metal plate in any one of Claims 1-8 characterized by the above-mentioned. 10. The substrate is provided with, as a pretreatment film for coating, a chromate treatment film equivalent to 5 to 200 mg / m ^{2 in} terms of metallic chromium or a phosphate treatment film of 0.2 to 5.0 g / m ^2. The solar heat reflective surface-treated metal plate according to any one of claims 1 to 9.